A Nonlinear Programming Solver based on Battery Efficiency Maximization for Quasi-Z-source Cascaded H- bridge Multilevel Inverter with PV and Battery

A nonlinear programming solver is used in this paper to optimize a proposed objective function to handle the energy management system (EMS) of a grid-connected quasi-Z-source cascaded H-bridge multilevel inverters with energy storage (ES-qZS-CHBMLIs) for photovoltaic (PV) plants. The solver (fmincon) optimizes a constrained nonlinear multivariable function based on maximizing the battery energy storage system (BES) efficiency. The proposed EMS is responsible for producing the demanded power while dispatching energy among the BES. Considering different battery parameters for each cascaded module working under variable grid references and PV powers, the efficiency is optimized for different conditions. Common control topologies are used for balancing the voltage level on the DC link, enhancing output power quality, reliability, and ensuring optimal operation of the PV power plants. A grid-connected single-phase configuration is designed in MATLAB-Simulink to evaluate the effectiveness of the proposed EMS. Every cascaded qZSI is connected to a 4.8 kW PV power plant, operating in different irradiance conditions, to validate the proposed configuration and the control system.