Effects of Voltage Sags on the Doubly Fed induction Generator using PI Controllers

Abstract

The paper presents dynamic and transient behaviour of the Doubly Fed Induction Generator (DFIG) in the wind farms. When Voltage sag or any faults occurs in the network, the variables in the doubly Fed Induction Generators are varying severely. If the voltage sag occurs, Active and Reactive power that generated by the DFIG will decrease and will increase respectively, The DC voltage link will be bigger, and the rotor current will increase. The DFIG in the wind farms uses Proportional Integral controller for controlling of electronic devices (Rotor Side Converter and Grid Side Converter). Even though the model of Doubly Fed Induction Generators and electronic device in the paper are linear, The Proportional Integral controllers cannot protect and control the variables. So, the power electronic converters and the DC-link can damage due to over voltages and over currents. Doubly Fed Induction Generator in the wind farm is simulated in MATLAB software. The results of the simulation present over voltage and over current in the DC-link and in the rotor of the Doubly Fed Induction Generator. In addition, it will explore the effect of Proportional Integral controller in Doubly Fed Induction Generator when three-phase short circuit fault occurs.

Nanocomposites of a Cashew Nut Shell Derived Epoxy Resin and Graphene Platelets: From Flexible to Tough

“…Consequently, the decline in toughness from 0.5 to 0.8 wt % GPL loading is due to the large shift in the peak of the loss modulus from 35 to 50 °C. Furthermore, the above suggestion from related literature 29 that GPL aggregation caused a reduction in ductility of the nanocomposite with an increase in GPL content from 0.5 to 0.8 wt % is clearly incorrect. Instead, the decrease in ductility is due to the remarkable increase in T g .…”

“…In comparison, utilization of graphene in DGEBA matrices by the same dispersion method demonstrates GPL percolation at 0.1 wt %. 29 The difference in percolation thresholds based on optimization of physical properties is attributed to the difference in aromatic content of the Cardolite NC-514 and DGEBA. Specifically, DEGBA is more aromatic than Cardolite NC-514.…”

“…Interpretations from published literature on related systems suggests that this reduction in nanocomposite ductility is due to an increase in GPL aggregation. 29 Further studies by DMA and SEM are discussed below that provide further information on whether or not GPL aggregation is responsible for this change in mechanical properties.…”

“…GPL was produced by thermal reduction and exfoliation of graphite oxide. 26−28 Briefly, graphite oxide was prepared by oxidizing graphite flakes (average diameter 48 μm) in a solution of concentrated sulfuric acid (95−98%), concentrated nitric acid (68%), hydrochloric acid (36−38%), and potassium chlorate (99.5%) for 96 h. One-step reduction and exfoliation of graphite oxide into GPL's was achieved by exposing the graphite oxide powder to a thermal shock (heating rate of 2000 °C/min) as described and characterized by Rafiee et al 25,26,29,30 Composite Fabrication. GPL for each weight loading was dispersed in 100 mL of acetone (0.045 g GPL for 0.1 wt %, 0.09 g GPL for 0.2 wt %, 0.225 g GPL for 0.5 wt %, and 0.36 g for 0.8 wt %) using an ultrasonic probe sonicator (Sonics Vibracell VC 750, Sonics and Materials Inc.,USA) at high amplitude for 1.5 h in an ice bath.…”