Accurate Modeling of Discontinuous Operating State for <i>LCC–LCC</i> Compensated Inductive-Power-Transfer Converters by Time-Domain Analysis

The LCC-LCC compensation topology has been widely applied to inductive-power-transfer (IPT) systems to achieve constant-current (CC) output for battery charging. However, the mathematical model for the CC output is usually derived by fundamental-harmonic analysis (FHA) applied in the frequency domain, which cannot describe the output current accurately when the load resistance is larger than a threshold value, i.e., <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$R_{L} \gt \pi \omega L_{fs}$ </tex-math></inline-formula>/2, because of the discontinuous part-sine current flowing into the rectifier. To tackle this problem, in this article, an accurate time-domain analysis (TDA) is first proposed to derive the mathematical model of output current for the LCC-LCC compensated IPT system. The derived output model shows that the output current would decrease with the increase of load resistance, which is totally different from the conclusion from FHA. Both simulation and experimental results are presented to validate the accuracy of our derived output current model by TDA, which is consistent with our theoretical results. The proposed method can provide guidance on how to design the parameters of LCC-LCC compensated IPT converters to achieve rated outputs with small tolerance errors for battery charging.