maximise efficiency & reliability - maintain ‘healthy’ electrical network with harmonic-less

Maximise Efficiency & Reliability: Maintain ‘healthy’ electrical network with harmonic-less

Ch’ng Eng Yong, CEng MEI, CEM, CMVP, PEM

July 2016

Schneider Electric 1

What are we discussing today

● Solve the harmonic issue, if possible, starting from the root of the problem.

●A cost effective solution requires the knowledge of the


●A cost effective solution requires the knowledge of the electrical power system and it is often a combination of several solutions.

●Harmonic mitigation solutions are available in market to fulfill your needs.

Agenda

●Why is there harmonic in the electrical network?

●General waveform signature (IEC 61000-3-6)

●Typical harmonic mitigation solutions



●Solutions comparison

●What’s next?

●Conclusion

Why is there harmonic in the electrical network?

●Look at the full-bridge rectifier schematic

●Diode forward bias: ●Anode is more positive than cathode ●DC bus voltage is less than supply voltage

DC bus voltage U

DC bus iC

U


iC

DC bus capacitor

current (I C)

Supply voltage (V)

Supply current

(i)

V = E - Zsi

iC

i

V

Why is there harmonic in the electrical network?

iC


Vc

-Vc

t

ei

Agenda







●What’s next?

●Conclusion

General waveform signature (IEC 61000-3-6)

CurrentType of Load Typical Waveform Distortion

Single Phase 80%Power Supply (high 3rd)

high 2nd, 3rd,Semiconverter 4th at partial

loads

6 Pulse Converter,capacitive smoothing, 80%no series inductance

0 10 20 30 40-1.0

-0.5

0.0

0.5

1.0

Time (mS)

Current

0 10 20 30 40-1.0

-0.5

0.0

0.5

1.0

Time (mS)

Current

-0.5

0.0

0.5

1.0

Current


no series inductance

6 Pulse Converter,capacitive smoothing 40%

with series inductance > 3%,or dc drive

6 Pulse Converterwith large inductor 28%

for current smoothing

12 Pulse Converter 15%

AC Voltage varies withRegulator firing angle

FluorescentLighting 17%

0 10 20 30 40-1.0

Time (mS)

0 10 20 30 40-1.0

-0.5

0.0

0.5

1.0

Time (mS)

Current

0 10 20 30 40-1.0

-0.5

0.0

0.5

1.0

Time (mS)

Current

0.0 10.0 20.0 30.0 40.0-1.000

-0.500

0.000

0.500

1.000

Time (mS)

Current

0 10 20 30 40-1.0

-0.5

0.0

0.5

1.0

Time (mS)

Current

0 10 20 30 40-1.0

-0.5

0.0

0.5

1.0

Time (mS)

Current

Typical harmonic mitigation solutions

●Equipment based solutions●DC/AC choke●Passive filter●Drive isolation transformer (DIT)●Multi-pulse VSD


●Multi-pulse VSD●Active front end (AFE)●C-less technology

●System based solutions●Passive filter (Tuned power factor correction)●Phase shifting transformer●Zero-sequence harmonic filter●Active harmonic filter

Harmonic mitigation solutions

I. DC/AC Line Chokes

II. Passive Filters

III. Zero-Sequence Harmonic Filter

IV. Drive Isolation Transformer (DIT)


V. Phase Shifting Transformer

VI. Multi-pulse VSD (12, 18, 24, …)

VII. Active Harmonic Filters (AHF)

VIII. Active Front End (AFE)

IX. C - Less Technology

DC choke & line choke (installation)


DC choke & line choke (performance)

●Effect of the choke: dt

diLVL =

0.0

0.5

1.0

Current

0.0

0.5

1.0

Current


Line current spectrum

1.211.54

4.51

6.77

12.36

15.32

20.77

22.88

25.16

0

5

10

15

20

25

30

1 3 5 7 9 11 13 15 17 19 21 23 25

Harmonic order

I (A

)

Without additional choke

THDI = 100%Line current spectrum

9.38

3.201.80

0.87 0.74 0.49 0.35 0.30

25.94

0

5

10

15

20

25

30

1 3 5 7 9 11 13 15 17 19 21 23 25

Harmonic order

I (A

)

With additional choke 3%

THDI = 40%

With additional large choke (>5%)

0 10 20 30 40-1.0

-0.5

Time (mS)

Current


1.211.54

4.51

6.77

12.36

15.32

20.77

22.88

25.16

0

5

10

15

20

25

30

1 3 5 7 9 11 13 15 17 19 21 23 25

Harmonic order

I (A

)

Without additional choke


9.38

3.201.80

0.87 0.74 0.49 0.35 0.30

25.94

0

5

10

15

20

25

30

1 3 5 7 9 11 13 15 17 19 21 23 25

Harmonic order

I (A

)

With additional choke 3%

THDI = 40%

With additional large choke (>5%)

0 10 20 30 40-1.0

-0.5

Time (mS)

Current

THDI = 30%

DC choke vs. line choke

● Influence of the nature of reactors ● In terms of harmonics, the results are quite similar.●DC bus choke is a little smaller and the voltage drop is lower.

Inductor 2mH in the DC busLine inductor 3 x 1mH Inductor 2mH in the DC busLine inductor 3 x 1mH


9,38

3,201,80

0,87 0,74 0,49 0,35 0,30

25,94

0

5

10

15

20

25

30

1 3 5 7 9 11 13 15 17 19 21 23 25

Harmonic order

I (A

)

THDI = 39.16 %

6,65

4,142,23 1,73 1,39 1,12 0,99 0,81

25,80

0

5

10

15

20

25

30

1 3 5 7 9 11 13 15 17 19 21 23 25

Harmonic order

I (A

)

THDI = 35.54 %

ChokeACChokeDC 3 =

9,38

3,201,80

0,87 0,74 0,49 0,35 0,30

25,94

0

5

10

15

20

25

30

1 3 5 7 9 11 13 15 17 19 21 23 25

Harmonic order

I (A

)

THDI = 39.16 %

9,38

3,201,80

0,87 0,74 0,49 0,35 0,30

25,94

0

5

10

15

20

25

30

1 3 5 7 9 11 13 15 17 19 21 23 25

Harmonic order

I (A

)

THDI = 39.16 %

9,38

3,201,80

0,87 0,74 0,49 0,35 0,30

25,94

0

5

10

15

20

25

30

1 3 5 7 9 11 13 15 17 19 21 23 25

Harmonic order

I (A

)

THDI = 39.16 %

6,65

4,142,23 1,73 1,39 1,12 0,99 0,81

25,80

0

5

10

15

20

25

30

1 3 5 7 9 11 13 15 17 19 21 23 25

Harmonic order

I (A

)

THDI = 35.54 %

6,65

4,142,23 1,73 1,39 1,12 0,99 0,81

25,80

0

5

10

15

20

25

30

1 3 5 7 9 11 13 15 17 19 21 23 25

Harmonic order

I (A

)

THDI = 35.54 %

ChokeACChokeDC 3 =

DC choke & line choke (practical considerations)

● Most cost effective solution (0-20% of drive cost).

● Reduce THDI around 30 - 50%.

● Bulky and heavy.

● Proper ventilation.

Advantages Concerns


● Reduce THDI around 30 - 50%.

● Line chokes protects the drive front end, limits voltage spikes and short circuit current.

● Depending on load condition, might not be able to meet standard requirements.

● Voltage drop ( >5%) can affect low line supply conditions. Lowers torque performance at full speed when voltage drop is higher.


I. DC/AC line chokes

Ii. Passive filters

Iii. Zero-sequence harmonic filter

Iv. Drive isolation transformer (DIT)


V. Phase shifting transformer

Vi. Multi-pulse VSD (12, 18, 24, …)

VII. Active harmonic filters (AHF)

Viii. Active front end (AFE)

Ix. C - less technology

Passive filter (tuned PFC)

●Two type of passive filter● Load based passive filter● Global passive filter

●Load based passive filter ● Designed & sized based on the load size (kW)


● Designed & sized based on the load size (kW)● Operate when the connected load is in operation

●Global passive filter● Designed & sized based on the system power factor requirements.● Compensation is based on required kVAR (PF) in the system.● Primary function: Harmonic filtering● Secondary function: Power factor correction● Different from Detuned Power Factor Correction (reverse role)

Passive filter – load based (performance)


With simple choke THDI 48% With passive filter THDI 10%With simple choke THDI 48% With passive filter THDI 10%

Global passive filter

●Don’t confuse with detuned Power Factor Correction (PFC)●Detuned tuning point is typically outside -8% of target harmonic order ● a.k.a. Anti-Resonant PFC●Primary function: PFC●Secondary function: Harmonic filtering (side-effect) – Not that effective


●Tuned/Passive harmonic filter PFC●Tuned tuning point is typically within -8% of target harmonic order ●Cannot fully compensate the according to harmonic.

●Both PFC’s activation based on displacement power factor

Power factor – which component?

Power factor in system with linear loads only.


P = kW (Real Power)

D = kVAH

(Distortion Power)

Q = kVAr (Reactive Power)

S = kVA (Apparent Power)

θTPF (True/Total Power Factor)

Power factor component in system with harmonics (linear + nonlinear loads)

Power factor components in system with harmonics

D = kVAH

(Distortion Power)

Q = kVAr (Reactive Power)

S = kVA (Apparent Power)

θTPF (True/Total Power Factor)

( )

22

1

22

222

11

kkk

rmsrms

THDTHDIV

IV

IV

DQPkVAS

rmsrms

++=

=

=++=

∑∞

=


P = kW (Real Power)

(True/Total Power Factor)

221

11

11

11

IV

IV

THDTHDS

THDTHDIVrmsrms

++=

++=

True/Total Power Factor : distPFdispPFTPF θθθ coscoscos ⋅=

Displacement Power Factor (Fundamental Components):

1

cosS

kWdispPF =θ

Distortion Power Factor (Harmonic Components): 22 11

1cos

IV

distPFTHDTHD ++

=θ

Passive filter (load based)

Advantages Concerns

● Able to reduce THDI to around 5 - 16%.

● Line chokes protects the drive front end, limits voltage spikes


● Expensive (50 - 80% drive cost).


front end, limits voltage spikes and short circuit current.

● Meet IEC 61000 requirements

● Designed for full load capacity to obtain effective impedance.

● Filter capacitor (passive filter) must be disconnected when VSD operates at no load or low load condition. (causing leading PF & voltage regulation concern is remain connected)



Ii. Passive filters









Zero-sequence harmonic filter

● Issue with neutral overloading

Phase A (50 Amps)

Phase B (50 Amps)

Electronic

Loads


Phase B (50 Amps)

Phase C (57 Amps)

Neutral (82 Amps)

Zero-sequence harmonic filter

●Typical solution for neutral overloading:●Upsize neutral: “200% Neutral” – 173% maximum current, so provides a

little extra margin ●Concern: All neutral connected components need to be upsized too.

●Zero-Sequence Harmonic Filter


●Zero-Sequence Harmonic Filter●Installed close to the nonlinear loads (e.g. DB)●Concern: Proper ventilation and bulky

●Active Harmonic Filter●Installed at upstream (Global solutions)●Concern: Expensive and bulky

Zero-sequence harmonic filter – principle


Zero-sequence harmonic filter –performance


Reduction ratio = 1:10



Ii. Passive filters









Drive isolation transformer (DIT)

●Designed with oversized core & special windings

●Can withstand high heat & harsh operational environment

●Electrically isolation secondary (Wye) source from primary (Delta)


●Secondary source (Wye) is grounded●Prevent transfer of common-mode noise and/or ground current●Reduce transients and surges

●Four Basic Functions:●Voltage change (Delta-Wye windings)●Common-mode noise & impulse reduction●Reduction of drive induced ground currents ●Reduction of drive distortion effects on system voltage

Drive isolation transformer (DIT)

Advantages Concerns● Trap triplen harmonic order in

delta windings (zero-sequence network)

● Protects the drive front end,


● Expensive (50 - 80% drive cost).


limits voltage spikes and short circuit current.

● Reduce common-mode noise, induced ground current, impulse from either both sides.

● Cannot completely isolate the harmonic (positive-sequence network)



Ii. Passive filters









Phase shifting transformer

●Phase shifting involves separating the electrical supply into two or more outputs.

●Each output being phase shifted with respect to each other with an appropriate angle for the harmonic pairs to be eliminated.

● The concept is to displace the harmonic current pairs in order to bring each to a 180o phase shift so that they cancel each other out.


180o phase shift so that they cancel each other out.●Positive-sequence currents will act against negative-sequence currents. ● Zero-sequence currents (triplen order) act against each other in a three-phase

system.●An angular displacement of:

● 60o is required between two three-phase outputs to cancel 3rd harmonic currents;● 30o is required between two three-phase outputs to attenuate the 5th and 7th harmonic

current pairs;● 20o is required between two three-phase outputs to cancel the 11th and 13th harmonic

current pairs.


30o with respect to

0o with respect to primary

An angular displacement

of 30 o


( )

−+−≅ ...11

11cos

7

7cos

5

5coscos

321

ttttti

ωωωωπ

ω

5th & 7th harmonics go away!

( )

−−+≅ ...11

11cos

7

7cos

5

5coscos

322

ttttti

ωωωωπ

ω

respect to primary

primary


Advantages Concerns

● Protects the drive front end, limits voltage spikes and short circuit current.

● Trap triplen harmonic order in

● Bulky, heavy

● Expensive (100% drive cost)


● Trap triplen harmonic order in delta windings

● Attenuations of 5th and 7th

harmonic currents with an angular displacement of 30o .

● Both transformers (same rating) have to be loaded equally to achieve optimum harmonic attenuation.

● Transformer must be able to withstand excessive heat due to harmonic current.



Ii. Passive filters









Multi-pulse VSD

●Harmonics can be reduced by phase multiplication.

● If n six-pulse rectifier sections…● have the same transformer ratios,● have transformers with identical impedance's,


● have transformers with identical impedance's,● are phase shifted exactly 60°/n degrees from each other (where n = set of

rectifiers) or 360o/m (where m = number of pulse)

●Then…● 2 set of rectifier sections phase shifted by 30° result in 12-pulse row up H7

are slightly reduced● 3 set of rectifier sections phase shifted by 20° result in 18-pulse row up to

H13 are slightly reduced

Multi-pulse VSD – 12 pulse VSD

●12 pulses supply structure ●Using the concept of phase-shifting transformer of 30o

Phase shifted by 30°


Delta

Star

6 pulsesrectifier

6 pulsesrectifier

M

Inverter

H5 and H7 attenuated


●18 pulses supply structure ●Using the concept of phase-shifting transformer of 20o


Multi-pulse VSD comparison (6, 12, 18 pulse)

● 12-Pulse converter

+

-

DC Bus Load

Delta

Delta

Wye

AC Line


A

B

C

DC+

DC-

LineReactor

Rectifier Assembly

TransformerTertiary

MultipulseTransformer

A

BC

1

2

3

4

56

7

8

9


DC LinkReactor

M


Externally mounted 3 winding transformer; more wire and cabling; complicated

Current slightly distorted Ithd 8% to 15% (depending on network impedance)

0

100

A

12 pulse

Large footprint, more steel & copper (losses)

Current wave form goodIthd 4% to 6% (depending on network impedance)

0.0s 0.02s

0

100

A

18 pulse

Tertiary

“C-less” or 3% reactance min (if included); small footprint, simplified cabling

Current waveform distortedIthd 30% to 50% with 3% reactor (depending on network impedance)

0

100

A

6 pulse

Multi-pulse VSD

Advantages Concerns

● Eliminates rows up to H7,(12p), up to H13(18p)

● Reduces THD(I) down to 10-15%(12p), 5-3%(18p)

● Very Bulky and heavy



10-15%(12p), 5-3%(18p)

● Suppresses line voltage transients

● Efficient on the all load range


● Needs 2 or 3 diodes bridge rectifier

● Needs a specific transformer windings

● More cost effective for high power VSD ( >100kW)



Ii. Passive filters









Active harmonic filter (AHF)

●Leading-edge technology for harmonic filtering● IGBTs, 20 kHz modulation, to synthesize the output current for injection●Real time control algorithms

●Responds instantly to inrush situations (100µs)●Full response in 8 msec for steady sate situations


●Full response in 8 msec for steady sate situations

Active harmonic filter – schematic diagram

IGBTs manage the power flow to/from the DC bus caps

decouples the filter board inductor/capacitor circuit from the

AC lines


three phase AC line connection remove the carrier frequency from

the current waveform sent into the AC lines.

200k AIC

Active harmonic filter – control block

AC Phase

VdcIGBT Converter

Lext CTi Lin

K1

R1

Cdc

CB


Load

Notch Filter

SMPS Board

Control Board

Regulation &

Monitoring

Control Signal

CTa

Active harmonic filter (performance)


Active harmonic filter (AHF)

Advantages Concerns

● Reduces THD(I) below 5%

● Several units can be installed on the same supply


● Reliability (more components)


● Global solutions

● Resonance elimination

● Corrects displacement power factor (cos θ)

● CT direction & location must be correct



Ii. Passive filters









Active front end

●The solution use an active rectifier bridge made with IGBTs instead of the standard 6 diodes rectifier.●The rectifier is controlled in order to ‘create’ a sinusoidal current into the

network (THDI <5%)● It has the advantage to reverse the power flow and allows the feedback


of energy into the network (regenerative mode when the motor slow down or during braking phase).

Current

Voltage

Active Front End

Active front end – comparison

Current THD (%)

Voltage THD (%)RSC=20

Voltage THD (%)RSC=100


+ Inductor

Active front end (AFE)

Advantages Concerns

● Nearly sinus supply (THDI<5%)


● Very expensive if reversibility not needed (150% drive cost)

● Need additional EMC filter


● Reversible, allows to feedback energy onto the network

● Can be embedded in the drive

● Need additional EMC filter

● Reliability (IGBT, more components)



Ii. Passive filters









C-less technology - principle

●DC bus capacitor value is reduced to 2-3% of standard AC drive capacitor value.

●Current only flows from the mains into the DC link when the mains voltage exceeds that of the capacitor (diode forward bias).


●The larger the DC link capacitor, the shorter the period of current flow, and the higher the peak current.

A non demanding load like a fan allows 95% reduction of the DC bus capacitance without significant reduction of performances.

Less capacitance --> less current harmonics

Rectifier D C Link Inverter

Thre

ePhase Power C

+

-

C-less technology – performance comparison

0 10 20 30 40-1.0

-0.5

0.0

0.5

1.0

Time (mS)

Current

0.0

0.5

1.0

Current


0 10 20 30 40-1.0

-0.5

Time (mS)

Current

0 10 20 30 40-1.0

-0.5

0.0

0.5

1.0

Time (mS)

Current

C-less technology

Advantages Concerns

● Reduces THD(I) below 35%without added filter


● Only for Fan, Pump and non demanding applications (HVAC)



● Lowest cost for harmonic mitigation

● More DC bus ripple so more torque ripple.

● More sensitive to network voltage drop and perturbation

Agenda







●What’s next?

●Conclusion

Solutions comparison

●Comparison between harmonic mitigation solutions at drive level

Nil Choke 3%-5%

Passive filter

C less 18 pulses

Active front end

Active filter

Current distortion THDI >80% <48% <5%-16% <30% <5%-10% <5 % <5%

Meet IEEE519 gen. app. no System dependent yes System dependent yes (18p) yes yes

Mitigation solutions


Meet IEEE519 gen. app. no System dependent yes System dependent yes (18p) yes yesMeet IEC 61000 3-12 no yes yes yes yes yes yesMeet IEC 61000 3-2 no no no no no yes yes

Drop voltage no yes no no no no noPower factor no/full load <0,8 0.75-0.95 0.75-1 0.95 0.90-0.99 1 1Load influence on THDI no yes yes no no no noEfficiency 100% 97% 98% 100% 96% 96% 96%Reliability High High Good Good Medium Good GoodEMC Poor Good Good Medium Good Medium MediumInfluence on VSD perf. no weak no Strong no no noResonance risk no weak yes no no no no

Cost effective very good good <100kW very good >200kW Medium Low harmonicPrice ratio /drive cost 100% 110%-120% 150%-200% 95% 200%-250% 250% 250%Foot print ration/drive 100% 120% 200% 100% 350% 150%-200% 300%-500%

Offer ATV <75kWATV >75kW

<75kW option ATV optionATV21

fan/pump only Square D USSinewave AccuSine

Altivar AFE

Where to install the solutions?


Solutions comparison

●Cost comparison between harmonic mitigation solutions at drive level

Harmonic Mitigation - Cost / Performance Comparison

300

5

Cost/VSD price


0

50

100

150

200

250

6 Pulse Drive C-Less DC chokesAC chokes

Passive Filters Multi-Pulse12p, 18p

Active Filters

THDI %

60-130 30-35

35-48

5-16

5-105

Agenda







●What’s next?

●Conclusion

What’s next?1st Step – Measure

●Select a good PQ tools and software●Portable power quality loggers●Power Quality Monitoring System

& Power Quality Meter

3rd Step – Implement


2nd Step – Analyze● Identify & Categorize the PQ

event according to standard (e.g. IEEE Std 1159-1995)

●Know the waveform signature

● Identify the severity of the event (Magnitude and duration)

3rd Step – Implement●Understand the effect of the

events●Propose solutions to apply

Agenda







●What’s next?

●Conclusion

What we were discussing

●Solve the harmonic issue, if possible, starting from the root of the problem.

●A cost effective solution requires the knowledge of the


●A cost effective solution requires the knowledge of the installation and it is often a combination of several solutions.

●Harmonic mitigation solutions are available in market to fulfill your needs.

3 main messages3 main

messages

Ch‘ng Eng Yong+6012 – 2750 876

[email protected]

You‘ve got questions?Contact


[email protected]

TT hank You


for your attentionTT hank You

maximise efficiency & reliability - maintain ‘healthy’ electrical network with harmonic-less

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