The Study Of Three-phase Four-wire Active Power Filter

The study did a research on harmonic sources appeared in the grid, extend form harmonic problem of electric vehicle charging stations. The existence of harmonic sources cause a large number of harmonic current and reactive current flow into the grid, and make a serious threat to the quality of the power and the safe operation of the accessed user equipment. More and more attention is paid on quality problems of power caused by a large amount of application of electronic equipment. Harmonic currents and reactive power are the two factors that endanger the safe operation of the grids. The increase of system reactive power will cause the increase of line losses of transmission and distribution grid, and the capacity of equipment; the increase of harmonic current will increase loss of electricity equipment, or even damage the equipment and bring a variety of adverse signal interference at the same time.This study did a research on the three-phase four-wire SAPF that can be applied to three-phase four-wire system. The research is based on instantaneous reactive power theory, and analysis instantaneous power components by the application of coordinate transformation, Fourier series decomposition, and symmetrical components. And discuss the influence of grid voltage distortion to d-p algorithm, while derivation the positive sequence and negative sequence component transformation matrix under the α-β orthogonal coordinate system by the use of symmetric vector method. Then introduce synchronous rotating coordinate system by calculating the fundamental positive sequence and negative sequence component, and use PAPK to transform to extract load current fundamental negative sequence active, and remove it from command current. So that the compensation power can maintain in the adjustment rang on the DC side bus voltage and ensure the power balance of SAPF. Finally verify the accuracy and feasibility of the improved algorithm form simulation experiments.After the completion of the study of core algorithm, research to realize the three-phase four-wire SAPF begin to start. First is the program of the overall system. Devise the main circuit topology, select the main components, set the relevant parameters, and propose the ideas of control the hardware system. That is adopted the modular thinking, combined with the advanced technology, defined the function of each module, study the principles, and design the realizable processes. Second, propose the ideas to realize the system software. That is by the use the modular thinking to achieve the requirements of control the system function, according to the function and works of various functional modules. Last, analyzed and summarized the experimental results and the completed research, and also prospect the future research work.