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

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

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1. What is the problem being studied?

• FACTS controller design and location for damping
  interarea modes.
• A TCSC application example is provided.

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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.
  

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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).

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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.

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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.

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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.

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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.

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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) SumRijk/(s - li) (i 1, 2, 3,
  ... n).
• The residues (Rijk's) can determined using Rijk
  Cj ti vi Bk .

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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.

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5. Continued

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

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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.

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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.

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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.

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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.