AC/DC Three-Level PWM Converter

AC/DC Three-Level PWM Converter is an example matlab file and why this file doesnt not work for negative active power reference.Does it needs to change the initial conditions set and if so how to do that ?

[Joel Van Sickel]

Hello Neethu,

Could you confirm that this is the model you are referencing? power_3levelVSC

It's documentation is here: https://www.mathworks.com/matlabcentral/answers/556774-ac-dc-three-level-pwm-converter

Is this the model you are asking about? If so, what block are you trying to modify with the above question?

Regards,

Joel

[NN]

yes, this model.

I tried to change the active power reference negative, by giving a negative value say -1 directly as idref instead of DC voltage regulator.But the model doesnt follow negative active power reference.Can i know how can i modify the model so that it follows negative id ref same like it follows negative iqref.

[NN]

[NN]

[Mohsen Aleenejad]

My understanding is that the topology is not physically able to follow the negative reference. The load consists of two parallel resistive branches. There is no power/energy generaor (at the right side of the converter) to constantly put back the energy into the 600V three phase system. As a rsult, the active power is always positive and Id cannot remain negative.

[NN]

Thank you .i tried connecting the right side of the converter with battery , still not following .Can you suggest some solution to this ?

[Mohsen Aleenejad]

You mean that you replaced the resistors with battery? or added battery to the existing resistors? The second option does not work for sure, and the first one works if you add some small resistors in series with capacitors like this:

the results:

However, my suggestion to you is simulating a model that is a real life application, like this one:

So, you should keep everything in the model like it was at the beginning. Do not use negative constant for id. Use the output of the corresponding control block, like it was before. Take out everything after the two Capacitors with middle point and place a three phase inverter and induction machine (like the above picture). Drive does not need any closed loop control, just run it with the simplest switching method, like open loop V/F. Change the load torque with a periodic function like sinusoidal. In this way, you will take the inuction machine to the motoring and regenerating mode periodically. If you want to keep the power and id negative all the time, then, set a negative value for the Torque load (instead of sinusoidal).

[Mohsen Aleenejad]

I hope this resolves your issue.

Good Luck

Mohsen

[NN]

Thank you Mohsen.I i wll surely check these otpions

[Mohsen Aleenejad]

I am happy that I could help.

Good Luck.

Answer 1

[Mohsen Aleenejad]

The reason is that the topology is not physically able to follow the negative reference. The load consists of two parallel resistive branches. There is no power/energy generaor (at the right side of the converter) to constantly put back the energy into the 600V three phase system. As a rsult, the active power is always positive and Id cannot remain negative.