JP2010088228A - Motor drive controller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce unevenness in torque caused by distortion of a magnetic field. <P>SOLUTION: A motor drive controller includes a control system which detects a phase current of a multi-phase motor such as a three-phase motor, converts it into two-phase rotational coordinates such as d-axis and a q-axis, and controls a current after conversion to a desired value. A current average value of a DC portion is detected for every control cycle, only a torque ripple frequency component is extracted therefrom, and the extracted torque ripple component is inverted to be added to the desired value of the current after coordinate conversion. As a result, without using harmonic distortion information on the magnetic flux intrinsic to the motor, the torque ripple in generation is detected to reduce the ripple by adjusting an applied current. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to drive control of a motor having a permanent magnet as a rotor, and more particularly to control for suppressing torque unevenness caused by a permanent magnet.

  A motor using a permanent magnet as a rotor does not cause copper loss on the rotor side, so there is an advantage that it becomes a high-efficiency motor. On the other hand, the magnetic field generated by the rotor and stator including the permanent magnet is a smooth sine. It is difficult to make it wavy, and torque ripple occurs.

  A method for reducing torque ripple is disclosed by focusing on the distortion of the magnetic field and flowing a current that cancels the influence of the distortion and has a constant torque (for example, Non-Patent Document 1).

FIG. 6 is a current waveform diagram of current control in a conventional motor control device, and FIG. 7 is an FFT analysis result of torque meter output in each control. The waveform diagram of FIG. 6 (a) shows general sine wave current control, but even in general sine wave current control, there is an influence of distortion of induced voltage, and torque as shown in FIG. 7 (a). Ripple (current frequency) 6th harmonic component is generated. Next, the waveform diagram of FIG. 6B is obtained by controlling so that the current approaches a sine wave, and the distortion of the motor phase current is very small. However, as shown in FIG. 7B, the sixth harmonic, which is a torque ripple, has increased. Further, the waveform diagram of FIG. 6C is a current waveform when the control is performed so that the harmonic current is positively passed and the torque becomes constant based on the fifth-order harmonic distortion of the magnetic field. Although the distortion of the current is larger than that in FIG. 6A, the sixth-order component that is a torque ripple is very small as shown in FIG. 7C (see, for example, Non-Patent Document 1). .
Yoshimoto, Kitajima et al. “Harmonic Current Control of IPMSM” The Institute of Electrical Engineers of Japan, Rotating Machine Study RM-03-50 (announced on July 11, 2003)

  However, in order to realize the technique of the non-patent document, it is necessary to know in advance the degree of distortion of the magnetic field. However, the distortion of the magnetic field varies depending on the structure of the motor, and requires a lot of information in advance.

  The present invention solves the above-described conventional problems, and an object thereof is to provide a motor drive control device capable of suppressing torque fluctuations without knowing the degree of magnetic field distortion in advance.

  In order to solve the above-described conventional problems, the motor drive control device of the present invention drives a multiphase motor by converting a DC power supply or a power supply obtained by rectifying an AC power supply into an arbitrary pseudo multiphase AC by a switching means. In the motor drive control device, the motor drive control device detects the current of the DC section, calculates the current of each phase of the multiphase motor from the control state of the switching means, and based on the calculated current, the rotating coordinate system A control system that converts the converted current information of the rotating coordinate system to a desired value, and detects and detects the average value of the direct current for each control period of the switching means. The desired current value of the rotating coordinate system is controlled so that the frequency component of an integral multiple of the average value excluding the fundamental wave of the current frequency of the multiphase motor decreases.

  As a result, even if there is a harmonic distortion of the magnetic flux, the same power is always generated and the torque can be kept constant. Control can be realized.

  The motor drive control device of the present invention can reduce torque ripple without using a parameter of harmonic distortion unique to the motor, and can realize quietness of equipment.

  A first invention is a motor drive control device for driving a multi-phase motor by converting a DC power source or a power source obtained by rectifying an AC power source into an arbitrary pseudo multi-phase AC by switching means, and the motor drive control device is a DC power source. The current of each phase of the multiphase motor is calculated from the control state of the switching means, converted into current information of the rotating coordinate system based on the calculated current, and the converted rotating coordinate system A control system for controlling the current information to a desired value, detecting an average value of DC current for each control period of the switching means, and a basis for a current frequency of the detected multi-phase motor In this motor drive control device, the desired current value of the rotating coordinate system is controlled so that the integral frequency component excluding the wave decreases.

  As a result, even if there is a harmonic distortion of the magnetic flux, the same power is always generated and the torque can be kept constant. Control can be realized.

  According to a second aspect of the invention, in the motor drive control device of the first aspect of the invention, the multi-phase motor has a phase number of 3, the permanent magnet is included in the rotor, and the rotational coordinate system is a two-phase based on the rotational phase of the permanent magnet. It is a coordinate, and the integer multiple frequency is assumed to be an integer multiple of 6 times the current frequency.

  As a result, the basic torque ripple component can be efficiently suppressed in the most commonly used permanent magnet rotor three-phase motor.

  According to a third aspect of the invention, in the motor drive control device of the first or second aspect of the invention, the amount of electric power for each control cycle obtained by multiplying the direct current value for each control cycle by the DC voltage value in the same section is used. The desired current value of the rotating coordinate system is controlled so that a frequency component that is an integral multiple excluding the fundamental wave of the current frequency of the multiphase motor decreases.

  As a result, the same effect can be produced even when the instantaneous voltage of the DC portion varies greatly from moment to moment, and the DC smoothing circuit can be reduced in size.

  The fourth invention is a method in which the means for detecting the direct current detects the voltage across the resistor inserted in the direct current portion, particularly in the motor drive control device according to any one of the first to third inventions. When the value becomes a certain value or more, the drive control is stopped.

  Thereby, the detection means for stopping protection and the detection means for control can be shared, and the apparatus can be simplified.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 is a diagram illustrating an overall configuration of a motor drive control device according to a first embodiment of the present invention. In FIG. 1, a three-phase bridge circuit 4 is connected to a DC power source 5, and the motor 1 is connected to the output of the three-phase bridge circuit 4. Here, the motor 1 is a three-phase motor and includes a permanent magnet in the rotor. In the drive control of the motor 1, the current to the motor 1 is detected by the current detector 6 in the direct current portion, the rotation state of the motor 1 is detected by the rotation detector 2, and the generation accuracy of the voltage applied to the motor 1 is improved. Therefore, the drive of the motor 1 is realized by detecting the voltage of the DC power source 5 and giving a control signal to the three-phase bridge circuit 4 by the control circuit 3 based on the result.

  The operation and action of the control circuit 3 in the motor drive control device configured as described above will be described.

  FIG. 2 is a block diagram showing an operation flow in the control circuit 3. In FIG. 2, the speed command ω * input from the outside is compared with the speed ω obtained by differentiating the detected phase obtained by the rotation phase detector 2 by the comparison circuit 202. The comparison result is sent as a speed error to the PI compensation means 203 for speed control. The PI compensation unit 203 performs a compensation calculation so as to stabilize the speed, and sends the calculation result to the current distribution unit 204 via the comparison unit 225. The current distribution unit 204 sets current command values Id and Iq when the current of the motor 1 is converted into the d-axis component and the q-axis component of the rotating coordinate system. Here, the distribution degree is set according to the output result of the PI compensation means 203. The d-axis current command and the q-axis current command obtained by the current distribution unit 204 are sent to the comparison units 205 and 206, where they are compared with the d-axis current and the q-axis current detected from the actual motor 1, and the difference is calculated. These are sent to the PI compensation means 207 and 208, respectively. The outputs of the PI compensation means 207 and 208 are sent to the three-phase / two-phase conversion means 209 and converted into voltage information to be applied to each phase of the motor 1. Voltage information for each phase is sent to the PWM comparison circuit 211, compared with a carrier signal (not shown), converted into an ON / OFF signal for each phase of the three-phase bridge circuit 4, and the three-phase bridge circuit 4 Sent to each phase.

  The pseudo alternating voltage created by the three-phase bridge circuit 4 is applied to the three-phase motor 1 to realize rotational driving. Further, a current sensor 6 is provided in the direct current portion of the three-phase bridge circuit 4 to measure the current to the motor 1. The measured DC current value is again distributed to the current information of each of the three phases according to the timing information used in the PWM comparison circuit 211. As a result, the phase current information of the motor 1 is transferred to the 2-phase / 3-phase converter 210. The current control system is configured by inputting and converting the current into d-axis current and q-axis current, and comparing them with respective current command values in the comparison means 205 and 206.

  The rotational position θ of the motor 1 is detected by the rotational position detector 2 and can be converted into rotational speed information ω by differentiating the information by the differentiating means 223. By comparing with the speed command ω *, A control system is configured to achieve control at a desired speed. Further, since the rotational position information θ is necessary at the time of the three-phase / two-phase conversion and the two-phase / three-phase conversion, the rotational position information θ is also input to the three-phase / 2-phase conversion means 209 and the two-phase / 3-phase conversion means 210. , Perform each conversion.

  On the other hand, the DC current information of the three-phase bridge circuit detected by the DC detector 6 is sent to the averaging means 221 to obtain the average value for each control cycle of the PWM comparison circuit. The relationship between the instantaneous value of the direct current and the average value for each control cycle will be described later. The obtained average DC current information for each control cycle is multiplied by the DC voltage information at that time by the multiplication means 226 and sent to the high-pass filter circuit 222. After the DC component and the low frequency component are removed by the high-pass filter 222, the high-pass filter 222 is sent to the comb filter 229. The configuration of the comb filter 229 will be described later. The comb filter 229 allows only a specific frequency and an integral multiple thereof to pass therethrough. A gain is given to the passed frequency component at block 224 and sent to the comparison means circuit 225 to adjust the current command value.

  FIG. 4 shows the current waveform (true instantaneous value) of the direct current portion in one control cycle detected by the direct current detector 6. In the DC portion, the phase current of the three-phase motor can be detected in a time-sharing manner depending on the switching state. FIG. 4 shows a state where U-phase and V-phase currents can be detected. At this time, the remaining W phase is a value having the opposite polarity of the sum of the currents of the U phase and V phase, and can be calculated by calculation. The averaging means 221 calculates an average value in this period, that is, a substantially instantaneous value for each period.

  FIG. 3A is a circuit block diagram illustrating a specific configuration example of the comb filter 229. In FIG. 3A, the filter input signal is sent to the adding means 502 and added with the output of the delay means 501. The result of the addition operation becomes an output and is input again to the delay means 501. The delay time of the delay means 501 is set to 1/6 of the motor current cycle. Although the delay time here is naturally changed according to the number of rotations of the motor, for example, the time corresponding to 1/6 rotation of the rotation phase using the information of the position detector 2 in FIG. To do the delay.

  FIG. 3B shows frequency-amplitude characteristics of the circuit shown in FIG. The amplitude ratio is “1 / Kcomb” times when the frequency of the signal is 6 times and an integral multiple thereof, and the amplitude ratio is very small in the middle. For this reason, it is possible to extract a signal whose signal frequency is 6 times or an integer multiple thereof. Furthermore, since the high-pass filter 222 is provided in FIG. 2, a characteristic that cuts off a signal at a low frequency such as a direct current is realized.

  If the loss of the motor is ignored, the power supplied to the motor is equal to the power that is the output of the motor, and the power is the product of the rotation speed and the torque. Here, if the rotation speed is constant, the change in the power supplied to the motor becomes a change in the torque. Therefore, the change in the torque can be detected by examining the change in the power supplied. In other words, if the power DC voltage passing through the DC portion is constant, the current in the DC portion is proportional to the power in the DC portion, and if the DC voltage is changing, multiplying the DC portion voltage by the current A substantially instantaneous value of power passing through the direct current portion can be calculated. Since the loss in conversion from direct current to pseudo alternating current is negligible, the power calculated in the direct current portion substantially matches the power supplied to the motor.

  Here, when the voltage of the DC part is constant, the average value of the current of the DC part for each control cycle is calculated, and on the rotation coordinate axis so that a component that is an integral multiple of the phase current frequency of this average current value is constant. When the current command is modulated and the voltage of the direct current portion fluctuates, the direct current and the direct current voltage for each control cycle are multiplied, and the same processing is performed using the direct current power for each control cycle. By controlling as described above, the power supplied to the motor in each control cycle is always constant, and if the motor speed is constant, the power is the product of the speed and torque, and the motor loss is ignored if the motor loss is ignored. Becomes constant. As a result, the torque ripple of the motor can be reduced.

  In addition, since the torque ripple based on the induced voltage distortion of the three-phase motor has a frequency component that is six times the current frequency of the three-phase motor and an integral multiple thereof, a comb filter as shown in FIG. By doing so, the component of torque ripple can be extracted. Further, the cause of torque ripple is distortion of the induced voltage. For example, when the induced voltage is small, the torque can be kept constant by controlling the flow of more current.

  As described above, by attenuating the harmonic component of the instantaneous value of power and the average power (substantially instantaneous value) in a short period, the same power is always generated even if there is a harmonic distortion of the magnetic flux. . As the rotational speed is attenuated by high-order rotational fluctuations due to inertial effects, it is possible to keep torque constant by preventing torque fluctuations that are difficult to detect as speed fluctuations, and quiet drive control Can be realized.

  The current command by the current distribution means 204, which is a current control operation, is modulated only by the 6th harmonic frequency, and the modulation operation is performed in other frequency regions as well as the current frequency of the three-phase motor. Since this is not performed, the motor drive performance is not impaired.

  It is obvious that the same effect can be obtained even if the order of the comb filter 229 and the high-pass filter 222 is reversed.

  Moreover, although the example of a structure of the comb filter was shown in FIG. 3, it is not limited to this example of a structure.

(Embodiment 2)
FIG. 5 is an overall configuration diagram of the motor drive device according to the second embodiment of the present invention. A detection resistor 706 is inserted in place of the current detector 6 in FIG. 1, and the current is detected as a voltage by the detection resistor 706. To do. The description of the same configuration as that of the second embodiment is omitted, and only different portions will be described. In FIG. 5, the detection resistor 706 is connected to the voltage level comparison means 750 together with voltage threshold information. Further, the signal from the voltage level comparison means 750 is input to a cutoff means 755 provided between the control circuit 3 and the three-phase bridge circuit 4 to control the signal cutoff operation.

  The operation and action of the motor drive control apparatus configured as described above will be described below.

  The current information obtained by the detection resistor 706 is sent to the control circuit 3 and also sent to the voltage level comparison means 750. Thereafter, the voltage level comparing means 750 compares the threshold value with a predetermined threshold value. Here, if the current exceeds the threshold value, the cutoff means 755 cuts off the control signal sent from the control circuit 3 to the three-phase bridge circuit 4 to stop the driving of the motor 1.

  Thus, the torque ripple of the motor drive device can be reduced by sending the obtained current information to the control circuit 3, and the voltage information can also be used as a motor safety device. Thus, the detection means for stopping and protecting the motor drive apparatus and the detection means for motor drive control can be shared, and the apparatus can be simplified.

  As described above, in the motor drive control device according to the present invention, torque ripple caused by distortion can be reduced without using information on harmonic distortion of the magnetic flux of the motor. It can be applied to devices and appliances such as household washing machines that avoid noise.

  In the embodiment of the present invention, a case is described where a detector is installed for detecting the rotational position of the motor. It is obvious that the same driving can be performed, and it can be applied to low vibration and low noise driving of a compressor such as a home air conditioner or a refrigerator, which is difficult to use the rotational position detector.

1 is an overall configuration diagram of a motor control device according to Embodiment 1 of the present invention. Block diagram showing the operation of the control circuit according to the first embodiment of the present invention. (A) Block diagram of comb filter in Embodiment 1 of the present invention (b) Diagram showing frequency-amplitude characteristics of the comb filter in Embodiment 1 of the present invention DC part current waveform diagram Overall configuration diagram of motor control apparatus according to Embodiment 2 of the present invention Current waveform diagram of current control in conventional motor controller The figure which shows the torque ripple characteristic in the conventional motor control device

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Motor 3 Control circuit 4 Three-phase bridge circuit 5 DC power supply 6 DC detector 220 2 phase / 3 phase converter 221 Averaging means 229 Comb filter 501 Delay means 706 Detection resistance 750 Voltage level comparison means 755 Shut off means

Claims (4)

A motor drive control device for driving a multiphase motor by converting a DC power supply or a power supply obtained by rectifying an AC power supply into an arbitrary pseudo multiphase AC by switching means, and the motor drive control device detects a current of a DC section. The current of each phase of the multiphase motor is calculated from the control state of the switching means, converted into current information of the rotating coordinate system based on the calculated current, and the converted current information of the rotating coordinate system is Having a control system that controls the value, detecting an average value of direct current for each control cycle of the switching means, and an integer multiple of the detected average value excluding the fundamental wave of the current frequency of the multiphase motor A motor drive control device that controls a current desired value of the rotating coordinate system so as to reduce a frequency component. The multiphase motor has a phase number of 3 and includes a permanent magnet in the rotor. The rotary coordinate system is a two-phase coordinate based on the rotational phase of the permanent magnet. The integer multiple frequency is an integer multiple of 6 times the current frequency. The motor drive control device according to claim 1, wherein the motor drive control device is provided. By using the amount of electric power for each control cycle obtained by multiplying the DC current value for each control cycle by the DC voltage value in the same interval, the frequency component of an integral multiple excluding the fundamental wave of the current frequency of the multiphase motor is reduced. The motor drive control device according to claim 1, wherein a desired current value of the rotating coordinate system is controlled. The means for detecting the direct current is a method for detecting the voltage across the resistor inserted in the direct current portion, and when this voltage becomes a value above a certain value, the drive control is stopped. Item 4. The motor drive control device according to any one of Items 1 to 3.

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