Description:“A METHOD AND A SYSTEM FOR PERFORMING AN ACTIVE CELL BALANCING IN A BATTERY ENERGY STORAGE SYSTEM”
The present subject matter relates to a field of batteries, in particularly, the present subject matter relates to a method for performing an active cell balancing in a Battery Energy Storage System (BESS).
BACKGROUND
Over the past two decades, BESS-driven equipment such as Electric Vehicles, Drones, Satellites and portable devices have become an essential part of our daily life. Depending on the required application voltage, it is necessary to connect the cells in a series configuration and to increase the overall capacity as well as to achieve the desired instantaneous current, the cells need to be connected in parallel when making battery packs for different purposes. The weakest cell, i.e., the cell having the lowest capacity and State-of-Charge (SOC), defines the status of the battery pack which leads to Overcharging, Undercharging and insufficient utilization of the available storage energy. This demands the need for charge transfer among all the cells to maintain equal SOC of all the cells in the battery pack to avoid wastage of energy, prevent degradation, and improve the overall efficiency of the battery pack. This invention introduces an energy-efficient, high-speed, and accurate active cell balancing methodology that involves simultaneous cell-to-cell balancing with Constant Current Constant Voltage (CC-CV) charging/discharging for prolonged battery life and improved safety. The bidirectional Discontinuous conduction mode (DCM) flyback converter-based, PWM duty cycle controlled active cell balancing methodology has been verified with 4S4P battery pack and the output results show a maximum balancing accuracy of 99.38%, 32.5% improvement in balancing time and an overall 81.47% reduction in terms of power consumption when compared to the state-of-the-art active cell balancing methodology. This invention provides a one stop solution for the series-parallel battery pack with significantly improved balancing speed while maintaining superior balancing accuracy and notable reduction in power consumption. This invention can provide faster and energy efficient cell balancing for nSmP series-parallel battery pack which results in betterment of battery life and improvement in safety and reliability of the entire Battery Energy Storage System.
Active cell balancing enhances the capacity utilization of the Battery Energy Storage System (BESS) which results in better energy efficiency and significant improvement in the overall performance of the BESS-driven system. This methodology prolongs the battery pack's lifetime by reducing capacity loss during both the charging and discharging cycles. It prevents the rapid temperature rise in the battery pack due to overcharging and undercharging and thus minimizes the risk of any unwanted circumstances like battery explosion or catching up of fire. This invention delivers a groundbreaking solution for series-parallel battery packs, boasting exceptional balancing speed alongside outstanding accuracy and a remarkable decrease in power consumption. By facilitating faster and more energy-efficient cell balancing for nSmP series-parallel battery packs, it not only extends battery life but also significantly enhances the safety and reliability of the entire Battery Energy Storage System.
There are different active cell balancing methodologies based on different topologies such as capacitors, inductors/transformers, and DC-DC converters. Among all the above-mentioned topologies, DC-DC converter-based active cell balancing topology outperforms other topologies in terms of their acceptability for centralized, distributed, and modularized approaches in various applications. Amongst all other DC-DC converters, the Flyback Converter offers the most reliability in terms of energy distribution due to its higher energy conversion efficiency, the ability to conduct bidirectional energy transfer operations, smaller form factor, low power consumption, and high-speed balancing. There are mainly two parameters for cell balancing i.e., cell voltage and SOC of the cell. Many battery chemistries do not have linear relation between cell voltage and cell SOC which leads to lack of accuracy when cell balancing is executed depending on the imbalance in cell voltages which demands the need for SOC based accurate cell balancing. Moreover, to balance an nSmP battery pack (S stands for serially connected cells and P stands for parallelly connected strings), the state-of-the-art cell balancing methodologies require separate cell balancing modules for balancing series and parallel connected cells which leads to high system latency, low balancing speed, making the entire battery pack less efficient and reliable.
There is a need for a solution to overcome above mentioned drawbacks.
SUMMARY
This summary may be provided to introduce concepts related to a method for performing an active cell balancing in a Battery Energy Storage System (BESS); the concepts are further described below in the detailed description. This summary may be not intended to identify key features or essential features of the claimed subject matter, nor maybe it intended to be used to limit the scope of the claimed subject matter.
The present subject matter provides a method for performing active cell balancing in a Battery Energy Storage System (BESS). The method includes determining, by a balancing controller engine, that a State Of Charge (SOC) difference between a plurality of cells of the BESS is greater than a predetermined threshold. The method includes grouping, by the balancing controller engine, the plurality of cells based upon the SOC difference between the plurality of cells. The method includes switching, by a plurality of Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) gate drivers, a MOSFET switch on for a MOSFET associated with each of the plurality of cells. The method includes creating, by each MOSFET, a path to flow a current from one or more cells with a higher SOC to at least one cell with a lower SOC amongst the plurality of cells. The method includes flowing, by a flyback converter, the current from the one or more cells with the higher SOC to the at least one cell with the lower SOC to perform the active cell balancing.
The present subject matter provides a system for performing an active cell balancing in a BESS. The system includes a balancing controller engine configured to determine that a State Of Charge (SOC) difference between a plurality of cells of the BESS is greater than a predetermined threshold. The balancing controller engine is configured to group the plurality of cells based upon the SOC difference between the plurality of cells. The system includes a plurality of Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) gate drivers configured to switch a MOSFET switch on for a MOSFET associated with each of the plurality of cells. Each MOSFET is configured to create a path to flow a current from one or more cells with a higher SOC to at least one cell with a lower SOC amongst the plurality of cells. The system includes a flyback converter configured to flow the current from the one or more cells with the higher SOC to the at least one cell with the lower SOC to perform the active cell balancing.
Various objects, features, aspects, and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figs. in which like numerals represent like components.
BRIEF DESCRIPTION OF THE DRAWINGS
The illustrated embodiments of the subject matter will be best understood by reference to the drawings, wherein like parts are designated by like numerals throughout. The following description may be intended only by way of example, and simply illustrates certain selected embodiments of devices, systems, and methods that are consistent with the subject matter as claimed herein, wherein:
Fig. 1 illustrates a schematic block diagram of a system configured to perform active cell balancing in a BESS, in accordance with an embodiment of the present subject matter;
Fig. 2 illustrates an operational flow diagram depicting a process for performing active cell balancing in a BESS, in accordance with an embodiment of the present subject matter;
Fig. 3 illustrates an architectural diagram of the system configured to perform active cell balancing, in accordance with an embodiment of the present subject matter;
Fig. 4 illustrates a diagram depicting a working of a simultaneous active cell balancing of a number of cells, in accordance with an embodiment of the present subject matter;
Figs. 5a-5d illustrate graphical representations depicting a comparison of a balancing time among a state-of-the-art series balancing (4S), a state-of-the-art parallel balancing (4P), a simultaneous series-parallel balancing (4S4P), and a performance of simultaneous series-parallel balancing during charging and discharging cycle, in accordance with an embodiment of the present subject matter;
Fig. 6 illustrates a graphical representation depicting a comparison of balancing current and power consumption among series balancing, parallel balancing and simultaneous series-parallel balancing, in accordance with an embodiment of the present subject matter; and
Fig. 7 illustrates a schematic block diagram depicting a method for performing active cell balancing, in accordance with an embodiment of the present subject matter.
DETAILED DESCRIPTION
The following may be a detailed description of embodiments of the disclosure depicted in the accompanying drawings. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered may not be intended to limit the anticipated variations of embodiments; on the contrary, the intention may be to cover all modifications, equivalents, and alternatives falling within the scope of the present disclosure as defined by the appended claims.
As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
Fig. 1 illustrates a schematic block diagram 100 of a system 102 configured to perform an active cell balancing in a BESS, in accordance with an embodiment of the present subject matter. The BESS is a number of cells. The system 102 may be configured to perform the active cell balancing on the number of cells in a series connection and a parallel connection simultaneously with a notable reduction in the number of balancing components which makes the system 102 faster, energy efficient and improves a lifespan of the BESS while enhancing a safety and a reliability of an entire BESS. This leads to an improvement in balancing Speed and reduction in power consumption which results in betterment of battery life and improvement in safety. The active cell balancing of a BESS driven equipment may be based on a State of Charge (SoC) of individual cells of the BESS. The system 102 may include a battery monitoring engine 104, a balancing controller engine 106, a number of Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) gate drivers 108, a number of MOSFETs 110, and a flyback converter 112.
In accordance with an embodiment of the present subject matter, the battery monitoring engine 104 may be configured to measure a value associated with each parametes amongst a number of parameters associated with the BESS. Examples of the number of parameters may include, but are not limited to, a voltage, a current, and a temperature. Upon calculating the value, the battery monitoring engine 104 may be configured to calculate a SOC difference between each cell based on the value of each parameter amongst the number of parameters. For determining the SOC difference, the battery monitoring engine 104 may be configured to determine a SOC associated with each cell amongst a number of cells of the BESS based on the value associated with each parameter amongst the number of parameters. In response to calculating the SOC difference, the battery monitoring engine 104 may be configured to transmit the SOC difference to the balancing controller engine 106.
Continuing with the above embodiment, the balancing controller engine 106 may be configured to receive the SOC difference between each cell from the battery monitoring engine 104. To that understanding, the balancing controller engine 106 may be configured to determine that the SOC difference between the number of cells of the BESS is greater than a predetermined threshold. The number of cells may be in a series connection and a parallel connection and the number of cells is being balanced simultaneously by the active cell balancing. In response to determining, the balancing controller engine 106 may be configured to group the number of cells based on at least one factor. For grouping the number of cells based on the at least one factor, the balancing controller engine 106 may be configured to determine whether the number of cells with the SOC difference greater than the predetermined threshold is at least three or less. Furthermore, the balancing controller engine 106 may be configured to group a cell with a higher SOC with another cell with a lower SOC amongst the number of cells upon determining that the number of cells with the SOC difference greater than the predetermined threshold is less than three. In another embodiment, the balancing controller engine 106 may be configured to group the number of cells based on the nearest distance between the number of cells upon determining that the number of cells is at least three. The nearest distance between the number of cells may be calculated based on a string sequence number and a series sequence number of the number of cells in the series connection and the parallel connection in the BESS.
To that understanding, upon grouping of the number of cells by the balancing controller engine 106, the number of Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) gate drivers 108 may be configured to switch a MOSFET switch on for a MOSFET 110 associated with each of the number of cells. For switching the MOSFET switch, the number of MOSFET gate drivers 108 may be configured to generate one or more PWM signals when the SOC difference is greater than the predetermined threshold. Upon generating the one or more PWM signals, the number of MOSFET gate drivers 108 may be configured to compute one or more duty cycles of one or more PWM signals based on a cell capacity of the number of cells and a required charge transfer amount, wherein the MOSFET switch is switched on based on the one or more duty cycles. Upon being switched on, each MOSFET 110 may be configured to create a path to flow a current from one or more cells with a higher SOC to at least one cell with a lower SOC amongst the number of cells.
Subsequent to creation of the path to flow the current by each MOSFET 110, the flyback converter 112 may be configured to flow the current from the one or more cells with the higher SOC to the at least one cell with the lower SOC to perform the active cell balancing. The current may flow in a bidirectional way. The flyback converter 112 may be a bidirectional Discontinuous Conduction Mode (DCM) flyback converter 112 configured to charge and discharge each cell amongst the number of cells for performing the active cell balancing. The flyback converter 112 may be configured to charge the other cell with the lower SOC and discharge the cell with the higher SOC simultaneously.
Moving forward, the balancing controller engine 106 may be configured to determine whether each cell amongst the number of cells is balanced or not. The balancing controller engine 106 may be configured to terminate the active cell balancing upon determining that each cell is balanced. In another embodiment, the balancing controller engine 106 may be configured to calculate the SOC difference for remaining unbalanced cells amongst the number of cells.
Fig. 2 illustrates an operational flow diagram depicting a process for performing active cell balancing in a BESS, in accordance with an embodiment of the present subject matter. The BESS is a number of cells that may be in a series connection and a parallel connection. The number of cells may be balanced simultaneously by the active cell balancing. The process may be performed by the system 102 as referred in fig. 1.
At step 202, the process may include, measuring a value associated with each parameter amongst a number of parameters associated with the BESS. The value may be measured by the battery monitoring engine 104 as referred in fig. 1. Examples of the number of parameters may include, but are not limited to, a voltage, a current, and a temperature.
At step 204, the process may include determining a SOC associated with each cell amongst a number of cells of the BESS based on the value associated with each parameter amongst the number of parameters. The SOC may be determined by the battery monitoring engine 104.
At step 206, the process may include calculating a SOC difference between each cell based on the value of each parameter amongst the number of parameters. The SOC difference may be calculated by the battery monitoring engine 104. The SOC difference may be transmitted by the battery monitoring engine 104 to the balancing controller engine 106.
At step 208, the process may include determining by the balancing controller engine 106, as referred in fig.1 that the SOC difference between a number of cells of the BESS is greater than a predetermined threshold upon receiving the SOC difference.
At step 210, the process may include determining whether the number of cells with the SOC difference greater than the predetermined threshold is at least three or less. The determination may be performed by the balancing controller engine 106. In an embodiment, where it is determined that the number of cells with the SOC difference greater than the predetermined threshold is at least three, the process may proceed towards step 212a. In another embodiment, where it is determined that the number of cells with the SOC difference greater than the predetermined threshold is less than three, the process may proceed towards step 212b.
At step 212a, the process may include grouping the number of cells based on a nearest distance between the number of cells upon determining that the number of cells is at least three. The grouping may be performed by the balancing controller engine 106. The nearest distance between the number of cells may be calculated based on a string sequence number and a series sequence number of the number of cells in the series connection and the parallel connection in the BESS.
At step 212b, the process may include grouping a cell with a higher SOC with another cell with a lower SOC amongst the number of cells upon determining that the number of cells with the SOC difference greater than the predetermined threshold is less than three. The grouping may be performed by the balancing controller engine 106.
At step 214, the process may include generating one or more PWM signals when the SOC difference is greater than the predetermined threshold. The one or more PWM signals may be generated by the number of MOSFET gate drivers 108.
At step 216, the process may include computing one or more duty cycles of one or more PWM signals based on a cell capacity of the number of cells and a required charge transfer amount by the number of MOSFET gate drivers 108. Further, each MOSFET switch related to each of the number of cells may be switched on based on the one or more duty cycles.
At step 218, the process may include creating a path to flow a current from one or more cells with a higher SOC to at least one cell with a lower SOC amongst the number of cells. The path may be created by each MOSFET switch of the MOSFET 110.
At step 220, the process may include flowing the current from the one or more cells with the higher SOC to the at least one cell with the lower SOC to perform the active cell balancing. The current may be flowed by the flyback converter 112 in a bidirectional way. The flyback converter 112 may be a bidirectional DCM flyback converter 112 configured to charge and discharge each cell amongst the number of cells for performing the active cell balancing. The flyback converter 112 may be configured to charge the at least one cell with the lower SOC and discharge the one or more cells with the higher SOC simultaneously. In an embodiment of the present subject matter, the process may further include determining by the balancing controller engine 106 whether each cell amongst the number of cells is balanced or not. The balancing controller engine 106 may be configured to terminate the active cell balancing upon determining that each cell is balanced. In another embodiment, the balancing controller engine 106 may be configured to calculate the SOC difference for remaining unbalanced cells amongst the number of cells.
Fig. 3 illustrates an architectural diagram of the system 102 configured to perform an active cell balancing, in accordance with an embodiment of the present subject matter. The active cell balancing is applicable on a BESS. The BESS is a number of cells. The system 102 may include a Constant Current-Constant Voltage (CC-CV) charging unit 302 along with components as disclosed in fig. 1 as part of the system 102. The system 102 may be a simultaneous series-parallel active cell balancing system including a CC-CV charging. Firstly, the number of cells may be charged using a CC method. During the charging using the CC method, a cell voltage may gradually be increased till the cell voltage reaches a maximum voltage limit. The charging method may then switch to a CV phase of the CC-CV charging. During the CV method, the cell voltage may remain constant but a current may decrease and approach zero to complete one CC-CV charging cycle. The CC-CV charging method may enhance a battery life and improves a safety of the BESS by preventing over-current during the CC method and avoiding over-voltage during the CV method.
Further, the system may include a sensing front-end 304. The sensing front-end may have a number of sensors configured to collect cell data (current, voltage, and temperature), send the cell data to the battering monitor engine 104 to estimate an SOC of individual cells. Further, SOC may be transmitted to the balancing controller engine 106 to execute the active cell balancing operation.
Continuing with the above embodiment, the system 102 may include a Cell Balancing Unit (CBU) 304 may having an Energy Distribution Unit (EDU)306, MOSFET Switches (MSW), and a control logic. The EDU 306 may include the flyback converter 112 which may be a one Bi-directional Flyback converter (FC) for each parallel string of cells, (2n+2) MOSFET gate drivers 108 for n number of series connected cells, and a PID controller. The (2n+2) MOSFET gate drivers 108 may be the number of MOSFET gate drivers 108 as referred in fig.1. Based on the SOC values received from the battery monitoring engine 104, the balancing controller engine 106 may compute a SOC difference between each cell and compare the same with a tolerable difference limit. If the SOC difference exceeds the acceptable range, the balancing controller engine 106 may generate one or more PWM gate signals to activate corresponding MOSFET switches for a certain period for the execution of the energy redistribution operation.
An mPnS BESS may include n number of series-connected cells and m number of parallel-connected strings. For n number of serially connected cells, the total number of MOSFET switches along with the gate drivers 108 required may be (2n+2). For m parallel strings, m EDU units may be required to perform simultaneous active cell balancing operation. The acceptable SOC difference (soc_ thr) may be set as 0.008 or 0.8%. When the imbalance exceeds the soc_thr, the cell balancing mechanism may get activated. The balancing controller engine 106 may find higher SOC cells and lower SOC cells and may group the higher SOC cells and lower SOC cells.
Depending on cell capacity and the amount of charge transfer required, duty cycles of the PWM signal may be computed for providing to the MOSFET Gate drivers 108 to switch on the corresponding MOSFET switches (MSW) and create the path to flow the cell balancing current for energy transfer. A dead time of 10% of the total duty cycle may be allocated between an energy distribution operation to avoid the “Shoot-through” and keep the MOSFET switches in their safe operating area (SOA). If the number of cells having SOC differences are more than the soc thr, then the energy transfer may occur between the nearest cells to avoid energy loss while covering longer paths. The distance between two cells Bxk and Byl may be calculated with the help of eq.(1), where x, y denotes the string sequence number, and k, l denotes the series sequence number of any cell in a string.

For instance, during SOC imbalance occurring in cells of different strings, Bxk and Byl may be the cells with SOC difference greater than soc_ thr. Here, Bxk may discharge through MSWx(2k−1) and MSWx(2k) while storing the energy within the primary winding of FCx by activating ISWX. When energy storing mechanism is complete, Byl may charge through MSWy(2l+1) and MSWy(2l−2) while activating OSWx of FCx for charging using the previously stored energy.
Similarly, if the SOC imbalance occurs in the same string, Byn and Byp may have SOC difference greater than soc_thr and SOC of Byn is higher than that of Byp. MSWy(2n−1) and MSWy(2n) may get turned on to discharge Byn and store an excess energy in a primary winding of FCy by activating the ISWy. When the energy is transferred completely to the primary winding (Lpr) of FCy, all the previously ON switches may get turned off and MSWy(2p+1) and MSWy(2p−2) may turn on while activating the OSWy to transfer the stored energy through secondary winding (Lse) of FCy and charge the Byp cell.
Fig. 4 illustrates a diagram depicting a working of a simultaneous active cell balancing of a number of cells, in accordance with an embodiment of the present subject matter. The number of cells is a BESS. In an embodiment, where there are occurrence of imbalance in multiple pairs of cells, the system 102 may group pairs based on a nearest distance between any two cells amongst the number of cells. To that understanding, if B21, B24, B23 and Bm3 have SOC imbalances beyond a tolerable limit (0.8% 0r 0.008) where B21 and B24 have higher SOC and B23 and Bm3 have lower SOC, the balancing controller engine 106 may select two pairs based on the nearest distance. The Euclidean distance between B21 and B23 is √(〖(2-2)〗^2+〖(3-1)〗^2 ) = 2 and between B21 and Bm3 is √(〖(m-2)〗^2+〖(3-1)〗^2 ), which is greater than 2 as m>2. The Euclidean distance between B24 and Bm3 is √(〖(m-2)〗^2+〖(4-3)〗^2 ), which may be less than the distance between B21 and Bm3. So B21 and B23 may redistribute the energy between themselves and B24 and Bm3 may redistribute energy between themselves simultaneously.
A Li-ion BESS configuration of 4S4P may be simulated in MATLAB Simulink R2023b using a Simscape Electrical library to validate the invention. Different cell capacities and initial SOC levels may be introduced for each cell to create cell imbalances. The BESS may have a usable capacity of 9.2Ah and each cell may have a nominal voltage of 3.6V and a maximum voltage of 4.2V. The BESS may be charged with a CC-CV charging method and discharged using a CC discharging method. The BESS may be simulated through multiple charge-discharge cycles to validate the proposed methodology. The simultaneous active cell balancing methodology may remain in operation throughout both the charging and discharging phases. A maximum balancing accuracy may be a capability of balancing the highest charge difference occurring between any two cells in the BESS. The maximum cell balancing accuracy obtained through the active cell balancing disclosed in the present subject matter (between B11 and B44) is 99.38%. For a 4S4P BESS configuration, a conventional series balancing for 4S configuration takes 1189 seconds to balance all the cells. The conventional parallel balancing for 4P configuration may takes 654 seconds to balance all the parallel strings. As mentioned earlier, conventional active cell balancing may be a sequential procedure, time taken for balancing all the cells in a 4S4P BESS is (1189+654) seconds i.e., 1843 seconds. The simultaneous series-parallel balancing for 4S4P configuration takes 1240 seconds to balance all the cells connected in series and parallel and may operate during both charging and discharging cycles. So, the active cell balancing methodology may address SOC imbalance among any cells located at any strings of a BESS. Thus, the methodology may show an improvement of 32.5% in terms of balancing speed.
Figs. 5a-5d illustrate graphical representations 500a-500d depicting a comparison of a balancing time among a state-of-the-art series balancing (4S), a state-of-the-art parallel balancing (4P), a simultaneous series-parallel balancing (4S4P), and a performance of simultaneous series-parallel balancing during charging and discharging cycle, in accordance with an embodiment of the present subject matter.
Figs. 5a-5d may disclose the balancing time comparison of the simultaneous series-parallel active cell balancing with different state-of-the-art active cell balancing techniques for a 4S4P BESS configuration. Fig. 5a may disclose a conventional series balancing for 4S configuration which takes 1189 seconds to balance all the cells. Fig. 5b may disclose the conventional parallel balancing for 4P configuration which takes 654 seconds to balance all the parallel strings. Conventional active cell balancing may be a sequential procedure, so the time taken for balancing all the cells in a 4S4P BESS is (1189+654) seconds i.e., 1843 seconds. Fig. 5c may disclose the simultaneous series-parallel balancing for 4S4P configuration which takes 1240 seconds to balance all the cells connected in series and parallel. Fig. 5d may disclose a performance of simultaneous series-parallel balancing during both charging and discharging cycles.
In case of state-of-the-art active cell balancing techniques, the series connected cells may be balanced first and thereafter cell balancing may be executed for parallel connected strings which is a sequential process not a simultaneous one and may take more time for all the cells in the BESS to get balanced whereas the present subject matter addressed a SOC imbalance among any cells located at any strings of a BESS. Thus, the active cell balancing disclosed in the present subject matter discloses an improvement of 32.5% in terms of balancing speed.
Fig. 6 illustrates a graphical representation 600 depicting a comparison of balancing current and power consumption among series balancing, parallel balancing and simultaneous series-parallel balancing, in accordance with an embodiment of the present subject matter. In fig. 3, it may be seen that only one flyback converter (one primary winding and one secondary winding) is connected for n number of series connected cells and for m number of parallel connected strings m number of flyback converters are required, which may be a significant reduction of components (windings and driving MOSFET switches) from the conventional active cell balancing techniques where each cell requires one flyback converter (or windings). The reduction of components in the Simultaneous series-parallel active cell balancing reduces the balancing current flowing through the balancing components during cell balancing, leading to the 81.47% reduction in power consumption when compared to the conventional series and parallel balancing as referred in Fig. 5.
Fig. 7 illustrates a schematic block diagram depicting a method 700 for performing an active cell balancing, in accordance with an embodiment of the present subject matter. The method 700 may be performed by the system and components thereof.
At block 702, the method 700 includes determining, by a balancing controller engine, that a State Of Charge (SOC) difference between a plurality of cells of the BESS is greater than a predetermined threshold.
At block 704, the method 700 includes grouping, by the balancing controller engine, the plurality of cells based upon the SOC difference between the plurality of cells.
At block 706, the method 700 includes switching, by a plurality of Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) gate drivers (108), a MOSFET switch on for a MOSFET (110) associated with each of the plurality of cells.
At block 708, the method 700 includes creating, by each MOSFET, a path to flow a current from one or more cells with a higher SOC to at least one cell with a lower SOC amongst the plurality of cells.
At block 710, the method 700 includes flowing, by a flyback converter (112), the current from the one or more cells with the higher SOC to the at least one cell with the lower SOC to perform the active cell balancing.
While the detailed description describes various embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. The scope of the invention may be determined by the claims that follow. The invention may not be limited to the described embodiments, versions, or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.
, Claims:We Claim:
1. A method (700) for performing active cell balancing in a Battery Energy Storage System ( BESS), comprising:
determining, by a balancing controller engine (106), that a State Of Charge (SOC) difference between a plurality of cells of the BESS is greater than a predetermined threshold;
grouping, by the balancing controller engine (106), the plurality of cells based upon the SOC difference between the plurality of cells;
switching, by a plurality of Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) gate drivers (108), a MOSFET switch on for a MOSFET (110) associated with each of the plurality of cells;
creating, by each MOSFET (110), a path to flow a current from one or more cells with a higher SOC to at least one cell with a lower SOC amongst the plurality of cells; and
flowing, by a flyback converter (112), the current from the one or more cells with the higher SOC to the at least one cell with the lower SOC to perform the active cell balancing.
2. The method (700) as claimed in claim 1, wherein the plurality of cells is in a series connection and a parallel connection and the plurality of cells is being balanced simultaneously by the active cell balancing.
3. The method (700) as claimed in claim 1, wherein the flyback converter (112) is a bidirectional Discontinuous Conduction Mode (DCM) flyback converter configured to charge and discharge each cell amongst the plurality of cells for performing the active cell balancing, further wherein the flyback convertor charges the at least one cell with the lower SOC and discharges the one or more cells with the higher SOC simultaneously.
4. The method (700) as claimed in claim 1, wherein grouping the plurality of cells based upon the SOC difference between the plurality of cells comprises:
determining, by the balancing controller engine (106), whether the plurality of cells with the SOC difference greater than the predetermined threshold is at least three or less; and
performing, by the balancing controller engine (106), one of:
grouping a cell with a higher SOC with another cell with a lower SOC amongst the plurality of cells upon determining that the plurality of cells with the SOC difference greater than the predetermined threshold is less than three; and
grouping the plurality of cells based on a nearest distance between the plurality of cells upon determining that the plurality of cells is at least three, wherein the nearest distance between the plurality of cells is calculated based on a string sequence number and a series sequence number of the plurality of cells in a series connection and a parallel connection in the BESS.
5. The method (700) as claimed in claim 1, wherein switching, by the plurality of MOSFET gate drivers (108), the MOSFET switch comprises:
generating one or more PWM signals when the SOC difference is greater than the predetermined threshold; and
computing one or more duty cycles of one or more PWM signals based on a cell capacity of the plurality of cells and a required charge transfer amount, wherein the MOSFET switch is switched on based on the one or more duty cycles.
6. The method (700) as claimed in claim 1, comprises:
measuring, by a battery monitoring engine (104), a value associated with each parameter amongst a plurality of parameters associated with the BESS;
calculating, by the battery monitoring engine (104), a SOC difference between each cell based on the value of each parameter amongst the plurality of parameters; and
transmitting, by the battery monitoring engine (104), the SOC difference, wherein the SOC difference is received by the balancing controller engine (106).
7. The method (700) as claimed in claim 1, further comprising:
determining, by the balancing controller engine (106), whether each cell amongst the plurality of cells is balanced or not; and
performing, by the balancing controller engine (106), one of:
terminating the active cell balancing upon determining that each cell is balanced; and
calculating the SOC difference for the remaining unbalanced cells amongst the plurality of cells.
8. The method (700) as claimed in claim 1, wherein the plurality of parameters comprises a voltage, a current, and a temperature.
9. The method (700) as claims in claim 1, wherein determining the SOC difference is based on:
determining, by the battery monitoring engine (104), a SOC associated with each cell amongst a plurality of cells of the BESS based on the value associated with each parameter amongst the plurality of parameters.
10. A system (102) for performing an active cell balancing in a BESS, comprising:
a balancing controller engine (106) configured to:
determine that a State Of Charge (SOC) difference between a plurality of cells of the BESS is greater than a predetermined threshold; and
group the plurality of cells based upon the SOC difference between the plurality of cells;
a plurality of Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) gate drivers (108) configured to switch a MOSFET switch on for a MOSFET (110) associated with each of the plurality of cells;
each MOSFET (110) configured to create a path to flow a current from one or more cells with a higher SOC to at least one cell with a lower SOC amongst the plurality of cells; and
a flyback converter (112) configured to flow the current from the one or more cells with the higher SOC to the at least one cell with the lower SOC to perform the active cell balancing.