The text below was part of an ongoing thread that I was participating on another board. Some of the members on the other board asked exactly what I was wishing to accomplish so the topic is treated in more detail than most. I'm still looking for a small (INEXPENSIVE) kit
I want to develop an inverter to take a 200v dc bus and convert it to120vac. I will use 4 mosfets configured in an H configuration. By controlling the switching trajectory of each fet the output will be sinusoidal in shape. Of course there will be some switching garbage in the way of harmonics that I will have to deal with. A mosfet will allow a carrier switching rate of say 20kHz no problem - the faster you switch the higher will be the spectrum of harmonic trash that needs to be filtered. So then the faster you switch the easier the filter design becomes. A switching rate that is an exact multiple of 60Hz would be good so that the carrier and the fundamental components can be synchronized - called synchronous pwm. This may be easier to implement with a small micro.
The 200v dc bus will probably come from 4 car batteries connected in series. This will go into a full bridge phase shift converter running at 100kHz or so - I've got a couple kicking around here that I have already built. The200v bus can be regulated to within a gnat's ass, so the sinewave inverter can run open loop without having to compensate for bus voltage variations.
So what the micro has to do is output the pwm routine to drive the 4 mosfets. This could be as simple as a counter and a table with the pwm times stored. Go to address 1 and load that number into the counters(and the info for state latch as well). Count down to zero and go to address2 and load that number into the counters. Perhaps there are 200 (for a 12kHz carrier) address that store the timing and state information for one sinewave.
There are only 4 possible states with the inverter while it is running.. Top right and bottom left both on. Top left and bottom right both on. Both top on, or both bottom on - each called a zero state. Only other possible state is all fets off, but that is never used while the inverter is running. Never are the top and bottom transistors in the same pole on, because that would put a direct short across the bus.
My microprocessor skills are almost non-existant so I am looking to getting my feet wet. Whatever platform I choose (based on you guy's input) it should be above everything else easy to learn. It must also have the computing power necessary to do the pwm routine. I'm basically looking for somebody to tell me to go to digikey and order such and such a kit.