Harmonic Control Of A Coking Plant Workshop Substation Based On Passive Filter

Variable frequency motor sets are widely used because of its technical and economical superiority in modern industry. At the same time, they cause more and more serious harmonic pollution, which have seriously influenced the power quality of electrical utilities. Because of its simple structure, less equipment investment, high operation reliability and low operation cost, passive power filter has become the most common harmonic control and reactive power compensation equipment in power system at present. The passive filter design method was studied, and the overall set of the passive filter cabinet was designed in this thesis.Firstly, this thesis takes harmonic contol project of a workshop substation in Hebei Xu-yang coking plant as the background. The three-phase voltage and three-phase current in power distribution transformer0.4kV side were measured. Through the analysis and calculation of the measured datas, the load characteristics was found, which changed stably and have high power factor. The harmonic contents were also derived out. Using capacitor bank for reactive compensation in the original site as a load disturbance source, through the steady-state measurement of harmonic current variation and the harmonic voltage variation before and after the capacitor bank was switched on, the system harmonic impedance locus was calculated, which was called harmonic impedance incremental calculation method. Through establishment of system harmonic model, the principle of capacitor causing harmonic amplification was analyzed. The comparison between harmonic impedance incremental calculation method based on steady-state measurement and approximate estimation of harmonic impedance method showed that the harmonic impedance incremental calculation method has a high precise. The results of the harmonic impedance based on the harmonic impedance incremental calculation method was finally adopted for the filter design.Secondly, according to the test data and the harmonic impedance calculation results, this thesis designed two kinds of filter design which were the5th single tuned filter and the5th and the7th single tuned plus the11th high-pass filter. And two kinds of filters were analyzed in detail. Considering the practical situation, the5th single tuned filter was determined to be used. Research on the5th single tuned passive filter cabinet. The cabinet’s components were calculated and analyzed. Electrical characteristics measurement of the cabinet was completed. The discharge circuit performance and transient switching performance were analyzed especially.At the end, system harmonic level of the passive filter cabinet was measured before and after the filter was swiched on. Using Matlab/Simulink established a passive filter system simulation model. The comparison between simulation results and measured results vertificated the accuracy of simulation models and the effectiveness of passive filter.