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  • #16
    Originally posted by solarix View Post
    ....

    Grid-tie inverters can't operate without a grid to follow and when the grid goes down, the inverter goes down too. POCO's that require "safety" AC disconnects to isolate the (evil) solar inverter from the grid so their lineman can work on powerlines during outages are just implementing stupid OSHA rules in an effort to make their competitor's installation costs as high as possible.
    Sounds like you have no idea why solar inverters have to disconnect from the grid for safety issues.

    It does not have anything to do with competitor's or costs. It is purely a SAFETY issue for anyone that may be working on the power lines.

    Saying anything else is just plain stupid.

    Comment


    • #17
      Originally posted by solarix View Post
      A basic circuit in electronics is the difference amplifier (or diff-amp). It is the basis of all control theory. One input is connected to your reference signal (grid AC) and the other input is connected to your inverter output. The output from the diff amp is then proportional to any difference between the two and is used to drive the inverter's power circuitry to minimize this difference. This "negative feedback loop" thus works to make the inverter's output just follow the grid's AC wave.Now, inverters may well have some digital sinewave approximation involved in the process to give it some help or smooth the signal etc., but the diff amp is the key.
      That doesn't make any sense. The AC input voltage is one voltage reference you could use. What's the other? (And you can't say "the inverter output" because the inverter output is the same as the AC input voltage. There's no difference; they are the same potential.)

      There are indeed a lot of control loops within the inverter. What you have described is not one of them.


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      • solarix
        solarix commented
        Editing a comment
        The control loop (diff amp circuit) in the inverter is what makes the inverter output match the grid voltage. Actually, there is an infinitesimally small difference between the inverter's output and the grid's voltage and this difference is sensed to control the circuitry. Maybe a better way to think about it is from an Amps perspective. The inverter is constantly having to figure out what current (amps) to push out onto the grid in order to output the momentary power level at whatever voltage the grid happens to be at that instant.
        The whole subject can be a career for the engineers involved and is indeed sophisticated so am sorry if I'm not boiling it down very well.

      • sdold
        sdold commented
        Editing a comment
        I could see how a differential amplifier could do this if the other input was derived from the inverter output current. The job of the differential amp would be to source current in proportion to grid voltage. Not saying it works that way, but I see how it could.
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