Steady state stability in power systems including nonlinear voltage dependent loads

In this paper, we propose a detailed flexible approach for incorporating static loads into the small signal analysis framework of a power system. In particular, constant power, constant current and constant impedance loads are illustrated. The incorporation of nonlinear voltage dependent loads into multimachine power system requires the development of the mathematical model of the power system with static loads. The differential algebraic equation (DAE) model of multimachine power system including nonlinear voltage dependent loads has been developed in this paper. Thus, the objective of this paper is to develop a general methodology of DAE model of power system with taking into account voltage dependency of static loads. The Western System Coordinating Council (WSCC) 3-machine, 9-bus system and the IEEE 14-bus test system are used to illustrate the application of all proposed models and techniques for different loading conditions. Results demonstrate that both constant power and constant current load models give poor results as far as network loadability is concerned, whereas constant impedance type load is more stable.