EMTP Simulation Of An Active Filter Operating With Weak AC Distribution System Rachit Arora

120 Pages·2000·4.82 MB·English

EMTP Simulation Of An Active Filter
Operating With Weak AC Distribution System
Rachit Arora
in
The Department
of
Electrical and Cornputer Engineering
Presented in Partiai FuifilIrnent of the Requirements
for the Degree of Master of Applied Science at
Concordi a Univeni ty
Montreal, Canada
January 1999
@ Rachit Arora, 1999
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Abstract
EMTP Simulation Of An Active Filter
Operating With A Weak AC Distribution System
Rachit Arora
An AC distribution system has a myriad of loads connected at the system bus.
Many of the DC based loads cause disturbance on the ac bus due to high harmonic load
currents. Traditionally passive filters are used for filtering these load harmonies. Recent
technologicai advances have enabled the use of high frequency switching devices in the
development of active filtenng techniques.
In this thesis, an active filter topology was selected for the system, and a test sys-
tem was modeled using EMTP. The objective of active filtering is to meet the harmonic
and reactive load locally, and thus removing the harmonic content of source cunents. The
AF controller based on the on-line power computation scheme was modeled. Tracking
-
control was demonstrated using two control methodologies hysteresis band control and
sliding mode control.
A performance cornparison was made between the two control schemes, and the
impact of various circuit and control parameters on the filtering performance was studied.
To assess the transient perfoxmance achieved with the control schemes presented, results
frorn EMV based studies for this distribution system under various AC-DC fault condi-
tions are analyzed.
Acknowledgrnent
1 would like to thank my supervisor, Dr. V. K. Sood for his financial support dunng
my Masters research work, and appreciate his valuable advice and patience with which he
guided me during my delibentions.
The other aspect of my stay here has been made possible in tne Company of many
fnends who have been a constant support with their love, affection and presence.
Thanks Meghana. Cthn~M. ahesh, Subha. ç! Pisini, Tanu & Vijq Miki. Uju. Dak-
sha. Jqa. Jasjit and Sraddha for everything. 1 aiso thank al1 my colleagues at GM 905, for
making the office a habitable place to stay late hours.
The assistance of Department secretaries and Computing Services is appreciated. 1
also owe my ,ptitude to Dr. B. N. Singh and Dr. A. Chandra of the ETS for assisting me
in technical clarifications.
My parents and my sister, Ruchi were always a source of encouragement and mon1
support. 1 dedicate this work to them.
Dedicated to
my parents
and my sister
Ruchi
CONTENTS
Page
List of Figures ................................................................................................. viii
List of Tables ................................................................................................... X
Cha~ter1 : Introduction ................................. .............................................
,.
Effect of Harmonics ......................................................................
Passive AC Filters .........................................................................
ProbIem Definition .......................................................................
Li terature Su rvey ..........................................................................
.......................................................................
Proposed Approac h
Thesis Outiine ....................................... ........
,
....................................................................
Chapter 2: Sy stem Configuration
2.1 Introduction ...................................................................................
1.2 ActiveFilters .................................................................................
..................................................
7.3 Active Filter Topology Selection
...............................................................................
7.4 System Mode1
7.5 Summafy .......................................................................................
Chapter 3: Control Circuits ........................................................................... 24
...................................................................................
3.1 Introduction 34
3.3 Rectifier Control Unit ................................................................... 24
3.3 AF Control Unit ............................................................................ 25
3.3.1 On-line Power Computation Scheme (Feedforward Control) 17
3.3.2 Tracking Control (Feedback Control) ............................ 35
3.3 2.1 Hysteresis Control ........................ .. ............ 35
3.3 .3 .2 Sl iding-Mode Control ..................................... 49
........................................................................................
3.4 Surnmary
Chapter 4: Transient Behavior of the Active Filter Mode1 ..............................
...................................................................................
4.1 Introduction
4.2 System Tests ...............................................................................
4.3 Initialization Tests .........................................................................
4.3.1 Initialization of Rectifier Control Unit ...........................
4.3.2 Initidization of AF Control Unit .........................,,.........
....
4.3.3 Cornpaison of Hysteresis and Sliding-Mode Control
.......................................................
4.3.4 Harmonic Analysis
1.4 Dynamics Tests ................................................................*.............
...........
4.4.1 Step change of 30% in DC current reference, IRr
4.4.3 Fault Tests .......................................................................
4.4.3.1 Single Phase Solid Line to Ground 3-cycle Fault at
AC Bus (Commutation Failure Test)
1.1.2.2 Single Phase Line to Ground 3-cycle Fauit at AC
bus (with fault impedance)
4.4.2.3 Line to Line 3-cycle Fault at AC bus (phases A. B)
3.4.2.4 Three Phase Solid Line to Ground Fault at AC bus
(Phases AJ3.C)
4.1.2.5 DC 6-cycle Fault at Rectifier load end ............
........................................................................................
4.5 Summary
...............................................................................
Chapter 5: Conclusions
References .......................................................................................................
.....................................................................................................
Appendix A
Appendix B ..................................................................................................
.....................................................................................................
Appendix C
vii
List of Figures
Page
.....................
Harmonic Elimination by magnetic compensation
Active Filter Topologies .............................................................
System Mode1 .............................................................................
High Pass Filter ...........................................................................
Converter Unit .............................................. ..............................
Voltage Source Inverter Unit ......................................................
Rectifier Control Unit .................................................................
System Modei ............................................................................
AF ControI Unit ............................... ........ ...................................
AF Control Unit Schematic ........................................................
..................
Simulation of On-line Power Computation Scheme
Hysteresis Controller implementation .....................................
Simulation of Hysteresis Controller .........................................
............................................
Variation of Hysteresis Bandwidth
.........................
Effect of variation of Hysteresis Bandwidth. hb
Variation of L, ..................... . ....................................................
Effect of variation of Lc ......................... ............. ......................
Effect of variation of Vdc ............................................................
Sl iding-Mode Controller implementation ................... ........ .....
.....................................
Simulation of Sliding-Mode convoller
Vanation of decision frequency ................................ ..... ..........
Effect of variation of decision frequency ................................. ...
Variation with Lc ............................................... ..................
Effect O. variation of Lc ............................ .. ..........................
viii
Effect of Vdc v"ation ................................................................
Initialization of Rectifier Unit ........................................ .............
Active Filter Initialization - Hysteresis control ...........................
Active Filter Initialization - Sliding-Mode Control ....................
Hysteresis Controller .t ransient response ...................................
Sliding-Mode Controller .t ransient response .............................
Hysteresis Controller .S ingle phase fault at AC bus ..................
Sliding-Mode Controllrr .S ingle phase fault at AC bus ............
Hysteresis Controller .S ingle phase fault (50%)a t .4 C bus ......
Sliding-Mode Controller .S ingle phase fault (50%) at AC bus
Hysteresis Controller .L ine-Line fault at AC bus (ph . A-B) .....
Sliding-Mode Controller .L ine-Line fault at AC bus (ph .A -B)
Hysteresis Controller .3 phase L-G fault at AC bus ..................
Sliding-Mode Controller .3 phase L-Gf ault at AC bus ............
Hysteresis Controller .F ault at DC load .............*......................
Sliding-Mode Controller .F ault ût DC load ..........................*..**
zndo rder high pass filter ............................................................
Single phase equivalent circuit ...................................................
Wave-shaping of if, in hysteresis band .......................................
List of Tables
Page
........................................
Variation of hysteresis bandwidth. hb 39
Vanation of Connection inductance. L, ...................................... 4 1-42
................................................
Viuiation of DC bus voltage. Vdc 45
Variation of decision frequency. fd ............................................ 53
.
Variation of Connection inductance Lc ...................................... 55-56
Variation of DC bus voltage. Vdc ................................................ 58
Harmonic Analyses (without AF compensation) ........................ 71
.............................
Harmonic Analyses (with AF compensation) 72