ABSTRACT
Wireless Power Transfer (WPT) systems are becoming increasingly important in modern electrical engineering applications such as electric vehicle charging, biomedical implants, portable electronics, robotics, and industrial automation. Conventional wired systems suffer from several limitations including mechanical wear, sparking, insulation failures, and reduced flexibility. Wireless power transfer eliminates direct electrical contact and enables safe and efficient energy transfer over an air gap. The Wireless power transfer technologies typically include inductive coupling, magnetic resonance, and capacitive coupling methods.
This report presents a detailed comparative analysis of Inductive Power Transfer (IPT), Capacitive Power Transfer (CPT), and Hybrid Power Transfer (HPT) systems using MATLAB/Simulink models. The IPT system transfers energy through magnetic field coupling between coils, whereas CPT transfers power through electric field coupling between capacitor plates. The HPT system combines both magnetic and electric field coupling mechanisms to enhance efficiency and power density.
INTRODUCTION
Recently, the application of wireless power transfer (WPT) in charging mobile devices and the electric vehicles is widely researched. WPT are generally classified as magnetic resonance, inductive coupling, and capacitive coupling. Magnetic resonance WPT uses resonance with the transmitting coil and receiving coil. The method has many advantages such as long distance transfer and user convenience. However, the system has not been commercialized because of electromagnetic interference (EMI), human activity, and some imposed regulations. Inductive coupling WPT follows the same principle of a transformer in the power converter. Despite having good efficiency and developed commercialization techniques, inductive coupling WPT has disadvantages such as one position power transfer, heat dissipation in the metal barrier, and the large coil volume. The prior two approaches employ the magnetic field, hence the presence of radiation noise and power transfer metal interference. In contrast, capacitive coupling wireless power transfer (CCWPT) uses electric field and displacement current to transfer wirelessly power; this approach is also called contactless power transfer. In simple structure of the CCWPT system, Direct current (DC) voltage is converted to alternating current (AC) voltage that supplies two primary metal plates using a high-frequency inverter. Two secondary plates are located adjacent the structure and the electric field enables the displacement current to flow. The DC output voltage can be obtained with a rectifier. Coupling capacitance is an important factor in transferring energy and operation stability. However, the realized capacitance is limited by the available area of the device being used. The power conversion circuit is a series resonant type circuit that produces high frequency AC voltage. In the other approaches, a simple full bridge inverter is used to make the series resonance between the inductor and coupling capacitor. If the obtained capacitance is very small, the simple resonant circuit limits the transferring. The quality factor is very high hence the operation is unstable. A high-frequency operation and impedance transformation is a viable solution to overcome this drawback. Operation frequency selection is necessary to meet wireless regulations in mobile wireless charger applications and standardize the operation frequency of industrial, scientific, and medical (ISM) band. A silicon power semiconductor cannot be driven with a very high frequency like the GHz operation.
Modern WPT systems are widely used in:
• Electric vehicle charging
• Biomedical implants
• Consumer electronics
• Underwater systems
• Aerospace applications
• Industrial automation
• Internet of Things (IoT) devices

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