Interesting Idea.
I have also been thinking about how to use a Class D type audio amplifier IC to drive the H-Bridge in order to get a very clean sine wave just for greater overall efficiency though. This is the class D amp IC I was planning on experimenting with some time. I would just use the outputs to drive a set of IRF2110 or similar high/low side driver IC's that run the line side connected H-Bridge.
I am not one that cares much about output filter size. The output filtering that I have been using is not all that large in comparison to the rest of the GTI device. Just a the right size PFC capacitor and a basic dual choke AC line filter with the right amp capacity has shown it works just fine. Or at least with the low frequency transformer design it does.
I also think that by using a line side coupled op amp with all of its power and control circuits placed on the line side of the GTI it should be able to directly sample the line side wave form and feed it directly to the amplifier IC. That way the slight phase lag is brought down to less than a degree or so.
The input power source could then just be a simple fly-back or some type of switching inverter (Modified store bought inverter?
) to take the variable input voltage and power available and then isolate and step it up to the line voltage levels that would supply the actual power to the H-bridge.
The down side to all of this is the overall complexity of the added switcher inverter isolation efficiency, 80 - 85% typical, plus the class D H-bridge drive and other factors dont add up to much greater overall efficiency gains or a overall improvement in line side wave form.
But the cost and complexity goes up.
If the input power source could be electrically isolated and was putting out a voltage high enough to run at line level voltages then the switching inverter isolation could be removed. I can see a theoretical GTI efficiency that would easily get into the 90 - 95+% overall peak operation efficiency. Maybe.
Theoreticaly speaking of course.