An electric quantity balancing control method and device for an energy storage system and an energy storage device

Abstract

This invention relates to the field of energy storage technology, and particularly to a power balancing control method, device, and energy storage device for energy storage systems. The method includes: initial power-on and automatic address allocation; acquiring the power levels of all battery packs; sorting the power levels of all battery packs; making an operating mode decision based on voltage difference; determining the system's charging and discharging state; if the system is in a discharging state, executing a discharging screening algorithm; if the system is in a charging state, executing a charging screening algorithm; and repeating the above steps cyclically, so that the power levels of each battery pack continuously converge towards the average value through dynamic adjustment, and the system returns to normal operation. Compared with existing technologies, the power balancing control method, device, and energy storage device of this invention can improve the intelligence and response speed of power balancing between battery packs, prevent premature aging of individual battery packs due to overcharging and discharging, delay the overall performance degradation of the energy storage system, and improve the reliability of system operation.

Description

[Technical Field] This invention relates to the field of energy storage technology, and in particular to a power balance control method, device and energy storage equipment for energy storage systems. [Background Technology] In existing technologies, for energy storage systems composed of multiple independent battery packs (or battery modules) connected in parallel, the power balance management between the packs is crucial for the overall system lifespan and efficiency. Existing implementation schemes mainly fall into the following categories: Centralized balancing scheme: A main controller monitors the status of all battery packs in real time and transfers energy from high-capacity battery packs to low-capacity battery packs through a centralized DC-DC converter or switching matrix. This scheme is complex in structure, expensive, and has a single point of failure risk; if the main controller fails, the entire system's balancing function is lost.

[0001] A distributed but simple balancing scheme: Each battery pack has a local management unit, but the balancing strategy is usually based on a fixed voltage threshold. For example, when the voltage of a battery pack is higher than a certain threshold, discharging is started, and charging is stopped when it is lower than another threshold. This scheme cannot make dynamic and intelligent decisions based on the overall power distribution and operating conditions of the system, resulting in slow balancing speed and low efficiency.

[0002] Equalization strategies based on droop control: In DC microgrids, some studies have used methods that correlate the droop coefficient with the state of charge (SOC) of energy storage units to achieve SOC equalization. These methods are mostly used for power distribution at the grid level, but they are not very effective in solving the real-time consistency problem caused by subtle differences in internal resistance and capacity between parallel battery packs, and their dynamic response and equalization speed may not meet the management requirements at the battery pack level.

[0003] Existing technologies also include a communication-based distributed battery management system. In this system, each battery pack has an independent BMS (Battery Management System) and connects to the main controller via communication networks such as CAN bus. The main controller collects the charge information of each pack and issues simple balancing commands. However, this approach typically requires manual pre-setting of the addresses of each battery pack, increasing the complexity of system integration and maintenance. Furthermore, its balancing algorithm is often rigid, unable to dynamically and selectively identify the battery packs most needed to participate or avoid based on the system's real-time charging / discharging status (charging / discharging), resulting in unsatisfactory balancing performance and an inability to effectively suppress the increase in charge dispersion among battery packs. At the circuit level, there is also a lack of effective hardware-level management of the charging and discharging permissions of individual battery packs under extreme conditions.

[0004] In summary, the disadvantages of existing technologies include: Complex address configuration: Existing distributed systems mostly rely on manual configuration of battery pack addresses, which is cumbersome and error-prone, and not conducive to large-scale application and later maintenance.

[0005] Rigid balancing strategy: The balancing strategy based on a fixed threshold cannot perceive the overall charging and discharging conditions of the system and cannot dynamically adjust the balancing target. This results in the high-capacity pack being overburdened at the end of the discharge phase, while the low-capacity pack is still being charged at the end of the charging phase, which accelerates the inconsistency between battery packs.

[0006] Poor system-level coordination: Existing solutions lack the means to perform intelligent scheduling based on the charging and discharging state at the system level, and fail to achieve coordinated control of "protecting low-capacity packs during discharging and protecting high-capacity packs during charging", thus failing to effectively converge the capacity of each pack to near the average value.

[0007] Insufficient safety under extreme operating conditions: There is a lack of effective hardware and control linkage mechanisms to limit adverse behavior of the battery pack when it is in extreme situations such as extremely low or extremely high charge (e.g., prohibiting discharge when the charge is extremely low and prohibiting charging when the charge is extremely high), which poses a safety risk. [Summary of the Invention] To overcome the above problems, this invention proposes a power balance control method, device, and energy storage equipment for energy storage systems that can effectively solve the above problems.

[0008] The present invention provides a technical solution to the above-mentioned technical problems: a power balancing control method for an energy storage system, comprising the following steps: Step S1, initial power-on and automatic address allocation: When the system is powered on for the first time, each battery pack automatically performs address allocation through the CAN communication bus. After successful address allocation, each battery pack has a unique identifier. Step S2: Obtain the power of all battery packs. The local controller of each battery pack collects its own current power through the acquisition protection chip and shares the information through the CAN communication bus. Step S3: Sort the battery pack power levels. The local controller sorts the current power levels of all battery packs and determines the battery packs with the highest and lowest power levels. Step S4: Based on the voltage difference, the operating mode decision is made. The voltage difference between any two battery packs in the system is calculated to obtain the maximum difference ΔV_max. ΔV_max is compared with the preset voltage difference threshold. If ΔV_max ≤ the preset voltage difference threshold, the system enters the normal mode. If ΔV_max > the preset voltage difference threshold, the system enters the equalization mode. Step S5: Determine the charging and discharging status of the system. The central control unit determines whether the entire energy storage system is currently in a discharging or charging state based on the direction of the total load or the total bus current. The working state of the DC-DC unit changes accordingly based on the current state of the system. Step S6: If the system is in a discharge state, execute the discharge screening algorithm; Step S7: If the system is in a charging state, execute the charging screening algorithm; Step S8: Repeat steps S2 to S7 to make the power of each battery pack continuously converge toward the average value in dynamic adjustment until ΔV_max falls back to within the preset differential pressure threshold, and the system returns to normal mode. Preferably, the preset differential pressure threshold is ΔV_set.

[0009] Preferably, in step S4, in normal mode, all battery packs participate in charging and discharging together according to the total system demand; within the platform voltage range, the system operates at an open-loop fixed resonant frequency, and both the LLC circuit and the synchronous rectifier circuit operate normally, achieving efficient bidirectional energy flow.

[0010] Preferably, in step S6, battery packs with power levels higher than the average power level or a certain set threshold are selected, and a discharge permission command is executed on these battery packs; for battery packs with lower power levels, a discharge prohibition command is executed.

[0011] Preferably, in step S7, battery packs with power levels below the average power level or a certain set threshold are selected, and charging instructions are executed for these battery packs; for battery packs with higher power levels, charging instructions are executed.

[0012] A power balancing control device for an energy storage system, integrated inside a battery pack, includes a local controller, a data acquisition and protection chip, battery cells, and a DC-DC converter unit. The data acquisition and protection chip is connected to the local controller, the battery cells are connected to the data acquisition and protection chip, and the DC-DC converter unit is connected to both the battery cells and the local controller. The DC-DC converter unit includes a high-voltage side LLC circuit, a transformer, and a low-voltage side synchronous rectification circuit. The high-voltage side LLC circuit and the low-voltage side synchronous rectification circuit are respectively connected to the transformer and to the local controller. The local controller controls the switching transistors of the high-voltage side LLC circuit and the low-voltage side synchronous rectification circuit via PWM signals.

[0013] Preferably, each battery pack is an independent energy unit; each battery pack is composed of lithium iron phosphate cells forming a 1P16S structure with a nominal voltage of 51.2V.

[0014] Preferably, the data acquisition and protection chip is an AFE model chip, which is responsible for acquiring the voltage, current, and temperature data of the cells in the battery pack.

[0015] Preferably, the local controller is an MCU or DSP microcontroller, which is responsible for communicating with the AFE chip of the battery pack and realizing charge and discharge management by controlling the DC-DC unit.

[0016] An energy storage device is characterized by comprising multiple independent battery packs and a central control unit, wherein all battery packs are interconnected with the central control unit via a CAN communication bus for transmitting power data, status information and control commands.

[0017] Compared with existing technologies, the power balancing control method, device, and energy storage equipment of this invention for energy storage systems achieve automatic address allocation, differential pressure threshold-triggered balancing mode, and dynamic battery pack screening control based on charge / discharge states. Furthermore, it combines LLC circuit operating mode control to achieve hardware-level management of charge / discharge permissions for individual battery packs. This invention can easily expand the system scale without manual address configuration, significantly improving the intelligence and response speed of power balancing between battery packs. It effectively protects low-capacity battery packs during discharge and high-capacity battery packs during charging, preventing premature aging of individual battery packs due to overcharging and discharging, thereby maintaining the capacity of each battery pack near the average level and delaying the overall performance degradation of the energy storage system. Simultaneously, hardware-enforced measures ensure safety under extreme operating conditions, improving the reliability of system operation. [Attached Image Description] Figure 1 This is a flowchart of the power balancing control method for energy storage systems according to the present invention; Figure 2 This is a structural diagram of the power balancing control device for energy storage systems according to the present invention.

Detailed Implementation Methods

[0018] It should be noted that in the embodiments of the present invention, all directional indications (such as up, down, left, right, front, back, etc.) are limited to relative positions on the specified view, rather than absolute positions.

[0019] Furthermore, in this invention, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0020] Please see Figure 1 and Figure 2 The energy balance control method for energy storage systems of the present invention, after the battery pack (battery cell) balance control method logic starts, the BMS system starts up and the local controller (local cell or local control unit) is initialized, including the following steps: Step S1, initial power-on and automatic address allocation.

[0021] In step S1, when the system is powered on for the first time, each battery pack automatically assigns an address via the CAN communication bus, without requiring manual configuration. After successful address assignment, each battery pack has a unique identifier. This process is completely automatic, requiring no manual dialing or setting, laying the foundation for subsequent accurate data exchange based on addresses.

[0022] Step S2: Obtain the battery pack charge levels.

[0023] In step S2, the local controller of each battery pack collects its own current power (such as voltage, current and SOC) through the acquisition protection chip, and shares the information through the CAN communication bus, thereby obtaining the current power of other battery packs in the system, and the system enters the normal operation cycle.

[0024] Step S3: Sort the battery pack capacity.

[0025] In step S3, the local controller sorts the current battery levels of all battery packs and determines the battery packs with the highest and lowest battery levels.

[0026] Step S4: Decision on operating mode based on differential pressure.

[0027] In step S4, the local controller of each battery pack collects power data from all other battery packs in the system.

[0028] The maximum voltage difference ΔV_max is obtained by calculating the voltage difference between any two battery packs in the system.

[0029] Compare ΔV_max with the preset differential pressure threshold (ΔV_set).

[0030] If ΔV_max ≤ the preset differential voltage threshold: the system enters "normal mode". All battery packs participate in charging and discharging together according to the total system demand to provide maximum throughput. In "normal mode", within the platform voltage range, the system operates at an open-loop fixed resonant frequency, and both the LLC circuit and the synchronous rectification circuit operate normally to achieve efficient bidirectional energy flow and provide maximum throughput.

[0031] If ΔV_max > preset differential pressure threshold: the system enters "equilibrium mode". Subsequent steps are then executed, including priority scheduling.

[0032] Step S5: Determine the system's charging and discharging status.

[0033] In step S5, the central control unit determines whether the entire energy storage system is currently in a discharging state (supplying power to the load) or a charging state (being charged by an external power source) based on the direction of the total load or the total bus current. The operating state of the DC-DC unit changes accordingly based on the current state of the system.

[0034] Step S6: If the system is in a discharge state, execute the discharge screening algorithm. That is, enter the discharge equalization mode.

[0035] In step S6, the core of the algorithm is to prioritize discharging the battery pack with higher charge to protect the battery pack with lower charge and prevent it from being damaged due to over-discharge.

[0036] Implementation details: Based on the ranking results, battery packs with power levels higher than the average or a set threshold are selected, and a "discharge allowed" command is executed on these battery packs. For battery packs with lower power levels (e.g., the lowest 1-2) or those with extremely low voltage, a "discharge prohibited" command is executed. The DC-DC converters of these prohibited battery packs will be controlled in a "chargeable but not dischargeable" mode by their local controller.

[0037] Step S7: If the system is in a charging state, execute the charging screening algorithm. That is, enter the charging equalization mode.

[0038] In step S7, the core of the algorithm is to prioritize charging the battery packs with lower power levels to protect the battery packs with higher power levels and prevent them from being damaged due to overcharging.

[0039] Implementation details: Based on the sorting results, battery packs with power levels below the average or a set threshold are selected, and a "charge allowed" command is executed for these battery packs. For battery packs with high power levels (e.g., the top 1-2) or those at extremely high voltage, a "charge prohibited" command is executed. The DC-DC converters of these prohibited battery packs will be controlled in a "dischargeable but not rechargeable" mode by their local controller.

[0040] Step S8 is executed repeatedly.

[0041] In step S8, steps S2 to S7 are repeated cyclically, so that the power of each battery pack continuously converges to the average value during dynamic adjustment until ΔV_max falls back to within the preset differential pressure threshold, and the system returns to "normal mode".

[0042] The control of the LLC circuit by the local MCU or DSP is the key to implementing the above-mentioned "discharge prohibited" and "charging prohibited" instructions, as well as dealing with extreme voltages.

[0043] Normal mode: Within the platform voltage range, the system operates at the open-loop fixed resonant frequency, and both the LLC circuit and the synchronous rectifier circuit operate normally, achieving efficient bidirectional energy flow.

[0044] No-load / low-load intermittent operation: To improve efficiency under light load, the MCU or DSP will control the circuit to enter an intermittent operating mode to reduce switching losses.

[0045] "Chargeable but not dischargeable" mode (corresponds to a low-battery pack being prohibited from discharging or the pack being at extremely low voltage): Triggering conditions: Receiving a system-level "discharge prohibited" command, or the local AFE chip detecting that the packet voltage is lower than the extremely low protection threshold.

[0046] Control action: The MCU or DSP controls the high-voltage side LLC circuit to work, while the low-voltage side synchronous rectifier circuit is turned off.

[0047] Effect: External electrical energy can charge the battery pack through the transformer and the working LLC circuit; however, due to the shutdown of the synchronous rectification, the energy of the battery pack cannot be released to the external load through the DC-DC unit, thus achieving "chargeable but not dischargeable".

[0048] "Disposable but not rechargeable" mode (corresponds to high-capacity packs being prohibited from charging or the pack being at extremely high voltage): Triggering conditions: Receiving a system-level "disable charging" command, or the local AFE chip detecting that the package voltage is higher than the extremely high protection threshold.

[0049] Control action: The STM32 controls the high-voltage side LLC circuit to shut down, while the low-voltage side synchronous rectifier circuit operates.

[0050] Effect: The energy of the battery pack can be discharged to the external load through the synchronous rectifier circuit and transformer; however, since the LLC circuit is closed, external power cannot charge the battery pack, thus achieving "dischargeable but not rechargeable".

[0051] The present invention provides a system-level dynamic collaborative balancing method: treating multiple parallel battery packs as a whole, and introducing a voltage difference threshold (such as ΔV_set) as a trigger condition through real-time power and voltage monitoring and communication, switching between "normal mode" and "balancing mode"; and in balancing mode, dynamically and specifically determining which packs should be prohibited from charging or discharging based on the macroscopic state of the system being charged or discharged, thereby achieving intelligent convergence of power between packs.

[0052] After the system is powered on for the first time, each battery pack automatically obtains a unique logical address through the communication bus, which simplifies the installation process, eliminates the need for manual intervention, and improves installation efficiency and reliability.

[0053] By individually controlling the operating states of the high-voltage and low-voltage switching transistors of the LLC circuit, the function of "charging only" or "discharging only" for a battery pack is realized at the hardware level, providing reliable execution guarantee for the above balancing strategy and improving safety in extreme situations.

[0054] The present invention provides a power balancing control device for an energy storage system, which is integrated inside a battery pack (battery cell) and includes a local controller, a data acquisition and protection chip, a battery cell, and a DC-DC unit. The data acquisition and protection chip is connected to the local controller, the battery cell is connected to the data acquisition and protection chip, and the DC-DC unit is connected to both the battery cell and the local controller.

[0055] The DC-DC unit includes a high-voltage side LLC circuit, a transformer, and a low-voltage side synchronous rectifier circuit. The high-voltage side LLC circuit and the low-voltage side synchronous rectifier circuit are respectively connected to the transformer, and the high-voltage side LLC circuit and the low-voltage side synchronous rectifier circuit are respectively connected to the local controller.

[0056] Each battery pack is an independent energy unit. Each battery pack consists of 1P16S lithium iron phosphate cells with a nominal voltage of 51.2V.

[0057] The data acquisition and protection chip uses an AFE model chip, which is responsible for collecting data such as voltage, current, and temperature of the cells in this battery pack, and provides overvoltage, undervoltage, and overcurrent protection functions.

[0058] The local controller uses an MCU or DSP microcontroller to communicate with the AFE chip of the battery pack and to manage charging and discharging by controlling the DC-DC unit.

[0059] The MCU or DSP microcontroller controls the switching transistors of the high-voltage side LLC circuit and the low-voltage side synchronous rectifier circuit through PWM signals.

[0060] The high-voltage side to low-voltage side turns ratio of the transformer is 7:1.

[0061] The present invention also provides an energy storage device, including multiple independent battery packs and a central control unit. All battery packs are interconnected with the central control unit via a CAN communication bus for transmitting power data, status information and control commands.

[0062] Compared with the prior art, the power balancing control method, device, and energy storage equipment of the present invention for energy storage systems have the following advantages: 1. By automatically assigning addresses, the inefficiency and error-prone nature of manually configuring battery pack addresses are resolved.

[0063] 2. Real-time acquisition and sorting of the power levels of all battery packs, and intelligent selection of battery packs that should participate or should be avoided based on whether the system is in a charging or discharging state, to achieve system-level collaborative balancing.

[0064] 3. When the pressure difference between the packages exceeds the set threshold (e.g., ΔV_set), it automatically enters the priority charging and discharging equalization mode; when the pressure difference returns to within the threshold, it resumes the normal common charging and discharging mode to balance equalization efficiency and system throughput.

[0065] 4. When the battery pack voltage is at an extreme level, the system can control the operating mode of the LLC circuit and the synchronous rectifier circuit to achieve the function of "can be charged but not discharged" or "can be discharged but not charged", thereby improving system safety.

[0066] 5. The power of each battery pack in the energy storage device is dynamically maintained within an average range, which slows down the overall lifespan degradation of the energy storage device, prevents individual battery packs from deteriorating prematurely due to long-term operation in poor power range, and ensures consistency among battery packs.

[0067] The above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any modifications, equivalent substitutions and improvements made within the concept of the present invention should be included within the patent protection scope of the present invention.

Claims

1. A power balancing control method for an energy storage system, characterized in that, Includes the following steps: Step S1, initial power-on and automatic address allocation: When the system is powered on for the first time, each battery pack automatically performs address allocation through the CAN communication bus. After successful address allocation, each battery pack has a unique identifier. Step S2: Obtain the power level of all battery packs. The local controller of each battery pack collects its own current power level through the acquisition protection chip and shares the information through the CAN communication bus. Step S3: Sort the battery pack power levels. The local controller sorts the current power levels of all battery packs and determines the battery packs with the highest and lowest power levels. Step S4: Based on the voltage difference, the operating mode decision is made. The voltage difference between any two battery packs in the system is calculated to obtain the maximum difference ΔV_max. ΔV_max is compared with the preset voltage difference threshold. If ΔV_max ≤ the preset voltage difference threshold, the system enters the normal mode. If ΔV_max > the preset voltage difference threshold, the system enters the equalization mode. Step S5: Determine the charging and discharging status of the system. The central control unit determines whether the entire energy storage system is currently in a discharging or charging state based on the direction of the total load or the total bus current. The working state of the DC-DC unit changes accordingly based on the current state of the system. Step S6: If the system is in a discharge state, execute the discharge screening algorithm; Step S7: If the system is in a charging state, execute the charging screening algorithm; Step S8: Repeat steps S2 to S7 to make the power of each battery pack continuously converge toward the average value in dynamic adjustment until ΔV_max falls back to within the preset differential pressure threshold, and the system returns to normal mode.

2. The power balancing control method for an energy storage system as described in claim 1, characterized in that, The preset differential pressure threshold is ΔV_set.

3. The power balancing control method for an energy storage system as described in claim 1, characterized in that, In step S4, under normal mode, all battery packs participate in charging and discharging together according to the total system demand; within the platform voltage range, the system operates at an open-loop fixed resonant frequency, and both the LLC circuit and the synchronous rectifier circuit operate normally, achieving efficient bidirectional energy flow.

4. The power balancing control method for an energy storage system as described in claim 1, characterized in that, In step S6, battery packs with power levels higher than the average power level or a certain set threshold are selected, and discharge permission commands are executed on these battery packs; for battery packs with lower power levels, discharge prohibition commands are executed.

5. The power balancing control method for an energy storage system as described in claim 1, characterized in that, In step S7, battery packs with power levels below the average power level or a certain set threshold are selected, and charging instructions are executed for these battery packs; for battery packs with higher power levels, charging instructions are executed.

6. A power balancing control device for an energy storage system, characterized in that, Integrated within the battery pack, the system includes a local controller, a data acquisition and protection chip, battery cells, and a DC-DC converter unit. The data acquisition and protection chip is connected to the local controller, and the battery cells are connected to the data acquisition and protection chip. The DC-DC converter unit is connected to both the battery cells and the local controller. The DC-DC converter unit includes a high-voltage side LLC circuit, a transformer, and a low-voltage side synchronous rectification circuit. The high-voltage side LLC circuit and the low-voltage side synchronous rectification circuit are connected to the transformer and the local controller, respectively. The local controller controls the switching transistors of the high-voltage side LLC circuit and the low-voltage side synchronous rectification circuit via PWM signals.

7. The power balancing control device for an energy storage system as described in claim 6, characterized in that, Each battery pack is an independent energy unit; each battery pack consists of 1P16S structure composed of lithium iron phosphate cells with a nominal voltage of 51.2V.

8. The power balancing control device for an energy storage system as described in claim 6, characterized in that, The data acquisition and protection chip uses an AFE model chip, which is responsible for collecting voltage, current, and temperature data of the cells in this battery pack.

9. The power balancing control device for an energy storage system as described in claim 8, characterized in that, The local controller uses an MCU or DSP microcontroller to communicate with the AFE chip of the battery pack and to manage charging and discharging by controlling the DC-DC unit.

10. An energy storage device, characterized in that, It includes multiple independent battery packs and a central control unit. All battery packs are interconnected with the central control unit via a CAN communication bus to transmit power data, status information and control commands.

Images