DESC:ENERGY STORAGE SYSTEM FOR ELIMINATING CIRCULATING CURRENT
CROSS-REFERENCE TO RELATED APPLICATIONS
The present application claims priority from Indian Provisional Patent Application No. 202321006468 filed on 01/02/2023, the entirety of which is incorporated herein by a reference.
TECHNICAL FIELD
The present disclosure generally relates to energy storage systems. Particularly, the present disclosure relates to an energy storage system for eliminating circulating current. Furthermore, the present disclosure relates to eliminating circulating current in an energy storage system.
BACKGROUND
Conventionally, the energy has been generated from non-renewable sources as the same has been a reliable source of energy for humans for a long period. However, non-renewable energy sources cause harm to the environment. As the environmental destruction and the depletion of energy resources continue, newer sources of renewable energy are increasingly drawing attention. Renewable energy that does not generate pollution. However, renewable energy sources are not able to supply constant power for a long period. Thus, a lot of research is being conducted for the development of energy storage systems, that in combination with renewable sources can replace the existing non-renewable energy sources in a cleaner manner.
The energy storage system typically comprises multiple racks of battery storage systems. Each rack of the battery storage system comprises multiple battery packs wherein each of the battery pack is a combination or arrangement of multiple battery devices coupled together to be used as a power source. The energy storage system that comprises series connections between the plurality of battery packs and parallel connections between a plurality of battery racks. The parallel connection increases the overall current capacity of the energy storage system by combining the current capacities of individual racks. Moreover, the aforementioned connections enable the energy storage system to meet the higher energy demands and provide higher power outputs.
During the operation of the energy storage system, due to differences in voltage among the individual battery racks, the current circulates across the parallel connection between the battery racks. The circulating current flows from the battery rack with a higher voltage to another rack with a lower voltage. The circulating current across the parallel connection between the battery racks does not contribute to external load power requirements. Moreover, the circulating currents cause additional resistive losses within the parallel connections, leading to increased heat generation within the energy storage system. Thus, the circulating current reduces the performance and efficiency of the energy storage system. The increased heat generation caused by circulating current accelerates the degradation of the elements of the energy storage system such as battery packs leading to reduced lifespan of the energy storage system and consequential economic losses.
Conventional methods available for eliminating the circulating current between the battery racks include passive balancing which involves the connection of a balancing resistor with each battery rack. However, the resistive balancing dissipates the energy resulting from the excess charge in the form of heat and thus wastes a huge amount of energy. Thus, the aforesaid method reduces the overall efficiency of the energy storage system and degrades the performance of the energy storage system.
Another existing method for eliminating the circulating current between the battery racks includes active balancing which involves connection of active balancing circuitry in parallel with each battery rack. The excess charge flows from the battery rack with a higher SoC to the other battery pack with a lower SoC until the equalization of the SoC of both battery racks occurs. Thus, the redistribution of charge among individual battery racks occurs. However, the implementation of active balancing involves a considerable increase in costs and increased complexity of the energy storage system.
Thus, there exists a need for an improved energy storage system that overcomes one or more problems associated as set forth above.
SUMMARY
An object of the present disclosure is to provide an energy storage system with improved elimination of circulating current inside the energy storage system.
Another object of the present disclosure is to provide a method of eliminating circulating current in an energy storage system.
In accordance with the first aspect of the present disclosure, there is provided an energy storage system. The energy storage system comprises a plurality of battery racks, at least one comparator circuit, and at least one boost converter. The battery rack comprises a plurality of battery packs. The comparator circuit is connected between two battery racks of the plurality of battery racks. The boost converter is connected with the comparator circuit between the two battery racks.
The present disclosure provides an improved energy storage system. The energy storage system as disclosed in the present disclosure is advantageous in terms of eliminating the circulating current across the parallel connection between the battery racks. The disclosed energy storage system has improved the overall efficiency and performance of the battery racks as the circulating current is eliminated resulting in efficient utilization of the energy of the battery packs. The disclosed energy storage system has improved thermal performance as the elimination of the circulating current results in less heat generation in the energy storage system. The disclosed energy storage system has improved the lifespan of the battery packs as the energy storage system prevents thermal damage to the battery packs.
In accordance with the second aspect of the present disclosure, there is provided a method of eliminating circulating current in an energy storage system. The method comprises comparing voltages of two battery racks connected in parallel with each other, using a comparator circuit; generating a signal corresponding to a difference in the compared voltages, using the comparator circuit; and boosting a lower voltage of the compared voltages based on the generated signal, using a boost converter.
Additional aspects, advantages, features, and objects of the present disclosure would be made apparent from the drawings and the detailed description of the illustrative embodiments constructed in conjunction with the appended claims that follow.
It will be appreciated that features of the present disclosure are susceptible to being combined in various combinations without departing from the scope of the present disclosure as defined by the appended claims.
BRIEF DESCRIPTION OF DRAWINGS
The summary above, as well as the following detailed description of illustrative embodiments, is better understood when read in conjunction with the appended drawings. For the purpose of illustrating the present disclosure, exemplary constructions of the disclosure are shown in the drawings. However, the present disclosure is not limited to specific methods and instrumentalities disclosed herein. Moreover, those in the art will understand that the drawings are not to scale. Wherever possible, like elements have been indicated by identical numbers.
Embodiments of the present disclosure will now be described, by way of example only, with reference to the following diagrams wherein:
FIG. 1 illustrates a block diagram of an energy storage system, in accordance with an aspect of the present disclosure.
FIG. 2 illustrates a flow chart of a method of eliminating circulating current in an energy storage system, in accordance with another aspect of the present disclosure.
In the accompanying drawings, an underlined number is employed to represent an item over which the underlined number is positioned or an item to which the underlined number is adjacent. A non-underlined number relates to an item identified by a line linking the non-underlined number to the item. When a number is non-underlined and accompanied by an associated arrow, the non-underlined number is used to identify a general item at which the arrow is pointing.
DETAILED DESCRIPTION
The following detailed description illustrates embodiments of the present disclosure and ways in which they can be implemented. Although some modes of carrying out the present disclosure have been disclosed, those skilled in the art would recognize that other embodiments for carrying out or practicing the present disclosure are also possible.
The description set forth below in connection with the appended drawings is intended as a description of certain embodiments of an energy storage system and is not intended to represent the only forms that may be developed or utilized. The description sets forth the various structures and/or functions in connection with the illustrated embodiments; however, it is to be understood that the disclosed embodiments are merely exemplary of the disclosure that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention.
While the disclosure is susceptible to various modifications and alternative forms, specific embodiment thereof has been shown by way of example in the drawings and will be described in detail below. It should be understood, however, that it is not intended to limit the disclosure to the particular forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alternatives falling within the scope of the disclosure.
The terms “comprise”, “comprises”, “comprising”, “include(s)”, or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a setup, or system that comprises a list of components or steps does not include only those components or steps but may include other components or steps not expressly listed or inherent to such setup or system. In other words, one or more elements in a system or apparatus preceded by “comprises... a” does not, without more constraints, preclude the existence of other elements or additional elements in the system or apparatus.
In the following detailed description of the embodiments of the disclosure, reference is made to the accompanying drawings which are shown by way of illustration-specific embodiments in which the disclosure may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosure, and it is to be understood that other embodiments may be utilized and that changes may be made without departing from the scope of the present disclosure. The following description is, therefore, not to be taken in a limiting sense.
The present disclosure will be described herein below with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in detail since they would obscure the description with unnecessary detail.
As used herein, the terms “energy storage system”, and “ESS” are used interchangeably and refer to a system that includes multiple individual battery packs connected together (forming a huge capacity) to store electrical energy in the form of chemical energy. The energy storage system provides a higher combined voltage or current capacity during external load requirements. The battery packs in the energy storage system includes a plurality of battery cells. Furthermore, the energy storage system may include additional circuitry, such as a battery management system (BMS), to ensure the safe and efficient charging and discharging of the battery packs.
As used herein, the terms “battery rack” and “plurality of battery rack” are used interchangeably and refer to a modular combination of individual battery packs. Each rack includes a plurality of battery packs that are connected in series. The battery racks are electrically connected in parallel with one another to supply the desired voltage and current capacity requirements.
As used herein, the terms “battery pack” and “plurality of battery packs” are used interchangeably and refer to the component that includes the assembly of cells connected together in series or/and parallel. The battery pack is integrated within a common housing or enclosure and configured to function collectively as a bigger energy storage unit. The battery pack may include various types of cells including cylindrical cells, prismatic cells, pouch cells, coin cells, or any customized shape cells.
As used herein, the term “comparator circuit” refers to the electronic circuit that compares two input voltages and outputs a digital signal indicating which voltage is greater. The comparator circuit, by comparison, identifies a difference in the voltage of battery racks and generates a corresponding signal. The signal may be a binary signal (digital signal) that indicates the difference in the compared voltages. The comparator circuit may be connected to the battery racks through a bridge connection. The comparator circuit may comprise an operational amplifier.
As used herein, the term “boost converter” refers to a DC-to-DC power converter that efficiently increases (steps up) the voltage from its input to its output. It's a type of switched-mode power supply (SMPS) that leverages energy storage in an inductor to achieve voltage conversion. The boost converter steps up the lower voltage of the battery rack to equalize the same with a higher voltage of the other battery rack, thus, creating an equilibrium in the voltage supplied to the load, leading to the elimination of circulating current.
As used herein, the term “inductor” refers to the electronic component of the boost converter to store the current flowing across the converter in the form of a magnetic field. The magnetic field collapses intermittently to develop the voltage for boosting the lower voltage received from the battery rack.
As used herein, the term “switch” refers to the electronic component of the boost converter to control the flow of current in the boost converter. The switch may include a Bipolar Junction Transistor or Metal-Oxide-Semiconductor Field-Effect Transistor. During the 'on' state, the switch allows the current to flow across the inductor. The flow of current stores energy in the inductor as the magnetic field. During the 'off' state, the switch disconnects the flowing current and the inductor releases the stored energy. The duty cycle of switching determines the amount of output voltage of the inductor. The larger the duty cycle, the higher the output voltage developed in the inductor. The switch is controlled by a microcontroller, typically utilizing pulse-width modulation (PWM) techniques to control the duty cycle and control the output voltage of the boost converter.
As used herein, the term “diode” refers to the electronic component of the boost converter to permit the flow of current from the inductor in one direction.
As used herein, the term ‘capacitor’ refers to the electronic component of the boost converter to smooth out any ripples or fluctuations in the output voltage. During the on-time of the switch, the capacitor stores energy by charging up through the output voltage from the inductor. The capacitor discharges the stored energy during the off-time of the converter, providing a steady supply of current to the load and boosting the output of the battery rack.
As used herein, the terms “control unit”, “microcontroller” and ‘processor’ are used interchangeably and refer to a computational element that is operable to respond to and process instructions that operationalize the domestic uninterrupted power supply system for charging and discharging the plurality of battery packs. Optionally, the control unit may be a micro-controller, a complex instruction set computing (CISC) microprocessor, a reduced instruction set (RISC) microprocessor, a very long instruction word (VLIW) microprocessor, or any other type of processing unit. Furthermore, the term “processor” may refer to one or more individual processors, processing devices, and various elements associated with a processing device that may be shared by other processing devices. Furthermore, the control unit comprises a software module residing in the control unit and executed by the microcontroller to control the operation of the active bridge modules of the system for charging batteries. It is to be understood that the software module may comprise algorithms and control instructions to control the operation of the active bridge modules of the system for charging batteries. It is to be understood that the control unit controls electronics such as inverters and rectifiers to control the charging and discharging of the plurality of battery packs.
As used herein, the term “communicably coupled” refers to a bi-directional connection between the various components of the system. The bi-directional connection between the various components of the system enables exchange of data between two or more components of the system. Similarly, bi-directional connection between the system and other elements/modules enables exchange of data between system and the other elements/modules.
Figure 1, in accordance with an embodiment, describes an energy storage system 100. The system 100 comprises a plurality of battery racks 102, at least one comparator circuit 106, and at least one boost converter 108. Each of the battery rack 102 comprises a plurality of battery packs 104. The comparator circuit 106 is connected between two battery racks 102 of the plurality of battery racks 102. The boost converter 108 is connected with the comparator circuit 106 between the two battery racks 102. The boost converter 108 supplies the power output of the energy storage system 100 to a load.
The present disclosure provides an improved energy storage system 100. Furthermore, the energy storage system 100 is advantageous in terms of eliminating circulating current across parallel connections between the battery racks 102. Furthermore, the disclosed energy storage system 100 has improved overall efficiency and performance of the battery racks 102 as the circulating current is eliminated resulting in efficient utilization of the energy of the battery packs 104. Furthermore, the disclosed energy storage system 100 has improved thermal performance as the elimination of the circulating current results in less heat generation in the energy storage system 100. Furthermore, the disclosed energy storage system 100 has improved the lifespan of the battery packs 104 as the energy storage system 100 prevents thermal damage to the battery packs 104. Beneficially, the energy storage system 100 is advantageous in terms of eliminating the need for active balancing between the plurality of battery racks 102, as a voltage of output power supplied to the load is balanced using a boost converter 108. Beneficially, the energy storage system 100 is advantageous in terms of eliminating the need for power transfer or power sharing between the plurality of battery racks 102 to equalize the voltages of the plurality of battery racks 102.
In an embodiment, the plurality of battery racks 102 are connected in parallel with each other. Beneficially, the parallel connection may increase the current capacity of the energy storage system 100. It is to be understood that in parallel connection, the current from each battery rack 102 flows independently and adds up. The additive contribution of current leads to a higher current capacity of the energy storage system 100.
In an embodiment, the plurality of battery packs 104 are connected in series with each other. It is to be understood that the plurality of battery packs 104 are connected in series with each other to form the battery rack 102. Beneficially, the series connection increases the voltage capacity of battery rack 102. It is to be understood that the series connection adds up the individual voltages of each battery pack 104, leading to a higher total voltage of battery rack 102.
Beneficially, the combination of the series connections and the parallel connections helps the energy storage system 100 achieve high current and voltage ratings.
In an embodiment, the comparator circuit 106 is configured to compare the voltages of the two battery racks 102 and generate a signal corresponding to a difference in the compared voltages. Beneficially, each input end of comparator circuit 106 receives the voltages across each of the battery rack 102. It is to be understood that the comparator circuit 106 compares the input voltages and generates the signal corresponding to a difference in the compared voltages of the battery racks 102.
In an embodiment, the boost converter 108 is configured to boost a lower voltage of the compared voltages based on the signal generated by the comparator circuit 106. Beneficially, the signal generated by the comparator circuit 106 may act as a reference for control of the boost converter 108. It is to be understood that the lower voltage of the compared voltages is boosted with the magnitude of the signal generated by the comparator circuit 106. It is to be understood that the boosting of lower voltage with the difference in the compared voltages would equalize the lower voltage and higher voltage of the compared voltages.
In an embodiment, the lower voltage is boosted to match a higher voltage of the compared voltages. It is to be understood that the lower voltage of the battery rack 102 is matched with the higher voltage of another battery rack 102 by the boost converter 108. It is to be understood that the boost converter 108 boosts the lower voltage to equalize it with the higher voltage of the compared voltages, however, the magnitude of current reduces during boosting the lower voltage, thus, overall power output remains the same from the battery rack 102 with lower voltage.
In an embodiment, the boost converter 108 comprises at least one inductor, at least one switch, at least one diode, and at least one capacitor. Furthermore, in an embodiment, the boost converter 108 may comprise a microcontroller, communicably coupled with the comparator circuit 106 and the components of the boost converter 108. It is to be understood that the at least one inductor of the boost converter 108 stores energy in a magnetic field and resists changes in current. Furthermore, the at least one switch of the boost converter 108 control the connection between the input voltage and the inductor. Furthermore, the at least one diode of the boost converter 108 ensures one-way flow of current, preventing backflow from the output. Furthermore, the at least one capacitor of the boost converter 108 smooths out voltage ripple at the output providing a stable DC voltage. It is to be understood that the boost converter 108 functions in two phases, namely switch-on phase and switch-off phase. In the switch-on phase, the switch closes to connect input voltage (lower voltage) to the inductor. A current start flowing in the inductor storing energy in magnetic field of the inductor. Simultaneously, the capacitor discharges supplying current to the load. In the switch-off phase, the switch opens disconnecting input voltage (lower voltage) from the inductor. The magnetic field of the inductor collapses inducing a voltage across the inductor. The induced voltage adds to the input voltage (lower voltage) resulting in the boosted voltage. The diode prevent flow back of the current to the input. The capacitor charges from the inductor, smoothing the boosted voltage to be provided to the load. The duty cycle of the switch is controlled by the microcontroller based on the signal generated by the comparator circuit 106.
In an embodiment, the lower voltages across the plurality of battery racks 102 are boosted to match the higher voltages until all the plurality of battery racks 102 are at the same voltage level. It is to be understood that all the possible pairs of battery racks 102 are connected with the at least one comparator circuit 106. It is to be understood that all the lower voltages of the battery racks 102 are boosted to match the higher voltage of the compared voltages. Beneficially, all the boosted voltage outputs are provided to the load, thus eliminating the need of any active balancing between the plurality of battery racks 102.
In an exemplary embodiment, when the voltage of one battery rack 102 is 240V and the voltage of another battery rack 102 is 220V, the comparator circuit 106 compares the voltages of battery racks 102 i.e. 240V and 220V, and generates a signal corresponding to the voltage difference of 20V i.e. (240V-220V =20V). The boost converter 108 is configured to boost the lower voltage i.e. 220V by 20V to make it 240V, thus, equalizing voltage outputs of both the battery racks 102. The original 240V from one battery rack 102 and the boosted 240V from boost converter 108 is provided to the load, eliminating the requirement of active balancing between the unbalanced battery racks 102.
In an embodiment, the system 100 comprises a plurality of battery racks 102, at least one comparator circuit 106 and at least one boost converter 108. Each of the battery rack 102 comprises a plurality of battery packs 104. The comparator circuit 106 is connected between two battery racks 102 of the plurality of battery racks 102. The boost converter 108 is connected with the comparator circuit 106 between the two battery racks 102. Furthermore, the plurality of battery racks 102 are connected in parallel with each other. Furthermore, the plurality of battery packs 104 are connected in series with each other. Furthermore, the comparator circuit 106 is configured to compare voltages of the two battery racks 102 and generate a signal corresponding to a difference in the compared voltages. Furthermore, the boost converter 108 is configured to boost a lower voltage of the compared voltages based on the signal generated by the comparator circuit 106. Furthermore, the lower voltage is boosted to match a higher voltage of the compared voltages. Furthermore, the boost converter 108 comprises at least one inductor, at least one switch, at least one diode and at least one capacitor. Furthermore, the lower voltages across the plurality of battery racks 102 is boosted to match the higher voltages until all the plurality of battery racks 102 are at same voltage level.
Figure 2, in accordance with another aspect, describes a method 200 of eliminating circulating current in an energy storage system 100. The method 200 starts at step 202 and completes at step 206. At step 202, the method 200 comprises comparing voltages of two battery racks 102 connected in parallel with each other, using a comparator circuit 106. At step 204, the method 200 comprises generating a signal corresponding to a difference in the compared voltages, using the comparator circuit 106. At step 206, the method 200 comprises boosting a lower voltage of the compared voltages based on the generated signal, using a boost converter 108.
In an embodiment, the method 200 comprises boosting the lower voltage to match a higher voltage of the compared voltages.
In an embodiment, the method 200 comprises connecting the plurality of battery racks 102 in parallel with each other.
In an embodiment, the method 200 comprises connecting the plurality of battery packs 104 in series with each other.
In an embodiment, the method 200 comprises configuring the comparator circuit 106 for comparing voltages of the two battery racks 102 and generating a signal corresponding to a difference in the compared voltages.
In an embodiment, the method 200 comprises configuring the boost converter 108 for boosting a lower voltage of the compared voltages based on the signal generated by the comparator circuit 106.
In an embodiment, the method 200 comprises boosting the lower voltages across the plurality of battery racks 102 to match the higher voltages until all the plurality of battery racks 102 are at same voltage level.
In an embodiment, the method 200 comprises comparing voltages of two battery racks 102 connected in parallel with each other, using a comparator circuit 106; generating a signal corresponding to a difference in the compared voltages, using the comparator circuit 106; and boosting a lower voltage of the compared voltages based on the generated signal, using a boost converter 108. Furthermore, the method 200 comprises boosting the lower voltage to match a higher voltage of the compared voltages. Furthermore, the method 200 comprises connecting the plurality of battery racks 102 in parallel with each other. Furthermore, the method 200 comprises connecting the plurality of battery packs 104 in series with each other. Furthermore, the method 200 comprises configuring the comparator circuit 106 for comparing voltages of the two battery racks 102 and generating a signal corresponding to a difference in the compared voltages. Furthermore, the method 200 comprises configuring the boost converter 108 for boosting a lower voltage of the compared voltages based on the signal generated by the comparator circuit 106. Furthermore, the method 200 comprises boosting the lower voltages across the plurality of battery racks 102 to match the higher voltages until all the plurality of battery racks 102 are at same voltage level.
It would be appreciated that all the explanations and embodiments of system 100 also apply mutatis-mutandis to the method 200.
In the description of the present invention, it is also to be noted that, unless otherwise explicitly specified or limited, the terms “disposed,” “mounted,” and “connected” are to be construed broadly, and may for example be fixedly connected, detachably connected, or integrally connected, either mechanically or electrically. They may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present invention can be understood in specific cases to those skilled in the art.
Modifications to embodiments and combinations of different embodiments of the present disclosure described in the foregoing are possible without departing from the scope of the present disclosure as defined by the accompanying claims. Expressions such as “including”, “comprising”, “incorporating”, “have”, and “is” used to describe and claim the present disclosure are intended to be construed in a non-exclusive manner, namely allowing for items, components or elements not explicitly described also to be present. Reference to the singular is also to be construed to relate to the plural where appropriate.
Although embodiments have been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More particularly, various variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the present disclosure, the drawings, and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art.
,CLAIMS:We Claim:
1. An energy storage system (100), the system (100) comprises:
- a plurality of battery racks (102), wherein each of the battery rack (102) comprises a plurality of battery packs (104);
- at least one comparator circuit (106), wherein one comparator circuit (106) is connected between two battery racks (102) of the plurality of battery racks (102); and
- at least one boost converter (108), wherein one boost converter (108) is connected with the comparator circuit (106) between the two battery racks (102).
2. The system (100) as claimed in claim 1, wherein the plurality of battery racks (102) are connected in parallel with each other.
3. The system (100) as claimed in claim 1, wherein the plurality of battery packs (104) are connected in series with each other.
4. The system (100) as claimed in claim 1, wherein the comparator circuit (106) is configured to compare voltages of the two battery racks (102) and generate a signal corresponding to a difference in the compared voltages.
5. The system (100) as claimed in claim 1, wherein the boost converter (108) is configured to boost a lower voltage of the compared voltages based on the signal generated by the comparator circuit (106).
6. The system (100) as claimed in claim 5, wherein the lower voltage is boosted to match a higher voltage of the compared voltages.
7. The system (100) as claimed in claim 5, wherein the boost converter (108) comprises at least one inductor, at least one switch, at least one diode and at least one capacitor.
8. The system (100) as claimed in claim 6, wherein the lower voltages across the plurality of battery racks (102) is boosted to match the higher voltages until all the plurality of battery racks (102) are at same voltage level.
9. A method (200) of eliminating circulating current in an energy storage system (100), the method (200) comprising:
- comparing voltages of two battery racks (102) connected in parallel with each other, using a comparator circuit (106);
- generating a signal corresponding to a difference in the compared voltages, using the comparator circuit (106); and
- boosting a lower voltage of the compared voltages based on the generated signal, using a boost converter (108).
10. The method (200) as claimed in claim 8, wherein the method (200) comprises boosting the lower voltage to match a higher voltage of the compared voltages.