Research On Active Power Filter Based On New Seven-level Converter

Since the third revolution of science and technology,the development of technology has caused a large number of power electronic devices to be widely used in industry,transportation,and life.While benefiting all aspects of human society,the application of a large number of power electronic devices has also generated a lot of harmonics.This has seriously reduced the power quality of the power grid.At the same time,due to the existence of the stumbling block of harmonic pollution,the further development of power electronics technology will become extremely difficult,so the management of harmonic pollution is of great significance.The active power filter can quickly and accurately track the harmonic command current,and has good real-time and dynamic characteristics.It has become the main method for harmonic suppression at the current stage.In order to improve the shortcomings of traditional multilevel active power filters with complex topology and excessive component usage,this dissertation proposes a new seven-level converter topology which uses fewer components and has a simpler and more reliable structure,and applies it to active power filters.This dissertation first analyzes the working principle of the new seven-level topology,including the power switch on-off and the DC capacitor charging and discharging status.The overall scheme design of the active power filter based on the new topology is designed,and a mathematical model is given.Secondly,the key control technology of the active power filter is introduced in detail in this dissertation.The harmonic current detection method based on the instantaneous reactive power theory is used to detect and separate the harmonic and reactive components,and repeated controller and quasi-proportional resonance controller are selected for tracking control of command current.This dissertation also proposes a two-stage capacitor voltage stabilization control strategy for DC capacitors,which performsvoltage regulator control on the DC capacitors of the new seven-level converter.Based on this,this dissertation uses MATLAB / Simulink to build a simulation model of an active power filter system based on the new seven-level converter topology,and simulates it under various conditions of the power grid and load to verify the compensation performance of the active power filter and the voltage regulation performance of the capacitor voltage regulation control strategy.Finally,based on the above theoretical analysis and simulation results,an experimental platform with DSP and FPGA as the control core and a system capacity of 13.2 k VA was built,and the program was written according to the relevant control strategies.The experimental platform was debugged with hardware and software and verified the feasibility and practicability of the active power filter based on the new seven-level converter proposed in this dissertation.