Voltage Stability Study On Grid-connected Running Wind Farm

In recent years, China’s wind power industry has made rapid development. However,with the continuous expansion of wind turbine unit capacity and wind farms, the adverseeffects of wind power on power grid have become more and more significant. Amongthem, the voltage stability problem of grid-connected running wind farms is causing awidespread concern. On the basis of the existing literatures and combining with thespecific requirements of state grid to grid-connected running wind farms, this thesisanalysed and researched that application of STATCOM to enhance the transient stabilitymargin and LVRT capability of fixed speed wind turbine generators, and throughsimulation experiments verified the feasibility of using STATCOM to improve the voltagestability and continuous running ability of grid-connected wind farms.First of all, this paper used a four-component method to establish the wind speedmodel, then building simplified mathematical models of various parts of the wind turbine.Through theoretical derivation, a steady-state model of the induction generator is obtained.The state equation of induction generator is also deduced in the synchronous rotatingcoordinate system, after that establishing the three-order mathematical model of theinduction generator. Secondly, building the steady-state and transient mathematical modelof STATCOM, analysing the control strategies of STATCOM and building a current directcontrolled STATCOM simulation model. Thirdly, analysis of the static and transientvoltage stability of fixed speed wind turbine generators. Electromechanical transientprocess of wind turbine generator in the wind speed changes has been studied throughsimulation experiments. Pointing out the shortcomings of fixed speed wind farms in thearea of voltage stability and theoretically analyzing the feasibility of STATCOM applied towind farms. Finally, according to analyzing the specifics of the wind farm, designing theinstalled capacity, main circuit of the STATCOM and main parameters of the inverter.Establishing the power system simulation model containing wind farm and STATCOM inMATLAB, and simulation calculation and analysis are carried out in two typicalconditions, wind speed mutations and power grid faults. Simulation results show that STATCOM provides reactive power quickly for the wind farm during and after largedisturbances, helps wind turbine generators to rebuilt terminal voltage, restrains the gridvoltage continuous drop and generator rotor acceleration, and wins time for pitch angleadjustment of the wind turbine. In a word, installing a appropriate STATCOM in the windfarm can enhance the transient stability Margin and LVRT capability of wind turbinegenerators, which improves the voltage stability of the grid-connected running windfarms.