Sma Solar Technology Ag

Institut Fuer Solare Energieversorgungs-technik (iset) Verein an Der Universitaet Gesamthochschule Kassel E.v.

Michael Viotto

Martin Putz

Christian Tschendel

Jens Friebe

Markus Hopf

Marcel Kratochvil

Peter Zacharias

Holger Behrends

Raimund Thiel

Klaus Rigbers

Thomas Wegener

Stephanie Coors

Bernhard Schropp

Johannes Lang

Heiko Fasshauer

A fail-safe operating method for a decentralized power generation plant DG includes determining a leakage capacitance of a generator of the DG before connecting the DG. The method also includes comparing the determined leakage capacitance with a predetermined first limit value, and connecting the DG to a grid only if the determined leakage capacitance is smaller than the predetermined first limit value. A decentralized power generation plant is configured to perform the method.

Fail-safe operating method for a decentralized power generation plant

The disclosure relates to a method for determining a characteristic curve for a photovoltaic (PV) string of a photovoltaic system having an inverter which is connected to the photovoltaic string and to a power supply network. The photovoltaic string includes a series connection of a plurality of photovoltaic modules, in which series connection at least one of the photovoltaic modules is integrated into the series connection of the photovoltaic modules via a DC/DC converter. The at least one DC/DC converter operates the photovoltaic module assigned thereto in a first operating mode M1 at a maximum power point by varying, over time, a conversion ratio of output voltage (U) to input voltage (U), and operates the photovoltaic module in a second operating mode M2 with a conversion ratio of output voltage (U) to input voltage (U) that is constant over time. The method includes operating the at least one DC/DC converter in the second operating mode M2 in response to a current signature for the current (I) through the photovoltaic string, determining the characteristic curve by varying the current Ior the voltage Uof the photovoltaic string by the inverter, and detecting values assigned to one another for current Iand voltage Uof the photovoltaic string in the second operating mode M2 of the DC/DC converter.

Method for determining a characteristic curve of a photovoltaic (PV) string, DC/DC converter, and photovoltaic system suitable for carrying out the method

The disclosure relates to a method for detecting an arc in a DC circuit. The method includes measuring and analyzing an AC component (I) of a current (I) flowing in the circuit and determining at least one parameter of the AC component (I). The level of a DC component (I) of the current (I) is varied and a degree of correlation between the level of the DC component (I) of the current (I) flowing in the DC circuit and the at least one parameter of the AC component (I) is determined. An arc is detected and selectively signaled based on the degree of the determined correlation. The disclosure also relates to an apparatus for carrying out the method and to an inverter comprising such an apparatus.

Method and apparatus for detecting an arc in a DC circuit

An inductor apparatus includes an inductor winding, a core defining a magnetic circuit for a magnetic flux generated by a current flowing through the inductor winding, at least one permanent magnet magnetically biasing the core by its permanent magnetization, and a magnetization device operable for adjusting a desired magnetization of the permanent magnet. The at least one permanent magnet is arranged within the magnetic circuit of the magnetic flux generated by the current flowing through the inductor winding. The magnetization device includes a magnetization winding and a circuitry configured to subject the magnetization winding to magnetization current pulses, thereby generating at a location of the permanent magnet a magnetic field which is able to change the permanent magnetization of the permanent magnet.

Dynamically biased inductor

A circuitry arrangement for a solar power plant includes a transformerless inverter for feeding electric power from at least one photovoltaic generator into an alternating power grid, a galvanic separation of all lines carrying current between the inverter and the power grid, and a DC voltage source in an offset path between one electric line at the input side of the galvanic separation and a reference potential. The DC voltage source provides an offset voltage. The offset path includes a DC branch and an AC branch connected in parallel. The direct voltage source is connected in series with a current sensor in the DC branch, and at least one capacitor is arranged in the AC branch. Further, a DC contactor triggered by the current sensor is arranged in the offset path.

Circuitry arrangement for a solar power plant comprising a DC voltage source for an offset voltage

The invention relates to a method and an apparatus for measuring the impedance of an energy supply system at a rated frequency by impressing a testing current () into the system and measuring () the resulting changes in a system current and a system voltage. According to the invention, the system current and the system voltage are measured during a first preselected time interval (T) without impressing of the testing current and are measured during a second preselected time interval (T) with the impressing of the testing current. The testing current is composed of at least one periodic signal with at least one testing frequency (f, f) that deviates from the rated frequency. Based on the measured system currents and system voltages, a Fourier analysis is used to determine a resulting impedance for the testing frequency (f, f). The impedance of the energy supply system at the rated frequency is derived from the impedance obtained for the testing frequency (f, f) (FIG.).

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Kassel, Germany

Michael Viotto