Three Phase dynamic load

Guys:

I´m an electric engineering student and I´m trying to create a IEEE-33 distribuion line topology with simulink as shown in figure 1. Source voltage is 138Kv and transformer reduces to 13.8 Kv.

 Instead of using fixed loads, I´m using three phase dynamic load with external control as show in figure 2.

 I´m facing a problem with with a very small model with three loads. Voltages and currents that are associated to these load models as show in figure 3 have strange behaviours. Results are like numeric noise. I was suspecting that the problem could be related with solve model but I tried fixed step and variable step with the same results.

Can anyone explain to me what is going on with the model and how to fix it ?

Sincerely, Andre Nudel

[Atieh Delavari]

Hi I think you should adjust configuration parameters to see better waves forms

Answer 1

[Sebastian Castro]

It could very well be numerical noise. I noticed you are still using the ode45 solver, which is the default for Simulink.

If you open up Model Configuration Parameters, and go to the Solver pane, try:

1. Change the solver to "ode23tb"
2. Change the Relative Tolerance parameter from "auto" to "1e-4"

Both of these constitute the recommended settings for SimPowerSystems models, as shown in the power_new function.

If you still get noise, try further reducing the Relative Tolerance and Absolute Tolerance parameters, as well as the Max step size. This may help further.

- Sebastian

[andre albagli]

Sebastian :

Thanks for your answer. I´ll do it straightaway and let you know.

Thanks! Andre

Answer 2

[andre albagli]

Sebastian:

I tried to change these parameters but the results are the same. Any other sugestion ?

[Sebastian Castro]

Hmm... I noticed your simulation is running in Discrete mode. Try either reducing the sample time or testing the model out in Continuous mode.

Another thing to try is use time invariant loads to see if the model works with those first.

[andre albagli]

Nope. The same result. Strange is if I use only two 3-phase dynamic load, this problem doesn´t happen.

I cannot see it there is a mistake or if it is a real numeric problem.

[Mohammed Masum Siraj Khan]

Please add a small sized resistive load at the same node of the dynamic load (show in figure), as "the dynamic load is a nonlinear model simulated by current sources, it cannot be connected to an inductive network (R-L in series)", and it creates distortion in voltage, and current. I think that this will solve your problem.