الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
In the midst of the growing penetration of renewable energy resources and Distributed Generation (DG), power quality is one of the main concerns. Current Source Inverter (CSI) proves to be a natural candidate in Photovoltaic panels and Fuel cells; owing to their voltage boosting capability and smooth DC link current. CSI also has the advantage of inherent protection against short circuit, which is common in distribution level. Chapter I introduces the CSI topology and lists some of its applications like HVDC transmission, medium voltage motor drives, Active power filters, and its use in distributed generation.
Chapter 2 discuss different Pulse Width Modulation techniques like Trapezoidal PWM, Selective Harmonic Elimination, and Space Vector modulation. A comparison between these modulation techniques is carried out and space vector modulation is chosen for this work.
A grid connected CSI requires a CL filter stage. In this work, the isolation transformer leakage inductance constitutes this filter inductance. This CL filter is lightly damped for efficiency constraints. Hence, it is subject to resonance if excited by inverter current harmonics, pre-existing grid voltage harmonics, or due to step changes in power. Chapter 3 discuss numerous passive damping techniques as well as active damping technique from literature that employed a virtual resistance at high frequencies.
However, this method shows limited gain and phase stability margins. In this work an active damping technique employing a virtual negative inductance for the CSI is proposed. The introduction of a virtual negative inductance around the resonance frequency causes active frequency shifting. The advantages of the proposed system are better time response and increased stability margins.
Since CSI is usually operated at lower switching frequency than that of voltage source inverter (VSI), it requires a CL filter tuned at low cut-off frequency. This creates a low impedance path for grid harmonics which could interfere with the inverter current and increases the total harmonic distortion (TIID). This low cut-off frequency puts limitations on control loop bandwidth. For severe voltage distortion,Active damping techniques discussed in chapter 3 to weed out resonance problems, are insufficient to form a clean DG power source.
In Chapter 4, an accurate harmonic extraction method was implemented to decompose positive and negative sequences of low order harmonics and convert all these Harmonic components to their dc values in their perspective synchronous reference frames. This extraction method facilitates the use of regular PI controllers in the harmonics cancellation process and helps to overcome the limited bandwidth and switching frequency in controller design.
An experimental setup has been built to substantiate the validity of the both of the proposed techniques, Active damping employing virtual negative inductance in Chapter 3 and Multi-Synchronous Reference frame MSRF Harmonic Rejection in Chapter 4.