EP-4738680-A1 - VOLTAGE CONTROL APPARATUS AND VOLTAGE CONTROL METHOD

EP4738680A1EP 4738680 A1EP4738680 A1EP 4738680A1EP-4738680-A1

Abstract

A voltage control apparatus includes an inverter that converts DC power output from a battery into AC power and supplies the AC power to a power grid and a controller connected to the inverter. The controller executes processing for, when a voltage drop of an output voltage of the inverter is equal to or larger than a threshold because of fluctuation in an AC voltage of the power grid, calculating virtual impedance using variables including an active voltage command value and a reactive voltage command value calculated by a voltage command value and an active current command value and a reactive current command value calculated by the output voltage of the inverter and the voltage command value, processing for calculating a virtual active voltage and a virtual reactive voltage by multiplying, by the virtual impedance, each of an active current and a reactive current calculated by an output current of the inverter, and processing for performing voltage control based on the virtual active voltage and the virtual reactive voltage such that each of the active current and the reactive current can approach each of the active current command value and the reactive current command value required of the power grid.

Inventors

BANI SHAMSEH, Mohammad
LI, HAIQING

Assignees

TMEIC Corporation

Dates

Publication Date: 20260506
Application Date: 20230630

Claims (6)

A voltage control apparatus comprising: an inverter that converts DC power output from a battery into AC power and supplies the AC power to a power grid; and a controller connected to the inverter, wherein the controller is configured to execute: processing for, when a voltage drop of an output voltage of the inverter is equal to or larger than a threshold because of fluctuation in an AC voltage of the power grid, calculating virtual impedance using variables including an active voltage command value and a reactive voltage command value calculated by a voltage command value and an active current command value and a reactive current command value calculated by the output voltage and the voltage command value; processing for calculating a virtual active voltage and a virtual reactive voltage by multiplying, by the virtual impedance, each of an active current and a reactive current calculated by an output current of the inverter; and processing for performing voltage control based on the virtual active voltage and the virtual reactive voltage such that each of the active current and the reactive current can approach each of the active current command value and the reactive current command value required of the power grid.
The voltage control apparatus according to claim 1, wherein the variables further include an active voltage and a reactive voltage calculated by the output voltage, and the controller is configured to, in the processing for calculating the virtual impedance, calculate the virtual impedance based on a condition that the reactive voltage is zero, the reactive voltage command value is zero, a voltage value obtained by subtracting the virtual active voltage and the active voltage from the active voltage command value is zero, and a voltage value obtained by subtracting the virtual reactive voltage and the reactive voltage from the reactive voltage command value is zero.
The voltage control apparatus according to claim 1, wherein the virtual impedance includes resistance and reactance, and the controller is configured to, in the processing for calculating the virtual impedance, calculate each of the resistance and the reactance corresponding to the output voltage.
The voltage control apparatus according to claim 1, wherein the active current command value is calculated by multiplying, by a constant value, a differential voltage obtained by calculating a difference between the voltage command value and the output voltage, and the reactive current command value is calculated such that a sum obtained by adding up a square value of the active current command value and a square value of the reactive current command value is 1.
The voltage control apparatus according to claim 4, wherein the active current command value is represented by a percentage, and when a calculation result of the active current command value exceeds 100%, the controller sets the active current command value to 100%.
A voltage control method comprising: converting, using an inverter, DC power output from a battery into AC power and supplying the AC power to a power grid; when a voltage drop of an output voltage of the inverter is equal to or larger than a threshold because of fluctuation in an AC voltage of the power grid, calculating virtual impedance using variables including an active voltage command value and a reactive voltage command value calculated by a voltage command value and an active current command value and a reactive current command value calculated by the output voltage and the voltage command value; calculating a virtual active voltage and a virtual reactive voltage by multiplying, by the virtual impedance, each of an active current and a reactive current calculated by an output current of the inverter; and performing voltage control based on the virtual active voltage and the virtual reactive voltage such that each of the active current and the reactive current can approach each of the active current command value and the reactive current command value required of the power grid.

Description

Technical Field The present disclosure relates to a technique for controlling an output voltage of an inverter. Background Art Patent Literature 1 discloses a technique that can stably continue operation in a power converter (that is, an inverter) that executes control simulating a synchronous generator. In this related art, when an AC voltage of a power grid fluctuates, voltage control is performed such that active power input and output between the power grid and the power converter decreases. Citation List Patent Literature [PTL 1] JP 7183486 B Summary of the Invention Problems to be Solved by the Invention A case is assumed in which a voltage control-type GFM (Grid Forming) inverter is used as an inverter that supplies an AC voltage to a power grid. In this case, as explained in Patent Literature 1, when the AC voltage of the power grid fluctuates, voltage control is performed to reduce a difference in active power input and output between the power grid and the power converter. However, even if the voltage control for stabilizing the active power is performed, it is likely that an output current of the inverter cannot reach a reference current required of the power grid and the power grid becomes unstable. Therefore, in order to supply stable active power to the power grid, it is necessary to perform the voltage control to output an active current and a reactive current required of the power grid. One object of the present disclosure is to provide a technique that, when an AC voltage of a power grid fluctuates, can perform voltage control to output an active current and a reactive current required of the power grid. Means for Solving the Problems A first aspect of the present disclosure relates to a voltage control apparatus. The voltage control apparatus includes an inverter that converts DC power output from a battery into AC power and supplies the AC power to a power grid. The voltage control apparatus further includes a controller connected to the inverter. The controller executes: processing for, when a voltage drop of an output voltage of the inverter is equal to or larger than a threshold because of fluctuation in an AC voltage of the power grid, calculating virtual impedance using variables including an active voltage command value and a reactive voltage command value calculated by a voltage command value and an active current command value and a reactive current command value calculated by the output voltage of the inverter and the voltage command value; processing for calculating a virtual active voltage and a virtual reactive voltage by multiplying, by the virtual impedance, each of an active current and a reactive current calculated by an output current of the inverter; and processing for performing voltage control based on the virtual active voltage and the virtual reactive voltage such that each of the active current and the reactive current can approach each of the active current command value and the reactive current command value required of the power grid. A second aspect of the present disclosure further includes the following characteristics in addition to the first aspect. The variables further include an active voltage and a reactive voltage calculated by the output voltage. In the processing for calculating the virtual impedance, the controller calculates the virtual impedance based on a condition that the reactive voltage is zero, the reactive voltage command value is zero, a voltage value obtained by subtracting the virtual active voltage and the active voltage from the active voltage command value is zero, and a voltage value obtained by subtracting the virtual reactive voltage and the reactive voltage from the reactive voltage command value is zero. A third aspect of the present disclosure further includes the following characteristics in addition to the first aspect. The virtual impedance includes resistance and reactance. In the processing for calculating the virtual impedance, the controller calculates each of the resistance and the reactance corresponding to the output voltage. A fourth aspect of the present disclosure further includes the following characteristics in addition to the first aspect. The active current command value is calculated by multiplying, by a constant value, a differential voltage obtained by calculating a difference between the voltage command value and the output voltage. The reactive current command value is calculated such that a sum obtained by adding up a square value of the active current command value and a square value of the reactive current command value is 1. A fifth aspect of the present disclosure further includes the following characteristics in addition to the fourth aspect. The active current command value is represented by a percentage. When a calculation result of the active current command value exceeds 100%, the controller sets the active current command value to 100%. An sixth aspect of the present disclosure relates to a voltag