Electricity: single generator systems – Automatic control of generator or driving means – Speed or frequency of generator
Reexamination Certificate
2001-10-26
2004-03-16
Lam, Thanh (Department: 2834)
Electricity: single generator systems
Automatic control of generator or driving means
Speed or frequency of generator
C322S017000, C322S027000, C322S028000
Reexamination Certificate
active
06707277
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a control method for a claw-pole synchronous machine which is designed to be operated as a three-phase generator or a three-phase electric motor. More particularly, the present invention is concerned with a claw-pole synchronous machine controlling method which can ensure enhanced controllability of operation of the claw-pole synchronous machine without incurring any appreciable increase in the size and the cost involved in the implementation thereof.
2. Description of Related Art
In general, the internal combustion engine for a motor vehicle or the like is equipped with a three-phase synchronous machine operated as a generator or a motor. For driving such three-phase synchronous machine by using an inverter-type power supply source, a control method based on a combination of a vector control and a field current control is adopted and well known in the art, as is disclosed in, for example, Japanese Patent Application Laid-Open Publication No. 182380/19996 (JP-A-8-182380).
For better understanding of the concept underlying the present invention, background technique thereof will first be described in some detail.
FIG. 6
is a perspective view showing a rotor of a general claw-pole synchronous machine.
In
FIG. 6
, the rotor comprises a shaft
10
, field poles (claw-poles)
11
and field coils
12
, which are formed in one body. Fan blades
14
for cooling the field coils
12
are disposed on periphery of both end surfaces of the rotor respectively.
At first, let's consider the case where the three-phase synchronous machine is operated as a motor (i.e., motor operation mode).
The torque Te generated by the three-phase synchronous machine in the motor operation mode is given by the following expression (1):
Te=
3{&PSgr;·
iq+
(
Ld−Lq
)
id·iq}
(1)
where &PSgr; represents total flux linkage determined by the field current if, Ld and Lq represent synchronous inductance transformed into d- and q-axis components, respectively, &PSgr;·iq represents a torque generated by the flux linkage &PSgr;, and the term (Ld−Lq)id·iq represents a reluctance torque, where id and iq represent armature phase currents, respectively, as elucidated below.
Further, the d-axis mentioned above represents the direct-axis direction which coincides with the field pole direction and the q-axis represents the quadrature-axis direction orthogonal to the field pole direction. In this connection, id and iq represent the armature phase currents for the vector control as transformed into the d- and q-axis components (direct- and quadrature-axis components), respectively. The armature phase currents id and iq bear the relation to the armature current i (phase current) which is given by the following expression (2).
i
2
=id
2
+iq
2
(2)
The armature current i is three-phase current. However, in the description which follows, it is assumed only for the convenience of description that the armature current i is two-phase current capable of generating a same electromotive force as the three-phase armature current i and represented by the phase current id along the d-axis (direct axis) coinciding with the field pole direction and the phase current iq along the q-axis (quadrature axis) which is orthogonal to the d-axis.
On the other hand, the output power Pg generated by the three-phase synchronous machine in the generator operation mode is given by:
Pg=
3
{&ohgr;·&PSgr;·iq+i
2
+&ohgr;(
Ld−Lq
)
id·iq}
(3)
where &ohgr; represents an electrical angular velocity which corresponds to the rotation speed, and R represents the armature resistance value in each phase. Incidentally, in the expressions mentioned above, the polarities are presumed to be positive in the motor operation mode.
In general, in the case of the synchronous machine of the salient-pole type, it is known that the relation between the synchronous inductances Ld and Lq satisfies the conditions given by the undermentioned expression (4):
Ld>Lq (4)
Further, in the synchronous machine of the cylindrical-pole type, it is also known that the relation between the synchronous inductances Ld and Lq satisfies the condition given by the following expression (5):
Ld=Lq (5)
Furthermore, in the synchronous machine of the embedded-pole type, the magnetic permeability in the d-axis direction (NS-pole direction) encompassing the magnet is smaller than the magnetic permeability in the q-axis direction (i.e., direction orthogonal to the NS-pole direction) encompassing magnetic materials such as iron. Thus, the relation between the synchronous inductances Ld and Lq satisfies the following condition:
Ld<Lq (6)
As can be seen from the expressions (1) and (3) mentioned previously, in the case of the synchronous machines of the salient-pole type and the cylindrical-pole type which satisfy the conditions given by the above-mentioned expressions (4) and (5), respectively, a maximum torque can be produced in the motor operation mode while a maximum output power can be generated in the generator operation mode when the synchronous machine is controlled with the direct-axis current id of zero (id=0) for a same armature current i.
On the other hand, in the case of the synchronous machine of the embedded-pole type satisfying the condition given by the above-mentioned expression (6), a maximum torque can be obtained in the motor operation mode while a maximum output power can be obtained in the generator operation mode when the synchronous machine is controlled with the direct-axis current id of negative polarity (id<0). This direct-axis current id of negative polarity will be referred to as the field weakening current.
By contrast, in the case of the claw-pole synchronous machine which belongs to the salient-pole type synchronous machine, the condition given by the expression (4) is satisfied. Consequently, the control is performed with the direct-axis current id of zero (id=0) and no field weakening control is carried out with the armature current.
By the way, the terminal voltage V of the synchronous machine can be determined in dependence on the rotation speed &ohgr;, the flux linkage &PSgr; between the flux generated by the field current if and the armature coils, the inductance Ld and the resistance R of the armature and given by the following expression (7).
V={
(&ohgr;·&PSgr;+&ohgr;·
Ld·id+R·iq
)
2
+(&ohgr;·
Lq·iq−R·id
)
2
} (7)
With the field weakening control with the aid of the armature current mentioned previously, it is intended to mean that the direct-axis current id of the armature is caused to flow in the inverse direction so that the magnetic flux is generated in the opposite direction relative to the counter electromotive force E (=&ohgr;·&PSgr;) of the armature with a view to making it possible to regulate or adjust the terminal voltage V given by the above expression (7) under the control with the inverter.
Accordingly, the armature direct-axis current id is caused to flow in such direction as to produce the magnetic flux in the opposite direction relative to the magnetic field generated by the field current if.
Parenthetically, when the phase difference angle between the counter electromotive force E of the armature and the armature current is represented by Ø, the direct-axis current (d-axis current) id and the quadrature-axis current (q-axis current) iq are given by the following expressions (8) and (9), respectively.
id=i·
sin Ø (8)
iq=i·
cos Ø (9)
Heretofore, in the inverter control of the armature current i in terms of the direct-axis current component id and the quadrature-axis current component iq, the field weakening control with the armature current i is not performed except for the embedded-pole type permanent-magnet synchronous machine exhibiting the inversed salient-pole characteristic.
Such being the circums
Nishimura Shinji
Yamamoto Tsunenobu
Lam Thanh
Mitsubishi Denki & Kabushiki Kaisha
Sughrue & Mion, PLLC
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