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I have been developing a simulation of the field oriented control of the three phase squirrel cage induction motor (control is oriented by the rotor flux). I have been using the Xcos which is an equivalent of the Simulink software. The simulation block diagram looks in this manner

enter image description here

Basically there are three main blocks

  • IM model

    -state space model of the induction motor in the continuous time domain

  • Observer

    -discrete block which calculates the unmeasurable components of the rotor flux space vector

  • Vector control

    -discrete block which calculates reference values of the components of the stator voltage based on given reference value of the flux and torque components of the stator current

I used the default setting of the Xcos solver i.e.

enter image description here

As soon as I start the simulation I receive following error message: Simulation problem: CVode: At t=0.78087, mxstep steps taken before reaching tout comming from the IM model block

enter image description here

and the simulation ends. I have attempted to find some information about this error and I have found that it is caused by an algebraic loop detected by the solver and it can be solved by reducing solver tolerances in the simulation setup. I thought that the algebraic loop is broken by the first order low pass filters at the inputs of the S/H blocks. Nevertheless I tried to reduce the solver tolerances

enter image description here

and I run the simulation again. This resulted into another error message - Simulation problem: singularity in a block again comming form the IM model block. This time from different place

enter image description here

Can anybody give me an advice how to resolve this issue or tell me what is going on in my simulation? Thank you in advance for any ideas.

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  • \$\begingroup\$ I do not use Simulink yet, but try a small or variable step size instead of no limit, as /0= singularity. For more details see my pasted answer from Researchgate. BTW how long did it take (hrs) to learn Simulink? \$\endgroup\$ Commented Oct 18, 2020 at 10:46
  • \$\begingroup\$ researchgate.net/post/…. Free registration.... \$\endgroup\$ Commented Oct 18, 2020 at 10:48
  • \$\begingroup\$ you have discrete blocks, there is no point using a variable step solver as the solver will need to align to your fixed-step update. switch to fixed that aligns to your fixed step (or a integrer fraction of it for resolution purposes) \$\endgroup\$ Commented Oct 18, 2020 at 11:17
  • \$\begingroup\$ @JonRB thank you for your reply. I had chosen fixed step solver (namely DOPRIS - Dormand-Prince 4(5) respectively Runge-Kutta 4(5)) and then I started the simulation again. Unfortunatelly I have again received: Simulation problem: singularity in a block. Again comming from the IM model block from the last place mentioned above. \$\endgroup\$ Commented Oct 19, 2020 at 6:53
  • \$\begingroup\$ I have tried to reduce the step size from the value equaled to the sampling period i.e. \$10^{-3}\,\mathrm{s}\$ to the \$10^{-5}\,\mathrm{s}\$ value and the simulation passed from the beginning to the end. Unfortunately the outcomes are very strange. \$\endgroup\$ Commented Oct 19, 2020 at 7:38

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Reset to default
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This problem solved by change to RK45 - Runge-Kutta 4(5) solver. Scilab 6.1.1

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