Wireless Inductive Charging of Electrical Vehicles: Electromagnetic Modelling and Interoperability Analysis
Development of contactless battery charging is an opportunity for electric vehicles. Compared to regular plugin cables, this solution is easy to use, robust and weather resistant. The power is transferred thanks to the magnetic coupling of inductive coils and a reduced magnetic circuit. The aim of this thesis is to contribute to propose a standard that would make possible to couple emitters with receivers from different suppliers, that is, to insure interoperability. As the system should also be tolerant to positioning and should respect human exposure recommendations, many configurations must be tested. In this thesis, an advanced and reliable modeling of the whole system is proposed. Using the finite element methods, the electrical characteristics (self, mutual inductances and coupling factor) of the inductive coupler are computed for different geometric and interoperability configurations. These values allow the dimensioning of the resonant converter. At this stage, different compensation topologies are considered. It is shown that the global resonant frequency can be derived and the topologies compared from a classical first harmonic approximation and analytical model. Then, a circuit model of the full system is developed in order to evaluate precisely the currents and voltages. Finally, the performance of a MPPT (Maximum Power Point Tracking) as frequency regulation algorithm is evaluated. From the currents computed at resonant frequency for the nominal operating point and the finite element model of the coupler, including the chassis of the vehicle, the radiated magnetic field is evaluated in order to check safety compliance. At each step of the modeling, the sensitivity of the system to the configuration parameters (positioning, interoperability) is analyzed. Measurements at the coupler level and for the full system are also used in this analysis and allow validating the model.
Keywords: EM modelling, resonant topologies, power electronics, interoperability, inductive charging.
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