Robust sliding mode control of three-phase four-switch PWM voltage-source rectifier with uncertainties and disturbances

Abstract

The research on developing component minimized voltage source rectifiers (VSRs) has grown recently, due to economic and reliability reason. Four-switch pulse width modulation (PWM) VSRs have the feature of structural simplicity and reduced cost, however controller design for four-switch PWM VSRs with uncertain term and external disturbances in the rotating d-q coordinates is rarely reported in the literature. From the aspect of control, the unity-power-factor control objective in rotating frame may be simplified to a simple set-point reference regulation problem. In this regard, this paper investigates the control of three-phase four-switch PWM VSR in d-q frame. To alleviate the performance degradation caused by parameter uncertainties and external disturbances, a cascaded control loop strategy based on the sliding mode control in d-q frame was proposed in this paper. The output of the outer-voltage loop controller was served as the reference for the d-axis current. Two different sliding mode surfaces were used to design the outer loop and two inner loop controllers respectively. Simulation results show that the proposed closed-form PWM duty ratio control law for the proposed rectifier can indeed achieve the desired property. Comparison study shows that the proposed method is superior to the traditional PI control. Moreover, the rectifier also possesses a regenerative capability which is useful for many applications.