INVESTIGATION OF MULTIPORT BIDIRECTIONAL DC-DC CONVERTERS IN HYBRID VEHICLES

Abstract

The demand for versatile electrical energy management systems that interface diverse energy sources, energy storage elements and loads, is increasing because of their potential applications in hybrid electric vehicle (HEVs) and fuel cell vehicles (FCVs), renewable energy generation systems and uninterruptible power supplies. The voltage levels and the voltage-current characteristics of the energy sources and the storage elements are normally different from those of the loads. Therefore, a power electronics system to interface sources, storage elements and loads need to be incorporated into energy management systems. In this report a novel Multi-port converter interfacing a photovoltaic array, battery and a DC load is proposed. It is composed of a uni-directional DC port for interfacing photovoltaic array, and two bi-directional DC port for interfacing battery and DC load. Compared to the traditional stand-alone photovoltaic power system, this system exhibits the advantages of better protection and more efficient control on charge/discharge of the battery. Furthermore, it can make better use of solar energy and realize energy management of the system. The key point of energy management for the system is to control the bi-directional converter efficiently, where bi-directional voltage and current must be controlled. In this report, the bi-directional control strategy of bi-directional converter is proposed, which operates at three operation modes: Buck (charge battery), Boost (discharge battery), and shut-down (SD). Maximum power point tracking control is used to extract the maximum power from the Photovoltaic array. Single power processing stage with multiple power ports offers an opportunity to make the whole system simpler, compact and more efficient. Finally, a simulation of 250W and 5 HP converter is built to verify the theoretical analysis and the control strategies. The simulation is tested for variable load and variable irradiance.