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Automatic Power Factor Correction

Article in SSRN Electronic Journal · March 2023

DOI: 10.2139/ssrn.4376134

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Engr. Talha Akhtar

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 Automatic Power Factor Correction
Engr.Talha Akhtar; MSc Engineering Management, University of Lincoln, Lincoln, UK, BSc Electrical
(Power) Engineering, Islamia University Bahawalpur, Bahawalpur, Pakistan.
Gmail:talhaakhtar169@gmail.com

Dated: 01/03/2023

Abstract

In the present technological revolution that the system becomes stable and hence
power is very precious. It is important to increases the efficiency of the system.
find out the causes of power loss and
Index Terms— Capacitor Banks,
improve the stability of the power system.
Microcontroller, Relay Drive, and
Due to industrialization, the use of inductive
Hardware.
load has increased, and power systems have
lost their efficiency. Hence need to improve I. Introduction
the power factor with a suitable method. The increasing demand for electrical power
and the awareness of the necessity of energy
An automatic power factor correction device
saving is much up to date these days. Also,
reads the power factor from line voltage and
the awareness of power quality is increasing,
line current by determining the delay in the
and power factor correction (PFC) and
arrival of the current signal with respect to
harmonic filtering will be implemented on a
the voltage signal from the AC mains with
growing scale. Enhancing power quality
high accuracy by using an internal timer.
improvement of power factor saves costs
These time values are then calibrated as
and ensures a fast return on investment. In
phase angle and corresponding power factor.
power distribution, in low- and medium-
Then the microcontroller calculates the
voltage networks, PFC focuses on the power
compensation requirement and accordingly
flow (cosϕ) and the optimization of voltage
switches on different capacitor banks.
stability by generating reactive power to
Automatic power factor correction
improve voltage quality and reliability at the
techniques can be applied to the IT
distribution level.
industries, power systems, and also
households to make them stable, and due to
Sources of Reactive Power (inductive Power Factor:
loads) Decrease the Power Factor: The power factor is the ratio between the
• Transformers KW and the KVA drawn by an electrical
• Induction Motors load where the KW is the actual load power
• Induction generators (windmill and the KVA is the apparent load power. It
generators) is a measure of how effectively the current is

• High Intensity (HID) lighting being converted into useful work output and
more particularly is a good indicator of the

Similarly, Consumers of Reactive Power effect of the load current on the efficiency of

Increase Power Factor: the supply system.[2]

• Capacitors
• Synchronous generators (utility &
emergency)
• Synchronous motors.
The Automatic Power factor Correction is a
very useful device for improving the power
factor and sufficient transmission of active
power. If the consumer connects an
inductive load, then the power factor is Fig.1

lagging in nature, if the power factor goes

Types of Power
below 0.95(lag) hence the Electric supply
company charge penalty to the consumer. True Power: -

So, it is essential to maintain the Power The actual amount of power being used, or

factor within the limit. Automatic Power dissipated, in a circuit is called true power. It

factor correction device reads the power is measured in watts and is symbolized

factor from line voltage and line current, mathematically by the capital letter P. True

calculates the compensation required, and power is a function of the circuit’s

according to that switches on different dissipative elements, such as resistances (R).

capacitor banks.[1]
Reactive Power: -
Reactive loads such as inductors and The resistive components are:
capacitors dissipate zero power, but the fact (I) Load current
that they drop voltage and draw current (II) Loss current
gives the perception that they do dissipate The inductive components are:
power. This “dissipated power” is called the (I) Leakage reactance
reactive power and is measured in Volt- (II) Magnetizing current
Amps-Reactive (VAR). Reactive power is
represented by the capital letter Q and is a
function of a circuit's reactance (X).

Apparent Power: -
The combination of true power and reactive
power is called apparent power. It is the
product of a circuit's voltage and current,
Fig.2
without reference to phase angle. Apparent
The current due to the leakage reactance is
power is measured in the unit of Volt-Amps
dependent on the total current drawn by the
(VA) and is symbolized by the capital letter
motor, but the magnetizing current is
S. Apparent power is a function of a circuit's
independent of the load on the motor. The
total impedance (Z).
magnetizing current will typically be
Power Factor Correction
between 20% and 60% of the rated full-load
Capacitive Power Factor correction is
current of the motor.
applied to circuits that include induction
II. Proposed System
motors as a means of reducing the inductive
Microcontroller-based automatic controlling
component of the current and thereby
of power factor with a monitoring system is
reducing the losses in the supply. There
shown in fig.3 capacitive load bank is used
should be no effect on the operation of the
which develops an electric load, is applied to
motor itself. An induction motor draws
an electrical power source, and converts or
current from the supply that is made up of
dissipates the resultant power output of the
resistive components and inductive
source. This way helps to improve the power
components.[8]
factor. The status of the APFC system is which is called a capacitor bank, they are
displayed on the LCD such as lagging or fixed and switched. Fixed banks are
leading, calculated power factor, etc. If there connected permanently to the primary
is any error then a buzzer is used to indicate conductors through fused switches. Switch
the information to the user. capacitor banks are tied to the primary
system through the automated switch,
allowing them to be put online and taken
offline as needed. A distribution power
system usually connects capacitors in
parallel rather connecting in series. The
function of the shunt power capacitor is to
provide leading KVAR to an electrical
system when and where needed.[5]
The actual capacitor in farads of a capacitor
Figure 3: Block diagram of PFC using 8051 bank can be calculated using the following
microcontrollers. Equation:
The microcontroller used is AT89C51 which
𝑉𝐴𝑅
is the heart and brain of the entire APFC C = 2∏𝑓∗𝑉𝑅2
system. It takes input from the user and zero
Where,
crossings of current, and voltage waveforms.
VAR = capacitor unit VAR rating
It controls the capacitor bank as required to
C= capacitor in farad
compensate for the leading or lagging power
F = frequency
factor.[4]
VR = capacitor unit rated voltage
Modules:
III. Calculating Capacitor Bank
Requirements • Power supply
Capacitors are commonly used within a lot • Zero crossing detector
of power systems, especially electronically • Motherboard
constructed circuitry. In three phase power • Port Assignment Algorithm
system, capacitors are normally installed • Function Generator Relay driver
within an isolating non-conductor metal box, • LCD Display
Power supply:

In this power supply, we are using a step- LED through resistors, When the o/p of the
down transformer, IC regulators, Diodes, IC i.e, the voltage is given to the LED, it
Capacitors, and resistors. Explanation: - The makes its forward bias and thus LED gloves
input supply i.e., 230V AC is given to the on state, and thus the +ve voltage is
primary of the transformer (the transformer obtained. Similarly, for –ve voltage, here
is an electromechanical static device that both +ve terminals of the diodes(D1 & D4)
transforms one coil to another without is connected to the –ve terminals of the
changing its frequency) due to the magnetic capacitors and thus to the I/p of the IC
effect of the coil the flux is induced in the regulator with respect to ground. The o/p of
primary is transfer to the secondary coil. The the IC regulator (7912) which is a –ve
output of the secondary coil is given to the voltage is given to the terminal of the LED,
diodes. Here the diodes are connected in through a resistor, which makes it forward
bridge type. Diodes are used for rectification bias, LED conducts and thus LED gloves in
purposes. The output of the bridge circuit is ON state, and thus the –ve voltage is
not pure dc, somewhat rippled ac is also obtained.[6]
present. For that capacitor is connected to
The mathematical relation between ac input
the output of the diodes to remove the
and dc output is
unwanted ac, capacitors are also used for
filtering purposes. Both (-ve) terminals of Vdc = Vm /3.141 (before capacitor)
the diode (D2 & D3) is connected to the
Vd = Vm (after capacitor)
(+ve) terminal of the capacitor and thus the
input of the IC Regulator (7805 & 7812).
Here we are using Voltage regulators to get
the fixed voltage to our requirements.” A
voltage regulator is a CKT that supplies a
constant voltage regardless of changes in
load currents. These ICs are designed as
fixed voltage regulators and with adequate
heat, sinking can deliver o/p Currents’ 1A.
The o/p of the IC regulator is given to the
 Motherboard:
Despite its relatively old age, the 89C51 is
one of the most popular microcontrollers in
use today. Many derivatives
microcontrollers have since been developed
that are based on--and compatible with--the
8051. Thus, the ability to program an 89C51
is an important skill for anyone who plans to
develop products that will take advantage of
Microcontroller.[7]
Fig.4
The capacitor’s ratings are chosen
considering the voltage and current ratings
of the power supply.
Zero crossing detector:

The zero crossing detector is a sine-wave to

square-wave converter. The reference
voltage in this case is set to zero. The output
voltage waveform shows when and in what
direction an input signal crosses zero volt. If
Fig.5: Mother Board Connection to LCD
the input voltage is a low-frequency signal,
then the output voltage will be less quick to
The 89C51 has three very general types of
switch from one saturation point to another.
memory. To effectively program the 8051, it
And if there is noise in between the two
is necessary to have a basic understanding of
input nodes, the output may fluctuate
these memory types. The memory types are
between positive and negative saturation
illustrated in the following graphic.
voltage Vsat. Here IC 311 is used as a zero-
They are:
crossing detector.
On-Chip Memory, External Code Memory,
and External RAM.
The controller operates on +5 V dc, so the Step-6: - Delay is called according to the
regulated +v 5 v is supplied to pin no. 40 number stored in the accumulator.
and ground at pin no. 20. The controller Step-7: - The signals, altered in phase are
used here need not be required to handle sent to the motherboard for power factor
high-frequency signals, so as 4 MHz crystal detection.
is used for operating the processor. Pin no. 9 Program:
is supplied with a +5V dc through a push $mod51
org 0000h
switch. To reset the processor. As prepare
mov r0,#00h
codes are stored in the internal flash mov p0,#00h
clr a
memory pin no. 31 is connected to + Vcc.
ljmp main
Port Assignment: org 000bh
acall timer
Port 1: - Input to LCD.
reti
Port 2: - Input to relay driver org 001bh
acall time0
Port3.0 &
setb tr1
Port 3.1: - Input port from the function reti
org 0050h
generator.
time0:
P1.6 is used as input port increment. cpl p1.1
mov tl1,#0dfh ;e5h
P1.7 is used as an input port decrement.
mov th1,#0b1h ;f5h
Algorithm: ret
org 0070h
(a) Altering phase of two signals.
timer:
Step-1: - Timer0 set and run till Timer1 is cpl p1.0
mov tl0,#0dfh
set or vice-versa.
mov th0,#0b1h
Step-2: - Two signals (current & voltage) setb tr0
ret
are introduced.
org 0100h
Step-3: - Phase angle between the two main:
clr 00
signals altered by incrementing or
mov p1,#00h
decrementing delay between the two. setb p1.7
setb p1.6
Step-4: - Delay of 0.1 ms is given while
mov ie,#10001010b
incrementing or decrementing. mov tmod,#11h
mov tl0,#0dfh
Step-5: - Accumulator stores the number of
mov th0,#0b1h
incrementing or decrementing operations. mov tl1,#0dfh
mov th1,#0b1h l1:
setb p1.0 djnz r1,l1
setb tr0 ret
here1: delay:
cjne r0,#00h,pass mov r7,#100d
setb p1.1 zz:
setb tr1 mov r6,#100d
sjmp here ww:
pass: ] mov r5,#50d
acall delay1 qq:
djnz r0,pass djnz r5,qq
sjmp here1 djnz r6,ww
here: djnz r7,zz
jb p1.7,here2 ret
stay: end
jnb p1.7,stay
cjne a,#10h,xx Results:
clr a
This method of improving the power factor
mov r0,#00h
sjmp main gives rise to the correction of the power
xx:
factor of inductive load.
acall delay
inc a Conclusions:
mov r0,a
It can be concluded that power factor
mov p0,a
clr tr0 correction techniques can be applied to
clr tr1
industries, power systems, and also
setb p0.7
sjmp main households to make them stable, and due to
here2:
that the system becomes stable and the
jb p1.6,here
stay1: efficiency of the system as well as the
jnb p1.6,stay1
apparatus increases. The use of a
cjne a,#00h,yy
sjmp here microcontroller reduces costs. Due to the
yy:
use of a microcontroller, multiple
acall delay
dec a parameters can be controlled and the use of
mov r0,a
extra hard wares such as timer, RAM, ROM,
mov p0,a
clr tr0 and input-output ports reduces. Care should
clr tr1
be taken for overcorrection otherwise the
sjmp main
delay1: voltage and current become more due to
kk:
which the power system or machine
mov r1,#100d
 becomes unstable and the life of capacitor References:
banks reduces.
[1] P. N. Enjeti and R martinez, “A high [4] 8052 simulator for windows version
performance single 3.604
phase rectifier with input power factor 25Jun1999,sim8052@vaultbbs.com
correction ,”IEEE [5] www.fsinc.com
Trans. Power [6] www.keil.com
Electron..vol.11,No.2,Mar.2003.pp 311-317 [7] Electric power industry reconstructing in
[2] J.G. Cho,J.W. Won,H.S. Lee , “Reduced India, Present
conduction loss scenario and future prospects, S.N. Singh,
zero-voltage-transition power factor senior
correction converter member, IEEE and S.C. Srivastava, Senior
with low cost,”IEEE Trans.Industrial Member, IEEE
Electron..vol.45,no [8] “Power factror correction”, Reference
3,Jun. 2000,pp395-400 design from
[3] “The 8051 Microcontroller and Freescale http://www.freescale.com
Embedded Systems” by
Muhammad Ali Mazidi and Janice Gillispie
Mazidi

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