Modeling And Optimizing Control Of Micro-compressed Air Energy Storage Generation System

Large-scale development and utilization of renewable energy has promoted the historical change of the global energy system,which is one of the important means to ease the energy crisis.However,solar energy,wind energy and other renewable energy sources have strong volatility and intermittent characteristics,which presents a new challenge to the energy storage in the power system.Among the many energy storage methods,compressed air energy storage(CAES)has attracted the attention of international community because of its advantages such as environment-friendly,long life,no phase loss and easy to monitor.At present,CAES system is developing in the direction of large-scale and miniaturization,and micro-CAES system with its location flexibility,economic and reliable advantages,increasingly gets academic and industry attention.However,CAES system is relatively inefficient compared to other energy storage technologies,which is one of the important factors hindering its large-scale development.Therefore,in order to improve the energy utilization and conversion capacity of CAES system,this paper takes micro-CAES generation system as the research object,starts from the modeling of key components,analyzes the variation regularity of system efficiency from multiple perspectives,and researches methods of efficiency optimal control.The premise of efficiency analysis and optimization and control of CAES system is to establish mathematical models of the key components of the system.In this paper,a scroll expander is used as the energy conversion device,and a hybrid modeling method of scroll expander based on theory and empiric is proposed.Considering the influence of gas leakage,over/under-expansion and friction,theoretical models of volume flow and output torque of scroll expander are established.The inlet pressure,temperature and speed are selected as control variables of the models,and the other parameters are lumped.Then a large number of experimental data is used to train the unknown parameters,and the hybrid models of scroll expander are obtained.The hybrid model takes into account both the accuracy of theoretical model and the practicality of empirical model,which is very suitable for efficiency analysis and optimization and control of micro-CAES system.On the basis of hybrid models of scroll expander,this paper introduces the concept of air power and establishes evaluation index of expansion efficiency.According to the efficiency evaluation index,this paper firstly analyzes variation regularity of expansion efficiency of scroll expander with inlet pressure,temperature and speed,which proves that there is an optimal speed at different inlet pressures to maximize expansion efficiency.Then the CAES system efficiency taken into account cold and heat is analyzed quantitatively and qualitatively,and the simulation results show that effectively using cold and heat can greatly improve the energy utilization capability of system.Finally,this paper quantitatively calculates the throttling loss caused by regulator valve from the point of view of air power,and analyzes the influence of different throttle pressure on system efficiency.Based on variation regularity of system efficiency,this paper proposes an efficiency optimization strategy,which ensures the balance of output power and power demand when the system is running steady state,and drives the system to run in high efficient area.The optimization strategy is based on the hybrid models of scroll expander,and the Lagrangian multiplier method is used to realize optimization algorithm and search the optimal working point.The optimization strategy is based on the advantages of hybrid models,which greatly simplifies complexity of optimization algorithm and satisfies accuracy and fastness of engineering demand.Therefore,it is very suitable for real-time optimization and control system.Finally,this paper introduces control platform of micro-CAES generation system,and verifies the rationality of the efficiency optimization strategy based on the hybrid models of scroll expander.The experimental results show that the optimization strategy proposed in this paper can control system output power to match real-time change of power demand,and drive the system to run in the high efficient area.