JP4669723B2 - Electric motor control device - Google Patents

Description

  The present invention relates to an electric motor control device that performs variable speed control of an electric motor by an inverter device that combines a plurality of unit inverters that convert alternating current to direct current by an AC / DC converter, smooth the smoothing capacitor, and then convert to alternating current by a single-phase inverter.

Conventionally, as a motor control device for variable speed control of an AC motor, a three-phase star connection is used for a unit inverter that converts AC to DC by a diode bridge circuit, smooths it with a smoothing capacitor, and then converts it to AC to obtain a single-phase output. There is an inverter device (for example, Patent Document 1).
JP 11-122943 A

  In a normal three-phase output inverter device, a direct-current voltage obtained by converting a power supply output into direct current by a three-phase diode bridge circuit and smoothing it with a smoothing capacitor is a ripple voltage 6 times the power supply frequency and its amplitude is 15 If the output of the three-phase inverter is synthesized, it becomes almost flat and no problem occurs.

  However, in the inverter device in which a plurality of unit inverters that obtain a single-phase output as described above are combined, the power pulsation for each phase has an amplitude of 100% and the frequency is as low as twice. As a result, there is a problem that the output frequency of the unit inverter approaches the resonance frequency of the resonance circuit composed of the AC power supply side inductance and the smoothing capacitor, and the DC voltage ripple becomes excessive.

  For this reason, there has been a problem that the rated capacity has to be increased in accordance with the maximum value of the voltage ripple, or the apparatus capacity has to be reduced.

  The present invention has been made in view of the above circumstances, and allows an AC motor to be used by effectively using the rated capacity of the apparatus without causing resonance of a DC voltage pulsating at twice the output frequency of the unit inverter. It is an object of the present invention to provide an electric motor control device capable of speed change control.

  In order to achieve the above object, the present invention constitutes an electric motor control device by the following means.

An electric motor control device corresponding to the present invention includes a plurality of AC / DC converters that convert AC to DC, a plurality of smoothing capacitors that respectively smooth DCs converted by the plurality of AC / DC converters, and the plurality of smoothing capacitors. smoothed DC respectively converted to single-phase alternating current, a plurality of unit inverters AC that each single-phase AC synthesized supplied to the electric motor, each of said plurality of smoothing capacitors and the plurality of AC to DC conversion device For suppressing the resonance of the voltage pulsation caused by the unit inverter close to the resonance frequency of the resonance circuit composed of the smoothing capacitor and the AC side inductance of the AC / DC converter A circuit having a damping effect is provided.

  According to the present invention, it is possible to suppress the pulsation of the DC voltage due to the double frequency of the output frequency of the unit inverter from being increased due to the resonance phenomenon.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a circuit configuration diagram showing a first embodiment of an electric motor control device according to the present invention.

  In FIG. 1, AC is an AC power source, and from this AC power source AC, single-phase AC is transferred to AC / DC converters 2 </ b> A, 2 </ b> B, 2 </ b> C composed of diode bridges via input reactors 1 </ b> A, 1 </ b> B, 1 </ b> C of respective phases A, B, C. Input and converted to DC. The direct current output from the AC / DC converters 2A, 2B, 2C is smoothed by the smoothing capacitors 4A, 4B, 4C and input to the single-phase inverters 5A, 5B, 5C, and the direct current is converted into single-phase alternating current and output. .

  Here, the A / B / C phase AC / DC converters 2A, 2B, 2C, the smoothing capacitors 4A, 4B, 4C and the single-phase inverters 5A, 5B, 5C are each configured as one unit inverter. The unit inverter is star-connected and connected to the AC motor 6, and the AC motor 6 is driven and controlled.

  In the motor control device having such a configuration, in the present embodiment, single-phase inverters 5A, 5B, 5C are provided between the AC / DC converters 2A, 2B, 2C of the respective phases A, B, C and the smoothing capacitors 4A, 4B, 4C. Circuit 3A, 3B, 3C having a damping effect for suppressing resonance of voltage ripple caused by power pulsation twice as high as the output frequency, and detecting means for detecting the DC electric quantity of the unit inverter of each phase A, B, C 7 is provided, and the DC electric quantity detected by the detecting means 7 is taken into the control circuit 8 to control the circuits 3A, 3B, 3C having a damping effect.

  Next, the operation will be described.

  Now, the unit inverter described above can be represented as an equivalent circuit as shown in FIG. That is, in FIG. 2, the AC / DC converter 2 comprising a diode bridge can be represented as a DC power source, the single-phase inverter 5 as an AC current source, and the current flowing through the smoothing capacitor 4 can be detected as a detection means for detecting the DC electric quantity. In this example, the current detection circuit 10 is provided, and the current detected by the current detection circuit 10 is taken into the control circuit 8.

  First, in the above equivalent circuit, when the circuit 3 having the damping effect and the control circuit 8 are not present, the voltage Vc of the smoothing capacitor 4 is set to 2 times the output frequency of the single-phase inverter 5 as shown in FIG. It pulsates. That is, the current Irec flowing from the DC power source through the reactor 1 is delayed in phase from the current Iinv flowing to the AC current source, and the voltage Vc of the smoothing capacitor 4 pulsates. When the frequency of this voltage is close to the resonance frequency of the input reactor 1 and the smoothing capacitor 4, resonance occurs and the voltage ripple is greatly increased from the theoretical value.

  Next, in the case where the circuit 3 and the control circuit 8 having a damping effect are provided, when the current detected by the current detection circuit 10 is taken into the control circuit 8, the control circuit 8 responds to the detected current value. The control signal is generated to control the circuit 3 having the damping effect, and the current Irec flowing through the circuit 3 having the damping effect rises early as shown in FIG. 3B, and the current Iinv flowing to the AC current source The phase is almost the same, and the fluctuation of the voltage Vc of the smoothing capacitor 4 is suppressed.

  The circuit 3 having the damping effect is not used for the purpose of controlling the voltage between both terminals of the smoothing capacitor 4 to be constant, but quickly raises the current Irec so that the voltage ripple of the smoothing capacitor 4 does not increase due to resonance. It is for raising.

  Therefore, by providing a circuit 3 having a damping effect for suppressing resonance of voltage ripple due to power pulsation twice the output frequency of the single-phase inverter 5 between the AC-DC converter 2 and the smoothing capacitor 4, the AC-DC converter 2 In addition, there is no need to increase the rated capacity of the single-phase inverter 5 or reduce the capacity of the apparatus, and the variable speed control of the AC motor can be performed by an existing apparatus.

  FIG. 4 is a circuit configuration diagram showing a second embodiment of the motor control device according to the present invention. The same parts as those in FIG. 1 are denoted by the same reference numerals and the description thereof is omitted, and only different points are described here.

  In the second embodiment, step-up choppers 9A, 9B, and 9C including a reactor, a diode, and a switching element are provided as a circuit having a damping effect for suppressing resonance of voltage ripple, and unit inverters for each phase of A, B, and C are provided. As a detecting means for detecting the DC electric quantity of 5A, 5B, 5C, a current detection circuit 10 for detecting the current flowing through the smoothing capacitor 4 is provided, and the current detected by the current detection circuit 10 is taken into the control circuit 8. A control signal is generated to control the step-up choppers 9A, 9B, and 9C.

  Here, as a control circuit for controlling the step-up chopper 9, as shown in FIG. 5, the current Ic flowing through the smoothing capacitor 4 is compared with a reference value (0 value), and the difference signal is multiplied by a coefficient k to generate PWM. The chopper switching signal is generated from the PWM circuit and the boost chopper 9 is controlled so that the current Ic flowing through the smoothing capacitor 4 becomes zero.

  Even with such a configuration, the same effects as those of the first embodiment can be obtained.

  FIG. 6 is a circuit configuration diagram for one phase showing a third embodiment of the motor control device according to the present invention. The same parts as in FIG. Only mention.

  In the third embodiment, a step-up chopper 11 composed of a diode and a switching element is provided as a circuit having a damping effect for suppressing voltage ripple resonance, and smoothing is performed as detection means for detecting the DC electric quantity of the unit inverter 5. A current detection circuit 10 for detecting the current flowing through the capacitor 4 is provided, and the current detected by the current detection circuit 10 is taken into the control circuit 8 to generate a control signal, thereby controlling the boost chopper 9. is there.

  This embodiment is characterized in that the reactor is omitted from the boost chopper 11 and is carried by the input reactor 1. Since all the circuit current flows through the reactor of the boost chopper, the merit of being able to omit the reactor is great.

  Even with such a configuration, the same effects as those of the first embodiment can be obtained.

  FIG. 7 is a one-phase circuit configuration diagram showing a fourth embodiment of the motor control apparatus according to the present invention. The same parts as those in FIG. Only mention.

  In the fourth embodiment, a circuit 12 including a single-phase inverter and a reactor is provided as a circuit having a damping effect for suppressing resonance of voltage ripple, and smoothing is performed as detection means for detecting the DC electric quantity of the unit inverter 5. A current detection circuit 10 for detecting the current flowing through the capacitor 4 is provided, and the current detected by the current detection circuit 10 is taken into the control circuit 8 to generate a control signal, thereby controlling the circuit 12 including the single-phase inverter and the reactor It is what you do.

  Even with such a configuration, the same effects as those of the first embodiment can be obtained.

  FIG. 8 is a one-phase circuit configuration diagram showing a fifth embodiment of the motor control apparatus according to the present invention. The same parts as those in FIG. Only mention.

  In the fifth embodiment, a circuit 13 composed of a diode and a switching element is provided as a circuit having a damping effect for suppressing resonance of voltage ripple, and a smoothing capacitor is used as a detecting means for detecting the DC electric quantity of the unit inverter 5. The current detection circuit 10 for detecting the current flowing in the circuit 4 is provided, the current detected by the current detection circuit 10 is taken into the control circuit 8 to generate a control signal, and the circuit 13 composed of the diode and the switching element is controlled. It is a thing.

  Even with such a configuration, the same effects as those of the first embodiment can be obtained.

  FIG. 9 is a circuit configuration diagram showing a sixth embodiment of the motor control device according to the present invention. The same parts as those in FIG. 1 are denoted by the same reference numerals and the description thereof is omitted, and only different points are described here.

  In the sixth embodiment, as the circuit 3 (3A to 3C) having a damping effect for suppressing the resonance of the voltage ripple, the boost chopper 9 of the second embodiment or the boost without the reactor of the third embodiment is provided. The chopper 11 or the circuit 12 composed of the single-phase inverter and the reactor of the third embodiment or the circuit 13 composed of the diode and the switching element of the fourth embodiment is provided, and detection for detecting the DC electric quantity of the single-phase inverter 5 As a means, a voltage detection circuit 14 for detecting the voltage of the smoothing capacitor 4 (4A to 4C) is provided, the voltage detected by the voltage detection circuit 14 is taken into the control circuit 8 to generate a control signal, and the damping effect is obtained. The circuit 3 (3A to 3C) is controlled.

  Even with such a configuration, the same effects as those of the first embodiment can be obtained.

  FIG. 10 is a circuit configuration diagram showing a seventh embodiment of the motor control apparatus according to the present invention. The same parts as those in FIG. 1 are denoted by the same reference numerals and the description thereof is omitted, and only different points are described here.

  In the seventh embodiment, as the circuit 3 (3A to 3C) having a damping effect for suppressing the resonance of the voltage ripple, the boost chopper 9 of the second embodiment or the boost without the reactor of the third embodiment is provided. The chopper 11 or the circuit 12 composed of the single-phase inverter and the reactor of the third embodiment or the circuit 13 composed of the diode and the switching element of the fourth embodiment is provided, and the DC electric power of the single-phase inverter 5 (5A to 5C) As a detection means for detecting the quantity, a circuit 15 for detecting a single-phase inverter voltage and current is provided, and the single-phase inverter voltage and current information detected by the detection circuit 15 is taken into the control circuit 8 to obtain power by calculation. A control signal is generated based on this electric power, and the circuit 3 having a damping effect is controlled.

  Even with such a configuration, the same effects as those of the first embodiment can be obtained.

  In the first to seventh embodiments described above, the circuit configuration in which three unit inverters are star-connected has been described. However, the present invention is not limited to such a circuit configuration, and a single-phase multilevel inverter, The present invention can also be applied to a phase inverter, and the same effect as described above can be exhibited.

The circuit block diagram which shows 1st Embodiment of the motor control apparatus by this invention. In the embodiment, an equivalent circuit diagram of one unit inverter. The wave form diagram for demonstrating the effect | action of the embodiment compared with the case where there is no circuit which has a damping effect. The circuit block diagram which shows 2nd Embodiment of the motor control apparatus by this invention. The block diagram of the control circuit in the embodiment. The circuit block diagram for 1 phase which shows 3rd Embodiment of the motor control apparatus by this invention. The circuit block diagram for 1 phase which shows 4th Embodiment of the motor control apparatus by this invention. The circuit block diagram for 1 phase which shows 5th Embodiment of the motor control apparatus by this invention. The circuit block diagram which shows 6th Embodiment of the motor control apparatus by this invention. The circuit block diagram which shows 7th Embodiment of the electric motor control apparatus by this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1,1A, 1B, 1C ... Input reactor, 2,2A, 2B, 2C ... AC-DC converter consisting of a diode bridge, 3,3A, 3B, 3C ... Damping effect circuit, 4,4A, 4B, 4C ... Smooth Capacitors 5, 5A, 5B, 5C ... single phase inverter, 6 ... AC motor, 7 ... detecting means, 8 ... control circuit, 9A, 9B, 9C ... boost chopper, 10 ... current detection for detecting current flowing in smoothing capacitor Circuit: 11 ... Boost chopper, 12 ... Circuit consisting of single phase inverter and reactor, 13 ... Circuit consisting of diode and switching element, 14 ... Voltage detection circuit for detecting voltage of smoothing capacitor, 15 ... Single phase inverter voltage and current The circuit to detect.

Claims (10)

A plurality of AC / DC converters for converting AC to DC ,
A plurality of smoothing capacitors that respectively smooth the direct current converted by the plurality of AC / DC converters ;
A plurality of unit inverters , each of which converts direct current smoothed by the plurality of smoothing capacitors into single-phase alternating current, and an alternating current in which the single-phase alternating currents are combined is supplied to the motor .
A voltage generated by the unit inverter is provided between each of the plurality of AC / DC converters and the plurality of smoothing capacitors, and at a resonance frequency of a resonance circuit including an AC-side inductance of the AC / DC converter and the smoothing capacitor. An electric motor control device comprising a circuit having a damping effect for suppressing a pulsation frequency from approaching and resonating . Circuit having a pre-Symbol damping effect, the motor controller according to claim 1, wherein the pulsating component of the output current is controlled so that the pulsation component in phase with the current input to the unit inverter. Circuit having a pre-Symbol damping effect, the motor control device according to claim 1, characterized in that the step-up chopper. It said circuit having a damping effect, the motor control unit of 請 Motomeko 3 wherein you characterized in that the current flowing in the smoothing capacitor is controlled to be zero. An input reactor is provided on each input side of the plurality of AC / DC converters,
Said circuit having a damping effect, said without providing the reactor between the AC-DC converter and the smoothing capacitor, 請 Motomeko 3 by using the input reactor you being a step-up chopper for boosting The motor control device described. The motor control device according to claim 1, wherein the circuit having the damping effect includes a single-phase inverter and a reactor . The motor control device according to claim 1, wherein the circuit having a damping effect includes a diode and a switching element. The circuit having the damping effect is controlled based on the current flowing through the smoothing capacitor.
The electric motor control device according to claim 3, wherein the electric motor control device is one of the following. The circuit having the damping effect is controlled based on the voltage of the smoothing capacitor.
The electric motor control device according to claim 3, wherein the electric motor control device is one of the following. The circuit having the damping effect is controlled based on the output power of the unit inverter.
The electric motor control device according to claim 3, wherein the electric motor control device is one of the following.

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