Reachability and model prediction based system protection schemes for power systems

Interconnected power systems have been disrupted by unforeseen disturbances from time to time when millions of consumers lose power supply at a very expensive cost. System protection and emergency control to counteract power system instability play an important role in power system operation. Motivated by the industry need to mitigate the effect of disturbances on system operation and improve power system security, this dissertation develops a general framework for system protection scheme based on reachability analysis and Model Predictive Control. A systematic framework to determine switching control strategies is proposed to stabilize the system following a disturbance based on reachability analysis. The computation of the stability region of a stable equilibrium point with the purpose of power system stability analysis is proposed and the validity of discrete controls in transient stability design is studied. Model Predictive Control (MPC) is also adopted to design system protection scheme. A control strategy for maintaining voltage stability following the occurrence of a contingency is presented. Based on economic consideration and control effectiveness, a control switching strategy consisting of a sequence and amounts of shunt capacitors to switch is identified for voltage restoration. The effect of the capacitive control on voltage recovery is measured via trajectory sensitivity. In addition, voltage stability margin is an indication of how far the post-transient operating point is from the voltage collapse point. It is an index of system security. A control scheme to restore voltage following a contingency and to maintain a pre-specified amount of post-transient voltage stability margin is proposed. Moreover, dissimilar controls exist in power system for voltage control. A mixed integer programming based algorithm is presented to study the optimal coordination of the dissimilar controls to improve voltage performance following large disturbances. The developed algorithms are implemented with MATLAB and tested on the WECC system to enhance the performance of voltage and the 39 bus New England system for preventing voltage collapse