The original meaning of your question is that wind turbines use conversion devices (windmills) to convert wind energy into electrical energy. So if the wind turbine does not work, is the wind energy greater than when the generator is working? Or is the wind speed greater than before?
For a closed space, according to the conservation of energy, this is the case. However, the working environment of the wind turbine is open, so whether the generator is working or not, it will not affect the wind speed.
The so-called wind energy is the mechanical energy corresponding to the flow of air - kinetic energy. The working process of the wind turbine is to convert part of the kinetic energy of the air into electrical energy, and the total kinetic energy of the air is very large, and due to its flow nature, so some of the air passes through the wind turbine, and the rest is immediately replenished there. Therefore, the wind speed will not be reduced due to the operation of the generator.
Who exactly is the "wind speed" you mentioned? This is the key to answering your question. Is it the wind speed at a specific point, or is it the overall, approximate, general wind speed?
If we talk about the overall wind speed: No need to do experiments, energy cannot be generated or disappeared out of thin air. Wind power generates electrical energy, so this part of the energy cannot be generated out of thin air. It is converted from the kinetic energy of the wind. The overall wind speed will naturally decrease after passing through the generator fan blades.
If it is a single point, then it is obvious that the flow rate at most points has decreased, and the flow rate at some points (a very small part compared to the majority) has accelerated.