Frequency Support for DFIG Using Improved Inertial Control Strategy

With the increased penetration of renewable energy, maintaining the system frequency stability is becoming more and more challenging due to the reduced inertia. This paper proposes an improved short-term over-production control strategy based on the virtual inertia provided by wind turbines. In particular, the limitations of the current short-time over-production control of DFIG wind turbines are investigated, including the excessive release of rotor kinetic energy and the secondary frequency drop. Then, an improved three-stage control strategy is proposed, including the frequency adjustment mode, the speed recovery mode and the maximum power tracking control mode. Test results on the 3-machine 9-bus system verify the effectiveness of the proposed control strategy in improving system transient frequency response performance.