Efficiency, Control, and Stability of Power Electronic Based SystemsIEEE COMPEL 2016 Trondheim Norway6-28-2016
Mohamed Belkhayat Ph. D.Research Engineer VI
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Outline
• Efficiency– Various Platforms– PWM Topologies and Techniques
• Power Density
• Control– Simple feedback, feed-forward, cross coupled, multi-loop control, network control
• Stability– DC Systems– AC Systems
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Efficiency: Electric Vehicles, KW Range
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Constant Power Loads and Negative Impedance Instability in Automotive Systems: Definition, Modeling, Stability, Ali Emadi, Et Al. IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY, VOL. 55, NO. 4, JULY 2006
https://commons.wikimedia.org/wiki/File:AaronsPrius.jpg
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Dream Liner 787: MW Range
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• Electric Engine Start
• Electric Wing Ice Protection
• Electric AC
• Electric Driven Hydro-Pumps
• Elimination of Pneumatic Bleed System
• Flight Control Actuators
• Avionics
• Electric Brakes
• Cabin Air Compressor
Boeing 787 has a approximately 1 MW of Power Electronic Loads
* Future Aircraft Power Systems- Integration ChallengesKamiar J. Karimi, PhD Senior Technical FellowThe Boeing Company 2007
Artwork: https://commons.wikimedia.org/wiki/Boeing_787#/media/File:All_Nippon_Airways_Boeing_787-8_Dreamliner_JA801A_OKJ.jpg
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Naval Platforms: ONR Global
CAPT Lynn Petersen
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Naval Platforms: ONR Global
CAPT Lynn Petersen
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Marine Power Systems Trends
PT
PTRedu
ctio
n G
ear
TG
TG ACGen
ACGen
Load
Motor
Load
Motor
Elec
tric
M
otor
PTG
PTG DCGen
DCGen
Load
Motor
Load
Motor
Conv
erte
r
Converter
Converter
Converter
Converter
Then - Good Stability/Power Quality Issues/Relatively Inefficient
Now - Possible Instabilities/High Power Quality/High Efficiency
Commercial Power Systems
Then - Good Stability/Power Quality Issues/Relatively Inefficient
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Now - Possible Instabilities/High Power Quality/High Efficiency
9Efficiency Trends in Power Converters
Extreme Efficiency Power Electronics IEEE (2012)J. W. Kolar, F. Krismer, Y. Lobsiger, J. M¨uhlethaler, T. Nussbaumer, J. Minib¨ock∗
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Power Density
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Efficiency, Control, and Stability
Inefficient
Easy to Control
Efficient
Harder to Control
Artwork: https://commons.wikimedia.org/wiki
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Efficiency, Control and Stability
Inefficient
Easy to Control
Efficient
Harder to Control
Artwork: https://commons.wikimedia.org/wiki
13Common Low Level Controls PWM
https://en.wikipedia.org/wiki/Space_vector_modulation
Simple Analytical and Graphical Toolsfor Carrier Based PWM MethodsAhmet M. Hava, Russel J. Kerkman, Thomas A LipoIEEE Transations on Power Electronics 1999
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Notional Power Electronic Converter Controls
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• Power Density
• Efficiency
• Optimum Control– PWM– ABC/DQ– Soft Start– Improved Load Step– Synchronization– Voltage Droop– Frequency Droop– Parallel Sharing– Phase Balancing– Stability
Rectifier B/B Stage Inverter
ICN
VCN
Transient Droop
Steady State Droop
Synchronization
ABC/DQPWM
Sharing/Phase Balancing
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Notional Maritime Diesel Generators Controls
• Power Density
• Efficiency
• Optimum Control– Fast Start– Improved Load Step– Synchronization– Voltage Droop– Speed Droop– Protection– Stability
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Engine Generator
AVRGOV
Transient Droop
Steady State Droop
Synchronization
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Maritime Grid System Stability
• Time Domain- Systems are simulated in Time Domain
– Nonlinearities included– Voltage, frequency, and
rotor angle stability– Linearized and
eigenvalues assessed
• Frequency Domain-Systems are linearized at an operating point.
– Systems are injected in time domain or
– Transfer function are generated using Jacobian
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TG
TG ACGen
ACGen
ES
Motor
Load
Motor
Converter
Converter
Converter
Converter
Converter
Negative Incremental Resistance
Power Electronics based systems are prone to negative impedance instability due to the constant-power load (CPL) nature and energy storage or filters present in the system.
A CPL example is a DC/AC inverter, which drives an electric motor and tightly regulates motor speed When input power voltage increases/decreases, input current decreases/increases This has a destabilizing effect on the system (source) connected to the CPL .This is referred to as “negative impedance instability”.
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18Brief History Of Impedance Methods• 1932 Nyquist stability criterion
• 1976 Middlebrook criterion for stability of DC power converter with input filter
• 1970- Virginia Tech, NSWC, Purdue and others advanced and implemented less conservative criteria
• 1977 MacFarlane, Generalized Nyquist
• 1990 John Caroll states opposing argument criterion for distributed systems
• 1994 Yao and Davat look at the application of GN to Power systems
• 1995 Mike Williams develops suppressed-carrier injection techniques • for AC system stability but not in DQ
• 1997- Purdue University, Virginia Tech extend Middlebrook criterion to AC systems using Generalized Nyquist and DQ impedances.
• 2000-P Measurement: V. Tech Boeing/NNS, Williams (Patent), NNS/UM (Corzine) (Patent), FSU CAPS (Patent) Others
• 2010-P Positive/Negative Sequence: RPI (sun), NTNU (Molinas), others..
DC
AC
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Impedance Based Methods:
DC Systems -• Make one perturbation (voltage/current) in the system• Measure the responses at the interface• Calculate the impedances
AC Systems -• DQ Method• Sequence, Modified Sequence • Impedance mapping, harmonic linerization (DC2ABC)• DQ2DC ideal converter
All frequencies creating instability are determined.
Benefits Over Fielded Stability Methods:• Satisfies the open architecture business model• Ensures system stability before system integration• Reduces integration and tuning cost• Provides a measure of stability in terms of margins.
Additional Applications:• Offers assessment of power quality, imbalances, and saturation effects • Facilitates control design, and EMI filter design• Provides model verification validation of critical components
Impedance Based Stability Assessment
Stand-Alone ConverterMiddlebrook
+-
vs
+v- Converter
+vL
-R
Pin Pout
i
Filter
is
vL = hc vvoc = hf vs
ZZ
vv
h hZ Z
L
s
f c
s i=
+1 /∞∞< <<-for 1/ ωis ZZ
[MIDD76C] Middlebrook, R. D., Input Filter Considerations in Design and Application of Switching Regulators,
IEEE Industry Applications Society Annual Meeting, October 11-14, 1976, Chicago, IL. IAS
DQ Impedance/Admittance Definitions
eqdS
eqdS
eqd vHiZv ∆+∆=∆ e
qdLeqd vYi ∆=∆
=
dddq
qdqqeqdS ZZ
ZZZ
=
dddq
qdqqeqdL YY
YYY
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Distributed AC/DC Systems Stability
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GeneratorAnd
Controls
Propulsion
Filter/Energy Storage
Propulsion
Propulsion
Propulsion
YqdLZqdL
YqdLZqdL
Ship Service
Ship Service
YqdLZqdL
Combat Load
YqdLZqdL
1
2
4
3
Filter/Energy Storage
GeneratorAnd
Controls
ZY Satisfies the Generalized Nyquist
Open Architecture Business Model
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Measurement: DC Systems
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Inj. Load
24Design and Implementation of Three-Phase AC Impedance Measurement Unit (IMU) with Series and Shunt Injection
24Applied Power Electronics Conference and Exposition (APEC), 2013 Twenty-Eighth Annual IEEE
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Impedance Measurement Unit (IMU)
IMU Background
Challenges: • Stability of power electronics systems• Impedance measurement needed on active
equipment
Solution: • Developed Impedance Measurement Unit • Three Year IRAD with Virginia Tech
Status: • Currently at NNS• Several Engineers were trained on IMU use• Resolved power supply stability issues on critical
systems• Testing is instituted for future platforms
Looking Ahead:• Upgrade Rating of Scaled Prototype IMU• Upgrade Software• Team with Commercial Manufacturer
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DQ Impedance Structures Needed for Various Systems
• Given stability margins find source and load impedances
• DC case algorithms exist
• AC case involves inverse Eigen Value Problem Algorithms still in research
• Structure of DQ impedance is not always symmetric
• Better structure identification is needed
• Better Controls-to-impedance shaping is needed
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+−
+=
sLRLLsLR
e
qdS ωω
Z
( ) ( )( ) ( )
+−
+=
ssLRsLsLssLR
ddb
qbqe
qdS ωω
Z
RL Load or Source
Unregulated Synchronous Generator
Ideal CPL Admittance in QD (Vd=0)
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Suggested Future Topics of Research
• DC Systems: given an architecture automatically assign impedance profile requirements at the various interfaces for a stable integrated system.
• AC Systems:
• A theoretical framework is needed that ties Direct/Quadraturereference frame, Dynamic Phasors, Positive/Negative Sequence, ABC phase domain, and harmonic linearization.
• Decoupling controls and Impedance shaping
• Same as DC systems above
• Measurement: better techniques for both low and high power