Title: ELECTRIC POWER QUALITY, HARMONIC REDUCTION AND ENERGY SAVING USING MODULATED POWER FILTERS AND CAPACITOR COMPENSATORS
1UNIVERSITY OF NEW BRUNSWICK
- ELECTRIC POWER QUALITY, HARMONIC REDUCTION AND
ENERGY SAVING USING MODULATED POWER FILTERS AND
CAPACITOR COMPENSATORS - POWER QUALITY-PQ
- Professor Dr. Adel M. Sharaf. P.Eng.
- UNB-ECE Dept
- Canada
2What is Power quality ?
- Definition Power quality problem is any power
problem manifested in voltage, current, or
frequency deviation that results in failure or
misoperation of customer equipment. - Power quality can be simply defined as shown in
the interaction diagram
- Harmonics
- Waveform Distortion
- Voltage Sags
- Voltage Swells
- Blackouts/Brownouts
- Transient
- Arc Type
- Temporal
- Converter Type
- Saturation Type
- NLL-Analog/Digital Switching
- Inrush
- Overcurrent
- Flickering
3Why are we concerned about PQ
- The Main reasons behind the growing concern about
PQ are - North American industries lose Tens-of-Billions
of Dollars every year in downtime due to power
quality problems. (Electrical Business Magazine) - Load nonlinearities in rising and is expected to
reach 50 to 70 in the year 2005 (Electric Power
Research Institute) Computers, UPS, fax
machines, printers, fluorescent lighting, ASD,
industrial rectifiers, DC drives, arc welders,
etc). - The characteristics of the electric loads have
changed. - Harmonics are continuous problem not transient or
intermittent.
4Power Quality Issue and Problems
- Power Quality issues can be roughly broken into a
number of sub-categories - Harmonics (sub, super and interharmonics)
- Voltage swells, sags, fluctuations, flicker, and
transients - Voltage magnitude and frequency deviation,
voltage imbalance (3ph sys.) - Hot grounding loops and ground potential rise
(GPR)Safety Fire Hazards - Monitoring and measurement.
5Power Quality PQ Issue
- Harmonics and NLL issues
- The harmonic issue (waveform distortion) is a top
priority to for all equipment manufacturer, users
and Electric Utilities (New IEC, ANSI, IEEE
Standards).
6SYSTEM MODELS
Single Line Diagram of Radial Utilization System
7Nonlinear Load Models
Volt-Ampere (VL IL)
Arc Type
Cyclical Load
Temporal time-dependent (Cyclical load)
8Nonlinear Load Models
Volt-Ampere (VL IL)
Industrial Motorized Load
Cyclical Motorized
Modulated Fanning Effect
Converter-Rectifier Modulated
9Nonlinear Load Models
Volt-Ampere (VL IL)
Limiter Type
Switch Mode Power Supply (SMPS)
FL-Starter Ballast Nonlinear
Magnetic Saturation type
10Nonlinear Load Models
Volt-Ampere (VL IL)
Adjustable Speed Drive (ASD)
Dual Loop Nonlinear
11Switched Modulated Power Filters and Capacitor
Compensators
Dual-Tuned-Arm Filter
TAF Static Capacitor Compensator
Tuned-Arm Filter (TAF)
Asymmetrical Tuned-Arm Filter (ATAF)
C-Type Filter
MPF/SPF(Family of Filters Compensators)
Developed by Dr. A. M. Sharaf
12Switched Modulated Power Filters and capacitor
Compensators
Economic Tuned-Arm Power Filter and Capacitor
Compensator Scheme (used in S-phase 2 wire loads)
- Motorized Inrush Loads
- Water Pumps
- A/C
- Refrigeration
- Blower / Fans
Switched Capacitor Compensator Scheme (used for
on/off Motorized loads)
13Novel Dynamic Tracking Controllers (Family of
Smart Controllers Developed by Dr. A. M. Sharaf)
- The Dynamic Control Strategies are
- Dynamic minimum current ripple tracking
- Dynamic minimum current level
- Dynamic minimum power tracking
- Dynamic minimum effective power ripple tracking
- Dynamic minimum RMS source current tracking
- Dynamic maximum power factor
- Minimum Harmonic ripple content
- Minimum reference harmonic ripple content
- Electric Power/Energy Savings
- Improve Supply PQ by reducing Harmonics and
improve power factor and enhance waveforms as
close as possible to sine wave
14Novel Dynamic Controllers
Dynamic Minimum-RMS Current tracking
Minimum Harmonic Reference Content
15Switching Devices (on/off or PWM)
The solid-state switches (S1, S2) are usually
(GTO, IGBT/bridge, MOSFET/bridge, SSR, TRIAC)
turns ON when a pulse g(t) is applied to its
control gate terminal by the activation switching
circuit. Removing the pulse will turn the
solid-state switch OFF TS/W1/fS (ton
toff) 0lttonltTS/W
16Switching Devices PWM Circuits
(1)
PWM Circuit (Developed by Dr. C. Diduch) for use
with Matlab/Simulink
(2)
PWM Circuit (Matlab/Simulink/Stateflow-Grundlagen)
17Concept of Modulated Power Filters (MPF)
The Linear Combination of two Unit Step Functions
to describe a Pulse of Amplitude 1 and duration
t0.
Tune Arm Filter layout
18Modulated Tuned Arm Filter (Sym. Asym.)
- Load is either
- Symmetrical Arc Type
- SMPS
- Adjustable Speed Drives
- Asymmetrical Arc-type
- Dynamic Controller
- -Min. effec. Power
- RMS current tracking
- Min. Harmonic Content
Single Line Diagram of System and Modulated / PWM
Tuned-Arm Filter
19Modulated Tuned Arm Filter with (SMPS) Load
Without (THD74)
With (THD9)
20Modulated Asymmetrical Tuned-Arm Filter
Without (THD42)
With (THD14)
With (THD7)
Without (THD18)
Nonlinear Temporal Load Parameters R1R01R11sin
(wr1t) E1E01E11sin(wr2t)
R2R02R22sin(wr1t) E2E02E22sin(wr2t)
R2 R1(1?) R018 R0212 R112 R226
wr115 E2 -E1(1?) E01 46 E0270
E1112 E2235 wr25
Dynamic Controller Dual loop of RMS current
tracking and Min. Harmonic Content
21A Low-cost Voltage Stabilization and Power
Quality Enhancement Scheme for a Small Renewable
Wind Energy Scheme
- Professor Dr. Adel M. Sharaf. P.Eng.
- UNB-ECE Dept
- Canada
22OUTLINE
- Introduction
- System Description
- Novel PWM Switching Control Scheme
- Modulated Power Filter Compensator
- Simulation Results
- Conclusion
23Introduction
- Motivation of renewable wind energy
- Fossil fuel shortage and its escalating prices
- Reducing environmental pollution caused by
conventional methods for electricity generation
24Introduction
- Challenges of the reliability of wind power
system - Load excursion
- Wind velocity variation
- Conventional passive capacitor compensation
devices become ineffective
25System Description
- Self-excited induction generator (SEIG)
- Transformers and short feeder
- Hybrid loads linear load and non-linear load
- The modulated power filter compensator (MPFC)
26Novel PWM Switching Control Scheme
27Novel PWM Switching Control Scheme
- Multi-loop dynamic error driven
- The voltage stabilization loop
- The load bus dynamic current tracking loop
- The dynamic load power tracking loop
- Using proportional, integral plus derivative
(PID) control scheme - Simple structure and fast response
28Novel PWM Switching Control Scheme
- Objective
- To stabilize the voltage under random load and
wind speed excursion - Maximize power/energy utilization
- The control gains (Kp, Ki) are selected using a
guided trial and error method to minimize the
objective function, which is the sum of all three
basic loops.
29The Functional Model of MPFC
- The capacitor bank and the RL arm are connected
by a 6-pulse diode to block the reverse flow of
current. - Capacitor size normally selected as 40-60 of
the non-linear load KVAR capacitor.
30Proposed MPFC Scheme and Its Functional Model
31Simulation Results
- Digital simulation environment
- MATLAB 7.0.1/SIMULINK
- Sequence of load excursion
- From 0s to 0.2s Both Linear Load 200 kVA (50)
and nonlinear Load 200 kVA (50) connected - From 0.2s to 0.4s Linear Load 200 kVA(50)
connected only - From 0.4s to 0.6s No load is connected
32System Dynamic Response Without MPFC
33System Dynamic Response With MPFC
34Error plane of the dynamic error driven controller
35Conclusions
- The digital simulation results validated that the
proposed low cost MPFC scheme is effective in
voltage stabilization for both linear and
nonlinear electrical load excursions. -
- The proposed MPFC scheme will be easily
integrated in renewable wind energy standalone
units in the range from 600kW to 1600kW.
36Reference
- 1 A.M.Sharaf and Liang Zhao, A Novel Voltage
Stabilization Scheme for Standalone Wind Energy
Using a Facts Dual Switching Universal Power
Stabilization Scheme, 2005 - 2 M.S. El-Moursi and Adel M. Sharaf, 'Novel
STATCOM controller for voltage stabilization of
wind energy scheme', Int. J. Global Energy
Issues, 2006. - 3 A. M. Sharaf and Guosheng Wang, Wind Energy
System Voltage and Energy Enhancement Using Low
Cost Dynamic Capacitor Compensation Scheme,
2004. - 4 A.M. Sharaf and Liang Yang, 'A Novel
Efficient Stand-Alone Photovoltaic DC Village
Electricity Scheme, 2005
37Reference
- 5 Pradeep K. Nadam, Paresk C. Sen, 'Industrial
Application of Sliding Mode Control', IEEE/IAS
International Conference On Industrial Automation
and Control, Proceedings, pp. 275-280, 1995 - 6 Paresk C. Sen, 'Electrical Motor and
Control-Past, Present and Future', IEEE
Transactions on Industrial Electronics, Vol.37,
No.6, pp.562-575, December 1990 - 7 Edward Y.Y. Ho, Paresk C. Sen, 'Control
Dynamics of Speed Drive System Using Sliding Mode
Controllers with Integral Compensation', IEEE
Transactions on Industry Applications, Vol.21,
NO.5, pp 883-892, September/October 1991.
38A FACTS based Dynamic Capacitor Scheme for
Voltage Stabilization and Power Quality
Enhancement
39Abstract
- Power Quality voltage problems in a power system
may be either at system frequency or due to
transient surges with higher frequency
components. - These are called switching-type over-voltages
which can be produced during opening or closing a
switch and can be severe in certain cases. -
- The paper presents a low-cost FACTS based dynamic
capacitor compensator DCC- scheme for voltage
compensation and power quality enhancement. - The FACTS DCC dynamic compensator is a member of
a family of smart power low cost compensators
developed by the First Author.
40Introduction
- The growing use of nonlinear industrial type or
inrush type electric loads can cause a real
challenge to power quality for electric utilities
around the world, especially in the current era
of the unregulated power market where
competition, supply quality, security and
reliability are key issues for any economic
survival. - Power Quality over voltage conditions in a power
system may be either at system frequency or due
to transient surges with higher frequency
components. - With EHV transmission systems, lightning is less
of a problem because lightning surges rarely
reach the impulse withstand voltage of the system
equipment, e.g. 400 kV circuit breakers are
impulse tested with an impulse 1425 kV , (1 us
wave front to peak voltage and 50 of peak
voltage). In EHV systems, switching surges thus
become relatively more important 1.
41Cont. / Introduction
- The problem of the dynamic switching overvolatges
affects also voltage stability of large non
linear / motorized loads. It can increase the
transmission line losses, and decrease the
overall power factor 8. - Solid state AC controllers are widely Solid state
AC controllers are widely used to convert AC
power for feeding number of electrical loads such
as adjustable speed drives, arc furnaces, power
supplies etc. - Some of theses power converter controllers behave
as nonlinear loads because they generally draw a
non- sinusoidal current from AC sources. -
- The paper presents a new low cost FACTS based
dynamic compensator scheme (DCC) for improving
the voltage stability and enhancing power quality
for hybrid linear/nonlinear and motorized load.
42The System under study
- Fig.1 (a) depicts the single line diagram of the
sample radial 138 kV (L-L) AC Power System.
43MATLAB Sim-Power System Model
- Fig.1 (b) shows the MATLAB block diagram.
44The MATLAB Sim-Power System functional model of
the hybrid (linear, non linear and motorized)
load is shown in Fig.2.
45New Dynamic Capacitor Compensator (DCC) scheme
comprising a switched power filter
46Controller Design
- Fig.4 shows the proposed novel Tri-loop (PI)
Proportional plus Integral, dynamic error driven
sinusoidal SPWM switching controller.
47Cont. / Controller Design
- The Tri-loop dynamic controller is used to
stabilize the load bus voltage by regulated pulse
width switching of the two IGBT solid state
switches. - The three regulating key loops are
- Loop 1 the main loop for the dynamic voltage
error using the RMS voltage at the load bus this
loop is to maintain the voltage at the load bus
at a reference value by modulating the admittance
of the compensator. - Loop 2 the dynamic error is using RMS dynamic
load current. This loop is an auxiliary loop to
compensate for any sudden electrical load
excursions. - Loop 3 the Harmonic ripple loop is used to
provide an effective dynamic tracking control to
suppress any sudden current ripples and
compensate the AC system power transfer
capability even under switching excursions.
48The following Figures show the load voltage,
current, and active power, reactive power, the
active vs. reactive power, and the transmitted
power loss without the proposed low cost FACTS
Dynamic Capacitor Compensator (DCC).
49The following Figures show the load voltage,
current, and active power, reactive power, the
active vs. reactive power, with the proposed low
cost FACTS Dynamic Capacitor Compensator (DCC).
50Conclusions
- The paper presents a low cost FACTS Based
Capacitor Compensator (DCC) for a radial 138 kV
L-L sample test system. Digital simulation and
comparison between without and with figures
validated the following - The receiving load bus voltage without the FACTS
Based Capacitor Compensator (DCC) was about 0.66
pu when reaching steady state. Using the FACTS
(DCC) compensator it is increased to about 0.96
pu (which is acceptable -5 from 1 pu). - The receiving load bus current is increased from
0.36 pu to 0.62 pu with the FACTS Based Capacitor
Compensator (DCC). - The received active power at the hybrid load bus
is increased from 0.36 pu to 0.95 pu. - The received reactive power at the hybrid load
side is decreased from 0.2 pu to -0.5pu. - The receiving end power factor is also increased
from 0.832 lag to 0.95 lag. - The transmitted power loss is decreased from
0.042 pu to 0.017 pu (about 40 less).
51References
- 1 Guile, Paterson, Electrical Power Systems
vol.2, Pergamon international library of science,
1977. - 2 A.M.Sharaf, Harmonic interference from
distribution systems, IEEE Winter Meeting, New
York, 1982. - 3 A.M.Sharaf, H.Huang, Flicker control using
rule based modulated passive power filters,
Electric Power System Research Journal 33 (1995)
49-52. - 4 A.M.Sharaf, C.Gua, and H.Huang, A Smart
Modulated Filter for Energy Conservation in
Utilization Network, IACPSS, April 6-8, 1997,
Al-Ain, UAE, pp 211-212. - 5 A.M.Sharaf, S.S.Shokralla and A.S.Abd
El-Ghaffar, Efficient Power Tracking using an
Error Driven Modulated Passive Filter, AEIC 95,
AL-AZHAR Conference, December 16 19, 1995. - 6 A.M.Sharaf, P.Kreidi, Power Quality
enhancement and harmonic reduction using dynamic
power filters, ELECTRIMACS 2002. Montreal,
Quebec, Canada, August 18-21, 2002. - 7 A.M.Sharaf, P.Kreidi, Power Quality
enhancement using a unified compensator and
switched filter , ICREPQ 2003, Vigo-Spain,
April 9-11, 2003. - 8 Uzunoglu, M., Kocatepe, C. and Yumurtaci, R.
(2004) Voltage stability analysis in the power
systems including non-linear loads, European
Transactions on Electrical Power,
JanuaryFebruary, Vol. 14, No. 1, pp.4156. - 9 B.Singh, V.Verma, A.Chandra and K.Al-Haddad,
Hybrid filters for power quality improvement,
IEE Proc.Gener.Transm.Distrib., Vol. 152, No.3,
May 2005.
52A NOVEL MAXIMUM POWER TRACKING CONTROLLER FOR A
STAND-ALONE PHOTOVOLTAIC DC MOTOR DRIVE
- A.M. Sharaf, SM IEEE
- Department of Electrical and Computer Engineering
- University of New Brunswick
53PRESENTATION OUTLINE
- Introduction
- System Model Description
- Novel Dynamic Error Driven Self Adjusting
Controller (SAC) - Digital Simulation Results
- Conclusions
- Future Work
54Introduction
- The advantages of PV solar energy
- Clean and green energy source that can reduce
green house gases - Highly reliable and needs minimal maintenance
- Costs little to build and operate (2-3/Wpeak)
- Almost has no environmental polluting impact
- Modular and flexible in terms of size, ratings
and applications
55 Maximum Power Point Tracking (MPPT)
- The photovoltaic system displays an inherently
nonlinear current-voltage (I-V) relationship,
requiring an online search and identification of
the optimal maximum power operating point. - MPPT controller/interface is a power electronic
DC/DC converter or DC/AC inverter system inserted
between the PV array and its electric load to
achieve the optimum characteristic matching. - PV array is able to deliver maximum available
solar power that is also necessary to maximize
the photovoltaic energy utilization in
stand-alone energy utilization systems (water
pumping, ventilation)
56- I-V and P-V characteristics of a typical PV array
at a fixed ambient temperature and solar
irradiation condition
57- The performance of any stand-alone PV system
depends on - Electric load operating conditions/Excursions/
Switching - Ambient/junction temperature (Tx)
- Solar insolation/irradiation variations (Sx)
58System Model Description
- Key components
- PV array module model
- Power conditioning filter
- ? Blocking Diode
- ? Input filter (Rf Lf)
- Storage Capacitor (C1)
- Four-Quadrant PWM converter feeding the
- PMDC (Permanent Magnet Direct Current)
- motor (1-15kW size)
59- Photovoltaic powered Four-Quadrant PWM converter
PMDC motor drive system
60Novel Dynamic Error Driven Self Adjusting
Controller (SAC)
- Three regulating loops
- The motor reference speed (?m-reference)
- trajectory tracking loop
- The first supplementary
- motor current (Im) limiting loop
- The second supplementary
- maximum photovoltaic power (Pg) tracking loop
61Dynamic tri-loop self adjusting control (SAC)
system
62- The global error signal (et) comprises
- 3-dimensional excursion vectors (ew, ei, ep)
- The control modulation ?Vc is
- ß is the specified squashing order (23)
- Re is the magnitude of the hyper-plane error
excursion vector at time instant k
63- The loop weighting factors (?w, ?I and ?p)
- and the parameters k0 and ß are assigned to
minimize the time-weighted excursion index J0 -
- where
- N T0/Tsample
- T0 Largest mechanical time constant (10s)
- Tsample Sampling time (0.2ms)
- t(k)kTsample Time at step k in seconds
64Digital Simulation Results
- Photovoltaic powered Four-Quadrant PWM converter
PMDC motor drive system model using the
MATLAB/Simulink/SimPowerSystems software
65 Test Variations of ambient temperature and
solar irradiation
- Variation of
- ambient temperature (Tx)
- Variation of
- solar irradiation (Sx)
66For trapezoidal reference speed trajectory
67For trapezoidal reference speed
trajectory(Continue)
- Pg vs. Ig Vg
- ?ref ?m vs. time
68For sinusoidal reference speed trajectory
69For sinusoidal reference speed trajectory(Continu
e)
- Pg vs. Ig Vg
- ?ref ?m vs. time
70- The digital simulation results validate the
tri-loop dynamic error driven Self Adjusting
Controller (SAC), ensures - Good reference speed trajectory tracking with
- a small overshoot/undershoot and minimum
- steady state error
- The motor inrush current Im is kept to a
specified - limited value
- Maximum PV solar power/energy tracking near
- knee point operation can be also achieved
71Conclusions
- The proposed dynamic error driven controller
requires only the PV array output voltage and
current signals and the DC motor speed and
current signals that can be easily measured. - The low cost stand-alone photovoltaic renewable
energy scheme is suitable for village electricity
application in the range of (150 watts to 15000
watts), mostly for water pumping and irrigation
use in arid developing countries.
72Future Work
- Other PV-DC, PV-AC and Hybrid PV/Wind energy
utilization schemes - New control strategies
73Future Work (Continue) Novel Dynamic Error
DrivenSliding Mode Controller (SMC)
-
- Three regulating loops
- The motor reference speed (?m-reference)
- trajectory tracking loop
- The first supplementary
- motor current (Im) limiting loop
- The second supplementary
- maximum photovoltaic power (Pg) tracking loop
74Dynamic tri-loop error-driven Sliding Mode
Control (SMC) system
75A Low Cost Dynamic Voltage Stabilization Scheme
for Standalone Wind Induction Generator System
76Outline
- 1.Introduction
- 2.Standalone Wind Energy System
- 3.Dynamic Series Switched Capacitor Compensation
including two parts Digital Simulation Models
and Dynamic Simulation Results - 4.Conclusions
- 5.Future Work
- References
-
-
771. Introduction
- Wind energy has become one of the most
significant, alternative energy resources. - Most wind turbines(15-200kw) use the three phase
asynchronous induction generator for its low
lost, reliable and less maintenance. - However, the voltage stability of a wind driven
induction generator system is fully dependent on
wind gusting conditions and electrical load
changes1-3. - New interface technology is needed such as DSSC
and other MPF/CCcompensation scheme 1-3.
78Introduction What is DSSC?
- DSSC is a low cost dynamic series switched
capacitor (DSSC) interface compensation scheme. - Capacitance in parallel or series of the DSSC
scheme are interfaced with the output feeder
lines. - DSSC scheme can be used to improve the induction
generator voltage stability and ensure dynamic
voltage stabilization under varying wind and load
conditions, thus prevent loss of severe generator
bus voltage excursions.
792. Standalone Wind Energy System
Figure 1 shows Standalone Wind Energy Conversion
Scheme Diagram with Hybrid Load and Dynamic
Series Switched Capacitor Compensations
802. Standalone Wind Energy System
Figure 2 shows Low Cost Dynamic Series Switched
Capacitor (DSSC) Stabilization Scheme using Gate
Turn off GTO switching Device
812. Standalone Wind Energy System
Figure 3 shows the Hybrid Electrical Load
823. Dynamic Series Switched Capacitor Compensation
- A sample test standalone wind induction generator
system (WECS) is modeled using the Matlab/
Simulink/ Sim-Power Block-set software
environment.
833. Dynamic Series Switched Capacitor Compensation
Figure 4 shows the Unified Systems
Matlab/Simulink Functional Model
843. Dynamic Series Switched Capacitor Compensation
Figure 5 shows Tri-loop Error
Driven PID Controlled PWM Switching Scheme
853. Dynamic Series Switched Capacitor Compensation
- Linear and non-linear load excursions
- Figure 6 in next slide depicts the digital
simulation dynamic response to both in linear and
nonlinear load excursion. - From time interval 0.1s to 0.3s, we applied 50
(100kVA) linear load from 0.4s-0.6s, we applied
60 (120kVA) non-linear load. - So the DSSC can stabilize for both linear and
nonlinear load excursions and ensure the
generator bus stabilization
863. Dynamic Series Switched Capacitor Compensation
- Without DSSC Compensation
Figure 6
873. Dynamic Series Switched Capacitor Compensation
- Under inrush induction motor load excursion
- Figure 7 in the next slide shows the dynamic
simulation response to the induction motor load
excursions. - From time 0.2s to0.4s, we applied about 20
(20kVA) induction motor load. - From the figure we can see that DSSC did not
compensate for this inrush motor load excursions
adequately.
883. Dynamic Series Switched Capacitor Compensation
- Without DSSC Compensation
Figure 7
893. Dynamic Series Switched Capacitor Compensation
- Under wind excursion
- Figure 8 in the next slide shows the dynamic
simulation response to wind excursions - From 0.3s-0.6s, the wind speed was decreased to
6m/s from initial value 10m/s. - From figure 8 we can see that DSSC did compensate
wind excursion, the voltage at generate bus keeps
1.0pu.
903. Dynamic Series Switched Capacitor Compensation
- Without DSSC Compensation
Figure 8
914. Conclusions
- The low cost DSSC compensation scheme is very
effective for the voltage stabilization under
linear, non-liner passive load excursions as well
as wind speed excursions. - But it can not compensate adequately for large
inrush dynamic excursions such as induction
motor. - The proposed low cost DSSC voltage compensation
scheme is only suitable for isolated wind energy
conversion systems feeding linear and non-linear
passive type loads.
925. Future Study
- Another new compensation scheme that can
compensate for a large inrush induction motor
excursion will be studied in my future research. - That scheme will be very effective for bus
voltage stabilization under linear, non-liner,
inrush motor load excursions and wind excursions.
93Reference
- 1. K.Natarajan, A.M Sharaf, S.Sivakumarand and
S.Nagnarhan, Modeling and Control Design for
Wind Energy Conversion Scheme using Self-Excited
Induction Generator, IEEE Trans. On E.C., Vol.2,
pp.506-512, Sept.1987. - 2. S.P.Singh, Bhim Singh and M.P.Jain,
Performance Characteristic and Optimum
Utilization of a Cage Machine as a Capacitor
excited Induction Generator, IEEE Trans. On
E.C., Vol. 5, No.4, pp.679-685, Dec.1990 - 3. A.Gastli, M.akherraz, M. Gammal,
Matlab/Simulink/ANN Based Modeling and
Simulation of A Stand-Alone Self-Excited
Induction Generator, Proc. of the International
Conference on Communication, Computer and Power,
ICCCP98, Dec.7-10 1998, Muscat, Sultanate of
Oman, pp.93-98
94(No Transcript)
95ULTRA HIGH SPEED PROTECTION OF SERIES COMPENSATED
TRANSMISSION LINES USING WAVELET TRANSFORMS
96Presentation Outline
- Introduction
- Wavelets
- Background Theory
- Proposed Scheme
- Study System Single Line Diagram
- Study System Test Cases
- Incremental Voltages and Currents
- Relaying Signals
- Wavelet Approximation
- Fault Direction Determination
- Travelling Waves
- Wavelet Thresholding
- Conclusion
97Introduction
- Ultra High Speed (UHS) relaying is a new area of
Power System Protection. - Protection of series compensated transmission
lines can be best accomplished by a UHS relaying
system. - But, UHS distance protection implementation
methods are fraught with difficulty. - In this paper, a novel non-unit UHS distance
protection scheme using wavelet transforms is
proposed.
98Wavelets
- Wavelets were first applied in the area of
geophysics. - Today, Wavelets are employed in a variety of
applications, from detecting High Impedance
Faults to compression of fingerprint files. - A signal can be decomposed using Wavelet
Transform as follows,
99 Proposed Scheme
- The measured phase voltages and currents are
decoupled to obtain the modal components . - Incremental voltage and current signals are
obtained. - Relaying signals a(t) and b(t)are obtained.
- Wavelet transform of relaying signals is obtained
to remove the high frequency travelling waves
from the relaying signals. The resultant signals
are denoted as Approx.a(t) and Approx.b(t). - A forward fault is indicated if Approx.b(t)
crosses a set threshold before Approx.a(t) does.
Similarly, a reverse fault is indicated if
Approx.a(t) crosses the threshold before
Approx.b(t).
100Proposed Scheme
- The incremental voltage signal is decomposed to
level1 using Wavelet transform. The DWT first
level coefficients are then used to reconstruct a
signal which has power system frequency
components and the decaying DC component removed
from the original signal. - Noise and reflections from other points can cause
relay mal-operation. Therefore, the travelling
waves are thresholded. - The fault distance is given by x(valpha/
(2tau)) where valpha is alpha -mode propagation
velocity, close to 2.99x108 m/s and tau is the
time from positive (negative) peak to the next
positive (negative) peak.
101 Study System Single Line Diagram
- 750kV, 250km un-transposed transmission line.
- Local source of 10GVA and a remote source of 6GVA.
Figure 1 Single Line
Diagram.
102 Study System Test Cases
- The fault distance measured from the local source
G1. - Voltage and current signals measured near the
local AC source G1. - Fault inception time t 28.5ms.
- Ground resistance 3 ohms.
103 Incremental Voltage (Case 1)
- The incremental voltage signal was obtained using
cycle subtraction.
- Figure 2a Incremental Voltage for Case 1.
104 Incremental Current (Case 1)
- The incremental current signal was obtained using
cycle subtraction.
- Figure 2b Incremental Current for Case 1.
105 Incremental Voltage (Case 2)
- The incremental voltage signal was obtained using
cycle subtraction.
Figure 3a Incremental Voltage
for Case 2.
106 Incremental Current (Case 2)
- The incremental current signal was obtained using
cycle subtraction.
Figure 3b Incremental Current
for Case 2.
107 Relaying Signals (Case 1)
- The synthesized relaying signals a(t) and b(t)
are shown in Figure 4. The value of Rs 200 ohms.
Figure 4 Relaying Signals at the Local
End for Case 1.
108 Relaying Signals (Case 2)
- The synthesized relaying signals a(t) and b(t)
are shown in Figure 5. The value of Rs 200 ohms.
Figure 5 Relaying Signals at the Local
End for Case 2.
109 Wavelet Approximation (Case 1)
- In order to utilize the relaying signals for
fault direction determination, travelling waves
are removed using Wavelet Transform.
Figure 6 Wavelet Approximated Relaying
Signals at the Local End for Case 1.
110 Wavelet Approximation (Case 2)
- In order to utilize the relaying signals for
fault direction determination, travelling waves
are removed using Wavelet Transform.
Figure 7 Wavelet Approximated Relaying
Signals at the Local End for Case 2.
111 Fault Direction Determination
- For cases 1 and 2, as evident in Figure 6 and
Figure 7 in previous slides, b(t) starts
increasing before a(t) , indicating a forward
fault.
112 Travelling Waves (Case 1)
- Wavelets transform is utilized to obtain the
travelling waves from the incremental voltage
signals. The Mother Wavelet chosen was
Daubechies db3.
Figure 8 Travelling Waves Signals obtained at
the Local End for Case 1.
113 Travelling Waves (Case 2)
- Wavelets transform is utilized to obtain the
travelling waves from the incremental voltage
signals. The Mother Wavelet chosen was
Daubechies db3.
Figure 9 Travelling Waves Signals obtained at
the Local End for Case 2.
114 Wavelet Thersholding (Case 1)
- The travelling waves signals are thresholded
using hard thresholding. Thresholding level
25kV.
Figure 10 Wavelet Thresholded Signals obtained
at the Local End for Case 1.
115 Wavelet Thresholding (Case 2)
- The travelling waves signals are thresholded
using hard thresholding. Thresholding level
25kV.
Figure 11 Wavelet Thresholded Signals obtained
at the Local End for Case 2.
116 Conclusion
- Novel UHS distance relaying scheme is presented.
- Fault distance is calculated using the travelling
waves present in the incremental voltage signal
directly. - The scheme is able to utilize the first backward
travelling wave entering the relay as opposed to
utilizing the synthesized relaying signals for
distance calculation, which is prone to error. - Cross-correlation function is not used to
determine the fault distance. - The relaying signals are processed using the
Wavelet transform instead of conventional
filtering methods.