A persistent DC circuit breaker provides a persistent single or dual DC voltage for a power distribution circuit coupled to a power panel. A control mechanism ensures a constant and consistent DC power output from the persistent DC circuit breaker. The persistent DC circuit breaker can replace an AC circuit breaker to convert an AC power panel into a coexisting AC and DC power panel or an entire DC power panel.

Disclosed is a BRCT clamping absorption circuit with short circuit protection, which relates to the technical field of short-circuit protection, includes a load module, a short-circuit detection module, a short-circuit protection module, a spike absorption module, a rectifying module, a clamping module and a main control module, wherein, the spike absorption module is connected with the load module, the rectifying module is connected with the spike absorption module, and the clamping module is connected with the rectifying module to form a clamping absorption protection for a spike voltage; the main control module is connected with the short-circuit detection module, and is used for controlling the on-off of a load regulator according to the short-circuit signal.

An AC/DC converter includes an AC circuit breaker, configured as a hybrid circuit or semiconductor circuit breaker; a rectifier; a smoothing capacitor; a semiconductor switch connected in series with the smoothing capacitor; and a first isolation relay for galvanic isolation. One input of the AC circuit breaker forms an AC input of the converter. One output of the AC circuit breaker is connected with an input of the rectifier. The smoothing capacitor, and the first semiconductor switch, connect a first output of the rectifier with its second output. The first output of the rectifier is connected with one input of the first isolation relay. The one output of the first isolation relay forms a first DC output of the AC/DC converter. The AC circuit breaker, the first semiconductor switch, and the first isolation relay are interconnected.

A control device for an MMC is disclosed. The control device for an MMC including a plurality of converter arms that include a plurality of sub-modules connected in series and that are connected to a DC link includes: an arm controller, which detects the arm current of a converter arm so as to determine whether a DC failure has occurred, and, if it is determined that the DC failure has occurred, transmits a bypass control signal for protecting a sub-module and notifies of the DC failure; a sub-module controller for controlling the sub-module so as to bypass a DC failure current according to the bypass control signal received from the arm controller; and a main controller, which detects, in real-time, the arm current of the converter arm and a voltage (DC link voltage) of the DC link, determines whether the DC failure is a temporary DC failure or a permanent DC failure on the basis of the detected arm current and DC link voltage if the occurrence of the DC failure is notified by the arm controller, and transmits, to the arm controller, a normal operation control signal for normal operation of the sub-module or a bypass control signal for bypassing of the DC failure current.

The problem to be solved is to provide a system and a method to protect the regulator rectifiers from the reverse voltage condition and the short circuit condition, and the problem is solved in the present invention by a system and a method that use a protection device including a control unit that receives an input from the circuit based on the reverse voltage condition and the short circuit condition, and based on the existence of at least one of the condition or a combination thereof, the control unit switches a switching unit from an ON state to an OFF state, thereby breaking the circuit between the regulator rectifier device and the load section, thus protecting the regulator rectifier device.

A first converter station is part of a high voltage direct current transmission system that includes a DC transmission link connected to the first converter station a second converter station. A DC current and a DC voltage of the DC transmission link are sensed by the first converter station. It is determined that the sensed DC current is equal to or larger than a threshold current value, that the sensed DC current is equal to or larger than the threshold current value, and that at least a partial recovery of the sensed DC voltage has occurred. On the basis that it is determined that the at least a partial recovery of the sensed DC voltage has occurred, it is determined that a phase-to-ground fault has occurred. In response to determining that a phase-to-ground fault has occurred, a power delivered by the first converter station can be reduced.

A high voltage DC (HVDC) system can include a generator configured to output alternating current (AC), a rectifier connected to the generator via AC phase lines, the rectifier configured to convert the AC to DC to output the DC to DC feeder lines, and a crowbar system. The crowbar system can include a switch module operatively connected to the AC phase lines to prevent AC from flowing to the rectifier in a cutoff state. The crowbar system can be configured to determine whether at least one cutoff condition exists. The at least one cutoff condition can be or include one or more of a DC overcurrent downstream of the rectifier, a DC overvoltage downstream of the rectifier, an AC overcurrent from the generator, or an arc fault. The crowbar system can be configured to control the switch module to the cutoff state if the at least one cutoff condition exists.

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.

An output device outputs a DC voltage applied between a first terminal and a second terminal via the drain and the source of a semiconductor switch. The output device includes a conversion circuit configured to convert the DC voltage into a voltage of a predetermined polarity, irrespective of the polarity of the DC voltage. A booster circuit boosts the voltage that was converted by the conversion circuit and applies the boosted voltage to the gate of the semiconductor switch. The semiconductor switch is on if the voltage of the control terminal with respect to the potential of the first terminal is at least a predetermined voltage.

An improved electric circuit structure for short circuit protection is applicable to examining a device under test, comprising a circuit breaking element, a thermistor, a filtering and rectifying module and a capacitor. A first end of the circuit breaking element is connected to a power source. The filtering and rectifying module is connected to a second end of the circuit breaking element, a ground, a first end of the thermistor and a first end of the capacitor. A second end of the capacitor is connected to a second end of the thermistor. The capacitor is connected in parallel with the device under test. The circuit breaking element disclosed in the present invention is a ceramic tube fuse and forms an open circuit when the device under test forms a short circuit. Meanwhile, the ceramic tube fuse withstands voltage between its first and second end without generating any physical damage.