SUPPLY DEVICE FOR AN ELECTRICAL MODULE WITH FUSE ELEMENT

Description

[0001] The invention relates to a switching module (2) for a modular multi-level converter, comprising power semiconductor switches (5) and an energy storage device (7).

[0002] Electrical or electronic assemblies that operate at a high-voltage potential, i.e., a potential above 1 kV relative to ground potential, are known, for example, from converter arrangements. A converter arrangement typically includes communication modules assigned to a converter and control modules for controlling the converter's power semiconductor switches. These and other assemblies require a supply voltage, which must be provided during operation of the assembly or converter.

[0003] WO 2009 / 003834 A1 discloses a power supply device that provides a power supply unit arranged at ground potential. The power supply unit of WO 2009 / 003834 A1 is connected to the module to be powered via potential-isolating means in the form of optical fibers. The power is transmitted from the power supply unit to the module via the optical fibers. Such a transmission of power supply from ground potential to high-voltage potential is relatively complex and cost-intensive.

[0004] A modular multi-level converter with a supply device comprising a series circuit of a series resistor and a supply unit is known from WO 2016 / 108597 A1. The object of the invention is to propose a switching module as mentioned above that is as cost-effective and reliable as possible.

[0005] Power supply devices for a modular multilevel converter have been disclosed in the following documents: EP2549634A1 and WO2016208894A1.

[0006] The invention solves the problem by means of a switching module having the features of claim 1. Accordingly, the supply device of the switching module comprises a series circuit comprising at least one series resistor and a supply unit, wherein the series circuit can be connected to an energy store and the supply unit can be connected to the assembly to be supplied, as well as a fuse element by means of which a short-circuit current through the supply unit can be electrically interrupted in the event of a short circuit.

[0007] According to the invention, the supply device is therefore arranged at a high-voltage potential during operation, just like the component to be supplied. Potential isolation between the supply device and the component is advantageously eliminated. The energy for supplying the component can be taken from the energy storage device at high-voltage potential by means of the supply device and made available to the component. In this way, electrical components that cannot be supplied from ground potential can also be advantageously supplied with energy.

[0008] The fuse element fulfills a safety function in the event of a fault in or on the supply unit. In the event of a short circuit in the supply unit, a short-circuit current can flow through the supply unit. This short-circuit current can lead to thermal overload of the series resistor. In such a case, the fuse element interrupts this short-circuit current and advantageously prevents the overload. In this way, insulation failure of the series resistor and thus destruction of the entire supply unit and adjacent components can be prevented. The fuse element is suitably arranged in series with the series resistor and the supply unit. The short-circuit current can be interrupted, for example, by interrupting the series connection. The short-circuit current is interrupted if a current path carrying the short-circuit current is interrupted.

[0009] The energy storage device is suitably a capacitor or a battery, or a series connection of capacitors and / or batteries. The energy storage device is connected or connectable to the series connection via its terminals. For connection to the energy storage device, the series connection comprises connecting terminals between which the series connection extends.

[0010] Preferably, the fuse element interrupts the series circuit as soon as a current through the series circuit exceeds a predetermined maximum current value or threshold. This ensures that in the event of a short circuit, for example, a short circuit at the terminals of the supply unit, the series circuit is quickly interrupted.

[0011] The safety element is purely passive. A purely passive safety element requires no additional power supply or control and is therefore particularly cost-effective and simple to construct.

[0012] For example, the fuse element can comprise a fuse wire that can be severed in the event of a short circuit. The fuse wire is expediently designed and dimensioned such that it is severed or otherwise rendered inoperative when a current exceeds a predetermined current value. In this way, the series circuit is safely interrupted electrically. The fuse wire is suitably arranged in the series circuit, for example, between the series resistor and the supply unit. The fuse wire is further designed such that it will not be severed under nominal conditions (in particular, at a nominal current through the series circuit).

[0013] Preferably, the fuse element is a sacrificial element. The sacrificial element interrupts the series circuit, permanently losing its functionality so that it cannot be restored. This simultaneously allows for a particularly reliable separation or interruption of the electrical series circuit.

[0014] It is considered particularly advantageous if the fuse element is designed in such a way that it at least partially evaporates in the event of a short circuit. This way, after the series connection is interrupted, no parts remain in the supply system that would require disposal.

[0015] A particularly compact form of the fuse element can be achieved if the fuse element is integrated into the series resistor, for example in a housing of the series resistor.

[0016] In addition, the at least one series resistor can be implemented as a flat resistor. Additional series resistors can be arranged in series with the series resistor.

[0017] According to one embodiment of the invention, the supply unit comprises a controllable, switchable switching element. The switching element can be, for example, an IGBT, a MOSFET, or the like. The supply unit can also comprise a series connection of several such switching elements.

[0018] Preferably, the switching element can be controlled in a pulsed manner by means of a control unit. The switching element is switched on and off at short intervals during operation. According to one variant, the switching element can be switched on by means of the control unit when a supply voltage for powering the module falls below a predetermined voltage threshold. Accordingly, it can be switched off or blocked when the supply voltage exceeds a further voltage threshold. In this way, a two-pulse control is provided that prevents overvoltage at the module to be supplied and can simultaneously provide power from the energy storage device as needed.

[0019] A particularly simple and reliable embodiment of the invention results, for example, when the series connection extends between a first and a second high-voltage side connection terminal, which are set up for connection to the energy storage device, wherein the series resistor is connected directly to the first connection terminal, and wherein the supply unit comprises a switched-mode power supply that comprises a switching element that can be switched on and off and a voltage tap, which are connected to one another in a series circuit, wherein a first connection of the switched-mode power supply is connected to the series resistor and a second connection of the switched-mode power supply is connected to the second connection terminal, wherein a first and a second low-voltage side connection terminal for connection to the module to be supplied are arranged on the voltage tap.

[0020] Preferably, a resistance element is provided, which is arranged in parallel with the switching unit or the switching power supply. The additional resistance element and the series resistor can together provide the additional function of a discharge resistor for the energy storage device.

[0021] Preferably, the series circuit extends between a first and a second high-voltage-side connection terminal (X1, X2), which are configured for connection to the energy storage device. The supply unit comprises a variable resistor and a voltage tap connected in series therewith, and the fuse element is arranged in series with the supply unit. The variable resistor is expediently implemented by a resistance element whose resistance value is variably adjustable.

[0022] The supply device is suitably designed for a voltage of 1 kV to 20 kV on the output side or energy storage side. This allows energy storage devices from converters in high-voltage systems to be advantageously used for the supply device. The supply device is expediently designed for a voltage of 100 V to 1 kV on the low-voltage side. The supply device has a low-voltage side that can be connected or is connected to the component to be supplied. On the low-voltage side, the supply device can thus provide a supply voltage between 100 V and 1 kV.

[0023] The supply unit can be designed in a cascade configuration. For example, at least one additional power supply is arranged parallel to the switching element. Using the additional power supply, the voltage on the low-voltage side can be further reduced depending on the application.

[0024] The invention is particularly suitable for use in a modular multi-level converter. A modular multi-level converter comprises converter arms extending between a DC voltage pole and an AC voltage connection or between two AC voltage connections. Each converter arm has a series connection of several two-pole switching modules. Each switching module comprises an energy storage device and a plurality of power semiconductor switching units, each having a controllable semiconductor switch that can be switched on and off. In each of the switching modules, control modules for controlling the semiconductor switches and the communication modules must be supplied with energy. The energy supply is advantageously realized by drawing energy from the energy storage device of the switching module itself. The switching modules can be implemented, for example, as half-bridge circuits or full-bridge circuits.

[0025] According to the invention, such a switching module for a modular multi-level converter is provided, which comprises power semiconductor switches and an energy storage device, wherein the supply device is connected in parallel with the energy storage device.

[0026] A particular advantage of this application is the protection provided by the fuse element against damage to the switching module in the event of short circuits on or in the energy storage device.

[0027] The invention will be described below with reference to Figures 1 to 3 be explained further.

[0028] Figure 1 shows an embodiment of a switching module according to the invention with a supply device in a schematic representation;

[0029] Figure 2 shows the embodiment of the Figure 1 in the event of a short circuit in a schematic representation;

[0030] Figure 3 shows another embodiment of a supply device.

[0031] In detail, Figure 1 a supply device 1 for a switching module 2 of a modular multi-level converter is shown. The switching module 2 is constructed in a half-bridge circuit. The switching module 2 thus comprises a series circuit with a first power semiconductor switching unit 3 and a second power semiconductor switching unit 4, each of which comprises a semiconductor switch 5 and a freewheeling diode 6. An energy storage device 7 in the form of a capacitor is arranged parallel to the two power semiconductor switching units. The switching unit 2 is connected to other identical switching units in a series circuit by means of its terminals 8 and 9. During operation of the modular multi-level converter, the switching module 2 is at a usually non-constant high-voltage potential. A voltage Uc of approximately 3 kV is dropped across the energy storage device 7.

[0032] The supply device 1 comprises a series circuit 10 consisting of a series resistor 11 and a supply unit 12. The supply unit 12 comprises a parallel circuit of a further resistance element 121 with a switching element 13. In the illustrated embodiment, the switching element 13 is an IGBT (integrated gate bipolar transistor). The series circuit 10 is connected in parallel with the energy storage device 7 on the high-voltage side.

[0033] In the illustrated embodiment, the supply unit 12 further comprises a voltage tap in the form of a medium-voltage capacitor 14. Low-voltage side connection terminals 15, 16 are arranged on the medium-voltage capacitor 14. Using the connection terminals 15, 16, the supply device 1 can be connected to the module to be supplied. During operation, a supply voltage Uv of 200 V is applied to the connection terminals 15, 16. If, depending on the module, a lower supply voltage, for example 15 V, is required, the connection terminals can be connected to another power supply that can transform the voltage from 200 V to 15 V.

[0034] The gate of switching element 13 is connected to a control 17. The control 17 controls the opening and closing or blocking of switching unit 13. Control occurs depending on the voltage drop at voltage tap 14. If the supply voltage Uv falls below a predetermined threshold, switching element 13 is switched on. If the predetermined threshold is exceeded, switching element 13 is switched off. This results in pulse-like control of switching element 13.

[0035] A fuse element 20a is arranged between the series resistor 11 and the supply unit 12. The fuse element 20a is intended to interrupt the series circuit 10 in the event of a fault. The fuse element 20a comprises a sacrificial element designed to evaporate when a current threshold is exceeded through the series circuit 10, thereby breaking the electrical connection between the series resistor 11 and the supply unit 12. Alternatively or in combination with the fuse element 20a, the supply device comprises a fuse element 20b arranged within the supply unit 12. In the event of a fault, the fuse element 20b interrupts the short-circuit current through the faulty switching element 13. The fuse elements 20a, b are constructed identically in the illustrated embodiment.

[0036] In Figure 2 are the supply device 1 and the switching module 2 of the Figure 1in the event of a fault. The short circuit indicated by arrow 18 due to a fault in the medium-voltage capacitor 14 or at the connecting terminals 15, 16 leads to a drop in the supply voltage Uv to zero. In this case, the control 17 keeps the switching element 13 permanently open. This, in turn, leads to a short-circuit current 19 through the series resistor 11 and can cause its thermal overload.

[0037] The short-circuit current 19 is higher than the current threshold value of the fuse element 20a. In the described fault case, the fuse element 20a evaporates, which in Figure 2 is indicated by a broken line 21. The short-circuit current 19 is thus interrupted before the thermal overload of the series resistor 11 can lead to damage to the supply device 1 or the switching module 2. The mode of operation of the fuse element 206 is corresponding.

[0038] Figure 3shows a supply facility 1a. Identical and similar elements are shown in the Figures 1 to 3 provided with the same reference symbols.

[0039] A fuse element 20c is arranged in series with the supply unit 12. The structure of the fuse element 20c corresponds to that of the fuse element 20a. A variable resistor 22 is arranged in series with the voltage tap 14. The variable resistor 22 can comprise switching elements, such as semiconductor switches, by means of which the resistance value of the variable resistor 22 can be increased or decreased.

[0040] The switching module 2 may comprise a discharge resistor for the energy storage device, which is arranged in parallel to the energy storage device 7.

Claims

1. Switching module (2) for a modular multistage converter, comprising power semiconductor switches (5) and an energy store (7), the switching module containing a supply device (1), connected in parallel with the energy store (7), for supplying electrical power to an electrical assembly at a high-voltage potential, having - a series circuit (10) composed of at least one series resistor (11) and a supply unit (12), wherein the series circuit (10) is connected in parallel with the energy store (7) and the supply unit (12) can be connected in parallel with the assembly that is to be supplied with power, the supply device being characterized in that it contains a fuse element (20a) arranged between the series resistor and the supply device, by means of which fuse element a short-circuit current through the supply unit (12) can be electrically interrupted in the event of a short circuit, wherein the fuse element (20a) is purely passive.

2. Switching module according to Claim 1, wherein the fuse element (20) interrupts the series circuit (10) as soon as a current through the series circuit (10) exceeds a predetermined maximum current value.

3. Switching module according to either one of the preceding claims, wherein the fuse element (20) comprises a fuse wire, which can be severed in the event of a short circuit.

4. Switching module according to any one of the preceding claims, wherein the fuse element (20) is a sacrificial element.

5. Switching module according to any one of the preceding claims, wherein the fuse element (20) is designed in such a way that it at least partly evaporates in the event of a short circuit.

6. Switching module according to any one of the preceding claims, wherein the fuse element (20) is integrated into the series resistor (11).

7. Switching module according to any one of the preceding claims, wherein the at least one series resistor (11) is a flat resistor.

8. Switching module according to any one of the preceding claims, wherein the supply unit (12) comprises a switching element (13) that can be switched on and off.

9. Switching module according to Claim 8, wherein the switching element (13) can be actuated in a pulse-like manner by means of an actuation unit (17).

10. Switching module according to any one of the preceding claims, wherein the series circuit (10) extends between a first and a second high-voltage-side connection terminal (X1, X2), which are configured for connection to the energy store (7), wherein the series resistor (11) is connected directly to the first connection terminal (X1), and wherein the supply unit (12) comprises a switched-mode power supply (13, 14), which comprises a switching element (13) that can be switched on and off and a voltage tap (14), which are connected to one another in a series circuit, wherein a first connection of the switched-mode power supply (13, 14) is connected to the series resistor (11) and a second connection of the switched-mode power supply (13, 14) is connected to the second connection terminal (X2), wherein a first and a second low-voltage-side connection terminal (15, 16) are arranged at the voltage tap (14) for connection to the assembly that is to be supplied with power.

11. Switching module according to any one of Claims 8 to 10, wherein a resistance element (121) arranged in parallel with the switching unit (13) or in parallel with the switched-mode power supply is provided.

12. Switching module according to any one of the preceding Claims 1-7, wherein the series circuit (10) extends between a first and a second high-voltage-side connection terminal (X1, X2), which are configured for connection to the energy store (7), wherein the supply unit comprises a variable resistor and a voltage tap (14) in series with said variable resistor, and wherein the fuse element is arranged in series with the supply unit.

13. Switching module according to any one of the preceding claims, wherein the supply device (1) is dimensioned on the energy store side for a voltage of 1 kV to 20 kV.

14. Switching module according to any one of the preceding claims, wherein the supply device (1) is dimensioned on the output side for a voltage of 100 V to 1 kV.