The oil density and volume elastic modulus of hydraulic fluid of the electro-hydraulic servo system in steam turbine change with the ambient temperature and pressure

and the system has unmodeled dynamic

which makes it difficult for the electro-hydraulic servo system to achieve a good tracking ability.Taking the electrohydraulic servo system in a 200 MW intermediate reheat condensing steam turbine as the research object

this paper established a mathematical model for bilateral oil motive

according to the principle of force balance and flow continuity.The influence of oil density and volume elastic modulus on the system performance was analyzed by simulation.On this basis

a sliding mode variable structure controller was designed

and the exponential convergence law design method was used to weaken the chattering problem in sliding mode variable structure control.The simulation system of the designed control system was simulated and verified by Matlab simulation platform

and compared with the PID control system with optimized parameter.The results show that

the controller designed in this paper has good tracking ability and adaptability to uncertain parameters and external load interference.