MULTI-LEVEL INVERTER
CASCADE H-BRIDGE INVERTER
INVERTER
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The voltage source inverters produce a
voltage or a current with levels either 0
or ±V dc they are known as two level
inverters.
To obtain a quality output voltage or a
current waveform with a minimum
amount of ripple content, they require
high switching frequency.
In high power and high voltage
applications, these two level inverters,
however, have some limitations in
operating at high frequency.
MULTI-LEVEL INVERTER
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The multi-level inverter is to synthesize
a near sinusoidal voltage from several
levels of dc voltages.
As number of levels increases, the
synthesized output waveform has more
steps, which provides a staircase wave
that approaches a desired waveform .
Also, as steps are added to waveform,
the harmonic distortion of the output
wave decreases, approaching zero as the
number of voltage levels increases
TYPES OF MULTI-LEVEL
INVERTER
The Multi-level inverters can be
classified into three types.
y 1. Diode – clamped Multi-level inverter
y 2. Flying – capacitor Multi-level inverter
y 3. Cascade Multi-level inverter
y
Diode- clamped Multi – level
inverter
¾Extension of NPC
¾Based on concept of using diodes to limit
power devices voltage stress
¾Structure and basic operating principle
ƒ Consists of series connected capacitors that divide DC bus
voltage into a set of capacitor voltages
ƒ A DCMI with nl number of levels typically comprises (nl-1)
capacitors on the DC bus
ƒ Voltage across each capacitor is VDC/(nl-1)
( nl nodes on DC bus, nl levels of output phase voltage , (2nl1) levels of output line voltage)
Flying capacitor multilevel
inverter
¾ Capable of solving capacitor voltage unbalance
problem and excessive diode count requirement in
DCMI
¾ Also known as imbricated cell multilevel inverter
(capacitors are arranged to float with respect to
earth)
¾ Structure and basic operating principle
ƒ Employs separate capacitors precharged to
[(nl-1)/(nl-1)xVDC], [(nl-2)/(nl-1)xVDC] …{[nl-(nl-1)]/[nl-1]xVDC}
ƒ Size of voltage increment between two capacitors defines size of
voltage steps in ICMI output voltage waveform
Cascade H-bridge
¾ Referred to as cascaded-inverters with Separate
DC Sources (SDCs) or series connected H-bridge
inverters
¾ Structure and basic operating principle
ƒ Consists of (nl–1)/2 or h number of single-phase H-bridge inverters
(MSMI modules)
ƒ MSMI output phase voltage
Vo = Vm1 + Vm2 + …….. Vmh
Vm1 : output voltage of module 1
Vm2 : output voltage of module 2
Vmh : output voltage of module h
x
Structure of a single-phase nl-level MSMI
Circuit diagram
.
1.
2.
3.
4.
The above circuit diagram can be
explained broadly by classifing into four
sub-circuits.
Dc power supply circuit.
Microcontroller circuit.
Driver circuit.
Mosfet circuit.
Dc power supply circuit
It consists of step down transformer,
diode bridge rectifier, regulators, capacitor,
resistance and led.
Step down transformer:In the primary winding the supply is 230v ac
supply and at the secondary winding the
output is 15v ac supply.
Diode bridge rectifier:The secondary winding output 15v ac
supply is given and to diode full bridge
rectifier.which rectifies the ac supply convert
to dc supply rated 12-15v dc supply.
y
.
Regulators:The output voltage 12-15v dc supply is regulated
to 12v by regulator Im7812 and 5v by regulator
Im7805.
Capacitor:The capacitor filters the voltage.
Resistance:The resistance is used to with stand high current
from regulators and to give low voltage to LED.
Led:To show that supply is there.
Microcontroller circuit
Microcontroller circuit is used to give to
pulses to mosfet circuit.
y It can give the pulses upto 5V.
y
Driver circuit
It acts just like a pulse generator .
y It consists of IR2110 .
y IR2110 can with stand the voltage upto
500volts
y The MOSFET requires 10-15v supply to
operate.
y
Mosfet circuit
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y
y
y
y
y
The mosfet circuit is connected in MATLAB
stimulation way.
Here we are considering IRFZ44n MOSFET.
There are eight mosfets.
In which S1,S2S5,S6 are positively connected
.
In which S3,S4,S7,S8 are negatively
connected.
In which S1,S2,S6,S8 are switched on and
other are switched off.
APPLICATIONS
Reactive power compensator
2. Back to Back intertie
3. Utility compatible adjustable speed
drives
1.
THANK YOU