Comprehensive evaluation on electric power quality of Wind Farm based on credibility theory

In this paper power quality comprehensive evaluation indicator series and all their level limits are built according to Technical Rule for Connecting Wind Farm to Power Network that prescribes a limit to voltage, frequency, power fluctuation, power quality, and so on. Membership degree of each indicator´s level limit is calculated by membership function, and its transformation to credibility measure is realized by credibility theory. Moreover, analytic hierarchy process (AHP) is applied to calculate the weight vector for each indicator, and finally the intuitive, only electric power quality evaluation result of the wind farm is obtained. An example analysis on data acquired during a certain period of time in a wind plant in Ningxia proves that this method is intuitive and feasible, and will solve the problem that the present comprehensive evaluation method will so confuse the duplex uncertainty of fuzziness and randomness in power quality indicators that may lead to inaccurate evaluation results.