I'm not an expert, however a synchronous motor, as the name say, has a speed synchronized with the frequency of the AC signal from which it is supplied.
Then to vary the speed you need a static inverter that allows to change the frequency of its output while the voltage is always the same (230V in your case).
Possibly the power dissipation of the motor will change with the speed, so probably you will have to account for this.
i think VFD for asynchronous motor speed control , normally comes with 3 phase 120Ddeg phase shift w,r,t voltage . , but i am looking for Asynchronous motor speed control , may be construction deffer from asynchronous...
"but i am looking for Asynchronous motor speed control , may be construction deffer from asynchronous...". Asynchronous motors are "universal motors" with brushes, they can be controlled by varying the voltage to them with something like a light dimmer with a triac.
frank