基于励磁电感计算的双馈风电场送出变差动保护  

Doubly-Fed Wind Farm Outgoing Transformer Differential Protection Based on Excitation Inductance Calculation

作　　者：孙德娟[1] 孙士云[1] 范小红 海世芳 王杨 Sun Dejuan;Sun Shiyun;Fan Xiaohong;Hai Shifang;Wang Yang(School of Electric Power Engineering Kunming University of Science and Technology,Kunming 650500,China)

机构地区：[1]昆明理工大学电力工程学院

出　　处：《电工技术学报》2020年第2期395-407,共13页Transactions of China Electrotechnical Society

基　　金：国家自然科学基金资助项目（51367009）

摘　　要：解析推导双馈风电场送出变发生对称与不对称故障时,短路电流经变压器变换的表达式,进一步推导送出变两侧的短路电流经傅里叶算法计算产生偏差的解析式,并通过仿真验证了傅里叶算法工频相量计算表达式的正确性,表明双馈风电场短路电流频率偏移会导致傅里叶算法无法准确提取工频相量,从而导致传统变压器保护动作性能受到影响。提出一种适用于双馈风电场送出变的差动保护新方案,该方案直接计算各相的瞬时励磁电感数值与方差并形成判据,将该判据与比率差动和差流速断相结合构成差动保护判据。在Matlab/Simulink中建立带撬棒(Crowbar)保护的双馈风电场送出系统和保护仿真模型,考虑变压器空载合闸、不同故障位置和故障类型以及双馈风电场转速和短路容量比变化等情况,分别分析并验证差动保护新方案的适用性,对比分析传统差动保护与新方案的动作性能,仿真结果表明,该新方案能较好地提高双馈风电场送出变差动保护的速动性与可靠性,改善了风电场短路电流频率偏移导致差动保护不能准确动作的问题。The expression of short circuit current through outgoing transformer is derived when the doubly fed wind farm occurs symmetrical and asymmetrical faults.Then,the formula of deviation caused by the calculation of short-circuit current on both sides of the transformer is further deduced by Fourier algorithm,and the Fourier algorithm power frequency phasor calculation expression is verified by simulation.It indicates that the short circuit current frequency offset of doubly fed wind farms will lead to the fact that Fourier algorithm can not accurately extract power frequency phasors.As a result,the performance of traditional transformer protection is affected.In this paper,a new scheme of differential protection applied to double fed wind farm outgoing transformer is put forward.The instantaneous excitation inductance values and variances of each phase in this scheme are calculated directly and a criterion is formed.Consequently,combined the criterion with ratio difference and differential velocity,a differential protection criterion is formed.A double fed wind farm delivery system with Crowbar protection and a protection simulation model are established in Matlab/Simulink.Considering the no-load closing of the transformer,fault location,fault type,speed change and short-circuit capacity ratio,the applicability of the new differential protection scheme is analyzed and verified by capacity ratio of the doubly-fed wind farm,and then the traditional differential protection and new scheme are compared and analyzed.The simulation results show that the new scheme can improve the speed and reliability of the differential protection sent by the double fed wind farm outgoing transformer,and improve the problem that the differential protection cannot operate accurately due to the deviation of short circuit current frequency in wind farm.

关 键 词：双馈风电场 频率偏移 傅里叶变换 励磁电感计算 差动保护 

分 类 号：TM77[电气工程—电力系统及自动化]