Mitigation of lateral misalignment problem in wireless power transfer applications

Abstract

Wireless power transfer (WPT) has been around for over a century originating with Nikola Tesla’s pioneering ideas; however, it has recently drawn more attention due to its broad applicability in various current scenarios. Having the features like high flexibility, convenience, safety, and aesthetics, the WPT is widely used in many applications such as biomedical implants, mobile phones, and electric vehicles. The performance of the WPT system is greatly a↵ected by misalignment between the transmitter (Tx) and the receiver (Rx) coils. In practice, perfect alignment is usually not ensured. Therefore, mitigation of the misalignment problem is currently a primary research direction. Among various such limitations, the lateral misalignment problem is most common in the WPT applications such as smartphones, drones, and electric vehicle charging stations, where the Tx and the Rx coils are co-planar but displaced. Hence, the primary objective of this thesis is to propose a solution to mitigate the lateral misalignment problem by employing the field forming technique. Additionally, a novel performance parameter called the Uniformity Factor (UF) is introduced to assess the potential misalignment tolerance of the proposed designs. The thesis is split up into seven chapters. Chapter 1 discusses the basics of the near-field WPTsystem, describing various potential research problems involved in the WPT system, and later identifies the most challenging issue, which is targeted in this thesis. Further, the already available solutions in the literary works are investigated intensively in Chapter 1. Simultaneously, Chapter 2 deals with a mathematical background of field-forming technique and circuit analysis of distinct compensation topologies, and design procedure of Tx coil antenna to maximize e ciency under a perfectly aligned Rx coil antenna. Whereas the Chapter 3 deals with novel S-parameter-based e ciency equations for series-series, series-parallel, parallel-series, and parallel-parallel compensation topologies. Also, Chapter 4 focuses on addressing lateral misalignment problems by targeting to induce uniform voltage at the Rx coil using single port Tx coil antennas. The best Tx coil antenna design using single port is found to be Design-1C (n=3) with UF in regards to induced voltage is 45.41%. On the contrary, Chapter 5 aims to mitigate the lateral misalignment problem by minimizing flux leakage using switchable circuits and detection coils using multi-port Tx coil antennas. The Design-2B multi-port Tx coil antenna achieves UF of 75.5% in induced voltage with power transfer e ciency of 80% which stands out among all the designs mentioned in this thesis. Furthermore, the investigation of Rx coil antenna is intensively done by performing parametric optimization of various parameters of Rx coil to encapsulate all the magnetic-field components to induce a uniform voltage in Chapter 6. Finally, the thesis work is summarized and concluded in Chapter 7.