A hybrid negative current compensation system for high-speed railway power system

The high-speed railway load is a single-phase load with high power, which can generate large negative sequence current (NSC). Many compensation methods have been applied to compensate NSC which is a big power quality problem of railway power supply system, and each method has its own characteristics. A hybrid compensation system is proposed in this paper. The system consists of two different compensation methods. One is based on railway power conditioner(RPC) with modular multilevel converter(MMC) structure(MRPC), and the other is based on Steinmetz compensation principle with magnetic static var compensation (MSVC). The MRPC has a fast response speed but expensive price, while the MSVC has a low response speed but much cheaper price. Compared with MRPC-ONLY compensation method, the hybrid compensation system has a lower cost by reducing the compensation capacity of MRPC with MSVC. Firstly, the compensation principles of the hybrid compensation system is analyzed in detail. Then, the collaboration control strategy of compensation system is proposed. Moreover, the cost of the hybrid compensation system and the MRPC-ONLY compensation method are compared. Finally, simulation and experiment results are both presented to verify the effectiveness of the hybrid compensation system and its control method.