| With the increase of the proportion of uncertain attribute load in the distribution network,the stability of the distribution network becomes more and more serious.Therefore,more and more people pay attention to the problem of power quality.How to improve the power quality has become the focus of both power supply and power consumption.Distribution network is an important link connecting all parts of power transmission,among which distribution transformer is the power equipment for power distribution to users,so whether the condition of this kind of equipment is good directly affects the stability of power supply of distribution network.Based on this background,the power quality and operation state of power distribution and transformer are studied.The main research contents include: establishment of multilevel fuzzy comprehensive evaluation model based on grey relation,comprehensive evaluation of power quality and operation state of distribution transformer,design and implementation of power quality on-line monitoring system of distribution transformer.Firstly,aiming at the problem that too many subjective factors of ahp lead to inaccurate evaluation results,a fuzzy comprehensive evaluation method based on improved combined weight was proposed,and a multi-level fuzzy comprehensive evaluation model was established.Triangle fuzzy number method,entropy method and ahp method are combined to form an improved combined weight method,which synthesizes the advantages and disadvantages of subjective and objective weighting method.The method is combined with the membership matrix to carry out the fuzzy comprehensive evaluation.At the same time,considering that many important information will be lost when the ultimate state is judged by the maximum membership principle,the ultimate state is determined by the maximum membership validity principle.The grey correlation analysis method is used to establish the fuzzy comprehensive evaluation of the second-level fuzzy,and the results of the first-level fuzzy comprehensive evaluation are verified,so that the evaluation results are more convincing.Secondly,the multi-level fuzzy comprehensive evaluation model is used to comprehensively evaluate the power quality of distribution trans-formers in terms of harmonic,voltage deviation and other power quality problems.Compared with other analysis results,the obtained evaluation results are more objective and reasonable.Then,aiming at the problem that the running state of distribution transformer seriously affects the safety of distribution system,a four-layer fuzzy comprehensive evaluation model suitable for the running state of distribution transformer is established and multilevel fuzzy comprehensive evaluation is carried out according to the need of practical maintenance.Finally,the power quality data collection and analysis are realized by building the power quality on-line monitoring system of distribution transformer. |
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