FCS Model-Free Predictive Control of a SP-CHB 5-Level Inverter as Shunt Active Power Filter Based on Extended State Observer Using Ultralocal Model

Abstract

Single-phase cascaded H-bridge (SP-CHB) multi-level inverters controlled with the finite-control-set model predictive control (FCS-MPC) can be used as shunt active power filters to improve power quality; however, the FCS-MPC scheme is highly dependent on system parameters. That is, when there is a mismatch between the actual parameters and those set in the algorithm, the performance of the control system deteriorates significantly. To address this issue, this paper introduces an FCS model-free predictive control (FCS-MFPC) that uses a discrete-time Extended State Observer (ESO) based on an Ultralocal Model. The discrete ESO was designed to guarantee parametric robustness and system stability. For this, the parameter-dependent components in the control system were equivalently treated as the lumped disturbance parameter, achieving an accurate prediction of the compesation current. The proposed FCS-MFPC scheme was verified through comprehensive simulations in MATLAB/Simulink. The simulation results verify that the proposed algorithm not only maintains robust operation during parameter mismatches, but also effectively mitigates harmonic distortions to improve power quality.