load and generator conversion

asked 2013-07-25 11:14:55 -0500

Anonymous

When I want to do pv analysis there is an error for mismatch that is said the largest mismatch is exceed this tolerance . what does it mean? and what is the purpose of load and generator conversion? thanks!

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Hi there, did you get this one sorted out? It sounds like your starting case isn't well tuned. Try checking the load flow case it's based on. Does it solve correctly?

JervisW ( 2013-07-31 02:54:52 -0500 )edit

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answered 2013-08-01 08:37:34 -0500

sheng

141 ●2 ●6

As JervisW has commented, before you run a PV analysis, you will need to ensure that your base case is a valid load flow solution.

PV analysis is a load flow based method widely used to determine static voltage collapse points (also known as nose or critical points). The basic notion is to increment power transfers between a pair of pre-defined source (sending) and sink (receiving) areas till a termination criterion is met.

In static voltage stability analysis, the nose point is assumed to occur when the load flow Jacobian becomes singular, i.e. determinant is zero, and load flow fails to converge due to numerical difficulties. The termination criteria available in PSS/E PV analysis includes monitoring bus voltage magnitudes and/or branch loading etc. When these options are enabled, incrementing of power transfers stop when any limit is breached, which is usually way before the nose point. However it is common these options are not enabled and as such, PV analysis only terminates when load flow fails so as to determine the last good load flow solution before the nose point. If that is the case, it is perfectly normal that PSS/E prints convergence issues during analysis.

The purpose of generation and load conversion to their Norton equivalent is usually for dynamic analysis etc, and is not related to static analysis such as PV/QV.

Hope this helps.

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Hi Sheng, out of curiosity - have you found the built in PSSE PV/QV tools useful? I've observed that the built in modules haven't seemed consistent with previous results and other PV tools, even when trying to apply the same methodology. Any tips on using the built in tools?

cajief ( 2013-08-01 09:09:58 -0500 )edit

PV/QV are traditional methods for static voltage stability analysis. It is no rocket science, and therefore the exact same settings used on the same case should always arrive at the same solution. In fact, you should achieve same results even by repeating load flow manually.

sheng ( 2013-08-01 18:03:52 -0500 )edit

If you need a more customisable PV/QV analysis with more flexibility than what PSS/E provides, I suggest writing your own PV/QV codes in python.

sheng ( 2013-08-01 18:09:37 -0500 )edit

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answered 2013-08-05 18:49:14 -0500

EBC
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I guess the error in mismatch comes from a diverged power flow case or you have reach the nose of the PV curve.