Optimum power flow control algorithm for an ultracapacitor bidirectional DC-DC converter

In this paper, new modulation schemes are proposed to minimise the circulating power flow, minimise RMS currents and maximise the operating efficiency of a voltage-fed phase-shifted bidirectional DC-DC converter for an ultracapacitor energy buffer, with an IGBT voltage doubler circuit. The mathematical analysis to obtain an optimum power flow controller of the bidirectional converter is presented. Theoretical and simulation results show that the proposed method can maintain minimum circulating power flow even if the ultracapacitor voltage is fluctuating between 50% and 100% of the rated voltage. Furthermore, using the proposed modulation methods a considerable improvement in converter efficiency (up to 93.4%) is achieved in comparison to that for the conventional phase-shift modulation method (around 80%). The proposed modulation scheme is verified by PSpice/Simulink co-simulation using SLPS.