Power System Oscillations Damping Control Strategy For Doubly Fed Induction Generator

As the high penetration of wind power, the power system small signal stability should be addressed. Wind power penetration levels have been rapid increased throughout the world wide. The growing trend will continue in the following decades. Among the various wind power generators, doubly fed induction generators (DFIGs) have shared a large market due to its advantages of relatively small size, low power rating of the back-to-back power electronic converters, high energy efficiency and the capability of flexible control. Thus, the DFIG based wind farms will play an important role in power systems operation. On the other hand, the increasing size of power systems have reported more problems such as interarea oscillation, which will threaten the stability of power systems operation. For the system with high penetration of wind generation, the advanced power electronic convertors in DFIG can be employed to damp the power system oscillations with increased flexibility.1. The dynamic model of DFIG based wind energy conversion system is modeled first. The modeled dynamic model including wind machine, DFIG, voltage sourse conveter based dc system and its control system. The dynamic model of DFIG based wind energy conversion system is the basic of the work in the followed sections.2. Reactive power modulation of DFIG is an effective way to damp interarea oscillation in large-scale wind power penetrated power systems. To achieve this, there are two different schemes, one is via reactive power feedback control, and another is via voltage feedback control. While both of the control schemes are feasible, their effectiveness may differ, and there has not been a systematic comparison between them. This paper investigates the differences between DFIG reactive power feedback control and voltage feedback control for interarea oscillation damping. In this study, the fixed phase modulation approach (also known as Bang-Bang control) is employed, and the bode plot,?-analysis and time domain simulation are conducted to examine the performance of the two control schemes against oscillation. The two-area four-machine system along with a DFIG-based wind generation integrated is employed for analysis in frequency domain and time domain. The robustness of the control schemes to various in system operation points and wind speed are also studied. The results from this paper can provide a deep insight into the understating of DIFG reactive modulation against oscillation and guiding controller design.3. This work proposes a novel nonlinear control strategy for DFIG to enhance the transient stability of a weak power system with DFIG integrated. The proposed approach utilizes the input-output linearization algorithm to exact linearize the nonlinear power system from selected inputs (active power and reactive power control of DFIG) to outputs (power angle and voltage behind transient resistance). Thus, the transient stability can be significantly improved based on linear quadratic regulator control method. The main features of the proposed control strategy for DFIG are it successfully deal with the nonlinear behaviour exist in the inputs to outputs and significantly enhanced the transient stability under various operation points. The numerical simulation results show that the proposed control strategy is effectively to improve the transient dynamic performance of power systems under different operating points.4. A Bang-Bang modulation based hybrid interarea oscillation control strategy for DFIG to improve the dynamic performance of power systems is proposed. The active power modulation of DFIG may result in its interactive effect with torsional oscillations. Thus, the modulation of DFIG reactive power is employed to rapidly attenuate the system's most dominant critical mode, which is identified by Prony analysis. The lead lag of the Bang-Bang modulation is confirmed through the frequency domain analysis based on the DFIG detail dynamic model. Compared to the conventional continuous damping control method, the proposed hybrid controller can damp the inerarea oscillation rapidly. A set of comprehensive case studies are conducted on a two-area power system. Simulation results show the improved system performance in interarea oscillation damping and demonstrate the effectivity and efficiency of the proposed control scheme in mitigating the critical oscillation modes of power systems.5. A second-order sliding mode control algorithm based interarea oscillation damping controller for DFIG. The proposed damping control strategy utilizes the reactive power modulation ability of DFIG to stabilize the power system in the event of oscillations caused by disturbances is proposed. The sliding mode based damping control law for DFIG is derived based on a two-area power system, and then extend to multi-area power system. The proposed damping controller is insensitive to modeling uncertainties and parameter variations. Thus, for the ranging of operation points, the proposed sliding mode based damping control should illustrate a better robustness than the conventional damping control. Simulation results for a two-area power system and a 10-machine 39-bus power system with DFIG based wind farms show the improved system performance in interarea oscillation damping and demonstrate the robustness of the proposed control scheme in a wide operation region.