Simulation Method of Modular Multilevel Converter Blocking State Based on RTDS
Wang Jiecong1, Liu Chongru1, Xu Dongxu1, Xie Guochao1, Zhu Yi2
1. State Key Lab for Alternate Electrical Power System with Renewable Energy Sources North China Electric Power University Beijing 102206 China; 2. State Grid Shandong Economics Research Institute Jinan 250021 China
Abstract Modular multilevel converter (MMC) has been widely used in the area of high-voltage direct current (HVDC) transmission due to its modular structure. The simulation of the MMC blocking state involves the simulation of the diode, which is a kind of uncontrolled power electronic device. However, without interpolation algorithm and flexible time-step in real-time digital simulation (RTDS), there are the problems of the numerical oscillations and the diode switching delay. Therefore, RTDS reduces the error through using small time-step solving power electronic circuit. However, the user-defined model in CBuilder does not provide small time-step simulation environment. An alternating way is to use the interface transformer connecting the small time-step model of diode, but the leakage reactance and other parameters of which will reduce the simulation accuracy. An MMC blocking model suitable for RTDS is proposed, in which the backward Euler method is adopted for arm reactor calculation to eliminate the numerical oscillation, and the diode is equivalent to a two-value resistor paralleled with an RC snubber circuit. The errors of the proposed model under steady-state and transient state as well as the error caused by the diode switching delay are analyzed and calculated. Furthermore, the method of the parameter setting to the proposed model is provided, which can improve the calculation precision and numerical stability.
Wang Jiecong,Liu Chongru,Xu Dongxu等. Simulation Method of Modular Multilevel Converter Blocking State Based on RTDS[J]. Transactions of China Electrotechnical Society, 2018, 33(16): 3686-3696.
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2018, Vol. 33 
