1. Reduced Losses in PV Converters by Modulation of the DC Link Voltage
Alex Van den Bossche1, Jean Marie Vianney Bikorimana2 and Firgan Feradov3
1 Department of Electrical Energy, Systems and Automation
Ghent University
2 Department of Electrical and Electronics
University of Rwanda
3 Faculty of Electronics
Technical university of Varna Bulgaria

2. Outline Introduction Losses in a PV converter link Current control
Problem
Proposed solution
Losses in a PV converter link
Active components
Passive components
Current control
Constant off time peak current control
Simulation
Experment results
Current control with a PWM high pass filter
Simulation
Conclusions
Questions
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3. Introduction- What is the problem?
Span life of the PV system
PV panel life span = 30 years
PV converter life = 10 years
PV system Cost
Grid cost connection = high
Labor work cost = high [4],
Converter = expensive
Converter materials and topologies
Electrolytic capacitors =less efficient
Polypropylene film capacitors=high efficient
No general standard control and topology
Controls are complex
Panels
Converter
Converter
Panels
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4. Introduction- What is the proposed solution?Q1 Q2 Q3 Q4 Q6 Q5 L1 L2
Advantages of the topology:
Lower current ripple
C1 = a typical V
capacitor
The C2 =
constant
EMC
Filter
Buck-Boost Converter
H-bridge inverter
Grid PV
Fig.1 Single phase PV converter using a three-phase bridge
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5. Introduction- What is the proposed solution?(cont’d)Q1 Q2 Q3 Q4 Q6 Q5 L1 L2
Fig.2 Control voltage across C2 capacitor
Fig.1 Single phase PV converter using a three-phase bridge
Fig.3 The PV converter switches behavior
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6. Losses in a PV Converter Link
Profits
Capacitors losses
Capacitor losses
Switching and conduction losses
Switching and conduction losses
=Total losses
=Total losses
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7. Fig. 4. Constant off Time Peak Current Control
Constant off time peak current control” (COPCC): protection and control combined
Current control at constant frequency:
50% duty cycle
Fig. 4. Constant off Time Peak Current Control
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8. Table I. Converter materials
Constant off Time Peak Current Control
Table I. Converter materials
Material
Type
Value
Capacitor, C1
electrolytic
2200 µF
Capacitor, C2
Polypropylene film
20 µF
Capacitor, C3
Inductor, L1
Amorphous iron
600 µH
Inductor, L2
1400 µH
IGBT
APTGF50X60T3G -
DC source V1
100V
Load
Resistive
50 Ω
Power stage
Current control
Overvoltage protection
Fig. 9. Buck-Boost Converter Step Up
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9. Simulation and Lab experment work
Distortion frequencies
No distortion frequencies (Fig.9 &11)
Fig. 8 &10. Constant Off time Peak Current Control without HP feedback
COPCC with HP filter:
+ fast and protection included - not easy for DSP or µcontroller
Fig. 9 &11. Constant Off time Peak Current Control with HP feedback
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10. Current control with High pass filter feedback
Fig.13. The PV converter current mode control block diagram
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11. Simulation results COPCC with second order HP filter:
Fig.14. Iref and IL2 of the Boost converter
Fig.14. Iref and IL2 of the Boost converter
COPCC with second order HP filter:
+ fast and protection included - Possible for DSP or µcontroller
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12. Conclusions Topology in Fig.1
Cost effective PV system
Polypropylene Capacitors in DC link
Topology in Fig.1
Current Control with HPF makes the grid stable
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13. Questions
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14. References
[1] S. Michael and B. Joe “Selecting Film Bus Link Capacitors for High Performance Inverter Applications,” Electronic Concepts Inc. Eatontown, NJ 07724
[2] M.H. Bierhoff, F.W. Fuchs, “Semiconductor Losses in Voltage Source and Current Source IGBT Converters Based on Analytical Derivation,”
[3]
[4] Lucas Laursen, “Production of Solar Panels Outpaced Investment Last year”, 1 Oct 2013.
[5] Rajendra Aparnathi and Ved Yvas Dwived, “LCL Filter for three Phase Stable Inverter Using Active Damping Method (Genetic Algorithm)”,
[6] Antonio Coccia, “Control Method for Single-Phase Grid Connected LCL Inverter”
[7] Daniel Wojciechowski, “Unified LCL Circuit for Modular Active Power filter”, International Journal for Computation and Mathematics in Electrical and Electronics Engineering,Vol.31 Iss:6,pp
[8] Jian Li, “Current-Mode Control: Modeling and its Digital Application”, Blacksburg, Virginia, 2009
[9] Alex Van den Bossche, Dimitar Vaskov B.,Thomas V, and Vencislav Cekov V., “Programmable Logic Based Brushless DC Motor Control” EPE 2011-Birmingham
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