WO2017215746A1 - Power converter - Google Patents

Abstract

The invention relates to a module (201) of a modular multi-level power converter (1), which comprises at least two electronic switching elements (202, 206) and an electrical energy store (210). Said module (201) further comprises a non-volatile electronic memory (230) for storing status information of the module, which has been determined during the operation of the module.

Description

Description Converter The invention relates to a module of a modular

 Multilevelstromrichters having at least two electronic switching elements and an electrical energy storage. Furthermore, the invention relates to a method for storing status information in a

Multilevel converters.

Such a module is known from the international patent applica ^¬ application WO 2012/113704 A2. Power converters are power electronic circuits for converting electrical energy. Power converters can be used to convert AC to DC, DC to AC, AC to AC of different frequency and / or amplitude or DC to DC to other voltages. Power converters may comprise a plurality of similar modules (also referred to as sub-modules) which are electrically connected in series. These modules each have at least two electronic switching ^¬ elements and an electrical energy storage. Such converters are referred to as modular multilevel converters and belong to the VSC power converters (VSC = voltage sourced converter). The electrical series connection of the modules can achieve high output voltages. The converters are easily adaptable to different voltages (scalable) and a desired output voltage can be generated relatively accurately. modular

Multilevel converters are often used in high-voltage range, for example, as power converters in high-tension ^¬ voltage direct current transmission systems or as reactive power tungskompensatoren men with flexible Drehstromübertragungssyste-. In order to be able to continue operating the converter even if a defect occurs on one or more modules, the converter has reserve modules which are ^{redundant in} the event of a defective converter (and therefore are not required for operation of the converter in the case of a defect-free converter ). If a module, a defect occurs on ^¬, this defective module is bypassed (shorted ^¬ closed), and in place of the defective module one of the available (excess, redundant) modules replacement is used. For the operator of the power converter can be interes ^¬ sant, more about the the operation of the converter (and in particular on the event of failure) to learn running in the modules operations.

The object of the invention is to provide a module and a method with which the processes taking place in the modules during operation of the power converter can be investigated.

This object is achieved by a module and by a method according to the independent claims. Advantageous embodiments of the module and method are given in the respective dependent claims.

Disclosed is a module of a modular

Multilevelstromrichters comprising at least two electronic switching elements and an electrical energy storage, the module having a nonvolatile electronic memory for storing detected during operation of the module status information of the module. It is particularly advantageous that the module comprising the non Peek ^¬ term electronic memory for storing the status information. This allows the status information to be stored in memory during operation of the module (in real time). As a result, this status information is saved and can later be read from memory and evaluated as needed. In this case, the status information can have measured values of the voltage of the electrical energy store and / or information about the switching states of the electronic switching elements. This status information can later be used to reconstruct the processes that have expired in the module.

The module may be configured such that the module has a voltage measuring sensor for measuring the voltage of the electrical energy store. By means of the voltage measuring sensor, the voltage of the electrical energy storage is ermit ^¬ telt; the measured voltage values are status information.

Further, the status information can comprise measurements of the temperature of the module (in particular measured values of the Tem ^¬ temperature of the switching elements and / or measured values of the temperature of the electrical energy storage).

The module can also be configured such that the module has a temperature measuring sensor for measuring the temperature of the module. The temperature of the module is measured by means of the temperature measuring sensor. These measured values of tempera ture of the module ^¬ form status information of the module. The module may be configured so that the module has a (mo ^¬ dulinterne) module control means which is adapted to store the status information in the memory. Furthermore, the control device is configured to determine the status information. The module control device thus receives, for example, a voltage measurement value from the voltage measurement sensor arranged on the electrical energy store and transmits this voltage measurement value to the electronic memory, whereupon the voltage measurement value is stored in the electronic memory. The module can also be configured so that the module ei ^¬ NEN output terminal for outputting the vomit ^¬ cherten in the memory comprises status information. The status information stored in the memory can later be read out via this output connection.

The module can also be configured such that the output ^terminal is connected to the memory (bypassing the module control device). It is particularly advantageous that the output terminal is attached Schlos ^¬ sen directly to the memory, thus bypassing the module control device. This has the advantage that later when a defect of the module, which also relates to the module control device, the status Informa ^¬ functions can still be rather read out by the output terminal from the storage.

The module may be configured so that the two electronic ^¬ rule switching elements of the module are arranged in a half bridge circuit. Such a module is also referred to as a half-bridge module or as a half-bridge submodule.

The module can also be designed such that the module has the two electronic switching elements and two further electronic ^¬ African switching elements, wherein the two electronic switching elements and the two other electronic switching ^¬ elements are arranged in a full bridge circuit. Such a module is also referred to as a full bridge module or as a full bridge submodule. The module can be designed so that the memory

Ring memory is. (A ring memory is a memory which if not all of its memory locations, the occupied memory locations overwrite starting at the first occupied respective memory locations.) A ring buffer is therefore advantageous because a ring buffer (because of overwriting the per ^¬ weils oldest stored status information) is always the the latest available status information. chert. Thus it can be reconstructed, for example, a defect occurs on the module based on the stored status information, which is just before the defect in the module pas ^¬ Siert. For example, it can be determined which voltage the electrical energy store has exhibited shortly before the defect and how the electronic switching elements were connected shortly before the defect. These are important Statusin ^¬ formations that may be in the investigation of the defect useful for example.

The module may be configured such that, upon occurrence ei ^¬ ner irregularity stored in the memory of the module status information is read out to the output terminal of the module with the operation of the module, to allow modulex- terne evaluation of the status information. Such an irregularity in the operation of the module may be playing as a departure from the target operating or an occurrence of a defect in the module at ^¬. The module can be designed so that the electronic switching elements, the electrical energy storage and the Spei ^¬ cher form a constructive unit. The electronic memory forms part of the module; the electronic ^¬ specific memory is thus incorporated in the module.

The module can also be configured such that the memory enables the status information to be stored at intervals of a few nanoseconds, in particular at intervals between 10 and 10000 nanoseconds. Preferably, the time intervals can ^¬ also carry between 100 and 1000 nanoseconds be. The memory is thus a sufficiently fast electronic memory, which can store the status information in these relatively short time intervals. Furthermore, a modular multilevel converter with at least one module, in particular with a plurality, is disclosed of modules, according to one of the variants described above.

Also disclosed are a high voltage DC transmission system and a reactive power

Compensation system with such a modular

Multilevel power converter.

A method for storing sta- Further disclosed tusinformationen in a multi-level converter, having a plurality of modules, said modules each min ^¬ least comprise two electronic switching elements and an electrical energy storage ^¬ rule, in which method

- be detected during operation of the multilevel converter in one of the modules status information that this

Module, and

- The status information is stored in a nonvolatile electronic memory of the module. The method can proceed in such a way that measured values of the voltage of the electrical energy store and / or information about the switching states of the electronic switching elements are stored as status information. The method can proceed in such a way that the voltage of the electrical energy store is measured by means of a voltage measuring sensor to form the measured values of the voltage of the electrical energy store. The method can proceed in such a way that measured values of the temperature of the module are stored as status information (in particular measured values of the temperature of the switching elements and / or measured values of the temperature of the electrical energy store). The method may be such that the temperature of the module is measured by means of a temperature measuring sensor to form the measured values of the temperature. The method may be such that the status information is stored in the memory by a (module-internal) module control device.

The method can proceed in such a way that part of the status information is transmitted by the module control device via an optical communication connection (in particular via an optical waveguide) to a central control device of the power converter, wherein the temporal resolution of the status information stored in the memory is greater, In particular, at least by a factor of 10 is greater than the temporal resolution of the part of the status information, which is transmitted to the central control device. In other words, the (temporal) storage rate of the Statusin ^¬ formations in the memory is greater, in particular at least a factor of 10 larger than the (time) transfer rate of the portion of the status information, which is transmitted to the central control device. Thus, more status information, in particular at least 10 times as much status information, is stored in the memory than is transmitted via the light waveguide to the central control device.

The method may be such that the status information stored in the memory of the module is provided to an output terminal of the module for output in order to enable an evaluation of the status information external to the module after occurrence of an irregularity in the operation of the module. The method can proceed so that the output terminal di rectly ^¬ (thus bypassing the module controller) connected to the memory. The process can proceed in such a way that the memory is a ring memory. The method may be such that the status information is stored in the memory at intervals of a few nanoseconds, in particular at intervals between 10 and 10000 nanoseconds. Preferably, the status information can also ^¬ at intervals between 100 and 1000 Na nosekunden are stored in the memory.

The method may be configured such that the two elekt ^¬ tronic switching elements of the module are arranged in a half bridge circuit.

The method can also be configured such that the module has the two electronic switching elements and two further electronic switching elements, wherein the two elekt ^¬ ronic switching elements and the two other electronic switching elements are arranged in a full bridge circuit.

The invention will be explained in more detail below with reference to ^exemplary embodiments. The same reference numbers refer to the same or equivalent elements. This is in

Figure 1 shows an embodiment of a power converter having a plurality of modules, in

Figure 2 shows an embodiment of a module, in

Figure 3 shows another embodiment of a

 Module, in

 Figure 4 shows an embodiment of the method for

 Storing status information, in

 Figure 5 shows an embodiment of a high voltage DC transmission system and in

Figure 6 shows an embodiment of a reactive power compensation system shown.

FIG. 1 shows a power converter 1 in the form of a modular multilevel converter 1 (modular multilevel converter, MMC). This multi-level power converter 1 has a first AC voltage connection 5, a second alternating voltage connection clamping ^¬ 7 and a third AC voltage connection 9. The first AC voltage connection 5 is electrically connected to a first phase module branch 11 and a second phase module branch 13. The first phase module branch 11 and the second phase module branch 13 form a first phase module 15 of the power converter 1. The end of the first phase module branch 11 facing away from the first AC voltage terminal 5 is electrically connected to a first DC voltage terminal 16; the first AC terminal 5 opposite end of the second phase module branch 13 is electrically connected to a second DC voltage terminal 17. The first DC voltage terminal 16 is a positive DC voltage connection clamping ^¬; the second DC voltage terminal 17 is a negative DC voltage terminal.

The second AC voltage terminal 7 is electrically connected to one end of a third phase ^module branch 18 and to one end of a fourth phase module branch 21. The third phase module branch 18 and the fourth phase module branch 21 form a second phase module 24. The third AC voltage terminal 9 is electrically connected to one end of a fifth phase module branch 27 and to one end of a sixth phase module branch 29. The fifth phase module branch 27 and the sixth phase module branch 29 form a third phase module 31.

The second alternating voltage terminal 7 facing away from the end of the third phase module branch 18 and the third alternating voltage terminal 9 facing away from the end of the fifth Phasenmo ^¬ dulzweigs 27 are electrically connected to the first direct voltage terminal 16th The second AC voltage source 7 end facing away from the fourth phase module branch 21 and the third AC voltage terminal 9 remote from the end of the sixth phase module branch 29 are electrically connected to the second DC voltage terminal 17.

Each phase module branch has a plurality of modules (1_1, 1_2, 1_3 ... 1_n, 1_n + 1, 1_n + 2, 1_n + 3, 1_n + 4, 2_1 ... 2_n + 4;

etc.) which is (are electrically connected by means of its galvanic Stromanschlüs ^¬ s) in series. Such modules are also referred to as submodules. In the ^exemplary embodiment of FIG. 1, each phase module branch has (n + 4) modules. The on ^¬ number of elekt ^¬ driven serially connected (by means of its galvanic current connections) modules can be very different, at least three modules are connected in series, but it can also, for example, 50, 100 or more modules may be electrically connected in series. In the embodiment, n = 36: the first phase module branch 11 thus comprises 36 modu ^¬ le 1_1, 1_2, 1_3, ... 1_36 and additionally L_n the reserve modules + l = 1_37, L_n + 2 = 1_38, L_n + 3 = 1_39 and l_n + 4 = 1_40. Of the 40 modules, 36 modules are required to operate the converter (36 operating modules) and 4 modules (modules 1_37 to 1_40) are reserve modules. The other phase module branches 13, 18, 21, 27 and 29 are similar to ^¬ built.

In the left-hand area of FIG. 1, a control device 35 (control system 35) for the modules 1_1 to 6_n + 4 is shown schematically. From this central control device 35 optical messages are transmitted via an optical communication connection 37 (for example via an optical waveguide) to the individual modules. The message transmission between the controller and a module is symbolically represented by a line 37; the direction of the message transmission is symbolized by the arrowheads on the lines 37. This is illustrated by the example of the modules 1_1, l_n and 4_n + l; Messages are sent to and from the other modules in the same way. sen modules receive messages. For example, the controller 35 sends a respective target value for the magnitude of the output voltage to provide the respective Mo ^¬ dul to the individual modules.

Each module is assigned a bypass switch, which can bridge (short-circuit) the module (in the event of a defect in the module). Such a bypass switch 56 is shown for reasons of clarity only in the module 6_2. All other modules are also associated with such a bypass switch. The bypass switch 56 is closed upon the occurrence of a defect on the module from a module 6_2 ^¬ internal module controller 220 (see FIG. 2).

2 shows the structure of a module 201 is provided exemplifies ^¬. It may be, for example, the module 1_1 of the first phase module branch 11 (or one of the walls ^¬ ren modules shown in Figure 1). The module is designed as a half-bridge module 201. The module 201 has a first turn-off semiconductor valve 202 with a first antiparallel-connected diode 204. Furthermore, the module 201 has a second turn-off Halbleiterven ^¬ til 206 with a second antiparallel diode 208 and an electrical energy storage 210 in the form of a

Capacitor 210 on. The first turn-off semiconductor valve 202 is a first electronic switching element 202; the second turn-off semiconductor valve 206 is a second electronic switching element 206. The first turn-off semiconductor valve 202 and the second turn-off semiconductor ^¬ valve 206 are each configured as an IGBT (insulated-gate bipolar transistor). The first turn-off semiconductor ^¬ valve 202 is electrically connected in series with the second turn-off semiconductor valve 206. At the point of connection be- see the two semiconductor valves 202 and 206 is a first galvanic connection module 212 disposed. At the connection of the second semiconductor valve 206, which opposite to the connection point, a second galvanic module connection 215 is arranged. The second module connection 215 is furthermore connected to a first connection of the energy store 210; a second terminal of the energy storage 210 is electrically connected to the terminal of the first semiconductor valve 202 opposite to the connection point.

The energy store 210 is thus electrically connected in parallel to the series connection of the first semiconductor valve 202 and the second semiconductor valve 206. By appropriate control of the first semiconductor valve 202 and the second semiconductor valve 206 by the module-internal electronic module control device 220 can be achieved that between the first Galvanic module terminal 212 and the second galvanic module terminal 215 either the voltage of the energy storage 210 is output or no voltage is output (ie, a zero voltage is output). By interaction of the modules of the individual Phasenmodul- branches so the respective desired output voltage of the converter can be generated.

For module-external communication, the module 201 has an optical communication connection 224, which is electrically connected to the module control device 220. See on the optical communications port 224, an optical communication channel 37 is Schlos ^¬ sen to the external module Kom ^¬ communication. The optical communication channel 37 may in particular be formed by one or more optical waveguides 37 (for example by POF optical waveguides or by PCS optical waveguides, POF = polymers optical fibers, PCS =

Polymer Clad silica). Thus, there exists a 37 optical communi cation ^¬ connection between the central control device 35 and the module 201. The module controller 220 can detect and information about the current status of the module (status information) (via the optical communication link 37) to the transmit central control device 35. The optical communication link 37 has a limited Datenübertra ^¬ transmission rate. In the embodiment, the optical communi ^¬ nikationsverbindung 37 is selected so that it has a transmission of status information in the timing of> 10 microseconds allows. A higher timing, that is, a greater data transmission rate over the optical Kommunikationsverbin ^¬ tion is not realized for economic reasons (costs for the optical waveguide, optical transmitter and optical receiver used).

The status information can include, for example, measured values of the voltage of the electrical energy store, information about the switching states of the electronic switching elements and / or measured values of the temperature of the module. Furthermore, the status information can also contain, for example, error bits, error messages, other voltage values occurring in the module or the like. exhibit. Furthermore, the module 201 has an electronic memory

230 on. This electronic memory 230 is configured as a non ^¬ volatile electronic memory (non-volatile electronic memory module, non-volatile electronic storage element). A nonvolatile memory is a memory which stores the stored data (here: the stored status information) even when the supply voltage of the memory is switched off or fails. For example, even when a failure of the inter module ^¬ NEN supply voltage of the non-volatile electronic memory 230 further stores the data stored in it status information.

The memory 230 has a plurality of memory cells 232. An arrow 234 indicates that the memory 230 is a ring buffer 230. In this ring buffer 230, the oldest stored status information is stored when new status information is stored. overwritten if there are no more free memory cells 232 in the memory.

The memory 230 is electrically connected to the module control device 220 by means of a first data transmission line 238. This allows the module controller 220 to store determined status information in the memory. Furthermore, the memory 230 is electrically connected to an output terminal 246 (status information output terminal 246, data output terminal 246) of the module 201 via a second data transmission line 242. The output terminal 246 is outside of the module (that is, from egg ^¬ nem module exterior space 250 of) accessible. By means of the second data transmission line 242 is the output terminal 246 directly (i.e., bypassing the Mo ^¬ dul controller 220) connected to the memory 230th This has the advantage that state information stored in the memory 230 can still be read out via the output connection 246 even if the module control device 220 no longer functions (for example because of a defect).

Furthermore, the module 201 has a voltage measuring sensor 250 whose voltage measuring terminals are electrically connected to the two poles of the electrical energy store 210. The voltage-measuring sensor 250 is thus connected in parallel with the energy storage elekt ^¬ step 210th The voltage measuring sensor 250 measures the appearing at the electrical energy storage device 210 voltage and transmits a measured value of the voltage of the electrical energy accumulator (measured voltage value ^¬) via a first electrical measuring line 252 220 to the Mo ^¬ dul controller Furthermore, the module 201 has a temperature -Messsensor 256 on. This temperature measuring sensor 256 is connected to the module module by means of a second electrical measuring line 260. Control device 220 electrically connected. The temperature measuring sensor measures a temperature occurring in the module and transmits a measured value of the temperature of the module (tempera ^¬ turmesswert) via the second electrical measuring line 260 to the module controller 220. In this case, the temperature measuring sensor, for example, measure the temperature of the energy storage 210 or the temperature of the first electronic switching element 202 or the temperature of the second electronic switching element 206. Accordingly, the temperature measuring sensor 256 may be arranged, for example, on the electrical energy store 210, on the first electronic switching element 202 or on the second electronic switching element 206. During operation of the modular multilevel converter 1, the following procedure is carried out in module 201:

The module controller 220 continuously determines status ^¬ information of the module. Such status information is in the exemplary embodiment for example, the switching states of the electronic switching elements 202 and 206, the measured values of voltage of the electrical energy storage device 210 and / or the temperature of the electrical energy accumulator 210. The switching ^¬ states of the electronic switching elements are, for example, switching element turned on ^λ or, Switching element switched off ^λ . These switching states of the electronic switching elements 202 and 206 are present in the module controller 220, because the module controller 220, the electronic

Switching elements 202 and 206 drives. The measured values of the tension ^¬ voltage of the electric energy storage module 210 receives the control device 220 of the voltage measuring sensor 250; the measured values of the temperature of the electrical energy store 210 are received by the module control device from the temperature measuring sensor 256. The module control device 220 transmits the ascertained

Status information on the first data transmission line 238 to the memory 230 and stores the determined status Information in the memory 230 from. The determination and storage of the status information takes place at intervals of a few nanoseconds. In the exemplary embodiment, the status information is stored in the memory 230 at intervals of 100 nanoseconds. Thus, the temporal course of the status information with a time resolution of 100 nanoseconds is present in the memory 230. The memory 230 is designed as such a fast electronic memory that it is capable of storing the status information in the 100 nanosecond cycle. (In other embodiments, the status information can also be determined at other time intervals and / or stored in the memory 230, for example at intervals 10-10000 Nanose ^¬ customer, particularly at time intervals between 100 and 1000 nanoseconds. So the status information can, for example, in Time intervals of 10 nanoseconds, at intervals of 1000 nanoseconds or at intervals of 10,000 nanoseconds determined and / or stored in the memory 230.)

Furthermore, the module controller 220 transmits a part of the status information via the optical communication connection 224 and the optical communication connection 37 to the central control device 35. Via the optical communication connection 37, the status information is transmitted, for example, at intervals of a few microseconds; in the exemplary embodiment at intervals of 10 micro ^¬ seconds. (In other embodiments, the status information may also be transmitted over the optical communications link 37 at other time intervals, for example at intervals of 20 microseconds, 30 microseconds, or 40 microseconds.) That is, the status information transmitted over the optical communications link 37 to the central controller 35 have a timeout of (only) 10 microseconds. In other words, in the same time, in the 100 times consecutive status information in the memory 230 are stored, only once a Hun ^¬ stelst this status information via the optical communication link 37 to the central control device 35 transmitted. Thus, the status information with a time triggering of 10 microseconds is available at the central control device 35. This is sufficient to the individual modules 1_1, 1_2 ... 6_n + 4 of the multilevel converter 1

(Multilevel converter 1) to control. However, the status information present at the central control device 35 is not sufficient to investigate rapid processes occurring in the modules in the nanosecond range. Just such fast processes in sizes ^¬ Regulations of 10 nanoseconds to about 10 microseconds but when errors occur in modules of interest.

These fast processes can be analyzed / examined by means of the status information stored in the memory. For such an analysis / examination, the status information stored in the module-internal memory 230 is provided. This status information has a time resolution that is 100 times greater than the status information available at the control device 35.

In the exemplary embodiment, it is assumed that an irregularity occurs in the module 201: There occurs a defect of the Mo ^¬ duls 201, wherein the second electronic switching element 206 and the module control device are destroyed 220th For later examination of this defect are stored in the centra ^¬ len controller 35 status information of little help, since they are present in the central control device status information only have the time resolution of 10 microseconds. The expired in the module before the defect fast processes (which have expired in times of less than 10 microseconds) can therefore not be examined by means of this present at the central control device 35 status information. The status information stored in the memory 230 has each However, a much higher temporal resolution, so that ^{¬ means of} this (stored in the memory 230) status information that occurred before the occurrence of the defect in the module operations can be examined in more detail. DA forth are through the output port 246, the data stored in the memory 230 status information read out (for example by means of a reading device which is connected to the Ausgabean ^¬ circuit 246 or is connected if necessary). Then the abgespeicher- th in the memory 230 status information via the output port 246 are issued and intermediately ^¬ chert example, in the reader. The read out from the memory 230 Statusinformati ^¬ ones can then be examined in detail. This Modulex ^¬ ternal examination / analysis of the status information can take place at a later date, for example, in a computer of the operator of the power converter.

The module control device 220 thus transmits only a part of the status information via the optical communication connection 37 to the central control device 35. In the exemplary embodiment, this part of the status information transmitted to the central control device is one hundredth of the status information stored in the memory 230. In other embodiments, the portion of the status information transmitted to the central controller may also be different, such as one tenth or one thousandth of the status information stored in the memory 230. FIG. 3 shows a further exemplary embodiment of a module 301 of the modular multilevel converter. This module 301 can be, for example, the module 1_2 (or also one of the other modules shown in FIG. 1). In addition to the first semiconductor valve 202 already known from FIG. 2, the second semiconductor valve 206, the first diode 204, the second diode 208 and the energy store 210, the module 301 illustrated in FIG. 3 has a third shut-off base. Res semiconductor valve 302 with an antiparallel-connected third diode 304 and a fourth turn-off semiconductor ^¬ valve 306 with a fourth antiparallel-connected diode 308 on. The third turn-off semiconductor valve 302 is a third electronic switching element 302; the fourth from ^¬ switchable semiconductor valve 306 is a fourth electronic ^¬ ULTRASONIC switching element 306. The third turn-off semiconductor ^¬ valve 302 and fourth turn-off semiconductor valve 306 are each constructed as an IGBT. In contrast to the circuit of Figure 2, the second galvanic module connector 315 is not connected elekt ^¬ driven with the second semiconductor valve 206, but with a center of an electrical series circuit of the third semiconductor valve 302 and the fourth semiconductor valve 306th

The module 301 of FIG. 3 is a so-called full-bridge module 301. This full-bridge module 301 is characterized by the fact that, with appropriate control of the four semiconductor valves between the first galvanic module connection 212 and the second galvanic module connection 315, either the positive voltage of the energy store 210, the negative voltage of the energy storage 210 or a voltage of zero (zero voltage) can be output. Thus, therefore, by means of the full bridge module 301, the polarity of the output voltage can be reversed. The power converter 1 can have either only half-bridge modules 201, only full-bridge modules 301 or also half-bridge modules 201 and full-bridge modules 301. Via the first galvanic module connection 212 and the second galvanic module connection 215, 315 flow large electrical currents of the power converter.

FIG. 4 is a summary of an exemplary process flow in a flowchart. Step 402: During operation of the multilevel converter, status information relating to this module is determined in one of the modules. Step 404:

 The status information is stored in the nonvolatile electronic memory of the module.

Process step 406:

A part of the status information is transmitted via an optical communication link to a central control device of the multilevel converter.

Step 408:

After the occurrence of an irregularity in the operation of Mo ^¬ duls the data stored in the memory which include the status information is outputted to the output terminal 246th The method step 406 is optional, that is, in the context of the described method, this method step is not necessary.

After the method step 408, a further method step 410 may be followed by: There is performed a module external sub ^¬ investigation / analysis of the of the output terminal 246 out give ^¬ NEN data / status information, for example on a computer of the operator of the converter. In Figure 5 is an embodiment of a schematic

High voltage DC transmission system 501 shown. This high-voltage DC transmission system 501 has two power converters 1, as shown in FIG. These two power converters 1 are electrically connected to one another on the DC voltage side via a high-voltage direct current connection 505. In this case, the two positive DC voltage connections 16 of the power converters 1 are connected by means of a first high-voltage direct current line 505a are electrically connected to each other; the two negative DC voltage connections 17 of the two power converters 1 are electrically connected to one another by means of a second high-voltage direct current line 505b. By means of such a high-voltage DC transmission system 501, electrical energy can be transmitted over long distances; the high voltage DC link 505 then has a corresponding length.

FIG. 6 shows an exemplary embodiment of a power converter 601 which serves as a reactive power compensator 601. This power converter 601 has only the three phase module branches 11, 18 and 27, which form three phase modules 605, 607 and 609 of the power converter. The number of

Phase modules 605, 607 and 609 corresponds to the number of ^{phases of} an AC voltage network 611 to which the power converter 601 is connected. The three phase module branches 11, 18 and 27 are connected to each other in a star shape. The star point opposite end of the three phase module branches is electrically connected to a respective phase ^¬ line 615, 617 and 619 of the three-phase AC voltage ^¬ network 611. (The three phase modules 605, 607 and 609 may in another embodiment at ^¬ point be connected in star connection and in delta connection.) The inverter 601 may supply the alternating voltage network 611 with reactive power or remove reactive power from the AC power supply 611.

A module of a modular multilevel converter as well as a method for storing status information in a multilevel converter have been described. During the operation of the multilevel converter in the module, status information is determined in the module, and this status information is stored in a nonvolatile electronic memory of the module. This storage is done with a very high temporal resolution, so that in the memory a temporally high-resolution set of status information is stored. If necessary (for example, after occurrence of a irregu ^¬ temperance or a defect on the respective module) kön- nen are read, the stored status information from the module in order to evaluate these outside the module.

It is of particular advantage that the status information is stored where it occurs and is determined: namely in the module. Thus, the Statusinformatio ^¬ nen need only be transmitted over short distances to the spatial memory. This also makes it possible to store the status information in the memory at a very fast time interval. Via the output port 246, the status information can then easily and in high quality from the

Module be read out. For the normal operation of the inverter, the status information is sufficient, which are transmitted via the opti ^¬ cal communication link to the central control device 35. For normal operation, the status information at the central controller 35 need not be present at the fast timing (sample rate) with which the status information is stored in the memory. The status information is thus treated differently, depending on whether it is the status information required for normal operation or the status information required for error analysis (error evaluation). The error information used in the memory of the module status information is used. The status information stored in the memory thus complements the coarsely sampled status information which is present in the central control device 35, in particular during the later evaluation / examination.

The described module and the described method preferably make it possible, after occurrence of an irregularity in the operation of the multilevel converter, in particular after occurrence of a failure of a module, the cause of the Irregularity or for the failure of the module to examine ^¬ chen.

Claims

Patent claims 1. Module (201) of a modular multilevel power converter (1), which has at least two electronic switching elements (202, 206) and an electrical energy storage (210), which means that - the module (201) has a non-volatile electronic memory (230) for storing status information of the module determined during operation of the module. 2. Module according to claim 1, there is no sign that - the status information, measured values of the voltage of the electrical energy storage (210) and/or information about the Have switching states of the electronic switching elements (202, 206). 3. Module according to claim 1 or 2, there is no sign that - The module has a voltage measuring sensor (250) for measuring the voltage of the electrical energy storage (210). 4. Module according to one of the preceding claims, there is no sign that - The status information has measured values of the temperature of the module (201). 5. Module according to one of the preceding claims, there is no sign that - The module has a temperature measuring sensor (256) for measuring the temperature of the module. 6. Module according to one of the preceding claims, characterized in that - The module has a module control device (220) which is set up to store the status information in the memory (230). 7. Module according to one of the preceding claims, there is no sign that - The module has an output connection (246) for outputting the status information stored in the memory (230). 8. Module according to claim 7, there is no sign that - The output connection (246) is ^connected to the memory (230). 9. Module according to one of the preceding claims, there is no sign that - The two electronic switching elements (202, 206) of the ^module are arranged in a half-bridge circuit. 10. Module according to one of the preceding claims, there is no sign that - The module (201) has the two electronic switching elements (202, 206) and two further electronic switching elements (302, 306), the two electronic switching ^elements (202, 206) and the two further electronic switching elements (302, 306) are arranged in a full bridge circuit. 11. Module according to one of the preceding claims, there is no sign that - The memory is a ring memory (230). 12. Module according to one of the preceding claims, there is no sign that - after an irregularity occurs in the operation of the module, those stored in the memory (230) of the module Status information can be read out at the output connection (246) of the module in order to enable an evaluation of the status information external to the module. 13. Module according to one of the preceding claims, there is no sign that - The electronic switching elements (202, 206), the electrical energy storage (210) and the memory (230) form a structural unit. 14. Module according to one of the preceding claims, there is no sign that - The memory (230) enables the status information to be stored at intervals of a few nanoseconds, in particular at intervals between 10 and 10,000 nanoseconds. 15. Modular multilevel power converter (1) with at least one module (1_1), in particular with a plurality of modules (1_1 ... 6_n+4), according to one of claims 1 to 14. 16. High-voltage direct current transmission system (501) with a modular multilevel power converter (1) according to claim 15. 17. Reactive power compensation system (601) with a modular multilevel power converter (1) according to claim 15. 18. Method for storing status information in a multilevel power converter (1) which has a large number of modules (201, 301), the modules each having at least two electronic switching elements (202, 206) and an ^electrical energy storage (210), whereby in the procedure - During operation of the multilevel converter, status information is determined (402) in one of the modules (201) that relates to this module, and - The status information is stored in a non-volatile electronic memory (230) of the module (201) (404). 19. Method according to claim 18, there is no sign that - Measured values of the voltage of the electrical energy storage (210) and/or information about the switching states of the electronic switching elements (202, 206) are stored as status information. 20. Method according to claim 18 or 19, there is no sign that - the voltage of the electrical energy storage (210) using a voltage measuring sensor (250) to form the Measured values of the voltage of the electrical energy storage device are ^measured . 21. Method according to one of claims 18 to 20, there is no sign that - Measured values of the temperature of the module (201) are saved as status information. 22. Method according to one of claims 18 to 21, there is no sign that - The temperature of the module (201) is measured by means of a temperature measuring sensor (256) to form the measured temperature values. 23. Method according to one of claims 18 to 22, there is no sign that - The status information is stored in the memory (230) by a module control device (220). 24. Method according to claim 23, characterized in that - Part of the status information is transmitted from the module control device (220) via an optical communication connection (37) to a central control device (35) of the power converter, whereby the temporal resolution of the status information stored in the memory (230) is greater, in particular greater by at least a factor of 10, than the temporal resolution of the part of the status information that is transmitted to the central control device (35). 25. Method according to one of claims 18 to 24, there is no sign that - the status information stored in the memory (230) of the module is made available for output at an output connection (246) of the module in order to enable an evaluation of the status information external to the module after an ^irregularity occurs in the operation of the module. 26. Method according to one of claims 18 to 25, there is no sign that - The output connection (246) is ^connected to the memory (230). 27. Method according to one of claims 18 to 26, there is no sign that - The memory is a ring memory (230). 28. Method according to one of claims 18 to 27, there is no sign that - The status information is stored in the memory (230) at intervals of a few nanoseconds, in particular at intervals between 10 and 10,000 nanoseconds. 29. Method according to one of claims 18 to 28, there is no sign that - The two electronic switching elements (202, 206) of the ^module (201) are arranged in a half-bridge circuit. 30. The method according to one of claims 18 to 29, d a d u r c h g e k e n n z e i c h n e t that - The module (301), the two electronic switching elements (202, 206) and two further electronic switching elements (302, 306), wherein the two electronic switching ^elements (202, 206) and the two further electronic switching elements (302, 306) are arranged in a full bridge circuit.