A Novel Non-Linear Control for Three-Phase Five-Level Cascaded H-Bridge Inverter Based Shunt Active Power Filter

Abstract

Abstract Cascaded H-Bridge multilevel inverter (CHB-MLI) based shunt active power filter (SAPF) provides a cost-worthy and realistic solution for mitigating current related power quality problems in case of medium-voltage and high-power grid. Mitigation of current harmonic component, reactive power minimization and power factor correction depend on accuracy of control technique applied to the CHB-MLI based SAPF unit. Switching technique dynamics is not considered by most of the researchers while designing control techniques applied to SAPF unit and hence it is assumed linear in order to make system simpler. A limited amount of literature is available which considers the non-linearity of CHB-MLI switching pattern while designing control theory for MLI based SAPF. Therefore, a novel non-linear control is proposed in this paper to enhance system steady-state and dynamic performance. This non-linear control is based on dynamic mathematical modeling of five-level CHB-MLI tied SAPF. Stability of proposed control strategy applied to CHB-MLI based SAPF is rigorously checked by using Lyapunov’s direct method. Proportional-Integral controller is used for stabilizing DC-link voltages to its proper reference value. This proposed control exhibits excellent dynamic performance and compensation criteria in comparison to conventional control techniques available in the literature. The effectiveness of the proposed control theory is tested rigorously in MATLAB/Simulink and verified through hardware prototype under steady-state and transient operating conditions. Rigorous analysis from hardware and simulation results confirms that source current waveform is in compliance with IEEE-519 standard defined THD limit.