A Study on Efficiency Improvement of Power Flow Control Using Four-Switch Buck-Boost Converter Focusing on Phase Shift

In this paper, we study the efficiency improvement of power flow control using four-switch buck-boost converters (FSBBCs). The power flow control in DC power networks has been studied so far using some bidirectional DC-DC converters. As one of the converters, FSBBC has been used as the power flow controller, and the effectiveness of the power flow control has been investigated. For implementing the power flow control using FSBBC, two operational modes, 2SW mode, and 4SW mode, need to be used. In 4SW operation mode, it is possible to arbitrarily set the phase shift of the switching of the arms. The phase shift does not affect the amount of power flow but affects the ripple and root-mean-square (RMS) value of the inductor current. Therefore, the phase shift affects the efficiency. This paper studies the efficiency improvement by considering the phase shift and proposes a simple and easy modulation method to achieve an appropriate phase shift and improve the efficiency of the power flow control. Experimental results validate the effectiveness.