This paper investigates the design of a robust H ∞ output feedback controller for a capacitive power transfer (CPT) system. Firstly, a first harmonic model of the CPT system is derived based on first harmonic approximation (FHA). Secondly, by linearizing the first harmonic model at its operation point, a linearized state space model is obtained. Thirdly, variations of coupling capacitances and load in the CPT system are described as polytopic uncertainties in the linearized state space model. Then, we propose a novel robust H ∞ output feedback controller design technique for the linearized state space model with polytopic uncertainties. Finally, both simulation and experiment are carried out to verify the effectiveness of the proposed controller design.INDEX TERMS Robust H ∞ control, dynamic system modelling, capacitive power transfer, class-E inverter.

In this paper, possible coupling configurations of a four-plate capacitive power transfer system are studied by varying the combinations of its input and output ports. A voltage source is applied between two of the four plates, and a load is connected to the other two to form different circuit topologies. A mathematical model based on a 4 × 4 mutual capacitance matrix is established for equidistantly placed four identical metal plates. Based on the proposed model, four separate circuit topologies are identified and analysed in detail and described in a general form. The electric field distributions of the coupling configurations are simulated by ANSYS Maxwell. The theoretical modeling and analysis are then verified by a practical system, in which four aluminum plates of 300 mm × 300 mm are used and placed with a gap of 10 mm between adjacent plates. The experimental results show that the measured output voltage and power under the four coupling configurations are in good agreement with the theoretical results. It has found that the voltage gain is the highest when the two inner plates are connected to the source, and this coupling configuration also has the lowest leakage electric field.

This paper explores the feasibility of applying the capacitive power transfer (CPT) technology in underground data transmission applications. Based on the electrical properties of soils, the paper extends the existing CPT air coupler model into a more generalized model. The autonomous push-pull inverter is selected to power the CPT system and modified to further the data transmission range. With a designed load shift keying (LSK) circuitry, this self-oscillating inverter regards the data as a sequence of impedance changes, resulting in operation frequency drifts. A Frequency Shift Keying (FSK) demodulator is applied to capture the frequency variations and recover back to data. The proposed design has been simulated, verified, and implemented on a complete prototype. Various testings have been carried out, and the results are satisfactory.

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