Research On Power Control Technology For Stand-alone Small Wind Power Generation Systems

For stand-alone small wind power generation systems, the Maximum Power Point Tracking (MPPT) control is an important method of improving power conversion efficiency, and the reasonable management and control of battery is an important means of prolonging their life. A power control strategy, which combines MPPT control and charging and discharging control of batteries with load tracking control, is given to make the small wind power generation systems to operate in both optimal and reliable conditions in this thesis. Firstly, the background of research work is introduced, and the domestic and oversea development of wind power is summarized. The configuration of small wind power generation systems with simple structure, which consists of wind turbine, PMSG, diode rectifying bridge, Buck converter, batteries, and controller, is put forward to realize the power control strategy. Based on the analysis of work principle of the system, the mathematic model of components and simulation model of entire system are established, and the relationship between output power of turbine and duty of Buck converter is calculated and drawn.Secondly, after analyzing several MPPT methods such as the small sine perturbation, optimum torque curve and perturbation observation, a variable step perturbation MPPT method is given, and the charging and discharging control of batteries is discussed. Based on analyzing the relationship between output power of turbine, and load power and batteries state, a power control strategy which integrates variable step perturbation MPPT, charging and discharging control of batteries and load tracking control is given for the small wind power generation systems. The simulation results show that, compared with the fixed step size MPPT, the variable step perturbation MPPT achieves better performance in precision and rapidity for the small wind power generation systems.Finally, the structure and parameters of main circuit for power control is designed in detail, and the inductor and Buck converter are made and tested in lab. The experimental results prove that the main circuit is feasible and correct.