Accionamientos Para Buques2

Frequency ConvertersFrequency Converters

Schematics of an AC VSD with DC LinkSchematics of an AC VSD with DC Link

Rectifier(AC to DC)

Inverter(DC to AC) Motor

Controller

Controls signals Measurements

Interface to control systems, commands and monitoring

Network DC Link Motor supply

Control of Power SemiconductorsControl of Power Semiconductors

ON OFF

ConductionLosses

SwitchingLosses

Off-stateLosses

Power SemiconductorsPower SemiconductorsUncontrolled devicesUncontrolled devices

The diode is an uncontrolled device. The diode is an uncontrolled device.

It will conduct current if positively biased, and block for currIt will conduct current if positively biased, and block for currents when ents when negatively biased, depending on the surrounding conditions.negatively biased, depending on the surrounding conditions.

u

i+u-

iu

i

symbol ui char. ideal analogy

Power SemiconductorsPower SemiconductorsTurnTurn--on controllable deviceson controllable devices

The thyristor is a device that without a gate firing signal willThe thyristor is a device that without a gate firing signal will block currents in both block currents in both directions. If positively biased and in blocking mode, a gate fidirections. If positively biased and in blocking mode, a gate firing signal (current ring signal (current pulse) is given, the thyristor will conduct until the surroundinpulse) is given, the thyristor will conduct until the surrounding circuits force the g circuits force the current to reverse. The thyristor will then enter blocking mode current to reverse. The thyristor will then enter blocking mode by itself, until by itself, until positively biased and a new gate firing signal is given.positively biased and a new gate firing signal is given.

u

i+u-

iu

i


Power SemiconductorsPower SemiconductorsTurnTurn--on and turnon and turn--off controllable devicesoff controllable devices

The transistor is the most known component. The transistor is the most known component.

If positively biased, the transistor can be turned on from a bloIf positively biased, the transistor can be turned on from a blocking condition by cking condition by giving a continuous gate firing signal. If removing the gate firgiving a continuous gate firing signal. If removing the gate firing signal, the transistor ing signal, the transistor will rewill re--enter blocking mode, even if positively biased. A transistor is enter blocking mode, even if positively biased. A transistor is normally not normally not designed to tolerate negative voltage bias, unless special considesigned to tolerate negative voltage bias, unless special considerationsderations

u

i+u-

iu

i


Variable Speed Drives (VSD)Variable Speed Drives (VSD)

The most commonly used converters for motor drives are: Voltage source inverter (VSI) type converters

for AC motors, normally asynchronous motors Cycloconverters (Cyclo) for AC motors,

normally for synchronous motors Current source inverter type (CSI) converters

for AC motors, normally synchronous motors DC converters, or SCR (Silicon Controlled Rectifier)

for DC motors

DC MotorDC Motor

DC

+-

R

E=nxIfxke

n +Ua-

Ua=E+RxIa

Ia

Ia

n

Ua

E

RxIa

Ua,max

If,maxIf

Control Strategies for AM (IM)Control Strategies for AM (IM)

Scalar ControlScalar Control Rotor Flux Vector ControlRotor Flux Vector Control Stator Flux Vector ControlStator Flux Vector Control

Vs

n : 1

Rs Ls Rr / sLr

LmRm Vs

Rs Ls Lr

LmRm

Rr / s* *

AC MotorAC Motor

AC

+-

R

E=nxxke

n +ua-

Ua=E+(jL+R)xIa= E+(j2fL+R)xIa =E+(j2PnL+R)xIa

ia

Ia

n

Ua

E

(jL+R)xIa

Ua,max

maxL

DOL Asynchronous MotorDOL Asynchronous Motor

Speed

Slip1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0

10.90.80.70.60.50.40.30.20.10 snn

s

s

nnn

Stator current

TorqueLoad curves- full pitch- zero pitch

DC Drive DC Drive (SCR (SCR -- silicon controlled rectifier)silicon controlled rectifier)

PM

cos = 0...0.96constant current

CSI Drive and Synchronous motorCSI Drive and Synchronous motor

PM

six-step waveformcos = 0...0.96

constant current

Cycloconverter and Synchronous MotorCycloconverter and Synchronous Motor

PM

Voltage Source Inverters (VSI)Voltage Source Inverters (VSI)

PM

cos = 0.95 (constant)

constant voltage

near sinusoidalcurrents

DOLasynchronousmotor + CPP

SCR DCmotor drive

Cyclo- 1

converterCSI (LCI) 2 VSI PWM 3

Start-up amps Typ. 5 x ratedcurrent

0(transformer

inrush)

0(transformer

inrush)

0(transformer

inrush)

0(transformer

inrush)Start-up torque transients Typ. 2-3 x

rated torque 0 0 Up to 50% of

rated torque 0

Power consumption, lowthrust

15% ofnominalpower

0 0 0 0

Amps at low thrust 45-55%of nominal

F(torque) F(torque) F(torque) 0

Power Factor - full load 0.85 > 0.9 > 0.76 > 0.9 > 0.95

Power factor variation withload (cos)

0.15 .. 0.85(non-linear)

0 .. 0.9(prop. speed)



> 0.95( constant)

Dynamic response (power,torque)

3-5 sec(pitch control)

< 100 ms < 100 ms Slower < 50 ms

Torque ripple None Smooth Smooth Pulsating SmoothZero-thrust crossing Smooth if

negative thrustallowed

Discontinuous Smooth Pulsating Smooth

Efficiency at full load High Lower High High HighHarmonic distortion:- at low speed /thrust- at full speed /thrust

NoneNone

F(torque)F(torque)

F(torque)F(torque)

F(torque)F(torque)

0F(power)

Short circuit contribution Typ. 5 xnominalpower

No No No No

Motor matching required - Some Some Yes NoCommutator No Yes No (sliprings) No (sliprings) No

1212--pulse Rectifierpulse Rectifier

Vdc =2x1.35xVll

Ddytransformer

Vdc =1.35xVll

Series connection Parallel connection

Ddytransformer

Harmonic distortion, 12Harmonic distortion, 12--pulsepulse11kV line-line voltages 11kV line currents

1750V line currents 1750V D-winding currents

Pulse Width Modulation

Generation of ONGeneration of ON--OFF signalsOFF signals

0 5 10 15 2

OnOff

Upper and lower switchingelements are switched in opposite orders:- ON: Upper = on, Lower = off- OFF: Upper = off, Lower = on

0 5 10 15 20 5 10 15 20 5 10 15 2

Pulse Width ModulationPulse Width Modulation

a

b

b-a

PM

ThreeThree--level, Zero Voltage Clampedlevel, Zero Voltage Clamped

Vdc/2

Phase 1

+

0

_

Phase 2 Phase 3

Vdc/2

+

0

_

Phase

+

0

_

Phase

+

0

_

Phase

+

0

_

Phase

+

0

_

Phase

+

0

_

Phase

Positive Current:

Negative Current:

a) b)

Motor Voltage, Current, TorqueMotor Voltage, Current, TorqueTorque

Line to line voltage

Current

Simulation and Control DiagramSimulation and Control Diagram

Speedcontrol

PI

Torquelimitation

Speedlimitation

Speedreference

Torquereference

Torquecontrol loop

Speed

Torquereference

1

1 + Ts

Torque

1

J s

Motorinertia

KpTiS

(1 + Tis)

Loadcurve

Operation Boundaries VSD IM(AM)Operation Boundaries VSD IM(AM)

Constant torqueregion

Field weakeningregion

RPM

Magnetic flux level

Maximum torque boundary

Maximum stator current boundary

Stator voltage

Stator frequency

Pitching momentlimitation

Operation Boundaries VSD IM(AM)Operation Boundaries VSD IM(AM)

Constant torqueregion

Field weakeningregion

Speed

Maximum torque boundaryBollard Pull, V=0

Sailing, V>0

RPM

Quadrants of OperationQuadrants of Operation

Speed

Torque

P0

P>0 P0, Torque

Power SemiconductorsPower Semiconductors

IGBTLow voltage

IGCTMedium voltage

690V Motor drive for AM(IM)690V Motor drive for AM(IM)

3.3kV Motor drive for AM(IM)3.3kV Motor drive for AM(IM)

HarmonicsHarmonics

HarmonicsHarmonicsAll periodic waveforms can be expressed as a sum of a All periodic waveforms can be expressed as a sum of a series of sinusoidal functions with frequency equal to the series of sinusoidal functions with frequency equal to the multiple of the fundamental frequency, i.e.:multiple of the fundamental frequency, i.e.:

...)sin(

...)3sin()2sin(

)sin()(

1

313

212

11

+

++

+

++

++

+

=

hh

dc

thu

tutu

tuutu

-150

-100

-50

0

50

100

150

0 8 16 24 32 40 48 56 64 72 80 88 96 104

112

120

128

136

144

152

160

168

176

184

192

200

208

216

224

232

240

248

256

264

272

280

288

296

304

312

320

328

336

344

352

360

Ideal current waveforms, Ideal current waveforms, large inductorlarge inductor

Vdc = 1.35xVll

6-pulse 12-pulse

Example Example -- square wavesquare wave

-15

-10

-5

0

5

10

15

0 8 16 24 32 40 48 56 64 72 80 88 96 104

112

120

128

136

144

152

160

168

176

184

192

200

208

216

224

232

240

248

256

264

272

280

288

296

304

312

320

328

336

344

352

360

h=1h=5

h=7h=11

h=13

)37sin(3710...)35sin(

3510...

)7sin(7

10)5sin(5

10)sin(10)(

11

311

1

tt

tt

ttu

+++

+

+++

=

Harmonic DistortionHarmonic Distortion

,...,,,h,..,,nxnh

1311752116

===

,...25,23,13,11,...2,1,112

===

hnxnh

6-Pulse

12-Pulse

)1(

2

2)(

%100i

iTHD h

h==

0 %

5 %

10 %

15 %

20 %

25 %

1 2 3 4 5 6 7 8 9 10 11 12

Ih(6-p)Ih(12p)

5 7 11 13 17 19 23 25 29 31 35 37

Harmonic AnalysisHarmonic Analysistwo different methodstwo different methods

Frequency domain calculationFrequency domain calculation Harmonic current injection and impedance modelsHarmonic current injection and impedance models Easy to build up large systemsEasy to build up large systems Short calculation times, also with large systemsShort calculation times, also with large systems Need accurate harmonic spectrum and modelsNeed accurate harmonic spectrum and models

Time domain calculationTime domain calculation Circuit diagramCircuit diagram modellingmodelling Complicated to build up large systemsComplicated to build up large systems Time consuming to simulate large systemsTime consuming to simulate large systems Calculates accurate harmonic spectrum withCalculates accurate harmonic spectrum with

proper modelsproper models

Example Power SystemExample Power System

Vessel Loads

Propulsion Auxilliaries

Single LineSingle Line

G G G G

M M

M M M

MMMM

M

Impedance model for Impedance model for harmonic current injection modelharmonic current injection model

10

1m

1m

2m

10 1m

1m

0.5m

10m

3m

2m

1mv_sin

Harm load 1

Load 1

Load 2

Load 3

Generator 1

Cable 1

3m

2m 2m

2m

Trafo 1

2m

v_sin

Bus 1

Bus 2

Load 4

101m

0

1

2

3

4

5

6

7

8

9

10

2 4 6 8

1

0

1

2

1

4

1

6

1

8

2

0

2

2

2

4

2

6

2

8

3

0

3

2

3

4

3

6

3

8

4

0

4

2

4

4

4

6

4

8

5

0

Circuit model for time simulationCircuit model for time simulation

EL R

EL R

EL R

EL R

EL R

EL R

R

EL R

EL R

EL R

L R

L R

L R

Harmonic distortion, 12Harmonic distortion, 12--pulsepulse11kV line-line voltages 11kV line currents

1750V line currents 1750V D-winding currents

Current and Voltage Distortion, VSICurrent and Voltage Distortion, VSI

Approx8% THD

Theoretical vs. real 12pTheoretical vs. real 12p--harmonicsharmonics

0

1

2

3

4

5

6

7

8

9

10

2 4 6 8

1

0

1

2

1

4

1

6

1

8

2

0

2

2

2

4

2

6

2

8

3

0

3

2

3

4

3

6

3

8

4

0

4

2

4

4

4

6

4

8

5

0

1h

ComparisonComparisonTime simulation Time simulation -- Injected harmonics (Injected harmonics (IIhh = 1/h)= 1/h)

0

1

2

3

4

5

6

7

8

9

10

2 4 6 8

1

0

1

2

1

4

1

6

1

8

2

0

2

2

2

4

2

6

2

8

3

0

3

2

3

4

3

6

3

8

4

0

4

2

4

4

4

6

4

8

5

0

Time sim.approx

8% THDv Inj. harm.approx

20% THDv

Harmonic AnalysisHarmonic Analysistwo different methodstwo different methods

Frequency domain calculationFrequency domain calculation Harmonic current injection and impedance modelsHarmonic current injection and impedance models Easy to build up large systemsEasy to build up large systems Short calculation times, also with large systemsShort calculation times, also with large systems Need accurate harmonic spectrum and modelsNeed accurate harmonic spectrum and models

Time domain calculationTime domain calculation Circuit diagramCircuit diagram modellingmodelling Complicated to build up large systemsComplicated to build up large systems Time consuming to simulate large systemsTime consuming to simulate large systems Calculates accurate harmonic spectrum withCalculates accurate harmonic spectrum with

proper modelsproper models

Managing HarmonicsManaging Harmonics

Generator design, Generator design, subtransient subtransient reactancereactance Selection of converter typeSelection of converter type Design of drive transformer / inductorDesign of drive transformer / inductor Passive filtersPassive filters Active filtersActive filters Clean power supplyClean power supply Selection of equipmentSelection of equipment Know your system!! Analysis and freq. scanKnow your system!! Analysis and freq. scan

Generator Generator SubtransientSubtransient ReactanceReactance

Harmonic currents injected in the system Harmonic currents injected in the system distort the voltage on generator terminalsdistort the voltage on generator terminals Subtransient Subtransient reactance is found either as:reactance is found either as:

Average Average subtransientsubtransient reactance: (reactance: (xxdd++xxqq)/2)/2 Negative sequence reactance: xNegative sequence reactance: x--

Low Low subtransient subtransient reactance will increase reactance will increase generators dimensions, weight, and costsgenerators dimensions, weight, and costs

LowLow subtransientsubtransient reactance will increase reactance will increase short circuit currentshort circuit current

Selection of Converter TypeSelection of Converter Type

Different topologies have different spectrumDifferent topologies have different spectrum VSI : low harmonicsVSI : low harmonics CSI : high harmonics, CSI : high harmonics, interharmonicsinterharmonics Cycle : wide band high high harmonicsCycle : wide band high high harmonics DC (SCR) : high harmonics, DC (SCR) : high harmonics, interharmonicsinterharmonics

Pulse number, i.e. 6, 12, 18, 24, 48,Pulse number, i.e. 6, 12, 18, 24, 48, Active front end (harmonicActive front end (harmonic--less design)less design)

Current and Voltage Distortion, CSICurrent and Voltage Distortion, CSI

Approx10% THD

1212--pulse Rectifierpulse Rectifier

Vdc =2x1.35xVll

Ddytransformer

Vdc =1.35xVll

Series connection Parallel connection

Ddytransformer

Design of Drive TransformerDesign of Drive Transformer

Drive transformer or inductorDrive transformer or inductor High s.c. impedance reduces harmonicsHigh s.c. impedance reduces harmonics High s.c. impedance give a load dependent High s.c. impedance give a load dependent

voltage drop, and reduced max power outputvoltage drop, and reduced max power output

Use of ZUse of Z--winding in order to achieve winding in order to achieve quasi 24 pulse with two 12 pulse convertersquasi 24 pulse with two 12 pulse converters quasi 48 pulse with two 24 pulse convertersquasi 48 pulse with two 24 pulse converters

EMC: Grounded shield between EMC: Grounded shield between pripri. and sec.. and sec.

Passive FiltersPassive Filters Passive filters are used to create a low Passive filters are used to create a low

impedance path for harmonic currents with a impedance path for harmonic currents with a serial resonanceserial resonance

Normally one or twoNormally one or two parallellparallell connected LC connected LC filters tuned to the frequency of the worst filters tuned to the frequency of the worst harmonic currents, e.g. for 12 pulse:harmonic currents, e.g. for 12 pulse: 11th harmonic (also efficient for 13th)11th harmonic (also efficient for 13th)

Warning 1: Parallel resonance occurs normally at Warning 1: Parallel resonance occurs normally at about 1/2 of series resonanceabout 1/2 of series resonance

Warning 2: Capacitive limit for generatorsWarning 2: Capacitive limit for generators

Passive FilteringPassive Filtering

G G G G

M M

M M

MMMM

filter filter

Passive FilteringPassive Filtering

L

C

First order undamped LC filter

Lg

Aggregated Generator / motor model

Z()

Frequency Response Z(Frequency Response Z())

Generator2 . . f . Lg

Filter

Resulting

f / f1

Z

5 7 11 13

Passive Filtering Passive Filtering -- two stepstwo steps

Z()

L

C

First order 5th harm undamped LC filter

Lg

Aggregated Generator / motor model

L

C

First order 3rd harmundamped LC filter

Frequency response Z(Frequency response Z())

Generator2 . . f . Lg

Filter

Resulting

f / f1

Z

5 7 11 13

Active FilterActive Filter

G

M

ActivefilterNon-

linear load

i1 i2

ig = i1+i2

1 3 5 7 9

1

1

1

3

1

5

1

7

1

9

2

1

2

3

2

5

2

7

2

9

3

1

3

3

3

5

3

7

3

9

4

1

4

3

4

5

4

7

4

9

5

1

5

3

5

5

5

7

5

9

6

1

6

3

6

5

6

7

6

9

7

1

7

3

7

5

7

7

7

9

8

1

8

3

8

5

8

7

8

9

igi1

i2

HF filter

Clean Power SupplyClean Power Supply

Rotating ConverterRotating ConverterMotorMotor--GeneratorGenerator

Static ConverterStatic ConverterPWM converter PWM converter with HF filterwith HF filter

UPSUPSPWM converter with PWM converter with HF filter and battery HF filter and battery DC link backupDC link backup

Dirty net withhigh distortion

Rectifier(AC to DC)

Inverter(DC to AC)

Inverter(DC to AC)

Rectifier(AC to DC)

M G

Clean net without distortion

Selection of Selection of EquimpentEquimpent

High tolerance for harmonic distortionHigh tolerance for harmonic distortion Uncompensated Uncompensated flouorescent flouorescent light, capacitive light, capacitive

compensators will be overloadedcompensators will be overloaded True RMS measurement circuits in protection True RMS measurement circuits in protection

devicesdevices Electronic rectifiers can be overloaded if high Electronic rectifiers can be overloaded if high

distortion, avoid sensitive equipmentdistortion, avoid sensitive equipment If necessary, local filtering or UPS supply.If necessary, local filtering or UPS supply.

Cheaper than overall filteringCheaper than overall filtering

Impedance model for Impedance model for harmonic current injection modelharmonic current injection model

10

1m

1m

2m

10 1m

1m

0.5m

10m

3m

2m

1mv_sin

Harm load 1

Load 1

Load 2

Load 3

Generator 1

Cable 1

3m

2m 2m

2m

Trafo 1

2m

v_sin

Bus 1

Bus 2

Load 4

101m

0

1

2

3

4

5

6

7

8

9

10

2 4 6 8

1

0

1

2

1

4

1

6

1

8

2

0

2

2

2

4

2

6

2

8

3

0

3

2

3

4

3

6

3

8

4

0

4

2

4

4

4

6

4

8

5

0

Frequency ScanFrequency Scan

102 103 104 1050

2000

4000

6000

8000

M

a

g

.

(

o

h

m

s

)

102 103 104 105

-100

-50

0

50

100

P

h

a

s

e

(

d

e

g

r

e

e

s

)

Frequency (Hz)

Frequency ScanFrequency Scan

102 103 104 1050

0.5

1

1.5

2x 10 4

M

a

g

.

(

o

h

m

s

)

102 103 104 105-100

-50

0

50

100

P

h

a

s

e

(

d

e

g

r

e

e

s

)

Frequency (Hz)

Transient OvervoltagesTransient Overvoltages

ResonanceResonance Faults (earth faults, short circuits)Faults (earth faults, short circuits) Switchgear operationsSwitchgear operations

OpenOpen inductive current interruptioninductive current interruption virtual choppingvirtual chopping restrikesrestrikes

CloseClose surge voltagessurge voltages prestrikesprestrikes

Transient Overvoltage ManagementTransient Overvoltage Management

Equipment designEquipment design power frequency: power frequency:

dielectric dielectric strengthtstrengtht high frequency: high frequency:

impulse voltageimpulse voltage

ProtectionProtection Surge arrestersSurge arresters Surge capacitorsSurge capacitors

Documents

Accionamientos Para Buques2