Research Of Harmonics Source Localization In Power System And Its Software Design

With the development of science and technology,the use of power electronic devices is becoming more and more common in our daily life.The use of electronic devices has a great impact on the power system,which makes it seriously polluted by harmonics increasingly serious,with people's demand for electric energy,the demand increases gradually,the power supplier needs to improve the quality of the distribution network.At present,the operation of distribution network is more and more seriously affected by harmonics,so the optimization of power quality and the control of harmonics are becoming more and more important.And the precondition and emphasis of harmonic control in distribution network is harmonic source location detection,the purpose of this paper is to realize the function of locating harmonic source quickly and accurately,it will be very important for harmonic control and power quality improvement.Firstly,the concept and model of power quality and harmonic source are systematically reviewed,and the harmonic and its characteristic quantity are introduced,then the principle of harmonic source location detection is expounded from the point of view of electrical engineering,to realize the function of harmonic source location,the first thing is to calculate the harmonic emission level of the system side and the user side at the common node,determine the respective harmonic responsibility of the system side and the user side.Then the methods of harmonic emission level estimation and harmonic impedance calculation based on partial least squares regression are analyzed,the harmonic voltage and harmonic current signals are measured synchronously at the common connection points,the partial least squares regression algorithm is used to solve the regression coefficient to decompose and filter the measured data,extract the most explanatory comprehensive variable for the dependent variable.The harmonic impedance of the system is mapped by the regression coefficient,and the harmonic emission level of the user is tracked and calculated.The calculation formula is derived,the concrete steps and flow chart are summarized.At the same time,the defects of this method are also pointed out,an improved partial least squares regression method is proposed for its limitation,first,orthogonal projection is used to process the sampled data,we can delete information about independent variables within an independent variable,thus,this new method improves the practicability and accuracy of the algorithm.Then the partial least squares regression method and the improved partial least squares regression method are applied by the simulation model established on Matlab/Simlink,the simulation results are analyzed and compared,it can be seen that the evaluation effect is relatively good,compared with the traditional evaluation method,the improved method has higher stability and accuracy.Finally,based on this method,this paper studies and designs the software of harmonic source location system based on Lab VIEW,by collecting the data of harmonic voltage and harmonic current at the common connection point(PCC),the harmonic impedance and harmonic emission levels of the system and the user at the common node are calculated by the software,judge the responsibility rate of each side,so the function of locating harmonic source on system side or user side can be realized.Through the field test in the laboratory,it is proved that the software has good function of locating harmonic source.