Abstract: An uninterruptible power supply (UPS) system includes a first port configured to be coupled to an AC power source and a second port configured to be coupled to a load. The system also includes a UPS circuit including a first converter circuit coupled to the first port, a second converter circuit coupled to the second port and a DC bus coupling the first converter circuit to the second converter circuit and configured to be coupled to an auxiliary power source and a third converter circuit coupled to the second port and configured to receive power from a variably available power source. The system further includes a control circuit operatively associated with the UPS circuit and the third converter circuit and configured to cooperatively control the UPS circuit and the third converter circuit to selectively transfer power to the load from the AC power source and the variably available power source and from the variably available power source to the AC power source.

Abstract: An uninterruptible power supply (UPS) system includes a first port configured to be coupled to an AC power source and a second port configured to be coupled to a load. The system also includes a UPS circuit including a first converter circuit coupled to the first port, a second converter circuit coupled to the second port and a DC bus coupling the first converter circuit to the second converter circuit and configured to be coupled to an auxiliary power source and a third converter circuit coupled to the second port and configured to receive power from a variably available power source. The system further includes a control circuit operatively associated with the UPS circuit and the third converter circuit and configured to cooperatively control the UPS circuit and the third converter circuit to selectively transfer power to the load from the AC power source and the variably available power source and from the variably available power source to the AC power source.

Abstract: An uninterruptible power supply (UPS) system includes a first port configured to be coupled to an AC power source and a second port configured to be coupled to a load. The system also includes a UPS circuit including a first converter circuit coupled to the first port, a second converter circuit coupled to the second port and a DC bus coupling the first converter circuit to the second converter circuit and configured to be coupled to an auxiliary power source and a third converter circuit coupled to the second port and configured to receive power from a variably available power source. The system further includes a control circuit operatively associated with the UPS circuit and the third converter circuit and configured to cooperatively control the UPS circuit and the third converter circuit to selectively transfer power to the load from the AC power source and the variably available power source and from the variably available power source to the AC power source.

Abstract: An uninterruptible power supply (UPS) system includes a first port configured to be coupled to an AC power source and a second port configured to be coupled to a load. The system also includes a UPS circuit including a first converter circuit coupled to the first port, a second converter circuit coupled to the second port and a DC bus coupling the first converter circuit to the second converter circuit and configured to be coupled to an auxiliary power source and a third converter circuit coupled to the second port and configured to receive power from a variably available power source. The system further includes a control circuit operatively associated with the UPS circuit and the third converter circuit and configured to cooperatively control the UPS circuit and the third converter circuit to selectively transfer power to the load from the AC power source and the variably available power source and from the variably available power source to the AC power source.

Abstract: A fault in a DC power source, such as a battery string or a string of photovoltaic cells, is identified by detecting a change in an AC component of a residual current of the DC power source. In some embodiments, the DC power source is coupled to at least one DC bus and the methods further include generating an AC voltage on the at least one DC bus. For example, the DC power source may be coupled to a modulated DC bus of an uninterruptible power supply (UPS) system comprising an inverter having an input coupled to the DC bus. The inverter may be configured to generate an AC output voltage and the AC component has a frequency that is a harmonic of a fundamental frequency of the AC output voltage, such as a third harmonic of the fundamental frequency of the AC output voltage.

Abstract: A fault in a DC power source, such as a battery string or a string of photovoltaic cells, is identified by detecting a change in an AC component of a residual current of the DC power source. In some embodiments, the DC power source is coupled to at least one DC bus and he methods further include generating an AC voltage on the at least one DC bus. For example, the DC power source may be coupled to a modulated DC bus of an uninterruptible power supply (UPS) system comprising an inverter having an input coupled to the DC bus. The inverter may be configured to generate an AC output voltage and the AC component has a frequency that is a harmonic of a fundamental frequency of the AC output voltage, such as a third harmonic of the fundamental frequency of the AC output voltage.

Abstract: An uninterruptible power supply (UPS) system includes a first port configured to be coupled to an AC power source and a second port configured to be coupled to a load. The system also includes a UPS circuit including a first converter circuit coupled to the first port, a second converter circuit coupled to the second port and a DC bus coupling the first converter circuit to the second converter circuit and configured to be coupled to an auxiliary power source and a third converter circuit coupled to the second port and configured to receive power from a variably available power source. A control circuit is configured to cooperatively control the UPS circuit and the third converter circuit.