When I start dynamic sumulation, after 0.2 sec my generator's angle start to change very sharply from 35 degrees to 1000 in 0.01 sec. But I'm not giving system any disturbances... Is it a problem of system initial instability? I mean steady state instability.
Who knows?
P.S.Power flow solved via Full newton Raphson P.S.S. I used CONL, CONG, ORDR, FACT, TYSL.
Such angle deviation without any perturbation usually means something is not quite right rather than instability. I would suggest checking STRT errors etc, and also are you plotting absolute angles rather than relative angles?
Machine angular instability can be avoided by lowering its power output. Assuming all other models are OK, reduce system load such that steady state power output of such machine is reduced below its output value leading to instability. Check and re-balance power output of all machines in study region to avoid having extremes in machine's mw output (one unit producing too much mw v. another producing too little).
Before executing a dynamic run, the steady state case shall be solved and converged to acceptable operating conditions. It is also good to check that ERUN and GRUN for all machines produce acceptable results. In some cases, lowering the 'integrating' step size can help if some models requires so (normally set to 1/4 of a cycle). In other cases, lowering the 'acceleration' factor would help (from default 1.0 to 0.6 or lower).
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