High Step-Up Current-Fed Diode-Clamped Resonant Converter for Overloaded Fuel-Cell Vehicles

We propose a high step-up current-fed diode-clamped resonant converter for overloaded fuel-cell vehicles. The electric motor is able to demand short-time peak torque during sudden acceleration phase or long-time excessive torque when the fuel-cell vehicles are overloaded. Then, the conventional converter suffers from a high current spike at the secondary-side switches. The proposed converter incorporates diode-clamped cell on the secondary side, and therefore does not have the high current spike, but retains the benefits of the conventional converter such as high step-up function, ripple-free characteristic, and soft switching capability. When the output power is over its maximum nominal value, the secondary-side switches are switched OFF with complete zero-voltage-switching (ZVS) and the secondary-side diodes are OFF with zero-current-switching (ZCS). As a result, the proposed converter exhibits high efficiency and long-term operation under the nominal power and even at peak power. Furthermore, we have analyzed voltage gain, ZVS/ZCS region, and current/voltage stress on the active power components when the output power is over its maximum nominal value, which is different from those when the output power is in its nominal range. The theoretical analysis of the proposed converter is presented, then validated using a laboratory-built prototype.