Flexible AC Transmission System (FACTS):
Alternating current transmission systems incorporating power electronic-based and other static controllers to enhance controllability and increase power transfer capability.
FACTS Controller:
What is FACTS? A power electronic-based system and other static equipment that provide control of one or more AC transmission system parameters.
Basic types of FACTS Controllers Based on the connection, generally FACTS controller can be classified as follows: Series controllers
Shunt controllers
Combined series-series controllers
Combined series-shunt controllers
A flexible alternating current transmission system (FACTS) is a system composed of static equipment used for the AC transmission of electrical energy. It is meant to enhance controllability and increase power transfer capability of the network. It is generally a power electronics-based system.
In conventional AC transmission system, the ability to transfer AC power is limited by several factors like thermal limits, transient stability limit, voltage limit, short circuit current limit etc. These limits define the maximum electric power which can be efficiently transmitted through the transmission line without causing any damage to the electrical equipments and the transmission lines. This is normally achieved by bringing changes in the power system layout. However this is not feasible and another way of achieving maximum power transfer capability without any changes in the power system layout. Also with the introduction of variable impedance devices like capacitors and inductors, whole of the energy or power from the source is not transferred to the load, but a part is stored in these devices as reactive power and returned back to the source. Thus the actual amount of power transferred to the load or the active power is always less than the apparent power or the net power. For ideal transmission the active power should be equal to the apparent power. In other words, the power factor (the ratio of active power to apparent power) should be unity. This is where the role of Flexible AC transmission System comes.
A flexible alternating current transmission system (FACTS) is a system composed of static equipment used for the AC transmission of electrical energy. It is meant to enhance controllability and increase power transfer capability of the network. It is generally a power electronics-based system.
In conventional AC transmission system, the ability to transfer AC power is limited by several factors like thermal limits, transient stability limit, voltage limit, short circuit current limit etc. These limits define the maximum electric power which can be efficiently transmitted through the transmission line without causing any damage to the electrical equipments and the transmission lines. This is normally achieved by bringing changes in the power system layout. However this is not feasible and another way of achieving maximum power transfer capability without any changes in the power system layout. Also with the introduction of variable impedance devices like capacitors and inductors, whole of the energy or power from the source is not transferred to the load, but a part is stored in these devices as reactive power and returned back to the source. Thus the actual amount of power transferred to the load or the active power is always less than the apparent power or the net power. For ideal transmission the active power should be equal to the apparent power. In other words, the power factor (the ratio of active power to apparent power) should be unity. This is where the role of Flexible AC transmission System comes.
Introduction
Definition of FACTS system
Necessity of facts devices
Shunt connected controllers
Types of facts controllers
Shunt connected controllers
Benefits of FACTS
The concept of FACTS (Flexible AC Transmission System) refers to a family of power electronics based devices able to enhance AC system controllability and stability and to increase power transfer capability.
The design of the different schemes and configurations of FACTS devices is based on the combination of traditional power system components (such as transformers, reactors, switches, and capacitors) with power electronics elements (such as various types of transistors and thyristors).
The significance of power factor correction (PFC) has long been visualized as a technology requirement for improving the efficiency of a power system network by compensating for the fundamental reactive power generated or consumed by simple inductive or capacitive loads. With the Information Age in full swing, the growth of high reliability, low cost electronic products have led utilities to escalate their power quality concerns created by the increase of such “switching loads.” These products include: entertainment devices such as Digital TVs, DVDs, and audio equipment; information technology devices such as PCs, printers, and fax-machines; variable speed motor drives for HVAC and white goods appliances; food preparation and cooking products such as microwaves and cook tops; and lighting products, which include electronic ballasts, LED and fluorescent lamps, and other power conversion devices that operate a variety of lamps. The drivers that have resulted in this proliferation are a direct result of the availability of low-cost switch-mode devices and control circuitry in all major end-use segments: residential, commercial, and industrial.
In the modern power system the reactive power compensation is one of the main issues, the transmission of active power requires a difference in angular phase between voltages at the sending and receiving points (which is feasible within wide limits), whereas the transmission of reactive power requires a difference in magnitude of these same voltages (which is feasible only within very narrow limits). The reactive power is consumed not only by most of the network elements, but also by most of the consumer loads, so it must be supplied somewhere. If we can't transmit it very easily, then it ought to be generated where it is needed." (Reference Edited by T. J. E. Miller, Forward Page ix).Thus we need to work on the efficient methods by which VAR compensation can be applied easily and we can optimize the modern power system. VAR control technique can provides appropriate placement of compensation devices by which a desirable voltage profile can be achieved and at the same time minimizing the power losses in the system. This report discusses the transmission line requirements for reactive power compensation. In this report thyristor switched capacitor is explained which is a static VAR compensator used for reactive power management in electrical systems.
Seminar Topic For Electrical and Electronics Engineering (EEE)
Introduction
Definition of FACTS system
Necessity of facts devices
Shunt connected controllers
Types of facts controllers
Shunt connected controllers
Benefits of FACTS
The concept of FACTS (Flexible AC Transmission System) refers to a family of power electronics based devices able to enhance AC system controllability and stability and to increase power transfer capability.
The design of the different schemes and configurations of FACTS devices is based on the combination of traditional power system components (such as transformers, reactors, switches, and capacitors) with power electronics elements (such as various types of transistors and thyristors).
The significance of power factor correction (PFC) has long been visualized as a technology requirement for improving the efficiency of a power system network by compensating for the fundamental reactive power generated or consumed by simple inductive or capacitive loads. With the Information Age in full swing, the growth of high reliability, low cost electronic products have led utilities to escalate their power quality concerns created by the increase of such “switching loads.” These products include: entertainment devices such as Digital TVs, DVDs, and audio equipment; information technology devices such as PCs, printers, and fax-machines; variable speed motor drives for HVAC and white goods appliances; food preparation and cooking products such as microwaves and cook tops; and lighting products, which include electronic ballasts, LED and fluorescent lamps, and other power conversion devices that operate a variety of lamps. The drivers that have resulted in this proliferation are a direct result of the availability of low-cost switch-mode devices and control circuitry in all major end-use segments: residential, commercial, and industrial.
In the modern power system the reactive power compensation is one of the main issues, the transmission of active power requires a difference in angular phase between voltages at the sending and receiving points (which is feasible within wide limits), whereas the transmission of reactive power requires a difference in magnitude of these same voltages (which is feasible only within very narrow limits). The reactive power is consumed not only by most of the network elements, but also by most of the consumer loads, so it must be supplied somewhere. If we can't transmit it very easily, then it ought to be generated where it is needed." (Reference Edited by T. J. E. Miller, Forward Page ix).Thus we need to work on the efficient methods by which VAR compensation can be applied easily and we can optimize the modern power system. VAR control technique can provides appropriate placement of compensation devices by which a desirable voltage profile can be achieved and at the same time minimizing the power losses in the system. This report discusses the transmission line requirements for reactive power compensation. In this report thyristor switched capacitor is explained which is a static VAR compensator used for reactive power management in electrical systems.
Seminar Topic For Electrical and Electronics Engineering (EEE)
The electricity supply industry is undergoing a profound transformation worldwide. Market forces, scarcer natural resources, and an ever-increasing demand for electricity are some of the drivers responsible for such unprecedented change. Against this background of rapid evolution, the expansion programs of many utilities are being thwarted by a variety of well-founded, environment, land-use, and regulatory pressures that prevent the licensing and building of new transmission lines and electricity generating plants.
FACTS : Flexible AC Transmission Systemfernando nuño
Los Sistemas de Transmisión AC Flexible (llamados FACTS) tienen un gran rango de aplicaciones gracias a su buena controlabilidad mediante sistemas electrónicos de potencia. Se presentan en este artículo los conceptos básicos ligados a estos dispositivos.
Los FACTS son utilizados para reducir costes y mejorar las líneas de distribución y trasporte de energía eléctrica, además de tener una gran flexibilidad para adaptarse a diferentes condiciones de trabajo.
Analysis of multi terminal hvdc transmission system feeding very weak ac netw...eSAT Journals
Abstract This paper presents a line commutated converter (LCC) based multi-terminal HVDC transmission (MTDC) system feeding very weak AC networks with hybrid reactive power compensators (RPC’s) at the inverter AC side. The hybrid compensator is accomplished by the equal mixing of any two of the following compensators: synchronous compensator (SC); static var compensator (SVC); static synchronous compensator (STATCOM). The four-terminal HVDC transmission system model is implemented in the Matlab with the firefly algorithm based optimal proportional integral (PI) controller for rectifiers and inverters control. The transient performances of hybrid RPC’s (SC+SVC, SVC+STATCOM and SC+STATCOM) are studied under various fault conditions and the results are compared with the performance of the SC, SVC and STATCOM to focus the high quality of the hybrid compensators. The simulation results authorize that the equivalent mixture of SC and STATCOM has a steady and fastest response. The results also reveal the supremacy of the firefly algorithm based optimal PI controller over the conventional PI controller. The harmonic present in the inverter side AC quantities is also calculated under steady state operation to assure the quality of power supply. Keywords: MTDC, Very weak AC system, Hybrid RPC, PI controller, Firefly Algorithm.
Role of Flexible AC Transmission in Power System ContingencySayantan Datta
Contingency refers to any abnormal condition which involves line overload, line outage, bus over-voltages and bus faults.
FACTS device are used to minimize this contingency condition.
Project is designed to develop a FACTs (Flexible AC Transmission) by TSR (Thyristor Switch Reactance) used in two ways. Read more about this project here.
The electricity supply industry is undergoing a profound transformation worldwide. Market forces, scarcer natural resources, and an ever-increasing demand for electricity are some of the drivers responsible for such unprecedented change. Against this background of rapid evolution, the expansion programs of many utilities are being thwarted by a variety of well-founded, environment, land-use, and regulatory pressures that prevent the licensing and building of new transmission lines and electricity generating plants.
The concept of FACTS (Flexible Alternating Current Transmission System) refers to a family of power electronics-based devices able to enhance AC system controllability and stability and to increase power transfer capability.
These slides present the introduction to FACTS devices. Later we will discuss about its modelling and control aspect applications. This comes under the topic on power electronics application in smart and microgrid systems.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Saudi Arabia stands as a titan in the global energy landscape, renowned for its abundant oil and gas resources. It's the largest exporter of petroleum and holds some of the world's most significant reserves. Let's delve into the top 10 oil and gas projects shaping Saudi Arabia's energy future in 2024.
Final project report on grocery store management system..pdfKamal Acharya
In today’s fast-changing business environment, it’s extremely important to be able to respond to client needs in the most effective and timely manner. If your customers wish to see your business online and have instant access to your products or services.
Online Grocery Store is an e-commerce website, which retails various grocery products. This project allows viewing various products available enables registered users to purchase desired products instantly using Paytm, UPI payment processor (Instant Pay) and also can place order by using Cash on Delivery (Pay Later) option. This project provides an easy access to Administrators and Managers to view orders placed using Pay Later and Instant Pay options.
In order to develop an e-commerce website, a number of Technologies must be studied and understood. These include multi-tiered architecture, server and client-side scripting techniques, implementation technologies, programming language (such as PHP, HTML, CSS, JavaScript) and MySQL relational databases. This is a project with the objective to develop a basic website where a consumer is provided with a shopping cart website and also to know about the technologies used to develop such a website.
This document will discuss each of the underlying technologies to create and implement an e- commerce website.
Hierarchical Digital Twin of a Naval Power SystemKerry Sado
A hierarchical digital twin of a Naval DC power system has been developed and experimentally verified. Similar to other state-of-the-art digital twins, this technology creates a digital replica of the physical system executed in real-time or faster, which can modify hardware controls. However, its advantage stems from distributing computational efforts by utilizing a hierarchical structure composed of lower-level digital twin blocks and a higher-level system digital twin. Each digital twin block is associated with a physical subsystem of the hardware and communicates with a singular system digital twin, which creates a system-level response. By extracting information from each level of the hierarchy, power system controls of the hardware were reconfigured autonomously. This hierarchical digital twin development offers several advantages over other digital twins, particularly in the field of naval power systems. The hierarchical structure allows for greater computational efficiency and scalability while the ability to autonomously reconfigure hardware controls offers increased flexibility and responsiveness. The hierarchical decomposition and models utilized were well aligned with the physical twin, as indicated by the maximum deviations between the developed digital twin hierarchy and the hardware.
Explore the innovative world of trenchless pipe repair with our comprehensive guide, "The Benefits and Techniques of Trenchless Pipe Repair." This document delves into the modern methods of repairing underground pipes without the need for extensive excavation, highlighting the numerous advantages and the latest techniques used in the industry.
Learn about the cost savings, reduced environmental impact, and minimal disruption associated with trenchless technology. Discover detailed explanations of popular techniques such as pipe bursting, cured-in-place pipe (CIPP) lining, and directional drilling. Understand how these methods can be applied to various types of infrastructure, from residential plumbing to large-scale municipal systems.
Ideal for homeowners, contractors, engineers, and anyone interested in modern plumbing solutions, this guide provides valuable insights into why trenchless pipe repair is becoming the preferred choice for pipe rehabilitation. Stay informed about the latest advancements and best practices in the field.
About
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
• Remote control: Parallel or serial interface.
• Compatible with MAFI CCR system.
• Compatible with IDM8000 CCR.
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
• Easy in configuration using DIP switches.
Technical Specifications
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
Key Features
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
• Remote control: Parallel or serial interface
• Compatible with MAFI CCR system
• Copatiable with IDM8000 CCR
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
Application
• Remote control: Parallel or serial interface.
• Compatible with MAFI CCR system.
• Compatible with IDM8000 CCR.
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
• Easy in configuration using DIP switches.
Student information management system project report ii.pdfKamal Acharya
Our project explains about the student management. This project mainly explains the various actions related to student details. This project shows some ease in adding, editing and deleting the student details. It also provides a less time consuming process for viewing, adding, editing and deleting the marks of the students.
Welcome to WIPAC Monthly the magazine brought to you by the LinkedIn Group Water Industry Process Automation & Control.
In this month's edition, along with this month's industry news to celebrate the 13 years since the group was created we have articles including
A case study of the used of Advanced Process Control at the Wastewater Treatment works at Lleida in Spain
A look back on an article on smart wastewater networks in order to see how the industry has measured up in the interim around the adoption of Digital Transformation in the Water Industry.
Cosmetic shop management system project report.pdfKamal Acharya
Buying new cosmetic products is difficult. It can even be scary for those who have sensitive skin and are prone to skin trouble. The information needed to alleviate this problem is on the back of each product, but it's thought to interpret those ingredient lists unless you have a background in chemistry.
Instead of buying and hoping for the best, we can use data science to help us predict which products may be good fits for us. It includes various function programs to do the above mentioned tasks.
Data file handling has been effectively used in the program.
The automated cosmetic shop management system should deal with the automation of general workflow and administration process of the shop. The main processes of the system focus on customer's request where the system is able to search the most appropriate products and deliver it to the customers. It should help the employees to quickly identify the list of cosmetic product that have reached the minimum quantity and also keep a track of expired date for each cosmetic product. It should help the employees to find the rack number in which the product is placed.It is also Faster and more efficient way.
2. What is FACTS?
Flexible AC Transmission System (FACTS):
Alternating current transmission systems incorporating power
electronic-based and other static controllers to enhance
controllability and increase power transfer capability.
FACTS Controller:
A power electronic-based system and other static equipment
that provide control of one or more AC transmission system
parameters.
General symbol of FACTS controller
3. Basic types of FACTS Controllers
Based on the connection, generally FACTS controller can be classified
as follows:
Series controllers
Shunt controllers
Combined series-series controllers
Combined series-shunt controllers
4. Basic types of FACTS Controllers
Series controllers
The series controller could be a variable impedance or a
variable source, both are power electronics based devices to serve
the desired needs. In principle, all series controllers inject voltage in
series with the line.
General symbol of Series controller
5. Shunt controllers
The shunt controllers may be variable impedance, variable
sources or combination of these. In principle, all shunt Controllers inject
current into the system at the point of connection. As long as the injected
current is in phase quadrature with the line voltage, the shunt Controller only
supplies or consumes variable reactive power.
General symbol of Shunt controller
6. Combined series-series controllers:
The combination could be separate series controllers or unified
series-series controller. Series Controllers provide independent series
reactive compensation for each line but also transfer real power among
the lines via the power link- Interline Power Flow Controller.
Symbol of Series- Series controller
7. Combined series-shunt controllers:
The combination could be separated series and shunt
controllers or a unified power flow controller. In principle, combined
shunt and series Controllers inject current into the system with the
shunt part of the Controller and voltage in series in the line with the
series part of the Controller.
Symbol of Series- Shunt controller
8. Brief Description and Definitions of FACTS
controllers
Shunt connected controllers
Series connected controllers
Combined shunt - series connected controllers
9. Shunt connected controllers
Static Synchronous Generator (SSG)
Static Synchronous Compensator (STATCOM)
Battery Energy Storage System (BESS)
Superconducting Magnetic Energy Storage (SMES)
Static Var Compensator (SVC)
Thyristor Controlled Reactor (TCR)
Thyrlstor Swltched Reactor (TSR)
Thyristor Switched Capacitor (TSC)
Static Var Generator or Absorber (SVG)
Thyristor Controlled Braking Resistor (TCBR)
Types of shunt connected controllers available in the market
10. Shunt connected controllers
Static Synchronous Compensator (STATCOM):
A Static synchronous generator operated as a shunt-connected static
var compensator whose capacitive or inductive output current can be
controlled independent of the ac system voltage.
STATCOM based on
voltage-sourced converters
STATCOM based on
current-sourced converters
In cost point of view, the voltage-sourced converters seem to be
preferred, and will be the basis for presentations of most converter-based
FACTS Controllers.
11. Static Var Compensator (SVC):
A shunt-connected static var generator or absorber whose
output is adjusted to exchange capacitive or inductive current so as to
maintain or control specific parameters of the electrical power system
(typically bus voltage).
The thyristor-controlled reactor (TCR) or thyristor-
switched reactor (TSR) for absorbing reactive power
and thyristor-switched capacitor (TCS) for supplying
the reactive power.
SVC is considered by some as a lower cost
alternative to STATCOM.
12. Series connected controllers
Static Synchronous Series Compensator (SSSC)
Interline Power Flow Controller (IPFC)
Thyristor Controlled Series Capacitor (TCSC)
Thyristor-Switched Series Capacitor (TSSC)
Thyristor-Controlled Series Reactor (TCSR)
Thyristor-Switched Series Reactor (TSSR)
Types of series connected controllers available in the market
13. Series connected controllers
Static Synchronous Series Compensator (SSSC):
In a Static Synchronous Series Compensator, output voltage is in
quadrature with, and controllable independently of, the line current for the
purpose of increasing or decreasing the overall reactive voltage drop
across the line
It is like a STATCOM, except that the
output ac voltage is in series with the line.
14. Thyristor Controlled Series Capacitor (TCSC):
A capacitive reactance compensator which consists of a
series capacitor bank shunted by a thyristor-controlled reactor in
order to provide a smoothly variable series capacitive reactance.
It is an alternative to SSSC.
The TCSC may be a single, large unit, or may consist of several equal or
different-sized smaller capacitors in order to achieve a superior
performance.
15. Unified Power Flow Controller (UPFC)
Thyristor-Controlled Phase Shifting Transformer (TCPST)
Interphase Power Controller (IPC):
Combined shunt-series connected controllers
Types of shunt series connected controllers available in the market
16. Combined shunt and series connected controllers
Unified Power Flow Controller (UPFC):
A combination of static synchronous compensator (STATCOM) and a
static series compensator (SSSC) which are coupled via a common dc link,
to allow bidirectional flow of real power between the series output terminals
of the SSSC and the shunt output terminals of the STATCOM, and are
controlled to provide concurrent real and reactive series line compensation
without an external electric energy source.
This is a complete Controller for
controlling active and reactive power
control through the line, as well as line
voltage control.
17. Thyristor-Controlled Voltage Limiter (TCVL) Thyristor-Controlled Voltage Regulator (TCVR) based
on tap changing;
Thyristor-Controlled Voltage Regulator (TCVR)
based on voltage injection.
Other controllers
18. Control of power flow as ordered.
Increase the loading capability of lines to their thermal capabilities,
including short term and seasonal.
Increase the system security through raising the transient stability limit,
limiting short-circuit currents and overloads, managing cascading
blackouts and damping electromechanical oscillations of power systems
and machines.
Provide secure tie line connections to neighboring utilities and regions
thereby decreasing overall generation reserve requirements on both sides.
Provide greater flexibility in siting new generation.
Reduce reactive power flows, thus allowing the lines to carry more
active power.
Increase utilization of lowest cost generation.
BENEFITS FROM FACTS TECHNOLOGY
20. Static VAR Compensator (SVC)
- A TCR and TSC are the most important building blocks of thyristor
based SVCs
Thyristor control reactor (TCR)
The controllable range of the TCR firing angle,
alpha, extends from 90 degree to 180 degree.
A firing angle of 90 degree results in full thyristor
conduction with a continuous sinusoidal current
flow in the TCR.
The current reduces to zero for a firing angle of
180 degree.
Thyristor firing at angles below 90 degree
introduces dc components in the current, disturbing
the symmetrical operation of the two anti parallel
valve branches.
BL
21. Let the source voltage be expressed as
The TCR current is then given by the following differential equation:
Where,
V=Peak value of the applied voltage
ω=Angular frequency of supply voltage.
24. Thyristor Switched Capacitors:
The capacitor voltage is not equal to the supply voltage when the thyristors are fired.
Immediately after closing the switch, a current of infinite magnitude flows and charges the
capacitor to the supply voltage in an infinitely short time. The switch realized by thyristors
cannot withstand this stress and would fail.
The capacitor voltage is equal to the supply voltage when the thyristors are fired. The
analysis shows that the current will jump immediately to the value of the steady-state current.
The steady state condition is reached in an infinitely short time. Although the magnitude of
the current does not exceed the steady-state values, the thyristors have an upper limit of di/
dt values that they can withstand during the firing process. Here, di/ dt is infinite, and the
thyristor switch will again fail.
25. It can therefore be concluded that this simple circuit of a TSC branch
is not suitable.
is a magnification
factor
26. Static VAR Compensator (shunt connected controller)
Note:
The control strategy usually aims to maintain the transmission line voltage at a fixed level.
30. Thyristor-controlled series capacitor, TCSC
- Series-connected controller
Advantage of Series Compensation
With series capacitors, the reactive power increases as
the square of line current, whereas with shunt capacitors,
the reactive power is generated proportional to the square
of bus voltage.
In a same system benefits as those of series
capacitors, shunt capacitors that are three to six times
more reactive power– rated than series capacitors need to
be employed.
Furthermore, shunt capacitors typically must be
connected at the line midpoint, whereas no such
requirement exists for series capacitors.
31. Variable-Series Compensation
1. Enhanced base-power flow and loadability of the
series-compensated line.
2. Additional losses in the compensated line from the
enhanced power flow.
3. Increased responsiveness of power flow in the series-
compensated line from the outage of other lines in the
system.
32. A basic TCSC module
TCSC CONTROLLER
A typical TCSC system.
34. Advantages of the TCSC
Rapid, continuous control of the transmission-line series-
compensation level.
Dynamic control of power flow in selected transmission
lines within the network to enable optimal power-flow
conditions and prevent the loop flow of power.
Suppression of subsynchronous oscillations.
Decreasing dc-offset voltages.
Enhanced level of protection for series capacitors.
Voltage support.
Reduction of the short-circuit current. During events of
high short-circuit current, the TCSC can switch from the
controllable-capacitance to the controllable-inductance
mode, thereby restricting the short-circuit currents.
36. Unified Power Flow Controller (UPFC):
A combination of static synchronous compensator (STATCOM) and
a static series compensator (SSSC) which are coupled via a common dc
link, to allow bidirectional flow of real power between the series output
terminals of the SSSC and the shunt output terminals of the STATCOM.
STATCOM
SSSC
38. If the amplitude of the output voltage is increased above that of
the utility bus voltage, Et, then a current flows through the reactance
from the converter to the ac system and the converter generates
capacitive-reactive power for the ac system.
If the amplitude of the output voltage is decreased below the
utility bus voltage, then the current flows from the ac system to the
converter and the converter absorbs inductive-reactive power from
the ac system.
If the output voltage equals the ac system voltage, the reactive-
power exchange becomes zero, in which case the STATCOM is said
to be in a floating state.
Power exchange
STATCOM Operation
39. In practice, the semiconductor switches of the converter are not
lossless, so the energy stored in the dc capacitor is eventually used
to meet the internal losses of the converter, and the dc capacitor
voltage diminishes.
When the STATCOM is used for reactive-power generation, the
converter itself can keep the capacitor charged to the required
voltage level. This task is accomplished by making the output
voltages of the converter lag behind the ac-system voltages by a
small angle (usually in the 0.18–0.28 range).
In this way, the converter absorbs a small amount of real power from
the ac system to meet its internal losses and keep the capacitor
voltage at the desired level.
41. SSSC Operation
For instance, if the injected voltage is in phase with the line current,
then the voltage would exchange real power.
On the other hand, if a voltage is injected in quadrature with the line
current, then reactive power—either absorbed or generated—would be
exchanged.
43. Inverter 2 provides the main function of the UPFC by injecting an
ac voltage Vpq with controllable magnitude Vpq (0 < Vpq < Vpq
max) and phase angle α(0< α< 360), at the power frequency, in
series with line via an insertion transformer.
The transmission line current flows through this voltage source
resulting in real and reactive power exchange between it and the ac
system. The real power exchanged at the ac terminal (i.e. at the
terminal of the injection transformer) is converted by the inverter into
dc power, which appears at the dc link as positive or negative real
power demand.
The basic function of Inverter 1 is to supply or absorb the real
power demanded by Inverter 2 at the common dc link.
Inverter 1 can also generate or absorb controllable reactive power,
if it is desired, and thereby it can provide independent shunt reactive
compensation for the line.
UPFC Operation
44. Interline Power Flow Controller (IPFC):
Power circuit
The basic difference with a UPFC is that the support system in the IPFC
is the series converter instead of a shunt converter.