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Transcript
International Conference on Electrical, Electronics, and Optimization Techniques (ICEEOT) - 2016
Designing of Phase Angle control and ON-OFF
Triggering circuit for SVC reactive Power
Compensator.
Mohammed Imran
Assistant Professor [FACTS] EED Dept
Muffakham Jah College of Engineering &Technology
Hyderabad, India
[email protected]
Mohammed abdul khader aziz biabani
[Power Electronics & systems] EED Dept
Muffakham Jah College of Engineering &Technology
Hyderabad, India
[email protected]
the different semiconductor power circuits, with their internal
control enabling them to produce var output proportional to an
input reference. A static var generator whose output is varied
so as to maintain or control specific parameters (e.g. voltage,
frequency) of the electric power system.
Abstract—In this paper, to control the reactive power svc
(Static Var Compensator) is used. The operation of SVC is
depends upon two strategies. One is TCR (Thyristor control
reactor) and other one is TSC (Thyristor switch capacitor). This
two strategies is controlled by designing triggering circuit using
single IC TCA 785. Depending upon varying load demand the svc
can operates in both modes either TCR or TSC using same IC
TCA 785 based triggering scheme. For the optimum solution for
reactive power compensation the strategy control is adopted by
using IC TCA 785. Both the control schemes is control by using
one IC TCA 785, by this cost of the system will be reduced at
domestic consumer level. Comparative and experimental results
for the proposed SVC have been shown.
Keywords—Phase angle
compensator and IC TCA 785.
control,
on-off
Modern static var generators are based on high-power
semiconductor switching circuits. These switching circuits
inherently determine some of the important operating
characteristics, such as the applied voltage versus obtainable
reactive output current harmonic generation, loss versus var
output, and attainable response time, setting limits for the
achievable performance of the var generator and, independent
of the external controls used, ultimately also that of the static
var compensator.
triggering,svc
II.
I. INTRODUCTION
THYRISTOR-CONTROLLED REACTOR (TCR)
An elementary single-phase thyristor-controlled
reactor (TCR), it consists of a fixed (usually air-core) reactor
of inductance L, and a bidirectional thyristor valve (or switch).
Currently available large thyristors can block voltage up to
4000 to 9000 volts and conduct current up to 3000 to 6000
amperes. Thus, in a practical valve many thyristors (typically
10 to 20) are connected in series to meet the required blocking
voltage levels at a given power rating. A thyristor valve can be
brought into conduction by simultaneous application of a gate
pulse to all thyristors of the same polarity. The valve will
automatically block immediately after the ac current crosses
zero, unless the gate signal is reapplied.
The capacitors generate and reactors (inductors) absorb
reactive power when connected to an ac power source. They
have been used with mechanical switches for controlled var
generation and absorption since the early days of ac power
transmission. Continuously variable var generation or
absorption for dynamic system compensation was originally
provided by over-or under-excited rotating synchronous
machines and, later by saturating reactors in conjunction with
fixed capacitor.
Since the high power, line-commutated thyristors in
conjunction with capacitors and reactors have been employed
in various circuit configurations to produce variable reactive
output. These in effect provide a variable shunt impedance by
synchronously switching shunt capacitors and/or reactors “in”
and “out” of the network. Using appropriate switch control,
the var output can be controlled continuously from maximum
capacitive to maximum inductive output at a given bus
voltage. More recently gate turn-off thyristors and other power
semiconductors with internal turn-off capability have been
used in switching converter circuits to generate and absorb
reactive power without the use of ac capacitors or reactors.
These perform as ideal synchronous compensators
(condensers), in which the magnitude of the internally
generated ac voltage is varied to control the var output. All of
III.
THYRISTOR-SWITCHED CAPACITOR (TSC)
A single-phase thyristor-switched capacitor (TSC) is consist of
a capacitor, a bidirectional thyristor valve, and a relatively
small surge current limiting reactor. This reactor is needed
primarily to limit the surge current in the thyristor valve under
abnormal operating conditions (e.g., control malfunction
causing capacitor switching at a “wrong time”, when transient
free switching conditions are not satisfied); it may also be
used to avoid resonances with the ac system impedance at
particular frequencies.
978-1-4673-9939-5/16/$31.00 ©2016 IEEE
1
IV.
AC PHASE ANGLE CONTROL AND BURST OR ON/OFF FIRING
A. Working of Logic chip as AC Phase Angle Control:
•
The operation and working of logic chip component
for phase control application is
•
One input is the short duration pulses of 30 micro sec
(comparator output).
•
To make the IC work as a Phase control firing circuit,
the other input is the High frequency oscillation
pulses from 555 astable multivibrator output. This
input is connected to pin 6 of TCA 785.
•
Thus, when the two inputs of logic are high the
output goes high and it results in high pulsed pulses
at pin 14 and pin 15 of TCA 785 IC and this circuit
arrangement works as an AC phase control circuit.
3
4
5
QU
Q2
VSYNC
6
7
8
9
10
11
12
13
14
15
16
I
QZ
V REF
R9
C10
V11
C12
L
Q1
Q2
VS
Output U
Output 1 inverted
Synchronous
voltage
Inhibit
Output Z
Stabilized voltage
Ramp resistance
Ramp capacitance
Control voltage
Pulse extension
Long pulse
Output 1
Output 2
Supply voltage
B. Working of Logic chip as Burst or ON/OFF Firing:
•
The operation and working of logic chip component
for ON/OFF firing application is
•
One input is the short duration pulses of 30 micro sec
(comparator output).
•
To make the IC work as ON/OFF firing circuit, the
other input is the low frequency oscillation pulses
from 555 astable multivibrator output. This input is
connected to pin 6 of TCA 785.
•
Thus, when one inputs of logic is high and the other
is low, the output goes low and it results in low
pulsed pulses at pin 14 and pin 15 of TCA 785 IC
and this circuit arrangement works as ON/OFF firing
circuit.
V.
Fig.1 Designed Gate Friring Circuit
Fig 1 shows the triggering circuit for 1-Ф AC voltage
controller using IC TCA 785. The AC input signal vs is
stepped down by the transformer and applied to pin 5. This
signal serves as synchronization signal.
SIMULATION RESULTS
The design and simulation results of reactive power
compensation for AC phase angle control, Burst or ON/OFF
firing and IC TCA 785 are presented in this paper.
The ramp voltage at pin 10 and the control and the
control voltage at pin 11. In that pin 12 is connected to
ground. Hence the firing pulses α to π is generated. Pin 6 is
fed with inhibit pulses from 555 timer in astable mode. These
pulses are applied at about 2kHz. Therefore the triggering
signals generated on pins 14 and 15 are pulsed. The pulse pin
14 and pin 15 are passed only when 555 timer output is high.
This results in pulse based drives for pulse amplifiers T1 and
T2. The pulse amplifier T1 generates firing pulses for SCR 2
firing pulses. The ramp resistor on pin 9 can be varied to vary
firing angle(α).
Design of Thyristor Gate firing circuit:
IC TCA 785 pin description:
TABLE 1
PIN
SYMBOL
GND
1
Q2
2
FUNCTION
Ground
Output 2 inverted
2
Internal Description of IC TCA 785:
C
V
12
SYNC
S
∞
V
∞
Fig.5 Generated Ramp Voltage at Pin 10
R V
9
stab
C
V
11
10
Fig.2 Intetnal structure of IC TCA 785
Fig.6 Short duration Triggering pulses at pin 14
Fig.3 Pin 5 arrangements
Fig.7 Short duration Triggering pulses at pin 15
AC Phase Control Firing Scheme Results:
Fig.4 Input to Pin 5
3
Fig.11 Expected waveform of astable 555 multivibrator
Fig.8 Triggering pulses at α=90 for TCR.
Fig.12 Output at pin 3 of 555 timer circuit
Burst or ON/OFF Firing Scheme Results:
Fig.9 Triggering pulses at α=135 for TCR
Astable 555 multivibrator:
V
R
CC
A
V
R
CC
B
V
0
Fig. 10 Circuit of astable 555 multivibrator
Fig.13 Triggering pulses from ON /OFF circuit
4
Observation for the Working model of SVC:
TABLE 2
Current(I)
Real
in Amps
power
(MW)
Reactive
power(MVAR)
capacitor
value in
µF
Voltage
(V) in
volts
20
14.99
0.20
2.64
1.41
40
15.01
0.40
5.29
2.83
60
15.02
1.20
17.51
4.25
80
15.24
1.45
21.31
5.82
100
15.28
2.56
38.42
7.35
120
23.08
3.75
84.19
20.07
140
25.18
6.92
174.146
25.88
160
25.28
7.82
195.68
28.01
TABLE 3
Current(I)
Real
power
(MW)
Firing
angle
(α)
Voltage
(V)
50
14.99
7.64
312.50
332.83
75
15.01
6.82
317.63
333.72
90
15.02
3.71
329.49
334.17
105
15.24
2.56
341.81
344.03
120
15.28
1.43
345.14
345.84
135
23.08
1.05
788.66
789.04
150
25.18
0.33
939.12
939.16
170
25.28
1.15
946.63
946.64
Fig 14 Firing angle equal to 90 degree with maximum
conduction
Reactive
power(MVAR)
Fig 15 Firing angle equal to 120 degrees
Fig 16 Firing angle equal to 165 degrees
VI.
CONCLUSION
Depending upon the two modes of operation of SVC using
single IC TCA 785, the simulations have been performed. In
the AC phase angle control, the output results at different
firing angle ‘α’ are shown. And the burst or ON/OFF firing
scheme of output waveforms are presented. Using one IC
TCA 785, both the operations have performed. The best
control strategy or scheme which is applicable for SVC
reactive power compensation is used.
Experimental results for TCR:
The following graphs obtained when oscilloscope
was connected to the circuit when the TCR was fired at
different angles. Channel one (CH1) is the voltage waveform
across the thyristor. Channel two (CH2) is the reactor current
waveform. Channel 3 (CH3) is the supply voltage waveform
and channel four (CH4) is the thyristor current waveform.
References
[1] B. Somanathan Nair. Digital Electronics And Logic Design, sixth printing
September 2006.ISBN-81-203-1956-7.
[2] Rajiv K. Varm R. Mohan Mathur. Thyristor-Based FACTS Controllers for
Electrical Transmission Systems, volume 1. John Wiley and Sons, USA,
febraury 2002. ISBN 978-0-471-20643-1
[3] Allan T Johns Yong Hua Song. Flexible AC Transmission Systems. The
institution of Electrical Engineers, London, 199. ISBN 0-85296-771-3.
5
[4] N. G. Hingorani and L. Gyugyi. understanding FACTS Concepts and
Technology of Flexible AC Transmission Systems, volume 1. 200. ISBN
0470852712.
Professor teaching courses Electrical Machines, Industrial
Electronic Systems, Power Electronics, Linear IC
Applications in the Department of Electrical & Electronics
Engineering, Muffakham Jah College of Engineering and
Technology, Banjara Hills, Hyderabad, India, His research
area of interests includes FACTS, Power Electronic
Converters, Reactive power compensation techniques, and
generations, power electronic,
and Automation based
Industrial Welding applications.
[5] Abhijit Chakrabarti and Sunita Halder. Power system analysis operation
and control, 3rd edition New delhi, 2010. ISBN-978-81-203-4015-2
[6] Miller. Reactive power Control in Electric Systems. USA, 1982. ISBN 04718-6933-3.
[7] Hingroani Lasezlo Gyugyi Naraing G. Understanding facts. IEEE press,
USA,2000. ISBN 0-7803-3455-8.
[8]
Mohammed Abdul Khader Aziz Biabani is
a Research student, [Power Electronic
&Systems] of Electrical & Electronics
Engineering department, from Muffakham
Jah College Of Engineering & Technology,
Affiliated
to
Osmania
University
Hyderabad, Telangana, India. Received his B.Tech degree in
Electrical & Electronics Engineering from Jawaharlal Nehru
Technological University Hyderabad, Telangana, India in
2013. His research interests include Power Electronic
Systems, Power Systems, and Industrial Electronic Systems.
U.A. Bakshi and V.U.Bakshi. Basic Electrical Engineering, 2nd revised
edition 2009. SBN-9788184316940
AUTHORS
Mohammed Imran received his Bachelors in
Electrical and Electronics Engineering from
JNTU Hyderabad, AP, India in 2009 and
Master’s Degree M.Sc in Electrical
Engineering from Staffordshire University,
Stafford, England in 2011 respectively. He is working as an
6