基于分散式储能的风电柔直并网直流故障穿越协调控制

DC Fault Ride Through Coordinated Control of Wind Power Flexible Direct Grid Connection Based on Decentralized Energy Storage

采用架空线的柔性直流输电技术是解决高渗透率、远距离可再生能源并网消纳的有效方案。然而,架空线路故障率较高,其直流故障穿越问题亟待研究。本文提出利用风场现有分散储能实现风电柔直并网直流故障穿越协调控制。首先,研究风电场接入多端柔性直流输电系统(multi-terminal HVDC based on MMC, MMC–MTDC)中MMC及风电场储能系统等主要组成部分的拓扑结构和基本工作原理;其次,针对大规模风电经柔直并网系统的直流故障,定量分析非故障极功率裕量,通过控制风电机组全功率变流器现有并联储能系统来消纳故障期间的不平衡功率;针对不同功率消纳方案,提出由储能系统、换流站、直流断路器和风电场协调配合进行故障穿越,根据直流断路器动作信号进行故障分类,改变换流站控制方式与风电场出力,从而实现不同故障类型的快速恢复。该策略能够保持系统在故障期间并网运行且不出现闭锁、过载等问题,提升系统的稳定性。最后,在PSCAD/EMTDC仿真平台搭建上述仿真模型,详细研究了风电场经MMC–MTDC并网系统的直流故障穿越策略,验证了本文所提出的基于储能系统的直流故障穿越策略能够维持故障期间的功率平衡,实现故障快速恢复,平稳实现直流故障穿越。本文所提故障穿越策略有望对新能源柔直并网提供必要的依据和参考。

Modular multilevel converter based high voltage direct current technology(MMC–MTDC) using overhead lines is an effective solution to solve the grid connected consumption of high proportion and long-distance renewable energy. However, the fault rate of overhead lines is high, and the DC fault ride through problem needs to be studied urgently. A coordinated control using the existing decentralized energy storage in the wind farm was proposed in this paper to realize the DC fault ride through of wind power generations in the MMC–MTDC. Firstly, the topology and basic working principle of MMC and energy storage systems of wind farms in the multi-terminal HVDC based on MMC were studied.Secondly, for the DC fault in the MMC–MTDC system with large-scale wind power integrated, the non-fault pole power margin was analyzed quantitatively. The unbalanced power during the fault period was absorbed by controlling the existing parallel energy storage system and the fullpower converter of wind turbines. For different power consumption schemes, a fault ride through method was proposed which combining the energy storage system, converter stations, DC circuit breakers and wind farms. According to the action signal of DC circuit breakers, the fault classification was carried out and the control mode of converter station and the output of wind farm were adjusted. Thus a rapid recovery of different faults can be realized. The proposed strategy can maintain the wind power system connected to the power system during the fault period without locking, overload and other problems, and improve the system stability. Finally, the simulation model was built on the PSCAD/EMTDC platform,and the DC fault ride through strategy of the wind farm through the MMC–MTDC grid connected system was studied in detail. It was verified that the proposed DC fault ride through strategy based on the energy storage system can maintain the power balance during the fault, realize rapid fault recovery, and achieve DC fault ride through smoothly. The proposed fault ride through strategy is expected to provide the necessary basis and reference for the renewable energy in the MMC–MTDC grid connected system.