具有故障隔离能力的新型MMC子模块及混联桥臂拓扑

针对半桥型模块化多电平换流器不具有直流故障阻断能力,柔性直流输电架空线方案存在较高暂态故障率问题,首先提出了一种三电容钳位型双子模块(TCDSM)拓扑。该拓扑与现有钳位双子模块相比,改善了基于钳位双子单元模块柔性直流输电直流侧短路反向电流故障隔离能力。然后,详细介绍了TCDSM拓扑的工作原理和性能分析,并提出了一种新型混联型桥臂换流站方案。新提出的混联型桥臂方案与钳位双子模块和半桥子模块组成的混联型桥臂方案相比,在不牺牲阻断能力的前提下,运行损耗基本相当,初始建站成本更低,从整体上优化了换流站建设成本。最后,通过仿真和实验结果验证了该拓扑及新型混联型桥臂方案的可行性。

A New Type of MMC Sub-module and Hybrid Arm Topology with Capability of Fault Isolation

The half-bridge modular multi-level converter does not have the DC fault blocking capability and the high transient failure rate of the scheme of voltage source converter based high voltage direct current(VSC-HVDC)transmission overhead line. This paper proposes a three-capacitor clamping double sub-module(TCDSM)topology. Compared with the existing clamping double sub-module, the topology improves the isolated current fault isolation capability of the DC-side short-circuit based on the clamping double sub-module VSC-HVDC transmission. The working mechanism and performance analysis of TCDSM topology is introduced in detail, and a new hybrid arm converter scheme is proposed. Compared with the hybrid arm system, which is composed of the clamping double sub-module and the half-bridge module, the cost of new operation is lower than that of the hybrid arm device without sacrificing the blocking capability, optimizing the overall converter station construction costs. Finally, the feasibility of the topology and the new hybrid arm is verified by simulation and experiment.