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DC to DC converter on wind turbine system.

Discussion in 'Power Electronics' started by fishinghat, Sep 3, 2018.

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  1. fishinghat

    fishinghat

    3
    0
    Sep 3, 2018
    I hope I am posting this in the right spot.

    First of all I am not an electrical engineer. I do have a degree in chemistry and a Master's in Environmental Engineering which means I know nothing about electrical so be patient with me.

    Situation...

    I have 3 small home made wind turbines.

    They can individually reach 12 volts or more when winds are very high but they are usually putting out 3 to 9 volts at 0.3 to 2 amps.

    Inorder to increase the output I put on a boost converter rated at 3 to 35 input to 3 to 35 volts output and no more than 6 amps. So far so good.

    Originally I had two turbines on line at the same time feeding to the dc to dc converter and then to my battery bank. The converter would kick on around 4.5 volts and begin supplying power to the battery banks. As the incoming voltage increased the outgoing voltage stayed at my set point of 12.5. Great.

    Now comes the confusion.

    1) I was told not to do it that way as you will only receive power from the most powerful turbine which will block the signal from the weaker turbine. Is that true or false?

    2) So I bought 2 more dc to dc converters with the same specs and set them to 12.5 volts each. I put one on each wind turbine line before the lines combine and of course a diode right after the dc to dc converter. To my surprise the incoming voltage was always the same as the output voltage if they were attached to the battery bank. I contacted the ,manufacturer and he said my incoming power was below the minimum watt rating. When I asked them what the minimum watts for the unit to begin converting to the 12.5 set point he stated he didn't know but I was certainly below that. For real!!?? Any comments?

    3) Finally I took the original dc to dc converter that kicked on at 4.5 volts with all wind turbines running through it and placed it in line to each individual wind turbine one at a time. During this test the other wind turbines not in use were taken off line so as not to interfer in any way.

    1st wind turbine - Kicked on at 4 V and properly converted.

    2nd wind turbine - Kicked on at 9 V and properly converted.

    3rd wind turbine - Kicked on at 6 volts and properly converted.

    Each wind turbine has similar output at the same wind speeds.

    Why the difference?

    I am lost for an answer to what to do next. Please feel free to ask questions.

    Thx
     
  2. kellys_eye

    kellys_eye

    4,277
    1,146
    Jun 25, 2010
    You need to measure the voltage AND current from the turbines to make a sensible determination.

    As the manufacturer stated, the converters will need a minimum POWER input to operate correctly and power is the voltage multiplied by the current so if the first turbine/converter kicked in at 4V and (maybe) 2A (8 watts) then the second kicked on at 9V and 0.888A (8 watts) the third would kick in at 6V and ?? amps?

    (note - ?? is for the OP to calculate).

    Of course I don't know the actual watt requirement for them to work - perhaps you can measure the current/volts and determine what they each need - since there will be tolerance differences between them.
     
  3. fishinghat

    fishinghat

    3
    0
    Sep 3, 2018
    Excellent info. It makes perfect sense. I have not only contacted the one manufacturer I mentioned but 3 others that sell the same size dc to dc convertors and they said that there is no minimum watt requirement (power).required. Obviously they just want to sell the devices and heck with the customers. I will have to get busy talking to other vendors and visiting other websites to find a unit that will work for me.

    Thanks so much for the help and have a good night.
     
  4. BobK

    BobK

    7,673
    1,684
    Jan 5, 2010
    You need an MPPT controller to get the max power out under varying conditions.

    Bob
     
  5. fishinghat

    fishinghat

    3
    0
    Sep 3, 2018
    True Bob but I live off of Social Security. I can afford a $10 dc to dc converter but not an mppt controller. lol
     
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