Synthetic evaluation of DC power quality based on combination weighting

Abstract

With the development of global renewable energy, DC transmission and DC power distribution technology have been applied on a large scale, and the requirements for DC power quality (PQ) are more stringent. Evaluating DC PQ reasonably and effectively has become a research hotspot at this stage. In this paper, a comprehensive analysis for various indexes of DC PQ is conducted to obtain a unified parameter for describing the characteristics of PQ from an overall perspective. First, weight values of PQ indexes are calculated by combining fuzzy analytic hierarchy process (FAHP) and the improved entropy weight method. FAHP can satisfy the consistency without the consistency test, and the improved entropy weight method is an objective weighting method that can effectively avoid the preference of subjective weighting method. Then, based on a triangular fuzzy function, the membership degree is obtained. Finally, a fuzzy comprehensive evaluation is made. An example analysis is carried out with the data provided by the Gree photovoltaic direct‐driven inverter multi‐variable refrigerant flow system to show the validity of the proposed method for evaluating DC PQ. © 2020 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

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“…Indicator I is extremely important than indicator J 2, 4,6,8 Intermediate value between the above adjacent judgments Explanation When index J is over index I, its scale value is the reciprocal of index I over index J objective. Combined with the combined weight formula in Li et al, 12 the formula is as follows:…”

“…The subjective weighting method adopts the analytic hierarchy process and the objective weighting method adopts the entropy weight method. 12 The entropy weight method determines the objective weight. Entropy weight method 13 is an objective weighting method.…”

“…Thus combining the subjective and objective weights can be combination weights, achieving the unity of the subjective and objective. Combined with the combined weight formula in Li et al, 12 the formula is as follows:…”

“…R = The maximum eigenvalue of matrix R is l max = 4:1213, CI = 0:0404, and CR = 0:0454 can be obtained from equations (12) and (13).Since CR \ 0.10, the consistency of the judgment matrix R is acceptable, so the eigenvalue method can be used to calculate the weight. The matrix C reflects the closeness of each evaluation object to the optimal scheme.…”

“…The subjective weighting method adopts the analytic hierarchy process and the objective weighting method adopts the entropy weight method. 12…”