TY - JOUR ID - 4363 TI - Control and Performance Assessment of Variable Rotor Resistance Based Wind Turbines Regarding the Aerodynamic Power Fluctuations JO - Scientia Iranica JA - SCI LA - en SN - 1026-3098 AU - Rahimi, Mohsen AD - Department of Electrical and Computer Engineering, University of Kashan, Kashan, Iran Y1 - 2018 PY - 2018 VL - 25 IS - 3 SP - 1593 EP - 1607 KW - Aerodynamic torque fluctuations KW - Limited variable speed wind turbine KW - Power-slip curve KW - Shaft stiffness KW - Wind turbine with variable rotor resistance DO - 10.24200/sci.2017.4363 N2 - This paper first deals with the analytical controller design in wind turbines with variable rotor-resistance control. Wind turbines with variable rotor-resistance control, known as limited variable speed wind turbine (LVS-WT), provide a limited variation of the generator speed. In the LVS-WT, the rotor current and consequently the output power can be controlled by varying the rotor resistance. Then modal and small signal analysis of the wind turbine is examined. It is found that for certain value of shaft stiffness, frequency of the mechanical modes coincides with the triple oscillation frequency appeared due to tower shadow effects. This in turn results in resonance phenomena magnifying the fluctuation of the generator power and electromagnetic torque. The paper next evaluates the impact of aerodynamic torque fluctuations on the dynamic response of the LVS-WT. In this way, analytical expressions for the fluctuations of the stator voltage and current, electromagnetic torque, and generator active power are proposed. These fluctuations arise as a consequence of the aerodynamic torque and rotor speed perturbations. The paper also investigates the effects of shaft stiffness, slope of power-slip curve and rotor resistance on the wind turbine response. At the end, results of theoretical analyses are verified by time domain simulations. UR - https://scientiairanica.sharif.edu/article_4363.html L1 - https://scientiairanica.sharif.edu/article_4363_94034a44d1fc6b95f2a2dbca2db41b8b.pdf ER -