光伏逆变器对称短路电流特性及等效模型研究

Research on the Characteristics of Symmetrical Short-circuit Current and Equivalent Model for the Photovoltaic Inverter

随着光伏发电渗透率的提高,其短路电流特性已经无法忽视。详细阐述了单级式光伏逆变器的拓扑结构、数学模型及并网控制,提出了一种基于无功电流注入的低电压控制策略。在此基础上定性分析了光伏逆变器对称短路电流特性,通过电流环控制参数设计并忽略直流电压的动态过程将其简化为受控电流源。最后,基于DIgSILENT/PowerFactory建立了详细的单级式光伏发电系统电磁暂态及受控源等值模型。仿真结果表明:当并网点电压因对称三相短路故障而导致轻度跌落或重度跌落时,电压环的动态响应是可以忽略的;当发生较深跌落但尚未使逆变器过流时,逆变器输出电流的暂态特性主要受有功电流影响;控制策略切换前后逆变器输出电流相位将发生偏移。实例分析验证了简化模型的有效性,为深入研究逆变型接口电源的故障特性奠定了基础。

With the increased penetration of photovoltaic(PV)system,the short-circuit current characteristicscan not be ignored. The topology,mathematical model and grid-connection method of single-stage PV inverter weredescribed in detail. A low voltage control strategy based on the injection of reactive current was proposed. On thisbasis,the symmetrical short-circuit current characteristics of inverter were analyzed qualitatively,and the inverterwas simplified as a controlled current source through the control parameter design of current loop and neglecting thedynamic process of the DC voltage. Finally,a detailed electromagnetic transient model and an equivalent model ofsingle-stage PV system were established based on DIgSILENT/PowerFactory. The simulation results show that thedynamic response of the voltage loop can be neglected when the voltage of the point of interconnection sags slightly ordeeply. When sag occurs and inverter current is no more than the maximum,the transient characteristics are mainlyaffected by the active component. The phase of inverter current will shift when control strategy is changed. Exampleanalysis verify the validity of the equivalent model,which laid the foundation for further research.