JP4923918B2 - Inverter device parallel operation device - Google Patents

Description

  The present invention relates to a parallel operation device for an inverter device in which outputs of two voltage source inverter devices are connected in parallel to drive a load, and more particularly to a technique for preventing a cross current between output phases.

  In order to expand the capacity of the three-phase voltage source inverter device that performs current control, the parallel operation device of the inverter device is configured to be connected in parallel for each output phase of two PWM inverters, for example. FIG. 5 shows a circuit configuration example of a main part of this parallel operation device.

  In FIG. 5, the voltage source inverter device is composed of inverter devices 2A and 2B in which a DC power source 1 is used as a common power source and six arms in which semiconductor switches and diodes are connected in antiparallel are bridge-connected, and each AC output terminal has 3 The phase reactors 3A and 3B and the output transformers 4A and 4B are connected in parallel to drive the common AC load 5.

  The control device 6 for parallel operation has a control system for performing speed control and torque control of the AC load 5, and the output voltage of the inverter is controlled by a current control circuit that uses the output of these control systems as a current command and a PWM calculation unit. Is PWM controlled.

  The control device of FIG. 5 shows only the current control circuit and the calculation block of the PWM calculation unit, and the inverter device 2A detected using a current detector for two phases with respect to the given current commands Iu * and Iw *. , 2B U and W phase output currents Iu1, Iw1, Iu2, and Iw2 are obtained, and the deviation is proportionally integrated (PI) to obtain U and W phase voltage control signals. A V-phase voltage control signal is obtained by addition and inversion, and the U, V, and W-phase voltage control signals are compared with a carrier (triangular wave) signal by each comparator to obtain a PWM waveform gate signal. These gate signals Gu1 (Gx1), Gv1 (Gy1), Gw1 (Gz1), Gu2 (Gx2), Gv2 (Gy2), and Gw2 (Gz2) are used to control the semiconductor switches of the inverter devices 2A and 2B.

  In such a parallel operation apparatus, when the DC link side is directly connected, a current path as shown in FIG. 6 is generated. However, in addition to the fact that there is no moderate impedance in this path, there is no current adjustment circuit between the inverter devices, so there is a circulating current (cross current) that flows through the AC power supply and load and does not work effectively. End up. In order to suppress this circulating current, insulating transformers 4A and 4B are provided on the AC side, interphase reactors are provided, or three-phase reactors 3A and 3B having a large designed zero-phase component are provided.

In addition, as a current adjustment method for suppressing the cross current, there is a method in which the output current of one inverter device is used as a current feedback signal of the own device and the current command of the other inverter device (see, for example, Patent Document 1). .
JP 2002-262577 A

  As described above, when the DC link and the AC side are directly connected, a current path as shown in FIG. 6 is generated. However, in addition to the fact that there is no appropriate impedance in this path, there is no current adjustment circuit, so that a circulating current (cross current) that flows to the AC power supply or load and does not work effectively flows. In order to suppress this circulating current, an expensive and large insulating transformer, an interphase reactor, or a three-phase reactor having a large designed zero-phase component is required on the AC side.

  Further, when the current adjusting circuit is provided, a current control loop is easily formed between the inverter devices, and there is a possibility that the current control becomes unstable against disturbance. In FIG. 6, in order to prevent cross current between phases where current detection is not performed, a current detector is provided for each phase of each inverter device, and phase-specific control by a phase-specific current control arithmetic circuit is required. Become.

  An object of the present invention is to provide a parallel operation device of an inverter device that can stably suppress cross current using a relatively small and inexpensive three-phase reactor.

  In order to solve the above-mentioned problems, the present invention connects a general three-phase reactor on the AC side, and suppresses the cross current by adding a few current detectors and a control circuit. It is characterized by.

( 1 ) The outputs of two voltage source inverter devices that share a DC power source are connected in parallel via three-phase reactors to drive the load, and the control device for each inverter device The deviation between the U and W phase current commands Iu * and Iw * and the individual U and W phase current detection values is proportionally integrated to obtain a U and W phase voltage control signal, and the V phase voltage is obtained from both voltage control signals. In the parallel operation device of the inverter device for obtaining the control signal,
The control device includes means for complementarily correcting the V-phase voltage control signals of both inverter devices by proportional control so that the deviation of the V-phase current detected by both inverter devices becomes the value “0”. It is characterized by that.

( 2 ) The outputs of two voltage source inverter devices that share a DC power source are connected in parallel through three-phase reactors, respectively, to drive the load. The deviation between the U and W phase current commands Iu * and Iw * and the individual U and W phase current detection values is proportionally integrated to obtain a U and W phase voltage control signal, and the V phase voltage is obtained from both voltage control signals. In the parallel operation device of the inverter device for obtaining the control signal,
The control device includes means for independently correcting the V-phase voltage control signals of both inverter devices by proportional control so that the deviation of the V-phase current detected by both inverter devices becomes the value “0”. It is characterized by that.

  As described above, according to the present invention, a three-phase reactor in which an AC-side insulating transformer, an interphase reactor, or a zero-phase component is greatly designed for parallel operation of a three-phase voltage source inverter device performing current control. Without adding a current detector, the addition of a current detector and a simple control circuit enables stable cross current suppression.

(Embodiment 1)
FIG. 1 is a main part circuit configuration diagram showing the present embodiment, and components equivalent to those in FIG. 5 are denoted by the same reference numerals.

  Power is supplied to the AC load 5 through the three-phase reactors 3A and 3B on the three-phase output sides of the inverter devices 2A and 2B. Among these, the zero-phase current transformer 7 for detecting the three-phase output zero-phase current Iz1 of the inverter device 2A is provided.

  The control device 6 is different from FIG. 5 in that the V-phase voltage command of the inverter device 2A not performing current detection is corrected by proportional control of the zero-phase current Iz1. In this proportional control, the zero-phase current Iz1 detected by the zero-phase current transformer 7 is amplified by the amplifier 8 having a gain Kp, and the V-phase voltage control signal is corrected by this value.

  In the above configuration, for the U and W phases of the inverter devices 2A and 2B, the current commands Iu * and Iw * are used as a common current command, and cross current is suppressed by PI control based on the respective current detection. If a cross current is to be generated between the V phases for which current detection is not performed, the cross current between the V phases appears as a zero phase current Iz1 by the above correction control, and the control device 6 suppresses the V phase voltage control signal, and the inverter device 2A. , 2B, the cross current between the V phases is suppressed to the value “0”.

  Therefore, according to the present embodiment, the addition of one zero-phase current transformer, relatively without preparing a transformer for insulation on the AC side, an interphase reactor, or a three-phase reactor with a large designed zero-phase component, Cross current can be suppressed using a small and inexpensive three-phase reactor. In addition, since individual current control of the inverter devices 2A and 2B is performed independently, stable cross current suppression can be performed.

(Embodiment 2)
FIG. 2 is a circuit diagram of the main part showing the present embodiment, and the part different from FIG. , 9B, and the input of the amplifier 8 is used as a differential signal of the detected currents of both current detectors 9A, 9B.

  With this configuration, the difference between the V-phase current of the inverter device 2A not performing current detection and the V-phase current of the inverter 2B is detected as a cross current, and the current is not detected so that the cross current is zero. The V phase voltage command is corrected by proportional control.

  Also in the present embodiment, it is possible to obtain the same effects as those of the first embodiment. In addition, the U, V, and W phase currents of the inverter devices 2A and 2B can be matched almost completely.

(Embodiment 3)
FIG. 3 is a circuit diagram of a main part showing the present embodiment. The difference from FIG. 2 is that the output of the amplifier 8 is inverted in addition to the correction of the V-phase voltage control signal of the inverter device 2A by the output of the amplifier 8. The amplifier 10 is inverted and amplified, and this output corrects the V-phase voltage control signal of the inverter device 2B.

  Therefore, according to the present embodiment, it is possible to obtain the same effects as those of the first and second embodiments. Moreover, in the second embodiment, only the inverter device 2A is corrected, but in this embodiment, the two devices are balanced and corrected in a complementary manner.

(Embodiment 4)
FIG. 4 is a circuit diagram of the main part showing the present embodiment. The difference from FIG. 2 is that the V-phase current of the inverter device 2A not performing current detection is detected by the two current detectors 9A and 9C. The V-phase current of the inverter device 2B is detected by the two current detectors 9B and 9D, and the control device 6 determines the difference between the currents detected by the current detectors as a cross current. The V-phase voltage control signal of the inverter devices 2A and 2B is corrected by proportional control so as to be zero.

  According to this embodiment, the same effect as Embodiments 1-3 can be obtained. Moreover, in the second embodiment, an amplifier for cross current correction is mounted on either the inverter device 2A or 2B, and a minute analog voltage signal line close to 0 must be routed. In this embodiment, Since the amplifier is individually provided, it is not necessary to route a minute analog voltage signal line.

The principal part circuit block diagram which shows Embodiment 1 of this invention. The principal part circuit block diagram which shows Embodiment 2 of this invention. The principal part circuit block diagram which shows Embodiment 3 of this invention. The principal part circuit block diagram which shows Embodiment 4 of this invention. The circuit structural example of the conventional parallel operation apparatus. V-phase cross flow explanatory diagram.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 DC power supply 2A, 2B Inverter apparatus 3A, 3B Three-phase reactor 6 Control apparatus 7 Zero phase current transformer 8, 11 Amplifier 9A, 9B Current detector 10 Inverting amplifier

Claims (2)

The outputs of two voltage source inverter devices that share a DC power supply are connected in parallel by interposing three-phase reactors, respectively, and the load is driven. The control device of each inverter device has a common U, W for each inverter device. The deviation between the phase current commands Iu * and Iw * and the individual U and W phase current detection values is proportionally integrated to obtain a U and W phase voltage control signal, and the V phase voltage control signal is obtained from both voltage control signals. In the parallel operation device of the inverter device to obtain,
The control device includes means for complementarily correcting the V-phase voltage control signals of both inverter devices by proportional control so that the deviation of the V-phase current detected by both inverter devices becomes the value “0”. A parallel operation device for an inverter device. The outputs of two voltage source inverter devices that share a DC power supply are connected in parallel by interposing three-phase reactors, respectively, and the load is driven. The control device of each inverter device has a common U, W for each inverter device. The deviation between the phase current commands Iu * and Iw * and the individual U and W phase current detection values is proportionally integrated to obtain a U and W phase voltage control signal, and the V phase voltage control signal is obtained from both voltage control signals. In the parallel operation device of the inverter device to obtain,
The control device includes means for independently correcting the V-phase voltage control signals of both inverter devices by proportional control so that the deviation of the V-phase current detected by both inverter devices becomes the value “0”. A parallel operation device for an inverter device.

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