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The main advantage of the doubly fed induction generators (DFIG) over the synchronous generators is the small size converter which is located in the rotor circuit. However, this advantage can cause a problem during grid faults, because the over voltages and currents that will occur on the rotor circuit can damage the rotor side converter (RSC), if it is not over-dimensioned or protected for such high...
This paper deals with the low voltage ride through (LVRT) capability of a wind farm comprises different arrangements of the fixed speed and variable speed turbines. Based on the grid code requirements it is seemed that the hybrid topologies can provide better performances than purely either fixed or variable speeds turbines during the fault conditions using DFIG or SCIG. In the hybrid topology two...
Negative impacts! of the grid faults! in the Doubly Fed Induction Generators (DFIGs) based wind turbines systems include the stator and rotor over currents, DC-link over voltage, electromagnetic torque oscillations, active and reactive power fluctuations at the grid connection point, potentially leading to destabilization of the power system network. For eliminating of the negative impacts, thus enhances...
Doubly-fed wind generator is highly sensitive to voltage variations of the grid, which poses limitations for wind power plants during the grid integrated operation. This paper proposes a new control strategy for rotor side converter of doubly-fed induction generator (DFIG) using energy-based control method based on Port-Control Hamiltonian (PCH) theory and L2 disturbance attenuation. The proposed...
Voltage dips caused by faults in the power supply, change the behavior of single phase induction machines because transient currents and torques occur. In order to find an optimal disconnecting and restart time, the effects on the machine and the process must be determined. The effects of such voltage dips on the transient behavior depend on the chosen start circuit of the machine. In this paper the...
This paper develops a control strategy for a large wind turbine based on the squirrel cage asynchronous generator (SCAG). In addition, the transient behavior during Low Voltage Ride Through (LVRT) of the system is studied. To this end, the wind turbine connected to the grid is controlled in such way to inject maximum power into the grid and provide a reactive power to regulate the grid voltage, in...
This paper deals with the behavior of DFIG under normal and abnormal condition of grid based on the parameters of DFIG such as power flow, stator and rotor current and DC link voltage. The stator side, rotor side and DC link are realized by their equivalent circuit for analysis under normal and dip condition. It is observed that during abnormal condition there is unbalance in stator and rotor current...
Variable-speed turbines have gained increasing importance in pumped-storage power plants since they present big advantages compared to the classical topology with a synchronous generator. Within the variable-speed solutions, the one employing a doubly-fed induction generator (DFIG) has become the preferred alternative for large installations since it provides the advantages of variable-speed operation...
This paper presents a detailed analysis of the dynamic behavior of Doubly Fed Induction Generator (DFIG) under asymmetrical voltage dips. Finite element analysis (FEA)for 1.5MW DFIG, back-to-back converter, DC-Link, step up transformer, voltage sag generator(VSG) and the control algorithm have been considered and coupled together by using a coupled simulation. The effect of asymmetrical voltage dips...
Power generation and grid stability have become key issues in the last decade. The high penetration of large capacity wind generation into the electric power grid has led to serious concerns about their influence on the dynamic behavior of power systems. The Low-Voltage Ride-Through (LVRT) capability of wind turbines during grid faults is one of the core requirements to ensure stability in the power...
Electromagnetic transients resulting from voltage dips complicate the low-voltage ride-through (LVRT) of doubly fed induction generator (DFIG) based wind turbines (WTs). To study the transients deeply, an analytical method to solve the dynamic response is presented in this paper. Although some attempts have been made in literature, the accuracy cannot be ensured, or the physical significance implied...
Recent developments show that renewable energy sources are considerably contributing to the electrical power generation and offer a future-oriented, sustainable and environmental-friendly alternative to fossil energy sources. Wind energy in particular has experienced a rapid growth over the past decades, so that wind energy conversion systems (WECS) will occupy an important role in the power generation...
This paper investigates the effect of Series Dynamic Breaking Resistor (SDBR) sizing on a Doubly Fed Induction Generator (DFIG) based wind power conversion system. The boundary of the SDBR value is firstly derived by taking into account the controllability of the rotor side converter and the maximum allowable voltage of the stator. Then the impact of the SDBR value on the rotor current, stator voltage,...
The Wind Turbine Systems (WTS) are required to ride through recurring grid faults in some countries. In this paper, the capability of Doubly Fed Induction Generator (DFIG) WTS to ride through recurring asymmetrical grid faults is evaluated and compared with the ride through capability under single asymmetrical grid fault. A mathematical model of the DFIG under recurring asymmetrical grid faults is...
New grid codes demand the wind turbine systems to ride through recurring grid faults. In this paper, the performance of the Doubly Fed Induction Generator wind turbine system under recurring grid faults is analyzed. The stator natural flux produced by the voltage recovery after the first grid fault may be superposed on the stator natural flux produced by the second grid fault, and it may result in...
The new grid codes demand the wind turbine systems to ride through recurring grid faults. Many control strategies have been proposed for the Doubly Fed Induction Generator under single grid fault, but their performance under recurring grid faults have not been studied yet. In this paper, five different control strategies for DFIG to ride through single grid faults are presented, and their performance...
In this paper a new coordinated fault ride through approach is proposed for wind turbines which are equipped with doubly-fed induction generators (DIFG). The proposed technique suggests a coordinating methodology between the demagnetizing current control method, STATCOM operation of the grid side converter (GSC), Rotor Current Limiter (RCL) method, and reactive power control of the rotor side converter...
This paper deals with a protection and control strategy to enhance the low voltage ride through capability of a wind turbine driven doubly fed induction generator (DFIG). As the wind power penetration continues to increase, wind turbines are required to provide Low Voltage Ride-Through (LVRT) capability. Crowbars are commonly used to protect the power converters during voltage dips and their main...
The paper presents some issues on testing the generators, integrated in wind turbine systems. Generators are subject to perturbations transmitted from the source to the source and to perturbations determined by the variable speed of the turbines' blades. The paper reviews the standards concerning tests in wind systems and depicts some specific tests, using a programmable source and specific standard...
Doubly-fed induction generator (DFIG) is one of important drive systems for wind turbine. It has been widely applied in the power grid today because of its less losses and simpler control strategies. Meanwhile, during voltage dips, the DFIG kept connecting with the grid can provide some reactive power so as to recover the grid voltage, which is called the ability of low voltage ride-through (LVRT)...
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