Energy storage system charging and discharging control method, device and equipment

Abstract

The present invention discloses a method, device and equipment for controlling charging and discharging of an energy storage system. The energy storage system includes a bidirectional DC converter and a battery module. The bidirectional DC converter includes an LLC resonant converter and a buck-boost converter which are sequentially cascaded with the battery module. The method includes: obtaining the operating status of the energy storage system in an effective working state; if it is determined according to the operating status that the protection trigger condition preset for the battery module is currently met, controlling the LLC resonant converter to be in working mode and switching the buck-boost converter from working mode to standby mode to put the battery module into standby state; when the battery module is triggered to exit the standby state based on external changes of the energy storage system, the energy storage system returns to an effective working state. The present invention solves the technical problem of excessive battery loss.

Description

Technical Field

[0001] The present invention belongs to the technical field of charge and discharge control, and in particular relates to a charge and discharge control method, device and equipment for an energy storage system. Background Art

[0002] The energy storage system consists of a battery module and a bidirectional DC converter (bidirectional DC-DC converter), and the bidirectional DC converter can include a cascaded LLC resonant converter and a buck-boost converter. The LLC resonant converter is responsible for raising the voltage of the battery module to the effective controllable range of the buck-boost converter to meet the DC bus voltage requirements. It is also necessary to control the battery module and the bidirectional DC converter of the energy storage system in a coordinated manner. The strategy of controlling the battery module and the bidirectional DC converter in a coordinated manner is too simple, resulting in excessive battery loss. Summary of the invention

[0003] The embodiments of the present invention provide a method, device and equipment for controlling charging and discharging of an energy storage system to solve the technical problem of excessive battery loss.

[0004] In a first aspect, an embodiment of the present invention provides a method for controlling charging and discharging of an energy storage system, wherein the energy storage system comprises a bidirectional DC converter and a battery module, wherein the bidirectional DC converter comprises an LLC resonant converter and a buck-boost converter which are sequentially cascaded with the battery module, and wherein the method comprises: obtaining an operating status of the energy storage system in an effective working state; if it is determined according to the operating status that a protection trigger condition preset for the battery module is currently met, controlling the LLC resonant converter to be in an operating mode and switching the buck-boost converter from the operating mode to a standby mode, so that the battery module enters a standby state; when the battery module is triggered to exit the standby state based on an external change of the energy storage system, the energy storage system returns to the effective working state.

[0005] In combination with the first aspect of the present invention, in some embodiments, it also includes: if the battery module is continuously in a charging state within a first preset time period and the current SOC of the battery module is greater than a preset first charging cutoff SOC, it is determined that the protection trigger condition is currently met, and the operating status includes: the current SOC and charging and discharging status of the battery module; switching the energy storage system from the effective working state to a high power maintenance state.

[0006] In combination with the first aspect of the present invention, in some embodiments, after switching the energy storage system from the effective working state to the high-power maintenance state, it also includes: if it is monitored that the energy storage system is connected to an external load or the current SOC of the battery module is less than a preset second charging cut-off SOC, the buck-boost converter is switched back from the standby mode to the working mode, so that the battery module exits the standby state and discharges to maintain the DC bus voltage, and the first charging cut-off SOC is greater than the second charging cut-off SOC; the energy storage system is returned from the high-power maintenance state to the effective working state.

[0007] In combination with the first aspect of the present invention, in some embodiments, it also includes: if it is monitored that the charging and discharging current of the battery module is continuously in a preset first current range within a second preset time period, it is determined that the protection trigger condition is currently met; the operating status includes: the current size of the charging and discharging current of the battery module; switching the energy storage system from the effective working state to the no-load maintenance state.

[0008] In combination with the first aspect of the present invention, in some embodiments, after switching the energy storage system from the effective working state to the no-load maintenance state, it also includes: if it is monitored that the charging and discharging current of the battery module is in a preset second current range, switching the buck-boost converter back from the standby mode to the working mode to make the battery module exit the standby state and discharge to maintain the DC bus voltage, wherein the lower limit value of the second current range is greater than the upper limit value of the first current range; switching the energy storage system from the no-load maintenance state back to the effective working state.

[0009] In combination with the first aspect of the present invention, in some embodiments, it also includes: when the energy storage system is in a grid-connected state, if the current SOC of the battery module is less than the preset first backup SOC and is continuously in a discharging state within a third preset time period, it is determined that the protection trigger condition is currently met, and the operating status includes: whether the energy storage system is in a grid-connected state, the current SOC of the battery module, and the charging and discharging status; the energy storage system is switched from the effective working state to a standing power maintenance state.

[0010] In combination with the first aspect of the present invention, in some embodiments, after switching the energy storage system from the effective working state to the standing power maintenance state, it also includes: if it is monitored that the energy storage system is in an off-grid state, the current SOC of the battery module is greater than the preset second standby SOC, or an external power supply is supplying power to the energy storage system, the buck-boost converter is switched back from the standby mode to the working mode so that the battery module exits the standby state and discharges to maintain the DC bus voltage, and the first standby SOC is less than the second standby SOC; the energy storage system is switched back from the standing power maintenance state to the effective working state.

[0011] In combination with the first aspect of the present invention, in some embodiments, before obtaining the operating status of the energy storage system in an effective working state, it also includes: when the energy storage system is started, if the DC bus voltage is continuously less than a preset first reference value within a fourth preset time period, or the battery module is continuously in a discharge state within the fourth preset time period, controlling the LLC resonant converter and the buck-boost converter to be in a sleep mode, and outputting a first alarm message, wherein the first alarm message is used to prompt that the battery module is discharged; switching the energy storage system from a low-power startup pre-charging state to a fully discharged state; when the energy storage system is started, if the SOC of the battery module is greater than the preset low-power startup SOC, switching the energy storage system from the low-power startup pre-charging state back to the effective working state.

[0012] In combination with the first aspect of the present invention, in some embodiments, it also includes: when the energy storage system is in an effective working state, if it is monitored that the energy storage system is in an off-grid state and the current SOC of the battery module is less than a preset first alarm SOC, a second alarm information is output, and the second alarm information is used to prompt that the battery module is low on power; the energy storage system is switched from the effective working state to a low-power charge and discharge state; when the energy storage system is in the low-power charge and discharge state, if it is monitored that the current SOC of the battery module is greater than a preset second alarm SOC, the energy storage system is switched from the low-power charge and discharge state to the effective working state, and the first alarm SOC is less than the second alarm SOC.

[0013] In combination with the first aspect of the present invention, in some embodiments, after switching the energy storage system from the effective working state to the low-power charge and discharge state, it also includes: if it is monitored that the current SOC of the battery module is less than the discharge cut-off SOC, controlling the LLC resonant converter and the buck-boost converter to be in sleep mode, and outputting the first alarm information, and the discharge cut-off SOC is less than the first alarm SOC; switching the energy storage system from the low-power charge and discharge state to the fully discharged state, when the energy storage system is in the fully discharged state, if the DC bus voltage continues to be greater than a preset second reference value within a fifth preset time length, controlling the LLC resonant converter and the buck-boost converter to switch to the working mode, and the first reference value is less than the second reference value; switching the energy storage system from the fully discharged state to the low-power start-up pre-charging state.

[0014] In a second aspect, an embodiment of the present invention provides a charge and discharge control device for an energy storage system, wherein the energy storage system comprises a bidirectional DC converter and a battery module, wherein the bidirectional DC converter comprises an LLC resonant converter and a buck-boost converter which are sequentially cascaded with the battery module, and wherein the device comprises: a status acquisition unit, for acquiring the operating status of the energy storage system in an effective working state; an effective work exit unit, for controlling the LLC resonant converter to be in an operating mode and switching the buck-boost converter from the operating mode to the standby mode if it is determined according to the operating status that a preset protection trigger condition for the battery module is currently met, so that the battery module enters a standby state; and an effective work entry unit, for returning the energy storage system to the effective working state when the battery module is triggered to exit the standby state based on external changes of the energy storage system.

[0015] In a third aspect, an embodiment of the present invention provides an electronic device for use in an energy storage system, the electronic device comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements any one of the methods described in the first aspect when executing the computer program.

[0016] One or more technical solutions provided by the embodiments of the present invention achieve at least the following technical effects or advantages:

[0017] The embodiment of the present invention obtains the operating status of the energy storage system in an effective working state. If it is determined according to the operating status that the preset protection trigger condition for the battery module is currently met, the LLC resonant converter is controlled to be in working mode and the buck-boost converter is switched from working mode to standby mode, so that the battery module enters the standby state. When the battery module is triggered to exit the standby state based on the external changes of the energy storage system, the energy storage system will return to the effective working state and perform normal charging and discharging to adjust the external quantity. Since the LLC resonant converter is controlled to be in working mode and the buck-boost converter is switched from working mode to standby mode after the protection trigger condition is met, the battery module will enter the standby state and will not continue to charge and discharge, thereby protecting the battery module to reduce battery loss and thereby increase the battery life. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0019] Figure 1 A schematic diagram of an energy storage system application scenario in an embodiment of the present invention;

[0020] Figure 2 It is a flow chart of a method for controlling charging and discharging of an energy storage system according to an embodiment of the present invention;

[0021] Figure 3 A schematic diagram of state switching of an energy storage system in an embodiment of the present invention;

[0022] Figure 4 It is a functional module diagram of the energy storage system charge and discharge control device in an embodiment of the present invention;

[0023] Figure 5 Schematic diagram of the structure of an electronic device in an embodiment of the present invention. DETAILED DESCRIPTION

[0024] 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.

[0025] In the present invention, descriptions such as "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0026] The embodiment of the present invention provides a method for controlling charging and discharging of an energy storage system, referring to Figure 1 As shown, the energy storage system includes a bidirectional DC converter and a battery module. The bidirectional DC converter is used to connect the battery module to the DC bus, wherein the bidirectional DC converter includes an LLC resonant converter and a buck / boost converter (Buck / Boost converter) which are sequentially cascaded with the battery module. It should be noted that the bidirectional DC converter is used to realize the bidirectional flow of DC power. The LLC resonant converter increases the voltage of the battery module to within the effective controllable range of the buck / boost converter. The buck / boost converter can increase or decrease the input voltage to meet the needs of the DC bus voltage. In actual application scenarios, there can also be external power supplies and multiple loads connected to the DC bus through an inverter, and the power generation system (such as photovoltaic components and wind power components) is connected to the DC bus through a DC converter.

[0027] refer to Figure 1 As shown, the energy storage system charge and discharge control method provided by the embodiment of the present invention includes steps S101 to S103. Figure 1 and Figure 2 The following is an explanation of the charging and discharging control method of the energy storage system:

[0028] S101: Obtaining the operating status of the energy storage system in an effective working state.

[0029] It should be noted that the effective working state refers to the state when the energy storage system is normally charged and discharged to adjust the external quantity and no alarm information is issued. Among them, normal charging and discharging to adjust the external quantity includes two situations: the battery module supplies power to the load and the external power supply charges the battery module. In the effective working state of the energy storage system, the LLC resonant converter and the buck-boost converter are both in working mode, so that the battery module can discharge to the outside or be charged by the external power supply.

[0030] It should be noted that the operating conditions obtained include: one or more information such as the charging and discharging current of the energy storage system, the connection status between the energy storage system and the power grid (grid-connected status or off-grid status), the current SOC (state-of-charge) of the battery module, and the charging and discharging status of the battery module.

[0031] The energy storage system is in the grid-connected state, which means that the external power source is connected to the energy storage system, and the external power source can charge the battery module. On the contrary, the off-grid state means that the external power source is disconnected from the energy storage system, and the external power source cannot charge the battery module.

[0032] S102: If it is determined according to the operating status that the preset protection trigger condition for the battery module is currently met, the LLC resonant converter is controlled to be in the working mode and the buck-boost converter is switched from the working mode to the standby mode, so that the battery module enters the standby state.

[0033] After the protection triggering condition is met, by controlling the LLC resonant converter to be in the working mode and switching the buck-boost converter from the working mode to the standby mode, the battery module will stop charging and discharging to protect the battery module and reduce the loss of the battery module.

[0034] It should be understood that one or more protection trigger conditions may be provided, and when any protection trigger condition is met, the LLC resonant converter is controlled to be in the working mode and the buck-boost converter is switched from the working mode to the standby mode. Three situations in which the protection trigger condition is currently met are given below:

[0035] Case 1:

[0036] A high power maintenance state can be set relative to the effective working state of the energy storage system. The high power maintenance state of the energy storage system refers to a state in which the current SOC of the battery module is higher than the preset first charging cut-off SOC and charging does not continue. It is a protection state set to prevent the battery module from overcharging in a high power state.

[0037] When the energy storage system is in an effective working state, if the battery module is continuously in a charging state within a first preset time and the current SOC of the battery module is greater than a preset first charging cut-off SOC, it is determined that the protection trigger condition is currently met. At this time, by controlling the LLC resonant converter to be in working mode and switching the buck-boost converter from working mode to standby mode, the battery module enters the standby state, and further, the energy storage system is switched from an effective working state to a high power maintenance state.

[0038] The bidirectional DC converter can establish communication with the BMS (Battery Management System) of the battery module to obtain the current SOC of the battery module and determine the relationship between the current SOC and the first charging cut-off SOC.

[0039] It should be noted that the first preset time length is set to prevent accidental errors, specifically to avoid a temporary increase in charging current that may lead to a misjudgment that the battery module is in a charging state. For example, the first preset time length is a value in seconds, such as 4 seconds.

[0040] It should be noted that the first charge cut-off SOC refers to the high charge state of the battery module. For example, the first charge cut-off SOC can be 95%. Of course, the first charge cut-off SOC is not limited to the above example. In the specific implementation process, the first charge cut-off SOC is modifiable within a preset range. When the battery module is continuously in a charging state within the first preset time, if the current SOC of the battery module is greater than the preset first charge cut-off SOC, the buck-boost converter is switched from the working mode to the standby mode so that the battery module is not allowed to continue to be charged, thereby effectively preventing the battery module from being overcharged.

[0041] It is understandable that monitoring whether the battery module is continuously in a charging state for the first preset time period can be performed by monitoring the charge and discharge current of the battery module. If the charge and discharge current is continuously less than the first current threshold value for the first preset time period, it indicates that the battery module is continuously in a charging state for the first preset time period. The first current threshold value should be a negative value, for example, it can be set to -1A.

[0042] Case 2:

[0043] A no-load maintenance state may be set relative to the effective working state of the energy storage system. The no-load maintenance state refers to a state in which the energy storage system is not connected to an external load, and is a protective state for preventing power loss of the battery module.

[0044] Based on this, if it is monitored that the charge and discharge current of the battery module is continuously in the preset first current range within the second preset time length, it is determined that the protection trigger condition is currently met. At this time, by controlling the LLC resonant converter to be in the working mode and switching the buck-boost converter from the working mode to the standby mode, the battery module enters the standby state, and further switches the energy storage system from the effective working state to the no-load maintenance state to avoid power loss of the battery module.

[0045] It should be noted that the second preset time length is set to prevent accidental errors, specifically to avoid misjudging that the energy storage system is not connected to the external load due to a temporary decrease in the charge and discharge current. Specifically, the second preset time length is a value in seconds, for example, it can be set to 10 seconds.

[0046] It should be noted that the first current range is a current range that characterizes the state of no charging and no discharging of the battery module. The current value in the first current range is a small current value. It can be to monitor whether the absolute value of the charge and discharge current is continuously in the first current range within the second preset time length. Based on this, the first current range is a positive value range, for example: it can be 0A~1A. It can also be to monitor whether the charge and discharge current is continuously in the first current range within the second preset time length. Based on this, the first current range is a positive and negative value range, for example: it can be -1A~1A.

[0047] Case three: A standing power maintenance state can be set relative to the effective working state of the energy storage system. The standing power maintenance state refers to the state when the current SOC of the battery module is lower than the preset first standby SOC in the grid-connected state. Therefore, the standing power maintenance state is a protection state set to prevent the battery module in a low power state from continuing to supply power to the external load in the grid-connected state.

[0048] Based on this, when the energy storage system is in a grid-connected state, if the current SOC of the battery module is less than the preset first backup SOC and is continuously in a discharging state within a third preset time period, it is determined that the protection trigger condition is currently met. At this time, by controlling the LLC resonant converter to be in working mode and switching the buck-boost converter from working mode to standby mode, not only the battery module enters the standby state, but also the energy storage system is further switched from the effective working state to the standing power maintenance state to avoid power loss of the battery module.

[0049] It should be noted that the first standby SOC is used to indicate that the battery module has entered a low power state. For example, the first standby SOC can be set to 20%. The user can modify the first standby SOC within a preset range. If the current SOC of the battery module is less than the preset first standby SOC in the grid-connected state, the buck-boost converter is switched from the working mode to the standby mode to prevent the battery module from continuing to discharge.

[0050] It should be noted that the third preset time length is set to prevent accidental errors, specifically to avoid a temporary increase in discharge current that may lead to a false judgment that the battery module is in a discharge state. Specifically, the third preset time length is a value in seconds, for example, it can be set to 4 seconds.

[0051] It is understandable that monitoring whether the battery module is continuously in a discharge state within the third preset time length can be performed by monitoring the charge and discharge current of the battery module. If the charge and discharge current of the battery module is greater than the second current threshold, it indicates that the battery module is in a discharge state. The second current threshold should be a positive value, for example, it can be set to 1A.

[0052] It is understandable that the purpose of the above step S102 is to put the battery module into standby mode in order to avoid battery loss caused by power loss, overcharging, etc. of the battery module. Therefore, under certain external conditions, the battery module needs to be restored to an effective working state, so after step S102, step S103 should also be included: when the battery module exits the standby state based on external changes in the energy storage system, the energy storage system returns to an effective working state.

[0053] It is understandable that corresponding to the above three situations that trigger the battery module to enter the standby state, there should also be three corresponding situations that cause the battery module to exit the standby state. The following are the three situations that cause the battery module to exit the standby state:

[0054] Corresponding situation 1:

[0055] If it is monitored that the energy storage system is connected to an external load or the current SOC of the battery module is less than the preset second charging cut-off SOC, the buck-boost converter is switched back to the working mode from the standby mode to allow the battery module to exit the standby state and discharge to maintain the DC bus voltage. The first charging cut-off SOC is greater than the second charging cut-off SOC; the energy storage system is returned from the high-power maintenance state to the effective working state.

[0056] The charge and discharge current of the battery module may be monitored. If the charge and discharge current is greater than a third current threshold, it indicates that the battery module is in a discharge state. The third current threshold should be a positive value, for example, it may be set to 4A.

[0057] It should be noted that the second charge cutoff SOC is used to characterize the high power state of the battery module. For example, if the first charge cutoff SOC is 95%, the second charge cutoff SOC can be 93%. The user can modify the second charge cutoff SOC within the preset range. When the energy storage system is monitored to be connected to an external load, if the current SOC of the battery module is less than the preset second charge cutoff SOC, the battery module is controlled to exit the standby state and supply power to the external load. The first charge cutoff SOC is greater than the second charge cutoff SOC, but the first charge cutoff SOC and the second charge cutoff SOC cannot differ too much. The purpose of this setting is to prevent the energy storage system from frequently switching between the high power maintenance state and the effective working state, affecting the system stability.

[0058] Corresponding situation 2:

[0059] If it is monitored that the charging and discharging current of the battery module is within a preset second current range, the buck-boost converter is switched back to the working mode from the standby mode to allow the battery module to exit the standby state and discharge to maintain the DC bus voltage, wherein the lower limit value of the second current range is greater than the upper limit value of the first current range; the energy storage system is switched back to the effective working state from the no-load maintenance state.

[0060] It should be noted that the second current range is a current range that characterizes the battery module during charging or discharging. The current value in the second current range is a large current value. It can be that the absolute value of the charge and discharge current of the monitored battery module is in the second current range, based on which, the second current range is a positive value interval, for example: it can be set to 4A to positive infinity. It can also be that the monitored charge and discharge current is in the second current range, based on which, the second current range is a positive and negative value interval, for example: it can be set to (-∞,-4A], [4A,∞].

[0061] Corresponding situation three:

[0062] If it is monitored that the energy storage system is in an off-grid state, the current SOC of the battery module is greater than the preset second backup SOC, or an external power supply is supplying power to the energy storage system, the buck-boost converter is switched back to the working mode from the standby mode to allow the battery module to exit the standby state, and discharge after exiting the standby state to maintain the DC bus voltage, and the first backup SOC is less than the second backup SOC; the energy storage system is switched back to the effective working state from the standing power maintenance state.

[0063] It should be noted that the second standby SOC represents a low power state of the battery module. For example, if the first standby SOC is set to 20%, the second standby SOC can be set to 22%. The user can modify the second standby SOC within the preset range. If the current SOC of the battery module is greater than the second standby SOC, the battery module is controlled to exit the standby state and start working. In addition, the first standby SOC is less than the second standby SOC, but the first standby SOC and the second standby SOC cannot differ too much. The purpose of this setting is to prevent accidental errors from causing the energy storage system to frequently switch between the standing power maintenance state and the effective working state.

[0064] It should be noted that in addition to corresponding situations one, two and three, which are switching back to the effective working state from other states, three states can also be set: low-battery startup pre-charging state, low-battery charging and discharging state, and fully discharged state. Among them, the low-battery startup pre-charging state is the state entered when the energy storage system is turned on or restarted. The low-battery charging and discharging state refers to the state when the energy storage system is off-grid and the SOC of the battery module is less than the preset first alarm SOC. The fully discharged state is a state in which the SOC of the battery module is lower than that of the low-battery charging and discharging state. Based on this, the situations of switching back to the effective working state also include situations A1 to A2:

[0065] A1: When the energy storage system is started, if the SOC of the battery module is greater than the preset low-battery start-up SOC, the energy storage system is switched from the low-battery start-up pre-charging state back to the effective working state.

[0066] It should be noted that the low-battery startup SOC represents a low-battery state of the battery module, and the user cannot modify the low-battery startup SOC. For example, the low-battery startup SOC may be 10% power.

[0067] It should be understood that when the energy storage system is started, it first enters the low-power startup pre-charging state. The LLC resonant converter and the buck-boost converter are both in working mode in the low-power startup pre-charging state. The energy storage system can charge and discharge normally in the low-power startup pre-charging state.

[0068] A2: When the energy storage system is in a low-power charge and discharge state, if it is monitored that the current SOC of the battery module is greater than the preset second warning SOC, the energy storage system is switched from the low-power charge and discharge state to the effective working state, and the first warning SOC is less than the second warning SOC.

[0069] It should be noted that the second warning SOC represents a low power state of the battery module. For example, if the first warning SOC is 10% power, the second warning SOC can be 12%. The user cannot modify the second warning SOC, and the first warning SOC is less than the second warning SOC, but the first warning SOC and the second warning SOC cannot differ too much. The purpose of this setting is to prevent accidental errors from causing the energy storage system to frequently switch between low power charging and discharging states and effective working states.

[0070] It should be noted that the energy storage system can continue to charge and discharge in the low-power charging and discharging state, and will control the LLC resonant converter and the buck-boost converter to be in the working mode, and output the second alarm information, which is used to prompt the low power.

[0071] It can be understood that when the energy storage system is in an effective working state, if it is monitored that the energy storage system is in an off-grid state and the current SOC of the battery module is less than the preset first alarm SOC, a second alarm message is output, and the second alarm message is used to prompt that the battery is low; the energy storage system is switched from the effective working state to the low-battery charging and discharging state.

[0072] It should be noted that the first warning SOC represents a low power state of the battery module, and the user cannot modify the first warning SOC. Specifically, the first warning SOC may be 10% power.

[0073] It should be noted that all the above states are states where the energy storage system still stores electrical energy. In addition, a fully discharged state of the energy storage system can also be set. In the fully discharged state of the energy storage system, the LLC resonant converter and the buck-boost converter are controlled to be in sleep mode, and the first alarm information is output. The first alarm information is used to prompt that the battery module is fully discharged. There may be the following two situations where B1 and B2 will enter the fully discharged state:

[0074] B1: When the energy storage system is in a low-power charge and discharge state, if it is monitored that the current SOC of the battery module is less than the discharge cut-off SOC, the LLC resonant converter and the buck-boost converter are controlled to be in sleep mode, and the first alarm information is output, and the discharge cut-off SOC is less than the first alarm SOC; the energy storage system is switched from a low-power charge and discharge state to a fully discharged state.

[0075] It should be noted that the discharge cut-off SOC represents the state of the battery module being fully discharged. For example, the discharge cut-off SOC may be 2% of the power. The user can modify the discharge cut-off SOC within a preset range. If the current SOC of the battery module is less than the discharge cut-off SOC, the battery module is not allowed to continue discharging to prevent battery module loss.

[0076] B2: Before obtaining the operating status of the energy storage system in an effective working state, it may also include: when the energy storage system is started, the energy storage system is in a low-power startup pre-charging state. If the DC bus voltage is continuously less than a preset first reference value within a fourth preset time period, or the battery module is continuously in a discharge state within the fourth preset time period, the LLC resonant converter and the buck-boost converter are controlled to be in a sleep mode, and a first alarm message is output, wherein the first alarm message is used to prompt that the battery module is discharged; the energy storage system is switched from the low-power startup pre-charging state to the discharged state.

[0077] It should be noted that the fourth preset time is set to prevent accidental errors, specifically to avoid misjudgment caused by the DC bus voltage being temporarily less than the first reference value. Specifically, the fourth preset time may be 1 minute. In addition, there are two cases for the value of the first reference value. If it is off-grid, the first reference value is a predetermined fixed voltage value. If it is on-grid, the first reference value is given according to the system state.

[0078] It can be understood that when the energy storage system is in a fully discharged state, if the DC bus voltage continues to be greater than the preset second reference value within the fifth preset time period, the LLC resonant converter and the buck-boost converter are controlled to switch to the working mode, and the first reference value is less than the second reference value; the energy storage system is switched from the fully discharged state to the low-battery start-up pre-charging state.

[0079] It should be noted that the fifth preset time is set to prevent accidental errors, specifically to avoid the problem of misjudgment caused by a temporary increase in the DC bus voltage. Specifically, the fifth preset time can be 1 minute. In addition, there are two cases for the value of the second reference value. If it is off-grid, the second reference value is a predetermined fixed voltage value. If it is on-grid, the second reference value is given according to the system state. In addition, the first reference value is less than the second reference value. The purpose of this setting is to prevent the fluctuation of the DC bus voltage from causing the energy storage system to frequently switch between the fully discharged state and the low-power start-up pre-charge state.

[0080] The embodiment of the present invention obtains the operating status of the energy storage system in an effective working state. If it is determined according to the operating status that the preset protection trigger condition for the battery module is currently met, the LLC resonant converter is controlled to be in working mode and the buck-boost converter is switched from working mode to standby mode, so that the battery module enters the standby state. When the battery module is triggered to exit the standby state based on the external changes of the energy storage system, the energy storage system will return to the effective working state and perform normal charging and discharging to adjust the external quantity. Since the LLC resonant converter will be controlled to be in working mode and the buck-boost converter will be switched from working mode to standby mode after the protection trigger condition is met, the battery module will stop charging and discharging to the outside, so that the battery module enters the standby state to protect the battery module, thereby solving the technical problem of excessive battery loss.

[0081] When the energy storage system is turned on or restarted, if the current DC bus voltage is lower than the reference value, the energy storage system enters the low-power startup pre-charging state. If the SOC of the battery module is greater than the low-power startup value, the energy storage system enters the effective working state.

[0082] The energy storage system is in effective working state most of the time and switches between various pre-set states:

[0083] In order to enhance the understanding of the switching process of the energy storage system between the various states set, refer to the following Figure 3 An example is shown below:

[0084] A1: In the effective working state, if the battery module is continuously in the charging state within the first preset time and the current SOC of the battery module is greater than the preset first charging cut-off SOC, the energy storage system switches from the effective working state to the high power maintenance state.

[0085] A2: In the high power maintenance state, if it is monitored that the energy storage system is connected to an external load or the current SOC of the battery module is less than the preset second charging cut-off SOC, the energy storage system returns from the high power maintenance state to the effective working state.

[0086] A3: In the effective working state, if it is monitored that the charge and discharge current of the battery module is continuously within the preset first current range within the second preset time period, the energy storage system is switched from the effective working state to the no-load maintenance state.

[0087] A4: In the no-load maintenance state, if it is monitored that the charge and discharge current of the battery module is within a preset second current range, the energy storage system is switched from the no-load maintenance state back to the effective working state.

[0088] A5: In the effective working state, when the energy storage system is in the grid-connected state, if the current SOC of the battery module is less than the preset first backup SOC and is continuously in the discharge state within the third preset time, the energy storage system is switched from the effective working state to the standing power maintenance state.

[0089] A6: In the standby power maintenance state, if it is monitored that the energy storage system is off-grid, the current SOC of the battery module is greater than the preset second backup SOC, or the external power supply is supplying power to the energy storage system, the energy storage system is switched from the standby power maintenance state back to the effective working state.

[0090] A7: In the low-battery startup pre-charging state, if the DC bus voltage is continuously less than the preset first reference value within a fourth preset time period, or the battery module is continuously in a discharging state within the fourth preset time period, the energy storage system is switched from the low-battery startup pre-charging state to the fully discharged state.

[0091] A8: In the low-battery startup pre-charging state, if the SOC of the battery module is greater than the preset low-battery startup SOC, the energy storage system is switched from the low-battery startup pre-charging state back to the effective working state.

[0092] A9: In the effective working state, if it is monitored that the energy storage system is in an off-grid state and the current SOC of the battery module is less than the preset first alarm SOC, the energy storage system is switched from the effective working state to the low-power charging and discharging state.

[0093] A10: In the low-power charge and discharge state, if it is monitored that the current SOC of the battery module is less than the discharge cut-off SOC, the energy storage system is switched from the low-power charge and discharge state to the full-power discharge state.

[0094] A11: In the low-power charge and discharge state, if it is monitored that the current SOC of the battery module is greater than the preset second warning SOC, the energy storage system is switched from the low-power charge and discharge state to the effective working state.

[0095] A12: In the fully discharged state, if the DC bus voltage continues to be greater than a preset second reference value within a fifth preset time period, the energy storage system is switched from the fully discharged state to a low-power start-up pre-charging state.

[0096] Based on the same inventive concept, an embodiment of the present invention provides a charge and discharge control device 10 for an energy storage system, wherein the energy storage system includes a bidirectional DC converter and a battery module, wherein the bidirectional DC converter includes an LLC resonant converter and a buck-boost converter for sequentially cascading with the battery module, Figure 4 As shown, the energy storage system charge and discharge control device includes: a status acquisition unit 110, which is used to obtain the operating status of the energy storage system in an effective working state; an effective work exit unit 120, which is used to control the LLC resonant converter to be in the working mode and switch the buck-boost converter from the working mode to the standby mode if it is determined according to the operating status that the protection trigger condition preset for the battery module is currently met, so that the battery module enters the standby state; an effective work entry unit 130, which is used to return the energy storage system to the effective working state when the battery module exits the standby state based on the external changes of the energy storage system.

[0097] It can be understood that the effective working exit unit 120 includes: a high-power exit sub-unit, which is used to determine that the protection trigger condition is currently met if the battery module is continuously in a charging state within a first preset time period and the current SOC of the battery module is greater than the preset first charging cut-off SOC, and the operating conditions include: the current SOC and charging and discharging status of the battery module; switching the energy storage system from the effective working state to the high-power maintenance state.

[0098] It can be understood that the effective work entry unit 130 includes: a high power entry sub-unit, which is used to switch the buck-boost converter from the standby mode back to the working mode if it is monitored that the energy storage system is connected to an external load or the current SOC of the battery module is less than the preset second charging cut-off SOC, so that the battery module exits the standby state and discharges to maintain the DC bus voltage, and the first charging cut-off SOC is greater than the second charging cut-off SOC; and return the energy storage system from the high power maintenance state to the effective working state.

[0099] It can be understood that the effective working exit unit 120 also includes: a no-load exit sub-unit, which is used to determine that the protection trigger condition is currently met if it is monitored that the charging and discharging current of the battery module is continuously in the preset first current range within the second preset time period; the operating conditions include: the current size of the battery module charging and discharging; switching the energy storage system from the effective working state to the no-load maintenance state.

[0100] It can be understood that the effective working entry unit 130 also includes: a no-load entry sub-unit, which is used to switch the buck-boost converter from the standby mode back to the working mode if it is monitored that the charging and discharging current of the battery module is in a preset second current range, so that the battery module exits the standby state and discharges to maintain the DC bus voltage, wherein the lower limit value of the second current range is greater than the upper limit value of the first current range; and switch the energy storage system from the no-load maintenance state back to the effective working state.

[0101] It can be understood that the effective working exit unit 120 also includes: a standing exit subunit, which is used to determine whether the protection trigger condition is currently met when the energy storage system is in a grid-connected state, if the current SOC of the battery module is less than the preset first backup SOC and is continuously in a discharging state for a third preset time period, and the operating conditions include: whether the energy storage system is in a grid-connected state, the current SOC of the battery module, and the charging and discharging state; and switch the energy storage system from the effective working state to the standing power maintenance state.

[0102] It can be understood that the effective working entry unit 130 also includes: a standby entry subunit, which is used to switch the buck-boost converter from the standby mode back to the working mode if it is monitored that the energy storage system is in an off-grid state, the current SOC of the battery module is greater than the preset second standby SOC, or the external power supply is supplying power to the energy storage system, so that the battery module exits the standby state and discharges to maintain the DC bus voltage, and the first standby SOC is less than the second standby SOC; and switch the energy storage system from the standby power maintenance state back to the effective working state.

[0103] It can be understood that the energy storage system charge and discharge control device 10 also includes: a first power-discharge switching unit, which is used to control the LLC resonant converter and the buck-boost converter to be in sleep mode and output a first alarm message when the energy storage system is started, if the DC bus voltage is continuously less than the preset first reference value within a fourth preset time period, or the battery module is continuously in a discharge state within the fourth preset time period, and the first alarm message is used to prompt that the battery module is discharged; switch the energy storage system from a low-power startup pre-charge state to a power-discharge state; a first effective working switching unit, which is used to switch the energy storage system from a low-power startup pre-charge state back to an effective working state when the energy storage system is started, if the SOC of the battery module is greater than the preset low-power startup SOC.

[0104] It can be understood that the energy storage system charge and discharge control device 10 also includes: a low-power switching unit, which is used to output a second alarm message when the energy storage system is in an effective working state, if it is monitored that the energy storage system is in an off-grid state and the current SOC of the battery module is less than the preset first alarm SOC, and the second alarm message is used to prompt that the battery module is low in power; switch the energy storage system from the effective working state to the low-power charge and discharge state; a second effective working switching unit, which is used to switch the energy storage system from the low-power charge and discharge state to the effective working state when the energy storage system is in a low-power charge and discharge state, if it is monitored that the current SOC of the battery module is greater than the preset second alarm SOC, and the first alarm SOC is less than the second alarm SOC.

[0105] It can be understood that the energy storage system charge and discharge control device 10 further includes: a second discharge switching unit, which is used to control the LLC resonant converter and the buck-boost converter to be in sleep mode if it is monitored that the current SOC of the battery module is less than the discharge cut-off SOC, and output the first alarm information, the discharge cut-off SOC is less than the first alarm SOC, and the energy storage system is switched from the low-power charge and discharge state to the discharge state; a start pre-charge switching unit, which is used to control the LLC resonant converter and the buck-boost converter to switch to the working mode when the energy storage system is in the discharge state, if the DC bus voltage continues to be greater than the preset second reference value within a fifth preset time length, and the first reference value is less than the second reference value; the energy storage system is switched from the discharge state to the low-power start pre-charge state.

[0106] It should be understood that more implementation details of the energy storage system charge and discharge control device 10 in the embodiment of the present invention can be found in the aforementioned energy storage system charge and discharge control method embodiment, and will not be repeated here for the sake of brevity.

[0107] Based on the same inventive concept, an embodiment of the present invention further provides an electronic device, such as Figure 5 As shown, it includes a memory 504, a processor 502, and a computer program stored in the memory 504 and executable on the processor 502. The processor 502 executes the program to implement the steps described in any implementation of the energy storage system charge and discharge control method embodiment.

[0108] Among them, Figure 5In the embodiment of the present invention, a bus architecture (represented by bus 500) is shown, which may include any number of interconnected buses and bridges, and bus 500 links various circuits including one or more processors represented by processor 502 and memory represented by memory 504. Bus 500 may also link various other circuits such as peripherals, voltage regulators, and power management circuits, which are well known in the art and are therefore not further described herein. Bus interface 505 provides an interface between bus 500 and receiver 501 and transmitter 503. Receiver 501 and transmitter 503 may be the same element, namely a transceiver, providing a unit for communicating with various other devices over a transmission medium. Processor 502 is responsible for managing bus 500 and general processing, while memory 504 may be used to store data used by processor 502 when performing operations.

[0109] The embodiment of the present invention obtains the operating status of the energy storage system in an effective working state. If it is determined according to the operating status that the preset protection trigger condition for the battery module is currently met, the LLC resonant converter is controlled to be in working mode and the buck-boost converter is switched from working mode to standby mode, so that the battery module enters the standby state. When the battery module is triggered to exit the standby state based on the external changes of the energy storage system, the energy storage system will return to the effective working state and perform normal charging and discharging to adjust the external quantity. Since the LLC resonant converter will be controlled to be in working mode and the buck-boost converter will be switched from working mode to standby mode after the protection trigger condition is met, the battery module will stop charging and discharging to the outside, so that the battery module enters the standby state to protect the battery module, thereby solving the technical problem of excessive battery loss.

[0110] The functions described herein may be implemented in hardware, software executed by a processor, firmware, or any combination thereof. If implemented in software executed by a processor, the functions may be stored as one or more instructions or codes on a computer-readable medium or transmitted via a computer-readable medium. Other examples and implementations are within the scope and spirit of the present invention and the appended claims. For example, due to the nature of software, the functions described above may be implemented using software executed by a processor, hardware, firmware, hard wiring, or a combination of any of these. In addition, each functional unit may be integrated into a processing unit, each unit may exist physically separately, or two or more units may be integrated into one unit.

[0111] In the several embodiments provided in this application, it should be understood that the disclosed technical content can be implemented in other ways. Among them, the device embodiments described above are only schematic. For example, the division of the units can be a logical function division. There may be other division methods in actual implementation. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of units or modules, which can be electrical or other forms.

[0112] The units described as separate components may or may not be physically separated, and the components of the control device may or may not be physical units, that is, they may be located in one place or distributed in multiple units. Some or all of the units may be selected according to actual needs to achieve the purpose of the present embodiment.

[0113] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution can be embodied in the form of a software product, and the computer software product is stored in a storage medium, including a number of instructions for a computer device (which can be a personal computer, a server or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), mobile hard disk, magnetic disk or optical disk and other media that can store program codes.

[0114] The above description is only an embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present invention shall be included in the scope of the claims of the present invention.

Claims

1. A method for controlling charging and discharging of an energy storage system, characterized in that: The energy storage system includes a bidirectional DC converter and a battery module, the bidirectional DC converter includes an LLC resonant converter and a buck-boost converter for sequentially cascading with the battery module, and the method includes: Acquiring an operating condition of the energy storage system in an effective working state, wherein in the effective working state of the energy storage system, the LLC resonant converter and the buck-boost converter are both in an operating mode, so that the battery module can be discharged externally or charged by an external power source; If it is determined according to the operating status that a protection trigger condition preset for the battery module is currently met, controlling the LLC resonant converter to be in an operating mode and switching the buck-boost converter from the operating mode to a standby mode, so that the battery module enters a standby state; When the battery module is triggered to exit the standby state based on an external change of the energy storage system, the energy storage system returns to the effective working state.

2. The method according to claim 1, characterized in that Also includes: If the battery module is continuously in a charging state within a first preset time period and the current SOC of the battery module is greater than a preset first charging cutoff SOC, it is determined that the protection trigger condition is currently met, and the operating status includes: the current SOC and the charging and discharging state of the battery module; The energy storage system is switched from the effective working state to a high power maintaining state.

3. The method according to claim 2, characterized in that After switching the energy storage system from the effective working state to the high power maintaining state, the method further includes: If it is monitored that the energy storage system is connected to an external load or the current SOC of the battery module is less than a preset second charge cut-off SOC, the buck-boost converter is switched back from the standby mode to the working mode, so that the battery module exits the standby state and discharges to maintain the DC bus voltage, and the first charge cut-off SOC is greater than the second charge cut-off SOC; Returning the energy storage system from the high power maintenance state to the effective working state.

4. The method according to claim 1, characterized in that Also includes: If it is monitored that the charge and discharge current of the battery module is continuously within a preset first current range within a second preset time period, it is determined that the protection trigger condition is currently met; The operating conditions include: the current magnitude of the battery module charging and discharging; The energy storage system is switched from the effective working state to a no-load maintenance state.

5. The method according to claim 4, characterized in that After switching the energy storage system from the effective working state to the no-load maintenance state, the method further includes: If it is monitored that the charge and discharge current of the battery module is within a preset second current range, the buck-boost converter is switched back from the standby mode to the working mode, so that the battery module exits the standby state and discharges to maintain the DC bus voltage, wherein the lower limit value of the second current range is greater than the upper limit value of the first current range; The energy storage system is switched from the no-load maintenance state back to the effective working state.

6. The method according to claim 1, characterized in that Also includes: When the energy storage system is in a grid-connected state, if the current SOC of the battery module is less than a preset first standby SOC and is continuously in a discharging state within a third preset time, it is determined that the protection trigger condition is currently met, and the operating status includes: whether the energy storage system is in a grid-connected state, the current SOC of the battery module, and the charging and discharging state; The energy storage system is switched from the effective working state to a standing power maintenance state.

7. The method according to claim 6, characterized in that After switching the energy storage system from the effective working state to the standby power maintenance state, the method further includes: If it is monitored that the energy storage system is in an off-grid state, the current SOC of the battery module is greater than the preset second standby SOC, or an external power source is supplying power to the energy storage system, the buck-boost converter is switched back from the standby mode to the working mode, so that the battery module exits the standby state and discharges to maintain the DC bus voltage, and the first standby SOC is less than the second standby SOC; The energy storage system is switched from the standby power maintenance state back to the effective working state.

8. The method according to claim 1, characterized in that Before obtaining the operating status of the energy storage system being in an effective working state, the method further includes: When the energy storage system is started, if the DC bus voltage is continuously less than a preset first reference value within a fourth preset time period, or the battery module is continuously in a discharging state within the fourth preset time period, the LLC resonant converter and the buck-boost converter are controlled to be in a sleep mode, and a first alarm message is output, where the first alarm message is used to prompt that the battery module is discharged; Switching the energy storage system from a low-power startup pre-charge state to a fully-charged state; When the energy storage system is started, if the SOC of the battery module is greater than a preset low-battery startup SOC, the energy storage system is switched from the low-battery startup pre-charging state back to the effective working state.

9. The method according to claim 8, characterized in that Also includes: When the energy storage system is in an effective working state, if it is monitored that the energy storage system is in an off-grid state and the current SOC of the battery module is less than a preset first warning SOC, a second warning message is output, where the second warning message is used to prompt that the battery module is low in power; Switching the energy storage system from the effective working state to a low-power charging and discharging state; When the energy storage system is in the low-power charge and discharge state, if it is monitored that the current SOC of the battery module is greater than the preset second warning SOC, the energy storage system is switched from the low-power charge and discharge state to the effective working state, and the first warning SOC is less than the second warning SOC.

10. The method according to claim 9, characterized in that After switching the energy storage system from the effective working state to the low-power charge and discharge state, the method further includes: If it is monitored that the current SOC of the battery module is less than the discharge cut-off SOC, the LLC resonant converter and the buck-boost converter are controlled to be in a sleep mode, and the first warning information is output, and the discharge cut-off SOC is less than the first warning SOC; Switching the energy storage system from the low-power charge-discharge state to a fully-charged state, when the energy storage system is in the fully-charged state, if the DC bus voltage is continuously greater than a preset second reference value within a fifth preset time period, controlling the LLC resonant converter and the buck-boost converter to switch to a working mode, and the first reference value is less than the second reference value; The energy storage system is switched from the fully discharged state to the low-battery start-up pre-charging state.

11. A charge and discharge control device for an energy storage system, characterized in that: The energy storage system includes a bidirectional DC converter and a battery module, wherein the bidirectional DC converter includes an LLC resonant converter and a buck-boost converter which are sequentially cascaded with the battery module, and the device includes: A status acquisition unit, used to acquire the operating status of the energy storage system in an effective working state, wherein in the effective working state of the energy storage system, the LLC resonant converter and the buck-boost converter are both in an operating mode, so that the battery module can discharge externally or be charged by an external power source; an effective operation exit unit, configured to control the LLC resonant converter to be in an operation mode and switch the buck-boost converter from the operation mode to the standby mode if it is determined according to the operation status that a protection trigger condition preset for the battery module is currently met, so that the battery module enters a standby state; An effective working entry unit is used to trigger the battery module to exit the standby state based on an external change of the energy storage system, so that the energy storage system returns to the effective working state.

12. An electronic device, applied to an energy storage system, characterized in that: The electronic device comprises: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the method according to any one of claims 1 to 10 when executing the computer program.

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