Structural Optimum Design And Energy Management Of Wind-compressed Air Energy Storage System

Small and medium sized wind power system is flexible and clean which can be an important means to develop renewable energy and ease the energy crisis.However,it needs storage devices to solve its natural imperfection such as power instability of wind turbine and huge amount of abandoned wind.Therefore,this paper proposes a wind-compressed air energy storage system based on multifunctional scroll machine.Its storage capacity is far more than other energy storage technologies,and has a low cost,long life,environmental friendly and other advantages in system integration.In order to combine compressed air energy storage with wind power systems more efficiently and ensure the system running smoothly,this paper research in three aspects:structure design,modeling and analysis of scroll machine characteristics and energy management strategies.Reducing structural links of energy conversion would significantly improve the efficiency of conversion from wind energy into compressed air energy.According to the different energy flow in different structure,the energy coupling structures of the system are divided into three ways:electric coupling,mechanical coupling and mixed electromechanical coupling.Analysis of the conventional structure characteristics shows that mechanical coupling structure with higher energy conversion efficiency while electric coupling structure is more flexible and easy to use.This paper designs a variety of structural scheme to take advantages of two coupling into account.By comparison of efficiency,cost,and feasibility,it ultimately uses mixed electromechanical coupling scheme as the structure of wind-compressed air energy storage system.Multifunctional scroll machine is the key equipment affect the efficiency of the compressed air energy storage and can be compressor or expander for different time.It has low system cost,low space usage and high flexibility.As a result,it needs precise control.However,the existing model of scroll machine is complex and not suitable for control application.This paper proposes hybrid volume flow and torque model of scroll machine working as compressor and also proposes evaluation index of energy storage efficiency.The effectiveness of the proposed model is validated by compressor experimental data.Results show the relations between volume flow and torque of scroll machine and its rotation speed and discharge pressure.It can conclude how the friction and over/under-voltage discharging conditions affect the energy storage efficiency.This paper proposed energy management strategies corresponding to its structure in order to ensure the smooth operation of the system.System has three operating modes:compression energy storage,expansion energy and wind turbine independent powering according to the running range of device.Each mode has its specific control objectives.In energy management strategies,operating mode decision strategy based on the logic threshold method is responsible for operating mode selection in accordance with the system working conditions while mode switching strategy based on the pre-synchronous method ensures the system responds quickly and smoothly during the transient of operating mode changes.Simulation results verify the effectiveness of the energy management strategies.Finally,presents the novel wind-compressed air energy storage system prototype including the selection and matching of key equipment and parameters.Focus on the wind turbine simulation principle and gear ratio selection method.