1

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

UNIVERSITY OF NEW BRUNSWICK

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:

Electrical GridUtility

Nonlinear LoadsIndustrial/Commercial/Residential

Consumers

VoltageQuality

CurrentQuality

PowerQuality

•Voltage Sags

•Voltage Swells

•Blackouts/Brownouts

•Transient

•Inrush

•Overcurrent

•Flickering

•Harmonics

•Waveform Distortion

•Arc Type

•Temporal

•Converter Type

•Saturation Type

•NLL-Analog/Digital Switching

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).

1

2

2

I

I

THD nn

i

DPFTHD

PFi21

1

6

SYSTEM MODELS

Single Line Diagram of Radial Utilization System

Converter Type Arc Type Dynamic Cyclical Ripple Inrush Temporal Motorized on/off SMPS ASD Saturation Type

NonlinearLoad

NLL

R s L sV s V L

YF(s)

on/off orPWM

Load Bus

ElectricUtility

Transformer

System+Transformer+FeederElectric

Equivalent(Plant) Load

Switched/ModulatedPower Filter or Static

Capacitor Compensator

i s

ControlSignals

SmartController

*V s

Ps

SMPFDifferent

Topologies

Nonlinear Load (NLL)

* Smart-controllers arebased on specified control

objectives

eight designs(Dr. A.M. Sharaf) YF (TAF, C-Type, HPDF, Special Topology)

7

Nonlinear Load Models

R s L sV s V Lis

D 1 D 2

E 1

R 1R 2

E 2Arc NonlinearLoad/ Cyclical

SymmetricalAsymmetrical

E1 different from E2R1 different from R2

Vs

Ls RsiS

iL

NonlinearLoad

R L

L L

Arc Type

Temporal time-dependent (Cyclical load)

Volt-Ampere (VL – IL)

Cyclical Load

8

Nonlinear Load ModelsCyclical nonlinear Load

Vs

Ls RsiS iL istator

irotor

imagnetizing

L m

L r

L sR s

rR

)( statorZ s

)( gmagnetizin

Z m

)(rotorZ r

V L

V L1 V L2

irist

im

Alpha: Slip Measure of Loading

Modulated Rectifier Circuit

R dcV d

IdL f

R s L sV s is

R ac

X ac

R ac

L ac

Modulated Loadt

Cyclical Motorized

Converter-Rectifier Modulated

Industrial Motorized

Load

Volt-Ampere (VL – IL)

Modulated Fanning Effect

9

Nonlinear Load Models

R s L sV s is

SMPS-Computer Network

idcR 1

L 1

V cC 1

Diode-Bridge

R Lamp Magnetic Saturation-Transformer

type Nonlinear Load

Fluorescent Lamp

L

Vs

Ls RsiS iL

V L

V feeder

Ballast

Starter

Switch Mode Power Supply (SMPS)

Magnetic Saturation type

Volt-Ampere (VL – IL)

Limiter Type

FL-Starter Ballast

Nonlinear

10

Nonlinear Load Models

Adjustable Speed Drive

C

Nonlinear Load

R sL s

V sis

PCC

M

Rectifier InverterAC Motor

AC Motor and Inverter have been replaced by an equivalent resistor

PCC:point of common coupling

V LL

P in

Adjustable Speed Drive (ASD)

Volt-Ampere (VL – IL)

Dual Loop Nonlinear

11

Switched Modulated Power Filters and Capacitor Compensators

L

R

C

V F

TAF

S

L1

R1

C1

V F

S1

ATAF

V > 0

L2

R2

C2

S2

V < 0

SPF/SCC

C f

iF

S1

S2

C f

L f

R f

A N

(V n)

S2=S1

GTO or (IGBTwith bridge)

Parameters: (C f, L f, R f)

R

C2

L

C1

V F

C-Type

S

Tuned-Arm Filter (TAF) Asymmetrical Tuned-

Arm Filter (ATAF)

TAF + Static Capacitor Compensator C-Type

Filter

MPF/SPF(Family of Filters – Compensators) Developed by Dr. A. M. Sharaf

on/off orPWM

iF2

V F

L1

R1

C1

L2

R2

C2

iF1

Dual-Tuned-Arm Filter

12

Switched Modulated Power Filters and capacitor Compensators

C S1

N

LL

M1

M2

diode Bridge

SPWMon/off

C S2

C PSwitched

Fixed

N

M1

To Load

L CT

CS

S1

CL

S2

S2=S1

M2

Motorized Inrush Loads

• Water Pumps

•A/C

•Refrigeration

•Blower / Fans

Economic Tuned-Arm Power Filter and Capacitor Compensator Scheme (used in S-phase 2 wire loads)

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:1. Dynamic minimum current ripple tracking

2. Dynamic minimum current level

3. Dynamic minimum power tracking

4. Dynamic minimum effective power ripple tracking

5. Dynamic minimum RMS source current tracking

6. Dynamic maximum power factor

7. Minimum Harmonic ripple content

8. 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

Delay

I(k)

I(k-1)

iSK p + K i /s PWM Filter

iFiRef =0 e

PI

Vc

RMSDetector

iL

Dynamic Minimum-RMS Current tracking

Notch Filter

0hrefi

Abs

Reject 60Hz

hi

iSK p + K i /s PWM Filter

iFe

PI

Vc

iL

Minimum Harmonic Reference Content

15

Switching Devices (on/off or PWM)

(a)

(b)

on/offTo GTO

SSR/TriacController-e 0

e0

e 0:Deadband/Bias

on/off

Bias

error

PI Controller

K p + K i /sV c

ton

0

10V

V c=(0-10V)

errorgenerated bythe Controller

V c ton

t on

PWM

0<t on <T s/wT s/w =1/f s/w

0

T s/w switch S1

S2NOT

S2=S1

To GTOSSR/TriacController

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/W=1/fS = (ton + toff) 0<ton<TS/W

1

0

tston

T S/W

g(t)

g(t)=1 switch closedg(t)=0 switch open

toff

16

Switching Devices – PWM Circuits

(1)

(2)

PWM Circuit (Developed by Dr. C. Diduch) for use with Matlab/Simulink

PWM Circuit (Matlab/Simulink/Stateflow-Grundlagen)

17

Concept of Modulated Power Filters (MPF)

L

R

C

V F

TAF

on/off or PWM

V F

IF

GTO, MOSFET,Triac, IGBT

Tune Arm Filter layout

v

t

t

u(t)

-u(t-t o)

u(t)-u(t-t o)

to

to

The Linear Combination of two Unit Step Functions to

describe a Pulse of Amplitude 1 and duration t0.

18

Modulated Tuned Arm Filter (Sym. & Asym.)

Single Line Diagram of System and Modulated / PWM Tuned-Arm Filter

Load is either:

•Symmetrical Arc Type

•SMPS

•Adjustable Speed Drives

•Asymmetrical Arc-type

L

R

C

V F

SMPS-ComputerNetwork

V g

V L

is

iL-totaliF

V s

feeder

utility

TransformerNLL 1

NLL 2

NLL 3

CR 1

L 1

Sample SMPS Load

~

R1= constant or variablyswitched

Dynamic Controller:

-Min. effec. Power

-RMS current tracking

-Min. Harmonic Content

19

Modulated Tuned Arm Filter with (SMPS) Load

Without (THD=74%) With (THD=9%)

20

Modulated Asymmetrical Tuned-Arm Filter

V sV L iL

R T LTfeederR f L f

R s=R T+R f

L s=L T+L f

TransformerUtility

)12( SS dual-

complementaryswitching

(ATAF)

V L

R 1

D A D B

E 1

iL

iL2iL1

)1(12 RR

)1(12 EE

NonlinearAsymmetrical

Load

V F

C2C1

L1

R2

D1 D2

ton1ton2

R1

L2

S1 S2

G

iF

Nonlinear Temporal Load Parameters:

R1=R01+R11sin(wr1*t); E1=E01+E11sin(wr2*t);

R2=R02+R22sin(wr1*t); E2=E02+E22sin(wr2*t);

R2= R1(1+) R01=8 R02=12 R11=2 R22=6 wr1=15

E2= -E1(1+) E01= 46 E02=70 E11=12 E22=35 wr2=5

Dynamic Controller: Dual loop of RMS current tracking and Min. Harmonic Content

Without (THD=42%)

Without (THD=18%)

With (THD=14%)

With (THD=7%)

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

-10

1

-20

2-1

0

1

Ei*r

The Error Diagram

Ev*rE

p*r

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

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.

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

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.

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.

Cont. / Controller DesignCont. / Controller Design

48

The following Figures show the load voltage, current, and active power, reactive power, the active vs. reactive power, and the transmitted power loss; withoutwithout 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, withwith the proposed low cost FACTS Dynamic Capacitor Compensator (DCC).

The following Figures show the load voltage, current, and active power, reactive power, the active vs. reactive power, withwith the proposed low cost FACTS Dynamic Capacitor Compensator (DCC).

50

ConclusionsConclusionsConclusionsConclusions

The paper presents a low cost FACTS Based Capacitor FACTS Based Capacitor Compensator (DCC)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 FACTS Based Capacitor Compensator (DCC)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).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).

The paper presents a low cost FACTS Based Capacitor FACTS Based Capacitor Compensator (DCC)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 FACTS Based Capacitor Compensator (DCC)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).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 [1] Guile, & Paterson, Electrical Power Systems: vol.2, Pergamon international library of science, 1977.library of science, 1977.

[2] A.M.Sharaf, “Harmonic interference from distribution systems”, IEEE [2] A.M.Sharaf, “Harmonic interference from distribution systems”, IEEE Winter Meeting, New York, 1982.Winter Meeting, New York, 1982.

[3] A.M.Sharaf, H.Huang, “Flicker control using rule based modulated passive [3] A.M.Sharaf, H.Huang, “Flicker control using rule based modulated passive power filters”, Electric Power System Research Journal 33 (1995) 49-52.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 [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 Conservation in Utilization Network”, IACPSS, April 6-8, 1997, Al-Ain, UAE, pp 211-212.211-212.

[5] A.M.Sharaf, S.S.Shokralla and A.S.Abd El-Ghaffar, “Efficient Power Tracking [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 using an Error Driven Modulated Passive Filter”, AEIC’ 95, AL-AZHAR Conference, December 16 – 19, 1995.Conference, December 16 – 19, 1995.

[6] A.M.Sharaf, P.Kreidi, “Power Quality enhancement and harmonic reduction [6] A.M.Sharaf, P.Kreidi, “Power Quality enhancement and harmonic reduction using dynamic power filters”, ELECTRIMACS 2002. Montreal, Quebec, Canada, using dynamic power filters”, ELECTRIMACS 2002. Montreal, Quebec, Canada, August 18-21, 2002.August 18-21, 2002.

[7] A.M.Sharaf, P.Kreidi, “Power Quality enhancement using a unified [7] A.M.Sharaf, P.Kreidi, “Power Quality enhancement using a unified compensator and switched filter “, ICREPQ’ 2003, Vigo-Spain, April 9-11, compensator and switched filter “, ICREPQ’ 2003, Vigo-Spain, April 9-11, 2003.2003.

[8] Uzunoglu, M., Kocatepe, C. and Yumurtaci, R. (2004) “Voltage stability [8] Uzunoglu, M., Kocatepe, C. and Yumurtaci, R. (2004) “Voltage stability analysis in the power systems including non-linear loads”, European analysis in the power systems including non-linear loads”, European Transactions on Electrical Power, January–February, Vol. 14, No. 1, pp.41–56.Transactions on Electrical Power, January–February, Vol. 14, No. 1, pp.41–56.

[9] B.Singh, V.Verma, A.Chandra and K.Al-Haddad, “Hybrid filters for power [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 quality improvement”, IEE Proc.Gener.Transm.Distrib., Vol. 152, No.3, May 2005.2005.

[1] Guile, & Paterson, Electrical Power Systems: vol.2, Pergamon international [1] Guile, & Paterson, Electrical Power Systems: vol.2, Pergamon international library of science, 1977.library of science, 1977.

[2] A.M.Sharaf, “Harmonic interference from distribution systems”, IEEE [2] A.M.Sharaf, “Harmonic interference from distribution systems”, IEEE Winter Meeting, New York, 1982.Winter Meeting, New York, 1982.

[3] A.M.Sharaf, H.Huang, “Flicker control using rule based modulated passive [3] A.M.Sharaf, H.Huang, “Flicker control using rule based modulated passive power filters”, Electric Power System Research Journal 33 (1995) 49-52.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 [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 Conservation in Utilization Network”, IACPSS, April 6-8, 1997, Al-Ain, UAE, pp 211-212.211-212.

[5] A.M.Sharaf, S.S.Shokralla and A.S.Abd El-Ghaffar, “Efficient Power Tracking [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 using an Error Driven Modulated Passive Filter”, AEIC’ 95, AL-AZHAR Conference, December 16 – 19, 1995.Conference, December 16 – 19, 1995.

[6] A.M.Sharaf, P.Kreidi, “Power Quality enhancement and harmonic reduction [6] A.M.Sharaf, P.Kreidi, “Power Quality enhancement and harmonic reduction using dynamic power filters”, ELECTRIMACS 2002. Montreal, Quebec, Canada, using dynamic power filters”, ELECTRIMACS 2002. Montreal, Quebec, Canada, August 18-21, 2002.August 18-21, 2002.

[7] A.M.Sharaf, P.Kreidi, “Power Quality enhancement using a unified [7] A.M.Sharaf, P.Kreidi, “Power Quality enhancement using a unified compensator and switched filter “, ICREPQ’ 2003, Vigo-Spain, April 9-11, compensator and switched filter “, ICREPQ’ 2003, Vigo-Spain, April 9-11, 2003.2003.

[8] Uzunoglu, M., Kocatepe, C. and Yumurtaci, R. (2004) “Voltage stability [8] Uzunoglu, M., Kocatepe, C. and Yumurtaci, R. (2004) “Voltage stability analysis in the power systems including non-linear loads”, European analysis in the power systems including non-linear loads”, European Transactions on Electrical Power, January–February, Vol. 14, No. 1, pp.41–56.Transactions on Electrical Power, January–February, Vol. 14, No. 1, pp.41–56.

[9] B.Singh, V.Verma, A.Chandra and K.Al-Haddad, “Hybrid filters for power [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 quality improvement”, IEE Proc.Gener.Transm.Distrib., Vol. 152, No.3, May 2005.2005.

A NOVEL MAXIMUM POWER TRACKING CONTROLLER FOR A STAND-ALONE PHOTOVOLTAIC DC MOTOR DRIVE

A.M. Sharaf, SM IEEEDepartment of Electrical and Computer

EngineeringUniversity 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)

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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 (ωm-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 ΔVc is

β is the specified squashing order (2~3) │Re│ is the magnitude of the hyper-plane

error excursion vector at time instant k

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The loop weighting factors (γw, γI and γp) and the parameters k0 and β 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)=k·Tsample: 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

ωref & ωm vs. time

Iam vs. time

ωm 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(Continue)

Pg vs. Ig & Vg

ωref & ωm vs. time

Iam vs. time

ωm 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 (ωm-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

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 changes[1-3].

New interface technology is needed such as DSSC and other MPF/CCcompensation scheme [1-3].

78

1. 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 excursionsFigure 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, ICCCP’98, Dec.7-10 1998, Muscat, Sultanate of Oman, pp.93-98

94

95

Dr. A. M. Sharaf, SMIEEE

ULTRA HIGH SPEED PROTECTION OF SERIES COMPENSATED TRANSMISSION LINES USING WAVELET TRANSFORMS

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.

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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

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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).

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/ (2*tau)) 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.

Incremental Voltage (Case 1)

The incremental voltage signal was obtained using cycle subtraction.

Figure 2a: Incremental Voltage for Case 1.

Incremental Current (Case 1)

The incremental current signal was obtained using cycle subtraction.

Figure 2b: Incremental Current for Case 1.

Incremental Voltage (Case 2)

The incremental voltage signal was obtained using cycle subtraction.

Figure 3a: Incremental Voltage for Case 2.

Incremental Current (Case 2)

Figure 3b: Incremental Current for Case 2.

The incremental current signal was obtained using cycle subtraction.

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.

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.

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.

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.

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.

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.

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.

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.

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.