Research On Optimal Control Of Power Point Tracking In The Hydraulic Wind Turbine

With the gradual degradation of the environment,clean energy is attracting more attention,and wind power as an important renewable energy,its proportion in the power grid is becoming larger and larger.To ensure more wind energy convert into electricity for users,increasing the utilization rate of wind energy has attracted more and more attention.But because the system is nonlinear and multivariable system,meanwhile wind energy has randomness and variability,there are still many problems to be solved.This paper taking the hydraulic type wind turbine(HWT)as research object,the main drive system is fixed displacement pump-double variable displacement motor closed hydraulic system.hydraulic energy as intermediate energy conversion medium,HWT converts wind energy into electric energy.The flexible transfer of energy is realized,meanwhile quality of energy is improved.In order to realize the wide application of HWT and improve its the utilization rate of wind energy,the maximum power point tracking(MPPT)control of HWT still needs to improve.In this paper,the MPPT optimal control of HWT is studied.Based on mechanistic modeling method,the mathematical model of wind speed,the mathematical model of wind turbine,the mathematical model of fixed displacement pump-variable displacement motor and power system are eatablished,and finally the state space model after grid is obtained.In the light of MPPT control method,the process of establishment about feedback linearization control and auto disturbance rejection control(ADRC)are analyzed.Based on the power transmission system of the fixed displcement pump-variable displacement motor,the principle of power tracking based on pressure control output is analyzed.Aiming at the MPPT control,the optimal power tracking curve is self optimizing control,which makes the theoretical optimal power tracing curve coincide with the actual power tracing curve,and the maximum power point is obtained.Based on the characteristics of B spline curve,taking the shortest maximum power point tracking time and the smooth tracking process as planning objectives,the trajectory of optimal power tracking is planned.Using feedback linearization method and taking the system high pressure as control output,MPPT theoretical control method according to system pressure is proposed,and combined with the engineering practice,the control algorithm is optimized.Based on the MATLAB/Simulink simulation model,simulation studies on the optimal power tracking control are conducted.According to the simulation results,the efficiency of hydraulic transmission system is theoreticaly analyzed.Through analyzing MPPT control strategy,which uses feedback linearization control method and taking system pressure as control output,the real time control performance and the robustness of the system still needs to be further improved,thus combined with the advantages of ADRC and taking rotate speed of the fixed disolacement pump as control output,finally MPPT control strategy is proposed.Changing system parameters,and based on MATLAB/Simulink simulation model,system control effect and robustness is researched.Finally,relying on Yanshan University 60 kVA hydraulic experimental platform,the experimental studies about the MPPT control effect are conducted.The experimental results verify the effectiveness of the proposed MPPT control law for HWT.