风电接入海上换流站的交流汇集出线双端均是电力电子电源,短路电流均呈现幅值受限和相角受控的特征,导致差动保护动作性能下降,存在拒动的风险.针对上述问题,分析了柔直换流站和风机变流器在故障暂态期间的故障特性,证实了区内故障线路两侧短路电流频谱特征存在很大的差异,基于此,利用时频能量系数衡量线路两侧短路电流的时频特性差异,提出适用于风电接入海上换流站交流汇集出线的高速保护原理.该时频能量系数综合幅值、频率和相角差异,具有较强的耐受过渡电阻和系统噪声的能力.所提保护衡量故障暂态的故障特性差异,理论上可以在 5 ms 内快速可靠识别区内外故障,硬件在环实验结果验证了所提保护的有效性.
High-speed Protection of AC Collection Lines Connecting Wind Power to Offshore Converter Stations
Both ends of the AC collection line connecting the wind power to the offshore converter station are power electronic power sources.The characteristic of the short-circuit current,characterized by limited amplitude and controlled phase angle,can deteriorate the performance of differential protection and increase the risk of refusal to operate.To address these issues,this paper analyzes the fault characteristics of the flexible DC converter station and the wind turbine converter in the fault transient state,uncovering significant differences in the short-circuit current spectrum when an internal fault occurs.Based on this,the time-frequency energy coefficient is used to measure the difference in time-frequency characteristics of short-circuit current on both sides of the line,and a high-speed protection principle for AC collection lines suitable for wind power connected to offshore converter stations is proposed.The time-frequency energy coefficient incorporates the difference of amplitude,frequency and phase angle,which has a strong ability to withstand transition resistance and system noise.The proposed protection measures the difference in fault characteristics of fault transients,and theoretically,it can quickly and reliably identify internal faults and external faults within 5 ms.The hardware-in-the-loop experimental results verify the effectiveness of the proposed protection.
offshore wind powerfault characteristicstime-frequency energy coefficienthigh speed protection
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