If I can able to understand ur requirement correctly (assuming it is a thermal power plant), u want to run two Generators in parallel in Island mode. In such a case u need to keep load on one Generator constand ( by keeping the Governor on load mode ) and remaining load on the 2nd one in Speed mode ( controlling the Frequency).
In this case all the load fluctuations shall be controlled through 2nd Generator. During this period you should be very carefull with parameters of Boilers side connected with 2nd Turbogenerator set.