U.S. patent application number 15/119730 was filed with the patent office on 2017-05-11 for apparatus for breaking line bidirectional current and control method thereof.
This patent application is currently assigned to NR ELECTRIC CO., LTD. The applicant listed for this patent is NR ELECTRIC CO., LTD, NR ENGINEERING CO., LTD. Invention is credited to Dongming CAO, Taixun FANG, Wei LU, Wei SHI, Yu WANG, Bing YANG, Hao YANG.
Application Number | 20170133835 15/119730 |
Document ID | / |
Family ID | 51242061 |
Filed Date | 2017-05-11 |
United States Patent
Application |
20170133835 |
Kind Code |
A1 |
CAO; Dongming ; et
al. |
May 11, 2017 |
APPARATUS FOR BREAKING LINE BIDIRECTIONAL CURRENT AND CONTROL
METHOD THEREOF
Abstract
An apparatus for breaking a line bidirectional current and a
control method therefore. The apparatus comprises a breaking
current branch circuit and an on-state current branch circuit, the
breaking current branch circuit comprises one nonlinear resistor
being connected in parallel to one first power semiconductor
device, or one nonlinear resistor being connected in parallel to at
least two first power semiconductor devices mutually connected in
series; and the on-state current branch circuit comprises at least
one bidirectional power semiconductor switch being connected in
series to at least one high-speed isolation switch. The apparatus
also comprises a bridge-type branch circuit. An apparatus for
breaking a line bidirectional current, thereby greatly reducing
costs of the apparatus and reducing difficulty in device layout,
mounting and wiring of the apparatus on the premise of ensuring a
breaking speed that is quick enough and a low loss.
Inventors: |
CAO; Dongming; (Nanjing,
CN) ; FANG; Taixun; (Nanjing, CN) ; WANG;
Yu; (Nanjing, CN) ; YANG; Hao; (Nanjing,
CN) ; YANG; Bing; (Nanjing, CN) ; SHI;
Wei; (Nanjing, CN) ; LU; Wei; (Nanjing,
CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NR ELECTRIC CO., LTD
NR ENGINEERING CO., LTD |
Nanjing
Nanjing |
|
CN
CN |
|
|
Assignee: |
NR ELECTRIC CO., LTD
Nanjing
CN
NR ENGINEERING CO., LTD
Nanjing
CN
|
Family ID: |
51242061 |
Appl. No.: |
15/119730 |
Filed: |
December 27, 2013 |
PCT Filed: |
December 27, 2013 |
PCT NO: |
PCT/CN2013/090613 |
371 Date: |
August 18, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01H 9/542 20130101;
H01H 9/548 20130101; H02H 3/087 20130101; H01H 33/596 20130101;
H02H 3/021 20130101; H02H 3/08 20130101 |
International
Class: |
H02H 3/02 20060101
H02H003/02; H01H 9/54 20060101 H01H009/54; H02H 3/08 20060101
H02H003/08; H01H 33/59 20060101 H01H033/59 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 31, 2013 |
CN |
201310037475.3 |
Claims
1. An apparatus for breaking a line bidirectional current,
comprising a breaking current branch circuit and an on-state
current branch circuit, wherein the breaking current branch circuit
comprises one nonlinear resistor being connected in parallel to one
first power semiconductor device, or one nonlinear resistor being
connected in parallel to at least two first power semiconductor
devices mutually connected in series; and the on-state current
branch circuit comprises at least one bidirectional power
semiconductor switch being connected in series to at least one
high-speed isolation switch, wherein: the apparatus also comprises
a bridge-type branch circuit, and the bridge-type branch circuit
comprises two bridge arms constituted by four identical current
commutation branch circuits, each current commutation branch
circuit comprising at least one second power semiconductor device
connected in series; every two of the four commutation branch
circuits are connected in series a same direction, and the formed
two bridge arms are further connected in parallel; and a connection
relationship of the apparatus is selected from a group consisting
of: a) the apparatus comprises a breaking current branch circuit,
an on-state current branch circuit, and a bridge-type branch
circuit, wherein two ends of the on-state current branch circuit
are respectively connected to bridge arm middle points of two
bridge arms of the bridge-type branch circuit, and the two bridge
arms are both connected in parallel to the breaking current branch
circuit; b) the apparatus comprises at least two groups of a
breaking current branch circuit, an on-state current branch
circuit, and a bridge-type branch circuit, wherein in each group,
two ends of the on-state current branch circuit are respectively
connected to bridge arm middle points of two bridge arms of the
bridge-type branch circuit, and the two bridge anus are both
connected in parallel to the breaking current branch circuit; and
all the on-state current branch circuits are connected in series in
sequence; c) the apparatus comprises an on-state current branch
circuit and at least two groups of a breaking current branch
circuit and a bridge-type branch circuit, wherein in each group,
two bridge arms of the bridge-type branch circuit are both
connected in parallel to corresponding breaking current branch
circuits, and bridge arm middle points of the bridge-type branch
circuit in each group are connected in series in sequence; and two
ends of the on-state current branch circuit are respectively
connected to bridge arm middle points of end portions of the first
bridge-type branch circuit and the last bridge-type branch circuit
in the circuits connected in series; and d) the apparatus comprises
an on-state current branch circuit, a bridge-type branch circuit,
and at least two breaking current branch circuits, wherein after
being connected in series in sequence, the respective breaking
current branch circuits are further connected in parallel to two
bridge arms of the bridge-type branch circuit, and two ends of the
on-state current branch circuit are respectively connected to
bridge arm middle points of the two bridge arms of the bridge-type
branch circuit.
2. The apparatus for breaking a line bidirectional current
according to claim 1, wherein: the first power semiconductor device
has a capability of switching on/off a current.
3. The apparatus for breaking a line bidirectional current
according to claim 1, wherein: the second power semiconductor
device does not have a capability of switching on/off a
current.
4. The apparatus for breaking a line bidirectional current
according to claim 1, wherein: the bidirectional power
semiconductor switch comprises third and fourth power semiconductor
devices that are connected in parallel to each other, and
directions of current switches of the third and fourth power
semiconductor devices are opposite to each other.
5. The apparatus for breaking a line bidirectional current
according to claim 1, wherein: the bidirectional power
semiconductor switch comprises two power semiconductor devices and
two diodes, wherein a fifth power semiconductor device is connected
in parallel to a first diode, and directions of current switches of
the two are opposite to each other; a sixth power semiconductor
device is connected in parallel to a second diode, and directions
of current switches of the two are opposite to each other; and the
two parallel connections are connected in series, directions of the
current switches of the fifth and sixth power semiconductor devices
are opposite to each other, and directions of the current switches
of the first and second diodes are opposite to each other.
6. The apparatus for breaking a line bidirectional current
according to claim 1, wherein: the commutation branch circuit also
comprises at least one second high-speed isolation switch, and the
second high-speed isolation switch and the second power
semiconductor device are connected in series to each other.
7. A control method for the apparatus for breaking a line
bidirectional current according to claim 1, defining that two
connection points between the on-state current branch circuit and
the bridge-type branch circuit in the apparatus are respectively
two ends of the apparatus, and the apparatus is connected in series
to a current path of a line by using the two ends, wherein: the
first high-speed isolation switch and the bidirectional power
semiconductor switch in the on-state current branch circuit are
closed, the second power semiconductor device in the bridge-type
branch circuit is closed, and the first power semiconductor device
in the breaking current branch circuit is closed; and the control
method comprises the following steps: if a switch-off signal of the
on-state current branch circuit is received, switching off the
bidirectional power semiconductor switch of the on-state current
branch circuit, so as to commutate a current to the bridge-type
branch circuit and the breaking current branch circuit; then
switching off the first high-speed isolation switch of the on-state
current branch circuit; and then if a switch-off signal of the
breaking current branch circuit is received, switching off the
first power semiconductor device in the breaking current branch
circuit, so as to commutate a current to the nonlinear
resistor.
8. (canceled)
9. The control method for the apparatus for breaking a line
bidirectional current according to claim 2, defining that two
connection points between the on-state current branch circuit and
the bridge-type branch circuit in the apparatus are respectively
two ends of the apparatus, and the apparatus is connected in series
to a current path of a line by using the two ends, wherein: the
first high-speed isolation switch and the bidirectional power
semiconductor switch in the on-state current branch circuit are
closed, the second power semiconductor device in the bridge-type
branch circuit is closed, and the first power semiconductor device
in the breaking current branch circuit is closed; and the control
method comprises the following steps: if a switch-off signal of the
on-state current branch circuit is received, switching off the
bidirectional power semiconductor switch of the on-state current
branch circuit, so as to commutate a current to the bridge-type
branch circuit and the breaking current branch circuit; then
switching off the first high-speed isolation switch of the on-state
current branch circuit; and then if a switch-off signal of the
breaking current branch circuit is received, switching off the
first power semiconductor device in the breaking current branch
circuit, so as to commutate a current to the nonlinear
resistor.
10. The control method for the apparatus for breaking a line
bidirectional current according to claim 3, defining that two
connection points between the on-state current branch circuit and
the bridge-type branch circuit in the apparatus are respectively
two ends of the apparatus, and the apparatus is connected in series
to a current path of a line by using the two ends, wherein: the
first high-speed isolation switch and the bidirectional power
semiconductor switch in the on-state current branch circuit are
closed, the second power semiconductor device in the bridge-type
branch circuit is closed, and the first power semiconductor device
in the breaking current branch circuit is closed; and the control
method comprises the following steps: if a switch-off signal of the
on-state current branch circuit is received, switching off the
bidirectional power semiconductor switch of the on-state current
branch circuit, so as to commutate a current to the bridge-type
branch circuit and the breaking current branch circuit; then
switching off the first high-speed isolation switch of the on-state
current branch circuit; and then if a switch-off signal of the
breaking current branch circuit is received, switching off the
first power semiconductor device in the breaking current branch
circuit, so as to commutate a current to the nonlinear
resistor.
11. The control method for the apparatus for breaking a line
bidirectional current according to claim 4, defining that two
connection points between the on-state current branch circuit and
the bridge-type branch circuit in the apparatus are respectively
two ends of the apparatus, and the apparatus is connected in series
to a current path of a line by using the two ends, wherein: the
first high-speed isolation switch and the bidirectional power
semiconductor switch in the on-state current branch circuit are
closed, the second power semiconductor device in the bridge-type
branch circuit is closed, and the first power semiconductor device
in the breaking current branch circuit is closed; and the control
method comprises the following steps: if a switch-off signal of the
on-state current branch circuit is received, switching off the
bidirectional power semiconductor switch of the on-state current
branch circuit, so as to commutate a current to the bridge-type
branch circuit and the breaking current branch circuit; then
switching off the first high-speed isolation switch of the on-state
current branch circuit; and then if a switch-off signal of the
breaking current branch circuit is received, switching off the
first power semiconductor device in the breaking current branch
circuit, so as to commutate a current to the nonlinear
resistor.
12. The control method for the apparatus for breaking a line
bidirectional current according to claim 5, defining that two
connection points between the on-state current branch circuit and
the bridge-type branch circuit in the apparatus are respectively
two ends of the apparatus, and the apparatus is connected in series
to a current path of a line by using the two ends, wherein: the
first high-speed isolation switch and the bidirectional power
semiconductor switch in the on-state current branch circuit are
closed, the second power semiconductor device in the bridge-type
branch circuit is closed, and the first power semiconductor device
in the breaking current branch circuit is closed; and the control
method comprises the following steps: if a switch-off signal of the
on-state current branch circuit is received, switching off the
bidirectional power semiconductor switch of the on-state current
branch circuit, so as to commutate a current to the bridge-type
branch circuit and the breaking current branch circuit; then
switching off the first high-speed isolation switch of the on-state
current branch circuit; and then if a switch-off signal of the
breaking current branch circuit is received, switching off the
first power semiconductor device in the breaking current branch
circuit, so as to commutate a current to the nonlinear
resistor.
13. The control method for the apparatus for breaking a line
bidirectional current according to claim 6, defining that two
connection points between the on-state current branch circuit and
the bridge-type branch circuit in the apparatus are respectively
two ends of the apparatus, and the apparatus is connected in series
to a current path of a line by using the two ends, wherein: the
first high-speed isolation switch and the bidirectional power
semiconductor switch in the on-state current branch circuit are
closed, the second power semiconductor device and the second
high-speed isolation switch in the bridge-type branch circuit are
closed, and the first power semiconductor device in the breaking
current branch circuit is closed; and the control method comprises
the following steps: if a switch-off signal of the on-state current
branch circuit is received, switching off the bidirectional power
semiconductor switch of the on-state current branch circuit, so as
to commutate a current to the bridge-type branch circuit and the
breaking current branch circuit; then, switching off the first
high-speed isolation switch of the on-state current branch circuit;
determining, on a bridge arm connected to a current input end, a
second power semiconductor device of a cathode directly or
indirectly connected to the current input end, and switching off a
second high-speed isolation switch of a commutation branch circuit
on which the second power semiconductor device is located; and
determining, on a bridge arm connected to a current output end, a
second power semiconductor device of an anode directly or
indirectly connected to the current output end, and switching off a
second high-speed isolation switch of a commutation branch circuit
on which the second power semiconductor device is located; then if
a switch-off signal of the breaking current branch circuit is
received, switching off the first power semiconductor device in the
breaking current branch circuit, so as to commutate a current to
the nonlinear resistor; and switching off the second high-speed
isolation switch that is in a closed state in the bridge-type
branch circuit to complete an entire breaking process.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to an apparatus for breaking a
line bidirectional current flowing and a control method for the
apparatus.
BACKGROUND
[0002] In a multi-end DC(DC) power transmission system, a
high-voltage DC circuit breaker is one of the most important
devices. In the multi-end DC power transmission system, because a
voltage level is high and the line resistance is low, once a line
short-circuit fault occurs, a DC power transmission network and an
alternating-current (AC) network are affected soon, and the fault
must be cleared quickly. Therefore, the high-voltage DC circuit
breaker needs to act fast and be able to reduce the fault duration
to the greatest extent or suppress a faulty current, thereby
reducing an attack of the fault on the AC/DC power transmission
network. Because the high-voltage DC circuit breaker is connected
in series to the power transmission line, in addition to that the
circuit breaker is required to have a relatively high speed of
switching on/off a circuit, the circuit breaker is required to have
a loss as less as possible. A direction of a current in the
high-voltage DC power transmission line is not determined, and the
current may have two directions. Therefore, a circuit breaker is
generally required to be able to distinguish DC current in two
directions.
[0003] In the Chinese patent application CN102780200A, a
conventional high-voltage DC circuit breaker is used to break a DC
current, and a structure of the conventional high-voltage DC
circuit breaker is constituted by three parts: an AC circuit
breaker, an LC oscillation circuit, and an energy consumption
element. After being opened, the AC circuit breaker generates an
electric arc, the voltage of the electric arc resonates in the LC
oscillation circuit, and when an oscillating current peak value
reaches a magnitude of the DC current, the oscillating current can
counterbalance the DC current, so that a zero crossing occurs at a
port of the circuit breaker, so as to help extinguish the electric
arc, thereby achieving the objective of switching off the DC
current. Such a breaking manner may break a current in two
directions and has an excessively small loss in normal working.
However, an are extinguishing time of a conventional high-voltage
DC circuit breaker is relatively long, which is about tens of
milliseconds, so that a requirement of quickly isolating a fault of
a multi-end DC power transmission system cannot be satisfied.
[0004] In the European patent EP0867998B1, a solid-state circuit
breaker structure based on a semiconductor device is proposed and
can be constituted by a switchable semiconductor device group and
an energy consumption element. The switchable semiconductor device
group is constituted by multiple low-voltage switchable
semiconductor elements, and because a breaking speed of the
switchable semiconductor device is extremely high, which is
microsecond-scaled, a DC faulty current can be quickly switched off
in this manner. However, because an on-state voltage drop of a
semiconductor device group is great, a power transmission loss is
increased, and power transmission efficiency is lowered.
[0005] In order to satisfy requirements of quickly isolating a DC
faulty current and maintaining relatively high power transmission
efficiency, the Chinese patent application CN102687221A discloses
an apparatus and a method for breaking an electrical current of a
power transmission or distribution line and a current limiting
arrangement. A main circuit breaker, a high-speed switch, an
auxiliary circuit breaker, and a non-linear resistor energy
consumption element are included. In normal working mode, a line
current flows through an auxiliary circuit and has a small on-state
loss; and in faulty mode, the current is commutated to the main
circuit breaker, and finally, the energy consumption element
absorbs a breaking capability.
[0006] After a high-voltage DC circuit-breaking apparatus switches
off a faulty current, the main circuit breaker withstands the
voltage of several hundred kV, and the number of power
semiconductor devices connected in series in one current direction
can easily reach several hundreds. Because the power semiconductor
device can only be conducted in a single direction, in order to
switch off a faulty current in two current directions, a basic
series-connection unit in the main circuit breaker in the
high-voltage DC circuit breaking apparatus uses an anti-parallel or
anti-series connection structure of two power semiconductor
devices, and a number of power semiconductor devices in the main
circuit breaker is doubled. During breaking in a first current
direction, power semiconductor devices in a second current
direction do not produce a beneficial effect on breaking the
current or withstanding the voltage, which is equivalent to that a
utilization ratio of the power semiconductor devices of the main
circuit breaker is only 50%. Because costs of the power
semiconductor devices occupy a large proportion of the total costs
of the apparatus, in order to implement a function of breaking a
current in two directions, costs of the apparatus are increased
considerably.
[0007] Not only the increase of the power semiconductor devices in
the second current direction in the main circuit breaker do not
produce a beneficial effect, but also the power semiconductor
devices in the second current direction are subject to the
disadvantageous influence of overvoltage and overcurrent generated
when the breaking occurs in the first direction. If the power
semiconductor devices in the second current direction and the power
semiconductor devices in the first current direction are in
anti-parallel connection, when the breaking occurs in the first
current direction, overvoltage is applied to the power
semiconductor devices in the second current direction, and this
voltage is a reverse voltage to the power semiconductor devices in
the second current direction and would cause damage to the devices;
and if the power semiconductor devices with an anti-parallel diode
in the second current direction and the power semiconductor devices
with an anti-parallel diode in the first current direction are
connected in series in opposite directions, an excessively high
abrupt current generated in the breaking process in the first
current direction would flow through a freewheeling diode in the
power semiconductor devices in the second current direction, which
also exerts disadvantageous influence on the service life of the
device.
[0008] The increased power semiconductor devices in the second
current direction would also exert disadvantageous influence on the
structural design and electrical design, and the power
semiconductor devices in the first current direction have a
consistent arrangement direction, so that the electric design and
the structural design have consistency. The increase of the power
semiconductor devices in the second current direction ruins the
consistency in the original arrangement direction, resulting in
increased difficulty in device layout, mounting, and wiring.
SUMMARY
Technical Problem
[0009] An objective of the present invention is to propose an
apparatus for breaking a line bidirectional current and a control
method therefor, thereby greatly reducing costs of the apparatus
and reducing difficulty in device layout, mounting and wiring of
the apparatus on the premise of ensuring a breaking speed that is
quick enough and a low loss.
Technical Solution
[0010] In order to achieve the foregoing objective, the solutions
used in the present invention are:
[0011] An apparatus for breaking a line bidirectional current
includes a breaking current branch circuit and an on-state current
branch circuit, where the breaking current branch circuit includes
one nonlinear resistor being connected in parallel to one first
power semiconductor device, or one nonlinear resistor being
connected in parallel to at least two first power semiconductor
devices mutually connected in series; and the on-state current
branch circuit includes at least one bidirectional power
semiconductor switch being connected in series to at least one
high-speed isolation switch, where:
the apparatus also includes a bridge-type branch circuit, and the
bridge-type branch circuit includes two bridge anus constituted by
four identical current commutation branch circuits, each current
commutation branch circuit comprising at least one second power
semiconductor device connected in series; every two of the four
commutation branch circuits are connected in series a same
direction, and the formed two bridge arms are further connected in
parallel; and a connection relationship of the apparatus is any one
of the following four: a) the apparatus includes a breaking current
branch circuit, an on-state current branch circuit, and a
bridge-type branch circuit, where two ends of the on-state current
branch circuit are respectively connected to bridge arm middle
points of two bridge anus of the bridge-type branch circuit, and
the two bridge arms are both connected in parallel to the breaking
current branch circuit; b) the apparatus includes at least two
groups of a breaking current branch circuit, an on-state current
branch circuit, and a bridge-type branch circuit, where in each
group, two ends of the on-state current branch circuit are
respectively connected to bridge arm middle points of two bridge
arms of the bridge-type branch circuit, and the two bridge arms are
both connected in parallel to the breaking current branch circuit;
and all the on-state current branch circuits are connected in
series in sequence; c) the apparatus includes an on-state current
branch circuit and at least two groups of a breaking current branch
circuit and a bridge-type branch circuit, where in each group, two
bridge arms of the bridge-type branch circuit are both connected in
parallel to corresponding breaking current branch circuits, and
bridge arm middle points of the bridge-type branch circuit in each
group are connected in series in sequence; and two ends of the
on-state current branch circuit are respectively connected to
bridge arm middle points of end portions of the first bridge-type
branch circuit and the last bridge-type branch circuit in the
circuits connected in series; and d) the apparatus includes an
on-state current branch circuit, a bridge-type branch circuit, and
at least two breaking current branch circuits, where after being
connected in series in sequence, the respective breaking current
branch circuits are further connected in parallel to two bridge
arms of the bridge-type branch circuit, and two ends of the
on-state current branch circuit are respectively connected to
bridge arm middle points of the two bridge arms of the bridge-type
branch circuit.
[0012] The foregoing first power semiconductor device has a
capability of switching on/off a current.
[0013] The foregoing second power semiconductor device does not
have a capability of switching on/off a current.
[0014] The bidirectional power semiconductor switch includes third
and fourth power semiconductor devices that are connected in
parallel to each other, and directions of current switches of the
third and fourth power semiconductor devices are opposite to each
other.
[0015] The bidirectional power semiconductor switch includes two
power semiconductor devices and two diodes, where a fifth power
semiconductor device is connected in parallel to a first diode, and
directions of current switches of the two are opposite to each
other; a sixth power semiconductor device is connected in parallel
to a second diode, and directions of current switches of the two
are opposite to each other; and the two parallel connections are
connected in series, directions of the current switches of the
fifth and sixth power semiconductor devices are opposite to each
other, and directions of the current switches of the first and
second diodes are opposite to each other.
[0016] The commutation branch circuit also includes at least one
second high-speed isolation switch, and the second high-speed
isolation switch and the second power semiconductor device are
connected in series to each other.
[0017] A control method for an apparatus for breaking a line
bidirectional current defines that two connection points between
the on-state current branch circuit and the bridge-type branch
circuit in the apparatus are respectively two ends of the
apparatus, and the apparatus is connected in series to a current
path of a line by using the two ends, where: the first high-speed
isolation switch and the bidirectional power semiconductor switch
in the on-state current branch circuit are closed, the second power
semiconductor device in the bridge-type branch circuit is closed,
and the first power semiconductor device in the breaking current
branch circuit is closed; and the control method includes the
following steps: [0018] if a switch-off signal of the on-state
current branch circuit is received, switching off the bidirectional
power semiconductor switch of the on-state current branch circuit,
so as to commutate a current to the bridge-type branch circuit and
the breaking current branch circuit; [0019] then switching off the
first high-speed isolation switch of the on-state current branch
circuit; and [0020] then if a switch-off signal of the breaking
current branch circuit is received, switching off the first power
semiconductor device in the breaking current branch circuit, so as
to commutate a current to the nonlinear resistor. A control method
for an apparatus for breaking a line bidirectional current defines
that two connection points between the on-state current branch
circuit and the bridge-type branch circuit in the apparatus are
respectively two ends of the apparatus, and the apparatus is
connected in series to a current path of a line by using the two
ends, where: the first high-speed isolation switch and the
bidirectional power semiconductor switch in the on-state current
branch circuit are closed, the second power semiconductor device
and the second high-speed isolation switch in the bridge-type
branch circuit are closed, and the first power semiconductor device
in the breaking current branch circuit is closed; and the control
method includes the following steps [0021] if a switch-off signal
of the on-state current branch circuit is received, switching off
the bidirectional power semiconductor switch of the on-state
current branch circuit, so as to commutate a current to the
bridge-type branch circuit and the breaking current branch circuit;
[0022] then, switching off the first high-speed isolation switch of
the on-state current branch circuit; determining, on a bridge arm
connected to a current input end, a second power semiconductor
device of a cathode directly or indirectly connected to the current
input end, and switching off a second high-speed isolation switch
of a commutation branch circuit on which the second power
semiconductor device is located; and determining, on a bridge arm
connected to a current output end, a second power semiconductor
device of an anode directly or indirectly connected to the current
output end, and switching off a second high-speed isolation switch
of a commutation branch circuit on which the second power
semiconductor device is located; [0023] then if a switch-off signal
of the breaking current branch circuit is received, switching off
the first power semiconductor device in the breaking current branch
circuit, so as to commutate a current to the nonlinear resistor;
and [0024] switching off the second high-speed isolation switch
that is in a closed state in the bridge-type branch circuit to
complete an entire breaking process.
Advantageous Effect
[0025] After using the foregoing solutions, the present invention
has the following features:
[0026] (1) A low on-state loss: When a line works normally, a line
current flows through a high-speed isolation switch having nearly
zero impedance and an on-state current branch circuit constituted
by a few power semiconductor devices having an extremely small
conduction voltage drop. Because a current commutation branch
circuit and a breaking current branch circuit need a higher
conduction voltage drop, almost no current flows through them, and
it is unnecessary to additionally mount a cooling system for the
current commutation branch circuit. A total loss of the apparatus
is extremely low.
[0027] (2) As compared with a conventional high-voltage DC circuit
breaker, the apparatus has a higher breaking speed, and uses a
power semiconductor device as a current breaking execution unit,
which is excessively fast, where a breaking speed of a general
power semiconductor device is merely tens of microseconds and can
be ignored. A total breaking time of the apparatus is mainly a
breaking time of a high-speed isolation switch. Currently, a
breaking time of a high-speed isolation switch may reach 1 to 3 ms,
and it could be predicted that the total breaking time of the
apparatus is about 3 to 5 ms, which is far higher than the breaking
speed of the conventional high-voltage DC circuit breaker.
[0028] (3) Bidirectional current breaking is implemented with
relatively low costs: In the present invention, the breaking
current branch circuit is constituted by power switch devices
connected in series in a same current direction, and by means of
the current commutation branch circuit, a bidirectional current in
the line flows through the breaking current branch circuit in the
same direction. When the line current is in a first current
direction, the direction of the current commutation branch circuit
(A, D) is consistent with the first current direction, the
direction of the power semiconductor devices in the current
commutation branch circuit (B, C) is opposite to the first current
direction, and the power semiconductor devices are in a reverse
cut-off state. When the line current is in a second current
direction, the direction of the current commutation branch circuit
(B, C) is consistent with the second current direction, the
direction of the power semiconductor devices in the current
commutation branch circuit (A, D) is opposite to the second current
direction, and the power semiconductor devices are in a reverse
cut-off state. Hence, when the line current directions are
different, directions of the currents flowing through the breaking
current branch circuit are consistent. The current commutation
branch circuit may have two composition manners: one manner is
connecting a few power semiconductor devices in series to one
high-speed isolation switch, where the high-speed isolation switch
is configured to isolate a relatively high switch-off voltage, and
the other manner is connecting a greater number of power
semiconductor devices in series to withstand a high switch-off
voltage. In the present invention, the first solution is preferred,
particularly, in a scenario where the voltage is excessively high.
The current commutation branch circuit includes a few power
semiconductor devices and four groups of high-speed isolation
switches in total, the number of power semiconductor devices is
excessively small, and the costs are low. The high-speed isolation
switches are separated only in a no-current state, it is
unnecessary to extinguish an electrical arc, only an effect of
isolating a voltage is produced, and the costs are low. As compared
with the patent CN102687221A, the total costs are reduced
considerably, the utilization efficiency of the power semiconductor
devices in the apparatus is improved, and meanwhile, a disadvantage
of the patent CN102687221A in implementing a bidirectional function
is avoided.
[0029] (4) The control method is used to when a current reaches a
limit value, add a specific number of nonlinear resistors to the
line by means of operation to produce effects of changing the
impedance of the line and limiting the rise of the faulty current,
which is an extension of application of the apparatus and has the
advantages of the apparatus.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] FIG. 1 is a diagram of an apparatus for breaking a line
bidirectional current according to the present invention;
[0031] FIG. 2 is a diagram illustrating a correspondence between a
first current direction and a direction of a power semiconductor
device:
[0032] FIG. 3 is a diagram illustrating a correspondence between a
second current direction and a direction of a power semiconductor
device;
[0033] FIG. 4 is a first illustrative diagram of a current
commutation branch circuit;
[0034] FIG. 5 is a second illustrative diagram of the current
commutation branch circuit;
[0035] FIG. 6 illustrates another embodiment of the present
invention;
[0036] FIG. 7 illustrates still another embodiment of the present
invention;
[0037] FIG. 8 illustrates further another embodiment of the present
invention;
[0038] FIG. 9 is a first embodiment of a bidirectional power
semiconductor switch in the present invention; and
[0039] FIG. 10 is a second embodiment of the bidirectional power
semiconductor switch in the present invention.
DETAILED DESCRIPTION
[0040] The technical solutions of the present invention are
described in detail below with reference to the accompanying
drawings and specific embodiments.
[0041] As shown in FIG. 1, the present invention provides an
apparatus 20 for breaking a line bidirectional current, including a
breaking current branch circuit 9 and an on-state current branch
circuit 30, where the breaking current branch circuit 9 includes
one nonlinear resistor 13 being connected in parallel to one first
power semiconductor device 5, or one nonlinear resistor 13 being
connected in parallel to at least two first power semiconductor
devices 5 mutually connected in series; and the on-state current
branch circuit 30 includes at least one bidirectional power
semiconductor switch 12 being connected in series to at least one
high-speed isolation switch 11, and when there are at least two
bidirectional power semiconductor switches 12 and at least two
high-speed isolation switches 11, the connection relationships
thereof are mutual series connections.
[0042] The apparatus also includes four current commutation branch
circuits A, B, C, D, where the four commutation branch circuits
have the identical structure, type of constituent device, and
parameter, each commutation branch circuit includes at least one
power semiconductor device 7 being connected in series to at least
one high-speed isolation switch 6. When there are at least two
power semiconductor devices 7, a connection relationship
therebetween is a series connection in the same direction, and when
there are at least two high-speed isolation switches 6, a
connection relationship therebetween is a mutual series connection
or an indirect series connection. Every two of the four commutation
branch circuits are connected in series in the same direction, and
the two parallel connections are further connected in parallel. In
this embodiment, the commutation branch circuits A, B are connected
in series in the same direction to constitute a bridge arm, and the
commutation branch circuits C, D are connected in series in the
same direction to constitute another bridge arm. The two bridge
arms are further connected in parallel, and the so-called "series
connection in the same direction" is specifically directed to the
power semiconductor devices 7.
[0043] A connection relationship of the apparatus is: an end of the
on-state current branch circuit 30 is connected to a middle point 3
of a bridge arm constituted by the commutation branch circuits A,
B, and a direction in which a current enters from the outside to
the connection point is defined as a first current direction 14;
another end of the on-state current branch circuit 30 is connected
to a middle point 4 of a bridge arm constituted by the commutation
branch circuits C, D, and a direction in which a current enters
from the outside to the connection point is defined as a second
current direction 15; the two bridge arms are both connected in
parallel to the breaking current branch circuit 9; and an input end
of the apparatus 20 is also connected to an end of a current
limiting reactor 19 to form a series connection, and a current
limiting reactor 10 is configured to limit the rise of a
short-circuit current.
[0044] In this embodiment, the power semiconductor device 5 in the
breaking current branch circuit 9 needs to have a capability of
switching on/off a current, where a gate switchable device such as
an IGBT, an IEGT, or a GTO, may be used; and the power
semiconductor device 7 in the commutation branch circuit does not
need to have a capability of switching on/off a current, where a
diode may be used.
[0045] Both of the commutation branch circuits A, D include at
least one high-speed isolation switch 6 being connected in series
to at least one power semiconductor device 7 in the first current
direction 14, and a correspondence between the current direction
and the direction of the power semiconductor device 7 is shown in
FIG. 2; and both of the current commutation branch circuits B, C
include at least one high-speed isolation switch 6 being connected
in series to at least one power semiconductor device 7 in the
second current direction 15, and a correspondence between the
current direction and the direction of the power semiconductor
device 7 is shown in FIG. 3. Using such an arrangement manner is
using a unidirectional conduction characteristic of a power
semiconductor device, so as to enable a bidirectional current in a
line to flow through the breaking current branch circuit 9 in the
same direction, for example, from a node 1 to a node 2 in FIG.
1.
[0046] The four commutation branch circuits are all constituted by
high-speed isolation switches 6 being connected in series to power
semiconductor devices 7, as shown in FIG. 4. A main function of a
high-speed isolation switch 6 is isolating a voltage. After
breaking of the breaking current branch circuit 9, an excessively
high breaking voltage is generated between the node 1 and the node
2, and this voltage is applied to the commutation branch circuit.
The high-speed isolation switch 6 may withstand an excessively high
breaking voltage, so that the power semiconductor device 7 in the
commutation branch circuit only needs to withstand an excessively
low breaking voltage. A few devices are required to be connected in
series. Such a manner saves costs of the apparatus.
[0047] The four commutation branch circuits may also be replaced in
a manner as shown in FIG. 5. In an optional manner, the commutation
branch circuit may be a series connection constituted by at least
one power semiconductor device 7. In such a manner, a high-speed
isolation switch is omitted, but the series connection of the power
semiconductor device 7 needs to be able to withstand an excessively
high voltage, so a great number of devices being connected in
series are needed.
[0048] The power semiconductor devices 7 in the commutation branch
circuit may be connected in parallel in the same direction, so as
to improve a current withstanding capability of the commutation
branch circuit.
[0049] The apparatus 20 is connected in series to a line 44, the
on-state current branch circuit 30 merely has a few power
semiconductor devices, and a conduction voltages drop is less. In a
normal state, when a line current flows through the on-state
current branch circuit 30, an excessively small loss is
generated.
[0050] The on-state current branch circuit 30 is constituted by at
least one bidirectional power semiconductor switch 12 and a
high-speed isolation switch 11, where the bidirectional power
semiconductor switch 12 includes a parallel connection between the
power semiconductor device 5 in the first current direction 14 and
the power semiconductor device 28 in the second current direction
15, as shown in FIG. 9.
[0051] The bidirectional power semiconductor switch 12 may be of
another structure, including a first parallel connection between
the power semiconductor device 5 in the first current direction 14
and the power semiconductor device 28 in the second current
direction 15 and a second parallel connection between the power
semiconductor device 25 in the second current direction 15 and the
power semiconductor device 27 in the first current direction 15, as
shown in FIG. 10.
[0052] An arrangement direction of the power semiconductor device 5
in the breaking current branch circuit 9 of the apparatus 20 is
always consistent with a line current direction, as shown in FIG. 2
and FIG. 3, and the current direction in the breaking current
branch circuit 9 is from the node 1 to the node 2. As compared with
the on-state current branch circuit 30, the breaking current branch
circuit 9 has a higher voltage blocking capability, and main
effects of the breaking current branch circuit 9 are switching off
a current in the line and being able to withstand a relatively high
breaking voltage. A branch circuit includes a lot of series
connections of power semiconductor devices 5, and after a breaking
instruction is received, breaking is performed on the power
semiconductor devices 5 simultaneously. After the breaking, a
breaking voltage is generated between the node 1 and the node 2,
the high voltage enables impedance of the nonlinear resistor 13
connected in parallel to the two ends of the branch circuit to
change. Finally, the current is commutated to the nonlinear
resistor 13, and the energy is absorbed by the nonlinear resistor
13.
[0053] The power semiconductor devices 5 in the breaking current
branch circuit 9 may be connected in parallel in the same
direction, so as to improve a current withstanding capability of
the branch circuit.
[0054] The present invention also includes a control method for the
apparatus 20 for breaking a line bidirectional current, where the
apparatus 20 is connected in series to a current path of the line
44, where the high-speed isolation switch 11 and the bidirectional
power semiconductor switch 12 in the on-state current branch
circuit 30 in the apparatus 20 are closed, the high-speed isolation
switches 6 and power semiconductor devices 7 of the four
commutation branch circuits A, B, C, D are closed, and the power
semiconductor device 5 in the breaking current branch circuit 9 is
closed; and the control method includes the following steps: [0055]
if a switch-off signal of the on-state current branch circuit 30 is
received, switching off the bidirectional power semiconductor
switch 12 of the on-state current branch circuit 30, so as to
commutate a current to the commutation branch circuits A, B, C, D
and the breaking current branch circuit 9; [0056] then determining
a current direction of the line 44, and if the current direction is
the first current direction 14, switching off the high-speed
isolation switches 6 of the current commutation branch circuits B,
C and the high-speed isolation switch 11 of the on-state current
branch circuit 30 simultaneously, where when the current direction
is the first current direction 14, as shown in FIG. 2, the current
commutation branch circuits B, C and the on-state current branch
circuit 30 withstand a high breaking voltage generated by breaking
of the breaking current branch circuit 9, so before the breaking of
the breaking current branch circuit 9, it is necessary to separate
the current commutation branch circuits B, C from the high-speed
isolation switch 11 of the on-state current branch circuit 30, so
as to prevent the power semiconductor device of the branch circuit
from being damaged because of withstanding the high breaking
voltage; moreover, the current commutation branch circuits A, D and
the breaking current branch circuit 9 are in a series connection,
through which a breaking current flows, but would not withstand a
high breaking voltage, and should be kept in a closed state; if the
current direction is the second current direction 15, switching off
the high-speed isolation switches 6 of the current commutation
branch circuits A, D and the high-speed isolation switch 11 of the
on-state current branch circuit 30 simultaneously, where when the
current direction is the second current direction 14, as shown in
FIG. 3, the current commutation branch circuits A, D and the
on-state current branch circuit 30 would withstand a high breaking
voltage generated by breaking of the breaking current branch
circuit 9, so before the breaking of the breaking current branch
circuit 9, it is necessary to separate the current commutation
branch circuits A, D from the high-speed isolation switch 11 of the
on-state current branch circuit 30, so as to prevent the power
semiconductor device of the branch circuit from being damaged by
the high breaking voltage; moreover, the current commutation branch
circuits B, C and the breaking current branch circuit 9 are in a
series connection, through which a breaking current flows, but
would not withstand a high breaking voltage, and should be kept in
a closed state; [0057] then if a switch-off signal of the breaking
current branch circuit 9 is received, switching off the power
semiconductor device 5 in the breaking current branch circuit, so
as to commutate a current to the nonlinear resistor 13; and [0058]
when determining that the line current is reduced to zero,
switching off the high-speed isolation switches 6 that are in a
closed state in the current commutation branch circuits A, B, C, D
to complete an entire breaking process.
[0059] The present invention further has several other
implementation structures, which are briefly described below.
[0060] As shown in FIG. 6, an apparatus 40 includes at least two
apparatuses 20 that are mutually connected in series and that are
connected in series to the current path of the line 44, where the
apparatus 40 is suitable for, when the current in the current path
exceeds a current limit, controlling a specific number of the at
least two apparatuses 20, so as to commutate a flowing current that
passes through the on-state current branch circuits 30 of the at
least two apparatuses 20 to the nonlinear resistor 13.
[0061] As shown in FIG. 7, the apparatus 41 connected in series to
the line 44 includes at least two current commutation branch
circuits A, B and current commutation branch circuits C, D being
connected in parallel to the breaking current branch circuit 9,
where the parallel connections are mutually connected in series,
and the series connection is connected in parallel to the on-state
current branch circuit 30. When the current in the current path
exceeds a current limit, operation is performed on the on-state
current branch circuit 30 and a specific number of the at least two
current commutation branch circuits A, B, and the parallel
connections between the current commutation branch circuits C, D
and the breaking current branch circuit 9 enable the current that
passes through the on-state current branch circuit 30 to be
commutated to the nonlinear resistors 13 in the at least two
parallel connections.
[0062] As shown in FIG. 8, an apparatus 42 connected in series to
the line 44 includes a series connection of at least two breaking
current branch circuits 9, where the breaking current branch
circuit 9 includes at least one power semiconductor device 5 being
connected in parallel to a nonlinear resistor 13 and further
includes an on-state current branch circuit 30 constituted by at
least one bidirectional power semiconductor switch 12 and at least
one high-speed isolation switch 11 that are connected in series;
further includes current commutation branch circuits A, B, C, D,
where each of the current commutation branch circuits A, B, C, D
includes a series connection between at least one power
semiconductor device 7 and at least one high-speed isolation switch
6, an end of the on-state current branch circuit 30 is connected to
a middle point 3 of a bridge arm constituted by the current
commutation branch circuits A, B, another end of the on-state
current branch circuit 30 is connected to a middle point 4 of a
bridge arm constituted by the current commutation branch circuits
C, D, and series connections between the two bridge arms and the at
least two breaking current branch circuits 9 constitute a parallel
connection.
[0063] When the current in the current path exceeds a current
limit, operation is performed on series connections between the
on-state current branch circuit 30 and a specific number of the at
least two breaking current branch circuits 9, so as to commutate
the current that passes through the on-state current branch circuit
30 to the nonlinear resistor 13 connected in series to to the at
least two breaking current branch circuits 9.
[0064] A specific implementation manner of the present invention is
described by using an embodiment:
[0065] The apparatus 20 is designed to be able to break a
bidirectional current of a .+-.400 kV high-voltage DC power
transmission line, and a current breaking capability is 2 kA.
[0066] As shown in FIG. 1, an apparatus 20 for breaking the line
bidirectional current includes a breaking current branch circuit 9,
current commutation branch circuits A, B, C, D, and an on-state
current branch circuit 30, where the breaking current branch
circuit 9 shall at least be able to withstand a breaking voltage of
800 kV, in consideration of a specific allowance, the design is
performed according to a breaking voltage of 1200 kV, and two 4.5
kV/1.6 kA IGBTs are connected in parallel to serve as a unit
device, and in consideration of an uneven voltage that may occur at
a critical moment, a specific allowance shall be reserved in the
voltage-resistance design on the device, so 400 unit devices are
needed to be connected in series to constitute an IGBT valve group,
where a total number of devices is 800. The arrangement directions
of all IGBTs are consistent.
[0067] The on-state current branch circuit 30 includes a
bidirectional power semiconductor switch 12 being connected in
series to a high-speed isolation switch 11, where the high-speed
isolation switch 11 requires a relatively high breaking speed, and
a port after the breaking can withstand a voltage of 1200 kV. The
IGBTs with 4.5 kV/1.6 kA freewheeling diodes are connected in
parallel in reverse to constitute a unit device, and the on-state
circuit branch circuit 30 needs three unit devices in total, which
are connected in series and then connected parallel to constitute a
valve group. Six unit devices are needed in total, and a total
number of devices is 12. The IGBTs and the freewheeling diodes are
arranged in two directions. The on-state current branch circuit 30
is connected to the bridge arm middle point 3 and bridge arm middle
point 4 on the two ends of the line.
[0068] The apparatus 20 further includes current commutation branch
circuits A, B, C, D, where the commutation branch circuits A, B
constitute a first bridge arm with a middle point connected to the
bridge arm middle point 3 of the line, the commutation branch
circuits C, D constitute a second bridge arm with a middle point
connected to the bridge arm middle point 4 of the line, and the two
bridge arms are both connected in parallel to the breaking current
branch circuit 9.
[0069] The apparatus 20 needs four current commutation branch
circuits in total, devices of the branch circuits are the same, and
each branch circuit includes a power semiconductor device 7 and a
high-speed isolation switch 6. A technical requirement on the
high-speed isolation switch 6 is basically consistent with that on
the on-state current branch circuit 30. The power semiconductor
device 7 only needs to withstand an excessively small breaking
voltage, and a few series connections are needed. A 4.5 kV/1.6 kA
diode is selected as the power semiconductor device 7, and three
diodes in total are needed to be connected in series and then
connected in parallel to constitute a diode group. Each branch
circuit needs six diodes, four current commutation branch circuits
need 24 diodes in total, and the arrangement directions of diodes
are shown in FIG. 2 and FIG. 3.
[0070] The control method includes the following steps:
[0071] In a normal situation, the high-speed isolation switch 11
and the bidirectional power semiconductor switch 12 in the on-state
current branch circuit 30 of the apparatus 20 are closed, the
high-speed isolation switches 6 and the power semiconductor devices
7 in the current commutation branch circuits A, B, C, D are closed,
and the power semiconductor device 5 in the breaking current branch
circuit 9 is closed. Because the on-state current branch circuit 30
only includes three IGBT series connections, while the breaking
current branch circuit 9 includes 400 IGBT series connections, a
rated voltage blocking capability of the breaking current branch
circuit 9 is far greater than that of the on-state current branch
circuit 30. That is, the on-state current branch circuit 30 has
relatively extremely small equivalent conduction resistance, and a
normal line current flows through the on-state current branch
circuit 30. [0072] If a switch-off signal of the on-state current
branch circuit 30 is received, the bidirectional power
semiconductor switch 12 of the on-state current branch circuit 30
is switched off, so as to commutate a current commutation branch
circuit and the breaking current branch circuit 9. If the current
direction is the first current direction 14, a path through which
the current flows is shown in FIG. 2. If the current direction is
the second current direction 15, a path through which the current
flows is shown in FIG. 3. [0073] Then, a current direction of the
line 44 is determined, if the current direction is the first
current direction 14, the high-speed isolation switches 6 of the
current commutation branch circuits B, C and the high-speed
isolation switch 11 of the on-state current branch circuit 30 are
switched off simultaneously, and if the current direction is the
second current direction 15, the high-speed isolation switches 6 of
the current commutation branch circuits A, D and the high-speed
isolation switch 11 of the on-state current branch circuit 30 are
switched off simultaneously. [0074] Then if a switch-off signal of
the breaking current branch circuit 9 is received, the IGBT valve
group in the breaking current branch circuit is switched off
simultaneously, so as to commutate the current to the nonlinear
resistor 13. [0075] When it is determined that the line current is
reduced to zero, the high-speed isolation switches 6 that are in a
closed state in the current commutation branch circuits A, B, C, D
are switched off to complete an entire breaking process.
[0076] The foregoing embodiments are merely used to describe the
technical solutions of the present invention instead of limiting
them. Although after reading the present application, a person
skilled in the art can make various modifications or changes by
referring to the foregoing embodiments, the modifications or
changes all fall within the protection scope of the claims of the
present application that is filed for a grant.
* * * * *