| Most power converters require input and output capacitor filters,whose purpose is tantamount to smooth voltage and suppress switching noise.However,covering the low frequency range requires huge bulk and uncontrollable large-capacity capacitors,which poses fundamental challenges to the use and promotion of some power electronic converters.With the development of new energy,power transportation and high-efficiency DC lighting,the increasing demand for high reliability and lightweight power converters also puts forward new requirements for the use of electrolytic capacitors.Therefore,the ripple cancelled came into being,and the virtual infinite capacitor(Virtual Infinite Capacitor,VIC)is part of the ripple cancellous.Because VIC can suppress random voltage fluctuations,there is no need to assume the current range in advance,and at the same time,the charge can be controlled by the charge controller to ensure the smoothness of the voltage,so this paper studies VIC.However,the traditional VIC control strategy has many measurement parameters,resulting in an increase in the cost of the VIC and a decrease in reliability.At the same time,there is a need for coordinated control between the VIC and Power Factor Correction(PFC)circuits,resulting in a reduction in power factor,which restricts the application of VIC.In response to the above problems,the specific work of this paper is as follows:(1)Introduce ripple cancelled and VIC.Analyze several structures and schemes of ripple cancellous in recent years,and analyze numerous applications of VIC.Analyze the working principle of VIC and charge controller,and adopt traditional sliding mode variable structure control strategy to control VIC.Finally,a PFC control strategy simulation model with VIC based on sliding mode movable structure is built,and the correctness of the VIC principle is verified.(2)A control strategy for restructuring the integral sliding mode movable structure is proposed.Taking the bidirectional buck/boost converter as an example,the principles of sliding mode variable structure control and PI control is analyzed,and reconstruction integral sliding mode variable structure control strategy are proposed.Based on the analysis of the VIC principle,a variable structure model was established,on which the formula derivation and equivalent replacement were carried out,a new sliding mode switching surface was constructed,and an integral reconstruction observer was proposed to replace the physical sensor for current sampling.Finally,Matlab simulation is used to compare the three control strategies to verify their feasibility and effectiveness.(3)Voltage-following constant duty cycle control strategy is suggested.The voltage follower is used to replace the traditional VIC charge controller to achieve decoupling control of the VIC and PFC circuits.Then,on the basis of studying the power of the power grid and the relationship between the power grid and the voltage ripple and capacitance,the voltage control strategy after the constant duty cycle is mathematically analyzed,and the constant duty cycle is used to improve the power factor of the PFC circuit.Finally,VIC simulation model of voltage-following constant duty cycle control strategy is constructed,and the influence of simulation experiment waveform on power factor is analyzed to verify its correctness.(4)Construction of Hardware In the Loop Simulation.Hardware In the Loop Simulation of FPC with VIC was built.Input is 35 VAC with output is 45 VDC,and it power is 68 W.It can test the correctness of the VIC principle. |
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