Enhancement Of Power Quality For Transmission System By UPQC
Ass. Prof-Jaya Gopinath Wagh. M.E Electrical power system
Arts, Science and Commerce College CIDCO
Uttamnagar, CIDCO, Nashik-422008 Maharashtra
E-mail: [email protected]
ABSTRACT
In the an improved Unified Power Quality Conditioner (iUPQC),
for power factor compensation, voltage and current harmonics
compensation, voltage sag and swell compensation, grid side bus
voltage regulation and load bus voltage regulation for the
combinations of linear and non-linear loads. The iUPQC will work as
both STATCOM and conventional UPQC compensation, at the grid side
and at the load side respectively. The iUPQC controller composes of
PLL and PWM controller which is used for generating reference
signal for shunt converter and also the Proportional Integral
Derivative controller (PID) which is used for generating reference
signal for series converter.
Now a day’s power physics devices square measure used
attributable to technological improvement. The increasing variety
of power physics hundreds typically utilized in trade attributable
to this load power quality downside arises. in line with this
thought of power electronic load need ideal curved offer voltage
for correct system operation. they're to blame for condition in
distribution system. in line with this state of affairs completely
different mitigating technique square measure enforced over the
years. a number of resolution involves versatile compensator called
improved unified power quality controller .by victimization this
controller we will compensate voltage sag/swell. conjointly offer
reactive power .This paper presents new management technique for
iupqc. in this pulse breadth modulation management is employed in
it .it is achieved by victimization voltage and current curved
references.
The experimental results verified by victimization improved
unified power quality controller. The grid-
voltage regulation was achieved by taking completely different
load conditions. These results have incontestable an appropriate
performance of voltage regulation at either side of the iUPQC, even
whereas compensating harmonic current and voltage imbalances.
Keywords: power quality voltage sag, voltage swell. iUPQC;
Micro-grids; Power quality; STATCOM; Unified Power Quality
Conditioner
INTRODUCTION
The employment of equipment, like data technology
instrumentality, power physics like variable speed drives,
programmable logic controllers, and energy economical lighting
semiconductor diode, static rectifier, converters to a whole
modification of electrical hundreds nature .according to this
thought , poor power quality might arises that result into
exaggerated power losses, abnormal and undesirable performance of
equipment’s. In power grid numbers of power quality issues square
measure occurred like voltage disturbance, current disturbance,
voltage sag, voltage swell, harmonics and reactive power
disturbance. thus consumer’s premises it's necessary to attenuate
these issues. . improve the voltage profile, stability of system,
sweetening of power quality and dependableness of power etc. the
assorted versatile AC gear square measure are available electrical
network. The FACTS based mostly application of power electronic
devices effective for the ability distribution systems to reinforce
the standard and also the dependableness of power fed to the
shoppers. The FACTS technology consists of high power physics
devices. By victimization this Facts device we will implement
system stability. thus iupqc is one in every of the most effective
solutions of degrading higher than downside.
The circuit of a iupqc consists of a mixture of a shunt active
filter and a series active filter connected in a very succeeding
configuration. this mixture permits the compensation of the load
current and also the offer voltage. Here we have a tendency to
contemplate electrical system with 2 buses i.e., bus A and bus B.
Bus A could be a bus of the ability system .Bus B could be a bus of
the small grid, wherever nonlinear hundreds square measure
connected, which needs premium-quality power offer. Our aim is to
urge the voltages at buses A and B should be regulated so as to
properly offer the sensitive hundreds and also the nonlinear
hundreds.This paper presents a new connection for a UPQC called
interline UPQC (IUPQC). The single-line diagram of an IUPQC
connected distribution system is shown in Fig. 1.
Fig.1: Single-line diagram of an IUPQC-connected distribution
system.
Two feeders, Feeder-1 and Feeder-2, which are connected to two
different substations, supply the system loads L-1 and L-2. The
supply voltages are denoted byVs1 and Vs2 It is assumed that the
IUPQC is connected to two buses B-1 and B-2, the voltages of which
are denoted by Vt1 and Vt2 respectively. Further two feeder
currents are denoted by is1 and is2 while the load currents are
denoted by il1 and il2. The load L-2 voltage is denoted by vt2. The
purpose of the IUPQC is to hold the voltages Vt1 and Vt2 constant
against voltage sag/swell, temporary interruption in either ofthe
two feeders. It has been demonstrated that the IUPQC can absorb
power from one feeder(Feeder-1)
System quantities
Values
System fundamental
50Hz
frequency (f)
Voltage source Vs1
11kV (L-L, rms), phase angle 0⁰
Voltage source Vs2
11kV (L-L, rms), phase angle 0⁰
Feeder-1 (Rs1+j2πfLs1)
Impedance : 6.05+j36.28Ω
Feeder-2 (Rs2+j2πfLs2)
Impedance : 3.05+j18.14Ω
Load L-11
Phase – a 24.2+j60.50Ω
Phase – b 36.2+j78.54Ω
Unbalanced RL
Phase – c 48.2+j94.25Ω
Component
Load L-12
A three phase diode rectifier that
Non-linear component
supplies a load of 250+j31.42Ω
Balanced load L-2
72.6+j54.44Ω
impedance
to hold Vt2 constant in case of a sag in the voltage Vs2 this
can be accomplished as the two VSCs are supplied by a common dc
capacitor. The dc capacitor voltage control has been discussed here
along with voltage reference generation strategy. Also, the limits
of achievable performance have been computed. The performance of
the IUPQC has been evaluated through simulation studies using
MATLAB.
1.SYSTEM DESCRIPTION WITH METHODOLOGY
For understanding the applicability of the improved iUPQC
controller. An electrical system with two buses, bus A and bus B.
Bus A of the power system, suppliessensitive loads and serve up
point of coupling of a microgrid. At bus B non- linear loads are
connected, which requires premium quality power supply, is a bus of
the microgrid. The voltages at bus A and bus B should be regulated
in order to supply properly the sensitive loads and the non-linear
loads. If using a STATCOM, it gives only voltage regulation at bus
A not mitigate harmonic currents drawn by the non-linear loads. On
the other hand, if using UPQC between bus A and bus B, it can only
compensate the harmonic currents of the non-linear loads and
compensate the voltage at bus B, but it cannot regulate the voltage
at bus A. Hence, to accomplish all the desired goals, a STATCOM at
bus A and a UPQC between bus A and B should be employed. However
the cost of this solution would be excessiveAn attractive solution
is the use of a modified iUPQC controller to provide beside all
those functionalities of this equipment and also reactive power
support to the bus A. The modified iUPQC can provide the following
functionalities:
· It controls the energy and power flow between the grid and the
microgrid.
· It provides voltage/frequency support at bus B of the
microgrid.
· It provides reactive power support at bus A of the power
system.
· It provides harmonic voltage and current isolation between bus
A and bus B.
· It provides good breaker as associate degree intertie between
the grid and also the small grid.
· It provides voltage and current imbalance compensation..
An IUPQC connected to a distribution system is shown in Fig. 4.
during this figure, the feeder impedances area unit denoted by the
Pairs (Rs1, Ls1) and (Rs2, Ls2). It may be seen that 2|the 2}
feeders offer the masses L-1 and L-The load L-1 is assumed to own
two separate components-an unbalanced half (L-11) and a non-linear
half (L-12). The currents drawn by these 2 masses area unit denoted
by it11 and it12 severally. we tend to additional assume that the
load L-2 could be a sensitive load that needs uninterrupted and
controlled voltage. The shunt VSC (VSC-1) is connected to bus B-1
at the top of Feeder-1, whereas the series VSC (VSC-2) is connected
at bus B-2 at the top of Feeder-2. The voltages of buses B-1 and B2
and across the sensitive load terminal area unit denoted by Vt1 and
Vt2 severally. The aim of the IUPQC is two-fold:
· To protect the sensitive load L-2 from the disturbances
occurring within the system by regulation the voltage (Vt2).
· To regulate the bus B-1 voltage Vt1 against sag/swell and or
disturbances within the system.
In order to achieve these aims, the shunt VSC-1 is operated as a
voltage controller whereas the series VSC-2 regulates the voltage
Vt2 across the sensitive load. The system parameters employed in
the study area unit given in Table I. The length of Feeder-1 is
indiscriminately chosen to be double that of Feeder-2. The voltage
of bus B-1 and cargo L-1 currents, once no IUPQC is connected to
the distribution system, area unit shown in Fig. 5.
Table:1 System Parameters during this figure and altogether the
remaining figures showing 3 part waveforms, the phases a, b and c
area unit delineate by solid, broken and dotted lines, severally.
It may be seen from Fig. 5(a) that because of the presence of
unbalanced and non-linear masses L-1, the voltage Vt1 is each
unbalanced and distorted. Also, the load L-11 causes associate
degree unbalance within the current it12 whereas load L-12 causes
distortion within the current it11. we tend to shall currently
demonstrate however these waveforms may be improved victimisation
the Interline Unified Power Quality Conditioner (IUPQC).
2. IUPQC CONFIGURATION
The improved unified power quality conditioner consists of Shunt
active filter and series active filter. it's nothing but the
blending of series ad shunt active power filters, that unit of
measurement connected in back to back by a typical DC electrical
device .
Fig 2 .iUPQC configuration
Fig.2shows the circuit of iupqc, for input signals we've to
ponder the voltages and currents measurements for iUPQC controller.
The iUPQC controller consists of two PWM converters connected
succeeding through a typical dc link. three single-phase
transformers unit of measurement utilised to insert the series
device between the flexibility system and conjointly the load. The
convenience of victimization or not shunt device is further related
to economical issues regarding voltage/current levels and power
ratings of the system and power converters of the iUPQC the iUPQC
contains a easier controller and reduced style of measurements.
exclusively the system voltage, the dc-link voltage and conjointly
the load current unit of measurement necessary as inputs to the
iUPQC controller.
3. OPERATION PRINCIPLE
Fig 3.Operating Principle of Iupqc.
Fig.3shows the principles of the iUPQC. The shunt active filter
generates a basic positive-sequence voltage at face price. the
compensated load is provided below regulated, curvilinear and
balanced voltage conditions (vL). On the other hand, the series
active filter imposes a basic positive-sequence current (iS) to be
drained from the network. In steady state, the series active filter
drains a positive-sequence current in section with the essential
positive-sequence component of the availability voltage vS. The
magnitude of iS correspond to the common active power demanded by
the load, and an energetic current component to create amends for
losses inside the iUPQC. Since the shunt active filter of the iUPQC
behaves as an ideal voltage offer, it offers ideally null
resistance for harmonic currents, whereas the series active filter
offers ideally infinite resistance, in line with this thought all
harmonic current injected by nonlinear load area unit progressing
to be forced to follow in to shunt active filter of iupqc and it
provides reactive power of the load, series filter drains
exclusively active portion of load current. 4.STRUCTURE
&MANAGEMENT
The IUPQC shown in Fig. one consists of 2 VSCs (VSC-1 and VSC-2)
that area unit connected back to back through a typical energy
storage dc electrical condenser Center for Disease Control and
Prevention. allow us to assume that the VSC-1 is connected in shunt
to Feeder-1 whereas the VSC-2 is connected asynchronous with
Feeder-2. every of the 2 VSCs is completed by 3 H-bridge
inverters.
Fig.4: Schematic structure of VSC.
Fig.5: Complete structure of an IUPQC.
Fig.6: Typical IUPQC connected in distribution System
The schematic structure of a VSC is shown in Fig. 4. during this
structure, every switch represents an influence semiconductor unit
(e.g., IGBT) associate degreed an anti-parallel diode as shown in
Fig. 4. All the electrical converters area unit equipped from a
typical single dc electrical condenser Center for Disease Control
and Prevention and every inverter incorporates a electrical device
connected at its output. the whole structure of a three-phase IUPQC
with 2 such VSCs is shown in Fig. 5. The secondary (distribution)
sides of the shunt-connected transformers (VSC-1) area unit
connected in star with the neutral purpose being connected to the
load neutral. The coil of the series-connected transformers (VSC-2)
area unit directly connected asynchronous with the bus B-2 and
cargo L-2. The ac filter capacitors Cf and Ck and also are
connected in every part (Fig. 5) to forestall the flow of the
harmonic currents generated because of switch. The six inverters of
the IUPQC area unit controlled severally. The switch action is
obtained victimisation output feedback management. The controller
is meant in discrete-time victimisation pole-shifting law within
the polynomial domain as mentioned in Appendix A.
5. IUPQC CONTROLLER
The controller of the iUPQC is very simple. it's supported the
p-q Theory. A basic a neighborhood of this controller is that the
synchronizing circuit supported a district Locked-Loop (PLL), that
tracks accurately the frequency and purpose of the essential
positive-sequence part of the supply voltage Vs. Fig. shows the
complete management diagram of the iUPQC controller. Since the
present approach of iUPQC is meant for application in three-phase
three-wire systems (without neutral conductor), zero-sequence
components unit of measurement out of interest. Hence, simplified
2x2 matrixes of the Clarke Transformations and a reduced numbers of
measurements could also be used as input signals for the iUPQC
controller.
Fig.7. Iupqc controller
6.FUZZY LOGCONTROLLERS
The word Fuzzy suggests that unclearness. opacity happens once
the boundary of piece of knowledge isn't clear-cut. In 1965
LotfiA.Zahed propounded the fuzzy pure mathematics. Fuzzy pure
mathematics exhibits vast potential for effective resolution of the
uncertainty within the downside. Fuzzy pure mathematics is a superb
mathematical tool to handle the uncertainty arising thanks to
unclearness. Understanding human speech and recognizing written
characters ar some common instances wherever opacity manifests.
Fuzzy pure mathematics is associate extension of classical pure
mathematics wherever components have variable degrees of
membership. formal logic uses the complete interval between zero
and one to explain human reasoning. In FLC the input variables ar
mapped by sets of membership functions and these ar referred to as
as “FUZZY SETS”.
Fig.8.Fuzzy Basic Module
Fuzzy set includes from a membership operate that might be
defines by parameters. the worth between zero reveals a degree of
membership to the fuzzy set. the method of changing the crisp input
to a fuzzy worth is termed as “fuzzification”. The output of the
fuzzier module is interfaced with the foundations. the essential
operation of FLC is made from fuzzy management rules utilizing the
values fuzzy sets generally for the error, amendment of error
action. The results ar combined to offer a crisp output, dominant
the output variable and this method is termed
“defuzzification”.
formal logic management Rules:
Fig.9: management Strategy supported forty nine Fuzzy management
rules with combination of seven error states multiplying with seven
changes of error states.
Fig. 10. Simulation diagram
Fig. 10a.Fig. 10a. iUPQC response at no load condition: (a) grid
voltages VA, (b) load voltages VB, and (c) grid currents
Fig. 10b..iUPQC fugacious response throughout the association of
a threephase diode rectifier: (a) load currents, (b) gridcurrents,
(c) load voltages and (d) grid voltages.
Fig.10c. iUPQC fugacious response throughout the association of
a twophase diode rectifier: (a) load currents, (b) supply currents,
(c) load voltages, and (c) supply voltages
The main blessings of the iUPQCar power quality enhancements
like power issue correction, voltage and current harmonics
mitigation, voltage sag and swell compensation, voltage regulation.
The iUPQC keeps clear the disturbances that affects the system, by
natural disturbance mitigation. Since the iUPQC provides grid
voltage regulation, thus it reduces the inner loop current power
within the iUPQC, this can be another power quality compensation
feature. The performance of iUPQC are often additional improved by
victimisation higher controller in situ of pelvic inflammatory
disease controller.
7.CONCLUSION
The paper illustrates the operation associated management of an
interline unified power quality conditioner (IUPQC). The device is
connected between 2 feeders returning from totally different
substations. associate unbalanced and non-linear load L-1 is
provided by Feeder-1 whereas a sensitive load L-2 is provided
through Feeder-2. the most aim of the IUPQC is to control the
voltage at the terminals of Feeder-1 and to safeguard the sensitive
load from disturbances occurring upstream. The performance of the
IUPQC has been evaluated below numerous disturbance conditions like
voltage sag in either feeder, fault in one in all the feeders and
cargo amendment. The IUPQC mentioned within the paper is capable of
handling system during which the masses ar unbalanced and
distorted. As so much because the common dc link voltage is at the
affordable level, the device works satisfactorily. The angle
controller ensures that the important power is drawn from Feeder-1
to carry the dc link voltage constant. Therefore, even for voltage
sag or a fault in Feeder-2, VSC-1 passes real power through the dc
capacitance onto VSC-2 to control the voltage Vt2. Finally once a
fault happens in Feeder-2 or Feeder-2 is lost, the facility needed
by the Load L-2 is provided through each the VSCs. this means that
the facility semiconductor switches of the VSCs should be rated
such the full power transfer through them should be attainable.
within the IUPQC configuration mentioned during this paper, the
sensitive load is totally protected against sag/swell and
interruption. lastly, the performance below a number of the most
important considerations of each client and utility e.g., harmonic
contents in hundreds, unbalanced hundreds, provide voltage
distortion, system disturbances like voltage sag, swell and fault
has been studied. The IUPQC has been shown to complete many of
those events with success.
REFERANCE
[1] F.Kamran& T. G. Habetler, “Combined defaulter management
of a series parallel device combination used as a universal power
filter,” IEEE Trans. Power lepton.,vol.13, no 1, pp. 160–168, Jan.
1998
[2] N. Voraphonpiput and S. Chatratana,“STATCOM analysis and
controller style for power grid voltage regulation,” in Proc.
IEEE/PES Transmiss. Distrib. Conf. Exhib.––Asia Pac., 2005, pp.
1–6.
[3]D. C. Bhonsle R. B. Kelkar style and Simulation of Single
part Shunt Active Power Filter victimisation MATLAB2011
International Conference on Recent Advancements in Electrical,
natural philosophy and management Engineering
[4]Aredes M, RM Fernandes (2009). A twin topology of unified
power quality conditioner: The iUPQC. In Proc. EPE Conf. Appl.
1-10.
[5]Karanki K, G Geddada, MK Mishra, metal Kumar (2013). A
changed Three-Phase Four-Wire UPQC Topology with Reduced DC-Link
Voltage Rating. IEEE Trans. Ind. Electron. 60(9): 3555-356.