Analysis Of Factors Affecting Dynamic Performance Of HVDC Transmission Control System And Research On Mitigation Strategy Of Commutation Failure

Commutation failure is a great threat to the safe operation of HVDC transmission system.The research shows that commutation failure is likely to occur when AC fault occurs in the inverter side.It is a common method to control commutation failure by adjusting PI parameters.The disadvantage is the actual trigger angle advance may be quite different from its output value,which means it has high volatility and poor universality.This paper mainly studies the commutation failure control strategy with more accurate trigger angle advance and wider universality.Based on the analysis of commutation failure mechanism,the influence of key parameters on inverter side and the range of trigger angle advance to effectively suppress commutation failure,this paper proposes the optimized commutation failure control strategy.Firstly,the basic concept of HVDC system is introduced.Considering that the amplitude and phase change of the voltage after the fault occurs,the commutation process of single and continuous commutation failure is analyzed based on the commutation voltage time area.Furthermore,in order to reveal the relationship between the performance of HVDC control system and the key parameters of inverter side in AC fault,this paper proposes the appropriate dynamic performance index for trigger angle advance and extinction angle.PSCAD and MATLAB are used to analyze the influence of dynamic performance.The simulation results show that trigger angle advance can improve the dynamic performance.But too large is not conducive to the recovery of the system from failure.Besides,the increase of extinction angle is beneficial to increase extinction area of the commutation process.But too much will increase the reactive power consumption and reduce the economy and safety reliability of the system.At last,based on the above research conclusions,a strategy about commutation failure control(CFCS)based on commutation area is proposed,which can adjust the trigger angle advance adaptively according to fault severity.The PSCAD/EMTDC simulation results show that compared with the existing control,CFCS can effectively reduce the probability of single and continuous commutation failures in HVDC system when AC failure occurs and the frequency of commutation failure is controlled within one time.The dynamic performance of HVDC control system can be improved by using CFCS.In this paper,how to improve the commutation failure suppression ability of HVDC transmission system is studied.The goal is to minimize the possibility of commutation failure.The research results have theoretical research significance and engineering practical value for improving the safe operation level of China’s power grid.