Load Flow StudyFast Decoupled Load Flow(FDLF)

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Overview Fast decoupled load flow Why FDLF? Flowchart Program Output Conclusion Reference

Fast decoupled load flow Algorithm is based on Newton-Raphson method. When transmission lines has a high X/R ratio, the newton Raphson

could be further simplified. Consider the Newton-Raphson load flow equation:

are less sensitive to and more sensitive to . are less sensitive to and more sensitive to . So, N and J elements can be eliminated.

=............(1)

cos, sin0G sin<<B, and Q<<B|V|2

With these assumptions H and L are square submatrices of dimension (n-1) and (m-1) respectively are:For i = k, H=L - B|V|2

For i, H=L - |V| |V| BWith further simplification,the matrix equation for the solution of load flow by FDLF method are:= ………..(2) =Where, B’ and B” are matrices of elements -B(i=2,…..n and k=2,….n) and -B(i=2,…..,m and k=2,….,m).

Why FDLF?

For practical accuracies, only 2-5 iterations are required. More reliable than NR method Speed is 5 times that of NR method Storage requirement is 60 percent of NR Constant jacobian Physically justifiable assumptions

FLOWCHART:

calculate

solve for

calculate  ∆𝑸𝒊𝒓      for    i =(2,3,4….  ……𝐦 ¿ (𝐏𝐐𝐛𝐮𝐬𝐞𝐬)

Solve for

PROGRAM-fdlf.txt

OUTPUT-

Conclusion Due to constant jacobian, defining functions are not sensitive to any

humps. It can be employed in optimization studies. Used for obtaining information of both real and reactive power for

multiple load flow studies.

References

M. A.PAI , Computer Techniques in Power System Analysis. D.P. Kothari, Modern Power System Analysis .

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