Analysis And Control Of Passive Virtual Capacitor

The inductive resonance coupling based wireless power transfer(WPT)is undergoing a long-term development and has been applied in many fields,such as electric vehicles,portable devices,and sensor networks.Compare to conventional inductive contactless power transfer methods,the inductive resonance coupling wireless power transfer method has many advantages,including high efficiency,long transmission distance,high penetrability.The main problem in inductive wireless power transfer is that the circuit of wireless power transfer system may work in non-resonance mode due to the variance of frequency,distance or the reactive impedance,which may reduce the transmission efficiency and increase risks of over-voltage of switches and current reverse in circuits.Besides,in multi-objective wireless power transfer systems,power of different loads can be influenced by many factors like mutual inductance,load weight and distance.Appropriate power distribution is also an emergent problem need to be solved.This paper aims to solve these two problems and verify the solutions theoretically and experimentally.As for resonance maintaining,a mathematical analysis is done firstly.Base on the analysis,the topology and circuit model of virtual capacitor is introduced.Then,the control method and detailed realizing is proposed.Finally,the simulation and experiment are carried out.Based on the resonance maintaining of the virtual capacitor,the problem of appropriate power distribution in multi-objective wireless power transfer system is studied.A mathematic-based analysis on load impedance and mutual inductance,which influence loads power,is done,and the topology that can control load impedance is proposed.According to the mathematic model and topology,a distribute control method which realizes appropriate power distribution is proposed.Finally,simulation and experiment for verifying the proposed method are carried out.At the end of this paper,a conclusion of the whole paper is done.According to the shortage of the passive virtual capacitor,future work is expected.