A device control method includes: receiving a turn-on signal of a target device, the turn-on signal being adapted to trigger the target device to start working; obtaining a compensation duration, the compensation duration being adapted to offset a delay caused when a voltage zero-crossing detection component detects voltage zero-crossing; and when a zero-crossing signal is received, after the compensation duration, controlling a designated component in the target device to be turned on or off. The zero-crossing signal is a signal sent when the voltage zero-crossing detection component detects that a voltage passes through a zero point. A power supply voltage detection method and a power supply voltage detection apparatus are also disclosed.

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.

A method for detection of a sub-synchronous oscillation in a power system includes measuring a three-phase measurement signal of an electric system value, analyzing the measurement signal to detect an oscillation component of the measurement signal having an oscillation frequency lower than a system frequency of the power system, deciding whether the detected oscillation component at the oscillation frequency qualifies as a sub-synchronous oscillation, and disconnecting a generator from the power system that might be affected by the sub-synchronous oscillation. To detect sub-synchronous oscillations with low computational effort and good accuracy, an amplitude of each phase of the oscillation component is calculated and compared against a threshold, a sub-synchronous oscillation is detected upon exceeding the threshold during a given time delay, and a fault signal is generated upon detecting a sub-synchronous oscillation. A device having a processing unit is also provided.

A ripple voltage detector circuit comprises a pulse generator, a direct current-to-direct current (DC-DC) converter coupled to the pulse generator, and a first control loop coupled to the pulse generator and the DC-DC converter. The first control loop is configured to measure an output voltage of the DC-DC converter, determine an output ripple voltage of the output voltage, determine a ripple coefficient based on the output ripple voltage, determine a reference peak inductor current based on the ripple coefficient, and determine a peak value of an inductor current during a switching cycle, and transition a switching state of the DC-DC converter based on the reference peak inductor current and the peak value of the inductor current.

The present disclosure relates to a wireless neutral current sensor (WNCS) for monitoring a neutral cable of a capacitor bank. The WNCS may include a power storage device that provides power to allow the WNCS to send a test signal to a capacitor bank controller (CBC) of the capacitor bank to confirm operation of the WNCS during commissioning. The WNCS may include processing and communication circuitry that, during operation, detects an electrical characteristic on the neutral cable. The processing and communication circuitry may provide a message indicating the electrical characteristic to the CBC.

A switching power circuit for charging a battery can include: four switches extending between two ports of a low-frequency AC input voltage and an energy storage circuit, where the energy storage circuit and a primary winding of a transformer are coupled between first and second nodes, the first node is a common node of the first and second switches, and the second node is a common node of the third and fourth switches; a rectification circuit having an input terminal coupled to a secondary winding of the transformer; a DC-DC converter having an input terminal coupled to an output terminal of the rectification circuit, and generates a charging current; and a control circuit that adjusts the charging current by controlling an operation of the DC-DC converter according to a charging requirement, in order to make an average value of the charging current meet the charging requirement.

An intelligent power distribution device is provided, which includes a power distribution diagnosis module and a power distribution monitoring module. The power distribution monitoring module includes a power measuring and controlling instrument. The power measuring and controlling instrument is configured to connect to a power supply line to be protected, and measure power data of the power supply line. The power distribution diagnosis module is connected to the power measuring and controlling instrument, and is configured to analyze the power data uploaded by the power measuring and controlling instrument, and protect the power supply line when it is determined based on an analysis result that the power supply line requires protection. Based on the analysis result of the power data of the power supply line, the intelligent power distribution device can protect the power supply line precisely and accurately, thereby improving protection effect of the power supply line.

An electrical wiring device including: a plurality of line terminals comprising a line-side phase terminal and a line-side neutral terminal; a plurality of load terminals comprising a load-side phase terminal and a load-side neutral terminal; a line conductor electrically coupling the line-side phase terminal to the load-side phase terminal; a neutral conductor electrically coupling the line-side neutral terminal to the load-side neutral terminal; and a controller configured to trigger a trip mechanism to electrically decouple the at least one of the plurality of line terminals from at least one of the plurality of load terminals based, at least in part, on comparing a magnitude of the current differential to a threshold, wherein the threshold is a function of the frequency of the current differential.

A power supply control circuit for controlling operation of a power supply for an electricity meter during an alternating current (AC) power outage includes: an input section configured to receive a representation of an output voltage of the power supply and a power loss signal; a comparator section configured to generate an output signal based on the power loss signal and the representation of the output voltage; and a feedback control section configured to control a feedback signal to the power supply based on the output signal from the comparator section. When activated by the output signal from the comparator section, the feedback control section is configured to change the feedback signal with respect to the feedback signal from a feedback circuit caused the output voltage. The change in the feedback signal causes the power supply to stop supplying the output voltage.

An input power monitoring circuit includes a rectifier circuit, a divided voltage generator circuit, a divided voltage comparator circuit, a switching circuit, and a computing device. The divided voltage comparator circuit is configured in such a manner that polarity of an output signal that is outputted from a first comparator upon a first rectified divided voltage exceeding a first comparison voltage is opposite to polarity of an output signal that is outputted from a second comparator upon a second rectified divided voltage exceeding a second comparison voltage. Output terminals of the first and second comparators are connected to each other. A connection point between the output terminals of the first and second comparators is connected to an input terminal of the switching circuit. The computing device measures frequency of a pulse signal outputted from the switching circuit, and determines the voltage state of input power based on the measured frequency.