An Effective Rotor Current Controller for Unbalanced Stand-Alone DFIG Systems in the Rotor Reference Frame

Abstract

This paper presents an effective rotor current controller for variable-speed stand-alone doubly fed induction generator (DFIG) systems feeding an unbalanced three-phase load. The proposed current controller is developed based on proportional plus two resonant regulators, which are tuned at the positive and negative slip frequencies and implemented in the rotor reference frame without decomposing the positive and negative sequence components of the measured rotor current. In addition, the behavior of the proposed controller is examined in terms of control performance and stability with respect to rotor speed variations, i.e., slip frequency variations. Simulations and experimental results are shown to validate the robustness and effectiveness of the proposed control method.

Improving Stability for Independent Power Control of Wind-Turbine Doubly Fed Induction Generator during Grid Unbalance With Pi-Fuzzy Controller

“…However, this is only verified with balanced grid voltage. To improve stability of the powers, inclusion of sequence component controller with Notch filter has been suggested by [6] and presented in Fig. 3 to eliminate negative sequence components.…”

Vector control optimization of DFIGs under unbalanced conditions

“…Authors in previous studies have designed current controllers for LSC, which compensate the negative sequence currents in the grid/load by negative sequence currents of LSC converter as the control inputs. In the studies of Phan, Lee, and Chun, current controllers are designed for the MSC to directly regulate both the positive and negative sequence components in an unbalanced stand‐alone DFIG system without the need for the sequential decomposition of the measured rotor currents.…”

“…Various current controllers for the DFIG current source converter have been proposed in the prior literature for controlling the rotor current to overcome unbalanced PCC voltages. [12][13][14][15][16][17][18][19][20][21][22][23] In other studies, [12][13][14][15] the negative sequence currents provided from both the machine-side converter (MSC) and the line-side converter (LSC) appear as the control input variables that are responsible to compensate the grid voltage unbalance in a synchronous reference frame. In different studies, [16][17][18][19] authors leverage the MSC controller to control the unwanted DFIG dynamics that resulted from the grid voltage unbalance.…”

“…Under permanent grid voltage unbalanced conditions, the DFIG's stator voltages and flux do not pose transient dynamics to the electric power; and therefore, electromagnetic torque equations can be linearized as functions of rotor current, which facilitates the application of current‐based vector control techniques. Various current controllers for the DFIG current source converter have been proposed in the prior literature for controlling the rotor current to overcome unbalanced PCC voltages . In other studies, the negative sequence currents provided from both the machine‐side converter (MSC) and the line‐side converter (LSC) appear as the control input variables that are responsible to compensate the grid voltage unbalance in a synchronous reference frame.…”