Controller for Single Phase Inverter with Inductive Load to test brand new MOSFETs

Discussion in 'General Electronics Chat' started by Bakez, Aug 30, 2012.

  1. Bakez

    Thread Starter New Member

    Aug 21, 2012
    28
    0
    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:

    [​IMG]

    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:

    [​IMG]

    and then I use this PI controller:

    [​IMG]

    I will post another post below with my working

    All help appreciated
     
    Last edited: Aug 30, 2012
  2. Bakez

    Thread Starter New Member

    Aug 21, 2012
    28
    0
    I think that the transfer function in the S domain for the load is:

    [​IMG]

    and the transfer functions for the control inverters are:

    [​IMG]

    [​IMG]

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

    [​IMG]
     
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