Maximizing Efficiency of Hybrid Compensated Inductive Power Transfer (IPT) Systems Under Load and Coupling Variations

Hybrid compensated inductive power transfer (IPT) systems offer high tolerance to pad misalignments, but achieving maximum efficiency with conventional control strategies still remains challenging, especially under significant variations in mutual inductance (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$M$</tex-math></inline-formula>) and output power (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${{P}_{\text{out}}}$</tex-math></inline-formula>). This article, therefore, proposes an optimal control strategy, based on all four variables, to maximize the efficiency of hybrid IPT systems regardless of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$M$</tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${{P}_{\text{out}}}$</tex-math></inline-formula> variations. Maximum efficiency is realized by meeting optimal conditions, and it involves maximizing the ac–ac efficiency through impedance matching and minimizing converter switching losses through zero-voltage switching. As hybrid IPT systems are complex in nature, these optimal conditions cannot be determined using conventional analytical methods. Hence, this article presents a novel two-step strategy that first numerically derives the optimal conditions and then determines the optimal variables using a numerical algorithm. The proposed numerical strategy is highly versatile, as it avoids cumbersome analytical derivations, overcomes the challenges of high nonlinearity and, more importantly, is applicable to IPT systems with any compensation topologies. The proposed strategy is experimentally validated using a 3-kW hybrid compensated prototype IPT system, benchmarking against traditional control strategies, and results are presented to demonstrate how higher efficiency can be achieved compared to traditional strategies under variations in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$M$</tex-math></inline-formula>, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${{P}_{\text{out}}}$</tex-math></inline-formula>, and output–input dc voltage ratios.