Study of Energy Storage System Applications in TVA system

1
Study of Energy Storage System Applications in
TVA system
Presented by Prof. Yilu Liu December 2, 2004, NCSU
Work sponsored by EPRI/TVA, Program Manager
Steve Eckroad FACTS/ESS PSS/E simulations by
Dr. Frank Zhang Generator torque and SuperVar
simulations by Mark Baldwin and Steven Tsai
The Bradley Department of Electrical and Computer
Engineering Virginia Polytechnic Institute
and State University Phone [phone],
Fax [phone] Email Yilu.Liu_at_vt.edu
2
Energy Storage System Applications in TVA System
Part I Electric Arc Furnace (EAF) Caused
Problems and Mitigation by FACTS/ESS
Part II Nashville Area Low Frequency Oscillation
Suppression by FACTS/ESS
Part III X/R Ratio Discussion Part IV Future
Study Needs
3
Part I A Solution for EAF Induced Problems in
TVA Power System by FACTS/ESS
Fig. I-1. The TVA Hoeganaes EAF sub-system
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Part I A Solution for EAF Induced Problems in
TVA System by FACTS/ESS
Fig. I-2. One-line diagram near EAF of the TVA
system. (Note the simulation includes the entire
TVA system and more!!)
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Measured voltage waveform at Hoeganaes
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Part I A Solution for EAF Induced Problems in
TVA Power System by FACTS/ESS
Fig. I-3. The rapid change of power drawn by a
40 MVA EAF.
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Part I A Solution for EAF Induced Problems in
TVA Power System by FACTS/ESS
Fig. I-4. Typical configuration of FACTS/ESS.
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Part I A Solution for EAF Induced Problems in
TVA Power System by FACTS/ESS
Fig. I-5. Output active power of 8MVA FACTS/ESS.
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Part I A Solution for EAF Induced Problems in
TVA Power System by FACTS/ESS
Fig. I-6. Output reactive power of 8MVA
FACTS/ESS.
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Part I A Solution for EAF Induced Problems in
TVA Power System by FACTS/ESS
Fig. I-8. Comparison of PCC bus voltage drop by
active load (33MW), reactive load (24MVAR) and
their combination (33MWj24MVAR).
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Part I A Solution for EAF Induced Problems in
TVA Power System by FACTS/ESS
Fig. I-9. Comparison of PCC bus Vangle changes
by active load (33MW), reactive load (24MVAR) and
the combination (33MWj24MVAR).
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Part I A Solution for EAF Induced Problems in
TVA Power System by FACTS/ESS
Fig. I-10. Comparison Unit 4 generator angle
change by active load (33MW), reactive load
(24MVAR) and their combination (33MWj24MVAR).
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Part I A Solution for EAF Induced Problems in
TVA Power System by FACTS/ESS
Fig. I-13. Oscillations in output active and
reactive power of Unit 4 generator.
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Three Separate Torque oscillations due to EAF
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Part I A Solution for EAF Induced Problems in
TVA Power System by FACTS/ESS
Fig. I-14. Comparison of PCC bus voltage
compensation effects by 8MVA FACTS/ESS. (actual
outputs are 10MVar Statcom, 3.2MW 7.3MVar
FACTS/ESS)
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Part I A Solution for EAF Induced Problems in
TVA Power System by FACTS/ESS
Fig. I-15. Comparison of PCC bus angle
compensation effects by 8MVA FACTS/ESS. (actual
outputs are 10MVar Statcom, 3.2MW 7.3MVar
FACTS/ESS)
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Part I A Solution for EAF Induced Problems in
TVA Power System by FACTS/ESS
Fig. I-16. Comparison of generator angle control
effects by 8MVA FACTS/ESS. (actual outputs are
10MVar Statcom, 3.2MW 7.3MVar FACTS/ESS)
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Part I A Solution for EAF Induced Problems in
TVA Power System by FACTS/ESS
Fig. I-17. Generator output active power
control by 8MVA FACTS/ESS. (actual outputs
10MVar Statcom, 3.2MW 7.3MVar FACTS/ESS)
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Part I A Solution for EAF Induced Problems in
TVA Power System by FACTS/ESS
Fig. I-18. PCC bus voltage control by 50MVA
FACTS/ESS. Actual outputs Statcom 27.5 MVar,
FACTS/ESS 20MW,25MVar.
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Part I A Solution for EAF Induced Problems in
TVA Power System by FACTS/ESS
Fig. II-17. PCC bus angle control by 50MVA
FACTS/ESS. Actual outputs Statcom 27.5 MVar,
FACTS/ESS 20MW,25MVar.
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Part I A Solution for EAF Induced Problems in
TVA Power System by FACTS/ESS
Fig. II-18. Generator angle control by 50MVA
FACTS/ESS Actual outputs Statcom 27.5 MVar,
FACTS/ESS 20MW, 25MVar.
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8 Mvar SuperVAR Compensation PCC Voltage
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Part II TVA Power System Low Frequency
Oscillation Suppression by FACTS/ESS
In this study, we use the Eastern U.S. system
that contains the major eastern portion of the
NERC. The simulated system is comprehensive
containing high level 765kV transmission circuits
and lower voltage distribution circuits. 5 cycle
3-phase short circuit fault north of Nashville.
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Part II TVA Power System Low Frequency
Oscillation Suppression by FACTS/ESS
Fig. II-1. TVA system one-line diagram near
Nashville area.
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Part II TVA Power System Low Frequency
Oscillation Suppression by FACTS/ESS
Fig. II-2. Generator angle oscillations in the 4
sub-areas. (The oscillation frequency is about
0.6 Hz.)
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Part II TVA Power System Low Frequency
Oscillation Suppression by FACTS/ESS
Fig. II-3. Relative generator angle in group
No.4 against Unit4 at Wilson.
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Part II TVA Power System Low Frequency
Oscillation Suppression by FACTS/ESS
Fig. II-4. Relative generator angle of Unit1
(Cumberland), Unit2 (Gallatin), and Unit3
(Kingston) against Unit4 (Wilson).
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Part II TVA Power System Low Frequency
Oscillation Suppression by FACTS/ESS
Fig. II-5. Low frequency oscillation
distribution in the close by areas.
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Part II TVA Power System Low Frequency
Oscillation Suppression by FACTS/ESS
(a) Active power control function of FACTS/ESS
(b) Reactive power control function of FACTS/ESS
Fig. II-6. Control function chart of FACTS/ESS
controller, remote signal for P control.
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Part II TVA Power System Low Frequency
Oscillation Suppression by FACTS/ESS
(a) Unit 4 (Wilson) generator speed deviation.
(b) Unit 4 (Wilson) generator angle.
Fig. II-7. Unit 4 (at Wilson) control effects by
different capacity FACTS/SMES located at
Hoeganaes. (Unit 2 control)
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Part II TVA Power System Low Frequency
Oscillation Suppression by FACTS/ESS
(a) Unit2 (Gallatin) generator rotor speed
deviation.
(b) Unit2 (Gallatin) generator angle.
(c) Unit2 (Gallatin) generator active power
output.
Fig. II-8. Unit2 (at Gallatin) control effects
by different capacity FACTS/SMES located at
Hoeganaes.
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Part II TVA Power System Low Frequency
Oscillation Suppression by FACTS/ESS
(a) FACTS/SMES output active power.
(b) FACTS/ESS output reactive power.
Fig. II-9. FACTS/SMES output active and reactive
power.
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Part II TVA Power System Low Frequency
Oscillation Suppression by FACTS/ESS
Fig. II-10. The relative angle oscillation
between Unit 2 (Gallatin) and Unit 4 (Wilson).
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Part II TVA Power System Low Frequency
Oscillation Suppression by FACTS/ESS
before
after
Fig. II-11. Low frequency oscillation control
results by 50MVA FACTS/SMES.
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Part II TVA Power System Low Frequency
Oscillation Suppression by FACTS/ESS
Fig. II-12. Location of the distributed
FACTS/ESS (local control).
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Part II TVA Power System Low Frequency
Oscillation Suppression by FACTS/ESS
Fig. II-13. Low frequency oscillation control
results by 4x12.5MVA distributed FACTS/SMES.
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Part II TVA Power System Low Frequency
Oscillation Suppression by FACTS/ESS
Fig. II-14. Low frequency oscillation control
results by 4x50MVA distributed FACTS/SMES.
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Energy Storage System Applications in TVA System
Conclusions

• The operation of EAF causes voltage flickers and
  P, Q, speed disturbances of the generators in the
  vicinity of the supply system.

2. FACTS with ESS can better help mitigate
voltage flickers, more effectively, in
suppressing EAF caused generator disturbance in
the nearby supply system.
3. Inter-area mode oscillations in the TVA
system has distinct patterns. Four groups of
generators oscillate against each other around
0.6 Hz.
4. FACTS/ESS can be a good tool to suppress the
low frequency oscillations. The distributed
FACTS/ESS has overall better effectiveness.
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Part III System X/R Ratio Discussion
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Part III System X/R Ratio Discussion
The discussion of X/R ratio should be from the
point of view of the entire upper system, which
means R and X are not just the impedance of the
upper transformers or lines (which could be
1040), they should be the Thevenin impedance
seen from the PCC bus of the upper system (for
TVA EAF case at PCC, Xn/Rn3.001). Both
simulation and calculation confirmed that the
active power drawn by EAF also contributes to
certain voltage flicker (Fig. I-8).
Fig. III-2. Discussion of X/R ratio.
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Part III X/R Ratio Discussion
Fig. III-3. Thevenin equivalent circuit of the
upper system seen at PCC bus from EAF (EAF load
not included in Zth!!)
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Part III System X/R Ratio Discussion
In Fig.I-8, we can also confirm the ratio of
voltage drop caused by 33MW active load and
24MVAR reactive load is about 0.458 in the TVA
system.
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Part III X/R Ratio DiscussionThe 25 bus system
example
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Part III System X/R Ratio Discussion25 bus
sample system R, X parameters
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Part III System X/R Ratio Discussion25 bus
sample system R, X parameters
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Part III System X/R Ratio DiscussionExample X/R
calculation
We use the generator at bus 101 data and the
typical transmission line data in the 25 bus
sample system. We assume the output active power
of generator is 900MW (the active power output of
generator at 101 bus), the total load PLoad is
810MW (90 of active generation of generator at
bus 101) and QLoad is 243MVAR (30 of PLoad).
VLLbase is 21.6kV and Sbase is 100MVA. The
impedance of the generator is Zs 0.01j0.3 pu
(generator data of 101 bus in the sample system).
The impedance of the transmission line is ZL1
ZL2 0.003j0.03 pu.   As shown in
Fig. 2-17, we can compute the RthjXth0.089j0.08
5?, and Xn/Rn ?1. In this example, the values of
Xth and Rth are not precise but enough to
demonstrate that the system X/R ratio is affected
significantly by the load. After adding
impedances of adjacent transformer and line, X/R
is still not large enough to omit R at EAF
bus.   In our 25 bus system system Thevenin
Impedance (RnjXn) seen at PCC bus is 0.00782
j0.02389 pu, which was calculated precisely in
PSS/E (PSS/E has the function of Thevenin
Impedance Calculation.). The Xn/Rn ratio is about
3.055. In this case, the active load can cause
obvious voltage drop as seen in our simulation
results. The voltage ratio is 0.445. In other
words, the active power of FACTS/ESS can play an
obvious role in voltage compensation as shown in
the study results.
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Related Publications from Virginia Tech Study

• Li Zhang, Yilu Liu, Michael R. Ingram, Dale T.
  Bradshaw, Steve Eckroad, and Mariesa L. Crow,
  Bulk Power System Low Frequency Oscillation
  Suppression By FACTS/ESS, Power System
  Conference Exposition, New York, October 2004.
• Li Zhang, Yilu Liu, Michael R. Ingram, Dale T.
  Bradshaw, Steve Eckroad, and Mariesa L. Crow,
  EAF Voltage Flicker Mitigation By FACTS/ESS,
  Power System Conference Exposition, New York,
  October 2004.
• Li Zhang and Yilu Liu, Coordination of SMES
  Control and Under Frequency Load Shedding,
  Second International Conference on Critical
  Infrastructures, Grenoble France, October 2004.
• Mark Baldwin The Effect of Arc Furnace Operation
  on Generator Torque Oscillations, Power System
  Conference Exposition, New York, October 2004.
• Steven Tasi, Yilu Liu, Michael R. Ingram
  SuperVar as Dynamic Reactive Compensation Source
  for TVA Arc Furnace, (to be submitted to IEEE
  PES 2005 general meeting)
• Li Zhang, Yilu Liu, Michael R. Ingram, Dale T.
  Bradshaw, Steve Eckroad, and Mariesa L. Crow,
  Bulk Power System Low Frequency Oscillation
  Suppression By Distributed FACTS/ESS, (to be
  submitted to IEEE Transmissions)
• Li Zhang, Yilu Liu, Michael R. Ingram, Dale T.
  Bradshaw, Steve Eckroad, and Mariesa L. Crow,
  FACTS/ESS Allocation Research for Damping Bulk
  Power System Low Frequency Oscillation, (to be
  submitted to PESC05, Brazil)
• Li Zhang and Yilu Liu, Coordination of UFLS and
  UFGC by Application of D-SMES, (to be submitted
  to IEEE PES 2005 general meeting)

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FUTURE STUDY NEEDS

• The energy storage system application in
  the Tennessee Valley Authority system is a
  complex task. The content in this report only
  touched a very small portion of it. A complete
  study could include but not be limited to the
  following aspects.
•  
• 1. Full analysis of potential applications of
  energy storage system in TVA
• include power flow control, oscillation
  damping, and voltage control, uneven power flow
  through the system (loop flows), transient and
  dynamic instability, subsynchronous oscillations,
  etc.  
• 2. The control coordination of the EAF caused
  problems and LFO by one concentrated ESS
• In this report, we studied solving the EAF
  induced problems and LFO by using the energy
  storage devices individually. It has economical
  benefit to use one ESS to help with the EAF
  induced problems and LFO together at the same
  time. Special control scheme will be needed for
  dual purpose control.
• 3. The capacity choice of the centralized ESS
• The optimization of the capacity choice of
  the ESS will be an important practical issue. 

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FUTURE STUDY NEEDS

• 4. The location choice of the centralized ESS
• As the simulation results indicated, the
  location of the centralized ESS compensators play
  an important role in the control effect. If the
  centralized compensation is preferred, the choice
  of the location of these compensators needs to be
  studied.
• 5. The application of Distributed ESS
• The Distributed Energy Storage System
  (D-ESS) is an new application issue of energy
  storage technology. As it is shown in our study,
  distributed energy storage devices can play
  certain unique role in damping the inter-area
  mode low frequency oscillation within a wide
  area. Some of the benefits of using the
  distributed energy storage device are
• Faster voltage recovery when compared
  with centralized approach in general.
•     Distributed sources.
• Modular design to meet future load
  growth and portable in case it has to be
• relocated.
• The application (including the
  choice of size, location, and control methods)
• of distributed energy storage
  devices should be optimized.
•  

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FUTURE STUDY NEEDS

• 6. Advanced control schemes
• We only use the simplest possible
  control in our study. The choice of control
  schemes are critical for the optimal utilization
  of the energy storage devices. The good control
  scheme can make the energy storage devices more
  flexible and efficient to use.
• 7. Wide area measurement based control
• In our study, the remote control was
  implemented by the application of wide area
  measurements from PMUs and FNET as inputs. As
  some power system problems like the inter-area
  mode low frequency oscillations span a wide area,
  the wide area measurement and control system will
  be more effective to solve such kinds of problem.
  The controller design can be potentially a lot
  simpler with more available information as
  inputs. 
• 8. Compare SuperVar with StatCom
• Preliminary study of SuperVar as
  dynamic Var source at Virginia Tech and future
  work need to compare it with StatCom for the
  impact on generator torque stress relief.
• 9. SCAP models still needed for PSS/E and
  EMTDC
• Need to developing SCAP model for PSS/E
• SCAP modeling for EMTDC is still at very
  early stage
• 10. ESS vs FACTS cost study
•