Proposed is an automatic transfer switch with an N-phase overlapping structure, the switch including: a driving unit including a drive shaft provided to generate power; a three-contact switching unit including a normal power shaft and an emergency power shaft provided to be rotated by the drive shaft, and a normal power terminal and an emergency power terminal for inputting/releasing normal power and emergency power; and an N-phase overlapping unit including a first insertion part having a first insertion hole, an N-phase normal contact terminal provided to input/release an N-phase normal power, a second insertion part having a second insertion hole, an N-phase emergency contact terminal provided to input/release an N-phase emergency power, and a connection bar connected between the first insertion part and the second insertion part so as to be interlocked with each other.

An uninterruptible power supply (UPS) is provided that includes a split direct current (DC) link having a first capacitor coupled between a positive DC link terminal and a first node, and a second capacitor coupled between the first node and a negative DC link terminal. The UPS also includes a rectifier coupled to an input of the split DC link and a controller coupled to the rectifier. The rectifier includes first, second, and third legs, wherein each leg is configured to convert a first alternating current (AC) voltage received from an AC source into a DC voltage to be provided to the split DC link, and a fourth leg configured to balance DC link voltages of the first and second capacitors. The controller is configured to maintain functionality of the rectifier during at least one of a partial utility power outage, a full utility outage, and a failure of at least one of the first, second, third, and fourth legs.

A power conversion circuit for an uninterruptible power system, including an inductor, a first capacitor, a second capacitor, a first switch, a second switch, a third switch, a first diode, a second diode, and a third diode body, is provided. A terminal of the second switch is electrically coupled to the inductor through the first switch, and another terminal of the second switch is electrically coupled to a neutral wire and the third switch. An anode and a cathode of the first diode are electrically coupled to the first switch and a positive DC bus, respectively. A cathode and an anode of the second diode are electrically coupled to the first switch and the third switch, respectively. A cathode and an anode of the third diode are electrically coupled to the third switch and a negative DC bus, respectively. In addition, an uninterruptible power system using the same is provided.

A method for selecting a power source for a load is provided. The method includes monitoring the primary power source, when the primary power source is providing power to the load, determining if a condition of the primary power source crosses a first threshold, when the condition crosses the first threshold, turning on a first power field effect transistor to couple a back-up power source to the load through a second power field effect transistor, when the primary power source is not providing power to the load, determining if a condition of the primary power source crosses a second threshold, and when the condition crosses the second threshold, switching off the first power field effect transistor to couple the primary power source to the load through a third power field effect transistor.

In an embodiment, an auxiliary-power-supply unit includes a connector and a controller configured to power a microgrid from a battery in response to determining that the connector is plugged into an outlet of the microgrid, and that the microgrid is uncoupled from a power grid. For example, the connector plugs into a wall outlet of a microgrid in, e.g., a home, and provides, from the battery during a power outage, auxiliary power to the microgrid and, therefore, provides auxiliary power to one or more devices, such as appliances, lights, computers, or televisions, that are connected to the microgrid.

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.

A device includes at least one isolating transformer. An input is coupled to the at least one isolating transformer and configured to receive input from an energy source. At least one power switch is coupled to the isolating transformer. A diode is coupled to the at least one isolating transformer. An energy storage medium is coupled to the diode. An inverter includes one or more inverter switches, an inverter input, and an inverter output. The inverter input is coupled to the diode and the energy storage medium. The inverter output is configured to be coupled to the power network, and the inverter is configured to create AC power for distribution to the power network. A controller is configured to modulate the at least one power switch to control power flow from the input and to modulate the state of the inverter switches to control power flow to the power network.

A method for selecting a power source for a load is provided. The method includes monitoring the primary power source, when the primary power source is providing power to the load, determining if a condition of the primary power source crosses a first threshold, when the condition crosses the first threshold, turning on a first power field effect transistor to couple a back-up power source to the load through a second power field effect transistor, when the primary power source is not providing power to the load, determining if a condition of the primary power source crosses a second threshold, and when the condition crosses the second threshold, switching off the first power field effect transistor to couple the primary power source to the load through a third power field effect transistor.

An uninterruptible power supply to be connected between an AC line and a load has a battery system, an inverter, a transformer, and a controller. The battery system stores battery power. The inverter is operatively connected to the battery system. The transformer comprises a primary winding adapted to be connected to the AC line, a load winding adapted to be 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 a third mode in which the inverter supplies power to the primary winding using battery power stored in the battery system.

A control system and hardware with a controllable input relay provides two different modes of operation—uninterruptable power supply (UPS) and mixed energy-AC support. For each operation mode, regulation of the DC-Link and neutral point balancing is guaranteed even for non-linear unsymmetrical AC loads. Moreover, in the mixed energy-AC support mode, unity power factor operation of AC input source, seamless zero current crossing, and very low total harmonic distortion (THD) is provided by the applied non-linear control algorithm. The system has a higher efficiency in comparison to other AC-DC-AC converters with smaller size and weight because of the elimination of the typical balancing circuit.