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How does large-scale wind farm power get inverted, or does it.

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  • How does large-scale wind farm power get inverted, or does it.

    Couldn't get a good answer by researching it. How does large-scale wind farm power get inverted from DC? Or does it? And does it sometimes sit idle? When the blades are spinning is it really making power always?

  • #2
    What I know of large scale wind turbines is that they can be designed to generate either AC or DC power.

    And yes they do sit idle for a number of reasons. The blades can be kept spinning on some units but the generator is disengaged so it does not produce power. If the wind get too much there are some that can actually turn on a "break" and keep from turning.

    The biggest problem is that some wind farms generate more power then can either be consumed or transmitted over the HV lines. Some POCO's will divert the power while others will shut down the farm or throttle it back.

    Small turbines can have a "shunt load" which will allow you to divert power to a false load if your turbine is producing too much. But those are generally smaller turbines.

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    • #3
      I haven't tried to pull a cut sheet yet. But right on the website it says "Produces 60 Cycle AC electricity within the turbine." Given that these are 2-5 MW each, I assume this must be 3-phase 4K, 11K or higher voltage.

      https://www.ge.com/renewableenergy/w...-wind/turbines

      Brakes, blade pitch control, and nacelle rotational control are pretty standard

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      • #4
        It seems like double conversion is standard now: Wild AC => DC => synchronous AC.

        https://en.wikipedia.org/wiki/Wind_turbine_design#Generator

        GE Uses the Double Fed Induction Generator Approach:


        https://en.wikipedia.org/wiki/Doubly...tion_generator

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        • #5
          It really depends on the manufacturer of the turbine. Some of them generate HV DC and are connected to DC transmission lines. Others generate AC (converted) and are connected to HV AC transmission lines.

          GE is not the only manufacturer of large wind turbines.

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          • #6
            Indeed. And some make AC, and then use an external substation to make DC for long distance transport (offshore), and then convert back to AC onshore. But in general, they are getting larger, and more sophisticated, dynamic, and autonomous year after year.

            I'm still amazed that one single windmill can output several megawatts.

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            • #7
              Originally posted by JSchnee21 View Post
              I......

              I'm still amazed that one single windmill can output several megawatts.
              I recently took a road trip from California to Tennessee and was amazed at how many turbines we saw. There was also a lot of new construction under way.
              I have read somewhere that wind turbines take a while to shut down. Maybe it depends on the type. I am thinking of California where curtailment in the morning is becoming more common. I did read that CAISO dis a test on some Solar Farms and found that solar can be curtailed almost instantly. @JSchnee do you know? If so it does make CAISO's job more complicated.

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              • #8
                Honestly, I do not know -- though it may depend on the definition of "instantly." There are a number of mechanisms to throttle back wind farm production by changing the orientation of the nacelles, pitch of the blades, applying braking to the drive shaft, and uncoupling (clutching) the alternator/generator from the drive shaft. All of which can be done remotely and in some cases autonomously on newer platforms. But these are all mechanical actuations which take some time, eventually cause wear, and can fail. So you wouldn't want to make more than handful of changes per day.

                As you drive around the Lancaster area in PA, there are a few small wind farms with very sizable turbines quite close to the country road you're on. It's really striking how huge they are. There are a few more on mountain ridges near state college, and many more in NY state.

                Unfortunately the health and environmental effects of wind farms in populated areas is not really clear yet. The constant low frequency vibrations and shadows can effect some people and animals. Not to mention the window shattering ice falls, number of birds and bats that get killed, and the changes in the local micro-environment due to changes in surface wind speeds.

                No solution is perfect, but solar PV is probably less objectionable. Of course it requires huge swaths of land that could be used for farming, housing, or other purposes. Plus runoff, erosion, etc.

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                • #9
                  Originally posted by JSchnee21 View Post
                  Honestly, I do not know -- though it may depend on the definition of "instantly." There are a number of mechanisms to throttle back wind farm production by changing the orientation of the nacelles, pitch of the blades, applying braking to the drive shaft, and uncoupling (clutching) the alternator/generator from the drive shaft. All of which can be done remotely and in some cases autonomously on newer platforms. But these are all mechanical actuations which take some time, eventually cause wear, and can fail. So you wouldn't want to make more than handful of changes per day.

                  As you drive around the Lancaster area in PA, there are a few small wind farms with very sizable turbines quite close to the country road you're on. It's really striking how huge they are.
                  Thanks, that does answer my question. I gues you can't just open the circuit like you can with solar. Also, because it is a mechanical process is is slower than the instantaneous process with solar farms. That would explain why solar gets curtailed more often than wind. Wind also tends to blow at night when we need more power.
                  Yes, they are huge, especially when you see a blade pulled behind a truck. They are too long for conventional trailers. Then there are the column sections that are 10 to 12 feet in diameter. They have to be accompanied by trucks bearing WIDE LOAD signs.
                  I guess everything is a trade off. I have heard the bird discussion but I also wonder how many birds died from coal mining and pollution from burning coal. They look slow but the tip of the blade is probably moving pretty fast.
                  Last edited by Ampster; 07-11-2019, 02:33 PM.

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                  • #10
                    Originally posted by Ampster View Post
                    .......I guess everything is a trade off. I have heard the bird discussion but I also wonder how many birds died from coal mining and pollution from burning coal.
                    Housecats and feral cats account for a large amount of bird kill.
                    Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
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                    • #11
                      Originally posted by Mike90250 View Post

                      Housecats and feral cats account for a large amount of bird kill.
                      Plus rats and mice.

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                      • #12
                        Originally posted by Ampster View Post

                        Plus rats and mice.
                        rats and mice likely have little to do with bird kill numbers, more the other way around
                        or were you trying to indicate that cats kill rats and mice? if so, seems unrelated to wind turbines.
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                        • #13
                          Originally posted by Mike90250 View Post

                          Housecats and feral cats account for a large amount of bird kill.
                          Actually cats are the number 1 killer of birds. The total is between 200 & 3000 million compared to wind turbine deaths which are less than 1/2 million.

                          Still I don't like the idea of any power source killing off living things but all sources have their bad side.

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                          • #14
                            Originally posted by SunEagle View Post
                            .............

                            Still I don't like the idea of any power source killing off living things but all sources have their bad side.
                            I agree but death by turbine in most cases is probably quick compared to respiratory diseases caused by pollution from coal burning power plants. That pollution affects more than birds. Environmental quality mprovements are not perfect.
                            Last edited by Ampster; 07-11-2019, 07:04 PM.

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                            • #15
                              Originally posted by JSchnee21 View Post
                              It seems like double conversion is standard now: Wild AC => DC => synchronous AC.
                              Yes microprocessors controlling the latest high power semiconductors have changed
                              everything. Been watching this happen, older than transistors. Bruce Roe

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