Commutation Failure Anysis In Multi-Infeed HVDC Systems Based On The EMTDC

Being promoted by the project of 'Xi Dian Dong Song' and the powernetworking in whole country more HVDC transmission projects are constructed,novel configuration of HVDC transmission systems-Multi-infeed DC was appearedin China Southern and East Power Grid. MIDC will widespread availability as thepower demands increase.Commutation failure is one of the most common faults in HVDC system. It wouldlead to the decrease of the direct voltage in the inverter, the increase of direct current,and the decrease or interruption of direct power which impact the power stabilityheavily. The interaction between subsystems make the commutation failure in theMulti-infeed HVDC system differentiate from that in the single-infeed HVDC system.So, it is very important to study on the commutation failure deeply and present somemeasures to decrease the commutation failure in the MIDC systems.This paper introduces the fundamental composition of the HVDC systems,standard control mode and regulate characteristic, then focus on the control mode ofthe CIGRE HVDC benchmark model,in order to ready for the next simulation. Fromthe operating principle of the converter, the mechanism of commutation failure, therelated factors effecting the commutation failure and the hazard of it are analyzed.Based on the extinct-angle formulas of single-infeed HVDC, this paper deducesextinct-angle formulas of Multi-infeed HVDC. Through the sensitivities analysis ofthe parameters in the formulas, effecting of the parameters to the commutation failureare disclosed.The electromagnetic-transient simulation software-PSCAD/EMTDC is used tocarry out the simulation tests on the Multi-infeed model which established based on the CIGRE HVDC model. Through series typical emulation the effect of the inverterAC systems strength, the coupling degree and the load characteristic on the couplingcritical distance is analyzed, so the factors that induce all the inverters suffer fromcommutation failures simultaneously is discussed. The final correlation conclusion isdisclosed in order to give some supplement to the planning and design of thosesimilar systems.