Energy storage system and detection method of energy storage system

Abstract

The present application discloses an energy storage system and a detection method for the energy storage system. The system includes: a controller, multiple battery clusters and multiple DC / DC converters, wherein the multiple DC / DC converters correspond to the multiple battery clusters one by one; each battery cluster in the multiple battery clusters is connected to a DC bus through a corresponding DC / DC converter, and the multiple battery clusters include a target battery cluster and other battery clusters as detected objects; the controller controls the DC / DC converters in the multiple DC / DC converters that are connected to the target battery cluster to input a detection current into the target battery cluster, wherein the detection current comes from all or part of the other battery clusters in the multiple battery clusters except the target battery cluster; according to the voltage change of the target battery cluster caused by the detection current, the parameters of the target battery cluster are obtained, wherein the parameters include one or more of the ohmic internal resistance, polarization internal resistance and polarization capacitance of the batteries in the target battery cluster. The scheme accurately and comprehensively detects the parameters of the battery and realizes online evaluation.

Description

Technical Field

[0001] The present application relates to the field of battery safety technology, and in particular to an energy storage system and a detection method for the energy storage system. Background Art

[0002] With the continuous development of battery technology, energy storage is now being used more and more widely, especially energy storage of new energy sources, such as photovoltaic power generation and wind power generation. At present, energy storage systems include multiple battery clusters, each of which includes multiple batteries. For example, an energy storage system includes hundreds to thousands of batteries connected in series and parallel.

[0003] Batteries in energy storage systems are generally required to have a lifespan of more than 10 years, but in actual use, problems such as sudden changes in internal resistance and decreased capacity may occur. Especially for multiple batteries connected in series, if one battery fails, all batteries connected in series will not be able to operate. If they continue to be used, they may trigger safety accidents such as battery explosions. Therefore, it is necessary to detect the status of batteries in the energy storage system and take timely measures when abnormalities occur in the batteries to avoid serious accidents.

[0004] Traditionally, there are two approaches to testing the battery status: one is material-level testing, and the other is external characteristic testing. Material-level testing requires the battery to be completely disassembled into the internal materials of the battery cell, such as the pole piece, diaphragm, and electrolyte, and then an in-depth analysis is conducted. This method is a destructive test that cannot retain the original function of the energy storage system and is extremely costly. During the external characteristic test, the energy storage system is in operation and the battery is in a passive state. The operating conditions are limited by the power dispatch of the entire power station, making it difficult to perform external characteristic testing on the battery. Summary of the invention

[0005] In order to solve the above technical problems, the present application provides an energy storage system and a detection method for the energy storage system, which can accurately and comprehensively detect various parameters of the battery in the energy storage system and perform online evaluation of the battery.

[0006] The present application provides an energy storage system, including: a controller, multiple battery clusters and multiple DC / DC converters, the multiple DC / DC converters correspond to the multiple battery clusters one by one, that is, one DC / DC converter is connected to one battery cluster; each battery cluster in the multiple battery clusters is connected to a DC bus through a corresponding DC / DC converter, and the multiple battery clusters include a target battery cluster and other battery clusters as detected objects; the controller is used to control the DC / DC converters in the multiple DC / DC converters corresponding to the target battery cluster to input a detection current into the target battery cluster, the detection current comes from all and part of the other battery clusters in the multiple battery clusters except the target battery cluster; according to the voltage change of the target battery cluster caused by the detection current, the parameters of the target battery cluster are obtained, and the parameters include one or more of the ohmic internal resistance, polarization internal resistance and polarization capacitance of the batteries in the target battery cluster.

[0007] When testing the batteries in the target battery cluster, the controller controls the power of the DC / DC converter connected to the target battery cluster, generates a test current to the target battery cluster through the DC / DC converter, and detects the voltage of each battery in the target battery cluster. It should be understood that when the current passes through the battery, the voltage of the battery will change, that is, the changed voltage is detected. The energy source of the test current can come from one battery cluster among the remaining battery clusters, or from multiple battery clusters among the remaining battery clusters.

[0008] The energy storage system provided in the embodiment of the present application does not require the addition of new equipment, thereby saving costs; and does not require an external energy source to perform performance testing on the batteries of the battery cluster. For example, it is not necessary to draw power from the AC power grid to perform battery testing, thereby avoiding interference with the AC power grid; and it is not necessary to set up a new external energy source, and only power can be drawn from the inside of the battery cluster. In addition, the energy storage system provided in the embodiment of the present application can not only obtain the ohmic internal resistance of the battery, but also the polarization internal resistance and polarization capacitance of the battery, thereby more comprehensively reflecting the performance of the battery. When a problem occurs with the battery, an alarm can be given in time, making it easier to take measures to avoid causing greater damage.

[0009] In one possible implementation, the parameters of the target battery cluster are the parameters of the battery model of the target battery cluster; the changing voltage includes the open circuit voltage and the port voltage of the batteries in the target battery cluster; the controller is specifically used to detect before or after the current disappears, and obtains the parameters of the battery model according to multiple change values ​​of the open circuit voltage and the port voltage of the batteries in the target battery cluster.

[0010] In one possible implementation, the controller is specifically used to perform curve fitting according to multiple change values ​​of the open circuit voltage of the batteries in the target battery cluster and multiple change values ​​of the port voltage, and obtain the parameters of the battery model according to the fitted curve; the curve is fitted by genetic algorithm or least squares method.

[0011] In a possible implementation, the battery model is obtained according to a simulation circuit corresponding to the target battery cluster, and the battery model is used to represent the relationship between the voltage, current and time of the batteries in the target battery cluster.

[0012] The present application does not limit the specific type of battery model, as long as the ohmic internal resistance, polarization internal resistance and polarization capacitance of the battery can be obtained according to the parameters in the battery model. For example, the battery model may include any of the following: Rint model, Thevenin model, PNGV model or second-order RC circuit model. It should be understood that the battery model is an equation including a fluctuating voltage, and the parameters of the battery model can be obtained by detecting the voltage change caused by the current, and then the ohmic internal resistance, polarization internal resistance and polarization capacitance of the battery can be obtained according to the parameters in the battery model.

[0013] Since the batteries in the energy storage system are generally lithium iron phosphate batteries, a second-order equivalent circuit model can be used. This circuit model includes two RC circuits in series to simulate the electrochemical polarization and concentration polarization phenomena of lithium batteries. When the battery model is a second-order RC circuit model, the polarization internal resistance includes the electrochemical polarization internal resistance and the concentration polarization internal resistance; the polarization capacitor includes the electrochemical polarization capacitor and the concentration polarization capacitor. This circuit model can accurately reflect the dynamic and static characteristics of the battery, and the RC order is not high, the solution is real-time, and the parameter identification is easy to achieve, which is convenient for engineering applications.

[0014] After obtaining the parameters of the battery model in the embodiment of the present application, the performance of the battery can be judged. The specific methods may include multiple methods, such as comparing with a preset threshold to determine whether the battery is damaged; in addition, comparing with the parameters of a new battery to determine whether the battery is damaged based on the deviation; in addition, comparing with the average parameter value of all battery clusters in the energy storage system to determine whether the battery is damaged. Four specific implementation methods are introduced below.

[0015] In one possible implementation, the controller is also used to compare the parameters of the battery model obtained this time with the parameters of the battery model obtained last time. If the deviation between the parameters of the battery model obtained this time and the parameters of the battery model obtained last time is within a preset range, the parameters of the battery model of the target battery cluster are updated; if the deviation between the parameters of the battery model obtained this time and the parameters of the battery model obtained last time is greater than the preset range, an alarm is issued for the battery corresponding to the battery model of the target battery cluster.

[0016] In one possible implementation, the controller is also used to compare the parameters of the battery model obtained this time with the average parameter values ​​of the battery model of the target battery cluster. If the deviation between the parameters of the battery model this time and the average parameter values ​​is within a preset range, the parameters of the battery model of the target battery cluster are updated; if the deviation between the parameters of the battery model this time and the average parameter values ​​is greater than the preset range, an alarm is issued for the battery corresponding to the battery model of the target battery cluster.

[0017] In one possible implementation, the controller is also used to compare the parameters of the battery model obtained this time with the parameters of the battery model obtained last time, and to compare the parameters of the battery model obtained this time with the average parameter value of the battery model of the target battery cluster. If the deviation between the parameters of the battery model obtained this time and the parameters of the battery model obtained last time is greater than a preset range, and the deviation between the parameters of the battery model obtained this time and the average parameter value is greater than the preset range, the battery corresponding to the battery model of the target battery cluster will sound an alarm.

[0018] It should be understood that the deviation of the above parameter comparison can be a specific value or a corresponding percentage, such as a deviation of 2%, 5%, etc.

[0019] In one possible implementation, the controller is specifically used for peak shaving of the energy storage system and when the target battery cluster is in an idle period when it is fully charged or empty, to control the DC / DC converter connected to the target battery cluster to inject a detection current into the target battery cluster; when the target battery cluster is fully charged, the detection current is a discharge current; when the target battery cluster is empty, the detection current is a charging current.

[0020] In a possible implementation, the controller is specifically used to supplement the power of the target battery cluster to a preset state of charge when the energy storage system is frequency modulating and in an idle period, and controls the DC / DC converter connected to the target battery cluster to inject a detection current into the target battery cluster.

[0021] Based on the above-provided energy storage system, the present application also provides a detection method for an energy storage system. The advantages brought by the corresponding scheme of the above energy storage system are also applicable to the method, which will not be repeated here. The energy storage system includes: multiple battery clusters and multiple DC / DC converters, and the multiple DC / DC converters correspond to the multiple battery clusters one by one; each battery cluster in the multiple battery clusters is connected to the DC bus through a corresponding DC / DC converter, and the multiple battery clusters include a target battery cluster and other battery clusters as the detected objects; the method includes: controlling the DC / DC converters corresponding to the target battery cluster in the multiple DC / DC converters to inject a detection current into the target battery cluster, and the detection current comes from all or part of the remaining battery clusters in the multiple battery clusters except the target battery cluster; obtaining the parameters of the target battery cluster according to the voltage change of the target battery cluster caused by the detection current, and the parameters include at least one or more of the ohmic internal resistance, polarization internal resistance and polarization capacitance of the batteries in the target battery cluster.

[0022] In one possible implementation, the parameters of the target battery cluster are the parameters of the battery model of the target battery cluster; the voltage change includes the change of the open circuit voltage of the batteries in the target battery cluster and the change of the port voltage; the parameters of the battery model of the target battery cluster are obtained according to the change voltage caused by the detection current, specifically including: before or after the detection current disappears, the parameters of the battery model are obtained according to multiple change values ​​of the open circuit voltage of the batteries in the target battery cluster and multiple change values ​​of the port voltage.

[0023] In one possible implementation, the parameters of the battery model are obtained according to multiple change values ​​of the open circuit voltage of the batteries in the target battery cluster and multiple change values ​​of the port voltage, specifically including: performing curve fitting according to the multiple change values ​​of the open circuit voltage of the batteries in the target battery cluster and multiple change values ​​of the port voltage, and obtaining the parameters of the battery model according to the fitted curve; the curve is fitted by a genetic algorithm or a least squares method.

[0024] In a possible implementation, the battery model includes any one of the following: a Rint model, a Thevenin model, a PNGV model, or a second-order RC circuit model.

[0025] After obtaining the parameters of the battery model in the embodiment of the present application, the performance of the battery can be judged. The specific methods may include multiple methods, such as comparing with a preset threshold to determine whether the battery is damaged; in addition, comparing with the parameters of a new battery to determine whether the battery is damaged based on the deviation; in addition, comparing with the average parameter value of all battery clusters in the energy storage system to determine whether the battery is damaged. Several specific implementation methods are introduced below.

[0026] In a possible implementation, the method further includes: comparing the parameters of the battery model obtained this time with the parameters of the battery model obtained last time, and if the deviation between the parameters of the battery model obtained this time and the parameters of the battery model obtained last time is within a preset range, updating the parameters of the battery model of the target battery cluster; if the deviation between the parameters of the battery model obtained this time and the parameters of the battery model obtained last time is greater than the preset range, alarming the battery corresponding to the battery model of the target battery cluster;

[0027] or,

[0028] Compare the parameters of the battery model obtained this time with the average parameter values ​​of the battery model of the target battery cluster. If the deviation between the parameters of the battery model this time and the average parameter values ​​is within a preset range, update the parameters of the battery model of the target battery cluster. If the deviation between the parameters of the battery model this time and the average parameter values ​​is greater than the preset range, alarm the battery corresponding to the battery model of the target battery cluster.

[0029] or,

[0030] The parameters of the battery model obtained this time are compared with the parameters of the battery model obtained last time, and the parameters of the battery model obtained this time are compared with the average parameter values ​​of the battery model of the target battery cluster. If the deviation between the parameters of the battery model obtained this time and the parameters of the battery model obtained last time is greater than a preset range, and the deviation between the parameters of the battery model obtained this time and the average parameter value is greater than the preset range, the battery corresponding to the battery model of the target battery cluster will sound an alarm.

[0031] In a possible implementation, a DC / DC converter among multiple DC / DC converters connected to a target battery cluster is controlled to inject a detection current into the target battery cluster, specifically including: when the energy storage system is performing peak regulation and the target battery cluster is in an idle period of full charge or empty charge, the DC / DC converter connected to the target battery cluster is controlled to inject a detection current into the target battery cluster; when the target battery cluster is fully charged, the detection current is a discharge current; when the target battery cluster is empty charge, the detection current is a charging current.

[0032] In one possible implementation, a DC / DC converter among multiple DC / DC converters connected to a target battery cluster is controlled to inject a detection current into the target battery cluster, specifically including: the energy storage system performs frequency modulation and replenishes the power of the target battery cluster to a preset state of charge during an idle period, and controls the DC / DC converter connected to the target battery cluster to inject a detection current into the target battery cluster.

[0033] This application has at least the following advantages:

[0034] The energy storage system includes: a controller, multiple battery clusters and multiple DC / DC converters, each battery cluster is connected to the DC bus through a corresponding DC / DC converter; the controller controls the corresponding DC / DC converter of the target battery cluster connected to the multiple DC / DC converters to inject a detection current into the target battery cluster, and the detection current comes from all or part of the remaining battery clusters in the multiple battery clusters except the target battery cluster; the parameters of the target battery cluster are obtained according to the voltage change caused by the detection current, and the parameters at least obtain one or more of the ohmic internal resistance, polarization internal resistance and polarization capacitance of the battery in the target battery cluster. The energy storage system provided by the embodiment of the present application does not need to add new equipment, thereby saving costs; and it does not require an external energy source to perform performance testing on the batteries of the battery cluster, for example, it does not need to draw power from the AC power grid side to perform battery testing, which can avoid interference with the AC power grid; it does not need to set up a new external energy source, and only needs to draw power from the battery cluster. In addition, the energy storage system provided in the embodiment of the present application can obtain not only the ohmic internal resistance of the battery, but also the polarization internal resistance and polarization capacitance of the battery when multiple parameters are obtained, thereby more comprehensively reflecting the performance of the battery. When a problem occurs in the battery, an alarm can be issued in time to facilitate taking measures to avoid causing greater damage. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 A schematic diagram of an energy storage system provided in an embodiment of the present application;

[0036] Figure 2 A schematic diagram of another energy storage system provided in an embodiment of the present application;

[0037] Figure 3 A schematic diagram of a simulation circuit corresponding to a battery model provided in an embodiment of the present application;

[0038] Figure 4 A schematic diagram of the HPPC of a battery provided in an embodiment of the present application;

[0039] Figure 5 A schematic diagram of detecting current under full power condition provided in an embodiment of the present application;

[0040] Figure 6 A schematic diagram of detecting current in an empty-electric condition provided in an embodiment of the present application;

[0041] Figure 7 A flow chart of a detection method for an energy storage system provided in an embodiment of the present application. DETAILED DESCRIPTION

[0042] The technical solutions in the embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application.

[0043] The terms "first", "second", etc. in the following description are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of this application, unless otherwise specified, "plurality" means two or more.

[0044] In this application, unless otherwise clearly specified and limited, the term "connection" should be understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection or an indirect connection through an intermediate medium. In addition, the term "coupling" can be a way of achieving electrical connection for signal transmission. "Coupling" can be a direct electrical connection or an indirect electrical connection through an intermediate medium.

[0045] In order to enable those skilled in the art to better understand the technical solution provided by the embodiments of the present application, the application scenarios of the technical solution are first introduced below in conjunction with the accompanying drawings.

[0046] The embodiment of the present application does not limit the energy source of the battery cluster in the energy storage system, which can be derived from solar energy, such as photovoltaic power generation; or from wind energy, such as wind power generation. This application only introduces the detection of batteries in the energy storage system, which is introduced below in conjunction with the accompanying drawings.

[0047] System Example

[0048] See also Figure 1 , which is a schematic diagram of an energy storage system provided in an embodiment of the present application.

[0049] The energy storage system generally includes multiple battery clusters. The embodiments of the present application do not limit the specific number of battery clusters, and the number of battery clusters can be set according to actual needs. In addition, the power station generally includes multiple energy storage systems to increase the capacity of the power station. The power station can control the energy storage system to connect to the grid when necessary. When the energy storage system is connected to the grid, it needs to output AC power for grid connection. Therefore, the energy storage system generally also includes an energy storage inverter (not shown in the figure). The present application does not specifically limit the specific topology of the energy storage inverter.

[0050] Since the battery cluster outputs direct current, multiple battery clusters are connected to the DC bus. Multiple DC / DC converters correspond to multiple battery clusters one by one, such as Figure 1 As shown, in the embodiment of the present application, each battery cluster corresponds to a DC / DC converter, for example Figure 1The embodiment of the present application does not limit the number of battery modules included in each battery cluster. The figure takes each battery cluster as an example, wherein each battery cluster includes n battery modules connected in series, that is, the first battery module 201, the second battery module 202, the third battery module 203, and the nth battery module 20n are connected in series to form the first battery cluster. The remaining battery clusters are similar and will not be described one by one here. In this embodiment, each battery module corresponds to a battery control unit (BMU, Battery Management Unit) as an example for introduction. The BMU can realize the monitoring of the voltage, current, and temperature of the battery. Since each battery cluster is not directly connected but connected to the DC bus through its corresponding DC / DC converter, the circulation between the battery clusters can be avoided.

[0051] In order to avoid affecting the AC side when detecting the battery, the energy storage system provided in the embodiment of the present application can generate a detection current on the DC bus, and the detection current can be injected into the battery cluster to be detected. It should be understood that the detection current can be a charging current or a discharging current. Therefore, when the detection current is a charging current, the direction of the detection current is to flow from the DC bus into the battery cluster to be detected, which is referred to as the target battery cluster for the convenience of description. When the detection current is a discharging current, the direction of the detection current is to flow from the target battery cluster to the DC bus.

[0052] In addition, the energy storage system provided in the embodiment of the present application injects the detection current into the entire target battery cluster for battery detection, but the specific detection is to detect the performance of a single battery in the battery cluster. Since the batteries in the battery cluster are connected in series, the detection current is equal, and the detection current is a known parameter during actual detection. As long as there is a problem with one battery, an alarm will be issued. Due to individual differences in batteries during actual use, some batteries may be intact, while others may have problems. Therefore, each battery needs to be tested.

[0053] See also Figure 2 , which is a schematic diagram of another energy storage system provided in an embodiment of the present application.

[0054] The energy storage system provided in the embodiment of the present application includes: a controller 300, a plurality of battery clusters and a plurality of DC / DC converters. Figure 2As shown, for the convenience of introduction, the energy storage system including three battery clusters is taken as an example for introduction. It should be understood that two battery clusters may be included, or a greater number of battery clusters may be included. The first battery cluster BAT1 is connected to the DC bus through the first DC / DC converter 101; the second battery cluster BAT2 is connected to the DC bus through the second DC / DC converter 102; and the third battery cluster BAT3 is connected to the DC bus through the third DC / DC converter 103. The controller 300 is connected to the first DC / DC converter 101, the second DC / DC converter 102, and the third DC / DC converter 103. The multiple battery clusters include a target battery cluster as a detected object and the remaining battery clusters.

[0055] The controller 300 is used to control the DC / DC converters corresponding to the target battery cluster among the multiple DC / DC converters to inject a detection current into the target battery cluster, wherein the detection current comes from all or part of the remaining battery clusters except the target battery cluster among the multiple battery clusters, wherein the detection current may be a charging current or a discharging current of the bus battery cluster; and obtain the parameters of the target battery cluster according to the voltage change caused by the detection current, wherein the parameters include at least one or more of the ohmic internal resistance, polarization internal resistance and polarization capacitance of the battery in the target battery cluster. For example, when the detection current is a charging current, the remaining battery clusters except the target battery cluster are used as energy sources; when the detection current is a discharging current, the remaining battery clusters except the target battery cluster are used as loads.

[0056] The parameters of the target battery cluster may be parameters of a battery model of the batteries in the target battery cluster. The battery model may be established based on an analog circuit equivalent to the battery, and the battery model is obtained based on the analog circuit corresponding to the target battery cluster. The battery model is used to represent the relationship between the voltage, current and time of the batteries in the target battery cluster.

[0057] The specific type of battery model is not limited in the embodiments of the present application, as long as the ohmic internal resistance, polarization internal resistance and polarization capacitance of the battery can be obtained according to the parameters in the battery model. For example, the battery model may include any of the following: Rint model, Thevenin model, PNGV model or second-order RC circuit model. It should be understood that the battery model is an equation including a fluctuating voltage, and the parameters of the battery model can be obtained by detecting the voltage change caused by the current, and then the ohmic internal resistance, polarization internal resistance and polarization capacitance of the battery can be obtained according to the parameters in the battery model.

[0058] Specifically, when the batteries in the target battery cluster are detected, the controller controls the power of the DC / DC converter connected to the target battery cluster, generates a detection current to the target battery cluster through the DC / DC converter, and detects the voltage of each battery in the target battery cluster. It should be understood that when the battery passes the current, the voltage of the battery will change, that is, the changed voltage is detected. The energy source of the detection current can come from one battery cluster among the remaining battery clusters, or from multiple battery clusters among the remaining battery clusters.

[0059] For example, when detecting the battery in the first battery cluster BAT1, taking the detection current as the charging current as an example, the first battery cluster BAT1 is the target battery cluster, and the controller 300 controls the first DC / DC converter 101 to inject the detection current into the first battery cluster BAT1, that is, to charge the first battery cluster BAT1 with the detection current, and the energy of the detection current comes from the second battery cluster BAT2 and the third battery cluster BAT3, that is, the detection current comes from the battery cluster inside the energy storage system, not from the outside, such as not from the power grid, so it has no effect on the AC side. For example, when the application scenario of the energy storage system is photovoltaic, the detection current does not come from the photovoltaic array, and has no effect on the photovoltaic system.

[0060] The energy storage system provided in the embodiment of the present application does not require the addition of new equipment, thereby saving costs; and does not require an external energy source to perform performance testing on the batteries of the battery cluster. For example, it is not necessary to draw power from the AC power grid to perform battery testing, thereby avoiding interference with the AC power grid; and it is not necessary to set up a new external energy source, and only power can be drawn from the inside of the battery cluster. In addition, the energy storage system provided in the embodiment of the present application can not only obtain the ohmic internal resistance of the battery, but also the polarization internal resistance and polarization capacitance of the battery, thereby more comprehensively reflecting the performance of the battery. When a problem occurs with the battery, an alarm can be given in time, making it easier to take measures to avoid causing greater damage.

[0061] The embodiments of the present application do not specifically limit the specific detection time. For example, the detection time can be actively set under peak load or frequency modulation conditions to minimize the impact on the normal operation of the energy storage system. For example, the time length for injecting the detection current can be set at the minute level, and the sampling of the detection data and the acquisition of the parameters of the battery model can be completed within 1 hour, such as sampling the port voltage and the open circuit voltage.

[0062] The following introduces the battery model as a second-order RC circuit model.

[0063] See also Figure 3 , which is a schematic diagram of a simulation circuit corresponding to a battery model provided in an embodiment of the present application.

[0064] In this embodiment, the battery model is introduced as a second-order RC circuit model as an example. Since the battery in the energy storage system generally adopts a lithium iron phosphate battery, a second-order equivalent circuit model can be used. The circuit model includes two RC circuits in series to simulate the electrochemical polarization and concentration polarization phenomena of the lithium battery. When the battery model is a second-order RC circuit model, the polarization internal resistance includes the electrochemical polarization internal resistance and the concentration polarization internal resistance; the polarization capacitor includes the electrochemical polarization capacitor and the concentration polarization capacitor. This circuit model can accurately reflect the dynamic and static characteristics of the battery, and the RC order is not high, the solution is real-time, and the parameter identification is easy to achieve, which is convenient for engineering application.

[0065] The resistor and capacitor in each RC circuit are connected in parallel. Figure 3 As shown, the first RC circuit includes a first resistor R P and the first capacitor C P , the second RC circuit includes a second resistor R e and the second capacitor C e , two RC resistors are connected in series with the ohmic internal resistance R Ω In series. Among them, the first capacitor C P The voltage across the two ends is V P Indicates that the second capacitor C e The voltage across the two ends is V e express.

[0066] Figure 3 Uoc represents the open circuit voltage of the battery, U L Indicates the terminal voltage of the battery. Figure 3 It can be seen that the port voltage U L Equal to Uoc, V P 、V e and R Ω The sum of the voltage Vr on the L =Uoc+V P +V e +Vr. It should be understood that for the battery, Uoc and U L Can be sampled.

[0067] Due to the characteristics of the battery, when the battery is charged or discharged, that is, when the current is detected, the battery voltage will change, and when the current disappears, the battery voltage will continue to change. The embodiment of the present application does not limit whether the changing voltage is the voltage generated when the detection current exists, or the changing voltage generated after the detection current disappears. That is, the changing voltage includes the open circuit voltage and port voltage of the battery in the target battery cluster; the controller is specifically used to obtain the parameters of the battery model according to multiple change values ​​of the open circuit voltage of the battery in the target battery cluster and multiple change values ​​of the port voltage before or after the detection current disappears. Since the battery model includes multiple parameters, multiple change values ​​of the changing voltage are required to obtain multiple parameters.

[0068] In order to obtain the parameters of the circuit model more accurately, curve fitting can be performed, for example, the controller is specifically used to perform curve fitting according to multiple change values ​​of the open circuit voltage of the battery in the target battery cluster and multiple change values ​​of the port voltage, and the parameters of the battery model are obtained according to the curve obtained by fitting; the embodiment of the present application does not limit the specific algorithm of curve fitting, for example, curve fitting is performed by genetic algorithm or least squares method. The fitted curve can be a voltage mutation curve when the detection current is generated; for example, within 5s of the detection current; it can also be a rebound curve after the detection current disappears; it can also be a depolarization curve when the detection current is stable, which is not specifically limited in the embodiment of the present application.

[0069] After obtaining the parameters of the battery model in the embodiment of the present application, the performance of the battery can be judged. The specific methods may include multiple methods, such as comparing with a preset threshold to determine whether the battery is damaged; in addition, comparing with the parameters of a new battery to determine whether the battery is damaged based on the deviation; in addition, comparing with the average parameter value of all battery clusters in the energy storage system to determine whether the battery is damaged. Several specific implementation methods are introduced below.

[0070] The first one:

[0071] Compare the parameters of the battery model obtained this time with the parameters of the battery model obtained last time. If the deviation between the parameters of the battery model obtained this time and the parameters of the battery model obtained last time is within a preset range, update the parameters of the battery model of the target battery cluster, that is, the change in the parameters is caused by normal aging of the battery, not by a fault. If the deviation between the parameters of the battery model obtained this time and the parameters of the battery model obtained last time is greater than the preset range, an alarm is issued for the battery corresponding to the battery model of the target battery cluster. If the deviation is too large, it means that there is a problem with the battery, and an alarm is required to replace or repair it in time.

[0072] Second type:

[0073] Compare the parameters of the battery model obtained this time with the average values ​​of the parameters of the battery model of the target battery cluster this time; if the deviation between the parameters of the battery model this time and the average values ​​of the parameters is within a preset range, update the parameters of the battery model of the target battery cluster, that is, the change in the parameters is caused by normal aging of the battery, not by a fault; if the deviation between the parameters of the battery model this time and the average values ​​of the parameters is greater than the preset range, an alarm is issued for the battery corresponding to the battery model of the target battery cluster; a large deviation indicates that there is a problem with the battery, and an alarm is required to replace or repair it in time;

[0074] The third type:

[0075] The parameters of the battery model obtained this time are compared with the parameters of the battery model obtained last time, and the parameters of the battery model obtained this time are compared with the average parameter values ​​of the battery model of the target battery cluster. If the deviation between the parameters of the battery model obtained this time and the parameters of the battery model obtained last time is greater than a preset range, and the deviation between the parameters of the battery model obtained this time and the average parameter value is greater than the preset range, the battery corresponding to the battery model of the target battery cluster will sound an alarm. If the deviation is too large, it means that there is a problem with the battery, and an alarm is required for timely replacement or repair.

[0076] The fourth type:

[0077] Compare the parameters of the battery model with the parameters of a new battery:

[0078] The battery parameters obtained according to the detection current are compared with the parameters of the new battery. If the deviation between the battery parameters and the parameters of the new battery is within the preset range, the parameters of the battery model of the target battery cluster are updated, that is, the change in parameters is caused by normal aging of the battery, not by a fault. If the deviation between the parameters of this battery model and the parameters of the new battery is greater than the preset range, an alarm is issued for the battery corresponding to the battery model of the target battery cluster. If the deviation is too large, it means that there is a problem with the battery, and an alarm is required for timely replacement or repair.

[0079] It should be understood that the deviation of the above parameter comparison can be a specific value or a corresponding percentage, such as a deviation of 2%, 5%, etc.

[0080] For new batteries, the hybrid pulse power characteristic (HPPC) working condition can be used to calibrate the battery parameters. The battery is adjusted to a preset number of states of charge (SOC) at a constant current (constant power). For example, the SOC changes at intervals of 10% or 15%, and the changes in the port voltage and open circuit voltage of the battery corresponding to each SOC are recorded to obtain the parameters of the battery model of the new battery by fitting.

[0081] See also Figure 4 , which is a schematic diagram of the HPPC of a battery provided in an embodiment of the present application.

[0082] Figure 4 The middle horizontal axis is time, in minutes (min); the left vertical axis is current, in A; the right vertical axis is SOC.

[0083] Figure 4The calibration is performed at intervals of 10% of the SOC, and 11 SOC points (0, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%) of the new battery are calibrated for the purpose of introduction. It should be understood that a larger number of SOC points can also be calibrated, so that a higher density of calibration parameters of the new battery can be obtained, such as 21 SOC points at intervals of 5%. The curve is fitted by recording the change values ​​of the port voltage and open circuit voltage of the new battery at each SOC point.

[0084] The following describes the process of battery detection of the energy storage system provided by the embodiment of the present application under two typical working conditions of peak load regulation and frequency regulation in combination with the accompanying drawings. The following first describes the detection of the battery under the peak load regulation condition.

[0085] See also Figure 5 , which is a schematic diagram of detecting current under full-charge conditions provided in an embodiment of the present application.

[0086] Figure 5 The horizontal axis represents time in minutes (min), and the vertical axis represents current in A. A negative detection current represents a discharge current, and a positive detection current represents a charge current.

[0087] The controller is specifically used for peak shaving of the energy storage system and when the target battery cluster is in an idle period with full charge, the target DC / DC converter is controlled to inject a detection current into the target battery cluster. Since the target battery cluster is fully charged and does not need to be charged, the corresponding detection current at this time is a discharge current, which can be a relatively large pulse discharge current. Figure 5 Taking the injected detection current of -300A as an example, it should be understood that since the detection current is a discharge current, it is expressed as a negative number.

[0088] In addition, there is another possible implementation method, in a fully charged state, a relatively large pulse current is used for discharge while a relatively small pulse current is used for charging. The relatively large pulse current discharge may be a rated current discharge.

[0089] In order not to affect the normal peak-shaving operation of the energy storage system, the target battery cluster can be detected during the idle period of peak-shaving.

[0090] The above describes the detection of the target battery cluster of the energy storage system when it is fully charged for peak load regulation. The following describes the detection of the target battery cluster when it is empty for peak load regulation.

[0091] See also Figure 6 , which is a schematic diagram of detecting current under empty-electric conditions provided in an embodiment of the present application.

[0092] Figure 6The horizontal axis represents time in minutes (min), and the vertical axis represents current in A. A negative detection current represents a discharge current, and a positive detection current represents a charge current.

[0093] The controller is specifically used for peak shaving of the energy storage system and when the target battery cluster is in an idle period with no electricity, it controls the target DC / DC converter to inject a detection current into the target battery cluster; since the target battery cluster needs to be charged when it is in an idle period, the detection current is a charging current, and at this time the charging current can be a larger pulse charging current. Figure 6 The larger charging current shown is 320A. It should be understood that when the battery is charged with a larger charging current, the battery may have a smaller discharge current. Figure 6 -160A in the middle indicates a smaller discharge current. That is, when the battery is empty, the detection current can be a larger charging current, but at the same time there may be a smaller discharge current. Figure 6 The above is only a schematic illustration, and the discharge current may not exist or be smaller, which will not be described in detail here. The larger current charging may be the rated current charging.

[0094] In actual energy storage systems, although the performance of new batteries is not much different when all battery clusters are new, individual batteries may age seriously and cause abnormalities over time. Therefore, under the same detection current, the curves of the changing voltages corresponding to each battery are inconsistent, that is, the relationship curve between voltage and time, for example, the horizontal axis can be time and the vertical axis can be voltage. Therefore, the parameters of the battery model can be obtained by fitting the curve, so as to judge whether there is a problem with the battery based on the parameters.

[0095] The above is an introduction to the battery detection of the energy storage system during peak load regulation. The following is an introduction to the battery detection of the energy storage system during frequency regulation.

[0096] In order not to affect the normal frequency regulation of the energy storage system, the target battery cluster can be detected during the idle period of frequency regulation.

[0097] The controller is specifically used to replenish the power of the target battery cluster to the preset state of charge SOC during the idle period of the energy storage system for frequency modulation, and control the target DC / DC converter to inject a detection current into the target battery cluster. The embodiment of the present application does not limit the size of the preset SOC, for example, it can be 50%, or it can be 40% or 60%. For example, after the SOC is replenished to the middle section, for example, about 50% during the idle period of frequency modulation, the battery detection is actively performed, and the detection current is injected into the battery of the target battery cluster. The detection current at this time can be the rated charging current or the rated discharging current.

[0098] In addition, the embodiments of the present application can also be used for scenarios where power is turned on after being left idle for a long time. For example, a bidirectional pulse status detection can be performed before the energy storage system works normally. For example, the battery is first charged with a detection current to detect the battery's port voltage and open-circuit voltage, and then the battery is discharged with a detection current to detect the battery's port voltage and open-circuit voltage. As long as the parameters detected when the battery is charging or discharging are abnormal, an alarm is issued for the battery.

[0099] The following is an introduction based on the specific parameters of the battery, as shown in Table 1. The data in Table 1 is only an example.

[0100] Table 1

[0101]

[0102]

[0103] Table 1 lists two batteries A and B in the target battery cluster. It should be understood that batteries A and B both refer to single cells in the target battery cluster. Table 1 only lists the state parameters of battery A in the previous detection, and battery B is not specifically listed.

[0104] As can be seen from Table 1, the current battery parameters are compared with the previous parameters, and the current battery parameters are compared with the average parameter values ​​of the target battery cluster. If the deviation between the current parameters and the previous parameters is greater than the preset range, and the deviation between the current parameters and the average parameter values ​​of the target battery cluster is also greater than the preset range, the battery is alarmed, indicating that there is a problem with the battery. The alarm is triggered only when both of the above judgment conditions are met, so as to avoid misdetection of the battery and affect the normal operation of the energy storage system. For example, if the battery detection frequency is low and the detection is performed only once in a long time, the natural aging of the battery will also cause a large deviation between the parameters obtained in this detection and the parameters obtained in the previous detection. In this way, if the deviation between the current parameters and the previous parameters is greater than the preset range, an alarm is triggered, which is obviously unreasonable.

[0105] It should be understood that the preset range is an absolute value relative to the deviation. As long as the absolute value of the deviation is within the preset range, for example, the preset range is 5%. The deviations of the various parameters of battery A in Table 1 above are normal, and the absolute value of the deviation of the ohmic internal resistance of battery B is greater than 5%, that is, the parameter deviation of battery B this time and battery B last time is -6%, and the deviation of the parameter average value of battery B this time and the target battery cluster this time is -8%. In this case, an alarm is issued for battery B. Although the concentration polarization internal resistance, electrochemical polarization internal resistance, concentration polarization capacitance, and electrochemical polarization capacitance of battery B are all normal, an alarm is issued for the battery as long as one of the multiple parameters is abnormal.

[0106] The concentration polarization internal resistance, electrochemical polarization internal resistance, concentration polarization capacitance, electrochemical polarization capacitance and ohmic internal resistance of the battery can be obtained according to the parameters of the battery model.

[0107] The energy storage system provided in the embodiment of the present application can be equivalent to a battery model through a second-order RC circuit, and the battery model is convenient for engineering applications; the parameters of the battery model can be used to obtain multiple parameters such as the battery's ohmic internal resistance, polarization capacitance, and polarization resistance, so as to comprehensively evaluate the battery state; and the remaining battery clusters are used to generate a detection current for the target battery cluster, without the need for an external energy source, so that costs can be saved and there will be no impact on the AC side. The energy storage system can detect batteries during idle periods of typical operating conditions such as frequency modulation and peak regulation, and try not to affect the normal operation of the energy storage system.

[0108] Method Embodiment

[0109] Based on an energy storage system provided in the above embodiment, an embodiment of the present application further provides a detection method for an energy storage system, which is described in detail below in conjunction with the accompanying drawings.

[0110] See also Figure 7 , which is a flow chart of a detection method for an energy storage system provided in an embodiment of the present application.

[0111] The energy storage system detection method provided in this embodiment, wherein the energy storage system includes: a plurality of battery clusters and a plurality of DC / DC converters, wherein the plurality of DC / DC converters correspond to the plurality of battery clusters one by one; each battery cluster in the plurality of battery clusters is connected to a DC bus through a corresponding DC / DC converter; the plurality of battery clusters include a target battery cluster as a detection object and other battery clusters;

[0112] The method includes:

[0113] S701: Control a DC / DC converter among the multiple DC / DC converters that is connected to a target battery cluster to inject a detection current into the target battery cluster, where the detection current comes from some or all of the remaining battery clusters among the multiple battery clusters except the target battery cluster;

[0114] Since each battery cluster is not directly connected to each other but connected to the DC bus through its own corresponding DC / DC converter, circulating current between battery clusters can be avoided.

[0115] S702: Obtaining parameters of the target battery cluster according to the change voltage caused by the detection current, the parameters including at least one or more of the ohmic internal resistance, polarization internal resistance and polarization capacitance of the batteries in the target battery cluster.

[0116] Among them, the parameters of the target battery cluster can be the parameters of the battery model of the batteries in the target battery cluster. The battery model can be established based on the analog circuit equivalent to the battery. The battery model is obtained based on the analog circuit corresponding to the target battery cluster. The battery model is used to represent the relationship between the voltage, current and time of the batteries in the target battery cluster.

[0117] The specific type of battery model is not limited in the embodiments of the present application, as long as the ohmic internal resistance, polarization internal resistance and polarization capacitance of the battery can be obtained according to the parameters in the battery model. For example, the battery model may include any one of the following: Rint model, Thevenin model, PNGV model or second-order RC circuit model. It should be understood that the battery model is an equation including a changing voltage, and the parameters of the battery model can be obtained by detecting the changing voltage caused by the current, and then at least one of the ohmic internal resistance, polarization internal resistance and polarization capacitance of the battery can be obtained according to the parameters in the battery model.

[0118] The detection method of the energy storage system provided in the embodiment of the present application can generate a detection current on the DC bus in order not to affect the AC side when detecting the battery. The detection current can be injected into the target battery cluster to be detected. It should be understood that the detection current can be the charging current of the target battery cluster or the discharging current. Therefore, when the detection current is a charging current, the direction of the detection current is to flow from the DC bus into the target battery cluster to be detected. When the detection current is a discharging current, the direction of the detection current is to flow from the target battery cluster to the DC bus.

[0119] In addition, the detection method of the energy storage system provided in the embodiment of the present application detects the batteries in the battery cluster. Although the detection current is injected into the entire target battery cluster, the specific detection is to detect the performance of a single battery in the battery cluster. Since the batteries in the battery cluster are connected in series, the detection current is equal. The detection current is a known parameter during actual detection. As long as there is a problem with one battery, an alarm will be issued. In actual use, there are individual differences in batteries. Some batteries may be intact, while others may have problems. Therefore, each battery needs to be tested.

[0120] The variable voltage includes the open circuit voltage and the port voltage of the battery in the target battery cluster; the parameters of the battery model of the target battery cluster are obtained according to the variable voltage caused by the detection current, specifically including:

[0121] Before or after the detection current disappears, the parameters of the battery model are obtained according to a plurality of change values ​​of the open circuit voltage and a plurality of change values ​​of the port voltage of the batteries in the target battery cluster.

[0122] The parameters of the battery model are obtained according to multiple change values ​​of the open circuit voltage of the battery in the target battery cluster and multiple change values ​​of the port voltage, specifically including:

[0123] Curve fitting is performed based on multiple change values ​​of the open circuit voltage of the battery in the target battery cluster and multiple change values ​​of the port voltage, and the parameters of the battery model are obtained based on the fitted curve; the curve is fitted by genetic algorithm or least square method. The fitted curve can be a voltage mutation curve when the detection current is generated; for example, within 5s of the detection current; it can also be a rebound curve after the detection current disappears; it can also be a depolarization curve when the detection current is stable, which is not specifically limited in the embodiments of the present application.

[0124] The detection method of the energy storage system provided in the embodiment of the present application further includes: comparing the parameters of the battery model obtained this time with the parameters of the battery model obtained last time, and if the deviation between the parameters of the battery model obtained this time and the parameters of the battery model obtained last time is within a preset range, updating the parameters of the battery model of the target battery cluster; if the deviation between the parameters of the battery model obtained this time and the parameters of the battery model obtained last time is greater than the preset range, alarming the battery corresponding to the battery model of the target battery cluster;

[0125] or,

[0126] Compare the parameters of the battery model obtained this time with the average values ​​of the parameters of the battery model of the target battery cluster this time; if the deviation between the parameters of the battery model this time and the average values ​​of the parameters is within a preset range, update the parameters of the battery model of the target battery cluster; if the deviation between the parameters of the battery model this time and the average values ​​of the parameters is greater than the preset range, alarm the battery corresponding to the battery model of the target battery cluster;

[0127] or,

[0128] The parameters of the battery model obtained this time are compared with the parameters of the battery model obtained last time, and the parameters of the battery model obtained this time are compared with the average parameter values ​​of the battery model of the target battery cluster. If the deviation between the parameters of the battery model obtained this time and the parameters of the battery model obtained last time is greater than a preset range, and the deviation between the parameters of the battery model obtained this time and the average parameter value is greater than the preset range, the battery corresponding to the battery model of the target battery cluster will sound an alarm.

[0129] Another possible implementation is to compare the parameters of the battery model with the parameters of the new battery:

[0130] The battery parameters obtained according to the detection current are compared with the parameters of the new battery. If the deviation between the battery parameters and the parameters of the new battery is within the preset range, the parameters of the battery model of the target battery cluster are updated, that is, the change in parameters is caused by normal aging of the battery, not by a fault. If the deviation between the parameters of this battery model and the parameters of the new battery is greater than the preset range, an alarm is issued for the battery corresponding to the battery model of the target battery cluster. If the deviation is too large, it means that there is a problem with the battery, and an alarm is required for timely replacement or repair.

[0131] It should be understood that the deviation of the above parameter comparison can be a specific value or a corresponding percentage, such as a deviation of 2%, 5%, etc.

[0132] The step of controlling a DC / DC converter connected to the target battery cluster among the plurality of DC / DC converters to inject a detection current into the target battery cluster specifically includes:

[0133] When the energy storage system is performing peak shaving and the target battery cluster is in an idle period of full or empty power, the DC / DC converter connected to the target battery cluster is controlled to inject a detection current into the target battery cluster; when the target battery cluster is fully charged, the detection current is a discharge current; when the target battery cluster is empty, the detection current is a charging current.

[0134] The step of controlling a DC / DC converter connected to the target battery cluster among the plurality of DC / DC converters to inject a detection current into the target battery cluster specifically includes:

[0135] The energy storage system performs frequency modulation and replenishes the target battery cluster to a preset state of charge during an idle period, and controls the target DC / DC converter to inject a detection current into the target battery cluster.

[0136] The embodiment of the present application does not limit the size of the preset SOC, for example, it can be 50%, or it can be 40% or 60%, etc. For example, after the SOC is replenished to the middle section, for example, about 50%, during the idle period of frequency modulation, the battery detection is actively performed, and the detection current is injected into the battery of the target battery cluster. At this time, the detection current can be the rated charging current or the rated discharging current.

[0137] The detection method of the energy storage system provided in the embodiment of the present application can be used to obtain a battery model equivalent to a second-order RC circuit, and the battery model is convenient for engineering applications; the parameters of the battery model can be used to obtain multiple parameters such as the battery's ohmic internal resistance, polarization capacitance, and polarization resistance, so as to comprehensively evaluate the battery state; and the remaining battery clusters are used to generate a detection current for the target battery cluster, without the need for an external energy source, so that costs can be saved and there will be no impact on the AC side. The energy storage system can detect batteries during idle periods of typical operating conditions such as frequency modulation and peak regulation, and try not to affect the normal operation of the energy storage system.

[0138] It should be understood that in this application, "at least one (item)" means one or more, and "more" means two or more. Any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of this application without departing from the content of the technical solution of this application shall still fall within the scope of protection of the technical solution of this application.

Claims

1. An energy storage system, characterized in that: include: A controller, a plurality of battery clusters and a plurality of DC / DC converters, wherein the plurality of DC / DC converters correspond to the plurality of battery clusters one by one; each battery cluster in the plurality of battery clusters is connected to a DC bus through a corresponding DC / DC converter, and the plurality of battery clusters include a target battery cluster as a detected object and other battery clusters; The controller is used to control the DC / DC converters among the multiple DC / DC converters connected corresponding to the target battery cluster to input a detection current into the target battery cluster, wherein the detection current is derived from all or part of the remaining battery clusters among the multiple battery clusters except the target battery cluster; and obtain parameters of the target battery cluster according to the voltage change of the target battery cluster caused by the detection current, wherein the parameters of the target battery cluster are parameters of a battery model of the target battery cluster, wherein the battery model includes an equation for a fluctuating voltage, and wherein the battery model is used to obtain the parameters of the target battery cluster through the voltage change caused by the detection current, wherein the parameters include one or more of the ohmic internal resistance, polarization internal resistance and polarization capacitance of the batteries in the target battery cluster.

2. The system according to claim 1, characterized in that The changed voltage includes an open circuit voltage and a port voltage of a battery in the target battery cluster; The controller is specifically used to obtain the parameters of the battery model according to multiple change values ​​of the open circuit voltage and multiple change values ​​of the port voltage of the batteries in the target battery cluster before or after the detection current disappears.

3. The system according to claim 2, characterized in that The controller is specifically used to perform curve fitting according to multiple change values ​​of the open circuit voltage and the port voltage of the batteries in the target battery cluster, and obtain the parameters of the battery model according to the fitted curve; the curve is fitted by genetic algorithm or least squares method.

4. The system according to claim 2 or 3, characterized in that: The battery model is obtained according to a simulation circuit corresponding to the target battery cluster, and the battery model is used to represent the relationship between the voltage, current and time of the batteries in the target battery cluster.

5. The system according to claim 4, characterized in that The battery model includes any one of the following: a Rint model, a Thevenin model, a PNGV model or a second-order RC circuit model.

6. The system according to any one of claims 2 to 5, characterized in that: The controller is further used to compare the parameters of the battery model obtained this time with the parameters of the battery model obtained last time, and if the deviation between the parameters of the battery model obtained this time and the parameters of the battery model obtained last time is within a preset range, the parameters of the battery model of the target battery cluster are updated; if the deviation between the parameters of the battery model obtained this time and the parameters of the battery model obtained last time is greater than the preset range, an alarm is issued for the battery corresponding to the battery model of the target battery cluster.

7. The system according to any one of claims 2 to 5, characterized in that: The controller is further used to compare the parameters of the battery model obtained this time with the average parameter values ​​of the battery model of the target battery cluster. If the deviation between the parameters of the battery model and the average parameter values ​​is within a preset range, the parameters of the battery model of the target battery cluster are updated; if the deviation between the parameters of the battery model and the average parameter values ​​is greater than the preset range, an alarm is issued for the battery corresponding to the battery model of the target battery cluster.

8. The system according to any one of claims 2 to 5, characterized in that: The controller is further used to compare the parameters of the battery model obtained this time with the parameters of the battery model obtained last time, and to compare the parameters of the battery model obtained this time with the average parameter value of the battery model of the target battery cluster. If the deviation between the parameters of the battery model obtained this time and the parameters of the battery model obtained last time is greater than a preset range, and the deviation between the parameters of the battery model obtained this time and the average parameter value is greater than the preset range, the battery corresponding to the battery model of the target battery cluster will sound an alarm.

9. The system according to any one of claims 1 to 6, characterized in that: The controller is specifically used for controlling a DC / DC converter connected to the target battery cluster to inject the detection current into the target battery cluster when the energy storage system is performing peak shaving and the target battery cluster is in an idle period of full charge or empty charge; when the target battery cluster is fully charged, the detection current is a discharge current; when the target battery cluster is empty charge, the detection current is a charging current.

10. The system according to any one of claims 1 to 7, characterized in that: The controller is specifically used to replenish the power of the target battery cluster to a preset state of charge when the energy storage system is frequency modulating and in an idle period, and to control the DC / DC converter connected to the target battery cluster to inject the detection current into the target battery cluster.

11. A detection method for an energy storage system, characterized in that: The energy storage system comprises: a plurality of battery clusters and a plurality of DC / DC converters, wherein the plurality of DC / DC converters correspond to the plurality of battery clusters one by one; each battery cluster in the plurality of battery clusters is connected to a DC bus through a corresponding DC / DC converter, and the plurality of battery clusters comprises a target battery cluster as a detected object and other battery clusters; The method includes: Controlling a DC / DC converter among the plurality of DC / DC converters connected to the target battery cluster to inject a detection current into the target battery cluster, wherein the detection current is derived from all or part of the remaining battery clusters among the plurality of battery clusters except the target battery cluster; Parameters of the target battery cluster are obtained according to the voltage change of the target battery cluster caused by the detection current. The parameters of the target battery cluster are parameters of a battery model of the target battery cluster. The battery model includes an equation for fluctuating voltage. The battery model is used to obtain the parameters of the target battery cluster through the voltage change caused by the detection current. The parameters include at least one or more of the ohmic internal resistance, polarization internal resistance and polarization capacitance of the batteries in the target battery cluster.

12. The method according to claim 11, characterized in that The voltage change includes a change in the open circuit voltage and a change in the port voltage of the battery in the target battery cluster; The step of obtaining the parameters of the battery model of the target battery cluster according to the changed voltage caused by the detection current specifically includes: Before or after the detection current disappears, the parameters of the battery model are obtained according to a plurality of change values ​​of the open circuit voltage and a plurality of change values ​​of the port voltage of the batteries in the target battery cluster.

13. The method according to claim 12, characterized in that The step of obtaining the parameters of the battery model according to the multiple change values ​​of the open circuit voltage and the multiple change values ​​of the port voltage of the batteries in the target battery cluster specifically includes: Curve fitting is performed according to multiple change values ​​of the open circuit voltage and the port voltage of the batteries in the target battery cluster, and the parameters of the battery model are obtained according to the fitted curve; the curve is fitted by genetic algorithm or least square method.

14. The method according to any one of claims 11 to 13, characterized in that: The battery model includes any one of the following: a Rint model, a Thevenin model, a PNGV model or a second-order RC circuit model.

15. The method according to claim 11, characterized in that Also includes: Compare the parameters of the battery model obtained this time with the parameters of the battery model obtained last time, and if the deviation between the parameters of the battery model obtained this time and the parameters of the battery model obtained last time is within a preset range, update the parameters of the battery model of the target battery cluster; if the deviation between the parameters of the battery model obtained this time and the parameters of the battery model obtained last time is greater than the preset range, alarm the battery corresponding to the battery model of the target battery cluster; or, Compare the parameters of the battery model obtained this time with the average values ​​of the parameters of the battery model of the target battery cluster this time; if the deviation between the parameters of the battery model this time and the average values ​​of the parameters is within a preset range, update the parameters of the battery model of the target battery cluster; if the deviation between the parameters of the battery model this time and the average values ​​of the parameters is greater than the preset range, alarm the battery corresponding to the battery model of the target battery cluster; or, The parameters of the battery model obtained this time are compared with the parameters of the battery model obtained last time, and the parameters of the battery model obtained this time are compared with the average parameter values ​​of the battery model of the target battery cluster. If the deviation between the parameters of the battery model obtained this time and the parameters of the battery model obtained last time is greater than a preset range, and the deviation between the parameters of the battery model obtained this time and the average parameter value is greater than the preset range, the battery corresponding to the battery model of the target battery cluster will sound an alarm.

16. The method according to any one of claims 11 to 15, characterized in that: The controlling a DC / DC converter among the plurality of DC / DC converters connected to the target battery cluster to inject a detection current into the target battery cluster specifically includes: When the energy storage system performs peak shaving and the target battery cluster is in an idle period of full charge or empty charge, the DC / DC converter connected to the target battery cluster is controlled to inject a detection current into the target battery cluster; when the target battery cluster is fully charged, the detection current is a discharge current; when the target battery cluster is empty charge, the detection current is a charging current.

17. The method according to any one of claims 11 to 16, characterized in that: The controlling a DC / DC converter among the plurality of DC / DC converters connected to the target battery cluster to inject a detection current into the target battery cluster specifically includes: The energy storage system performs frequency modulation and replenishes the target battery cluster to a preset state of charge during an idle period, and controls a DC / DC converter connected to the target battery cluster to inject a detection current into the target battery cluster.

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