自阻自均压模块化多电平换流器子模块拓扑及控制

Self-Block and Voltage Balance Modular Multilevel Converter Sub Module Topology and Control

基于模块化多电平换流器的高压直流输电需应对直流线路可能短路故障和子模块数量过多带来的电容电压均衡问题。为保证模块之间独立工作为约束条件,该文首先分析全桥拓扑故障抑制机理。然后基于故障钳位电路和开关电容多电平思想,设计一种具有直流故障电流阻断和内部电容电压均衡能力的自阻自均压型子模块拓扑,不仅能满足直流故障电流阻断要求,还将参与排序均衡的电容数量减少一倍。同时研究自阻、自均压拓扑两种不同闭锁模式下直流故障抑制特性、电平输出优先的自均压控制策略以及非闭锁直流故障抑制策略。最后通过PSCADEMTDC仿真模型验证该文所提自阻自均压拓扑直流故障抑制及控制策略的有效性。

High-voltage DC transmission based on modular multilevel converters(MMC)needs to deal with possible short-circuit faults on the DC line and the capacitor voltage balance problem caused by too many sub modules.To ensure sub modules working independently as a constraint,the paper first analyzes the full bridge topology fault suppression mechanism.Then a sub module topology with DC link fault blocking and internal capacitor balance ability is designed based on the fault clamp circuit and switch capacitor multilevel ideas.Thus,it will not only meet the self-suppression requirement but also reduce the number of capacitors participating in the sort balancing algorithm to half.What is more,for the self blocking and voltage balance topology,the DC link fault suppression characteristics under two different blocking modes,i.e.self-balancing control strategy based on the voltage level output priority and the unblocking DC link fault suppression strategy,are also studied.Finally,a PSCAD-EMTDC simulation model is used to verify the effectiveness of the proposed topology of DC link fault suppression and control strategy.