Control methods for dynamical storage systems in wind parks

The amount of electricity generated by wind energy converters has significantly increased on a global level, especially in the last decade. The intermittent nature of onshore and offshore wind resources imposes substantial technoeconomic restrictions which become more challenging as the share of wind power in the electrical networks increases. Dynamical energy storage systems can be employed in order to smoothen the fluctuating power output of grid-connected wind parks and to improve the quality power connected to the grid. A dynamical energy storage system acts as an intermediate wind energy buffer, compensating for short-term fluctuations of the energy source and variations in the load. This paper presents three different control methods for such a system that uses a flywheel as a storage device; namely the tolerance-band method, the SK-method and the adaptive tolerance band method. The performance of each control method is investigated in the time and frequency domain and their advantages and limitations are discussed.