The Islanding Detection Method Research Of Distrubited Generation Grid-connected Inverter

The distributed generation(DG)grid-connected inverter islandingdetection technology is studied, and a joint islanding detection method basedonFast Fourier Transform(FFT) and wavelet transform is proposesd in thispaper. The main research contents are as follows:(1) the mechanism of the islanding detectionmethoed based on invertersideis analyzed,the islanding detectionstandardsof the DG grid-connectedsystemaresummarized, the characteristics of various detection methods arecompared, several effective indicators to judge the islandingdetectionmethodsare given.(2) based on the equivalent testing circuit of the DGgrid-connectedislanding,the relationship between the distributed powersupply and power output signal is analysed quantitatively; based on thevoltage harmonic signal, a joint detection method of combining FFT andwavelet transformis proposed, which seperatively usesFFT to deal with lowfrequency partof the voltage harmonic signalof islanding, and uses wavelettransform to deal with the high frequency part,to get the specific harmonicamplitude and the threshold of wavelet coefficients, and the islanding isdetected by juding if both of the two values are over their respectivethreshold.(3) the vector control method based on grid voltage oriented is adoptedto control theDG grid-connected system, the LC filter of the system andtheRLC load of the islading detection are designed, and the simulation modelof the DGgrid-connected islading detectionisestablished in theMatlab/Simulink, the islanding in detection blind area and other power quality disturbances are respectivelysimulated, the results show thattheDGgrid-connected islanding detection method given in the paper has nodetection blind area, can effectively avoid the misoperation caused by powerquality disturbance; and the high frequency impedance method is comparedwith the method proposed in the paper, the results show that the methodgiven in the paper has a faster detection speed.(4)theDG grid-connectedislanding detection systembased on RT-LABhardware-in-the-loop platform is established, the hardware designand thesoftware programmeof the system arecompleted, and the correctness of theislanding detection method given in the paper is verified through theexperiment results.