Ultracapacitors (UCs) are promising energy storage devices that can enhance fuel economy and performance of electric vehicles (EVs) and plug-in electric vehicles (PHEVs) by means of assisting primary energy source in peak power demands and capturing regenerative braking energy. This manuscript introduces another merit of UCs which is utilizing the UC as an active power filter in PHEV charging process. With the proposed simple control scheme, UC ensures constant battery charging current where unity power factor operation is provided by AC/DC charger. As a result, the DC/DC power stage in conventional charger structure is eliminated. The analyses show that battery current ripple less than 4%, total harmonic distortion (THD) less than 1.5% and power factor (PF) higher than 0.996 can be achieved with the proposed power electronic structure and active filtering control scheme.
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