阅读说明：本技术 永磁同步电机驱动系统的母线电容容量监测方法 (Bus capacitor capacity monitoring method of permanent magnet synchronous motor driving system ) 是由 徐明章 罗伦 王榆林 文成全 于 2021-08-05 设计创作，主要内容包括：本说明书实施例提供一种永磁同步电机驱动系统的母线电容容量监测方法,方法包括：预先标定永磁同步电机在额定转速下预设比值与母线电容容量之间的曲线关系,在曲线关系中确定母线电容的不同减少程度各自对应的容量区间；在连续工作时长超过预设时长之后,判断永磁同步电机的转速与额定转速之间的差值的绝对值是否小于预设值；若是,则将永磁同步电机的转速调至额定转速；当永磁同步电机工作在额定转速之后,监测当前的母线电压最小值,确定母线电容的当前容量,向上位机发出相应的报警信息,并对永磁同步电机驱动系统进行相应的处理。本发明可以提高提高驱动系统的可靠性。(The embodiment of the specification provides a bus capacitor capacity monitoring method for a permanent magnet synchronous motor driving system, which comprises the following steps: calibrating a curve relation between a preset ratio of the permanent magnet synchronous motor at a rated rotating speed and the capacity of the bus capacitor in advance, and determining capacity intervals corresponding to different reduction degrees of the bus capacitor in the curve relation; after the continuous working time length exceeds a preset time length, judging whether the absolute value of the difference value between the rotating speed of the permanent magnet synchronous motor and the rated rotating speed is smaller than a preset value or not; if so, adjusting the rotating speed of the permanent magnet synchronous motor to the rated rotating speed; when the permanent magnet synchronous motor works at a rated rotating speed, the current minimum value of the bus voltage is monitored, the current capacity of the bus capacitor is determined, corresponding alarm information is sent to an upper computer, and corresponding processing is carried out on a permanent magnet synchronous motor driving system. The invention can improve the reliability of the driving system.)

1. A bus capacitor capacity monitoring method of a permanent magnet synchronous motor driving system is characterized by comprising the following steps:

calibrating a curve relation between a preset ratio of the permanent magnet synchronous motor at a rated rotating speed and the capacity of the bus capacitor in advance, and determining capacity intervals corresponding to different reduction degrees of the bus capacitor in the curve relation; the different reduction degrees have different degrees of influence on the operation process of the permanent magnet synchronous motor driving system; the preset ratio is the ratio between the minimum value of the bus voltage and the peak value of the bus voltage;

after the continuous working time of the permanent magnet synchronous motor driving system exceeds a preset time, judging whether the absolute value of the difference value between the rotating speed of the permanent magnet synchronous motor and the rated rotating speed is smaller than a preset value; if so, adjusting the rotating speed of the permanent magnet synchronous motor to the rated rotating speed;

when the permanent magnet synchronous motor works at the rated rotating speed, monitoring the current bus voltage minimum value in real time, and calculating the current ratio between the current bus voltage minimum value and the bus voltage peak value in real time;

determining the current capacity of the bus capacitor in the curve relation according to the current ratio; determining the reduction degree of the bus capacitor according to the capacity interval where the current capacity is located; and sending corresponding alarm information to an upper computer according to the reduction degree, and carrying out corresponding processing on the permanent magnet synchronous motor driving system.

2. The method of claim 1, wherein the pre-calibration of the curve relationship comprises:

selecting a plurality of mains supply voltages in a mains supply voltage change interval; selecting a plurality of capacitors according to the rated capacity and the preset capacity reduction step length of the bus capacitor of the permanent magnet synchronous motor driving system;

controlling the rotating speed of the permanent magnet synchronous motor at the rated rotating speed under each mains supply voltage in the plurality of mains supply voltages, and replacing the bus capacitor of the permanent magnet synchronous motor driving system in the plurality of capacitors according to the sequence of capacitor capacity from high to low;

after the bus capacitor is replaced by any one of the capacitors, monitoring a plurality of operation indexes of the permanent magnet synchronous motor driving system, and recording the current minimum value of the bus voltage and the current capacity of the capacitor when any one of the operation indexes exceeds the preset index standard;

under the same capacitor, averaging the minimum values of the bus voltages respectively recorded when the same operation indexes under the multiple mains voltages have the same change, so as to obtain the average minimum value of the bus voltage corresponding to the capacitor;

calculating the ratio between the average minimum value of the bus voltage and the peak value of the bus voltage corresponding to the plurality of capacitors to obtain the preset ratio corresponding to the plurality of capacitors;

determining the curve relation according to the capacities of the capacitors and the preset ratios respectively corresponding to the capacitors;

and in the process of replacing the bus capacitor by adopting the plurality of capacitors, determining different capacitor capacity intervals corresponding to different influence severity degrees generated on the operation process of the permanent magnet synchronous motor driving system according to the change conditions of a plurality of operation indexes of the permanent magnet synchronous motor driving system.

3. The method of claim 2, wherein the plurality of operational metrics includes a vibration amplitude of the permanent magnet synchronous motor and a mains input current harmonic;

the monitoring of a plurality of operation indexes of the permanent magnet synchronous motor driving system and the recording of the current minimum value of the bus voltage and the current capacity of the capacitor when any operation index exceeds the preset index standard thereof comprise the following steps:

monitoring the vibration amplitude and the mains supply input current harmonic, recording the current minimum value of the bus voltage and the current capacitance if at least one operation index of the vibration amplitude and the mains supply input current harmonic exceeds the corresponding index standard, and taking the current capacitance as the lower limit value of a first capacitance interval, wherein the upper limit value of the first capacitance interval is a preset prior value, and the influence severity degree corresponding to the first capacitance interval is slight.

4. The method of claim 3, wherein monitoring a plurality of operating criteria of the PMSM drive system and recording a current minimum bus voltage value and a current capacity of the capacitor when any operating criteria exceeds its preset criteria, further comprises:

if any one of under-voltage, over-voltage, capacitor explosion and inverter damage occurs in the permanent magnet synchronous motor driving system, recording the current minimum value of the bus voltage and the current capacity of the capacitor, and taking the capacity of the current capacitor as the lower limit value of a second capacity interval, wherein the upper limit value of the second capacity interval is the lower limit value of the first capacity interval, and the influence severity degree corresponding to the second capacity interval is moderate.

5. The method of claim 4, wherein the capacitive capacity region further comprises a third capacity region and a fourth capacity region; the upper limit value of the third capacity interval is the lower limit value of the second capacity interval, the lower limit value of the third capacity interval is 0, and the severity of the influence corresponding to the third capacity interval is severe; the upper limit value of the fourth capacity interval is the rated capacity, the lower limit value of the fourth capacity interval is the preset prior value, and the fourth capacity interval is the normal operation interval of the permanent magnet synchronous motor driving system.

6. The method according to claim 5, characterized in that the degree of reduction of the bus capacitance is determined according to a capacity interval in which the current capacity is located; according to the reduction degree, corresponding alarm information is sent to the upper computer, and the alarm information comprises at least one of the following items:

if the capacity interval in which the current capacity is located is the first capacity interval, the reduction degree of the bus capacitor is light, alarm information of slight reduction of the bus capacitor capacity is sent to the upper computer, and the permanent magnet synchronous motor driving system continues to normally operate;

if the current capacity is in the capacity interval and the second capacity interval, the reduction degree of the bus capacitor is moderate, alarm information of moderate reduction of the bus capacitor capacity is sent to the upper computer, and compensation control is carried out on the permanent magnet synchronous motor driving system through d/q axis voltage;

if the current capacity is in the capacity interval and the third capacity interval, the reduction degree of the bus capacitor is severe, alarm information of the severe reduction of the bus capacitor capacity is sent to the upper computer, and the permanent magnet synchronous motor driving system is controlled to stop running.

7. The method of claim 6, wherein said compensation controlling of said PMSM drive system via d/q axis voltages comprises:

calculating a difference value between the bus voltage peak value and the bus voltage minimum value, carrying out PR adjustment on the difference value, and decoupling data obtained by PR adjustment to obtain a q-axis adjustment voltage value and a d-axis adjustment voltage value;

determining a q-axis current command value and a d-axis current command value, performing PI (proportional integral) adjustment on the q-axis current command value and the d-axis current command value respectively to obtain a q-axis voltage output value and a d-axis voltage output value, subtracting the q-axis voltage output value from the q-axis adjustment voltage value to obtain a q-axis voltage command value, and subtracting the d-axis voltage output value from the d-axis adjustment voltage value to obtain a d-axis voltage command value;

and performing voltage control on the permanent magnet synchronous motor driving system through the q-axis voltage command value and the d-axis voltage command value.

8. The method of claim 7,

before the calculating the difference between the bus voltage peak value and the bus voltage minimum value, the method further includes: determining a maximum output voltage value of an inverter, and calculating the square of the current output voltage of the inverter, wherein the square of the current output voltage is the sum of squares of the current d-axis voltage and the current q-axis voltage; calculating the square of a weak magnetic voltage threshold according to the maximum output voltage value of the inverter; judging whether the square of the current output voltage is larger than or equal to the square of the weak magnetic voltage threshold value or not; if yes, starting weak magnetism, enabling d-axis current to enter a weak magnetism state, and allowing execution of a step of calculating a difference value between the bus voltage peak value and the bus voltage minimum value;

correspondingly, in the process of carrying out voltage control on the permanent magnet synchronous motor driving system through the q-axis voltage command value and the d-axis voltage command value, calculating the maximum value of the q-axis voltage according to the square of the weak magnetic voltage threshold value and the d-axis voltage command value; judging whether the q-axis voltage command value is larger than the maximum q-axis voltage value; if so, taking the maximum value of the q-axis voltage as the q-axis voltage command value, and otherwise, keeping the q-axis voltage command value unchanged; judging whether the square of the current output voltage of the inverter is smaller than the square of the weak magnetic voltage threshold value or not in real time; and if so, exiting the field weakening state, setting the d-axis current command value to be 0, and stopping performing voltage control on the permanent magnet synchronous motor driving system through the q-axis voltage command value and the d-axis voltage command value.

9. The method of claim 8, wherein the maximum output voltage value is calculated using a first formula comprising:

in the formula, V_maxIs the maximum output voltage value, V_DCIs the bus voltage of the inverter.

10. The method of claim 8, wherein calculating the q-axis voltage maximum is performed using a second formula comprising:

in the formula, V_qmaxIs the maximum value of the q-axis voltage,is the square of the d-axis voltage command value,is the square of the weak magnetic voltage threshold.

Technical Field

One or more embodiments of the present disclosure relate to the field of motor technologies, and in particular, to a method for monitoring a bus capacitor capacity of a driving system of a permanent magnet synchronous motor.

Background

The permanent magnet synchronous motor has the characteristics of simple structure, high efficiency, high power factor, high power density, high torque-current ratio, low rotational inertia, easiness in heat dissipation, maintenance and the like. With the rapid development of new materials, mechatronics, power electronics, computers, control theory and other high and new technologies, the permanent magnet synchronous motor driving system is widely applied to industries such as industry and household appliances. At present, the topology structure of the widely used permanent magnet synchronous motor driving system is shown in fig. 1, and the topology structure has the advantages of simplicity, low cost and capability of being applied to a power conversion system with single-phase power supply and three-phase power supply. However, the bus capacitor capacity of the driving system in such a structure gradually decreases with the use time, so that the performance of the driving system gradually deteriorates, for example, the current harmonics of the mains input become large, the vibration of the motor becomes large, and finally a fault occurs, and the driving system cannot work normally.

The bus capacitor has the following functions: (1) compensating the difference between the required power of the inverter and the output power of the rectifier bridge, which changes by twice or six times of the power frequency; (2) reducing current harmonics of the switching frequency to enter a power grid; (3) the demagnetizing energy of the motor under the condition that all power switching devices are turned off in the emergency stop state is absorbed; 4) providing an instantaneous peak power; (5) the inverter is protected from grid transient peak impacts. However, the bus capacitor generally uses an electrolytic capacitor, the capacity of the capacitor of this type is gradually reduced along with the working time, and finally reaches the life cycle, and the performance of the driving system of the permanent magnet synchronous motor is gradually deteriorated in the process, and finally the driving system cannot work normally.

The external factors influencing the attenuation speed of the bus capacitor capacity of the permanent magnet synchronous motor driving system are as follows: (1) ambient temperature; the higher the temperature, the faster the capacitance decay; (2) current ripples; the larger the ripple is, the faster the capacitance attenuation is; (3) a working voltage; the closer to the nominal operating voltage of the capacitor, the lower the reliability. These external factors tend to act in an overlapping manner to gradually reduce the capacitance of the bus capacitor until the drive system fails to function properly.

At present, the following passive measures are generally adopted in the industry: (1) the electrolytic capacitor with the long service life is selected as much as possible; (2) the allowance of the bus capacitor is increased; (3) the device is directly replaced as soon as the life cycle is reached, but the life is related to the service environment and is difficult to accurately judge. The above measures cannot fundamentally improve the reliability of the drive system.

Disclosure of Invention

One or more embodiments of the present specification describe a method for bus capacitor capacity monitoring of a PMSM drive system.

The invention provides a bus capacitor capacity monitoring method of a permanent magnet synchronous motor driving system, which comprises the following steps:

calibrating a curve relation between a preset ratio of the permanent magnet synchronous motor at a rated rotating speed and the capacity of the bus capacitor in advance, and determining capacity intervals corresponding to different reduction degrees of the bus capacitor in the curve relation; the different reduction degrees have different degrees of influence on the operation process of the permanent magnet synchronous motor driving system; the preset ratio is the ratio between the minimum value of the bus voltage and the peak value of the bus voltage;

after the continuous working time of the permanent magnet synchronous motor driving system exceeds a preset time, judging whether the absolute value of the difference value between the rotating speed of the permanent magnet synchronous motor and the rated rotating speed is smaller than a preset value; if so, adjusting the rotating speed of the permanent magnet synchronous motor to the rated rotating speed;

when the permanent magnet synchronous motor works at the rated rotating speed, monitoring the current bus voltage minimum value in real time, and calculating the current ratio between the current bus voltage minimum value and the bus voltage peak value in real time;

determining the current capacity of the bus capacitor in the curve relation according to the current ratio; determining the reduction degree of the bus capacitor according to the capacity interval where the current capacity is located; and sending corresponding alarm information to an upper computer according to the reduction degree, and carrying out corresponding processing on the permanent magnet synchronous motor driving system.

In the bus capacitor capacity monitoring method of the permanent magnet synchronous motor driving system provided in the embodiment of the present specification, a curve relationship between a preset ratio and the bus capacitor capacity is calibrated in advance, and a degree of influence of different capacity intervals on an operation process of the permanent magnet synchronous motor driving system is determined, where the preset ratio is a ratio between a bus voltage minimum value and a bus voltage peak value, that is, a variation trend of the bus voltage minimum value is represented by a ratio between the bus voltage minimum value and the bus voltage peak value, so that an influence of factors such as commercial power variation on the bus voltage minimum value is reduced. And the motor keeps the rated rotating speed in the calibration process, and the influence of the change of the rotating speed of the motor on the minimum value of the bus voltage can be reduced. After the relevant data is calibrated, in an actual application scene, after the motor continuously works for a period of time, whether the rotating speed of the motor is near the rated rotating speed is judged, and the rotating speed of the motor is adjusted to the rated rotating speed only when the rotating speed of the motor is near the rotating speed of the motor, so that the influence of the monitoring process of the bus capacitor on the normal work of the motor is reduced. The method comprises the steps of monitoring the minimum value of the current bus voltage, calculating the current ratio, determining the corresponding current capacity in the curve relation calibrated in the prior art, and accordingly determining the capacity interval corresponding to the bus capacitor, knowing the reduction degree of the bus capacitor and the influence of what degree the permanent magnet synchronous motor driving system generates, and further performing corresponding processing and sending corresponding alarm information. The method can distinguish the heavy reduction of the bus capacitor, and also can distinguish the light reduction and the medium reduction, so that corresponding treatment can be carried out before the permanent magnet synchronous motor driving system is damaged, for example, before the heavy reduction, the bus capacitor is declared to be maintained, the bus capacitor is replaced, the permanent magnet synchronous motor driving system is prevented from being out of order after the bus capacitor enters the heavy reduced capacity interval, and the reliability of the permanent magnet synchronous motor driving system can be improved.

Drawings

In order to more clearly illustrate the embodiments of the present specification or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present specification, and other drawings can be obtained by those skilled in the art without creative efforts.

FIG. 1 is a prior art topology block diagram of a PMSM drive system;

FIG. 2 is a schematic flow chart of a bus capacitor capacity monitoring method of a PMSM drive system according to an embodiment of the present invention;

FIG. 3 is a schematic diagram of the waveforms of the mains and bus voltages in one embodiment of the invention;

FIG. 4 is a graphical representation of a relationship of curves in an embodiment of the present invention;

FIG. 5 is a flow chart of d/q voltage compensation control in one embodiment of the present invention.

Detailed Description

The scheme provided by the specification is described below with reference to the accompanying drawings.

The invention provides a bus capacitor capacity monitoring method of a permanent magnet synchronous motor driving system, which comprises the following steps of S100-S400:

s100, calibrating a curve relation between a preset ratio of the permanent magnet synchronous motor at a rated rotating speed and the capacity of the bus capacitor in advance, and determining capacity intervals corresponding to different reduction degrees of the bus capacitor in the curve relation;

wherein the different degrees of reduction have different degrees of severity of the effect on the operation process of the permanent magnet synchronous motor driving system; the preset ratio is the ratio between the minimum value of the bus voltage and the peak value of the bus voltage.

It can be understood that the more the bus capacitor capacity is reduced, the more serious the influence on the operation process of the permanent magnet synchronous motor driving system is. The reduction degree of the bus capacitor capacity can be divided into mild degree, moderate degree and severe degree, and correspondingly, the influence degree on the operation process of the permanent magnet synchronous motor driving system is also divided into mild degree, moderate degree and severe degree. The capacity of the bus capacitor is slightly reduced, compared with the normal condition, the performance of the permanent magnet synchronous motor driving system is not influenced, but the fluctuation of the bus voltage is increased, but is within the normal range; the moderate reduction of the bus capacitance will deteriorate key indexes of the driving system of the permanent magnet synchronous motor compared with normal conditions, for example, the harmonic wave of the alternating current input current becomes large, the torque ripple of the permanent magnet synchronous motor becomes large, the fluctuation of the bus voltage becomes large, and the fluctuation of the bus voltage may exceed the normal range. The bus capacitor capacity is severely reduced, and compared with the normal condition, the permanent magnet synchronous motor driving system has the phenomena of over/under voltage protection, bus capacitor damage (such as burst), inverter power device damage and the like. At present, no effective method can be used for prejudging mild reduction and moderate reduction, and capacity reduction can be found only after definite faults occur (such as capacitor explosion, frequent over/under voltage protection and the like) through measuring the capacity of the bus capacitor.

Referring to fig. 3, two sinusoidal waveforms are waveforms of the commercial power, and the bus voltage formula: u. of_dc＝|u_ac|(|u_ac|＞U_mx) Or U_mx(|u_ac|≤U_mx)，u_acIs mains voltage, the horizontal axis 2 pi is a period, U_MIs the peak bus voltage, C_eIs the rated capacity, K, of a bus capacitor in a permanent magnet synchronous motor driving system_XIs a coefficient of less than 1, K_XC_eDifferent bus capacitor capacities (representing the capacity of the bus capacitor at different degrees of reduction), U, in a typical pmsm drive system_mxThe bus voltage minimum value is corresponding to different bus capacitance capacities in the permanent magnet synchronous motor driving system. When K is_XWhen the capacitance is 1, the bus capacitance is rated capacity C_eAt this time, the corresponding bus voltage waveform in one period includes four sections, the first section is a straight line section, the second section is a section of curve overlapped with the first sine wave, the third section is a straight line section positioned between the two sine waves, and the fourth section is a section of curve overlapped with the second sine wave. When the bus capacitance decays to K_xC_eThe bus voltage waveforms are similar except that as the bus capacitance decreases, the bus voltageAll four segments of the waveform move downward. As can be seen from FIG. 3, the bus voltage peak U_MDoes not vary, is equal to the maximum amplitude, U, of the sine wave_mxThe amplitude of the intersection point of the straight line section and the curve section is U along with the reduction of the capacitance of the bus_mxWill gradually decrease. That is, the minimum value U of the bus voltage_mxHas a certain relation with the capacity of the bus capacitor, therefore, for a definite permanent magnet synchronous motor driving system, the U can be passed_mxThe capacity change of the bus capacitor is judged according to the level of the voltage.

However, in practical conditions, the input voltage of the utility power is changed, which results in the U of the bus capacitor with the same capacity_mxAnd may be varied within certain limits. Meanwhile, the motor rotating speed of the permanent magnet synchronous motor driving system also changes within a certain range, which can also cause the U of the bus capacitor with the same capacity_mxAnd may vary within certain limits. Thus passing through U_mxThe accuracy of judging the capacity variation trend of the bus capacitor is influenced by the commercial power, the rotating speed of the motor and the like. When the commercial power changes, U_MAnd U_mxWill change along with the trend, and in order to reduce the influence caused by the change of the commercial power, U is used_mx/U_MRepresents U_mxI.e., in S100, a preset ratio is used to represent U_mxThe trend of change of (c). Secondly, to reduce the load, the weight is reduced to U_mxThe influence of the motor is considered to weak magnetic control, load weight and other factors, and the rated rotating speed of the motor is selected as the rotating speed of the test point. The motor works at a rated rotating speed through a variable frequency speed regulation technology, and the change of the rotating speed of the motor to the U is reduced_mxThe influence of (c). The rotation speed of the motor is the rated rotation speed when the calibration is performed in S100.

In a specific implementation, S100 may specifically include the following steps S110 to S170:

s110, selecting a plurality of mains supply voltages in a mains supply voltage change interval; selecting a plurality of capacitors according to the rated capacity and the preset capacity reduction step length of the bus capacitor of the permanent magnet synchronous motor driving system;

it can be understood that, since the utility voltage has a certain variation range, for example, floating within upper and lower 10% of 220v, a plurality of voltage values, for example, three voltages/frequencies 187v/50Hz, 220v/50Hz, 242v/50Hz, need to be selected within the variation interval of the utility voltage, wherein the frequencies are the same.

It will be appreciated that during the pre-calibration phase, a plurality of different capacitance values may be used to represent different degrees of capacitance reduction of the bus capacitor. For example, rated capacity of C_eAt 10% C_eFor the preset capacity reduction step, the capacities of the plurality of capacitors that can be selected are respectively: c_e、90％C_e、80％C_e、70％C_e、60％C_e、50％C_e、40％C_e、30％C_e、20％C_e、10％C_e。

S120, controlling the rotating speed of the permanent magnet synchronous motor to be the rated rotating speed under each mains supply voltage in the plurality of mains supply voltages, and replacing the bus capacitor of the permanent magnet synchronous motor driving system in the plurality of capacitors according to the sequence of capacitor capacity from high to low;

s130, after the bus capacitor is replaced by any one of the capacitors, monitoring a plurality of operation indexes of the permanent magnet synchronous motor driving system, and recording the current minimum value of the bus voltage and the current capacity of the capacitor when any one of the operation indexes exceeds the preset index standard;

for example, the motor speed is adjusted to the rated speed at 187V/50Hz, and then the capacity is C_eThe capacitance of the bus replaces the capacitance of the bus, so that whether the capacitance of the bus is attenuated at the moment is uncertain. The method comprises the steps of monitoring a plurality of operation indexes of the permanent magnet synchronous motor driving system to determine whether the operation indexes are changed or not, and recording relevant data such as the changed indexes, the capacitance when the indexes are changed and the current minimum value of the bus voltage. Then the capacity was 90% C_eThe bus capacitor is replaced by the capacitor, and index monitoring, data recording and the like are carried out. Then the capacity is 80% C_eThe bus capacitor is replaced by the capacitor, and index monitoring, data recording and the like are carried out. And the like until all the capacitors are replaced. Then, electricity was supplied at 220v/50HzAnd regulating the rotation speed of the machine to the rated rotation speed, and repeatedly executing the process. Finally, the rotating speed of the motor is adjusted to the rated rotating speed at 242v/50Hz, and the process is repeatedly executed.

S140, under the same capacitor, averaging the minimum values of the bus voltages respectively recorded when the same operation indexes under the multiple mains voltages have the same change, so as to obtain the average minimum value of the bus voltage corresponding to the capacitor;

for example, for 70% C_eWhen the vibration amplitude of the permanent magnet synchronous motor under 187v/50Hz, 220v/50Hz and 242v/50Hz exceeds a preset range, the three current bus voltage minimum values recorded under the three voltages are averaged to obtain the bus voltage average minimum value corresponding to the capacitor.

S150, calculating the ratio between the average minimum value of the bus voltage and the peak value of the bus voltage corresponding to the capacitors to obtain the preset ratio corresponding to the capacitors;

for example, the ratios between the average minimum value of the bus voltage and the peak value of the bus voltage respectively corresponding to the 10 capacitors are respectively calculated, so as to obtain 10 preset ratios.

S160, determining the curve relation according to the capacities of the capacitors and the preset ratios respectively corresponding to the capacitors;

for example, the graph of the curve relationship shown in fig. 4 can be obtained by plotting the 10 points corresponding to the 10 predetermined ratios and the 10 capacitance values on the graph with the predetermined ratio as the horizontal axis and the capacitance value as the vertical axis, and connecting the points by smooth lines.

S170, in the process of replacing the bus capacitor by the plurality of capacitors, determining different capacitor capacity intervals corresponding to different influence severity degrees generated on the operation process of the permanent magnet synchronous motor driving system according to the change conditions of a plurality of operation indexes of the permanent magnet synchronous motor driving system.

After the curve relation graph is obtained, the operation condition of the permanent magnet synchronous motor driving system at the moment can be known according to different change conditions of the operation indexes corresponding to different points on the curve relation, further the influence severity of different capacitance capacities on the permanent magnet synchronous motor driving system can be known, and a plurality of different capacity intervals can be determined according to different influence severity.

In specific implementation, the plurality of operation indexes may include a vibration amplitude of the permanent magnet synchronous motor and a mains supply input current harmonic; at this time, S130 may include: monitoring the vibration amplitude and the mains supply input current harmonic after the bus capacitor is replaced by any one of the capacitors, recording the current minimum value of the bus voltage and the current capacitance if at least one operation index of the vibration amplitude and the mains supply input current harmonic exceeds the corresponding index standard, and taking the current capacitance as the lower limit value of a first capacitance interval, wherein the upper limit value of the first capacitance interval is a preset prior value, and the influence severity degree corresponding to the first capacitance interval is mild.

That is, the upper limit value of the first capacity interval is a preset prior value, for example, 80% C_eThe lower limit value is a capacitance capacity corresponding to at least one of the vibration amplitude and the harmonic of the mains input current exceeding a corresponding standard, e.g. 70% C_e. When the capacity of the bus capacitor is attenuated to a first capacity interval, at least one operation index of the vibration amplitude and the mains supply input current harmonic exceeds a corresponding index standard, and the influence degree is mild.

In a specific implementation, S130 may further specifically include: if any one of under-voltage, over-voltage, capacitor explosion and inverter damage occurs in the permanent magnet synchronous motor driving system, recording the current minimum value of the bus voltage and the current capacity of the capacitor, and taking the capacity of the current capacitor as the lower limit value of a second capacity interval, wherein the upper limit value of the second capacity interval is the lower limit value of the first capacity interval, and the influence severity degree corresponding to the second capacity interval is moderate.

That is, the upper limit value of the second capacity interval is the lower limit value of the first capacity interval, for example, 70% C_eLower limit value ofCapacitance capacity, e.g. 40% C, corresponding to any one of undervoltage, overvoltage, capacitor rupture and inverter damage_e. When the capacity of the bus capacitor is attenuated to the second capacity interval, any one of undervoltage, overvoltage, capacitor explosion and inverter damage is caused, and the influence degree is moderate.

Of course, the capacitance capacity interval further includes a third capacity interval and a fourth capacity interval; the upper limit value of the third capacity interval is the lower limit value of the second capacity interval, the lower limit value of the third capacity interval is 0, and the severity of the influence corresponding to the third capacity interval is severe; the upper limit value of the fourth capacity interval is the rated capacity, the lower limit value of the fourth capacity interval is the preset prior value, and the fourth capacity interval is the normal operation interval of the permanent magnet synchronous motor driving system.

That is, the upper limit value of the third capacity interval is the lower limit value of the second capacity interval, for example, 40% C_eThe lower limit value is 0. When the capacity of the bus capacitor is attenuated to a third capacity interval, the permanent magnet synchronous motor driving system cannot work, and the influence degree is severe.

And a fourth capacity interval is also set, the upper limit value of the fourth capacity interval is the rated capacity, the lower limit value of the fourth capacity interval is the upper limit value of the first capacity interval, and the fourth capacity interval is a normal operation interval of the permanent magnet synchronous motor driving system, so that the fourth capacity interval is a normal floating interval of the bus capacitance.

Referring to fig. 4, a curve OA section corresponds to a fourth capacity interval, and the operation of the driving system of the permanent magnet synchronous motor in the interval is not affected; the AB section corresponds to a first capacity interval, and the influence degree on a permanent magnet synchronous motor driving system is slight; the BC section corresponds to a second capacity interval, and the influence degree on a permanent magnet synchronous motor driving system is moderate; and the point C and below correspond to a third capacity interval, the influence degree on the permanent magnet synchronous motor driving system is severe, and at the moment, the permanent magnet synchronous motor driving system has serious faults, cannot work and needs to be immediately processed.

In specific implementation, different processing measures are required to be taken when the capacitance of the bus is attenuated to different capacitance intervals: (1) the capacitance of the bus capacitor is in a fourth capacitance interval (for example, Ce-80% Ce, namely OA section of curve relation), no treatment is carried out, and the system continues to operate normally; (2) when the capacity of the bus capacitor is in a third capacity interval (namely below the capacity corresponding to the C point), the operation needs to be stopped, and an alarm is given to the upper computer to 'the capacity of the bus capacitor is severely reduced'; (3) when the capacity of the bus capacitor is in a first capacity interval (for example, 80-70% Ce, namely an AB section), the system normally operates, and an alarm is given to the upper computer to 'the capacity of the bus capacitor is slightly reduced'; (4) when the capacity of the bus capacitor is in a second capacity interval (for example, the capacity change corresponding to 70% Ce-C points, namely a BC section), the system normally operates, and alarms to the upper computer that the capacity of the bus capacitor is reduced moderately; meanwhile, adaptive d-q axis voltage compensation control is adopted to improve the stability of the system and maintain the operation of the system, a control block diagram of the system is shown in fig. 5, and a specific compensation control process is described in detail later.

In specific implementation, the curve relationship, the key point information (for example, the upper and lower limit values of each capacity interval), and the processing modes corresponding to each capacity interval in fig. 4 are all stored in the control unit MCU. It is understood that the above-mentioned S100 is the step required to be executed in the preparation stage, and the following S200 to S400 are the steps in the actual application stage.

S200, after the continuous working time of the permanent magnet synchronous motor driving system exceeds a preset time, judging whether the absolute value of the difference value between the rotating speed of the permanent magnet synchronous motor and the rated rotating speed is smaller than a preset value or not; if so, adjusting the rotating speed of the permanent magnet synchronous motor to the rated rotating speed;

in an actual application scenario, because the reduction of the bus capacitor capacity is a slow process, the monitoring is not required to be performed in real time in the operation stage of the permanent magnet synchronous motor driving system, and whether the monitoring is performed or not can be determined after the permanent magnet synchronous motor driving system continuously works for a period of time. The preset time period may be set as desired, for example, 24 hours.

When the continuous work of the permanent magnet synchronous motor driving system exceeds the preset time, whether the rotating speed of the permanent magnet synchronous motor is close to the rated rotating speed or not is judged, and if the rotating speed of the permanent magnet synchronous motor is not close to the rated rotating speed, the rotating speed of the permanent magnet synchronous motor does not need to be regulated to the rated rotating speed forcibly, so that the normal work of the permanent magnet synchronous motor driving system is not influenced. And only when the rotating speed of the permanent magnet synchronous motor is close to the rated rotating speed, namely the absolute value of the difference value between the rotating speed of the permanent magnet synchronous motor and the rated rotating speed is smaller than a preset value, the rotating speed of the permanent magnet synchronous motor is regulated to the rated rotating speed, and the capacity monitoring is determined, so that the influence of the capacity monitoring on the normal work of a driving system of the permanent magnet synchronous motor is reduced.

S300, after the permanent magnet synchronous motor works at the rated rotating speed, monitoring the current bus voltage minimum value in real time, and calculating the current ratio between the current bus voltage minimum value and the bus voltage peak value in real time;

s400, determining the current capacity of the bus capacitor in the curve relation according to the current ratio; determining the reduction degree of the bus capacitor according to the capacity interval where the current capacity is located; and sending corresponding alarm information to an upper computer according to the reduction degree, and carrying out corresponding processing on the permanent magnet synchronous motor driving system.

And after the rotating speed of the permanent magnet synchronous motor is adjusted to the rated rotating speed, monitoring the minimum value of the bus voltage in real time, and further calculating the current ratio between the current minimum value of the bus voltage and the peak value of the bus voltage. Then, the current capacity corresponding to the current ratio is found in the curve relation, and then the capacity interval where the current capacity is located can be determined, and corresponding processing is further carried out.

In particular implementations, S400 may include at least one of:

(1) if the capacity interval in which the current capacity is located is the first capacity interval, the reduction degree of the bus capacitor is light, alarm information of slight reduction of the bus capacitor capacity is sent to the upper computer, and the permanent magnet synchronous motor driving system continues to normally operate;

that is to say, when current electric capacity was in first capacity interval, the reduction degree of bus voltage was lighter, and PMSM actuating system continued normal operating this moment, but needs the host computer to send alarm information to inform the host computer that the bus electric capacity is slightly reduced this moment.

(2) If the current capacity is in the capacity interval and the second capacity interval, the reduction degree of the bus capacitor is moderate, alarm information of moderate reduction of the bus capacitor capacity is sent to the upper computer, and compensation control is carried out on the permanent magnet synchronous motor driving system through d/q axis voltage;

that is to say, when the current capacity is in the second capacity interval, need carry out voltage compensation control, and need the host computer to send alarm information to inform the host computer that bus capacitance capacity is moderate to reduce this moment.

(3) If the current capacity is in the capacity interval and the third capacity interval, the reduction degree of the bus capacitor is severe, alarm information of the severe reduction of the bus capacitor capacity is sent to the upper computer, and the permanent magnet synchronous motor driving system is controlled to stop running.

That is to say, when the current capacity is in the third capacity interval, the upper computer is required to send out alarm information to inform the upper computer that the bus capacitance capacity is severely reduced at the moment, and the permanent magnet synchronous motor driving system is controlled to stop running.

In a specific implementation, referring to fig. 5, the above process of performing compensation control on the permanent magnet synchronous motor driving system through the d/q axis voltage may include the following steps:

s410, calculating a difference value between the bus voltage peak value and the bus voltage minimum value, carrying out PR adjustment on the difference value, decoupling data obtained by PR adjustment to obtain a q-axis adjustment voltage valueAnd d-axis regulated voltage value

Wherein, PR adjustment refers to adjustment by using a proportional resonance adjuster.

S420, determining a q-axis current command valueAnd d-axis current command valueFor the q-axis current command valueAnd the d-axis current command valueRespectively carrying out PI regulation to obtain a q-axis voltage output value u_qAnd d-axis voltage output value u_dAnd outputting the q-axis voltage as an output value u_qRegulating voltage value with the q axisMaking difference to obtain q-axis voltage command valueOutputting the d-axis voltage to a value u_dRegulating voltage value with the d-axisMaking difference to obtain d-axis voltage command value

S430, commanding value through the q-axis voltageAnd the d-axis voltage command valueAnd carrying out voltage control on the permanent magnet synchronous motor driving system.

That is to say, the output signal obtained after PR adjustment is decoupled to the d/q axis output voltage signal, so that the given bus voltage of the vector control of the permanent magnet synchronous motor can quickly track the actual bus voltage, and the stable control capability of the permanent magnet synchronous motor driving system is improved.

It can be seen that, in the foregoing procedure, the flux weakening control is turned on, and in order to control entry and exit of the flux weakening state and control rapid stabilization of the flux weakening state, before S410, the method further includes:

s405, determining a maximum output voltage value of the inverter, and calculating the square of the current output voltage of the inverter, wherein the square of the current output voltage is the sum of the squares of the current d-axis voltage and the current q-axis voltage; calculating the square of a weak magnetic voltage threshold according to the maximum output voltage value of the inverter; judging whether the square of the current output voltage is larger than or equal to the square of the weak magnetic voltage threshold value or not; if yes, opening the field weakening, and allowing the d-axis current to enter a field weakening state to execute the step S410;

wherein the maximum output voltage value may be calculated using a first formula, the first formula including:

in the formula, V_maxIs the maximum output voltage value, V_DCIs the bus voltage of the inverter.

Wherein, the square of the weak magnetic voltage threshold can be calculated by adopting the following formula:

in the formula (I), the compound is shown in the specification,is the square of the weak magnetic voltage threshold, V_maxAnd alpha is a weak magnetic voltage coefficient, wherein the maximum output voltage value is alpha. By adjusting the system, the time for entering or exiting the weak magnetic state can be determined, so that the rapid speed can be realizedInto or out of a flux weakening state.

Correspondingly, S410 specifically includes: in the process of carrying out voltage control on the permanent magnet synchronous motor driving system through the q-axis voltage command value and the d-axis voltage command value, calculating the maximum value of the q-axis voltage according to the square of the weak magnetic voltage threshold value and the d-axis voltage command value; judging whether the q-axis voltage command value is larger than the maximum q-axis voltage value; if so, taking the maximum value of the q-axis voltage as the q-axis voltage command value, and otherwise, keeping the q-axis voltage command value unchanged; judging whether the square of the current output voltage of the inverter is smaller than the square of the weak magnetic voltage threshold value or not in real time; and if so, exiting the field weakening state, setting the d-axis current command value to be 0, and stopping performing voltage control on the permanent magnet synchronous motor driving system through the q-axis voltage command value and the d-axis voltage command value.

Wherein the q-axis voltage maximum may be calculated using a second formula, the second formula including:

in the formula, V_qmaxIs the maximum value of the q-axis voltage,is the square of the d-axis voltage command value,is the square of the weak magnetic voltage threshold.

It can be seen that, in this process, whether to enter or exit the field weakening state is judged by the square of the field weakening voltage threshold, and in the field weakening state, the maximum value of the q-axis voltage is calculated by the d-axis voltage command value, and the q-axis voltage command value is limited by the maximum value of the q-axis voltage, that is, the q-axis voltage is suppressed by the d-axis voltage, so as to prevent the q-axis voltage command value from being too high, and realize stable control of the field weakening state.

The invention provides a bus capacitor capacity monitoring method of a permanent magnet synchronous motor driving system, which calibrates a curve relation between a preset ratio and the bus capacitor capacity in advance, and determines the influence degree of different capacity intervals on the operation process of the permanent magnet synchronous motor driving system, wherein the preset ratio is the ratio between the minimum value of bus voltage and the peak value of the bus voltage, namely the ratio between the minimum value of the bus voltage and the peak value of the bus voltage is adopted to represent the change trend of the minimum value of the bus voltage, so that the influence of factors such as commercial power change on the minimum value of the bus voltage is reduced. And the motor keeps the rated rotating speed in the calibration process, and the influence of the change of the rotating speed of the motor on the minimum value of the bus voltage can be reduced. After the relevant data is calibrated, in an actual application scene, after the motor continuously works for a period of time, whether the rotating speed of the motor is near the rated rotating speed is judged, and the rotating speed of the motor is adjusted to the rated rotating speed only when the rotating speed of the motor is near the rotating speed of the motor, so that the influence of the monitoring process of the bus capacitor on the normal work of the motor is reduced. The method comprises the steps of monitoring the minimum value of the current bus voltage, calculating the current ratio, determining the corresponding current capacity in the curve relation calibrated in the prior art, and accordingly determining the capacity interval corresponding to the bus capacitor, knowing the reduction degree of the bus capacitor and the influence of what degree the permanent magnet synchronous motor driving system generates, and further performing corresponding processing and sending corresponding alarm information. The method can distinguish the heavy reduction of the bus capacitor, and also can distinguish the light reduction and the medium reduction, so that corresponding treatment can be carried out before the permanent magnet synchronous motor driving system is damaged, for example, before the heavy reduction, the bus capacitor is declared to be maintained, and the bus capacitor is replaced, so that the permanent magnet synchronous motor driving system is prevented from being out of order after the bus capacitor enters a heavily reduced capacity interval.

The embodiments in the present specification are described in a progressive manner, and the same and similar parts among the embodiments are referred to each other, and each embodiment focuses on the differences from the other embodiments. In particular, as for the apparatus embodiment, since it is substantially similar to the method embodiment, the description is relatively simple, and for the relevant points, reference may be made to the partial description of the method embodiment.

Those skilled in the art will recognize that, in one or more of the examples described above, the functions described in this disclosure may be implemented in hardware, software, hardware, or any combination thereof. When implemented in software, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium.

The above-mentioned embodiments, objects, technical solutions and advantages of the present invention are further described in detail, it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention, and are not intended to limit the scope of the present invention, and any modifications, equivalent substitutions, improvements and the like made on the basis of the technical solutions of the present invention should be included in the scope of the present invention.