Research On Comprehensive Evaluation Of Power Quality

With the expansion of the industrial scale and the rapid development of electronic technology, electricity has become one of the indispensable energy from all walks of life in modern society. The stand or fall of power quality has important influence on the overall efficiency of national economy and the quality of user’s life. Therefore, more and more power sectors and power users pay attention to the reasonable use of power quality evaluation methods and the accurate evaluation of power quality.At first, I constructed the power quality evaluation index system, described the meaning of individual power quality index and introduced the national standard limit value of each index in this part. Then according to the limit value, the user needs and expert opinions, I divided every index into five levels. The five levels as a evaluation method can be used to evaluate the single index of power quality.Second, I made a comparative study of comprehensive evaluation methods and empowerment methods of power quality. The comprehensive evaluation models of fuzzy comprehensive evaluation method, matter-element analysis method, grey correlation analysis method, ideal solution method and osculating value method were constructed respectively. The fuzzy comprehensive evaluation process of the combining of a ridge membership function, a weighted average synthetic method and a weighted average recognition principle was proposed. Using an combination empowerment method of improved analytic hierarchy process(ahp) and entropy weight method to determine the weight of each index. A combination evaluation method was designed to solve the problem of the difference in comprehensive evaluation level values of five comprehensive evaluation methods. Then the multi-index comprehensive evaluation of power quality was realized by these methods.The result is that the fuzzy comprehensive evaluation method is the most reasonable and stable method of the five methods used above and the combination evaluation idea is feasible.Third, through the analysis of the evaluation way of regional power grid power quality, I proposed power quality evaluation process and method of regional power grid based on the substation and voltage grade.Finally, 9 single index of power quality, 39 monitoring stations and 12 substations were evaluated by using samples from S city in Jilin province. The result is that the power quality of voltage deviation index and long time flicker index are two worst indexes. There are 11 unqualified monitorings. In addition, the power quality of J substation and L substation are unqualified. At last, the power quality of the whole S city is in the fourth grade.