JP2007104822A - Parallelization system of power converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a parallelization system of a power converter that suppresses a cross current between inverters, and improves operation continuity by arranging the inverters control circuits that are independent from one another in terms of control. <P>SOLUTION: In the system that parallel-connects the unit voltage-type inverters 1, and feeds AC power to a motor 3 as the parallelization system of the power converter, a reactor 2 having the large reactance of a value expressed by a per-unit system with a capacity of the unit voltage-type inverter 1 as a reference is arranged at the output side of each unit voltage-type inverter 1, by comparing this reactance with the armature-leakage reactance of the motor 3 of a value expressed by a per-unit system with a motor capacity of the motor 3 as a reference. Consequently, the cross current flowing between the unit voltage-type inverters 1 is suppressed, and the control circuits independent from the other unit voltage-type inverters 1 in terms of control are added to the parallelization system. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a parallel system for power converters in which power converters are connected in parallel.

In general, unit voltage source inverters that convert a DC voltage into an AC voltage are connected in parallel to increase the capacity of the power converter. At this time, a cross current flows separately from the load current between the unit inverters due to the AC output voltage difference between the unit inverters. Therefore, an imbalance occurs in the shared current of each unit inverter due to the cross current. To solve this problem, a reactor (balancer) with a small inductance value is connected to the AC output section of each unit inverter, the magnitude of the cross current is reduced, and the cross current flowing between each unit inverter is detected, and the control circuit A power conversion device that controls the average value of the cross current to be zero has been proposed (see, for example, Patent Document 1).
Japanese Patent No. 2619851

  However, the power converter as described above has an advantage that the size of the reactor can be reduced, but it is necessary to share the information of the detected cross current between the unit inverters connected in parallel. The circuits could not be made independent of each other. For this reason, when repairing or replacing the failed unit inverter, there is a risk that the operation of the other normal unit inverter may be hindered.

  In addition, since the reactor is not large enough, it is not possible to deal with an excessive cross current in the case of a unit inverter element failure, etc., and the failure may spread to other healthy unit inverters. there were.

  Therefore, an object of the present invention is to provide a power conversion device that can suppress the cross current between the inverters and can improve the operation continuity by having the control circuits independent from each other. It is to provide a parallel system.

  A parallel system of power converters according to an aspect of the present invention is a system in which at least two power converters are connected in parallel, and each power converter includes DC power supply means for supplying DC power; An inverter that converts DC power from DC power supply means into AC power and supplies the AC power to an AC load, an electric quantity detection means that detects an electric quantity of the AC power output from the inverter, and the electric quantity Based on the amount of electricity detected by the detection means, the amount of AC power output from the inverter is controlled, a control circuit independent of the control of each power converter other than the power converter, the inverter, and the inverter The AC load is connected to the AC load in parallel and connected to the AC load in a unit method based on the total capacity of the inverters of the power converters. Compared to inductance, a configuration in which a reactor reactance is large values, expressed in per-unit based on the capacitance of the inverter.

  ADVANTAGE OF THE INVENTION According to this invention, the parallel current system of the power converter device which can suppress the cross current between each inverter and can improve driving | operation continuity because each inverter has a control circuit independent from each other is controllable. Can be provided.

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

(First embodiment)
FIG. 1 is a block diagram illustrating a configuration of a parallel system of the power conversion device according to the present embodiment.

  In this system, a configuration including a DC power source 19, a unit voltage source inverter 1, a smoothing capacitor 7, a reactor 2, a current detector 8, and an AC current control circuit 9 is connected in parallel as one power converter. And the AC load motor 3 to which AC power is supplied from the two power converters.

  The DC power source 19 is connected to the input side of the unit voltage type inverter 1. The DC power supply 19 supplies DC power to the unit voltage type inverter 1. The DC power supply 19 supplies a DC voltage source independent of the unit voltage source inverter 1 of another power converter. For example, the DC power source 19 is a solar cell, a fuel cell, a storage battery, an electric double layer capacitor, or the like.

  The smoothing capacitor 7 is connected in parallel between the DC power source 19 and the unit voltage type inverter 1. The smoothing capacitor 7 converts the DC voltage from the DC power source 19 into a constant smooth DC voltage and supplies it to the unit voltage type inverter 1.

  The unit voltage source inverter 1 is a device that performs power conversion from direct current to alternating current by cutting out an alternating current waveform from an established direct current voltage. For example, the unit voltage type inverter 1 is a self-excited three-phase bridge circuit.

  The configuration of the self-excited three-phase bridge circuit will be described with reference to FIG.

  As shown in FIG. 10, the self-excited three-phase bridge circuit is mainly configured by a combination of a switching element 15 and a diode 16. The self-excited three-phase bridge circuit applies the positive and negative electrodes of the DC voltage supplied from the DC power supply 19 to the positive terminal 17P and the negative terminal 17N, respectively, and controls the respective gates of the switching elements 15 to generate DC power. It converts into alternating current power and outputs three-phase alternating current power from alternating current terminal 18A, 18B, 18C.

  The current detector 8 is attached to the output side of the unit voltage type inverter 1. The current detector 8 detects the AC output current value output from the unit voltage source inverter 1, and inputs this AC current detection value to the AC current control circuit 9.

  The alternating current control circuit 9 controls the unit voltage type inverter 1 so that the alternating current detection value follows the set alternating current command value.

  With reference to FIG. 12, the structural example of the alternating current control circuit 9 is demonstrated.

  The AC current control circuit 9 includes three-phase / dq conversion circuits 21 and 22, subtractors 23 and 24, PI control circuits 25 and 26, and a dq / 3-phase conversion circuit 27.

  The control phase angle θ is a parameter representing the dq orthogonal two axes, and is used when the three-phase amount and the value on the dq orthogonal two axes are mutually subjected to rotational coordinate conversion. The control phase angle θ is used in the three-phase / dq conversion circuits 21, 22 and the dq / 3-phase conversion circuit 27.

  The three-phase / dq conversion circuit 21 receives AC current command values IU *, IV *, and IW *, which are command values for three-phase amounts of U phase, V phase, and W phase. The three-phase / dq conversion circuit 21 converts the input AC current values IU *, IV *, and IW * into two DC amounts Id * and Iq * on two orthogonal axes of dq, and subtracters 23 and 24, respectively. To enter.

  The three-phase / dq conversion circuit 22 receives AC current values IU, IV, and IW, which are three-phase amounts of the U-phase, V-phase, and W-phase detected by the current detector 8. The three-phase / dq conversion circuit 22 converts the input alternating current values IU, IV, and IW into two direct current amounts Id and Iq on dq orthogonal two axes, and inputs them to the subtracters 23 and 24, respectively.

  The subtracter 23 takes the difference between the DC amounts Id * and Id input from the three-phase / dq conversion circuits 21 and 22 and inputs the difference to the PI control circuit 25.

  The subtractor 24 takes the difference between the DC amounts Iq * and Iq input from the three-phase / dq conversion circuits 21 and 22 and inputs the difference to the PI control circuit 26.

  The PI control circuit 25 performs proportional-integral control on the difference amount input from the subtracter 23, and inputs the obtained voltage command value Vd * on two orthogonal axes to the dq / 3-phase conversion circuit 27.

  The PI control circuit 26 performs proportional-integral control on the difference amount input from the subtractor 24, and inputs the obtained voltage command value Vq * on two orthogonal axes to the dq / 3-phase conversion circuit 27.

  The dq / 3-phase conversion circuit 27 receives voltage command values Vd * and Vq * on two orthogonal axes input from the PI control circuits 25 and 26, converts them into three-phase quantities, and converts them into three-phase AC voltage command values. Outputs VU *, VV *, and VW *.

  With the above-described configuration, the unit voltage source inverter 1 converts a DC voltage into a three-phase AC voltage according to the three-phase AC voltage command value output from the AC current control circuit 9.

  The reactor 2 is connected in series between the output side of the unit voltage type inverter 1 and a connection point with another unit voltage type inverter 1 connected in parallel. Reactor 2 has a value Xm that represents the armature leakage reactance of motor 3 in terms of the unit method with respect to the motor capacity, and a value Xo that represents the reactance of reactor 2 in terms of the unit method with reference to the unit inverter capacity. ) Satisfied relationship.

Xo> Xm (1)
According to this embodiment, the following operations and effects can be obtained.

  By adjusting the number of unit voltage type inverters connected in parallel, a large-capacity power conversion device can be realized according to the purpose and application.

  Between each unit voltage type inverter, there is a reactance that is at least twice as large as the armature leakage reactance of the motor. Therefore, even if no special control circuit is provided, the cross current is included in the load current. The ripple current is almost the same as the ripple current. Therefore, the cross current is small even when a unit inverter fails, and the spread of the failure to other unit inverters can be suppressed.

  The AC current control circuits 9 of the unit voltage source inverters 1 are independent from each other, and the other unit voltage source inverters 1 are not affected by the control. Further, since the DC power source 19 is provided independently for each unit voltage source inverter 1, each unit voltage source inverter 1 can be operated individually. Therefore, even if only the unit voltage source inverter 1 that has failed during operation is stopped, the other normal unit voltage source inverter 1 can be operated. Thereby, while replacing or repairing the failed unit voltage source inverter 1, the normal unit voltage source inverter 1 can supply the AC power to the motor 3, and the power conversion device can improve the operation continuity. Can be provided.

  Accordingly, in the configuration in which the unit voltage source inverters 1 are connected in parallel, the cross current between the inverters can be suppressed, and each unit voltage source inverter has a control circuit and a DC power source that are independent from each other. The parallelization system of the power converter device which can improve is provided.

(Second Embodiment)
FIG. 2 is a block diagram illustrating a configuration of a parallel system of the power conversion device according to the present embodiment.

  In this system, instead of the DC power supply 19 of the system shown in FIG. 1, the converter 4 connected to the DC power input side of the unit voltage source inverter 1 and the input insulation connected to the AC power input side of the converter 4 1 except that a transformer 5 is provided and an AC power supply 6 is connected to the input side of the input isolation transformer 5. The same parts as those in FIG. 1 are denoted by the same reference numerals, detailed description thereof will be omitted, and different parts will be mainly described. In the following description of each embodiment, the same description is omitted.

  The AC power supply 6 supplies AC power to the input isolation transformer 5.

  The input isolation transformer 5 is supplied with AC power from an AC power source 6 and supplies AC power to the converter 4. The input isolation transformer 5 insulates the input side to which the AC power supply 6 is connected and the output side to which the converter 4 is connected.

  The converter 4 converts AC power from the input isolation transformer 5 into DC power and supplies DC power to the unit voltage type inverter 1. For example, the converter 4 is a diode rectifier circuit.

  A configuration example of the diode rectifier circuit will be described with reference to FIG.

  The diode rectifier circuit is mainly composed of a combination of diodes 16 as shown in FIG. Each phase of the three-phase AC power is input to AC terminals 18A, 18B, and 18C, and DC power is output from the positive terminal 17P and the negative terminal 17N.

  According to the present embodiment, the AC power supplied from the AC power supply 6 is supplied to the converter 4 via the input insulating transformer 5 to insulate the AC power supply 6 from the converter 4 and make the converter 4 independent. A DC voltage source can be used.

  Therefore, the same operation and effect as in the first embodiment can be obtained using an AC power supply as a supply source.

(Third embodiment)
FIG. 3 is a block diagram illustrating a configuration of a parallel system of the power conversion device according to the present embodiment.

  This system is the same as FIG. 2 except that the power supply system 10 is connected as an AC load instead of the motor 3 of the system shown in FIG. 2 and the reactance of the reactor 2 is changed.

  Reactor 2 is a value Xs that represents the power system reactance of power supply system 10 in the unit method based on the total capacity of all inverters connected in parallel, and a value that represents the reactance of reactor 2 in the unit method based on the unit inverter capacity. If X is Xo, the relationship of the formula (2) is satisfied.

Xo> Xs (2)
According to this embodiment, even if the AC load is a power supply system, the same actions and effects as those of the second embodiment can be obtained.

(Fourth embodiment)
FIG. 4 is a block diagram illustrating a configuration of a parallel system of the power conversion device according to the present embodiment.

  This system is the same as FIG. 2 except that an output transformer 11 is provided instead of the reactor 2 of the system shown in FIG.

  The output transformer 11 has a value Xm in which the armature leakage reactance of the motor 3 is expressed in the unit method with reference to the motor capacity, and a value Xt in which the leakage reactance of the output transformer 11 is expressed in the unit method with reference to the unit inverter capacity. Then, the relationship of Formula (3) is satisfied.

Xt> Xm Formula (3)
According to the present embodiment, the output AC voltage of the unit voltage type inverter 1 can be transformed, and the same operations and effects as those of the second embodiment can be obtained.

(Fifth embodiment)
FIG. 5 is a block diagram illustrating a configuration of a parallel system of the power conversion device according to the present embodiment.

  This system is the same as FIG. 4 except that the power supply system 10 is connected as an AC load instead of the motor 3 of the system shown in FIG. 4 and the leakage reactance of the output transformer 11 is changed.

  The output transformer 11 is a unit of the value Xs expressed in the unit method based on the total capacity of all inverters connected in parallel with the power system reactance of the power system 10 and the leakage reactance of the output transformer 11 based on the unit inverter capacity. When the value Xt expressed by the modulo is satisfied, the relationship of Expression (4) is satisfied.

Xt> Xs (4)
According to this embodiment, even if the AC load is a power supply system, the same operations and effects as those of the fourth embodiment can be obtained.

(Sixth embodiment)
FIG. 6 is a block diagram illustrating a configuration of a parallel system of the power conversion device according to the present embodiment.

  This system is the same as FIG. 2 except that a three-level inverter 12 is provided instead of the unit voltage source inverter 1 of the system shown in FIG.

  A configuration example of the three-level inverter 12 will be described with reference to FIG.

  As shown in FIG. 13, the three-level inverter 12 is mainly composed of a combination of a switching element 15 and a diode 16.

  The three-level inverter 12 converts the DC power into AC power by applying the positive and negative electrodes of DC power to the positive terminal 17P and the negative terminal 17N, respectively, and controlling the gates of the switching elements 15, thereby converting the AC power into the AC terminal. Three-phase AC power is output from 18A, 18B, and 18C.

  The three-level inverter 12 increases the AC output voltage of the inverter by a factor of two by providing a neutral point potential to the DC input voltage source and further configuring each arm in series.

  According to the present invention, the output voltage of the power conversion device can be increased, and the same operations and effects as in the second embodiment can be obtained.

(Seventh embodiment)
FIG. 7 is a block diagram illustrating a configuration of a parallel system of the power conversion device according to the present embodiment.

  This system is the same as that shown in FIG. 2 except that PWM control circuits 13A and 13B are provided between the AC current control circuit 9 and the unit voltage type inverter 1, respectively, in each power conversion device of the system shown in FIG. Same as 2.

  The unit voltage type inverter 1 is a PWM inverter.

  A configuration example of the PWM control circuits 13A and 13B will be described with reference to FIG.

  The PWM control circuits 13A and 13B are circuits for controlling the unit voltage source inverter 1 by PWM control (pulse width modulation control).

  The PWM control circuits 13A and 13B compare the three-phase AC voltage command values VU *, VV *, and VW * that are sine waves with the PWM carrier wave Tri that is a triangular wave by using the comparator circuit 31, and the unit voltage source inverter 1 The gate drive signals Gu, Gx, Gv, Gy, Gw, Gz for switching are output.

  The phases of the PWM carrier waves respectively input to the PWM control circuits 13A and 13B are shifted by 360 ° / n, where n is a parallel number (n is an integer of 2 or more). Specifically, in this system, since two power conversion devices are connected in parallel, the phase of the PWM carrier wave is shifted by 180 °.

  Here, the case where the number of power converters connected in parallel is two has been described, but the same configuration can be applied to the case of three or more.

  According to this embodiment, the harmonic component contained in the three-phase AC voltage at the parallel connection point can be reduced by shifting the phase of each PWM carrier wave.

  Therefore, the AC side output harmonics of the power converter can be reduced, and the same actions and effects as those of the second embodiment can be obtained.

(Eighth embodiment)
FIG. 8 is a block diagram showing the configuration of the parallel system of the power conversion device according to this embodiment.

  This system is the same as FIG. 4 except that the output transformer 11 of each power converter of the system shown in FIG. 4 is replaced with the output transformers 11A and 11B.

  The output transformer 11A is an output transformer having a delta-delta (Δ-Δ) connection.

  The output transformer 11B is an output transformer having a delta star (Δ-Y) connection.

  With these configurations, when the parallel number is n (n is an integer of 2 or more), the phase difference between the primary winding and the secondary winding of the output transformer 11A and the output transformer 11B is 60 ° / n each other. It is off. Specifically, in this system, since two power converters are connected in parallel, the phase difference between the primary winding and the secondary winding of the output transformer 11A and the output transformer 11B is shifted by 30 °. I am doing so.

  Here, the case where the number of power converters connected in parallel is two has been described, but the same configuration can be applied to the case of three or more.

  According to this embodiment, the harmonic component contained in the three-phase AC voltage at the parallel connection point can be reduced by shifting the phase difference between the primary winding and the secondary winding of each output transformer.

  Therefore, the AC side output harmonics of the power converter can be reduced, and the same actions and effects as those of the second embodiment can be obtained.

(Ninth embodiment)
FIG. 9 is a block diagram illustrating a configuration of a parallel system of the power conversion device according to the present embodiment.

  This system includes a switch 14 between the unit voltage source inverter 1 and the reactor 2 in each power conversion device of the system shown in FIG. 2, and further includes a switch 14 between the converter 4 and the input insulation transformer 5. 2 is the same as FIG.

  The switch 14 is a circuit breaker or a disconnector. Alternatively, both of the breaker and the disconnector may be provided as a set.

  According to this embodiment, when an abnormality such as a failure occurs in each unit voltage type inverter or converter, the corresponding unit voltage type inverter and converter can be easily separated, making repair easy and easy. Can be exchanged. Moreover, these repairs and replacements can be performed while continuing normal operation of the power converter.

  Therefore, the maintainability and the operation continuity of the parallel system of the power conversion device can be improved, and the same operation and effect as in the second embodiment can be obtained.

  Each embodiment may be modified as follows.

  In each embodiment, the inverter connected in parallel is not limited to a voltage source inverter. For example, a current source inverter may be used as long as the configuration of each embodiment is adapted. Similarly, a voltage detector may be provided instead of the current detector 8, or another device for detecting an electric quantity may be used.

  In each embodiment, it is good also as a structure which provides the direct-current power supply 19 which is the structure of 1st Embodiment instead of the converter 4 and the input insulation transformer 5. FIG.

  In each embodiment, the unit voltage source inverter 1 is configured by a three-level inverter similar to that of the sixth embodiment, so that the operation and effect of the sixth embodiment are obtained together with the operation and effect of the embodiment. Can do.

  In each embodiment, the unit voltage source inverter 1 is configured by a PWM inverter similar to the seventh embodiment, so that the operation and effect of the seventh embodiment can be obtained together with the operation and effect of the embodiment. it can.

  In the eighth embodiment, the combination of the connections of the output transformers is not limited to the combination of the Δ-Δ connection and the Δ-Y connection. For example, a combination of Y-Y connection and Y-Δ connection may be used, or any other combination. A suitable combination of connections can be selected according to various conditions such as the number of power converters connected in parallel. Moreover, by applying to the configuration of another embodiment using an output transformer, the operation and effect of the eighth embodiment can be obtained together with the operation and effect of the embodiment.

  In the ninth embodiment, the number and position of the switches can be arbitrarily selected. Thus, maintainability and the like can be improved by making the configuration more suitable for the configuration of the system and the environment to which it is applied. Further, by providing a similar switch in the configuration of the other embodiment, the operation and effect of the ninth embodiment can be obtained together with the operation and effect of the embodiment.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the components without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

The block diagram for demonstrating the structure of the system which concerns on the 1st Embodiment of this invention. The block diagram for demonstrating the structure of the system which concerns on the 2nd Embodiment of this invention. The block diagram for demonstrating the structure of the system which concerns on the 3rd Embodiment of this invention. The block diagram for demonstrating the structure of the system which concerns on the 4th Embodiment of this invention. The block diagram for demonstrating the structure of the system which concerns on the 5th Embodiment of this invention. The block diagram for demonstrating the structure of the system which concerns on the 6th Embodiment of this invention. The block diagram for demonstrating the structure of the system which concerns on the 7th Embodiment of this invention. The block diagram for demonstrating the structure of the system which concerns on the 8th Embodiment of this invention. The block diagram for demonstrating the structure of the system which concerns on the 9th Embodiment of this invention. The block diagram for demonstrating the structural example of the unit voltage type inverter which concerns on each embodiment. The circuit diagram for demonstrating the structural example of the diode rectifier circuit which concerns on each embodiment. The circuit diagram for demonstrating the structural example of the alternating current control circuit which concerns on each embodiment. The circuit diagram for demonstrating the structural example of the 3 level inverter which concerns on 6th Embodiment. The circuit diagram for demonstrating the structural example of the PWM control circuit which concerns on 7th Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Unit voltage type inverter, 2 ... Reactor, 3 ... Electric motor, 7 ... Smoothing capacitor,
8 ... Current detector, 9 ... AC current control circuit, 19 ... DC power supply.

Claims (12)

A system in which at least two power converters are connected in parallel,
Each of the power conversion devices
DC power supply means for supplying DC power;
An inverter that converts DC power from the DC power supply means into AC power and supplies the AC power to an AC load;
An electric quantity detection means for detecting the electric quantity of the AC power output from the inverter;
Based on the amount of electricity detected by the amount of electricity detecting means, the amount of AC power output from the inverter is controlled, and a control circuit independent from the control of each power converter other than the power converter,
Compared with the reactance of the AC load having a value expressed in a unit method with reference to the total capacity of the inverters connected to the inverter and the AC load, and connected to each other in parallel. And a reactor having a large reactance having a value expressed by a unit method with reference to the capacity of the inverter. A system in which at least two power converters are connected in parallel,
Each of the power conversion devices
DC power supply means for supplying DC power;
An inverter that converts direct current power from the direct current power supply means into alternating current power and supplies the alternating current power as an alternating current load to a power supply system;
An electric quantity detection means for detecting the electric quantity of the AC power output from the inverter;
Based on the amount of electricity detected by the amount of electricity detecting means, the amount of AC power output from the inverter is controlled, and a control circuit independent from the control of each power converter other than the power converter,
Compared to the power system reactance of the power system of the value represented by the unit method with reference to the total capacity of the inverters connected between the inverter and the AC load and connected to each other in parallel. And a reactor having a large reactance having a value expressed by a unit method with respect to the capacity of the inverter as a reference. A system in which at least two power converters are connected in parallel,
Each of the power conversion devices
DC power supply means for supplying DC power;
An inverter that converts DC power from the DC power supply means into AC power, and supplies the AC power to the motor as an AC load;
An electric quantity detection means for detecting the electric quantity of the AC power output from the inverter;
Based on the amount of electricity detected by the amount of electricity detecting means, the amount of AC power output from the inverter is controlled, and a control circuit independent from the control of each power converter other than the power converter,
Compared with the armature leakage reactance of the motor, which is connected between the inverter and the AC load, and the value expressed in the unit method with the motor capacity of the motor as a reference, in the unit method with the capacity of the inverter as a reference A parallel system for a power converter, comprising: a reactor having a large reactance of a value represented. A system in which at least two power converters are connected in parallel,
Each of the power conversion devices
DC power supply means for supplying DC power;
An inverter that converts the DC power from the DC power supply means to AC power and supplies the AC power to an AC load;
An electric quantity detection means for detecting the electric quantity of the AC power output from the inverter;
Based on the amount of electricity detected by the amount of electricity detecting means, the amount of AC power output from the inverter is controlled, and a control circuit independent from the control of each power converter other than the power converter,
Compared to the reactance of the AC load of the value expressed in the unit method based on the total capacity of the inverters of the power converters connected between the inverter and the AC load and connected in parallel, A parallel system for power converters, comprising: a transformer having a large leakage reactance represented by a unit method based on the capacity of the inverter. A system in which at least two power converters are connected in parallel,
Each of the power conversion devices
DC power supply means for supplying DC power;
An inverter that converts direct current power from the direct current power supply means into alternating current power and supplies the alternating current power as an alternating current load to a power supply system;
An electric quantity detection means for detecting the electric quantity of the AC power output from the inverter;
Based on the amount of electricity detected by the amount of electricity detecting means, the amount of AC power output from the inverter is controlled, and a control circuit independent from the control of each power converter other than the power converter,
Compared to the power system reactance of the power system of the value represented by the unit method with reference to the total capacity of the inverters connected between the inverter and the AC load and connected to each other in parallel. And a transformer having a large leakage reactance having a value expressed by a unit method with respect to the capacity of the inverter as a reference. A system in which at least two power converters are connected in parallel,
Each of the power conversion devices
DC power supply means for supplying DC power;
An inverter that converts DC power from the DC power supply means into AC power, and supplies the AC power to the motor as an AC load;
An electric quantity detection means for detecting the electric quantity of the AC power output from the inverter;
Based on the amount of electricity detected by the amount of electricity detecting means, the amount of AC power output from the inverter is controlled, and a control circuit independent from the control of each power converter other than the power converter,
Compared with the armature leakage reactance of the motor, which is connected between the inverter and the AC load, and the value expressed in the unit method with the motor capacity of the motor as a reference, in the unit method with the capacity of the inverter as a reference A parallel system for a power converter, comprising: a transformer having a large leakage reactance of the value indicated. The inverter of each power converter is
It is a 3 level inverter, The parallelization system of the power converter device of any one of Claims 1-6 characterized by the above-mentioned. The DC power supply means of each power converter is
A converter that converts AC power into DC power,
Each of the power conversion devices
The AC power supply is supplied from an AC power supply, the AC power is supplied to the converter, and an input insulation transformer is provided that insulates the AC power supply from the converter. The parallelization system of the power converter device of Claim 1. Each of the power conversion devices
The path of the inverter of the power converter is electrically connected to the AC load without being electrically connected to or separated from the path of the inverter of each of the power converters other than the power converter. A first switch that contacts and separates;
AC power is supplied to the DC power supply means of the power converter without electrically connecting or disconnecting a path for supplying AC power to the DC power supply means of each of the power converters other than the power converter. The parallel system for power converters according to any one of claims 1 to 8, further comprising a second switch that electrically connects and separates a path for supply. The parallel system for power converters according to claim 3, further comprising: the electric motor supplied with the AC power from the inverter of each of the power converters. The number of the power converters connected in parallel is n which is an integer of 2 or more,
The inverter of each power converter is
A PWM inverter controlled using a carrier wave for PWM control;
The PWM control carrier wave of the inverter of each power converter is
4. The power conversion device parallelization system according to claim 1, wherein the phase angle is shifted by 360 ° / n. 5. The number of the power converters connected in parallel is n which is an integer of 2 or more,
The transformer of each power converter is
The parallel system of the power converter according to any one of claims 4 to 6, wherein a phase difference between the primary winding and the secondary winding is shifted by 60 ° / n.

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