SPACE VECTOR MODULATION

FOR TWO LEG INVERTERSPRESENTED

By

SUDHAKAR AKKISUDHAKAR AKKI

Reg.No:1610910044

UNDER THE GUIDANCE OF

Mr. NALINKANT MOHANTYASST.PROF( Sr.G )

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.

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

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.

Block diagram of the project

Principle of Space Vector PWM

Treats the sinusoidal voltage as a constant amplitude vector rotating

at constant frequency

This PWM technique approximates the reference voltage Vref by a combination

of the Four switching patterns (V1 to V4)

Coordinate Transformation (abc reference frame to the stationary d-q frame)

: A three-phase voltage vector is transformed into a vector in the stationary d-q coordinate

frame which represents the spatial vector sum of the three-phase voltage

The vectors (V1 to V4) divide the plane into Four sectors (each sector: 90 degrees)

Vref is generated by two adjacent non-zero vectors and two zero vectors

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)

SPACE VECTOR PWM FOR 2-LEG INVERTER

Space vectors representation

Magnitude, angle& sector representation

Alpha

Beta

Determine time duration T1, T2, T0

1

1

2

2

T cos

T sin

VsTsV

VsTsV

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

Switching times of each sector

Simulation circuit of 2 leg inverter by SVM

Sectors for 2-leg inverter

Angle

Sectors

Sectors for 3-leg inverter

Switching time duration

Switching time duration for two leg inverter

Connotative Modulation Functions for 2leg

Connotative Modulation Functions for 3 leg

Phase voltages of 3-leg inverters

Line Voltages

Switching time duration for two leg inverter with un-equal vector magnitudes….

FFT analysis

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.

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 ICTA’05, 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 dc – link 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

THANK YOU