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1
Simulation of Power Electronic Systems with
Christian Schaffner, Plexim GmbH
2
Contents
Company PleximSimulation of power electronic systems
ChallengesSystem vs. circuit simulation
Advantages of software PLECSState-space equationsIdeal switches
Control of simulation step size Variable vs. fixed time steps
Simulation of parasitic effectsDiode reverse recovery
Live Demos
3
Who We Are
Start-up in SwitzerlandSwiss Federal Institute of Technology (ETH), ZurichPlexim founded in 2002Customers in more than 25 countries5 employeesProfitable from beginning
PLECSToolbox for SimulinkSimulation of power electronics and electrical drives
4
Development of power electronic systems today
Use of traditional simulation programs:Complicate to operateConvergence problemsLong computation timeExpensive (TCO)
Implications:Need for specialized personnelProducts not optimizedLong time-to-marketExpensive end products
5
System vs. Circuit Simulation
System simulators(MATLAB/Simulink)
⊕ Easy set-up of controllers
Circuit equations must be provided
Circuit simulators(Simplorer, PSpice, Saber)
⊕ Easy set-up of circuit
Incorporation of controllers often difficult
Switch models too detailed
Requirement: Accurate and efficient simulation ofelectrical circuit and control system
PLECS
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Simulink toolbox PLECS
Simulation of power electronic systems in PLECSEvaluation of new conceptsVirtual prototypesPerformance optimization
Controls modeled in SimulinkPost processing in MATLAB
TechnologyC++, Matlab (GUI)FLEXlm (license management)Multiple OS support
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Customer Benefits
PLECS:Ease of useInherently robust algorithmFast simulation (factor 10...100 speed gain)Best cost-benefit ratio for most applicationsExtensibility through open model architecture
⇒ Reduced R&D costsReduced time-to-marketReduced quality costs
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Example: Direct Torque Control
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Working Principle of PLECS
Circuit transformed into state-variable systemOne set of matrices per switch combination
AB C
D
1s
Sw
itch
man
ager
PLECS S-function
Simulink
u
g
y
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High Speed Simulations with Ideal Switches
Conventional continuous diode modeArbitrary static anddynamic characteristicSnubber often required
Ideal diode model in PLECSInstantaneous on/offcharacteristicOptional on-resistanceand forward voltage
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Comparison: Diode Rectifier
Simulation with conventional and ideal switches
Simulation steps:1160 → 153Computation time:0.6s → 0.08s
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Benchmarks
Examples from SimPowerSystemsComparison from ETH Zurich
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Variable Time-Step Simulation: Buck Converter
Transistor conductsDiode blocks
LiLi
DiDu
Du
Di
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Variable Time-Step Simulation: Buck Converter
Transistor opensImpulsive voltage across inductor
LiLi
DiDu
Du
Di
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Variable Time-Step Simulation: Buck Converter
Impulsive voltage closes diode
LiLi
DiDu
Du
Di
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Variable Time-Step Simulation: Buck Converter
Transistor openDiode conducts
LiLi
DiDu
Du
Di
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Variable Time-Step Simulation: Buck Converter
Switch timing Problem:Diode opens too lateImpulsive voltage across inductor
LiLi
DiDu
Du
Di
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Variable Time-Step Simulation: Buck Converter
Zero-Crossing Detection:Time-step is reducedDiode opens exactly at the zero-crossing
LiLi
DiDu
Du
Di
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Innovation Built into PLECS
Combination of existing concepts:Power semiconductors modeled as ideal switchesCircuit as explicit differential equationsVirtual Dirac voltages for diode control
Innovation: Concepts above made feasible throughOwn algorithmsNumerical methods
Outlook:Real-time simulation
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Variable vs. Fixed Time-Step Simulation
Variable Time-Step
⊕ Highest Accuracy
Can get slow for large system
Fixed Time-Step
⊕ Can speed up simulation for large systems
⊕ Hardware controls are often implemented in fixed time-step
Non-sampled switching events (diodes, thyristors) require special handling
Conclusion: Both simulation methods have their application
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Handling of Non-Sampled Switching EventsD
iode
cur
rent
sD
iode
vol
tage
Non-sampledzero-crossing
Backward interpolationDiode 3 starts conducting
Forward stepForward step
Non-sampledzero-crossing
Forward stepBackward interpolationSync. with sample time
Forward step
Backward interpolationDiode 2 stops conducting
Backward interpolationSync. with sample time
Forward step
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Standard Diode Model Characterized by Ron / Vf
Diode turn-off in different blocking conditionsTest circuit:
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Standard Diode Model Characterized by Ron / Vf
Diode turn-off in different blocking conditionsTest circuit:
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Dynamic Diode Model with Reverse Recovery
Behavioral Model
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Dynamic Diode Model with Reverse Recovery
Reverse recovery current and over voltagein different blocking conditions
Behavioral diode model:
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Competitive offerings
designed for power electronics
➼
➼
➼
↓
$➼➼PSIM
$$➼➼PSpice
$$$➼➼SABER
$$➼➼➼Simplorer
$➼➼➼SimPowerSystems
$➼➼➼➼➼➼➼PLECS
cost↓
fast↓
easy to use↓
ideal switches↓
variable time-step↓
fixed time-step↓
open architecture↓
integrated with Simulink
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Reference Customers
Some of our customers:ABBAlstomBombardierBoschConti TEMICHiltiPanasonicPhilipsSiemensSmiths AerospaceTyco Electronic Power S.Vestas Wind Systems
RWTH AachenAalborg UniversityCERNChalmers UniversityDLRTU DresdenFlorida State UniversityGhent UniversityImperial College LondonUniversity of ManchesterPurdue UniversityWarsaw University of Technology
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Application example: Efficiency comparison
Project at ABBAir-cooled MVdrive systemMeasurement oflosses difficultPLECS used forsimulation of
Switching lossesFilter lossesHarmonics
Source: Y. Suh, J. Steinke, P. Steimer: Efficiency comparison of voltage source and current source drive systems for medium voltage applications, EPE 2005 Photo: ABB
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Application example: Optimum controller design
Project at ABB Corporate ResearchMultilevel AC-DC converter system with 16 stages12 switches per stage⇒ 192 independent switches
Simulink used for controlsPLECS used for electricalcircuit
Source: O. Aydin, A. Akdag, P. Stefanutti, N. Hugo: Optimum controller design for a multilevel AC-DC converter system, APEC 2005
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Outlook
Continuous research
Behavioral device models (Q2 2006)Diode with reverse recovery
Thermal simulation (Q3 2006)Switching losses
Real-time simulation (Q1 2007)Project with ETH Zurich funded by Swiss government
Magnetic circuit simulation (Q3 2007)Saturation, hysteresis
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Thank you
i-Math Pte Ltd (Sole Distributor for PLECS in ASEAN region)10 Ubi Crescent #06-37Ubi TechPark Lobby C
Singapore 408564Tel: (65) 6742 1250Fax: (65) 6742 1440
Email: [email protected]: www.i-math.com.sg
For more information about PLECS, please contact us at