Research Of The Electro-hydraulic Proportional Control System In The Turbine HP Bypass

Nowadays,turbine high pressure(HP) bypass system of abroad is fully developed.But the beginning of studies about it in China is later than others countries and most of equipments used in domestic power plants were imported and in-depth studies about the design of equipments is relatively less.HP bypass valve is the most important part in the HP bypass system.The failure of the valve will threaten the safe-efficient processing and sometimes cause the stop and accidents of the EGS.So the controls of the high-pressure bypass valve become critical.For controlling the bypass valve,the electric-hydraulic servo-system will be a popular option by the power plants.And the servo-valve which used to transfer the electricity to hydraumatic will influence the safe-stable processing of EGS.At present, electric-hydraulic valve of the DEH system in the power plants has a higher failure rate because of the problems such as lock,block and large quantity of leaking insight.For solving the problems above,the subject of this paper basing on the bypass system of the techno-developing EGS of 2x300MW in a generating station in Gan-Su is to design the HP bypass hydraulic control system.Then the advantages and the practicability of the proportional valve instead of servo valve are specially studied.A set of electro-hydraulic proportional position control system for high pressure bypass valves is designed and the mathematics dynamic model of the system is established.There are two kinds of adjusting ways to meet the instable system:cascade lag adjustment and PID adjustment.According to the disadvantages of the PID adjustment,the fuzzy self-tuning PID controller is designed by MATLAB simulation to combining with the electric-hydraulic proportional control technology for reducing the disadvantage of the nonlinear nature of the hydraulic system and the parameters' multivariate character to develop the performance and efficiency.And the comparisons to the common PID are processed.The results of the simulation shows that,comparing to the common one,the fuzzy self-tuning PID has a better real-time quality,shorter responding time,smaller overshoot and smoother phase step responding.It is shows that,as the electric-hydraulic servo-system,using the proportional control system in the high pressure bypass control can meet the requirements of system control.Finally,the achievements and disadvantages of the bypass valve studying has be given and has an expectation for the future of the subject.The conclusion can be a reference to such theory studying using proportional valve to control the HP bypass valve and can somehow guide the practicing subjects.