Multi-level battery system nuclear capacity control method for power frequency modulation energy storage station

Abstract

The invention discloses a multi-level battery system nuclear capacity control method for an electric power frequency modulation energy storage station, and the method aims at the energy storage station which comprises a plurality of transformers, a plurality of energy storage containers hung below each transformer, and a plurality of PCS groups and parallel battery cabinets arranged in each container. The method comprises an energy storage container level capacity checking mode and / or a battery cabinet level capacity checking mode, and capacity checking is achieved by selecting an even number of energy storage containers to carry out internal energy mutual dragging in an energy storage container level; in the battery cabinet layer, an even number of battery cabinets are selected to carry out internal energy mutual dragging so as to realize capacity checking; meanwhile, a one-by-one cut-off charging and discharging control strategy of the direct-current side parallel battery pack is also provided. According to the method, the SOC accumulated deviation caused by long-term frequency modulation operation is effectively solved, the capacity evaluation accuracy is improved, the minimum interference on the frequency modulation service in the capacity checking process is realized, and the system availability rate is remarkably improved.

Description

Capacity control method for multi-level battery systems used in power frequency regulation energy storage stations Technical Field

[0001] This application belongs to the field of power energy storage technology, specifically relating to a multi-level battery system capacity control method for power frequency regulation energy storage stations. Background Technology

[0002] With the increasing demands on frequency regulation capabilities in power systems, large-scale energy storage power stations employing parallel systems of multiple transformers, multiple energy storage containers, multiple PCS groups, and multiple battery cabinets are being widely used in power frequency regulation scenarios.

[0003] In existing technologies, a typical energy storage frequency regulation site usually includes: multiple transformers; multiple energy storage containers connected to each transformer; and multiple PCS groups and parallel battery cabinets within each energy storage container. During long-term frequency regulation operation, to ensure the system has bidirectional regulation capabilities, the energy storage system typically operates within approximately 50% of its State of Charge (SOC). In existing systems, the SOC in this range is generally estimated using a current integral-based method.

[0004] However, under conditions of parallel operation of multiple PCS groups and multiple battery cabinets, current sampling errors, PCS output deviations, and differences in battery consistency will gradually lead to a shift in the State of Charge (SOC) between different parallel battery groups, and this shift will accumulate with the increase of operating time. When the SOC deviation widens, it will cause the following problems: inaccurate assessment of the system's available capacity; degraded frequency regulation performance, with some battery groups triggering protection prematurely; and the need for frequent shutdowns for capacity verification (capacity verification), affecting the continuous operation of the site. In addition, in existing capacity verification schemes, the full charge or discharge process usually only ends when any parallel group on the DC side reaches a threshold, without sufficient correction for the remaining parallel battery groups, further amplifying the SOC deviation.

[0005] Therefore, there is an urgent need for a nuclear capacity control method applicable to multi-level energy storage systems, which can achieve system capacity calibration and SOC consistency recovery without significantly affecting frequency regulation operation. Summary of the Invention

[0006] The purpose of this invention is to provide a capacity control method for a multi-level battery system in a power frequency regulation energy storage station, so as to solve the technical problems of battery SOC deviation accumulation, inaccurate capacity assessment, and the impact of capacity control process on system operation after long-term operation of the energy storage system in the prior art.

[0007] To achieve the above objectives, this invention provides a multi-level battery system capacity control method for power frequency regulation energy storage stations. The energy storage station includes multiple transformers, each transformer is equipped with multiple energy storage containers, each energy storage container contains multiple PCS groups, and each PCS group has multiple battery cabinets connected in parallel. The method includes an energy storage container-level capacity control mode and / or a battery cabinet-level capacity control mode. The energy storage container-level capacity control mode includes: within the same transformer, selecting an even number of energy storage containers, controlling half of the containers to charge, and the other half to discharge, completing capacity control based on the energy "pull-through" between the energy storage containers. The battery cabinet-level capacity control mode includes: within the same energy storage container, selecting an even number of battery cabinets, controlling half of the battery cabinets to charge, and the other half to discharge, completing capacity control based on the energy "pull-through" between the battery cabinets.

[0008] Furthermore, in the energy storage container-level capacity-controlled mode, the required charging and discharging power of each PCS group is calculated by the controller PUC of the energy storage container, and the output of each PCS group is dynamically adjusted by the PID algorithm so that the net power exchange on the low-voltage side of the transformer is lower than a preset threshold. Specifically, the controller PUC of the energy storage container calculates the required charging and discharging power of each PCS group based on the voltage and current information of the battery pack collected by the battery cabinet and the output power information of each PCS group read.

[0009] Furthermore, the capacity approval process for both the energy storage container-level and battery cabinet-level capacity approval modes sequentially includes the following stages: Discharge stage: discharging the battery pack to its lowest voltage and continuing for a first preset time; Discharge waiting stage: waiting for the battery pack temperature to drop below a first temperature threshold and continuing for a second preset time; Full charge stage: charging the battery pack to its highest voltage and continuing for a third preset time; Full charge waiting stage: waiting for the battery pack temperature to drop below a second temperature threshold and continuing for a fourth preset time; Discharge stage: discharging the battery pack to its lowest voltage and continuing for a fifth preset time; Recharge stage: recharging the battery pack's state of charge (SOC) to a target value, where the target value is 50% SOC.

[0010] Furthermore, during the energy "pull-to-pull" process of the energy storage container-level core capacity mode and the battery cabinet-level core capacity mode, the power increase and decrease are both adjusted gradually, with the gradual adjustment rate of power increase and decrease being 0.5-1.5 kW / s.

[0011] Furthermore, in the energy storage container-level capacity-capacity mode or the battery cabinet-level capacity-capacity mode, the charging and discharging control strategy for the DC-side parallel battery packs includes a full-charge control sub-strategy and / or a venting control sub-strategy. The full-charge control sub-strategy involves simultaneously charging all DC-side parallel battery packs participating in the capacity-capacity scheme. When any parallel battery pack reaches the full-charge threshold, that battery pack is disconnected from the DC side, while the remaining parallel battery packs continue charging until all parallel battery packs are fully charged. The venting control sub-strategy involves simultaneously discharging all DC-side parallel battery packs participating in the capacity-capacity scheme. When any parallel battery pack reaches the venting threshold, that battery pack is disconnected from the DC side, while the remaining parallel battery packs continue discharging until all parallel battery packs are fully vented.

[0012] Furthermore, in the full charge control sub-strategy, after detecting that any parallel battery pack has reached the full charge threshold, the system power is first reduced to zero. After confirming that the current of the parallel battery pack is less than the safety threshold, the disconnection operation is then performed.

[0013] To achieve the above objectives, the present invention also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the core capacity control method as described above.

[0014] To achieve the above objectives, the present invention also provides an energy storage station control system, including a station-level energy management system (EMS) and multiple energy storage container-level controllers (PUCs). The energy storage container-level controller (PUC) includes a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement the capacity control method as described above.

[0015] Compared with the prior art, the present invention has the following beneficial technical effects: (1) The present invention realizes the internal circulation of energy through the layered energy-to-capacity method of energy storage container level and / or battery cabinet level, which greatly reduces the dependence and impact of the capacity process on the external power grid and reduces the capacity cost.

[0016] (2) By adopting the “one-by-one cut-off” charge / discharge control strategy of the parallel battery packs on the DC side, the present invention ensures that each parallel battery pack can be fully and completely charged and discharged, fundamentally correcting the SOC deviation of all parallel battery packs and restoring the consistency of the battery system capacity.

[0017] (3) The capacity control method provided by the present invention can flexibly select the capacity mode according to the operation and maintenance needs. It can perform synchronous calibration of the entire group of energy storage containers or perform online independent capacity control of a single energy storage container, which significantly reduces the overall system downtime and improves the availability of energy storage sites and the continuity of frequency regulation services. Attached Figure Description

[0018] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0019] Figure 1 is a schematic diagram of the system structure of the energy storage station in Embodiment 1 of the present invention; Figure 2 is a schematic diagram of the energy storage container-level capacity control mode in the embodiment of the present invention; Figure 3 is a schematic diagram of the battery cabinet-level capacity control mode in the embodiment of the present invention; Figure 4 is a flowchart of the DC-side parallel battery pack full charge control sub-strategy in the embodiment of the present invention; Figure 5 is a flowchart of the DC-side parallel battery pack emptying control sub-strategy in the embodiment of the present invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and technical effects of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings, multiple embodiments, and comparative examples. In the following description, the same components are referred to by the same reference numerals.

[0021] Example 1 This example provides a multi-level battery system capacity control method suitable for power frequency regulation energy storage stations. The structure of the energy storage station is shown in Figure 1, including multiple transformers, each transformer connected to multiple energy storage containers, each energy storage container containing multiple PCS groups, and each PCS group connected to multiple battery cabinets in parallel. Specifically, in this example, there are 10 transformers, each transformer connected to 6 energy storage containers, each energy storage container containing 2 PCS groups, and each PCS group connected to 4 battery cabinets in parallel. The station is uniformly managed by the station-level energy management system (EMS), and each energy storage container is managed by the container-level controller (PUC). The PUC interacts with the corresponding energy storage container's battery management system (BMS) and PCS via CAN communication, and is responsible for managing the PCS groups and battery cabinets (BC) within that energy storage container.

[0022] To address the issue of accumulated SOC deviation among multiple parallel battery packs caused by current sampling errors and PCS group output deviations after long-term 50% SOC frequency regulation operation of the system, this embodiment proposes the following solution: First, this embodiment proposes two capacity control modes: (1) Energy storage container-level capacity control mode: As shown in Figure 2, taking 6 energy storage containers under one transformer as an example, 3 of them are selected for charging and the other 3 are for discharging. The container-level controller PUC is responsible for coordination and control. Based on the battery voltage and current information collected by the battery cabinet BC and the output power information of the PCS group, the required charging and discharging power of the corresponding PCS group is calculated, and the PCS group is dynamically adjusted through the PID algorithm. Output, so that the charging and discharging power cancels each other on the low-voltage side of the transformer, realizing the internal energy "pull-to-pull", thereby minimizing the impact of the capacity filling process on the external power grid (for example, the net power exchange on the low-voltage side of the transformer is less than 5%); (2) Battery cabinet level capacity filling mode: As shown in Figure 3, inside an energy storage container, four battery cabinets are selected for charging, and another four battery cabinets are discharged. The container-level controller PUC controls the PCS group in this energy storage container to realize the "pull-to-pull" of energy between the battery cabinets. This mode can realize the independent capacity filling of a single energy storage container and complete the capacity calibration of the energy storage container without affecting the frequency regulation operation of other energy storage containers.

[0023] Secondly, during the charging and discharging process of the two core capacity modes mentioned above, this embodiment also proposes a precise control strategy of "one-by-one cut-off" to ensure that each parallel battery pack can be completely corrected.

[0024] Taking the full charge process as an example, as shown in Figure 4: (1) Charge all parallel battery packs participating in the capacity test; (2) Continuously monitor the voltage, SOC and other status of each battery pack; (3) When it is detected that any battery pack reaches the full charge threshold (for example, the highest voltage of the battery pack reaches 3.6V and lasts for 10s), the system first controls the corresponding PCS group to adjust the charging and discharging power to 0; (4) After the current of the battery pack drops below the safety threshold (for example, less than 5A), it is disconnected from the DC bus by a contactor or circuit breaker; (5) The system resumes charging the remaining parallel battery packs until the next battery pack reaches the full charge threshold, and repeats steps (3) and (4) until all battery packs are fully charged and disconnected.

[0025] The discharge process is similar. As shown in Figure 5, battery packs that have reached the discharge threshold (e.g., the lowest voltage of the battery pack reaches 2.7V and lasts for 10 seconds) are disconnected one by one until all battery packs have been discharged and disconnected.

[0026] In a complete battery life cycle, the above charging / discharging process can be embedded into the following six stages: Discharge stage: Discharge the battery pack to the minimum voltage and maintain it for a first preset time, where the minimum voltage is set to 2.7V and the first preset time is 10s; Discharge waiting stage: Wait for the battery pack temperature to drop below a first temperature threshold and maintain it for a second preset time, where the first temperature threshold is 27℃ and the second preset time is 30s; Full charge stage: Charge the battery pack to the maximum voltage and maintain it for a third preset time, executing the above "one-by-one cut-off" full charge control strategy until all battery packs reach the full charge threshold, where the maximum voltage... The voltage is set to 3.6V, and the third preset time is 10s; Full charge waiting stage: wait for the battery pack temperature to drop below the second temperature threshold and continue for a fourth preset time, where the second temperature threshold is 27℃ and the fourth preset time is 30s; Discharge stage: discharge the battery pack to the minimum voltage and continue for a fifth preset time, executing the above "one-by-one cut-off" discharge control strategy until all battery packs reach the discharge threshold, where the minimum voltage is set to 2.7V and the fifth preset time is 10s; Recharge stage: recharge the battery pack's state of charge (SOC) to the target value to prepare for re-entry into frequency regulation operation, where the target value is 50% SOC.

[0027] By combining the aforementioned hierarchical "paired" capacity mode with the precise charge and discharge control strategy of "one-by-one cut-off", this embodiment completely solves the problem of SOC calibration in multi-level parallel energy storage systems.

[0028] Example 2 provides an alternative solution based on Example 1. Specifically, in the energy storage containerized capacity-based model, the number of transformers, the number of energy storage containers connected to each transformer, and the number of PCS groups and battery cabinets within each energy storage container can all be adjusted proportionally according to the actual site scale, as long as the number of the two sets of equipment "towing" each other within a certain level is even. For example, 2, 4, or 6 energy storage containers can be selected for towing.

[0029] The six stages of the core capacity can be combined or separated according to the chemical characteristics or operating strategy of the battery pack.

[0030] For example, in scenarios where time requirements are not high, the waiting time can be appropriately extended; or, if the battery pack consistency is good, some waiting stages can be simplified; the SOC recharge target value during the recharge stage can also be adjusted to other values ​​according to the application scenario, such as 45% or 55%; in addition to the PID algorithm, other advanced control algorithms can also be used for power regulation.

[0031] These simple adjustments and modifications should all be considered within the scope of protection of this invention.

[0032] In summary, the method, medium, and system provided by this invention, through innovative layered drag structure and precise step-by-step disconnection control, effectively improve the operation and maintenance level of large-scale energy storage systems, and have high practical value and broad application prospects.

[0033] The above provides a detailed description of a multi-level battery system capacity control method for power frequency regulation energy storage stations provided in this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the embodiments above are only for the purpose of helping to understand the core ideas of this application. It should be noted that those skilled in the art can make several improvements and modifications to this application without departing from the principles of this application, and these improvements and modifications also fall within the protection scope of the claims of this application.

Claims

1. A method for capacity control of a multi-level battery system in a power frequency regulation energy storage station, wherein the energy storage station includes multiple transformers, each transformer is equipped with multiple energy storage containers, each energy storage container contains multiple PCS groups, and each PCS group has multiple battery cabinets connected in parallel, characterized in that... The method includes a container-level capacity control mode and / or a cabinet-level capacity control mode, wherein: the container-level capacity control mode includes: within the same transformer, selecting an even number of energy storage containers, controlling half of the energy storage containers to charge, and the other half of the energy storage containers to discharge, and completing the capacity control based on the energy "pull-to-pull" between the energy storage containers; the cabinet-level capacity control mode includes: within the same energy storage container, selecting an even number of battery cabinets, controlling half of the battery cabinets to charge, and the other half of the battery cabinets to discharge, and completing the capacity control based on the energy "pull-to-pull" between the battery cabinets.

2. The nuclear capacity control method according to claim 1, characterized in that, In the energy storage container-level capacity-controlled mode, the required charging and discharging power of each PCS group is calculated by the controller PUC of the energy storage container, and the output of each PCS group is dynamically adjusted by the PID algorithm to ensure that the net power exchange on the low-voltage side of the transformer is lower than the preset threshold. Specifically, the controller PUC of the energy storage container calculates the required charging and discharging power of each PCS group based on the voltage and current information of the battery pack collected by the battery cabinet and the output power information of each PCS group read.

3. The nuclear capacity control method according to claim 1, characterized in that, The capacity approval process for both the energy storage container-level capacity approval mode and the battery cabinet-level capacity approval mode includes the following stages in sequence: venting stage: discharging the battery pack to the lowest voltage and continuing for a first preset time; Discharge waiting phase: Waiting for the battery pack temperature to drop below the first temperature threshold and continue for a second preset time; Full charge phase: Charge the battery pack to the highest voltage and continue for a third preset time; Full charge waiting phase: Wait for the battery pack temperature to drop below the second temperature threshold and continue for a fourth preset time. Discharge phase: Discharge the battery pack to the lowest voltage and continue for the fifth preset time; Recharge phase: Recharge the battery pack's state of charge (SOC) back to the target value.

4. The nuclear capacity control method according to claim 3, characterized in that, During the recharge phase of the nuclear capacity process, the target value is 50% SOC.

5. The nuclear capacity control method according to claim 4, characterized in that, During the energy "pull-to-pull" process of the energy storage container-level core capacity mode and the battery cabinet-level core capacity mode, both the power increase and power decrease are adjusted gradually.

6. The nuclear capacity control method according to claim 5, characterized in that, The gradual adjustment rate of power increase and power decrease is 0.5-1.5 kW / s.

7. The nuclear capacity control method according to claim 1, characterized in that, In the energy storage container-level or battery cabinet-level capacity-capacity ...

8. The nuclear capacity control method according to claim 7, characterized in that, In the full charge control sub-strategy, after detecting that any parallel battery pack has reached the full charge threshold, the system power is first reduced to zero. After confirming that the current of the parallel battery pack is less than the safety threshold, the disconnection operation is then performed.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it implements the nuclear capacity control method as described in any one of claims 1 to 8.

10. An energy storage station control system, comprising a station-level energy management system (EMS) and multiple energy storage container-level controllers (PUCs), wherein each energy storage container-level controller (PUC) includes a memory and a processor, the memory storing a computer program, characterized in that, When the processor executes the computer program, it implements the nuclear capacity control method as described in any one of claims 1 to 8.

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