Comparison of fault-ride-through capability of dual and single-rotor wind turbines

The majority of wind turbines currently in operation have the conventional concept design. That is a single-rotor wind turbine (SRWT) which is connected through spur gearbox to a generator. Recently, dual-rotor wind turbine (DRWT) has been introduced to the market. It has been proven that the steady state performance of the DRWT system for extracting energy is better than the SRWT. But, a comparison of fault-ride-through capability of these two types of turbines requires further research. In this paper, the fault-ride-through capability of DRWT and SRWT are evaluated and compared when generating units are operating at constant pitch angle and constant speed modes. Constant pitch angle mode is simulated to investigate the natural damping of DRWT and SRWT. To verify the time domain simulation results, damping characteristics of DRWT and SRWT are also compared through eigenvalue analysis and speed droop characteristics of the control system. The accuracy of the aerodynamic model of the DRWT is enhanced by including the stream tube effect in the simulation. It was uncovered that DRWT introduces higher damping torque to the network in both constant speed and constant pitch angle modes. This advantage improves the transient performance of DRWT-based wind farms.