ADPSS Based Short-circuit Current Calculation Method of MMC

Abstract

Modular multilevel converter (MMC) has broad application prospects in new energy transmission. When a MMC is connected to an active AC grid, it is necessary to calculate the three-phase symmetrical short-circuit current contribution of MMC to ensure the safety of power system. The existing method used in actual engineering projects consider MMC as a current source of which the amplitude is the current limiting amplitude of current limiter. It is safe but has too much margin to be accurate. This paper proposes a new method to calculate short-circuit current that can be used in actual engineering project. This paper analyses the characteristics of MMC short-circuit current first, and proposes the key factors affect short-circuit current contributed by MMC during an actual operating condition. On this basis, simulation trials on advanced digital power system simulator (ADPSS) are designed to get the characteristic curves of short-circuit current which can be used to calculate short-circuit current in actual operation of the engineering project. Finally, this paper uses Zhangbei MMC-HVDC project as an example to apply the new method and show the effectiveness and superiority of the method proposed by this paper.