SVC Control Strategy Optimization For Dealing With DC Continuous Commutation Failure

Commutation failure is one of the most common faults in high voltage direct current(HVDC)power transmission.If it is not handled properly,it may lead to continuous commutation failure or even DC blocking,the continuous huge power impact will seriously affect the safe and stable running of the power system.Dynamic reactive power compensation for the receiving-side AC system can effectively improve the power recovery characteristics of the system after commutation failure and reduce the risk of DC continuous commutation failure.Therefore,the research on the suppression of DC continuous commutation failure by Static Var Compensator(SVC)has profound theoretical significance and practical value.Firstly,the prediction criterion of DC continuous commutation failure is improved.The mechanism,influencing factors and countermeasures of continuous commutation failure are analyzed.Based on the commutation area method,a prediction criterion of continuous commutation failure is constructed,which can evaluate the risk of DC continuous commutation failure.At the same time,HVDC system is built in the electromagnetic transient simulation software PSCAD to study the dynamic reactive power demand of the inverter station and the rule of reactive power exchange in the AC/DC system during commutation failure and power recovery.Secondly,a TCR-TSC type SVC control strategy optimization scheme based on continuous commutation failure prediction information is designed.Aiming at the problem that when there is a serious fault on AC system,the suppression effect of SVC on continuous commutation failure is not obvious even making it against the subsequent power recovery of DC system,a TCR-TSC type SVC simulation model is built on PSCAD simulation platform.Based on the rule of AC/DC system reactive power exchange,a TCR-TSC type SVC control strategy optimization scheme based on the prediction information of continuous commutation failure is designed.On the basis of the constant voltage control,an additional control based on continuous commutation failure prediction information is added to control the switching of the TSC branch capacitor.The working characteristics of SVC during DC commutation failure and recovery process are optimized and the effect of suppressing DC continuous commutation failure is improved.Finally,the Cigre-benchmark DC system model and actual power grid model are used to verify the suppression effect of the proposed SVC control strategy for continuous commutation failure.The simulation results show that the optimized SVC can promote the system recovery after commutation failure and reduce the risk of DC continuous commutation failure.In addition,Aiming at the DC transmission system equipped with synchronous compensator(SC),synchronous compensator simulation model is built in PSCAD.The voltage and reactive power dynamic characteristics of the SC and SVC are compared.The adaptability of the proposed SVC control strategy is verified when the SC is connected to the DC system.