| The application of wireless power transfer technology combined with Supercapacitor energy storage technology in modern tram can realize the non catenary power supply technology with the advantages of flexibility,safety and low cost and so on.The variation of the parking position error and the equivalent load in the process of Supercapacitor charging will cause the change of the electrical parameters of the primary side and secondary side,which will affect the operating characteristics of the WPT system.In addition,the Supercapacitor is usually charged in a constant current mode,but in the existing WPT system output control methods,the research on the control method of constant current output is very little.In this paper,the influence of mutual inductance and equivalent load on the transmission characteristics of WPT system were analyzed,and the constant current charging method of Supercapacitor was studied.Based on the dynamic modeling of WPT system,the controller parameters were designed.In this paper,the mathematical model of SS type WPT system was established,which included two parts.The steady state model of SS type WPT system was established by mutual inductance model.In steady state,the circuit was analyzed and the equivalent resistance model was deduced,and the transmission characteristics were analyzed,including the influence of mutual inductance and equivalent resistance on voltage gain,current gain,transmission efficiency and transmission power.Then,the dynamic models of the primary and secondary circuits were established,and the transfer functions were derived.Secondly,this paper mainly studied the control scheme of Supercapacitor constant current charging without communication,mainly divided into two parts.In the first part,using the mutual inductance model,the control method of the constant current of the primary side and the control method of the constant current charging of the Supercapacitor were analyzed.The control method for keeping the constant current of primary side by phase-shift control and keeping the charging current constant of Supercapacitor by controlling the duty cycle of buck circuit were determined.According to the formula of the optimal load,the reference value of the primary current and the Supercapacitor charging current were derived.In the second part,according to the transfer function of the primary and the secondary side,the controller parameters of the primary and the secondary side were designed,and the effectiveness of the control method were verified by MATLAB/Simulink simulation software.Finally,this paper used the lkW experimental platform to verify the control method proposed in this paper.Mainly include:When the secondary open loop,the stability and effectiveness of the primary controller were verified with the load changed;After the closed loop control was added to the secondary side,the effectiveness of the primary controller and the secondary controller were verified under the condition of load variation.At the same time,the efficiency of the WPT system was measured under the condition of the same output state and the different primary current,and the correctness of the method for selecting the reference value of the primary current was verified. |
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