Mistake with PWM generation using Simulink

Dear Matlab/Simulink community,

Since I have not solved the problem and have not found an answer why I receive such a output, I would be happy when you could help me out.

The actual project is much more extensive but easy schematic what I want to do is here:

For that I am using 2-level PWM generator: https://se.mathworks.com/help/physmod/sps/powersys/ref/pwmgenerator2level.html

In the DC-link (DC voltage after the converter) the DC voltage output should be more-less constant (with a little noise) but right now it very far away from the desired output:

Does anyone have a idea what might cause this problem?

Answer 1

[Joel Van Sickel]

Hello An,

you are trying to use the PWM generator block as an active rectifier. While this certainly can be done, it is not as simple as hooking up an open three phase control to a three phase source. You can do this when running it is an inverter with a dc source, because you don't need to be syncrhonized to your input. However, for an active rectifier, you need to be syncrhonized to the three phase input voltage if you want to generate a dc signal.

This page has more information on how to do that: https://www.mathworks.com/help/physmod/sps/powersys/ref/activerectifier.html

Here is an example on file exchange as well: https://www.mathworks.com/matlabcentral/fileexchange/63357-active-front-end-rectifier

Regards,

Joel

[An]

Dear Joel,

Thank you for your reply!

Actually, in my real project it is the controlled system but at first I received simila wrong results in DC-link.

Part of the system looks like that:

and pulses are generated in control subsystem:

In the documentation is written that input "Uref" of PWM generator has to be between -1 and 1 but I am not sure because it makes things even more complicated and I am not using per unit system.

If I don't use input between -1 and 1, then I get this result in DC-link:

And Vabc voltage in the stator becomes like that:

How would be the best way to solve the issue? Do I need to build PWM generator from scratch?

[An]

And if I change some parameters for pulse generator, like add a gain which makes input between -1 and 1 and switching frequency and making sure than carrer wave is between -1 and 1 too, then I receive this for three-phase voltage:

[Joel Van Sickel]

Hello An,

That last signal is the standard results from an inverter. What kind of waveform are you hoping for? For some references on motor control, please look at this link to start digging into motor control. https://www.mathworks.com/solutions/power-electronics-control/motor-control.html

Regards,

Joel