Provided is a premagnetization device for a converter system that is connectable to a three-phase electrical grid that has a three-phase power transformer, a converter connected to the power transformer and a circuit-breaker on the grid side of the power transformer. The premagnetization device is premagnetizes the power transformer in a state isolated from the grid. The premagnetization device uses a single-phase reference voltage (Uref) that has a fixed relationship to the grid voltage (Ugrid) with regard to the voltage parameters, in order to generate, based on the measured instantaneous reference voltage (Uref) and the known fixed parameter relationships, by actuating the converter, a three-phase alternating voltage synchronous to the grid voltage (Ugrid) on the grid side of the power transformer.

A power distribution system has a power converter with a plurality of semiconductor switching devices per phase, a PWM controller, and a current limitation controller. The current limitation controller is adapted, at least when a short-circuit fault is detected, to calculate the difference between a measured current for each phase and a reference current for the corresponding phase. If the calculated difference is located outside a predetermined current range centered about the reference current for the corresponding phase, the current limitation controller will allow the semiconductor switching devices of the corresponding phase to be turned on and off by the PWM controller. Otherwise, if the calculated difference is located inside the predetermined current range, the current limitation controller will control the semiconductor switching devices for the corresponding phase to be turned off irrespective of the PWM control strategy applied by the PWM controller.

A method and a device provide protection for a multi-terminal HVDC grid against faults. The method includes measuring a DC displacement voltage having a polarity and a value, determining if a short circuit fault exists by comparing the DC displacement voltage with a threshold displacement voltage and identifying a fault type based on the polarity and the value of the DC displacement voltage. The disclosed device contains a converter having a positive pole and a negative pole, a DC-switch substation, a DC line connecting the converter and the DC-switch substation and a transient fault detector. The transient fault detector contains a positive voltage sensor sensing a positive transient voltage of the positive pole and a negative voltage sensor sensing a negative transient voltage of the negative pole and a control unit which is adapted to derive a DC displacement voltage from the positive and the negative transient voltages.

A convertor apparatus includes: a main circuit unit which converts an alternating current to a direct current and outputs the same to a DC link; a DC link capacitor; an alternating current voltage detection unit which detects an alternating current voltage crest value of the main circuit unit; a DC link capacitor voltage detection unit which detects a DC link capacitor voltage value; an initial charging unit which includes a switch for opening and closing an electrical path between the main circuit unit and the DC link capacitor and a charging resistor; a current detection unit which detects a current value flowing into the main circuit unit or flowing out of the main circuit unit; and a voltage reference value setting unit which sets the voltage reference value in accordance with the current value when the switch is adapted from to be opened into to be closed.

An IGBT short-circuit detection and protection circuit, comprising: a driving unit, the output end thereof outputting a PWM driving signal and being connected to gate ends of a first IGBT (IGBT1) and a second IGBT (IGBT2), so as to simultaneously control the turning ON/OFF of the first IGBT and the second IGBT; a comparing unit, comprising a threshold pin and a detection pin (Vdesat), the threshold pin being connected to a threshold voltage, the detection pin being connected by means of a first diode (D1) and a second diode (D3) to collectors (C) of the first IGBT and the second IGBT, respectively, the detection pin supplying a detection current to the first diode and the second diode, cathodes of the first diode and the second diode being connected to the collectors of the first IGBT and the second IGBT, respectively; when the voltage at the detection pin is higher than the threshold voltage, the driving unit controlling the first IGBT and the second IGBT to be turned off. The IGBT short-circuit detection protection circuit achieves bidirectional short-circuit protection of two IGBTs in inverse series connection, without requiring an additional protection circuit.

A DC power transmission system interconnects a plurality of AC systems via a DC line. A plurality of power conversion devices are connected between the plurality of AC systems and the DC line. One of the plurality of power conversion devices controls the voltage on the DC line, while the remaining power conversion device controls a current input and output to and from the DC line. In a restart which resumes power conversion from a stopped state for controlling a DC current on the DC line, the power conversion device performing current control monitors the voltage on the DC line and starts a restart operation without transmitting or receiving information to or from the other power conversion device.

A power receiving device includes: a power receiving unit configured to wirelessly receive power from a power transmitting unit of a power transmitting device; a rectifier circuit; a charging relay provided between the rectifier circuit and the power storage device; a voltage sensor configured to sense a voltage applied from the power receiving unit to the rectifier circuit; and a charging ECU configured to wirelessly communicate with the power transmitting device via a communication device. After wireless communication with the power transmitting device is established before a power request is output to the power transmitting device, the charging ECU closes the charging relay and also performs a short-circuit determination process, by using a value of a voltage sensed by the voltage sensor with the charging relay closed, to determine whether the rectifier circuit has a short circuit fault.

The invention relates to a redox flow battery system, comprising a controller and a battery inverter, which is suitable for charging and/or discharging a battery. The battery inverter comprises: a) a plurality of battery connections, to each of which at least one battery can be connected; b) a first measuring device, which is suitable for measuring the voltage at a battery connection and which is connected to the controller with regard to signaling; c) a second measuring device, which is suitable for measuring the current at a battery connection and which is connected to the controller with regard to signaling; d) a grid connection, which can be connected to an alternating-current supply grid; and e) a plurality of DC/DC converters, of which at least one has a first bridge circuit directly connected to a battery connection.

A fault current limiting control and protection coordination method for a converter of a flexible direct current transmission system operating in an islanding state is provided. The current output command limit Imax is used to limit the current commands of inner loop currents, and in the event of a fault, Imax is set equal to or slightly larger than a value for an AC line overcurrent protection section.

Provided is an MMC and a DC failure blocking method therefor, the MMC and the method being capable of DC failure blocking and reducing loss using a combination of half-bridge submodules and full-bridge submodules for converter arms of the MMC. According to the present invention, there is provided a modular multilevel converter (MMC) including multiple converter arms, each converter arm having: N (N2, an integer) submodules connected to each other in series; and a circuit opening unit connected to the N submodules in series to open a circuit of the converter arm, wherein the N submodules are n (n<N) submodules including full-bridge circuits and N-n submodules including half-bridge circuits.