Robust backstepping control strategy of limiting DC-link voltage fluctuation for DFIG-based WECS under harmonically distorted grid voltage

A robust backstepping controller with nonlinear damping is designed for a back-to-back pulse width modulation converter in doubly fed induction generator for wind energy conversion systems under harmonically distorted grid voltage. The designed controller achieves the exponential ultimate boundedness of the DC-link voltage fluctuation with an arbitrarily fast decay rate and an arbitrarily small bound in the presence of harmonically distorted grid voltage. A desirable feature that distinguishes the proposed controller from other existing controllers is that the proposed controller is able to perform both the normal control operation and grid fault with a single reference input, and it is constructed only by static feedback of measured states. As a result, the control input becomes smooth and easy to implement without requiring of differentiation or switching operations that occur the chattering effect. The exponential boundedness and performance of the designed controller are demonstrated by simulation using SimPowerSystems in Matlab and compared with a proportional-integral controller.