Solid state protection for dc networks

Abstract

Fault protection systems, methods, techniques, and apparatus are disclosed. One exemplary embodiment is a protection system including a solid-state switchgear, a current-isolating switchgear, and a controller. The solid-state switchgear is coupled between a switching device of a power converter and a DC link capacitor of the power converter. The current-isolating switchgear is coupled between the DC link capacitor and a DC network. The controller is configured to determine that a fault is occurring within the DC network, and in response to determining that a fault is occurring, to disconnect the solid-state switchgear; while the solid-state switchgear is disconnected, to receive measurements corresponding to the electrical characteristics of a fault current flowing through the current-isolating switchgear; and to determine the location of the fault based on the received measurements.

Description

Background Technology

[0001] This disclosure generally relates to fault protection. A direct current (DC) distribution system includes power converters interconnected via DC distribution lines, and also includes protection systems for detecting and isolating faults, such as short-circuit faults. These protection systems can be placed near each power converter and along the DC distribution lines throughout the DC distribution system. In response to a detected fault on the DC distribution line, the protection system located next to the power converter isolates the power converter from the DC distribution line until the fault is isolated. Existing protection systems for DC distribution systems have several deficiencies and disadvantages. Unmet needs include reducing the hardware requirements of protection systems, reducing fault current interruption stress, and improving fault location accuracy. For example, conventional protection systems must interrupt high-amplitude fault currents to isolate the detected fault. Furthermore, conventional protection systems use only a small set of measurements taken between the onset of the fault and its isolation to determine the fault location. In view of these and other deficiencies in the art, there is a pressing need for the apparatuses, methods, systems, and techniques disclosed herein. Summary of the Invention

[0002] Now, in order to clearly, concisely, and accurately describe the non-limiting exemplary embodiments of this disclosure, their making and use methods, and processes, and to enable the practice, making, and use of them, reference is made to certain exemplary embodiments, including the exemplary embodiments shown in the figures, and these exemplary embodiments are described using specific language. However, it should be understood that the scope of this disclosure is not thereby limited, and this disclosure includes and protects such variations, modifications, and applications of the exemplary embodiments that would be conceived by those skilled in the art benefiting from this disclosure.

[0003] Exemplary embodiments of this disclosure include systems, methods, techniques, and apparatus for fault protection systems. Other embodiments, forms, objects, features, advantages, aspects, and benefits of this disclosure will become apparent from the following description and accompanying drawings. Attached Figure Description

[0004] Figure 1 An exemplary DC power distribution system is illustrated.

[0005] Figure 2 This is a flowchart illustrating an exemplary process for responding to a DC fault.

[0006] Figure 3 The illustration shows an exemplary protection system responding to a DC fault state. Figure 1 A set of diagrams showing the electrical characteristics of a DC power distribution system.

[0007] Figure 4 Another exemplary DC power distribution system is illustrated.

[0008] Figures 5A to 5B An exemplary power converter is illustrated. Detailed Implementation

[0009] refer to Figure 1 The illustration depicts an exemplary direct current (DC) power distribution system 100. It should be understood that system 100 can be implemented in a variety of applications, including public power grids, vehicle power systems, marine power systems, multi-drive power systems, DC charging systems, high-voltage power systems, medium-voltage power systems, and low-voltage power systems, to name just a few.

[0010] DC power distribution system 100 includes a bidirectional power converter 110 configured to convert power transmitted between AC network 101 and DC network 130. Power converter 110 includes a switching device 111 and a DC link capacitor 114.

[0011] Switching device 111 includes a plurality of semiconductor devices 112a-f arranged on three branches coupled across DC bus 113. The first branch includes semiconductor devices 112a and 112b coupled in series at the midpoint connection. The second branch includes semiconductor devices 112c and 112d coupled in series at the midpoint connection. The third branch includes semiconductor devices 112e and 112f coupled in series at the midpoint connection. In the illustrated embodiment, semiconductor devices 112a-f are insulated-gate bipolar transistors (IGBTs) coupled to freewheeling diodes in anti-parallel configuration. In other embodiments, switching device 111 includes bipolar junction transistors (BJTs), metal-oxide-semiconductor field-effect transistors (MOSFETs), gate-turn-off thyristors (GTOs), MOS-controlled thyristors (MCTs), integrated gate-commutated thyristors (IGCTs), silicon carbide (SiC) switching devices, gallium nitride (GaN) switching devices, or any other type of switching device configured to selectively control current flow.

[0012] In the illustrated embodiment, AC network 101 includes three phases, each coupled to a midpoint connection of three branches of switching device 111. In other embodiments, switching device 111 may be adapted to couple to an AC network with a different number of phases, or may be adapted to couple to a second DC network. In some embodiments, AC network 101 is a power generation device, such as a wind turbine or a natural gas generator, to name just a few examples.

[0013] Switching device 111 can be controlled by controller 127 or by a separate controller. Switching device 111 can be configured to transmit power unidirectionally or bidirectionally. For example, switching device 111 can be configured to receive AC power from AC network 101, convert the received power to DC power, and output the DC power to DC network 130. Switching device 111 can also be configured to receive DC power 130 from DC network, convert the received power to AC power, and output the AC power to AC network 101. In other embodiments, switching device 111 can be organized into another topology, such as a multilevel converter, a DC / DC buck converter, a DC / DC boost converter, or a topology with more or fewer phase branches, to name just a few examples. It should be understood that switching device 111 can be any topology and has components configured to receive DC power from DC network 130 or provide DC power to DC network 130.

[0014] DC link capacitor 114 is configured to reduce transients transmitted between switching device 111 and DC network 130, or to smooth DC power. DC link capacitor 114 is also configured to store energy during operation of DC distribution system 100. During operating system 100, a capacitor voltage V exists across DC link capacitor 114. C And the current I C A current flows through DC link capacitor 114. In some embodiments, DC link capacitor 114 is configured as an aluminum electrolytic capacitor, a film capacitor, or a combination thereof, to name just a few. In some embodiments, DC link capacitor 114 is a plurality of capacitors.

[0015] DC network 130 includes DC distribution lines 131 and 133. In the illustrated embodiment, a short-circuit fault 135 is occurring across DC distribution lines 131 and 133 on DC network 130. The portions of DC distribution lines 131 and 133 located between fault 135 and protection system 120 have line inductance 137.

[0016] Importantly, during a DC fault, a fault current flows through current path 103, which includes capacitor 114, current isolation switch 123, and portions of lines 131 and 133 with line inductance 137, such that line current I... L It can be equal to the capacitor current I C With the solid-state switch 121 disconnected to isolate the power converter 110 from the fault 135, after the capacitor 114 is fully discharged, the fault current 135 does not switch from the current path 103 to the second current path 105, which includes the diode of the switch 111.

[0017] Protection system 120 is configured to isolate converter 110 from fault 135 on DC network 130. In some embodiments, protection system 120 or a portion thereof is incorporated into the housing of converter 110. In some embodiments, protection system 120 or a portion thereof may be a retrofit kit configured to be coupled to converter 110.

[0018] Protection system 120 includes a solid-state switch 121, a current-isolating switch 123, a measuring device 125, and a controller 127 including a communication port 129. Solid-state switch 121 is coupled to a DC bus 113 between switch 111 and DC link capacitor 114. Solid-state switch 121 is configured to selectively block current flow between switch 111 and DC link capacitor 114. Solid-state switch 121 can include any type of semiconductor switch. It should be understood that the illustrated solid-state switch is not coupled in parallel with an energy-dispersing device such as a metal-oxide rheostat (MOV). Because protection system 120 is arranged such that solid-state switch 121 disconnects only when no fault current is conducted, and only when low current (such as a current less than the fault current, a current less than twice the nominal current, or no current at all), solid-state switch 121 does not need to be coupled in parallel with an MOV.

[0019] A current-isolating switch 123 is coupled between the DC link capacitor 114 and the DC network 130. The current-isolating switch 123 is configured to selectively prevent current from flowing between the power converter 110 and the DC network 130. The current-isolating switch 123 can be a mechanical switching device or any other type of switching device configured to current-isolate the power converter 110 and the DC network 130. For example, the current-isolating switch 123 may include a mechanical cut-off switch configured to disconnect in a state where no current or load current is conducted. During operating system 100, the line current I... L The current flows through the current isolation switch 123 to reach the DC network 130.

[0020] In some embodiments, the protection system 120 is configured to isolate the power converter 110 from ground faults and short-circuit faults. For ground fault protection, the protection system 120 additionally includes: another solid-state switching device coupled between the negative terminal of the DC bus 113 and the DC capacitor 114 and the switching device 111; and another current-isolating switching device 133 coupled between the DC link capacitor 114 and the DC distribution line 133.

[0021] Measuring device 125 is configured to measure the electrical characteristics of the DC power flowing through current-disconnecting switch 123 and transmit the measurement to controller 127. For example, measuring device 125 can measure current I. L The magnitude is given by way of example only. In some embodiments, the measuring device 125 includes more than one measuring device. In some embodiments, the measuring device 125 is configured to measure the capacitor voltage V. C In some embodiments, the measuring device 125 may include a current sensor, a current transformer, a voltage sensor, or a voltage transformer, to name just a few examples.

[0022] Controller 127 is configured to operate solid-state switching device 121, operate current-isolating switching device 123, and receive measurements from measuring device 125. In the illustrated embodiment, controller 127 includes: a communication port 129 configured to allow controller 127 to communicate with the controller of another protection system; a central control system; or another device configured to monitor or control DC power distribution system 100. In some embodiments, controller 127 includes multiple communication ports or no communication ports.

[0023] During operation of the DC power distribution system 100, the controller 127 is configured to receive measurements from the measuring device 125 and determine whether a fault condition has begun to occur. In response to determining that a fault is occurring, the controller 127 is configured to disconnect the solid-state switching device 121, receive measurements from the measuring device 125, and use the discharge capacitor current I... C The corresponding measurements determine the fault location, and the current isolation switch 123 is disconnected based on the received measurements. The solid-state switch 121 is closed in response to the determination that the fault 135 has been removed, and the current isolation switch 123 is closed in response to the determination that the DC link capacitor 114 has been charged.

[0024] In some embodiments, controller 127 uses measurements or determined fault directions received from other protection systems or a central control system to determine the fault location. In some embodiments, controller 127 transmits information such as measured or determined fault directions based on measurements received from measuring device 125 to the central control system, enabling the central control system to aggregate information from other protection systems and use the aggregated information to determine the fault location. In some embodiments, the central control system then transmits a disconnect command to the protection device closest to the fault to remove the fault from the DC power distribution system.

[0025] In some embodiments, controller 127 is configured to determine that a fault is occurring within power converter 110 or AC network 101, and in response to determining that a fault is occurring, disconnect solid-state switching device 121. Because solid-state switching device 121 prevents current from flowing from capacitor 114 to switching device 111, switching device 111 does not need to include desaturation protection to protect it from capacitor current discharge. It should be understood that any or all of the foregoing features of components of system 100 may also be present in other components disclosed herein.

[0026] refer to Figure 2 There is a flowchart illustrating the use of an exemplary protection system (such as...) Figure 1 The protection system 120 in the example is an exemplary protection system process 200 in response to a DC fault in a DC power distribution system. Process 200 may be implemented in whole or in part in one or more protection system controllers disclosed herein. It should also be understood that several variations and modifications of process 200 are contemplated, including omitting, for example, one or more aspects of process 200, adding other conditions and operations, and / or reorganizing or separating operations and conditions into separate processes.

[0027] Process 200 begins with operation 201, in which the controller of the protection system determines that a fault is occurring within the DC network. In some embodiments, the controller determines that a fault is occurring based on measurements received from the protection system's measuring devices. In other embodiments, the controller determines that a fault is occurring based on information received from another device via a controller communication port.

[0028] Process 200 proceeds to operation 203, where the controller disconnects the solid-state switching device coupled between the switching device of the power converter and the DC link capacitor of the power converter. Because fault current is flowing in the current path formed by the DC link capacitor, the current-isolation switching device, and the DC network, the solid-state switching device disconnects at a low current (also referred to as fault current) state where the amplitude of the conducted current is less than the amplitude of the received fault current. The low current may include a current amplitude less than twice the nominal current amplitude. In other embodiments, the solid-state switching device disconnects without conducting current.

[0029] Process 200 proceeds to operation 205, where the measuring device measures the current flowing through the current-disconnecting switchgear, which is discharging to the fault through the DC link capacitor. In conventional fault location, voltage and / or current are collected to calculate the fault location before the protective device disconnects. Typically, in DC systems, DC circuit breakers disconnect very quickly, such as within 2 ms, to avoid large currents damaging power electronic equipment. Therefore, measurements that can be used for fault location are collected within a short time period. In contrast, when the solid-state switchgear 121 disconnects, the discharge current and induced voltage continue and can be measured to determine the fault location. This allows for the collection of more measurements to improve the accuracy of the determined fault location.

[0030] Process 200 proceeds to operation 207, where the controller determines the location of the fault based on measurements collected during operation 205. The controller may determine the fault location solely based on measurements taken from measuring devices while the DC link capacitor is discharging. The controller may also determine the fault location based on measurements received from other protection systems within the DC power distribution system. In some embodiments, the controller determines the fault location by transmitting measurements or fault direction based on measurements to a central control system. The central control system can then transmit the fault location based on multiple measurements received from other measuring devices within the DC power distribution system.

[0031] In some embodiments, the controller determines the location of the fault by calculating the inductance of the distribution line between the fault and the measuring device using measurements. Using known line inductance characteristics and the calculated inductance, the controller can determine the distance between the fault and the measuring device. In some embodiments, the controller determines the location of the fault using the fault direction and other determined fault directions received from other devices in the DC distribution system 100, which are determined using measurements.

[0032] Process 200 proceeds to operation 209, in which the controller disconnects the current isolating switchgear. The controller may disconnect the current isolating switchgear in response to determining that the fault current amplitude has decreased to zero. It should be understood that when the distribution line has a higher fault current tolerance than the power converter 110, the current isolating switchgear does not need to interrupt the discharge current because the discharge current will dissipate without damaging the distribution line.

[0033] Process 200 proceeds to operation 211, where the controller waits until the located fault has ended or been isolated from a healthy portion of the DC power distribution system and thus removed from the DC power distribution system. In some embodiments, the controller waits for an instruction from the central control system indicating that the fault has been removed, or the controller waits until it determines that the fault has been removed based on measurements from measuring devices in the protection system.

[0034] Process 200 proceeds to operation 213, where the controller closes the solid-state switching device in response to determining that the fault has been removed. The controller closes the solid-state switching device to charge the DC link capacitor using the switching device of the power converter.

[0035] Process 200 proceeds to operation 215, where the controller determines that the DC link capacitor has been charged. For example, the controller can determine that the DC link capacitor has been charged by determining that the voltage across the DC link capacitor has exceeded a charging threshold.

[0036] Process 200 proceeds to operation 217, where the controller, in response to determining that the DC link capacitor has been charged, closes the current isolation switch, thereby allowing the DC power distribution system to return to normal operation.

[0037] refer to Figure 3 Multiple graphs 300 illustrate the electrical characteristics of the DC power distribution system 100 during a fault. It should be understood that the voltages and currents illustrated in the multiple graphs 300 are merely examples of voltage and current values ​​for an exemplary system. Graph 310 illustrates the capacitor voltage V. C Graph 320 illustrates the current I. C Multiple graphs 300 include times t1 to t3.

[0038] Before time t1, the diodes of power converter 110 conduct current I with nominal current amplitude. diodes And capacitor 114 is fully charged. At time t1, fault 135 begins to occur across distribution lines 131 and 133. Between time t1 and time t3, current I... C (or mainly current I) C The current I composed of ) L Increase to peak value before dropping to zero, and capacitor voltage V C The current I decreases to zero as capacitor 114 discharges. When solid-state switching device 121 is disconnected at time t2 between time t1 and t3, the current I... diodes The solid-state switch 121 can conduct low current between times t1 and t2, but not between times t1 and t3. At time t2, between times t1 and t3, the solid-state switch 121 is open, allowing the isolation switch 111 and fault 135 to be separated, without interrupting the fault current flowing through the current path 103. After the solid-state switch 121 is open but before time t3, the measuring device 125 can measure not only the current discharging from the capacitor 114, but also the voltage of the discharge current, such as the capacitor voltage V. C .

[0039] At time t3, the current IC The fault has been reduced to zero, and the current isolating switch 123 is open without conducting current. It should be understood that the protection system 120 is configured to isolate fault 135 without opening switch 121 or 123 when conducting fault current. In some embodiments, the protection system 120 is configured to isolate fault 135 by opening both switch 121 and 123 without conducting fault current.

[0040] refer to Figure 4 The illustration depicts an exemplary DC power distribution system 400, which includes a DC network 440 interconnecting power converters 410, 420, and 430. Power converter 410 includes a switching device 411 and a DC link capacitor 413. Power converter 420 includes a switching device 421 and a DC link capacitor 423. Power converter 430 includes a switching device 431 and a DC link capacitor 433. System 400 also includes protection systems 415, 425, and 435, respectively coupled to power converters 410, 420, and 430. DC network 440 includes a line inductance 441 in each of the distribution wires in DC network 440. DC network 440 also includes a plurality of protective switches 443.

[0041] System 400 also includes a central control system 450 configured to communicate with protection systems 415, 425, and 435 and a plurality of protection switches 443. In response to determining that a fault 401 is occurring in the DC network 440, each of the protection systems 415, 425, and 435 performs an exemplary protection procedure, such as... Figure 2 The process in 200.

[0042] As part of the operation for determining the location of a fault, protection systems 415, 425, and 435 can transmit measurement-based information to the central control system 450. This information includes the measurement itself or the fault direction determined using the measurement. The central control system 450 can use the received information to determine the location of fault 401. For example, the central control system 450 can use the fault direction determined by the protection systems to determine the location of the fault.

[0043] In response to determining the location of fault 401, the central control system 450 transmits a disconnect command to the nearest switching device (in this case, multiple protective switches 443) to the fault 401. The protective device 443 closest to the location of fault 401 performs exemplary protection operations, such as... Figure 2Operation 209 in process 200. In some embodiments, multiple protection switches 443 are disconnected once the fault current amplitude decreases to the nominal current level. Once the multiple protection switches 443 are disconnected, fault 401 is removed, and the remaining healthy portion of system 400, including power converters 410, 420, and 430, can resume normal operation by recharging DC link capacitors 413, 423, and 433 and reconnecting them to DC network 440.

[0044] refer to Figure 5A The circuit diagram illustrates an exemplary switching device 500 configured to convert power transmitted between a three-phase network and a DC network. The switching device 500 includes three branches, including branch 510. Each branch includes a semiconductor device, such as semiconductor device 511 in branch 510. Each semiconductor device is coupled in parallel with an RC snubber circuit (such as RC snubber circuit 513 coupled in parallel with semiconductor device 511). Decoupling capacitors are coupled in parallel with each branch, such as decoupling capacitor 515 coupled in parallel with branch 510. The multiple RC snubber circuits and decoupling capacitors are configured to protect the switching device 500 from overvoltage conditions caused by disconnecting solid-state switching devices coupled to the exemplary protection system of the switching device 500.

[0045] refer to Figure 5B The circuit diagram illustrates an exemplary switching device 520 configured to convert power transmitted between a three-phase network and a DC network. Switching device 520 includes three branches, including branch 530. Each branch includes a semiconductor device such as semiconductor device 531, as in branch 530. Each semiconductor device is coupled in parallel with an RC snubber circuit such as an RC snubber circuit 533 coupled in parallel with semiconductor device 531. Another RC snubber circuit includes: a capacitor 525 and a resistor 523 coupled in series across DC bus 521; and a diode 527 coupled in parallel with resistor 523. The RC snubber circuit is configured to protect switching device 500 from overvoltage conditions caused by disconnecting solid-state switching devices coupled to the exemplary protection system of switching device 500.

[0046] Further written descriptions of several exemplary embodiments will now be provided. One embodiment is a protection system comprising: a solid-state switching device coupled between a switching device of a power converter and a DC link capacitor of the power converter, the switching device being configured to convert power transmitted between a DC network and a second network; a current-isolating switching device coupled between the DC link capacitor and the DC network; and a controller configured to determine that a fault is occurring within the DC network, disconnect the solid-state switching device in response to determining that a fault is occurring, receive, upon disconnection of the solid-state switching device, a measurement corresponding to the electrical characteristics of a fault current flowing through the current-isolating switching device, and determine the location of the fault based on the received measurement.

[0047] In some forms of the aforementioned protection system, the controller is configured to disconnect the solid-state switchgear when a fault current is conducted in a current path including the DC link capacitor but excluding the solid-state switchgear. In some forms, the controller is configured to disconnect the current-isolating switchgear in response to a decrease in the magnitude of the fault current to zero. In some forms, the controller is configured to close the solid-state switchgear in response to determining that a fault has been removed from the DC network, and in response to determining that the switchgear has charged the DC link capacitor. In some forms, the controller is configured to disconnect the solid-state switchgear in response to determining that a fault is occurring, even when the solid-state switchgear is not conducting a fault current. In some forms, the fault current is a discharge current flowing from the DC link capacitor to the fault. In some forms, the controller is configured to disconnect the solid-state switchgear in response to determining that a second fault is occurring within the switchgear. In some forms, determining the fault location includes transmitting information based on received measurements to a central control system, wherein the central control system determines the fault location based on the aggregation of information received from multiple protection systems, including the protection system.

[0048] Another exemplary embodiment is a method for protecting a direct current (DC) power distribution system, comprising: operating a power converter including a switching device and a DC link capacitor; operating a protection system including a solid-state switching device coupled between the switching device of the power converter and the DC link capacitor and a current-isolated switching device coupled between the DC link capacitor and a DC network, the switching device being configured to convert power transmitted between the DC network and a second network; determining that a fault is occurring; in response to determining that a fault is occurring, disconnecting the solid-state switching device; while the solid-state switching device is disconnected, receiving a measurement corresponding to the electrical characteristics of a fault current flowing through the current-isolated switching device; and determining the location of the fault based on the received measurement.

[0049] In some forms of the aforementioned method, the method includes: disconnecting a current-isolating switchgear in response to a decrease in the magnitude of the fault current to zero. In some forms, the method includes: closing a solid-state switchgear in response to determining that a fault has been removed from the DC network; charging a DC link capacitor using a switching device; and closing the current-isolating switchgear in response to determining that the DC link capacitor is charged. In some forms, disconnecting the solid-state switchgear occurs when the solid-state switchgear is not conducting fault current. In some forms, the fault current is a discharge current flowing from the DC link capacitor to the fault. In some forms, the method includes: disconnecting the solid-state switchgear in response to determining that a second fault is occurring within the switching device. In some forms, determining the fault location includes: transmitting information based on received measurements to a central control system; and determining the fault location based on the aggregation of information received from multiple protection systems, including protection systems. In some forms, disconnecting the solid-state switchgear occurs when the fault current is conducted in a current path that includes the DC link capacitor but not the solid-state switchgear.

[0050] Another exemplary embodiment is a direct current (DC) power distribution system including a power converter comprising a switching device and a DC link capacitor, the switching device being configured to convert power transmitted between a DC network and a second network; and a protection system comprising a solid-state switching device coupled between the switching device and the DC link capacitor, a current-isolating switching device coupled between the DC link capacitor and the DC network, and a controller configured to determine that a fault is occurring within the DC network, disconnect the solid-state switching device in response to determining that a fault is occurring, receive measurements corresponding to the electrical characteristics of a fault current flowing through the current-isolating switching device while the solid-state switching device is disconnected, and determine the location of the fault based on the received measurements.

[0051] In some forms of the aforementioned DC power distribution system, the system includes a central control system configured to receive information based on measurements received from a protection system, determine the fault location based on the aggregation of information received from multiple protection systems including the protection system, and transmit a disconnect command to multiple switching devices of the DC power distribution system closest to the fault location. In some forms, the controller is configured to disconnect solid-state switching devices, where the fault current includes a current path that includes a DC link capacitor but not the solid-state switching device, and wherein the controller is configured to disconnect a current-isolating switching device in response to a decrease in the magnitude of the fault current to zero. In some forms, the controller is configured to disconnect the solid-state switching device in response to a determination that a fault is occurring, even when the solid-state switching device is not conducting the fault current, and wherein the fault current is a discharge current flowing from the DC link capacitor to the fault.

[0052] It should be contemplated that, unless expressly stated otherwise, aspects, features, processes, and operations from the various embodiments may be used in any of the other embodiments. Some of the illustrated operations may be implemented by a computer including a processing device that executes a computer program product on a non-transitory computer-readable storage medium, wherein the computer program product includes instructions that cause the processing device to perform one or more operations or to issue commands to other devices to perform one or more operations.

[0053] Although this disclosure has been detailed and described in the accompanying drawings and foregoing description, it should be considered illustrative rather than restrictive in nature. It should be understood that only certain exemplary embodiments have been shown and described, and it is intended to protect all changes and modifications falling within the spirit of this disclosure. It should be understood that while the use of words such as “preferred,” “preferred,” “ideal,” or “more preferred” used in the foregoing description to indicate that the features described so far may be preferred, it may not be necessary, and embodiments lacking the same content may be contemplated as being within the scope of this disclosure, defined by the appended claims. When reading the claims, it is intended that, unless specifically stated otherwise in the claims, the use of words such as “a,” “an,” “at least one,” or “at least one part” is not intended to limit the claims to only one. The term “of” may imply association or connection with another item, and belonging to or being associated with another item, as the context of its use suggests. Unless expressly indicated otherwise, the terms “coupled to,” “coupled with,” etc., include indirect connection and coupling, and also include, but do not require, direct coupling or connection. Unless otherwise expressly stated to the contrary, when the language “at least one part” and / or “part” is used, the item may include a part and / or the entire item.

Claims

1. A protection system, comprising: A solid-state switching device is coupled between a switching device of a power converter and a DC link capacitor of the power converter, the switching device being configured to convert power transmitted between a DC network and a second network. A current-isolation switching device is coupled between the DC link capacitor and the DC network; as well as The controller is configured to determine that a fault is occurring within the DC network; In response to determining that the fault is occurring, the solid-state switching device is disconnected; With the solid-state switchgear disconnected, measurements corresponding to the electrical characteristics of the fault current flowing through the current isolation switchgear are received; and the location of the fault is determined based on the received measurements.

2. The protection system of claim 1, wherein the controller is configured to disconnect the solid-state switching device when the fault current is conducted in a current path including the DC link capacitor but excluding the solid-state switching device.

3. The protection system of claim 2, wherein the controller is configured to disconnect the current isolation switching device in response to the amplitude of the fault current decreasing to zero.

4. The protection system of claim 3, wherein the controller is configured to: close the solid-state switching device in response to determining that the fault has been removed from the DC network; and close the current isolation switching device in response to determining that the switching device has charged the DC link capacitor.

5. The protection system of claim 1, wherein the controller is configured to disconnect the solid-state switch in response to determining that a fault is occurring when the solid-state switch is not conducting the fault current.

6. The protection system according to claim 1, wherein the fault current is a discharge current flowing from the DC link capacitor to the fault.

7. The protection system of claim 1, wherein the controller is configured to disconnect the solid-state switching device in response to determining that a second fault has occurred within the switching device.

8. The protection system according to claim 1, wherein determining the fault location comprises: The received measurement information is transmitted to a central control system, wherein the central control system determines the fault location based on the aggregation of information received from multiple protection systems, including the protection system.

9. A method for protecting a direct current (DC) power distribution system, comprising: Operating a power converter, the power converter including a switching device and a DC link capacitor; An operation protection system includes a solid-state switching device and a current-isolation switching device. The solid-state switching device is coupled between the switching device of the power converter and the DC link capacitor, and the current-isolation switching device is coupled between the DC link capacitor and the DC network. The switching device is configured to convert the power transmitted between the DC network and a second network. A fault has been identified; In response to determining that the fault is occurring, the solid-state switching device is disconnected; With the solid-state switchgear disconnected, measurements corresponding to the electrical characteristics of the fault current flowing through the current isolation switchgear are received. as well as The location of the fault is determined based on the received measurements.

10. The method of claim 9, comprising: In response to the amplitude of the fault current decreasing to zero, the current isolation switching device is disconnected.

11. The method of claim 10, comprising: In response to determining that the fault has been removed from the DC network, the solid-state switching device is closed; The switching device is used to charge the DC link capacitor; as well as In response to determining that the DC link capacitor is charged, the current isolation switch is closed.

12. The method of claim 9, wherein disconnection of the solid-state switch occurs when the solid-state switch is not conducting the fault current.

13. The method of claim 9, wherein the fault current is a discharge current flowing from the DC link capacitor to the fault.

14. The method of claim 9, comprising: In response to determining that a second fault is occurring within the switching device, the solid-state switching device is disconnected.

15. The method of claim 9, wherein determining the fault location comprises: The received measurement information is transmitted to the central control system. The location of the fault is determined based on the aggregation of information received from multiple protection systems, including the protection system.

16. The method of claim 9, wherein the disconnection of the solid-state switch occurs when the fault current is conducted in a current path including the DC link capacitor but not the solid-state switch.

17. A direct current (DC) power distribution system, comprising: A power converter, including a switching device and a DC link capacitor, wherein the switching device is configured to convert power transmitted between a DC network and a second network; as well as Protection system, including: A solid-state switching device is coupled between the switching device and the DC link capacitor; A current-isolating switching device is coupled between the DC link capacitor and the DC network; and The controller is configured to: determine that a fault is occurring within the DC network; in response to determining that the fault is occurring, disconnect the solid-state switching device; while the solid-state switching device is disconnected, receive a measurement corresponding to the electrical characteristics of a fault current flowing through the current isolation switching device; and determine the location of the fault based on the received measurement.

18. The DC power distribution system according to claim 17, comprising: The central control system is configured to receive information based on measurements received from the protection system, determine the location of the fault based on the aggregation of information received from multiple protection systems including the protection system, and transmit disconnect commands to multiple switching devices of the DC power distribution system closest to the fault location.

19. The DC power distribution system of claim 17, wherein the controller is configured to: disconnect the solid-state switching device when the fault current includes a current path, the current path including the DC link capacitor but not the solid-state switching device, and wherein the controller is configured to disconnect the current isolation switching device in response to the magnitude of the fault current decreasing to zero.

20. The DC power distribution system of claim 17, wherein the controller is configured to: disconnect the solid-state switch in response to determining that a fault is occurring, while the solid-state switch is not conducting the fault current, and wherein the fault current is a discharge current flowing from the DC link capacitor to the fault.

Images