Model Predictive Control for Three-Phase PWM Rectifier with Active Power Decoupling Circuit Under Unbalanced Grid Voltages

Abstract

For the conventional control strategy of the three-phase pulse width modulation (PWM) rectifier, sinusoidal symmetrical ac currents and ripple free dc voltage cannot be achieved simultaneously under unbalanced grid voltages. For this reason, a model predictive control (MPC) for three-phase PWM rectifier with active power decoupling (APD) circuit is proposed. Specifically, sinusoidal symmetrical ac currents without negative sequence components can be obtained by means of MPC for the main circuit of PWM rectifier; meanwhile, MPC of the APD circuit contributes to the double-line-frequency ripple power decoupling for the ripple free dc voltage regulation even with a reduced dc link capacitor. Thanks to the high flexibility of MPC, the control strategy for both aforementioned circuits can be integrated in a unified model predictive controller, which avoids the separate controls for the two circuits and simplifies the control implementation. In addition, combined with direct power control in an $\beta-\alpha$ frame, the proposed MPC strategy tracks several associated instantaneous power values rather than voltage or current waveforms, so that it has the advantages of simple principle, fast response, strong robustness and easy implementation. The simulation results have verified the effectiveness of the proposed MPC strategy for PWM rectifier without bulky capacitor.