The Research on the Characteristic of Fault Current of Doubly-Fed Induction Generator

Recent years, more and more wind power plants with the doubly-fed induction generation (DFIG) are built in China. With the development of the distributed sources, it was critical to present the new protection schemes and the key point is understands the characteristics of DFIG fault current. Because the complex in the generator´s structure, the related references about this topic were relatively less. The DFIG generator has a three-phase wound rotor, which was supplied by a pulse width modulation (PWM) converter. When a fault occurs, the transient process was not only determined by machine itself but also the outer exciting system. So the waveform of fault current has variety. Only use the theory analysis was hard to describe the characteristic of fault current. The author adopt the simulation method combined theoretical analysis to investigate short-circuits current. In order to delineate various waveforms of current accurately, the emphasis lay on building the whole system model completely and precisely. This paper first analyzed the component of fault current in theory, and then built the specific model of rotor side exciting PI controllers and the active crowbar protections. Based on the various fault current waveforms, the characteristic of fault current were presented at last.