Research On Mid-Point Capacitor DC-Link Active Power Filter

With the development of the power electronics, the non-linear load leads to a great amount of harmonics and is becoming the greatest threat of power system running steadily. For the safety problem of transmitting and transforming power is critical for our country’s developing continuously, theoretical research and industrial product on power harmonic suppression becomes the focus around the world.Aimed at the disadvantage of traditional ac-link shunt active power filter(active power filter, APF), this dissertation proposes a new APF topology, which named the mid-point capacitor dc-link APF, to achieve better compensation performance and greater capacity. The main work mainly expounds the new topology, operating principle, control strategy, and the modulation strategy. To verify the feasibility, the simulation of the new topology has shown at last.First of all, structure and operating principle of the proposed topology is given. Based on this foundation, feasibility of the mid-point capacity dc-link APF has been checked.By using the basic circuit principle, this paper builds a mathematic model of the new topology, which points out that the capacitors in dc side exists voltage bias, and coupling.Then, two loop control system is designed to achieve the goal. The current inner loop obtains the reference after the power of the whole system has been carried out. On the other hand, combined with features of the new topology, the paper mainly designs the decouple control strategy, which contains a simple and useful decoupling matrix. The modulation strategy of high frequency switches and commutation strategy of low frequency switches is respectively selected further more.For simplifying the engineering application, the paper gives the option of the main circuit component parameter. Finally, a simulation on the MATLAB platform is built to validate the feasibility of the proposed topology with all of these theoretical designs. While compared on the compensation performance and capacity under the same load, the result verifies that this new topology has an advantage on these aspects.