基于模糊逻辑的UPFC线路新型正序故障分量方向元件

统一潮流控制器(UPFC)可以灵活控制线路潮流,提高电力系统运行稳定性,但其接入会对线路保护的动作性能产生影响。针对UPFC线路正序故障分量方向元件在反方向故障时易发生误动的问题,提出了基于模糊逻辑的适用于UPFC线路的新型正序故障分量方向元件。首先,通过增加UPFC线路侧电压互感器,与原有的母线电压和线路电流测点组成新型保护单元。在此基础上,对传统方向元件的动作区域进行划分,进而应用模糊逻辑,通过设置合理的隶属度函数、权重和故障方向判据,利用综合隶属度函数实现故障方向的判别。最后,基于PSCAD/EMTDC的大量仿真结果表明,新型方向元件在UPFC不同运行方式、不同故障类型和过渡电阻等条件下,均可正确判别故障方向,保障了UPFC接入后电网的安全可靠运行。

Fuzzy Logic Based Novel Directional Relay Using Positive-sequence Fault Component for Line Equipped with Unified Power Flow Controller

The unified power flow controller (UPFC) has the ability to control the line power flow flexibly, which improves the stability of power system operation. However, the access of UPFC has impact on the performance of line protection. The directional relay using positive-sequence fault component may misoperate for fault in reverse direction on the line equipped with UPFC. To solve this problem, this paper proposes a novel directional relay based on fuzzy logic for the line equipped with UPFC. Firstly, this paper develops a novel protection unit composed of the measuring points of bus voltage and line current of UPFC line side where an additional potential transformer is needed for measuring it. Then, the action region of the traditional directional relay is divided, and the fuzzy logic is applied to construct the novel directional relay. By setting rational membership functions, weights and fault direction criterion, the fault direction can be identified accurately by using the comprehensive membership function. Finally, the simulation results based on PSCAD/EMTDC show that the novel directional relay can correctly identify the fault direction under the conditions of different operation modes of UPFC, fault types and transition resistances, which ensures the safe and reliable operation of the power system equipped with UPFC.