Analysis on idle-load grid-connection transient impact current of DFIG

If grid-connection impact current is very large, the power grid and dual PWM converters will be damaged. It is necessary to analyze the grid-connection transient current. In this paper based on stator rotor differential equations under the two-phase rotating coordinate system, the grid-connection transient transition process as well as the principle of impact current generation was analyzed in detail, the expression of idle-load grid-connection transient impact current of doubly-fed induction generator (DFIG) was deduced. The relevant factors which affect the value of the impact currents were analyzed and the relationship between grid-connection impact current and the voltage error was obtained. The voltage errors which included voltage amplitude error and phase error were the errors between network voltage and idle-load stator output voltage. The appropriate measures are taken to be able to reduce the impact current and improve system stability.