基于虚拟能量调节偏差的MMC-HVDC输电线路保护方案

柔性直流输电对继电保护的速动性及可靠性提出了更高的要求。为实现直流故障的快速可靠识别，文中分析了模块化多电平换流器(MMC)的控制参数在系统发生故障时的响应特性，并提出了一种MMC型高压直流输电线路保护新方案。根据MMC控制参数定义了虚拟能量调节偏差，利用虚拟能量调节偏差对系统故障时的响应特性识别直流线路故障，并结合虚拟能量调节偏差的比值进行故障类型的判别。该保护方案融合了交直流侧的故障信息，提高了保护的可靠性，保护判据利用了换流器控制参数信息，无须测量线路的电气量。仿真结果表明，所提保护方案可以快速准确动作且具有较强的耐过渡电阻能力。

Protection Scheme for MMC-HVDC Transmission Line Based on Virtual Energy Regulation Deviation

Flexible DC transmission sets higher requirements on the quick operation and reliability of relay protection. In order to identify DC faults quickly and reliably, this paper analyzes the response characteristics of control parameters of modular multilevel converter (MMC) in case of system faults, and proposes a new protection scheme of MMC based high-voltage direct current (HVDC) transmission lines. According to the MMC control parameters, the virtual energy regulation deviation is defined, the response characteristics of the virtual energy regulation deviation to the system fault are used to identify the DC line fault, and the ratio of the virtual energy deviation is used to distinguish the fault type. The protection scheme integrates the fault information on the AC and DC sides to improve the reliability. The protection criterion uses the converter control parameter information without measuring the electrical quantity of the line. The simulation results show that the proposed protection scheme can operate quickly and accurately and has strong resistance to transition resistance.