Unbalance compensation method for three-level static synchronous compensator

Abstract

The invention provides an unbalance compensation method for a three-level static synchronous compensator (STATCOM), belonging to the technical field of reactive compensation for power systems. The method comprises the following steps of: detecting an asymmetrical current at a load side under the conditions of unbalanced power gird and asymmetrical load, and carrying out sequence decomposition; respectively carrying out dq transformation on the obtained positive and negative sequence currents to obtain DC references, and realizing the complete decoupling of positive and negative sequence active and reactive currents by using PI decoupling control to obtain the positive and negative sequence reference voltage vector of a three-level STATCOM output voltage; and finally, carrying out simplified three-level SVPWM (Space Vector Pulse Width Modulation) to obtain PWM (Pulse Width Modulation) driving signals to control the action of a switch device to produce a required compensation current. The invention overcomes the influence of the unbalanced power grid and the asymmetrical load on the performance of the three-level STATCOM, the reactive current and the negative sequence current under the conditions of unbalanced power gird and asymmetrical load can be accurately compensated, the stable balance of capacitance and voltage at a DC side is maintained, and the unbalance compensation method has the advantages of quick dynamic response and no static errors.

Description

technical field [0001] The invention belongs to the technical field of power system power quality control, and in particular relates to an unbalance compensation method of a three-level static synchronous compensator. Background technique [0002] The operating conditions of the distribution network are relatively complex, and various reasons may cause the asymmetry of the power system. Unbalanced loads and grid voltage asymmetry often occur, especially for single-phase loads such as railway locomotives. If the negative-sequence current is not compensated in time and injected into the power grid, it will cause great harm to generators, condensers, relay protection, automatic devices, and instruments. It is of great practical significance to compensate the negative sequence current and reactive current of unsymmetrical loads with fast dynamic response and no static error current. The static synchronous compensator can comprehensively solve various power quality problems in t...

AI Technical Summary

Problems solved by technology

However, unbalanced power grids and loads are common in practice. When the grid voltage and loads are asymmetrical, the performance of the controller based on the symmetric assumption will deteriorate, and in more serious cases, the STATCOM device will even be burned out.

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