Development of Small Signal Model and Stability Analysis of PV-Grid Integration System for EV Charging Application

In this paper, grid interactive photovoltaic (PV) system is designed for an electric vehicle (EV) charging application and stability of the system is analyzed. The small signal model for the system is derived by averaging and linearizing the state space equations and the condition for stable operation of PV integrated charger system is identified from the transfer functions. The proposed charger system implements a coordinated control between the converters to maintain a power balance between the sources and load. System stability is examined using root-locus plots and in addition, the controller is designed to improve the overall stability and reliability of the system. The proposed method provides a general framework for modelling EV charging systems which also details the importance of deriving the model with multiple energy sources. Further, proposed topology has bi-directional capability, which transfers excess PV power to the grid during off-charging hours. The efficacy of the proposed method is verified using the MATLAB Simulink environment for the different scenarios i.e., variation in the irradiation and disturbances in the grid voltage. The experimental study is conducted on a 1.5 kW laboratory prototype using a low-cost digital signal processing (DSP) controller (launchpad TMS320F28027F) and the measured results authenticate the simulation findings.