Small Signal Stability And Damping Characteristics Analysis Of Power System Connected DFIG

In recent years, with the rapid development of power electronic technology, the variable speed wind turbines, especially in variable speed constant frequency doubly-fed wind power Generator(Doubly Fed Induction Generator, DFIG) in a more efficient use of wind power, and the capacity of the rotor side converter is only 20% ~ 30% of wind power capacity and other advantages, make the DFIG has been widely used. And as the proportion of wind power capacity in power system constantly improve, the influence of wind power on power system stability is increasingly significant, concentration and large-scale wind farms connected to the electricity grid will also lead to damping characteristics change. Therefore this article mainly aims at containing doubly-fed wind power generator system small signal stability and damping characteristics study, established the dynamic model of DFIG wind power generating unit, analyzes the simple system oscillation modes and damping characteristics of the super capacitor virtual inertial control to improve system stability and damping characteristics. The main contents of this paper are as follows:(1)The overall analysis of topic background and the research status quo, based on the study of the composition and working principle of DFIG wind power system, established the doubly-fed wind power connected to the mathematical model of the small signal stability of power system, it includes shafting models, and doubly-fed induction generator synchronous rotating coordinates equation of state, established the doubly-fed induction wind turbines converter and its control model, and got for small signal stability analysis of the dynamic model of the doubly-fed wind power generator.(2)In Matlab/Simulink software platform built on the doubly-fed induction wind turbines simple model of the system. Wind turbines are analyzed with the method of eigenvalue analysis of the simple system oscillation mode and its damping characteristics, and through the calculation of the oscillation mode participation factors to analyze the mechanism of oscillation mode. The analysis results show that the DFIG wind turbines of wind power system oscillation mode and simple attenuation model, and the damped oscillation pattern is bigger, has good damping characteristics.(3)The paper established the doubly-fed wind power generator and infinity system consisting of a simple system, through the analysis of the characteristic value analysis method with simple system small signal stability of DFIG wind power unit and its damping characteristics, and calculate the characteristic value of characteristic matrixes, analysis system oscillation mode and its participation factor, understand the causes of oscillation mode in the system.Set up simulation model on Matlab/Simulink platform, the simulation results show that the DFIG wind turbines in the simple system oscillation mode attenuation model, and the damping characteristics of the system is as the oscillation mode damping ratio varies, damping ratio increases the damping characteristics better.(4)Based on wind generator electromagnetic torque affect system damping principle of variable speed wind turbines increases after the super capacitor is analyzed, and through access to DC link inverter DC- DC converter, using virtual inertia control analysis of the impact on the system damping characteristics. Finally through the Matlab/Simulink simulation, validation virtual inertial control based on super capacitor effect the damping of the system.