The Study On Harmonic Source Identification And Harmonic Responsibility Division In Power System

With the considerable use of nonlinear loads in power system, harmonic pollution in the power system tends to be more and more serious. Harmonic not only can cause abnormal work of electrical equipment, but also will destroy the stable operation of the power grid. In practice, the distribution network systems are endowed with a lot of harmonic sources. So each bus voltage distortion is not caused by the single harmonic source, but the effect of combined action of all harmonic sources in the grid. It is the difficult problem of power quality management to precisely divide each harmonic source in power networks contribution to the common coupling point bus voltage harmonic distortion.The existing identification and positioning methods concerning the distribution of harmonic source are summarized in this thesis. Furthermore, the advantages and disadvantages of these methods are summarized from the perspective of qualitative and quantitative analysis.For the problems of harmonic impedance is not readily to get in using harmonic impedance identification of harmonic sources, put forward the improved partial least-squares method is used to analyses the harmonic impedance estimates that estimate instead of actual measurements,and combined with impedance method by judging harmonic current flowed from that side more to determine the main harmonic source,thus achieve the purpose of identifying harmonic source.At the same time,because the focal node harmonic voltage can be made of each harmonic electric subsection phasor projection on the linear superposition, the node in the system harmonic voltage can be made of the harmonic source with the equation of time harmonic current. Based on this idea, the harmonic responsibility division method of improved partial least-squares regression is proposed. According to the measured data, the multiple feeder system of harmonic source load harmonic responsibility is qualified. Based on the current and harmonic voltage measured from the common connection point in every, using regression coefficient is obtained by using improved partial least squares. And then, the evaluation of harmonic responsibility is made on the basis of the relation of harmonic voltage and the mapping relation between the product of the regression coefficient and harmonic current. This method makes compensation for that the partial least squares method may abstain the constituents that has nothing to do with the response. It will be more excellent when the choice-making of data is not needed, especially when there are numerous data in the harmonic system. Finally, the system is equivalent to the thevenin equivalent circuit. From the module of the electric power system in Simulink, the corresponding simulation model is set up and carried on the simulation analysis to verify the effectiveness of the proposed method.