Permanent magnet synchronous motor field weakening control method and device based on overmodulation
阅读说明：本技术 一种基于过调制的永磁同步电机弱磁控制方法与装置 (Permanent magnet synchronous motor field weakening control method and device based on overmodulation ) 是由 赵茵茵 刘波 汤小平 于 2020-10-27 设计创作，主要内容包括：本发明涉及一种基于过调制的永磁同步电机弱磁控制装置和方法,所述方法包括获取弱磁控制阈值电压u_(smax)；实时获取永磁同步电机定子端电压矢量幅值u_s；比较定子端电压矢量幅值u_s与弱磁控制阈值电压u_(smax)的大小,若定子端电压矢量幅值u_s小于弱磁控制阈值电压u_(smax),以i_d＝0控制算法控制永磁同步电机,并以现有的SVPWM线性调制算法控制永磁同步电机逆变器；若定子端电压矢量幅值u_s等于弱磁控制阈值电压u_(smax),继续增加电机转速或者负载,则以弱磁控制算法控制永磁同步电机,并以SVPWM过调制算法控制永磁同步电机逆变器。与现有技术,本发明弱磁控制过程动态性能良好。(The invention relates to a permanent magnet synchronous motor field weakening control device and method based on overmodulation, wherein the method comprises the step of obtaining field weakening control threshold voltage u smax (ii) a Obtaining stator terminal voltage vector amplitude u of permanent magnet synchronous motor in real time s (ii) a Comparing stator terminal voltage vector magnitude u s And weak magnetic control threshold voltage u smax If the stator terminal voltage vector magnitude u s Less than the weak magnetic control threshold voltage u smax To i with d Controlling the permanent magnet synchronous motor by a control algorithm of 0, and controlling a permanent magnet synchronous motor inverter by the existing SVPWM linear modulation algorithm; if stator terminal voltage vector magnitude u s Equal to the field weakening control threshold voltage u smax And continuously increasing the rotating speed or the load of the motor, controlling the permanent magnet synchronous motor by a weak magnetic control algorithm, and controlling the permanent magnet synchronous motor inverter by an SVPWM overmodulation algorithm. Compared with the prior art, the invention has the weak magnetic control processThe dynamic performance is good.)
1. A permanent magnet synchronous motor field weakening control device based on overmodulation is characterized by comprising the following components: the device comprises a position regulator, a speed regulator, a weak magnetic control module, a first coordinate converter, a second coordinate converter, a third coordinate converter, a space vector pulse width modulator, an inverter circuit, a current sampling module, a position detection module and a motor rotating speed calculation module;
the above-mentionedThe output end of the position regulator is connected with the input end of the speed regulator, and the position regulator is used for processing the difference value of the position instruction value and the position feedback value to obtain a speed instruction value omega*；
The output end of the speed regulator is connected with the input end of the weak magnetic control module, and the speed regulator is used for regulating a speed command value omega*Processing the difference value of the speed feedback value omega to obtain a direct-axis current instruction value id *；
The output end of the weak magnetic control module is connected with the input end of the first coordinate converter, and the weak magnetic control module is used for controlling a direct-axis current instruction value id *And a direct axis current feedback value idProcessing to obtain direct axis voltage command valueAnd the command value of the quadrature axis voltage
The output end of the first coordinate converter is connected with the input end of the space vector pulse width modulator, and the first coordinate converter is used for regulating the direct-axis voltage instruction valueAnd the command value of the quadrature axis voltageCarrying out coordinate conversion;
the output end of the space vector pulse width modulator is connected with the input end of the inverter circuit;
the output end of the inverter circuit is connected with the input end of the current sampling module and the permanent magnet synchronous motor;
the output end of the current sampling module is connected with the input end of the second coordinate converter, the output end of the second coordinate converter is connected with the input end of the third coordinate converter, and the output end of the three coordinate converter is connected with the input end of the weak magnetic control module;
the position detection module is used for detecting the position of the rotor of the permanent magnet synchronous motor in real time, and the output end of the position detection module is connected with the input end of the position regulator and the input end of the motor rotating speed calculation module;
the output end of the motor rotating speed calculating module is connected with the input end of the speed regulator; and the motor rotating speed calculation module is used for processing the position feedback value to obtain a speed feedback value omega.
2. The overmodulation-based permanent magnet synchronous motor field weakening control device according to claim 1, wherein the field weakening control module comprises a direct-axis current regulator and a quadrature-axis voltage calculation module;
the input end of the direct-axis current regulator is connected with the output end of the speed regulator, and the direct-axis current regulator is used for obtaining a direct-axis voltage command value
The input end of the quadrature axis voltage calculation module is connected with the output end of the direct axis current regulator, and the quadrature axis voltage calculation module is used for calculating the direct axis voltage command value according to the direct axis voltage command valueAnd field weakening control threshold voltage usmaxCalculating to obtain a quadrature axis voltage command value
3. The field weakening control device of the permanent magnet synchronous motor based on overmodulation according to claim 2, wherein the quadrature axis voltage command valueThe calculation formula of (a) is as follows:
wherein the content of the first and second substances,is a command value of the quadrature axis voltage,is a direct axis voltage command value, usmaxThe threshold voltage is controlled for field weakening.
4. The field weakening control device of the permanent magnet synchronous motor based on overmodulation according to claim 2, wherein the direct current regulator is a PI regulator.
5. A permanent magnet synchronous motor field weakening control method based on overmodulation is characterized by comprising the following steps:
according to the DC bus voltage UdcObtaining weak magnetic control threshold voltage usmax；
Obtaining stator terminal voltage vector amplitude u of permanent magnet synchronous motor in real times；
Comparing stator terminal voltage vector magnitude usAnd weak magnetic control threshold voltage usmaxIf the stator terminal voltage vector magnitude usLess than the weak magnetic control threshold voltage usmaxTo i withdControlling the permanent magnet synchronous motor by a control algorithm of 0, and controlling a permanent magnet synchronous motor inverter by the existing SVPWM linear modulation algorithm;
if stator terminal voltage vector magnitude usEqual to the field weakening control threshold voltage usmaxAnd continuously increasing the rotating speed or the load of the motor, controlling the permanent magnet synchronous motor by a weak magnetic control algorithm, and controlling the permanent magnet synchronous motor inverter by an SVPWM overmodulation algorithm.
6. The field weakening control of the permanent magnet synchronous motor based on overmodulation according to claim 5Method, characterized in that said field weakening controls a threshold voltage usmax0.577 times of DC bus voltage Udc。
7. The field weakening control method of the permanent magnet synchronous motor based on overmodulation according to claim 5, characterized in that the field weakening control algorithm specifically comprises:
calculating to obtain a speed command value omega according to the position command value and the position feedback value*(ii) a The position instruction value is a given value, and the position feedback value is obtained by detecting the permanent magnet synchronous motor by a position detection module;
according to the speed command value omega*Calculating with the velocity feedback value omega to obtain a direct-axis current command value id *(ii) a The speed feedback value omega is obtained by calculating the position feedback value through a motor rotating speed calculation module;
according to the direct-axis current instruction value id *And a direct axis current feedback value idCalculating to obtain a direct axis voltage instruction valueThe velocity feedback value idAcquiring a parameter value obtained by carrying out coordinate transformation twice on the current of the permanent magnet synchronous motor for a current sampling module;
according to the direct-axis voltage command value udAnd said field weakening control threshold voltage usmaxCalculating to obtain a quadrature axis voltage command value
8. The field weakening control method of the permanent magnet synchronous motor based on the overmodulation as claimed in claim 5, wherein the SVPWM overmodulation algorithm specifically comprises:
defining an actual voltage vector u and a reference voltage vector u of an inverter outputrThe amplitude coefficient formula is:
wherein the content of the first and second substances,2/3U representing the magnitude of the voltage vector corresponding to the hexagonal inscribed circle in the SVPWM voltage vector diagramdcRepresents the magnitude, u, of the vertex voltage vector in the SVPWM voltage vector diagramrI denotes a reference voltage vector urAmplitude of
The amplitude of the voltage vector corresponding to the inscribed circleAmplitude 2/3U of the vertex voltage vectordcAnd the reference voltage vector urAmplitude | u ofrVoltage U of DC busdcCalculating per unit value for the reference to obtain a new calculation formula of the amplitude coefficient:
determining the vertex voltage vector uxReference voltage vector urA relation with an actual voltage vector u output by the inverter;
according to the vertex voltage vector uxNumber x of and the reference voltage vector urPhase angle theta ofrAccording to the action time calculation formula to calculate the vertex voltage vector uxThe action time of (c); the function time calculation formula is based on the vertex voltage vector uxReference voltage vector urDetermining a relational expression of the vector u and the actual voltage output by the inverter;
obtaining an overmodulation signal according to the action time;
and performing overmodulation control on the permanent magnet synchronous motor by using the overmodulation signal.
9. The overmodulation-based flux-weakening control method for the permanent magnet synchronous motor according to claim 8, wherein the action time calculation formula is as follows:
10. the field weakening control method of the permanent magnet synchronous motor based on overmodulation as claimed in claim 5, wherein when the permanent magnet synchronous motor exits field weakening control, the motor phase voltage is kept at the field weakening control threshold voltage usmaxAnd the value of the direct-axis current at the stator end is greater than 0.
Technical Field
The invention belongs to the technical field of servo drive, and particularly relates to a permanent magnet synchronous motor field weakening control method and device based on overmodulation.
Background
In servo control applications, the servo control is limited by the input voltage of a driver, and when a Permanent Magnet Synchronous Motor (PMSM) is required to operate above a base speed, the motor needs to be subjected to flux weakening control.
A traditional negative id compensation flux weakening algorithm is adjusted based on quadrature-direct axis currents id and iq, and a motor stator current track is planned on an id-iq coordinate plane. In the adjusting process, a pure integral controller or a proportional integral controller is usually adopted to carry out pure integral or proportional integral control on the difference value of the vector amplitude of the output voltage and the set output voltage threshold value so as to adjust the weak magnetic current. However, the simple PI regulation is difficult to balance between fast dynamic response and reliable operation, and when the motor operates at high speed, the current regulator is easy to saturate, which also affects the stable operation of the motor.
The existing flux weakening control algorithm has low utilization rate of direct current bus voltage and has higher requirements on switching conditions of entering flux weakening control and exiting flux weakening control.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a permanent magnet synchronous motor field weakening control device and method based on overmodulation. The problem that the utilization rate of the direct current bus voltage is low in the existing weak magnetic control is solved by combining overmodulation algorithm control with weak magnetic control, and the switching condition of the permanent magnet synchronous motor for exiting the weak magnetic control is simplified by keeping the motor phase voltage as the weak magnetic control threshold voltage when the permanent magnet synchronous motor exits the weak magnetic control.
In order to achieve the purpose, the invention provides the following scheme:
a permanent magnet synchronous motor field weakening control device based on overmodulation comprises: the device comprises a position regulator, a speed regulator, a weak magnetic control module, a first coordinate converter, a second coordinate converter, a third coordinate converter, a space vector pulse width modulator, an inverter circuit, a current sampling module, a position detection module and a motor rotating speed calculation module;
the output end of the position regulator is connected with the input end of the speed regulator, and the position regulator is used for processing the difference value of the position instruction value and the position feedback value to obtain a speed instruction value omega*；
The output end of the speed regulator is connected with the input end of the weak magnetic control module, and the speed regulator is used for regulating a speed command value omega*Processing the difference value of the speed feedback value omega to obtain a direct-axis current instruction value id *；
The output end of the weak magnetic control module is connected with the input end of the first coordinate converter, and the weak magnetic control module is used for controlling a direct-axis current instruction value id *And a direct axis current feedback value idProcessing to obtain direct axis voltage command valueAnd the command value of the quadrature axis voltage
The output end of the first coordinate converter is connected with the input end of the space vector pulse width modulator, and the first coordinate converter is used for regulating the direct-axis voltage instruction valueAnd the command value of the quadrature axis voltageCarrying out coordinate conversion;
the output end of the space vector pulse width modulator is connected with the input end of the inverter circuit;
the output end of the inverter circuit is connected with the input end of the current sampling module and the permanent magnet synchronous motor;
the output end of the current sampling module is connected with the input end of the second coordinate converter, the output end of the second coordinate converter is connected with the input end of the third coordinate converter, and the output end of the three coordinate converter is connected with the input end of the weak magnetic control module;
the position detection module is used for detecting the position of the rotor of the permanent magnet synchronous motor in real time, and the output end of the position detection module is connected with the input end of the position regulator and the input end of the motor rotating speed calculation module;
the output end of the motor rotating speed calculating module is connected with the input end of the speed regulator; and the motor rotating speed calculation module is used for processing the position feedback value to obtain a speed feedback value omega.
The weak magnetic control module comprises a direct-axis current regulator and a quadrature-axis voltage calculation module;
the input end of the direct-axis current regulator is connected with the output end of the speed regulator, and the direct-axis current regulator is used for obtaining a direct-axis voltage command value
The input end of the quadrature axis voltage calculation module is connected with the output end of the direct axis current regulator, and the quadrature axis voltage calculation module is used for calculating the direct axis voltage command value according to the direct axis voltage command valueAnd field weakening control threshold voltage us maxCalculating to obtain a quadrature axis voltage command value
The quadrature axis voltage command valueThe calculation formula of (a) is as follows:
wherein the content of the first and second substances,is a command value of the quadrature axis voltage,is a direct axis voltage command value, us maxThe threshold voltage is controlled for field weakening.
A permanent magnet synchronous motor field weakening control method based on overmodulation comprises the following steps:
according to the DC bus voltage UdcObtaining weak magnetic control threshold voltage us max；
Obtaining stator terminal voltage vector amplitude u of permanent magnet synchronous motor in real times；
Comparing stator terminal voltage vector magnitude usAnd weak magnetic control threshold voltage us maxIf the stator terminal voltage vector magnitude usLess than the weak magnetic control threshold voltage us maxTo i withdControlling the permanent magnet synchronous motor by a control algorithm of 0, and controlling a permanent magnet synchronous motor inverter by the existing SVPWM linear modulation algorithm;
if stator terminal voltage vector magnitude usEqual to the field weakening control threshold voltage us maxAnd continuously increasing the rotating speed or the load of the motor, controlling the permanent magnet synchronous motor by a weak magnetic control algorithm, and controlling the permanent magnet synchronous motor inverter by an SVPWM overmodulation algorithm.
The weak magnetic field controls the threshold voltage us max0.577 times of DC bus voltage Udc。
The flux weakening control algorithm specifically comprises the following steps:
calculating to obtain a speed command value omega according to the position command value and the position feedback value*(ii) a The position instruction value is a given value, and the position feedback value is obtained by detecting the permanent magnet synchronous motor by a position detection module;
according to the speed command value omega*Calculating with the velocity feedback value omega to obtain a direct-axis current command value id *(ii) a The speed feedback value omega is obtained by calculating the position feedback value through a motor rotating speed calculation module;
according to the direct-axis current instruction value id *And a direct axis current feedback value idCalculating to obtain a direct axis voltage instruction valueThe velocity feedback value idAcquiring a parameter value obtained by carrying out coordinate transformation twice on the current of the permanent magnet synchronous motor for a current sampling module;
according to the direct-axis voltage command value udAnd said field weakening control threshold voltage us maxCalculating to obtain a quadrature axis voltage command value
The SVPWM overmodulation algorithm specifically comprises the following steps:
defining an actual voltage vector u and a reference voltage vector u of an inverter outputrThe amplitude coefficient formula is:
wherein the content of the first and second substances,2/3U representing the magnitude of the voltage vector corresponding to the hexagonal inscribed circle in the SVPWM voltage vector diagramdcRepresents the magnitude, u, of the vertex voltage vector in the SVPWM voltage vector diagramrI denotes a reference voltage vector urAmplitude of
The amplitude of the voltage vector corresponding to the inscribed circleAmplitude 2/3U of the vertex voltage vectordcAnd the reference voltage vector urAmplitude | u ofrVoltage U of DC busdcCalculating per unit value for the reference to obtain a new calculation formula of the amplitude coefficient:
determining the vertex voltage vector uxReference voltage vector urA relation with an actual voltage vector u output by the inverter;
according to the vertex voltage vector uxNumber x of and the reference voltage vector urPhase angle theta ofrAccording to the action time calculation formula to calculate the vertex voltage vector uxThe action time of (c); the function time calculation formula is based on the vertex voltage vector uxReference voltage vector urDetermining a relational expression of the vector u and the actual voltage output by the inverter;
obtaining an overmodulation signal according to the action time;
and performing overmodulation control on the permanent magnet synchronous motor by using the overmodulation signal.
The action time calculation formula is as follows:
when the permanent magnet synchronous motor exits the field weakening control, the phase voltage of the motor is kept to be the field weakening control threshold voltage us maxAnd the value of the direct-axis current at the stator end is greater than 0.
According to the specific embodiment provided by the invention, the invention discloses the following technical effects:
1. the permanent magnet synchronous single machine flux weakening control method provided by the invention does not need to decouple the alternating current and the direct current, and directly controls the direct current to realize flux weakening control on the permanent magnet synchronous motor by utilizing the characteristic that the alternating current and the direct current are limited by the maximum output voltage of a driver after the system enters flux weakening control.
2. The SVPWM overmodulation algorithm and the SVPWM linear modulation algorithm provided by the invention are compatible, and the inverter is allowed to smoothly transit in all SVPWM modulation intervals, so that the phase voltage output by the system has higher linearity.
3. The SVPWM overmodulation algorithm provided by the invention does not need to store angle values in advance, and the burden of a CPU is reduced.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without inventive exercise.
FIG. 1 is a block diagram of a flux weakening control system of a permanent magnet synchronous motor;
FIG. 2 is a block diagram of the flux weakening control algorithm shown in the dashed box of FIG. 1;
FIG. 3 is a flow chart of field weakening control and SVPWM control;
FIG. 4 is a SVPWM voltage vector diagram;
FIG. 5 is a flow chart of a flux weakening control method of a permanent magnet synchronous motor;
FIG. 6 is a flow chart of an overmodulation control algorithm.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. 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.
The invention aims to provide a permanent magnet synchronous motor flux weakening control device and method based on overmodulation, and aims to solve the problems that the utilization rate of a direct current bus voltage is not high in an existing flux weakening control algorithm, and the requirement of a system on switching conditions of entering flux weakening control and exiting flux weakening control is high.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.
Example 1:
the pure field weakening control cannot enable the permanent magnet synchronous motor to utilize the direct current bus voltage to the maximum extent. In order to enable the permanent magnet synchronous motor to utilize the direct-current bus voltage to the maximum extent, the embodiment provides a permanent magnet synchronous motor field weakening control device based on overmodulation. As shown in fig. 1, the field weakening control device for the permanent magnet synchronous motor based on overmodulation includes: the device comprises a position regulator, a speed regulator, a weak magnetic control module, a first coordinate converter, a second coordinate converter, a third coordinate converter, a space vector pulse width modulator, an inverter circuit, a current sampling module, a position detection module and a motor rotating speed calculation module.
In the control of the permanent magnet synchronous motor, in order to obtain the control characteristics similar to a direct current motor, a coordinate system is established on a motor rotor, the coordinate system and the rotor synchronously rotate, and the direction of a rotor magnetic field is taken as a straight axis, and the direction vertical to the rotor magnetic field is taken as an intersecting axis. The weak magnetic control idea of the permanent magnet synchronous motor is from the magnetic regulation control of a separately excited direct current motor, when the terminal voltage of the separately excited direct current motor reaches the maximum voltage, the magnetic flux can be changed only by reducing the exciting current of the motor, and the motor can operate at a higher rotating speed at a constant power under the condition of ensuring the voltage balance. That is, the separately excited dc motor can achieve the purpose of field weakening and speed expansion by reducing the exciting current. For a permanent magnet synchronous motor, excitation magnetomotive force cannot be adjusted due to the generation of permanent magnets, and the voltage balance of the motor during high-speed operation can be maintained only by adjusting stator current, namely increasing the demagnetization current component of a stator straight shaft, so that the aim of field weakening and speed expansion of the permanent magnet synchronous motor is fulfilled. In this embodiment, the connection relationship among the components in the permanent magnet synchronous motor weak magnetic control device based on overmodulation is as follows:
the output end of the position regulator is connected with the input end of the speed regulator, and the position regulator is used for processing the difference value of the position instruction value and the position feedback value to obtain a speed instruction value omega*；
The output end of the speed regulator is connected with the input end of the weak magnetic control module, and the speed regulator is used for regulating a speed command value omega*Processing the difference value of the speed feedback value omega to obtain a direct-axis current instruction value id *；
The output end of the weak magnetic control module is connected with the input end of the first coordinate converter, and the weak magnetic control module is used for controlling a direct-axis current instruction value id *And a direct axis current feedback value idProcessing to obtain direct axis voltage command valueAnd the command value of the quadrature axis voltage
The output end of the first coordinate converter is connected with the input end of the space vector pulse width modulator, and the first coordinate converter is used for regulating the direct-axis voltage instruction valueAnd the command value of the quadrature axis voltageCarrying out coordinate conversion;
the output end of the space vector pulse width modulator is connected with the input end of the inverter circuit;
the output end of the inverter circuit is connected with the input end of the current sampling module and the permanent magnet synchronous motor;
the output end of the current sampling module is connected with the input end of the second coordinate converter, the output end of the second coordinate converter is connected with the input end of the third coordinate converter, and the output end of the three coordinate converter is connected with the input end of the weak magnetic control module;
the position detection module is used for detecting the permanent magnet synchronous motor in real time, and the output end of the position detection module is connected with the input end of the position regulator and the input end of the motor rotating speed calculation module;
the output end of the motor rotating speed calculating module is connected with the input end of the speed regulator; and the motor rotating speed calculation module is used for processing the position feedback value to obtain a speed feedback value omega.
In the embodiment, since the traditional id compensation flux-weakening control algorithm is based on direct-axis current regulation and quadrature-axis current regulation, the current track of the motor stator is planned on a coordinate plane of the direct-axis current and the quadrature-axis current. The method needs to design two current loops of a direct-axis current loop and a quadrature-axis current loop at the same time, and adopts a pure integral controller or a proportional integral controller in the adjusting process to carry out pure integral or proportional integral control on the difference value of the vector amplitude of the output voltage and the set output voltage threshold value so as to adjust the weak magnetic current. When the motor runs in a high-speed area, the coupling between the direct-axis current regulator and the quadrature-axis current regulator is strengthened, and the current regulator is easy to saturate so as to influence the performance of the motor. Therefore, the invention provides a weak magnetic control module only adjusting direct-axis current by utilizing the characteristic of coupling direct-axis current and quadrature-axis current, which comprises the following specific steps:
as shown in fig. 2, the flux-weakening control module specifically includes a direct-axis current regulator and a quadrature-axis voltage calculation module; the direct-axis current regulator may be a PI regulator or a PR regulator, and is used for obtaining a direct-axis voltage command valueThe quadrature axis voltage calculation module is used for calculating a direct axis voltage instruction value according to the quadrature axis voltage instruction valueAnd field weakening control threshold voltage us maxCalculating to obtain a quadrature axis voltage command valueSpecific cross-axis electricityPressure command valueThe calculation formula of (2) is as follows:
in the weak magnetic control area, the AC-DC axis voltage and current meet the following two conditions:
us 2＝ud 2+uq 2≤us max 2
is＝id 2+iq 2≤is max 2
wherein u issIs the stator terminal voltage vector magnitude, isThe current vector amplitude of the stator end is limited by the DC bus voltage U of the driverdc，usThere is a maximum value us maxLimited by temperature rise limit, isThere is a maximum value is max。
As can be seen from fig. 3, the direct axis voltage command value and the quadrature axis voltage command value obtained by the field weakening control module are input to the space vector pulse width modulator after coordinate transformation, and the SVPWM control has linear modulation and overmodulation functions. The principle of the overmodulation algorithm is that the amplitude and phase transformation of an output voltage vector reflects the amplitude and phase transformation of a given voltage vector as much as possible, and when the amplitude of the given voltage vector of the permanent magnet synchronous motor is larger than a specific value, the system works in a pure six-beat state. As can be seen from fig. 4, the small radius is 0.577 times the amplitude of the dc bus voltage, and the large radius is 0.667 times the amplitude of the dc bus voltage. In contrast, all inverters working in the linear modulation state have the problem that the voltage of a direct current bus cannot be fully utilized, and therefore the utilization rate of the permanent magnet synchronous motor on the voltage of the direct current bus can be improved by carrying out overmodulation control on the inverters. Under the condition of improving the rotating speed of the permanent magnet synchronous motor through weak magnetic control, the rotating speed of the motor can be further improved through combination with overmodulation control, and the dynamic performance of the system is improved.
Example 2:
the present embodiment is configured to provide an overmodulation-based flux weakening control method for a permanent magnet synchronous motor, which operates with the overmodulation-based flux weakening control apparatus described in embodiment 1, and as shown in fig. 5, the overmodulation-based flux weakening control method for a permanent magnet synchronous motor includes the following steps:
step 1: according to the DC bus voltage UdcObtaining weak magnetic control threshold voltage us max；
The weak magnetic control threshold voltage is us max0.577 times of DC bus voltage UdcSince the value of the small radius in fig. 4 is also 0.577 times the amplitude of the dc bus voltage, the pm synchronous motor performs overmodulation control while performing field weakening control. The permanent magnet synchronous motor is controlled simultaneously by the field weakening control and the overmodulation, so that the invention can realize the balance on the quick dynamic response and the reliable operation of the rotating speed of the motor.
Step 2: obtaining stator terminal voltage vector amplitude u of permanent magnet synchronous motor in real times；
Permanent magnet synchronous motor stator terminal voltage vector amplitude usThe method is obtained in real time, namely whether the permanent magnet synchronous motor needs to be subjected to field weakening control needs to be detected in real time.
And step 3: comparing stator terminal voltage vector magnitude usAnd weak magnetic control threshold voltage us maxThe size of (d);
in order to ensure that the permanent magnet synchronous motor stably runs in a full speed range, the motor is required to be in a speed idThe control area and the weak magnetic control area are switched smoothly as 0. At idAnd when the stator end voltage vector amplitude is equal to the weak magnetic control threshold voltage amplitude, the rotating speed or the load of the motor is continuously increased, and the control is switched to weak magnetic control. From idThe condition of switching the control to the weak magnetic control is as follows;
when the motor exits the field weakening control, the phase voltage of the motor is kept as the field weakening control threshold voltage us maxAnd the value of the direct-axis current at the stator end is greater than 0, so that the system can be prevented from oscillating due to the coupling of the direct-axis current and the quadrature-axis current.
Step 301: if stator terminal voltage vector magnitude usLess than the weak magnetic control threshold voltage us maxTo i withdControlling the permanent magnet synchronous motor by a control algorithm of 0, and controlling a permanent magnet synchronous motor inverter by the existing SVPWM linear modulation algorithm;
defining a modulation ratio M, wherein the calculation formula of the modulation ratio M is as follows:
wherein the content of the first and second substances,the hexagonal peak voltage vector magnitude, | u, shown in FIG. 4rI denotes a reference voltage vector urAmplitude of r*Represents | urL is expressed by UdcAnd performing per unit value calculation for the benchmark.
In a linear modulation area, the space vector pulse width modulation has good linear gain, and the maximum amplitude of the fundamental wave of the phase voltage of the output phase of the inverter can reach 0.577UdcAt this time, when the modulation ratio is 0.866, that is, when the modulation ratio is greater than zero and less than or equal to 0.866, the SVPWM operates in the linear modulation region. Fundamental amplitude of inverter output phase voltage exceeds 0.577UdcWhen the SVPWM works in an overmodulation region, the maximum amplitude of the fundamental wave of the output phase voltage of the inverter isNamely, when the modulation ratio is more than 0.866 and less than or equal to 1, the SVPWM works in an overmodulation region.
Let thetarAs a reference voltage vector urThe phase angle of (1), then the reference voltage vector urThe polar coordinate expression of (a) is:
in the present embodiment, assuming the first sector in the reference voltage vector bitmap 4, the reference voltage vector urCan be expressed as:
wherein, TsFor one switching period, T, of SVPWM1，T2As a vertex voltage vector u1And the vertex voltage vector u2The action time of (1).
Calculating a vertex voltage vector u by using the existing SVPWM linear modulation algorithm1With the vertex voltage vector u2Time of action T1And T2The following can be obtained:
wherein, | urI denotes a reference voltage vector urAmplitude of (U)dcRepresenting the magnitude of the DC bus voltage, θrRepresenting a reference voltage vector urThe phase angle of (c).
Step 302: if stator terminal voltage vector magnitude usEqual to the field weakening control threshold voltage us maxAnd continuously increasing the rotating speed or the load of the motor, controlling the permanent magnet synchronous motor by a weak magnetic control algorithm, and controlling the permanent magnet synchronous motor inverter by an SVPWM overmodulation algorithm.
In this embodiment, the field weakening control specifically includes:
calculating to obtain a speed command value omega according to the position command value and the position feedback value*(ii) a The position instruction valueThe position feedback value is a given value and is obtained by detecting the permanent magnet synchronous motor by a position detection module;
according to the speed command value omega*Calculating with the velocity feedback value omega to obtain a direct-axis current command value id *(ii) a The speed feedback value omega is obtained by calculating the position feedback value through a motor rotating speed calculation module;
according to the direct-axis current instruction value id *And a direct axis current feedback value idCalculating to obtain a direct axis voltage instruction valueThe velocity feedback value idAcquiring a parameter value obtained by carrying out coordinate transformation twice on the current of the permanent magnet synchronous motor for a current sampling module;
according to the direct axis voltage instruction valueAnd said field weakening control threshold voltage us maxCalculating to obtain a quadrature axis voltage command value
The rotation speed regulator outputs a direct-axis current command value i containing electrode field weakening information and torque informationd *The direct-axis voltage command value can be obtained through the adjustment of the direct-axis current regulatorIn the algorithm, no quadrature axis current regulator and quadrature axis voltage command valueAccording to the direct-axis voltage command valueAnd field weakening control threshold voltage us maxAnd (4) calculating. The invention does not need to consider decoupling of the direct and quadrature currents.
In this embodiment, the overmodulation algorithm control specifically includes:
step 3021: defining an actual voltage vector u and a reference voltage vector u of an inverter outputrThe amplitude coefficient formula is:
wherein the content of the first and second substances,2/3U representing the magnitude of the voltage vector corresponding to the hexagonal inscribed circle in the SVPWM voltage vector diagramdcRepresents the magnitude, u, of the vertex voltage vector in the SVPWM voltage vector diagramrI denotes a reference voltage vector urAmplitude of
Step 3022: the amplitude of the voltage vector corresponding to the inscribed circleAmplitude 2/3U of the vertex voltage vectordcAnd the reference voltage vector urAmplitude | u ofrVoltage U of DC busdcCalculating per unit value for the reference to obtain a new calculation formula of the amplitude coefficient:
step 3023: determining the vertex voltage vector uxReference voltage vector urRelation with the actual inverter output voltage vector u:
where k is the new amplitude coefficient, uxIs a vector of the vertex voltage urIs a vector of reference voltages.
Step 3024: according to the vertex voltage vector uxNumber ofx and the reference voltage vector urPhase angle theta ofrThe relation calculates the vertex voltage vector u according to the function time calculation formulaxThe action time of (c); the function time calculation formula is based on the vertex voltage vector uxReference voltage vector urDetermining a relational expression of the vector u and the actual voltage output by the inverter; assume reference voltage vector urThe vertex voltage vector u at the time of the first sector in the SVPWM voltage vector diagram of FIG. 41With the vertex voltage vector u2Time of action T1And T2Comprises the following steps:
step 3025: obtaining an overmodulation signal according to the action time;
step 3026: and performing overmodulation control on the permanent magnet synchronous motor by using the overmodulation signal.
When the overmodulation algorithm is used for controlling, the vertex voltage vector u is subjected to1With the vertex voltage vector u2Time of action T1And T2The calculation method of (1) and the existing VPWM linear modulation algorithm to the vertex voltage vector u1With the vertex voltage vector u2Time of action T1And T2The calculation methods are similar, so that the invention can enable the inverter to be in smooth transition in all SVPWM modulation intervals, and enable the output phase voltage of the inverter to have higher linearity.
Specifically, the vertex voltage vector uxThe specific value of x and the reference voltage vector phase angle thetarThe relationship of (A) is as follows in Table 1:
TABLE 1
Compared with the existing single current regulator flux weakening algorithm, the flux weakening control algorithm provided by the invention does not increase the calculation complexity, can enable the motor to operate in an overcurrent state within a short time, and expands the flux weakening range. When the flux weakening algorithm is used for controlling the permanent magnet synchronous motor, the over-modulation algorithm is combined, so that the direct-current side voltage of the inverter can be fully utilized, and the dynamic performance and the loading capacity of the motor are improved. The linear modulation region and the overmodulation region are compatible in algorithm, the system does not need to switch the overmodulation algorithm, the amplitude of the phase voltage output by the inverter has good linear gain, and the running stability of the overmodulation region is improved.
The principles and embodiments of the present invention have been described herein using specific examples, which are provided only to help understand the method and the core concept of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In view of the above, the present disclosure should not be construed as limiting the invention.