Damping Torque Analysis of Virtual Inertia Control for DFIG-Based Wind Turbines

The increasing penetration of large-scale wind generation in power systems will challenge the power system inertia due to the reason that the converter based variable speed wind turbines have no contribution to the system inertia. Traditionally, a doubly fed induction generator (DFIG)-based wind power plant naturally does not provide frequency response because of the decoupling between the output power and the frequency. Moreover, DFIGs also lack power reserve margin because of the maximum power point tracking (MPPT) operation. In this paper, a virtual inertial control strategy of the DFIG based wind turbines called supplementary control loop for inertial response is investigated. When the system frequency is changing severely, the output power of DFIG should respond to it rapidly through the virtual inertial controller at the same time. The rotor speeds of wind turbines can also be adjusted into this procedure. The inertial control methods proposed in this paper can supply controllable virtual inertia of DFIGs to the power system so that the system frequency stability can be strengthened through inertial control of wind turbines on the basis of damping torque analysis.