Active equalization control method for SOC of multiple battery modules of energy storage system SCLBC

Abstract

The invention belongs to the technical field of power electronics and the technical field of new energy storage, and relates to an energy storage system SCLBC multi-battery module SOC active balance control method which comprises the steps that a charging process control method and a discharging process control method are adopted, sampling equipment including a BMS sends information to a controller, the controller synthesizes information such as SOC of all modules, the information is analyzed and processed, and the SOC of all the modules is obtained. The obtained single-module power regulation information is transmitted to each corresponding module, and a bidirectional DC-DC converter in each module regulates the duty ratio to make a response, so that the power reaches a set value, and a control target is completed; by monitoring the state of the battery in real time, analyzing the proper working state and dynamically adjusting the working mode of each battery to adjust the working state, the service life of the battery is prolonged, the energy consumption is ensured to be the lowest as far as possible and the balance control is completely realized, so that the problems of limited conditions and imperfect control methods of the control method in the prior art are solved.

Description

Technical Field

[0001] The present invention belongs to the fields of power electronics technology and new energy storage technology, and relates to an active balancing control method for SOC of multiple battery modules of an energy storage system SCLBC. Background Art

[0002] Energy storage systems can balance the volatility of renewable energy, store excess electricity, and release it when power generation is insufficient, thereby improving the overall efficiency of renewable energy and reducing wind and solar power abandonment. Through energy storage, the power grid can respond to load fluctuations more smoothly and reduce the risk of power outages. Energy storage systems can also serve as a backup power source to provide emergency power support in the event of sudden failures. Among today's energy storage systems, electrochemical energy storage is the most widely used. SCLBC (series lithium battery cells) multi-module batteries are individually connected to the converter and all outputs are connected in series to effectively solve the needs of high-voltage and high-power input and output charging and discharging of energy storage. When the SOC of the single cells in the battery pack is unbalanced, it may lead to reduced system capacity, shortened cycle life and other safety hazards.

[0003] The SOC (State of Charge) balancing control method is mainly used in battery management systems (BMS) to ensure that the charging state of each single cell in the battery pack is consistent. This method is essential for extending battery life, improving battery performance and safety. Common SOC balancing control methods include: Passive balancing: releasing excess power from batteries with higher power to the ground through resistors. Active balancing: transferring power from batteries with higher power to batteries with lower power through electrical energy transfer. Energy storage elements such as capacitors and inductors can be used, or DC-DC converters can be used. Combined balancing technology: combining passive and active balancing strategies, flexibly selecting different balancing methods according to actual conditions to optimize system performance and cost.

[0004] However, the SOC balance control method in the prior art has the following defects:

[0005] Passive balancing: Energy loss. Passive balancing dissipates excess power in the form of heat, resulting in significant energy waste. This not only reduces the overall energy efficiency, but also makes the system uneconomical when running for a long time. Low efficiency. Since excess power needs to be consumed to achieve balancing, the overall efficiency of charging and discharging is affected, especially in large-scale battery packs, the wasted energy will be more obvious. Time requirements. Passive balancing usually takes a long time to complete the balancing process, especially when the single cells in the battery pack are very different, which may cause the battery pack to fail to quickly recover to the optimal state under certain working conditions. Unable to improve aging batteries. For aging or degraded single cells, passive balancing cannot effectively compensate for their capacity attenuation, but may further increase the burden on other batteries. Heat generation problem. Since excess power is released in the form of heat, it may cause the system to overheat, thereby affecting the safety and reliability of the battery pack.

[0006] Active balancing: High complexity. The active balancing system has a complex structure and requires more circuits, control algorithms and components, which increases the difficulty of design and manufacturing costs. In addition, there are challenges in system maintenance and troubleshooting. Rising costs. Due to the involvement of additional hardware components and complex control strategies, the initial investment and maintenance costs of active balancing technology are relatively high, which puts pressure on the overall project budget. Difficulty of control. Active balancing requires real-time monitoring and adjustment of the status of each single cell in the battery pack to ensure precise control of the energy transfer process. The complexity and rigor of this control are particularly prominent under dynamic load conditions. Heat dissipation issues. Although active balancing can improve energy efficiency, additional heat may be generated during the energy transfer process. Effective heat dissipation measures need to be considered to avoid damage to the battery pack. Reliability test. Due to the increased complexity of the system, new failure modes may be introduced. The real-time monitoring and control of each battery by the active balancing system also requires high-reliability hardware support.

[0007] Combined balancing: System design complexity: Combined balancing technology combines the advantages of passive and active balancing, but it also brings higher design and implementation complexity, requiring stronger engineering capabilities and skills. Increased operating costs. Since the functions of two balancing schemes need to be implemented, the implementation and maintenance costs of combined balancing technology are often higher than those of single technology, which may affect its market competitiveness. Coordination issues. In practical applications, different balancing strategies need to be well coordinated to ensure that the system operates in the best condition. If not properly managed, it may lead to poor balancing effects and even cause other problems. Relying on advanced control algorithms, combined balancing technology usually requires complex control algorithms to manage, which places higher requirements on the system's computing power and response speed, and may also cause potential reliability problems.

[0008] Therefore, a SOC control method with long battery life, low energy consumption and balanced control is needed to solve the above technical problems. Summary of the invention

[0009] The technical solution adopted by the present invention to solve the technical problem is: an active balancing control method for SOC of multiple battery modules of an energy storage system SCLBC, a charging process control method A, and a discharging process control method B;

[0010] The charging process control method A comprises the following steps:

[0011] Step A1: Record the SOC number of each battery pack and obtain the maximum SOC value SOC max , minimum SOC min With the average SOC ave ;

[0012] Step A2: Calculate the difference between the maximum SOC and the minimum SOC, record it as R, and calculate SOCH i =1 / (SOC i +Δ)+α;

[0013] Step A3: When R>ε%, bypass the battery pack with the largest SOC value and return to step A1; when R<ε%, group the packs based on SOC;

[0014] Step A4: Via SOCH i Calculate the adjustment amount of each module, and set the total amount to TSOCH;

[0015] Step A5: Calculate the maximum adjustment value P within the range max ; Among them, P max =1 / TSOCH / (SOC min +Δ)+α / TSOCH;

[0016] Step A6: Determine the adjustment range; when SOC i -SOC ave <-βSOC ave When within the range, for the battery pack with smaller SOC, adjust its given ratio to P max , while the given adjustments of the remaining packs are adjusted autonomously based on the calculated ones;

[0017] When SOC i -SOC ave ≥-βSOC ave When the SOC of the battery pack with a smaller SOC is outside the range, the given value is adjusted to the upper limit value, and the given value adjustments of the remaining packs are determined independently according to the calculation results;

[0018] Among them, the coefficient β ranges from 5% to 20%;

[0019] Step A7: Adjustment amount constraint; when the adjustment amount constraint condition is met, the extreme difference limit is determined; otherwise, after adding the correction amount, the process returns to step A3 to group each pack based on the SOC as the scale;

[0020] Step A8: When the range is less than the limit value ζ, a control instruction is issued; otherwise, after adding the correction amount, return to step A3 to group each pack based on the SOC;

[0021] The discharge process control method B comprises the following steps:

[0022] Step B1: Record the SOC number of each battery pack and obtain the maximum SOC value SOC max , minimum SOC min With the average SOC ave ;

[0023] Step B2: Calculate the difference between the maximum SOC and the minimum SOC, record it as R, and calculate SOCH i =1 / (1-SOC i +Δ)+α;

[0024] Step B3: When R>ε%, bypass the battery pack with the largest SOC value and return to step B1; when R<ε%, group the packs based on SOC;

[0025] Step B4: Through SOCH i Calculate the adjustment amount of each module, and set the total amount to TSOCH;

[0026] Step B5: Calculate the maximum adjustment value P within the range max ; Among them, P max =1 / TSOCH / (1-SOC max +Δ)+α / TSOCH;

[0027] Step B6: Determine the adjustment range; when SOC i -SOC ave >βSOC ave When within the range, for the battery pack with larger SOC, adjust its given ratio to P max , while the given adjustments of the remaining packs are adjusted autonomously based on the calculated ones;

[0028] When SOC i -SOC ave ≤βSOC aveWhen the SOC of the battery pack with a larger SOC is outside the range, the given value is adjusted to the upper limit value, and the given value adjustments of the remaining packs are determined independently according to the calculation results;

[0029] Among them, the coefficient β ranges from 5% to 20%;

[0030] Step B7: Adjustment amount constraint; when the adjustment amount constraint condition is met, the extreme difference limit is determined; otherwise, after adding the correction amount, the process returns to step B3 to group each pack based on the SOC as the scale;

[0031] Step B8: When the extreme difference is less than the limit value ζ, a control instruction is issued; otherwise, after adding the correction amount, return to step B3 to group each pack based on the SOC.

[0032] Preferably, in step A4 and step B4,

[0033] When inputting to the battery side, i.e. in step A4:

[0034] TSOCH=∑VAL Ctrl

[0035]

[0036] When outputted from the battery side, that is, in step B4:

[0037] TSOCH=∑VAL Ctrl

[0038]

[0039] Preferably, in step A1 and step B1, the average value SOC ave for:

[0040] Preferably, the value of the SOC is expressed as:

[0041]

[0042] Among them, SOC0 represents the initial value of SOC, C e Indicates the battery capacity, i in Indicates the battery current.

[0043] Preferably, the energy storage system in the control method includes: a single battery module composed of multiple internal battery cells connected in series, a DC-DC converter responsible for the bidirectional flow transmission of electric energy, a sampling device including a BMS, and an energy bus in which multiple modules are connected in series to the bus voltage for energy supply; the sampling device is used to collect data from the battery module and its internal battery cells and obtain information in the power circuit; the energy bus is used to output electric energy to the outside.

[0044] More preferably, the data of the battery module and its internal cells include: temperature, voltage, current, humidity; the information in the power circuit includes: voltage, current.

[0045] The beneficial effects of the present invention are:

[0046] 1. The present invention monitors the state of the battery in real time, analyzes the suitable working state, dynamically adjusts the working mode of each battery to adjust the working state, improves the battery life, ensures the lowest possible exhaustion and complete realization of balanced control. The present invention solves the problems of limited control conditions and imperfect control methods in the prior art.

[0047] 2. The present invention uses a soft control method based on the hardware of the power circuit, and does not add an additional balancing circuit, thereby overcoming the defects of energy dissipation and hardware consumption of energy-consuming and non-energy-consuming (passive balancing and active balancing) methods in pure hardware control. At the same time, it is extensive and universal, not targeted at specific circuit topologies, and runs fast, stably and reliably. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 It is a flow chart of the charging process control of the SOC active balancing control method of the energy storage system SCLBC multi-battery module of the present invention;

[0049] Figure 2 It is a discharge process control flow chart of the present invention;

[0050] Figure 3 It is a structural diagram of the energy storage system SCLBC of the present invention;

[0051] Figure 4 It is a topological diagram of a single-module interleaved parallel bidirectional DC-DC of the present invention;

[0052] Figure 5 It is the system structure and control schematic diagram of the present invention;

[0053] Figure 6 is a diagram showing changes in the adjustment amount during the SOC balancing control process of the present invention;

[0054] Figure 7 It is a state diagram of SOC changes during the balancing control of the present invention.

[0055] In the figure: 31, single battery module; 32, bidirectional DC-DC converter; 33, sampling equipment represented by BMS; 34, energy bus with busbar voltage supply; 51, system structure; 52, single module internal structure; 53, single module bidirectional DC-DC converter topology; 54, dual closed-loop control and system control block diagram. DETAILED DESCRIPTION

[0056] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the relevant technologies in the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0057] refer to Figures 1 to 7 This embodiment provides an energy storage system with active SOC balancing control of multiple battery modules, showing the overall structure of the system, in which multiple single battery modules are connected in series to form a multi-module system.

[0058] like Figure 3 As shown, 31 is a single battery module, which is composed of multiple internal cells connected in series. 32 is a DC-DC converter, which is responsible for the bidirectional flow transmission of electric energy. 33 is a sampling device including a BMS (battery management system), which collects data such as temperature, voltage, current, humidity, etc. of the battery module and its internal cells, and obtains information such as current and voltage in the power circuit, and transmits it to the host computer and controller through CAN communication. 34 is an energy bus in which multiple modules are connected in series to the bus voltage for energy supply, and the output electric energy can be supplied to power-consuming equipment or scenarios such as data centers.

[0059] As a DC-DC converter in energy storage systems, such as Figure 4 As shown, the DC-DC converter is a single-module interleaved parallel bidirectional Buck / Boost topology. The parameters of the DC-DC converter are as follows in Table 1:

[0060]

[0061] Table 1

[0062] like Figure 5 As shown in the figure, the DC-DC converter and sampling device in a single battery module are collectively referred to as the battery module controller. The four switches of the interleaved parallel bidirectional Buck / Boost converter are controlled to adjust the power action of each battery module. The dual closed-loop control of the current inner loop and the voltage outer loop is used as the bottom control method. The system control is at the top level, collecting the information required by each part of the system and sending instructions to each battery module.

[0063] Figure 5 In the figure, 51 is a simplified structure of the whole system, which reflects the characteristics of multiple battery modules connected in series. 52 is the internal structure of a single module, including staggered parallel bidirectional Buck / Boost converters and control systems. 53 is a single module bidirectional DC-DC converter circuit, which is the direct bearer of the underlying battery module control. 54 is a dual closed-loop control and system control block diagram, which reflects the dual closed-loop control of the current inner loop and the voltage outer loop and the system-level control structure at the upper level, which is for the stable operation of the system and the real-time decision-making processing of SOC balance.

[0064]

[0065] SOC0 represents the initial value of SOC, C e Indicates the battery capacity, i in Indicates the battery current.

[0066] Charging process control flow Figure 1 As shown:

[0067] The SOC information received from each single battery pack is recorded as SOC i (The i-th battery pack is SOCi), get the maximum and minimum SOC max , SOC min .

[0068] R=SOC max -SOC min .

[0069] Calculate the difference between the maximum and minimum values ​​and record it as R.

[0070]

[0071] SOCH i =1 / (SOC i +Δ)+α

[0072] When R>ε%, the battery pack with the largest SOC value is bypassed and the cycle is re-entered in the direction of the arrow.

[0073] When R<ε%, each pack is grouped based on SOC.

[0074] TSOCH=∑VAL Ctrl

[0075]

[0076] By SOCH i Calculate the adjustment amount of each module and set the total amount to TSOCH.

[0077] P max =1 / TSOCH / (SOC min +Δ)+α / TSOCH.

[0078] P max This is the maximum adjustment value within the range.

[0079] Due to power, battery and hardware limitations, the adjustment range is determined.

[0080] SOC i -SOC ave<-βSOC ave , within the range.

[0081] SOC i -SOC ave ≥-βSOC ave , out of range.

[0082] β = 5% to 20%.

[0083] When within the range, for the battery pack with smaller SOC, adjust its given ratio to P max , and the given adjustments of the rest of the packs are autonomously adjusted according to the calculated results. When the range is exceeded, the given value of the battery pack with a smaller SOC is adjusted to the upper limit value, and the given adjustments of the rest of the packs are autonomously determined according to the calculated results.

[0084] When the adjustment amount constraint condition is met, that is, the adjustment amount range is not less than a certain limit value λ, the extreme difference limit value is judged. Otherwise, the steps of the previous stage are repeated after adding the correction amount.

[0085] When the extreme difference is less than the limit value ζ, a control instruction is issued. Otherwise, the steps of the previous stage are repeated after adding the correction amount.

[0086] The discharge process control flow is as follows: Figure 2 As shown:

[0087] The SOC information received from each single battery pack is recorded as SOC i (The i-th battery pack is Si), and the maximum and minimum SOC values ​​are obtained max , SOC min .

[0088] R=SOC max -SOC min .

[0089] Calculate the difference between the maximum and minimum values ​​and record it as R.

[0090]

[0091] SOCH i =1 / (1-SOC i +Δ)+α

[0092] When R>ε%, the battery pack with the largest SOC value is bypassed and the cycle is re-entered in the direction of the arrow.

[0093] When R<ε%, each pack is grouped based on SOC.

[0094] TSOCH=∑VAL Ctrl

[0095]

[0096] By SOCH i Calculate the adjustment amount of each module and set the total amount to TSOCH.

[0097] P max =1 / TSOCH / (1-SOC max +Δ)+α / TSOCH.

[0098] P max This is the maximum adjustment value within the range.

[0099] Due to power, battery and hardware limitations, the adjustment range is determined.

[0100] SOC i -SOC ave >βSOC ave , within the range.

[0101] SOC i -SOC ave ≤βSOC ave , out of range.

[0102] β = 5% to 20%.

[0103] When within the range, for the battery pack with larger SOC, adjust its given ratio to P max , and the given adjustments of the rest of the packs are autonomously adjusted according to the calculated results. When the range is exceeded, the given value of the battery pack with a larger SOC is adjusted to the upper limit value, and the given adjustments of the rest of the packs are autonomously determined according to the calculated results.

[0104] When the adjustment amount constraint condition is met, that is, the adjustment amount range is not less than a certain limit value λ, the extreme difference limit value is judged. Otherwise, the steps of the previous stage are repeated after adding the correction amount.

[0105] When the extreme difference is less than the limit value ζ, a control instruction is issued. Otherwise, the steps of the previous stage are repeated after adding the correction amount.

[0106] Figure 6 This is a diagram showing the changes in the adjustment amount during the SOC balancing control process. There are a total of 12 battery modules, which shows the changes in the adjustment amount during the entire control process. The lower the SOC, the greater the power. The multi-level adjustment makes the control process smooth and rapid.

[0107] Figure 7 It is a state diagram of SOC changes during balanced control. It can be seen intuitively that the trend of SOC values ​​is obviously concentrated in one place, and the rapidity and stability of the balanced process are achieved as much as possible within the control range.

[0108] In this implementation, sampling devices including the BMS send information to the controller, which integrates information such as the SOC of each module, analyzes and processes it, and transmits the obtained single-module power adjustment information to each corresponding module. The bidirectional DC-DC converter in the module adjusts the duty cycle to respond so that the power reaches the set value and the control target is achieved.

[0109] Based on the hardware of the power circuit, a soft control method is used without adding an additional balancing circuit, which overcomes the defects of energy dissipation and hardware consumption of energy-consuming and non-energy-consuming (passive balancing and active balancing) methods in pure hardware control. At the same time, it is extensive and universal, not targeted at specific circuit topologies, and runs fast, stably and reliably.

[0110] This embodiment can also be applied to the SOC balancing control between multiple cells in a battery pack, which requires the cells to have a similar DC-DC converter structure. The bidirectional DC-DC converter can also be replaced by various DC-DC circuits such as Buck, Boost, Cuk, BuckBoost, DAB, etc. The SOC estimation method can be replaced by various SOC estimation methods including Kalman filtering method, ampere-hour integration method, coulomb counting method, and electrochemical impedance spectroscopy.

[0111] In summary, the present invention monitors the status of the battery in real time, analyzes the suitable working status, dynamically adjusts the working mode of each battery to adjust the working status, improves the battery life, ensures the lowest possible depletion and complete realization of balanced control, and solves the problems of limited control conditions and imperfect control methods in the prior art.

[0112] It should be emphasized that the above are only preferred embodiments of the present invention and do not limit the present invention in any form. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. Energy storage system SCLBC multi-battery module SOC active balancing control method, characterized in that: include: Charging process control method A, discharging process control method B; The charging process control method A comprises the following steps: Step A1: Record the SOC number of each battery pack and obtain the maximum SOC value SOC max , minimum SOC min With the average SOC ave ; Step A2: Calculate the difference between the maximum SOC and the minimum SOC, record it as R, and calculate SOCH i =1 / (SOC i +Δ)+α; Step A3: When R>ε%, bypass the battery pack with the largest SOC value and return to step A1; when R<ε%, group the packs based on SOC; Step A4: Via SOCH i Calculate the adjustment amount of each module, and set the total amount to TSOCH; Step A5: Calculate the maximum adjustment value P within the range max ; Among them, P max =1 / TSOCH / (SOC min +Δ)+α / TSOCH; Step A6: Determine the adjustment range; when SOC i -SOC ave <-βSOC ave When within the range, for the battery pack with smaller SOC, adjust its given ratio to P max , while the given adjustments of the remaining packs are adjusted autonomously based on the calculated ones; When SOC i -SOC ave ≥-βSOC ave When the SOC of the battery pack with a smaller SOC is outside the range, the given value is adjusted to the upper limit value, and the given value adjustments of the remaining packs are determined independently according to the calculation results; Among them, the coefficient β ranges from 5% to 20%; Step A7: Adjustment amount constraint; when the adjustment amount constraint condition is met, the extreme difference limit is determined; otherwise, after adding the correction amount, the process returns to step A3 to group each pack based on the SOC as the scale; Step A8: When the range is less than the limit value ζ, a control instruction is issued; otherwise, after adding the correction amount, return to step A3 to group each pack based on the SOC; The discharge process control method B comprises the following steps: Step B1: Record the SOC number of each battery pack and obtain the maximum SOC value SOC max , minimum SOC min With the average SOC ave ; Step B2: Calculate the difference between the maximum SOC and the minimum SOC, record it as R, and calculate SOCH i =1 / (1-SOC i +Δ)+α; Step B3: When R>ε%, bypass the battery pack with the largest SOC value and return to step B1; when R<ε%, group the packs based on SOC; Step B4: Through SOCH i Calculate the adjustment amount of each module, and set the total amount to TSOCH; Step B5: Calculate the maximum adjustment value P within the range max ; Among them, P max =1 / TSOCH / (SOC max +Δ)+α / TSOCH; Step B6: Determine the adjustment range; when SOC i -SOC ave >βSOC ave When within the range, for the battery pack with larger SOC, adjust its given ratio to P max , while the given adjustments of the remaining packs are adjusted autonomously based on the calculated ones; When SOC i -SOC ave ≤βSOC ave When the SOC of the battery pack with a larger SOC is outside the range, the given value is adjusted to the upper limit value, and the given value adjustments of the remaining packs are determined independently according to the calculation results; Among them, the coefficient β ranges from 5% to 20%; Step B7: Adjustment amount constraint; when the adjustment amount constraint condition is met, the extreme difference limit is determined; otherwise, after adding the correction amount, the process returns to step B3 to group each pack based on the SOC as the scale; Step B8: When the extreme difference is less than the limit value ζ, a control instruction is issued; otherwise, after adding the correction amount, return to step B3 to group each pack based on the SOC.

2. The energy storage system SCLBC multi-battery module SOC active balancing control method according to claim 1 is characterized in that: In the step A4 and step B4, When inputting to the battery side, i.e. in step A4: TSOCH=∑VAL Ctrl When outputted from the battery side, that is, in step B4: TSOCH=∑ CHOICE Ctrl 3. The energy storage system SCLBC multi-battery module SOC active balancing control method according to claim 1 is characterized in that: In the steps A1 and B1, the average value SOC ave for:

4. The energy storage system SCLBC multi-battery module SOC active balancing control method according to claim 1 is characterized in that: The value of the SOC is expressed as: Among them, SOC0 represents the initial value of SOC, C e Indicates the battery capacity, i in Indicates the battery current.

5. The energy storage system SCLBC multi-battery module SOC active balancing control method according to claim 1, characterized in that: The energy storage system in the control method comprises: a single battery module (31) formed by connecting a plurality of internal battery cells in series, a DC-DC converter (32) responsible for bidirectional flow transmission of electric energy, a sampling device (33) including a BMS, and an energy bus (34) connected in series with a plurality of modules to supply energy through a bus voltage; The sampling device (33) is used to collect data of the battery module and its internal battery cells and obtain information in the power circuit; The energy bus (34) is used to output electrical energy to the outside.

6. The energy storage system SCLBC multi-battery module SOC active balancing control method according to claim 5 is characterized in that: The data of the battery module and its internal cells include: temperature, voltage, current, and humidity; the information in the power circuit includes: voltage and current.

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