Development Of Type I Three-level Active Filter Compensation Device

During the process of current social development,electric energy has become the most important energy source with main characteristics of cleanness,efficiency and wide range of application.With the advancement of science and technology,the power equipment connected to the power grid is becoming more and more complex.With the large-scale use of various modern power electronic equipment,people pay more and more attention to the related issues of power quality.Among the many factors that affect the power quality,the harmonic problem has become one of the most important and most concerned factors.Active power filter(APF),as the most effective and widely used means to control harmonic pollution in power grid,has become the focus of scholars.This paper takes ?-type three-level active filter as the research object,and designs an active filter compensation device that can realize the detection and compensation of the specified harmonic.The research is carried out from three aspects: harmonic detection,voltage and current closed-loop control and device development.First of all,this paper introduces the working principle of the shunt active filter,and then introduces the main circuit topology of the ?-type three-level filter used in this article and analysis the operating status.On this basis,the mathematical model of the ?-type three-level three-wire active filter is established.And the mathematical model under the three-phase static coordinate system is transformed to the two-phase rotating coordinate system for the subsequent controller design.In the study of harmonic detection,by analyzing the harmonic composition in the lowvoltage system,this paper adopts a method of half cycle DFT to measure harmonics,which only needs half cycle sampling data to participate in the calculation.Compared with the full cycle DFT,this method can greatly reduce the calculation amount and improve the efficiency of harmonic detection.In practical application,a sliding window iterative algorithm is introduced to improve the real-time performance of harmonic detection.In the design process of the voltage and current closed-loop controller,the PI controller of the voltage outer loop and the current inner loop is designed firstly.In order to improve the disadvantage that the pure PI control can not accurately track the high frequency harmonic current,the repetitive control method is introduced,and the repetitive controller and the PI controller are designed and used together.The Bode diagram and the THD value of the simulation current show that the controller can accurately track the high frequency harmonic current Frequency harmonic current.Finally,the perfect hardware circuit and software program of the ?-type three-level active filter compensation device are designed.DSP is used as the main control chip,and the analog quantity and switch quantity acquisition and output circuit and power circuit and drive circuit and clock and memory circuit are designed in detail.