Fuzzy reasoning for knowledge-based assessment of dynamic voltage security

An easy-to-use knowledge-based fuzzy approach is proposed to evaluate the dynamic voltage security including both voltage collapse and unacceptable voltage profiles following disturbances. The dynamic voltage-stability behaviour of the power system, however complex and nonlinear in nature, is simply mapped into a fuzzy severity index by means of approximate fuzzy reasoning and a series of fuzzy calculus. In addition to providing a mere two-region demarcation, the fuzzy severity index can also generally give a relative severity indication to discriminate between various post-disturbance system states. A systematic methodology for initial fuzzy-parameter setting and fuzzy-variable selection is also presented and discussed.