Edge position detection of on-line charged vehicles with segmental wireless power supply

Online charged electrical vehicles (EVs) with segmental wireless power supply obtain energy from power tracks without a physical cable contact while traveling.When a vehicle moves from one segmental track to another, the power supply coils should switch accordingly to provide energy continually at various positions. As the secondary coil fixed in the vehicle moves along the primary coil mounted in the segmental track, the mutual inductance of these two coils changes accordingly, which results in the varying of the phase angle that the current lags the voltage in the resonant circuit at the primary side. The paper presents a method to decide the power switching time through detecting the changing of the phase angle. A higher phase angle varying range (PAVR) is preferred to achieve a better position judgment. Quality factors at the primary and secondary sides, as well as the mutual inductance between two sides for the higher PAVR, are analyzed. The phase angle change can be detected in the circuit at the primary side when an EV leaves the energized coil region. Besides that, a detecting signal is introduced to find the approaching of EVs for those de-energized coils. The system robustness and magnetic saturation are also analyzed. A scaled-down laboratory prototype is set up to test the proposed method. Within parameter drifts of ±4% of the rating inductance or capacitance, the prototypeworks perfectly under the rated operation frequency and switching threshold angle. Experiments show that the position detection method can detect not only the approaching but the leaving of vehicles as well.