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Discrete Time Modeling And Control Of DC/DC Switching Converter For Solar Energy Systems

Discrete Time Modeling And Control Of DC/DC Switching Converter For Solar Energy Systems. Shaghayegh Kazemlou Advisor : Dr. Shahab Mehraeen Louisiana State University. Advanced Mechanical Design December 2008. Outline. Part I: Grid-connected Renewable System

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Discrete Time Modeling And Control Of DC/DC Switching Converter For Solar Energy Systems

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  1. Discrete Time Modeling And Control Of DC/DC Switching Converter For Solar Energy Systems ShaghayeghKazemlou Advisor: Dr. ShahabMehraeen Louisiana State University Advanced Mechanical Design December 2008

  2. Outline • Part I: Grid-connected Renewable System • Part II: Converter Discrete-Time Model • Part III: Converter Discrete-time Control Design • Part IV: Simulation Results • Part V: Summary and Future Works

  3. Part I Grid-connected Renewable System Advanced Mechanical Design December 2008

  4. Solar System Model • Solar panels • DC-DC buck converter • Grid-tie inverter (GTI) Solar power generation system • stabilizing the inverter DC-link capacitor • Omitting solar power oscillations Objective

  5. Grid-Tie Inverter Solar power generation system controller dynamics Synchronous Generator (SG)

  6. Grid-Tie Inverter Model/Observer SG dynamical equations Inverter dynamical equations ( ) • Inverter gain ( ) and ac voltage angle ( ) are the control inputs

  7. Part II Converter Discrete-Time Model Advanced Mechanical Design December 2008

  8. DC-DC Buck Converter dc-dc buck converter control system • Objective: Maintaining the solar power constant by adjusting duty cycle d

  9. Converter Discrete-Time Model • Converter discrete-time equations • Photovoltaic array output current is a nonlinear function of

  10. Part III Converter Discrete-time Control Design Advanced Mechanical Design December 2008

  11. State Feedback Controller Input: • Tracking error : stable

  12. Neural Network function approximation : activation function • Weight estimation error : • NN weight update law : : positive design constant

  13. Part IV Simulation Results Advanced Mechanical Design December 2008

  14. Simulation Results • System parameters • AVR+PSS mechanism for inverter • operational frequency of the converter : 10 kHz • three-phase resistive load with on each phase • Disturbance : load change from to at • solar module maximum power : • solar module maximum power point voltage :

  15. Simulation Results • Solar Voltage Less than MPP Voltage: Converter input power Converter input voltage • Disturbance between t=1.4s to t=1.6s

  16. Simulation Results • Solar Voltage Less than MPP Voltage: Converter output voltage Converter inductance current Converter input current

  17. Simulation Results • Solar Voltage higher than MPP Voltage: Converter input power Converter input voltage Converter output voltage

  18. Simulation Results • Input Voltage Adjustment to Load Change: Converter input power Converter input voltage Converter output voltage

  19. Summary • The inverter is controlled bya novel stabilizer similar to power system stabilizer (PSS). • The interaction of the solar array dc-dc converter with the GTI is addressed. • A nonlinear discrete-time model of a photovoltaic-connected buck converter was presented. • Adaptive neural network (NN) controller is employed to enhance stability of dc-dc converter connected to grid-tie inverter (GTI) in the presence of power system disturbances. • Simulation results of the controller imply that the converter input voltage and power as well as the inductor current are stabilized which verifies the accuracy of the converter discrete-time model and the effectiveness of the proposed discrete-time controller.

  20. Recommendations for Future Works • Improve the efficiency and effectiveness of discrete-time adaptive neural network in the power system stability and control • The system model can be developed to a more general distributed generation system where other renewable generators or synchronous generators all are interconnected. In this case each system is influenced by other subsystem’s states and a more general control method is necessary. • The solar system connected dc-dc converter can be modeled in a dc distribution system with interconnected subsystems working in high penetration of renewable generation.

  21. Thank You for Your Attention

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