This paper first presents a hybrid-switching stepdown dc-dc converter, and then, by introducing transformer isolation, a novel hybrid-switching phase-shift full-bridge dc-dc converter is derived for electric vehicle battery chargers. The proposed converter provides wide zero-voltage-switching range in the leading-leg switches, achieves zero-current-switching for lagging-leg switches, and uses a hybrid-switching method to avoid freewheeling circulating losses in the primary side. Because the resonant capacitor voltage of the hybrid-switching circuit is applied between the bridge rectifier and the output inductor for the duration of the freewheeling intervals, a smaller sized output inductor can be utilized. With the current rectifier diode of the hybrid-switching circuit providing a clamping path, the voltage overshoots that arise during the turn-off of the rectifier diodes are eliminated and the voltage stress of bridge rectifier is clamped to the minimal achievable value, which is equal to secondary-reflected input voltage of the transformer. The inductive energy stored in the output inductor and the capacitive energy stored in the resonant capacitor of the hybrid-switching circuit are transferred to the output simultaneously during the freewheeling intervals with only one diode in series in the current path, achieving more effective and efficient energy transfer. The effectiveness of the proposed converter was experimentally verified using a 3.6-kW prototype circuit designed for electric vehicle onboard chargers. Experimental results of the hardware prototype show that the converter achieves a peak efficiency of 98.1% and high system efficiencies over wide output voltage and power ranges.Index Terms-Hybrid-switching method, phase-shift full-bridge dc-dc converter, plug-in electric vehicle battery charger, zerocurrent-switching, zero-voltage-switching.

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In this paper a new methodology is presented to calculate the average power quickly and accurately for the single-phase paralleled inverters intended to be applied in a droop-control microgrid system. Most existing droop control systems utilize a simple first-order filter to calculate the active and reactive power. The added filter can smooth the calculated results but it tends to hurt the system dynamic response due to a low cut-off frequency that is intended to get enough ripple attenuation. This low frequency pole in the low-pass filter could also introduce system instability under certain load conditions. A new filter calculation methodology is thus proposed to achieve better ripple attenuation with faster response by combining a low-pass filter, a delay, and summation blocks. Both simulation and experiment are used to verify the effectiveness of the proposed power calculation methodology.I.

Driven by worldwide demands for renewable energy source, photovoltaic (PV) inverters, which are the most important part for energy conversion, have seen a considerable amount of innovations in recent years. The trends for PV inverters are toward high efficiency, high reliability, low ground leakage current, low-output ac-current distortion, and reactive power capability. This paper provides an efficiency optimized design of an Auxiliary Resonant Snubber with CoupledMagnetic Reset Zero-voltage switching (ZVS) inverter for PV application. The main device is Power MOSFETs, which have low conduction loss and could achieve ZVS in all load condition. The auxiliary devices are low current, low cost IGBTs and Diodes, which could achieve zero-current switching (ZCS). To achieve high efficiency, resonant circuit is analyzed to optimally design the resonant components, which is based on the guarantee of full range ZVS, gating delay-time design, and lower power loss in auxiliary circuit. The power loss model is also analyzed to select suitable power device and further improve the efficiency. At last, experiment results of a 5kW single phase inverter in PV system was presented, which has more than 99% CEC efficiency and work in full load condition without cooling fan. Besides, reactive power capability is also demonstrated.

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