MATLAB: Warning: Matrix is close to singular or badly scaled ( simulink model with simscape blocks simpowersystems)

controlMATLABpower_electronics_controlsimpowersystemsSimscapeSimscape Electricalsimulink

I have my model having simpower systems generating the follwoing warnings. solutions are availalbe for matlab code but none for simulink model containing simscape blocks.

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Warning: Matrix is close to singular or badly scaled. Results may be inaccurate. RCOND = 1.667047e-18.

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Thanks in Advance

Best Answer

Hello Sreeraj,

there is the chance you can get good results even with this warning, so you might be able to ignore it. The main issue is likely that you have an area where resistances are too low. I see this warning the most when using specialized power systems and having breakers in the system. In those cases, increasing the breaker resistance will make the error go away. If you have other components with very low resistance, you could also try increasing the resistance of them.

Regards,

Joel

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MATLAB: Matrix is close to singular or badly scaled in SPS

Hi Tony,

The reason could be that the model is a very stiff system. If it contains a Universal Bridge snubber, you may want to check the compatibility of the time constant of the network and that of the snubber.

To get the stiffness ratio, use the following command:

 >> sps=power_analyze(gcs,'detailed');  max(eig(sps.A))/min(eig(sps.A))

-Rohit

MATLAB: Method of short-circuit calculation is used in Simscape

In Three Phase Fault block of Simscape-Electrical-Specialized Power Systems for short-circuits simulation the fault is implemented by a combination of breaker and breaker Resistance (Ron).

When fault condition is to be simulated, the breaker is closed and the breaker resistance (typically in ohms) will be negligible compared to load resistance (typically in Mohms) thus simulating large fault current in the circuit.

During normal operating conditions, breaker will be on and it has infinite resistance.

The following documentation on Three-Phase fault documents this: https://www.mathworks.com/help/releases/R2018b/physmod/sps/powersys/ref/threephasefault.html?s_tid=doc_ta

Simulink Solver will form simultaneous differential equations for entire system if continuous solver is chosen and algebraic equations if discrete solver is chosen.

All the equations will be solved to produce the simulation result. As Simulink solver is computationally capable of handling complex equations, superposition principle is not used.

Best Answer

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MATLAB: Matrix is close to singular or badly scaled in SPS

MATLAB: Method of short-circuit calculation is used in Simscape

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