Abstract: A method for three-phase infeed of electrical power from a DC source into a three-phase AC grid by means of an inverter includes measuring phase-specific grid voltages of the three-phase AC grid, and determining a grid frequency from the measured phase-specific grid voltages. The method also includes generating phase-specific voltage reference values from the phase-specifically measured grid voltages and the determined grid frequency, and generating phase-specific target current values using phase-specific predetermined target current amplitude values, the phase-specific voltage reference values and respective grid voltage amplitudes.

Abstract: A method for three-phase infeed of electrical power from a DC source into a three-phase AC grid by means of an inverter includes measuring phase-specific grid voltages of the three-phase AC grid, and determining a grid frequency from the measured phase-specific grid voltages. The method also includes generating phase-specific voltage reference values from the phase-specifically measured grid voltages and the determined grid frequency, and generating phase-specific target current values using phase-specific predetermined target current amplitude values, the phase-specific voltage reference values and respective grid voltage amplitudes.

Abstract: A method for operating an island system is disclosed. The island system includes a group of voltage-controlling converters, wherein each of the voltage-controlling converters of the group are configured to convert power of respectively connected regenerative power sources into AC power in accordance with a respective frequency-power characteristic curve. The island system also includes a load having a power consumption that depends on a voltage amplitude of an AC voltage of the island system, and a control unit that is configured to transmit a default value of the voltage amplitude to the group of voltage-controlling converters. The method adapts the power to be consumed by the load.

Abstract: A method for operating an island system is disclosed. The island system includes a group of voltage-controlling converters, wherein each of the voltage-controlling converters of the group are configured to convert power of respectively connected regenerative power sources into AC power in accordance with a respective frequency-power characteristic curve. The island system also includes a load having a power consumption that depends on a voltage amplitude of an AC voltage of the island system, and a control unit that is configured to transmit a default value of the voltage amplitude to the group of voltage-controlling converters. The method adapts the power to be consumed by the load.

Abstract: The subject matter of the invention is a method for detecting an isolated network for an inverter (2) carrying a converter voltage that is adapted for connection in parallel with a grid (5) having a mains frequency and electric loads and that is decoupled from the grid (5) by a choke (3), a test signal being superimposed upon the converter voltage at a test frequency the frequency of which is smaller than the mains frequency, the amplitude of the test signal being much smaller than the nominal voltage amplitude of the mains voltage on the one side but still just large enough on the other side for changes in reactive power to be detectable as a result of the test signal, a reactive power share being determined, which oscillates with the test frequency, this share not being allowed to fall below an imposed minimum for an isolated operation to be reliably excluded.

Abstract: The subject matter of the invention is a method for detecting an isolated network for an inverter (2) carrying a converter voltage that is adapted for connection in parallel with a grid (5) having a mains frequency and electric loads and that is decoupled from the grid (5) by a choke (3), a test signal being superimposed upon the converter voltage at a test frequency the frequency of which is smaller than the mains frequency, the amplitude of the test signal being much smaller than the nominal voltage amplitude of the mains voltage on the one side but still just large enough on the other side for changes in reactive power to be detectable as a result of the test signal, a reactive power share being determined, which oscillates with the test frequency, this share not being allowed to fall below an imposed minimum for an isolated operation to be reliably excluded.