An uninterruptible power supply apparatus includes a switch, a first inductor, a direct current controlling unit, a first bridge arm, a second bridge arm and a third bridge arm. When the switch switches the first inductor coupled to an alternative current (AC) power, the AC power converts into a bus voltage via the first inductor, the first bridge arm and the second bridge arm, and converts into an output power via the second bridge arm and the third bridge arm. When the switch switches the first inductor coupled to a DC power, the DC power converts into the bus voltage via the DC controlling unit and the first inductor, and converts into the output power via the second bridge arm and the third bridge arm.

An uninterruptible power supply adapted to be connected between an AC line and a load a battery system for storing battery power, an inverter, a transformer, and a controller. The inverter is operatively connected to the battery system. The transformer comprises a primary winding adapted to be operatively connected to the AC line, a load winding adapted to be operatively connected to the load, and an inverter winding operatively connected to the inverter. The controller controls the inverter to operate in a first mode in which the inverter supplies power to the battery system, a second mode in which the inverter supplies power to the load winding using battery power stored in the battery system, and, based on a cost value indicative of reduction of life of the battery system, a third mode in which the inverter supplies power to the primary winding using battery power stored in the battery system.

Example control methods and apparatus are described. An example control method for an uninterruptible power supply system includes: when a bypass power supply branch supplies power to a load, outputting a first drive signal to a first switch device and outputting a second drive signal to a second switch device; and controlling the first drive signal and the second drive signal to have a phase difference with an input voltage of the bypass power supply branch; or when a load current of the bypass power supply branch is less than a first threshold, outputting an inverter control signal to control an inverter power supply branch to charge an energy storage battery; or when a current of the inverter power supply branch flows back to an input end of the bypass power supply branch, turning off the first switch device and the second switch device via the inverter power supply branch.

According to one aspect, embodiments of the invention provide a UPS comprising a plurality of DC busses configured to receive DC power from a converter, the plurality of DC busses including a positive DC bus configured to maintain a positive DC voltage level, a mid-point DC bus, and a negative DC bus configured to maintain a negative DC voltage level, a 3-level inverter coupled to the plurality of DC busses and configured to convert the DC power from the plurality of DC buses into output AC power, and a controller configured to monitor the positive and negative DC voltage levels, identify an imbalance between the positive and negative DC voltage levels, and selectively control, based on the imbalance, the 3-level inverter to operate in a 2-level mode of operation and a 3-level mode of operation to transfer energy between the positive and negative DC busses.

An uninterruptible power supply includes: a converter (4) configured to convert alternating-current power supplied from an alternating-current power supply (51) into direct-current power; an inverter (7) configured to convert the direct-current power generated by the converter or direct-current power of a storage battery (52) into alternating-current power and supply the alternating-current power to a load (53, 54); and a control circuit (14) configured to control the inverter. When activating the inverter, the control circuit gradually increases a voltage value (V) of an output voltage (VO) and a frequency (F) of the output voltage (VO) while maintaining a ratio of the voltage value (V) and the frequency (F) at a fixed value (F).

The present application discloses a direct current (DC) converter including a voltage divider for dividing a voltage provided by a DC voltage source, having a positive DC voltage input terminal, a negative DC voltage input terminal, and a divided voltage output terminal; a conversion circuit having a first switch, a second switch, an inductor unit, a first unidirectional conductor, and a second unidirectional conductor; a positive converted voltage output terminal; and a negative converted voltage output terminal.

A changeover device for selectively supplying power to at least one load from a grid or a bidirectional inverter includes an input having a grid neutral conductor connection and a grid phase conductor connection for connection to the grid. The changeover device further includes a first output having an inverter neutral conductor connection and an inverter phase conductor connection for connecting the bidirectional inverter, a second output having a load neutral conductor connection and a load phase conductor connection for connecting the load and a switching circuit, the actuator of which is connected to an actuator input of the changeover device. The switching circuit includes a first and a second normally closed contact and a normally open contact that are connected in an interconnection to the grid phase conductor connection, the inverter phase conductor connection, and the load phase conductor connection. An associated method is also disclosed.

When a power outage occurs, an uninterruptable power supplies may lose all grid connections including a neutral connection which may be connected to ground. To avoid the loss of a ground connection to the power circuits of the UPS, a switch unit may be used to selectively connect a neutral conductor of the circuit to a ground terminal. The switch unit may comprise a power relay, a fast switch device (FSD), and a controller. The power relay and FSD may be connected in series between the neutral conductor of the circuit and a ground terminal. The controller may be configured to: close the FSD when the voltage between ground and neutral (Vng) goes above a first threshold, open the FSD when the voltage between any grid connection and neutral (Vg) goes above a second threshold, and close the FSD when Vg is below the second threshold.

The present specification relates to a power supply device and a power supply system capable of uninterrupted power supply, which includes a circuit breaker for regulating connection to a power bus to which a plurality of power supply devices are connected, wherein the circuit breaker is opened or closed according to various situations occurring in the system so as to control power supply and demand.

A power system including a rectifier and an inverter. The rectifier has a plurality of phase input terminals and a plurality of rectifier output terminals that provide respective rectified outputs, rectifier circuity that rectifies the signals on the phase input terminals to generate respective rectified outputs on the rectifier output terminals, a rectifier neutral to receive a power source neutral, and capacitors connected between the rectifier neutral and the rectifier output terminals. The inverter includes a respective plurality of inverter input terminals respectively connected to the rectifier output terminals, a plurality of inverter output terminals, and an inverter neutral. The rectifier neutral and the inverter neutral are coupled by a conductor to form a same neutral.