Inter-cluster circulating current suppressor for battery clusters of energy storage system and control method of inter-cluster circulating current suppressor

Abstract

The invention provides an inter-cluster circulating current suppressor for battery clusters of an energy storage system and a control method of the inter-cluster circulating current suppressor. The circulating current suppressor comprises n groups of battery clusters which are connected in parallel, n bidirectional DC / DC converters P1-Pn, an isolation power supply PU and a circulating current controller CZ. The positive electrodes of the A ports of P1-Pn are electrically connected with the n groups of battery clusters in a one-to-one correspondence manner, and the negative electrodes of the A ports of P1-Pn are jointly connected to a common bus DCbus-; the output end of the PU is in positive and negative connection with B ports of P1-Pn, the positive electrode of the input end of the PU is connected to a common bus DCbus +, and the negative electrode of the input end of the PU is connected to a common bus DCbus-; and one connecting end of the CZ is respectively connected to P1-Pn, and the other connecting end of the CZ is connected to a common bus DCbus +. According to the invention, the output current of each battery cluster can be dynamically adjusted, so that the output current of each battery cluster is kept in an error allowable range, thereby realizing the equalization of each battery cluster and achieving the purpose of restraining the circulating current.

Description

Technical Field

[0001] The present invention relates to the technical field of battery energy storage, and in particular to an inter-cluster circulating current inhibitor for battery clusters of an energy storage system and a control method thereof. Background Art

[0002] In the energy sector, the transition to clean energy has become a common goal for countries around the world. The accumulation of technology, market and experience in new energy fields such as photovoltaics and wind power in recent years will accelerate the replacement of traditional fossil energy. Compared with fossil energy, new energy power generation is characterized by imbalance and instability, which also promotes the demand for energy storage systems in the power generation and grid fields, such as renewable energy grid connection on the power generation side and power peak regulation and system frequency regulation on the grid side. These energy storage systems are usually configured according to a certain installed capacity ratio of new energy, and the volume of a single project is generally large. In order to achieve a higher cost-effectiveness, these energy storage systems mostly use multiple battery clusters connected in parallel to output to the subsequent energy storage inverter.

[0003] In fact, there are differences between battery clusters, such as the current remaining capacity SOC, voltage, internal resistance, etc. of each battery cluster. After being connected in parallel, the battery cluster with high voltage will charge the battery cluster with low voltage, thus forming a circulation. The generation of circulation will cause additional battery loss, reduce system benefits, accelerate battery aging, and even cause battery cell damage, resulting in safety accidents.

[0004] Therefore, it is necessary to design a circulating current suppressor to effectively suppress the circulating current and ensure the safety of the battery system. Summary of the invention

[0005] Based on this, it is necessary to provide an energy storage system battery cluster inter-cluster circulating current inhibitor and a control method thereof to address the circulation problem caused by the existing battery clusters after being connected in parallel due to the differences in their own battery states.

[0006] To achieve the above object, the present invention adopts the following technical solutions: An inter-cluster circulating current suppressor for battery clusters of an energy storage system comprises n parallel-connected battery clusters, n bidirectional DC / DC converters P1-Pn, an isolation power supply PU and a circulating current controller CZ.

[0007] The positive electrodes of the A ports of P1 to Pn are electrically connected to the n battery clusters one by one, and the negative electrodes of the A ports of P1 to Pn are connected to the common bus DCbus- where the DC buses of the battery clusters are gathered.

[0008] The negative and positive output terminals of PU are connected to the positive and negative terminals of B ports of P1~Pn, the positive input terminal of PU is connected to the common bus DCbus+ of the DC bus of the battery cluster, and the negative input terminal of PU is connected to the common bus DCbus-.

[0009] One of the connection ends of CZ is connected to P1~Pn respectively, and the other connection end is connected to the common bus DCbus+, which is used to control the direction and size of the output current of P1~Pn.

[0010] Furthermore, a current sensor is connected in series between the common bus DCbus+ and the circulating current controller CZ.

[0011] Furthermore, each battery cluster includes m battery cells connected in series, the positive electrode of the battery cell at the head end of each battery cluster is electrically connected to the common bus DCbus+, and the negative electrode of the battery cell at the tail end of each battery cluster is electrically connected to the positive electrode of the corresponding bidirectional DC / DC converter A port.

[0012] Furthermore, the circulation controller CZ is also electrically connected to the battery management module.

[0013] Furthermore, the battery management module includes a first-level management unit, a second-level management unit and a third-level management unit; wherein, The first-level management unit is used to collect voltage, current and temperature information of a single battery cell; The second-level management unit is used to collect the voltage, current and temperature information of each battery cluster, and summarize the data according to the battery cell information of the first management unit to obtain the battery cluster data information; The third-level management unit is used to collect the voltage, current and temperature information of all battery clusters, and summarize and save the data according to the battery cluster data information of the second-level management unit.

[0014] Furthermore, the battery management module also includes an auxiliary management unit for collecting the DC voltage and DC current of each battery cluster and the insulation state of the common bus.

[0015] The present invention also relates to a method for controlling circulating current between battery clusters in an energy storage system, which is applied to the aforementioned circulating current suppressor between battery clusters in an energy storage system. The method for controlling circulating current between battery clusters in an energy storage system comprises the following steps: Obtain the total current information Ibus of the battery cluster bus, the current remaining capacity SOC and health status SOH of each battery cluster, and then obtain the battery status of the battery cluster; The maximum discharge current Imax of the battery cluster is determined according to the battery status of the battery cluster, and the reference operating current Iref of each battery cluster is obtained by calculating the ratio of the total current information Ibus of the busbar of the battery cluster and the number n of the current parallel battery clusters; According to the maximum discharge current Imax of each battery cluster and the reference working current Iref, the output current of the battery cluster to the common bus is adjusted in real time, so that the current difference ΔI between the output current of each battery cluster and the reference working current Iref satisfies ΔImin≦ΔI≦ΔImax; wherein ΔImin is a preset minimum current difference value, and ΔImax is a preset maximum current difference value.

[0016] The present invention also relates to a computer terminal, which includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, the steps of the aforementioned method for controlling circulating current between battery clusters of an energy storage system are implemented.

[0017] The present invention also relates to a computer-readable storage medium having a computer program stored thereon, characterized in that when the program is executed by a processor, the steps of the aforementioned method for controlling circulating current between battery clusters of an energy storage system are implemented.

[0018] Compared with the prior art, the beneficial effects of the present invention include: 1. The present invention controls the output current direction and size of each bidirectional DC / DC converter A port through the circulating current controller CZ, and can dynamically adjust the output current of each battery cluster to the common bus, so that the output current of each battery cluster is kept within the allowable error range, thereby achieving the balance of each battery cluster and achieving the purpose of suppressing circulating current; 2. The present invention detects the total bus current information Ibus of the battery cluster, the current remaining capacity SOC of each battery cluster, the health status SOH and other information through the current sensor and the battery management module, so as to calculate the reference working current Iref of the battery cluster, so that the circulating current controller CZ can control the bidirectional DC / DC converter according to the reference working current Iref. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The disclosure of the present invention is described with reference to the accompanying drawings. It should be understood that the drawings are only for illustrative purposes and are not intended to limit the scope of protection of the present invention. Among them: Figure 1 This is a circuit diagram of an inter-cluster circulating current suppressor for an energy storage system battery cluster introduced in Example 1 of the present invention; Figure 2 This is a flow chart of a method for controlling circulating current between battery clusters in an energy storage system introduced in Example 2 of the present invention. DETAILED DESCRIPTION

[0020] It is easy to understand that according to the technical solution of the present invention, without changing the essential spirit of the present invention, a person skilled in the art can propose a variety of interchangeable structural modes and implementation modes. Therefore, the following specific implementation modes and drawings are only exemplary descriptions of the technical solution of the present invention, and should not be regarded as the whole of the present invention or as a limitation or restriction to the technical solution of the present invention.

[0021] Example 1 See also Figure 1This embodiment introduces an inter-cluster circulating current suppressor for battery clusters of an energy storage system, including n parallel-connected battery clusters, n bidirectional DC / DC converters P1-Pn, an isolated power supply PU and a circulating current controller CZ.

[0022] The positive poles of the A ports of P1~Pn are electrically connected to the n battery clusters one by one, and the negative poles of the A ports of P1~Pn are connected to the common bus DCbus- where the DC bus of the battery clusters is collected. The negative pole and positive pole of the output end of PU are connected to the positive pole and negative pole of the B port of P1~Pn, and the positive pole of the input end of PU is connected to the common bus DCbus+ where the DC bus of the battery clusters is collected, and the negative pole of the input end of PU is connected to the common bus DCbus-. One of the connection ends of CZ is connected to P1~Pn respectively, and the other connection end is connected to the common bus DCbus+, which is used to control the direction and size of the output current of P1~Pn.

[0023] Each battery cluster contains m cells connected in series. The positive electrode of the cell at the head end of each battery cluster is electrically connected to the common bus DCbus+, and the negative electrode of the cell at the tail end of each battery cluster is electrically connected to the positive electrode of the corresponding bidirectional DC / DC converter A port. Figure 1 As shown, the positive electrode of the head-end battery cell PACK1-1 in battery cluster 1 is electrically connected to the common bus DCbus+, and the negative electrode of the tail-end battery cell PACK1-m in battery cluster 1 is electrically connected to the positive electrode of the A port of P1. PACK1-1, PACK1-2, ..., PACK1-m are electrically connected in positive and negative directions in sequence to form a battery cluster 1 connected in series. The connection method of battery cluster 2, battery cluster 3, ..., battery cluster n is the same as that of battery cluster 1. Taking battery cluster n as an example, the positive electrode of the head-end battery cell PACKn-1 in battery cluster n is electrically connected to the common bus DCbus+, and the negative electrode of the tail-end battery cell PACKn-m in battery cluster n is electrically connected to the positive electrode of the A port of Pn. PACKn-1, PACKn-2, ..., PACKn-m are electrically connected in positive and negative directions in sequence to form a battery cluster n connected in series.

[0024] The B ports of P1~Pn are connected in parallel and connected to the output end of PU, and the input port of the isolated power supply is powered by the common bus DCbus. P1~Pn are electrically connected to the circulating current controller CZ respectively, so the circulating current controller CZ can control P1~Pn respectively, thereby achieving the purpose of adjusting the output current of the battery cluster connected to P1~Pn. P1~Pn all send relevant working parameters such as output current and output voltage to the circulating current controller CZ. Since P1~Pn is a bidirectional DC / DC converter, it is responsible for monitoring and managing the charging and discharging process, adjusting the charging method according to the optimal charging curve, and protecting the battery. It can work in both forward and reverse states to achieve bidirectional transmission of energy.

[0025] In addition, the circulating current controller CZ is also connected to the current sensor and the battery management module. The battery sensor is connected in series between the common bus DCbus+ and the circulating current controller CZ to obtain the current information of the common bus DCbus+. The battery management module includes a first-level management unit, a second-level management unit, a third-level management unit and an auxiliary management unit.

[0026] The first-level management unit is used to collect the voltage, current and temperature information of a single battery cell and upload it to the second-level management unit. The second-level management unit is used to collect the voltage, current and temperature information of each battery cluster, and summarize the data based on the battery cell information uploaded by the first management unit to obtain the battery cluster data information, and then upload it to the third-level management unit. The third-level management unit is used to collect the voltage, current and temperature information of all battery clusters, and summarize and save the data based on the battery cluster data information uploaded by the second-level management unit. The auxiliary management unit is used to collect the DC voltage and DC current of each battery cluster and the insulation status of the common bus, and upload them to the second-level management unit.

[0027] The three-level management unit adopts a tree management mode, which is progressive and can accurately obtain the voltage, current and temperature information of each battery cluster, the battery cells in each battery cluster, and the voltage, current and temperature information of the battery stack composed of all battery clusters. Analysis based on this information can serve for subsequent regulation. When the battery has abnormal faults such as overvoltage, undervoltage, overcurrent (short circuit), leakage (insulation), etc., the battery can be disconnected through other modules such as the battery protection unit to prevent the battery from being overcharged or over-discharged.

[0028] Since the temperature environment has a great impact on the working state of the battery, temperature sensors and other temperature sensing elements need to be reasonably arranged in the battery cluster to obtain the temperature of the battery cluster in time. For example, temperature sensors are set in each battery cluster and at the intersection of each battery cluster to obtain more comprehensive temperature information.

[0029] In addition, the current remaining capacity SOC and health status SOH information of each battery cluster obtained by the battery management module is one of the important bases for judging the battery status. Generally speaking, SOH is a value between 0-100%, and a value will be pre-examined. When SOH is lower than the preset value, it is considered that the battery is no longer usable. It can be expressed by battery capacity or internal resistance change. When using capacity, the actual capacity of the current battery is estimated through the battery operation process data, and the ratio to the rated capacity is SOH. SOC can be calculated by Kalman filter algorithm, sliding mode variable structure method, EKF (extended Kalman filter) algorithm or ampere-hour integration method. Since the calculation process may have large errors, the calculation process can be combined with correction strategies to improve accuracy. Correction strategies such as capacity correction, voltage correction, and charging state correction at different temperatures and SOH. In this way, the accuracy of the calculated SOC is improved.

[0030] In addition to the current remaining capacity SOC and health status SOH information of the battery cluster, the depth of discharge (DOD), functional state (SOF), energy state (SOE), fault and safety status (SOS) can also be obtained according to actual needs.

[0031] Therefore, by obtaining information such as the current remaining capacity SOC and health status SOH of the battery cluster, the battery status can be determined, and the battery limit can be further obtained, which also serves to adjust the output current of the battery cluster for P1~Pn.

[0032] Based on this, the output current direction and size of each DC / DC converter port A are controlled by the circulating current controller CZ, and the output current of each battery cluster to the common bus DCbus can be dynamically adjusted to be small, thereby achieving balance among the clusters and achieving the purpose of suppressing circulating current.

[0033] Example 2 See also Figure 2 This embodiment introduces a method for controlling circulation between battery clusters in an energy storage system, comprising the following steps: Step 1: Obtain the total current information Ibus of the battery cluster bus, the current remaining capacity SOC and health status SOH of each battery cluster, and then obtain the battery status of the battery cluster.

[0034] Step 2: Determine the maximum discharge current Imax of the battery cluster according to the battery status of the battery cluster, and calculate the reference operating current Iref of each battery cluster according to the total current information Ibus of the battery cluster bus and the current number of parallel battery clusters n. The calculation formula is Iref=Ibus / n.

[0035] Step 3: According to the maximum discharge current Imax of each battery cluster and the reference working current Iref, the output current of the battery cluster to the common bus is adjusted in real time, so that the current difference ΔI between the output current of each battery cluster and the reference working current Iref satisfies ΔImin≦ΔI≦ΔImax; wherein ΔImin is a preset minimum current difference value, and ΔImax is a preset maximum current difference value.

[0036] The total current information Ibus of the battery cluster busbar, the current remaining capacity SOC and health status SOH of each battery cluster can be obtained from the battery management module. The error tolerance range is preset, so that the current difference ΔI between the output current of each battery cluster and the calculated reference operating current Iref is within the error tolerance range, which can suppress the circulation between the battery clusters.

[0037] Example 3 This embodiment introduces a computer terminal, which includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, the steps of the aforementioned method for controlling circulating current between battery clusters of an energy storage system are implemented.

[0038] When applied, it can be applied in the form of software, such as being designed as an independently running program and installed on a computer terminal, which can be a computer, a smart phone, etc. It can also be designed as an embedded running program and installed on a computer terminal, such as a single-chip microcomputer.

[0039] Example 4 This embodiment introduces a computer-readable storage medium on which a computer program is stored, characterized in that when the program is executed by a processor, the steps of the aforementioned method for controlling circulating current between battery clusters of an energy storage system are implemented.

[0040] When applied, it can be applied in the form of software, such as a program designed to be independently run on a computer-readable storage medium. The computer-readable storage medium can be a USB flash drive designed to be a USB shield, and the USB flash drive is designed to be a program that starts the entire method through an external trigger.

[0041] The technical scope of the present invention is not limited to the contents in the above description. Those skilled in the art can make various deformations and modifications to the above embodiments without departing from the technical idea of ​​the present invention, and these deformations and modifications should all fall within the protection scope of the present invention.

Claims

1. A circulating current suppressor between battery clusters of an energy storage system, characterized in that: It includes: n groups of batteries connected in parallel; n bidirectional DC / DC converters P1-Pn, the positive electrodes of the A ports of P1-Pn are electrically connected to the n battery clusters one by one, and the negative electrodes of the A ports of P1-Pn are connected to the common bus DCbus- where the DC buses of the battery clusters are gathered; The isolated power supply PU, the output negative pole and the output positive pole of the PU are connected with the positive pole and the negative pole of the B port of P1~Pn, the input positive pole of the PU is connected to the common bus DCbus+ of the DC bus of the battery cluster, and the input negative pole of the PU is connected to the common bus DCbus-; The circulating current controller CZ has one connection end connected to P1~Pn respectively, and the other connection end connected to the common bus DCbus+, which is used to control the output current direction and size of P1~Pn.

2. The energy storage system battery cluster inter-cluster circulating current suppressor according to claim 1, characterized in that: A current sensor is connected in series between the common bus DCbus+ and the circulating current controller CZ.

3. The energy storage system battery cluster inter-cluster circulating current suppressor according to claim 1, characterized in that: Each battery cluster includes m battery cells connected in series. The positive electrode of the battery cell at the head end of each battery cluster is electrically connected to the common bus DCbus+, and the negative electrode of the battery cell at the tail end of each battery cluster is electrically connected to the positive electrode of the corresponding bidirectional DC / DC converter A port.

4. The energy storage system battery cluster inter-cluster circulating current suppressor according to claim 1, characterized in that: The circulating current controller CZ is also electrically connected to the battery management module.

5. The energy storage system battery cluster inter-cluster circulating current suppressor according to claim 4, characterized in that: The battery management module includes a first-level management unit, a second-level management unit and a third-level management unit; wherein, The first-level management unit is used to collect voltage, current and temperature information of a single battery cell; The second-level management unit is used to collect the voltage, current and temperature information of each battery cluster, and summarize the data according to the battery cell information of the first management unit to obtain the battery cluster data information; The third-level management unit is used to collect the voltage, current and temperature information of all battery clusters, and summarize and save the data according to the battery cluster data information of the second-level management unit.

6. The inter-cluster circulating current suppressor of the energy storage system battery cluster according to claim 5, characterized in that: The battery management module also includes an auxiliary management unit for collecting the DC voltage and DC current of each battery cluster and the insulation state of the common bus.

7. A method for controlling circulating current between battery clusters in an energy storage system, which is applied to the circulating current suppressor between battery clusters in an energy storage system as claimed in any one of claims 1 to 6, and the method for controlling circulating current between battery clusters in an energy storage system comprises the following steps: Obtain the total current information Ibus of the battery cluster bus, the current remaining capacity SOC and health status SOH of each battery cluster, and then obtain the battery status of the battery cluster; The maximum discharge current Imax of the battery cluster is determined according to the battery status of the battery cluster, and the reference operating current Iref of each battery cluster is obtained by calculating the ratio of the total current information Ibus of the battery cluster bus and the number n of the current parallel battery clusters; According to the maximum discharge current Imax of each battery cluster and the reference working current Iref, the output current of the battery cluster to the common bus is adjusted in real time, so that the current difference ΔI between the output current of each battery cluster and the reference working current Iref satisfies ΔImin≦ΔI≦ΔImax; wherein ΔImin is a preset minimum current difference value, and ΔImax is a preset maximum current difference value.

8. A computer terminal comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the program, the steps of the method for controlling circulating current between battery clusters in an energy storage system as claimed in claim 7 are implemented.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by the processor, the steps of the method for controlling circulating current between battery clusters in an energy storage system as claimed in claim 7 are implemented.

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