Summary of "TCSC Controller Design for Damping Interarea Oscillations" by Yan, Liu & McCalley

1. What is the problem being studied? FACTS controller design and location for damping interarea modes. A TCSC application example is provided.

2. Is it an important problem? Why or why not? Yes. With deregulation and increased system loading, interarea problems are becoming more significant. FACTS devices have a great deal of potential to influence the system response in this time frame.

2. Continued They also provide the unique advantage from the deregulation point of view, of being located within the transmission system (as opposed to a generation facility).

3. What are the main results? Provides a method for ranking various input/output pairs for control of interarea oscillations. Tie line flow was more effective an input signal than the speed difference signal.

3. Continued Modal and functional sensitivity methods are used to determine the location and design of a TCSC controller. These methods, originally applied to PSS design, were adapted for FACTS controller applications.

4. What method is used to produce the results? Functional sensitivities or the residue method was used for determining controller inputs and outputs and locations. Modal sensitivities are used to determine the candidate lines.

4. Continued Residues are used to determine the controller design parameters, and two different inputs are tested. The design is tested by determining the maximum line loading without the TCSC and with each of the two control schemes.

4. Continued - 2 Assume the transfer function between the kth input and the jth output of a system are given by Gjk(s). Then Gjk(s) = Sum[Rijk/(s - li)] (i = 1, 2, 3, ... n). The residues (Rijk's) can determined using Rijk = Cj ti vi Bk .

5. What are the assumptions in the paper? Are they realistic? In the design of the controller, the controller gain (K) is assumed to be small.

5. Continued They also assumed that the system and control loop is as in the figure below.

5. Continued - 2 The form of H(s) is {sT/(1 + sT)}[(1 + sT1)/(1 + sT2)]m where m is the number of compensation stages At each stage the angle of each compensation block should be less than 60°. The assumptions seem to be fairly realistic.

6. How sensitive are the results to the assumptions? The authors don't comment or provide much insight to this. The application is tested for a range of conditions to find the maximum transfer capabilities. The "best" controller (the one using the tie-line flow input) did have the smaller gain of the two.

7. What did you learn from this paper? This paper verifies many of the ideas discussed in this class and shows the power of linear analysis in designing controllers for large systems. The results show the potential of the TCSC for improving system flexibility and oscillations. The better results for tie-line flow may or may not indicate a general trend.

8. Describe the similarities and differences of this paper? This paper is aimed at the interarea oscillation problem and provides a fairly simple scheme for designing a linear controller based on linear analysis. It does not deal with the TCSC model itself, or with nonlinear theory as many papers do. It is a well-written paper.