25-08-2012, 01:38 PM
FLEXIBLE A.C. TRANSMISSION SYSTEMS
FLEXIBLE A.C.DOC (Size: 225 KB / Downloads: 34)
ABSTRACT:
The rapid development of power electronics technology provides exciting opportunities to develop new power system equipment for better utilization of existing systems. Such as enhancing the security, capacity and flexibility of power transmission systems. FACTS solutions enable power grid owners to increase existing transmission network capacity while maintaining or improving the operating margins necessary for grid stability. Supply of reliable, high-quality electrical energy at a reasonable cost is at the heart of the nation's economy. The electric power system is one of the nation's important infrastructures, and the infrastructure most closely tied with the gross domestic product. In view of changes in both the operating and business sector of the electric utility industry. Provisions of the Energy Policy Act of 1992, and electric utilities to provide open access to the transmission system have mandated these changes.
Several advanced methods are developed for maintaining a high degree of power quality and reliability under a deregulated environment. At the distribution level, flexible control strategies involve computerized automation of system control devices such as capacitor banks; under load tap changing transformers (Ultc’s) and voltage regulators. In the transmission system, a new method of achieving this control is through the use of power electronics based Flexible AC Transmission System (FACTS) devices. This paper provides a comprehensive guide to FACTS, covering all the major aspects in research and development of FACTS technologies. Various real-world applications are also included to demonstrate the issues and benefits of applying FACTS.The objective of this project is to create a multi-institutional power curriculum to address this new environment and technologies.
INTRODUCTION:
Over the years, it has become clear that the maximum safe operating capacity of the transmission system is often based on
voltage and angular stability rather than on its physical limitations. So rather than constructing new lines, industry has tended towards the development of technologies or devices that increase transmission network capacity while maintaining or even improving grid stability. Many of these now established technologies fall under the title of FACTS (Flexible AC Transmission Systems). They not only improve the capacity of power transmission systems, but flexibility is also greatly enhanced.
The FACTS is not a single high power controller, but rather a collection of controllers, which can be applied individually or in co-ordination with others to control one or more of the interrelated system parameters mentioned above. A well-chosen FACTS controller can overcome the specific limitations of a designated transmission line or a corridor. Because all FACTS controllers represent applications of the same basic technology, there production can eventually take advantage of technologies of scale.
BASIC TYPES OF FACTS CONTROLLERS:
FACTS devices are integrated in a system for a variety of reasons, such as power flow control, reactive power (var) compensation, loop flows or ancillary functions like damping of oscillations. These devices can be applied in shunt, in series, and in some cases, both in shunt and series. Series devices include Thyristor-controlled series capacitors (TCSC) and Fixed series capacitors (SC). Shunt devices include static vary compensators (SVC), and SVC Light® (otherwise known as STATCOM)
STATIC SERIES COMPENSATORS:
Fixed series capacitors (SC):
The series controller can be a variable impedance, such as capacitor, reactor. Or a power electronics based variable source of min frequency, sub synchronous and harmonic frequencies (or a combination) to serve the desired need .in principle all controllers inject voltage in series with the line. Even variable impedance multiplied by the current flow through it, represents an injected series voltage in the line. as long as the voltage is in phase quadrature with line current, the series controller only supplies or consumes variable reactive power . any other phase relationship will involve handling of real power as well. Static series compensation is used in order to decrease the transfer reactance of a power line at power frequency.
STATCOM:
STATCOM (Static Compensator) has a characteristic similar to the synchronous condenser, but as an electronic device, it has no inertia and is superior to the synchronous condenser in several ways - better dynamics, a lower investment cost, and lower operating and maintenance costs. STATCOM is to be selected when the technical performance in a specific application so requires. However, utilizing thyristors with turn-off capability (GTO or IGCT), which is the common approach in the industry, does not allow the full potential of a STATCOM concept to be obtained.
Applications of FACTS in Power Systems:
FACTS can confine or neutralize electrical disturbances such as voltage sags and fluctuations, flicker, harmonic distortion, and phase unbalance in three-phase systems. In addition, improved economy of the process or processes in question will also be achieved. FACTS are designed to remove such constraints in a fast and intelligent way so that planners', investors' and operators' goals are met without them having to undertake major system additions.
FACTS solutions enable power grid owners to increase existing transmission network capacity while maintaining or improving the operating margins necessary for grid stability. As a result, more power can reach consumers with very little impact on the environment, project implementation times are shorter, and investment costs are lower when compared with the alternative of building new transmission lines or power generation facilities. Flexibility is provided as FACTS can influence several parameters in the grid, such as active and reactive power flows.
CONCLUSIONS:
1) Control of power flow as ordered. The use of control of the power flow may be to follow a contract, meet the utilities own needs, ensure optimum power flow, ride through emergency conditions, or a combination thereof.
2) Increase the loading capability of lines to their thermal capabilities, including short term and seasonal. This can be accomplished by overcoming other limitations and sharing of power among lines according to their capability.
3) Increase the system security through raising the transient stability limit, limiting short-circuit currents and overloads, managing cascading blackouts and damping electro mechanical oscillations of power systems and machines.
FLEXIBLE A.C.DOC (Size: 225 KB / Downloads: 34)
ABSTRACT:
The rapid development of power electronics technology provides exciting opportunities to develop new power system equipment for better utilization of existing systems. Such as enhancing the security, capacity and flexibility of power transmission systems. FACTS solutions enable power grid owners to increase existing transmission network capacity while maintaining or improving the operating margins necessary for grid stability. Supply of reliable, high-quality electrical energy at a reasonable cost is at the heart of the nation's economy. The electric power system is one of the nation's important infrastructures, and the infrastructure most closely tied with the gross domestic product. In view of changes in both the operating and business sector of the electric utility industry. Provisions of the Energy Policy Act of 1992, and electric utilities to provide open access to the transmission system have mandated these changes.
Several advanced methods are developed for maintaining a high degree of power quality and reliability under a deregulated environment. At the distribution level, flexible control strategies involve computerized automation of system control devices such as capacitor banks; under load tap changing transformers (Ultc’s) and voltage regulators. In the transmission system, a new method of achieving this control is through the use of power electronics based Flexible AC Transmission System (FACTS) devices. This paper provides a comprehensive guide to FACTS, covering all the major aspects in research and development of FACTS technologies. Various real-world applications are also included to demonstrate the issues and benefits of applying FACTS.The objective of this project is to create a multi-institutional power curriculum to address this new environment and technologies.
INTRODUCTION:
Over the years, it has become clear that the maximum safe operating capacity of the transmission system is often based on
voltage and angular stability rather than on its physical limitations. So rather than constructing new lines, industry has tended towards the development of technologies or devices that increase transmission network capacity while maintaining or even improving grid stability. Many of these now established technologies fall under the title of FACTS (Flexible AC Transmission Systems). They not only improve the capacity of power transmission systems, but flexibility is also greatly enhanced.
The FACTS is not a single high power controller, but rather a collection of controllers, which can be applied individually or in co-ordination with others to control one or more of the interrelated system parameters mentioned above. A well-chosen FACTS controller can overcome the specific limitations of a designated transmission line or a corridor. Because all FACTS controllers represent applications of the same basic technology, there production can eventually take advantage of technologies of scale.
BASIC TYPES OF FACTS CONTROLLERS:
FACTS devices are integrated in a system for a variety of reasons, such as power flow control, reactive power (var) compensation, loop flows or ancillary functions like damping of oscillations. These devices can be applied in shunt, in series, and in some cases, both in shunt and series. Series devices include Thyristor-controlled series capacitors (TCSC) and Fixed series capacitors (SC). Shunt devices include static vary compensators (SVC), and SVC Light® (otherwise known as STATCOM)
STATIC SERIES COMPENSATORS:
Fixed series capacitors (SC):
The series controller can be a variable impedance, such as capacitor, reactor. Or a power electronics based variable source of min frequency, sub synchronous and harmonic frequencies (or a combination) to serve the desired need .in principle all controllers inject voltage in series with the line. Even variable impedance multiplied by the current flow through it, represents an injected series voltage in the line. as long as the voltage is in phase quadrature with line current, the series controller only supplies or consumes variable reactive power . any other phase relationship will involve handling of real power as well. Static series compensation is used in order to decrease the transfer reactance of a power line at power frequency.
STATCOM:
STATCOM (Static Compensator) has a characteristic similar to the synchronous condenser, but as an electronic device, it has no inertia and is superior to the synchronous condenser in several ways - better dynamics, a lower investment cost, and lower operating and maintenance costs. STATCOM is to be selected when the technical performance in a specific application so requires. However, utilizing thyristors with turn-off capability (GTO or IGCT), which is the common approach in the industry, does not allow the full potential of a STATCOM concept to be obtained.
Applications of FACTS in Power Systems:
FACTS can confine or neutralize electrical disturbances such as voltage sags and fluctuations, flicker, harmonic distortion, and phase unbalance in three-phase systems. In addition, improved economy of the process or processes in question will also be achieved. FACTS are designed to remove such constraints in a fast and intelligent way so that planners', investors' and operators' goals are met without them having to undertake major system additions.
FACTS solutions enable power grid owners to increase existing transmission network capacity while maintaining or improving the operating margins necessary for grid stability. As a result, more power can reach consumers with very little impact on the environment, project implementation times are shorter, and investment costs are lower when compared with the alternative of building new transmission lines or power generation facilities. Flexibility is provided as FACTS can influence several parameters in the grid, such as active and reactive power flows.
CONCLUSIONS:
1) Control of power flow as ordered. The use of control of the power flow may be to follow a contract, meet the utilities own needs, ensure optimum power flow, ride through emergency conditions, or a combination thereof.
2) Increase the loading capability of lines to their thermal capabilities, including short term and seasonal. This can be accomplished by overcoming other limitations and sharing of power among lines according to their capability.
3) Increase the system security through raising the transient stability limit, limiting short-circuit currents and overloads, managing cascading blackouts and damping electro mechanical oscillations of power systems and machines.