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

Ahsanullah Memon,Abdul Hafeez,Muhammad Naveed Aman,Tariq Kamal,Mohd Wazir Mustafa,Mukhtar Ullah

doi:10.3390/en14154461

Abstract

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.

Highlights

Renewable energy systems are gaining traction in mainstream power generation as a result of their environmental friendliness and a growing global demand for energy
We focus on the rotor side converter for reactive current control to reduce the voltage drop at the point of common coupling (PCC) and improve the low voltage ride through (LVRT) characteristics of the brushless doubly-fed induction generator
After the fault is cleared, the voltage transients using the proposed technique are significantly reduced. This is due to two reasons, first, the fuzzy logic controller manages to turn off the compensation mode when the voltage starts to improve after fault clearing, and second, the reference value derived from the mathematical model results in better stability

Summary

Introduction

Renewable energy systems are gaining traction in mainstream power generation as a result of their environmental friendliness and a growing global demand for energy. Wind energy generation systems with variable speeds and constant frequencies have grown in popularity over the last decade, owing to their increased aerodynamic range, which results in increased efficiency [1], for example, the Doubly-Fed Induction Generator. Current wind energy generation systems, such as doubly-fed induction generators, employ a brush gear, making deployment and maintenance in remote locations, such as offshore applications, difficult. The brushless doubly-fed induction generator does not contain the brush gear, which results in increased reliability [2]. Brushless doubly-fed induction generators have recently attracted the attention of a large number of researchers and industrial applications

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Conclusion