Sma Solar Technology Ag

Christian Halt

Christian Hardt

Christoph Jordaan

An inverter and a method for detecting a phase failure in an energy supply grid during operation of an inverter, which is connected to the energy supply grid for feeding electrical energy via a YNd transformer is disclosed. The method includes transforming the values of the output currents into a symmetrical positive-sequence current value and into a symmetrical negative-sequence current value of a coordinate system rotating at a fundamental frequency of the energy supply grid. The method further includes determining a ratio of the negative-sequence current value to the positive-sequence current value, and signalling a phase failure in the energy supply grid if the determined ratio is greater than a preset threshold value for longer than a preset time period. The disclosure furthermore relates to an inverter designed for implementing the method.

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Melsungen, Germany

Christian Halt