Protection methods for power distribution systems

Abstract

This disclosure relates to a method for protecting a power distribution system having an electric grid electrically coupled to electric branch lines, wherein the electric branch lines include a plurality of switches for connecting or disconnecting the electric branch lines at each location on the electric branch line, and loads are electrically coupled to nodes on the electric branch lines. The method includes detecting a fault on the electric branch line based on monitored voltage and / or current on the electric branch line, limiting the power flow from the nodes to the loads based on the detection of the fault, adjusting the voltage and / or current on the electric branch line based on the detection of the fault, determining the location of the fault based on the adjusted voltage and / or current on the electric branch line, and disconnecting a portion of the power distribution system based on the determined location of the fault. This disclosure also relates to the respective controllers and systems.

Description

Technical Field

[0001] Technical Field The present disclosure relates to a method, a controller, and a power distribution system for protecting a power distribution system.

Background Art

[0002] Background In a power distribution system that supplies power from a power source to a load, faults cause a number of problems. A conventional solution for fault removal is to install a DC circuit breaker to interrupt the path through which power flows. However, such a solution not only increases the power loss during operation but is also cost-ineffective.

[0003] FIG. 1 shows a conventional medium voltage DC (MVDC) system for data center applications. In FIG. 1, power is supplied from a high-level power source, such as an AC network, to an IT load via a power converter and a bus that electrically couples the power source to the load. In particular, a grid AC / DC rectifier electrically couples the power source to the MVDC bus, converts the power from the power source, and further distributes it to the IT rooms via the MVDC bus. Each IT room includes a galvanic isolator for stepping down the MVDC to a low voltage DC (LVDC) level that is consumed by an IT load and a battery connected to the LVDC bus. In addition to the illustrated data center applications, another typical application includes an MVDC power distribution system for DC loads of an electrical vehicle charging station (EVCS), particularly together with an electrically coupled battery energy storage device. In such an MVDC system, short-circuit faults cause a number of problems, and conventional fault removal solutions increase power loss and are cost-ineffective.

Summary of the Invention

Problems to be Solved by the Invention

[0004] Therefore, methods, controllers, and the distribution system itself need to be improved to protect the power distribution system. [Means for solving the problem]

[0005] overview This disclosure relates to a method for protecting a power distribution system having an electric grid electrically coupled to electric branch lines, wherein the electric branch lines include a plurality of switches for connecting or disconnecting the electric branch lines at each location on the electric branch lines, and loads are electrically coupled to nodes on the electric branch lines, and the method includes detecting a fault on the electric branch line based on monitored voltage and / or current on the electric branch line, limiting the power flow from the nodes to the loads based on the detection of the fault, adjusting the voltage and / or current on the electric branch line based on the detection of the fault, determining the location of the fault based on the adjusted voltage and / or current on the electric branch line, and disconnecting a portion of the power distribution system based on the determined location of the fault.

[0006] In one embodiment, the restriction involves controlling a galvanic isolator that electrically couples the load to the node, or includes controlling a galvanic isolator.

[0007] In one embodiment, the adjustment involves injecting a predetermined current into an electric branch line, particularly by controlling a power converter that electrically couples the electric grid to the electric branch line, or including injecting a predetermined current into an electric branch line, and the fault location is determined based on the adjusted current.

[0008] In one embodiment, the method further includes limiting the power flow from the electric grid to the electric branch line by, in particular, controlling a power converter that electrically couples the electric grid to the electric branch line before disconnecting.

[0009] In one embodiment, disconnecting means disconnecting at least two of a plurality of switches when it is determined that the fault location is on a branch line between at least two switches, or includes disconnecting at least two of a plurality of switches.

[0010] In one embodiment, at least two of the multiple switches are adjacent to each other and have nodes located in particular between at least two switches.

[0011] In one embodiment, the method further includes restarting the power distribution system by unrestricting the restricted power flow from the node to the load after disconnection, and by controlling the power flow from the electrical grid to the load after disconnection.

[0012] In one embodiment, the two ends of an electric branch wire are electrically coupled to a power converter, and the electric grid is electrically coupled to the electric branch wire, forming a loop.

[0013] In one embodiment, one end of the electric branch wire is electrically coupled to a first power converter which is further electrically coupled to the electric grid, and the other end of the electric branch wire is electrically coupled to a second power converter which is further electrically coupled to the electric grid.

[0014] In one embodiment, at least one of a plurality of switches disconnects the electrical branch wire. In one embodiment, the adjustment further includes enabling power flow from the electric grid to electric branch lines, particularly by controlling a second power converter.

[0015] In one embodiment, the adjustment involves injecting a predetermined current into an electrical branch wire, or including injecting a predetermined current into an electrical branch wire, particularly by controlling the first power converter and the second power converter.

[0016] In one embodiment, determining the location of a fault is based on adjusting the current on an electrical branch line.

[0017] In one embodiment, the method further includes restarting the power distribution system by unrestricting the restricted power flow from the node to the load after disconnection, and by enabling power flow from the electrical grid to the load, in particular by controlling the first and second power converters after disconnection.

[0018] The disclosure further relates to a controller for protecting a power distribution system having an electric grid electrically coupled to electric branch lines, wherein the electric branch lines include a plurality of switches for connecting or disconnecting the electric branch lines at each location on the electric branch lines, and loads are electrically coupled to nodes on the electric branch lines, and the controller is configured to detect a fault occurring on the electric branch lines based on the monitored voltage and / or current of the electric branch lines, limit the power flow from the nodes to the loads based on the detection of the fault, adjust the voltage and / or current on the electric branch lines based on the detection of the fault, determine the location of the fault, and disconnect a portion of the power distribution system based on the determined location of the fault.

[0019] In one embodiment, the controller is further configured to perform a method according to any one of the embodiments disclosed herein.

[0020] The disclosure further relates to a power distribution system comprising an electric grid electrically coupled to electric branch lines, wherein the electric branch lines comprises a plurality of switches for connecting or disconnecting the electric branch lines at each location on the electric branch lines, and loads are electrically coupled to nodes on the electric branch lines, and the power distribution system further comprises a controller according to any one of the embodiments disclosed herein.

[0021] A method according to any one of the embodiments disclosed herein may be used to advantageously monitor and / or estimate quantities of an industrial asset, such as operational performance, operating status, or information regarding external conditions or adjacent systems. One particular quantity to monitor and / or estimate is the health status of an industrial asset, which makes it possible to understand the degradation of the asset, predict its remaining useful life (RUL), and derive decisions for operation, maintenance, and repair. The information thus obtained can be used to inform human operators, managers, or stakeholders, to support their operational or other decisions, or to partially or fully automate the operation of the asset.

[0022] The various exemplary embodiments of this disclosure are directed toward providing features that will be readily apparent by referring to the following description in conjunction with the accompanying drawings. Exemplary systems, methods, and apparatus are disclosed herein by various embodiments. However, it should be understood that these embodiments are presented as examples and not as limitations, and it will be apparent to those skilled in the art who have read this disclosure that various modifications to the disclosed embodiments can be made while remaining within the scope of this disclosure.

[0023] Therefore, this disclosure is not limited to the exemplary embodiments and uses described and illustrated herein. Furthermore, the specific order and / or hierarchy of steps in the methods disclosed herein is merely an exemplary approach. Based on design preferences, the specific order or hierarchy of steps in the disclosed methods or processes can be rearranged while remaining within the scope of this disclosure. Accordingly, those skilled in the art will understand that the methods and techniques disclosed herein present various steps or operations in a sample order, and that this disclosure is not limited to the specific order or hierarchy presented unless otherwise specified.

[0024] Hereinafter, exemplary embodiments of the present disclosure will be described. Note that some aspects of any one of the described embodiments may be found in some other embodiments as well, unless otherwise specified or obvious. However, for better understanding, each aspect will be described in detail only when it is first mentioned, and repeated descriptions of the same aspect will be omitted.

[0025] The above and other aspects and their embodiments are described in more detail in the drawings, the description, and the claims.

Brief Description of the Drawings

[0026] [Figure 1] Shows a conventional power grid. [Figure 2] Shows a flowchart of a method according to an embodiment of the present disclosure. [Figure 3a)] Shows a power distribution system according to an embodiment of the present disclosure under normal operating conditions. [Figure 3b)] Shows a power distribution system according to an embodiment of the present disclosure under fault conditions. [Figure 3c)] Shows a power distribution system according to an embodiment of the present disclosure under fault conditions. [Figure 3d)] Shows a power distribution system according to an embodiment of the present disclosure under fault conditions. [Figure 3e)] Shows a power distribution system according to an embodiment of the present disclosure under normal operating conditions after a fault. [Figure 4] Shows a flowchart of a method according to an embodiment of the present disclosure. [Figure 5] Shows a flowchart for a fault location determination method according to an embodiment of the present disclosure. [Figure 6] Shows a flowchart for a post-fault restart process according to an embodiment of the present disclosure. [Figure 7] Shows a power distribution system according to an embodiment of the present disclosure. [Figure 8a)] Shows a controller for a power distribution system according to an embodiment of the present disclosure. [Figure 8b)] This disclosure shows a power distribution system according to one embodiment. [Modes for carrying out the invention]

[0027] Detailed explanation of disclosure Figure 2 shows a flowchart of a method according to one embodiment of the present disclosure. In particular, the method is for protecting a power distribution system having an electrical grid electrically coupled to an electrical branch line, which includes a plurality of switches for connecting or disconnecting the electrical branch line at each location on the electrical branch line, and the load is electrically coupled to a node on the electrical branch line. The power distribution system may be equivalently called a power distribution system.

[0028] In S201, a fault on the electric branch line is detected based on the monitored voltage and / or current of the electric branch line. The monitored voltage and / or current may be measured at any location on the electric branch line, in particular at any one of the locations of multiple switches. Detection may also be based on the voltage and / or current measured at any location on the electric branch line, in particular at the voltage and / or current measured at each of the locations of multiple switches. Detection may further be based on any other electrical or physical parameters of the power distribution system and / or any components contained therein.

[0029] In S202, based on the detection of a fault, the power flow from the node to the load is limited. The term “limited” may be semantically equivalent to other terms such as “alter,” “reduce,” “interrupt,” or “disconnect,” and can therefore be used interchangeably. In one embodiment, limiting is or includes controlling a galvanic isolator that electrically couples the load to the node. The galvanic isolator may be a solid-state transformer (SST). In one embodiment, limiting is performed after executing S202 and / or before executing S203. Limiting in S202 may also be performed if it is determined that no fault has occurred, for example, if the fault detection yielded a false negative response.

[0030] In S203, based on the detection of a fault, the voltage and / or current on the electrical branch line are adjusted. The term “adjust” may be semantically equivalent to other terms such as “set” or “control,” and it will be understood by those skilled in the art that they can be used interchangeably. In one embodiment, adjusting is or includes injecting a predetermined current into the electrical branch line. In one embodiment, adjusting is or includes controlling a power converter, which electrically couples the electrical grid to the electrical branch line. In one embodiment, adjusting is performed after performing S202 and / or before performing S204. Adjusting in S203 may also be performed if it is determined that no fault has occurred, for example, if the fault detection yielded a false negative response.

[0031] In S204, the fault location is determined based on the regulated voltage and / or current on the electrical branch line. The regulated voltage and / or current may be measured at any location on the electrical branch line, in particular at any one of the locations of a plurality of switches. The fault location may also be a fault range, and the fault is located within the fault range. In one embodiment, the fault range is determined by the regulated voltage and / or current measured at at least two different locations on the electrical branch line, in particular at at least two different locations where two different switches of the plurality of switches are located, and the fault range is between at least two different switches of the plurality of switches. In one embodiment, determining the fault location is based on regulating the current on the electrical branch line.

[0032] In S205, a portion of the power distribution system is disconnected based on the determined fault location. In one embodiment, disconnecting means disconnecting at least two of a plurality of switches, or including disconnecting at least two of a plurality of switches, if it is determined that the fault location is on an electrical branch line between at least two switches.

[0033] In one embodiment, the method further includes restricting the power flow from the electric grid to the electric branch lines. The restricting may be performed after and / or before performing S203. The restricting may involve controlling a power converter, or may include controlling a power converter that electrically couples the electric grid to the electric branch lines.

[0034] In one embodiment, the method further includes restarting the power distribution system by unrestricting the restricted power flow from the node to the load after disconnecting (S205), and by controlling the power flow from the electrical grid to the load after disconnecting (S205). Restarting may be performed after S205. The term “unrestrict” may be semantically equivalent to other terms such as “change,” “increase,” and “unblock,” and can therefore be used interchangeably. In one embodiment, unrestricting includes controlling a galvanic isolator that electrically couples the load to the node, or controlling a galvanic isolator. The galvanic isolator may be a solid-state transformer (SST).

[0035] In one embodiment, at least two of the multiple switches are adjacent to each other, and in particular, a node is located between at least two of the multiple switches.

[0036] In one embodiment, the two ends of an electric branch wire are electrically coupled to a power converter to form a loop. The power converter electrically couples the electric grid to the electric branch wire. The loop may be a ring main unit. The loop may be electrically disconnected by at least one of a plurality of switches that disconnect the electric branch wire. In the same embodiment, reactivation further includes reconnecting at least one of the plurality of switches that disconnect the electric branch wire. In the same embodiment, adjustment further includes enabling power flow from the electric grid to the electric branch wire.

[0037] In one embodiment, one of the two ends of an electric branch wire is electrically coupled to a first power converter, the first power converter is further electrically coupled to the electric grid, and the other end of the two ends of the electric branch wire is electrically coupled to a second power converter, the second power converter is further electrically coupled to the electric grid. In the same embodiment, at least one of a plurality of switches disconnects the electric branch wire. In the same embodiment, reactivating further includes reconnecting at least one of the plurality of switches that disconnects the electric branch wire. In the same embodiment, adjusting further includes enabling power flow from the electric grid to the electric branch wire. In the embodiment, adjusting is or includes injecting a predetermined current into the electric branch wire by controlling the first power converter and the second power converter in particular. In the same embodiment, the method further includes limiting power flow from the electric grid to the electric branch wire. The limiting may be performed after performing S203 and / or before performing S205. The aforementioned restriction may involve controlling the first power converter and / or the second power converter, or may include controlling the first power converter and / or the second power converter. The aforementioned restriction may involve restricting the first power converter when it is determined that the fault location is between the first power converter and the location of at least one of the switches that disconnects the electrical branch wire, or restricting the second power converter when it is determined that the fault location is between the second power converter and the location of at least one of the switches that disconnects the electrical branch wire, or may include restricting the first power converter or the second power converter.

[0038] In this specification, the term "disconnector" may be used interchangeably with the term "switch."

[0039] Figures 3a) to 3e) illustrate a power distribution system according to an embodiment of the present disclosure operating based on an exemplary method disclosed herein. In particular, the power distribution system 300 includes an electrical grid 310 electrically coupled to the electrical branch 330, which includes a plurality of switches 331, 332, 333, 334, 335, and 336 for connecting or disconnecting the electrical branch 330 at each location on the electrical branch 330, and a load 350 electrically coupled to a node on the electrical branch 330. For ease of viewing, only a selection of the plurality of switches 331, 332, 333, 334, 335, and 336 are referenced by their reference numbers in Figures 3a) to 3e), and the numbering begins at the top of the electrical branch 330, where one of the two ends of the electrical branch is electrically coupled to the first power converter 311, and increases along the electrical branch 330 to the other of the two ends of the electrical branch. The electrical grid 310 is electrically coupled to one end of the two ends of the electrical branch line 330 via a first power converter 311, and to the other end of the two ends of the electrical branch line 330 via a second power converter 312. The electrical grid 310 may also be electrically coupled to the first power converter 311 and the second power converter 312 via a point of common coupling (PCC). The electrical grid 310 may be a power source, in particular an AC power source, more specifically an AC network. The electrical grid 310 may include a PCC. The first power converter 311 and the second power converter 312 are AC / DC power converters. The load 350 is electrically coupled to a node via an SST 340, the node is located on an electrical branch line between a second switch 331 and a third switch 332, among a plurality of switches 331, 332, 333, 334, 335, and 336. The SST330 is electrically coupled to a node on the electrical branch line 330 via an auxiliary switch 343. A set of two consecutive switches that include a node to which a load is electrically coupled can be called a pair of consecutive switches. For example, the second switch 331 and the third switch 332 are a pair of consecutive switches. The seventh switch 334 and the eighth switch 335 on the electrical branch line 330 disconnect the electrical branch line 330.It will be understood by those skilled in the art that any other switch among the multiple switches 331, 332, 333, 334, 335, and 336 may be selected to disconnect the electrical branch wire. Such a disconnection configuration allows power to flow from the first power converter 311 and the second power converter 312 to the electrical branch wire 330. The first bus 321 electrically couples the first power converter 311 to one of the two ends of the electrical branch wire 330, and the second bus 322 electrically couples the second power converter 312 to the other of the two ends of the electrical branch wire 330. The first bus 321 or the second bus 322 may be any one of an electrical interconnection, an electric bus, an electric busbar, or a PCC. In addition, an external power source 370 (e.g., a battery), distinct from the electric grid 310, is electrically coupled to the IT load 350 via a DC-DC (DC / DC) power converter 360. The DC / DC power converter 360 may be replaced with a switch. It will be understood by those skilled in the art that further loads can be electrically coupled to the electrical branch wire 330. An MVDC system is shown in Figures 3a) to 3e) for illustrative purposes, and it will be further understood by those skilled in the art that the methods disclosed herein are also applicable to any AC and / or DC systems.

[0040] Figure 3a) shows a power distribution system according to one embodiment of the present disclosure under normal operating conditions. The term “normal operating conditions” refers to operating conditions without abnormalities. For example, an abnormality could be a fault on an electrical branch line, such as a short-circuit fault. For example, an abnormality could be a failure in any of the electrical components included in the power distribution system. Under normal operating conditions, power is supplied from the electrical grid 310 to the first and second buses 321 and 322 via the first and second power converters 311 and 312, respectively, and further supplied from the first and second buses 321 and 322 to loads electrically coupled to the electrical branch line 330. Under normal operating conditions, the power flow from the external power source 370 to the IT load 350 is limited by the DC / DC power converter 360. Under normal operating conditions, fault occurrences on the electrical branch line 330 are detected based on the monitored voltage and / or current of the electrical branch line. The method described above may be one embodiment of S201. Such fault occurrence detection may be performed repeatedly. While the method described above is being performed, the seventh switch 334 and the eighth switch 335 disconnect the electrical branch wire 330. When a fault is detected on the electrical branch wire, the power distribution system 300 performs the following method according to one embodiment of the present disclosure, as shown in Figure 3b).

[0041] Figure 3b) shows a power distribution system according to one embodiment of the present disclosure under fault conditions. A fault (indicated by lightning in Figures 3b) to 3e) occurs on an electrical branch line 330 between the third switch 332 and the fourth switch 333, among a plurality of switches 331, 332, 333, 334, 335, and 336, and when the fault is detected, the power flow from the node to the IT load 350 is limited by controlling the SST 340, for example, according to S201. Note that the exact location of the fault on the electrical branch line may be uncertain at this stage, but simply detecting the occurrence of the fault may suffice. Simultaneously with or before limiting the power flow from the node to the IT load 350 (i.e., on the electrical branch line 330 between the second switch 331 and the third switch 332 to which the IT load 350 is electrically coupled), the DC / DC power converter 360 is controlled to allow power flow from the external power supply 370 to the IT load 350, thereby ensuring that the power supply to the IT load 350 is not interrupted during the fault removal process disclosed herein. The method described above may be one embodiment of S202. Once the power flow from the node to the IT load 350 is limited, the current on the electrical branch line 330 can be regulated by controlling the first power converter 311 and the second power converter 312 to inject a predetermined current into the electrical branch line 330. The method described above may be one embodiment of S203. Next, based on the regulated current on the electrical branch line 330, the fault location is determined. The method described above may be one embodiment of S204. While the method described above is being performed, the seventh switch 334 and the eighth switch 335 are still disconnecting the electrical branch wire 330. Once the fault location is determined, the power distribution system 300 performs the following method according to one embodiment of the present disclosure, as shown in Figure 3c).

[0042] Figure 3c) shows a power distribution system according to one embodiment of the present disclosure under fault conditions. When it is determined that the fault location is between the third switch 332 and the fourth switch 333 among the multiple switches 331, 332, 333, 334, 335, and 336, the power flow from the electrical grid 310 to the electrical branch lines 330 is limited by controlling the first power converter 311. In one embodiment, the second power converter 322 is similarly controlled. In particular, when it is determined that the fault is between the eighth switch 335 and the 14th switch 336, the power flow from the electrical grid 310 to the electrical branch lines 330 is limited by controlling the second power converter 312. In one embodiment, both the first power converter 311 and the second power converter 312 are controlled to limit the power flow. While the above method is being performed, the seventh switch 334 and the eighth switch 335 remain disconnected from the electrical branch lines 330. Next, as shown in Figure 3d), a fault point isolation method according to one embodiment of the present disclosure is performed.

[0043] Figure 3d) shows a power distribution system according to one embodiment of the present disclosure under fault conditions. When it is determined that the fault is located between the third switch 332 and the fourth switch 333, and the power flow from the electrical grid 310 to the electrical branch wire 330 is controlled, a portion of the electrical branch wire 330 is disconnected by opening the third switch 332 and the fourth switch 333, i.e., by disconnecting the electrical branch wire at the respective locations of the third switch 332 and the fourth switch 333. In this embodiment, for illustrative purposes, the two switches closest to the fault location (i.e., the third switch 332 and the fourth switch 333) are disconnected to isolate the fault, but it will be understood by those skilled in the art that, as long as the fault is located within a selected combination of at least two switches, it is possible to disconnect any portion of the electrical branch wire by controlling any combination of at least two of the multiple switches 331, 332, 333, 334, 335, and 336 for the same purpose. For example, the third switch 332 and the seventh switch 334 may be controlled to disconnect a portion of the electrical branch wires between them. The method described above may be one embodiment of S205.

[0044] Figure 3e) shows a power distribution system according to one embodiment of the present disclosure under normal operation after a failure. After a portion of the electrical branch line 330 between the third switch 332 and the fourth switch 333 is disconnected, the power flow from the external power source 370 is restricted by the DC / DC power converter 360, and the IT load 350 receives power from the electrical grid 310. That is, restarting under normal operation conditions after a failure involves enabling power flow from the electrical grid 310 to the electrical branch line 330 by controlling the first power converter 311 and the second power converter 312, and enabling power flow from the node to the IT load 350 by controlling the SST 340. In this embodiment, the seventh switch 334 and the eighth switch 335 are closed, i.e., the electrical branch wires 330 are connected at their respective positions, thereby supplying power to the portion of the electrical branch wire 330 between the fourth switch 333 and the seventh switch 334 via the second power converter 312 after the power supply to that portion of the electrical branch wire 330 between the fault location is interrupted by the isolated portion of the electrical branch wire 330 around the fault location. The method shown in Figure 4 can be implemented in combination with the power distribution systems shown in Figures 3a) to 3e).

[0045] Figure 4 is a flowchart of a method according to one embodiment of the present disclosure. In S401, a periodic protective inspection is performed. In S402, an MVDC fault is determined. S402 may be equivalent to S201. In S403, further actions are determined based on the fault occurrence determined in S402. If no fault is detected, the method jumps to another process (S404). In one embodiment, the other process in S404 includes fault detection in S402. If a fault is detected, the SST is shut off, battery energy is enabled (S405), and the grid AC / DC converter output is controlled to output a preset current (S406). Next, in S407, a fault location process is performed and repeatedly checked until a fault location is determined (S408). In one embodiment, after a predefined number of iterations or a predefined period, the loop formed by S407, S408, and the negative result of S408 is interrupted, and the method jumps to another block, e.g., S409. In the same embodiment, after a predefined number of iterations or a predefined period, the fault point may be determined as a predefined point on the electrical branch line. Blocks S405-S408 may correspond to the method shown in the system shown in Figure 3b). Once the fault point is determined, the rectifier current set by S406 is interrupted by controlling the grid AC / DC converter (S409). S409 may correspond to the method shown in the system shown in Figure 3c). The fault point is then isolated by opening an adjacent switch (S410). S410 may correspond to the method shown in the system shown in Figure 3d). In S411, the system enters a restart process. S411 may correspond to the method shown in the system shown in Figure 3e). The terms “restart” or “reoperation” refer to the action of controlling the relevant components included in the system to return it to normal operation, particularly after protective measures such as cutting a portion of the electrical branch line have been applied.

[0046] Figure 5 shows a flowchart for a fault location determination method according to one embodiment of the present disclosure. The method shown in Figure 5 may be one embodiment of the fault location determination in S407. When an MVDC fault is detected, the current on the electrical branch line may be regulated, as shown in Figure 3b), and in particular, a predetermined current may be injected into the electrical branch line by controlling the first power converter and the second power converter. In S502, the regulated current is measured at each of the positions of a plurality of switches on the electrical branch line (S503). Next, in S504, the number of the last disconnector with current along the current direction is found. That is, the position of the last switch through which the regulated current passes is determined, in particular within a predetermined range. For example, referring to Figure 3b), the current flows from the first bus 321 to the seventh switch 334, and the third switch 332 is determined to be the last switch through which the injected current passes. In S505, the number of the first disconnector without current along the current direction is found. That is, the position of the first switch through which the regulated current does not pass is determined. In S506, the fault zone is identified by the two disconnectors identified in S504 and S505. That is, the locations determined in S504 and S505 indicate that the fault is located between them. In S507, the fault zone and the two disconnectors identified in S504 and S505 are output for further processing or signal generation.

[0047] Figure 6 shows a flowchart for a post-fault restart process according to one embodiment of the present disclosure. The method shown in Figure 6 may be one embodiment of the restart process in S411. In S601, fault isolation is performed. S601 may correspond to S410. In S602, switches that are open under normal operating conditions are closed, and in S603, the grid AC / DC converters are un-triggered. Referring to, for example, Figure 3e), the seventh switch 334 and the eighth switch 335 are closed (S603), and the first power converter 311 and the second power converter 312 are controlled to allow power flow from the electrical grid 310 to the electrical branch line 330. In S604, all SSTs in the MVDC bus are un-triggered and restarted. Referring to, for example, Figure 3e), SST 340 is controlled to allow power flow from the electrical branch line 330 to the IT load 350. In S605, the power distribution system is operated again under normal operating conditions.

[0048] Figure 7 shows a power distribution system according to one embodiment of the present disclosure. In particular, the power distribution system comprises the system shown in Figures 3a) to 3e), and further comprises a controller and a plurality of intelligent electronic devices (IEDs). The controller is configured to perform a method according to any one of the embodiments disclosed herein. The controller may be further configured to communicate, in particular bidirectionally, with any one of the components included in the system. In one embodiment, the controller receives or acquires measured values ​​and / or signals and generates control signals and / or communication signals based on the received or acquired measured values ​​and / or signals. Each of the plurality of IEDs may be a voltage and / or current sensor, or may be equipped with a voltage and / or current sensor. Each of the plurality of IEDs may be positioned at each of the switches included in the electrical branch wire to connect and disconnect the electrical branch wire at each of the respective locations. It will be understood by those skilled in the art that the number of plurality of IEDs may differ from the number of switches. The controller may be configured to control the plurality of switches. The plurality of IEDs may be configured to control the plurality of switches. The grid AC / DC converter may be a modular multilevel converter (MMC) having full bridge cells as shown in Figure 7, or it may include an MMC. The MMC may have m full bridge cells in the branch line. In one embodiment, m is given as follows:

[0049]

number

[0050] Here, n is the number of cells in the electric branch line, ceil() is a function that rounds the elements to the nearest integer as it approaches infinity, U ac,max This is the maximum voltage of the AC grid, U c,min This is the minimum voltage of an operating cell, assuming that all cells have the same voltage.

[0051] Figure 8a) shows a controller for a power distribution system according to one embodiment of the present disclosure. Controller 810 may be the controller shown in Figure 7. In one embodiment, controller 810 is further configured to perform a method according to any one of the embodiments disclosed herein. The controller 810 is a controller for protecting a power distribution system 800 which has an electric grid 820 electrically coupled 823 to an electric branch line 830, the electric branch line 830 which has a number of switches 840 for connecting or disconnecting the electric branch line 830 at each location on the electric branch line 830, and a load 850 which is electrically coupled 835 to a node on the electric branch line 830, and the controller is configured to detect a fault on the electric branch line 830 based on the monitored voltage and / or current of the electric branch line, limit the power flow from the node to the load 850 based on the detection of the fault, adjust the voltage and / or current on the electric branch line 830 based on the detection of the fault, determine the location of the fault, and disconnect a portion of the power distribution system 800 based on the determined location of the fault.

[0052] Figure 8b) shows a power distribution system according to one embodiment of the present disclosure. The distribution system 800 is a distribution system comprising an electric grid 820 electrically coupled 823 to electric branch lines 830, the electric branch lines 830 comprising a plurality of switches 840 for connecting or disconnecting the electric branch lines 830 at each location on the electric branch lines 830, loads 850 electrically coupled 835 to nodes on the electric branch lines 830, and the distribution system 800 further comprises a controller according to any one of the embodiments disclosed herein.

[0053] While various embodiments of this disclosure have been described above, it should be understood that they are presented only as examples and not as limitations. Similarly, various figures may illustrate exemplary architectures or configurations provided to enable those skilled in the art to understand the exemplary features and functions of this disclosure. However, those skilled in the art will understand that this disclosure is not limited to the illustrated exemplary architectures or configurations and can be implemented using various alternative architectures and configurations. Furthermore, as will be understood by those skilled in the art, one or more features of one embodiment can be combined with one or more features of other embodiments described herein. Therefore, the breadth and scope of this disclosure should not be limited by any of the exemplary embodiments described above.

[0054] Furthermore, it should be understood that any reference to elements in this specification using designations such as “first,” “second,” etc., does not generally limit the quantity or order of those elements. Rather, these names can be used in this specification as a convenient means of distinguishing two or more elements or examples of elements. Thus, references to first and second elements do not mean that only two elements can be used, or that the first element must in some way precede the second element.

[0055] Furthermore, those skilled in the art will understand that information and signals can be represented using any of the various different techniques and methods. For example, data, instructions, commands, information, signals, bits, and symbols that may be referenced in the above description can be represented by voltage, electric current, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

[0056] Those skilled in the art will further recognize that any of the various exemplary logic blocks, units, processors, means, circuits, methods, and functions described in relation to the embodiments disclosed herein can be implemented by various forms of programs or design code incorporating electronic hardware (e.g., digital implementations, analog implementations, or a combination of both), firmware, instructions (which may be referred to herein as “software” or “software units” for convenience), or any combination thereof.

[0057] To clearly demonstrate this compatibility of hardware, firmware, and software, various exemplary components, blocks, units, circuits, and steps are described above in general terms with respect to their functions. Whether such functions are implemented as hardware, firmware, or software, or a combination of these technologies, depends on the specific application and design constraints imposed on the overall system. A person skilled in the art may implement the described functions in various ways for each specific application, but such implementation decisions do not deviate from the scope of this disclosure. According to various embodiments, processors, devices, components, circuits, structures, machines, units, etc., can be configured to implement one or more of the functions described herein. The terms “configured to” or “configured for” as used herein with respect to a specified operation or function mean a processor, device, component, circuit, structure, machine, unit, etc., that is physically built, programmed and / or positioned to implement the specified operation or function.

[0058] Furthermore, those skilled in the art will understand that the various exemplary methods, logic blocks, units, devices, components, and circuits described herein can be implemented, or carried out, within an integrated circuit (IC) which may include a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic device, or any combination thereof. The logic blocks, units, and circuits may further include antennas and / or transceivers for communicating with various components within a network or device. While a general-purpose processor may be a microprocessor, in alternative examples, the processor may be any conventional processor, controller, or state machine. The processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors working with a DSP core, or any other suitable configuration for carrying out the functions described herein. When implemented in software, the functions may be stored as one or more instructions or codes on a computer-readable medium. Therefore, the steps of the methods or algorithms disclosed herein can be implemented as software stored on a computer-readable medium.

[0059] Computer-readable media include both computer storage media and communication media, which include any media that can enable the transfer of computer programs or code from one place to another. Storage media can be any available media that can be accessed by a computer. Such computer-readable media, but not limited to examples, may include RAM, ROM, EEPROM, CD-ROM or other optical disk storage devices, magnetic disk storage devices or other magnetic storage devices, or any other media that can be used to store desired program code in the form of instructions or data structures and can be accessed by a computer.

[0060] Furthermore, embodiments of this disclosure may utilize memory or other storage devices, as well as communication components. For clarity, it will be understood that the above description has illustrated embodiments of this disclosure with reference to different functional units and processors. However, it will be clear that any appropriate distribution of functionality between different functional units, processing logic elements, or domains may be used without prejudice to this disclosure. For example, a function shown to be performed by a separate processing logic element or controller may be performed by the same processing logic element or controller. Thus, references to specific functional units are not intended to indicate a strict logical or physical structure or organization, but merely to refer to appropriate means for providing the described functionality.

[0061] Various modifications to the embodiments described herein will be readily apparent to those skilled in the art, and the general principles defined herein can be applied to other embodiments without departing from the scope of this disclosure. Therefore, this disclosure is not intended to be limited to the embodiments shown herein, but should be given the broadest scope consistent with the novel features and principles disclosed herein, as set forth in the following claims.

Claims

1. A method for protecting a power distribution system having an electric grid electrically coupled to electric branch lines, wherein the electric branch lines are provided with a plurality of switches for connecting or disconnecting the electric branch lines at each location on the electric branch lines, and the loads are electrically coupled to nodes on the electric branch lines, and the method is Based on the monitored voltage and / or current of the electric branch wire, a fault is detected on the electric branch wire. Based on the detection of a fault, the power flow from the node to the load is limited, Based on the detection of a fault, the voltage and / or current on the electrical branch line are adjusted. Determining the fault location based on the adjusted voltage and / or current on the aforementioned electric branch line, Based on the determined fault location, a portion of the power distribution system will be disconnected. Methods that include...

2. The method according to claim 1, wherein the restriction is to control a galvanic isolator that electrically couples the load to the node, or to control a galvanic isolator.

3. The adjustment described above involves, in particular, injecting a predetermined current into the electric branch wire by controlling a power converter that electrically couples the electric grid to the electric branch wire, or including injecting a predetermined current into the electric branch wire. The method according to claim 1 or 2, wherein the fault location is determined based on the adjusted current.

4. The method according to any one of claims 1 to 3, further comprising, before the aforementioned disconnection, limiting the power flow from the electric grid to the electric branch line by, in particular, controlling a power converter that electrically couples the electric grid to the electric branch line.

5. The method according to any one of claims 1 to 4, wherein the disconnection is to disconnect at least two of the plurality of switches when it is determined that the fault location is on the branch line between at least two switches, or to disconnect at least two of the plurality of switches.

6. The method according to claim 5, wherein at least two of the plurality of switches are adjacent to each other and in particular have the node located between the at least two switches.

7. The aforementioned method, After the aforementioned disconnection, the restricted power flow from the node to the load is released. After the aforementioned disconnection, the power flow from the electrical grid to the load is controlled. The method according to any one of claims 1 to 6, further comprising restarting the power distribution system by means of the method.

8. The method according to any one of claims 1 to 7, wherein the two ends of the electric branch wire are electrically coupled to a power converter, and the electric grid is electrically coupled to the electric branch wire to form a loop.

9. One of the two ends of the electric branch wire is electrically connected to a first power converter which is further electrically connected to the electric grid, and the other end of the electric branch wire is electrically connected to a second power converter which is further electrically connected to the electric grid. The method according to any one of claims 1 to 7, wherein at least one of the plurality of switches disconnects the electrical guy wire.

10. The method according to claim 9, wherein the adjustment further includes enabling power flow from the electric grid to the electric branch line, in particular by controlling the second power converter.

11. The adjustment described above involves, in particular, injecting a predetermined current into the electrical branch wire by controlling the first power converter and the second power converter, or including injecting a predetermined current into the electrical branch wire. The method according to claim 9 or 10, wherein determining the location of a fault is based on adjusting the current on the electrical branch line.

12. The aforementioned method, After the aforementioned disconnection, the restricted power flow from the node to the load is released. After the aforementioned disconnection, the power flow from the electrical grid to the load is enabled, in particular by controlling the first power converter and the second power converter. The method according to any one of claims 9 to 11, further comprising restarting the power distribution system by means of the method.

13. A controller for protecting a power distribution system having an electric grid electrically coupled to electric branch lines, wherein the electric branch lines are provided with a plurality of switches for connecting or disconnecting the electric branch lines at each location on the electric branch lines, and loads are electrically coupled to nodes on the electric branch lines, and the controller, Based on the monitored voltage and / or current of the electric branch line, a fault is detected on the electric branch line. Based on the detection of the occurrence of a fault, the power flow from the node to the load is limited. Based on the detection of a fault, the voltage and / or current on the electrical branch line are adjusted. Based on the adjusted voltage and / or current on the aforementioned electric branch line, the fault location is determined. Based on the determined fault location, a portion of the power distribution system is disconnected. A controller configured in such a way.

14. The controller according to claim 13, further configured to perform the method described in any one of claims 2 to 12.

15. A power distribution system comprising an electric grid electrically coupled to electric branch lines, wherein the electric branch lines are provided with a plurality of switches for connecting or disconnecting the electric branch lines at each location on the electric branch lines, loads are electrically coupled to nodes on the electric branch lines, and the power distribution system further comprises the controller according to claim 13 or 14.

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