Abstract: An uninterruptible power supply (UPS) system with stranded power recovery has a plurality of UPS modules with one or more of the UPS modules usable to provide stranded power to a recovered power bus. When a UPS module is used to provide stranded power to the recovered power bus, the AC/AC converter associated with that UPS module provides AC power that is synchronized with AC power being provided to the recovered power bus by each of the other AC/AC converters that are providing AC power. In this manner all of the AC/AC converters that are providing AC power to the recovered power bus have the same voltage, the same frequency, and are in phase.

Abstract: An uninterruptible power supply (UPS) system with stranded power recovery has a plurality of UPS modules with one or more of the UPS modules usable to provide stranded power to a recovered power bus. When a UPS module is used to provide stranded power to the recovered power bus, the AC/AC converter associated with that UPS module provides AC power that is synchronized with AC power being provided to the recovered power bus by each of the other AC/AC converters that are providing AC power. In this manner all of the AC/AC converters that are providing AC power to the recovered power bus have the same voltage, the same frequency, and are in phase.

Abstract: An uninterruptible power supply (UPS) system with stranded power recovery has a plurality of UPS modules with one or more of the UPS modules usable to provide stranded power to a recovered power bus. When a UPS module is used to provide stranded power to the recovered power bus, the AC/AC converter associated with that UPS module provides AC power that is synchronized with AC power being provided to the recovered power bus by each of the other AC/AC converters that are providing AC power. In this manner all of the AC/AC converters that are providing AC power to the recovered power bus have the same voltage, the same frequency and are in phase.

Abstract: The present disclosure relates to a system for controlling power walk-in for an uninterruptible power supply (UPS) being switched to receive AC power from an AC generator. The system may have a control system and a power walk-in (PWI) subsystem. The PWI subsystem may be controlled in part by the control system. The PWI subsystem may be configured to control at least one of an input current or an input power of an AC signal being provided by an AC generator during a power walk-in operation to attempt to maintain a minimum frequency of the AC signal from the AC generator during the power walk-in operation.

Abstract: An uninterruptible power supply (UPS) system with stranded power recovery has a plurality of UPS modules with one or more of the UPS modules usable to provide stranded power to a recovered power bus. When a UPS module is used to provide stranded power to the recovered power bus, the AC/AC converter associated with that UPS module provides AC power that is synchronized with AC power being provided to the recovered power bus by each of the other AC/AC converters that are providing AC power. In this manner all of the AC/AC converters that are providing AC power to the recovered power bus have the same voltage, the same frequency and are in phase.

Abstract: The present disclosure relates to a system for controlling power walk-in for an uninterruptible power supply (UPS) being switched to receive AC power from an AC generator. The system may have a control system and a power walk-in (PWI) subsystem. The PWI subsystem may be controlled in part by the control system. The PWI subsystem may be configured to control at least one of an input current or an input power of an AC signal being provided by an AC generator during a power walk-in operation to attempt to maintain a minimum frequency of the AC signal from the AC generator during the power walk-in operation.

Abstract: A method reduces inrush currents in a transformer-less rectifier UPS system when an input circuit breaker of the UPS system is closed from an open position. The circuit breaker is coupled between an AC power input and an AC input of a rectifier of the UPS system and a DC output of the rectifier is coupled to a DC bus of the UPS system. Before the circuit breaker is closed, the DC bus is charged to a DC voltage having a level that is equal to a peak AC voltage level of a line-line AC voltage of AC input power to the UPS system. The rectifier is operated as an inverter to provide an AC output voltage at the AC input of the rectifier that is equal to an AC voltage at the AC power input and when it is equal, the circuit breaker is closed.

Abstract: The present disclosure relates to a load sharing system having a plurality of power supplies for powering a plurality of corresponding loads. Each one of the power supplies is associated with at least one of the loads. A power bus is also provided. A plurality of inductors is connected to the power bus. Each one of the inductors is further connected to at least one of the loads and to at least one of the power supplies, such that each adjacent pair of the inductors is connected in parallel relative to at least one of the loads. Each of the inductors has an inductance value sufficient so that if a fault develops on the power bus it serves to isolate the power supplies from the power bus. The inductance value further is such that if any one of the power supplies fails, the specific pair of inductors coupled in parallel to the load associated with the failed power supply allows the load to draw power over the power bus from other ones of the power supplies through the specific pair of inductors.

Abstract: A common mode choke in a 3-wire transformer free UPS system with which different rectifier and bypass power sources are used is eliminated by using different types of PWM control depending on whether the inverter is paralleled with the bypass power source. When the inverter is paralleled with the bypass power source, a type of PWM control is used that does not have common mode voltage injection. When the inverter is not paralleled with the bypass power source, a type of PWM control is used that has common mode voltage injection. In an aspect, the PWM control that does not have common mode voltage injection is sine-triangle PWM and the PWM control that has common mode voltage injection is space-vector PWM.

Abstract: A method is provided for balancing power amongst parallel connected power converters in an uninterruptible power supply (UPS). The method includes: applying a control signal to each of the parallel connected power converters, where the control signals applied to the parallel connected power converters are derived from a common control signal output by a centralized controller; receiving measurements of current being supplied by each power converter to the load; and adjusting phase of voltage applied to at least one of the power converters based on the received current measurements, such that the phase adjustment causes same magnitude of current to flow though each filter. Advancing phase angle of the voltage increases current supplied by the at least one power converter while retarding phase angle of the voltage decreases current supplied by the at least one power converter.

Abstract: A real current meter reads current from a current probe coupled around power lines of a transformer-based UPS system coupled to a transformer having a high resistance ground with a HRG resistance and determines a real current component of the current read from the current probe.

Abstract: When the preferred voltage source for a static transfer switch is a UPS, there can be a brief interruption in the voltage received from the UPS while the UPS is switching from economy mode to normal mode. Operation of the static transfer switch can be improved during such voltage disturbances. Specifically, the static transfer switch may be in data communication with the UPS and thereby made aware that the voltage disturbance is temporary. As a result, the static transfer switch can avoid an unnecessary transfer to an alternate voltage source.

Abstract: A method reduces inrush currents in a transformer-less rectifier UPS system when an input circuit breaker of the UPS system is closed from an open position. The circuit breaker is coupled between an AC power input and an AC input of a rectifier of the UPS system and a DC output of the rectifier is coupled to a DC bus of the UPS system. Before the circuit breaker is closed, the DC bus is charged to a DC voltage having a level that is equal to a peak AC voltage level of a line-line AC voltage of AC input power to the UPS system. The rectifier is operated as an inverter to provide an AC output voltage at the AC input of the rectifier that is equal to an AC voltage at the AC power input and when it is equal, the circuit breaker is closed.

Abstract: A UPS includes an input that receives first power from a utility source to power a load and receives second power from the utility source. The load is separate from the UPS. An inverter receives when in a first mode, the first and second power and when in a second mode, the second power and not the first power. The second power is used to power the inverter. A bypass circuit is connected to the input and bypasses the inverter to supply the first power to an output of the UPS when operating in the second mode. A control module detects a voltage at the output of the UPS, integrates the voltage to generate a first sum, and subsequent to completing a transition between the first and second modes, adjusts an output voltage of the inverter based on the first sum to balance the voltage of the UPS.

Abstract: A method is provided for operating a static transfer switch to eliminate transformer inrush current in the presence of residual flux. The method includes: detecting an interrupt of electric power at an output terminal of the static transfer switch; controlling amplitude of voltage at the output terminal using phase fired control of one or more silicon controlled rectifiers interposed between a voltage source and the output terminal, where the amplitude of voltage is set at a value less than a peak value of the sinusoidal waveform; and increasing the amplitude of voltage at the output terminal incrementally until the amplitude reaches a peak value.

Abstract: The present disclosure relates to a load sharing system having a plurality of power supplies for powering a plurality of corresponding loads. Each one of the power supplies is associated with at least one of the loads. A power bus is also provided. A plurality of inductors is connected to the power bus. Each one of the inductors is further connected to at least one of the loads and to at least one of the power supplies, such that each adjacent pair of the inductors is connected in parallel relative to at least one of the loads. Each of the inductors has an inductance value sufficient so that if a fault develops on the power bus it serves to isolate the power supplies from the power bus. The inductance value further is such that if any one of the power supplies fails, the specific pair of inductors coupled in parallel to the load associated with the failed power supply allows the load to draw power over the power bus from other ones of the power supplies through the specific pair of inductors.

Abstract: A method is provided for balancing power amongst parallel connected power converters in an uninterruptible power supply (UPS). The method includes: applying a control signal to each of the parallel connected power converters, where the control signals applied to the parallel connected power converters are derived from a common control signal output by a centralized controller; receiving measurements of current being supplied by each power converter to the load; and adjusting phase of voltage applied to at least one of the power converters based on the received current measurements, such that the phase adjustment causes same magnitude of current to flow though each filter. Advancing phase angle of the voltage increases current supplied by the at least one power converter while retarding phase angle of the voltage decreases current supplied by the at least one power converter.

Abstract: A real current meter reads current from a current probe coupled around power lines of a transformer-based UPS system coupled to a transformer having a high resistance ground with a HRG resistance and determines a real current component of the current read from the current probe.

Abstract: A DC offset voltage in an AC input voltage to a transformer and associated saturation current are eliminated by the placement of an anti-parallel diode pair circuit in series between a source of the AC input voltage and a primary winding of the transformer. The anti-parallel diode pair circuit has an input coupled to an output by parallel connected oppositely biased branch diode circuits. Each branch diode circuit has at least one diode where the diode of one such branch diode circuit is biased in one direction and the diode of the other such branch diode circuit is biased in an opposite direction and each branch diode circuit has the same number of diodes as the other branch diode circuit.

Abstract: A method is disclosed for reducing an influence of voltage ripple on battery test measurements of battery cells coupled in series that form a direct current (DC) bus. A calibration operation is used to obtain a ratiometric difference between first and second series connected battery cells of the DC bus, which is indicative of a variance in their respective output voltages. Voltage measurements across each of the two cells may then be obtained at least substantially simultaneously. The ratiometric difference may be used to modify the voltage measurement taken across the second cell to produce a modified voltage measurement of the second cell. A difference between the measured voltage across the first battery cell and the modified voltage measurement may then be determined, which represents a filtered DC test voltage that has substantially all of the voltage ripple removed therefrom.