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 centred 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 switching power supply includes an output circuit connected to a secondary coil of a transformer via a secondary switching element and a synchronous rectification control circuit controlling ON/OFF of the secondary switching element based on a detected source-drain voltage of the secondary switching element. The synchronous rectification control circuit includes a voltage detection circuit detecting the source-drain voltage, a switch driving circuit switching the secondary switching element ON/OFF based on the detected source-drain voltage, an auxiliary power supply circuit generating an auxiliary supply voltage from said source-drain voltage, a voltage decrease detection circuit detecting an abnormal voltage drop in a DC output voltage of the output circuit, and a power supply switching circuit switching a power supply for the voltage detection circuit and switch driving circuit from the DC output voltage to the auxiliary supply voltage when the abnormal voltage drop is detected.

In a multilevel converter, three circuit breakers are respectively connected between three arms and three reactors. One circuit breaker is a DC circuit breaker configured to interrupt direct current when a short circuit accident occurs between two DC power transmission lines. Each of the two circuit breakers is an AC circuit breaker configured to interrupt alternating current when the short circuit accident occurs. When the short circuit accident occurs, the two AC circuit breakers are brought into the non-conductive state and then the DC circuit breaker is brought into the non-conductive state, thereby interrupting the short circuit current.

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 switching power supply includes an output circuit connected to a secondary coil of a transformer via a secondary switching element and a synchronous rectification control circuit controlling ON/OFF of the secondary switching element based on a detected source-drain voltage of the secondary switching element. The synchronous rectification control circuit includes a voltage detection circuit detecting the source-drain voltage, a switch driving circuit switching the secondary switching element ON/OFF based on the detected source-drain voltage, an auxiliary power supply circuit generating an auxiliary supply voltage from said source-drain voltage, a voltage decrease detection circuit detecting an abnormal voltage drop in a DC output voltage of the output circuit, and a power supply switching circuit switching a power supply for the voltage detection circuit and switch driving circuit from the DC output voltage to the auxiliary supply voltage when the abnormal voltage drop is detected.

A semiconductor device for power supply control includes an on/off control signal generation circuit which generates a control signal for turning on or off a switching element; a current detection terminal to which voltage in proportion to a current flowing in a primary-side winding wire of a transformer is input; a pull-up unit with high impedance provided between the current detection terminal and a terminal to which an internal power supply voltage is applied; and a terminal monitoring circuit which determines that the current detection terminal is abnormal when comparing the voltage of the current detection terminal with a predetermined voltage and detecting that the voltage of the current detection terminal is higher than the predetermined voltage. When the terminal monitoring circuit detects abnormality of the current detection terminal, a signal generation of the on/off control signal generation circuit is stopped by a signal output from the terminal monitoring circuit.

An electric grid includes feed-ins, loads, and a distribution grid, which is arranged therebetween. The distribution grid comprises at least one busbar and at least one device for opening or closing a DC circuit. The at least one device includes an electric switch for opening or closing the DC circuit, a fault current detector, a trigger unit, a precharging device, and a control unit for automatically closing the electric switch after the precharging process. The electric switch opens the DC circuit via the trigger unit if a fault current is detected by the fault current detector, and the precharging device restores the voltage on the busbar prior to closing the electric switch.

A device is for opening or closing a DC circuit with at least one busbar. The device includes an electric switch for opening or closing the DC circuit; a fault current detector; a trigger unit and a precharging device. The electric switch opens the DC circuit via the trigger unit upon a fault current being detected by the fault current detector. Further, the precharging device restores the voltage on the busbar prior to closing the electric switch. The device further includes a control unit for automatically closing the electric switch after the pre-charging process.

An electrical network includes feed-in devices, loads, and a distribution grid, which is arranged therebetween and comprises at least one busbar and at least one device for opening or closing a DC circuit. The at least one device includes: an electric switch for opening or closing the DC circuit; a fault current detection device; a trigger unit; a precharging device; and a control unit for automatically closing the electric switch after the precharging process. The electric switch opens the DC circuit via the trigger unit if a fault current is detected by the fault current detector, and the precharging device restores the voltage on the busbar prior to closing the electric switch. Multiple loads can be individually electrically separated via a respective electromechanical switch, and multiple loads can be electrically separated as a group via the at least one device.

An AC circuit breaker is provided between an AC system and an AC-DC converter, and a DC circuit breaker is provided between a DC line and the AC-DC converter. A bypass switch capable of short-circuiting a converter cell included in the AC-DC converter is connected to the AC-DC converter. At the time of a fault in the DC line, the bypass switch is turned on to interrupt the supply of DC power from the AC system to the DC line.