An Active Damping Control Strategy for Grid-Tied Type-4 Wind Turbine Generator Based on Energy Feedback

Abstract

In a grid-tied type-4 wind turbine generator (WTG) system, the frequency of sub/super-synchronous oscillation varies in a wide range, making it difficult to suppress the oscillation. In view of this problem, an active damping control strategy based on energy feedback is proposed. First, the energy balance equation of stored energy, dissipation energy, and interaction energy in a grid-tied type-4 WTG system is established. And the mathematical relationship between the increasing/decreasing trend of stored energy and the divergence/convergence of oscillation, no matter how the oscillation frequency varies, is derived. Then, by calculating the contribution degrees of different energy feedback branches to the variation rate of stored energy, the key energy feedback branches that cause the stored energy to increase are selected. And then, with the variation rate of stored energy being made negative as the control objective, this article derives a reactive current compensation function and constructs an additional energy feedback branch to eliminate the effect of key energy feedback branches, thus realizing active damping suppression of oscillations in a broad frequency band. Finally, the real-time digital simulator based hardware-in-loop test platform with a practical controller of a real 2.5-MW type-4 WTG and experimental platform are both built on which the proposed strategy is verified. Simulation results show that the proposed method can realize effective damping control of oscillations in a broad frequency range. In addition, this article is accompanied by a video demonstrating hardware-in-loop test results.