Multilevel inverter.pptx

download Multilevel inverter.pptx

of 74

Transcript of Multilevel inverter.pptx

  • 8/20/2019 Multilevel inverter.pptx

    1/74

    Multilevel inverter

  • 8/20/2019 Multilevel inverter.pptx

    2/74

    Introduction of Power Electronics

    • It is primarily concerned with application ofsolid state devices for conversion and control ofelectrical power.

    • With the development of power semiconductortechnology, power handling capabilities andswitching speed of the power devices increasestremendously.

    • And with the development of digital signalprocessor, we can easily achieved smoothcontrol over power semiconductor switches .

  • 8/20/2019 Multilevel inverter.pptx

    3/74

    Introduction of PowerElectronics

    • Inverter fed AC motor drives is themaor application of power electronicscircuits !nown as adustable speed

    drives "A#$%.

    • PWM based inverter reduces theamplitudes of lower order harmonics in

    the terminal voltage by shifting thedominating harmonics towards higherfre&uencies.

  • 8/20/2019 Multilevel inverter.pptx

    4/74

    Introduction of 'wo(levelinverter

  • 8/20/2019 Multilevel inverter.pptx

    5/74

    Waveform of two-levelinverter

    • Produce pulsed outputvoltage waveform,which contain afundamentalcomponent and other

    harmonics centre onthe switching fre&uencyand its multiples.

    • )igher switchingfre&uency leads tobetter output voltageand current waveform,reduced harmonicscurrents and fastercontrol of drive.

  • 8/20/2019 Multilevel inverter.pptx

    6/74

    $isadvantage of 'wo(levelinverter

    • #witching losses

    • )igh d*+dt due to high switching fre&uency

    Electromagnetic interference "EMI%

    • #tress on the insulation of the machine windings

    • Each devices has to be rated to bloc! entire $C

    lin! voltage during its o time – #o application of two(level inverter is restricted to

    low and medium power application.

  • 8/20/2019 Multilevel inverter.pptx

    7/74

    $e-nition of Multi(levelinverter

    • eduction of disadvantage of two(levelinverter has been made possible by the useof dierent class of PWM inverters, termed

    as Multi(level Inverter.

    /Multi(level inverter are power converterscomposed by an array of semiconductor and

    capacitor voltage sources, that when properlycontrolled, can generate stepped waveformoutput voltage with adustable fre&uency andamplitude0

  • 8/20/2019 Multilevel inverter.pptx

    8/74

  • 8/20/2019 Multilevel inverter.pptx

    9/74

    Advantage of Multi(level inverterwith respect to two(level inverter

    • It is possible to obtain lower d*+dt across powersemiconductor devices.

    • It is possible to reduce the EMI problems.

    2ess stress on the insulation of machine phase windings.• It is possible to obtain machine current with reduced

    harmonics, resulting into reduced tor&ue pulsations in thedrive system.

     –

    3nfortunately, multilevel converters do have somedisadvantages. 4ne particular disadvantage is the greaternumber of power semiconductor switches needed. Althoughlower voltage rated switches can be utili1ed in a multilevelconverter, each switch re&uires a related gate drive circuit. 'hismay cause the overall system to be more e5pensive and

    comple5.

  • 8/20/2019 Multilevel inverter.pptx

    10/74

    66' Analysis

  • 8/20/2019 Multilevel inverter.pptx

    11/74

     ')$ Comparision

  • 8/20/2019 Multilevel inverter.pptx

    12/74

    Applications

    • )igh power drives li!e – 2aminators

     – Mills

     – Conveyors

     – Pumps

     – 6ans

     – 7lowers

     – Compressors etc8.

  • 8/20/2019 Multilevel inverter.pptx

    13/74

    Concepts of Multi(levelinverter

    • Considering that m  is the number ofsteps of the phase voltage with respectto the negative terminal of the inverter,

     – 'hen the number of steps in the voltagebetween two phases of the load is ! 9 :m;

  • 8/20/2019 Multilevel inverter.pptx

    14/74

    Concepts of Multi(levelinverter

    •  'he term multilevel starts with the three(level inverter introduced by =abae et al.

    • 7y increasing the number of levels in theinverter, the output voltages have moresteps generating a staircase waveform,which has a reduced harmonic distortion.

    • )owever, a high number of levelsincreases the control comple5ity andintroduces voltage imbalance problems.

  • 8/20/2019 Multilevel inverter.pptx

    15/74

    7asic 4perating Principle

  • 8/20/2019 Multilevel inverter.pptx

    16/74

    Multilevel Inverter 'opologies

    •  'hree dierent maor multilevelconverter structures have beenapplied in industrial applications>

  • 8/20/2019 Multilevel inverter.pptx

    17/74

    Multilevel $iode Clamped +=eutral Point Inverter, =PCM2I

  • 8/20/2019 Multilevel inverter.pptx

    18/74

  • 8/20/2019 Multilevel inverter.pptx

    19/74

  • 8/20/2019 Multilevel inverter.pptx

    20/74

  • 8/20/2019 Multilevel inverter.pptx

    21/74

  • 8/20/2019 Multilevel inverter.pptx

    22/74

  • 8/20/2019 Multilevel inverter.pptx

    23/74

  • 8/20/2019 Multilevel inverter.pptx

    24/74

  • 8/20/2019 Multilevel inverter.pptx

    25/74

    Comparison of three(level inverterwith two(level inverter

    • *oltage stress on the switches of a three(levelinverter is e&ual to half to that of a conventionaltwo(level inverter or e&ual to voltage across onecapacitor which is *dc+:.

    •  'wo switches of a pole is always open for anyvoltage level and thus share the voltage stresse&ually.

    •  'hus voltage rating of the switches is half the $Clin! voltage and the bloc!ing voltage rating of theclamping diode is also half the $C lin! voltage.

  • 8/20/2019 Multilevel inverter.pptx

    26/74

  • 8/20/2019 Multilevel inverter.pptx

    27/74

    • $iode in the -ve level con-guration has to berated for dierent voltages, which can be higherthan the bloc!ing voltage of the switching devices.

    • 7loc!ing voltage of each clamping diode dependson its position in the structure.

    • 6or n level inverter, voltage across clamping diodeis

    *diode 9 *dc "n(

  • 8/20/2019 Multilevel inverter.pptx

    28/74

  • 8/20/2019 Multilevel inverter.pptx

    29/74

  • 8/20/2019 Multilevel inverter.pptx

    30/74

  • 8/20/2019 Multilevel inverter.pptx

    31/74

  • 8/20/2019 Multilevel inverter.pptx

    32/74

    #witching states of one -ve(level

    phase leg

  • 8/20/2019 Multilevel inverter.pptx

    33/74

  • 8/20/2019 Multilevel inverter.pptx

    34/74

  • 8/20/2019 Multilevel inverter.pptx

    35/74

    E5planation

    • $iode clamped multi(level inverter is also !nown asneutral point clamped because of mid voltage levelis formed by clamping the switching devices to theneutral point of the $C bus.

    •  'herefore , the ma5imum voltage stress on theswitch is limited to the voltage across each

    capacitor *dc+"m(

  • 8/20/2019 Multilevel inverter.pptx

    36/74

    • 6or an = level "between the phase and thenegative rail% $iode clamped inverter,

     –

     'he number of levels in the line(to(line voltagewaveform will be ! 9 :=(<

     – 'he number of levels in the line to load neutralof a star or wye load will be p 9 :!(<

     –

     'he number of capacitors re&uired,independent of the number of phase, is =cap 9

    =(<

     – While the number of clamping diodes of

    une&aul voltage rating per phase is $clamp 9:"=(

  • 8/20/2019 Multilevel inverter.pptx

    37/74

    6eatures

  • 8/20/2019 Multilevel inverter.pptx

    38/74

    Advantages

    • When the number of levels is high ,the harmonics content is low enoughto avoid the need for -lters.

    • Inverter eciency is high because alldevices are switched at thefundamental fre&uency.

    •  'he control method is simple.

  • 8/20/2019 Multilevel inverter.pptx

    39/74

    $isadvantage

    • Increase in the number of clamping diodesleads to a comple5 bus structure andma!e the =PC inverter system impractical

    to implement when the number of levelsis suciently high.

    • Capacitor voltage can uctuate over afundamental cycle "depending on the load

    current drawn from the $C lin!% and thismeans that devices are subected bloc!higher voltages than the ideal condition.

  • 8/20/2019 Multilevel inverter.pptx

    40/74

    Multilevel Capacitor Clamped+6lying Capacitor Inverter, CCM2I

  • 8/20/2019 Multilevel inverter.pptx

    41/74

  • 8/20/2019 Multilevel inverter.pptx

    42/74

  • 8/20/2019 Multilevel inverter.pptx

    43/74

  • 8/20/2019 Multilevel inverter.pptx

    44/74

  • 8/20/2019 Multilevel inverter.pptx

    45/74

    #witching 'able for ? level 6C

    inverter

    PoleVoltage

    Vao

    Voltage

    Level

    State if theSwitch

    Eect on ying capacitorvoltage

    #< #: #? #B

    *dc+: ; < < D D =o EectD D < D < D Charging

    D D D < D < $ischarging

    (*dc+: ( D D < < =4 Eect• #< and #B, as well as #: and #? are

    two dierent complementary pairs ofthe switch.

    6i 2 l 6l i C it

  • 8/20/2019 Multilevel inverter.pptx

    46/74

    6ive 2evel 6lying CapacitorInverter

    4 l f 6l i C it

  • 8/20/2019 Multilevel inverter.pptx

    47/74

    4ne leg of 6lying CapacitorInverter

    #witching state for level 6C Inverter

  • 8/20/2019 Multilevel inverter.pptx

    48/74

    #witching state for level 6C Inverter

    Polevolta

    ge

    State of the switch

    S1 S2 S3 S S! S" S# S$

    V%c&2

    1 1 1 1 ' ' ' '

    V%c&

    1 1 1 ' 1 ' ' '

    ' 1 1 1 ' ' ' 11 ' 1 1 ' ' 1 '

    '

    1 1 ' ' 1 1 ' '

    ' ' 1 1 ' ' 1 1

    1 ' 1 ' 1 ' 1 '

    1 ' ' 1 ' 1 1 '

    ' 1 ' 1 ' 1 ' 1

    ' 1 1 ' 1 ' ' 1

    -

    V%c&

    1 ' ' ' 1 1 1 '

    ' ' ' 1 ' 1 1 1

  • 8/20/2019 Multilevel inverter.pptx

    49/74

    Advantage of edundancy

    • As before with the =PCM2I only one switch need

    to be opened and one to be closed to changeone state to another. 'his leads to that theinverter can be modulated at low "fundamental%switching fre&uency since a stepped sinusoidal

    waveform can be created when every switch is

  • 8/20/2019 Multilevel inverter.pptx

    50/74

    E5planation

    •  'his circuit is called the yingcapacitor inverter, as independentcapacitors clamp the device voltage

    to one capacitor voltage level.•  'he switches in the pair always be in

    complementary states.

  • 8/20/2019 Multilevel inverter.pptx

    51/74

    6eatures

  • 8/20/2019 Multilevel inverter.pptx

    52/74

    6eatures:. 7alancing capacitor voltage

     – As we already !nown that, the switching combination for voltagelevel e5cept upper and lower one is greater than one.

     – #uch redundancy of the multi(level con-guration is a uni&uefeature and it is an advantage to maintain the capacitor voltagebalance.

     –

    7ut redundant switching states, vital to capacitor voltagebalancing, are sacri-ced to achieve a higher number of outputvoltage levels.

     –  'o produce same output voltage, the inverter has to switcheddierent combination so that it easier to manipulate thecapacitor voltage and !eep them at their proper value.

     – #ince the same current ows through all the active capacitors ina state, energy can be transferred from more charged to lesscharged capacitors, balancing the capacitors voltages betweenthe capacitors that are conducting.

     –  'hus by proper selection of switching combination , the 6C multi(level inverter may be used in real power conversion.

  • 8/20/2019 Multilevel inverter.pptx

    53/74

    Advantage

    • 2arge amount of storage capacitorscan provide capabilities during poweroutages.

    • Provides switch combinationredundancy for balancing dierentcapacitor voltage levels.

    • )armonic content is low enough toavoid the need of -lters.

    • 7oth real and reactive power ow

    can controlled.

  • 8/20/2019 Multilevel inverter.pptx

    54/74

    $isadvantage

    • An e5cessive number of storagecapacitor is re&uired when thenumber of levels is high. #o cost of

    the converter becomes high.•  'he inverter control can be very

    complicated.

    • #witching fre&uency and switchinglosses are high for real powertransmission.

    Cascaded Multi cell Inverter

  • 8/20/2019 Multilevel inverter.pptx

    55/74

    Cascaded Multi cell Inverter,CMCI

  • 8/20/2019 Multilevel inverter.pptx

    56/74

    Cascaded Multi cell Inverter, CMCI

  • 8/20/2019 Multilevel inverter.pptx

    57/74

  • 8/20/2019 Multilevel inverter.pptx

    58/74

  • 8/20/2019 Multilevel inverter.pptx

    59/74

  • 8/20/2019 Multilevel inverter.pptx

    60/74

  • 8/20/2019 Multilevel inverter.pptx

    61/74

  • 8/20/2019 Multilevel inverter.pptx

    62/74

  • 8/20/2019 Multilevel inverter.pptx

    63/74

  • 8/20/2019 Multilevel inverter.pptx

    64/74

  • 8/20/2019 Multilevel inverter.pptx

    65/74

  • 8/20/2019 Multilevel inverter.pptx

    66/74

  • 8/20/2019 Multilevel inverter.pptx

    67/74

  • 8/20/2019 Multilevel inverter.pptx

    68/74

  • 8/20/2019 Multilevel inverter.pptx

    69/74

  • 8/20/2019 Multilevel inverter.pptx

    70/74

  • 8/20/2019 Multilevel inverter.pptx

    71/74

  • 8/20/2019 Multilevel inverter.pptx

    72/74

    Introduction

    • It is a relatively new converter structure, cascaded(inverters with separate dc sources.

    •  'his new converter can avoid e5tra clamping diodesor voltage balancing capacitors.

    •  'o comply with the de-nition of the previouslymentioned diode(clamp and ying(capacitormultilevel converters, the /level0 in a cascaded(inverters based converter is de-ned by m9:s;

  • 8/20/2019 Multilevel inverter.pptx

    73/74

    Advantage

    • e&uires the least number of components among allmultilevel converters to achieve the same number ofvoltage levels.

    • Modulari1ed circuit layout and pac!aging is possiblebecause each level has the same structure, and there areno e5tra clamping diodes or voltage balancing capacitors.

    • #oft(switching can be used in this structure to avoid bul!yand lossy resistor(capacitor(diode snubbers.

    • 6or real power conversions, "ac to dc and dc to ac%, the

    cascaded(inverter needs separate dc sources. 'hestructure of separate dc sources is well suited for variousrenewable energy sources such as fuel cell, photovoltaicand biomass etc.

  • 8/20/2019 Multilevel inverter.pptx

    74/74

    $isadvantage

    • =eeds separate dc sources for realpower conversions, and thus itsapplications are somewhat limited.