Comparative Analysis of Isolated and Non-Isolated Bi-Directional DC-DC Converters for DC Microgrid

In this paper, a comparative analysis is done between two bi-directional DC-DC converters i.e. transformerless and with transformer. Traditional batteries are unidirectional and large in size but bi-directional DC-DC converter (BDC) interconnected between battery and 400V DC bus provides wide voltage gain ratios and facilitates power flow in buck mode (charging) and boost mode (discharging). Energy storage is required in isolated microgrid in order to save power during OFF-load period and to deliver when excess loads are connected; therefore it is necessary that battery must be bi-directional. This bi-directional battery has applications in nanogrid or microgrid for energy storage, electric heavy vehicles, uninterrupted power supply, etc. The two BDCs are modeled, simulated, controlled and operated in different modes using MATLAB/SIMULINK. The results of comparison using various criteria are discussed in this work.