3KW wind powers system

A simple one would be an alternator from a car, a pinwheel type fan, a few batteries (12V) and a place high enough to catch the wind and not bonk someone on the head.

You have not mentioned if this is a continuous load or storage. Watts per hour minimum, seems to be a better unit to use. A 3kW system gets pretty complicated if this is the base load.

It's a decision you need to make, whether you want to spend more money and less time, or spend more time and less money.

For the former, you can go with a wind turbine of 3kW rating by choosing one that is already tested (by several manufacturers, google 3kW wind power system) and already in the market and then do the installation yourself.

For the later, I don't know if it will be of your advantage, if it benefits you a lot by "re-inventing the wheels", for this will mean a lot of your efforts and time.