الفهرس 
مقدمه الدراسهOnly 14 pages are availabe for public view
 |  | from | 162 |  |  |
| | | from | 162 | | |
Abstract
In the last 60 years, the development of the rectifier and semiconductor
technology has led to a variety of applications in all industries. Major applications
include static power converters and drive systems. It has long been known that this
equipment produces harmonics in the AC and DC power systems. The passive
filter was designed to reduce the harmonics and improve the power factor. The
passive filter consists of passive elements such as capacitor, inductor and resistor.
However ,theses elements are limited and their values are determined and tuned or
detuned to eliminate or reduce certain harmonics not all harmonics. Also the
passive filters have not the adaptive ability to suppress any circuit harmonic. With
advent of power electronics, a new device called active power filter is developed.
The active power filter has the adaptation capability to eliminate all harmonics
over wide range of operating conditions. The active power filter have two major
types ,namely shunt and series active power filters. The present thesis investigates
the capability of the Pulse Width modulation PWM converter system with
distributed generators to operate as a shunt active power filter in order to improve
the power quality and eliminate the harmonics due to nonlinear loads or distorted
source or both.
The harmonic equivalent circuit of sample power system is developed. The
above circuit consists of harmonic current source due to nonlinear load, harmonic
voltage source of distorted source, transmission line impedance and capacitor for
power factor correction. The shunt active power filter is simulated in this circuit as
variable admittance element. There are two control parameters of the proposed
shunt active power filter, one of them is conductance while gain factor is second
one. The relationship between the shunt active power filter current and harmonic
source of nonlinear load in terms of shunt active power filter control variables is
obtained. Also the relation between shunt active power filter current and harmonic
voltage source of distorted source voltage in terms of shunt power filter control
parameters is developed. A control strategy is established to estimate the two
control variables of shunt active power filter. Therefore the shunt power filter
currents is regulated to suppress and compensate the load harmonics and voltage
source harmonics. The essential feature of the proposed control strategy is that the
load voltage signal is filtered using passive filter to get the fundamental and
harmonic components. Then these components are manipulated based on the two
control variables of the shunt active power filter. The results are the required filter
currents which are fed to the PWM converter to suppress the harmonics and
regulate the dc voltage of the converter circuit. Therefore the load point voltage (
point of common coupling) and source current are filtered and will become pure
sine wave.
iv
Moreover, the effect of the load connected to the dc side of the converter on
the performance of the shunt active power filter and load voltage and source
current wave forms is studied. It is found that the power quality of the power
system is enhanced.
To validate the effectiveness and the powerful of the proposed control
strategy, the instantaneous power theory (p-q theory) is used to control PWM
converter. Therefore the only harmonic currents of the converter operating as
shunt active filter are injected to the power system to eliminate the load voltage
and source current harmonics. A comparison between the power quality of the
power system using the proposed control strategy and p-q theory is reported.In the last 60 years, the development of the rectifier and semiconductor
technology has led to a variety of applications in all industries. Major applications
include static power converters and drive systems. It has long been known that this
equipment produces harmonics in the AC and DC power systems. The passive
filter was designed to reduce the harmonics and improve the power factor. The
passive filter consists of passive elements such as capacitor, inductor and resistor.
However ,theses elements are limited and their values are determined and tuned or
detuned to eliminate or reduce certain harmonics not all harmonics. Also the
passive filters have not the adaptive ability to suppress any circuit harmonic. With
advent of power electronics, a new device called active power filter is developed.
The active power filter has the adaptation capability to eliminate all harmonics
over wide range of operating conditions. The active power filter have two major
types ,namely shunt and series active power filters. The present thesis investigates
the capability of the Pulse Width modulation PWM converter system with
distributed generators to operate as a shunt active power filter in order to improve
the power quality and eliminate the harmonics due to nonlinear loads or distorted
source or both.The harmonic equivalent circuit of sample power system is developed. The
above circuit consists of harmonic current source due to nonlinear load, harmonic
voltage source of distorted source, transmission line impedance and capacitor for
power factor correction. The shunt active power filter is simulated in this circuit as
variable admittance element. There are two control parameters of the proposed
shunt active power filter, one of them is conductance while gain factor is second
one. The relationship between the shunt active power filter current and harmonic
source of nonlinear load in terms of shunt active power filter control variables is
obtained. Also the relation between shunt active power filter current and harmonic
voltage source of distorted source voltage in terms of shunt power filter control
parameters is developed. A control strategy is established to estimate the two
control variables of shunt active power filter. Therefore the shunt power filter
currents is regulated to suppress and compensate the load harmonics and voltage
source harmonics. The essential feature of the proposed control strategy is that the
load voltage signal is filtered using passive filter to get the fundamental and
harmonic components. Then these components are manipulated based on the two
control variables of the shunt active power filter. The results are the required filter
currents which are fed to the PWM converter to suppress the harmonics and
regulate the dc voltage of the converter circuit. Therefore the load point voltage (
point of common coupling) and source current are filtered and will become pure
sine wave.Moreover, the effect of the load connected to the dc side of the converter on
the performance of the shunt active power filter and load voltage and source
current wave forms is studied. It is found that the power quality of the power
system is enhanced.To validate the effectiveness and the powerful of the proposed control
strategy, the instantaneous power theory (p-q theory) is used to control PWM
converter. Therefore the only harmonic currents of the converter operating as
shunt active filter are injected to the power system to eliminate the load voltage
and source current harmonics. A comparison between the power quality of the
power system using the proposed control strategy and p-q theory is reported.