Ansoft HFSS Fundamentals - ModeFRONTIER

PV01

Photovoltaic Systems

Simplorer

Simplorer R19.1 User’s Guide PV01-1

Solar System Modeling in Simplorer

By

Steve Chwirka

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Section 1 (PV Characterization)Note can open the project “PV_comp_save_R19p1.aedt” and then open the

“1_PV_char” design instead of going thru the following lab to create it.

To run the simulations that are shown in the following lab, use the Right

Mouse Button (RMB) over the TR, “para_irrad” and “para_temp”, then

select “Analyze” (see below)

Lab: Invoke Simplorer, change the name of the Project to “PV_comp” and

change the name of the first design to be “1_PV_char”

Select the menu “File - > Save As” and save it to the lab location on your

computer

This example was created to show a variety of Simplorer’s capabilities wrt

modeling PV cells.

Using table look up modeling approaches

Hierarchical circuit level modeling

VHDL-AMS modeling

Understanding PV characterization f(temp, Irrad, model parameters)

Use of on sheet plots, TR probes, and Numeric displays

Understanding unique X-Y plotting (ie I f(V)) plotting

Setting up project variables

Setting up and running parametric sweeps

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Table look up Model for a Solar Cell/Array

The solar cell can be thought of as a current source in the desired operating

region, therefore we will use a controlled current source in conjunction with the

table look up model.

The table lookup date will consist of the I-V data (current vs voltage) for the cell

or array

The voltage across the cell/array will be fed back into the model to yield the

correct current as a function of the voltage based on the look up data

NOTE there are two types of table lookup models that will be used in this

example, one for the I-V relationship of the solar cell/array, and the other will be

for the Resistance vs Time relationship for the load resistance. The load

resistance will be swept over time to yield the I-V curve of the Solar Cell/Array

Load the following models into the schematic area and connect as shown

NOTE when you bring in a component (drag and place), then use RMB (Right

Mouse Button) and select “finish”

NOTE the ground can be placed by using “Ctrl – G” or from the “Draw” menu

The Voltage and Watt meters are found in:

Basic Elements/Measurements/Electrical/ (VM, WM)

The 2D lookup table “XY” for the Solar Cell is found in:

Basic Elements/Tools/Characteristics/”XY:2D…”

The 2D lookup table “Datapairs” for the Load is found in :

Basic Elements/Tools/Time Functions/ “Datapairs:2D..”

Note all “circuit” elements (resistors, capacitors, inductors, sources, etc :

Basic Elements/Circuits/*

The “controlled current source” is found in:

Basic Elements/Circuits/Sources/IC:Controlled Current Source

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Double click the mouse over the X-Y table look up block, and name it “SA_data”

Double click the mouse over the t-Y table look up block, and name it “Load_data”,

go to the “Output/Display” tab, then un-check the “show pin” (keep the check on

the SDB, this will put the value in the data base file for us to plot later)

Double click on the Voltage meter (VM1) and under the “Output/Display” tab,

select “show pin” box for “V” – Voltage, this will put a pin on the symbol that

represents the voltage measured. Use RMB over VM and “flip horizontal” so the

pin is pointing to the right.

Double click on the Controlled Current Source, and under the “Parameters” tab,

select the “Nonlinear Voltage Controlled”, “Control Component” to “Use Pin”,

“Characteristic” to “use pin”, and name it “isolar”

Double click on the resistor load, and make the resistance to be “Load_data.VAL”

(the resistance will now be defined in the table look up model for “Load_data”

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Connect the controlled current’s inputs, note the “controlled” voltage pin’s input

comes from the voltage meter across the Solar Cell/Array, and the

“characteristic” pin comes from the XY table look up block. See below for the final

connections

The SA_data lookup block will now add the characteristic data

Double click on the SA_data XY block, select the “dataset” , then select the

“datasets..” button

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Select the “Add” button

Give it a name “solar_char”, then select “Import Dataset”

Locate the “solar_lookup.csv” file, and select it

Select “OK” , name it “$solar_char”, select “OK”

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Select “Done”, then “OK”

Now add characteristic for the load resistance, double click on the table look up

block “Load_data”, then select “Characteristic”

Select “Datasets..”

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Note the “solar_char” data set that was created prior for the Solar Cell/Array

shows up, select “Add” to add another dataset.

Fill in the X Y data (the X is time, the Y is the resistance) as shown below, give it

the name of Rload_ns1np1 (note other labs will have different load transients

based on the ns and np of the solar configuration), Select “OK” when done.

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Note there now shows two data sets available to use, select “Done”

Note the pull down menu now allows you to select between data sets that exist,

select the Rload_ns1np1, then Select “OK”, then “OK” again for next window

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Zoom out on the schematic, Add two rectangle plots onto the schematic using the

menu “Draw -> Report -> Rectangular Plot” as shown below. Note when it asks

for a waveform, just close it for now. Resize the plots as desired

Note in the “Project Manager” window to the left, under the “Results” are the

default names for these plots, name the first one “IV Curve 1”, and the second

one “PV Curve 1” as shown below.

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On the schematic, select one of the plots, then RMB ->View -> Visibility, this will

bring up the next window

Select the “Legends” tab, and select to view the “Header” (which is the name we

gave the plot), and deselect the “Legend” as shown below. The plot on the

schematic should now show the name as shown below. Repeat this for the other

plot

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Set up the transient analysis, in the “Project Manager” window to the left, double

click on the “TR” Analysis. Fill it out as shown below (Tend = 10s, Hmin = 1ms,

Hmax = 10ms), select “OK”

Double click on the plots in the schematic to select waveforms to display, select

the “IV Curve 1” plot, and then select the current in the Watt Meter (WM1.I) as the

Y axis, then the voltage across the Watt Meter (WM1.V) for the X axis (note you

will have to uncheck the “Default” box for the X axis). When done, select “Add

trace”, then “close”. Repeat for the other plot, except plot WM1.P (Power) vs

WM1.V to yield the PV curves.

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Run the Transient simulation by selecting the “TR” in the project manager

window, RMB -> Analyze

The results should be as shown below for the IV and PV characteristic of the

solar cell/array based on the table look up data

Save the Project using main menu “File -> Save”. In the next section, a

hierarchical model of a solar cell will be created.

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Hierarchical Modeling of a Solar Cell

Add a hierarchical SubCircuit block using the menu “Simplorer Circuit ->

SubCircuit -> Add SubCircuit” this will automatically drop you into the subcircuit

work with.

Note in the Project Manager window to the left, a new simplorer design is added

with a default name, select it and change the name to “SolarCellsys”

Note the following circuit will be created for the solar cell model, the symbol will

be edited later

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First create the variables that will be used to define the solar cell model by adding

in 8 “Interface Ports”, and defining them as “Quantity” (which simply means they

are not electrical connections, but input variables). Place 8 of these onto the

schematic.

Double click on each one and define it as “Quantity” (Direction “in” meaning

input), give it the name and default value as follows

area = 100 (area of cell in cm2)

j0 = 10.0p (spice diode current density coeff)

jsc = 0.038 (Isc density coeff)

rs = 0.0001 (series resistance)

rsh = 10000 (shunt resistance)

isc_coeff = 50.0u (temp coeff)

tempr = 25 (cell temperature)

n = 1.2 (diode factor for Voc)

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Add 4 more interface ports, define them as “Quantities”, Direction “in” as well and

give them the names and default values as shown below

Name: ns

Domain: Quantity

Type: Real

Direction: in

Port Value: 1

Name: np

Domain: Quantity

Type: Real

Direction: in

Port Value: 1

Name: kt

Domain: Quantity

Type: Real

Direction: in

Port Value: 0

Name: irrad_static

Domain: Quantity

Type: Real

Direction: in

Port Value: 1000

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Add 2 more interface ports and define them as “conservative” , “electrical”

connections to the model (ie the output pins)

Name them “p” and “m”

Add a current source, spice diode, 2 resistors, and ICA block

The current source is found in:

Basic Elements/Circuit/Sources/I:Current Source

The spice diode is found in:

Basic Elements/Circuit/Spice-Compatible Models/Diode/SPICE_D

The ICA (initial Condition) block is found in:

Basic Elements/Tools/Equations/FML_Init:Initial Values

Add equation: tcell:=tempr + irrad_static*kt

Arrange, name, and connect them as shown below

Define the series resistor’s value as rs*(ns/np) and the shunt resistor as

rsh*(ns/np)

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Define the current source value as an equation:

(jsc/1000*irrad_static*area + isc_coeff*area*(tempr - 25))*np

Select the “Output/Display” tab on the current source and select to display “both”

the “IS” variable and its “Value” on the schematic

Set the diode variables TEMP = tcell, IS = j0*area*np, N = n*ns, and EG =

1.11*ns. set to display both variable and its value on the schematic

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The following is how the subcircuit should now look, “File-> save” the project:

Close out the subcircuit and return to the top level schematic by using the

RMB -> pop up

Note when you want to push down into this hierarchical design from the top

schematic, select it, RMB -> push down

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The default symbol for the hierarchical solar cell should appear as shown below.

Note in simplorer, even though a variable has been defined as a “Quantity”, we

can still make it a pin and connect to it even though its not a “conservative’ pin.

This is why all the variables initially show up as pins.

Double click on the symbol and select to not show the “Quantities” pins by de-

selecting the “show pin” box

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Edit the symbol by selecting it, RMB -> edit symbol , this will bring up the symbol

editor

Delete the “Quantity” pins (they wont be used as pins) and place the “p” and “m”

pins 3 squares apart (this is the standard pin spacing for resistors, capacitors,

etc…)

Delete the default graphics box and tick mark

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Add in graphics from a file (bmp, jpg etc..) using the menu “Draw -> Image”,

locate the lab files where there are some existing graphics to be used in these

labs, select the “solarcells.bmp”. note when the image is brought in, you will have

initial control to size it, just place it and it can be resized later.

Move and resize the graphics so the final symbol appears as shown below:

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Close out the symbol editor window using the “x” in the upper right corner, (do not

close out the entire project using the red X), do not use “File -> close” ! This

closes the entire project as well. (select “OK” to save changes on symbol)

The top level schematic should now appear as shown below:

Select (by drawing a box) around the Watt Meter, R, and two plots, then use “ctrl-

C” to copy, and “ctrl-V” to paste, move the copied elements as shown below

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Connect up the hierarchical solar cell to the circuit, and define the new plots to

show the IV Curves based on Watt Meter 2 (WM2) and the PV Curves again

based on WM2 (See page 9 for review of process) NOTE this time instead of

“Add Trace”, use “Apply Trace” because we want to replace the existing copied

over waveform with a totally new one, if we select “Add Trace” this would simply

add another waveform to the plot

name the plots in the project manager window to be “IV Curves 2” and “PV

Curves 2”

Note all values for the subcircuit solar model will be the defaults

Note the value for R2 that was copied over is still pointing to the table look up

value of “Load_data.VAL”

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Run the TR simulation using the blue arrow at the top of the simplorer window,

the results should be as shown below:

VHDL-AMS Modeling of a Solar Cell/Module/Array

This section will show the modeling of a solar cell using the modeling language

VHDL-AMS. This approach allows the creation of the characteristic equations to

be created directly, instead of trying to implement them using dependent sources

and electronic devices to emulate the behavior. This also allows the model to be

scale-able to create solar cells or modules or arrays. This also is more efficient

since we are not creating un-needed voltage and current nodes that are created

when implementing the equations using electrical devices and dependent

sources. Simplorer also provides VHDL-AMS modeling tools that make the

modeling process fast and easy to edit and verify. This model also allows both

the irradiation and temperature to be transient in nature. The hierarchical version

had to have a static Irradiation and temperature due to the use of the diode.

The VHDL-AMS model “PV_Array.vhd” has already been created and exists in

the lab files.

To import this model, use the menu “Tools -> Project Tools -> Import Simplorer

Models..” go to the location of the “PV_Array.vhd” model, and select it.

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When the pop up window appears, simply select “OK” to import the model, Note

the model now shows up in the Project Manager window under the “Definitions”

/”Components” folder.

Drag and drop this model into the schematic from the “Components” folder, Note

a default symbol was created during import.

To view the actual model, select the symbol in the schematic and RMB -> Edit

Model. This brings up the VHDL-AMS Model Editor window, Select the different

tabs at the bottom to see both sections of the model (Entity and Architecture). As

you develop the VHDL-AMS model, you can go back and forth (Edit the model,

verify syntax, simulate it, edit it, verify syntax, simulate it….

Close out the VHDL-AMS Model Editor by using the “x” in the upper right (just

like closing out the symbol editor)

Edit the VHDL-AMS “PV_Array” symbol, select it, RMB -> Edit Symbol

It is desired that this symbol be the same size as the hierarchical version

RMB -> zoom out (to give a broader view of the symbol)

Select the “vp” and “vm” pins and flip horizontally, do the same for the “vi” and

“vt” pins (note “vp” and “vm” are the electrical output of the model, “vi” is the

irradiance input, “vt” is the temperature input.

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Place the “vp” and “vm” pins 3 squares apart (as was done for the hierarchical

symbol), place the “vi” and “vt” pins on the left side (4 squares across from the

“vp” and “vm” pins, and delete the default graphics (see below)

Import new graphics using menu “Draw -> Image” and go to where the

“PV_Array_sym.bmp” file exist, place it and size it accordingly so it appears as

shown below. Close out the symbol editor and save changes

4 squares

3 squares

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Select the WM2, R2 , and their plots to copy (note draw a box as shown below to

select them, (no need to completely surround each component that you want to

select) use “ctrl-C” to copy and “ctrl-V” to paste

Position the copied components as shown below, connect up the “PV_array”

model.

Add two voltage source to represent the temperature and Irradiation inputs, give

them a voltage of 1000 and 25, add 4 page connectors (“Draw -> Page

Connectors) and name two of them “temper”, and the other two “Sun”, connect

them as shown below.

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Rename the new plots to be “IV Curves 3” and PV Curves 3”

If needed, Select each of the new plots, RMB -> View -> Visibility , Set the

display of the new plots to display the “Header”

Set up the new plots for WM3.I vs WM3.V (IV Curves 3)

WM3.P vs WM3.V (PV Curves 3)

as was done in the previous examples.

(Don’t forget to use the “Apply Trace”

instead of the “Add Trace”)

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Edit the PV_array model parameter “kt” to be “0”, this will cause the input at the

“vt” pin to represent the cell temperature instead of the ambient temperature

Run the TR simulation using the blue arrow at the top of the simplorer window,

the results should appear as shown below

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Evaluate the effects of the series and shunt resistance on the IV curves

Set the series resistance “rs” for the hierarchical model to 0.1, and set the shunt

resistance for the VHDL-AMS “PV_array” model “rshr” to 1.

Run the TR transient simulation, you should observe the results as shown below

Note the slopes caused by the high series resistance or low shunt resistance are

equal to the value of “rs” and “rshr”

Measure the slopes by opening the plots from the project manager window

(under the results folder), double click on the “IV Curve 2”, then using the RMB

menu, select “Marker -> add delta marker”, place the two points near the bottom

of the curve as shown (hit ESC to get out of marker mode), note the InvSlope is

the resistance value given in milliohms, or 0.108 (which is basically the value

place on “rs”)

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Remove the delta markers using RMB -> Marker -> Clear All

Double click on the “IV Curve 3” now, then using the RMB menu, select “Marker

-> add delta marker”, place the two points near the top of the curve as shown (hit

ESC to get out of marker mode), note the InvSlope is the resistance value given

in milliohms, or 1.0 (which is the value place on “rshr”)

Clear the markers using RMB -> Marker -> clear all

Double click on the “PV_char” design in the project manager window to get back

to the main schematic

Reset the value of “rs” for the hierarchical “SolarCell” model back to 0.0001, and

the value for “rshr” of the VHDL-AMS “PV_array” model to 10000

Run the TR transient analysis to make sure you have the original results as

shown below. File->Save

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Temperature and Irradiance effect on the IV and PV solar curves

set up project variables that can be swept, select the menu “Project -> Project

Variables”

Select “add” at the bottom, then define a variable “cell_irrad” (to represent the

cell irradiation from the sun) and give it a default value of 1000 , select “OK”

Add another variable named “cell_temp” and give it a default value of 25. Note

the results below. Note a “$” is added indicating it’s a “Project variable”, hit “OK”

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Change the two voltage sources that represent the irradiation from the sun and

the cell temperature to use the project variables just created.

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Add the variable “$cell_temp” to the hierarchical “SolarCellsys” model for the

value of tempr, and “$cell_irrad” for the value of irrad_static, File -> Save

Set up the parametric sweep analysis by selecting “Optimetrics” in the project

manager window, RMB -> Add -> Parametric..

Select “Add”, then in the next

Window define the variable to use

“$cell_temp”, set to sweep in

Linear steps between 10C to 70C

In steps of 20, select the “Add”

Select “OK”

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View the values that will be swept during the parametric sweep analysis by

selecting the “Table” tab, note this table can be edited. The parametric analysis

will set the value for $cell_temp to 10, then run the TR analysis, it will then set

the $cell_temp variable to 30 and run the TR analysis…. Etc. A plot can be

created to view the different TR simulations wrt the different temperature settings.

Select “OK”, note in the project manager window under the “optimetrics” now

exist the parametric setup just created, change the name to “para_temp”

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Add another parametric analysis for the variable “$cell_irrad”

Change the name to “para_irrad”

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Select the 4 plots (IV Curve 2, IV Curve 3, PV Curve 2, PV Curve 3) use “cntrl-C”

to copy, then “cntrl-V” to paste next to the existing graphs as shown below

Set the graphs to view the “Header” instead of the “legend” by selecting the plot,

RMB -> view -> visibiliby, select the “Legends” tab, and check “Header”, uncheck

“Legend”

Change the names of the plots in the project manager window to show the

following

(IV Curve 2_temp, PV Curve 2_temp, IV Curve 3_irrad, PV Curve 3_irrad)

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Double click on the “IV Curve 2_temp” plot, select “Optimetrics setup” to be

“para_temp”, select the Y axis to be WM2.I (current in Watt Meter 2), select the X

axis to be “WM2.V” (Voltage across Watt Meter 2), this will yield the IV curves

Select the “family” tab, select “Sweeps”, select the variable “$cell_temp”, select

“…”, select box “use all values”

Select “Apply Trace” to erase previous plots and use this set up. “close”

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Double click on the “PV Curve 2_temp” plot, select “Optimetrics setup” to be

“para_temp”, select the Y axis to be WM2.P (power in Watt Meter 2), select the X

axis to be “WM2.V” (Voltage across Watt Meter 2), this will yield the PV curves.

Select the “family” tab, select “Sweeps”, select the variable “$cell_temp”, select



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Double click on the “IV Curve 3_irrad” plot, select “Optimetrics setup” to be

“para_irrad”, select the Y axis to be WM3.I (current in Watt Meter 3), select the X

axis to be “WM3.V” (Voltage across Watt Meter 3), this will yield the IV curves

Select the “family” tab, select “Sweeps”, select the variable “$cell_irrad”, select



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Double click on the “PV Curve 3_irrad” plot, select “Optimetrics setup” to be

“para_irrad”, select the Y axis to be WM3.P (power in Watt Meter 3), select the X

axis to be “WM3.V” (Voltage across Watt Meter 3), this will yield the PV curves.

Select the “family” tab, select “Sweeps”, select the variable “$cell_irrad”, select



File -> Save

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Run the parametric analysis that sweeps the temperature; select the “para_temp”

under the “Optimetrics” use RMB -> Analyze.

The results should appear as shown below

Note as temperature increase, the Isc increases, however the Voc decreases to a

larger percentage, therefore since P = I*V, as temperature increases, the max

power available from the solar cell/array decreases. Note that the Vmp (voltage

at the max power point) also changes

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Run the parametric analysis that sweeps the Sun’s irradiation; select the

“para_irrad” under the “Optimetrics” use RMB -> Analyze.

The results should appear as shown below

Note as irradiation decreases, the Isc decreases, driving the available power

down as well. Note the Vmp remains fairly constant

File -> Save

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Section 2 (Shadow Analyses)Depending on how solar cells are arranged in modules and the final array,

shadowing issues can cause major loss of power if not circumvented. The use of

bypass diodes can help to salvage some of the power under shadowing

situations. How the bypass diodes and how the solar arrays are configured will

yield different results that need to be understood.

Open the project PV_comp_save_R19p1.aedt, and then double click the mouse

over the design “2_Shadowing_1_ser_par2” as shown below.

On the left is Six Cells in series, with one bypass diode, on the right is Six Cells in

parallel, with one bypass diode. In both cases, the top cell will be shadowed to

view the impact.

Note the use of the ICA block to define the variables for each Cell, and Note the

parameters of each Cell refers to the values from the ICA block

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Note the top cells that will be shadowed have the variable “shadow” for the

Irradiation input

This variable will be set to 0.1 (shadow condition) and then 1000 for full Sun

Condition in a parametric analysis. The results will compare the two.

Run the parametric analysis by expanding the “Optimetrics” folder under this

design in the Project Manager window, and RMB (Right Mouse Button) over the

parametric analysis to run -> Analyze

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Results of the parametric analysis are show below

Red is the shadowed results and yields less peak power in both cases, however

the series configuration has a greater loss in peak power.

Under no shadowing, both configurations have the same peak power since both

have the same number of cells (Even though the currents and voltages are

different based on the configuration, ie series vs. parallel).

The parallel configuration does better under shadowing as it shows much more

peak power. Note the effect of the bypass diode on the parallel configuration has

no effect, could remove it and get the same results, however in more complex

series/parallel combinations, this diode would be needed.

If the bypass diode in both configurations were taken out, the series configuration

would yield no power output, while the parallel would still provide the power

shown.

Note the large voltage delta in the series configuration under shadowing, we lose

the “supply” of one cell (less 0.7 Voc), and add in a “loss” of the diode drop (0.8)

so the delta is approx 1.4V (this yields the much lower peak power)

This is a simple example of different configurations and the use of bypass diodes,

Arrays are configured of much more complex combinations and simulation aids in

the evaluation of optimizing the design.

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Section 2 (Shadow Analyses) Cont’dOpen the “2_Shadowing_par_mod2” design

This design shows a simple, yet more complex configuration. 3 Cells are

connected in parallel across the top, and then duplicated 5 more times below.

These parallel strings are then connected in series. A bypass diode is placed

across each parallel string.

Total Cells = 18, Total Bypass Diodes = 6, Max Peak Power = 36W

Note the 3 parallel Cells yield 3*Cell current, and the 6 series connections yields

6*Cell voltage which can be observed in the non-shadowed results

Isc/Cell = 4.0 (due to temperature increase on Cell due to Irradiation),,

therefore new Isc = 3*4.0 = 12A

Voc/Cell = 0.63 (due to temperature increase on Cell due to Irradiation),

therefore new Voc = 6*0.63 = 3.8Voc

Run the parametric analyses which yields the results shown below

Note the results for the shadowed simulation (Red)

Note since there are multiple peaks in the PV curves, this can cause

issues when designing Peak Power Tracking control

Shadowed Cells

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Section 2 (Shadow Analyses) Cont’dOpen the “2_Shadowing_ser_mod2” design

This configuration is a variation of the previous design. In this design, there are 6

Cells connected in Series, then duplicated to the right, these series strings are

then connected in parallel. Two bypass diodes are placed across each series

string (Note same shadowing pattern is used).

Total Cells = 18, Total Bypass Diodes = 6, Max Peak Power = 36W

Same as previous design, only different configuration

Note the 6 series Cells yield 6*Cell voltage, and the 3 parallel connections yields

3*Cell current which can be observed in the non-shadowed results

Voc/Cell = 0.63 (due to temperature increase on Cell due to Irradiation),

therefore new Voc = 6*0.63 = 3.8Voc (Same as Previous Design)

Isc/Cell = 4.0 (due to temperature increase on Cell due to Irradiation),,

therefore new Isc = 3*4.0 = 12A (Same as Previous Design)

Run the parametric analyses which yields the results shown below

Note the results for the shadowed simulation (Red)

Note that even though we have the same number of Cells and

bypass diodes, and same Isc, Voc, Peak Power, the shadowed

results are very different

Shadowed Cells

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Section 3 (Evaluate Maximum Power Points Vmp, Imp, Pmp)Open the Design “3_PV_PPP”, this design now uses the VHDL-AMS version of

the Solar model which is much more versatile.

Allows time varied input for Irradiation and Temperature

Calculates the Solar Array “capacity” (based on input Temp and Irradiation)

around the Peak Power Point vs. what is actually delivered

pmp (Peak Power Point), vmp (Voltage at PPP), Imp (Current at PPP)

This Design shows that if the actual Temperature is combined with Irradiation

levels, the actual I-V and P-V cures look a bit different now.

Run the Parametric Analysis under the “Optimetrics” folder in Proj Mgr

As Irradiation increases, the Current increases, however the Cell

temperature also increases, which causes the Voltage to decrease. (See

graph far left)

Note the measurements from the simulation compare favorably to the

Internal Calculations for values around the PPP.

If the User would like to know the setup process for the parametric sweep and

Measurements shown in this Design, see next pages, otherwise scroll to page 58

for the next section.

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Add two Plots , “Draw -> Results -> Rectangular Plots” (do not add traces at this

time, simply close) and two numeric plots “Draw -> Results -> Numeric Display”

(do not add traces at this time, simply close) arrange them as shown below

Define the “TR” transient analysis (Tend = 10s, Hmin = 1ms, Hmax = 100ms)

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Define a parametric sweep analysis, select “Optimetrics” in the project manager

window, RMB -> Add -> Parametric..

Add two variable to be swept, “Add” , select the project variable “$amb_temp”,

select “single value”, make the value = 20, select “Add>>” , “OK”

Add the second variable, “Add”, select the project variable “cell_irrad”, select

“single value”, make the value = 350, select “Add>>”, “OK”

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Select the “Table” tab and note we have the following

Add two more entries using the “Add” button, then edit them to appear as shown

below, select “OK”. Note it is more accurate when varying the irradiation, to also

vary the temperature associated with the change in irradiation, File - > Save

Set up the plots, double click on the first Rectangular plot to set up for the IV

Curves, select the “Optimetrics setup” to be the “ParametricSetup1” select the Y

axis to be “WM1.I”, select the X axis to be “WM1.V”, select the “Families” tab,

make sure all are set to “All”, select “Add Trace”, “close”

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Select the second rectangular plot and set up for the PV Curves, double click on

the Rectangular plot, select the “Optimetrics setup” to be the “ParametricSetup1”

select the Y axis to be “WM1.P”, select the X axis to be “WM1.V”, select the

“Families” tab, make sure all are set to “All”, select “Add Trace”, “close”

Set up the output dialog for the

Solar model variables so they can be plotted,

select the menu

“Simplorer Circuit -> Output Dialog”,

Scroll down and expand “SA” (note this

Was the name given to the solar model)

Select Vmp, Imp, and Pmp

Select “Add”, then “OK”

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Set up the numeric displays, double click on the first numeric display, select the

“Optimetrics setup” to be the “ParametricSetup1” select the Y axis to be

“SA.pmp””, leave the X axis to be Default - Time, select the “Families” tab, make

sure all are set to “All”, select “Add Trace”, “close”

Set up the next numeric display, double click on the 2nd numeric display, select

the “Optimetrics setup” to be the “ParametricSetup1” select the Y axis to be

“SA.vmp””, leave the X axis to be Default - Time, select the “Families” tab, make

sure all are set to “All”, select “Add Trace”, “close”

Set the rectangular plot displays to view the header instead of the legend, change

the names in the project manager window to be “IV_Curve” and “PV Curve”

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The circuit should now appear as shown below

In the project managers window, double click on the “PV Curve” report, place the

mouse in the plot area, RMB -> Trace Characteristics -> Add

Add in Math,max,Full Range, “Add”, then Math,XatYmax,full range, “Add”, “Done”

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Double click on the design “3_PV_PPP” to get back to the schematic

File -> Save

Run the parametric analysis, select “ParametricSetup1” RMB -> Analyze

View the measurements on the “PV Curve” on the schematic by selecting the “PV

Curve” plot, RMB -> view -> visibility, select the “legend” tab, select BOTH

Header and Legend

Select the “PV Curve” plot and stretch it horizontally so the measurements are all

displayed

With the “PV Curve” selected “RMB -> edit in place” and move the legend to the

lower left corner

Double click on each of the numeric plots and select the “apply trace” button to

view the results.

Stretch the numeric displays to view all the data, then RMB -> edit in place, using

“ctrl” key, select all the names on the left side, in the “properties” window (lower

left) select the “Data Table” tab at the bottom then de-select the “show solution”

and “show Variation” boxes. Now select the “Data Filter” tab and change the

“Field Width” to 4, and “Field Precision” to 2. Repeat for the other numeric

display.

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The results should now appear as shown below

Make the measurement text larger by selecting the “PV Curve” plot, RMB -> edit

in place, select the title area of the measurement block, note the “Properties”

window and select the “Legend” tab, select the “Font” button and set for “8”

File -> Save

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Section 4 (Modeling Irradiance and Temperature transients)Open Design “4_irrad_temp_profile”, this Design will show modeling of the

Transient Irradiation and Temperature thru a 24 hour period.

Initial modeling was done using a lookup table from Irradiation measurements

Equation blocks were then created to implement Equation representation for the

Irradiation data and Temperature profile

Since there seemed to be a relationship between the Irradiation and

Temperature, a new Equation block was created to calculate the Temperature

based on the Irradiation Data. This way only the Irradiation data is needed and

the Temperature would be calculated based on that.

Run the TR Analysis and note results below

If User would like to understand the Process involved in setting up these blocks,

see next pages, otherwise skip to page 67 (section 5)

Plot of actual data from table lookup model

vs.

Equation model

Temperature Plots:

Equation based

Vs

Using relationship to Irradiation

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In this lab we will create irradiation and temperature transient sources to be used

in PV system analysis

Insert a 2D table look up block (t,y)

Basic Elements/Tools/Time Functions/Datapairs: 2D Look up

Double click on the block, name it “irrad_data” and hide the output pin

(Output/Display tab/Show pin)

Import the data file for the example irradiation, double click on table look up

block, select the “Characteristic” button, select the “Datasets…” button, the

existing data sets will be displayed that were created in previous labs

Select the “Add” button, name the new data set “irrad_data”, select the “Import

Dataset..” button, select the excel (*.xls) file type, and search for the

“irrad1_data.xls” file, select “OK” to Sheet1

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The resultant data should appear as shown below

Note the irradiation data looks very much like half of a sine wave, select “OK”,

“done”. “OK”, “OK” to get back to the schematic.

Add an equation block to create an equation that can represent the above data

based on a sine wave

Basic Elements/Tools/Equations/FML:Equation

Double click on the EQU block, name it “Irrad_behav” (for behavioral model) and

insert the following equations (select to “show” on the schematic) Note to insert

equations, use the universal icon in simplorer for insert

maxpt_ir:=1000

minpt_ir:=25

period:=86400

omega:=2*pi*(1/period)

v1_ir:=(maxpt_ir-minpt_ir)*-sin(omega*time) + minpt_ir

if(v1_ir > minpt_ir) {v2_ir:=v1_ir;} else {v2_ir:=minpt_ir;}

Note the period (seconds) is for 24 hour period, “maxpt_ir” is for the maximum

peak value of irradiaton, “minpt_ir” is for the minimum value for irradiation, “v1_ir”

is a sine wave that has offsets so that the peak is “maxpt_ir” and the minimum is

“minpt_ir”, the last equation for “v2_ir” cuts off the sine wave at the “minpt_ir”

value (much like a rectifier)

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Select the menu “Simplorer Circuit -> Output Dialog” to define variables that can

be plotted, select the “Equation variables” and select “v2_ir’, Note the variable for

the table look up block “irrad_data.VAL” should already be selected, if not, select

it as well.

Add a rectangular plot, and define the inputs to be “irrad_data.VAL” and “v2_ir”,

(NOTE to select several waveforms to be plotted, hold down the “ctrl” key), select

“Add Trace”, then “close”

set the view setting on the plot to display the “Header” instead of the “legend”

Change the name of the plot in the project manager window to “irrad_data vs Eq”

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Set up the “TR” analysis for simulation over 24 hours, select End Time, Hmin,

and Hmax pull down to be in “min”, then select the value Tend = 1440min, Hmin

= 1min, Hmax = 100 min

Run the “TR” analysis using the blue arrow button at the top of the simplorer

window, the results should appear as shown below. Note the behavioral equation

based model for the irradiation fits very well with the actual test data.

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Select the plot, RMB -> edit in place, select the x axis, note in the “properties”

window, select the “Scaling” tab, uncheck the “Auto Units” and change the default

units to “hours”

Select the EQU block, copy and paste it, change the name of the new block to

“Amb_tempr_behav”, edit the equations and replace all “_ir” with “_t” then

change the value for “maxpt_t:=40” and “minpt_t:=10” which should yield the

following

Note this would represent the change in temperature as a function of time that

relates to the change in irradiation - temperature in degree C.

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Select the menu “Simplorer Circuit -> Output Dialog” and select “v2_t” under the

Equation variables so it can be plotted, select “Add” then “OK”

Add another rectangular plot, define the trace as “v2_t”, then “Add Trace”

Change the view on the new plot to display the “Header” instead of the “Legend”

Change the name of the plot in the project manager window to be

“Ambient temperature”

Run the TR analysis with the blue arrow at the top of the simplorer window, the

results should appear as shown below

The concept here is that the above sources can be used for system level analysis

to provide the “transient” ambient temperature and irradiance to the Solar

system.

Note because both the irradiance and temperature use the same basic

equations, there is a linear relationship between them, Add another rectangular

plot and plot Y axis to be “v2_t” (temperature) and the X axis to be “v2_ir”

(irradiation)

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Run the transient TR analysis and the results appear as shown below

Note this is a straight line equation (Ambient temperature = 0.03*irradiation + 10)

This equation can now also be used at the system level to calculate the ambient

temperature based on the irradiance.

Add another EQU block

Add the equation amb_eq:=0.03*v2_ir + 10 this will take the results from the

“irrad_behav” equation block (v2_ir) and calculate the ambient temperature, this

can then be compared with the equation block that calculates the ambient

temperature

Add the new equation variable “amb_eq” to the output dialog window “Simplorer

Circuit -> Output Dialog” , select the equation section, then “amb_eq”, select

“Add”, “OK”

Add a new rectangular plot, define the trace to be “amb_eq”

Run a new “TR” transient analysis and compare the results from using the

“amb_eq” equation, vs the equation block “Amb_tempr_behav”, both agree.

View the final results on the next page

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The final results of the irradiance and ambient temperature characterization are

shown below

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Section 5 (PV sizing)Open design “5_PV_sys_VL”, this example looks at the importance of how to

size the solar array (number of series cells and number of parallel cells) to

achieve the desired voltage and power levels.

The Equation block uses equations defined in the previous design for the

Irradiation (v2_ir), and the ambient temperature (amb_eq).

The Voltage sources connected to the “vi” (irradiation input to the solar array

model), and “vt” (ambient temperature input to the solar array model) use the

variables defined in the equation blocks (v2_ir, amb_eq)

The load is fixed at 12V, which in effect controls the Solar Array Voltage

operating point.

Run the TR analysis

Note the Solar Array model provides equations that calculate the Peak Power

Points (P,V,I) capacity at any given input to the model. This “capacity” is shown

as the Red curve, and the actual power delivered is the Blue curve. In this

example it shows the Solar Array is not very well designed and only 65% of the

peak power available is being utilized.

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A parametric analysis was set up to vary the number of series cells in the solar

array model, and note the efficiency (utilization) of the system.

Run the parametric analysis

From the plot of the parametric analysis it can be seen that the best utilization of

the solar array is when the number of series cells (ns_v) is 22. this is because at

22 series cells, the peak power point of the Solar array occurs at 12V (desired

load voltage). Note if more power were needed, additional “parallel” cells would

be added to the 22 series cells

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To further explain the previous results, consider the following plots that show the

IV and PV curves for the same solar array as “ns” is swept from 36 to 20 as was

done in the parametric analysis. The 12v load voltage is shown.

This shows that the 12v operating point of the load, (if ns=36 series cells), is well

to the “left” of the peak power point, and the power level is approx 150W.

As the number of series cells is decreased, we still get the same current into the

load, and thus the same power to the load, however we are now operating closer

to the peak power point, therefore we get more percentage of the available peak

power (ie the efficiency is increasing).

As the ns is decreased further (ns=20), we see the Vmp (voltage at max power

point) decrease “below” the Vload of 12v and therefore shows we are now

operating on the “right” side of the PV curve, and therefore start to lose power

quickly

If the User would like to see the steps for the parametric setup, see next page,

otherwise advance to page 71 for the next section

ns = 36 has the

Peak Power Point

Far away from the

Operating voltage

operating point 12v

Note at ns=22,

Operating at the peak

Power point now

At ns = 20, end up

Operating on the

Right side of PV curve

Therefore steep loss of

Power possible.

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This sections shows how to set up a parametric analysis to sweep the number of

series cells

Double click on the PV_array model, and set the value of ns to be a variable

“ns_v” (don’t use the quotes, where the “v” stands for variable), note this will

create a “local design variable” as opposed to a “project variable” and so will only

be available to this design. When the window appears, define the default to be 36

Select “optimetrics” in the project manager widow RMB -> add -> parametric..

Select “Add” to add the variable just created “ns_v”

Set up the sweep of the number of series cells to go from 20 to 36 in steps of 1

Select the plot “Peak Efficiency” and copy and paste it

Set the visibility of the new plot for the “Header”

Change the name in the project manager window of the new plot to “Peak Eff vs

Series Cells”

Double click on the plot (note the equation from the original plot should still be

there (max(WM_SA.P)/max(SA.pmp)*100), change the “Optimetrics setup” for

the parametricSetup1, note the default X axis should be the swept variable “ns_v”

Select “Apply Trace” , then “close”

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Section 5 (PV sizing) Cont’dOpen the “5_PV_sys2” design and run the “para_config” parametric analysis.

This sets the number of series and parallel cells in two different configuration to

further understand the need to size the solar array appropriately. Each

configuration is using basically the same total number of cells.

For a 24 V load, the configuration is set to ns (series cells) = 36, np (parallel

cells) = 3 (blue curve). Note the peak power point occurs at 24V to deliver the

maximum available power from the solar array to the load.

For a 12V load, the configuration is set to ns (series cells) = 22, np (parallel cells)

= 5 (red curve). Note the peak power point occurs at 12V to deliver the maximum

available power from the solar array to the load.

Note since both configurations use basically the same total number of cells, each

has the same amount of peak power available. The only difference is at which

voltage this occurs.

Note also if using the 24V configuration (blue), then going to a 12V load would

still yield approx. 140W delivered, however if using the 12V configuration and

then going to a 24V load, there would be no power available for the load.

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Section 6 (Introducing a system level battery model)Open Design “6_Battery_test” and run the TR analysis.

This test setup uses a “system” level battery model created specifically for

evaluating energy balance for long simulation times (days, weeks, months..). The

model includes efficiency factors that take into account the need to charge more

AH (Amp-Hours) than is discharged out of the battery, in order to return to the

same SOC (State of Charge).

A detailed battery model that exactly models the overcharge regions would take

to long to simulate and is not required for the types of simulations desired for

energy balance and sizing. Note the results for the “Battery Voltage” of this

“system” level battery(Blue) compared to a more detailed model (Red).

Note the data for the detailed battery was imported into a table lookup

model in order to compare to the “system” level battery.

This battery model will be used in the Solar Power System for sizing (number of

cells in series and/or parallel, and AH rating) to achieve the desired energy

balance of the system (ie during the day, the battery will be charged enough to

supply the load power during the night time (and accounts for the efficiency of the

battery).

If the User would like to review the process for setting up the table lookup models

used in this design, see following pages, otherwise end here

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Table look up models set up:

Add to the schematic two (t, y) datapairs table lookup block

Basic Elements/Tools/Time Functions/Datapairs: 2D look up

Double click on one of the table look up blocks, name it “Batt_data” , then go to

the “Output/Display” tab and un-check the “show pin” box (keep the check under

SDB so we can plot this from the database later)

Double click on the other table look up block and name it “load_current” and

again un-check the “show pin”

Double click on the current source and give it a value of “load_current.VAL”,

choose the “Output/Display” tab and select to view the value of “IS”,

Arrange and connect them as shown below

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Add the load current profile by using the table look up block

Double click on the “load_current” table look up block

Select “Characteristic”, then select “Datasets…” note all the previous

datasets created in this lab should appear

Select “Add” and name the new data set “battery_load_current_80” (which

will refer to an 80% discharge load), edit the values as shown below, then

select, “OK”… “Done” …. “OK”

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Select to make this periodic by selecting the “Period” box and give it a period of

36000s, and select the “Periodical” to be “yes”, select “OK”

Double click on the “Batt_data” table look up model, select “Characteristic”, select

“Datasets…”, “Add”, give the new data set the name “battery_voltage_ref_80”

Select the “Import Dataset” button, select the filter for “Comma Sep value (*.csv)

and locate the file “battery_voltage_ref_80.csv”, “Open” , select “OK” at the next

window.

Select “OK” …. “Done” … “OK” (no need to make this periodic) “OK”

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Part 2 of the PV labs will use the “PV_sys_save_R19p1.aedt”

project that contains the designs discussed here

Section 7 (PV initial sizing)Open “PV_sys_save_R19p1.aedt”

Open the design “7_PV_sizing” , This will be used to evaluate the required series

and parallel cells to achieve a desired load voltage of 12V at 100W during “most”

of the day.

The irradiation used will be an average value based on a full day’s irradiation

yielding the input of 637W/m2

The temperature will be worse case high temperature based on the day

(remember that as temperature increases, the maximum power available from

the solar array decreases) so this yields worse case lowest power by using the

input of 40C

Double click on the solar array and define the number of series cells to be ns=26,

and number of parallel cells np = 3, run the TR analysis

Note we want to operate near the peak power point. It appears for the cells

defined (Voc = 0.7), that 26 series cells is enough to operate at 12v, however

note the power curve at 12v shows less than the 100 watts needed.

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Change the values for np to be 4 (leave ns = 26) and rerun the TR analysis

Note at 12v, there is enough power for the 100W load with additional margin to

account for variations during morning when the irradiation is less than 637 W/m2

It is shown (above) at ns=26, the peak power point is beyond the 12V load that

we want to size for. Set ns = 22, keep np = 4, and re-run the simulation. This

yields the peak power point at 12V and is above 100W

File -> Save

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Section 8 (check sizing vs. actual irradiation and load)

The next step will be to add the100W load (12V @ 100W yields Rload = 1.44)

into a system level analysis that now defines the irradiation and temperature

based on a typical day, and see how the system behaves.

Open the new design “8_PV_act_irrad” (Note ns=22, np=4 for the solar array)

Run the TR simulation and note the results below

Note the load voltage and power meet the requirements (greater than 12V and

100W)

Note the plot “SA Pmp vs. P_act” showing the available power of the solar array

(red) and the power actually being used (blue), the efficiency is quite low here

because we had to size the solar array to get 12V at 100W during most of the day

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Set ns = 18 to represent shadowing and re-run the simulation.

Note the results now show there is not enough Voltage or power to the load

under this condition.

Note however there is still excess power available from the solar array

It will be seen in the next section by using a peak power tracker DC/DC

converter, the load can take advantage of this excess solar array power under

shadowing conditions.

Change ns back to 22, re-run the simulation, and save

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Section 9 (Adding a Peak Power Tracker - PPT)Open the design named “9_PV_PPT” , this design adds a Peak Power Tracking

DC/DC converter to now drive the 100W load under the same shadowing

configuration as the previous design (ie ns = 18)

Double click on the PPT block and note there are inputs for efficiency of the

converter and output voltage

Run the TR simulation and not the results below

Note the load now has the available 12V 100W power under the shadowing

conditions where the previous design without the PPT did not. This is because

the PPT can adjust the voltage load of the solar array to maintain maximum

output of the solar array, while also providing the desired voltage to the load. In

other words, it loads the solar array to operate at its Peak Power Point.

Note even this configuration has excess solar array capacity at peak sun times

File -> SAVE

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Section 10 (Adding Energy Storage – Battery)In this section, a battery will be added to the system to understand how that

affects the performance and sizing of the PV system

Open the design “10_PV_Batt”

The idea here is that the battery will supply the power to the 12V, 100W (8.333A)

load for 12 hours during the night, and get charged up during the other 12 hour

daylight period (the load is being supplied 100W during both day and night).

To determine the AH rating needed to supply the 100W for 12 hours during the

day, we need 8.333A * 12 hours = 100AH, however this assumes a fully

discharged battery at the end, we only want a 20% discharge, therefore

100AH/0.2 = 500AH rating

Need to double the solar array current to supply both battery and load current

during the day, also the current to charge the battery requires more than the

discharge current due to the efficiency of the battery, therefore np is now set to 9

There is also a new diode drop to the battery that needs to be overcome so the

series cells is increased by 1, therefore ns is now set to 23

Run the TR simulation and note results below.

Note load power is above 100W for both day and night

Note the Solar Array is still not being fully utilized as there is extra power at the

peak power point

Note the battery current “batt_iout” goes negative which indicates discharge

during night period

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Set ns to be 20 to indicate a shadowing effect on the solar array, and re-run the

TR analysis.

Note the power to the load during the night is now no longer supplied and the

power utilization is very poor as seen by the large amount of solar array power

available that is not being used.

Note in the next design it will be shown using a peak power tracker would create

full utilization of the solar array and allow much more power to the load at night

giving this same shadowing pattern

Set ns back to 23, re-run the TR, and save

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Section 11 (Adding Peak Power Tracking along with the battery)

This section will add to the previous lab section by adding a DCDC peak power

tracking converter providing power to the battery and load. This allows more

efficient use of the solar array and can help to circumvent varying conditions that

can cause power loss such as the shadowing effect in the previous section.

Open the design “11_PV_PPT_Batt”

Note the same shadowing conditions (ns = 20) is configured in this example


Note the load now has much more power than before during the night, and the

solar array utilization is at 100% due to the addition of the PPT

File -> Save

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Section 12 (Adding load converters)

In this section, localized conversation for the loads will be added to show a more

complete system

Open the design “12_PV_PPT_Batt_DCDC”, this shows a system with the

detailed solar array irradiation and temperature profiles, the Solar Array, the PPT,

a Battery, and now includes a load side DCDC converter to power a load

Note both the PPT and load DCDC converter have losses, and the efficiency of

these two blocks can be defined as inputs.


Note the system is using the full solar array capability by using the PPT.

File -> Save

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Section 12 (Adding load converters cont’d)

Open the design “12_PV_PPT_Batt_DCDC2”, this design adds a second DCDC

load converter to create two DC buses for loads (12V and 24V)

Run the TR simulation and note the results shown below

These types of simulation can be performed to evaluate and validate energy

balance in a solar powered system with battery charging for night time power.

File -> Save

Ansoft HFSS Fundamentals - ModeFRONTIER

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