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 VoltsThe 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 Inductor1mH 25A500uH 35AGate DriverMOSFET or IGBT2.5A 500VSolar Panel x 450W12VMOSFETVds = 250VId = 110APdiss = 694WHeatsink
10 DC Subsystem Components Current Sensor30A63-69 mV/ASensing Op ampUsed with voltage dividerDSP BoardTMS320F2812
11 MPPT “Perturb and Observe” method Change Boost Converter duty cycle based on change in PV powerChanging duty cycle changes the current drawn from the PVAnytime the system is not at the maximum power point, it is not at it’s most efficient point
18 Solar Insolation Peoria, IL PV Models in SimulinkMade models of PVs using resources from the University of Colorado at BoulderInsolation – a measure of solar energy on an area over a given amount of time.Usually in units of W/m^2Solar Insolation Peoria, ILJanFebMarchAprilMayJuneJulyAugSepOctNovDeckWh/(m^2 day)3.2714.1094.6424.9215.2395.7405.8805.7275.6394.5622.9572.721W/m^2
26 Boost Converter Lab Testing Built boost converter from components Dr. Na provided.
27 Boost Converter Lab Testing 0 to 3.3V signal from DSP board controlling the MOSFETAt a switching frequency of 10kHz with a 50% duty cycle the 5V input voltage was boosted to about 10V.Increasing duty cycle, increased VoutDecreasing duty cycle, decreased VoutAfter testing this setup we will be able to build our Boost converter circuit quickly.
34 AC Subsystem - Inverter Inverter topologyInverter operationSimulations
35 AC Subsystem Inverter Topology Inverter single phase H-bridge
36 AC Subsystem Inverter Operation - Bipolar A reference sinusoidal waveform is compared to a triangular carrier waveformWhen the reference voltage is equal to the carrier voltage a transition in the switching signal occurs
37 AC Subsystem Inverter Operation - Bipolar Simulation schematic
38 AC Subsystem Inverter Operation - Bipolar Reference (blue) and carrier (red) waveformsSwitching signal
39 AC Subsystem Inverter Operation - Bipolar Inverter output. Switches from +Vd to -Vd
40 AC Subsystem Inverter Operation - Bipolar Switching signal is inverted and fed to other pair of switchesSwitch pairs are switched simultaneouslyOnly one reference signal needed, but performance is poor
41 AC Subsystem Inverter Operation - Unipolar Two reference sinusoids are compared to a triangular waveformSwitch pairs not switched simultaneously
42 AC Subsystem Inverter Operation - Unipolar Simulation schematic
43 AC Subsystem Inverter Operation - Unipolar References and carrier wavesSwitching signal 1Switching signal 2OutputImage source: Tian
45 AC Subsystem - Output Filter Inverter output includes switching harmonicsFilter smoothes output
46 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%.
47 AC Subsystem Key Components Inverter switchesGate drivesPower supplies
48 Commercial Grid Tie Inverters CompanySMA Solar TechnologyXantrexProductSunny Boy 700-USGT2.8AC Power460W, 120Vac2700 W, 208Vac / 2800W, 240VacAC Voltage OutputVacVac / VacOutput FrequencyHzHarmonics> 3%Max. efficiency92.4%94.6%Power FactorUnity> 0.95 %
51 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 <Tafticht, T., K. Agbossou, M. Doumbia, and A. Cheriti. "An Improved Maximum Power Point Tracking Method for Photovoltaic Systems." Renewable Energy 33.7 (2008):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.