TYPES OF VOLTAGE INSTABILITY AND THE ASSOCIATED MODELING FOR TRANSIENT MIDTERM STABILITY SIMULATION

This paper provides a precise power system model which is suitable for voltage instability analysis. This model includes generator flux deca y and exciter dynamics, the load drop compensator, generator flux satu ration, field current limits, under-load tap changers, and switchable shunt capacitors. Four types of voltage instability and several subtyp es (type I, types IIC, IIS and IID; types IIIS and IIID; and types IVS and IVD) are defined and discussed in this paper. The modeling requir ements and examples in the literature for each type and subtype are gi ven. It is also shown that the load flow solution is not always a cons ervative predictor of voltage instability compared with the equilibriu m solution of the transient stability model.