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Simulink Universal Bridge with ideal switches

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Federico on 18 Mar 2017
Answered: Alisha Schor on 21 Mar 2017
Dear All, can some one explain to me what does the following sentence, that I can find in the documentation concerning the Universal Bridge Block in the configuration Switching-function based VSC, mean?
" When you select Switching-function based VSC, a switching-function voltage source converter type equivalent model is used, where switches are replaced by two voltage sources on the AC side and a current source on the DC side. This model uses the same firing pulses as for other power electronic devices and it correctly represents harmonics normally generated by the bridge."
I was convinced that the block were equivalent to
Thank you very much in advance, Federico

Answers (1)

Alisha Schor
Alisha Schor on 21 Mar 2017
The "Switching-function based VSC" and "Average-model based VSC" are options for equivalent models to represent the output value of the voltage source converter. These are helpful in speeding up simulations where capturing the behavior of each switching action may lead to extraordinarily long computation time. Thus, they are representations of the switch configuration you have shown, which can be implemented exactly with the Ideal Switch parameter of the Universal Bridge Block.
The example model that follows, "power_sfavg", is helpful for comparing these two approximations to the ideal behavior.
Change Model 1 to represent the Ideal Switch, and then run the model to compare the "Switching-function based VSC" and the "Average-model based VSC." You can view the outputs by double-clicking the green Scope. Model 1 is displayed in yellow, Switching-function approximation in blue, and Average-model approximation in red. You can see that the switching-function captures each switch quite accurately, despite not being an exact representation. You can also right-click on each of the Universal Bridge blocks and choose "Mask > Look under mask", and then double click on the model subsystem to see how each representation is built.


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