An integrated cascaded multi-port converter and battery energy storage system equalization circuit

Abstract

The application discloses a kind of integrated cascade multi-port converter and battery energy storage system equalization circuit, the integrated cascade unit includes first switch tube, second switch tube, third switch tube, fourth switch tube, equalization bus capacitor, filter inductance, filter capacitor, first voltage divider capacitor and second voltage divider capacitor, wherein: one end of equalization bus capacitor is connected with first switch tube, third switch tube and one end of first voltage divider capacitor, the other end of first switch tube is connected with second switch tube and one end of filter inductance, the other end of third switch tube is connected with fourth switch tube and one end of filter capacitor, the other end of filter inductance is connected with the other end of filter capacitor, the other end of first voltage divider capacitor is connected with one end of second voltage divider capacitor, the other end of equalization bus capacitor is connected with second switch tube, fourth switch tube and the other end of second voltage divider capacitor.Employing the embodiment of the application can obtain more compact structure and higher integration.

Description

Technical Field

[0001] This invention relates to the field of battery balancing technology, and more specifically, to an integrated cascaded multiport converter and a battery energy storage system balancing circuit. 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 an integrated cascaded multiport converter and a battery energy storage system balancing circuit. This allows for the simultaneous balancing of multiple unbalanced battery cells by configuring a single integrated cascaded multiport converter, while reducing the number of switches, resulting in a more compact structure and higher integration.

[0005] To address the aforementioned problems, a first aspect of the present invention provides an integrated cascaded multiport converter, comprising multiple integrated cascaded units. Each integrated cascaded unit includes a first switch, a second switch, a third switch, a fourth switch, an equalization bus capacitor, a filter inductor, a filter capacitor, a first voltage divider capacitor, and a second voltage divider capacitor, wherein:

[0006] 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.

[0007] A second aspect of the present invention provides a battery energy storage system balancing circuit, the battery energy storage system balancing circuit comprising an integrated cascaded multiport converter composed of m integrated cascaded units as described in claim 1, an energy storage system, and a switch array, the energy storage system comprising m series-connected battery packs, each battery pack comprising n series-connected individual cells, the switch array comprising m (n+1) selection switches, each battery pack corresponding to n+1 selection switches, the positive and negative terminals of each individual cell being connected to one end of a selection switch respectively, two adjacent individual cells in each battery pack sharing one selection switch, the other end of the selection switch with odd number being connected to the other end of a filter capacitor, and the other end of the selection switch with even number being connected to one end of the filter capacitor.

[0008] Optionally, the battery energy storage system balancing circuit 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.

[0009] Optionally, the battery energy storage system balancing circuit further includes an AC-to-DC converter, which includes a fifth switching transistor, a sixth switching transistor, a third voltage-dividing capacitor, a fourth voltage-dividing capacitor, and a bus capacitor, wherein: One end of the fifth switch is connected to one end of the third voltage divider capacitor, one end of the bus capacitor, and the positive terminal of the first individual battery cell. The other end of the fifth switch is connected to one end of the secondary winding of the transformer and one end of the sixth switch. 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 switch is connected to the other end of the fourth voltage divider capacitor, the other end of the bus capacitor, and the negative terminal of the last individual battery cell.

[0010] Optionally, during the balancing process 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 cascade unit 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 cascade unit 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 through the transformer and the AC-to-DC converter.

[0011] Optionally, 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.

[0012] Optionally, during battery pack-to-cell balancing, the two selection switches connected to both sides of the undercharged cell are closed, the integrated cascade unit corresponding to the undercharged cell operates in buck mode, and 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 positive and the polarity of one end of the balancing bus capacitor to negative, and the energy is then transferred from the balancing bus capacitor to the undercharged cell.

[0013] Optionally, the power transferred is: , in, The total voltage of the energy storage system is [value missing]. The duty cycle of the first switch, the fourth switch, and the sixth switch. 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.

[0014] Optionally, during single-cell balancing, 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, and 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.

[0015] Optionally, 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. 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 integrated cascaded unit provided by this invention includes a first switching transistor, a second switching transistor, a third switching transistor, a fourth switching transistor, a balancing bus capacitor, a filter inductor, a filter capacitor, a first voltage divider capacitor, and a second voltage divider capacitor. Specifically: one end of the balancing bus capacitor is connected to one end of the first switching transistor, the third switching transistor, and one end of the first voltage divider capacitor; the other end of the first switching transistor is connected to one end of the second switching transistor and one end of the filter inductor; the other end of the third switching transistor is connected to one end of the fourth switching transistor and one end of 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; and the other end of the balancing bus capacitor is connected to the other ends of the second switching transistor, the fourth switching transistor, and the second voltage divider capacitor.

[0017] In this way, the first, second, third, and fourth switching transistors, the balancing bus capacitor, the filter inductor, and the filter capacitor form a bidirectional Buck-Boost unit, while the third and fourth switching transistors, the first voltage divider capacitor, and the second voltage divider capacitor form a DC-to-AC unit. By reusing the third and fourth switching transistors, the number of switches in the integrated cascade unit can be reduced, resulting in a more compact size and higher integration. Multiple such integrated cascade units can form an integrated cascaded multiport converter for battery energy storage system balancing circuits, thus reducing the number of switches 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 cascade unit, 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. Attached Figure Description

[0018] Figure 1 A schematic diagram of an integrated cascaded unit is provided. Figure 2 A schematic diagram of the equalization circuit for a battery energy storage system is provided. Figure 3 A schematic diagram of another battery energy storage system balancing circuit 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 an even number of undercharged individual cells to the battery pack is provided. Figure 7 for Figure 6A 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 single cell to 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 Simulation waveform diagrams for different operating modes are provided. Detailed Implementation

[0019] The present invention will be further described below with reference to specific embodiments.

[0020] like Figure 1 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.

[0021] 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.

[0022] 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.

[0023] like Figure 2 As shown, a schematic diagram of a battery energy storage system balancing circuit is provided. The battery energy storage system balancing circuit includes m... Figure 1 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) selection switches, each battery pack corresponds to n+1 selection switches, the positive and negative terminals of each individual battery are respectively connected to one end of a selection switch, two adjacent individual batteries in each battery pack share one selection switch, the other end of the selection switch with odd number is connected to the other end of the filter capacitor, and the other end of the selection switch with even number is connected to one end of the filter capacitor.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] Or as Figure 2 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.

[0029] 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 2 Take a high-frequency transformer, which includes multiple primary windings and a single secondary winding, as an example.

[0030] Or as Figure 2 As 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, the bus capacitor One end and the first single cell The positive terminal connection of 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, the bus capacitor The other end and the last single cell The negative terminal connection.

[0031] This integrated cascaded multiport converter comprises multiple integrated cascaded single-phase transformers 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.

[0032] like Figure 3 As shown, this provides a schematic diagram of another battery energy storage system balancing circuit. This battery energy storage system balancing circuit also includes a monitoring circuit and a control circuit. Each individual battery cell 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 cell. Therefore, this monitoring circuit can be a current monitoring circuit, a voltage detection circuit, or an SOC monitoring circuit; no specific limitation is made here.

[0033] In a specific embodiment of the present invention, the monitoring circuit transmits the sampled values ​​to the microcontroller. The microcontroller calculates the state of charge (SOC) of each cell in the battery pack based on the sampled values ​​to determine the cells to be balanced, and sorts the unbalanced cells according to the difference between the SOC of each cell and the average SOC of the battery string. Then, the microcontroller drives the switch array to close the corresponding module selection switch, allowing the individual cells to connect to the port of the integrated cascaded converter. Then, the polarity is adjusted by the switching transistor, and the connected single battery cell then performs charging and discharging operations under the corresponding working circuit structure.

[0034] When the difference between the SOC value of a single cell and the average SOC value of the battery string is greater than the set maximum equalization threshold, the converter will operate in a discharging state to release the energy in the overcharged cell to the battery string or other groups of individual cells; when the difference between the SOC value of a single cell and the average SOC value of the battery string is less than the set minimum equalization threshold, the converter will operate in a charging state to release the energy in the battery string or other groups of individual cells to the undercharged cell.

[0035] In this embodiment, the PWM signal generated by the microcontroller can control the conduction of each switching transistor through the drive circuit, thus achieving the switching of the operating mode of the integrated cascaded multiport converter. Since the odd-numbered and even-numbered battery cells are connected to the converter port voltage via a switch array... Depending on the polarity of the voltage and the object of energy transfer, the microcontroller classifies the equalization circuit into three operating states based on the voltage polarity and the converter's operating state: single-cell to battery pack equalization, battery pack to single-cell equalization, and single-cell to single-cell equalization.

[0036] 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. 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. Energy is then transferred from the balancing bus capacitor to the energy storage system through the transformer and the AC-to-DC converter.

[0037] When used for balancing from individual cells to the battery pack, 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.

[0038] 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 A schematic diagram of the switching timing and voltage / current waveforms of various parameters during operation. Overcharged single-cell batteries are... and , connected to Two selector switches on both sides and Closed, connected to Two selector switches on both sides and closure. and The corresponding integrated cascaded unit operates in boost mode, with energy drawn from... and Transferred to the equalization bus capacitor and The integrated cascade unit will balance the bus capacitance. and Adjust the polarity of one end (upper side in the diagram) to positive, and adjust the equalization bus capacitor. and The polarity of the other end (lower side in the diagram) is adjusted to negative, and energy is then transferred from the equalization bus capacitor. and The energy is transmitted to the energy storage system via a transformer and an AC-to-DC converter.

[0039] 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:

[0040] 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: .

[0041] Therefore, if used express and ,use express and The expression for the power transmitted from the low-voltage side to the high-voltage side is: .

[0042] 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.

[0043] When used for balancing from battery pack to individual cells, the power transferred is: , in, The total voltage of the energy storage system is [value missing]. The duty cycle of the first switch, the fourth switch, and the sixth switch. 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.

[0044] Please refer to Figure 6 and Figure 7 , Figure 6A schematic diagram of the balancing path from an even number of undercharged individual cells to the battery pack is provided. Figure 7 for Figure 6 A schematic diagram of the switching timing and voltage / current waveforms of various parameters during operation. The undercharged single-cell battery is... and , connected to Two selector switches on both sides and Closed, connected to Two selector switches on both sides and closure. and The corresponding integrated cascaded unit operates in buck mode, where energy is transferred from the energy storage system to the equalization bus capacitor via AC-to-DC conversion and a transformer. and The integrated cascade unit will balance the bus capacitance. and The polarity of the other end (lower side in the diagram) is adjusted to positive to balance the bus capacitor. and The polarity of one end (upper side in the diagram) is adjusted to negative, and energy is then transferred from the equalization bus capacitor. and Transfer to undercharged individual cells and .

[0045] 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.

[0046] 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 used express and ,use express and The expression for the power transmitted from the low-voltage side to the high-voltage side is: .

[0047] When used for single-cell to single-cell balancing, 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.

[0048] When used for cell-to-cell balancing, 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. 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.

[0049] Please refer to Figure 8 and Figure 9 , Figure 8 A schematic diagram of the equalization path from one cell to another is provided. Figure 9 for Figure 8 A schematic diagram of the switching timing and voltage / current waveforms of various parameters during operation. Overcharged single-cell batteries are... Undercharged single-cell batteries are , connected to Two selector switches on both sides and Closed, connected to Two selector switches on both sides and closure. The corresponding integrated cascaded unit operates in boost mode, drawing energy from the overcharged individual battery cells. Transfer to overcharged individual cells The corresponding balancing bus capacitor in the integrated cascade unit The integrated cascaded unit corresponding to the overcharged single cell will balance the bus capacitance. Adjust the polarity of one end (upper side in the diagram) to positive, and adjust the equalization bus capacitor. The polarity of the other end (lower side in the diagram) is adjusted to negative, and energy is then transferred from the equalization bus capacitor. The power is transmitted to the undercharged individual cells via a transformer. The corresponding balancing bus capacitor in the integrated cascade unit ; Undercharged single cell battery The corresponding integrated cascaded unit operates in buck mode, and the undercharged single cell battery... The corresponding integrated cascaded unit will balance the bus capacitance. The polarity of the other end (lower side in the diagram) is adjusted to positive to balance the bus capacitor. The polarity of one end is adjusted to negative, and energy is then transferred from the equalization bus capacitor. Transfer to undercharged individual cells .

[0050] 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:

[0051] Therefore, if used express Then the power of energy transfer is: .

[0052] Simulation verification was conducted using a single cell with a voltage of 3.7V, a long series battery pack containing 13 cells (total voltage 48.1V), and a resistor as the output load. The relevant waveforms for each operating mode are shown below. Figure 10 As shown, the results indicate that the integrated cascaded multiport converter meets the design requirements.

[0053] In summary, the present invention has the following beneficial effects: 1) Multi-port parallel balancing with strong scalability and adaptability: The integrated cascaded multi-port topology supports flexible expansion of the number of ports, and can connect and balance multiple unbalanced batteries at one time. It breaks through the limitation of traditional solutions that can only balance a single cell or a group of batteries in the same state at a time, greatly improving the balancing efficiency of long series and large-capacity battery packs, and perfectly adapting to complex application scenarios with significant inconsistencies such as long battery strings.

[0054] 2) Optimized switch reuse, resulting in significant advantages in integration and cost: The number of power devices is reduced through dual innovative designs. First, the selection switch is shared between odd and even cell units, reducing the 2n bidirectional switches required for each battery pack in the traditional architecture to n+1. Second, the polarity switch and the power switch of the DC-DC converter are reused, significantly reducing hardware costs. At the same time, the system structure is made more compact, greatly improving integration and power density, effectively solving the pain points of large size and redundant devices in traditional solutions.

[0055] 3) High gain + continuous current, balancing efficiency and battery protection: Based on the Buck-Boost integrated cascade structure, it significantly improves the balanced voltage gain of long series battery packs, ensuring fast and efficient energy transfer; at the same time, it achieves continuous and stable balanced current, avoiding potential damage to individual battery cells caused by current surges, balancing high balanced efficiency and battery friendliness, and helping to extend battery life.

Claims

1. An integrated cascaded multiport converter, characterized in that, The integrated cascaded multiport converter includes multiple integrated cascaded units. Each integrated cascaded unit includes a first switch, a second switch, a third switch, a fourth switch, 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.

2. A battery energy storage system equalization circuit, characterized in that, The battery energy storage system balancing circuit includes an integrated cascaded multi-port converter composed of m integrated cascaded units as described in claim 1, an energy storage system, and a switch array. The energy storage system includes m battery packs connected in series, each battery pack including n individual cells connected in series. The switch array includes m (n+1) selection switches, each battery pack corresponding 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 the other end of the filter capacitor, and the other end of the selection switch with an even number is connected to one end of the filter capacitor.

3. A battery energy storage system balancing circuit according to claim 2, characterized in that, The battery energy storage system balancing circuit 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. 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.

4. A battery energy storage system balancing circuit according to claim 3, characterized in that, The battery energy storage system balancing circuit also includes an AC-to-DC converter, which comprises a fifth switching transistor, a sixth switching transistor, a third voltage-dividing capacitor, a fourth voltage-dividing capacitor, and a bus capacitor, wherein: One end of the fifth switch is connected to one end of the third voltage divider capacitor, one end of the bus capacitor, and the positive terminal of the first individual battery cell. The other end of the fifth switch is connected to one end of the secondary winding of the transformer and one end of the sixth switch. 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 switch is connected to the other end of the fourth voltage divider capacitor, the other end of the bus capacitor, and the negative terminal of the last individual battery cell.

5. A battery energy storage system balancing circuit according to claim 4, characterized in that, When balancing from a single cell to the battery pack, the two selector 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, and energy is transferred from the overcharged single cell to the balancing bus capacitor. The integrated cascade unit 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 through the transformer and the AC-to-DC converter.

6. A battery energy storage system balancing circuit according to claim 5, characterized in that, The power of energy transfer 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.

7. A battery energy storage system balancing circuit according to claim 4, characterized in that, When 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.

8. A battery energy storage system balancing circuit according to claim 7, characterized in that, The power of energy transfer is: ， in, The total voltage of the energy storage system is [value missing]. The duty cycle of the first switch, the fourth switch, and the sixth switch. 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.

9. A battery energy storage system balancing circuit according to claim 4, characterized in that, When balancing individual cells, the two selector switches connected to both sides of the overcharged individual cell are closed. The integrated cascade unit corresponding to the overcharged individual cell operates in boost mode. Energy is transferred from the overcharged individual cell to the balancing bus capacitor in the integrated cascade unit corresponding to the overcharged individual cell. The integrated cascade unit corresponding to the overcharged individual cell adjusts the polarity of one end of the balancing bus capacitor in the integrated cascade unit corresponding to the overcharged individual 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 individual cell to the negative terminal. Energy is then transferred from the balancing bus capacitor in the integrated cascade unit corresponding to the overcharged individual cell to the balancing bus capacitor in the integrated cascade unit corresponding to the undercharged individual 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.

10. A battery energy storage system balancing circuit according to claim 9, characterized in that, 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. 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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