Multi-level converter with mechanically switched discharge resistor and earthing switch

Abstract

Multi-level converter (1), comprising - a capacitor (2); - a resistor (3); - a first switch (4) actuated by a first motor drive (40); - a second switch (5) actuated by a second motor drive (50); wherein - in a closed state, the first switch connects the capacitor (2) to the resistor (3) and short-circuits the same; in the closed state, the second switch (5) connects the capacitor (2) to an earthing potential (20).

Description

[0001] Multi-level converter with mechanically switched discharge resistor and earthing switch

[0002] The invention relates to a multi-level converter.

[0003] Multi-level converters generally consist of a multitude of semiconductor switches, capacitors, and coils. The capacitors regularly store large amounts of energy. To enable safe maintenance or troubleshooting of a multi-level converter, all components must be de-energized before maintenance.

[0004] The object of the invention is to provide a multi-level converter which is easy to maintain and simple in design and which can also be safely and repeatedly put into a voltage-free state.

[0005] This object is achieved by a device according to claim 1. Advantageous further developments are described in the subclaims.

[0006] According to a first embodiment, the invention proposes a multi-level converter comprising: a capacitor; a resistor; a first switch actuated by a first motor drive; a second switch actuated by a second motor drive; wherein the first switch, in a closed state, connects the capacitor to the resistor and short-circuits it; the second switch, in a closed state, connects the capacitor to a ground potential; the first switch is closed before the second switch.

[0007] The multi-level converter is designed for particularly simple and cost-effective isolation, i.e., for discharging and grounding. The multi-level converter then assumes a voltage-free state. The first and second switches have their own motor drives, which can be controlled separately. After the capacitor is short-circuited by the first switch using a resistor or via the resistor, the capacitors are largely discharged. The second switch finally grounds the capacitor and ensures that the multi-level converter is de-energized. When activated, the switches are thus closed in a fixed sequence.

[0008] The multi-level converter can be configured in any desired manner, wherein the first switch comprises a first and a second contact tooth; the first and the second contact tooth are electrically connected to the resistor; the first contact tooth, the resistor and the second contact tooth form an electrical series circuit.

[0009] The contact teeth each have contact surfaces.

[0010] The multi-level converter can be designed in any desired manner, wherein the second switch comprises a movable contact; the movable contact is electrically connected to the ground potential.

[0011] The movable contact can be designed as a contact rail, which is electrically connected to the earth potential, for example via cables.

[0012] The multi-level converter can be designed in any desired manner, wherein a contact module is provided with a first connection contact and a second connection contact; the first connection contact has a first contact point and a second contact point; the second connection contact has a first contact point and a second contact point.

[0013] The multi-level converter can be designed in any desired manner, wherein in the closed state of the first switch the first contact tooth contacts the first contact point of the first connection contact and the second contact tooth contacts the first contact point of the second connection contact and in the closed state of the second switch the movable contact contacts the second contact point of the first connection contact and the second contact point of the second connection contact.

[0014] The first switch is thus formed by the contact teeth and the first contact points of the first and second connection contacts. The second switch is thus formed by the movable contact and the second contact points of the first and second connection contacts.

[0015] Alternatively, the contact rail contacts the first and second connection contacts.

[0016] The multi-level converter can be designed in any way, with the capacitor being part of a cell.

[0017] The multi-level converter can be designed in any desired manner, wherein a plurality of capacitors are provided which are part of a single cell; a plurality of cells are provided; each cell is assigned a first and a second connection contact; each cell can be discharged via two contact teeth and a resistor; each cell can be grounded via a common movable contact.

[0018] Depending on requirements, a multi-level converter can have multiple capacitors arranged individually or collectively in cells. In a multi-cell embodiment, each cell must be designed to be connectable to the first and second switches. Each cell can be assigned a separate resistor or resistors. Each cell is connected to a common second switch so that they can be connected to ground potential via the second switch. Each cell can be assigned its own first switch, through which the cell capacitors are discharged.

[0019] The multi-level converter can be designed in any way, with twelve cells being provided and each cell delivering a voltage of 2kV.

[0020] The multi-level converter can be designed in any way, whereby the multi-level converter operates in a medium voltage range of 20 kV.

[0021] The multi-level converter can be designed in any way, with each cell having at least one semiconductor switching element and one inductance.

[0022] According to a further embodiment, a method for isolating a multi-level converter is provided, wherein in a first step, the first switch is actuated by a first motor drive and thereby short-circuits a capacitor with a resistor; in a second step, the second switch is actuated by a second motor drive and thereby connects the capacitor to a ground potential; the second step is only carried out once the capacitor has been discharged.

[0023] When the multi-level converter is de-energized, the capacitors are discharged, and after they are discharged, they are additionally grounded. It is important that the grounding, i.e., the activation of the second switch, only occurs when the capacitors are completely or at least almost completely discharged. This ensures safe work on the multi-level converter.

[0024] The invention and its advantages are described in more detail below with reference to the accompanying drawings. They show:

[0025] Fig. 1 shows a circuit of a multi-level converter;

[0026] Fig. 2 shows a first detailed view of the multi-level converter with a first and a second switch;

[0027] Fig. 3 a second detailed view of the multi-level converter with the first and second switches;

[0028] Fig. 4 a detailed view of the first and second switches.

[0029] Identical reference numerals are used for identical or equivalently functioning elements of the invention. Furthermore, for the sake of clarity, only those reference numerals are shown in the individual figures that are necessary for the description of the respective figure. The illustrated embodiments merely represent examples of how the multi-level converter according to the invention can be designed and thus do not represent a conclusive limitation of the invention.

[0030] Figure 1 shows a first embodiment of a multi-level converter 1. This has at least one capacitor 2, which is part of a cell 9. Furthermore, at least one resistor 3 is provided, which can be switched in parallel with the capacitor 2 or connected to it with the aid of a first switch 4 and a first motor drive 40, whereby the capacitor 2 is short-circuited to or via the resistor 3. Furthermore, a second switch 5 is provided, which can connect the capacitor 2 to a ground potential 20 with the aid of a second motor drive 50. When the capacitor 2 is short-circuited to or via the resistor 3, the capacitor 2 is discharged. When the capacitor 2 is connected to the ground potential 20, the capacitor 2 is grounded. The short-circuiting always occurs before grounding.After short-circuiting the associated discharge of the capacitor and grounding, work on the multi-level converter, such as maintenance, etc., can be carried out without any danger to persons. In the embodiment shown here, the multi-level converter 1 has a cell 9 with a capacitor 2. Preferably, the multi-level converter 1 can have twelve cells 9, each with at least one capacitor 2.

[0031] Figures 2 to 4 show a detailed representation of the multi-level converter 1, as well as the first and second switches 4, 5. All elements of the multi-level converter 1 are arranged in a housing 10 with a frame. The first switch 4 has at least one first contact tooth 4.1 and one second contact tooth 4.2. Each contact tooth consists of a carrier with a first and a second contact plate, wherein the contact plates are arranged on two opposite sides of the carrier. Each of the contact teeth 4.1, 4.2 or the contact plates of each contact tooth is preferably electrically connected to at least one resistor 3 via a first and a second line 6.1, 6.2. The contact teeth 4.1, 4.2 and the at least one resistor 3 form an electrical series circuit via the lines 6.1, 6.2. Furthermore, the contact teeth 4.1, 4.2 are arranged on a switch strip 41.The switching strip 41 is made of a non-conductive material so that the two contact teeth 4.1, 4.2 are insulated, i.e., not electrically conductive, from one another. The switching strip 41 is preferably connected to the first motor drive 40 via a mechanism 42, which is designed, for example, as a toggle lever device. The first motor drive 40 is preferably designed as a linear motor with a rotating spindle.

[0032] The second switch 5 has a movable contact 5.1, which is designed as a contact rail. The movable contact 5.1 or the rail is preferably connected to ground potential 20 via a line (not shown here). The second switch 5, and in particular its movable contact 5.1, is preferably actuated via a further mechanism 52, which is designed, for example, as a toggle lever device, and the second motor drive 50. The second motor drive 50 is preferably designed as a linear motor with a rotating spindle.

[0033] Furthermore, a contact module 7 is provided, which can be switched by both the first and the second switch 4, 5. The contact module 7 has at least one first connection contact 7.1 and at least one second connection contact 7.2, which are arranged on an insulating material carrier. Both connection contacts 7.1, 7.2 each have a first contact point 7.11, 7.21 and a second contact point 7.12, 7.22. The first connection contact 7.1 is electrically connected to a first side 2.1 of the capacitor 2, and the second connection contact 7.2 is electrically connected to a second side 2.2.

[0034] The first motor drive 40 actuates the first switch 4 in such a way that the first motor drive 40 acts on the mechanism 42 of the switching strip 41. The switching strip 41 performs a vertical movement from bottom to top toward the contact module 7. When the first switch 4 is actuated, the first contact tooth 4.1 is connected via the first contact point 7.11 of the first connection contact 7.1, and the second contact tooth 4.2 is connected via the first contact point 7.21 of the second connection contact 7.2. In this process, the capacitor 2 is short-circuited and discharged via the resistor 3.

[0035] The second motor drive 50 actuates the second switch 5 such that the second motor drive 50 acts on the movable contact 5.1 by means of the mechanism 52. The movable contact 5.1 performs a vertical movement from bottom to top towards the contact module 7. In doing so, a distance of at least 280mm is preferably covered. This distance is particularly intended for an application range of the multi-level converter of 20kV. In other words, the second contact points 7.12, 7.22 of the connection contacts 7.1, 7.2 are at least 280mm away from the movable contact 5.1 in the open, i.e. non-conductive, state. When the second switch 5 is actuated, the movable contact 5.1 is thus electrically connected to the connection contacts 7.1, 7.2 via the respective second contact points 7.12, 7.22. This establishes a connection between the ground potential 20 and the capacitor 4; capacitor 2 is grounded.

[0036] The contact module 7 with its connection contacts 7.1, 7.2 thus provides a common contact point for the connection to the resistor 3 and the earth potential 20. Both the switching strip 41 and the movable contact 5.1, which is designed as a rail, are moved by the corresponding motor drives 40, 50 through a vertical movement and ultimately carry out the switching.

[0037] The first switch 4, i.e., the switching strip 41, with the contact teeth 4.1, 4.2, is always actuated before the second switch 5, i.e., the first movable contact 5.1. A defined time period must be observed between the actuation of the first switch 4 and the second switch 5, during which a complete discharge of the capacitor can be assumed. The switching contacts 7.1, 7.2 of the switching strip 7 are preferably designed as spring-loaded contact blades.

[0038] The multi-level converter 1 can have a plurality of capacitors 2. Preferably, each capacitor is assigned a first switch, a second switch, and a resistor. If there are a plurality of first switches, these are jointly driven or actuated via the first motor drive 40. A plurality of second switches are jointly driven or actuated via the second motor drive 50.

[0039] The motor drives 40, 50 are actuated or controlled by a control device. The control device has means or is configured such that the first motor drive 40 and then the second motor drive 50 are always actuated. For this purpose, the multi-level converter 1 can have limit switches that transmit the actuation of the first and second switches 4, 5 to the control device. This determines the switching sequence of the first and second switches 4, 5. In a multi-level converter with multiple cells 9 and multiple capacitors 2, the switches 4, 5 are present in multiples. The contact module 7 accordingly has a pair of separate connection contacts 7.1, 7.2 for each cell 9 or capacitor 2. A pair of contact teeth 4.1, 4.2 with corresponding contact surfaces is also present. The movable contact 5.1 is designed to be large enough to contact all the connection contacts of the multi-level converter and thus to ground several cells 9 with all the capacitors 2.

[0040] List of reference symbols

[0041] 1 multi-level converter

[0042] 2 capacitor

[0043] 3 Resistance

[0044] 4 first switch

[0045] 4.1 first contact tooth

[0046] 4.2 second contact tooth

[0047] 5 second switch

[0048] 6.1 first line

[0049] 6.2 second line

[0050] 7 Contact module

[0051] 7.1 first connection contact

[0052] 7.2 second connection contact

[0053] 7.11 first contact point of 7.1

[0054] 7.21 first contact point of 7.2

[0055] 7.12 second contact point of 7.1

[0056] 7.22 second contact point of 7.2

[0057] 9 Cell

[0058] 10 housings

[0059] 20 Earth potential

[0060] 40 first motor drive

[0061] 42 Mechanism 50 second motor drive

[0062] 52 Mechanism

Claims

Patent claims 1. Multi-level converter (1) comprising a capacitor (2); a resistor (3); a first switch (4) actuated by a first motor drive (40); a second switch (5) actuated by a second motor drive (50); wherein the first switch (4), when closed, connects the capacitor (2) to the resistor (3) and short-circuits it; the second switch (5), when closed, connects the capacitor (2) to an earth potential (20).

2. Multi-level converter (1) according to claim 1, wherein the first switch (4) comprises a first and a second contact tooth (4.1, 4.2); the first and the second contact tooth (4.1, 4.2) are electrically connected to the resistor (3); the first contact tooth (4.1), the resistor (3) and the second contact tooth (4.2) form an electrical series circuit.

3. Multi-level converter (1) according to one of claims 1 to 2, wherein the second switch (5) comprises a movable contact (5.1); the movable contact (5.1) is electrically connected to the earth potential (20).

4. Multi-level converter (1) according to one of claims 1 to 3, wherein a contact module (7) is provided with a first contact point (7.1) and a second contact point (7.2); the first contact point (7.1) has a first contact point (7.11) and a second contact point (7.12); the second contact point (7.2) has a first contact point (7.21) and a second contact point (7.22).

5. Multi-level converter (1) according to any one of claims 1 to 4, wherein in the closed state of the first switch (4) the first contact tooth (4.1) contacts the first contact point (7.11) of the first switching contact (7.1) and the second contact tooth (4.2) contacts the first contact point (7.21) of the second switching contact (7.1) and In the closed state of the second switch (5) the movable contact (5) contacts the second contact point (7.12) of the first switching contact (7.1) and second contact point (7.22) of the second switching contact (7.1).

6. Multi-level converter (1) according to one of claims 1 to 5, wherein a cell (9) is provided and the capacitor (2) is a part of the cell (9).

7. Multi-level converter (1) according to any one of claims 1 to 6, wherein the cell (9) can have several capacitors (2).

8. Multi-level converter (1) according to one of claims 1 to 7, wherein several cells (9) are provided; each cell (9) is assigned a first and a second switching contact (7.1, 7.2); each cell (9) can be discharged via two contact teeth (4.1, 4.2) and a resistor (3); each cell (9) can be grounded via a common movable contact (5.1).

9. Multi-level converter (1) according to any one of claims 1 to 8, wherein twelve cells (9) are provided and each cell (9) outputs a voltage of 2kV.

10. Multi-level converter (1) according to any one of claims 1 to 9, wherein the multi-level converter operates in a medium voltage range of 20kV.

11. Multi-level converter (1) according to any one of claims 1 to 10, wherein each cell (9) has at least one semiconductor switching element and one inductor.

12. Method for unlocking a multi-level converter (1) according to any one of claims 1 to 11, wherein in a first step the first switch (4) is actuated by a first motor drive (40) and thereby short-circuits a capacitor (2) with a resistor (3); in a second step the second switch (5) is actuated by a second motor drive (50) and thereby connects the capacitor (2) to an earth potential (20); the second step is only carried out when the capacitor (2) has been discharged.

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