Load-Independent Voltage and Current Transfer Characteristics of High-Order Resonant Network in IPT System

Load-independent output characteristics of Inductive Power Transfer (IPT) system is of increasing interest in Electric Vehicle (EV) and LED lighting applications. All compensation networks in IPT system are actually high-order resonant circuits. In a high-order resonant network, there are multiple resonant frequencies to get load-independent voltage output and current output. It is critical to analyze the resonant conditions to achieve high efficiency in both load-independent voltage output and current output modes. This paper proposed a general modeling method for arbitrary high-order resonant networks to get both the load-independent voltage and current transfer characteristics. A high-order circuit can be modeled as a combination of a LC network, multi-stage T-circuit, and/or multi-stage Π-circuit in series. The proposed method is verified by applying to voltage-fed double-sided LCC, SS, S-SP, LCC-S and current-fed CLC-LC compensation networks in IPT system. The MATLAB simulation and experimental prototype of a constant voltage-fed double-sided LCC compensated IPT system with up to 3.3-kW power transfer are built. The efficiency of the double-sided LCC compensated IPT system is up to 92.9% and 90.6% when the IPT system operates at resonant frequencies that achieve constant current output and constant voltage output respectively, which are compliance with the frequency requirement by SAE J2954 standard.