Sma Solar Technology Ag

Burkhard Müller

Andreas Falk

Frank Greizer

Matthias Victor

An inverter with galvanic separation including a resonant converter and an upstream mounted boost chopper is intended to provide galvanic separation in the context of a variable input and output voltage as it exists in photovoltaic systems, with the efficiency being intended to be optimized over the entire input voltage range. This is achieved in that a boost chopper or a buck chopper is mounted upstream of the resonant converter.

Inverter employing a boost chopper circuit and a resonant converter circuit

The subject matter of the invention is a method of measuring a grounding current of a photovoltaic power system incorporating a photovoltaic inverter, a measurement current being led through two shunts (Rs, Rs) disposed at different points, the measurement current being a current that may flow alternatively at two different points at different electric potentials, the current flowing at a potential that differs by at least 50 V from the potential of the point of evaluation, the shunts (Rs, Rs) being inserted in such a manner in a current mirror circuit that the voltage drop caused by the measurement in the shunts generates an asymmetry in the current mirror the magnitude of which is proportional to the measurement current, and the measurement current being the grounding current of the photovoltaic power system with optional positive or negative pole grounding.

Method for measuring a current, in particular by means of a grounding apparatus

The subject matter of the invention is an inverter (), more specifically for use in a photovoltaic plant () with a direct voltage input (connection terminals) for connection to a generator () and an alternating voltage output (connection terminals) for feeding into an energy supply network () as well as with a DC-AC converter () with semiconductor switch elements () and an intermediate circuit (), at least one short-circuit switch element () being connected in parallel to the generator (), so that the voltage will not exceed a maximum voltage value neither at the connection terminals () of the generator () nor between the connection terminals () of the inverter. This is achieved in that the inverter () comprises, in the intermediate circuit (), a buffer capacitor () that is connected to the generator () through a protection diode () so that said buffer capacitor () will not be discharged upon actuation of the short-circuit switch element (), the generator () working according to a clock rate in the short-circuit mode of operation.

Switching device and method, in particular for photovoltaic generators

The measuring array with an earth connection point () for determining the insulation resistance (R) of an energized electrical apparatus or of an installation with a supply voltage Uwith a positive pole () and a negative pole (), two switches (S, S) or a corresponding two-way switch being provided for creating a current path between one of the two poles and said earth connection point () in order to determine the insulation resistance (R) generally obtained when one or a plurality of insulation faults occur at any potential reference, two measurements being performed one after the other for determining the insulation resistance, the first switch (S) being closed and the second switch (S) open during the first of these two measurements and the first switch (S) being open and the second switch (S) closed during the second of these measurements.

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Kassel, Germany

Burkhard Müller