Abstract:Wireless power transmission technology is widely used in many fields due to its convenience, flexibility, safety and efficiency. The optimization of its transmission characteristics is one of the key issues in the current research. Through theoretical discussion, electromagnetic simulation analysis, and experimental method verification, this work analyzed the influence of position of relay coil on the output power and transmission efficiency in the three-coil wireless power transmission system. And a transmission strategy using a DC-DC conversion circuit was designed to maintain the transmission efficiency at a high level by adjusting equivalent impedance of load without changing the placement of relay coil. Experiments show that the proposed transmission strategy is not only suitable for the situation where relay coil is fixed and load resistance is changed, but also can maintain high transmission efficiency when load remains the same but position of relay coil changes.