Design and small signal analysis of solar PV fed FPGA based Closed Loop control Bi-Directional DC-DC converter

This paper describes the development of Bi-Directional DC-DC converter (BDC) for solar application for charging and discharging the battery based on availability of supply. BDC can operated in two modes i.e., if supply is available at solar PV side BDC acts as boost converter otherwise acts as buck mode. During day time when sunlight is available, BDC acts as a Buck Converter for charging the battery. During night time, when sunlight is not available BDC acts as a Boost converter to provide supply to the load from the battery. Small signal analysis is used to design BDC operating in both modes in Matlab. Transfer functions of BDC in both modes are derived using the aforementioned analysis. Bode plots of the plant transfer function (buck & boost) were plotted to judge the stability of BDC. Controllers (type-3—boost, PID—buck) for both modes are designed by using small signal analysis. These controllers are designed in FPGA to generate PWM signals for controlling the switches in BDC.