The Transient Characteristics Analysis of Doubly-Fed Induction Generator during the Asymmetric Voltage Sag

2014 ◽  
Vol 644-650 ◽  
pp. 3509-3514
Author(s):  
Jian Hua Zhang ◽  
Hao Ran Shen ◽  
Lei Ding ◽  
Chun Lei Dai
Keyword(s):  
Control Strategy ◽  
Reactive Power ◽  
Low Voltage ◽  
Voltage Drop ◽  
Voltage Sag ◽  
Grid Voltage ◽  
Low Voltage Ride Through ◽  
Double Frequency ◽  
Characteristics Analysis ◽  
Doubly Fed

In order to analyze the control strategy of the low voltage ride through (LVRT) of DFIG during the asymmetric voltage sag, it is necessary to analyze the transient performance of a DFIG during the asymmetric voltage sag. In this paper, analyzed the influence of the asymmetric grid voltage to DFIG and the analysis method of the asymmetric voltage sag, and on the basis of positive and negative sequence mathematical model, analyzed the composition of stator output active and reactive power under the condition of asymmetric grid voltage. And built a DFIG asymmetric voltage drop simulation model of 1.5MW in MATLAB/Simulink, the simulation results shows that the stator voltage, current, active power and reactive power all present a double frequency ripple during the asymmetric voltage sag, consistent with theoretical analysis. It can provide theoretical basis for double-fed motor control strategy of asymmetric LVRT.

scholarly journals Control Strategy of Three-Phase Photovoltaic Inverter under Low-Voltage Ride-Through Condition

2015 ◽  
Vol 2015 ◽  
pp. 1-23 ◽  
Author(s):  
Xianbo Wang ◽  
Zhixin Yang ◽  
Bo Fan ◽  
Wei Xu
Keyword(s):  
Control Strategy ◽  
Reactive Power ◽  
Low Voltage ◽  
Voltage Drop ◽  
Stable Operation ◽  
Power Fluctuation ◽  
Negative Sequence ◽  
Grid Voltage ◽  
Low Voltage Ride Through ◽  
Grid Side

The new energy promoting community has recently witnessed a surge of developments in photovoltaic power generation technologies. To fulfill the grid code requirement of photovoltaic inverter under low-voltage ride-through (LVRT) condition, by utilizing the asymmetry feature of grid voltage, this paper aims to control both restraining negative sequence current and reactive power fluctuation on grid side to maintain balanced output of inverter. Two mathematical inverter models of grid-connected inverter containing LCL grid-side filter under both symmetrical and asymmetric grid are proposed. PR controller method is put forward based on inverter model under asymmetric grid. To ensure the stable operation of the inverter, grid voltage feedforward method is introduced to restrain current shock at the moment of voltage drop. Stable grid-connected operation and LVRT ability at grid drop have been achieved via a combination of rapid positive and negative sequence component extraction of accurate grid voltage synchronizing signals. Simulation and experimental results have verified the superior effectiveness of our proposed control strategy.

Study on Transient Characteristic of the DFIG LVRT

2013 ◽  
Vol 791-793 ◽  
pp. 1832-1836
Author(s):  
Jian Hua Zhang ◽  
Rong Luan ◽  
Hao Ran Shen
Keyword(s):  
Control Strategy ◽  
Reactive Power ◽  
Low Voltage ◽  
Voltage Sag ◽  
Voltage Sags ◽  
Doubly Fed Induction Generator ◽  
Low Voltage Ride Through ◽  
Harmonic Currents ◽  
Doubly Fed ◽  
Operation Characteristics

In order to analyze the operational capability of the low voltage ride through ( LVRT) of a gird-connected wind turbine with doubly fed induction generator (DFIG) effectively, it is necessary to evaluate operation characteristics of DFIG under a grid fault.By using the transient principle of the flux of stator and rotor, the expressions of transient currents of stator and rotor of DFIG are derived under the grid voltage sag. The transient process is analyzed by using the Matlab to derive the correctness of the expression. A control strategy is presented to eliminate harmonic currents by proposing the essential factors of over-current of stator and rotor. The output active power and reactive power are calculated by using the derived expression with different voltage sags. Based on the theoretical analysis, a DFIG is established to analysis the model of LVRT. Simulation results show that the control strategy is able to eliminate the harmonic currents and achieve the requirements of LVRT.

scholarly journals An Enhanced Low Voltage Ride-Through Control Scheme of a DIFG based WTG Using Crowbar and Braking Chopper

2021 ◽  
Vol 16 (1) ◽  
pp. 61-67
Author(s):  
Kishan Jayasawal ◽  
Khagendra Thapa
Keyword(s):  
Reactive Power ◽  
Low Voltage ◽  
Turbine Generator ◽  
Grid Voltage ◽  
Low Voltage Ride Through ◽  
Control Scheme ◽  
Safe Limit ◽  
Grid Codes ◽  
Doubly Fed ◽  
Rotor Side Converter

The grid codes define low voltage ride-through (LVRT) as capability of wind turbine generator (WTG) to support the grid voltage by injecting reactive power and suppress the rise of DC-link voltage and inrush rotor current in the rotor side converter (RSC) of the doubly fed induction generator (DFIG) during a fault. Moreover, the rotor current increases significantly during severe disturbances if any protection schemes are not employed. Therefore, the protection schemes must be used to avoid the damage to the converter during a fault. This paper proposes an enhanced LVRT control scheme of a DFIG employing a crowbar in the RSC side and braking chopper across the DC-link capacitor. The DFIG is highly delicate to grid voltage fluctuation during a fault because the DFIG is directly linked to the grid via stator. During severe fault the crowbar regulates the rotor current within an acceptable range and the braking chopper discharges the DC-link capacitor via resistor within a safe limit. The proposed LVRT control scheme is performed for a 2.4-MW DFIG using a MATLAB/SIMULINK simulator. The results delineate that the proposed control scheme is able to rapidly decrease the rotor current and repress the escalation in DC-link voltage during a grid fault.

scholarly journals Design of Capacitive Bridge Fault Current Limiter for Low-Voltage Ride-Through Capacity Enrichment of Doubly Fed Induction Generator-Based Wind Farm

2021 ◽  
Vol 13 (12) ◽  
pp. 6656
Author(s):  
A. Padmaja ◽  
Allusivala Shanmukh ◽  
Siva Subrahmanyam Mendu ◽  
Ramesh Devarapalli ◽  
Javier Serrano González ◽  
...  
Keyword(s):  
Wind Farm ◽  
Reactive Power ◽  
Low Voltage ◽  
Voltage Drop ◽  
Short Circuit ◽  
Fault Current ◽  
Fault Current Limiter ◽  
Low Voltage Ride Through ◽  
Current Limiter ◽  
Doubly Fed

The increase in penetration of wind farms operating with doubly fed induction generators (DFIG) results in stability issues such as voltage dips and high short circuit currents in the case of faults. To overcome these issues, and to achieve reliable and sustainable power from an uncertain wind source, fault current limiters (FCL) are incorporated. This work focuses on limiting the short circuit current level and fulfilling the reactive power compensation of a DFIG wind farm using a capacitive bridge fault current limiter (CBFCL). To deliver sustainable wind power to the grid, a fuzzy-based CBFCL is designed for generating optimal reactive power to suppress the instantaneous voltage drop during the fault and in the recovery state. The performance of the proposed fuzzy-based CBFCL is presented under a fault condition to account for real-time conditions. The results show that the proposed fuzzy-based CBFCL offers a more effective solution for overcoming the low voltage ride through (LVRT) problem than a traditional controller.

The Research for Control Strategy of Low Voltage Ride-through Based on DFIG

2013 ◽  
Vol 373-375 ◽  
pp. 1299-1303
Author(s):  
Si Qing Sheng ◽  
Huan Li ◽  
Lin Tao Fan
Keyword(s):  
Control Strategy ◽  
Reactive Power ◽  
Low Voltage ◽  
Fault System ◽  
Low Voltage Ride Through ◽  
Power Load ◽  
Point Of Common Coupling ◽  
Compensation Device ◽  
Doubly Fed ◽  
Doubly Fed Generator

The doubly-fed wind power generation system containing crowbar protection circuit will change from reactive power source to reactive power load during the low voltage ride-through, which is likely to aggravate burdens to the fault system. Aiming at solving this problem, the paper will introduce the STATCOM compensation device, and put forward a comprehensive control strategy. Under the coordinated control strategy, the STATCOM will cooperate with the compensation capacity of the doubly-fed generator to support the reactive power. The voltage at point of common coupling will be raised and the ability of low voltage ride-through of the wind turbines will be improved. A simulative model of doubly-fed induction generator is established in MATLAB and the strategys rationality and effectiveness will be verified by the simulative results.

Voltage Sag Detection in Grid-Connected Photovoltaic Power Plant for Low Voltage Ride-Through Control

2019 ◽  
Vol 12 (4) ◽  
pp. 384-392 ◽  
Author(s):  
Ali Qasem Al-Shetwi ◽  
Muhamad Zahim Sujod
Keyword(s):  
Reactive Power ◽  
Low Voltage ◽  
Detection Methods ◽  
Normal Operation ◽  
Positive Sequence ◽  
Voltage Sag ◽  
Good Precision ◽  
Grid Voltage ◽  
Low Voltage Ride Through ◽  
Photovoltaic Power

Background: Due to the high level of photovoltaic power plants (PVPPs) penetration into power grids, disconnections of these plants during faults are no longer possible as it may cause problems concerning stability, quality, and operation of the power system. Therefore, new grid codes have been established with low voltage ride-through (LVRT) capability standard requirements for grid-connected PVPPs that should be met. Therefore, for an efficient LVRT control, the fast and precise sag detection strategy is essential for the system to switch from normal operation to LVRT mode of operation. Methods: For this purpose, this paper presents a two automatic fault detection methods which are RMS-based (d-q) components of grid voltage and positive sequence voltage. These methods were utilized to determine the beginning and end of a voltage sag and to determine the sag depth to regulate the required reactive current that should be injected according to the LVRT standard requirements. The operating method depends on calculating present grid voltage under faults to the nominal voltage that identifies the sags’ depth and therefore inject the required amount of reactive power accordingly. Also, a comparison between the two proposed methods regarding response speed and accuracy was made. The effectiveness of these detection strategies is that it can be integrated into the voltage source inverter (VSI) without utilizing additional external hardware or software programming. Results: The simulation results demonstrated a good precision and how straightforward the proposed methods’ usage is, proving that the RMS method is faster and more accurate than positive sequence method. Conclusion: In conclusion, it was found that RMS detection algorithm is preferred for a more accurate and efficient LVRT control.

Low Voltage Ride through of Wind Turbine Based on New SGSC Converter Structure

2013 ◽  
Vol 448-453 ◽  
pp. 2185-2190 ◽  
Author(s):  
He Nan Dong ◽  
Yun Dong Song ◽  
Gang Wang ◽  
Zuo Xia Xing
Keyword(s):  
Power Systems ◽  
Wind Turbine ◽  
Control Strategy ◽  
Large Scale ◽  
Reactive Power ◽  
Low Voltage ◽  
Short Circuit ◽  
Simulation Software ◽  
Low Voltage Ride Through ◽  
Doubly Fed

The proportion of wind power in power systems is increasing year by year. Large-scale wind turbine off the grid when grid system failures. So the wind turbine needs to low voltage ride through (LVRT) function of wind turbine. Aiming at this problem, which in this article by DIgSILENT simulation software build 1.5MW doubly-fed wind turbine(DFIG) model, using active Crowbar and series grid side converter (SGSC) control strategy to realize the simulation of low voltage ride through of wind turbine. The control strategy of active Crowbar is mainly through the short circuit of rotor side converter to realize LVRT, and needs to be matched with the active and reactive power control strategy. SGSC is a novel converter structure, which mainly through compensating stator flux drop to realize LVRT. Finally this two kinds of control strategies were compared, demonstrated SGSC control strategy can achieve the low voltage ride through capabilities of the doubly-fed wind turbine.

Research on the Control Strategy of DFIG Grid Side Converter under Unbalanced Grid Voltage Conditions

2012 ◽  
Vol 260-261 ◽  
pp. 454-459
Author(s):  
Fei Song ◽  
Dan Zhu ◽  
Kan Tang ◽  
Xue Jing Liu
Keyword(s):  
Control Strategy ◽  
Reactive Power ◽  
Voltage Drop ◽  
Current Control ◽  
Transient Model ◽  
Grid Voltage ◽  
Doubly Fed ◽  
Grid Side ◽  
Grid Side Converter ◽  
The Impact

This paper studies on the electromagnetic transient model of doubly-fed wind turbine grid-side converter under the imbalanced grid condition. And on this basis, the paper analysis the impact of doubly-fed converter when grid voltage asymmetric drop. It puts forward a dual PLL and dual current control combination of doubly-fed converter grid side control strategy. This strategy achieves grid voltage positive and negative sequence fast separation when asymmetric grid voltage drop occur, achieves the active output power secondary fluctuate suppression under the imbalanced grid voltage condition, avoids DC voltage rise at the fault moment and also achieves converter reactive power support under the imbalanced grid fault. The simulation and experimental results show that the proposed control strategy is correct and with the application value of engineering

scholarly journals Dynamic Low Voltage Ride through Detection and Mitigation in Brushless Doubly Fed Induction Generators

Energies ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4461
Author(s):  
Ahsanullah Memon ◽  
Mohd Wazir Mustafa ◽  
Muhammad Naveed Aman ◽  
Mukhtar Ullah ◽  
Tariq Kamal ◽  
...  
Keyword(s):  
Fuzzy Logic ◽  
Fuzzy Logic Controller ◽  
Low Voltage ◽  
Voltage Drop ◽  
Low Voltage Ride Through ◽  
Induction Generators ◽  
Doubly Fed Induction Generators ◽  
Reactive Current ◽  
Doubly Fed ◽  
Rotor Side Converter

Brushless doubly-fed induction generators have higher reliability, making them an attractive choice for not only offshore applications but also for remote locations. These machines are composed of two back-to-back voltage source converters: the grid side converter and the rotor side converter. The rotor side converter is typically used for reactive current control of the power winding using the control winding current. A low voltage ride through (LVRT) fault is detected using a hysterisis comparison of the power winding voltage. This approach leads to two problems, firstly, the use of only voltage to detect faults results in erroneous or slow response, and secondly, sub-optimal control of voltage drop because of static reference values for reactive current compensation. This paper solves these problems by using an analytical model of the voltage drop caused by a short circuit. Moreover, using a fuzzy logic controller, the proposed technique employs the voltage frequency in addition to the power winding voltage magnitude to detect LVRT conditions. The analytical model helps in reducing the power winding voltage drop while the fuzzy logic controller leads to better and faster detection of faults, leading to an overall faster response of the system. Simulations in Matlab/Simulink show that the proposed technique can reduce the voltage drop by up to 0.12 p.u. and result in significantly lower transients in the power winding voltage as compared to existing techniques.

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