Studies Of Comprehensive Evaluation Methods Of Power Quality

Due to the complexity and randomness of the grid disturbance, there are some difficulties to make an comprehensive evaluation of power quality indicators. Currently there is no an accurate and generally accepted quantitative calculation comprehensive evaluation method. Make an correct evaluation of power quality not only necessary to clarify responsibilities and obligations of electricity users and electricity sectors, to improve power quality and meet customers' needs, but also for electric power industry to adapt to market competition and sustainable development. According to actual needs, the paper puts forward an comprehensive evaluation method based on fuzzy backward cloud model, and the method is used for power quality comprehensive evaluation.The paper analyzed the domestic and international power quality evaluation methods, in-depth discussed the fuzzy evaluation method and cloud model evaluation method, and put forward. fuzzy backward cloud model based on this.The model organic combination of randomness of cloud theory and fuzziness of fuzzy theory, to determine the fuzzy membership function by cloud theory, and use fuzzy logic calculate the eigenvalues of the cloud model, introduce the randomness of cloud model to fuzzy logic, constitute mutual mapping between the concepts of qualitative and quantitative. Power quality comprehensive evaluation is the use of this feature, convert rank qualitative concept into quantitative expression. The simulation results show that the results derived from fuzzy backward cloud are more objective.Using cooperative game combinatorial optimization method to determine the final weights of the power quality indicators, combined the results of several typical subjective weighting methods and objective weighting methods.Determine the standard grade cloud model of each index based on the boundaries of each index level. Using of the final weight of each indicator and fuzzybackward model to determine comprehensive standard cloud, to complete the comprehensive evaluation of power quality disturbance by calculating the similarity.Power quality evaluation method simulation. Adopt the method of paper provided, according to voltage deviation, voltage sag and other seven power indexes to comprehensive evaluate power quality level. By comparing the power quality comprehensive evaluation results of traditional cloud model, the fuzzy evaluation model and fuzzy backward cloud model, proved the method in this paper is more objective, accurate and stable.