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Title: ELECTRIC POWER QUALITY, HARMONIC REDUCTION AND ENERGY SAVING USING MODULATED POWER FILTERS AND CAPACITOR COMPENSATORS


1
UNIVERSITY 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

2
What 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

3
Why 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.

4
Power 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.

5
Power 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).

6
SYSTEM MODELS
Single Line Diagram of Radial Utilization System
7
Nonlinear Load Models
Volt-Ampere (VL IL)
Arc Type
Cyclical Load
Temporal time-dependent (Cyclical load)
8
Nonlinear Load Models
Volt-Ampere (VL IL)
Industrial Motorized Load
Cyclical Motorized
Modulated Fanning Effect
Converter-Rectifier Modulated
9
Nonlinear Load Models
Volt-Ampere (VL IL)
Limiter Type
Switch Mode Power Supply (SMPS)
FL-Starter Ballast Nonlinear
Magnetic Saturation type
10
Nonlinear Load Models
Volt-Ampere (VL IL)
Adjustable Speed Drive (ASD)
Dual Loop Nonlinear
11
Switched 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
12
Switched 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)
13
Novel 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

14
Novel Dynamic Controllers
Dynamic Minimum-RMS Current tracking
Minimum Harmonic Reference Content
15
Switching 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
16
Switching Devices PWM Circuits
(1)
PWM Circuit (Developed by Dr. C. Diduch) for use
with Matlab/Simulink
(2)
PWM Circuit (Matlab/Simulink/Stateflow-Grundlagen)
17
Concept 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
18
Modulated 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
19
Modulated Tuned Arm Filter with (SMPS) Load
Without (THD74)
With (THD9)
20
Modulated 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
21
A 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

22
OUTLINE
  • Introduction
  • System Description
  • Novel PWM Switching Control Scheme
  • Modulated Power Filter Compensator
  • Simulation Results
  • Conclusion

23
Introduction
  • Motivation of renewable wind energy
  • Fossil fuel shortage and its escalating prices
  • Reducing environmental pollution caused by
    conventional methods for electricity generation

24
Introduction
  • Challenges of the reliability of wind power
    system
  • Load excursion
  • Wind velocity variation
  • Conventional passive capacitor compensation
    devices become ineffective

25
System Description
  • Self-excited induction generator (SEIG)
  • Transformers and short feeder
  • Hybrid loads linear load and non-linear load
  • The modulated power filter compensator (MPFC)

26
Novel PWM Switching Control Scheme
27
Novel 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

28
Novel 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.

29
The 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.

30
Proposed MPFC Scheme and Its Functional Model
31
Simulation 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

32
System Dynamic Response Without MPFC
33
System Dynamic Response With MPFC
34
Error plane of the dynamic error driven controller
35
Conclusions
  • 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.

36
Reference
  • 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

37
Reference
  • 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.

38
A FACTS based Dynamic Capacitor Scheme for
Voltage Stabilization and Power Quality
Enhancement
39
Abstract
  • 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.

40
Introduction
  • 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.

41
Cont. / 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.

42
The System under study
  • Fig.1 (a) depicts the single line diagram of the
    sample radial 138 kV (L-L) AC Power System.

43
MATLAB Sim-Power System Model
  • Fig.1 (b) shows the MATLAB block diagram.

44
The MATLAB Sim-Power System functional model of
the hybrid (linear, non linear and motorized)
load is shown in Fig.2.
45
New Dynamic Capacitor Compensator (DCC) scheme
comprising a switched power filter
46
Controller Design
  • Fig.4 shows the proposed novel Tri-loop (PI)
    Proportional plus Integral, dynamic error driven
    sinusoidal SPWM switching controller.

47
Cont. / 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.

48
The 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).
49
The 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).
50
Conclusions
  • 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).

51
References
  • 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.

52
A 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

53
PRESENTATION OUTLINE
  • Introduction
  • System Model Description
  • Novel Dynamic Error Driven Self Adjusting
    Controller (SAC)
  • Digital Simulation Results
  • Conclusions
  • Future Work

54
Introduction
  • 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)

58
System 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

60
Novel 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

61
Dynamic 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

64
Digital 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)

66
For trapezoidal reference speed trajectory
  • Ig vs. time
  • Pg vs. time
  • Vg vs. time
  • Vg vs. Ig

67
For trapezoidal reference speed
trajectory(Continue)
  • Pg vs. Ig Vg
  • ?ref ?m vs. time
  • Iam vs. time
  • ?m vs. Te

68
For sinusoidal reference speed trajectory
  • Ig vs. time
  • Pg vs. time
  • Vg vs. time
  • Vg vs. Ig

69
For sinusoidal reference speed trajectory(Continu
e)
  • Pg vs. Ig Vg
  • ?ref ?m vs. time
  • Iam vs. time
  • ?m vs. Te

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

71
Conclusions
  • 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.

72
Future Work
  • Other PV-DC, PV-AC and Hybrid PV/Wind energy
    utilization schemes
  • New control strategies

73
Future 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

74
Dynamic tri-loop error-driven Sliding Mode
Control (SMC) system
75
A Low Cost Dynamic Voltage Stabilization Scheme
for Standalone Wind Induction Generator System
76
Outline
  • 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

77
1. 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.

78
Introduction 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.

79
2. Standalone Wind Energy System
Figure 1 shows Standalone Wind Energy Conversion
Scheme Diagram with Hybrid Load and Dynamic
Series Switched Capacitor Compensations
80
2. Standalone Wind Energy System
Figure 2 shows Low Cost Dynamic Series Switched
Capacitor (DSSC) Stabilization Scheme using Gate
Turn off GTO switching Device
81
2. Standalone Wind Energy System
Figure 3 shows the Hybrid Electrical Load
82
3. 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.

83
3. Dynamic Series Switched Capacitor Compensation
Figure 4 shows the Unified Systems
Matlab/Simulink Functional Model
84
3. Dynamic Series Switched Capacitor Compensation
Figure 5 shows Tri-loop Error
Driven PID Controlled PWM Switching Scheme
85
3. 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

86
3. Dynamic Series Switched Capacitor Compensation
  • Without DSSC Compensation
  • With DSSC Compensation

Figure 6
87
3. 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.

88
3. Dynamic Series Switched Capacitor Compensation
  • Without DSSC Compensation
  • With DSSC Compensation

Figure 7
89
3. 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.

90
3. Dynamic Series Switched Capacitor Compensation
  • Without DSSC Compensation
  • With DSSC Compensation

Figure 8
91
4. 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.

92
5. 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.

93
Reference
  • 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
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95
ULTRA HIGH SPEED PROTECTION OF SERIES COMPENSATED
TRANSMISSION LINES USING WAVELET TRANSFORMS
  • Dr. A. M. Sharaf, SMIEEE

96
Presentation 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

97
Introduction
  • 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.

98
Wavelets
  • 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,
  • where

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).

100
Proposed 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.
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