The Research Of Three-phase DC Side Active Power Filter Based On Asymmetrical Dual-Boost Structure

With the development of power electronics, the power electronic devices are alsoused widely and play very important role in the national economy. But these deviceswill produce a lot of harmonics when they are used and the influence of these harmonicsto the grid are increasingly serious, various kinds of faults and accidents caused byharmonics occur continually which causes a lot of unnecessary losses to the nationaleconomy, production and life.Foreign institutions investigate the maximum harmonic source of different powerconsumers and find the maximum harmonic source from rectifiers account for89%. Soall of the countries around the world do a lot of research for the elimination ofharmonics of the rectifier bridge load and foreign countries mainly forced the powerconsumers to improve the power electronic devices to avoid producing harmonics.However our country is still a developing country, it is impossible to improve all thepower electronic equipments, so we mainly eliminate harmonics by installing harmonicfilter devices, that’s active power filter. For three-phase rectifier bridge load, thestructure of parallel APF mainly has three-phase ac and dc side APF. While compared tothe ac side APF, the dc side APF has the advantage of simple structure and lowcompensation capacity and has an enormous application prospect. So this paper mainlyproposes a symmetric dual boost three phase dc side filter for three-phase rectifierbridge. Compared with traditional dc side APF, the asymmetrical dual Boost structurereduces the number of active switches and capacities. and the cost, and improve thereliability of the circuit. So it has the enormous application prospect.Based on the asymmetrical dual boost structure, this paper proposes circuits ofasymmetrical dual boost three phase dc side filter based on the low frequency switchesand the asymmetrical dual boost three phase dc side filter based on coupled impedanceand their principles are introduced. Due to the special timing sequence requirements ofthe three switches in the asymmetrical dual boost structure, this paper uses the doubleedge modulation method to ensure the proper work of the circuit.In the aspect of control strategy, this paper uses the double loop average currentcontrol. This paper firstly establishes the model of the circuit’s voltage loop and currentloop. Because there is no steady-operating point, so we use twice-averaged method tocreate transfer function of the voltage-loop. Then we get the compensator parameters based on this model. The feasibility of the proposed filter structure and the correctnessof the design process are verified by simulation.By comparing the compensating capacity and switch stress of asymmetrical dualboost three phase dc side filter and the traditional three phase dc side filter, thetechnological superiority of asymmetrical dual boost three phase dc side filter isstrongly proved.