Analytical Solution For Minimum RMS Current and Reactive Power Modulation of A Soft Switched Dual Active Bridge Converter

Dual active bridge converter is very attractive for bidirectional power conversion for its simple control, easy to achieve soft switching and wide power flow and operating voltage range. Triple phase shift modulation is one of the most popular choice of modulation due as it widens the soft switching range over complete power flow range. However, being a three degree of freedom scheme, finding an optimum operating point based on the phase shift and conduction angles of the active bridge which minimizes the rms current and the losses due to reactive power flow is not easily obtained. In this paper, a harmonic model is discussed which allows analytical optimization when the phase shift is considered constant. Analytical expression for the optimum operating point is derived to achieve minimized rms current, circulating current and reactive power while maintaining soft switching conditions. Theoretical analysis has been verified by Matlab simulation and experimental result provided for a 100W dual active bridge converter.