voltage regulation in a distribution system using oltc · voltage regulation in a distribution...

IJSRD - International Journal for Scientific Research & Development| Vol. 6, Issue 03, 2018 | ISSN (online): 2321-0613

All rights reserved by www.ijsrd.com 2056

Voltage Regulation in a Distribution System using OLTC

M.Kayalvizhi1 T.Rampradesh2

1UG Scholar 2Associate Professor 1,2IFET College of engineering, Villupuram, Tamilnadu, India

Abstract— The aim of this project is to determine dispatch

schedule for the on load tap changer optimally, distributed

generator settings, shunt capacitor switching, generation

profile per day. It proposes the voltage control and reactive

coordinative control. It helps in reducing the real power

losses, improves the voltage profile. This can be done by

using the squared deviations of the bus voltages. The

proposed methods can be used to adjust the taps of OLTC,

values of the capacitor banks and adjusting the value of

AVR. The mentioned method using Dynamic programming

(DP), Branch and bounce method (BB), voltage sensitivity

factor internally (VSF). And also minimize the states to 24.

The result shows that regulation of power by changing the

taps, and also shows effectiveness by reducing in cost,

reducing the voltage deviation factor.

Key words: On Load Tap Changer, Power Quality

Maintenance, Smart- Distribution System

I. INTRODUCTION

In distribution lines many power quality problems are

occurring due to the reason that increase of load in the utility

sides such as home, industries, business centers. Along with

load variation the line impendence increasing also increases

the problems. Hence the whole system will be affected by

the power quality issues. The main reason is that the

utilization of more energy during the requirements of the

power for specified applications.

The power demands increase hence the power

quality problems also increases. Because of existing system

has no the capability to do the regulation quickly. It can be

done by the tap change

This will be the key factor for the regulation of the

power according to our demands of the power. There are

various tap changers are used in the existing power system.

They are off load tap changers, on load tap changers,

mechanical no load tap changers, electromechanical on load

tap changers, thysristor assisted tap changers, solid state tap

changers.

Mostly mechanical no load tap changers are used in

all distribution system to employ voltage regulation.

However they are not having the capability to be as on load

tap changers. On load tap changer has automatically

changing the taps. Even though they are widely applied in

all the power transformers, low cost and maintenance is

provided. They are operated by the specialized workers

only. Here also the de- energized, so the cost of the system

will be increased. And then electromechanical on load tap

changers, they will do the tap changing while connected

with the load hence it is known to be automatically doing

the tap changing. But they need high cost to implement. And

it also causes the arc producing and carbonization. Hence go

for the electronic OLTC. This taps have advantages of

detecting the load variation and send the signals to the

microcontroller to connect the taps with the transformer

according to the load.

In this system, going to reduce the switches those

are going to tap with the transformers. Hence the losses

occurring in the system is reduced, and also efficient tap

changing is provided. Automatic voltage regulation is done

by the tap changing circuit which is connected to the

transformer. Hence they don’t need external circuits for

compensation of the power quality problems. They are easy

to operate and control automatically due to the reason that

they are highly protected from the high voltage stresses and

over current during the operations.

It identifies the fault conditions through the sensing

transformer, and sending the signals to the relay to

disconnect the main line from the load. It will be a secured

method to obtain the goal. They have high reliability and

steady state operation. Dielectric strength will be high. They

have controlled voltage and current values and it is

represented by the simulation output in the simulation result.

The hardware implementation is given that shown in figure.

It will be key factor for the future scope of the electrical

development.

II. SYSTEM DESIGN

III. BLOCK DIAGRAM

It consists of the 230 volt ac supply that can be stepped

down into 12 volt ac supply through the step down

transformer.


(IJSRD/Vol. 6/Issue 03/2018/492)


IV. GENERATION SIDE

After that the full bridge rectifier is used to rectify the ac

voltage into dc supply.

V. RECTIFIER CIRCUIT

In order to remove the ripple contents that present in the

rectified voltage capacitor is connected across the rectifier

circuit. The pure dc voltage is given to the IC regulators,

7812 IC regulator convert the 12 volt AC voltage into 12

volt DC voltage. And then 7805 IC regulator convert the 12

volt AC supply into 5 volt DC. The voltage from the 7812

IC regulator is given to the relay circuit. The voltage from

the 7805 IC regulator is given to the microcontroller as input

supply.

When the over load conditions occur the voltage is

reducing, the current will be increased. Hence the demands

in the generating side are increased. The generating

transformer is suffering from the power factor lagging due

to the voltage generation capacity is increased beyond the

limit.

While connecting the normal load to the

distribution transformer there is no problem arising in the

transformer. Increasing in load causes the voltage to be

mitigated through the generation unit, due to lag of voltage

in distribution side. Consider while connecting the extra

load in the load side, the taps in the current transformer is

automatically changing according to the load requirements.

VI. ON LOAD TAP CHANGING

In addition to distribution transformer the current

transformer is adding to mitigate the voltage reduction. It is

switched by the relay circuit. By frequent monitoring of the

voltage and current in the distribution transformer, we can

add or remove the taps from the transformer.

When the current is high, switching speed is high.

When current is low, switching period is low. Hence

according to the variation of the current in the transformer,

tap changing is done.

The dispatch scheduling must be done in order to

minimize the system losses. The current and voltage through

the shunt capacitance and the tap changings are monitoring

whole day. Hence the schedules to control the voltage and

reactive power can be obtained.

The voltage is varying according to the load

variation in a day so the tapping also according to the load.

The optimal dispatch control is mainly used to minimize the

reactive power losses, improve the system voltage profile

and DG output. Distribution generator output obtained based

on the time series. This dispatch problem can be analyzing

through voltage sensitivity factor the dynamic

programming and branch and bounce method .

Voltage sensitivity factor gives the flow of voltage

through the network and nodal voltages. Hence the variation

in the current is determined. Dynamic programming is used

to optimization of the problem. It is the method for solving

the complex problem into simpler one. It will compare with

the previous solutions and give the best solutions.

Branch and bounce method is used to solve discrete

optimization problems and also for small instances of the

hard problems. It uses the upper and lower bounds methods.

The tap position is limited to small, hence the computational

problems are reduced.

Evaluation index is used to get the system losses

and receiving power factor. We can calculate the cost of the

power losses and the electricity price.

VII. SIMULATION WORK




A. Simulation circuit for the OLTC

B. Grid voltage, Load voltage, Injected voltage

This waveform shows the result of the grid voltage, load

voltage, injected voltage. It can be seen that the voltage is

regulated through the OLTC and capacitors.

C. Output Grid voltage

This shows the simulation result of the grid voltage while

provide to the grid from the generator. It shows the normal

voltage in the beginning and in the middle it gives the

dipping of voltages and finally provides the regulated

voltage in pure sinusoidal waveform.

D. Output Grid current

This waveform shows the result of output current. It gives

the normal current at the beginning stage, when the fault

condition occurs it gives the over current

E. V and I in mux

This waveform shows the result of voltage in the

multiplexer. It can be seen that output from the multiplexer,

give the rectified output in form pure sinusoidal waveform

F. Gate pulses

This waveform shows the result of the gate pulses that

would be given to the thyristor switches to trigger.

G. DC link voltage1

This waveform shows the result of the DC link voltage1. It

can be seen that the rise of the voltage at the beginning and

after control it maintained at the maximum voltage




H. DC link voltage

It shows the dc link voltage from the circuit.

I. Load voltage

This waveform shows that load voltage is in controlled state

after the tap changing done in the transformer.

J. Injected voltage

This waveform shows that the injected voltage is regulated

through the rectifier network connected across the circuit

before given to the load.

VIII. HARDWARE DEVELOPMENT

Photo copy of the hardware

IX. RESULT:

X. CONCLUSION:

This project proposes the voltage and current control of the

distribution generator using the OLTC. By changing the

transformer taps to mitigate the voltage reduction in the

system. It involves using the dynamic programming, VSF,

Branch and bounce methods. It is convenient to use this

method to identify the voltage reduction and changing the

taps. It reduces the power losses, increases the voltage

profile. Evolution index is used to determine the cost and

values of power factor.

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Parameters Ratings

Input voltage 230 v single phase

Input current 1.3A while tapping

Output voltage 230 v single phase

Output current 240 v while over voltage changes

Maximum timing switching 1 seconds

Minimum timing switching 15 seconds

Variable resistor level 10 kohms




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voltage regulation in a distribution system using oltc · voltage regulation in a distribution...

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