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

IntroductionQuality:

A measure of excellence or a state of being free from defects, deficiencies and significant 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 MagnitudeFrequency 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 ConstantI 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

6/21/2014 Power Quality Improved using DVR 8

• Interruption

• Harmonics

Major Power Quality (PQ) Problems

6/21/2014 Power Quality Improved using DVR 9

Source: EPRI, 1994

Spikes, 7%

Sags, 56%

Outages,

6%

Swells,

31%

Importance of Voltage Sag

6/21/2014 Power Quality Improved using DVR 10

Textile Industry

Plastics Industry

Glass Industry

Process Industry

Semiconductors

Rs.60k

Rs. 60L Rs6 Cr Rs. 60 CrLosses per Voltage Sag Event

Rs.600k

PQ Improvement Techniques

Series CompensationDVRSSC

Shunt CompensationSTATCOMTCSCSeries and Shunt Compensation

TCSCUPFC

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

6/21/2014 Power Quality Improved using DVR 14

a

N

VaN

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