【摘要】 模块化多电平换流器(Modular multilevel converter,MMC)是高压直流(High Voltage Direct Current,HVDC)输电系统中一种新型电压源换流器拓扑,每个桥臂由多个子模块(Sub-module,SM)串联而成。在系统正常运行前需对子模块预充电,以使其达到额定电压。首先,介绍了从直流侧进行预充电的方式,并指出了其存在的诸多不足。为探索一种满意的启动方式,在详细分析换流器预充电动态过程的基础上,将此过程分为两个阶段。对于不可控阶段,阐述了换流器瞬间过电流的形成机制和抑制措施;对于可控阶段,提出了电容电压参考值设定、相间电压平衡和相内电压平衡的控制算法。最后,在Matlab/Simulink中建立了仿真模型并在实验室搭建了实验平台,仿真及实验结果验证了控制策略的正确性与可行性。更多还原

【Abstract】 Modular multilevel converter(MMC) is a novel topology of voltage source converter applied in High Voltage Direct Current(HVDC) transmission system and its bridge arm is in series by a number of sub-modules(SM). Every SM needs pre-charging to reach the rated voltage before normal operation of the system. At first, a pre-charging mode from DC side is presented and its shortcomings are pointed out in this paper. In order to search for a satisfying starting-up mode, on the basis of a detailed analysis of the pre-charging dynamic process, the procedure is divided into two stages. For the uncontrollable stage, the formation mechanism and suppression measures of transient over current are set forth. For the controllable stage, a reference value setting mode of the capacitor voltage, control algorithms of phase-to-phase voltage balance and voltage balance within phase are put forward. Finally, a simulation model is built in Matlab/Simulink and an experiment platform is built in the lab. The correctness and feasibility of the control strategies are verified by the results of simulation and experiment.更多还原