Flicker Mitigation by Active Power Control of Variable-Speed Wind Turbines with Full-Scale Back-to-Back Power Converters Essay

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640 IEEE TRANSACTIONS ON ENERGY CONVERSION, VOL. 24, NO. 3, SEPTEMBER 2009 Flicker Mitigation by Active Power Control of Variable-Speed Wind Turbines With Full-Scale Back-to-Back Power Converters Weihao Hu, Student Member, IEEE, Zhe Chen, Senior Member, IEEE, Yue Wang, Member, IEEE, and Zhaoan Wang, Senior Member, IEEE Abstract—Grid-connected wind turbines are fluctuating power sources that may produce flicker during continuous operation. This paper presents a simulation model of a megawatt-level variablespeed wind turbine with a full-scale back-to-back power converter developed in the simulation tool of PSCAD/EMTDC. Flicker emission of this system is investigated. Reactive power compensation is mostly adopted for flicker mitigation. However, the flicker mitigation technique shows its limits, when the grid impedance angle is low in some distribution networks. A new method of flicker mitigation by controlling active power is proposed. It smoothes the 3p active power oscillations from wind shear and tower shadow effects of the wind turbine by varying the dc-link voltage of the full-scale converter. Simulation results show that damping the 3p active power oscillation by using the flicker mitigation controller is an effective means for flicker mitigation of variable-speed wind turbines with full-scale back-to-back power converters during continuous operation. Index Terms—Distribution systems, flicker, flicker mitigation controller (FMC), variable-speed wind turbine. I. INTRODUCTION B ECAUSE of energy shortage and environment pollution, the renewable energy, especially wind energy, has attracted more attentions all over the world. As the wind power penetration into the grid is increasing quickly, the influence of wind turbines on the power quality is becoming an important issue. One of the important power quality aspects is flicker. Flicker has widely been

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