Abstract: An electrical converter is disclosed which includes a main stage for converting a DC voltage into an intermediate voltage with at least two voltage levels, a filter cell stage with a filter cell for each phase of the intermediate voltage, and a pre-charge circuit adapted for pre-charging the filter cells. The pre-charge circuit includes an auxiliary power source connected between one phase of an output of the electrical converter and a neutral point of a DC link, wherein all phases of the output of the electrical converter are connected. A method for pre-charging filter cells is disclosed which includes switching the main stage such that all phases of the output of the main stage are directly connected to the neutral point, switching at least one of the filter cells into a rectifying state, and switching the pre-charge circuit on and charging the cell capacitor by the pre-charge circuit.

Abstract: An apparatus includes a main switch, arranged in series between an apparatus-input and an apparatus-output, a first parallel-diode in backward direction and a second parallel-diode in forward direction, the first and second parallel-diodes arranged in series and in parallel to the main switch with a first central node between them; a first branch diode in forward direction and a second branch diode in backward direction, the first and second branch diodes arranged in series between the apparatus-input and the apparatus-output; a chopper-circuit arranged between the first and second central nodes, the chopper-circuit comprising a chopper capacitor arranged between the first and second central nodes and a chopper semiconductor arranged in series with a chopper resistor between the first and second so that the sub-circuit comprising the branch diodes and the chopper-circuit limits the current in case of a short circuit by leading the current through this sub-circuit.

Abstract: An electrical converter (10) comprises a main stage (12) adapted for converting a DC voltage into an intermediate voltage comprising at least two voltage levels and a filter cell stage (14) with a filter cell (30) for each phase of the main stage (12), each filter cell (30) being adapted for adding or subtracting a cell voltage of the filter cell (30) to the intermediate voltage.

Abstract: A Solid State Circuit Breaker (SSCB) arrangement has an input side and an output side, and comprises a connective circuit between the input terminal and the output terminal at the first voltage, and/or a connecting circuit between the input terminal and the output terminal at the second voltage. The SSCB further comprises a vertical freewheeling circuit coupled between a first connection point between the input terminal and the output terminal at the first voltage and a second connection point between the input terminal and the output terminal at the second voltage, wherein the freewheeling circuit includes a switchable interruptible freewheeling path.

Abstract: A DC microgrid includes a power electronic converter, a protection unit configured to be in a through state, a CL state, or an open state, a bus-bar connected to the output of the protection unit, and at least one sub-system connected to the bus-bar. Sub-systems are hierarchically organized in at least one hierarchy level, the at least one hierarchy level being defined by a number of breakers arranged between the protection unit and the sub-system. The method includes setting the protection unit into the through state, and when the measured voltage is lower than the first voltage and/or the measured current is higher than the first current, moving to a current-limited CL state for an on-timeslot and, subsequently, for an off-timeslot, to the open state, in which no current is delivered.

Abstract: An electrical converter comprises a main stage adapted for converting a DC voltage into an intermediate voltage comprising at least two voltage levels and a filter cell for each phase of the intermediate voltage, each filter cell being adapted for adjusting a cell voltage with the intermediate voltage. A control method comprises: determining a main pulse pattern for the main stage, wherein the main pulse pattern comprises switching instants for the main stage over a modulation period; and determining a cell pulse pattern, wherein the cell pulse pattern comprises switching instants for the filter cells over the next modulation period. The method additionally comprises: modifying the main pulse pattern and the cell pulse pattern by moving at least one transition time of a switching instant and applying at least a next switching instant from the main pulse pattern and the cell pulse pattern.

Abstract: The present disclosure provides a grid forming vector current control system configured to emulate a virtual synchronous machine (VSM). The disclosed system comprises a droop control unit, a current control unit, a virtual admittance unit and a phase locked loop (PLL) unit. The virtual admittance unit and the PLL unit are configured to emulate an inertia of the VSM. A virtual current source is connected in parallel to the VSM.

Abstract: A system and method for compensating a faulty switch in a multi-level flying capacitor converter includes a converter capacitor arranged in parallel to an input, a first and second converter switches arranged respectively between first and second ends of the converter capacitor, first and second bypass switches respectively arranged in parallel to the first and second converter switches, wherein operation includes detecting a faulty converter level that includes at least one of the first and second converter switches, discharging all capacitors arranged in parallel to the input of the multi-level converter, wherein all capacitors comprise the converter capacitors and an input capacitor; closing the first and second bypass switches of the faulty converter level; adapting a modulation of the converter switches of the other converter levels; and restarting the multi-level converter.

Abstract: Described herein is a method of operating a power electronic converter device for an electrical power conversion system. The power electronic converter device includes a converter circuit including an input side, an output side, a first converter, and at least one second converter. The second converter includes at least one floating cell with a DC intermediate circuit and semiconductor devices. The method includes: switching the semiconductor devices of the floating cell at switching instants determined with optimized pulse patterns or carrier-based pulse width modulation; determining a fundamental voltage component for the floating cell; and generating the fundamental voltage component in the actual voltage of the floating cell by modifying the switching instants, such that a voltage VC AF of the DC intermediate circuit is lying in a given reference voltage range for balancing the DC intermediate circuit of the floating cell.

Abstract: A flying capacitor switching cell-system includes at least two flying capacitor switching cells, wherein each of the cells comprises an arrangement of at least one semiconductor system, and wherein the cells are in parallel in an electrical circuit.

Abstract: An uninterruptible power supply device includes a rectifier module coupled to an electrical power grid, an inverter module coupled to the rectifier module, and a battery converter module. The rectifier module can process a higher amount of electric power as the designed electrical power provided by the inverter module to enable the uninterruptible power supply device to provide stabilization support to the electrical power grid, wherein the rectifier module comprises at least two rectifier submodules, each dimensioned to process an amount of electrical power according to a capability of the inverter module to process power. The rectifier module is configured to electrically couple the rectifier submodules selectable to process a higher amount of electric power as the inverter module to provide stabilization support to the electrical power grid.

Abstract: A modulator for a flying-capacitor type multilevel converter receives, at an input, a time-variant reference signal and provides, at an output, a sequence of target levels, to provide switching signals for switching between discrete output levels of the multilevel converter according to the shape of the reference signal. The modulator determines a critical level as an intermediate output level of the multilevel converter which is closest to the level of the reference signal; and outputs only target levels corresponding to output levels different from the critical level.

Abstract: A converter system includes a rectifier, a DC link stage and an inverter connected in series. A control unit includes a slow reference frame angle determination unit that generates a slow reference frame angle ?r,slow representing an angle that is slowly following a grid phase deviation, and a fast Phase Locked Loop generating a fast reference frame angle ?r,fast representing an angle that is fast following a grid phase deviation. The control unit uses the slow reference frame angle ?r,slow and the fast reference frame angle ?r,fast to control the rectifier output current, and the fast reference frame angle ?r,fast to control the inverter output voltage and to synchronize the inverter output voltage with the grid voltage.

Abstract: An electrical converter includes a main converter for generating a first output voltage and a converter cell for converting the first output voltage into a second output voltage. A method for operating an electrical converter includes: receiving a reference voltage for the electrical converter; pulse width modulating the reference voltage with a first modulation frequency for generating a first switching signal for the main converter; switching the main converter with the first switching signal to generate the first output voltage; estimating the first output voltage from the first switching signal; determining a voltage error by subtracting the estimated first output voltage from the reference voltage; pulse width modulating the voltage error with a second modulation frequency, which is higher than the first modulation frequency, for generating a further switching signal for the converter cell; and switching the converter cell with the further switching signal to generate the second output voltage.

Abstract: A grid forming vector current control system can be used for controlling a grid intertie. A first terminal is connected to a first power grid and a second terminal is connected to a second power grid. The terminals each include current control unit, a virtual admittance unit, and a phase locked loop (PLL) unit. The virtual admittance unit and the PLL unit are configured to emulate an inertia of a virtual synchronous machine (VSM) and a virtual current source is connected in parallel to the VSM. A controller is configured to use transient power consumed by the first VSM to generate a power-equivalent current reference to control the second virtual current source and to use transient power consumed by the second VSM to generate a power-equivalent current reference to control the first virtual current source.

Abstract: A grid forming vector current control system can be used for controlling a grid intertie. A first terminal is connected to a first power grid and a second terminal is connected to a second power grid. The terminals each include current control unit, a virtual admittance unit, and a phase locked loop (PLL) unit. The virtual admittance unit and the PLL unit are configured to emulate an inertia of a virtual synchronous machine (VSM) and a virtual current source is connected in parallel to the VSM. A controller is configured to use transient power consumed by the first VSM to generate a power-equivalent current reference to control the second virtual current source and to use transient power consumed by the second VSM to generate a power-equivalent current reference to control the first virtual current source.

Abstract: A system and method for compensating a faulty switch in a multi-level flying capacitor converter includes a converter capacitor arranged in parallel to an input, a first and second converter switches arranged respectively between first and second ends of the converter capacitor, first and second bypass switches respectively arranged in parallel to the first and second converter switches, wherein operation includes detecting a faulty converter level that includes at least one of the first and second converter switches, discharging all capacitors arranged in parallel to the input of the multi-level converter, wherein all capacitors comprise the converter capacitors and an input capacitor; closing the first and second bypass switches of the faulty converter level; adapting a modulation of the converter switches of the other converter levels; and restarting the multi-level converter.

Abstract: A modulator for a flying-capacitor type multilevel converter receives, at an input, a time-variant reference signal and provides, at an output, a sequence of target levels, to provide switching signals for switching between discrete output levels of the multilevel converter according to the shape of the reference signal. The modulator determines a critical level as an intermediate output level of the multilevel converter which is closest to the level of the reference signal; and outputs only target levels corresponding to output levels different from the critical level.

Abstract: Described herein is a method of operating a power electronic converter device for an electrical power conversion system. The power electronic converter device includes a converter circuit including an input side, an output side, a first converter, and at least one second converter. The second converter includes at least one floating cell with a DC intermediate circuit and semiconductor devices. The method includes: switching the semiconductor devices of the floating cell at switching instants determined with optimized pulse patterns or carrier-based pulse width modulation; determining a fundamental voltage component for the floating cell; and generating the fundamental voltage component in the actual voltage of the floating cell by modifying the switching instants, such that a voltage VC AF of the DC intermediate circuit is lying in a given reference voltage range for balancing the DC intermediate circuit of the floating cell.

Abstract: A protection circuit for a power converter with cascaded bipolar and/or unipolar semiconductors is provided. The protection circuit includes at least one comparator circuit which is adapted to monitor a voltage characteristic on a collector-emitter path of at least one semiconductor which is arranged in a polarity selection stage of the power converter and/or to monitor a voltage characteristic on at least one capacitor, which is arranged in the power converter. The at least one comparator circuit is further adapted to output an electrical signal, representing the voltage characteristic of the semiconductor and/or the at least one capacitor to at least one evaluation unit. The at least one evaluation unit is further adapted to evaluate the result from the at least one comparator circuit and to deactivate the semiconductors in case that the voltage characteristic of the semiconductors and/or the capacitors deviate from a predetermined threshold.