Nowadays, the penetration of wind and solar sources is relatively high in Micro Grid. Wind speed and solar radiation forecasting hardly gives an exact value and leads to the values in intervals. Therefore forecasted output powers of these sources are also in the intervals. The constraint on power balance in Micro Grid has the right-hand-side uncertainty, in the interval. So for Micro-Grid in grid connection mode, the presence of the distributed generations based on wind and solar energy sources makes optimal dispatching problems of distributed generations become an uncertainty problem. The optimal solutions for the lower and upper ends of this interval are the best and the worst optimal solution. This paper proposes to treat the above problem as the optimal problem with two objectives: reach the best and the worst solution. The principle of fuzzy set and the Particle Swarm Optimization algorithm will be applied for solving the multi-objective problem. The final optimal value will belong to an interval. Meanwhile, the output power of the swing generator varies to respond to the uncertainty of wind and solar source power. An example of a low-voltage MG with three distributed generators is considered with two cases: connecting to the utility grid via the circuit breaker and via power controller.
