电流源型机电混合式直流断路器在特高压直流输电系统中的应用

Application of Current-source Hybrid Electro-mechanical DC Circuit Breaker in UHVDC Transmission Systems

传统机械式直流断路器通过在直流电流上迭加一个振幅逐渐增大的振荡电流来制造一个"人工电流零点",完成电路开断。这将导致该断路器在开断时会承受很大的正向电流,增大对断路器开关触头的损伤。针对传统直流断路器存在的这一缺点提出了一种新型电流源型机电混合式直流断路器,利用电力电子器件构造换流电路,控制产生大小和波形均可控的叠加电流,在产生过零点的同时减小电流的正向幅值,能有效减小高压直流断路器分闸时产生的电弧,减小对直流开关触头的损伤,延长其寿命。通过MATLAB/Simulink仿真验证了该断路器成功开断工况电流和故障电流,并大幅降低了正向电流。进一步以正在筹建的蒙西特高压直流工程为例,通过PSCAD/ETMDC仿真平台,模拟该断路器作为直流金属回路转换开关成功开断直流线路故障电流并保持系统电压稳定的过程。仿真结果验证了所提出的新型直流断路器能够快速有效地开断直流线路故障电流,可以作为单极闭锁的后备动作方案。

Traditional mechanical DC breaker interrupts DC circuit by oscillation current superposition method, thus the breaker will bear remarkable forward current when interrupting, increasing damage to the switch contacts of circuit breaker. Considering the shortcomings of traditional DC breaker, we put forward a novel current-source hybrid electromechanical DC circuit breaker. By constructing commutation circuit with power electronic devices, current with controllable magnitude and waveforms can be produced, and positive amplitude of the current is reduced while a current zero is produced. It can effectively reduce the generated arc when HVDC circuit breaker opens, and reduce damage to DC switch contacts to extend its lifetime. DC circuit breaker can effectively switch offrated current and fault current, and it is verified by MATLAB/Simulink simulation software. Moreover, the condition of DC breaker used as metallic return transfer breaker interrupting DC line fault current is simulated with PSCAD/ETMDC. The Mengxi UHVDC project is simulated with PSCAD/ETMDC, and the simulated results validate that the proposed new DC breaker can interrupt the DC line fault current efficiently, and can be used as backup protection of unipolar blocking.