High Efficiency Control Method for Non-Isolated Three-Port DC/DC converter

This paper presents a non-isolated three-port DC/DC converter which is optimized to connect a three-wire, bipolar ±380 VDC microgrid to different sources and loads like photovoltaics, batteries and fuel cells. A novel control method is used to reduce the switching losses and achieve an extremely high efficiency over a broad operating range. Conventionally, pulse-width modulation (PWM) with a constant switching frequency is used to generate switching pulses. Yet, in order to reduce switching losses and increase the overall system efficiency, Triangular Current Mode (TCM) or Critical Current Mode (CrCM) control is introduced to achieve Zero Voltage Switching (ZVS) for every operating point. This also allows the use of higher switching frequencies resulting in greatly reduced passive component sizes. Conclusively, a 6 kW prototype DC/DC converter is presented to verify the proposed control method. The prototype achieves a peak efficiency of 99.3%.