Direct current to direct current power converter system and non-transitory computer readable medium

Abstract

The invention provides regulated uninterruptible power to sensitive and / or critical loads, providing a non-transitory computer readable medium for operating a direct current to direct current power converter system including a positive bus interface; a negative bus interface; a positive battery interface; a negative battery interface; a first converter stage coupled to the positive bus interface and the negative bus interface; a transformer coupled to the first converter stage; a second converter stage coupled to the transformer, the positive battery interface, and the negative battery interface; a bus balancer circuit coupled to the transformer; and a controller configured to identify an imbalance between a positive voltage level on the positive direct current bus and a negative voltage level on the negative direct current bus, and in response to identifying the imbalance, operate the bus balancer circuit to transform the first converter stage, the transformer, and the second converter stage into a reverse buck-boost converter configured to transfer energy between the positive bus interface and the negative bus interface.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to U.S. Provisional Patent Application No. 62 / 950,550, filed December 19, 2019, entitled DC-DC Power Converter with Four-Way Power Conversion, and U.S. Non-Provisional Patent Application No. 16 / 749,202, filed January 22, 2020, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This invention generally relates to uninterruptible power supplies (UPS). Background Technology

[0004] Background Art: Power devices such as uninterruptible power supplies (UPS) are known to be used to provide regulated, uninterrupted power to sensitive and / or critical loads such as computer systems and other data processing systems. Known UPSs include online UPSs, offline UPSs, online interactive UPSs, and others. Online UPSs provide regulated AC power and backup AC power after a primary source of AC power is interrupted. Offline UPSs do not provide regulation of the input AC power, but provide backup AC power when the primary source of AC power is interrupted. Online interactive UPSs are similar to offline UPSs in that they switch to battery power in the event of a power outage and also include a multi-tap transformer for regulating the output voltage provided by the UPS. Summary of the Invention

[0005] At least one aspect of the present invention is directed to a DC-DC power converter system, comprising: a positive bus interface configured to be coupled to a positive DC bus; a negative bus interface configured to be coupled to a negative DC bus; a positive battery interface configured to be coupled to a positive terminal of a battery; a negative battery interface configured to be coupled to a negative terminal of the battery; a first converter segment coupled to the positive bus interface and the negative bus interface; a transformer coupled to the first converter segment; and a second converter segment coupled to the transformer. The transformer includes: a positive battery interface and a negative battery interface; a bus balancer circuit coupled to the transformer; and a controller coupled to the positive bus interface, the negative bus interface, and the bus balancer, the controller being configured to identify an imbalance between a positive voltage level on the positive DC bus and a negative voltage level on the negative DC bus, and in response to identifying the imbalance, operating the bus balancer circuit to convert the first converter segment, the transformer, and the second converter segment into a reverse buck-boost converter, the reverse buck-boost converter being configured to transfer energy between the positive bus interface and the negative bus interface.

[0006] According to one embodiment, the first converter segment is a half-bridge converter. In one embodiment, the first converter segment includes a plurality of switches and a resonant inductor, the plurality of switches being coupled between the positive bus interface and the negative bus interface, and the resonant inductor being coupled between the plurality of switches and the transformer. In another embodiment, the transformer includes a first winding and a second winding, the first winding being coupled to the resonant inductor and the second winding being coupled to the second converter segment. In one embodiment, the bus balancer circuit is coupled across the first winding. In another embodiment, the bus balancer circuit includes a bidirectional thyristor coupled across the first winding, and wherein, when operating the bus balancer circuit to convert the first converter segment, the transformer, and the second converter segment into a reverse buck-boost converter, the controller is also configured to operate the bidirectional thyristor to short-circuit the first winding.

[0007] According to another embodiment, the transformer further includes a center tap located between a first portion and a second portion of the second winding, the center tap being coupled to the negative battery interface, and wherein the second converter segment includes a first diode and a second diode, the first diode being coupled between the first portion of the second winding and the positive battery interface, and the second diode being coupled between the second portion of the second winding and the positive battery interface.

[0008] According to one embodiment, the bus balancer circuit is coupled across the second winding. In one embodiment, the bus balancer circuit includes a plurality of switches coupled across the second winding, and wherein, when operating the bus balancer circuit to convert the first converter segment, the transformer, and the second converter segment into a reverse buck-boost converter, the controller is further configured to operate the plurality of switches in the bus balancer circuit to short-circuit the second winding. In another embodiment, the second converter segment includes a push-pull converter. In one embodiment, the transformer further includes a center tap located between a first portion and a second portion of the second winding, the center tap being coupled to the positive battery interface, and wherein the push-pull converter includes a first switch coupled between the first portion of the second winding and the negative battery interface, the first switch being coupled between the second portion of the second winding and the negative battery interface.

[0009] According to one embodiment, the second converter segment includes a full-bridge converter. In one embodiment, the full-bridge converter includes a plurality of switches coupled to the second winding, the positive battery interface, and the negative battery interface.

[0010] Another aspect of the invention relates to a non-transitory computer-readable medium storing multiple sequences of computer-executable instructions for operating a DC-DC converter system coupled to a positive DC bus and a negative DC bus of an uninterruptible power supply. The DC-DC converter system includes a first converter segment coupled to the positive DC bus and the negative DC bus, and a transformer coupled to the first converter segment. The multiple sequences of computer-executable instructions include instructions to at least one controller to: identify an imbalance between a positive voltage level on the positive DC bus and a negative voltage level on the negative DC bus; configure the first converter segment, the transformer, and the second converter segment as a reverse buck-boost converter in response to identifying the imbalance; and operate the reverse buck-boost converter to transfer energy between the positive DC bus and the negative DC bus.

[0011] According to one embodiment, the first converter segment includes a half-bridge converter having a plurality of switches and a resonant inductor. The plurality of switches are coupled to the positive DC bus and the negative DC bus. The resonant inductor is coupled between the plurality of switches and the transformer, wherein the transformer includes a first winding and a second winding. The first winding is coupled to the resonant inductor, and the second winding is coupled to the second converter segment. The plurality of instructions further instruct the at least one controller to configure the first converter segment, the transformer, and the second converter segment as the reverse buck-boost converter by operating the first converter segment and the second converter segment to short-circuit one of the first winding and the second winding of the transformer.

[0012] According to another embodiment, the plurality of instructions further instruct the at least one controller to short-circuit the first winding by operating a bus balancer circuit, thereby short-circuiting one of the first and second windings of the transformer. In one embodiment, the plurality of instructions further instruct the at least one controller to operate the bus balancer circuit by operating a bidirectional thyristor to short-circuit the first winding. In another embodiment, the second converter segment includes one of a push-pull converter and a full-bridge converter, and the plurality of instructions further instruct the at least one controller to operate a bus balancer circuit to short-circuit the second winding, thereby short-circuiting one of the first and second windings. In one embodiment, the plurality of instructions further instruct the at least one controller to operate the bus balancer circuit by operating a plurality of switches to short-circuit the second winding.

[0013] At least one aspect of the present invention is directed to a DC-DC power converter system, comprising: a positive bus interface configured to be coupled to a positive DC bus; a negative bus interface configured to be coupled to a negative DC bus; a positive battery interface configured to be coupled to a positive terminal of a battery; a negative battery interface configured to be coupled to a negative terminal of the battery; a first converter segment coupled to the positive bus interface and the negative bus interface; a transformer coupled to the first converter segment; a second converter segment coupled to the transformer, the positive battery interface, and the negative battery interface; and a means for configuring the DC-DC power converter and a resonant inductor thereunder as a reverse buck-boost converter when a voltage imbalance is identified on the positive bus interface and the negative bus interface, and for operating the reverse buck-boost converter to transfer energy between the positive bus interface and the negative bus interface. Attached Figure Description

[0014] At least one embodiment will now be discussed with reference to the accompanying drawings, which are not intended to be drawn to scale. The drawings are included to provide illustration and further understanding of the aspects and embodiments, and are incorporated in and form part of this specification, but are not intended to define any limitations of the invention. In the drawings, each identical or substantially identical component shown in the various figures is illustrated using similar numerals. For clarity, not every component may be labeled in every figure. In the drawings:

[0015] Figure 1 This is a schematic diagram of a traditional online uninterruptible power supply topology based on the many aspects described in this article;

[0016] Figure 2 This is a schematic diagram of a DC-DC power converter based on the various aspects described in this article;

[0017] Figure 3 This is a schematic diagram of a reverse buck-boost converter based on the many aspects described in this article;

[0018] Figure 4 This is a schematic diagram of another embodiment of a DC-DC power converter according to the many aspects described herein;

[0019] Figure 5 This is a schematic diagram of another embodiment of a DC-DC power converter according to the various aspects described herein; and

[0020] Figure 6This is a schematic diagram of another embodiment of a DC-DC power converter according to the many aspects described herein. Detailed Implementation

[0021] The examples of methods and systems discussed herein are not limited to the details of construction and the arrangement of components as set forth in the following description or illustrated in the accompanying drawings. The numerous methods and systems described herein can be implemented in other embodiments and can be practiced or performed in various ways. The numerous examples of specific implementations provided herein are for illustrative purposes only and are not intended to be limiting. In particular, the numerous actions, components, elements, and features discussed in connection with any one or more examples are not intended to exclude a similar role in any other example.

[0022] Similarly, the terms and terminology used herein are for descriptive purposes and should not be considered limiting. Any reference to examples, embodiments, components, elements, or actions of systems and methods mentioned herein in the singular may also encompass multiple embodiments, including a plural, and any reference to any embodiment, component, element, or action in the plural form herein may also encompass multiple embodiments including only a singular. References in the singular or plural form are not intended to limit the currently disclosed systems or methods, their components, actions, or elements. The use of “including,” “comprising,” “having,” “containing,” “involving,” and variations thereof herein is intended to cover the items listed thereafter and their equivalents, as well as additional items. References to “or” may be interpreted inclusively, such that any term described using “or” may refer to a single, more than one, or any of all the terms described. Furthermore, in the event of any inconsistency in the use of terminology between this document and documents incorporated herein by reference, the use of terminology in the incorporated references shall be supplementary to this document. For irreconcilable differences, the terminology used in this document shall prevail.

[0023] As mentioned above, many power devices, such as uninterruptible power supplies (UPS), are used to provide regulated, uninterrupted power to sensitive and / or critical loads.

[0024] A traditional online uninterruptible power supply topology 100 (e.g., in...) Figure 1The diagram shows a front-end power factor correction (PFC) circuit 102 that rectifies input AC power supplied to an input 101 by an electric power company and feeds DC power to a separate DC bus 104 (having a positive DC bus 105 and a negative DC bus 107) in an online operating mode. The separate DC bus 104 is immediately connected to an inverter circuit 108 that generates an AC output voltage from the DC power on the DC bus 104 in an online operating mode and supplies the AC output voltage to a load coupled to an output 111. In the absence of mains power, the UPS 100 operates in a battery (i.e., standby) mode, wherein the front-end PFC circuit 102 is turned off by the controller 114, and the decoupled DC bus 104 is fed power drawn from a battery 106 by a conventional DC-DC power converter 110. In the online operation mode, the DC power on the decoupled DC bus 104 is also used to charge the battery 106 via the DC-DC power converter 110.

[0025] Conventional DC-DC power converters, such as those in Figure 1 The converter 110 shown has a relatively high number of components, cost, and overall system size. Furthermore, such DC-DC power converters are limited in that they do not provide the ability to independently control multiple voltage levels of the separate DC buses 104. For example, in the battery operation mode, where DC power is supplied from the battery 106 to the separate DC buses 104, the same amount of power is injected into each individual DC bus 105, 107 in each switching cycle of the DC-DC power converter 110. Therefore, multiple voltage levels of individual DC buses cannot be controlled based on load demand, and may lead to voltage imbalances in the DC buses under many unique load conditions (e.g., due to half-wave rectifier load or only a transient current returning to a load on one of the multiple DC buses 105, 107).

[0026] In at least one embodiment, this document describes a DC-to-DC power converter that can actively correct for multiple bus imbalances caused by an unbalanced load or fault condition. To resolve the bus imbalance issue, the DC-to-DC power converter can divert power from one DC bus to another.

[0027] Figure 2 This is a schematic diagram of a DC-DC power converter 200 according to at least one aspect described herein. The DC-DC power converter 200 can be used, for example, in a UPS, as a conventional DC-DC power converter (e.g., in...). Figure 1 This is a replacement for the DC-to-DC power converter 110 in the UPS 100. The DC-to-DC power converter 200 is a dual active bridge converter, comprising a half-bridge converter segment 201 on the DC bus side 205 and a push-pull converter segment 203 on the battery side 207. More specifically, the DC-to-DC power converter 200 includes a positive bus interface 202, a negative bus interface 204, a first switch (Q1) 206, a second switch (Q2) 208, and a resonant inductor (L... r 210, a transformer 214, a third switch (Q3) 216, a fourth switch (Q4) 218, a bus balancing circuit 220, an output capacitor 222, a positive battery interface 224, a negative battery interface 226, and a controller 228. In some embodiments, the transformer 214 may have a certain amount of leakage inductance, and in such an embodiment, this leakage inductance may be included in the resonant inductor (L... r In 210. According to at least one embodiment, the transformer 214 includes a first winding 230 and a second winding 232. Figure 2 As shown, in at least one embodiment, the second winding 232 includes a first portion 234, a second portion 236, and a center tap 238. According to at least one embodiment, the bus balancing circuit 220 includes a fifth switch (Q5) 240 and a sixth switch (Q6) 242. In at least one embodiment, one or more of the switches (Q1-Q6) in the converter 200 are field-effect transistors (FETs); however, in other embodiments, other suitable switches / transistors may be utilized.

[0028] The positive bus interface 202 is configured to be coupled to a positive bus of a power system (e.g., a UPS). Figure 1 The positive bus 105 of the UPS 100 shown is described. The negative bus interface 204 is configured to be coupled to a negative bus of a power system (e.g., a UPS such as...). Figure 1The negative bus 107 of the UPS 100 shown. The drain of the first switch 206 is coupled to the positive bus interface 202. The source of the second switch 208 is coupled to the negative bus interface 204. The drain of the second switch 208 is coupled to the source of the first switch 206. The source of the first switch 206 is also coupled to the resonant inductor (L). r )210's first terminal. The resonant inductor (L r A second terminal of the transformer 210 is coupled to a first terminal of the first winding 230 of the transformer 214. A second terminal of the first winding 230 of the transformer 214 is coupled to ground 231. A magnetizing inductor (L) of the transformer 214 m )212 is presented in Figure 2 Such as existing across the first winding 230.

[0029] A first end of the second winding 232 is coupled to the drain of the third switch 216. A second end of the second winding 232 is coupled to the drain of the fourth switch 218. The source of the third switch 216 is coupled to the source of the fourth switch 218. The center tap 238 (located between the first portion 234 and the second portion 236 of the transformer 232) is coupled to the positive battery interface 224. The source of the fourth switch 218 is also coupled to the negative battery interface 226. The capacitor 222 is coupled between the positive battery interface 224 and the negative battery interface 226. The positive battery interface 224 is configured to be coupled to a positive terminal of a battery. The negative battery interface 226 is configured to be coupled to a negative terminal of the battery.

[0030] The bus balancing circuit 220 is coupled across the second winding 232 of the transformer 214. For example, in at least one embodiment, the drain of the fifth switch 240 is coupled to the first end of the second winding 232, the source of the fifth switch 240 is coupled to the source of the sixth switch 242, and the drain of the sixth switch 242 is coupled to the second end of the second winding 232. The controller 228 is coupled to the gate of each switch (Q1-Q6) in the converter 200. The operation of the converter 200 is discussed below.

[0031] The controller 228 can operate the converter as a charger (e.g., by operating the plurality of switches Q1-Q6) (e.g., in the online operation mode discussed above) to provide stable DC power derived from the positive bus interface 202 and the negative bus interface 204 to a battery coupled to the plurality of battery interfaces 224, 226 for charging the battery. As described above, the controller 228 can also operate the converter 200 in a battery operation mode (e.g., by operating the plurality of switches Q1-Q6) to provide stable DC power derived from a battery coupled to the plurality of battery interfaces 224, 226 to the positive bus interface 202 and the negative bus interface 204.

[0032] In the online or battery operation mode, the controller 228 is configured to monitor a voltage level on the positive DC bus (i.e., the voltage level at the positive bus interface 202) and a voltage level on the negative DC bus (i.e., the voltage level at the negative bus interface 204). Based on the plurality of monitored voltage levels, if a voltage imbalance is identified between the positive bus interface 202 (i.e., the positive DC bus) and the negative bus interface 204 (i.e., the negative DC bus), the controller 228 is also configured to operate the converter 200 to transfer energy between the positive bus interface 202 (i.e., the positive DC bus) and the negative bus interface 204 (i.e., the negative DC bus).

[0033] For example, in the online or battery operation mode, when the controller 228 detects that there is no voltage imbalance between the positive bus interface 202 (and therefore the positive DC bus) and the negative bus interface 204 (and therefore the negative DC bus), the controller operates the fifth switch 240 and the sixth switch 242 to open, and operates the first switch 206, the second switch 208, the third switch 216, and the fourth switch 218 with, for example, multiple duty gating signals of 50%. During such operation, the converter 200 is able to provide bidirectional power conversion, and the phase relationship between the half-bridge converter section 201 and the push-pull converter section 203 determines the resonant inductor (L... r How 210 is charged and the direction and level of power supplied by the converter 200 to the bus interfaces 202, 204 or the battery interfaces 224, 226. The first switch 206, the second switch 208, and the resonant inductor (L... rThe converter is rated to handle the full swing of current for the dual active bridge converter 200 at a relatively high frequency. In at least one embodiment, the converter 200 is capable of providing soft switching of the plurality of switches Q1-Q4, wherein multiple switching transitions of the plurality of switches Q1-Q4 occur when the device voltage or current is zero or very close to zero.

[0034] When the controller 228 detects a voltage imbalance between the positive bus interface 202 (i.e., the positive DC bus) and the negative bus interface 204 (i.e., the negative DC bus) (e.g., due to an unbalanced load, nonlinear load, fault condition, etc.), the controller operates the fifth switch 240 and the sixth switch 242 to close, and the third switch 216 and the fourth switch 218 to open. During this operation, the second winding 232 of the transformer 214 in the push-pull converter section 203 is short-circuited, and the half-bridge converter section 201 becomes an inverted buck-boost converter capable of transmitting power between the positive bus interface 202 (i.e., the positive DC bus) and the negative bus interface 204 (i.e., the negative DC bus).

[0035] Figure 3 This is a schematic diagram illustrating a reverse buck-boost converter 300 obtained when the second winding 232 of the transformer 214 in the push-pull converter section 203 is short-circuited due to the fifth switch 240 and the sixth switch 242 being closed and the third switch 216 and the fourth switch 218 being opened. The magnetizing inductance (L) of the transformer 214... m )212 and the resonant inductor (L r )210 series coupled, but in Figure 3 It is not shown in the text.

[0036] The resulting reverse buck-boost converter 300 is a bidirectional DC-DC converter capable of transferring desired energy between the positive bus interface 202 (i.e., the positive DC bus) and the negative bus interface 204 (i.e., the negative DC bus). The reverse buck-boost converter 300 provides power conversion between the two DC buses according to the ratings of the first switch 206, the second switch 208, and the inductor 210. The controller 228 selectively operates the first switch 206 and the second switch 208, causing the buck-boost converter 300 to operate to transfer energy between the positive bus interface 202 (i.e., the positive DC bus) and the negative bus interface 204 (i.e., the negative DC bus), responding as desired to various potential scenarios.

[0037] For example, the controller 228 can operate the first switch 206 and the second switch 208 to transfer energy between the positive bus interface 202 (i.e., the positive DC bus) and the negative bus interface 204 (i.e., the negative DC bus) to quickly resolve an unbalanced load and / or fault condition. The controller 228 can also operate the first switch 206 and the second switch 208 to resolve a half-wave rectifying load without generating a DC current in the neutral line 233. Additionally, the controller 228 can operate the first switch 206 and the second switch 208 to transfer energy from one DC bus to another to increase hold-up time during transitions to a battery mode. In such a scenario, the size of the numerous capacitors coupled between each DC bus and ground can be reduced.

[0038] As described above, the DC-to-DC power converter 200 can actively correct various bus imbalance issues in a UPS caused by an unbalanced load or fault condition. The DC-to-DC power converter 200 includes a bus balancing circuit 220, which enables the converter 200 to transform into a reverse buck-boost converter capable of transferring energy from one DC bus to another. As described above, the DC-to-DC power converter is a dual active bridge converter, which can employ various buck-converter-derived topologies on both the primary and secondary sides. Figure 2The embodiment shown employs a half-bridge converter segment 201 on the DC bus side 205 and a push-pull converter segment 203 on the battery side 207; however, in other embodiments, a similar bus balancing circuit can be used for different types of converters, including a half-bridge converter and a resonant inductor intended for soft switching of the converter in a conventional dual active bridge converter. Regardless of topology differences, the bus balancing circuit described above can transform the half-bridge and the resonant inductor into an inverting buck-boost converter to transfer energy from one DC bus to another.

[0039] Figure 4 This is a schematic diagram of another embodiment of a DC-DC power converter 400 according to at least one aspect described herein. The DC-DC power converter 400 can be used in a UPS and replace the above-described DC-DC power converter. Figure 2 The converter 200 discussed. The DC-DC power converter 400 is a dual active bridge converter, which includes a half-bridge converter section 401 on the DC bus side 405 and a full-bridge converter section 403 on the battery side 407. More specifically, the DC-DC power converter 400 includes a positive bus interface 402, a negative bus interface 404, a first switch (Q1) 406, a second switch (Q2) 408, and a resonant inductor (L... r 410, a transformer 414, a third switch (Q3) 416, a fourth switch (Q4) 418, a fifth switch (Q5) 417, a sixth switch (Q6) 419, a bus balancing circuit 420, an output capacitor 422, a positive battery interface 424, a negative battery interface 426, and a controller 428. The transformer 414 has a certain amount of leakage inductance, and this leakage inductance is included in the resonant inductor (L... r In at least one embodiment, the transformer 414 includes a first winding 430 and a second winding 432. According to at least one embodiment, the bus balancing circuit 420 includes a seventh switch (Q7) 440 and an eighth switch (Q8) 442. In at least one embodiment, one or more switches (Q1-Q8) in the converter 400 are field-effect transistors (FETs); however, in other embodiments, other suitable switches / transistors may be used.

[0040] The positive bus interface 402 is configured to be coupled to a positive bus of a power system (e.g., a UPS). Figure 1 The positive bus of the UPS 100 shown. The negative bus interface 404 is configured to be coupled to a negative bus of a power system (e.g., a UPS such as Figure 1The negative bus of the UPS 100 shown. The drain of the first switch 406 is coupled to the positive bus interface 402. The source of the second switch 408 is coupled to the negative bus interface 404. The drain of the second switch 408 is coupled to the source of the first switch 406. The source of the first switch 406 is also coupled to the resonant inductor (L). r )410's first terminal. The resonant inductor (L r A second terminal of the transformer 410 is coupled to a first terminal of the first winding 430 of the transformer 414. A second terminal of the first winding 430 of the transformer 414 is coupled to ground 431. A magnetizing inductor (L) of the transformer 414 m )412 is presented in Figure 4 Such as existing across the first winding 430.

[0041] A first end of the second winding 432 is coupled to the source of the third switch 416. A second end of the second winding 432 is coupled to the source of the fifth switch 417. The source of the third switch 416 is also coupled to the drain of the fourth switch 418. The source of the fifth switch 417 is coupled to the drain of the sixth switch 419. The drains of the third switch 416 and the fifth switch 417 are coupled to the positive battery interface 424. The sources of the fourth switch 418 and the sixth switch 419 are coupled to the negative battery interface 426. The capacitor 422 is coupled between the positive battery interface 424 and the negative battery interface 426. The positive battery interface 424 is configured to be coupled to a positive terminal of a battery. The negative battery interface 426 is configured to be coupled to a negative terminal of the battery.

[0042] The bus balancing circuit 420 is coupled across the second winding 432 of the transformer 414. For example, in at least one embodiment, the drain of the seventh switch 440 is coupled to a first end of the second winding 432, the source of the seventh switch 440 is coupled to the source of the eighth switch 442, and the drain of the eighth switch 442 is coupled to a second end of the second winding 432. The controller 428 is coupled to the gate of each switch (Q1-Q8) in the converter 400.

[0043] The operation of the converter 400 is similar to that described above. Figure 2The operation of the converter 200 discussed herein. For example, the controller 428 may operate the converter 400 as a charger (e.g., in an online operating mode) to provide DC power derived from the plurality of DC buses to a battery coupled to the plurality of bus interfaces 424, 426, and as a backup DC source to provide backup DC power derived from the battery to the plurality of DC buses. Furthermore, as described above, the controller may operate the bus balancer circuit 420 to short-circuit the second winding 432 of the transformer 414 to convert the converter 400 into a reverse buck-boost converter capable of transferring energy from one DC bus to another.

[0044] As described above, the bus balancer circuit is implemented in a converter to allow for four-way power conversion. However, such a bus balancer circuit can also be used in a converter to provide three-way power conversion. For example: Figure 5 This is a schematic diagram of another DC-DC power converter 500 according to at least one aspect described herein. The DC-DC power converter 500 can be used in a UPS and replace the above-described reference. Figure 2 The converter 200 discussed herein. The DC-DC power converter 500 is an LLC-based converter, which includes a half-bridge converter segment 501 on a DC bus side 505 and a second converter segment 503 on a battery side 507. More specifically, the DC-DC power converter 500 includes a positive bus interface 502, a negative bus interface 504, a first switch (Q1) 506, a second switch (Q2) 508, and a resonant inductor (L... r 510. A resonant capacitor (C) r 513, a transformer 514, a first diode 516, a second diode 518, a bus balancing circuit 520, an output capacitor 522, a positive battery interface 524, a negative battery interface 526, and a controller 528. The transformer 514 has a certain amount of leakage inductance, and the leakage inductance is included in the resonant inductor (L). r )510 in.

[0045] According to at least one embodiment, the transformer 514 includes a first winding 530 and a second winding 532. For example... Figure 5As shown, in at least one embodiment, the second winding 532 includes a first portion 534, a second portion 536, and a center tap 538. According to at least one embodiment, the bus balancing circuit 520 includes a triac (transistor) 521 for alternating current. In at least one embodiment, one or more switches (Q1-Q2) in the converter 500 are field-effect transistors (FETs); however, in other embodiments, other suitable switches / transistors may be utilized.

[0046] The positive bus interface 502 is configured to be coupled to a positive bus of a power system (e.g., a UPS). Figure 1 The positive bus of the UPS 100 shown. The negative bus interface 504 is configured to be coupled to a negative bus of a power system (e.g., a UPS such as Figure 1 The negative bus of the UPS 100 shown. The drain of the first switch 506 is coupled to the positive bus interface 502. The source of the second switch 508 is coupled to the negative bus interface 504. The drain of the second switch 508 is coupled to the source of the first switch 506. The source of the first switch 506 is also coupled to the resonant inductor (L). r The first terminal of 510. The resonant inductor (L r A second terminal of transformer 510 is coupled to a first terminal of the first winding 530 of transformer 514. A second terminal of the first winding 530 of transformer 514 is coupled to the first capacitor (C). r A first terminal of 513. The first capacitor (C) r A second terminal of transformer 513 is coupled to ground 531 via a neutral line 233. A magnetizing inductor (L...) of transformer 514... m )512 is presented in Figure 5 Such as existing across the first winding 530.

[0047] A first end of the second winding 532 is coupled to the anode of the first diode 516. The cathode of the first diode 516 is coupled to the positive battery interface 524. A second end of the second winding 532 is coupled to the anode of the second diode 518. The cathode of the second diode 518 is coupled to the positive battery interface 524. The center tap 538 (located between the first portion 534 and the second portion 536 of the transformer 532) is coupled to the negative battery interface 526. The output capacitor 522 is coupled between the positive battery interface 524 and the negative battery interface 526. The positive battery interface 524 is configured to be coupled to a positive terminal of a battery. The negative battery interface 526 is configured to be coupled to a negative terminal of the battery.

[0048] The bus balancing circuit 520 is coupled across the first winding 530 of the transformer 514. For example, in at least one embodiment, a first anode of the bidirectional thyristor 521 is coupled to a first end of the first winding 530 of the transformer 514, while a second anode of the bidirectional thyristor 521 is coupled to ground 531. The controller 528 is coupled to the gate of each switch (Q1-Q2) in the converter 200 and the gate of the bidirectional thyristor 521.

[0049] The controller 528 can operate the converter 500 as a charger (e.g., in an online operating mode) to provide DC power derived from the plurality of DC buses to a battery coupled to the plurality of bus interfaces 524, 526. Furthermore, when the controller 528 detects an imbalance among the plurality of DC buses in a corresponding UPS, the controller can operate the bidirectional thyristor 521 to short-circuit the first winding 530 of the transformer 514 and the resonant capacitor 513, thereby converting the converter 500 into a reverse DC-to-DC buck-boost converter, which can be operated to transfer energy from one DC bus to another, as described above. Once the DC buses are balanced, the controller 528 turns off the bidirectional thyristor 521, reducing the current through the bidirectional thyristor 521 to zero, and the converter 500 operates as a charger again.

[0050] according to Figure 6 In another embodiment shown, an LCC converter 600 may include the above-mentioned... Figure 5The same DC balancing features (e.g., the bus balancing circuitry) are described in the LLC converter 500. The LCC converter 600 is substantially similar to the LLC converter 500 (and similar components refer to the same reference numerals), except that the LCC 600 differs from the LLC converter 500 in that another capacitor 602 is added in parallel with the primary winding of the transformer (e.g., the first winding 530 of the transformer 514). Many DC bus balancing operations for the LCC converter 600 are described above. Figure 5 The situation is essentially the same for the LLC converter 500 described above.

[0051] As described above, a controller is configured to monitor and control the operation of a DC-DC power converter, as discussed herein. Using data stored in associated memory, the controller is operable to execute one or more instructions that may result in manipulation of the conductive state of one or more switches. In some examples, the controller may include one or more processors or other types of controllers. The controller may perform some of the many functions discussed herein on the processor and perform another portion using an application-specific integrated circuit (ASIC) adapted to perform a particular operation. Examples of the invention can use many specific combinations of hardware and software to perform the operations described herein, and the invention is not limited to any particular combination of hardware and software components.

[0052] A DC-DC power converter is provided that can actively correct multiple bus balancing issues in a UPS caused by an unbalanced load or fault condition. The DC-DC power converter includes a bus balancing circuit that enables the converter to be transformed into a reverse buck-boost converter, capable of transferring energy from one DC bus to another. The bus balancing circuit operates by transforming a half-bridge and resonant inductor into a reverse buck-boost converter to transfer energy from one DC bus to another. As described above, the DC-DC power converter is implemented as an online UPS. However, such a DC-DC power converter can be implemented with any other type of UPS having a separate DC bus. Furthermore, such a DC-DC power converter can be implemented for use in a renewable energy-based system to meet the typical requirement of balancing multiple DC buses.

[0053] Therefore, having described several aspects of at least one embodiment of the invention, various changes, modifications, and improvements will readily occur to those skilled in the art. Such changes, modifications, and improvements are intended to be part of this disclosure and are intended to fall within the spirit and scope of the invention. Therefore, the foregoing description and drawings are merely illustrative.

Claims

1. A DC-DC power converter system, characterized in that: The DC-DC power converter system includes: A positive bus interface, wherein the positive bus interface is configured to be coupled to a positive DC bus; A negative bus interface, wherein the negative bus interface is configured to be coupled to a negative DC bus; A positive battery interface, the positive battery interface being configured to be coupled to a positive terminal of a battery; A negative battery interface, the negative battery interface being configured to be coupled to a negative terminal of the battery; A first converter segment, the first converter segment being coupled to the positive bus interface and the negative bus interface; A second converter segment is coupled to the positive battery interface and the negative battery interface; A transformer includes a first winding and a second winding, the first winding being coupled to a first converter section and the second winding being coupled to a second converter section; A bus balancer circuit, said bus balancer circuit being coupled to the transformer; and A controller coupled to the positive bus interface, the negative bus interface, and the bus balancer, the controller being configured to identify an imbalance between a positive voltage level on the positive DC bus and a negative voltage level on the negative DC bus, and in response to identifying the imbalance, to operate the bus balancer circuit to selectively short-circuit either the first winding or the second winding of the transformer to convert the first converter segment, the transformer, and the second converter segment into a reverse buck-boost converter, the reverse buck-boost converter being configured to transfer energy between the positive bus interface and the negative bus interface.

2. The DC-DC power converter system according to claim 1, characterized in that: The first converter segment is a half-bridge converter.

3. The DC-DC power converter system according to claim 1, characterized in that: The first converter segment includes multiple switches and a resonant inductor. The multiple switches are coupled between the positive bus interface and the negative bus interface, and the resonant inductor is coupled between the multiple switches and the transformer.

4. The DC-DC power converter system according to claim 3, characterized in that: The first winding is coupled to the resonant inductor.

5. The DC-DC power converter system according to claim 4, characterized in that: The bus balancer circuit is coupled across the first winding.

6. The DC-DC power converter system according to claim 4, characterized in that: The bus balancer circuit includes a bidirectional thyristor coupled across the first winding, and wherein, when the bus balancer circuit is operated to convert the first converter segment, the transformer, and the second converter segment into a reverse buck-boost converter, the controller is also configured to operate the bidirectional thyristor to short-circuit the first winding.

7. The DC-DC power converter system according to claim 4, characterized in that: The transformer further includes a center tap located between a first portion and a second portion of the second winding, the center tap being coupled to the negative battery interface, and wherein the second converter segment includes a first diode and a second diode, the first diode being coupled between the first portion of the second winding and the positive battery interface, and the second diode being coupled between the second portion of the second winding and the positive battery interface.

8. The DC-DC power converter system according to claim 4, characterized in that: The bus balancer circuit is coupled across the second winding.

9. The DC-DC power converter system according to claim 4, characterized in that: The bus balancer circuit includes a plurality of switches coupled across the second winding, and wherein, when the bus balancer circuit is operated to convert the first converter segment, the transformer, and the second converter segment into a reverse buck-boost converter, the controller is also configured to operate the plurality of switches in the bus balancer circuit to short-circuit the second winding.

10. The DC-DC power converter system according to claim 1, characterized in that: The second converter segment includes a push-pull converter.

11. The DC-DC power converter system according to claim 10, characterized in that: The transformer further includes a center tap located between a first portion and a second portion of the second winding, the center tap being coupled to the positive battery interface, and wherein the push-pull converter includes a first switch and a second switch, the first switch being coupled between the first portion of the second winding and the negative battery interface, and the second switch being coupled between the second portion of the second winding and the negative battery interface.

12. The DC-DC power converter system according to claim 1, characterized in that: The second converter segment includes a full-bridge converter.

13. The DC-DC power converter system according to claim 12, characterized in that: The full-bridge converter includes multiple switches that are coupled to the second winding, the positive battery interface, and the negative battery interface.

14. A non-transitory computer-readable medium, characterized in that: The non-transitory computer-readable medium stores multiple sequences of computer-executable instructions for operating a DC-DC converter system coupled to a positive DC bus and a negative DC bus of an uninterruptible power supply. The DC-DC converter system includes a first converter segment coupled to the positive and negative DC buses, a second converter segment coupled to a positive and a negative battery interface, and a transformer including a first winding and a second winding, the first winding coupled to the first converter segment and the second winding coupled to the second converter segment. The multiple sequences of computer-executable instructions include instructions to at least one controller to perform: Identify an imbalance between a positive voltage level on the positive DC bus and a negative voltage level on the negative DC bus; In response to identifying the imbalance, the first converter section, the transformer, and the second converter section are configured as a reverse buck-boost converter by short-circuiting one of the first winding and the second winding of the transformer; and The reverse buck-boost converter is operated to transfer energy between the positive DC bus and the negative DC bus.

15. The non-transitory computer-readable medium according to claim 14, characterized in that: The first converter segment includes a half-bridge converter having multiple switches and a resonant inductor. The multiple switches are coupled to the positive DC bus and the negative DC bus, and the resonant inductor is coupled between the multiple switches and the transformer, wherein the first winding is coupled to the resonant inductor.

16. The non-transitory computer-readable medium according to claim 15, characterized in that: The multiple instructions also instruct the at least one controller to short-circuit the first winding by operating a bus balancer circuit, thereby short-circuiting one of the first and second windings of the transformer.

17. The non-transitory computer-readable medium according to claim 16, characterized in that: The multiple instructions also instruct the at least one controller to operate the bus balancer circuit by operating a bidirectional thyristor to short-circuit the first winding.

18. The non-transitory computer-readable medium according to claim 15, characterized in that: The second converter segment includes one of a push-pull converter and a full-bridge converter, and the plurality of instructions further instruct the at least one controller to short-circuit the second winding by operating a bus balancer circuit, thereby short-circuiting one of the first winding and the second winding.

19. The non-transitory computer-readable medium according to claim 18, characterized in that: The multiple instructions also instruct the at least one controller to operate the bus balancer circuit by operating multiple switches to short-circuit the second winding.

20. A DC-DC power converter system, characterized in that: The DC-DC power converter system includes: A positive bus interface, wherein the positive bus interface is configured to be coupled to a positive DC bus; A negative bus interface, wherein the negative bus interface is configured to be coupled to a negative DC bus; A positive battery interface, the positive battery interface being configured to be coupled to the positive terminal of a battery; A negative battery interface, the negative battery interface being configured to be coupled to a negative terminal of the battery; A first converter segment, the first converter segment being coupled to the positive bus interface and the negative bus interface; A second converter segment is coupled to the positive battery interface and the negative battery interface; A transformer includes a first winding and a second winding, the first winding being coupled to a first converter section, and the second winding being coupled to a second converter section; and A device, when a voltage imbalance is identified on the positive bus interface and the negative bus interface, is configured to configure the DC-DC power converter and one of its resonant inductors as a reverse buck-boost converter by short-circuiting one of the first winding and the second winding of the transformer, and to operate the reverse buck-boost converter to transfer energy between the positive bus interface and the negative bus interface.

21. A method for operating a DC-DC converter system, characterized in that: The DC-DC converter system is coupled to a positive DC bus and a negative DC bus of an uninterruptible power supply (UPS). The DC-DC converter system includes a first converter segment coupled to the positive DC bus and the negative DC bus, a second converter segment coupled to a positive battery interface and a negative battery interface, and a transformer including a first winding and a second winding, the first winding coupled to the first converter segment and the second winding coupled to the second converter segment. The method includes: Identify an imbalance between a positive voltage level on the positive DC bus and a negative voltage level on the negative DC bus; In response to identifying the imbalance, the first converter section, the transformer, and the second converter section are configured as a reverse buck-boost converter by short-circuiting one of the first winding and the second winding of the transformer; and The reverse buck-boost converter is operated to transfer energy between the positive DC bus and the negative DC bus.

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