This paper discusses the impact of voltage control of VSC HVDC systems on the transient stability of power systems. The critical clearing time of a generator can be increased by improving the post fault voltage response of the system. VSC HVDC systems offer fast voltage control which would impact positively on the transient stability of the connected AC system. This was investigated using a test system in which a VSC is connected near a conventional generator. Simulations were carried-out for two different cases: VSC with AC voltage control, and VSC with reactive power control at which the reactive power is controlled at zero. The critical clearing time was used as the indicator of system stability. This paper shows that the critical clearing time can be significantly improved by having a VSC with AC voltage control nearby.
S. Arunprasanth, U.D. Annakkage, C. Karawita, and R. Kuffel, Presented at the CIGRÉ Canada Conference on Power Systems, Vancouver, Canada, Oct. 2016, paper 814
KEYWORDS: Transient stability, voltage source converter, modular multilevel converter, real-time digital simulator, and short circuit ratio