Abstract
The bus voltage of local substations in the power system has been controlled so as to be maintained within the regulated range by reactive power control of the phase modifying equipments (PME) [1]〜[3]. In such a control, the switching operation of the PME sometimes cannot be implemented suitably even in a vicinity of the upper and lower limits of the regulated range of the bus voltage. And this causes unnecessary reactive power. As a result, the reactive power increases, especially in a long distance transmission, and hence the transmission loss increases. Some of the authors have investigated the optimal control of the PME by using the fuzzy reasoning [4] for maintaining the bus voltage within the desired range and at the same time for reducing the transmission loss through suppression of the generation of the unnecessary reactive power [5]〜[8]. In the control, since the fuzzy rules were constructed by using bus voltage and reactive power obtained in the past, when the load power changes due to the change in weather condition, the resultant rules become unsuitable, and hence sometimes unexpected control of the PME took place [7]. In the present paper, by using the self-organizing map (SOM) [11]〜[13] which is known as an effective technique to the classification of multi-dimensional data, changes of the bus voltage and the load power arepredicted. And these predicted results are applied to tuning of the fuzzy rules with an aid of the steepest descent method. Finally, the control of the PME corresponding to the change of the load power can be realized. The effectiveness of our method is proved with numerical results by using real data in a power system.
