双馈型电源短路电流统一解析方法及特性分析研究

Study on Unified Analysis Method and Characteristics in Fault Currents of Doubly-Fed Induction Generators

新能源电源故障电流特性研究是电网故障分析和保护原理研究的重要基础。双馈型电源由于结构特殊且暂态特性复杂,特别是在不对称故障条件下,与低电压穿越控制策略有关,且控制策略多样化,导致其故障电流特性理论分析较为薄弱。针对此,建立双馈型电源在电网不对称故障条件下的数学模型,考虑陷波器和RSC励磁调节特性的影响,建立转子电流内环控制系统简化的等效模型。在此基础上,推导PI控制器参数的解析表达式,分析控制系统相位裕度和穿越频率取值范围,建立双馈型电源转子电流的简化计算模型,最后形成适用于不同控制策略的双馈型电源短路电流统一解析表达式,为含新能源电源接入的电网故障分析方法和继电保护新原理的提出奠定了重要基础。利用PSCAD/EMTDC搭建仿真平台,证明了建立的双馈型电源短路电流统一解析表达式的正确性。

The analysis for the fault current characteristics of the new energy sources is the basis in relay protection and fault analysis of the power grid.For generators of doubly-fed type,due to its special structure and complicated transient characteristics,especially under asymmetric fault conditions,the fault current characteristics of doubly-fed induction generator(DFIG)are related to low-voltage through control strategy,and there are a lot of control strategies.In order to address this issue,the unified analysis method in the fault currents of a DFIG is studied.Firstly,the mathematical model of a DFIG under the asymmetric fault conditions is proposed.Then,the equivalent models of inner rotor current control loop are established by considering the dynamic response of a rotor-side converter(RSC)and the notch filters,and the simplified calculation models of rotor fault current are established.As a result,the unified fault current analytical expressions of a DFIG are obtained,which is applicable for different control strategies.Finally,simulation examples in PSCAD/EMTDC verify the theoretical analysis results.