Analysis of sub‐synchronous resonance in doubly‐fed induction generator‐based wind farms interfaced with gate – controlled series capacitor

Abstract

This paper first presents a step-by-step tutorial on modal analysis of a doubly-fed induction generator (DFIG)-based series compensated wind farm. The model of the system includes a wind turbine aerodynamics, a sixth-order order induction generator, a second-order two-mass shaft system, a fourth-order order series compensated transmission line, an eighth-order rotor-side converter (RSC) and grid-side converter (GSC) controllers, and a first-order DC-link model. Then, using modal analysis and time-domain simulations, it is shown that a fixed-series compensated DFIG is highly unstable due to the subsynchronous resonance (SSR) mode. In order to damp the SSR mode, the wind farm is interfaced with the gate-controlled series capacitor (GCSC) -which is a new series flexible AC transmission system (FACTS) device. A SSR damping controller (SSRDC) is designed for the GCSC using residue-based analysis and root locus diagrams, and an effective input control signal (ICS) to the SSRDC is identified in order to simultaneously increase damping of both the SSR and super-synchronous (SupSR) modes. The IEEE first benchmark model on SSR is adapted with an integrated DFIG-based wind farm to perform studies. Matlab/Simulink is used as a tool for designing process, and PSCAD/EMTDC is used for time-domain simulations.Nomenclature R line transmission line resistance (pu) X line transmission line reactance (pu) X T transformer reactance (pu) X S system reactance (pu) X C fixed series capacitor (pu) X tg transformer reactance in grid-side converter (GSC) (pu) i lq , i ld transmission line qd-axis currents (pu) i qg , i dg GSC qd-axis currents (pu) i qs , i ds stator qd-axis currents (pu) i qr , i dr rotor qd-axis currents (pu) v qs , v ds generator's terminal qd-axis voltages (pu) v qc , v dc qd-axis voltages across the fixed series capacitor (pu) v qr , v dr generator's rotor qd-axis voltages (pu) v qg , v dg GSC terminal qd-axis voltages (pu) E Bq , E Bd infinite bus qd-axis voltages (pu) Q s 0.5(v qs i ds −v ds i qs ), stator reactive power (pu) P s 0.5(v qs i qs + v ds i ds ), stator active power (pu) Q r 0.5(v qr i dr −v dr i qr ), rotor reactive power (pu) P r 0.5(v qr i qr + v dr i dr ), rotor active power (pu) Q g 0.5(v qg i dg −v dg i qg ), GSC reactive power (pu) P g 0.5(v qg i qg + v dg i dg ), GSC active power (pu) Q line 0.5(v ql i dl −v dl i ql ), transmission line reactive power (pu) P line 0.5(v ql i ql + v dl i dl ), transmission line active power (pu)T e 0.5X M (i qs i dr −i ds i qr ), electric torque (pu) i 0s , v 0s stator zero sequence components (pu) i 0r , v 0r rotor zero sequence components (pu) T tg mechanical torque between two masses (pu) P w , T w wind power and wind torque (pu) D g , D t damping coefficient of generator and turbine (pu) D tg damping coefficient between two masses (pu) K tg inertia constant of turbine and generator (pu) H t , H g inertia constants of turbine and generator (s) C DC-link capacitor (F) I DC DC-link current (A) v DC DC-link voltage (V) V w wind speed (m/s) R rotor radius of the wind...

Active fault location in distribution network using time-frequency reflectometry

“…The purpose of series compensation in transmission lines are to decrease the line equivalent inductance, and consequently to increase the system stability and maximum transferable power of the line [26]- [30]. Verification of the proposed fault location technique in the presence of series compensation demonstrates its universality and the fact that this method could also be applicable to the transmission networks.…”

Multi-parameter bifurcation analysis of subsynchronous interactions in DFIG-based wind farms

“…In this case, the typical choices are the rotor speed, the current through the line and the voltage across the series capacitor. In [13,19] it is shown that the voltage across the capacitor has the best characteristics, but it requires a remote measurement that introduces a time delay in the control loop. An alternative to this signal is proposed in [13,17] where the voltage across the capacitor is calculated integrating the line current.…”

“…A procedure to study SSI in wind farms was presented in [11] and a general methodology was proposed in [12]. Mitigation strategies using dedicated controllers were analyzed in [6,[13][14][15][16][17][18], and using Flexible AC Transmission Systems (FACTS) in [19][20][21]. SSO also appeared in a 150 MVA DFIG wind farm located in Minnesota, USA.…”

Advanced Vector Control Design for DFIM-Based Hydropower Storage for Fault Ride-Through Enhancement

“…The controller of the ASPSH is composed of three separate parts including hydro pump turbine (HPT) controller, the RSC controller, and the GSC controller. The RSC and GSC controllers are similar to the DFIG-based wind turbine [1] in generating mode, while the HPT controller is an additional controller for the ASPSH, adjusting the rotor speed as well as contributing in the frequency control of the grid. However, the plant contributes in the grid frequency control via the RSC in the motor mode, and the HPT is controlled to optimize the HPT efficiency, as shown in Fig.…”

“…The DFIM uses a back-to-back converter, whose power rating is partial scale of the DFIM rated power, between the rotor and stator terminal that can transfer the mechanical power through both the stator and the rotor [1]. The transferred power through the rotor depends on the value of the rotor slip.…”