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A novel soft switching inverter using two small coupled magnetics in one resonant pole is proposed to guarantee the main switches operating at zero-voltage-switching (ZVS) from zero load to full load and the auxiliary switches at zero-currentswitching (ZCS) with load adaptability and small current stress. Since independent magnetics structure avoids the unwanted magnetizing current freewheeling loop, the size of the coupled magnetics can be minimized with low magnetizing inductance and the saturable inductor is eliminated. Detailed circuit operation is described and voltage-second balance condition of the magnetics is expressed mathematically. A 4-kW hardware prototype has been designed, fabricated and tested to verify the validity of the novel circuit and the improved performs of the proposed soft switching inverter. Experimental results show excellent agreement with analytical results.

This paper presents new functionality for high power battery chargers by incorporating an impedance measurement algorithm. The measurement of battery impedance can be performed by the battery charger to provide an accurate equivalent model for battery management purposes. In this paper, an extended control capability of the on-board battery charger for electric vehicles is used to measure on-line impedance of the battery. The impedance of the battery is measured by 1) injecting ac current ripple on top of the dc charging current, 2) transforming voltage and current signals using a virtual α-β stationary coordinate system, d-q rotating coordinate system, and two filtering systems, 3) calculating ripple voltage and current values, and 4) calculating the angle and magnitude of the impedance. The contributions of this research are the use of the d-q transformation to attain the battery impedance, theta and its ripple power, as well as providing a controller design procedure which has impedance measurement capability. The on-line impedance information can be utilized for diverse applications, such as 1) a theta control for sinusoidal current charging, 2) the quantifying of reactive current and voltage, 3) ascertaining the state of charge, 4) determining the state of health, and 5) finding the optimized charging current. Therefore, the benefit of this method is that it can be deployed in already existing high power chargers regardless of battery chemistry. Validations of the proposed approach were made by comparing measurement values by using a battery charger and a commercial frequency response analyzer.Index Terms-Impedance measurement, high power battery charger, d-q transformation.0093-9994 (c)

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