Abstract
Commutation failure is a key issue that affects the safe operation of HVDC transmission systems. Scholars at home and abroad have conducted research on the mechanism, evaluation indicators, and control strategies of commutation failure. However, most of the researches are aimed at the working conditions of commutation failure caused by a short-circuit fault on the AC side. There are few studies on the commutation failure caused by the harmonic injection on the AC side and the distortion of the AC bus voltage waveform. This paper clarifies the mechanism of commutation failure caused by waveform distortion, and proposes an index of harmonic commutation margin. On this basis, an evaluation method for commutation failure caused by waveform distortion is proposed. By predicting the commutation voltage-time area and optimization methods to assess whether the current voltage conditions have the risk of commutation failure. Finally, an electromagnetic transient simulation model is established on PSCAD/EMTDC, and the evaluation method in this chapter is verified by simulating the working conditions of the inverter side bus voltage waveform distortion. The results show its effectiveness in evaluating the commutation failure. The research provides a theoretical basis to the implementation of the control function and has broad engineering application prospects.
Highlights
Compared with the AC transmission, HVDC has better economic benefits in long distance, high-capacity transportation, wide application in power system networking [1].HVDC projects have played a vital role in China
Most studies on commutation failure are designed for AC system short-circuit fault conditions and most of the criteria of these methods are based on the amplitude of the voltage, so it is impossible to consider the influence of voltage waveform distortion such as harmonics on the commutation process in the transient process of the system[7]
One study [9] uses an optimized method to present the index LTHD, which characterizes the influence of the magnetizing inrush current on commutation, and provides a quantitative basis for solving the commutation failure caused by waveform distortion
Summary
Compared with the AC transmission, HVDC has better economic benefits in long distance, high-capacity transportation, wide application in power system networking [1].HVDC projects have played a vital role in China. Most studies on commutation failure are designed for AC system short-circuit fault conditions and most of the criteria of these methods are based on the amplitude of the voltage, so it is impossible to consider the influence of voltage waveform distortion such as harmonics on the commutation process in the transient process of the system[7]. One study [9] uses an optimized method to present the index LTHD, which characterizes the influence of the magnetizing inrush current on commutation, and provides a quantitative basis for solving the commutation failure caused by waveform distortion. It is of great significance to study the influence mechanism of voltage waveform distortion on commutation and propose corresponding evaluation indicators to implement the control effect in advance. The research provides a theoretical basis to the implementation of the control function and has broad engineering application prospects
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