Flexible AC Transmission FACTS-Technology and Novel Flexible AC Transmission FACTS-Technology and Novel Control Strategies For Power System Control Strategies For Power System

Stability EnhancementStability Enhancement

Mohamed Shawky ElMoursiMohamed Shawky ElMoursi

SupervisorSupervisor

Prof. Dr. A. M. Sharaf, P.Eng.Prof. Dr. A. M. Sharaf, P.Eng.

Electrical and Computer Engineering DepartmentElectrical and Computer Engineering DepartmentUniversity of New BrunswickUniversity of New Brunswick

October 20, 2004October 20, 2004

CONTENTCONTENT

Voltage stabilityVoltage stability

Harmonic/ SSR stabilityHarmonic/ SSR stability

Renewable Dispersed Energy SystemsRenewable Dispersed Energy Systems

FACTSFACTS

Flexible AC Transmission System (Facts) is a new integrated Flexible AC Transmission System (Facts) is a new integrated

concept based on power electronic switching converters and dynamic concept based on power electronic switching converters and dynamic

controllers to enhance the system utilization and power transfer capacity as controllers to enhance the system utilization and power transfer capacity as

well as the stability, security, reliability and power quality of AC system well as the stability, security, reliability and power quality of AC system

interconnectionsinterconnections..

OPPORTUNITIESOPPORTUNITIES

Control power so that it flows on the desired routes.Control power so that it flows on the desired routes.

Increase loading capacity of transmission lines.Increase loading capacity of transmission lines.

Prevent blackouts.Prevent blackouts.

Improve generation productivity.Improve generation productivity.

Effective use of upgrading/ uprating. Effective use of upgrading/ uprating.

FACTS KEY DEVICESFACTS KEY DEVICES

Static Synchronous Compensator (STATCOM)Static Synchronous Compensator (STATCOM)

Static Synchronous Series Compensator (SSSC)Static Synchronous Series Compensator (SSSC)

Unified Power Flow Controller (UPFC)Unified Power Flow Controller (UPFC)

STATIC SYNCHRONOUS COMPENSATOR (STATCOM)STATIC SYNCHRONOUS COMPENSATOR (STATCOM)

It is a static synchronous generator as shunt static var compensator whose It is a static synchronous generator as shunt static var compensator whose

capacitive or inductive current can be controlled independent of the system capacitive or inductive current can be controlled independent of the system

voltage.voltage.

The STATCOM scheme in parallel with AC power grid system and is The STATCOM scheme in parallel with AC power grid system and is

controlled by a dynamic controller as shown in Fig.1.controlled by a dynamic controller as shown in Fig.1.

Fig.1 Sample three-Bus study test system with the STATCOM located

at bus B2 to stabilize the AC system

Novel ControllerNovel Controller

The new control system is based on a The new control system is based on a

decoupled control strategy using both decoupled control strategy using both

direct and quadrature current direct and quadrature current

components of the STATCOM AC components of the STATCOM AC

current.current.

The operation of the STATCOM The operation of the STATCOM

scheme is Validated in both the scheme is Validated in both the

capacitive and inductive modes of capacitive and inductive modes of

operation.operation. Fig. 2 Proposed STATCOM Decoupled Control System

Preliminary Simulation ResultsPreliminary Simulation Results

0 .0 0 0 .4 0 0 .8 0 1 .2 0 1 .6 0 2 .0 0

0 .0 0

0 .4 0

0 .8 0

1 .2 0

T im e (S ec)

VL

L in e V o ltag e

V L in e

0 .0 0 0 .4 0 0 .8 0 1 .2 0 1 .6 0 2 .0 0

-0 .4 0

0 .0 0

0 .4 0

0 .8 0

1 .2 0

T im e (S ec )P

& Q

of

the

STA

TC

OM

A c tive & R ea ctive p ow er o f S T A T C O M

P

Q

0.0 0 0 .4 0 0 .8 0 1 .2 0 1 .6 0 2 .0 0

-2 .0 0

-1 .0 0

0 .0 0

1 .0 0

2 .0 0

T im e (S ec )

Id &

Iq

of t

he S

TA

TC

OM

d irect & q u a d ra tu re o f S T A T C O M

P

Q

0 .0 0 0 .4 0 0 .8 0 1 .2 0 1 .6 0 2 .0 0

-4 .0 0

-2 .0 0

0 .0 0

2 .0 0

4 .0 0

T im e (S ec )

Id &

Iq

of t

he T

rans

mis

sion

Lin

e

T ra n sm iss io n L in e d -q cu rren ts (p u )

Id

Iq

0 .00 0 .40 0 .80 1 .20 1 .60 2 .00

-2 .00

-1 .00

0 .00

1 .00

2 .00

3 .00

T im e (S ec)

P &

Q o

f th

e T

rans

mis

sion

Lin

e

A c tive & R eactive P ow er o f th e T ran sm ission L in e

P

Q

0 .0 0 0 .4 0 0 .8 0 1 .2 0 1 .6 0 2 .0 0

-0 .4 0

0 .0 0

0 .4 0

0 .8 0

1 .2 0

T im e (S ec)

Vdc

C a p a cito r d c V o lta g e (p u )

V d c

System is subjected to load switching at t=0.5 sec (inductive load added), t=1 sec (capacitive load added) and t=1.5 (Both inductive and capacitive load removed)

STATIC SYNCHRONOUS SERIES COMPENSATOR

It is a static synchronous generator operated without an external energy

source as a series compensator.

The o/p voltage is in quadrature with and controllable independently of the

line current.

It is increase or decrease the overall reactive voltage drop across the line

and thereby controlling the transmitted electric power.

Fig. 3 Single line diagram representing the series SSSC scheme interfaced at sending end of the Transmission line (Bus B1)

Novel ControllerNovel Controller

The main function of the SSSC is

to regulate the TL power flow PL.

This can be accomplished by

either direct control of the line

current or indirect control by

compensating for the TL

impedance, Xs via a

compensating injected voltage,

Vs. Fig. 4. Control Structure of the SSSC scheme.

Xref = Negative Vs lags IL by 90° plus (Capacitive Compensation)

Xref = Positive Vs Leads IL by 90° plus (Inductive Compensation)

SUPPLEMENTARYT CONTROL LOOP DESIGN IN SSSCSUPPLEMENTARYT CONTROL LOOP DESIGN IN SSSC

To enhance the dynamic performance To enhance the dynamic performance

of the SSSC device an supplementary of the SSSC device an supplementary

regulator loop is added using the dc regulator loop is added using the dc

capacitor voltage. capacitor voltage.

The operation of the SSSC scheme is The operation of the SSSC scheme is

validated in both the capacitive and validated in both the capacitive and

inductive modes of operation under inductive modes of operation under

severe disturbance such as switching severe disturbance such as switching

loads and fault condition loads and fault condition

Fig.5. Supplementary regulator for the SSSC controller to reduce oscillatory

Simulation Results For SSSCSimulation Results For SSSC

Fig. 6. Simulation results of the SSSC in capacitive mode

Fig. 7. Simulation results of the SSSC in inductive mode

UNIFIED POWER FLOW CONTROLLER (UPFC)UNIFIED POWER FLOW CONTROLLER (UPFC)

The UPFC scheme consists of two The UPFC scheme consists of two basic switching power converter basic switching power converter namely shunt and series converters namely shunt and series converters connected to each other through a dc connected to each other through a dc link capacitor.link capacitor.

The shunt converter operates exactly The shunt converter operates exactly as STATCOM for reactive as STATCOM for reactive power compensation and voltage power compensation and voltage stabilization.stabilization.

The series converter operates as The series converter operates as SSSC to control the real power flowSSSC to control the real power flow

Fig.8. FACTS UPFC controller scheme

PROPOSED NOVEL CONTROL STRATEGY

The developed novel control strategy

for the UPFC scheme is based on the

magnitude and angle of series

inserted voltage and shunt reactive

current.

Novel Control in the STATCOM Novel Control in the STATCOM shunt converter 1shunt converter 1

SSSC-Converter (2) controllerSSSC-Converter (2) controller

Fig.9. Proposed STATCOM Decoupled Current Control System for the shunt converter (1)

Fig. 10. Control Block diagram of SSSC series converter (2) scheme.

The system is subjected to severe disturbance single line to ground fault at load bus at time 0.3 sec for a duration of 80 ms.

Simulation Results for (UPFC)Simulation Results for (UPFC)

Fig. 11. The UPFC digital Simulation Results Under single phase Fault Condition at load bus

Alpha vs time Iqref,Iqm vs time Id, Iq of STATCOM vs time P & Q of STATCOM vs time

P, Q of SSSC vs time Vdc vs time Line Voltage vs time Line voltage and current vs time

CAPABLITIES OF DIFFERENT FACTS CONTROLLERSCAPABLITIES OF DIFFERENT FACTS CONTROLLERS

ControllerController Voltage Voltage Control Control

Transient Transient stabilitystability

Damping Damping Power Power

Oscillations Oscillations

Reactive Reactive Power Power

CompensationCompensation

Power Flow Power Flow ControlControl

SSR SSR

MitigationMitigation

STATCOMSTATCOM XX xx xx xx

SSSCSSSC XX xx xx xx xx xx

UPFCUPFC XX xx xx xx xx XX

POWER QUALITY ENHANCEMENTPOWER QUALITY ENHANCEMENT

This chapter studies the power system power quality and harmonics and This chapter studies the power system power quality and harmonics and

SSR/ Tortional stability enhancement to reduce harmonics, improve the SSR/ Tortional stability enhancement to reduce harmonics, improve the

power quality and enhance the system harmonic stability. power quality and enhance the system harmonic stability.

Three different cases were studied in order to improve power quality and Three different cases were studied in order to improve power quality and

enhance system stability using a enhance system stability using a novel Active Power Filternovel Active Power Filter (APF) (APF)

combining with and combining with and Tuned arm filterTuned arm filter switched capacitive compensation.switched capacitive compensation.

A COMBINED CAPACITIVE COMPENSATION AND A COMBINED CAPACITIVE COMPENSATION AND ACTIVE POWER FILTERACTIVE POWER FILTER

The Power Filter Scheme

The power filter scheme consists

of both a passive filter and active

filter. The passive filter removes

any load harmonics just as a

conventional one does and the

added active filter plays a role in

improving the filtering action. Fig. 12.a. Sample study of the unified power system

Novel Tri Loop Dynamic Controller DesignNovel Tri Loop Dynamic Controller Design

The proposed SSCC capacitor switching controller is an error driven, error-scaled self adjusting nonlinear tri loop dynamic controller used the load voltage, instantaneous and RMS load currents deviation signals as shown in Fig 12 (a, b).

Fig. 12.a. Sample study of the unified power system

Developed By Dr. Sharaf

222Re Iiv eee

(Excursion- Level Magnitude)

Fig. 12.b. The SSCC series capacitor switching compensator scheme using two stage compensation per phase dynamic capacitor switching

Simulation ResultsSimulation Results

Load Voltages

Time (sec)

Voltage of phase a

1.04 1.13 1.22 1.31 1.4 1.49-3

+1VLa

Voltage of phase b

1.04 1.13 1.22 1.31 1.4 1.49-1

+1.25VLb

Voltage of phase c

1.04 1.13 1.22 1.31 1.4 1.49-1.25

+1.25VLc

Voltage at Load Bus

Time (sec)

Phase Voltage Va

1.03 1.128 1.226 1.324 1.422 1.52-1.25

-0.75

-0.25

+0.25

+0.75

+1.25Va

Phase Voltage Vb

1.03 1.128 1.226 1.324 1.422 1.52-1.25

-0.75

-0.25

+0.25

+0.75

+1.25Vb

Phase Voltage Vc

1.03 1.128 1.226 1.324 1.422 1.52-1.25

-0.75

-0.25

+0.25

+0.75

+1.25Vc

Power capacity Transfer

Time (sec)

P&Q

0 0.6 1.2 1.8 2.4 3 -5

+1

+7

+13

+19

+25P Q

Capacity of power transfer

Time (sec)

power transfer P&Q

0 0.6 1.2 1.8 2.4 3 -10

+6

+22

+38

+54

+70P Q

Fig. 13. The simulation results when the system subjected to 3- phase fault disturbance

Without SSCC & APF With SSCC & APF

A COORDINATED CAPACITIVE COMPENSATION AND A COORDINATED CAPACITIVE COMPENSATION AND TUNED ARM FILTER TUNED ARM FILTER

This chapter presents a nonlinear This chapter presents a nonlinear

coordinated dynamic error driven coordinated dynamic error driven

scaled error-controller for both scaled error-controller for both

the static series capacitor the static series capacitor

switching compensator SSCC and switching compensator SSCC and

the added tuned arm filter TAF, the added tuned arm filter TAF,

for the for the enhancement of voltage, enhancement of voltage,

transient stability, capacity of tie transient stability, capacity of tie

line power transfer and the power line power transfer and the power

qualityquality. .

Fig. 13. Single line diagram sample study of the unified power system with one novel

coordinated CC/TAF filter

SSCC switched/modulated Tuned Arm Filter ControllerSSCC switched/modulated Tuned Arm Filter Controller

The proposed self adjusting Tri-loop error scaled controller is based on The proposed self adjusting Tri-loop error scaled controller is based on

the the load voltage, RMS source current and the dynamic current ripple load voltage, RMS source current and the dynamic current ripple

deviation signalsdeviation signals..

Fig 13. Proposed novel tri loop error-driven, error -scaled Tri-loop dynamic feed back controller.

Developed By Dr. Sharaf

Simulation Results For SSCC/TAF SchemeSimulation Results For SSCC/TAF Scheme

Without SSCC & TAF With SSCC & TAF

Fig 14. the p.u. load voltage at bus 4, terminal voltage at bus 2, total load current iL and the induction load current when the system subjected to 3 phase fault at bus 2

Fig 15. The Power Transfer levels P& Q without and with SSCC&TAF

Fig 16. Comparison of the load voltage, load current and %THD voltage and current without and with (SSCC & TAF)

Renewable EnergyRenewable Energy

The research will investigate the use of renewable dispersed energy system The research will investigate the use of renewable dispersed energy system

(wind-small hydro, hybrid scheme) and resulting grid interface problems (wind-small hydro, hybrid scheme) and resulting grid interface problems

and need for effective mitigative FACTS-based solution. Both stand-alone and need for effective mitigative FACTS-based solution. Both stand-alone

and grid connect wind energy conversion will be studiedand grid connect wind energy conversion will be studied

CONCLUSIONCONCLUSION

The research investigates FACTS topologies & novel control strategies for The research investigates FACTS topologies & novel control strategies for

voltage stability enhancement, T.L power flow control and harmonic/ SSR voltage stability enhancement, T.L power flow control and harmonic/ SSR

mode stabilization of an interconnected AC system.mode stabilization of an interconnected AC system.

The use of FACTS devices in renewable energy utilization is also studied The use of FACTS devices in renewable energy utilization is also studied

for small Hydro/ Wind hybrid renewable energy scheme.for small Hydro/ Wind hybrid renewable energy scheme.

FUTURE WORKFUTURE WORK

Validation of (UPC) Universal Power Compensator controllable scheme Validation of (UPC) Universal Power Compensator controllable scheme

using the dynamic error driven controllers (P, Q) in SSR-stability using the dynamic error driven controllers (P, Q) in SSR-stability

enhancement.enhancement.

Application of the (UPC) Universal Power Compensator using dual Tri Application of the (UPC) Universal Power Compensator using dual Tri

loop stabilization control for wind & small hydro.loop stabilization control for wind & small hydro.

ACCEPTED PUBLICATIONACCEPTED PUBLICATION

A.M. Sharaf and M. S. El-MoursiA.M. Sharaf and M. S. El-Moursi, " A Novel Dynamic Controller For Stability Enhancement Using Capacitive Series , " A Novel Dynamic Controller For Stability Enhancement Using Capacitive Series Compensators" Compensators" 2004 IEEE International Symposium on Industrial Electronics,2004 IEEE International Symposium on Industrial Electronics, May 4-7 , 2004, Palais des Congrès May 4-7 , 2004, Palais des Congrès

Expositions, Expositions, Ajaccio, France.Ajaccio, France.

A.M. Sharaf and M. S. El-MoursiA.M. Sharaf and M. S. El-Moursi" Stability And Power Quality Enhancement Using A Coordinated Capacitive " Stability And Power Quality Enhancement Using A Coordinated Capacitive Compensation And Tuned Arm Filter" , Compensation And Tuned Arm Filter" , the 29th Annual Conference of the IEEE Electronics Society Sundaythe 29th Annual Conference of the IEEE Electronics Society Sunday , November , November

2-Thursday, November 6, 2003 conference Center, Roanoke , Virginia, USA.2-Thursday, November 6, 2003 conference Center, Roanoke , Virginia, USA.

A.M. Sharaf and M. S. El-MoursiA.M. Sharaf and M. S. El-Moursi," Stability And Power Quality Enhancement Using A Combined ," Stability And Power Quality Enhancement Using A Combined Capacitive Compensation And Active Power Filter" Capacitive Compensation And Active Power Filter" ICECS 2003, 10th IEEE International Conference ICECS 2003, 10th IEEE International Conference

onon ElectronicsElectronics, Circuits and Systems, 14.12.2003-17.12.2003, , Circuits and Systems, 14.12.2003-17.12.2003, Sharjah, United Arab Emirates.Sharjah, United Arab Emirates.

A.M. Sharaf and M. S. El-MoursiA.M. Sharaf and M. S. El-Moursi," Voltage Stabilization And Reactive Compensation Using A FACTS- ," Voltage Stabilization And Reactive Compensation Using A FACTS- STATCOM Scheme"STATCOM Scheme" IEEE Power Delivery Trans. Proc. 2004. IEEE Power Delivery Trans. Proc. 2004.

A.M. Sharaf and M. S. El-MoursiA.M. Sharaf and M. S. El-Moursi," Transmission System Reactive Compensation And Stability ," Transmission System Reactive Compensation And Stability Enhancement Using A 48-Pulse Static Synchronous Series Compensator" Enhancement Using A 48-Pulse Static Synchronous Series Compensator" IEEE Power Delivery Trans. IEEE Power Delivery Trans.

Proc. 2004.Proc. 2004.

A.M. Sharaf and M. S. El-MoursiA.M. Sharaf and M. S. El-Moursi," Power System Stabilization And reactive Compensation ," Power System Stabilization And reactive Compensation Using FACTS-Unified Power Flow Controller" Using FACTS-Unified Power Flow Controller" IEEE Power Delivery Trans. Proc. 2004.IEEE Power Delivery Trans. Proc. 2004.

SUBITTED JOURNAL PAPERSSUBITTED JOURNAL PAPERS