5.4. Concept of the Controlling Unstable Equilibrium Point

The analytical concepts behind the controlling UEP and its importance in determining an accurate estimate of the region of stability were discussed earlier in Chapter 4. In this section we present a technique to determine the correct controlling UEP based on the physical behavior of the power system. As described in Section 5.3, the determination of the correct controlling UEP is essential for accurate transient stability assessment using the TEF method. The assessment is made by comparing the system transient energy at the end of the disturbance to the critical value of energy, which is the potential energy at the correct controlling UEP. Hence, the accuracy of the assessment hinges on obtaining the correct controlling UEP.

The UEP represents a set of generators’ angles which satisfy equation (5.20)