Design Of Wireless Power Transfer System With Low-power And Multi-directional Loads

In addition to high-power applications such as electric vehicles,wireless power transfer(WPT)technology has also been applicated in many low-power and even micro-power applications,such as the large number of wireless sensors because of the development of Io T technology and implantable medical devices,etc.Considering the cost and space,the traditional one-to-one WPT scheme is not suitable for many low-power applications.The multi-load WPT technology is a research hotspot.In the current research,the load power supply is mostly limited by the transmission direction of the transmitting coil.Therefore,in order to power the loads in multiple directions,this paper proposes two power supply schemes for multi-directional low-power loads based on magnetically coupled resonant WPT technology.The former is a WPT system with the dynamic transmitter based on physical rotation,and the latter is with the static transmitter based on magnetic field rotation.The research contents and key points in this paper are as follows:First,in order to solve the problem of the mutual inductance between coils in multi-directional WPT systems,a general mathematical model is established for a two-coil structure in this paper.Taking the circular plane spiral coil as a research object,the mutual inductance in the three cases of the parallel misalignment with non-coaxial centers of coils,the angle misalignment with coaxial centers,the parallel and angle misalignment with non-coaxial centers are studied,and the mutual inductance between the cylindrical spiral coils with the cross structure are studied too.In addition,the influence of Mn-Zn ferrite on the self-inductance and mutual-inductance of the coil are analyzed.The analysis provides a certain reference for the following two multi-directional WPT schemes.Second,the first scheme for the power supply of multi-directional loads is proposed and studied.The proposed scheme consists of a two-stage magnetically coupled resonant WPT structure,the primary stage of which is a one-to-one structure,and the secondary stage is a one-to-many structure.The transmission characteristics of the system with single and multiple loads are discussed,and the dynamic coupling model of the secondary stage is established.The influence of the rotary speed and the transmission distance on output voltage and efficiency are analyzed.In addition,an active converter is inserted in the AC/DC module to guarantee a constant load voltage,and the experimental results further prove the effectiveness of the proposed scheme with constant voltage output.At last,different from the dynamic transmitter in the first scheme,the second scheme with a static transmitter for the power supply of multi-directional loads is proposed and studied.In this scheme,an orthogonal structure is adopted which consists of two transmitting coils,and the suitable phase difference of the excitation current makes the magnetic field distribution around the orthogonal transmitter uniform.Magnetic field distribution model of the orthogonal transmitter is established,and the relationship between the magnetic field strength around the transmitter and the phase difference of the excitation current is explored.The optimal phase difference occurs when the magnetic field distribution is the most uniform,and in this case,the equivalent circuit model is established to analyze its transmission characteristics.In addition,in order to achieve the maximum power output when the load is changed,the active converter is used,and all the above analysis is verified by experiment.