WO2024028769A1

WO2024028769A1 - Uninterrupted power supply system and method for providing power flow with input power factor correction

Info

Publication number: WO2024028769A1
Application number: PCT/IB2023/057795
Authority: WO
Inventors: Champak Kundu; Sayan Das; Archak Sadhukhan; Sujit Kumar Biswas; Arkendu Mitra
Original assignee: Epoch Innova Private Limited
Priority date: 2022-08-04
Filing date: 2023-08-01
Publication date: 2024-02-08

Abstract

An uninterrupted power supply system (10) for providing power flow with input power factor correction is provided. The uninterrupted power supply system includes a rectifier unit (20) including a first plurality of switches (30). The rectifier unit is to provide a direct current (DC) voltage. The uninterrupted power supply system includes a buck converter unit (50) to step down the direct current (DC) voltage supplied by the rectifier unit to charge an energy storage unit (60). The uninterrupted power supply system includes a boost converter unit (70) to step up an output voltage of the energy storage unit to provide a stepped up voltage. The uninterrupted power supply system includes an inverter unit (80) including a second plurality of switches (90) to invert the stepped up voltage provided by the boost converter to feed one or more loads (100). The second plurality of switches are interconnected in an H bridge configuration and controlled by a second plurality of corresponding pulses.

Description

UNINTERRUPTED POWER SUPPEY SYSTEM AND METHOD FOR PROVIDING POWER FEOW WITH INPUT POWER FACTOR CORRECTION

EARLIEST PRIORITY DATE

This Application claims priority from a Complete patent application filed in India having Patent Application No. 202231044651, filed on August 04, 2022, and titled “UNINTERRUPTED POWER SUPPLY SYSTEM AND METHOD FOR PROVIDING POWER FLOW WITH INPUT POWER FACTOR CORRECTION”.

FIELD OF INVENTION

Embodiments of the present disclosure relate to the field of uninterrupted power supply and more particularly to an uninterrupted power supply system and method for providing power flow with input power factor correction.

BACKGROUND

An uninterruptible power supply (UPS) is a system that provides emergency power to a load when an input power source fails. The UPS differs from an auxiliary or emergency power system or standby generator in such a way that the UPS provide near- instantaneous protection from input power interruptions, by supplying energy stored in batteries, supercapacitors, or flywheels. The on-battery run-time of the UPS is relatively short depending on storage capacity of the batteries but sufficient to start a standby power source or properly shut down a protected equipment. The UPS is a type of continual power system. The UPS is used to protect hardware such as computers, data centers, telecommunication equipment or other electrical equipment where an unexpected power disruption could cause injuries, fatalities, serious business disruption or data loss. The UPS units range in size from ones designed to protect a single computer to large units powering entire data centers or buildings.

The existing UPS is bulky due to presence of low frequency transformers. Also, the UPS fails to isolate input terminals and output terminals. Failure to isolate the input terminals and the output terminals may introduce electromagnetic noise in the system thereby affecting power quality. Further, the UPS fails to provide power factor compensation. Due to low power factor, transmission loss increases, and operational cost increases. The lower power factor also negatively affect voltage regulation. Failure to charge lithium ion batteries due to low current rating is another drawback of the existing UPS.

Hence, there is a need for an improved uninterrupted power supply system and method for providing power flow with input power factor correction to address the aforementioned issue(s).

BRIEF DESCRIPTION

In accordance with an embodiment of the present disclosure, an uninterrupted power supply system for providing power flow with input power factor correction is provided. The uninterrupted power supply system includes a rectifier unit including a first plurality of switches. The rectifier unit is adapted to provide a direct current (DC) voltage corresponding to an alternating current (AC) voltage supplied by a voltage source. The first plurality of switches are controlled by a first plurality of corresponding pulses to maintain an alternating current (AC) supplied by the voltage source in phase with the alternating current (AC) voltage supplied by the voltage source. The uninterrupted power supply system also includes a buck converter unit electrically coupled to the rectifier unit. The buck converter unit is adapted to step down the direct current (DC) voltage supplied by the rectifier unit to charge an energy storage unit. The uninterrupted power supply system further includes a boost converter unit electrically coupled to the energy storage unit. The boost converter unit is adapted to step up an output voltage of the energy storage unit to provide a stepped up voltage when the voltage source fails to provide the alternating current (AC) voltage. The uninterrupted power supply system also includes an inverter unit electrically coupled to the boost converter unit. The inverter unit includes a second plurality of switches adapted to invert the stepped up voltage provided by the boost converter to feed one or more loads. The second plurality of switches are interconnected in an H bridge configuration and controlled by a second plurality of corresponding pulses. The rectifier unit, the buck converter unit, the boost converter unit, and the inverter unit are adapted to conduct bidirectionally. In accordance with another embodiment of the present disclosure, a method of operation of an uninterrupted power supply system for providing power flow with input power factor correction is provided. The method includes providing, by a rectifier unit, a direct current (DC) voltage corresponding to an alternating current (AC) voltage supplied by a voltage source. The rectifier unit includes a first plurality of switches controlled by a first plurality of corresponding pulses to maintain an alternating current (AC) supplied by the voltage source in phase with the alternating current (AC) voltage supplied by the voltage source. The method also includes stepping down, by a buck converter unit, the direct current (DC) voltage supplied by the rectifier unit to charge an energy storage unit. The method further includes stepping up, by a boost converter unit, an output voltage of the energy storage unit to provide a stepped up voltage when the voltage source fails to provide the alternating current (AC) voltage. The method also includes inverting, by a second plurality of switches of an inverter unit, the stepped up voltage provided by the boost converter to feed one or more loads. The second plurality of switches are interconnected in an H bridge configuration and controlled by a second plurality of corresponding pulses. The rectifier unit, the buck converter unit, the boost converter unit, and the inverter unit are adapted to conduct bidirectionally.

To further clarify the advantages and features of the present disclosure, a more particular description of the disclosure will follow by reference to specific embodiments thereof, which are illustrated in the appended figures. It is to be appreciated that these figures depict only typical embodiments of the disclosure and are therefore not to be considered limiting in scope. The disclosure will be described and explained with additional specificity and detail with the appended figures.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure will be described and explained with additional specificity and detail with the accompanying figures in which:

FIG. 1 is a schematic representation of an uninterrupted power supply system for providing power flow with input power factor correction in accordance with an embodiment of the present disclosure; FIG. 2 is a schematic representation of one embodiment of the uninterrupted power supply system of FIG. 1, depicting a rectifier unit in accordance with an embodiment of the present disclosure.

FIG. 3 is a graphical representation of another embodiment of the uninterrupted power supply system of FIG. 1, depicting alternating current (AC) voltage, alternating current (AC) and direct current (DC) voltage in accordance with an embodiment of the present disclosure;

FIG. 4 is a schematic representation of another embodiment of the uninterrupted power supply system of FIG. 1, depicting equivalent diagram of a buck converter unit in accordance with an embodiment of the present disclosure;

FIG. 5 is a graphical representation of another embodiment of the uninterrupted power supply system of FIG. 1, depicting switching pulses, primary voltage of a first isolation transformer, secondary voltage of a first isolation transformer, current through a second inductor in accordance with an embodiment of the present disclosure;

FIG. 6 is a graphical representation of another embodiment of the uninterrupted power supply system of FIG. 1, depicting direct current (DC) voltage at input side of the buck converter unit, current flowing through high voltage side of the first isolation transformer and the current flowing through low voltage side of the first isolation transformer in accordance with an embodiment of the present disclosure;

FIG. 7 is a schematic representation of another embodiment of the uninterrupted power supply system of FIG. 1, depicting the boost converter unit in accordance with an embodiment of the present disclosure;

FIG. 8 is a schematic representation of another embodiment of the uninterrupted power supply system of FIG. 1, depicting direct current (DC) bus voltage, terminal voltage of the energy storage unit, current flowing through primary winding of the second isolation transformer in accordance with an embodiment of the present disclosure;

FIG. 9 is a graphical representation of another embodiment of the uninterrupted power supply system of FIG. 1, depicting the inverter unit in accordance with an embodiment of the present disclosure; FIG. 10 is a graphical representation of another embodiment of the uninterrupted power supply system of FIG. 1, depicting interposition of a triangular wave on a first wave and a second wave, a voltage across the first leg, a voltage across the second leg, and a voltage across the output terminals of the inverter unit in accordance with an embodiment of the present disclosure;

FIG. 11 is a graphical representation of another embodiment of the uninterrupted power supply system of FIG. 1, depicting sinusoidal pulse width modulated line voltage generated by the inverter unit, output voltage of the inverter unit, output current of the inverter unit in accordance with an embodiment of the present disclosure;

FIG. 12 is a schematic representation of another embodiment of the uninterrupted power supply system of FIG. 1, depicting various configurational stages in accordance with an embodiment of the present disclosure; and

FIG. 13 is a flow chart representing the steps involved in a method of operation of an uninterrupted power supply system for providing power flow with input power factor correction in accordance with an embodiment of the present disclosure.

Further, those skilled in the art will appreciate that elements in the figures are illustrated for simplicity and may not have necessarily been drawn to scale. Furthermore, in terms of the construction of the device, one or more components of the device may have been represented in the figures by conventional symbols, and the figures may show only those specific details that are pertinent to understanding the embodiments of the present disclosure so as not to obscure the figures with details that will be readily apparent to those skilled in the art having the benefit of the description herein.

DETAILED DESCRIPTION

For the purpose of promoting an understanding of the principles of the disclosure, reference will now be made to the embodiment illustrated in the figures and specific language will be used to describe them. It will nevertheless be understood that no limitation of the scope of the disclosure is thereby intended. Such alterations and further modifications in the illustrated system, and such further applications of the principles of the disclosure as would normally occur to those skilled in the art are to be construed as being within the scope of the present disclosure. The terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process or method that comprises a list of steps does not include only those steps but may include other steps not expressly listed or inherent to such a process or method. Similarly, one or more devices or sub-systems or elements or structures or components preceded by "comprises... a" does not, without more constraints, preclude the existence of other devices, sub-systems, elements, structures, components, additional devices, additional sub-systems, additional elements, additional structures, or additional components. Appearances of the phrase "in an embodiment", "in another embodiment" and similar language throughout this specification may, but not necessarily do, all refer to the same embodiment.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this disclosure belongs. The system, methods, and examples provided herein are only illustrative and not intended to be limiting.

In the following specification and the claims, reference will be made to a number of terms, which shall be defined to have the following meanings. The singular forms “a”, “an”, and “the” include plural references unless the context clearly dictates otherwise.

Embodiments of the present disclosure relate to an uninterrupted power supply system and method for providing power flow with input power factor correction. In accordance with an embodiment of the present disclosure, an uninterrupted power supply system and method for providing power flow with input power factor correction is provided. The uninterrupted power supply system includes a rectifier unit including a first plurality of switches. The rectifier unit is adapted to provide a direct current (DC) voltage corresponding to an alternating current (AC) voltage supplied by a voltage source. The first plurality of switches are controlled by a first plurality of corresponding pulses to maintain an alternating current (AC) supplied by the voltage source in phase with the alternating current (AC) voltage supplied by the voltage source. The uninterrupted power supply system also includes a buck converter unit electrically coupled to the rectifier unit. The buck converter unit is adapted to step down the direct current (DC) voltage supplied by the rectifier unit to charge an energy storage unit. The uninterrupted power supply system further includes a boost converter unit electrically coupled to the energy storage unit. The boost converter unit is adapted to step up an output voltage of the energy storage unit to provide a stepped up voltage when the voltage source fails to provide the alternating current (AC) voltage. The uninterrupted power supply system also includes an inverter unit electrically coupled to the boost converter unit. The inverter unit includes a second plurality of switches adapted to invert the stepped up voltage provided by the boost converter to feed one or more loads. The second plurality of switches are interconnected in an H bridge configuration and controlled by a second plurality of corresponding pulses. The rectifier unit, the buck converter unit, the boost converter unit, and the inverter unit are adapted to conduct bidirectionally.

FIG. 1 is a schematic representation of an uninterrupted power supply system (10) for providing power flow with input power factor correction in accordance with an embodiment of the present disclosure. The uninterrupted power supply system (10) includes a rectifier unit (20) including a first plurality of switches (30). The rectifier unit (20) is adapted to provide a direct current (DC) voltage corresponding to an alternating current (AC) voltage supplied by a voltage source (40). The first plurality of switches (30) are controlled by a first plurality of corresponding pulses to maintain an alternating current (AC) supplied by the voltage source (40) in phase with the alternating current (AC) voltage supplied by the voltage source (40). In one embodiment, the rectifier unit (20) is capable of boosting the direct current voltage (DC) to any desired level. In some embodiments, the rectifier unit (20) may be capable of rectifying three phase alternating current (AC) voltage supplied by the voltage source (40). Working of the rectifier unit (20) is explained in detail in FIG. 2.

FIG. 2 is a schematic representation of one embodiment of the uninterrupted power supply system (10) of FIG. 1, depicting a rectifier unit (20) in accordance with an embodiment of the present disclosure. The first plurality of switches (30) includes a first switch (170), a second switch (180), a third switch (190) and a fourth switch (200). The first plurality of switches (30) are interconnected in an H bridge configuration. The first plurality of switches (30) may include, but not limited to, semiconductor switches such as metal oxide semiconductor field effect transistor (MOSFET), insulated gate bipolar transistor (IGBT), silicon super junction along with respective anti-parallel diodes. The anti-parallel diodes may have adequate current carrying capability. A first inductor (210) may assist boost operation of the direct current (DC) voltage and a first parallel capacitor (220) may smoother! the direct current (DC) voltage. During positive half cycles of the voltage source (40), the first inductor (210) may store energy when the second switch (180) is closed, and alternating current (AC) may flow to a neural line via an anti-parallel diode associated with the fourth switch (200).

Also, when the second switch (180) is open, energy stored in the first inductor (210) may flow through output terminals (230) through the anti-parallel diode associated with the first switch (170) and return back to the neutral line through the anti -parallel diode associated with the fourth switch (200). Similarly, during negative half cycle, the first switch (170) is turned on and the alternating current may flow from neutral to the antiparallel diode associated with the third switch (190) and back to the first inductor (210) through first switch (170). When the first switch (170) is tuned off, the first inductor (210) will discharge stored energy to the output terminals (230) through the anti-parallel diode associated with the third switch (190) and the alternating current (AC) returned back to phase through the antiparallel diode associated with the second switch (180). Graphical representation of the alternating current (AC) voltage (240), the alternating current (AC) (250) and the direct current (DC) voltage (260) is shown in FIG. 3.

Referring back to the FIG. 1, the uninterrupted power supply system (10) also includes a buck converter unit (50) electrically coupled to the rectifier unit (20). The buck converter unit (50) is adapted to step down the direct current (DC) voltage supplied by the rectifier unit (20) to charge an energy storage unit (60). In some embodiments, the energy storage unit (60) may include, but not limited to, a battery, a super capacitor and the like. In one embodiment, the buck converter unit (50) may include a first isolation transformer (110) adapted to isolate the energy storage unit (60) and the voltage source (40). In such an embodiment, the first isolation transformer (110) may be electrically coupled to the inverter unit (80) via a first bridge rectifier (130) when the voltage source (40) is supplying the alternating current (AC) voltage. In one embodiment, the buck converter unit (50) may include a third plurality of switches (150) composed of a material comprising silicon carbide or gallium nitride. In some embodiments, the buck converter unit (50) may be adapted to charge the energy storage unit (60) by at least one of a mode comprising constant current mode, and a constant voltage mode. In such an embodiment, the buck converter unit (50) may initially charge the energy storage unit (60) by constant current mode. Once the energy storage unit (60) achieves required voltage by constant current mode charging, the buck converter unit (50) may charge the energy storage unit (60) by constant voltage mode. Working of the buck converter unit (50) is explained in FIG. 4.

FIG. 4 is a schematic representation of another embodiment of the uninterrupted power supply system (10) of FIG. 1, depicting equivalent diagram of the buck converter unit (50) in accordance with an embodiment of the present disclosure. The third plurality of switches (150) include a fifth switch (270), a sixth switch (280), a seventh switch (290), an eighth switch (300), a nineth switch (310), a tenth switch (320), an eleventh switch (330) and a twelfth switch (340). Also, inductors coupled in series with primary coil and secondary coil of the first isolation transformer (110) is replaced by a second inductor (350). A second parallel capacitor (360) and a third parallel capacitor (370) may smoothen the input and output of the buck converter unit (50).

Further, working of the buck converter unit (50) may be explained as two parts such as mode 1 operation and mode 2 operation. In the mode 1 operation, negative current flow through the second inductor (350) may happen through, negative terminal of the buck converter unit (50), the eighth switch (300), the eleventh switch (330), the output terminals (380), the tenth switch (320), the second inductor (350), the first switch (170), and positive terminal of the buck converter unit (50). Positive current flow through the second inductor (350) may happen through, the positive terminal of the buck converter unit (50), the second inductor (350), the tenth switch (320), the output terminals (380), the eleventh switch (330), the eighth switch (300), and the negative terminals of the buck converter unit (50). During the negative current flow through the second inductor (350), slope of current flow is equal to sum of the input voltage and output voltage of the buck converter unit (50) divided by the inductance of the second inductor (350).

Also, during the positive current flow through the second inductor (350), slope of the current flow is equal to difference of the input voltage and output voltage of the buck converter unit (50) divided with the inductance of the second inductor (350). In the mode 2 operation, the fifth switch (270) and the nineth switch (310) remain turned on. Assuming, voltage across the output terminals of the buck converter unit (50) is positive during the positive current flow through the second inductor (350). The nineth switch (310) and the twelfth switch (340) start conducting. But there exist a delay for turning off the tenth switch (320) and the eleventh switch (330) before conduction of the nineth switch (310) and the twelfth switch (340) resulting in a zero voltage switching (ZVS). Current through the second inductor (350) may ramp down with a negative slope from a positive value to a negative value during the mode 2 operation.

Additionally, slope of the current flow is equal to negative of sum of the input voltage and output voltage of the buck converter unit (50) divided by the inductance of the second inductor (350). During this period the nineth switch (310) and the twelfth switch (340) remain in conduction mode, and the sixth switch (280) and the seventh switch (290) starts conducting, thereby making the input voltage of the buck converter unit (50) negative. Slope of the current flow is equal to difference between the output voltage and the input voltage divided with the inductance of the second inductor (350). The sixth switch (280) and the seventh switch (290) keep on conducting and the tenth switch (320) and the eleventh switch (330) start to conduct, thereby repeating the cycle.

Moreover, due to diagonal switching of the third plurality of switches (150) primary of the first isolation transformer (110) and the secondary of the first isolation transformer (110) receives pulsated voltage. Phase difference of the pulsated voltages may distinguish direction of the power transfer. Switching pulses (390), primary voltage (400) of the first isolation transformer (110), secondary voltage (410) of the first isolation transformer (110), current (420) through the second inductor (350) is shown in FIG. 5. Direct current (DC) voltage (430) at input side of the buck converter unit (50), current (440) flowing through high voltage side of the first isolation transformer (110) and the current (760) flowing through low voltage side of the first isolation transformer (110) is shown in FIG. 6.

Referring back to the FIG. 1, the uninterrupted power supply system (10) further includes a boost converter unit (70) electrically coupled to the energy storage unit (60). The boost converter unit (70) is adapted to step up an output voltage of the energy storage unit (60) to provide a stepped up voltage when the voltage source (40) fails to provide the alternating current (AC) voltage. In one embodiment, the boost converter unit (70) may include a second isolation transformer (120) adapted to isolate the energy storage unit (60) and the one or more loads (100). In one embodiment, the second isolation transformer (120) may be interfaced with the inverter unit (80) via a second bridge rectifier (140) adapted to rectify an output voltage provided by the boost converter unit (70). In one embodiment, the boost converter unit (70) may include a fourth plurality of switches (160) composed of a material comprising silicon carbide or gallium nitride. Working of the boost converter unit (70) is explained in detail in FIG.

7.

FIG. 7 is a schematic representation of another embodiment of the uninterrupted power supply system (10) of FIG. 1, depicting the boost converter unit (70) in accordance with an embodiment of the present disclosure. The fourth plurality of switches (160) includes a thirteenth switch (450), a fourteenth switch (460), a fifteenth switch (470) and a sixteenth switch (480). The fourth plurality of switches (160) may act as a square wave generator. The thirteenth switch (450) and the fifteenth switch (470) may conduct together, and the fourteenth switch (460) and sixteenth switch (480) may conduct together with 50 percentage duty cycles for each switch. The boost converter unit (70) includes a third inductor (490) and a fourth inductor (500) and a resonant capacitor (510). Primary winding of the second isolation transformer (120) receives square waves generated by the fourth plurality of switches (160) and the primary winding may transmit the square waves to the secondary winding.

Also, the second bridge rectifier (140) convert output of the second isolation transformer (120) to direct current. An output capacitor (520) may smoothen the direct current provided by the second bridge rectifier (140) Resonant frequency of the boost converter unit (70) is adjusted by varying the third inductor (490), fourth inductor (500) and the resonant capacitor (510). Difference between current flowing through the third inductor (490) and the fourth inductor (500) may be allowed to pass through the second isolation transformer (120). When current through the third inductor (490) exceeds the current through the fourth inductor (500) freewheeling operation occurs thereby nullifying the current flowing through secondary of the second isolation transformer (120). In such a scenario, the fourth inductor (500) arrive in resonance condition with the third inductor (490) and the resonant capacitor (510) and frequency at which the fourth inductor (500) arrive in resonance condition may be less than that of the actual resonance frequency.

Referring back to the FIG. 1, the uninterrupted power supply system (10) also includes an inverter unit (80) electrically coupled to the boost converter unit (70). The inverter unit (80) includes a second plurality of switches (90) adapted to invert the stepped up voltage provided by the boost converter unit (70) to feed one or more loads (100). The second plurality of switches (90) are interconnected in an H bridge configuration and controlled by a second plurality of corresponding pulses. The rectifier unit (20), the buck converter unit (50), the boost converter unit (70), and the inverter unit (80) are adapted to conduct bidirectionally. In one embodiment, the first plurality of switches (30), the second plurality of switches (90), the third plurality of switches (150) and the fourth plurality of switches (160) may be controlled by corresponding closed loop control technique. Direct current (DC) bus voltage (770), terminal voltage (780) of the energy storage unit (60), current (790) flowing through primary winding of the second isolation transformer (120) is shown in FIG. 8. Working of the inverter unit (80) is described in detail in FIG. 9.

FIG. 9 is a schematic representation of another embodiment of the uninterrupted power supply system (10) of FIG. 1, depicting the inverter unit (80) in accordance with an embodiment of the present disclosure. The second plurality of switches (90) includes a seventeenth switch (530), an eighteenth switch (540), a nineteenth switch (550), and a twentieth switch (560). The seventeenth switch (530) and the eighteenth switch (540) constitutes a first leg (570) of the inverter unit (80). The nineteenth switch (550) and the twentieth switch (560) constitutes the second leg (580) of the inverter unit (80). The second plurality of corresponding pulses are being generated by interposing a triangular wave (FIG. 10, 590) with a first wave (FIG. 10, 600) and a second wave (FIG. 10, 610) which are 180 degree out of phase. When value of the triangular wave (590) is greater than value of the first wave (600) the seventeenth switch (530) is turned on.

Further, when value of the triangular wave (590) is less than the first wave (600) the eighteenth switch (540) is turned on. The seventeenth switch (530) and the eighteenth switch (540) are getting complimentary pulses. When value of the triangular wave (590) is greater than value of the second wave (610) the nineteenth switch (550) is turned on. When value of the triangular wave (590) is less than the second wave (610) the twentieth switch (560) is turned on. The nineteenth switch (550) and the twentieth switch (560) are getting complimentary pulses. When the seventeenth switch (530) and the twentieth switch (560) are turned on simultaneously, voltage across the first leg (570) is an input voltage provided to the inverter unit (80), voltage across the second leg (580) is zero, and voltage across output terminals (620) of the inverter unit (80) is the input voltage provided to the inverter unit (80). When the eighteenth switch (540) and the nineteenth switch (550) are turned on simultaneously, voltage across the first leg (570) is zero, voltage across the second leg (580) is input voltage provided to the inverter unit (80), and voltage across output terminals (620) of the inverter unit (80) is negative value of the input voltage provided to the inverter unit (80).

Furthermore, when the seventeenth switch (530) and the nineteenth switch (550) are turned on simultaneously, voltage across the first leg (570) and the second leg (580) is the input voltage provided to the inverter unit (80), and voltage across output terminals (620) of the inverter unit (80) is zero. When the eighteenth switch (540) and the twentieth switch (560) are turned on simultaneously, voltage across the first leg (570), the second leg (580), and the output terminals (620) are zero. Interposition of the triangular wave (590) on the first wave (600) and the second wave (610), the voltage across (630) the first leg (570), the voltage (640) across the second leg (580), and the voltage (650) across the output terminals (620) of the inverter unit (80) is shown in FIG. 10. Sinusoidal pulse width modulated line voltage (660) generated by the inverter unit (80), output voltage (670) of the inverter unit (80), output current (680) of the inverter unit (80) is shown in FIG. 11. Output voltage (670) may be obtained after filtering the sinusoidal pulse width modulated line voltage (660) by a LC filter. Various configurational stages of the uninterrupted power supply system (10) is shown in FIG. 12.

FIG. 12 is a schematic representation of another embodiment of the uninterrupted power supply system (10) of FIG. 1, depicting various configurational stages in accordance with an embodiment of the present disclosure. Interconnection of stage 1 (690), stage 2 (700) and stage 3 (710) may function as a power factor corrected battery charger, or a power factor corrected float cum boost charger, or a power factor corrected direct current supply. Interconnection of the stage 1 (690), the stage 2 (700) and the stage 4 (720) may function as a static voltage cum frequency stabilizer, or a power factor corrected variable frequency drive. Interconnection of the stage 2 (700) and the stage four may function as a sine wave inverter. The stage 1 (690) may alone function as a bidirectional alternating current (AC) to direct current (DC) converter or an active power filter. The stage 1 (690), the stage 2 (700), the stage 3 (710) and the stage 4 (720) may function as single phase to three phase bi-directional converter upon omitting the first bridge rectifier (130), a series inductor and a parallel capacitor associated with the first bridge rectifier (130). In such a scenario the first coupling points (730) are connected to second coupling points (740) and the stage 4 (720) may include a three phase inverter.

Further, the stage 1 (690), the stage 2 (700), the stage 3 (710) and the stage 4 (720) may function as three phase to single phase bi-directional converter upon omitting the first bridge rectifier (130), the series inductor, the parallel capacitor associated with the first bridge rectifier (130) and connecting the first coupling points (730) to second coupling points (740). In such a scenario the stage 1 (690) may include a three phase rectifier. The stage 1 (690), the stage 2 (700), the stage 3 (710) and the stage 4 (720) may function as a solid state transformer. The stage 2 (700) and the stage 4 (720) along with a series inductor (750) may function as a grid interactive inverter. In one embodiment, when the voltage source is feeding power, the stage 3 (710) may act as a buck converter to charge the energy storage unit (60). When the voltage source fails, the stage 3 (710) may act as a boost converter boosting the voltage of the energy storage unit (60) to feed the loads via the stage 4 (720). The capacitor connected in parallel with the first isolation transformer (130) may ensure continuous flow of power to the load during switching of the stage 3 (710).

FIG. 13 is a flow chart representing the steps involved in a method (800) of operation of an uninterrupted power supply system for providing power flow with input power factor correction in accordance with an embodiment of the present disclosure. The method (800) includes providing a direct current (DC) voltage corresponding to an alternating current (AC) voltage supplied by a voltage source in step 810. In one embodiment, providing a direct current (DC) voltage corresponding to an alternating current (AC) voltage supplied by a voltage source includes providing a direct current (DC) voltage corresponding to an alternating current (AC) voltage supplied by a voltage source by a rectifier unit. The rectifier unit includes a first plurality of switches controlled by a first plurality of corresponding pulses to maintain an alternating current (AC) supplied by the voltage source in phase with the alternating current (AC) voltage supplied by the voltage source. In one embodiment, the rectifier unit is capable of boosting the direct current voltage (DC) to any desired level. In some embodiments, the rectifier unit may be capable of rectifying three phase alternating current (AC) voltage supplied by the voltage source. The method (800) also includes stepping down the direct current (DC) voltage supplied by the rectifier unit to charge an energy storage unit in step 820. In one embodiment, stepping down the direct current (DC) voltage supplied by the rectifier unit to charge an energy storage unit includes stepping down the direct current (DC) voltage supplied by the rectifier unit to charge an energy storage unit by a buck converter unit. In some embodiments, the energy storage unit may include, but not limited to, a battery, a super capacitor and the like. In one embodiment, the buck converter unit may include a first isolation transformer adapted to isolate the energy storage unit and the voltage source. In such an embodiment, the first isolation transformer may be electrically coupled to the inverter unit via a first bridge rectifier when the voltage source is supplying the alternating current (AC) voltage. In one embodiment, the buck converter unit may include a third plurality of switches composed of a material comprising silicon carbide or gallium nitride.

The method (800) further includes stepping up an output voltage of the energy storage unit to provide a stepped up voltage when the voltage source fails to provide the alternating current (AC) voltage in step 830. In one embodiment, stepping up an output voltage of the energy storage unit to provide a stepped up voltage when the voltage source fails to provide the alternating current (AC) voltage includes stepping up an output voltage of the energy storage unit to provide a stepped up voltage when the voltage source fails to provide the alternating current (AC) voltage by a boost converter unit. In one embodiment, the boost converter unit may include a second isolation transformer adapted to isolate the energy storage unit and the one or more loads. In one embodiment, the second isolation transformer may be interfaced with the inverter unit via a second bridge rectifier adapted to rectify an output voltage provided by the boost converter. In one embodiment, the boost converter unit may include a fourth plurality of switches composed of a material comprising silicon carbide or gallium nitride. In some embodiments, the buck converter may be adapted to charge the energy storage unit by at least one of a mode comprising constant current mode, and a constant voltage mode.

The method (800) also includes inverting the stepped up voltage provided by the boost converter to feed one or more loads in step 840. In one embodiment, inverting the stepped up voltage provided by the boost converter to feed one or more loads includes inverting the stepped up voltage provided by the boost converter to feed one or more loads by a second plurality of switches of an inverter unit. The second plurality of switches are interconnected in an H bridge configuration and controlled by a second plurality of corresponding pulses. The rectifier unit, the buck converter unit, the boost converter unit, and the inverter unit are adapted to conduct bidirectionally. In one embodiment, the first plurality of switches, the second plurality of switches, the third plurality of switches and the fourth plurality of switches may be controlled by corresponding closed loop control technique.

Various embodiments of the uninterrupted power supply system and method for providing power flow with input power factor correction described above enable various advantages. Provisional of the first isolation transformer and the second isolation transformer provides isolation thereby eliminating the electromagnetic interference thereby improving power quality. The first isolation transformer and the second isolation transformer also support high frequency operation, thereby reducing footprint of the uninterrupted power supply system. The uninterrupted power supply system is modular and easy to operate. Provision of the rectifier unit equipped with power factor correction capability improves power factor. Improving the power factor increases efficiency by reducing loses, reduces operational cost, and also provides better regulation. Also the uninterrupted power supply system is capable of being reconfigured as the power factor corrected battery charger, the power factor corrected float cum boost charger, the power factor corrected direct current supply, the static voltage cum frequency stabilizer, the power factor corrected variable frequency drive, the sine wave inverter, the bidirectional alternating current (AC) to direct current (DC) converter, the active power filter, the single phase to three phase bi-directional converter, the three phase to single phase bi-directional converter, the three phase rectifier, the solid state transformer, and the grid connected inverter. The uninterrupted power supply system is capable of transmitting power bidirectionally.

It will be understood by those skilled in the art that the foregoing general description and the following detailed description are exemplary and explanatory of the disclosure and are not intended to be restrictive thereof. While specific language has been used to describe the disclosure, any limitations arising on account of the same are not intended. The figures and the foregoing description give examples of embodiments. Those skilled in the art will appreciate that one or more of the described elements may well be combined into a single functional element. Alternatively, certain elements may be split into multiple functional elements. Elements from one embodiment may be added to another embodiment. For example, the order of processes described herein may be changed and are not limited to the manner described herein. Moreover, the actions of any flow diagram need not be implemented in the order shown; nor do all the acts need to be necessarily performed. Also, those acts that are not dependent on other acts may be performed in parallel with the other acts. The scope of embodiments is by no means limited by these specific examples.

Claims

WE CLAIM:

1. An uninterrupted power supply system (10) for providing power flow with input power factor correction comprising: a rectifier unit (20) comprising a first plurality of switches (30), wherein the rectifier unit (20) is adapted to provide a direct current (DC) voltage corresponding to an alternating current (AC) voltage supplied by a voltage source (40), wherein the first plurality of switches (30) are controlled by a first plurality of corresponding pulses to maintain an alternating current (AC) supplied by the voltage source (40) in phase with the alternating current (AC) voltage supplied by the voltage source (40); a buck converter unit (50) electrically coupled to the rectifier unit (20), wherein the buck converter unit (50) is adapted to step down the direct current (DC) voltage supplied by the rectifier unit (20) to charge an energy storage unit (60); a boost converter unit (70) electrically coupled to the energy storage unit (60), wherein the boost converter unit (70) is adapted to step up an output voltage of the energy storage unit (60) to provide a stepped up voltage when the voltage source (40) fails to provide the alternating current (AC) voltage; and an inverter unit (80) electrically coupled to the boost converter unit (70), wherein the inverter unit (80) comprises a second plurality of switches (90) adapted to invert the stepped up voltage provided by the boost converter to feed one or more loads (100), wherein the second plurality of switches (90) are interconnected in an H bridge configuration and controlled by a second plurality of corresponding pulses, wherein the rectifier unit (20), the buck converter unit (50), the boost converter unit (70), and the inverter unit (80) are adapted to conduct bidirectionally.

2. The uninterrupted power supply system (10) as claimed in claim 1, wherein the buck converter unit (50) comprises a first isolation transformer (110) adapted to isolate the energy storage unit (60) and the voltage source (40).

3. The uninterrupted power supply system (10) as claimed in claim 1, wherein the boost converter unit (70) comprises a second isolation transformer (120) adapted to isolate the energy storage unit (60) and the one or more loads (100).

4. The uninterrupted power supply system (10) as claimed in claim 2, wherein the first isolation transformer (110) is electrically coupled to the inverter unit (80) via a first bridge rectifier (130) when the voltage source (40) is supplying the alternating current (AC) voltage.

5. The uninterrupted power supply system (10) as claimed in claim 3, wherein the second isolation transformer (120) is interfaced with the inverter unit (80) via a second bridge rectifier (140) adapted to rectify an output voltage provided by the boost converter.

6. The uninterrupted power supply system (10) as claimed in claim 1, wherein the buck converter unit (50) and the boost converter unit (70) comprises a third plurality of switches (150) and fourth plurality of switches (160), wherein the first plurality of switches (30), the second plurality of switches (90), the third plurality of switches (150) and the fourth plurality of switches (160) are composed of a material comprising silicon carbide or gallium nitride.

7. The uninterrupted power supply system (10) as claimed in claim 6, wherein the first plurality of switches (30), the second plurality of switches (90), the third plurality of switches (150) and the fourth plurality of switches (160) are controlled by corresponding closed loop control technique.

8. The uninterrupted power supply system (10) as claimed in claim 1, wherein the buck converter unit (50) is adapted to charge the energy storage unit (60) by at least one of a mode comprising a constant current mode, and a constant voltage mode.

9. A method (800) comprising: providing, by a rectifier unit, a direct current (DC) voltage corresponding to an alternating current (AC) voltage supplied by a voltage source, wherein the rectifier unit comprises a first plurality of switches controlled by a first plurality of corresponding pulses to maintain an alternating current (AC) supplied by the voltage source in phase with the alternating current (AC) voltage supplied by the voltage source; (810) stepping down, by a buck converter unit, the direct current (DC) voltage supplied by the rectifier unit to charge an energy storage unit; (820) stepping up, by a boost converter unit, an output voltage of the energy storage unit to provide a stepped up voltage when the voltage source fails to provide the alternating current (AC) voltage; (830) and inverting, by a second plurality of switches of an inverter unit, the stepped up voltage provided by the boost converter to feed one or more loads, wherein the second plurality of switches are interconnected in an H bridge configuration and controlled by a second plurality of corresponding pulses, wherein the rectifier unit, the buck converter unit, the boost converter unit, and the inverter unit are adapted to conduct bidirectionally. (840)