The Research Of Parallel Active Power Filter Based On Adaptive Algorithm

With the rapid development of power electronic technology,the application of power electronic devices is becoming more and more extensive,This has brought great convenience to people's life,But the power electronic device has the characteristics of nonlinearity,so the harmonic pollution of power system is becoming increasingly serious and the power factor decreased significantly.Traditional passive power filter as a passive compensation device,has been unable to meet the requirements of the compensation.While active power filter(APF)is a kind of active compensation device,which can compensate the harmonics of different frequency and amplitude.So it gets more and more attention.This paper mainly reaseach on the Three-phase Three-wired Shunt Active Filters.the two key technologies of APF are studied which is based on the topology and principle of it are introduced: The harmonic current detection and the control strategy.In this paper,the adaptive harmonic detection algorithm is selected for harmonic current detection,this algorithm based on adaptive noise cancellation.In view of the traditional variable step algorithm based on hyperbolic tangent function,a new harmonic detection algorithm was proposed.The new harmonic detection algorithm utilizes the mean value estimation of the feedback error to control the step size and the weights update,which can effectively reduce the influence of the system noise in the gradient estimation.In addition,the normalized algorithm is introduced in the process of updating weights to further enhance the disturbance capability of the algorithm.Finally,the momentum factor is added in the iterative process of weight value in order to further accelerate the convergence rate.the inner loop of the control circuit applies the hysteresis control,for the sake of overcoming the problem that the frequency is not fixed in the hysteresis loop control,a clock is set up and the regular time hysteresis control method is adopted.In addition,The outer loop of the control circuit uses PI control to maintain the DC side voltage.Finally,the simulation model is built by MATLAB/simulink.The simulation results verified the feasibility and effectiveness of the scheme.