The most widely adopted category of the mid-range wireless power transmission (WPT) systems is based on the magnetic resonance coupling (MRC), which is appropriate for a very wide range of applications. The primary concerns of the WPT/MRC system design are the power transfer capabilities. Using the scattering parameters based on power waves, the power transfer of an asymmetric WPT/MRC system with the series-series compensation structure is studied in this paper. This approach is very convenient since the scattering parameters can provide all the relevant characteristics of the WPT/MRC system related to power propagation. To maintain the power transfer capability of the WPT/MRC system at a high level, the scattering parameter S21 is used to determine the operating frequency of the power source. Nevertheless, this condition does not coincide with the maximum possible power transfer efficiency of the system. In this regard, the WPT/MRC system is thereafter configured with a matching circuit, whereas the scattering parameter S21′ S21’is used to calculate and then adjust the matching frequency of the system. This results in the maximum available power transfer efficiency and thereby increases the overall performance of the system. Theoretical investigations are followed by numerical simulation and experimental validation.

In this paper, we proposed a novel steady-state multiple parameters estimation method of the two-coil inductive power transfer (IPT) system based on the measurement of the primary-side voltage and current fundamentals. The method is used to estimate key parameters, such as mutual inductance and equivalent load resistance, as well as receiver self-inductance and compensation capacitance values, and the total parasitic resistance of the secondary side. The method also allows the identification of the secondaryside resonant frequency. The parameters estimation procedure involves three operating modes of the IPT system: 1) open-circuit of the secondary side, 2) short-circuit of the secondary side, and 3) load connection. Each of these modes allows the identification of different parameters. To make the system operate in predefined modes, two switches are added to the receiver circuit. These switches are controlled from the secondary side, while the parameters estimation process, including load voltage and/or current control, is fully conducted on the primary side. The experimental tests on the prototype have validated the proposed method and demonstrated its effectiveness. The method can be applied to a new generation of highperformance wireless battery charging systems, where the single transmitter unit can be used to charge the battery pack in different devices.INDEX TERMS Inductive power transmission, parameters estimation, mutual coupling.

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