A method, a control circuit, and a power converter arrangement are disclosed. The method includes: coupling three power converters (1, 2, 3) with each other; connecting each of the three power converters (1, 2, 3) to a 3-phase power source (4) configured to provide three supply voltages (Ua, Ub, Uc); and regulating a respective input signal (V1, V2, V3; I1, I2, I3) of each of the three power converters (1, 2, 3) dependent on a common mode signal (Scm).

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.sub.L) of the filter inductor and determining a coil voltage (u.sub.L) of the filter inductor, determining a first value (L(I.sub.X)) of the filter inductor for a first value 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.

In one embodiment, a method of operating a power electronic converter device for an electrical power converter system is provided. The power electronic converter device includes a converter circuit, a first converter, and a second converter. The first converter and the second converter are switch with a switching pattern such that the first converter and the second converter generate voltages with stepwise voltages changes and an output voltage of the power electronic converter device results frum a superposition of the voltages of the first converter and the second converter. The switching pattern includes switching instants for the second converter such that the voltage of the second converter leaves the fundamental voltage component of the voltage of the first converter unchanged, such that the second converter does not generate a fundamental component of the output voltage.

A multi-pulse line-interphase transformer converter includes an electric part that includes magnetic components configured to be connected to a three-phase AC grid, and an electric part that includes a multi-phase voltage system configured to be connected to a common DC capacitor. The electric part splits each AC grid phase n times into two phases, resulting in a plurality of intermediate phases at an internal interface, each intermediate phase corresponding to a pulse of the multi-pulse line-interphase transformer converter. The intermediate phases are connected to the multi-phase voltage system. The multi-phase voltage system comprises bridges with actively controlled switches. The bridges are connected in parallel to the common DC capacitor.

A multi-pulse line-interphase transformer converter includes an electric part that includes magnetic components configured to be connected to a three-phase AC grid, and an electric part that includes a multi-phase voltage system configured to be connected to a common DC capacitor. The electric part splits each AC grid phase n times into two phases, resulting in a plurality of intermediate phases at an internal interface, each intermediate phase corresponding to a pulse of the multi-pulse line-interphase transformer converter. The intermediate phases are connected to the multi-phase voltage system. The multi-phase voltage system comprises bridges with actively controlled switches. The bridges are connected in parallel to the common DC capacitor.

A power conversion device includes: a power converter connected to an AC grid to which a load is connected; and a control circuit. The control circuit includes a harmonic compensation unit that includes a current command generation unit and a limit coefficient calculation unit and compensates for harmonic current contained in load current. The current command generation unit generates compensation current desired values for respective frequency components, and corrects the compensation current desired values using corresponding limit coefficients, to generate compensation current commands for respective frequency components. The limit coefficient calculation unit calculates each limit coefficient, on the basis of the compensation current desired value for each frequency component, and maximum voltage and maximum current that the power converter can output.

A power conversion device includes: a power converter connected to an AC grid to which a load is connected; and a control circuit. The control circuit includes a harmonic compensation unit that includes a current command generation unit and a limit coefficient calculation unit and compensates for harmonic current contained in load current. The current command generation unit generates compensation current desired values for respective frequency components, and corrects the compensation current desired values using corresponding limit coefficients, to generate compensation current commands for respective frequency components. The limit coefficient calculation unit calculates each limit coefficient, on the basis of the compensation current desired value for each frequency component, and maximum voltage and maximum current that the power converter can output.

Provided is an active filter circuit connected to a power-receiving terminal of a power line for an alternating-current power supplied to a power converter device from an alternating-current power grid or a direct-current power source interconnected with the alternating-current power grid, or for a direct-current power supplied from the direct-current power source for reducing a harmonic component of a conduction noise propagating to the power line and outputting the reduced harmonic; and a controller for monitoring a variation in the state of an input power entering a power source module for generating drive power for an active element constituting the active filter circuit, or a variation in the state of the drive power supplied from the power source module, and diagnosing an abnormality of a circuit operation for a circuit including the active element of the active filter circuit therein.

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 V.sub.C AF of the DC intermediate circuit is lying in a given reference voltage range for balancing the DC intermediate circuit of the floating cell.

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 V.sub.C AF of the DC intermediate circuit is lying in a given reference voltage range for balancing the DC intermediate circuit of the floating cell.