Why does MAtLAB returns Error using eval undefined function or variable SI.

I`m triyng to simulate electrical system, consisting of 3-phase programmable voltage source, power transformer, 8 electric motors, distributed parameters line and breakers for each motor. SImulation doesn`t start, a message is returned Error using==>evalUndefined function or variable SI.

I`m using Matlab r2007b

[Walter Roberson]

One of your blocks has an initial value or a parameter defined in terms of a variable Sl but that variable does not exist in the scope being searched.

[Ivan Nedeltchev]

Fine, i realize this, i check all of blocks, there is not variable SI inside, motors in model are Asynchronous machine pu units. And i do not know how to handle this... According to Matlab "Help" SI is about synchronous machines and refers to International System of Units

[Walter Roberson]

Can you attach your .mdl ?

[Ivan Nedeltchev]

Here it is. I`m not very good in it...

[Walter Roberson]

Warning: You have required continuous-time simulation of a system containing switches or nonlinear elements.

The ode23tb variable-step stiff solver with relative tolerance set to 1e-4 generally gives best accuracy and simulation performance.

For some highly nonlinear models it may be necessary to set the "Solver reset method" parameter to "Robust".

See "Improving Simulation Performance" chapter in Specialized Power Systems documentation for additional information on how to select an appropriate

integration method.

To ignore Simscape Electrical Specialized Power Systems warnings, select "Disable Specialized Power Systems warnings" in the Powergui Preferences tab.

and more importantly,

Inconsistency of excitation current and no-load losses in positive sequence:

Excitation current Iexc.= 1.2 % of nominal current

No-load losses = 5.2 % of nominal power (52 Watts)

Iexc.(in %) should be > P_NoLoad (in %)

[Walter Roberson]

After I push the transformers up to 6% Iexc, I encounter problems with the voltage sources.

You have two voltage sources, and two transformers, with only one of the two appearing to be connected.

The source that is connected has its B and C outputs join together and go into B of the transformer, with no connection to C. The C should connect to C.

After that you get into

The following two blocks cannot be connected in series:

Block 1: 'A_stator: Bal. pump8'

Block 2: 'winding_2_self: Three-Phase Transformer Inductance Matrix Type (Two Windings)'

The first block, modeled as a current source, cannot be connected in series with the inductive element of the second block.

Add a high-value resistance in parallel with one of the two block.

You can also specify high-value resistive snubbers if the blocks have a snubber device.You can avoid the use of the snubber by selecting the 'Continuous' simulation type in the Solver tab of the Powergui and deselecting the 'Disable ideal switching' option in the Preferences tab of Powergui block

Answer 1

[Bjorn Gustavsson]

When you get an error like "undefined function or variable SI" you do this:

whos SI % Would list all variables
% See if you get anything - very likely not
which SI -all % should list all instances of functions SI
whos -global SI % Should list variables that are global between some functions not necessarily the base workspace
dbstop if error

Then you restart your simulation from scratch, when it gets to the offending line you get a prompt and access to the workspace of the function where things went wrong - so that you can inspect variables, and also step up and down in the function-stack.

Given the informatino you cant expect much more help than that.

HTH