DAPC-White Paper by Shiva

8/3/2019 DAPC-White Paper by Shiva

http://slidepdf.com/reader/full/dapc-white-paper-by-shiva 1/10

Digital Active Power Conditioner (DAPC)

Written and Compiled by

Shivaji Waghmare

Addl. Gen. Manager - (R & D)

DB Power Electronics (P) Ltd. Pune

© 2006 DB Power Electronics (P) Ltd. All rights reserved. No part of this publication may be used, reproduced, photocopied, transmitted or stored in anyretrieval system of any nature, without the written permission of the copyright owner. www.dbups.com Rev. 2006-1.0 1



Table of Contents

INTRODUCTION............................................................................................................................ 3

HARMONIC DISTORTION SOURCES AND EFFECTS ............................................................................. 3HARMONIC FILTERING AND REACTIVE POWER COMPENSATION ....................................................... 3

PASSIVE FILTER........................................................................................................................... 3

(A) 3-PHASE LINE R EACTORS ......................................................................................................... 3

(B) TUNED SINGLE ARM PASSIVE FILTER ......................................................................................... 4

(C) PHASE MULTIPLICATION METHOD ............................................................................................ 4

ACTIVE FILTER ............................................................................................................................ 5

SHUNT ACTIVE FILTER .................................................................................................................... 5

COMPARATIVE STUDY OF DIFFERENT FILTERS.............................................................. 6

DIGITAL ACTIVE POWER CONDITIONER (DAPC) FROM DB......................................... 7

I NTRODUCTION ............................................................................................................................... 7

OPERATING PRINCIPLE .................................................................................................................... 7

POWER CIRCUIT .............................................................................................................................. 7

PROTECTIONS.................................................................................................................................. 7

ALARMS AND PARAMETER DISPLAY .................................................................................................. 8

LOCAL ALARMS .............................................................................................................................. 8

I NDICATIONS .................................................................................................................................... 8

FEATURES AND SPECIFICATIONS.......................................................................................... 8

FEATURES ....................................................................................................................................... 8

SPECIFICATIONS .............................................................................................................................. 8

TEST RESULT ................................................................................................................................ 9

120 K VA UPS TESTED WITH AF-150 A......................................................................................... 9

C. PF + HARMONIC CORRECTION ..................................................................................................... 9

APPLICATION AREAS............................................................................................................... 10

ACTIVE FILTER SIZING CALCULATOR.............................................................................. 10





INTRODUCTION

Harmonic distortion sources and effects

Events over the last several years have focused attention on

certain types of loads on the electrical system that results in

power quality problems for the user and utility alike. Equipmentwhich has become common place in most facilities including

Computer Power supplies

Solid state Lighting ballast

Adjustable Speed Drives (ASDs),

Uninterruptible Power Supplies (UPSs)

are the examples of non-linear loads.

Non-linear loads generate voltage and current harmonics which

can have adverse effects on equipments, designed for operation

as linear loads (i.e. Loads designed to operate on a sinusoidal

waveform of 50 or 60 Hz.).Effects of Non-linear load

Higher heating losses in the Transformers.

Harmonics can have a detrimental effect on emergency

generators, telephones and other sensitive electrical equipments.

When reactive power compensation (in the form of passive

power factor improving capacitors) is used with non-linear loads,

resonance conditions can occur that may result in even higher

levels of harmonic voltage and current distortion, thereby

causing equipment failure, disruption of power service, and fire

hazards in extreme conditions.

The electrical environment has absorbed most of these problems

in the past. However, the problem has now reached a magnitude

where Europe, the US, and other countries have proposed

standards to responsibly engineer systems considering the

electrical environment. IEEE 519-1992 and IEC 555 have

evolved to become a common requirement cited when specifying

equipment on newly engineered projects. The broad band

harmonic filter was designed in part, to meet these

specifications. The present IEEE 519-1992 document establishes

acceptable levels of harmonics (voltage and current) that can be

introduced into the incoming feeders by commercial and

industrial users. Where there may have been little cooperation

previously from manufacturers to meet such specifications, the

adoption of IEEE 519-1992 and other similar world standards

now attract the attention of everyone.

Harmonic filtering and reactive power compensation

Various techniques of improving the input current waveform are

discussed below. The intent of all techniques is to make the input

current more continuous so as to reduce the overall current

harmonic distortion. The different techniques can be classified

into four broad categories;

(a) Introduction of Line reactors and / or DC link chokes

(b) Passive Filters (Series, Shunt, and Low Pass broad band

filters)

(c) Phase Multiplication (12-pulse, 18-pulse rectifier systems)

(d) Active Harmonic Compensation.

The following paragraphs will briefly discuss the available

technologies, their relative advantages and disadvantages. The

term 3-phase Line Reactor or just Reactor is used in the

following paragraphs to denote 3-phase line inductors.

PASSIVE FILTER

(a) 3-Phase Line Reactors

Line reactors offer significant magnitudes of inductance, which

can alter the way that current is drawn by a non-linear load such

as an input rectifier bridge. The reactor makes the current

waveform less discontinuous resulting in lower current

harmonics. Since the reactor impedance increases with fre-

quency, it offers larger impedance to the flow of higher order

harmonic currents. It is thus instrumental in impeding higher

frequency current components while allowing the fundamental

frequency component to pass through with relative ease.

On knowing the input reactance value, one can estimate the

expected current harmonic distortion. A table illustrating the

expected input current harmonics for various amounts of input

reactance is shown in table below.

Input reactance is determined by the accumulated impedance of

the AC reactor, DC link choke (if used), input transformer and

cable impedance. To maximize the input reactance while

minimizing AC voltage drop, one can combine the use of both

AC input reactors and DC link chokes. One can approximate the

total effective reactance and view the expected harmonic current

distortion from the above chart. The effective impedance value

in % is based on the actual loading as derived below;

Percent Harmonics vs. Total Line Impedance

Harmonic 3% 4% 5% 6% 7% 8% 9% 10%

5th 40 34 32 30 28 26 24 23

7th 16 13 12 11 10 9 8.3 7.5

11th 7.3 6.3 5.8 5.2 5 4.3 4.2 4

13th 4.9 4.2 3.9 3.6 3.3 3.15 3 2.8

17th 3 2.4 2.2 2.1 0.9 0.7 0.5 0.4

19th 2.2 2 0.8 0.7 0.4 0.3 0.25 0.2%THID 44.13 37.31 34.96 32.65 30.35 28.04 25.92 24.68



(b) Tuned single arm passive filter (c) Phase Multiplication Method

The principle of a tuned arm passive filter is shown in Figure 1.

A tuned arm passive filter should be applied at the single lowest

harmonic component where there is significant harmonic

generation in the system. For systems that mostly supply an

industrial load this would probably be the fifth harmonic. Above

the tuned frequency the harmonics are absorbed but below that

frequency they may be amplified.

By increasing pulse, numbers of harmonics in the line current

can be reduced.

6-pulse rectifier without inductor

Manufacturing cost 100%

Typical harmonic current components.

Fundamental 5th 7th 11th 13th 17th 19th

100% 63% 54% 10% 6,1% 6,7% 4,8%

6-pulse rectifier with inductor

Figure 1 - Tuned single arm passive filter . Manufacturing cost 120%. AC or DC choke added.

Typical harmonic current components.Detuned - Single tuning frequency

Above tuned frequency harmonics absorbedFundamental 5th 7th 11th 13th 17th 19th

100% 30% 12% 8.9% 5.6% 4.4% 4.1%

Below tuned frequency harmonics may be amplified

Harmonic reduction limited by possible over compensation at

the supply frequency and network itself

This kind of filter consists of an inductor in series with a

capacitor bank and the best location for the passive filter is close

to the harmonic generating loads. This solution is not normally

used for new installations.

Tuned multiple arm passive filter

The principle of this filter is shown in Figure 2 This filter hasseveral arms tuned to two or more of the harmonic components,

which should be the lowest significant harmonic frequencies in

the system. The multiple filter has better harmonic absorption

than the one arm system.

Figure 3

12-pulse with double wound transformer


Figure 2 - Tuned multiple arm passive filter.

Fundamental 5th 7th 11th 13th 17th 19th

100% 3.6% 2.6% 7.5% 5.2% 1.2% 1.3%Capacitive below tuned frequency/Inductive above

Better harmonic absorption

Design consideration to amplification harmonics by filter

Limited by KVAr and network

The multiple arm passive filters are often used for large DC

drive installations where a dedicated transformer is supplying the

whole installation.




Shunt Active filter

Fundamental only

Supply

Active

Filter

icompensation

idistortion

Load

Figure 5 - External active filter principle diagram.

The active filter compensates the harmonics generated by

nonlinear loads by generating the same harmonic components in

opposite phase as shown in Figure 6. External active filters are

most suited to multiple small drives. They are relatively

expensive compared to other methods.

Figure 4 24-pulse rectifier


ACTIVE FILTER

Clean

Feeder

current

H a r m o n i c s

W a v e f o r m s

Load

current

Active filter

current+

A passive tuned filter introduces new resonances that can cause

additional harmonic problems. New power electronics

technologies are resulting in products that can control harmonic

distortion with active control. These active filters, see Figure 5,

provide compensation for harmonic components on the utility

system based on existing harmonic generation at any given

moment in time. Figure 6

There are different types of active filter configurations.

• Series active filter

• Shunt active filter

• Hybrid active filter.

• Active front end IGBT based PWM rectifier

• Most popular is Shunt Active filter.




Comparative Study of Different Filters

Parameters Capacitor filter Tuned filter Active filter

Type Passive Passive

IGBT based digitally

controlled

CompensationOnly compensates power factor

Compensates Harmonic Multipletuned filters are required, one for each harmonic

Compensates PF and

Harmonics. One filter cancompensate multiple

harmonics simultaneously

Suitability

Not suitable in case of

more voltage distortion andcurrent distortion

Performance varies over

frequency variation and variationin voltage distortion.

Performance is dependent on loadlevel

Performance remains

constant over frequencyand voltage variation.

Suitable in any type of environment

ResonancePossibility of resonance.This results in premature

failure of capacitor.

Possibility of resonance if tunedat higher frequency. Performance

depends on source impedance

No possibility of resonance. Stable

operation

Size and weight Bulky in sizeBulky in size when multiple

harmonics are to be compensated

Light weight. Size doesnot change even if required to compensatemore harmonics

LifeLimited life in case of morevoltage and current

harmonics

More life as compared to

capacitor filter

Longer life, since

performance remainsconstant and resonance is

avoided

Cost CheapCostlier as compared to capacitor

filter

Initial cost is more as

compared to both thefilters

No load condition

Imposes capacitive PFwhen load is reduced.

Contactors are required tocompensate for leading pf.

Imposes leading PF atfundamental frequency. So notsuitable for generator source.Compensated filter is required for

generator. Performance is tunedat full load

No capacitive PF at noload. Smooth PF

compensation. No problemto Generator source.

Performance remainsconstant over load

variation

3rd harmonic

compensation Not possible Becomes very bulky

Same filter can be used to

compensate 3rd harmonicwithout increasing the size

Selectivity Andharmonic

Compensation No selectivity

Physical components are requiredto be changed

Stability through software.Cost vs. performance is

easily possible. Thismakes it more cost

effective and flexible

Capacity increasePossible by adding morecapacitor

Redesigning is required for change of load.

More units can be addedlater on for increasing

capacity

Safety

To take of resonance problem, lot of fuses must be used. Also resonance

causes failure of other sensitive circuits

Breakers and fuses must be added per tuned filter. Also transientvoltage absorbers must be used to

avoid of other circuitry in case of resonance

Only one set of Breakersand fuses are required for

all harmonics

Power loss Low loss More loss Moderate losses




SelectivityDigital Active Power Conditioner (DAPC)from DB User can select whether to compensate both harmonics and PF or

to compensate either harmonics or power factor (Displacement

factor).Introduction

This filter works in shunt with the load. Due to this it is easier to

add it in the existing setup, even without taking load shutdown.Also it facilitates to use it at the source end with higher currents

and lower harmonics.

Power Circuit

It is based on High speed IGBT working at higher switching

frequencies. Due to which the required inductor value is reduced.

This helps in making corrections even at higher input voltages

without increasing DC operating voltages. Also it helps to

reduce losses in IGBT.

It is based on 32 bit DSP with full digital control. Digital control

makes it more stable, easy upgradeable, more flexible and no

variation or degradation of performance over a long period of

operation. Total operational technology can be changed without

changing any hardware component.

Optimized switching performance of IGBT inverter helps to

reduce EMI noise as well as improve efficiency of the inverter.

Figure 8 - Single Line Diagram for DAPC

Figure 7 Protections

DAPC is protected against

• Slow protection andOperating principle

• Fast ProtectionIt is based on source current harmonic sensing. Source current is

fed to high speed AD converter of DSP. Source current

harmonics are extracted by the DSP. These harmonics are

injected to the load by the filter. This in turn takes only

fundamental harmonic current from the mains.

Slow protection

It is for slow variations in input voltages and load. This is done

by sensing RMS values of load currents and input voltages. Each

input phase voltage is sensed independently and if, any phase

voltage is out of limit, DAPC is automatically isolated from

input.Harmonic compensation

Selective harmonic elimination method helps it to use it cost

effectively. Compromise in cost and performance can be easily

achieved. These can be set on field easily either by the traineduser or DB service engineer with the help of switches on the

control board. 5th, 7th, 11th, 13th, 17th and 19th harmonics can be

easily selected for their compensation. Also Programmable

harmonic reduction is possible.

Overload and over temperature

Filter RMS load current and Heat sink temperature of IGBT is

continuously monitored. At any instant the filter load or IGBT

temperature is exceeded than its preset level, current limit is

automatically reduced. This prevents tripping of the filter due to

overload or over temperature. It keeps filter running at reduced

capacity level (10% capacity reduction). This can happen in the

event of elevated ambient temperature. Reactive compensation

Along with harmonic compensation DAPC can compensate for

lagging or leading power factor. This compensation is also

programmable. User can have precise required PF correction set

as per his requirement. This also helps in compromising cost vs

performance. User can have PF compensation up to 0.95 or more

to reduce required capacity of Active filter. PF up to unity is possible from 0.6 lag to 0.6 lead.

Fast acting protections

These are achieved by using;

1. High speed semiconductor fuses

2. High speed protection to IGBTs.




High speed mains abnormal sensing, which includes phase

reversal and negative sequence component sensing in the input

voltage. Filter will immediately isolate form mains and again

reconnect automatically after sensing confirming mains

healthiness. This requires no manual intervention.

1. Mains abnormal

2. Over temperature

3. Over load

4. Phase reversal

Dual levels with different delays DC Over voltage protection

with hardware and software. 5. DC over voltage

6. Filter trip300% over current protection for IGBT. (Redundant protections)

External Inhibit. (Includes filter off due to hardware protections

and ON/OFF switch operation).It is ensured that IGBT is protected against all severe operating

conditions.

FMECA statistical techniques are used for these protections. Indications

Appropriate alarm is provided for all Faults and Alarms

conditions.

Following LED indications are provided on the display.

1. Filter ON

2. Filter OFFAlarms and Parameter Display

3. OV/OC

4. Sync OK.

Remote alarms

Voltage free contacts are provided for

1. Filter running

2. Filter trip

Figure 9 - Front Panel LCD Display on DAPC

Monitoring of filter through PC is possible by

1. MODBUS connectivityRemote as well as local alarms are provided for getting the status

of DAPC. 2. Monitoring through SNMP and web browser

(optional features)Following parameters are displayed locally as well as remotely;

1. Input 3 phase voltage

2. Input frequency

Features and specifications3. DC bus voltage

4. Filter currents for all three phases

Features5. Heat sink temperature

1. Closed loop active filter with source current sensing

Local Alarms 2. High attenuation upto 96% of individual harmonics

A user friendly LCD display, along with Keypad is used locally

to indicate parameters, alarms and faults. Following alarms are

provided on LCD;

3. Programmable selective harmonic elimination

4. PF compensation, leading as well as lagging

5. Selection between PF and harmonic compensation

6. Remote monitoring and diagnosis

7. IGBT based inverter design

Specifications

3 phase / 3 wire non-zero sequence compensation




Parameter DAPC 60 DAPC 100 DAPC 150

Input Voltage

range Frequency

400V, 3 Ph +10%, -15%, 50 Hz.

45 to 55 Hz

Capacity 60 A 100 A 150 A

HarmonicFiltering

5th to 19th harmonic compensation.Attenuation ratio up to 96%

Power loss infilter < 1700 w < 2800 w < 3500 w

IP ProtectionIP 32

IP42 optionalDimensions (mm)

(WxDxH)800 x 600 x

1000+100 P

800 x 600 x

1600 + 100 P

800 x 600 x

1600+ 100 P

Weight in kg. 150 275 275

Colour Havells Gray

InstallationFloor mounting. Lifting lugs provided

Cable Entry from bottom(From top Optional)

Ambient -5 to 40 0C

Humidity Up to 90 0 Rh, non condensing

OptionRemote monitoring through MODBUS,

SNMP, Web browser

Standards

• Meets IEEE 519 for compensatedharmonics.

• IEC 62040 Part II for conductedemission. Class A, for restricted use.

Potential free

contactsFilter Trip and Filter ON

B. Only Harmonic Correction

Input Current 146 A

VTHD 3.7 %

PF 0.92

DAPC Current 48 A

Voltage 221 V

ITHD 4.0 %

Power 93 kW

Figure 11

C. PF + Harmonic Correction

TEST RESULTInput Current 135 A

VTHD 2.2 %

PF 1.00

AF Bridge 95 A

Voltage 223V

ITHD 3.9 %

Power 93 kW

120 kVA UPS Tested with AF-150 A

A. Without Active Filter

Input Current 164 A

VTHD 4.8 %

PF 0.87

Voltage 217 V

ITHD 27.4 %

Power 93 kW

Figure 12

Figure 10




Application areas Active Filter Sizing Calculator

1. At the Input side of Rectifier, AC Drive, UPS

Harmonic & PF compensation

Figure 13 Figure 16

Active Filter Sizing is a tool developed to find the required size

of the DAPC.2. PF Compensation

The data gathered at the site, where the DAPC is required to be

installed, need to be inserted in to appropriate fields of Active

Filter Sizing calculator. It will then size the DAPC and its output

characteristic will also be displayed.

Figure 14

Following are the details for the Active Filter Sizing Calculator :

Load Current - Here enter the per phase current in Amp of the

Load.

ITHD % - Enter the Current Total Harmonic Distortion

measured on the load side.

KW – Calculate the total power in KW, consumed by the load.

PF – The Load power factor.

Nom Volt Ph to Ph – Enter the Phase-to-Phase voltage.

After entering all this data, please check what type of Power

Factor compensation is required at the site. Though Unity is

always better, the cost implication for achieving it need to be

considered. Click the radio button for the percentage required.

(in the above example it is clicked at 50%)

3. At the source input

Figure 15

Now press calculate button to get the following results;

Output Effective Power factor

Output Filter Current

The “filter current” field is the required size of the DAPC.


DAPC-White Paper by Shiva

Documents

Transcript of DAPC-White Paper by Shiva