Sizing and simulation of a low cost flywheel based energy storage system for wind diesel hybrid systems

Wind diesel hybrid systems are isolated systems combining diesel generators with wind turbine generators. In order to reduce substantially the fuel consumption the system should be able to work with the diesel generators not running. However, this requires additional equipment and increases the control complexity. A short-term energy storage system allows reducing the number of start-stop cycles in the diesel generators. For this aim, a low speed flywheel based energy storage system can be used, as it is a robust and low cost solution. The necessary characteristics are analyzed and an example of sizing with an asynchronous machine and a steel flywheel is given. The power converters and the asynchronous machine can be controlled as if they were a servo but, in order to attain more robustness, it is better to control the asynchronous machine to maintain a constant DC-voltage and the grid converter to follow the necessary power references. Finally, in order to verify the proposed low speed flywheel based energy storage system, it is simulated along with a complete wind diesel hybrid system.