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How does it connect to the power grid?
The wind turbines generate power by rotating a
permanent magnet generator which generates three phase AC at the
frequency of the turbine's rotation. The AC power from the generator is
not only the wrong voltage to be connected to the local power grid, but
also, as the wind speed changes so does the rotational speed of the
turbine, and therefore the frequency of the power generated. The power
from the generator therefore needs to be converted to DC and then fed
into a special electronic device called an inverter, to ensure that it
is always at the correct frequency and voltage for the local grid.
Any power you generate will be first used by your own
property, thereby saving you the maximum amount possible on your
electricity bill. Any excess energy your wind turbine generates, e.g. on
windy days or at night, is "spilled" to the power grid and your
electricity supplier pays you for it.
In order to charge your electricity supplier for any
energy that you export to the grid, you need to have a new
bi-directional electricity meter installed which will work both when you
buy (import) and sell (export) electricity. Depending upon your local
requirements, there may be additional meters needed to record energy
generation to enable a claim for a Government subsidy.
Shown below is a simplified block diagram of how all
the system components are connected in the UK.
The inverter also provides essential safety features
to control the power output from the turbine, and to automatically
switch off the current if the grid connection should fail. This means
that should the grid connection fail, the inverters will switch off
their output and there is therefore no danger to any maintenance
engineers fixing the fault. This does however mean that the wind turbine
will produce no power to the property if the mains connection fails.
Iskra however shortly hopes to offer an off-grid
package which when combined with a battery pack, and optionally solar PV
panels and/or a diesel generator will enable the generation of “mains”
power where there is no grid connection.
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