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.