半/全桥混合型DC Chopper拓扑及其控制策略

Half/Full Bridge Hybrid DC Chopper Topology and Its Control Strategy

DC Chopper能在海上风电柔性直流输电系统主网侧发生短路故障时耗散系统的盈余功率,并实现故障穿越。针对全桥型集中式模块化DC Chopper使用IGBT和二极管数目多的问题,提出了一种半桥/全桥混合型集中式模块化DC Chopper拓扑。该拓扑采用半桥子模块替换桥臂中一部分仅起到电压支撑作用的全桥子模块,并根据桥臂电流单向性的特点,省略掉子模块中部分IGBT,仅保留其反并联二极管,大幅降低了设备的成本。在此基础上,针对现有的集中式模块化拓扑控制策略精确度低的问题,进而提出了一种利用方波正半波幅值调节耗散功率、利用占空比平衡桥臂能量的控制策略,实现了对耗散功率和桥臂能量的精确控制。在Matlab/Simulink中开展了海上风电柔性直流输电系统故障穿越的仿真研究,验证了所提出的DC Chopper拓扑及控制方案具有良好的故障穿越效果。

DC Chopper can dissipate the surplus power of a system and realize fault ride-through when a short-circuit fault occurs on the main grid side of offshore wind power plants based on the MMC-HVDC transmission system.Aiming at the problem that the full-bridge centralized modular topology uses a large number of IGBTs and diodes,we propose a half/full bridge hybrid centralized modular DC Chopper topology.The topology uses half-bridge sub-modules to replace part of the full-bridge sub-modules that only play a role in voltage support in the DC Chopper;meanwhile,according to the unidirectional characteristic of the bridge arm current,some IGBTs in the sub-modules can be omitted,and their anti-parallel diodes are retained,which greatly reduces the cost of the equipment.On this basis,aiming at the problem of low accuracy in the existing centralized modular topology control strategy,we propose a control strategy that the positive amplitude of square wave is utilized to adjust power dissipation and the duty cycle to balance bridge arm energy,by which the accurate control of power dissipation and bridge arm energy can be realized.A simulation study of fault ride-through of offshore wind power plants based on the MMC-HVDC transmission system is performed on the Matlab/Simulink,verifying that the proposed DC Chopper topology and control strategy have a good fault ride-through effect.