Fronius International Gmbh

Michael Rothböck

Harald Josef Kreuzer

Stefan Wieser

Roland Pieler

A switching arrangement of an inverter with a filter circuit and a grid relay. For the filter circuit use is made of an equivalent circuit consisting of effective filter inductance, from filter inductance and topology of the filter circuit and effective filter capacitance, from the filter capacitance and topology of the filter circuit. The effective filter inductance and the effective filter capacitance are system parameters. To determine system parameters, a voltage pulse is applied between a first conductor output and a second conductor output when the grid relay is open; the first conductor output and the second conductor output are connected via the switching arrangement to form a closed oscillating circuit a current value of the effective filter inductance and the effective filter capacitance is determined from a current curve and/or voltage curve in the resonant circuit as system parameters for controlling the switching arrangement.

Determination of filter parameters in an inverter

A method for operating an inverter includes applying, via a switching unit of the inverter, an AC voltage to a phase line in which a filter inductor is arranged, determining a coil current (i) of the filter inductor and determining a coil voltage (u) of the filter inductor, determining a first value (L(I)) of the filter inductor for a first value of the coil current (I), determining an inductance profile of the filter inductor with respect to the coil current, using the determined first value of the filter inductance and optionally using the at least one determined further value of the filter inductance, and controlling the switching unit of the inverter, via a control unit, to generate an alternating current in the phase line. At least one parameter of the control process is continuously adapted to the momentary coil current according to the determined current-dependent inductance profile.

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Wels-Thalheim, Austria

Michael Rothböck