Hi
I need frequency converters attached to a digital thermostat in order to automatically increase or decrease the speed of the fan depending on the desired temperature. Note the following clarifications:

I have 6 separate greenhouses with each greenhouse having 10 fans (3 phase, 380V, 1.1 Kw),
I have 2 separate bird aviaries with each having 2 fans (3 phase, 380V, 1.1 Kw),
I have an experimental area with 2 smaller fans (3 phase, 380V, 0.55 Kw),

The number of frequency converters required depends on the number of fans that each frequency converter could handle /control together. I sure hope I do not have to install separate converter for each fan. If it is up to me, then I would need one frequency converter per separate unit, which would 9 frequency changers + 9 companion digital thermostat.

anyone helps!

Yeah, the fans can be controlled by frequency converter automatically according to the temperature you desired on the thermostat.

Here is the suggestion:
1. 2unit frequency converters(1.5kW) control 2fans, 4unit frequency converters(2.2kW) control 8fans, total 6units frequency converters.
2. 2unit frequency converters(1.5kW) control 2fans.
3. 1unit frequency converters(1.5kW) control 2fans(0.55kW).
So you just need 5units 1.5kW and 4unit 2.2kW frequency converters.