Design and control of isolated bi-directional DC-DC converter for photovoltaic applications

In Photovoltaic systems, batteries play a vital role in providing reliable power to the loads. The voltage level of the batteries is typically much lower than the DC bus voltage. Thus a power converter with high conversion ratio and bidirectional power flow capability is required for charging and discharging of batteries. This paper presents an isolated bidirectional DC-DC converter used as a battery charger/discharger circuit in photovoltaic applications. The Dual Active Bridge converter consists of two full-bridge circuits connected by means of a high frequency transformer. This converter provides bidirectional power flow by controlling the two bridges independently. The advantages of the converter are galvanic isolation between input and output, lower number of passive components, high power density and high efficiency. By controlling the phase shift between the bridges, power flow is controlled. The performance of the converter is studied for different modes of operation. Simulations are carried out using MATLAB/Simulink and the viability of the technique has been validated experimentally using a laboratory prototype.