A single-stage interleaved equalization circuit for a battery energy storage system

Abstract

The application discloses a single-stage staggered equalization circuit of a battery energy storage system, which comprises a plurality of battery equalization modules, and the output end of an energy storage system in each battery equalization module is connected with the input end of an integrated cascaded multi-port converter through a switch array, and the output end of the integrated cascaded multi-port converter is connected with the input end of an energy storage system in another battery equalization module. In this way, the plurality of battery equalization modules can be connected in a staggered mode, parallel equalization of multiple batteries and the plurality of battery equalization modules is realized, and energy can be exchanged between single batteries and the battery equalization modules and directly transferred between the single batteries.

Description

Technical Field

[0001] This invention relates to the field of battery balancing technology, and more specifically, to a single-stage interleaved balancing circuit for a battery energy storage system. Background Technology

[0002] Long-series battery packs are prone to inconsistent charge levels due to differences in performance parameters among individual cells and uneven performance during charging and discharging. As the batteries age, this imbalance worsens, leading to reduced energy efficiency and potential safety hazards. Therefore, designing an active balancing management system that balances efficiency, speed, and structural practicality is of significant research and economic value for fully realizing battery potential, ensuring safe system operation, and promoting green transformation.

[0003] To address the aforementioned technical issues, the Jiangmen Power Supply Bureau of Guangdong Power Grid Co., Ltd. filed a patent application with publication number CN121238757A, entitled "An Active Battery Balancing System and Method." This method uses a half-bridge LLC converter as a unified energy conversion unit, in conjunction with a switch array to selectively connect individual battery cells. However, this method can only balance one battery cell at a time. To ensure balancing speed when there are many batteries, multiple converters are needed to achieve simultaneous balancing of multiple battery cells. Summary of the Invention

[0004] To address the aforementioned problems in the existing technology, the present invention aims to provide a single-stage interleaved balancing circuit for a battery energy storage system. By interleaving multiple battery balancing modules, parallel balancing of multiple batteries and multiple battery balancing modules is achieved, enabling energy to be exchanged between individual batteries and battery balancing modules, as well as directly transferred between individual batteries.

[0005] To address the aforementioned problems, this invention provides a single-stage interleaved equalization circuit for a battery energy storage system. The single-stage interleaved equalization circuit includes multiple battery equalization modules. The output terminal of the energy storage system in each battery equalization module is connected to the input terminal of an integrated cascaded multiport converter via a switch array. The output terminal of the integrated cascaded multiport converter is connected to the input terminal of the energy storage system in another battery equalization module.

[0006] Optionally, the output of the integrated cascaded multiport converter is connected to the input of the energy storage system in another battery balancing module, including: the output of the integrated cascaded multiport converter in the current battery balancing module is connected to the input of the energy storage system in the next battery balancing module, and the output of the integrated cascaded multiport converter in the last battery balancing module is connected to the input of the energy storage system in the first battery balancing module.

[0007] Optionally, the energy storage system in each battery balancing module includes m series-connected battery packs and the integrated cascaded multiport converter includes m integrated cascaded units. Each battery pack includes n series-connected individual cells. The switch array includes m (n+1) selection switches. Each battery pack corresponds to n+1 selection switches. The positive and negative terminals of each individual cell are respectively connected to one end of a selection switch. Two adjacent individual cells in each battery pack share one selection switch. The other end of the selection switch with an odd number is connected to one of the input terminals of the corresponding integrated cascaded unit, and the other end of the selection switch with an even number is connected to the other input terminal of the corresponding integrated cascaded unit.

[0008] Optionally, the integrated cascaded unit includes a first switching transistor, a second switching transistor, a third switching transistor, a fourth switching transistor, an equalization bus capacitor, a filter inductor, a filter capacitor, a first voltage divider capacitor, and a second voltage divider capacitor, wherein:

[0009] One end of the balancing bus capacitor is connected to one end of the first switching transistor, the third switching transistor, and the first voltage divider capacitor. The other end of the first switching transistor is connected to one end of the second switching transistor and the filter inductor. The other end of the third switching transistor is connected to one end of the fourth switching transistor and the filter capacitor. The other end of the filter inductor is connected to the other end of the filter capacitor. The other end of the first voltage divider capacitor is connected to one end of the second voltage divider capacitor. The other end of the balancing bus capacitor is connected to the other end of the second switching transistor, the fourth switching transistor, and the second voltage divider capacitor.

[0010] Optionally, one input terminal of the integrated cascade unit includes the other end of the filter capacitor, and the other input terminal of the integrated cascade unit includes one end of the filter capacitor.

[0011] Optionally, the integrated cascaded multiport converter further includes a transformer, one end of the primary winding of the transformer is connected to one end of the filter capacitor, the other end of the third switch and one end of the fourth switch, and the other end of the primary winding of the transformer is connected to the other end of the first voltage divider capacitor and one end of the second voltage divider capacitor.

[0012] Optionally, the integrated cascaded multiport converter further includes an AC-to-DC converter, which includes a fifth switch, a sixth switch, a third voltage divider capacitor, a fourth voltage divider capacitor, and a bus capacitor, wherein: One end of the fifth switching transistor is connected to one end of the third voltage divider capacitor and one end of the bus capacitor. The other end of the fifth switching transistor is connected to one end of the secondary winding of the transformer and one end of the sixth switching transistor. The other end of the third voltage divider capacitor is connected to the other end of the secondary winding of the transformer and one end of the fourth voltage divider capacitor. The other end of the sixth switching transistor is connected to the other end of the fourth voltage divider capacitor and the other end of the bus capacitor.

[0013] Optionally, the output of the integrated cascaded multiport converter includes one end and the other end of the bus capacitor, and the input of the energy storage system includes one end of the first cell of the first battery pack and the other end of the last cell of the last battery pack.

[0014] Optionally, when balancing from a single cell to the battery pack or from the battery pack to a single cell in a single battery balancing module, the power transferred is: , in, The total voltage of the energy storage system is [value missing]. The duty cycle of the second, third, and fifth switching transistors. The phase shift duty cycle between the primary and secondary sides of the transformer is given. This refers to the equivalent leakage inductance between the primary and secondary windings of the transformer. The switching frequency of the first switch, the second switch, the third switch, and the fourth switch.

[0015] Optionally, when balancing individual cells from one battery pack to another in a single battery balancing module, the power transferred is: , in, This refers to the voltage of the filter capacitor in the integrated cascaded unit corresponding to the undercharged individual battery cell. The duty cycle of the second, third, and fifth switching transistors. The phase shift duty cycle between the primary and secondary sides of the transformer is given. The leakage inductance of the secondary winding of the transformer. The switching frequency of the first switch, the second switch, the third switch, and the fourth switch.

[0016] To address the aforementioned problems, the single-stage interleaved balancing circuit for a battery energy storage system provided by this invention includes multiple battery balancing modules. The output terminal of the energy storage system in each battery balancing module is connected to the input terminal of an integrated cascaded multiport converter via a switch array. The output terminal of the integrated cascaded multiport converter is connected to the input terminal of the energy storage system in another battery balancing module. This allows multiple battery balancing modules to be interleaved, achieving parallel balancing of multiple batteries and multiple battery balancing modules. This enables energy to be exchanged both between individual batteries and battery balancing modules, as well as directly transferred between individual batteries. Attached Figure Description

[0017] Figure 1 A schematic diagram of a single-stage interleaved equalization circuit for a battery energy storage system is provided. Figure 2 A schematic diagram of an integrated cascaded unit is provided. Figure 3 A schematic diagram of a battery balancing module is provided. Figure 4 A schematic diagram of the balancing path from an odd-numbered overcharged individual cell to the battery pack is provided. Figure 5 for Figure 4 A schematic diagram of the switching timing and voltage and current waveforms of each parameter during operation; Figure 6 A schematic diagram of the balancing path from the battery pack to the even-numbered undercharged individual cells is provided. Figure 7 for Figure 6 A schematic diagram of the switching timing and voltage and current waveforms of each parameter during operation; Figure 8 A schematic diagram of the equalization path from an odd-numbered overcharged single cell to a single cell is provided. Figure 9 for Figure 8 A schematic diagram of the switching timing and voltage and current waveforms of each parameter during operation; Figure 10 A schematic diagram of a single-stage interleaved equalization circuit for a battery energy storage system is provided for simulation. Figure 11 A simulation waveform diagram of the equalization working mode from a single cell to a battery pack is provided. Figure 12 A simulation waveform diagram is provided for the battery pack to single cell equalization working mode. Figure 13 A simulation waveform diagram of a single-cell to single-cell equalization working mode is provided. Detailed Implementation

[0018] The present invention will be further described below with reference to specific embodiments.

[0019] The present invention first provides a single-stage interleaved equalization circuit for a battery energy storage system. The single-stage interleaved equalization circuit for a battery energy storage system includes multiple battery equalization modules. The output terminal of the energy storage system in each battery equalization module is connected to the input terminal of an integrated cascaded multiport converter through a switch array. The output terminal of the integrated cascaded multiport converter is connected to the input terminal of the energy storage system in another battery equalization module.

[0020] The battery balancing module is used to balance the charge of individual cells or battery packs within the included energy storage system. An integrated cascaded multiport converter is used for DC-DC conversion. In this embodiment, the output of the integrated cascaded multiport converter is connected to the input of the energy storage system in another battery balancing module. This connection can be such that the output of the integrated cascaded multiport converter in the first battery balancing module is connected to the input of the energy storage system in the second battery balancing module, the output of the integrated cascaded multiport converter in the second battery balancing module is connected to the input of the energy storage system in the third battery balancing module, and so on, until the output of the integrated cascaded multiport converter in the kth battery balancing module is connected to the input of the energy storage system in the first battery balancing module. Alternatively, the output of the integrated cascaded multiport converter in the first battery balancing module can be connected to the input of the energy storage system in the third battery balancing module, and so on. No further limitation is made here.

[0021] like Figure 1 As shown, a schematic diagram of a single-stage interleaved balancing circuit for a battery energy storage system is provided. In this circuit, the output of the integrated cascaded multiport converter in the current battery balancing module is connected to the input of the energy storage system in the next battery balancing module, and the output of the integrated cascaded multiport converter in the last battery balancing module is connected to the input of the energy storage system in the first battery balancing module. Specifically, the output of the integrated cascaded multiport converter in the first battery balancing module is connected to the input of the energy storage system in the second battery balancing module, the output of the integrated cascaded multiport converter in the second battery balancing module is connected to the input of the energy storage system in the third battery balancing module, and so on, until the output of the integrated cascaded multiport converter in the kth battery balancing module is connected to the input of the energy storage system in the first battery balancing module.

[0022] As can be seen, in this embodiment of the invention, the single-stage interleaved balancing circuit of the battery energy storage system includes multiple battery balancing modules. The output terminal of the energy storage system in each battery balancing module is connected to the input terminal of an integrated cascaded multiport converter via a switch array. The output terminal of the integrated cascaded multiport converter is connected to the input terminal of the energy storage system in another battery balancing module. This allows multiple battery balancing modules to be interleaved, achieving parallel balancing of multiple batteries and multiple battery balancing modules, enabling energy to be exchanged between individual batteries and battery balancing modules, as well as directly transferred between individual batteries.

[0023] like Figure 2 As shown, a schematic diagram of an integrated cascade unit is provided. The integrated cascade unit includes a first switching transistor. Second switching transistor Third switching transistor Fourth switching transistor 1. Equalizing bus capacitor Filter inductor Filter capacitor First voltage divider capacitor Second voltage divider capacitor ,in: The equalization bus capacitor One end is connected to the first switching transistor The third switching transistor and the first voltage divider capacitor One end is connected to the first switching transistor. The other end is connected to the second switching transistor and the filter inductor One end is connected to the third switch transistor. The other end is connected to the fourth switch. and the filter capacitor One end is connected to the filter inductor. The other end is connected to the filter capacitor The other end is connected to the first voltage divider capacitor. The other end is connected to one end of the second voltage divider capacitor. Connection, the equalization bus capacitor The other end is connected to the second switching transistor The fourth switching transistor and the second voltage divider capacitor The other end is connected.

[0024] Among them, the first switching transistor Second switching transistor Third switching transistor Fourth switching transistor 1. Equalizing bus capacitor Filter inductor and filter capacitor Composed of a bidirectional Buck-Boost unit, the first switching transistor Second switching transistor Forming a pair of complementary conducting bridge arms, the third switching transistor and the fourth switching transistor This forms another pair of complementary conducting bridge arms. The third switching transistor... Fourth switching transistor First voltage divider capacitor Second voltage divider capacitor Composed of a DC-AC converter unit, third switching transistor and the fourth switching transistor Forming a pair of complementary conducting bridge arms, the first voltage divider capacitor Second voltage divider capacitor This forms another pair of complementary conducting arms. For filter capacitors voltage, It serves as both the output voltage of the bidirectional Buck-Boost unit and the input voltage of the DC-AC unit. This is the output voltage of the DC-AC unit. (The sentence is incomplete and requires more context to translate accurately.) Connect to the energy storage system, Connecting to a transformer allows for charging and discharging of batteries in an energy storage system.

[0025] As can be seen, in this embodiment of the invention, the bidirectional Buck-Boost unit and the DC-AC unit share two switching transistors, which can reduce the number of switches in the integrated cascaded unit, thereby achieving a more compact size and higher integration.

[0026] Optionally, the energy storage system in each battery balancing module includes m series-connected battery packs and the integrated cascaded multiport converter includes m integrated cascaded units. Each battery pack includes n series-connected individual cells. The switch array includes m (n+1) selection switches. Each battery pack corresponds to n+1 selection switches. The positive and negative terminals of each individual cell are respectively connected to one end of a selection switch. Two adjacent individual cells in each battery pack share one selection switch. The other end of the selection switch with an odd number is connected to one of the input terminals of the corresponding integrated cascaded unit, and the other end of the selection switch with an even number is connected to the other input terminal of the corresponding integrated cascaded unit.

[0027] like Figure 3 As shown, a schematic diagram of a battery balancing module is provided. The battery balancing module includes m components as shown in the diagram. Figure 2 The integrated cascaded units shown comprise an integrated cascaded multiport converter, an energy storage system, and a switch array. The energy storage system includes m battery packs connected in series, and each battery pack includes n individual cells connected in series. The switch array includes m (n+1) selector switches, each battery pack corresponds to n+1 selector switches, the positive and negative terminals of each individual battery are respectively connected to one end of a selector switch, two adjacent individual batteries in each battery pack share one selector switch, the other end of the selector switch with odd number is connected to one of the input terminals of the corresponding integrated cascade unit, and the other end of the selector switch with even number is connected to the other input terminal of the corresponding integrated cascade unit.

[0028] In this configuration, one input terminal of the integrated cascade unit includes the other end of the filter capacitor, and the other input terminal of the integrated cascade unit includes one end of the filter capacitor. The other end of the selector switch with an odd-numbered sequence number is connected to one input terminal of the corresponding integrated cascade unit, and the other end of the selector switch with an even-numbered sequence number is connected to the other input terminal of the corresponding integrated cascade unit. That is, the other end of the selector switch with an odd-numbered sequence number is connected to the other end of the filter capacitor, and the other end of the selector switch with an even-numbered sequence number is connected to one end of the filter capacitor.

[0029] Where i ranges from 1 to m, and j ranges from 1 to n, for example, in a battery pack. Includes n individual cells Battery pack Includes n individual cells ..., battery pack Includes n individual cells Both m and n are integers greater than 0.

[0030] battery pack The corresponding n+1 selection switches are , ...battery pack The corresponding n+1 selection switches are , , ··· , ······, battery pack The corresponding n+1 selection switches are , ··· )composition.

[0031] In traditional balancing architectures, each battery pack requires 2n selection switches, and the voltage polarity of the unbalanced unit connected to the bidirectional converter is fixed. In the balancing architecture of this invention, each integrated cascaded unit adjusts the voltage polarity of the unbalanced unit by setting four polarity switches, reducing the number of bidirectional switches in the switch array to n+1. The polarity switches include a first switch, a second switch, a third switch, and a fourth switch. Each odd-numbered cell in the battery pack adjusts its polarity via the first and fourth switches, while each even-numbered cell adjusts its polarity via the second and third switches. Regardless of whether the number of cells is odd or even, adjusting the polarity via the polarity switches allows for equalization of the bus capacitor. It withstands voltages that are positive at the top and negative at the bottom, thus keeping the polarity of the half-bridge input port unchanged.

[0032] As can be seen, multiple of these integrated cascaded units can form an integrated cascaded multiport converter for use in the battery energy storage system balancing circuit. This reduces the number of switches required in the battery energy storage system balancing circuit. During operation, the balancing of unbalanced batteries with different voltage polarities is achieved by controlling the operating state of the integrated cascaded units, avoiding the coordination problems of selection switches and polarity switches. Furthermore, only one integrated cascaded multiport converter is needed to simultaneously balance multiple unbalanced battery cells, resulting in a more compact structure and higher integration.

[0033] Or as Figure 3 As shown, the battery energy storage system balancing circuit also includes a transformer, one end of the primary winding of the transformer being connected to the filter capacitor. ··· One end of the third switch transistor ··· The other end and the fourth switch ··· One end of the transformer is connected to the primary winding, and the other end of the transformer is connected to the first voltage-dividing capacitor. ··· The other end and the second voltage divider capacitor ··· One end is connected.

[0034] The transformer can be a high-frequency transformer that includes multiple primary windings and a single secondary winding, or it can be a transformer unit composed of multiple high-frequency transformers. Figure 3 Take a high-frequency transformer, which includes multiple primary windings and a single secondary winding, as an example.

[0035] Or as Figure 3As shown, the battery energy storage system balancing circuit also includes an AC-DC converter, which includes a fifth switching transistor. Sixth switch tube Third voltage divider capacitor Fourth voltage divider capacitor and bus capacitors ,in: The fifth switching transistor One end is connected to the third voltage divider capacitor one end and the bus capacitor One end is connected to the fifth switch transistor. The other end is connected to one end of the secondary winding of the transformer and the sixth switch. One end is connected to the third voltage divider capacitor. The other end is connected to the other end of the transformer secondary winding and the fourth voltage divider capacitor. One end is connected to the sixth switch transistor. The other end is connected to the fourth voltage divider capacitor. The other end and the bus capacitor The other end is connected.

[0036] The integrated cascaded multiport converter comprises multiple cascaded units, a transformer, and the AC-to-DC converter. In this integrated cascaded multiport converter, the switching signals of the first and fourth switches, the second and third switches, and the fifth and sixth switches are complementary. The switching frequencies of the first, second, third, fourth, fifth, and sixth switches can be the same.

[0037] The output of the integrated cascaded multiport converter includes the bus capacitor. The energy storage system has one end and the other end, and the input end includes the first single cell of the first battery pack. One end and the last single cell of the last battery pack The other end.

[0038] like Figure 1 As shown, the output of the integrated cascaded multiport converter in the first battery balancing module is connected to the input of the energy storage system in the second battery balancing module, i.e., the bus capacitor in the first battery balancing module. The two ends and the individual cells in the second battery balancing module One end and single cell The other end is connected; the output of the integrated cascaded multiport converter in the second battery balancing module is connected to the input of the energy storage system in the third battery balancing module, i.e., the bus capacitor in the second battery balancing module. The two ends and the individual cells in the third battery balancing module One end and single cell The other end is connected; ... The output of the integrated cascaded multiport converter in the k-th battery balancing module is connected to the input of the energy storage system in the 1st battery balancing module, i.e., the bus capacitor in the k-th battery balancing module. The two ends of the battery are connected to the individual cells in the first battery balancing module. One end and single cell The other end is connected.

[0039] Furthermore, such as Figure 1 As shown, the single-stage interleaved equalization circuit of the battery energy storage system may also include a monitoring circuit and a control circuit. Each individual battery in the energy storage system is connected to the input terminal of the monitoring circuit, allowing the monitoring circuit to obtain sampled values ​​of parameters such as voltage, current, and state of charge (SOC) of each individual battery. Therefore, the monitoring circuit can be a current monitoring circuit, a voltage detection circuit, or an SOC monitoring circuit, and no limitation is made here.

[0040] In one specific embodiment of the present invention, the monitoring circuit transmits the sampled values ​​to the microcontroller. The microcontroller compares and calculates the battery parameters of each individual cell in each battery pack to determine the cells to be balanced. Then, it drives the switch array to close the bidirectional switch of the corresponding module, allowing the individual cells to be connected to the port of the integrated cascaded converter. The polarity is then adjusted via a power switch, allowing the connected individual battery cells to perform charging and discharging operations under the corresponding operating circuit structure. In this embodiment, the PWM signal generated by the microcontroller controls the conduction of each switching transistor through a drive circuit, thus enabling the switching of the operating mode of the single-stage interleaved equalization architecture.

[0041] Because odd-numbered and even-numbered battery cells are connected to the port voltage of the integrated cascaded multiport converter via a switch array. Based on the different polarities of the voltage and the different objects of energy transfer, the microcontroller classifies the single-stage interleaved balancing circuit of the battery energy storage system into three operating states according to the voltage polarity and the operating state of the dual integrated cascaded multi-port converter: single-cell to battery pack balancing, battery pack to single-cell balancing, and single-cell to single-cell balancing. The following detailed explanation uses odd-numbered single-cell cells as an example for boost mode, even-numbered single-cell cells as an example for buck mode, and odd-numbered single-cell to odd-numbered single-cell balancing as an example.

[0042] The microcontroller calculates the state of charge (SOC) of each individual battery in the energy storage system based on sampled values ​​and sorts the unbalanced batteries according to the difference between the SOC of each individual battery and the average SOC of the battery pack. When the difference between the SOC of an individual battery and the average SOC of the battery pack is greater than the set maximum balancing threshold, the converter will operate in a discharging state to release the energy in the overcharged battery to the battery pack of other battery balancing modules or other individual batteries within that battery balancing module; when the difference between the SOC of an individual battery and the average SOC of the battery pack is less than the set minimum balancing threshold, the converter will operate in a charging state to release the energy in the battery pack of other battery balancing modules or other individual batteries within that battery balancing module to the undercharged battery.

[0043] When used for balancing from a single cell to the battery pack, the two selection switches connected to both sides of the overcharged single cell are closed. The integrated cascaded multiport converter corresponding to the overcharged single cell operates in boost mode, and energy is transferred from the overcharged single cell to the balancing bus capacitor. The integrated cascaded multiport converter adjusts the polarity of one end of the balancing bus capacitor to the positive terminal and the polarity of the other end of the balancing bus capacitor to the negative terminal. The energy is then transferred from the balancing bus capacitor to the energy storage system of other battery balancing modules through the transformer and the AC-to-DC converter.

[0044] Please refer to Figure 4 and Figure 5 , Figure 4 A schematic diagram of the balancing path from an odd-numbered overcharged individual cell to the battery pack is provided. Figure 5 for Figure 4 The diagram shows the switching timing and voltage / current waveforms of various parameters during operation. This battery energy storage system's single-stage interleaved balancing circuit includes three battery balancing modules, and the individual cells within these modules... and single cell battery All batteries are in an overcharged state. The microcontroller controls the converter to operate in boost mode. The bidirectional switches in the switch array of the three battery balancing modules... , , and Closure. Coordination. Figure 5 The switching timing in the module allows energy to be supplied from three battery balancing modules. and The data is transmitted to the three battery balancing modules respectively. and The polarity is adjusted by integrating cascaded units, and finally, energy is transferred from the first battery balancing module through an integrated cascaded multi-port converter. and The energy is transferred from the battery pack to the second battery balancing module. and The energy is transferred from the battery pack to the third battery balancing module. and The battery pack is transferred to the first battery balancing module.

[0045] Wherein, the power transferred during the balancing of individual cells to the battery pack in a single battery balancing module is: , in, The total voltage of the energy storage system is [value missing]. The duty cycle of the second, third, and fifth switching transistors. The phase shift duty cycle between the primary and secondary sides of the transformer is given. This refers to the equivalent leakage inductance between the primary and secondary windings of the transformer. The switching frequency of the first switch, the second switch, the third switch, and the fourth switch.

[0046] The following is a derivation of the expression for the power transfer from a single cell to the battery pack: The transformer turns ratio is 1:1:N. The total voltage of the energy storage system. The duty cycle of the second, third, and fifth switching transistors. For work cycles. The phase shift duty cycle between the primary and secondary sides of the transformer indicates that the converter is operating in boost mode. When >0, the voltage relationship between the primary and secondary sides of the converter and the volt-second balance relationship of the inductor can be written as follows: , Voltage gain: , Overcharged single cell For example, the voltage across each capacitor: , Overcharged single cell battery The corresponding leakage inductance of the primary winding, Overcharged single cell battery The corresponding leakage inductance of the primary winding, This represents the leakage inductance of the secondary winding. After the "Y-Δ" transformation, the equivalent circuit of the second-stage circuit structure based on the "Δ" type transformer model can be obtained, where... , and It is the equivalent leakage inductance between the windings of the transformer: , For flowing through and current The initial value is then used to input the high-voltage side into one port on the low-voltage side during one switching cycle. The current can be expressed as: , Right now:

[0047] For overcharged single-cell batteries The expression for the power transmitted from the low-voltage side to the high-voltage side is: , For overcharged single-cell batteries The expression for the power transmitted from the low-voltage side to the high-voltage side is: .

[0048] Therefore, if using express and ,use express and The expression for the power transmitted from the low-voltage side to the high-voltage side is: .

[0049] When used for balancing from the battery pack to individual cells, the two selection switches connected to both sides of the undercharged individual cell are closed. The integrated cascade unit corresponding to the undercharged individual cell operates in buck mode. Energy is transferred from the energy storage system to the balancing bus capacitor through the AC-to-DC converter and the transformer. The integrated cascade unit adjusts the polarity of the other end of the balancing bus capacitor to the positive terminal and adjusts the polarity of one end of the balancing bus capacitor to the negative terminal. Energy is then transferred from the balancing bus capacitor to the undercharged individual cell.

[0050] Please refer to Figure 6 and Figure 7 , Figure 6 A schematic diagram of the balancing path from the battery pack to the even-numbered undercharged individual cells is provided. Figure 7 for Figure 6 The diagram shows the switching timing and voltage / current waveforms of various parameters during operation. This battery energy storage system's single-stage interleaved balancing circuit includes three battery balancing modules, and the individual cells within these modules... and single cell battery All batteries are in an undercharged state, and the microcontroller controls the converter to operate in buck mode. The bidirectional switches in the switch array of the three battery balancing modules... , , and Closure. Coordination. Figure 7 In the switching sequence, the energy from the energy storage system in the first battery balancing module is transferred to the third battery balancing module through an integrated cascaded multiport converter. and The energy from the energy storage system in the second battery balancing module is transferred to the first battery balancing module via an integrated cascaded multiport converter. and The energy from the energy storage system in the third battery balancing module is transferred to the second battery balancing module via an integrated cascaded multiport converter. and Finally, by adjusting the polarity through an integrated cascade unit, energy is distributed from the three battery balancing modules. and Transmitted to their respective and middle.

[0051] The following is a derivation of the expression for the power transfer from the battery pack to the individual cells: The phase shift duty cycle between the primary and secondary sides of the converter operating in buck mode <0.

[0052] Voltage gain: , For the specific derivation method, please refer to the previous embodiment. The power expression for power transmitted from the high-voltage side to the low-voltage side is as follows: , , Therefore, if using express and ,use express and The expression for the power transmitted from the low-voltage side to the high-voltage side is: .

[0053] When used for single-cell to single-cell balancing, for each battery balancing module, the two selection switches connected to both sides of the overcharged single cell are closed. The integrated cascade unit corresponding to the overcharged single cell operates in boost mode. Energy is transferred from the overcharged single cell to the balancing bus capacitor in the integrated cascade unit corresponding to the overcharged single cell. The integrated cascade unit corresponding to the overcharged single cell adjusts the polarity of one end of the balancing bus capacitor in the integrated cascade unit corresponding to the overcharged single cell to the positive terminal and adjusts the polarity of the other end of the balancing bus capacitor in the integrated cascade unit corresponding to the overcharged single cell to the negative terminal. Energy is then transferred from the balancing bus capacitor in the integrated cascade unit corresponding to the overcharged single cell to the balancing bus capacitor in the integrated cascade unit corresponding to the undercharged single cell through the transformer. When the two selector switches connected to both sides of the undercharged single cell are closed, the integrated cascade unit corresponding to the undercharged single cell operates in buck mode. The integrated cascade unit corresponding to the undercharged single cell adjusts the polarity of the other end of the equalization bus capacitor in the integrated cascade unit corresponding to the undercharged single cell to positive and adjusts the polarity of one end of the equalization bus capacitor in the integrated cascade unit corresponding to the undercharged single cell to negative. Energy is then transferred from the equalization bus capacitor to the undercharged single cell.

[0054] Please refer to Figure 8 and Figure 9 , Figure 8 A schematic diagram of the equalization path from an odd-numbered overcharged single cell to a single cell is provided. Figure 9 for Figure 8 The diagram shows the switching timing and voltage / current waveforms of various parameters during operation. This battery energy storage system's single-stage interleaved balancing circuit includes three battery balancing modules, and the individual cells within these modules... In an overcharged state, and individual battery cells The battery is in an undercharged state. The microcontroller controls the converter to operate in a single-cell-to-single-cell balancing state, using bidirectional switches in the switch array of the three battery balancing modules. , , and Closure. Coordination. Figure 9 In the switching timing, for each battery balancing module, energy is drawn from its respective... Passed to The polarity is adjusted by integrating cascaded units, and then the energy is transferred from... Passed to Then, by adjusting the polarity through integrated cascade units, energy flows from their respective... Passed to .

[0055] Wherein, when balancing individual cells from one battery pack to another battery pack in a single battery balancing module, the power of energy transfer is: , in, This refers to the voltage of the filter capacitor in the integrated cascaded unit corresponding to the undercharged individual battery cell. The duty cycle of the second, third, and fifth switching transistors. The phase shift duty cycle between the primary and secondary sides of the transformer is given. The leakage inductance of the secondary winding of the transformer. The switching frequency of the first switch, the second switch, the third switch, and the fourth switch.

[0056] The following is a derivation of the expression for the power transfer from one cell to another: Voltage gain: , The expression for the power transferred from a single cell in one battery pack to a single cell in another battery pack is:

[0057] Therefore, if using express Then the power of energy transfer is: .

[0058] Simulation verification was performed using a battery string consisting of 24 individual cells (divided into 3 modules, each module containing 8 cells; each module is further divided into 2 battery packs, each battery pack containing 4 cells). Figure 10 The specific simulation structure is shown.

[0059] When performing a single-cell to battery pack equalization simulation, set the single-cell M1_B of one battery pack in the first module. 11 The initial SOC value is 85.5%, and the single cell M1_B of the other battery pack... 21 The initial SOC value is 86%; the single cell M2_B of one battery pack in the second module is set. 11 The initial SOC value is 86.5%, and the single cell M2_B of the other battery pack... 21 The initial SOC value is 87%; the single cell M3_B of one battery pack in the third module is set. 11The initial SOC value is 87.5%, and the single cell M3_B of the other battery pack... 21 The initial SOC value of the first cell is 88%. The initial SOC value of the remaining 18 individual cells is 85%.

[0060] When performing battery pack-to-cell equalization simulation, set the cell M1_B of one battery pack in the first module. 11 The initial SOC value is 84.5%, and the single cell M1_B of the other battery pack... 21 The initial SOC value is 84%; the individual cell M2_B of one battery pack in the second module is set. 11 The initial SOC value is 83.5%, and the single cell M2_B of the other battery pack... 21 The initial SOC value is 83%; the single cell M3_B of one battery pack in the third module is set. 11 The initial SOC value is 82.5%, and the single cell M3_B of the other battery pack... 21 The initial SOC value of the first cell is 82%. The initial SOC value of the remaining 18 individual cells is 85%.

[0061] When performing single-cell-to-single-cell equalization simulation, set the single cell M1_B of one battery pack in the first module. 11 The initial SOC value is 87%, and the single cell M1_B of the other battery pack... 21 The initial SOC value is 86%; the single cell M2_B of one battery pack in the second module is set. 11 The initial SOC value is 84%, and the single cell M2_B of the other battery pack... 21 The initial SOC value is 83%; the single cell M3_B of one battery pack in the third module is set. 11 The initial SOC value is 82%, and the single cell M3_B of the other battery pack... 21 The initial SOC value of the first cell is 81%. The initial SOC value of the remaining 18 individual cells is 85%.

[0062] Equalization simulation waveforms for each working mode are as follows: Figure 11 , 12 As shown in Figures 1 and 13, the results indicate that the single-stage interleaved equalization circuit for the battery energy storage system provided by this invention meets the design requirements.

[0063] In summary, the single-stage interleaved equalization circuit for battery energy storage systems provided by this invention has the following beneficial effects: 1) Based on a multi-module staggered topology and a "cell-module integration" collaborative mechanism, this architecture enables multi-dimensional direct energy transfer between cells, between cells and modules, and between modules, breaking through the port capacity limitations of traditional single-module solutions. Compared to centralized solutions that can only balance a single cell or a group of batteries in the same state at a time, this architecture can expand through module staggering to simultaneously handle unbalanced batteries of multiple cells and multiple modules, significantly improving the effective capacity of the balancing port. It is perfectly adapted to large-scale battery systems with ultra-long series connections, large capacity, and high inconsistency, and its balancing efficiency and scenario adaptability are significantly better than single-module architectures.

[0064] 2) Multi-stage balancing architectures suffer from drawbacks such as large size, high cost, and low efficiency. A single-stage topology eliminates the intermediate energy conversion stage of traditional multi-stage balancing architectures, significantly reducing energy loss, shortening the balancing path, reducing the number of power devices, enhancing structural practicality, and significantly improving energy transfer efficiency. The Buck-Boost integrated cascade structure in each module, combined with the inherent advantages of multi-module interleaving, further broadens the dynamic adjustment range of the balancing voltage gain, ensuring rapid and efficient energy transfer between different modules and batteries in different states. Simultaneously, the interleaved topology and continuous current control strategy work together to avoid potential damage to individual battery cells from sudden current changes, balancing high balancing efficiency with battery life protection, achieving the goals of efficient balancing and battery friendliness.

[0065] 3) This innovative "cell-module integration" collaborative logic ensures SOC consistency for each battery cell through precise monitoring and balancing at the cell level, while optimizing the overall balancing rhythm through module-level energy management and scheduling, preventing local imbalances from affecting system performance. Compared to traditional balancing solutions that only focus on cells or modules, this architecture achieves precise balancing at the microscopic level and efficient overall coordination at the macroscopic level. It is particularly suitable for complex scenarios with large differences in battery consistency, offering superior balancing stability and reliability.

Claims

1. A single-stage interleaved equalization circuit for a battery energy storage system, characterized in that, The single-stage interleaved equalization circuit of the battery energy storage system includes multiple battery equalization modules. The output terminal of the energy storage system in each battery equalization module is connected to the input terminal of an integrated cascaded multiport converter through a switch array. The output terminal of the integrated cascaded multiport converter is connected to the input terminal of the energy storage system in another battery equalization module.

2. A single-stage interleaved equalization circuit for a battery energy storage system according to claim 1, characterized in that, The output of the integrated cascaded multiport converter is connected to the input of the energy storage system in another battery balancing module, including: the output of the integrated cascaded multiport converter in the current battery balancing module is connected to the input of the energy storage system in the next battery balancing module, and the output of the integrated cascaded multiport converter in the last battery balancing module is connected to the input of the energy storage system in the first battery balancing module.

3. A single-stage interleaved equalization circuit for a battery energy storage system according to claim 2, characterized in that, The energy storage system in each battery balancing module includes m series-connected battery packs and the integrated cascaded multiport converter includes m integrated cascaded units. Each battery pack includes n series-connected individual cells. The switch array includes m (n+1) selection switches. Each battery pack corresponds to n+1 selection switches. The positive and negative terminals of each individual cell are respectively connected to one end of a selection switch. Two adjacent individual cells in each battery pack share one selection switch. The other end of the selection switch with an odd number is connected to one of the input terminals of the corresponding integrated cascaded unit, and the other end of the selection switch with an even number is connected to the other input terminal of the corresponding integrated cascaded unit.

4. A single-stage interleaved equalization circuit for a battery energy storage system according to claim 3, characterized in that, The integrated cascaded unit includes a first switching transistor, a second switching transistor, a third switching transistor, a fourth switching transistor, an equalization bus capacitor, a filter inductor, a filter capacitor, a first voltage divider capacitor, and a second voltage divider capacitor, wherein: One end of the balancing bus capacitor is connected to one end of the first switching transistor, the third switching transistor, and the first voltage divider capacitor. The other end of the first switching transistor is connected to one end of the second switching transistor and the filter inductor. The other end of the third switching transistor is connected to one end of the fourth switching transistor and the filter capacitor. The other end of the filter inductor is connected to the other end of the filter capacitor. The other end of the first voltage divider capacitor is connected to one end of the second voltage divider capacitor. The other end of the balancing bus capacitor is connected to the other end of the second switching transistor, the fourth switching transistor, and the second voltage divider capacitor.

5. A single-stage interleaved equalization circuit for a battery energy storage system according to claim 4, characterized in that, One input terminal of the integrated cascade unit includes the other end of the filter capacitor, and the other input terminal of the integrated cascade unit includes one end of the filter capacitor.

6. A single-stage interleaved equalization circuit for a battery energy storage system according to claim 5, characterized in that, The integrated cascaded multiport converter also includes a transformer, one end of the primary winding of the transformer is connected to one end of the filter capacitor, the other end of the third switch and one end of the fourth switch, and the other end of the primary winding of the transformer is connected to the other end of the first voltage divider capacitor and one end of the second voltage divider capacitor.

7. A single-stage interleaved equalization circuit for a battery energy storage system according to claim 6, characterized in that, The integrated cascaded multiport converter also includes an AC-to-DC converter, which comprises a fifth switch, a sixth switch, a third voltage divider capacitor, a fourth voltage divider capacitor, and a bus capacitor, wherein: One end of the fifth switching transistor is connected to one end of the third voltage divider capacitor and one end of the bus capacitor. The other end of the fifth switching transistor is connected to one end of the secondary winding of the transformer and one end of the sixth switching transistor. The other end of the third voltage divider capacitor is connected to the other end of the secondary winding of the transformer and one end of the fourth voltage divider capacitor. The other end of the sixth switching transistor is connected to the other end of the fourth voltage divider capacitor and the other end of the bus capacitor.

8. A single-stage interleaved equalization circuit for a battery energy storage system according to claim 7, characterized in that, The output of the integrated cascaded multiport converter includes one end and the other end of the bus capacitor, and the input of the energy storage system includes one end of the first cell of the first battery pack and the other end of the last cell of the last battery pack.

9. A single-stage interleaved equalization circuit for a battery energy storage system according to claim 8, characterized in that, When balancing individual cells to the battery pack and from the battery pack to individual cells in a single battery balancing module, the power transferred is: ， in, The total voltage of the energy storage system is [value missing]. The duty cycle of the second, third, and fifth switching transistors. The phase shift duty cycle between the primary and secondary sides of the transformer is given. This refers to the equivalent leakage inductance between the primary and secondary windings of the transformer. The switching frequency of the first switch, the second switch, the third switch, and the fourth switch.

10. A single-stage interleaved equalization circuit for a battery energy storage system according to claim 9, characterized in that, When balancing individual cells from one battery pack to another in a single battery balancing module, the power transferred is: ， in, This refers to the voltage of the filter capacitor in the integrated cascaded unit corresponding to the undercharged individual battery cell. The duty cycle of the second, third, and fifth switching transistors. The phase shift duty cycle between the primary and secondary sides of the transformer is given. The leakage inductance of the secondary winding of the transformer. The switching frequency of the first switch, the second switch, the third switch, and the fourth switch.

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