Research On Optimization Of Compensation Accuracy For Shunt Active Power Filter

In recent years, the harmonic problems caused by nonlinear load become more and more serious, active power filter(APF) as an effective method of harmonic governance, more and more people have paid close attention to. As for active power filter, its compensation accuracy is paid close attention to, so how to improve the compensation accuracy of active power filter has become a hot research topic in the field of this technology. Therefore, this paper takes the active power filter as the research object, and focuses on how to improve its compensation accuracy, mainly to do the following:Firstly, the operation principle of shunt active power filter is introduced briefly, and the link of digital APF system is defined. The mathematical model of digital APF is established, which is based on the delay analysis and the current loop control algorithm.Secondly, a detailed analysis of the delay into each link of digital APF system is conducted in this paper, and the analysis results show that the delay caused by delayed a beat, anti-aliasing filter and output filter is larger than others. Analysis of the effect of time delay on the compensation precision of digital APF system is conducted, and the conclusion is that the time delay will reduce the compensation accuracy.Then, this paper introduces the principle and method of harmonic detection method of sliding window iterative algorithm based on discrete Fourier transform. Based on sliding window iterative discrete Fourier transform harmonic detection method in grid frequency fluctuation will have the problem of error detection, this paper puts forward a kind of grid frequency adaptive sliding window iterative discrete Fourier harmonic detection method. The simulation results verify the effectiveness of the algorithm.Then, the compensation performance of APF based on PI control is researched. For the problem that APF system based on PI control has low compensation precision, this paper researches the resonant control which with high precision based on the internal model principle. For the problem that the resonant control has accuracy problem in grid frequency fluctuations, the resonant control algorithm with frequency adaptive is proposed, simulation results verify the validity of the algorithm.Finally, according to the conclusion that the delay caused by digital PI control system reasons for the problem that APF system based on PI control has low compensation precision, this paper put forward a kind of control method based on time delay compensation, the simulation results show that the control method based on time delay compensation can effectively improve APF’s compensation accuracy.