Wind Power Stabilizing Control Method Of Hybrid Energy Storage System Based On SOC Hierarchical Optimization

The combination of wind farms and energy storage system can solve the volatilityand intermittent of the wind power output power, and reduce the adverse effects of thewind farm output fluctuations on the grid. As hybrid energy storage combines theadvantages of two complementary technologies to provide large power and energycapacities, research based on hybrid energy storage system to stabilize fluctuations inwind power control strategy is particularly important.This paper focuses on the development of a control strategy for optimal use of thehybrid energy storage system (HESS) for smoothing out fluctuation of wind power.Considering an approach based on SOC graded optimization by HESS is proposed,which is the solution of the optimal control problem defined, to incorporate theeffectiveness of smoothing and the operating constraints of the HESS, such as state ofcharge limits, charge/discharge current limits, and lifetime.First of all, research the HESS structure which is consist of vanadium redox flowbattery (VRB) and super capacitor, and design the structure of a hybrid energy storagefor stabilize wind power. According to the simulation needs, design the equivalentmodel and determine the key parameters of the model. Based on the model, analysis ofthe charge and discharge characteristics of HESS, which has guidance significance fordesign and optimization the control strategy of hybrid energy storage running and windpower stabilize.Then, to solve the overall charge and discharge capacity of energy storage devicesand different energy storage devices SOC coordination problems when stabilize thewind power, the paper focuses on the method of based on SOC grading optimizedhybrid storage stabilizing wind power. The method uses a two-tier distributed controlstructure, including optimal control layer and the coordination control layer.Optimization of the control layer on the basis of the low-pass filtering dynamicallyadjust the power setting of the energy storage system for power optimization, which the adjustment amount is decided by stabilize performance requirements by the wind powerand the hybrid storage system this overall SOC state; modulation control layercalculated set power for each storage according to the energy storage device to therespective SOC state and the charge-discharge characteristics, the set power byoptimization control layer calculated power allocation, to achieve the SOC coordinatedcontrol of energy storage device and the fast tracking power setting.The simulation of hybrid energy storage system and wind power builds on thePSCAD/EMTDC platform, designed to verify the effectiveness of the method.Simulation results show that the energy storage system can complete the specified bandfluctuation compensation and HESS remaining capacity remained within reasonablerange, while optimizing the SOC of the energy storage device, to avoid the energystorage device deep charge and extend its life.