Optimized design of resonant controller for stator current harmonic compensation in DFIG wind turbine systems

This paper presents an analytical method to optimize the parameters of resonant controller which is used in a Doubly-Fed Induction Generator (DFIG). In the DFIG control system, the fundamental current loop is controlled by PI-controllers, and the stator harmonic current loop is controlled by resonant controllers. The effects of the resonant controller on the system stability and the steady-state performance are discussed in details. The analysis shows that the resonant controller has an important impact on the system stability when the resonant frequency is close to the crossover frequency of the open loop gain. The gain of the resonant controller is mainly determined by the DFIG transient inductance, the proportional gain of the PI controller, and the required phase margin. Based on the analytical expression of the phase margin and the crossover frequency of the control system, a systematic design procedure of the resonant controller parameters is presented. The maximum possible gain of the resonant controller can be directly evaluated from the procedure. Simulations and experiments are presented to validate the complete analysis.