Research on Effect and Prioritization of the Reformation from LCC-HVDC to VSC-HVDC

There are a large number of line commutated converter based high voltage direct current (LCC-HVDC) systems operating in China, threatening the security and stability of the power grid. Therefore, replacing some aging LCC-HVDC systems with voltage source converter based direct current (VSC-HVDC) systems is feasible, considering the development of relevant technologies. This paper presents four indexes to measure the demand and effect of reforming a LCC-HVDC system to a VSC-HVDC system. These indexes are the multiple infeed interaction fact (MIIF), the multiple infeed operating short circuit ratio (MIOSCR), the urgency coefficient of reformation and the average rise of fault voltage of key buses. After that, we proposes some principles of giving the prioritization of the reform schemes of different HVDC systems in one grid. Especially, we illustrate the necessity of reforming LCC-HVDC systems to VSC-HVDC systems in Shanghai and give the prioritization of the reform schemes, which is finally verified in simulation.