Search

Low-voltage ride-through is important for the operation stability of the system in balanced- and unbalanced-grid-fault-connected doubly fed induction generator-based wind turbines. In this study, a new LVRT capability approach was developed using positive–negative sequences and natural and forcing components in DFIG. Besides, supercapacitor modeling is enhanced depending on the voltage–capacity relation. Rotor electro-motor force is developed to improve low-voltage ride-through capability against not only symmetrical but also asymmetrical faults of DFIG. The performances of the DFIG with and without the novel active–passive compensator–supercapacitor were compared. Novel active–passive compensator–supercapacitor modeling in DFIG was carried out in MATLAB/SIMULINK environment. A comparison of the system behaviors was made between three-phase faults, two-phase faults and a phase–ground fault with and without a novel active–passive compensator–supercapacitor modeling. Parameters for the DFIG including terminal voltage, angular speed, electrical torque variations and d–q axis rotor–stator current variations, in addition to a 34.5 kV bus voltage, were investigated. It was found that the system became stable in a short time and oscillations were damped using novel active–passive compensator–supercapacitor modeling and rotor EMF. [ABSTRACT FROM AUTHOR]

The effects of nonlinear load models on the system are an important issue in terms of power quality. In this study, the effect of nonlinear load models in the grid-connected Doubly Fed Induction Generator (DFIG) based wind turbine was investigated. Exponential, constant impedance, constant current, constant active power (ZIP) and induction motor are used as nonlinear load model. Composite load modeling is consist of exponential-ZIP-induction motor. Composite load modeling is turn on and turns off system within different times. Analysis and stability analysis of the composite load modeling were examined. This simulation study was carried out in MATLAB / SIMULINK environment. 34.5 kV bus voltage, DFIG terminal voltage, DFIG electrical torque, DFIG d-q axis stator current variations and DFIG d-q axis rotor current variations in composite load model analysis are examined. As a result of, it has been seen that composite load modeling which is activated as short time is effective on the power system. [ABSTRACT FROM AUTHOR]

• Decoupled power-based sliding mode control modeling strategy was developed for uncertain parameters and chattering problems in DFIG. • The rotor electromotive force model was developed to provide dynamic stability in DFIG. • The stator electromotive force model was developed to improve the performance of the simulation study. • The developed models were examined via balanced and unbalanced fault analyses. Low-voltage ride through (LVRT) capability is the principal method used to counteract voltage dips and over-current, which are caused by various balanced and unbalanced faults. However, in providing LVRT capability during faults, oscillations that occur in parameter changes should be damped for a short time. In this study, a decoupled power-based sliding mode control (SMC) in doubly-fed induction generator (DFIG)-based wind turbines was developed in order to eliminate the oscillation problems that may occur during balanced and unbalanced faults. Besides, while the stator electromotive force model in DFIG is developed with the aim of improving simulation performance and enabling ease of calculation, the rotor electromotive force model is developed to dynamic stability in the system during various faults. The results obviously indicated that the proposed decoupled power-based SMC and stator-rotor electromotive force models enhanced the LVRT capability of the grid-code requirement and quickly restored dynamic stability to the system. [Display omitted] [ABSTRACT FROM AUTHOR]

Grid-connected doubly-fed induction generator (DFIG)-based wind turbines are very sensitive to voltage dip problems that occur in grid side. Therefore, different low-voltage ride-through (LVRT) capability methods are used to decrease the voltage dip problems. In this study, it is aimed to present a hybrid control approach to provide LVRT capability in DFIG. Moreover, it is aimed to develop electromotive-force (emf) models in a stator-rotor circuit. The rotor emf model is used to compensate for the voltage dip and reduce the oscillations while using the stator emf model to ensure the ease of calculation and accuracy of the simulation study. In the results, this paper is reporting that the hybrid control approach proposed in this study has given yield effective and better results in comparison with those of the conventional DFIG model. [ABSTRACT FROM AUTHOR]

• A new rotor resistance unit was developed for low voltage ride through capability in a doubly fed induction generator. • Stator and rotor dynamic modeling were developed against symmetrical and symmetrical faults. • Electromotive force models are developed in stator and rotor circuits. • A comparison was made of symmetrical and symmetrical faults with and without proposed model. It is very important to obtain smooth power and limit over-currents in grid-connected doubly fed induction generator (DFIG)-based wind turbines. Therefore, the rotor resistance unit can be used for power and over-currents control in DFIG. However, it may be insufficient to reduce oscillations in large power systems. This study aims to develop a new rotor resistance unit for low voltage ride through (LVRT) capability in DFIG. Moreover, electromotive-force (emf) models have been also developed in the stator and rotor circuit. The stator emf model of the simulation study was developed in the DFIG for accuracy and speed, while the rotor emf model was developed for over-current occurring in transient situations. In using the new rotor resistance unit and the stator-rotor emf, it was observed that the system stabilized in a short time, and the oscillations formed by the balanced and unbalanced faults on the grid side were damped. [ABSTRACT FROM AUTHOR]