Coordinated Control Strategy of Wind Turbine Generator and Energy Storage Equipment to Avoid Frequency Secondary Drop
In the modern power system with high penetration of wind energy,the wind turbine generators participate in the frequency regulation by releasing rotor kinetic energy to improve the frequency stability.But there is a problem of insufficient support effect due to under-regulation or secondary frequency drop(SFD)caused by over-regulation.Energy storage equipment frequency regulation is not affected by time-space factors,which can improve the effectiveness of the primary frequency regulation.First,this paper analyzes the mechanism between the SFD and the wind turbine control strategies based on the Unified Transfer Function Structure(UTFS).Then,the regulation parameters of wind turbine generators are calculated,which can avoid the SFD and make full use of the rotor kinetic energy.Moreover,the frequency security margin is proposed and expanded equivalently by calculating the minimum output of energy storage based on the relationship matrix.Based on the above analysis,considering the influence of space-time factors on the system frequency regulation,this paper proposes a new coordinated control strategy at multi-time scales for wind turbine generator and energy storage equipment to provide adequate regulation with avoiding SFD.Finally,this paper establishes a simulation model with high penetration of wind energy including four machines and four zones in DigSILENT.The results show that the proposed control strategy avoids the SFD while making full use of the frequency regulation capability of the wind turbines at different wind speeds,and improves the frequency security margin of the whole network.
power system with high wind energy penetrationsecondary frequency dropunified transfer function structurecoordinated frequency regulation of wind turbine generator and energy storage equipment
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