A power supply apparatus supplies a bus voltage V.sub.BUS to a power receiving apparatus via a cable. A power supply circuit generates the bus voltage VBUS. The bus switch SW is arranged on a path of a bus line extending from the output of the power supply circuit. A power supply side controller is capable of communicating with a power receiving side controller of the power receiving apparatus. The power supply side controller determines the voltage to be supplied, based on a negotiation result. Furthermore, the power supply side controller controls the bus switch SW. When a predetermined state repeatedly occurs in the power supply circuit, a short circuit detection circuit judges that a short-circuit abnormality has occurred.

A motor drive apparatus includes: a rectifier; an inverter; a DC link voltage detection unit; an input current detection unit configured to detect input current inputted to the rectifier; a DC link voltage comparison unit configured to compare a DC link voltage with a first voltage threshold value and with a second voltage threshold value; a current comparison unit configured to compare the input current with a current threshold value; and an abnormality detection unit configured, in a case that the DC link voltage is smaller than the first voltage threshold value or that the DC link voltage is greater than the second voltage threshold value, to determine that a first abnormality has occurred when the input current is smaller than the current threshold value and to determine that a second abnormality has occurred when the input current is equal to or greater than the current threshold value.

A method of monitoring an electrical system may include providing a ground fault detection unit, operating a transformer rectifier unit to provide DC power to a load, sensing, via a current sensor, a ground current at or about an output of the transformer rectifier, and/or monitoring a sensor output from the current sensor via the ground fault detection circuit. The ground fault detection circuit may be configured to detect ground faults at frequencies of at least 30 kHz.

A power conversion device includes a converter, a first capacitor, and a second capacitor. The first capacitor is connected between a DC positive bus and a DC neutral point bus. The second capacitor is connected between the DC neutral point bus and a DC negative bus. The converter includes a diode rectifier connected between an AC power supply and each of the DC positive bus and the DC negative bus, and a first AC switch electrically connected between the AC power supply and the DC neutral point bus. The power conversion device further includes a first fuse electrically connected between the first AC switch and a connection point between the first and second capacitors.

A matrix converter includes one or more current sensors structured to sense current flowing through the matrix converter, a matrix of switches including a number of solid state transistors, and a control circuit structured to detect faults in power flowing through the matrix converter based on the sensed current, to control the matrix of switches to drive an external device, and to control the matrix of switches to switch to prevent power from flowing internal to the matrix converter, or external to the external device in response to detecting a fault in power flowing through the matrix converter.

The present disclosure discloses a resistive sub-module hybrid MMC and a direct current fault processing strategy thereof. The hybrid MMC prevents fault current from entering a direct current system from the alternating current side by artificially creating three-phase earthing short circuit on the alternating current side of a converter during the direct current fault processing process, and can reduce the number of required power electronic devices compared with the module hybrid MMC. At the same time, the direct current fault processing speed of the hybrid MMC is fast, and the duration of the artificially creating three-phase short circuit fault in the fault processing process is less than 60 ms, which will not have a great impact on the alternating current system. The present disclosure greatly reduces the cost of building an overhead line high-voltage flexible direct current transmission system, and has very strong reference significance and use value in engineering.

A power conversion circuit having a solid-state circuit breaker integrated therein is disclosed. With a disconnect switch between a utility source and the power conversion apparatus described for meeting UL489, the power conversion circuit includes an input connectable to an AC source, a rectifier circuit connected to the input to convert an AC power input to a DC power, and a DC link coupled to the rectifier circuit to receive the DC power therefrom. The rectifier circuit comprises a plurality of phase legs each including thereon an upper switching unit and a lower switching unit, wherein at least one of the upper and lower switching units on each phase leg comprises a bi-directional switching unit that selectively controls current and withstands voltage in both directions, so as to provide a circuit breaking capability that selectively interrupts current flow through the rectifier circuit, while maintaining original power conversion functionalities.

A protection circuit including an inrush current detector operable to detect an inrush current from a DC link is disclosed herein. The inrush current detector includes a transistor switch that is turned on in normal operation of the protection circuit. The protection circuit operates to detect when the voltage across the transistor switch exceeds a threshold voltage in response to a detected inrush current, and in response operates to turn off the transistor switch.

A protection arrangement for a multiphase uninterruptible power supply system including a vacuum circuit breaker connected in series with an inductive element, where the inductive element includes, for every phase, two series-connected magnetically coupled windings separated by a tap point. The protection arrangement includes one first group of protective components per phase, each first group including a first protective component having a first end connected to a link between the vacuum circuit breaker and the inductive element and a second end connected to a corresponding tap point, where at least one protective component in each first group is a surge arrester.

A power converter and method for providing surge protection to the power converter is provided herein. An over voltage protection portion of a protection circuit is coupled between the rail voltage and ground reference of the power converter, and senses a first magnitude of the rail voltage. An under voltage protection portion of the protection circuit is coupled to a controller of the power converter and further between the rail voltage and the ground reference, and senses a second magnitude of the rail voltage to be transmitted to the controller. A regulator block is coupled between the over voltage protection portion and the under voltage protection portion, and is configured to compare the first magnitude of the rail voltage to a reference voltage of the regulator block, and to short circuit the under voltage protection portion when the first magnitude of the rail voltage is greater than the reference voltage.