Online battery power automatic calibration system and method

Abstract

The present invention discloses an online battery power automatic calibration system and method, in which the output end of each battery PACK in the system is connected to a PACK controller; each battery cluster is provided with a cluster controller, and the PACK controller is in communication connection with the cluster controller of the battery cluster to which it belongs; wherein the PACK controller is provided with a front-end analog sampling module for collecting the single cell voltage of the battery PACK, and the PAKC controller controls the charge and discharge power of the battery PACK and performs SOC calibration on the battery PACK. The present invention controls the charge and discharge power of each battery PACK by adding a PACK controller to the output of each battery PACK, and by rotating the control of the battery PACK power, online SOC calibration can be performed on each battery PACK during the charge and discharge operation, thereby avoiding the disadvantages of shutdown calibration, increasing the utilization rate of the energy storage system, and reducing maintenance costs and maintenance time.

Description

Technical Field

[0001] The present invention relates to the technical field of energy storage systems, and in particular to an online battery power automatic calibration system and method. Background Art

[0002] In the energy storage system, single cells are connected in series and parallel to form a battery box, and battery boxes are connected in series and parallel to form a battery cluster. Multiple battery clusters are directly connected in parallel to the same DC busbar. In the energy storage system, the battery power (SOC, State of charge) is estimated by the ampere-hour integration method and the open circuit voltage method.

[0003] The ampere-hour integration method estimates the battery SOC based on the SOC at the initial moment. By calculating the integral of the charge and discharge current and the corresponding time within a certain period of time, the percentage of the changed power is calculated, and finally the difference between the initial SOC and the changed SOC, that is, the remaining power, is obtained. However, the SOC at the initial moment of this method is not easy to determine and there is a certain error in accuracy. Moreover, as time goes by, the error will also accumulate and increase, so the accuracy of current measurement is required to be very high.

[0004] The open circuit voltage method uses the OCV (Open Circuit Voltage) characteristics of the battery and uses the voltage after standing still as the basis for SOC estimation. The open circuit voltage method is simple and easy to use, and has high accuracy when the battery is standing still for a long enough time, but it is not applicable under actual working conditions. Therefore, the open circuit voltage method is generally combined with other methods to jointly predict SOC.

[0005] At present, the most commonly used method in the industry is the open circuit voltage + ampere-hour integration method: OCV calibration is performed in areas where OCV-SOC linearization is relatively good, and the ampere-hour integration is used to estimate the SOC in other areas. Peak-shaving and frequency-regulating energy storage power stations need to operate for a long time, and there is no window period for open circuit voltage estimation. The cumulative error caused by the ampere-hour integration method is proportional to the operating time. Therefore, the current conventional practice for peak-shaving and frequency regulation is to shut down once every few days to calibrate the SOC for open circuit voltage, which reduces the utilization rate of the energy storage system and increases maintenance time and maintenance costs. Therefore, it is urgent to solve the problem of automatic SOC calibration of continuously operating energy storage power stations. Summary of the invention

[0006] The purpose of the present invention is to provide an online battery power automatic calibration system and method, which can perform SOC calibration without stopping the system, increase the utilization rate of the energy storage system, and reduce the maintenance cost and maintenance time of the energy storage system.

[0007] To achieve the above object, the present invention provides the following solutions:

[0008] An online battery power automatic calibration system includes a plurality of battery clusters connected in parallel to the same DC busbar, each battery cluster includes a plurality of battery PACKs arranged in series, parallel or series-parallel mode, and the output end of each battery PACK is connected to a PACK controller; the PACK controller is equipped with a front-end analog sampling module for collecting the single cell voltage of the battery PACK;

[0009] Each battery cluster is provided with a cluster controller, and the PACK controller is communicatively connected with the cluster controller of the battery cluster in which it is located;

[0010] The PAKC controller controls the charge and discharge power of the battery PACK and performs SOC calibration on the battery PACK.

[0011] Furthermore, a plurality of battery clusters are combined to form a battery stack, and each battery stack is provided with a stack controller, and the cluster controller is communicatively connected with the stack controller of the battery stack in which it is located.

[0012] The present application provides an online battery power automatic calibration method, which is applied to the above-mentioned online battery power automatic calibration system, and includes the following steps:

[0013] S1, obtaining the single cell voltage of the battery PACK;

[0014] S2, judging whether the battery PACK is in the OCV-SOC linear region based on the voltage of the single cells in the battery PACK;

[0015] S3, for the battery PACK in the OCV-SOC linear region, a static instruction is sent to its corresponding PACK controller, and the PACK controller controls the current flowing through the battery PACK to be less than the set current threshold, so that the current battery PACK is in a static state, and the static time is recorded;

[0016] S4, when the static time reaches the set time threshold, a calibration instruction is sent to the PACK controller, and the PACK controller performs SOC calibration on the battery PACK after receiving the calibration instruction.

[0017] Furthermore, the obtaining of the single cell voltage of the battery PACK specifically includes:

[0018] The front-end analog sampling module collects the single cell voltage of the battery PACK and transmits it to the PACK controller. After receiving the single cell voltage of the battery PACK, the PACK controller transmits it to the cluster controller, which then transmits it to the stack controller.

[0019] Furthermore, the cluster controller or the stack controller completes the following operations: determining whether the battery PACK is in the OCV-SOC linear region, sending a rest instruction to the PACK controller, recording the rest time, and sending a calibration instruction to the PACK controller.

[0020] Furthermore, the OCV-SOC linear region is a voltage below 3.2V and above 3.34V.

[0021] Furthermore, the set current threshold is 1-3A, and the set time threshold is 30 minutes.

[0022] Furthermore, the method further comprises:

[0023] After the PACK controller completes the SOC calibration of the battery PACK, it feeds back a calibration completion signal to the cluster controller;

[0024] After receiving the calibration completion signal, the cluster controller determines whether to send an exit-stationary instruction to the PACK controller according to the current charge and discharge direction and the power level of the battery PACK.

[0025] Further, judging whether to send an instruction to exit the standby state to the PACK controller according to the current charge and discharge direction and the power level of the battery PACK specifically includes:

[0026] When the energy storage system is discharging, if the battery PACK in the static state has a power level less than the first voltage value, it is not allowed to exit the static state;

[0027] When the energy storage system is charging, if the battery PACK in the static state has a power greater than a second voltage value, it is not allowed to exit the static state, and the first voltage value is less than the second voltage value;

[0028] According to the above principles, if the static battery PACK does not meet the conditions that do not allow exiting the static state, an instruction to exit the static state is issued, and the next battery PACK in the OCV-SOC linear region is rotated, and steps S3-S4 are repeated.

[0029] Furthermore, if the battery cluster includes a plurality of battery PACKs connected in series, a battery PACK in a static state forms a loop with other battery PACKs operating normally through its corresponding PACK controller.

[0030] According to the specific embodiments provided by the present invention, the online battery power automatic calibration system and method provided by the present invention disclose the following technical effects:

[0031] 1. By adding a PACK controller to each battery PACK output, the charge and discharge power of each battery PACK is controlled. Based on this topology, the battery PACK power is controlled in rotation, so that each battery PACK can be calibrated online during the charge and discharge process, avoiding the disadvantage of shutdown calibration.

[0032] 2. This calibration method determines whether the battery PACK is in the OCV-SOC linear region through voltage sampling, and sets the threshold corresponding to the rest time and the current threshold to allow the battery to rest for a period of time to ensure that the chemical reaction tends to equilibrium, so as to obtain an accurate OCV value and provide conditions for open circuit voltage calibration SOC. When the resting PACK exits the resting state, the next PACK is rotated to perform zero-power operation. This can be repeated to complete the SOC calibration of each PACK online. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0034] Figure 1 The hardware topology diagram of the DC-side parallel energy storage system according to an embodiment of the present invention;

[0035] Figure 2 This is a control principle block diagram of the online battery power automatic calibration system of the present invention;

[0036] Figure 3 is an OCV-SOC curve diagram of a lithium-ion battery according to an embodiment of the present invention;

[0037] Figure 4 This is a schematic diagram of a module of a battery PACK according to an embodiment of the present invention;

[0038] Figure 5 It is a flow chart of the online battery power automatic calibration method of the present invention;

[0039] Figure 6 FIG. 1 is a circuit diagram of a battery cluster where a battery PACK is located in a static state according to an embodiment of the present invention. DETAILED DESCRIPTION

[0040] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] The purpose of the present invention is to provide an online battery capacity automatic calibration system and method to solve the problem of automatic SOC calibration of a continuously running energy storage system.

[0042] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0043] like Figure 1-2 As shown, the online battery power automatic calibration system provided by the present invention includes: multiple battery clusters connected in parallel to the same DC busbar, each battery cluster includes multiple battery PACKs arranged in series, parallel or series-parallel mode. The present invention takes the series mode as an example, and the output end of each battery PACK is connected to a PACK controller (PC); the PACK controller (PC) is equipped with a front-end analog sampling module for collecting the single cell voltage of the battery PACK. For example, the front-end analog sampling module adopts DCDC (direct current to direct current converter), such as Figure 4 As shown;

[0044] Each battery cluster is provided with a cluster controller (CC), and the PACK controller (PC) is in communication connection with the cluster controller (CC) of the battery cluster to which it belongs; the PACK controller (PC) controls the charge and discharge power of the battery PACK and performs SOC calibration on the battery PACK.

[0045] PAKC controller (PC) controls the charging and discharging power by forming a DCDC (DC to DC converter) through power electronic devices.

[0046] SOC calibration is done by sampling the voltage of a single cell and looking up the SOC-OCV characteristic curve (looking up the corresponding SOC value through the open circuit voltage of a single cell). The SOC-OCV curve is a unique property of the battery, which is fixed and related to the battery life and temperature.

[0047] A plurality of battery clusters are combined to form a battery stack, and each battery stack is provided with a stack controller (SC). The cluster controller (CC) is communicatively connected with the stack controller (SC) of the battery stack in which it is located.

[0048] The PACK controller can be placed outside the battery PACK as an independent control module to facilitate compatibility with traditional battery PACKs. Each PACK controller communicates with the corresponding cluster controller (CC) through a communication network, and multiple cluster controllers (CCs) communicate with a stack controller (SC). Figure 2 The communication, for example, may adopt RS422 communication or optical fiber communication, or use a point-to-point communication method with higher real-time performance.

[0049] Stack controller (SC): A battery stack-level controller that coordinates and controls the charge and discharge of each battery cluster;

[0050] Cluster controller (CC): a cluster-level controller that coordinates the operations of various controllers within a battery cluster;

[0051] PACK controller (PC): A battery PACK-level controller that controls the charging and discharging of the battery PACK, and also has functions such as battery voltage and temperature collection.

[0052] Battery PACK: includes battery modules, battery management units, fire sensors and electrical and structural components required for integration. Among them, the battery module is a battery assembly consisting of battery cells connected in series, parallel or series-parallel, and has only one pair of positive and negative output terminals. It should also include components such as housing, management and protection devices.

[0053] The present invention controls the power of each PACK by adding a PACK controller (PC) to each battery PACK output. The open circuit voltage method and the ampere-hour integration method are used to estimate the battery SOC. By controlling the battery PACK power in rotation, conditions are provided for open circuit voltage calibration, and online SOC calibration can be achieved without stopping the machine.

[0054] like Figure 5 As shown, the present application provides an online battery power automatic calibration method, which is applied to the above-mentioned online battery power automatic calibration system, and includes the following steps:

[0055] S1, obtaining the single cell voltage of the battery PACK;

[0056] S2, judging whether the battery PACK is in the OCV-SOC linear region based on the voltage of the single cells in the battery PACK;

[0057] S3, for the battery PACK in the OCV-SOC linear region, a static instruction is sent to the corresponding PACK controller, and the PACK controller controls the current flowing through the battery PACK to be less than the set current threshold, so that the current battery PACK is in a static state, and the static time is recorded; for example, the set current threshold is 1-3A, when the current flowing through the battery PACK is less than the set current threshold, it is considered that the battery PACK is working in a zero-power operation state and is in a static state; this is because it is impossible to control the absolute zero power in engineering applications, therefore, the current is generally controlled within a certain range and is considered to be in a zero-power operation state;

[0058] S4, when the static time reaches the set time threshold, a calibration instruction is sent to the PACK controller, and the PACK controller performs SOC calibration on the battery PACK after receiving the calibration instruction.

[0059] Wherein, step S1, obtaining the single cell voltage of the battery PACK, specifically includes:

[0060] The front-end analog sampling module collects the single cell voltage of the battery PACK and transmits it to the PACK controller. After receiving the single cell voltage of the battery PACK, the PACK controller transmits it to the cluster controller, which then transmits it to the stack controller.

[0061] The cluster controller or the stack controller completes the following operations: determining whether the battery PACK is in the OCV-SOC linear region, sending a rest instruction to the PACK controller, recording the rest time, and sending a calibration instruction to the PACK controller.

[0062] Generally, the voltage of lithium-ion battery cells is below 3.2V and above 3.34V, which is the OCV-SOC linear region. In this region, a relatively high-precision SOC calibration value can be obtained. Figure 3 The OCV-SOC curve of a lithium-ion battery is used as an example for explanation.

[0063] The battery needs to be left standing for a period of time to ensure that the chemical reaction is balanced and to obtain an accurate OCV value. In general engineering applications, the battery standing time is generally set at 30 minutes, so before calibrating the SOC, the current flowing through the battery needs to be controlled to be less than a certain threshold, generally 1-3A. Therefore, the set current threshold is 1-3A, and the set time threshold is 30 minutes.

[0064] The method further comprises:

[0065] After the PACK controller completes the SOC calibration of the battery PACK, it feeds back a calibration completion signal to the cluster controller;

[0066] After receiving the calibration completion signal, the cluster controller determines whether to send an exit command to the PACK controller according to the current charge and discharge direction and the power level of the battery PACK, including:

[0067] When the energy storage system is discharging, if the battery PACK in the static state has a power level less than a first voltage value (for example, 3.2V), it is not allowed to exit the static state, otherwise it will soon cause a discharge ban and cause the system to shut down;

[0068] When the energy storage system is charging, if the battery PACK in the static state has a power level greater than a second voltage value (e.g., 3.34V), it is not allowed to exit the static state, and the first voltage value is less than the second voltage value, otherwise it will soon cause charging to be prohibited and cause the system to shut down;

[0069] According to the above principles, if the static battery PACK does not meet the conditions that do not allow exiting the static state, an instruction to exit the static state is issued, and the next battery PACK in the OCV-SOC linear region is rotated, and steps S3-S4 are repeated.

[0070] In a specific embodiment, when the energy storage system is running, the charge and discharge power of each battery PACK can be controlled by the PAKC controller (PC). Through coordinated control by the stack controller or cluster controller, one PACK in the battery cluster is controlled to operate at 0 power in turn in the area where OCV-SOC linearization is relatively good, and other PACKs continue to be put into use. In this way, a static condition can be provided for the PACK open circuit voltage method. When the static PACK reaches the static time, the next PACK is rotated to operate at 0 power. This can be repeated to complete the SOC calibration of each PACK online.

[0071] When the cluster controller detects that a battery PACK currently has the conditions for online calibration (the voltage of the battery PACK is in the OCV-SOC linear region), the cluster controller will issue a static command to the PACK controller. After receiving the static command, the PACK controller switches the working mode to prevent current from flowing through the corresponding battery PACK. The cluster controller starts timing synchronously, but when the time reaches the set threshold (30 minutes), the cluster controller issues a calibration command to the static PACK controller. After receiving the calibration command, the PACK controller starts to calibrate the SOC and feedbacks the calibration completion to the cluster controller after completion. After receiving the calibration completion, the cluster controller determines whether to issue a command to exit the static state based on the current charge and discharge direction and battery power. When the energy storage system is discharging, if the static battery PACK has a very low power (less than 3.2V), it is not allowed to exit the static state, otherwise it will soon cause a discharge ban and cause the system to shut down; when the energy storage system is charging, if the static battery PACK has a very high power (greater than 3.34V), it is not allowed to exit the static state, otherwise it will soon cause a charging ban and cause the system to shut down. According to the above principle, if the static battery PACK meets the exit static condition, an exit static command is issued to rotate the next battery PACK that meets the static condition.

[0072] The module in the static state will not flow current that affects the calibration, but will form a loop with the system through the DCDC in the PAKC controller (PC) to ensure the normal operation of other batteries. Figure 6 The energy storage system shown is working normally. By controlling PC2 to work in the static mode, a system loop is formed through PC2, and the current does not pass through PACK2, so that PACK2 meets the static condition.

[0073] In summary, in the present invention, by improving the hardware topology structure, each battery PACK is provided with a PACK controller to control its power; in the calibration method, each PACK is controlled to 0 power, and each PACK is calibrated in rotation during the charging and discharging process, thereby avoiding the disadvantage of shutdown calibration.

[0074] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. An online battery capacity automatic calibration system, comprising multiple battery clusters connected in parallel to the same DC busbar, each battery cluster comprising multiple battery packs connected in series, parallel, or series-parallel, characterized in that: The output end of each battery PACK is connected to a PACK controller; the PACK controller is equipped with a front-end analog sampling module for collecting the voltage of the single cell of the battery PACK; Each battery cluster is provided with a cluster controller, and the PACK controller is in communication connection with the cluster controller of the battery cluster in which it is located; The PACK controller controls the charge and discharge power of the battery PACK and performs SOC calibration on the battery PACK; The online battery capacity automatic calibration method applied to the online battery capacity automatic calibration system comprises the following steps: S1, obtain the single cell voltage of the battery pack; S2, based on the voltage of the single cells in the battery pack, determines whether the battery pack is in the OCV-SOC linear region; S3: For a battery pack in the OCV-SOC linear region, a rest instruction is sent to its corresponding pack controller. The pack controller controls the current flowing through the battery pack to be less than a set current threshold, so that the current battery pack is in a rest state, and the rest time is recorded. S4, when the static time reaches the set time threshold, a calibration instruction is sent to the PACK controller, and the PACK controller performs SOC calibration on the battery PACK after receiving the calibration instruction; The method further comprises: After the PACK controller completes the SOC calibration of the battery PACK, it feeds back a calibration completion signal to the cluster controller; After receiving the calibration completion signal, the cluster controller determines whether to send an exit command to the pack controller based on the current charge and discharge direction and the battery pack's power level. Specifically, the command includes: When the energy storage system is discharging, if the voltage corresponding to the power level of the battery PACK in the static state is less than the first voltage value, exiting the static state is not allowed; When the energy storage system is charging, if the voltage corresponding to the power level of the battery PACK in the static state is greater than a second voltage value, exiting the static state is not allowed, and the first voltage value is less than the second voltage value; According to the above principles, if the static battery pack does not meet the conditions that do not allow it to exit the static state, an instruction to exit the static state is issued, and the next battery pack in the OCV-SOC linear region is rotated, and steps S3-S4 are repeated; If the battery cluster includes a plurality of battery packs arranged in series, a battery pack in a static state forms a loop with other normally operating battery packs through its corresponding pack controller.

2. The online battery capacity automatic calibration system according to claim 1, characterized in that: A plurality of battery clusters are combined to form a battery stack. Each battery stack is provided with a stack controller. The cluster controller is in communication connection with the stack controller of the battery stack in which it is located.

3. The online battery capacity automatic calibration system according to claim 1, characterized in that: The obtaining of the single cell voltage of the battery PACK specifically includes: The front-end analog sampling module collects the single cell voltage of the battery PACK and transmits it to the PACK controller. After receiving the single cell voltage of the battery PACK, the PACK controller transmits it to the cluster controller, and then the cluster controller transmits it to the stack controller.

4. The online battery capacity automatic calibration system according to claim 3, characterized in that: The cluster controller or stack controller performs the following operations: determining whether the battery PACK is in the OCV-SOC linear region, sending a rest instruction to the PACK controller, recording the rest time, and sending a calibration instruction to the PACK controller.

5. The online battery capacity automatic calibration system according to claim 1, characterized in that: The OCV-SOC linear region is a voltage below 3.2V and above 3.34V.

6. The online battery capacity automatic calibration system according to claim 1, characterized in that: The set current threshold is 1-3A, and the set time threshold is 30 minutes.

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