A control method of a resistance-inductance type current limiter based on energy consumption branch multiplexing, and a resistance-inductance type current limiter

Abstract

The application discloses a control method of a resistance-inductance type current limiter based on energy consumption branch multiplexing. For a multi-terminal direct-current power grid, resistance-inductance type current limiters share one energy consumption branch on multiple direct-current lines at the outlet side of the same bus. When the system is normally operated, thyristors in the resistance-inductance type current limiter are turned off, and direct-current only flows through the current limiting branch of the current limiter. After the system fails and before the circuit breaker acts, the thyristors in the resistance-inductance type current limiter remain in the off state. During the period of removing the fault current by the circuit breaker, the thyristors of the energy consumption branch are turned on, so as to separate the fault energy of the line and the current limiter. After the direct-current fault is removed, the thyristors of the energy consumption branch are always turned on, the residual energy of the fault current limiter is dissipated by the energy consumption branch, and the fault current limiter returns to the initial state after the energy of the reactor is dissipated. The method has simple topology and control logic and high reliability, can effectively reduce the number of energy consumption devices, and improves the economy of the current limiting equipment.

Description

Technical Field

[0001] This invention relates to the field of DC power transmission technology, and in particular to a control method for a resistive inductive current limiter based on the multiplexing of energy-consuming branches, as well as the resistive inductive current limiter. Background Technology

[0002] The use of flexible DC interconnection is an important development trend for my country's future power grid. Flexible DC technology based on modular multilevel converters (MMC) possesses four-quadrant control capabilities for active and reactive power, making it a crucial technical means applicable to scenarios such as large-capacity cross-regional power transmission, large-scale consumption of renewable energy, and isolated power supply. However, DC systems are characterized by "low inertia and low impedance," meaning that once a DC fault occurs, the fault current rises rapidly and reaches a large peak value. During the fault process, the DC fault current does not naturally cross zero, making DC fault clearing a major constraint on the development of DC power grids. DC power grid fault clearing schemes are mainly divided into two types: using converters with fault clearing capabilities or using DC circuit breakers. After a fault occurs, converters with fault clearing capabilities can autonomously isolate the fault, but this scheme lacks selectivity, and the recovery time of a fully functional converter station is relatively long. DC circuit breakers have selective fault clearing capabilities, but current DC circuit breaker technology needs improvement, and the investment cost is very high. Therefore, adding fault current limiters to suppress fault current and reduce the requirements for circuit breaker breaking capacity, thereby reducing costs, is a potential improvement scheme.

[0003] The main current-limiting elements of current limiters are typically resistors, inductors, or a combination of resistors and inductors. Resistive current limiters have weak current-limiting effects but fast fault clearing speed, while inductive current limiters are the opposite. Resistive-inductive current limiters are a better choice, combining both current-limiting capability and fault clearing speed. To further reduce investment in metal oxide varistor (MOV) surge arresters and accelerate fault current clearing, the current limiter topology requires additional energy-consuming branches. Since a current limiter needs to be configured at both ends of each line, the overall energy-consuming device of the current-limiting equipment will be large in size and costly. Summary of the Invention

[0004] The purpose of this invention is to provide a control method for a resistive inductive current limiter based on the multiplexing of energy-consuming branches, as well as a resistive inductive current limiter. The topology and control logic of the method and the resistive inductive current limiter are simple and highly reliable. They can effectively reduce the number of energy-consuming devices, thereby reducing the size and weight of the current limiting device and improving the economy of the current limiting device.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] A control method for a resistive-inductive current limiter based on energy-consuming branch multiplexing, the method comprising:

[0007] For multi-terminal DC grids, multiple DC lines on the same bus outlet side can share a single energy-consuming branch for resistive inductive current limiters.

[0008] When the system is running normally, the thyristor in the resistive-inductive current limiter is turned off, and the DC current flows only from the current limiting branch of the current limiter.

[0009] After a system fault occurs and before the circuit breaker operates, the thyristors in the inductive current limiter remain in the off state, and the current limiter current limiting branch reactors L1 and L2 located on the fault line suppress the increase of fault current.

[0010] During the circuit breaker operation to clear the fault current, the thyristor of the energy-consuming branch is turned on to separate the fault energy of the line and the current limiter reactance. The current limiter reactance of multiple lines consumes energy through the same energy-consuming branch.

[0011] After the DC fault is cleared, the thyristor T1 in the energy-consuming branch is turned on, and the remaining energy of the fault current limiter reactor is dissipated by the energy-consuming branch. After the reactor energy is dissipated, the fault current limiter returns to its initial state.

[0012] An inductive current limiter based on the reuse of energy-consuming branches, the inductive current limiter includes a current-limiting branch and an energy-consuming branch, the current-limiting branch is configured at both ends of each DC line; the energy-consuming branch is shared by lines connected to the same bus outlet side; the current-limiting branch and the energy-consuming branch are connected through two sets of diodes in the same direction, so that the inductance of the current-limiting branch and the energy-consuming branch can form a loop;

[0013] The current-limiting branch includes inductors L1 and L2 connected in series, which provide a path for steady-state current during normal system operation and play an inductive current-limiting role after a line fault occurs, suppressing the growth of fault current.

[0014] The energy-dissipating branch includes a resistor R1, a thyristor T1, and a resistor R2 connected in series. The thyristor T1 is turned on in the direction that the resistor R2 points towards the resistor R1. It is used to limit the fault current in the early stage of the fault, and after the DC circuit breaker operates, it is used to separate the energy of the line from the inductance of the current-limiting branch of the current limiter, so that the fault energy in the inductor is dissipated by the energy-dissipating branch of the current limiter.

[0015] As can be seen from the technical solution provided by the present invention, the above method and the topology and control logic of the resistive inductive current limiter are simple and highly reliable. They can effectively reduce the number of energy-consuming devices, thereby reducing the size and weight of the current limiting device and improving the economy of the current limiting device. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic flowchart of the control method for a resistive-inductive current limiter based on the multiplexing of energy-consuming branches provided in an embodiment of the present invention;

[0018] Figure 2 This is a schematic diagram of the topology of a resistive-inductive current limiter for multiple lines sharing a power-consuming branch, as described in an embodiment of the present invention.

[0019] Figure 3 This is a schematic diagram of the DC current path in the resistive-inductive current limiter during normal operation of the system described in this embodiment of the invention;

[0020] Figure 4 This is a schematic diagram of the DC current path in the resistive-inductive current limiter before the circuit breaker operates after a fault, as described in an embodiment of the present invention.

[0021] Figure 5 This is a schematic diagram of the DC current path in the resistive-inductive current limiter during the fault current clearing stage of the circuit breaker operation, as described in this embodiment of the invention.

[0022] Figure 6 This is a schematic diagram of the DC current path in the resistive-inductive current limiter during the recovery phase after the fault current is cleared, as described in an embodiment of the present invention. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments, and do not constitute a limitation of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0024] like Figure 1 The diagram shown is a schematic flowchart of a resistive-inductive current limiter control method based on energy-consuming branch multiplexing provided in an embodiment of the present invention. The method includes:

[0025] Step 1: For multi-terminal DC grids, make the inductive current limiter share a single energy-consuming branch on multiple DC lines on the same bus outlet side.

[0026] In this step, such as Figure 2The diagram shows a topology of a resistive inductive current limiter that allows multiple lines to share a power-consuming branch, as described in an embodiment of the present invention. The resistive inductive current limiter includes a current-limiting branch and a power-consuming branch. Resistive inductive current limiters located on multiple lines on the same side of the converter station can share the same power-consuming branch, reducing the redundant configuration of power-consuming devices, which is beneficial to reducing the overall size of the current-limiting equipment and improving the economy of the current-limiting equipment.

[0027] The current-limiting branch is configured at both ends of each DC line; the energy-consuming branch is shared by the lines connected to the same bus outlet side; the current-limiting branch and the energy-consuming branch are connected through two sets of diodes in the same direction, so that the inductance of the current-limiting branch and the energy-consuming branch can form a loop.

[0028] The current-limiting branch includes inductors L1 and L2 connected in series, which provide a path for steady-state current during normal system operation and play an inductive current-limiting role after a line fault occurs, suppressing the growth of fault current.

[0029] The energy-consuming branch includes a resistor R1, a thyristor T1 and a resistor R2 connected in series, with the thyristor T1 conducting in the direction that resistor R2 points towards resistor R1.

[0030] In the early stages of a fault, it is used to limit the fault current. After the DC circuit breaker operates, it is used to separate the energy of the line from the current-limiting branch inductor of the current limiter, so that the fault energy in the inductor is dissipated by the energy-dissipating branch of the current limiter, avoiding energy dissipation through the metal oxide varistor (MOV) of the DC circuit breaker, and reducing the total energy dissipation of the DC circuit breaker.

[0031] Step 2: When the system is running normally, the thyristor in the resistive-inductive current limiter is turned off, and the DC current flows only from the current limiting branch of the current limiter.

[0032] In this step, such as Figure 3 The diagram shows the DC current path in the inductive current limiter of the system under normal operation according to the embodiment of the present invention. For a stable DC current, the inductors L1 and L2 of the current limiting branch exhibit extremely small impedance, so the current limiter generates very small power loss under steady state.

[0033] Step 3: After a system fault occurs and before the circuit breaker operates, the thyristors in the inductive current limiter remain in the off state, and the current limiter branch reactors L1 and L2 located on the fault line suppress the increase of fault current.

[0034] In this step, such as Figure 4The diagram shown is a schematic diagram of the DC current path in the resistive-inductive current limiter before the circuit breaker operates after a fault occurs, according to an embodiment of the present invention. If a fault occurs in line 1 of the n lines, the thyristor in the resistive-inductive current limiter remains in the off state after the fault occurs and before the circuit breaker operates. The inductors L1 and L2 of the current limiting branch of the current limiter in line 1 can suppress the increase of fault current without delay.

[0035] Meanwhile, current from other lines is fed into line 1, and diode T, which connects the current-limiting branch and the energy-consuming branch, is also fed into line 1. l1_1 T li_1 ,

[0036] T li_2 (i=2,3…,n) Therefore, it is turned on, and the feed current is suppressed by the resistance R2 of the current-limiting branch and the energy-consuming branch of the non-faulty line.

[0037] Step 4: During the circuit breaker operation to clear the fault current, the thyristor of the energy-consuming branch is turned on to separate the fault energy of the line and the current limiter reactor. The current limiter reactors of multiple lines consume energy through the same energy-consuming branch.

[0038] In this step, such as Figure 5 The diagram shows the DC current path in the inductive current limiter during the fault current clearing stage of the circuit breaker operation according to an embodiment of the present invention. If a fault occurs in line 1 of the n lines, the thyristor T1 of the energy-consuming branch is turned on during the fault current clearing stage of the circuit breaker operation.

[0039] With the connection of the circuit breaker MOV, the DC fault current decreases. The freewheeling current of the inductor L1 in the current-limiting branch circulates through the energy-dissipating branch, and the freewheeling current of the inductor L2 in the current-limiting branch circulates through the resistor R2 in the energy-dissipating branch. This separates the fault energy in line 1 and the current limiter. The circuit breaker only needs to dissipate the fault energy in line 1, which significantly reduces the energy consumption burden of the circuit breaker, thereby improving the utilization rate of the device and the economy of the current-limiting equipment.

[0040] Step 5: After the DC fault is cleared, the thyristor T1 in the energy-consuming branch is turned on, and the remaining energy of the fault current limiter reactor is dissipated by the energy-consuming branch. After the reactor energy is dissipated, the fault current limiter returns to its initial state.

[0041] In this step, such as Figure 6 The diagram shows the recovery stage after the fault current is cleared according to the embodiment of the present invention. It is a schematic diagram of the DC current path in the resistive-inductive current limiter. If line 1 in the n lines fails, after the DC fault is cleared, the thyristor T1 in the energy-consuming branch is always on, and the remaining energy of the fault current limiter reactance is dissipated by the energy-consuming branch.

[0042] In this circuit, the energy in the inductor L1 of the current-limiting branch is dissipated by the resistors R1 and R2 of the energy-consuming branch, and the energy in the inductor L2 of the current-limiting branch is dissipated by the resistor R2 of the energy-consuming branch. After this, the faulty current limiter returns to its initial state.

[0043] This invention also provides a resistive-inductive current limiter based on the reuse of energy-consuming branches. The resistive-inductive current limiter includes a current-limiting branch and an energy-consuming branch. The current-limiting branch is configured at both ends of each DC line. The energy-consuming branch is shared by lines connected to the same bus outlet side. The current-limiting branch and the energy-consuming branch are connected through two sets of diodes in the same direction, so that the inductance of the current-limiting branch and the energy-consuming branch can form a loop.

[0044] The current-limiting branch includes inductors L1 and L2 connected in series, which provide a path for steady-state current during normal system operation and play an inductive current-limiting role after a line fault occurs, suppressing the growth of fault current.

[0045] The energy-dissipating branch includes a resistor R1, a thyristor T1, and a resistor R2 connected in series. The thyristor T1 is turned on in the direction that the resistor R2 points towards the resistor R1. It is used to limit the fault current in the early stage of the fault, and after the DC circuit breaker operates, it is used to separate the energy of the line from the inductance of the current-limiting branch of the current limiter, so that the fault energy in the inductor is dissipated by the energy-dissipating branch of the current limiter.

[0046] Based on the aforementioned resistive-inductive current limiter, during normal system operation, the thyristor in the resistive-inductive current limiter is turned off, and the DC current flows only from the current limiting branch of the current limiter.

[0047] After a system fault occurs and before the circuit breaker operates, the thyristors in the inductive current limiter remain in the off state, and the current limiter current limiting branch reactors L1 and L2 located on the fault line suppress the increase of fault current.

[0048] During the circuit breaker operation to clear the fault current, the thyristor of the energy-consuming branch is turned on to separate the fault energy of the line and the current limiter reactance. The current limiter reactance of multiple lines consumes energy through the same energy-consuming branch.

[0049] After the DC fault is cleared, the thyristor T1 in the energy-consuming branch is turned on, and the remaining energy of the fault current limiter reactor is dissipated by the energy-consuming branch. After the reactor energy is dissipated, the fault current limiter returns to its initial state.

[0050] It is worth noting that the contents not described in detail in the embodiments of the present invention belong to the prior art known to those skilled in the art.

[0051] In summary, the method and resistive-inductive current limiter described in this embodiment of the invention are simple to operate and highly reliable. They can reduce the number of current limiting devices on energy-consuming devices and semiconductor devices without increasing control complexity, reduce the overall size of the current limiting devices, improve the overall economy of the current limiter, and are suitable for multi-terminal DC grid scenarios.

[0052] Furthermore, those skilled in the art will understand that all or part of the steps in the methods of the above embodiments can be implemented by a program instructing related hardware, and the corresponding program can be stored in a computer-readable storage medium, such as a read-only memory, a disk, or an optical disk.

[0053] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims. The information disclosed in the background section is intended only to enhance the understanding of the overall background technology of the present invention and should not be construed as an admission or implication in any way that such information constitutes prior art known to those skilled in the art.

Claims

1. A control method of a resistance-inductance type current limiter based on energy dissipation branch multiplexing, characterized by, The method comprises: For a multi-terminal DC power grid, a resistive-inductive current limiter shares an energy consumption branch on multiple DC lines at the same bus outlet side, wherein: The resistive-inductive current limiter comprises a current limiting branch and an energy consumption branch, the current limiting branch is arranged at both ends of each DC line; the energy consumption branch is shared by lines at the same bus outlet side; each current limiting branch is connected to the shared energy consumption branch through two groups of diodes in the same direction, so that the inductance of the current limiting branch and the energy consumption branch can form a loop; The current limiting branch comprises inductances L1 and L2 connected in series, which are used to provide a flow path for steady-state current during normal operation of the system, and play an inductive current limiting role after a line fault occurs to inhibit the growth of fault current; The energy consumption branch comprises resistors R1, thyristor T1 and resistor R2 connected in series, the conduction direction of thyristor T1 is that resistor R2 points to resistor R1; resistor R2 is connected in parallel across inductance L2 through a diode; one end of resistor R1 is connected to the bus outlet, and the other end of resistor R1 is connected to one end of thyristor T1; the other end of thyristor T1 is connected to one end of inductance L1 through a diode, and the other end of inductance L1 is connected to the bus outlet; the energy consumption branch is used to limit fault current at the initial stage of the fault, and is used to separate the energy of the inductance of the line and the current limiting branch of the current limiter after the action of the DC circuit breaker, so that the fault energy in the inductance is dissipated by the energy consumption branch of the current limiter; During normal operation of the system, the thyristor in the resistive-inductive current limiter is turned off, and the DC current only flows through the current limiting branch of the current limiter; After the system failure and before the circuit breaker action, the thyristor in the resistance-inductance type current limiter remains off state, and the inductance L1 and L2 of the current limiting branch on the fault line inhibits the growth of the fault current; specifically including: if the line 1 of the n lines fails, after the failure and before the circuit breaker action, the thyristor in the resistance-inductance type current limiter remains off state, and the inductance L1 and L2 of the current limiting branch of the line 1 inhibits the growth of the fault current; at the same time, the current of other lines is fed to the line 1, and the diode T l1_1 , T li_1 , T li_2 (i=2,3…,n) is thus turned on, and the feeding current is inhibited by the resistance R2 of the current limiting branch and the energy consumption branch of the non-fault line; During the period of clearing fault current by the circuit breaker, the thyristor of the energy consumption branch is turned on to separate the fault energy of the fault line and the inductance of the current limiter, and the inductances of the current limiters of multiple lines dissipate energy through the same energy consumption branch; After the DC fault is cleared, the thyristor T1 of the energy consumption branch is turned on, the remaining energy of the inductance of the current limiter is dissipated by the energy consumption branch, and after the electrical energy is completely dissipated, the fault current limiter returns to the initial state; wherein the energy in the inductance L1 of the current limiting branch is dissipated by the resistors R1 and R2 of the energy consumption branch, and the energy in the inductance L2 of the current limiting branch is dissipated by the resistor R2 of the energy consumption branch, and thereafter the fault current limiter returns to the initial state.

2. The control method of claim 1, wherein, During the period of clearing fault current by the circuit breaker, the thyristor of the energy consumption branch is turned on to separate the fault energy of the fault line and the inductance of the current limiter, and the inductances of the current limiters of multiple lines dissipate energy through the same energy consumption branch, wherein: If line 1 of the n lines fails, during the period of clearing fault current by the circuit breaker, the thyristor T1 of the energy consumption branch is turned on.

3. The control method of claim 1, wherein, After the DC fault is cleared, the thyristor T1 of the energy consumption branch is turned on, the remaining energy of the inductance of the current limiter is dissipated by the energy consumption branch, and after the electrical energy is completely dissipated, the fault current limiter returns to the initial state, wherein: If line 1 of the n lines fails, after the DC fault is cleared, the thyristor T1 of the energy consumption branch is always turned on, and the remaining energy of the inductance of the current limiter is dissipated by the energy consumption branch.

4. A resistance-inductance type current limiter based on energy dissipation branch multiplexing, characterized by, The resistive-inductive current limiter is controlled by the resistive-inductive current limiter control method based on energy consumption branch multiplexing according to any one of claims 1-3.

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