CN115912569A - Control method of multi-branch topological structure battery system - Google Patents
Control method of multi-branch topological structure battery system Download PDFInfo
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Abstract
A control method of a multi-branch topological structure battery system belongs to the technical field of battery system energy management. The control method comprises the following steps: s1: when SOC correction is needed, selecting a cluster in a battery system, distributing charge and discharge power to complete full charge and discharge of one round, correcting the SOC of the battery to be 100% when the battery is full, and correcting the SOC of the battery to be 0% when the battery is empty; and distributing the power of the rest battery clusters according to the rest required power. S2: and after the selected battery cluster finishes one round of full discharge, the full discharge capacity after full charge obtained by the ampere-hour integration method is used as the actual available capacity of the battery, so that the battery capacity correction is realized, and the accuracy of the ampere-hour integration method is further improved. S3: and after the selected battery cluster is fully charged for one round, distributing power to enable the SOC of the battery cluster to be equal to the average value of the SOCs of the other battery clusters, and finishing the SOC correction of the battery cluster. S4: and (5) repeating the steps 1 to 3, and completing SOC correction of the remaining battery clusters one by one.
Description
Technical Field
The invention belongs to the technical field of energy management of battery systems, relates to a control method of a multi-branch topological structure battery system, and particularly relates to a multi-branch topological structure battery system control method based on full-discharge SOC correction.
Background
At present, there are two main types of battery system architectures: centralized topologies and multi-branch topologies. In the centralized topology structure, a battery pack or a battery cluster is connected in parallel on the direct current bus side of an AC/DC bidirectional converter, and the alternating current side of the converter is connected with a power grid or an alternating current load. The centralized topological structure system only comprises a single-stage structure of an AC/DC link, the control is simple, and the loss of the converter link is small. The centralized topology structure has the defects that the charging and discharging management of each battery pack string cannot be respectively carried out, and the voltage range of the direct current side is narrow; when the AC side or the DC side has faults, the DC side can bear impact current for a short time, and the service life of the battery is reduced; when the consistency of the batteries is poor, the probability of shutdown of the whole unit is protected due to inconsistency, and the maintenance workload of the consistency of the batteries is greatly increased. The multi-branch topological structure is divided into a direct current side parallel connection mode and an alternating current side parallel connection mode. For the direct-current side parallel multi-branch topological structure, each battery pack or battery cluster is firstly connected with the next level of DC/DC, and the secondary DC/DC converter is connected in parallel with the direct-current side of the AC/DC bidirectional converter to realize the multi-branch topological structure. For the alternating current side parallel multi-branch topological structure, the multi-branch topological structure is realized by adopting a multi-AC/DC converter in a parallel mode at the alternating current side, and due to the existence of a multi-machine parallel resonance factor, the expansibility of the topological structure is limited. Compared with a centralized topological structure, the multi-branch topological structure is wide in direct-current side voltage working range, the clustering charging and discharging management of the battery is easy to realize, and the multi-branch topological structure not only has better compatibility, but also has stronger expansibility and maintainability.
The state of charge, SOC, of a battery is an important measure of its performance. Specifically, in engineering applications, state of charge SOC refers to the ratio of the remaining capacity of the battery to its rated capacity at full charge. Where SOC =100% indicates that the battery is in a fully charged state, and SOC =0% indicates that the battery is in a fully discharged state. Estimation of the SOC of a battery has been a major and difficult point of battery research. The accurate SOC estimation is the main basis for ensuring the charging and discharging of the battery in the working range, and is the premise of prolonging the service life of the battery, optimizing the use working condition and ensuring the energy use efficiency.
The estimation method of the SOC of the battery comprises an open-circuit voltage method, an ampere-hour integration method, a neural network algorithm based on data driving, a Kalman filtering algorithm based on a model and the like. In engineering application, most of the current real-time online SOC estimation adopts a mode of combining an ampere-hour integration method and a Kalman filtering method based on a battery model, and an open-circuit voltage method is adopted for correction when a battery is kept still for a long time.
The ampere-hour integration-based estimation method obtains the electric quantity of a battery charged or discharged through the integration of current in time, thereby obtaining the estimation value of the SOC of the battery. The battery model has the function of realizing the relationship conversion between the battery terminal voltage and the battery OCV in the battery operation process, thereby truly and accurately realizing the accurate estimation of the battery SOC. The Kalman filtering algorithm takes an ampere-hour integration method as state estimation, takes a model algorithm as observation correction, and is essentially characterized in that the precision of the ampere-hour integration method is improved by adopting the model algorithm. The ampere-hour integration method can gradually track the change of the electric quantity of the battery, so that higher precision can be obtained in the integration process.
However, a part of batteries have wider voltage platforms, particularly lithium iron phosphate batteries, under the same temperature and the same charging and discharging working conditions, the lithium iron phosphate batteries have two voltage platforms in a 30% -90% SOC variation range, the OCV difference in the voltage platform range does not exceed 15mV, the middle-section flatness of an SOC-OCV curve influences the convergence rate of iterative algorithms such as Kalman filtering and the like, and also limits the accuracy of initial value correction in an ampere-hour integration method. Therefore, the SOC estimation accuracy of batteries with a wide voltage platform, represented by lithium iron phosphate batteries, is lower than that of other types of batteries.
The main measures for improving the accuracy of the ampere-hour integration method are as follows: the method comprises the steps of correcting the initial SOC of the battery, correcting the battery capacity of corresponding working conditions, improving the sampling precision of current and the like. Among them, the correction of the initial SOC is the most important means for improving the accuracy of the ampere-hour integration method. Among the correction methods of the initial SOC, the full-charge correction and the OCV correction are most commonly used. The full-charge correction refers to correcting the initial SOC to 100% each time the battery is fully charged using a standard method, and the OCV correction refers to recalibrating the initial SOC of the battery using a correspondence between the battery SOC and the OCV.
The Chinese invention application with the publication number of CN112345942A and the name of 'a battery system and BMS and full-charge and full-discharge SOC calibration method' provides a battery system and BMS and full-charge and full-discharge SOC calibration method thereof, which is applied to the BMS in the battery system, and after receiving parameter information reported by each CMU, an SMU records the mapping relation between the extreme monomer voltage and the SOC in each parameter information at preset voltage intervals; after receiving SOC correction parameters reported by a CMU triggering a full-discharge condition, correcting the mapping relation between the extreme single-cell voltage and the SOC corresponding to the CMU, and then sending the corrected parameters to each CMU; and each CMU carries out SOC calibration according to the current extreme single voltage and the corrected single voltage-SOC mapping relation, thereby realizing the total calibration of a plurality of parallel RACKs. The technical scheme is not suitable for a long-term shallow charging and shallow discharging battery system, and when the system is limited by actual operation conditions and is difficult to enter a full-charging and discharging state, the technical scheme cannot actively realize full-charging and discharging SOC correction; meanwhile, the technical scheme is not suitable for a multi-branch topological structure battery system, and the SOC of the batteries in the non-fully charged battery cluster is corrected through the mapping relation of the SOC, so that the high consistency of each battery cluster is required. Similar to an energy storage battery system which is utilized in an echelon manner, consistency among battery clusters of the battery system is poor, even a multi-branch topological structure of different batteries is adopted, and the technical scheme corrects the SOC through the mapping relation of the SOC and fails. In addition, the full charge and discharge SOC calibration method of the technical scheme is actually used for separating full charge correction from full discharge correction, and a battery cluster which is preferentially in a full charge state usually cannot be fully charged first, so that battery capacity correction is not easy to realize.
The initial SOC is corrected using the SOC-OCV curve of the battery, which must be robust. By robust, it is meant that the curve maintains a high degree of consistency for the same input (e.g., same temperature, SOC, etc.). For the battery with unobvious hysteresis characteristics, the OCV curve of the battery has stability, can be used as a basis for correcting the initial SOC, and can further improve the corrected ampere-hour integration method precision by a method for calibrating the SOC-OCV curve cluster of the battery. Compared with the traditional single OCV curve, the calibration precision of the initial value of the SOC can be obviously improved by using the SOC-OCV curve cluster, the application range of the method on the SOC interval is expanded, the initial value correction frequency is improved, and the error accumulation is reduced. However, some batteries have obvious hysteresis characteristics (such as lithium iron phosphate batteries), and during dynamic charge and discharge, OCV corresponding to the same SOC are different, that is, the stability of the OCV curve is poor, so that the initial SOC correction accuracy is reduced.
In summary, for a battery with a wide voltage platform or a significant hysteresis characteristic, the accuracy of the existing SOC estimation method is low. Therefore, there is an urgent need for an SOC correction method that is applicable to various batteries including such batteries and that can be applied to a multi-branched topology battery system that does not require battery consistency.
Disclosure of Invention
For batteries with a wider voltage platform or obvious hysteresis characteristics, the accuracy of the existing SOC estimation method is lower than that of other types of batteries. In order to solve the problem, the invention provides the following specific technical scheme.
A control method of a multi-branch topological structure battery system is characterized by comprising the following steps:
s1: when SOC correction is needed, selecting a cluster in a battery system, distributing charge and discharge power to complete a round of full charge and discharge: charging and fully charging the battery cluster, then discharging and discharging, wherein the SOC of the battery is corrected to be 100% when the battery is fully charged, and the SOC of the battery is corrected to be 0% when the battery is discharged; and distributing the power of the rest battery clusters according to the rest required power.
S2: and after the selected battery cluster finishes one round of full discharge, the full discharge capacity after full charge obtained by the ampere-hour integration method is used as the actual available capacity of the battery, so that the battery capacity correction is realized, and the accuracy of the ampere-hour integration method is further improved.
S3: and after the selected battery cluster is fully charged for one round, distributing power to enable the SOC of the battery cluster to be equal to the average value of the SOCs of the other battery clusters, and finishing the SOC correction of the battery cluster.
S4: and (5) repeating the steps 1 to 3, and completing SOC correction of the remaining battery clusters one by one.
The method provided by the invention realizes the SOC correction of the battery based on full charge and discharge, performs the SOC correction by full charge and full discharge in one charge and discharge cycle instead of performing the full charge SOC correction and the full discharge SOC correction independently, and can solve the technical problem that the battery with a wider voltage platform or obvious hysteresis characteristic has lower precision by using the existing SOC estimation method. The full charge and discharge in one charge and discharge cycle can also correct the actual available capacity of the battery, namely the full discharge and discharge capacity of the battery after full charge obtained by the ampere-hour integration method is used as the actual available capacity of the battery, and the precision of the ampere-hour integration method is further improved.
In engineering application, the battery is limited by the actual operation condition of the battery, and the battery can not be ensured to be in a full-charge state. The method provided by the invention realizes the full-charge and full-discharge SOC correction through the clustered charge and discharge management, and is particularly suitable for a multi-branch topological structure battery system.
Further, the remaining power of the battery clusters in step S1 is distributed evenly according to the method of distributing the remaining required power.
Further, the power of the rest of the battery clusters in the step S1 is weighted and distributed according to the respective current SOC according to the method for distributing the remaining required power.
Further, the multi-branch topological structure battery system is a direct-current side parallel multi-branch topological structure battery system.
Further, the multi-branch topological structure battery system is an alternating-current side parallel multi-branch topological structure battery system.
Furthermore, the multi-branch topological structure battery system is a large-scale battery energy storage system formed by connecting a plurality of centralized topological structure battery systems in parallel. The invention also discloses a large-scale battery energy storage system formed by connecting a plurality of centralized topological structure battery systems in parallel, which can also be regarded as a multi-branch topological structure, and the AC/DC converter direct-current side battery is regarded as a whole, namely the AC side multi-branch topological structure in parallel.
Compared with the prior art, the control method of the multi-branch topological structure battery system provided by the invention has the following beneficial effects. (1) The control method provided by the invention can solve the problem that the accuracy of the existing SOC estimation method is lower than that of other types of batteries for the batteries with wider voltage platforms or obvious hysteresis characteristics. The method does not depend on the OCV curve of the battery, accords with the definition of the SOC of the battery on engineering application, and is suitable for various types of batteries. (2) The control method provided by the invention can be used for dealing with the conditions that the battery is difficult to enter a full-charge state and full-discharge state and is limited by the actual operation working condition of the battery in engineering application, and the application range of SOC correction of the full-charge state and full-discharge state of the battery is widened. (3) The control method provided by the invention has the advantages of simple principle, easy realization, no need of hardware modification of the existing battery system and higher practical value in engineering.
Drawings
Fig. 1 is a flowchart of full charge SOC correction.
Fig. 2 is a flowchart of a control method of a multi-branch topology battery system according to the present invention.
Fig. 3a-3c are exemplary battery system topologies, where fig. 3a is a centralized topology, fig. 3b is a dc side parallel multi-branch topology, and fig. 3c is an ac side parallel multi-branch topology.
Fig. 4 is a schematic diagram of power mode control operation.
Detailed Description
The technical scheme of the invention is clearly and completely described below by combining the attached drawings of the specification. It is to be understood that the described embodiments are merely exemplary of some, and not necessarily all, embodiments of the invention. All other embodiments, which can be obtained by a person skilled in the art without making any creative effort based on the embodiments of the present invention, belong to the protection scope of the present invention.
A control method of a multi-branch topology battery system, with a flow shown in fig. 2, includes the following steps:
s1: when SOC correction is needed, selecting a cluster in a battery system, and distributing charge and discharge power to complete one round of full charge and full discharge: the battery cluster is charged and fully charged, then discharged and discharged, the SOC of the battery is corrected to 100% when the battery is fully charged, the SOC of the battery is corrected to 0% when the battery is discharged, and the full charge and full discharge SOC correction flow is shown in fig. 1. The power of the rest of the battery clusters is flexibly distributed according to the remaining required power, and as shown in fig. 4, the modes of average distribution, weighted distribution according to the respective current SOC, and the like can be adopted.
A typical battery system topology is shown in fig. 3a-3 c: wherein fig. 3a is a centralized topology, fig. 3b and fig. 3c are multi-branch topologies related to the present invention, fig. 3b is a dc side parallel multi-branch topology, and fig. 3c is an ac side parallel multi-branch topology.
S2: and after the selected battery cluster finishes one round of full discharge, the full discharge capacity after full charge obtained by the ampere-hour integration method is used as the actual available capacity of the battery, so that the battery capacity correction is realized, and the accuracy of the ampere-hour integration method is further improved.
S3: and after the selected battery cluster is fully charged for one round, distributing power to enable the SOC of the battery cluster to be equal to the average value of the SOCs of the other battery clusters, and finishing the SOC correction of the battery cluster.
S4: and (5) repeating the steps 1 to 3, and completing SOC correction of the remaining battery clusters one by one.
Example 1
A multi-branch topology battery system is disclosed, which is a multi-branch topology with parallel connection at the AC side, as shown in FIG. 3 c. The number of the battery clusters is 8, and the external required charge and discharge power is 200kW. The control method of the multi-branch topological structure battery system based on full-charge SOC correction comprises the following specific implementation steps:
s1: when the system is charged, one battery cluster is selected, the charging power of the battery cluster is 32kW, the charging power of the other battery clusters is 24kW, and the SOC of the selected battery cluster is corrected to be 100% when the selected battery cluster is fully charged. When the system discharges, the discharging power of the selected battery cluster is made to be 32kW, the discharging power of the other battery clusters is made to be 24kW, and the SOC of the selected battery cluster is corrected to be 0% when the selected battery cluster is discharged.
S2: and after the selected battery cluster finishes one round of full discharge, the full discharge capacity of the fully charged battery obtained by the ampere-hour integration method is used as the actual available capacity of the battery, so that the battery capacity correction is realized, and the accuracy of the ampere-hour integration method is further improved.
S3: and after the selected battery cluster is fully charged for one round, distributing power to enable the SOC of the battery cluster to be equal to the average value of the SOCs of the other battery clusters, and finishing the SOC correction of the battery cluster.
S4: and (5) repeating the steps 1 to 3, and completing SOC correction of the remaining battery clusters one by one.
Example 2
A multi-branch topology battery system is a DC-side parallel multi-branch topology, as shown in FIG. 3 b. The number of the battery clusters is 8, and the rated power of the system is 200kW. When the system is kept still for a long time, namely the external required charge-discharge power is 0kW, the control method of the multi-branch topological structure battery system based on full charge-discharge SOC correction comprises the following specific implementation steps:
s1: one of the batteries was selected to be charged at 25kW power, the remaining batteries were discharged, the total discharge power was 25kW, and the SOC of the selected battery was corrected to 100% when it was fully charged. After the selected battery cluster is fully charged, the battery cluster is discharged with 25kW power, the other battery clusters are charged, the total charging power is 25kW, and the SOC of the selected battery cluster is corrected to be 0% when the selected battery cluster is discharged.
S2: and after the selected battery cluster finishes one round of full discharge, taking the full discharge capacity of the battery after full charge obtained by an ampere-hour integration method as the actual available capacity of the battery, and realizing the correction of the battery capacity.
S3: after the selected battery cluster is fully charged for one round, reasonably distributing power to enable the SOC of the battery cluster to be equal to the average value of the SOCs of the other battery clusters, and completing the SOC correction of the battery cluster.
S4: and (5) repeating the steps 1 to 3, and completing SOC correction of the remaining battery clusters one by one.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made in the above embodiments by those of ordinary skill in the art without departing from the principle and spirit of the present invention. The scope of the invention is defined by the claims and their equivalents.
Claims (6)
1. A control method of a multi-branch topological structure battery system is characterized by comprising the following steps:
s1: when SOC correction is needed, selecting a cluster in a battery system, distributing charge and discharge power to complete a round of full charge and discharge: charging and fully charging the battery cluster, then discharging and discharging, wherein the SOC of the battery is corrected to be 100% when the battery is fully charged, and the SOC of the battery is corrected to be 0% when the battery is discharged; distributing the power of the rest battery clusters according to the rest required power;
s2: after the selected battery cluster finishes one round of full discharge, the full discharge capacity after full charge obtained by an ampere-hour integration method is used as the actual available capacity of the battery, so that the battery capacity correction is realized;
s3: after the selected battery cluster is fully charged for one round, distributing power to enable the SOC of the selected battery cluster to be equal to the average value of the SOCs of the other battery clusters, and completing the SOC correction of the selected battery cluster;
s4: and (5) repeating the steps 1 to 3, and completing SOC correction of the remaining battery clusters one by one.
2. The control method according to claim 1, wherein the remaining power of the battery clusters in step S1 is distributed evenly according to the distribution method of the remaining required power.
3. The control method according to claim 1, wherein the remaining battery cluster power in step S1 is distributed in a weighted manner according to the remaining required power distribution method and according to the respective current SOC.
4. The control method according to claim 1, wherein the multi-branch topology battery system is a direct current side parallel multi-branch topology battery system.
5. The control method according to claim 1, wherein the multi-branch topology battery system is an alternating-current side parallel multi-branch topology battery system.
6. The control method according to claim 1, wherein the multi-branch topological structure battery system is a large-scale battery energy storage system formed by connecting a plurality of centralized topological structure battery systems in parallel.
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| CN116526641A (en) * | 2023-07-05 | 2023-08-01 | 合肥华思系统有限公司 | Full charge SOC calibration method, medium and equipment of centralized energy storage system |
| CN116526641B (en) * | 2023-07-05 | 2023-09-19 | 合肥华思系统有限公司 | Full charge SOC calibration method, medium and equipment of centralized energy storage system |
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