Frequency regulation

Discussion in 'General Electronics Chat' started by jathrox, Sep 20, 2010.

  1. jathrox

    Thread Starter New Member

    Sep 20, 2010
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    How do utilities with large scale wind turbines (1 MW+) regulate frequency? The reason I ask is that the turbines produce power in varying wind speeds and at various outputs. How can the output be lower than its designed and still maintain the correct frequency?
     
  2. tom66

    Senior Member

    May 9, 2009
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    I think for wind turbines etc. a DC output is produced and this is then put through an electronic inverter or other mechanism (maybe motor turning motor.) For higher power wind turbines maybe a CVT would be used to regulate frequency.

    Large scale, frequency is regulated to within ±0.015 Hz (with a daily average of 50±0.001 Hz or 60±0.001Hz) by burning more or less fuel in the generators. If there is a sudden demand which causes the frequency to drop, then spinning reserve may be used: essentially, generators that are running or can start very quickly to supply load.

    Nowadays most of it is based on electronic control, human operators only watch the frequency. It is very important that frequency stay regulated between power plants, otherwise, the power grids must be kept separate (cannot combine power) and often this is not an option (because it makes systems vulnerable to single failure.)

    This page shows the current grid frequency of the UK: http://www.dynamicdemand.co.uk/grid.htm#
     
  3. sceadwian

    New Member

    Jun 1, 2009
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    I would think the reverse is true, but that's only from my course understanding that CVTs are more practical to make for lower torque applications rather than high torque ones.

    If I'm not mistaken there are absolutely massively large scale rotary transformers that are being developed for transfer power between separate power grids for phase (aka fine frequency) matching. In places like this US it's not so simple as there isn't just one grid, there are dozens if not multiple dozens of separate grids, some synced to allow transfer between each grid. The entire UK has an effective area of 94k miles. the US is 3.7 million square miles. The logistics are quiet complicated.
     
  4. Ghar

    Active Member

    Mar 8, 2010
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    I'm under the impression that wind turbines regulate frequency regulating by controlling torque through blade pitch and the motor speed electrically, I'm not sure which method they'd use more.

    I watched a wind farm before and all the turbines had a rotational period of exactly 16.7 seconds as far as my stopwatch hand could tell, which of course is 0.060 Hz. That's easily converted to 60 Hz with a gear box and a multipole rotor.

    If you can't maintain that you disable the turbine.

    I'm sure there exist units that operate differently, there's no unique solution.
     
  5. t_n_k

    AAC Fanatic!

    Mar 6, 2009
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  6. sceadwian

    New Member

    Jun 1, 2009
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    Even good stop watch accuracy is only about .1 if a second accurate, there's not way to analyze it other than through direct sensor measurement.
     
  7. Ghar

    Active Member

    Mar 8, 2010
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    I know, but it does suggest constant frequency.
    I timed this over several days in various wind conditions.
    I do admit I 'rounded' my approximate measurements to a value that makes sense ;)
    It was always between 16 and 17 seconds.
     
  8. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    The NEWEST way is the DC to AC conversion method. The older common method was the use of induction MOTORS.

    When the wind would start to blow the company would turn on the motors using the grid power. When the torque from the wind EXCEEDED the motor power the motor becomes a generator and since it is already hooked up to the grid, simply starts putting power out onto the grid.

    It's not quite as simple as that since lots power conditioning and phasing equipment is used for the big big wind farms, but basically, that was how it operated.
     
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