power (not only semiconductor) converters. power semiconductor converters equipment for changing...
TRANSCRIPT
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.)