计及负序控制策略的光伏逆变器故障特性分析

Fault characteristic analysis of photovoltaic inverter considering negative sequencecontrol strategy

光伏接入系统发生不对称故障时,逆变器会同时控制正序电流和负序电流的输出,但目前针对计及负序控制策略的逆变器故障特性研究较少。为此,首先推导了逆变器稳态短路电流的求解方法。然后考虑不同的负序控制策略,研究了不对称故障下逆变器输出的短路电流特征和等效负序阻抗特征,揭示了光伏发电在不同控制策略和不同故障类型下故障特性的相似性和差异性。最后搭建仿真模型,对理论分析结果进行了验证。结果表明,在新能源接入电网的故障特性及保护原理研究中需充分考虑负序控制策略的影响。

In case of an asymmetrical fault in PV accessed system,the inverter will simultaneously control the out⁃puts of positive and negative sequence currents.However,there are few studies on inverter fault characteristics con⁃sidering negative sequence control strategy.Therefore,the solution method for the steady-state short-circuit current of the inverter is firstly derived.Then the short-circuit current characteristics and equivalent negative-sequence im⁃pedance characteristics of the inverter output under asymmetrical faults are investigated by considering different negative sequence control strategies.The similarity and difference in the fault characteristics of photovoltaic power generation under different control strategies and different fault types are demonstrated.Finally,a simulation model is built to verify the theoretical analysis results.The results show that the influence of negative sequence control strategy should be fully considered in the study of fault characteristics and protection principle with the integration of new energies.