Sliding mode control approach for voltage regulation in microgrids with DFIG based wind generations

This paper presents a direct torque and reactive power control method which addresses the problem of voltage regulation in microgrids including doubly fed induction generator (DFIG) based wind generation. Due to significant line resistances in a microgrid, active power variations produced by wind turbines can lead to significant fluctuations in voltage magnitudes and results in power quality problems. This paper uses a nonlinear sliding mode control scheme to directly control torque and reactive power of a DFIG system. The control system adjusts the reactive power of DFIG to achieve voltage quality improvement in the important central bus of a microgrid. There is no decoupled proportional-integral (PI) control based method, therefore the control system is not highly dependent to the accuracy of the system parameters. Also, the method is local and can be implemented in the absence of a widespread communication system or remote measurement. 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 are presented to assess the voltage fluctuation compensation and control system robustness.