An Overview on
Power Quality
Improvement
using Multilevel Inverter based
Dynamic Voltage Restorer
Ms. M. Maheswari
6/21/2014
Power Quality Improved using DVR
1
Introduction
Quality:
A measure of excellence or a state of
being free from defects, deficiencies and signifi
cant variations.
Power Quality:
Worthiness of electrical power to
consumer devices i.e. not to disturb or damage
appliances and devices.
6/21/2014
Power Quality Improved using DVR
2
Parameters considered
for Power Quality
Voltage Magnitude
Frequency
Wave-shape.
6/21/2014
Power Quality Improved using DVR
3
Effects of Power Quality
 Power Quality issues cause business problems such
as:
– Lost productivity, wastage of manpower and
equipments
– Customer and/or management dissatisfaction
– Heavy financial impact
 According to Electric Light and Power Magazine,
30% to 40 % of All Business Downtime Is Related to
Power Quality issues.
6/21/2014
Power Quality Improved using DVR
4
Why Power Quality is Big issue
Presently?
– Widespread Usage of Sensitive Loads in
all Applications (PLC based equipments,
Computers and the like)
– For certain devices, a momentary
disturbance may result in
• scrambled data
• interrupted communications
• a frozen mouse
• system crashes and equipment failure
6/21/2014
Power Quality Improved using DVR
5
Power Quality = Voltage Quality
P=V*I * CosΦ
V – Supply Voltage – Always Constant
I and CosΦ – Depends on the nature of load
6/21/2014
Power Quality Improved using DVR
6
Power Quality / Voltage Quality
Issues
• Voltage Sag
• Voltage Swell
6/21/2014
Power Quality Improved using DVR
7
Power Quality / Voltage Quality Issues
• Interruption
• Harmonics
6/21/2014
Power Quality Improved using DVR
8
Major Power Quality (PQ) Problems
Outages,
6%
Spikes, 7%
Swells,
Sags, 56%
31%
Source: EPRI, 1994
6/21/2014
Power Quality Improved using DVR
9
Importance of Voltage Sag
Textile Industry
Plastics Industry
Glass Industry
Process Industry
Semiconductors
Rs.60k
Rs.600k
Rs. 60L
Rs6 Cr
Rs. 60 Cr
Losses per Voltage Sag Event
6/21/2014
Power Quality Improved using DVR
10
PQ Improvement Techniques
Series Compensation
DVR
SSC
Shunt Compensation
STATCOM
TCSC
Series and Shunt Compensation TCSC
UPFC
6/21/2014
Power Quality Improved using DVR
11
Dynamic Voltage Restorer (DVR)
 Series compensation device
 Protects sensitive electric loads
from PQ problems
Implemented
through
power
electronic controllers that use
voltage source converters (VSC).
6/21/2014
Power Quality Improved using DVR
12
Block Diagram of DVR
6/21/2014
Power Quality Improved using DVR
13
Operation of DVR
a
VaN
N
6/21/2014
Power Quality Improved using DVR
14
Twentyseven Level Inverter
6/21/2014
Power Quality Improved using DVR
15
Questions???
6/21/2014
Power Quality Improved using DVR
16
6/21/2014
Power Quality Improved using DVR
17