Design Of Three-level LCL Active Power Filter

With the gradual use of power electronic device,a large number of nonlinear loads bring serious harmonic pollution to the power grid.The requirements for power quality in China is becoming higher and higher with the development of power industry.Active power filter is getting more and more attention as an important link of harmonic control in power quality.This paper firstly has a brief introduce on the basic principle of active power filter,then,make a discuss on the performance of low-pass filter in the instantaneous reactive power harmonic current detection method,verified by simulation and determined the optimal parameter selection of Butter-worth low-pass filter.In this paper,the amplitude-frequency characteristics of L type and LCL type output filters are compared.Finally choose LCL as the output filter of APF.To the problem of resonant peak,the method of LCL capacitor branch series resistance is chosen by comparison.In this paper,a series damping parameter tuning method based on attenuation coefficient and damping loss constraints is proposed.On the premise of satisfying the harmonic distortion rate,the harmonic suppression at the switching frequency is guaranteed.and verified the rationality if the theory by matlab simulation model.Finally,a three-level LCL active power filter model is built based on the designed parameters.The digital control is realized by DSP,and the feasibility of the theory is further verified.