Determinação do desempenho de sistemas de transferência de energia sem fio sem medição direta no lado da carga

Abstract

A typical N-coils wireless power transfer (WPT) system usually consists of resonant circuits designed for a certain resonance frequency. Depending on the number of coils, this system consists of a source circuit, intermediate circuits and a load circuit. The control and optimization of these systems requires continuous monitoring of their performance or, similarly, some output parameters. However, depending on the application of WPT system, such as in implantable medical devices and enclosed devices, direct measurement of these parameters in the load circuit in general is not feasible, as it may require the implementation of additional wireless communication systems. Therefore, there has been great interest in developing solutions for determining the performance of WPT systems without the need for direct measurement of the load circuit. The solution presented in this work is based on the relationship between some figures of merit that are representative for WPT systems and thus allows to monitor and control automatically (simply, without any direct measurement in the load circuit) the system performance from WPT to N-coils facing load variations and/or mutual inductance between intermediate and load coils. The proposed method is theoretically presented for a generic WPT system composed of N-coils, and is then applied to WPT systems composed of two-, three- and four- coils, including their experimental validations. The qualities and limitations of the proposed method are discussed in detail, as well as the characteristics of a WPT system from a new point of view, using the derived relations. Finally, a simple automatic control system is implemented to demonstrate the applicability of the theory presented. The practical results presented demonstrate an adequate correlation in relation to the theoretical data, validating the method developed. In addition, the application of the theory in an automatic control system of the performance of WPT systems demonstrates the application potential of the method developed and confirms the relations presented for the calculation of maximum efficiency and maximum power transfer capacity.