The excess amount is equivalent to 6.83% of the 17.55 million tons it had agreed to supply this year, it said in a statement.
This means power plants will receive an extra 10,000 tons a month for the next two months.
In July alone the excess supply will be 500,000 tons.
National utility EVN had requested Vinacomin and another coal supplier, Dong Bac Corp, to ensure adequate supply in June and July amid a severe electricity shortage in the north due to low water levels in hydropower dams.
Recent rains have helped increase storage but the plants are still running below full capacity to save water for the upcoming hot weather.