Description:FIELD OF THE INVENTION
The present invention relates to a field of power electronics and in particularly relates to a Power electronics transformer (PET) for switching current voltage and a method thereof.

BACKGROUND OF THE INVENTION

With the development of distributed new energy power generation technology and the increase of direct current power equipment, the demand for low voltage direct current power distribution is rising. Conventional solutions generally use an industrial frequency transformer to convert a medium voltage alternating current (MVAC) into a low voltage alternating current first, and then use an AC/DC converter to convert the low voltage alternating current to a low voltage direct current (LVDC).

A transformer can be used to change and transmit electric power from one voltage level to another voltage level. It can also maintain isolation between two voltage level circuitry. Typically, the transformer is one of the heaviest, bulkiest and most expensive parts in a transmission and distribution system. The large size of the transformer is due, in part, to the low frequency of operation. Power density increases as the operating frequency of the transformer increases, resulting in a smaller transformer size and weight. To change operating frequency from a Hz level to a kHz level, power electronics can be used. Power electronics in combination with reduced sized, high-frequency transformers is known as power electronic transformers.

Power electronics transformers have emerged as very exciting alternative to the conventional line frequency transformer, as they offer significantly high power density and are active devices as opposed to a passive line frequency transformer. As a result, they are being employed in numerous applications such as smart grids, micro grids, electric vehicle charging systems, railway traction and transmission and distribution systems and so on.

A conventional PET incorporates a high-frequency link for the purpose of imparting galvanic isolation between the primary and secondary sides, in addition to various stages of power conversion viz., (a) low frequency ac to dc; (b) dc to high frequency ac which is fed to the primary side of the high frequency transformer; (c) high frequency ac of the secondary of the high frequency transformer is converted to dc; and (d) dc is then converted to low frequency ac. There are numerous PET available in the market as follows:

In one solution, a power electronic transformers having a high-frequency link is provided. The apparatus include a transformer having a primary winding and a secondary winding, the transformer is configured to receive a primary power signal having a first frequency, a primary converter configured to selectively oscillate polarity of the primary windings with respect to the secondary windings at a second frequency, the second frequency substantially substantially higher than the first frequency, a secondary converter coupled to the secondary winding, the secondary converter configured to provide a load power signal using a high frequency power signal generated using the secondary winding. The secondary converter can be configured to reduce current flow in the primary winding when the polarity of the primary winding is switched, the reduced current follow is configured to reduce disturbances resulting from leakage inductance of the transformer.

In another solution, a power conversion device, includes a multilevel converter configurable to convert an input waveform having a first frequency into a second waveform having a second frequency, wherein the second frequency is higher than the first frequency; a transformer coupled to the multilevel converter and configurable to transform the second waveform from a first voltage level to a second voltage level, wherein the first voltage level is higher than the second voltage level; and a switched inverter circuit coupled to the transformer and configurable to convert the transformed, second waveform into a third waveform for use with a power application.

The above-mentioned prior arts disclose about the PETs but has following limitations:
(a) Requirement of high (or medium) frequency magnetic material (e.g. ferrite, amorphous or nano-crystalline magnetic materials) which are difficult to process for core-design and the methodology is difficult, cumbersome and expensive.
(b) Requirement of high frequency power switches (and complex techniques to operate them and reduce the switching losses) and associated gate driver units.
(c) Many stages of power conversion, leading to a greatly increased component count and reduced reliability.

Therefore, in order to overcome the limitation of the above mentioned prior arts, there exists a need for developing a Power electronics transformer (PET) and a process for switching current voltage.

The technical advancements disclosed by the present invention overcomes the limitations and disadvantages of existing and conventional systems and methods.

SUMMARY OF THE INVENTION

The present invention relates to a field of power electronics and in particularly relates to a Power electronics transformer (PET) for switching current voltage and a method thereof.

An object of the present invention is to utilize formulated switched-capacitors based power converters units which are capable of performing multiple functions: voltage transformation (step-up or step-down), ac-to-dc conversion, dc-to-ac conversion, and enabling galvanic isolation between the primary and secondary sides at the all the switching combinations.

Another objective of the present invention is to provide switched-capacitors which inherent capability of stepping-up/stepping down the voltage levels.

Yet another objective of the present invention is to perform operation in three modes: buck mode, boost mode and unity-gain mode.

In an embodiment, a Power electronics transformer (PET) for switching current voltage is provided. The transformer includes a first switched capacitor based power convertor incorporated with a semiconductor-based-galvanic-isolation to receive an input of alternative current (AC) voltage from a load, wherein the first switched capacitor based power convertor with the semiconductor-based-galvanic-isolation adapted to convert the alternative current (AC) voltage into Direct current (DC) voltage; wherein if the first power convertor provides gain in the output DC voltage while converting from the AC voltage into the DC voltage and the output DC voltage gets higher than a predefined threshold voltage then the first power convertor acts as a buck convertor adapted to reduce the high DC voltage to the predefined threshold DC voltage; a second switched capacitor based power convertor incorporated with the semiconductor-based-galvanic-isolation adapted to receive Direct current (DC) voltage from the first switched capacitor based power convertor, wherein if the received DC voltage is lower than predefined threshold DC voltage then the second switched capacitor based power convertor acts a boost convertor adapted to increase low DC voltage to the predefined threshold DC voltage; wherein if the received DC voltage is higher than the predefined threshold voltage then the second switched capacitor based power convertor acts the buck convertor adapted to reduce the high DC voltage to the predefined threshold DC voltage; wherein the second switched capacitor based power convertor adapted to convert the Direct current (DC) voltage into alternative current (AC) voltage, wherein the second switched capacitor based power convertor adapted to provide final AC voltage to a source.

In another embodiment, wherein the second switched capacitor based power convertor is electrically connected with the first switched capacitor based power convertor.

In another embodiment, wherein the first switched capacitor based power convertor receives alternative current (AC) voltage as an input from n number of phases.

In another embodiment, the first switched capacitor based power convertor provides a wide range of the output DC voltage for a fixed input AC voltage.

In another embodiment, the second switched capacitor based power convertor provides alternative current (AC) voltage as an output to m number of phases.
In another embodiment, wherein the second switched capacitor based power convertor further configured to add number of levels to waveform of the Output AC voltage.

In another embodiment, the semiconductor based galvanic isolation comprising a first set of power switches and a second set of power switches, wherein when the first set of power switches are in ON state then the semiconductor based galvanic isolation does not conduct current in the transformer.

In another embodiment, when the second set of power switches are in OFF state then the semiconductor based galvanic isolation conducts current in the transformer.

In another embodiment, a process for switching current voltage by implementing transformer is provided. The process includes of receiving, by a first switched capacitor based power convertor, an input of alternative current (AC) voltage from a load; converting, by the first switched capacitor based power convertor, the alternative current (AC) voltage into Direct current (DC) voltage, wherein the first switched capacitor based power convertor is incorporated with a semiconductor-based-galvanic-isolation; reducing, by the first convertor as a buck convertor, high DC voltage to predefined threshold DC voltage when the first power convertor provides gain in the output DC voltage while converting from the AC voltage into the DC voltage and the output DC voltage gets higher than the predefined threshold voltage; receiving, by a second switched capacitor based power convertor, Direct current (DC) voltage from the first switched capacitor based power convertor, wherein the second switched capacitor based power convertor is incorporated with the semiconductor-based-galvanic-isolation; increasing, by the second power convertor as a boost convertor, the low DC voltage to the predefined threshold DC voltage when the received DC voltage is lower than predefined threshold DC voltage; providing, by the second switched capacitor based power convertor, final AC voltage to a source.

In another embodiment, the method includes of reducing, by the second switched capacitor based power convertor acts a buck convertor, the DC voltage from high DC voltage to the predefined threshold DC voltage when the received DC voltage is higher than the predefined threshold voltage.

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

BRIEF DESCRIPTION OF FIGURES

These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
Figure 1 illustrates illustrates a flow diagram of process for switching current voltage by implementing transformer in accordance with an embodiment of the present invention;
Figure 2 illustrates a block diagram of Power electronics transformer (PET) for switching current voltage in accordance with an embodiment of the present invention;
Figure 3 illustrates connection of the first power convertor Power and second power convertor with the semiconductor-based-galvanic-isolation in electronics transformer (PET) in accordanve with an embodiment of the present invention;
Figure 4 illustrates claimed PET with semiconductor-based-galvanic-isolation in first stage in accordanve with an embodiment of the present invention;
Figure 5 illustrates claimed PET with semiconductor-based-galvanic-isolation in second stage in accordanve with an embodiment of the present invention;
Figure 6 illustrates exemplary implementation of claimed PET with semiconductor-based-galvanic-isolation at first stage in accordanve with an embodiment of the present invention;
Figure 7 illustrates exemplary implementation of claimed PET with semiconductor-based-galvanic-isolation at second stage in accordanve with an embodiment of the present invention.
Further, skilled artisans will appreciate that elements in the drawings are illustrated for simplicity and may not have been necessarily been drawn to scale. For example, the flow charts illustrate the method in terms of the most prominent steps involved to help to improve understanding of aspects of the present disclosure. Furthermore, in terms of the construction of the device, one or more components of the device may have been represented in the drawings by conventional symbols, and the drawings may show only those specific details that are pertinent to understanding the embodiments of the present disclosure so as not to obscure the drawings with details that will be readily apparent to those of ordinary skill in the art having benefit of the description herein.
DETAILED DESCRIPTION:
For the purpose of promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated system, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.
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 invention and are not intended to be restrictive thereof.
Reference throughout this specification to “an aspect”, “another aspect” or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrase “in an embodiment”, “in another embodiment” and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.
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 process or method. Similarly, one or more devices or sub-systems or elements or structures or components proceeded by "comprises...a" does not, without more constraints, preclude the existence of other devices or other sub-systems or other elements or other structures or other components or additional devices or additional sub-systems or additional elements or additional structures or additional components.
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The system, methods, and examples provided herein are illustrative only and not intended to be limiting.
Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
The present invention develops a truly zero-magnetics-technology for power-electronics-transformers (PETs), using the newly proposed concepts of semiconductor based galvanic isolation and switched-capacitors based ac-to-dc and dc-to-ac conversion. The present invention vastly reduces the design complexity, design costs and number of stages in conventional PETs and greatly increase their power density. The present invention eliminates the need for intermediate high frequency operation in conventional PETs, thereby increasing the efficiency. It has two back-to-back connected switched-capacitors-based units (SCUs). Each SCU is capable of performing both ac-to-dc and dc-to-ac power conversions. Each (newly conceptualized) SCU also incorporates galvanic isolation between input and output using semiconductor based switching structure. Thus, a galvanically isolated voltage-transformation (i.e. step-up or step-down) function in the claimed trasformer is performed by the SCUs, with the front-end (or primary) SCU performing a unity power factor operation along with a wide range of controllable output dc, whereas the secondary SCU performs dc-ac conversion.

Figure 1 illustrates a flow diagram of process (100) for switching current voltage by implementing transformer in accordance with an embodiment of the present invention. The process comprising steps of:
Step (102) discloses about receiving, by a first switched capacitor based power convertor, an input of alternative current (AC) voltage from a load;
Step (104) discloses about converting, by the first switched capacitor based power convertor, the alternative current (AC) voltage into Direct current (DC) voltage, wherein the first switched capacitor based power convertor is incorporated with a semiconductor-based-galvanic-isolation;
Step (106) discloses about reducing, by the first convertor as a buck convertor, high DC voltage to predefined threshold DC voltage when the first power convertor provides gain in the output DC voltage while converting from the AC voltage into the DC voltage and the output DC voltage gets higher than the predefined threshold voltage;
Step (108) discloses about increasing, by the second power convertor as a boost convertor, the low DC voltage to the predefined threshold DC voltage when the received DC voltage is lower than predefined threshold DC voltage; and
Step (110) discloses about providing, by the second switched capacitor based power convertor, final AC voltage to a source.

In an embodiement, the method (100) includes of reducing, by the second switched capacitor based power convertor acts a buck convertor, the DC voltage from high DC voltage to the predefined threshold DC voltage when the received DC voltage is higher than the predefined threshold voltage.

Figure 2 illustrates a block diagram of Power electronics transformer (PET) (200) for switching current voltage in accordance with an embodiment of the present invention. The transformer (200) includes a first switched capacitor based power convertor (202) incorporated with a semiconductor-based-galvanic-isolation (206) to receive an input of alternative current (AC) voltage from a load, wherein the first switched capacitor based power convertor (202) with the semiconductor-based-galvanic-isolation (206) adapted to convert the alternative current (AC) voltage into Direct current (DC) voltage; wherein if the first power convertor (202) provides gain in the output DC voltage while converting from the AC voltage into the DC voltage and the output DC voltage gets higher than a predefined threshold voltage then the first power convertor (202) acts as a buck convertor adapted to reduce the high DC voltage to the predefined threshold DC voltage; a second switched capacitor based power convertor (204) incorporated with the semiconductor-based-galvanic-isolation (206) adapted to receive Direct current (DC) voltage from the first switched capacitor based power convertor (202), wherein if the received DC voltage is lower than predefined threshold DC voltage then the second switched capacitor based power convertor (204) acts a boost convertor adapted to increase low DC voltage to the predefined threshold DC voltage; wherein if the received DC voltage is higher than the predefined threshold voltage then the second switched capacitor based power convertor (204) acts the buck convertor adapted to reduce the high DC voltage to the predefined threshold DC voltage; wherein the second switched capacitor based power convertor (204) adapted to convert the Direct current (DC) voltage into alternative current (AC) voltage, wherein the second switched capacitor based power convertor (204) adapted to provide final AC voltage to a source.
In another embodiment, wherein the second switched capacitor based power convertor (204) is electrically connected with the first switched capacitor based power convertor (202).

In another embodiment, wherein the first switched capacitor based power convertor (202) receives alternative current (AC) voltage as an input from n number of phases.

In another embodiment, the first switched capacitor based power convertor (202) provides a wide range of the output DC voltage for a fixed input AC voltage.

In another embodiment, the second switched capacitor based power convertor (204) provides alternative current (AC) voltage as an output to m number of phases.

In another embodiment, wherein the second switched capacitor based power convertor (204) further configured to add number of levels to waveform of the Output AC voltage.

In another embodiment, the semiconductor based galvanic isolation (206) comprising a first set of power switches (206a) and a second set of power switches (206b), wherein when the first set of power switches (206a) are in ON state then the semiconductor based galvanic isolation does not conduct current in the transformer.

In another embodiment, when the second set of power switches (206b) are in OFF state then the semiconductor based galvanic isolation (206) conducts current in the transformer.

Figure 3 illustrates connection of the first power convertor Power and second power convertor with the semiconductor-based-galvanic-isolation in electronics transformer (PET) in accordanve with an embodiment. The switched capacitors based power converters units (SCUs) are used to provide galvanic isolation with the help of semiconductor power switches. The claimed PET utilizes semiconductor based galvanic isolation. The SCUs comprise power switches. When a power switch is in OFF state, it does not conduct current whereas in the ON state, it conducts. Since there are multiple power switches in each SCU, there are numerous switching combinations (i.e some switches are ON while some are OFF). Now, a SCU can be so structured that for some of switching combinations, few of the SCs are electrically connected to the source side and electrically disconnected from the load. Similarly, for other switching states, few of the SCs are electrically disconnected from the source, but are electrically connected with the load, thereby feeding power to it. Hence, these SCs also act as buffer for the flow of power between the source and the load.
The first set of switched-capacitors based power converter unit (SCU-I) with the capability to perform ac-to-dc power conversion with unity power factor operation along with a wide range of controllable dc output. The SCUs is able to operate in three modes while performing ac-to-dc conversion: buck mode, boost mode and unity-gain mode.
Figure 4 illustrates claimed PET with semiconductor-based-galvanic-isolation in first stage in accordanve with an embodiment of the present invention and Figure 5 illustrates claimed PET with semiconductor-based-galvanic-isolation in second stage in accordanve with an embodiment of the present invention. The claimed PET utilizes newly formulated SC based multilevel converters to achieve voltage transformation. These converters are capable of performing dc-to-ac as well as ac-to-dc power conversion. So, while performing a dc-to-ac conversion, if a SC based converter offers voltage gain (i.e. inherent boost), then it will perform a buck operation while doing ac-to-dc conversion. This has been demonstrated by the investigators in the OTD section.
The claimed PET utilizes semiconductor based galvanic isolation. The SCUs comprise power switches. When a power switch is in OFF state, it does not conduct current whereas in the ON state, it conducts. Since there are multiple power switches in each SCU, there are numerous switching combinations (i.e some switches are ON while some are OFF). Now, a SCU can be so structured that for some of switching combinations, few of the SCs are electrically connected to the source side and electrically disconnected from the load. Similarly, for other switching states, few of the SCs are electrically disconnected from the source, but are electrically connected with the load, thereby feeding power to it. Hence, these SCs also act as buffer for the flow of power between the source and the load. One such power converter topology formulated by the investigators is described in the OTD section of the proposal. Both the SCUs can thus be structured to form a back-to-back configuration to perform the desired functions without the need of a high frequency isolation link.
Incorporating semiconductor-based-galvanic-isolation (SGI) to both the sets of SCUs. Each SCU has input and output terminals. The topology and modulation scheme are to be conceptualized in a manner that in each state (with a specific set of power switches conducting), the input and output terminals are electrically isolated.
Figure 6 illustrates exemplary implementation of claimed PET with semiconductor-based-galvanic-isolation at first stage in accordanve with an embodiment of the present invention. The power circuit of SCU-I has five power switches in one-leg, and an ability to generate three output levels in the pole voltage. On using two similar legs generate a five-level voltage waveform at the rectifier input, viz. ±2Vdc, ±Vdc and 0. The switching states are shown in Table I, along with the charging/discharging status of the capacitors.
Figure 7 illustrates exemplary implementation of claimed PET with semiconductor-based-galvanic-isolation at second stage. Integration of the SCUs with SGI in a back-to-back manner to achieve ac-ac conversion with voltage transformation and galvanic isolation. These SCUs are to be conceptualized for both single- and three-phase systems and integrated control schemes are to be developed. The conceptualized SCUs are to be analysed by carrying out simulation and experimental studies, for step-up and step-down operations with controllable voltage level and frequency. The topologies conceptualized for SCU-I and SCU-II will be connected back-to-back with an integrated control to achieve the purpose.

The drawings and the forgoing description give examples of embodiments. Alternatively, certain elements are split into multiple functional elements. Elements from one embodiment may be added to another embodiment. For example, orders of processes described herein are 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 of the acts necessarily need to be 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. Numerous variations, whether explicitly given in the specification or not, such as differences in structure, dimension, and use of material, are possible. The scope of embodiments is at least as broad as given by the following claims.
Benefits, other advantages, and solutions to problems have been described above with regard to specific embodiments. However, the benefits, advantages, solutions to problems, and any component(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential feature or component of any or all the claims. , Claims:1. A Power electronics transformer (PET) for switching current voltage, said transformer comprising:
a first switched capacitor based power convertor incorporated with a semiconductor-based-galvanic-isolation to receive an input of alternative current (AC) voltage from a load, wherein the first switched capacitor based power convertor with the semiconductor-based-galvanic-isolation adapted to convert the alternative current (AC) voltage into Direct current (DC) voltage;
wherein if the first power convertor provides gain in the output DC voltage while converting from the AC voltage into the DC voltage and the output DC voltage gets higher than a predefined threshold voltage then the first power convertor acts as a buck convertor adapted to reduce the high DC voltage to the predefined threshold DC voltage;
a second switched capacitor based power convertor incorporated with the semiconductor-based-galvanic-isolation adapted to receive Direct current (DC) voltage from the first switched capacitor based power convertor, wherein if the received DC voltage is lower than predefined threshold DC voltage then the second switched capacitor based power convertor acts a boost convertor adapted to increase low DC voltage to the predefined threshold DC voltage;
wherein if the received DC voltage is higher than the predefined threshold voltage then the second switched capacitor based power convertor acts the buck convertor adapted to reduce the high DC voltage to the predefined threshold DC voltage;
wherein the second switched capacitor based power convertor adapted to convert the Direct current (DC) voltage into alternative current (AC) voltage, wherein the second switched capacitor based power convertor adapted to provide final AC voltage to a source.
2. The transformer as claimed in claim 1, wherein the second switched capacitor based power convertor is electrically connected with the first switched capacitor based power convertor.
3. The transformer as claimed in claim 1, wherein the first switched capacitor based power convertor receives alternative current (AC) voltage as an input from n number of phases.
4. The transformer as claimed in claim 3, wherein the first switched capacitor based power convertor provides a wide range of the output DC voltage for a fixed input AC voltage.
5. The transformer as claimed in claim 1, wherein the second switched capacitor based power convertor provides alternative current (AC) voltage as an output to m number of phases.
6. The transformer as claimed in claim 5, wherein the second switched capacitor based power convertor further configured to add number of levels to waveform of the Output AC voltage.
7. The transformer as claimed in claim 1, wherein the semiconductor based galvanic isolation comprising a first set of power switches and a second set of power switches, wherein when the first set of power switches are in ON state then the semiconductor based galvanic isolation does not conduct current in the transformer.
8. The transformer as claimed in claim 7, wherein when the second set of power switches are in OFF state then the semiconductor based galvanic isolation conducts current in the transformer.
9. A process for switching current voltage by implementing transformer as claimed in claim 1, wherein the process comprising:
receiving, by a first switched capacitor based power convertor, an input of alternative current (AC) voltage from a load;
converting, by the first switched capacitor based power convertor, the alternative current (AC) voltage into Direct current (DC) voltage, wherein the first switched capacitor based power convertor is incorporated with a semiconductor-based-galvanic-isolation;
reducing, by the first convertor as a buck convertor, high DC voltage to predefined threshold DC voltage when the first power convertor provides gain in the output DC voltage while converting from the AC voltage into the DC voltage and the output DC voltage gets higher than the predefined threshold voltage;
receiving, by a second switched capacitor based power convertor, Direct current (DC) voltage from the first switched capacitor based power convertor, wherein the second switched capacitor based power convertor is incorporated with the semiconductor-based-galvanic-isolation;
increasing, by the second power convertor as a boost convertor, the low DC voltage to the predefined threshold DC voltage when the received DC voltage is lower than predefined threshold DC voltage;
providing, by the second switched capacitor based power convertor, final AC voltage to a source.
10. The process as claimed in claim 9, further comprising of reducing, by the second switched capacitor based power convertor acts a buck convertor, the DC voltage from high DC voltage to the predefined threshold DC voltage when the received DC voltage is higher than the predefined threshold voltage.