ABSTRACT:

Unified Power Quality Conditioner (UPQC) forharmonic elimination and simultaneous compensation ofvoltage and current, which improves the power quality offeredfor other harmonic sensitive loads. UPQC consist of combinedseries active power filter that compensates voltage harmonics ofthe power supply, and shunt active power filter thatcompensates harmonic currents of a non-linear load. In thispaper a new control algorithm for the UPQC system isoptimized and simplified without transformer voltage, load andfilter current measurement, so that system performance isimproved. The proposed control technique has been evaluatedand tested under dynamical and steady state load conditionsusing MATLAB software.

CHAPTER - 1

1.INTRODUCTION

Continuous and fast development of power system has made FACTS an

effective tool for its development. Among various FACTS controllers

Unified Power Quality Conditioner [UPQC] is chosen as it embraces all

basic attributes of the transmission.

The mathematical model of the UPQC is developed and employed for the

load flow control studies. By using UPQC the power flow control becomes

more flexible than ever. But it has a drawback which requires pre-specified

condition such as the power flow in the transmission line where it is being

embedded. As no one has prior knowledge about this the pre-specified

power flow and voltage are arbitrary. This projects aims to present a

systematic and efficient method for performing load flow calculation of a

generalized power system with multi-machines and multiUPQC’s.

1.2 FACTS

INTRODUCTION TO FACTS

We need transmission interconnections because, apart from delivery, the

purpose of the transmission network is to pool plants and load centers in

order to minimize the total power generation capacity and fuel cost.

Transmission interconnections enable taking advantage of diversity of

loads, availability of sources, and fuel price in order to supply electricity to

the loads at minimum cost with a required reliability. In general, if a power

delivery system was made up of radial lines from individual local generators

without being part of a grid system, many more generation resources would

be needed to serve the load with the same reliability, and the cost of

electricity would be much higher. With that perspective, transmission is

often an alternative to a new generation resource. Less transmission

capability means that more generation resources would be required

regardless of whether the system is made up of large or small power plants.

In fact small distributed generation becomes more economically viable if

there is a backbone of a transmission grid. One cannot be really sure about

what the optimum balance is between generation and transmission unless the

system planners use advanced methods of analysis which integrate

transmission planning into an integrated value – based

transmission/generation planning scenario. The cost of transmission lines

and losses, as well as difficulties encountered in building new transmission

lines, would often limit the available transmission capacity. It seems that

there are many cases where economic energy or reserve sharing is

constrained by transmission capacity, and the situation is not getting any

better. In a deregulated electric service environment, an effective electric

grid is vital to the competitive environment of reliable electric service. On

the other hand, as power transfers grow, the power system becomes

increasingly more complex to operate and the system can become less secure

for riding through the major outages. It may lead to large power flows with

inadequate control, excessive reactive power in various parts of the system,

large dynamic swings between different parts of the system and bottlenecks,

and thus the full potential of transmission interconnections cannot be

utilized. The power systems of today, by and large, are mechanically

controlled. There is a widespread use of microelectronics, computers and

high speed communications for control and protection of present

transmission systems; however, when operating signals are sent to the power

circuits, where the final power control action is taken, the switching devices

are mechanical and there is little high speed control. Another problem with

mechanical devices is that control cannot be initiated frequently, because

these mechanical devices tend to wear out very quickly compared to static

devices. In effect, from the point of view of both dynamic and steady – state

operation, the system is really uncontrolled. Power system planners,

operators, and engineers have learned to live with this limitation by using a

variety of ingenious techniques to make the system work effectively, but at a

price of providing greater operating margins and redundancies. These

represent an asset that can be effectively utilized with prudent use of FACTS

technology on a selective, as needed basis. In recent years, greater demands

have been placed on the transmission network, and these demands will

continue to increase because of the increasing number of nonutility

generators and heightened competition among utilities themselves. Added to

this is the problem that it is very difficult to acquire new rights of way.

Increased demands on transmission, absence of long-term planning, and the

need to provide open access to generating companies and customers, all

together have created tendencies toward less security and reduced quality of

supply. The FACTS technology is essential to alleviate some but not all of

these difficulties by enabling utilities to get the most service from their

transmission facilities and enhance grid reliability. It must be stressed,

however, that for many of the capacity expansion needs, building of new

lines or upgrading current and voltage capability of existing lines and

corridors will be necessary.

2.2 Opportunities for FACTS:

What is most interesting for transmission planners is that FACTS technology

opens up new opportunities for controlling power and enhancing the usable

capacity of present, as well as new and upgraded. The possibility that current

through a line can be controlled at a reasonable cost enables a large potential

of increasing the capacity of existing lines with larger conductors, and use of

one of the FACTS Controllers to enable corresponding power to flow

through such lines under normal and contingency conditions.

These opportunities arise through the ability of FACTS Controllers to

control the interrelated parameters that govern the operation of transmission

systems including series impedance, shunt impedance, current, voltage,

phase angle, and the damping of oscillations at various frequencies below

the rated frequency. These constraints cannot be overcome, while

maintaining the required system reliability, by mechanical means without

lowering the useable transmission capacity. By providing added flexibility,

FACTS Controllers can enable a line to carry power closer to its thermal

rating. Mechanical switching needs to be supplemented by rapid-response

power electronics. It must be emphasized that FACTS is an enabling

technology, and not a one-on-one substitute for mechanical switches.

The FACTS technology is not a single high-power Controller, but rather a

collection of Controllers, which can be applied individually or in

coordination 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, their production can

eventually take advantage of technologies of scale. Just as the transistor is

the basic element for a whole variety of microelectronic chips and circuits,

the thyristor or high-power transistor is the basic element for a variety of

high-power electronic Controllers.

FACTS technology also lends itself to extending usable transmission limits

in a step-by-step manner with incremental investment as and when required.

A planner could foresee a progressive scenario of mechanical switching

means and enabling FACTS Controllers such that the transmission lines will

involve a combination of mechanical and FACTS Controllers to achieve the

objective in an appropriate, staged investment scenario.

It is also worth pointing out that, in the implementation of FACTS

technology, we are dealing with a base technology, proven through HVDC

and high-power industrial drives. Nevertheless, as power semiconductor

devices continue to improve, particularly the devices with turn-off

capability, and as FACTS Controller concepts advance, the cost of FACTS

Controllers will continue to decrease. Large-scale use of FACTS technology

is an assured scenario.

1.3 Limiting the load capability

Assuming that the ownership is not an issue, and the objective is to make the

best use of the transmission asset, and to maximize the loading capability

(taking into account contingency conditions), what limits the loading

capability, and what can be done about it?

Basically, there are three kinds of limitations:

_ Thermal

_ Dielectric

_ Stability

Thermal: Thermal capability of an overhead line is a function of the

ambient temperature, wind conditions, condition of the conductor, and

ground clearance. It varies perhaps by a factor of 2 to 1 due to the variable

environment and the loading history. The nominal rating of a line is

generally decided on a conservative basis, envisioning a statistically worst

ambient environment case scenario. Yet this scenario occurs but rarely

which means that in reality, most of the time, there is a lot more real time

capacity than assumed. Some utilities assign winter and summer ratings, yet

this still leaves a considerable margin to play with. There are also off-line

computer programs that can calculate a line’s loading capability based on

available ambient environment and recent loading history. Then there are the

on-line monitoring devices that provide a basis for on-line real-time loading

capability. These methods have evolved over a period of many years , and,

given the age of automation (typified by GPS systems and low-cost

sophisticated communication services), it surely makes sense to consider

reasonable, day to day, hour to hour, or even real-time capability

information. Sometimes, the ambient conditions can actually be worse than

assumed, and having the means to determine actual rating of the line could

be useful.

During planning/design stages, normal loading of the lines is frequently

decided on a loss evaluation basis under assumptions which may have

changed for a variety of reasons; however losses can be taken into account

on the real-time value basis of extra loading capability.

Of course, increasing the rating of a transmission circuit involves

consideration of the real-time ratings of the transformers and other

equipment as well, some of which may also have to be changed in order to

increase the loading on the lines. Real-time loading capability of

transformers is also a function of ambient temperature, aging of the

transformer and recent loading history.

Off-line and on-line loading capability monitors can also be used to obtain

real time loading capability of transformers. Also, the transformer also lends

itself to enhanced cooling.

Then there is the possibility of upgrading a line by changing the conduction

to that of a higher current rating, which may in turn require structural

upgrading.

Finally, there is the possibility of converting a single-circuit to a double-

circuit line.

Once the higher current capability is available, then the question arises of

how it should be used. Will the extra power actually flow and be

controllable? The FACTS technology can help in making an effective use of

this newfound capacity.

Dielectric: From an insulation point of view, many lines are designed very

conservatively. For a given nominal voltage rating, it is often possible to

increase normal operation by +10% voltage (i.e.500kV-550kV) or even

higher. Care is then needed to ensure that dynamic and transient

overvoltages are within limits. Modern gapless arresters, or line insulators

with internal gapless arresters, or powerful thyristor-controlled overvoltage

suppressors at the substations can enable significant increase in the line and

substation voltage capability. The FACTS technology could be used to

ensure acceptable over-voltage and power flow conditions.

Stability: There are a number of stability issues that limit the transmission

capability. These include:

_ Transient stability

_ Dynamic stability

_ Steady-state stability

_ Frequency stability

_ Voltage collapse

_ Sub synchronous resonance

The FACTS technology can certainly be used to overcome any of the

stability limits, in which case the ultimate limits would be thermal and

dielectric.

1.4 RELATIVE IMPORTANCE OF CONTROLLABLE

PARAMETERS:

_ Control of the line impedance X (e.g., with a thyristor-controlled series

capacitor) can provide a powerful means of current control

_ Injecting a voltage in series with the line, and perpendicular to the

current flow, can increase or decrease the magnitude of current flow.

Since the current flow lags the driving voltage by 90 degrees, this

means injection of reactive power in series, (e.g., with static

synchronous series compensation) can provide a powerful means of

controlling the line current, and hence the active power when the angle

is not large.

_ Injecting voltage in series with the line and with any phase angle with

respect to the driving voltage can control the magnitude and the phase

of the line current. This means that injecting a voltage phasor with

variable phase angle can provide a powerful means of precisely

controlling the active and reactive power flow. This requires injection

of both active and reactive power in series.

_ Because the per unit line impedance is usually a small fraction of the

line voltage, the MVA rating of a series Controller will often be a

small fraction of the throughput line MVA..

_ When the angle is not large, which is often the case, control of X or the

angle substantially provides the control of active power.

Control of angle (with a Phase Angle Regulator, for example), which

in turn controls the driving voltage, provides a powerful means of

controlling the current flow and hence active power flow when the

angle is not large.

Combination of the line impedance control with a series Controller and

voltage regulation with a shunt controller can also provide a costeffective

means to control both the active and reactive power flow

between the two systems.

1.5 CHECKLIST OF POSSIBLE BENEFITS FROM FACTS

TECHNOLOGY:

FACTS Controllers enable the transmission owners to

obtain, one or more of the following benefits:

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.

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 there

by decreasing over all generation reserve requirements on both sides.

Provide greater flexibility in siting new generation.

Upgrade of lines.

Reduce reactive power flows, thus allowing the lines to carry more active

power.

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. It is also important to note that thermal capability of a line varies

by a very large margin based on the environmental conditions and loading

history _ Reduce loop flows.

Increase utilization of lowest cost generation. One of the principal reasons

for Transmission interconnection is to utilize lowest cost generation.

1.6. BASIC TYPES OF FACTS CONTROLLERS:

In general, FACTS controllers can be divided into four categories:

1.Series controllers

2.Shunt controllers

3.Combined series – series controllers

4.Combined series – shunt controllers

CHAPTER - 2

2.1 SERIES CONTROLLERS:

The series controller could be a variable impedance, such as capacitor,

reactor, etc., or a power electronics based variable source of main frequency,

sub synchronous and harmonic frequencies to serve the desired need. In

principle, all series controllers inject voltage in series with the line. Even a

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 the line current, the series controller only supplies (or)

consumes variable reactive power.

The basic type of series controller with and without energy storage element

is shown in figure 3.1.

Figure2.1 Series

SERIES CONTROLLERS

2.2 SHUNT CONTROLLERS:

As in the case of series controllers, the shunt controllers may be variable

impedance, Variable source, or a combination of these. In principle, all shunt

controllers inject current into the system at the point of connection. Even a

variable shunt impedance connected to the line voltage causes a variable

current flow and hence represents injection of current into the line. As long

as the injected current is in phase quadrature with the line voltage, the shunt

controller only supplies or consumes variable reactive power. The basic type

of shunt controllers are shown in figure.

2.3 COMBINED SERIES-SERIES CONTROLLERS:

This could be a combination of separate series controllers, which are

controlled in a coordinated manner, is a multilane transmission system or it

could be a united controller in which series controllers provide independent

series reactive compensation for each line but also transfer real power

among the line via the power link. The real power transfer capability of the

unified series – series controller,

referred to as interline power flow controller, makes it possible to balance

both the real and reactive power flow in the lines and there by maximize the

utilization of the transmission system. Note that the term “Unified” here

means that the dc terminals of all controller converters are all connected

together for real power transfer.

2.4 COMBINED SERIES-SHUNT CONTROLLERS:

This could be a combination of separate shunt and series controllers, which

are controlled in a coordinated manner, or a Unified Power Flow Controller

with series and shunt elements. 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.

The schematic diagram of UPFC is shown in figure.

GENERATING STATION

TRANSMISSION LINES

UPFC

LOAD

CONTROL UNIT

CHAPTER – 3

BLOCK DIAGRAM:

BLOCK DESCRIPTION:

Circuit diagram:

Kgfvlsaj’kfgasghs’g

CIRCUIT DESCRIPTION:

CHAPTER – 4

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.

The UPFC, by means of angularly unconstrained series voltage injection, is

able to control, concurrently or selectively, the transmission line voltage,

impedance, and angle or, alternatively, the real and reactive power flow in

the line. The UPFC may also provide independently controllable shunt

reactive compensation.

In UPFC, which combines a STATCOM and an SSSC the active power for

the series unit (SSSC) is obtained from the line itself via the shunt unit

STATCOM. The latter is also used for voltage control with control of its

reactive power. This is a complete controller for controlling active and

reactive power control through the line, as well as line voltage control.

Additional storage such as super conducting magnet connected to the dc link

via an electronic interface would provide the means of further enhancing the

effectiveness of the UPFC. The controller exchange of real power with an

external source, such as storage is much more effective in control of system

dynamics than modulation of the power transfer within a system.

4. THE UNIFIED POWER FLOW CONTROLLER

The unified power flow controller (UPFC) concept was proposed by Gyugyi

in 1991.

The UPFC was derived for the real time control and dynamic compensation

of ac transmission systems, providing multifunctional flexibility required to

solve many of the problems facing the power delivery industry. Within the

framework of traditional power transmission concepts, the UPFC us able to

control, simultaneously or selectively, all the parameters affecting power

flow in the transmission line (i.e., voltage, impedance, and phase angle), and

this unique capability is signified by the adjective “unified” in its name.

Alternatively, it can independently control both the real and reactive power

flow in the line. The reader should recall that, for all the Controllers

discussed in the previous chapters, the control of real power is associated

with similar change in reactive power, i.e., increased real power flow also

resulted in increased reactive line power.

In order to increase the system reliability and provide flexibility for future

system changes, the UPFC installation was required to allow self-sufficient

operation of the shunt converter as an independent STATCOM and the

series converter as an independent Static Synchronous Series Compensator

(SSSC). It is also possible to couple both converters together to provide

either shunt only or series only compensation over a doubled control range.

BASIC OPERATING PRINCIPLES:

From the conceptual view point, the UPQC is a generalized synchronous

voltage source (SVS), represented at the fundamental (power system)

frequency by voltage phasor Vpq with controllable magnitude Vpq (0< Vpq

< Vpqmax) and in series with the transmission line, as illustrated for the

usual elementary two-machine system (or for two independent systems with

a transmission link intertie) in Figure . In this functionally unrestricted

operation, which clearly includes voltage and angle regulation, the SVS

generally exchanges both reactive and real power with the transmission

System. Since, as established previously, a SVS is able to generate only the

reactive power exchanged, the real power must be supplied to it, or absorbed

from it, by a suitable power supply or sink. In the UPFC arrangement the

real power exchanged is provided by one of the end buses (e.g., the sending-

end bus), as indicated in Figure .

In the presently used practical implementation, the UPFC consists of two

voltage-source converters. These back-to-back converters, labeled

“Converter 1” and Converter 2” in the figure 4.1, are operated from a

common dc link provided by a dc storage capacitor. As indicated before, this

arrangement functions as an ideal ac-to-ac power converter in which the real

power can freely flow in either direction between the ac terminals of the two

converters, and each converter can independently generate (or absorb)

reactive power at its own ac output terminal.

Converter 2 provides the main function of the UPFC by injecting voltage

Vpq with controllable magnitude Vpq and phase angle in series with the

line via an insertion transformer. This injected voltage acts essentially as a

synchronous ac voltage source. The transmission line current flows through

this voltage source resulting in reactive and real power exchange between it

and the ac system. The reactive power exchanged at the ac terminal (i.e., at

the terminal of the series insertion transformer) is generated internally by the

converter. The real power exchanged at the ac terminal is converted into dc

power which appears at the dc link as a positive or Negative real power

demand.

The basic function of Converter 1 is to supply or absorb the real power

demanded by Converter 2 at the common dc link to support the real power

exchange resulting from the series voltage injection. This dc link power

demand of Converter 2 is converted back to ac by Converter 1 and coupled

to the transmission line bus via a shunt- connected transformer. In addition

to the real power need of Converter 2, Converter 1 can also generate or

absorb controllable reactive power, if it is desired, and thereby provide

independent shunt reactive compensation for the line. It is important to note

that whereas there is a closed direct path for the real power negotiated by the

action of series voltage injection through Converters 1 and 2 back to the line,

the corresponding reactive power exchanged is supplied or absorbed locally

by Converter 2 and therefore does not have to be transmitted by the line.

Thus, converter 1 can be operated at a unity power factor or be controlled to

have a reactive power exchange with the line independent of the reactive

power exchanged by Converter 2. Obviously, there can be no reactive power

flow through the UPQC dc link.

4.2 UPQC OPERATION STRATEGY:

During system disturbances, mechanically switched shunt capacitor banks

and associated controls are generally slow to react. Under actual system

contingency conditions, all of these banks may not switch on (hunting

concerns) or some may over-correct the voltage and lock-out. To resolve this

situation, the UPFC is required to maintain a predetermined reactive power

margin to maximize the shunt converter’s dynamic reactive power reserve

for system contingency conditions. This ensures that the controllable

reactive power range of the shunt converter is available at all times to

compensate for dynamic system disturbances. The shunt capacitor banks

will be switched on and off to maintain the reserve UPFC and SVC margins

during steady state load fluctuations.

POWER FLOW CONTROL. Actual flow on the line could be higher

depending on other prevailing system conditions. The UPFC, therefore, may

be required to slightly reduce the line loadings. Line reactive power flow and

its direction will be monitored to help maintain the dynamic reactive power

margin of the shunt inverter.

The series power flow control becomes important during contingency

conditions. The control objective is to increase the line loading. This control

is to be activated as soon as any one of the line loadings exceeds 90% of

their respective emergency thermal ratings. The UPFC has to increase line

loading until the critical line loadings are reduced below the defined levels

or the UPFC reaches its rating limit.

4.3 DESCRIPTION OF THE UPQC:

The Unified Power Flow Controller is designed to meet the defined system

requirements, in particular, to provide fast reactive shunt compensation.

In order to increase the system reliability and provide flexibility for future

system changes, the UPFC installation was required to allow self-sufficient

operation of the shunt converter as an independent STATCOM and the

series converter as an independent Static Synchronous Series Compensator

(SSSC). It is also possible to couple both converters together to provide

either shunt only or series only compensation over a doubled control range.

Power Circuit Structure

The UPFC equipment comprises two identical GTO thyristor-based

converters.

Each converter includes multiple high-power GTO valve structures feeding

an intermediate (low-voltage) transformer. The converter output is a three-

phase voltage set of nearly sinusoidal (48 pulse) quality that is coupled to

the transmission line by a conventional (three-winding to three-winding)

main coupling transformer. The shunt connected transformer has a delta-

connected primary, and the series transformer has three separate primary

windings each rated for the phase voltage. To maximize the versatility of the

installation, two identical main shunt transformers and a single main series

transformer have been provided. With this arrangement, a number of power

circuit configurations are possible. Converter 1 can operate as a STATCOM

with either one of the two main shunt transformers, while Converter 2

operates as an SSSC. Alternatively, Converter 2 can be connected to the

spare main shunt transformer and can operate as an additional STATCOM.

Control System Both converters comprising the UPFC are controlled from

a single central control system housed in three cabinets in the control room.

Two of the cabinets house the relay interface and signal conditioning, while

a single cabinet contains the control electronics.

The actual control algorithms that govern the instantaneous operation of the

two converters are performed in the real-time control electronics which

employs multiple digital signal processors. The real-time control

communicates with the pole electronics mounted on each pole via the valve

interface that is linked to the poles by fiber-optic cables. The status

processor is connected to every part of the system, including the cooling

system and all of the poles, by serial communications. During run time it

continually monitors the operation of all subsystems, collecting analyzing

status information. It is responsible for all start-up and shutdown sequences

and for the organizing and annunciation of all alarm conditions. The status

processor is serially connected to a graphical display terminal which

provides the local operator interface. A hierarchical arrangement of

graphical display screens gives the operator access to all system settings and

parameters, and provides extensive diagnostic information right down to the

individual GTO modules.

A typical layout of UPQC installed in a substation is shown in the figure.

4. UPQC layout

CHAPTER - 5

5.1 MODELLING

MODELLING OF UPQC:

The Model of the UPQC can be illustrated by the equivalent circuit

shown in figure5.1.Each of the three following basic controllable parameters

of the UPFC are modulated separately and they fall in the region.

UT [0,UTmax], φT [0,2π], Iq [-Iqmax, Iqmax]∈ ∈ ∈

The mathematical relations of the UPFC parameters are given by,

Us = UP + UT

Is = IP-Iq- It

arg (Iq) = arg (UP) ± π/2

In this model , we have considered the UPFC is placed at the centre of a

medium transmission line(100km). The equations for sending end active and

reactive power can be obtained from the real and imaginary powers of power

equation as follows:

Ps= Real part of [Vs∟α × Is*]

=0.138+0.25× sin(αb-α ) -0.138× cosα

Qs= Imaginary part of [Vs∟α × Is*]

=1.56-1.56 ×cos α + 0.25 × cos(α-αb)

+0.02 sin(α-αb)-0.138sinα

The variation limits of αb and α are according to the following to the

following relation:

0 ≤ αb ≤ 2п

0≤ α ≤ 0.71 radians

5.2 LOAD FLOW EQUATIONS WITH UPQC:

For the UPFC embedded transmission line with one end denoted as

node 1 and the other as node m, the load-flow equations can be expressed as:

PG1 – PL1 = Σ j l Ui Uj (Gij cosij + Bij Sinij).------------------(5.1)∈

QG1 – QL1 = Σ j l Ui Uj (Gij Sinij – Bij Sinij)-------------------(5.2)∈

i =1,2,………n; but i # l, m.

PGl – PLl = Σ j m U1 Uj (Gij Cosij + Bij Sinij) + ΔPl ---------(5.3)∈

QGl – QLl = Σ j m U1 Uj (Gij Sinij – Bij Cosij) + ΔQl-------(5.4)∈

PGm – PLm = Σ j m UmUj (Gmj Cosmj + Bmj Sinmj) + ΔPm----(5.5)∈

QGm – QLm= Σ j m UmUj (Gmj Sinmj - Bmj Cosmj) + ΔQm----(5.6)∈

CHAPTER – 6

ATMEGA CONTROLLER

ATMEGA 8089S52 DESCRIPTION-

AT89S52 MICROCONTROLLER

Features

Compatible with MCS®-51 Products

8K Bytes of In-System Programmable (ISP) Flash Memory –

Endurance: 1000 Write/Erase Cycles

4.0V to 5.5V Operating Range

Fully Static Operation: 0 Hz to 33 MHz

Three-level Program Memory Lock

256 x 8-bit Internal RAM

32 Programmable I/O Lines

Three 16-bit Timer/Counters

Eight Interrupt Sources

Full Duplex UART Serial Channel

Low-power Idle and Power-down Modes

Description

The AT89S52 is a low-power, high-performance CMOS 8-bit microcontroller

with 8K bytes of in-system programmable Flash memory. The device is manufactured

using Atmel’s high-density nonvolatile memory technology and is compatible with the

Indus-try-standard 80C51 instruction set and pin out. The on-chip Flash allows the

program memory to be reprogrammed in-system or by a conventional nonvolatile

memory pro-grammer. By combining a versatile 8-bit CPU with in-system programmable

Flash on a monolithic chip, the Atmel AT89S52 is a powerful microcontroller which

provides a highly-flexible and cost-effective solution to many embedded control

applications.

The AT89S52 provides the following standard features: 8K bytes of Flash, 256

bytes of RAM, 32 I/O lines, Watchdog timer, two data pointers, three 16-bit

timer/counters, a six-vector two-level interrupt architecture, a full duplex serial port, on-

chip oscillator, and clock circuitry. In addition, the AT89S52 is designed with static logic

for operation down to zero frequency and supports two software selectable power saving

modes. The Idle Mode stops the CPU while allowing the RAM, timer/counters, serial

port, and interrupt system to continue functioning. The Power-down mode saves the

RAM con-tents but freezes the oscillator, disabling all other chip functions until the next

interrupt or hardware reset.

Figure.3.5. Block diagram of the microcontroller

Figure.3.6. Pin diagram of 89s52

Pin Description

VCC

Supply voltage.

GND

Ground.

Port 0

Port 0 is an 8-bit open drain bidirectional I/O port. As an output port, each pin

can sink eight TTL inputs. When 1s are written to port 0 pins, the pins can be used as

high-impedance inputs. Port 0 can also be configured to be the multiplexed low-order

address/data bus during accesses to external program and data memory. In this mode, P0

has internal pull-ups. Port 0 also receives the code bytes during Flash programming and

outputs the code bytes during program verification. External pull-ups are required during

program verification.

Port 1

Port 1 is an 8-bit bidirectional I/O port with internal pull-ups. The Port 1

output buffers can sink/source four TTL inputs. When 1s are written to Port 1 pins, they

are pulled high by the inter-nal pull-ups and can be used as inputs. As inputs, Port 1 pins

that are externally being pulled low will source current (IIL) because of the internal pull-

ups. In addition, P1.0 and P1.1 can be configured to be the timer/counter 2 external count

input (P1.0/T2) and the timer/counter 2 trigger input (P1.1/T2EX), respectively, as shown

in the following table. Port 1 also receives the low-order address bytes during Flash

programming and verification.

Table.3.3. Port functions

Port 2

Port 2 is an 8-bit bidirectional I/O port with internal pull-ups. The Port 2

output buffers can sink/source four TTL inputs. When 1s are written to Port 2 pins, they

are pulled high by the internal pull-ups and can be used as inputs. As inputs, Port 2 pins

that are externally being pulled low will source current (IIL) because of the internal pull-

ups. Port 2 emits the high-order address byte during fetches from external program

memory and during accesses to external data memory that uses 16-bit addresses (MOVX

@ DPTR). In this application, Port 2 uses strong internal pull-ups when emitting 1s.

During accesses to external data memory that uses 8-bit addresses (MOVX @ RI), Port 2

emits the contents of the P2 Special Function Register. Port 2 also receives the high-order

address bits and some control signals during Flash programming and verification.

Port Pin Alternate Functions

P1.0 T2 (external count input to Timer/Counter 2), clock-out P1.1 T2EX

(Timer/Counter 2 capture/reload trigger and direction control) P1.5 MOSI (used for In-

System Programming) P1.6 MISO (used for In-System Programming) P1.7 SCK (used

for In-System Programming)

Port 3

Port 3 is an 8-bit bidirectional I/O port with internal pull-ups. The Port 3

output buffers can sink/source four TTL inputs. When 1s are written to Port 3 pins, they

are pulled high by the internal pull-ups and can be used as inputs. As inputs, Port 3 pins

that are externally being pulled low will source current (IIL) because of the pull-ups. Port

3 receives some control signals for Flash programming and verification. Port 3 also

serves the functions of various special features of the AT89S52, as shown in the

following table.

Table.3.4.Alternate Port functions of 89s52

RST

Reset input. A high on this pin for two machine cycles while the oscillator is

running resets the device. This pin drives high for 98 oscillator periods after the

Watchdog times out.

ALE/PROG

Address Latch Enable (ALE) is an output pulse for latching the low byte of

the address during accesses to external memory. This pin is also the program pulse input

(PROG) during Flash programming. In normal operation, ALE is emitted at a constant

rate of 1/6 the oscillator frequency and may be used for external timing or clocking

purposes. Note, however, that one ALE pulse is skipped during each access to external

data memory. If desired, ALE operation can be disabled by setting bit 0 of SFR location

8EH. With the bit set, ALE is active only during a MOVX or MOVC instruction.

Otherwise, the pin is weakly pulled high. Setting the ALE-disable bit has no effect if the

microcontroller is in external execution mode.

PSEN

Program Store Enable (PSEN) is the read strobe to external program memory.

When the AT89S52 is executing code from external program memory, PSEN is activated

twice each machine cycle, except that two PSEN activations are skipped during each

access to external data memory.

EA/VPP

External Access Enable. EA must be strapped to GND in order to enable the

device to fetch code from external program memory locations starting at 0000H up to

FFFFH. Note, however, that if lock bit 1 is programmed, EA will be internally latched on

reset. EA should be strapped to VCC for internal program executions. This pin also

receives the 12-volt programming enable voltage (VPP) during Flash programming.

XTAL1

Input to the inverting oscillator amplifier and input to the internal clock

operating circuit.

XTAL2

Output from the inverting oscillator amplifier.

Memory Organization

MCS-51 devices have a separate address space for Program and Data

Memory. Up to 64K bytes each of external Program and Data Memory can be addressed.

Program Memory

If the EA pin is connected to GND, all program fetches are directed to

external memory. On the AT89S52, if EA is connected to VCC, program fetches to

addresses 0000H through 1FFFH are directed to internal memory and fetches to

addresses 2000H through FFFFH are to external memory.

Data Memory

The AT89S52 implements 256 bytes of on-chip RAM. The upper 128 bytes

occupy a parallel address space to the Special Function Registers. This means that the

upper 128 bytes have the same addresses as the SFR space but are physically separate

from SFR space. When an instruction accesses an internal location above address 7FH,

the address mode used in the instruction specifies whether the CPU accesses the upper

128 bytes of RAM or the SFR space.

CHAPTER – 7

ANALYSIS OF UPFC

7.1 INTRODUCTION TO MATLAB

MATLAB (matrix laboratory) is a numerical computing environment and

fourth-generation programming language. Developed by MathWorks,

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.

Although MATLAB is intended primarily for numerical computing, an

optional toolbox uses the MuPAD symbolic engine, allowing access to

symbolic computing capabilities. An additional package, Simulink, adds

graphical multi-domain simulation and Model-Based Design for dynamic

and embedded systems.

In 2004, MATLAB had around one million users across industry and

academia.[2] MATLAB users come from various backgrounds of

engineering, science, and economics. MATLAB is widely used in academic

and research institutions as well as industrial enterprises.

7.2 SIMULATION SETUP:

The simulation model including a power system with a transmission line.

The UPFC installed near the sending end effectively controls the power flow

from sending to receiving end.

CHAPTER – 8

CONCLUSION