A battery equalization method and system based on gas-liquid thermal coupling model

Abstract

The present invention provides a battery and other electricity equalization method and system based on a gas-liquid thermal coupling model, characterized in that it includes five steps: step one: a battery remaining capacity and rechargeable capacity estimation method based on a gas-liquid thermal coupling model; step two: calculating the coefficient of variation of the remaining capacity of a series battery group and the coefficient of variation of the rechargeable capacity; step three: a coefficient of variation discrimination strategy; step four: a battery and other electricity equalization method based on a gas-liquid thermal coupling model; step five: a battery and other electricity equalization system based on a gas-liquid thermal coupling model. The gas-liquid thermal coupling model of the present invention takes into account both structural simplicity and estimation accuracy, with a small amount of calculation and high estimation accuracy, and is very easy to implement on a single-chip microcomputer; based on the gas-liquid thermal coupling model and the double extended Kalman filter algorithm, the parameters of the gas-liquid thermal coupling model are identified online and the state of charge of the battery is estimated online, which can improve the robustness and convergence speed of the battery state of charge estimation method to the initial value error. The battery and other electricity equalization method based on the gas-liquid thermal coupling model of the present invention improves the remaining electricity consistency and rechargeable electricity consistency of the series battery group and the electricity equalization speed, and significantly improves the energy utilization rate and safety of the series battery group.

Description

Technical Field

[0001] The present invention relates to the field of battery equalization management, and specifically to a method and system for rapid equalization of battery and other electric quantities based on a gas-liquid thermal coupling model, and in particular to rapid equalization of a series-connected battery pack for electric vehicles. Background Art

[0002] When lithium batteries are used in groups, due to differences in voltage, capacity and other parameters between single cells, these inconsistencies can easily lead to deterioration of battery performance during the battery charging and discharging process, thus affecting the service life and safety performance of electric vehicles. In order to improve the overall performance and extend the service life of the series battery pack, it is necessary to effectively balance the series battery pack. By detecting the parameters of the series battery pack and identifying its power state, the single cells with high power are discharged and the single cells with low energy are charged, so that the power state of each single cell tends to be consistent, and the goal of full charging and full discharging of the series battery pack is achieved.

[0003] At present, the balancing technology of series battery packs can be divided into two categories: energy dissipation type and non-energy consumption type. Energy dissipation type balancing is to connect a resistor in parallel to each battery in the series battery pack, and use the resistor discharge shunt method to achieve power balancing. This method is simple, but there are problems such as energy waste and safety hazards. Non-energy consumption type balancing achieves power balancing inside the series battery pack through a more efficient balancing strategy, avoiding unnecessary energy loss, being more environmentally friendly, and effectively improving the efficiency and safety of the series battery pack.

[0004] Existing battery balancing strategies face the problem of inaccurate battery power estimation, resulting in low battery balancing efficiency and even balancing time, because the balanced power cannot be effectively determined. The present invention discloses a non-energy dissipative battery power balancing method and system based on a gas-liquid dynamics model to solve the above battery balancing problem. Summary of the invention

[0005] The present invention proposes a battery and other electricity balancing method and system based on a gas-liquid thermal coupling model.

[0006] The technical solution of the present invention is: a battery and other power equalization method and system based on a gas-liquid thermal coupling model, characterized in that it includes the following steps:

[0007] Step 1: A method for estimating the remaining capacity and rechargeable capacity of a battery based on a gas-liquid-thermal coupling model;

[0008] Step 2: Calculate the coefficient of variation of the remaining capacity and the coefficient of variation of the rechargeable capacity of the series battery pack;

[0009] Step 3: Coefficient of variation determination strategy;

[0010] Step 4: Battery equalization method based on gas-liquid thermal coupling model;

[0011] Step 5: Battery and other energy balancing systems based on gas-liquid-thermal coupling model.

[0012] In the above scheme, the method for estimating the remaining capacity and rechargeable capacity of a battery based on a gas-liquid-thermal coupling model in step 1 is characterized by:

[0013] C rest =C all ×SOC 2 (Formula 1)

[0014] C abch =C all ×(1-SOC 2 ) (Formula 2)

[0015]

[0016] In the formula, C rest is the remaining capacity, C abch is the chargeable capacity, C all is the actual capacity, "d" is added before the letter to indicate the differential of the parameter, t is the time, and " k " represents the state of the parameter at the kth moment, k = 0, 1, 2, 3..., SOC is the state of charge, and I is the current.

[0017] In the step 1, a battery remaining capacity estimation method based on a gas-liquid-thermal coupling model is used. Formula 1, Formula 2, and Formula 3 all require estimation of the battery state of charge. Specifically, a double extended Kalman filter algorithm is used to online identify the parameters of the gas-liquid-thermal coupling model and online estimate the battery state of charge.

[0018] The dual extended Kalman filter algorithm online identifies the parameters of the gas-liquid-thermal coupling model and online estimates the state of charge of the battery, specifically:

[0019]

[0020] According to the state equation of the gas-liquid thermal coupling model, Formula 4 is specifically:

[0021]

[0022] According to the state equation of the gas-liquid thermal coupling model, Formula 5 is specifically:

[0023]

[0024] Where θ is the state variable for online identification of gas-liquid thermal coupling model parameters. The four parameters to be identified in the gas-liquid thermal coupling model are k 1 , k2 , k 3 , k 4 , d is the observed quantity of the online identification of the gas-liquid thermal coupling model parameters, h is the function of the model parameter observation quantity, λ is the input quantity of the model parameter observation quantity function, I is the current and charging is positive and discharging is negative, T k is the battery temperature, U OCI is the battery open circuit voltage, x is the state quantity of the battery SOC estimated online, f is the function of the battery SOC state quantity, u is the input quantity of the battery SOC state quantity function, y is the observation quantity of the battery SOC estimated online, g is the function of the battery SOC observation quantity, and μ is the input quantity of the battery SOC observation quantity function;

[0025] ① Initialization:

[0026]

[0027] Where P θ is the covariance matrix of θ, Q θ is the system noise variance of the online identification of gas-liquid thermal coupling model parameters, R θ is the measurement noise variance of the gas-liquid thermal coupling model parameters for online identification, P x is the covariance matrix of x, Q x is the system noise variance of online estimation of battery SOC, R x is the measurement noise variance for online estimation of battery SOC;

[0028] ②Update the time value of the parameter observer:

[0029]

[0030]

[0031]

[0032] In the formula, the superscript letter plus "-" represents the prior state of the parameter, the superscript letter plus "+" represents the posterior state of the parameter, the superscript letter plus "T" represents the transpose of the matrix, and A is the coefficient matrix of the model parameter state quantity;

[0033] ③Update the time value of the state observer:

[0034]

[0035]

[0036]

[0037] Where, B is the coefficient matrix of the battery SOC state;

[0038] ④Update the measurement value of the state observer:

[0039]

[0040] In the formula, K x is the Kalman gain of x, D is the coefficient matrix of the battery SOC observation, and E is the unit matrix of the same order as the operation matrix;

[0041] ⑤Update the measured value of the parameter observer:

[0042]

[0043] In the formula, K θ is the Kalman gain of θ, C is the coefficient matrix of the model parameter observations;

[0044] ⑥ Update k:

[0045] k=k+1(Formula 17)

[0046] ⑦ Repeat steps ② to ⑥ to achieve online identification of parameters of the gas-liquid thermal coupling model and online estimation of the battery state of charge;

[0047] In the above scheme, the step 2 calculates the coefficient of variation Φ of the remaining capacity of the series battery pack rest and the coefficient of variation of the chargeable capacity Φ abch , characterized in that:

[0048]

[0049] In the formula, s rest is the standard deviation of the remaining capacity of the series battery pack, is the average value of the remaining capacity of the series battery pack, s abch is the standard deviation of the chargeable capacity of the series battery pack, is the average value of the rechargeable capacity of the series-connected battery pack, N is the total remaining capacity of the series-connected battery pack (N≥2), i is the serial number of the series-connected battery (i≤N), i=1,2,3…;

[0050] In the above scheme, the variation coefficient discrimination strategy in step 3 is characterized by:

[0051]

[0052] In the formula, Φ new is the coefficient of variation of the actual capacity of the new series battery pack;

[0053] In the above scheme, the fourth step is a battery equalization method based on a gas-liquid-thermal coupling model, characterized in that:

[0054] Determine whether the battery is in a discharge standby state or a charge standby state;

[0055] When the battery is in a discharge standby state, the batteries in the series battery pack are sorted from low to high according to the remaining capacity, and then the remaining capacity of all batteries is subtracted from the remaining capacity of the lowest battery to obtain the remaining capacity difference ΔC of each battery. rest , and then calculate the average value of the remaining capacity difference

[0056]

[0057] Calculate the discharge balance capacity of each battery

[0058]

[0059] Discharge the battery to a positive value to balance the capacity (i.e. ) are transferred to the transfer capacitor in descending order. The larger the positive discharge balancing capacity is, the higher the priority of the transfer. When the transfer capacitor is fully charged or the positive discharge balancing capacity is fully transferred to the transfer capacitor, the electricity in the transfer capacitor is transferred to the negative discharge balancing capacity (i.e. ) in the battery, the amount of electricity transferred in is equal to the absolute value of the negative discharge balancing capacity. If the amount of electricity in the transfer capacitor is lower than the absolute value of the negative discharge balancing capacity of the transferred battery, all of it will be transferred in. The larger the absolute value of the negative discharge balancing capacity is, the higher the priority of the transfer.

[0060] According to the positive discharge balance capacity transfer-out and negative discharge balance capacity transfer-in rules of the battery, until the discharge balance capacity transfer of all batteries is completed, it can be known from the conversion formula that one ampere-hour capacity is equal to 3,600 coulombs of electricity that the batteries in the series battery group have equal remaining electricity;

[0061] When the battery is in a charging standby state, the batteries in the series battery pack are sorted from low to high according to the rechargeable capacity, and then the rechargeable capacity of the lowest battery is subtracted from the rechargeable capacity of all batteries to obtain the rechargeable capacity difference ΔC of each battery. abch , and then calculate the average value of the difference in rechargeable capacity

[0062]

[0063] Calculate the charge equalization capacity of each battery

[0064]

[0065] Negative charge equalization capacity (i.e. ) of the battery, it is necessary to transfer the power of the negative charge equalization capacity absolute value (i.e. ) to the transfer capacitor. The larger the absolute value of the negative charge equalization capacity is, the higher the priority of the transfer. When the transfer capacitor is fully charged or the absolute value of the negative charge equalization capacity is fully transferred to the transfer capacitor, the power in the transfer capacitor is transferred to the positive charge equalization capacity (i.e. ) in the battery, the amount of electricity transferred in is equal to the positive balancing capacity of the corresponding battery. If the amount of electricity in the transfer capacitor is lower than the positive charging balancing capacity of the transferred battery, all of it is transferred in. The larger the value of the positive charging balancing capacity is, the higher the priority of the transfer is.

[0066] According to the negative value charge equalization capacity transfer out and positive value charge equalization capacity transfer in rules of the battery, until the charge equalization capacity transfer of all batteries is completed, it can be known from the conversion formula that one ampere-hour capacity is equal to 3,600 coulombs of electricity that the batteries in the series battery group have equal chargeable capacity;

[0067] Calculate the coefficient of variation of the balanced series battery group again and go to step 3;

[0068] In the above scheme, the battery equalization system based on the gas-liquid-thermal coupling model in step 5 is characterized by comprising a data acquisition module, a battery capacity estimation module, a variation coefficient calculation module, a variation coefficient judgment module, a battery equalization module, a circuit protection module, a display module, and a buzzer; the data acquisition module collects the terminal voltage, current and temperature of each battery in series of the series battery group, and sends them to the battery capacity estimation module; the battery capacity estimation module estimates the remaining capacity and rechargeable capacity of the battery according to the method of step 1, and sends them to the variation coefficient calculation module; the variation coefficient calculation module calculates the variation coefficient of the remaining capacity and the variation coefficient of the rechargeable capacity of the series battery group according to the method of step 2, and sends them to the variation coefficient judgment module; the variation coefficient judgment module completes the variation coefficient judgment operation according to the method of step 3; if the series battery group needs to be balanced, the battery equalization module completes the equalization operation of the series battery group according to step 4; the circuit protection module always monitors the parameter safety of the battery equalization system, and if the battery is over-voltage, over-current, over-temperature, and the variation coefficient of the series battery group increases after equalization, the equalization operation of the series battery group is stopped and the fault reminder is pushed to the display module and the buzzer is started.

[0069] In the above scheme, the method for estimating the remaining capacity and rechargeable capacity of the battery based on the gas-liquid-thermal coupling model in step 1, in addition to the double extended Kalman filter algorithm, also includes genetic algorithm, particle filter algorithm, simulated annealing algorithm, observer, neural network algorithm, other artificial intelligence algorithms, other Kalman filter algorithms, etc.

[0070] Compared with the prior art, the present invention has the following beneficial effects:

[0071] Estimating the remaining capacity and rechargeable capacity of the battery based on the gas-liquid-thermal coupling model requires less calculation and is more accurate.

[0072] The coefficient of variation method is used to determine the balancing strategy of the series battery pack, which can avoid the influence of the dimensions of different physical quantities and has excellent adaptability to different batteries.

[0073] The transfer capacitor acts as an intermediate container for power transfer, which can greatly simplify the structure of the series battery pack balancing circuit, thereby reducing hardware costs and lowering the difficulty of balancing control.

[0074] Battery and other power balancing methods can truly achieve full charging and full discharging of series-connected battery packs and maximize the energy utilization of series-connected battery packs. BRIEF DESCRIPTION OF THE DRAWINGS

[0075] Figure 1 The present invention provides a method and system for equalizing the amount of electricity such as batteries based on a gas-liquid thermal coupling model;

[0076] Figure 2 This is a series battery pack model of the present invention;

[0077] Figure 3 To balance the chargeable capacity and residual capacity distribution of the batteries in the front series battery group A to E of the present invention;

[0078] Figure 4 The equalization circuit model of the series battery pack of the present invention;

[0079] Figure 5 The distribution of the chargeable capacity and the remaining capacity of the batteries in the series battery group A to E after discharge equalization of the present invention;

[0080] Figure 6 A model of a series battery pack having equal residual power after discharge equalization according to the present invention;

[0081] Figure 7 The distribution of the chargeable capacity and the remaining capacity of the batteries in the series battery group A to E after charge equalization of the present invention;

[0082] Figure 8 A model of a series battery pack having equal chargeable capacity after charge equalization according to the present invention;

[0083] Fig. 9 is the capacity parameter of the series-connected battery of the present invention. DETAILED DESCRIPTION

[0084] The present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation modes, but the protection scope of the present invention is not limited thereto.

[0085] The technical solution of the present invention is: a battery equalization method and system based on a gas-liquid thermal coupling model, referring to Figure 1 , its characteristics are:

[0086] Step 1: A method for estimating the remaining capacity and rechargeable capacity of a battery based on a gas-liquid-thermal coupling model;

[0087] Step 2: Calculate the coefficient of variation of the remaining capacity and the coefficient of variation of the rechargeable capacity of the series battery pack;

[0088] Step 3: Coefficient of variation determination strategy;

[0089] Step 4: Battery equalization method based on gas-liquid thermal coupling model;

[0090] Step 5: Battery and other energy balancing systems based on gas-liquid-thermal coupling model.

[0091] In the above scheme, the method for estimating the remaining capacity and rechargeable capacity of a battery based on a gas-liquid-thermal coupling model in step 1 is characterized by:

[0092] C rest =C all ×SOC 2 (Formula 1)

[0093] C abch =C all ×(1-SOC 2 ) (Formula 2)

[0094]

[0095] In the formula, C rest is the remaining capacity, C abch is the chargeable capacity, C all is the actual capacity, "d" is added before the letter to indicate the differential of the parameter, t is the time, and " k " represents the state of the parameter at the kth moment, k = 0, 1, 2, 3..., SOC is the state of charge, and I is the current.

[0096] In the step 1, a battery remaining capacity estimation method based on a gas-liquid-thermal coupling model is used. Formula 1, Formula 2, and Formula 3 all require estimation of the battery state of charge. Specifically, a double extended Kalman filter algorithm is used to online identify the parameters of the gas-liquid-thermal coupling model and online estimate the battery state of charge.

[0097] The dual extended Kalman filter algorithm online identifies the parameters of the gas-liquid-thermal coupling model and online estimates the state of charge of the battery, specifically:

[0098]

[0099] According to the state equation of the gas-liquid thermal coupling model, Formula 4 is specifically:

[0100]

[0101] According to the state equation of the gas-liquid thermal coupling model, Formula 5 is specifically:

[0102]

[0103] Where θ is the state variable for online identification of gas-liquid thermal coupling model parameters. The four parameters to be identified in the gas-liquid thermal coupling model are k 1 , k 2 , k 3 , k 4 , d is the observed quantity of the online identification of the gas-liquid thermal coupling model parameters, h is the function of the model parameter observation quantity, λ is the input quantity of the model parameter observation quantity function, I is the current and charging is positive and discharging is negative, T k is the battery temperature, U OCI is the battery open circuit voltage, x is the state quantity of the battery SOC estimated online, f is the function of the battery SOC state quantity, u is the input quantity of the battery SOC state quantity function, y is the observation quantity of the battery SOC estimated online, g is the function of the battery SOC observation quantity, and μ is the input quantity of the battery SOC observation quantity function;

[0104] ① Initialization:

[0105]

[0106] Where P θ is the covariance matrix of θ, Q θ is the system noise variance of the online identification of gas-liquid thermal coupling model parameters, R θ is the measurement noise variance of the gas-liquid thermal coupling model parameters for online identification, P x is the covariance matrix of x, Q x is the system noise variance of online estimation of battery SOC, R x To estimate the measurement noise variance of the battery SOC online, the initialization step can assign the parameters to initial values ​​greater than zero, such as all values ​​are assigned to 0.002;

[0107] ②Update the time value of the parameter observer:

[0108]

[0109] In the formula, the superscript letter plus "-" represents the prior state of the parameter, the superscript letter plus "+" represents the posterior state of the parameter, the superscript letter plus "T" represents the transpose of the matrix, and A is the coefficient matrix of the model parameter state quantity;

[0110] ③Update the time value of the state observer:

[0111]

[0112] Where, B is the coefficient matrix of the battery SOC state;

[0113] ④Update the measurement value of the state observer:

[0114]

[0115] In the formula, K x is the Kalman gain of x, D is the coefficient matrix of the battery SOC observation, and E is the unit matrix of the same order as the operation matrix;

[0116] ⑤Update the measured value of the parameter observer:

[0117]

[0118] In the formula, K θ is the Kalman gain of θ, C is the coefficient matrix of the model parameter observations;

[0119] ⑥ Update k:

[0120] k=k+1(Formula 17)

[0121] ⑦ Repeat steps ② to ⑥ to achieve online identification of parameters of the gas-liquid thermal coupling model and online estimation of the battery state of charge;

[0122] In the above scheme, the step 2 calculates the coefficient of variation Φ of the remaining capacity of the series battery pack rest and the coefficient of variation of the chargeable capacity Φ abch , characterized in that:

[0123]

[0124] In the formula, s rest is the standard deviation of the remaining capacity of the series battery pack, is the average value of the remaining capacity of the series battery pack, s abch is the standard deviation of the chargeable capacity of the series battery pack, is the average value of the rechargeable capacity of the series battery group, N is the total remaining capacity of the series battery group (N≥2), i is the serial number of the series battery (i≤N), i=1,2,3…; according to Fig. 9 The remaining capacity of batteries A to E and formula 18 can be used to calculate the coefficient of variation Φ of the remaining capacity of the series battery pack. rest =0.268, according to Fig. 9 The rechargeable capacity of batteries A to E and formula 21 can be used to calculate the coefficient of variation Φ of the rechargeable capacity of the series battery pack. abch =0.247;

[0125] In the above scheme, the variation coefficient discrimination strategy in step 3 is characterized by:

[0126]

[0127] In the formula, Φ new is the coefficient of variation of the actual capacity of the new series battery pack; Fig. 9 The actual capacity of the new battery A~E and formula 18 can be used to calculate the coefficient of variation Φ of the actual capacity of the new series battery pack new =0.040. According to formula 24, 0.268>0.040, 0.247>0.040 needs to go to step 4 to perform balancing;

[0128] In the above scheme, the fourth step is a battery equalization method based on a gas-liquid-thermal coupling model, characterized in that:

[0129] Determine whether the battery is in a discharge standby state or a charge standby state;

[0130] When the battery is in a discharge standby state, the batteries in the series battery pack are sorted from low to high according to the remaining capacity, and then the remaining capacity of all batteries is subtracted from the remaining capacity of the lowest battery to obtain the remaining capacity difference ΔC of each battery. rest , and then calculate the average value of the remaining capacity difference

[0131]

[0132] Calculate the discharge balance capacity of each battery

[0133]

[0134] According to formula 26, the discharge equalization capacities of batteries A to E are 0.114Ah, -0.306Ah, -0.106Ah, 0.304Ah, and -0.006Ah respectively;

[0135] Discharge the battery to a positive value to balance the capacity (i.e. ) are transferred to the transfer capacitor in descending order, that is, Figure 4 The charge and discharge balance control selection switch in the transfer capacitor transfers 0.304Ah of battery D and 0.114Ah of battery A to the transfer capacitor. The larger the value of the positive discharge balance capacity is, the higher the priority of the transfer. When the transfer capacitor is fully charged or the positive discharge balance capacity is fully transferred to the transfer capacitor, the power in the transfer capacitor is transferred to the negative discharge balance capacity (i.e. ) in the battery, the amount of electricity transferred is equal to the absolute value of the negative discharge balancing capacity. If the amount of electricity in the transfer capacitor is lower than the absolute value of the negative discharge balancing capacity of the transferred battery, all of it will be transferred. The larger the absolute value of the negative discharge balancing capacity is, the higher the priority of the transfer is. Figure 4The charge and discharge balance control switch in the transfer capacitor transfers the capacity to battery B, battery C and battery E respectively. The transfer capacity of the three batteries is 0.306Ah, 0.106Ah and 0.006Ah respectively. Figure 5 As shown, the series battery group has the same residual capacity. Theoretically, the capacity of the series battery group after discharge equalization increases from 1.65Ah before equalization to 1.965Ah, and the residual capacity of the series battery group increases by 19.1%. The more significant the inconsistency of the series battery group, the more obvious the residual capacity improvement effect will be.

[0136] According to the positive discharge balance capacity transfer-out and negative discharge balance capacity transfer-in rules of the battery, until the discharge balance capacity transfer of all batteries is completed, it can be known from the conversion formula that one ampere-hour capacity is equal to 3,600 coulombs of electricity that the batteries in the series battery group have equal remaining power, such as Figure 6 As shown, based on the principle that the current of batteries in series is the same, the battery pack in series can achieve full discharge;

[0137] When the battery is in a charging standby state, the batteries in the series battery pack are sorted from low to high according to the rechargeable capacity, and then the rechargeable capacity of the lowest battery is subtracted from the rechargeable capacity of all batteries to obtain the rechargeable capacity difference ΔC of each battery. abch , and then calculate the average value of the difference in rechargeable capacity

[0138]

[0139] Calculate the charge equalization capacity of each battery

[0140]

[0141] According to formula 28, the charge equalization capacities of batteries A to E are -0.060Ah, 0.170Ah, 0.300Ah, -0.210Ah, and -0.200Ah respectively;

[0142] Negative charge equalization capacity (i.e. ) of the battery, it is necessary to transfer the power of the negative charge equalization capacity absolute value (i.e. ) to the transfer capacitor, i.e. Figure 4 The charge and discharge balance control selection switch in the transfer capacitor transfers 0.210Ah of battery D, 0.200Ah of battery E and 0.060Ah of battery A to the transfer capacitor. The larger the absolute value of the negative charge balance capacity is, the higher the priority of the transfer. When the transfer capacitor is fully charged or the absolute value of the negative charge balance capacity is fully transferred to the transfer capacitor, the power in the transfer capacitor is transferred to the positive charge balance capacity (i.e. ) in the battery, the amount of electricity transferred is equal to the positive balancing capacity of the corresponding battery. If the amount of electricity in the transfer capacitor is lower than the positive charging balancing capacity of the transferred battery, all of it will be transferred. The larger the value of the positive charging balancing capacity is, the higher the priority of the transfer is. Figure 4 The charge and discharge balance control switch in the transfer capacitor transfers the capacity to battery C and battery B respectively. The transfer capacity of the two batteries is 0.300Ah and 0.170Ah respectively. Figure 7 As shown, the series battery group has the same rechargeable capacity. Theoretically, after charge equalization, the capacity of the series battery group increases from 1.04Ah before equalization to 1.25Ah, and the rechargeable capacity of the series battery group increases by 20.2%. The more significant the inconsistency of the series battery group, the more obvious the effect of improving the rechargeable capacity will be.

[0143] According to the negative value charge equalization capacity transfer out and positive value charge equalization capacity transfer in rules of the battery, until the charge equalization capacity transfer of all batteries is completed, it can be known from the conversion formula that one ampere-hour capacity is equal to 3,600 coulombs of electricity that the batteries in the series battery group have equal chargeable capacity, such as Figure 8 As shown, based on the principle that the current of batteries in series is the same, the battery pack in series can be fully charged;

[0144] Calculate the coefficient of variation of the series battery group after equalization again and go to step 3. This case achieves one-time equalization. In real equalization, the actual number of equalization times is determined according to the inconsistency of the series battery group.

[0145] In the above scheme, the battery equalization system based on the gas-liquid-thermal coupling model in step 5 is characterized by: comprising a data acquisition module, a battery capacity estimation module, a variation coefficient calculation module, a variation coefficient judgment module, a battery equalization module, a circuit protection module, a display module, and a buzzer; the data acquisition module collects the terminal voltage, current and temperature of each battery in series of the series battery group, and sends them to the battery capacity estimation module; the battery capacity estimation module estimates the remaining capacity and rechargeable capacity of the battery according to the method of step 1, and sends them to the variation coefficient calculation module; the variation coefficient calculation module calculates the variation coefficient of the remaining capacity and the variation coefficient of the rechargeable capacity of the series battery group according to the method of step 2, and sends them to the variation coefficient judgment module; the variation coefficient judgment module completes the variation coefficient judgment operation according to the method of step 3; if the series battery group needs to be balanced, the battery equalization module completes the equalization operation of the series battery group according to step 4; the circuit protection module always monitors the parameter safety of the battery equalization system, and if the battery is over-voltage, over-current, over-temperature, and the variation coefficient of the series battery group increases after equalization, the equalization operation of the series battery group is stopped and the fault reminder is pushed to the display module and the buzzer is started.

[0146] In the above scheme, in the above scheme, the method for estimating the remaining capacity and rechargeable capacity of the battery based on the gas-liquid-thermal coupling model in step 1, in addition to the double extended Kalman filter algorithm, also includes genetic algorithm, particle filter algorithm, simulated annealing algorithm, observer, neural network algorithm, other artificial intelligence algorithms, other Kalman filter algorithms, etc.

Claims

1. A battery equalization method based on a gas-liquid thermal coupling model is proposed, characterized in that: The following steps are involved: Step 1: A method for estimating the remaining capacity and rechargeable capacity of a battery based on a gas-liquid-thermal coupling model; Step 2: Calculate the coefficient of variation of the remaining capacity and the coefficient of variation of the rechargeable capacity of the series battery pack; Step 3: Coefficient of variation determination strategy; Step 4: Battery equalization method based on gas-liquid thermal coupling model; Step 5: Battery and other power balancing system based on gas-liquid-thermal coupling model; The step 1 is a method for estimating the remaining capacity and rechargeable capacity of a battery based on a gas-liquid-thermal coupling model: C rest =C all ×SOC2 (Formula 1) C abch =C all ×(1-SOC2) (Formula 2) In the formula, C rest is the remaining capacity, C abch is the chargeable capacity, C all is the actual capacity, dt is the differential with respect to time t, the parameter with subscript k represents the state of the parameter at time k, where k = 0, 1, 2, 3..., SOC is the state of charge, and I is the current; The second step is to calculate the coefficient of variation Φ of the remaining capacity of the series battery pack. rest and the coefficient of variation of the chargeable capacity Φ abch , specifically: In the formula, s rest is the standard deviation of the remaining capacity of the series battery pack, is the average value of the remaining capacity of the series battery pack, s abch is the standard deviation of the chargeable capacity of the series battery pack, is the average value of the rechargeable capacity of the series-connected battery pack, N is the total remaining capacity of the series-connected battery pack (N≥2), i is the serial number of the series-connected battery (i≤N), i=1,2,3…; The variation coefficient determination strategy of step 3 is specifically as follows: In the formula, Φ new is the coefficient of variation of the actual capacity of the new series battery pack; The fourth step is a battery equalization method based on a gas-liquid-thermal coupling model, specifically: ① Determine whether the battery is in a discharge standby state or a charge standby state; ② When the battery is in the discharge standby state, sort the batteries in the series battery pack from low to high according to the remaining capacity, and then subtract the remaining capacity of the lowest battery from the remaining capacity of all batteries to obtain the remaining capacity difference ΔC of each battery rest , and then calculate the average value of the remaining capacity difference ③Calculate the discharge balance capacity of each battery ④Discharge the battery to a positive value to balance the capacity (i.e. ) are transferred to the transfer capacitor in descending order. The larger the positive discharge balancing capacity is, the higher the priority of the transfer. When the transfer capacitor is fully charged or the positive discharge balancing capacity is fully transferred to the transfer capacitor, the electricity in the transfer capacitor is transferred to the negative discharge balancing capacity (i.e. ) in the battery, the amount of electricity transferred in is equal to the absolute value of the negative discharge balancing capacity. If the amount of electricity in the transfer capacitor is lower than the absolute value of the negative discharge balancing capacity of the transferred battery, all of it will be transferred in. The larger the absolute value of the negative discharge balancing capacity is, the higher the priority of the transfer. ⑤ According to the positive discharge balance capacity transfer-out and negative discharge balance capacity transfer-in rules of the battery, until the discharge balance capacity transfer of all batteries is completed, it can be known from the conversion formula that one ampere-hour capacity is equal to 3,600 coulombs of electricity that the batteries in the series battery pack have equal remaining power; ⑥ When the battery is in the charging standby state, sort the batteries in the series battery pack from low to high according to the rechargeable capacity, and then subtract the rechargeable capacity of the lowest battery from the rechargeable capacity of all batteries to obtain the rechargeable capacity difference ΔC of each battery abch , and then calculate the average value of the difference in rechargeable capacity ⑦Calculate the charge balance capacity of each battery ⑧ Negative charge equalization capacity (i.e. ) of the battery, it is necessary to transfer the power of the negative charge equalization capacity absolute value (i.e. ) to the transfer capacitor. The larger the absolute value of the negative charge equalization capacity is, the higher the priority of the transfer. When the transfer capacitor is fully charged or the absolute value of the negative charge equalization capacity is fully transferred to the transfer capacitor, the power in the transfer capacitor is transferred to the positive charge equalization capacity (i.e. ) in the battery, the amount of electricity transferred in is equal to the positive balancing capacity of the corresponding battery. If the amount of electricity in the transfer capacitor is lower than the positive charging balancing capacity of the transferred battery, all of it is transferred in. The larger the value of the positive charging balancing capacity is, the higher the priority of the transfer is. ⑨ Follow the negative value charge equalization capacity transfer out and positive value charge equalization capacity transfer in rules of the battery until the charge equalization capacity transfer of all batteries is completed. From the conversion formula that one ampere-hour capacity is equal to 3,600 coulombs of electricity, it can be seen that the batteries in the series battery group have equal chargeable capacity; ⑩ Calculate the coefficient of variation of the balanced series battery pack again and go to step 3.

2. According to the method for equalizing the amount of electricity of a battery based on a gas-liquid-thermal coupling model according to claim 1, the method for estimating the remaining capacity and rechargeable capacity of a battery based on a gas-liquid-thermal coupling model in step 1, formula 1, formula 2, and formula 3 all require estimating the state of charge of the battery, and specifically adopt a double extended Kalman filter algorithm to online identify the parameters of the gas-liquid-thermal coupling model and online estimate the state of charge of the battery, specifically: In the formula, the parameter with subscript k represents the state of the parameter at time k, where k = 0, 1, 2, 3...; According to the state equation of the gas-liquid thermal coupling model, formula 4 is specifically: According to the state equation of the gas-liquid thermal coupling model, Formula 5 is specifically: Where θ is the state quantity of the online identification of the gas-liquid thermal coupling model parameters, the four parameters to be identified of the gas-liquid thermal coupling model are k1, k2, k3, and k4, d is the observation quantity of the online identification of the gas-liquid thermal coupling model parameters, h is the function of the model parameter observation quantity, λ is the input quantity of the model parameter observation quantity function, I is the current and charging is positive and discharging is negative, T k is the battery temperature, U OCI is the battery open circuit voltage, x is the state quantity of the online estimation of the battery SOC, f is the function of the battery SOC state quantity, u is the input quantity of the battery SOC state quantity function, y is the observation quantity of the online estimation of the battery SOC, g is the function of the battery SOC observation quantity, μ is the input quantity of the battery SOC observation quantity function, and U OCP (x k ) represents the open circuit voltage at the previous moment, corresponding to U OCI_k-1 ; ① Initialization: Where P θ is the covariance matrix of θ, Q θ is the system noise variance of the online identification of gas-liquid thermal coupling model parameters, R θ is the measurement noise variance of the gas-liquid thermal coupling model parameters for online identification, P x is the covariance matrix of x, Q x is the system noise variance of online estimation of battery SOC, R x is the measurement noise variance for online estimation of battery SOC; ②Update the time value of the parameter observer: In the formula, the parameter with a superscript of - represents the prior state of the parameter, the parameter with a subscript of + represents the posterior state of the parameter, the matrix with a superscript of T represents the transpose of the matrix, and A is the coefficient matrix of the model parameter state quantity; ③Update the time value of the state observer: Where, B is the coefficient matrix of the battery SOC state; ④Update the measured value of the state observer: In the formula, K x is the Kalman gain of x, D is the coefficient matrix of the battery SOC observation, and E is the unit matrix of the same order as the operation matrix; ⑤Update the measured value of the parameter observer: In the formula, K θ is the Kalman gain of θ, C is the coefficient matrix of the model parameter observations; ⑥ Update k: k=k+1(Formula 17) ⑦ Repeat steps ② to ⑥ to achieve online identification of parameters of the gas-liquid thermal coupling model and online estimation of the battery's state of charge.

3. A system for implementing the battery equalization method based on the gas-liquid thermal coupling model as described in any one of claims 1-2, characterized in that: It includes a data acquisition module, a battery capacity estimation module, a variation coefficient calculation module, a variation coefficient determination module, a battery and other power balancing module, a circuit protection module, a display module, and a buzzer.

4. According to claim 3, a system for realizing a battery or other electricity equalization method based on a gas-liquid-thermal coupling model, said step 5 is a battery or other electricity equalization system based on a gas-liquid-thermal coupling model, characterized in that: ① The data acquisition module collects the terminal voltage, current and temperature of each battery in series and sends them to the battery capacity estimation module; ② The battery capacity estimation module estimates the remaining battery capacity and rechargeable capacity according to the method in step 1, and sends them to the coefficient of variation calculation module; ③ The coefficient of variation calculation module calculates the coefficient of variation of the remaining capacity of the series battery pack and the coefficient of variation of the rechargeable capacity according to the method in step 2, and sends them to the coefficient of variation determination module; ④ The coefficient of variation determination module completes the determination operation of the coefficient of variation according to the method in step 3; If the series battery group needs to be balanced, the battery equalization module completes the equalization operation of the series battery group according to step 4; ⑤ The circuit protection module always monitors the parameter safety of the battery and other power balancing systems. If the battery is over-voltage, over-current, over-temperature, and the coefficient of variation of the series battery group increases after power balancing, the series battery group balancing operation is stopped and the fault reminder is pushed to the display module and the buzzer is started.

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