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 E-mail: alex.vandenbossche@ugent.be 2 Department of Electrical and Electronics University of Rwanda E-mail: jbikorimana@nur.ac.rw 3 Faculty of Electronics Technical university of Varna Bulgaria E-mail: firgan@mail.bg

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 2/12

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 3/12

Introduction- What is the proposed solution? Q1 Q2 Q3 Q4 Q6 Q5 L1 L2 Advantages of the topology: Lower current ripple C1 = a typical 150-250 V capacitor The voltage @ C2 = constant EMC Filter Buck-Boost Converter H-bridge inverter Grid PV Fig.1 Single phase PV converter using a three-phase bridge 4/12

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 5/12

Losses in a PV Converter Link Profits Capacitors losses Capacitor losses Switching and conduction losses Switching and conduction losses =Total losses =Total losses 6/12

Fig. 4. Constant off Time Peak Current Control Constant off time peak current control” (COPCC): protection and control combined Current control at constant frequency: Instability @ 50% duty cycle Fig. 4. Constant off Time Peak Current Control 7/12

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 8/12

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 9/12

Current control with High pass filter feedback Fig.13. The PV converter current mode control block diagram 10/12

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 11/12

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 12/12

Questions 13/12

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] http://www.digikey.com/product-detail/en/APTGF50X60T3G/APTGF50X60T3G-ND/1920455 [4] Lucas Laursen, “Production of Solar Panels Outpaced Investment Last year”, 1 Oct 2013. http://spectrum.ieee.org/energywise/energy/renewables/production-of-solar-panels-outpaced-investments-last-year [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.1985-1997. [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 14/11