Small-Signal Modelling and Analysis of DC Distributed Power Systems
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Transcript of Small-Signal Modelling and Analysis of DC Distributed Power Systems
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© Per Karlsson Small Signal Modelling and Analysis of DC Distributed Power Systems
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IE http://www.iea.lth.se/
Per Karlsson
Small-Signal Modelling and Analysis of DC Distributed Power Systems
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© Per Karlsson Small Signal Modelling and Analysis of DC Distributed Power Systems
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Presentation Outline
• Introduction
• DC power distribution
• DC bus voltage control
• Small-signal modelling
• Small-signal models compared to previous work
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© Per Karlsson Small Signal Modelling and Analysis of DC Distributed Power Systems
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Energy Supply in the Future
http://www.toshiba.com
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© Per Karlsson Small Signal Modelling and Analysis of DC Distributed Power Systems
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Renewable Energy Sources &Distributed Generation
• Several renewable energy sources need assistance from power electronics
• Most consumer and office electronic equipment operate on rectified AC
DC might as well be used for local distribution systems
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© Per Karlsson Small Signal Modelling and Analysis of DC Distributed Power Systems
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DC Distributed Power SystemRing Bus
http://www.bigfrogmountain.com/
http://www.cogreenpower.org/
http://www.tecowestinghouse.com/
http://networkpower.exide.com/
http://www.elektro-helios.se/
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© Per Karlsson Small Signal Modelling and Analysis of DC Distributed Power Systems
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Droop DC Bus Voltage Control
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© Per Karlsson Small Signal Modelling and Analysis of DC Distributed Power Systems
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nConverterBode-Diagrams
Bode diagram of the closed loopsystem from id,ref to iq.
Bode diagram of the closed loopsystem from iq,ref to iq.
Solid: dead-beat gain (ki = 1), Dashed: half dead-beat gain (ki = 0.5)Dash-dotted: 25% of dead-beat gain (ki = 0.25).
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© Per Karlsson Small Signal Modelling and Analysis of DC Distributed Power Systems
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nConstant Power Load
- Negative Small-Signal Resistance
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© Per Karlsson Small Signal Modelling and Analysis of DC Distributed Power Systems
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nTwo-Converter System
Bode-Diagrams
Bode diagram for the completesystem from iqr,ref to vs forRdc = 1.0 and Ldc = 0.3 - 32 mH
Note that the transformers needed for galvanic separation are not included in the small-signal model!
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© Per Karlsson Small Signal Modelling and Analysis of DC Distributed Power Systems
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Droop DC Bus Voltage ControlDynamic Properties of the Two-Converter System
Measured (left) and simulated (right) sending end (blue) and receiving end (red) voltage (top) and power (bottom), in the case of Rdc=1.0 , Ldc=32 mH and Zsc=0.25+j0.25 .
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© Per Karlsson Small Signal Modelling and Analysis of DC Distributed Power Systems
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Small-Signal Modellingvs Switch Mode Modelling and Measurements
Sending end voltage in the case of Rdc=1.0 and Ldc=32 mH.Green: Experiment,Blue: Switch-mode simulationRed: Small-signal simulation
• The dominant poles are the same as the ones found in earlier investigations.
• The converter dynamics do not have to be included in the analysis.
• The assumption that Gconv = 1 is applicable due to the low bandwidth.
• A constant power load results in a unstable pole of the DC power system.
• The unstable node is cancelled for the closed loop system.