JP2015233372A - Control method of multi-coil ac motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control method of a multi-coil motor which prevents a current from being varied between coils.SOLUTION: First and second coils (3 and 4) of a multi-coil AC motor (1) include first and second inverter circuits (22 and 30) and first and second currents in dq coordinates are detected in the coils. When a voltage command in the dq coordinates is given, the voltage command is converted into phase voltages of phases of an AC voltage, such that the first inverter circuit (22) is controlled. On the other hand, the second inverter circuit (30) is controlled in such a manner that the current of the second coil is matched with the first current. Namely, a deviation of the second current relative to the first current is obtained, a compensation voltage in the dq coordinates is calculated from the deviation and added to the voltage command, thereby obtaining a compensated voltage command. The compensated voltage command is converted into the phase voltages of the phases of the AC voltage, thereby controlling the second inverter circuit (30).

Description

  The present invention relates to a method for controlling a multi-winding AC motor having a plurality of windings.

  In an AC motor, for example, a three-phase AC motor, U-phase, V-phase, and W-phase coils are provided in a fixed stator. The coils composed of the U phase, V phase, and W phase are grouped into three, and the respective windings are connected and arranged at an angle of 120 degrees. In the case of an AC motor having a large capacity, a plurality of sets of such coils are provided. For example, in the case of a six-slot three-phase AC motor, two sets of one set of coils consisting of U-phase, V-phase, and W-phase are provided, and in the case of a nine-slot three-phase AC motor, three sets are provided. Yes. Since one set of windings is provided for one set of coils, two sets and three sets of windings are provided for a 6-slot and 9-slot three-phase AC motor. Such an AC motor is called a multi-winding AC motor or a multi-winding AC motor.

  The multi-winding AC motor is driven by the same number of inverter circuits as the number of windings, and the AC voltage is supplied by controlling a plurality of inverter circuits. FIG. 2 shows a conventional example of a control device for a multi-winding AC motor. In this conventional example, the multi-winding AC motor 51 is composed of two sets of windings of first and second windings 52 and 53, and each winding is Y-connected. For these first and second windings 52 and 53, first and second inverter circuits 55 and 56 are provided to supply a three-phase AC voltage comprising a U phase, a V phase and a W phase. The AC motor 51 is driven. Although the first and second inverter circuits 55 and 56 can be controlled by various control methods, the control device 58 shown in FIG. 2 is a device that is controlled by a relatively simple control method. is there. The control device 58 includes a first inverter circuit 55 and includes a master control unit 60 that controls the first inverter circuit 55 and a slave control unit 61 that includes and controls the second inverter circuit 56. A target value of the rotational speed of the multi-winding AC motor 51 required from the outside, that is, a speed command is given to the master control unit 60. In the master control unit 60, the speed command is processed by the speed controller 63, and a current command required to realize this is calculated. By the way, the multi-winding motor 51 is provided with an encoder 64, and the encoder 64 measures an actual value of the rotational speed, that is, an actual speed. This actual speed is also input to the speed controller 63. Accordingly, the speed controller 63 calculates the current command so that the deviation between the speed command and the actual speed becomes small. This current command is a current command in the dq coordinate, and a q-axis current for generating torque and a d-axis current for generating magnetic flux are calculated. The current command calculated in this way is input to the current controller 65. By the way, the current sensor 66 is provided in at least two phases on the three-phase voltage line output from the first inverter circuit 55 so that the U-phase, V-phase, and W-phase currents are detected. Yes. These are the phase currents of the first winding 52. These phase currents are converted into currents in the dq coordinate based on the rotational position of the encoder 64 in the current detector 67 of the master control unit 60. That is, it is the current of the first winding 52. Such a current is also input to the current controller 65. The current controller 65 calculates the voltage command in the dq coordinate so as to realize the given current command and reduce the deviation between the current command and the current, and sends the voltage command to the PWM generator 68. The PWM generator 68 converts the voltage command in the dq coordinate into phase voltages in the U phase, V phase, and W phase, and performs PWM conversion to obtain a PWM control signal. The first inverter circuit 55 is controlled by this PWM control signal. A three-phase AC voltage is generated by the first inverter circuit 55 and is supplied to the first winding 52. On the other hand, the voltage command generated by the current controller 65 of the master control unit 60 is also sent to the PWM generator 70 of the slave control unit 61. The PWM generator 70 converts the voltage command in the dq coordinate into phase voltages in the U phase, the V phase, and the W phase, and performs PWM conversion to obtain a PWM control signal. The second inverter circuit 56 is controlled by this PWM control signal. A three-phase AC voltage is generated by the second inverter circuit 56 and supplied to the second winding 53.

JP 2007-244209 A

  Patent Document 1 proposes a control device for controlling a multi-winding AC motor by another control method. The control device described in Patent Document 1 is also composed of a master control unit and a slave control unit, and an AC voltage generated by each inverter circuit of the master control unit and the slave control unit is a multi-winding AC motor. The first and second windings are supplied. In the control device of this document, the PWM carrier carrying the PWM control signal is synchronized by the master control unit and the slave control unit. As a result, the PWM control signals applied to the inverter circuits of the master control unit and the slave control unit can be substantially completely synchronized.

  When the multi-winding AC motor is controlled, it can be controlled by the relatively simple conventional control device described in FIG. 2 or can be controlled by the control device described in Patent Document 1. However, there are also problems to be solved. Specifically, there is a problem that current imbalance occurs between the windings and deterioration tends to proceed in a specific winding, or performance cannot be obtained. This will be explained. Each winding of a multi-winding AC motor is manufactured so that the electrical and magnetic characteristics are almost equal, but these characteristics are not necessarily equal. For example, there is a slight difference in resistance. In addition, since the inverter circuit that supplies an AC voltage to each of such windings has a slight difference in the performance of the switching element, the performance of all the inverter circuits is slightly different. By the way, in the multi-winding AC motor, the coils of the respective windings are magnetically coupled to each other and interfere with each other. That is, interference inductance works. Then, the control for the predetermined winding affects the control for the other windings. As described above, there is a slight difference in the electrical and magnetic characteristics of each winding, and there is also a slight difference in the performance of the inverter circuit. However, the current of each winding of the multi-winding AC motor is slightly different. However, in practice, it is difficult to control all inverter circuits equally due to the influence of the interference inductance, so that the difference in current between the windings cannot be ignored. That is, current variation between the windings inevitably occurs. If it does so, deterioration will advance early in a specific coil | winding, and it will become easy to break down a multiwinding AC motor. Also, the expected performance cannot be obtained. Therefore, for example, it is conceivable to evaluate the influence of the interference inductance and control the AC voltage so as to cancel this influence. This is because an increase in current variation can be suppressed, and such a problem is almost solved. By the way, various control methods for canceling the influence of such interference inductance have been proposed. However, in either method, it is necessary to accurately measure the interference inductance or complicated calculation is required, and the control device becomes expensive. That is, it is difficult to adopt a control method that cancels the influence of interference inductance. Now, considering the current variation between windings in detail, when driving a multi-winding AC motor at a high frequency, the influence of the interference inductance is large, but the current variation state changes at a high speed, so it is long. In the time accumulated state, the current variation between the windings can be ignored. That is, there is almost no problem that the progress of deterioration concentrates on a specific winding, and the expected performance can be obtained in a multi-winding AC motor. On the other hand, when the multi-winding AC motor is driven at a low frequency, the influence of the interference inductance is relatively small, but the state of current variation continues for a relatively long time. Then, the progress of deterioration is concentrated on a specific winding. And the expected performance cannot be obtained.

  An object of the present invention is to provide a control method for a multi-winding AC motor that solves the above-described problems, and specifically, when driving a multi-winding AC motor at a low frequency. Another object of the present invention is to provide a control method for a multi-winding AC motor in which the progress of deterioration does not concentrate on a specific winding, the multi-winding AC motor is less likely to fail, and the expected performance can be obtained. .

  The present invention is configured as a control method for a multi-winding AC motor, and first to n-th inverter circuits are provided in each of the first to n-th windings of the multi-winding AC motor. The first to n currents, which are currents in the dq coordinate, are detected for each of the first to n windings. When a voltage command in the dq coordinate is given, the first inverter circuit is controlled by a PWM control signal obtained by converting the voltage command into a phase voltage of each phase of the AC voltage and performing PWM conversion. On the other hand, the other inverter circuits, that is, the second to n-th inverter circuits are controlled so that the current of the winding to be supplied with the voltage coincides with the first current. Specifically: When m is an arbitrary number from 2 to n, the m-th inverter circuit obtains a deviation of the m-th current from the first current, calculates a compensation voltage in the dq coordinate from the deviation, The compensated voltage command is added to obtain a compensated voltage command, the compensated voltage command is converted into a phase voltage of each phase of the AC voltage, and this is controlled by a PWM control signal obtained by PWM conversion.

That is, in order to achieve the above object, the first aspect of the invention controls the first to n inverter circuits based on the voltage command in the dq coordinate, and the first to n windings of the multi-winding AC motor. When the AC voltage is supplied to each of the wires to drive the multi-winding AC motor, the first to n currents in the dq coordinate are detected for each of the first to n windings, and the first For the inverter circuit 1, the voltage command is converted into a phase voltage of each phase of the AC voltage, and this is controlled by a PWM control signal obtained by PWM conversion, and m is an arbitrary number from 2 to n. For the m-th inverter circuit, a deviation of the m-th current with respect to the first current is obtained, a compensation voltage in the dq coordinate is calculated from the deviation, and the compensation voltage is added to the voltage command. Then compensate the voltage finger And converting the compensated voltage command into a phase voltage of each phase of an AC voltage, and controlling this by a PWM control signal obtained by PWM conversion. It is configured as a control method.
According to a second aspect of the present invention, in the control method of the first aspect, a current command in a dq coordinate is calculated from a speed command given from outside and a rotational speed detected in the multi-winding AC motor, The current command is calculated from a current command and the first current, and is configured as a control method for a multi-winding AC motor.

  As described above, according to the present invention, the first to n inverter circuits are controlled based on the voltage command in the dq coordinate, and the AC voltage is supplied to each of the first to n windings of the multi-winding AC motor. The multi-winding AC motor is driven by the control method of the multi-winding AC motor. Then, the first to n currents which are currents in the dq coordinate are detected for each of the first to n windings. In addition, the first inverter circuit is controlled by a PWM control signal obtained by converting the voltage command into a phase voltage of each phase of the AC voltage and performing PWM conversion. Therefore, at least the control of the first inverter circuit is the same as the control of a general multi-winding AC motor. However, according to the present invention, when m is an arbitrary number from 2 to n, the m-th inverter circuit obtains the deviation of the m-th current from the first current, and the compensation voltage in the dq coordinate is obtained from the deviation. Calculate and add the compensation voltage to the voltage command to obtain a post-compensation voltage command, convert the post-compensation voltage command to a phase voltage of each phase of the AC voltage, and obtain a PWM control signal obtained by PWM conversion It is configured to be controlled by. That is, the control of the second to n-th inverter circuits implements control specific to the present invention. This control results in the currents in the second to nth windings being equal to the current in the first winding. That is, variation in current between windings is suppressed, and it is possible to prevent the progress of deterioration from concentrating on a specific winding, thereby making it difficult for a multi-winding AC motor to fail. The multi-winding AC motor has the expected performance.

It is a block diagram which shows the control method of the multiwinding AC motor which concerns on embodiment of this invention. It is a block diagram which shows the control method of the conventional multiwinding AC motor.

  Embodiments of the present invention will be described below. The control method for a multi-winding AC motor according to the present embodiment is intended for a multi-winding AC motor having two or more sets of windings. The multi-winding AC motor provided will be described as an object.

  A multi-winding AC motor 1 according to the present embodiment is an AC motor driven by a three-phase AC voltage, and includes first and second windings 3 and 4 as shown in FIG. Yes. In other words, the multi-winding AC motor 1 is a 6-slot motor in which two sets of U-phase, V-phase, and W-phase coils are provided on the stator. Windings 3 and 4 are provided. The multi-winding AC motor 1 is provided with an encoder 6 so that the rotation angle is detected. The U-phase, V-phase, and W-phase voltage lines constituting the first winding 3 are provided with current sensors 16 on at least two-phase voltage lines. As a result, phase currents can be detected for at least two phases, and the U, V, and W phases are Y-connected, so the remaining one phase current can be calculated easily from the phase currents of the other phases. it can. That is, the phase current can be detected substantially. Similarly, the U, V, and W phase voltage lines constituting the second winding 4 are also provided with current sensors 17 in at least two phase voltage lines, whereby the phase current of each phase is It can be detected. The current sensors 16 and 17 may be provided for all three phases.

  Such a multi-winding AC motor 1 according to the present embodiment is driven by the control device 8 according to the present embodiment. The control device 8 includes a master control unit 10 that controls the three-phase AC voltage supplied to the first winding 3 and a slave control unit 11 that controls the three-phase AC voltage supplied to the second winding 4. . A target rotational speed of the multi-winding AC motor 1, that is, a speed command, is input to the control device 8 from an external device such as a controller (not shown) and input to the master control unit 10. Specifically, the master controller 10 is provided with a speed controller 13 and is input to the speed controller 13. The speed controller 13 is also supplied with the rotational speed of the multi-winding AC motor 1 detected by the encoder 6, that is, the actual speed. The speed controller 13 calculates a target current, that is, a current command so that a speed command that is the target rotation speed can be achieved, but corrects the current command by feedback control so that a deviation between the speed command and the actual speed becomes small. The current command calculated in this way is composed of the d-axis current in the dq coordinate and the target current of the q-axis current. That is, the command is composed of a q-axis current for generating torque and a d-axis current for generating magnetic flux. The current controller 15 of the master control unit 10 receives such a current command input. The current controller 15 also receives a first current input from the current detector 19. The first current is a current flowing through the first winding 3, and the current detector is based on the U-phase, V-phase, and W-phase phase currents detected by the current sensor 16 and the rotation angle detected by the encoder 6. 19 is converted into dq coordinate current. That is, the first current is an actually measured current flowing through the first winding 3 and can be said to be a current represented by dq coordinates. The current controller 15 calculates the voltage command in the dq coordinate so that the input current command is realized, but corrects the voltage command by feedback control so that the deviation of the first current with respect to the current command becomes small. The voltage command calculated in this way is input to the PWM generator 21. The PWM generator 21 converts the voltage command represented by the dq coordinates to obtain phase voltages of the U phase, V phase, and W phase, and PWM converts them to obtain a PMW control signal. The first inverter circuit 22 of the master control unit 10 is controlled by the obtained PWM control signal. Then, a three-phase AC voltage is generated from the first inverter circuit 20 and supplied to the first winding 3.

  In the control device 8 according to the present embodiment, the voltage command of the dq coordinate calculated by the current controller 15 of the master control unit 10 is also sent to the slave control unit 11, and the slave control unit 11 is also based on this voltage command. Thus, the AC voltage supplied to the second winding 4 is controlled. However, the slave control unit 11 performs control so that the current flowing through the second winding 4 is equal to the current flowing through the first winding 3. Specifically, the compensation voltage is added to the voltage command, and control is performed according to the corrected command. First, the compensation voltage will be described. The compensation voltage is added to the voltage command for the purpose of making the current of the second winding 4, ie, the second current, coincide with the current of the first winding 3, ie, the first current. This is a voltage for adjusting this, and is a voltage represented by dq coordinates. This compensation voltage is calculated in the current deviation compensation calculator 25 of the slave control unit 11. Prior to the calculation, the current deviation compensation calculator 25 receives the first and second currents. Since the first current is calculated by the current detector 19 of the master control unit 10 as already described, this input is received. On the other hand, the second current is calculated by the current detector 27 of the slave control unit 11. That is, the current detector 27 reads the three-phase current of the second winding 4 from the current sensor 17 and converts the current into the current in the dq coordinate based on the rotation angle obtained from the encoder 6 to obtain the second current. . The current deviation compensation calculator 25 calculates a deviation for the input first and second currents. That is, the deviation of the d-axis current and the deviation of the q-axis current are calculated. A compensation voltage is then calculated based on this deviation. For example, the compensation voltage may be obtained by multiplying the deviation of the first and second currents by a predetermined constant, or the time difference of the deviation of the first and second currents is integrated, and the predetermined constant is added to the integrated value. The compensation voltage may be obtained by multiplication. In response to the input of the voltage command from the current controller 15 of the master controller 10 and the compensation voltage from the current deviation compensation calculator 25, the adder 24 adds these to obtain a compensated voltage command. In the slave control unit 11, the PWM generator 28 converts the post-compensation voltage command to obtain phase voltages of the U-phase, V-phase, and W-phase, and PWM converts them to obtain a PMW control signal. The second inverter circuit 30 of the slave control unit 11 is controlled by the obtained PWM control signal. Then, a three-phase AC voltage is generated from the second inverter circuit 30 and supplied to the second winding 4. Since the slave control unit 11 performs the control as described above, the second current flowing through the second winding 4 is controlled so as to coincide with the first current flowing through the first winding 3. That is, the variation in current between the windings 3 and 4 is suppressed.

  In the above description, the multi-winding AC motor 1 composed of two sets of windings 3 and 4 has been described as an example. However, even a multi-winding AC motor having three or more sets of windings is controlled similarly. be able to. When three or more windings are provided, the first winding is controlled by the master control unit 10, and the other windings, that is, the second, third,... Windings are controlled. Is controlled by the slave control unit 11. In this way, as can be easily understood by those skilled in the art, the second, third,... Currents that are the currents of the second, third,... Windings are the currents of the first winding. Control is made to match the first current.

1 Multiwinding AC Motor 3 First Winding 4 Second Winding 6 Encoder 8 Control Device 10 Master Control Unit 11 Slave Control Unit 13 Speed Controller 15 Current Controller 16 Current Sensor 17 Current Sensor 19 Current Detector 21 PWM generator 22 first inverter circuit 24 adder 25 current deviation compensation calculator 27 current detector 28 PWM generator 30 second inverter circuit

Claims (2)

The first to n inverter circuits are controlled based on the voltage command in the dq coordinate, and an AC voltage is supplied to each of the first to n windings of the multi-winding AC motor to drive the multi-winding AC motor. When
Detecting first to n currents which are currents in dq coordinates for each of the first to n windings;
For the first inverter circuit, the voltage command is converted into a phase voltage of each phase of the AC voltage, and this is controlled by a PWM control signal obtained by PWM conversion.
When m is an arbitrary number from 2 to n, for the m-th inverter circuit, a deviation of the m-th current from the first current is obtained, and a compensation voltage in a dq coordinate is calculated from the deviation, The compensated voltage command is obtained by adding the compensation voltage to the voltage command, the compensated voltage command is converted into a phase voltage of each phase of the AC voltage, and this is controlled by a PWM control signal obtained by PWM conversion. A control method for a multi-winding AC motor, characterized in that:   2. The control method according to claim 1, wherein a current command in a dq coordinate is calculated from a speed command given from outside and a rotational speed detected in the multi-winding AC motor, and the current command and the first current are calculated. The method for controlling a multi-winding AC motor is characterized in that the current command is calculated from

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