WO2021100116A1

WO2021100116A1 - Power conversion device

Info

Publication number: WO2021100116A1
Application number: PCT/JP2019/045247
Authority: WO
Inventors: 章太渡辺; 友一坂下; 聡士小鹿; 研吾内山
Original assignee: 三菱電機株式会社
Priority date: 2019-11-19
Filing date: 2019-11-19
Publication date: 2021-05-27
Also published as: JPWO2021100116A1; JP7146115B2

Abstract

This power conversion device has a plurality of single-phase inverters (2I, 3I), at least one of which is connected to an external power supply (10S), wherein the voltage ratios between the DC power supply voltages of the respective single-phase inverters (2I, 3I) are constant, and is provided with: a comparison unit (22) for calculating comparison standard values by dividing the voltage ratios by the ratios between the detected voltage values of the DC power supply voltages of the single-phase inverters (2I, 3I) and the target values of the respective DC power supply voltages and performing comparison processing on the comparison standard values; and an output pattern determination unit (23) for determining, on the basis of the comparison results obtained by the comparison unit (22) and a predetermined selection condition, an output pattern that is a combination of the single-phase inverters (2I, 3I) from which voltages are to be output. The comparison unit (22) compares an average value of at least some of the plurality of comparison standard values with the respective comparison standard values.

Description

Power converter

This application relates to a power conversion device.

A power conversion device capable of obtaining a desired output waveform by gradation control by combining a plurality of inverters has been put into practical use.

A control method has been proposed in which the voltage of the capacitor of each inverter is controlled to be constant by adjusting the charge / discharge current of each inverter at the same time as obtaining an arbitrary output voltage (for example, Patent Document 1).

Japanese Patent No. 4490309 (paragraphs [0006]-[0008] and FIG. 1)

In the control method of Patent Document 1, as the number of inverters increases, the combination of outputs of each inverter that can be selected and the number of capacitors that need to be kept constant increase, so that it becomes difficult to keep the voltage of the capacitors constant. .. As a result, there is a problem that the capacitor voltage varies, and a desired output voltage cannot be realized.

The present application discloses a technique for solving the above-mentioned problems, and power conversion capable of keeping the capacitor voltage constant and outputting an arbitrary voltage even if the number of inverters constituting the power conversion device increases. The purpose is to provide the device.

The power conversion device disclosed in the present application is one or more single-phase inverters selected from a plurality of single-phase inverters by connecting a plurality of AC sides of a single-phase inverter that converts DC power of a DC power source into AC power in series. In a power converter that controls the overall output voltage by the sum of the generated voltages to supply power to the load, each of the plurality of single-phase inverters includes a power storage element that generates a DC power supply voltage, and at least one of the plurality of single-phase inverters. One is connected to an external power supply, the ratio of the target value of the DC power supply voltage of each single-phase inverter is constant, and it is detected by the voltage detecting means for detecting the DC power supply voltage of a plurality of single-phase inverters and the voltage detecting means. A comparison unit that calculates a comparison standard value by dividing by the ratio of the DC power supply voltage of multiple single-phase inverters to the target value of each DC power supply voltage, and compares the calculated multiple comparison standard values, and the comparison unit. The comparison unit includes an output pattern determination unit that determines an output pattern that is a combination of one or more single-phase inverters that should output a voltage among a plurality of single-phase inverters based on the result and predetermined selection conditions. , An average value comparison unit that compares at least some of the average values of multiple comparison standard values with each comparison standard value as a comparison process, and a standard that compares each comparison standard value with another comparison standard value as a comparison process. It includes at least one of the value comparison units.

According to the power conversion device disclosed in the present application, even if the number of inverters increases, the capacitor voltage can be kept constant and an arbitrary voltage can be output.

It is a block diagram of the main circuit part which concerns on the power conversion apparatus by Embodiment 1. FIG. It is a block diagram of the control part which concerns on the power conversion apparatus by Embodiment 1. FIG. It is a block diagram of the comparison part of the control part which concerns on the power conversion apparatus by Embodiment 1. FIG. It is a block diagram of the modification part of the comparison part of the control part which concerns on the power conversion apparatus by Embodiment 1. FIG. It is a block diagram of an example of the main circuit part which concerns on the power conversion apparatus by Embodiment 1. FIG. It is a block diagram of one example of the comparison part of the control part which concerns on the power conversion apparatus by Embodiment 1. FIG. FIG. 5 is an explanatory diagram of an example of the relationship between the number of gradations and the output pattern according to the power conversion device according to the first embodiment. It is a block diagram of the modification of the main circuit part which concerns on the power conversion apparatus by Embodiment 1. FIG. It is a block diagram of another example of the main circuit part which concerns on the power conversion apparatus by Embodiment 1. FIG. It is a block diagram of the control part which concerns on the power conversion apparatus by Embodiment 2. It is a block diagram of the comparison part of the control part which concerns on the power conversion apparatus by Embodiment 2. It is a block diagram of one example of the comparison part of the control part which concerns on the power conversion apparatus by Embodiment 2. It is a block diagram of the control part which concerns on the power conversion apparatus by Embodiment 3. FIG. It is a block diagram of the comparison part of the control part which concerns on the power conversion apparatus by Embodiment 3. FIG. It is a block diagram of the modification part of the comparison part of the control part which concerns on the power conversion apparatus by Embodiment 3. FIG. It is a block diagram of one example of the comparison part of the control part which concerns on the power conversion apparatus by Embodiment 3. FIG.

Embodiment 1.
In the first embodiment, the plurality of single-phase inverters are composed of a main inverter group composed of one or a plurality of single-phase inverters to which DC power is supplied from the outside, and a sub-inverter group composed of a plurality of other single-phase inverters. The voltage ratio of each DC power supply of the main and sub-inverter groups is substantially constant, and the total DC power supply voltage of the main inverter group is set to be larger than the total DC power supply voltage of the sub-inverter group by a predetermined ratio, and the voltage is detected. A comparison unit that calculates a comparison standard value by dividing by the ratio of the DC power supply voltage of a plurality of single-phase inverters detected by the means and the target value of each DC power supply voltage, and performs comparison processing of the calculated multiple comparison standard values. , Equipped with an output pattern determination unit that determines the combination of outputs of each single-phase inverter, and the comparison unit includes an average value comparison unit that compares at least a part of the average values of a plurality of comparison standard values with each comparison standard value. , The output pattern determination unit selects the output combination of each single-phase inverter so that each DC voltage of the sub-inverter group becomes substantially constant by charging / discharging via each single-phase inverter using the output result of the comparison unit. It relates to a power converter.

Hereinafter, regarding the configuration and operation of the power conversion device according to the first embodiment, FIG. 1 which is a configuration diagram of a main circuit unit of the power conversion device, FIG. 2 which is a configuration diagram of a control unit, and a configuration diagram of a comparison unit of the control unit. FIG. 3, FIG. 4, which is a configuration diagram of a modified example of the comparison unit of the control unit, FIG. 5, which is a configuration diagram of an example of the main circuit unit, and FIG. 6 which is a configuration diagram of an example of the comparison unit of the control unit. Based on FIG. 7, which is an explanatory diagram of an example of the relationship between the number of gradations and an output pattern, FIG. 8 which is a configuration diagram of a modified example of the main circuit unit, and FIG. 9 which is a configuration diagram of another example of the main circuit unit. Will be explained.

The overall configuration and operation of the power conversion device of the first embodiment will be described with reference to FIGS. 1 and 2.
The power conversion device includes the main circuit unit 1 of FIG. 1 and the control unit 20 of FIG.

First, the configuration and operation of the main circuit unit 1 of the power conversion device will be described with reference to FIG.
The main circuit unit 1 includes a sub-inverter group 2 which is a second inverter group, a main inverter group 3 which is a first inverter group, a changeover switch 4, a charging resistor 5, an output filter 6, an inverter voltage detection circuit 7D, and an inverter voltage detection circuit 7D. The output voltage detection circuit 8 is provided.
A load 11 is connected to the output of the main circuit unit 1.
The entire sub-inverter group 2 and main inverter group 3 are referred to as an inverter unit.

The sub-inverter group 2 is composed of single-phase inverters 2I1, 2I2, ..., 2Im (m is an integer of 2 or more). When the single-phase inverter of the sub-inverter group 2 is described as a representative, it is described as the single-phase inverter 2I.
Further, the main inverter group 3 is composed of single-phase inverters 3Im + 1, ..., 3Im + n (n is an integer of 1 or more). When the single-phase inverter of the main inverter group 3 is described as a representative, it is described as the single-phase inverter 3I.
Further, when it is not necessary to distinguish the inverter voltage detection circuits 7D1, 7D2, ..., 7Dm, 7Dm + 1, which are voltage detecting means for detecting the output voltage of each single-phase inverter 2I and 3I, the inverter voltage detection is performed. Described as circuit 7D.

Each single-phase inverter 2I, 3I is a self-extinguishing semiconductor switching element (g11, g12, g21, g22) such as a plurality of IGBTs (Insulated Gate Bipolar transformers) in which a plurality of diodes are connected in antiparallel and a power storage element. It consists of a full bridge circuit with a capacitor.
In FIG. 1, the reference numerals of the diode and the capacitor are omitted for simplification.

The capacitors of the single-phase inverters 2I and 3I are DC power supplies of the single-phase inverters 2I and 3I.
The voltage of the DC power supply of the single-phase inverters 2I1 to 2Im of the sub-inverter group 2 V1, V2, ..., Vm, and the voltage of the DC power supply of the single-phase inverter 3Im + 1 to 3Im + n of the main inverter group 3. The voltage ratio (V1: V2: ...: Vm + n) is controlled to be substantially constant for the voltages Vm + 1 to Vm + n.
As for the voltage of the capacitor which is the DC power supply of the single-phase inverters 3Im + 1 to 3Im + n of the main inverter group 3, only the voltage of the capacitor of the single-phase inverter 3Im + 1 is detected.
Hereinafter, the voltage of the capacitor which is a DC power supply will be appropriately referred to as a DC power supply voltage or a capacitor voltage.

The total DC power supply voltage of the main inverter group 3 (Vm + 1 + Vm + 2 + ... + Vm + n) is controlled to be larger than the total DC power supply voltage of the sub-inverter group 2 (V1 + V2 + ... + Vm) at a predetermined ratio.
In the case of the first embodiment, V1: V2: ...: Vm + n is controlled to 1: 2: ...: 2 ^ (m + n-1). The details of the control will be described later.
The single-phase inverters 3Im + 1 ..., 3Im + n of the main inverter group 3 are supplied with electric power by the external power supplies 10S1, ..., 10Sn.
When it is not necessary to distinguish each external power supply 10S1, ..., 10Sn, it is described as an external power supply 10S.

Each single-phase inverter 2I, 3I can generate positive and negative and zero voltages as outputs.
For example, in the single-phase inverter 2I1, when the output is positive, the semiconductor switching elements g11 and g22 are turned on, and when the output is negative, the semiconductor switching elements g12 and g21 are turned on. When the output is 0, the semiconductor switching elements g11 and g21 (or g12 and g22) are turned on.

The inverter unit includes a sub-inverter group 2 and a main inverter group 3, and the AC side of each single-phase inverter 2I1 to 2Im, 3Im + 1 to 3Im + n is connected in series. By combining the generated voltages of the single-phase inverters 2I1 to 2Im, 3Im + 1 to 3Im + n, a predetermined voltage is output as the total by gradation control.
The inverter unit supplies power to the load 11 via the output filter 6 with a predetermined voltage whose gradation is controlled.
When the output voltage ratio of each single-phase inverter 2I1 to 2Im, 3Im + 1 to 3Im + n is controlled as V1: V2: ...: Vm + n is 1: 2: ...: 2 ^ (m + n-1), the inverter unit The output voltage of is V1 (gradation number 1) from 0 (gradation number 0) to V1 × {2 ^ (m + n-1)} (gradation number 2 ^ (m + n-1)). it can.

A charging resistor 5 and a changeover switch 4 are installed at the output end of the inverter unit.
The changeover switch 4 connects the AC output end of the sub-inverter group 2 to the charging resistor 5 when the power conversion device is started to initially charge each DC power source of the sub-inverter group 2. The changeover switch 4 is connected to the output filter 5 side at the time of normal output.
This initial charge is performed by the control described later. In FIG. 1, the changeover switch 4 is connected to the AC output of the sub-inverter group 2, but may be connected to the output side of the main inverter group 3. Further, the changeover switch 4 and the charging resistor 5 may be installed on the output side of the output filter 6.

Further, the initial charge of each DC power source of the sub-inverter group 2 may be performed by passing a charging current through the load 11. In this case, since the charging current is passed through the load 11, the charging resistor 5 and the changeover switch 4 are unnecessary.
Further, the initial charge of each DC power source of the sub-inverter group 2 may be performed by connecting an external power source to the sub-inverter group 2 only at the time of the initial charge. In this case, since the DC power supply of each single-phase inverter 2I1 of the sub-inverter group 2 is directly charged, the charging resistor 5 and the changeover switch 4 are unnecessary.

The capacitor voltage which is the DC power supply voltage of each single-phase inverter 2I of the sub-inverter group 2 and the capacitor voltage which is the DC power supply voltage of one or more single-phase inverters 3I of the main inverter group 3 are detected by the inverter voltage detection circuit 7D. ..
FIG. 1 shows an example of detecting only the capacitor voltage, which is the DC power supply voltage of the single-phase inverter 3Im + 1, which has the smallest voltage in the main inverter group 3.
Hereinafter, a case where only the capacitor voltage, which is the DC power supply voltage of the single-phase inverter 3Im + 1, which has the smallest voltage in the main inverter group 3, is detected will be described.
The same method can be applied even if a capacitor voltage, which is a DC power supply voltage other than the single-phase inverter having the smallest voltage in the main inverter group 3, is detected.

The voltage output to the load 11 is detected by the output voltage detection circuit 8. The installation position of the output voltage detection circuit 8 may be any position as long as it can detect the output voltage of the inverter unit, and may be, for example, the front stage of the output filter 6 or the front stage of the changeover switch 4.

Next, the configuration and operation of the control unit 20 will be described with reference to FIG.
The control unit 20 includes a gradation number determination unit 21, a comparison unit 22, an output pattern determination unit 23, and a gate signal generation unit 24.

The gradation number determination unit 21 determines the gradation number in order to control the output voltage Vo to the output voltage command value based on the output voltage Vo detected by the output voltage detection circuit 8 and the output voltage command value.
Specifically, the difference between the output voltage detection value Vo and the output voltage command value is input to the PI (Proportional-Integral) controller, and the output result of the PI controller is used as the number of gradations.
The PI control may be any control such as P (Proportional) control and PID (Proportional-Integral-Differential) control that operates so as to bring the output voltage detection value Vo closer to the output voltage command value.
Further, a rounding process or a limiter process for a value smaller than the number adopted for the number of gradations of the PI calculation result (the portion after the decimal point) may be added.

Next, the configuration and operation of the comparison unit 22 will be described with reference to FIG.
The comparison unit 22 includes a divider 22D, an average calculator 22H, and an average value comparator 22AC which is an average value comparison unit. In the figure, the OPD is an output pattern determination unit.
For example, the dividers have different inputs and outputs, but have the same functions, so the divider 22D is used. Further, although the input and output of the average value comparator are different, the functions are the same, so the average value comparator 22AC is used. Similarly, in the subsequent configuration diagrams of the comparison section, the code numbers of each arithmetic unit are not distinguished.

The capacitor voltages V1 to Vm + 1 of the single-phase inverters 2I and 3I detected by the inverter voltage detection circuit 7D are input to the comparison unit 22. The input capacitor voltages V1 to Vm + 1 are converted, that is, standardized, into signals V1 * to Vm + 1 * having uniform voltage levels by the divider 22D. This standardized signal is referred to as a comparative standard value.
That is, the comparative standard value is calculated by dividing by the ratio of the DC power supply voltage of the plurality of single-phase inverters detected by the voltage detecting means and the target value of each DC power supply voltage.

Specifically, for example, the capacitor voltage Vm of the single-phase inverter 2Im detected by the inverter voltage detection circuit 7Dm is divided by Km, which is the ratio of the target value of the capacitor voltage in the divider 22D.
Here, for K1 to Km + 1, the ratio of the target values of the capacitor voltages of the single-phase inverters 2I1 to 2Im and 3Im + 1 is (V1: V2: ...: Vm + 1) = (1: 2: ...: 2 ^ m). Then, for example, K1 = 1, K2 = 2, ..., Km + 1 = 2 ^ m may be set.

The average value Wave is calculated by the average calculator 22H from the standardized signal, that is, the comparative standard values V1 * to Vm + 1 *. The average value Wave is compared with the comparison standard value (V2 * to Vm + 1 *) by the average value comparator 22AC, and m average value comparison signals are output.

The comparison unit 22 in the first embodiment may output the comparison result using the calculated average value, and may change the calculation method of the average value as shown in FIG. 4, for example.
FIG. 4 is a configuration diagram of a modified example of the comparison unit, and is referred to as the comparison unit 22A in order to distinguish it from the comparison unit 22 of FIG.
The comparison unit 22A includes a divider 22AD, an average calculator 22AH, and an average value comparator 22AAC. In the figure, the OPD is an output pattern determination unit.

In FIG. 4, the average value Vave-1 is calculated from the comparative standard values V1 * to Vm + 1 * by the average calculator 22AH, and the average value Vave-2 is calculated from the comparative standard values V1 * to Vm * by the average calculator 22AH. Further, the average value Wave-m is calculated from the comparative standard values V1 * and V2 * by the average calculator 22AH.
The average value Vave-1 is compared with the comparison standard value Vm + 1 * and the average value comparator 22AAC, the average value Vave-2 is compared with the comparison standard value Vm * and the average value comparator 22AAC, and the average value Vave-m is the comparison standard. The value V2 * is compared with the average value comparator 22AAC, and each average value comparison signal is output.
That is, assuming that L is an integer in the range of (1 <L ≦ m + 1), the comparison standard value from 1 to VL is used for the calculation of the average value to be compared with the comparison standard value VL *.

Generalizing the configuration of the comparison unit of the first embodiment, when the sub-inverter group is composed of Y single-phase inverters, the comparison unit includes Y or more average value comparison units.

The operation of the output pattern determination unit 23 will be described.
The output pattern determination unit 23 determines the combination (output pattern) of the outputs of each single-phase inverter by the operation described later based on the gradation number determined by the gradation number determination unit 21 and the comparison result output from the comparison unit 22. ..
The control unit 20 controls the capacitor voltages of the single-phase inverters 2I and 3I to be substantially constant based on the output pattern and the number of gradations determined by the output pattern determination unit 23.

The gate signal generation unit 24 generates a gate signal for operating the single-phase inverters 2I and 3I based on the output result of the output pattern determination unit 23.
Specifically, a gate drive signal for driving the semiconductor switching elements g11 to g22 of each single-phase inverter 2I and 3I is generated from the output pattern.

Next, a specific example of the operation of the output pattern determination unit 23 will be described with reference to FIGS. 5 to 7.
The output pattern determination unit 23 determines an output pattern from a plurality of output patterns that realize the number of gradations obtained from the gradation number determination unit 21 by using the output result of the comparison unit 22. At that time, the output pattern is determined according to the following rules. Determine the output pattern.
(A) Determine the output from a single-phase inverter with a large capacitor voltage.
(B) In a certain single-phase inverter, when the capacitor voltage is larger than the average value, the output is selected in the order of +, 0,-. If the capacitor voltage is smaller than the average value, the output is selected in the order of-, 0, +.

The operation of the output pattern determination unit 23 will be described with reference to FIG. 5, which is a configuration diagram of an example of the main circuit unit 1.
FIG. 5 shows an example in which the sub-inverter group 2 is composed of three single-phase inverters 2I1, 2I2, 2I3, and the main inverter group 3 is composed of one single-phase inverter 3I4.
In order to distinguish it from the main circuit unit 1 in FIG. 1, the main circuit unit 1A is used. Further, the sub-inverter group 2A and the main inverter group 3A are used.
The output voltage of the single-phase inverter 2I1 is detected by the inverter voltage detection circuit 7D1, the output voltage of the single-phase inverter 2I2 is detected by the inverter voltage detection circuit 7D2, and the output voltage of the single-phase inverter 2I3 is detected by the inverter voltage detection circuit 7D3. ing. Further, the output voltage of the single-phase inverter 3I4 is detected by the inverter voltage detection circuit 7D4.
For the sake of simplicity, the changeover switch 4 and the charging resistor 5 are omitted.

The capacitor voltages V1, V2, V3, and V4 of the single-phase inverters 2I1, 2I2, 2I3, and 3I4 are controlled to be substantially constant at 1: 2: 4: 8. Further, the first single-phase inverter, the second single-phase inverter, the third single-phase inverter, and the fourth single-phase inverter will be described in order from the single-phase inverter having the smallest capacitor voltage.
In this example, the single-phase inverter 2I1 corresponds to the first single-phase inverter, the single-phase inverter 2I2 corresponds to the second single-phase inverter, the single-phase inverter 2I3 corresponds to the third single-phase inverter, and the single-phase inverter 3I4. Corresponds to the fourth single-phase inverter.

FIG. 6 shows an example of a comparison unit corresponding to the main circuit unit 1A of FIG.
Here, in FIG. 6, the comparison unit 22B is used to distinguish it from the comparison unit 22 in FIG. 3 and the comparison unit 22A in FIG.
The comparison unit 22B includes a divider 22BD, an average calculator 22BH, and an average value comparator 22BAC. In the figure, the OPD is an output pattern determination unit.

The capacitor voltage of each single-phase inverter 2I1, 2I2, 2I3, 3I4 is V1 = 0.9V, V2 = 1.9V, V3 = 4.1V, V4 = 8.1V, and the output of the gradation number determination unit 21 is 3. Imagine if there was one.
In the comparison unit 22B, the divider 22BD calculates V1 * = 0.9V, V2 * = 0.95V, V3 * = 1.025V, and V4 * = 1.0125V.
The average value Wave≈0.972 is calculated by the average calculator 22BH.
The comparison results V4 *> Vave, V3 *> Vave, and V2 * <Vave are output from the average value comparator 22BAC.

As shown in FIG. 7, there are five output patterns, patterns A to E, when the number of gradations is 3.
In pattern A, + is output (3 = 1 + 2) by the first single-phase inverter and the second single-phase inverter.
In pattern B, the third single-phase inverter outputs + and the first single-phase inverter outputs − (3 = 4-1). In pattern C, + is output by the first and third single-phase inverters, and-is output by the second single-phase inverter (3 = 4-2 + 1).
In pattern D, + is output by the fourth single-phase inverter, and-is output by the first and third single-phase inverters (3 = 8-4-1).
In the pattern E, the first and fourth single-phase inverters output +, and the second and third single-phase inverters output − (3 = 8-4-2 + 1).

A specific example of the operation of the output pattern determination unit 23 will be described. In this example, the output pattern is determined according to the following rules.
(A) The output is determined from a single-phase inverter having a large capacitor voltage V1 to V4.
(B) In each single-phase inverter, when the comparison standard value is larger than the average value, the output is selected in the order of priority of +, 0,-. If the comparison standard value is smaller than the average value, the output is selected in the order of-, 0, +.

Specifically, the output of the fourth single-phase inverter having the largest capacitor voltage is determined in order.
Since the comparative standard value of the fourth single-phase inverter is larger than the average value (V4 *> Wave), the output of the fourth single-phase inverter is selected in the order of +, 0,-. Of the five patterns with the number of gradations 3, patterns D and E in which the fourth single-phase inverter has a + output are selected.
Next, consider a third single-phase inverter with a large capacitor voltage. Since the comparative standard value of the third single-phase inverter is larger than the average value (V3 *> Wave), the output of the third single-phase inverter is selected in the order of +, 0,-. Since the outputs of the third single-phase inverters of patterns D and E are both −, only one of patterns D and E cannot be selected, so both patterns D and E are selected.
Next, consider a second single-phase inverter with a large capacitor voltage. Since the comparative standard value of the second single-phase inverter is smaller than the average value (V2 * <Vave), the output of the second single-phase inverter is selected in the order of −, 0, +.
Since the pattern D has 0 output and the pattern E has-output, the pattern E in which the second single-phase inverter has-output is selected. By the above operation, the pattern E is selected under the above conditions and output to the gate signal generation unit 24.

In the above description of the first embodiment, the method of determining the output from the single-phase inverter having a large capacitor voltage is shown by the output pattern determination unit 23, but the order of the single-phase inverters that determine the output can be freely changed. There is no problem.
For example, the output may be determined from a single-phase inverter having a small capacitor voltage. However, fluctuations in the capacitor voltage of a single-phase inverter with a large capacitor voltage appear more as fluctuations in the output voltage, so it is desirable to determine from the output of a single-phase inverter with a large capacitor voltage.

In the above description of the first embodiment, the configuration in which the output voltage Vo of the main circuit unit 1 is detected and the output voltage Vo is brought close to the voltage command value has been described.
The output current Io of the main circuit unit 1 may be detected and the output current Io may be brought close to the current command value. FIG. 8 shows a configuration diagram of a main circuit unit when the output current Io is controlled so as to approach the current command value. In FIG. 8, the main circuit unit 1B is used to distinguish it from the main circuit unit 1 of FIG.
The output voltage detection circuit 8 of FIG. 1 may be changed to the output current detection circuit 12, and the control unit 20 may change the signal input to the gradation number determination unit 21 to the output current detection value and the output current command value.

Next, an example of providing an inverter voltage detection circuit for detecting the capacitor voltage of a plurality of single-phase inverters of the main inverter group 3 will be described with reference to FIG.
In order to distinguish it from the main circuit unit 1A in FIG. 5, the main circuit unit 1C is used. Further, the sub-inverter group 2C and the main inverter group 3C are used.
FIG. 9 shows an example in which the sub-inverter group 2 is composed of two single-phase inverters 2I1 and 2I2, and the main inverter group 3 is composed of two single-phase inverters 3I3 and 3I4.
The external power supply 10S1 is connected to the single-phase inverter 3I3, and the external power supply 10S2 is connected to the single-phase inverter 3I4.
For the sake of simplicity, the changeover switch 4 and the charging resistor 5 are omitted.

The capacitor voltages V1, V2, V3, and V4 of the single-phase inverters 2I1, 2I2, 3I3, and 3I4 are controlled to be substantially constant at 1: 2: 4: 8. Further, the first single-phase inverter, the second single-phase inverter, the third single-phase inverter, and the fourth single-phase inverter will be described in order from the single-phase inverter having the smallest capacitor voltage.
In this example, the single-phase inverter 2I1 corresponds to the first single-phase inverter, the single-phase inverter 2I2 corresponds to the second single-phase inverter, the single-phase inverter 3I3 corresponds to the third single-phase inverter, and the single-phase inverter 3I4. Corresponds to the fourth single-phase inverter.

The control method (selection procedure) described above with reference to FIGS. 5 to 7 can be applied to the main circuit unit 1C having the configuration shown in FIG.
Specifically, as in the case where the sub-inverter group 2 has three single-phase inverters and the main inverter group 3 has one single-phase inverter, the third single-phase inverter is regarded as not connected to an external power source. Each single-phase inverter 2I1, 2I2, 3I3, 3I4 can be controlled by using the output pattern selection procedure. In this case, the power capacity of the external power supply 10S can be reduced.

Further, the 4th single-phase inverter 3I4 is not used for constant capacitor voltage control, and is operated as + output when the number of gradations is 8 or more and 0 output when the number of gradations is 7 or less, and the total of the first to third single-phase inverters. The three units may perform constant capacitor voltage control by the control method (selection procedure) described above.
In this case, the inverter voltage detection circuit 7D4 of the fourth single-phase inverter 3I4 and one stage of the single-phase inverter of the control unit 20 can be omitted.

In the above description of the first embodiment, the configuration in which the external power supply 10S is not connected to the sub-inverter group 2 has been described. However, in order to stabilize the capacitor voltage of the sub-inverter group 2, the external power supply 10S may also be connected to the sub-inverter group 2.
Even in this case, by applying the present embodiment, the power supply capacity required for the external power supply 10S is reduced as compared with the conventional power conversion device to which the gradation control is applied, and the device is compact and inexpensive. be able to.

In the power conversion device of the first embodiment, the ratio (comparative standard value) between the capacitor voltage of each single-phase inverter and the target value of the capacitor voltage of each single-phase inverter is calculated and compared with the average value of the calculated comparative standard values. The output pattern is selected using the comparison result with the standard value. As a result, the charge / discharge current of each single-phase inverter of the sub-inverter group 2 is adjusted, and a desired output voltage is output while keeping the voltage ratio of each single-phase inverter (2I1 to 2Im, 3Im + 1 to 3Im + n) substantially constant. It becomes possible. Therefore, it is possible to eliminate the need for a power source for supplying electric power to the sub-inverter group 2, so that the device is small and inexpensive.

Further, in the output pattern determination unit of the first embodiment, by selecting the output code in order from the inverter having the largest capacitor voltage, the capacitor voltage fluctuation of the single-phase inverter having the largest capacitor voltage is suppressed, and the output voltage fluctuates greatly. Can be suppressed.

Further, in the output pattern determination unit 23, (A) the output is determined from the single-phase inverter having a large capacitor voltage, and (B) in a certain single-phase inverter, when the comparison standard value is larger than the average value, +, 0,-. The output pattern can be determined by a simple rule that the output is selected in the order of priority, and if the comparison standard value is smaller than the average value, the output is selected in the order of priority of-, 0, +. Since this rule can be applied even when the number of single-phase inverters increases, it is possible to control each capacitor voltage substantially constantly while outputting an arbitrary output voltage even when the number of single-phase inverters increases.

In the first embodiment, in order to make it easier to understand the overall configuration and operation of the power conversion device, the sub-inverter group 2 and the main inverter group 3 have been described separately. However, the whole may be treated as one single-phase inverter group, at least one of the single-phase inverters may be connected to an external power supply, and the voltage ratio of the DC power supply voltage of each single-phase inverter may be controlled to be constant.

As described above, in the power conversion device of the first embodiment, the plurality of single-phase inverters are a main inverter group composed of one or a plurality of single-phase inverters to which DC power is supplied from the outside, and a plurality of other single-phase inverters. It is composed of a sub-inverter group consisting of inverters, and the voltage ratio of each DC power supply of the main and sub-inverter groups is almost constant. A plurality of comparisons calculated by dividing by the ratio of the DC power supply voltage of a plurality of single-phase inverters detected by the voltage detecting means and the target value of each DC power supply voltage to calculate a comparison standard value, which is largely set by a predetermined ratio. A comparison unit that performs standard value comparison processing and an output pattern determination unit that determines the combination of outputs of each single-phase inverter are provided, and the comparison unit includes an average value of at least a part of a plurality of comparison standard values and each comparison standard value. The output pattern determination unit uses the output result of the comparison unit to make each DC voltage of the sub-inverter group substantially constant by charging / discharging via each single-phase inverter. The combination of outputs of the single-phase inverter is selected.
Therefore, the power conversion device of the first embodiment can keep the capacitor voltage constant and output an arbitrary voltage even if the number of inverters increases.

Embodiment 2.
The power conversion device of the second embodiment includes a standard value comparison unit that compares a comparison standard value with another comparison standard value as a comparison unit.

Regarding the power conversion device of the second embodiment, FIG. 10 is a configuration diagram of a control unit, FIG. 11 is a configuration diagram of a comparison unit of the control unit, and FIG. 12 is a configuration diagram of an example of the comparison unit of the control unit. The difference from the first embodiment will be mainly described. The drawings of the first embodiment will be referred to as appropriate.
In the configuration diagram of the second embodiment, the same or corresponding parts as those of the first embodiment are designated by the same reference numerals.

The configuration of the control unit 30 will be described with reference to FIG.
The control unit 30 includes a gradation number determination unit 21, a comparison unit 32, an output pattern determination unit 33, and a gate signal generation unit 24. The difference from the control unit 20 of the first embodiment is the comparison unit 32 and the output pattern determination unit 33.

The configuration and operation of the comparison unit 32 will be described with reference to FIG.
The comparison unit 32 includes a divider 32D and a standard value comparator 32SC which is a standard value comparison unit. In the figure, the OPD is an output pattern determination unit.

In the comparison unit 32, the capacitor voltages V1 to Vm + 1 of each single-phase inverter 2I and 3I detected by the inverter voltage detection circuit 7D are input. The input capacitor voltages V1 to Vm + 1 are standardized by the divider 32D to the comparative standard values V1 * to Vm + 1 * whose voltage levels are aligned.

The comparison unit 32 compares the standardized comparison standard values V1 * to Vm + 1 * with the standard value comparator 32SC to clarify the magnitude relationship of the comparison standard values V1 * to Vm + 1 *, and determines the output pattern as a result. Output to unit 33.
The comparison unit 32 in the second embodiment is different from the first embodiment in that the sum calculation is not performed, that is, the averaging calculation is not performed. When m + 1 voltage is detected by the inverter voltage detection circuit 7D, the magnitude relationship of all comparison standard values can be calculated if there are (m + 1) × m / 2 or more standard value comparators.

Generalizing the configuration of the comparison unit of the second embodiment, when the sub-inverter group is composed of Y single-phase inverters, the comparison unit is composed of (Y + 1) × Y / 2 or more standard value comparison units. Will be done.

The operation of the output pattern determination unit 33 will be described.
The output pattern determination unit 33 determines the combination of outputs (output pattern) of each single-phase inverter based on the number of gradations determined by the gradation number determination unit 21 and the comparison result output from the comparison unit 32.
The control unit 30 controls the capacitor voltages of the single-phase inverters 2I and 3I to be substantially constant based on the output pattern and the number of gradations determined by the output pattern determination unit 33.

The gate signal generation unit 24 generates a gate signal for operating each single-phase inverter 2I and 3I based on the output result of the output pattern determination unit 33.

The output pattern determination unit 33 determines an output pattern from a plurality of output patterns that realize the number of gradations obtained from the gradation number determination unit 21 by using the output result of the comparison unit 32. At that time, the output pattern is determined according to the following rules. Determine the output pattern.
(A) The output is determined from a single-phase inverter having a large comparison standard value V1 * to Vm + 1 *.
(B) The output of each single-phase inverter is selected in the order of +, 0,-.

The operation of the output pattern determination unit 33 will be described with reference to the example shown in FIG. 5 of the first embodiment.
FIG. 5 shows an example in which the sub-inverter group 2 is composed of three single-phase inverters 2I1, 2I2, 2I3, and the main inverter group 3 is composed of one single-phase inverter 3I4.
The capacitor voltages V1, V2, V3, and V4 of the single-phase inverters 2I1, 2I2, 2I3, and 3I4 are controlled to be substantially constant at 1: 2: 4: 8.

FIG. 12 shows an example of the comparison unit 32 of the second embodiment corresponding to the main circuit unit 1A of FIG.
Here, in FIG. 12, the comparison unit 32A is used to distinguish it from the comparison unit 32 of FIG.
The comparison unit 32A includes a divider 32AD and a standard value comparator 32ASC. In the figure, the OPD is an output pattern determination unit.

It is assumed that the capacitor voltage of each single-phase inverter is V1 = 0.9V, V2 = 1.9V, V3 = 4.1V, V4 = 8.1V, and the output of the gradation number determination unit 21 is 3.
In the comparison unit 32A, the divider 32AD calculates V1 * = 0.9V, V2 * = 0.95V, V3 * = 1.025V, and V4 * = 1.0125V.
The comparison result V3 *> V4 *> V2 *> V1 * is output from the standard value comparator 32ASC.

The specific operation of the output pattern determination unit 33 will be described.
As shown in FIG. 7, there are five output patterns, patterns A to E, when the number of gradations is 3.
The output pattern determination unit 33 determines in order from the output of the third single-phase inverter having the largest comparison standard value. Since the outputs are selected in the order of priority of +, 0,-, patterns B and C in which the third single-phase inverter has a + output are selected.
Next, the output of the fourth single-phase inverter with the larger comparative standard value is selected. The output is selected in the order of priority of +, 0,-, but since the output of the fourth single-phase inverter of patterns B and C is 0, it cannot be selected by the fourth single-phase inverter.
Next, a second single-phase inverter having a large comparative standard value will be examined. Since the output of the second single-phase inverters of patterns B and C is 0 for pattern B and − for pattern C, pattern B with 0 output is selected.
By the above operation, the pattern E is selected under the above conditions and output to the gate signal generation unit 24.

Here, an example is shown in which the output pattern determination unit 33 selects an output from a single-phase inverter having a large comparison standard value, but if the output pattern is determined using the magnitude relationship of the comparison standard value, the output is determined. There is no problem even if you change the order.
For example, the output may be selected from a single-phase inverter having a smaller comparison standard value. In this case, the output of the single-phase inverter is selected in the order of-, 0, +.

According to the second embodiment, the comparison standard value is calculated from the ratio of the target value of the capacitor voltage of each single-phase inverter and the capacitor voltage of each single-phase inverter, and the output pattern is used by using the comparison result of the calculated comparison standard value. Select. As a result, the charge / discharge current of each single-phase inverter of the sub-inverter group 2 is adjusted, and a desired output voltage can be output while keeping the voltage ratio of each single-phase inverter 2I and 3I substantially constant. Therefore, it is possible to eliminate the need for a power source for supplying electric power to the sub-inverter group 2, so that the device is small and inexpensive.

Further, since the output pattern determination unit of the second embodiment selects the output code in order from the single-phase inverter having the larger comparative standard value, it is possible to prevent the capacitor voltage of the single-phase inverter from increasing significantly, and the voltage. It is possible to prevent the adverse effect on the capacitor due to the rise.

Further, the output pattern determination unit 33 determines the output from the single-phase inverter having the larger comparison standard value V1 * to Vm + 1 *, and (B) the output of each single-phase inverter has priority in the order of +, 0,-. The output pattern can be determined by a simple rule of selecting with. Since this rule can be applied even when the number of single-phase inverters increases, it is possible to control each capacitor voltage substantially constantly while outputting an arbitrary output voltage even when the number of single-phase inverters increases.

As described above, the power conversion device of the second embodiment includes a standard value comparison unit for comparing a comparison standard value with another comparison standard value as a comparison unit.
Therefore, the power conversion device of the second embodiment can keep the capacitor voltage constant and output an arbitrary voltage even if the number of inverters increases.

Embodiment 3.
The power conversion device of the third embodiment has an average value comparison unit that compares at least a part of the average values of a plurality of comparison standard values with each comparison standard value as a comparison unit, and each comparison standard value and another comparison standard. It is equipped with both standard value comparison units that compare values.

Regarding the power conversion device of the third embodiment, FIG. 13 is a configuration diagram of a control unit, FIG. 14 is a configuration diagram of a comparison unit of the control unit, FIG. 15 is a configuration diagram of a modified example of the comparison unit of the control unit, and The difference from the first embodiment will be mainly described with reference to FIG. 16, which is a configuration diagram of an example of the comparison unit of the control unit. The drawings of the first embodiment will be referred to as appropriate.
In the configuration diagram of the third embodiment, the same or corresponding parts as those of the first embodiment are designated by the same reference numerals.

The configuration of the control unit 40 will be described with reference to FIG.
The control unit 40 includes a gradation number determination unit 21, a comparison unit 42, an output pattern determination unit 43, and a gate signal generation unit 24. The difference from the control unit 20 of the first embodiment is the comparison unit 42 and the output pattern determination unit 43.

The configuration and operation of the comparison unit 42 will be described with reference to FIG.
The comparison unit 42 includes a divider 42D, an average calculator 42H, an average value comparator 42AC which is an average value comparison unit, and a standard value comparator 42SC which is a standard value comparison unit. In the figure, the OPD is an output pattern determination unit.

In the comparison unit 42, the capacitor voltages V1 to Vm + 1 of each single-phase inverter 2I and 3I detected by the inverter voltage detection circuit 7D are input. The input capacitor voltages V1 to Vm + 1 are standardized by the divider 42D to the comparative standard values V1 * to Vm + 1 * whose voltage levels are aligned.

The comparison unit 42 calculates the average value Wave from the standardized comparison standard values V1 * to Vm + 1 * with the average calculator 42H. The average value Wave and the comparison standard values V4 * to Vm + 1 * are compared with the average value comparator 42AC. Further, the comparison standard values V3 * to V1 * are compared by the standard value comparator 42SC, respectively, and the magnitude relationship is clarified. Then, the difference between the average value Wave and the comparison standard values V4 * to Vm + 1 * and the magnitude relationship between the comparison standard values V1 * to V * 3 are the outputs of the comparison unit 42.
The comparison unit 42 in the third embodiment is different from the first and second embodiments in that both the comparison using the average value and the comparison not using the average value are used.

Note that the comparison unit 42 may use both a comparison using the average value and a comparison not using the average value, and for example, the calculation method of the average value may be changed as shown in FIG. Further, the ratio of the comparison using the average value and the comparison not using the average value may be changed.

For example, FIG. 15 will explain an example in which the comparison standard values V3 * to Vm + 1 * are compared with the average value, and only the comparison standard values V2 * and V1 * are compared in magnitude.
The comparison unit 42A includes a divider 42AD, an average calculator 42AH, an average value comparator 42AAC, and a standard value comparator 42ASC. In the figure, the OPD is an output pattern determination unit.

The average value Wave calculated by the average calculator 42AH and the comparison standard values V3 * to Vm + 1 * are compared by the average value comparator 42AAC. Further, the comparison standard values V1 * to V2 * are compared by the standard value comparator 42ASC, and the magnitude relationship thereof is clarified. Then, the difference between the average value Wave and the comparative standard values V3 * to Vm + 1 * and the magnitude relationship between the comparative standard values V1 * to V * 2 are the outputs of the comparison unit 42A.

Generalizing the configuration of the comparison unit of the third embodiment, when the sub-inverter group is composed of Y single-phase inverters, X is a condition of (0 <X <Y), and the comparison unit is (X + 1). Includes × X / 2 or more average value comparison units and YX / 2 or more standard value comparison units.

The operation of the output pattern determination unit 43 will be described.
The output pattern determination unit 43 in the third embodiment determines an output pattern to be used by using the output result of the comparison unit 42 from the output patterns that realize the number of gradations obtained from the gradation number determination unit 21. The output pattern determination unit 43 in the third embodiment determines the output pattern according to the following rules.
(A) Select the output in the order of the comparison result using the average value and the comparison result not using the average value.
(B) When using the comparison result using the average value, follow the following rules (same as the first embodiment).
(B1) Determine the output from a single-phase inverter with a large capacitor voltage.
(B2) In a single-phase inverter, if the comparison standard value is larger than the average value, the output is selected in the order of +, 0,-, and if the comparison standard value is smaller than the average value,-, 0. Select the output in the order of priority, +.

(C) The comparison result without using the average value follows the following rule (same as the second embodiment).
(C1) The output is determined from a single-phase inverter having a large comparison standard value V1 * to Vm + 1 *.
(C2) The output of each single-phase inverter is selected in the order of priority of +, 0,-.

The operation of the output pattern determination unit 43 will be described with reference to the example shown in FIG. 5 of the first embodiment.
FIG. 5 shows an example in which the sub-inverter group 2 is composed of three single-phase inverters 2I1, 2I2, 2I3, and the main inverter group 3 is composed of one single-phase inverter 3I4.
The capacitor voltages V1, V2, V3, and V4 of the single-phase inverters 2I1, 2I2, 2I3, and 3I4 are controlled to be substantially constant at 1: 2: 4: 8.

FIG. 16 shows an example of the comparison unit 42 of the third embodiment corresponding to the main circuit unit 1A of FIG.
Here, in FIG. 16, the comparison unit 42B is used to distinguish it from the comparison unit 42 in FIG.
The comparison unit 42B includes a divider 42BD, an average calculator 42BH, an average value comparator 42BAC, and a standard value comparator 42BSC. In the figure, the OPD is an output pattern determination unit.

It is assumed that the capacitor voltage of each single-phase inverter is V1 = 0.9V, V2 = 1.9V, V3 = 4.1V, V4 = 8.1V, and the output of the gradation number determination unit 21 is 3.
In the comparison unit 42B, V1 * = 0.9V, V2 * = 0.95V, V3 * = 1.025V, and V4 * = 1.0125V are calculated by the divider 42BD. Wave ≈ 0.972 is calculated by the average calculator 42BH. Further, V4 *> Wave is output from the average value comparator 42BAC, and V3 *> V2 *> V1 * is output from the standard value comparator 42BSC.

The specific operation of the output pattern determination unit 43 will be described.
As shown in FIG. 7, there are five output patterns, patterns A to E, when the number of gradations is 3.
The output pattern determination unit 43 first selects an output pattern based on the comparison result using the average value.
In this example, only the 4th single-phase inverter is compared using the average value, and the comparison standard value of the 4th single-phase inverter is larger than the average value (V4 *> Wave), so + Select the output in the order of priority, 0,-.
As a result, among the five patterns A to E, the patterns D and E in which the output of the fourth single-phase inverter is + are selected.

Since the only single-phase inverter that makes comparisons using the average value is the fourth single-phase inverter, the output pattern is then determined based on the comparison results that do not use the average value.
Since V3 *> V2 *> V1 *, the output of the third single-phase inverter having the largest comparative standard value is determined in order.
The output is selected in the order of priority of +, 0, and-, but patterns D and E cannot be selected because the third single-phase inverter is both-output.
Next, a second single-phase inverter having a large comparative standard value will be examined.
Since the output of the second single-phase inverters of patterns D and E is 0 for pattern D and − for pattern E, pattern D with 0 output is selected.
By the above operation, the pattern D is selected under the above conditions and output to the gate signal generation unit 24.

Here, an example is shown in which the output is determined in the order of the comparison result using the average value and the comparison result not using the average value, but the comparison result not using the average value and the comparison result using the average value are used in this order. You may select the output.
Further, a comparison using an average value for a single-phase inverter having a large capacitor voltage may be used, and a comparison using an average value may be used for a single-phase inverter having a small capacitor voltage.
However, since a single-phase inverter with a small capacitor voltage is more likely to cause a voltage rise due to the charging current, it is desirable to use a comparison result that does not use an average value that can suppress the voltage rise for a single-phase inverter with a small capacitor voltage. ..

According to the third embodiment, the comparison standard value is calculated from the ratio of the target value of the capacitor voltage of each single-phase inverter and the capacitor voltage of each single-phase inverter, and the comparison using the average value of the calculated comparison standard values is performed. The output pattern is selected using the comparison result between the calculated comparison standard values.
As a result, the charge / discharge current of each single-phase inverter of the sub-inverter group 2 is adjusted, and a desired output voltage can be output while keeping the voltage ratio of each single-phase inverter 2I and 3I substantially constant. As a result, it is possible to eliminate the need for a power source for supplying electric power to the sub-inverter group 2, so that the device is compact and inexpensive.

Further, in the output pattern determination unit of the third embodiment, it is possible to prevent the capacitor voltage of the single-phase inverter from rising significantly while preventing the output of the single-phase inverter for comparison using the average value from fluctuating from the target value. it can. Therefore, it is possible to prevent a large fluctuation in the capacitor voltage of the single-phase inverter and prevent an adverse effect on the capacitor due to the voltage rise.

Further, the output pattern determination unit 43 can determine the output pattern by a simple rule. Since this rule can be applied even when the number of single-phase inverters increases, it is possible to control each capacitor voltage substantially constantly while outputting an arbitrary output voltage even when the number of single-phase inverters increases.

As described above, in the power conversion device of the third embodiment, as a comparison unit, an average value comparison unit that compares at least a part of the average values of the plurality of comparison standard values with each comparison standard value, and each comparison standard. It is equipped with both a standard value comparison unit that compares a value with other comparison standard values.
Therefore, the power conversion device of the third embodiment can keep the capacitor voltage constant and output an arbitrary voltage even if the number of inverters increases.

Although the present application describes various exemplary embodiments and examples, the various features, embodiments, and functions described in one or more embodiments are applications of a particular embodiment. It is not limited to the above, and can be applied to the embodiment alone or in various combinations.
Therefore, innumerable variations not illustrated are envisioned within the scope of the techniques disclosed in the present application. For example, it is assumed that at least one component is modified, added or omitted, and further, at least one component is extracted and combined with the components of other embodiments. ..

This application can be widely applied to power conversion devices because it is possible to keep the capacitor voltage constant and output an arbitrary voltage even if the number of inverters increases.

1,1A, 1B, 1C main circuit section, 2,2A, 2C sub-inverter group, 2I1,2I2,2I3,2Im, 3I3,3I4,3Im + 1,3Im + n single-phase inverter, 3,3A, 3C main inverter group, 4 switching Switch, 5 Charging resistor, 6 Output filter, 7D1, 7D2, 7D3, 7D4, 7Dm, 7Dm + 1 Inverter voltage detection circuit, 8 Output voltage detection circuit, 10S1,10S2, 10Sn External power supply, 11 Load, 12 Output current detection circuit, 20 Control unit, 21 Gradation number determination unit, 22, 22A, 22B, 32, 32A, 42, 42A, 42B Comparison unit, 23, 33, 43 Output pattern determination unit, 24 Gate signal generation unit, 22D, 22AD, 22BD , 32D, 32AD, 42D, 42AD, 42BD Divider, 22H, 22AH, 22BH, 42H, 42AH, 42BH Average calculator, 22AC, 22AAC, 22BAC, 42AC, 42AAC, 42BAC Average value comparator, 32SC, 32ASC, 42SC, 42ASC, 42BSC standard value comparator, g11, g12, g21, g22 semiconductor switching element.

Claims

Multiple AC sides of a single-phase inverter that converts DC power of a DC power supply to AC power are connected in series, and the total output is calculated by summing the generated voltages of one or more of the single-phase inverters selected from the plurality of single-phase inverters. In a power converter that controls voltage and supplies power to a load
Each of the plurality of single-phase inverters includes a power storage element that generates a DC power supply voltage, and at least one of the plurality of single-phase inverters is connected to an external power supply, and a target value of the DC power supply voltage of each of the single-phase inverters is provided. The ratio of
A voltage detecting means for detecting the DC power supply voltage of the plurality of single-phase inverters, and
A comparative standard value is calculated by dividing by the ratio of the DC power supply voltage of the plurality of single-phase inverters detected by the voltage detecting means to the target value of each of the DC power supply voltages, and the calculated comparative standard values are obtained. And the comparison part that performs the comparison processing of
Output pattern determination that determines an output pattern that is a combination of one or more of the single-phase inverters for which a voltage should be output among the plurality of single-phase inverters based on the comparison result by the comparison unit and predetermined selection conditions. With a part
The comparison unit is an average value comparison unit that compares at least a part of the average values of the plurality of comparison standard values with each of the comparison standard values as the comparison process, and each of the comparison standard values and others as the comparison process. A power conversion device including at least one of the standard value comparison units for comparing with the comparison standard value of the above.
The plurality of single-phase inverters include a first inverter group including one or a plurality of the single-phase inverters to which the DC power supply is supplied from the outside, and a plurality of the single-phase inverters other than the first inverter group. Consists of a second group of inverters
The power conversion device according to claim 1, wherein when the second inverter group is composed of Y single-phase inverters, the comparison unit includes Y or more average value comparison units.
Each of the single-phase inverters is configured to be able to output +, 0, and-voltages by the DC power supply voltage.
The selection conditions are "determine the output from the single-phase inverter having a large DC power supply voltage" and "select the output in the order of +, 0,-if the comparative standard value is larger than the average value". The power conversion device according to claim 2, further comprising "selecting the output in the order of priority of-, 0, + when the comparative standard value is smaller than the average value".
The plurality of single-phase inverters include a first inverter group including one or a plurality of the single-phase inverters to which the DC power supply is supplied from the outside, and a plurality of the single-phase inverters other than the first inverter group. Consists of a second group of inverters
The first aspect of claim 1, wherein when the second inverter group is composed of Y single-phase inverters, the comparison unit is composed of (Y + 1) × Y / 2 or more standard value comparison units. Power converter.
Each of the single-phase inverters is configured to be able to output +, 0, and-voltages by the DC power supply voltage.
The selection condition includes "determining the output from the single-phase inverter having the larger comparative standard value" and "selecting the output of each of the single-phase inverters in the order of priority of +, 0,-". Item 4. The power conversion device according to item 4.
The plurality of single-phase inverters include a first inverter group including one or a plurality of the single-phase inverters to which the DC power supply is supplied from the outside, and a plurality of the single-phase inverters other than the first inverter group. Consists of a second group of inverters
When the second inverter group is composed of Y single-phase inverters, X is a condition of (0 <X <Y), and the comparison unit is (X + 1) × X / 2 or more of the standard. The power conversion device according to claim 1, further comprising a value comparison unit and YX or more of the average value comparison units.
Each of the single-phase inverters is configured to be able to output +, 0, and-voltages by the DC power supply voltage.
When the average value comparison unit is used, the selection conditions are "determine the output from the single-phase inverter having a large DC power supply voltage" and "+, 0,-when the comparison standard value is larger than the average value". "Select the output in the order of priority, and if the comparison standard value is smaller than the average value, select the output in the order of-, 0, +".
When the standard value comparison unit is used, "the output is determined from the single-phase inverter having the larger comparison standard value" and "the output of each of the single-phase inverters is selected in the order of priority of +, 0,-". 6. The power conversion device according to claim 6.
The power conversion device according to any one of claims 2 to 7, wherein at least one DC power source of the second inverter group is supplied from the outside.