CN-122001034-A - Reactive synchronous fault ride-through control method and system for grid-structured converter

CN122001034ACN 122001034 ACN122001034 ACN 122001034ACN-122001034-A

Abstract

The invention provides a reactive synchronous fault ride-through control method and system for a grid-connected converter, and relates to the technical field of power systems. The method comprises the steps of judging whether a power grid fails or not based on the obtained grid-connected point voltage of the grid-connected converter, switching the grid-connected converter to a fault traversing mode if the power grid fails, freezing the angular frequency output by the grid-connected converter at the current moment, generating a reference phase angle in a fault period based on the frozen angular frequency in the fault traversing mode, correcting the reference phase angle based on deviation between a measured value of a target electric quantity and a preset reference value to obtain an output phase angle reference value of the grid-connected converter in the fault period, and controlling the output of the grid-connected converter based on the output phase angle reference value to provide reactive support and keep transient synchronization with the power grid in the fault period. The invention solves the problem that the grid-structured converter cannot take the current limiting, the transient synchronous stability and the power grid voltage supporting capability into consideration.

Inventors

YANG YUEXI
WANG SICHAO
ZHOU XIAO
DU ZHENYU
ZHAO ZIWEI
PENG CHENG

Assignees

中国电力科学研究院有限公司
国家电网有限公司

Dates

Publication Date: 20260508
Application Date: 20251226

Claims (11)

1. The reactive synchronous fault ride-through control method of the network-structured converter is characterized by comprising the following steps of: judging whether the power grid fails or not based on the obtained grid-connected point voltage of the grid-structured converter, switching the grid-structured converter into a fault traversing mode if the power grid fails, and freezing the angular frequency output by the grid-structured converter at the current moment; Correcting the reference phase angle based on the deviation between the measured value of the target electric quantity and a preset reference value to obtain an output phase angle reference value of the grid-structured converter during the fault period; controlling the output of the grid-formed converter based on the output phase angle reference value to provide reactive support and maintain transient synchronization with the grid during a fault; Wherein the target electric quantity is reactive current or reactive power.
2. The method according to claim 1, wherein the determining whether the power grid fails based on the obtained grid-tie point voltage of the grid-tied converter comprises: and if the voltage of the grid connection point of the grid-structured converter is smaller than a first voltage threshold value, judging that the power grid fails.
3. The method of claim 1, wherein generating the reference phase angle during the fault based on the frozen angular frequency comprises: And performing time integral operation on the frozen angular frequency to obtain a reference phase angle in the fault period.
4. A method according to claim 3, wherein said correcting said reference phase angle based on a deviation between a measured value for a target electrical quantity and a preset reference value results in an output phase angle reference value of said grid-formed converter during a fault, comprising: Generating the phase angle correction term through proportional control, integral control or proportional integral control based on a deviation between the measured value of the target electric quantity and a reference value of the target electric quantity; and correcting the reference phase angle by using the phase angle correction term to obtain an output phase angle reference value of the grid-structured current converter in the fault period.
5. The method of claim 4, further comprising, prior to generating the phase angle correction term: And filtering the deviation between the measured value of the target electric quantity and the reference value of the target electric quantity.
6. The method according to claim 2, further comprising, after controlling the output of the grid-tied inverter based on the output phase angle reference value: if the grid-connected point voltage is monitored to be greater than or equal to a second voltage threshold value, switching the grid-formed converter to a normal control mode, and setting the phase angle correction term to zero; And in the normal control mode, obtaining an output phase angle reference value of the grid-structured converter based on time integration of the frozen angular frequency so as to realize resynchronization with a power grid after a fault, wherein the second voltage threshold is larger than the first voltage threshold.
7. The method of claim 6, wherein the normal control mode is a control mode based on active power synchronization or based on direct current voltage synchronization.
8. A reactive synchronous fault ride-through control system for a grid-tied converter, comprising: The system comprises a mode switching module, a grid-connected converter, a fault crossing mode and a power grid switching module, wherein the mode switching module is used for judging whether a power grid fails based on the acquired grid-connected point voltage of the grid-connected converter; The system comprises a fault crossing module, a phase angle correction module, a reference phase angle correction module and a control module, wherein the fault crossing module is used for generating a reference phase angle during a fault based on frozen angular frequency; A fault ride-through control module for controlling the output of the grid-formed converter based on the output phase angle reference value to provide reactive support and maintain transient synchronization with the grid during a fault; Wherein the target electric quantity is reactive current or reactive power.
9. The system of claim 8, wherein the coordinate system of the control system is a three-phase stationary coordinate system, a two-phase stationary coordinate system, or a two-phase rotating coordinate system.
10. A power electronic device comprising the control system of claim 8 or 9, the power electronic device being any one of a wind power converter, a photovoltaic inverter, an energy storage converter, and a flexible direct current power transmission converter.
11. A readable storage medium, having stored thereon an execution program, which when executed, implements the method of any of claims 1 to 7.

Description

Reactive synchronous fault ride-through control method and system for grid-structured converter Technical Field The invention relates to the technical field of power systems, in particular to a reactive synchronous fault ride-through control method and system of a grid-connected converter. Background When the power grid generates phase, frequency and voltage disturbance, the synchronous generator can spontaneously provide active and reactive power to support the power grid to stably operate. The grid-formed converter is used as an equivalent controlled voltage source, has the characteristics similar to synchronous generators, and is beneficial to system stability. When a power grid fails seriously, a traditional grid-structured current converter usually adopts direct current limiting or virtual impedance-based current limiting to protect the current converter from overcurrent. However, these methods change the equivalent output impedance of the converter and even destroy the voltage source characteristics thereof, thereby significantly affecting the angular characteristics of the system, and possibly causing the system to lose a stable equilibrium point, thereby losing synchronization during a fault or after a fault is cleared. Aiming at the research of transient state synchronous stability, the influence of current limiting measures on the power angle curve of the grid-structured converter is analyzed, and whether the grid-structured converter can keep synchronous with a power grid during faults is analyzed, so that reliable fault recovery is realized. Reactive power and dynamic voltage support, however, are critical measures to cope with fault-induced voltage recovery delays, short-term voltage instability. Therefore, how to combine the current limiting capability, transient synchronization stability and power grid voltage supporting capability of the grid-formed converter becomes an important problem to be solved. Disclosure of Invention The invention provides a reactive synchronous fault ride-through control method and a reactive synchronous fault ride-through control system for a grid-structured converter, which are used for solving the problem that the current limit, the transient synchronous stability and the power grid voltage supporting capability of the existing grid-structured converter cannot be considered. In one aspect, the invention provides a reactive synchronous fault ride-through control method of a grid-connected converter, which comprises the following steps: judging whether the power grid fails or not based on the obtained grid-connected point voltage of the grid-structured converter, switching the grid-structured converter into a fault traversing mode if the power grid fails, and freezing the angular frequency output by the grid-structured converter at the current moment; Correcting the reference phase angle based on the deviation between the measured value of the target electric quantity and a preset reference value to obtain an output phase angle reference value of the grid-structured converter during the fault period; controlling the output of the grid-formed converter based on the output phase angle reference value to provide reactive support and maintain transient synchronization with the grid during a fault; Wherein the target electric quantity is reactive current or reactive power. Optionally, the determining whether the power grid fails based on the obtained grid-connected point voltage of the grid-connected converter includes: and if the voltage of the grid connection point of the grid-structured converter is smaller than a first voltage threshold value, judging that the power grid fails. Optionally, the generating the reference phase angle during the fault based on the frozen angular frequency includes: And performing time integral operation on the frozen angular frequency to obtain a reference phase angle in the fault period. Optionally, the correcting the reference phase angle based on the deviation between the measured value for the target electric quantity and a preset reference value to obtain an output phase angle reference value of the grid-type converter during the fault period includes: Generating the phase angle correction term through proportional control, integral control or proportional integral control based on a deviation between the measured value of the target electric quantity and a reference value of the target electric quantity; and correcting the reference phase angle by using the phase angle correction term to obtain an output phase angle reference value of the grid-structured current converter in the fault period. Optionally, before generating the phase angle correction term, further comprising: And filtering the deviation between the measured value of the target electric quantity and the reference value of the target electric quantity. Optionally, after controlling the output of the grid-type converter based on the output phase angle reference value, f