基于孪生模型的模块化多电平换流器保护

Protection for Modular Multilevel Converter Based on Twin Model

随着柔性直流输电技术的发展,模块化多电平换流器(MMC)由于其拓扑优势越来越受到关注。作为直流输电换流阀的主要元件,子模块与桥臂电抗器故障将对换流站安全稳定运行造成严重影响,现有差动保护均无法有效识别此类故障。文中提出了基于孪生模型的MMC保护原理,结合MMC的控制信息建立数字孪生模型,通过动态状态估计构建保护判据。所提保护方案能够准确检测MMC换流器故障,包括桥臂电抗器匝间短路故障、子模块开路故障及桥臂相间短路故障。根据保护动作类型提出两套保护判据。仿真结果表明,所提保护方案能够可靠地自适应辨识MMC区内故障,具有良好的速动性以及耐受过渡电阻能力。

With the development of flexible direct current transmission technology,modular multilevel converters(MMCs)are receiving increasing attention due to their topological advantages.As the main component of the DC transmission converter valves,the faults of the submodules and bridge arm reactors will have a serious impact on the safe and stable operation of the converter station,but the existing differential protection cannot effectively identify it.This paper proposes the principle of MMC protection based on the twin model,establishes a digital twin model based on the control information of MMC,and constructs the protection criteria through dynamic state estimation.The proposed protection scheme can accurately detect the faults in MMC converters,including inter-turn short-circuit faults in bridge arm reactors,open-circuit faults in submodules,and phase-to-phase short-circuit faults in bridge arm reactors.Two sets of protection criteria are proposed based on the protection operation type.The simulation results show that the proposed protection scheme can reliably and adaptively identify the faults within the MMC region,and has good speed response and ability to withstand transition resistance.