US-12620910-B2 - Power conversion device, recording medium, and control method

US12620910B2US 12620910 B2US12620910 B2US 12620910B2US-12620910-B2

Abstract

A power conversion device is disclosed in which a grid following amplitude command value and a grid following phase command value are output in response to receiving a switching signal instructing switching from grid following control to grid forming control. The grid following amplitude command value indicates a target value of an amplitude computed by the grid following control. The grid following phase command value indicates a target value of a phase computed by the grid following control. When the grid following control is switched to the grid forming control, an initial value of the target value of the amplitude in the grid forming control to be the grid following amplitude command value is set, and an initial value of the target value of the phase in the grid forming control to be the grid following phase command value is set.

Inventors

Yukina AKIYAMA
Shunsuke KAWACHI
Yuki Kudo
Yoko Sakauchi
Koji Toba
Kenji Mitsumoto
Daisuke Takeda

Assignees

KABUSHIKI KAISHA TOSHIBA
Toshiba Energy Systems & Solutions Corporation

Dates

Publication Date: 20260505
Application Date: 20211216

Claims (12)

1 . A power conversion device comprising: a conversion circuit configured to convert DC power output from a power supply into AC power and output the AC power; a grid forming control circuit configured to generate a first modulation command to change an amplitude and a phase of an output voltage from the conversion circuit by grid forming control for maintaining the amplitude and the phase of the output voltage at given set values; a grid following control circuit configured to generate a second modulation command to change the amplitude and the phase of the output voltage by grid following control for causing the amplitude and the phase of the output voltage to follow an amplitude and a phase of a grid voltage as a voltage of a given power grid; a modulation circuit configured to change the amplitude and the phase of the output voltage on the basis of the first modulation command or the second modulation command; a switching circuit configured to switch, in accordance with a switching signal, input to the modulation circuit such that either the first modulation command or the second modulation command is input to the modulation circuit; a command value output circuit configured to output a grid following amplitude command value and a grid following phase command value in response to receiving the switching signal instructing switching from the grid following control to the grid forming control, the grid following amplitude command value indicating a target value of an amplitude computed by the grid following control, the grid following phase command value indicating a target value of a phase computed by the grid following control; and an initial value adjusting circuit configured to, when the grid following control is switched to the grid forming control, set an initial value of the target value of the amplitude in the grid forming control to be the grid following amplitude command value, and set an initial value of the target value of the phase in the grid forming control to be the grid following phase command value.
2 . The power conversion device according to claim 1 , wherein the initial value adjusting circuit includes a filter circuit configured to perform predetermined filter processing on the grid following amplitude command value output from the command value output circuit.
3 . The power conversion device according to claim 2 , wherein the filter circuit is a circuit of a first-order delay filter.
4 . The power conversion device according to claim 2 , wherein the filter circuit is a circuit of a rate limiter.
5 . A non-transitory computer-readable recording medium on which programmed instructions are recorded, the instructions causing a computer to execute processing, the computer including a conversion circuit serving to convert DC power output from a power supply into AC power and output the AC power, the processing to be executed by the computer comprising: processing of generating a first modulation command to change an amplitude and a phase of an output voltage from the conversion circuit by grid forming control for maintaining the amplitude and the phase of the output voltage at given set values; processing of generating a second modulation command to change the amplitude and the phase of the output voltage by grid following control for causing the amplitude and the phase of the output voltage to follow an amplitude and a phase of a grid voltage as a voltage of a given power grid; processing of changing the amplitude and the phase of the output voltage on the basis of the first modulation command or the second modulation command; processing of switching, in accordance with a switching signal, input to a modulation circuit serving to change the amplitude and the phase of the output voltage, the switching being performed such that either the first modulation command or the second modulation command is input to the modulation circuit; processing of outputting a grid following amplitude command value and a grid following phase command value in response to receiving the switching signal instructing switching from the grid following control to the grid forming control, the grid following amplitude command value indicating a target value of an amplitude computed by the grid following control, the grid following phase command value indicating a target value of a phase computed by the grid following control; and initial value adjusting processing of, when the grid following control is switched to the grid forming control, setting an initial value of the target value of the amplitude in the grid forming control to be the grid following amplitude command value, and setting an initial value of the target value of the phase in the grid forming control to be the grid following phase command value.
6 . The recording medium according to claim 5 , wherein the initial value adjusting processing includes performing predetermined filter processing on the grid following amplitude command value.
7 . The computer program according to claim 6 , wherein the predetermined filter processing is processing serving as a first-order delay filter.
8 . The computer program according to claim 6 , wherein the predetermined filter processing is processing serving as a rate limiter.
9 . A control method implemented by a device including a conversion circuit, a grid forming control circuit, a grid following control circuit, a modulation circuit, and a switching circuit, the conversion circuit serving to convert DC power output from a power supply into AC power and output the AC power, the grid forming control circuit serving to generate a first modulation command to change an amplitude and a phase of an output voltage from the conversion circuit by grid forming control for maintaining the amplitude and the phase of the output voltage at given set values, the grid following control circuit serving to generate a second modulation command to change the amplitude and the phase of the output voltage by grid following control for causing the amplitude and the phase of the output voltage to follow an amplitude and a phase of a grid voltage as a voltage of a given power grid, the modulation circuit serving to change the amplitude and the phase of the output voltage on the basis of the first modulation command or the second modulation command, the switching circuit serving to switch, in accordance with a switching signal, input to the modulation circuit such that either the first modulation command or the second modulation command is input to the modulation circuit, the control method comprising: outputting a grid following amplitude command value and a grid following phase command value in response to receiving the switching signal instructing switching from the grid following control to the grid forming control, the grid following amplitude command value indicating a target value of an amplitude computed by the grid following control, the grid following phase command value indicating a target value of a phase computed by the grid following control; and, performing initial value adjusting processing when the grid following control is switched to the grid forming control, the initial value adjusting processing including setting an initial value of the target value of the amplitude in the grid forming control to be the grid following amplitude command value, and setting an initial value of the target value of the phase in the grid forming control to be the grid following phase command value.
10 . The control method according to claim 9 , wherein the initial value adjusting processing further includes performing predetermined filter processing on the grid following amplitude command value.
11 . The control method according to claim 10 , wherein the predetermined filter processing is processing serving as a first-order delay filter.
12 . The control method according to claim 10 , wherein the predetermined filter processing is processing serving as a rate limiter.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is national stage application of International Application No. PCT/JP2021/046412, filed on Dec. 16, 2021, which designates the United States, incorporated herein by reference. FIELD Embodiments described herein relate generally to a power conversion device, a recording medium, and a control method. BACKGROUND In recent years, utilization of an inverter power supply is developed. The inverter power supply converts DC power output from power supplies such as generators utilizing renewable energy and storage batteries into AC power and outputs the AC power. As a control system for inverter power supplies, a grid forming (GFM) type and a grid following (GFL) type have been known. Control of the GFM type (hereinafter referred to as GFM control) is control for maintaining an amplitude and a phase of an output voltage of an inverter power supply at given set values. Control of the GFL type (hereinafter referred to as GFL control) is control for causing the amplitude and the phase of the output voltage of the inverter power supply to follow an amplitude and a phase of a voltage of a given power grid. The GFM control and the GFL control described above may be switched in accordance with use situations and the like of the inverter power supply. BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a block diagram of an example of a configuration of a power system of an embodiment; FIG. 2 is a block diagram of an example of a hardware configuration of a power conversion device of the embodiment; FIG. 3 is a block diagram of an example of a functional configuration of the power conversion device of the embodiment; FIG. 4 is a control block diagram of an example of processing in a GFM controller and GFL controller of the embodiment; and FIG. 5 is a flowchart of an example of processing at the time of switching from GFL control to GFM control by the power conversion device of the embodiment. DETAILED DESCRIPTION A power conversion device of an embodiment includes a conversion circuit, a grid forming control circuit, a grid following control circuit, a modulation circuit, a switching circuit, a command value output circuit, and an initial value adjusting circuit. The conversion circuit is configured to convert DC power output from a power supply into AC power and output the AC power. The grid forming control circuit is configured to generate a first modulation command to change an amplitude and a phase of an output voltage from the conversion circuit by grid forming control for maintaining the amplitude and the phase of the output voltage at given set values. The grid following control circuit is configured to generate a second modulation command to change the amplitude and the phase of the output voltage by grid following control for causing the amplitude and the phase of the output voltage to follow an amplitude and a phase of a grid voltage as a voltage of a given power grid. The modulation circuit is configured to change the amplitude and the phase of the output voltage on the basis of the first modulation command or the second modulation command. The switching circuit is configured to switch, in accordance with a switching signal, input to the modulation circuit such that either the first modulation command or the second modulation command is input to the modulation circuit. The command value output circuit is configured to output a grid following amplitude command value and a grid following phase command value in response to receiving the switching signal instructing switching from the grid following control to the grid forming control. The grid following amplitude command value indicates a target value of an amplitude computed by the grid following control. The grid following phase command value indicates a target value of a phase computed by the grid following control. The initial value adjusting circuit is configured to, when the grid following control is switched to the grid forming control, set an initial value of the target value of the amplitude in the grid forming control to be the grid following amplitude command value, and set an initial value of the target value of the phase in the grid forming control to be the grid following phase command value. The following describes an embodiment with reference to the accompanying drawings. FIG. 1 is a block diagram of an example of a configuration of a power system 1 of the embodiment. The power system 1 includes an inverter power supply 11, a transformer 12, and a power grid 13. The power system 1 can be, for example, a so-called microgrid system that constitutes the self-contained power grid 13 utilizing a distributed power supply including power supplies such as the inverter power supply 11. The inverter power supply 11 includes a power supply 20 and a power conversion device 21. The power supply 20 is a unit for outputting DC power and can be, for example, a generator utilizing renewable energy (for example, sunlight, w