Sma Solar Technology Ag

Martin Putz

Michael Viotto

Christian Tschendel

Andreas Falk

Jens Friebe

Burkard Mueller

Steffen Aust

The disclosure relates to a device and associated method for electrolysis from photovoltaically generated DC power, including an electrolyzer and a DC/DC converter. The DC/DC converter feeds DC power to the electrolyzer, 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 in such a way that the second disconnector is opened in the event that a predefinable limit value of the fault current is exceeded.

Device for electrolysis from photovoltaically supplied power and a method of operating such a device

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.

Fail-safe operating method for a decentralized power generation plant

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.

Method for measuring insulation resistance in inverters with multipoint topology, and inverter with multipoint topology

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. The method includes a) applying a first DC voltage value to the first terminal when the isolation relay is closed using the variable voltage source, b) applying a second DC voltage value to the first terminal when the isolation relay is closed using the variable voltage source, c) generating an AC voltage at the first terminal using the variable voltage source when the isolation relay is closed, d) generating the AC voltage at the first terminal using the variable voltage source when the isolation relay is open, and e) testing a function of the isolation relay by comparing an amplitude of the test voltage between the acts c) and d).

Single-fault-tolerant isolation resistance determination in a photovoltaic system

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.

Inverter having grid disconnection point and insulation resistance measurement and method for measuring an insulation resistance

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.

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Kassel, Germany

Martin Putz