| In recent years,with the rapid development of economy,more and more power electronic devices and nonlinear loads are widely used in various fields.There have a serious impact on the power quality of the public power grid.On the other hand,Sensitive equipment have higher requirement were being placed on the power quality.Active power filter(APF)is widely used in low voltage distribution network as an important means to restrain the harmonic pollution and improve power quality.when the APF is working,the on-off of the switch will produce the ripple current.Switching ripple current will increase the loss of other load in the power grid,reduce their service life.Compared with the L filter,the LCL filter has higher high frequency impedance,which can filter the ripple current,and has been applied to a variety of power electronic equipments.When the LCL filter is applied to the APF,it not only should consider the switching ripple current suppression capability of LCL filter and the resonance problems,but also consider the impact of LCL filter on tracking performance for APF.This paper simplifies the mathematical model of LCL filter and obtains a simple and effective design method for LCL filter.On the resonance problem of LCL filter,the passive damping method and active damping method are studied to suppress the resonance,and the stability of the discrete system is analyzed.The control method,which combines fractional harmonic detecting and feedforward compensation,is applied to the APF system based on LCL filter.The basic principle,advantages and realization methods of the control method are analyzed.The simulation model is built in MATLAB/Simulink to verify the correctness and effectiveness of LCL filter design and APF control method.On the basis of the existing hardware platform,the hardware and software system is improved and optimized,so that the APF experimental device is designed to achieve the related functions.The system runs stably,and the compensation result is also expected. |
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