Nested three‐layer optimisation method for magnetic coils used in 3 kW vehicle‐mounted wireless power transfer system

Abstract

Wireless power transfer is becoming more and more popular, especially for the charging design of electric vehicles. In this study, a novel nested three-layer optimisation method based on finite element model (FEM) is proposed to determine the structure of magnetic coils, which can increase the coupling coefficient, and hence, improve the transfer efficiency. The boundary conditions which consider practical situations for electric vehicles are first elaborated, then the optimisation flow is detailed and further analysed. Two magnetic coils are fabricated based on the optimised structure parameters, and their electric parameters, including self-inductances, mutual inductances as well as parasitic resistances, are measured and compared with those extracted from FEM, in addition, the magnetic flux densities around magnetic coils are also analysed. At last, a 3 kW prototype with 95% efficiency over a 20 cm transfer distance is achieved to validate this research results.

Multi-Load Mode Analysis for Electric Vehicle Wireless Supply System

“…As a result, n = 2 is a unique point in that the red curve in Figure 6 has both a positive and negative slope around the resonant frequency. The simulation results demonstrate the validity of the boundary condition established by Equation (9).…”

“…In [8], a dynamic wireless supply system with a narrow track rail width and a large air gap for EV was proposed. The work in [9] proposed an optimization method to determine the structure of magnetic coils. In [10], the multi-objective function of battery life and peak output power was constructed, and the arrangement rules of wireless charging devices were studied.…”

Review of inductively coupled power transfer for electric vehicle charging

“…Still, the funnel and conical shapes decrease the tolerance of horizontal misalignment, which is inferior to that of planar circular type. Meanwhile, Wang et al [44] proposed a procedure to design a circular magnetic structure using a nested three-layer optimisation algorithm excluding the ferrite core and aluminium plate size which are important to take into consideration. Some papers proposed multiple coil systems in EV wireless charging application such as in [45,46].…”

“…Adding lumped inductors into the compensation network has been done in [7,44,[59][60][61][62]. Li et al [63] proposed the inductorcapacitor (LC) compensation at the primary side, tuned to slightly higher than the resonant frequency for inductive operation, but this compensation is limited to under-coupled and critically coupled circumstances.…”

“…The coil induces one direction of flux that magnifies at the centre of the pad. This design enhances the flux projection towards the receiver coil to solve the weak coupling issue of the circular coil due to uniform distribution of magnetic flux [23, 44]. Although the DD pad coupling is stronger than that of the circular at the aligning position, there is a ‘blind spot’ misalignment that exists at the longitudinal, or X ‐direction offset, as illustrated in Fig.…”