Application Research Of STATCOM In The Multi-infeed HVDC Commutation Failure

With the rapid development of China’s economy, the multi-infeed HVDC system structure will appear more and more in the country. Commutation failure is one of the most common and serious failures in HVDC system. It may result in the DC current rush-increasing, converter valve life shortening, DC transmission power reducing, AC system voltage instability in the inverter side weakening and other serious consequences. If improperly handled after the fault, it may lead to subsequent commutation failure, and continuous commutation failures could cause the converter station bipolar latching, eventually leadto the DC transmission power interruption.In this case, a vigorous reactive power support can improve operational performance HVDC system and inhibit the continuous commutation failure that may occur in themulti-infeed HVDC system.Therefore, the applied research of STATCOM in multi-infeed HVDC system has profound theoretical and practical significance.Firstly, the mechanism, influencing factors and recovery strategies of HVDC commutation failure were theoretical researched in the article. Based onsummarizing presentresearch results, the article conducts apreliminary exploration on the mechanism of multi-infeed HVDC commutation failure phenomenon, and leads to theeffect of dynamic reactive power compensation devicesusing forease commutation failure phenomena. Meanwhile, the simulation model in the electromagnetic transient simulation software PSCAD isestablished and thenthe typical commutation failure is simulated.Next, after a simple comparison of two dynamic reactive power compensation devices, the articlechooses static synchronous compensator (STATCOM) to solve the commutation failure problem.The main circuit topology of STATCOM is chosen by many aspects, such as transient stability, economy and engineering practicality. Then select and design△ chain-type main circuit structureusing in thisoperating condition.Ultimately, the simulation model STATCOM with designed main circuit structure and double-infeed HVDC is established. Based on the model, the article designsacoordinationcontrol strategy between STATCOM and HVDC system.Finally, Static targets and simulation waveformsboth verified that the STATCOM canenhance the immunity of commutation failure and reduce the risk of multi-infeed commutation failure to a certain extent. In addition, adding STATCOM on the AC bus of inverter has positive effects on expanding the AC bus voltage operating range and increasing the power recovery capability.This article is from the actual project needs, study the application of the dynamic reactive power compensation STATCOM in HVDC transmission system commutation failures.The system with STATCOM has a better behavior,by simulatingwith the electromagnetic transient simulation.The applied research has a profound practical significance in thefield of gridsecurity and stability.