U.S. patent application number 09/927553 was filed with the patent office on 2002-02-28 for high-voltage dc/dc converter.
Invention is credited to Reinold, Harry.
Application Number | 20020024824 09/927553 |
Document ID | / |
Family ID | 7651819 |
Filed Date | 2002-02-28 |
United States Patent
Application |
20020024824 |
Kind Code |
A1 |
Reinold, Harry |
February 28, 2002 |
High-voltage DC/DC converter
Abstract
A high-voltage DC/DC converter is described. The high-voltage
DC/DC converter contains a number of primary-side converter modules
and at least one secondary-side converter module. The DC
connections of the primary-side converter modules are connected in
series between the connections of a high-voltage DC distribution
network. The DC connections of the secondary-side converter modules
are connected in parallel between the connections of a further DC
network. Each of the primary-side converter modules contains a
primary-side converter bridge, a primary-side capacitor, a
primary-side series resonant capacitor, a transformer and a
secondary-side series resonant capacitor. The secondary-side
converter module contains a secondary-side converter bridge and a
secondary-side capacitor.
Inventors: |
Reinold, Harry; (Landau,
DE) |
Correspondence
Address: |
LERNER AND GREENBERG, P.A.
Post Office Box 2480
Hollywood
FL
33022-2480
US
|
Family ID: |
7651819 |
Appl. No.: |
09/927553 |
Filed: |
August 9, 2001 |
Current U.S.
Class: |
363/17 |
Current CPC
Class: |
H02M 1/0074 20210501;
H02M 3/28 20130101; H02M 3/285 20130101 |
Class at
Publication: |
363/17 |
International
Class: |
H02M 003/335 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 9, 2000 |
DE |
100 38 814.0 |
Claims
I claim:
1. A high-voltage DC/DC converter, comprising: a number of
primary-side converter modules having DC connections, said DC
connections of said primary-side converter modules connected in
series between connections of a high-voltage DC distribution
network, each of said primary-side converter modules having a
primary-side converter bridge, a primary-side capacitor connected
to said primary-side converter bridge, a primary-side series
resonant capacitor connected to said primary-side converter bridge,
a transformer connected to said primary-side series resonant
capacitor and to said primary-side converter bridge, and a
secondary-side series resonant capacitor connected to said
transformer; and at least one secondary-side converter module
having DC connections, said DC connections of said secondary-side
converter modules connected in parallel between connections of a
further DC network, said secondary-side converter module having a
secondary-side converter bridge and a secondary-side capacitor
connected to said secondary-side converter bridge.
2. The high-voltage DC/DC converter according to claim 1, wherein
both said primary-side converter bridge and said secondary-side
converter bridge have semiconductor switches which can be switched
on and off actively.
3. The high-voltage DC/DC converter according to claim 1, wherein
said primary-side converter bridge has a semiconductor switch which
can be switched on and off actively, and said secondary-side
converter bridge is formed of diodes.
4. The high-voltage DC/DC converter according to claim 1, wherein
said primary-side converter bridge is formed of diodes, and said
secondary-side converter bridge includes semiconductor switches
which can be switched on and off actively.
Description
BACKGROUND OF THE INVENTION
[0001] Field of the Invention
[0002] The invention relates to a high-voltage DC/DC converter, and
is preferably used in the field of high-voltage DC transmission
(HVDCT).
[0003] A high-voltage DC distribution network with a feeder or
feeders and a branch or branches are used in connection with
high-voltage DC/DC converters. The two ends of the high-voltage DC
distribution network are connected to a first converter and to a
second converter respectively, with respective energy-storage
capacitors, with an earthed center point, being provided in each
case. The two converters respectively, have connections,
respectively, on the other side for three-phase networks. The first
converter is preferably used as a feeder rectifier, and for this
purpose is connected to a power station. The second converter
preferably operates as an inverter, for feeding into a branching
supply network.
[0004] The high-voltage DC distribution network is furthermore
connected to a third converter and to the high-voltage DC/DC
converter. The third converter is provided on the other side with
connections for a preferably low-voltage three-phase network, and
may operate either as an inverter for feeding from the distribution
network into the three-phase network, or as an inverter for feeding
from the three-phase network into the high-voltage DC distribution
network.
[0005] The high-voltage DC/DC converter is connected via
connections to the distribution network, and has connections for a
further preferably low-voltage (medium-voltage) DC network. First,
it is possible to use the high-voltage DC/DC converter for feeding
the DC network (for example a medium-voltage DC distribution
network) from the high-voltage DC distribution network. Second, it
is possible to use the high-voltage DC/DC converter for feeding the
high-voltage DC distribution network from the DC network. In the
latter case, the high-voltage DC/DC converter is connected, for
example, to a solar power station or to a wind-driven power
station.
SUMMARY OF THE INVENTION
[0006] It is accordingly an object of the invention to provide a
high-voltage DC/DC converter which overcomes the above-mentioned
disadvantages of the prior art devices of this general type, which
can be produced cost-effectively for various primary-side and
secondary-side voltage requirements.
[0007] With the foregoing and other objects in view there is
provided, in accordance with the invention, a high-voltage DC/DC
converter. The high-voltage DC/DC converter has a number of
primary-side converter modules having DC connections. The DC
connections of the primary-side converter modules are connected in
series between connections of a high-voltage DC distribution
network. Each of the primary-side converter modules have a
primary-side converter bridge, a primary-side capacitor connected
to the primary-side converter bridge, a primary-side series
resonant capacitor connected to the primary-side converter bridge,
a transformer connected to the primary-side series resonant
capacitor and to the primary-side converter bridge, and a
secondary-side series resonant capacitor connected to the
transformer. At least one secondary-side converter module having DC
connections is provided. The DC connections of the secondary-side
converter modules are connected in parallel between connections of
a further DC network. The secondary-side converter module have a
secondary-side converter bridge and a secondary-side capacitor
connected to the secondary-side converter bridge.
[0008] The advantages that can be achieved by the invention are, in
particular, that the proposed module concept allows the
high-voltage DC/DC converter to be matched to the specified voltage
of the high-voltage DC distribution network in a very simple and
universal manner. That is to say the number of converter modules
that need to be connected in series is governed by the voltage of
the high-voltage DC distribution network. All that is required is
to configure, manufacture and stock a very small number (for
example three) of different types of converter modules (with
different current, voltage and rating data) in order to allow all
the conceivable variations in the field of high-voltage DC supply
technology and branching technology to be covered.
[0009] Since the converter modules are produced in relatively large
quantities, this results in cost advantages in comparison to a
solution approach without using modules. The time penalty required
to implement a project is considerably reduced, and spares
stockholdings are simplified.
[0010] Advantageously, there is no need for any synchronized drive
for a series circuit containing a large number of active
semiconductor devices disposed between the high-voltage
connections.
[0011] In accordance with an added feature of the invention, both
the primary-side converter bridge and the secondary-side converter
bridge have semiconductor switches which can be switched on and off
actively.
[0012] In accordance with an additional feature of the invention,
the primary-side converter bridge has a semiconductor switch which
can be switched on and off actively, and the secondary-side
converter bridge is formed of diodes.
[0013] In accordance with a further feature of the invention, the
primary-side converter bridge is formed of diodes, and the
secondary-side converter bridge includes semiconductor switches
which can be switched on and off actively.
[0014] Other features which are considered as characteristic for
the invention are set forth in the appended claims.
[0015] Although the invention is illustrated and described herein
as embodied in a high-voltage DC/DC converter, it is nevertheless
not intended to be limited to the details shown, since various
modifications and structural changes may be made therein without
departing from the spirit of the invention and within the scope and
range of equivalents of the claims.
[0016] The construction and method of operation of the invention,
however, together with additional objects and advantages thereof
will be best understood from the following description of specific
embodiments when read in connection with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a schematic diagram of a basic version of a
high-voltage DC/DC converter according to the invention;
[0018] FIG. 2 is a schematic diagram of a simplified version of the
high-voltage DC/DC converter for an energy flow from a high-voltage
side to a medium-voltage side;
[0019] FIG. 3 is a schematic diagram of a simplified version of the
high-voltage DC/DC converter for an energy flow from the
medium-voltage side to the high-voltage side;
[0020] FIG. 4 is a schematic diagram of a simplified version of the
high-voltage DC/DC converter for the energy flow from the
medium-voltage side to the high-voltage side, with relatively low
rating requirements; and
[0021] FIG. 5 is a schematic diagram of a high-voltage DC
distribution network with a feeder or feeders and a branch or
branches.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0022] In all the figures of the drawing, sub-features and integral
parts that correspond to one another bear the same reference symbol
in each case. Referring now to the figures of the drawing in detail
and first, particularly, to FIG. 5 thereof, there is shown a
high-voltage DC distribution network with a feeder or feeders and a
branch (tap) or branches. The two ends of the high-voltage DC
distribution network 1 are connected to a converter 2 and to a
converter 5, respectively, with respective energy-storage
capacitors 4 and 6, with an earthed center point, being provided in
each case. The two converters 2 and 5, respectively, have
connections 3 and 7, respectively, on the other side for
three-phase networks. The converter 2 is preferably used as a
feeder rectifier, and for this purpose is connected to a power
station. The converter 5 preferably operates as an inverter, for
feeding into a branching supply network.
[0023] The high-voltage DC distribution network 1 is furthermore
connected to a converter 8 and to a high-voltage DC/DC converter
10. The converter 8 is provided on the other side with connections
9 for a preferably low-voltage three-phase network, and may operate
either as an inverter for feeding from the distribution network 1
into the three-phase network, or as an inverter for feeding from
the three-phase network into the high-voltage DC distribution
network 1.
[0024] The high-voltage DC/DC converter 10 is connected via
connections 12, 13 to the distribution network 1, and has
connections 11 for a further preferably low-voltage
(medium-voltage) DC network. First, it is possible to use the
high-voltage DC/DC converter 10 for feeding the DC network (for
example a medium-voltage DC distribution network) from the
high-voltage DC distribution network 1. Second, it is possible to
use the high-voltage DC/DC converter 10 for feeding the
high-voltage DC distribution network 1 from the DC network. In the
latter case, the high-voltage DC/DC converter 10 is connected, for
example, to a solar power station or to a wind-driven power
station.
[0025] FIG. 1 shows a basic version of the high-voltage DC/DC
converter 10. One important feature is the DC isolation between the
connections 12, 13 to the high-voltage DC distribution network 1 on
the one side, and the medium-voltage-side connections 11 (for
example 5 kV voltage between the connections 11) on the other side.
The DC isolation is provided by n transformers 18.1 to 18.n.
Primary coils of the transformers 18.1 to 18.n are connected to AC
connections of converter bridges 14.1 to 14.n, with the connections
being made via series resonant capacitors 17.1 to 17.n. DC
connections of the converter bridges 14.1 to 14.n are connected in
series between the connections 12, 13, with a capacitor 15.1 to
15.n in each case being disposed between the DC connections. This
results in a series capacitor circuit between two high-voltage-side
connections 12, 13 (for example 70 kV voltage between the
connections 12, 13). A center point of the series capacitor circuit
is connected to earth via an earth connection 16.
[0026] The secondary coils of the transformers 18.1 to 18.n are
connected to AC connections of converter bridges 20.1 to 20.n, with
the connections being made via series resonant capacitors 19.1 to
19.n. Two converter bridges 20.1 to 20.n are in each case connected
in series in pairs via their DC connections, with a capacitance
21.1 to 21.n in each case being disposed between the DC
connections. The pairs formed in this way are connected via their
outer DC connections and parallel to the connections 11. The center
connections of the pairs are connected to one another. A common
junction point of all the center connections of the pairs is
connected to the connections 11 via resistors 22.
[0027] In the basic version of the high-voltage DC/DC converter 10
shown in FIG. 1, both the converter bridges 14.1 to 14.n and the
converter bridges 20.1 to 20.n are each fitted with semiconductor
switches which can be switched on and off actively, such as IGBTs,
GTOs, MOSFETs, in the four bridge arms. This allows optimum
control/regulation of the energy flow or current flow both from the
high-voltage DC distribution network 1 to the medium-voltage-side
connections 11 and, in the opposite direction, from the connections
11 to the high-voltage DC distribution network 1. The semiconductor
switches which can be switched on and off actively are preferably
operated at a relatively high switching frequency in the range 2 to
10 kHz, which advantageously reduces the physical size of the
transformers in comparison to operation at a low frequency. A
combination of zero current switching (ZCS) and zero voltage
switching (ZVS) is advantageously used for operation.
[0028] As can be seen from FIG. 1, the high-voltage DC/DC converter
10 is composed of n converter modules that are each in the form of,
and operated as, series-resonant DC/DC converters. A converter
module such as this generally contains the primary-side converter
bridge 14.n, a primary-side capacitor 15.n, a primary-side series
resonant capacitor 17.n, a transformer 18.n, a secondary-side
converter bridge 20.n, a secondary-side capacitor 21.n and a
secondary-side series resonant capacitor 19.n. Depending on the
semiconductor switches used in the converter bridges, a converter
module is suitable for having a specific maximum voltage (module
voltage)--for example of 2.5 kV--applied to it.
[0029] One advantageous feature is that a transformer may be
insulated only for the module voltage, that is to say for example
for 2.5 kV. The transformation ratio between the primary and
secondary windings is preferably approximately 1:1. The transformer
can be very compact with little stray flux, which is generally a
major advantage for resonant DC/DC converters.
[0030] These n converter modules are generally connected in series
on the primary side between the connections 12, 13 of the
high-voltage DC distribution network, and are generally connected
in parallel on the second side between the connections 11 of the
further DC network. Since the voltage of this further DC network
is, however, too high for the semiconductor switches in a single
converter module, two converter modules are in each case connected
in series first on the secondary side, as is shown in FIG. 1.
[0031] As can easily be seen, the proposed module concept allows
the high-voltage DC/DC converter 10 to be matched to the specified
voltage of the high-voltage DC distribution network 1 in a very
simple and universal manner, that is to say the number of converter
modules which need to be connected in series is governed by the
voltage of the high-voltage DC distribution network 1. If, for
example, the voltage of the high-voltage DC distribution network 1
is 70 kV, then 28 primary-side converter modules have to be
provided in series, assuming a semiconductor switch is configured
for a withstand voltage of 2.5 kV.
[0032] FIG. 2 shows a simplified version of the high-voltage DC/DC
converter 10, which allows energy or current to flow only from the
high-voltage DC distribution network 1 to the connections 11 (from
the high-voltage side to the medium-voltage side). In this
simplified version, which is suitable for feeding a medium-voltage
DC distribution network, the converter bridges 20.1 to 20.n are
fitted with diodes in each of the four bridge arms. The rest of the
circuit is the same as that in the embodiment in FIG. 1. FIG. 3
shows a simplified version of the high-voltage DC/DC converter 10,
which allows energy or current to flow only from the connections 11
to the high-voltage DC distribution network 1 (from the
medium-voltage side to the high-voltage side). In this simplified
version, which is suitable for feeding from a medium-voltage DC
distribution network or for feeding from a medium-voltage power
source--for example relatively large wind-driven power stations or
solar power stations--the converter bridges 14.1 to 14.n are fitted
with diodes in each of the four bridge arms. The rest of the
circuit is the same as that in the embodiment in FIG. 1.
[0033] FIG. 4 shows a simplified version of the high-voltage DC/DC
converter 10, which allows energy or current to flow only from the
connections 11 to the high-voltage DC distribution network 1 (from
the medium-voltage side to the high-voltage side) for relatively
low rating requirements. In this simplified version, which is
suitable for feeding from a medium-voltage DC distribution network
or for feeding from a medium-voltage power source--for example
relatively small wind-driven power stations or solar power
stations--, the converter bridges 14.1 to 14.n are fitted with
diodes in each of the four bridge arms. All the secondary coils of
the transformers 18.1 to 18.n are connected in parallel to the AC
connections of a single converter bridge 20, with the connections
being made via resonant capacitors 19.1 to 19.n. The DC connections
of the converter bridge 20 form the connections 11 between which a
capacitor 21 is disposed. The converter bridge 20 is fitted with
semiconductor switches which can be switched on and off actively,
such as IGBTs, GTOs, MOSFETs, in the four bridge arms. The rest of
the circuit is the same as that in the embodiment in FIG. 1.
* * * * *