Modeling and Implementation of a Long-Distance Seawater Single-Wire CPT System for Underwater Sensor

A long-distance, strong-misalignment tolerance seawater capacitive power transfer system with two insulated electric-field couplers and single-wire for underwater sensors is proposed in this article, and it has the advantages of low cost, low weight and hard worn-out compared with traditional structure. First, quasi electric double layer theory for coupler in seawater is proposed, and seawater between two couplers can be considered as equipotential medium is demonstrated in detail. Second, model of seawater electric-field coupled channel is built. The feasibility of long distance and strong misalignment tolerance is proved. Then, double T-LCL compensation network is investigated and selected for constant output voltage, zero phase angle (ZPA), and antifrequency-offset. Experimental results in lab show that the system can deliver 732.1 W at a dc-dc efficiency of 89.2%. In actual ocean, the experimental transmission distance is 10 m, achieving 206.8 W power transmission and 83% efficiency, which verifies the proposed program is adapted to power supply of sensors in complex ocean environment and the advantages of long distance. This article is also accompanied by a video file demonstrating experiment in actual ocean.