STABILTY OF POWER TRANSMISSION

OF HVDC SYSTEM USING FACTS

CONTROLLERSUnder the guidance of Ms. Saritha DEVI

MOHD ILIYAS 09RT1A0214

MOHD FAISAL MADANI 09RT1A0217MOHD VEQAR UDDIN 09RT1A0231

Contents:

• Objective• Stability• F.A.C.T.S theory• Types of Facts controllers• Circuit diagram• Unified power flow controller• Advantages• References

OBJECTIVE:

• Modern power systems are highly complex and are expected to fulfil the growing demands of power wherever required, with acceptable quality and costs.

• The necessity to deliver cost effective energy in the power market has

become a major concern in this emerging technology era. Therefore,

establishing a desired power condition at the given points are best

achieved using power controllers such as the well known High Voltage

Direct Current (HVDC) and Flexible Alternating Current Transmission

System (FACTS) devices.

• High Voltage Direct Current (HVDC) is used to transmit large amounts of

power over long distances. The factors to be considered are Cost, Technical

Performance and Reliability.

STABILITY

The voltage stability may be defined as the ability of a power system to maintain steady acceptable voltage at all busses in the system at normal operating conditions and after being subjected to disturbances.

The main factor causing voltage instability is the inability of the power system to meet the demands for reactive power in the heavily stressed system keeping desired voltages.

There is a need to ensure stability and reliability of the power system due to economic reasons.

POWER TRANSMISSION• A large majority of power transmission lines

are AC lines operating at different voltages (10 kV to 800 kV). The distribution networks generally op-erate below 100 kV.

• For bulk power upto 1000 MW and for long distances >800 km we use HVDC transmission of rating generally of ± 600 kV DC

POWER FACTOR

• Power factor (PF) is the name given to the ratio of the active or usable power measured in kilowatts (KW), to the total power (active and reactive) measured in kilovolt amperes (KVA).ie: Power Factor = KW / KVA.

• Cosϕ = active power / apparent power

CIRCUIT DIAGRAM

Smoothing Reactors

• DC systems often require a smoothening of the direct current wave shape to reduce losses and improve system performance.

• Series reactors inserted in DC systems offer this response and additionally operate as current limiting devices in the event of a fault. Smoothing reactors are widely used in industrial applications and HVDC links.

Why HVDC ?

• ADVANTAGES OVER AC : • It requires only 2 conductors as 3 in a.c tr• There is no skin effect • It has less corona• Voltage drop is less than ac • There are no stability problems• It has less losses• It is used in underwater(submarine) transmission

Basic HVDC circuitTYPES OF HVDC LINKS:

MONO POLARBIPOLAR

HOMO POLARBACK TO BACK

FACTS THEORY

• Power electronic based systems and other static equipment that provide controllability of power flow and voltage are termed as FACTS

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

TYPES OF FACTS

F.A.C.T.S

Series compensation

Shunt compensation Series-series compensation

Series-shunt compensation

Unified Power flow Controller

• The Unified Power Flow Controller (UPFC) is the most versatile FACTS controller for the regulation of voltage and power flow in a transmission line.

• It consists of two voltage source converters (VSC) one shunt connected and the other series connected.

• The UPFC scheme consists of two basic switching power

converter namely shunt and series converters connected to

each other through a dc link capacitor.

• The controller can control active and reactive power flows in

a transmission line.

UPFC -Circuit diagram

SOFTWARE USED• MATLAB (matrix laboratory) is a numerical computing environment and

fourth-generation programming language. Developed byMathWorks, MATLAB allows matrix manipulations, plotting of functions and data, implementation of algorithms, creation of user interfaces, and interfacing with programs written in other languages, including C, C++, Java, and Fortran

• SIMULINK developed by MathWorks, is a data flow graphical programming language tool for modeling, simulating and analyzing multidomain dynamic systems. Its primary interface is a graphical block diagramming tool and a customizable set of block libraries.

SIMULATION

• Simulation is the imitation of the operation of a real-world process or system over time.

• The act of simulating something first requires that a model be developed; this model represents the key characteristics or behaviors of the selected physical or abstract system or process.

• Simulation is also used when the real system cannot be engaged, because it may not be accessible, or it may be dangerous or unacceptable to engage, or it is being designed but not yet built, or it may simply not exist.

SIMULATION CIRCUIT

SIMULATION RESULTS AT RECTIFIER SIDE

SIMULATION RESULTS AT INVERTER SIDE

Advantages:

It controls the power flow in the transmission line, effectively.

Reduces the total harmonic distortion (THD) as well.

CONCLUSION

.Thus by using HVDC and The flexible ac transmission system (FACTS) concepts stability can be improved to the existing ac transmission system, and unified power is maintained

References:

• 1. E.M. Yap, Student Member, IEEE School of Electrical

and Computer Engineering, RMIT University, Melbourne, AU

• 2. Hideaki Fujita, Member, IEEE, Yasuhiro Watanabe, and

Hirofumi Akagi, Fellow, IEEE, “Control and Analysis of a

Unified Power Flow Controller” IEEE TRANSACTIONS ON

POWER ELECTRONICS, VOL. 14, NO. 6, NOVEMBER

1999

THANK YOU