模糊综合评价在电压暂降源识别中的应用

Application of Comprehensive Fuzzy Evaluation Method on Recognition of Voltage Sag Disturbance Sources

电压暂降扰动发生源的分类与识别是合理制定电压暂降治理方案的基础。分析了由短路故障、变压器空载励磁和大型感应电机启动引起的电压暂降的特征,指出了这些特征可能存在的模糊性;选取了三相电压不平衡度、暂降持续时间比和2次谐波增量组成评价指标集,利用层次分析法确定各个指标的权重;基于建立模糊隶属函数的待定系数法,参考95%概率大值的定义,提出了一种模糊隶属函数参数的估计准则,分别构造了每类暂降关于各个指标的模糊隶属函数;计算综合指标隶属度,根据最大隶属度原则判定暂降源类型。通过仿真和实测数据的验证,并与典型暂降源识别方法相对比,表明了文中提出的模糊隶属函数参数的估计准则能够有效减小样本误差的影响,从而具有较高的准确率。

Classification and recognition of voltage sag disturbance sources is a foundation of mitigating voltage sags. This paper analyzed characteristics of various kinds of voltage sags, including sags caused by short-circuit fault, transformer energization and large induction motor starting. Fuzziness hiding behind them was revealed. Three features were selected to form an evaluation index set, i.e. three-phase voltage unbalance factor, duration ratio and increments of second harmonic. Then weight of each feature was calculated with analytic hierarchy process（AHP）. A novel estimation criterion for fuzzy membership function parameters was proposed, inspired from 95% probability value, based on undetermined coefficient method to establish the functions. Fuzzy membership functions were created for each index and comprehensive index membership degrees were calculated to judge disturbance source according to maximum of the degrees. The presented estimation criterion can efficiently reduce influence of sample errors and thus improve accuracy of whole process. It was verified by comparison with a typical method and by using data obtained from both simulations and measurements.