num="0029">During the backup mode of operation, power provided to the DC bus 106 is provided by the battery 110, and during the online mode of operation, power provided to the DC bus 106 is provided by a power source (e.g., a grid) connected to the input 102. Power provided to the DC bus 106 is subsequently drawn by the DC/AC inverter 114 to generate AC power, and to supply the AC power to an external load connected to the output 116.

In some examples, it may be advantageous to utilize an alternate power source (e.g., a renewable power source such as a photovoltaic array) to minimize usage of grid power and reduce energy cost. In one example, the renewable power source may be coupled to the grid at the input 102 of the UPS 100 and power may be drawn from the renewable power source to power the load, charge the battery 110, or backfeed the grid. Due to the intermittent nature of renewable energy sources (e.g., solar, wind, etc.), there are numerous standards that govern the interconnection of renewable power sources to the grid. For example, the IEEE-1547/UL-1741 standard includes coupling renewable power sources to an DC/AC grid-tie inverter and operating the AC/DC grid-tie inverter as a current source against a stiff, constant voltage source (i.e., the grid). As such, according to the IEEE-1547/UL-1741 standard, when power from the grid is unavailable (i.e., no constant voltage source), power may not be drawn from the renewable power source via the AC/DC grid-tie inverter.

Additionally, the renewable power source may be coupled to the AC/DC grid-tie inverter via an intermediate DC/DC converter. As such, power drawn from the renewable power source may experience numerous conversion stages when powering the load or charging the battery. In one example, power drawn from the renewable power source may pass through the intermediate DC/DC converter, the DC/AC grid-tie inverter, the AC/DC converter 104 of the UPS 100, and the DC/AC inverter 114 of the UPS 100 before being provided to the load coupled to the output 116. Likewise, to charge the battery 110, power drawn from the renewable power source may pass through the intermediate DC/DC converter, the DC/AC grid-tie inverter, the AC/DC converter 104 of the UPS 100, and the DC/DC inverter 108 of the UPS 100 before being provided to the battery 110. Such conversion stages may increase loss associated with the power drawn from the renewable power source, reducing efficiency.

Systems and methods are provided herein for improved utilization of renewable power sources with UPS's. In at least one embodiment, power drawn from renewable power sources may be provided directly to the battery or DC bus of a UPS, without a dependence on grid availability. In some embodiments, by providing the power drawn from the renewable power sources directly to the battery or the DC bus, the number of power conversion stages utilized to support the load or charge the battery using power from the renewable power sources may be reduced, improving efficiency.

FIG. 2 illustrates a power supply system 200 in accordance with aspects described herein. The power supply system 200 includes a UPS and at least one renewable power source 202. In some examples, the UPS included in the power system 200 may be the UPS 100 of FIG. 1. As shown, the at least one renewable power source 202 may be coupled between the DC/DC converter 108 and the battery 110 of the UPS 100 via one or more charge controllers 204.

In one example, the power system 200 may include a first renewable power source 202a, a second renewable power source 202b, and a third renewable power source 202c. Likewise, the power system 200 may include a first charge controller 204a, a second charge controller 204b, and a third charge controller 204c corresponding to each of renewable power sources 204a-204c. In some examples, each renewable power source 202a-202c may be a photovoltaic array and the corresponding charge controllers 204a-204c may be maximum power point tracking (MPPT) controllers. The controller 112 may communicate with each charge controller 204a-204c to monitor each renewable power source 202a-202c. In one example, each charge controller 204a-204c may track the maximum power point of its corresponding renewable power source 202a-202c (i.e., the maximum level of power capable of being provided by the renewable power source in view of current environmental conditions) and provide the maximum power point information to the controller 112. As such, the controller 112 may operate each charge controller 204a-204c to draw a desired amount of power from each of the renewable power sources 202a-202c. In some examples, the desired amount of power drawn from each of the renewable power sources 202a-202c may be the maximum amount corresponding to the maximum power point information.

In one example, the controller 112 may monitor the input 102, the output 116, and the battery 110 of the UPS 100 to determine optimal utilization of the DC power drawn from the renewable power sources 202a-202c. For example, when grid power is available and the battery 110 is fully charged, the controller 112 may operate the DC/DC converter 108 such that DC power drawn from the renewable power sources 202a-202c via the charge controllers 204a-204c is provided to the DC bus 106. In some examples, the controller 112 may operate each charge controller 204a-204c such that the maximum amount of DC power is drawn from one or more of the renewable power sources 202a-202d and provided to the DC bus 106. In one example, the DC power drawn from the renewable power sources 202a-202c via the charge controllers 204a-204c may have a first voltage level and the DC/DC converter 108 may convert the first voltage level to a second voltage level (e.g., a DC bus level). The controller 112 may operate the DC/AC inverter 114 such that the DC power provided to the DC bus 106 from the renewable power sources 202a-202c via the DC/DC converter 108 is converted to AC power and provided to the load coupled to the output 116.

In some examples, the controller 112 may monitor the output 116 to determine the power demand of the load (i.e., the load on the DC/AC inverter 114). The controller 112 may compare the maximum power point information received from the charge controllers 204a-204c to the power demand of the load and determine if the renewable power sources 202a-202c are capable of providing a sufficient amount of power to support the load. In other examples, the controller 112 may monitor the DC bus 106 to determine if the power provided by the renewable power sources 202a-202c is sufficient to support the load. For example, the controller 112 may monitor the DC bus 106 for voltage fluctuations indicating an insufficient amount of power is being provided to the load.

In one example, based on an indication that the renewable power sources 202a-202c can provide a sufficient amount of power to support the load, the controller 112 may operate the AC/DC converter 104 of the UPS 100 such that AC power is not drawn from the grid. In some examples, the controller 112 may determine (based on the maximum power point information) that the renewable power sources 202a-202c are capable of providing excess power in addition to what is needed to support the load and the excess power may be fed to the grid. In one example, the power supply system 200 may include an optional bypass line 206 and a bypass relay 208, and the bypass relay 208 may be closed to couple the output 116 to the input 102. The AC/DC converter 104 may be operated such that excess AC power provided to the input 102 via the bypass line 206 is fed back to the grid. In one example, the bypass line 206 and the bypass relay 208 may be included in the UPS 100. Alternatively, based on an indication that the renewable power sources 202a-202c are unable to provide a sufficient amount of power to support the load, the controller 112 may operate the AC/DC converter 104 such that AC power is drawn from the grid, converted to DC power, and provided to the DC bus 106 to supplement the DC power provided from the renewable power sources 202a-202c. In some examples, if the renewable power sources 202a-202c are unavailable, the bypass relay 208 may be closed to couple the input 102 to the output 116 such that unregulated AC power is provided from the grid to support the load.

Further, being that the renewable power sources 202a-202c are coupled to the DC bus 106 via the charge controllers 204a-204c, the DC/AC inverter 114 may function as a constant voltage source allowing DC power to be drawn from the renewable power sources 202a-202c. In some examples, the DC/AC inverter 114 may provide reactive power control of the DC power drawn from the renewable power sources 202a-202c. As such, DC power may be drawn from the renewable power sources 202a-202c without an active connection to the grid. For example, when grid power is unavailable, the controller 112 may still operate the DC/DC converter 108 such that DC power drawn from the renewable power sources 202a-202c via the charge controllers 204a-204c is provided to the DC bus 106. The controller 112 may operate the DC/AC inverter 114 such that the power provided to the DC bus 106 from the renewable power sources 202a-202c via the DC/DC converter 108 is converted to AC power and provided to the load. Based on an indication that the renewable power sources 202a-202c are unable to provide a sufficient amount of power to support the load, the controller 112 may operate the DC/DC converter 108 such that DC power is drawn from the battery 110 and provided to the DC bus 106 to supplement the DC power provided from the renewable power sources 202a-202c.

In some examples, based on an indication that the battery 110 is at least partially uncharged, the controller 112 may operate the DC/DC converter 108 such that a first portion of the DC power drawn from the renewable power sources 202a-202c is provided to the DC bus 106 to support the load and a second portion is provided to the battery 110 for charging. In one example, the battery 110 may include a battery management system, and the controller 112 may control the battery management system of the battery 110 to facilitate charging. For example, the controller 112 may turn on the battery management system to allow DC power drawn from the renewable power sources 202a-202c to charge the battery 110. Likewise, the controller 112 may turn off the battery management system once the battery 110 is fully charged such that all DC power drawn from the renewable power sources 202a-202c is provided to the DC bus 106 via the DC/DC converter 108. If the DC power drawn from the renewable power sources 202a-202c is insufficient to provide a minimum charging current to the battery 110, the controller 112 may operate the DC/DC converter 108 such that DC power (converted from AC grid power) is provided from the DC bus 106 to the battery 110 for charging.

FIG. 3 illustrates another embodiment of a power supply system 300 in accordance with aspects described herein. In one example, the power supply system 300 may be similar to the power supply system 200 of FIG. 2, except the power supply system 300 includes alternate power sources 302a-302d coupled to the DC bus 106 of the UPS 100. In some examples, the alternate power sources 302a-302d may be coupled to the DC bus 106 via DC/DC converters 304a-304d.

In one example, each alternate power source 302a-302d may be a renewable power source (e.g., a photovoltaic array); however, in some examples, one or more of the alternate power sources 302a-302d may be a different type of power source. For example, alternate power sources 302a and 302b may be non-renewable power sources (e.g., fuel cells) and alternate power sources 302c and 302d may be renewable power sources (e.g., photovoltaic arrays). In other examples, different types and combinations of power sources may be used. Likewise, different types of converters may be used for the DC/DC converters 304a-304d. For example, being that the alternate power sources 302c and 302d are renewable power sources, the DC/DC converters 304c and 304d may be MPPT controllers (similar to the charge controllers 204a-204c of FIG. 2). Likewise, the DC/DC converters 304a and 304b may be a different type of DC/DC converter such as a full bridge or flyback converter.

The controller 112 may communicate with each DC/DC converter 304a-304d to monitor the output power capability of each alternate power source 302a-302d. In some examples, the controller 112 may communicate with one or more interfaces of the alternate power sources 302a-302d directly to monitor output power capability. As such, the controller 112 may operate each DC/DC converter 304a-304d to draw a desired amount of power from each of the alternate power sources 302a-302d. In some examples, the desired amount of power drawn from each of the alternate power sources 302a-302d may be a maximum amount corresponding to output power capability each alternate power source 202a-202d; however, in other examples, the desired amount may be different than the maximum amount.