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Photovoltaic Power Converter

Photovoltaic Power Converter. Students: Thomas Carley Luke Ketcham Brendan Zimmer Greg Landgren. Advisors: Dr. Woonki Na Dr. Brian Huggins Dr. Yufeng Lu. Bradley University Department Of Electrical Engineering 11/30/11.

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Photovoltaic Power Converter

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  1. Photovoltaic Power Converter Students: Thomas Carley Luke Ketcham Brendan Zimmer Greg Landgren Advisors: Dr. Woonki Na Dr. Brian Huggins Dr. Yufeng Lu Bradley University Department Of Electrical Engineering 11/30/11

  2. Presentation Outline • Summary and Overall System Block Diagram • DC Subsystem • Maximum Power Point Tracking • Boost Converter Testing • AC Subsystem • Schedule • Component List

  3. Project Summary • Supplies DC and AC Power • Photovoltaic Array • Boost Converter to step up PV voltage • Maximum Power Point Tracking • DC-AC converter for 120Vrms • LC filter

  4. System Block Diagram

  5. DC Subsystem • Boost Converter • Maximum Power Point Tracking (MPPT) System

  6. Simulation Results

  7. Boost Converter Full Bridge

  8. DC Subsystem Requirements • The boost converter shall accept a voltage from the photovoltaic cells. • The input voltage shall be 48 Volts. • The average output shall be 200 Volts +/- 25 Volts. • The voltage ripple shall be less than 3 Volts • The boost converter shall perform maximum power point tracking. • The PWM of the boost converter shall be regulated based on current and voltage from the PV array. • The efficiency of the MPPT system shall be above 85%.

  9. DC Subsystem Key Components • MOSFET • Vds = 250V • Id = 110A • Pdiss = 694W • Heatsink • Inductor • 1mH 25A • 500uH 35A • Gate Driver • MOSFET or IGBT • 2.5A 500V • Solar Panel x 4 • 50W • 12V

  10. DC Subsystem Components • Current Sensor • 30A • 63-69 mV/A • Sensing Op amp • Used with voltage divider • DSP Board • TMS320F2812

  11. MPPT • “Perturb and Observe” method • Change Boost Converter duty cycle based on change in PV power • Changing duty cycle changes the current drawn from the PV • Anytime the system is not at themaximum power point, it is notat it’s most efficient point

  12. MPPT Flowchart

  13. Boost Without MPPT

  14. Boost With MPPT

  15. MPPT Circuit

  16. Output Power Without MPPT

  17. Output Power With MPPT

  18. PV Models in Simulink • Made models of PVs using resources from the University of Colorado at Boulder • Insolation – a measure of solar energy on an area over a given amount of time. • Usually in units of W/m^2

  19. I P V V

  20. Insolation = 200, 400, 600, 800, 1000 W/m2 P I V V

  21. I V P V

  22. Boost Converter Lab Testing • Built boost converter from components Dr. Na provided.

  23. Boost Converter Lab Testing • 0 to 3.3V signal from DSP board controlling the MOSFET • At a switching frequency of 10kHz with a 50% duty cycle the 5V input voltage was boosted to about 10V. • Increasing duty cycle, increased Vout • Decreasing duty cycle, decreased Vout • After testing this setup we will be able to build our Boost converter circuit quickly.

  24. DSP Board Programming • Spectrum Digital eZdsp F2812 • Texas Instruments Code Composer • Matlab/Simulink

  25. Simulink A/D Interfacing

  26. Simulink PWM Generation

  27. Manual PWM Duty Ratio Control

  28. PWM GenerationExperimental Results 80% Duty Ratio 30% Duty Ratio

  29. AC Subsystem • Inverter • Output filter

  30. AC Subsystem - Inverter • Inverter topology • Inverter operation • Simulations

  31. AC SubsystemInverter Topology Inverter single phase H-bridge

  32. AC SubsystemInverter Operation - Bipolar • A reference sinusoidal waveform is compared to a triangular carrier waveform • When the reference voltage is equal to the carrier voltage a transition in the switching signal occurs

  33. AC SubsystemInverter Operation - Bipolar Simulation schematic

  34. AC SubsystemInverter Operation - Bipolar Reference (blue) and carrier (red) waveforms Switching signal

  35. AC SubsystemInverter Operation - Bipolar Inverter output. Switches from +Vd to -Vd

  36. AC SubsystemInverter Operation - Bipolar • Switching signal is inverted and fed to other pair of switches • Switch pairs are switched simultaneously • Only one reference signal needed, but performance is poor

  37. AC SubsystemInverter Operation - Unipolar • Two reference sinusoids are compared to a triangular waveform • Switch pairs not switched simultaneously

  38. AC SubsystemInverter Operation - Unipolar Simulation schematic

  39. AC SubsystemInverter Operation - Unipolar References and carrier waves Switching signal 1 Switching signal 2 Output Image source: Tian

  40. Inverter Operation - Comparison Bipolar harmonic output Unipolar harmonic output

  41. AC Subsystem - Output Filter • Inverter output includes switching harmonics • Filter smoothes output

  42. AC Subsystem Requirements • The AC side of the system shall invert the output of the boost converter. • The output of the inverter shall be 120 Volts RMS. • The output shall be 60Hz +/- 0.1Hz. • The inverter output shall be filtered by a LC filter. • The filter shall remove high switching frequency harmonics. • Total harmonic distortion of the output shall be less than 15%.

  43. AC Subsystem Key Components • Inverter switches • Gate drives • Power supplies

  44. Commercial Grid Tie Inverters

  45. Schedule

  46. Component List

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