Study On The Variable Pitch System Of The Horizontal Axis Tidal Current Turbines

With the shortage of energy, the development of renewable energy sources must be taken on the agenda. As one of the renewable energy sources, tidal current owns a large potent to develop, especially for coastal cities. The horizontal axis tidal current turbine is a new complex electromechanical system making use of tidal current. In recent years, countries over the world have been involved in the field of tidal current, and it has become the focus of the study to improve the tidal current turbines’efficiency of capturing energy. It is an effective way to improve efficiency through the use of variable pitch system. Aiming the variable pitch system of500W horizontal axis tidal current turbines, there is theoretical analysis, structural design, strength analysis, simulation and experimental study of control system in this paper.According to the project design requirements of the Beijing Municipal Education Commission on tidal current energy, at first, this paper expounds th theoretical basis and pitching principles of tidal current turbines and have theoretical calculations of parameters required for pitching (lift-drag coefficient and load), which verifies that lift-drag coefficient of tidal current turbines’airfoil can be obtained by Xfoil aerodynamic software under the same Reynolds through FLUENT which is a CFD software, and after known the lift-drag coefficient, the program of pitch load calculation is compiled to prove that pitch load of tidal current turbines come from hydrodynamic torque and friction torque mainly.Consider to some factors as structure, environment and cost, a pitch institution is designed by known pitching parameters and established a three-dimensional model on PRO/E, which has a certain reference value for the design of prototype. At the same time, a finite element software is used for strength check and static strength analysis of key parts (pitch gear, pitch bearing) to prove that this pitch institution is reliable.Pitching control system is the key to complete pitching movement, so a three closed-loop PID control system of pitch actuator is established by Simulink to have a dynamic simulation in this paper. The system influence which come from input signal, KpKi of position-loop and disturbance signal is analyzed to prove that suitable PID parameters can improve response accuracy and response speed of control system. Furthermore, a fuzzy control theory is used to optimize the control system, and take a comparison between PID control and fuzzy control. At last, an effective improvement is proposed. Finally, a half-simulation bench is set up to monitor the pitching position by PC based on the PLC, which proves that PID control is effective for pitch control system.