Active battery management system fed from a modified t-type two-way converter

Abstract

The invention relates to an active battery management system (BMS) for battery energy storage systems (ESS) fed from a modified T-type bidirectional converter

Description

[0001] ACTIVE BATTERY MANAGEMENT SYSTEM FED FROM A MODIFIED T-TYPE TWO-WAY CONVERTER

[0002] Technical Field

[0003] The invention relates to an active battery management system (BMS) for battery energy storage systems (BES) fed from a modified T-type bidirectional converter.

[0004] State of the Art

[0005] Management circuits for battery energy storage systems are included in the state of the art. For example, the Voltage Source Converter (VSC) is a widely used topology for three-phase AC systems and is preferred among other converters in the literature due to its ease of control, low cost and simplicity. In VSC topology, switching losses are reduced by keeping the switching speed low. Considering that the body diode conduction of MOSFETs in voltage- source converter topologies may cause the switching element to fail, it is recommended to prefer IGBT as the switching element. In this approach, no measures are taken for battery health. Each battery cannot be controlled for charging and discharging separately. At the same time, when there is a problem in a single battery in the battery group, all batteries in that battery group are out of circuit.

[0006] In the neutral clamped converter (NPC) method, the three-level neutral clamped converter (NPC) is a widely used topology for ESS (energy storage system) applications. The advantage of this converter topology is that the magnitude of the output voltage can be increased and the filter requirement can be reduced due to improved harmonic performance. This is made possible by clamping half of the DC busbar voltage by NPC diodes, which reduces the voltage requirement of the switches. The disadvantage of the topology is the need for more complex control and modulation techniques compared to two-level converters. Although the conduction loss increases in a three-level inverter due to the additional neutral point switches, a smoother waveform is obtained with increasing voltage level. Therefore, a three-level inverter has lower electromagnetic interference (EMI), small output filter size, low switching loss and low output voltage THD (total harmonic distortion) compared to a two-level inverter. In this approach, no measures are taken for battery health. Each battery cannot be individually controlled for charging and discharging. At the same time, if there is a problem in a single battery in the battery group, all batteries in that battery group are disabled. Active Neutral Clamped Converter (ANPC) Method The active NPC (ANPC) converter topology, which is formed by replacing the clamping diodes in the conventional NPC topology with semiconductor switches, is another topology used in ESSs. The ANPC topology has better capacitor voltage compensation and more switching states. It also has the advantage of better loss distribution between semiconductor switches. However, the system cost is higher due to the larger number of semiconductor switches in the ANPC topology. By using switches instead of clamping diodes at neutral in ANPC topology, the problem of power loss distribution between switches becomes controllable. In this approach, no measures are taken for the health of each battery individually. At the same time, when a single battery in a battery group has a problem, all batteries in that battery group are disabled. Each battery cannot be controlled for charging and discharging separately.

[0007] FC-Floating Capacitor Method Another example of a three-level converter is the flying capacitor (FC) converter, which is similar to the conventional NPC topology. Unlike the conventional NPC, this topology uses capacitors instead of clamping diodes to divide the DC voltage input and is therefore also called capacitor clamped. In this approach, no provision is made for the health of each battery individually. At the same time, if there is a problem in a single battery in the battery group, all batteries in that battery group are disabled. Each battery cannot be individually controlled for charging and discharging.

[0008] Series Connected DC Busbar Method Series DC or AC busbar configurations are widely adopted for large-scale ESS applications. It shows a series DC busbar structure that can provide high DC busbar voltage and galvanic isolation. This topology is suitable for DC inputs with low voltage or large variation. However, efficiency is reduced when there are large voltage variations. Another disadvantage of this structure is the connection of battery groups to the DC busbars. When there is a problem with a single battery in a battery group, all the batteries in that battery group go out of circuit. Therefore, there is no charge and discharge control for each battery.

[0009] Since battery-based energy storage facilities require high power, they need to be fed from the electricity grid or solar panels (charging). These facilities are also required to return the energy stored in the battery to the grid at appropriate times (discharge). The facility installed for this purpose;

[0010] When the ESS is fed from the grid (during charging), it is desired that the waveform of the current drawn from the grid is in sine form (in accordance with the standards) and that the ESS does not draw reactive power from the grid (GF -Power Factor, PFC-Power Factor Correction request)) (RULE 1).

[0011] Likewise, during the return of the energy stored in the batteries to the grid (discharge), both the THD (Total Harmonic Distortion) value of the current pumped into the grid should be low and the waveform of the sinusoidal voltage produced should be in sinus form and in accordance with the standards (RULE 2).

[0012] The electronic circuits in ESS facilities must be manufactured in such a way that they can both charge and discharge (suitable for two-way energy flow). Therefore, the electronic circuit should be able to operate in both rectification (charging) and inverting (discharging) mode. The electronic circuit specified in figure- 1 suitable for both operating conditions must fulfill the requirements of RULE 1 and RULE 2.

[0013] The biggest cost in ESSs is the battery pack. The purpose of the battery charging / discharging circuits in the electronic circuit is to ensure that all batteries in the ESS are charged (RULE 3) and discharged (RULE 4) in accordance with the "conditions recommended by the R&D units of the companies producing these batteries".

[0014] While performing all these operations, it is desired that the electrical losses in electronic circuits are minimized, in other words, the efficiency of the entire circuit should be high (RULE 5).

[0015] Of the 5 RULES listed above, the most economically valuable for ESS is the full fulfillment of RULES 3 and 4. In ESSs, the biggest share of the system cost is the battery facility. For this reason, the difference between the cost of storing energy in the ESS facility and the sales gain to be obtained by selling the stored energy to the grid (profit) is of vital importance for the ESS investor. If the batteries cannot be charged / discharged properly in accordance with the charging / discharging conditions recommended by the battery manufacturer, in addition to the life (cycle life) of the batteries (charge / discharge), which decreases proportionally with the increase in the number of cycles, the life of the batteries in the facility will decrease even more and the ESS investor will have to spend a very significant part of the commercial profit from energy purchase / sale to purchase new batteries again.

[0016] This is not acceptable for any ESS investor. As a result, RULES 3 and 4 are the most important issues that the ESS investor cannot compromise on. RULE 1 and RULE 2 relate to the standards that the grid operator requires the ESS owner to meet. If these two standards are not met, the connection of the ESS facility to the grid is not allowed. RULE 5 is essential for the ESS owner to maximize profits from energy trading. If the electrical losses in the facility are high (low efficiency), some of the stored energy is discharged into the atmosphere as heat instead of being sold to the grid. This situation is commercially unacceptable for the ESS investor.

[0017] An ESS facility must meet RULES 1 and 2 as defined above, otherwise it will not be allowed by the AUTORITY to connect to the electricity grid. RULES 3 and 4 are "very" important for the profit-oriented ESS investor, while the AUTORITY is not interested in these two rules. However, the reduced lifespan of batteries due to non-compliance with healthy charging / discharging rules is very important for environmental health in terms of chemical waste. Moreover, any positive solution that extends battery life is supported by the Public Authority.

[0018] Sulfation is a phenomenon that occurs when lead sulfate (PbSO4) crystals, which are formed during the electrochemical reaction for energy transfer due to the nature of the battery operation, are deposited on the surface of the battery plates. When lead-acid batteries are under undercharged or overcharged for a long time, the lead sulfate precipitate crystallizes and deposits on the battery plates. Over time, the internal impedance of the lead-acid battery increases due to the accumulation of lead sulfate on the battery plate and the battery capacity decreases and the battery life shortens. If the accumulated lead sulfate crystals are not intervened, the so-called irreversible sulfation, which usually corresponds to the sulfation of the negative plate, occurs and the battery becomes unusable. Nickel cadmium (NiCd) batteries are the battery technology most commonly used today in safety-demanding areas such as aviation due to their reliability, durability, low self-discharge and ability to operate at low temperatures. However, as with any battery chemistry, NiCd batteries have their drawbacks, the most important of which is the problem of memory effect, which is unique to nickel-based batteries. The memory effect in NiCd batteries is also referred to as voltage collapse in some sources. When a NiCd battery is partially discharged and recharged repeatedly without full discharge, a reversible drop in voltage and loss of capacity can occur. Since the battery is able to remember the energy drawn in previous discharges, it gives the same amount in subsequent repeated discharges. Since the cell seems to "remember" the low capacity, this voltage drop phenomenon is often referred to as the memory effect. The voltage drop occurs because only a fraction of the active materials in the cell are discharged and recharged during a shallow discharge or partial discharge. The physical properties of uncycled active materials change, crystallization occurs around the negative pole. The extent of voltage drop and capacity loss depends on the depth of discharge and can be avoided by discharging the battery to an appropriate cut-off voltage. NiCd batteries use an oxidation-reduction (redox) chemical reaction to generate the desired electric current. As NiCd batteries are used, cadmium hydroxide crystals form on the surface of the battery plates. Over time, these crystals accumulate on the surface of the plate, degrading the battery's performance and rendering it unusable. Many methods and device designs called desulfator or rejuvenator have been proposed to remove sulfate by applying different types of charging pulses to dissolve the crystals deposited on the battery plates and to solve the memory problem in nickel-based batteries.

[0019] If the battery chemistry used in the ESS system is "lead orNiCd" based, the life of such batteries can be increased several times by undergoing a chemical reaction known as desulfation (antisulfation). This is "very valuable" for the ESS investor in the medium and long term. For every solution that extends battery life (instead of buying new batteries), the ESS investor will make extra profit. Desulphation is the process of applying direct current to the battery (weekly / monthly / yearly) at periodic intervals, at a specific frequency and amplitude.

[0020] Description of Figures

[0021] Figures related to the electronic circuit

[0022] Figure 1 : Illustration of the general block structure of the electronic circuit system

[0023] Figure 2: Illustration of the energy flow in the charging process of the electronic circuit system Figure 3: Illustration of the PFC circuit

[0024] Figure 4: Illustration of the bridge diode rectification subcircuit

[0025] Figure 5: Illustration of the subcircuit consisting of C-valued capacitors aimed at keeping the DC voltage constant

[0026] Figure 6: PFC circuit

[0027] Figure 7: Measurement of grid currents and measurement of grid voltages

[0028] Figure 8: Inverter trigger pulses in charging mode

[0029] Figure 9: Energy input to the electronic circuit in the discharge process and the flow of discharge energy in the electronic circuit

[0030] Figures related to the battery charging and discharging circuit

[0031] Figure 10: Battery charging and discharging circuit and its subcomponents

[0032] Figure 11 : DC / DC converter circuit

[0033] Figure 12: Discharge control circuit of the whole ESS Illustrations of electronic circuits and battery charging and discharging circuits used together

[0034] Figure 13: Electronic circuit and battery charging and discharging circuits and subcomponents

[0035] Figure 14: Illustration of the charging / discharging operation command from the system main controller

[0036] Figure 15: Illustration of the complement operation state of switch SI and switch S2 according to their charging / discharging states

[0037] Figure 16: Illustration of the charging circuit of one battery container and discharge control circuit of one battery container for phase A

[0038] Element Numbers in Figures

[0039] In order to better explain the battery and charging circuit developed with this invention, the parts and elements in the figures are numbered and the equivalent of each number is given below:

[0040] 1. Electronic circuit

[0041] 1.1. PFC circuit

[0042] 1.2. Negative and positive DC busbar voltage measurement circuit

[0043] 1.3. Bridge diode rectifier

[0044] 1.4. 3-level 6-switch bidirectional inverter

[0045] 1.5. Circuit consisting of C-valued capacitors aimed at keeping the DC voltage constant

[0046] 2. Battery charging and discharging circuit

[0047] 2.1. High frequency ferrite core BMS transformer

[0048] 2.2. Rectifier circuit of a single phase center-split transformer

[0049] 2.3. Step-down DC / DC converter circuit

[0050] 2.4 Battery

[0051] 2.5. Battery charge / discharge circuit (Battery charge-discharge control module identical for each BMS transformer)

[0052] 2.6. Battery charge / discharge circuit (Battery charge-discharge control module identical for each BMS transformer)

[0053] 2.7. Battery container connected between phases AB

[0054] 2.8. Battery container connected between phases BC

[0055] 2.9. Battery container connected between phases CA

[0056] 2.10. Battery container charging circuit

[0057] 2.11. Battery container discharging circuit 2.12. Discharge control circuit of the entire energy storage system

[0058] 2.13. Discharge control switch

[0059] 2.14. Discharge control (bypass) diode

[0060] 2.15. Thermal magnetic switch

[0061] 2.16. Diode to ensure that energy flows in one direction

[0062] 2.17. Positive DC busbar

[0063] 2.18. Negative DC busbar

[0064] 2.19. Series connection circuit of diodes and switches used in battery discharge control circuit

[0065] 2.20. Controlled switch that ensures healthy charging of the battery and desulfation of the battery

[0066] 2.21. One-phase center-split transformer

[0067] 2.22. Connection points of the battery charging and discharging circuit to the electrical circuit

[0068] 2.23. Cell current sensor

[0069] 2.24. Cell temperature sensor

[0070] 2.25. Cellular microcontroller

[0071] 2.26. Optocouplers providing serial communication with the main controller

[0072] 3.1. SI switch

[0073] 3.2. S2 switch

[0074] 3.3. Charge mode

[0075] 3.4. Discharge mode

[0076] 3.5. Mode selection

[0077] 3.6. Input signal value

[0078] 3.7. Mains (AG, OG, YG)

[0079] 3.8. Mains transformer

[0080] 3.9. Mains current measurement

[0081] 3.10. Mains voltage measurement

[0082] 3.11. Mains current / voltage measurement

[0083] 3.12. EMI filter

[0084] 3.13. LCL filter

[0085] 3.14. Charge mode-2

[0086] 3.15. Discharge mode-2

[0087] 3.16. Mode selection button Detailed Description of the Invention

[0088] The system of the invention offers a solution both for the 5 rules described above and for desulfation, which extends battery life in some battery types.

[0089] The invention is also flexible enough to adapt to any type of battery charging / discharging voltage and current, and is also suitable for the use of supercapacitors.

[0090] The most important potential threat, especially for Lithium batteries, is thermal runaway. Thermal runaway can be evaluated as the chemical reactions that take place inside the battery generate high heat, this heat accelerates the reaction and an uncontrollable temperature increase occurs. As a result of thermal leakage, the battery may become unusable and there is a high probability of explosion. The most common cause of thermal leakage is overcharging. In studies, there was a significant decrease in the energy capacity of the lithium battery that reached 125% SoC value. At 146% SoC value, thermal leakage was experienced (Liu et al., 2020). In the same study, it was shown that charging at high currents will also cause thermal leakage of the battery. In another study, batteries were overcharged under constant temperature and the decrease in SoH values was observed. According to the results obtained, it was observed that overcharging at low currents decreased the battery capacity by a small amount, while the battery capacity decreased significantly as the overcharged current increased (Sun et al., 2022). In another study, it was observed that a battery that has been deeply discharged 100 times experiences a capacity loss between 7% and 10% (L. Li et al., 2023). The above-mentioned loss rates can be viewed from two perspectives: a) the damage caused by the inefficient operation of the ESS where not enough energy is stored in the batteries, and b) if the battery capacity decreases, this affects all batteries in the series branch. In this case, the series branch of the ESS with the batteries that have lost capacity is either continued to be operated at full low power or the inefficient battery(s) are replaced with new ones. This has a negative impact on the cost of the battery, which is the most important item in the ESS. The additional material cost due to the structure of the proposed topology will be negligibly small compared to the loss cost in these two items. In addition, the additional materials will be purchased once and will not be replaced even if the battery life expires.

[0091] The invention consists of a battery charging and discharging circuit (2). The battery charging and discharging circuit (2) can be used individually or in combination with the electronic circuit (1). The battery charging and discharging circuit (2) is a unique circuit that will charge / discharge the batteries in accordance with the charge / discharge curves prepared by the battery manufacturers for the battery users in order to extend the battery life. When the literature is examined, it is requested to take measures for battery health in such circuits. This is because batteries are the most costly part of battery energy storage systems. The total cost of electronic circuits used in high-power battery-based energy storage systems (ESS-BESS) is negligible compared to the total cost of batteries.

[0092] In addition, the most threatening factor to the safety of the entire system is the explosion and / or fire of the batteries, which is caused by improper use of the battery.

[0093] Another advantage of the battery charging and discharging circuit (2) is that it provides the opportunity to extend the life of lead and NiCd batteries in energy storage systems without removing them from their location and automatically, by desulfation method. In the literature, there is no approach to desulfate the batteries in the energy storage system where they are located (automatically and without additional labor). In current practices around the world, the desulfation process is carried out by taking the battery out of the energy storage system, connecting it to battery desulfation machines and starting the desulfation process. After the process is finished, the battery is reinserted back into the ESS (maintenance team transfer and additional labor). The DC / DC circuit functions as a desulfation device for the ESS when the S3 switch (from the control end) shown in Figure 1 is controlled using appropriate control signals.

[0094] As a result, the battery charging and discharging circuit (2) is a new product in terms of its RULES 3, RULES 4 and desulfation contributions to batteries. In addition to the electronic circuit (1), it can also be used in combination with other circuits of the same design to provide these functions.

[0095] Charging in the battery charge and discharge circuit (2):

[0096] In the battery charging and discharging circuit (2) shown in Figure 10, a 3-phase high frequency AC voltage is applied to the input of the circuit. Figure 10 shows the circuit diagram of this custom-made transformer for phase A only. The battery container (2.7) circuit connected between phases AB for phase A is also included in the circuit parts of the battery container (2.8) connected between phases BC for phase B and the battery container (2.9) connected between phases CA for phase C in Figure 10. They are not drawn separately in Figure 10 (in order not to enlarge the figure). The novelty of the invention is that the 3-phase, high-frequency AC voltage signal applied to the primary circuit of the transformer is reduced in amplitude on the secondary side, rectified, passed through the DC / DC converter shown in Figure 11 and applied to each battery at the current and voltage value that will ensure the health of this battery.lt is also possible to use other types of DC / DC (step-down) converters instead of the step-down DC / DC converter circuit (2.3) in Figure 11. When other 2-way inverters used in the literature are used instead of the 3-level 6-switch bidirectional inverter (1.4), the triggering signals shown in Figure-8 also change. What makes the invention unique is not the type of change in the triggering signals or the use of any other type of bidirectional inverter instead of the 3-level 6- switch bidirectional inverter (1.4) circuit. The invention remains unique even if any 3-phase bidirectional inverter is used instead of the 3-level 6-switch bidirectional inverter (1.4) circuit. The 3-level 6-switch two-way inverter (1.4) circuit may also be replaced by a 2,3,4...n-level inverter or an NPC type inverter or an ANPC type inverter or a VSC converter.

[0097] Figure- 11 shows some of the charge and discharge management hardware required for each battery cell. The cellular microcontroller (2.25) is the required cellular controller for each cell. The cellular microcontroller (2.25) measures the charge-discharge current of the battery cell with the cell current sensor (2.23), cell voltage, temperature with the cell temperature sensor (2.24), and communicates serially with the central controller through optocouplers (2.26) which provide serial communication with the optoisolated main controller. In accordance with the commands received from the central controller for this cell, the controlled switch (2.20), which ensures that the battery is charged and desulfated properly, applies a PWM signal at the duty value and the discharge control switch (2.13) generates the necessary on / off signal for discharge control.

[0098] Figure 10 shows the representation of the primary and secondary windings for phase A (for one container only) of a high frequency ferrite core BMS transformer (2.1) and a custom-made transformer. The size of the primary and secondary windings and the number of turns varies depending on the power of the energy storage facility. The number of secondary windings Bl, B2,... shown in the subcircuit of the high frequency ferrite core BMS transformer (2.1) is equal to the number of batteries connected in series in one battery container in phase A of the transformer in the energy storage facility. In phase A, a large number of containers (depending on the energy storage power) containing sub-circuits such as battery container charging circuit (2.10) and battery container discharging circuit (2.11) can be multiplied by parallelizing each other. As a result, the number of sub-circuits of the battery charge / discharge circuit (2.6) in phase A and the battery container (2.7) connected between phases AB varies depending on the energy storage power. The battery charging / discharging circuit (2.6) in phase A feeds one battery. The battery container (2.7) circuit connected between the AB phases represents all the A phase battery charging / discharging circuits (2.6) connected in parallel to the A phase. For example, if a total of 600 batteries are connected in series in the storage facility, one third of them (i.e. 200 units) will be connected to phase AB, one third to phase BC and one third to phase CA. Each of the 200 batteries connected between phase AB is fed by the battery charge / discharge circuit (2.6) in phase A. The battery container (2.7) circuit connected between phases AB is the name given to all 200 parallel connected A phase battery charging / discharging circuits (2.6). As a result, while there is one battery in the A phase battery charging / discharging circuit (2.6), there are 200 batteries in the battery container (2.7) circuit connected between the AB phases.

[0099] The definitions described above also apply to containers in phases B and C. For example, even though the input terminals of all containers in phase A are connected in parallel to each other, all batteries at different container outputs are connected in series. This ensures that the total voltage value of the storage facility increases. The same is true for all containers in phases B and C. As a result, all batteries at all container outputs in phases A, B and C are also connected in series with each other. In short, for example, if the number of batteries connected in series at all container outlets in phase A is 100, the total number of batteries connected in series in the energy storage facility will be 3 times that number, i.e. 300. The number of series arms (by creating parallel arms) to which the batteries connected to each phase are connected can be increased as much as desired. This number varies depending on the energy storage power. Although the number of series arms is given as 1 in Figure 13, the transformer primary windings connected to phases A, B and C can also be connected to each other in a triangular or star shape.

[0100] The rectifier circuit of the one-phase center-split transformer shown in Figure 11 converts the secondary voltage into DC voltage through the diodes shown in (2.2). The step-down DC / DC converter circuit (2.3) is a DC / DC step-down circuit and is used to generate the DC voltage required by the batteries. The battery (2.4) is shown in Figure 11 and each DC / DC step-down circuit is used to supply (charge) only one battery.

[0101] In the DC / DC converter step-down circuit shown in Figure 10, the high frequency ferrite core BMS transformer (2.1) is used to step down the high AC voltage at the input of the battery charging and discharging circuit (2) shown in Figure 10. The rectifier circuit (2.2) of the one- phase center-split transformer shown in Figure 11 is used to rectify the AC voltage at the secondary of the transformer. In Figure 11, with the help of the controlled switch (2.20), which ensures healthy charging of the battery and desulfation of the battery (2.4), the DC voltage and DC current value of the battery (2.20) are provided at the most appropriate value to ensure the battery charging health recommended by the manufacturer.

[0102] Discharge operation in the battery charge and discharge circuit (2):

[0103] Figure 12 shows the discharge control circuit (2.12) of the entire energy storage system. The discharge control switch (2.13) is also shown here. The discharge of the batteries starts when all of the discharge control switches (2.13) are activated. If there is a problem in the battery discharged by the discharge control switch (2.13), the discharge control switch (2.13) is deactivated by the central control unit and the discharge control (bypass) diode (2.14) is activated. Thus, there is no obstacle to discharge of intact batteries. When the thermal magnetic switch (2.15) is activated, the discharge process starts in the energy storage system. The diode (2.16), which ensures that the energy flows in one direction, ensures that the stored energy is discharged in one direction and at the same time prevents the energy that may flow in the opposite direction during charging from entering the discharge control circuit. At terminals Fl and F2 the energy stored in the batteries is sent to the desired circuit. This circuit can be the DC busbars feeding an inverter or another consumer running on DC power.

[0104] The battery and charging circuit (2), which has a high voltage positive DC busbar (2.17) to which the inverter is connected and a negative voltage negative DC busbar (2.18) to which the inverter is connected, can be used alone or in combination with an electronic circuit (1). The electronic circuit (1) is a unique circuit that transmits the electrical energy received from the power grid to the battery charging and discharging circuit (2). When the literature is examined, it is desired to design this circuit in accordance with two-way power flow (charge and discharge). In these circuits, both the THD (Total Harmonic Distortion) value and the Power Factor (GF -PF) value of the current drawn from the grid should be low in the rectification (charging) mode, while in the inverting (discharging) mode, both the THD value of the grid current should be low, the PF value should be high and the voltage waveform produced by the inverter should be close to the sine form.

[0105] When there is a problem in any of the batteries connected in series, hundreds of batteries connected in series are affected by this situation, and even all batteries in this series arm may become dysfunctional. When a problem occurs in any battery in the series branch, the problematic battery is bypassed by the discharge control switch (2.13) and the discharge control (bypass) diode (2.14). In this way, other batteries in the series connected arm are prevented from being adversely affected by this event. Instead of this disabled battery, a spare battery waiting full at the end of this branch is activated by the control system controlling the whole system, thus preventing the storage system from losing power. The battery container discharge circuit (2.11) also allows for such a backup. References

[0106] Liu, Y., Huo, R., Qin, H., Li, X., Wei, D., Zeng, T. 2020. "Overcharge investigation of degradations and behaviors of large format lithium ion battery with Li(Ni0.6Co0.2Mn0.2)02 cathode". Journal of Energy Storage, 31, 101643.

[0107] Li, Y., Yin, P., Chen, J. 2023. "Active Equalization of Lithium-Ion Battery Based on Reconfigurable Topology". Applied Sciences, 13(2), 1154.

[0108] Sun, P., Zhang, X., Wang, S., Zhu, Y. 2022. "Lithium-ion battery degradation caused by overcharging at low temperatures". Thermal Science and Engineering Progress, 30, 101266.

Claims

CLAIMS1. Battery charging and discharging circuit (2), characterized by;• A battery container circuit (2.7) connected between phases AB for phase A, a battery container circuit (2.8) connected between phases BC for phase B and a battery container circuit (2.9) connected between phases CA for phase C,• A battery container charging circuit (2.10) consisting of a high frequency ferrite core BMS transformer (2.1) to reduce the high AC voltage at the input of a battery charging and discharging circuit (2), a rectifier circuit (2.2) of a one-phase center-split transformer for rectifying the AC voltage at the secondary of the transformer, a stepdown DC / DC converter circuit (2.3) and a battery (2.4),• A battery container discharge circuit (2.11) to replace the problematic battery that has been removed from the circuit, so that the storage system does not lose power by waiting for the connected branch to be full at the end,• A battery discharge control circuit (2.12) having a discharge control switch (2.13), which is activated to discharge the batteries, a thermal magnetic switch (2.15), which initiates the discharge process in the energy storage system, a diode (2.16), which ensures that the energy flows in one direction, which ensures that the stored energy is discharged unidirectionally, a high voltage positive DC busbar (2.17) to which the converter is connected, a negative voltage negative DC busbar (2.18) to which the converter is connected, and a series connection circuit (2.19) of diodes and switches.

2. A battery charging and discharging circuit (2) according to claim 1, characterized in that it comprises a cellular microcontroller (2.25) for measuring the charge-discharge current of the battery cell with a cell current sensor (2.23) and the cell voltage and temperature with a cell temperature sensor (2.24).

3. A battery charging and discharging circuit (2) according to claim 1, characterized in that it comprises a cellular microcontroller (2.25) in serial communication with the central controller via optocouplers (2.26) in serial communication with the optoisolated main controller.

4. A battery charging and discharging circuit (2) according to claim 1, characterized in that it comprises a controlled switch (2.20) which ensures healthy charging and desulfation of the battery in accordance with commands from the central controller for the cell.

5. A battery charging and discharging circuit (2) according to claim 1, characterized in that it comprises a discharge control diode (2.14) which is activated if there is a problem in the battery discharged by the discharge control switch (2.13).

6. A battery charging and discharging circuit (2) according to claim 1, characterized in that it comprises a diode (2.16) for ensuring that energy flows in one direction during charging, which prevents energy flowing in the opposite direction towards this circuit from entering the discharge control circuit.