Behavioural mechanism and stability control of VSC–HVDC/weak AC hybrid grid after large disturbances

Abstract

Flexible DC transmission technology based on voltage source converter (VSC) is an effective solution to solve the reliability of power supply to weak AC systems. In this study, a VSC-high-voltage DC (HVDC) electromechanical transient simulation model is established based on the Chongqing-Hubei flexible DC transmission project which is the highest voltage level and the largest transmission capacity in the world. This model can be used to simulate the behaviour of the limiters and AC fault ride through strategies. A large disturbance measurement method for VSC's non-linear power characteristics is proposed. Stability of flexible DC and weak AC hybrid grid under large disturbance are analysed, behaviour mechanisms and key influence factors of different instability forms are revealed. In this way, a solution is proposed to improve the hybrid grid's ability against large disturbances. By the construction of the VSC-HVDC electromechanical transient simulation model, the correctness of the mechanism analysis and effectiveness of the solution are verified.