Research Of Shunt Active Power Filter In Three-phase Three-wire System Based On DSP Control

With the continuous development of power electronics technology, the increasinglywidespread application of power electronic devices in the grid harmonic pollution moreserious, a large number of harmonic currents and the impact of reactive power to the gridvoltage and current to produce a serious distortion, thus caused a serious impact on the powersystem. Active Power Filter is a new power electronic devices, it can dynamically suppressharmonics and reactive power compensation. Compared with the passive filter cancompensate the harmonics change in the size and frequency as well as changes in the reactivepower is now widely used in a device of power system harmonic compensation.Active Power Filter is a strong coupling, time-varying nonlinear system, control is morecomplicated. This paper studies project design and implementation of shunt active powerfilter control system, including the control method of harmonic current detection, the spacevector strategy, the design of hardware and the development of prototype.This paper presents an introduction to the cause and perniciousness of the harmoniccurrent, the ways to suppress harmonic and the active power filter development, classificationand the basic principle. According to the application of the three-phase three-wire voltageactive power filter, in order to design control system, this paper transformed the mathematicalmodel of three-phase under static coordinates a-b-c reference frame to the synchronouscoordinates of d-q model.Secondly, p-q harmonic current detection and ip-iqharmonic current detection based oninstantaneous reactive power theory were introduced, and two detection methods werecompared. Because of active power filter is a high coupled system, so the method based onthe network voltage feed-forward decoupling the double closed loop PI control strategy, amathematical model in rotating d-q coordinate system decouples. Combined with the theoryof AC motor vector control, given the space voltage vector control of three-phase three-wiresystem of active power filter, a detailed analysis of process of its implementation, by building Matlab simulation model, the feasibility and effectiveness of the proposed shunt active powerfilter control method is verified by simulation results. Meanwhile, for the entire systemsimulation, the simulation results show that the device can compensate harmonics andreactive power on the grid, the grid power factor has been greatly improved.Finally, based on all theory and simulation above, a three-phase three-wire shunt activepower filter prototype based on DSP is constructed and debugged. Through the experimentsindicate that the active power filter developed in this paper can well compensate harmonicsand reactive current.