Windmill makers solved this problem in the 19th century by simply turning the turbine away from the direction of the wind.
Installing a Reeves drive, as used in snowmobiles and ATVs, between the turbine and the generator would work, although it would lose some efficiency. The principle behind the Reeves drive was invented in the early 1800s, if memory serves. A variation would use a bicycle derailleur.
None of this solves the problem of getting power when there’s no wind.