Environmental Engineering Reference
In-Depth Information
6.7 Generator and Converter Characteristics
Table 6.5 provides a summarized overview of the characteristics of synchronous and
asynchronous generators and power electronic converters relevant to the issues discussed
in this chapter. Further information on the topics of this chapter can be found in Refer-
ences [3 - 9] .
Table 6.5
System - relevant characteristics of generators and converters
Rotating machines
Power - electronic converters
Synchronous
Induction
(asynchronous)
Line - commutated
(old - thyristors)
Self - commutated
(modern - PWM)
Operating speed
(rev/min)
Exactly
synchronous
speed
Slightly above
synchronous
speed when
generating,
above and
below
synchronous in
DFIG systems
Reactive power
Either generate
or consume;
often
controlled by
an AVR,
which may be
set to give
constant bus
voltage or
constant
power factor.
Machine
itself
will consume;
may have
power factor
correction
capacitors
fi tted or may
consume or
generate if
fi tted with
PWM
converter
Consume
Either generate or
consume; often
designed to
operate at unity
power factor
Starting currents
Should be
insignifi cant
Signifi cant unless
a soft - starter is
used
None
None
Fault contribution
Signifi cant
Usually
insignifi cant
Insignifi cant
Insignifi cant
Synchronisation
procedure
required
Yes
No
No
No
Risk of islanding
High (if
completely
unprotected)
Low but slightly
increased when
power factor
correction
capacitors are
fi tted
None
Low (unless
designed to)
