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[Help] MPPT Solar Controller schematic

Discussion in 'Datasheets, Manuals or Parts' started by Elecholic, Apr 24, 2009.

  1. chrismicro

    chrismicro New Member

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    Precise, you can only find the Maximum Power Point if the panel is directed to best position to the sun and most authors DO agree with me, only the misinformed disagree. The only reason I'm on this thread is because one of my students directed me to it. One question: what is the meaning of the word Tracking? Answer: To follow something! I rest my case. How the hell can you follow the maximum power point in a stationary panel? the maximum power it can deliver depend on two things, the temperature of the panel and its position to the sun.
     
  2. KeepItSimpleStupid

    KeepItSimpleStupid Well-Known Member Most Helpful Member

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    Technically, you can track the MPP of a stationary panel. For that, you change the operating point of the panel.

    Moving the panel can position it so the max intensity is falling on it, but the panel may not be operating at it's max power point. That's also a function of the inverter.
     
  3. chrismicro

    chrismicro New Member

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    If you can call a discharging inductor an inverter go for it, that is al a buck DC-DC converter is. we are getting no ware with this conversation, all I can say is, some scholars need to have there heads examined.
     
  4. dave

    Dave New Member

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  5. chrismicro

    chrismicro New Member

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    Mppt sch

    I include a schematic of a so-called MPPT that my one student got from the net and after spending a lot of time and money on the project, the only part that was working, was the 555 clock for the flipflop, that I designed for him.
     

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  6. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    Sorry but I think you are way off.
     
  7. KeepItSimpleStupid

    KeepItSimpleStupid Well-Known Member Most Helpful Member

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    I'm not sure how to design one, but you may have to do what might be called a double-conversion. Let's say you wanted 24V out and you wanted MPPT.

    I'd probably use a micro to measure the the I and V of the array and you would have 0-Jsc and 0-Voc as limits. One of the issues is, if Voc is too high the inverter my not start. I had that happen on an install (that occurred in the late 70's or so) that I debugged about 10 years later. I found out the system never worked. This was a research system and no one cared until I was involved in a Demand Side Management research project.

    So, a computer would keep modifying the output voltage setpoint while monitoring the product of V and I and store this energy into a capacitor bank. Another inverter would take this varying voltage and attempt to create 24V from it.

    You then have to charge the battery with something higher than 24V and also create a 24V bus.

    Conceptually, I think it's a tough problem.

    What probably happens is that the MPPT system charges the battery. If the battery is charged and/or there is no load then it shuts down. The system draws from the battery which has an inverter attached to it, so as the battery voltage drops, the inverter takes make up the difference.

    In a grid-tie inverter, you can regulate how much power you feed back to the grid and it may be an easier design.

    Large grid tie inverters (10 MW) can actually operate in all 4 quadrants, thus it can locally power factor correct.
     
  8. KMoffett

    KMoffett Well-Known Member

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    I think there is confusion with Maximum Power Point. There are probably two concepts that are getting mixed. Though somewhat related they are two different functions, one based on the input and the other on the output. MPPT for "maximum power input" to the panel would mean moving the panel to point most directly at the Sun. MMPT for "maximum power transfer" from the panel to the load is a function of the P=V*I output curve of the panel. That is about 60% of the open-circuit voltage times the short-circuit current. This is where the charger/inverter controller adjusts for maximum power point. Like maximum power is transferred when the load impedance matches the source impedance.

    http://en.wikipedia.org/wiki/Maximum_power_point_tracking

    Ken
     
    Last edited: Nov 25, 2011
  9. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    No you can do it on any stationary panel array.
     
  10. KeepItSimpleStupid

    KeepItSimpleStupid Well-Known Member Most Helpful Member

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  11. dougy83

    dougy83 Well-Known Member

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    There is potential to get the most power out of a panel directly pointing at the sun (comparing to a panel that is not directed towards the sun), yes. You will not get the maximum available power from the panel unless you adjust the panel output voltage appropriately, however. This is what MPPT converters do.

    How can someone that cannot (or is so unwilling to) learn, teach?

    I was almost going to explain to you; but surely you would have come across it in the 200 articles you read. The power output from a solar panel having fixed illumination depends on the voltage the the panel is operated at - there is a optimum voltage, which is where the MPP is. This voltage changes depending on illumination level and temperature and consequently has to be adjusted to maintain maximum power. The constant adjustment is the 'tracking'.

    The reason the conversation is in your mind going nowhere, is because what you are writing is both ignorant and arrogant. It is bad news that there are students listening to what you say.

    what an achievement.
     

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  12. KMoffett

    KMoffett Well-Known Member

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    Funny, that was the top link of the first page when Google'ing: MPPT

    Ken
     
  13. KeepItSimpleStupid

    KeepItSimpleStupid Well-Known Member Most Helpful Member

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    Link was a nice read.

    Now I wonder what the OP's students' think?
     
  14. WeThePeople

    WeThePeople New Member

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    WRONG !

    The maximum power point is never, and I repeat never,
    directly related to absolute angle to the solar source,
    as opposed to the sun/clouds/seasonal angle/trees/etc.
    that affects the output of segments of a panel regulated
    by a MPPT buck-balancing circuit seeking optimum ratio.
    (OK, to all and any other method considered really...)

    PV DOES NOT (directly) interface with batteriy technology efficiently !

    MPPT IS NEEDED BECAUSE of the many variables like the above short list
    and too many others like panel temperature and installation wiring losses too.

    Your premise that ideal angle of exposure is paramount is not in question,
    but that the acronym MPPT has anything to do with physical steller tracking is.

    The severe mismatch of solar contribution variables available to use for storage
    to proper storage charge practices of current affordable storage mediums now
    is the whole point of this topic in the first place, and a college course paper too.

    Look at the graphs presented and become more familier with what MPPT means,
    and leave the "Wiki" out of this please (others...).

    Sun angle Tracking SHOULD be a very serious consideration,
    as should heat harvesting for DHW to keep panels cool too,
    IF you are the kind of person REQUIRED to avail the advantages,
    and your target area isn't prone to violent wind events like hurricanes.
    (Acronym DHW = Domestic Hot Water, like "SuperHeat" AC recovery)

    I should point out I replied to a solar-related definition of a MPPT topic,
    but this in direct juxtapositional association to all forms of usefull sourcing.

    Doesn't matter if it is (just) a water wheel in the local brook,
    or an overly-overlapped winding stratigy in a wind harvester,
    or a biodiesel/wood-gas powered lawnmower with an altermator.
    (OK, it would be easier to control the alternator field factor, but ...)

    "Tracking" does NOT automatically denote PHYSICAL tracking of a PV-panel,
    adjustment of a water-wheel's and/or wind-blade's blade pitch live-time,
    or regulation of engine RPM or field excitation potential of a driven alternator.

    But I will give you this, the acronym of MPPT is too much like JPEG...

    It means both:
    Japanese Picture EXPERTS Group
    Japanese Picture ENTERTAINMENT Group
    Depending on which shore you are standing on.

    The acronym must be nested in proper context !

    We live in a world where resourcing just about any acronym collection website
    WILL sadly result in the incurance of too many meanings for one single acronym.

    But as far as electronic definitions are concerned, "(Maximum) Power Point Tracking" means
    the tracking of the best use of supply potential differential (V) to Maximum flow available (I)
    to feed a (usually) mis-matched end usage load to maximize THROUGHPUT between the two.

    Sadly, this complies better to a grid-tie feedback ratio,
    than it does for solar collection and storage for later use.

    Often, in the case of solar, to favor the highest charge storage ratio for later usage,
    as to the opposing the optimum "Power Point" charge ratio method of storage stratigy,
    is hampered by the lack of a crystal ball to optimize the charge method to use that day.

    Personally (sorry), I feel the whole thing is wrong anyway...

    strongest charge versus optimum charge choice seems to never be implemented.

    A simple button to indicate clouds expected later in a given day
    should be available to shift to the maximum charge available,
    as opposed to MPPT charge strategy of for storage medium lifetime.

    There is a misnomer that maximum power point transfer
    results in the most current to the storage medium though.

    Logic dictates that it should, right ?

    Don't get me wrong, it has many similarities to three stage charging,
    but maximum charge until an available voltage cutoff is not the best
    stratigy if you want your batteries to survive the maximum charge cycles.

    I'll catch flack for that statement (unless running Nickle-Iron Edison batteries),
    or (instead) using those wonderful Carbon positive plate batteries if your lucky,
    your going to have to choose between maximum charge point and accepted losses/aging,
    or maximum power point "Target" charging to optimise battiery lifespan instead.

    simple/simple (KISS)



    Your interpretation of the word "Tracking" is leaning way to much
    towards the physical and literal sense of the usage of the word,
    it is actually (only) a plot-point of X/Y vector graphing in electronics.

    Odd that is the case in a technical forum where the very phrase
    "Power Point Tracking" is of course usually referred to as the
    "Tracking" of an ACTUAL power point for the most efficient use
    of the available Voltage x Current characteristics of the source
    to feed the end result load at the most efficient power transfer level.

    And to be clear, the word "Power" is one I usually hate to use at all,
    too vague...

    It assumes our given values of (as example)
    Horsepower/RPM is to a given Torque/RPM.

    We all know that is a tough-sell from trials.



    Well, I'll give you that one, as two of the top five...



    I'm not singling you out,
    or making this personal,
    you just hit the best set of
    topics points with your post.

    Maybe it's better said that you
    introduced doubt about them.

    MPPT is the best requirement to persue,
    Tracking is inexpensive electrically to design,
    and often prohibitavely expensive to implement.

    It also has much much higher destruction risks !

    Seen any "Green" installers pivoting panels lately,
    especially the "Gov" approved installers (Sorry guys),
    oh heck no, bolt them to the deck, collect, signoff...

    Having panels that are free for the wind to interact with and/or destroy
    is just to much of a liabilty for them to sign off (on) as opposed to full-bolt.

    Again, Personally, an enviroment where collection is live-time strategized
    to store on fast-moving cloud days to a capacitor bank consisting of those
    high farad "stiffening" capacitors that dump when the panels drops input
    just seems like the most econical medium to feed an MPPT charge pump.
    (Again, I'll receive opposition that MPPT is a charge pump implementation)

    Slow collect, high impulse discharge implementations for charging are better.

    Sure are better for avoiding sulphation as most know anyway...

    But straight-MPPT is better for none-techno' people.

    Yeah, this was the dumbed-down version,
    oh, and I spell like crap, sorry about that...

    Paul
    Mon 02-13-12 (Web-Whore Mirroring Indicator...)
    (My first post is URL LImited so I cannot prove whore status by provided source URL... )





    OK, I've seen only sixteen circuits so far, all fair, all Google'd,
    but a dedicated chipset that minimizes externals has not been found.

    I am sure a chip that has minimal externals exists,
    steer me please, thank you.
     
    Last edited: Feb 13, 2012

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