C

1. WOLLO UNIVERSITY
KOMBOLCHA INSTITUTE OF TECHNOLOGY
SCHOOL OF ELECTRICAL AND COMPUTER
ENGINEERING
MASTER OF SCIENCE IN POWER SYSTEM
ENGINEERING
Reviewing Article
TITLE: - Effects of FACTS Devices on a Power System
Which Includes a Large Wind Farm
Authors: Wei Qiao, Student Member, IEEE, Ronald G. Harley, Fellow, IEEE, and
Ganesh K.Venayagamoorthy, Senior Member, IEEE
Prepared by: BINIAM HAILEMARIAM ……SGSR/0316/15
SUBMITED TO: ASSEFA SISAY (ASS.PROFF)
JANUARY , 2024
KOMBOLCHA, ETHIOPIA

2. Abstract
This paper explores the integration of Flexible AC Transmission System (FACTS) devices,
specifically a STATCOM and an SSSC, into a 12-bus multi machine benchmark power system
with a large wind farm, aiming to address operational challenges like voltage regulation, power
flow control, transient stability, and power oscillation damping in the face of increasing
renewable energy penetration and competitive electricity markets.
I. INTRODUCTION
The introduction of the article provides a comprehensive overview of the challenges faced by
power systems due to the increasing penetration of renewable energy, specifically wind power. It
highlights the issues related to induction generators in wind turbines, emphasizing the impact of
grid faults on voltage collapse. The evolving role of wind power in large-scale power systems is
discussed, acknowledging the need for wind farms to provide voltage and frequency support as
their penetration grows. The article also recognizes the challenges arising from the deregulated
electricity industry, leading to congestion in transmission systems.
The role of Flexible AC Transmission System (FACTS) devices, particularly STATCOM and
SSSC, is introduced as a potential solution to address operating problems in power systems. The
distinction between shunt FACTS (STATCOM) and series FACTS (SSSC) devices is explained,
along with their capabilities in providing voltage support, power flow control, transient stability
improvement, and power oscillation damping.
Strengths
1. Comprehensive Coverage: The introduction provides a thorough overview of the challenges
posed by renewable energy integration, addressing both technical issues related to wind turbines
and broader concerns in the electricity industry.
2. Clear Explanation of FACTS Devices: The distinction between shunt and series FACTS
devices is well-explained, and their potential applications in addressing power system challenges
are highlighted.
Weaknesses
1. Lack of Specifics: While the introduction sets the stage for the importance of FACTS devices,
it does not delve into specific details of the proposed solutions for the 12-bus multimachine
benchmark power system. Readers may be left wanting more information on the methodology
and specific outcomes.
2. Limited Citations: The introduction lacks citations to specific studies or data, which could
strengthen the credibility of the presented information. Including references to relevant research
would enhance the academic rigor of the article.

3. 3. Assumption of Reader Knowledge: The article assumes a certain level of familiarity with
power systems and FACTS devices, which might make it less accessible to readers without a
strong background in the field.
II. POWER SYSTEM MODEL
The power system model in the article is an extension of the original 4-machine 12-bus
benchmark power system, incorporating a large wind farm, a STATCOM, and an SSSC. The
system comprises six 230-kV buses, two 345-kV buses, and four 22-kV buses, covering three
geographical areas with different generation and load characteristics. The wind farm, represented
by G4, is in Area 2, and a STATCOM is placed at bus 6 to provide voltage support for the wind
farm. An SSSC is added at one end of the 345-kV transmission line 7-8 to relieve congestion and
enhance power oscillation damping. The generators are modeled with details like automatic
voltage regulator (AVR), exciter, and turbine governor dynamics.
Strengths
1. Realistic System Representation: The power system model reflects a realistic and complex
scenario by considering different geographical areas, types of generators, and transmission line
configurations. This enhances the relevance of the study to real-world power systems.
2. Inclusion of Wind Farm: Incorporating a large wind farm (G4) into the power system model
reflects the contemporary trend of increasing wind power penetration. This allows the study to
address challenges specific to wind generation integration.
3. Utilization of FACTS Devices: The placement of a STATCOM for dynamic voltage support
for the wind farm and an SSSC to relieve congestion and improve power oscillation damping
demonstrates the practical application of FACTS devices in addressing power system challenges.
Weaknesses
1. Lack of Detailed Explanation: While the article mentions the addition of a wind farm,
STATCOM, and SSSC to the power system model, it lacks a detailed explanation of the specific
parameters, settings, and considerations for these additions. Readers may desire more clarity on
the modeling details.
2. Assumption of Modeling Tools: The article mentions simulation in the PSCAD/EMTDC
environment without providing a justification for this choice or explaining the advantages and
limitations of this tool. Details on simulation methodologies and validation processes are not
discussed.
Overall Assessment
The power system model presented in the article is robust in its representation of a complex
power system scenario, incorporating wind generation and FACTS devices. However, it could

4. benefit from more detailed explanations of the added components, consideration of different
modeling tools, and exploration of sensitivity analyses to enhance the clarity, reliability, and
generalizability of the study.
III. WIND FARM MODEL
The wind farm model in the article employs an aggregated representation, combining over one
hundred individual wind turbines and Doubly Fed Induction Generators (DFIGs) into a single
equivalent DFIG driven by a unified wind turbine. Each individual wind turbine and DFIG
corresponds to a 3.6 MW wind turbine generator system. The DFIG configuration includes a
wound-rotor induction machine fed from both stator and rotor sides. A partial-load variable
frequency converter (VFC) controls the power flow between the rotor circuit and the grid. The
VFC consists of two four-quadrant IGBT PWM converters, connected back-to-back with a dc-
link capacitor. The model includes a crow-bar for rotor-side converter (RSC) protection during
grid faults.
The control of the VFC involves RSC control and grid-side converter (GSC) control. The RSC
governs stator-side active and reactive powers independently through vector control, and the
GSC aims to keep the dc-link voltage constant while regulating reactive power.
For transient stability studies, a two-mass model is used to represent the wind turbine generator
shaft system. The mechanical power extracted from the wind is calculated based on air density,
rotor area, wind speed, and power coefficient.
Strengths
1. Detailed Wind Farm Representation: The model offers a detailed representation of the wind
farm, considering individual wind turbines and DFIGs, providing a realistic approach to studying
the impact of wind power on the power system.
2. Comprehensive Control System: The article presents a comprehensive control system for the
VFC, involving both RSC and GSC controls. The inclusion of protection mechanisms like the
crow-bar enhances the robustness of the wind farm model.
Weaknesses
1. Complexity and Lack of Clarity: The detailed technical descriptions of the VFC control and
other components may be challenging for readers without a strong background in power systems
and control engineering, potentially limiting accessibility.
2. Assumptions and Lack of Validation: The article introduces various assumptions, such as the
power coefficient being a function of the tip speed ratio and blade pitch angle, without detailed
discussion or validation. A more thorough explanation of these assumptions and their impact on
results would enhance the credibility of the model.

5. Vdc
dc
V *
dv
V *
i
qv
Fig. 5. Overall control scheme of the STATCOM
3. Limited Explanation of Two-Mass Model: The article mentions the use of a two-mass model
for transient stability studies but provides limited explanation or justification for this choice. A
more in-depth discussion of the model selection would improve the reader's understanding.
Overall Assessment
The wind farm model presented in the article is comprehensive and detailed, capturing the
intricacies of individual wind turbines and DFIGs. However, the complexity of the technical
details and the lack of clarity in certain aspects may pose challenges for readers. A more
thorough explanation of assumptions, validation, and model selection would strengthen the
overall presentation of the wind farm model.
IV. FACTS DEVICES
The article discusses the modeling and control schemes of two Flexible AC Transmission
System (FACTS) devices: the Static Synchronous Compensator (STATCOM) and the Static
Synchronous Series Compensator (SSSC). Both devices are modeled as Pulse Width Modulation
(PWM) voltage-source converters, utilizing GTO thyristors in appropriate multi-phase circuit
configurations with a dc-link capacitor. The STATCOM is a shunt-connected device aimed at
voltage support, while the SSSC is a series-connected device designed for power oscillation
damping in a transmission line.
Static Synchronous Compensator (STATCOM)
Objective: The primary objective of the STATCOM is to regulate the voltage at the Point of
Common Coupling (PCC) rapidly and maintain the dc-link voltage constant. This helps enhance
the capability of the wind farm to ride through transient disturbances in the grid.
Control Scheme: The overall control scheme involves generating a set of balanced three-phase
sinusoidal voltages with controllable amplitude and phase angle. The control scheme aims to
regulate the voltage at the PC

6. P* 78
Fig. 7. Schematic diagram of the SSSC external damping controller
Strengths
1. Clear Objective: The article clearly states the primary objective of the STATCOM, which is to
regulate voltage at the PCC, enhancing wind farm capability during transient disturbances.
2. Simplified Control Scheme: The control scheme is presented in a clear and concise manner,
making it accessible to readers. The focus on voltage regulation is emphasized.
Weaknesses
1. Lack of Specifics: While the article mentions the control scheme, it lacks specific details about
the parameters and settings used in the control strategy. More information on the internal
workings could enhance clarity.
Static Synchronous Series Compensator (SSSC)
Objective: The SSSC, as a series FACTS device, injects a controllable voltage in quadrature with
the line current, providing controllable capacitive or inductive reactance compensation. It is also
designed to improve damping of low-frequency power oscillations in a power network.
Control Scheme: The SSSC's internal control scheme involves ensuring that the injected
controllable voltage remains in quadrature with the transmission line current. Additionally, an
external controller, known as CONVEC, is employed to damp transient power oscillations.
Strengths
1. Comprehensive Control Scheme: The article provides a detailed internal control scheme for
the SSSC, addressing the need for the injected voltage to be in quadrature with the line current.
2. Inclusion of External Controller (CONVEC): The use of an external controller to damp
transient power oscillations adds a layer of sophistication to the SSSC's control strategy.
Weaknesses

7. 1. Complexity: The detailed technical description of the internal control scheme and the
CONVEC may be complex for some readers, potentially requiring more clarity or visual aids.
2. Parameter Selection Discussion: Similar to the STATCOM, the article lacks in-depth
discussions on the rationale behind specific parameter selections for the SSSC. Providing
insights into parameter choices could improve transparency.
Overall Assessment
The article provides a solid overview of the modeling and control schemes of STATCOM and
SSSC, emphasizing clear objectives for each device. However, more detailed information on
internal workings and parameter choices, along with potential simplifications or visual aids,
could enhance reader understanding.
V. SIMULATION RESULTS
The simulation results presented in the article focus on the effects of Flexible AC Transmission
System (FACTS) devices, specifically the Static Synchronous Compensator (STATCOM) and
the Static Synchronous Series Compensator (SSSC), on a 12-bus power system with a large wind
farm. The study examines the system's responses to various transient disturbances, such as
transmission congestion relief, short circuits, and the dynamic performance of the wind farm.
Key Simulation Results
A. Transmission Congestion Relief by the SSSC
- SSSC application on line 7-8 is shown to relieve transmission congestion between Areas 1 and
3.- Active power flow in line 1-6 is reduced, staying within the capacity limit, while line 7-8's
active power flow increases, effectively utilizing its capacity.
- The external damping controller (CONVEC) significantly improves power oscillation damping.
B. Three-Phase Short Circuit Test on Line 1-6 (STATCOM)
- A three-phase short circuit at bus 1 end of line 1-6 is simulated.
- With STATCOM, the DFIG rotor power remains within VFC power capacity limits, ensuring
stability.
- Without STATCOM, rotor power exceeds limits, potentially leading to disconnection of the
wind farm.
- STATCOM effectively controls the voltage at the Point of Common Coupling (PCC),
enhancing wind farm capability during grid disturbances.
C. Three-Phase Short Circuit Test on Line 7-8 (STATCOM and SSSC)

8. - STATCOM and SSSC are employed, and a short circuit is applied at bus 7 end of line 7-8.
- With CONVEC, system oscillations are quickly damped, and the active power delivered by line
7-8 stabilizes.
- Without CONVEC, the system exhibits slight damping to oscillations.
D. Three-Phase Short Circuit Test on Line 7-8 with the Loss of Line 4-5 (STATCOM and
SSSC):
- Operating with STATCOM and SSSC, a short circuit is applied to bus 7 end of line 7-8 with
line 4-5 open.
- CONVEC demonstrates effective dynamic damping performance, quickly damping system
oscillations.
Strengths
1. Comprehensive Analysis: The simulation results provide a comprehensive analysis of the
impact of FACTS devices on various scenarios, including congestion relief, short circuits, and
dynamic wind farm performance.
2. Identification of Device Effectiveness: The results clearly demonstrate the effectiveness of
FACTS devices, particularly the STATCOM and SSSC, in enhancing system stability, relieving
congestion, and damping oscillations.
Weaknesses
1. Lack of Quantitative Metrics: While the simulation results qualitatively demonstrate the
effectiveness of FACTS devices, the absence of quantitative metrics or performance indices may
limit a more precise assessment of their impact.
2. Complexity for Non-Experts: The technical details and numerous figures might be
overwhelming for readers without a strong background in power systems and control
engineering.
3. Limited Discussion on Limitations: The article lacks discussions on the limitations or potential
challenges associated with the proposed solutions and simulations.
Overall Assessment
The simulation results effectively showcase the benefits of FACTS devices in mitigating power
system challenges. However, addressing the lack of quantitative metrics, simplifying complex
technical details, and discussing limitations would enhance the overall impact and accessibility
of the presented results.

9. VI. CONCLUSION
The conclusion of the article emphasizes the challenges posed by the increasing penetration of
renewable energy, growing demands, limited resources, and deregulated electricity markets in
modern power systems. The study investigates the application of Flexible AC Transmission
System (FACTS) devices, specifically a STATCOM and an SSSC, to enhance the dynamic and
transient performance of a 12-bus multimachine power system with a large wind farm. The
results indicate that these FACTS devices contribute to dynamic voltage control, grid disturbance
resilience, dynamic power flow control, congestion relief, and improvement in power oscillation
damping and transient stability.
Strengths
1. Clear Objectives: The conclusion succinctly restates the objectives of the study, providing a
clear understanding of the problem addressed.
2. Comprehensive Contributions: The conclusion effectively summarizes the positive impacts of
FACTS devices on various aspects of power system operation, including voltage control, grid
disturbance resilience, power flow control, congestion relief, and stability enhancement.
3. Actionable Insights: By highlighting the positive outcomes, the conclusion provides actionable
insights for power system operators and planners interested in improving the performance of
systems integrating renewable energy sources.
Weaknesses
1. Limited Discussion on Challenges: The conclusion lacks explicit discussions on the potential
challenges, drawbacks, or limitations associated with the application of FACTS devices.
Addressing these aspects would provide a more balanced perspective.
2. Quantitative Metrics: Similar to the main body of the article, the conclusion does not include
quantitative metrics or performance indices to quantify the improvements achieved by FACTS
devices. Including such metrics would enhance the precision of the findings.
Overall Assessment
The conclusion effectively summarizes the key findings and contributions of the study. However,
providing more explicit discussions on potential challenges and incorporating quantitative
metrics would strengthen the conclusion and offer a more comprehensive perspective for readers
and practitioners in the field.
VII. REFERENCES

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Amount of Wind Power,” Ph.D. dissertation, Technical University of Denmark, Kgs.
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[3] W. Qiao, G. K. Venayagamoorthy, and R. G. Harley, “Real-time implementation of a
STATCOM on a wind farm equipped with doubly fed induction generators,” to be
presented at the IEEE IAS 41th
Annual Meeting, Tampa, FL, USA, Oct. 8-12, 2006.
[4] L. Gyugyi, C. D. Schauder, and K. K. Sen, “Static synchronous series compensator: a
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