A frequency converter includes a monitoring unit that has respective first drive signals of gate drivers of a bidirectional power converter applied to it and that is designed to detect the failure of at least one mains phase of a three-phase AC grid voltage that is supplied to the bidirectional power converter based on a temporal profile of the respective first drive signals.

A frequency converter has a first intermediate circuit arm on which a positive intermediate circuit potential is present during operation of the frequency converter, a second intermediate circuit arm on which a negative intermediate circuit potential is present during operation of the frequency converter, an inverter having a first input terminal and a second input terminal, wherein the inverter has a number of bridge arms, wherein each of the bridge arms has an upper semiconductor switching device and a lower semiconductor switching device, wherein the upper semiconductor switching device and the lower semiconductor switching device are looped-in in series between the first input terminal and the second input terminal, and wherein a connection node of the upper semiconductor switching device and the lower semiconductor switching device forms an output terminal of the inverter. A reactor is looped-in between the first intermediate circuit arm and the first input terminal of the inverter. A shunt resistor is looped-in between the second intermediate circuit arm and the second input terminal of the inverter. An evaluation unit is configured, on the basis of a voltage across the shunt resistor, to detect a ground fault on the upper semi-conductor switching devices of the inverter.

According to an embodiment, a capacitor diagnosis device includes a sensor, a frequency spectrum analysis unit, a frequency component extraction unit, and a diagnosis processing unit. The sensor detects a physical quantity that changes with an current flowing through a capacitor in a power conversion unit (PCU) for converting DC power smoothed by the capacitor connected in parallel to DC link(s) into AC power according to a power running operation. The frequency spectrum analysis unit generates a frequency spectrum based on a detection result of the sensor detected during the power running operation of the PCU. The frequency component extraction unit extracts a component of a specific frequency band related to a frequency depending on a configuration of the PCU based on the frequency spectrum. The diagnosis processing unit diagnoses a state of the capacitor based on at least a magnitude of the extracted component of the specific frequency band.

For Direct Current (DC) bus voltage control, a method generates a q-axis reference current from a DC voltage error that includes a DC voltage input modified by a DC bus voltage in a closed outer loop. The method further generates a d-axis reference current from the DC voltage error, wherein the second-order harmonic in the d-axis reference current is delayed from that in q-axis reference current by 90 degrees. The method generates a q-axis current from the q-axis reference current. The method generates a d-axis current from the d-axis reference current. The second-order harmonic in d-axis current is offset from the second-order harmonic in q-axis current by 90 degrees. The method controls the DC bus voltage of a voltage control plant to mitigate a second-order harmonic in the DC bus voltage with the second-order harmonics in the q-axis current and the d-axis current.

A method for operating a multi-level bridge power converter includes arranging a plurality of switching devices including at least four inner switching devices and at least two outer switching devices in an active neutral point clamped topology. The method also includes determining whether any of the switching devices is experiencing a failure condition by implementing a failure detection algorithm. The failure detection algorithm includes generating a blocking state logic signal by comparing a switching device voltage and a threshold reference voltage for each of the switching devices, determining an expected voltage blocking state for each of the switching devices based on gate drive signals of the switching devices and an output current direction, and detecting whether a failure condition is present in any of the switching devices based on the blocking state logic signals and the expected voltage blocking states of the switching devices.

An electric power converter for a photovoltaic energy source, including: an inverter to receive a dynamically changing DC signal generated by the photovoltaic energy source and to generate a corresponding dynamically changing AC signal having a frequency substantially equal to a mains supply frequency; and an electromagnetic apparatus, including: a magnetic core and a plurality of windings around the magnetic core. The windings include: one or more input windings to receive the dynamically changing AC signal as an AC input; one or more output windings to provide an AC output signal; and control windings configured to control electromagnetic coupling between the input and output windings; and a control component configured to dynamically control electrical currents through the control windings so that the electrical characteristics of the AC output signal are relatively constant despite the dynamically changing AC signal and include a fundamental frequency equal to the mains supply frequency.

The invention relates to an energy transfer system (300) for wireless energy transfer with a transmitter unit (100) and a receiver unit (200) separate from the transmitter unit, wherein the transmitter unit (100) has a primary coil (L.sub.1) that can be supplied with a predetermined supply voltage (U.sub.v), and wherein the receiver unit (200) has a secondary coil (L.sub.2) to which a DC link capacitor (C.sub.z) is connected by a rectifier (210). According to the invention, the energy transfer system (300) comprises a device (230) designed to determine a value of a DC link voltage (U.sub.z) applied on the DC link capacitor (C.sub.z) when the supply voltage (U.sub.v) is applied on the primary coil (L.sub.1), and a device (240) designed to perform at least one predetermined function based on the determined value of the DC link voltage (U.sub.z) or a variable (K) derived therefrom. The invention also relates to a receiver unit (200) configured to interact for wireless energy transfer with a transmitter unit (100) separate from the receiver unit, said transmitter unit (100) comprising a primary coil (L.sub.1) that can be supplied with a supply voltage (U.sub.v), wherein the receiver unit (200) comprises a secondary coil (L.sub.2) to which a DC link capacitor (C.sub.z) is connected by a rectifier (210). According to the invention, the receiver unit contains a device (230) designed to determine a value of a DC link voltage (U.sub.z) applied on the DC link capacitor (C.sub.z) when a supply voltage (U.sub.v) is applied on the primary coil (L.sub.1) and a device (240) designed to perform at least one predetermined function based on the determined value of the DC link voltage (U.sub.z) or a variable (K) derived therefrom.

Examples of the disclosure include a UPS comprising an output to be coupled to a load, a first converter leg to provide a first voltage to the output and including at least one of a first relay or fuse, a second converter leg in parallel with the first converter leg including at least one of a second relay or fuse and configured to provide a second voltage to the output out of phase with the first converter leg providing the first voltage signal, current sensors coupled to the first and second converter legs, respectively, and configured to provide a first signal indicative of a current in the first converter leg and a second signal indicative of a current in the second converter leg, respectively, and at least one controller to receive the signals, determine a current difference between the converter legs based on the signals, and decrease the current difference.

A converter for an air conditioning system including a rectifier section configured to receive an AC input voltage; a voltage regulator section coupled to the rectifier section, the voltage regulator section configured to control a DC output voltage across a positive DC bus and a negative DC bus; and a controller in communication with the rectifier section and the voltage regulator section, the controller configured to control the converter such that the DC output voltage is greater than AC input voltage by an offset.

A power electronic device comprising a grid side (L1, L2, L3) connected to a capacitor bank (2) is described, the capacitor bank (2) being connected to ground via a switch. Such power electronic device should be used in different types of grid with low costs. To this end a varistor (5) is connected in parallel to the switch.