Flywheel Battery with AC Switching PFC Front End for UPS

Abstract

According to one aspect of a flyback battery with an AC switched PFC front end for a UPS, the present invention provides a UPS including: an input terminal; an output terminal; a battery circuit; a PFC stage; a switch configured to selectively couple an interface of the PFC stage to the input terminal in an online mode and to the battery circuit in a standby mode; a positive DC bus; a negative DC bus; and a controller configured to: operate the PFC stage in the online mode to provide DC power derived from the input AC power to the DC bus; operate the PFC stage in the standby mode to provide DC power derived from the standby DC power to the DC bus; operate the battery circuit in a first stage of the standby mode to couple a positive terminal of a DC power source to the interface; and operate the battery circuit in a second stage of the standby mode to couple a negative terminal of the DC power source to the interface.

Description

Technical Field

[0001] The present invention generally relates to an uninterruptible power supply (UPS). Background Art

[0002] It is known to use power equipment such as an uninterruptible power supply (UPS) to provide regulated and uninterrupted power to sensitive and / or critical loads such as computer systems and other data processing systems. Known uninterruptible power supplies include online UPSs, offline UPSs, online interactive UPSs, and other types. An online UPS provides regulated AC power and backup AC power when the main AC power source is interrupted. An offline UPS generally does not provide regulation of the input AC power but provides backup AC power when the main AC power source is interrupted. An online interactive UPS is similar to an offline UPS in that they switch to battery power during a power outage, but generally also include a multi-tap transformer for regulating the output voltage provided by the UPS. Summary of the Invention

[0003] At least one aspect of the present invention is directed to an uninterruptible power supply (UPS) comprising: an input terminal configured to be coupled to an AC power source and configured to receive input AC power; an output terminal configured to provide output power to a load; a battery circuit configured to be coupled to a DC power source and configured to receive backup DC power; a power factor correction (PFC) stage including an interface; an input switch configured to selectively couple the interface of the PFC stage to the input terminal in an online operation mode and selectively couple to the battery circuit in a backup operation mode; a positive DC bus coupled to the PFC stage; a negative DC bus coupled to the PFC stage; and a controller coupled to the battery circuit and the PFC stage, the controller configured to: operate the PFC stage in the online operation mode to provide DC power derived from the input AC power to the positive DC bus and the negative DC bus; operate the PFC stage in the backup operation mode to provide DC power derived from the backup DC power to the positive DC bus and the negative DC bus; operate the battery circuit in a first stage of the backup operation mode to couple a positive terminal of the DC power source to the interface of the PFC stage; and operate the battery circuit in a second stage of the backup operation mode to couple a negative terminal of the DC power source to the interface of the PFC stage.

[0004] According to one embodiment, the UPS further includes a neutral line, and the battery circuit includes: a first switch configured to be coupled between the input switch and the negative terminal of the DC power supply; a second switch configured to be coupled between the negative terminal of the DC power supply and the neutral line; a third switch configured to be coupled between the input switch and the positive terminal of the DC power supply; and a fourth switch configured to be coupled between the positive terminal of the DC power supply and the neutral line. In one embodiment, when operating the battery circuit to couple the positive terminal to the interface of the PFC stage, the controller is further configured to operate the third switch to couple the positive terminal to the interface of the PFC stage through the input switch, and is configured to operate the second switch to couple the negative terminal to the neutral line.

[0005] According to another embodiment, when operating the battery circuit to couple the negative terminal of the DC power supply to the interface of the PFC stage, the controller is further configured to operate the first switch to couple the negative terminal to the interface of the PFC stage through the input switch, and is configured to operate the fourth switch to couple the positive terminal to the neutral line. In one embodiment, the PFC stage includes: an inductor coupled to the interface; a plurality of switches coupled to the inductor; a first bus capacitor coupled to the positive DC bus; and a second bus capacitor coupled to the negative DC bus. In another embodiment, when operating the PFC stage to supply DC power from the standby DC power to the positive DC bus and the negative DC bus, the controller is further configured to operate the plurality of switches in the first stage of the standby operation mode to generate a positive DC voltage on the positive DC bus.

[0006] According to one embodiment, when operating the PFC stage to supply DC power from the standby DC power to the positive DC bus and the negative DC bus, the controller is further configured to operate the plurality of switches in the second stage of the standby operation mode to generate a negative DC voltage on the negative DC bus. In one embodiment, the plurality of switches includes: a fifth switch coupled to the inductor; a sixth switch coupled between the fifth switch and the neutral line; a seventh switch coupled between the inductor and the positive DC bus; and an eighth switch coupled between the inductor and the negative DC bus. In another embodiment, when operating the plurality of switches in the first stage of the standby operation mode to generate the positive DC voltage on the positive DC bus, the controller is further configured to operate the fifth switch, the sixth switch, and the seventh switch as a boost converter to generate the positive DC voltage.

[0007] According to another embodiment, when operating the plurality of switches in the second stage of the standby operation mode to generate the negative DC voltage on the negative DC bus, the controller is further configured to operate the fifth switch, the sixth switch, and the seventh switch as a boost converter to generate the negative DC voltage. In one embodiment, the UPS further includes an inverter coupled between the DC bus and the output terminal and configured to provide an output AC voltage waveform derived from at least one of the input AC power and the standby DC power, wherein the controller is further configured to synchronize the positive DC voltage generated on the positive DC bus with a positive half cycle of the output AC voltage waveform; and wherein the controller is further configured to synchronize the negative DC voltage generated on the negative DC bus with a negative half cycle of the output AC voltage waveform. In one embodiment, the PFC stage includes a Vienna rectifier.

[0008] Another aspect of the present invention relates to a method for operating a UPS, the UPS including: an input terminal configured to be coupled to an AC power source; an output terminal configured to provide output power to a load; a battery circuit; a PFC stage; a positive DC bus; and a negative DC bus, wherein the method includes the steps of: receiving input AC power from the input terminal of the AC power source; receiving standby DC power at the battery circuit from the DC power source; operating the UPS in an online operation mode in response to determining that the input AC power is greater than an input power threshold; operating the UPS in a standby operation mode in response to determining that the input AC power is less than the input power threshold; selectively coupling the input terminal to an interface of the PFC stage in the online operation mode; selectively coupling the battery circuit to the interface of the PFC stage in the standby operation mode; converting the input AC power into DC power provided to the positive DC bus and the negative DC bus in the online operation mode using the PFC stage; converting the standby DC power into the DC power provided to the positive DC bus and the negative DC bus in the standby operation mode using the PFC stage; coupling a positive extreme of the DC power source to the interface of the PFC stage using the battery circuit in a first stage of the standby operation mode; and coupling a negative extreme of the DC power source to the interface of the PFC stage using the battery circuit in a second stage of the standby operation mode.

[0009] According to one embodiment, coupling the positive terminal of the DC power source to the interface of the PFC stage in the first stage includes: operating a first switch to couple the positive terminal to the interface of the PFC stage; and operating a second switch to couple the negative terminal to a neutral line. In one embodiment, coupling the positive terminal of the DC power source to the interface of the PFC stage in the second stage includes: operating a third switch to couple the negative terminal to the interface of the PFC stage; and operating a fourth switch to couple the positive terminal to a neutral line. In another embodiment, in the standby operation mode of using the PFC stage, converting the standby DC power into the DC power supplied to the positive DC bus and the negative DC bus includes: generating a positive DC voltage on the positive DC bus during the first stage of the standby operation mode; and generating a negative DC voltage on the negative DC bus during the first stage of the standby operation mode.

[0010] According to another embodiment, generating the positive DC voltage on the positive DC bus includes: operating a plurality of switches in the PFC stage as a boost converter to generate the positive DC voltage. In one embodiment, generating the negative DC voltage on the negative DC bus includes: operating the plurality of switches in the PFC stage as a boost converter to generate the negative DC voltage. In another embodiment, the UPS further includes an inverter configured to provide an output AC voltage waveform derived from at least one of the input AC power and the standby DC power, and wherein the method further includes: synchronizing the positive DC voltage generated on the positive DC bus with a positive half-cycle of the output AC voltage waveform; and synchronizing the negative DC voltage generated on the negative DC bus with a negative half-cycle of the output AC voltage waveform.

[0011] At least one aspect of the present invention is directed to an uninterruptible power supply (UPS) including: an input terminal configured to be coupled to an AC power source and configured to receive input AC power; an output terminal configured to provide output power to a load; a positive DC bus; a negative DC bus; a PFC stage coupled to the positive DC bus and the negative DC bus and configured to convert the input AC power into regulated DC power supplied to the positive DC bus and the negative DC bus; and a plurality of devices for selectively coupling the PFC stage to one of the input terminal and a DC power source, and for operating the PFC stage to convert standby DC power from a battery into the regulated DC power supplied to the positive DC bus and the negative DC bus. Description of the Drawings

[0012] Aspects of at least one embodiment are discussed below with reference to the accompanying drawings, which are not drawn to scale. The drawings are included to provide illustration and further understanding of the aspects and embodiments, and are incorporated into and form a part of this specification, and are not intended as a defining limit of the invention. In the drawings, like or nearly like components that are shown in the various drawings are represented by like numerals. For clarity purposes, not every component may be labeled in every figure. In the figures:

[0013] Figure 1 is a schematic diagram of a UPS according to multiple aspects described herein;

[0014] Figure 2 is a schematic diagram of an embodiment of a converter according to multiple aspects described herein;

[0015] Figure 3 is a schematic diagram of an embodiment of a converter operating in a positive terminal in a backup operation mode according to multiple aspects described herein;

[0016] Figure 4 is a schematic diagram of an embodiment of a converter operating in a negative terminal in a backup operation mode according to multiple aspects described herein; and

[0017] Figure 5 is a schematic diagram of an embodiment of a three-phase converter according to multiple aspects described herein. Detailed Description

[0018] 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 description or illustrated in the drawings. The methods and systems are capable of being implemented in other embodiments and practiced or carried out in various ways. The specific implementation examples provided herein are for illustrative purposes only and are not intended to be limiting. In particular, the acts, components, or features discussed in connection with any one or more examples or embodiments are not intended to exclude similar functions in other examples.

[0019] In addition, the language and terminology used herein are for descriptive purposes only and should not be regarded as limiting. Any reference herein to an instance, embodiment, component, element, or act of a system or method in the singular may also include embodiments that include a plurality, and any reference herein to any embodiment, component, element, or act in the plural may also include embodiments that include only the singular. References in the singular or plural forms are not intended to limit the presently disclosed system or method, its components, acts, or elements. As used herein, the terms "including," "comprising," "having," "containing," "involving," and their variants mean including the listed items and their equivalents, as well as additional items. The reference "or" may be construed as inclusive, such that any item described using "or" may indicate any one of the single-described item, more than one-described item, and all-described items. Further, if there is an inconsistency in the usage of terms between this document and the documents incorporated herein by reference, the usage of terms in the incorporated reference document is supplementary to this document; for irreconcilable contradictions, the usage of terms in this document shall prevail.

[0020] As discussed above, power devices such as uninterruptible power supplies (UPSs) are typically used to provide regulated, uninterrupted power to sensitive and / or critical loads. Conventional online UPSs use a power factor correction circuit (PFC) 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 is typically used to charge the battery when the mains power is available. In the absence of mains power, the battery discharges and supplies DC power to the DC bus. The inverter generates an AC output voltage provided to a load from the DC power on the DC bus. Since the DC bus is powered by the mains or the battery, the output power of the UPS will not be interrupted if the mains power fails and the battery is fully charged. A typical online UPS may also operate in a bypass mode, in which unconditional power with basic protection functions is directly provided to the load from the AC power through a bypass line.

[0021] UPSs with relatively high rated power typically include batteries with relatively high voltage levels. The relatively high voltage levels of the batteries in large power UPSs may make it practical to use a non-isolated boost converter to convert the battery voltage to a level suitable for powering the inverter stage. This is because boost converters generally have high efficiency when the input voltage of the boost converter is close to (e.g., only slightly lower than) the target regulated output voltage. For example, in some conventional large power UPS systems, the front-end PFC stage of the UPS is used as a boost converter to convert the DC power from the battery into regulated DC power provided to the inverter during battery-on mode.

[0022] In at least one embodiment, a more efficient PFC converter front-end circuit is described herein that can be used as a boost converter during battery-on mode to convert the DC power from the battery into regulated DC power provided to the inverter of the UPS.

[0023] Figure 1 FIG. 7 is a block diagram of an online UPS 100 according to one aspect of the present invention. The UPS 100 includes an input terminal 102, a converter 104, a positive DC bus 106, a negative DC bus 107, an inverter 108, an output terminal 110, and a controller 114. The input terminal 102 is coupled to the converter 104. The positive DC bus 106 and the negative DC bus 107 are coupled between the converter 104 and the inverter 108. The output terminal 110 is coupled to the inverter 108. The controller 114 is coupled to the input terminal 102, the output terminal 110, the converter 104, the positive DC bus 106, the negative DC bus 107, and the inverter 108. The converter 104 is further configured to be coupled to a battery 112.

[0024] The input terminal 102 is configured to be coupled to an AC main power supply and receive input AC power having an input voltage level. The controller 114 monitors the input AC power received by the input terminal 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 terminal 102. When the AC power provided to the input terminal 102 is acceptable (i.e., above an input power threshold), the controller 114 operates the UPS 100 in an online operating mode. In the online operating mode, the AC power from the input terminal 102 is provided to the converter 104. According to one embodiment, the converter 104 is a power factor correction converter 104. However, in other embodiments, other types of converters may be used.

[0025] The controller 114 operates the converter 104 to convert the AC power into DC power and supply the DC power to the positive DC bus 106 and the negative DC bus 107. In one embodiment, DC power is also supplied from the converter 104 to the battery 112 to charge the battery 112. In another embodiment, DC power from the positive DC bus 106 and the negative DC bus 107 is supplied to the battery 112 through a DC / DC converter to charge the battery 112. In the online operation mode, the inverter 108 receives DC power from the positive DC bus 106 and the negative DC bus 107, and the controller 114 operates the inverter 108 to convert the DC power into regulated AC power and supply the regulated AC power to a load coupled to the output terminal 110.

[0026] When the AC voltage supplied to the input terminal 102 is unacceptable (i.e., below an input power threshold), the controller 114 operates the UPS 100 in a standby operation mode. In the standby operation mode, the DC power from the battery 112 is regulated (e.g., by the converter 104) and supplied to the positive DC bus 106 and the negative DC bus 107. The inverter 108 receives the DC power from the positive DC bus 106 and the negative DC bus 107, and the controller 114 operates the inverter 108 to convert the DC power into regulated AC power and supply the regulated AC power to the output terminal 110.

[0027] Figure 2is a schematic diagram showing an embodiment of the converter 104. The converter 104 includes an input line 202, a neutral line 204, an input switch 206, a battery circuit 208, and a PFC stage 209. The PFC stage 209 includes an interface 203, an inductor 210, a first switch (Q1) 212, a second switch (Q2) 214, a third switch (Q3) 216, a fourth switch (Q4) 218, a first bus capacitor 220, and a second bus capacitor 222. The battery circuit 208 includes a fifth switch (Q5) 226, a sixth switch (Q6) 228, a seventh switch (Q7) 230, and an eighth switch (Q8) 232. In one embodiment, the first switch (Q1) 212 to the eighth switch (Q8) 232 are gallium nitride (GaN) field-effect transistors (FETs). However, in other embodiments, different types of switches or transistors may be used. For example, in one embodiment, the first switch (Q1) 212 to the eighth switch (Q8) 232 are metal-oxide-semiconductor field-effect transistors (MOSFETs). In another embodiment, thyristors may be used for the fifth switch (Q5) 226 to the eighth switch (Q8) 232. In at least one embodiment where the first switch (Q1) 212 to the eighth switch (Q8) 232 are GaN FETs and / or MOSFETs, the first switch (Q1) 212 to the eighth switch (Q8) 232 include built-in body diodes coupled between the drain and the source. The body diodes 227 of the fifth switch (Q5) 226 to the eighth switch (Q8) 232 are shown in Figure 2 although the body diodes of the first switch (Q1) 212 to the fourth switch (Q4) 218 are not shown for illustrative purposes.

[0028] The input line 202 and the neutral line 204 are configured to be coupled to an input power source (e.g., mains power) through the input terminal 102. The neutral line 204 is coupled to ground 224 (Pgnd). The input switch 206 can be configured to selectively couple either the input line 202 or the battery circuit 208 to one of the interfaces 203. The interface 203 is coupled to a first end of the inductor 210. A second end of the inductor 210 is coupled to the drain of the first switch (Q1) 212. The source of the first switch (Q1) 212 is coupled to the source of the second switch (Q2) 214. The drain of the second switch (Q2) 214 is coupled to the neutral line 204. The second end of the inductor 210 is also coupled to the source of the third switch (Q3) 216 and the drain of the fourth switch (Q4) 218. The drain of the third switch (Q3) 216 is coupled to the positive DC bus 106. The source of the fourth switch (Q4) 218 is coupled to the negative DC bus 107. The first bus capacitor 220 is coupled between the positive DC bus 106 and the neutral line 204. The second bus capacitor 222 is coupled between the negative DC bus 107 and the neutral line 204.

[0029] The drain of the fifth switch (Q5) 226 and the source of the seventh switch (Q7) 230 are coupled to the input switch 206. The source of the fifth switch (Q5) 226 is configured to be coupled to a negative terminal 111 of the battery 112. The drain of the seventh switch (Q7) 230 is configured to be coupled to a positive terminal 113 of the battery 112. The source of the sixth switch (Q6) 228 is configured to be coupled to the negative terminal 111 of the battery 112. The drain of the eighth switch (Q8) 232 is configured to be coupled to the positive terminal 113 of the battery 112. The drain of the sixth switch (Q6) 228 and the source of the eighth switch (Q8) are coupled to the neutral line 204. The controller 114 is coupled to the gates of each of the first switch (Q1) 212 to the eighth switch (Q8) 232 and the input switch 206, and is configured to transmit a plurality of control signals to each of the first switch (Q1) 212 to the eighth switch (Q8) 232 and the input switch 206 (i.e., control their operations).

[0030] As described above, the controller 114 monitors the input AC power received through the input terminal 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 terminal 102. When the input AC power supplied to the input terminal 102 is acceptable (i.e., higher than an input power threshold), the controller 114 operates the UPS 100 in an online operating mode. In the online operating mode, the controller 114 operates the input switch 206 to couple the input line 202 to the inductor 210 through the interface 203. When the input line 202 is coupled to the inductor 210, the controller 114 operates the first switch (Q1) 212, the second switch (Q2) 214, the third switch (Q3) 216, and the fourth switch (Q4) 218 in combination with the inductor 210 and the bus capacitors 220, 222 to generate a positive output DC voltage on the positive DC bus 106 and a negative output DC voltage on the negative DC bus 107. In at least one embodiment, the controller 114 also operates the first switch (Q1) 212, the second switch (Q2) 214, the third switch (Q3) 216, and the fourth switch (Q4) 218 to provide power factor correction (PFC).

[0031] When the AC power supplied to the input terminal 102 is unacceptable (i.e., lower than an input power threshold), the controller 114 operates the UPS 100 in a standby operating mode. In the standby operating mode, the converter 104 operates in multiple stages. For example, Figure 3 is a schematic diagram of a first stage of the standby operating mode, in which a positive DC voltage is generated on the positive DC bus 106, and Figure 4 is a schematic diagram of a second stage of the standby operating mode, in which a negative DC voltage is generated on the negative DC bus 107.

[0032] During the first stage of the standby operating mode, for example, as Figure 3As shown, the controller 114 operates the input switch 206 to couple the battery circuit 208 to the inductor 210 through the interface 203. Also in the first stage of the standby operation mode, the controller 114 operates the converter 104 to couple the positive terminal 113 to the battery 112 and the negative terminal of the battery 112 to the neutral line 204. For example, in at least one embodiment, the controller 114 operates the sixth switch (Q6) 228 to close, to couple the positive terminal 113 to the inductor 210 (through the input switch 206 and the interface 203), and operates the seventh switch (Q7) 230 to close, to couple the negative terminal 111 to the neutral line 204. In Figure 3 is shown the closed sixth switch (Q6) 228 and the closed seventh switch (Q7) 230 as a result of the direct connection.

[0033] In the first stage of the standby operation mode, when the sixth switch (Q6) 228 and the seventh switch (Q7) 230 are closed, the body diodes of the fifth switch (Q5) 226 and the eighth switch (Q8) 232 are reverse biased and as Figure 3 shown the current path 302 is generated. The controller 114 operates the first switch (Q1) 212, the second switch (Q2) 214 and the third switch (Q3) 216 as a boost converter to charge the bus capacitor 220 coupled to the positive DC bus 106 (i.e., to generate a positive DC voltage on the positive DC bus 106). More specifically, the controller 114 alternately switches the first switch (Q1) 212, the second switch (Q2) 214 and the third switch (Q3) 216 to generate a desired positive voltage level on the positive DC bus 106. For example, when the first switch (Q1) 212 and the second switch (Q2) 214 are closed, the current path 302 flows from the inductor 210 through the first switch (Q1) 212 and the second switch (Q2) to the neutral line 204, energy is stored in the inductor 210, and the current flowing through the inductor 210 increases.

[0034] When the first switch (Q1) 212 and the second switch 214 are subsequently opened, a current path is created from the inductor 210 to the positive DC bus 106 through the body diode of the third switch (Q3) 216. The third switch (Q3) 216 can then be operated by the controller 114 to close. By operating the switches as described above, a desired positive DC voltage level can be generated on the positive DC bus 106.

[0035] During the second stage of the standby operation mode, for example, as Figure 4 shown, the controller 114 operates the input switch 206 to couple the battery circuit 208 to the inductor 210 through the interface 203. Also during the second stage of the standby operation mode, the controller 114 operates the converter 104 to couple the negative terminal 111 of the battery 112 to the inductor 210 and the positive terminal 113 of the battery 112 to the neutral line 204. For example, in at least one embodiment, the controller 114 operates the fifth switch (Q5) 226 to close to couple the negative terminal 111 (through the input switch 206 and the interface 203) to the inductor 210, and the eighth switch (Q8) 233 to close to couple the positive terminal 113 to the neutral line 204. The closed fifth switch (Q5) 226 and the closed eighth switch (Q8) 232 are shown in Figure 4 as a result of the direct connection.

[0036] During the second stage of the standby operation mode, when the fifth switch (Q5) 226 and the eighth switch (Q8) 232 are closed, the body diodes 227 of the sixth switch (Q6) 228 and the seventh switch (Q7) 230 are reverse biased and a current path 402 is generated as Figure 4 shown. The controller 114 operates the first switch (Q1) 212, the second switch (Q2) 214, and the fourth switch (Q4) 218 as a boost converter to charge the second bus capacitor 222 coupled to the negative DC bus 107 (i.e., to generate a negative DC voltage on the positive DC bus 107). More specifically, the controller 114 alternately switches the first switch (Q1) 212, the second switch (Q2) 214, and the fourth switch (Q4) 218 to generate a desired negative voltage level on the negative DC bus 107. For example, when the first switch (Q1) 212 and the second switch (Q2) 214 are closed, the current path 402 flows from the neutral line 204 to the inductor 210 through the second switch (Q2) 214 and the first switch (Q1) 212, energy is stored in the inductor 210, and the current flowing through the inductor 210 increases (in a direction opposite to that during the first stage of the standby operation mode).

[0037] When the first switch (Q1) 212 and the second switch 214 are subsequently opened, a current path is created through the body diode of the fourth switch (Q4) 218 from the negative DC bus 107 to the inductor 210. The fourth switch (Q4) 218 can then be operated by the controller 114 to close. By operating the switches as described above, a desired negative DC voltage level can be generated on the negative DC bus 107.

[0038] As described above, in the standby operation mode, the converter 104 generates a positive DC voltage on the positive DC bus 106 (during the first stage of the standby operation mode), and a negative DC voltage on the negative DC bus 107 (during the second stage of the backup operation mode). In at least one embodiment, the controller 114 synchronizes the operation of the converter 104 in the standby operation mode with the operation of an inverter 108 coupled to the positive DC bus 106 and the negative DC bus 107. For example, the controller 114 can synchronize the first stage of the standby operation mode (i.e., when the positive terminal 113 of the battery 112 is coupled to the inductor 210, and the converter operates to generate a positive DC voltage on the positive DC bus 106) with a positive half cycle of the output waveform provided by the inverter 108 to the output terminal 110. The controller 114 can further synchronize the second stage of the standby operation mode (i.e., when the negative terminal 113 of the battery 112 is coupled to the inductor 210, and the converter operates to generate a negative DC voltage on the negative DC bus 106) with a negative half cycle of the output waveform provided by the inverter 108 to the output terminal 110.

[0039] As described above, the controller 114 is configured to monitor and control the operation of the UPS 100. Using data stored in an associated memory, the controller 114 is operable to execute one or more instructions, which may result in manipulation of the conductive states of one or more switches. In some examples, the controller 114 can include one or more processors or other types of controllers. The controller 114 can execute a portion of the functions discussed herein on a processor and use an application specific integrated circuit (ASIC) customized for performing a particular operation to execute another portion. Many specific combinations of hardware and software can be used to perform the operations described herein according to examples of the present invention, and the present invention is not limited to any particular combination of hardware and software components.

[0040] As described above, the PFC converter 104 is used in the single-phase UPS 100. However, in other embodiments, the PFC converter 104 can be used with any other type of single-phase online UPS having a positive DC bus and a negative DC bus. For example, in one embodiment, the PFC converter 104 is used in a 120V (RMS value) UPS system with a 120V (nominal) battery. In such a system, the DC voltage level on the DC bus is regulated to approximately 200V. In another embodiment, the PFC converter 104 is used in a 230V (RMS value) UPS system with a 192V (nominal) battery. In such a system, the DC voltage level on the DC bus is regulated to approximately 400V.

[0041] In at least one embodiment, the converter can also be used in higher power UPSs having three-phase inputs. For example, Figure 5 is a schematic diagram of a converter 500 used in a three-phase UPS.

[0042] As Figure 5 shown, the converter 500 includes: a plurality of inputs 502a to 502c (e.g., each configured to be coupled to one phase of a three-phase power source (phase A, phase B, and phase C)), a battery circuit 504 (e.g., the battery circuit 208 as Figure 2 shown), and a Vienna rectifier. Input switches 503a to 503c are configured to selectively couple the Vienna rectifier 506 to the corresponding inputs 502a to 502c or the battery circuit 504. In at least one embodiment, the Vienna rectifier 506 includes silicon carbide (SiC) diodes 508 and MOSFETs 510. However, in other embodiments, the Vienna rectifier 506 is configured differently.

[0043] As Figure 5 shown, the converter 500 operates in substantially the same manner as the converter 103 described above with reference to Figures 2 to 4 except that it generates a regulated DC output from all three-phase inputs instead of from a single-phase input.

[0044] As described above, during the standby operation mode (i.e., the battery-on operation mode), the PFC converter can be reused in the UPS to convert the DC power from the battery 112 into regulated DC power. The above-described converter can operate with lower losses / higher efficiency.

[0045] According to at least one embodiment, since the fifth switch (Q5) 226 to the eighth switch (Q8) 232 operate at line frequency and only switch the battery voltage, switches with lower voltage (e.g., MOSFETs with lower voltage) can be used as the fifth switch (Q5) 226 to the eighth switch (Q8) 232. In one embodiment, the first switch (Q1) 212 to the eighth switch (Q8) 232 are GaN FETs and / or metal oxide semiconductor field effect transistors; however, in other embodiments, different types of switches or transistors can be used.

[0046] In one embodiment, the third switch (Q3) 216 and the fourth switch (Q4) 218 are switches or transistors. However, in at least one embodiment, the third switch (Q3) 216 and the fourth switch (Q4) 218 can be replaced by diodes.

[0047] As described above, the battery circuit 208 is coupled to the dual DC bus PFC stage through an AC switch (e.g., as Figure 2 shown). However, in other embodiments, the battery circuit 208 can be coupled to different types of PFC stages.

[0048] According to one embodiment, in the case of a switch failure, the battery circuit (e.g., Figure 2 shown) includes fuses in series with the fifth switch (Q5) 226 to the eighth switch (Q8) 232.

[0049] Accordingly, several aspects of at least one embodiment of the present invention have been described. It should be understood that various changes, modifications, and improvements will readily occur to those skilled in the art. These changes, modifications, and improvements are intended to be part of the present disclosure and are intended to fall within the spirit and scope of the present invention. Therefore, the foregoing description and drawings are merely exemplary.

Claims

1. An uninterruptible power supply (UPS), characterized in that, The UPS includes: An input terminal configured to be coupled to an AC power source and configured to receive input AC power; An output terminal configured to provide output power to a load; A battery circuit configured to be coupled to a DC power source and configured to receive standby DC power; A power factor correction (PFC) stage including an interface; An input switch configured to selectively couple the interface of the PFC stage to the input terminal in an online operation mode and selectively couple to the battery circuit in a standby operation mode; A positive DC bus coupled to the PFC stage; A negative DC bus coupled to the PFC stage; A controller coupled to the battery circuit and the PFC stage, the controller being configured to: operate the PFC stage in the online operation mode to provide DC power derived from the input AC power to the positive DC bus and the negative DC bus; operate the PFC stage in the standby operation mode to provide DC power derived from the standby DC power to the positive DC bus and the negative DC bus; operate the battery circuit in a first stage of the standby operation mode to couple a positive terminal of the DC power source to the interface of the PFC stage; and operate the battery circuit in a second stage of the standby operation mode to couple a negative terminal of the DC power source to the interface of the PFC stage; and A neutral line, wherein the battery circuit includes: A first switch configured to be coupled between the input switch and the negative terminal of the DC power source; A second switch configured to be coupled between the negative terminal of the DC power source and the neutral line; A third switch configured to be coupled between the input switch and the positive terminal of the DC power source; and A fourth switch configured to be coupled between the positive terminal of the DC power source and the neutral line.

2. The UPS according to claim 1, characterized in that: When operating the battery circuit to couple the positive terminal to the interface of the PFC stage, the controller is further configured to operate the third switch to couple the positive terminal to the interface of the PFC stage through the input switch, and configured to operate the second switch to couple the negative terminal to the neutral line.

3. The UPS according to claim 2, characterized in that: When operating the battery circuit to couple the negative terminal of the DC power source to the interface of the PFC stage, the controller is further configured to operate the first switch to couple the negative terminal to the interface of the PFC stage through the input switch, and configured to operate the fourth switch to couple the positive terminal to the neutral line.

4. The UPS according to claim 3, characterized in that: The PFC stage includes: An inductor coupled to the interface; Multiple switches coupled to the inductor; A first bus capacitor coupled to the positive DC bus; and A second bus capacitor coupled to the negative DC bus.

5. The UPS according to claim 4, characterized in that: When operating the PFC stage to supply DC power derived from the standby DC power to the positive DC bus and the negative DC bus, the controller is further configured to operate the plurality of switches in the first stage of the standby operation mode to generate a positive DC voltage on the positive DC bus.

6. The UPS according to claim 5, characterized in that: When operating the PFC stage to supply DC power derived from the standby DC power to the positive DC bus and the negative DC bus, the controller is further configured to operate the plurality of switches in the second stage of the standby operation mode to generate a negative DC voltage on the negative DC bus.

7. The UPS according to claim 6, characterized in that: The plurality of switches includes: a fifth switch coupled to the inductor; a sixth switch coupled between the fifth switch and the neutral line; a seventh switch coupled between the inductor and the positive DC bus; and an eighth switch coupled between the inductor and the negative DC bus.

8. The UPS according to claim 7, characterized in that: When operating the plurality of switches in the first stage of the standby operation mode to generate the positive DC voltage on the positive DC bus, the controller is further configured to operate the fifth switch, the sixth switch, and the seventh switch as a boost converter to generate the positive DC voltage.

9. The UPS according to claim 8, characterized in that: When operating the plurality of switches in the second stage of the standby operation mode to generate the negative DC voltage on the negative DC bus, the controller is further configured to operate the fifth switch, the sixth switch, and the eighth switch as a boost converter to generate the negative DC voltage.

10. The UPS according to claim 6, characterized in that: The UPS further includes an inverter coupled between the positive DC bus, the negative DC bus, and the output, and configured to provide an output AC voltage waveform derived from at least one of the input AC power and the standby DC power, wherein the controller is further configured to synchronize the positive DC voltage generated on the positive DC bus with a positive half-cycle of the output AC voltage waveform; and wherein the controller is further configured to synchronize the negative DC voltage generated on the negative DC bus with a negative half-cycle of the output AC voltage waveform.

11. The UPS according to claim 1, wherein: The PFC stage includes a Vienna rectifier.

12. A method for operating an uninterruptible power supply (UPS) system, characterized in that, The UPS system includes an input terminal configured to be coupled to an AC power source and configured to receive input AC power, an output terminal configured to provide output power to a load, a battery circuit configured to be coupled to a DC power source and receive standby DC power, a PFC stage, a positive DC bus, a negative DC bus, and a neutral line. The battery circuit includes a first switch, a second switch, a third switch, and a fourth switch. The first switch is configured to be coupled between an input switch and a negative terminal of the DC power source. The second switch is configured to be coupled between the negative terminal of the DC power source and the neutral line. The third switch is configured to be coupled between the input switch and a positive terminal of the DC power source. The fourth switch is configured to be coupled between the positive terminal of the DC power source and the neutral line. The method includes: Operating the UPS in an online operation mode in response to determining that the input AC power is greater than an input power threshold; Operating the UPS in a standby operation mode in response to determining that the input AC power is less than the input power threshold; Selectively coupling the input terminal to an interface of the PFC stage in the online operation mode; Selectively coupling the battery circuit to the interface of the PFC stage in the standby operation mode; Controlling the PFC stage to convert the input AC power into DC power provided to the positive DC bus and the negative DC bus in the online operation mode; Controlling the PFC stage to convert the standby DC power into the DC power provided to the positive DC bus and the negative DC bus in the standby operation mode; In a first stage of the standby operation mode, coupling a positive terminal of the DC power source to the interface of the PFC stage using the battery circuit; and In a second stage of the standby operation mode, coupling a negative terminal of the DC power source to the interface of the PFC stage using the battery circuit.

13. The method according to claim 12, characterized in that: In the first stage, coupling the positive terminal of the DC power source to the interface of the PFC stage using the battery circuit, which is performed by the following steps: Operating the third switch of the battery circuit to couple the positive terminal to the interface of the PFC stage; and Operating the second switch of the battery circuit to couple the negative terminal to the neutral line.

14. The method according to claim 13, wherein: In the second stage, coupling the negative terminal of the DC power source to the interface of the PFC stage using the battery circuit, which is performed by the following steps: Operating the first switch of the battery circuit to couple the negative terminal to the interface of the PFC stage; and Operating the fourth switch of the battery circuit to couple the positive terminal to the neutral line.

15. The method according to claim 14, characterized in that: In the standby operation mode, controlling the PFC stage to convert the standby DC power into the DC power provided to the positive DC bus and the negative DC bus, which is performed by the following steps: In a first stage of the standby operation mode, control the PFC stage to generate a positive DC voltage on the positive DC bus; and In a second stage of the standby operation mode, control the PFC stage to generate a negative DC voltage on the negative DC bus.

16. The method according to claim 15, wherein, Further comprising: Operating a plurality of switches in the PFC stage as a boost converter to generate the positive DC voltage.

17. The method according to claim 16, wherein Further comprising: Operating the plurality of switches in the PFC stage as the boost converter to generate the negative DC voltage.

18. The method according to claim 15, wherein: Further comprising coupling an inverter to the positive DC bus and the negative DC bus, the inverter configured to provide an output AC voltage waveform derived from at least one of the input AC power and the standby DC power, and wherein the method further comprises: Synchronizing the positive DC voltage generated on the positive DC bus with a positive half-cycle of the output AC voltage waveform; and Synchronizing the negative DC voltage generated on the negative DC bus with a negative half-cycle of the output AC voltage waveform.

19. A non-transitory computer-readable medium storing a sequence of computer-executable instructions for operating an uninterruptible power supply (UPS), characterized in that: The UPS has: an input terminal configured to be coupled to an AC power source and configured to receive input AC power; an output terminal configured to provide output power to a load; a battery circuit configured to be coupled to a DC power source and receive standby DC power; a PFC stage; a positive DC bus coupled to the PFC stage; a negative DC bus coupled to the PFC stage; a neutral line; and at least one processor; wherein the battery circuit includes a first switch, a second switch, a third switch, and a fourth switch, the first switch configured to be coupled between an input switch and a negative terminal of the DC power source, the second switch configured to be coupled between the negative terminal of the DC power source and the neutral line, the third switch configured to be coupled between the input switch and a positive terminal of the DC power source, the fourth switch configured to be coupled between the positive terminal of the DC power source and the neutral line, and wherein the sequence of computer-executable instructions includes a plurality of instructions that direct at least one processor to perform the following operations: In response to determining that the input AC power is greater than an input power threshold, operate the UPS in an online operation mode; In response to determining that the input AC power is less than the input power threshold, operate the UPS in a standby operation mode; In the online operation mode, operate the UPS to selectively couple the input terminal to an interface of the PFC stage; In the standby operation mode, operate the UPS to selectively couple the battery circuit to the interface of the PFC stage; In the online operation mode, control the PFC stage to convert the input AC power into DC power provided to the positive DC bus and the negative DC bus; In the standby operation mode, control the PFC stage to convert the standby DC power into the DC power provided to the positive DC bus and the negative DC bus; In a first stage of the standby operation mode, the positive terminal of the DC power supply is coupled to the interface of the PFC stage by the battery circuit; and In a second stage of the standby operation mode, the negative terminal of the DC power supply is coupled to the interface of the PFC stage by the battery circuit.

20. The non-transitory computer-readable medium according to claim 19, wherein: The computer-executable instructions further direct the at least one processor to operate the battery circuit to couple the positive terminal of the DC power supply to the interface of the PFC stage in the first stage, which is performed by: operating the third switch of the battery circuit to couple the positive terminal to the interface of the PFC stage; and operating the second switch of the battery circuit to couple the negative terminal to the neutral line.

21. The non-transitory computer-readable medium according to claim 20, wherein: The computer-executable instructions further direct the at least one processor to operate the battery circuit to couple the negative terminal of the DC power supply to the interface of the PFC stage in the second stage, which is performed by: operating the first switch of the battery circuit to couple the negative terminal to the interface of the PFC stage; and operating the fourth switch of the battery circuit to couple the positive terminal to the neutral line.

22. The non-transitory computer-readable medium according to claim 21, wherein: The computer-executable instructions further direct the at least one processor to operate the PFC stage in the standby operation mode to convert the standby DC power into the DC power provided to the positive DC bus and the negative DC bus, which is performed by the following steps: In the first stage of the standby operation mode, controlling the PFC stage to generate a positive DC voltage on the positive DC bus; and In the second stage of the standby operation mode, controlling the PFC stage to generate a negative DC voltage on the negative DC bus.

23. The non-transitory computer-readable medium according to claim 22, wherein: The computer-executable instructions further direct the at least one processor to control the PFC stage to generate the positive DC voltage on the positive DC bus by operating a plurality of switches in the PFC stage as a boost converter to generate the positive DC voltage.

24. The non-transitory computer-readable medium according to claim 23, wherein: The computer-executable instructions further direct the at least one processor to control the PFC stage to generate the negative DC voltage on the negative DC bus by operating a plurality of switches in the PFC stage as a boost converter to generate the negative DC voltage.

25. The non-transitory computer-readable medium according to claim 22, wherein: The UPS further includes an inverter configured to provide an output AC voltage waveform derived from at least one of the input AC power and the standby DC power, and wherein the computer-executable instructions further direct the at least one processor to: synchronize the positive DC voltage generated on the positive DC bus with a positive half-cycle of the output AC voltage waveform; and synchronize the negative DC voltage generated on the negative DC bus with a negative half-cycle of the output AC voltage waveform.

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