Fully electric ships have become popular to meet the demand for emission-free transportation and improve ships' functionality, reliability, and efficiency. Previous studies reviewed the shipboard power systems, the different types of shipboard energy storage devices, and the influences of the shore-to-ship connection on ports' electrical grid. However, the converter topologies used in the electrification of ships have received very little attention. This article presents a comprehensive topological review of currently available shore-to-ship and shipboard power converters in the literature and on the market. The main goal is to anticipate future trends and potential challenges to stimulate research to accelerate more efficient and reliable electric ships.

This paper studies the capacitive coupling in a capacitive power transfer (CPT) system designed for charging applications. It proposes mathematical models using the conformal transformation for calculating air-gapped and underwater capacitance and verifies the proposed models using COMSOL multiphysics and measurements. The measured results show that we can achieve nano-farad capacitance ranges if we submerge the capacitor in seawater. The seawater’s capacitance slightly changes when we increase the gap distance or the operating frequency. As the under seawater CPT system can be an attractive option for loosely-coupled charging applications, we further examine the system by focusing on the cross-coupling effects. The results show that the cross-coupling between the plate degrades the system’s power transfer capability and efficiency. With negligible cross-coupling effects, the system gives 129 W output power at an efficiency of 81.2%.

Capacitive power transfer (CPT) is a near-field wireless power transfer (WPT) technology that has attracted attention in different charging applications. By utilizing electric fields, CPT gives charging systems advantages in terms of cost, weight, flexibility, and mobility. This paper surveys a number of empirical published works in a period between 2015 and 2023. Additionally, it discusses theoretical and practical design considerations of a CPT system to understand and improve the technology and its applications. The paper studies the one- and two-port measuring approaches using vector network analyzers to determine the coupling parameters and compares the measurements to the simulated values using COMSOL Multiphysics©. The two-port approach gives more accurate results than the one-port approach. The paper designs and tests a 13.56MHz cpt system using the two-port measurement results. The system transfers 100W at 87.4% efficiency and 30mm separation distance. Lastly, the paper discusses the design limitations and challenges of the CPT systems, aiming to emphasize the design obstacles that can drive the advancement of the CPT systems for wireless charging applications.

Capacitive power transfer (CPT) has attracted attention for on-road electric vehicles, autonomous underwater vehicles, and electric ships charging applications. High power transfer capability and high efficiency are the main requirements of a CPT system. This paper proposes three possible solutions to achieve maximum efficiency, maximum power, or conjugate-matching. Each solution expresses the available load power and the efficiency of the CPT system as functions of capacitive coupling parameters and derives the required admittance of the load and the source. The experimental results demonstrated that the available power and the efficiency decrease by the increasing of the frequency from 300 kHz to 1 MHz and the separation distance change from 100 to 300 mm. The maximum efficiency solution gives 83% at 300 kHz and a distance of 100 mm, while the maximum power solution gives the maximum normalized power of 0.994 at the same frequency and distance. The CPT system can provide a good solution to charge electric ships and underwater vehicles over a wide separation distance and low-frequency ranges.

This paper investigates the use of the class-E inverter for power factor correction (PFC) applications. Analytical and state-space models are derived showing the class-E inverter's capability of achieving inherent PFC operation with a constant duty cycle. The inherent PFC operation limits the controller responsibility to the regulation of the output voltage, which is key for resonant converters with challenging control. A converter incorporating a diode bridge, a class-E inverter, and a class-D rectifier is presented for the PFC stage in single-phase offline converters. A prototype is designed to validate the analysis and presented design method. The prototype operates with zero-voltage switching (ZVS) across the load range and achieves up to 211 W of output power at an efficiency of 88%, with an inherent power factor of 0.99 and a total harmonic distortion (THD) of 8.8 %. Frequency modulation is used to achieve lower output power down to 25 W, with a power factor of 0.95, THD of 28 %, and an efficiency of 88 %.