Low Voltage Distribution Network Harmonic Analysis And Control On Key Technology Research

In recent years, low voltage distribution network harmonic analysis and control technology of power system has become an important research field. At present, More and more nonlinear electrical equipment in the low-voltage user terminal widely used, it gave the low-voltage power distribution network brings a lot of harmonic pollution, it makes the low voltage distribution network electric energy quality drops badly. The accident caused by harmonic pollution happen ceaselessly, so the real-time analysis, measurement of power system harmonic content and grasping the harmonic content by nonlinear device generated is very necessary to reducing the harmonic harm.In this paper, the commonly used in power system harmonic analysis method and control measures, reactive power compensation technology are introduced. In view of the advantages and disadvantages of various methods for harmonic analysis, this paper proposed one kind improved harmonic analysis method which is based on the least squares method and FFT. By making simulation analysis and comparison analysis, this method proved that it can get more accurate harmonic parameters. Finally, this paper combining with the actual engineering have a harmonic analysis to the quartz electric heating tube power regulating device and calculate the harmonic current and reactive power compensation and take corresponding measures to make the power factor to achieve state specified values above0.9. The work in this thesis is as follows:Firstly, the paper mainly introduce this topic research goal and the significance and point out the necessity of harmonic analysis and management. The analysis shows that the harmonic presence in the electric system will bring a lot of harm to the low-voltage distribution network. It introduces the harmonic development, the harmonic current research situation at home and abroad and the development trend.And then, from the shallower to the deeper introduced the concept of harmonic, harmonic generation mechanism, general harmonic standards and limits, various harmonic analysis methods and their advantages and disadvantages, synchronous sampling concepts, the Fourier series and the derivation process of the coefficient, the simplification of Fourier series based on the waveform symmetry, harmonic phasor deconvolution, Fourier transform, DFT harmonic analysis method, FFT harmonic analysis method, the cause analysis of spectral leakage and fence effect, the advantages and disadvantages of various window functions which were used to reducing spectrum leakage and fence effect at the present stage, windowed interpolation harmonic analysis method and steps.Secondly, this paper proposed one kind improved harmonic analysis method which is based on the least squares method and FFT. Through making simulation analysis and comparison analysis, this method proved that it can get more accurate harmonic parameters.Thirdly, it introduced the load character of low pressure distribution network, harmonic distortion influence on power system, the methods of restraining harmonic wave, various harmonic filter, the definition of Reactive power compensation and power factor, the main factors affecting power factor, reactive power hazards, the meaning of reactive power compensation, reactive power compensation method and its comparison, the influence of harmonic on shunt capacitor in and restraining measures.Finally, combined with practical engineering, this paper did some harmonic analysis and reactive compensation calculation for the power supply and distribution system which used thyristor controlled phase shift voltage device control quartz heating pipe, given accurate calculation formula of the harmonic content power factor and the selection method of active power filter and reactive power compensation. Then we can draw the conclusion that just rely on reactive power compensation is difficult to meet the power requirements for power factor in nonlinear circuits. The solution should focus on reasonable selecting process scheme. The best method is no pollution or less pollution.