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

Load-independent output characteristics of an inductive power transfer (IPT) system are of increasing interest in electric vehicle and LED lighting applications. All compensation networks in the 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 an LC network, a multistage T-circuit, and/or multistage Pi-circuit in series. The proposed method is verified by applying to voltage-fed double-sided inductor-capacitor-capacitor (LCC), series-series (SS), S-SP, LCC-S, and current-fed CLC-LC compensation networks in the IPT system. The MATLAB simulation and the 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.