Analysis and simulation of a new three phase LLCC resonant inverter for fuel cell applications

Abstract

In this paper a new three phase LLCC resonant inverter for fuel cell applications is discussed. The proposed system consists of two power stages, which are boost dc-dc converter and three-phase bridge inverter with resonant tank. The boost dc-dc converter is controlled by adjusting its duty cycle to supply and maintain particular dc input voltage to the bridge inverter due to polarization characteristic of fuel cell. The resonant tank is operated at its geometric mean frequency to achieve unity voltage gain so that the output voltage of the inverter will not be affected by load variation. Hence, no external feedback is needed for the three-phase bridge inverter, thus simplifying the control of the inverter. The operating principle of the three-phase resonant inverter is analyzed and Matlab/Simulink simulation is conducted based on the analysis. The simulation shows that resonance has been achieved and the output voltage of the inverter is not influenced by load variation. Resonance technique for the proposed inverter is also shown to result in Zero Voltage Switching (ZVS). Furthermore, the inverter has very low THD of output voltage and output current.