> true, you can drive an h-bridge with a pre-canned pwm waveform whose phase you adjust with a latency measured not just in milliseconds but in seconds I’m not

> true, you can drive an h-bridge with a pre-canned pwm waveform whose phase you adjust with a latency measured not just in milliseconds but in seconds I’m not sure what you’re trying to say with this paragraph so I’m not going to respond to it. > think it's sufficient to not make your p coefficient overwhelmingly large. a sufficiently large i coefficient will also make What I’m saying is that making the P term small enough not to pin the PWM means that it won’t do anything useful, though I do see I wasn’t originally as clear as I could have been on that point. Either there won’t be enough gain or you will pin the output. There is no meaningful range of values in the middle, especially when the system needs to work outside the laboratory and you can’t tweak the parameters every other day. If you rely completely on the I term, you’ll have stability problems. So now it requires a lot of D term… and now you’ve gone full circle and we’re back to “the whole thing won’t work without a time constant which makes it totally useless to run a PWM and barely useful for the outer loop.” > you can totally use current feedback from the output of your smps to drive the pwm, and that seems to me like it would be a very good idea I did mention that already… along with the fact that you need to set some target for your current feedback using an outer control loop. You can set the target by measuring frequency error averaged across several cycles. Again, you need on the order of 100 ms to make that work. Whatever way you slice it, the grid backup battery is not going to start exporting power to the grid in less than a cycle, and certainly not in less than a millisecond.