Development of the medium and low voltage DC distribution system is of great significance to a regional transmission of electric energy,increasing a penetration rate of new energy,and enhancing a safety of the operati...Development of the medium and low voltage DC distribution system is of great significance to a regional transmission of electric energy,increasing a penetration rate of new energy,and enhancing a safety of the operation of the AC/DC interconnected grid.This paper first summarizes the medium and low voltage DC distribution system schemes and plans put forward by many countries,and then elaborate status of under-construction medium and low voltage DC distribution system project cases in China.Based on these project cases,this paper analyzes key issues involved in the medium and low voltage DC distribution system topologies,equipment,operation control technologies and DC fault protections,in order to provide theoretical and technical reference for future medium and low voltage DC distribution system-related projects.Finally,this paper combines a current China research status to summarize and give a prediction about the future research direction of medium and low voltage DC distribution system,which can provide reference for the research of medium and low voltage DC distribution system.展开更多
直流故障穿越是柔性直流输电(voltage sourced converter based high voltage direct current transmission,VSCHVDC)技术面临的重要问题之一。全桥型模块化多电平换流器(full bridge modular multilevel converter,FBMMC)能够快速清除...直流故障穿越是柔性直流输电(voltage sourced converter based high voltage direct current transmission,VSCHVDC)技术面临的重要问题之一。全桥型模块化多电平换流器(full bridge modular multilevel converter,FBMMC)能够快速清除直流侧故障,是实现直流故障穿越的理想拓扑。该文首先分析现有换流阀闭锁保护策略下电容放电阶段和换流阀闭锁阶段的等效电路,推导电容电压和电流的解析式。针对实际工程中功率模块具有恒功率负载特性,换流站闭锁期间功率模块电容电压逐渐发散并最终导致交流断路器跳闸的问题,提出一种FBMMC-HVDC的故障穿越控制保护策略。在故障穿越期间,换流器处于可控状态,能够避免电容电压发散,无需切断交直流系统连接;在故障清除后能够立即恢复正常运行,具备暂时性和永久性直流故障穿越能力。在PSCAD/EMTDC软件中构建了FBMMC-HVDC仿真模型,对比上述两种保护策略,分析两种策略各自的优缺点。展开更多
采用架空线柔性直流输电技术进行远距离输电是大规模风电场友好型并网的有效手段。针对架空线路易发生故障的问题,采用对称双极主接线并配置直流断路器是其主要解决方案之一。该文基于双极接线方案运行方式灵活及直流断路器的故障清除能...采用架空线柔性直流输电技术进行远距离输电是大规模风电场友好型并网的有效手段。针对架空线路易发生故障的问题,采用对称双极主接线并配置直流断路器是其主要解决方案之一。该文基于双极接线方案运行方式灵活及直流断路器的故障清除能力,提出风电经架空线基于模块化多电平换流器的柔性直流输电(modular multilevel converter based high voltage direct current,MMC-HVDC)并网的直流故障穿越协调控制策略。根据非故障极的功率转带能力,将故障清除后的不平衡功率分配划分为自消纳情景和非自消纳情景。针对自消纳情景,通过合理切换双极MMC的控制模式,可在提高非故障极功率转带能力的同时自主消纳不平衡功率,进而有效降低转移功率的影响范围;针对非自消纳情景,设计考虑风机转速约束的风电场超速减载协调控制策略,优化分配各风电机组承担的减载功率,充分利用其转子动能和捕获风功率的变化实现精确减载;同时通过控制模式切换使非故障极MMC自主运行于满载状态,减小单极退出运行对受端交流系统的影响。最后,基于Matlab/Simulink仿真模型验证所提直流故障穿越协调控制策略的有效性。展开更多
基金supported by the National Key Rese arch and Development Program of China(2018YFB0904100)Science and Technology Project of State Grid(SGHB0000KXJS1800685)
文摘Development of the medium and low voltage DC distribution system is of great significance to a regional transmission of electric energy,increasing a penetration rate of new energy,and enhancing a safety of the operation of the AC/DC interconnected grid.This paper first summarizes the medium and low voltage DC distribution system schemes and plans put forward by many countries,and then elaborate status of under-construction medium and low voltage DC distribution system project cases in China.Based on these project cases,this paper analyzes key issues involved in the medium and low voltage DC distribution system topologies,equipment,operation control technologies and DC fault protections,in order to provide theoretical and technical reference for future medium and low voltage DC distribution system-related projects.Finally,this paper combines a current China research status to summarize and give a prediction about the future research direction of medium and low voltage DC distribution system,which can provide reference for the research of medium and low voltage DC distribution system.
文摘直流故障穿越是柔性直流输电(voltage sourced converter based high voltage direct current transmission,VSCHVDC)技术面临的重要问题之一。全桥型模块化多电平换流器(full bridge modular multilevel converter,FBMMC)能够快速清除直流侧故障,是实现直流故障穿越的理想拓扑。该文首先分析现有换流阀闭锁保护策略下电容放电阶段和换流阀闭锁阶段的等效电路,推导电容电压和电流的解析式。针对实际工程中功率模块具有恒功率负载特性,换流站闭锁期间功率模块电容电压逐渐发散并最终导致交流断路器跳闸的问题,提出一种FBMMC-HVDC的故障穿越控制保护策略。在故障穿越期间,换流器处于可控状态,能够避免电容电压发散,无需切断交直流系统连接;在故障清除后能够立即恢复正常运行,具备暂时性和永久性直流故障穿越能力。在PSCAD/EMTDC软件中构建了FBMMC-HVDC仿真模型,对比上述两种保护策略,分析两种策略各自的优缺点。
文摘采用架空线柔性直流输电技术进行远距离输电是大规模风电场友好型并网的有效手段。针对架空线路易发生故障的问题,采用对称双极主接线并配置直流断路器是其主要解决方案之一。该文基于双极接线方案运行方式灵活及直流断路器的故障清除能力,提出风电经架空线基于模块化多电平换流器的柔性直流输电(modular multilevel converter based high voltage direct current,MMC-HVDC)并网的直流故障穿越协调控制策略。根据非故障极的功率转带能力,将故障清除后的不平衡功率分配划分为自消纳情景和非自消纳情景。针对自消纳情景,通过合理切换双极MMC的控制模式,可在提高非故障极功率转带能力的同时自主消纳不平衡功率,进而有效降低转移功率的影响范围;针对非自消纳情景,设计考虑风机转速约束的风电场超速减载协调控制策略,优化分配各风电机组承担的减载功率,充分利用其转子动能和捕获风功率的变化实现精确减载;同时通过控制模式切换使非故障极MMC自主运行于满载状态,减小单极退出运行对受端交流系统的影响。最后,基于Matlab/Simulink仿真模型验证所提直流故障穿越协调控制策略的有效性。
