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short circuit current from the source. • Voltage Swell: Voltage swell can be defined as the opposite of voltage sag. It is a temporary increase in voltage for a limited amount of time and caused by sudden decrease in total load size. The effect of these two disturbances can be prevented or decreased by a decent voltage regulator. • Momentary interruptions: It is an instantaneous drop on supply voltage. The differences between voltage sag and momentary interruption are their duration and the amount of voltage drop. The latter happens in smaller amount of time with a higher voltage drop. • Transients: Transient can be defined as an increase in supply frequency for a short time duration. The frequency of oscillation can vary from several multiples of supply frequency to hundreds of kHz. Switching transients, capacitor energization and lightning can cause transient. • Voltage Unbalance: It is the presence of negative and zero sequence components in supply voltage. For a balanced three phase supply, the amplitude of each phase would be the same and at the same time, the phase difference between them would be 120 o whereas these quantities do not hold in the unbalanced case. The reasons can be listed as the uneven distribution of single phase loads to each three phases, a short circuit in one phase or unstable utility supply. • Harmonics: Harmonic is a current or voltage waveform whose frequency is an integer multiple of the fundamental frequency. It deteriorates the pure sinusoidal waveform, and causes extra current flowing through the transmission lines that does not contribute any work done. It arises from the nonlinear loads connected to the utility such as switching mode power supplies, variable frequency drives, etc. Harmonics are the most common threat for power quality issues. It can be extracted from the supply voltage or current waveform by fourier analysis. • Voltage Fluctuations: It is described by the intermittent but small variation in rms line voltage. The arc furnaces and cycloconverters can cause 2
this disturbance since they do not operate at the fundamental frequency of the supply voltage. These electromagnetic disturbances have been categorized as ”Short Duration Variations”, ”Long Duration Variations”, etc. in [3]. The latter which typically lasts more than 1 minute is divided into smaller groups which have mainly led to the improvement of Flexible AC Transmission System (FACTS) technology. They are namely sustained interruptions, undervoltages and overvoltages. Sustained interruption is considered as the decrease of the supply voltage to zero for more than one minute. It generally represents a permanent fault in the electrical network. Overvoltage can be caused by a capacitive load which decreases the power factor at the coupling point at the same time. Since the FACTS Devices have an ability to compensate the load by absorbing inductive reactive power from the network, the power factor at the coupling point where the load is connected is improved. As a result, the voltage is reverted and the power quality is increased indirectly. The opposite of the events that cause overvoltages result in undervoltages. In other words, the load is highly inductive this time and causes the supply voltage reduced. Compensation of inductive reactive power by generating capacitive reactive power increases the power factor at the coupling point. Therefore, an increased power quality is achieved indirectly. In the next section, a brief description of FACTS technology and its benefits will be explained. 1.2 Principles of FACTS Due to the reasons mentioned in previous section, the power quality became a significant consideration. In addition to this, electricity authorities (such as the Institute of Electrical and Electronics Engineers (IEEE) and International Electrotechnical Commission (IEC)) published some standards that suggest limits to the pollution ratio of the electricity to prevent further drawbacks of disturbances. Some of the countries published regulations under the guidance of these standards. As an example, the limits for current harmonics are introduced in Table 1.1 [31]. 3
Page 1 and 2: DESIGN AND IMPLEMENTATION OF THYRIS
Page 3 and 4: I hereby declare that all informati
Page 5 and 6: ÖZ TRİSTÖR ANAHTARLAMALI ŞÖNT
Page 7 and 8: ACKNOWLEDGMENTS I would like to exp
Page 9 and 10: 2.3 Switching Performance of TSC .
Page 11 and 12: LIST OF TABLES TABLES Table 1.1 Cur
Page 13 and 14: Figure 2.9 (a) Equivalent circuit r
Page 15 and 16: Figure 4.8 Resultant line-to-line v
Page 17 and 18: Figure 4.38 3 Phase current wavefor
Page 19: CHAPTER 1 INTRODUCTION 1.1 Power Qu
Page 23 and 24: driving algorithm and it has to wit
Page 25 and 26: how to improve the transient respon
Page 27 and 28: From the practical view, the less t
Page 29 and 30: CHAPTER 2 PROBLEM DEFINITION AND PR
Page 31 and 32: as switching devices instead of ant
Page 33 and 34: Directly Connected Clients 35 33 30
Page 35 and 36: 2.2.2 Harmonic Filtration A pure si
Page 37 and 38: components dramatically. The follow
Page 39 and 40: 20A 20A 15A 15A Line Current 10A Li
Page 41 and 42: VS RS XS VL Source Load IL Ic Compe
Page 43 and 44: a couple of cycles. However, at lea
Page 45 and 46: i + + VT - T1 T2 V + VC - L C Figur
Page 47 and 48: 2.15 shows that there are some comp
Page 49 and 50: waveform directly follows the sourc
Page 51 and 52: is known as copper loss of the tran
Page 53 and 54: components parallel to the thyristo
Page 55 and 56: Ls Coupling Transformer V TCR TSC L
Page 57 and 58: +1.0 Reactive Power, Q (pu) Inducti
Page 59 and 60: V V max V max = voltage limit I Cma
Page 61 and 62: power system. Voltage source conver
Page 63 and 64: timing of switching must be when th
Page 65 and 66: Table 3.1: Type of the excavators a
Page 67 and 68: 3.3 Selection Criterion of Capacito
Page 69 and 70: minutes should be given to self-dis
Page 71 and 72:
possible in order to achieve a tran
Page 73 and 74:
advantage. It is not affected by th
Page 75 and 76:
(a) (b) Figure 3.7: PSCAD model of
Page 77 and 78:
this value is at least twice of the
Page 79 and 80:
of the reverse recovery current and
Page 81 and 82:
curve in its datasheet should be ta
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Figure 3.13: The current distributi
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stays in inductive or capacitive re
Page 87 and 88:
”ENB A, ENB B and ENB C” are co
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3.7 Key Points in Design of TSC Cab
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chapter, some basic calculations to
Page 93 and 94:
CHAPTER 4 EXPERIMENTAL RESULTS 4.1
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(a) Contactor Switched Plain Capaci
Page 97 and 98:
ated capacitor current. This inrush
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current. Line-to-line voltage is al
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(a) Three phase current waveform at
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4.2.2 Contactor Switched Shunt Filt
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to high inrush current causes a con
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(a) Voltage Waveform across the cap
Page 109 and 110:
Page 111 and 112:
This transient has also negligible
Page 113 and 114:
(a) Three phase current waveform at
Page 115 and 116:
Figure 4.17: Resultant 3φ Capacito
Page 117 and 118:
Page 119 and 120:
Figure 4.21: Resultant line-to-line
Page 121 and 122:
Figure 4.24: Firing pulses, voltage
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566 uF 2x6.0 MVA TM 34.5 kV 500 / 5
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Experimental results will be presen
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+1.6 +0.66 Thyristor Voltage (kV) -
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+1.5 +1.0 Capacitor Voltage (kV) +0
Page 131 and 132:
+1.5 +1.0 Capacitor Voltage (kV) +0
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increase in current can be approxim
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would be given to the supply voltag
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250 1 cycle transient fft 200 I Pha
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4.4 TSC Cabinet Interior Equipment
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4.5 Discussion In contactor or thyr
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• Delta-connected TSC topology is
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[13] Tabandeh, M., Alavi, M.H., Mar
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[38] Bilgin, H.F., “Design and Im
Page 149 and 150:
Since the roots of this equation ar
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APPENDIX B DISTINCTIVE CURVES OF TH
Page 153 and 154:
135 Figure B.2: Stored charge and r
Page 155 and 156:
APPENDIX C DETAILS OF THE CONTROL C
Page 157 and 158:
139 Figure C.2: P-CAD 2002 Schemati
Page 159 and 160:
Page 161 and 162:
Page 163 and 164:
Page 165 and 166:
147 Figure C.10: P-CAD 2002 Schemat
Page 167 and 168:
149 Figure D.1: General view of the
Page 169 and 170:
APPENDIX E APPLICATION MODEL OF THE
Page 171 and 172:
153 Figure E.2: 3 dimensional plot
Page 173 and 174:
155 Figure F.1: Installed SVC syste
Page 175 and 176:
157 Figure F.3: Installed SVC syste
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