POWER QUALITY IMPROVEMENT IN DC DRIVES BY SUPPRESSING HARMONICS

Under the guidance ofProf. K.V.DEVADAS

Head of the Department, E&EKVGCE- Sullia.

Presented by,ARAVIND NARAGUND4th sem. M.Tech (CAID)

KVGCE- Sullia

ABSTRACT

This project presents various techniques like passive filter, shunt active

filter, sinusoidal pulse width modulation and selective harmonic elimination for

harmonic reduction. The power quality parameters such as “Total Harmonic

Distortion of voltage” (THDV) and “Total Harmonic Distortion of current”

(THDI) has determined in each case of above said techniques for different ratings

of DC motor and also extended the work to higher pulse converters (up to 96

pulse). By using MATLAB for simulation, the clear comparison of power quality

parameters has made between before and after application of above discussed

techniques.

1. INTRODUCTION

Figure : Three phase bridge rectifier circuit for speed control of DC motor

Power quality Current quality Voltage quality Total harmonic distortion

2. POWER QUALITY IMPROVEMENT TECHNIQUESThe following are types of the filters generally used. (a) Passive filters (b) Active filters and (c) Hybrid filters

2.1) Passive Filters

Passive implementations of linear filters are based on combinations of

resistors(R), inductors(L) and capacitors(C). These types are collectively known

as passive filters, because they do not depend upon an external power supply

and/or they do not contain active components such as transistors.

2.2) Shunt Active Filter

Figure : Basic Scheme of shunt active filter

Figure: Voltage source converter topology for active filters.

VOLTAGE SOURCE CONVERTERS

Multi-pulse systems result in two major accomplishments namely, 1. Reduction of ac input line current harmonics. 2. Reduction of DC output voltage ripple.

2.3) Multipulse Converters

2.3.1 12-PULSE CONVERTER

2.3.2 24-PULSE CONVERTER

Two twelve pulse converters phase shifted by 15 degrees from

each other, can provide a twenty four, obviously with much lower

harmonics on ac and DC side. Its ac output voltage would have order

harmonics i.e., 23rd, 25th, 47th , 49th harmonics with magnitudes of

1/23rd , 1/25th , 1/47th ,1/49th ,…respectively, of the phase shift.

2.3.3 36, 48 AND 96-PULSE CONVERTERHigher number of pulse converters can be

implemented by connecting appropriate number of six pulse converter either in series or parallel with proper degree of phase shift between them. The connection for 36, 48 and 96-pulse converter is shown in fig 3.8, 3.9 & 3.10 respectively.

3. MATLAB/SIMULINK MODELS AND RESULTS

3.1) 6 Pulse Converter

THDI before application of Filter = 15.32%

3.2) 6 Pulse Converter with Passive Filter

THDI after application of Passive Filter = 4.16

3.3 ) Application of Shunt Active Filter to 6 Pulse Converter.

After Application of Shunt Active Filter, THDV = 2.07, THDI = 0.91

3.4) 6 Pulse Controlled Converter

Before application of PWM Signals THDV = 1.462, THDI = 0.4179

3.5) After application of PWM Signals

After application of PWM Signals THDV = 0.60, THDI = 0.20

3.6) 12 Pulse Converter

For 12 Pulse Converter THDV = 1.37, THDI = 1.95

3.7) 24 Pulse Converter

For 24 Pulse Converter THDV =1.30, THDI = 1.93

3.8) 36 Pulse Converter

For 36 Pulse Converter THDV =1.26 ,THDI = 1.94

3.9) 48 Pulse Converter

For 48 Pulse Converter THDV =1.02,THDI =2.32

3.10) 96 Pulse Converter

For 96 Pulse Converter THDV =1.36,THDI =2.00

Table 1 Comparison of THDI for Multipulse convertersRating of Motor in

HP

4 pulse Converte

r

6 pulse Converte

r

12 pulse Converte

r

24 pulse Converte

r

36 pulse Converte

r

48 pulse Converte

r

96 pulse Converte

r

%THDI %THDI %THDI %THDI %THDI %THDI %THDI

5 37.16 3.11 2.46 2.40 2.31 2.47 2.3810 7.24 3.11 2.78 2.44 2.13 2.44 2.1920 6.42 1.67 2.22 2.20 2.03 2.38 2.0430 5.92 2.56 2.06 2.04 1.96 1.94 1.9840 6.26 2.41 1.95 1.93 1.92 2.35 1.98

Table 2 Comparison of THDV for Multipulse convertersRating of Motor in

HP

4 pulse Converte

r

6 pulse Converte

r

12 pulse Converte

r

24 pulse Converte

r

36 pulse Converte

r

48 pulse Converte

r

96 pulse Converte

r

%THDV %THDV %THDV %THDV %THDV %THDV %THDV

5 6.35 1.51 1.30 1.15 1.03 1.07 1.1110 6.33 1.51 2.07 1.46 1.07 1.07 1.1120 7.21 2.79 1.50 1.37 1.14 1.07 1.1630 6.34 1.60 1.43 1.34 1.2 1.20 1.2540 5.11 1.53 1.37 1.30 1.24 1.04 1.34

Plot of %THDI vs Different Rating(in HP) of DC Motor

Plot of %THDV vs Different Rating(in HP) of DC Motor

4. CONCLUSION

Power Quality related issues, and various harmonic suppression

techniques are discussed in detail. The reduction techniques such as passive filter,

shunt active filter and multipulse converters are simulated using Matlab/Simulink.

From the simulated results, it’s found that quality of power has improved after

application of filters. For multipulse converters with increase in number of pulses,

the total harmonic distortion has reduced and thus quality of power is improved. And

it’s also found that the power quality parameters such as THDV and THDI has

reduced for large DC motor loads.

REFERENCES

[1] John N. Chiasson, Leon M. Tolbert, Keith J. McKenzie, Zhong Du, A Complete Solution to the Harmonic Elimination Problem, IEEE Transactions on Power Electronics, vol. 19, no. 2, march 2004 (491-499).

[2] M.Izhar, C.M.Hadzer,S.Masri and S.Idris, A Study of the Fundamental Principles to Power System Harmonic, National Power and Energy Conference 2003 Proceedings, BangiMalaysia. (Page no: 225-231). [3] Tony Hoevenaars, Kurt LeDoux, Matt Colosino, Interpreting IEEE Std 519 and Meeting its Harmonic Limits in VFD Applications, Paper No. PCIC-2003-15. [4] Math H J Bollen, “Understanding Power Quality Problems; Voltage sags and interruptions”, Wiley India, 2011.

[5] Roger C Dugan, et.al, “Electrical power Systems Quality”,3rd Edition, TMH, 2012.

THANK YOU