Design and testing of an armature-reaction-compensated permanent magnet synchronous generator for island operation
Kamiev, Katteden (2013-11-15)
Väitöskirja
Kamiev, Katteden
15.11.2013
Lappeenranta University of Technology
Acta Universitatis Lappeenrantaensis
Julkaisun pysyvä osoite on
https://urn.fi/URN:ISBN:978-952-265-486-1
https://urn.fi/URN:ISBN:978-952-265-486-1
Tiivistelmä
At present, permanent magnet synchronous generators (PMSGs) are of great interest.
Since they do not have electrical excitation losses, the highly efficient, lightweight and
compact PMSGs equipped with damper windings work perfectly when connected to a
network. However, in island operation, the generator (or parallel generators) alone is
responsible for the building up of the network and maintaining its voltage and reactive
power level. Thus, in island operation, a PMSG faces very tight constraints, which are
difficult to meet, because the flux produced by the permanent magnets (PMs) is
constant and the voltage of the generator cannot be controlled. Traditional electrically
excited synchronous generators (EESGs) can easily meet these constraints, because the
field winding current is controllable. The main drawback of the conventional EESG is
the relatively high excitation loss.
This doctoral thesis presents a study of an alternative solution termed as a hybrid
excitation synchronous generator (HESG). HESGs are a special class of electrical
machines, where the total rotor current linkage is produced by the simultaneous action
of two different excitation sources: the electrical and permanent magnet (PM)
excitation. An overview of the existing HESGs is given. Several HESGs are introduced
and compared with the conventional EESG from technical and economic points of view.
In the study, the armature-reaction-compensated permanent magnet synchronous
generator with alternated current linkages (ARC-PMSG with ACL) showed a better
performance than the other options. Therefore, this machine type is studied in more
detail. An electromagnetic design and a thermal analysis are presented. To verify the
operation principle and the electromagnetic design, a down-sized prototype of 69 kVA
apparent power was built. The experimental results are demonstrated and compared
with the predicted ones. A prerequisite for an ARC-PMSG with ACL is an even number
of pole pairs (p = 2, 4, 6, …) in the machine. Naturally, the HESG technology is not
limited to even-pole-pair machines. However, the analysis of machines with p = 3, 5, 7,
… becomes more complicated, especially if analytical tools are used, and is outside the
scope of this thesis. The contribution of this study is to propose a solution where an ARC-PMSG replaces an
EESG in electrical power generation while meeting all the requirements set for
generators given for instance by ship classification societies, particularly as regards
island operation.
The maximum power level when applying the technology studied here is mainly limited
by the economy of the machine. The larger the machine is, the smaller is the efficiency
benefit. However, it seems that machines up to ten megawatts of power could benefit
from the technology. However, in low-power applications, for instance in the 500 kW
range, the efficiency increase can be significant.
Since they do not have electrical excitation losses, the highly efficient, lightweight and
compact PMSGs equipped with damper windings work perfectly when connected to a
network. However, in island operation, the generator (or parallel generators) alone is
responsible for the building up of the network and maintaining its voltage and reactive
power level. Thus, in island operation, a PMSG faces very tight constraints, which are
difficult to meet, because the flux produced by the permanent magnets (PMs) is
constant and the voltage of the generator cannot be controlled. Traditional electrically
excited synchronous generators (EESGs) can easily meet these constraints, because the
field winding current is controllable. The main drawback of the conventional EESG is
the relatively high excitation loss.
This doctoral thesis presents a study of an alternative solution termed as a hybrid
excitation synchronous generator (HESG). HESGs are a special class of electrical
machines, where the total rotor current linkage is produced by the simultaneous action
of two different excitation sources: the electrical and permanent magnet (PM)
excitation. An overview of the existing HESGs is given. Several HESGs are introduced
and compared with the conventional EESG from technical and economic points of view.
In the study, the armature-reaction-compensated permanent magnet synchronous
generator with alternated current linkages (ARC-PMSG with ACL) showed a better
performance than the other options. Therefore, this machine type is studied in more
detail. An electromagnetic design and a thermal analysis are presented. To verify the
operation principle and the electromagnetic design, a down-sized prototype of 69 kVA
apparent power was built. The experimental results are demonstrated and compared
with the predicted ones. A prerequisite for an ARC-PMSG with ACL is an even number
of pole pairs (p = 2, 4, 6, …) in the machine. Naturally, the HESG technology is not
limited to even-pole-pair machines. However, the analysis of machines with p = 3, 5, 7,
… becomes more complicated, especially if analytical tools are used, and is outside the
scope of this thesis. The contribution of this study is to propose a solution where an ARC-PMSG replaces an
EESG in electrical power generation while meeting all the requirements set for
generators given for instance by ship classification societies, particularly as regards
island operation.
The maximum power level when applying the technology studied here is mainly limited
by the economy of the machine. The larger the machine is, the smaller is the efficiency
benefit. However, it seems that machines up to ten megawatts of power could benefit
from the technology. However, in low-power applications, for instance in the 500 kW
range, the efficiency increase can be significant.
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