Cascade Control Theory for Prevention of a Large-Scale Blackout

Abstract

Currently, the prevention of a fault cascade during large-scale power blackouts is solely dependent on system operators. However, it seems impossible for operators to calmly decide and perform an appropriate shutdown in an emergency when unpredictable events continuously develop. Therefore, it is desirable to construct a “fault cascade control system”, which collects information on the entire system, shuts down generators and loads, and reduces the responsibility of the operators. The theory proposed in this paper has the following features. (i) The voltages and currents are represented in terms of complex values and the power system is represented using Kirchhoff's first and second laws. (ii) Linear power equations are presented, in which generators and loads show constant current characteristics independent of voltages. Then, the opening and closing of branches are simulated by equivalent virtual phase shifters and changes in the system conditions are simulated by a pivot operation in the linear programming (LP) method. Branch overload, node voltage anomalies, and disconnection from the system are detected. The fault cascade control system adopts the implicit enumeration method to resolve system anomalies based on the value of control variables that can be either 1 or 0. We developed a program on the basis of this theory, and verified the validity of the theory by simulating a route cutoff fault in a 500/275kV loop system.