An electrical assembly comprises a power converter including first and second DC terminals and an AC terminal. The electrical assembly also includes a grounding circuit to connect the AC terminal to ground. The grounding circuit defines first and second current flow paths between the AC terminal and ground. The first current flow path includes a switching element. The second current flow path includes a first current flow control element that is configured to operate in a first mode in which it reduce the flow of current between the AC terminal and ground when the first current flow path is open. The electrical assembly additionally includes a control unit configured to operate the switching element to maintain open the first current flow path following an occurrence of a DC network fault. The power converter is configured to continue transferring power between the DC and AC networks throughout the DC network fault.

In a multilevel converter, three first rectifying elements are respectively connected between three arms and a negative voltage terminal. Three second rectifying elements are respectively connected to the three first rectifying elements in antiparallel. During a normal operation, current flows in the three first rectifying elements and the three second rectifying elements. When a short circuit accident occurs between two DC power transmission lines, the three first rectifying elements are brought into the non-conductive state, thereby interrupting and quickly attenuating inter-arm direct current flowing in four arms and the like.

A fault current limiting control and protection coordination method for a converter of a flexible direct current transmission system operating in an islanding state, wherein the current output command limit Imax is used to limit the current commands I*.sub.Ldq of inner loop dq currents, and in the event of the fault of AC system, Imax is set equal to or slightly larger than a value for an AC line overcurrent protection section III. The value for the II section of the converter bridge arm overcurrent protection is smaller than the value for the II section of the AC line overcurrent protection or the value is equal; the set value for AC line overcurrent protection section I is smaller than the set value for converter bridge arm overcurrent protection section I; the value for proximal AC line overcurrent protection section II is less than or equal to the value for converter bridge arm overcurrent protection section II, and under such condition, the delay is longer than the AC line overcurrent protection section II. At the time of detecting a fault on the connected line side of the converter, the value of current output command limit Imax of the converter is changed from the allowable multiple of output current of the converter under normal condition to the value for the AC line protection section III in the event of fault. And, partial short circuit current is provided by limiting the output current of the converter, the AC fault is removed by the value for AC protection section III without affecting the normal operation of the converter. After the AC side fault is removed, Imax is restored to an allowable multiple of output current of the converter under normal condition. The method of switching Imax is that: pre-setting a series or curve of n groups of two-dimensional numerical values (U.sub.Lj, Imaxj) (j=1, 2, . . . n), the limit current command value Imax is obtained by using interpolation or lookup table method, to limit the output current value of the converter operating in passive state.

A method detects a working voltage collapse by use of an electric component, in which the exceeding of a critical characteristic of the working voltage is monitored and an excess is detected as a collapse. Accordingly, in order to recognize the collapse breakdown in a simple trouble-free manner, a model voltage generated by a model circuit is used as the critical characteristic.

An electrical system for an aircraft includes an AC electric power source electrically connected to a rotary electric motor via a plurality of AC contactors. An AC/DC inverter is electrically connected to the rotary electric motor, a DC power bus is electrically connected to the AC/DC inverter, and a plurality of sensors are arranged to monitor electric currents between the AC electric power source and the rotary electric motor. A first controller is arranged to control the AC/DC inverter; and a second controller is arranged to monitor the sensors and are operatively connected to the AC contactors. The second controller is operable to monitor, via the sensors, the electric currents between the AC electric power source and the rotary electric motor, and detect a fault based upon the electric currents, and deactivate the AC contactors in response to the fault.

A premagnetization device is disclosed for a converter system 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 configured to suitably premagnetize 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 converter system and a method for premagnetizing a three-phase power transformer of a converter system are also disclosed.

An electric circuit arrangement and a method for generating electric current pulses to a load, the electric circuit arrangement including a switch and a current source in series connection with the load; wherein the switch is arranged to operate in at least an on state and an off state, thereby selectively connecting or disconnecting the current source to or from the load so as to generate the electric current pulses. With such architecture, the circuit performs with a better efficiency than a cascaded architecture.

Each arm circuit of a power conversion device includes a plurality of cascaded cell blocks and a plurality of bypass circuits connected in parallel to the respective cell blocks. Each cell block includes: a first connection node on a high potential side and a second connection node on a low potential side for connection to another cell block; and a plurality of converter cells cascaded between the first and second connection nodes, each converter cell containing an energy storage. The plurality of converter cells include at least one first converter cell of a full-bridge (or hybrid) configuration and at least one second converter cell of a half-bridge configuration.

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.

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.