分区互联装置桥臂闪络故障保护策略设计

随着城市电网的发展,电磁环网送电能力受限和短路电流超标问题越来越突出。分区互联装置是解决未来电磁环网有关问题的重要手段。提出了一种单变压器分区互联装置设计方案。系统故障时,单变压器分区柔性直流输电系统的故障特性和双变压器柔性直流输电系统的故障特性存在较大差别。当桥臂发生闪络故障时,换流器闭锁后交流系统通过子模块二极管形成故障通路,造成交流电流直流偏置,交流断路器将无法正常断开。为此,针对分区互联装置单变压器的拓扑结构,分析了桥臂闪络故障的故障特性,提出了基于闭合子模块旁路开关的保护动作策略,实现了故障情况下交流电流直流分量的快速衰减,确保了交流断路器可靠动作。通过单变压器分区互联装置PSCAD/EMTDC仿真测试,验证了故障分析及保护策略设计的正确性。

Protection Scheme Design for Interconnecting Device Under Arm Flashover Fault

With the development of the city power grid, the problems of the limited power supply capacity of electromagnetic loop network and short-circuit overweight are more and more prominent, interconnecting device is an important method to solve electromagnetic loop problems in the future.This paper proposes the design scheme of a single-transformer interconnecting device.During system failure, the fault characteristics of single-transformer interconnecting flexible HVDC system are extremely different from those of double-transformers flexible HVDC system.When the arm flashover occurs, the AC system can form a fault path through the diode in submodule after converter is blocked, which will cause DC offset of AC current and AC circuit breaker cannot be able to disconnect.Therefore, according to the topology of single-transformer in interconnecting device, this paper analyzes the fault characteristics of arm flashover fault, and proposes the protection strategy based on closing sub-module bypass switch, which can realize the rapid attenuation of the DC component in AC current and ensure the reliable operation of AC circuit breakers.Through the simulation test of single-transformer interconnecting device in PSCAD/EMTDC, it verifies the correctness of the fault analysis and protection strategy design in this paper.