柔性直流输电系统运行机理分析及主回路相关参数设计

分别从交流侧和直流侧分析柔性直流输电系统中电压源换流器的运行特性，并从稳态和瞬态角度分析直流电流和直流电压的数学表达。在此基础上，从3个方面对柔性直流输电系统主回路中的换流电抗器参数进行设计；考虑到交流系统三相不平衡时的直流电压波动，设计了直流侧电容器的参数。最后基于电磁暂态仿真软件PSCAD/EMTDC按所设计的参数对柔性直流输电系统进行了仿真分析，仿真结果表明该设计方法是合理可行的。

Analysis on Operational Mechanism of VSC-HVDC and Relevant Parameter Design of Its Main Circuit

The operational characteristics of voltage source converter (VSC) in flexible HVDC power transmission system are analyzed from AC side and DC side respectively, and from the viewpoint of steady state and transient state the mathematical expressions of DC current and DC voltage are analyzed. On this basis, from three aspects the parameters of converter reactor in the main circuit of flexible HVDC system are designed; considering the fluctuation of DC voltage caused by three-phase unbalance of AC system, the parameter of capacitor at DC side is designed. By means of electromagnetic transient simulation software PSCAD/EMTDC, with the designed parameters the flexible HVDC system is simulated. Simulation results show that the proposed design approach is reasonable and feasible.