摘要
对于大规模海上风电场经MMC型柔性直流输电并网系统,在陆上侧交流故障穿越过程中,由于卸荷电路是在直流电压达到一定基准电压时才开始工作,导致陆上侧换流器子模块电压存在过大的冲击,有损坏功率元器件的风险。为解决该暂态过程中子模块电容电压过高的问题,分析了模块化卸荷电路的拓扑结构与控制方法,并根据交流故障期间的系统特性对控制策略进行改进,通过控制模式的切换并配合改变参考波定值,充分利用MMC自身特性,在保证系统故障穿越性能的前提下对子模块电压进行抑制。根据荷兰海上风电柔直外送项目的参数,在PSCAD/EMTDC中搭建了两端双极柔性直流输电系统模型,验证了所提改进控制策略可有效抑制子模块的过电压水平。
For the large-scale offshore wind farm connected with multilevel modular converter based high voltage direct current(MMCHVDC)system,during the fault ride-through process of the offshore AC system,the braking chopper starts to work when the DC voltage reaches a certain reference voltage,which leads to over-voltage of the onshore converter sub-module,which may damage power components.In order to solve the problem that the capacitor voltage of the sub-module is too high in the transient process,the topology structure and control method of the modular braking chopper are analyzed,and the control strategy is improved according to the system characteristics during the AC fault.By switching the control mode and changing the voltage reference value,the inherent characteristics of MMC are fully utilized to ensure the fault ride-through performance of the system.The sub-module over-voltage is suppressed.Finally,according to the parameters of the offshore wind farm integration project in Holland,a two terminal bipolar flexible DC transmission system is built in PSCAD/EMTDC to verify the effectiveness of the improved control strategy.
作者
苏匀
马小婷
李少华
SU Yun;MA Xiao-ting;LI Shao-hua(Xi’an XD Power Systems Co.,Ltd,Xi’an 710065,China;Xi’an Gentle Mellow Technology Co.,Ltd,Xi’an 710075,China)
出处
《电工电气》
2021年第4期11-16,共6页
Electrotechnics Electric
基金
广东省重点领域研发计划资助项目(2019B111109001)。
关键词
MMC-HVDC
故障穿越
模块化卸荷电路
子模块电压抑制
海上风电场
multilevel modular converter based high voltage direct current(MMC-HVDC)
fault ride-through
modular braking chopper
sub-module voltage suppression
offshore wind farm
