This is an interesting project I have where I will be testing the efficiency of never before used MOSFETs. However the general setup of the test circuit is very common - it is just a single phase inverter or HBridge with an inductive load:

The problem I have is I am not good at control theory. I need to design a PWM PI controller that will control the sinusoidal current output through the inductor. So I will have a reference current and the error on the output current will be used to control the duty cycle of the PWM and hence the average voltage, and therefore output current.

I am not good at transfer functions, although I know I have to design this in the z domain as I will have to implement the controller digitally, and I have to incorporate some sort of delay as the duty cycle of the PWM can only change once per cycle. Also I think the DUT can be controlled open loop so I only have to design a PI controller for the control side.

Basically I think I have this transfer function in the S-Domain and have no idea how to get it into the Z domain:

and then I use this PI controller:

I will post another post below with my working

All help appreciated

 

I think that the transfer function in the S domain for the load is:

and the transfer functions for the control inverters are:

The delay of half a period can be taken as (according to a book):