WO2013045174A1

WO2013045174A1 - Distributing data in a control system of a power converter

Info

Publication number: WO2013045174A1
Application number: PCT/EP2012/066087
Authority: WO
Inventors: Patrick Bohren
Original assignee: Abb Technology Ag
Priority date: 2011-08-18
Filing date: 2012-08-17
Publication date: 2013-04-04

Abstract

A power converter (12) comprises a building block (24) and a control system (30), wherein the building block (24) comprises power electronics. The control system (30) comprises a master control unit (26a) and at least one slave control unit (26b, c) for controlling the power electronics of the building block (24). A method for controlling the power converter (12), comprises the steps of: Updating slave device specific data in a memory area (42b) of at least one slave control unit (26b, c); Transferring the device specific data of the slave control unit (26b, c) to the master control unit (26a); Updating the slave device specific data of the slave control unit (26b, c) in a memory area (42a) of the master control unit (26a); Updating device specific data of the master control unit (26a) in the memory area (42a) of the master control unit (26a); Transferring data of the memory area (42a) of the master control unit (26a) to the at least one slave control unit (26b, c); Updating the memory area (42b) of the at least one slave control unit (26b, c) with the transferred data from the master control unit (26a); and controlling the building block (24) with the at least one slave control unit (26b, c) according to the device data in the memory area (42b) of the at least one slave control unit (26b, c).

Description

DESCRIPTION

Distributing data in a control system of a power converter

FIELD OF THE INVENTION

The invention relates to the field of high power electronics. In particular, the invention relates to a method for controlling a power converter, a computer program, a computer readable medium, a control system and a power converter.

BACKGROUND OF THE INVENTION

For generation an alternating current for an electrical drive, a power converter may be used, which may comprise a rectifier, DC-link and inverter. Especially in high power converters, the rectifier, DC-link and the inverter are modularized into building blocks, which process only a part of the current and which may independently be exchanged. Usually each building block comprises an associated control unit, which controls the power electronic component of the respective building block.

There are other applications of high power converters with modularized building blocks, for example for interconnecting two power grids.

To operate a converter with multiple independent control units, a communication between the control units is needed. For example, the control units may have a communication topology, where each slave control unit sends its status information in a message to a master control unit. The master control unit then processes the received information and combines the slave control unit information with its own information, which is after that distributed to the slave control units. This approach may have the disadvantage that due to the processing of each message in the master drive, additional time delay is introduced. Additionally, the processing needs calculation power and due the collection and rearranging of status information, an extension of the software is rather complicated. DESCRIPTION OF THE INVENTION

It is an object of the invention to provide a converter with modularized control units that has short dead times in the communication between the control units.

This object is achieved by the subject-matter of the independent claims. Further exemplary embodiments are evident from the dependent claims and the following description.

An aspect of the invention relates to a method for distributing data in a control system of a power converter and for controlling the power converter.

The control system may comprise a plurality of control units which are adapted for controlling power semiconductors of the power converter. The control units may be equally designed. One of the control units may be configured as a master control unit and the other control units may be configured as slave control units. The power converter may comprise one or more power electronic building blocks and each power electronic building block may be associated with or may comprise a (slave) control unit of the control system. The system may comprise only one slave control unit. The control system may comprise a main control unit that is not associated with a building block.

According to an embodiment of the invention, the method comprising the steps of: Updating slave device specific data in an memory area of the slave control unit; Transferring the device specific data of the slave control unit to the master control unit; Updating the slave device specific data of the slave control unit in an memory area of the master control unit; Updating device specific data of the master control unit in the memory area of the master control unit; Transferring data of the memory area of the master control unit to the slave control unit; Updating the memory area of the slave control unit with the transferred data from the master control unit; Controlling a building block with the associated slave control unit according to the device data in the memory area of the slave control unit.

In other words, each of the control units comprises an interface, which is a memory area of the control unit. The memory area may be separated from the control functions controlling the power semiconductors. The data in the memory area may be transferred between the control units independent from the operation of these control functions. Furthermore, the control functions may access data in the memory area without taking care for the distribution of the data. The control system may therefore have transparent data distribution, transparent data exchange and/or transparent data update (transparent with respect to the control functions).

Because of the transparent data distribution, the system may easy be extended or updated.

After the data distribution, the memory areas of all control units may contain the same data (information). In such a way, each control unit may get all information or data of all other control units instead of getting only a preprocessed and reduced information set.

The control system may comprise a plurality of slave device control units, for example a first slave control unit and a second slave control unit.

According to an embodiment of the invention, the method comprises the steps of: Updating slave device specific data in a memory area of the first slave control unit, and slave device specific data in an memory area of the second slave control unit; Transferring the device specific data of the first slave control unit and the second slave control unit to the master control unit; Updating the slave device specific data of the first slave control unit and the second slave control unit in a memory area of the master control unit; Updating device specific data of the master control unit in the memory area of the master control unit; Transferring data of the memory area of the master control unit to the first slave control unit and the second slave control unit; and Updating the memory area of the first slave control unit and the memory area of the second slave control unit with the transferred data from the master control unit.

The data distribution may be executed by a distribution module of a control unit and a control of power semiconductors may be executed by a control module of the control unit. For distributing the data between the control units, no interactions between the distribution module and the control module is needed which may make the data distribution very fast. A further aspect of the invention relates to a computer program, which, when being executed by at least one processor (processors of the control units), is adapted to carry out the steps of the method as described in the above and in the following.

A further aspect of the invention relates to a computer readable medium in which such a computer program is stored. For example, the computer program may be stored in a non- volatile memory of a control unit. For example, a computer-readable medium may be a floppy disk, a hard disk, an USB (Universal Serial Bus) storage device, a RAM (Random Access Memory), a ROM (Read Only memory) and an EPROM (Erasable Programmable Read Only Memory). A computer readable medium may also be a data communication network, e.g. the Internet, which allows downloading a program code.

A further aspect of the invention relates to a control system of a power converter, wherein the control system comprises a plurality of control units interconnected by a communication system and wherein the control system is adapted for executing the steps of the method as described in the above and the following.

It has to be understood that features of the method as described in the above and in the following may be features of the system as described in the above and in the following.

A further aspect of the invention relates to a power converter, which comprises a control system as described in the above and in the following and a plurality of building blocks comprising power semiconductors. Each building block of the power converter is associated with a control unit of the control system. In such a way the data communication between the building blocks may be transparent and fast.

These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter of the invention will be explained in more detail in the following text with reference to exemplary embodiments which are illustrated in the attached drawings. Fig.1 schematically shows a drive system according to an exemplary embodiment of the invention.

Fig.2 schematically shows a control system according to an embodiment of the invention.

Fig. 3 schematically shows a control system according to an embodiment of the invention.

Fig. 4 schematically shows a communication interface according to an embodiment of the invention.

Fig. 5 shows a flow diagram for a method for distributing data in a control system according to an embodiment of the invention.

Fig. 6 schematically shows a message according to an embodiment of the invention.

In principle, identical parts are provided with the same reference symbols in the figures. DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Fig. l shows a drive system 10 comprising a converter 12 supplying an electrical motor 14 with electrical power. For example, the converter 12 may be an ACS 6000 Multi drive or ACS 2000 drive from ABB.

The converter 12 is supplied by an electrical grid 16 which provides a multi-phase AC current which is rectified into a DC current by a rectifier 18 of the converter 12. The DC current is supplied to an inverter 20 via a common DC-link 22, which is interconnected between the rectifier 18 and the inverter 20. The inverter 20 generates the AC current for the electrical motor 14 from the DC current in the DC link 22.

The rectifier 18 and the inverter 20 (as well as other component of the converter 20) comprise building blocks 24, each of which comprises power electronics for switching medium or high voltages and/or medium or high currents. For example, a building block 24 may be a module or unit of the converter 12 that may be easy installed in the converter 12 ant that may be easily exchanged. The power electronics may be power semiconductors.

Each building block 24 comprises a control unit 26 for controlling the building block 24 and in particular the power semiconductors of the building block 26.

The converter 12 may further comprise an auxiliary control unit 28, for example for controlling a further component of the converter 12 like a low voltage source.

The auxiliary control unit 28 may be seen as a further control unit 26 of a control system 30 of the converter 12.

A control unit 26 may be built in the building block 24 (part of the building block). However, it may be possible that a control unit 26 is a separate exchangeable unit or module of the converter 12.

Fig. 2 shows a control system 30 of a converter 12 in more detail. The control system 30 comprises a plurality of control units 26a, 26b, 26c that are interconnected via a communication link 32. The control units 26a, 26b, 26c (and the building block 24) may be seen as link participants of the communication link 32.

The control units 26a, 26b, 26c may be designed equally and each control unit 26a, 26b, 26c may comprise a control module 34a, 34b, 34c for controlling the power electronics, a data distribution module 36a, 36b, 36c and a communication module 38a, 38b, 38c.

In the following the functionality of the modules (which may be software modules or which may be units of the control system 30 with hardware of its own) will be explained with respect to the control unit 26a. However, unless otherwise stated, the functionality and design of the modules of the control units 26a, 26b, 26c is the same.

The control module 34a may be a board with a processor on which software for controlling power electronics is running. The control module 26a may be adapted to control power semiconductors of an associated building block 24 of the power converter 12. The control module 26a may execute control functions for controlling the associated building block 24.

The data distribution module 36a may be adapted for storing device specific values received from the control module 26a and the communication module 38a in an interface 42a, which may be a memory area of the data distribution module 36a. The data distribution module 36a may be adapted for preprocessing data stored in the interface 42a, for example for calculating comprehensive values, like sum values, from data stored in the interface 42a.

The data distribution module 36a may be a further board with a further processor on which software for managing the data distribution between the different control units 26a, 26b, 26c is running. These tasks may be performed by an FPGA of the data distribution module 36a. In such a way, it is possible to implement calculations (preprocessing) or boolean logic already on a hardware level (FPGA) of the control unit 26a for accelerating the data update. However, the data distribution module 36a may be a part of the board of the control module 34a.

The control module 34a may be interconnected with the data distribution module 36a via a parallel interface or PCIe 40 and may be adapted to access the interface 42a of the data distribution module 36a for exchanging data with the data distribution module 36a. For example, the interface 42a of the data distribution module 36a is a memory area 42a of the data distribution module 36a, which is accessible for reading and/or writing from the control module 34a. Because of the data distribution module 36a, the data exchange between the control units 26a may be independent from software functions of the control module 26a.

The communication module 38a may be adapted for data communication with a communication module 38b of a further control unit 26b (slave control unit). The communication module 38a may be a further board with a further processor or may be part of the control module 34a or the data communication module 36a. The data distribution module 36a of the control unit 26a may be adapted to send data messages via the communication module 38a to one of the other control units 26b, 26c.

The control units 26a, 26b, 26c may be interconnected in different manners. The communication link 32 may have different topologies. Each control unit 26a, 26b, 26c connected to the communication link 32 may write (or send) its own status information or signals (data) it wants to make available to the other control units 26a, 26b, 26c in a dedicated interface 42a, 42b, 52c. The underlying transportation layer takes the data and delivers them to the other control units 26a, 26b, 26c of the communication link 32. This can for example be done either in a ring connection or as star topology.

For example, in Fig. 2, the communication module 38a is adapted for sending data messages to communication modules 38b, 38c via glass fibre cables 44a, 44b comprising two channels for interchanging messages in both directions. In particular, the control unit 26a is connected with the glass fibre cable 44a with the control unit 26b and with the glass fibre cable 44b with the control unit 26c. The communication modules 38b, 38c may only send messages to the communication module 38a. With this design, the communication link 32 may have star topology. A star topology may have the advantage that some additional fast processing independent of the control module 34a is possible (as summing up the power or current consumption of the building blocks 24) and may reduce additionally the communication time to get control units 26a, 26b, 26c updated.

In other words, the control system 30 may comprise a star connected communication network 32 with transparent data exchange between all devices in the system.

Summarized, the master control unit 26a and the first and second slave control units 26a, 26b may be interconnected in a star topology.

As another example, the communication modules 38a, 38b, 38c shown in Fig. 3 are adapted for sending massages over an Ethernet link 46 and the communication link 32 may comprise Ethernet connections. In such a way, each control unit 26a, 26b, 26c is adapted to send messages to each other control unit 26a, 26b, 26c. Instead of a star connected communication network 44a, 44b with e.g. fibre optic communication channels, an Ethernet network 46 may also be used.

In this case, a real star connection topology may be used.

Alternatively, a virtual start topology may be implemented as following: The control units 26a, 26b, 26c send the information they want to distribute as broadcast message over the Ethernet link 46. As each control unit 26a, 26b, 26c sends ist data by broadcast message, each control unit 26a, 26b, 26c becomes virtually a star point with the same possibilities as described above.

The communication channels 44a, 44b, 46 may provide a physical layer that supports CRC (cyclic redundancy check) protection (or error correcting code) of the transported information to ensure reliable data content.

The communication modules 38a, 38b, 38c may provide a data transportation layer that is adapted to send messages of different lengths.

With the data distribution modules 36a, 36b, 36c a protocol layer may be implemented that defines one or more message types with which device specific data from the control modules 26a, 26b, 26c and data preprocessed by the data distribution modules 36a, 36b, 36c may be transported between the control units 26a, 26b, 26c. In particular, the protocol layer established by a data distribution module 36a may preprocess certain data to lower the control processor load of the control module 34a and to fasten the update. This could be used e.g. for calculating the sum of the actual power or current.

In addition to the transportation layer an additional protocol layer may be used which makes certain pre-calculations or sums up of status information without the need of software interactions of the control module 34a.

One of the control units 26a, 26b, 26c may be configured as a master control unit 26a. The other control units may be configured as at least one slave control unit 26b, 26c. In the case of the star-connected topology of the system 30 of Fig. 2, this is the control unit 26a. In the case of the topology of Fig. 3, every control unit 26a, 26b, 26c may be configured as the master control unit. Since the control units 26a, 26b, 26c may be equally designed, the respective control unit 26a may be simply reconfigured by exchanging software in the data distribution unit 36 or by changing configuration parameters of the data distribution unit 36.

Summarized, the master control unit 26a and the first and second slave control unit 26b, 26c may be equally designed on the hardware level and the master control unit 26a and the first and second slave control unit 26b, 26c may be configured by software.

The master control unit 26a may have some more functions built in, but the control module 34a may have no more information available as all other control modules 34b, 34c. The control modules 34a, 34b, 34c may be equally designed may run the same software.

It may be possible to reconfigure the system 30 and/or to transfer the master functions to another control unit 26b, 26c on the fly. Also due to the flexible configuration possibility, it is possible to transfer additional data which is only used by part of the control units 26a, 26b, 26c.

The transportation layer may take care of delivering all the data which is received from each individual control unit 26a, 26b, 26c to all other control units 26a, 26b, 26c. With this implementation, all participating control units 26a, 26b, 26c may get all information equitable.

Since each power electronic building block 24 of the converter 12 may comprise a control unit 26, the control system 30 may simplify the communication between individual power electronic building blocks 24 at the same DC link 22 in for example a medium voltage multi drive system 10. The control system 30 may be easily extended due to the flexible design, e.g. for adding more building block 24 to the DC link 22 or other control devices to the communication link 32 or to transfer more data between the control units 26. Additionally the data distribution may be independent on the used physical transportation layer, which could be for example fiber optics or a serial link.

Fig. 4 shows an example of a communication interface 42a over which the control module 34a may interchange data with the data distribution module 36a. The interfaces 42b, 42c may be equally designed like the interface 42a.

The communication interface 42a may be a memory area 42a, which contains a comprehensive section 50 and device specific sections 52a, 52b, 52c.

In the comprehensive section 50, comprehensive data values 54 relating to all control units 26a, 26b, 26c may be stored and may be read by the respective control module 34a, 34b, 34c. An example of such a data value is the overall sum of power∑P, the power all building blocks 24 of the rectifier 18 and/or the inverter 20 are currently processing.

In the device specific sections 50a, 50b, 50c, device specific data values 56 relating to one specific control unit 26a, 26b, 26c may be stored and read by the control modules 34a, 34b, 34c. The data values of the device specific section 50a, 50b, 50c may be written be the associated control module 34a, 34b, 34c and may be write protected for the other control modules 34a, 34b, 34c. Examples of such data values are the power P the power semiconductors of a building block 24 are currently processing and different status values Si, S_¾ S₃ of a building block 24. ∑P may be the sum of the powers P of all device specific sections 50a, 50b, 50c.

Summarized, the interface 42a may comprise device specific data 50a, 50b, 50c which may comprise device specific values P, SI, S2, S3 and/or comprehensive data 50 which may comprise comprehensive values∑P. The device specific data may comprises a power value P and/or a status value SI of a control unit 26a. The interface 42a of a control unit 26a may comprise a memory area 42a of a memory of the control unit 26a. A device specific value P, SI, S2, S3 and a comprehensive value∑P may be stored in the memory area 42a.

Each of the interfaces 42a, 42b, 42c may be seen as a communication interface between independent control units 26a, 26b, 26c in a common dc link drive 12 where the control units 26a, 26b, 26c may be up to several motor control units or up to several active frontend control units or up to several auxiliary control units where the individual status information of the control units 26a, 26b, 26c are distributed independently by the control module or processor 34a, 34b, 34c.

Fig. 5 shows a flow diagram for a method for distributing data in a control system 30. In principle, the slave control units 26b, 26c are responsible for updating their device specific data values 56 and the master control unit 26a is responsible for distributing the data.

In step S10, the control module 34b of the slave control unit 26b updates its device specific data values 56 in the device specific section 50b via the interface 42b, for example by writing them in the memory area 42b of the data distribution unit 36b of the controller unit 26b.

The method may comprise the step of updating slave device specific data 50b in an interface 42b of a first slave control unit 26b.

In step S12, the data distribution unit 36b of the slave control unit 26b composes a message of the device specific data values 56 of the section 50b and sends the message via the communication module 38b of the slave control unit 26b to the master control unit 26a.

The method may comprise the step of transferring the device specific data 50b of the first slave control unit 26b to the master control unit 26a.

In step SI 4, the message is received by the communication module 38a of the master control unit 26a, dispatched by the data distribution module 36a of the master control unit 26a and the data values 56 of the slave control unit 26b are written by the data distribution unit 36a of the master control unit 26a into the device specific section 50b of the interface 42a of master control unit 26a.

Steps S10 and S12 are analogically performed by the other slave control units 26c and the received messages are dispatched by the master control unit 26a like in step S14. In step S I 6, the control module 34a of the master control unit 26a updates its device specific data values 56 in the device specific section 50a via the interface 42a, for example by writing them in the memory area 42a of the data distribution unit 36a of the master control unit 26a.

The method may comprise the step of updating the slave device specific data 50b of the first slave control unit 26b in an interface 42a of the master control unit 26a.

In step S I 8, the data distribution module 36a of the master control unit 26a calculates the overall power∑P by adding the device specific power values P and writes this data value 50 into the interface 42a of the master control unit 26a.

The method may comprise the step of calculating a comprehensive data value∑P with the master control unit 26a. The comprehensive data value∑P may updated or stored in the interface 42a of the master control unit 26a and may be later transferred to the first and/or second slave control unit 26b, 26c. The comprehensive data value∑P may be calculated from device specific values P and/or may be a sum of device specific values P.

Now, all data values in the interface 42a of the master control unit 26a are updated values (after a first time cycle).

In step S20, the data distribution unit 36a of the master control unit 26a composes a message of the data values 54, 56 of the interface 42a of the master control unit 26a and sends this message to a first slave control unit 26b. As an alternative, only the data values of the comprehensive section 50 and the device specific sections 50c of the other slave control units 26c are used for composing the message. The same information may be sent to all control units 26a, 26b, 26c from the star point or individually message contents may be used (for example do not send the own status of a control unit downwards).

The method may comprise the step of transferring data of the interface 42a of the master control unit 26a to the first slave control unit 26b.

In step S22, the message is received by the communication module 38b of the first slave control unit 26b and dispatched by the data distribution module 36b of the slave control unit 26b. By the data distribution module 36b, the comprehensive data values 54 are written to the comprehensive section 50 and the device specific data values 56 are written to the respective device specific sections of the interface 42b of the slave control module 26b. The method may comprise the step of updating the interface 42b of the first slave control unit 26b and the interface 42b of the second control unit 26c with the transferred data from the master control unit 26a.

Steps S20 and S22 are analogically performed for the other slave control units 26c. In the end, all interfaces 42a, 42b, 42c of all control units 26a, 26b, 26c contain updated data values (after a second time cycle). These data values are locally stored in all control units 26a, 26b, 26c and may be read by the control module 34 of each control unit 26a, 26b, 26c.

In such a way, after a defined time all control units 26a, 26b, 26c get all information of all other control units 26a, 26b, 26c.

Fig. 6 shows a message 60 that may be sent between the control units 26a, 26b, 26c and that may be composed and evaluated by a data distribution module 36a, 36b, 26c The message 60 may comprise an address A, one (or more) fixed data fields P and generic data fields Di, D₂, D₃, D₄, ....

Such a message 60 may be encoded or decoded by a data distribution module 36a, 36b, 36c in the following way:

A fixed data value field P may always contain data associated with a specific place (or address) of the interface 42a, 42b, 42c.

For example, when sending such a message 60, the data distribution module 36a of the master control unit 26a writes the overall sum of power∑P into the fixed data field P. When receiving such a message, the data distribution module 36b, 36c of a slave control unit 26b, 26c will interpret the fixed data field P as the sum∑P and will write it into the specific place of the interface 42b, 42c.

On the other hand, when sending such a message 60, the data distribution module 36b, 36c of a slave control unit 26b, 26c will write the device specific power P into the fixed data field P.

When receiving such a message, the data distribution module 36a of the master control unit 26b will interpret the fixed data field P as the device specific power P of the respective control unit 26b 26c.

Summarized, during transfer of data from a slave control unit 26b, 26c to the master control unit 26a, the fixed data field P may be used for transferring a device specific value P from which the comprehensive value∑P is calculated. During transfer of data from the master control unit 26a to a slave control unit 26b, 26c, the fixed data field P may be used for transferring a comprehensive value∑P. In such a way, individually addressed data may be transferred.

The generic data fields Di, D₂, D₃, D₄ may be used for block transfer of data. Each of the data values 54, 56 have specific addresses in the memory area 42a (the same addresses as in 42b, 42c). The data value in the data field Di is written into the address A of the memory area 42a; the data value in the data field D₂ is written into the address A+l of the memory area 42a and so on. In such a way, block transfer of data may be used to transfer several data in one frame.

Summarized, data between the master control unit 26a and a slave control unit 26b, 26c may be transferred via a message 60 comprising a fixed data value field P and block transfer fields Di, D₂, D₃, D .

If only messages according to 60 are transferred, a fixed transfer schema is used to transfer data.

It is also possible that several types of messages are sent between the control units 26a, 26b, 26c. Such messages may include a message ID field to indentify the message content.

In general, the data which is transferred may be customized and may either contain a static information part (for example P) which may be transferred with highest priority and additional information which may be transferred with lower priority (for example Si). The high priority data may be sent cyclically, the low priority data may be sent paged.

A message ID may be added to static information or additional information. This may allow for adapting the message content dependent on some additional conditions.

While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art and practising the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single processor or controller or other unit may fulfil the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.

Claims

1. A method for controlling a power converter (12),

the power converter (12) comprising at least one building block (24) and a control system (30), wherein the at least one building block (24) comprises power electronics, wherein the control system (30) comprises a master control unit (26a) and at least one slave control unit (26b, c) for controlling the power electronics of the at least one building block (24),

the method comprising the steps of:

Updating slave device specific data in a memory area (42b, c) of at least one slave control unit (26b, c);

Transferring the device specific data of the at least one slave control unit (26b, c) to the master control unit (26a);

Updating the slave device specific data of the at least one slave control unit (26b, c) in a memory area (42a) of the master control unit (26a);

Updating device specific data of the master control unit (26a) in the memory area (42a) of the master control unit (26a);

Transferring data of the memory area (42a) of the master control unit (26a) to the at least one slave control unit (26b, c);

Updating the memory area (42b) of the at least one slave control unit (26b, c) with the transferred data from the master control unit (26a);

Controlling the at least one building block (24) with the at least one slave control unit (26b, c) according to the device data in the memory area (42b, c) of the at least one slave control unit (26b, c).

2. The method of claim 1,

wherein the device specific data comprises at least one of a power value (P) and a status value (Si) of a control unit (26a, 26b, 26c).

3. The method of claim 1 or 2, further comprising the steps of: Calculating a comprehensive data value (∑P) with the master control unit (26a), wherein the comprehensive data value (∑P) is updated in the memory area (42a) of the master control unit (26a) and transferred to the at least one slave control unit (26b, c).

4. The method of claim 3,

wherein the comprehensive data value (∑P) is a calculated from device specific values (P).

5. The method of one of the preceding claims,

wherein data between the master control unit (26a) and a slave control unit (26b,

26c) is transferred via a message (60) comprising a fixed data value field (P) and block transfer fields (Di).

6. The method of claim 5,

wherein during transfer of data from the master control unit (26a) to a slave control unit (26b, 26c), the fixed data value field (P) is used for transferring a comprehensive value

(∑P);

wherein during transfer of data from a slave control unit (26b, 26c) to the master control unit (26a), the fixed data value field (P) is used for transferring a device specific value (P) from which the comprehensive value (∑P) is calculated.

7. The method of one of the preceding claims,

wherein a device specific value (P, Si) and a comprehensive value (∑P) are stored in the memory area (42a, 42b, 42c).

8. A computer program, which, when being executed by at least one processor, is adapted to carry out the steps of the method of one of claims 1 to 7.

9. A computer readable medium in which a computer program according to claim 8 is stored.

10. A control system (30) of a power converter (12),

wherein the control system (30) comprises a master control unit (26a) and at least one slave control unit (26b, c) for controlling the power electronics of the at least one building block (24) interconnected by a communication system;

wherein the control system (30) is adapted for executing the steps of the method of one of the claims 1 to 7.

11. The control system (30) of claim 10,

wherein the control system (30) comprises a master control unit (26a) and at least two slave control units (26b, c) for controlling the power electronics of the at least one building block (24) interconnected by a communication system and wherein the communication system has a star topology.

12. The control system of claim 10 or 11,

wherein the master control unit (26a) and the at least one slave control unit (26b, 26c) are equally designed and the master control unit (26a) and the at least one slave control unit (26b, 26c) are configured by software.

13. The control system of one of claims 10 to 12,

wherein each control unit (26a, b, c) comprises a control module (34a, b, c), a data distribution module (36a, b, c) and a communication module (38a, b, c);

wherein each control module (34a, b, c) is adapted to control power semiconductors of an associated building block (24) of the power converter (12);

wherein the communication module (38a) of the master control unit (26a) is adapted for data communication with a communication module (38b, c) of a slave control unit (26b, c);

wherein each data distribution module (36a, b, c) is adapted at least one of

- for storing device specific values received from the control module (34a, b, c) and the communication module (38a, b, c) in a memory area (42a)

- and for preprocessing data stored in the memory area (42a).

14. A power converter ( 12), compri sing :

a control system (30) according to one of the claims 10 to 13;

at least one or a plurality of building blocks (24) comprising power semiconductors; wherein each building block (24) of the power converter (12) is associated with a control unit (26a, b, c) of the control system (30).