Double Fed Induction Generator (DFIG)

— Wind energy has become one of the subjects of much recent research and development all over the world. Interconnection of wind farms into power grids, especially weak grids, brings voltage stability problems during grid-side disturbances. This paper studies the voltage stability of a large doubly-fed induction generator (DFIG)-based wind farm, connected to a modified IEEE 14 bus network during system disturbances such as load change, three-phase fault, or voltage swell/sag. Flexible AC transmission system devices (FACTS), such as static bar compensator (SVC) and static synchronous compensator (STATCOM), are installed along with wind farms to maintain voltage and frequency within grid codes. MATLAB/SIMULINK and Power System Analysis Toolbox (PSAT) package are used for the simulation.

Renewable Energy Sources (RES) nowadays are integrated in a rapid way into power system and smart grids.Wind energy and in general RES penetration into power systems create several technical challenges and opportunities as well. In order the system stability and steady state operation to be ensured in power systems steady analysis and dynamic analysis are necessary. These configurations are applied in this study for load flow and transient stability analysis. IEEE 9-bus system is integrated with a Doubly-Fed Induction Generator Wind Farm and a three-phase fault is applied in a load bus. The aim and objective of this study is the behavior of IEEE 9-bus system with a DFIG Wind Farm during disturbances. Moreover critical fault clearing time is identified in this study for the corresponding three-phase fault. This study/work is conducted with the help of
PSS/E 34 software simulation tool of Siemens.

Implementations of mini hydro schemes with conventional hydraulic, electrical equipment's and controllers have proven very expensive and uneconomical. Many developing countries that are in need of rural electrification have encountered economical problem when setting up these mini hydro schemes. To address this problem, alternative options and new designs of these equipment's have been explored by many researchers around the world. The application of these new designs would reduce the overall cost of mini hydro development and would help in making it a cost effective technology. These new designs will also help developing countries to provide electricity to rural areas or remote regions where interconnection of transmission line from the electrical grid is uneconomical. The new designs can also be an enabling factor in boosting up electricity generation using a renewable energy source. This paper provides survey of all these alternative options and new designs in the controller, hydraulic turbine and generators that have been implemented in different countries of the world.

Doubly-fed induction generator (DFIG) based wind turbine generators (WTG) needs to be connected back to integrated power grid after tripping due to disturbances and emergencies in power grid. Re-connection can cause switching transients which may affect overall grid stability. This situation can be avoided if proper synchronization can be ensured for smooth transition of DFIG from island mode to grid-connected mode. To this effect, in this paper, a direct voltage control based synchronization method is introduced that can ensure low or no transient effect during synchronization of DFIG to the grid. The controller is synthesized based on a multi-channel identification methodology and integrated using a designed grid connection logic for soft synchronization. The architecture is implemented on a modified IEEE 39 bus system with DFIG and tested on a real-time simulation platform with different wind speed conditions. It is observed that the proposed architecture makes the grid more stable (with swings in voltage or frequency reduced as much as 60%) during re-connection of wind generators.

Meeting grid code requirement creates an obligation to smart WTs disconnection following some electrical or mechanical events. Increasing the penetration level of wind turbines (WTs) in different voltage levels of the network have a major effect on this condition. In this regard, soft and rapid synchronization control of doubly fed induction generator (DFIG) to reduce the dynamic and transient effects of DFIG on a smart grid is very important. This paper gives a review on WTs power generation and a basic requirement to operate in a stable manner in connection to the network at first. After that, different startup and synchronization methods will be described. Then, a new synchronization method for grid connection of DFIG driven by WT is proposed. In this method, the rotor side converter is synchronized with the induced voltage at the rotor winding of DFIG while the stator windings have been connected to the grid and the rotor accelerates normally with the wind torque. This startup process is soft and the synchronization is carried out between two low voltages Original Research Article Nayeripour et al.; JENRR, 1(3): 1-13, 2018; Article no.JENRR.42795 2 with very low frequency and may overcome some difficulties and limitations of previous methods since it uses the rotor side converter as power electronics switches instead of the mechanical circuit breaker at stator side and causes the synchronization to be more accurate and controllable. The proposed method is evaluated with EMTDC/PSCAD simulation to show the performance of soft starting synchronization with lower electrical transients in comparison with traditional methods.

This paper treats the modeling, and the control of a wind power system based on a doubly fed induction generator DFIG, the stator is directly connected to the grid, while the rotor is powered by multilevel inverters. In order to get a decoupled system of controlfor an independently transits of active and reactive power, a vector control method based on stator flux orientation SFOC is considered: Direct vector control based on PI controllers. Cascaded H-bridge CHBI multilevel inverters are used in the rotor circuit to study its effect on supply power quality. All simulation models are built in MATLAB/Simulink software. Results and waveforms clearly show the effectiveness of vector control strategy. Finally, performances of the system will tested and compared for each levels of inverter.

Propiedad de Valeo Distribución España. Prohibida su reproducción. © 1999 El compresor es una máquina que transforma la energía mecánica suministrada por el motor del vehículo, de forma que aspira el fluido refrigerante, procedente del evaporador y bajo la forma de vapor a baja presión y temperatura, para después impulsarlo hacia el condensador, en forma de vapor a alta presión y temperatura. El fluido sufre pues un incremento de presión y temperatura en el compresor. Si se representa el proceso de compresión del fluido en un diagrama de Mollier (presión-entalpía), se puede observar como no solo aumenta su presión y su temperatura, sino también su entalpía. En realidad, es la aportación externa de entalpía la que provoca que aumente su presión y temperatura. Y esa entalpía es generada en forma de energía mecánica por la correa del alternador, que arrastra la polea del compresor. El compresor se encuentra fijado directamente sobre el bloque motor, y es accionado normalmente por la correa que mueve la bomba de liquido de refrigeración y el alternador. Es fundamental que el montaje se haga de forma correcta ya que si se rompiera el soporte, debido a la situación del compresor, las consecuencias podrían ser muy graves.

This paper proposes the adaptive particle swarm optimization (APSO) technique to control the active and reactive power produced by a variable wind energy conversion system and the exchanged power between the electric grid and the system during a voltage dip (VD). Besides, to get the variable speed wind energy maximum power, a maximum power point (MPP) methodology is utilized. The system under study is a 5 MW wind turbine connected via a gearbox to a doubly-fed induction generator (DFIG). The DFIG stator is branched directly to the electrical network, while the Back-to-Back converters couple the rotor to the grid. The decoupled vector control of the rotor side converter and the grid side converter is established primarily by a conventional proportional-integral (PI) and a second level by an intelligent PI whose gains are tuned using the proposed control. The performances and results obtained by APSO tuned PI controllers are analyzed and compared with those attained by classical PI controllers through the MATLAB/Simulink. The superiority of the advised technique is examined during a two-phase short-circuit fault condition and confirmed by the reduced oscillations.

A doubly-fed induction generator (DFIG) is considered one of the most suitable generators for the variable wind speed due to its different composition from the rest of the other generators. This paper presents optimal design, power management, and control of hybrid photovoltaic (PV) and battery energy storage systems (BESS) for grid-connected DFIG Based wind energy conversion systems (WECS). The proposed system integrates the BESS-PV hybrid system with the DFIG grid-connected system via the DC-link of the back-to-back converter. The main objective of the paper is to maintain a constant DC-link voltage (Vdc), keep the stator and rotor currents stable and smooth, and maintain constant and smooth active power during the variation in wind speed. The proposed optimized control methodology includes a moth-flame optimized fuzzy logic controller (MFO-FLC) to extract the maximum power of PV power under variable solar radiation. Moreover, a constantcurrent constant-voltage controller (CC-CV) for BESS is implemented using MFO-PI. MATLAB/ SIMULINK® platform was used to verify the design and control of the proposed system. The simulation results demonstrated the effectiveness of the optimized control methodology under variable solar radiation and wind speed conditions. The active power transferred to the grid through the grid side converter of the DC-link is smoothed and maximized by approximately 22% from its actual value during low wind speed and 1000 w/m 2 while preserving a constant DC-link voltage during transient and steady-state conditions.

— Although the concept of smart grid has been inspiring for applying complex algorithms and strategies in operating of power systems, but verification of these algorithms are presumed on reliable and accurate simulation framework. To address this significant aspect of the smart grid, a simulation framework is developed through interfacing between MATLAB/SIMULINK with Java Agent Development Environment (JADE). Furthermore, based on the proposed simulation framework a multi-agent protection system (MAPS) has been identified where different agent types collaborate in system protection tasks. The main objective of this paper is to highlight the requirements for an effective simulation framework to integrate MAPS into future smart grids.

—-Wind energy plays an increasingly important role in the world because it is friendly to the environment and limitless. During the last decades, the concept of a variable-speed wind turbine (WT) has been receiving increasing attention due to the fact that it is more controllable, efficient, and has good power quality. In order to most effectively utilize the wind energy and improve the efficiency of wind generation system an optimum control strategy of doubly-fed induction generators (DFIG) is proposed. This paper presents a stator flux oriented vector control strategy for a 2MW/690V doubly fed induction generator (DFIG)-based wind energy generation system to control the rotor side converter to control the active and reactive power and grid side converter control to maintain dc link voltage constant. Keywords— Doubly fed induction generator (DFIG), Vector control, active and reactive power control, Wind power.

In this research, a Type 2 adaptive fuzzy controller approach is formulated and designed to be applied to variable speed doubly fed induction generator-based wind turbines directly connected to the grid. It brings this study to evaluate the whole operation of the system to capture the highest rate of power in the wind turbines. The controlling approach is considered to keep the stator reactive power to the ideal value. In contrast to the other researches, here the controlling technique is developed through the nonlinear systems.  By the aim of making progress in system operation, in contrast with the Type 1 adaptive fuzzy system, type two adaptive fuzzy theory is proposed to approximate a large number of uncertainties and the dynamic nonlinearities, exists in tracking errors which may limit the system performance. Feedback linearization control approach helps us to algebraically alter the system into a linearized plant. Thanks to the Lyapunov theorem, the introduced type two adaptive fuzzy approach is proved to meet the uniformly ultimately boundness (UUB) property. On the other hand, it results better tracking function. The simulation outputs represent that the proposed technique is robust enough in presence of parameter variations and unstructured uncertainties.

This manuscript deals with reactive power management, analysis and solution with the static Var compensator (SVC) and UPFC for Grid connected DFIG wind farm system mitigation. The purpose of the paper is to derive and analyze a reactive power control strategy of SVC dedicated for DFIG mitigation. The FACT device Static Var compensator is connected with load bus. Paper has demonstrated the improvement in voltages, power transferred to grid, active and reactive power control. Simulink software is used for the work. Paper demonstrated the simulation results for with and without SVC and UPFC for Grid connected Doubly Fed Induction Generator wind farm system.

A new method to evaluate the steady state performance of a three-phase self excited induction generator based on conductance minimization is proposed. Among the priorities of this method are the absence of convergence problem, flexibility and the ability to be augmented to RC loads and loads with compensation. Simple methods to find the frequency, magnetizing reactance and minimum required capacitance are proposed. Simulation results show the agreement of this method with other common methods.

The following article presents the control of the power generated by the Doubly Fed Induction Generator, integrated into the wind system, whose rotor is linked to the power converters (Rotor Side Convert (RSC) and Grid Side Converter (GSC)) interfaced by the DC-BUS and connected to the grid via a filter (Rf, Lf) in order to obtain an optimal power to the grid and to ensure system stability. The objective of this study is to understand and to make the comparison between Sliding mode Control technique and the Flux Oriented Control in order to control the Doubly Fed Induction Generator powers exchanged with the grid, it also aims at maintaining the DC-BUS voltage constant and a unit power factor at the grid connection point.The results of simulation show the performance of the Sliding mode Control in terms of monitoring, and robustness with regard to the parametric variations, compared to the Flux Oriented Control. The performance of the systems was tested and compared with the use of MATLAB/Simulink software

Doubly-fed induction generator (DFIG)-based wind turbines utilise small-scale voltage sourced converters with a limited overcurrent withstand capability, which makes the DFIG-based wind turbines very vulnerable to grid faults. Often, modern DFIG systems employ a crowbar protection at the rotor circuit to protect the rotor side converter (RSC) during grid faults. This method converts the DFIG to a squirrel cage induction generator, which does not comply with the new grid codes. The recent grid codes need wind turbines to stay connected to the utility grid during and after power system faults, especially in high penetration level of wind power. Furthermore, the crowbar switch is expensive. This paper proposes a novel DC-link switchable resistive-type fault current limiter (SRFCL) to improve the LVRT capability of the DFIG. The proposed SRFCL is employed in the DC side of the RSC. The SRFCL solves crowbar protection activation problems and eliminates subsequent complications in the DFIG system. The proposed SRFCL does not have any significant impact on the overall performance of the DFIG during normal operation. Whenever the fault, whether symmetrical or asymmetrical, occurs, the SRFCL not only limits rotor over-currents but also prevents rotor speed acceleration and restricts high torque oscillations even during zero grid voltage, as recommended by some grid codes. To prove the effective operation of the SRFCL on the RSC fault current limitation, analytical analysis is performed in each switching interval. The proposed approach is compared with the crowbar-based protection method. Simulation studies are carried out in PSCAD/EMTDC software. In addition, a prototype is provided to demonstrate the main concept of the proposed approach.

Wind energy is one of the world’s leading promising renewable energy sources, due to that there is a prediction that wind generation systems will provide maximum power supply and have good integration with the electric grid. To fulfill the increasing power demand, wind power generation systems need more advanced, novel, and robust control approaches to achieve a more stable operation of the controller and to improve the overall efficiency of the system. This paper presents an optimal design and tuning of fuzzy logic controllers (FLC) for a 1.5-MW doubly fed induction generator (DFIG), grid-connected, wind energy conversion system (WECS) using intelligent methodologies such as particle swarm optimizer (PSO), the gray wolf optimization (GWO), moth-flame optimizer (MFO), and multi-verse optimizer (MVO). FLC scaling factors are optimized for both dc-link voltage controller and current regulators of the grid-side converter and rotor-side converter of the back to back of DFIG wind turbine...

The standard grid codes suggested, that the wind generators should stay in connected and reliable active and reactive power should be provided during uncertainties. This paper presents an independent control of Grid Side Converter (GSC) for a doubly fed induction generator (DFIG). A novel GSC controller has been designed by incorporating a new Enhanced hysteresis comparator (EHC) that utilizes the hysteresis band to produce the suitable switching signal to the GSC to get enhanced controllability during grid unbalance. The EHC produces higher duty-ratio linearity and larger fundamental GSC currents with lesser harmonics. Thus achieve fast transient response for GSC. All these features are confirmed through time domain simulation on a 15 KW DFIG Wind Energy Conversion System (WECS).

The rapid growth of wind power systems worldwide will likely see the integration of large wind farms with electrical network that are series compensated stable transmission of bulk power. Using Flexible AC Transmission System (FACTS) devices are considered in order to maintain stability and provide the reactive power requirement of the grid and transfer the maximum power extracted from wind turbine to consumers. This paper presents the complete modeling and real-time simulation of wind turbine driven doubly-fed induction generator (DFIG) which feeds ac power to the utility grid. Keywords-DFIG, DC Control Link, UPFC, Wind Energy Conversion System (WEBS), Direct Torque Control Technique (DTC)

In this paper the quality of power generated from a wind energy conversion system employing a double fed induction generator (DFIG) is investigated. The DFIG performance is tested with 3 types of converters interfacing the rotor with the grid. These are: universal converter, 2-level bridge converter, and 3-level bridge converter. A comparison between the power quality issues with and without filters for each system is done and the optimum system from technical & economic views is concluded.

— In this paper the dynamic performance of a stand-alone wind-driven Single Machine-Brushless Double Fed Generator (SM-BDFIG), supplying different loads in remote area is investigated. The battery embedded in the frame of the specially designed SM-BDFIG is used for energy storage in the super synchronous range of operation. The stored energy is used to supply enough slip power for the rotor circuit of the generator in the sub-synchronous range of operation, to feed the rotor with the necessary DC power at synchronous speed, and also to supply the priority loads at low wind speeds equal or below the cut-in speed. A programmable logic controller (PLC) is designed to control the operation of the rotor converters according to the wind speed and to manage the whole stand-alone system. The dynamic performance of the generator at variable wind speeds is studied. The effect of varying loads on the generator currents, voltages, and electromagnetic torque are given for variable wind speeds. Also the effect of sudden change in the wind speed on the SM-BDFIG performance is investigated. The investigation is done at synchronous speed as well as sub-synchronous and super-synchronous speeds. Results proved the stable operation of the proposed machine as generator at within the whole speed range (from sub-synchronous speed to super-synchronous) stably. Keywords — Single Machine Brushless Doubly-Fed Induction Generator "SM-BDFIG", 3-phase bridge rectifier, super-synchronous operation, Battery charge, and DC link.