A couple of years ago when I turfed the back yard, I had dug a trench and installed two separate conduits running from under the house to the veggie patch. One of the conduits was to run power through it. I have normal AC house power through there and I also ran an additional 3 2-pair wire for DC usage. At the time I wasn’t sure what I would use it for, but I am glad I did install those wires!
Fast forward to today and I needed 3 wires to run two sets of 300 fairy lights. Each set of lights had its own controller and running them at the same time would eventually cause the flashing/pattern of the lights to go out of sync. So opening up the controller and wiring it so that one controller controls both sets of lights worked very well.
The lights have two separate circuits, one circuit controls half the lights. This is how it is able to make them flash in different sequences. So the power needed was two positive leads and one negative. Running at +12v DC.