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Synchronous machine saturation instabilities

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Scott Hill
Scott Hill on 4 Jul 2018
Commented: Meme Young on 9 Jun 2020
Simulating the synchronous machine below, i am unable to model saturation without immediately creating a numerical instability. The data has been sourced from factory tests, and manufacturer calculated datasheet values where tests were not possible. Decreasing sample time from 25µs to 0.25µs improves stability, but creates unacceptable simulation times.
Characteristics of the data that i am aware of:
  1. OC saturation curve (from test data) does not intersect the declared 1pu operating point for excitation current @ nominal volts. Scaling the saturation data to fit (1,1) has not helped.
  2. X''d & X''q are more different (compared to each other) than anticipated
  3. Increasing the parasitic load on the machine from 5-15% improves stability, but then offsets the true operating point for the rest of the model.
SM.Rating.S = 1938e3;
SM.Rating.Vline = 690;
SM.Rating.F = 60;
SM.Rating.Poles = 4;
SM.Mech.gensetH = 0.8516;
SM.Imped_Std.Ra = 0.0054; %Stator resistance @ 75degC [pu]
SM.Imped_Std.Xdst_RI = 13.7e-2; %X"d unsat pu
SM.Imped_Std.Xdt_RI = 21.9e-2; %X'd unsat pu
SM.Imped_Std.Xd_RI = 222e-2; %Xd unsat pu
SM.Imped_Std.Xqst_RI = 18.4e-2; %X"q unsat pu
SM.Imped_Std.Xq_RI = 113e-2; %Xq unsat pu
SM.Imped_Std.X1 = 6.6e-2; %Stator winding leakage reactance pu
SM.TimeConsts.Tdst_RI = 0.017; %T"d
SM.TimeConsts.Tdt_RI = 0.267; %T'd
SM.TimeConsts.Tqst_RI = 0.018; %T"q
SM.base.Iexc = 0.85;
SM.SatData.If_OC_ST = [0.19 0.35 0.55 0.6 0.67 .72 .8 .89 .92 .98 1.09 1.31 1.61 2.52]/SM.base.Iexc;
SM.SatData.V_OC = [259 374 553 586 621 659 689 716 724 742 760 793 828 897]/SM.Rating.Vline;
My first post; so please advise if i can compose my questions better! Thanks

Answers (1)

Meme Young
Meme Young on 7 Jun 2020
Hi Dude I am doing sync machine modelling as well. It seems that you are imitating the simulink sync machine model. How do you use these parameters in Simulink?
Meme Young
Meme Young on 9 Jun 2020
Yes, thank you, I am trying to describe the difference between
Synchronous Machine pu Fundamental block
Synchronous Machine pu Standard block.
I am just trying to find a way to create 2 Synchronous machines, one is pu fundemental and the other is pu standard, and they have identical transient and steady-state characteristics. That means I need to find a way to convert parameters between pu standard and pu fundemental, but no documentation of matlab mentioned the exact way. The references of matlab documentation is also very confusing and chaotic, and the parameters and circuits in these references may not be suitable for matlab sync machine models at all. I am wondering if you could figure it out.

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