Saturation in Synchronous Machine Salient Pole

If i use the following saturation vector (20 elements) in the model, i get a strange saturation curve which ends at 0.55 for If

U=[0, 0.045, 0.145, 0.3, 0.54, 0.68, 0.79, 0.86, 0.92, 0.96, 1.00, 1.04, 1.09, 1.13, 1.19, 1.21, 1.23, 1.24, 1.27, 1.29]

If=[0, 0.033, 0.099, 0.20, 0.36, 0.46, 0.56, 0.66, 0.76, 0.86, 1.00, 1.17, 1.50, 1.83, 2.49, 2.82, 3.14, 3.48, 4.14, 4.79]

If i use a smaller vector I get the following saturation curve

If=[0,0.56,1,1.99,2.98,4.79]

U=[0,0.79,1,1.15,1.22,1.29]

I don't understand, why the first curve, which shoul be more accurate is almost linear because simscape stops calculating in the linaer part of the curve. The overall simulation result is also wrong, because the pu voltage is not 1 for if=1, it is somthing like 1.6

Answer 1

[MULI]

Hi Jakob,

I understand that you are facing an issue related to the configuration of the saturation curve in a salient pole synchronous machine block.

The unexpected simulation results due to two main problems:

Non-Reciprocal Per-Unit Field Current:

• The saturation data entered into the model is not in the correct form It should be in terms of reciprocal per-unit field current, but the data provided was non-reciprocal.
• This discrepancy leads to incorrect output voltage when the no-load excitation current is applied.

Saturation Data Consistency:

• The longer saturation data set (20 elements) has segments where the voltage-current relationship is not monotonically decreasing.
• This inconsistency can cause inaccuracies in the simulation results. The shorter data set (6 elements) does not exhibit this issue.
• Ensure the longer dataset is monotonically decreasing to match the shorter, accurate dataset.

This is a bug reported in R2024a and it was rectified in the latest release R2024b.

Hope this answers your query!