直流系统分层接入方式下滤波器断路器的分断特性分析

Breaking Characteristics of AC-filter Breaker for UHVDC with Hierarchical Connection to AC Grid

特高压直流分层接入高低端换流器后,会对换流站及所接入交流系统的过电压、谐振特性等产生影响,交流滤波器断路器的分断性能对系统的可靠运行影响显著。针对±800k V直流系统分层接入方式下交流滤波器的断路器分断特性开展研究,建立了系统电磁过程电路分析模型,分析了不同工况条件和故障类型条件下断路器的特性。结果表明,双极运行工况下直流线路出现接地故障需要切除全部交流滤波器时,断路器断口恢复电压峰值最大;交流系统出现接地故障切除全部交流滤波器时,开断电流峰值最大;随着滤波器无功容量的增大,断路器开断电流增加。切除相同容量大组滤波器时,小方式下断路器开断电流比大方式下开断电流更大;在同一系统运行方式下切大组滤波器和切小组滤波器的断路器最大断口恢复电压差异较小,断口恢复电压仅与系统运行方式和交流母线电压有关,而与滤波器容量关系不大。该文工作将为特高压直流系统设计和运行提供参考。

When a UHVDC project is hierarchically connected to AC grid,the performance of AC-filter breaker significantly influences the operation reliability.To study the breaking characteristics of the AC filter breaker of±800 k V UHVDC hierarchical connection to AC grid,a circuit analysis model is established.It is concluded that when a DC line ground fault occurs and all AC filters need to be removed under the bipolar operation mode,the break recovery voltage peak value between the AC-filter breaker reaches the maximum.When all AC filters are removed during a ground fault in the AC net,the breaking current peak value is the highest.As the filter reactive power capacity increases,the breaking current of the circuit breaker increases.When cutting off a large group of filters of the same capacity,the breaking current under the small operation mode is greater than the one under the large operation mode.Under the same operation mode,the peak break recovery voltage is similar when filter groups with different capacity are cutting off.It is verified that the break recovery voltage is mainly related to the system operation mode and the AC bus voltage,but is negligibly related to the filter capacity.