Control device and method of frequency converter and frequency converter
阅读说明：本技术 一种变频器的控制装置、方法和变频器 (Control device and method of frequency converter and frequency converter ) 是由 李燕 张统世 乔一伦 于 2020-06-15 设计创作，主要内容包括：本发明公开了一种变频器的控制装置、方法和变频器,该装置包括：第一采样模块,用于采集逆变器侧待控设备处的第一信号；第二采样模块,用于采集逆变器和整流器之间的母线信号；第三采样模块,用于采集整流器侧电网处的第二信号；控制器,用于根据第一信号和母线信号,生成第一PWM信号,第一PWM信号用于控制逆变器中的开关管；和/或,根据第二信号和母线信号,生成第二PWM信号,第二PWM信号用于控制整流器中的开关管。本发明的方案,可以解决变频器容易产生电磁干扰而限制了其应用场合的问题,达到提升变频器的抗干扰性能从而拓宽其应用场合的效果。(The invention discloses a control device and a method of a frequency converter and the frequency converter, wherein the device comprises: the first sampling module is used for acquiring a first signal at the to-be-controlled equipment at the inverter side; the second sampling module is used for acquiring bus signals between the inverter and the rectifier; the third sampling module is used for collecting a second signal at the power grid on the rectifier side; the controller is used for generating a first PWM signal according to the first signal and the bus signal, and the first PWM signal is used for controlling a switching tube in the inverter; and/or generating a second PWM signal according to the second signal and the bus signal, wherein the second PWM signal is used for controlling a switching tube in the rectifier. The scheme of the invention can solve the problem that the frequency converter is easy to generate electromagnetic interference so as to limit the application occasions, and achieves the effect of improving the anti-interference performance of the frequency converter so as to widen the application occasions.)
1. A control device of a frequency converter is characterized in that the frequency converter comprises: an inverter and a rectifier; control device of converter includes: a sampling unit and a controller; the sampling unit includes: the device comprises a first sampling module and a second sampling module, or the second sampling module and a third sampling module, or the first sampling module, the second sampling module and the third sampling module; wherein the content of the first and second substances,
the first sampling module is used for acquiring a first signal at the to-be-controlled equipment at the inverter side;
the second sampling module is used for acquiring bus signals between the inverter and the rectifier;
the third sampling module is used for collecting a second signal at a power grid on the rectifier side;
the controller is used for generating a first PWM signal according to the first signal and the bus signal, and the first PWM signal is used for controlling a switching tube in the inverter; and/or generating a second PWM signal according to the second signal and the bus signal, wherein the second PWM signal is used for controlling a switching tube in the rectifier.
2. The control device of a frequency converter according to claim 1, wherein,
the controller is also used for controlling the inverter in a vector control mode based on the first PWM signal; and controlling the rectifier in a full-control rectification mode based on the second PWM signal.
3. The control device of a frequency converter according to claim 1, wherein,
the first sampling module collects a first signal at a device to be controlled at the inverter side, and comprises: acquiring a first signal at a device to be controlled at the inverter side by a differential sampling circuit in a differential sampling mode;
and/or the presence of a gas in the gas,
the third sampling module collects a second signal at the rectifier side grid, and comprises: and acquiring a second signal at the power grid on the rectifier side by adopting a differential sampling mode through a differential sampling circuit.
4. The control device of a frequency converter according to claim 1, wherein,
the controller generates a first PWM signal, comprising: generating a first PWM signal by a random zero vector modulation circuit in a sector-free fast random zero vector SVPWM modulation mode; and/or the presence of a gas in the gas,
the controller generates a second PWM signal, comprising: and generating a second PWM signal by a random zero vector modulation circuit in a sector-free fast random zero vector SVPWM modulation mode.
5. The control device of the frequency converter according to claim 4, wherein the random zero vector modulation circuit comprises: the device comprises an anti-park module, an anti-clark conversion module, a modulated wave calculation module, a random number generation module, a modulated wave generation module of random zero vectors and a PWM wave generator;
wherein the content of the first and second substances,
the anti-park module is used for converting the direct axis voltage and the quadrature axis voltage into two-phase static voltages under a two-phase static coordinate system;
the reverse click conversion module is used for converting the two-phase static voltage into a three-phase static voltage under a three-phase static coordinate system;
the modulation wave calculation module is used for calculating the value of the modulation wave after determining the maximum value and the minimum value in the three-phase static voltage;
the random number generation module is used for generating random numbers in a set interval;
the modulation wave generation module of the random zero vector is used for generating the modulation wave of the random zero vector according to the value of the modulation wave and the random number of the set interval;
and the PWM wave generator is used for generating PWM waves according to the modulation waves of the set carrier and the random zero vector.
6. The apparatus for controlling a frequency converter according to claim 5, wherein the random number generation module generates random numbers for a set interval, and comprises:
the random number generation module is used for generating random numbers in a set interval by adopting a linear congruence method and a mathematical recursion formula;
alternatively, the first and second electrodes may be,
the random number generation module is used for generating random numbers in a set interval by adopting a Matteur rotation algorithm, a square mid-fetching method and/or a tabulation and table look-up method.
7. The control device of the frequency converter according to claim 5, wherein the random zero vector modulated wave generating module generates a random zero vector modulated wave, comprising:
if the random value of the zero vector is as followsComputingThen, the modulation wave value of the random zero vector is:
alternatively, the first and second electrodes may be,
if the random value of the zero vector is according to TR＝min(Ta0,Tb0,Tc0) Calculating the modulation wave value of the random zero vector as follows:
8. the control device of the inverter according to any one of claims 1 to 7, wherein the inverter comprises: a four-quadrant frequency converter; the four-quadrant frequency converter adopts a totally enclosed shell, and/or is provided with a shielding part for shielding interference signals.
9. A frequency converter, comprising: a control apparatus of a frequency converter according to any one of claims 1 to 8.
10. A compressor, comprising: the frequency converter of claim 9.
11. An air conditioner, comprising: the compressor of claim 10.
12. A method of controlling a frequency converter according to claim 9, wherein the frequency converter comprises: an inverter and a rectifier; the control method of the frequency converter comprises the following steps:
acquiring a first signal at a device to be controlled at the inverter side through a first sampling module;
collecting a bus signal between the inverter and the rectifier through a second sampling module;
acquiring a second signal at the power grid on the rectifier side through a third sampling module;
generating a first PWM (pulse-width modulation) signal according to the first signal and the bus signal by a controller, wherein the first PWM signal is used for controlling a switching tube in the inverter; and/or generating a second PWM signal according to the second signal and the bus signal, wherein the second PWM signal is used for controlling a switching tube in the rectifier.
13. The method of claim 12, wherein the inverter is controlled by the controller in a vector control manner based also on the first PWM signal; and controlling the rectifier in a full-control rectification mode based on the second PWM signal.
14. The method of controlling a frequency converter according to claim 12, wherein,
the method includes the steps that a first signal of a device to be controlled on the inverter side is acquired through a first sampling module, and the method includes the following steps: acquiring a first signal at a device to be controlled at the inverter side by a differential sampling circuit in a differential sampling mode; and/or the presence of a gas in the gas,
the second signal of rectifier side electric wire netting department is gathered through third sampling module, includes: and acquiring a second signal at the power grid on the rectifier side by adopting a differential sampling mode through a differential sampling circuit.
15. The method of controlling a frequency converter according to claim 12, wherein,
generating, by a controller, a first PWM signal comprising: generating a first PWM signal by a random zero vector modulation circuit in a sector-free fast random zero vector SVPWM modulation mode; and/or the presence of a gas in the gas,
generating, by a controller, a second PWM signal comprising: and generating a second PWM signal by a random zero vector modulation circuit in a sector-free fast random zero vector SVPWM modulation mode.
16. The method of claim 15, wherein the generating the first PWM signal and/or the second PWM signal by a random zero vector modulation circuit comprises:
converting the direct-axis voltage and the quadrature-axis voltage into two-phase static voltages under a two-phase static coordinate system through a reverse park module;
converting the two-phase static voltage into a three-phase static voltage under a three-phase static coordinate system through an inverse clark conversion module;
calculating the value of a modulation wave after determining the maximum value and the minimum value in the three-phase static voltage through a modulation wave calculation module;
generating a random number in a set interval by a random number generation module;
generating a modulation wave of a random zero vector according to the value of the modulation wave and the random number of the set interval by a modulation wave generation module of the random zero vector;
and generating a PWM wave by a PWM wave generator according to the modulation wave of the set carrier and the random zero vector, wherein the PWM signal is a first PWM signal and/or a second PWM signal.
17. The method of claim 16, wherein the generating random numbers of the set interval by the random number generation module comprises:
the random number generation module is used for generating random numbers in a set interval by adopting a linear congruence method through a mathematical recursion formula;
alternatively, the first and second electrodes may be,
and the random number generation module is used for generating the random number in the set interval by adopting a Matteset rotation algorithm, a square mid-fetching method and/or a tabulation and table look-up method.
18. The method of controlling a frequency converter according to claim 16,
the module for generating the modulated wave of the random zero vector through the modulated wave of the random zero vector comprises:
if the random value of the zero vector is as follows
alternatively, the first and second electrodes may be,
if the random value of the zero vector is as followsAnd calculating, wherein the modulation wave value of the random zero vector is as follows:
Technical Field
The invention belongs to the technical field of frequency converters, and particularly relates to a control device and method of a frequency converter and the frequency converter, in particular to a high-power frequency converter and a control device and method thereof.
Background
When the frequency converter adopts high-frequency switch modulation, the problem of electromagnetic interference is easily generated, and the application occasions of the frequency converter are limited.
The above is only for the purpose of assisting understanding of the technical aspects of the present invention, and does not represent an admission that the above is prior art.
Disclosure of Invention
The invention aims to provide a control device and a control method of a frequency converter and the frequency converter, aiming at overcoming the defects that the frequency converter is easy to generate electromagnetic interference so as to limit the application occasions, and achieving the effect of improving the anti-interference performance of the frequency converter so as to widen the application occasions.
The invention provides a control device of a frequency converter, comprising: a frequency converter, comprising: an inverter and a rectifier; control device of converter includes: a sampling unit and a controller; a sampling unit comprising: the device comprises a first sampling module and a second sampling module, or the second sampling module and a third sampling module, or the first sampling module, the second sampling module and the third sampling module; the first sampling module is used for acquiring a first signal at a device to be controlled at the inverter side; the second sampling module is used for acquiring bus signals between the inverter and the rectifier; the third sampling module is used for collecting a second signal at the power grid on the rectifier side; the controller is used for generating a first PWM signal according to the first signal and the bus signal, and the first PWM signal is used for controlling a switching tube in the inverter; and/or generating a second PWM signal according to the second signal and the bus signal, wherein the second PWM signal is used for controlling a switching tube in the rectifier.
Optionally, the controller is further configured to control the inverter in a vector control manner based on the first PWM signal; and controlling the rectifier in a full-control rectification mode based on the second PWM signal.
Optionally, the first sampling module acquires a first signal at a device to be controlled on the inverter side, and includes: acquiring a first signal at a device to be controlled at the inverter side by a differential sampling circuit in a differential sampling mode; and/or the third sampling module acquires a second signal at the rectifier-side power grid, and comprises: and acquiring a second signal at the power grid on the rectifier side by adopting a differential sampling mode through a differential sampling circuit.
Optionally, wherein the controller generates the first PWM signal, comprising: generating a first PWM signal by a random zero vector modulation circuit in a sector-free fast random zero vector SVPWM modulation mode; and/or the controller generates a second PWM signal comprising: and generating a second PWM signal by a random zero vector modulation circuit in a sector-free fast random zero vector SVPWM modulation mode.
Optionally, the random zero vector modulation circuit includes: the device comprises an anti-park module, an anti-clark conversion module, a modulated wave calculation module, a random number generation module, a modulated wave generation module of random zero vectors and a PWM wave generator; the anti-park module is used for converting the direct axis voltage and the quadrature axis voltage into two-phase static voltages under a two-phase static coordinate system; the reverse click conversion module is used for converting the two-phase static voltage into a three-phase static voltage under a three-phase static coordinate system; the modulation wave calculation module is used for calculating the value of the modulation wave after determining the maximum value and the minimum value in the three-phase static voltage; the random number generation module is used for generating random numbers in a set interval; the modulation wave generation module of the random zero vector is used for generating the modulation wave of the random zero vector according to the value of the modulation wave and the random number of the set interval; and the PWM wave generator is used for generating PWM waves according to the modulation waves of the set carrier and the random zero vector.
Optionally, the generating module generates a random number in a set interval, and includes: the random number generation module is used for generating random numbers in a set interval by adopting a linear congruence method through a mathematical recursion formula; or, the random number generating module is used for generating the random number of the set interval by adopting a Matteur rotation algorithm, a square mid-fetching method and/or a tabulation and table look-up method.
Optionally, modulation wave generation of random zero vectorsThe module generates a modulated wave of random zero vectors, comprising: if the random value of the zero vector is as followsAnd calculating, wherein the modulation wave value of the random zero vector is as follows:or if the random value of the zero vector is according to TR＝min(Ta0,Tb0,Tc0) Calculating the modulation wave value of the random zero vector as follows:
optionally, the frequency converter includes: a four-quadrant frequency converter; the four-quadrant frequency converter adopts a totally enclosed shell, and/or is provided with a shielding part for shielding interference signals.
In accordance with the above apparatus, another aspect of the present invention provides a frequency converter, including: the control device of the frequency converter.
In accordance with the inverter, the present invention provides a compressor, comprising: the frequency converter described above.
In accordance with the above compressor, a further aspect of the present invention provides an air conditioner, comprising: the compressor described above.
In another aspect, the present invention provides a method for controlling a frequency converter, where the frequency converter includes: an inverter and a rectifier; the control method of the frequency converter comprises the following steps: acquiring a first signal at a device to be controlled at the inverter side through a first sampling module; collecting a bus signal between the inverter and the rectifier through a second sampling module; acquiring a second signal at the power grid on the rectifier side through a third sampling module; generating a first PWM (pulse-width modulation) signal according to the first signal and the bus signal by a controller, wherein the first PWM signal is used for controlling a switching tube in the inverter; and/or generating a second PWM signal according to the second signal and the bus signal, wherein the second PWM signal is used for controlling a switching tube in the rectifier.
Optionally, the controller is further configured to control the inverter in a vector control manner based on the first PWM signal; and controlling the rectifier in a full-control rectification mode based on the second PWM signal.
Optionally, the acquiring, by the first sampling module, a first signal at the inverter-side device to be controlled includes: acquiring a first signal at a device to be controlled at the inverter side by a differential sampling circuit in a differential sampling mode; and/or, acquiring a second signal at the rectifier-side power grid through a third sampling module, wherein the second signal comprises: and acquiring a second signal at the power grid on the rectifier side by adopting a differential sampling mode through a differential sampling circuit.
Optionally, wherein the generating, by the controller, the first PWM signal comprises: generating a first PWM signal by a random zero vector modulation circuit in a sector-free fast random zero vector SVPWM modulation mode; and/or, generating, by the controller, a second PWM signal, comprising: and generating a second PWM signal by a random zero vector modulation circuit in a sector-free fast random zero vector SVPWM modulation mode.
Optionally, generating the first PWM signal and/or the second PWM signal by a random zero vector modulation circuit includes: converting the direct-axis voltage and the quadrature-axis voltage into two-phase static voltages under a two-phase static coordinate system through a reverse park module; converting the two-phase static voltage into a three-phase static voltage under a three-phase static coordinate system through an inverse clark conversion module; calculating the value of a modulation wave after determining the maximum value and the minimum value in the three-phase static voltage through a modulation wave calculation module; generating a random number in a set interval by a random number generation module;
generating a modulation wave of a random zero vector according to the value of the modulation wave and the random number of the set interval by a modulation wave generation module of the random zero vector; and generating a PWM wave by a PWM wave generator according to the modulation wave of the set carrier and the random zero vector, wherein the PWM signal is a first PWM signal and/or a second PWM signal.
Optionally, the generating, by the random number generating module, a random number for the set interval includes: the random number generation module is used for generating random numbers in a set interval by adopting a linear congruence method through a mathematical recursion formula; or, the random number generating module is used for generating the random number of the set interval by adopting a Matteur rotation algorithm, a square mid-fetching method and/or a tabulation and table look-up method.
Optionally, the generating, by the modulated wave generating module of a random zero vector, a modulated wave of a random zero vector includes: if the random value of the zero vector is as follows
according to the scheme, by adopting the design of the full-control rectification and inversion control system, the sector-free fast random zero vector SVPWM modulation is realized, the sector division and the zero vector time calculation are not needed, the space of a CPU (Central processing Unit) can be effectively saved, and the program operation time is reduced.
Furthermore, the scheme of the invention effectively disperses the harmonic components around the switching frequency and integral multiple thereof by adopting a sector-free fast random zero vector SVPWM modulation method, so that the frequency spectrum is more uniform, the electromagnetic interference and high-frequency noise of the frequency converter are improved, the electromagnetic compatibility of the system is improved, and the anti-interference capability of the system is improved.
Furthermore, according to the scheme of the invention, through carrying out differential sampling design on the key signal samples of the frequency converter, the problem that the key signals are influenced by interference to influence the control effect can be solved, and the anti-interference capability of the frequency converter is improved.
Therefore, according to the scheme of the invention, differential sampling is adopted for signal sampling of rectification and inversion control of the four-quadrant frequency converter, and a sector-free random zero vector control mode is adopted for modulation of the switching tube, so that the problem that the frequency converter is easy to generate electromagnetic interference and limits the application occasions is solved, for example, the problem that the high-power high-speed frequency converter is easy to generate electromagnetic interference or is limited in application occasions due to insufficient anti-interference capacity is solved, and the effect of improving the anti-interference performance of the frequency converter and widening the application occasions is achieved.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.
The technical solution of the present invention is further described in detail by the accompanying drawings and embodiments.
Drawings
Fig. 1 is a schematic structural diagram of a control device of a frequency converter according to an embodiment of the present invention;
FIG. 2 is a schematic structural diagram of an embodiment of a high power four quadrant converter system of the present invention;
FIG. 3 is a schematic diagram of a differential sampling circuit according to an embodiment of the present invention;
FIG. 4 is a schematic structural diagram of a fully-controlled rectifier control system according to an embodiment of the present invention;
FIG. 5 is a schematic structural diagram of an inverter control system according to an embodiment of the present invention;
FIG. 6 is a schematic structural diagram of an embodiment of a random zero vector modulation circuit according to the present invention;
FIG. 7 is a schematic structural diagram of an embodiment of a PWM generating circuit according to the present invention;
FIG. 8 is a flowchart illustrating a method for controlling a frequency converter according to an embodiment of the present invention;
fig. 9 is a schematic flowchart of an embodiment of generating the first PWM signal and/or the second PWM signal by the random zero vector modulation circuit in the method of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below with reference to the specific embodiments of the present invention and the accompanying drawings. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
According to an embodiment of the present invention, there is provided a control apparatus of a frequency converter. Referring to fig. 1, a schematic diagram of an embodiment of the apparatus of the present invention is shown. The control device of the frequency converter can be mainly applied to the frequency converter in a magnetic suspension centrifugal machine, in particular to a four-quadrant frequency converter. Frequency converter, in particular four-quadrant frequency converter, may comprise: an inverter and a rectifier, such as a high power four quadrant inverter system, may include both rectifying and inverting portions. The control device of the frequency converter, especially the four-quadrant frequency converter in the magnetic suspension centrifuge can include: a sampling unit and a controller. The sampling unit and the controller are respectively connected to a frequency converter, in particular a four-quadrant frequency converter. A sampling unit, which may include: the device comprises a first sampling module and a second sampling module, or the second sampling module and a third sampling module, or the first sampling module, the second sampling module and the third sampling module.
Specifically, the first sampling module may be configured to acquire, at an inverter side of the frequency converter, a first signal at a device to be controlled at the inverter side. The first signal may comprise a current signal. For example: in the inversion part, a differential sampling circuit is used for collecting current signals of the motor, so that the interference of the signals during sampling is reduced.
Wherein, the converter can include: four-quadrant frequency converter. The four-quadrant frequency converter adopts a totally enclosed shell, and/or is provided with a shielding part for shielding interference signals. The four-quadrant frequency converter adopts a totally-enclosed design with fixed-point accurate shielding in structure.
Therefore, in order to further improve the electromagnetic compatibility of the system, the frequency spectrum of a main interference source in the frequency converter is analyzed, a proper material is selected for shielding, and the frequency converter is wholly in a totally-enclosed and fixed-point precise shielding structural form.
In an optional example, the acquiring, by the first sampling module, a first signal at the inverter-side device to be controlled may include: and acquiring a first signal at the to-be-controlled equipment at the inverter side by using a differential sampling circuit, such as a first differential sampling circuit, in a differential sampling mode. For example: and the inversion part acquires a motor current signal through the differential sampling circuit in the figure 3, reduces the interference of the signal during sampling, simultaneously acquires the bus voltage, and obtains a PWM signal for adjusting the switching tube at the inversion end according to the control principle in the figure 5.
In particular, the second sampling module may be configured to acquire a bus signal between the inverter and the rectifier.
In particular, the third sampling module may be configured to acquire, at a rectifier side of the frequency converter, a second signal at a rectifier-side grid. The second signal may include a grid voltage and current signal. For example: in the rectification part, the differential sampling circuit is used for collecting the voltage of the power grid and the input current signal, so that the interference of the signal during sampling can be reduced.
In an optional example, the third sampling module collects a second signal at the rectifier-side power grid, and may also include: and acquiring a second signal at the power grid on the rectifier side by using a differential sampling circuit, such as a second differential sampling circuit, in a differential sampling mode. For example: a rectification part: the differential sampling circuit in fig. 3 is used for collecting the power grid voltage and the input current signal, so that the interference of the signal during sampling can be reduced, the bus voltage is collected at the same time, and the PWM signal for regulating the switching tube at the rectifying end is obtained according to the control principle in fig. 4. Taking ab two-phase as an example, the sampling value entering the control chip after differential sampling is as follows:
for example: and carrying out differential sampling design on key signal sampling of the frequency converter. If voltage and current sampling adopts differential sampling, the anti-interference capability is good.
Preferably, the first sampling module and/or the third sampling module may employ a differential sampling circuit.
Therefore, by adopting the design that differential sampling is carried out on key signals of the frequency converter, the problem that the key signals are influenced by interference to control the effect is solved, and the anti-interference capability of the frequency converter is improved.
Specifically, the controller may be configured to generate a first PWM signal according to the first signal and the bus signal, and output the first PWM signal to a control end of the inverter, where the first PWM signal may be used to control a switching tube in the inverter; and according to the second signal and the bus signal, generating a second PWM signal and then outputting the second PWM signal to the control end of the rectifier, wherein the second PWM signal can be used for controlling a switching tube in the rectifier.
From this, through the current signal of first sampling module sampling contravariant side, second sampling module sampling bus voltage, the grid voltage and the input current signal of third sampling module sampling rectifier side, current signal and the generating PWM signal that can be used for controlling the dc-to-ac converter of current signal and the bus voltage according to the contravariant side through the controller, the generating PWM signal that can be used for controlling the rectifier bridge of power grid voltage and input current signal and the bus voltage according to the rectifier side through the controller, thereby realize the control to dc-to-ac converter and rectifier bridge, can promote the interference killing feature of converter.
In an alternative example, the controller generating the first PWM signal based on the first signal and the bus signal may include: generating a first PWM signal by a random zero vector modulation circuit in a sector-free fast random zero vector SVPWM modulation mode; and/or the controller generates a second PWM signal according to the second signal and the bus signal, which may include: and generating a second PWM signal by a random zero vector modulation circuit in a sector-free fast random zero vector SVPWM modulation mode.
For example: the frequency converter causes the amplitude of higher harmonic to be too large because of the modulation of the high-frequency switch, so that the electromagnetic compatibility of the frequency converter can not meet the requirement. The PWM generation mode of the controller is changed from common SVPWM modulation to sector-free fast random zero vector SVPWM modulation, and the electromagnetic noise of the frequency converter is improved. The random zero vector modulation circuit is adopted, sector division and zero vector time calculation are not needed, the program is simpler and more convenient, the space of a CPU (central processing unit) can be effectively saved, and the program running time is reduced.
Therefore, the problem of large higher harmonic amplitude of the conventional SVPWM method can be solved by adopting the sector-free fast random zero vector SVPWM method, so that the electromagnetic noise of the frequency converter is improved. Sector division and zero vector time calculation are not needed, and the problems of complex algorithm, multiple program execution steps and long execution time in some schemes are solved, so that the space of a CPU (Central processing Unit) can be effectively saved, and the program operation time is reduced.
Optionally, the random zero vector modulation circuit may include: the device comprises an anti-park module, an anti-clark conversion module, a modulated wave calculation module, a random number generation module, a modulated wave generation module of random zero vectors and a PWM wave generator. For example: the device comprises a voltage reverse park module, a reverse clark conversion module, a modulated wave calculation module, a random zero vector modulated wave generation module and a PWM wave generator which are sequentially arranged. And the random number generation module is connected to the modulation wave generation module of the random zero vector.
Specifically, the anti-park module can be used for converting the direct-axis voltage and the quadrature-axis voltage into two-phase static voltages under a two-phase static coordinate system.
For example: inverse PARK will direct axis voltage UdAnd quadrature axis voltage uqConversion to u under two-phase stationary coordinate systemα、uβ. Principle of anti-park transformation of anti-park block of voltage:
specifically, the reverse click transformation module may be configured to convert the two-phase static voltage into a three-phase static voltage in a three-phase static coordinate system.
For example: reverse CLARK transformation converts two-phase static voltage into U under three-phase static coordinate systema、Ub、Uc. Principle of inverse clark transformation module:
specifically, the modulation wave calculation module may be configured to calculate a value of the modulation wave after determining a maximum value and a minimum value in the three-phase static voltage.
For example: principle of modulated wave calculation by the modulated wave calculation module: the maximum value and the minimum value of the three voltages after the reverse click transformation are firstly obtained, namely:
then, the value of the modulated wave is calculated:
Specifically, the random number generation module may be configured to generate a random number in a set interval.
More optionally, the random number generation module generates the random number in the set interval, and may include any one or more of the following random number generation methods.
The first random number generation method: the random number generation module can be used for generating random numbers in a set interval by adopting a linear congruence method and a mathematical recursion formula.
For example: principle of the random number generation module: the random number adopts a linear congruence method, and generates the random number between set intervals such as (-1,1) through a mathematical recursion formula, wherein the expression is as follows:
in order to make the random number distribution as uniform as possible, a and b are both prime numbers, NsIs the maximum word length of the random number, b and NsAnd each is a 4K +1 form.
The second random number generation method: the random number generation module can be used for generating random numbers in a set interval by adopting a Matteset rotation algorithm, a square mid-fetching method and/or a tabulation and table look-up method.
For example: the random number generation method is applicable to any random number generation method, such as a MatteSatt rotation algorithm, a square-winning method, a tabulation and table-look-up method, and the like, in addition to the methods in the above embodiments.
Therefore, the random number is generated in various modes, so that the use mode of the scheme of the invention is more flexible and convenient, and the application range of the scheme of the invention is favorably widened.
Specifically, the module for generating a modulated wave with a random zero vector may be configured to generate a modulated wave with a random zero vector according to a value of the modulated wave and a random number of the set interval.
More alternatively, the modulated wave generation module of the random zero vector may generate the modulated wave of the random zero vector, and may include any one of the following modulated wave generation methods.
First modulated wave generation method:
if the random value of the zero vector is as follows
second modulation wave generation method:
if the random value of the zero vector is according to TR＝min(Ta0,Tb0,Tc0) Calculating the modulation wave value of the random zero vector as follows:
for example: the zero vector modulation method is suitable for all occasions adopting SVPWM modulation. For example, the modulated wave calculation of the random zero vector of the modulated wave generation module of the random zero vector may have two calculation modes, which are:
the first calculation method: random value of zero vector inAnd calculating, wherein the modulation wave value of the random zero vector is as follows:
the second calculation method is as follows: random value of zero vector by TR＝min(Ta0,Tb0,Tc0) Calculating the modulation wave value of the random zero vector as follows:
therefore, the modulation wave of the random zero vector is calculated through various calculation modes, so that the use mode of the scheme of the invention is more flexible and convenient, and the application range of the scheme of the invention is favorably widened.
Specifically, the PWM wave generator may be configured to generate a PWM wave from a modulated wave in which a carrier wave and a random zero vector are set.
For example: principle of PWM wave generator: comparing carrier wave with modulated wave to obtain PWM wave, where the carrier wave is greater than the modulated wave by 1, the carrier wave is less than the modulated wave by 0, and the period of the carrier wave is TpwmThe carrier wave adopts an UP-DOWN mode, and the amplitude value of the carrier wave isAs shown in fig. 6.
In an optional embodiment, the controller may be further configured to control the inverter in a vector control manner based on the first PWM signal; and controlling the rectifier in a full-control rectification mode based on the second PWM signal.
For example: the high-power frequency converter can be used for driving a magnetic suspension centrifuge in special application occasions, in order to reduce harmonic waves of an input end and improve the power factor of the input end, the rectifying end of the frequency converter adopts full-control rectification, and the inverting end adopts vector control. The design of the full-control rectification and inversion control system has the advantages that the sector-free fast random zero vector SVPWM modulation is realized, the sector division and the zero vector time calculation are not needed, the program is simple and convenient, the space of a CPU (Central processing Unit) can be effectively saved, and the program operation time is reduced.
In a preferred embodiment, for the above embodiments, the frequency converter adopts a four-quadrant frequency converter, the first sampling module adopts a first differential sampling circuit (which may be the differential sampling circuit shown in fig. 3), and acquires a first signal at the device to be controlled on the inverter side by using a differential sampling manner; the third sampling module adopts a second differential sampling circuit (which may be the differential sampling circuit shown in fig. 3) and acquires a first signal at the to-be-controlled device on the inverter side by using a differential sampling mode; the controller generates a first PWM signal by adopting a non-sector fast random zero vector SVPWM modulation mode according to the first signal and the bus signal, and controls the inverter by adopting a vector control mode based on the first PWM signal; the controller also generates a second PWM signal by adopting a sector-free fast random zero vector SVPWM modulation mode according to the second signal and the bus signal, and controls the rectifier by adopting a full-control rectification mode based on the second PWM signal.
For example: the frequency converter system is a four-quadrant frequency converter, differential sampling is adopted for signal sampling of rectification and inversion control, a sector-free random zero-vector control mode is adopted for modulation of a switching tube, a totally-enclosed design and a fixed-point accurate shielding design are structurally adopted, the problem that the amplitude of higher harmonics of the frequency converter caused by high-frequency switching modulation is overlarge can be solved, the switching frequency and harmonic components around integral multiples of the switching frequency are effectively dispersed, the frequency spectrum is more uniform, the electromagnetic interference and high-frequency noise of the frequency converter are improved, the electromagnetic compatibility of the system is improved, and the anti-interference capability of the system is improved.
Therefore, differential sampling is adopted for signal sampling of rectification and inversion control, a sector-free random zero vector control mode is adopted for modulation of a switching tube, the problem that the amplitude of higher harmonics of a frequency converter is overlarge due to high-frequency switching modulation can be solved, harmonic components around switching frequency and integral multiple of the switching frequency are effectively dispersed, the frequency spectrum is more uniform, electromagnetic interference and high-frequency noise of the frequency converter are improved, electromagnetic compatibility of a system is improved, and the anti-interference capability of the system is improved.
Through a large number of tests, the technical scheme of the invention is adopted, and the design of the full-control rectification and inversion control system is adopted, so that the sector-free fast random zero vector SVPWM modulation is realized, the sector division and the zero vector time calculation are not needed, the space of a CPU (Central processing Unit) can be effectively saved, and the program operation time is reduced.
According to an embodiment of the present invention, there is also provided a frequency converter corresponding to a control apparatus of the frequency converter. The frequency converter may include: the control device of the frequency converter.
The magnetic suspension centrifuge can realize oil-free, friction-free and high-speed operation due to the adoption of the magnetic suspension technology, can greatly reduce the vibration and noise of the unit, and is very suitable for application occasions with special requirements on noise, vibration and the like. However, the driving source of the magnetic suspension centrifuge is a high-power frequency converter, and because the rotating speed of the centrifuge is high (for example, the rotating speed of the centrifuge is more than 2 ten thousand), the frequency converter is usually modulated by a high-frequency switch, which easily causes the problem of electromagnetic interference, especially high-frequency harmonic interference; in addition, because the system power is large and the interference is serious, the anti-interference capability of the frequency converter also needs to be ensured. Such problems make the magnetic suspension centrifuge impossible to be applied to special occasions with strict requirements on noise, vibration and EMC.
In an optional embodiment, the scheme of the invention provides a high-power frequency converter and a control method thereof, which can at least solve the problem that the frequency converter is easy to generate electromagnetic interference so as to limit the application occasions of the frequency converter, improve the anti-interference performance of the frequency converter so as to widen the application occasions of the frequency converter, particularly improve the EMC performance of a magnetic suspension frequency converter, and enable the magnetic suspension frequency converter to meet the requirements of some special application occasions.
Specifically, according to the scheme of the invention, the frequency converter system is a four-quadrant frequency converter, differential sampling is adopted for signal sampling of rectification and inversion control, a sector-free random zero vector control mode is adopted for modulation of a switching tube, and a totally-enclosed fixed-point precise shielding design is adopted in structure, so that the problem of overlarge higher harmonic amplitude of the frequency converter caused by high-frequency switching modulation can be solved, the switching frequency and harmonic components around integral multiples of the switching frequency are effectively dispersed, the frequency spectrum is more uniform, the electromagnetic interference and high-frequency noise of the frequency converter are improved, the electromagnetic compatibility of the system is improved, and the anti-interference capability of the system is improved.
The four-quadrant frequency converter is adopted, so that the bidirectional flow of energy can be realized, and meanwhile, the frequency converter is high in power factor and basically free of pollution to a power grid.
In an optional example, in the scheme of the invention, the design of the full-control rectification and inversion control system has no sector, fast random zero vector SVPWM modulation, sector division and zero vector time calculation are not needed, the program is simple and convenient, the space of a CPU can be effectively saved, and the program running time is reduced. By adopting the sector-free fast random zero vector SVPWM modulation method, the problem of large higher harmonic amplitude of the conventional SVPWM modulation method can be solved, so that the electromagnetic noise of the frequency converter is improved; sector division and zero vector time calculation are not needed, and the problems of complex algorithm, multiple program execution steps and long execution time in some schemes are solved, so that the space of a CPU (Central processing Unit) can be effectively saved, and the program operation time is reduced.
And carrying out differential sampling design on key signal samples of the frequency converter. By adopting the design that differential sampling is carried out on key signals of the frequency converter, the problem that the key signals are influenced by interference to control the effect is solved, and the anti-interference capability of the frequency converter is improved.
In an alternative embodiment, a specific implementation process of the scheme of the present invention can be exemplarily described with reference to the examples shown in fig. 2 to fig. 7.
Fig. 2 is a schematic structural diagram of an embodiment of a high-power four-quadrant converter system according to the present invention.
The high-power frequency converter in the scheme of the invention can be used for driving a magnetic suspension centrifuge in a special application occasion, in order to reduce harmonic waves at the input end and improve the power factor at the input end, the rectification end of the frequency converter adopts full-control rectification, the inversion end adopts vector control, the simplified schematic diagram of a high-power four-quadrant frequency converter system is shown in figure 2, and the high-power four-quadrant frequency converter system can comprise two parts of rectification and inversion.
In fig. 2, the compressor M, the four-quadrant inverter and the grid are arranged in sequence. The four-quadrant inverter includes an inverter and a rectifier. The output end of the compressor M is connected to the first input end of the controller through the current differential sampling module. The first PWM signal output by the first output end of the controller is output to the control end of the inverter, and the second PWM signal output by the second output end of the controller is output to the control end of the rectifier. The output end of the inverter is also connected to the controller through the bus voltage sampling module. The output end of the rectifier is also connected to a third input end of the controller through a voltage or current differential sampling module. In the scheme shown in fig. 2, differential sampling is adopted for voltage and current sampling, so that the anti-interference capability is good. In the scheme shown in fig. 2, the PWM generation mode of the controller is changed from the ordinary SVPWM modulation to the non-sector fast random zero vector SVPWM modulation, which improves the electromagnetic noise of the frequency converter. In fig. 2, the differential sampling circuit shown in fig. 3 can be used for differential sampling of voltage and current.
Fig. 3 is a schematic structural diagram of a differential sampling circuit according to an embodiment of the present invention. Fig. 4 is a schematic structural diagram of a fully-controlled rectification control system according to an embodiment of the present invention.
A rectification part: the differential sampling circuit in fig. 3 is used for collecting the grid voltage and the input current signal, so that the interference of the signal during sampling can be reduced, the bus voltage can be collected (for example, the bus voltage can be collected by using a conventional non-differential sampling mode), and the PWM signal for adjusting the switching tube at the rectifying end can be obtained according to the control principle in fig. 4.
Taking ab two-phase as an example, the sampling value entering the control chip after differential sampling is as follows:
wherein X is a general finger, and the voltage sampling is the a-phase voltage UaAnd b-phase voltage Ub(ii) a The current sampling is the a-phase current IaAnd b-phase current Ib。
Fig. 5 is a schematic structural diagram of an inverter control system according to an embodiment of the present invention. In fig. 5, the random zero vector SVPWM modulation module is adopted, so that the electromagnetic noise of the frequency converter is improved, the sector division and the zero vector time calculation are not required, and the problems of complicated algorithm, multiple program execution steps and long execution time are solved, so that the space of the CPU can be effectively saved, and the program operation time is reduced.
An inversion part: the differential sampling circuit in fig. 3 is used for collecting current signals of the motor, reducing signal interference during sampling, collecting bus voltage, and obtaining a PWM signal for regulating the switching tube at the inversion end according to the control principle in fig. 5.
The frequency converter causes the amplitude of higher harmonic to be too large because of the modulation of a high-frequency switch, so that the electromagnetic compatibility of the frequency converter can not meet the requirement.
Fig. 6 is a schematic structural diagram of a random zero vector modulation circuit according to an embodiment of the present invention. In fig. 6, sector division and zero vector time calculation are not required, the program is simpler and more convenient, the space of the CPU can be effectively saved, and the program running time is reduced.
A block diagram of random SVPWM modulation is shown in fig. 6 and may include: the device comprises a voltage reverse park module, a reverse clark conversion module, a modulated wave calculation module, a random number generation module, a random zero vector modulated wave generation module and a PWM wave generator. The device comprises a voltage reverse park module, a reverse clark conversion module, a modulated wave calculation module, a random zero vector modulated wave generation module and a PWM wave generator which are sequentially arranged. And the random number generation module is connected to the modulation wave generation module of the random zero vector. The principle of the parts in fig. 6 is as follows:
inverse PARK will direct axis voltage UdAnd quadrature axis voltage uqConversion to u under two-phase stationary coordinate systemα、uβ. Principle of anti-park transformation of anti-park block of voltage:
wherein u isd: a direct axis voltage; u. ofq: quadrature axis voltage uαuβα shaft voltage and β shaft voltage under a two-phase static coordinate system respectively, theta is a motor phase angle (a power grid voltage phase angle in full-control rectification and a motor rotor position angle in inversion vector control), sin theta is a sine of the phase angle, and cos theta is a cosine of the phase angle.
Inverse CLARK transformationConverting two-phase static voltage into U under three-phase static coordinate systema、Ub、Uc. Principle of inverse clark transformation module:
wherein the content of the first and second substances,
uαuβrespectively α axle voltage and β axle voltage under two-phase static coordinate systema、ub、ucThe three-phase static coordinate system comprises a phase voltage a, a phase voltage b and a phase voltage c.
Principle of modulated wave calculation by the modulated wave calculation module:
the maximum value and the minimum value of the three voltages after the reverse click transformation are firstly obtained, namely:
then, the value of the modulated wave is calculated:
wherein, TpwmIs the switching period of the switching tube, and is also the carrier period, VdcIs the value of the bus voltage umaxuminThe maximum value and the minimum value of phase a, phase b and phase c voltages in a three-phase static coordinate system are respectively; t isa0Tb0Tb0The values of the modulated waves of the a-phase, b-phase, and c-phase are respectively.
Principle of the random number generation module:
the random number adopts a linear congruence method, and generates the random number between set intervals such as (-1,1) through a mathematical recursion formula, wherein the expression is as follows:
in order to make the random number distribution as uniform as possible, a and b are both prime numbers,Nsis the maximum word length of the random number, b and NsA is in the form of 4K + 1; rn+1Is a random number at time n +1, RnIs a random number at time n.
The modulated wave calculation of the random zero vector of the modulated wave generation module of the random zero vector can have two calculation modes, which are respectively:
the first calculation method: random value of zero vector in
the second calculation method is as follows: random value of zero vector by TR＝min(Ta0,Tb0,Tc0) Calculating the modulation wave value of the random zero vector as follows:
the first of the two calculation modes deduces a direct mathematical expression of a random part through a mathematical formula, and programming is realized by directly solving through the formula; formula derivation is not needed before the second mode is realized, but one more step is needed to be added during programming realization, and T is solveda0Tb0Tb0Is measured.
Fig. 7 is a schematic structural diagram of a PWM generating circuit according to an embodiment of the present invention.
Principle of PWM wave generator: comparing carrier wave with modulated wave to obtain PWM wave, where the carrier wave is greater than the modulated wave by 1, the carrier wave is less than the modulated wave by 0, and the period of the carrier wave is TpwmThe carrier wave adopts an UP-DOWN mode, and the amplitude value of the carrier wave isAs shown in fig. 7.
In addition, in order to further improve the electromagnetic compatibility of the system, the frequency spectrum of a main interference source in the frequency converter is analyzed, a proper material is selected for shielding, and the frequency converter is wholly in a totally-enclosed and fixed-point precise shielding structural form.
Furthermore, the method for generating random numbers in the scheme of the invention is also suitable for any other random number generation methods besides the methods in the above embodiments, such as a Matteast rotation algorithm, a square-extraction-of-middle method, a tabulation and table lookup method, and the like; in addition, the zero vector modulation method is suitable for all occasions adopting SVPWM modulation.
Since the processing and functions implemented by the frequency converter of this embodiment substantially correspond to the embodiments, principles, and examples of the apparatus shown in fig. 1, reference may be made to the related descriptions in the foregoing embodiments without details in the description of this embodiment.
Through a large number of tests, the technical scheme of the invention effectively disperses the switching frequency and harmonic components around integral multiple thereof by adopting a sector-free fast random zero vector SVPWM modulation method, so that the frequency spectrum is more uniform, the electromagnetic interference and high-frequency noise of the frequency converter are improved, the electromagnetic compatibility of the system is improved, and the anti-interference capability of the system is improved.
According to an embodiment of the present invention, in cooperation with the inverter described above, a further aspect of the present invention provides a compressor, including: the frequency converter described above.
According to an embodiment of the present invention, in cooperation with the above-mentioned compressor, a further aspect of the present invention provides an air conditioner including: the compressor described above.
According to an embodiment of the present invention, a method for controlling a frequency converter corresponding to the frequency converter is also provided, as shown in fig. 8, which is a schematic flow chart of an embodiment of the method of the present invention. The control method of the frequency converter can be mainly applied to the frequency converter in a magnetic suspension centrifugal machine, in particular to a four-quadrant frequency converter. Frequency converter, in particular four-quadrant frequency converter, may comprise: an inverter and a rectifier, such as a high power four quadrant inverter system, may include both rectifying and inverting portions. The control method of the frequency converter, in particular the four-quadrant frequency converter in the magnetic suspension centrifuge can comprise the following steps: step S110 to step S140.
At step S110, a first signal at a device to be controlled at the inverter side is acquired at the inverter side of the frequency converter through a first sampling module. The first signal may comprise a current signal. For example: in the inversion part, a differential sampling circuit is used for collecting current signals of the motor, so that the interference of the signals during sampling is reduced.
In an optional example, the acquiring, by the first sampling module, the first signal at the inverter-side device to be controlled in step S110 may include: and acquiring a first signal at the to-be-controlled equipment at the inverter side by using a differential sampling circuit, such as a first differential sampling circuit, in a differential sampling mode. For example: and the inversion part acquires a motor current signal through the differential sampling circuit in the figure 3, reduces the interference of the signal during sampling, simultaneously acquires the bus voltage, and obtains a PWM signal for adjusting the switching tube at the inversion end according to the control principle in the figure 5.
At step S120, bus signals between the inverter and the rectifier are collected through a second sampling module.
At step S130, a second signal at the rectifier side grid is acquired at the rectifier side of the frequency converter by a third sampling module. The second signal may include a grid voltage and current signal. For example: in the rectification part, the differential sampling circuit is used for collecting the voltage of the power grid and the input current signal, so that the interference of the signal during sampling can be reduced.
In an optional example, the collecting, by the third sampling module, the second signal at the rectifier-side power grid in step S130 may include: and acquiring a second signal at the power grid on the rectifier side by using a differential sampling circuit, such as a second differential sampling circuit, in a differential sampling mode. For example: a rectification part: the differential sampling circuit in fig. 3 is used for collecting the power grid voltage and the input current signal, so that the interference of the signal during sampling can be reduced, the bus voltage is collected at the same time, and the PWM signal for regulating the switching tube at the rectifying end is obtained according to the control principle in fig. 4. Taking ab two-phase as an example, the sampling value entering the control chip after differential sampling is as follows:
for example: and carrying out differential sampling design on key signal sampling of the frequency converter. If voltage and current sampling adopts differential sampling, the anti-interference capability is good.
Therefore, by adopting the design that differential sampling is carried out on key signals of the frequency converter, the problem that the key signals are influenced by interference to control the effect is solved, and the anti-interference capability of the frequency converter is improved.
At step S140, generating, by the controller, a first PWM signal according to the first signal and the bus signal, and outputting the first PWM signal to a control terminal of the inverter, where the first PWM signal may be used to control a switching tube in the inverter; and according to the second signal and the bus signal, generating a second PWM signal and then outputting the second PWM signal to the control end of the rectifier, wherein the second PWM signal can be used for controlling a switching tube in the rectifier.
From this, through the current signal of first sampling module sampling contravariant side, second sampling module sampling bus voltage, the grid voltage and the input current signal of third sampling module sampling rectifier side, current signal and the generating PWM signal that can be used for controlling the dc-to-ac converter of current signal and the bus voltage according to the contravariant side through the controller, the generating PWM signal that can be used for controlling the rectifier bridge of power grid voltage and input current signal and the bus voltage according to the rectifier side through the controller, thereby realize the control to dc-to-ac converter and rectifier bridge, can promote the interference killing feature of converter.
In an alternative example, the generating the first PWM signal according to the first signal and the bus signal by the controller in step S140 may include: generating a first PWM signal by a random zero vector modulation circuit in a sector-free fast random zero vector SVPWM modulation mode; and/or generating, by the controller, a second PWM signal according to the second signal and the bus signal, may include: and generating a second PWM signal by a random zero vector modulation circuit in a sector-free fast random zero vector SVPWM modulation mode.
For example: the frequency converter causes the amplitude of higher harmonic to be too large because of the modulation of the high-frequency switch, so that the electromagnetic compatibility of the frequency converter can not meet the requirement. The PWM generation mode of the controller is changed from common SVPWM modulation to sector-free fast random zero vector SVPWM modulation, and the electromagnetic noise of the frequency converter is improved. The random zero vector modulation circuit is adopted, sector division and zero vector time calculation are not needed, the program is simpler and more convenient, the space of a CPU (central processing unit) can be effectively saved, and the program running time is reduced.
Therefore, by adopting the sector-free fast random zero vector SVPWM modulation method, the problem of large higher harmonic amplitude of the conventional SVPWM modulation method can be solved, and the electromagnetic noise of the frequency converter is improved; sector division and zero vector time calculation are not needed, and the problems of complex algorithm, multiple program execution steps and long execution time in some schemes are solved, so that the space of a CPU (Central processing Unit) can be effectively saved, and the program operation time is reduced.
Optionally, the specific process of generating the first PWM signal and/or the second PWM signal by the random zero vector modulation circuit may be further described with reference to a flowchart of an embodiment of generating the first PWM signal and/or the second PWM signal by the random zero vector modulation circuit in the method of the present invention shown in fig. 9, where the specific process may include: step S210 to step S260.
Step S210, the direct axis voltage and the quadrature axis voltage are converted into two-phase stationary voltages in a two-phase stationary coordinate system through the inverse park module.
For example: inverse PARK will direct axis voltage UdAnd quadrature axis voltage uqConversion to u under two-phase stationary coordinate systemα、uβ. Principle of anti-park transformation of anti-park block of voltage:
and step S220, converting the two-phase static voltage into a three-phase static voltage under a three-phase static coordinate system through an inverse clark conversion module.
For example: reverse CLARK transformation converts two-phase static voltage into U under three-phase static coordinate systema、Ub、Uc. Reverse click changePrinciple of inverse clark transformation of transform block:
in step S230, after determining the maximum value and the minimum value in the three-phase static voltage through the modulated wave calculation module, the value of the modulated wave is calculated.
For example: principle of modulated wave calculation by the modulated wave calculation module: the maximum value and the minimum value of the three voltages after the reverse click transformation are firstly obtained, namely:
then, the value of the modulated wave is calculated:
In step S240, a random number generating module generates a random number in a set interval.
More optionally, the step S240 of generating the random number in the set interval by the random number generation module may include any one or more of the following random number generation manners.
The first random number generation method: the random number generation module can be used for generating random numbers in a set interval by adopting a linear congruence method and a mathematical recursion formula.
For example: principle of the random number generation module: the random number adopts a linear congruence method, and generates the random number between set intervals such as (-1,1) through a mathematical recursion formula, wherein the expression is as follows:
in order to make the random number distribution as uniform as possible, a and b are both prime numbers, NsIs the maximum word length of the random number, b and NsAnd each is a 4K +1 form. And/or the presence of a gas in the gas,
the second random number generation method: the random number generation module can be used for generating random numbers in a set interval by adopting a Matteset rotation algorithm, a square mid-fetching method and/or a tabulation and table look-up method.
For example: the random number generation method is applicable to any random number generation method, such as a MatteSatt rotation algorithm, a square-winning method, a tabulation and table-look-up method, and the like, in addition to the methods in the above embodiments.
Therefore, the random number is generated in various modes, so that the use mode of the scheme of the invention is more flexible and convenient, and the application range of the scheme of the invention is favorably widened.
Step S250, generating a modulated wave of a random zero vector according to the value of the modulated wave and the random number of the set interval by the modulated wave generating module of the random zero vector.
More alternatively, the modulated wave generating module of the random zero vector in step S250 may generate the modulated wave of the random zero vector, and any one of the following modulated wave generating methods may be used.
First modulated wave generation method:
if the random value of the zero vector is as follows
second modulation wave generation method:
if the random value of the zero vector is according to TR＝min(Ta0,Tb0,Tc0) Calculating the modulation wave value of the random zero vector as follows:
for example: the zero vector modulation method is suitable for all occasions adopting SVPWM modulation. For example, the modulated wave calculation of the random zero vector of the modulated wave generation module of the random zero vector may have two calculation modes, which are:
the first calculation method: random value of zero vector inAnd calculating, wherein the modulation wave value of the random zero vector is as follows:
the second calculation method is as follows: random value of zero vector by TR＝min(Ta0,Tb0,Tc0) Calculating the modulation wave value of the random zero vector as follows:
therefore, the modulation wave of the random zero vector is calculated through various calculation modes, so that the use mode of the scheme of the invention is more flexible and convenient, and the application range of the scheme of the invention is favorably widened.
And step S260, generating a PWM wave through a PWM wave generator according to the set carrier and the modulation wave of the random zero vector, wherein the PWM signal is a first PWM signal and/or a second PWM signal.
For example: principle of PWM wave generator: comparing carrier wave with modulated wave to obtain PWM wave, where the carrier wave is greater than the modulated wave by 1, the carrier wave is less than the modulated wave by 0, and the period of the carrier wave is TpwmThe carrier wave adopts an UP-DOWN mode, and the amplitude value of the carrier wave is
In an alternative embodiment, the method may further include: controlling the inverter by the controller in a vector control mode based on the first PWM signal; and controlling the rectifier in a full-control rectification mode based on the second PWM signal.
For example: the high-power frequency converter can be used for driving a magnetic suspension centrifuge in special application occasions, in order to reduce harmonic waves of an input end and improve the power factor of the input end, the rectifying end of the frequency converter adopts full-control rectification, and the inverting end adopts vector control. The design of the full-control rectification and inversion control system has the advantages that the sector-free fast random zero vector SVPWM modulation is realized, the sector division and the zero vector time calculation are not needed, the program is simple and convenient, the space of a CPU (Central processing Unit) can be effectively saved, and the program operation time is reduced.
In a preferred embodiment, for the above embodiments, the frequency converter adopts a four-quadrant frequency converter, the first sampling module adopts a first differential sampling circuit (which may be the differential sampling circuit shown in fig. 3), and acquires a first signal at the device to be controlled on the inverter side by using a differential sampling manner; the third sampling module adopts a second differential sampling circuit (which may be the differential sampling circuit shown in fig. 3) and acquires a first signal at the to-be-controlled device on the inverter side by using a differential sampling mode; the controller generates a first PWM signal by adopting a non-sector fast random zero vector SVPWM modulation mode according to the first signal and the bus signal, and controls the inverter by adopting a vector control mode based on the first PWM signal; the controller also generates a second PWM signal by adopting a sector-free fast random zero vector SVPWM modulation mode according to the second signal and the bus signal, and controls the rectifier by adopting a full-control rectification mode based on the second PWM signal.
For example: the frequency converter system is a four-quadrant frequency converter, differential sampling is adopted for signal sampling of rectification and inversion control, a sector-free random zero-vector control mode is adopted for modulation of a switching tube, a totally-enclosed design and a fixed-point accurate shielding design are structurally adopted, the problem that the amplitude of higher harmonics of the frequency converter caused by high-frequency switching modulation is overlarge can be solved, the switching frequency and harmonic components around integral multiples of the switching frequency are effectively dispersed, the frequency spectrum is more uniform, the electromagnetic interference and high-frequency noise of the frequency converter are improved, the electromagnetic compatibility of the system is improved, and the anti-interference capability of the system is improved.
Therefore, differential sampling is adopted for signal sampling of rectification and inversion control, a sector-free random zero vector control mode is adopted for modulation of a switching tube, the problem that the amplitude of higher harmonics of a frequency converter is overlarge due to high-frequency switching modulation can be solved, harmonic components around switching frequency and integral multiple of the switching frequency are effectively dispersed, the frequency spectrum is more uniform, electromagnetic interference and high-frequency noise of the frequency converter are improved, electromagnetic compatibility of a system is improved, and the anti-interference capability of the system is improved.
Since the processing and functions implemented by the method of this embodiment basically correspond to the embodiments, principles and examples of the frequency converter, reference may be made to the related descriptions in the foregoing embodiments without being detailed in the description of this embodiment.
Through a large number of tests, the technical scheme of the embodiment is adopted, and differential sampling design is carried out on the key signals of the frequency converter, so that the problem that the key signals are influenced by interference to control the effect can be solved, and the anti-interference capability of the frequency converter is improved.
In summary, it is readily understood by those skilled in the art that the advantageous modes described above can be freely combined and superimposed without conflict.
The above description is only an example of the present invention, and is not intended to limit the present invention, and it is obvious to those skilled in the art that various modifications and variations can be made in the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the claims of the present invention.
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