Research On Resonance Damping Technology Of Active Front End LCL Filter

Compared to conventional passive front-end solutions that use diode rectifier or thyristor rectification to obtain DC bus voltage from the grid,inverters with Active Front End(AFE)solutions offer many significant advantages,including lower current harmonic component,high power factor,energy feedback and networking functions etc.However,during active front-end operation,the switching operation of the power device introduces the switching times and their integer multiple harmonic current components.In order to suppress these current harmonics,a filter is added between the converter and the grid.The LCL filter is widely used as an interface for converters and power grids with the advantages of small size and high frequency attenuation effects.However,LCL-type filter is a third-order system,the frequency response at the resonant frequency resonant spikes and phase transition,which is likely to cause the converter oscillation or even unstable,so it’s needed to increase the system damping to eliminate the resonance problem.In this paper,based on the study of the resonant suppression method of LCL filter at home and abroad,a 5kW AFE system is designed.Firstly,considering the IEEE standard of grid current,the parameters of LCL filter are designed,and a simple passive damping scheme is designed.At the same time,according to the parasitic resistance effect of the actual inductance,a new scheme of passive damping using the actual inductance parameter is proposed,and the design and evaluation of the passive damping control scheme are carried out.Secondly,the active damping algorithm based on virtual resistance method(capacitive current feedback)and low-pass filter method is designed without considering any passive damping.The controlling system is designed by means of system modeling,ensuring good static and dynamic characteristics.And the advantages and disadvantages of various active damping methods were analyzed by comparing the performance of the against the weak network.Finally,some design schemes are validated on the DSpace-based experimental platform.The results of the simulation and experimental comparison show the correctness of these designs.