Modeling And Analysis For Doubly-fed Wind Power Generation System

In recent years Governments are highly concerned about environmental issues,thus new energy has been vigorously developed.In this trend with high power density,mature technology,and small footprint the wind energy power generation system has been gotten high attention.With high penetration of wind energy system the wind farm has high probability to connect to a weak grid.The key to solving the unmoral interaction between wind turbine and power system is making it clear that intrinsic characteristic and external characteristic of wind turbine.And it is great importance to select a right time-scale to analysis the intrinsic characteristic and external characteristic of wind turbine.Therefore,this paper focuses on the problem of small interference stability caused by large-scale doubly-fed wind power generation when accessing weak grids,method for simplifying inner and outer loops by using current vector control strategy.Models of doubly-fed wind power generation systems at different time scales are established.The mechanism of the influence of the parameters of each link under the control strategy of current vector on the small disturbance stability of the doubly-fed wind power system when it is connected to the weak grid is obtained.The main works and innovation of this paper are as follows:1.We introduced the future power grid,summary of the impact of improved wind power penetration and analysis the Doubly-fed motor mathematical model and vector control strategy for Doubly-fed wind power generation system.2.The mathematical model of doubly-fed induction machine is established in Matlab environment,and its steady state operation state is analyzed.Three different operating states of the doubly-fed motor are analyzed.3.The structure of the control system of the doubly-fed wind turbine controlled by vector,based on the mathematical model of the grid-side converter and the rotor-side converter,establishes the model of the doubly-fed wind power generation system in Matlab and simulates it.4.The doubly-fed wind power generation system with different time scales was built under weak grid conditions.The model of double-fed wind power generation system connected to weak grid was built in PSCAD/EMTDC and Matlab environment,and theoretical analysis and verification were carried out.5.In this paper,the influence of various control parameters of the doubly-fed wind power generation system using current vector control strategy on the small disturbance stability of the system under weak grid conditions is studied.The conditions of the grid connection point under weak network conditions are more complicated,such as imbalance,harmonics need to be further studied.