scholarly journals Fast Stepwise Inertial Control Scheme of a DFIG for Reducing Second Frequency Drop

2021 ◽  
Vol 11 (17) ◽  
pp. 8259
Author(s):  
Yien Xu ◽  
Dejian Yang ◽  
Jiejie Huang ◽  
Xinsong Zhang ◽  
Liang Hua
Keyword(s):  
Wind Speed ◽  
Rotor Speed ◽  
Induction Generators ◽  
Doubly Fed Induction Generators ◽  
Frequency Drop ◽  
Control Scheme ◽  
Grid Codes ◽  
Inertial Control ◽  
Doubly Fed ◽  
System Frequency

With the fast growth in the penetration of wind power, doubly fed induction generators (DFIGs) are recommended for their ability to enforce grid codes that provide inertial control services by releasing rotational energy. However, after supporting the system frequency, a second frequency drop (SFD) is prone to occurring to regain the rotor speed caused by the sudden reduction in output. In this article, we propose a torque limit-based fast stepwise inertial control scheme of a DFIG using a piecewise reference function for reducing the SFD while preserving the frequency nadir (FN) with less rotor energy released. To achieve the first objective, the power reference increases to the torque limit and then decays with the rotor speed toward the preset operating point. To achieve the second objective, the power reference smoothly lessens over time based on the exponential function. The performance of the proposed stepwise inertial control strategy was studied under various scenarios, including constant wind speed and ramp down wind speed conditions. The test results demonstrated that the frequency stability is preserved during the frequency support phase, while the second frequency drop and mechanical stress on the wind turbine reduce during the rotor speed restoration phase when the DFIG implements the proposed stepwise inertial control scheme.

scholarly journals An Improved Droop Control Scheme of a Doubly-Fed Induction Generator for Various Disturbances

Energies ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7980
Author(s):  
Yien Xu ◽  
Pei Chen ◽  
Xinsong Zhang ◽  
Dejian Yang
Keyword(s):  
Rate Of Change ◽  
Frequency Regulation ◽  
Droop Control ◽  
Doubly Fed Induction Generator ◽  
Control Coefficient ◽  
Induction Generators ◽  
Doubly Fed Induction Generators ◽  
Control Scheme ◽  
Doubly Fed ◽  
System Frequency

Doubly-fed induction generators (DFIGs) participate in the system frequency regulation using a fixed-coefficient droop control scheme. Nevertheless, the frequency-supporting capability of this control scheme with fixed gain is limited for different disturbances. This paper suggests an improved droop control scheme for a DFIG that can both alleviate the frequency nadir and maximum rate of change of frequency (ROCOF) during the frequency regulation. To achieve this, an adaptive droop control coefficient based on the ROCOF is suggested. The proposed droop control coefficient is a linear function of the ROCOF. Therefore, the proposed scheme can adjust the control coefficient according to the varying ROCOF. Simulation results clearly demonstrate that the proposed droop control scheme shows better effectiveness in improving the maximum ROCOF and frequency nadir under various sizes of disturbance, even in a varying wind speed.

scholarly journals Fast Frequency Response of a Doubly-Fed Induction Generator for System Inertia Support

2020 ◽  
Vol 10 (8) ◽  
pp. 2934
Author(s):  
Dejian Yang ◽  
Hong-Chao Gao ◽  
Lei Zhang ◽  
Jingjiao Li ◽  
Xinsong Zhang ◽  
...  
Keyword(s):  
Kinetic Energy ◽  
Recovery Process ◽  
Test Results ◽  
Rotor Speed ◽  
Short Term ◽  
Induction Generators ◽  
Doubly Fed Induction Generators ◽  
Frequency Drop ◽  
Doubly Fed ◽  
System Inertia

Converter-interfaced doubly-fed induction generators (DFIGs) can provide short-term frequency support (STFS) capability by releasing rotating kinetic energy. After arresting the frequency decrease, the rotor speed should return to its initial operating condition. During the rotor speed recovery process, special attention should paid to the performance of the rotor speed restoration duration and size of the second frequency drop (SFD). This paper suggests an enhanced STFS method of DFIGs to preserve better performance of the frequency nadir with less released rotating kinetic energy and accelerate the rotor speed restoration. To this end, a rotor speed-varying incremental power is proposed and is added to the maximum power tracking (MPT) operation reference during STFS, thereby releasing less rotating kinetic energy from DFIGs; afterward, the power reference smoothly decreases to the reference for MPT operation during the preset period. Test results clearly demonstrate that since even less rotating kinetic energy is utilized, the proposed method can preserve better performance of heightening the frequency nadir; furthermore, the proposed method accelerates the rotor speed restoration when the proposed strategy produces the same SFD as the conventional method, thereby improving the power grid resilience.

Modelling Wind Farm with Doubly Fed Induction Generators Based on Characteristic Fusion

2014 ◽  
Vol 494-495 ◽  
pp. 1820-1824
Author(s):  
Dong Ning Wei ◽  
Xue Min Zhang ◽  
Jian Min Ye
Keyword(s):  
Wind Speed ◽  
Wind Farm ◽  
Measurement Data ◽  
Equivalent Model ◽  
Modelling Framework ◽  
Induction Generators ◽  
Doubly Fed Induction Generators ◽  
Wake Model ◽  
Basic Characteristics ◽  
Doubly Fed

In this paper, a novel modelling approach based on characteristic fusion is proposed and used to build a static equivalent model of wind farm. Firstly, the modelling framework based on characteristic fusion is given. Secondly, the basic characteristics of wind farm including characteristic of wind turbine generator (WTG), wind speed spatial distribution and characteristic of wind farm are analyzed according to the framework. Then detailed modelling process is provided utilizing SVR as a fusion tool. This approach combines the advantages of both mechanism and non-mechanism methods with both satisfactory fitting ability and generalization ability. It only requires the maximum and minimum value of wind speed among the wind farm, rather than accurate wake model as mechanism method nor massive measurement data as non-mechanism method. Numerical simulation indicates the effectiveness and robustness of the proposed method. When available data is reduced or includes bad measurement, the proposed method can still keep favorable performance.

Voltage Stability Analysis of a Distributed Network Incorporating Wind Power Resource

2013 ◽  
pp. 1-11
Author(s):  
Denis Juma ◽  
Bessie Monchusi ◽  
Josiah Munda ◽  
Adisa Jimoh
Keyword(s):  
South Africa ◽  
Stability Analysis ◽  
Wind Speed ◽  
Voltage Stability ◽  
Wind Farm ◽  
Load Flow ◽  
Distributed Network ◽  
Induction Generators ◽  
Doubly Fed Induction Generators ◽  
Doubly Fed

This paper investigates the impacts of a wind farm connected at Harterbeespoort substation in South Africa on voltage stability of the power network. The site wind speed was determined and analyzed for viability. A comparison is made between the use of Doubly-Fed Induction Generators and Self-excited Induction Generators driven by the wind turbines. The resulting P-V and Q-V curves from load flow studies are presented and analyzed. The models for this study were implemented in DigSILENT PowerFactory.

scholarly journals Correlation Analysis between Wind Speed/Voltage Clusters and Oscillation Modes of Doubly-Fed Induction Generators

Energies ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 2370 ◽  
Author(s):  
Jierong Miao ◽  
Da Xie ◽  
Chenghong Gu ◽  
Xitian Wang
Keyword(s):  
Wind Speed ◽  
Association Rules ◽  
Influence Factors ◽  
Small Signal ◽  
Grid Voltage ◽  
Generating Sets ◽  
Induction Generators ◽  
Doubly Fed Induction Generators ◽  
Oscillation Modes ◽  
Doubly Fed

Potential machine-grid interactions caused by large-scale wind farms have drawn much attention in recent years. Previous work has been done by analyzing the small–signal modeling of doubly-fed induction generators (DFIGs) to obtain the oscillation modes. This paper, by making use of the metered power data of wind generating sets, studies the correlation between oscillation modes of the DFIG system and influence factors which includes wind speed and grid voltage. After the metered data is segmented, the Prony algorithm is used to analyze the oscillation modes contained in the active power. Then, the relevant oscillation modes are extracted in accordance with the small-signal analysis results. Meanwhile, data segments are clustered according to wind speed and grid voltage. The Apriori algorithm is finally used to discuss the association rules. By training the mass of data of wind generating sets, the inevitable association rules between oscillation modes and influence factors can be mined. Therefore, the prediction of oscillation modes can be achieved based on the rules. The results show that the clustering number quite affects the association rules. When the optimal cluster number is adopted, part of the wind speed/voltage clusters can analyze the certain oscillation modes. The predicted results are quite consistent with the practical data.

scholarly journals Torque Limit-Based Inertial Control of a DFIG for Rapid Frequency Stabilization

2021 ◽  
Vol 9 ◽  
Author(s):  
Yien Xu ◽  
Hongmei Wang
Keyword(s):  
Kinetic Energy ◽  
Power Grid ◽  
Frequency Stabilization ◽  
Rotor Speed ◽  
Point Tracking ◽  
Frequency Drop ◽  
Inertial Control ◽  
Power Point ◽  
Doubly Fed ◽  
High Level

With the increasing penetration of renewable energy generation, the frequency stability of a power grid can be significantly threatened. A doubly-fed induction generator (DFIG) participates in the frequency support of a power grid by releasing kinetic energy (KE) to boost the frequency nadir (FN). However, during rotor speed restoration, it is difficult to counterbalance the size of a second frequency drop (SFD) and the rotor speed recovery duration. This paper proposes an improved torque limit-based inertial control (TLBIC) to raise the FN by releasing less kinetic energy while guaranteeing rapid frequency stabilization with reduced SFD. To this end, when detecting a disturbance, the DFIG enhances the active reference power to the torque limit, and then the active power reduces smoothly based on an exponential function until the maximum power point tracking (MPPT) curve is met, and the rotor speed reverts to the initialization operating condition along the MPPT curve. A simulation system model with various wind power penetrations is established in EMTP-RV. Results show that the proposed scheme boosts the FN at a high level with less KE and guarantees rapid frequency stabilization.

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