TWI420799B - Control system of three - phase AC induction motor driver and its field weakening control method - Google Patents

Description

Control system of three-phase AC induction motor driver and weak magnetic control method thereof

The invention relates to a control system of a three-phase AC induction motor driver and a weak magnetic control method thereof, in particular to a three-phase AC induction motor driver with weak magnetic control above a rated speed.

The conventional three-phase AC induction motor drive device mainly generates the stator current on the q-axis coordinate, and the magnetic flux generated by the three-phase AC induction motor rotor flux interacts with the d-axis coordinate. The function is to achieve the vector control of the three-phase AC induction motor; and the back electromotive force generated by the three-phase AC induction motor is proportional to the rotational speed. When the rotational speed rises, the voltage supplied by the DC link capacitor is insufficient to overcome the three-phase AC induction motor. When the back electromotive force is generated, the three-phase AC induction motor has a limitation on the range of high-speed operation. Therefore, if the three-phase AC induction motor is operated at a higher speed, generally, the driver will adjust the d-axis. The current is used to reduce the rotor flux, thereby overcoming the back electromotive force generated at high speeds and increasing the operating speed range. This method is also known as field weakening control; however, the known field weakening control law (vector control inverter control) Automatic parameter adjustment method, Republic of China Patent No. 84113378) is based on the data of the rotational speed to generate a command inversely proportional to the d-axis rotor flux or current value, but Under the prior art, the maximum output voltage of the driver and the limitation condition of the rated current of the motor are not considered, so that the utilization of the maximum DC link voltage and the maximum output torque are not guaranteed to be effectively achieved; The law of magnetic control (control method of induction electric motor, Republic of China Patent No. 94120978) uses the magnitude of the calculated back electromotive force to judge whether the motor speed exceeds the rated rotation. The weak magnetic control is performed by this speed, but in this prior art, the weak magnetic control is required to perform complicated mathematical operations, and the mathematical formula calculated under the prior art is affected by the change of the motor parameters. Therefore, the well-known weak magnetic control law (inductive electric control method, Republic of China Patent No. 94120978) cannot achieve the maximum output torque; in addition, the conventional technology does not consider the three-phase AC induction motor at the maximum slip. There is a limit condition for the maximum escape torque at the differential speed, so it is impossible to consider the judgment and operation of entering the second weak field of the higher speed in the weak magnetic interval.

It can be seen that there are still many shortcomings in the above-mentioned methods of use, which is not a good design, but needs to be improved.

In view of the shortcomings derived from the above-mentioned methods, the inventor of the present invention has improved and innovated, and after years of painstaking research, he finally succeeded in completing the control system of the three-phase AC induction motor driver and its weak magnetic control method. .

The object of the present invention is to provide a control system for a three-phase AC induction motor driver and a weak magnetic control method thereof, which can automatically achieve the utilization of the maximum DC link voltage, so that the three-phase AC induction motor can automatically exceed the rated speed. The motor is detected as entering the first weak magnetic zone or the second weak magnetic zone at a higher speed.

A secondary object of the present invention is to provide a control system for a three-phase AC induction motor driver and a field weakening control method thereof, which can be applied to different speeds of different weak magnetic sections and can provide a large output. Torque capability to solve technical problems and potential shortcomings in the prior art.

A control system for a three-phase AC induction motor driver and a weak magnetic control method thereof, wherein the control system comprises a driver control module, a weak magnetic control module, an AC power supply, and a power loop module , a current sensing module and an AC motor module, the invention utilizes the switching period of the pulse width modulation control of the AC motor frequency converter and its inverter control, analyzes and obtains the effective switching time and the difference, and is weak The magnetic control module (the difference between the effective switching time and the (T _A + T _B ) obtained by the inverter control analysis) instantly generates an adapted magnetizing current command (corrected value of the d-axis current command) to achieve effective amplification. The utilization of the DC link voltage, and the d-axis current value can be automatically adjusted to achieve the weak magnetic control, so that the AC motor module has a larger output when the rated motor speed exceeds the rated speed and operates at different rotational speeds in different weak magnetic fields. torque capacity; the use of the present invention is also the use of a space vector modulation rule (the effective switching time of the effective voltage vector T _a, T _B), to analyze whether the use of the large linear Link capacitor voltage, and when _{T A + T B = T Z} , which is equal to the switching period T _Z pulse width modulation control (command for achieving the amplification efficiency of the DC link capacitor voltage), and represents the current DC The voltage utilization of the chain capacitor is larger than that of the space vector modulation method in the linear region; in addition, if the motor continues to increase the speed in this case, in addition to continuing to meet the T _A + T _B = T _Z condition, it must be used. The technique of field weakening control can be achieved; in addition, when the voltage vector value of T _A + T _B = T _Z is greater than the voltage vector value of the maximum linear region, it means that the inverter output voltage space vector trajectory will operate at the maximum limit. Hexagonal, so when the stator current value is limited by the rated current, it means that the three-phase AC induction motor operates under the conditions of maximum voltage and maximum current, and this is the three-phase AC induction motor operating at the first weakening The condition of the maximum output torque under the zone; and when the speed continues to increase and the slip speed of the three-phase AC induction motor reaches the maximum slip speed of the motor, this represents a three-phase AC induction motor In the second weak magnetic zone, if the motor is operated at the maximum voltage and the maximum current obtained under the maximum slip speed, this is the maximum output turn of the three-phase AC induction motor operating under the second weak magnetic zone. The condition of the moment.

Please refer to FIG. 1A and FIG. 1B. FIG. 1 is a structural diagram and a circuit diagram of a control system for a three-phase AC induction motor driver and a weak magnetic control method thereof. The system includes: a driver control module 1 and a weak magnetic field. The control module 2, the power circuit module 4, the current sensing module 5 and the AC motor module 6 are connected, and the driver control module 1 includes adders 1011, 1012, 1013, subtractors 1021, 1022. 1023, d-axis current controller 103, speed controller 104, q-axis current controller 105, limiter 106, voltage decoupling compensator 107, coordinate converters 1081, 1082, space vector modulator 109, rotor The speed estimator 110, the counter 111, the slip speed estimator 112, and the integrator 113, the driver control module 1 uses the encoder 602 to obtain the position information of the three-phase AC induction motor; and the field weakening control module 2 And the drive control module 1 is connected, and the field weakening control module 2 includes: (1) a limiter 201 to limit the correction value of the magnetic flux current command to a negative value range and limit three-phase AC induction Motor d-axis rotor flux or d-axis current will not be less than zero A value close to zero; (2) weakening current controller 202 for generating a correction value of the magnetic flux current command; (3) a subtractor 203, to the pulse width modulation control of the switching period T _Z subtracts The filtered effective switching time sum (T _A + T _B ); (4) a low pass filter 204 for filtering out the effective switching time and the high frequency signal of (T _A + T _B ); (5) Adder 2051, 2052, the adder 2051 is used to add the effective switching times (T _A , T _B ) of the effective voltage vectors in the space vector modulation law; and the adder 2052 is to set the d-axis rated current value. Adds the correction value i _{ds _ fw} of the d-axis current command and serves as a true d-axis current command reference value. (6) The maximum q-axis current command calculator 206 analyzes and calculates the maximum q-axis current command value used.

The field weakening control module 2 filters the effective switching time of the effective voltage vector of the space vector modulator 109 and (T _A + T _B ), and filters the high frequency signal through the low pass filter 204. The subtracter 203 performs a subtraction comparison with the switching period T _{Z of the} pulse width modulation control, and then performs adjustment by the field weakening current controller 202, and cooperates with the limiter 201 to ensure that when T _A + T _B When =T _Z , the output of the limiter 201 is a negative value i _{ds _ fw} as a correction value of the d-axis current command (the d-axis current is not limited by the adjustment of the field weakening current controller to make the rotor magnetic Passing less than zero or close to zero); and the output of the limiter 201 is again via the adder 2052 and the d-axis rated current value Add as a true d-axis current command reference An AC power source 3 is connected to the power circuit module 4 and is an input power source; a power circuit module 4 is connected to the driver control module 1, the AC power source 3, the current sensing module 5, and the AC The motor module 6 is connected, and the power circuit module 4 includes a rectifier module 401 (acceptable input of single-phase or three-phase mains power), a DC link capacitor 402 (for input of the frequency conversion module), and frequency conversion The module 403 includes a switching element capable of providing a three-phase pulse voltage output and is coupled to an input side of the three-phase AC induction motor, and a driving signal is controlled by the driver control module 1 to control switching of the switching element in the variable frequency module. Therefore, when the energy of the mains terminal is input by the AC power source 3, the AC power is rectified into a DC power with chopping through the rectifying module 401, and then filtered by the DC link capacitor 402, and the control signal is output to the frequency conversion by the space vector modulator 109. The module 403 drives the switching component to convert the DC energy; the current sensing module 5 includes three current sensors 501, 502, 503, and the current sensing module 5 and the driver control module 1 are powered back. Module 4 and the AC motor 6 with interfacing modules, responsible for the feedback of the motor phase currents i _u, i _v and i _w; a module AC motor 6, the drive system and the control module 1, the power circuit module 4, the current sensing module 5 is connected, wherein the AC motor module 6 comprises a three-phase AC induction motor 601 and an encoder 602 (coupled on the same rotating shaft), wherein the encoder 602 can be incremental The encoder, the driver control module 1 generates the stator current on the q-axis coordinate via the speed controller 104 according to the rotor position and/or speed fed back by the encoder 602, and the established magnetic flux and d- The three-phase AC induction motor rotor magnetic flux interaction on the shaft coordinates realizes the vector control of the three-phase AC induction motor; the driver control module 1 can convert the pulse wave information of the encoder 602 into an AC motor through the counter 111. The rotor angle, the rotor angle is obtained by the rotor speed estimator 110 to obtain the speed of the motor. Therefore, the motor speed is also used as feedback information by the speed controller 104, and the motor rotor speed is obtained by the adder 1013. Differential speed The estimator 112 uses the slip speed analyzed by the d-axis current and the q-axis current, and the d-axis current value is determined by the field weakening control architecture, and the maximum current limiting condition is determined by the different weak magnetic interval. The different q-axis current limit value is determined), and then the integrator 113 can obtain the synchronous rotation angle; and the synchronous rotation angle can be used as the coordinate conversion of the coordinate converters 1081 and 1082, when the current sensors 501, 502, 503 are returned. Transmitting the three-phase currents i _u , i _v and i _{w of the} motor and converting the variables of the three-phase stationary coordinates into the variables of the two-phase synchronous rotating coordinates through the coordinate converter 1082 and And the subtractor 1021, 1023 is subtracted from the current command, and then adjusted by the d-axis current controller 103 and the q-axis current controller 105, and the two current controllers (d-axis current controller) The output of the 103 and q-axis current controller 105) plus the compensation value of the voltage decoupling compensator 107 (transmitted through the adders 1011, 1012), and then the coordinates of the two-phase synchronous rotating coordinates by the coordinate converter 1081 and Converting to a variable of a two-phase stationary coordinate to obtain a voltage space vector command of the space vector modulator 109; and in a full speed mode, a rotational speed ω _{r of the} three-phase AC induction motor and a rotational speed command The adjustment is made via the subtractor 1022 and through the speed controller 104, and the output of the speed controller 104 is coupled to the limiter 106, which can be used as a limit for the q-axis current command and the output torque, with respect to the limit value of the limiter. It can be calculated by the maximum q-axis current command calculator 206. In addition to avoiding the driver or motor operating above the rated current, the maximum current value can also be limited according to the conditions under different weak magnetic conditions.

Please refer to FIG. 2A, FIG. 2B and FIG. 2C, which are the voltage space vector diagram, the voltage vector synthesis diagram and the pulse wave of the space vector modulation of the control system of the three-phase AC induction motor driver and the weak magnetic control method thereof. The formal diagram, in which Figure 2A shows the relationship between the voltage space vector command and the sector, the relationship is the maximum limit range and the maximum linear range of the voltage vector of the space vector modulation law, and when T _A +T _{When B} = T _Z , it means that the voltage vector is currently rotating on the hexagonal trajectory of the maximum limit range, so the voltage utilization is larger than the circular interval of the maximum linear range; and Figure 2B shows that the voltage space vector is at Schematic diagram of the first interval (Sector 1); additionally, the switching timing of the voltage vector synthesized in Fig. 2B and the schematic diagrams of T _A , T _B , and T _Z , wherein T _A and T _B are effective switching times, respectively, and T _Z is The switching period of the pulse width modulation control, and T _Z =1/(KT _s ), where T _s is the sampling period of the pulse width modulation control, and K is a constant.

Please refer to FIG. 3 , which is a flow chart of the control system of the three-phase AC induction motor driver and the field weakening control method thereof. The steps are as follows: 1. Using the effective switching time of the effective voltage vector and (T _A + T _B ), after filtering the high frequency signal through the low pass filter, subtracting from the switching period T _Z of the pulse width modulation control; 2. generating a d-axis current command through a weak magnetic current controller Correct the value and limit its value; 3. This has a limited d-axis current command correction value (by the limiter to ensure that when T _A + T _B = T _Z , the output of the limiter is a negative value i _{ds _ fw} , as the correction value of the d-axis current command, and limit the d-axis current not to be adjusted by the field weakening current controller so that the rotor flux is less than zero or close to zero) and then the original d-axis current command Add by adder as a true d-axis current command reference ; 4. Use this d-axis current command value The maximum q-axis current command value under different weak field _conditions is limited with the maximum slip speed ω _{sl_MAX} (the calculation of the maximum q-axis current command value is also different under different weak field conditions).

Please refer to FIG. 4 , which is a flowchart of the implementation of the control system of the three-phase AC induction motor driver and the maximum q-axis current command calculator of the field weakening control method thereof. The steps are as follows: 1. Firstly, the effective voltage vector is determined to be effective. Whether the switching time sum (T _A + T _B ) is greater than or equal to the switching period (T _Z ) of the pulse width modulation control, the judgment analysis is as follows: (1) If T _A + T _{B is} greater than or equal to T _Z , then enter The motor speed is higher than the rated speed; (2) If T _A + T _{B is} less than T _Z , the motor speed is lower than the rated speed (the motor is operated in the constant torque range and the maximum q-axis current command) The value is determined by the rated current of the motor and its value is equal to 2. When the motor speed is higher than the rated speed, first analyze the maximum q-axis current command value (obtained by the motor rated current) , then analyze the maximum q-axis current command value (Analyzed by the maximum slip speed); 3. Next, judge the q-axis current command value calculated by using different conditions in the weak magnetic interval: (1) greater than or equal to , which means that the current q-axis current command limit value is determined by the maximum slip speed (representing the motor operation under the second weak magnetic zone, so the maximum q-axis current command value is ); (2) if Less than , indicating that the limit value of the q-axis current command is determined by the rated current (representing that the motor operation is still operating under the first weak magnetic zone, so the maximum q-axis current command value is ).

Please refer to FIG. 5 , which is a schematic diagram of the simulation result of the control system of the three-phase AC induction motor driver and the weak magnetic control method thereof. When the rotor speed of the three-phase AC induction motor reaches the rated speed (1.0 pu) or more, the T _A at this time When +T _{B is} increased to T _Z (1.0 pu), the field weakening control will start, that is, the beginning of the first weak magnetic zone; as shown in the figure, the correction value of the d-axis current command i _{ds _ fw} Starts as the speed rises and increases to a negative value, while the d-axis current Then, as the speed rises, it begins to decrease, thereby maintaining the large voltage utilization of the DC link capacitor and overcoming the increase of the back electromotive force of the AC motor. When the rotational speed tends to be stable, the back electromotive force does not change any more, so the d-axis current It will also be stable; in addition, while the speed continues to rise, the limit value of the maximum q-axis current is also limited by the maximum slip speed. Observing the slip speed from the figure, it can be seen that the motor has a response during the acceleration process. Restricted by the maximum slip speed, it means that the motor is running to the second weak magnetic zone, and the motor speed is entering a higher speed state.

The control system of the three-phase AC induction motor driver and the weak magnetic control method thereof provided by the invention have the following advantages when compared with other conventional technologies:

1. The control system of the three-phase AC induction motor driver of the present invention and the weak magnetic control method thereof, the instant application of the adaptive magnetization current command through the weak magnetic control module, thereby effectively utilizing the utilization rate of the DC link voltage, so that the three-phase communication When the induction motor exceeds the rated speed, the motor can be automatically judged to enter the first weak magnetic zone or the second weak magnetic zone at a higher speed.

2. The control system of the three-phase AC induction motor driver of the present invention and the weak magnetic control method thereof can provide a large output torque capability under different rotation speeds of different weak magnetic sections, thereby solving the conventional knowledge. Technical issues and potential shortcomings in technology.

The detailed description of the preferred embodiments of the present invention is intended to be limited to the scope of the invention, and is not intended to limit the scope of the invention. The patent scope of this case.

To sum up, this case is not only innovative in terms of technical thinking, but also able to enhance the above-mentioned multiple functions compared with conventional articles. It should be submitted in accordance with the law in accordance with the statutory invention patents that fully meet the novelty and progressiveness, and you are requested to approve this article. Invention patent application, in order to invent invention, to the sense of virtue.

1‧‧‧Drive Control Module

1011‧‧‧Adder

1012‧‧‧Adder

1013‧‧‧Adder

1021‧‧‧Subtractor

1022‧‧‧Subtractor

1023‧‧‧Subtractor

103‧‧‧d-axis current controller

104‧‧‧Speed Controller

105‧‧‧q-axis current controller

106‧‧‧Restrictor

107‧‧‧Voltage decoupling compensator

1081‧‧‧Coordinate Converter

1082‧‧‧Coordinate Converter

109‧‧‧Space Vector Modulator

110‧‧‧Rotor speed estimator

111‧‧‧ counter

112‧‧‧Slip speed estimator

113‧‧‧ integrator

2‧‧‧Weak magnetic control module

201‧‧‧Restrictor

202‧‧‧ weak magnetic current controller

203‧‧‧Subtractor

204‧‧‧low pass filter

2051‧‧‧Adder

2052‧‧‧Adder

206‧‧‧Maximum q-axis current command calculator

3‧‧‧AC power supply

4‧‧‧Power loop module

401‧‧‧Rectifier Module

402‧‧‧DC link capacitor

403‧‧‧Variable frequency module

5‧‧‧ Current sensing module

501‧‧‧ Current Sensor

502‧‧‧ Current Sensor

503‧‧‧ Current Sensor

6‧‧‧AC motor module

601‧‧‧Three-phase AC induction motor

602‧‧‧Encoder

FIG. 1A is a structural diagram of a control system of a three-phase AC induction motor driver and a weak magnetic control method thereof according to the present invention; FIG. 1B is a control system of a three-phase AC induction motor driver according to the present invention and a weak magnetic control method thereof FIG. 2A is a voltage space vector diagram of a space vector modulation of a control system of a three-phase AC induction motor driver and a field weakening control method thereof; FIG. 2B is a three-phase AC induction motor driver of the present invention; The voltage vector synthesis diagram of the space vector modulation of the control system and its weak magnetic control method; FIG. 2C is the pulse wave form of the space vector modulation of the control system of the three-phase AC induction motor driver and the weak magnetic control method thereof FIG. 3 is a flow chart of a control system of a three-phase AC induction motor driver and a weak magnetic control method thereof for a weak magnetic control method according to the present invention; FIG. 4 is a control system of a three-phase AC induction motor driver and a weak magnetic control method thereof according to the present invention; The flow chart of the implementation of the maximum q-axis current command calculator; and FIG. 5 is a schematic diagram of the simulation result of the control system of the three-phase AC induction motor driver and the weak magnetic control method thereof.

1‧‧‧Drive Control Module

2‧‧‧Weak magnetic control module

3‧‧‧AC power supply

4‧‧‧Power loop module

5‧‧‧ Current sensing module

6‧‧‧AC motor module

Claims (12)

A control system for a three-phase AC induction motor driver includes: a driver control module coupled to a weak magnetic control module, a power loop module, a current sensing module, and an AC motor module, the driver control The module uses the encoder of the AC motor module to obtain information about the position of the AC motor; a weak magnetic control module is connected to the driver control module, and the weak magnetic control module includes a limiter, a field weakening current controller, a subtractor, a low pass filter, an adder, and a maximum q-axis current command calculator, wherein the low pass filter is coupled to the adder and the subtractor, and the low pass filter The device is configured to filter out the high-frequency signal of the effective switching time, and the effective switching time is obtained by adding the effective switching times TA and TB of the effective voltage vectors in the space vector modulation law by the adder; The AC power source is connected to the power circuit module and is an input power source; the power circuit module is connected with the driver control module, the AC power supply, the current sensing module and the AC motor module. A current sensing module includes three current sensors, and the current sensing module is connected with the power control module and the AC motor module of the driver control module, and is mainly responsible for the feedback motor Phase current; an AC motor module is connected with the driver control module, the power circuit module, and the current sensing module; the switching cycle of the pulse width modulation of the AC motor inverter is controlled by the AC motor Control, analyze and obtain the difference between the effective switching time and the instantaneous magnetization current command through the weak magnetic control module to achieve effective utilization of the DC link voltage utilization, so that the intersection When the flow motor module exceeds the rated speed, it has the maximum output torque capability under different speeds of different weak magnetic fields. A control system for a three-phase AC induction motor driver according to claim 2, wherein the subtractor is connected to the limiter by a field weakening current controller, and the subtractor is configured to adjust a pulse width The switching period T _{Z of the} variable control is subtracted from the filtered effective switching time sum (T _A + T _B ), and the field weakening current controller is used to generate a correction value of the magnetic flux (d-axis) current command. The limiter is responsible for limiting the correction value of the magnetic flux (d-axis) current command to a negative interval, and limiting the three-phase AC induction motor d-axis rotor magnetic flux or d-axis current is not less than zero or close to The value of zero. The control system of the three-phase AC induction motor driver according to claim 1, wherein the maximum q-axis current command calculator is mainly used for analyzing and calculating the maximum q-axis current command value used, and according to different weak The condition under the magnetic interval limits the maximum current value. The control system of the three-phase AC induction motor driver according to claim 1, wherein the driver control module comprises an adder, a subtractor, a d-axis current controller, a speed controller, and a q-axis. Current controllers, limiters, voltage decoupling compensators, coordinate converters, space vector modulators, rotor speed estimators, counters, slip speed estimators, integrators. The control system of the three-phase AC induction motor driver according to claim 5, wherein the output of the d-axis current controller and the q-axis current controller plus the compensation value of the voltage decoupling compensator is further The coordinate converter converts the variables of the two-phase synchronous rotating coordinates into the variables of the two-phase stationary coordinates to obtain the voltage space vector command of the space vector modulator. The control system of the three-phase AC induction motor driver according to claim 4, wherein the speed controller is connected to the limiter and the subtractor, and the limit controller of the speed controller output can be used as Q-axis current command and output torque limit, and the speed controller can be based on the speed command To adjust the speed ω _{r of the} three-phase AC induction motor. A field weakening control method for a three-phase AC induction motor driver, the steps comprising: 1) using a valid switching time of the effective voltage vector and (T _A + T _B ), filtering the high frequency signal through a low pass filter, Subtracting from the switching period T _Z of the pulse width modulation control; 2) generating a correction value of the d-axis current command through a field weak current controller and limiting the value thereof; 3) the d-axis current having the limit Command correction value and original d-axis current command Add by adder as a true d-axis current command reference 4) Use this d-axis current command value The maximum q-axis current command value under different weak field _conditions is limited with the maximum slip speed ω _{sl_MAX} . The field weakening control method for a three-phase AC induction motor driver according to claim 7, wherein the correction value of the d-axis current command generated by the field weakening current controller limits the three-phase AC induction motor through the limiter The d-axis rotor flux or d-axis current will not be less than zero or close to zero. The weak magnetic control method of the three-phase AC induction motor driver according to claim 7, wherein the calculation of the maximum q-axis current command value is different under different weak magnetic fields. The weak magnetic control method for a three-phase AC induction motor driver according to claim 7, wherein the switching period of the pulse width modulation control is T _Z =1/(KT _s ), and the T _s is a pulse wave The width modulation controls the sampling period, and K is a constant. The weak magnetic control method for a three-phase AC induction motor driver according to claim 7, wherein the maximum q-axis current command obtained by the maximum slip speed can be used for judging Whether to break into the second weak magnetic zone of high-speed field weakening. A field weakening control method for a three-phase AC induction motor driver according to claim 7, wherein the limit value of the limiter of the q-axis current command is Below the rated speed is obtained by analyzing the rated current of the motor, and entering the first weak magnetic zone above the rated speed is obtained by analyzing the rated current of the motor, and when entering the second weak magnetic zone, the maximum slip speed of the motor is utilized. To analyze and obtain.