A combined fault ride-through and power smoothing control method for full-converter wind turbines employing Supercapacitor Energy Storage System

• A combined fault ride-through and power smoothing control scheme for WTGs is proposed.
• A Supercapacitor Energy Storage System is integrated in the power converter system.
• An analytical expression for the sizing of the SCESS is calculated.
• Optimal utilization of the SCESS by controlling the SoC is performed.

As the wind power installations are increasing in number, Wind Turbine Generators (WTG) are required to have Fault Ride-Through (FRT) capabilities. Lately developed grid operating codes demand the WTGs to stay connected during fault conditions, supporting the grid to recover faster back to its normal state. However, forcing a WTG to remain connected during a grid fault has consequences on the conventional protection devices, as they might become blind to over-currents and short circuits. This paper proposes a new control algorithm combined with a power management method, which fulfills the demand to keep the WTG connected to the grid during a fault, but disconnects the WTG when the fault insists. The energy generated while riding through a grid fault, is stored in a Supercapacitor Energy Storage System (SCESS). Furthermore, the SCESS is exploited for smoothing medium frequency wind power fluctuations, providing a high quality power profile. The simulation results which are performed on a 2 MW synchronous generator with external excitation, verify strongly the proposed power management method.