Multi-port hybrid DC circuit breaker topology sharing main turn-off branch and control method

Abstract

The invention belongs to the field of direct-current circuit breakers, particularly relates to a multi-port hybrid direct-current circuit breaker topology sharing a main turn-off branch and a control method of the multi-port hybrid direct-current circuit breaker topology, and aims to solve the problem that a direct-current circuit breaker is too large in cost and size. According to the invention, a first end of a DC system and a second end of a main turn-off branch are connected to a first node; the second end of the direct current system and the first end of the main turn-off branch are connected to a second node; the direct current system comprises N direct current branches; the first end of each direct current branch is connected to a first node, and the second end of each direct current branch is connected to a second node; for the nth direct current branch, the first end of the nth through-current branch is connected to the first node, the second end of the nth through-current branch and the input end of the nth diode branch are connected to the nth end point, the output end of the nth diode branch is connected to the second node, and the nth end point is connected to the nth port. The voltage utilization rate is improved.

Description

Background Art

[0002] In recent years, renewable energy technologies mainly based on wind power and photovoltaic power have been continuously developing, and the installed capacity has been increasing. However, the existing AC power grid is difficult to absorb large-scale renewable energy. Based on this, the flexible DC transmission technology has developed rapidly. The DC system fault current develops rapidly, which poses high requirements for the protection and fault isolation technology of the DC power grid. Due to the characteristics of fast response speed and good fault isolation selectivity, DC circuit breakers have been widely used in various DC system projects. At present, DC circuit breakers mainly include two types: solid-state DC circuit breakers and hybrid DC circuit breakers. The hybrid DC circuit breaker combines the advantages of mechanical DC circuit breakers and solid-state DC circuit breakers, uses a fast mechanical switch to conduct normal load current and a solid-state main breaking switch to interrupt fault current, and at the same time has low on-state loss and fast fault current interruption ability. With the further development of various distributed power sources, it has become a trend for future power grid development to form two-terminal or even multi-terminal DC transmission systems. However, at present, when implementing bidirectional shutdown or multi-port use in the hybrid DC circuit breaker scheme, a large number of fully controlled power electronic devices, arresters and other devices need to be used, which greatly increases the cost and volume of the DC circuit breaker.

[0003] Therefore, the existing DC circuit breakers have the problem that a large number of fully controlled power electronic devices, arresters and other devices need to be used, which greatly increases the cost and volume of the DC circuit breaker. Summary of the Invention

[0004] In order to solve the above problems in the prior art, that is, the existing DC circuit breakers have the problem that a large number of fully controlled power electronic devices, arresters and other devices need to be used, which greatly increases the cost and volume of the DC circuit breaker, the present invention provides a multi-port hybrid DC circuit breaker topology sharing a main breaking branch. The multi-port hybrid DC circuit breaker topology includes:

[0005] A main breaking branch and a DC system; the first end of the DC system is connected to the second end of the main breaking branch to a first node G1; the second end of the DC system is connected to the first end of the main breaking branch to a second node G2;

[0006] The DC system includes N DC branches; the first end of each DC branch is connected to the first node G1, and the second end of each DC branch is connected to the second node G2;

[0007] Each DC branch includes a current-carrying branch, a diode branch, and a port;

[0008] For the nth DC branch, the first end of the nth current-carrying branch is connected to the first node G1, the second end of the nth current-carrying branch and the input end of the nth diode branch are connected to the nth end point, the output end of the nth diode branch is connected to the second node G2, and the nth end point is connected to the nth port. n is any number belonging to 1 to N.

[0009] In a preferred embodiment, the main turn-off branch includes:

[0010] The main turn-off branch includes a unidirectional fully controlled power electronic device branch and a lightning arrester;

[0011] The first end of the lightning arrester and the output end of the unidirectional fully controlled power electronic device branch are connected to the first node G1; the second end of the lightning arrester and the input end of the unidirectional fully controlled power electronic device branch are connected to the second node G2;

[0012] The unidirectional fully controlled power electronic device branch includes M series-connected unidirectional fully controlled power electronic devices; the output end of the first unidirectional fully controlled power electronic device is connected to the first node G1; the input end of the mth unidirectional fully controlled power electronic device is connected to the input end of the (m + 1)th unidirectional fully controlled power electronic device, and the output end of the Mth unidirectional fully controlled power electronic device is connected to the second node G2; m is any number belonging to 1 to M - 1.

[0013] In a preferred embodiment, each current-carrying branch includes a fully controlled power electronic device and a mechanical switch;

[0014] For the nth current-carrying branch, the input end of the nth unidirectional fully controlled power electronic device is connected to the nth end point, the output end of the nth unidirectional fully controlled power electronic device is connected to the second end of the nth mechanical switch, and the first end of the nth mechanical switch is connected to the first node G1.

[0015] In a preferred embodiment, each diode branch includes:

[0016] For the nth diode branch, the nth diode branch includes T series-connected diodes, the output end of the first diode is connected to the nth end point, the input end of the Tth diode is connected to the second node G2; the input end of the tth diode is connected to the output end of the (t + 1)th diode. t is any number belonging to 1 to T - 1.

[0017] The second aspect of the present invention proposes a control method for a multi-port hybrid DC circuit breaker topology sharing a main turn-off branch, which works based on the above multi-port hybrid DC circuit breaker topology sharing a main turn-off branch. The control method includes:

[0018] When the DC system is operating normally, the mechanical switches on the N current-carrying branches are all open. When the mechanical switches are open, the current transfer between the DC system and the main shutdown branch and the N diode branches is disconnected;

[0019] For the currents on the n ports, real-time current transfer is performed based on the n unidirectional fully controlled power electronic devices on the n current-carrying branches.

[0020] In a preferred embodiment, the control method further includes:

[0021] When a DC short-circuit fault occurs in the DC branch where the k-th port of the DC system is located, the current of the k-th port will rise rapidly. When the detection device detects that the current of the k-th port is greater than the threshold, the connection between the k-th current-carrying branch and the k-th port is disconnected, and the mechanical switches on the 1st to the k-1th and the k + 1th to the Nth current-carrying branches are turned on; then the short-circuit current of the k-th port will flow through the 1st to the k-1th and the k + 1th to the Nth current-carrying branches to the main shutdown branch, then through the main shutdown branch to the k-th diode branch, and finally to the k-th port. During the process of the short-circuit current flowing back to the k-th port through the main shutdown branch, the short-circuit current is consumed by the arrester on the main shutdown branch;

[0022] When the detection device detects that the current on the k-th port returns to the normal range, the mechanical switches on the 1st to the k-1th and the k + 1th to the Nth current-carrying branches are disconnected, and then the unidirectional fully controlled power electronic devices on the 1st to the k-1th and the k + 1th to the Nth current-carrying branches operate normally.

[0023] Advantages of the present invention:

[0024] (1) By sharing a main shutdown branch, the present invention reduces the number of fully controlled power electronic devices and arresters, and improves the voltage utilization rate of the power electronic devices;

[0025] (2) By sharing the main shutdown branch, the present invention reduces the cost and volume of the multi-port hybrid DC circuit breaker;

[0026] (3) By using fast mechanical switches to conduct normal load current and solid-state main break switches to interrupt fault current, the present invention has low on-state loss and fast fault current interruption ability. Description of the Drawings

[0027] By reading the detailed description of the non-restrictive embodiments with reference to the following drawings, other features, objects, and advantages of the present application will become more apparent:

[0028] Figure 1 is a topology of a multi-port hybrid DC circuit breaker sharing a main shutdown branch according to an embodiment of the present invention;

[0029] Figure 2 is the schematic diagram of the normal operation of a multi-port hybrid DC breaker topology sharing a main turn-off branch according to an embodiment of the present invention;

[0030] Figure 3 is the schematic diagram of fault handling when a short-circuit fault occurs in a multi-port hybrid DC breaker topology sharing a main turn-off branch according to an embodiment of the present invention;

[0031] Figure 4 is the schematic diagram of the multi-port hybrid DC breaker topology sharing a main turn-off branch after short-circuit fault handling according to an embodiment of the present invention; Specific embodiments

[0032] The present application will be further described in detail below with reference to the accompanying drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the related invention, rather than limiting the invention. In addition, it should be noted that, for the sake of description, only the parts related to the relevant invention are shown in the drawings.

[0033] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The present application will be described in detail below with reference to the drawings and embodiments.

[0034] The present invention provides a multi-port hybrid DC breaker topology sharing a main turn-off branch, and the multi-port hybrid DC breaker topology includes:

[0035] A main turn-off branch and a DC system; the first end of the DC system is connected to the second end of the main turn-off branch to a first node G1; the second end of the DC system is connected to the first end of the main turn-off branch to a second node G2;

[0036] The DC system includes N DC branches; the first end of each DC branch is connected to the first node G1, and the second end of each DC branch is connected to the second node G2;

[0037] Each DC branch includes a current-carrying branch, a diode branch, and a port;

[0038] For the nth DC branch, the first end of the nth current-carrying branch is connected to the first node G1, the second end of the nth current-carrying branch and the input end of the nth diode branch are connected to the nth end point, the output end of the nth diode branch is connected to the second node G2, and the nth end point is connected to the nth port. n is any number belonging to 1 to N.

[0039] As Figure 1 shown, the multi-port hybrid DC breaker topology sharing a main turn-off branch according to the first embodiment of the present invention, the multi-port hybrid DC breaker topology includes:

[0040] The main shutdown branch and the DC system; the first end of the DC system and the second end of the main shutdown branch are connected to the first node G1; the second end of the DC system and the first end of the main shutdown branch are connected to the second node G2;

[0041] In this embodiment, the main shutdown branch includes a unidirectional fully controlled power electronic device branch and a lightning arrester; the first end of the lightning arrester and the output end of the unidirectional fully controlled power electronic device branch are connected to the first node G1; the second end of the lightning arrester and the input end of the unidirectional fully controlled power electronic device branch are connected to the second node G2;

[0042] The unidirectional fully controlled power electronic device branch includes M series-connected unidirectional fully controlled power electronic devices; the output end of the first unidirectional fully controlled power electronic device is connected to the first node G1; the input end of the m-th unidirectional fully controlled power electronic device is connected to the input end of the m + 1-th unidirectional fully controlled power electronic device, and the output end of the M-th unidirectional fully controlled power electronic device is connected to the second node G2. m is any number belonging to 1 to M - 1.

[0043] The DC system includes N DC branches; the first end of each DC branch is connected to the first node G1, and the second end of each DC branch is connected to the second node G2;

[0044] Each DC branch includes a current-carrying branch, a diode branch, and a port; for the n-th DC branch, the first end of the n-th current-carrying branch is connected to the first node G1, the second end of the n-th current-carrying branch and the input end of the n-th diode branch are connected to the n-th end point, the output end of the n-th diode branch is connected to the second node G2, and the n-th end point is connected to the n-th port.

[0045] In this embodiment, each current-carrying branch includes a fully controlled power electronic device and a mechanical switch; for the n-th current-carrying branch, the input end of the n-th unidirectional fully controlled power electronic device is connected to the n-th end point, the output end of the n-th unidirectional fully controlled power electronic device is connected to the second end of the n-th mechanical switch, and the first end of the n-th mechanical switch is connected to the first node G1.

[0046] In this embodiment, each diode branch includes: for the n-th diode branch, the n-th diode branch includes T series-connected diodes, the output end of the first diode is connected to the n-th end point, the input end of the T-th diode is connected to the second node G2; the input end of the t-th diode is connected to the output end of the t + 1-th diode. t is any number belonging to 1 to T - 1.

[0047] The control method for the multi-port hybrid DC circuit breaker topology with a shared main shutdown branch described above includes:

[0048] When the DC system is operating normally, the mechanical switches on N current-carrying branches are all open. When the mechanical switches are open, the current transfer between the DC system, the main turn-off branch, and the N diode branches is disconnected;

[0049] For the current on the nth port, real-time current transfer is performed based on the nth unidirectional fully controlled power electronic device on the nth current-carrying branch.

[0050] When a DC short-circuit fault occurs in the DC branch where the kth port of the DC system is located, the current at the kth port will rise rapidly. When the detection device detects that the current at the kth port is greater than the threshold, the connection between the kth current-carrying branch and the kth port is disconnected, and the mechanical switches on the 1st to the (k - 1)th and the (k + 1)th to the Nth current-carrying branches are turned on; then the short-circuit current at the kth port will flow through the 1st to the (k - 1)th and the (k + 1)th to the Nth current-carrying branches to the main turn-off branch, then through the main turn-off branch to the kth diode branch, and finally to the kth port. During the process of the short-circuit current flowing back to the kth port through the main turn-off branch, the short-circuit current is consumed by the arrester on the main turn-off branch;

[0051] When the detection device detects that the current at the kth port returns to the normal range, the mechanical switches on the 1st to the (k - 1)th and the (k + 1)th to the Nth current-carrying branches are disconnected, and then the unidirectional fully controlled power electronic devices on the 1st to the (k - 1)th and the (k + 1)th to the Nth current-carrying branches operate normally.

[0052] When N is equal to 3, taking the fault of the 3rd port as an example, as Figure 2 shown, when the DC system is operating normally, the mechanical switches on the 3 current-carrying branches are all open, then the current transfer between the DC system, the main turn-off branch, and the 3 diode branches is disconnected;

[0053] For the currents on the 3 ports, real-time current transfer is performed based on the 3 unidirectional fully controlled power electronic devices on the 3 current-carrying branches.

[0054] As shown in Figure 3, when a DC short-circuit fault occurs in the DC branch where the 3rd port of the DC system is located, the current at the 3rd port will rise rapidly. When the detection device detects that the current at the 3rd port is greater than the threshold, the connection between the 3rd current-carrying branch and the 3rd port is disconnected, and the mechanical switches on the 1st to the 2nd current-carrying branches are turned on; then the short-circuit current at the 3rd port will flow through the 1st to the 2nd current-carrying branches to the main turn-off branch, then through the main turn-off branch to the 3rd diode branch, and finally to the 3rd port. During the process of the short-circuit current flowing back to the 3rd port through the main turn-off branch, the short-circuit current is consumed by the arrester on the main turn-off branch;

[0055] As Figure 4As shown in the figure, when the detection device detects that the current on the third port returns to the normal range, the mechanical switches on the first and second current-carrying branches are disconnected, and then the unidirectional fully controlled power electronic devices on the first to second current-carrying branches operate normally.

[0056] Those skilled in the art can clearly understand that for the convenience and simplicity of description, the specific working process and related explanations of the above-described system can refer to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0057] It should be noted that the multi-port hybrid DC breaker topology with a shared main turn-off branch provided in the above embodiments is only illustrated by the division of the above functional modules. In practical applications, the above functions can be allocated to different functional modules as needed, that is, the modules or steps in the embodiments of the present invention can be further decomposed or combined. For example, the modules in the above embodiments can be combined into one module, or further split into multiple sub-modules to complete all or part of the functions described above. The names of the modules and steps involved in the embodiments of the present invention are only used to distinguish each module or step, and are not regarded as an improper limitation of the present invention.

[0058] The control method of the multi-port hybrid DC breaker topology with a shared main turn-off branch according to the second embodiment of the present invention operates based on the above multi-port hybrid DC breaker topology with a shared main turn-off branch. The control method includes:

[0059] When the DC system is operating normally, the mechanical switches on the N current-carrying branches are all disconnected. Disconnecting the mechanical switches disconnects the current transfer between the DC system, the main turn-off branch, and the N diode branches.

[0060] For the current on the nth port, real-time current transfer is performed based on the nth unidirectional fully controlled power electronic device on the nth current-carrying branch.

[0061] When a DC short-circuit fault occurs in the DC branch where the kth port of the DC system is located, the current of the kth port will rise rapidly. When the detection device detects that the current of the kth port is greater than the threshold, the connection between the kth current-carrying branch and the kth port is disconnected, and the mechanical switches on the first to k-1 and k+1 to N current-carrying branches are turned on; then the short-circuit current of the kth port will flow through the first to k-1 and k+1 to N current-carrying branches to the main turn-off branch, and then through the main turn-off branch to the kth diode branch, and finally to the kth port. During the process of the short-circuit current flowing back to the kth port through the main turn-off branch, the short-circuit current is consumed by the arrester on the main turn-off branch;

[0062] When the detection device detects that the current on the k-th port returns to the normal range, disconnect the mechanical switches on the first to k-1-th and k+1-th to N-th current-carrying branches, and then the unidirectional fully-controlled power electronic devices on the first to k-1-th and k+1-th to N-th current-carrying branches operate normally.

[0063] Although the various steps are described in the above order in the above embodiments, those skilled in the art can understand that in order to achieve the effects of this embodiment, different steps do not have to be executed in such an order. They can be executed simultaneously (in parallel) or in a reversed order, and these simple changes are all within the protection scope of the present invention.

[0064] The terms "first", "second", etc. are used to distinguish similar objects, rather than to describe or represent a specific order or sequence.

[0065] The term "comprising" or any other similar term is intended to cover non-exclusive inclusion, so that a process, method, article or device / equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or also includes elements inherent in these processes, methods, articles or devices / equipment.

[0066] So far, the technical solution of the present invention has been described in conjunction with the preferred embodiments shown in the drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the protection scope of the present invention.

Claims

1. A multi-port hybrid DC circuit breaker topology with a shared main disconnecting branch, characterized in that: The multi-port hybrid DC circuit breaker topology includes: A main shut-off branch, a DC system; a first end of the DC system and a second end of the main shut-off branch are connected to a first node G1; a second end of the DC system and a first end of the main shut-off branch are connected to a second node G2; The DC system includes N DC branches; a first end of each DC branch is connected to a first node G1, and a second end of each DC branch is connected to a second node G2; N is a positive integer; Each DC branch includes a current-passing branch, a diode branch, and a port; For the nth DC branch, the first end of the nth current-carrying branch is connected to the first node G1, the second end of the nth current-carrying branch and the input end of the nth diode branch are connected to the nth endpoint, the output end of the nth diode branch is connected to the second node G2, and the nth endpoint is connected to the nth port; n is any number from 1 to N.

2. The multi-port hybrid DC circuit breaker topology with a shared main disconnecting branch according to claim 1, characterized in that: The main shut-off branch comprises: The main shut-off branch includes a unidirectional fully-controlled power electronic device branch and a lightning arrester; The first end of the arrester and the output end of the unidirectional fully-controlled power electronic device branch are connected to the first node G1; the second end of the arrester and the input end of the unidirectional fully-controlled power electronic device branch are connected to the second node G2; The unidirectional fully-controlled power electronic device branch includes M unidirectional fully-controlled power electronic devices connected in series; the output end of the first unidirectional fully-controlled power electronic device is connected to the first node G1; the input end of the mth unidirectional fully-controlled power electronic device is connected to the input end of the m+1th unidirectional fully-controlled power electronic device, and the output end of the Mth unidirectional fully-controlled power electronic device is connected to the second node G2; M is a positive integer; m is any number from 1 to M-1.

3. The multi-port hybrid DC circuit breaker topology with a shared main disconnecting branch according to claim 2, characterized in that: Each current-carrying branch includes a fully controlled power electronic device and a mechanical switch; For the nth current-passing branch, the input end of the nth unidirectional fully-controlled power electronic device is connected to the nth terminal, the output end of the nth unidirectional fully-controlled power electronic device is connected to the second end of the nth mechanical switch, and the first end of the nth mechanical switch is connected to the first node G1.

4. The multi-port hybrid DC circuit breaker topology with a shared main disconnecting branch according to claim 3, characterized in that: Each diode branch consists of: For the nth diode branch, the nth diode branch includes T diodes connected in series, the output end of the 1st diode is connected to the nth endpoint, the input end of the Tth diode is connected to the second node G2; the input end of the tth diode is connected to the output end of the t+1th diode, and t is any number from 1 to T-1.

5. A control method for a multi-port hybrid DC circuit breaker topology with a shared main disconnecting branch, based on the multi-port hybrid DC circuit breaker topology with a shared main disconnecting branch according to any one of claims 1 to 4, characterized in that: The control method comprises: When the DC system is operating normally, the mechanical switches on the N current-carrying branches are all disconnected, thus disconnecting the current transmission between the DC system and the main shutdown branch and the N diode branches; for the current on the n ports, the current is transferred in real time based on the n unidirectional fully-controlled power electronic devices on the n current-carrying branches.

6. The control method of a multi-port hybrid DC circuit breaker topology with a shared main disconnecting branch according to claim 5, characterized in that: The control method further comprises: When a DC short circuit fault occurs in the DC branch where the kth port on the DC system is located, the current of the kth port will rise rapidly. When the detection device detects that the current of the kth port is greater than the threshold value, the connection between the kth flow branch and the kth port is disconnected, and the mechanical switches on the 1st to k-1th and k+1th to Nth flow branches are turned on; then the short-circuit current of the kth port will flow to the main shut-off branch through the 1st to k-1th and k+1th to Nth flow branches, and then flow to the kth diode branch through the main shut-off branch, and finally flow to the kth port. In the process of the short-circuit current flowing back to the kth port through the main shut-off branch, the short-circuit current is consumed by the lightning arrester on the main shut-off branch; When the detection device detects that the current on the kth port returns to the normal range, the mechanical switches on the 1st to k-1th and k+1th to Nth current branches are disconnected, and then the unidirectional fully-controlled power electronic devices on the 1st to k-1th and k+1th to Nth current branches operate normally.

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