Research On Key Technology Of Three-phase Four-leg Active Power Filter

At present,the power quality control of building distribution network is one of the key problems of power system.In this paper,the three-phase four-leg Active Power Filter is taken as the research object.The main work is as follows :1?The working principle of APF is analyzed,the mathematical model of APF in abc and dq0 coordinates is established,and the principle of current decoupling control in these two coordinates is illustrated respectively.2?The resonance suppression method of LCL filter in APF is studied.Firstly,the root cause of the resonance of LCL filter is analyzed,then the resonance suppression method based on passive damping is compared and improved,followed by an in-depth analysis of the resonance suppression method based on active damping.3?The grid-connected current control algorithm of APF is studied.Firstly,the three bridge legs of the APF are designed to decouple the current from the fourth bridge leg in the harmonic detection link.Combined with PI control and repetitive controller,a dual-mode control method is designed to solve the problem of grid frequency offset,the number of sampling points per fundamental cycle of dual-mode repetitive control is non-positive integer,and the traditional phase compensation link cannot accurately obtain the appropriate integer beats.The dual-mode control method can eliminate the odd and even harmonics in the grid,and realize the fractional-order phase compensation.4?Finally,the experimental results verify the feasibility and effectiveness of the proposed method.Figure [95] Table [6] Reference [72]...