Trends in Electrical Engineering Volume 1, Issue 1, May, 2011, Pages 12-21. ____________________________________________________________________________________________ © STM Journals 2011. All Rights Reserved. 12 Investigation of DC link Capacitor Failures in DFIG based Wind Energy Conversion System Ali M. Eltamaly* & Ammar Anwar Khan King Saud University, Riyadh, Saudi Arabia Author for Correspondence *Author for Correspondence E-mail: eltamaly@ksu.edu.sa Mob: +966553334130 I. INTRODUCTION DFIG proves itself as one of the successful generator topologies for wind energy conversion systems due to its variable speed operation and low power rating three phase AC/DC/AC converter. AC/DC/AC PWM converters are widely used in motor drives, wind power generation [1], unified power quality conditioners [2] etc. These converters usually consist of DC link of array of electrolytic capacitors as energy buffer. Electrolytic capacitors are preferred due to their large capacitance per volume and low cost per capacitance. However they are sensitive to temperature, frequency and have low reliability [3-4]. The lifetime of electrolytic capacitor is usually shorter than the other components of the converter. Reference [1] reported that 72% of the power supplies failures were due to electrolytic capacitor failures. The capacitors are considered to be over when, with the passage of time, their capacitance is decreased by more than 25% [5]. It has been reported in many researches that electrolytic capacitors are the weakest link in power electronic converters [7-12]. The failure of DC link electrolytic capacitor can lead to either short circuit or open circuit of DC link while remaining the converters intact. The capacitor degradation is due to the effects of thermal, electrical, mechanical and environmental stresses and there can be any reason of its failure. The primary failure mechanism is the evaporation of electrolytic solution and its loss through end seal. Temperature rise accelerates the evaporation rate. This evaporation leads to the decrease in capacitance and increase in ESR (equivalent series resistance) which increases the losses. Thus the degradation process continues till the capacitor fails. Other modes of failures are mentioned as [7]: Abstract This paper presents the effects of DC link electrolytic capacitor failure of DFIG based wind energy conversion system (WECS). The degradation of electrolytic capacitor can lead to the failure of DC link. As DFIG based WECS utilize low power converter, so there is a need to explore the effects of capacitor failure. This failure (short circuit of capacitor or open circuit) leads to the power outages, high machine currents, high transient currents in rotor circuit, low terminal voltage of the generator and increase in generator speed. For this purpose aggregated model of DFIG is implemented in the MATLAB/ Simulink to study the effects of DC link capacitor short/open circuit on different parameters of system. Keywords: DFIG, DC link failure, capacitor short circuit, stator flux orientation, capacitor open circuit.