Research On Control Of Series-parallel Compensated Wireless Power Transfer Systems Using Parameter Estimation

With the rapid development of industrialization in modern society,people begin to pursue lighter and safer electronic devices.In recent years,wireless power transmission technology as a new power supply mode has provided a new charging approach for electronic devices.Because the physical connection between power supply and load is avoided,wireless power transmission technology greatly improves portability and safety of electric devices.In addition,it also improves users' experience and has become a hot spot in academia and industry.This paper takes the series-parallel magnetic induction type wireless power transmission system as the research object.Furthermore,it studies the control method to maintain high efficiency of the system and the constant output voltage for the condition of variable coupling coefficient.Based on modeling and analyzing of the series-parallel compensation network,it can be seen that there are series resonant pairs and parallel resonant pairs in the system.Among them,equivalent leakage inductance and series compensation capacitor constitute series resonant pair,and equivalent magnetic inductance and parallel compensation capacitor constitute parallel resonant pair.When system is fully compensated,input votage and input current are in phase,achieveing unity power factor,and reactive power is approximately zero.Besides,the output voltage is only related to the coupling coefficient and independent of the load.When the coupling coefficient changes,the parallel resonance pair can be maintained,but the series resonance pair fails.This results in input votage and current no longer in phase,the unit power factor is lost,and the system losses increase.Besides,the output voltage changes accordingly.Aim to achieve unity power factor,this paper proposes to replace the series compensation capacitor with switch-controlled capacitor,and to track the variable coupling coefficient to realize dynamic complete compensation.Aim to achieve constant output voltage,this paper studies the single-phase full-bridge inverter phaseshift method(single-stage method)and the method of cascading buck circuit in front of inverter(two-stage method).The above two methods are realized based on the parameter estimation techonology.In this paper,the input voltage and input current of the transmitter are detected,and the Goertzel algorithm is applied to predict the coupling coefficient in real time.This unilateral sampling parameter estimation techonology eliminates the traditional communication circuit,simplifies the control circuit,reduces the size and cost of the system,and solves the problem of interference caused by the coupling inductance magnetic field on the signal.Finally,the parameter design and control circuit design of the serial-parallel magnetic induction wireless power transmission system are carried out.Based on the proposed coupling coefficient parameter estimation technology,the dynamic compensation of the switch-controlled capacitor is realized,and the experimental prototypes of two control methods are completed by the TMS320F28335 DSP controller.The experimental results verify the correctness of the theoretical analysis.