الفهرس 
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Abstract
Power quality problems are increasing rapidly, especially current
harmonics, reactive power, and neutral current. Current harmonics lead
to various issues in distribution systems and consumer products such as
overheating machines, unsafe operation of safety equipment,
overheating transformers, etc. Further neutral current leads to
overheating and also to neutral line damage. High reactive
current/power also increases network losses and reduces their
reliability. The unbalance reasons essentially come from three sources;
asymmetric supply, asymmetric network, and finally from the scattered
distributed loads. In order to protect equipment from power
interruption, various forms of power improvement devices have
progressed over the years. This thesis decreases the problems of
unbalance by compensating the source current harmonics and the
reactive power utilizing a shunt active power filter (SAPF).
In literature, many topologies are proposed to solve power
quality problems. The concept for solving the problem is based on
controlling each phase independently. Therefore, creating a neutral
point connection is a key to construct the four-wire such as Mid
Capacitor Point, Four-Leg Inverter, and three single-phase of H-bridge.
In this thesis, the Four-Leg Inverter (4LI) is selected as a compensator.
The performance of SAPF depends on inverter parameters, control
schemes, and reference current detection control techniques. Increasing
nonlinear load leads to growing the SAPF rating also increases the
accumulating system capacity and cost. This thesis tries to enhance the
SAPF performance by using a suitable control scheme. The control
system of SAPF consists of three parts: harmonic extraction (including
reference current generation), DC-link voltage control, and current
control.
This dissertation presents an investigation and evaluation of the
performance of the SAPF based on 4LI utilizing different DC-voltage
and current controllers: the HCC, conventional PI, FLCT-1, and FLCT2
controllers. These controllers are compared with the proposed
controller which is the simplified universal intelligent (SUI-PI)
i
controller. In addition, this thesis presents the three-dimensional space
vector modulation (3DSVM) which is considered an effective
switching technique for the 4LI. The proposed system is simulated on
the Matlab /Simulink software to study the dynamic performance under
three different unbalanced and/or nonlinear loads. The THD values are
compared before and after the compensation process for the each of the
proposed controllers under different study cases.
A laboratory setup of the proposed system is implemented to
verify the performance of the proposed five types of controllers,
mentioned above. The different controllers are realized on DS 1202
Micro-Lab box and the other components are implemented on
Hardware in the Loop (HIL-402) real-time platform. The results
indicate that the different functionalities of the 4LI based SAPF are
achieved using the proposed five controllers. In addition, performance
comparison is presented under unbalanced and nonlinear loads. The
results show that the proposed SUI-PI controller offers the best
performance among other controllers.