The Unified Power Quality Controller (UPQC) device is an integration of a series active filter and a shunt active filter. The main purpose of a UPQC is to compensate for voltage flicker/, reactive power, and harmonics. It has the capability of improving power quality at the point of installation on power distribution systems or industrial power systems.This paper utilizes the UPQC to enhance the lowvoltage ride-through (LVRT) capability of the doubly fed induction generator (DFIG)-based wind energy conversion system (WECS) according to the grid connection requirement. UPQC is applied to protect the system from ground faults, allows fast restoring of generation system steady state characteristics, improves the system power factor, and prevent the system from rotor over-current and dc-link overvoltage.
This paper investigates two methods for mitigation of voltage dips and voltage swells in a grid to which a wind energy conversion system (WECS) is connected. The two mitigation methods are the dynamic voltage restorer (DVR) and the static synchronous compensator (STATCOM). The wind energy system employs permanent magnet synchronous generator (PMSG). It is well known that the voltage dips affect the PMSG adversely, leading to unlimited increase in its speed. Hence, quick voltage dip mitigation is required. The responses of both DVR and STATCOM to voltage dips as well as voltage swells are investigated and compared. The control algorithms employed with each device are presented. The need for applying additional filters to suppress harmonic contents of each system (the system employing DVR and that employing STATCOM) is studied. Also, the active and reactive power behaviors in each system during and after fault recovery are investigated. The simulation results compared for voltage dips and voltage swells show the less harmonic contents for the system employing the DVR. However, the response of the two systems to faults is comparable.
The artificial neural networks (ANN) direct inverse control and the direct adaptive control are presented in this paper to control the armature voltage and the field voltage of the separatelyexcited dc motor to yield maximum efficiency speed control. The optimal ratio K between thearmaturecurrentand the field current giving minimum losses is ahalytically derived as a function of speed. Two identical ANN'S have been utilized, one for armature control. the other for field control. An online training algorithm is presented for efficient and stable operation rather than fixed weights and biases for the ANN'S. Experimental results are recorded for step change in the load torque and step change in the reference speed. Good agreement was found between the simulation results and the experiinental results. A distinct improvement in the system efficiency is observed especially at light load conditions.
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