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Network simulator

Discussion in 'Electrical Engineering' started by Louis, Jul 5, 2007.

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  1. Louis

    Louis Guest

    Hello,

    I plan to create a simplified electrical network simulator.

    The goal is only to provide power nodes (in and out) and lines through those
    nodes and to compute lines charges in regard of power production and
    consumption.

    Algorithms found on the web are too complicated for my purpose.

    Is an algorithm based on "shortest way path" is convenient ?

    Is power producted goes to all consumption nodes regarless of their distance
    or is the "near" production node giving power at consumption node?

    Regards,


    Louis
     
  2. Don Kelly

    Don Kelly Guest

    ----------------------------
    It would be nice to know what you are talking about. If you are looking at
    power systems , then this is well established (see Load flow). How simple an
    algorithm do you want? The basic ones now in use are not inherently complex
    in concept. Simplifying these would lead to results that might well be
    meaningless (one could ignore line resistance for example). How the "power
    flow" is distributed depends on several parameters so one cannot simply use
    shortest path methods.
     
  3. Louis

    Louis Guest

    Hello Don,

    Thank you for your reply.

    Did you know any reference on the web at a "simple" low fload algorithm?
    (all those I have found are too many complex for my own use...)

    Many thanks again,


    Louis.
     
  4. Don Kelly

    Don Kelly Guest

    I don't know what is on the net. Most references use a form of
    Newton-Raphson iteration and some older ones use Gauss-Seidel. Both are
    basically root finding iterative algorithms. Beyond this there are methods
    of reducing the size of the problem or even subdividing it for large
    systems. These mainly are aimed at reduction of storage needs for solution.
    The same approaches ignoring line resistance may offer some advantage in
    programming and speed but will also ignore any line losses.
    You have not indicated how large a system that you want to deal with and how
    good do you want the results to be.
     
  5. Don Kelly

    Don Kelly Guest

    ----------------------------
    Matrix re-ordering, at least rowwise is simple and quick. Sparsity
    techniques are generally used along with Newton-Raphson rather than
    Gauss-Seidel. N-R generally does the job with fewer iterations while there
    is more work per iteration, there is still an advantage.
    I believe that the original writer was looking for something simpler. One
    such is a simplified N-R method where the Jacobean doesn't change (as it
    normally does in the full blown version) so that the work per iteration is
    reduced. This might be closer to what he wanted.
    Stott& Alsac " Fast Decoupled Load Flows", Trans IEEE (PAS), Vol PAS93,
    May-June 1974, pp859-69

    Some approximations are involved to gain speed. Nowadays, computers are
    considerably faster but for rapidly repeated solutions any speed advantage
    with reasonable accuracy is beneficial and the fixed Jacobean helps a lot
    there as its inverse can be found once and re-used.
    By the way- I said 5 simultaneous non-linear equations- only 4 required
    (breaking two complex equations into 4 real equations is the normal
    approach).
     
  6. Louis

    Louis Guest

    Hello,

    Thanks for your reply.

    In fact the goal is a simulation of a simple network (about 10 power sources
    and 50 power consumption).

    I look for a "fast" method beacause I want to simulate line broken and so on
    with an high rate of occurrence.

    So the perfect algorithm is not truely need... A "approximate" method will
    be fine, and that's why I wrote about "shortest path" in my first message.

    Another ask is:
    power from "power sources" is it going to all consumption points or only to
    nearest points of consumption.

    As can I obtain a apparent good result with those type of algortithm?

    Thanks again,


    Louis.
     
  7. Don Kelly

    Don Kelly Guest

    ----------------------------
    The trick is to use a Gause Seidel first iteration -then switch to the
    faster converging Newto-Raphson or some simplified variation of it.
    However, for a small system as indicated, there are many programs
    available. It is not hard to write one to suit one's purposes. As for broken
    line (assuming that this means the line is out of service -not
    faulted) -there are methods to handle changes to the system admittance
    matrix.
    For a decent computer, it is easy enough to simply rebuild the admittance
    matrix from modified input data -as needed and solve accordingly without
    getting wound up in complexity. After all the concept involved is the same
    for 5 busses as for 5000 busses- the difference being the methods to keep
    storage and array manipulation down-which is not of concern in this case.
     
  8. Louis

    Louis Guest

    Thanks for all your reply,

    Regards,


    Louis.
     
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