Power system with current sensor for fault detection

Abstract

The embodiment of the invention relates to a power system with a current sensor for fault detection. The power system includes: a DC bus; a plurality of power modules each including a capacitor, each power module being connected to the DC bus in parallel with the other power modules; a plurality of arc suppression devices configured to short the DC bus in the event of a DC bus fault; a plurality of current sensors, each arranged to measure a current between the DC bus and a DC side of a respective power module; and a control system that associates each current sensor with an arc suppression device of the plurality of arc suppression devices, where the control system is configured to, only when at least two current sensors of the current sensors simultaneously measure a current above a threshold current, determine the arc suppression device of the plurality of arc suppression devices, one or more arc suppression devices associated with the at least two current sensors are triggered to short the DC bus.

Description

Technical Field

[0001] This disclosure generally relates to power systems, such as electric drive systems. Background Technology

[0002] An electric drive is a system that includes a power converter (typically an inverter) and a control system for controlling the inverter. Electric drive systems can be used, for example, to control multiple electric motors in industrial settings such as pulp and paper manufacturing or metal manufacturing, in ships, for integrating battery or fuel cell energy storage systems, and for active front-end converters for bidirectional energy flow into and out of the AC grid.

[0003] More specifically, a drive system may include a DC bus with multiple power converters connected in parallel to it. In the event of an internal arcing fault on the DC bus, the capacitor banks of the power converters / power modules discharge rapidly into the arc due to their parallel connection. Since there are typically many power converters in a drive system, such as around 50, capacitor discharge causes significant damage to the installation. Today, the cabinets housing the power converters are constructed to withstand the increased stress caused by the internal arcing. Therefore, the cabinets are excessively large to withstand explosions and prevent them from opening. In the event of an internal arcing fault, it can take months in some cases to repair or replace the damaged equipment.

[0004] To limit damage to the drive system caused by arcing faults on the DC bus, the drive system may include a controllable arc suppression device for locally short-circuiting the DC bus near the arc. Summary of the Invention

[0005] One way to detect faults in a drive system is to trigger one or more arc suppression devices to partially short-circuit the DC bus by photodetecting the generated arc. However, photodetection has proven too effective and offers virtually no selectivity in fault detection. For example, when an internal fault occurs in a power module due to the high current involved, an arc is likely to be generated. The light from the arc reflects off the inner wall of the cabinet where the power modules are housed. The light is likely to be detected by a photodetector, triggering the arc suppression device. Because power module faults are more frequent than DC bus faults, and because the probability of detecting any fault with generated light using a photodetector is very high, the drive system will suffer more downtime than expected. Furthermore, faults on power modules can be handled by DC fuses, allowing the entire system to resume operation.

[0006] In view of the above, the inventors have discovered that fault detection should more selectively trigger the arc suppression device only when a fault occurs on the DC bus, rather than when a fault occurs at the power module level. This will maximize the operating time of the drive system.

[0007] Therefore, the purpose of this disclosure is to provide a power system that solves or at least mitigates the problems of the prior art.

[0008] Therefore, a power system is provided according to a first aspect of the present disclosure, the power system comprising: a DC bus; a plurality of power modules, each including a capacitor or a battery, each power module being connected in parallel with the other power modules to the DC bus; a plurality of arc suppression devices configured to short-circuit the DC bus in the event of a DC bus fault; a plurality of current sensors, each arranged to measure the current between the DC bus and the DC side of a corresponding power module; and a control system that associates each current sensor with an arc suppression device among the plurality of arc suppression devices, wherein the control system is configured to trigger one or more arc suppression devices associated with the at least two current sensors to short-circuit the DC bus only when at least two of the current sensors simultaneously measure a current above a threshold current.

[0009] Fault detection is faster than previous methods that relied on light detection from an electric arc, is selective because the location of the fault is known from the current sensor, and is safer for false triggering events because it requires at least two current sensors to simultaneously measure currents above a threshold current.

[0010] Faults on the DC bus can be arc faults.

[0011] The power system can be, for example, a low-voltage or medium-voltage power system.

[0012] Triggering an arc suppression device may involve setting the arc suppression device to a conducting state.

[0013] According to one embodiment, at least two of the at least two current sensors are arranged to measure the current between the DC bus and a corresponding power module of two adjacently positioned power modules. The two adjacently positioned power modules are thus located adjacent to each other along the DC bus. This further reduces the risk of false triggering events because if both adjacent current sensors simultaneously measure currents above a threshold current, it can be determined with greater probability that the measured high current is due to a fault on the DC bus rather than, for example, a fault in one of the power modules.

[0014] According to one embodiment, the control system is configured to trigger one or more arc suppression devices only when the measured current flows from the power module to the DC bus. This indicates that the current flows from the power module, i.e., from the capacitor bank, rather than from the DC bus to the power module, which further provides an indication that the fault is on the DC bus rather than in the power module.

[0015] According to one embodiment, a current sensor is arranged to measure the current flowing between the positive busbar of the DC bus and the corresponding power module. Since the current flows from the positive busbar to the negative busbar, this provides an indication that the fault is on the DC busbar and not in the power module.

[0016] Alternatively, a current sensor can be arranged to measure the current flowing between the negative busbar and the corresponding power module.

[0017] As an example, at least some of the power modules are power converters.

[0018] According to one embodiment, at least some of the power modules are power converters.

[0019] According to one example, each power module is one of an inverter, a DC / DC converter, a line-side active and / or passive rectifier, a DC / DC chopper, and / or a braking chopper.

[0020] According to one embodiment, the control system is configured to compare the current measured by the current sensor with a threshold current.

[0021] According to one embodiment, the control system includes a plurality of controllers, each controller being configured to control a power module or a group of power modules, and each controller being associated with one or more current sensors and configured to trigger one or more associated arc suppression devices.

[0022] According to one embodiment, the power system is a multi-drive system. The DC bus is a common DC bus used for all power modules.

[0023] According to a second aspect, a method is provided for triggering arc suppression devices in a power system, the power system comprising: a DC bus; a plurality of power modules, each including a capacitor, each power module being connected in parallel to the DC bus with other power modules; a plurality of arc suppression devices configured to short-circuit the DC bus in the event of a DC bus fault; a plurality of current sensors, each arranged to measure the current between the DC bus and the DC side of a corresponding power module; and a control system that associates each current sensor with an arc suppression device among the plurality of arc suppression devices, the method comprising: a) triggering one or more arc suppression devices associated with at least two current sensors to short-circuit the DC bus by means of the control system only when at least two of the current sensors simultaneously measure a current above a threshold current.

[0024] One embodiment includes comparing the current measured by the current sensor with a threshold current before step a).

[0025] According to one embodiment, at least two of the at least two current sensors are arranged to measure the current between the DC bus and a corresponding power module of two adjacently positioned power modules.

[0026] According to one embodiment, triggering is performed only when the current flow direction of the measured current is from the power module to the DC bus.

[0027] According to one embodiment, a current sensor measures the current flowing between the positive busbar of the DC bus and the corresponding power module.

[0028] According to one embodiment, at least some of the power modules are inverters.

[0029] Generally, all terms used in the claims will be interpreted according to their ordinary meaning in the technical field, unless otherwise expressly defined herein. Unless otherwise expressly stated, all references to “a / an / element, device, component, apparatus”, etc., shall be openly interpreted as referring to at least one instance of an element, device, component, apparatus, etc. Attached Figure Description

[0030] Specific embodiments will now be described by way of example with reference to the accompanying drawings, in which:

[0031] Figure 1 An example of a power system is illustrated schematically;

[0032] Figure 2 A power module connected to a DC bus is schematically shown; and

[0033] Figure 3 The illustration schematically depicts the situation under DC bus failure. Figure 1 The power system in the middle. Detailed Implementation

[0034] The concept of the invention will now be described more fully below with reference to the accompanying drawings, in which exemplary embodiments are shown. However, the concept of the invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided by way of example, so that this disclosure will be thorough and complete, and will fully convey the scope of the inventive concept to those skilled in the art. Throughout the specification, the same reference numerals denote the same elements.

[0035] Figure 1 This is a circuit diagram of an example of power system 1. Power system 1 can be, for example, a drive system such as a multi-drive system.

[0036] The power system 1 includes a DC bus 3.

[0037] According to this example, DC bus 3 includes a first busbar 3a and a second busbar 3b.

[0038] DC bus 3 can be a low-voltage or medium-voltage DC bus.

[0039] DC bus 3 is connected to rectifier 4. Rectifier 4 can be connected to an AC power network, such as a three-phase power network.

[0040] The power system 1 includes multiple power modules 5. Each power module 5 includes a capacitor or capacitor bank, and / or a battery.

[0041] Power module 5 can be, for example, a power converter such as an inverter.

[0042] Power modules 5 are connected to DC bus 3. Each power module 5 is connected to a first busbar 3a and a second busbar 3b. Each power module 5 may have a DC side and an AC side. The DC side is connected to DC bus 3. The AC side is configured to be connected to an AC load (such as an electric motor), or a power transformer, a power source (such as AC grid power), or an AC generator. According to one example, power module 5 may have two DC sides, one DC side connected to the DC bus, and the other DC side connected to a brake chopper or a DC / DC converter connected to an energy storage device (such as a battery or fuel cell).

[0043] The power modules 5 are connected in parallel to each other to the DC bus 3.

[0044] The power system 1 includes multiple cabinets 9. Each cabinet 9 includes one or more power modules 5 arranged inside the cabinet 9.

[0045] When power system 1 is already installed, cabinets 9 are typically arranged in a chain, one after another. The physical length of DC bus 3 usually depends on the number of cabinets 9.

[0046] According to this example, each rack 9 includes three power modules 5, but each rack can have a different number of power modules 5. For example, each rack can have one, two, or four power modules 5. All racks 9 can have the same number of power modules 5, or the number of power modules 5 can differ in some or all of the racks 9.

[0047] The power system 1 includes a control system. The control system can be configured to control all power modules 5. In some examples, the control system includes multiple controllers, each configured to control a specific power module 5 or a group of power modules 5. For example, each or some of the controllers can be configured to control all power modules 5 arranged in the cabinet 9.

[0048] The power system 1 includes multiple arc suppression devices 11. The arc suppression devices 11 are connected to the DC bus 3. The arc suppression devices 11 can be connected across a first busbar 3a and a second busbar 3b. Each arc suppression device 11 is configured to short-circuit the DC bus 3 by short-circuiting the first busbar 3a and the second busbar 3b. The arc suppression devices 11 are configured to short-circuit the DC bus 3 in response to a fault on the DC bus 3, as will be described in more detail herein.

[0049] The arc suppression device 11 has a lower voltage drop on the first busbar 3a and the second busbar 3b than the arc voltage on the DC busbar 3.

[0050] Each arc suppression device 11 may include one or more switching devices. The switching device may have a first pin connected to a first busbar 3a and a second pin connected to a second busbar 3b. In the case of multiple switching devices, the switching devices may be connected in parallel across the first busbar 3a and the second busbar 3b. The switching device may be, for example, a semiconductor device.

[0051] When the switching device is a semiconductor device, the first busbar 3a and the second busbar 3b are short-circuited by switching (multiple) semiconductor devices to the on state, connected via one or more semiconductor devices.

[0052] Each semiconductor device can be, for example, a thyristor or transistor, such as an insulated gate bipolar transistor (IGBT) or an insulated gate commutated transistor (IGCT).

[0053] Each arc suppression device 11 is assigned to K power modules 5, where K can be an integer equal to or greater than 1. k can be, for example, 2, 3, 4, 5, 6, 7, 8, or 9. According to... Figure 1 In the example shown, each arc suppression device 11 is assigned to three power modules 5. Therefore, in this example, K = 3.

[0054] Arc suppression device 11 can be arranged, for example, between adjacent power modules 5 or between adjacent cabinets 9.

[0055] The power system 1 includes multiple current sensors 13. The power system 1 may include, for example, the same number of current sensors 13 as the power modules 5. For instance, if the power system 1 includes N power modules 5, then the power system 1 may include N current sensors 13. Each current sensor 13 is configured to measure the current between the DC bus 3 and the corresponding power module 5.

[0056] Each current sensor 13 can be arranged to measure the current flowing between the positive busbar of the DC bus 3 (the first busbar 3a in this example) and the corresponding power module 5. The current sensor 13 can therefore measure the current flowing from the corresponding power module 5 to the positive busbar.

[0057] The current sensor 13 is configured to transmit current measurements to the control system.

[0058] The control system associates each current sensor 13 with one of a plurality of arc suppression devices 11. According to one example, multiple current sensors 13 may be associated with the same arc suppression device 11, and / or one or more current sensors 13 may be associated with more than one arc suppression device 11. In one example, each controller may associate one or more current sensors 13 with one or more arc suppression devices 11 of the power system 1, the current sensors 13 being configured to measure the current between the power module(s) 5 and the DC bus 3, and the controllers being configured to control the power module(s) 5.

[0059] Figure 2 A portion of the power system 1 is schematically shown, with a single power module 5a shown in cabinet 9.

[0060] The controller 15 can control a single power module 5a or more than one power module 5, such as all the power modules 5 arranged in the cabinet 9.

[0061] The current sensor 13a is configured to measure the current from the power module 5a to the positive busbar (i.e., the first busbar 3a of the DC busbar 3).

[0062] The controller 15 is configured to receive current measurements from the current sensor 13a, which is configured to measure the current from the power module 5a to the first DC bus 3a.

[0063] The controller 15 is configured to control the arc suppression device 11a associated with the power module 5a based on the measured current from the current sensor 13a. The controller 15 is configured to trigger the arc suppression device 11a, or one or more arc suppression devices 11 associated with these current sensors 13a, 13, to short-circuit the DC bus 3 only when at least two of the current sensors 13 (including current sensor 13a) simultaneously measure a current above a threshold current.

[0064] Preferably, if at least two current sensors 13 of two adjacently positioned power modules 5 simultaneously measure a current higher than a threshold current, the triggering of the arc suppression device 11 is performed solely by the controller 15. The controllers 15 can be configured to communicate with each other such that, in the event that current sensors 13 of adjacently positioned power modules 5 controlled by different controllers 15 measure a current higher than the threshold current, at least all relevant controllers 15 receive information that a current higher than the threshold current has been measured. In another example, the controllers 15 are independent; that is, the controllers 15 are not configured to communicate with each other.

[0065] It should be noted that if the current sensors 13 of more than two adjacent power modules 5 measure a current higher than the threshold current, for example, if the current sensors 13 of any of the three, four, five, ..., M power modules 5 arranged one after another (where M is the number of power modules 5 in the power system 1) measure a current higher than the threshold current, then the trigger will also occur.

[0066] The controller 15 is configured to trigger one or more arc suppression devices 11a only when the current flow direction of the measured current is from the power module 5a to the DC bus 3, except that the measured current is higher than the threshold current.

[0067] Power system 1 may include a fuse 12 disposed on the DC side of power module 5 and connected to DC bus 3. In the event of an internal fault in power module 5, fuse 12 is triggered. Due to the selectivity of fuse 12, power system 1 continues to operate.

[0068] Figure 3 An operational example of power system 1 is shown in the event of an arc fault occurring on DC bus 3. According to this example, an arc fault occurs in the region of DC bus 3 where power modules 5b and 5c are connected, resulting in an arc 17 on DC bus 3.

[0069] Current sensors 13b-13c, configured to measure the current in the regions of power modules 5b and 5c, will measure the current flowing to DC bus 3 that is above a threshold current. One or more controllers 15, arranged to control power modules 5b and 5c, will compare the measured current with the threshold current. As a result, controller 15 will trigger arc suppression device 11b to short-circuit DC bus 3 near arc 17. The current will thus be diverted from arc 17.

[0070] The concept of the invention has been described above with reference to several examples. However, it will be readily understood by those skilled in the art that other embodiments besides those disclosed above are also possible within the scope of the concept of the invention as defined by the appended claims.

Claims

1. A power system (1), comprising: DC bus (3), Multiple power modules (5), each including a capacitor or a battery, are connected in parallel to the DC bus (3) with the other power modules (5). Multiple arc suppression devices (11) are configured to short-circuit the DC bus (3) in the event of a fault on the DC bus (3). Multiple current sensors (13) are each arranged to measure the current between the DC bus (3) and the DC side of the corresponding power module (5), and The control system associates each current sensor (13) with one of the plurality of arc suppression devices (11). The control system is configured to trigger one or more arc suppression devices (11) associated with the at least two current sensors (13) to short-circuit the DC bus (3) only when at least two of the current sensors (13) simultaneously measure a current higher than a threshold current.

2. The power system (1) according to claim 1, wherein at least two of the at least two current sensors (13) are arranged to measure the current between the DC bus (3) and a corresponding power module among two adjacently positioned power modules (5).

3. The power system (1) according to claim 1 or 2, wherein the control system is configured to trigger the one or more arc suppression devices (11) only when the current flow direction of the measured current is from the power module (5) into the DC bus (3).

4. The power system (1) according to claim 3, wherein the current sensor (13) is arranged to measure the current flowing between the positive busbar of the DC bus (3) and the corresponding power module (5).

5. The power system (1) according to any one of the preceding claims, wherein at least some of the power modules (5) are power converters.

6. The power system (1) according to any one of the preceding claims, wherein the control system is configured to compare the current measured by the current sensor (13) with the threshold current.

7. The power system (1) according to any one of the preceding claims, wherein the control system comprises: Multiple controllers (15) are configured to control power modules (5) or a group of power modules (5), and each controller (15) is associated with one or more current sensors (13) and configured to trigger one or more associated arc suppression devices (11).

8. The power system (1) according to any one of the preceding claims, wherein the power system (1) is a multi-drive system.

9. A method for triggering an arc suppression device (11) in a power system (1), the power system (1) comprising: DC bus (3); multiple power modules (5), each including a capacitor, each power module (5) being connected in parallel to the DC bus (3) with other power modules (5); multiple arc suppression devices (11) configured to short-circuit the DC bus (3) in the event of a fault on the DC bus (3); multiple current sensors (13), each arranged to measure the current between the DC bus (3) and the DC side of the corresponding power module (5); And a control system that associates each current sensor (13) with an arc suppression device (11) among the plurality of arc suppression devices (11), the method comprising: a) The control system triggers one or more arc suppression devices (11) associated with the at least two current sensors (13) to short-circuit the DC bus only when at least two of the current sensors (13) simultaneously measure a current higher than the threshold current.

10. The method of claim 9, further comprising comparing the current measured by the current sensor (13) with the threshold current prior to step a).

11. The method according to claim 9 or 10, wherein at least two of the at least two current sensors (13) are arranged to measure the current between the DC bus and a corresponding power module among two adjacently positioned power modules (5).

12. The method according to any one of claims 9 to 11, wherein the triggering is additionally performed only when the current flow direction of the measured current is from the power module (5) to the DC bus (3).

13. The method according to claim 12, wherein the current sensor (13) measures the current flowing between the positive busbar of the DC bus (3) and the corresponding power module (5).

14. The method according to any one of claims 9 to 13, wherein at least some of the power modules in the power module (5) are power converters.

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