A Modeling Method for Inverter Switching Function Applicable to Asymmetric Operation State

Abstract

The invention discloses a converter switch function modeling method suitable for asymmetrical operation state, which belongs to the technical field of power system operation and control. According to the three-phase commutation voltage on the AC side of the converter, calculate the phase-locked loop output synchronous initial phase of the converter control system under the asymmetrical operation state; calculate the conduction offset angle and actual trigger angle of the three-phase converter valve; calculate The size of the commutation angle between the three-phase converter valves of the converter; establish the switching function model of the converter; calculate the DC side voltage of the converter, the AC side current of the converter, and the power injected into the converter. The commutation process of the converter during asymmetric operation is considered in detail, and the influence of the second harmonic current on the DC side on the commutation duration is considered in detail. The calculation process of the switching function model is simplified by ignoring unnecessary sub-harmonics. The analysis and calculation accuracy of the converter in the asymmetric operation of the AC system is effectively improved.

Description

technical field [0001] The invention belongs to the technical field of power system operation and control, and in particular relates to a converter switch function modeling method suitable for asymmetrical operation state. Background technique [0002] High-voltage direct current transmission has technical advantages such as large transmission capacity, long transmission distance, high controllability, and flexible operation, and there is no stability restriction problem due to transmission distance. It has obvious advantages in long-distance large-capacity transmission and regional system interconnection. With the vigorous advancement of the national smart grid construction, it is estimated that around 2020, my country's power grid will plan to build more than 40 DC transmission systems of different voltage levels. By then, my country will become the country with the most extensive DC transmission applications in the world. [0003] The wide application of high-voltage DC t...

AI Technical Summary

Problems solved by technology

The traditional switching function model assumes that the three-phase AC voltage is symmetrical, and the switching action of the three-phase converter valves of the converter remains symmetrical. It has high accuracy in analyzing the characteristics of the converter in normal operation, but when the AC system is in asymmetrical operation , the conduction characteristics of the three-phase converter valves of the converter and the commutation angles between the three-phase converter valves are not the same, which will significantly reduce the accuracy of the traditional switching function model

However, some existing methods for improving the switching function model of the converter in the asymmetric operating state, although there is some improvement in accuracy, but when considering the impact of the asymmetric operating state, they have not done a detailed and comprehensive analysis.

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