Sma Solar Technology Ag

Harald Drangmeister

Thomas Wegener

Daniel Clemens

Alexander Unru

Henrik Wolf

Tobias Mueller

Pablo Ignacio Correa Vasquez

-Ing Henrik Wolf

Tobias MÜLLER

A method for determining capacitance values of capacitances of a photovoltaic system including a multiphase inverter which includes an output current filter on an alternating current side thereof and is connected to a multiphase energy supply network via a switching element and is associated with at least one intermediate circuit capacitance on the direct current side thereof is provided. The method includes disconnecting the photovoltaic system from the energy supply network by opening the switching element; operating the inverter to set up an island network after the disconnecting, wherein an in-phase AC voltage is applied to at least two outputs of an inverter bridge of the multiphase inverter and a flow of current is produced between the at least one intermediate circuit capacitance and at least one filter capacitance of the output current filter; measuring currents (Ia, Ib, Ic) flowing at the outputs of the inverter bridge and at least one voltage present at one of the capacitances, and determining a capacitance value of at least one of the capacitances using the determined voltage and the measured currents (Ia, Ib, Ic).

Method and inverter for determining capacitance values of capacitances of an energy supply system

An inverter device for feeding electrical energy from a DC-power source into a power grid includes a pair of bus lines to be connected to the DC-power source; a plurality of capacitors connected in series between the bus lines; a surveying topology surveying an integrity of the plurality of capacitors, and to provide a signal indicating a loss of integrity of one capacitor of the plurality of capacitors; a voltmeter measuring a voltage drop over the plurality of capacitors; a DC/AC-inverter; and a controller. in case of the signal indicating a loss of integrity of one capacitor of the plurality of capacitors, the controller compares the voltage drop over the plurality of capacitors to a lost integrity threshold voltage value, and reduces a current load to the plurality of capacitors by reducing the power uptake of the DC/AC-inverter, when the voltage drop exceeds the lost integrity threshold voltage value.

Inverter device comprising a topology surveying a series of capacitors

A topology for surveying the integrity of a plurality of capacitors connected in series between a pair of bus lines arranged to be connected to a DC-power source comprises a plurality of resistors connected in series between the pair of bus lines, the plurality of resistors being connected in parallel to the plurality of capacitors; and a comparator comparing the electric potential of an intermediate point between two capacitors of the plurality of capacitors with the electric potential of an intermediate point between two resistors of the plurality of resistors. The comparator provides a signal signaling a difference between these two electric potentials, which indicates a loss of integrity of one capacitor of the plurality of capacitors.

Topology surveying a series of capacitors

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Kassel, Germany

Harald Drangmeister