A battery health difference-based power balance control method

Abstract

The application discloses a kind of based on battery health difference electric quantity balance control method, comprising the following steps: step 1: obtaining the online running data information of each battery monomer;Step 2: the SOH value of battery is calculated using battery state estimation algorithm, and the SOC value of battery is updated in combination with the change of battery health degree;Step 3: according to the SOC difference value of each battery monomer, in combination with each battery health degree, switch MOSFET conduction degree is controlled respectively, and battery pack electric quantity balance control is realized.The application can accurately detect the SOH value of aging battery according to battery state estimation algorithm, and update to obtain SOC value, can also adjust balance control strategy according to battery monomer health state, accurately control battery monomer charge-discharge rate using more reasonable weight factor, realize battery pack electric quantity balance, overall improve the life of battery system.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of battery detection and control, and more particularly relates to a power balance control method based on battery health difference. BACKGROUND

[0002] A battery system is usually composed of multiple battery groups in parallel, and each battery group usually has multiple battery monomers in series. During operation, due to the state difference of each battery monomer, it may have a certain impact on the use of the battery system. Therefore, in order to ensure the normal operation of the battery system, it needs to be controlled. The key to current control is to accurately obtain the remaining power of each battery. The state of charge (SOC) is often used in the prior art to reflect the remaining power of the battery. Its value is defined as the ratio of the remaining power of the battery to the total capacity of the battery, usually expressed in percentage. Its value range is 0-1, when SOC=0, it means that the battery monomer is completely discharged, and when SOC=1, it means that the battery monomer is completely charged. The battery system balancing control is to estimate the SOC of the battery monomer, and at the same time, taking the SOC value of the battery monomer as the control object, designing the weight factor, achieving the purpose of dynamically adjusting the charging and discharging rate of the battery monomer, realizing the power balance of the whole battery system, and ensuring the safe and stable operation of the battery system.

[0003] The SOC estimation and balancing control module of the commonly used battery system generally assumes that each battery and module in the battery system has the same battery capacity, that is, the state of health (SOH) of the battery is the same in the technical field. However, in actual operation, due to the influence of heat, current and mechanical error of equipment inside the battery system and other factors, the battery monomer will appear different degrees of aging phenomenon. These aging phenomena will change the health status of the battery inside the battery system, causing the remaining available capacity of the battery to gradually decrease. If the SOC balancing controller continues to run under the assumption that the battery capacity is the same, the battery with lower health degree (actual capacity value is smaller) will have a higher SOC value than other batteries, and will be exhausted earlier than other batteries. In this case, the battery system may be over-discharged, resulting in system failure or even fire accident.

[0004] The purpose of the present application is to provide a power balance control method based on battery health difference, so as to more accurately detect the SOH and SOC value of the aging battery, adjust the control strategy according to the health state of the battery monomer, and accurately control the charging and discharging rate of the battery monomer with a more reasonable weight factor, realize the power balance of the battery group, and improve the life of the whole battery system. SUMMARY

[0005] (1) Technical problems to be solved

[0006] Based on the defects mentioned in the background art, the application discloses a battery health difference-based power balance control method, so that the SOH and SOC values of the aging battery can be more accurately detected, the control strategy is adjusted according to the battery monomer health state, the battery monomer charging and discharging rate is accurately controlled by using a more reasonable weight factor, the power balance of the battery pack is realized, and the life of the battery system as a whole is improved.

[0007] (II) Technical solutions

[0008] The application discloses a battery health difference-based power balance control method, comprising the following steps:

[0009] Step 1: Obtain online running data information of each battery monomer;

[0010] Step 2: Calculate the SOH value of the battery by using a battery state estimation algorithm, and update the SOC value of the battery in combination with the change of the battery health degree;

[0011] The battery state estimation algorithm comprises:

[0012] Step 2.1: The collected data are screened and analyzed, the discharge interval is extracted from the continuous signals of repeated charging and discharging intervals, two similar discharge sections are analyzed, the range with similar initial SOC and final SOC is found, the current I cell is integrated to obtain a current cumulative value ISUM:

[0013]

[0014] Step 2.2: The current mutation characteristics appearing in the battery use process are used, the results of voltage step or discontinuity change become the key indicators for battery internal resistance estimation, the voltage and current change values at the discontinuous time are captured, and the battery internal resistance estimation value R = R(k) can be obtained, that is,

[0015]

[0016] In the formula, k represents the current mutation time, δ represents a sampling delay time, I cell is the current of the battery monomer, V cell is the terminal voltage of the battery monomer; based on the estimated battery internal resistance R, the internal voltage V cell of the battery can be estimated based on the measured terminal voltage V T , and the specific expression is:

[0017] V T = V cell +I cell R (6)

[0018] Step 2.3: Based on the collected battery terminal voltage data and the calculated internal resistance value R, the open circuit voltage V OC value can be derived, and based on the measured input data V cell and I cell , the initial estimate of polarization parameter and the initial polarization voltage V p can be obtained. Throughout the calculation process, it is assumed that the polarization voltage V p does not change, and based on the battery system measured terminal voltage V T modified by the polarization voltage V p estimated by the parameter, the OCV data can be calculated, and based on the corresponding current I cell and its current cumulative value ISUM and open circuit voltage value V OC , the estimated ISUM-OCV curve of the continuous discharge interval can be plotted.

[0019] V OC = V cell + I cell R + V p = V T + V p (7)

[0020] Step 2.4: Based on the constructed ISUM-OCV curve and the reference SOC-OCV curve difference comparison, the estimation of the remaining available capacity of the battery and the calculation of the battery state can be carried out. Using the SOC-OCV curve of the new battery as the reference curve, the ISUM-OCV curve of the aged battery is normalized based on the correct battery remaining available capacity Q avail value, and coincides with the reference SOC-OCV curve. Based on formula (1), the specific conversion process of the capacity is shown in formula (8). With the aging of the battery, the ISUM-OCV curve of the battery is continuously adjusted based on the estimated value of the battery remaining available capacity Q avail to find the correct Q avail value, so that the current SOC-OCV curve matches the reference curve.

[0021]

[0022] where SOC t and SOC0 are the battery state of charge and the initial state of charge value at the current time t, respectively. Based on the Q avail value obtained by differentiating the ISUM-OCV curve from the SOC-OCV curve, the SOH value of the battery is calculated, and the SOC value of the battery is updated.

[0023] Step 3: Based on the SOC difference value of each battery monomer and the health degree of each battery, the conduction degree of the MOSFET switch is controlled respectively to realize the battery pack power balance control.

[0024] Preferably, the step 2.2 further comprises: selecting δ=(1 / 10)τ, the overall internal resistance sampling delay time should satisfy the following condition:

[0025] τ=R p C p ≥n(t[k+δ]-t[k]) (4)

[0026] |I cell [k+δ]-I cell [k]|≥ε (5)

[0027] wherein, R p represents the polarization internal resistance of the battery, C p represents the polarization capacitance of the battery; t[k+δ] and t[k] both represent the data corresponding time obtained by extending the sampling process interval of the battery by δ; n(x) is a multiple relationship function of x, and ε is a preset threshold value.

[0028] If the discontinuity does not satisfy the formula (4) and (5), it is determined that the battery internal resistance R=R(k) estimated by the formula (2) is inaccurate.

[0029] Preferably, the preset threshold value ε is 0.3A, and the multiple relationship function n(x)=10*x.

[0030] Preferably, the step 2.4 further comprises: calculating SOH according to the formula (9), and accurately updating the SOC value of the battery according to the formula (10).

[0031]

[0032] wherein, Q avail is an estimated battery remaining capacity value, Q nom is the rated capacity of the battery monomer, and ∑I cell Δt represents the cumulative value of the collected current data within the time Δt, which is used to calculate the cumulative consumed electric quantity of the battery.

[0033] Preferably, the step 3 further comprises: obtaining the SOC ref of the entire series battery pack by using the mean value method according to the formula (11), wherein n represents the number of series battery monomers in the battery pack.

[0034]

[0035] With the SOC ref of the battery pack, the SOC of each battery monomer in the battery pack can be calculated.The difference value, and each battery monomer can adjust the power consumption speed according to the difference value, the SOC control loop output is the battery reference current difference value, and the difference comparison control of the actual battery current can obtain the appropriate switch conduction duty cycle to control the current balance of the whole battery pack, and the result output by the proportional integral control is:

[0036] Delta I refi =(SOC ref -SOC celli )X G SOC (z) (12)

[0037]

[0038] D i =(I load -I celli - Delta I refi )X G cur (z) (14)

[0039] In the formula, G SOC (z) is a digital SOC balance PI controller, K P-SOC and K I-SOC are parameters of the controller, and the parameters are set in a reasonable range to ensure that the control loop responds quickly and accurately; Delta I refi is an output end of the SOC loop control of the controller; D i is an output end of the current loop control of the controller, to control the conduction of the corresponding switch MOSFET; G cur (z) is also a digital current balance PI controller, and the parameters of the PI controller need to be continuously adjusted in the process of realizing the SOC balance control of the battery system, so that the controller output result D i is stabilized in a reasonable range.

[0040] In addition, the application also discloses a power balance control system based on battery health difference, comprising:

[0041] At least one processor; and at least one memory connected with the processor in communication, wherein:

[0042] The memory stores program instructions executable by the processor, and the processor calling the program instructions can execute the power balance control method based on the battery health difference according to any one of the above.

[0043] (Three) beneficial effects

[0044] (1) the method of the present application can realize online estimation of battery internal resistance and battery remaining available capacity by using part of battery operation data, monitor battery health state change, and be closer to actual use of the battery system; after adding the influence factor of actual available capacity of the battery in the method for controlling SOC balance of the battery system, the traditional SOC balance control strategy is updated, the energy of the battery system can be more reasonably and fully utilized, and the service life of the battery system is prolonged; the determination of the battery health state value (SOH) is obtained by differential comparison of the ISUM-OCV curve and the reference SOC-OCV curve, which can accurately detect the SOH and SOC values of the aging battery, but it depends too much on the accuracy of the equivalent circuit model of the battery, and its application range is wider.

[0045] (2) the corresponding power balance control method after the battery health difference recognition is added in the method of the present application, the power balance purpose of the battery system can still be realized. At the same time, after balancing, the discharge rate of the battery monomer is different, the discharge current of the battery monomer with high health degree is larger, and the discharge current of the battery with low health degree is the minimum value, through the differential use of the battery, the energy utilization efficiency of the whole battery system can be improved, a more safe battery system is obtained, and the service life of the battery system is improved. BRIEF DESCRIPTION OF DRAWINGS

[0046] In order to more clearly illustrate the technical solutions in the present application or prior art, the drawings needed by the embodiments will be briefly introduced as follows:

[0047] Figure 1 the overall structure diagram of the power balance control system of the present application;

[0048] Figure 2 the flow chart of the battery SOC balance control method of the present application;

[0049] Figure 3 the internal structure block diagram of the SOC balance control of the present application;

[0050] Figure 4 the control system structure diagram of the present application;

[0051] Figure 5 the battery internal resistance estimation value and internal voltage value diagram obtained according to the battery operation data in the embodiment of the present application, the data obtained by the algorithm is 8 times, wherein figure (a) is the battery internal resistance estimation result diagram, and figure (b) is the internal voltage change diagram obtained according to the battery internal resistance;

[0052] Figure 6 the SOH algorithm result diagram in the embodiment of the present application, wherein figure (a) is the ISUM-OCV curve of the two listed batteries and the reference health battery, and figure (b) is the SOC-OCV curve of the two listed batteries and the reference health battery.

[0053] Figure 7 Figure 1 is a diagram of the battery balancing control result after considering the identification of battery health differences in an embodiment of the present invention, where Figure (a) is the battery system SOC change curve, and Figure (b) is the controller output current curve. DETAILED DESCRIPTION

[0054] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0055] Figure 1 The figure shows the overall structure of the power balance control system of the present invention. The battery pack in the system includes multiple battery modules, each of which includes a battery cell BT i And a DC / DC converter, i takes a value of 1 to n, n is the total number of battery cells, wherein the positive and negative electrodes of the n battery cells of the battery system are connected in series in sequence, and one end of each DC / DC converter is connected to the battery cell BT. i The positive and negative poles are connected, and the other end is connected in parallel with the other n-1 DC / DC converter ends to realize the load connection. The input end of each DC / DC converter is also equipped with a MOSFET controllable switch S1~S n The gate controls the on and off of the switch through the drive circuit to achieve accurate control of the power consumption of the entire battery cell. The battery system with SOC balancing controller is configured with battery side output and converter side output. At the same time, multiple isolated low-power DC / DC converters are used in the battery system architecture to achieve one DC / DC converter controlling one battery cell BT. i The present invention monitors battery voltage and current information through an SOC balance control strategy, and generates a digital PWM control signal to control the isolation converter, thereby accurately regulating the battery SOC balance process.

[0056] In order to accurately detect Figure 1 The SOH and SOC values ​​of the battery cells are adjusted and the effect of balancing control is improved to achieve the purpose of improving the overall energy utilization efficiency and service life of the battery system. The present invention designs a power balancing control method based on battery health differences. The method is a power balancing control method with battery health difference identification in the battery system, including the following main steps:

[0057] Step 1: Obtain online operating data information of each battery cell;

[0058] Step 2: Calculate the SOH value of the battery using the battery state estimation algorithm, and update the SOC value of the battery combined with the change of the battery health degree;

[0059] Step 3: According to the SOC difference value of each battery monomer, combined with the health degree of each battery, control the conduction degree of the switch MOSFET respectively, realize the battery pack power balance control.

[0060] The following will be a detailed description of steps 1-3:

[0061] In another embodiment, in step 1, the collection of battery system operation data is realized by the ADC sampling module of f28335 micro control unit (MCU), mainly collecting the voltage data and current data of the battery during operation, which can be used for online state estimation of the battery.

[0062] In another embodiment, in step 2, the battery state estimation based on the battery operation data is mainly based on the first-order RC equivalent circuit model of the battery (i.e. an ohmic internal resistance and a polarization RC parallel circuit in series), from the collected current and voltage data to determine the data analysis interval, extract the effective internal resistance and open circuit voltage (OCV) data, through the change difference value of OCV and the relationship between SOC and rated capacity to get the remaining available capacity of the battery, finally estimate the state value of the battery according to the actual remaining available capacity, including SOC and SOH.

[0063] Specifically, the battery state estimation algorithm in step 2 includes the following four steps:

[0064] Step 2.1: The collected data is screened and analyzed, and the discharge interval is extracted from the continuous signal of repeated charging and discharging interval. The voltage signal is the terminal voltage of the battery. Through the analysis of local charging and discharging data, the internal voltage change of the battery can be simulated as a whole, so that it changes within a limited range in each cycle. At the same time, in order to ensure the accuracy of the internal state estimation of the battery, the proposed method analyzes two similar discharge sections to find the range with similar initial SOC and final SOC. Specifically, the collected current I cell is integrated to get the current cumulative value, denoted as ISUM, and the ISUM value of the same stage is selected to analyze the current of the corresponding section, which ensures the uniformity of the overall control variable. The formula of the current cumulative value is:

[0065]

[0066] Step 2.2: Using the current mutation characteristics that occur during battery use, the result of voltage step or discontinuous change becomes the key indicator for battery internal resistance estimation. Since the battery open circuit voltage OCV and polarization voltage are continuous functions, any terminal voltage discontinuity is directly caused by the ohmic internal resistance. By capturing the voltage and current change values ​​at the discontinuous moment, the battery internal resistance estimate can be obtained, that is,

[0067]

[0068] Where, k represents the moment of current mutation, δ represents the sampling delay time, I cell is the current of the battery cell, V cell is the terminal voltage of the battery cell.

[0069] The current distribution has many jumps. Choosing as many data points as possible for battery internal resistance estimation can counteract some erroneous estimation results caused by noise and measurement errors. At the same time, selecting a sampling delay time δ can avoid oscillation errors caused by parasitic components and sensors in the power circuit. However, doing so will cause another problem. Since the current jump will cause transient changes in the RC circuit, the polarization voltage V p In short, there are two transients that need to be handled overall: one is a high-frequency transient (due to unmodeled parasitic elements and sensor response), and the other is a low-frequency transient (due to the time constant τ = R in the RC circuit). p C p , R p and C p The overall internal resistance calculation process should be done after the high-frequency transient and before the low-frequency transient takes effect. Therefore, δ = (1 / 10)τ is selected to ensure that the high-frequency transient has passed during sampling. In addition, the current I cell [k] is considered as a step change, I cell The step change should be greater than the preset threshold ε. This algorithm uses a calculation benchmark of 0.3A. In summary, the overall internal resistance sampling delay time should meet the following conditions:

[0070] T=R p C p ≥n(t[k+δ]-t[k]) (4)

[0071] |I ceu [k+δ]-I cell [k]|≥ε (5)

[0072] Where R p Refers to the polarization internal resistance of the battery, C pRefers to the polarization capacitance of the battery; t[k+δ] and t[k] both represent the corresponding moments of the data obtained by extending the battery sampling interval by δ; n refers to the multiple relationship function corresponding to the two time constants, that is, n(x) = k*x. In this example, the multiple coefficient k = 10 is used.

[0073] If the discontinuity does not satisfy equations (4) and (5), the battery internal resistance R = R(k) estimated by equation (2) is inaccurate. Based on the estimated battery internal resistance R, the terminal voltage V can be measured. cell Estimate the battery internal voltage V T , the specific expression is:

[0074] V T =V cell +I cell R (6)

[0075] Step 2.3: Combining the collected battery terminal voltage data with the calculated internal resistance value R, the open circuit voltage V can be derived. OC The specific formula is shown in formula (7). According to the measured input data V cell and I cell , we can get the initial estimated value of polarization parameters and the initial polarization voltage V p The entire calculation process assumes that the polarization voltage V p There is no change, because the slight change of polarization parameters in each cycle will not significantly affect the final estimation result of the battery. Therefore, according to formula (7), the battery internal voltage V is modified by the terminal voltage measured by the battery system. T , combined with the polarization voltage V obtained by parameter estimation p , OCV data can be calculated according to the corresponding current I cell Its current accumulated value ISUM and open circuit voltage value V OC , the estimated ISUM-OCV curve of continuous discharge intervals can be drawn.

[0076] V OC =V cell +I cell R+V p =V T +V p (7)

[0077] Step 2.4: The remaining available capacity of the battery can be estimated and the battery state can be calculated by comparing the difference between the constructed ISUM-OCV curve and the reference SOC-OCV curve. Specifically, the SOC-OCV curve of a new battery (assuming SOH = 100%) is used as the reference curve, and the ISUM-OCV curve after battery aging is calculated based on the correct remaining available capacity Q of the battery. availThe value of Q is obtained by normalizing the ISUM-OCV curve to match the reference SOC-OCV curve. In combination with equation (1), the conversion process of the capacity is shown in equation (8). The reason is that the SOC-OCV curve of the battery does not change significantly with the change of the battery health. With the aging of the battery, the ISUM-OCV curve of the battery is estimated according to the remaining available capacity of the battery Q avail The value of Q is obtained by normalizing the ISUM-OCV curve to match the reference SOC-OCV curve. In combination with equation (1), the conversion process of the capacity is shown in equation (8). The reason is that the SOC-OCV curve of the battery does not change significantly with the change of the battery health. With the aging of the battery, the ISUM-OCV curve of the battery is estimated according to the remaining available capacity of the battery Q avail The value of Q is obtained by normalizing the ISUM-OCV curve to match the reference SOC-OCV curve. In combination with equation (1), the conversion process of the capacity is shown in equation (8). The reason is that the SOC-OCV curve of the battery does not change significantly with the change of the battery health. With the aging of the battery, the ISUM-OCV curve of the battery is estimated according to the remaining available capacity of the battery Q

[0078] In theory, two points on the ISUM-OCV curve are enough to estimate the battery capacity, however, in actual operation, the longer the length of the ISUM-OCV curve, the more accurate the capacity estimation will be, because in some cases there may be estimation errors due to noise and measurement errors.

[0079]

[0080] Wherein, SOC t and SOC0 are the battery state of charge and the initial state of charge value at the current time t, respectively;

[0081] Therefore, according to the Q avail value obtained by differentiating the ISUM-OCV curve from the SOC-OCV curve, the health state value of each battery monomer can be calculated, the SOH can be calculated according to equation (9), and the SOC value of the battery can be accurately updated according to equation (10).

[0082]

[0083] In the formula, Q avail is the estimated remaining available capacity value of the battery, Q nom refers to the rated capacity of the battery monomer, and ∑I cell Δt represents the cumulative value of the collected current data within time Δt, which is used to calculate the cumulative consumed power of the battery.

[0084] It should be pointed out that the battery state estimation algorithm of the present application does not consider the influence of working temperature on the battery. If the influence of temperature change is needed to be added, the reference SOC-OCV curve needs to be modified, because the SOC-OCV curve can also be a function of temperature.

[0085] In another embodiment, after the SOC value of each battery monomer is accurately obtained in step 3, the SOC value of each battery monomer is marked as SOC celli , and the SOC balancing control of the battery system can be performed. Specifically, the overall control process includes the calculation of the reference SOC ref , the adjustment of the controller parameters, the adjustment of the result output, and the internal principle diagram of the SOC balancing controller, which is shown in Figure 3as shown.

[0086] As Figure 3 shown, the SOC of the entire series battery in step 3 ref can be obtained by the mean method according to formula (11), and n represents the number of series battery monomers in the battery pack.

[0087]

[0088] With the SOC ref value of the battery pack, each battery monomer can adjust the power consumption speed according to the difference. It should be pointed out that the SOC control loop output is the battery reference current difference, and the difference comparison control with the actual battery current can obtain the appropriate switch conduction duty ratio, which can control the current balance of the entire battery pack. The control scheme this time adopts proportional-integral (PI) control, and the results of the controller output are shown in the following equation:

[0089] ΔI refi = (SOC ref -SOC celli ) × G SOC (z) (12)

[0090]

[0091] D i = (I load -I celli -ΔI refi ) × G cur (z) (14)

[0092] In the formula, G SOC (z) is a digital SOC balance PI controller / compensator; K P-SOC and K I-SOC are parameters of the controller, and these parameters are set in a reasonable range to ensure that the control loop responds quickly and accurately; ΔI refi is the output end of the controller SOC loop control; D i is the output end of the controller current loop control, which is also the final output of the entire controller; G cur (z) is also a digital current balance PI controller / compensator, and its parameters are set the same as the SOC balance controller. In the process of realizing SOC balance control of the battery system, the parameters of the PI controller / compensator need to be adjusted constantly, so that the controller output result is stable in a reasonable range.

[0093] Based on the above analysis, after the battery monomer adds the influence factor of battery health difference, the SOC value corresponding to the battery with poor health degree will decrease accordingly, and the overall SOC refThe values will lag behind the changes. After adjusting the entire battery system through the PI controller / compensator, it can be known that the current I cell output by the converter connected to the battery with a lower SOC value will decrease, and the conduction degree of the corresponding converter MOSFET switch will also decrease, so that less energy is drawn from the battery with poor health, and more energy is drawn from the relatively healthy battery monomer, so that all battery monomers reach the end of discharge at the same time.

[0094] From the introduction of step 3 above, through the design of an improved SOC balancing control system, the appropriate duty cycle is set based on the health status of the given battery monomer, and the charging and discharging rate of the battery monomer is controlled, so that the battery system realizes power balancing. This method improves the accuracy of battery health perception, thereby achieving more accurate SOC balancing effect.

[0095] In another embodiment, as Figure 3 shown, the present application also provides a battery system power balancing controller structure to realize the power balancing control method of the present application. The control system includes a data acquisition circuit, a data processing circuit, a signal control circuit, a data transmission circuit, a computer calculation module, a chip power supply circuit and a reset circuit. Each module in the controller cooperates with each other to ensure the safe and efficient operation of the battery system. By fully utilizing the functions of each link, a more reliable and durable energy storage battery application solution is provided for users.

[0096] The data acquisition circuit is a crucial component of the battery management system, and its function is not only to collect information of all battery monomers in real time, but also to record the state change of the controller switch. During the operation of the battery system, the data acquisition circuit can accurately obtain the voltage, current and other important parameters of each battery monomer and transmit them to the data processing circuit in time for processing. At the same time, the data acquisition circuit also monitors the on-off state of the MOSFET switch in the controller to ensure the safe and stable operation of the battery system.

[0097] The data processing circuit undertakes the core task of accurate calculation and analysis of the collected battery system information, mainly including the calculation of the SOC and SOH values of the battery monomers. The accurate calculation of these values is crucial for the performance evaluation and management of the battery system. In addition, the data processing circuit can also receive the calculation results from the computer calculation module in real time, so that the battery management system maintains the latest data state and ensures the systematicness and reliability of the battery.

[0098] The signal control circuit is used to control the data acquisition frequency and the on-off state of the MOSFET switch in the controller. Through reasonable signal control, more accurate monitoring and operation control of the battery system can be achieved, and the use efficiency and life of the battery can be improved.

[0099] The data transmission circuit is an intermediate transmission channel between the data acquisition circuit and the computer terminal, and sends the signals and data collected by the chip to the computer terminal for further analysis and processing. It plays an important role in connecting the data acquisition system and the computer terminal, ensuring smooth transmission and processing of data.

[0100] The computer calculation module is the brain of the entire system, responsible for in-depth analysis and calculation of the data collected by the chip, mainly including calculation of the battery internal resistance value R and the remaining available capacity Q avail estimation. At the same time, it can also make corresponding decisions and adjustments based on the data results to optimize the operating state of the battery system. In addition, as a complex electronic device, the chip is equipped with a power supply loop and a reset loop during operation to ensure normal operation. These design measures provide important protection for the stability and reliability of the data acquisition system.

[0101] The control system uses TI microcontroller chip TMS28335, which functions to collect battery cell voltage and current data, program with supporting software to calculate SOC and SOH, and at the same time, the program realizes battery system power balance control. The algorithm for identifying differences in battery health is implemented based on MATLAB software and mainly runs on a computer. The remaining available capacity of each battery cell is sent to the TI microcontroller from the SOH estimator to achieve battery system power balance control with battery health difference identification.

[0102] By implementing the power balance control method with battery health difference identification, the overall energy of the battery system can be fully utilized, i.e. after balancing the entire battery system, the battery cells with high health levels discharge at a faster rate, while the battery cells with low health levels discharge at a slower rate, thereby achieving the result that the usage frequency of battery cells tends to be consistent, the health level of battery cells differs less, and the service life of the entire battery system is extended.

[0103] To verify the precise calculation and power balance control effect of the present application, the present application is based on Figure 1 The circuit diagram of the present application is constructed as an experiment, a battery system composed of 5 battery cells in series powers a constant load, and the controller uses 5 isolated boost circuits, with the TMS28335 microcontroller assisting the controller in data and signal acquisition. First, the operating data of the battery system is collected and sent to the computer terminal, and the obtained battery cell voltage and current operating data are processed, the battery internal resistance value is obtained according to the current sudden change value, and the ISUM-OCV curve of each battery cell is formed. At the same time, the reference curve (healthy battery ISUM-OCV curve and SOC-OCV curve) is plotted in the graph for subsequent normalized operation curve to obtain the remaining available capacity value of the battery cell. The obtained internal resistance of the battery cell is plotted and shown in Figure 5In (taking two battery data as an example), the results of the two curves are shown in Figure 6 middle. Figure 5 Figure (a) shows the estimated value of the battery internal resistance obtained based on the battery operation data. Figure 5 Figure (b) shows the internal voltage variation of the battery. The data estimated by the algorithm is based on the information collected during battery operation, and is calculated 8 times in total. From the figure, we can see the average value of the battery internal resistance. We can preliminarily conclude that the health of battery #5 is worse than that of battery #1. Figure 6 Figure (a) shows the ISUM-OCV curves of battery cells with different health levels and the reference. Figure 6 The curve in Figure (a) is normalized to obtain the SOC-OCV curve consistent with the reference battery ( Figure 6 (b) Figure), the result of normalization is the remaining available capacity value of each battery cell. Figure 6 As can be seen from the display, these normalized SOC-OCV curves are similar to each other, and the remaining available capacity obtained for battery #5 is smaller than that for battery #1.

[0104] After the SOH algorithm calculates, the remaining available capacity of the battery cell is transmitted to the data processing circuit of the controller chip, and the original SOC and SOH values ​​are updated. The controller is updated to recognize the battery health difference and perform the power balancing control. According to the SOC control loop and the battery current control loop, the current result diagram of each battery cell after balancing control is obtained. For details, see Figure 7 . Figure 7 As can be seen from Figure (a), the SOC value of battery #1 changes the least, and the SOC value of battery #5 changes the most, that is, the health of battery #5 is the worst. Figure 7 As shown in Figure (b), after battery balancing, the stable output current of battery #1 is greater than that of battery #5, which is consistent with the balance control theory.

[0105] The experimental data and results show that the power balancing control method of this embodiment, which incorporates battery health differential identification, can achieve power balancing for the battery system. Furthermore, after balancing, the discharge rates of the battery cells are differentiated: healthy cells have a higher discharge current, while unhealthy cells have a minimum discharge current. This differentiated battery usage improves the overall energy utilization efficiency of the battery system, resulting in a safer battery system and extending its service life.

[0106] In the above-mentioned embodiments of the present application, the control method and the corresponding steps thereof can be realized in the form of a software program, which can be stored in a computer readable storage medium. The software function unit is stored in a storage medium, including a plurality of instructions for enabling a computer device (which can be a personal computer, a server, or a network device, etc.) or a processor to execute part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes a variety of storage media that can store program codes, such as a U disk, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk, etc.

[0107] Finally, it should be pointed out that the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A battery health difference based power balance control method, characterized in that, The method comprises the following steps: Step 1: obtaining online running data information of each battery monomer; Step 2: calculating the SOH value of the battery by using a battery state estimation algorithm, and updating the SOC value of the battery in combination with the change of the battery health degree; The battery state estimation algorithm comprises: Step 2.1: The collected data is filtered and analyzed to extract the discharge intervals from the continuous signal of repeated charge and discharge intervals, and the collected current I cell is integrated to obtain the current cumulative value ISUM: Step 2.2: obtaining the battery internal resistance estimation value R=R(k) by capturing the voltage and current change values at discontinuous moments, that is, where k denotes the time of current abrupt change, δ denotes the sampling delay time, I cell is the current of the battery cell, V cell is the terminal voltage of the battery cell; the battery internal voltage V T is estimated according to formula (6), and the specific expression is: V T = V cell + I cell R (6) Step 2.3: The battery internal voltage V obtained is modified by the terminal voltage measured by the battery system according to formula (7) T , the polarization voltage V obtained in combination with the parameter estimation p , the OCV data is calculated according to the corresponding current I cell , and the current accumulation value ISUM and the open circuit voltage value V OC , the estimated ISUM-OCV curve of the continuous discharge interval is drawn; V OC = V cell + I cell R + V p = V T + V p (7) Step 2.4: Estimation of the remaining available capacity of the battery and calculation of the state of the battery using the SOC-OCV curve of the new battery as the reference curve and the ISUM-OCV curve of the aged battery in accordance with the correct remaining available capacity Q avail of the battery, implementing normalization processing, coinciding with the reference SOC-OCV curve, combining formula (1), and the specific conversion process of the capacity is shown in formula (8). With the aging of the battery, the ISUM-OCV curve of the battery is adjusted in accordance with the estimated value Q avail of the remaining available capacity of the battery to find the correct Q avail value so that the current SOC-OCV curve matches the reference curve. wherein SOC t and SOC0are the battery state of charge and initial state of charge value at the current time t, respectively; Q avail value obtained from the difference between the ISUM-OCV curve and the SOC-OCV curve, to calculate the SOH value of the battery according to equation (9) and update the SOC value of the battery according to equation (10); In the formula, Q nom denotes the rated capacity of the battery cell, ∑I cell Δt represents the cumulative value of the collected current data within the time Δt; Step 3: controlling the on degree of the switch MOSFET in combination with the SOC difference value of each battery monomer and the battery health degree, so as to realize the battery pack power balance control. 2.The battery health difference based power balance control method of claim 1, wherein, The step 2.2 further comprises: selecting δ=(1 / 10)τ, and the overall internal resistance sampling delay time should satisfy the following conditions: τ = R p C p ≥ n(t[k + δ] - t[k]) (4) |I cell [k+δ]-I cell [k]|≥ε (5) In the formula, R p denotes the polarization resistance of the battery, C p denotes the polarization capacitance of the battery; t[k+δ] and t[k] each represent a data corresponding time obtained by extending the time interval δ of the battery sampling process; n(x) is a multiple relationship function of x, and ε is a preset threshold value. If the discontinuity does not satisfy the formulas (4) and (5), it is determined that the battery internal resistance R=R(k) estimated by the formula (2) is inaccurate. 3.The battery health difference based power balance control method of claim 2, wherein, Taking the preset threshold value ε as 0.3A, the multiple relationship function n(x)=10*x. 4.The battery health difference based power balance control method of claim 1, wherein, Step 3 also includes: SOC of the whole series battery pack ref Using the mean value method, according to formula (11), n represents the number of series battery cells in the battery pack; With the SOC of the battery pack ref value, each battery cell adjusts the power consumption speed according to the difference value, the SOC control loop outputs the battery reference current difference value, and the appropriate switch conduction duty cycle is obtained through the differential comparison control of the actual battery current, so as to control the current balance of the whole battery pack. Through proportional integral control, the output result of the controller is: ΔI refi = (SOC ref -SOC celli ) x G SOC (z) (12) D i = (I load - I celli - ΔI refi ) x G cur (z) (14) In the formula, G SOC (z) is a digital SOC balance PI controller; K P-SOC and K I-SOC are parameters of the controller, and to ensure that the control loop responds quickly and accurately, these parameters are set within a reasonable range; ΔI refi is the output end of the controller SOC loop control; D i is the output end of the controller current loop control, to control the conduction of the corresponding switch MOSFET; G cur (z) is also a digital current balance PI controller, and the parameters of the PI controller need to be continuously adjusted in the process of realizing SOC balance control by the battery system, so that the controller output result D i is stable within a reasonable range.

5. A battery health disparity power balance control system, comprising: Comprise: At least one processor; And at least one memory connected with the processor in communication, wherein: The memory stores program instructions executable by the processor, and the processor calling the program instructions can execute the power balance control method of the battery health difference according to any one of claims 1 to 4.

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