Patent Application
20210152081
The invention relates to a modular multilevel power converter with a plurality of power converter modules each of which comprises a direct voltage source, for example a capacitor.
In order to perform maintenance work on such a power converter, it is necessary to ensure beforehand that the direct voltage sources are discharged, and that at least one pole of each direct voltage source is at ground potential. The potential connection is, for example, achieved through a large number of sliding contacts connected in series, or through manually inserted bridging cables. However, if two contacts fail the large number of contacts connected in series can lead to interrupting the ground potential.
The invention is based on the object of providing a potential equalization system for a modular multilevel power converter with a plurality of power converter modules each of which comprises a direct voltage source, which improves the connectability of the direct voltage sources to a ground potential.
The object is achieved according to the invention through a potential equalization system with the features of claim 1 and a modular multilevel power converter with the features of claim 10.
Advantageous elaborations of the invention are the object of the subsidiary claims.
A potential equalization system according to the invention for a modular multilevel power converter that comprises a plurality of power converter modules (3), each with a direct voltage source (13), comprises pole contacts, each of which is electrically connected to one pole of a direct voltage source, and at least one electrically conductive contacting element that is movable between a first end position in which it is electrically disconnected from the power converter modules and a second end position in which it contacts pole contacts of different direct voltage sources and which can be placed at a ground potential, for example by a manual, mechanical or electrical drive.
Thus in a potential equalization system for a modular multilevel power converter according to the invention, poles of direct voltage sources of different power converter modules of the power converter can be placed at a ground potential in that pole contacts, each of which is joined to the poles, are electrically connected to one another by a contacting element, and the contacting element is placed at the ground potential. As a result, in the event of a failure of individual pole contacts, the direct voltage sources that are connected via the other pole contacts to the contacting element remain connected to the ground potential. This advantageously increases the safety of the connection of many direct voltage sources to the ground potential in comparison to a connection through a plurality of contacts connected in series.
One embodiment of the invention provides that at least one contacting element is an electrical shield (i.e., a shielding screen) for shielding a plurality of power converter modules that can be rotated about an axis of rotation between the first end position and the second end position. The electrical shield for example comprises a shielding tube (shield tube) from which at least one shield contact protrudes which, in the second end position of the shield, contacts at least one pole contact, and the axis of rotation of the shield is a longitudinal axis of the shield tube. At least one shield contact is, for example, designed as a handle arranged at the shield tube which, in the second end position of the shield, contacts a plurality of pole contacts. The shield is, for example, manufactured of aluminum.
The elaborations of the invention referred to above make use of a shield of power converter modules, which is a rule is in any case necessary, as a contacting element, or they provide the contacting element with a shielding function. The material and construction effort is thereby advantageously reduced in comparison with separately implemented shields and contacting elements.
A further elaboration of the invention provides that at least one contacting element is an electrically conductive contact cable, for example a copper cable, that can be guided by an electrically insulating guide cable guided via pole contacts of different direct voltage sources, is, in the first end position, not adjacent to any pole contact and is, in the second end position, adjacent to the pole contacts via which the guide cable is guided. The guide cable is, for example, guided by a first cable drum, the contact cable is guided by a second cable drum, and both cable drums are mounted on a drive shaft that can be driven manually, mechanically, or electrically.
A contacting element implemented as a contact cable enables an electrical connection of the pole contacts that can be adjusted flexibly to the spatial distribution of the pole contacts, and also in particular a connection of pole contacts that are spaced relatively far apart from one another.
A modular multilevel power converter according to the invention, in particular a self-commutated modular multilevel power converter, comprises a plurality of power converter modules, each with a direct voltage source which is for example designed as a capacitor or as an electrical interconnection of a plurality of capacitors, and a potential equalization system according to the invention. The advantages of a power converter of this sort result from the advantages referred to above of a potential equalization system according to the invention, and are therefore not described here again.
In a further elaboration of the invention, the power converter comprises a plurality of module groups each of which comprises a plurality of power converter modules, each with at least one pole contact. For each module group, the potential equalization system comprises a contacting element that contacts all the pole contacts of the module group in its second end position. This elaboration of the invention takes into consideration the fact that the power converter modules of a modular multilevel power converter frequently form a plurality of module groups that are, for example, disposed at a spatial distance from one another. In this case it can be advantageous to provide a contacting element for each module group. It can be provided here that all the contacting elements are electrically connected together in their second end positions. This advantageously simplifies the connection to the ground potential. A common drive can furthermore be provided with which all the contacting elements can be driven simultaneously. As a result, the expenditure of costs and material for moving the contact elements can on the one hand be reduced, and the movements of the contacting elements can on the other hand be more easily synchronized.
The above-described properties, features and advantages of this invention, as well as the manner in which these are achieved, will be made clearer and more easily understandable in connection with the following description of exemplary embodiments that are explained in more detail in connection with the drawings. Here:
Parts that correspond to one another are given the same reference signs in the figures.
Each power converter module 3 comprises a half-bridge of semiconductor switches 9 each of which is, for example, designed as a bipolar transistor with an insulated gate (IGBT: insulated gate bipolar transistor), with which a freewheeling diode 11 is connected antiparallel. Each power converter module 3 further comprises a direct voltage source 13 that is designed as a capacitor. One pole of the direct voltage source 13 is electrically connected to the pole contact 15 of the power converter module 3, via which the pole can be electrically contacted.
The contacting element 17 of each module group 5 to 7 can be moved between a first end position in which it is electrically disconnected from the power converter modules 3 of the module group 5 to 7, and a second end position, in which it contacts all of the pole contacts 15 of the module group 5 to 7 and connects the direct voltage sources 13 of the power converter modules 3 of the module group 5 to 7 in parallel. The contacting element 17 of a first module group 5 also contacts, in its second end position, a grounding contact 19 to which a ground potential can be applied via a first grounding switch 21. The contacting element 17 of a second module group 6 also contacts, in its second end position, a first connecting contact 23 that is electrically connected to a pole contact 15 of the first module group 5. The contacting element 17 of the third module group 7 also contacts, in its second end position, a second connecting contact 25 that is electrically connected to a pole contact 15 of the second module group 6. The ground potential can be applied via a second grounding switch 22 to a pole contact 15 of the third module group 7. When all of the contacting elements 17 are in their second end position, the ground potential can therefore be applied to all the pole contacts 15 by closing at least one grounding switch 21, 22.
Each contacting element 17 can be moved by a drive 27 between its two end positions. The drives 27 of the contacting elements 17 can also be implemented as a common drive 27 for all contacting elements 17.
Each shield comprises a shield tube 29 and can be rotated between its two end positions about an axis of rotation 31 that is a longitudinal axis of the shield tube 29. A shield contact 33 protrudes from each shield tube 29, and is designed as a handle arranged at the shield tube 29. The shields are manufactured, for example, from aluminum.
The drive 27 comprises a drive bar 35 that can be rotated about its longitudinal axis under manual, mechanical or electrical drive, and for each shield tube 29 a gear element 37 that brings about a rotation of the shield tube 29 about the axis of rotation 31 from a rotation of the drive bar 35 about its longitudinal axis. For example, the drive bar 35 and each gear element 37 form a worm gear, wherein the drive bar 35 is designed as the worm of the worm gear, and the gear element 37 is designed as the worm wheel of the worm gear.
The
The guide cable 39 is guided via a first cable drum 41, deflection rollers 43, the pole contacts 15 and a grounding contact 19.
When in its first end position, the contact cable is wound around a second cable drum 42, and is pulled by the guide cable 39 from the first end position, via an intermediate position shown in
The cable drums 41, 42 are mounted on a drive shaft 45 that can be driven manually, mechanically or electrically.
Although the invention has been illustrated and described in more detail through preferred exemplary embodiments, the invention is not restricted by the disclosed examples, and other variations can be derived from this by the expert without leaving the protective scope of the invention.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2018/066230 | 6/19/2018 | WO | 00 |
