3 PHASE MULTILEVEL INVERTER USING.pdf

3 PHASE MULTILEVEL INVERTER USING BIDIRECTIONAL CHOPPER CELL Project report submitted in partial fulfillment of the requirements for the award Of the degree of BACHELOR OF TECHNOLOGY IN ELECTRICAL AND ELECTRONICS ENGINEERING By K.MANJU NAGA SRI (08241A0221) G.RAMYA (08241A0236) B.VANI (08241A0253) B.SHRUTHI (09245A0206) Under the guidance of Mr.E.VENKATESWARULU Associate Professor

Department of Electrical and Electronics Engineering GOKARAJU RANGARAJU INSTITUTE OF ENGINEERING AND TECHNOLOGY, BACHUPALLY, HYDERABAD-72 2012

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GOKARAJU RANGARAJU INSTITUTE OF ENGINEERING AND TECHNOLOGY HYDERABAD, ANDHRA PRADESH DEPARTEMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING

C E R T I F I C A T E This is to certify that the project report entitled 3-PHASE MULTILEVEL INVERTER USING BIDIRECTIOAL CHOPPER CELL that is being submitted by K.MANJU NAGA SRI, G.RAMYA, B.VANI, B.SHRUTHI in partial fulfillment for the award of the degree of Bachelor of technology in Electrical and Electronics Engineering to the Jawaharlal Nehru Technological University in a record of bonafide work carried out by them under my guidance and supervision. The results embodied in this project report have not been submitted to any other University or Institute for the award of any Graduation degree. Mr.P.M.Sarma Mr.E.Venkateswarlu External examiner HOD, EEE Assistant Professor,EEE GRIET, Hyderabad GRIET, Hyderabad (Internal Guide)

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ACKNOWLEDGEMENT This is to place on record my appreciation and deep gratitude to the persons without whose support this project would never seen the light of day. We immensely be grateful to Prof.P.S.Raju, Director, G.R.I.E.T. and Prof.Jandhyala N Murthy, Principal, G.R.I.E.T. for having permitted us to carry out this project. I wish to express my propound sense of gratitude to DR.Satyendra Saxena, G.R.I.E.T for his guidance, encouragement, and for all the facilities to complete this project. I also express my sincere thanks to Prof.P.M.Sarma, Head of the department, G.R.I.E.T for extending his help. I have immense pleasure in expressing my thanks and deep sense of gratitude to my guide Mr.E.Venkateswarlu, Assistant Professor, Department of Electrical Engineering, G.R.I.E.T for his guidance throughout this project. Finally I express my sincere gratitude to Mr.M.Chakravarthy, Associate Professor, Department of Electrical and Electronics Engineering, G.R.I.E.T and all the members of faculty and my friends who contributed their valuable advice and helped to complete the project successfully.

K.MANJU NAGASRI (08241A0221)

G.RAMYA (08241A0236)

B.VANI (08241A0253)

B.SHRUTHI (09245A0206)

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ABSTRACT This report comprises of the operation of 3 phase multilevel inverter using bidirectional chopper cells. This report gives the detailed overview about basic operation of inverter, types of inverters. The difference of 3 phase multilevel inverter using bidirectional chopper cells and normal basic inverters is shown Simulation for a 2 level inverter using bidirectional has been performed .The simulations have been carried out in PSIM software. Total Harmonic Distortion (THD) calculations have been done practically. Output voltages at different frequencies and voltages have been observed during simulation. Output voltages have been observed in the C.R.O.

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CONTENTS

Chapter 1: INTRODUCTION

1.1Inverter 1

1.2Types of Inverter 1

Chapter 2: MULTILEVEL INVERTER

2.1 Multilevel Concept 6

2.2 Types of Multilevel Inverters 8

2.2.1 Diode Clamped Multilevel Inverter 9

2.2.2 Flying Capacitor Multilevel Inverter 11

2.2.3 Cascaded Bridge Multilevel Inverter 14

2.2.4 Multilevel Inverter Using Bidirectional Chopper Cell 17

Chapter 3: SIMULATION

3.1 Description 20

3.2 Calculations 23

3.3 Results 24

3.4 Output Graphs 25

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3.5 Output voltage waveforms at different frequencies 26

3.6 Pulses to Mosfets 28

Chapter 4: . HARDWARE DESCRIPTION 4.1 Power Supply Circuit 31

4.2 Main Circuit 33

4.3 Driver Circuit 34

4.4 Over View Of entire circuit 35

4.5 Output Wave Form 36

Chapter 5:CONCLUSION & SCOPE OF FUTURE 37

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References 38

Appendix A 39

Appendix B 45

Appendix C 46

Appendix D 47

Appendix E 53

Appendix F 57

Appendix G 60

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LIST OF FIGURES

Fig 1.1 (a) circuit diagram (b) voltage waveforms

Fig 2.1 Three-phase multi level power processing system

Fig 2.2 Schematic single pole of multi level inverter by a switch

Fig 2.3 Typical output voltage of a five level Multi Level Inverter

Fig 2.4 Diode Clamped Multilevel Inverter

Fig 2.5 line voltage waveform for 6 level diode clamped inverter

Fig 2.6 Diode clamped six level inverter voltage levels and

corresponding switch states

Fig 2.7 Three phase six level structure of a flying capacitor

Fig 2.8 Switching States

Fig 2.9 Single phase structure of a multilevel cascaded H bridge inverter

Fig 2.10 Output phase voltage waveform of an 11-level cascade inverter

with 5 separate dc sources

Fig 2.11 Bidirectional Chopper Cell

Fig 3.1 Circuit diagram

Fig 3.2 Output voltage

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Fig 3.3 Output Current

Fig 3.4 Output Voltage at Vin=5V, at F=20HZ

Fig 3.5 Output Voltage at Vin=5v, F=40HZ

Fig 3.6 Output Voltage at Vin =5v,F=50Hz

Fig 3.7 Output Voltage at Vin =5v,F=60Hz

Fig 3.8 Output Voltage at Vin=5v,F=100Hz

Fig 3.9 Output Voltage at Vin=5v, F=50Hz

Fig 3.10 Output Voltage at V=5v, F=150HZ

Fig 3.11 Pulses to Mosfets M1, M2






Fig 4.1 Power supply Circuit for microcontroller

Fig 4.2 Main Circuit

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Fig 4.3 Driver Circuit

Fig 4.4 Overview of entire circuit

Fig 4.5 Output wave form

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CHAPTER 1 INTRODUCTION 1.1 INVERTER

Inverter:

Inverter is a device that converts electrical power from dc form to ac form using electronic

circuits.

Fig 1.1 (a) circuit diagram (b) voltage waveforms

A single-phase inverter, in which M1 & M2 Conduct for half a period and M3 & M4 conduct for

the other half. The output voltage can be controlled by varying the conduction time of the

transistors.

Static Switches: Since the power devices can be operated as static switches or contactors, the

supply to these switches could be either AC or DC, and the switches are called as AC static

switches or DC switches.

1.2 Types of inverters:

1. Square wave

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2. Modified square wave

Multilevel

Pure sine wave

Resonant inverter

Grid tie inverter

Synchronous inverter

Stand-alone inverter

Solar inverter

icro-inverter

3.

4.

5.

6.

7.

8.

9.

10. Solar m

11. Air conditioner inverter

12. CCFL inverter

1 .Square wave:

The square wave output has a high harmonic content, not suitable for certain AC loads

such as motors or transformers. Square wave units were the pioneers of inverter development.

2. Modified sine wave:

The output of a modified square wave, quasi square, or modified sine wave inverter is

similar to a square wave output except that the output goes to zero volts for a time before

switching positive or negative. It is simple and low cost (~$0.10USD/Watt) and is compatible

with most electronic devices, except for sensitive or specialized equipment, for example certain

laser printers, fluorescent lighting, audio equipment .Most AC motors will run off this power

source albeit at a reduction in efficiency of approximately 20%[2].

3 .Multilevel:

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Multilevel inverter is a power electronic system that synthesizes a desired voltage from several

levels of direct current voltage as inputs. The advantages of using multilevel topology include

reduction of power ratings of power devices and lower cost. There are three topologies - diode

clamped inverter, flying capacitor inverter and cascaded inverter.

4. Pure sine wave:

A pure sine wave inverter produces a nearly perfect sine wave output (less than 3% total

harmonic distortion) that is essentially the same as utility-supplied grid power. Thus it is

compatible with all AC electronic devices. This is the type used in grid-tie inverters. Its design is

more complex, and costs more per unit power. The electrical inverter is a high-power electronic

oscillator. It is so named because early mechanical AC to DC converters were made to work in

reverse, and thus were "inverted", to convert DC to AC.

5. Resonant inverter:

Resonant inverters are based on electrical resonance current oscillations.Resonant inverters

are electrical inverters based on resonant current oscillation. In series resonant inverters the

resonating components and switching device are placed in series with the load to form an under

damped circuit. The current through the switching devices fall to zero due to the natural

characteristics of the circuit. If the switching element is a thyristor, it is said to be self-

commutated.

6. Grid tie inverter:

A grid-tie inverter (GTI) is a special type of inverter that converts direct current (DC)

electricity into alternating current (AC) electricity and feeds it into an existing electrical grid.

GTIs are often used to convert direct current produced by many renewable energy sources, such

as solar panels or small wind turbines, into the alternating current used to power homes and

businesses. The technical name for a grid-tie inverter is "grid-interactive inverter". They may

also be called synchronous inverters. Grid-interactive inverters typically cannot be used in

standalone applications where utility power is not available.

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Inverters take DC power and invert it to AC power so it can be fed into the electric utility

company grid. The grid tie inverter must synchronize its frequency with that of the grid (e.g. 50

or 60 Hz) using a local oscillator and limit the voltage to no higher than the grid voltage. A high-

quality modern GTI has a fixed unity power factor, which means its output voltage and current

are perfectly lined up, and its phase angle is within 1 degree of the AC power grid. The inverter

has an on-board computer which will sense the current AC grid waveform, and output a voltage

to correspond with the grid.

Grid-tie inverters are also designed to quickly disconnect from the grid if the utility grid goes

down. This is an NEC requirement that ensures that in the event of a blackout, the grid tie

inverter will shut down to prevent the energy it produces from harming any line workers who are

sent to fix the power grid.

7. Synchronous inverter:

A synchronous inverter is an inverter that additionally feeds power to and from the public

power grid. During a period of overproduction from the generating source, power is routed into

the power grid, thereby being sold to the local power company. During insufficient power

production, it allows for power to be purchased from the power company.

8. Stand-alone inverter:

A stand-alone inverter is an electrical inverter that converts direct current into alternating

current independently of a utility grid. Stand-alone inverters are often used to convert direct

current produced by many renewable energy sources like solar panels or small wind turbines,

into the alternating current used to power homes and small industries. These types of inverters

are mostly used in residential buildings, in remote locations which are devoid of the utility grid

and are powered by renewable energy sources.

9. Solar inverter:

A solar inverter, or PV inverter, converts the variable direct current output of a photovoltaic

(PV) solar panel into a utility frequency alternating current that can be fed into a commercial

electrical grid or used by a local, off-grid electrical network. It is a critical component in a

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photovoltaic system, allowing the use of ordinary commercial appliances. Solar inverters have

special functions adapted for use with photovoltaic arrays, including maximum power point

tracking and anti-islanding protection.

10. Solar micro-inverter:

A solar micro-inverter converts direct current from a single solar panel. Micro-inverters contrast with conventional string or central inverter devices, which are connected to multiple

solar panels.

11. Air conditioner inverter:

An air conditioner inverter modulates the frequency of the alternating current to control the

speed of the air conditioner motor to achieve continuous adjustment of temperature control.

12. CCFL inverter:

A CCFL inverter powers a cold cathode fluorescent lamp.

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CHAPTER 2

MULTILVEL INVERTER

2.1 Multi Level Concept

For a three-phase inverter system, as shown in Fig 1, with an input DC voltage of Vdc

given to series connected capacitors, which constitute the energy tank for the inverter. The

Multilevel inverter is connected to these nodes. Each capacitor has the same voltage Em which is

given by Em = Vdc / (m-1) , where m is denotes the number of levels.

.

The term level is referred to as the number of nodes to which the inverter can be accessible.

Fig 2.1Three-phase multi level power processing system

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18

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switching device is required to block only a voltage level of Vdc, the clamping diodes require

different ratings for reverse voltage blocking. Using phase a of Figure 1 as an example, when all

the lower switches Sa1 through Sa5 are turned on, D4 must block four voltage levels, or 4Vdc.

Similarly, D3 must block 3Vdc, D2 must block 2Vdc, and D1 must block Vdc. If the inverter is

designed such that each blocking diode has the same voltage ratings the active switches, Dn will

require n diodes in series; consequently, the number of diodes required for each phase would be

(m-1) (m-2). Thus, the number of blocking diodes is quadratically related to the number of

levels in a diode-clamped converter .

Advantages:

All of the phases share a common dc bus, which minimizes the capacitance requirements of the

converter. For this reason, a back-to-back topology is not only possible but also practical for uses

such as a high-voltage back-to-back inter-connection or an adjustable speed drive.

The capacitors can be pre-charged as a group.

Efficiency is high for fundamental frequency switching.

Disadvantages:

Real power flow is difficult for a single inverter because the intermediate dc levels will tend

to overcharge or discharge without precise monitoring and control.

The number of clamping diodes required is quadratically related to the number of levels,

which can be cumbersome for units with a high number of levels.

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FIGURE 2.4

DIODE CLAMPED MULTILEVEL INVERTER

Fig 2.5line voltage waveform for 6 level diode clamped inverter

Fig 2.6.diode clamped six level inverter voltage levels and corresponding switch states

2.2.2 FLYING CAPACITOR MULTILEVEL INVERTER:

The structure of this inverter is similar to that of the diode-clamped inverter except that

instead of using clamping diodes, the inverter uses capacitors in their place. The circuit topology

of the flying capacitor multilevel inverter is shown in Figure 2. This topology has a ladder

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structure of dc side capacitors, where the voltage on each capacitor differs from that of the next

capacitor. The voltage increment between two adjacent capacitor legs gives the size of the

voltage steps in the output waveform.

Fig 2.7Three phase six level structure of a flying capacitor

One advantage of the flying-capacitor-based inverter is that it has redundancies for inner

voltage levels; in other words, two or more valid switch combinations can synthesize an output

voltage. Table 2 shows a list of all the combinations of phase voltage levels that are possible for

the six-level circuit shown in Figure 1, Unlike the diode-clamped inverter, the flying capacitor

inverter does not require all of the switches that are on (conducting) be in a consecutive series.

Moreover, the flying-capacitor inverter has phase redundancies, whereas the diode clamped

inverter has only line-line redundancies. These redundancies allow a choice of

charging/discharging specific capacitors and can be incorporated in the control system for

balancing the voltages across the various levels.

In addition to the (m-1) dc link capacitors, the m-level flying-capacitor multilevel inverter will

require (m-1) (m-2)/2 auxiliary capacitors per phase if the voltage rating of the capacitors is

identical to that of the main switches. One application proposed in the literature for the

multilevel flying capacitor is static var generation.

Advantages:

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Phase redundancies are available for balancing the voltage levels of the capacitors.

Real and reactive power flow can be controlled. The large number of capacitors enables the

inverter to ride through short duration outages and deep voltage sags.

Disadvantages:

Control is complicated to track the voltage levels for all of the capacitors. Also, pre-charging all

of the capacitors to the same voltage level and startup are complex.

Switching utilization and efficiency are poor for real power transmission.

The large numbers of capacitors are both more expensive and bulky than clamping diodes in

multilevel diode-clamped converters. Packaging is also more difficult in inverters with a high

number of levels

.

Fig 2.8SWITCHING STATES

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2.2.3 CASCADED H BRIDGES:

A single-phase structure of an m-level cascaded inverter is illustrated in Figure 31.1. Each

separate dc source (SDCS) is connected to a single-phase full-bridge, or H-bridge, inverter. Each

inverter level can generate three different voltage outputs, +Vdc, 0, and Vdc by connecting the dc

source to the ac output by different combinations of the four switches, S1, S2, S3, and S4. To

obtain +Vdc, switches S1 and S4 are turned on, whereas Vdc can be obtained by turning on

switches S2 and S3. By turning on S1 and S2 or S3 and S4, the output voltage is 0. The ac outputs

of each of the different full-bridge inverter levels are connected in series such that the

synthesized voltage waveform is the sum of the inverter outputs. The number of output phase

voltage levels m in a cascade inverter is defined by m = 2s+1, where s is the number of separate

dc sources. An example phase voltage waveform for an 11-level cascaded H-bridge inverter with

5 SDCSs and 5 full bridges is shown in Figure 3.

The phase voltage van = va1 + va2 + va3 + va4 + va5.

For a stepped waveform such as the one depicted in Figure 4 with s steps, the Fourier Transform

for this waveform follows

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Fig 2.9Single phase structute of a multilevel cascaded H bridge inverter

Fig 2.10 Output phase voltage waveform of an 11-level cascade inverter with 5 separate dc sources

The general features of a multi level inverter are as follows:

The output voltage and power increase with number of levels. Adding a voltage involves adding main switching device to each phase.

The harmonic content decreases as the number of levels increase and filtering requirements are reduced.

With additional voltage levels, the voltage waveform has more free switching angles which can be pre-selected for harmonic elimination.

In the absence of any PWM techniques, the switching losses can be avoided. Increasing output voltage and power does not require an increase in rating of individual

device.

Static and dynamic voltage sharing among the switching devices is built into the structure either through clamping diodes or capacitors.

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Since these do not encounter any voltage sharing problems, these multi level inverters can be easily applied for large motor drives and utility supplies.

The fundamental output voltage is set by the dc bus voltage Vdc which can be controlled through a dc link.

Power factor is close to unity. No electromagnetic induction is produced.

In view of the above, the multi level inverters can be applied in the following

situations:

These are meant for high power applications, such as in utility systems for controlled sources of reactive power.

In steady-state operation, an inverter can produce a controlled reactive current and operates as static volt-ampere reactive compensator (SVC / STATCON).

These inverters reduce the size of compensator and improve its performance during power system contingencies.

Because of the use of a high voltage inverter, it can be directly connected to high voltage system (e.g~13 kV) distribution system, eliminating the distribution transformer and

reducing the system cost.

The harmonic content of the inverter waveform can be reduced with appropriate control techniques, and thereby the efficiency can be improved.

Keeping the above in view, the main two applications for multi level inverters are

1. Reactive power compensation

2. Back to back inter-tie

3. Utility compatible adjustable speed drive.

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2.2.4MULTILEVEL INVERTERS USING BIDIRECTIONAL CHOPPER

CELLS:

BIDIRECTIONAL CHOPPER CELLS:

This BIDIRECTIONAL CHOPPER CELL has been used in this project for Multi Level

inverters. This cell consists of two IGBTs, which are connected through a capacitor, known as

flying capacitor. This is called as bidirectional, since when the firing is allowed to the gates,

the IGBT switches act as if they are closed and conduct, else through the capacitor which is

charged and discharged. Hence the name is bidirectional.

The fig 2.5 indicates the stepped wave form of output voltage in case of diode clamped multi

level inverter. The average of these steps is considered as the sinusoidal output.

Due to the floating capacitor in this bidirectional chopper cell the steps in the wave for have

been eliminated. The outputs for various levels of inverters and converters are also indicated

after simulation. Harmonic contents used to eliminate the steps that would have been present in

the waveform as in multi level cascaded system for which the average output is considered as

sinusoidal. But due to this capacitor, even without firing signal for the gates of the IGBTs, the

cell is able to send current through the circuit, and hence the steps are eliminated, giving out a

complete sinusoidal waveform.

As the levels are increased, the purity of waveform increases, reducing the harmonic content

drastically in the output.

Fig 2.11 BIDIRECTIONAL CHOPPER CELL

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The Bidirectional Chopper Cells consists of power transistors. Power transistors have controlled

turn on and turn off characteristics. The transistors that are used as switching elements are

operated in the saturations region, resulting in a low on state voltage drop. The switching speed

of modern transistors is much higher than that of thyristors and they are extensively used in DC

to DC and DC to AC converters, with inverse parallel connected diodes to provide bidirectional

current flow.

The power transistors can be classified broadly into five categories:

a. Bipolar Junction Transistors (BJTs): A bipolar transistor is formed by adding a second p- or n- region to a p-junction diode. With two n-regions and one p-region, two

junctions are formed and it is known as NPN transistor. With two p-regions and one n-

region, it is called a PNP transistor. The three terminals are named as collector, emitter

and base. A bipolar transistor has two junctions; collector-base junction (CBJ) and base-

emitter junction (BEJ). It is a current-controlled device and requires base current for

current flow in the collector.

b. Metal Oxide Semiconductor Field Effect Transistors (MOSFETs): A power MOSFET is a voltage-controlled device. The switching speed is very high and

switching times are nanoseconds. These do not have problems of second breakdown as in

BJTs. These MOSFETS, however, have the problems of electro static discharge. It is

relatively difficult to protect the MOSFETs in short circuit fault conditions.

c. COOLMOS: This is a new technology for high voltage power MOSFETS, which implements a compensation structure in the vertical drift region of a MOSFET to

improve the on-state resistance. It has a lower on-state resistance for the same package

compared with that of other MOSFETs. The conduction losses are at least five times less

as compared with those of the conventional MOSFET technology. It is capable of

28

handling two to three times more output power as compared with that of conventional

MOSFET in the same package. The active chip area of COOLMOS is approximately 5

times smaller than that of standard MOSFET.

d. Static Induction Transistors (SITs): An SIT is a high power, high frequency device. It is solid state version of the triode vacuum tube. It is a vertical structure device

with short multi channels. It is not subjected to area limitation and is suitable for high

speed, high power operation.

e. Insulated-Gate Bipolar Transistors (IGBTs) : An IGBT combines the advantages of BJTs and MOSFET. An IGBT has high input impedance, like MOSFETs

and low on-state conduction losses, like BJTs. However, there is no second breakdown

problem as in BJTs. By chip design and structure, the equivalent drain to source

resistance is controlled to behave like that of a BJT.

29

CHAPTER 3

SIMULATION

Simulation of 2-level inverter with Bidirectional Chopper Cell

Circuit Diagram:

Fig 3.1 Circuit diagram

3.1 Description:

1. The connection diagram indicates the two level multi level inverter with two bidirectional

chopper cells per phase, one level being in positive-half cycle and one level for negative-half

cycle.

2The supply input of Vdc =12V is given to two numbers distribution capacitors of 220F in

series. Thus, the applied input voltage is shared equally by them, making the applied DC

Voltage of 6V to each half.

30

3.This distributed DC voltage line is connected to three legs of bidirectional chopper cells

positive-half (on top side) and negative-half (on bottom side) to form three- phase groups on

positive-half and three-phase groups on negative-half.

4. Output from each phase-group is connected to a filter inductance of 100 mH in each

phase-group on both positive and negative half sides.

5. Each phase is connected to R load of 10 ohms.

6. After the load, the three phases are joined together to form star point and is connected to

the midpoint of the two distributor capacitors as a return path.

7. Voltmeters are provided to measure load voltages. Also, the load currents are measured by

the ammeters provided in each phase.

.

8. The firing angles are so chosen for bidirectional chopper cells, that each leg contains the

two firings which are equal to the level of the multi level inverter.

9. The floating capacitor connected across each bidirectional cell is chosen as one 0.1mf.

Since the bidirectional cells are connected in series, the connection of floating capacitors in

this phase group becomes series connection when the gate signal is in switched off condition.

This being a short interval of the firing angles, it is assumed that the floating capacitors are in

series.

Thus, the total effective floating capacitors capacitance for each leg half (phase group)

becomes one half of this capacitance, i.e. 0.05mf.

10. To make an equal firing distribution among the cells, when R phase is considered, the

firings are chosen with max 2 angles to maintain the level of inverter, which is equal to 2 i.e.

0 /180 means 0 to 180 is on. The negative-half of the R phase firing is chosen as 180 / 360,

31

such that this phase is shifted by 180 degrees with respect to the positive side of sinusoidal

wave.

11. Similarly, the Y & B phases are selected with a phase difference of 120 degrees with

each another. Their corresponding negative halves are chosen by adding further 180 degrees

to the respective positive phase groups. Thus, the firing angles have been decided.

Simulation Control: Time step: 1E-005; Total time: 0.20 sec

Parameters : Input voltage Vdc, Distribution Capacitances C1 & C2 = 220uf

Firing Angles (in degrees)

Table 3.1

PHASE GATES TRIGGERING

ANGLE(DEGREES)

R PHASE Gr1, Gr2 : 50 2

Gr3, Gr4 : 50 4

0 / 180

180 /360

Y PHASE Gy1, Gy2 : 50 2

Gy3, Gy4 : 50 4

120 / 300

-60/120

B PHASE Gb1, Gb2 : 50 2

Gb3,Gb4 : 50 4

-120 / 60

60 /240

32

Other Parameters

Filter Inductances: Lr1, Lr2; Ly1, Ly2; Lb1 & Lb2 = 100 mH each

R phase floating capacitors Cr1 to Cr2: 0.1mf

Y phase floating capacitors Cy1 to Cy2: 0.1mf

B phase floating capacitors Cb1 to Cb2: 0.1mf

Load: Resistance Rr, Ry & Rb = 10 ohms

3.2 Calculations:

The calculations are made to find out duration in terms of time constants which are offered due

to the passive elements used in the respective circuit.

i. The time constant for each phase group is given by:

1 = (LC) = (100 x 10-3 x 0.05 x 10-3) = 2.23ms.

ii. The supply is available for a maximum firing angle of 60, the frequency being

50 Hz. The time period 2 for 90 is 90 / (50 x 360) = 4.3 ms.

33

3.3Results:

The following tables indicate the outputs obtained for multi level inverter of four level by

simulating the circuit through PSIM.

Table 1: Indicates the parameters maintained in the circuit and simulated output results

indicating the values of phase voltages, Line voltages and load current with a series R load of

10ohms connected at the output side.

These tables indicate the various parameters maintained in each case study and the

values obtained by simulation of the circuit diagram indicated in fig 3.1. These circuits have

switches according to firing angles.

TABLE1

Level Vdcin Cd Cc Lf/leg Maxno.offirings

VL(Vry)

Volts

IL(Amps)

2 15 2x220F 0.1f 100Mh 2 10 1.5

34

3.4 Output Graphs:

Fig 3.2 Output voltage

Fig 3.3 Output Current

35

3.5 0utput voltages at different frequencies

Table 3.2

FREQUENCY(HZ) OUTPUTVOLTAGE(VOLTS)

OUTPUTGRAPHS

20HZ 7V

40HZ 7V

50HZ 10V

60HZ 10.5V

36

80HZ 5V

100HZ 4V

120 3.5V

150 2.5V

37

3.6 PULSES TO MOSFETS

PULSE TO MOSFETS M1, M2:

PULSES TO MOSFETS M3,M4:

PULSES TO MOSFETS M5, M6:

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PULSES TO MOSFETS M7, M8:

39

PULSES TO MOSFETS M9,M10

PULSES TO MOSFETS M11,M12

40

CHAPTER 4

HARDWARE DESCRIPTION

4.1 POWER SUPPLY SECTION

4.1.1 Power Supply to the Microcontroller:

Figure 4: Power supply Circuit for microcontroller

Power supply block consists of following units:

1) Step down transformer.

2) Full wave rectifier circuit.

3) Input filter.

4) Voltage regulators.

5) Output filter.

6) Indicator unit.

41

Step down transformer: The step-down transformer is used to step down the supply voltage of 230v ac from mains to

lower values, as the various devices used in this project require reduced voltages. The outputs

from the secondary coil which is center tapped are the ac values of 0v, 15v and-15v.The

conversion of these ac values to dc values is done using the full wave rectifier unit.

Rectifier Unit: The rectifier circuit is used to convert the ac voltage into its corresponding dc voltage.

The most important and simple device used in rectifier circuit is the diode. The simple function

of the diode is to conduct when forward biased and not to conduct in reverse bias.

Regulator unit:

Regulator regulates the output voltage to a specific value. The output voltage is

maintained irrespective of the fluctuations in the input dc voltage. Whenever there are any ac

voltage fluctuations, the dc voltage also changes.

Regulators used in this application are:

1.7805 which provides 5v dc

2.7812 which provide 12v dc

Output Filter: This filter is fixed after the Regulator circuit to filter any of the possibly found

ripples in the output received finally. Capacitors used here are of value 10UF.

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4.2 MAIN CIRCUIT:

Fig 4.2 Main circuit

This board has inverter circuit along with the 12V power supply. The output of the IC IR2110 is

given to the mosfets gate terminals. This inverter is a 2 level inverter which takes 12V DC as an

input and gives out 3-phase AC.

Inverter circuit consists of 3 legs each representing one of the 3 phases; each leg has 2

bidirectional chopper cells, one on the top and one at the bottom. Top cell is responsible for

positive half of the AC output, bottom cell is responsible for negative half of the ac output..

43

4.3 DRIVER CIRCUIT:

Fig 4.3 Driver circuit

This board contains driver circuit; it also consists of microcontroller circuit for producing gate

pulses for the mosfets used in the inverter circuit.

The driver circuit has got two ICS

1. 74HCT245 (for improving current level to a sufficient value in order to drive the mosfets)

..

2. Ir2110 (for improving voltage level to a sufficient value in order to drive the mosfets)

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4.3 OVERVIEW OF THE ENTIRE CIRCUIT:

Fig 4.4 over view of entire circuit

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4.4 OUTPUT WAVEFORM OF ONE OF THE PHASES IN CRO:

4.5 Output Waveform

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CHAPTER -5

CONCLISION AND FUTURE SCOPE OF STUDY

5.1 Conclusion:

It is observed that in multilevel inverter using bidirectional chopper cells sinusoidal output is

obtained instead of stepped a output as in case of other types of inverters.

5.2Future scope of study:

This project can be an application in UPS.

47

REFERENCES

Microcontrollers by Masjidi

www.wikipedia.com/8051

www.isis.com/proteus

Muhammad H.Rashid Power Electronics circuits, Devices and Applications third Edition

2006.

www.irf.com/technical-info/appnotes/an-978.pdf

www.irf.com/product-info/datasheets/data/ir2110.pdf

www.alldatasheet.com/datasheet-pdf/pdf/15580/PHILIPS/74HCT245D.html

APPENDIX A

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GENERAL INFORMATION OF P SIM PACKAGE

A.1 INTRODUCTION

PSIM is a simulation package specifically designed for power electronics and

motor control. With fast simulation and friendly user interface, PSIM provided a powerful

simulation environment for power electronics, analog and digital control and motor drive

system studies.

This simulation package covers three add-on modules viz.

Motor Drive Module Digital Control Module Sim Coupler Module

The Motor Drive Module has built in machine models and mechanical load models for drive

system studies.

The Digital Control Module provides discrete elements such as zero-order hold, Z-domain

transfer function blocks, quantization blocks, digital filters, for digital control analysis.

The Sim Coupler Module provides interface between PSIM and Matlab/SIMULINK for co-

simulation.

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The PSIM simulation package consists of three programs:

Circuit Schematic Program PSIM PSIM simulator Waveform processing program SIMVIEW

The manual describes various chapters consisting of

Circuit structure Software/Hardware requirement Parameter specification format Power and control circuit components Specification of transient analysis and A.C. Analysis Use of schematic program SIMVIEW Error and warning messages

A.2 CIRCUIT STRUCTURE

The circuit is represented in PSIM in four blocks viz.,

Power Circuit Control circuit Sensors Switch controllers

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Switch

Controller

Controlcircuit

Sensors

Powercircuit

The Power circuit consists of switching devices, RLC branches, transformers, and coupled

inductors.

The Control circuit is represented in block diagram, This also contains components in s

domain and z domain, logic components (such as logic gates and flip flops), and nonlinear

components (such as multipliers and dividers) are used in the control circuit.

Sensors measure power circuit voltages and currents and pass the values to the control

circuit.

Gating signals are then generated from the control circuit and sent back to the power circuit

through switch controllers to control switches.

A.3 SOFTWARE/HARDWARE REQUIREMENT

PSIM runs in Microsoft Windows environment 98/NT/2000/XP on personal computers. The

minimum RAM memory is 32MB.

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A.3.1 INSTALLING THE PROGRAM

A quick installation guide is provided in the flier PSIM-quick guide and on the CD_ROM.

Some of the files in the PSIM directory are as follows:

Psim.dll describes PSIM simulator Psim.exe describes PSIM circuit schematic editor Simview.exe describes Wave form processor SIMVIEW Psim.lib, psimimage.lib PSIM libraries *.hlp Help files *.sch Sample schematic circuit files

File extensions used in PSIM are:

*.sch PSIM schematic file (binary) *.cct PSIM netlist file (text) *.txt PSIM simulation output file (text) *.fra PSIM ac analysis file (text) *.smv SIMVIEW wave form file (binary)

A.5 SIMULATING A CIRCUIT

To simulate the sample one-quadrant chopper circuit chop.sch:

Start PSIM. Choose OPEN from the file menu to load the file chop.sch

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From the SIMULATE menu, choose Run PSIM to start the simulation. The simulation results will be saved to file chop.txt. Any warning messages occurred in the

simulation will be saved to file message.doc

If the option AUTO-RUN SIMVIEW is not selected in the options menu, from the simulate menu, choose Run SIMVIEW to start SIMVIEW. If the Option Auto run

SIMVIEW is selected, SIMVIEW is launched automatically. In SIMVIEW the curves

for display are selected.

A.6 COMPONENT PARAMETER SPECIFICATION AND

FORMAT

The Parameter dialog window of each component in PSIM has three tabs:

Parameters Other information Color

The Parameters in the PARAMETERS tab are used in the simulation.

The information in the OTHER INFO tab is not used in the simulation. It is for reporting

purposes only and will appear in the parts list in VIEW/ELEMENT LIST in PSIM.

Information such as device rating, manufacturer, and part number can be stored under the

OTHER INF tab.

The component color can be set in the COLOR tab.

Parameters under the Parameters tab can be a numerical value or a mathematical expression. A

resistance for example can be expressed in one of the following ways:

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12.5

12.5k

12.5Ohm

12.5kOhm

25./2.Oh

R1+R2

R1*0.5+Vo+0.7)/Io

Where R1, R, Vo, and Io are symbols defined either in a parameter file or in a main circuit if this

resistor is in a sub-circuit.

Power of ten suffix letters is allowed in PSIM.

The following suffix letters are supported:

G 109

M 106

k or K 103

m 10-3

u 10-6

n 10-9

p 10-12

54

APPENDIX B

SOFTWARE USED PROTEUS

It is used for the real time simulation of the Circuits involving complex ICs,

Microcontrollers, Electromechanical devices etc.

System components

ISIS Schematic Capture - a tool for entering designs.

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APPENDIX C

SOFTWARE USED KEILuVISION

Keil was founded in 1986 to market add-on products for the development tools provided by many of the silicon vendors. Keil implemented the first C compiler designed from the ground-up specifically for the 8051 microcontroller. Keil provides a broad range of development tools like ANSI C compiler, assemblers, debuggers and simulators, linkers, IDE, library managers, real-time operating systems and evaluation for 8051, 251, ARM, and XC16x/C16x/ST10 families.

Compiling a C program in EAGLE

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APPENDIX D

DATA SHEET IR2110

Features Floating channel designed for bootstrap operation

Fully operational to +500V or +600V

Tolerant to negative transient voltage dV/dt immune

Gate drive supply range from 10 to 20V

Under voltage lockout for both channels

3.3V logic compatible

Separate logic supply range from 3.3V to 20V

Logic and power ground 5V offset

CMOS Schmitt-triggered inputs with pull-down

Cycle by cycle edge-triggered shutdown logic

Matched propagation delay for both channels

Outputs in phase with inputs

OFFSET VOLTAGE (IR2110) 500V max.

IO+/- 2A / 2A

OUTPUT VOLTAGE 10 - 20V

ton/off (typ.) 120 & 94 ns

Delay Matching (IR2110) 10 ns max.

Description

The IR2110/IR2113 are high voltage, high speed power MOSFET and IGBT drivers with

independent high and low side referenced output channels. Proprietary HVIC and latch immune

CMOS technologies enable ruggedized monolithic construction. Logic inputs are compatible

with standard CMOS or LSTTL output, down to 3.3V logic. The output drivers feature a high

pulse current buffer stage designed for minimum driver cross-conduction. Propagation delays are

matched to simplify use in high frequency applications. The floating channel can be used to drive

57

an N-channel power MOSFET or IGBT in the high side configuration which operates up to 500

or 600 volts.

PIN DIAGRAM

IR2110

58

APPENDIX E

DATA SHEET 74HCT245

FEATURES Octal bidirectional bus interface Non-inverting 3-state outputs Output capability: bus driver GENERAL DESCRIPTIONS The 74HC/HCT245 are high-speed Si-gate CMOS devices and are pin compatible with

low power Schottky TTL (LSTTL). They are specified in compliance with JEDEC

standard no. 7A.The 74HC/HCT245 are octal transceivers featuring non-inverting 3-state bus

compatible outputs in both send and receive directions. The 245 features an output enable

(OE) input for easy cascading and a send/receive (DIR) for direction control. OE controls the

outputs so that

the buses are effectively isolated. The 245 is similar to the 640 but has true (non-inverting) outputs.

74HCT245

63

PIN DIAGRAM

64

FUNCTIONAL BLOCK DIAGRAM

66

APPENDIX F

DATA SHEET- IRFZ44N

FEATURES:

1 Advanced Process Technology

2Ultra Low On-Resistance

3Dynamic dv/dt Rating

4175C Operating Temperature

5Fast Switching

6 Fully Avalanche Rated

Advanced HEXFET Power MOSFETs from International Rectifier utilize advanced processing

techniques to achieve extremely low on-resistance per silicon area. This benefit, combined with

the fast switching speed and ruggedized device design that HEXFET power MOSFETs are well

known for, provides the designer with an extremely efficient and reliable device for use in a wide

variety of applications.

The TO-220 package is universally preferred for all commercial-industrial applications at power

dissipation levels to approximately 50 watts. The low thermal resistance and low package cost of

the TO-220 contribute to its wide acceptance throughout the industry.

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APPENDIX G

DATA SHEET AT89C51 Features

8K Bytes of In-System Reprogrammable Flash Memory

Endurance: 1,000 Write/Erase Cycles

Compatible with MCS-51 Products

Fully Static Operation: 0 Hz to 24 MHz

Three-level Program Memory Lock

256 x 8-bit Internal RAM

32 Programmable I/O Lines

Three 16-bit Timer/Counters

Eight Interrupt Sources

Programmable Serial Channel

Low-power Idle and Power-down Modes

The AT89C52 is a low-power, high-performance CMOS 8-bit microcomputer with 8K bytes of

Flash programmable and erasable read only memory (PEROM). The device is manufactured

using Atmels high-density nonvolatile memory technology and is compatible with the industry-

standard 80C51 and 80C52 instruction set and pin out. The on-chip Flash allows the program

memory to be reprogrammed in-system or by a conventional nonvolatile memory programmer.

By combining a versatile 8-bit CPU with Flash on a monolithic chip, the Atmel AT89C52 is a

powerful micro computer which provides a highly-flexible and cost-effective solution to many

embedded control applications.

VCC Supply voltage.

GND Ground.

70

Port 0:

Port 0 is an 8-bit open drain bi-directional I/O port. As output port, each pin can sink eight TTL

inputs. When 1s are written to port 0 pins, the pins can be used as high impedance

Inputs. Port 0 can also be configured to be the multiplexed low order address/data bus during

accesses to external program and data memory. In this mode, P0 has internal pullups.

Port 0 also receives the code bytes during Flash programming and outputs the code bytes during

programverification. External pullups are required during program verification.

Port 1: Port 1 is an 8-bit bi-directional I/O port with internal pull ups. The Port 1 output buffers

can sink/source four TTL inputs. When 1s are written to Port 1 pins, they are pulled high by

the internal pull ups and can be used as inputs. As inputs, Port 1 pins that are externally being

pulled low will source current (IIL) because of the internal pull ups. In addition, P1.0 and P1.1

can be configured to be the timer/counter 2 external count input (P1.0/T2) and the timer/counter

2 trigger input (P1.1/T2EX), respectively. Port 1 also receives the low-order address bytes during

Flash programming and verification

Port 2 Port 2 is an 8-bit bi-directional I/O port with internal pull ups. The Port 2 output buffers can

sink/source four TTL inputs .When 1s are written to Port 2 pins, they are pulled high by

The internal pull ups and can be used as inputs. As inputs, Port 2 pins that are externally being

pulled low will source current (IIL) because of the internal pull ups. Port 2 emits the high-order

address byte during fetches from external program memory and during accesses to external data

memory that uses 16-bit addresses (MOVX @DPTR). In this application, Port 2 uses strong

internal pull-ups when emitting 1s. During accesses to external data memory that use 8-bit

addresses (MOVX @ RI), Port 2emits the contents of the P2 Special Function Register.

Port 2 also receives the high-order address bits and some control signals during Flash

programming and verification.

Port 3 is an 8-bit bi-directional I/O port with internal pull ups. The Port 3 output buffers can

sink/source four TTL inputs. When 1s are written to Port 3 pins, they are pulled high by

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the internal pull ups and can be used as inputs. As inputs, Port 3 pins that are externally being

pulled low will source current (IIL) because of the pull-ups .Port 3 also receives some control

signals for Flash programming and verification.

Reset input. A high on this pin for two machine cycles while the oscillator is running resets the

device.

ALE/PROG Address Latch Enable is an output pulse for latching the low byte of the address

during accesses to external memory. This pin is also the program pulse input (PROG) during

Flash programming .In normal operation, ALE is emitted at a constant rate of 1/6 the oscillator

frequency and may be used for external timing or clocking purposes. Note, however, that one

ALE pulse is skipped during each access to external data

memory. If desired, ALE operation can be disabled by setting bit 0 of SFR location 8EH. With

the bit set, ALE is active only during a MOVX or MOVC instruction. Otherwise, the pin is

weakly pulled high. Setting the ALE-disable bit has no effect if the microcontroller is in external

execution mode.

PSEN : Program Store Enable is the read strobe to external program memory. When the

AT89C52 is executing code from external program memory, PSEN is activated twice each

machine cycle, except that two PSEN activations are skipped during each access to external data

memory.

EA/VPP: External Access Enable. EA must be strapped to GND inorder to enable the device to

fetch code from external program memory locations starting at 0000H up to FFFFH. Note,

however, that if lock bit 1 is programmed, EA will be internally latched on reset.EA should be

strapped to VCC for internal program executions. This pin also receives the 12-volt

programming enable voltage(VPP) during Flash programming when 12-voltprogramming is

selected.

XTAL1: Input to the inverting oscillator amplifier and input to the

internal clock operating circuit.

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XTAL2: Output from the inverting oscillator amplifier.

PIN DIAGRAM:

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