Finite-Control-Set Model Predictive Control for Single-Phase CHB 5-Level Inverter as an Active Power Filter With Discrete-Time FO-PI DC-Link Controller

This paper presents a finite-control-set model predictive control (FCS-MPC) with fractional-order proportional-integral (FO-PI) controller to regulate the dc-link voltage of a single–phase cascaded H–bridge (CHB) 5-level inverter working as a shunt active power filter (APF). By using the FCS-MPC scheme in a single–phase CHB multilevel inverter as an APF, it is possible to generate a compensation current that tracks its reference with maximum precision, in addition, it presents a quick dynamic reaction to disturbances. When the compensation current is injected into the electrical system, current harmonic distortions are effectively reduced. To simplify the number of evaluations in the algorithm, the voltages on the dc-link of each H-bridge are equalized by a redundant selection of switching states of the multilevel inverter. The discrete-time model of the single-phase shunt APF, the technique to generate the compensation current reference signal, and the developed FCS-MPC algorithm are explained in detail. Furthermore, to keep the dc-link voltage steady, with minimal disturbance, it is proposed to use a discrete-time FO-PI controller. The effectiveness of the proposed control scheme is investigated in steady-state, as well as dynamic transients caused by sudden load changes. The developed control algorithm is verified through experimental tests conducted on a 5 kVA single-phase CHB 5-level inverter-based shunt APF.