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This paper presents a sliding mode controller to address the problem of voltage regulation in microgrids involving doubly fed induction wind generators (DFIGs). The control objective is to achieve terminal voltage regulation while ensuring maximum power point tracking (MPPT). The control development is based on voltage sensitivity analysis to eliminate the possibility of interference with the other voltage regulation devices in the microgrid. The proposed method: 1) does not require synchronous coordinate transformation, 2) eliminates the need for decoupled proportional-integral (PI) loops, and 3) is local and can be implemented in the absence of widespread communication systems or remote measurements. Additionally, its control performance is not degraded by errors in system parameters. The performance of the method is illustrated on the IEEE 13-bus distribution network. Dynamic models are considered for the DFIG, converters, and internal controllers along with their operational limits. Stochastic fluctuations in wind speed are modeled with NREL Turbsim while accounting for the tower shadow and wind shear. Dynamic simulations (in PSCAD/EMTDC) are presented to assess the control performance with voltage fluctuation compensation and control system robustness.
Date of Publication: Jan. 2013