The Investigation Of Control For Natural Gas Pipeline Based On State Space Model

As a complex non-linear system with time-lag,the model obtained by traditional methods,which describes the characteristics of natural gas pipeline,is not able to meet the request of on-line control for its lower computational efficiency.In this paper,the state equation theory that is commonly used in modern control theory is proposed to build the model.As a lumped parameter model,the state space model based on the state equation can satisfy the computational efficiency request of dynamic on-line control with sufficient accuracy.The state space model of pipeline needs to be analyzed for its applicability because there are some approximate and linear substitutions in the process of modeling.In order to determine the optimal scope of application of the state space model established in this paper,the transfer function model is first derived from the basic equation of pipeline,and then the expression of the state space model is derived from the transfer function model.The parameters of the model are calculated by programming on the platform of MATLAB.The results are filled into the visual model established in MATLAB-Simulink to simulate and compare with the simulation results of SPS software.The optimal applicable length of the pipeline state space model is verified.The state space model is analyzed by using the Bode diagram commonly used in control theory.The robustness of the proposed pipeline state space model is verified,and the model basis for dynamic control is determined.The parameter identification of natural gas pipeline model is used to supplement the model.The state space model of pipeline is established by means of identification and its applicability is analyzed.It is considered that the model established by mechanism modeling is more suitable for dynamic control simulation of pipeline.In order to realize the dynamic control of pipeline,the model predictive control in modern control theory is adopted.The foundation of the control is SCADA system and PID controller of pipeline.MPC control is added on the basis of PID control through hierarchical control.Visual simulation model of actual pipeline system is established in MATLAB-Simulink,and dynamic control of natural gas pipeline is studied.Through the research in this paper,it can be preliminarily recognized that the state space model that is commonly used in control theory,is suitable for dynamic control of pipelines.Through comparative analysis,the rationality and accuracy of the state space model established in this paper are illustrated from the applicability and robustness of the model.At the same time,when using state space model to model long-distance pipeline system,the number of pipeline segments needed in modeling can be reduced without affecting the simulation accuracy.The dynamic control of pipeline is carried out by model predictive control based on state space model.The simulation results accord with the control expectation.The optimal control of pipeline in steady-state transition process is preliminarily realized.The validity of model predictive controller is determined,which lays a theoretical foundation for the realization of on-line control of natural gas pipeline.