A comprehensive study of autonomous PV system with battery storage providing power for a general AC load

In this paper, an autonomous photovoltaic (PV) power generation/storage system connected to an AC nonlinear load is investigated. Depending on the load demand, the PV output power and the battery condition, five modes of operation are feasible with the changing load power. The steady-state analysis of the system for the entire operating modes is presented. Based on the concept of controllability sensitivity, the influence of the input variables on the state variables is obtained. How the estimated states for feedback control contribute in the measured variables is also explored using the observability sensitivity concept. In view of these findings, an input-output nonlinear PID controller scheme is designed to control the overall system. A computer simulation of the controlled power system using the MATLAB/Simulink software demonstrates the effectiveness of the control method.