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In case of three-phase short circuit fault occurring at the terminal of a doubly-fed induction generator (DFIG), the rotor current characters of DFIG are analyzed from the viewpoint of the flux linkage, and the expression of the rotor current is deduced together with the estimated expression of the maximum rotor current. Based on above analysis, the max rotor currents and their appearing times with...
With the development of modern wind energy generation, higher requirements to the grid in case of a failure were raised. In order to faciliate the recovery of power, while voltage dips in a certain range, protecting the rotor side converter and providing reactive power to the grid are both needed according to the requirements. This paper takes DFIG for example, in order to protect the rotor side converter,...
Brushless Doubly-Fed Machine (BDFM) is a machine which incorporates the robustness of the squirrel cage induction machine while having the speed and power factor control of a synchronous machine. A special kind of rotor called Nested-Loop rotor plays an important part in the BDFM, coupling the two stator fields. In future BDFM will share a large part in wind power market. This paper presents a mathematical...
Power system with high penetration of wind power requires a developed control strategy to obtain optimal dynamic performance under load variations. An algorithm utilizing internal model control (IMC) design method for the control of doubly fed induction generator (DFIG) operating at variable speed constant frequency is proposed. The proposed structure is a stand-alone generating system and feeds a...
The paper presents advanced vector control system for AC-DC-AC converter operating as grid interface for renewable energy systems. The control method is based on Direct Torque Control with Space Vector Modulation (DTC-SVM) for Machine Side Converter (MSC) and Direct Power Control with Space Vector Modulation (DPCSVM) for Line Side Converter (LSC). The whole control and protection system has been implemented...
The use of doubly fed induction generators (DFIG) in large wind turbines has become quite common over the last few years. However, DFIG are very sensitive to grid disturbances, especially to voltage dips, therefore low voltage ridethrough(LVRT) technology for DFIG becomes one of the critical technology in the uninterrupted operation of wind power generation. In order to help the study of low voltage...
A fifth order model of a doubly fed induction generator (DFIG) is proposed with stator flux orientation (SFO) vector control. Induction generator equipped with the as-built wind turbine scheme and grid system is modelled in MATLAB/SIMULINK. Different controllable parameters are identified. A control system is designed to improve the stability of the generator, which is connected with the back to back...
In this paper, a vector control mechanism has been suggested and applied to simulate the operation of a Doubly-Fed Induction Generator (DFIG) attached to an isolated off-the-grid wind turbine, to demonstrate that these generators can be used at lower costs to control the power quality in stand alone wind turbines. In order to achieve this end, the alignment of the d-axis of the synchronously rotating...
Three-phase induction motor due to simple structure, reliable operation, as well as the advantages of low cost is widely used in industrial, agricultural production and the areas of daily life. However, induction motors starting directly have great impacts on the power grid and electrical equipment. There are different performance requirements in different applications, and increasing emphasis on...
Wind energy penetration to the power market has been continuously increasing over the past decades. High penetration level requires the wind energy generation to be more reliable. For wind farms equipped with doubly fed induction generators (DFIGs), a successful low voltage ride-through scheme has been a key issue to achieve reliable and uninterrupted wind energy generation. This paper proposes a...
This paper analyzes the behavior of DFIG and converter in the case of grid fault including symmetrical and unsymmetrical fault. First, the simple space vector models are presented to estimate the moduli of DFIG stator voltage in different grid fault. Then with the symmetrical components method, the dynamic response of DFIG and converter in grid fault is analyzed in details, and the equations of grid...
A detailed mathematical model of doubly-fed induction generator (DFIG) is derived according to generator convention. A novel S-Function is proposed to describe the mathematical model of DFIG. The simulation subsystems of no-load operation and generator operation are developed based on state equations. The control of the rotor current inner loop and the rotating speed outer loop are designed based...
Traditional wind power generation is directly or step-down cut in, and the current impact is extremely high. In this paper, according to the characteristic of AC-excited variable speed constant frequency (VSCF) wind power generation, a vector control technique is applied in doubly fed induction generator (DFIG), and an idle load cutting-in control strategy is presented based on grid voltage orientation...
Nowadays, the most widely used variable speed wind turbine type for units above 1 MW is doubly fed induction generator (DFIG). As the wind power penetration continues to increase, wind turbines are required to remain connected during grid faults to ride-through the faults. This paper gives a control oriented modeling of DFIG wind turbines by using causal ordering graph (COG). The control system consists...
Aim to reduce the cost of wind energy conversion system and improve its performance, a novel variable-speed wind energy generation scheme which is based on the combination of PMSG and super sparse matrix converter (SSMC) is presented in this paper. The whole physical system including SSMC is modeled. Coordinate transformation, active power conservation principle and singular perturbation theory are...
This paper focuses on the development of maximum wind power extraction strategies for variable speed constant frequency (VSCF) grid-connected wind power generation systems with a doubly fed induction generator (DFIG). A new control method is proposed by directly controlling the DFIG rotor current to follow an optimal condition for not only the extracted maximum power of the wind turbine below the...
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