| In recent years,energy storage has become more and more mature and widely used due to its characteristic rapidity and flexibility.For one thing,the energy storage power station can supply the auxiliary service of peak shaving and frequency control,which can smooth fluctuations of large-scale renewable sources and improve the performance of frequency control and peak shaving.For another thing,scattered small and medium-capacity energy storages in the distribution network provide services such as voltage regulation and power flow optimization which can broaden the types of grid auxiliary services.This paper studies energy storage systems of different sizes in different types of ancillary services,which aim to improve the power quality such as frequency and voltage.This paper concentrates on control technology of energy storage for auxiliary services,that includes following research works:1)Because different types of energy storage have different control methods and response capabilities,the operation control methods for different types of auxiliary services are also inconsistent.Firstly,this paper establishes the general models for energy storage system,discusses the working principle of the energy storage and converter,and study its influence on the operation control of the energy storage system.Secondly,this section discusses the large-capacity energy storage power station based on the general model providing the foundation for auxiliary services and simplifies the model to meet the regulation needs of energy storage.Finally,considering the differences between distributed energy storage in the distribution network and energy storage power station,this section establishes model for distributed energy storage system suitable for voltage control in the distribution network.2)In the process of large-capacity energy providing auxiliary services of peak shaving and frequency control at the level of transmission grid,energy storage can suppress frequency fluctuation and reduce difference between peak and off-peak.When the energy storage provides auxiliary service frequency control,a robust control strategy is designed to solve the problem of the multiple types of uncertainties in the secondary frequency modulation process of power grid.In the aspect of peak-shaving with energy storage,the section focuses on economic optimization of operation.Firstly,in view of the communication delay and uncertainties in the frequency modulation service,this section designs a control strategy for frequency control service of the power grid based on the robust control method.Secondly,concerning to running cost or economy in the auxiliary service of peak shaving,this section designs a control strategy for minimizing the cost of the system at the long-time scale.Finally,the section analyzes the evaluation of control objective and use regional grid system containing energy storage to verify the proposed method.3)In the service of voltage adjustment in the distribution network,this paper focuses on the voltage control method of the auxiliary voltage regulation.The method can fully utilize the small-capacity distributed energy storage systems and photovoltaics at the distribution network level to realize fast recovery control on voltage over-limit.Firstly,this section establishes dynamic models for different local working methods of photovoltaics and energy storages and combine the voltage sensitivity model of the distribution network,which divides the overall distribution network into small regions through the ε decomposition method to achieve System decoupling between different areas of the distribution network.The method constructs a distributed voltage control mode for each sub-region according to the formed distributed voltage control structure,so a distributed model predictive control method is designed to realize the dynamic recovery of the voltage and to maintain the control constraints of the output of distributed energy storages and photovoltaics during the control process. |
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