Research On The Application In Special Load Case Of Active Power Filter

Recently, a large number of power electronic devices connected to powersystem greatly endanger the safe operation of power systems and other powerconsumers due to mass of harmonic current it generate now. Active power filtercan suppress harmonic and compensate reactive power at the same time, with fastresponse and a good dynamic compensation effect, moving toward large-scaleindustrial application. However, there were met some potential problems with theapplication of APF in the complex industrial filed. Therefore, to study theapplication of APF on the various load condition has important theoretical andpractical significance of the project. This thesis will research these issues basedon the industrial application of SAPF.Firstly, this paper presents with the working principle and structure of APF,continues with harmonic detection and directive current control methods of APF.After comparing the several commonly used harmonic current detection, thispaper put forward a new type of harmonic detection method based on theorthogonality of trigonometric function. Through the analysis of traditionalhysteresis comparison of high switch frequency, with easily burned power device,this paper used timing hysteresis comparison of track mode with fixed switchingfrequency and output current can track instruction current well. In view of theDC side voltage instability phenomenon, this paper used by increasing thecharging current with the instruction current and regulating voltage with PIcontrol.Secondly, this paper research further on the APF in the application of twokinds of special load case. When compensating harmonic source containingreactive compensation capacitor bank, the investment of APF can easily bringresonant excitation source to system and lead to the harmonic amplification andsystem instability, so this paper used third-order Butterworth low-pass filter to remove high-frequency switching harmonic current and the simulation resultsshow the correctness of the theoretical analysis. In view of linear load changes,instruction current lag of one period, therefore this paper put forward linearprediction method which based on Newton interpolation algorithm to predict thiscycle instruction current for realizing real-time compensation. The simulationresults verify the validity of the proposed algorithm. In view of the load changeirregularly, this paper put forward a new control mode by using the grid currenttracking load of fundamental current and the simulation results show that thecompensation effect is good.Lastly, we design an experiment equipment of Shunt Active Power Filterwhich uses DSP and CPLD as the control core. Then we do research of the abovealgorithm and control strategy on the experimental platform. The experimentalresults and simulation results are consistent, prove the correctness of theproposed algorithm and have important reference value for engineeringapplication.