U.S. patent application number 13/835089 was filed with the patent office on 2014-09-18 for variable speed constant frequency system with generator and rotating power converter.
The applicant listed for this patent is Hamilton Sundstrand Corporation. Invention is credited to Jacek F. Gieras, Steven J. Moss, Gregory I. Rozman.
Application Number | 20140266077 13/835089 |
Document ID | / |
Family ID | 50239553 |
Filed Date | 2014-09-18 |
United States Patent
Application |
20140266077 |
Kind Code |
A1 |
Rozman; Gregory I. ; et
al. |
September 18, 2014 |
VARIABLE SPEED CONSTANT FREQUENCY SYSTEM WITH GENERATOR AND
ROTATING POWER CONVERTER
Abstract
An electric power generating system includes a brushless wound
field synchronous generator with n-number of power generating
channels and n-number of bidirectional switches alternatively
controlled to provide ac power at the output. Each power generating
channel includes a control rotating transformer, a rotating power
converter supplying power to field winding from the rotating power
supply, and a center-tap single phase armature winding connected to
the bidirectional switches. Rotating power converter modulates
current in the field winding to obtain desired frequency and phase
at the system output.
Inventors: |
Rozman; Gregory I.;
(Rockford, IL) ; Gieras; Jacek F.; (Glastonbury,
CT) ; Moss; Steven J.; (Rockford, IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Hamilton Sundstrand Corporation |
Windsor Locks |
CT |
US |
|
|
Family ID: |
50239553 |
Appl. No.: |
13/835089 |
Filed: |
March 15, 2013 |
Current U.S.
Class: |
322/25 |
Current CPC
Class: |
H02P 9/305 20130101;
H02P 9/48 20130101 |
Class at
Publication: |
322/25 |
International
Class: |
H02P 9/30 20060101
H02P009/30 |
Claims
1. A generator system comprising: a generator having a stationary
portion and a rotating portion, the generator comprising: an
exciter field winding disposed on the stationary portion; a
rotating power supply comprising: a three-phase exciter armature
winding disposed on the rotating portion; a three-phase 6-pulse
rectifier disposed on the rotating portion that converts AC power
from the exciter armature winding into DC power; a DC capacitor
disposed on the rotating portion; at least one generator channel,
comprising: a main field winding disposed on the rotating portion;
a main field power converter disposed on the rotating portion that
delivers power to the main field winding; a single phase armature
winding disposed on the stationary portion to provide AC power at
an output of the at least one generator channel; a control
transformer primary winding disposed on the stationary portion; a
control transformer secondary windings disposed on the rotating
portion to electrically communicate with the control transformer
primary winding; a set of gate drives that electrically communicate
with the control transformer secondary winding, the set of gate
drives disposed on the rotating portion that communicates with the
main field power converter; at least one output channel in
electrical communication with a respective at least one generator
channel, the at least one output channel comprising: first and
second bidirectional switches; an output filter including a filter
capacitor; and first and second interface inductors connected
between the bidirectional switches and the output filter; and a
control unit in electrical communication with the at least one
output channel and a respective generator channel, the control unit
configured to generate control signals based on an output voltage
at the output and a capacitor filter current flowing through the
filter capacitor.
2. The generator system of claim 1, wherein each bidirectional
switch includes a semiconductor switch and a plurality of diodes
forming an H-bridge.
3. The generator system of claim 1, wherein the single phase
armature winding is formed as a center-tap winding having an
upper-half winding and a lower-half winding, the first
bidirectional switch connected to the upper-half winding and the
second bidirectional switch connected the lower-half winding.
4. The generator system of claim 1, wherein the output filter
includes a series inductor and the filter capacitor connected in
parallel to a load connected to the output, a current sensor
monitoring filter capacitor current, and voltage sensor monitoring
voltage across the filter capacitor.
5. The generator system of claim 1, wherein the control unit
modulates control transformer primary winding of the at least one
generator channel based on the output of the voltage and current
sensors, and alternates switching of the first and second
bidirectional switches to generate an alternating current having a
desired frequency at the output.
6. The generator system of claim 5, wherein the control unit
regulates an exciter field current flowing through the exciter
field winding as a function of a generator shaft speed to obtain a
constant voltage at the main field winding.
7. The generator system of claim 1, wherein the main field power
converter comprises: a high-side switch connected between a
positive DC voltage of a rotating DC bus and a high side of a
respective main field winding; a low-side switch connected between
a negative DC voltage of the rotating DC bus and a low side of a
respective main field winding; a first diode connected between the
high side of a respective main field winding and the negative DC
voltage; and a second diode connected between the low side of a
respective main field winding and the positive DC voltage.
8. The generator system of claim 7, wherein the high-side switch
and the low-side switch are turned On to allow the DC voltage
provided by the rotating DC bus to be supplied to a respective main
field winding and turned Off to rapidly reduce current to zero in
the main field winding.
9. The generator system of claim 8, wherein the current in the main
field winding is modulated to obtain sinusoidal voltage waveform at
a load connected to the output, the current modulated at a desired
frequency and a desired phase to satisfy multi-phase system
requirements.
Description
CROSS-REFERENCE TO RELATED APPLICATION(S)
[0001] Reference is made to application Ser. No. 13/833,809,
entitled "GENERATOR ARCHITECTURE WITH MAIN FIELD ROTATING POWER
CONVERTER", application Ser. No. 13/833,212, entitled "GENERATOR
ARCHITECTURE WITH PMG EXCITER AND MAIN FIELD ROTATING POWER
CONVERTER", application Ser. No. 13/836,428, entitled "EPGS
ARCHITECTURE WITH MULTI-CHANNEL SYNCHRONOUS GENERATOR AND COMMON
FIELD REGULATED EXCITER", application Ser. No. 13/836,255, entitled
"METHOD OF CONTROLLING ROTATING MAIN FIELD CONVERTER", and
application Ser. No. 13/836,007, entitled "EPGS ARCHITECTURE WITH
MULTI-CHANNEL SYNCHRONOUS GENERATOR AND COMMON UNREGULATED PMG
EXCITER", which are filed on even date herewith, are assigned to
same assignee as this application, and which the entire disclosure
off all above-reference applications hereby being incorporated by
reference.
BACKGROUND
[0002] The present inventive concept is related to generator
architectures and in particular to generator architectures
utilizing main field rotating power converters.
[0003] In the simplest terms, generators convert mechanical energy
to electrical energy via the interaction of rotating magnetic
fields and coils of wire. A multitude of generator architectures
have been developed with various means of providing interaction
between magnetic fields and coils of wire. For example, a permanent
magnet generator (PMG) utilizes permanent magnets to generate a
constant magnetic field, which is rotated via the mechanical energy
supplied by a prime mover such that the rotating magnetic field
interacts with the stator coils to provide an output voltage.
Another type of generator supplies current through a field coil to
generate the desired magnetic field, which is rotated via the
mechanical energy supplied by a prime mover, such that a rotating
magnetic field is created that interacts with stator coils to
provide an output voltage.
[0004] In the former example, the output voltage supplied by the
PMG depends only on the magnitude of the mechanical energy supplied
by the prime mover. In the latter example, the output voltage of
the generator can be regulated by varying the current supplied to
the field coil. For applications in which the output voltage must
be regulated, the latter example, known as a wound field
synchronous machine, is widely utilized. A PMG is sometimes
utilized in conjunction with the brushless wound field synchronous
machine to source the current supplied to an exciter field winding
to regulate the output of the wound field synchronous machine.
[0005] For example, in aircraft applications, a typical variable
frequency generator (VFG) includes a permanent magnet section, an
exciter section, and a main generator section. The permanent magnet
portion includes permanent magnets employed on the rotating
portion, which generate an alternating current voltage on the
stator portion. The AC voltage provided by the permanent magnet
portion is rectified and selectively applied to the exciter winding
on the stationary portion of the exciter. The exciter field current
interacts with the rotating exciter armature windings to provide an
AC voltage. A rotating rectifier rectifies the AC voltage and
supplies the DC voltage to a main field winding on the rotating
portion of the main generator section. Rotation of the motive power
shaft and the main field winding induces three-phase AC output
voltage on the generator armature winding. The magnitude of the AC
generator output voltage is regulated by controlling the current
supplied to the exciter field coil on the stationary portion of the
exciter. The three-phase output voltage and frequency of the
generator is subjected to the speed of motive power shaft. To
achieve a three-phase constant frequency and constant voltage
power, a three-phase dc link inverter is employed between the
generator output and the load. This type of an electric power
generating system is commonly known as a variable speed constant
frequency (VSCF) system. However, conventional (VSCF) have a
reduced power density and do not provide a means of controlling the
generating system to control the power density.
SUMMARY
[0006] A generator system comprises a generator having a stationary
portion and a rotating portion, a number of identical output
channels and a control unit. The generator comprises an exciter
field, a rotating power supply, and a number of identical generator
channels. The exciter field winding is disposed on the stationary
portion. The rotating power supply disposed on the rotating portion
and comprises of a three-phase exciter armature winding connected
to a 6-pulse rectifier, and a dc bus capacitor. Each generator
channel comprises a control transformer primary winding disposed on
the stationary portion, a main field winding disposed on the
rotating portion, a main field power converter disposed on the
rotating portion that delivers modulated dc power from the rotating
power supply, a center-tap single phase armature winding disposed
on the stationary portion to produce dc modulated power. Output
channel comprises of a set of two bidirectional switches connected
to the generating channel outputs of the single phase armature
winding and alternatively controlled to provide alternative power
at desired frequency. Each output channel further includes an
output filter connected to the bidirectional switches via interface
inductors. Each generating channel yet further includes control
transformer secondary windings and a set of gate drives disposed on
the rotating portion and communicating control signals to the main
field power converter switches to provide desired frequency at the
load. The generator system further includes a variable speed
constant frequency control unit (VSCFCU) in electrical
communication with the generator and output channels. The VSCFCU is
configured to generate the control signals based on the output
phase voltage and output filter capacitor current to provide
n-phase constant voltage constant frequency ac power at the
load
[0007] These and other features of the present invention can be
best understood from the following specification and drawing, the
following of which is a brief description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a circuit diagram of an electric power generation
and distribution system including a variable speed constant
frequency unit according to an embodiment of the present
invention.
DETAILED DESCRIPTION
[0009] FIG. 1 is a circuit diagram of electric power generating
system 50 according to an embodiment of the present inventive
concept. System 50 includes a generator 52 and a variable speed
constant frequency control unit (VSCFCU) 54. In at least one
embodiment illustrated in FIG. 1, the generator is a multi-channel
generator 52, which includes a plurality of channels. A switching
unit 56 may be connected to the output of each channel of the
multi-channel generator 52 to provide a desired frequency and phase
at the load 57. Each switching unit 56 includes a pair of
bi-directional switches 58, 60, which are discussed in greater
detail below. In addition, an output filter 62, such as an LC
filter, is connected to the output of each switching unit 56 via a
set of interface inductors 64 to filter out a high frequency
component. Phase voltage, e.g., voltage across filter capacitor 66,
and capacitor current delivered by the current sensor 68 are fed
back to the VSCFCU 54. The VSCFCU 54 may be in connection with each
switching unit 56 to control each respective pair of bi-directional
switches 58, 60. Accordingly, the VSCFCU 54 may control the
modulation of the output voltage at each channel based on the
feedback phase voltage and capacitor current (Icx). Current sensor
68 may be coupled to the output of each filter 62 to provide Icx to
the VSCFCU 54.
[0010] Generator 52 includes stationary portion 70 and rotating
portion 72. Generator 52 includes a controlled rotating DC power
supply and a number of generator channels. The amount of channels
included in the system 50 may include, but are not limited to, 1
channel, 2 channels, 3 channels, etc. An example of a three-channel
system is illustrated in FIG. 1, which may generate a three-phase
AC output with 120.degree. degrees with respect to the three
channels (phases). Although only a single channel will be described
from here on out, it is appreciated that all the channels included
in the system 50, for example all three channels, operate in a
similar manner.
[0011] A stationary part of each generating channel includes a
center-tap single-phase main armature winding 74, and a primary
winding 76 disposed on the stationary portion 70. A rotating part
of each generating channel includes a channel main field winding
78, a main field rotating power converter 80, and secondary control
windings 82 and 84 of the controlled rotating transformer connected
to the inputs of respective gate drives 86 and 88. The rotating
part of the each channel is disposed on the rotating portion 72 of
the generator 52.
[0012] The generator includes a controlled rotating power supply
having a stationary part and a rotating part. The stationary part
includes an exciter field winding 90 disposed on the stationary
portion 70 of the generator 52. The rotating part includes a
three-phase exciter armature winding 92 connected to a 6-pulse
rotating rectifier 94, and a DC bus capacitor CdcR, all of which
are disposed on the stationary rotating portion 72 of the generator
52. The AC power supplied by the exciter armature winding 92 is
converted into a DC power by the rotating rectifier 94. The main
field rotating power converter 80 selectively delivers the
rectified DC power at the rotating DC bus to the channel main field
winding 78. The rotating portion 72 further includes the hi-side
gate driver 86 and the lo-side gate driver 88. The hi-side gate
driver 86, a lo-side gate driver 88 may selectively be controlled
by the VSCFCU 54 to output the signals that to selectively control
a respective main field rotating power converter 80.
[0013] In the embodiment shown in FIG. 1, each channel main field
rotating power converter 80 includes a high-side switch T1r, a
low-side switch T2r, and diodes D1r and D2r. By controlling the
high-side/low-side switches T1r, T2r via a control signal sent by a
respective hi-side gate driver 86/a lo-side gate driver 88, each
individual channel may be independently controlled. For example,
when switches T1r and T2r of the main field rotating power
converter 80 are both turned On, then the positive DC voltage
provided by the rotating DC bus is applied to the respective
channel main field winding 78 and allows current to build up in the
respective channel main field winding 78. In particular, a
conductive current path is created from the rotating DC bus through
switch T1r to the respective channel main field winding 78 and then
through switch T2r. By keeping one of the switch (T2r) On and
pulse-width modulating switch T1r the current in the channel main
field winding 78 is modulated. When T1r is On the voltage across
the main field winding 78 (which is equal to the rotating DC bus
voltage), and main field current increases. When T1r is Off the
main field current circulates through T2r and D2r and decreases.
The voltage across the main field winding 78 is near zero. In order
to balance switching losses between T1r and T2r switches, the
operating mode of the switches can be alternating: T2r switch is
closed, while T1r is in PWM mode for a period of time, and then T2r
switch is in PWM mode, while T1r is closed for the same period of
time, and so on. When switches T1r and T2r of the main field
rotating power converter 80 are both Off, then current flows
through diodes D1r and D2r and voltage across the channel main
field winding 78 equals negative rotating DC bus voltage forcing
current stored in the main field winding 78 to rapidly decrease to
zero. The negative energy is fed back to the rotating DC power
supply.
[0014] The pair of bi-directional switches 58, 60 included in each
switching unit 56 alternate a modulated DC power to achieve a
balanced AC output at the desired frequency. In at least one
embodiment illustrated in FIG. 1, each channel single phase main
armature winding 74 is formed as a center-tapped winding having the
center connected to a neutral potential point, (e.g., ground) to
define an upper-half winding and a lower-half winding. Each
switching unit 56 includes a first bidirectional switch 58 and a
second bidirectional switch 60. The first bidirectional switch 58
is connected to the upper winding of a respective main armature
winding 74 and the second bidirectional switch 60 is connected to
the lower winding. Accordingly, the first and second bidirectional
switches 58, 60 alternate the voltage at the upper-half and
lower-half windings. In at least one embodiment illustrated in FIG.
1, each bidirectional switch 58, 60 includes four diodes and an
IGBT switch. The four diodes are constructed as an H-bridge. The
IGBT switch is connected in parallel with the H-bridge, and the
gate of the IGBT switch is connected to the respective half of the
winding, i.e., the upper-half winding or the lower-half winding.
The outputs of the first and second bidirectional switches 58, 60
are connected to an input of a respective LC filter 62 via
interface inductors 64 to reduce circulating current during IGBT
switches commutation. The LC filter 62 filters out the high
frequency components from the modulated signal output from the
respective bidirectional switches 58, 60.
[0015] The VSCFCU 54 monitors the current supplied to exciter field
winding 90 and the phase voltage at the output of one or more of
the channels via the feedback phase voltage. Accordingly, the
VSCFCU 54 may regulate the current supplied to exciter field
winding 90 to maintain constant generator system output voltage. In
another embodiment, the exciter current supplied to the exciter
field winding 90 may be controlled to obtain near speed independent
voltage at the rotating DC bus.
[0016] In addition, the VSCFCU 54 may modulate the current applied
to the generator channel primary windings 76, thereby modulating
the current realized at the respective main field winding 74. More
specifically, the VSCFCU 54 receives the feedback phase voltage and
capacitive current signals (Icx) and may modulate the main field
current in response to these signals. The main field current is
modulated to achieve constant desired voltage, constant desired
frequency, and desired phase shift between the output channels.
[0017] While the present inventive concept has been described with
reference to an exemplary embodiment(s), it will be understood by
those skilled in the art that various changes may be made and
equivalents may be substituted for elements thereof without
departing from the scope of the invention. In addition, many
modifications may be made to adapt a particular situation or
material to the teachings of the invention without departing from
the essential scope thereof. Therefore, it is intended that the
present general inventive concept not be limited to the particular
embodiment(s) disclosed, but that the present general inventive
concept will include all embodiments falling within the scope of
the appended claims.
* * * * *