Research On Performance Characteristics And Control Strategy Of Wind-storage System

Wind power is a widely used green renewable energy in the world and has developed rapidlyin China at recent years. However, due to the randomness, volatility and intermittency, which arethe substantive characteristics of wind, large-scale integration has an adverse impact on safe andstable operation of grid. One of the effective solutions is to configure battery energy storagesystem for wind farms. As a result, concerning research on storage capacity and wind-storagecombination control has become a hotspot.As the expensive cost and short life, most of the time small scale of storage system is used tosmooth wind power fluctuations, which brings challenges to control strategy of batteries. In thisarticle, research is based on a real medium-sized wind farm, focusing on using lithium-ion batterysystem to smooth output power fluctuations of the all-DFIG wind farm and virtual inertiacompensation strategy for transient support on grid, also, reactive power/voltage control on PCCis implemented at the same time. Achievements are mainly from the following respects:At first dynamic models of the double-fed induction generator and lithium ion battery arebuilt as a basis of simulation. Then analyse the characteristics of wind farm original power outputand control strategy combined battery SOC control and first-order low-pass filtering algorithm forsmoothing output fluctuations is presented, which manages to prevent excessivecharging/discharging when power change is limited under sustained winds in the capacityconfiguration of battery system equals to10%of wind farm rated power.Then wind-storage coordinated control strategy on inertia response is discussed. Responseexcited by rotor kinetic energy control on DFIG is proved to be able to suppress transient frequency disturbance. However, performance is limited by operation point of generator. Thus,theory analysis on virtual inertia compensation and configuration capacity of storage system iscarried out and coordination rules of wind and storage system are presented. By utilizing storagesystem to supplement DIFG power gap, transient frequency support is achieved while safe andeconomic integration is available.Also, study on fluctuations of PCC voltage and power factor arising from large-scale windpower integration, is conducted. Take account of the negative correlations between active andreactive power output of DFIG, this article put forward a coordinated control strategy of givingpriority to storage system, supplemented by wind farm. Minimum capacity of PCS underactive/reactive power control is then taken into consideration.Control strategies discussed above are intended to apply in a wind-storage demonstrationproject. On-site commissioning tests in a wind farm with a large capacity of2MW battery storagesystem installed are in progress, practical feasibility and availability are then verified from theactual statistics.