Decommissioned battery pack multi-path equalization topology based on fuzzy control and equalization method thereof

Abstract

The invention provides a decommissioned battery pack multi-path equalization topology based on fuzzy control and an equalization method thereof. The topology comprises N decommissioned batteries connected in series, 2N + 2 bidirectional switches, four switching tubes, an inductor, an information acquisition unit and a fuzzy control unit, the information acquisition unit is used for acquiring SOC information of each retired battery; and the fuzzy control unit is used for controlling the on-off conditions of all the bidirectional switches and all the switching tubes based on a fuzzy control rule according to the SOC information of each retired battery so as to realize energy balance between the retired batteries. According to the invention, the multi-path equalization topology of the decommissioned batteries based on the fuzzy control strategy is established, so that when the energy of the decommissioned batteries is inconsistent, the on-off of the bidirectional switch is controlled, and the inductor is used as a carrier to carry out energy transfer, thereby realizing lossless energy equalization and effectively avoiding peak occurrence; and meanwhile, a fuzzy control strategy is combined to dynamically adjust the equalizing current, so that rapid energy equalization between the batteries is realized.

Description

Technical Field

[0001] The present disclosure relates to the technical field of energy storage systems, and in particular to a multi-path balancing topology of a retired battery pack based on fuzzy control and a balancing method thereof. Background Art

[0002] Batteries or supercapacitors are widely used in various energy storage system-related fields. However, batteries generally have a service life and need to be replaced or retired. Today, the handling of a large number of retired batteries has become a difficult problem. Although retired batteries can be used in cascades in some application scenarios, due to the large individual differences between retired batteries, it is easy for one or more retired batteries to be overcharged or over-discharged during the use of retired batteries in series, making the differences between retired batteries more obvious, resulting in a decrease in the overall performance of the series battery pack and affecting its service life. Therefore, how to achieve the balance and safety of the circuit when retired batteries are used in series to form a battery pack is an urgent problem that technicians in this field need to solve. Summary of the invention

[0003] The purpose of the embodiments of the present disclosure is to provide a multi-path balancing topology of a retired battery pack based on fuzzy control and a balancing method thereof, so as to solve the problems of circuit balancing and safety in the prior art when retired batteries are connected in series to form a battery pack.

[0004] The embodiment of the present disclosure adopts the following technical solution: a multi-path balancing topology of a retired battery pack based on fuzzy control, comprising: N retired batteries B connected in series, 2N+2 bidirectional switches S, 4 switch tubes Q, an inductor L, an information collection unit and a fuzzy control unit, wherein N is a positive integer greater than 1, and each of the retired batteries B n The anode of the bidirectional switch S 2n-1 The first end and the bidirectional switch S 2n The first end of each of the retired batteries B n The cathode of the bidirectional switch S 2n+1 The first end and the bidirectional switch S 2n+2 The first end of the first switch tube Q is connected, n∈{1, 2, ..., N}, the second ends of all odd-numbered bidirectional switches are connected to the node X, and the second ends of all even-numbered bidirectional switches are connected to the node Y; 1 The source of the second switch tube Q 2 The source of the first switch tube Q 1 The drain of the second switch tube Q is connected to the node X. 2 The drain of the third switch tube Q 3 The drain of the third switch tube Q 3 The source of the fourth switch tube Q 4The source of the fourth switch tube Q 4 The drain of the inductor is connected to the node Y, the first end of the inductor is connected to the node X, and the second end of the inductor is connected to the second switch tube Q 2 The information collection unit is used to collect information from each of the retired batteries B n SOC information of the retired battery B; the fuzzy control unit is used to n The SOC information of the retired batteries is used to control the on-off status of all the bidirectional switches and the on-off status of all the switch tubes based on fuzzy control rules to achieve energy balance between the retired batteries.

[0005] The embodiment of the present disclosure also provides a multi-path balancing method applied to the above-mentioned retired battery group multi-path balancing topology based on fuzzy control, comprising: receiving information collected by an information collection unit for each retired battery B n SOC information of each of the retired batteries B n The SOC information of the retired batteries is used to control the on-off status of all bidirectional switches and the on-off status of all switch tubes based on fuzzy control rules to achieve energy balance between the retired batteries.

[0006] The beneficial effects of the embodiments of the present disclosure are as follows: the present disclosure constructs a multi-path balancing topology for retired batteries based on a fuzzy control strategy, so that when the energy between retired battery cells or battery packs is inconsistent, by controlling the on and off of a bidirectional switch, inductance is used as a carrier to transfer energy, thereby achieving lossless energy balancing and effectively avoiding the occurrence of spikes; at the same time, combined with the fuzzy control strategy, the balancing current is dynamically adjusted through the real-time collected battery SOC information, further achieving rapid energy balancing between battery cells or battery packs. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] In order to more clearly illustrate one or more embodiments of this specification or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this specification. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0008] Figure 1 It is a structural schematic diagram of a multi-path balancing topology of a retired battery pack based on fuzzy control in the first embodiment of the present disclosure;

[0009] Figure 2 A schematic diagram of energy balance between any battery cells in the first embodiment of the present disclosure;

[0010] Figure 3It is a schematic diagram of energy balancing between any battery monomer and any battery group in the first embodiment of the present disclosure;

[0011] Figure 4 It is a schematic diagram of energy balancing between any battery pack and any battery cell in the first embodiment of the present disclosure;

[0012] Figure 5 It is a schematic diagram of energy balancing between any battery groups and any battery groups in the first embodiment of the present disclosure;

[0013] Figure 6 This is a control logic diagram of the fuzzy control unit in the first embodiment of the present disclosure;

[0014] Figure 7 4 is a flow chart of the equalization method in the second embodiment of the present disclosure. DETAILED DESCRIPTION

[0015] In order to enable those skilled in the art to better understand the technical solutions in one or more embodiments of this specification, the following will be combined with the drawings in one or more embodiments of this specification to clearly and completely describe the technical solutions in one or more embodiments of this specification. Obviously, the described embodiments are only part of the embodiments of this specification, not all of the embodiments. Based on one or more embodiments of this specification, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of this document.

[0016] Batteries or supercapacitors are widely used in various energy storage system-related fields. However, batteries generally have a service life and need to be replaced or retired. Today, the handling of a large number of retired batteries has become a difficult problem. Although retired batteries can be used in cascades in some application scenarios, due to the large individual differences between retired batteries, it is easy for one or more retired batteries to be overcharged or over-discharged during the use of retired batteries in series, making the differences between retired batteries more obvious, resulting in a decrease in the overall performance of the series battery pack and affecting its service life. Therefore, how to achieve the balance and safety of the circuit when retired batteries are used in series to form a battery pack is an urgent problem that technicians in this field need to solve.

[0017] In order to solve the above problems, the first embodiment of the present disclosure provides a multi-path balancing topology of retired battery packs based on fuzzy control, such as Figure 1 As shown, the topology includes at least N retired batteries B connected in series, 2N+2 bidirectional switches S, 4 switch tubes Q, an inductor L, an information acquisition unit and a fuzzy control unit, wherein N is a positive integer greater than 1, that is, two or more retired batteries B are connected in series in the topology of this embodiment.

[0018] In the topological structure of this embodiment, all retired batteries B are connected in series, and each retired battery B n The anode of the bidirectional switch S 2n-1 The first end and the bidirectional switch S 2n The first end of each of the retired batteries B n The cathode of the bidirectional switch S 2n+1 The first end and the bidirectional switch S 2n+2 The first end of the connection, retired battery B n It is used to refer to any retired battery in the topology, n∈{1, 2, ..., N}. In fact, the retired battery B n The cathode of the bidirectional switch S is connected 2n+1 and bidirectional switch S 2n+2 , which also serves as retired battery B n+1 The anode of the battery is connected to a bidirectional switch, decommissioning the battery B n The anode of the bidirectional switch S is connected 2n-1 and bidirectional switch S 2n At the same time, it is used as retired battery B n-1 Among all the bidirectional switches, the second ends of all odd-numbered bidirectional switches are connected to node X, and the second ends of all even-numbered bidirectional switches are connected to node Y. 1 The source of the second switch tube Q 2 The source of the first switch tube Q 1 The drain of the second switch tube Q is connected to the node X. 2 The drain of the third switch tube Q 3 The drain of the third switch tube Q 3 The source of the fourth switch tube Q 4 The source of the fourth switch tube Q 4 The drain of the inductor is connected to the node Y, the first end of the inductor is connected to the node X, and the second end of the inductor is connected to the second switch tube Q 2 Drain connection.

[0019] When actually building a multi-way balancing topology, the retired battery can be any type of battery or supercapacitor, and the battery pack connected in series can be a mixture of multiple types of batteries. The bidirectional switch includes two unidirectional switches, the sources of the two unidirectional switches are connected, and the drains of the two unidirectional switches are respectively connected to other components in the topology as the first and second ends of the bidirectional switches, and the gates of the two unidirectional switches are driven based on the same signal. In actual selection, the unidirectional switch selects an IGBT transistor or a MOS transistor with a body diode. Figure 1The unidirectional switch shown in the figure is implemented using an N-type MOS tube. Under gate drive, when the bidirectional switch is turned on, current is allowed to flow in from the first end and out from the second end, or to flow in from the second end and out from the first end.

[0020] The information collection unit 10 in the topology is used to collect the information of each retired battery B n The SOC (battery state of charge / remaining power, State of Charge) information of the retired battery B can be directly collected by the information collection unit 10 through the existing technology. This embodiment does not impose any specific restrictions, as long as it can collect the SOC information for each retired battery B. n The fuzzy control unit 20 receives the SOC information collected by the information collection unit 10, and its output end is connected to the gate of each bidirectional switch and each switch tube, and controls the on-off status of all bidirectional switches and the on-off status of all switch tubes based on the fuzzy control rules to realize the transfer of energy from the rich battery (group) to the poor battery (group) to achieve energy balance.

[0021] Specifically, a rich battery refers to a battery with a higher remaining power among all retired batteries in series, and a rich battery group refers to a plurality of adjacent batteries with a higher remaining power among all retired batteries in series. Similarly, a poor battery refers to a battery with a lower remaining power among all retired batteries in series, and a poor battery group refers to a plurality of adjacent batteries with a lower remaining power among all retired batteries in series. During the use of the series battery group, for example, when supplying power to a load or charging through a power supply, the information acquisition unit 10 collects the remaining power of each retired battery in real time, and the fuzzy control unit 20 obtains the SOC information collected by the information acquisition unit 10 in real time, and calculates the SOC information according to each of the retired batteries B. n The SOC information of the current moment is calculated by calculating the difference ΔSOC between the maximum and minimum values ​​of all SOC information, and the average SOC value of all SOC information. avg Based on the above calculation results, it is detected whether there is a retired battery Bn that meets the balancing condition. The balancing condition in this embodiment includes at least the following formula:

[0022] SOC L ≤SOC n ≤SOC H (1)

[0023] |SOC n -SOC avg |≥δ 1 (2)

[0024] Among them, SOC L Used to indicate the lower limit SOC value of retired batteries, SOC HUsed to indicate the upper limit SOC value of retired batteries, SOC n For retired battery B n SOC value, δ 1 is the preset threshold. n When the equilibrium condition is met, it means that the retired battery B n The remaining power of the battery pack is higher or lower than the average remaining power of the battery pack, and there is energy imbalance between the batteries. In order to balance the energy between the batteries, the fuzzy control unit 20 can enter the balancing mode to transfer the energy between the batteries. It should be noted that SOC L and SOC H Combined with the type of retired batteries, the preset threshold δ 1 It is pre-set according to the type of retired batteries, the actual situation of the retired batteries, etc., and this embodiment does not limit its specific value.

[0025] In this embodiment, when there is a retired battery B that meets the balancing condition n In the case of retired battery B n The actual remaining capacity of the retired battery B is determined by n Is it a rich battery or a poor battery? If the retired battery B n is a rich battery, then the battery with the least remaining power is determined as the weak battery from all the remaining batteries. n If it is a low-energy battery, the battery with the most remaining power is determined from all the remaining batteries as the rich-energy battery, and the calculated difference ΔSOC and average SOC avg Fuzzification processing, fuzzy control rule matching and defuzzification processing are performed in sequence to determine the balancing current of the energy-rich battery and the energy-deficient battery during the energy balancing process, that is, the amount of electricity transferred from the energy-rich battery to the energy-deficient battery each time. After the balancing current is determined, a PWM signal for controlling the bidirectional switch and the switch tube can be generated through a PI controller based on the balancing current and the actual current in the current circuit, and the opening time or opening degree of the bidirectional switch and the switch tube can be modulated based on the duty cycle of the effective level in the PWM signal to achieve energy balancing between retired batteries.

[0026] In the process of energy balancing, the fuzzy control unit 20 first turns on the bidirectional switches at both ends of the energy-rich battery to connect it with the inductor L and charge the inductor L; then turns off the bidirectional switches at both ends of the energy-rich battery, and successively turns on the first switch tube and the second switch tube to make the inductor L enter the freewheeling state to eliminate the current spike; finally turns off the first switch tube and the second switch tube, and turns on the bidirectional switches at both ends of the energy-deficient battery to realize the energy release of the inductor L to the energy-deficient battery. It should be noted that corresponding to each retired battery, its cathode and anode are connected to two bidirectional switches at the same time. In the process of inductive energy storage or inductive energy release, the fuzzy control unit 20 should avoid turning on the odd-side bidirectional switches at both ends of the battery at the same time or turning on the even-side bidirectional switches at both ends of the battery at the same time, and the same applies to the energy-rich battery group or the energy-deficient battery group.

[0027] Figures 2 to 5 Several balanced situations of this embodiment are shown, among which, Figure 2 It is a schematic diagram of energy balance between any battery cells. Figure 3 It is a schematic diagram of energy balance between any battery cell and any battery group. Figure 4 It is a schematic diagram of energy balance between any battery pack and any battery cell. Figure 5 The diagram is a schematic diagram of energy balancing between any battery groups.

[0028] When the series battery pack is used to power the load, Figure 2 , assuming B 1 For energy-rich batteries, B 3 It is a deficient battery, that is, when the entire series energy storage group discharges to the load, B 1 Through the balanced topology circuit to B 3 Transfer energy. 1 When storing energy in the inductor L, the bidirectional switch S 2 , S 3 And the switch tube Q 3 , Q 4 Conductivity, such as Figure 2 As shown in (a); when the inductor L is freewheeling, all bidirectional switches are closed, and the switch tube Q 1 , Q 2 Successively conduct, the switch tube Q 3 , Q 4 Close, such as Figure 2 (b) shows the inductance L to B 3 When releasing energy, the bidirectional switch S 5 , S 8 And the switch tube Q 3 , Q 4 Turn on, switch tube Q 1 , Q 2 Shut down, such as Figure 2 (c) shows that the energy from B is completed.1 To B 3 The process of transmission.

[0029] When the series battery pack is in a charging state, combined with Figure 3 , with B 1 For energy-rich batteries, B 3 B 4 The DC power supply is used to charge the entire series energy storage group as an example to illustrate that when the entire series energy storage group is charged, B 1 Through the balanced topology circuit to B 3 B 4 Transfer energy. 1 When storing energy in the inductor L, the bidirectional switch S 2 , S 3 And the switch tube Q 3 , Q 4 Conductivity, such as Figure 3 As shown in (a); when the inductor L is freewheeling, all bidirectional switches are closed, and the switch tube Q 1 , Q 2 Successively conduct, the switch tube Q 3 , Q 4 Close, such as Figure 3 (b) shows the inductance L to B 3 B 4 When releasing energy, the bidirectional switch S 5 , S 10 And the switch tube Q 3 , Q 4 Turn on, switch tube Q 1 , Q 2 Shut down, such as Figure 3 (c) shows that the energy from B is completed. 1 To B 3 B 4 The process of transmission.

[0030] When the series battery pack is at rest, Figure 4 , with B 1 B 2 For the energy-rich battery pack, B 4 The example of the whole series energy storage group being in a static state is given as a depleted battery. 1 B 2 When storing energy in the inductor L, the bidirectional switch S 2 , S 5 And the switch tube Q 3 , Q 4 Conductivity, such as Figure 4 As shown in (a); when the inductor L is freewheeling, all bidirectional switches are closed, and the switch tube Q 1 , Q 2 Successively conduct, the switch tube Q 3, Q 4 Close, such as Figure 4 (b) shows the inductance L to B 4 When releasing energy, the bidirectional switch S 7 , S 10 And the switch tube Q 3 , Q 4 Turn on, switch tube Q 1 , Q 2 Shut down, such as Figure 4 (c) shows that the energy from B is completed. 1 B 2 To B 4 The process of transmission.

[0031] When the series battery pack is at rest, Figure 5 , with B 1 B 2 For the energy-rich battery pack, B 3 B 4 For example, the entire series energy storage group is in a static state. 1 B 2 When storing energy in the inductor L, the bidirectional switch S 2 , S 5 And the switch tube Q 3 , Q 4 Conductivity, such as Figure 5 As shown in (a); when the inductor L is freewheeling, all bidirectional switches are closed, and the switch tube Q 1 , Q 2 Successively conduct, the switch tube Q 3 , Q 4 Close, such as Figure 5 (b) shows the inductance L to B 3 B 4 When releasing energy, the bidirectional switch S 5 , S 10 And the switch tube Q 3 , Q 4 Turn on, switch tube Q 1 , Q 2 Shut down, such as Figure 5 (c) shows that the energy from B is completed. 1 B 2 To B 3 B 4 The process of transmission.

[0032] In some embodiments, the fuzzy control unit 20 includes at least a fuzzifier 21, a fuzzy inference engine 22 and a defuzzifier 23. Figure 6As shown, the fuzzy inference engine stores fuzzy control rules, and the fuzzy control unit 20 also includes a PI adjustment controller 24. In the process of determining the balanced current, the fuzzy inference engine first converts the calculated ΔSOC into a first fuzzy variable based on a preset difference fuzzy rule, and converts the average SOC into a first fuzzy variable based on a preset average fuzzy rule. avg Transformed into the second fuzzy variable. For example, set the range of ΔSOC to [0, 30], set SOC avg The range of is [0, 100]. According to the above range, the difference fuzzy rule is set to configure the difference fuzzy quantity to [0, 5, 10, 15, 20, 30], and corresponding to the interval formed by the above two consecutive values, the corresponding fuzzy set is set to [SS (very small), S (small), M (medium), B (large), BB (very large)], that is, when the value of ΔSOC is 4, the corresponding first fuzzy variable is SS, and when the value of ΔSOC is 17, the corresponding first fuzzy variable is B; similarly, the average value fuzzy rule is set to configure the average value fuzzy quantity to [0, 20, 40, 60, 80, 100], and corresponding to the interval formed by the above two consecutive values, the corresponding fuzzy set is set to [SS (very small), S (small), M (medium), B (large), BB (very large)], that is, in SOC avg When the value of is 35, the corresponding second fuzzy variable is S. avg When the value of is 48, the corresponding second fuzzy variable is M.

[0033] Then, the fuzzy inference engine determines the current fuzzy variable I corresponding to the first fuzzy variable and the second fuzzy variable based on the fuzzy control rule. The fuzzy control rule of this embodiment is shown in Table 1, that is, the corresponding current fuzzy variable i is found in Table 1 based on the values ​​of the first fuzzy variable and the second fuzzy variable. o :

[0034] Table 1

[0035]

[0036] The above fuzzy control rule setting can be set according to the following conditions:

[0037] (1) When ΔSOC and SOC avg When both are relatively small, a smaller output current is used for balancing, which can ensure the balancing rate and effect while avoiding over-discharge or over-balancing of the battery;

[0038] (2) When ΔSOC and SOC avg When both are relatively large, a larger output current is used for balancing, which can ensure the balancing rate and effect;

[0039] (3) When ΔSOC is small and SOCavg When the voltage is larger, a smaller output current is used for balancing, which can ensure the balancing rate and effect while avoiding overcharging or over-balancing of the battery;

[0040] (4) When ΔSOC is large and SOC avg When it is smaller, a larger output current is used for balancing, which can ensure the balancing rate and effect.

[0041] However, it should be noted that the conditions referred to when setting the fuzzy control rules include but are not limited to the above conditions, and the fuzzy inference engine can also be set according to actual conditions or special needs, which is not limited in this embodiment.

[0042] After the current fuzzy quantity is determined, the current fuzzy quantity can be converted into the balancing current according to the current fuzzy rule through the defuzzifier. Similar to the difference fuzzy rule or the average fuzzy rule, the fuzzy set corresponding to the current fuzzy quantity is also [SS (very small), S (small), M (medium), B (large), BB (very large)]. According to the actual retired battery situation, the configuration of the fuzzy quantity is set for the above fuzzy set. For example, when the current fuzzy quantity is S, the corresponding balancing current fuzzy quantity is 2A, when the current fuzzy quantity is M, the corresponding balancing current fuzzy quantity is 3A, when the current fuzzy quantity is BB, the corresponding balancing current fuzzy quantity is 5A, etc. After determining the current fuzzy quantity, the defuzzifier determines a fuzzy quantity of the balancing current and uses it as the balancing current i in this balancing process. o .

[0043] The fuzzy control unit 20 controls the bidirectional switches and switch tubes that need to be turned on in the topology according to the balancing current determined by the defuzzifier, so that the inductor L switches between energy storage and energy release actions, and completes the energy balance between the rich energy battery and the poor energy battery corresponding to the balancing current. It should be noted that in the energy balancing process between the rich energy battery and the poor energy battery, the inductor L may need to perform multiple energy storage and energy release operations to complete the energy balance between the two. Assuming that the rich energy battery has 50 units of electricity and the poor energy battery has 10 units of electricity, when the two are balanced, 20 units of electricity in the rich energy battery need to be transferred to the poor energy battery so that both have 30 units of electricity. However, in a single charge and discharge process of the inductor L, the maximum amount of electricity that can be transferred is 5 units, so at least 4 charge and discharge processes are required to complete a complete balancing process.

[0044] In the actual implementation process, if the retired battery group connected in series is in the state of supplying power to the load or being charged by a DC power supply, the power of all retired batteries will change over time. In the balancing process of the energy-rich battery and the energy-deficient battery in the balancing mode, the unit power of the two will also change. Corresponding to this change, the power required to be balanced between the energy-rich battery and the energy-deficient battery will also change. If the balancing is always performed according to the unchanged situation, there may be a phenomenon of over-discharge or over-balancing of the battery. Therefore, the fuzzy control unit 20 can collect the SOC information of each retired battery in real time based on the information collection unit 10, and adjust the balancing current corresponding to each energy storage and release process of the inductor in real time during a complete balancing process.

[0045] The PI adjustment controller 24 converts the balanced current i output by the defuzzifier 23 into o and the actual current i in the current circuit i As input, after PI regulation, PWM drive signals of different switches are generated; among them, when the balanced current i o and the actual current i i When the actual current i i has converged, and when the equilibrium current i o and the actual current i i When the current is not equal, the actual current can be quickly converged to the equilibrium current i by adjusting the PI parameters. o , thereby improving the equalization rate and achieving smooth switching between different equalization modes.

[0046] This embodiment builds a multi-path balancing topology for retired batteries based on a fuzzy control strategy, so that when the energy between retired battery cells or battery packs is inconsistent, by controlling the on and off of a bidirectional switch, the inductor is used as a carrier to transfer energy, thereby achieving lossless energy balancing and effectively avoiding the occurrence of spikes; at the same time, combined with the fuzzy control strategy, the balancing current is dynamically adjusted through the real-time collected battery SOC information, further achieving rapid energy balancing between battery cells or battery packs.

[0047] Based on the same inventive concept, the second embodiment of the present disclosure provides a multi-path balancing method based on fuzzy control of a retired battery pack multi-path balancing topology applying the first embodiment of the present disclosure. The method mainly refers to a method performed by a fuzzy control unit, and its flow chart is as follows: Figure 7 As shown, it mainly includes steps S10 and S20:

[0048] S10, receiving the information collected by the information collection unit for each retired battery B n SOC information;

[0049] S20, according to each retired battery B nThe SOC information is used to control the on-off status of all bidirectional switches and the on-off status of all switch tubes based on fuzzy control rules to achieve energy balance between retired batteries.

[0050] In conjunction with the multi-path balancing topology of the retired battery group based on fuzzy control in the first embodiment of the present disclosure, the fuzzy control unit can obtain the information of each retired battery B in real time from the information collection unit. n The SOC information of each retired battery B n The statistics and processing of SOC information are used to determine the energy-rich battery (group) and energy-deficient battery (group) that need to be balanced, and the energy balancing between the energy-rich battery (group) and the energy-deficient battery (group) is achieved by controlling the on-off status of different switching tubes.

[0051] Specifically, the fuzzy control unit obtains the real-time information of each retired battery B n After the SOC information is obtained, the difference ΔSOC between the maximum and minimum values ​​of all SOC information at the current moment and the average SOC value of all SOC information are calculated. avg Based on the above calculation results, it is detected whether there is a retired battery B that meets the balancing condition. n , the equilibrium condition in this embodiment at least includes the following formula:

[0052] SOC L ≤SOC n ≤SOC H (1)

[0053] |SOC n -SOC avg |≥δ 1 (2)

[0054] Among them, SOC L Used to indicate the lower limit SOC value of retired batteries, SOC H Used to indicate the upper limit SOC value of retired batteries, SOC n For retired battery B n SOC value, δ 1 is the preset threshold. n When the equilibrium condition is met, it means that the retired battery B n The remaining power of the battery is higher or lower than the average remaining power of the battery pack, and there is energy imbalance between the batteries. In order to balance the energy between the batteries, the fuzzy control unit can enter the balancing mode to transfer the energy between the batteries. It should be noted that SOC L and SOC H Combined with the type of retired batteries, the preset threshold δ 1It is pre-set according to the type of retired batteries, the actual situation of the retired batteries, etc., and this embodiment does not limit its specific value.

[0055] In this embodiment, when there is a retired battery B that meets the balancing condition n In the case of retired battery B n The actual remaining capacity of the retired battery B is determined by n Is it a rich battery or a poor battery? If the retired battery B n is a rich battery, then the battery with the least remaining power is determined as the weak battery from all the remaining batteries. n If it is a low-energy battery, the battery with the most remaining power is determined from all the remaining batteries as the rich-energy battery, and the calculated difference ΔSOC and average SOC avg Fuzzification processing, fuzzy control rule matching and defuzzification processing are performed in sequence to determine the balancing current of the energy-rich battery and the energy-deficient battery during the energy balancing process, that is, the amount of electricity transferred from the energy-rich battery to the energy-deficient battery each time. After the balancing current is determined, a PWM signal for controlling the bidirectional switch and the switch tube can be generated through a PI controller based on the balancing current and the actual current in the current circuit, and the opening time or opening degree of the bidirectional switch and the switch tube can be modulated based on the duty cycle of the effective level in the PWM signal to achieve energy balancing between retired batteries.

[0056] In the process of determining the balancing current, the fuzzy controller first converts the calculated ΔSOC into a first fuzzy variable based on a preset difference fuzzy rule, and converts the average SOC into a first fuzzy variable based on a preset average fuzzy rule. avg Transformed into the second fuzzy variable. For example, set the range of ΔSOC to [0, 30], set SOC avg The range of is [0, 100]. According to the above range, the difference fuzzy rule is set to configure the difference fuzzy quantity to [0, 5, 10, 15, 20, 30], and corresponding to the interval formed by the above two consecutive values, the corresponding fuzzy set is set to [SS (very small), S (small), M (medium), B (large), BB (very large)], that is, when the value of ΔSOC is 4, the corresponding first fuzzy variable is SS, and when the value of ΔSOC is 17, the corresponding first fuzzy variable is B; similarly, the average value fuzzy rule is set to configure the average value fuzzy quantity to [0, 20, 40, 60, 80, 100], and corresponding to the interval formed by the above two consecutive values, the corresponding fuzzy set is set to [SS (very small), S (small), M (medium), B (large), BB (very large)], that is, in SOC avg When the value of is 35, the corresponding second fuzzy variable is S. avgWhen the value of is 48, the corresponding second fuzzy variable is M.

[0057] Then, the fuzzy inference engine determines the current fuzzy variable I corresponding to the first fuzzy variable and the second fuzzy variable based on the fuzzy control rule. The fuzzy control rule of this embodiment is shown in Table 1, that is, the corresponding current fuzzy variable i is found in Table 1 based on the values ​​of the first fuzzy variable and the second fuzzy variable. o :

[0058] Table 1

[0059]

[0060] After the current fuzzy quantity is determined, the current fuzzy quantity can be converted into the balancing current according to the current fuzzy rule through the defuzzifier. Similar to the difference fuzzy rule or the average fuzzy rule, the fuzzy set corresponding to the current fuzzy quantity is also [SS (very small), S (small), M (medium), B (large), BB (very large)]. According to the actual retired battery situation, the configuration of the fuzzy quantity is set for the above fuzzy set. For example, when the current fuzzy quantity is S, the corresponding balancing current fuzzy quantity is 2A, when the current fuzzy quantity is M, the corresponding balancing current fuzzy quantity is 3A, when the current fuzzy quantity is BB, the corresponding balancing current fuzzy quantity is 5A, etc. After determining the current fuzzy quantity, the defuzzifier determines a fuzzy quantity of the balancing current and uses it as the balancing current i in this balancing process. o .

[0061] According to the balancing current determined by the defuzzifier, the bidirectional switches and switch tubes that need to be turned on in the topology are controlled to switch the inductor L between the energy storage action and the energy release action, and complete the energy balance between the rich energy battery and the poor energy battery corresponding to the balancing current. It should be noted that in the energy balancing process between the rich energy battery and the poor energy battery, the inductor L may need to perform multiple energy storage and energy release operations to complete the energy balance between the two. Assuming that the rich energy battery has 50 units of electricity and the poor energy battery has 10 units of electricity, when the two are balanced, 20 units of electricity in the rich energy battery need to be transferred to the poor energy battery so that both have 30 units of electricity. However, in a single charge and discharge process of the inductor L, the maximum amount of electricity that can be transferred is 5 units, so at least 4 charge and discharge processes are required to complete a complete balancing process.

[0062] In the actual implementation process, if the retired battery group connected in series is in the state of supplying power to the load or being charged by a DC power supply, the power of all retired batteries will change over time. In the balancing process of the rich energy battery and the weak energy battery in the balancing mode, the unit power of the two will also change. Corresponding to this change, the power required to be balanced between the rich energy battery and the weak energy battery will also change. If the balancing is always performed according to the unchanged situation, there may be battery over-discharge or over-balancing. Therefore, the fuzzy control unit can collect the SOC information of each retired battery in real time based on the information collection unit, and adjust the balancing current corresponding to each energy storage and release process of the inductor in real time during a complete balancing process.

[0063] The PI control controller converts the balanced current i output by the defuzzifier into o and the actual current i in the current circuit i As input, after PI regulation, PWM drive signals of different switches are generated; among them, when the balanced current i o and the actual current i i When the actual current i i has converged, and when the equilibrium current i o and the actual current i i When the current is not equal, the actual current can be quickly converged to the equilibrium current i by adjusting the PI parameters. o , thereby improving the equalization rate and achieving smooth switching between different equalization modes.

[0064] This embodiment builds a multi-path balancing topology for retired batteries based on a fuzzy control strategy, so that when the energy between retired battery cells or battery packs is inconsistent, by controlling the on and off of a bidirectional switch, the inductor is used as a carrier to transfer energy, thereby achieving lossless energy balancing and effectively avoiding the occurrence of spikes; at the same time, combined with the fuzzy control strategy, the balancing current is dynamically adjusted through the real-time collected battery SOC information, further achieving rapid energy balancing between battery cells or battery packs.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present disclosure, rather than to limit them. Although the present disclosure has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present disclosure.

Claims

1. A multi-path balancing topology for retired battery packs based on fuzzy control, characterized in that: include: N retired batteries B connected in series, 2N+2 bidirectional switches S, 4 switch tubes Q, an inductor L, an information collection unit and a fuzzy control unit, where N is a positive integer greater than 1. Each of the retired batteries B n The anode of the bidirectional switch S 2n-1 The first end and the bidirectional switch S 2n The first end of each of the retired batteries B n The cathode of the bidirectional switch S 2n+1 The first end and the bidirectional switch S 2n+2 The first end of each of the bidirectional switches is connected to node X, n∈{1,2,…,N}, the second ends of all odd-numbered bidirectional switches are connected to node X, and the second ends of all even-numbered bidirectional switches are connected to node Y; The source of the first switch tube Q1 is connected to the source of the second switch tube Q2, the drain of the first switch tube Q1 is connected to the node X, the drain of the second switch tube Q2 is connected to the drain of the third switch tube Q3, the source of the third switch tube Q3 is connected to the source of the fourth switch tube Q4, the drain of the fourth switch tube Q4 is connected to the node Y, the first end of the inductor is connected to the node X, and the second end of the inductor is connected to the drain of the second switch tube Q2; The information collection unit is used to collect information about each of the retired batteries B n SOC information; The fuzzy control unit is used to n The SOC information of the retired batteries is used to control the on-off status of all the bidirectional switches and the on-off status of all the switch tubes based on fuzzy control rules to achieve energy balance between the retired batteries.

2. The multi-path balancing topology of retired battery groups according to claim 1, characterized in that: The fuzzy control unit is specifically used for: According to each of the retired batteries B n The SOC information of all the SOC information is calculated, and the difference ΔSOC between the maximum value and the minimum value of all the SOC information is calculated, and the average value SOC of all the SOC information is calculated. avg ; Detect whether there is a retired battery B that meets the balancing condition n ; In the presence of the retired battery B that meets the equilibrium condition n In the case of avg Performing fuzzification processing, fuzzy control rule matching and defuzzification processing in sequence to determine a balanced current; According to the balancing current and the actual current in the current circuit, a PWM signal for controlling all the bidirectional switches and all the switch tubes is generated through a PI controller to achieve energy balancing among the retired batteries.

3. The multi-path balancing topology of retired battery groups according to claim 2, characterized in that: The information collection unit is also used to collect the information of the retired battery B in real time during the energy balancing process between the retired batteries. n SOC information; The fuzzy control unit is further used to adjust the value of the balancing current according to the SOC information collected in real time by the information collection unit, and generate a new PWM signal according to the adjusted balancing current and the actual current in the current circuit.

4. The multi-path balancing topology of a retired battery group according to any one of claims 1 to 3, characterized in that: Each of the bidirectional switches includes two unidirectional switches, the sources of the two unidirectional switches are connected, the drains of the two unidirectional switches serve as the first end and the second end of the bidirectional switch respectively, and the unidirectional switches are IGBT transistors or MOS transistors.

5. A multi-path balancing method for a retired battery pack multi-path balancing topology based on fuzzy control applied to any one of claims 1 to 4, characterized in that: include: Each retired battery B collected by the receiving information collection unit n SOC information; According to each of the retired batteries B n The SOC information of the retired batteries is used to control the on-off status of all bidirectional switches and the on-off status of all switch tubes based on fuzzy control rules to achieve energy balance between the retired batteries.

6. The multipath equalization method according to claim 5, characterized in that: According to all the retired batteries B n The SOC information of the decommissioned batteries is used to control the on-off status of all bidirectional switches and the on-off status of all switch tubes based on fuzzy control rules to achieve energy balance between the decommissioned batteries, including: According to each of the retired batteries B n The SOC information of all the SOC information is calculated, and the difference ΔSOC between the maximum value and the minimum value of all the SOC information is calculated, and the average value SOC of all the SOC information is calculated. avg ; Detect whether there is a retired battery B that meets the balancing condition n ; In the presence of the retired battery B that meets the equilibrium condition n In the case of avg Performing fuzzification processing, fuzzy control rule matching and defuzzification processing in sequence to determine a balanced current; According to the balancing current and the actual current in the current circuit, a PWM signal for controlling all the bidirectional switches and all the switch tubes is generated through a PI controller to achieve energy balancing among the retired batteries.

7. The multipath equalization method according to claim 6, characterized in that: The equilibrium condition at least includes the following formula: SOC L ≤SOC n ≤SOC H (1) |SOC n -SOC avg |≥δ1 (2) Among them, SOC L Used to indicate the lower limit SOC value of retired batteries, SOC H It is used to indicate the upper limit SOC value of the retired battery, and δ1 is the preset threshold value.

8. The multipath equalization method according to claim 6, characterized in that: The difference ΔSOC and the average SOC avg Performing fuzzification processing, fuzzy control rule matching and defuzzification processing in sequence to determine the balanced current includes: The difference ΔSOC is converted into a first fuzzy variable according to a difference fuzzy rule, and the average SOC is converted into a first fuzzy variable according to an average fuzzy rule. avg Transformed into the second fuzzy variable; Determining current fuzzy variables corresponding to the first fuzzy variable and the second fuzzy variable in the fuzzy control rule; The current fuzzy variable is converted into a balanced current according to a current fuzzy rule.

9. The multipath equalization method according to any one of claims 5 to 8, characterized in that: Also includes: The retired battery B collected in real time by the receiving information collection unit during the energy balancing process n SOC information; According to the SOC information collected in real time by the information collection unit, the value of the balancing current is adjusted, and a new PWM signal is generated according to the adjusted balancing current and the actual current in the current circuit.

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