A power supply system comprises a primary regulation system, a secondary regulation system, and a controller. The primary regulation system comprises a primary transformer and a primary tap switch array. The secondary regulation system comprising a secondary transformer and an adjustment power signal generator. The controller is configured to control the adjustment power signal generator to apply an adjustment power signal to the secondary transformer. The secondary transformer is configured to combine the adjustment power signal with a base power supply signal from the primary transformer.

An apparatus for high-speed switching between a plurality of power sources includes a switch-mode isolation transformer. The switch-mode isolation transformer includes a plurality of isolated primary windings. Each of the plurality of isolated primary windings can be electrically isolated from others of the isolated primary windings and selectively couplable to a power source of the plurality of power sources. The switch-mode isolation transformer further includes a secondary winding coupled to a load. The apparatus further includes a controller to selectively couple one of the plurality of power sources through a corresponding isolated primary winding, responsive to detecting an adverse condition in another power source of the plurality of power sources. Other methods and systems are also described.

At least some embodiments herein provide a UPS comprising an input, a transformer including at least one primary winding, a relay, a sense circuit, and a current control circuit, wherein the sense circuit is configured to monitor input power, control the relay to couple, in a first mode, the input to the at least one primary winding when input power is above an input threshold, and control the relay to decouple, in a second mode, the input from the at least one primary winding when input power is below the input threshold, and wherein the current control circuit is configured, in the first mode, to control current from an AC source through the at least one primary winding to generate an output voltage and, in the second mode, to control current from a DC source through the at least one primary winding to generate the output voltage.

An uninterruptible power supply for providing an output power signal to a load comprises a ferroresonant transformer, a resonant capacitor, and an inverter. The resonant capacitor is operatively connected to the ferroresonant transformer. The inverter is operatively connected to the ferroresonant transformer. The inverter is configured to generate the output power signal based on at least one inverter control signal such that the output power signal is a quasi square wave having at least one change of phase and an upper limit. The at least one inverter control signal is held in an OFF state during at least a portion of the at least one change of phase, pulse-width modulated during at least a portion of the at least one change of phase, and held in an ON state when the output power signal is at the upper limit.

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.

Sharing of load current in desired ratios between multiple electrical voltage sources is achieved without coupling between the sources by controlling a selection switch to select each voltage source for a proportion of the time at a high rate, the switching rate components being prevented from being seen by either the load or the sources through use of low-pass filters.

Disclosed is a voltage regulating circuit, comprising an input end, an output end, a protecting switch, a first switch, a second switch, a third switch, a first coil and a second coil. The third switch comprises a first terminal and a second terminal. The second terminal of the third switch is connected to a third terminal of the first switch. One end of the first coil is connected to a second terminal of the first switch, and the other end of the first coil is connected to a third terminal of the first switch. One end of the second coil is connected to a first terminal of the third switch, and the other end of the second coil is connected to a fourth terminal of the protecting switch. Different connections between switches and the transformer provide various voltage adjustments to reduce power loss and to increase power transformation efficiency.

An uninterruptible power supply (UPS) and methods of operation are provided. The UPS includes a transformer configured to receive power from a utility. The transformer includes a primary winding, a secondary winding, and a tertiary winding. The UPS also includes a rectifier coupled to the secondary winding and an inverter coupled to an output of the rectifier, wherein a connection between the rectifier and the inverter defines a DC link. The inverter is configured to output a first regulated voltage configured to be provided to a load. The UPS further includes a voltage-boost converter coupled to the tertiary winding and is configured to output a second regulated voltage to be combined with the first regulated voltage.

A ferroresonant transformer assembly, which is adapted to be connected to a primary power source, an inverter system, a resonant capacitor, and at least one load, comprises a core, a main shunt, and first, second, and third windings. The main shunt is arranged to define a primary side and a secondary side of the ferroresonant transformer. The first windings are arranged on the primary side of the ferroresonant transformer and are configured to be operatively connected to the primary power source. The second windings are arranged on the secondary side of the ferroresonant transformer and are configured to be operatively connected to the inverter system. The third windings arranged on the secondary side of the ferroresonant transformer and are configured to be selectively operatively connected to or disconnected from the resonant capacitor.

Disclosed is a voltage regulating circuit, comprising an input end, an output end, a protecting switch, a first switch, a second switch, a third switch, a first coil and a second coil. The third switch comprises a first terminal and a second terminal. The second terminal of the third switch is connected to a third terminal of the first switch. One end of the first coil is connected to a second terminal of the first switch, and the other end of the first coil is connected to a third terminal of the first switch. One end of the second coil is connected to a first terminal of the third switch, and the other end of the second coil is connected to a fourth terminal of the protecting switch. Different connections between switches and the transformer provide various voltage adjustments to reduce power loss and to increase power transformation efficiency.