1

CHAPTER 1

INTRODUCTION

2

1. INTRODUCTION

1.1 HYBRID ACTIVE POWER FILTER

In this modern society, domestic customers‘ app liances normally draw large harmonic

and reactive current from the system. High harmonic current causes various problems in

power systems and consumer products, such as overheating in equipment and

transformer, blown capacitor fuses, excessive neutral current, low power factor, etc.. On

the other hand, loadings with low power factor draw more reactive current than those

with high power factor. The larger the reactive current/power, the larger the system

current losses and lower the network stability Thus, electrical utilities usually charge the

industrial and commercial customers a higher electricity cost with a low power factor

situation. To eliminate the harmonic and reactive current problems, application of

power filters is one of the most suitable solutions. Since the first installation of passive

power filters (PPFs) in the mid 1940s, PPFs have been widely used to suppress

harmonic current and compensate reactive power in distribution power systems due to

their low-cost, simplicity, and high-efficiency characteristics. However, they have many

disadvantages such as low dynamic performance, filtering characteristics easily be

affected by small variations of the system parameter values and resonance problems

Since the concept ―active ac power filter‖ was first developed by Gyugyi in 1976], the

research studies of the active power filters (APFs) for current quality compensation

have been prospered since then. Although APFs overcome the disadvantages inherent in

PPFs, the initial and operational costs are relatively high due to its high dc- link

operating voltage during inductive loading. This results in slowing down their large-

scale applications in distribution networks. Later on, different hybrid APF (HAPF)

topologies composed of active and passive parts in series and/or parallel have been

proposed, in which the active part is a controllable power electronic converter, and the

passive part is formed by RLC component. This combination aims to improve the

compensation characteristics of PPFs and reduces the voltage and/or current ratings

(costs) of the APFs, thus providing a cost-effective solution for compensating reactive

and harmonic current problems Among HAPF topologies in a transformer less LC

3

coupling HAPF (LC-HAPF) has been proposed and applied recently for current quality

compensation and damping of harmonic propagation in distribution power system in

which it has less passive components and lower dc- link operating voltage comparing

with an APF In addition, LC HAPF is normally designed to deal with harmonic current

rather than reactive power compensation the inverter part is responsible to compensate

harmonic currents only and the passive part provides a fixed amount of reactive power.

In practical case, the load-side reactive power consumption usually varies from time to

time, and if the loading mainly consists of induction motors such as centralized an air-

conditioning system, its reactive power consumption will be much higher than the

harmonic power consumption As a result, it is necessary for the LC-HAPF to perform

dynamic reactive power compensation together with harmonic current compensation.

Even though the reactive power compensating range is small with a low dc- link voltage,

the LC-HAPF can still provide dynamic reactive power compensation. Thus, its reactive

power compensation ability (within its specification)

1.2 MULTILEVEL INVERTER AND CHARACTERISTICS

The elementary concept of a multilevel inverter to achieve higher power is to use power

semiconductor switches with several lower voltage dc sources to perform the power

conversion by synthesizing a staircase voltage waveform. Capacitors, batteries and

renewable energy voltage sources can be used as the multiple dc voltage sources. The

commutation of the power switches aggregate these multiple dc sources in order to

achieve high voltage at the output.

A multilevel inverter has several advantages over a conventional two level inverter that

uses high switching frequency pulse width modulation (PWM) .The features of a

multilevel inverter can be summarized as follows: Multilevel inverters not only can

generate the output voltages with very low distortion ,also reduces the dv/dt stresses:

therefore electromagnetic compatibility (EMC) problems can be reduced.

4

Multilevel inverters produce smaller common mode (CM) voltage ;therefore, the stress

in the bearing of a motor connected to a multilevel motor drive can be reduced.

Furthermore, CM voltage can be eliminated by using advanced modulation techniques.

Multilevel inverters can draw input current with low distortion.

Multilevel inverters can operate at both fundamental switching frequency and high

switching frequency PWM. It should be noted that lower switching frequency usually

means lower switching loss and higher efficiency.

Multilevel inverters do have some disadvantages such as each switch requires a related

gate drive circuit. This may cause the overall system to be more expensive and

complex.

The principal function of the inverters is to generate an ac voltage from a dc source

voltage. If the dc voltage is composed by many small voltage sources connected in

series, it becomes possible to generate an output voltage with several steps. Multilevel

inverters include an arrangement of semiconductors and dc voltage sources required to

generate a staircase output voltage waveform. Figure. 1.1 shows the schematic diagram

of voltage source- inverters with a different number of levels.

Figure.1.1 Basic Multilevel Inverters (a) Two levels, (b) Three levels, and

(c) m Levels.

5

It is well known that a two level inverter, such as the one shown in Figure. 1.1(a),

generates an output voltage with two different values (levels), VC and ―zero,‖ with

respect to the negative terminal of the dc source (―0‖), while a three- level module,

Figure.1.1 (b) generates three different voltages at the output (2VC, VC, and ―zero‖).

The different positions of the ideal switches are implemented with a number of

semiconductors that are in direct relation with the output voltage number of levels.

Multilevel inverters are implemented with small dc sources to form a staircase ac

waveform, which follows a given reference template. For example, having ten dc

sources with magnitudes equal to 20 V each, a composed 11- level waveform can be

obtained (five positive, five negatives, and zero with respect to the middle point

between the ten sources), generating a sinusoidal waveform with 100-V amplitude as

shown in Figure. 1.2, and with very low THD.

Figure. 1.2 Voltage Waveform from an 11-Level Inverter.

6

It can be observed that the larger the number of the inverter dc supplies, the greater the

number of steps that can be generated, obtaining smaller harmonic distortion. However,

the number of dc sources is directly related to the number of levels through the

equation:

n = m-1

Where ‗n‘ is the number of dc supplies connected in series and ‗m‘ is the number of the

output voltage levels. In order to get a 51-level inverter output voltage, 50-V supplies

would be required, which is too much for a simple topology. Besides the problem of

having to use too many power supplies to get a multilevel inverter, there is a second

problem which is also important, the number of power semiconductors required to

implement the commutation circuit, as shown in Figure.1.1 Technical literature has

proposed two converter topologies for the implementation of the power commutation,

using force-commutated devices [transistors or gate turnoff Thyristors (GTOs).

1.2. CLASSIFICATION OF MULTI LEVEL INVERTERS

The multilevel inverters can be classified as follows:

Diode clamped multilevel inverter

Flying capacitor multilevel inverter

Cascaded multilevel inverter

1.2.1. DIODE-CLAMPED INVERTER

This inverter consists of a number of semiconductors connected in series, and another

identical number of voltage sources, also connected in series. These two chains are

connected with diodes at the upper and lower semiconductors as shown in Figure.1.2.1

(a).

7

Figure.1.2.1 (A) The M-Level (B) Three-Level Diode-Clamped Inverter

Topology

For an m - level converter, the required number of transistors is given by

T= 2(m-1) ….…… (2)

Then, for the example of a 51-level converter, 100 power transistors would be required

(which is an enormous amount of switches to be controlled). One of the most utilized

configure rations with this topology is that of the three- level inverter, which is shown in

Figure. 1.2.1. (b). The capacitors act like two dc sources connected in series.

8

Thus, in the diagram, each capacitor accumulates 1/2 Vdc, giving voltages at the output

of 1/2 Vdc, 0, or 1/2 Vdc with respect to the middle point between the capacitors.

1.2.2 CAPACITOR-CLAMPED INVERTER

This inverter has a similar structure to that of the diode-clamped, however it can

generate the voltage steps with capacitors connected as shown in Figure.1.2.2. The

problem with this converter is that it requires a large number of capacitors, which

translates to a bulky and expensive converter as compared with the diode-clamped

inverter.

Figure. 1.2.2 The M-Level Capacitor-Clamped Inverter.

Besides, the number of transistors used is the same with the diode-clamped inverter, and

therefore, for a 51- level inverter, 100 power transistors are required. In order to

overcome all these problems, a third topology, which will be called the ―transistor-

clamped inverter‖ will be presented and analyzed.

9

1.2.3. TRANSISTOR-CLAMPED INVERTER

The transistor-clamped inverter has the advantage of requiring the same number of

power transistors as the levels generated, and therefore, half with respect to the previous

topologies reduces the semiconductors. A 51-level converter requires 51 transistors

(instead of 100 transistors). Figure 1.2.3 shows the circuit topology of a - level transistor

clamped inverter, which satisfies

T = m …….. (3)

Figure 1.2.3 The M-Level Transistor-Clamped Inverter.

10

In this topology, the control of the gates is very simple because only one power

transistor is switched-on at a time. Then, there is a direct relation between the output

voltage, Vout, and the transistor that has to be turned-on. However, and despite the

excellent characteristics of this topology, the number of transistors is still too large to

allow the implementation of a practical converter with more than 50 levels. One

solution for increasing the number of steps could be the use of ―H‖ converters, like the

one shown in Figure. 6, which consists of connecting two of the previously discussed

topologies in series (two legs). If transistor-clamped inverters are used to build an ―H‖

converter, the number of transistors required for an -level inverter is 1, which means

only one more transistor than what is required for a simple leg configure ration.

However, the number of dc sources is reduced to 50%, which is the most important

advantage of ―H‖ converters.

1.2.4. CASCADED MULTILEVEL INVERTER

Another characteristic is that the ―H‖ topology has many redundant combinations of

switches‘ positions to produce the same voltage levels. As an example, the level ―zero‖

can be generated with switches in position S(1) and S(2), or S(3) and S(4), or S(5) and

S(6), and so on. Another characteristic of ―H‖ converters is that they only produce an

odd number of levels, which ensures the existence of the ―0V‖ level at the load .For

example, a 51- level inverter using an ―H‖ configuration with transistor-clamped

topology requires 52 transistors, but only 25 power supplies instead of the 50 required

when using a single leg. Therefore, the problem related to increasing the number of

levels and reducing the size and complexity has been partially solved, since power

supplies have been reduced to 50%.

11

Figure 1.2.4. The m-level inverter using an “H” bridge.

1.3 SELECTION OF MULTI LEVEL INVERTER

Compared with the diode-clamped and flying-capacitors inverter, Cascaded

inverter requires least number of components i.e. the cascaded inverter does not

require any voltage-clamping diodes or voltage balancing capacitors to achieve

the same number of voltage levels.

Soft switching technique can be used to reduce switching losses and device

stresses.

From the above discussion an optimized circuit layout and packaging are possible with

cascade topology because each level has the same structure and there are no extra

clamping diodes or voltage balancing capacitors.

12

1.4 FEATURES OF CASCADED MULTILEVEL INVERTER

The main features are as follows:

For real power conversions from AC to DC and then DC to AC the cascaded

inverter need separate dc sources. The structure of separate dc sources is well

suited for various renewable energy sources such as fuel cell, photovoltaic and

biomass.

Connecting DC sources between two converters in a back-to- back fashion is not

possible because a short circuit can be introduced when two back-to-back

converters are not switching synchronously.

The major advantages of the cascaded inverter are as follows:

Compared with the diode-clamped and flying-capacitors inverter, it requires

least number of components i.e. the cascaded inverter does not require any

voltage-clamping diodes or voltage balancing capacitors to achieve the same

number of voltage levels.

Optimized circuit layout and packaging are possible because each level has the

same structure and there are no extra

Soft switching technique can be used to reduce switching losses and device

stresses.

The major disadvantages of the cascaded inverter are as follows:

It needs separate dc sources for real power conversions, thereby limiting its

applications.

1.5 NEED FOR OPTIMIZATION

In order to overcome the major disadvantage of the cascaded multilevel inverter

mentioned above an optimization technique is carried out to minimize the

number of power supplies and power semiconductor switching devices for the

13

given number of levels by applying the appropriate combinations of the

switching devices. It is achieved by applying the sinusoidal switching frequency

modulation.

Inverter

configuration

Diode-Clamp

Inverter

Flying-Capacitors

Inverter

Cascaded

Inverters

Main Switching Devices

2(m-1) 2(m-1) 2(m-1)

Main

Diodes

2(m-1) 2(m-1) 2(m-1)

Clamping Diodes

(m-1)(m-2) 0 0

DC Bus

Capacitors

(m-1) (m-1) (m-1)/2

Balancing Capacitors

0 (m-1)(m-2)/2 0

Table.1.5 Comparison of power component requirements per phase leg among

three Multilevel Inverter

14

CHAPTER 2

LITERATURE SURVEY

15

S. Rahmani, A. Hamadi, N. Mendalek, and K. Al-Haddad, A new control technique for

three-phase shunt hybrid power filter,” IEEE Trans. Ind. Electron., vol. 56, no. 8, pp. 2904–

2915, Aug. 2009

This paper proposed three phase shunt hybrid active filter, it improves the dynamic reactive

power compensation and also enhances the harmonic current compensation but still the

switching losses are more.

W. Tangtheerajaroonwong, T. Hatada, K. Wada, and H. Akagi, “Design and performance

of a transformerless shunt hybrid filter integrated into a three-phase diode rectifier,” IEEE

Trans. Power Electron., vol. 22, no. 5, pp. 1882–1889, Sep. 2007.

This paper proposed transformer less shunt hybrid filter which provides less passive components,

lower dc link operating voltage but there is no reactive power compensation.

S. T. Senini and P. J.Wolfs, “Systematic identification and review of hybrid active filter

topologies” in Proc. IEEE 33rd Annu. Power Electro Spec. Conf. (PESC), 2002, vol. 1, pp.

394–399.

This paper proposed hybrid active filter topologies which are simpler in structure and provides

more efficiency yet the dynamic performance is low.

P. Salmeron and S. P. Litr an, “A control strategy for hybrid power filter to compensate

four-wires three-phase systems,” IEEE Trans. Power Electron., vol. 25, no. 7, pp. 1923–

1931, Jul. 2010.

This paper proposed the series active filter and shunt passive filter, the active filter is able to

compensate the reactive power, this strategy improves the passive filter compensation

characteristics.

H. -L. Jou, K. -D. Wu, J.- C. Wu, C. -H. Li, and M. -S. Huang, “Novel power converter

topology for three phase four-wire hybrid power filter,” IET Power Electron., vol. 1, pp.

164–173, 2008

16

This paper proposed thee phase four wire hybrid power filter it uses the less number of switches

to reduce the manufacturing cost.

C.-S. Lam, W.-H. Choi, M.-C. Wong, and Y.-D. Han, “Adaptive dc-link voltage controlled

hybrid active power filters for reactive power compensation,” IEEE Trans. Power

Electron., vol. 27, no. 4, pp. 1758–1772, Apr. 2012.

This paper improves the power and harmonic compensation also reduces the switching loss and

noise using adaptive control method.

17

CHAPTER 3

ASYMMETRICAL DC SOURCE BASED MLI

18

POWER ELECTRONICS

Power electronics combine power, electronics and control. Control deals with the steady-

state and dynamic characteristics of closed-loop systems. Power deals with the static and

rotating power equipment for the generation, transmission and distribution of electric

energy. Electronics deal with the solid-state devices and circuits for signal processing to

meet the desired control objectives.

Power electronics are based primarily on the switching of the power semiconductor

devices. With the development of power semiconductor technology, the power-handling

capabilities and the switching speed of the power devices have improved tremendously.

ASYMMETRICAL DC SOURCE BASED MLI

BLOCK DIAGRAM:

Figure: Block Diagram of Asymmetrical DC Source Based MLI

19

DC source :

It is the first stage of this project. So it gives the DC supply to Inverter. The DC source may be

Battery or fuel cell or rectified from AC source

Multi level inverter:

It is used to convert dc to ac voltage.theselective harmonic elimination method is used to control

the inverter outpout. The output voltage has nine steps so it is called nine level output and this

inverter is called as nine level inverter.

AC Load:

Multi level inverter is generate ac output voltage . it is used to run single phase ac motor and any

appliance required for ac voltage.

Micro controller:

Micro controller is used to generate triggering pulse for mosfets. It is used to control the outputs.

Micro controller have more advantage compare then analog circuits and micro processor such as

fast response, low cost, small size and etc.

Driver 1 & 2:

It is also called as power amplifier because it is used to amplify the pulse output from micro

controller. It is also called as opto coupler IC. It provides isolation between microcontroller and

power circuits.

Regulated Power supply (RPS):

RPS give 5V supply for micro controller and 12V supply for driver. It is converted from AC

supply. AC supply is step down using step down transformer.

20

3.1 CIRCUIT DIAGRAM

Figure.3.1 Circuit Diagram of Proposed MLI

3.2 CIRCUIT DESCRIPTION

A cascaded multilevel inverter consists of a series of H-bridge (single phase full bridge) inverter

units. The general function of this multilevel inverter is to synthesize a desired voltage from

several dc sources (SCDs), which may be obtained from batteries, fuel cells. Figure.3.1 shows

optimized topology of single-phase cascaded inverter. The ac terminal voltages of each bridge

are connected in series. Unlike the diode clamp or flying-capacitors inverter, the cascaded

inverter does not require any voltage-clamping diodes or voltage balancing capacitors. This

configuration is useful for constant frequency applications such as active front-end rectifiers,

active power filters, and reactive power compensation.

AU

XIL

IAR

Y

BR

IDG

E

MA

IN B

RID

GE

21

In this case, the power supply could also be voltage regulated dc capacitor. The circuit diagram

consists of two cascade bridges. The load id is connected in such away that the sum of output of

these bridges will appear across it. The ratio of the power supplies between the auxiliary bridge

and the main bridge is 1:3. One important characteristic of multilevel converters using voltage

escalation is that electric power distribution and switching frequency present advantages for the

implementation of these topologies.

3.3 PRINCIPLE OF OPERATION

The phase output voltage is synthesized by the sum of two inverter outputs. Each inverter bridge

is capable of generating three different levels of voltage outputs. The main bridge can generate

+3Vdc, 0, -3Vdc and the auxiliary bridge can generate +Vdc, 0, -Vdc. By using appropriate

combinations of switching devices many voltage levels are obtained. When the positive group

switches are turned on the voltage across that particular bridge is positive. When the negative

group switches are turned on the voltage across that particular bridge is negative.

When S1, S2 are turned on the voltage across the main bridge is +3Vdc. When S3, S4 are turned on

the voltage across the main bridge is -3Vdc.When S5, S6 are turned on the voltage across the

auxiliary bridge is +Vdc. When S7, S8 are turned on the voltage across the auxiliary bridge is -Vdc.

To obtain +2Vdc the switch combinations S1, S2, S7 & S8 are turned on.

To obtain +4Vdc the switch combinations S1, S2, S5 & S6 are turned on. To obtain -2Vdc the

switch combinations S3, S4, S5 & S6 are turned on. To obtain -4Vdc the switch combinations S3,

S4, S7 & S8 are turned on. The following table shows the switching strategy of transistors at

each level. The status of the switch is ‗0‘, that switch is in OFF condition. The status of the

switch is ‗1‘, that switch is in ON condition.

22

Voltage

Level

S1

S2

S3

S4

S5

S6

S7

S8

-4Vdc 0 0 1 1 0 0 1 1

-3Vdc 0 0 1 1 0 0 0 0

-2Vdc 0 0 1 1 1 1 0 0

-1Vdc 0 0 0 0 0 0 1 1

0 0 0 0 0 0 0 0 0

+1Vdc 0 0 0 0 1 1 0 0

+2Vdc 1 1 0 0 0 0 1 1

+3Vdc 1 1 0 0 0 0 0 0

+4Vdc 1 1 0 0 1 1 0 0

Table 3.3 Switching Strategies At Each Level.

PULSE GENERATION:

Space Vector Modulation (SVM)

Space Vector Modulation (SVM) is quite different from the PWM methods. With PWMs, the

inverter can be thought of as three separate push-pull driver stages, which create each phase

waveform independently. SVM, however, treats the inverter as a single unit, specifically the

inverter can be driven to eight unique states. The concept of space vector is derived from the

rotating field of ac machine which is used for modulating the inverter output voltage.

23

If three phase sinusoidal and balanced voltages are applied to a three-phase load, it can be shown

that the space vector V with magnitude Vm rotates in a circular orbit at angular velocity ω where

the direction of rotation depends on the phase sequence of the voltages. SVM is a digital

modulating technique, where the objective is to generate PWM load line voltages that are in

average equal to a given load line voltage. This is done in each sampling period by properly

selecting the switch states of the inverter and the calculation of the appropriate time period for

each state.

BLOCK DIAGRAM:

DC source :

It is the first stage of this project. So it is give the DC supply to Inverter. The DC source may

be Battery or fuel cell or rectified from AC source

24

Inverter:

It converts DC supply to AC output. This converter is used to eliminate a selective harminics in

the line current.the inverter output is injected through shunt transformer into line.

Filter:

Inverter has more harmonics it should be removed with help of LC filter circuit

AC source:

It is the first stage of this project. So it is give the AC supply to rectifier. The input side having

one inductive filter. It is used to improve the input power factor.

AC Load:

Multi level inverter is generate ac output voltage . it is used to run single phase ac motor and any

appliance required for ac voltage

Conventional System Drawbacks

Passive filters are not suitable for variable load

Line losses and instability due to harmonics

More current and Voltage distortion

Less efficiency

Advantages of Proposed system

Less harmonics

improve the voltage waveform from distortion

Improve the power quality

Reactive power compensation

Improve the stability

Applications

Power quality improvement in Grid

Voltage stability improvement in Grid

Power Control improvement in Grid

25

CHAPTER 4

SOFTWARE ANALYSIS

26

4. SIMULATION

4.1 GENERAL

Simulation has become a very powerful tool on the industry application as well as in academics,

nowadays. It is now essential for an electrical engineer to understand the concept of simulation

and learn its use in various applications. Simulation is one of the best ways to study the system

or circuit behavior without damaging it .The tools for doing the simulation in various fields are

available in the market for engineering professionals. Many industries are spending a

considerable amount of time and money in doing simulation before manufacturing their product.

In most of the research and development (R&D) work, the simulation plays a very important

role. Without simulation it is quiet impossible to proceed further. It should be no ted that in power

electronics, computer simulation and a proof of concept hardware prototype in the laboratory are

complimentary to each other. However computer simulation must not be considered as a

substitute for hardware prototype. The objective of this chapter is to describe simulation of

impedance source inverter with R, R-L and RLE loads using MATLAB tool.

4.1.2 INTRODUCTION TO MATLAB

MATLAB is a high-performance language for technical computing. It integrates computation,

visualization, and programming in an easy-to-use environment where problems and solutions are

expressed in familiar mathematical notation. Typical uses includes

1. Math and computation

2. Algorithm development

3. Data acquisition

4. Modeling, simulation, and prototyping

5. Data analysis, exploration, and visualization

6. Scientific and engineering graphics

7. Application development, including graphical user interface building

27

MATLAB is an interactive system whose basic data element is an array that does not require

dimensioning. This allows you to solve many technical computing problems, especially those

with matrix and vector formulations, in a fraction of the time it would take to write a program in

a scalar non interactive language such as C or FORTRAN.

The name MATLAB stands for matrix laboratory. MATLAB was originally written to provide

easy access to matrix software developed by the LINPACK and EISPACK projects. Today,

MATLAB engines incorporate the LAPACK and BLAS libraries, embedding the state of the art

in software for matrix computation.

MATLAB has evolved over a period of years with input from many users. In university

environments, it is the standard instructional tool for introductory and advanced courses in

mathematics, engineering, and science. In industry, MATLAB is the tool of choice for high-

productivity research, development, and analysis.

MATLAB features a family of add-on application-specific solutions called toolboxes. Very

important to most users of MATLAB, toolboxes allow you to learn and apply specialized

technology. Toolboxes are comprehensive collections of MATLAB functions (M-files) that

extend the MATLAB environment to solve particular classes of problems. Areas in which

toolboxes are available include signal processing, control systems, neural networks, fuzzy logic,

wavelets, simulation, and many others.

4.1.3 THE MATLAB SYSTEM.

The MATLAB system consists of five main parts:

Desktop Tools and Development Environment

This is the set of tools and facilities that help you use MATLAB functions and files. Many of

these tools are graphical user interfaces. It includes the MATLAB desktop and Command

Window, a command history, an editor and debugger, a code analyzer and other reports, and

browsers for viewing help, the workspace, files, and the search path.

28

The MATLAB Mathematical Function Library

This is a vast collection of computational algorithms ranging from elementary functions, like

sum, sine, cosine, and complex arithmetic, to more sophisticated functions like matrix inverse,

matrix eigen values, Bessel functions, and fast Fourier transforms.

The MATLAB Language

This is a high- level matrix/array language with control flow statements, functions, data

structures, input/output, and object-oriented programming features. It allows both "programming

in the small" to rapidly create quick and dirty throw-away programs, and "programming in the

large" to create large and complex application programs.

Graphics

MATLAB has extensive facilities for displaying vectors and matrices as graphs, as well as

annotating and printing these graphs. It includes high- level functions for two-dimensional and

three-dimensional data visualization, image processing, animation, and presentation graphics. It

also includes low-level functions that allow you to fully customize the appearance of graphics as

well as to build complete graphical user interfaces on your MATLAB applications.

The MATLAB External Interfaces/API

This is a library that allows you to write C and FORTRAN programs that interact with

MATLAB. It includes facilities for calling routines from MATLAB (dynamic linking), calling

MATLAB as a computational engine, and for reading and writing MAT-files.

MATLAB Documentation

MATLAB provides extensive documentation, in both printed and online format, to help you

learn about and use all of its features. If you are a new user, start with this Getting Started book.

It covers all the primary MATLAB features at a high level, including many examples. The

MATLAB online help provides task-oriented and reference information about MATLAB

features. MATLAB documentation is also available in printed form and in PDF format.

29

MATLAB Online Help

To view the online documentation, select MATLAB Help from the Help menu in MATLAB.

The MATLAB documentation is organized into these main topics:

The Role of Simulation in Design

Electrical power systems are combinations of electrical circuits and electro mechanical devices

like motors and generators. Engineers working in this discipline are constantly improving the

performance of the systems. Requirements for drastically increased efficiency have forced power

system designers to use power electronic devices and sophisticated control system concepts that

tax traditional analysis tools and techniques. Further complicating the analyst's role is the fact

that the system is often so nonlinear that the only way to understand it is through simulation.

Land-based power generation from hydroelectric, steam, or other devices is not the only use of

power systems. A common attribute of these systems is their use of power electronic s and

control systems to achieve their performance objectives.

Sim Power Systems is a modern design tool that allows scientists and engineers to rapidly and

easily build models that simulate power systems. Sim Power Systems uses the Simulink

environment, allowing you to build a model using simple click and drag procedures. Not only

can you draw the circuit topology rapidly, but your analysis of the circuit can include its

interactions with mechanical, thermal, control, and other disciplines. This is possible because all

the electrical parts of the simulation interact with the extensive Simulink modeling library. Since

Simulink uses MATLAB as its computational engine, designers can also use MATLAB

toolboxes and Simulink block sets. Sim Power Systems and Sim Mechanics share a special

Physical Modeling block and connection line interface.

4.1.4 Sim Power Systems Libraries

We can rapidly put Sim Power Systems to work. The libraries contain models of typical power

equipment such as transformers, lines, machines, and power electronics. These models are

proven ones coming from textbooks, and their validity is based on the experience of the Power

Systems Testing and Simulation Laboratory of Hydro-Québec, a large North

30

Matlab Library

American utility located in Canada, and also on the experience of Ecole de Technologie

supérieure and Université Laval. The capabilities of Sim Power Systems for modeling a typical

electrical system are illustrated in demonstration files. And for users who want to refresh their

knowledge of power system theory, there are also self- learning case studies.

The Sim Power Systems main library, powerlib, organizes its blocks into libraries according to

their behavior. The powerlib library window displays the block library icons and names. Double-

click a library icon to open the library and access the blocks. The main Sim Power Systems

powerlib library window also contains the powergui block that opens a graphical user interface

for the steady-state analysis of electrical circuits.

31

4.1.5 Advantages of MATLAB

MATLAB is a widely used tool in the electrical engineering community.

MATLAB is used for analyzing power system steady-state behavior and its capabilities

for simulating transients in power systems and power electronics. It can be used for

simple mathematical manipulations with matrices.

SIMULATION RESULTS:

4.2 EXISTING SYSTEM:

Figure 4.2 Conventional system

32

Figure 4.3: RMS voltage the x-axis represents time, y-axis represents power

Figure 4.4: Real power &reactive power the x-axis represents time, y-axis represents power

33

FFT Analysis:

Fundamental (50Hz)=5474,THD=3.24%

Frequency (Hz)

Figure 4.5: FFT analysis

Figure 4.6: Proposed circuit

34

PROPOSED SIMULINK MODEL:

Figure 4.7: Proposed Circuit

Figure 4.8: Phase voltage

35

Figure 4.9: RMS voltage

Figure 4.10: Real and reactive power

Figure 4.11: FFT analysis

36

CHAPTER 5

CONCLUSION

37

5. CONCLUSION

In this project nine level inverter have been proposed using MATLAB/SIMULINK. The space

vector pulse width modulation technique (SVPWM) was used. The factors such as total

harmonic distortion (THD), RMS voltage, real and reactive power compensation are analyzed.

The proposed multilevel inverter based hybrid active power filter in three phase‘s four wire

systems provides low harmonics, reactive power compensation and higher RMS voltage. The

hybrid active power (HAPF) improves the compensation characteristics, thus providing cost

effective solution for compensating reactive and harmonic current problems.

38

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