scholarly journals Improved Short-Circuit Current Calculation of Doubly Fed Wind Turbines With Uninterrupted Excitation

2021 ◽  
Vol 9 ◽  
Author(s):  
Jun Yin
Keyword(s):  
Short Circuit ◽  
Relay Protection ◽  
Control Unit ◽  
Short Circuit Current ◽  
Doubly Fed Induction Generator ◽  
Transient Model ◽  
Real Time Digital Simulator ◽  
Doubly Fed ◽  
Current Calculation ◽  
Actual Control

With the enlarging scale of a doubly fed induction generator (DFIG) connected to a power system, the influence of short-circuit current on the system relay protection could not be ignored. Setting and configuring relay protection would be affected by an imprecise short-circuit current calculation. However, some existing studies only consider the condition that the input is the Crowbar and the rotor excitation is blocked. China's new network standard requires the output reactive support current of a DFIG and will change the characteristics of short-circuit current. To solve this problem, on the basis of analyzing the characters of the transient equivalent potential of a DFIG, the transient model of a DFIG with uninterrupted excitation is provided. Based on the characteristics of a non-abrupt change of flux linkage and the requirement of a new grid standard reactive support current, the short-circuit current calculation method of a DFIG with uninterrupted excitation is put forward. Based on the real-time digital simulator (RTDS), a digital-analog experimental platform containing the actual control unit of the DFIG converter is founded, the proposed short-circuit current root mean square (RMS) value calculating method is validated.

scholarly journals Short-Circuit Current Calculation and Harmonic Characteristic Analysis for a Doubly-Fed Induction Generator Wind Turbine under Converter Control

Energies ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 2471 ◽  
Author(s):  
Jing Li ◽  
Tao Zheng ◽  
Zengping Wang
Keyword(s):  
Wind Turbine ◽  
Analytical Model ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Induction Generator ◽  
Doubly Fed Induction Generator ◽  
Stator Current ◽  
Dc Bus ◽  
Bus Voltage ◽  
Doubly Fed

An accurate calculation of short-circuit current (SCC) is very important for relay protection setting and optimization design of electrical equipment. The short-circuit current for a doubly-fed induction generator wind turbine (DFIG-WT) under excitation regulation of a converter contains the stator current and grid-side converter (GSC) current. The transient characteristics of GSC current are controlled by double closed-loops of the converter and influenced by fluctuations of direct current (DC) bus voltage, which is characterized as high order, multiple variables, and strong coupling, resulting in great difficulty with analysis. Existing studies are mainly focused on the stator current, neglecting or only considering the steady-state short-circuit current of GSC, resulting in errors in the short-circuit calculation of DFIG-WT. This paper constructs a DFIG-WT total current analytical model involving GSC current. Based on Fourier decomposition of switch functions and the frequency domain analytical method, the fluctuation of DC bus voltage is considered and described in detail. With the proposed DFIG-WT short-circuit current analytical model, the generation mechanism and evolution law of harmonic components are revealed quantitatively, especially the second harmonic component, which has a great influence on transformer protection. The accuracies of the theoretical analysis and mathematical model are verified by comparing calculation results with simulation results and low-voltage ride-through (LVRT) field test data of a real DFIG.

Symmetrical Short Circuit Current Characteristics of Doubly Fed Induction Generator Wind Turbine with Crowbar Protection

2012 ◽  
Vol 512-515 ◽  
pp. 782-787
Author(s):  
Jia Jun Zhai ◽  
Bu Han Zhang ◽  
Kui Wang ◽  
Wen Shao ◽  
Cheng Xiong Mao
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Induction Generator ◽  
Doubly Fed Induction Generator ◽  
Operating Characteristics ◽  
Doubly Fed ◽  
Crowbar Protection ◽  
Short Circuit Fault

Doubly fed induction generator (DFIG) is now becoming one of most widely used wind turbines in global market for wind power generation, due to its outstanding advantages. However, the DFIG is sensitive to grid faults. The DFIG will have to be removed from the grid if there’s no protection appliance in it. Therefore, the crowbar protection is widely used in the world for improving the low voltage ride-through ability of wind turbines. This paper analysed the operating characteristics and short-circuit current of DFIG under symmetrical short-circuit fault with respect to different sags to grid voltage, which on the basis of DFIG wind turbine with crowbar protection. And the expressions of short-circuit current under symmetrical short-circuit fault for DFIG were derived. The effectiveness of the expression was simulated in PSCAD/EMTDC.

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