Project review

DIFFERENT PWM CONTROLLED BASED

FSTPI FED IM DRIVE

PRESENTED

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

Amplitude modulation ratio (ma)

A01A0

10

Vofcomponentfrequecnylfundamenta:)(Vwhere,

,2/

)(

dc

A

tri

controla V

Vofvaluepeak

vofamplitude

vofamplitudepeakm

Frequency modulation ratio (mf)

frequencylfundamentafandfrequencyPWMfwhere,, 1s1

f

fm s

f

mf should be an odd integer

if mf is not an integer, there may exist sub harmonics at output voltage

if mf is not odd, DC component may exist and even harmonics are present at output voltage

mf should be a multiple of 3 for three-phase PWM inverter

An odd multiple of 3 and even harmonics are suppressed

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

Space Vector PWM for 3leg inverter

Where, upper transistors: S1, S3, S5

lower transistors: S4, S6, S2

switching variable vector: a, b, c Eight possible combinations of on and off patterns for the three upper transistors (S1, S3, S5)

The eight combinations, phase voltages and output line to line voltages

Basic switching vectors and Sectors

6 active vectors (V1,V2, V3, V4, V5, V6)

Axes of a hexagonal

DC link voltage is supplied to the load

Each sector (1 to 6): 60 degrees

2 zero vectors (V0, V7)

At origin

No voltage is supplied to the load

cn

bn

an

q

d

V

V

V

2

3

2

30

2

1

2

11

3

2V

V

frequency)lfundamentaf(where,

t2ππtω)V

V(tanα

VVV

s

ssd

q1

2q

2dref

Voltage Space Vector and its components in (d, q).

cnbnan

cnbnq

cnbnan

cnbnand

V2

3V

2

3V

cos30Vcos30V0V

V2

1V

2

1V

cos60Vcos60VVV

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

: abc to dq

Step 2. Determine time duration T1, T2, T0

)60α0(where,

)3/(sin

)3/(cosV

3

2T

0

1V

3

2T

)(sin

)(cosVT

)VTV(TVT

VdtVdtVV

dc2dc1refz

2211refz

T

TT

0

TT

T1

2

T

0

T

0

1ref

z

21

21z 1

π

π

α

α

dc

ref

sz210

2

1

V3

2

Vaand

f

1Twhere,),(

)3/(sin

)(sin

)3/(sin

)3/(sin

TTTT

aTT

aTT

z

z

z

Switching time duration at any Sector

60α0

6)toSector1is,(that6through1nwhere,,

3

1cossin

3

1sincos

3

3

1sin

3

sin3

coscos3

sin3

3sin

3

3

1

3sin

3

210

2

1

TTTT

nn

V

refVT

n

V

refVTT

nn

V

refVT

n

V

refVT

n

V

refVTT

z

dc

z

dc

z

dc

z

dc

z

dc

z

Space Vector PWM switching patterns at each sector.

Sector 1. Sector 2.

Step 3. Determine the switching time of each transistor (S1 to S6)

Switching Time Table at Each Sector

Simulation Diagram of SVM 3leg inverter

Time durations T1, T2, T0

Switching Times

Line voltages

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 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

Switching losses also reduced by space vector modulation

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

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

Switching Time for Each Sector of two-leg inverter

Simulation of 3phase to 2phase

Simulation for Sector Identification

Angle& Sectors

Sector

Angle

Sector

Simulation circuit for 2 leg inverter by SVM

Switching time duration for two leg inverter

Connotative Modulation Functions for 2leg

Line Voltages

Third Harmonic Injection

Third Harmonic Injection to Switching Times

Third Harmonic Switching Times

Line voltages for 2 leg Inverter

Rotor & Stator currents

Speed& Torque Characteristics

SVPWM APPLIED TO THE 2-LEG INVERTER UNDER DC-LINKVOLTAGE RIPPLE CONDITIONS

The phase-to zero voltages

under balanced load conditions

phase-to-neutral voltages VAN, VBN andVCN

The phase-to-neutral output voltages can be transformedinto space vector

Phase-to-zero and phase-to-neutral output voltages

Voltage vectors in αβ plane

Unbalanced dc-link voltages

The Time Durations In sector 1: 0≤α≤π

(a) Timing of gate pulse of space vector PWM (b) Timing of gate pulse of carrier–based PWM In sector 2: π≤α≤2π

V t is the instantaneous carrier signal.

Simulation Circuit of proposed method

Reference signals Vrefb and Vrefc

Line voltages

Speed & Torque Characteristics

FFT analysis

Comparison of Different PWM techniques for FSTPIs

Sine PWM SV PWM Scalar PWM Carrier PWM

Calculation Burden Low Very High Medium Low

THD 20.08% 1.86% 14.79% 4.07%

Output Voltage Normal Normal Maximum Normal

DC-link voltage ripple

Resolved

Switching loss high low low high

CONCLUSION

• In this 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, Scalar PWM & Modified SVPWM of FSTPIs is presented.

BIBLIOGRAPHYJournals

[1]. “Adaptive Carrier-based PWM for a Three-Phase Inverter under DC-link Voltage Ripple Conditions” Tuyen D. Nguyen*,

Hong-Hee Lee† and Hoang M. Nguyen* Journal of Electrical Engineering & Technology Vol. 5, No. 2, pp. 290~298, 2010

[2]. 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

[3]. “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.

[4]. 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.

Books

[5]. P.S.Bimbhra, “Power Electronics”, Khanna publications.

[6]. Muhammad H.Rashid “Power Electronics Circuits, devices, and Applications”, Prentice-Hall of India Private Limited,

Third Edition, 2004.

Thesis References

[7]. Jin-woo Jung, “Space Vector PWM Inverter”, The Ohio State University, February, 2008.

Website references

[8]. www.ieeexplore.com

THANK YOU