The Study On The Control Strategy And Testing Method Of Wind Turbine Gennerator System For Low Voltage Ride Through Characteristic

Wind energy as a renewable energy has aroused people's more and more attention, and wind energy generation which can fulfill the usage of living power and industrial power is one kind of the utilization of renewable energy. With increased demand of it, the installed capacity of wind energy is increasing year by year. It means that the proportion of wind energy in electrical power system is increasing. So the grid department proposed the LVRT(Low Voltage Ride Through) requirement of wind turbine to keep the stability and safety of grid system in this condition. In this paper, 1.5MW double-fed wind turbine generator system is studied, whose complete model is built in Digsilent. And then, the low voltage ride through characteristic based on active Crowbar and SGSC is simulated and analyzed respectively for the transient characteristics.Firstly, the principle of wind turbine is analyzed, and the mathematical models of double-fed induction generator in ABC still coordinate system and dq rotation coordinate system are given. The vector control strategy of double-fed induction generator is given based on stator flux direction to realize the independent control of active power and reactive power of the stator. The vector control strategy of grid-side inverter is analyzed to build the model of grid-side inverter. The model of driving chain is built based on reduced mathematical model of driving chain of double-fed wind turbine.Secondly, the transient characteristics of double-fed wind turbine generator system are simulated and studied during the grid voltage drop. The transient characteristics of wind turbine with LVRT function based on the active Crowbar, active power and reactive power control strategy are simulated and studied at the conditions of different voltage drop depth and lasting time.Again, on the basis of analyzing SGSC stabilizing the stator flux of double-fed induction generator, the control strategy based on SGSC compensating stator flux is proposed to realize the low voltage ride through function of double-fed wind turbine generator. In addition, this method is simulated and analyzed. And then, the influence of different recovery rate of active power on the driving chain is simulated and studied after the restoration of grid voltage.Finally, the method and contents of LVRT testing of wind turbine are provided, and the validity of the used model is analyzed based on actual LVRT testing results of double-fed wind turbine.