JP2012205423A - Motor control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor control device capable of securing starting property of a motor in a configuration having no smoothing capacitor.SOLUTION: The motor control device includes: a rectification part which performs full-wave rectification on an AC power supply voltage and outputs a pulsating voltage; a drive part which drives the motor using the pulsating voltage; and a control part which controls the drive part. The control part includes: a detection part which detects a valley of the pulsating voltage; a generation part which generates a PWM carrier signal by using the detected timing of the valley as a base point; and a formation part which forms a PWM signal using the detected PWM carrier signal and outputs it to the drive part.

Description

  The present invention relates to a motor control device.

  In Patent Document 1, as an inverter device that reduces the influence of a smoothing capacitor that is unnecessary or significantly reduced in capacity, when the induced voltage on the motor side becomes higher than the inverter output voltage, the control unit Describes a technique for advancing the output timing of an inverter by a time corresponding to a preset angle signal. Thereby, according to patent document 1, it is supposed that the influence of a pulsation voltage can be reduced.

JP-A-10-150795

  In the technique described in Patent Document 1, it is necessary to set in advance the phase advance amount when the saturation state is reached, and the phase advance amount needs to be changed depending on the rotation speed and the load state. Therefore, for the phase advance amount, it is necessary to calculate and set the phase advance amount corresponding to various rotation speeds and load states in advance from the measurement by the actual machine, and the setting of the phase advance amount is complicated, And difficult.

  Further, in the technique described in Patent Document 1, the torque fluctuation in the saturated state is suppressed by advancing the phase of the inverter output voltage. Since it is lower than the time, there is a possibility that the influence of the pulsating voltage cannot be reduced by adjusting the phase lead amount. That is, the startability of the motor tends to be poor.

  The present invention has been made in view of the above, and an object of the present invention is to obtain a motor control device that can easily improve motor startability in a configuration that does not have a smoothing capacitor or that has a reduced capacity. And

  In order to solve the above-described problems and achieve the object, a motor control device according to the present invention includes a rectification unit that outputs a pulsation voltage by full-wave rectification of an AC power supply voltage, and uses the pulsation voltage. And a control unit for controlling the driving unit, the control unit detecting a valley of the pulsating voltage, and a PWM carrier based on the timing of the detected valley It has a generating part which generates a signal, and a generating part which generates a PWM signal using the generated PWM carrier signal, and outputs it to the drive part.

  The motor control device according to the present invention further includes a determining unit that determines a duty ratio of the PWM signal to be generated according to the level of the pulsating voltage for each period of the PWM carrier signal. The generation unit generates a PWM signal with a duty ratio determined by the determination unit.

  In the motor control device according to the present invention as set forth in the invention described above, the generating section generates a PWM carrier signal having a cycle of 1 / integer of a half cycle of the AC power supply voltage.

  The motor control device according to the present invention has an effect that the startability of the motor can be easily improved in a configuration having no smoothing capacitor or having a reduced capacity.

FIG. 1 is a diagram illustrating a configuration of a motor control device according to the embodiment. FIG. 2 is a diagram illustrating the operation of the motor control device according to the embodiment. FIG. 2 is a diagram illustrating the operation of the motor control device according to the embodiment. FIG. 4 is a diagram illustrating the operation of the motor control device according to the embodiment. FIG. 5 is a diagram illustrating the operation of the motor control device according to the comparative example.

  Embodiments of a motor control device according to the present invention will be described below in detail with reference to the drawings. In addition, this invention is not limited by this embodiment.

  A control apparatus 100 for a motor M according to an embodiment will be described with reference to FIG. FIG. 1 is a diagram illustrating a configuration of a control device 100 for the motor M.

  For example, the control device 100 outputs a preset start voltage to each phase to start the motor M. The control device 100 includes a rectification unit 10, a drive unit 20, and a control unit 50.

  The rectifying unit 10 receives an AC power supply voltage from the AC power supply E. The rectifying unit 10 performs full-wave rectification on the AC power supply voltage (waveform indicated by a broken line in FIG. 3) and outputs a pulsating voltage (waveform indicated by a solid line in FIG. 3). That is, the rectifier 10 outputs the full-wave rectified pulsating voltage without smoothing.

  The driving unit 20 receives the pulsating voltage from the rectifying unit 10. The drive unit 20 drives the motor M using the pulsating voltage. Specifically, the drive unit 20 includes an IPM (Intelligent Power Module) 21. The IPM 21 receives a PWM (Pulse Width Modulation) signal from the control unit 50, converts the pulsation voltage into, for example, a three-phase AC voltage and outputs it to the motor M in accordance with the PWM signal.

  The control unit 50 outputs a PWM signal to the drive unit 20 so as to control the drive unit 20. Specifically, the control unit 50 includes a zero cross detector (detection unit) 30 and a microcomputer 40.

  The zero cross detector 30 has an input side connected to the nodes N3 and N4 on the P line Lp and the N line Ln between the rectifying unit 10 and the drive unit 20, and an output side connected to the microcomputer 40. For example, the zero-cross detector 30 compares the signal acquired from the node N3 and the signal acquired from the node N4 to detect a point where the difference between the two becomes the minimum as a valley portion of the pulsation voltage. In other words, the zero cross detector 30 detects the zero cross point of the AC power supply voltage. As shown in FIG. 3, zero cross points P <b> 1 to P <b> 3 in the waveform of the AC power supply voltage indicated by a broken line are also points that become valleys in the pulsation voltage indicated by a solid line. That is, the zero cross detector 30 shown in FIG. 1 detects the zero cross point of the AC power supply voltage as a valley of the pulsating voltage. The zero-cross detector 30 outputs a detection result, that is, a zero-cross signal (see FIG. 4) indicating the zero-cross point, to the microcomputer 40.

  The microcomputer 40 receives a zero cross signal from the zero cross detector 30. The microcomputer 40 generates a PWM signal according to the zero cross signal and outputs it to the IPM 21. Further, the microcomputer 40 acquires a pulsating voltage from the nodes N1 and N2 on the P line Lp and the N line Ln between the rectifying unit 10 and the driving unit 20. Specifically, the microcomputer 40 includes a generation unit 41, a determination unit 42, and a generation unit 43.

  The generation unit 41 generates a PWM carrier signal using a valley portion (for example, zero cross points P1 to P3) of the pulsation voltage detected by the zero cross detector 30 as a base point. The PWM carrier signal is, for example, a triangular wave (see FIG. 4). In addition, the generation unit 41 generates a PWM carrier signal having a cycle that is 1 / integer of a half cycle of the AC power supply voltage. That is, the period of the PWM carrier signal is 1 / integer of one period of the pulsating voltage (the period from the valley to the next valley) (see FIG. 4). In other words, the period of the PWM carrier signal is an even multiple of the frequency of the AC power supply voltage. The generation unit 41 outputs the generated PWM carrier signal to the generation unit 43.

  The determination unit 42 determines the duty ratio of the PWM signal to be generated by the generation unit 43. Specifically, the determination unit 42 acquires the pulsating voltage from the nodes N1 and N2 for each period of the PWM carrier signal. And the determination part 42 determines the duty ratio of a PWM signal so that the starting voltage output to each phase of a motor is not influenced by a pulsation voltage according to the level of a pulsation voltage. The determination unit 42 outputs the determined result, that is, the PWM duty ratio signal to the generation unit 43. The PWM duty ratio signal is, for example, a threshold value to be compared with the PWM carrier signal.

  For example, as illustrated in FIG. 4, when the pulsation voltage is level V1, the determination unit 42 determines the duty ratio of the PWM signal as the first value, and the threshold corresponding to the duty ratio of the first value. TH1 is output as a PWM duty ratio signal. The determination unit 42 determines the duty ratio of the PWM signal to be a second value smaller than the first value when the pulsation voltage is the level V2 higher than the level V1, and corresponds to the duty ratio of the second value. The threshold value TH2 is output as a PWM duty ratio signal. The determination unit 42 determines the duty ratio of the PWM signal to be a third value larger than the first value when the pulsation voltage is the level V3 lower than the level V1, and corresponds to the duty ratio of the third value. The threshold value TH3 is output as a PWM duty ratio signal. Thereby, the determination part 42 can determine the duty ratio of a PWM signal in the form corresponding to the level of a pulsation voltage.

  The generation unit 43 receives the PWM carrier signal from the generation unit 41 and receives the PWM duty ratio signal from the determination unit 42. The generation unit 43 compares the PWM carrier signal and the PWM duty ratio signal (threshold value), and generates a PWM signal as a comparison result. For example, the generation unit 43 sets the PWM signal to the ON level if the amplitude of the PWM carrier signal is larger than the PWM duty ratio signal (threshold), and turns off the PWM signal if the amplitude of the PWM carrier signal is smaller than the PWM duty ratio signal (threshold). Level.

  For example, as illustrated in FIG. 4, when the PWM duty ratio signal is the threshold value TH1, the generation unit 43 compares the PWM carrier signal with the threshold value TH1 and generates a PWM signal with the duty ratio of the first value. To do. When the PWM duty ratio signal is a threshold value TH2 higher than the threshold value TH1, the generation unit 43 compares the PWM carrier signal with the threshold value TH2, and generates a PWM signal with a duty ratio having a second value smaller than the first value. Generate. When the PWM duty ratio signal is a threshold value TH3 lower than the threshold value TH1, the generation unit 43 compares the PWM carrier signal with the threshold value TH3 and generates a PWM signal with a duty ratio of a third value larger than the first value. Generate. Thereby, the generation unit 43 generates a PWM signal with the duty ratio determined by the determination unit 42.

  Next, the operation of the control device 100 for the motor M when the motor M is started will be described with reference to FIGS. FIG. 2 is a data flow diagram mainly showing the operation in the microcomputer 40. Below, the case where the motor M is a motor which drives a compressor is illustrated exemplarily.

  The motor starting voltage Vs shown in FIG. The microcomputer 40 detects the zero-cross signal so that the PWM signal becomes ON level while avoiding the saturation period Td in which the amplitude of the pulsating voltage is smaller than the motor starting voltage Vs, and starts outputting the PWM signal based on the timing. I do. Specifically, the following control is performed.

  The compressor operation / stop determination unit 401 supplies a detection start instruction to the PWM output start unit 402 when receiving a compressor operation instruction for instructing start of the compressor. The compressor operation / stop determination unit 401 supplies a detection stop instruction to the PWM output start unit 402 upon receiving a compressor stop instruction for instructing the stop of the compressor.

  When the PWM output start unit 402 receives an instruction to start detection, the PWM output start unit 402 is ready to receive a zero cross signal from the zero cross detector 30. When receiving the zero cross signal, the PWM output start unit 402 supplies a PWM output instruction to the PWM signal output unit 431. In addition, when receiving a detection stop instruction, the PWM output start unit 402 supplies a PWM stop instruction to the PWM signal output unit 431.

  When receiving the PWM output instruction, the PWM signal output unit 431 supplies the PWM carrier cycle timing signal to the PWM carrier cycle processing unit 411.

  When receiving the PWM carrier cycle timing signal, the PWM carrier cycle processing unit 411 generates a PWM carrier signal based on the received timing. As a result, the PWM carrier cycle processing unit 411 generates a PWM carrier signal based on the valleys of the pulsating voltage (for example, zero cross points P1 to P3 shown in FIG. 4), and generates the PWM signal via the PWM duty ratio calculation unit 421. Supply to the output unit 431. Also, the PWM carrier cycle processing unit 411 supplies a PWM duty ratio calculation instruction to the PWM duty ratio calculation unit 421 in response to receiving the PWM carrier cycle timing signal.

  When receiving the PWM duty ratio calculation instruction, the PWM duty ratio calculation unit 421 acquires the pulsation voltage from the nodes N1 and N2. Then, the PWM duty ratio calculation unit 421 determines the duty ratio of the PWM signal according to the level of the pulsating voltage. The PWM duty ratio calculation unit 421 outputs the determined result, that is, the PWM duty ratio signal to the PWM signal output unit 431. The PWM duty ratio signal is, for example, a threshold value to be compared with the PWM carrier signal.

  The PWM signal output unit 431 compares the PWM carrier signal and the PWM duty ratio signal (threshold value), and generates a PWM signal as a comparison result. For example, the PWM signal output unit 431 sets the PWM signal to the ON level if the amplitude of the PWM carrier signal is larger than the PWM duty ratio signal (threshold), and the PWM signal if the amplitude of the PWM carrier signal is smaller than the PWM duty ratio signal (threshold). Is set to OFF level. The PWM signal output unit 431 outputs the generated PWM signal to the IPM 21.

  Here, it is desirable that the ON section where the PWM signal at the previous time and the future time is at the ON level is one that avoids the saturated period Td. As factors that determine this, it is necessary to define the PWM carrier cycle and the PWM maximum duty. That is, parameters that satisfy the following formulas 1 and 2 are stored in the storage unit 403 in advance, and each unit in the microcomputer 40 appropriately refers to them.

      PWM signal carrier cycle x n times = half cycle of power supply (1)

      PWM signal carrier cycle ≧ Td Equation 2

  Equation 1 above saturates the PWM signal carrier cycle start or end point by setting the carrier cycle of the PWM signal to a time that is a fraction of the power supply half cycle (half cycle of the AC power supply voltage). The center of the state section Td. Also, the above formula 2 is for preventing the middle of the carrier period of the PWM signal from reaching the saturation state interval Td. The generating unit 41 determines the PWM carrier cycle so as to satisfy Equation 1 and Equation 2.

  Even if the PWM signal output unit 431 has not received a PWM output instruction, the PWM signal output unit 431 supplies the PWM carrier cycle timing signal to the PWM carrier cycle processing unit 411 at the timing when the cycle of the PWM carrier signal has elapsed. That is, the loop of the PWM signal output unit 431, the PWM carrier cycle processing unit 411, and the PWM duty ratio calculation unit 421 is repeated for each cycle of the PWM carrier signal. This causes the PWM duty ratio calculation unit 421 to review the duty ratio of the PWM signal for each period of the PWM carrier signal.

  Here, suppose that the rectification unit 10 has a smoothing capacitor. In this case, the circuit of the rectifying unit 10 tends to increase in size and cost as a whole.

  On the other hand, in the embodiment, the rectifying unit 10 does not have a smoothing capacitor. As a result, the circuit of the rectifying unit 10 can be kept compact overall, and the cost can be reduced.

  Alternatively, suppose a case where the PWM signal is turned on during the saturated period Td as shown in FIG. 5 in a configuration in which the rectifying unit 10 does not have a smoothing capacitor. In this case, the voltage output from the rectifying unit 10 to the driving unit 20 is a pulsating voltage including a ripple. However, even if the PWM signal is ON within the saturated period Td that is generated due to the pulsating voltage, The voltage level is lower than the motor starting voltage Vs, and the motor starting voltage Vs tends not to be secured. For this reason, since the voltage applied to the motor M has an unstable waveform as shown in FIG. 5, the startability of the motor M tends to be significantly reduced.

  On the other hand, in the embodiment, in the configuration in which the rectifying unit 10 does not have a smoothing capacitor, the zero cross detector 30 detects the valley of the pulsating voltage, and the PWM carrier is based on the timing of the valley where the generator 41 is detected. A signal is generated, and the generation unit 43 generates a PWM signal using the generated PWM carrier signal and outputs the PWM signal to the drive unit 20. As a result, as shown in FIG. 4, the PWM signal can be generated so that the PWM signal becomes ON level while avoiding the saturated period Td, so that the voltage applied to the motor M can be stabilized. The startability of the motor can be ensured. That is, in a configuration that does not have a smoothing capacitor, the motor startability can be easily improved.

  Alternatively, let us consider a case where field weakening control is performed in which the phase of the output voltage of the drive unit 20 is advanced when the rectifying unit 10 does not have a smoothing capacitor and the saturation period Td is reached. In this case, it is necessary to set in advance the phase advance amount when the saturation state is reached, and the phase advance amount needs to be changed depending on the rotational speed and the load state. Therefore, for the phase advance amount, it is necessary to calculate and set the phase advance amount corresponding to various rotation speeds and load states in advance from the measurement by the actual machine, and the setting of the phase advance amount is complicated, And difficult.

  On the other hand, in the embodiment, since the period of the PWM carrier signal may be adjusted in relation to the period of the AC power supply voltage, the adjustment is easy. That is, it is easy to set the period of the PWM carrier signal according to the actual machine.

  In addition, when performing the field-weakening control described above, the phase of the inverter output voltage is advanced when the saturation state is reached, so that it is difficult to suppress torque pulsation at the time of startup where the required torque itself is low, and the startability of the motor is reduced. There is a tendency.

  On the other hand, in the embodiment, as shown in FIG. 4, the PWM signal can be generated so that the PWM signal becomes ON level while avoiding the saturated period Td. In addition, torque pulsation can be suppressed, and motor startability can be easily improved. That is, in a configuration that does not have a smoothing capacitor, the motor startability can be easily improved.

  1 illustrates a configuration in which the rectifying unit 10 does not include a smoothing capacitor, the rectifying unit 10 may include a smoothing capacitor in which the capacity of the smoothing capacitor is smaller than a general capacitance value. Even in this case, the voltage output from the rectifying unit 10 to the driving unit 20 is still a pulsating voltage including a large amount of pulsating components, and therefore there is a saturated period Td.

  Therefore, the zero cross detector 30 detects the valley of the pulsating voltage, the generation unit 41 generates a PWM carrier signal based on the detected timing of the valley, and the generation unit 43 uses the generated PWM carrier signal. By generating the PWM signal and outputting it to the drive unit 20, the PWM signal can be generated so that the PWM signal becomes ON level while avoiding the saturated period Td, as in the above embodiment.

  As described above, the motor control device according to the present invention is useful for motor control.

10 Rectifier 20 Drive 21 IPM
30 Zero Cross Detector 40 Microcomputer 41 Generation Unit 42 Determination Unit 43 Generation Unit 50 Control Unit 100 Control Device 401 Compressor Operation / Stop Determination Unit 402 PWM Output Start Unit 403 Storage Unit 411 PWM Carrier Period Processing Unit 421 PWM Duty Ratio Calculation Unit 431 PWM signal output section

Claims (3)

A rectifying unit for full-wave rectifying the AC power supply voltage and outputting a pulsating voltage;
Using the pulsating voltage, a drive unit that drives a motor;
A control unit for controlling the driving unit;
With
The controller is
A detector for detecting a valley of the pulsating voltage;
A generator for generating a PWM carrier signal based on the detected timing of the valley,
A generating unit that generates a PWM signal using the generated PWM carrier signal and outputs the PWM signal to the driving unit;
A motor control device comprising: The control unit further includes a determination unit that determines a duty ratio of the PWM signal,
The determining unit determines a duty ratio of the PWM signal according to the level of the pulsating voltage for each period of the PWM carrier signal,
The motor control device according to claim 1, wherein the generation unit generates a PWM signal at a duty ratio determined by the determination unit. 3. The motor control device according to claim 1, wherein the generation unit generates a PWM carrier signal having a cycle of an integer of a half cycle of the AC power supply voltage.

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