基于对称双极接线的全桥型MMC-HVDC直流侧短路故障穿越控制 方法

基于模块多电平换流器的高压直流输电技术(High Voltage Direct Current Transmission Technology Based on Modular Multilevel Converte, MMC-HVDC)因开关频率低、运行损耗小及易于扩展多端网络等优点被广泛应用。直流侧短路故障因短路电流大,故障电流上升速率快且难以抑制,对MMC-HVDC的发展造成了严重困扰。提出一种MMC-HVDC直流侧短路故障穿越控制方法,该方法基于对称双极接线的全桥型MMC-HVDC,且在直流侧采用高阻接地及金属回线,在发生直流侧短路故障时利用全桥型模块多电平换流器及时反转输出直流电压极性,实现故障电流抑制。同时利用金属回线构建成新的功率回路,快速恢复故障期间的有功功率传输。所提出的故障穿越策略,可以有效消除MMC-HVDC系统在发生直流侧短路故障时换流设备受到的故障电压及电流应力,同时避免换流器闭锁,防止功率缺失。最后,利用PSCAD/EMTDC仿真验证了所提出的直流侧短路故障穿越控制方法的有效性。

DC short circuit fault ride-through method based on symmetrical bipolar FBSM-MMC HVDC system

High-Voltage Direct Current transmission based on Modular Multilevel Converter (MMC-HVDC) has gained a lot of attention because of its significant advantages, such as low switching frequency, low operation loss, modular structure and so on. The DC side short-circuit fault has caused serious trouble for the development of MMC-HVDC because of its large short-circuit current, fast rise rate of fault current and difficult suppression. A DC side short-circuit fault ride-through control method for MMC-HVDC is proposed. The method is based on a full-bridge MMC-HVDC with symmetrical bipolar connection, and adopts high-resistance grounding and metal return lines on the DC side. When a DC side short-circuit fault occurs, the full-bridge module multilevel converter is used to reverse, in a timely fashion, the polarity of the output DC voltage to realize fault current suppression. At the same time, a new power loop is constructed using the metal return lines, and the active power transmission during the fault period is quickly restored. The proposed fault ride-through strategy can effectively eliminate the fault voltage and current stress of the converter equipment when the MMC-HVDC system is short-circuited on the DC side, and at the same time avoids converter blocking and power loss. Finally, PSCAD/EMTDC simulation is used to verify the effectiveness of the proposed DC side short-circuit fault ride-through control method.This work is supported by National Natural Science Foundation of China (No. 2018YFB0904500).