Sma Solar Technology Ag

Sma Railway Technology Gmbh

Dirk Hermeling

Andreas Falk

Marcel Kratochvil

Alexander Unru

Christian Hardt

Karl Nesemann

Reinhard Lehmann

Ralf Juchem

Neidhardt Bechtel

Mario Willenberg

Josef Petschenka-Rininsland

Tim Roesinger

Mohamed Mostafa

Volker Bergs

A method and related apparatus for extending a DC voltage range of a rectifier circuit for the supply, from an AC grid, of a DC load which is connected to a DC rectifier output of the rectifier circuit, wherein an AC rectifier input of the rectifier circuit is connected via a grid connection point to the AC grid, wherein the rectifier circuit includes an AC/DC converter having an AC input and a DC output, wherein the AC/DC converter includes a converter circuit having semiconductor switches and freewheeling diodes connected in an antiparallel arrangement thereto, wherein an inductance is connected between the AC input of the AC/DC converter and the grid connection point. The method includes setting a desired DC operating voltage Uon the DC output of the AC/DC converter or on the DC rectifier output, or both, by an actuation of semiconductor switches of the AC/DC converter, wherein, when the desired DC operating voltage Ulies below a value of an amplitude Ûof an alternating voltage on the AC input of the AC/DC converter, the semiconductor switches of the AC/DC converter are actuated for an exchange of reactive power Q(t) with the AC grid, which has a voltage-lowering effect upon the amplitude Ûof the AC voltage at the AC input of the AC/DC converter, such that the amplitude Ûapproaches the desired DC operating voltage U, and wherein the exchange of the reactive power Q(t) with the AC grid is executed during or shortly before an electrical connection or an electrical isolation of the DC load to or from the rectifier circuit.

Method for extending a voltage range of a rectifier, rectifier for carrying out the method, and electrolysis system

A battery inverter system includes a plurality of battery inverter units, wherein each of the battery inverter units includes a multiphase inverter and a battery unit connected to the inverter on the DC side. The battery unit includes a plurality of individual units connected in parallel to one another and protected against overcurrent by means of rack fuses, and the battery inverter units are connected in parallel on the AC side and are configured to operate with a common drive pulse pattern. The battery inverter units are interconnected on the DC side via compensation fuses, wherein the compensation fuses are provided such that in the event of a short circuit in one of the inverters, the compensation fuses are triggered faster than the rack fuses.

Battery inverter system

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.

Method for operating an island system, and island system

An apparatus for determining insulation resistance at a PV generator includes a first unit configured to shift a generator potential at an output terminal of the PV generator, and a second unit. The second unit is configured to determine the insulation resistance by: connecting a measurement voltage to the output terminal of the PV generator, measuring a first current value and a first voltage value at the output terminal of the PV generator before the measurement voltage is connected, measuring a second current value and a second voltage value at the output terminal of the PV generator after the measurement voltage is connected, and determining the insulation resistance of the PV generator based on the measured first and second current values and the measured first and second voltage values. The first and second units are connected in series.

Apparatus for determining insulation resistance at a PV generator, and photovoltaic installation

In monitoring an isolation of an ungrounded power grid an AC voltage source is connected to the power grid via at least one test resistor. A test signal with a periodic continuous voltage course with regard to ground and with a frequency is applied to the power grid by means of the AC voltage source. A leakage current flowing due to the test signal is measured; and an ohmic isolation resistance is determined from the leakage current. The frequency of the test signal is varied such that an active current part of the leakage current keeps a predetermined recommended value at varying leakage capacitances of the power grid. This provides for a desired level of accuracy at maximum speed of isolation or ground fault detection.

Isolation monitoring using a test signal of variable frequency

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Petershagen, Germany

Dirk Hermeling