Studies On Voltage Stability Of Grid-Connected Wind Farm

Due to the increasingly serious problem of the environment and resources, renewable resource development and utilization have been paid more attention to. The use of wind energy for electricity generation as a mature technology of renewable energy use patterns have developed rapidly. The installed capacity of wind power increased constantly year by year. In the world, wind power is the most rapidly growing renewable energy beside hydroelectricity. The integration of lots of wind power and grid changed original load flow of the power system. Moreover, wind energy is random and wind farm is composed of large number of induction generators which are different from synchronous machine. Therefore, wind power will influence the stability of power system. With the increasing size of single wind farm and the increasing share of wind power in power system, the effect of wind power to power system is more and more serious. Researching on wind power integration has become a problem demanding prompt solution in the development of wind power. Voltage stability issues about wind power integration are investigated in this paper, and the main contents are as follow:1. Dynamic model of fixed-speed wind turbine equipped with induction generator (IG) and variable-speed wind turbine equipped with doubly-fed induction generator (DFIG) are studied. Wind speed model, aerodynamic model, shaft system model, pitch controller model, IG model and DFIG model are analyzed. The overall models of the two kinds of wind turbine are given.2. New methods are put forward witch are used to treat different wind farms node in load flow calculation in power systems, and the entire algorithms are realized through MATLAB programs. The methods are used to calculate example system load flow and the results indicate that they are veracious and efficacious: the amount of calculation is reduced and the computing speed is increased in the premise of guarantee calculation precision. In a word, the methods are practical.3. Steady state voltage stability of power system including wind power is studied in two aspects: voltage stability of wind farm and how voltage stability of power system is influence when wind farm is connected.P-V curve is used to analyze various factors which influent wind farm node voltage; P-V curve and Q-V characteristic of wind farm are combined to analyze steady-state voltage stability of an example system, and voltage stability limits of the wind farm are given under different operating mode.Modal analysis is introduced to the field of research on effect of wind power integration to grid voltage stability. The minimum eigenvalue and participation factor of IEEE 39-bus test system including wind farm are calculated and analyzed.4. Transient voltage stability of power system including wind power is studied. The simulation model of example power system is designed by Matlab/Simulink tool. Under different conditions such as various wind speed and transmission line fault, the system is simulated and analyzed. In addition, the effect of static VAR compensator and using DFIG instead of IG on transient voltage stability are respectively studied.