Power Quality Improvement Using A DVR (Dynamic Voltage Restorer) ABSTRACT Power quality is one of major problems in the today’s scenario. It has become important with the introduction of complex devices, whose performance is very sensitive to the quality of power supply. Power quality problem is an occurrence developed as a nonstandard voltage, current or frequency that results in a failure of end use equipment. Some of the major problems dealt here is the power sag and swell. This paper describes the effectiveness of using dynamic voltage restorer (DVR) in order to mitigate voltage sags and swells in low voltage distribution systems. Dynamic Voltage Restorer can provide the most cost effective solution to mitigate voltage sags and swells that is required by customer. The Dynamic Voltage Restorer (DVR) is a rapid, flexible and resourceful solution to power quality problems.

1. P O W E R Q U A L I T Y I M P R O V E M E N T U S I N G D V R
PR ESEN TED
BY
A .S.SA I SU M A N TH
( 1 2 R9 1 A 024 8 )
TEEGALA KRISHNA REDDY ENGINEERING COLLEGE
A
TECHNICAL SEMINAR
ON
Technical seminar coordinators
Mr A. Naga Sridhar Asst. professor
Mr B. Ramesh Asst. professor
Head of the department
Prof P. Krishna

2. ABSTRACT
Power quality is one of major problems in the
today’s scenario. It has become important with the
introduction of complex devices, whose performance is
very sensitive to the quality of power supply. Power
quality problem is an occurrence developed as a
nonstandard voltage, current or frequency that results
in a failure of end use equipment. Some of the major
problems dealt here is the power sag and swell. This
paper describes the effectiveness of using dynamic
voltage restorer (DVR) in order to mitigate voltage sags
and swells in low voltage distribution systems. Dynamic
Voltage Restorer can provide the most cost effective
solution to mitigate voltage sags and swells that is
required by customer. The Dynamic Voltage Restorer
(DVR) is a rapid, flexible and resourceful solution to
power quality problems.

3. INTRODUCTION
• Power quality is of great importance in all modern
environments where electricity is involved
• It has become important with the introduction of
complex devices, whose performance is very
sensitive to the quality of power supply.
• Power quality problem is an occurrence developed
as a nonstandard voltage, current or frequency
that results in a failure of end use equipment.
• These problems may cause the apparatus
tripping, shutdown commercial, domestic and
industrial equipment, and miss process of drive
system.

4. Extensive use of sensitive electronic equipment has
increased power quality problems like
1.Transients
2.voltage sag
3.voltage swell
4.voltage interruption

5. DYNAMIC VOLTAGE RESTORER
The Dynamic Voltage Restorer
(DVR), also referred to as the Series
Voltage Booster (SVB) or the Static
Series Compensator (SSC), is a device
that utilizes solid state (or static)
power electronic components, and is
connected in series to the utility
primary distribution circuit.
• Dynamic Voltage Restorer is a power electronic device that
can protect sensitive loads from various disturbances in the power
supply.
• The basic principle of a DVR is simple, by supplying a
voltage of desired magnitude and frequency, the DVR
restores the load voltage to a desired pre-sag voltage
quantity even when source voltage is not balanced.

6. • Circuit Diagram of DVR
• Equivalent circuit diagram of DVR

7. BASIC CONFIGURATIONS OF DVR
DVR comprises of three main parts
1. Voltage
injection
transformer
2.Energy storage
unit
3. Inverter
4.Passive filters
5.By-pass switch

8. VOLTAGE SAG (OR DIP)
• Description: A decrease of the normal voltage level
between 10 and 90% of the nominal RMS voltage at the
power frequency, for durations of 0.5 cycle to 1 minute.

9. Causes:
• Faults on the transmission or distribution
network (most of the times on parallel feeders).
• Faults in consumer’s installation.
• Connection of heavy loads and start-up of large
motors.
Consequences:
• Malfunction of microprocessor-based control
systems(PCs, PLCs, ASDs, etc.)
• Tripping of contactors and relays
• Disconnection and loss of efficiency in rotating
machines.

10. THREE-PHASE SAG VOLTAGES

11. VOLTAGE SWELL
• Description: Momentary increase of the voltage, at
the power frequency, outside the normal tolerances,
with duration of more than one cycle and typically
less than a few seconds.

12. Causes:
• Start/stop of heavy loads
• badly dimensioned power sources
• badly regulated transformers (mainly during
off-peak hours).
Consequences:
• Data loss, flickering of lighting and screen
• stoppage or damage of sensitive equipment if
the voltage values are too high.

13. THREE-PHASE SWELL VOLTAGES

14. ADVANTAGES
• DVR is mostly preferred because it is less expensive. If
compared to DSTATCOM and UPS, DVR is a lot
cheaper.
• UPS requires a lot of maintenance which may be due
to problems of battery leakage and replacement.
• DVR is small in size and is a better power effective
device as compared to others link UPS, SMES and
DSTATCOM.
• DVR also compensates line voltage harmonics

15. LIMITATIONS
to keep its cost low as well as to reduce the
voltage drop across it in standby mode.
• In order to reduce the cost of DVR, the
energy storage size of DVR is kept low. Due
to voltage dips, the stored energy can deplete
fast and therefore to avoid load tripping due
to insufficient stored energy, an adequate
control is required.
• DVR has a limited
current conduction
and voltage
injection capability
,due to such design
of DVR

16. CONCLUSION
• Therefore, when applying DVRs, it is vital to
consider
1.Nature of the load
2.Voltage supply
3.Transmission system
• This also explains various advantages and
limitations related to DVR