Embodiments of the present disclosure relate to method and apparatus for detecting grid islanding in a grid supporting voltage source converter. The method includes modulating an output voltage at an output of the grid supporting voltage source converter; determining at least one grid parameter at an input to the grid supporting voltage source converter; and detecting the grid islanding for the grid supporting voltage source converter based on the at least one grid parameter.

Embodiments of the present disclosure relate to method and apparatus for detecting grid islanding in a grid supporting voltage source converter. The method includes modulating an output voltage at an output of the grid supporting voltage source converter; determining at least one grid parameter at an input to the grid supporting voltage source converter; and detecting the grid islanding for the grid supporting voltage source converter based on the at least one grid parameter.

An example system includes an aggregator configured to receive a service collaboration request and iteratively determine, based on minimum and maximum power values for DERs under its management, an optimized operation schedule. The aggregator may also be configured to iteratively determine, based on the optimized operation schedule, an estimated flexibility range for devices under its management and output an indication thereof. The system may also include a power management unit (PMU) configured to iteratively receive the indication and determine, based on a network model that includes the estimated flexibility range, a reconfiguration plan and an overall optimized operation schedule for the network. The PMU may also be configured to iteratively cause reconfiguration of the network based on the plan. The PMU and aggregator may also be configured to iteratively, at a fast timescale, cause energy resources under their management to modify operation based on the overall optimized operation schedule.

An Uninterruptible Power Supply (UPS) including an input configured to receive input AC power, a backup power input configured to receive backup DC power having a first voltage level from a backup power source, a converter configured to convert the input AC power from the input and the backup DC power from the backup power input into DC power having a second voltage level, the converter including an input selection circuit configured to selectively couple the converter to the input and the backup power input, an inductor, a first converter switch configured to couple a first end of the inductor to a neutral connection, and a second converter switch configured to couple a second end of the inductor to the backup power input via the input selection circuit.

Disclosed is a power failure detection device and method capable of issuing a power failure alert early. The device includes a voltage reduction circuit, a detection voltage generating circuit, a detection circuit, and a transmitting circuit. The voltage reduction circuit is or includes at least one active electronic component, and generates an output voltage according to an input voltage higher than the output voltage. The detection voltage generating circuit is coupled between the voltage reduction circuit and a low voltage terminal, and generates a detection voltage according to the output voltage that is between the output voltage and the voltage of the low voltage terminal. The detection circuit generates a detection result according to the detection voltage and a trigger voltage. The transmitting circuit sends a power failure alert to a far-end device on condition that the detection result indicates that the detection voltage is lower than the trigger voltage.

A low-voltage direct supply system capable of switching between solar energy and mains supply comprises: a solar and stable-voltage energy storage branch system used for providing solar power supply and charging through multiple groups of extensible solar panels and an energy storage battery pack; a mains power supply stable-switching branch system used for quickly switching to mains power supply without shocks through a mains supply conversion module and charging the energy storage battery pack; a power supply load detection and control branch system used for detecting a voltage, a charge/discharge current, and a balance between supply and demand of the energy storage battery pack and performing switching control on branch systems; and an output balance and low-voltage direct supply branch system used for performing balanced low-voltage direct supply on a load side according to a control output signal of the power supply load detection and control branch system.

A power source combination circuit has a combination circuit and a controller. The combination circuit includes a first power source, a first field-effect transistor, a second power source, and a second field-effect transistor. The controller is configured to control the combination circuit to supply power to a load circuit, obtain a first input voltage, a second input voltage, and a third input voltage, and diagnose, based on the obtained voltages, whether the combination circuit is in a normal state or an abnormal state. The first input voltage is an input side voltage of the first field-effect transistor, the second input voltage is an input side voltage of the second field-effect transistor, and the third input voltage is a voltage at a power source input end of the load circuit.

A power source combination circuit has a combination circuit and a controller. The combination circuit includes a first power source, a first field-effect transistor, a second power source, and a second field-effect transistor. The controller is configured to control the combination circuit to supply power to a load circuit, obtain a first input voltage, a second input voltage, and a third input voltage, and diagnose, based on the obtained voltages, whether the combination circuit is in a normal state or an abnormal state. The first input voltage is an input side voltage of the first field-effect transistor, the second input voltage is an input side voltage of the second field-effect transistor, and the third input voltage is a voltage at a power source input end of the load circuit.

A valve opening circuit mounted on a heat pump device having a valve on a refrigerant circuit includes a DC electric path to which a DC voltage generated from an AC voltage for normal use is applied, a valve drive circuit that opens and closes the valve by using the DC voltage of the DC electric path, a control unit that acquires a control power source voltage based on the DC voltage of the DC electric path and controls the valve drive circuit, and a power feed port connected to the DC electric path and connectable to a DC power source line provided from outside for emergency. The control unit causes the valve drive circuit to open the valve when the AC voltage is lost and the DC voltage is fed from the DC power source line to the power feed port.

A method and apparatus for supplying clean and economical electricity. The apparatus includes a self-charging inverter and a changeover system. The self-charging inverter can be connected to two batteries in which one battery can provide electricity while another battery is charged simultaneously. The changeover system can switch the power supply from an exhausted battery to a charged battery without interrupting the power supply. The changeover system is automated by including a voltage sensor to detect the charge level of the two batteries.