A FCS-MPC for Low-Switching-Frequency Grid-Tied CHB Inverters Complying With EN50160 and IEEE Std 1547-2018 Standards

This paper presents a novel multi-objective finite-control-set model predictive control strategy for LCL-filtered grid-connected three-phase five-level cascaded H-bridge multilevel inverters operating at low-switching frequency. The key novelty lies in the proposed algorithm capability to ensure compliance with EN 50160 and IEEE Std 1547-2018 standards even under low-switching frequency conditions, without requiring a fixed switching frequency and symmetrical voltage waveform, typically guaranteed by a devoted modulation stage, and without oversizing the LCL filter. To achieve this goal, a multi-term cost function is designed to regulate inverter-side currents, capacitor voltages, and switching effort. For control validation, comparative analysis between the proposed strategy and the phase-shifted pulse width modulation-based voltage-oriented control is conducted at the same average switching frequency. Results show that only the proposed control strategy meets the grid standard requirements. Furthermore, the proposed FCS-MPC maintains standard compliance while further reducing the switching frequency, thus outperforming the voltage-oriented control. Finally, the proposed strategy exhibits intrinsic active damping capability and guarantees superior steady-state and dynamic performance compared to standard active damping strategies in the literature.