Research On Current-fed Wireless Power Transfer System Based On Switch-controlled Capacitors

In order to meet the increasing convenience demand in the field of electrified transportation and electronic consumption,the wireless power transfer system has been widely concerned.Inductive power transfer technology has the advantages of high transmitting power,medium transmitting distance and high safety,and is considered to be more suitable for commercial applications such as electric vehicles and portable equipment.The self-inductance or leakage inductance of the loosely coupling transformer is compensated by the capacitors compensation network to obtain the maximum transmitting power and efficiency in inductive power transfer technology.In practical applications,the inevitable misalignment and load regulating problems limit the application of the IPT system.The changed load resistance and inductive reactance make the resonance point of the system shift,which leads to the system output characteristics inconsistent with the requirements of zero phase angle operation,minimum apparent power,low voltage and current stresses of MOSFETs.A current-fed wireless power transfer system based on switch-controlled capacitors is proposed to solve existing problems with inductive power transfer.According to the characteristics of the varied parameter of the loosely coupling transformer in the case of misalignment,the system takes self-inductance as compensation object and adopts PS/S compensation network based on the mutual inductance model.The PS/S compensation network combines the advantages of series and parallel compensation and improves the performance of the system through the capacitance dynamically adjusting.The proposed parallel switchcontrolled capacitors structure is suitable for the inductive power transfer system with load regulating and misalignment problems.A controllable shift phase angle is applied to adjust the charge and discharge time of the switch-controlled capacitor in a cycle.Once the operating parameters of system change,the equivalent capacitance of the switch-controlled capacitor can be dynamically adjusted to achieve the inverter output voltage and current in phase.The DC voltage gain is affected by operating parameters to change.A novel modulation method in the current-fed inductive power transfer system is proposed to regulate the DC output voltage.A 120-W experiment prototype was built to verify the theoretical analysis and derivation of the proposed current-fed PS/S compensation network based on switch-controlled capacitors and novel modulation method.Simulation and experiment results verify the feasibility and superiority of the proposed topology and modulation method under the condition of load regulating and misalignment.