Robust Adaptive Control for Maintaining the Grid Reliability and Electricity Market Availability Under N-m Grid Contingencies

Past research, as well as current operational procedures, indicates that harnessing the control of transmission assets can provide substantial benefits. Numerous System Integrity Protection Schemes (also known as Special Protection Schemes or Remedial Action Schemes) that involve both pre-contingency transmission switching actions as well as post-contingency switching actions exist today [1]. Such SIPSs demonstrate that changing the topology of the network can be beneficial in meeting reliability standards, even during emergency conditions. Research on transmission switching as a corrective mechanism has demonstrated its ability to help alleviate line overloading, voltage violations, reduce system losses, increase transfer capabilities, manage congestion, and help balance the generation rejection and load shedding. After a contingency, or multiple contingencies, there may be lines that are tripped (opened) that do not have an actual fault. These lines are, therefore, capable of being switched back into service once it is determined which lines do not have a fault. However, it is well-known that reconfiguring the topology changes flows throughout the network; it is possible that reclosing a line will cause line overloads since corrective switching research has demonstrated that opening a line may alleviate line overloads or voltage violations. As a result, a transmission switching program must be solved to determine which lines should be reclosed and in what sequence. Generally, transmission switching programs are very difficult to solve. They require a binary variable to represent the status of each line that is being considered for a switching action. This creates a complex combinatorial problem. Therefore, there is the underlying question as to whether a transmission switching program can be solved fast enough during a multi-contingency emergency to determine which lines should be reclosed and in what sequence. However, the combinatorial solutions for this particular transmission switching problem are limited. First, only lines that are tripped but yet do not have a fault are candidates for switching. Second, the motivation of this transmission switching problem is first to avoid a cascading outage. This translates the problem into a feasibility study as opposed to an optimization study; the first task will be to determine if switching the line back into service will improve system reliability. The first task can then be solved by a simple heuristic that can quickly determine which line to reclose first and then repeat this process. The next task, which is not as time sensitive as the previous task, is to regain global optimality of system operations based on an optimal transmission switching model. The use of FACTS devices will be considered as an alternative approach.