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INTRODUCTION

Semiconductor switches mainly determine the overall price of power

converters.

The main objective of this project is to prove 2leg inverters are the best

option for low power applications for getting the good performance.

Two leg inverter produces the square wave or quasi-square wave. but low

power applications allow the two leg inverter output.

In many industrial applications, it is often required to vary the output

voltage of the inverter due to the following reasons

To cope with the dc I/p voltage.

To regulate the voltage of inverters

To satisfy the constant voltage & frequency for control requirement.


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Pulse-Width Modulated For VSI

Disadvantages of PWM

semiconductor devices must have low turn-on and turn-off times. so, they are very expansive

Reduction of available voltage

Increase of switching losses due to high PWM frequency

Control of inverter output voltage with out any additional components

Reduction of lower harmonics

The most common PWM approach is sinusoidal PWM. In this method a

triangular wave is compared to a sinusoidal wave of the desired frequency and the

relative levels of the two waves is used to control the switching of devices in each

phase leg of the inverter.

Objective of PWM


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Space vector modulation

In sinusoidal PWM, 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

The space vector method is a d,q model PWM approach

Modulation index is high

SVM produces 15% higher then the sinusoidal PWM in output voltages

Simple, inherently digital calculation of the switching times.

SVPWM has been gaining more attention in the industry.


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Block diagram of the project


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Comparison of Sine PWM and Space Vector PWM

Space Vector PWM generates less harmonic distortion

in the output voltage or currents in comparison with sine PWM

Space Vector PWM provides more efficient use of supply voltage

in comparison with sine PWM

Voltage Utilization: Space Vector PWM = 2/3 times of Sine PWM Realization of Space Vector PWM

Step 1.Determine Vd, Vq, Vref, and angle ()

Step 2.Determine time duration T1, T2, T0

Step 3.Determine the switching time of each transistor (S1 to S4)


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SPACE VECTOR PWM FOR 2-LEG INVERTER


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Space vectors representation


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Alpha

Beta

Determine time duration T1, T2, T0

1

1

2

2

T cos

T sin

VsTs

V

VsTs

V


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Determine the switching timeof each transistor (S1 to S4)


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Simulation circuit of 2 leg inverter by SVM


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S f 3 l i


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Sectors for 3-leg inverter

Switching time duration


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Switching time duration for two leg inverter


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Connotative Modulation Functions for 2leg


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Line Voltages


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Switching time duration for two leg inverter

with un-equal vector magnitudes.

FFT analysis


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CONCLUSION

In this dissertation work, it is shown that two-leg inverters are the best

option for high performance low power applications. It can be resolved

by comparing the no of semiconductor switches usage in 2-leg and 3-leg

inverters and moreover two leg inverters allow the asymmetrical

voltages

To enable this, space vector pulse width modulation (SVPWM)

technique for two-leg and three-leg inverters is presented.


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BIBLIOGRAPHY

[1]. Hind Djeghloud and Hocine Benalla, Space Vector Pulse Width Modulation Applied

to The Three-Level Voltage Inverter, 5th International Conference on Technology and

Automation ICTA05, Thessaloniki, Greece, Oct 2010.

[2]. Jin-woo Jung, Space Vector PWM Inverter, The Ohio State University, February,

2008.

[3]. Jae Hyeong Seo; Chang Ho Choi; Dong Seok Hyun, A New Simplified space-Vector

PWM Method for Three-Level Inverters, IEEE Transactions on Power Electronics,

Volume 16, Issue 4, Jul 2010, Pages 545 - 550

[4]. Muhammad H.Rashid Power Electronics Circuits, devices, and Applications,

Prentice-Hall of India Private Limited, Third Edition, 2004.

[5]. the adaptive space vector pwm for four switch three phase inverter fed induction

motor with dclink voltage imbalance by Hong Hee Lee*, Phan Quoc Dzung**, Le

Dinh Khoa**, Le Minh Phuong**, Huynh Tan Thanh***School of Electrical Engineering,

University of Ulsan Ulsan, Korea.

[6]. P.S.Bimbhra, Power Electronics, Khanna publications.

[7]. Overview of MATLAB Simulink

Http://www.mathworks.com/products/simulink/description/overview.shtml


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THANK YOU

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