JP2015208106A - Motor drive device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To resolve a problem that, in a conventional motor drive device, although a DC link voltage is enhanced by elongating a short circuit time to a reactor, when the short circuit time to the reactor is elongated too much, a core of the reactor is magnetically saturated, and an excessive current flows in the reactor, and thereby, the reactor is overheated, which may cause breakage of the reactor.SOLUTION: A motor drive device executes: a short circuit time control of correcting a short circuit time to a reactor by increasing and decreasing the short circuit time, setting an upper limit time for the short circuit time of the reactor, and in a case where the short circuit time to the reactor after correction exceeds the upper limit time, restricting the short circuit time so as not to exceed the upper limit time; and a rotation number control of performing deceleration processing on the inverter in a case where a measurement value of a DC link voltage becomes lower than a low-voltage side limit voltage for a target voltage and becomes lower than the DC link voltage measured previously.

Description

  The present invention relates to a motor driving device that boosts a voltage by a partial switching circuit including a reactor.

  As a motor driving device as described above, AC power supplied from an external AC power source is boosted by a partial switching circuit, then rectified and converted to DC power, and the DC power is further converted to AC power at a predetermined frequency by an inverter. There is known one that drives a motor by converting to (for example, see Patent Document 1).

  In this case, when the voltage of the AC power supplied from the outside decreases, the DC power supplied to the inverter is increased by increasing the energy stored in the reactor by increasing the short-circuit time to the reactor in the partial switching circuit. Control is performed so as to maintain the voltage of power, that is, the DC link voltage.

JP 2001-95262 A (FIG. 1)

  In the above-described conventional motor drive device, the DC link voltage is increased by increasing the short-circuit time to the reactor, but if the short-circuit time to the reactor is too long, the core of the reactor is magnetically saturated, When the excessive current flows, the reactor is overheated and the reactor may be damaged.

  In view of the above problems, an object of the present invention is to provide a motor drive device that does not damage the reactor even when the voltage of the AC power supplied from the outside decreases.

  In order to solve the above problems, a motor driving device according to the present invention boosts AC power supplied from an external AC power source by a partial switching circuit including a reactor, and rectifies the AC power to a DC power having a desired DC link voltage. After the conversion, the inverter is converted into AC power having a predetermined frequency, and the DC link voltage is monitored in the motor drive device that drives the motor with the AC power source. When the DC link voltage deviates from the predetermined target voltage, In order to make the DC link voltage match this target voltage, the short-circuit time to the reactor is corrected by increasing / decreasing, and the upper limit time of the reactor short-circuit time is set, and the short-circuit time to the reactor after the correction is set to the upper limit When the value exceeds, the short-circuit time control that limits the short-circuit time so that it does not exceed the upper limit time, and the measured value of the DC link voltage is lower than the target voltage. A case drops below the field voltage, and, if they lower than the DC link voltage measured last time, and performing a rotational speed control for deceleration processing to said inverter.

  The above configuration is characterized in that the short-circuit time control to the reactor and the rotational speed control with respect to the rotational speed of the motor are performed. In particular, when the power supply voltage decreases, the DC link voltage is prevented from decreasing by increasing the short-circuit time to the reactor, but in order to prevent the reactor from magnetic saturation, an upper limit time for the short-circuit time to the reactor is provided. Keep it. This can prevent the magnetic saturation of the reactor, but if the DC link voltage is lowered, there is a possibility that problems such as step-out occur in the motor. Therefore, in the rotational speed control, when the DC link voltage decreases, the rotational speed of the motor is temporarily decreased to wait for the recovery of the DC link voltage.

  In the above-described rotation speed control, it is desirable to set a lower limit value of the rotation speed and limit the rotation speed after the deceleration process so that it does not fall below this lower limit value.

  As is apparent from the above description, the present invention can prevent the reactor from being magnetically saturated by setting the upper limit time for the short circuit time to the reactor, and by providing this upper limit time, the DC link voltage can be reduced. Even if it falls, the motor step-out can be prevented by temporarily reducing the rotational speed of the motor.

The block diagram which shows the structure of one embodiment of this invention Diagram showing the configuration of a partial switching circuit Flow chart showing short-circuit time control Flow chart showing rotation speed control

  Referring to FIG. 1, reference numeral 1 denotes an example of a motor driving device according to the present invention. The motor drive device 1 is provided with a partial switching circuit 3 to which AC power supplied from an external AC power supply PS is input. In order to determine the switching timing in the partial switching circuit 3, the AC power supply A phase detector 12 for detecting the phase is provided in parallel.

  The DC power boosted by the partial switching circuit 3 and rectified to DC is supplied to the inverter 4, converted into AC power having a predetermined frequency, and supplied to the motor 5. The voltage of the DC power supplied from the partial switching circuit 3 to the inverter 4, that is, the DC link voltage is detected by the voltage detection unit 13.

  Signals detected by the voltage detector 13 and the phase detector 12 are input to the microcomputer 2. On the basis of these input signals, the microcomputer 2 controls the partial switching circuit 3 for a short-circuiting time to a reactor, which will be described later, and controls the rotational speed of the motor 5 for the inverter 4.

  Referring also to FIG. 2, the partial switching circuit 3 has a built-in reactor 31, and the direct current rectified by the rectifier 32 is turned on when the IGBT (insulated gate bipolar transistor) 33 is on. Supplied. The reactor 31 stores energy during a short circuit. When the IGBT 33 is turned off, the stored energy becomes a counter electromotive force and is superimposed on the AC power from the outside to boost the voltage of the AC power from the outside. Then, the boosted AC power is rectified by another rectifier 34 and supplied to the inverter 4. The microcomputer 2 controls the on / off timing of the IGBT 33.

  The short-circuit time control for the partial switching circuit 3 will be described with reference to FIG. This short circuit time control is performed at regular intervals. The microcomputer 2 takes in the DC link voltage detected by the voltage detector 13 at a preset cycle (SA1). The microcomputer 2 compares the acquired DC link voltage Vdc with the voltage target value Vc to determine whether the value of the DC link voltage Vdc falls into one of the following three categories (SA2). These three sections are a section in which the hysteresis value a of the DC link voltage is set and the actual DC link voltage Vdc falls between (Vc + a) and (Vc−a), and Vdc <(Vc−a). ) And Vdc> (Vc + a).

  When the DC link voltage Vdc falls between (Vc + a) and (Vc−a), the short-circuit time of the reactor 31 is not changed assuming that the DC voltage Vdc is in a normal state. Next, when Vdc> (Vc + a), since the short circuit time of the reactor 31 is too long, the parameter relating to the short circuit time of the reactor 31 is replaced with a new parameter having a short short circuit time (SA5).

  It should be noted that Vdc <(Vc−a). In this case, since the DC link voltage Vdc is low, it is necessary to extend the short circuit time of the reactor 31, but it cannot be made longer than the predetermined upper limit time. Therefore, it is determined whether or not the short circuit time at that time has already been extended until the upper limit time is reached (SA3). If the short-circuit time is extended to the upper limit time at this time, the short-circuit time cannot be extended any further, so that the short-circuit time is maintained at that time. On the other hand, if the short-circuit time at that time has not been extended to the upper limit time, the short-circuit time can still be extended. Therefore, the process proceeds to step SA4, and the parameters related to the short-circuit time of the reactor 31 are set to the predetermined short-circuit time. Replace with new parameters with extended time.

  If this parameter is maintained as it was last time or has been replaced to reduce the short circuit time, the short circuit time is adjusted using that parameter. Check if the upper limit time is exceeded by the extension, and if the short circuit time by the parameter after extension exceeds the upper limit time, change the parameter again so that the short circuit time becomes the upper limit time. The short-circuit time is actually adjusted (SA6).

  Thus, if the short-circuit time of the reactor 31 is limited by the upper limit time and cannot be extended for a predetermined time, the DC link voltage Vdc supplied to the inverter 4 may be lower than the voltage target value Vc. Thus, if the rotation speed of the motor 5 is continuously maintained in a state where the DC link voltage Vdc is lowered, problems such as stepping out of the motor 5 occur.

  Therefore, the microcomputer 2 controls the rotational speed of the motor 5 so that such a problem does not occur. Referring to FIG. 4, this rotational speed control is performed on inverter 4, and is performed at predetermined intervals similarly to the short-circuit time control shown in FIG.

  If the DC link voltage Vdc is Vdc> Vc compared to the voltage target value Vc, the inverter 4 is supplied with sufficient voltage power, so there is no need to reduce the rotational speed, but if Vdc <Vc. In this case, it is necessary to change the rotation speed (SB1).

  When Vdc <Vc, the DC link voltage measured last time is compared with the DC link voltage measured this time. If the current measured value is lower, that is, if the DC link voltage continues to decrease, the motor 5 The deceleration process is performed (SB2 → SB5). However, before performing the deceleration process, it is determined whether the rotational speed at that time has already been reduced to the lower limit value (SB5). If the rotational speed has already been reduced to the lower limit value, the next step SB6 is passed. . In this step SB6, the parameter relating to the rotational speed is replaced with a new parameter decelerated by a predetermined speed.

  If the DC link voltage measured this time is higher than the DC link voltage measured last time in step SB2, the DC link voltage is recovering and the rotational speed of the motor 5 has already been recovered at that time. Is in a decelerated state, it is necessary to perform acceleration processing to recover the rotational speed (SB2 → SB3).

  However, before performing the acceleration process, it is determined whether the rotational speed at that time has already been accelerated to the upper limit value (SB5). If the rotational speed has already been accelerated to the upper limit value, the next step SB4 is passed. . In step SB4, the parameter relating to the rotational speed is replaced with a new parameter accelerated at a predetermined speed. The upper limit value is the original rotation speed, that is, the rotation speed when there is no decrease in the DC link voltage.

  When the parameter is changed in this way, the rotational speed of the motor 5 is adjusted by the changed parameter. If the result of deceleration processing in step SB6 is below the lower limit value, the parameter is changed again. Set the rotation speed to the lower limit. Further, if the result of the acceleration process in step SB4 exceeds the upper limit value, the parameter is changed again so that the rotational speed becomes the upper limit value (SB7).

  Finally, the previously measured voltage value used in step SB2 is updated with the current voltage value acquired in step SB1 (SB8).

  In addition, this invention is not limited to an above-described form, You may add a various change in the range which does not deviate from the summary of this invention.

DESCRIPTION OF SYMBOLS 1 Motor drive device 2 Microcomputer 3 Partial switching circuit 4 Inverter 5 Motor 12 Phase detection part 13 Voltage detection part 31 Reactor 32 Rectifier 34 Rectifier Vc Voltage target value Vdc DC link voltage a Hysteresis value

Claims (2)

  The AC power supplied from an external AC power source is boosted by a partial switching circuit equipped with a reactor, rectified and converted to DC power of a desired DC link voltage, and then converted to AC power of a predetermined frequency by an inverter. In the motor driving apparatus that drives the motor with the AC power supply, the reactor is configured to monitor the DC link voltage and to match the DC link voltage with the target voltage when the DC link voltage deviates from a predetermined target voltage. Correct and increase or decrease the short-circuit time to the reactor, and set an upper limit time for the reactor short-circuit time, so that if the short-circuit time to the reactor after correction exceeds this upper-limit time, the short-circuit time will not exceed the upper-limit time. This is a case where the short-circuit time control to be limited and the measured value of the DC link voltage are lower than the lower limit voltage of the target voltage, and If you are lower than the link voltage, the motor driving apparatus characterized by performing the rotation speed control for deceleration processing to said inverter.   2. The motor drive device according to claim 1, wherein in the rotation speed control, a lower limit value of the rotation speed is set, and the rotation speed after the deceleration process is limited so as not to fall below the lower limit value.

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