Study On Problem Of Distribution Network Voltage Fluctuation And Flicker

With the rapid development of Chinense economy and the improvement ofscience and technology, the demand electronic power is lager and lager. At the sametime, electricity load is becoming nonlinear, asymmetry and volatility. As theproportion of these electricity load increase, brings new threaten to the qualityof the power grid. As an important index of power quality, voltage fluctuation andflicker is receiving more and more attention.This paper starts with the basic concepts of voltage fluctuation and flicker. Thenintroduce the definition and characteristic quantities and evaluation standards offlicker, finally the harm and compensating measures of flicker is mentioned. Theexisting detection method for voltage fluctuation and flicker and its principals andcharacteristics are also discussed in this paper. On the basis of the block diagram forthe flicker measuring apparatus recommended by IEC, by modeling and emulation,this paper tests and verifies the feasibility of the squaring demodulation methodrecommended by IEC for the detection of voltage fluctuation and flicker. On this basis,the sources of error and its improving measures are briefly discussed. The actor findsthat some of the power quality test points’ three-phase voltage flicker is far beyondthe normal range when the testing the power quality of a substation. So usesimulation software to find the advantages and disadvantages of square method atthe situation of single-phase grounding. Finally improve the square detection methodto avoid the flicker aberration that happened on the single-phase grounding situation.For the detection of non-stationary voltage flicker signal with sudden change, thepaper focuses on the method based on wavelet transform and simulating synchronouswave detection. By emulation, this method is proved to be effective for the detectionof fluctuation and flicker signal. With the wavelet multi-resolution analysis, theamplitude, frequency and other information of the fluctuation and flicker signal canbe accurately detected, so is the stating time and ending time of the fluctuation andflicker.