Study of fuzzy controller for voltage and reactive power in substation using rough set theory

The extraction of fuzzy rules is always a bottleneck to fuzzy control systems. This paper proposes a new method to extract the fuzzy rules using rough set theory. The method is applied to obtain fuzzy control rules for substation voltage and reactive power controllers. Even lacking the experience of experts, the fuzzy control rules still could be extracted by the method. By reducing the decision table and calculating the rough subjection degree of every rule, the fuzzy control rules of an on-load tap changer and shunt capacitor with suitable belief degree, are formed. The proposed method not only overcomes the disadvantage of the repeating control in the traditional nine-area control method, but. also avoids the imperfect fuzzy rules extracted by experience of experts directly. As a result, the control rules are objective and the number of regulating on-load tap changers and shunt capacitors is reduced. The test results show that the control effect is satisfied. The proposed method could promote the application of fuzzy control techniques.