A converter and a method of operating a converter. The converter comprising a DC link capacitor, an upper arm (S1) and a lower arm (S4) with switching cells in series, an upper switch (S2) and a lower switch (S3). The upper switch (S2) and the lower switch (S3) are connected together and the connection point forming an output voltage terminal (a). The converter comprising further an upper valve component and a lower valve component, which are arranged such that the upper valve component allows current from the center point of the DC link capacitor towards the upper arm and the lower valve component allows current from the lower arm towards center point of the DC link capacitor. A current path through the upper valve component or the lower valve component comprises inductance to form a resonance circuit.

A converter and a method of operating a converter. The converter comprising a DC link capacitor, an upper arm (S1) and a lower arm (S4) with switching cells in series, an upper switch (S2) and a lower switch (S3). The upper switch (S2) and the lower switch (S3) are connected together and the connection point forming an output voltage terminal (a). The converter comprising further an upper valve component and a lower valve component, which are arranged such that the upper valve component allows current from the center point of the DC link capacitor towards the upper arm and the lower valve component allows current from the lower arm towards center point of the DC link capacitor. A current path through the upper valve component or the lower valve component comprises inductance to form a resonance circuit.

A method and apparatus for controlling a neutral point clamped inverter circuit, and a neutral point clamped inverter. It is detected that whether the inverter circuit operates in an abnormal state. In a case that the inverter circuit operates in the abnormal state, a control mode of the inverter circuit is changed to a specified control mode in which a transistor that may be damaged is in an off state. In this way, there is not current flowing through the transistor, avoiding damage of the transistor and thereby improving safety of the inverter circuit.

A method and apparatus for controlling a neutral point clamped inverter circuit, and a neutral point clamped inverter. It is detected that whether the inverter circuit operates in an abnormal state. In a case that the inverter circuit operates in the abnormal state, a control mode of the inverter circuit is changed to a specified control mode in which a transistor that may be damaged is in an off state. In this way, there is not current flowing through the transistor, avoiding damage of the transistor and thereby improving safety of the inverter circuit.

A frequency converter module includes a frequency control management module. An input port of the frequency conversion control management module is electrically connected to an input port of a power supply module. The power accuracy monitoring module includes an initial power measuring module, a power prediction correction module, and an actual power display storage module. An output port of the initial power measuring module is electrically connected to an input port of the power prediction correction module. An output port of the power prediction correction module is electrically connected to an input port of the actual power display storage module.

A method for generating an alternating electric current is provided. The method includes generating a plurality of component currents, superposing the component currents to form a summation current. Each component current is modulated by voltage pulses and the voltage pulses for each component current are generated by a component switching device by virtue of the component switching device generating the voltage pulses by switching between different input voltages. The method includes specifying a tolerance band for the summation current having an upper and a lower tolerance limit, where the summation current is detected and the switching of each component switching means is controlled to generate the voltage pulses for modulating the component current depending on the detected summation current with respect to the tolerance band. The plurality of component switching devices are switched at least partly or predominantly in a manner asynchronous with respect to one another.

A method for operating switching elements of a multilevel energy converter using at least three electric potentials and to which a multiphase electrical machine is connected. Switching elements of the multilevel energy converter are operated in a predefined clock mode by corresponding switching signals. The switching signals for the switching elements are each assigned to one of the phases and are determined in accordance with each desired voltage signal, in order to apply a phase voltage to each phase of the multiphase electrical machine. The switching signals are determined additionally in accordance with a predefined overlaying voltage signal such that an overlaying voltage dependent on the overlaying voltage signal is overlaid onto each phase voltage.

A power conversion device in an embodiment includes a first power converter; a plurality of direct current-direct current (DCDC) converter devices; and a second power converter. The first power converter includes a plurality of first positive-side arms; a plurality of first negative-side arms; a first positive-side star connection line configured to connect the plurality of first positive-side arms in a star shape; a first negative-side star connection line configured to connect the plurality of first negative-side arms in a star shape; and a first terminal configured to connect the first positive-side star connection line and the first negative-side star connection line to each phase of a power supply side alternating current (AC) system and the plurality of first positive-side arms and the plurality of first negative-side arms mutually convert a first AC power and a first DC power of the power supply side AC system. A plurality of DCDC converter devices mutually convert the first DC power and the second DC power. The second power converter includes a plurality of second positive-side arms; a plurality of second negative-side arms; a second positive-side star connection line configured to connect the plurality of second positive-side arms in a star shape; a second negative-side star connection line configured to connect the plurality of second negative-side arms in a star shape; and a second terminal configured to connect the second positive-side star connection line and the second negative-side star connection line to each phase of a load-side AC system, and the plurality of second positive-side arms and the plurality of second negative-side arms mutually convert the second DC power and the second AC power.

Herein provided is a controller for a current inverter. The controller comprises a reference generator configured for obtaining source voltage and current values from an electrical source, generating a voltage error function based on source and reference voltages, and generating a current error function based on source and reference currents. The controller also comprises an output controller for receiving from the reference generator the voltage and current error functions and configured for producing at least one control signal based on the voltage and current error functions. The controller also comprises a state feedback controller configured for: adjusting the at least one control signal, based on parameters of the electrical source, to produce at least one adjusted control signal, and outputting the at least one adjusted control signal to the current inverter.

A flying capacitor (FC)-type 3-level power conversion device turns on or off first to fourth semiconductor switching elements based on comparison between a flying capacitor voltage and a half of higher-voltage side filter capacitor voltage, comparison between the higher-voltage side filter capacitor voltage and the flying capacitor voltage plus a lower-voltage side filter capacitor voltage, comparison between the flying capacitor voltage and the lower-voltage side filter capacitor voltage, and comparison between the lower-voltage side filter capacitor voltage or the higher-voltage side filter capacitor voltage and a filter capacitor voltage command value, so that an electric current flows along a path including a filter reactor L and charging a flying capacitor so as to charge a lower-voltage side filter capacitor or a higher-voltage side filter capacitor to predetermined values.