A power device fault detection circuit includes a first fault detector configured to measure an output signal of at least one power device and output a first fault signal when a voltage of the output signal of the at least one power device exceeds a first voltage reference level after a first time period; and a second fault detector configured to measure an output signal of the at least one power device and output a second fault signal when a voltage of the output signal of the at least one power device exceeds a second voltage reference level after a second time period, where the first time period implemented by the first fault detector is shorter than the second time period implemented by the second fault detector.

The invention discloses a commutation failure protection method, and apparatus, computer device and storage medium thereof. The method comprises: collecting three-phase AC currents on a valve-side of a converter, a DC current on a high-voltage side and a DC current on a neutral terminal; selecting a minimum value of an absolute value of the three-phase AC currents on the valve side as an AC characteristic quantity, and selecting a maximum value of the DC current on the high-voltage side and the DC current on the neutral terminal as a DC characteristic quantity; according to the AC characteristic quantity and the DC characteristic quantity, constructing a minimum characteristic quantity; comparing the minimum characteristic quantity with a first preset threshold, and outputting a commutation judgment result; according to the commutation judgment result, constructing a commutation time interval; comparing the commutation time interval with a second preset threshold and a third preset threshold, and outputting a commutation failure protection judgment result to determine whether a commutation failure occurs. The invention uses minimum current sequence characteristics to track a commutation process of a converter valve, and when a commutation failure occurs, it may make timely, accurate and reliable judgment, thereby ensuring safe operation of valve equipment.

An isolated switched-mode power converter converts power from an input source into power for an output load. Power switches within a primary-side power stage control the amount of power input to the power converter and, ultimately, provided to the output load. A digital controller on the secondary side of the power converter generates signals to control the power switches. This controller also senses a rectified voltage on the secondary side of the power converter and uses this sensed voltage to detect fault conditions of the primary side. For example, the sensed rectified voltage is used to detect undervoltage or overvoltage conditions of the input power source of the power converter, or faulty power switches within the primary-side power stage.

A short-circuit protection apparatus includes a first detection branch, a second detection branch, and a controller. The first detection branch includes a first sampling resistor and a first sampling capacitor that is connected in parallel to the first sampling resistor. A difference between an absolute value of a second sampling voltage and an absolute value of a first sampling voltage is a first difference. The controller obtains a comparison result between an absolute value of a first sampling voltage at two terminals of the first sampling resistor and an absolute value of a second sampling voltage at two terminals of the second sampling resistor, and if a difference between the absolute value of the second sampling voltage and the absolute value of the first sampling voltage is a second difference and the second difference is less than the first difference, controls the target circuit to stop working.

A system, a switch assembly and an associated method. The system includes a number of switch assemblies, each including a switch module, isolation circuits, a detection unit, and a drive unit. The switch module includes power switch devices connected in parallel. The switch modules are connected in series. The isolation circuits each are connected in series to a gate terminal of at least one corresponding power switch device of the power switch devices. Each isolation circuit includes a capacitor or a controllable switch. The detection unit detects faults in at least one of the power switch devices. The drive unit is coupled to the switch module via the isolation circuits for driving the power switch devices of the corresponding switch module, and when the fault is detected, the drive unit is for turning on the power switch devices parallel connected to the at least one of faulty power switch devices.

A method and apparatuses for handling delayed zero crossing in fault current through a circuit breaker are disclosed. An interface arrangement is configured to couple an alternating current, AC, power system with a direct current, DC, power system, or vice versa. The interface arrangement includes at least one converter for conversion of AC power to DC power, or vice versa, which includes a DC side for coupling of the converter to the DC power system and an AC side for coupling of the converter to the AC power system. A circuit breaker is arranged in a current path between the AC side of the at least one converter and the AC power system. There may be a risk of delayed zero crossing in fault current occurring in case a fault occurs in a predefined portion of the interface arrangement. If a fault is sensed to occur in the interface arrangement within the predefined portion of the interface arrangement, opening of contacts of the circuit breaker can be delayed by a selected delay time period, compared to if the fault would have been within a portion of the interface arrangement different from the predefined portion.

A method manages a fault on a DC voltage side of a converter assembly including a modular multistage converter with switching modules having semiconductor switches and an energy store. Some switching modules are a first type and others are a second type. During operation, a positive switching module voltage, negative switching module voltage or zero voltage are generated at terminals of switching modules of the first type, and a positive switching module voltage or zero voltage are generated at terminals of switching modules of the second type. Upon detecting a DC voltage side fault, switching modules of the first type are actuated such that the polarity of their energy store voltages corresponds to the polarity of a fault current, and energy stores of switching modules of the first type are charged to a voltage exceeding their rated voltage. A converter assembly carrying out the method is also provided.

A direct-current power supply device includes a reactor, a bridge circuit that converts alternating-current voltage output from an alternating-current power supply, which is connected to the reactor, into direct-current voltage, a capacitor that smoothes the output voltage of the bridge circuit, a current detector that detects a first current flowing as an alternating current between the alternating-current power supply and the bridge circuit, a current detector that detects a second current flowing as a direct current between the bridge circuit and the capacitor, an overcurrent determination unit that determines on the basis of a detected first current value whether or not the first current is an overcurrent, and an overcurrent determination unit that determines on the basis of a detected second current value whether or not the second current is an overcurrent. The bridge circuit stops operating when a determination result of either the overcurrent determination unit or the overcurrent determination unit indicates an overcurrent.

A direct-current power supply device includes a reactor, a bridge circuit that converts alternating-current voltage output from an alternating-current power supply, which is connected to the reactor, into direct-current voltage, a capacitor that smoothes the output voltage of the bridge circuit, a current detector that detects a first current flowing as an alternating current between the alternating-current power supply and the bridge circuit, a current detector that detects a second current flowing as a direct current between the bridge circuit and the capacitor, an overcurrent determination unit that determines on the basis of a detected first current value whether or not the first current is an overcurrent, and an overcurrent determination unit that determines on the basis of a detected second current value whether or not the second current is an overcurrent. The bridge circuit stops operating when a determination result of either the overcurrent determination unit or the overcurrent determination unit indicates an overcurrent.

An active bridge rectifier circuit includes a rectifier unit and a control unit. The rectifier unit includes a first upper bridge switch, a second upper bridge switch, a first lower bridge switch, and a second lower bridge switch. The control unit includes a first signal comparator and a second signal comparator. The first signal comparator compares a live wire signal provided from a live wire end with a neutral wire signal provided from a neutral wire end to generate a first comparison signal. The second signal comparator compares the live wire signal with the neutral wire signal to generate a second comparison signal. The first comparison signal controls the first upper bridge switch and the first lower bridge switch. The second comparison signal controls the second upper bridge switch and the second lower bridge switch.