Research On Control Strategy Of Wind Power Grid Connected Inverter

With the rapid development of the real economy,the demand for electricity is increasing,energy and environmental issues have become the focus of the society,which promotes the research and development in the field of renewable energy power generation.Wind energy has become a focus of power generation in the field of new energy because of its large reserves and geographical dispersion,but its cost problem restricts the development of wind power technology.Therefore,the research on wind power products with low price,stable performance and high efficiency has become the focus of wind power technology research.Excellent grid-connected control strategy can effectively improve the stability and efficiency of grid-connected power generation system,reduce system costs,and play a vital role in the promotion and popularization of wind power generation.In view of the above problems,the structure of wind power generation system is compared and analyzed in this thesis,and determines that the front end is passive rectification,the middle is half bridge isolated type NPC DC-DC,and the latter stage is two level three phase inverter wind power grid connection structure.Then,the soft switching and working principle of DC-DC converter are elaborated,and the MPPT strategy of variable pitch fan using PMSG power generation is compared and analyzed.Several sensorless grid voltage estimation methods and grid-connected control strategies are compared and analyzed.The improved deadbeat grid-connected control strategy based on DOB grid voltage prediction is emphatically studied.The working principle of SVPWM modulation,the design and parameter tuning process of SRF-PLL are introduced in detail.By observing the grid voltage with disturbance observer,the voltage sensor needed in the traditional grid-connected control strategy is omitted,which saves the system cost.Combined with improved deadbeat current grid-connected control strategy is used to adjust the P and Q outputs.It realizes the continuous and stable output of wind power generation system under uncertain conditions such as grid imbalance,and solves the problems of poor robustness and high harmonic content of grid-connected current of traditional wind power grid-connected system,which effectively prevents the inverter overcurrent phenomenon when grid voltage is transient.The system has fast dynamic response tracking characteristics,higher accuracy and lower cost.Finally,the modeling and simulation are carried out by using MATLAB software and its Simulink toolbox.The results show that the DOB-based grid voltage estimation method can accurately estimate the grid voltage,which is almost the same as using the voltage sensor,and SRF-PLL can use the estimated grid voltage to achieve accurate phase-locked.The SVPWM modulation mode has a fixed frequency,which can synthesize the control signal with the optimal vector,thereby improving the utilization of the input voltage on the DC side.Compared with the traditional PI and DPC control,the grid-connected control with improved deadbeat control has higher accuracy,robustness and faster response speed,and the OTC control method of wind power MPPT is effective,which verifies the feasibility of the selected grid-connected strategy.