Extraction Of Microgird’s Information Based On Adaptive Notch Filter And Its Applications

In order to monitor the operation state of the power system real time, the systemparameters that contain frequency, amplitude, phase-angle, harmonics and sequencecomponent of unbalance status must be measured precisely and fast. Estimation of theseparameters is very important in control scheme for grid-connected distributed generation(DG) system. Whether their true values are detected accurately and rapidly will directlyinfluence the effect quality of connected-grid DG. Adaptive notch filter (ANF) is animportant technique which can provide fast and accurate estimation of the signal’sinformation in the presence of frequency and amplitude variations.Firstly, the fundamental theory of ANF is introduced. Its performance is evaluatedthrough theoretical analysis contained transfer function, amplitude-frequency andphase-frequency curves and simulations on estimation of frequency, amplitude andharmonic.Secondly, for single-phase system, a new approach for reactive power measurementbased on ANF is proposed. With regard to three-phase system, a new three-phase ANF isproposed and an approach for extraction of sequence components is introduced. Moreover,a simple harmonic detection method for three-phase system is presented. Simulationsresults confirm the validity of these techniques.Thirdly, applications of ANF in grid-connected distributed generation system arestudied. Control schemes for single-phase and three-phase grid-connected distributedgeneration system based on adaptive notch filter are proposed. The validity of these twocontrol methods are confirmed by simulations compared with the traditional approachbased on phase-locked loop (PLL).Finally, the equation of the exiting ANF is modified on the base of analysis ofshortcoming of ANF. Then, the amplitude adaptive notch filter (AANF) is obtained. Itsperformance for estimation of power system parameters is researched. Its structure ismodified continue and simplified AANF is presented. Its function for frequency andamplitude tracking is compared with traditional ANF. Simulation results demonstrate that the AANF and simplified AANF have a better performance than ANF.