Abstract
Compensation is crucial in the inductive power transfer system to achieve load-independent constant voltage or constant current output, near-zero reactive power, higher design freedom, and zero-voltage switching of the driver circuit. This article proposes a simple, comprehensive, and innovative graphic design methodology for compensation topology to realize load-independent output at zero-phase-angle frequencies. Four types of graphical models of the loosely coupled transformer that utilize the ideal transformer and gyrator are presented. The combination of four types of models with the source-side/load-side conversion model can realize the load-independent output from the source to load. Instead of previous design methods of solving the equations derived from the circuits, the load-independent frequency, zero-phase angle (ZPA) conditions, and source-to-load voltage/current gain of the compensation topology can be intuitively obtained using the circuit model given in this paper. In addition, not limited to only research of the existing compensation topology, based on the design methodology in this paper, 12 novel compensation topologies that are free from the constraints of transformer parameters and independent of load variations are stated and verified by simulations. In addition, a novel prototype of primary-series inductor–capacitance–capacitance (S/LCC) topology is constructed to demonstrate the proposed design approach. The simulation and experimental results are consistent with the theory, indicating the correctness of the design method.
Highlights
Compared to traditional plug-in systems, inductive wireless energy transmission systems have advantages such as flexibility, convenience, electrical isolation, and strong environmental adaptability [1]
Based on the above experimental results, we get the following: at zero-phase angle frequency, the equivalent impedance of the S/LCC circuit is a pure resistance, minimizing the VA ratings; on the basis of the realization of ZPA characteristics, it is very convenient and easy to implement zero-voltage switching (ZVS) just by slightly changing the value of the primary compensation capacitor; the S/LCC has excellent constant-voltage characteristics; and the load changes in a large range while the output-constant voltage is almost unchanged, which simplifies the design of the system control circuit
Unlike boring and time-consuming design methods for manipulating circuit equations, using the circuit model given in this paper the load-independent frequency, ZPA conditions, and source-to-load voltage/current gain of the compensation topology can be obtained almost by inspection conveniently, giving a new perspective being free from the constraints of complex equations
Summary
Compared to traditional plug-in systems, inductive wireless energy transmission systems have advantages such as flexibility, convenience, electrical isolation, and strong environmental adaptability [1]. It has been employed in many applications. In the field of electric vehicles, the inductive power transfer (IPT) method has a greater advantage for the electric vehicle (EV) battery charger due to its convenience and safety as compared to the plugged-in charger [2]. In order to transfer power within a certain distance in the IPT system, a loosely coupled transformer (LCT) that involves the primary coil and the secondary coil must be used. Compensation circuits are generally required to achieve or improve the following characteristics:
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