Grid-Connected Solar Microinverter Reference …

1 1 2010 microchip technology Incorporated. All Rights Reserved. grid connected Solar Microinverter Reference design using the dsPIC DSC Slide 1 Grid-Connected Solar Microinverter Reference DesignHello, and welcome to this web seminar on microchip s grid connected Solar Microinverter Reference design . My name is Mike Curran, and I am an Applications Engineer in the High Performance Microcontroller Division of 2010 microchip technology Incorporated. All Rights Reserved. Grid-Connected Solar Microinverter Reference design Using the dsPIC DSC Slide 2 Session Agenda Solar Microinverter Overview Photovoltaic Cell Characteristics Solar Microinverter Configurations Grid-Connected Solar Microinverter Reference design Software Integration SummaryIn this webinar, we will go through the design of microchip s Grid-Connected Solar Microinverter Reference design .

2 Including hardware details and the system let s get started with some photovoltaic cell characteristics and background information of the Solar Inverter 2010 microchip technology Incorporated. All Rights Reserved. Grid-Connected Solar Microinverter Reference design Using the dsPIC DSC Slide 3 Photovoltaic (PV) CellA PV cell is a current source, not a voltage source!RpRsSimplified circuit model of a Solar cellVoIoEffective use of series connected Solar cells depends on identical currents being generated by each ~ VoltsIo ~ 1 to 3 AmpsPV cells are semiconductor devices, with electrical characteristics similar to a diode; however, a PV cell is a source of electricity, rather than an electrical load, and operates as a current source when light energy, such as sunlight makes contact with it.

3 The circuit shown is an equivalent model of a PV cell. Next, we will look at more details of a PV cell and its characteristics. 4 2010 microchip technology Incorporated. All Rights Reserved. Grid-Connected Solar Microinverter Reference design Using the dsPIC DSC Slide 4PV Cell CharacteristicsVoltageCurrentI-V versus Illumination (36 cell string)1020304050642G = 1000 W/m2G = 300 W/m2G = 600 W/m2 Maximum Power Point642 VoltageCurrentI-V versus Temp (36 cell string)1020304050G = 1000 W/m210 C60 CMaximum Power PointSolar cell s output continually varies with LIGHT and TEMPVOPENISCVOPENISCL ight intensity as well as temperature affect PV cell characteristics.

4 Current generated by a PV cell is directly proportional to light intensity. Voltage also changes with fluctuating light levels, but by much less. Voltage is more affected by changes in the temperature of the PV cell rather than the current. An increase in the cell temperature decreases the voltage and increases the current by a very small amount. The short-circuit current (ISC) from a cell is nearly proportional to the illumination, while the open-circuit voltage (VOPEN) may drop only 10% with an 80% drop in important result of these two effects is that the power of a PV cell decreases when light intensity decreases and/or temperature increases.

5 5 2010 microchip technology Incorporated. All Rights Reserved. Grid-Connected Solar Microinverter Reference design Using the dsPIC DSC Slide 5 Solar Cell Power CurvesVoltagePowerI-V versus Illumination (36 cell string)1020304050150 W100 W50 WG = 1000 W/m2G = 300 W/m2 Maximum Power PointG = 600 W/m2An increase in the output current after the Maximum Power Point will rapidly drop its output voltage and could produce power only 1 half of the open-circuit voltageand1 half of the short-circuit current . The usable power output could thus drop from 70% of the open-circuit voltage times the short-circuit current (VOPENX ISC ) to 50% or even as little as 25%.

6 The amount of power generated by a PV cell depends on the operating voltage of the PV cell array. Its V-I and V-P characteristic curves specify a unique operating point at which maximum possible power is delivered. At the Maximum Power Point, the PV operates at its highest efficiency6 2010 microchip technology Incorporated. All Rights Reserved. Grid-Connected Solar Microinverter Reference design Using the dsPIC DSC Slide 6PV Cell ShadingModuleShaded Cell(s)String 2 String 1 InverterInverterCooler area due to previous shadingPV manufacturer processes produce cells with relatively large variance in their power output capability.

7 They seek to reduce their variance by using advanced manufacturing technology . Regardless, panel models on the market today still have 3 to 5% variance in their output. Highest voltage strings or unshaded stings provide the bulk of power, and lower voltage strings due to shading or lower temperatures contribute little 2010 microchip technology Incorporated. All Rights Reserved. Grid-Connected Solar Microinverter Reference design Using the dsPIC DSC Slide 7 Session Agenda Solar Microinverter overview Photovoltaic Cell Characteristics Solar Microinverter Configurations Grid-Connected Solar Microinverter Reference design Software Integration SummaryNext, we will take a closer look at different Solar inverter 2010 microchip technology Incorporated.

8 All Rights Reserved. Grid-Connected Solar Microinverter Reference design Using the dsPIC DSC Slide 8 Solar Power Evolution: Grid-Connected InverterInverterMultiple Solar modules connected in series and parallel provide 200 -400 volts output and 10 to 50 Amps. Combinations of these panels are then connected to a single centralized inverter to yield 120/240 VAC at medium power levels (2 -10KW)This system is connected to the AC power lines, hence known as grid -Tied system. The customer sells power to the power company during the day, and buys power from the power company during the night.

9 The grid -Tied approach eliminates expensive and short lived inverter has the potential for a single point failure and has a non-optimal power harvest from the Solar panel, especially in partial shading the case of multiple inverter systems each string regardless of the output voltage will contribute the maximum power it can because each inverter is optimizing the power output of its string. Tests indicate 20 34% additional energy 2010 microchip technology Incorporated. All Rights Reserved. Grid-Connected Solar Microinverter Reference design Using the dsPIC DSC Slide 9 Solar Power Evolution: Grid-Connected Module Incorporated Inverters (MIC)Module Incorporated Inverters(MIC) Each Solar panel module incorporates its own inverter.

10 An MIC is also known as a Microinverter .The incorporation of inverters into the Solar panels greatly reduces installation labor costs, improves safety, and maximizes the Solar energy is an example of a Module Incorporated Inverter(MIC) Each Solar panel module incorporates its own inverter. An M-I-C inverter is also known as a Microinverter .The incorporation of inverters into Solar panels greatly reducesinstallation labor costs, improves safety, and maximizes the Solar energy 2010 microchip technology Incorporated. All Rights Reserved.