ups technical note no. 4

GE Consumer & Industrial Power Protection

UPS technical note no. 4 Digital Energy™ Uninterruptible Power Supply

UPS harmonics on input mains SitePro 400 Vac CE - Series 6

SG Series 400 Vac CE - Series 0

GE Digital Energy General Electric Company CH – 6595 Riazzino (Locarno) Switzerland T +41 (0)91 / 850 51 51 F +41 (0)91 / 850 51 44 www.gedigitalenergy.com

UPS technical note no. 4 - UPS harmonics on input mains - page 2/33

TCN_XXE_004_XXX_XXX_XGB_0411.doc - November 2004

Document information: Application: SitePro 400 Vac CE - Series 6; SG Series 400 Vac CE – Series 0 Release: November 2004 File name: TCN_XXE_004_10K_M50_6GB_0409_GE_INSPIRA.doc Author: Diego Toledo Department: System & Application Engineering Up-dating

Release

Concerns

April 2004 General layout and data revision; introduction of input filter 11th + 13th harmonics and Active Filter

September 2004 Data for SG Series 400 Vac CE

November 2004 New GE fonts

© 2004 by GE Consumer & Industrial All rights reserved. The information contained in this publication is intended solely for the purposes indicated. The present publication not to be reproduced, either in part or in its entirety, without the prior written consent of GE. The illustrations and plans describing the equipment are intended as general reference only and are not necessarily complete in every detail. The content of this publication may be subject to modification without prior notice.



Contents

1 Abstract ............................................................................................................................................................................................ 4

2 Understanding harmonics problems................................................................................................................................. 4

2.1 Harmonics .......................................................................................................................................................................... 4 2.2 Harmonics effects........................................................................................................................................................... 5 2.3 Harmonics theoretical concept................................................................................................................................ 6 2.3.1 Fourier analysis ........................................................................................................................................................ 6 2.3.2 Periodic alternating rms value .......................................................................................................................... 7 2.3.3 Current harmonic distortion............................................................................................................................... 7 2.3.4 Voltage harmonic distortion............................................................................................................................... 7 2.3.5 Power factor for loads affected by harmonics ......................................................................................... 8 2.4 Rectifier harmonics ........................................................................................................................................................ 9 2.5 Rectifier Harmonics compensation..................................................................................................................... 10

3 Standard requirement............................................................................................................................................................ 10

4 SitePro configuration characteristics ............................................................................................................................. 11

4.1 SitePro configurations ............................................................................................................................................... 11 4.2 SitePro harmonics data............................................................................................................................................. 12 4.3 SitePro - 6 pulse rectifier........................................................................................................................................... 13 4.4 SitePro - 6 pulse rectifier and 5th harmonic filter.......................................................................................... 14 4.5 SitePro - 12 pulse rectifier without galvanic separation........................................................................... 15 4.6 SitePro - 12 pulse rectifier with galvanic separation.................................................................................. 16 4.7 SitePro - 6 pulse rectifier and DCU ...................................................................................................................... 17 4.8 SitePro - 12 pulse rectifier with/without galvanic separation and DCU............................................ 18 4.9 SitePro - 12 pulse rectifier with/without galvanic separation and 11th +13th harm. filter ..... 19 4.10 SitePro - 6 pulse rectifier with 5th harmonic filter and Active Filter ..................................................... 20

5 SG Series CE configuration characteristics.................................................................................................................. 21

5.1 SG Series CE configurations.................................................................................................................................... 21 5.2 SG Series CE harmonics data................................................................................................................................. 22 5.3 SG Series CE - 6 pulse rectifier ............................................................................................................................... 23 5.4 SG Series CE - 6 pulse rectifier with 5th harmonic filter ............................................................................. 24 5.5 SG Series CE - 6 pulse rectifier with 5th and 11th harmonic filter........................................................... 25 5.6 SG Series CE - 12 pulse rectifier without galvanic separation ............................................................... 26 5.7 SG Series CE - 12 pulse rectifier with galvanic separation ...................................................................... 27 5.8 SG Series CE - 6 pulse rectifier with 5th harmonic filter and Active Filter .......................................... 28

6 Rectifier with phase shift displacement ........................................................................................................................ 29

6.1 Quasi 12 pulse rectifier configuration by two parallel UPS..................................................................... 30 6.2 Quasi 18 pulse rectifier configuration................................................................................................................ 31 6.3 Quasi 24 pulse rectifier configuration (for 6 pulse UPS) ............................................................................ 32 6.4 Quasi 24 pulse rectifier configuration (for 12 pulse UPS) ......................................................................... 33



1 Abstract As well known an UPS thyristorized rectifier generates harmonics on the upstream input mains. These can cause several problems on the other load connected on the same electrical network and also on the input transformer. After a short presentation on theoretical harmonics concept and on the effects on the installation involved, the document describes the possible solutions adapted on the SitePro UPS to their compensation.

2 Understanding harmonics problems

2.1 Harmonics

In an electric energy production and distribution system the mains voltage can be considered as an ideal sinusoidal wave with a constant frequency. However, in reality the public mains undergoes voltage and frequency variations. In particular, an increasing actual problem is the perturbations caused by the harmonics generated by non-linear loads connected to the mains. Harmonics are perturbations with frequencies multiple of the fundamental frequency, which will be superimposed (added) to the fundamental; e.g. in an electrical system at nominal (fundamental) frequency 50 Hz, the fifth harmonic is at 250 Hz, the seventh at 350 Hz, etc. The resulting waveform is clearly not more a sine-wave but a distorted wave. The presence of non-linear loads connected to mains generates harmonics in current, which by circulating in the line impedance lead to voltage harmonics distortion. Therefore, harmonics current depend from the load, while the harmonics voltage depends from the source and the line’s impedance.

Fig. 2.1-1 Fundamental wave and harmonics Fig. 2.1-2 Distorted wave due to harmonics

5th harmonic 7th harmonic

fundamental distorted wave fundamental

harmonics



2.2 Harmonics effects

Non-linear loads can be considered as current harmonics generator, that causing various problems on the other application involved. Here are short descriptions of their effects:

Short-term effects: • problems on telecommunications systems • inconveniences in switches and differentials • variations of motor electric torque with relative speed variation • acoustical noise

Long-term effects: • cables over-heating • supplementary losses in power transformers:

- skin effect (higher resistance) - hysteresis and eddy currents - increase of rms current value

• additional losses in rotating machines: - stator winding and magnetic structure - rotor damping circuit and rotor teeth

• heating in cables: - increase rms current value - skin effect (higher resistance) - capacitors over-heating

Admissible harmonic limits: • cables: max core-shielding voltage distortion 10% • asynchronous machines: max current distortion 1.5 ÷ 3.5% • synchronous machines: max current distortion 1.3 ÷ 1.4% • power capacitors: max overvoltage 10% for standard capacitors, network with low harmonic

content 20 ÷ 35% for capacitors design for network with middle harmonic content 50 ÷ 100% for capacitors design for network with high harmonic content • sensitive electronic equipment: 5% voltage distortion with max 3% for each single harmonic



2.3 Harmonics theoretical concept

2.3.1 Fourier analysis

According to Fourier analysis each periodic function may be represented as a series, which is composed by: • a constant value; that represent the current or voltage DC component, where applicable • a sinusoidal component with frequency f (in electrical application usually 50 or 60 Hz), named

fundamental frequency • sinusoidal components with frequency multiple of the fundamental frequency, named harmonics The Fourier series is therefore represented by the following formula

)sin(**2)sin(**2)sin(**2)(2

1101

0 hh

n

hhh

n

h

thFtFFthFFtF ϕωϕωϕω ++++=++= ∑∑==

where • 0F : DC component, normally equal to zero in AC electrical applications

• 1F : rms value of the fundamental component at a frequency f

• fπω 2= : fundamental angular frequency

• 1ϕ : phase displacement

• hF : rms of the n harmonic, with frequency n*f

• hϕ : phase displacement between n harmonic current and voltage

The Fourier analysis gives the harmonics analysis in magnitude and phase angle. These information are fundamental for a correct analysis of the problems caused and the way to reduce their effects. Typically the harmonics spectrum is showed as for the diagram here showed. It shows the single harmonic related to the fundamental wave.

100

6.23 4.8 2.6 2.6 2 0.6 0.8 0.5 0.5

0

10

20

30

40

50

60

70

80

90

100

1 5 9 13 17 21 25 29harmonic order (n)

curr

ent h

arm

onic

s %

Fig. 2.3.1-1 Example of harmonics spectrum for a load affected by 5th, 7th, 11th, etc. harmonics



2.3.2 Periodic alternating rms value

According to IEC Standard this value is defined as

∫=T

rms dttFT

F0

2)(1

where • T is the period of the function. • F (t) is the periodic function under analysis Using the harmonic analysis, the rms value may be represented as follow

∑=

=n

hhrms FF

1

2

2.3.3 Current harmonic distortion

Current harmonic distortion Two are the value that characterized current harmonic: • individual current harmonics 100*%

1IIi h

h =

that represents the influence of each individual harmonic related to the fundamental sine-wave value. • total current harmonic distortion

100%1

1

2

I

ITHDi

n

hh∑

==

that represents the ratio between the whole harmonics content respect to the fundamental sine-wave value. Current rms value As above showed the rms value is expressed by

∑=

=n

hhrms II

1

2

taking into consideration the harmonic analysis the formula may be expressed as

∑∑∑===

+=⎟⎟⎠

⎞⎜⎜⎝

⎛+=+=

n

hh

n

h

hn

hhrms iI

IIIIII

2

21

2

2

11

2

221 11

where

- hi : individual current harmonic, expressed in p.u..

2.3.4 Voltage harmonic distortion

Voltage harmonic distortion As showed the presence of non-linear load cause current distortion in electrical network and as consequence voltage distortion. Ohm law (V=R*I) is applicable only for linear circuits; therefore it is applicable for each single harmonic value, but not for the rms value. Two are the value that characterized current harmonic: • individual voltage harmonics



100*%1U

Uu hh =

that represents the influence of each individual harmonic related to the fundamental sine-wave value. • total voltage harmonic distortion

100%1

1

2

U

UTHDv

n

hh∑

==

that represents the ratio between the whole harmonics voltage respect to the fundamental sine-wave value. THDv = Total Harmonics Voltage Distortion; this value is used to indicate the voltage harmonics contents. The maximum THDv value are regulated by EN-50160-3, EN-61000-2-2 and IEC 61000-2-2 Standard. Voltage rms value As above showed the rms value is expressed by

∑=

=n

hhrms UU

1

2

taking into consideration the harmonic analysis the formula may be expressed as

∑∑∑===

+=⎟⎟⎠

⎞⎜⎜⎝

⎛+=+=

n

hh

n

h

hn

hhrms uU

UUUUUU

2

21

2

2

11

2

221 11

where

- hu : individual voltage harmonic, expressed in p.u..

2.3.5 Power factor for loads affected by harmonics

Since the absorbed current of non-linear load is not a sinusoidal form, it is not possible to apply the traditional concept of a phase displacement in electrical degrees. The Power Factor (PF) is the ratio of power consumption in kW to kVA. PF = kW / kVA. In an electrical system four are the electrical power: P = active power Q= reactive power S = apparent power = 22 QP +

H = harmonic power A = total apparent power = 22 HS +

Note that the total apparent power takes into consideration the “active power” the “reactive power” due to magnetics or capacitive circuits and the reactive “harmonic power” due to harmonics pollutons.

P active power

Q reactive power

H h

arm

onic

pow

er

φ

A total apparent power

S apparent power

Fig. 2.3.5-1 Power cube



Rectifier upstream harmonics

6-pulse rectifier: k = 1: Hn = 5th and 7th harmonics k = 2: Hn = 11th and 13th harmonics k = 3: Hn = 17th and 19th harmonics k = 4: Hn = 23rd and 25th harmonics

12-pulse rectifier: k = 1: Hn = 11th and 13th harmonics k = 2: Hn = 23rd and 25th harmonics

18-pulse rectifier: k = 1: Hn = 17th and 19th harmonics k = 2: Hn = 35th and 37th harmonics

24-pulse rectifier : k = 1: Hn = 23rd and 25th harmonics

2.4 Rectifier harmonics

Typical non-linear loads are the rectifiers with semiconductors, which generate harmonics according to the following formula: Hn = k*p ± 1 where Hn: harmonics’ number; k: constant equal to 1, 2, 3, p: number of conversions or rectifier’s pulses The six-pulse rectifier produces harmonics at 6th ±1, that is at one more and one less than each multiple of six. Note: A rectifier generates current harmonics. The magnitude of these harmonic currents depends on: • type of rectifier circuit • input line impedance • quality of the supply itself. The product of the current harmonics and the impedance at different frequencies creates voltage distortion. Theoretically, for a perfect source with zero impedance and a perfectly smooth D.C. the rms value of the harmonics is given by: I(n) = Io/n where In: is the value of the harmonic; Io: is the value of the fundamental n the harmonic order so there would be 20% for 5th harmonic, 9% for 11th harmonic and so on. Since a UPS is a non-linear load for its power source, it is necessary to analyze if the harmonics generated have no influence with other loads connected to the same network.

0102030405060708090

100

1 5 9 13 17 21 25 29harmonic order (n)

curr

ent h

arm

onic

s %

1/n

theoretical

Fig. 2.4-1 Harmonics spectrum



2.5 Rectifier Harmonics compensation

Different are the ways to reduce the reinjection of harmonics and consequently voltage distortion on the equipment connected to the same mains as the rectifier: • At a project phase of the electrical mains distribution, the UPS system is separated from other

equipment by a separate mains transformer, i.e. the UPS has a dedicated electrical line. • By the addition of harmonic filters, which act as a short-circuit path for these harmonics. • With the increase of the pulse number of the rectifier; by 6 pulse double bridge rectifier with or

without galvanic separation 30° el. degree shift out of phase. • For parallel installation (2x) one UPS can be equipped with a 30° phase shift transformer. The result is

practically the same as the double bridge (12 pulse rectifier). Note Since the harmonics reduction implies an investment, the first step is analyzing whether it is really necessary to reduce the harmonics distortion.

3 Standard requirement Harmonics compatibility with public low-voltage supplies is defined by IEC61000-2-2. The input total voltage distortion factor D< 8% with the following maximum level of individual voltage (up to 40th harmonic):

Odd harmonics non multiple of 3

Odd harmonics non multiple of 3

Even harmonics

Harmonic order

n

Harmonic voltage

%

Harmonic order

N

Harmonic voltage

%

Harmonic order

n

Harmonic voltage

%

5 6 3 5 2 2 7 5 9 1.5 4 1

11 3.5 15 0.3 6 0.5 13 3 21 0.2 8 0.5 17 2 >21 0.2 10 0.5 19 1.5 12 0.2 23 1.5 >12 0.2 25 1.5

>25 0.2+0.5x25/n Note: All the above harmonics levels are assumed not to occur simultaneously. As above showed the Standard requirement is related to the THDv (Total Voltage Harmonics Distortion); this is related to the current harmonics by the Input Mains reactance that is different for any application, therefore in common use the THDi (Total Current Harmonics Distortion) is request. In fact this value can be easily measured an less influenced by the Input Mains reactance.



4 SitePro configuration characteristics

4.1 SitePro configurations

SitePro are UPS designed to be used in several type of applications. For this reason different type of configuration are possible to comply with the specific requirement. Here below find out a detailed analysis of the different options available. Configuration Benefit Limitation

6 pulse (standard) Lk

• Simple solution • Less expensive configuration

• High harmonics contents • Generator might be

overheat • Distortion on equipments on

same input mains

6 pulse +

5th harm. Filter

Lk

• Attenuation of 5th and partially 7th harmonics

• Input power factor correction • Best price/performance

• Possible problems with some old GenSet regulation

12 pulse without galvanic

separation Lk

• Elimination of 5th, 7th, 17th, 19th, 29th, 31st harmonics

• No influence with GenSet. Regulation

• No galvanic separation • No power factor correction

12 pulse with

galvanic separation

Lk


• No influence with GenSet. regulation

• Galvanic separation

• No power factor correction

DCU Lk

• Attenuation of 5th to 13th harmonics

• Power factor correction ca. 0.98

• As capacitive load might have resonance with p.f. capacitors


12 pulse rectifier

+ DCU

Lk

• Elimination or attenuation of most harmonics

• Galvanic separation where adopted

• Power factor correction ca. 0.98

• As capacitive load might have resonance with p.f. capacitors

• Possible problems with GenSet. Regulation

• Expensive configuration 12 pulse rectifier

+ input filter 11th & 13th

harmonics.

Lk

• Elimination or attenuation of most harmonics

• Galvanic separation where adopted

• Power factor correction >0.85

• 12 pulse rectifier is required

6 pulse +

5th harm. Filter

+ Active Filter.

Lk

• Dynamic compensation of all harmonics

• Power factor correction >0.95 • High performance at full and

partial loads

• 5th harmonic filter cabinet required

• Costly solution



4.2 SitePro harmonics data Generated currents-harmonics contents in %

Harmonics order Configuration 5 7 11 13 17 19 23 25 29 31 THDi

6 pulse 24.5 7.7 6.3 4.2 2.3 2.2 0.7 0.9 0.5 0.5 27 %

6 pulse + 5th harmonics filter 6.2 3.0 4.8 2.6 2.6 2.0 0.6 0.8 0.5 0.5 10 %

12 pulse without galvanic separation -- -- 7.2 5.7 -- -- 1.4 1.0 -- -- 9.4 %

12 pulse with galvanic separation -- -- 7.2 5.7 -- -- 1.4 1.0 -- -- 9.4 %

DCU 3.8 2.6 1.4 1.1 3.6 2.7 1.4 1.0 0.8 0.6 7.0 %

12 pulse with / without galvanic separation + DCU -- -- 1.4 1.1 -- -- 1.4 1.0 -- -- < 5 %

(2.5÷4.5)

12 pulse with / without galvanic sep. + input filter 11th & 13th harmonics

1.5 -- 0.5 0.5 -- -- 0.5 -- -- -- < 5 % (3÷4.5)

6 pulse + 5th harmonics filter + Active Filter 1.5 0.7 0.7 1.3 0.7 0.7 1.3 0.7 0.5 0.5 5 %

(4÷5)

The above table shows the harmonics value measured on some applications. The value is influenced by input mains characteristics; therefore in practical applications the values measured on the application could be different from the values above indicated.



4.3 SitePro - 6 pulse rectifier

MAINS

INPUT

UPS

Lk

RECTIFIER

BATTERY

SSM

INVERTER LOADS

Fig. 4.3-1 Electrical configuration

Characteristics • standard UPS configuration

Harmonics compensation • THDi ca. 27%

Power factor • p.f. = 0.80 approximately

Benefit • simple solution • less expensive configuration

Limitation • high harmonics contents

• generator might be overheat • distortion on other equipment on the same mains

100

24.5

7.7 6.3 4.2 2.7 2.2 0.7 0.9 0.50.50

102030405060708090

100

1 5 9 13 17 21 25 29harmonic order (n)

curr

ent h

arm

onic

s %

THDi = 27%


Fig. 4.3-3 UPS input current waveform



4.4 SitePro - 6 pulse rectifier and 5th harmonic filter

LOADS

SSM

5th HARMONIC

MAINS

INPUT

BATTERY

RECTIFIER INVERTER

UPS

Lk

5th

Fig. 4.4-1 Electrical configuration Characteristics • the filter is realized in order to limit the effect of 5th

and partially 7th harmonics on rectifier input mains • automatic on-off connection at ~50% load

(adjustable). The on-off insertion is related to avoid the capacitive power on the electrical network at partial load, due to the fact that the utility supplier does not allow it.

• for power range 20÷40 kVA mounted inside the UPS cabinet; additional battery cabinet is required

• for power range > 60 kVA in a separated cabinet

Harmonics compensation • affect 5th and partially 7th harmonic

• THDi ca. 10%

Power factor compensation • p.f. = 0.90

Benefit • best price/ performance compromise

Limitation • as capacitive load might have resonance • possible problems with some old GenSet

regulation.

100

6.23 4.8 2.6 2.6 2 0.6 0.8 0.50.5

0102030405060708090

100

1 5 9 13 17 21 25 29harmonic order (n)

curr

ent h

arm

onic

s %

THDi = 10%


Fig. 4.4-2 Harmonic spectrum



4.5 SitePro - 12 pulse rectifier without galvanic separation

INPUT

MAINS

RECTIFIER

BATTERY

INVERTER

UPS

SSM

LOADSLk

Fig. 4.5-1 Electrical configuration Characteristics • realized by two input rectifier 30° el. shifted. One

rectifier is connected to the input mains by a Dy transformer; the other one by an input coil.

• available for power range >40 kVA

Harmonics compensation • suppression of 5th, 7th, 17th, 19th, 29th, 31st,…..

harmonics • THDi ca. 9.4%

Power factor compensation • none (standard p.f.=0.80)

Benefit • good THDi compensation • no influence with GenSet. regulation

Limitation • no galvanic separation • no power factor correction

100

7.2 5.71.4 1

0102030405060708090

100

1 5 9 13 17 21 25 29harmonic order (n)

curr

ent h

arm

onic

s %

THDi = 9.4%





4.6 SitePro - 12 pulse rectifier with galvanic separation

SSM

MAINS

INPUT

BATTERY

RECTIFIER

INVERTER

UPS

LOADS


Characteristics • realized by two input rectifier 30 el. degr. shifted.

The two rectifiers are connected to the input mains by a Ddy transformer.

• available for power range >40 kVA

Harmonics compensation • elimination of 5th, 7th, 17th, 19th, 29th, 31st,

…harmonics • THDi ca. 9.4%


Benefit • good THDi compensation • no influence with GenSet. regulation

Limitation • no power factor correction Quasi 12 pulse configuration for parallel standard units In case of two (or multiple of two) UPSs in parallel, it is possible to obtain the same result by realizing the configuration “quasi 12 pulse” by installing alternatively one UPS with a Dd0 transformer (0 el. degr. phase shift) and the other UPS with a Dy11 transformer 30 el. degr. out of phase. This solution is applicable for all UPSs.

100

7.2 5.71.4 1

0102030405060708090

100

1 5 9 13 17 21 25 29harmonic order (n)

curr

ent h

arm

onic

s %

THDi = 9.4%





100

3.8 2.6 1.4 1.1 3.6 2.7 1.4 10

102030

4050

6070

8090

100

1 5 9 13 17 21 25 29harmonic order (n)

curr

ent h

arm

onic

s %

4.7 SitePro - 6 pulse rectifier and DCU

LOADS

SSM

MAINS

INPUT

BATTERY

INVERTER

UPS

RECTIFIER

Lk

DCU11th7th5th 13th


Characteristics • the DCU is a filter with a special dynamic feature.

Depending of the percentage of the load it will automatically disconnect, in part or totally, in order that with a partial load the input power factor never becomes capacitive, situation not allowed by the utility.

• two automatic on-off step connection: - 1st step switched on at ~50% load (adjustable) - 2nd step switched on at ~75% load (adjustable)

• The on-off insertion is related to avoid the capacitive power on the electrical network at partial load, due to the fact that the utility supplier does not allow it.

• available for power range > 40 kVA, mounted in additional separated cabinet

Harmonics compensation • compensation for 5th; 7th; 11th; 13th and partially

23rd and 25th harmonics • THDi ca. 7%

Power factor compensation • p.f. up to 0.98

Benefit • high THDI compensation • power factor compensation near to 1

Limitation • as capacitive load might have resonance with p.f.

capacitors • possible problems with some GenSet regulation.

THDi = 7 %





4.8 SitePro - 12 pulse rectifier with/without galvanic separation and DCU

INPUT

BATTERY

UPS

SSM

LOADS

5th 11th7th 13th

MAINS

RECTIFIER

INVERTER

DCU

Fig. 4.8-1 Electrical configuration Characteristics. • this solution add the feature of 12 pulse and DCU

filter • available for power range >40 kVA • solution used where high harmonics

compensation is required.

Harmonics compensation • elimination of 5th, 7th, 17th, 19th, 29th, 31st, ……

harmonics • compensation for 11th; 13th and partially 23rd and

25th harmonics • THDi ca. 2.5 ÷ 4.5%; typical <5%

Power factor compensation • p.f. up to 0.98

Benefit • elimination or attenuation of most harmonics • galvanic separation when selected in the 12 pulse • power factor correction near to 1

Limitation • as capacitive load might have resonance • expensive configuration • possible problems with some GenSet regulation.

100

1.4 1.1 1.1 10

10203040506070

8090

100

1 5 9 13 17 21 25 29harmonic order (n)

curr

ent h

arm

onic

s %

THDi < 5%





4.9 SitePro - 12 pulse rectifier with/without galvanic separation and 11th +13th harm. filter

INPUT

MAINS

RECTIFIER

UPS

INVERTER

BATTERY

SSM

LOADS

11 th 13 th

Lk

INPUT FILTER 11th+13th HARM. Fig. 4.9-1 Electrical configuration

Characteristics. • input filter for 11th and 13th harmonics is a

passive filter realized by coils and capacitance, designed to compensate the residual current harmonics generated by the UPS rectifier in 12 pulse configuration (with or without galvanic separation).

• the filter is design to operate constantly connected, independently to the UPS load level.

• available for power range >80 kVA • solution used where high harmonics

compensation is required.

Harmonics compensation • compensation of all harmonics produced by the

UPS rectifier • THDi ca. 3 ÷ 4.5%; typical <5%

Power factor compensation • p.f. = 0.88; typical > 0.85

Benefit • elimination or attenuation of most harmonics • galvanic separation when selected in the 12 pulse • power factor correction

Limitation • 12 pulse rectifier configuration is required



100

1.5 0.7 0.7 1.3 0.7 0.6 1.3 0.7 0.50.5

0102030405060708090

100

1 5 9 13 17 21 25 29harmonic order (n)

curr

ent h

arm

onic

s %

THDi < 5%



4.10 SitePro - 6 pulse rectifier with 5th harmonic filter and Active Filter

ACTIVE FILTER

BATTERY

INPUT

MAINS RECTIFIER

UPS

Lk

SSM

INVERTER LOADS

5th HARMONIC5th


Characteristics. • realized by the combination of a 5th harmonic filter

and an IGBT (Insulated Gate Bipolar Transistors) power bridge, which injects harmonic currents into the electrical network with exactly the opposite phase to those that are to be filtered.

• dynamic and selective harmonic compensation by the Fast Fourier Transform (FFT) algorithm.

• basically available for power range 80 –120 kVA • solution used where high harmonics compensation

is required.


UPS rectifier • THDi ca. 4 ÷ 5%; typical <5%

Power factor compensation • p.f. > 0.95

Benefit • dynamic compensation of all harmonics • power factor correction • high performance at full and partial loads

Limitation • 5th harmonic filter required


100

1.5 0.7 0.7 1.3 0.7 0.6 1.3 0.7 0.50.5

0102030405060708090

100

1 5 9 13 17 21 25 29harmonic order (n)

curr

ent h

arm

onic

s %

THDi = 5%




5 SG Series CE configuration characteristics

5.1 SG Series CE configurations

SG Series CE are UPS designed to be used in several type of applications. For this reason different type of configuration are possible to comply with the specific requirement. Here below find out a detailed analysis of the different options available. Configuration Benefit Limitation

6 pulse (standard)

• Simple solution • Less expensive configuration

• High harmonics contents • Emergency GenSet might be

overheat • Distortion on equipments on

same input mains

6 pulse +

5th harm. Filter

• Attenuation of 5th and partially 7th harmonics

• Input power factor correction • Best price/performance


6 pulse +

5th and 11th harm. Filter

• Attenuation of 5th and 11th and most on the other harm.

• Input power factor correction • Good price/performance


12 pulse without galvanic

separation


• No influence with GenSet. Regulation

• No galvanic separation • No power factor correction

12 pulse with

galvanic separation


• No influence with GenSet. regulation

• Galvanic separation

• No power factor correction

6 pulse +

5th harm. Filter

+ Active Filter.

• Dynamic compensation of all harmonics

• Power factor correction >0.95 • High performance at full and

partial loads

• Costly solution (justified by the high performance level)



5.2 SG Series CE harmonics data Generated currents-harmonics contents in %

Harmonics order Configuration 5 7 11 13 17 19 23 25 29 31 THDi

6 pulse 24 7 5 4 1 1 1 <1 <1 <1 26 %

6 pulse + 80 – 120 kVA 5 2.5 5 1.5 2 1 1 <1 <1 <1 8 %

5th harmonic filter 160 – 200 kVA 4 2.5 4 1.5 1 1 1 <1 <1 <1 7 %

6 pulse + 5th and 11th 80 – 120 kVA 5 2.5 1.5 1 1.5 <1 <1 <1 -- -- 6 %

harmonics filter 160 – 200 kVA 3.5 2.5 1 1 <1 <1 <1 <1 -- -- 5 %

12 pulse without galvanic separation -- -- 7 2.5 -- -- 1.5 1.5 <1 -- 8 %

12 pulse with galvanic separation -- -- 7 2.5 -- -- 1.5 1.5 <1 -- 8 %

6 pulse + 5th harmonics filter + Active Filter 1.5 1 1 1 <1 <1 <1 <1 <1 <1 3 %

The above table shows the harmonics value measured on some applications. The value is influenced by input mains characteristics; therefore in practical applications the values measured on the application could be different from the values above indicated.



5.3 SG Series CE - 6 pulse rectifier

MAINS

INPUT

UPS

Lk

RECTIFIER

BATTERY

SSM

INVERTER LOADS

Fig. 5.3-1 Electrical configuration Characteristics • standard UPS configuration

Harmonics compensation • THDi ca. 26% Power factor • p.f. = 0.80 approximately

Benefit • simple solution • less expensive configuration

Limitation • high harmonics contents • generator might be overheat • distortion on other equipment on the same mains



100

24

7 5 4 1 1 1 <1 <1<10

102030405060708090

100

1 5 9 13 17 21 25 29harmonic order (n)

curr

ent h

arm

onic

s %

THDi = 26%



5.4 SG Series CE - 6 pulse rectifier with 5th harmonic filter

Lk2

UPS WITH 5th HARMONIC FILTER

MAINS

INPUT

Lk1

INVERTER

BATTERY

5thRECTIFIER

SSM

LOADS


and partially 7th harmonics on rectifier input mains • automatic on-off connection at ~50% load

(adjustable according to the specific installation requirement). The on-off insertion is related to avoid the capacitive power on the electrical network at partial load, due to the fact that the utility supplier does not allow it.

Harmonics compensation • affect 5th and partially 7th harmonic • THDi ca. 8% for SG Series 80 - 120 kVA

THDi ca. 7% for SG Series 160 - 200 kVA

Power factor compensation • p.f. = 0.92

Benefit • best price/ performance compromise

Limitation • possible problems with some old GenSet

regulation

100

5 2.5 51.5 2 1 1 <1<1<1

0102030405060708090

100

1 5 9 13 17 21 25 29harmonic order (n)

curr

ent h

arm

onic

s %



SG 80-120 kVA THDi = 8% SG 160-200 kVA THDi = 7%



5.5 SG Series CE - 6 pulse rectifier with 5th and 11th harmonic filter

5th

UPS WITH 5th AND 11th HARMONIC FILTERS

MAINS

INPUT

Lk1

RECTIFIER

BATTERY

INVERTER

SSM

LOADS

11th

Lk2


and 11th harmonics on rectifier input mains • automatic on-off connection at ~50% load

(adjustable according to the specific installation requirement). The on-off insertion is related to avoid the capacitive power on the electrical network at partial load, due to the fact that the utility supplier does not allow it.

Harmonics compensation • affect 5th and partially 7th harmonic • THDi ca. 6% for SG Series 80 - 120 kVA

THDi ca. 5% for SG Series 160 - 200 kVA

Power factor compensation • p.f. = 0.96 ÷ 0.97

Benefit • good price/ performance compromise

Limitation • possible problems with some old GenSet

regulation

100

3.5 2.5 1 1 <1<1<1<10

102030405060708090

100

1 5 9 13 17 21 25 29harmonic order (n)

curr

ent h

arm

onic

s %



SG 80-120 kVA THDi = 6% SG 160-200 kVA THDi = 5%



5.6 SG Series CE - 12 pulse rectifier without galvanic separation

INPUT

MAINS

RECTIFIER

BATTERY

INVERTER

UPS

SSM

LOADSLk2

Lk1

Fig. 5.6-1 Electrical configuration Characteristics • realized by two input rectifier 30° el. shifted. One

rectifier is connected to the input mains by a Dy transformer; the other one by an input coil.

Harmonics compensation • suppression of 5th, 7th, 17th, 19th, 29th, 31st,…..

harmonics • THDi ca. 8%


Benefit • good compensation • no influence with GenSet. regulation

Limitation • no galvanic separation • no power factor correction

100

2.5 27

2.5 0.5 0.5 1.5 1.50

102030405060708090

100

1 5 9 13 17 21 25 29harmonic order (n)

curr

ent h

arm

onic

s %

THDi = 8%






5.7 SG Series CE - 12 pulse rectifier with galvanic separation

SSM

MAINS

INPUT

BATTERY

RECTIFIER

INVERTER

UPS

LOADSLk1

Lk2

Fig. 5.7-1 Electrical configuration Characteristics • realized by two input rectifier 30 el. degr. shifted.

The two rectifiers are connected to the input mains by a Ddy transformer.

Harmonics compensation • elimination of 5th, 7th, 17th, 19th, 29th, 31st,

…harmonics • THDi ca. 8%


Benefit • good THDI compensation • no influence with GenSet. regulation

Limitation • no power factor correction

Quasi 12 pulse configuration for parallel standard units In case of two (or multiple of two) UPSs in parallel, it is possible to obtain the same result by realizing the configuration “quasi 12 pulse” by installing alternatively one UPS with a Dd0 transformer (0 el. degr. phase shift) and the other UPS with a Dy11 transformer 30 el. degr. out of phase. This solution is applicable for all UPSs.

100

72.5 1.5 1.5 0.5

0102030405060708090

100

1 5 9 13 17 21 25 29harmonic order (n)

curr

ent h

arm

onic

s %

THDi = 8%




5.8 SG Series CE - 6 pulse rectifier with 5th harmonic filter and Active Filter

UPS WITH 5th HARMONIC FILTER

Lk1

INPUT

MAINSLk2

BATTERY

INVERTERRECTIFIER5th

SSM

LOADS

ACTIVE FILTER


Characteristics. • realized by the combination of a 5th harmonic

filter and an IGBT (Insulated Gate Bipolar Transistors) power bridge, which injects harmonic currents into the electrical network with exactly the opposite phase to those that are to be filtered.

• dynamic and selective harmonic compensation by the Fast Fourier Transform (FFT) algorithm.

• solution used where high harmonics compensation is required.


UPS rectifier • THDi typical < 3%

Power factor compensation • p.f. > 0.95

Benefit • dynamic compensation of all harmonics • power factor correction • high performance at full and partial loads

Limitation • Costly solution, justified by the high performance

level

100

1.5 1 1 1 <1<1<1<1 <10

102030405060708090

100

1 5 9 13 17 21 25 29harmonic order (n)

curr

ent h

arm

onic

s %



THDi = 3%



6 Rectifier with phase shift displacement For parallel UPS configuration a rectifier phase shift displacement could be realized. The formula here showed define the required phase shift:

FkP

*6360

=∗

where P: rectifier number F: transformer phase displacement (electrical degrees) k: ±1, ±2,… The limitation of this solution is that in case of extension units, the same input mains harmonics characteristics are carry out by adding a complete UPS group (2, 3 or 4 units according to the configuration chosen). Phase shift below 30 el. degr. is realized by zig-zag transformers. Due to the difficulties in the transformer construction the smallest reasonable phase shift is 15 el. degr. (24 pulse configuration); smallest phase shift 12 el. degr. (30 pulse) or 10 el. degr. (36 pulse) are very difficult and expensive. Generated currents-harmonics contents in %

Harmonics order Configuration

5 7 11 13 17 19 23 25 29 31 THDi

6 pulse rectifier 24 7 5 4 1 1 1 <1 <1 <1 26 ÷ 27%

quasi 12 pulse rectifier 2 1.5 7 6 <1 <1 1.5 1 -- -- 9.7 %

quasi 18 pulse rectifier -- -- -- -- 4 3.5 -- -- -- -- <7 %

quasi 24 pulse rectifier -- -- -- -- -- -- 1.5 1.0 -- -- <5 % (ca. 3%)

Rectifiers number

Pulse number

Transformer displacement

[electrical deg.]

1 6 0

2 quasi 12 0 - 30°

3 quasi 18 -20° - 0 - +20°

4 quasi 24 -15° - 0 +15° - +30°



6.1 Quasi 12 pulse rectifier configuration by two parallel UPS

RECTIFIER

BATTERY

LOADS

INVERTER

OUTPUT BUSBAR

BATTERYSSM

INVERTER

RECTIFIER MAINS

+30°

UPS 1

MAINSINPUT

BYPASS MAINS

SSM

UPS 2

0° RECTIFIER


Characteristics • the required phase shift is 30 el. degr.; this is

realized by using: - no. 1 Dy11 transformer (30 el. degr.) - no. 1 Ddo transformer (0 el. degr.) in case a galvanic separation is required

• available for 2 or multiple UPSs

Harmonics compensation • elimination of 5th, 7th, 17th, 19th, 29th, 31st, ……

harmonics • THDi ca. 9.7%


Benefit • simple solution with good price/performance ratio • good THDI compensation

Limitation • in case of extension units, the same input mains harmonics characteristics are available by adding 2

(or multiple) units

100

2 1.57 6

1.5 1<1<10

102030405060708090

100

1 5 9 13 17 21 25 29harmonic order (n)

curr

ent h

arm

onic

s %

THDi = 9.7%




100

3.54

0102030405060708090

100

1 5 9 13 17 21 25 29harmonic order (n)

curr

ent h

arm

onic

%

6.2 Quasi 18 pulse rectifier configuration

-20°

BATTERY

0° RECTIFIERRECTIFIER

INVERTER

LOADS

BATTERY

OUTPUT BUSBAR

SSM

INVERTER

SSM

RECTIFIER MAINS

UPS 1

MAINSINPUT

BYPASS MAINS

UPS 2

BATTERY

INVERTER

RECTIFIER+20°

SSM

UPS 3



realized by using: - no. 2 zig-zag transformers (20°el. degr.) - no. 1 Ddo transformer in case galvanic separation is required (0 el. degr.)


Harmonics compensation • elimination of 5th, 7th, 11th, 13th, 23rd, 25th, 29th, 31st,

…… harmonics • THDi typical < 7 %


Benefit • elimination of most harmonics

Limitation • zig-zag transformer is more expensive than normal Dy or Dd transformer • in case of extension units, the same input mains harmonics characteristics are available by adding 3

(or multiple) units • in case of one UPS shut down, the rectifier bridge became unbalanced and even harmonics will be

product

THDi < 7 %




100

11.50

102030405060708090

100

1 5 9 13 17 21 25 29harmonic order (n)

curr

ent h

arm

onic

s %

6.3 Quasi 24 pulse rectifier configuration (for 6 pulse UPS)

BATTERY

OUTPUT BUSBAR

RECTIFIER MAINS

BYPASS MAINS

RECTIFIER

INVERTER

BATTERY

-15°

SSM

UPS 1

MAINSINPUT

LOADS

INVERTER

RECTIFIER0°

SSMBATTERY

UPS 2

SSM

INVERTER

RECTIFIER+15°

UPS 3

RECTIFIER

INVERTER

+30°

SSM

UPS 4

BATTERY



realized by using: - no. 2 zig-zag transformers (15 el. degr.) - no. 1 Dy11 transformer (30 el. degr.) - no. 1 Ddo transformer in case galvanic separation is required (0 el. degr.)


Harmonics compensation • elimination of 5th, 7th, 11th, 13th, 17th, 19th, 29th, 31st,

……harmonics • THDi < 5 %; typical 3%


Benefit • elimination of most harmonics

Limitation • practically this configuration is difficult to realize; realize four rectifier system with a perfect 15 el.

degree shift is not easy due to the tolerance in the transformer wiring connections • zig-zag transformer is more expensive than normal Dy or Dd transformer • in case of extension units, the same input mains harmonics characteristics are available by adding 4

(or multiple) units • in case of one UPS shut down, the rectifier bridge became unbalanced and even harmonics will be

product

THDi < 5%




100

11.50

102030405060708090

100

1 5 9 13 17 21 25 29harmonic order (n)

curr

ent h

arm

onic

s %

6.4 Quasi 24 pulse rectifier configuration (for 12 pulse UPS)

INPUTMAINS

BATTERY

INVERTER

UPS 1

SSM

0° +30°

BATTERY

-15°

LOADS

SSM

INVERTER

+15°

UPS 2

OUTPUT BUSBAR

RECTIFIER MAINS

BYPASS MAINS



realized by using: - no. 1 Ddy transformer (0° - 30 el. degr.) - no. 1 Dzz transformer (-15 - +15 el. degr.)

• available for 2 or multiple UPSs Harmonics compensation • elimination of 5th, 7th, 11th, 13th, 17th, 19th, 29th, 31st,

……harmonics • THD(I) < 5 %; typical 3 % Power factor compensation • none (standard p.f.=0.80) Benefit • elimination of most harmonics Limitation • practically this configuration is difficult to realize;

realize four rectifier system with a perfect 15 el. degree shift is not easy due to the tolerance in the transformer wiring connections

• zig-zag transformer is more expensive than normal transformer • in case of extension units, the same input mains harmonics characteristics are available by adding 2

(or multiple) units

THDI < 5 %


ups technical note no. 4

Documents