Battery module double-layer equalization circuit

Abstract

The invention relates to the field of battery management, in particular to a battery module double-layer equalization circuit which comprises an inter-group equalization circuit and a plurality of single equalization circuits. PWM control is performed on the switching tubes of the inter-group equalization circuit and the single equalization circuit by using the fuzzy control rule, so that inter-group capacity equalization of a high-potential area and a low-potential area of the battery module and single capacity equalization of a high-SOC battery and a low-SOC battery are realized, and the capacity consistency of each single battery in the battery module is improved. The method is mainly applied to battery modules in the fields of power batteries and energy storage batteries, and through a double-layer equalization circuit and a fuzzy control rule, the equalization time is effectively shortened, and the capacity consistency of the single batteries is improved.

Description

Technical Field

[0001] The present invention relates to the field of battery management, and in particular to a double-layer equalization circuit for a battery module. Background Art

[0002] Power batteries or energy storage batteries are generally connected in series to form battery modules, and then applied to actual systems through a single module or multiple modules in series and parallel. During the use of the battery module, the capacity of the internal battery cells will gradually increase, eventually causing the capacity of the battery module to be lower than the rated capacity. The main reason is that there is a "barrel effect" in the performance of the battery module. The available capacity of the group mainly refers to the capacity value of the battery with the lowest capacity. The greater the difference between the capacity value of this battery and other batteries, the more serious the performance degradation of the battery module.

[0003] In order to ensure the performance of the battery module during operation, it is necessary to balance and control its capacity through battery management technology to improve the capacity consistency of each battery cell in the battery module. At present, balancing technologies include external compensation balancing, single cell capacity transfer balancing, group capacity transfer balancing and other methods, but there are still deficiencies in balancing time, balancing loss, consistency level, etc., resulting in the balancing effect cannot meet the actual system requirements. Therefore, it is of great significance to develop an efficient battery balancing circuit and its control system to balance the battery module to improve its output performance. Summary of the invention

[0004] The purpose of the present invention is to overcome the problem that the balancing effect of the existing balancing control means in the prior art cannot meet the actual system requirements, and to provide a battery module double-layer balancing circuit.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] A double-layer balancing circuit for a battery module, the double-layer balancing circuit comprising an inter-group balancing circuit and N-1 single-cell balancing circuits, where N is the number of battery cells in the battery module;

[0007] The inter-group balancing circuit includes a switch tube M m1 , switch tube M m2 , reverse diode D m1 , reverse diode D m2 、Inductance L m The switch tube M m1 and the reverse diode D m1 The switch tube M is connected in parallel to form a parallel structure. m2 and the reverse diode D m2 The two parallel structures are connected in series to form an inter-group series connection structure, and the connection point is connected to the inductor Lm The two ends of the inter-group series connection structure are respectively connected to the positive electrode connection point and the negative electrode connection point of the battery module; the inductor L m The other end is connected to any node in the battery module except the positive electrode connection point and the negative electrode connection point;

[0008] The single-unit balancing circuit includes a switch tube M sn1 , switch tube M sn2 , reverse diode D sn1 , reverse diode D sn2 、Inductance L sn The switch tube M sn1 and reverse diode D sn1 The switch tube M is connected in parallel to form a parallel structure. sn2 and reverse diode D sn2 The two parallel structures are connected in series to form a single-body series connection structure, and the connection point is connected to the inductor L sn The two ends of the monomer series connection structure are respectively connected to the positive electrode connection point of the n+1th battery monomer and the negative electrode connection point of the nth battery monomer in the battery module; the inductor L sn The other end is connected to the positive electrode connection point of the nth battery cell in the battery module, n∈(0,N);

[0009] The double-layer balancing circuit is controlled by a preset balancing control method, and the balancing current is adjusted by using a preset fuzzy control rule.

[0010] As a preferred solution of the present invention, the balancing control method in the double-layer balancing circuit comprises the following steps:

[0011] S1. Obtain the SOC values ​​of all battery cells in the battery module and calculate the average SOC value, record the serial number Nh of the battery cell with the highest SOC and the serial number Nl of the battery cell with the lowest SOC, calculate the difference between the highest SOC and the lowest SOC to obtain the SOC extreme difference, and calculate the difference between the SOC of each cell and the average SOC value to obtain the average SOC difference of the battery cells;

[0012] S2, determining whether the SOC extreme difference is greater than a preset equalization opening threshold;

[0013] If it is less than or equal to the balance opening threshold, return to S1; if it is greater than the balance opening threshold, enter S3;

[0014] S3, comparing the potential regions of the battery cells corresponding to the serial numbers Nh and Nl;

[0015] If they are in the high potential area and the low potential area respectively, then enter S4; if they are both in the high potential area or the low potential area, then enter S5; wherein the high potential area and the low potential area are divided according to a preset division rule;

[0016] S4, judging the magnitude relationship between the sequence number Nh and the sequence number Nl;

[0017] If the sequence number Nh is greater than the sequence number Nl, the switch tube M of the inter-group balancing circuit is turned on. m1 , the current is adjusted by the preset fuzzy control rules, and the energy in the high potential area is stored in the inductor L m Middle; Waiting for switch tube M m1 Closed, inductance L m The energy stored in will be transferred through the reverse parallel diode D m2 The low potential area is charged until it flows through the inductor L m The current is less than the set value;

[0018] If the sequence number Nh is less than the sequence number Nl, the switch tube M of the inter-group balancing circuit is turned on. m2 , the current is adjusted by the preset fuzzy control rules, and the energy in the low potential area is stored in the inductor L m Middle; Waiting for switch tube M m2 Closed, inductance L m The energy stored in will be transferred through the reverse parallel diode D m1 The high potential area is charged until it flows through the inductor L m The current is less than the set value;

[0019] Return to S1;

[0020] S5, determining the magnitude relationship between the sequence number Nh and the sequence number Nl;

[0021] If the sequence number Nh is greater than the sequence number Nl, then enter S6; if the sequence number Nh is less than the sequence number Nl, then enter S7;

[0022] S6, turn on the switch tube M of the single-unit balancing circuit s(Nh-1)1 , the current is adjusted by the preset fuzzy control rules to store the energy in the battery cell Nh into the inductor L s(Nh-1) middle;

[0023] Waiting for switch tube M s(Nh-1)1 Closed, if the inductor L s(Nh-1) Connected to the positive connection point of the battery cell N1, the battery cell N1 is charged evenly; if the inductor L s(Nh-1) If it is not connected to the positive electrode connection point of the battery cell N1, the switch tube M is turned on. s(Nh-2)1 , keep the same current size, and change the inductor L s(Nh-1) The energy stored in the inductor Ls(Nh-2) middle;

[0024] The battery number is reduced by 1 each time, and the above process is repeated until the balanced charging of the battery cell N1 is completed, and then the process returns to S1;

[0025] S7, turn on the switch tube M of the single-unit balancing circuit s(Nh)2 , the current is adjusted by the preset fuzzy control rules to store the energy of the battery cell Nh into the inductor L s(Nh) middle;

[0026] Waiting for switch tube M s(Nh)2 Closed, if the inductor L s(Nh) Connected to the negative electrode connection point of the battery cell N1, the battery cell N1 is charged evenly; if the inductor L s(Nh) If it is not connected to the negative electrode connection point of the battery cell N1, the switch tube M is turned on. s(Nh+1)2 , keep the same current size, and change the inductor L s(Nh) The energy stored in the inductor L s(Nh+1) middle;

[0027] The battery serial number is increased by 1 each time, and the above process is repeated until the balanced charging of the battery cell N1 is completed, and then the process returns to S1.

[0028] As a preferred solution of the present invention, the division rule of the high potential area and the low potential area of ​​the battery module in S3 is:

[0029] The inductor L in the inter-group balancing circuit m The node connected to the battery module is the boundary, the area between the node and the positive connection point of the battery module is the high potential area of ​​the battery module, and the area between the node and the negative connection point of the battery module is the low potential area of ​​the battery module.

[0030] As a preferred solution of the present invention, the inductor L m The node connected to the battery module is the intermediate node of the battery module.

[0031] As a preferred solution of the present invention, the fuzzy control rule is to use the SOC average value and the SOC extreme difference to fuzzify the input, and use the switch tube duty cycle to fuzzify the output.

[0032] As a preferred solution of the present invention, the fuzzy control rule of the inter-group balancing circuit is to control the duty cycle of the switch tube by calculating the difference between the SOC average values ​​of the high potential area and the low potential area and judging the interval in which they are located, thereby adjusting the size of the inter-group balancing current.

[0033] As a preferred solution of the present invention, the fuzzy control rule of the inter-group balancing circuit includes the following steps:

[0034] The SOC average value is divided into three regions, defined as S1, M1, and L1; the SOC extreme difference is divided into five regions, defined as VS2, S2, M2, L2, and VL2; the switch duty cycle is divided into five regions, defined as VS3, S3, M3, L3, and VL3;

[0035] Determine the interval in which the difference between the SOC average values ​​of the high potential area and the low potential area is located;

[0036] If it is in the S1 area, the control duty cycle is S3; if it is in the M1 area, the control duty cycle is M3; if it is in the L1 area, the control duty cycle is L3.

[0037] As a preferred solution of the present invention, the fuzzy control rule of the monomer balancing circuit is to control the duty cycle of the switch tube by judging the interval of the SOC average value and the SOC extreme difference, thereby adjusting the size of the monomer balancing current.

[0038] As a preferred solution of the present invention, the fuzzy control rule of the monomer balancing circuit includes the following steps:

[0039] The SOC average value is divided into three regions, defined as S1, M1, and L1; the SOC extreme difference is divided into five regions, defined as VS2, S2, M2, L2, and VL2; the switch duty cycle is divided into five regions, defined as VS3, S3, M3, L3, and VL3;

[0040] Determine the range of the SOC average value and the SOC extreme value;

[0041] If the average SOC value is in the S1 region, the duty cycles are controlled to S3, M3, L3, VL3, and VL3 respectively in the five regions of VS2, S2, M2, L2, and VL2 corresponding to the extreme SOC values;

[0042] If the average SOC value is in the M1 region, the duty cycles are controlled to VS3, S3, M3, L3, and VL3 in the five regions of SOC extreme difference VS2, S2, M2, L2, and VL2, respectively;

[0043] If the average SOC value is in the L1 area, the duty cycles in the five areas of VS2, S2, M2, L2, and VL2 corresponding to the extreme SOC values ​​are controlled to VS3, VS3, S3, M3, and L3 respectively.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] The double-layer balancing circuit described in the present invention includes an inter-group balancing circuit and several single-cell balancing circuits. The circuit can perform PWM control on the switch tubes of the inter-group balancing circuit and the single-cell balancing circuit according to the SOC difference of the battery cells in the battery module by using fuzzy control rules, thereby achieving inter-group capacity balancing in the high-potential area and low-potential area of ​​the battery module, and single-cell capacity balancing of high-SOC batteries and low-SOC batteries, so as to improve the capacity consistency of each battery cell in the battery module. The present invention is mainly aimed at battery modules in the field of power batteries and energy storage batteries. Through the double-layer balancing circuit and fuzzy control rules, the balancing time is effectively reduced and the capacity consistency of battery cells is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 This is an electrical schematic diagram of a topological structure in a double-layer balancing circuit of a battery module according to Embodiment 1 of the present invention;

[0047] Figure 2 A schematic flow chart of a balancing control method in a double-layer balancing circuit of a battery module according to Embodiment 2 of the present invention;

[0048] Figure 3 This is an electrical schematic diagram of a topological structure in a double-layer balancing circuit of a battery module according to Embodiment 3 of the present invention;

[0049] Figure 4 A membership diagram of the SOC mean value in a double-layer balancing circuit of a battery module according to Embodiment 3 of the present invention;

[0050] Figure 5 A membership diagram of SOC extreme difference in a double-layer balancing circuit of a battery module according to Embodiment 3 of the present invention;

[0051] Figure 6 This is a membership diagram of the duty cycle of the switch tube in a double-layer balancing circuit of a battery module described in Example 3 of the present invention. DETAILED DESCRIPTION

[0052] The present invention is further described in detail below in conjunction with test examples and specific implementation methods. However, this should not be understood as the scope of the above subject matter of the present invention being limited to the following embodiments, and all technologies realized based on the content of the present invention belong to the scope of the present invention.

[0053] Example 1

[0054] like Figure 1 As shown, a battery module double-layer balancing circuit includes an inter-group balancing circuit and N-1 single-cell balancing circuits, where N is the number of battery cells in the battery module;

[0055] The inter-group balancing circuit includes a switch tube M m1 , switch tube Mm2 , reverse diode D m1 , reverse diode D m2 、Inductance L m The switch tube M m1 and the reverse diode D m1 The switch tube M is connected in parallel to form a parallel structure. m2 and the reverse diode D m2 The two parallel structures are connected in series to form an inter-group series connection structure, and the connection point is connected to the inductor L m The two ends of the inter-group series connection structure are respectively connected to the positive electrode connection point and the negative electrode connection point of the battery module; the inductor L m The other end is connected to any node in the battery module except the positive electrode connection point and the negative electrode connection point.

[0056] The single-unit balancing circuit includes a switch tube M sn1 , switch tube M sn2 , reverse diode D sn1 , reverse diode D sn2 、Inductance L sn The switch tube M sn1 and reverse diode D sn1 The switch tube M is connected in parallel to form a parallel structure. sn2 and reverse diode D sn2 The two parallel structures are connected in series to form a single-body series connection structure, and the connection point is connected to the inductor L sn The two ends of the monomer series connection structure are respectively connected to the positive electrode connection point of the n+1th battery monomer and the negative electrode connection point of the nth battery monomer in the battery module; the inductor L sn The other end is connected to the positive electrode connection point of the nth battery cell in the battery module, n∈(0,N).

[0057] The double-layer balancing circuit is controlled by a preset balancing control method, and the balancing current is adjusted by using a preset fuzzy control rule.

[0058] Example 2

[0059] This embodiment is a specific implementation of the balancing control method in a double-layer balancing circuit of a battery module described in Embodiment 1. Figure 2 As shown, the following steps are included:

[0060] S1. Obtain the SOC values ​​of all battery cells in the battery module and calculate the average SOC value. Record the serial number Nh of the battery cell with the highest SOC and the serial number Nl of the battery cell with the lowest SOC. Calculate the difference between the highest SOC and the lowest SOC to obtain the SOC extreme value. Calculate the difference between the SOC of each cell and the average SOC value to obtain the average SOC difference of the battery cells.

[0061] S2, determining whether the SOC extreme difference is greater than a preset equalization opening threshold;

[0062] If it is less than or equal to the balance opening threshold, return to S1; if it is greater than the balance opening threshold, enter S3.

[0063] S3, comparing the potential regions of the battery cells corresponding to the serial numbers Nh and Nl;

[0064] If they are respectively in the high potential area and the low potential area, then enter S4; if they are both in the high potential area or the low potential area, then enter S5; wherein the high potential area and the low potential area are divided according to a preset division rule.

[0065] Furthermore, the division rules of the high potential area and the low potential area of ​​the battery module are as follows:

[0066] The inductor L in the inter-group balancing circuit m The node connected to the battery module is the boundary, the area between the node and the positive connection point of the battery module is the high potential area of ​​the battery module, and the area between the node and the negative connection point of the battery module is the low potential area of ​​the battery module.

[0067] Furthermore, the inductor L m The node connected to the battery module is the middle node of the battery module, so that the number of battery cells in the high potential area is equal to the number of battery cells in the low potential area.

[0068] S4, judging the magnitude relationship between the sequence number Nh and the sequence number Nl;

[0069] If the sequence number Nh is greater than the sequence number Nl, the switch tube M of the inter-group balancing circuit is turned on. m1 , the current is adjusted by the preset fuzzy control rules, and the energy in the high potential area is stored in the inductor L m Middle; Waiting for switch tube M m1 Closed, inductance L m The energy stored in will be transferred through the reverse parallel diode D m2 The low potential area is charged until it flows through the inductor L m The current is less than the set value.

[0070] If the sequence number Nh is less than the sequence number Nl, the switch tube M of the inter-group balancing circuit is turned on. m2, the current is adjusted by the preset fuzzy control rules, and the energy in the low potential area is stored in the inductor L m Middle; Waiting for switch tube M m2 Closed, inductance L m The energy stored in will be transferred through the reverse parallel diode D m1 The high potential area is charged until it flows through the inductor L m The current is less than the set value.

[0071] Return to S1.

[0072] Furthermore, the fuzzy control rule uses the SOC average value and the SOC extreme difference to fuzzify the input, and uses the switch tube duty cycle to fuzzify the output.

[0073] Furthermore, the fuzzy control rule of the inter-group balancing circuit is to control the duty cycle of the switch tube by calculating the difference between the SOC average values ​​of the high potential area and the low potential area and judging the interval in which they are located, thereby adjusting the magnitude of the inter-group balancing current. Specifically, the fuzzy control rule of the inter-group balancing circuit includes the following steps:

[0074] The SOC average value is divided into three regions, defined as S1, M1, and L1; the SOC extreme difference is divided into five regions, defined as VS2, S2, M2, L2, and VL2; the switch duty cycle is divided into five regions, defined as VS3, S3, M3, L3, and VL3;

[0075] Determine the interval in which the difference between the SOC average values ​​of the high potential area and the low potential area is located;

[0076] If it is in the S1 area, the control duty cycle is S3; if it is in the M1 area, the control duty cycle is M3; if it is in the L1 area, the control duty cycle is L3.

[0077] S5, determining the magnitude relationship between the sequence number Nh and the sequence number Nl;

[0078] If the sequence number Nh is greater than the sequence number Nl, then enter S6; if the sequence number Nh is less than the sequence number Nl, then enter S7.

[0079] S6, turn on the switch tube M of the single-unit balancing circuit s(Nh-1)1 , the current is adjusted by the preset fuzzy control rules to store the energy in the battery cell Nh into the inductor L s(Nh-1) middle.

[0080] Waiting for switch tube M s(Nh-1)1 Closed, if the inductor L s(Nh-1) Connected to the positive connection point of the battery cell N1, the battery cell N1 is charged evenly; if the inductor L s(Nh-1)If it is not connected to the positive electrode connection point of the battery cell N1, the switch tube M is turned on. s(Nh-2)1 , keep the same current size, and change the inductor L s(Nh-1) The energy stored in the inductor L s(Nh-2) middle.

[0081] The battery number is reduced by 1 each time, and the above process is repeated until the balanced charging of the battery cell N1 is completed, and then the process returns to S1.

[0082] Furthermore, the fuzzy control rule of the single-cell balancing circuit is to control the duty cycle of the switch tube by judging the interval of the SOC average value and the SOC extreme difference, thereby adjusting the size of the single-cell balancing current. Specifically, the fuzzy control rule of the single-cell balancing circuit includes the following steps:

[0083] The SOC average value is divided into three regions, defined as S1, M1, and L1; the SOC extreme difference is divided into five regions, defined as VS2, S2, M2, L2, and VL2; the switch duty cycle is divided into five regions, defined as VS3, S3, M3, L3, and VL3;

[0084] Determine the range of the SOC average value and the SOC extreme value;

[0085] If the average SOC value is in the S1 region, the duty cycles are controlled to S3, M3, L3, VL3, and VL3 respectively in the five regions of VS2, S2, M2, L2, and VL2 corresponding to the extreme SOC values;

[0086] If the average SOC value is in the M1 region, the duty cycles are controlled to VS3, S3, M3, L3, and VL3 in the five regions of SOC extreme difference VS2, S2, M2, L2, and VL2, respectively;

[0087] If the average SOC value is in the L1 area, the duty cycles are controlled to VS3, VS3, S3, M3, and L3 respectively in the five areas of SOC extreme difference VS2, S2, M2, L2, and VL2.

[0088] S7, turn on the switch tube M of the single-unit balancing circuit s(Nh)2 , the current is adjusted by the preset fuzzy control rules to store the energy of the battery cell Nh into the inductor L s(Nh) middle.

[0089] Waiting for switch tube M s(Nh)2 Closed, if the inductor L s(Nh) Connected to the negative electrode connection point of the battery cell N1, the battery cell N1 is balanced charged; if the inductor L s(Nh) If it is not connected to the negative electrode connection point of the battery cell N1, the switch tube M is turned on. s(Nh+1)2, keep the same current size, and change the inductor L s(Nh) The energy stored in the inductor L s(Nh+1) middle.

[0090] The battery serial number is increased by 1 each time, and the above process is repeated until the balanced charging of the battery cell N1 is completed, and then the process returns to S1.

[0091] Example 3

[0092] This embodiment is a specific experimental example of using a battery module double-layer balancing circuit and a corresponding balancing control method described in Embodiment 2.

[0093] In this embodiment, the battery module is composed of 12 batteries connected in series. Figure 3 As shown, the double-layer balancing circuit includes an inter-group balancing circuit and 11 single-unit balancing circuits. The inter-group balancing circuit includes a switch tube M m1 , switch tube M m2 , reverse diode D m1 , reverse diode D m2 、Inductance L m ; Switching tube M m1 and reverse diode D m1 The parallel structure is formed, and the switch tube M m2 and reverse diode D m2 The two parallel structures are connected in series to form a series connection structure, and the connection point is connected to the inductor L m The two ends of the series connection structure between the groups are respectively connected to the positive connection point and the negative connection point of the battery module; the inductor L m The other end is connected to the positive connection point of the sixth battery cell in the battery module.

[0094] The single-unit balancing circuit includes a switch tube M sn1 , switch tube M sn2 , reverse diode D sn1 , reverse diode D sn2 、Inductance L sn ; Switching tube M sn1 and reverse diode D sn1 The parallel structure is formed, and the switch tube M sn2 and reverse diode D sn2 The two parallel structures are connected in series to form a single-body series connection structure. The connection point is connected to the inductor L sn The two ends of the monomer series connection structure are respectively connected to the positive electrode connection point of the n+1th battery and the negative electrode connection point of the nth battery in the battery module; the inductor L snThe other end is connected to the positive electrode connection point of the nth battery in the battery module.

[0095] According to the double-layer balancing circuit, the balancing control process described in Example 2 is used to control the switch tubes of the inter-group balancing circuit and the single-unit balancing circuit, and the fuzzy control rule is used to adjust the balancing current. The steps include:

[0096] S1. Obtain the SOC values ​​of all battery cells in the battery pack and calculate the SOC average value. Record the battery number Nh with the highest SOC and the battery number Nl with the lowest SOC. Calculate the difference between the highest SOC and the lowest SOC to obtain the SOC range. Calculate the difference between the SOC of each cell and the SOC average value to obtain the SOC average difference of each cell. The membership diagram of the SOC average value is as follows: Figure 4 As shown in the figure, the average SOC value is divided into three regions: [0, 0.20], [0.20, 0.85], and [0.85, 1.00], which are defined as S1, M1, and L1 respectively; that is, when the average SOC value is in the interval [0, 0.20], the corresponding membership function is S1 (small), when it is in the interval [0.20, 0.85], the corresponding membership function is M1 (medium), and when it is in the interval [0.85, 1.00], the corresponding membership function is L1 (large). Similarly, the membership diagram of the SOC extreme value is as follows Figure 5 As shown, the SOC extreme difference is divided into five regions: [0, 0.005], [0.005, 0.015], [0.015, 0.03], [0.03, 0.05], and [0.05, 0.10], which are defined as VS2, S2, M2, L2, and VL2 respectively; that is, when the SOC extreme difference is in the interval [0, 0.005], the corresponding membership function is VS2 (extremely small), when it is in the interval [0.005, 0.015], the corresponding membership function is S2 (small), when it is in the interval [0.015, 0.03], the corresponding membership function is M2 (medium), when it is in the interval [0.03, 0.05], the corresponding membership function is L2 (large), and when it is in the interval [0.05, 0.10], the corresponding membership function is VL2 (maximum).

[0097] S2, determine whether the SOC extreme difference is greater than the balance opening threshold, if it is less than or equal to the balance opening threshold, return to step S1; if it is greater than the balance opening threshold, enter step S3. The balance opening threshold can be set to 1.5.

[0098] S3, compare the potential areas of the corresponding battery cells of Nh and Nl, if they are in the high potential area and the low potential area respectively, then go to step S4; if they are both in the high potential area or the low potential area, then go to step S5. If Nh is 1 and Nl is 3, it can be known that the corresponding battery cells are both in the low potential area, then go to step S5.

[0099] S4. If Nh is greater than Nl, the switch M of the inter-group balancing circuit is turned on first. m1 , the current is adjusted by fuzzy control rules to store the energy in the high potential area of ​​the battery module into the inductor L m Middle; Waiting for switch tube M m1 Closed, inductance L m The energy stored in will be transferred through the reverse parallel diode D m2 The low potential area of ​​the battery module is charged until the current flowing through the inductor is less than a certain set value. If Nh is less than Nl, the switch tube M of the inter-group balancing circuit is turned on first. m2 , the current is adjusted by fuzzy control rules to store the energy in the low potential area of ​​the battery module into the inductor L m Middle; Waiting for switch tube M m2 Closed, inductance L m The energy stored in will be transferred through the reverse parallel diode D m1 The high potential area of ​​the battery module is charged until the current flowing through the inductor is less than a certain set value. Then return to step S1. In this step, it can be set that when the inductor current is less than 5% of the maximum balancing current, the inter-group charging is stopped; if the maximum balancing current is 2A, the set value is 0.1A. In addition, the balancing current size is adjusted by adjusting the switch duty cycle; further, the membership diagram of the switch duty cycle is as follows Figure 6 As shown, the duty cycle of the switch tube is divided into five regions: [0.465, 0.477], [0.477, 0.484], [0.484, 0.495], [0.495, 0.506], and [0.506, 0.53], which are defined as VS3, S3, M3, L3, and VL3 respectively; that is, when the duty cycle of the switch tube is in the interval of [0.465, 0.477], the corresponding membership The function is VS3 (extremely small), when it is in the interval [0.477, 0.484], the corresponding membership function is S3 (small), when it is in the interval [0.484, 0.495], the corresponding membership function is M3 (medium), when it is in the interval [0.495, 0.506], the corresponding membership function is L3 (large), and when it is in the interval [0.506, 0.53], the corresponding membership function is VL3 (maximum). In this embodiment, since both the battery cell Nh and the battery cell Nl are in the low potential area, step 4 is not performed.

[0100] S5-S7: These three steps are the direction of energy transfer, which is obtained by comparing the size of Nh and Nl. Since Nh is 1 and Nl is 3 in this embodiment, step 5 is executed. First, the switch tube M of the single cell balancing circuit corresponding to the battery cell 1 is turned on. s(1)2 , the current is adjusted by fuzzy control rules to store the energy of battery cell 1 into the inductor L s(1) In. Waiting for the switch tube M s(1)2Closed, because at this time the inductance L s(1) If the negative electrode of the battery cell 3 is not connected to the negative electrode connection point, the switch M of the battery cell 2 corresponding to the cell balancing circuit is turned on. s(2)2 , keep the same current size, and change the inductor L s(1) The energy stored in the inductor L s(2) In. Waiting for the switch tube M s(2)2 Closed, because at this time L s(2) Connected to the negative connection point of battery cell 3, so the inductor L s(2) The battery cell 3 will be charged evenly. Then the process returns to step 1.

[0101] Each time, the sequence number is increased by 1, and the above process is repeated until the balanced charging of the battery cell N1 is completed. That is, the energy is transferred one by one along the inductance of the single-cell balanced circuit. When the energy is stored in the inductance of the single-cell balanced circuit corresponding to the battery cell N1, the inductance releases the energy to the battery cell N1, and charges it evenly, and no energy is transferred between the inductors. Then, the process returns to step S1.

[0102] According to the above-mentioned battery module double-layer balancing circuit and its corresponding balancing control method, the battery pack is set to a static condition and the initial SOC of each cell is distributed between 50% and 75%, that is, the SOC range reaches 25%; the experimental results show that: after 16000 seconds, the SOC range drops to 0.26%, and the capacity of each battery cell in the battery pack tends to be consistent; indicating that the battery module double-layer balancing circuit and its balancing control method have good balancing performance.

[0103] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A battery module double-layer balancing circuit, characterized in that: The double-layer balancing circuit includes an inter-group balancing circuit and N-1 single-cell balancing circuits, where N is the number of battery cells in the battery module; The inter-group balancing circuit includes a switch tube M m1 , switch tube M m2 , reverse diode D m1 , reverse diode D m2 、Inductance L m The switch tube M m1 and the reverse diode D m1 The switch tube M is connected in parallel to form a parallel structure. m2 and the reverse diode D m2 The two parallel structures are connected in series to form an inter-group series connection structure, and the connection point is connected to the inductor L m The two ends of the inter-group series connection structure are respectively connected to the positive electrode connection point and the negative electrode connection point of the battery module; the inductor L m The other end is connected to any node in the battery module except the positive electrode connection point and the negative electrode connection point; The single-unit balancing circuit includes a switch tube M sn1 , switch tube M sn2 , reverse diode D sn1 , reverse diode D sn2 、Inductance L sn The switch tube M sn1 and reverse diode D sn1 The switch tube M sn2 and reverse diode D sn2 The two parallel structures are connected in series to form a single-body series connection structure, and the connection point is connected to the inductor L sn The two ends of the monomer series connection structure are respectively connected to the positive electrode connection point of the n+1th battery monomer and the negative electrode connection point of the nth battery monomer in the battery module; the inductor L sn The other end is connected to the positive electrode connection point of the nth battery cell in the battery module, n∈(0,N); The double-layer balancing circuit is controlled by a preset balancing control method, and the balancing current is adjusted by using a preset fuzzy control rule.

2. A battery module double-layer balancing circuit according to claim 1, characterized in that: The balancing control method in the double-layer balancing circuit comprises the following steps: S1. Obtain the SOC values ​​of all battery cells in the battery module and calculate the average SOC value, record the serial number Nh of the battery cell with the highest SOC and the serial number Nl of the battery cell with the lowest SOC, calculate the difference between the highest SOC and the lowest SOC to obtain the SOC extreme difference, and calculate the difference between the SOC of each cell and the average SOC value to obtain the average SOC difference of the battery cells; S2, determining whether the SOC extreme difference is greater than a preset equalization opening threshold; If it is less than or equal to the balance opening threshold, return to S1; if it is greater than the balance opening threshold, enter S3; S3, comparing the potential regions of the battery cells corresponding to the serial numbers Nh and Nl; If they are in the high potential area and the low potential area respectively, then enter S4; if they are both in the high potential area or the low potential area, then enter S5; wherein the high potential area and the low potential area are divided according to a preset division rule; S4, judging the magnitude relationship between the sequence number Nh and the sequence number Nl; If the sequence number Nh is greater than the sequence number Nl, the switch tube M of the inter-group balancing circuit is turned on. m1 , the current is adjusted by the preset fuzzy control rules, and the energy in the high potential area is stored in the inductor L m Middle; Waiting for switch tube M m1 Closed, inductance L m The energy stored in will be transferred through the reverse parallel diode D m2 The low potential area is charged until it flows through the inductor L m The current is less than the set value; If the sequence number Nh is less than the sequence number Nl, the switch tube M of the inter-group balancing circuit is turned on. m2 , the current is adjusted by the preset fuzzy control rules, and the energy in the low potential area is stored in the inductor L m Middle; Waiting for switch tube M m2 Closed, inductance L m The energy stored in will be transferred through the reverse parallel diode D m1 The high potential area is charged until it flows through the inductor L m The current is less than the set value; Return to S1; S5, determining the magnitude relationship between the sequence number Nh and the sequence number Nl; If the sequence number Nh is greater than the sequence number Nl, then enter S6; if the sequence number Nh is less than the sequence number Nl, then enter S7; S6, turn on the switch tube M of the single-unit balancing circuit s(Nh-1)1 , the current is adjusted by the preset fuzzy control rules to store the energy in the battery cell Nh into the inductor L s(Nh-1) middle; Waiting for switch tube M s(Nh-1)1 Closed, if the inductor L s(Nh-1) Connected to the positive connection point of the battery cell N1, the battery cell N1 is charged evenly; if the inductor L s(Nh-1) If it is not connected to the positive electrode connection point of the battery cell N1, the switch tube M is turned on. s(Nh-2)1 , keep the same current size, and change the inductor L s(Nh-1) The energy stored in the inductor L s(Nh-2) middle; The battery number is reduced by 1 each time, and the above process is repeated until the balanced charging of the battery cell N1 is completed, and then the process returns to S1; S7, turn on the switch tube M of the single-unit balancing circuit s(Nh)2 , the current is adjusted by the preset fuzzy control rules to store the energy of the battery cell Nh into the inductor L s(Nh) middle; Waiting for switch tube M s(Nh)2 Closed, if the inductor L s(Nh) Connected to the negative electrode connection point of the battery cell N1, the battery cell N1 is balanced charged; if the inductor L s(Nh) If it is not connected to the negative electrode connection point of the battery cell N1, the switch tube M is turned on. s(Nh+1)2 , keep the same current size, and change the inductor L s(Nh) The energy stored in the inductor L s(Nh+1) middle; The battery serial number is increased by 1 each time, and the above process is repeated until the balanced charging of the battery cell N1 is completed, and then the process returns to S1.

3. A battery module double-layer balancing circuit according to claim 2, characterized in that: The division rules of the high potential area and the low potential area of ​​the battery module in S3 are: The inductor L in the inter-group balancing circuit m The node connected to the battery module is the boundary, the area between the node and the positive connection point of the battery module is the high potential area of ​​the battery module, and the area between the node and the negative connection point of the battery module is the low potential area of ​​the battery module.

4. A battery module double-layer balancing circuit according to claim 3, characterized in that: The inductance L m The node connected to the battery module is the intermediate node of the battery module.

5. A battery module double-layer balancing circuit according to claim 2, characterized in that: The fuzzy control rule is to use the SOC average value and the SOC extreme difference to fuzzify the input, and use the switch tube duty cycle to fuzzify the output.

6. A battery module double-layer balancing circuit according to claim 5, characterized in that: The fuzzy control rule of the inter-group balancing circuit is to calculate the difference between the SOC average values ​​of the high potential area and the low potential area and determine the interval in which they are located. The duty cycle of the switch tube is controlled to adjust the size of the inter-group balancing current.

7. A battery module double-layer balancing circuit according to claim 6, characterized in that: The fuzzy control rule of the inter-group balancing circuit comprises the following steps: The SOC average value is divided into three regions, defined as S1, M1, and L1; the SOC extreme difference is divided into five regions, defined as VS2, S2, M2, L2, and VL2; the switch duty cycle is divided into five regions, defined as VS3, S3, M3, L3, and VL3; Determine the interval in which the difference between the SOC average values ​​of the high potential area and the low potential area is located; If it is in the S1 area, the control duty cycle is S3; if it is in the M1 area, the control duty cycle is M3; if it is in the L1 area, the control duty cycle is L3.

8. A battery module double-layer balancing circuit according to claim 5, characterized in that: The fuzzy control rule of the single-cell balancing circuit is to control the duty cycle of the switch tube by judging the interval of the SOC average value and the SOC extreme difference, thereby adjusting the size of the single-cell balancing current.

9. A battery module double-layer balancing circuit according to claim 8, characterized in that: The fuzzy control rule of the monomer balancing circuit includes the following steps: The SOC average value is divided into three regions, defined as S1, M1, and L1; the SOC extreme difference is divided into five regions, defined as VS2, S2, M2, L2, and VL2; the switch duty cycle is divided into five regions, defined as VS3, S3, M3, L3, and VL3; Determine the range of the SOC average value and the SOC extreme value; If the average SOC value is in the S1 region, the duty cycles are controlled to S3, M3, L3, VL3, and VL3 in the five regions of VS2, S2, M2, L2, and VL2 corresponding to the extreme SOC values; If the average SOC value is in the M1 region, the duty cycles are controlled to VS3, S3, M3, L3, and VL3 in the five regions of SOC extreme difference VS2, S2, M2, L2, and VL2, respectively; If the average SOC value is in the L1 area, the duty cycles are controlled to VS3, VS3, S3, M3, and L3 respectively in the five areas of SOC extreme difference VS2, S2, M2, L2, and VL2.

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