Patent Description:
Power devices, such as uninterruptible power supplies (UPSs), may be used to provide regulated, uninterrupted power for sensitive and/or critical loads, such as computer systems and other data-processing systems. Existing UPSs include online UPSs, offline UPSs, line-interactive UPSs, as well as others. UPSs may provide output power to a load. The output power may be derived from a primary source of power, such as a utility-mains source, and/or derived from a backup source of power, such as an energy-storage device.

<CIT> relates to a hybrid power converter with a variable speed energy generating device and a hybrid uninterruptible power supply.

<CIT> concerns a power supply apparatus includes an uninterruptible power supply (UPS) having an input configured to be coupled to a first power source and an output configured to be coupled to a load and a first static switch configured to provide a switchable bypass path from the first power source to the load.

According to at least one aspect of the present disclosure, an uninterruptible power supply (UPS) system is provided comprising at least one energy-storage-device connection configured to be coupled to an energy-storage device, a first output connection configured to be coupled to a main power source providing main power, a second output connection configured to be coupled to at least one load, a first power converter coupled to the at least one energy-storage-device connection, a second power converter coupled to the at least one energy-storage-device connection, and at least one controller coupled to the first power converter and the second power converter, the at least one controller being configured to control the UPS system to connect the first power converter and the second power converter to the first output connection and the second output connection, control the UPS system to disconnect the first power converter from the second output connection responsive to detecting a fault in the main power, control the first power converter to provide power to the first output connection responsive to detecting the fault in the main power, and control the UPS system to disconnect the second power converter from the first output connection responsive to detecting the fault in the main power.

In some examples, the first power converter has a first power rating less than a power rating of the at least one load, and the second power converter has a second power rating less than the power rating of the at least one load. In various examples, the UPS system includes a first switch coupled between the first power converter and the second power converter. In at least one example, disconnecting the first power converter from the second output connection and disconnecting the second power converter from the first output connection includes opening the first switch.

In some examples, the at least one controller is further configured to determine whether the fault in the main power has ended within a predetermined amount of time since detecting the fault in the main power, and close the first switch responsive to determining that the fault in the main power has not ended within the predetermined amount of time. In various examples, the UPS system includes a second switch coupled between the first power converter and the first output connection. In at least one example, the first switch closes faster than the second switch.

In some examples, the at least one controller is further configured to determine whether the fault in the main power has ended within a predetermined amount of time since detecting the fault in the main power, close the first switch responsive to determining that the fault in the main power has not ended within the predetermined amount of time, and open the second switch responsive to closing the first switch. In various examples, the at least one controller is further configured to control the first power converter to provide power to the second output connection responsive to opening the second switch.

In at least one example, the at least one controller is further configured to determine whether the fault in the main power has ended within a predetermined amount of time since detecting the fault in the main power, and disconnect the first power converter from the first output connection responsive to determining that the fault in the main power has not ended within the predetermined amount of time. In some examples, the at least one controller is further configured to connect the first power converter to the second output connection responsive to disconnecting the first power converter from the first output connection.

In various examples, the at least one controller is further configured to control the first power converter to provide power to the second output connection in parallel with the second power converter responsive to connecting the first power converter to the second output connection. In at least one example, controlling the first power converter to provide power to the first output connection provides fault-ride-through protection to one or more loads coupled to the first output connection. In some examples, the at least one controller is further configured to control the second power converter to provide power to the second output connection during the fault in the main power.

According to at least one aspect of the disclosure, a non-transitory computer-readable medium storing thereon sequences of computer-executable instructions for controlling an uninterruptible power supply including at least one energy-storage-device connection configured to be coupled to an energy-storage device, a first output connection configured to be coupled to a main power source providing main power, a second output connection configured to be coupled to at least one load, a first power converter coupled to the at least one energy-storage-device connection, and a second power converter coupled to the at least one energy-storage-device connection is provided, the sequences of computer-executable instructions including instructions that instruct at least one processor to control the uninterruptible power supply to connect the first power converter and the second power converter to the first output connection and the second output connection, control the uninterruptible power supply to disconnect the first power converter from the second output connection responsive to detecting a fault in the main power, control the first power converter to provide power to the first output connection responsive to detecting the fault in the main power, and control the uninterruptible power supply to disconnect the second power converter from the first output connection responsive to detecting the fault in the main power.

In some examples, the uninterruptible power supply includes a first switch coupled between the first power converter and the second power converter, and disconnecting the first power converter from the second output connection and disconnecting the second power converter from the first output connection includes opening the first switch. In various examples, the uninterruptible power supply includes a first switch coupled between the first power converter and the second power converter, and the instructions further instruct the at least one processor to determine whether the fault in the main power has ended within a predetermined amount of time since detecting the fault in the main power, and close the first switch responsive to determining that the fault in the main power has not ended within the predetermined amount of time.

In at least one example, the uninterruptible power supply includes a first switch coupled between the first power converter and the second power converter and a second switch coupled between the first power converter and the first output connection, and the instructions further instruct the at least one processor to determine whether the fault in the main power has ended within a predetermined amount of time since detecting the fault in the main power, close the first switch responsive to determining that the fault in the main power has not ended within the predetermined amount of time, and open the second switch responsive to closing the first switch.

In some examples, the instructions further instruct the at least one processor to control the first power converter to provide power to the second output connection responsive to opening the second switch. In various examples, the instructions further instruct the at least one processor to determine whether the fault in the main power has ended within a predetermined amount of time since detecting the fault in the main power, and disconnect the first power converter from the first output connection responsive to determining that the fault in the main power has not ended within the predetermined amount of time.

In at least one example, the instructions further instruct the at least one processor to connect the first power converter to the second output connection responsive to disconnecting the first power converter from the first output connection. In some examples, controlling the first power converter to provide power to the first output connection provides fault-ride-through protection to one or more loads coupled to the first output connection. In various examples, the instructions further instruct the at least one processor to control the second power converter to provide power to the second output connection during the fault in the main power.

According to at least one example, a method of controlling an uninterruptible power supply including at least one energy-storage-device connection configured to be coupled to an energy-storage device, a first output connection configured to be coupled to a main power source providing main power, a second output connection configured to be coupled to at least one load, a first power converter coupled to the at least one energy-storage-device connection, and a second power converter coupled to the at least one energy-storage-device connection is provided, the method comprising controlling the uninterruptible power supply to connect the first power converter and the second power converter to the first output connection and the second output connection, controlling the uninterruptible power supply to disconnect the first power converter from the second output connection responsive to detecting a fault in the main power, controlling the first power converter to provide power to the first output connection responsive to detecting the fault in the main power, and controlling the uninterruptible power supply to disconnect the second power converter from the first output connection responsive to detecting the fault in the main power.

Examples of the methods and systems discussed herein are not limited in application to the details of construction and the arrangement of components set forth in the following description or illustrated in the accompanying drawings. The methods and systems are capable of implementation in other embodiments and of being practiced or of being carried out in various ways. Examples of specific implementations are provided herein for illustrative purposes only and are not intended to be limiting. In particular, acts, components, elements, and features discussed in connection with any one or more examples are not intended to be excluded from a similar role in any other examples.

Any references to examples, embodiments, components, elements or acts of the systems and methods herein referred to in the singular may also embrace embodiments including a plurality, and any references in plural to any embodiment, component, element or act herein may also embrace embodiments including only a singularity. References in the singular or plural form are not intended to limit the presently disclosed systems or methods, their components, acts, or elements. The use herein of "including," "comprising," "having," "containing," "involving," and variations thereof is meant to encompass the items listed thereafter and equivalents thereof as well as additional items.

References to "or" may be construed as inclusive so that any terms described using "or" may indicate any of a single, more than one, and all of the described terms. In addition, in the event of inconsistent usages of terms between this document and documents incorporated herein by reference, the term usage in the incorporated features is supplementary to that of this document; for irreconcilable differences, the term usage in this document controls.

A power grid is connected to one or more loads and one or more power sources to provide power to the one or more loads. In some examples, a power grid may be connected to additional devices configured to support the one or more loads connected to the power grid. For example, such additional devices may include battery-energy-storage systems (BESSs), uninterruptible power supplies (UPSs), and so forth.

A BESS may be configured to exchange power with a power grid to absorb surplus power from the power grid (for example, surplus renewable energy) and inject power to the grid. The BESS may store power in one or more energy-storage devices, such as batteries. For example, a BESS may include a bi-directional AC/DC converter configured to be coupled to a battery or other energy-storage device. The BESS may receive DC power from, or provide DC power to, the energy-storage device, and provide AC power to, or receive AC power from, the power grid.

For example, in a power grid powered at least in part by renewable-energy sources (for example, wind turbines), the BESS may draw and store energy from the power grid when power supply exceeds demand (for example, while wind speeds around the wind turbines are high). The BESS may provide energy to the power grid when, for example, demand exceeds supply from the renewable-energy sources. In this manner, power may be stored for later use when supply exceeds demand.

In some examples, a BESS may also provide backup power to one or more loads when power on the power grid experiences a grid disturbance, such as a voltage sag or blackout. For example, the BESS may draw DC power from the energy-storage device, convert the DC power to AC power, and provide the converted AC power to the power grid to power the one or more loads. In this manner, the BESS may offer fault ride through (FRT) by enabling the BESS to remain connected to the power grid for the duration of a fault, such as a transient voltage sag, thereby "riding through" (that is, remaining connected during) the fault.

A UPS may be configured to provide uninterrupted power to one or more loads. For example, a UPS may be coupled to a main-power source, such as a power grid, and a backup-power source, such as a battery. The UPS may provide power derived from the back-up power source to the one or more loads when, for example, power on the power grid is not acceptable (for example, by being disturbed or unavailable).

Some UPS architectures may be capable of quickly disconnecting critical loads from the power grid when grid power is not acceptable, or may be implemented between the power grid and the critical loads such that the critical loads are substantially always isolated from the power grid. In such architectures, high-quality power may be provided to the critical loads even immediately after a grid disturbance occurs. In some examples, certain BESS architectures (for example, including a single AC/DC converter) may not be configured to provide high-quality power continuously, for example, immediately after a grid disturbance occurs. Accordingly, certain UPSs may be more desirable than BESSs for powering critical loads. However, certain UPS topologies may be more complex and/or include additional components as compared to certain BESSs.

For example, a UPS may include a first DC/AC converter coupled to a power grid and to an energy-storage device, and a second DC/AC converter coupled to a critical load and to the energy-storage device. In this manner, the critical load may be isolated from the power grid. However, the first DC/AC converter and the second DC/AC converter may be isolated from one another. Each of the converters may thus be sized to power their respective loads individually. For example, the first DC/AC converter may be sized to power non-critical loads on the power grid and the second DC/AC converter may be sized to power the critical loads isolated from the power grid. Although such an architecture may enable power to be provided to critical and non-critical loads during power disturbances, the UPS may be larger, more complex, and/or more expensive than certain BESSs, for example.

Example power devices described herein, which may include and/or be referred to as UPSs, can provide similar functionality as existing BESSs and/or existing UPSs with a smaller, less complex, and/or less expensive topology. Example power devices may include and/or be referred to herein as UPSs. In one example, a UPS includes a first DC/AC converter switchably coupled in parallel with a second DC/AC converter. The first DC/AC converter and the second DC/AC converter may have a power rating that is less than (for example, approximately half) a power rating of the loads that the converters are configured to power. The first DC/AC converter and the second DC/AC converter may normally be coupled in parallel such that a combined power rating of the DC/AC converters is substantially equal to or greater than the power rating of the loads.

In the event of a grid fault, the DC/AC converters may be switchably disconnected from one another. The DC/AC converters may be switchably disconnected quickly enough to prevent the grid fault from substantially adversely affecting the critical loads, such as by providing low-quality (for example, caused by the grid fault) power to the critical loads. During the fault, the first DC/AC converter may power the non-critical loads and provides power to the power grid to provide fault ride through. For example, the first DC/AC converter may inject power to the power grid as requested by the power grid during the fault. The second DC/AC converter may power the critical loads. For example, the second DC/AC converter may transition from grid-following operation while operating as a battery-energy-storage system to grid-forming operation to operate as an uninterruptible power supply. After a determined amount of time (for example, a maximum expected duration of a transient fault, as compared to an extended outage), the DC/AC converters may again be switchably coupled in parallel to power the critical loads. In some examples, the determined amount of time may be sufficiently short such that the DC/AC converters are capable of powering the converters' respective loads despite the fact that the power ratings of the DC/AC converters may individually be less than the power ratings of the loads.

If the grid fault remains after the predetermined amount of time (for example, because the grid fault is a non-transient fault, such as a blackout condition), the parallel-connected DC/AC converters may remain decoupled from the non-critical loads and the power grid while remaining coupled to the critical loads. Conversely, if the grid fault no longer exists after the predetermined amount of time (for example, because the grid fault is a transient fault, such as a voltage sag), the parallel-connected DC/AC converters may again be coupled to the non-critical loads in addition to the critical loads. Accordingly, example UPSs may provide similar functionality as known UPSs and/or BESSs in a smaller, less complex, and/or less expensive topology.

<FIG> illustrates a block diagram of a power system <NUM> according to an example. The power system <NUM> includes at least one main power source <NUM> ("main power source <NUM>"), at least one uninterruptible power supply (UPS) <NUM> ("UPS <NUM>"), at least one load <NUM> ("loads <NUM>"), and at least one energy-storage device <NUM> ("energy-storage device <NUM>"). It is to be appreciated that components of the power system <NUM> may perform additional operations than known components having similar names as those of the power system <NUM>. For example, although the UPS <NUM> may perform operations of an uninterruptible power supply, the UPS <NUM> may also perform operations of other power devices, such as battery-energy-storage systems.

The main power source <NUM> is coupled to the UPS <NUM> and to the loads <NUM> via a power connection <NUM>. The power connection <NUM> may be, for example, a power grid. The main power source <NUM> may include several power sources, such as generators, wind turbines, and so forth, configured to distribute power to one or more devices such as the UPS <NUM> and the loads <NUM>. The UPS <NUM> may be coupled to the power connection <NUM> at a main-power connection, the energy-storage device <NUM> at an energy-storage-device connection, and to the loads <NUM> at one or more output connections. The loads <NUM> may be coupled to the power connection <NUM> and to the UPS <NUM> at one or more respective load connections. The energy-storage device <NUM> may be coupled to the UPS <NUM>.

The loads <NUM> may include at least one standard load <NUM> ("standard loads <NUM>"), at least one essential load <NUM> ("essential loads <NUM>"), and/or at least one critical load <NUM> ("critical loads <NUM>"). Standard loads may include loads that are powered down if the main power source <NUM> is no longer able to provide acceptable power (for example, power having parameters within certain ranges, such as by having an AC voltage within a desired range). A standard load may include, for example, a microwave oven. Essential loads may include loads for which fault ride through (FRT) is desired, but for which uninterrupted power is not required (for example, after main power fails but before a backup-power source, such as a generator, starts up). An essential load may include, for example, emergency lights in a commercial building. Critical loads may include loads for which uninterrupted power is desired. A critical load may include, for example, certain medical devices in a hospital.

The main power source <NUM> may be configured to provide main power to the UPS <NUM> and to at least one of the loads <NUM>. In some examples, the main power source <NUM> may provide power directly to the standard loads <NUM>, the essential loads <NUM>, and the critical loads <NUM>. While the main power source <NUM> provides power to the standard loads <NUM>, the essential loads <NUM>, and the critical loads <NUM>, the UPS <NUM> may also draw power from the main power source <NUM> to charge the energy-storage device <NUM>. The UPS <NUM> may also draw power from the energy-storage device <NUM> and provide power to the power grid supplying the standard loads <NUM>, the essential loads <NUM>, and the critical loads <NUM> in conjunction with the main power source <NUM>, for example, by injecting power to the power grid. The UPS <NUM> may inject power to the loads <NUM> to increase a power factor of the loads <NUM>, for example.

In the event of a grid fault, the UPS <NUM> may disconnect the main power source <NUM> from the critical loads <NUM> and begin providing uninterrupted power directly to the critical loads <NUM>. The UPS <NUM> may also provide power to the power grid, the essential loads <NUM>, and/or the standard loads <NUM> for at least a transient period of time to support FRT. In some examples, the power system <NUM> may include a switching device (for example, a slow switch) controllable by the UPS <NUM> and configured to disconnect the essential loads <NUM> from the main power source <NUM> and the standard load <NUM> while maintaining the essential loads <NUM> connected to the UPS <NUM> during the grid fault. If the fault lasts for more than a determined amount of time (for example, an expected duration of a transient grid fault, as distinguished from a longer term main-power outage), then the UPS <NUM> may stop providing power to the essential loads <NUM> and/or the standard loads <NUM> and only provide power to the critical loads <NUM>. In this manner, the UPS <NUM> provides FRT for the essential loads <NUM> and/or the standard loads <NUM>, and provides uninterrupted power to the critical loads <NUM>.

<FIG> illustrates a block diagram of the power system <NUM> according to another example. The power system <NUM> includes the main power source <NUM>, the UPS <NUM>, the loads <NUM>, and the energy-storage device <NUM>. The UPS <NUM> includes a first power converter <NUM>, a second power converter <NUM>, a first switching device <NUM>, a second switching device <NUM>, at least one controller <NUM> ("controller <NUM>"), one or more voltage sensors and/or one or more current sensors <NUM> ("voltage and current sensors <NUM>"), a first power input and/or output connection <NUM> ("first output connection <NUM>"), a second power input and/or output connection <NUM> ("second output connection <NUM>"), at least one energy-storage-device connection <NUM> ("energy-storage-device connection <NUM>"), and a third switching device <NUM>. In some examples, the first power converter <NUM> and the second power converter <NUM> may each be implemented as a DC/AC power converter. In other examples, such as examples in which the main power source <NUM> is configured to provide DC power, the power converters <NUM>, <NUM> may be implemented as DC/DC power converters.

The first power converter <NUM> is coupled to the energy-storage-device connection <NUM> at a first connection, and to the first switching device <NUM> and the second switching device <NUM> at a second connection. In examples in which the first power converter <NUM> is a DC/AC converter, the first power converter <NUM> may receive and/or provide DC power at the first connection, and may receive and/or provide AC power at the second connection. In various examples, the first power converter <NUM> may be communicatively coupled to the controller <NUM>.

The second power converter <NUM> is coupled to the energy-storage-device connection <NUM> at a first connection, and to the first switching device <NUM> and the critical loads <NUM> (via the second output connection <NUM>) at a second connection. In examples in which the second power converter <NUM> is a DC/AC converter, the second power converter <NUM> may receive and/or provide DC power at the first connection, and may receive and/or provide AC power at the second connection. In various examples, the second power converter <NUM> may be communicatively coupled to the controller <NUM>.

The first switching device <NUM> is coupled to the first power converter <NUM> and the second switching device <NUM> at a first connection, is coupled to the voltage and current sensors <NUM> at a second connection, and is configured to be coupled to the controller <NUM> at a control connection. In various examples, the first switching device <NUM> may be considered to be coupled between the first power converter <NUM> and the first output connection <NUM>. The second switching device <NUM> is coupled to the first power converter <NUM> and the first switching device <NUM> at a first connection, is coupled to the second power converter <NUM> and the critical loads <NUM> at a second connection, and is configured to be coupled to the controller <NUM> at a control connection. In various examples, the second switching device <NUM> may be considered to be coupled between the first power converter <NUM> and the second power converter <NUM>.

The switching devices <NUM>, <NUM> may include one or more switches. In some examples, the second switching device <NUM> may be implemented as a switching device that is configured to switch relatively quickly, such as a solid-state fast switch (for example, an IGBT, MOSFET, and so forth) or hybrid fast switch, as compared to other switching devices, such as static switches. The first switching device <NUM> may be implemented as a similar switching device in some examples, or may be implemented as a slower switching device in other examples, such as a relay, SCR, thyristor, and so forth.

The controller <NUM> is communicatively coupled to the first power converter <NUM>, the second power converter <NUM>, the first switching device <NUM>, the second switching device <NUM>, the voltage and current sensors <NUM>, and the third switching device <NUM>. In some examples, the controller <NUM> may be communicatively coupled to the energy-storage device <NUM>. In various examples, the controller <NUM> may send one or more control signals to the power converters <NUM>, <NUM> to control operation of the power converters <NUM>, <NUM>. The controller <NUM> may also send one or more control signals to the switching devices <NUM>, <NUM>, <NUM> to control a switching state of the switching devices <NUM>, <NUM>, <NUM>. A switching state may include, for example, closed and conducting or open and non-conducting. The controller <NUM> may receive voltage and/or current information from the voltage and current sensors <NUM>. In some examples, the controller <NUM> may be coupled to at leas one grid controller coupled to the main power source <NUM> and configured to, for example, request power injection from the UPS <NUM>.

The voltage and current sensors <NUM> are coupled to the first switching device <NUM> at a first connection, and to the first output connection <NUM> at a second connection. The voltage and current sensors <NUM> may include multiple sensors. The voltage and current sensors <NUM> may be coupled to the controller <NUM>. The voltage and current sensors <NUM> may sense voltage and/or current information indicative of a voltage and/or current of the power connection <NUM> and provide the voltage and/or current information to the controller <NUM>. In some examples, the voltage and current sensors <NUM> may be implemented at additional or different locations in the UPS <NUM>, such as by being part of one or both of the converters <NUM>, <NUM>. In some examples, the voltage and current sensors <NUM> may be implemented in a different location in the power system <NUM>, which may be at least partially external to the UPS <NUM>. For example, a first set of one or more sensors may be implemented internal to the UPS <NUM> and a second set of one or more sensors may be implemented external to the UPS <NUM>. In another example, all of the voltage and current sensors <NUM> may be implemented external to the UPS <NUM>.

The first output connection <NUM> is coupled to the voltage and current sensors <NUM> and to the essential load <NUM> and the third switching device <NUM> via the power connection <NUM>. In various examples, the first output connection <NUM> may receive power from, and provide power to, the power connection <NUM>. For example, the first output connection <NUM> may receive power from the main power source <NUM> and/or provide power to the loads <NUM>. Accordingly, no limitation is implied by examples in which the first output connection <NUM> is referred to as an output connection.

The second output connection <NUM> is coupled to the second switching device <NUM> and the second DC/AC converter <NUM> and to the critical loads <NUM>. In various examples, the second output connection <NUM> may receive power from, and provide power to, the critical loads <NUM>. For example, the second output connection <NUM> may receive power from the critical loads <NUM> where, for example, the critical loads <NUM> include regenerative loads. Accordingly, no limitation is implied by examples in which the second output connection <NUM> is referred to as an output connection.

The energy-storage-device connection <NUM> is coupled to the energy-storage devices <NUM> and to the power converters <NUM>, <NUM>. In various examples, the energy-storage-device connection <NUM> may receive power from, and provide power to, the energy-storage devices <NUM>. For example, the power converters <NUM>, <NUM> may provide power to the energy-storage devices <NUM> via the energy-storage-device connection <NUM> to recharge the energy-storage devices <NUM> with energy derived from the main power source <NUM>. In some examples, the power converters <NUM>, <NUM> may additionally or alternatively draw power from the energy-storage devices <NUM> via the energy-storage-device connection <NUM> to discharge power to one or more of the loads <NUM>. In various examples, the energy-storage-device connection <NUM> may include multiple energy-storage-device connections each coupled to one or more energy-storage devices. In some examples in which the energy-storage-device connection <NUM> includes multiple energy-storage-device connections, the first power converter <NUM> is coupled to one or more first energy-storage-device connections, and the second power converter <NUM> is coupled to one or more second energy-storage-device connections. In other examples, the energy-storage-device connection <NUM> includes a single energy-storage-device connection configured to be coupled to both of the power converters <NUM>, <NUM>.

The third switching device <NUM> is coupled to the main power source <NUM> and the standard load <NUM> at a first connection, and to the essential load <NUM> and the first power connection <NUM> at a second connection. In some examples, the third switching device <NUM> is optional and may be omitted by being replaced with a short circuit. The third switching device <NUM> may disconnect the main power source <NUM> and the standard load <NUM> from the UPS <NUM> while enabling the essential load <NUM> to remain coupled to the UPS <NUM> via the first power connection <NUM>. In other examples, the third switching device <NUM> is omitted such that the main power source <NUM> and the standard load <NUM> are coupled to the first power connection <NUM> directly.

The controller <NUM> may be coupled to the power converters <NUM>, <NUM> and the switching devices <NUM>, <NUM>, <NUM> (connections not illustrated for clarity). The controller <NUM> may control the UPS <NUM> to operate in one or more modes of operation based on, for example, power received from the main power source <NUM>. For example, the controller <NUM> may control operate of the converters <NUM>, <NUM> and/or the switching devices <NUM>, <NUM>, <NUM> based on the power received from the main power source <NUM>. As discussed in greater detail below, the controller <NUM> may select a mode of operation of the UPS <NUM> based at least in part on parameters of main power received from the main power source <NUM>, such as a voltage level of the main power.

<FIG> illustrates a process <NUM> of operating the UPS <NUM> according to an example. At least a portion of the process <NUM> may be executed at least in part by the controller <NUM>. For purposes of example, an example of the process <NUM> is described in which grid power is initially determined to be normal, as discussed below. It is to be appreciated that, in other examples, the process <NUM> may begin at a different act and/or under different conditions.

At act <NUM>, the controller <NUM> determines that main power is normal. Main power may refer to power on the power connection <NUM>, which may be provided by the main power source <NUM>. Main power may also be referred to as "grid power" in examples in which the power connection <NUM> is representative of a power-grid connection. The controller <NUM> may receive voltage and/or current information (or "power information") from the voltage and current sensors <NUM>. The power information may be indicative of a state and/or parameters of the grid power. The controller <NUM> may determine a state or parameters of the grid power based on the power information. , such as voltage parameters, frequency parameters, and so forth. For example, the controller <NUM> may determine that the grid power is normal based on a determination that a current and/or voltage of the grid power are within certain expected, normal ranges, as opposed to experiencing voltage spikes and sags, for example.

At act <NUM>, the controller <NUM> controls the first switching device <NUM> and the second switching device <NUM> to be in a closed and conducting position. The controller <NUM> may close the switching devices <NUM>, <NUM> responsive to determining that the grid power is normal at act <NUM>. <FIG> illustrates a block diagram of the power system <NUM> in which the switching devices <NUM>, <NUM> are in a closed and conducting position. As illustrated by <FIG>, the power converters <NUM>, <NUM> are coupled in parallel via the second switching device <NUM>. Accordingly, in some examples, a power output of the parallel-connected power converters <NUM>, <NUM> may be approximately equal to a sum of the power outputs of the power converters <NUM>, <NUM>. In some examples, the power converters <NUM>, <NUM> each have a power rating that is half of a power rating of the loads <NUM>. However, while the power converters <NUM>, <NUM> are coupled in parallel, a combined power rating of the power converters <NUM>, <NUM> may be substantially equal to or greater than the power rating of the loads <NUM>. In some examples, the controller <NUM> may also control the third switching device <NUM> to be in a closed and conducting position at act <NUM>.

At act <NUM>, the controller <NUM> controls the power converters <NUM>, <NUM> to operate in a normal mode of operation. In the normal mode of operation, the controller <NUM> may control the power converters <NUM>, <NUM> to draw main power from the main power source <NUM> via the power connection <NUM> and charge the energy-storage device <NUM> with the main power. For example, the controller <NUM> may control the power converters <NUM>, <NUM> to charge the energy-storage device <NUM> responsive to determining that a charge level of the energy-storage device <NUM> is below a threshold charge level. The controller <NUM> may be communicatively coupled to the energy-storage device <NUM> to receive charge information from the energy-storage device <NUM>. The charge information may be indicative of a charge level of the energy-storage device <NUM>. Controlling the power converters <NUM>, <NUM> may include controlling the power converters <NUM>, <NUM> to draw AC power from the power connection <NUM>, convert the AC power to DC power, and provide the DC power to the energy-storage device <NUM>.

Also, in the normal mode of operation, the controller <NUM> may also control the power converters <NUM>, <NUM> to draw backup power from the energy-storage device <NUM> and provide power derived from the backup power to one or more of the loads <NUM>. For example, the controller <NUM> may provide power to the loads <NUM> to improve a power factor of power provided to the loads <NUM>. The controller <NUM> may receive power information from the voltage and/or current sensors <NUM> and determine, based on the power information, whether to provide power to the loads <NUM>. In some examples, the controller <NUM> may exchange information with a grid controller monitoring the power connection <NUM> and operate based on the received information. For example, the controller <NUM> may receive a request from the grid controller to provide power to the power connection <NUM> to provide frequency support, peak power shaving, and so forth.

At act <NUM>, the controller <NUM> determines whether a grid disturbance is detected. A grid disturbance may be an example of a power fault, or "fault. " The controller <NUM> may determine whether a grid disturbance is present on the power connection <NUM> based on power information received from the voltage and current sensors <NUM>. The controller <NUM> may determine whether a grid disturbance is present by determining whether a voltage, current, or parameter derived therefrom (for example, power) meets one or more grid-disturbance criteria. Grid-disturbance criteria may include one or more ranges or thresholds of values. For example, a voltage sag, which may be a type of grid disturbance, may be detected responsive to determining that a voltage on the power connection <NUM> drops below a certain threshold voltage for more than a threshold amount of time (which may include, for example, zero seconds). Other grid disturbances, such as a current or power falling outside of or within certain ranges, may also be detectable by the controller <NUM>.

If the controller <NUM> does not detect a grid disturbance (<NUM> NO), then the process <NUM> returns to act <NUM>. The controller <NUM> repeatedly controls the converters <NUM>, <NUM> in the normal mode of operation at act <NUM> and determines whether a grid disturbance is detected at act <NUM> until a grid disturbance is detected (<NUM> YES). For example, the controller <NUM> may repeatedly execute the acts periodically, aperiodically, continuously, and so forth. If a grid disturbance is detected (<NUM> YES), then the process <NUM> continues to act <NUM>.

At act <NUM>, the controller <NUM> disconnects the first power converter <NUM> from the second output connection <NUM> and disconnects the second power converter <NUM> from the first output connection <NUM>. For example, the controller <NUM> may control the second switching device <NUM> to be in an open and non-conducting position. As discussed above, the second switching device <NUM> may be a fast-switching device, such as a solid-state breaker, such that the critical loads <NUM> may be quickly disconnected from the main power source <NUM> in the event of a grid disturbance. In this manner, the critical loads <NUM> may be isolated from low-quality power.

<FIG> illustrates a block diagram of the power system <NUM> in which the first switching device <NUM> is in a closed and conducting position and the second switching device <NUM> is in an open and non-conducting position. <FIG> may therefore illustrate the power system <NUM> during a grid disturbance. As illustrated by <FIG>, the power converters <NUM>, <NUM> are not coupled in parallel when the second switching device <NUM> is opened. A connection between the power converters <NUM>, <NUM> via the second switching device <NUM> is illustrated in dashed lines to indicate that substantially no power passes through the second switching device <NUM>. In some examples, the controller <NUM> may control the third switching device <NUM> to be closed and conducting such that the main power source <NUM> and the standard loads <NUM>, in addition to the essential loads <NUM>, remain coupled to the first power connection <NUM>. In other examples, the controller <NUM> may control the third switching device <NUM> to be open and non-conducting such that only the essential loads <NUM> are coupled to the first power connection <NUM>.

At act <NUM>, the controller <NUM> controls the power converters <NUM>, <NUM> to operate in a ride-through mode. The controller <NUM> may operate the power converters <NUM>, <NUM> in the ride-through mode during a grid disturbance up to a determined amount of time. For example, the determined amount of time may represent an expected duration of a transient disturbance, as distinguished from a non-transient fault, such as a power outage.

During the ride-through mode, the controller <NUM> may control the first power converter <NUM> to provide power to the essential loads <NUM> and/or the standard loads <NUM> to provide FRT protection. In some examples, the controller <NUM> may control the first power converter <NUM> to provide power only to the essential loads <NUM>, and not the standard loads <NUM>, to provide FRT protection. For example, the controller <NUM> may control the third switching device <NUM> to open such that FRT is provided only to the essential loads <NUM>. As discussed above, the essential loads <NUM> may include loads for which FRT protection is desired, but for which uninterrupted power may not be required. Accordingly, the first power converter <NUM> may not provide power to the standard loads <NUM> during a grid disturbance in some examples. In one example, the controller <NUM> controls the first power converter <NUM> in a grid-following mode to provide FRT protection.

The controller <NUM> may also control the second power converter <NUM> to provide uninterrupted power to the critical loads <NUM> during the grid disturbance. In one example, the controller <NUM> controls the second power converter <NUM> in a grid-forming mode to provide uninterrupted power to the critical loads <NUM>. The controller <NUM> may continue to control the power converters <NUM>, <NUM> to power their respective loads in the ride-through mode such that the loads <NUM> remain powered at least through a transient fault.

At act <NUM>, the controller <NUM> determines, after a specified time period, whether the grid disturbance has ended. The specified time period may represent an expected duration of a transient grid disturbance, as distinguished from a non-transient fault, such as a power outage. For example, the specified time period may be <NUM>, <NUM>, <NUM>, or another time period. If the controller <NUM> determines, after the specified time period, that the grid disturbance has ended (<NUM> YES), then the process <NUM> returns to act <NUM> and resumes the normal mode of operation. For example, the controller <NUM> may determine that the grid disturbance has ended responsive to determining that the power information no longer satisfies the criteria of a grid disturbance, as discussed above at act <NUM>. If the controller <NUM> determines that the grid disturbance has not ended (<NUM> NO), then the process <NUM> continues to act <NUM>.

At act <NUM>, the controller <NUM> disconnects the first power converter <NUM> from the first output connection <NUM> and connects the first power converter <NUM> to the second output connection <NUM>. For example, the controller <NUM> may control the first switching device <NUM> to be in an open and non-conducting position and the second switching device <NUM> to be in a closed and conducting position. In some examples, the controller <NUM> may introduce a delay between opening the first switching device <NUM> and closing the second switching device <NUM> to ensure that the first switching device <NUM> is open before the second switching device <NUM> is closed, thereby avoiding cross-conduction. As discussed above, in some examples the power converters <NUM>, <NUM> may each have a power rating that is less than a power rating of the loads <NUM>. Although the power converters <NUM>, <NUM> may be capable of providing adequate power to the loads <NUM> during the grid disturbance in the ride-through mode, the power converters <NUM>, <NUM> may not be configured to provide power to the loads <NUM> for significantly longer than the specified time period of act <NUM> at least in part because of the lower power rating of the power converters <NUM>, <NUM>. Accordingly, at act <NUM>, the first power converter <NUM> may be disconnected from the power connection <NUM> via the first switching device <NUM> and connected in parallel with the second power converter <NUM> to the critical load <NUM>. As discussed above, a combined power rating of the power converters <NUM>, <NUM> may be substantially equal to or greater than a power rating of the critical loads <NUM>.

At act <NUM>, the controller <NUM> controls the power converters <NUM>, <NUM> in a backup mode of operation. <FIG> illustrates a block diagram of the power system <NUM> in the backup mode of operation. As illustrated in <FIG>, the controller <NUM> controls the power converters <NUM>, <NUM> to provide uninterrupted power to the critical loads <NUM> during the backup mode of operation. Conversely, the standard loads <NUM> and the essential loads <NUM> may not receive power. As discussed above, the standard loads <NUM> and the essential loads <NUM> may not receive uninterrupted power, although a user may re-classify an essential or standard load as a critical load to provide uninterrupted power to the re-classified load in some examples. Accordingly, the UPS <NUM> continues to provide uninterrupted power to the critical loads <NUM> while power is unavailable from the main power source <NUM>. In some examples, the controller <NUM> controls the third switching device <NUM> to be open and non-conducting in the backup mode of operation. In other examples, the controller <NUM> controls the third switching device <NUM> to be closed and conducting in the backup mode of operation.

At act <NUM>, the controller <NUM> determines whether main power is restored. The controller <NUM> may receive power information from the voltage and current sensors <NUM> and determine, based on the power information, whether main power is restored. The controller <NUM> may determine that main power is restored responsive to determining that acceptable main power is available via the power connection <NUM>. The controller <NUM> may evaluate one or more parameters, such as voltage and current, to determine whether the main power is acceptable. For example, the controller <NUM> may determine whether the one or more parameters fall within one or more desired ranges. If the controller <NUM> determines that grid power is restored (<NUM> YES), then the process <NUM> returns to act <NUM> and again operates in the normal mode, reconnecting the converters <NUM>, <NUM> to the output connections <NUM>, <NUM> at act <NUM>. If the controller <NUM> determines that grid power is not restored (<NUM> NO), then the process <NUM> continues to act <NUM>.

At act <NUM>, the controller <NUM> determines whether the energy-storage device <NUM> is discharged. The energy-storage device <NUM> may be considered discharged when a charge level of the energy-storage device <NUM> falls below a discharge level. As appreciated by one or ordinary skill in the art, an energy-storage device may be considered discharged even when some charge remains in the energy-storage device because a complete discharge may adversely affect a state of health of the energy-storage device. Accordingly, the controller <NUM> may determine that the energy-storage device <NUM> is discharged even when charge remains in the energy-storage device <NUM>.

In some examples, the controller <NUM> is communicatively coupled to, and receives charge information from, the energy-storage device <NUM>. The controller <NUM> may determine whether the energy-storage device <NUM> is discharged based on the charge information. In some examples, the charge information includes a direct indication that the energy-storage device <NUM> is discharged. In another example, the charge information includes information that the controller <NUM> uses to determine whether the energy-storage device <NUM> is discharged, such as a current state of charge of the energy-storage device <NUM> which the controller <NUM> may compare to a discharge threshold. If the controller <NUM> determines that the energy-storage device <NUM> is not discharged (<NUM> NO), then the process <NUM> returns to act <NUM>, and acts <NUM>-<NUM> are repeatedly executed until main power is restored (<NUM> YES) or the energy-storage device <NUM> is discharged (<NUM> YES). If the energy-storage device <NUM> is discharged (<NUM> YES), then the process <NUM> continues to act <NUM>.

At act <NUM>, the controller <NUM> controls the UPS <NUM> to stop discharging power to the critical loads <NUM>. The controller <NUM> may determine that, because main power and stored backup power are unavailable, the UPS <NUM> may no longer be capable of powering the critical loads <NUM>. Accordingly, the controller <NUM> may control the power converters <NUM>, <NUM> to discontinue providing output power to the critical loads <NUM>.

The process <NUM> may then end. In various examples, the process <NUM> may begin again at act <NUM> when main power is again normal.

It is to be appreciated that, although in some examples a UPS (for example, the UPS <NUM>) may include two DC/AC converters (for example, the power converters <NUM>, <NUM>), in other examples the UPS may include more than two DC/AC converters. In some examples, a power rating of each of n DC/AC converters may be sized to be about <NUM>/n of a power rating of loads powered by the UPS. For example, a UPS may include three DC/AC inverters each having a power rating that is approximately one-third of a power rating of loads powered by the UPS.

It is to be appreciated that different switching arrangements than those identified above are within the scope of the disclosure. The principles of the disclosure include any of various switching-device configurations of a UPS in which one or more switching devices disconnect critical loads (for example, critical loads <NUM>) from a power connection (for example, power connection <NUM>) in response to a grid disturbance while continuing to power one or more critical, essential, and/or standard loads (for example, during the grid disturbance). As discussed above, one or more switching devices may be coupled to the UPS but may not be included within the UPS. Similarly, in some examples, the controller <NUM> may be at least partially external to the UPS <NUM>.

Various controllers, such as the controller <NUM>, may execute various operations discussed above. Using data stored in associated memory and/or storage, the controller <NUM> also executes one or more instructions stored on one or more non-transitory computer-readable media, which the controller <NUM> may include and/or be coupled to, that may result in manipulated data. In some examples, the controller <NUM> may include one or more processors or other types of controllers. In one example, the controller <NUM> is or includes at least one processor. In another example, the controller <NUM> performs at least a portion of the operations discussed above using an application-specific integrated circuit tailored to perform particular operations in addition to, or in lieu of, a general-purpose processor. As illustrated by these examples, examples in accordance with the present disclosure may perform the operations described herein using many specific combinations of hardware and software and the disclosure is not limited to any particular combination of hardware and software components. Examples of the disclosure may include a computer-program product configured to execute methods, processes, and/or operations discussed above. The computer-program product may be, or include, one or more controllers and/or processors configured to execute instructions to perform methods, processes, and/or operations discussed above.

Claim 1:
An uninterruptible power supply (UPS) system (<NUM>) comprising:
at least one energy-storage-device connection (<NUM>) configured to be coupled to an energy-storage device (<NUM>);
a first output connection (<NUM>) configured to be coupled to a main power source (<NUM>) providing main power;
a second output connection (<NUM>) configured to be coupled to at least one load (<NUM>, <NUM>);
a first power converter (<NUM>) coupled to the at least one energy-storage-device connection (<NUM>);
a second power converter (<NUM>) coupled to the at least one energy-storage-device connection (<NUM>); and
at least one controller (<NUM>) coupled to the first power converter and the second power converter, the at least one controller being configured to
control the UPS system to connect the first power converter (<NUM>) and the second power converter (<NUM>) to the first output connection and the second output connection,
control the UPS system to disconnect the first power converter (<NUM>) from the second output connection (<NUM>) responsive to detecting a fault in the main power,
control the first power converter (<NUM>) to provide power to the first output connection (<NUM>) responsive to detecting the fault in the main power, and
control the UPS system to disconnect the second power converter (<NUM>) from the first output connection (<NUM>) responsive to detecting the fault in the main power.