A novel direct active power control method for DFIG wind turbine applications

A new approach for ac-dc power conversion with fast dynamic response is proposed which is based on direct active power control (DAPC). The reference dc current with negligible transients is achieved under balanced and unbalanced source voltage conditions. Unlike conventional ac-dc systems, the output dc voltage can be higher or lower than the maximum value of input voltage. In the buck operating mode, smaller voltage rating of switches can be selected and high voltage supplies can operate with low voltage switches. As the high frequency current harmonics are minimal; there is no need to use ferrite cores or high frequency inductors. This results in a simple product which is particularly suitable for high power applications. As the only measurements in the ac side are the three phase currents, the PLL circuit is eliminated, computation time is reduced and high sampling rates are not required. The unique features of this new approach make it a viable solution for the grid side converter in doubly-fed induction generators for wind power applications. Simulations results show feasibility of this new approach as a power source converter.