Low-Carrier-Ratio Model Predictive Control for 100 kHz Large-Signal Multiphase Converters With Low THD

High switching frequency grid-connected converters are widely used in renewable energy generation, which is prone to cause serious broadband oscillation. The broadband impedance measurement device with low total harmonic distortion (THD) is an effective means to analyze the stability of grid-connected system. This article proposes a low-carrier-ratio model predictive control (LCR-MPC) for 100 kHz lager-signal multiphase converters with low THD. Compared to the conventional low-carrier-ratio methods with huge offline calculation burden, the proposed LCR-MPC can calculate the switching angles online with a low calculation burden. First, the fast selection of optimal state and the online calculation of initial switching angles are proposed. Then, a finite set of switching angles is constructed by the virtual carriers to meet constraints. The finite set is used by MPC for online calculation with low THD. Finally, the performance of LCR-MPC is verified by comparing simulation and experimental results with carrier phase shift pulsewidth modulation (CPS-PWM) and optimized pulse patterns for a six-phase converter. Compared with CPS-PWM, the average THD improvement of the proposed method is 4.45% at a carrier ratio of 6.