Research On Active Power Filter Based On Multi-internal Models Compound Control And Its Application In Micro Grid

Domestic and foreign experts have proposed the concept of micro grid in recent years in order to deal with the adverse effects of large-scale new energy grid connected to traditional grid and solve the contradiction between the distributed generation and the stable operation of traditional power grid. However grid connected devices as well as single-phase/three-phase inverters and other nonlinear load are widely used in micro grid. The result is that a large number of harmonics and unbalanced currents are injected into the micro grid.which seriously endanger the safe and reliable operation of micro grid system. It seriously endanger the safe and reliable operation of the system. In order to solve this problem, the active power filter is used to improve the power quality of micro grid, which has become a hot research direction.In this paper, it is proposed to use multi-internal models compound control strategy to design the current loop controller of three-phase four-wire APF in the αβγ static coordinate system, which combined with the theoretical knowledge and key technology of active power filter. And a three-phase four-wire APF prototype for low voltage micro grid is developed through theoretical analysis, mathematical modeling, software simulation and hardware platform testing. The following results are obtained through the research of this paper:(1)On the basis of summarizing the relevant theoretical knowledge of active power filter and the latest research results of power quality in micro grid and its control technology, it is proposed to use multi-internal models compound control strategy to design the current loop controller of three-phase four-wire APF in the αβγ static coordinate system based on the principle of non harmonic detection control.(2)The four leg inverter is selected as the main circuit of the three-phase four-wire APF based on the comparative analysis of different topologies. And the grid side current and DC bus voltage are selected as the three-phase four-wire APF state variables to establish its mathematical model.(3)The multi-internal models compound control strategy in the αβγ static coordinate system has the advantages of high dynamic response speed, high steady state precision and small calculation quantity. The fast tracking of the fundamental component can be achieved by using the characteristics of frequency adaptability and stability margin of resonant vector control. And the effective tracking control of periodic harmonic signals is realized by using the characteristics of repetitive control computation.(4)The three-phase four-wire APF with multi-internal models compound control strategy is realized by modeling analysis, programming software, hardware design and experimental platform, and is verified by simulation and experiment.(5)The research results showed that the three-phase four-wire APF with multi-internal models compound control strategy in this paper can effectively solve current waveform distortion, low power factor, load imbalance problem in micro grid of low voltage, and had a strong guiding significance for the further engineering application in micro grid.