Abstract: To measure an insulation resistance of a DC voltage source connected to a split intermediate circuit, a midpoint potential of the DC voltage source is shifted by different operation of two voltage converters by way of which two poles of the DC voltage source are each connected to one of two parts of the split intermediate circuit. A change in a residual current across all lines that carry a current flowing across the intermediate circuit from the DC voltage source, resulting from the shifting of the midpoint potential of the DC voltage source, is measured.

Abstract: The disclosure relates to a device for electrolysis from photovoltaically generated DC power, including an electrolyzer and a DC/DC converter. The DC/DC converter is configured to feed DC power to the electrolyzer via a DC bus, wherein: the DC power is generated by a photovoltaic (PV) sub-generator connected to the DC/DC converter. The PV sub-generator is connected to the DC/DC converter via a first disconnector that is coupled to an isolation monitoring structure in such a way that closure of the first disconnector requires a successful check for sufficient isolation of the PV sub-generator. The PV sub-generator has a main string and a second disconnector arranged between the main string and the first disconnector. The second disconnector is coupled to a fault current monitoring circuit of the main string in such a way that the second disconnector is opened in the event that a predefinable limit value of the fault current is exceeded. The disclosure also relates to a method.

Abstract: A fail-safe operating method for a decentralized power generation plant DG includes determining a leakage capacitance of a generator of the DG before connecting the DG. The method also includes comparing the determined leakage capacitance with a predetermined first limit value, and connecting the DG to a grid only if the determined leakage capacitance is smaller than the predetermined first limit value. A decentralized power generation plant is configured to perform the method.

Abstract: A fail-safe operating method for a decentralized power generation plant DG includes determining a leakage capacitance of a generator of the DG before connecting the DG. The method also includes comparing the determined leakage capacitance with a predetermined first limit value, and connecting the DG to a grid only if the determined leakage capacitance is smaller than the predetermined first limit value. A decentralized power generation plant is configured to perform the method.

Abstract: A method for a single-fault-tolerant determination of an isolation resistance of a photovoltaic system including an inverter and a solar generator connected thereto is disclosed. The isolation resistance is determined as a function of a test voltage drop in a resistor network, wherein the resistor network is connected to a variable voltage source by way of a first terminal, to a first pole of the solar generator by way of a second terminal and to a ground terminal of the inverter via an isolation relay by way of a third terminal. A capacitor is disposed between the ground terminal and the first pole of the solar generator.

Abstract: A method for measuring insulation resistance in an inverter that has a DC link circuit and a bridge circuit, connected to the DC link circuit, for driving an AC current via a bridge center tap is disclosed. The method includes connecting the bridge center tap to a grounding point, successively connecting, by way of the bridge circuit, the bridge center tap that is connected to the grounding point to two points of the ungrounded DC link circuit that differ in terms of voltage, and measuring the current flowing from the two points that differ in terms of voltage to the grounding point. The two points of the ungrounded DC link circuit that differ in terms of voltage are selected from a group of points that includes at least one intermediate voltage point of the DC link circuit in addition to two end points of the DC link circuit, such that the voltages present between the two points that differ in terms of voltage and the grounding point do not exceed a predefined voltage limit value.

Abstract: A fail-safe operating method for a decentralized power generation plant DG includes determining a leakage capacitance of a generator of the DG before connecting the DG. The method also includes comparing the determined leakage capacitance with a predetermined first limit value, and connecting the DG to a grid only if the determined leakage capacitance is smaller than the predetermined first limit value. A decentralized power generation plant is configured to perform the method.

Abstract: An inverter including a circuit arrangement configured to measure an insulation resistance is disclosed. The inverter includes at least one half-bridge including at least two switching elements extending between respective end points, and a grid disconnection point comprising a series circuit comprised of two disconnection devices. The series circuit is arranged between a center point of the half-bridge and an AC voltage terminal of the inverter, which AC voltage terminal is configured to connect to a phase conductor or a neutral conductor of an AC voltage grid. The circuit arrangement includes a resistor and a voltage measurement apparatus. The resistor is arranged electrically in parallel with one of the disconnection devices and the voltage measurement apparatus is arranged electrically between the output-side terminal of the resistor and one of the end points of the half-bridge.

Abstract: A method for a single-fault-tolerant determination of an isolation resistance of a photovoltaic system including an inverter and a solar generator connected thereto is disclosed. The isolation resistance is determined as a function of a test voltage drop in a resistor network, wherein the resistor network is connected to a variable voltage source by way of a first terminal, to a first pole of the solar generator by way of a second terminal and to a ground terminal of the inverter via an isolation relay by way of a third terminal. A capacitor is disposed between the ground terminal and the first pole of the solar generator.

Abstract: A method for detecting high-frequency AC currents in a DC circuit including a common mode choke with two partial windings includes tapping voltages dropping across the two partial windings due to the AC current, superposing the tapped voltages, and obtaining a superposed AC voltage wherein differential mode portions of the tapped voltages are summed constructively and common mode portions of the voltages are summed destructively; and measuring the superposed AC voltage.

Abstract: An inverter including a circuit arrangement configured to measure an insulation resistance is disclosed. The inverter includes at least one half-bridge including at least two switching elements extending between respective end points, and a grid disconnection point comprising a series circuit comprised of two disconnection devices. The series circuit is arranged between a center point of the half-bridge and an AC voltage terminal of the inverter, which AC voltage terminal is configured to connect to a phase conductor or a neutral conductor of an AC voltage grid. The circuit arrangement includes a resistor and a voltage measurement apparatus. The resistor is arranged electrically in parallel with one of the disconnection devices and the voltage measurement apparatus is arranged electrically between the output-side terminal of the resistor and one of the end points of the half-bridge.

Abstract: A method for detecting high-frequency AC currents in a DC circuit including a common mode choke with two partial windings includes tapping voltages dropping across the two partial windings due to the AC current, superposing the tapped voltages, and obtaining a superposed AC voltage wherein differential mode portions of the tapped voltages are summed constructively and common mode portions of the voltages are summed destructively; and measuring the superposed AC voltage.