Improved Asymmetric Double-Vector Model-Predictive Current Control of Power Converters With Current Harmonic Minimization and Switching Frequency Reduction

Double-vector model-predictive current control (MPCC) has been widely studied and applied to control pulsewidth modulated (PWM) rectifiers. A recent study showed that the pulse pattern arrangement of two vectors has a significant influence on their current harmonics and switching frequency, and the best pattern includes an appropriate zero vector in the middle of the vector sequence and a nonzero vector equally distributed on both sides of the zero vector; this paradigm is called traditional symmetric double-vector MPCC (TSDV-MPCC). This article proposes two improved asymmetric double-vector MPCC (IADV-MPCC) methods. In IADV-MPCC I, the duration of the nonzero vector is optimized to achieve minimal current harmonics; this strategy no longer maintains symmetric distribution features on both sides of the zero vector. In IADV-MPCC II, not only the duration of the nonzero vector is optimized; the vector sequence is also optimized by relaxing the vector combination to two nonzero vectors at high modulation indices. Furthermore, the vector sequence is dynamically adjusted to achieve a reduced switching frequency. The proposed IADV-MPCC is compared to a series of MPCC methods, including TSDV-MPCC, MPCC using two nonzero vectors (MPC2) and deadbeat control based on space vector modulation (DB-SVM). The experimental results confirm that, compared to TSDV-MPCC, the current total harmonic distortion (THD) and switching frequency are reduced by more than 48% and 20%, respectively, at high modulation indices. Compared to MPC2, the current THD is reduced by 22.58%, while maintaining a similar switching frequency. Compared to DB-SVM, the current THD and switching frequency are reduced by more than 17% and 15%, respectively, at high modulation indices. Finally, the proposed IADV-MPCC exhibits similar dynamic response to the other methods.