Study On Bi AC-DC-AC Topology And Control Strategy Of ICPT System

As a novel power transfer technology, inductively coupled power transfer(ICPT)technology has been widely researched and applied. Traditional AC-DC-AC type ICPTsystem has several drawbacks such as low system efficiency, control complexity andlow power density, which restricts the popularization and application of wireless powertransfer technology in practical system. Variation of load and operation randomness willdegrade the performance and stability of ICPT system. Thus how to improve systemstability with varying load is an critical and urgent problem to solve.This paper proposed a bi AC-DC-AC converter. The filter capacitor and rectifiercould be reduced and conversion efficiency, power density and input power factor couldbe improved. Based on impedance analysis, the LCL-S type topology was analyzed, toobtain the output-input relation of primary resonant current. A steady primary resonantcurrent control method was proposed to enhance the power transfer magnetic fieldstability against dynamic variation of primary resonant current caused by uncertain load.To deal with the application difficulty of feedback on RMS current, a waveformanalysis was used to decrease the control complexity, and guarantee the stability ofprimary resonant current with varying load. Furthermore, to ensure the legality andsafety of load, a useful unexpected load detection technique based on the measurementof resonant current peak was introduced.To satisfy various voltage level requirements, two output voltage adjustable controlmethod, the equal pulse width chopping control and the resonant half-sine waveintermittent control, were proposed based on the characteristics of primary andsecondary side. Moreover, how to choose between the soft-switching implementationmethod and intermittent method for the output voltage adjustable control were proposedin this paper.Based on MATLAB/SIMULINK and experimental study, the stability of controllerwere verified. The results indicated that the stability of system with steady primaryresonant current control method was better, and the proposed adjustable control methodcould meet various load voltage requirements.