| Summary: | Bidirectional wireless power transmission (BD-WPT) systems are applicable to occasions that need bidirectional energy flows, such as vehicle-to-grid technology. The traditional BD-WPT systems work at a fixed frequency and the optimal transmission efficiency of the systems is fixed. Combining the frequency characteristics of AC resistance, the mathematical model of variable frequency BD-WPT system is built in this paper. Then, the characteristics of transmission efficiency and the characteristics of maximum active power are analyzed based on the model. In order to make the BD-WPT system have higher transmission efficiency, a BD-WPT system with variable structural parameters and the corresponding segmented powerefficiency coordinated control strategy are proposed in this paper. According to different reference power on the secondary side, the BD-WPT system can work in different resonant frequency segments by controlling the switching of corresponding relays in the capacitor arrays on the primary and secondary sides and changing working frequency of the H-bridge converters on the primary and secondary sides. By using the proposed control strategy, the transmission power, and direction, can be tunable segmentally while maintaining high transmission efficiency. The proposed concept is verified to be effective through experiment.
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