To provide a method of controlling combustion stability while using a simple, practicable and relatively inexpensive means for a pulsation valve.

The method using a controller comprises steps of: receiving information about environmental and operating conditions; comparing the environmental and operating conditions with previously programmed information to determine whether the possibility of combustion instability exists or not; determining the best fuel modulation frequency and amplitude matching to the environmental conditions to reduce the combustion instability when the possibility of the combustion instability exists; and actuating at least one fuel control valve for matching to the best fuel modulation frequency and amplitude to reduce the combustion instability when the possibility of the combustion instability exists.