MAJOR PROJECT REPORT
ON
POWER QUALITY IMPROVEMENT OF DISTRIBUTED GENERATION SYSTEM WITH UPQC
USING MATLAB/SIMULINK
Submitted to
JAWAHARLAL NEHRU TECHNOLOGY UNIVERSITY
HYDERABAD(T.S)
In partial of the requirements for the award of
BACHELOR OF TECHNOLOGY
in
ELECRICAL AND ELECTRONICS ENGINEERING
Presented by
K. MAHSH BABU 18UC5A0212
Under the Guidance of
Ms.G.Anusha Asst. Prof
TALLA PADMAVATHI COLLEGE OF ENGINEERING
(Approved by AICTE, Affiliated to JNTU, Hyderabad)
Somidi,Tekulagudam,Kazipet,Warangal -506003 (TS)
Introduction
1. In the present world of electrical power system the use of power
electronic devices plays a vital role in the power systems.
2. The main drawback of these power electronic devices is that they
are always connected to nonlinear loads which leads to power
quality problems like voltage sags, swells, interruption and
harmonics.
3. To overcome this difficulty, UPQC with distributed
generation(DG) is combined such that it can compensate voltage and
current quality problems and improves power factor.
Block diagram of UPQC
The system considered is as shown in the fig1. In which a three
phase four wire system is connected to UPQC through linear
transformer which limits the flow of current to series inverter
of UPQC. UPQC is connected before the load to make the load
voltage distortion free. In the UPQC model there are two voltage
source inverters with a common DC link.
Where a series inverter
acts as variable voltage source which is in series to AC line
and shunt inverter acts as variable current source which is
connected in shunt to AC line. A DC link is a capacitor. Voltage
across this provides self supporting DC voltage for proper
operation of both inverters and it also acts as source of active
and reactive power. The load connected is a non linear which
draws discontinuous current and a varying impedance. It is a
combination of diode feeding RL system.
Series Inverter Controller:
A series inverter is responsible for the mitigation of supply
side disturbances such as voltage sag, swell, flickers and
interruptions. It inserts the voltage in such a way that to
maintain load voltages at desired level, balanced and
distortion free.
A unit vector
template is obtained by multiplying input voltage with the
gain. For better synchronization of these signals, unit vector
template is passed through PLL. PLL is used to detect the
fundamental positive sequence component of the voltage at
PCC.
Shunt inverter control :
The voltage from the
series inverter is passed through the DC link which acts as
a source to shunt inverter. This is connected across the
load which is responsible for mitigating current related
problems such as poor power factor, load harmonics and load
unbalance.
The shunt inverter
injects the current to the system such that the load current
becomes balanced. The current compensation is done by the
controller; the controller used here is a P-Q controller.
Distributed generation :
The interest in DG
system has been increased rapidly the world wide concern
about environment pollution and energy shortage has led to
increasing interest in generation of renewable electrical
energy.
DG in simple
terms can be defined as a small scale generation it is
active generating unit that is connected in distribution
level. Different types DG systems are PV system, wind
turbine; fuel cell etc.
wind power has
become fastest growing energy source among various
renewable energy source. Wind turbine has packaged system
that includes rotor generation, turbine blades and
drive.
As the wind blows
through the blades the air exerts a force that causes the
blades to turn the rotor and rotor coverts kinetic energy
into mechanical energy which is fed to generator. It
converts mechanical energy to electrical energy.
Cage induction machines are undoubtedly the workhorse of the industry
and can be still regarded as the main competitor to permanent-magnet
machines. This is because they are self starting, rugged, reliable, and
efficient and offer a long trouble free working life. Of these cage
induction machines, three phase machines are significantly less
expensive, more efficient, and smaller in frame size in comparison with
their single-phase counterpart of similar power ratings. Consequently,
three-phase cage induction motors are economically more appealing and
have thus become the preferred choice for numerous applications, even at
derated power levels as encountered in the Steinmetz configuration.
The novel technique proposed in this paper also uses a three phase
cage induction machine, exploiting its economical advantage, to
generate single-phase electricity at variable rotor speeds without an
intermediate inverter stage. The technique configures the three stator
windings of the three-phase cage induction machine in a novel way to
create separate or rather decoupled excitation and power windings. In
this configuration, any one of the three phase windings is solely used
in isolation for excitation, whereas the remaining two are connected
in series to generate power at a desired frequency while the rotor is
driven at any given speed. Alternatively, the machine can be also
configured in such a way that the two series-connected windings
provide the excitation while the single winding generates. The
proposed TSCAOI winding configuration of a three-phase cage induction
machine. As mathematically shown in the following section, the TSCAOI
winding.
configuration magnetically decouples both excitation and power
windings from each other and thus allows for independent control as in
the case of a single-phase induction motor with an auxiliary winding.
In the proposed technique,
excitation for the generator is provided through the single winding,
which is powered by a battery using either a simple square-wave
inverter or a controlled rectifier. The former is the simplest and can
be operated at the desired generation frequency using a less
sophisticated controller to provide the reactive-power requirement of
the generator. In the latter case, the system is relatively
sophisticated but facilitates bidirectional power flow, allowing for
both energy storage and later retrieval. The level of excitation in
both cases is governed by the voltage generated in the power
winding.
A controller, comprising of a
voltage feedback, can be employed to regulate the excitation. The
controller in the simplest form may provide only the reactive power
requirement of the generator (not the load) and, at a more
sophisticated level, may be used to control both the active- and
reactive-power flows in accordance with the phase angle and the
voltage magnitude between the inverter and the excitation winding.
In the proposed technique,
excitation for the generator is provided through the single winding,
which is powered by a battery using either a simple square-wave
inverter or a controlled rectifier.
The former is the simplest
and can be operated at the desired generation frequency using a less
sophisticated controller to provide the reactive-power requirement of
the generator.The system is relatively sophisticated but facilitates
bidirectional power flow, allowing for both energy storage and later
retrieval. The level of excitation in both cases is governed by the
voltage generated in the power winding. A controller, comprising of a
voltage feedback, can be employed to regulate the excitation.
MATLAB Simulation Circuit
MATLAB Simulation Results
In this paper, three phase four wire 230V (line-neutral) 50Hz
system is considered. There are two operation modes in the proposed
system. One is called the interconnected mode, in which the DG
provides power to the source and the load.
The other is called the
islanding mode, in which the DG provides power to the load only
within its power rating. The operation of proposed system was
verified through MATLAB/SIMULINK software.It shows the waveforms of
source current, shunt inverter current and load current
respectively.
When a non-linear load
injects harmonic current then it can be compensated using shunt
inverter current of UPQC to make source current sinusoidal.It shows
the Fast Fourier Transform (FFT) analysis of load current and source
current. As shown in FFT analysis, the Total Harmonic Distortion
(THD) of supply current is 0.69% and that of load current is
28%.
A . UNBALANCED VOLTAGE SAG
Wind turbine
Fig 1. Shows the unbalanced voltage sag appears in the power system when
there is fault between any
two phases
to ground
Wind Turbine
Fig.2 .shows the compensated voltage at the load side after
unbalanced fault in the source side
B. BALANCED VOLTAGE SAG
Source Voltage
Fig 3.Shows balanced voltage sag appears in the power system when
there is fault between three phases to ground
Load Voltage
Fig.4. shows compensated voltage at the load side after balanced
fault in the source side
C. VOLTAGE INTERRUPTION
Fig .5. Interrupted Source voltage in the power system
D.CURRENT COMPENSATION
Fig.8. Compensated current at the load side
Advantages
1. UPQC can compensate both voltage related problems such
as voltage harmonics, voltage sags/swells, and voltage
flicker.
2. The UPQC maintains load end voltage at the rated value
even in the presence of supply voltage sag.
3. The Synchronous machines made to operate at a leading
power factor and thereby improve the power factor.
Disadvantages
1. It requires dc excitation which must be supplied from
external source.
2. It requires high numbers of switching devices to enhance
the capacity.
1. UPQC is a multifunction power conditioner that can
be used to compensate various voltage disturbances of the
power supply, to correct voltage fluctuation, and to prevent
the harmonic load current from entering the power
system.
2. Distributed Generation plays a vital role in this
project which is used for improving power
factor.
3. It is used in power houses and sub-stations in parallel to
the bus bars to improve power factor. For this purpose it is
run without mechanical load on it and over excited.
4. In factories having large number of induction motors or
transformers operating at lagging power factor, it is used
for improving power factor
In this project, the combined operation of UPQC with DG is
performed.This
project analizes the problems related to voltage and current of
the power system such as
voltage sag, swell, interruption and harmonics which
affects the quality of the power.
The operation of UPQC with DG has been evaluated through
simulation studies using
MATLAB/SIMULINK software.
DOWLOAD PROJECT FILES ON MATLAB/SIMULINK
PDF FILE :
https://drive.google.com/file/d/1rjfBfobUUBVUU9bx1vgepC2EtJAuoEtG/view?usp=sharing
DOC FILE :
https://drive.google.com/file/d/1RpTbEdSliUjHRJw5i_S4Rh2v-jzIbYMX/view?usp=sharing
PPT FILE :
https://drive.google.com/file/d/1r9U-dnDT8V0HA7jKDQG6eyI2dcvLTv4K/view?usp=sharing
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