非隔离型低压柔性互联装置的低频地线环流产生机理及抑制策略  

Mechanism and Suppression Strategy of Low-frequency Ground Circulating Current for Non-isolated Flexible Interconnection Device

作　　者：袁宇波 刘瑞煌 史明明 雷家兴 刘利国 张宸宇 YUAN Yubo;LIU Ruihuang;SHI Mingming;LEI Jiaxing;LIU Liguo;ZHANG Chenyu(State Grid Jiangsu Electric Power Company Ltd.,Research Institute,Nanjing 210009,Jiangsu Province,China;School of Electrical Engineering,Southeast University,Nanjing 210096,Jiangsu Province,China;State Grid Jiangsu Electric Power Company Ltd.,Nanjing 210024,Jiangsu Province,China)

机构地区：[1]国网江苏省电力有限公司电力科学研究院,江苏省南京市210009 [2]东南大学电气工程学院,江苏省南京市210096 [3]国网江苏省电力有限公司,江苏省南京市210024

出　　处：《电网技术》2024年第9期3965-3973,I0101,共10页Power System Technology

基　　金：国网江苏省电力有限公司科技项目(基于国产宽禁带器件的多端口柔性互联装置,J2023008)。

摘　　要：柔性互联装置是实现低压配电网潮流优化和新能源高效消纳的关键装备,有必要去除隔离变压器以提高效率和功率密度。但实际运行中面临严重的地线环流问题,恶化装置电能质量和安全稳定运行能力。为此,建立了低压配电网直接接地和变流器调制算法影响下非隔离型柔性互联装置地线环流分析数学模型,揭示了变流器共模电压注入、电网运行工况差异产生基波和三次谐波地线环流的机理。在此基础上,给出了一种闭环抑制方法,通过比例–多模谐振控制器对地线环流进行闭环控制,并通过改进的载波调制算法在逆变侧各桥臂中注入附加的共模电压信号,以维持双侧变流器的共模电压平衡,进而消除低频地线环流。控制器在环的半实物仿真结果表明,采用所提控制策略后,不同电网工况下非隔离型柔性互联装置的低频地线环流均得到充分抑制,有效提升了装置的电能质量和运行可靠性。Flexible interconnection devices are key equipment for optimizing low-voltage distribution network flow and efficiently integrating new energy sources.It is necessary to remove isolation transformers to improve efficiency and power density.However,in actual operation,they face a serious problem of grounding the circulating current,which deteriorates the device's power quality and operational stability.To address this issue,a mathematical model was established to analyze ground circulating current in non-isolated flexible interconnection devices,considering direct grounding and inverter modulation algorithm effects in low-voltage distribution networks.The model revealed the mechanisms behind the injection of common-mode voltage by inverters and the generation of fundamental and third harmonic ground loop currents due to differences in grid operating conditions.On this basis,a low-frequency loop current closed-loop suppression strategy was proposed using a proportional-multiple-mode resonance controller.An improved carrier modulation algorithm was then used to inject additional common-mode voltage signals into each bridge arm on the inverter side to maintain the balance between both sides,thus eliminating low-frequency ground circulating current.The semi-physical simulation results of the controller show that,with the proposed control strategy,low-frequency ground circulating current in non-isolated flexible interconnection devices is effectively suppressed under different grid conditions,significantly improving the device power quality and operational reliability.

关 键 词：柔性互联装置 无隔离变压器 地线环流 共模电压 三相四桥臂变流器 

分 类 号：TM721[电气工程—电力系统及自动化]