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Cascaded multilevel converter for Photovoltaic applications
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Cascaded multilevel converter for Photovoltaic applications



my first presentation in CBNU

my first presentation in CBNU



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Cascaded multilevel converter for Photovoltaic applications Presentation Transcript

  • 1. Cascaded Multilevel Converter and Their Applications in photovoltaic Systems
  • 2. Outlines
    • Photo Voltaic Systems
    • 3. Cascaded Multilevel Converter
    • 4. Control Systems
    • 5. Conclusions
    • 6. Future Works
  • PV Systems - Overview
    • Different power configurations
    • 7. Different topologies for power converter
    • 8. Different control structures
    • 9. Current control (THD limits)
    • 10. Specific control functions
    • 11. MPPT
    • 12. PLL
    • 13. Ancillary functions (Future)
  • PV Cells Configurations
  • 14. Power configuration for PV systems
    PV Cells Configuration
    Central Inverter
    10 kW -250 kW, 3 phase several string in parallel
    High efficiency, low cost, low reliability, not optimal MPPT
    Used for power plant
    String inverters
    1.5 – 5 kW, typical residential applications
    Each string has its own inverter enabling better MPPT
    The strings can have different orientations
    Three phase inverter for power < 5 kW
    Module inverters
    50 – 180 W, each panel has its own inverter
    Lower efficiency, difficult maintenance
    Higher cost / kW p
  • 15. Power Configurations for PV Systems
    Without boost /with boost of dc voltage
    Galvanic isolation necessary some places
    LF/HF transformer (Cost-Volume issue)
    The optimal topology is not matured yet as for drives
    Transformer less topologies having higher efficiency are emerging
  • 16. Equivalent circuit for a PV cell
    Vpv : PV array output voltage (V)
    Ipv : PV array output current (A)
    Ns : number of cells connected in series
    np : number of strings connected in parallel
    q: charge of electron
    k : Boltzmanconstant
    A :pnjunction ideality factors (2.15)
    T : Cell temperature
    Irs : Cell reverse saturation current
    Iscr : cell short circuit current at reference temperature and radiation
    ki: short circuit current temperature coefficient
    s : solar radiation
    Using this PV array model it is possible to simulate the dynamic performance of the power and control systems and MPPT strategy in response to the radiation and temperature step changes
  • 17. V-I characteristic under different irradiance conditions
    Behavior of system under different irradiance value, bigger irradiance value the bigger value of V-I
  • 18. Generic Single Phase H-bridges Converter
    a. Generic single phase string converter
    b. Generic single phase H-bridges converter
  • 19. Cascaded Multilevel Inverter Features
    can generate output voltage with extremely low distortion and lower dv/dt.
    circuit layout has more flexibility.
    compared to other multi level topologies, CMC requires least number of components, because there is no need for clamping diodes and flying capacitors.
    The number of output voltage levels can be easily adjusted by adding or removing the H-Bridges cells.
  • 20. Cascaded Multilevel inverter System Overview
  • 21. Inverter topology and carrier shifting control scheme
  • 22. Switching Pattern of 11-level cascade inverter
  • 23. PWM Control features
    To balance power sharing between the modules, this switching scheme gives a very balanced averaged power sharing between all modules.
    In reality, inter cycle difference of power still exists in each module.
  • 24. General control methodology of Converter
    Shows the block diagram of generalized voltage control for any k-thmodule.
  • 25. Voltage Control Loop of Each module
    Describe how to generated DC voltage of each module of PV module. The corresponding digital filtered voltages Vdckare sent to next stage where the power control is carried out.
  • 26. Power Control Loop
    Power Control loop output is Vht, whose Vht that must be synthesized by the converter.
  • 27. Phase locked loop (PLL) configuration
    Typical PLL algorithms include inverse park-based PLL, hilbert transformer-based PLL, and transport delay-based PLL
  • 28. Simplified output circuit and unitary factor power operation
    Power flow controlled according to
  • 29. MPPT algorithms
    Instead of sensing the individual panel voltages (depend on temperature and irradiance), MPPT algorithms determines the optimal point of operation of the panel by calculating the output power and phase angle variation.
    It monitor output voltage and current parameters by making small changes on phase angle and looking at the power variation
    In this PV configuration a perturbation and observation (P&O) algorithms has been used.
  • 30. Conclusions
    This project uses string or multi string array configuration, and multilevel converter without DC-DC converter and without isolation (transformer less).
    This project uses 11-level PWM H-bridge cascade PV converter, which uses PLL and MPPT with separate solar DC panel DC source to enable grid interaction.
    Each PV array will have its specific MPP. And MPPT algorithms using P&O algorithms.
    Present new control strategy for CMC to gain the best performance of the systems under all environmental conditions.
  • 31. Future Works
    Implementation of MPPT algorithms each solar array.
    Implementation Of PWM control.
    Finding best filter configuration for inverter output.
    Implementation Of PLL to inverter.
    Making general controls methodology working properly.
  • 32. Thank you for your attention