Simulation Modeling And Control Of Recuperative Microturbine-based Combined Cooling,Heating And Power System

Compared with traditional centralized energy supply system,distributed energy systems can provide users with various forms of energy directly to achieve energy-step-utilization.Microturbine-based combined cooling,heating and power(MGT-CCHP)system is an important form of distributed energy system with the properties of clean,efficient and flexible.At present,researches on MGT-CCHP systems at home and abroad mostly focus on static performance analysis and development of main equipment.There are few research results on dynamic performance analysis and control strategies for the system.Since the microturbines in the market are often operated in full recuperative mode,this paper focuses on the recuperative MGT-CCHP system,and conducts research work around the system’s simulation modeling and control.Firstly,according to the modularization modeling idea,the mathematics model of all parts of the MGT-CCHP system is established based on the three conservation laws.These modules are connected on the Simulink simulation platform of Matlab software to establish the total system mathematics model.Then,taking an MGT-CCHP system consisting of an 80 kW recuperative microturbine,a 75 kW single-effect LiBr–H2O absorption chiller,and a 115 kW heating system as an example,the paper designs system’s static parameters and analyzes the dynamic responses when major manipulated and disturbance variable steps were performed.The results verified the correctness of the mechanism model and the coupling relationship between the input and output of the system.As the mechanism model is too complicated to reproduce and the simulation operation speed is slow,it’s not suitable for designing control strategy.The paper proposes a block structure nonlinear modeling method,and a multivariable Hammerstein model of MGT-CCHP system is identified based on the input and output data.The Hammerstein model identification methods based on Least Squares Support Vector Machine(LSSVM)and Recursive Least Squares(RLS)are respectively discussed.Considering the identification effect and the model structure,the latter is selected as the main identification method of MGT-CCHP system.The simulation results show that under the step disturbance of manipulated variables,the outputs of Hammerstein model fit well with the mechanism model.Finally,the paper designs a nonlinear predictive control algorithm based on Hammerstein model to achieve the load tracking control of MGT-CCHP system.The algorithm uses the fuel as the feedforward information of the nonlinear channel controller.Then,according to the twostep control strategy of the Hammerstein model,the controller solves the control law of the linear dynamic part,and the actual manipulated variable can be obtained by extracting the root of the nonlinear static part.From the simulation results,the proposed algorithm is better than the traditional PID controller and can meet the system’s coordination control requirements.