Multi-Period Asymmetrical Voltage Cancellation Modulation Strategy for Efficiency Improvement of IPT System With a Wide Output Power Range

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Abstract
The inherent tradeoff between reactive losses and switching losses in inductive power transfer (IPT) systems makes it particularly challenging to maintain high efficiency across a wide output power range. This article proposes a multi-period asymmetrical voltage cancellation (MP-AVC) modulation strategy, where multiple switching periods are combined into a modulation period and the half-wave pulses within a modulation period are asymmetrically canceled. By adopting MP-AVC, the power factor angle of the IPT system will vary periodically around 0° at a consistently low level, ensuring zero-voltage switching (ZVS) operation with low reactive losses. Meanwhile, the equivalent switching count of MOSFETs will decrease as output power decreases, which significantly reduces the switching losses. In addition, the output characteristics, operating principle, and comparison with other modulation strategies are presented. Finally, a 4.3 kW prototype is developed, achieving efficiencies of 97.54%, 97.36%, and 92.29% at output power of 4.3 kW, 2.2 kW, and 27.35 W, respectively.

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