Efficiency Analysis and Optimization Control for Input-Parallel Output-Series Wireless Power Transfer Systems

Wireless power transfer (WPT) technology has shown its significant role in various applications, such as electric vehicles and consumer electronics. In this paper, an input-parallel output-series circuit topology based on a compact double-sided decoupled coupler is presented to upgrade the power capacity of the WPT system with low-power and low-cost semiconductors. To avoid the potential risk of magnetic saturation, the phase difference between the transmitter currents is controlled to be 90° to achieve a symmetrical magnetic flux distribution for the magnetic coupler. Most importantly, an analytical model, which illustrates the relation between the efficiency and the ratio of the output voltages of the transmitter-side inverters under various misalignments, has been derived. Based on this, a control strategy is developed to maximize the energy efficiency under various misalignment conditions. The experimental results based on a 2.5-kW laboratory prototype show that, in comparison with the traditional method with identical inverters output voltages, the overall efficiency is improved by 2.32% by using the proposed method.