Abstract: A device and corresponding method for monitoring a photovoltaic system to detect an occurrence of events impairing normal operation of the photovoltaic system is provide. The photovoltaic system includes a photovoltaic generator including a first group of photovoltaic modules and a second group of photovoltaic modules being different from the first group. The device includes a first and a second pair of coupling means, both pairs including signal coupling-in means for coupling a test signal into the photovoltaic generator, and a signal coupling-out means for coupling out a response signal from the photovoltaic generator, the first pair of coupling means configured to selectively detect the occurrence of the events in the first group of photovoltaic modules, and the second pair of coupling means configured to selectively detect the occurrence of the events in the second group of photovoltaic modules.

Abstract: An inverter includes a DC/AC converter, a DC intermediate circuit on the direct current input side of the DC/AC converter, multiple DC/DC converters connected in parallel to one another on the output side to the DC intermediate circuit, multiple inputs each coupled to one of the DC/DC converters, and an EMC filter connected between the inputs and the DC/DC converters. The EMC filter includes chokes in all current-carrying lines between the inputs and the DC/DC converters and filter capacitors between the inputs and the DC/DC converters leading from all the current-carrying lines to ground. The chokes in all current-carrying lines from the at least two inputs are formed by means of choke windings on a common core of a current-compensated choke.

Abstract: A DC/AC converter for converting DC power of a number of inductively connected generators into power grid conformal AC power for feeding into a connected power grid with a number of phases, includes an intermediate circuit with a positive and a negative intermediate circuit connection, and for each phase, a bridge. Each bridge includes a first switch between the positive intermediate circuit connection and a phase terminal, a second switch connected between a positive generator terminal of the generator and the phase terminal, a third switch connected between a negative generator terminal of the generator and the phase terminal, and a fourth switch between the negative intermediate circuit connection and the phase terminal.

Abstract: The disclosure relates to a method for signaling partial shadowing within a PV generator including at least two partial PV generators connected in parallel. The method includes performing a reference impedance measurement on each of the at least two partial PV generators in a state of uniform irradiation of the PV generator, and determining at least one reference resonant property of each of the at least two partial PV generators from the reference impedance measurement. Furthermore, impedance measurements are carried out on the at least two partial PV generators at a first operating point of the PV generator during operation of the PV generator. Resonant properties of the partial PV generators are determined from the impedance measurements. Partial shadowing within the PV generator is detected and signaled if a difference between the resonant properties of the partial PV generators at the first operating point differs from a difference between the reference resonant properties of the partial PV generators.

Abstract: For monitoring an inverter that includes separate input-side connectors for multiple direct-current generators with regard to the occurrence of a critical fault current, differential currents in at last two pairs of input lines are measured separately in the inverter. The at last two pairs of input lines conduct the currents that are fed in at different input-side connectors, and all pairs of input lines in their entirety transmit all currents that are fed in at the connectors. The differential currents are compared with a limit value separately for each pair of input lines. A case of the limit value being exceeded is recognized as a fault. In addition, a sum of simultaneously occurring differential currents in all pairs of input lines is determined and the sum is compared with a further limit value, wherein a case of the further limit value being exceeded is also recognized as a fault.

Abstract: A method for operating an inverter which is connected to an energy supply grid via a transformer for feeding in electrical energy into the energy supply grid, includes measuring output currents and output voltages of the inverter, and actuating power switches of the inverter using actuation signals that are generated as a function of the measured output currents and the measured output voltages at a fundamental frequency of the energy supply grid. The actuation signals are further generated as a function of a harmonic component of the measured output voltages of the inverter at a multiple of the fundamental frequency using a control loop with positive feedback.

Abstract: 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.

Abstract: The disclosure relates to a capacitor arrangement for an input circuit or intermediate circuit of a voltage transformer comprising at least two capacitors and two connection nodes. Switching elements are provided, by means of which the at least two capacitors are connected in parallel with each other in a first operating state and are connected in series with each other in a second operating state. The disclosure also relates to a voltage transformer arrangement comprising such a capacitor arrangement and an operating method for a capacitor arrangement.

Abstract: A grid-connected inverter for feeding current via a transformer into an electric power grid includes an output bridge arrangement that is actuated via a pulse width modulator, wherein a periodic auxiliary signal is used to determine switching times of the output bridge arrangement. The inverter also includes a synchronization unit for phase synchronization of the auxiliary signal with the electric power grid, wherein the synchronization unit is configured to set a predetermined phase offset (??0) of the periodic auxiliary signal with respect to a phase of the electric power grid.

Abstract: The disclosure relates to a circuit arrangement for suppressing an arc occurring during a switching process, wherein a current bypass path comprises a PTC resistor connected in series with a fuse. The current bypass path is provided in parallel with a switch. The disclosure also relates to a photovoltaic power plant with a photovoltaic generator which is connected to an inverter via DC lines. In this arrangement, such a circuit arrangement is arranged in at least one of the DC lines.

Abstract: A method of detecting an arc fault in a power circuit includes injecting an AC-signal into the power circuit and measuring a response signal that is related to the injected AC-signal in the power circuit. The method further includes determining a frequency response of the power circuit from the response signal, analyzing the frequency response, and identifying a preferred frequency. A signal related to AC-current flowing in the power circuit within the preferred frequency range is measured and an occurrence of an arc fault in the power circuit is signaled depending on the measured signal. A system for detecting an arc fault is designed to perform a method as described before.

Abstract: The disclosure relates to a method for operation of a photovoltaic installation for feeding electrical power into a medium-voltage power supply grid, with the photovoltaic installation having a plurality of photovoltaic modules, at least one inverter and at least one medium-voltage transformer, and with the primary side of the medium-voltage transformer being connected directly to an alternating-current (AC) low-voltage output of the inverter, and at least one direct-current (DC) switching member being arranged between the photovoltaic modules and a DC input of the inverter. When the electrical power produced by the photovoltaic modules in the photovoltaic installation is not sufficient for feeding electrical power into the supply grid, the photovoltaic modules are disconnected from an inverter on the DC voltage side while, in contrast, the inverter remains connected to the medium-voltage power supply grid on the AC voltage side by the medium-voltage transformer.

Abstract: A disconnect unit and an associated method in a photovoltaic system includes a plurality of input power lines configured to receive power from a photovoltaic (PV) generator, and deliver the received power to an inverter. The disconnect unit further includes a sensor configured to determine a voltage at the plurality of input power lines, and a controller configured to selectively disconnect and reconnect one or more of the plurality of input power lines based on the determined voltage.

Abstract: An electronic device includes a housing, a circuit board, a plurality of holders having mechanical connectors to the housing and to the circuit board and mechanically fixing the circuit board within the housing, and at least one capacitor having a first electrode, a second electrode and a dielectric arranged between the first and second electrodes. The first electrode is electrically connected to a contact on the circuit board, and the second electrode is electrically connected to the housing. The at least one capacitor is part of one of the plurality of holders; and the dielectric of the capacitor is part of a thermal insulation between the connectors to the circuit board and to the housing.

Abstract: For protecting a photovoltaic generator comprising photovoltaic modules, having an open circuit voltage higher than an insulation design voltage of its photovoltaic modules and being connected to an AC power grid via an inverter against a surge voltage relative to ground resulting from a ground fault and exceeding the insulation design voltage, the photovoltaic generator is surveyed for the occurrence of the ground fault or the surge voltage. Upon the actual occurrence of the ground fault or the surge voltage, at first, the photovoltaic generator is separated from an input-side intermediate link capacitance of the inverter, and the inverter is separated from the AC power grid. Then, the intermediate link capacitance is discharged via a resistor, prior to permanently closing semiconductor switches of an inverter bridge of the inverter and to reconnecting the photovoltaic generator to the input-side intermediate link capacitance of the inverter to short circuit the photovoltaic generator.

Abstract: The disclosure relates to a method for localizing and quenching an arc in a PV generator of a PV system, wherein the PV generator includes at least two PV subgenerators. An arc quenching circuit is associated with each PV subgenerator. The method includes detecting an arc in the PV generator. Then, a probability value is determined for each of the PV subgenerators, wherein the probability value is correlated with a probability that the arc is located in the corresponding PV subgenerator. A sequence for activating the arc quenching circuits is then determined that is dependent on the determined probability values. Then, the arc quenching circuits are activated successively in the order of the determined sequence.

Abstract: A method for the operational control of an inverter designed for DC/AC voltage conversion that has at least one direct-voltage input and that can be connected to a power supply grid via at least one alternating-voltage output, the inverter being involved in a power flow interaction with the grid in such a manner that, during operation of the inverter, a leakage current IA can occur, wherein the leakage current IA is controlled in the operational control.

Abstract: The disclosure relates to a tracking method for a voltage transformer, in particular an inverter, of a photovoltaic system. In the method, an intermediate circuit voltage is repeatedly decreased or increased in one direction to a lower or higher voltage by voltage steps of a specified magnitude. The method is characterized in that an average rate of change of the intermediate circuit voltage in a partial time period between two voltage steps is limited by a maximum average rate of change, the maximum average rate of change being defined according to the magnitude of the intermediate circuit voltage. The disclosure further relates to a tracking device designed to perform the tracking method and to an inverter equipped with the tracking device.

Abstract: The disclosure relates to a method for detecting an arc in a DC circuit. The method includes measuring and analyzing an AC component (IAC) of a current (I) flowing in the circuit and determining at least one parameter of the AC component (IAC). The level of a DC component (IDC) of the current (I) is varied and a degree of correlation between the level of the DC component (IDC) of the current (I) flowing in the DC circuit and the at least one parameter of the AC component (IAC) 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.

Abstract: An inverter includes a DC/AC converter connectable to a DC power grid, at least one DC/DC converter arranged upstream of the DC/AC converter and providing a galvanic isolation, and a DC voltage link at the input of the at least one DC/DC converter and connectable to at least one DC power source. The inverter also includes at least one further DC voltage link which is galvanically isolated from the first DC voltage link by the DC/DC converter, on-board voltage rails supplying a controller and other auxiliary devices of the inverter with electric energy; and an on-board supply unit. The on-board supply unit is configured and adapted to feed the electric energy into the on-board voltage rails both out of the first DC voltage link and out of the at least one further DC voltage link.