摘要
针对卸荷可能诱发半导体器件过流闭锁,威胁交直流混联电网安全稳定的问题,提出1种计及直流卸荷动作特性的基于模块化多电平换流器的柔性直流输电系统(MMC-HVDC)等值模型,推导了由换流站电容、直流线路和泄能电阻构成的二阶放电回路的电流时域解析式。通过分析故障换流站有功功率不同受限程度下直流电压的振荡特征及其影响因素,发现了相同故障持续时间下卸荷电流峰值与投切频率负相关,计算计及暂态冲击电流的卸荷投入门槛,进而提出了计及卸荷电流冲击的MMC-HVDC改进卸荷保护方法。算例表明,所提方法能有效抑制卸荷引发的暂态冲击电流,降低交流故障持续时间内卸荷投切频次,提高MMC-HVDC交流故障穿越的可靠性。
Aiming at the problem that unloading may induce overcurrent locking of semiconductor devices and threaten the safety and stability of AC-DC hybrid power grid,a equivalent model of flexible DC transmission system based on modular multi-level converter(MMC-HVDC)that takes into account the action characteristics of DC unloading is proposed.And the current time-domain analytical equation in the second-order discharge loop consisting of converter station capacitance,DC line and energy-discharging resistor is derived.By analyzing the oscillating characteristics of the DC voltage and its influencing factors in different faulty converters with different degrees of active power limitation,it is found that the peak of the DC current is negatively correlated with the switching frequency with same fault duration,the unloading input threshold calculation method taking into account the DC current transient impulses is proposed,and an improved MMC-HVDC unloading protection method that takes into account the impact of unloading current is proposed.Case studies show that the proposed method can effectively suppress the DC current transient impulses induced by unloading,reduce the frequency of unloading switching during the duration of AC faults,and improve the reliability of MMC-HVDC AC fault ride-through.
作者
熊俊
钟璐
梁晓斌
于乐
XIONG Jun;ZHONG Lu;LIANG Xiaobin;YU Le(Southwest Branch of State Grid Corporation of China,Chengdu 610094,China)
出处
《智慧电力》
北大核心
2024年第5期74-81,共8页
Smart Power
基金
国家自然科学基金资助项目(52277079)
国家电网有限公司科技项目(SGSW0000DDKZZXJS2200080)。
