Academic literature on the topic 'Crowbar Operation'

So far, active crowbars are a preferred technique for doubly fed induction generator (DFIG) wind turbines, which is used to protect the power converter against over-current and undesirably high dc link voltage during voltage dip. However, its main drawbacks are that (1) the DFIG absorbs reactive power from the grid during grid voltage dips, (2) the crowbar activation increases the acceleration of the rotor and so, deteriorates the dynamic stability of DFIG, and (3) the control is not flexible for long-time voltage sags. In the paper, three different initiating logic control methods of crowbar protection are compared, and how low-voltage ride-through (LVRT) characteristics of DFIG wind turbines with active crowbar are affected by different switching logic control modes of the crowbar are investigated. According to the comparison results, an improved crowbar switching control strategy is proposed to reduce its operation time and improve the LVRT capability of DFIG wind turbines. In addition, an emergency pitch blade angle control scheme to reduce the acceleration of the rotor and prevent the over-speeding of rotor is presented in detail, and as a result, the LVRT capability of DFIG wind turbines is enhanced even during long-time voltage sags. Finally, the presented control strategies are validated in simulation tool Matalab/Simulink for a 1.5MW generator.

Brushless doubly fed reluctance generators (BDFRGs) are hopeful generators for using inside variable speed wind turbines (VSWTs), as these generators introduce a promising economical value because of their lower manufacturing and maintenance costs besides their higher reliability. For integrating WT generators, global networks codes require enabling these generators to stay connected under grid disturbances. The behavior of the BDFRG is strongly affected by grid disturbances, due to the small rating of the used partial power converters, as these converters cannot withstand high faults currents which leads to quick tripping of BDFRG. VSWTs can be safeguarded against faults using the crowbar. Usually, the conventual crowbar is shunt connected across the converter to protect it, but this configuration leads to absorbing reactive power with huge amounts from the grid, leading for more voltage decaying and more power system stability deterioration. This study proposes a simpler self-controllable crowbar to enhance the ability of the BDFRG to remain in service under faults. The operation technique of the proposed crowbar is compared to other crowbar operation techniques, the effectiveness of the proposed system would be analyzed. Through the simulation results and behavior analysis, the proposed crowbar technique demonstrates a decent improvement in the conduct of the studied system under faults.