Research On Multi-nozzle Synchronous Control System For Impulse Turbine

Hydropower is clean energy and is indispensable to make the coordinated development of people and nature.Hydropower develops from low head to high head gradually in China.Impulse turbines have a significant potential for development due to their ability to run under high head.The research on the impulse turbine is still on the initial stage in China and the development of impulse turbine is also from single nozzle to the multi-nozzle.Multi-nozzle synchronous control system for impulse turbine is a blank so far.As the multi-nozzle in the process of movement will have additional radial force without synchronation,it make serious impact on the efficiency and life of the turbine,resulting in a great security risk.In this paper,the hydraulic system is used to control the displacement of the nozzle of the impulse turbine,it realizes the synchronous control of the multi-nozzle,it is of great significance to study the needle displacement synchronous control system with excellent performance.In this paper,by reviewing a large number of the literature of hydraulic synchronization fields,the research significance and research direction of the synchronous system of the multi-jet impulse turbine are analyzed.The research on the synchronization problem of multi-nozzle is transformed into the study of multi-cylinder hydraulic synchronous system.This paper summarizes the development of hydraulic synchronization system,summarizes the problems existing in this field and puts forward the development direction of multi-cylinder synchronous control in the future.In this paper,a hydraulic synchronous control system with valve-controlled asymmetric cylinder is designed.The components of the system are analyzed theoretically and the mathematical model is established.The state equations of system is obtained and the simulation model of the system is established by using the Control and Simulation module in Lab VIEW.Considering the poor robustness of the PID controller and the lack of self-learning ability,the artificial immune algorithm is adopted as the single cylinder control algorithm.The system load type is set to no-load,constant load and variable load and the simulation is under signals of step signal,sinusoidal signal of different frequencies and slope signal.The role of antibody suppression function in system response is analyzed and the dynamic performance of the system in PID control and artificial immune control is compared.The simulation results show that the response speed is faster,the overshoot is small,the robustness is stronger than that of the PID control under the artificial immune control,so the artificial immune controller is used as the single cylinder controller of the system.In this paper,the synchronization principle and characteristics of master-slave,same synchronization and deviation coupling are analyzed and the shortcomings of these synchronization methods are summarized combined with the characteristics of the nozzle synchronization control system.A synchronization method is proposed to introduce the BP neural network on the basis of the deviation coupling.The displacement error of the multi-cylinder is nonlinearly mapped,and the relative error and the absolute error of each cylinder displacement are taken into account.The original system uses the PID controller,the improved synchronization system adopts the combination of artificial immune control and improved devia tion coupling.Step signals,sinusoidal signals of different frequencies and ramp signals are given to the simulation.The simulation results show that the improved synchronization system can improve the response performance of the system and greatly improve the synchronization accuracy of the system.The improvement of the measurement and control program of the hydraulic characteristic test bench of Harbin Electrical Company is completed and the functions of real-time monitoring and data post-processing of multi-nozzle displacement and synchronization error are realized.The characteristics of single cylinder control and multi-cylinder synchronization of the original system are analyzed theoretically.The experimental results show that the response speed of the synchronization system is improved obviously and the overshoot amount is significantly reduced,which reduces the dead zone influence in the original system to a certain extent.The dynamic response characteristics and synchronization accuracy have been greatly improved.This study has laid a foundation for the study of the hydraulic characteristics of the impulse turbine during the transition process,which is of great significance to the design of the engineering machinery control system of the multi-executing mechanism.