Method and apparatus for operating a converter in a converter-based power distribution system, and power distribution system having a plurality of converter-based power transmission units

1. A method for operating a converter in an energy distribution system, wherein, by means of the converter, an electrical energy provided by a source is fed into an AC electricity network at a coupling point or electrical energy is drawn from the AC electricity network at the coupling point, wherein the AC electricity network is coupled at further coupling points to further converters for feeding in or drawing electrical energy, wherein the AC electricity network can be connected to a further electricity distribution network at a connection point in order to feed the electrical energy to remote loads or to obtain the electrical energy from remote energy sources, wherein the converter has an inverter provided with power switches in order to provide an electrical variable, comprising the following steps:

providing one or a plurality of system state variables indicating a system state of the electricity network;

selecting one of a plurality of commutation patterns depending on the one or the plurality of system state variables; and

driving the inverter according to the selected commutation pattern,

wherein the one or the plurality of system state variables comprise(s) at least one of the following variables:

an indication about an active and/or reactive power present at the coupling point;

an indication about a harmonic spectrum of the electrical variable at the connection point in the electricity network;

an indication about an impedance or a frequency-dependent impedance profile of the electricity network at at least one point of the AC electricity network;

an indication about an active and/or reactive power transmitted by the electricity network; and

an indication about a configuration of the energy distribution system,

wherein the one or the plurality of system state variables comprise(s) an indication about a resonant frequency of the energy distribution system, wherein the commutation pattern is selected such that a reduced or no excitation takes place at the resonant frequency.

2. The method as claimed in claim 1 , wherein the one of the plurality of commutation patterns is selected depending on identification information identifying the converter.

3. The method as claimed in claim 1 , wherein the one or the plurality of system state variables is or are received or detected via an external communication connection.

4. The method as claimed in claim 1 , wherein the plurality of selectable commutation patterns, upon provision of an in-phase fundamental of the electrical variable, bring about harmonics which have different phase angles and are provided in antiphase.

5. The method as claimed in claim 1 , wherein the plurality of commutation patterns differ from one another in terms of a switching specification and/or a switching frequency.

6. The method as claimed in claim 1 , wherein the commutation pattern comprises a predefined switching scheme or a switching scheme generated online.

7. The method as claimed in claim 6 , wherein the switching scheme generated online is carrier-based.

8. An energy distribution system comprising a plurality of converters for a plurality of sources of electrical energy, the energy distribution system feeding electrical energy provided by the sources into an AC electricity network at coupling points or for drawing electrical energy from the AC electricity network at the coupling points, wherein the AC electricity network can be connected to a further electricity distribution network at a connection point in order to feed the electrical energy to remote loads or to obtain the electrical energy from remote energy sources,

wherein each of the converters has an inverter provided with power switches for providing an electrical variable, and a control unit for driving the inverter,

wherein the control unit is designed

to obtain one or a plurality of system state variables indicating a system state of the AC electricity network;

to select one of a plurality of commutation patterns depending on the one or the plurality of system state variables; and

to drive the inverter according to the selected commutation pattern,

wherein the control unit is designed to obtain one or a plurality of the following system state variables and to select one of a plurality of commutation patterns depending on the one or the plurality of the following system state variables:

an indication about an active and/or reactive power present at the coupling point;

an indication about a harmonic spectrum of the electrical variable at a connection point or the coupling point in the electricity network;

an indication about an impedance or a frequency-dependent impedance profile of the electricity network at at least one point of the AC electricity network;

an indication about an active and/or reactive power transmitted by the electricity network; and

an indication about a configuration of the energy distribution system

wherein the respective converters are provided with different selection schemes such that, in the case of an indicated system state, the converters select commutation patterns which result in at least one partial cancellation for at least one harmonic of the electrical variable on the AC electricity network.

9. The energy distribution system as claimed in claim 8 , wherein the control unit is designed to obtain the one or the plurality of system state variables via an external communication connection, and/or wherein the control unit has a detection unit in order to detect the one or the plurality of system state variables.

10. The energy distribution system as claimed in claim 8 , wherein a storage unit for storing identification information is provided, such that one of the plurality of commutation patterns is selected depending on the identification information of the converter.

11. An energy transmission system comprising the converters as claimed in claim 8 and comprising a load that obtains electrical energy via one of the converters, or one of the sources that feed electrical energy into the AC electricity network via one of the converters.

12. The energy distribution system as claimed in claim 8 , wherein the converters are operated with a respective commutation pattern that is dependent on the location of their respective coupling point in the electricity network.

13. The energy distribution system as claimed in claim 8 , wherein at least two of the converters are designed to be operated with complementary commutation patterns which bring about in antiphase the electrical variables for at least one harmonic in the AC electricity network.

14. The energy distribution system as claimed in claim 8 , wherein a detection unit is provided in order to detect the system state and to communicate it to one or a plurality of the converters.

15. The energy distribution system as claimed in claim 8 , wherein at least one filter unit is provided in order to carry out a filtering of harmonics in the electricity network depending on the system state.

16. The energy distribution system as claimed in claim 8 , wherein the converters are implemented in each case with an assigned selection scheme, such that they are operated with commutation patterns which minimizes the resulting defined harmonic spectrum on the AC electricity network at least in a predefined frequency range.

17. A method for operating the plurality of converters in an energy distribution system as claimed in claim 8 , wherein commutation patterns are selected by each of the converters in the case of an indicated system state in accordance with the assigned selection scheme so as to result in at least one partial cancellation for at least one harmonic of the electrical variable on the AC electricity network.

18. A method for operating a converter in an energy distribution system, wherein, by means of the converter, an electrical energy provided by a source is fed into an AC electricity network at a coupling point or electrical energy is drawn from the AC electricity network at the coupling point, wherein the AC electricity network is coupled at further coupling points to further converters for feeding in or drawing electrical energy, wherein the AC electricity network can be connected to a further electricity distribution network at a connection point in order to feed the electrical energy to remote loads or to obtain the electrical energy from remote energy sources, wherein the converter has an inverter provided with power switches in order to provide an electrical variable, comprising the following steps:

providing one or a plurality of system state variables indicating a system state of the electricity network;

selecting one of a plurality of commutation patterns depending on the one or the plurality of system state variables; and

driving the inverter according to the selected commutation pattern,

wherein the one or the plurality of system state variables comprise(s) at least one of the following variables:

an indication about an active and/or reactive power present at the coupling point;

an indication about a harmonic spectrum of the electrical variable at the connection point in the electricity network;

an indication about an impedance or a frequency-dependent impedance profile of the electricity network at at least one point of the AC electricity network;

an indication about an active and/or reactive power transmitted by the electricity network; and

an indication about a configuration of the energy distribution system,

wherein the commutation pattern comprises a predefined switching scheme or a switching scheme generated online; and

wherein the switching scheme generated online is carrier-based.

19. The method as claimed in claim 18 , wherein the one of the plurality of commutation patterns is selected depending on identification information identifying the converter.

20. A method for operating a converter in an energy distribution system, wherein, by means of the converter, an electrical energy provided by a source is fed into an AC electricity network at a coupling point or electrical energy is drawn from the AC electricity network at the coupling point, wherein the AC electricity network is coupled at further coupling points to further converters for feeding in or drawing electrical energy, wherein the AC electricity network can be connected to a further electricity distribution network at a connection point in order to feed the electrical energy to remote loads or to obtain the electrical energy from remote energy sources, wherein the converter has an inverter provided with power switches in order to provide an electrical variable, comprising the following steps:

providing one or a plurality of system state variables indicating a system state of the electricity network;

selecting one of a plurality of commutation patterns depending on the one or the plurality of system state variables; and

driving the inverter according to the selected commutation pattern,

wherein the one or the plurality of system state variables comprise(s) at least one of the following variables:

an indication about an active and/or reactive power present at the coupling point;

an indication about a harmonic spectrum of the electrical variable at the connection point in the electricity network;

an indication about an impedance or a frequency-dependent impedance profile of the electricity network at at least one point of the AC electricity network;

an indication about an active and/or reactive power transmitted by the electricity network; and

an indication about a configuration of the energy distribution system,

wherein the plurality of selectable commutation patterns, upon provision of an in-phase fundamental of the electrical variable, bring about harmonics which have different phase angles and are provided in antiphase.