Analysis of Inductive Power Transfer Systems for Electric Vehicle Charging Applications

Abstract

This research report is structured in 7 Chapters which pretend to guide the reader from a general point of view of Wireless Power Transfer (WPT) and its applications, to a deep and better understanding of Inductive Power Transfer (IPT) applied to Wireless Electric Vehicle Charging Systems (WEVCS). To do so, after the background introduction, each chapter studies a different part of the IPT system, ending up with the analysis of the simulation and hardware results.The background introduction is shown in Chapter 3, and explainshow energy started to be transferred wirelessly along history, classifying WPT into near-field (NF) and far-field (FF). Focus has been placed in NF WPT explaining inductive, capacitive and resonant variants, as the main existing forms of transferring energy through electromagnetic waves. Additionally, applications of NF have been commented concerning the charge of portable devices, electric transportation or biomedical implants. Wireless chargersfor electric vehicles are within the scope of this report. Hence,a detailed explanation of the two main topologies, static wireless charging (SWC) and dynamic wireless charging (DWC) has been given. To finish the review, information regarding a safe application following the current regulations has been mentioned as long as the principal standards that aimto smooththe path towards an early adaptation of IPT technology for EV charging purposes.In Chapter 4,IPT has been demonstratedwith mathematical expressions so as to be able to model thesystem that hereinafter will be simulated and validated. It starts with the formulation to get the relationship between the flux linkage and the currents, followed by an equivalent circuit representation. An initial analysis of the results can bealready obtained at this point.Howeverto increase the coupler’s efficiency a compensation network is added to either the equivalent circuit and the previous equations. The last part of the chapter is the design process of the coupler following an iterated procedure, where based on the charging specifications, by fixing some desired parameters the transmitter and receiver coils can be developed. Chapter 5explains the power electronics converters, essential in this system to increase the frequency up to de kHz range and reduce the size of its passive components. The converters used in the simulation and the hardware implementation are a DC/AC H-bridge inverter with Silicon Carbide (SiC) MOSFETs due to the high switching frequency intended to be used, and a diode bridge rectifier to turn the AC into DC and be able to charge thevehicle’s battery. Both converters have been simulated, first separately and then together to see the overall performance. Finally, a low pass filter has been added to smooth the ripple of the voltage and current of the load.The final components ordered have been listed and explained in Chapter 6, using the real values of the parameters given by the supplier to calculate and simulate the results. The results have been put together in Chapter 7, on theone hand the simulation results obtained with Matlab/Simulink and on the other hand the tests carried through with the hardware in the laboratory. The 4Reportgoal of this last chapter is to validate the theoretical results. An intermediate stage is the simulation, which is crucial to learn the performance of the system in non-common situations. That is why several cases have been studied, varying the position of the coils in the three axis, and analysinghow the misalignment affects to the efficiency. This study is important, for dynamic charging testing is oneofthe targets set for this project and future work.

Outgoing

Original document

The different versions of the original document can be found in:

• http://hdl.handle.net/2117/165458