mixing multiple power sources
There are various ways to do this.  One way is to connect the wind turbine to a grid power inverter.  Power from the turbine will be dumped back onto the grid when it exceeds what you are using (when the LEDs are off).  Otherwise, it will offset the power drawn from the grid.  For example, if the turbine is putting out 300W and your are using 500W, 200W of that will come from the grid and 300W from the turbine, minus losses in the system of course.

Depending on how important efficiency is and whether grid power going down is a issue, you could run the LEDs from DC with a battery.  Both the turbine and the grid charge the battery as needed, but less will be automatically drawn from the grid when power comes from the tubine.