You start with the power plants that require the least power for their own operation, use diesel generators to power them (controls, excitation windings, systems for fuel or whatever power source they use, etc.), start them up and bring them online to the grid, with all branches and load disconnected, except the power plants that require a bit more to power up, then rinse and repeat, probably also connecting load as required, for minimum load and probably also to keep the power factor within reasonable limits (not sure how important the latter is with such low load, but I guess it could be).