Theoretical And Experimental Study On Pitch Control System Drived By Valve-controlled Motor Of Hydraulic Type Wind Turbine

Variable pitch control system is an important part of the modern large-scale windturbine. With the development of large-scale wind turbine process, higherrequirements for the pitch drive torque, reliability and control performance of thesystem has been put forward. The complex system structure for taking the hydrauliccylinder as the pitch drive components, the high failure rate, and the nonlinear existsbetween the hydraulic cylinder load force and resistance moment, impact on theresponse characteristics of the system seriously. To solve all these problems, this paperproposes the variable pitch-controlled system, which based on valve control hydraulicmotor. With the valve control hydraulic motor as the research object, the pitch loadcharacteristics, friction compensation, simulation speed shock, load simulation, andpitch control technology have been researched. This paper aims to master the criticaltheory, method, and the technique of the variable pitch control system of the valvecontrol hydraulic motor, as well as provide the theory evidence for the hydraulic windturbine pitch control technique.The load characteristics of variable pitch were researched, and calculation modelof blade element momentum theory propeller pitch load was constructed based on theinfluence of load. Variable pitch wind model, the wind wheel blade parameters ofdynamic model were analysied. Combined with the features of wind speed, theregularities of variable pitch load changes with the angle are obtained under differentwind speed.The effects of friction compensation valve-controlled hydraulic motor pitchcontrol precision were studied. Combined with LuGre dynamic friction model,mathematical model of valve-controlled hydraulic motor position control system wasbuilt, and the factors of the precision of pitch angle control were analysed. Theanalysis results show that the dynamic friction torque of valve control hydraulic motorpitch angle control precision influence is very big. This article uses the geneticalgorithm to identify the LuGre friction model parameters, and put forward the valve-controlled hydraulic motor pitch angle control system adaptive frictioncompensation strategy, comparing with the traditional PID control with feedforwardcompensation method, using the adaptive compensation method can achieve goodcompensation effect under different loading conditions, eliminating the friction causedthe hydraulic motor of low speed creeping phenomenon, improve the accuracy of pitchangle control.In this paper, the shock problems occurring in the process of variable pitch windspeed were researched. For pitch angle control in the process of variable pitch motorspeed impact and positive reverse rotation speed asymmetric problems, thevalve-controlled hydraulic motor variable speed and position of composite controlstrategy were put forward. Considering the characteristics of fluctuated remarkably forwind turbines variable pitch wind load, speed and position fuzzy control method wasput forward, and variable propeller motor speed feedforward model was constructed.The motor rotate speed in the process of variable pitch was planned and the positionvariable pitch motor speed feedforward and position feedback compound control wasimplemented. In different variable pitch load conditions the simulation research onsystem has been carried on. Experimental results show that the speed and positioncontrol can restrain the pitch speed impact.Based on the research on hydraulic type wind turbine, the method of using valvecontrol hydraulic motor as the variable pitch control system is proposed, and thehydraulic type wind turbine generation power in rated load area control strategy is putforward. The hydraulic type wind turbine semi-physical simulation platform was built,and according to variable propeller pitch load simulation problem, variable pitch windload simulation system is presented. The mathematical model of valve-controlledhydraulic motor loading system was established, and the system of surplus torque isanalyzed. An improved aided synchronous compensation of surplus torque suppressionmethod is proposed and the feasibility of this method is verified. On semi-physicalsimulation platform, the hydraulic type of wind turbines variable pitch control strategyis proposed. The simulation results show that power control requirements can besatisfied in hydraulic type wind turbine rated load by using valve control hydraulic motor variable pitch control system.Finally, in the laboratory, valve-controlled hydraulic motor variable pitch controland variable pitch load simulation system were set up. In this paper, based on LuGredynamic friction model, proposed the adaptive compensation control method, thevalve controlled hydraulic motor variable pitch speed impact suppression method,improvement of auxiliary synchronous surplus torque suppression method is verifiedexperimentally. According to semi-physics experiment of power control in hydraulictype wind turbine rated load, the results show that the presented theory and controlmethod are feasible.