Improved Backstepping Control Strategy for Current Source Rectifier Under Nonideal Grid Conditions

The control performance of grid-connected current source rectifiers (CSRs) deteriorates significantly in the presence of model mismatches and external disturbances, particularly under nonideal grid conditions, leading to significant grid current distortion and active power oscillations. Aiming at this problem, this article proposes a novel backstepping control (BSC) strategy integrated with an improved sliding mode disturbance observer (ISMDO) for the power tracking inner-loop of CSRs. Different from the control schemes based on conventional instantaneous power theory (CIPT), an improved BSC controller is developed by integrating the expanded reactive power theory with the BSC control architecture, which not only retains the inherent merit of BSC in ensuring globally asymptotic stability but also effectively reduces grid current distortion and suppresses active power oscillations without requiring additional power compensation and positive/negative sequence extraction. Meanwhile, to accelerate the convergence of estimation errors while mitigating chattering, an ISMDO with a variable gain term is constructed to estimate disturbances for feedforward compensation, which assists the modified BSC controller in rejecting parameter variations and external disturbances, thereby further enhancing the controller's robustness and tracking accuracy. Finally, the relevant comparative experimental results validate the superiority of the proposed method.