| The distributed integrated energy system is a new development and research direction of the power system.It has great potential and advantages in the efficient use of energy and flexible scheduling.It is one of the important ways to alleviate the energy shortage and improve the single energy structure in my country.In this paper,a distributed integrated energy system consisting of a micro-turbine combined cooling and power system,a photovoltaic cell array,a proton exchange membrane fuel cell stack,a storage battery and an electric refrigerator is designed.The research work is carried out around the dynamic modeling and coordinate control of the system,that is,through the mechanism and experimental modeling method,dynamic models of each subsystem is built on the MATLAB/Simulink platform,and the control strategies are designed for the power control of each subsystem,the voltage control of the DC bus,and the coordinate control of the entire system.Based on the idea of modular modeling,the micro-turbine combined cooling and power system is decomposed according to the working principle,and its mechanism model is established based on conservation laws of physics.Disturbance simulation experiments were carried out on the system to verify the correctness of the model and analyze the main factors affecting the cooling power,which provided a basis for designing control strategies.Based on the mechanism model,the recursive least squares algorithm is used to identify the Hammerstein model of the system.To achieve cold load tracking,a nonlinear dynamic matrix control based on Hammerstein model is proposed.The algorithm compensates the nonlinearity of the model by inverting the nonlinear part,and transforms the control of the nonlinear object into a linear problem.The simulation results show that the proposed algorithm has better cooling load tracking effect and stronger anti-interference ability than traditional PID controllers.The modeling and control of other power generation subsystems in the DC microgrid have been studied,the conductance increment method is used to realize the maximum power tracking control of photovoltaic power generation system;the bidirectional DC/DC converter is used to control the battery charge and discharge power;the current feedforward is used to control the power of the proton exchange membrane fuel cell power generation system;the auto disturbance rejection controller is used to control DC bus voltage.The simulation results show that the control effect of each power generation subsystem on the DC side is good.On the basis of completing the design of the control strategy of each subsystem,the entire distributed integrated energy system is collaboratively controlled from two time scales.On a small time scale,the grid-connected control of the DC microgrid was studied,and the synchronous PI current control algorithm was used to realize the tracking control of active power and reactive power.The current changes on both sides of the inverter are coordinated with the current feedforward control of the fuel cell,the auto disturbance rejection control of DC bus voltage and the charge and discharge control of battery on the DC side to achieve the energy supply and demand balance of the grid-connected integrated energy system.Simulation results show that the electric power tracking control effect is good on the AC side is good,and the output alternating current meets the electricity standard.On a large time scale,the energy scheduling of the system is studied.The optimal function of economy is taken as the objective function,then a day-to-day economic scheduling model is established,with the start-stop of the equipment and the coupling of cold and electricity fully considered.The OPTI toolbox is used to solve 0-1 mixed integer nonlinearity Planning model.The simulation results show that the proposed optimization model is reasonable and has reference significance for the coordinate power tracking of each subsystem. |
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