Control Strategy For HESS Participating In LFC Of Power Grid

With a large number of intermittent new energies being integrated into the power grid,new power systems are faced with many problems such as low inertia,insufficient frequency regulation capacity,and poor frequency control performance.Since energy storage has the characteristics of flexible control,precise output,and rapid adjustment,large-scale energy storage has significant advantages in participating in the frequency regulation of power systems.In response to the power demand of the load frequency control(LFC),it is not only necessary to coordinate the energy storage with the traditional units but also to effectively manage the state of charge(SOC)to improve the comprehensive efficiency of the energy storage.Considering the hybrid energy storage system(HESS)consisting of different types of electric energy storage units,this thesis focuses on the problems of the HESS participating in the LFC of the power grid.We fully take into account the characteristic differences of various energy storage units in the dynamic response time,the charging/discharging power limitation,and the storage capacity,and investigate the MPC-based LFC design method for the power system.The main work of this thesis is as follows:(1)A dynamic LFC model of the power system with HESS is established.Firstly,the frequency regulation mechanism of the power system and the LFC modes of the interconnected power grid are analyzed.Then,the charging/discharging characteristics and the dynamic mathematical model of the HESS are studied.Finally,the dynamic mathematical model for the HESS participating in the LFC of the power system is established by combining the HESS model with the typical LFC model.The established model lays the foundation for the subsequent control strategy design.(2)A decentralized-MPC-based method for the HESS participating in the LFC of the power grid is proposed.Firstly,according to the LFC model of the power grid with the HESS,considering the operational constraints of traditional generation units and various energy storage units,the LFC objectives,and the SOC balancing requirements,a decentralized predictive model for the LFC of the regional power grid is established.Then,an optimal control sequence is solved by the real-time rolling optimization.The optimal control sequence is used for the LFC commands of the traditional generation units and the hybrid energy storage units.Finally,the effectiveness of the proposed LFC method is verified by case studies.(3)A distributed-MPC-based method for the HESS participating in the LFC of the power grid is proposed.First,based on the decentralized predictive model of the regional power grid,we further consider the coupling relationship between regional power grids and establish the corresponding distributed predictive model.Then,the optimal LFC strategy is obtained by solving the distributed predictive model.Finally,we compare and analyze the control performances of the decentralized LFC method and the distributed LFC method through simulations.