Simulating Nonlinear Circuits with Python Power Electronics: An Open-Source Simulator, Based on Python™

219 Pages·2018·5.6 MB·English

Shivkumar V. Iyer
Simulating
Nonlinear Circuits
with Python Power
Electronics
An Open-Source Simulator, Based
on Python™
Simulating Nonlinear Circuits with Python Power
Electronics
Shivkumar V. Iyer
Simulating Nonlinear
Circuits with Python Power
Electronics
An Open-Source Simulator, Based
™
on Python
123
ShivkumarV.Iyer
Ontario
Canada
ThisbookisbasedonthefreeandopensourcesoftwarePythonPowerElectronicshostedat
the websitehttp://www.pythonpowerelectronics.com
ThesoftwarehasbeenreleasedundertheBSD3.0licensewhichbefoundintheLicensefile
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ISBN978-3-319-73983-0 ISBN978-3-319-73984-7 (eBook)
https://doi.org/10.1007/978-3-319-73984-7
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To Rakhat
Acknowledgements
IwouldliketothankProf.BinWuandProf.BalaVenkateshoftheDepartmentof
Electrical and Computer Engineering, Ryerson University, for their interest and
supportinthedevelopmentofPythonPowerElectronics.Iwouldalsoliketothank
Dr. Dan McGillivray who was the Executive Director of the Centre for Urban
Energy, Ryerson University, for the many conversations we had related to the
potential of the software. I would like to thank Mukundan R. of the National
InstituteofIndustrialEngineering forhisconstantadvice andsuggestions.Iwould
like to thank Zoubin Zarin for his advice in developing the software and with
publishingthisbook.IwouldliketothankJanamejayaCforbeingaloyalfollower
of the project and his constant encouragement. I would like to thank the Python
communityanditsmanyactivemembersforalltheirsupportandforhavingmeas
a speaker in PyCon Canada 2016 and PyCon Canada 2013.
Shivkumar V. Iyer
vii
Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 Concept Behind Simulation. . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 The Reason for Simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.3 Simulation in Power Electronics and the Challenges. . . . . . . . . . 5
1.4 Python Power Electronics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.5 Outline of the Book . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.6 About the Book . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2 Introduction to Python . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2.2 Overview of Python . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.3 Getting Started . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.4 Integers, Floats, and Strings . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
2.5 Lists and Tuples. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.6 Dictionaries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
2.7 Examples of Python Code in the Simulator—Lists
and Matrices. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
2.8 Examples of Python Code in the Simulator—Strings . . . . . . . . . 26
2.9 Examples of Python Code in the Simulator—Dictionaries. . . . . . 30
2.10 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
3 User Interface. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
3.2 Circuit Representation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
3.3 Processing of Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
3.4 Data Structures of Components . . . . . . . . . . . . . . . . . . . . . . . . . 42
3.4.1 Resistor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
3.4.2 Inductor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
3.4.3 VoltageSource . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
3.4.4 Capacitor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
ix
x Contents
3.4.5 Ammeter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
3.4.6 Voltmeter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
3.4.7 VariableResistor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
3.4.8 VariableInductor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
3.4.9 ControlledVoltageSource . . . . . . . . . . . . . . . . . . . . . . . 50
3.4.10 Diode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
3.4.11 Switch. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
3.5 Logical Flow of the Simulation . . . . . . . . . . . . . . . . . . . . . . . . . 52
3.5.1 Launch Simulator. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
3.5.2 Simulation Parameters . . . . . . . . . . . . . . . . . . . . . . . . . 53
3.5.3 Create Component Objects . . . . . . . . . . . . . . . . . . . . . . 54
3.5.4 Circuit Parameters File . . . . . . . . . . . . . . . . . . . . . . . . . 55
3.5.5 Update Component Parameters . . . . . . . . . . . . . . . . . . . 55
3.6 Iterative Procedure During the Simulation . . . . . . . . . . . . . . . . . 56
3.6.1 Simulation Time Instant . . . . . . . . . . . . . . . . . . . . . . . . 57
3.6.2 Update Branch Data. . . . . . . . . . . . . . . . . . . . . . . . . . . 57
3.6.3 Generate Input Voltage. . . . . . . . . . . . . . . . . . . . . . . . . 57
3.6.4 Run Control Code . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
3.6.5 Perform Circuit Analysis . . . . . . . . . . . . . . . . . . . . . . . 58
3.6.6 Update Component Objects . . . . . . . . . . . . . . . . . . . . . 59
3.6.7 Write Output Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
3.7 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
4 Interface for User Control Functions . . . . . . . . . . . . . . . . . . . . . . . . 63
4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
4.2 Inclusion of Control in the Simulator. . . . . . . . . . . . . . . . . . . . . 64
4.3 Special Variables in Control Code. . . . . . . . . . . . . . . . . . . . . . . 69
4.4 Time Scheduling Control Code . . . . . . . . . . . . . . . . . . . . . . . . . 74
4.5 Interfacing Control Code. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
4.6 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
5 Case Study—Shunt VAR Compensator . . . . . . . . . . . . . . . . . . . . . . 85
5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
5.2 Description of the Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
5.3 Parameters of the Simulation and the Circuit . . . . . . . . . . . . . . . 89
5.4 First Stage in Control Development—Grid Synchronization . . . . 94
5.5 Second Stage in Control Development—Current Reference
Generation and Closed-Loop Current Control. . . . . . . . . . . . . . . 102
5.6 Final Stage of Control Development—The Entire Circuit
with the VSC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114
5.7 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128
6 Nodes, Branches, and Loops. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131
6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131
6.2 Jump Labels. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132
Contents xi
6.3 Nodes and Branches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135
6.4 Short Branches and Nodes . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139
6.5 Connectivity Map for Nodal Analysis . . . . . . . . . . . . . . . . . . . . 141
6.6 Loops . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144
6.7 Loop Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153
6.8 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155
7 Circuit Analysis—Loop Analysis. . . . . . . . . . . . . . . . . . . . . . . . . . . . 157
7.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157
7.2 Matrices for Loop Analysis. . . . . . . . . . . . . . . . . . . . . . . . . . . . 159
7.3 Solving the Matrix Equation . . . . . . . . . . . . . . . . . . . . . . . . . . . 163
7.4 Mapping Branch Currents and Loop Currents. . . . . . . . . . . . . . . 167
7.5 Effects of Time Constants on Loop Analysis . . . . . . . . . . . . . . . 170
7.6 Effect of Stiff Loops . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173
7.7 Loop Manipulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175
7.8 Limitation of Loop Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . 180
7.9 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182
8 Circuit Analysis—Nodal Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . 185
8.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185
8.2 Concept of Nodal Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186
8.3 Limitation of Loop Analysis in Nonlinear Circuits . . . . . . . . . . . 190
8.4 Applying Nodal Analysis in Nonlinear Circuits . . . . . . . . . . . . . 193
8.5 Continuing with Loop Analysis. . . . . . . . . . . . . . . . . . . . . . . . . 196
8.6 Event-Driven Circuit Updates . . . . . . . . . . . . . . . . . . . . . . . . . . 200
8.7 Process Flow in the Simulator. . . . . . . . . . . . . . . . . . . . . . . . . . 202
8.8 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204
9 Conclusions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207
9.1 Advantages of the Simulator . . . . . . . . . . . . . . . . . . . . . . . . . . . 207
9.2 Drawbacks of the Simulator and Scope for Future Work. . . . . . . 209
9.3 Future of the Project. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212
Bibliography .. .... .... .... ..... .... .... .... .... .... ..... .... 215
Chapter 1
Introduction
Abstract Thischapterintroducestheconceptofsimulationbydescribingitsuse-
fulness with a few general engineering examples. The chapter then describes the
current stateof the power systemand the recent changes thathave occurred along
withthechangesthatareexpectedinthefuture.Thechapterdescribesthechallenge
oftacklingclimatechangewithrenewableenergyandtherecentadvancesinwind
andsolarenergy.Withthisbackground,thechapterintroducesPythonPowerElec-
tronicsanddescribestheusefulnessofafreeandopen-sourcecircuitsimulatorand
buildingacommunityofpowerengineers.
· · ·
Keywords Simulation Modernpowersystems Renewableenergy Climate
· · ·
change Smartgrids Powerquality Open-sourcetechnology
1.1 ConceptBehindSimulation
Simulationfromitsbasicdefinitionistheimitationofanactualprocess.Inmodern
times,thesoftwaredefinitionofsimulationisalsoavailable—therepresentationof
the behavior or characteristics of one system through the use of another system,
especially a computer program designed for the purpose. Though most engineers
spendasignificantamountoftimesimulatingthesystemstheystudy,simulationas
theabove-definedconceptissomethingalmosteveryonehasbeenexposedtoatsome
pointoftime.Simulationbyitsdefinitioniswhenareal-worldprocessisrepeated.
Letuslookatsomeexamplesofsimulationthatweneverstoppedtothinkabout.
For most of us who were born when computers were ubiquitous household
machines,thefirstformofsimulationsiscomputergames.Acomputergamemay
be a car racing game, a war or fighting game, playing chess against the computer,
oroneofthestrategygamesthathavebecomeverypopularrecently.Almostallof
theseareimitationsofreal-worldevents.Behindthefancygraphicsandthecelebrity
statuscharactersliesaverycomplexalgorithmthatcreatestheenvironmentwhere
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S.V.Iyer,SimulatingNonlinearCircuitswithPythonPowerElectronics,
https://doi.org/10.1007/978-3-319-73984-7_1