JP5313493B2 - Motor drive device - Google Patents

Description

  The present invention relates to a motor drive device that charges regenerative energy generated during motor deceleration to a capacitor, uses it as powering energy during acceleration, and regenerates energy that exceeds the capacity of the capacitor back to AC power by power regeneration.

  FIG. 1 is a circuit diagram showing a configuration of a conventional motor driving device described in Patent Document 1. In FIG. In FIG. 1, a motor drive device 1 receives, for example, AC power from a three-phase commercial power source (AC power source) 9 having an AC voltage of 200 V via a reactance 8, and converts the DC power into DC power. An inverter circuit 3 for converting to AC power having a voltage and a frequency and supplying the AC power to the motor 4, an inverter control circuit 5 for controlling the inverter circuit 3 to output AC power having a desired voltage and frequency from the inverter circuit 3, and a converter A charging capacitor 6 connected between the circuit 2 and the inverter circuit 3 and a converter control circuit 7 are provided.

  The converter control circuit 7 controls the converter circuit 2 to generate regenerative power when the voltage across the capacitor 6 (DC link voltage) exceeds the upper limit voltage due to regenerative power (regenerative energy or deceleration energy) generated when the motor 4 is decelerated. Is regenerated to the power source to reduce the DC link voltage, and charging of the regenerative power to the capacitor 6 is stopped.

  In the above conventional motor drive device, the regenerative energy generated when the motor 4 is decelerated is charged in the capacitor 6 and used as powering energy when the motor 4 is accelerated, and the regenerative energy exceeding the capacity of the capacitor 6 is used. The AC power supply 9 is restored by power regeneration. Therefore, in order to charge more regenerative energy with less capacitor capacity, it is necessary to set the allowable increase in the DC link voltage high. In other words, it is necessary to set the power regeneration regeneration start voltage as high as possible within the allowable range for the withstand voltage specification of the element used for the peak value of the input voltage.

JP 2006-54947 A

  As a method of returning the regenerative current to the power supply (power regeneration), the switching element is controlled to be turned on / off so that the regenerative current is supplied to two phases having a high absolute value of the power supply voltage. When the switching element is on, the DC link and the three-phase AC power supply 9 are connected, and the DC link voltage appears in the interphase voltage that feeds back the regenerative current of the power supply voltage. In order to prevent the DC link voltage from interfering with the input voltage from the three-phase AC power source 9, the power regeneration start voltage is usually not set so high as to the peak value of the input voltage.

  However, in the conventional motor driving device shown in FIG. 1, the power regeneration start voltage is set very high with respect to the peak value of the input voltage, so that the input power supply voltage during power regeneration is affected by the interference of the DC link voltage. Distortion may adversely affect other devices connected to the same power supply system as the AC power supply 9.

This problem will be described with reference to FIG.
FIG. 2 is a graph showing voltage waveforms at various parts during motor deceleration and power regeneration in the conventional motor driving apparatus shown in FIG. In FIG. 2, the horizontal axis represents time t in seconds (s), and the vertical axis represents voltage V or current A in units of 200 volts or 200 amps. FIG. 2 shows a graph in the case where the regeneration start voltage of the power regeneration converter is set to 390V and the regeneration pause voltage is set to 370V in order to charge the charging capacitor 6 with regenerative energy. As shown in waveform 2 in FIG. 2, the input voltage during power regeneration (output voltage from the three-phase AC power source 9) is greatly distorted due to the distortion of the voltage across the capacitor 6 (DC link voltage). I understand.
An object of the present invention is to solve such a problem in a motor drive device and suppress distortion of an input power supply voltage during power regeneration.

  What is provided by the first aspect of the present invention is a smoothing capacitor connected to the DC side of the converter circuit and a charging capacitor connected to the DC side of the inverter circuit and charging regenerative energy from the motor. A first circuit for passing a current in one direction from the smoothing capacitor to the charging capacitor between the smoothing capacitor and the charging capacitor; and a smoothing capacitor by stepping down the voltage of the charging capacitor by the first circuit And a step-down circuit for supplying to the motor.

  According to the second aspect, the first circuit is composed of a diode.

  According to the third aspect, when the charging capacitor is charged by the regenerative energy from the motor and the voltage rises, the voltage of the charging capacitor is higher than the peak voltage of the input voltage from the AC power supply, and the withstand voltage of the charging capacitor is increased. When the lower first threshold voltage is exceeded, the step-down circuit is operated to discharge energy from the charging capacitor to the smoothing capacitor, and the second threshold voltage where the voltage of the charging capacitor is lower than the first threshold voltage. The operation of the step-down circuit was stopped when it became lower.

  According to the fourth aspect, when the voltage of the smoothing capacitor charged from the charging capacitor through the step-down circuit rises and exceeds the third threshold voltage higher than the peak value of the input voltage from the AC power supply, the power regeneration operation is performed. I did it.

  With the above configuration, distortion of the input voltage when the power is regenerated is suppressed.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The same reference numerals denote the same parts throughout the drawings.
FIG. 3 is a circuit diagram showing the configuration of the motor drive apparatus according to the embodiment of the present invention. In FIG. 3, in the motor drive device 1a including the power regeneration type converter circuit 2 including the smoothing capacitor 6 and the inverter circuit 3, regenerative energy is charged between the converter circuit 2 and the inverter circuit 3 (DC link). A charging capacitor 10 is connected in parallel.

  Each of the converter circuit 2 and the inverter circuit 3 has the same configuration as that in the conventional motor driving apparatus, and is a bridge circuit including a power element (for example, a transistor) and a diode connected to the power element in antiparallel. It has.

  Here, the regeneration start voltage of the power regeneration type converter circuit 2 is set to a voltage (third threshold voltage) slightly higher than the peak value of the normally set input voltage.

  Further, a diode 16 is connected in series between the power regeneration type converter circuit 2 and the charging capacitor 10 so that the charging capacitor 10 is connected to the cathode side. A step-down circuit 14 is connected in the reverse direction to the forward direction of the diode 16.

  When the motor 4 is accelerated, power is supplied from the converter circuit 2 to the inverter circuit 3 through the diode 16. However, since the regenerative energy when the motor 4 is decelerated is blocked by the diode 16, the power regeneration type converter circuit 2. It is not returned to the AC power source 9 via.

  For this reason, when the motor 4 starts to decelerate, the regenerative energy is charged in the charging capacitor 10 and the voltage of the charging capacitor 10 rises, but the output part of the power regeneration converter circuit 2 (both ends of the smoothing capacitor 6). Remains at the peak value of the input voltage.

  When the voltage across the charging capacitor 10 exceeds the first threshold voltage that is higher than the peak voltage of the input voltage from the input AC power supply 9 and lower than the withstand voltage of the charging capacitor 10, the step-down circuit 14 Operates, thereby passing the regenerative energy to the power regeneration type converter circuit 2 through the smoothing capacitor 6 while stepping down to a voltage (about power regeneration start voltage) slightly higher than the peak value of the input voltage.

  Since the voltage across the smoothing capacitor 6 (the voltage at the output of the power regeneration type converter circuit 2) is stepped down to a value close to the peak value of the input voltage by the step-down circuit 14, even if power regeneration is performed, The distortion of the voltage is small and does not adversely affect other devices connected to the same power supply system.

  When the voltage across the charging capacitor 10 becomes lower than the second threshold voltage, which is lower than the first threshold voltage, the step-down circuit 14 stops its operation, thereby maintaining the voltage of the charging capacitor 10 high, so that Prepare for energy supply during motor acceleration.

  The preliminary charge / discharge circuit 17 connected between the step-down circuit 14 and the charging capacitor 10 is for suppressing an inrush current when the power is turned on.

  Regenerative energy that is generated by the motor drive device 1a shown in FIG. 3 when the regenerative energy generated during motor deceleration is received by the charging capacitor 10 and used as powering energy during acceleration and exceeds the capacity of the charging capacitor 10. Can suppress distortion of the input voltage at the time of power regeneration in the motor drive device that returns to the AC power supply 9 by power regeneration.

Hereinafter, the operation of the apparatus shown in FIG. 3 will be described in more detail.
(1) After the power is turned on, the DC charging voltage for performing the initial charging of the charging capacitor 10 by the preliminary charging circuit 17 becomes equal to the peak value of the input voltage by the initial charging. Here, the operation of the pre-charging circuit 17 is irrelevant to the present invention, and the description thereof is omitted.

  (2) The motor 4 is accelerated. At this stage, since the regenerative energy is not charged in the charging capacitor 10, energy is supplied from the AC power source 9. The diode 16 becomes conductive because a voltage is applied in the forward direction.

  (3) The motor 4 starts decelerating. At this stage, the regenerative energy is charged in the charging capacitor 10. The voltage of the charging capacitor 10 increases according to the amount of regenerative energy. Since a voltage is applied to the diode 16 in the reverse direction, regenerative energy does not flow to the power regeneration type converter circuit 2. The output voltage of the power regeneration type converter circuit 2 remains at the peak value of the input voltage.

  (4) The voltage across the charging capacitor 10 rises to near the breakdown voltage of the charging capacitor 10 exceeding the first threshold voltage. At this stage, the regenerative energy cannot be charged to the charging capacitor 10 any more. Next, the step-down circuit 14 starts to operate. The step-down circuit 14 drops the regenerative energy to the power regeneration type converter circuit 2 by stepping down to about the power regeneration start voltage while monitoring the output voltage of the power regeneration type converter circuit 2. At this time, the smoothing capacitor 6 connected to the DC link that is the output of the power regeneration type converter circuit 2 is used as the output voltage smoothing capacitor of the step-down circuit 14.

  (5) The regenerative energy is returned to the AC power source 9 by the power regeneration type converter circuit 2. At this stage, the power regeneration type converter circuit 2 is supplied with regenerative energy from the step-down circuit 14, and therefore its output voltage rises. The power regeneration type converter circuit 2 starts power regeneration when the voltage at its output section is slightly higher than the peak value of the input voltage (when the third threshold voltage is reached). The control circuit 7 controls on / off of switching elements composed of power elements in the converter circuit 2 so that a regenerative current flows in two phases with a high absolute value of the power supply voltage with respect to the AC power supply 9, and regenerative energy is supplied to the AC power supply 9 Return to. At this time, since the output voltage of the power regeneration type converter circuit 2 is sufficiently stepped down by the step-down circuit 14, even if the voltage appears in the input power supply voltage, it can be suppressed by the AC reactor 8.

  (6) The voltage between the terminals of the charging capacitor 10 decreases. At this stage, the regenerative energy is returned from the power regeneration converter circuit 2 to the AC power supply 9 via the step-down circuit 14, so the voltage across the charging capacitor 10 decreases. When the voltage across the charging capacitor 10 becomes lower than the second threshold voltage, which is lower than the first threshold voltage, the step-down circuit 14 stops its operation. When the step-down circuit 14 stops its operation, the regenerative energy is charged into the charging capacitor 10 again. When the voltage of the charging capacitor 10 again exceeds the third threshold voltage and becomes the first threshold voltage near the capacitor withstand voltage, the step-down circuit 14 operates again.

  (7) The motor 4 is accelerated. At this stage, the regenerative energy charged in the charging capacitor 10 is used. The regenerative energy charged in the charging capacitor 10 is supplied from the AC power source 9 so that the energy required for accelerating the motor 4 cannot be supplemented.

  Thereafter, the operations (3) to (7) are repeated.

  FIG. 4 is a graph showing voltage waveforms at various parts during motor deceleration and power regeneration in the motor drive apparatus shown in FIG. In FIG. 4, the horizontal axis represents time t in units of seconds (s), and the vertical axis represents voltage V or current A having 200 volts or 200 amperes as one unit. Waveform 1 shows the voltage waveform of each part when the step-down circuit 14 operates during motor deceleration, and waveform 2 shows the input voltage waveform during power regeneration.

  During motor deceleration, as shown by waveform 1, the voltage across charging capacitor 10 and the voltage across smoothing capacitor 6 (the output voltage of power regeneration converter circuit 2) are separated. Further, during power regeneration, as shown in waveform 2, it can be seen that the voltage across smoothing capacitor 6 (the output voltage of power regeneration converter circuit 2) is near the peak value of the input voltage. Compared with the conventional waveform 2 shown in FIG. 2, there is almost no distortion of the input voltage waveform.

  According to the present invention, in the motor drive device, distortion of the input power supply voltage at the time of power regeneration can be suppressed, so that no adverse effect is exerted on other devices connected to the same power supply system.

It is a circuit diagram which shows the structure of the conventional motor drive device. It is a graph which shows each part voltage waveform during the motor deceleration in the conventional motor drive device shown in FIG. 1, and a power regeneration. It is a circuit diagram which shows the structure of the motor drive device by one embodiment of this invention. It is a graph which shows each part voltage waveform during the motor deceleration in the motor drive device shown in FIG. 3, and a power supply regeneration.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a Motor drive device 2 Power regeneration type converter circuit 3 Inverter circuit 4 Motor 6 Smoothing capacitor 10 Charging capacitor 14 Step-down circuit 16 Diode

Claims (2)

A converter circuit having a power regeneration function that converts input AC power from an AC power source into DC power, and an inverter circuit that receives the DC power, performs DC-AC power conversion, and drives the motor by the obtained AC power A motor drive device comprising:
A smoothing capacitor connected to the DC side of the converter circuit;
Connected to the DC side of the inverter circuit, and a charging capacitor for charging regenerative energy from the motor;
A first circuit for passing a current in one direction from the smoothing capacitor to the charging capacitor between the smoothing capacitor and the charging capacitor;
A step-down circuit for stepping down the voltage of the charging capacitor by the first circuit and supplying the voltage to the smoothing capacitor;
Equipped with a,
When the charging capacitor is charged by the regenerative energy from the motor and the voltage rises, the voltage of the charging capacitor is higher than the peak voltage of the input voltage from the AC power supply and lower than the withstand voltage of the charging capacitor. When the threshold voltage of 1 is exceeded, the step-down circuit is operated to discharge energy from the charging capacitor to the smoothing capacitor, and a second voltage lower than the first threshold voltage is applied to the charging capacitor. A motor driving device characterized in that the operation of the step-down circuit is stopped when it becomes lower than a threshold voltage . The power regeneration operation is performed when the voltage of the smoothing capacitor charged through the step-down circuit from the charging capacitor rises and exceeds a third threshold voltage higher than the peak value of the input voltage from the AC power supply. Item 2. The motor drive device according to Item 1 .

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