Research On MC-WPT System Based On Topology Switching Between Constant Voltage And Constant Current

Wireless Power Transmission(WPT)is a new non-contact transmission technology.It can transmit electric energy from the power supply end to the user end without contact,which avoids direct electrical contact.At the same time,it plays an important role in the occasions with high requirements of water-proof and explosion-proof.At present,WPT is developing rapidly,especially Magnetic Coupling Inductive Wireless Power Transfer(MC-WPT),which has developed rapidly in the past 30 years and has become a mature WPT technology.Battery charging is a very important application scenario of MC-WPT.MC-WPT has entered our life,in forms of mobile phone wireless charging technology,electric vehicle wireless charging technology and so on.However,battery charging does not only need to supply constant voltage or constant current.At present,the charging curve of lithium battery which is the most widely used is the process of constant current first and then constant voltage.In order to fit the charging curve in different stages of constant voltage and constant current output,there are currently mainly methods such as voltage regulation,topology switching,and frequency conversion.At present,the voltage regulation method which is most widely used is to add DC-DC module to the inverter input or the rectifier output of MC-WPT.However,there are some problems in the way of voltage regulation,such as complex control,large loss of voltage regulation,primary and secondary side communication,etc.Therefore,this paper uses the topology switching method to match the constant voltage and constant current curve of battery charging.This method has the characteristics of natural constant voltage and constant current,and does not need to add complex control system or voltage regulation link.Similarly,the traditional switching topology is mainly in the form of variable capacitance parameters in primary and secondary side,but this method will lead to system detuning and greatly reduce the efficiency of the system.In addition,there are some types such as LCC-S/double-sided LCC structure.By skillfully using the switch position,the number of switches can be reduced,but the voltage stress of the switch tube is ignored,so it can only be applied to some small power occasions.Therefore,a new topology structure of LCC-LCC-T for switching between constant voltage and constant current is proposed to solve the problems of current topologies,such as low transmitting power and not on resonance oscillation.This paper aims to find a topology structure for switching between constant voltage and constant current to make up for some problems in the development of constant voltage and constant current system,such as complex control,low transmitting power and low efficiency.In this paper,the structure of each part of MC-WPT is introduced and analyzed.Then,the constant voltage and constant current topology modes are analyzed by AC Impedance Analysis Method,and the output relationship is obtained.And the the effect of constant voltage and constant current is analyzed.Then,the topology parameters and the switching control circuit are designed.the control flow of the experiment is clarified.Finally,the effectiveness of the switching topology are verified through MATLAB/SIMULINK simulation,and the feasibility of the proposed switching topology LCC-LCC-T is verified by building an experimental platform.The experimental results show that the topology switching structure can approximately adapt to the charging characteristic curve of lithium battery,and has high load adaptability.Though the equivalent load changes from 5 to300 Ohm,the topology still has excellent constant voltage and constant current performance,and has higher transmission efficiency.