考虑送端影响的海上风电经柔直并网系统电压支撑强度量化分析

Quantitative Analysis on Voltage Support Strength of Offshore Wind Power Grid-connected System via VSC-HVDC Considering the Influence of Sending-side Grid

为弥补当前海上风电经柔直并网系统电压支撑强度评价指标的受端电压支撑因素考虑不足和忽略送端对受端影响等问题,提出考虑送端影响的海上风电经柔直馈入短路比。首先,分析海上风电经柔直并网系统结构与控制方式,明晰柔性直流输电系统中送端大容量海上风电有功出力对受端交流电网的电压稳定影响;其次,提出受端交流电网影响因子,将受端电网中各有功、无功源对并网点电压的影响进行等效量化;然后基于影响因子,提出海上风电经柔直馈入短路比,不仅能反映送端对受端的影响,还兼顾换流站对并网点电压的支撑作用,使指标具有较高适用性;最后,通过实际电网仿真验证了所提指标的有效性,并获得临界短路比以完善电压支撑强度评价指标,研究结论可用于海上风电经柔直并网系统的规划和运行。

This paper proposes a novel method to calculate the offshore wind power and VSC-HVDC grid-connected system short circuit ratio(OWVSCR)to reflect the influence of voltage support factors at the sending-end and receiving-end.Firstly,the structure and control mode of offshore wind power system via VSC-HVDC connecting to the grid is analyzed,and the influence of large-capacity offshore wind power active output on the voltage stability of the AC power grid is clarified.Secondly,the receiving-side AC grid interaction factor(RAIF)is designed to quantify the influence of each active and reactive power source on the voltage of the point of common coupling.Then,based on the influence factors,the OWVSCR is proposed,which can not only reflect the influence of the sending-side grid to the receiving-side grid but also consider the supporting effect of the converter station on the voltage of the point of common coupling,so that the index has better adaptability.Finally,the proposed index is verified by the actual power grid simulation analysis,and the critical short-circuit ratio is obtained to improve the voltage support strength evaluation index.The research conclusions can be used in the planning and operatingof the offshore wind power and VSC-HVDC grid-connected system.