State control method for energy storage system and photovoltaic energy storage system

Abstract

The invention relates to a state control method for an energy storage system and a photovoltaic energy storage system, and the method comprises the steps: judging whether an energy storage inverter is in a grid-connected state or an off-grid state; if the energy storage inverter is in the grid-connected state and the discharging state, port outflow current of the power grid is obtained; if the energy storage inverter is in the grid-connected state and the charging state, port inflow current of the power grid is obtained; and when it is detected that the mains supply port current GPC, the inverter port current IPC and the off-grid port current EPC conform to a first preset condition, carrying out charging and discharging power output limitation on the energy storage inverter so as to complete protection of the relay. Compared with the prior art, according to the scheme, the service life of the relay can be remarkably prolonged, the service life of the energy storage inverter is prolonged, and then the personal safety of household electricity utilization is effectively protected.

Description

Technical Field

[0001] The present invention relates to the field of photovoltaic energy storage, and in particular to a state control method for an energy storage system and a photovoltaic energy storage system. Background Art

[0002] With the transformation of the global energy structure and the advancement of sustainable development strategies, photovoltaic energy storage, as a clean and renewable energy storage method, has an increasing downstream demand. One of the key components in the photovoltaic energy storage system is the energy storage relay, or relay for short, which undertakes important functions such as circuit connection and disconnection and overload protection.

[0003] However, in actual R&D and application scenarios, many energy storage relays are overloaded under various working conditions, which seriously affects the performance and safety of photovoltaic energy storage systems. Therefore, the industry needs to design a technical solution for state control of energy storage systems to improve the performance of relays and enhance the safety of household electricity use. Summary of the invention

[0004] The technical problem to be solved by the present invention is: how to design a technical solution for state control of an energy storage system, which can significantly improve the life of relays and increase the service life of energy storage inverters compared with the prior art, thereby effectively protecting the personal safety of household electricity users.

[0005] To solve the above problems, the embodiments of the present invention propose a state control method for an energy storage system and a photovoltaic energy storage system, which can significantly improve the life of relays and increase the service life of energy storage inverters compared with the prior art, thereby effectively protecting the personal safety of household electricity users.

[0006] In a first aspect, the present invention provides a state control method for an energy storage system, see Figure 1 As shown, the method includes: S10, judging the state of the energy storage inverter, whether it is in a grid-connected state or an off-grid state; S21, if the energy storage inverter is in a grid-connected state and in a discharging state, obtaining the port outflow current of the grid; S22, if the energy storage inverter is in a grid-connected state and in a charging state, obtaining the port inflow current of the grid; S30, when it is detected that the mains port current GPC, the inverter port current IPC, and the off-grid port current EPC meet the first preset condition, limiting the charging and discharging power output of the energy storage inverter, thereby completing the protection of the relay.

[0007] In the above scheme, the corresponding photovoltaic energy storage system can be found in Figure 2 As shown, the INV-Port in the figure corresponds to the inverter port current IPC; further, the ESP-Port in the figure corresponds to the off-grid port current EPC, and the Gird-Port in the figure corresponds to the mains port current GPC.

[0008] Furthermore, the inverter port INV-Port in the figure corresponds to the off-grid port relay Relay1 and the off-grid port relay Relay2; further, the off-grid port EPS-Port in the figure corresponds to the off-grid port relay Relay7 and the off-grid port relay Relay8; further, the AC power port Gird-Port in the figure corresponds to the off-grid port relay Relay3 and the off-grid port relay Relay5.

[0009] Its further technical solution is that, in S21, if the energy storage inverter is in a grid-connected state and in a discharging state, the port outflow current of the power grid is obtained, including: if the energy storage inverter is in a grid-connected state and in a discharging state, first obtain the mains port active power GPP, and then obtain the mains port current GPC according to the mains port active power GPP, that is, the port outflow current of the power grid; the formula for obtaining the mains port active power GPP is: mains port active power GPP = inverter port power IPP - off-grid port power EPP; the formula for obtaining the mains port current GPC is: mains port current GPC = mains port active power GPP ÷ mains voltage GV.

[0010] Its further technical solution is that, in S22, if the energy storage inverter is in a grid-connected state and in a charging state, the port inflow current of the power grid is obtained, including: if the energy storage inverter is in a grid-connected state and in a charging state, first obtain the mains port active power GPP, and then obtain the mains port current GPC according to the mains port active power GPP, that is, the port inflow current of the power grid; the formula for obtaining the mains port active power GPP is: mains port active power GPP = inverter port power IPP - off-grid port power EPP; the formula for obtaining the mains port current GPC is: mains port current GPC = mains port active power GPP ÷ mains voltage GV.

[0011] Its further technical solution is to use the preset maximum current upper limit as a critical value to measure whether the relay is about to reach the upper limit; the S30, when it is detected that the mains port current GPC, the inverter port current IPC, and the off-grid port current EPC meet the first preset condition, limits the charging and discharging power output of the energy storage inverter, thereby completing the protection of the relay, including: obtaining the current value of the inverter port current IPC and the current value of the off-grid port current EPC; detecting whether there is at least one port current among the three port currents of the mains port current GPC, the inverter port current IPC, and the off-grid port current EPC that exceeds the preset maximum current upper limit; the preset maximum current upper limit is equal to the maximum rated current value Irelay×the preset lower limit ratio Lr; if none of the three port currents exceeds the preset maximum current upper limit, keep the current state unchanged; if at least one of the three port currents exceeds the preset maximum current upper limit, refer to the adjustment formula of the current error value Ierr, and perform power adjustment based on the adjustment result corresponding to the adjustment formula, thereby completing the protection of the relay.

[0012] In the above scheme, continue to refer to Figure 2 , obtain the current value of the inverter port current IPC, and the current value of the off-grid port current EPC, wherein the current value of the inverter port current IPC corresponds to CT1 in the figure, wherein the current value of the off-grid port current EPC corresponds to CT2 in the figure. Further, the "Irelay" in the maximum rated current value Irelay can be specifically divided into I and relay, which are combined into the symbol Irelay that can be understood by those skilled in the art. Referring to this case, the meanings of other symbols in this application are also the same or similar.

[0013] In the above scheme, the value of the preset lower limit ratio Lr can be any value of 80% or above, for example, it can be 85% or 90% or 95%. In one embodiment, when it is detected that the mains port current GPC, the inverter port current IPC, and the off-grid port current EPC, one of the three port currents, has a current value greater than the "maximum rated current value Irelay×preset lower limit ratio Lr", that is, when the current value is greater than the "maximum rated current value Irelay×95%", it means that the relay is about to reach the upper limit, that is, the preset maximum current upper limit value; further, the charging and discharging power output of the energy storage inverter is limited, and the specific limiting method is to refer to the adjustment formula of the current error value Ierr, and adjust the power based on the adjustment result corresponding to the adjustment formula, thereby completing the protection of the relay.

[0014] A further technical solution is that the adjustment formula of the reference current error value Ierr is used to perform power regulation based on the adjustment result corresponding to the adjustment formula, including: calculating the value of the current error value Ierr by the following formula: Ierr=Max(GPC, IPC, EPC)-Irelay×Lr.

[0015] In the above formula, the specific meaning of Max (GPC, IPC, EPC) is to select the largest one from GPC, IPC, and EPC; when the current error value Ierr is less than or equal to 0, it means that the output current of the AC port current GPC, the inverter port current IPC, and the off-grid port current EPC is less than or equal to the rated current of the relay, and there is no need to adjust the power of the energy storage inverter to reduce the current resistance of the relay; when the current error value Ierr is greater than 0, it means that there is an overcurrent risk in the relay, and then the power control of the energy storage inverter is performed to protect the relay until the current reference value Iref is reduced to 0; if when the current reference value Iref is reduced to 0, one of the relays still exceeds the maximum rated current value of the relay Irelay×the preset lower limit ratio Lr, directly execute the relay protection step of S40.

[0016] Its further technical solution is that the power control protection relay is then performed through the energy storage inverter until the current reference value Iref is reduced to 0, including: if the energy storage inverter is in a charging state, the grid relay has the largest anti-overload capacity, and the grid exists to charge the energy storage inverter and carry the load of the off-grid port, then it enters the charging state, corresponding to the charging state, the output current value Iset is set to be less than 0, the current error value Ierr is greater than 0, and a forward current is output through PI regulation to make the energy storage inverter slowly switch from charging to discharging, thereby reducing the grid relay's anti-overload capacity; if the energy storage inverter is in a discharging state, the off-grid port relay Relay7 and the off-grid port relay Relay8 have the largest anti-overload capacity, and the off-grid port current EPC corresponding to the off-grid port EPS-Port is greater than the maximum rated current value Irelay, and the relay is disconnected for protection to protect the relay life.

[0017] In the above scheme, the maximum value screening process is as follows:

[0018] If the mains port current GPC>inverter port current IPC, and the mains port current GPC>off-grid port current EPC, then the mains port current GPC is the largest.

[0019] If the off-grid port current EPC> the mains port current GPC, and the off-grid port current EPC> the inverter port current IPC, then the off-grid port current EPC is the largest.

[0020] If the inverter port current IPC> the mains port current GPC, and the inverter port current IPC> the off-grid port current EPC; then the inverter port current IPC is the largest.

[0021] After obtaining the maximum current value, when the preset lower limit ratio Lr is equal to 95%, the error value between the maximum current port current and the rated current of the relay, that is, the current error value Ierr, is obtained, and the formula is as follows:

[0022] Current error value Ierr = maximum port current MPC - maximum rated current value Irelay × 0.95;

[0023] The maximum port current MPC, that is, the value of Max (GPC, IPC, EPC), is the maximum current value among the three port currents: the mains port current GPC, the inverter port current IPC, and the off-grid port current EPC.

[0024] First, if the current error value Ierr≤0, it means that the maximum port current of the off-grid, energy storage inverter, and grid port does not exceed the upper limit of the maximum rated current of the relay, and the relay is not overloaded. At this time, the current error value Ierr is finally output as the current given value IderRef=0 after PI adjustment, and the energy storage inverter does not need to perform loading / unloading processing to reduce the overload resistance of the relay.

[0025] Second, if the current error value Ierr is greater than 0, it means that the maximum port current of the off-grid, energy storage inverter, and grid port exceeds the upper limit of the maximum rated current of the relay, and the energy storage inverter needs to be used for loading / reducing control to reduce the load resistance of the relay, as follows:

[0026] If the energy storage inverter is in the charging state, the overload resistance of the grid relay is the largest. If the grid exists to charge the energy storage inverter and to carry the load of the off-grid port, then the output current value Iset is set to be less than 0, and the current error value Ierr is greater than 0. Through PI adjustment, a forward current is output to make the energy storage inverter slowly switch from charging to discharging, reducing the overload resistance of the grid relay.

[0027] If the energy storage inverter is in the discharging state, the off-grid port relay Relay7 and the off-grid port relay Relay8 have the largest overload resistance, and the off-grid port current EPC corresponding to the off-grid port EPS-Port is greater than the maximum rated current value Irelay, and the relay is disconnected to protect the relay life.

[0028] A further technical solution is that the current of the inverter port is controlled by the energy storage inverter, and safety can be ensured by presetting the maximum charge and discharge rated power to a power value not exceeding the maximum rated current value Irelay×preset lower limit ratio Lr.

[0029] A further technical solution is that after determining whether the state of the energy storage inverter is in a grid-connected state or an off-grid state, the method further includes: S40, if the state of the energy storage inverter is in an off-grid state, disconnecting the relay for protection according to a second preset condition.

[0030] Its further technical solution is that S40, through a second preset condition, disconnects the relay for protection, including: disconnecting the relay through the AC port current GPC being greater than the maximum rated current value Irelay; the inverter port current IPC being greater than the maximum rated current value Irelay; and the off-grid port current EPC being greater than the maximum rated current value Irelay, thereby protecting the relay life.

[0031] In a second aspect, the present invention proposes a photovoltaic energy storage system, which is used in the state control method as described in the first aspect. The solution described in this application is derived from the feedback of problems in actual research and development work. Compared with the prior art, it can significantly improve the life of relays and increase the service life of energy storage inverters, thereby effectively protecting the personal safety of household electricity users. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

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

[0034] Figure 1 A flow chart of a state control method for an energy storage system provided in an embodiment of the present invention.

[0035] Figure 2 A system block diagram of a photovoltaic energy storage system provided in an embodiment of the present invention.

[0036] Figure 3 A first schematic diagram of a state control method for an energy storage system provided by an embodiment of the present invention.

[0037] Figure 4 A second schematic diagram of a state control method for an energy storage system provided in an embodiment of the present invention.

[0038] Figure 5 A schematic diagram of the framework of an electronic device provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0039] 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 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.

[0040] It should be understood that when used in this specification and the appended claims, the terms "include" and "comprises" indicate the presence of described features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or other features, integers, steps, operations, elements, components and / or combinations thereof.

[0041] It should also be understood that the terms used in the present specification are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0042] It should be further understood that the term "and / or" used in the present specification and the appended claims refers to one or any combination and all possible combinations of the associated listed items, and includes these combinations.

[0043] As used in this specification and the appended claims, the term "if" may be interpreted as "when" or "upon" or "in response to determining" or "in response to detecting," depending on the context. Similarly, the phrases "if it is determined" or "if [described condition or event] is detected" may be interpreted as meaning "upon determination" or "in response to determining" or "upon detection of [described condition or event]" or "in response to detecting [described condition or event]," depending on the context.

[0044] Example 1

[0045] See also Figures 1 to 4 , among which Figure 1 A flow chart of a state control method for an energy storage system provided in an embodiment of the present invention, wherein Figure 2 A photovoltaic energy storage system, in which Figure 3 is a first schematic diagram with setting the output current value Iset as input, wherein Figure 4 is a second schematic diagram with a reference current error value Ierr as input. An embodiment of the present invention provides a state control method for an energy storage system, the state control method for an energy storage system comprising:

[0046] S10, determining the state of the energy storage inverter, whether it is in a grid-connected state or an off-grid state.

[0047] S21, if the energy storage inverter is in a grid-connected state and in a discharging state, obtain the current flowing out of the port of the grid.

[0048] S22, if the energy storage inverter is in a grid-connected state and in a charging state, obtain the current flowing into the port of the grid.

[0049] S30, when it is detected that the mains port current GPC, the inverter port current IPC, and the off-grid port current EPC meet the first preset condition, the charging and discharging power output of the energy storage inverter is limited, thereby completing the protection of the relay.

[0050] In the above scheme, the corresponding photovoltaic energy storage system can be found in Figure 2 As shown, the INV-Port in the figure corresponds to the inverter port current IPC; further, the ESP-Port in the figure corresponds to the off-grid port current EPC, and the Gird-Port in the figure corresponds to the mains port current GPC.

[0051] Furthermore, the inverter port INV-Port in the figure corresponds to the off-grid port relay Relay1 and the off-grid port relay Relay2; further, the off-grid port EPS-Port in the figure corresponds to the off-grid port relay Relay7 and the off-grid port relay Relay8; further, the AC power port Gird-Port in the figure corresponds to the off-grid port relay Relay3 and the off-grid port relay Relay5.

[0052] In one embodiment, the S21, if the energy storage inverter is in a grid-connected state and in a discharging state, obtaining the port outflow current of the grid includes:

[0053] If the energy storage inverter is in the grid-connected state and in the discharging state, the mains port active power GPP is first obtained, and then the mains port current GPC, that is, the port outflow current of the power grid, is obtained according to the mains port active power GPP.

[0054] The formula for obtaining the mains port active power GPP is: mains port active power GPP = inverter port power IPP - off-grid port power EPP.

[0055] The formula for obtaining the AC port current GPC is: AC port current GPC = AC port active power GPP ÷ AC voltage GV.

[0056] In one embodiment, the S22, if the energy storage inverter is in a grid-connected state and in a charging state, obtaining the current flowing into the port of the grid includes:

[0057] If the energy storage inverter is in the grid-connected state and in the charging state, the mains port active power GPP is first obtained, and then the mains port current GPC is obtained according to the mains port active power GPP, that is, the port inflow current of the power grid.

[0058] The formula for obtaining the mains port active power GPP is: mains port active power GPP = inverter port power IPP - off-grid port power EPP.

[0059] The formula for obtaining the AC port current GPC is: AC port current GPC = AC port active power GPP ÷ AC voltage GV.

[0060] In one embodiment, a preset maximum current upper limit value is used as a critical value to measure whether the relay is about to reach the upper limit; S30, when it is detected that the mains port current GPC, the inverter port current IPC, and the off-grid port current EPC meet the first preset condition, the energy storage inverter is charged and discharged. The power output is limited to complete the protection of the relay, including:

[0061] Obtain the current value of the inverter port current IPC and the current value of the off-grid port current EPC.

[0062] Detect the mains port current GPC, the inverter port current IPC, and the off-grid port current EPC to see if at least one of the three port currents exceeds a preset maximum current upper limit value; the preset maximum current upper limit value is equal to the maximum rated current value Irelay×the preset lower limit ratio Lr.

[0063] If none of the three port currents exceeds the preset maximum current upper limit, the existing state remains unchanged.

[0064] If at least one of the three port currents exceeds the preset maximum current upper limit, the power is adjusted based on the adjustment result corresponding to the adjustment formula with reference to the adjustment formula of the current error value Ierr, thereby completing the protection of the relay.

[0065] In one embodiment, the adjustment formula of the reference current error value Ierr and the power adjustment based on the adjustment result corresponding to the adjustment formula include:

[0066] The current error value Ierr is calculated using the following formula:

[0067] Ierr=Max(GPC,IPC,EPC)-Irelay×Lr.

[0068] In the above formula, when the current error value Ierr is less than or equal to 0, it means that the output current of the AC port current GPC, the inverter port current IPC, and the off-grid port current EPC is less than or equal to the rated current of the relay, and there is no need to adjust the power of the energy storage inverter to reduce the current resistance capacity of the relay.

[0069] When the current error value Ierr is greater than 0, it indicates that there is an overcurrent risk in the relay. Next, the energy storage inverter is used to perform power control to protect the relay until the current reference value Iref is reduced to 0.

[0070] If, when the current reference value Iref is reduced to 0, one of the relays still exceeds the maximum rated current value of the relay Irelay×the preset lower limit ratio Lr, the relay protection step of S40 is directly executed.

[0071] In one embodiment, the following step of performing power control to protect the relay through the energy storage inverter until the current reference value Iref is reduced to 0 includes:

[0072] If the energy storage inverter is in the charging state, the grid relay has the greatest anti-overload capacity. If the grid exists to charge the energy storage inverter and also to carry the load of the off-grid port, it will enter the charging state. Corresponding to the charging state, the output current value Iset is set to be less than 0, and the current error value Ierr is greater than 0. Through PI adjustment, a forward current is output to make the energy storage inverter slowly switch from charging to discharging, reducing the grid relay's anti-overload capacity.

[0073] If the energy storage inverter is in the discharging state, the off-grid port relay Relay7 and the off-grid port relay Relay8 have the largest overload resistance, and the off-grid port current EPC corresponding to the off-grid port EPS-Port is greater than the maximum rated current value Irelay, and the relay is disconnected to protect the relay life.

[0074] In one embodiment, the current of the inverter port is controlled by the energy storage inverter, and safety can be ensured by presetting the maximum charge and discharge rated power to a power value not exceeding the maximum rated current value Irelay×the preset lower limit ratio Lr.

[0075] In one embodiment, after determining whether the state of the energy storage inverter is in a grid-connected state or an off-grid state, the method further includes: S40, if the state of the energy storage inverter is in an off-grid state, disconnecting the relay for protection according to a second preset condition.

[0076] In one embodiment, S40, through a second preset condition, disconnects the relay for protection, including: disconnecting the relay when the AC port current GPC is greater than the maximum rated current value Irelay; the inverter port current IPC is greater than the maximum rated current value Irelay; the off-grid port current EPC is greater than the maximum rated current value Irelay to protect the relay life.

[0077] The present application also proposes a photovoltaic energy storage system, which is used to execute the state control method described in any of the above embodiments.

[0078] To sum up, in the existing research and development and application scenarios, many energy storage relays are overloaded under various working conditions. The existence of this problem seriously affects the performance and safety of the photovoltaic energy storage system. Based on this problem, the present application proposes a state control method for an energy storage system and a photovoltaic energy storage system. The beneficial effect is that compared with the prior art, it can significantly improve the life of the relay and increase the service life of the energy storage inverter, thereby effectively protecting the personal safety of household electricity users.

[0079] Example 2

[0080] See also Figure 5 , Figure 5 The block diagram of an electronic device provided by the present invention. The electronic device can be a terminal or a server, wherein the terminal can be an electronic device with communication function such as a smart phone, a tablet computer, a laptop computer, a desktop computer, a personal digital assistant, and a wearable device. It includes a processor 111, a communication interface 112, a memory 113, and a communication bus 114, wherein the processor 111, the communication interface 112, and the memory 113 communicate with each other through the communication bus 114.

[0081] The memory 113 is used to store computer programs.

[0082] In one embodiment of the present invention, the processor 111 is used to implement the method provided by any one of the aforementioned method embodiments when executing the program stored in the memory 113 .

[0083] It should be understood that in the embodiment of the present application, the processor 111 may be a central processing unit (CPU), and the processor 502 may also be other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. Among them, the general-purpose processor may be a microprocessor or the processor may also be any conventional processor, etc.

[0084] It is understood by those skilled in the art that all or part of the processes in the method for implementing the above embodiment can be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a storage medium, which is a computer-readable storage medium. The computer program is executed by at least one processor in the computer system to implement the process steps of the embodiment of the above method.

[0085] Those of ordinary skill in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described in the above description according to function. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions, but such implementation should not be considered to be beyond the scope of the present invention.

[0086] In the several embodiments provided by the present invention, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of each unit is only a logical function division, and there may be other division methods in actual implementation. For example, units or components can be combined or integrated into another system, or some features can be ignored or not executed.

[0087] The steps in the method of the embodiment of the present invention can be adjusted in order, combined and deleted according to actual needs. The units in the device of the embodiment of the present invention can be combined, divided and deleted according to actual needs. In addition, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0088] 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 storage medium. Based on this understanding, the technical solution of the present invention is essentially 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, terminal, or network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present invention.

[0089] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0090] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

[0091] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed by the present invention, and these modifications or replacements should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A state control method for an energy storage system, It is characterized in that The method comprises: S10, determining the state of the energy storage inverter, whether it is in a grid-connected state or an off-grid state; S21, if the energy storage inverter is in a grid-connected state and in a discharging state, obtaining the current flowing out of the port of the grid; S22, if the energy storage inverter is in a grid-connected state and in a charging state, obtaining the current flowing into the port of the grid; S30, when it is detected that the mains port current GPC, the inverter port current IPC, and the off-grid port current EPC meet the first preset condition, the charging and discharging power output of the energy storage inverter is limited, thereby completing the protection of the relay.

2. The state control method according to claim 1, It is characterized in that The step S21, if the energy storage inverter is in a grid-connected state and in a discharging state, obtaining the current flowing out of the port of the grid includes: If the energy storage inverter is in the grid-connected state and in the discharging state, first obtain the mains port active power GPP, and then obtain the mains port current GPC according to the mains port active power GPP, that is, the port outflow current of the power grid; The formula for obtaining the mains port active power GPP is: mains port active power GPP = inverter port power IPP - off-grid port power EPP; The formula for obtaining the AC port current GPC is: AC port current GPC = AC port active power GPP ÷ AC voltage GV.

3. The state control method according to claim 2, It is characterized in that The step S22, if the energy storage inverter is in a grid-connected state and in a charging state, obtaining the current flowing into the port of the grid includes: If the energy storage inverter is in the grid-connected state and in the charging state, first obtain the mains port active power GPP, and then obtain the mains port current GPC according to the mains port active power GPP, that is, the port inflow current of the power grid; The formula for obtaining the mains port active power GPP is: mains port active power GPP = inverter port power IPP - off-grid port power EPP; The formula for obtaining the AC port current GPC is: AC port current GPC = AC port active power GPP ÷ AC voltage GV.

4. The state control method according to claim 3, It is characterized in that The preset maximum current upper limit value is used as a critical value to measure whether the relay is about to reach the upper limit; S30, when it is detected that the mains port current GPC, the inverter port current IPC, and the off-grid port current EPC meet the first preset condition, the charging and discharging power output of the energy storage inverter is limited, thereby completing the protection of the relay, including: Obtain the current value of the inverter port current IPC and the current value of the off-grid port current EPC; Detect the mains port current GPC, the inverter port current IPC, and the off-grid port current EPC to determine whether at least one of the three port currents exceeds a preset maximum current upper limit value; the preset maximum current upper limit value is equal to the maximum rated current value Irelay×the preset lower limit ratio Lr; If none of the three port currents exceeds the preset maximum current upper limit, the current status remains unchanged; If at least one of the three port currents exceeds the preset maximum current upper limit, the power is adjusted based on the adjustment result corresponding to the adjustment formula with reference to the adjustment formula of the current error value Ierr, thereby completing the protection of the relay.

5. The state control method according to claim 4, It is characterized in that The reference current error value Ierr adjustment formula and power regulation based on an adjustment result corresponding to the adjustment formula include: The current error value Ierr is calculated using the following formula: Ierr=Max(GPC,IPC,EPC)-Irelay×Lr; In the above formula, when the current error value Ierr is less than or equal to 0, it means that the output current of the mains port current GPC, the inverter port current IPC, and the off-grid port current EPC is less than or equal to the rated current of the relay, and there is no need to adjust the power of the energy storage inverter to reduce the current resistance capacity of the relay; When the current error value Ierr is greater than 0, it indicates that the relay has an overcurrent risk. Next, the energy storage inverter is used to perform power control to protect the relay until the current reference value Iref is reduced to 0. If, when the current reference value Iref is reduced to 0, one of the relays still exceeds the maximum rated current value of the relay Irelay×the preset lower limit ratio Lr, the relay protection step of S40 is directly executed.

6. The state control method according to claim 5, It is characterized in that Next, the power control protection relay is performed through the energy storage inverter until the current reference value Iref is reduced to 0, including: If the energy storage inverter is in the charging state, the overload resistance of the grid relay is the largest. If the grid exists to charge the energy storage inverter and to carry the load of the off-grid port, it will enter the charging state. Corresponding to the charging state, the output current value Iset is set to be less than 0, and the current error value Ierr is greater than 0. Through PI regulation, a forward current is output to make the energy storage inverter slowly switch from charging to discharging, reducing the overload resistance of the grid relay. If the energy storage inverter is in the discharging state, the off-grid port relay Relay7 and the off-grid port relay Relay8 have the largest overload resistance, and the off-grid port current EPC corresponding to the off-grid port EPS-Port is greater than the maximum rated current value Irelay, and the relay is disconnected to protect the relay life.

7. The state control method according to claim 6, Features: The current of the inverter port is controlled by the energy storage inverter, and safety can be ensured by presetting the maximum charge and discharge rated power to a power value not exceeding the maximum rated current value Irelay×the preset lower limit ratio Lr.

8. The state control method according to claim 1, It is characterized in that After determining whether the state of the energy storage inverter is in a grid-connected state or an off-grid state, the method further includes: S40: If the energy storage inverter is in an off-grid state, the relay is disconnected for protection according to a second preset condition.

9. The state control method according to claim 8, It is characterized in that The step S40, disconnecting the relay for protection according to the second preset condition, includes: The relay is disconnected and protected by the AC port current GPC being greater than the maximum rated current value Irelay; the inverter port current IPC being greater than the maximum rated current value Irelay; and the off-grid port current EPC being greater than the maximum rated current value Irelay, thereby protecting the relay life.

10. A photovoltaic energy storage system, It is characterized in that The photovoltaic energy storage system is used to execute the state control method as described in any one of claims 1 to 9.

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