Study on Rotational Speed Feedback Torque Control for Wind Turbine Generator System

In partial load torque control for variable speed wind turbine generators(VSWTG) rotational speed, which will be feedback signal, is very important parameter. The mathematical model of wind turbine and control regulation for maximizing energy conversion yield has been introduced in this paper. The control system stability and dynamic response are analyzed when using the wind turbine rotor side rotational speed (RSRS) and the generator side rotational speed(GSRS) as feedback signal in torque control respectively ,and the effect the drive train damping and wind speed on system stability are investigated simultaneously. Analysis- and simulation results show that, when using RSRS the stability of wind turbine control system depends on the damping of drive train and the coming wind speed strongly, while the system will be always stable in partial load torque control when using GSRS although wind speed and damping have some effect on the wind turbine system stability. Two real wind turbines of 1.5MW double fed asynchronous generator(DFIAG) are simultaneouly tested with different feedback rotational speed respectively. Test results show that, when using RSRS the generator rotational speed will fluctuate strongly with severe torsion vibrations in higher wind speed, while the wind turbine operate normally for GSRS feedback, which make a very good agreement with analysis- and simulation results.