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50 Planning the electrical installation
Checking the compatibility of the generator and the
converter
The converter is compatible with induction generators and permanent magnet generators.
1.
Select the generator according to the ratings table in the technical data.
2.
Check that the generator and the converter have the same voltage rating. Check also
that the voltage ratings match the voltage to be connected to the grid-side converter.
Note: You can rise the converter DC link voltage 10% of its natural level (by a parameter
setting). The effect is equivalent to a 10% voltage rise at the generator terminals. Before
you use this feature, make sure that the generator insulation can withstand the higher
voltage level.
DC bus voltage is not increased from nominal (de-
fault)
DC bus voltage is increased from nominal by para-
meter setting
U
= rated grid-side voltage of the converter
N
U
= equivalent grid-side voltage of the converter in V AC, U
ACeq
U
= maximum DC bus voltage of the converter in V DC. You can set the voltage reference with para-
DC
meter in grid-side converter control program for 1.1 · 1.41 · U
to a lower value but the program restricts it to a value of at least 1.41 · U
3.
Make sure that the generator is suitable for the converter use, ie, it can withstand the
voltage peaks at of the converter:
•
Use insulated N end (non-driven end) bearing in the generator.
•
Make sure that the generator insulation meets the requirements in the table below.
•
Select the cables according to the instruction in this manual.
•
Install the converter and its cabling as instructed in this manual.
Protecting the generator insulation and bearings
￭
The generator-side converter output of the wind turbine converter comprises – regardless
of output frequency – pulses of approximately the converter DC bus voltage with a very
short rise time. This is the case with all converters employing modern IGBT technology.
The voltage of the pulses can be almost double at the generator terminals, depending on
the attenuation and reflection properties of the generator cable and the terminals. This in
turn can cause additional stress on the generator and generator cable insulation.
Modern variable speed converters with their fast rising voltage pulses and high switching
frequencies can cause current pulses that flow through the generator bearings, which can
gradually erode the bearing races and rolling elements.
ABB power modules are equipped with internal du/dt filters which reduce the bearing currents
and stress on the generator insulations. In addition, a common mode filter can be used to
reduce such stresses on the generator-side. Hence, the converter can be equipped with
following filters:
When
the generator voltage rating should be
U
N
U
ACeq
= U
/ 1.41
ACeq
DC
at maximum. You can set the reference
N
.
N
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