Research, Unity Power Factor And Particle Swarm Optimization-based Active Power Filter

With the development of the the technique of power electronics ,the load with nonlinear,impactive,unbalanced characteristics have been increasingly used in power network. They generate lots of harmonics. APF(Active Power Filter)has been a key project in power electronics application technology,as the most effective method to solve harmonic and reactive power currents pollution,and improve the power quality.Firstly,this paper depicts the reasons of harmonic and reactive power's bringing and the harm,then introduces the methods of harmonic restraining and reactive power compensation. Secondly,the basic theory,the class,the harmonic current detectiong and current control methods in common use are described and summarized in detail.Based on the analysis of harmonic and reactive current detection technique based on unity power factor,the drawback of the butterworth low-pass filter which is used generally is described ,such as output ripple and failling to satisfy better precise and more high response speed. In order to solve the problems,this paper presents a novel optimization design method for digital low-pass filter which uses synthetically the average low-pass filter and butterworth filter,the improved method reduced the detecting error and obtain better precise and more high response speed. In this paper,the forward system is added to the conventional triangular carrier current control method, which is used in active power filter generally,to improve the frequency characteristics. The feasibility and superiority of the improved current control method are examined by dynamic simulation and theoretical analysis.This paper expatiate the basic theory of active power filter based on unity power factor control,and then,from the point of view of the active power balance,derivates the mathematical model of three phase three wire active power filter. In order to solve the problem of the tuned parameters of PI controller and the single controller failling to satisfy the requirement to the following performance in the system startup period the disturbance rejection performance during the steady state,the Particle Swarm Optimization is proposed to optimize the PI parameters and subdivision control method is adopted. The simulation results verify the methods can improve the system dynamic response characteristics effectively. Finally,through system simulation in the software of MATLAB,the results show that this compensating approach is viable.