Keywords: wind energy conversion systems, WECS, doubly fed induction generators, DFIG, back-to-back VSCs, nonlinear load, active power filtering, active power flow control, reactive power flow control, sub-synchronous mode, super-synchronous mode, power electronics, wind power, wind turbines, pulse width modulation, PWM, voltage source converters, wind speed, simulation
Sub and super-synchronous wind turbine-doubly fed induction generator system implemented as an active power filter
This paper deals with a wind energy conversion system (WECS), based on a doubly fed induction generator (DFIG) and an electromechanical active power filter (APF). The objective is to respond simultaneously to electric energy requirement and power quality concerns. The proposed WECS is able not only to track the maximum power point of the wind energy but also to dampen harmonic currents from the grid line. To achieve these purposes, back-to-back pulse width modulation (PWM) voltage source converters (VSCs) are employed to excite the DFIG rotor. To control the power converters, two regulation loops, following the field oriented control (FOC) method, have been conceived. The first loop, dedicated to the rotor converter, enables a decoupled control of active and reactive powers flows. As well, it permits the cancellation of the most noteworthy harmonics from the utility current. The second loop, devoted to the front-end converter (FEC), makes it possible to regulate the DC-bus voltage shared between the two converters. Furthermore, the paper provides a study of the DFIG sub and super-synchronous operating modes which can be reached by acting on the wind speed. To demonstrate the performance of aforementioned WECS, a Matlab/Simulink model was established and simulated. Results seem to be very promising.