In order to use the dynamic low-voltage fuel cell stack in a fuel cell vehicle with a constant high voltage (400 V) dc bus, a capacitor-clamped H-type boost dc-dc converter with a wide voltage gain is proposed in this paper. In the input-voltage side, a capacitor clamped H-type structure is adopted to reduce input current ripple, avoid narrow-pulse of pulsewidth modulation voltage waveforms, and decrease the conduction loss of power switches; while in the output-voltage side, a switched-capacitor structure is adopted to achieve high voltage gain and decrease the voltage stress of all power semiconductors and capacitors. The operating principle, characteristic, control strategy, parameters design, and comparison with other converters are analyzed, and a 400 W prototype is developed. As a result, the converter can transform low-voltage from 25 V to 70 V in to 400 V with a wide voltage-gain range, which maximum efficiency is 94.72%. The experimental results also validate the aforementioned characteristics of the proposed converter and the correctness of theoretical analysis. This converter is suitable to serve as power interface for fuel cell vehicles.

In this paper, a bidirectional inductor-inductor-capacitor-inductor (LLCL) resonant dc-dc converter is presented. Compared with the conventional LLC, a parallel-connected inductors structure is employed into the resonant tank. By virtue of this unique resonant tank, LLCL exhibits the following desirable features: 1) good voltage gain regulation capability in bidirectional power flow applications; 2) zero-voltage-switching turn-on of the power switches in a wide load range; 3) compared with the other bidirectional LLC-type resonant converters, lower resonant tank currents and lower resonant capacitor voltage stress are achieved under the same working conditions. The topology derivation and operating principles of LLCL are shown, and the vital characteristics of LLCL are especially discussed. Moreover, based on battery applications in energy storage systems, in order to make the voltage gain range of LLCL meet the requirements while minimizing the resonant tank currents, a parameter design method is conducted. Finally, a 500-W prototype is established to verify the operating principles and design effects of the proposed converter.

This paper presents a new soft switching high voltage gain interleaved dc-dc converter with a three-windings coupled inductor for a fuel cell vehicle. Two interleaved and intercoupled boost cells are connected by the input parallel and output series (IPOS) configuration, realizing low input current ripple and high voltage gain simultaneously. All power switches can operate under soft switching conditions by only adding a simple auxiliary circuit composed of one auxiliary inductor and one power switch. Besides, the auxiliary inductor is coupled with the main inductors, which results in a rapid zero convergence of the auxiliary current and a small conduction loss of the auxiliary circuit. The operating principle, steady state characteristic, comparison with other converters, and parameter design are analyzed in this paper. Finally, the main characteristics of the proposed converter are verified by a 1-kW laboratory prototype.

The second-order ripple power of single-phase converter causes second-order ripple voltages on the DC bus. For eliminating second-order ripple components, passive power decoupling methods including DC bus electrolytic capacitors have some shortcomings, such as low power density and poor stability of converters. Thus, an active power decoupling method based on a single-phase converter is proposed in this paper. The control method, taking single-phase voltage source pulse width modulation (PWM) rectifier (single-phase VSR) as the basic converter and adopting a buck-boost power decoupling circuit, introduces second-order ripple of DC bus voltage into a power decoupling circuit. The ripple acts as compensation of the phase deviation between the command value and the actual value of the second-order ripple current. Therefore, estimation of the second-order ripple current is more accurate, the power decoupling circuit absorbs the second-order ripple power behind the H-bridge more completely, and the DC bus voltage ripple is effectively suppressed accordingly. Finally, experimental results of the single-phase VSR are given to verify the validity of the proposed method.

Hybrid energy storage systems (HESS) play an important role in maintaining the power balance of a direct current (DC) micro-grid. A HESS is mainly composed of high power density super-capacitors (SCs) and high energy density batteries. According to the operational requirements of an SC, a bidirectional DC-DC converter with the characteristics of a good dynamic response and a wide voltage conversion ratio is needed to interface the SC and a high-voltage DC bus. In this paper, a novel common grounded H-type bidirectional converter characterized by a good dynamic response, a low inductor current ripple, and a wide voltage conversion ratio is proposed. In addition, it can avoid the narrow pulse of pulse width modulation (PWM) voltage waveforms when a high voltage conversion ratio is achieved. All of these features are beneficial to the operation of the SC connected to a DC bus. The operating principle and characteristics of the proposed converter are presented in this paper. A 320 W prototype with a wide voltage conversion ranging from 3.3 to 8 in step-up mode and 1/8 to 1/3 in step-down mode has been constructed to validate the feasibility and effectiveness of the proposed converter.