Harmonic Assessment And Management For Regional Grids

With the continuous expansion of the scale of the regional power grid, nonlinear loadsas harmonic source in power system significantly increase and the capacity of a singlenonlinear load increases. The problems of harmonic pollution caused by current and voltagewaveform distortion become severe. A large number of harmonics current generated by theharmonic source is injected into the grid. The overall trend in the harmonic levels isincreasing in common connection point, resulting in the deviation of sinusoidal voltage anddeteriorating the power quality. The safe and stable operation of power equipments and theentire power system is gradually endangered. Given this background, harmonic assessmentand management for regional grids are investigated in this thesis which is mainly organizedfrom the following aspects:(1) Method for calculating harmonic current limits considering a load coincidencefactor is presented. Based on the national standard GB/T14549-93and IEC standard61000-3-6, the relationship between the power supply equipment capacity at the point ofcommon coupling and the customer protocol capacity is formulated. The coincidence factorin the IEC standard is carefully examined and proposed to be employed in the nationalstandard. A new method is next presented to determine the harmonic current limits. Theproposed method is demonstrated by the joint support from the national standard GB/T14549-93and IEC standard61000-3-6.(2) The assessment of total distorted rate of the harmonics is presented. In this paper,the probability statistics is improved. The total distorted rates of the harmonics of threephases in the common connection point are evaluated with the grade, fully consideringvolatility of indicators in the assessment process. The comprehensive evaluation result ofharmonic voltage in the common connection point is acquired after gaining the weights forthree-phase by the sequence synthesis. The harmonic comprehensive evaluation caneffectively measure the harmonic levels for regional grids.(3) The constructive frame structures of the technical guide and managementregulation for regional grids are presented. For the problems existing in the harmonicmanagement of regional grids, this paper suggests building up the frame structures of thetechnical guide and management regulation for regional grids. The technical guide willprovide technical support for the harmonic management work. The management regulationwill clearly define the responsibilities of some departments in the harmonic management work. It has positive implications for regional grids’ harmonics to form normalizedmonitoring, scientific suppression and standardized management.Finally, several conclusions are obtained based on the research and directions in futureare indicated.