Sma Solar Technology Ag

Wilfried Groote

Sven Bremicker

Frank Greizer

Matthias Victor

Bernd Engel

Torben Westphal

Holger Becker

Thorsten Dingel

Ralf Joachim Laschinski

Günther Cramer

Guenther Cramer

Christian Bode

Wolfgang Reichenbaecher

Alexander Ahlborn

Alexander Nuss

Wolfgang Dipl-Ing Reichenbächer

When determining a fault current portion Iin a differential current i(t) measured by an inverter, an AC voltage u(t) applied to an AC output of the inverter is measured and a periodic reference function y(t) of alternating sign is generated as a function of the measured AC voltage u(t) in order to determine an AC fault current portion Iin the differential current i(t). The differential current i(t) is multiplied by the periodic reference function y(t), and the product of the differential current i(t) and the reference function (y(t)) is averaged over an integral number of periods of the reference function y(t). The reference function y(t), at least for one operating state of the inverter, is generated with a predefined phase offset with respect to the measured AC voltage u(t) and/or with a frequency which is an integer multiple of the frequency of the measured AC voltage u(t).

Method and apparatus for determining a fault current portion in a differential current

A method of converting a direct voltage generated by a decentralized power supply system into three-phase alternating voltage by means of a plurality of single-phase inverters (WR-WR), said alternating voltage being provided for supplying an electric mains, is intended to avoid inadmissible load unbalances using single-phase inverters. This is achieved in that, upon failure of one inverter (WR-WR), an asymmetrical power supply distribution is reduced by limiting the output of the other inverters. The method makes it possible to simplify three-phase voltage monitoring.

Method for converting direct voltage into three phase alternating voltage

A method for determining a load capability of a direct current ('DC') voltage source connectable to an alternating current ('AC') power grid having a predetermined frequency via an inverter and a grid disconnect switch includes controlling, while the grid disconnect switch is in an open position, the inverter so as to convert a DC input voltage to a test frequency different than the predetermined frequency of the AC power grid so as to increase a test load acting on the DC voltage source above an internal consumption of the inverter at the predetermined frequency. The DC input voltage is measured while the grid disconnect switch is in the open position.

Determination of the load capability of a DC voltage source which is connectable to an electric power grid via an inverter and a grid disconnect switch

Method for converting direct voltage into three-phase alternating voltage

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Vellmar, Germany

Wilfried Groote