Power (not only semiconductor) converters. Power semiconductor converters Equipment for changing...

Power (not only semiconductor) converters

Power semiconductor converters

• Equipment for changing quality of electrical energy

(voltage, current, frequency, no. of phases, impedance, etc

• Conversion of energy „nearly“ without power losses

• The most often converters:

– rectifiers (diodes, not controlled)

– frequency converters (non-direct, with DC link)

• The most often applications:

– Power supply, AC drivers

History of converters

• electro-mechanical principle– beginning by Tesla and Edison– rotating rectifiers, switching of windings, brushes

• electro-magnetic principle– groups of machines: Ward-Leonardo

AC vers. DC

end of 19th. century

• Selenium based rectifiers:– end of 19. century, low currents

• Mercury based rectifiers:– current of ions in a steam of Hg

– Cathode – liquid of Hg, Anode – solid

– range of kA, kV, traction power supply

– In Prague from 1929 since 1967

• Thyratrone – units of kV, units of A

History of converters

Siemens 15 kV / 1A

Semiconductor converters

• In Czech from the end of 50. ČKD Elektrotechnika• In 1964 introduced ČKD Polovodiče – Pankrác

discrete devices

modules

converters

silicon

heat sinks, accessories

Converters - overviewrectifiers: AC/DC

inverter: DC/AC

Frequency converter:AC/AC

(direct/indirect)

DC converter: DC/DC

AC – effective

DC - average

dtuT

U 21

dtuT

U AV .1

Most often converters - SMPS

• SMPS – Switch Mode Power Source• all chargers, PC supplies, household

appliances

• Aim – reducing of mass and dimension of transformers in comparison with classic linear power supply

• Product S·B · N stands for a cubic (volume) of transformer

2

1

1

2

1

2

f

f

S

S

N

N

NBSfU i 44,4

Most often converter- DC supply

Power supply for industry

• DC sources

Without PFC

Active PFC

Power factor correction – better efficiency

passive – big choke (coil)

active – adapted DC link, better PF, more expensive

4.1 Charakteristika vysokofrekvenčního rušení

Example of high frequency disturbance - SMPS

0

5

10

15

20

0 30 60 90 120 150

f (kHz)

U (mV)

Basic blocs of SMPS and frequency spectrum

M

Disturbance /noise voltage/ of brush DC driver

1 ms

1 kV

usměrňovač můstkový měnič transformátor usměrňovač stabilizace

síť spotřebič

4.3 Šíření rušení po vedení

Noise-suppressing filters (EMC) – basic circuit solution• symmetric and asymmetric voltage – more types of L, C• impedance miss-matching = low efficiency• reducing of mass and dimensions of coils• limits for capacitors Cx/Cy = leakage currents• additional functions = surge protections, switches, etc.

FILTR

L

N

PE

1

2

1 – symetrické napětí2 – nesymetrické napětí

Zdroj rušení

Přijímač rušení

L1

L1

CY

CY

CX

L

N

PE

L

N

PE

4.3 Šíření rušení po vedení

Assembly and mounting of filters

• placing and mounting of filters = influence of efficiency• separating of input/output, no loops, minimizing of lengths/areas• placing directly at input• good connections between chassis and filters (grounding)

dobře špatně

filtr filtr filtr

YES NO NO NO YES

4.3 Šíření rušení po vedení

EMC chokes – most simple solutions

• connected in series in lines• rated for nominal current• overdosing of cores (not convenient)• compensated chokes

– Subtraction of magnetic fluxes– Not efficient for symmetrical voltage

I,F

I,F I

I

F = 0

not-compensated chokes Current compensated chokes

Nízkofrekvenční a přechodné rušivé jevy

Harmonic, inter-harmonic currentImmediate power p V·A Product of immediate V and I

Apparent power S V·A Product of effective V and I

Active power P W Average value of immediate power p (for periodical signals)

Non-active power Q~V·A, var Square root of difference between S and P

(just for periodical conditions)

Reactive power Q V·A, var Non active power for linear double-pole device (R, L, C)

Power factor - general definitions: P/S

cos cos - Just for harmonic signals is P/S equal to cos !

Phase angle °, rad Angle from voltage to current vector

Definitions according ČSN IEC 60050-131: Basic circuit theory

-400

-200

0

200

400

0 5 10 15 20

napětí

proud

U (V) I (mA)

(ms)

Nízkofrekvenční a přechodné rušivé jevy

Typical currents - consumption

Harmonic conditions: Non-harmonic conditions:

-400

-200

0

200

400

0 5 10 15 20

napětí

proudU (V) I (mA)

(ms)

voltage

current

voltage

current

Nízkofrekvenční a přechodné rušivé jevy

Power triangle, power factor

S = UI

P = UI cos f

Q = UI sin f

f

Harmonic conditions:• linear devices (R, L, C)• sinusoidal current

General non harmonic conditions:• nonlinear devices (etc. rectifiers)• general consumption of current

S

P

Q~

cos SP

UI

IU

S

P hhhh

1

cos

1111 cos

cos I

I

UI

UI

S

P

Nízkofrekvenční a přechodné rušivé jevy

Deformation and displacing of current/voltage waveforms

-400

-200

0

200

400

0 5 10 15 20

napětí

proudU (V) I (mA)

(ms)

-400

-200

0

200

400

0 5 10 15 20

napětí

proud

U (V) I (mA)

(ms)

Deformation only of current waveform Deformities of voltage and current waveforms (simultaneously)

voltage

current

voltage

current

Nízkofrekvenční a přechodné rušivé jevy

Influence of higher Harmonics components

• creation of non-active power, increase of apparent power

• it makes power factor worse

• it makes bigger power losses

• increase of loading for compensation capacitors

• increase of pulsing moments (AC drivers)

• higher harmonics currents are not compensated (neutral conductor!!!)

• overloading of neutral conductor

Nízkofrekvenční a přechodné rušivé jevy

Reducing of harmonics currents (components of current)

• PFC – Power Factor Correction (removing of root cause)• compensations (passive/active filters) – removing of consequences• principle of PFC – prolongation of current consumption (chokes)

pasivní PFC aktivní PFCpassive PFC active PFC

Nízkofrekvenční a přechodné rušivé jevy

Passive PFC

-400

-200

0

200

400

0 5 10 15 20

napětí

proud

U (V) I (mA)

(ms)

Consumption of current – time dependence

Spectrum of harmonics

0

50

100

1 11 21 31 41

voltage

current

Nízkofrekvenční a přechodné rušivé jevy

Active PFC

Consumption of current – time dependence

Spectrum of harmonics

-400

-200

0

200

400

0 5 10 15 20

napětí

proud

U (V) I (mA)

(ms)

0

50

100

1 11 21 31 41

voltage

current

Nízkofrekvenční a přechodné rušivé jevy

Filters for compensation

Passive filters:• resonance LC circuits for actual harmonics• short circuit for undesired harmonics• disadvantage – accumulation of harmonics from the nearest networks

Active filters:• transistor based PWM converters• active filter are producing (by means of PWM) higher harmonics (IH) and reactive components (IJ) of the load current (IZ)• more complicated circuit

Main parts of frequency converters

• Backplain board

• Power modules

• Aluminum body (heat

sink)

• Cooling fan (at the

bottom)

• Cooling from bottom to

the top

• Control circuits,

keyboard at front side • Aluminum and plastics

• Control panel, keyboard

Cooling of modules

Typical devices

• Power modules – integrated semicon. devices• cooling – passive/active air-based• Inductance-less housing• Potential-free

copper bases

• DC link (circuit) – battery of electrolytic capacitors• Electrolytic cap. – up to 450/500 V• 102 F / 500 V, endurance up 600 V• outlets – screws or SNAP-IN for

soldering into PCB

Unconventional converters (I)• for car …. 12/24 VDC• for power supply… 12VDC / 230 VAC• massive outlets (terminals)• heat transfer through whole body• compact design• very expensive

Up/down DC converters:

Unconventional converters (II)

Traction converter for trains (CZ type 560)

• supply voltage 2x 465 V• output voltage 730 V• output current 630 A (permanently)• output current 1200 A (1 min)• nominal power 420 kW perman.• 465 kW per hour• IGCT thyristors• operating frequency 600 Hz• active cooling 4000 m3 / hour• dimensions 1015 × 930 × 1250 mm• weight 460 kg

Unconventional converters (III)

Extensible rectifier for underground in Prague

• installed at line C

• three-phase bridge, all diodes made as pairs

• input voltage 660 V AC / 50 Hz

• output voltage 884 V DC

• max. input voltage 2000 V

• output current IDC = 3000 A (permanently)

• IDC = 4500 A (2 hour)

• IDC = 9000 A (1 min.)