Method for operating an electrical network

Abstract

Method for operating an electrical network including a first subnetwork and a second subnetwork which are connected to one another via a transformer and are DC-isolated from one another by the latter. A primary side of the transformer with a first number of turns is assigned to the first subnetwork and a secondary side of the transformer with a second number of turns is assigned to the second subnetwork. The first subnetwork has a multi-level converter having a plurality of individual modules, and each individual module has an electrical energy store. The multi-level converter provides at least one first incoming electrical AC voltage which is modulated with at least one second incoming electrical AC voltage. A resulting electrical voltage is made available to the transformer and is transformed by the transformer to an outgoing electrical voltage which is made available to the second subnetwork.

What is claimed is: 
     
         1 . A method for operating an electrical network comprising a first subnetwork and a second subnetwork which are connected to one another via a transformer and are DC-isolated from one another by the transformer,
 a primary side of the transformer with a first number of turns being assigned to the first subnetwork and a secondary side of the transformer with a second number of turns being assigned to the second subnetwork,   the first subnetwork having a multi-level converter having a plurality of individual modules, each individual module having an electrical energy store,   the multi-level converter providing at least one first incoming electrical AC voltage which is modulated with at least one second incoming electrical AC voltage, a resulting electrical voltage being made available to the transformer and being transformed by the transformer to an outgoing electrical voltage which is made available to the second subnetwork.   
     
     
         2 . The method as claimed in  claim 1 , in which provision is made for the at least one first incoming AC voltage to have an amplitude with a first value and a frequency with a first value, and for the at least one second incoming AC voltage to have an amplitude with a second value and a frequency with a second value, the first value of the amplitude of the at least one first incoming AC voltage being set to be greater than the second value of the amplitude of the second incoming AC voltage, and the first value of the frequency of the at least one first incoming AC voltage being set to be less than the second value of the frequency of the at least one second incoming AC voltage. 
     
     
         3 . The method as claimed in  claim 1 , in which the at least one first incoming AC voltage is modulated with the at least one second incoming AC voltage at a reference point of the multi-level converter. 
     
     
         4 . The method as claimed in  claim 3 , in which a neutral point of the multi-level converter is selected as the reference point. 
     
     
         5 . The method as claimed in  claim 1 , in which the at least one second incoming AC voltage is modulated onto the at least one first incoming AC voltage, the resulting voltage being provided as a sum of the incoming AC voltages. 
     
     
         6 . The method as claimed in  claim 1 , in which the multi-level converter provides a plurality of incoming first AC voltages which are phase-shifted with respect to one another and are modulated with the at least one second incoming AC voltage. 
     
     
         7 . A multi-level converter configured to be arranged in an electrical network, the electrical network comprising a first subnetwork and a second subnetwork,
 the first and second subnetworks are configured to be connected to one another via a transformer and are configured to be DC-isolated from one another by the transformer,   a primary side of the transformer with a first number of turns is to be assigned to the first subnetwork and a secondary side of the transformer with a second number of turns is to be assigned to the second subnetwork,   the multi-level converter is configured to be arranged in the first subnetwork and has a plurality of individual modules, each individual module having an electrical energy store,   the multi-level converter being configured to provide at least one first incoming electrical AC voltage and to modulate the at least one first incoming electrical AC voltage with at least one second incoming electrical AC voltage,   a resulting electrical voltage is to be (i) made available to the transformer, (ii) transformed by the transformer to an outgoing electrical voltage, and (iii) made available to the second subnetwork.   
     
     
         8 . The multi-level converter as claimed in  claim 7 , which is assigned a monitoring unit which is configured to set values of at least one physical parameter of either the first incoming electrical AC voltage or the second incoming electrical AC voltage. 
     
     
         9 . The multi-level converter as claimed in  claim 7 , in which at least two individual modules have the same design. 
     
     
         10 . The multi-level converter as claimed in  claim 7 , which is configured to produce the at least one first incoming AC voltage from an individual voltage from an energy store of at least one of the individual modules. 
     
     
         11 . The multi-level converter as claimed in  claim 10 , which is configured to connect at least two of the individual modules in series or in parallel with one another and to provide the at least one first incoming AC voltage from a combination of individual voltages of the at least two individual modules to be combined with one another. 
     
     
         12 . The multi-level converter as claimed in  claim 7 , which has a plurality of sections, each section having a combination of a plurality of individual modules connected to one another, and each section is respectively to be used to produce the first incoming AC voltage. 
     
     
         13 . The multi-level converter as claimed in  claim 7 , which is assigned at least one additional energy store which is configured to provide the at least one second incoming AC voltage. 
     
     
         14 . The multi-level converter as claimed in  claim 7 , in which energy stores of the individual modules are in the form of DC voltage sources, the multi-level converter having at least one converter which is configured to convert an individual voltage in the form of a DC voltage from an energy store of at least one of the individual modules into an AC voltage and to provide the at least one first incoming AC voltage therefrom. 
     
     
         15 . An energy supply system having an electrical network comprising a first subnetwork and a second subnetwork which are connected to one another via a transformer and are DC-isolated from one another by the transformer,
 a primary side of the transformer with a first number of turns being assigned to the first subnetwork and a secondary side of the transformer with a second number of turns being assigned to the second subnetwork,   the first subnetwork having a multi-level converter having a plurality of individual modules, each individual module having an electrical energy store,   the multi-level converter being configured to provide at least one first incoming electrical AC voltage and to modulate the first incoming electrical AC voltage with at least one second incoming electrical AC voltage, and a resulting electrical voltage is to be made available to the transformer, the transformer being configured to transform the resulting electrical voltage into an outgoing electrical voltage and to make the outgoing electrical voltage available to the second subnetwork.   
     
     
         16 . The energy supply system as claimed in  claim 15 , in which the first number of turns of the primary side of the transformer is greater than the second number of turns of the secondary side of the transformer. 
     
     
         17 . The energy supply system as claimed in  claim 15 , which is to be arranged in a motor vehicle. 
     
     
         18 . The energy supply system as claimed in  claim 15 , in which an electrical machine is assigned to the first subnetwork as consumer and has a plurality of phases, the multi-level converter being configured to respectively provide each phase with the first incoming electrical AC voltage.