A Novel Distance Measurement Method Based on Reflected Impedance for Resonant Wireless Power Transmission System

The traditional WPT (Wireless Power Transmission) system can not provide the most efficient power transmission due to the position uncertainty of the receiving coil. When the receiving coil is too close to the transmitting coil, the frequency will split, causing the low transmission efficiency. On the contrary, when the receiving coil is far away from the transmitting coil, the air loss of the transmission power will increase, leading to the same result. A novel distance measurement method based on reflected impedance (DMRI) for resonant wireless power transmission system is introduced, which could acquire the distance between the receiving and transmitting coil by measuring the reflected impedance at the transmitting end. A theoretical circuit model is established. The relation expression between the reflected impedance and the transmission distance is derived and a simulation model is built. The error between the simulation distance and DMRI distance is about 1.6%. In addition, a WPT experimental system is built, the error between the experimental distance and DMRI distance is about 3.7%. The proposed method has a minor error and could accurately calculate the distance between the transmitting and receiving coil.