scholarly journals A new rotor speed observer for stand-alone brushless doubly-fed induction generators

2017 ◽  
Author(s):  
Yi Liu ◽  
Wei Xu ◽  
Teng Long ◽  
Frede Blaabjerg
Keyword(s):  
Rotor Speed ◽  
Induction Generators ◽  
Doubly Fed Induction Generators ◽  
Doubly Fed

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.

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 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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