optimal allocation and sizing of statcom for power system dynamic performance enhancement

184 Pages·2013·10.99 MB·English

OPTIMAL ALLOCATION AND SIZING OF STATCOM
FOR POWER SYSTEM DYNAMIC PERFORMANCE
ENHANCEMENT

by
Sebastian Wildenhues

A thesis submitted in partial fulfillment of the requirements for the degree of

MASTER OF SCIENCE
in
ELECTRICAL ENGINEERING

University of Duisburg-Essen
Department Electrical Engineering and Information Technology
Institute of Electrical Power Systems

Referents:
Univ. Prof. Dr.-Ing. habil. István Erlich
Prof. Dr.-Ing. Holger Hirsch

Advisor:
Dr.-Ing. José L. Rueda
ABSTRACT

Deregulation and liberalization of the electricity markets, fundamentally changing patterns in
production, as well as an ever-increasing power demand and pronounced environmental
awareness lead to significant challenges for today’s utilities. Studies of recent blackouts
revealed an intricate relationship existing between insufficient reactive power support and
unreliable system operation. Besides, the disappearance of large central generating units in
some countries introduces a strong demand for strategic implementation of devices providing
enhanced control actions concerning the dynamic security and performance of power systems
during emergencies. The question, however, is not only to determine, if a compliant system
state can be reached in such frameworks, but rather to find out, how this can be achieved in a
cost-optimal fashion. This study is therefore devoted to the problem of joint optimal
determination of location and size of multiple dynamic VAr sources.
It develops an integrated multi-contingency approach using STATCOM that rigorously
exploits technical requirements while ensuring optimality of investments. First, a set of
credible disturbances is filtered out through an alternative formulation of contingency
severity index (CSI). Recent heuristic Mean-Variance Mapping optimization (MVMO)
algorithm is then applied in combination with an intervention scheme ensuring efficient
utilization of computational resources, which is essential due to consideration of the full
dynamic system model. A so called Trajectory Violation Integral (TVI) is introduced to
determine solution’s feasibility and continuously control the evolutionary search process.
The methodology is applied to the IEEE New England 39-Bus test system while
PowerFactory and Matlab software packages are used. Fast and robust communication is
realized by an user-written C++-interface. The results show sensitivities of STATCOM
allocation with respect to three major factors, including: fault clearing time, transient voltage
requirements and dynamic load portion. Finally, cost versus dynamic performance benefit is
further improved by introducing a method that explicitly makes use of economies of scale:
large devices are preferred over smaller ones attained from the optimization by proper
adjustment of voltage control droop characteristics. An adaptive search space modification
ensures that the iterative concentration proceeds in a controlled and reasonable way.
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KURZFASSUNG

Die Deregulierung und Liberalisierung der Energiemärkte, eine sich grundlegend wandelnde
Erzeugungsstruktur, sowie der stetig zunehmende Bedarf nach elektrischer Energie bei
gleichzeitig ausgeprägtem Umweltbewusstsein der Bevölkerung stellen die Netzbetreiber vor
erheblichen Herausforderungen. Studien von neulich eingetretenen Blackouts deuten darauf
hin, dass sich eine unzuverlässige Betriebsweise in näherem Zusammenhang bringen lässt
mit der unzureichenden Bereitstellung von Blindleistung. Daneben besteht in einigen
Ländern durch den Wegfall konventioneller Großkraftwerke die starke Notwendigkeit,
strategisch Maßnahmen vorzusehen, welche das dynamische Verhalten, und damit
insbesondere die betriebliche Sicherheit im Falle von Störereignissen, d.h. Netzfehlern,
betreffen. Grundsätzlich stellt sich jedoch nicht allein die Frage, ob sich angesichts dieser
Rahmenbedingungen ein den technischen Regeln entsprechender Systemzustand
herbeiführen lässt, sondern zunehmend auch, wie dies mit Blick auf ein ganzheitliches
Optimum umzusetzen ist. Daher widmet sich diese Untersuchung der Frage zur
gleichzeitigen und optimalen Bestimmung von Einbauort sowie Größe mehrerer
Einrichtungen für die dynamische Blindleistungskompensation.
Es wird ein integrierter Mehrfehler-Ansatz unter Verwendung von STATCOMs entwickelt,
der die auferlegten technischen Anforderungen auf kostenoptimale Weise einzuhalten im
Stande ist. Nachdem ein Satz kritischer Fehler festgelegt worden ist, wird das kürzlich
vorgestellte heuristische Mean-Variance Mapping Optimierungsverfahren (MVMO)
angewandt und kombiniert mit einer Interventionsstrategie, welche effizienten Nutzen von
den vorhandenen Rechenkapazitäten macht. Letzteres stellt einen entscheidenden Aspekt dar,
da das vollständig ausmodellierte Elektroenergiesystem zum Einsatz kommt. Weiterhin wird
eine integrale Größe eingeführt, welche einerseits die technische Machbarkeit eines MVMO-
Vorschlags aufzeigt, als auch den Suchprozess in kontinuierliche Weise steuert. Angewandt
auf das IEEE New England 39 Knoten Testnetz, liefern die Ergebnisse anschaulich
Sensitivitäten der vorgeschlagenen Installationen bezüglich Fehlerklärungsdauer, Strenge der
Spannungsanforderung, sowie dem Anteil der dynamischen Last an der Gesamtlast.
PowerFactory und Matlab werden verwendet, wobei eine selbstentwickelte C++-Schnittstelle
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der schnellen und robusten Kommunikation dient. Schließlich lässt sich das Kosten-Nutzen-
Verhältnis der dynamischen Blindleistungs-bereitstellung weiter verbessern, indem explizit
von den sich ergebenden Skaleneffekten Gebrauch gemacht wird: große STATCOM-
Einheiten werden begünstigt gegenüber kleineren durch angemessene Anpassung der
Spannungsstatiken in den zugehörigen Reglern. Dabei stellt eine adaptive Anpassung des
Suchraumes sicher, dass der iterative Prozess in koordinierter und begründeter Weise abläuft.
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TABLE OF CONTENTS

ABSTRACT .........................................................................................................................................................II
KURZFASSUNG ............................................................................................................................................... III
TABLE OF CONTENTS .................................................................................................................................... V
LIST OF TABLES .......................................................................................................................................... VIII
LIST OF FIGURES ........................................................................................................................................... IX
LIST OF ABBREVIATIONS ........................................................................................................................ XIV
1 INTRODUCTION..................................................................................................................................... 15
1.1 GENERAL ASPECTS .............................................................................................................................. 15
1.2 PROBLEM FIELD ................................................................................................................................... 16
1.3 MOTIVATION ....................................................................................................................................... 19
1.4 SCOPE OF THE THESIS .......................................................................................................................... 20
1.5 SUMMARY OF THE FOLLOWING CHAPTERS .......................................................................................... 22
2 MODELS AND TOOLS ........................................................................................................................... 23
2.1 POWER SYSTEM STABILITY CLASSIFICATION ...................................................................................... 23
2.2 IEEE NEW ENGLAND 39-BUS TEST SYSTEM ....................................................................................... 25
2.3 STATIC SYNCHRONOUS COMPENSATOR (STATCOM) ........................................................................ 27
2.3.1 Principle of Operation ............................................................................................................... 27
2.3.2 Improvement of Transient Stability Margin ............................................................................... 29
2.3.3 Modeling and Control ................................................................................................................ 33
2.3.4 Investment Costs ......................................................................................................................... 43
2.4 LOADS ................................................................................................................................................. 44
2.4.1 Static Portion ............................................................................................................................. 46
2.4.2 Dynamic Portion ........................................................................................................................ 47
2.5 MEAN-VARIANCE MAPPING OPTIMIZATION ........................................................................................ 50
2.5.1 Why to use a Heuristic Optimization / Evolutionary Computation? .......................................... 51
2.5.2 Introduction to the Algorithm ..................................................................................................... 53
2.5.3 Swarm Variant MVMOS ............................................................................................................. 57
2.6 SIMULATION AND OPTIMIZATION ENVIRONMENT ................................................................................ 59

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3 CONTINGENCY ASSESSMENT ........................................................................................................... 62
3.1 GENERAL ASPECTS .............................................................................................................................. 62
3.2 INTEGRAL BASED APPROACH ............................................................................................................... 64
3.2.1 Definition of CSI......................................................................................................................... 65
3.2.2 Numerical Results ...................................................................................................................... 67
4 OPTIMAL ALLOCATION AND SIZING OF STATCOM FOR POWER SYSTEM DYNAMIC
PERFORMANCE ENHANCEMENT .............................................................................................................. 73
4.1 GENERAL ASPECTS .............................................................................................................................. 73
4.2 IMPLEMENTATION ................................................................................................................................ 75
4.2.1 Voltage Trajectory Boundary ..................................................................................................... 75
4.2.2 Problem Formulation ................................................................................................................. 76
4.2.3 Handling of Feasible and Infeasible Individuals ....................................................................... 78
4.2.4 Procedure ................................................................................................................................... 81
4.2.5 Specification of Candidate Locations ......................................................................................... 83
4.2.6 Integrated Mixed-Integer Search Strategy ................................................................................. 84
4.3 NUMERICAL RESULTS .......................................................................................................................... 92
4.3.1 General Aspects ......................................................................................................................... 92
4.3.2 MVMO Parameter Tuning.......................................................................................................... 93
4.3.3 Effect of Intervention Strategy .................................................................................................. 117
4.3.4 Impact of Set of Contingencies ................................................................................................. 121
4.3.5 Problem Space I: Fault Clearing Time and Dynamic Load Portion ........................................ 124
4.3.6 Problem Space II: Voltage Requirements and Dynamic Load Portion .................................... 131
4.3.7 Pre-/Post-OASDPE Dynamic Performance ............................................................................. 133
5 IMPROVED UTILIZATION OF STATCOM AND FURTHER COST REDUCTION BY
CASCADED OASDPE ..................................................................................................................................... 139
5.1 GENERAL ASPECTS ............................................................................................................................ 139
5.2 IMPLEMENTATION .............................................................................................................................. 140
5.2.1 Procedure ................................................................................................................................. 140
5.2.2 Voltage Control Gain Adaption ............................................................................................... 142
5.2.3 Search Space Adaption ............................................................................................................. 143
5.3 NUMERICAL RESULTS ........................................................................................................................ 145
5.3.1 Investment Costs ....................................................................................................................... 145
5.3.2 Evolution of Search Progress ................................................................................................... 147
6 CONCLUSIONS AND FUTURE WORK ............................................................................................ 153
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LIST OF REFERENCES ................................................................................................................................. 158
APPENDICES .................................................................................................................................................. 165
APPENDIX I IEEE NEW ENGLAND 39-BUS TEST SYSTEM ........................................................................ 165
APPENDIX II STATCOM MODEL IN DSL ................................................................................................. 174
APPENDIX III NUMERICAL RESULTS ........................................................................................................... 176
EIDESSTATTLICHE ERKLÄRUNG ........................................................................................................... 184

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List of Tables

Table 2.1 Exponents describing Polynomial Static Load Model ............................................ 47
Table 2.2 Parameters of Induction Motor’s Equivalent Circuit representing Dynamic Portion
of Load ............................................................................................................................ 50
Table 4.1 Samples for Discussion of Integrated Mixed-Integer Search ................................. 87
Table 4.2 Search Paradigms and Classification of Study Cases for Parameter Tuning ......... 96
Table 4.3 MVMO Parameter Settings .................................................................................. 117
Table A.1 Generator Operational Data ................................................................................. 165
Table A.2 Generator Type Data (1) ...................................................................................... 165
Table A.3 Generator Type Data (2) ...................................................................................... 165
Table A.4 Parameters of Power System Stabilizer ............................................................... 166
Table A.5 Parameters of ESDC1A Field Excitation System (1) [47] ................................... 166
Table A.6 Parameters of ESDC1A Field Excitation System (2) ........................................... 167
Table A.7 Parameters of Turbine-/Governor System ........................................................... 167
Table A.8 Transformer Type Data (OLCTs’ Data not listed) .............................................. 168
Table A.9 Line Type Data .................................................................................................... 168
Table A.10 Static Portion of Total Load, P .......................................................................... 169
Table A.11 Static Portion of Total Load, Q .......................................................................... 170
Table A.12 Dynamic Portion of Total Load, Aggregate Motor Ratings (1) ......................... 171
Table A.13 Dynamic Portion of Total Load, Aggregate Motor Ratings (2) ......................... 171
Table A.14 Dynamic Portion of Total Load, Aggregate Motor Inertias (1) ......................... 172
Table A.15 Dynamic Portion of Total Load, Aggregate Motor Inertias (2) ......................... 173
Table A.16 Derived Statistics corresponding to top of Figure 4.33 ..................................... 176
Table A.17 MVMO Parameter Allocation for Establishment of Problem Space I .............. 177

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List of Figures

Figure 1.1 Classification of Power System Stability [5]......................................................... 24
Figure 2.1 IEEE New England 39-Bus Test System .............................................................. 25
Figure 2.2 a) Schematic of STATCOM; b) Representation as Voltage Source and Reactance;
c) Basic Vector Diagram neglecting Losses ................................................................... 27
Figure 2.3 Voltage-Current Characteristic of STATCOM (left) and SVC (right) ................. 28
Figure 2.4 Midpoint- STATCOM (left) and SVC (right) ....................................................... 30
Figure 2.5 Power-Angle Curves of Midpoint STATCOM (left) and SVC (right) of same
Rating .............................................................................................................................. 31
Figure 2.6 Effectiveness of Midpoint STATCOM (left) and SVC (right) of same Rating for
the Improvement of Transient Stability Margin (TSM) ................................................. 32
Figure 2.7 STATCOM Topology in PowerFactory Software ................................................ 34
Figure 2.8 STATCOM Circuit ................................................................................................ 35
Figure 2.9 STATCOM Control Structure ............................................................................... 37
Figure 2.10 DC Circuit ........................................................................................................... 38
Figure 2.11 DC (top) and AC (bottom) Voltage Controller ................................................... 39
Figure 2.12 Unit Tripping in STATCOM Control.................................................................. 40
Figure 2.13 Current Controller ............................................................................................... 42
Figure 2.14 STATCOM Investment Cost Modeling with Assumptions ................................ 43
Figure 2.15 Static and Dynamic Portion of Load in PowerFactory Software ........................ 44
Figure 2.16 Torque-Speed (Slip) Characteristics of Induction Machine ................................ 48
Figure 2.17 Equivalent Circuit of Induction Machine ............................................................ 48
Figure 2.18 Example of a Deceptive Solution Space as explored by MVMO [53]................ 52
Figure 2.19 Flowchart of MVMO ........................................................................................... 54
Figure 2.20 Set of MVMO Mapping Functions along 1000 Function Evaluations The search
progresses from yellow (early stage) to red (final stage). ............................................... 55
Figure 2.21 Creation of Offspring in MVMOS ....................................................................... 58
Figure 2.22 Simulation and Optimization Environment ......................................................... 60
Figure 2.23 Real-Time Visualization of Relevant Quantities ................................................. 61
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Figure 3.1 Principle of Integral Based Severity Index for Contingency Assessment ............. 64
Figure 3.2 Contingency Selection Procedure.......................................................................... 66
Figure 3.3 Study Case a Mean of Bus Voltages corresponding to N-1 Line Contingencies
(top) Ranked CSI (bottom) ............................................................................................. 68
Figure 3.4 Study Case b Mean of Bus Voltages corresponding to N-1 Line Contingencies
(top) Ranked CSI (bottom) ............................................................................................. 69
Figure 3.5 Absolute CSI t = [0.1..0.11..0.15] sec,  = 0.3 p.u. ........................................ 71
Cl dyn
Figure 3.6 CSI t = [0.1..0.11..0.15] sec,  = 0.3 p.u. ........................................................ 72
Cl dyn
Figure 4.1 OASDPE Operation as Graphical Interpretation of Transient Voltage Responses73
Figure 4.2 Voltage Trajectory Boundary Function ................................................................. 76
Figure 4.3 MVMO Archive Update ........................................................................................ 78
Figure 4.4 OASDPE Procedure .............................................................................................. 81
Figure 4.5 Candidate Specification Procedure........................................................................ 84
Figure 4.6 Integrated Mixed-Integer Search (1) ..................................................................... 86
Figure 4.7 Integrated Mixed-Integer Search (2) ..................................................................... 87
Figure 4.8 Impact of th t = 0.15 sec,  = 0.5 p.u.,  = 0.05 5 Stochastically Independent
u Cl dyn
Runs ................................................................................................................................ 89
Figure 4.9 Impact of th t = 0.1 sec,  = 0 p.u.,  = 0.05 (top) t = 0.15 sec,  = 0.5
l Cl dyn Cl dyn
p.u.,  = 0.05 (bottom) 5 Stochastically Independent Runs ............................................ 91
Figure 4.10 MVMO Parameter Tuning Procedure ................................................................. 95
Figure 4.11 Study Cases for Parameter Tuning: a (top); b (middle); c (bottom) Minimum of
Bus Voltages corresponding to N-1 Line Contingencies ................................................ 97
Figure 4.12 Variation of M, Study Case a Mean of Fitness 10 Stochastically Independent
Runs ................................................................................................................................ 98
Figure 4.13 Study Case a Minimum of Bus Voltages along Search Progress for n = 1 (top)
p
Reactive Power Contribution along Search Progress for n = 1 (bottom) ...................... 99
p
Figure 4.14 Variation of M, Study Case b Mean of Fitness; bottom: Fitness and Best
Allocation for M = 5 (top) 10 Stochastically Independent Runs .................................. 101
Figure 4.15 Variation of M, Study Case b Calculation Time corresponding to 10
Stochastically Independent Runs (top) ......................................................................... 103
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