Uninterruptible power supply systems and methods using isolated interface for variably available 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. A control circuit is configured to cooperatively control the UPS circuit and the third converter circuit.

1 . An uninterruptible power supply (UPS) system, comprising:
 a first port configured to be coupled to an AC power source;   a second port configured to be coupled to a load;   a UPS circuit comprising 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;   a third converter circuit coupled to the second port and configured to receive power from a variably available power source; and   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.   
     
     
         2 . The UPS system of  claim 1 , wherein the DC bus of the UPS circuit comprises a first DC bus coupled to an auxiliary power source, wherein the system comprises a second DC bus coupled to the third converter circuit and wherein the first DC bus and the second DC buses are not connected in common to the auxiliary power source. 
     
     
         3 . The UPS system of  claim 1 , wherein the UPS circuit and the third converter are implemented in respective first and second power conversion modules, each of the first and second power conversion modules including a pair of converter units coupled by a DC bus. 
     
     
         4 . The UPS system of  claim 3 , wherein the DC bus of the second power conversion module is configured to be coupled to the variably available power source. 
     
     
         5 . The UPS system of  claim 1 , wherein the control circuit is configured to selectively transfer power from the variably available power source to the AC power source via the UPS circuit. 
     
     
         6 . The UPS system of  claim 1 , wherein the DC bus comprises a first DC bus, wherein the UPS system further comprises a second DC bus configured to be coupled to the variably available power source and a fourth converter circuit coupled to the first port and to the third converter circuit by the second DC bus and wherein the control circuit is operatively associated with the fourth converter circuit and configured to selectively transfer power from the variably available power source to the AC power source via the fourth converter circuit. 
     
     
         7 . The UPS system of  claim 1 , wherein the auxiliary power source comprises a battery. 
     
     
         8 . An uninterruptible power supply (UPS) system, comprising:
 a first port configured to be coupled to an AC power source;   a second port configured to be coupled to a load;   a plurality of power conversion modules, each comprising a first converter unit, a second converter unit and a DC bus coupling the first converter unit to the second converter unit, wherein the second converter units of the power conversion modules are coupled in common to the second port, wherein a first converter unit of a first one of the power conversion modules is coupled to the first port, wherein the DC bus of the first one of the power conversion modules is coupled to an auxiliary power source and wherein the DC bus of a second one of the power conversion modules is coupled to a variably available power source; and   a control circuit operatively associated with the plurality of power conversion modules and configured to cause the power conversion modules 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.   
     
     
         9 . The UPS system of  claim 8 , wherein each of the power conversion modules comprises a DC bus interface unit, and wherein the DC bus interface unit of the second one of the power conversion modules is configured to couple the DC bus of the second one of the power conversion modules to the variably available power source. 
     
     
         10 . The UPS system of  claim 8 , wherein the second converter units of the power conversion modules are configured to operate as inverters and wherein the first converter unit of the first power conversion module is configured to operate as a rectifier. 
     
     
         11 . The UPS system of  claim 8 , wherein the control circuit is configured to cause transfer of power from the variably available power source to the auxiliary power source and/or the AC power source via the second converter unit of the first one of the power conversion modules. 
     
     
         12 . The UPS system of  claim 8 , wherein the first converter unit of the second one of the power conversion modules is coupled to the first port and wherein the control circuit is configured to cause transfer of power from the variably available power source to the AC power source via the first converter unit of the second one of the power conversion modules. 
     
     
         13 . The UPS system of  claim 8 , wherein each of the first and second converter units of the power conversion modules is configurable to provide an active half-bridge circuit. 
     
     
         14 . The UPS system of  claim 8 , wherein the auxiliary power source comprises a battery. 
     
     
         15 . A method comprising:
 populating a UPS system with a plurality of power conversion modules, each comprising a first converter unit, a second converter unit and a DC bus coupling the first converter unit to the second converter unit;   coupling the second converter units of the power conversion modules in common to the second port;   coupling a first converter unit of a first one of the power conversion modules to an AC power source;   coupling the DC bus of a second one of the power conversion modules to a variably available power source; and   selectively transferring 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.   
     
     
         16 . The method of  claim 15 , wherein each of the power conversion modules comprises a DC bus interface unit, and wherein coupling the DC bus of a second one of the power conversion modules to a variably available power source comprises coupling the DC bus of the second power conversion module to the variably available power source via the DC bus interface unit of the second power conversion module. 
     
     
         17 . The method of  claim 15 , comprising operating the second converter units of the power conversion modules as inverters and operating the first converter unit of the first power conversion module as a rectifier. 
     
     
         18 . The method of  claim 15 , wherein selectively transferring 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 comprises transferring power from the variably available power source to the auxiliary power source and/or the AC power source via the second converter unit of the first one of the power conversion modules. 
     
     
         19 . The method of  claim 15 , further comprising:
 coupling the first converter unit of the second one of the power conversion modules to the first port; and   transferring power from the variably available power source to the AC power source via the first converter unit of the second one of the power conversion modules.   
     
     
         20 . The method of  claim 15 , wherein the auxiliary power source comprises a battery.