Analysis and experimentation of a novel modulation technique for a dual-output WPT inverter

Dynamic wireless power transfer systems require to supply many transmitting coils deployed under the road surface and arranged along the so-called track. This layout entails the use of a large number of inverters or of devices that switch the power to the proper coils. This paper presents a technique that uses a single three phase inverter to supply two coils with voltages having different and independently adjustable amplitudes of their first harmonic component. Differently from the well-known phase shift technique, the amplitude and the phase of the voltages are not correlated. Moreover, the presented technique has the ability of inherently reducing the phase difference between the two output currents when the supplied loads are partially reactive. This feature enhances the power transfer capability of the inverter when both the track coils are coupled with the same pickup. After presenting this technique, the paper analyzes the functioning of the dual-output inverter in different load conditions recognizing the boundaries of four different modes of operation. For each of them the analytical expression of the amplitude and phase of the generated voltages are given. The theoretical findings are validated by experiments performed on a prototypal setup that implements the presented modulation technique.