AC Switching PFC with Integrated Charger and DC-DC for Online UPS Systems

Abstract

An uninterruptible power supply (UPS) includes an input terminal, a backup power input terminal, a positive DC bus and a negative DC bus, and a converter, wherein the input terminal is configured to receive input AC power having an input AC voltage, the backup power input terminal is configured to couple to a backup power source and provide DC power to the backup power source for charging, the positive and negative DC busses are current-coupled to the backup power input terminal, the converter is coupled to the input terminal, the backup power input terminal, the positive and negative DC busses, the converter includes a first inductor, a second inductor, a first converter switch configured to couple the first inductor to a neutral connection, a second converter switch configured to couple the second inductor to the positive DC bus, and a third converter switch configured to couple the second inductor to the negative DC bus, wherein the UPS is voltage-frequency independent.

Description

Technical Field

[0001] Embodiments of the present disclosure relate generally to power conversion, and more particularly, to AC-DC power conversion in an uninterruptible power supply. Background Art

[0002] Uninterruptible Power Supplies (UPS) are used to provide backup power to electrical equipment or loads in the event of a failure in the main power supply or mains. Typical loads include computer systems, but other loads such as heating / cooling / ventilation systems, lighting systems, network switches and routers, and secure data center management systems can also receive between 1 and 20 kVA of backup power for several hours. Summary of the invention

[0003] At least one aspect of the present disclosure relates to an uninterruptible power supply (UPS). The UPS includes an input terminal, a backup power input terminal, a positive DC bus and a negative DC bus, and a converter. The input terminal is configured to receive an input AC power having an input AC voltage, the backup power input terminal is configured to couple to a backup power source and provide DC power to the backup power source for charging, the positive DC bus and the negative DC bus are galvanically coupled to the backup power input terminal, the converter is coupled to the input terminal, the backup power input terminal, and the positive DC bus and the negative DC bus, the converter includes a first inductor, a second inductor, a first converter switch configured to couple the first inductor to a neutral connection, a second converter switch configured to couple the second inductor to the positive DC bus, and a third converter switch configured to couple the second inductor to the negative DC bus, wherein the UPS is voltage-frequency independent.

[0004] In one embodiment, the UPS includes a controller coupled to the converter and configured to: in a first operating mode and during a positive half cycle of the input AC voltage, operate the first converter switch to provide DC power derived from the input AC power to the positive DC bus via the first inductor, and operate at least one of the second converter switch or the third converter switch to provide DC power derived from at least one of the positive DC bus or the negative DC bus to the backup power input via the second inductor, in a first operating mode and during a negative half cycle of the input AC voltage, operate the first converter switch to provide DC power derived from the input AC power to the negative DC bus via the first inductor, and operate at least one of the second converter switch or the third converter switch to provide DC power derived from at least one of the positive DC bus or the negative DC bus to the backup power input via the second inductor. In some embodiments, the UPS includes an input terminal selection circuit configured to couple the converter to the input during the first operating mode and to couple the converter to the backup power input during the second operating mode. In various embodiments, the controller is configured to monitor the input AC power, operate the UPS in a first operating mode in response to determining that the input AC power is acceptable, and operate the UPS in a second operating mode in response to determining that the input AC power is unacceptable. In certain embodiments, the backup power input is configured to receive backup DC power from a backup power source, and the converter further includes a fourth converter switch configured to couple the second inductor to the backup power input.

[0005] In some embodiments, the controller is configured to: operate the first converter switch in the second operating mode to provide DC power derived from the backup DC power to the positive DC bus via the first inductor, and operate the fourth converter switch in the second operating mode to provide DC power derived from the backup DC power to the negative DC bus via the second inductor. In one embodiment, the converter also includes a fifth converter switch configured to couple the second inductor to the neutral connection, and the controller is configured to: operate the fifth converter switch in the second operating mode to provide DC power derived from the backup DC power to the positive DC bus via the second inductor, and operate the fourth converter switch in the second operating mode to provide DC power derived from the backup DC power to the negative DC bus via the second inductor. In one embodiment, the first converter switch is a bidirectional switch circuit including a first switch and a second switch coupled in series. In certain embodiments, the converter includes a first diode coupled between the first converter switch and the positive DC bus, a second diode coupled between the first converter switch and the negative DC bus, a fourth converter switch configured to couple the second inductor to the backup power input, and a fifth converter switch configured to couple the second inductor to the neutral connection. In various embodiments, the first inductor, the first switch of the first converter switch, the body diode of the second switch of the first converter switch, and the first diode are configured to operate as a boost converter in a first operating mode during a positive half cycle of the input AC voltage to provide DC power derived from the input AC power to the positive DC bus.

[0006] In some embodiments, the second inductor, the third converter switch, and the body diode of the fourth converter switch are configured to operate as a buck-boost converter in a first operating mode to provide DC power derived from the negative DC bus to the backup power input. In one embodiment, the first inductor, the second switch of the first converter switch, the body diode of the first switch of the first converter switch, and the second diode are configured to operate as a boost converter in a first operating mode during a negative half cycle of the input AC voltage to provide DC power derived from the input AC power to the negative DC bus. In various embodiments, the second inductor, the second converter switch, and the body diode of the fifth converter switch are configured to operate as a buck converter in a first operating mode to provide DC power derived from the positive DC bus to the backup power input. In certain embodiments, the first inductor, the first switch of the first converter switch, the body diode of the second switch of the first converter switch, and the first diode are configured to operate as a boost converter in a second operating mode to provide DC power derived from the backup DC power to the positive DC bus.

[0007] In one embodiment, the second inductor, the fourth converter switch, the body diode of the second converter switch, and the fifth converter switch are configured to operate as a boost converter in the second operation mode to provide DC power derived from the backup DC power to the positive DC bus. In some embodiments, the second inductor, the fourth converter switch, the body diode of the third converter switch, and the fifth converter switch are configured to operate as a buck-boost converter during the second operation mode to provide DC power derived from the backup DC power to the negative DC bus. In various embodiments, the UPS includes an output terminal and an inverter, the output terminal configured to provide output terminal AC power to a load, the inverter coupled to the output terminal and configured to convert DC power from the positive DC bus and the negative DC bus to output terminal AC power and provide the output terminal AC power to the output terminal.

[0008] Another aspect of the present disclosure relates to a non-transitory computer-readable medium having stored thereon a sequence of computer-executable instructions for controlling an uninterruptible power supply (UPS), the uninterruptible power supply (UPS) comprising an input terminal, a backup power input terminal, a positive DC bus, a negative DC bus, and a converter. The input terminal is configured to receive an input AC power having an input AC voltage, the backup power input terminal is configured to couple to a backup power source and provide DC power to the backup power source for charging, the converter is coupled to the input terminal, the backup power input terminal, and the positive and negative DC busses, the converter comprising a first inductor, a second inductor, a first converter switch configured to couple the first inductor to a neutral connection, a second converter switch configured to couple the second inductor to the positive DC bus, and a third converter switch configured to couple the second inductor to the negative DC bus. The sequence of computer executable instructions includes instructions that instruct at least one processor to perform the following operations: in a first operating mode and during a positive half cycle of an input AC voltage, operate the first converter switch to provide DC power derived from the input AC power to a positive DC bus via a first inductor, and operate at least one of the second converter switch or the third converter switch to provide DC power derived from at least one of the positive DC bus or the negative DC bus to a backup power input via a second inductor, in a first operating mode and during a negative half cycle of the input AC voltage, operate the first converter switch to provide DC power derived from the input AC power to the negative DC bus via the first inductor, and operate at least one of the second converter switch or the third converter switch to provide DC power derived from at least one of the positive DC bus or the negative DC bus to the backup power input via the second inductor.

[0009] In one embodiment, the sequence of instructions includes instructions to cause the at least one processor to monitor input AC power received at the input, in response to determining that the input AC power is acceptable, operate the UPS in a first operating mode, and in response to determining that the input AC power is unacceptable, operate the UPS in a second operating mode. In some embodiments, the UPS includes an input selection circuit, and the sequence of instructions includes instructions to cause the at least one processor to control the input selection circuit to couple the converter to the input during the first operating mode, and control the input selection circuit to couple the converter to the backup power input during the second operating mode. In various embodiments, the backup power input is also configured to receive backup DC power from a backup power source, and the converter includes a fourth converter switch configured to couple a second inductor to the backup power input. In certain embodiments, the sequence of instructions includes instructions to cause the at least one processor to operate the first converter switch to provide DC power derived from the backup DC power to the positive DC bus via the first inductor in the second operating mode, and to operate the fourth converter switch to provide DC power derived from the backup DC power to the negative DC bus via the second inductor in the second operating mode.

[0010] In some embodiments, the converter includes a fifth converter switch configured to couple the second inductor to the neutral connection, and the sequence of instructions includes instructions to cause the at least one processor to operate the fifth converter switch in the second operating mode to provide DC power derived from the backup DC power to the positive DC bus via the second inductor, and to operate the fourth converter switch in the second operating mode to provide DC power derived from the backup DC power to the negative DC bus via the second inductor.

[0011] Another aspect of the present disclosure relates to a method of assembling an uninterruptible power supply (UPS), the method comprising: providing an input terminal configured to receive input AC power having an input AC voltage, providing a backup power input terminal configured to couple to a backup power source and provide DC power to the backup power source for charging, galvanically coupling a positive DC bus and a negative DC bus to the backup power input terminal, and coupling a converter to the input terminal, the backup power input terminal, and the positive and negative DC busses, the converter comprising a first inductor, a second inductor, a first converter switch configured to couple the first inductor to a neutral connection, a second converter switch configured to couple the second inductor to the positive DC bus, and a third converter switch configured to couple the second inductor to the negative DC bus, wherein the UPS is voltage-frequency independent. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Various aspects of at least one embodiment are discussed below with reference to the accompanying drawings, which are not intended to be drawn to scale. The accompanying drawings are included to provide illustration and further understanding of the various aspects and embodiments, and are incorporated into and constitute a part of this specification, but are not intended to be used as a definition of limitations of the present invention. In the drawings, each identical or nearly identical component shown in various figures is represented by the same reference numeral. For clarity, not every component may be labeled in every figure. In the drawings:

[0013] Figure 1 is a functional block diagram of a UPS according to various aspects described herein;

[0014] Figure 2 is a schematic diagram of a UPS front-end topology according to various aspects described herein;

[0015] Figure 3A and Figure 3B yes Figure 2 A schematic diagram of a UPS front end topology illustrating a PFC function during an online mode of operation according to various aspects described herein;

[0016] Figure 4A and Figure 4B yes Figure 2 A schematic diagram of a UPS front end topology illustrating charger functionality during an online mode of operation according to various aspects described herein;

[0017] Figure 5A and Figure 5B yes Figure 2 A schematic diagram of a UPS front-end topology illustrating a backup mode of operation according to various aspects described herein; and

[0018] Figure 6 yes Figure 2 Schematic diagram of a UPS front end topology illustrating a backup mode of operation during a positive DC bus cycle in accordance with various aspects described herein. DETAILED DESCRIPTION

[0019] The examples of the methods and systems discussed herein are not limited in application to the details of the construction and arrangement of the components set forth in the following specification or shown in the accompanying drawings. The methods and systems can be implemented in other embodiments and can be practiced or executed in various ways. The examples of specific embodiments provided herein are for illustrative purposes only and are not restrictive. In particular, the actions, components, elements, and features discussed in conjunction with any one or more examples are not intended to be excluded from similar roles in any other examples.

[0020] In addition, the wording and terminology used herein are for the purpose of description and should not be considered as limiting. Any reference to the examples, embodiments, components, elements or actions of the systems and methods mentioned in the singular herein may also cover multiple embodiments, and any reference to any embodiments, components, elements or actions mentioned in the plural herein may also cover embodiments containing only the singular. References in singular or plural form are not intended to limit the currently disclosed systems or methods, their components, actions or elements. "Including", "including", "having", "containing", "involving" and their variations used herein are intended to cover the items listed thereafter and their equivalents and additional items. References to "or" may be interpreted as inclusive, so that any term described using "or" may indicate any of the single, multiple and all of the terms described. In addition, in the case of inconsistent use of terms between this document and the documents incorporated herein by reference, the use of terms in the incorporated references is a supplement to the use of terms in this document; for irreconcilable inconsistencies, the term "use" in this document shall prevail.

[0021] As described above, power devices such as uninterruptible power supplies (UPS) can be used to provide regulated uninterruptible power to sensitive and / or critical loads. An online UPS uses a power factor correction converter (PFC) circuit to rectify the input AC power provided by the power company to provide DC power to at least one DC bus. The rectified DC power on the DC bus can be used to charge the battery when the mains power is available. In the absence of mains power, the battery discharges and provides DC power to the DC bus. Based on the DC power on the DC bus, the inverter generates an AC output voltage provided to the load. Since power is provided to the DC bus from the mains or the battery, if the mains fails and the battery is fully charged, the output power of the UPS is not interrupted. An online UPS can also operate in a bypass mode, in which unregulated power with basic protection is provided directly to the load from the AC power source via a bypass line.

[0022] In many cases, the front-end topology of an online UPS includes a PFC converter to provide DC power to the DC bus when the AC mains is available, and includes a separate DC / DC converter to provide DC power to the DC bus from a battery when the AC mains is not available. In some cases, the front-end topology may include a separate charger (i.e., a DC / DC converter) configured to charge the battery. Therefore, these front-end UPS topologies typically have a high component count, which may result in increased cost, increased system complexity, and reduced power density. In addition, such front-end UPS topologies typically include components that are not used or idle during at least one operating mode of the UPS.

[0023] A more cost-effective and compact front-end topology for an online UPS is provided herein. In at least one embodiment, the front-end topology includes an integrated converter configured to operate as a PFC converter, a DC / DC converter, and a battery charger. In one example, the integrated converter is configured to provide power to a positive DC bus and a negative DC bus while charging the battery using power from the positive and negative DC buses. In some examples, the improved front-end topology can have a reduced component count, thereby increasing the power density of the UPS and reducing cost.

[0024] Figure 1 1 is a block diagram of an embodiment of an online UPS 100 that can provide regulated power from input AC power received at an input 102 and backup DC power from a backup power source 112 (e.g., a battery) to an output 110. The UPS 100 can be configured to provide output AC power that is independent of the input AC power in voltage and frequency. In some examples, the backup power source 112 can be included in the UPS 100; however, in other examples, the backup power source 112 can be external to the UPS 100. The UPS 100 includes a converter 104, a DC bus 106, an inverter 108, and a controller 114 for controlling the converter 104 and the inverter 108. The DC bus 106 is coupled between the converter 104 and the inverter 108.

[0025] The input 102 is configured to receive input AC power having an input voltage level from an AC power source. The controller 114 monitors the input AC power received by the input 102 and is configured to operate the UPS 100 in different operating modes based on the state of the input AC power received by the input 102. When the AC power provided to the input 102 is acceptable (i.e., above an input power quality threshold), the controller 114 operates the UPS 100 in an online operating mode.

[0026] In the online operation mode, AC power from the input terminal 102 is provided to the converter 104. The controller 114 operates the converter 104 to convert the AC power to DC power and provide the DC power to the DC bus 106. The DC power from the DC bus 106 is provided to the inverter 108. In addition, the DC power from the DC bus 106 can be provided to the battery 112 for charging directly from the converter 104 or via a separate DC / DC converter (e.g., a charger). The controller 114 operates the inverter 108 to convert the DC power to regulated AC power and provide the regulated AC power to the load coupled to the output terminal 110.

[0027] When the AC power provided to the input 102 is unacceptable (i.e., below an input power quality threshold), the controller 114 operates the UPS 100 in a backup operating mode. In the backup operating mode, DC power from the backup power source 112 is provided to the DC bus 106. The inverter 108 receives DC power from the DC bus 106, and the controller 114 operates the inverter 108 to convert the DC power from the DC bus 106 into regulated AC power and provide the regulated AC power to the output 110.

[0028] As described above, many online UPS topologies employ separate DC / DC converters to convert input AC power and backup DC power. For example, in such a topology, converter 104 may include a PFC converter and a separate DC / DC converter, the PFC converter being configured to provide DC power derived from input AC power to DC bus 106 during an online operating mode, and the separate DC / DC converter being configured to provide DC power derived from backup DC power to DC bus 106 during a backup operating mode. In some examples, the DC / DC converter may be configured to charge battery 112 from the DC bus; however, in other examples, converter 104 (or UPS 100) may include a separate charger (i.e., DC / DC converter) to charge battery 112.

[0029] Although this topology can be used to provide uninterruptible power, the use of multiple converters requires the use of additional components. For example, the charger may include additional components such as switches, diodes, inductors, transformers (e.g., step-down transformers), etc., to provide DC power derived from the input AC power or DC bus to the battery for charging. Therefore, these multiple converter topologies may increase cost and complexity while reducing the power density of the UPS.

[0030] In addition, in certain environments (e.g., developing economies), frequent and prolonged power outages may drive the need for large (or high-power) battery packs. In this case, the charger included in the converter 104 (or UPS 100) may be configured as a high-power charger. In other examples, the charger may be configured as a high-power charger to support a specific type of battery (e.g., lithium) and / or to provide specific features (e.g., fast charging). In some examples, configuring the charger as a high-power converter may further increase the size and cost of the UPS 100.

[0031] Therefore, it may be advantageous to configure the front end topology of UPS 100 (e.g., converter 104) as an integrated converter capable of providing DC power derived from input AC power or backup DC power to DC bus 106 and charging battery 112 using the DC power derived from DC bus 106.

[0032] Figure 2 is a schematic diagram of a front-end topology 200 according to various aspects described herein. In one example, the front-end topology 200 is configured to be included in an online UPS (i.e., a voltage-frequency independent UPS). For example, the front-end topology 200 includes Figure 1 The converter 104 and DC bus 106 of the UPS 100 include a converter 204 and a DC bus 206. In some examples, the DC bus 206 includes a positive DC bus 206a and a negative DC bus 206b.

[0033] As shown, the front-end topology 200 includes an input 202 coupled to an input AC source 203 and a backup power input 214 coupled to a backup power source 212 (e.g., a battery). In some examples, the backup power source 212 can be included in a UPS; however, in other examples, the backup power source 212 can be separate from the UPS. In some examples, the front-end topology 200 is configured with a through-neutral connection connected to the input 202 and the backup power source 212 to minimize EMI / EMC issues.

[0034] In one example, the converter 204 includes a first converter switch 216, a second converter switch 218, a third converter switch 220, a fourth converter switch 222, and a fifth converter switch 224, an input terminal selection circuit 226, a first inductor 228, a second inductor 230, a first diode 232, and a second diode 234. In one embodiment, the converter switches 216-224 are metal oxide semiconductor field effect transistors (MOSFETs); however, in other embodiments, different types of switches or transistors (e.g., insulated gate bipolar transistors (IGBTs)) may be utilized. In some examples, each switch has a gate, a drain, and a source. In this context, a "drain" may refer to any device terminal where current enters a switch. Similarly, a "source" may refer to any device terminal where current leaves a switch.

[0035] In some examples, the first converter switch 216 is a bidirectional switch circuit that includes a first switch 216a coupled in series with a second switch 216b. As such, the first converter switch 216 can be operated in a first state by turning on (i.e., closing) the first switch 216a and turning off (i.e., opening) the second switch 216b to provide a conductive path through the body diodes of the first switch 216a and the second switch 216b. Likewise, the first converter switch 216 can be operated in a second state by turning on (i.e., closing) the second switch 216b and turning off (i.e., opening) the first switch 216a to provide a conductive path through the body diodes of the second switch 216b and the first switch 216a.

[0036] As shown, the input terminal selection circuit 226 is configured to couple the first inductor 228 to one of the input terminal 202 or the backup power input terminal 214. In one example, a first end of the first inductor 228 is coupled to the first converter switch 216, an anode of the first diode 232, and a cathode of the second diode 234, and a second end of the first inductor 228 is coupled to the input terminal selection circuit 226. The cathode of the first diode 232 is coupled to the positive DC bus 206a, and the anode of the second diode 234 is coupled to the negative DC bus 206b. In some examples, a first end of the second inductor 230 is coupled to the first converter switch 218 and the fifth converter switch 224, and a second end of the second inductor 230 is coupled to the third converter switch 220 and the fourth converter switch 222. The second converter switch 218 is coupled between the first end of the second inductor 230 and the positive DC bus 206a, and the fifth converter switch 224 is coupled between the first end of the second inductor 230 and the neutral line. The third converter switch 220 is coupled between the second end of the second inductor 230 and the negative DC bus 206 b , and the fourth converter switch 222 is coupled between the second end of the second inductor 230 and the backup power input 214 .

[0037] In one example, positive DC bus capacitor 236a is coupled between positive DC bus 206a and a neutral line, and negative DC bus capacitor 236b is coupled between negative DC bus 206b and a neutral line. In some examples, DC bus capacitors 236a, 236b are polarized capacitors. For example, positive DC bus capacitor 236a can have a positive side coupled to positive DC bus 206a and a negative side coupled to a neutral line. Similarly, negative DC bus capacitor 236b can have a positive side coupled to a neutral line and a negative side coupled to negative DC bus 206b. Figure 2 As shown, the DC busses 206 a , 206 b are galvanically coupled to a backup power input 214 .

[0038] In at least one example, the converter 204 of the front-end topology 200 can be operated in various operation modes. For example, in the online operation mode of the UPS, the control input terminal selection circuit 226 couples the second end of the first inductor 228 to the input terminal 202, so that the AC power from the input terminal 202 is provided to the converter 204. The converter 204 converts the AC power into DC power and provides the DC power to the DC bus 206a, 206b. In addition, during the online operation mode, the converter 204 can be operated to provide the DC power derived from the DC bus 206a, 206b to the backup power input 214 to charge the backup power source 212.

[0039] In some examples, converter 204 is configured to operate as a bidirectional converter. Thus, converter 204 can be considered "bidirectional" because converter 204 can provide power to backup power input 214 (i.e., backup power source 212) and can also draw power from backup power input 214. In contrast, certain unidirectional chargers can be configured to provide power to an energy storage device or input, but may not draw power from the energy storage device or input.

[0040] Figure 3A and Figure 3B is a schematic diagram illustrating the PFC function of the converter 204 during an online operating mode of the UPS and the positive and negative half cycles of the input AC voltage corresponding to the input AC power.

[0041] like Figure 3A As shown, during the online operation mode and the positive half cycle of the input AC voltage, the first converter switch 216 is operated to provide DC power derived from the input AC power (provided by the input AC source 203) to the positive DC bus 206a. In some examples, the first converter switch 216, the first inductor 228, and the first diode 232 operate as a PFC boost converter to provide DC power to the positive DC bus 206a.

[0042] In one example of an online operation mode during a positive half-cycle of the input AC voltage, the first switch 216a of the first converter switch 216 is turned on and off to provide a PFC boost converter operation. For example, when the first switch 216a is turned on (i.e., closed), the first end of the first inductor 228 is coupled to the neutral line. Therefore, a conductive path 302 for input AC power is provided through the first converter switch 216, thereby exciting the inductor 228. In one example, the conductive path 302 includes a body diode of the second switch 216b of the first converter switch 216. Similarly, when the first switch 216a is turned off (i.e., disconnected), the first inductor 228 is decoupled from the neutral line. In this way, a conductive path 304 for input AC power is provided through the first inductor 228 and the first diode 232 to provide DC power to the positive DC bus 206a and charge the positive DC bus capacitor 236a.

[0043] like Figure 3B As shown, during the online operation mode and the negative half cycle of the input AC voltage, the first converter switch 216 is operated to provide DC power derived from the input AC power (provided by the input AC source 203) to the negative DC bus 206b. In some examples, the first converter switch 216, the first inductor 228, and the second diode 234 operate as a PFC boost converter to provide DC power to the negative DC bus 206b.

[0044] In one example of an online operation mode during a negative half-cycle of the input AC voltage, the second switch 216b of the first converter switch 216 is turned on and off to provide a PFC boost converter operation. For example, when the second switch 216b is turned on (i.e., closed), the first end of the first inductor 228 is coupled to the neutral line. In this way, a conductive path 402 for input AC power is provided through the first converter switch 216, thereby exciting the first inductor 228. In one example, the conductive path 402 includes a body diode of the first switch 216a of the first converter switch 216. Similarly, when the second switch 216b is turned off (i.e., disconnected), the first inductor 228 is decoupled from the neutral line. In this way, a conductive path 404 for input AC power is provided through the first inductor 228 and the second diode 234 to provide DC power to the negative DC bus 206b and charge the negative DC bus capacitor 236b.

[0045] As described above, during the online operation mode of the UPS, the converter 204 may be operated to provide DC power derived from the DC busses 206a, 206b to the backup power input 214 to charge the backup power source 212. In one example, in the online operation mode, the converter 204 may charge the backup power source 212 using DC power derived from the positive DC bus 206A and / or the negative DC bus 206B during both the positive and negative half cycles of the input AC voltage.

[0046] Figure 4A and Figure 4B is a schematic diagram illustrating the charger function of converter 204 during an online operating mode of the UPS.

[0047] like Figure 4A As shown, during the online operation mode, the third converter switch 220 can be operated to provide the DC power derived from the negative DC bus 206B (i.e., the negative DC bus capacitor 236B) to the backup power input terminal 214 to charge the backup power source 212. In some examples, the third converter switch 220, the second inductor 230, and the body diode of the fourth converter switch 222 operate as a buck-boost converter to provide the DC power derived from the negative DC bus 206B to the backup power input terminal 214.

[0048] In one example, the third converter switch 220 is turned on and off to provide a buck-boost converter operation. For example, when the third converter switch 220 is turned on (i.e., closed), the second end of the second inductor 230 is coupled to the negative DC bus 206b. In this way, a conductive path 306 for DC power stored by the negative DC bus capacitor 236b is provided through the third converter switch 220, thereby energizing the second inductor 230. In one example, the conductive path 306 includes the body diode of the fifth converter switch 224; however, in some examples, the fifth converter switch 224 can be turned on (i.e., closed) to minimize losses. Similarly, when the third converter switch 220 is turned off (i.e., disconnected), the second inductor 230 is decoupled from the negative DC bus 236b. In this way, a conductive path 308 is provided through the body diode of the fourth converter switch 222 and the body diode of the fifth converter switch 224 (or the fifth converter switch 224), thereby allowing the second inductor 230 to stop being energized and provide DC power to the backup power input terminal 214 to charge the backup power source 212. In some examples, the DC power provided to the backup power input terminal 214 may have a voltage level that is different (e.g., lower) than the voltage level of the negative DC bus 206B.

[0049] In one example, in an online operating mode of the UPS, the converter 204 can be operated to provide DC power derived from the negative DC bus 206 b to the backup power input 214 during the positive and negative half cycles of the input AC voltage. For example, when the converter 204 provides DC power to the positive DC bus 206 a (e.g., Figure 3A ) and negative DC bus 206B (e.g., Figure 3B ) provides power, the third converter switch 220 can be operated as described above.

[0050] Similarly, if Figure 4B As shown, during the online operation mode, the second converter switch 218 can be operated to provide DC power derived from the positive DC bus 206A (i.e., the positive DC bus capacitor 236A) to the backup power input terminal 214 to charge the backup power source 212. In some examples, the second converter switch 218, the second inductor 230, and the body diode of the fifth converter switch 224 operate as a buck converter to provide the DC power derived from the positive DC bus 206A to the backup power input terminal 214.

[0051] In one example, the second converter switch 218 is turned on and off to provide a buck converter operation. For example, when the second converter switch 218 is turned on (i.e., closed), the first end of the second inductor 230 is coupled to the positive DC bus 206a. In this way, a conductive path 406 for DC power stored by the positive DC bus capacitor 236a is provided through the second converter switch 218, thereby energizing the second inductor 230. In one example, the conductive path 406 includes the body diode of the fourth converter switch 222; however, in some examples, the fourth converter switch 222 can be turned on (i.e., closed) to minimize losses. Similarly, when the second converter switch 218 is turned off (i.e., disconnected), the second inductor 230 is decoupled from the positive DC bus 236a. In this way, a conductive path 408 is provided through the body diode of the fourth converter switch 222 (or the fourth converter switch 222) and the body diode of the fifth converter switch 224, thereby allowing the second inductor 230 to stop being energized and provide DC power to the backup power input terminal 214 to charge the backup power source 212. In some examples, the DC power provided to the backup power input terminal 214 can have a voltage level that is different (e.g., lower) than the voltage level of the positive DC bus 206a.

[0052] In one example, in an online operating mode of the UPS, the converter 204 can be operated to provide DC power derived from the positive DC bus 206a to the backup power input 214 during the positive and negative half cycles of the input AC voltage. For example, when the converter 204 supplies DC power to the positive DC bus 206a (e.g., Figure 3A ) and negative DC bus 206b (e.g., Figure 3B ) provides power, the second converter switch 218 can be operated as described above.

[0053] In one example, the charging capacity of the converter 204 corresponds to the power demand at the output 110 of the UPS 100 (i.e., the output of the inverter 108). For example, when the UPS is not experiencing a full load at the output 110, the converter 204 can operate at a charging capacity of up to 50% of the capacity of the inverter 110. In this way, the charging capacity of the converter 204 can be scaled or adjusted based on the power demand at the output 110 of the UPS 100 (i.e., the load on the inverter 108). In some examples, the second inductor 230 can be sized (e.g., increased) to provide a different charging capacity (up to the full capacity of the inverter 110).

[0054] In the backup operation mode, the control input terminal selection circuit 226 couples the second end of the inductor 228 to the backup power input terminal 214 so that the backup DC power from the backup power source 212 is provided to the converter 204. The converter 204 converts the backup DC power to DC power and provides the DC power to the DC bus 206a, 206b.

[0055] Figure 5A and Figure 5B is a schematic diagram illustrating the operation of converter 204 during a backup operating mode of the UPS.

[0056] like Figure 5A As shown, during the backup operation mode and the positive DC bus cycle, the first converter switch 216 is operated to provide DC power derived from the backup DC power (provided by the backup power source 212) to the positive DC bus 206a. In some examples, the first converter switch 216, the first inductor 228, and the first diode 232 operate as a boost converter to provide DC power to the positive DC bus 206a.

[0057] In one example of a standby operating mode during a positive DC bus cycle, the first switch 216a of the first converter switch 216 is turned on and off to provide a boost converter operation. For example, when the first switch 216a is turned on (i.e., closed), the first end of the first inductor 228 is coupled to the neutral line. Therefore, a conductive path 502 for standby DC power is provided through the first converter switch 216, thereby energizing the first inductor 228. In one example, the conductive path 502 includes a body diode of the second switch 216b of the first converter switch 216. Similarly, when the first switch 216a is turned off (i.e., disconnected), the first inductor 228 is decoupled from the neutral line. In this way, a conductive path 504 for standby DC power is provided through the first inductor 228 and the first diode 232 to provide DC power to the positive DC bus 206a and charge the positive DC bus capacitor 236a.

[0058] like Figure 5B As shown, during the backup operation mode and the negative DC bus cycle, the fourth converter switch 222 is operated to provide DC power derived from the backup DC power to the negative DC bus 206 b. In some examples, the fourth converter switch 222, the second inductor 230, and the body diode of the third converter switch 220 operate as a buck-boost converter to provide DC power to the negative DC bus 206 b.

[0059] In one example of a standby operation mode during a negative DC bus cycle, the fourth converter switch 222 is turned on and off to provide a buck-boost converter operation. For example, when the fourth converter switch 222 is turned on (i.e., closed), the second end of the second inductor 230 is coupled to the standby power input 214. Therefore, a conductive path 506 for standby DC power is provided through the fourth converter switch 222, thereby energizing the second inductor 230. In one example, the conductive path 506 includes the fifth converter switch 224, which is turned on (i.e., closed) during the negative DC bus cycle. Similarly, when the fourth converter switch 222 is turned off (i.e., disconnected), the second inductor 230 is decoupled from the standby power input 214. In this way, a conductive path 508 is provided through the body diode of the third converter switch 220, allowing the second inductor 230 to stop energizing and provide DC power to the negative DC bus 206b and charge the negative DC bus capacitor 236b.

[0060] In one example, a positive DC bus cycle during the backup operating mode corresponds to a positive half cycle of the output AC voltage. Likewise, a negative DC bus cycle during the backup operating mode corresponds to a negative half cycle of the output AC voltage. In some examples, the output AC voltage is provided by an inverter (e.g., Figure 1 The inverter 108) is provided.

[0061] In some examples, alternative control schemes may be used to provide DC power to the DC buses 206a, 206b during the backup operating mode. Figure 6 is a schematic diagram illustrating alternative operation of converter 204 for a positive DC bus cycle during a backup operating mode of the UPS.

[0062] like Figure 6 As shown, during the backup operation mode and the positive DC bus cycle, the fifth converter switch 224 can be operated to provide DC power derived from the backup DC power (provided by the backup power source 212) to the positive DC bus 206a. In some examples, the fifth converter switch 224, the second inductor 230, and the body diode of the second converter switch 218 operate as a boost converter to provide DC power to the positive DC bus 206a.

[0063] In one example of a standby operating mode during a positive DC bus cycle, the fifth converter switch 224 is turned on and off to provide a boost converter operation. For example, when the fifth converter switch 224 is turned on (ie, closed), the first end of the second inductor 230 is coupled to the neutral line. In this way, a conductive path 602 for standby DC power is provided through the fifth converter switch 224, thereby energizing the second inductor 230. In one example, the conductive path 602 includes the fourth converter switch 222, which is turned on (ie, closed) during the positive DC bus cycle. Similarly, when the fifth converter switch 224 is turned off (ie, disconnected), the second inductor 230 is decoupled from the neutral line. In this way, a conductive path 604 is provided through the body diode of the second converter switch 218, thereby allowing the second inductor 230 to stop energizing and provide DC power to the positive DC bus 206a and charge the positive DC bus capacitor 236a.

[0064] In one example, converter 204 can be configured to utilize the Figure 6 control scheme and utilizes the negative DC bus cycle during the backup operation mode Figure 5B In some examples, to support Figure 6 , the second inductor 230 is sized (eg, increased) to match the full capacity of the inverter 108. Due to the sizing of the second inductor 230, the converter 204 can operate with a charging capacity up to the full capacity of the inverter 108 during the online operation mode.

[0065] As described above, a more cost-effective and compact front-end topology for an online UPS is provided herein. In at least one embodiment, the front-end topology includes an integrated converter configured to operate as a PFC converter, a DC / DC converter, and a battery charger. In one example, the integrated converter is configured to provide power to the positive DC bus and the negative DC bus while charging the battery using power from the positive DC bus and the negative DC bus. In some examples, by utilizing different components of the integrated converter to charge the battery from the DC bus while providing power to the DC bus, a separate charger and associated components can be eliminated from the front-end topology (and UPS). In this way, the improved front-end topology can have a reduced number of components, thereby increasing the power density of the UPS and reducing costs.

[0066] In at least one embodiment, an uninterruptible power supply is described herein, comprising an input terminal, an energy storage device interface, an output terminal, a power factor correction circuit (PFC), a capacitor, a bidirectional converter, and a switch, wherein the input terminal is configured to receive input power from an input power source, the input terminal having a mains neutral connection coupled to a reference node, the energy storage device interface is configured to couple to an energy storage device to provide backup power, the energy storage device interface has an energy storage device neutral connection coupled to the reference node, the output terminal is configured to provide output power derived from at least one of the input power and the backup power, the power factor correction circuit (PFC) comprising a PFC input terminal, the capacitor coupled to the PFC and galvanically coupled to the energy storage device interface, the bidirectional converter coupled to the input terminal and coupled to the energy storage device interface, and the switch coupled to the energy storage device interface and the PFC input terminal.

[0067] Having thus described several aspects of at least one embodiment of the present invention, it will be appreciated that various changes, modifications and improvements will readily occur to those skilled in the art. These changes, modifications and improvements are intended to be a part of this disclosure and are intended to be within the spirit and scope of the present invention. Therefore, the foregoing description and accompanying drawings are exemplary only.

Claims

1. An uninterruptible power supply UPS, comprising: An input terminal configured to receive input AC power having an input AC voltage; a backup power input terminal configured to be coupled to a backup power source and to provide DC power to the backup power source for charging; a positive DC bus and a negative DC bus galvanically coupled to the backup power input; and a converter coupled to the input, the backup power input, and the positive DC bus and the negative DC bus, the converter comprising a first inductor, a second inductor, a first converter switch, a second converter switch, and a third converter switch, the first converter switch being configured to couple the first inductor to a neutral connection, the second converter switch being configured to couple the second inductor to the positive DC bus and provide power between the second inductor and the positive DC bus through the second converter switch, the third converter switch being configured to couple the second inductor to the negative DC bus and provide power between the second inductor and the negative DC bus through the third converter switch, wherein the UPS is voltage-frequency independent.

2. The UPS of claim 1 , further comprising at least one controller coupled to the converter and configured to: in a first operating mode and during a positive half cycle of the input AC voltage, operating the first converter switch to provide DC power derived from the input AC power to the positive DC bus via the first inductor, and operating at least one of the second converter switch or the third converter switch to provide DC power derived from at least one of the positive DC bus or the negative DC bus to the backup power input via the second inductor; and In the first operating mode and during a negative half cycle of the input AC voltage, the first converter switch is operated to provide DC power derived from the input AC power to the negative DC bus via the first inductor, and at least one of the second converter switch or the third converter switch is operated to provide DC power derived from at least one of the positive DC bus or the negative DC bus to the backup power input via the second inductor.

3. The UPS of claim 2, further comprising an input selection circuit configured to couple the converter to the input during the first operating mode and to couple the converter to the backup power input during a second operating mode.

4. The UPS of claim 2, wherein the at least one controller is further configured to monitor the input AC power, operate the UPS in the first operating mode in response to determining that the input AC power is acceptable, and operate the UPS in the second operating mode in response to determining that the input AC power is unacceptable.

5. The UPS of claim 2, wherein the backup power input is further configured to receive backup DC power from the backup power source, and the converter further comprises a fourth converter switch configured to couple the second inductor to the backup power input.

6. The UPS of claim 5, wherein the at least one controller is further configured to: operating the first converter switch in a second operating mode to provide DC power derived from the backup DC power to the positive DC bus via the first inductor; and The fourth converter switch is operated in the second operating mode to provide DC power derived from the backup DC power to the negative DC bus via the second inductor.

7. The UPS of claim 5, wherein the converter further comprises a fifth converter switch configured to couple the second inductor to the neutral connection, and wherein the at least one controller is further configured to: operating the fifth converter switch in a second operating mode to provide DC power derived from the backup DC power to the positive DC bus via the second inductor; and The fourth converter switch is operated in the second operating mode to provide DC power derived from the backup DC power to the negative DC bus via the second inductor.

8. The UPS of claim 1, wherein the first converter switch is a bidirectional switch circuit comprising a first switch and a second switch coupled in series.

9. The UPS of claim 8, wherein the converter further comprises a first diode coupled between the first converter switch and the positive DC bus, a second diode coupled between the first converter switch and the negative DC bus, a fourth converter switch configured to couple the second inductor to the backup power input, and a fifth converter switch configured to couple the second inductor to the neutral connection.

10. The UPS of claim 9, wherein the first inductor, the first switch of the first converter switch, the body diode of the second switch of the first converter switch, and the first diode are configured to operate as a boost converter during a positive half cycle of the input AC voltage in a first operating mode to provide DC power derived from the input AC power to the positive DC bus.

11. The UPS of claim 9, wherein the second inductor, the third converter switch, and the body diode of the fourth converter switch are configured to operate as a buck-boost converter in a first operating mode to provide DC power derived from the negative DC bus to the backup power input.

12. The UPS of claim 9, wherein the first inductor, the second switch of the first converter switch, the body diode of the first switch of the first converter switch, and the second diode are configured to operate as a boost converter during a negative half cycle of the input AC voltage in a first operating mode to provide DC power derived from the input AC power to the negative DC bus.

13. The UPS of claim 9, wherein the second inductor, the second converter switch, and the body diode of the fifth converter switch are configured to operate as a buck converter in a first operating mode to provide DC power derived from the positive DC bus to the backup power input.

14. The UPS of claim 9, wherein the first inductor, the first switch of the first converter switch, the body diode of the second switch of the first converter switch, and the first diode are configured to operate as a boost converter in a second operating mode to provide DC power derived from a backup DC power to the positive DC bus.

15. The UPS of claim 9, wherein the second inductor, the fourth converter switch, the body diode of the second converter switch, and the fifth converter switch are configured to operate as a boost converter in a second operating mode to provide DC power derived from a backup DC power to the positive DC bus.

16. The UPS of claim 9, wherein the second inductor, the fourth converter switch, the body diode of the third converter switch, and the fifth converter switch are configured to operate as a buck-boost converter during a second operating mode to provide DC power derived from a backup DC power to the negative DC bus.

17. The UPS of claim 1, further comprising: an output terminal configured to provide output AC power to a load; as well as An inverter is coupled to the output terminal and is configured to convert DC power from the positive DC bus and the negative DC bus into the output AC power and provide the output AC power to the output terminal.

18. The UPS of claim 1, wherein the backup power input is further configured to receive backup DC power from the backup power source, and the converter further comprises a fourth converter switch configured to couple the second inductor to the backup power input.

19. The UPS of claim 1, wherein the first converter switch comprises a bidirectional switching circuit.

20. The UPS of claim 19, wherein the bidirectional switch circuit comprises a first switch and a second switch.

21. A non-transitory computer-readable medium having stored thereon a computer-executable instruction sequence for controlling an uninterruptible power supply UPS, the uninterruptible power supply UPS comprising an input terminal, a backup power input terminal, a positive DC bus, a negative DC bus, and a converter, the input terminal being configured to receive an input AC power having an input AC voltage, the backup power input terminal being configured to be coupled to a backup power source and provide DC power to the backup power source for charging, the converter being coupled to the input terminal, the backup power input terminal, and the positive DC bus and the negative DC bus, the converter comprising: a first inductor, a second inductor, a first converter switch configured to couple the first inductor to a neutral connection, a second converter switch configured to couple the second inductor to the positive DC bus, and a third converter switch configured to couple the second inductor to the negative DC bus, the computer executable instruction sequences comprising instructions to instruct at least one processor to: in a first operating mode and during a positive half cycle of the input AC voltage, operating the first converter switch to provide DC power derived from the input AC power to the positive DC bus via the first inductor, and operating at least one of the second converter switch or the third converter switch to provide DC power derived from at least one of the positive DC bus or the negative DC bus to the backup power input through the second inductor; as well as In the first operating mode and during a negative half cycle of the input AC voltage, the first converter switch is operated to provide DC power derived from the input AC power to the negative DC bus via the first inductor, and at least one of the second converter switch or the third converter switch is operated to provide DC power derived from at least one of the positive DC bus or the negative DC bus to the backup power input through the second inductor.

22. The non-transitory computer readable medium of claim 21, wherein the sequence of instructions comprises instructions that cause the at least one processor to: monitoring the input AC power received at the input; In response to determining that the input AC power is acceptable, operating the UPS in the first operating mode; and In response to determining that the input AC power is unacceptable, operating the UPS in a second operating mode.

23. The non-transitory computer readable medium of claim 22, wherein the UPS comprises an input selection circuit, and the sequence of instructions comprises instructions to cause the at least one processor to: During the first operating mode, controlling the input terminal selection circuit to couple the converter to the input terminal; and During the second operating mode, the input selection circuit is controlled to couple the converter to the backup power input.

24. The non-transitory computer-readable medium of claim 22, wherein the backup power input is further configured to receive backup DC power from the backup power source, and the converter includes a fourth converter switch configured to couple the second inductor to the backup power input.

25. The non-transitory computer readable medium of claim 24, wherein the sequence of instructions comprises instructions to cause the at least one processor to: operating the first converter switch in the second operating mode to provide DC power derived from the backup DC power to the positive DC bus via the first inductor; and The fourth converter switch is operated in the second operating mode to provide DC power derived from the backup DC power to the negative DC bus via the second inductor.

26. The non-transitory computer readable medium of claim 24, wherein the converter comprises a fifth converter switch configured to couple the second inductor to the neutral connection, and the sequence of instructions comprises instructions to cause the at least one processor to: operating the fifth converter switch in the second operating mode to provide DC power derived from the backup DC power to the positive DC bus via the second inductor; and The fourth converter switch is operated in the second operating mode to provide DC power derived from the backup DC power to the negative DC bus via the second inductor.

27. A method of controlling an uninterruptible power supply (UPS), the UPS comprising an input terminal, a backup power input terminal, a positive DC bus, a negative DC bus, and a converter, the input terminal being configured to receive an input AC power having an input AC voltage, the backup power input terminal being configured to be coupled to a backup power source and to provide DC power to the backup power source for charging, the converter being coupled to the input terminal, the backup power input terminal, and the positive DC bus and the negative DC bus, the converter comprising a first inductor, a second inductor, a first converter switch configured to couple the first inductor to a neutral connection, a second converter switch configured to couple the second inductor to the positive DC bus, and a third converter switch configured to couple the second inductor to the negative DC bus, the method comprising: in a first operating mode and during a positive half cycle of the input AC voltage, operating the first converter switch to provide DC power derived from the input AC power to the positive DC bus via the first inductor, and operating at least one of the second converter switch or the third converter switch to provide DC power derived from at least one of the positive DC bus or the negative DC bus to the backup power input through the second inductor; as well as In a first operating mode and during a negative half cycle of the input AC voltage, the first converter switch is operated to provide DC power derived from the input AC power to the negative DC bus via the first inductor, and at least one of the second converter switch or the third converter switch is operated to provide DC power derived from at least one of the positive DC bus or the negative DC bus to the backup power input terminal through the second inductor.

28. An uninterruptible power supply UPS, comprising: An input terminal configured to receive input AC power having an input AC voltage; a backup power input terminal configured to be coupled to a backup power source and to provide DC power to the backup power source for charging; a positive DC bus and a negative DC bus galvanically coupled to the backup power input; and a converter coupled to the input, the backup power input, and the positive DC bus and the negative DC bus, the converter comprising a first inductor, a second inductor, a first converter switch configured to couple the first inductor to a neutral connection, a second converter switch configured to couple the second inductor to the positive DC bus, and a third converter switch configured to couple the second inductor to the negative DC bus, wherein the UPS is voltage-frequency independent, and wherein the first converter switch is a bidirectional switching circuit comprising a first switch and a second switch coupled in series.

Images