Contactless Self-Tuned Capacitive Coupled Power Transfer System Using Series Resonant Inverter and MPPT Controller

Inductive Power Transfer (IPT) has received most of the interest until now; new researches on Capacitive Power Transfer (CPT) have led to proposals for high power, long distance applications, such as electric vehicle charging or handheld devices. So the traditional conception of capacitive wireless transmission only for low power and short distances is slowly changing. Here the proposed CPT system can track the maximum power transfer capability over a wide load variation even when the resonant circuit is not fully tuned. The maximum power transfer is achieved by designing a DC-DC buck-boost converter with duty cycle control for dynamic impedance matching. In the inductively coupled power transfer (ICPT) method, the power is transferred wirelessly between separated coils via MF, while the CPT relies on the electric field (EF) to transfer power between two pairs of metal plates. By applying capacitive coupling by means of electric field, wireless power transfer can be realized between a transmitter and a receiver. The presented capacitive link design can reduce the receiver to the bare minimum, the capacitance plates and the load. All tuning for variable coupling occurs at the transmitter side, therefore lowering the costs and making data communication no longer necessary. State of the art of CPT converters includes a significant variety of resonant topologies, including different number of switches in the inverter, from single switch to a half or full bridge, different resonant tanks and impedance adaptation networks. This work is focused on simplicity, using as simple high frequency inverter and series resonant tank. Bearing in mind that the goal of this research was to achieve efficiency as high as possible, and that a high switching frequency is needed to compensate for the low capacitance value and to select the resonant tank and the inverter best suited for the application.