Apologies for bumping an old thread, but I did find an amazing Linux utility which allows me to control my Corsair HX1200i PSU:
https://github.com/liquidctl/liquidctl
You can easily install it using python3:
sudo pip3 install liquidctl
To configure, read, and set my power supply information
sudo liquidctl list
sudo liquidctl initialize
sudo liquidctl status
sudo liquidctl set corsair speed 100
sudo liquidctl status |grep Total Power