| In recent years,the instability and unpredictability of wind power generation system has led to the aggravation of the power fluctuation in power system,which brings great challenges to the stable operation of the power system.It is conductive to deploy appropriate storage device in order to transfer renewable energy with a low power factor,oscillation and instability into high-valued and stable electrical products.Eventually,it improves consumptive ability of wind power,and relieve the adverse effects caused by renewable energy to the power.Superconducting Magnetic Energy Storage(SMES)combined with mature power electronic technology and control technology can be used to compensate the power fluctuation in the power system accurately and timely.In this prospect,SMES is able to actively accomplish the stabilization near the fault point in order to improve the stability of the power system.Compared with other energy storage methods,SMES has obvious advantages of lossless storage and millisecond level response.However,using superconducting tape material,SMES needs low temperature environment mainly about cryogenic equipment to work,which gets together contribute to considerable costs.As for widely deployment in distributed power generation,the expensive construction cost is the key factor that restricts its application.In recent years,the research of hybrid energy storage technology with superior aspects on economic and performance has become a new solution.Hybrid Energy Storage System(HESS)is composed of the power type and the capacity type storage devices.Each type storage device plays their respective advantages,through coordinated control to achieve high energy storage/release energy power management such as high power,large capacity,fast response,high compatibility and high dynamic performance at the same time.Compared with traditional single energy storage system centralized control mode,the HESS has enormous difference in topology design and control algorithm.For the reason that the storage devices have nonlinear,time-varying and coupling characteristics,when it comes to the HESS,it has much more complexity of the above characteristics.Few literatures considered the above characteristics,especially the variations of the internal or the external disturbances.Therefore,it is of utmost necessary to analyze the structure and the coordinated control method of the HESS.Based on the above outstanding problems,the structure optimization of the HESS and the corresponding design of the control system are analyzed and studied in this dissertation.In establishing the structure of the HESS,firstly,by analyzing the factors that affect the performance of SMES,it is to calculate reliable electromagnetic parameters and to establish the SMES mathematical model.After,we analyzed the mechanism of storage system to stabilize the fluctuation of power system,and in-depth analyzing the complementary characteristics of battery and the SMES in power and energy density aspects.At last,under the premise of retaining the advantages of SMES,we analyzed and discussed how to reduce the proportion of SMES in HESS to reduce the cost,and a cascaded structure of two-level HESS model has been established.In terms of designing a control strategy,we introduce a robust control method specifically for nonlinear,time-varying,coupled and uncertain systems: Active Disturbance Rejection Control(ADRC).We take a comprehensive consideration of the difficulty in establishing the accurate dynamic model of hybrid energy storage system in a wind power generation with actual internal and external disturbances.Based on the ADRC has the advantages of small overshoot,fast convergence,high precision and strong anti-interference ability,we established a charge/discharge comprehensive control strategy,which does not depend on accurate dynamic model of the wind power system or the HESS.Then,we applied the COMSOL for the multi-physics simulation of SMES-battery hybrid energy storage system,which aims to illustrate the hybrid mode and the cascaded structure of the charge/discharge and effective extension of storage equipment service life has sufficient the advantages in the real physical environment.At last,the MATLAB/Simulink platform is applied to test the hybrid energy storage system performances in constant voltage charging,constant current charging,grid-connected mode and specified power discharging.Combined with experimental examples of in-depth analysis,attention has to be paid to improve anti-disturbance ability when the wind power fluctuation and the system parameters change occurred.The dynamic performances under different control strategies with various combinations of energy storage are compared and analyzed,and the relevant conclusions are given under the quantitative evaluations index.It is verified that the cascaded hybrid energy storage system and ADRC strategy can improve stability and suppress disturbances due to various reasons in the application of “wind-storage-grid” system,which has better dynamic characteristics and adaptability.Therefore,the research content of this project is oriented to the actual need of wind power generation system,and has a good base of application.It can also be extended to research on related topics such as “photovoltaic power generation and energy storage”,“photovoltaic-wind generation and energy storage”.It will also provide theoretical support for further research on improving the uninterrupted operational capability of wind power generation. |
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