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

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

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

System Block Diagram

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

Simulation Results

Boost Converter Full Bridge

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%.

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

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

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 the maximum power point, it is not at it’s most efficient point

MPPT Flowchart

Boost Without MPPT

Boost With MPPT

MPPT Circuit

Output Power Without MPPT

Output Power With MPPT

Solar Insolation Peoria, IL 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 Solar Insolation Peoria, IL   Jan Feb March April May June July Aug Sep Oct Nov Dec kWh/(m^2 day) 3.271 4.109 4.642 4.921 5.239 5.740 5.880 5.727 5.639 4.562 2.957 2.721 W/m^2 136.292 171.208 193.417 205.042 218.292 239.167 245.000 238.625 234.958 190.083 123.208 113.375

I P V V

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

I V P V

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

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.

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

Simulink A/D Interfacing

Simulink PWM Generation

Manual PWM Duty Ratio Control

PWM Generation Experimental Results 80% Duty Ratio 30% Duty Ratio

AC Subsystem Inverter Output filter

AC Subsystem - Inverter Inverter topology Inverter operation Simulations

AC Subsystem Inverter Topology Inverter single phase H-bridge

AC Subsystem Inverter 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

AC Subsystem Inverter Operation - Bipolar Simulation schematic

AC Subsystem Inverter Operation - Bipolar Reference (blue) and carrier (red) waveforms Switching signal

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

AC Subsystem Inverter 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

AC Subsystem Inverter Operation - Unipolar Two reference sinusoids are compared to a triangular waveform Switch pairs not switched simultaneously

AC Subsystem Inverter Operation - Unipolar Simulation schematic

AC Subsystem Inverter Operation - Unipolar References and carrier waves Switching signal 1 Switching signal 2 Output Image source: Tian

Inverter Operation - Comparison Bipolar harmonic output Unipolar harmonic output

AC Subsystem - Output Filter Inverter output includes switching harmonics Filter smoothes output

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%.

AC Subsystem Key Components Inverter switches Gate drives Power supplies

Commercial Grid Tie Inverters Company SMA Solar Technology Xantrex Product Sunny Boy 700-US GT2.8 AC Power 460W, 120Vac 2700 W, 208Vac / 2800W, 240Vac AC Voltage Output 106 - 132 Vac 183 - 229 Vac / 211 - 264 Vac Output Frequency 59.3 - 60.5 Hz Harmonics > 3% Max. efficiency 92.4% 94.6% Power Factor Unity > 0.95 %

Schedule

Component List

References “PV Module Simulink Models.” ECEN2060. University of Colorado Boulder. Rozenblat, Lazar. "A Grid Tie Inverter for Solar Systems." Grid Tie Inverter Schematic and Principles of Operation. 6 Oct. 2011. <http://solar.smps.us/grid-tie-inverter-schematic.html>. Tafticht, T., K. Agbossou, M. Doumbia, and A. Cheriti. "An Improved Maximum Power Point Tracking Method for Photovoltaic Systems." Renewable Energy 33.7 (2008): 1508-516. Tian, Yi. ANALYSIS, SIMULATION AND DSP BASED IMPLEMENTATION OF ASYMMETRIC THREE-LEVEL SINGLE-PHASE INVERTER IN SOLAR POWER SYSTEM. Thesis. Florida State University, 2007.  Zhou, Lining. EVALUATION AND DSP BASED IMPLEMENTATION OF PWM APPROACHES FOR SINGLE-PHASE DC-AC CONVERTERS. Thesis. Florida State University, 2005.

Questions?