A modified FCS-MPC with fixed switching frequency for VSI based on conditional suboptimal switching

The conventional FCS-MPC operates by selecting a switching state per control cycle through cost function optimization. However, it is possible for this method to consistently select the same switching state, resulting in high THD and switching frequency variability. This paper proposes a modified FCS-MPC with fixed switching frequency for voltage source inverters (VSIs) based on conditional suboptimal switching. When the optimal vector matches the previous one, the vector that sub-optimizes the cost function is selected. Simultaneously, a duty cycle modulation scheme applies to this suboptimal state via time-modulated actuation. The proposed strategy reduces THD while fix the switching frequency. Hardware experiments are conducted to verify the effectiveness of the proposed strategy.