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Unformatted text preview: Fundamentals of Power Electronics Chapter 3: Steadystate equivalent circuit modeling, ... 1 Chapter 3. SteadyState Equivalent Circuit Modeling, Losses, and Efficiency 3.1. The dc transformer model 3.2. Inclusion of inductor copper loss 3.3. Construction of equivalent circuit model 3.4. How to obtain the input port of the model 3.5. Example: inclusion of semiconductor conduction losses in the boost converter model 3.6. Summary of key points Fundamentals of Power Electronics Chapter 3: Steadystate equivalent circuit modeling, ... 2 3.1. The dc transformer model Basic equations of an ideal dcdc converter: P in = P out V g I g = V I ( η = 100%) V = M ( D ) V g (ideal conversion ratio) I g = M ( D ) I These equations are valid in steadystate. During transients, energy storage within filter elements may cause P in ≠ P out Switching dcdc converter D Control input Power input Power output I g I + V – + V g – Fundamentals of Power Electronics Chapter 3: Steadystate equivalent circuit modeling, ... 3 Equivalent circuits corresponding to ideal dcdc converter equations P in = P out V g I g = V I V = M ( D ) V g I g = M ( D ) I Dependent sources DC transformer Power output + V – I + – M ( D ) V g Power input + V g – I g M ( D ) I D Control input Power input Power output + V – + V g – I g I 1 : M ( D ) Fundamentals of Power Electronics Chapter 3: Steadystate equivalent circuit modeling, ... 4 The DC transformer model Models basic properties of ideal dcdc converter: • c onversion of dc voltages and currents, ideally with 100% efficiency • c onversion ratio M controllable via duty cycle • S olid line denotes ideal transformer model, capable of passing dc voltages and currents • T imeinvariant model (no switching) which can be solved to find dc components of converter waveforms D Control input Power input Power output + V – + V g – I g I 1 : M ( D ) Fundamentals of Power Electronics Chapter 3: Steadystate equivalent circuit modeling, ... 5 Example: use of the DC transformer model 1. Original system 2. Insert dc transformer model 3. Push source through transformer 4. Solve circuit V = M ( D ) V 1 R R + M 2 ( D ) R 1 D R V 1 R 1 + – + V g – + V – Switching dcdc converter 1 : M ( D ) R V 1 R 1 + – + V g – + V – R M ( D ) V 1 M 2 ( D ) R 1 + – + V – Fundamentals of Power Electronics Chapter 3: Steadystate equivalent circuit modeling, ... 6 3.2. Inclusion of inductor copper loss Dc transformer model can be extended, to include converter nonidealities. Example: inductor copper loss (resistance of winding): Insert this inductor model into boost converter circuit: L R L L + – C R + v – 1 2 i V g R L Fundamentals of Power Electronics Chapter 3: Steadystate equivalent circuit modeling, ......
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This note was uploaded on 07/15/2011 for the course EEL 4244 taught by Professor Lee during the Spring '09 term at FSU.
 Spring '09
 LEE

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