it could be the alt making the weird noise , i know some of Hughs machines have been grid tied and the hum/noise changed a bit/lot ..... ( louder ? )
with battery based systems ( i think ) things tend to be quieter......
i tried a very basic pwm controller ( no batteries/capacitors ) on the mill ...kind of one big mosfet ......the modulation of the current made the alt sound like something out of war of the worlds ....a loud modulating groaning sound ....it basically turned the alt into a loudspeaker .......the mosfet blew up pretty quickly after and shorted the mill
wood blades are usually quieter than most as well....strange you hadnt the noise issue before.....maybe your new blades are pushing it harder ...
putting some big capacitors on the rectifier might help .....i,m not sure if thats a good thing for your invertors though ....it may help ...ish.......
i dont use batts on the mill now ...just big capacitors then into a pwm dump .......but the mill will kill them too over time
your watching it close though ......thats a good approach
edit....just checking the caps on the mill rectifer ....their 2 10000uF 80V electrolytics in parallel .....
your in unkown terrority .....