DESIGN AND IMPLEMENTATION OF FIVE LEVEL INVERTER FOR REDUCING THD USING PWM

International Engineering Journal For Research & Development

Vol.4 Issue 1

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E-ISSN NO:-2349-0721

DESIGN AND IMPLEMENTATION OF FIVE LEVEL INVERTER FOR REDUCING THD USING PWM Kanchan Agashe 1 ,Dipali Gaikwad 2 , Harsha Kohad 3 ,Karishma Thakre 4, Kalyani Kurekar 5 , Kanchan Raut 6, Kalyani Kukwas 7 Student of B.E. , Department of electrical engineering Smt.Rajshree Mulak College of Engineering Nandanvan, Nagpur

Kanchanagashe95@gmail.com , dipaligaikwad410@gmail.com , Harshakohad23@gmail.com , Karishmathakre10@gmail.com , kalyanikurekar04@gmail.com , kanchanraut269@gmail.com , kalyanikukwas87@gmail.com . _______________________________________________________________________________________ take a DC voltage from a battery or a solar panel as

ABSTRACT:-

input, and convert it into an AC voltage output.

This paper is based on the design and implementation of single phase 5 level inverter

DC to AC converters are known as

based on POD technique. In this, we use four

inverter. The output voltage waveforms of ideal

carrier wave and single sine wave for pulse

inverter should be sinusoidal .However, the

generation. The entire system is designed and

waveform of practical inverter are non sinusoidal

implemented using MATLB. The inverter is

and contain certain harmonics. For low and

connected to R-load and performance is analyzed.

medium power application , square –wave or quasi-

Hardware is implemented using ATmega328

square wave voltages may be acceptable ; and for

microcontroller.

high power application low distorted sinusoidal waveform are required. With the availability of

Keywords:-Microcontroller, Multilevel inverter , POD technique , Pulse width modulation (PWM).

high speed power semiconductor devices the harmonic content of output voltage can be minimize or reduced significantly by switching techniques.

I.

INTRODUCTION Inverter can be broadly classified into two types :

The adoption of AC power has created a trend where most devices adapt AC power from an

1) Single phase inverter

outlet into DC power for use by the device.

2) Three phase inverter

However, AC power is not always available and the need for mobility and simplicity has given batteries an advantage in portable power. Thus, for portable AC power, inverters are needed. Inverters

Each type can used controlled turn ON and turn OFF devices eg: BJT,MOSFET An inverter is called a voltage fed inverter (VFI) if input voltage remain constant . An inverter is called current fed inverter (CFI) if the input

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current is maintained constant. An inverter is

own dc source, which for an induction motor

called variable dc linked inverter if the input

would be a battery unit, fuel cell or solar cell.

voltage is controllable . An inverter is called

Each SDC (separate D.C. source) is associated

resonant pulse inverter if output voltage or

with a single phase full-bridge inverter.

current of the inverter is forced to pass through zero by creating an LC resonant circuit.

II.

PULSE WIDTH MODULATION (PWM)

a) Type of multilevel inverter

PWM stands for pulse width modulation technique in which sine wave and carrier wave are

1. Diode Clamed Inverter

compared for pulse generation. These pulses are Disadvantage:

used to turn ON switches of multilevel inverter.

Pulse width modulation technique is a modulation

-

Excessive clamping diode is required

technique use to encode a message into pulsating

when the number of level is high.

signal. In PWM ,we use the intersection of a sine wave with a triangular wave to generate firing

2. Flying Capacitor Multilevel Inverter

pulses.

Disadvantage: -

In this N –level inverter, N-1 triangular

An excessive number of storage capacitor is required when the number of level is high . High level inverter is more difficult

carrier signals with the same frequency and amplitude are used so that they fully occupy bands over the range +Vdc to -Vdc.

to package with the bulky power capacitor 1) Alternate phase disposition (APOD):

and are more expensive too.

Every carrier waveform is in out 3. Cascaded Multilevel Inverter

of phase with its neighbor carrier by 180.

Advantages: 1.

Compared with the diode –clamped and flying capacitor inverter, it required the least number of components to achieve the same number of voltage level.

2.

Optimized circuit layout and packing are possible because each level has the same structure and there is no extra clamping diode or voltage balancing capacitor.

Fig 1 : APOD Cascaded H-Bridge (CHB) configuration

has recently become very popular in highpower AC

supplies

applications.

and A

adjustable-speed

cascade

multilevel

drive inverter

2) Phase opposition disposition (POD): All carrier waveform above zero reference are in phase and they 1800out of phase with those

consists of a series of H-bridge (single-phase full bridge) inverter units. Each H-bridge unit has its

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International Engineering Journal For Research & Development carrier waveform which are below the zero reference.

Vol.4 Issue 1

Imagine a power system with an AC source and an electrical load

Fig 2 :POD

Fig 4: Power system with AC source and electrical load Now imagine that this load is going to

3) Phase disposition(PD): All carrier waveform are in phase

take on one of two basic types: linear or non linear.

The type of load is going to affect the power quality of the system. This is due to the current draw of each type of load. Linear loads draw current that is sinusoidal in nature so they generally do not distort the waveform (Figure 5). Most household appliances are categorized as linear loads. Non

linear loads, however, can draw

current that is not perfectly sinusoidal (Figure 6).

Since the current waveform deviates from a sine wave, voltage waveform distortions are created.

Fig 3: PD

III.

TOTAL HARMONIC DISTORTION (THD)

The total harmonic distortion is a measurement of the harmonic distortion present and is defined as the ratio of the sum of the power of all harmonic components to the power of the fundamental frequency. Device causing harmonics are present in all industrial, commercial and residential installation. Harmonics are cause by non liner load. A load is said to be non linear when the current it draws does not have the same waveform as the supply voltage.

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Fig 5 : Ideal sine wave

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Fig 4: Power system with AC source and electrical

Fig 6: Distorted sine wave

load

As can be observed from the waveform in

Now imagine that this load is going to

Figure 6, waveform distortions can drastically alter

take on one of two basic types: linear or non linear.

the shape of the sinusoid. However, no matter the

The type of load is going to affect the power

level of complexity of the fundamental wave, it is

quality of the system. This is due to the current

actually just a composite of multiple waveforms

draw of each type of load. Linear loads draw

called harmonics. Harmonics have frequencies that

current that is sinusoidal in nature so they generally

waveform’s

do not distort the waveform (Figure 5). Most

fundamental frequency. For example, given a 60Hz

household appliances are categorized as linear

fundamental waveform, the 2nd, 3rd, 4th and

loads. Non

are

integer

multiples

of

the

th

linear loads, however, can draw

5 harmonic components will be at 120Hz, 180Hz,

current that is not perfectly sinusoidal (Figure 6).

240Hz and 300Hz respectively. Thus, harmonic

Since the current waveform deviates from a sine

distortion is the degree to which a waveform

wave, voltage waveform distortions are created.

deviates from its pure sinusoidal values as a result of the summation of all these harmonic elements.

The

ideal

sine

wave

has

zero

harmonic

components. In that case, there is nothing to distort this perfect wave.

I.

BLOCK DIAGRAM OF MULTILEVEL INVERTER

Imagine a power system with an AC source and an electrical load

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Fig 5 : Ideal sine wave

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Fig 6: Distorted sine wave

As can be observed from the waveform in Figure 6, waveform distortions can drastically alter A Signal is supplied from single phase grid. It

the shape of the sinusoid. However, no matter the level of complexity of the fundamental wave, it is actually just a composite of multiple waveforms called harmonics. Harmonics have frequencies that are

integer

multiples

of

the

waveform’s

fundamental frequency. For example, given a 60Hz fundamental waveform, the 2nd, 3rd, 4th and 5thharmonic components will be at 120Hz, 180Hz, 240Hz and 300Hz respectively. Thus, harmonic distortion is the degree to which a waveform deviates from its pure sinusoidal values as a result

consists of a diode rectifier, DC link filter and an inverter. The rectifier converts supply AC voltage into DC voltage. The DC voltage is filtered by a capacitor in the DC link. The inverter converts the DC to variable voltage, The rectifier section of an block, called the front end, is responsible for generating current harmonics into the power supply system. Therefore, to reduce the total harmonic distortion (THD) of phase current it is necessary to add additional capacitors.

of the summation of all these harmonic elements.

The

ideal

sine

wave

has

zero

harmonic

components. In that case, there is nothing to distort this perfect wave.

I.

IV.

CASCADED 5 LEVEL INVERTER

BLOCK DIAGRAM OF MULTILEVEL INVERTER

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frequency switching capability of MOSFETs, and tend to be used at frequencies lower than 29kHz. They can handle high currents, are able to output greater than 5kW, and have very good thermal operating ability, being able to operate properly above 100 Celsius. The major disadvantages of IGBTs are their unavoidable current tail when they turn off. Essentially, when the IGBT turns off, the current of the gate transistor cannot dissipate immediately, which causes a loss of power each time this occurs. This tail is due to the very design of the IGBT and cannot be remedied. IGBTs also have no body diode, which can be good or bad depending on the application. IGBTs tend to be

Output S1

S2

S3

S4

S5

S6

S7

S8

0V

0

0

0

0

0

0

0

0

Vs V

1

1

0

0

0

1

0

1

2Vs V

1

1

0

0

1

1

0

0

Vs V

1

1

0

0

0

1

0

1

0V

0

0

0

0

0

0

0

0

-Vs V

0

0

1

1

1

0

1

0

-2Vs V

0

0

1

1

0

0

1

1

-Vs V

0

0

1

1

1

0

1

0

used

in

high

power

applications,

such

as

uninterruptible power supplies of power higher than 5kW, welding, or low power lighting The major components are I. II.

Transformer Z44 MOSFET

III.

ATmega328 microcontroller

IV.

7805 IC

While designing this circuit, a choice had to be made between the two main types of switches used in power electronics. One is the power MOSFET,

Fig 7: Experiment set up

which is much like a standard

MOSFET, but designed to handle relatively large voltages and currents. The other is the insulated gate bipolar transistor, or IGBT. Each has its advantages, and there is a high degree of overlap in the specifications of the two.

IGBTs tend to be used in very high voltage applications, nearly always above 200V, and generally above 600V. They do not have the high

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Fig 9: output of PWM

VII . MATLAB SIMULATION MODEL Scope1

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Sine Wave

Scope

Repeating Sequence1

Scope3

Repeating Sequence2

Repeating Sequence3

Repeating Sequence4

>=

A

Relational Operator

Goto

>=

B

Relational Operator1

Goto2

<= Relational Operator2

<= Relational Operator3

C Goto4

D Goto8

Fig 8: PWM generation In MATLAB simulation model of PWM generation , we use one sine wave and four triangular wave. Out of this four triangular wave ,

Fig 10: MATLAB model of 5 level inverter

two triangular wave which are above the zero are in

In this, we use tow H -bridge which is connected in

phase while, the two triangular wave below zero

cascaded. The two different dc source of 110 V are

are in phase and they are uot of phase to that which

used separately for each H -bridge.

are above the zero . The frequenvy of triangular wave is 3KHz. Relational operators are use to make the comparision of sine wave and triangular wave .

Fig 11: output of MATLAB model of 5 level inverter CONCLUSION In this paper, a five level cascaded Hbridge multilevel with multicarrier pulse width modulation and embedded MATLAB function, is presented. The simulation results show that the total harmonic distortion is low for multicarrier modulation method. The total harmonic distortion

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can be further reduced by using filter circuit. also

Journal of Engineering Technology

hardware implementation done for the comparison

and advanced Engineering volume

of result at different resistive load. It gives a

3,issue 4 , April 2013 , 55 to 58.

different result of currents and voltages for different resistive loads.

6.

S.Devraj, Dr Anitha G S “POD PWM based capacitor clamed multilevel inverter” International journal of technical Research and Application

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