hai nitin,
make your solar array string volatge to 675 v and consider the panel wattage with respect to a motor current rating and desided how many panel in series and parrallel. the easiest way for the vfd solution is to go with a delta e series inverter which is having a built in mppt algorithum. or design your own feed back using a resistive network which feeds variable power of 0 to 10 v with reference with the solar panel volatage and feed it in its speed setting port where there is a provision for external voltage or potentio meter input.