Research On Active Inertia Support And Primary Frequency Control Of Doubly Fed Induction Generator

The doubly fed induction generator does not have the inertial response capabilities of synchronous generators.Large scale grid connection will weaken the inertial response capabilities of power systems.When the power is unbalanced,it is difficult for the system to maintain the frequency variation within the specified range,which adversely affects stable operation.This paper focuses on the in depth analysis of the impact of wind power on the power system frequency and the doubly fed induction generator participating in the primary frequency regulation of the power system.The main research contents are as follows:First,the research on doubly fed induction generator modeling and its influence on grid frequency were carried out.Analyze the working principle and mathematical model of doubly fed induction generator,including the structure,operation mathematical model and generator mathematical model.An equivalent method based on equivalent loss for a wind farm power collection system is proposed,and the reason for reducing the system’s equivalent inertia by incorporating a doubly fed induction generator into a power system is analyzed by formula deduction.In the DIg SILENT/Power Factry simulation software,a grid connected model of doubly fed induction generator is set up for simulation,and the impact of power imbalance on load sudden increase or decrease under different penetration rates of wind power is analyzed.After the wind turbine has not replaced or replaced the synchronous generator,the power system frequency,wind turbine speed and active power output are analyzed to verify the correctness of the analysis.Secondly,according to the working principle of the doubly fed induction generator,the virtual inertial control strategy of additional speed optimization of doubly fed induction generator is proposed.Adding the speed optimization module to the traditional virtual inertia control enables the rotor of the wind turbine to release or absorb more energy,and it can smooth the power and reduce the impact on the grid.A rotor speed protection module is added to the control strategy to prevent the rotor speed from being too low or too high,which will cause the wind turbine to out of service or cause damage to the wind turbine,so that the wind turbine will have the same characteristics as a conventional synchronous generator.At the same time,the coordination control between the virtual inertia and the primary frequency control at the level of the wind farm is proposed,and the correctness of the control theory is demonstrated in the simple system and the actual power grid.Finally,Carried out short-term wind power prediction based on BP neural network with adaptive mutation bat optimization.This paper the characteristics of wind power prediction is discussed on the importance of wind power in frequency control.On the basis,a short-term wind power prediction method combined adaptive mutation bat algorithm(AMBA)and BP neural network,which is based on the variance of the population fitness for the randomness of wind power output.According to variance of population fitness and the size of the current optimal solution,the model determines the mutation probability of the current optimal individual and the t-distribution variation of the global optimal individual,and two optimization of the mutated bat individuals.Then network parameters of BP neural network are optimized by AMBA,and then prediction accuracy of BP neural network is improved.Analyzing the example,prediction effect of AMBA-BP model is compared with other model prediction results.The results show that the model can effectively improve prediction accuracy of short-term wind power.