Balanced Dual-Side LCC Compensation in IPT Systems Implementing Unity Power Factor for Wide Load Range and Misalignment Tolerance

Abstract

Misalignment tolerance and wide load range capability are necessary for a practical inductive power transfer (IPT) system. In pursuit of high-performance, input unity power factor and high efficiency are expected. In this paper, a balanced design method of dual-side LCC compensation is proposed to achieve input unity power factor over wide misalignment and load ranges. With the proposed method, dual-side LCC compensation is in a balanced state where zero phase angle frequencies coincide with designed voltage gain frequencies under coupling and load variations. Unity power factor can be implemented while maintaining voltage gain with frequency control. Possible output power versus frequency characteristics of this balanced dual-side LCC compensation are categorized and fully analyzed. One of them, with strong power regulation capability and high misalignment adaptability, is selected as the design target. Coil currents are optimized using a surplus degree of design freedom while selecting parameters. Unity power factor and coil current optimization ensure low losses in devices and coils, which benefits system efficiency. Thus, a wide load range, high misalignment tolerance, nearly zero reactive power, and high efficiency can be simultaneously implemented. The proposed method is verified on a 2.1kW prototype. The coil size of both primary and secondary sides is 600mm <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">×</i> 600mm, and the air gap is 150mm. Load power varies from 10% to 100% within the coupling range from 0.15 to 0.35. Nearly unity power factor is realized under various working conditions. The maximum dc-dc efficiency reaches 96.4%.