Impact analysis of wind generation on voltage stability and system load margin

Due to the environmental concerns and induced political incentives, wind power penetration has been increasing in many countries around the world. However, wind power generation is very different from conventional power generation due to stochastic and intermittent nature of the wind. The wind power may not be available or generating the demanded amount as needed. Thus, these mandates to promote wind power need to be balanced by studies on their impacts on power system operations and control. However, new approach is needed to properly quantify the voltage stability of power system. Accordingly, this paper addresses the modeling of the stochastic and intermittent wind generation and its use to predict the associated stability margin in terms of system load margin. To model the variation nature of stochastic and intermittent wind power injection as the load increases, we propose to use the Weibull distribution of wind speed to model the intermittent factor. The slip of asynchronous wind generators is introduced as a new state variable, and thus new power balance equations including the slip as a state variable are formulated. The balance between the average electromechanical power conversion and mechanical power of wind turbines is utilized to incorporate wind stochastic and intermittent uncertainty. As a first step, we investigate the impacts of the wind generation on static power flows. In terms nonlinear control terminology, we are investigating the stochastic nature of the equilibrium points associated with the uncertainty of the wind generation. Accordingly, we derive a novel sensitivity index of voltage stability considering the stochastic and intermittent nature of wind speed through the slip effect, using the Jacobian matrix for the newly formulated power flow equations. In addition, the probabilistic stability margins in terms of load for various wind speed distribution and penetration are investigated by use of the proposed CPF and Monte Carlo method. The - roposed methods are illustrated on the IEEE 39-bus system and the results show that the stochastic and intermittent wind power injection will significantly affect the stability margin and its slip.