| With the emergence of a large number of portable electronic products,the traditional wired transmission methods no longer fully meet the simple and convenient needs of users,which greatly stimulates the development of Wireless Power Transfer(WPT)technology.The omnidirectional WPT technology has become the mainstream research direction due to its high degree of freedom in power transmission.However,during the wireless charging process,the uncertainty of the relative position between the power supply device and the charging device restricts the stability of the power supply.Therefore,this article takes the omnidirectional WPT system as the research object,focusing on the output power stability control strategy based on front-end mutual inductance information parameter estimation.The specific research content is as follows:Firstly,based on the magnetic coupling structure composed of three-phase orthogonal transmitting coils and a receiving coil,the principle of current amplitude control is described.The current amplitude of the three-phase transmitting coils is controlled to change the synthesized current vector value,so that a spatially controllable magnetic field vector can be generated.According to the Neumann formula,the calculation expression of mutual inductance between the receiving coil and each phase of the transmitting coil at different transmission distances and transmission orientations is derived.It can be seen that different transmission distances and transmission orientations will cause changes in mutual inductance between magnetic coupling mechanisms.Secondly,in order to compensate for the limitations of the four basic compensation networks applied in the omnidirectional WPT system,a three-phase LCC-S compensated omnidirectional WPT system is used in this paper.The system structure and working principle are described,and circuit modeling is performed,relevant analysis shows that the mutual inductance information is a key factor affecting the transmission characteristics of the system.Therefore,an estimation method for the front-end mutual inductance information parameters is proposed,it eliminates the influence of input variables(elevation θ and azimuth φ)on mutual inductance information variables through magnetic field direction control,the mutual inductance information parameter is maximized,and the maximum value of mutual inductance information based on input power information at different states is estimated.Under the condition of constant load,without the need for load side feedback,a load stable power control method based on transmitter current amplitude control is studied by means of the estimated mutual inductance information parameters and the load received power equation.Finally,based on the above theoretical analysis,a three-phase LCC-S omnidirectional WPT system is designed,with the control goal of achieving a stable power output of 30W for both resistive and rectifier loads at the receiving end within a transmission distance of 25cm～45cm.The experimental results show that under two working conditions,based on the online estimation results of front-end mutual inductance information parameters,the current amplitude control of the three-phase coils at the transmitting end can make the load receive power close to the target power.The system power transmission and conversion efficiency curves under the rectifier load are drawn to compare the load receiving powers and efficiencies under different transmission distances and transmission directions,and the validity and feasibility of the control strategy has been verified. |
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