HARMONIC REDUCTION IN POWER SYSTEM Ankit Vashi B.E. ...

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Figure 13: Multi Level Inverter. [7] 4.3 Methods for Harmonic Reduction in Inverters: As explained earlier, one of the most important aspect of a system is the reduction of harmonics that are present in the system. In case of an inverter, it is very important to remove the harmonics from the ac output. The harmonics present in a dc to ac inverter are very much obvious compared to the harmonics that can be present in an ac to dc converter. This is because of the output of dc to ac inverter being ac. Thus, the filters that are used in dc to ac inverter have different designs compared to the filters used in ac to dc converters. In case of ac to dc 26
converters, the main objective is to improve the output voltage ripple. Thus, passive filters can be easily used in order to improve the output of an ac to dc converter. While, in case of dc to ac inverter, the harmonic reduction is harder and it also includes the use of active filters. As the output of dc to ac inverters is alternating, it is very important to produce sinusoidal output waveforms. In order to produce such sinusoidal waveforms, filters are implemented which reduce the harmonic effect by removing the third and higher harmonics from the system. The filters used to remove the harmonics from the inverters are more complex and consists of large number of inductors and capacitors to remove the harmonics of higher order. This also results into more costly filters to remove harmonics from the inverter. Thus, in order to avoid the cost of such expensive and complex filters controlling the width or reducing the number of pulses may result into reduction of harmonics. One such technique is explained below.[6][7] 4.3.1 Pulse Width Modulation Technique: Figure 14 shows a single phase inverter block diagram with a high frequency filter that is used in order to remove the harmonics from the output waveform. Here, vo is the ac output while vin is the input dc voltage. 27
Page 1 and 2: HARMONIC REDUCTION IN POWER SYSTEM
Page 3 and 4: I certify that this student has met
Page 5 and 6: TABLE OF CONTENTS List of Figures
Page 7 and 8: LIST OF FIGURES 1. Figure 1: Single
Page 9 and 10: Chapter 1 INTRODUCTION The term har
Page 11 and 12: 2.2 Transients: In terms of power s
Page 13 and 14: obtained during the event is consid
Page 15 and 16: Non-linear loads are considered as
Page 17 and 18: an inductance is a passive filter.
Page 19 and 20: 3.2 Roles of Filters in Power Syste
Page 21 and 22: 3.3.1 Types of Passive Filters: The
Page 23 and 24: Figure 4 : Three Phase, Three Wire
Page 25 and 26: 3.4 Active Filters : Active filters
Page 27 and 28: Figure 9 : Single Phase Active Filt
Page 29 and 30: Theoretically the output voltage wa
Page 31 and 32: consists of four IGBT devices (also
Page 33: 4.2.3 Multi Level Inverters : Figur
Page 37 and 38: order to reduce the harmonics is kn
Page 39 and 40: Note: For figures 16 and 17, • ts
Page 41 and 42: Figure 18 : Plot of Switching angle
Page 47 and 48: cos(7*s1)-cos(7*s2)+cos(7*s3)-cos(7
Page 49: REFERENCES 1.) Roger C. Dugan, Mark

HARMONIC REDUCTION IN POWER SYSTEM Ankit Vashi B.E. ...

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