19-03-2011, 12:28 PM
PRESENTED BY:
D. Srikanth Reddy
B.B. Venkata Lakshmi
Ch. Lakshmi Devi
R. Phani Vidyadhar
T. Jagadish
N. Sandeep Kumar
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ABSTRACT
Transmission lines in congested areas are often driven close to or even beyond their limits in order to satisfy the increased electric power consumption and trades. Thus, secure operation and reliable supply is endangered by the higher risks for faulted lines. But the construction of additional power lines is often difficult for environmental, economical and political reasons. This is where the technology of FACTS provides a significant opportunity. Power Flow Control devices such as Flexible AC Transmission Systems (FACTS) provide the opportunity to influence power flows and voltages and therefore to enhance system security, e.g. by resolving congestions and improving the voltage profile.
FACTS devices are able to influence power flows and voltages to different degrees depending on the type of the device. The focus in this research lies on the Static Var Compensator (SVC), the Thyristor-Controlled Series Compensator (TCSC) and the Thyristor-Controlled Phase Shifting Transformer (TCPST). Typically, the devices are divided into three categories: shunt-connected, series-connected and a combination of both. The SVC belongs to the shunt-connected devices and is since long in operation in various places. Conceptually, it is a variable shunt reactance which injects or absorbs reactive power in order to control the voltage at a given bus. Both TCSC and TCPST are series-connected devices. The TCSC mainly controls the active power in a line by adapting the line reactance. This type of device is in operation at a few places but is still in the stage of development. The principle of a TCPST is very similar to a conventional phase angle regulator (PAR). A voltage in quadrature to the primary bus voltage is incorporated introducing a phase shift to control the transmission angle. The difference compared with the PAR is that the mechanical tap changer is replaced by a thyristor-controlled equivalent allowing for faster control.
This proposed work describes a development of a control system and control strategies capable of governing multiple flexible AC transmission system (FACTS) devices. The main purposes of the proposed coordinated control system is to remove overloads and to achieve specified power flows in transmission lines of a power system in the normal and N-1 steady-state operational modes. Proposed control strategies are based on heuristic rules; therefore they do not require intensive computations. The proposed methods will be applied to modified IEEE test systems and Indian practical systems.
AIM OF THE PROJECT
The power flow of the bus system is compared when multiple FACTS devices are included with the power flow the bus system without any FACTS devices.
What is facts?
The FACTS technology is a collection of controllers, which can be applied individually or in coordination with others to control one or more of the interrelated system parameters, such as series impedance, shunt impedance, current, voltage, and damping of oscillations.
ABOUT FACTS
Flexible AC Transmission Systems.
FACTS are nothing but power electronic devices.
A FACTS is a system composed of static equipment used for the AC transmission of electrical energy.
Without FACTS
Normally consumers do not use electricity in a smooth , predictable way.
Uncontrollable environmental and consumer contingencies create demand peaks which turn normally sufficient transmission systems into challenging ‘bumpy roads’ for power providers.
With FACTS
FACTS increases the capacity and stability of electricity throughout transmission.
Hence, this helps power providers meet demand peaks through existing transmission lines by keeping electricity flowing efficiently, like traffic on a smooth highway.
How FACTS can control the power flow?
For any transmission line, the power transmitted between two nodes(sending and receiving end) in a power system depends on:
Voltage at both ends(i.e. Potential difference).
Impedance of the line.
Angle difference between both systems.
Different FACTS devices can actively one or more of the above parameters (which are stated in the previous slide) and can the power flow in the transmission line.
Why FACTS?
Controllability of power flow (both active and reactive power).
Capacity and flexibility of power transmission systems can be improved.
Increase the amount of power(capacity) that can be imported over existing transmission lines.
Reduce the need for construction of new transmission lines, capacitors, reactors, etc.
Enhances the security.
Improve system stability.
Performance of long distance AC transmission lines can be improved.
Improve the load ability of the system.
It is a alternative of building new transmission lines or power generation facilities.
Environmental benefits.
• Types of FACTS controllers
• Symbols of different types of FACTS
SERIES CONTROLLERS
It could be a variable impedance such as capacitor, reactor, etc.
Inject voltage in series with the line.
If voltage is in phase quadrature with the line current, it only supplies or absorbs the variable reactive power .
More suitable for power flow control.
SHUNT CONTROLLERS
It could be a variable impedance, variable source or a combination of these.
All shunt controllers inject current into the system at the point of connection.
If injected current is in quadrature with the line voltage, it only supplies or absorbs the variable reactive power.
Control system voltage and reactive power.
COMBINED SERIES-SHUNT CONTROLLERS
It could be a combination of separate shunt and series controllers as coordinated or unified. For example : UPFC
Combined series and shunt controller injects current into the system with shunt part and voltage in series with series part of controller.
A combination of series and shunt controllers can provide the best of effective power/current flow and line voltage.
