The non-planned isolated process of microgrid is studied when the microsources are under power control or voltage frequency control. An output power control strategy for the microsource and one for the utility grid are presented， with the isolated voltage criteria introduced into the strategies. The focuses of the two strategies are different in that the former is more in conformity with the microgrid characteristics of flexible isolated operation， while the latter facilitates the management of the utility grid. It is advisable to comprehensively consider the requirements of microgrid and utility grid when working out the microgrid control strategies. Modeling and simulation results in PSCAD show that both strategies maintain microgrid stable operation whether in the grid-connected mode or in isolated mode， while the strategy with voltage frequency control is even more convenient in making the microgrid restore stability.