Energy efficiency evaluation method of rural low-voltage distribution network based on combination weight method

Abstract: Aimed at understanding the overall energy efficiency level of rural low-voltage distribution network, and on the basis of analyzing current research on energy saving indexes of distribution network, the energy efficiency evaluation index system and evaluation model of rural low-voltage distribution network were established in this article. Firstly, according to relevant standards and rules, a set of comprehensive index system for evaluating energy efficiency of rural low-voltage distribution network was established. The index system consisted of seven second grade indexes, such as the electric network structure, network equipment, power quality, network loss, economic operation of power network, reactive power compensation and distributed generation. Particularly, electric network structure index included 4 third grade indexes: the proportion of distribution transformer located at the load center and 380V line power radius beyond the standard, the percentage of small section for 380 V line and connecting line; the network equipment index contained 3 third grade indexes: the ratio of efficient type distribution transformer, non-standardized distribution transformer capacity and energy-efficient low-voltage line; the power quality index consisted of 4 third grade indexes: the qualified rate of 380 V three-phase load unbalance degree, 380/220 V voltage monitoring point, 380V voltage and current total harmonic distortion; the network loss index included 4 third grade indexes: the comprehensive loss rate of distribution transformer and low voltage, the number of serious exceed the standard rate of loss rate for single distribution transformer and low voltage; the economic operation of power network index consisted of one third grade index that distribution transformer load rate of interval number in the economic; the reactive power compensation index included 4 third grade indexes: reactive power compensation device installation and operation rate, distribution transformer monthly average power factor qualification rate, reactive power compensation capacity accounted for distribution transformer capacity ratio; the distributed generation index include the capacity and generating capacity ratio of distributed generation accessed to the low voltage district; all together 22 third grade indexes. Then, the calculation method for 22 third grade indexes was determined, the 22 single efficiency indexes were obtained and the comprehensive evaluation model which was proposed based on principal component analysis and analytic hierarchy process was used to calculate energy efficiency of rural low-voltage distribution network. The concrete methods were: according to the principal component analysis, the index matrix for each second grade indexes was determined, and by means of 0-9 scaling method of analytic hierarchy process, the comprehensive weight of the second grade index was determined, thus the method overcame the shortcomings of single weighting method and realized the combination of the quantitative result from energy efficiency index and the qualitative result from the judge of relevant experts ,which made the evaluation results more reasonably. Finally, Taking low-voltage distribution network of three districts in rural as example, the evaluation result of three districts obtained by the method proposed in the paper were completely in conformity with the result of actual distribution network efficiency, which indicated that the proposed method in this paper was the effective and practicable. It provides a reference for implementing electric-saving reconstruction and energy-saving assessment of rural low-voltage distribution network in China.