FLEXIBLE AC TRANSMISSION SYSTEM- ”FACTS”

1) INTRODUCTION2) CLASSIFICATION 3) SERIES COMPENSATOR4) PARALLEL COMPENSATOR5) COMBINED COMPENSATOR6) IPSC7) SCCL8) COMPARISON WITH HVDC

TOPICS

Power system can be separated into three areas :- 1.Generation 2.Transmission 3.Distribution

POWER SYSTEM

LONG DISTANCE TRANSMISSION SYSTEMS

• Voltage stability

• Reactive power problems • Steady state stability

• Transient Stability

INTERCONNECTED SYSTEMS

• Load Flow Problems (needs management of

Congestion) • Voltage Stability • Frequency Control

• Oscillation Stability • Inter-Area Oscillations

LIMITATIONS OF LARGE AC SYSTEMS

“A power electronic based system and other static equipment that provide control of one or more AC transmission system parameters to enhance controllability and increase power transfer capability”.

FLEXIBLE AC TRANSMISSION SYSTEM – DEFINITION

The two main reasons for incorporating FACTS devices in electric power systems are:

Raising dynamic stability limits.

Provide better power flow control.

Reasons for operating the FACTS

• Improved power transmission capability.

• Improved system stability.

• Improved power quality.

• Minimized transmission losses.

Benefits of facts

Typical Power System

We know that,

Three main variables that can be directly controlled in the power system to impact its performance. These are :

a. Voltageb. Anglec. Impedance

Power Flow Control1400 MW

The power electronics interface facilitates the transfer of power from the source to the load by converting voltages and currents from one form to another.

ThyristorGTO’sIGBT

~ LConverter

Source Output to Load- Adjustable DC- Sinusoidal AC- High-frequency ACController

Power Electronics Interface

Role of Power Electronics

FACTS CONTROLLERS

SERIES

SSSC TCSC

SHUNT

SVC STATCOM

COMBINED

UPFC IPF C

TYPE OF FACTS CONTROLLERS

Generation of FACTS

1 Generation of FACTS (SVC & TCSC)

2 Generation of FACTS (STATCOM & SSSC).

3 Generation of FACTS (UPFC & IPFC).

Details

Static Synchronous Series Compensator (SSSC)

• Power factor correction through continuous voltage injection and in combination with a properly structured controller.

•  Load balancing in interconnected distribution networks.

•  It can also help to cover the capacitive and reactive power demand.

•  Power flow control.•  Reduces harmonic distortion by active filtering.

Benefits of SSSC

Thyristor Controlled Series Compensator(TCSC)

Series Capacitor banks installations protected by thyristors.

BENEFITS • Increased Power Transfer Capability. • Improved Transient Stability. • Lower Transmission Losses. • Improved Grid voltage control.

OTHER APPLICATIONS • Power Oscillation Damping. • Sub-synchronous Resonance Mitigation. • Transient Stability Mitigation.

Comparison:

Static Var Compensator(SVC)

Details

Static Var Compensator(SVC)The static Var compensator regulates the voltage by controlling the amount of reactive power absorbed from or injected into the power system. For example, it generates reactive power by switching capacitor banks when the system voltage is low or loads are inductive. Consequently, the reactive power demand of the lagging load is supplied by the SVC – relieving the distributing lines from delivering it. Thus, the voltage drop decreases and the voltage at the load terminals shall improve.

Likewise, the static var compensator absorbs reactive power when the system voltage is high or loads are capacitive. In this case, the SVC uses the reactors to consume the VARs from the system, thereby lowering the system voltage.

SVC

• Maximized power compensation

• Near-instantaneous response to system voltage variations

• Increased customer’s economic benefits

• Eliminate harmonics and reduce voltage distortion with appropriate shunt filters

• Load balancing on three-phase systems

Benefits of SVC

STATCOM

STATCOM- Static Compensator

Comparison:

)Unified Power Flow Controller (UPFC)

CONTROLLER-OPERATION

It is a Combined Series-Shunt Controller.

STATCOM and SSSC used for shunt and series compensation respectively.

BENEFITS

• Increases Transmission line capacity (by installing a series capacitor which reduces the net series impedance) .

• Power System Oscillation Damping.

• Control of active and reactive power flow at both sending and receiving end.

Reactive power is generated or absorbed by the shunt inverter to control bus voltage.

Reactive power is generated or absorbed by the series inverter to control the real and/or reactive power flow on the transmission line.

A portion of the real power flow on the transmission line is drawn from the bus by the shunt inverter to charge the DC capacitor.

Real power is inserted into the line through the series inverter.

Interline Power Flow Controller-UPFC

REASONS OF SHORT CIRCUIT CURRENT • Increasing Generation in high load density networks. • Interconnection between systems.

If the short-circuit current rating of the equipment in the system is exceeded, the equipment must be either upgraded or replaced, both are either very cost- or time-intensive.

Previously,Current Limitation by using reactor was done but it reduces system stability.

SCCL (Short Circuit Current Limitation) WITH FACTS

This new device operateswith zero impedance insteady-state conditionsand in case of a shortcircuit, it is switched to thelimiting-reactor impedancewithin a few milliseconds.

Uses a reactor along withTPSC (Thyristor ProtectedSeries Compensator).

HVDC • Economically transmit

electrical energy long distances via overhead lines or cable.

• Connects asynchronous grids or grids with

different frequencies.

• Costly equipments used and takes time-not so widespread.

FACTS • Offers low-cost power

delivery with the same advantages as HVDC.

• Increases Capacity of existing electrical

Transmission System.

• Rapidly Implemented Installations.

HVDC and FACTS

Thanks to All of

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