Enhancement of LVRT Ability of DFIG Wind Turbine by an Improved Protection Scheme with a Modified Advanced Nonlinear Control Loop (original) (raw)
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LVRT Control Strategy of DFIG based Wind Turbines Combining Passive and Active Protection
2017
Due to its advantages, Doubly Fed Induction Generator (DFIG) is the most used generator in the wind power area. However, the DFIG provides electrical power at a constant frequency even if the rotor speed varies; also, it allows a better capture of wind energy. Although the DFIG has a high sensitivity regarding the electrical faults, which brings up many challenges in terms of compliance: Power provider and electrical operator (in terms of production continuity and quality of energy). Actually, the grid connection requirements impose strict rules to respect for Low Voltage Ride Through (LVRT) and grid support capabilities following the Grid Code (GC). Therefore, it’s crucial for wind turbines (WT) to propose an advanced control. In fact, when detecting voltage dips, WTs must stay connected to the grid to provide the required reactive power in order to have a safe and reliable operation. The objective of this article is to propose a new LVRT strategy able to keep WTs connected to the ...
LVRT Control Strategy of DFIG Based Wind Turbines Combined the Active and Passive Protections
International Journal of Renewable Energy Research, 2017
Due to its advantages, Doubly Fed Induction Generator (DFIG) is the most used generator in the wind power area. However, the DFIG provides electrical power at a constant frequency even if the rotor speed varies, also it allows a better capture of wind energy. Although the DFIG has a high sensitivity regarding the electrical faults, which brings up many challenges in terms of compliance: Power provider and electrical operator (in terms of production continuity and quality of energy). Actually, the grid connection requirements impose strict rules to respect for Low Voltage Ride Through (LVRT) and grid support capabilities following the Grid Code (GC). Therefore, it’s crucial for wind turbines (WT) to propose an advanced control. In fact, when detecting voltage dips, WTs must stay connected to the grid to provide the required reactive power in order to have a safe and reliable operation. The objective of this article is to propose a new LVRT strategy able to keep WTs connected to the g...
Enhancement of LVRT Capability of DFIG Wind Turbine by Using Advanced Control Strategy
In this paper, doubly fed induction generator (DFIG) based wind turbine (WT) low voltage ride through (LVRT) capability is enhanced by using advanced control strategy for the rotor side converter (RSC) and grid side converter (GSC) to meet grid code requirements. The conventional crowbar with constant resistance method is used to protect and improve the LVRT. However, its response varies accordingly to the voltage dip level. In addition conventional method may be over or under estimate fault in certain condition which results in damage to the converters and DFIG. The proposed advanced control strategy introduces the instantaneous DC link current of the RSC as compensating term on GSC control scheme to smooth the DC link voltage fluctuations during the grid at the point of common coupling (PCC). By using pitch control, the wind energy is captured as rotor inertia during faults which significantly reduce the oscillations in the stator and rotor currents and the DC bus voltage during fault, the remaining energy is available to the grid after fault clearance and also it ensures smooth release of the excessive inertia energy into the grid. A time domain model for the 1.5 MW DFIG test system with the decoupled dq controller is implemented using MATLAB/SIMULINK and its effectiveness has been demonstrated through various simulation cases. The proposed control strategy results compared with conventional crowbar method shows not only the enhancement of LVRT capability of DFIG, but also helps maintaining continuous active and reactive power control during the grid fault. Keywords: Doubly fed induction generator (DFIG), wind turbine, low voltage ride through (LVRT), power system fault, MATLAB/Simulink.
A New Approach LVRT Control with Enhanced Reactive Power Support for DFIG Wind Turbines
The paper presents a new control strategy to enhance the ability of reactive power support of a doubly fed induction generator (DFIG) based wind turbine during serious voltage dips. The proposed strategy is an advanced low voltage ride through (LVRT) control scheme, with which a part of the captured wind energy during grid faults is stored temporarily in the rotors inertia energy and the remaining energy is available to the grid while the DC-link voltage and rotor current are kept below the dangerous levels. After grid fault clearance, the control strategy ensures smooth release of the rotor’s excessive inertia energy into the grid. Based on these designs, the DFIG’s reactive power capacity on the stator and the grid side converter is handled carefully to satisfy the new grid code requirements strictly. Simulation studies are presented and discussed.
Wind Energy
This paper presents a new robust and effective control strategy to mitigate symmetrical voltage dips in a grid-connected doubly-fed induction generator (DFIG) wind energy conversion system without any additional hardware in the system. The aim is to control the power transmitted to the grid so as to keep the electrical and mechanical quantities above their threshold protection values during a voltage dip transient. To achieve this, the references of the powers are readjusted to adapt the wind energy conversion system to the fault conditions. Robust control strategies, combining the merits of sliding mode theory and fuzzy logic are then proposed in this paper. These controllers are derived from the dynamic model of the DFIG considering the variations in the stator flux generated by the voltage drop. This approach is found to yield better performance than other control design methods which assume the flux in the stator to remain constant in amplitude. This control scheme is compliant with the fault-ride-through grid codes which require the wind turbine generator to remain connected during voltage dips. A series of simulations scenarios are carried out on a 3 MW wind turbine system to demonstrate the effectiveness of the proposed control schemes under voltage dips and parameters uncertainties conditions.
Control Theory and Technology, 2019
This paper presents a new control strategy for the rotor side converter of Doubly-Fed Induction Generator based Wind Turbine systems, under severe voltage dips. The main goal is to fulfill the Low Voltage Ride Through performance, required by modern grid codes. In this respect, the key point is to limit oscillations (particularly on rotor currents) triggered by line faults, so that the system keeps operating with graceful behavior. To this aim, a suitable feedforward-feedback control solution is proposed for the DFIG rotor side. The feedforward part exploits oscillation-free reference trajectories, analytically derived for the system internal dynamics. State feedback, designed accounting for control voltage limits, endows the system with robustness and further tame oscillations during faults. Moreover, improved torque and stator reactive power tracking during faults is achieved, proposing an exact mapping between such quantities and rotor-side currents, which are conventionally used as controlled outputs. Numerical simulations are provided to validate the capability of the proposed approach to effectively cope with harsh faults.
E3S Web of Conferences, 2021
For grid-connected DFIG-based wind turbine, Fault Ride Through (FRT) or Low Voltage Ride Through (LVRT) capability is vital problem that need to be improved. This paper proposes an Active Disturbance Rejection Control (ADRC) strategy applied to Doubly Fed Induction Generator (DFIG) based Wind turbine (WT), which integrates a Dynamic Voltage Restorer (DVR). The DVR connect in series the DFIG output terminal and the utility grid. The ADRC scheme of the new topology DFIG-based WT with integrated DVR is designed to compensate grid voltage disturbances, which in turn meet LVRT requirement and increase the level of wind power penetration. The performance of this WT-DFIG-DVR structure is investigated in different operating scenarios in order to show the skills of the designed controllers.
IEEE Transactions on Industry Applications
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 grid during transient conditions. The doubly-fed induction generators (DFIGs) offer several advantages when utilized in wind turbines, but discussions about their LVRT capabilities are limited. This paper presents a comprehensive study of the LVRT of gridconnected DFIG-based wind turbines. It provides a detailed investigation of the transient characteristics and the dynamic behavior of DFIGs during symmetrical and asymmetrical grid voltage sags. A detailed theoretical study supported by computer simulations is provided. This paper also provides a new rotorside control scheme for DFIG-based wind turbines to enhance its LVRT capability during severe grid voltage sags. The proposed control strategy focuses on mitigating the rotor-side voltage and current shock during abnormal grid conditions, without any additional cost or reliability issues. As a result, the DFIG performance is improved and utility company standards are fulfilled. Computer simulations are used to verify the expanded ride-through capability of the novel strategy and its effective performance compared to the conventional control schemes.
Development of LVRT and HVRT control strategy for DFIG based wind turbine system
2010 IEEE International Energy Conference, 2010
With a rapid increase of large wind farms across the globe, a problem associated with the wind turbine is voltage fluctuation of the grid during power generation. Voltage fluctuation could be over voltage or voltage dips and under those conditions the performance of the wind turbines is normally deteriorated. Over voltage withstanding capability of the wind turbine is normally known as High Voltage Ride Through (HVRT) and on the other hand capability of wind turbines during voltage dips is known as Low Voltage Ride Through (LVRT). The problems due to sudden over voltage and voltage dips are normally associated with the power electronic converters fed wind turbines and are being affected by the poor grid conditions. In this paper, an algorithm has been formulated to handle such situations in order to overcome the effects of over voltage and low voltage grid conditions and to save the doubly fed induction generator based wind turbines without affecting the performance. System modeling and simulation results presented in this paper prove the effectiveness of the proposed strategy.