Hi swagatamI am a b tech student at tshwane university of technology (in south
Africa).i have been given a task to design and implement an mppt on my
industrial project.i am really confused and not sure where to
start.yesterday when I was searching for something that can help me I
came across your file about an mppt. so I want a really help on where I
have to start on my design and implementation of an mppt. this project
has to be on a PC board.with solar panel,mppt,battery, maybe an inverter
before the load.please can you assist I am totally new to this type of
research. i will appreciate your help.you can talk to me via email
This is my technical specifications on mppt.
I will have two 16v solar panels connected in series......to charge a 24v battery (can also do two 12v connected in series)
So I want to have an mppt circuit that can best suit the combination
above.if possible it must be a circuit that works automatically meaning
it should be able to switch of the circuit when the battery is fully
charged and also be able to switch on the circuit when the battery is
not fully charged.
I have also heard that there are some techniques that can be used to
design and implement an mppt.the following are the two I have done
research a little about them.
1. pertube and observe method (uses voltage sensor parameter)
2. Incremental conductance method (uses voltage and current sensor parameters)
So now I really don't know what I should focus on.please help with the
circuit based on the technical specification I have provided.please let
me know if there is something I haven't specified.kind regard Enos
The working principle of the following solar charger simulates the principle of incremental MPPT voltage sensing, and regulating it as per the connected battery charging requirements.
I have also discussed this in one of my previous posts where the design is in a manual adjustment form.
The circuit regulates the required amount of voltage to the battery by sensing the maximum power point of the solar panel, and by inserting or bypassing a group of diodes accordingly in series with the supply path.
The functioning may be accurately understood by studying the following example:
As shown in the circuit diagram, the total drop by the diodes when all are in series would be around 20 x 0.6 = 12V.
Let's assume we have a solar panel with maximum power point at around 26V and we want to utilize this level for charging a 12V battery having 14.4 V as the optimal charging voltage.
To initiate the MPPT function we adjust the 10K preset of the IC LM3915 which is a dot/display mode LED voltage indicator such that all its output become low (all LEDs ON) at the suggested 26V.
At this position the gates of all the mosfets become negatively biased so that all of them stay shut off.
With all the mosfets shut off, all the diodes get in the path of the supply dropping about 12 volts, which gets deducted from the solar panel total voltage, offering about 26 - 12 = 14V across the battery, which is just about the required optimal charging voltage for the battery.
The above situation prevents the solar panel voltage from dragging down to the battery voltage level yet confirms an optimal charging conditions for the battery.
Now suppose the panel voltage drops by a couple of volts due to reduced sunlight or other similar issues.
This drop in the potential creates a proportionate drop at pin#5 of the IC which in turn switches OFF one or two of its outputs starting from pin#10 and downward.
This forces the relevant mosfets to conduct and bypass a couple of diodes or more thereby allowing a proportionate compensation for the battery under charge.
This ensures that the battery is never deprived of the required charging voltage even under adverse conditions where the solar panel has dropped considerably. The functioning also ensures that even under adverse conditions the MPP of the panel is never compromised, and its voltage never dragged down by the battery under charge.
As discussed above the IC LM3915 tracks and monitors the maximum power point of the panel which is actually the maximum open circuit voltage of the particular panel under the given conditions, and toggles the series diodes appropriately such that the battery is charged optimally even under worst situations without compromising with the maximum power point of the solar panel.
The above design can be further enhanced by adding this current and voltage controlled tracker circuit in between the output of the circuit and the battery.
All Diodes = 6A4
All Mosfets = 50V, 10A or similar, N-channel
All gate resistors = 47 ohms
Warning: This circuit will not track the IV curve of the panel.