SOC control method and system based on voltage droop equalization

Abstract

The invention discloses an SOC control method and system based on voltage droop equalization, and the method comprises the steps: reading a sampled total voltage value through ADC sampling, and reading a current soc value stored in a memory; according to a droop algorithm, distributing the power and the voltage value of each module according to the soc values from large to small; the distributed power value and voltage value are optimized, the voltage value is used as a correction fine tuning outer ring, and the power emitted by the pack with the larger SOC value is controlled to be larger, so that the soc between the packs is balanced, and in a pure direct current energy storage cabinet system, when the DC-DC cascade system works in a PWM state to perform active balance control, the power of the pack is balanced, and the power of the pack is balanced. The bus voltage of the DC-DC in the PWM state is distributed according to the SOC difference of the modules, so that the different DC-DC can operate according to the maximum power and the minimum power in the PWM state, and the SOC of the battery modules with the large difference is converged to the average value at the fastest speed.

Description

Technical Field

[0001] The present invention belongs to the field of control of the charge / discharge power conversion system of an electrochemical energy storage battery, and realizes the balanced control of the state of charge (SOC) between different battery modules during the charging and discharging dynamic process of the battery energy storage system. Specifically, it relates to a voltage droop-based SOC control method and system. Background Art

[0002] It is of great significance in improving battery utilization and ensuring the safe and stable operation of the system. By adding a DC-DC converter between each battery module and the grid-side voltage source converter PCS, an obvious benefit is that the charging / discharging power of each battery module can be continuously adjusted by adjusting the power of the DC-DC converter operating in the PWM state, and the power of each battery module can be adjusted according to the states such as the SOC and temperature of each battery module, which is convenient for realizing the balanced control of the module state. Then, how to reasonably design the control method, which not only achieves the balance goal, but also completes the constant power, constant current, and constant voltage operation modes of battery charging and discharging, and also enables the system to operate stably, becomes an important issue.

[0003] Taking the cascaded energy storage system as the background, the present invention mainly proposes a control strategy related to the PWM state of the DC-DC converter. On the one hand, it uses the largest bus voltage difference between the DC-DC converters to make the largest SOC difference in the cascaded system decay as soon as possible. On the other hand, it keeps the sum of the DC-DC bus voltages in the cascade equal to the DC voltage reference value of the PCS.

[0004] For example, in Chinese Patent Application No.: 202211204986.5, an additional balance circuit between adjacent battery modules is provided. Its balanced power flow does not pass through the external charge / discharge interface, so the balance can also be carried out when there is no energy exchange with the outside. The disadvantage is that the balanced control between relatively far modules has to go through a large number of components, resulting in high power loss; the sum of the battery module voltages drops after bypass and cannot be compensated, and the system cannot operate normally when the sum of the battery module voltages drops below the PCS. In terms of balanced control, the distribution of the converter power among multiple modules becomes a difficult point.

[0005] Chinese Patent Application Number for Invention: 202310209921.8. An equalizing DC bus is added outside the battery module. All series-connected battery modules are connected to the equalizing DC bus through isolated DC-DC converters. The equalization between any two modules can independently turn on the corresponding DC-DC converter. The equalization between battery modules only passes through two of the said DC-DC converters, and the loss is relatively small compared to the equalization power transfer loss of non-adjacent modules in the previous reference patent. However, the cost of the isolated DC-DC converter is relatively high, and the volume, weight, and heat generation problems of the isolation transformer are not conducive to integration with the battery module. Similarly, the total voltage of the battery module decreases after bypass and cannot be compensated. Since each DC-DC converter operates independently, the degree of freedom of its control strategy is relatively large.

[0006] In the above two typical reference patents, since the power of the equalizing DC-DC converter is decoupled from the grid-side power, the equalization control has little impact on the operation of the grid-side converter. The series voltage is only related to the voltage of the battery module, and there is no requirement for the total voltage of the converter.

[0007] Chinese Patent Application Number for Invention: 202310366020.X. A power electronic half-bridge switch is connected in parallel at both ends of the battery module. By closing the upper switch tube, the battery module is connected, and multiple battery modules are connected in series. By closing the lower switch tube, the battery module is disconnected. Compared with directly connecting the battery modules in series to form a high-voltage energy storage battery cluster, it is convenient to connect or disconnect a certain battery module or some battery modules. Pulse modulation is performed on the drive signals of the upper and lower switch tubes to achieve voltage regulation. In this application, a switching device is also added on the basis of the half-bridge module to enable adjacent modules to switch between series and parallel connections, increasing the degree of control freedom, but it does not mention the equalization control strategy.

[0008] Chinese Patent Application Number for Invention: 202310162462.2. After the battery modules are connected in series into clusters through DC-DC converters, multiple clusters are connected in parallel to form a battery matrix. This invention aims at SOC equalization and proposes a method for distributing the total current among clusters and a method for distributing the cluster voltage among the modules within the cluster. However, the voltage distribution among the modules within the cluster is restricted by the SOC ratio relationship, and the fastest SOC equalization speed that can be brought by the upper and lower power limits of the DC-DC converter is not utilized.

[0009] The prior art introduces a DC-DC converter between the battery module and the grid-side voltage source converter PCS, and realizes continuous adjustment of the charging and discharging power of each battery module by adjusting the power in its PWM working state. This can perform power distribution according to state parameters such as the SOC and temperature of each module, which is beneficial to realizing the balanced control of the module state. In a cascaded energy storage system, by designing relevant control strategies for the PWM state of the DC-DC converter, the maximum bus voltage difference between DC-DC converters can be effectively utilized to accelerate the attenuation of the SOC difference in the cascaded system, while keeping the sum of the cascaded DC-DC bus voltages equal to the DC voltage reference value of the PCS. By setting an equalizing power flow in the balancing circuit of adjacent additional battery modules, an equalizing operation can be realized without energy exchange with the outside. And by adding an equalizing DC bus outside the battery module, all series-connected battery modules can be connected to the bus through an isolated DC-DC converter, so as to realize the balanced control between any two modules. In the scheme of paralleling a power electronic half-bridge switch at both ends of the battery module, the upper tube of the switch is controlled to close to realize the series connection of multiple battery modules, and the lower tube is closed to withdraw the corresponding module, so as to flexibly adjust the access state of the modules in the system. In a system where battery modules are connected in series through a DC-DC converter and then multiple clusters are connected in parallel, the prior art has proposed a method for distributing the total current between clusters with the goal of SOC balance, and a method for distributing the cluster voltage between modules. These technical solutions all reflect the idea of power regulation through a DC-DC converter, providing an important reference for the balanced control of battery modules. At the same time, the prior art has also explored various application schemes of DC-DC converters in battery module series systems, providing broad ideas for the research of system control methods. However, for the system architecture in which the battery module is only connected to the DC-DC converter and directly connected to the grid-side converter PCS after being connected in series through the DC-DC converter, its corresponding specific control method and innovative technical solution are still insufficient, especially lacking in-depth research and systematic solutions in terms of system-level control strategies and optimization algorithms, which indicates that further exploration and more innovative ideas are still needed in this field to improve the design and control of such systems. Summary of the Invention

[0010] The purpose of the present invention is to provide a voltage droop-based balanced SOC control method and system to overcome the deficiencies of the prior art.

[0011] To achieve the above purpose, the technical solution adopted by the present invention is as follows: A voltage droop-based balanced SOC control method includes the following steps: S1, read the sampled total voltage value through ADC sampling, and read the current soc value stored in the memory; S2. According to the droop algorithm, allocate the power magnitude and the voltage value of each module in descending order of the SOC value. S3. Optimize under the allocated power value and voltage value. The voltage value serves as the correction fine-tuning outer loop, controlling the pack with a larger SOC value to emit more power, thereby balancing the SOC between packs.

[0012] Preferably, obtain the voltage signal through a voltage division circuit or a direct sampling circuit, and convert the analog signal into a digital signal with the aid of an ADC chip.

[0013] Preferably, use a voltage division circuit to obtain the voltage signal and convert it into a digital signal through an ADC chip: after the external voltage is input, a voltage division circuit composed of precision resistors is adopted to attenuate the high-voltage signal proportionally within the range of the ADC chip's measurement range.

[0014] Preferably, the direct sampling circuit obtains the voltage signal and converts it into a digital signal through an ADC chip: the signal conditioning circuit constructed by an operational amplifier buffers and filters the voltage signal and then inputs it into the ADC chip.

[0015] Preferably, according to the droop algorithm, allocate the power magnitude and the voltage value of each module in descending order of the SOC value. The droop algorithm realizes the dynamic allocation of energy by constructing an accurate power distribution matrix.

[0016] Preferably, the power distribution formula adopted by the droop algorithm is: P_i = P_{max}×(SOC_i - SOC_{min}) / (SOC_{max} - SOC_{min}); where P_i is the power allocated to the i-th module, P_{max} is the maximum allowable allocated power, SOC_i is the SOC value of the i-th module, and SOC_{max} and SOC_{min} are the maximum and minimum SOC values among all modules respectively.

[0017] Preferably, the voltage value is superimposed as the correction fine-tuning outer loop, and the superimposing method includes weighted summation of the voltage error signal and the output of the droop power control algorithm.

[0018] A voltage droop-based SOC balancing control system, including a sampling module, a power distribution module, and a control module; The sampling module reads the total sampled voltage value through ADC sampling and reads the current SOC value stored in the memory; The power distribution module allocates the power magnitude and the voltage value of each module in descending order of the SOC value according to the droop algorithm; The control module optimizes the allocated power value and voltage value. The voltage value serves as the outer loop for calibration and fine-tuning, controlling the power output of packs with larger SOC values to be greater, thereby balancing the SOC among packs.

[0019] Preferably, a voltage signal is obtained through a voltage division circuit or a direct sampling circuit, and the analog signal is converted into a digital signal with the aid of an ADC chip.

[0020] Preferably, a voltage division circuit is used to obtain the voltage signal and convert it into a digital signal through an ADC chip: after the external voltage is input, a voltage division circuit composed of precision resistors is adopted to attenuate the high-voltage signal proportionally within the range of the ADC chip; a direct sampling circuit obtains the voltage signal and converts it into a digital signal through an ADC chip: the voltage signal is buffered and filtered by a signal conditioning circuit constructed by an operational amplifier and then input into the ADC chip.

[0021] Compared with the prior art, the present invention has the following beneficial technical effects: The present invention provides a method for balancing SOC based on voltage droop control. The total voltage value of the sample is read through ADC sampling, and the current SOC value stored in the memory is read; according to the droop algorithm, the power magnitude and the voltage value of each module are allocated in descending order of the SOC value; the allocated power value and voltage value are optimized. The voltage value serves as the outer loop for calibration and fine-tuning, controlling the power output of packs with larger SOC values to be greater, thereby balancing the SOC among packs. In a pure DC energy storage cabinet system, when the DC-DC cascade system operates in the PWM state for active balancing control, the bus voltage magnitude of the PWM state of the DC-DC is allocated according to the SOC difference among the modules, enabling different DC-DCs to operate at the maximum power and minimum power respectively in the PWM state, and enabling the SOC of battery modules with large differences to converge to the average value at the fastest speed.

[0022] Through the design of weighted summation, the system can effectively avoid the failure problem of droop control under low-power conditions while maintaining the constancy of the total bus voltage, improving the stability and response speed of the system. Description of the Drawings

[0023] Figure 1 It is a flowchart of the method for balancing SOC based on voltage droop control in an embodiment of the present invention.

[0024] Figure 2 It is a diagram of a module-level cascade battery energy storage system based on a DC-DC converter in an embodiment of the present invention.

[0025] Figure 3 It is a diagram of the total power control of the balancing controller in an embodiment of the present invention.

[0026] Figure 4 It is a schematic diagram of bus voltage distribution in the discharge mode in the embodiment of the present invention.

[0027] Figure 5 It is a schematic diagram of bus voltage distribution in the charging mode in the embodiment of the present invention.

[0028] Figure 6 It is a process diagram of calculating the upper and lower limits of the bus voltage in the embodiment of the present invention. Specific embodiments

[0029] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0030] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of the present invention described herein can be implemented in an order different from those illustrated or described herein. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0031] As Figure 1 shown, the present invention provides a voltage droop-based equalization SOC control method, which specifically includes the following steps: S1, read the total voltage value of the sample through ADC sampling, and read the current soc value stored in the memory; S2, according to the droop algorithm, allocate the power magnitude and the voltage value of each module in the order from large to small of the soc value; S3. Optimize at the allocated power value and voltage value. The voltage value serves as the correction fine-tuning outer loop, controlling the power output of the pack with a larger SOC value to be greater, thereby equalizing the SOC among packs. The present invention conducts active equalization control through a DC-DC cascaded system in the PWM state. According to the SOC (State of Charge) differences of battery modules, the bus voltage of the DC-DC is dynamically allocated, enabling the modules with larger differences to operate at maximum power or minimum power, thus accelerating the equalization convergence of the SOC. This control method not only improves the operating efficiency of the battery energy storage system but also ensures the stability of the total bus voltage after cascading through measures such as speculation, allocation, and correction compensation, avoiding the impact of voltage fluctuations on the system. At the same time, the scheme adopts a constant power mode, with the PCS operating in a constant voltage mode and the DC-DC operating in a constant power mode, further optimizing the power distribution and enabling the SOC differences among modules to quickly tend to be consistent. Through the droop control mechanism, the allocation of the bus voltage is directly related to the SOC value. During charging, the module with a low SOC obtains a higher voltage, and during discharging, the module with a high SOC obtains a higher voltage, ensuring the rapid response and precise execution of the equalization control. This design has significant advantages in the battery energy storage system, effectively extending the battery life and improving the overall performance of the system.

[0032] In the specific embodiment of the present application, the ADC sampling technology is utilized to obtain the voltage signal through a voltage division circuit or a direct sampling circuit, and the analog signal is converted into a digital signal by means of an ADC chip, achieving the precise measurement of the total voltage value of the battery module.

[0033] The method of ADC sampling to read the sampled total voltage value includes using a voltage division circuit or a direct sampling circuit to obtain the voltage signal and converting it into a digital signal through an ADC chip.

[0034] In the specific embodiment of the present application, a voltage division circuit is used to obtain the voltage signal and convert it into a digital signal through an ADC chip: after the external voltage is input, a voltage division circuit composed of precision resistors is adopted to attenuate the high-voltage signal proportionally within the range of the ADC chip's measurement range.

[0035] The direct sampling circuit obtains the voltage signal and converts it into a digital signal through an ADC chip: the voltage signal is buffered and filtered by a signal conditioning circuit constructed by an operational amplifier and then input into the ADC chip. Both circuit solutions transmit the analog voltage signal to the analog input terminal of the ADC chip, utilize the successive approximation register (SAR) or Σ-Δ modulator inside the chip for analog signal digital conversion, and output the conversion result to the microcontroller for processing through a parallel or serial interface.

[0036] Specifically, according to the droop algorithm, the power magnitude and the voltage value of each module are allocated in the order of decreasing SOC value. The droop algorithm realizes dynamic energy allocation by constructing an accurate power distribution matrix, and its power distribution formula is calculated based on accurate SOC parameters. The power distribution formula adopted by the droop algorithm is: P_i = P_{max}×(SOC_i - SOC_{min}) / (SOC_{max} - SOC_{min}); Where P_i is the power allocated to the i-th module, P_{max} is the maximum allowable allocated power, SOC_i is the SOC value of the i-th module, and SOC_{max} and SOC_{min} are the maximum and minimum SOC values among all modules respectively. The above parameterized power distribution method ensures the accuracy and dynamic reliability of energy transmission. It can dynamically adjust the power output according to the SOC difference of the modules, ensuring that the high-SOC module outputs less power and the low-SOC module outputs more power, so as to quickly converge to the average SOC level during the charging or discharging process. Through this mechanism, the system can achieve precise control of the bus voltage in the PWM state of DC-DC cascade and ensure the stability of the total bus voltage, avoiding energy waste or shortened battery life caused by SOC imbalance. This design not only improves the balancing efficiency of the energy storage system, but also enhances the reliability and response speed of the system, and is applicable to large-scale energy storage scenarios such as power grid peak shaving and renewable energy integration, with significant practical application value.

[0037] Optimize under the allocated power value and voltage value. The voltage value to be optimized is within the allowable fluctuation range of the module rated voltage; specifically, the voltage value range is controlled between 90% and 110% of the module rated voltage. Specifically, for a module with a nominal voltage of 12V, the optimizer limits the received voltage value within the range of 10.8V to 13.2V; for a module with a nominal voltage of 24V, it is limited between 21.6V and 26.4V. This range setting is based on the safe operation characteristics of the module and the requirements of relevant electrical codes, ensuring that the optimizer can reliably receive and process voltage signals during the normal operation of the module, and at the same time avoiding data distortion or equipment damage caused by too high or too low voltage.

[0038] In the specific implementation manner of this application, the voltage value is superimposed as a correction fine-tuning outer loop, and the superimposing method includes weighted summation of the voltage error signal and the output of the droop power control algorithm.

[0039] After preprocessing the voltage error signal and the output of the droop power control algorithm respectively, a linear weighted summation calculation is performed on the two through a preset weight coefficient. Among them, after the voltage error signal is processed by a first-order low-pass filter, it is superimposed on the output value of the droop power control algorithm with an adjustment factor. The weighted summation coefficient is dynamically adjusted according to the system operating state to ensure effective fine-tuning correction under different working conditions. At the same time, the output value after weighted summation is limited within a preset safe range to prevent overshoot or undershoot of the system.

[0040] The equalization process of the SOC continues until the difference in the SOC values of all modules is within the preset threshold range.

[0041] When the DC-DC cascade system operates in the PWM state for active equalization control, the bus voltage magnitude of the PWM state of the DC-DC is allocated according to the difference in the SOC of the modules, so that different DC-DCs can operate at the maximum power and the minimum power respectively in the PWM state, and the SOC of the battery modules with larger differences converges to the average value at the fastest speed.

[0042] By adopting a DC-DC cascade system in a pure DC energy storage cabinet system and combining active equalization control in the PWM (pulse width modulation) state, efficient equalization of the SOC (state of charge) of battery modules is achieved. The voltage value range received by the optimizer is within the allowable fluctuation range of the rated voltage of the module, which not only ensures the stability of the system operation, but also effectively prevents damage to the battery module caused by overvoltage or undervoltage. By allocating the bus voltage in the PWM state of the DC-DC according to the difference in the SOC of the modules, the system can make different DC-DCs operate at the maximum power and the minimum power respectively, thereby accelerating the convergence of the SOC of the battery modules with larger differences to the average value and significantly improving the equalization efficiency. In addition, the constant control of the total bus voltage further maintains the voltage stability of the system through measures such as speculation, allocation, and correction compensation, ensuring the reliability of the equalization process. This design is not only applicable to large-scale energy storage systems, but also can effectively extend the service life of battery modules and improve the energy efficiency ratio of the overall system. For example, in an actual energy storage power station, this equalization control strategy can help quickly balance the charge and discharge states of battery modules in energy systems with large fluctuations such as photovoltaic or wind power generation, thereby improving the stability and energy utilization rate of the system.

[0043] For the constant control of the total bus voltage, in the equalization control algorithm, the stability of the total bus voltage after cascading is maintained through the designed measures such as speculation, allocation, and correction compensation.

[0044] The equalization process of the SOC monitors the SOC values of each module in the system in real time, and adopts a combination of active equalization and passive equalization. Among them, active equalization transfers energy between adjacent modules by controlling the energy transfer circuit, and passive equalization dissipates energy through a shunt resistor. At the same time, the equalization current is set within the range of 1-5A to balance the equalization efficiency and safety. Finally, when the difference between the SOC values of all modules and the target value is within the preset threshold range of ±0.5%, the system automatically terminates the equalization process and enters the standby state.

[0045] The superimposed manner of the correction and fine-tuning outer loop further optimizes the system performance by performing weighted summation on the voltage error signal and the output of the droop power control algorithm. The present invention uses droop control to dynamically adjust the output power of the battery module, and the droop coefficient is used to adjust the proportion of current distribution. During the SOC equalization control process, the system accurately distributes the bus voltage of the DC-DC converter according to the state of charge (SOC) difference of the battery modules, so that the high-SOC module and the low-SOC module operate at the minimum power and the maximum power respectively, thereby accelerating the equalization convergence of the SOC. Through the design of weighted summation, the system can effectively avoid the failure problem of droop control under low-power conditions while maintaining the constant total bus voltage, improving the stability and response speed of the system. This strategy significantly improves the service life and energy utilization efficiency of the battery pack in practical applications, especially in multi-level energy storage systems that require rapid equalization of battery modules.

[0046] The module-cascaded battery energy storage system based on the DC-DC converter is as Figure 2 shown: A battery module is composed of several energy storage battery monomers connected in series. A non-isolated DC-DC converter (abbreviated as DC-DC) is added between each battery module and the grid-side voltage source converter PCS. The DC-DC has a battery-side port and a bus-side port, and integrates a supporting control unit.

[0047] At the output end of the battery module, the DC-DC battery-side port is first connected to form a power electronic battery pack. The positive pole of the module is connected to the battery-side positive pole BATP of the DC-DC, and the negative pole of the module is connected to the battery-side negative pole BATN of the DC-DC; there is only one connection point between two adjacent DC-DCs, and the positive pole BUSP is connected to the negative pole BUSN, so that the battery modules are indirectly connected in series into a cluster, and the whole cluster is connected to the DC port of the grid-side front-end power converter PCS to connect the battery cluster to the grid. The state of the battery module is monitored by the module-level battery management unit BMU and sent to the main control unit RCU of the battery management system. RCU sends the module port voltage and module SOC required by the present invention to the equalization controller SBC. All state switching logics and control algorithms described in the present invention are executed in the SBC, and control instructions are sent to each DC-DC.

[0048] The instructions issued by the SBC include the control reference value I of the current magnitude of each DC-DC ref .

[0049] In the present invention, the SOC of each module has been sent from the RCU to the SBC, and the problem of obtaining the SOC of the battery module is not involved. As Figure 6 shown, the control reference value of the total DC-DC bus voltage of the SBC, that is, the DC voltage command V of the PCS RPCS can be sent by the upper-level communication or preset. The SBC uses each SOC value and I ref , and the droop coefficient G P and V RPCS and other necessary signals to calculate the I of each DC-DC ref .

[0050] In the present invention, the system is in a constant power mode, where the PCS operates in a constant voltage mode, and each DC-DC operates in a constant power mode. Therefore, the DC-side current of the PCS follows the current of the DC-DC bus-side port, and the sum of the DC-DC bus-side voltages V bus is equal to the DC-side voltage of the PCS. By the battery voltage and the droop coefficient K G distributing the current magnitude of the DC-DC, the power of the DC-DC is distributed. The module SOC refers to the maximum value of the SOC of each battery cell in the module during charging and the minimum value of the SOC of each battery cell in the module during discharging.

[0051] As Figure 1 shown, the end of the DC-DC connected to the battery is the battery side, and the end cascaded with other DC-DCs is the bus side. Most of the internal switching tubes of the DC-DC are full-controlled power electronic switching devices. The DC-DC performs droop control on the current magnitude of the DC-DC through V bus , with accurate control and fast speed. Under the time scale of the dynamic process of SOC equalization control, it can be considered that the actual value V of each DC-DC bus voltage bus is the result of voltage redistribution after power distribution.

[0052] The cascade follows the concept of a power electronic converter with a sub-module series topology. The sub-modules of this type of power electronic converter operate actively and can be put into redundancy or bypassed. Cascade is commonly used instead of series to express its particularity.

[0053] As Figure 3 , V busTotal is the sum of the total bus voltages, and P ref is the power command received by the SBC equalization control. Through Figure 5 calculation, the reference I ref and V bus, so as to perform power distribution. Implement current droop control in the battery controller, make a depression amplitude for the droop product, and at the same time superimpose the bus voltage error to prevent droop failure at low power. The calculation formula for the current target value of the battery controller is as follows: ( : The battery controller receives the target current sent by the equalization controller, : The real-time bus voltage of the battery controller, V bus : The battery controller receives the target voltage sent by the equalization controller) so as to equalize the SOC.

[0054] The module realizes power redistribution by adjusting the magnitude of the bus voltage. When charging, the bus voltage allocated to the battery with low power is high, and the bus voltage allocated to the battery with high power is low, so as to achieve charging balance. At the same time, if the lowest voltage allocated exceeds the lowest voltage value V busLimitL , it is set as the lowest voltage V busLimitL , and the voltages of the remaining modules are redistributed to ensure that the total bus voltage remains unchanged, as shown in Figure 4 .

[0055] When discharging, the bus voltage allocated to the battery with low power is low, and the bus voltage allocated to the battery with high power is high, so as to achieve charging balance. At the same time, if the highest voltage allocated exceeds the highest voltage value V busLimitU , it is set as the highest voltage V busLimitU , and the voltages of the remaining modules are redistributed to ensure that the total bus voltage remains unchanged, as shown in Figure 5 .

[0056] When the DC-DC converter of the cascaded energy storage system works, the SOC equalization control is realized through three steps: (1) Distribute the power of the DC-DC according to the power SOC size, (2) Perform the DC-DC bus voltage distribution equalization control algorithm linearly according to the SOC size, (3) Adjust the DC-DC converter bus voltage control reference value again within the allowed range; In the second step of the equalization control, during the distribution according to the SOC size during discharging, when the SOC value is large, the bus voltage distribution is large, and when the SOC value is small, the line voltage distribution is small, so that the maximum and minimum SOCs of the system converge to the SOC average value at the fastest speed. During charging, when the distribution is according to the SOC size, when the SOC value is large, the bus voltage distribution is small, and when the SOC value is small, the line voltage distribution is large, so that the maximum and minimum SOCs of the system converge to the SOC average value at the fastest speed.

[0057] The SOC (State of Charge) represents the percentage of the remaining power of the battery module and is a key parameter for measuring the battery state. This technical solution adopts active equalization control in the PWM (Pulse Width Modulation) state in the DC-DC cascade system, dynamically distributes the bus voltage according to the SOC difference of the modules, and enables different DC-DCs to operate at the maximum power and the minimum power respectively, so as to quickly narrow the SOC difference between the modules and achieve efficient equalization. The core principle of this design is to ensure the rapid convergence of the battery module SOC in the constant power mode by precisely controlling the voltage and power distribution of the DC-DC. In specific implementation, measures such as speculation, distribution, and correction compensation are adopted to maintain the stability of the total bus voltage. At the same time, combined with the droop control algorithm, the current and bus voltage of the DC-DC are dynamically adjusted, so that the low-power module can obtain a higher voltage distribution during charging, and the high-power module can obtain a higher voltage distribution during discharging, ensuring the efficiency and stability of the equalization process. This solution significantly improves the speed and accuracy of the SOC equalization of the battery module, is applicable to large-scale energy storage systems, and can effectively extend the battery life and improve the overall efficiency of the system.

[0058] It should be noted that: the sequence of the above embodiments of this application is only for description and does not represent the advantages and disadvantages of the embodiments. In some cases, the actions or steps recorded in the specification and claims can be executed in a sequence different from that in the embodiments, and the desired results can still be achieved. In addition, the processes depicted in the drawings do not necessarily require a specific sequence or a continuous sequence to achieve the desired results. In some embodiments, multitasking and parallel processing are also feasible or advantageous.

[0059] Those of ordinary skill in the art can understand that all or part of the steps for implementing the above embodiments can be completed by hardware, or can be completed by a program instructing the relevant hardware. The program can be stored in a computer-readable storage medium, and the storage medium can be a read-only memory, a disk, an optical disc, etc.

[0060] The above are only the preferred embodiments of this application, and should not be construed as limitations to this application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of this application shall be included within the protection scope of this application.

Claims

1. A voltage droop-based SOC balancing control method, characterized in that It includes the following steps: S1. Read the total sampled voltage value through ADC sampling and read the current soc value stored in the memory; S2. According to the droop algorithm, allocate the power magnitude and the voltage value of each module in descending order of the soc value; S3. Optimize the allocated power value and voltage value. The voltage value serves as a correction and fine-tuning outer loop to control the larger the SOC value of the pack, the greater the power emitted, thereby balancing the soc between packs.

2. The method for controlling SOC based on voltage droop equalization according to claim 1, characterized in that Obtain the voltage signal through a voltage division circuit or a direct sampling circuit, and convert the analog signal into a digital signal with the help of an ADC chip.

3. The method for controlling the equalization of SOC based on voltage droop according to claim 2, wherein, Obtain the voltage signal using a voltage division circuit and convert it into a digital signal through an ADC chip: After the external voltage is input, a voltage division circuit composed of precision resistors is used to attenuate the high voltage signal proportionally within the range of the ADC chip; Obtain the voltage signal through a direct sampling circuit and convert it into a digital signal through an ADC chip: The voltage signal is buffered and filtered by a signal conditioning circuit constructed by an operational amplifier and then input into the ADC chip.

4. The method for controlling SOC based on voltage droop equalization according to claim 2, characterized in that, Obtain the voltage signal through a direct sampling circuit and convert it into a digital signal through an ADC chip: The voltage signal is buffered and filtered by a signal conditioning circuit constructed by an operational amplifier and then input into the ADC chip.

5. A voltage droop equalization SOC control method according to claim 1, characterized in that According to the droop algorithm, allocate the power magnitude and the voltage value of each module in descending order of the soc value. The droop algorithm realizes dynamic energy allocation by constructing an accurate power distribution matrix.

6. The method for controlling the equalization of SOC based on voltage droop according to claim 5, wherein The power distribution formula adopted by the droop algorithm is: P_i = P_{max}×(SOC_i - SOC_{min}) / (SOC_{max} - SOC_{min}); where P_i is the power allocated to the i-th module, P_{max} is the maximum allowable allocated power, SOC_i is the SOC value of the i-th module, and SOC_{max} and SOC_{min} are the maximum and minimum SOC values among all modules respectively.

7. A voltage droop-based balanced SOC control method according to claim 1, characterized in that The voltage value is superimposed as a correction and fine-tuning outer loop. The superimposing method includes weighted summation of the voltage error signal and the output of the droop power control algorithm.

8. A voltage droop-based SOC balancing control system, characterized in that, A sampling module, a power distribution module, and a control module; The sampling module reads the total sampled voltage value through ADC sampling and reads the current soc value stored in the memory; The power distribution module allocates the power magnitude and the voltage value of each module in descending order of the soc value according to the droop algorithm; The control module optimizes the allocated power value and voltage value. The voltage value serves as a correction and fine-tuning outer loop to control the larger the SOC value of the pack, the greater the power emitted, thereby balancing the soc between packs.

9. A voltage droop equalization SOC control method according to claim 8, characterized in that Obtain the voltage signal through a voltage division circuit or a direct sampling circuit, and convert the analog signal into a digital signal with the help of an ADC chip.

10. A voltage droop-based balanced SOC control method according to claim 8, characterized in that, Obtain the voltage signal using a voltage division circuit and convert it into a digital signal through an ADC chip: After the external voltage is input, a voltage division circuit composed of precision resistors is used to attenuate the high voltage signal proportionally within the range of the ADC chip; Obtain the voltage signal through a direct sampling circuit and convert it into a digital signal through an ADC chip: The voltage signal is buffered and filtered by a signal conditioning circuit constructed by an operational amplifier and then input into the ADC chip.

Images