双馈风电系统中VRB储能型网侧九开关变换器

摘要

双馈感应电机(DFIG)风力发电系统定子侧直接挂网运行,使故障穿越运行显得尤为重要.在研究多种故障电压补偿方案与九开关变换器脉宽调制策略的基础上,提出新颖的采用九开关变换器替代双馈风电系统网侧变换器实现并网控制与电压串补一体化方案.在对九开关变换器的数学模型、调制方法、工作状态、网侧九开关变换器的控制策略、直流侧电压分配以及全钒液流电池储能环节电路模型进行理论分析的基础上,建立网侧采用九开关变换器的 DFIG 风电系统仿真模型.设计多种并网点电网电压短路故障工况,分别对风电系统的电气参数和运行特性进行深入仿真研究.研究结果表明九开关变换器能维持 DFIG 机端电压稳定,使双馈风电机组在对称与不对称电网电压故障下实现柔性故障穿越运行.%Stator side of doubly-fed induction generator (DFIG) wind generation system connects to grid directly, which makes the fault ride through especially important. On the basis of studying a variety of fault voltage compensation schemes and pulse width modulation strategies of nine-switch converter, a novel nine-switch converter is proposed to replace the grid side converter of DFIG system for grid connection control and voltage series compensation. This paper analyzes the mathematical model, modulation strategy, working state and control strategy of grid side nine switch converter, as well as the DC bus voltage distribution and vanadium redox flow battery energy storage circuit model. Then, the simulation model of DFIG system that replaces grid side converter with nine-switch converter is established. A variety of PCC voltage short circuit fault conditions were designed, and the electrical parameters and operating characteristics of the wind generation system were studied. The results show that the nine-switch converter can maintain the voltage stability of the DFIG and realize flexible fault ride through of the double-fed wind turbine under symmetrical and asymmetrical grid voltage faults.