Observer-based variable-structure control for a three-phase pulse-width modulation rectifier

Introduction. Three-phase pulse-width modulation (PWM) rectifiers are widely used in modern power conversion systems due to their ability to provide high power quality and a controllable DC-link voltage. Problem. The nonlinear and coupled dynamics of PWM rectifiers make their control challenging. Under load variations, conventional linear controllers often show limited robustness, slower dynamic response, and degraded power quality. Goal. To develop a robust control and observation strategy for a three-phase PWM rectifier based on variable-structure voltage-oriented control in order to improve current tracking, ensure effective DC-link voltage regulation, achieve unity power factor, and enhance robustness under load variations. Methodology. A cascaded control structure is adopted, with an outer loop regulating the DC-link voltage and an inner loop controlling current components using variable-structure control. A variable-structure observer with adaptive compensation is also proposed for accurate grid voltage estimation, compensating for low-pass filter effects and reducing chattering. Results. Simulations show that the proposed strategy achieves fast dynamic response, accurate current tracking, effective DC-link voltage regulation, and significantly reduced input current total harmonic distortion, maintaining robust operation under load variations. Scientific novelty. Integrating voltage-oriented control with a variable-structure observer featuring adaptive compensation, improving voltage estimation and overall control robustness. Practical value. The proposed strategy offers an efficient and reliable solution for high-performance three-phase PWM rectifiers, enhancing power quality and reducing dependence on voltage sensors. References 16, table 1, figures 17.