Least action principle for real-time mitigation of angle instability in power systems

Michael Sherwood

The use of synchrophasors in power systems has been increasing due to the necessity in real-time monitoring of critical areas in a system. The advantages of synchrophasors are evident in their use in the Wide Area Monitoring System where monitoring the voltage magnitudes and angles in real-time is critical in maintaining operational reliability. Problems arising from deregulation combined with excessive loading have made power systems less secure. To help alleviate these issues, it is essential that the reliability status of a system can be assessed as quickly as possible. Synchrophasors combined with a high speed communication network can allow development of automatic control actions, which in turn give operators more time to take preventive actions to keep the system from collapsing. The use of synchrophasors or Phasor Measurement Units in automatic generation shedding schemes, as well as load shedding schemes have been proposed in the past. When such an action is initiated, it is extremely important to know that it is the correct one to take since load shedding results in customer inconvenience and lost revenue. On the other hand the total loss of a system such as from blackouts leads to an adverse impact on society. One method for determining the stability is the transient energy function. The use of transient energy functions in determining stability has shown potential in determining load or generation shedding. The computation of transient energy functions using real-time data from synchrophasors is therefore an attractive solution to mitigating stability. Least action principle is proposed in theoretical physics for abstract modeling. Here, the concepts of least action principle are applied for assessing and mitigating angle instability in power systems. From the computation of potential and kinetic energy, a different quantity known as the Lagrangian is formed. The Effort, which is the time integral of the Lagrangian, is then calculated and is used in determining the critical generators for initiating generation shedding. The IEEE New England 39 bus test system is used to test the algorithms. From the results it appears that the use of Effort of each machine is reliable in determining the set of critical generators following a disturbance.

Least action principle for real-time mitigation of angle instability in power systems

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