Interleaved,switched-inductor,multi-phase,multi-device DC/DC boost converter for non-isolated and high conversion ratio fuel cell applications

Fuel cell power conditioners often require high step-up voltage gains to accommodate low input fuel cell voltages into high voltage busses. Traditional non-isolated DC-DC boost converters are unable to offer such as gains because of several parasitic elements and non-ideal behaviour of power semiconductors and driving circuits. Moreover, paralleled converters are also desirable to simplify power-up scaling and to reduce input/output current ripples. In this context, a very versatile non-isolated, high step-up voltage gain, interleaved boost converter is presented in this work. Steady-state analysis, simulation and evaluation of different converter structures are discussed in detail. Finally, a 500-W experimental prototype for Nexa Ballard 1.2 kW fuel cell specifications has been implemented and tested to verify the performance.     

Integrated modeling and control of a PEM fuel cell power system with a PWM DC/DC converter

A fuel cell powered system is regarded as a high current and low voltage source. To boost the output voltage of a fuel cell, a DC/DC converter is employed. Since these two systems show different dynamics, they need to be coordinated to meet the demand of a load. This paper proposes models for the two systems with associated controls, which take into account a PEM fuel cell stack with air supply and thermal systems, and a PWM DC/DC converter. The integrated simulation facilitates optimization of the power control strategy, and analyses of interrelated effects between the electric load and the temperature of cell components. In addition, the results show that the proposed power control can coordinate the two sources with improved dynamics and efficiency at a given dynamic load.     

A high voltage ratio and low stress DC–DC converter with reduced input current ripple for fuel cell source

A new single-switch non-isolated dc–dc converter with high-voltage gain and reduced semiconductor voltage stress is proposed in this paper. The proposed topology is derived from the conventional boost converter integrated with self-lift Sepic converter for providing high voltage gain without extreme switch duty-cycle. The reduced voltage stress across the power switch enables the use of a lower voltage and R_DS-ON MOSFET switch, which will further reduce the conduction losses. Moreover, the low voltage stress across the diodes allows the use of Schottky rectifiers for alleviating the reverse-recovery current problem, leading to a further reduction in the switching and conduction losses. Furthermore, the “near-zero” ripple current can be achieved at the input side of the converter which will help improve the fuel cell stack life cycle. The principle of operation, and theoretical are performed. Experimental results of a 100 W/240 V_dc output with 24 V_dc input voltage are provided to evaluate the performance of the proposed scheme.     

Power switch failures tolerance and remedial strategies of a 4-leg floating interleaved DC/DC boost converter for photovoltaic/fuel cell applications

In recent years, many researchers have proposed new DC/DC converters in order to meet the fuel cell requirements. The reliability of these DC/DC converters is crucial in order to guarantee the availability of fuel cell systems. In these converters, power switches ranked the most fragile components. In order to enhance the reliability of DC/DC converters, fuel cell systems have to include fault-tolerant topologies. Usually, dynamic redundancy is employed to make a fault-tolerant converter. Despite this kind of converter allows ensuring a continuity of service in case of faults, the use of dynamic redundancy gets back to increase the complexity of the converter. In order to cope with reliability expectations in DC/DC converters, floating interleaved boost converters seem to be the best solution. Indeed, they have much to offer for fuel cells and DC renewable energy sources (i.e. photovoltaic system), including reduced input current ripple and reliability in case of faults. Despite the offered benefits of this topology, operating degraded modes lead up to undesirable effects such as electrical overstress on components and input current ripple increasing. The aim of this paper is to carry out a thorough analysis of these undesirable effects and to propose remedial strategies to minimize them.