Analysis Of The Dynamic Behavior Of Micro Gas Turbines Based On Model Predictive Control

As a distributed energy equipment,microturbines have great advantages in terms of small size,light weight,high efficiency and low emissions,microturbines have been rapidly developed in recent years.Microturbines can not only use a variety of fuels,but can also be mixed with a variety of energy systems,such as fuel cells,solar energy,wind energy,etc.In order to further obtain better dynamic performances of micro gas turbine,it is necessary to make continuous innovation on the modeling and control of micro gas turbines.The main characteristics of the regenerative microturbine are firstly extracted,a nonlinear dynamic mathematical model is established.The polynomial approximate expressions are used to describe the characteristics of the compressor,turbine and the regenerator,and the component model is determined according to the design parameters of the Capstones C30.According to the principle of energy conservation,the three main processes of energy exchange are selected: the regenerator heat exchange process,the combustion exothermic process and the dynamic process of the rotor system,and the dynamic model of the system is established.The simulation model is established,the correctness of the nonlinear dynamic model is verified.The variable speed operation mode can ensure the optimal efficiency of the micro gas turbine.Through this operation mode,the optimized efficiency solution of the state variable with the load change is obtained as the control target.Against poor behavior issue of control of microturbine,a linear model predictive control is established.The predictive model of linear model predictive control is obtained by linearizing the nonlinear MGT model at the equilibrium point.According to the system performance requirements,the objective function is established and can be solved as a quadratic programming problem.The first element of the obtained optimized sequence is applied to the system.Considering the nonlinear characteristics of the system,a nonlinear model predictive control is established.A quasi-infinite horizon is achieved by adding a terminal penalty term and a terminal penalty origin constraint to the objective function,the stability of the nonlinear system is guaranteed.The objective function is solved by sequential quadratic programming.Finally,the systems of microturbine based on model predictive control and state feedback control are established,the dynamic characteristics of microturbine based on different control strategies are analyzed.Through the simulation results of unconstrained model predictive control,the influence of horizon and weighting matrix is analyzed.The results show that the weighting matrixes have a significant effect on the performance of control than the horizon.The effects of different control parameters on nonlinear model predictive control are simulated.The results show that the horizon has an influence on response time and overshoot.The simulation results of unconstrained model predictive control are compared with the simulation results of state feedback control.The dynamic response processes are analyzed to verify the potential and advantages of model predictive control in control of microturbine.Under the two conditions of stepwise load changes and period disturbance load change,the simulation results of linear and nonlinear model predictive control are compared,and the common dynamic characteristics and the characteristics of the two control strategies are analyzed.The results show that the nonlinear model predictive control has a shorter adjustment time and a smoother response curve under stepwise load changes;under periodic disturbance load changes,the performances of nonlinear model predictive control show that the speed is the best for tracking the reference curve.The simulation results verify that the microturbine based on nonlinear model prediction has better dynamic performance and steady-state accuracy.