MATLAB: SIMULINK BASICS For Particular Applications

ode23tbSimscape Electricalsimulink

Hello Sir,
I want to know on below things about MATLAB Simulink.
1)How to Select Resolver in Simulink ? for Particular Applications. Like ode23tb , ode45 or FixedPoint Resolver VariablePoint Resolve what ? for particular application
2)What is the difference between Powergui Continuous or Discrete ? How to Select it for particular application.
3) How to chose Simulation Stop Time ? for different Circuit
I have to work on IGBT with ON , OFF State Feature from MATLAB  and Transformer etc . 
My Design show No Errors. But Unable to see output waveform after 16 Hours of Simulation.
— KR

Best Answer

Hi,
ode45 is simulink default solver, a medium-order, whereas ode23 is a low-order solver.
These are variable-step solvers, which will adapt their step-time regarding the dynamics of the equations outputs.
Depending on the accuracy and the type of differential equations you have to solve, you will choose between different solvers with different integration methods. https://fr.mathworks.com/help/matlab/ref/ode23.html
Fixed-step solvers can be used to accelerate you simulations, but be aware that the accuracy will be impacted depending on how you choose your step-time. Furthermore, you might get numerical oscillations when simulating systems with high dynamics (e.g SPS transformers with saturable cores). If you have a full discrete model (fixed sample time), you can use a discrete solver with the time-step equal to your design's minimum sample time.
- PowerGUI is SimPowerSystems solver. You need it to run simulations while using SPS elements. When using the continuous one, the solver step will vary along the simulation, resulting in long simulations. When choosing a discrete solver, you'll specify the time-step regarding your system's dynamics.
For example, if you have IGBTs switching @16kHz, you would then want to have between 50 to 100 steps between switching events, resulting in a time-step of approximately 1µs.
But keep in mind that it is all about making a trade-off between accuracy and simulation speed.
Finally, you will choose your simulation stop time regarding the purpose of your simulations and your system's dynamics. You might want to know if you want to observe steady-states or transients, or run a complete scenario.
For your application with SPS & transformers, I'd recommend using ode23t with a continuous or maybe a discrete PowerGUI if needed.
Regards,
Greg
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