基于软硬件协调的并网光伏发电系统不对称故障穿越能力提升策略

Asymmetric fault ride through capability enhancement scheme forgrid-connected photovoltaic systems based on coordinated control

针对并网光伏发电系统不对称故障穿越问题,提出了一种改进光伏控制策略结合超导故障限流器的协调穿越方案。不对称故障期间,光伏系统执行在线电流限制算法和两阶段降功率控制以减小所用限流器阻值,限流器自动触发辅助限制故障电流。引入对称分量法实现协调运行下数学模型的解耦推导,基于该数学模型,设计了一套相匹配的考虑不对称故障下故障点正负序相角差的限流器阻值优化整定方法,并给出了设计目标与整定阻值的限定分布范围。在MATLAB/Simulink中搭建仿真模型,验证了所提方案能够限制光伏逆变器暂态输出电流,同时改善直流电压稳定性以及提升阵列侧功率水平,从而综合提升光伏系统的不对称故障穿越能力。

A coordinated fault ride through scheme with an improved photovoltaic(PV)control strategy combined with a superconducting fault current limiter(SFCL)is proposed for enhancing the asymmetric fault ride through capability of grid-connected PV systems(GCPVS).In the asymmetric grid fault,the GCPVS performs an online current-limiting algorithm and two-stage decreasing power control to reduce the resistance of SFCL,with the SFCL automatically triggered to assist in limiting the fault current.The symmetric component method is introduced to realize the decoupling derivation of the mathematical model under coordinated operation;based on this mathematical model,a method is designed to determine the optimal resistance of SFCL considering the difference between positive and negative sequence phase angle at the fault point in the asymmetric fault,and the design objectives as well as the distribution range of the determined resistance value are given.A simulation model is built in MATLAB/Simulink to verify the fact that the proposed scheme can limit the transient output current of the inverter,improve the DC voltage stability and enhance the power level at the array side,thus comprehensively improving the asymmetric fault ride through capability of the GCPVS.