This paper presents a nonisolated, high boost ratio hybrid transformer dc–dc converter with applications for low-voltage renewable energy sources. The proposed converter utilizes a hybrid transformer to transfer the inductive and capacitive energy simultaneously, achieving a high boost ratio with a smaller sized magnetic component. As a result of incorporating the resonant operation mode into the traditional high boost ratio pulsewidth modulation converter, the turn-off loss of the switch is reduced, increasing the efficiency of the converter under all load conditions. The input current ripple and conduction losses are also reduced because of the hybrid linear-sinusoidal input current waveforms. The voltage stresses on the active switch and diodes are maintained at a low level and are independent of the changing input voltage over a wide range as a result of the resonant capacitor transferring energy to the output of the converter. The effectiveness of the proposed converter was experimentally verified using a 220-W prototype circuit. Utilizing an input voltage ranging from 20 to 45 V and a load range of 30–220 W, the experimental results show system of efficiencies greater than 96% with a peak efficiency of 97.4% at 35-V input, 160-W output. Due to the high system efficiency and the ability to operate with a wide variable input voltage, the proposed converter is an attractive design for alternative low dc voltage energy sources, such as solar photovoltaic modules and fuel cells.

A novel soft-switching hybrid converter combining the phase-shift full-bridge (FB) and half-bridge (HB) LLC resonant converters' configuration with shared zero-voltage switching (ZVS) lagging leg is proposed to ensure the switches in the lagging leg operating at fully ZVS condition. The dual outputs of the proposed hybrid FB-HB converter are connected in series and the whole dc-output voltage can be regulated by the PWM phase-shift control within the desired voltage range. A resonant circuit is used in the secondary side of the FB converter to reset the primary current during the freewheeling period, as well as to transfer more input energy and clamp secondary rectifier voltage. The proposed converter is attractive for hybrid electric vehicle/electric vehicle on-board charger applications. The principle of operation, the validity, and performance are illustrated and verified on a 3.7-kW experimental circuit. Experimental results show that the proposed converter can get good efficiency curves at different operation points, and the maximum efficiency is 98.30%.

This study presents the experimental study and analysis of double‐LCL resonant compensation network based wireless power transfer (WPT) system for electric vehicles. The WPT system could accomplish both constant current and the unity‐power‐factor for the transmitting terminal and the receiving terminal. In addition, the transmitting terminal inverter can achieve zero‐voltage‐switching. The multi‐physical characteristics of the transmitting and receiving terminals based on LCL resonant compensation network are analysed in detail. Finally, three‐dimensional finite element analysis and an experimental system with circular pads is setup to verify the theoretical analysis under different loads and horizontal/vertical misalignment conditions. At the condition of 200 mm gap and no horizontal misalignment, the system can supply the maximum output power of about 7.36 kW having the maximum efficiency of 95.87%.

This paper presents a new type of three-phase voltage source inverter (VSI), called three-phase dual-buck inverter. The proposed inverter does not need dead time, and thus avoids the shoot-through problems of traditional VSIs, and leads to greatly enhanced system reliability. Though it is still a hard-switching inverter, the topology allows the use of power MOSFETs as the active devices instead of IGBTs typically employed by traditional hard-switching VSIs. As a result, the inverter has the benefit of lower switching loss, and it can be designed at higher switching frequency to reduce current ripple and the size of passive components. A unified pulsewidth modulation (PWM) is introduced to reduce computational burden in real-time implementation. Different PWM methods were applied to a three-phase dual-buck inverter, including sinusoidal PWM (SPWM), space vector PWM (SVPWM) and discontinuous space vector PWM (DSVPWM). A 2.5 kW prototype of a three-phase dual-buck inverter and its control system has been designed and tested under different dc bus voltage and modulation index conditions to verify the feasibility of the circuit, the effectiveness of the controller, and to compare the features of different PWMs. Efficiency measurement of different PWMs has been conducted, and the inverter sees peak efficiency of 98.8% with DSVPWM.

This paper presents a new type of cascade inverter based on dual buck topology and phase-shift control scheme. The proposed cascade dual buck inverter with phase-shift control inherits all the merits of dual buck type inverters and overcomes some of their drawbacks. Compared to traditional cascade inverters, it has much enhanced system reliability thanks to no shoot-through problems and lower switching loss with the help of using power MOSFETs. With phase-shift control, it theoretically eliminates the inherent current zero-crossing distortion of the single-unit dual buck type inverter. In addition, phase-shift control and cascade topology can greatly reduce the ripple current or cut down the size of passive components by increasing the equivalent switching frequency. A cascade dual buck inverter has been designed and tested to demonstrate the feasibility and advantages of the system by comparing single-unit dual buck inverter, 2-unit and 3-unit cascade dual buck inverters at the same 1 kW, 120 V ac output conditions.

The input-parallel output-parallel (IPOP) dc–dc converters are suitable for low-voltage and high-current applications, especially using high-frequency isolation instead of traditional line-frequency transformer for ac–dc converters in dc distribution. Compared to the existing closed-loop control for IPOP dc–dc converters, the magnetic-coupling current-balancing (MC-CB) cells based IPOP LLC resonant converter modules are proposed in this paper, which can realize the IPOP system work under open-loop operating condition naturally. The LLC modules can be used as a high-frequency isolation dc transformer operating under the quasi-resonant mode, which can achieve zero-voltage switching (ZVS) for inverter side and zero-current switching (ZCS) for rectifier side ensuring high power density and high efficiency. The proposed MC-CB cells for IPOP LLC resonant converter modules can adaptively ensure both the input-current sharing (ICS) and the output-current sharing (OCS) among constituent modules to make the IPOP system operate stably. Additionally, the steady-state and dynamic-state current-sharing performance of MC-CB cells for the IPOP converter system are analyzed based on a magnetic model. In the end, a hardware prototype has been designed and tested. The experimental results have verified the validity and performance of the proposed MC-CB cells for the IPOP LLC resonant converter modules.