A system and method for quickly detecting fault current on a power line in an electrical power distribution network. A switch assembly includes a detecting circuit for quickly detecting the fault current on the power line. The circuit includes a Rogowski coil wrapped around the power line that provides an output measurement signal that is proportional to a change in the current flow on the line, and a passive integrator responsive to the output measurement signal from the Rogowski coil that integrates the output measurement signal over time. The circuit also includes an amplifier responsive to and amplifying the integrated output measurement signal and a microcontroller responsive to the amplified output measurement signal that calculates the current flow on the line using the amplified output measurement signal. A current transformer harvests energy from the power line to power the circuit when the fault current is occurring.

A control device for an AC rotating machine includes: switching control means for controlling inverters and motor relays 15; and abnormality detection means for detecting an abnormality in each system and outputting a result of the detection to the switching control means. When the abnormality detection means detects an abnormality in at least one of the systems, the switching control means causes the motor relay to block a circuit between windings and the inverter in the system in which the abnormality has been detected, and continues normal control in a system other than the system in which the abnormality has been detected.

Provided is an inverter device that quickly detects an abnormality of a power device, which is an output unit of the inverter device, and of gate drive to be able to safely control and stop the inverter device. The inverter device includes a gate voltage detection unit 19 that detects a gate voltage VG of the power device with respect to a given threshold voltage, and a drain voltage detection unit 30 that detects a drain voltage with respect to a given threshold voltage. A microcontroller 10 compares a gate drive signal 40 with a gate voltage detection signal 41 to make a diagnosis and compares the gate drive signal 40 with a drain voltage detection signal 42 to make a diagnosis, thereby making a diagnosis on normal drive and detection of the gate voltage VG and on normal drive and detection of the power device. In addition, by generating a gate drive signal to the power device, from a gate voltage detection signal from a counter power device, a dead time is reduced.

A hybrid modular multilevel converter having fault blocking capability, and a control method thereof are disclosed. The hybrid modular multilevel converter has an ABC three-phase structure, each phase includes an identical upper arm and lower arm, and the upper arm and the lower arm are each composed of N submodules, including M unipolar full bridge submodules and N-M half bridge submodules, which are connected in series; two identical arm inductors are connected in series between a lower end of the upper arm and an upper end of the lower arm in a same phase; and upper arms and lower arms of three phases are connected in a staggered manner through six thyristor branches, the upper ends of the upper arms of the three phases are short-circuited and are connected to a DC side via a first isolating switch.

A motor control apparatus for controlling a power supply to an electrical motor (M) connected to an output terminal (3) of the motor control apparatus (1) comprising: an overcurrent protection circuit (1A) having a power switch (5) through which the electrical motor (M) receives an electrical load current (I.sub.L) and having a sensor component (4) connected in series with the power switch (5) and adapted to generate directly a voltage drop (ΔU.sub.4) corresponding to the current rise speed of the electrical load current (I.sub.L) flowing from an input terminal (2) of the motor control apparatus (1) via the sensor component (4) and the power switch (5) to the output terminal (3) and having a driver circuit (6) adapted to detect an occurring overcurrent depending on the voltage drop (ΔU.sub.4) generated by the sensor component (4) and/or depending on a voltage drop (ΔU.sub.5) along the power switch (5) and adapted to switch off said power switch (5) upon detection of an overcurrent within a switch-off period of less than one millisecond; and/or comprising a power supply control circuit (10) having a sensor component (9) adapted to measure at the input terminal (2) a supply voltage notified to a control unit (8) of the motor control apparatus (1) adapted to control an electrical power supplied to the electrical motor (M) depending on an operation mode of the electrical motor (M).

A control device for a power converter that can suppress oscillation of an output voltage of the power converter. The control device for the power converter includes an overvoltage detector configured to detect an overvoltage on an output side of the power converter and a controller configured to, when the overvoltage on the output side of the power converter is detected by the overvoltage detector, perform gate block after reducing a current command value given to the power converter. With the configuration, when the overvoltage on the output side of the power converter is detected, the control device performs the gate block after reducing the current command value given to the power converter. Accordingly, it is possible to suppress oscillation of an output voltage of the power converter.

A load abnormality detecting circuit for an inverter to detect abnormality of a load during an operation of the inverter which has a self-arc-extinguishing element as a switching element and a phase synchronizing loop controlling an output frequency to be a resonance frequency of the load, the load abnormality detecting circuit includes a phase shift detection part that detects a phase shift between a gate voltage signal controlling ON/OFF of the self-arc-extinguishing element and an output current of the inverter which is applied to the load, and that sends a first abnormal load signal based on the phase shift.

A method for locating a ground fault in an IT network which has a converter with a rectifier connected to a power transmission network, a DC link and an inverter connected to an electrical machine includes measuring a common-mode voltage property of the converter or of the power transmission network and comparing the common-mode voltage property with an output voltage property of an output voltage of the inverter. When the IT network experiences a ground fault, the comparison of the common-mode voltage property with the output voltage property is used to determine whether a machine area of the IT network connected downstream of the converter, which includes the electrical machine and a connecting line between the electrical machine and the converter, causes the ground fault.

A motor control method includes acquiring n-phase currents, where n is an integer of three or more, of a first inverter, a GND current of the first inverter, n-phase currents of a second inverter, and a GND current of the second inverter, generating a first fault signal indicating presence or absence of a shunt resistor fault in the first inverter based on the n-phase currents and GND current of the first inverter and generating a second fault signal indicating presence or absence of a shunt resistor fault in the second inverter based on the n-phase currents and GND current of the second inverter, referring to a table representing a relationship between a set of levels of the first fault signal and the second fault signal and control modes and selecting one of the control modes, and controlling a motor in accordance with the selected control mode.

An electrical installation having a first source of power, such as the utility grid, and a second source of power from an electronic DC-to-AC converter, comprises a smart load center for selecting the source of power independently for each of a number of branch circuits protected by circuit breakers to be the first source or the second source. The smart load center comprises a software-controlled processor for operating the transfer relays that select the first or second source of power for each branch circuit. In the event that a current overload on a branch circuit connected to the DC-to-AC converter causes it to trip before the branch circuit breaker clears the overload, all circuits are transferred to the first power source to trip the fault breaker and then the microprocessor enters a restart sequence to verify that the fault is cleared or else to take other action.