How to represent bidirectional Mosfet switches using sub cycle average model

Question

In RTBox1 modelling, we can represent the Full bridge and half bridge using sub-cycle average configuration so that we can use the PWM capture block as a digital input in plant modelling. However, how do I represent a bidirectional switch in a sub-cycle average configuration?

If the bidirectional switch's average model representation is impossible, the digital input block can only be used in RTBox1. So, will this create any problems?

Answer 1

Sub-cycle averaging consists of averaging all of the individual gate signal inputs and applying that to an integrated model at the power module level. See the "3-Level Half Bridge (T-Type)" power module for an example of a power module which essentially has a bidirectional switch in the neutral path.  If there is no analog in the power module library, you will have to derive your own model.  What topology are you modeling?

See the introductory paper on sub-cycle averaging and paper on multi-level topologies.

You can use a digital input connected to a switch, but note that sampling a PWM signal once per simulation step the simulation results in poor performance unless the model step size is very small compared to the switching period.

Comments

Thanks, Bryan, for the information.

There is no Bidirectional switch block available in the power module library. Yes, it is there in a T-Type structure. I am trying to simulate HERIC topology, i.e. (transformer-less inverter) in RTBox1. 

I have checked the subsystem model of the sub-cycle averaging power modules, but it seems pretty tricky to build. I will refer to the above IEEE papers. 

If you have the bidirectional switch (MOSFET) power module library, please share it with me using my email ID.

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Thanks for the additional information Sanket.  I have built a HERIC power module as part of a previous development effort.  I'll send it to you via email.