模块化多电平变流器高压直流输电系统直流故障改进控制策略  

Improved Control Strategy for DC Fault in Modular Multi-Level Converter-HVDC System

作　　者：姚骏[1] 谭义[1] 裴金鑫 熊小伏[1] 欧阳金鑫[1] Yao Jun;Tan Yi;Pei Jinxin;Xiong Xiaofu;Ouyang Jinxin(State Key Laboratory of Power Transmission Equipment&System Security and New Technology Chongqing University Chongqing 400044 China)

机构地区：[1]输配电装备及系统安全与新技术国家重点实验室(重庆大学),重庆400044

出　　处：《电工技术学报》2018年第14期3306-3318,共13页Transactions of China Electrotechnical Society

基　　金：国家重点研发计划(2017YFB0902000);国家自然科学基金(51477016)资助项目

摘　　要：针对模块化多电平变流器高压直流(MMC-HVDC)输电系统直流故障,首先建立全桥型MMC-HVDC系统的详细数学模型,并对故障期间系统过电压或过电流的产生机理及其发展过程展开深入分析,分析结果表明:在直流双极短路和单极接地故障期间,MMC-HVDC系统正、负极直流母线电压与MMC上、下桥臂电压的直流分量不匹配,导致桥臂电容迅速放电,进而引起系统严重过电流。因而提出在直流故障期间将MMC上、下桥臂实行分离控制,并使上、下桥臂电压的直流分量跟随正、负极直流母线电压而变化,从而实现MMC-HVDC系统直流故障下的安全、稳定运行,所提控制策略实现了MMC-HVDC系统三种直流故障穿越控制的有效简化和统一。另外,为提升直流单极接地和断线故障条件下MMC-HVDC系统的经济运行能力,进一步提出了一种新型功率指令优化策略。最后基于PSCAD/EMTDC仿真证明了所提MMC-HVDC系统直流故障控制策略以及功率指令优化策略的正确性与可行性。Aiming at the direct current(DC)faults of the full-bridge modular multi-level converter-high voltage direct current(MMC-HVDC)transmission system,the detailed mathematical model is established.In addition,the mechanism and progress of the over-voltage or over-current stress of MMC-HVDC system are analyzed in depth.The results show that,during the DC pole-to-pole and unipolar earth fault,the positive-and negative-pole DC bus voltages of MMC-HVDC system mismatch the DC components of the MMC upper and lower arm voltages,which leads to rapid discharge of the arm capacitance.Consequently,the system will suffer serious over current.Therefore,an improved control strategy is proposed by separately controlling the upper and lower arms of the MMC during the DC fault.With the proposed method,the DC components of the upper and lower arm voltages will follow the change of the positive-and negative-pole DC bus voltages,which ensures the safe and stable operation of the MMC-HVDC system.The proposed control strategy realizes the effective simplification and unification of fault ride-through control under three typical DC faults.In addition,in order to further improve the economic operation capability of the MMC-HVDC system under the DC unipolar earth and disconnection faults,an optimized power allocation strategy is proposed.Finally,the simulation results in PSCAD/EMTDC verify the correctness and feasibility of the proposed improved control strategy and optimized power allocation strategy for the MMC-HVDC system under DC faults.

关 键 词：模块化多电平变流器高压直流输电 全桥子模块 直流故障 故障穿越控制 

分 类 号：TM721[电气工程—电力系统及自动化]