Participation of wind turbines in frequency control of a hybrid renewable energy system

Abstract

This paper presents frequency control of a hybrid renewable energy system comprised of wind farms, fuel cell and battery with the main contribution of wind energy conversion system. Wind farm generated power varies by wind speed changes and therefore, high penetration of wind farms into the network decreases the system inertia and causes severe frequency deviation. Due to this fact, it is necessary to involve wind turbines in frequency control structure. The amount of kinetic energy stored in the rotating blades of wind turbines has a significant value, which has to be used in an efficient way to mitigate frequency deviation. On the other hand, adjusting the blade pitch angle is one of the most applicable approaches for regulating aerodynamic torque in wind turbine. Inertia control and direct pitch angle control of the wind turbine are introduced to improve the frequency deviation of the hybrid system. In addition to this, battery energy storage and fuel cell are utilized in order to help the frequency control. Utilization of proposed controls on wind turbines leads to lower size battery requirements that decreases the system cost. Simulation results are presented to analyse time domain behaviour of the mentioned hybrid system.