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

US8854846B2 · kind B2 · utility

Assignee

• SMA Solar Technology AG · DE

Inventors

• Alexander Nuss · Kassel, DE
• Christian Bode · Braunschweig, DE
• Wilfried Groote · Vellmar, DE

Key dates

• Filing date: Oct 15, 2013
• Grant date: Oct 7, 2014
• Expiry date: Oct 15, 2033

Classification

• Technology area (CPC G): Physics
• CPC primary: G01R31/42
• WIPO field: Electrical machinery, apparatus, energy
• WIPO sector: Electrical engineering

Abstract

When determining a fault current portion IF in a differential current idiff(t) measured by an inverter, an AC voltage uAC(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 uAC(t) in order to determine an AC fault current portion IFin the differential current idiff(t). The differential current idiff(t) is multiplied by the periodic reference function y(t), and the product of the differential current idiff(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 uAC(t) and/or with a frequency which is an integer multiple of the frequency of the measured AC voltage uAC(t).