JP2017034737A - Power conversion device controller, control method, and control program, and power conversion system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible, even in a non-steady state at the time of excessive response caused by load fluctuations, to perform output control for handling the state.SOLUTION: A power conversion device controller includes: an output calculation unit 40 that calculates required output necessary for a power conversion device 100 including a plurality of stages of inverters 10, 20; a pulse width setting unit 41 that, on the basis of the required output, sets a pulse width of each of the inverters 10, 20; a phase difference setting unit 42 that sets a phase difference between output of the plurality of stages of inverters 10, 20; a switching control unit 43 that, on the basis of the set pulse width and phase difference, controls switching of switching elements 1 of the plurality of stages of inverters 10, 20; a determination unit 44 that, on the basis of the required output, determines a non-steady state; and a change unit 45 that, when the non-steady state has been determined, changes the phase difference between the output of the plurality of stages of inverters 10, 20 to make synthetic output of the plurality of stages of inverters 10, 20 be output depending on the non-steady state.SELECTED DRAWING: Figure 1

Description

  Embodiments described herein relate generally to a control device, a control method, a control program, and a power conversion system for a power conversion device having a plurality of inverters.

  A power conversion device that converts power between alternating current and direct current is used in various applications. For example, as an inverter that converts direct current into alternating current and supplies power to a load, an apparatus including a bridge circuit having four switches as a basic configuration has been used.

  In such a power conversion device, power semiconductor elements such as GTO and IGBТ are generally used as switching elements that perform switching that is switched on and off. The voltage output from the power conversion device becomes a square wave output by switching of the power semiconductor element.

JP-A-9-205797

  As described above, the voltage waveform or current waveform output by switching of the switching element is a square wave, and therefore includes a distorted wave. In general, if the output frequency of the inverter is fHz, odd-numbered harmonics such as 3fHz (third harmonic), 5fHz (fifth harmonic), etc. are included. It is. If a current containing a large amount of high frequency flows to the load, noise may flow into the peripheral device and the like, which may have an adverse effect.

  In order to cope with this, a method of multiplexing inverters and combining the outputs of several square wave inverters is known. This is to reduce harmonics by changing the phase of the plurality of inverter outputs. However, in such a method, the voltage that can be output by the inverter may be limited, and thus there is a possibility that the current cannot be controlled in accordance with the command value from the control device during a transient response due to a load change.

  An object of the present invention is to provide a control device, a control method, a control program, and a power conversion system for a power conversion device capable of output control corresponding to an unsteady state such as an excessive response due to a load change. To do.

  In order to solve the above-described problems, a control device for a power conversion device according to an embodiment is calculated by an output calculation unit that calculates a required output necessary for a power conversion device having a plurality of stages of inverters, and the output calculation unit. Based on the required output, a pulse width setting unit for setting the pulse width of each inverter, a phase difference setting unit for setting the phase difference between the outputs of the plurality of inverters, and the pulse width set by the pulse width setting unit And a switching control unit that controls switching of switching elements in a plurality of inverters based on the phase difference set by the phase difference setting unit, and an unsteady state based on a required output calculated by the output calculation unit When the determination unit that determines that the state is determined and the determination unit determines that it is in an unsteady state, the phase difference between the outputs of the plurality of inverters is changed. Characterized in that it has a changing unit to output corresponding synthetic output a plurality of stages of inverters in the non-steady state, the.

The block diagram which shows the structural example of the power conversion system of embodiment Waveform diagram showing each inverter output and combined output of power converter in steady state Waveform diagram showing each inverter output and combined output of power converter in unsteady state Waveform diagram showing each inverter output and combined output of power converter in steady state Waveform diagram showing each inverter output and combined output of power converter in unsteady state

This embodiment will be described with reference to FIGS. FIG. 1 is a configuration example of the power conversion system S. 2 to 5 are explanatory diagrams illustrating pulse waves of the output P1 of the first inverter 10, the output P2 of the second inverter 20, and the combined output Ps.
[A. Configuration of Embodiment]
As shown in FIG. 1, the power conversion system S of the present embodiment includes a power conversion device 100 and a control device 400.

[1. Power conversion device]
The power conversion device 100 includes a plurality of stages of inverters. Having a plurality of stages of inverters means that the plurality of inverters are connected so as to obtain electric power obtained by combining the outputs of the inverters.

  An example of such a power conversion device 100 will be described with reference to FIG. The power conversion apparatus 100 of FIG. 1 is an example of a circuit configuration of a voltage type multiple inverter. The power conversion apparatus 100 is connected to a DC voltage source 200 serving as a power source. The power converter 100 is connected to a load 300 that consumes AC power output from the power converter 100. The output of the power converter 100 is electric power from the viewpoint of supplying energy consumed by the load 300, but is a voltage in the comparison of the output of the voltage type inverter and its waveform.

  The power conversion apparatus 100 includes a first inverter 10 and a second inverter 20 as a plurality of stages of inverters. The first inverter 10 is a bridge circuit composed of four switching elements 1. That is, two sets of two switching elements 1 connected in series are connected in parallel. As the switching element 1, for example, a power semiconductor element such as GTO or IGBT can be used.

  A feedback diode 2 is connected to each switching element 1 in parallel. The two switching elements 1 in each set are connected via the reactor 11 and the primary side of the transformer 12. The second inverter 20 has the same configuration as that of the first inverter 10, and the two switching elements 1 of each set are connected via the primary side of the reactor 21 and the transformer 22.

  The input sides of the first inverter 10 and the second inverter 20 are connected to the DC voltage source 200 in parallel. On the other hand, the output sides of the first inverter 10 and the second inverter 20 are connected to the load 300 in series. That is, the secondary sides of the transformers 12 and 22 are connected to the load 300 in series.

  The power conversion apparatus 100 converts the DC voltage from the DC voltage source 200 into a single-phase AC voltage. At this time, the first inverter 10 and the second inverter 20 output a square-wave AC voltage by alternately turning on and off the pair of switching elements 1 on the respective diagonal lines. The output AC voltage is boosted via the transformers 12 and 22 and supplied to the load 300.

[2. Control device]
The control device 400 is a device that controls the operation of the power conversion device 100. The control device 400 includes an output calculation unit 40, a pulse width setting unit 41, a phase difference setting unit 42, a switching control unit 43, a determination unit 44, a changing unit 45, and a storage unit 46.

[Output calculation section]
The output calculation unit 40 is a processing unit that calculates a required output necessary for the power conversion apparatus 100. The required output is an output that the power conversion apparatus 100 should supply in relation to the load 300. The output calculation unit 40 calculates a required output based on, for example, information input from the outside. The information input from the outside is various parameters indicating the state of the load current. For example, a detection value from the detection unit T that detects the current flowing through the load is used. That is, the output calculation unit 40 can control the load current by feedback.

[Pulse width setting section]
The pulse width setting unit 41 is a processing unit that sets the pulse width of each inverter based on the required output calculated by the output calculation unit 40. For example, the pulse width setting unit 41 calculates and sets the pulse widths of the first inverter 10 and the second inverter 20 so that the output of the power conversion device 100 becomes a required output.

  The pulse width is the width from the positive or negative rising edge to the falling edge of the square wave. Here, for convenience of explanation, the rising edge width and the falling edge width are not considered. In the present embodiment, the pulse width is expressed as a frequency. The pulse widths of the outputs of the first inverter 10 and the second inverter 20 are 0 ° at the minimum and 180 ° at the maximum. For example, the voltage range that can be output by the voltage-type first inverter 10 and the second inverter 20 is determined by the voltage of the DC voltage source 200 and the pulse width.

[Phase difference setting section]
The phase difference setting unit 42 is a processing unit that sets a phase difference between outputs of a plurality of inverters. The phase difference is a phase shift of a square wave having a predetermined frequency. In the present embodiment, the phase difference setting unit 42 sets the phase difference between the output of the first inverter 10 and the output of the second inverter 20. For example, the phase difference between the output voltages of the first inverter 10 and the second inverter 20 is a deviation width of rising or falling. In the present embodiment, this phase difference is also expressed as a frequency. As will be described later, this phase difference may be changed by the changing unit 45.

[Switching control unit]
The switching control unit 43 is a processing unit that controls switching of the switching element 1 in the power conversion device 100 based on the pulse width calculated by the pulse width setting unit 41 and the phase difference set by the phase difference setting unit 42. . Switching control refers to controlling on / off switching of the switching element 1. Specifically, the switching control unit 43 controls switching by generating and outputting a gate signal for switching on and off each switching element 1 at a predetermined timing.

[Determining part]
The determination unit 44 is a processing unit that determines that the state is an unsteady state based on the required output calculated by the output calculation unit 40. Here, the steady state and the unsteady state will be described. First, the steady state is a state in which power can be supplied stably. For example, when the load current detected by the detection unit T is stable and the required voltage does not change rapidly, it is included in the steady state. In this case, the required output calculated by the output calculation unit 40 is stable.

  On the other hand, the unsteady state is a state from the state deviating from the steady state to the stabilization. For example, since the load fluctuation due to the transient response is large, the required output calculated by the output calculation unit 40 based on the current value detected by the detection unit T is the combined output of a plurality of inverters based on the pulse width or phase difference in the steady state. May exceed the maximum value of. In the present embodiment, the maximum output voltage value of the first inverter 10 and the second inverter 20 is exceeded. Such a case is included in the unsteady state.

  The determination of whether or not the unsteady state is caused by the determination unit 44 is performed, for example, by comparing the required output with a threshold value. With the maximum value of the output voltage as a threshold value, if the required output by the calculation of the output calculation unit 40 exceeds this threshold value, it can be determined that the state is unsteady. For example, when the voltage required for the load rapidly increases due to the load current detected by the detection unit T, the maximum voltage minus the required voltage becomes negative, and it is determined that the state is unsteady.

[Change section]
When the determination unit 44 determines that the determination unit 44 is in the unsteady state, the change unit 45 changes the phase difference between the outputs of the plurality of stages of inverters so that the combined output of the plurality of stages of inverters is output according to the unsteady state. It is. For example, the changing unit 45 reduces the phase by a value obtained by multiplying the maximum voltage minus the required voltage by a coefficient for conversion to a necessary phase. As a result, the phase changes by an amount corresponding to the insufficient voltage, and voltage control can be performed based on the phase only in the non-steady state. At this time, the pulse width is 180 °.

  Alternatively, the phase may be switched. For example, when the determination unit 44 determines that the state is unsteady, the phase difference set by the phase difference setting unit 42 is switched between the first phase difference and the second phase difference. As a result, there is a margin in the output voltage, so that the output voltage can be controlled based on the pulse width.

  The first phase difference is a phase difference for a steady state. The phase difference for the steady state refers to a phase difference that allows the power conversion apparatus 100 to obtain an output corresponding to the steady state. The output corresponding to the steady state refers to an output from which a necessary load current can be obtained in the steady state.

  The first phase difference is, for example, 60 ° as shown in FIG. If the pulse width of the output P1 of the first inverter 10 and the output P2 of the second inverter 20 is 180 ° and the phase difference is 60 °, the conduction angle is 120 °. The conduction angle is a frequency notation indicating the width of current flowing when voltage is applied. In the present embodiment, the conduction angle of the output of the power conversion device 100, that is, the combined output Ps of a plurality of inverters, is a width in which the rising edges of the first inverter 10 and the second inverter 20 overlap. This width is the pulse width of the combined output Ps. There is no portion where the plus / minus of the outputs P1 and P2 are canceled and become zero, and the voltage increases at the portion where the plus overlaps.

  Note that, by setting the phase difference, harmonics of a predetermined order can be removed with respect to the output frequency of each inverter. For example, if the phase difference is 60 °, the third harmonic R1 of the first inverter 10 and the third harmonic R2 of the second inverter 20 can be removed as will be described later.

  The second phase difference is a phase difference for the unsteady state. The phase difference for the unsteady state refers to a phase difference that allows the power conversion apparatus 100 to obtain an output corresponding to the unsteady state. The output corresponding to the unsteady state refers to an output that can obtain a current that is at least larger than the load current necessary for the steady state and equal to or less than the load current necessary for the unsteady state. The output may be a current that is larger than the load current required in the unsteady state.

  The second phase difference is, for example, 50 ° as shown in FIG. If the pulse width of the output P1 of the first inverter 10 and the output P2 of the second inverter 20 is 180 ° and the phase difference is 50 °, the conduction angle of the combined output Ps is 130 °. In this case, since the conduction angle is larger than that in the steady state, an output corresponding to the unsteady state can be obtained.

  In this case as well, an effect of reducing harmonics of a predetermined order with respect to the output frequency of the plurality of inverters can be obtained with an upper limit equal to the first phase difference. For example, even if the phase difference is 50 °, the effect of reducing the third harmonic R1 of the first inverter 10 and the third harmonic R2 of the second inverter 20 can be obtained as described later.

  Note that the change of the phase difference by the changing unit 45 only needs to be changed at least after the unsteady state is determined until the steady state is reached. Therefore, for example, it may be returned to the steady state 1 second to several seconds after switching to the unsteady state.

[Storage unit]
The storage unit 46 is a processing unit that stores various types of information necessary for the processing of the control device 400. For example, a current value detected by the detection unit T, a threshold value for determining an unsteady state, and the like can be stored. As described above, the threshold value can be the maximum value of the combined output of a plurality of inverters in a steady state.

  Furthermore, the storage unit 46 includes a first phase difference storage unit 46a and a second phase difference storage unit 46b. The first phase difference storage unit 46a is a processing unit that stores a first phase difference that is a phase difference for a steady state. The second phase difference storage unit 46b is a processing unit that stores a second phase difference that is a phase difference for an unsteady state. Note that the second phase difference may be a specific phase difference, or may be set as a fluctuation range with respect to the first phase difference.

  Such a storage unit 46 can typically be configured by a storage medium such as a built-in or externally connected memory, but any storage medium that can be used at present or in the future can be used. A register or the like used for calculation can also be understood as the storage unit 46.

  The control device 400 as described above can be realized by controlling a computer including a CPU and the like with a predetermined program. The program in this case implements the processing unit as described above by physically utilizing computer hardware.

  A method for executing processing by the processing unit, a program, and a recording medium on which the program is recorded are also an aspect of the present embodiment. Moreover, how to set the range processed by hardware and the range processed by software including a program is not limited to a specific mode. For example, a circuit configured to realize the above processing is also an aspect of the embodiment.

  The control device 400 includes an input / output unit and the like (not shown). The input / output unit can be configured by, for example, an operation panel, a keyboard, a mouse, a display, an input / output terminal, and the like. The input / output unit can input information necessary for starting, stopping, and other processes described above, and can display information stored in the storage unit 46, processing results of each unit, and the like. .

[B. Operation of the embodiment]
The operation of the present embodiment as described above will be described with reference to FIGS. In the following description, the phase difference generated between the output P1 of the first inverter 10 and the output P2 of the second inverter 20 is referred to as an interstage phase difference.

  From the start, the switching control unit 43 controls the switching of the switching element 1 and controls the outputs of the first inverter 10 and the second inverter 20. That is, the DC voltage supplied from the DC voltage source 200 is converted into an AC voltage by switching control and supplied to the load 300. This switching control is performed based on the pulse width set by the pulse width setting unit 41 and the phase difference set by the phase difference setting unit 42.

  The pulse width setting unit 41 appropriately adjusts the pulse width to be set according to the required output calculated by the output calculation unit 40. The phase difference set in the phase difference setting unit 42 is the first phase difference in the steady state. Thus, the pulse width is controlled so that a stable combined output corresponding to the load current can be obtained.

  As in this embodiment, the combined output Ps when the output P1 of the first inverter 10 and the output P2 of the second inverter 20 are connected in series is equal to the sum of both outputs. For example, as illustrated in FIG. 2, when the power conversion apparatus 100 is driven with a phase difference of 60 °, the combined output Ps has a conduction angle of 120 ° at the maximum. If the interphase phase difference is not controlled, that is, if the interphase phase difference is 0 °, the combined output Ps has a conduction angle of 180 ° at the maximum. For this reason, when the interphase phase difference is controlled, the conduction angle is narrowed and the output voltage is limited as compared with the case where the interphase phase difference is not controlled.

  However, paying attention to harmonics, if the output of a plurality of stages of inverters is controlled so that an interstage phase difference is generated, the harmonics at the outputs of the plurality of stages are canceled out, so that harmonics of a desired order can be removed. For example, as shown in FIG. 2, focusing only on the third harmonic, when the interphase phase difference is controlled, the third harmonic R1 of the first inverter 10 and the third harmonic of the second inverter 20 are controlled. The phase of the wave R2 is also shifted. For this reason, the third harmonics R1 and R2 generated in the first inverter 10 and the second inverter 20 are canceled out, and the third harmonic can be removed as a whole.

  Here, for example, a case is assumed in which an excessive response due to a load variation or the like occurs when the control is performed with a voltage with which there is no margin in output due to restrictions on circuit constants. In this case, even if it is attempted to control a desired current to flow to the load with a conduction angle of 120 ° at the maximum, the voltage that can be output by the power conversion device 100 is limited. For this reason, there is a possibility that the current flowing through the load cannot be controlled according to the command value.

  In such a case, the required output calculated by the output calculation unit 40 exceeds the maximum value of the combined output of the first inverter 10 and the second inverter 20 due to the phase difference in the steady state. Therefore, the determination unit 44 compares the pulse width calculated by the output calculation unit 40 with a threshold value, and determines that the state is in an unsteady state in order to exceed the threshold value.

  Then, the changing unit 45 switches the phase difference set by the phase difference setting unit 42 to the second phase difference. As a result, the phase difference between the stages is narrowed, so that the output voltage is increased and a desired current can be supplied to the load even during an excessive response. For example, as shown in FIG. 3, the pulse width of the combined output is increased by 10 ° compared to the phase difference between steps when the phase difference is 50 ° in the non-steady state and the phase difference is 50 °. be able to. The current required for the load can be supplied by narrowing the interphase phase difference in this way only at the time of excessive response.

  When returning from the unsteady state to the steady state, the determination unit 44 determines that the output calculated by the output calculation unit 40 is equal to or less than the threshold value. Then, the changing unit 45 returns the phase difference set by the phase difference setting unit 42 to the first phase difference. As described above, since the unsteady state is a very short time, the time from switching to the second phase difference to returning to the first phase difference is short. In addition, after switching to a 2nd phase difference, you may set so that it may return to a 1st phase difference, after predetermined time passes. In the description, the switching from the first phase difference to the second phase difference has been described, but the same is true even if the phase difference is continuously changed.

[C. Effects of the embodiment]
(1) In the present embodiment as described above, the output calculation unit 40 that calculates the required output required for the power conversion device 100 having a plurality of inverters, the first inverter 10 and the second inverter 20, and the output calculation Based on the required output calculated by the unit 40, a pulse width setting unit 41 that sets the pulse width of each inverter and a phase difference setting unit 42 that sets the phase difference between the outputs of the inverters in a plurality of stages are provided. And it has the switching control part 43 which controls switching of the switching element 1 in the power converter device 100 based on the pulse width set by the pulse width setting part 41, and the phase difference set by the phase difference setting part 42. Furthermore, based on the required output calculated by the output calculation unit 40, a determination unit 44 that determines that the state is an unsteady state, and if the determination unit 44 determines that the state is an unsteady state, the phase difference between the outputs of the plurality of inverters Is changed to change the combined output of the plurality of inverters into an output corresponding to the unsteady state.

  In this way, by changing the phase difference according to the unsteady state, the range of the maximum combined output by the first inverter 10 and the second inverter 20 can be expanded. Even when the output is insufficient, the output of the power conversion device 100 can be increased.

(2) In the present embodiment, a first phase difference storage unit 46a that stores a first phase difference that is a phase difference for a steady state, and a second phase difference that is a phase difference for an unsteady state Has a second phase difference storage unit 46b. And if the determination part 44 determines with the non-steady state, the change part 45 will switch the phase difference which the phase difference setting part 42 sets between a 1st phase difference and a 2nd phase difference.

  For this reason, in the first phase difference in the steady state, even when the output is insufficient when the load fluctuates due to an excessive response, the desired current flows to the load 300 by switching to the second phase difference in the unsteady state. It can respond at high speed.

(3) The first phase difference and the second phase difference are phase differences that reduce harmonics of a predetermined order with respect to the output frequency of each inverter. For this reason, it is possible to prevent the influence of the harmonics on the outside while supplying a desired current to the load 300 in both the steady state and the unsteady state.

(4) The determination unit 44 determines whether the required output exceeds the maximum value of the combined output of the plurality of inverters due to the pulse width or phase difference in the steady state. For this reason, even if the required output is excessive compared to the steady state, a desired current can be supplied to the load 300 by phase difference control or pulse width control corresponding to the output.

(5) The output calculation unit 40 calculates the pulse width of the output of each inverter based on the detected value of the load current flowing through the load 300 connected to the power conversion device 100. For this reason, it is possible to perform constant control of the output current by feedback of the output current, and it is possible to quickly detect an output shortage and realize control for an excessive response.

[D. Other Embodiments]
(1) In the above embodiment, the two-stage example of the first inverter 10 and the second inverter 20 has been described as a plurality of stages of inverters. However, the output can be increased by increasing the number of stages to two. May be. In the case of an even number of stages, such as 4 stages or 6 stages, it may be configured by simply overlapping two stages. Further, in the case of an odd number of stages, it is necessary to adjust the turns ratio of the transformer.

(2) Specific set values such as required output, pulse width, and phase difference are not limited to the above-described embodiment. It may be possible to adjust the balance between the effect of expanding the combined output by reducing the phase difference and the effect of reducing the harmonics by shifting the phase difference. Depending on the setting of the phase difference, harmonics of other orders such as the fifth order can be removed.

(3) Although the above embodiment is a voltage type inverter, it can be applied even to a current type inverter. That is, the relationship between the output, the pulse width, and the phase difference in the above embodiment is the same for the output current pulse.

(4) Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 1 Switching element 2 Diode 10 1st inverter 11, 21 Reactor 12, 22 Transformer 20 2nd inverter 40 Output calculating part 41 Pulse width setting part 42 Phase difference setting part 43 Switching control part 44 Determination part 45 Change part 46 Storage part 46a 1st phase difference memory | storage part 46a 2nd phase difference memory | storage part 100 Power converter 200 DC voltage source 300 Load 400 Control apparatus T Detection part S Power conversion system

Claims (8)

An output calculation unit for calculating a required output necessary for a power converter having a plurality of stages of inverters;
Based on the required output calculated by the output calculation unit, a pulse width setting unit for setting the pulse width of each inverter;
A phase difference setting unit for setting the phase difference of the output of the multi-stage inverter;
Based on the pulse width set by the pulse width setting unit and the phase difference set by the phase difference setting unit, a switching control unit that controls switching of switching elements in a plurality of inverters;
Based on the required output calculated by the output calculation unit, a determination unit that determines that it is in an unsteady state;
When the determination unit determines that it is in an unsteady state, by changing the output of a plurality of inverters, a change unit that makes the combined output of the plurality of inverters an output according to the unsteady state;
The control apparatus of the power converter device characterized by having. A first phase difference storage unit that stores a first phase difference that is a phase difference for a steady state;
A second phase difference storage unit that stores a second phase difference that is a phase difference for an unsteady state;
Have
The change unit switches the phase difference set by the phase difference setting unit between the first phase difference and the second phase difference when the determination unit determines that the state is an unsteady state. The control device for the power conversion device according to claim 1.   The power converter according to claim 2, wherein the first phase difference and the second phase difference are phase differences that reduce harmonics of a predetermined order with respect to an output frequency of each inverter. Control device.   The said determination part determines whether the said required output exceeds the maximum value of the synthetic | combination output of the said multistage inverter by the phase difference of a steady state, The any one of Claims 1-3 characterized by the above-mentioned. The control apparatus of the power converter device of description.   5. The electric power according to claim 1, wherein the output calculation unit calculates the required output based on a detected value of a load current flowing in a load connected to the power conversion device. Control device for the conversion device. A computer or electronic circuit
An output calculation process for calculating a required output required for a power converter having a plurality of stages of inverters;
Based on the required output calculated by the output calculation process, a pulse width setting process for setting the pulse width of each inverter;
A phase difference setting process for setting the phase difference of the output of the multi-stage inverter;
Based on the pulse width set by the pulse width setting process and the phase difference set by the phase difference setting process, a switching control process for controlling switching of switching elements in a plurality of inverters;
Based on the required voltage calculated by the output calculation process, a determination process for determining an unsteady state;
When it is determined that the unsteady state is determined by the determination process, by changing the phase difference between the outputs of the plurality of inverters, a change process for changing the combined output of the plurality of inverters to an output corresponding to the unsteady state;
The control method of the power converter device characterized by performing. On the computer,
An output calculation process for calculating a required output required for a power converter having a plurality of stages of inverters;
Based on the required output calculated by the output calculation process, a pulse width setting process for setting the pulse width of each inverter;
A phase difference setting process for setting the phase difference of the output of the multi-stage inverter;
Based on the pulse width set by the pulse width setting process and the phase difference set by the phase difference setting process, a switching control process for controlling switching of switching elements in a plurality of inverters;
Based on the required output calculated by the output calculation process, a determination process for determining that it is in an unsteady state;
When it is determined that the unsteady state is determined by the determination process, by changing the phase difference between the outputs of the plurality of inverters, a change process for changing the combined output of the plurality of inverters to an output corresponding to the unsteady state;
A control program for a power conversion device, characterized in that   A power conversion system comprising: a power conversion device according to claim 1, wherein a power conversion device having a plurality of stages of inverters is connected to the control device for the power conversion device according to claim 1.

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