Internal power distribution method for battery energy storage system

Abstract

The invention provides an internal power distribution method for a battery energy storage system, which belongs to the technical field of electric energy storage and comprises the following steps of: constructing a charge-discharge function taking SOC as a variable; acquiring a power regulation instruction issued by the power dispatching center, performing distribution by combining a charging and discharging function, and then performing regulation according to a limiting condition; summing the power regulation instructions of all the battery units, calculating the power regulation instructions issued by the power dispatching center and the residual power deviation of the instruction sum, distributing the battery units which do not reach the maximum charging and discharging power in combination with a charging and discharging function, and adjusting according to limiting conditions; and ending the power distribution when a power distribution completion condition of the energy storage system is met, and continuing the distribution when the power distribution completion condition is not met. According to the method, the equalization speed and degree of the SOC of the battery unit are improved, the sustainable regulation and control capability of the BESS is improved, the power regulation instruction tracking effect of the BESS is improved, new energy power fluctuation is stabilized, and safe and stable grid connection of new energy is assisted.

Description

Technical Field

[0001] The present invention belongs to the technical field of electric energy storage, and in particular relates to a method for distributing power inside a battery energy storage system. Background Art

[0002] BESS is the abbreviation of battery energy storage system.

[0003] SOC is the abbreviation of state of charge.

[0004] With the low-carbon goal of the power grid, new energy sources are connected to the power grid on an increasingly large scale. However, the randomness and intermittency of new energy sources cause the power fluctuation of grid connection to be large, which has an adverse impact on the safe and stable operation of the power grid. The emergence of battery energy storage system BESS makes it possible to quickly charge and discharge the power grid. BESS can realize the transfer of energy in time and space, and is an important means to assist the grid connection of new energy sources.

[0005] However, in the current BESS operation process, the battery power supply often operates irregularly due to unreasonable control strategies, causing the SOC of the battery cells inside the BESS to be unbalanced. When the SOC of the battery cells is unbalanced, the sustainable regulation capability of the BESS will be greatly reduced, which will affect the BESS's accurate tracking of the regulation instructions issued by the dispatching center, thereby affecting the safe and stable grid connection of new energy.

[0006] In summary, BESS can prevent excessive power fluctuations in the connection of new energy to the grid, but the imbalance of battery unit SOC during the operation of the existing BESS reduces the sustainable regulation capability of BESS, affecting the safety and stability of the connection of new energy to the grid.

[0007] This is a shortcoming of the prior art. Therefore, in view of the above defects in the prior art, it is very necessary to provide a method and device for internal power distribution of a battery energy storage system. Summary of the invention

[0008] In view of the defect that BESS in the prior art can prevent excessive power fluctuations in the connection of new energy to the grid, but the imbalance of SOC of battery cells during the operation of the existing BESS leads to a reduction in the sustainable regulation capability of the BESS, affecting the safety and stability of the connection of new energy to the grid, the present invention provides a method and device for internal power distribution of a battery energy storage system to solve the above technical problems.

[0009] The present invention provides a method for distributing power within a battery energy storage system, comprising the following steps:

[0010] S1. Construct a charge and discharge function with SOC as a variable for the battery unit in the energy storage system to characterize the charge and discharge capacity of the battery unit;

[0011] S2. Obtain the power regulation instruction of the energy storage system issued by the power dispatching center, allocate the power regulation instruction in combination with the charge and discharge function of the battery unit, and then adjust the allocated power regulation instruction according to the SOC operation limit and maximum charge and discharge power limit of each battery unit;

[0012] S3. Sum the power regulation instructions of all battery cells of the energy storage system to obtain the actual power regulation instruction of the energy storage system, and calculate the difference between the power regulation instruction of the energy storage system issued by the power dispatching center and the actual power regulation instruction as the remaining power deviation;

[0013] S4. Count the battery cells in the energy storage system that have not reached the maximum charge and discharge power, allocate the remaining power deviation in combination with the charge and discharge function of the battery cell, and then adjust the power regulation instructions allocated to the battery cell according to the SOC operation limit and the maximum charge and discharge power limit of the battery cell;

[0014] S5. Determine whether the energy storage system power distribution completion determination condition is met, and end the power distribution if it is met, and return to step S3 if it is not met.

[0015] Furthermore, the specific steps of step S1 are as follows:

[0016] S11. Taking the SOC of the battery cell in the energy storage system at a set time as a variable, construct a charging function of the battery cell to characterize the charging capacity of the battery cell;

[0017] S12. Taking the SOC of the battery cell in the energy storage system at a set time as a variable, a discharge function of the battery cell is constructed to characterize the discharge capacity of the battery cell.

[0018] Furthermore, the charging function of the battery unit in step S11 is expressed as follows:

[0019]

[0020] Among them, f ch (S i,t-1 ) represents the charging function value of the battery cell at time t-1, S i,t-1 is the state of charge of the i-th battery cell at time t-1;

[0021] The discharge function of the battery cell in step S12 is expressed as follows:

[0022]

[0023] Among them, f dis (Si,t-1 ) represent the discharge function value of the battery cell at time t-1, S i,t-1 is the state of charge of the i-th battery cell at time t-1.

[0024] Furthermore, the specific steps of step S2 are as follows:

[0025] S21. Obtain the power adjustment command issued by the power dispatching center to the energy storage system, where a positive value indicates discharge and a negative value indicates charge;

[0026] S22. Calculate the sum of the charging function values ​​of all battery cells using the charging function of the battery cell, and calculate the charging distribution ratio of each battery cell according to the ratio of the charging function value of each battery cell to the sum of the charging function values ​​of all battery cells, and when charging, distribute the power adjustment instructions issued by the power dispatching center to the battery cells according to the charging distribution ratio;

[0027] S23. Use the discharge function of the battery cell to calculate the sum of the discharge function values ​​of all battery cells, and calculate the discharge distribution ratio of each battery cell according to the ratio of the discharge function value of each battery cell to the sum of the discharge function values ​​of all battery cells, and when discharging, distribute the power adjustment instructions issued by the power dispatching center to the battery cells according to the discharge distribution ratio;

[0028] S24. Perform an SOC over-limit check on the power regulation instructions assigned to each battery cell, and adjust the power regulation instructions assigned to the battery cell when the SOC exceeds the limit to obtain the power regulation instructions after the SOC adjustment; S25. Perform a maximum charge and discharge power over-limit check on the power regulation instructions assigned to each battery cell, and adjust the power regulation instructions assigned to the battery cell when the maximum charge and discharge power exceeds the limit to obtain the power regulation instructions after the maximum charge and discharge power adjustment.

[0029] Furthermore, the calculation formula of the power adjustment instruction of the battery unit in step S22 and step S23 is as follows:

[0030]

[0031] Among them, P bi is the power regulation instruction of the ith battery unit, N B1 is the number of battery cells in the battery energy storage system, S j,t-1 is the SOC of the jth battery cell at time t-1;

[0032] In step S24, when the SOC exceeds the limit,

[0033] When the power adjustment command of the battery cell is negative, if the SOC of the battery cell exceeds the SOC operation upper limit, the power adjustment command of the battery cell is changed to 0;

[0034] When the power regulation instruction of the battery cell is positive, if the SOC of the battery cell is lower than the SOC operation lower limit, the power regulation instruction of the battery cell is changed to 0;

[0035] The power adjustment command of the battery unit after SOC over-limit processing is as follows:

[0036]

[0037] Among them, P bi,t is the power regulation instruction of the ith battery unit at time t, P bmax is the maximum charge and discharge power of the battery cell, charging takes a negative value and discharging takes a positive value, S bmax and S bmin They are the upper and lower SOC operating limits of the battery unit respectively;

[0038] In step S25, when the maximum charge and discharge power exceeds the limit,

[0039] When the power regulation instruction assigned to the battery unit exceeds its maximum charge and discharge power, the power regulation instruction of the battery unit is changed to its maximum charge and discharge power. The power regulation instruction of the battery unit after the maximum charge and discharge power exceeds the limit is shown in the following formula:

[0040]

[0041] Among them, P bi,t is the power regulation instruction of the ith battery unit at time t, P bmax It is the maximum charge and discharge power of the battery cell. Charging takes a negative value and discharging takes a positive value.

[0042] Furthermore, the specific steps of step S3 are as follows:

[0043] S31. Dividing the battery cells in the energy storage system into a maximum charge and discharge group that has reached the maximum charge and discharge power and a non-maximum charge and discharge group that has not reached the maximum charge and discharge power;

[0044] S32. Use the power adjustment instruction of the maximum charge and discharge group and the power adjustment instruction of the non-maximum charge and discharge group to represent the power adjustment instruction of all battery cells in the energy storage system and serve as the actual power adjustment instruction of the energy storage system;

[0045] S33. Subtract the power regulation instruction of the energy storage system issued by the power system from the actual power regulation instruction of the energy storage system, and use the difference as the remaining power deviation.

[0046] Furthermore, in step S32, the actual power adjustment instruction of the energy storage system is expressed as:

[0047]

[0048] The remaining power deviation in step S33 is expressed as: P re =P B -P bs

[0049] Among them, P bs is the sum of all battery unit power regulation instructions, N B1 is the number of battery cells in the largest charge and discharge group in the energy storage system, N B2 is the number of battery cells in the non-maximum charge and discharge group in the energy storage system, P bi is the power regulation instruction of the ith battery unit, P bm is the power adjustment instruction that needs to be added for the mth battery unit that has not reached the maximum charge and discharge power instruction, P B is the BESS power adjustment command, P re is the residual power deviation. Further, the specific steps of step S4 are as follows:

[0050] S41. Count the battery cells in the non-maximum charge and discharge group that have not reached the maximum charge and discharge power;

[0051] S42. For a non-maximum charge and discharge group, the charging function is used to calculate the sum of the charging function values ​​of all battery cells, and the charging distribution ratio of each battery cell is calculated according to the ratio of the charging function value of each battery cell to the sum of the charging function values ​​of all battery cells, and when charging, the remaining power deviation is distributed to the battery cells according to the charging distribution ratio;

[0052] S43. For a non-maximum charge and discharge group, the discharge function is used to calculate the sum of the discharge function values ​​of all battery cells, and the discharge distribution ratio of each battery cell is calculated according to the ratio of the discharge function value of each battery cell to the sum of the discharge function values ​​of all battery cells, and when discharging, the remaining power deviation is distributed to the battery cells according to the discharge distribution ratio;

[0053] S44. For the non-maximum charge and discharge group, the power adjustment command assigned to the battery cell is checked for SOC over-limit, and the power adjustment command assigned to the battery cell is adjusted when the SOC exceeds the limit to obtain the power adjustment command after the SOC adjustment;

[0054] S45. For the non-maximum charge and discharge group, the power regulation instructions allocated to the battery cells are checked for maximum charge and discharge power exceeding the limit, and the power regulation instructions allocated to the battery cells are adjusted when the maximum charge and discharge power exceeds the limit to obtain the power regulation instructions after the maximum charge and discharge power is adjusted.

[0055] Furthermore, the calculation formula of the power adjustment instruction of the battery unit of the non-maximum charge and discharge group in step S42 and step S43 is as follows:

[0056]

[0057] Among them, S n,t-1 is the state of charge of the nth battery cell in the non-maximum charge and discharge group at time t-1, N B2 is the number of the second battery cells in the non-maximum charge and discharge group, f ch () represents the charging function, f dis () represents the discharge function, m represents the mth battery cell in the non-maximum charge and discharge group;

[0058] In step S44, for the non-maximum charge and discharge group, when the SOC exceeds the limit,

[0059] When the power adjustment command of the battery unit is negative, if the SOC of the battery unit exceeds the SOC operation upper limit, the power adjustment command of the battery unit is changed to 0;

[0060] When the power regulation instruction of the battery cell is positive, if the SOC of the battery cell is lower than the SOC operation lower limit, the power regulation instruction of the battery cell is changed to 0;

[0061] The power adjustment command of the battery unit after SOC over-limit processing is as follows:

[0062]

[0063] Among them, P bi,t is the power regulation instruction of the ith battery unit in the non-maximum charge and discharge group at time t, P bmax is the maximum charge and discharge power of the battery cell, charging takes a negative value and discharging takes a positive value, S bmax and S bmin are the SOC operating upper limit and SOC operating lower limit of the second battery unit respectively;

[0064] In step S45, when the maximum charge and discharge power exceeds the limit,

[0065] When the power adjustment instruction assigned to the battery unit in the non-maximum charge and discharge group exceeds its maximum charge and discharge power, the power adjustment instruction of the battery unit in the non-maximum charge and discharge group is changed to its maximum charge and discharge power. The power adjustment instruction of the battery unit after the maximum charge and discharge power exceeds the limit is shown in the following formula:

[0066]

[0067] Among them, P bi,t is the power regulation instruction of the ith battery unit in the non-maximum charge and discharge group at time t, P bmax It is the maximum charge and discharge power of the battery cell. Charging takes a negative value and discharging takes a positive value.

[0068] Furthermore, the specific steps of step S5 are as follows:

[0069] S51. Set the judgment condition for the completion of energy storage system power distribution as:

[0070] The first condition is: the residual power deviation is 0;

[0071] The second condition is that the power regulation instructions of all battery units in the energy storage system have reached their respective maximum charge and discharge powers;

[0072] The third condition is: the state of charge of all battery cells in the energy storage system has exceeded the limit;

[0073] S52. Determine whether the current power adjustment instruction of the energy storage system satisfies at least one of the determination conditions;

[0074] If so, it is determined that the power allocation is completed;

[0075] If not, continue to calculate the remaining power deviation, continue to allocate, and return to step S3.

[0076] The beneficial effects of the present invention are:

[0077] The internal power distribution method of the battery energy storage system provided by the present invention can accelerate the balancing speed of the battery cell SOC and improve the balancing degree of the battery cell SOC when the BESS is running, for the battery energy storage system equipped with the centralized battery energy storage power station and the new energy power generation, thereby improving the sustainable regulation capability of the BESS and the tracking effect of the BESS on its power regulation instructions, so that the BESS can more effectively smooth out the power fluctuation of the new energy and assist the new energy to be safely and smoothly integrated into the power grid.

[0078] In addition, the invention has a reliable design principle, a simple structure and a very broad application prospect.

[0079] It can be seen that compared with the prior art, the present invention has outstanding substantive features and significant progress, and the beneficial effects of its implementation are also obvious. BRIEF DESCRIPTION OF THE DRAWINGS

[0080] 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.

[0081] Figure 1 It is a flow chart of an embodiment of a method for distributing power within a battery energy storage system of the present invention.

[0082] Figure 2It is a schematic diagram for explaining in detail the internal power distribution method of the battery energy storage system of the present invention.

[0083] Figure 3 It is a schematic diagram of the charge and discharge function values ​​of the battery unit under different SOCs of the present invention.

[0084] Figure 4 It is a schematic diagram of the overall SOC change of the battery energy storage system of the present invention.

[0085] Figure 5 It is a schematic diagram of the SOC change during the operation of the battery unit of the present invention.

[0086] Figure 6 It is a schematic diagram of the response of the battery energy storage system of the present invention to its power regulation instruction.

[0087] Figure 7 It is a schematic diagram of the SOC changes of each battery unit during the operation of the conventional power distribution method of the present invention.

[0088] Figure 8 It is a schematic diagram of the response of the battery energy storage system to its power regulation instruction in the conventional power distribution method of the present invention. DETAILED DESCRIPTION

[0089] 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 should fall within the scope of protection of the present invention. Please refer to Figure 1 The figure shows a specific implementation of a method for distributing power within a battery energy storage system, comprising the following steps:

[0090] S1. Construct a charge and discharge function with SOC as a variable for the battery unit in the energy storage system to characterize the charge and discharge capacity of the battery unit;

[0091] S2. Obtain the power regulation instruction of the energy storage system issued by the power dispatching center, allocate the power regulation instruction in combination with the charge and discharge function of the battery unit, and then adjust the allocated power regulation instruction according to the SOC operation limit and maximum charge and discharge power limit of each battery unit;

[0092] S3. Sum the power regulation instructions of all battery cells of the energy storage system to obtain the actual power regulation instruction of the energy storage system, and calculate the difference between the power regulation instruction of the energy storage system issued by the power dispatching center and the actual power regulation instruction as the remaining power deviation;

[0093] S4. Count the battery cells in the energy storage system that have not reached the maximum charge and discharge power, allocate the remaining power deviation in combination with the charge and discharge function of the battery cell, and then adjust the power regulation instructions allocated to the battery cell according to the SOC operation limit and the maximum charge and discharge power limit of the battery cell;

[0094] S5. Determine whether the energy storage system power distribution completion determination condition is met, and end the power distribution if it is met, and return to step S3 if it is not met.

[0095] The charge and discharge function designed by the present invention can fully characterize the charge and discharge capabilities of battery cells under different SOCs; a BESS power regulation instruction allocation method based on the charge and discharge function is provided; when there is a residual power deviation between the BESS power regulation instruction and the power regulation instructions of all battery cells, an improved battery cell SOC consistency power allocation method is designed to allocate the residual power deviation to the battery cells that have not reached the maximum charge and discharge power instruction.

[0096] In this embodiment, the specific steps of step S1 are as follows:

[0097] S11. Taking the SOC of the battery cell in the energy storage system at a set time as a variable, construct a charging function of the battery cell to characterize the charging capacity of the battery cell;

[0098] S12. Taking the SOC of the battery cell in the energy storage system at a set time as a variable, constructing a discharge function of the battery cell to characterize the discharge capacity of the battery cell;

[0099] The charging function of the battery cell in step S11 is expressed as follows:

[0100]

[0101] Among them, f ch (S i,t-1 ) represents the charging function value of the battery cell at time t-1, S i,t-1 is the state of charge of the i-th battery cell at time t-1;

[0102] The discharge function of the battery cell in step S12 is expressed as follows:

[0103]

[0104] Among them, f dis (S i,t-1 ) represent the discharge function value of the battery cell at time t-1, S i,t-1 is the state of charge of the i-th battery cell at time t-1;

[0105] The charge and discharge function values ​​of the battery cell under different SOC are as follows: Figure 3 As shown;

[0106] The specific steps of step S2 are as follows:

[0107] S21. Obtain the power adjustment command issued by the power dispatching center to the energy storage system, where a positive value indicates discharge and a negative value indicates charge;

[0108] S22. Calculate the sum of the charging function values ​​of all battery cells using the charging function of the battery cell, and calculate the charging distribution ratio of each battery cell according to the ratio of the charging function value of each battery cell to the sum of the charging function values ​​of all battery cells, and when charging, distribute the power adjustment instructions issued by the power dispatching center to the battery cells according to the charging distribution ratio;

[0109] S23. Use the discharge function of the battery cell to calculate the sum of the discharge function values ​​of all battery cells, and calculate the discharge distribution ratio of each battery cell according to the ratio of the discharge function value of each battery cell to the sum of the discharge function values ​​of all battery cells, and when discharging, distribute the power adjustment instructions issued by the power dispatching center to the battery cells according to the discharge distribution ratio;

[0110] S24. Perform an SOC over-limit check on the power regulation instructions assigned to each battery cell, and adjust the power regulation instructions assigned to the battery cell when the SOC exceeds the limit to obtain the power regulation instructions after the SOC adjustment; S25. Perform a maximum charge and discharge power over-limit check on the power regulation instructions assigned to each battery cell, and adjust the power regulation instructions assigned to the battery cell when the maximum charge and discharge power exceeds the limit to obtain the power regulation instructions after the maximum charge and discharge power adjustment;

[0111] The calculation formula of the power adjustment instruction of the battery unit in step S22 and step S23 is as follows:

[0112]

[0113] Among them, P bi is the power regulation instruction of the ith battery unit, N B1 is the number of battery cells in the battery energy storage system, S j,t-1 is the SOC of the jth battery cell at time t-1;

[0114] In step S24, when the SOC exceeds the limit,

[0115] When the power adjustment command of the battery unit is negative, if the SOC of the battery unit exceeds the SOC operation upper limit, the power adjustment command of the battery unit is changed to 0;

[0116] When the power regulation instruction of the battery cell is positive, if the SOC of the battery cell is lower than the SOC operation lower limit, the power regulation instruction of the battery cell is changed to 0;

[0117] The power adjustment command of the battery unit after SOC over-limit processing is as follows:

[0118]

[0119] Among them, P bi,t is the power regulation instruction of the ith battery unit at time t, P bmax is the maximum charge and discharge power of the battery cell, charging takes a negative value and discharging takes a positive value, S bmax and S bmin They are the upper and lower SOC operating limits of the battery unit respectively;

[0120] In step S25, when the maximum charge and discharge power exceeds the limit,

[0121] When the power regulation instruction assigned to the battery unit exceeds its maximum charge and discharge power, the power regulation instruction of the battery unit is changed to its maximum charge and discharge power. The power regulation instruction of the battery unit after the maximum charge and discharge power exceeds the limit is shown in the following formula:

[0122]

[0123] Among them, P bi,t is the power regulation instruction of the ith battery unit at time t, P bmax is the maximum charge and discharge power of the battery cell, with negative values ​​for charging and positive values ​​for discharging;

[0124] The specific steps of step S3 are as follows:

[0125] S31. Dividing the battery cells in the energy storage system into a maximum charge and discharge group that has reached the maximum charge and discharge power and a non-maximum charge and discharge group that has not reached the maximum charge and discharge power;

[0126] S32. Use the power adjustment instruction of the maximum charge and discharge group battery unit and the power adjustment instruction of the non-maximum charge and discharge group to represent the power adjustment instruction of all battery units in the energy storage system and as the actual power adjustment instruction of the energy storage system;

[0127] S33. Use the power regulation instruction of the energy storage system issued by the power system to make a difference with the actual power regulation instruction of the energy storage system, and use the difference as the remaining power deviation;

[0128] In step S32, the actual power adjustment instruction of the energy storage system is expressed as:

[0129]

[0130] The remaining power deviation in step S33 is expressed as: P re =P B -P bs

[0131] Among them, P bs is the sum of all battery unit power regulation instructions, N B1 is the number of battery cells in the largest charge and discharge group in the energy storage system, N B2 is the number of battery cells in the non-maximum charge and discharge group in the energy storage system, P bi is the power regulation instruction of the ith battery unit, P bm is the power adjustment instruction that needs to be added for the mth battery unit that has not reached the maximum charge and discharge power instruction, P B is the BESS power adjustment command, P re is the residual power deviation; the specific steps of step S4 are as follows:

[0132] S41. Count the battery cells in the non-maximum charge and discharge group that have not reached the maximum charge and discharge power;

[0133] S42. For a non-maximum charge and discharge group, the charging function is used to calculate the sum of the charging function values ​​of all battery cells, and the charging distribution ratio of each battery cell is calculated according to the ratio of the charging function value of each battery cell to the sum of the charging function values ​​of all battery cells, and when charging, the remaining power deviation is distributed to the battery cells according to the second charging distribution ratio;

[0134] S43. For a non-maximum charge and discharge group, the discharge function is used to calculate the sum of the discharge function values ​​of all battery cells, and the discharge distribution ratio of each battery cell is calculated according to the ratio of the discharge function value of each battery cell to the sum of the discharge function values ​​of all battery cells, and when discharging, the remaining power deviation is distributed to the battery cells according to the discharge distribution ratio;

[0135] S44. For the non-maximum charge and discharge group, the power adjustment command assigned to the battery cell is checked for SOC over-limit, and the power adjustment command assigned to the battery cell is adjusted when the SOC exceeds the limit to obtain the power adjustment command after the SOC adjustment;

[0136] S45. For non-maximum charge and discharge groups, the power adjustment instructions assigned to the battery cells are checked for maximum charge and discharge power exceeding the limit, and the power adjustment instructions assigned to the battery cells are adjusted when the maximum charge and discharge power exceeds the limit to obtain the power adjustment instructions after the maximum charge and discharge power is adjusted;

[0137] The calculation formula of the power adjustment instruction of the battery unit of the non-maximum charge and discharge group in step S42 and step S43 is as follows:

[0138]

[0139] Among them, S n,t-1 is the state of charge of the nth battery cell in the non-maximum charge and discharge group at time t-1, NB2 is the number of battery cells in the non-maximum charge and discharge group, f ch () represents the charging function, f dis () represents the discharge function, m represents the mth battery cell in the non-maximum charge and discharge group;

[0140] In step S44, for the non-maximum charge and discharge group, when the SOC exceeds the limit,

[0141] When the power adjustment command of the battery cell is negative, if the SOC of the battery cell exceeds the SOC operation upper limit, the power adjustment command of the battery cell is changed to 0;

[0142] When the power regulation instruction of the battery cell is positive, if the SOC of the battery cell is lower than the SOC operation lower limit, the power regulation instruction of the battery cell is changed to 0;

[0143] The power adjustment command of the battery unit after SOC over-limit processing is as follows:

[0144]

[0145] Among them, P bi,t is the power regulation instruction of the ith battery unit in the non-maximum charge and discharge group at time t, P bmax is the maximum charge and discharge power of the battery cell, charging takes a negative value and discharging takes a positive value, S bmax and S bmin They are the upper and lower SOC operating limits of the battery unit respectively;

[0146] In step S45, when the maximum charge and discharge power exceeds the limit,

[0147] When the power adjustment instruction assigned to the battery unit in the non-maximum charge and discharge group exceeds its maximum charge and discharge power, the power adjustment instruction of the battery unit in the non-maximum charge and discharge group is changed to its maximum charge and discharge power. The power adjustment instruction of the battery unit after the maximum charge and discharge power exceeds the limit is shown in the following formula:

[0148]

[0149] Among them, P bi,t is the power regulation instruction of the ith battery unit in the non-maximum charge and discharge group at time t, P bmax is the maximum charge and discharge power of the battery cell, with negative values ​​for charging and positive values ​​for discharging;

[0150] The specific steps of step S5 are as follows:

[0151] S51. Set the judgment condition for the completion of energy storage system power distribution as:

[0152] The first condition is: the residual power deviation is 0;

[0153] The second condition is that the power regulation instructions of all battery units in the energy storage system have reached their respective maximum charge and discharge powers;

[0154] The third condition is: the state of charge of all battery cells in the energy storage system has exceeded the limit;

[0155] S52. Determine whether the current power adjustment instruction of the energy storage system satisfies at least one of the determination conditions;

[0156] If so, it is determined that the power allocation is completed;

[0157] If not, continue to calculate the remaining power deviation, continue to allocate, and return to step S3.

[0158] It should be understood that the order of execution of the steps in the above embodiment does not mean that the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiment of the present invention.

[0159] In order to further understand the present invention and verify the effectiveness of the invented power allocation method, the power allocation method is simulated using the dispatching instructions issued by a power dispatching center to a centralized battery energy storage power station. The scale of the battery energy storage power station is 10MW / 10MWh, and other relevant parameters are shown in Table 1 below:

[0160] Table 1

[0161]

[0162] When BESS responds to the power adjustment command issued by the dispatch control center, the overall SOC change of the battery energy storage system is as follows: Figure 4 As shown in Figure 2, the SOC changes of each battery cell are as follows: Figure 5 As shown, it can be seen that during the response of the battery energy storage system, the SOC of all battery cells gradually tends to be balanced;

[0163] The response of BESS to its power regulation command is shown in the attached figure. Figure 6 As shown in the figure, it can be seen that at most times, BESS can accurately track its power adjustment instructions. At some times, BESS fails to accurately track its power adjustment instructions. This is because the instructions issued by the dispatching center exceed the maximum charge and discharge power limit of BESS. At this time, BESS can only track with the maximum charge and discharge power.

[0164] In order to further highlight the superiority of the present invention, the internal power distribution method of the battery energy storage system of the present invention is compared with the power distribution method of the traditional energy storage system. The SOC change of the battery unit under the traditional power distribution method is shown in the attached figure. Figure 7The comparison of the SOC balancing speed and balancing degree under the two methods is shown in Table 2. It can be seen that the SOC standard deviation under the traditional method is less than 10 -3 , 10 -6 The balancing time required for the power distribution method is 181min and 479min respectively, while the SOC standard deviation is less than 10 -3 , 10 -6 The balancing time required for the conventional method is only 158 min and 463 min, respectively, which verifies that the present invention has a faster SOC balancing speed. The SOC standard deviation at the end of the response under the conventional method is 1.17×10 -16 , while the SOC standard deviation of the present invention at the end of the response is 5.85×10 -17 , which verifies that the present invention has a higher degree of balance;

[0165] Table 2

[0166]

[0167] The response of BESS to its power regulation command under the traditional power allocation method is as follows: Figure 8 As shown in the figure, the BESS fails to accurately track its power regulation instruction. The tracking of the power regulation instruction of the BESS under the two methods is shown in Table 3. It can be seen that the traditional power allocation method makes it difficult for the BESS to respond with the maximum charge and discharge power when it is not tracked, resulting in a large tracking error. However, the BESS can track with the maximum charge and discharge power under the present invention, so the tracking error is small. The total error of the tracking effect of the traditional power allocation method is as high as 6.8597MW, while the total error of the tracking effect under the present invention is only 2.6803MW, which verifies that the present invention can enable the battery energy storage system to more accurately track the power regulation instruction issued by the power dispatching center.

[0168] Table 3

[0169]

[0170] Although the present invention has been described in detail with reference to the accompanying drawings and in combination with the preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, a person of ordinary skill in the art may make various equivalent modifications or substitutions to the embodiments of the present invention, and these modifications or substitutions shall be within the scope of the present invention. Any person of ordinary skill in the art may easily think of changes or substitutions within the technical scope disclosed by the present invention, and these shall be within the scope of protection of the present invention.

Claims

1. A method for distributing power within a battery energy storage system, characterized in that: The steps include: S1. Construct a charge and discharge function with SOC as a variable for the battery unit in the energy storage system to characterize the charge and discharge capacity of the battery unit; S2. Obtain the power regulation instruction of the energy storage system issued by the power dispatching center, allocate the power regulation instruction in combination with the charge and discharge function of the battery unit, and then adjust the allocated power regulation instruction according to the SOC operation limit and maximum charge and discharge power limit of each battery unit; S3. Sum the power regulation instructions of all battery cells of the energy storage system to obtain the actual power regulation instruction of the energy storage system, and calculate the difference between the power regulation instruction of the energy storage system issued by the power dispatching center and the actual power regulation instruction as the remaining power deviation; S4. Count the battery cells in the energy storage system that have not reached the maximum charge and discharge power, allocate the remaining power deviation in combination with the charge and discharge function of the battery cell, and then adjust the power regulation instructions allocated to the battery cell according to the SOC operation limit and the maximum charge and discharge power limit of the battery cell; S5. Determine whether the energy storage system power distribution completion determination condition is met, and end the power distribution if it is met, and return to step S3 if it is not met.

2. The internal power distribution method of the battery energy storage system according to claim 1, characterized in that: The specific steps of step S1 are as follows: S11. Taking the SOC of the battery cell in the energy storage system at a set time as a variable, construct a charging function of the battery cell to characterize the charging capacity of the battery cell; S12. Taking the SOC of the battery cell in the energy storage system at a set time as a variable, a discharge function of the battery cell is constructed to characterize the discharge capacity of the battery cell.

3. The internal power distribution method of the battery energy storage system according to claim 2, characterized in that: The charging function of the battery cell in step S11 is expressed as follows: Among them, f ch (S i,t-1 ) represents the charging function value of the battery cell at time t-1, S i,t-1 is the state of charge of the i-th battery cell at time t-1; The discharge function of the battery cell in step S12 is expressed as follows: Among them, f dis (S i,t-1 ) represent the discharge function value of the battery cell at time t-1, S i,t-1 is the state of charge of the i-th battery cell at time t-1.

4. The internal power distribution method of the battery energy storage system according to claim 2, characterized in that: The specific steps of step S2 are as follows: S21. Obtain the power adjustment command issued by the power dispatching center to the energy storage system, where a positive value indicates discharge and a negative value indicates charge; S22. Calculate the sum of the charging function values ​​of all battery cells using the charging function of the battery cell, and calculate the charging distribution ratio of each battery cell according to the ratio of the charging function value of each battery cell to the sum of the charging function values ​​of all battery cells, and when charging, distribute the power adjustment instructions issued by the power dispatching center to the battery cells according to the charging distribution ratio; S23. Use the discharge function of the battery cell to calculate the sum of the discharge function values ​​of all battery cells, and calculate the discharge distribution ratio of each battery cell according to the ratio of the discharge function value of each battery cell to the sum of the discharge function values ​​of all battery cells, and when discharging, distribute the power adjustment instructions issued by the power dispatching center to the battery cells according to the discharge distribution ratio; S24. Perform an SOC over-limit check on the power adjustment instructions assigned to each battery cell, and adjust the power adjustment instructions assigned to the battery cell when the SOC exceeds the limit to obtain the power adjustment instructions after the SOC adjustment; S25. Perform a maximum charge and discharge power limit check on the power regulation instructions assigned to each battery unit, and adjust the power regulation instructions assigned to the battery unit when the maximum charge and discharge power exceeds the limit to obtain a power regulation instruction after the maximum charge and discharge power is adjusted.

5. The internal power distribution method of the battery energy storage system according to claim 4, characterized in that: The calculation formula of the power adjustment instruction of the battery unit in step S22 and step S23 is as follows: Among them, P bi is the power regulation instruction of the ith battery unit, N B1 is the number of battery cells in the battery energy storage system, S j,t-1 is the SOC of the jth battery cell at time t-1; In step S24, when the SOC exceeds the limit, When the power adjustment command of the battery cell is negative, if the SOC of the battery cell exceeds the SOC operation upper limit, the power adjustment command of the battery cell is changed to 0; When the power regulation instruction of the battery cell is positive, if the SOC of the battery cell is lower than the SOC operation lower limit, the power regulation instruction of the battery cell is changed to 0; The power adjustment command of the battery unit after SOC over-limit processing is as follows: Among them, P bi,t is the power regulation instruction of the ith battery unit at time t, P bmax is the maximum charge and discharge power of the battery cell, charging takes a negative value and discharging takes a positive value, S bmax and S bmin They are the upper and lower SOC operating limits of the battery cell respectively; In step S25, when the maximum charge and discharge power exceeds the limit, When the power regulation instruction assigned to the battery unit exceeds its maximum charge and discharge power, the power regulation instruction of the battery unit is changed to its maximum charge and discharge power. The power regulation instruction of the battery unit after the maximum charge and discharge power exceeds the limit is shown in the following formula: Among them, P bi,t is the power regulation instruction of the ith battery unit at time t, P bmax It is the maximum charge and discharge power of the battery cell. Charging takes a negative value and discharging takes a positive value.

6. The internal power distribution method of the battery energy storage system according to claim 4, characterized in that: The specific steps of step S3 are as follows: S31. Dividing the battery cells in the energy storage system into a maximum charge and discharge group that has reached the maximum charge and discharge power and a non-maximum charge and discharge group that has not reached the maximum charge and discharge power; S32. Use the power adjustment instruction of the maximum charge and discharge group battery unit and the power adjustment instruction of the non-maximum charge and discharge group to represent the power adjustment instruction of all battery units in the energy storage system and as the actual power adjustment instruction of the energy storage system; S33. Subtract the power regulation instruction of the energy storage system issued by the power system from the actual power regulation instruction of the energy storage system, and use the difference as the remaining power deviation.

7. The internal power distribution method of the battery energy storage system according to claim 6, characterized in that: In step S32, the actual power adjustment instruction of the energy storage system is expressed as: The remaining power deviation in step S33 is expressed as: P re =P B -P bs Among them, P bs is the sum of all battery unit power regulation instructions, N B1 is the number of battery cells in the largest charge and discharge group in the energy storage system, N B2 is the number of battery cells in the non-maximum charge and discharge group in the energy storage system, P bi is the power regulation instruction of the ith battery unit, P bm is the power adjustment instruction that needs to be added for the mth battery unit that has not reached the maximum charge and discharge power instruction, P B is the BESS power adjustment command, P re is the residual power deviation.

8. The internal power distribution method of the battery energy storage system according to claim 6, characterized in that: The specific steps of step S4 are as follows: S41. Count the battery cells in the non-maximum charge and discharge group that have not reached the maximum charge and discharge power; S42. For a non-maximum charge and discharge group, the charging function is used to calculate the sum of the charging function values ​​of all battery cells, and the charging distribution ratio of each battery cell is calculated according to the ratio of the charging function value of each battery cell to the sum of the charging function values ​​of all battery cells, and when charging, the remaining power deviation is distributed to the battery cells according to the charging distribution ratio; S43. For a non-maximum charge and discharge group, the discharge function is used to calculate the sum of the discharge function values ​​of all battery cells, and the discharge distribution ratio of each battery cell is calculated according to the ratio of the discharge function value of each battery cell to the sum of the discharge function values ​​of all battery cells, and when discharging, the remaining power deviation is distributed to the battery cells according to the discharge distribution ratio; S44. For the non-maximum charge and discharge group, the power adjustment command assigned to the battery cell is checked for SOC over-limit, and the power adjustment command assigned to the battery cell is adjusted when the SOC exceeds the limit to obtain the power adjustment command after the SOC adjustment; S45. For the non-maximum charge and discharge group, the power regulation instructions allocated to the battery cells are checked for maximum charge and discharge power exceeding the limit, and the power regulation instructions allocated to the battery cells are adjusted when the maximum charge and discharge power exceeds the limit to obtain the power regulation instructions after the maximum charge and discharge power is adjusted.

9. The internal power distribution method of the battery energy storage system according to claim 8, characterized in that: The calculation formula of the power adjustment instruction of the battery unit of the non-maximum charge and discharge group in step S42 and step S43 is as follows: Among them, S n,t-1 is the state of charge of the nth battery cell in the non-maximum charge and discharge group at time t-1, N B2 is the number of battery cells in the non-maximum charge and discharge group, f ch () represents the charging function, f dis () represents the discharge function, m represents the mth battery cell in the non-maximum charge and discharge group; In step S44, for the non-maximum charge and discharge group, when the SOC exceeds the limit, When the power adjustment command of the battery cell is negative, if the SOC of the battery cell exceeds the SOC operation upper limit, the power adjustment command of the battery cell is changed to 0; When the power regulation instruction of the battery cell is positive, if the SOC of the battery cell is lower than the SOC operation lower limit, the power regulation instruction of the battery cell is changed to 0; The power adjustment command of the battery unit after SOC over-limit processing is as follows: Among them, P bi,t is the power regulation instruction of the ith battery unit in the non-maximum charge and discharge group at time t, P bmax is the maximum charge and discharge power of the battery cell, charging takes a negative value and discharging takes a positive value, S bmax and S bmin They are the upper and lower SOC operating limits of the battery cell respectively; In step S45, when the maximum charge and discharge power exceeds the limit, When the power adjustment instruction assigned to the battery unit in the non-maximum charge and discharge group exceeds its maximum charge and discharge power, the power adjustment instruction of the battery unit in the non-maximum charge and discharge group is changed to its maximum charge and discharge power. The power adjustment instruction of the battery unit after the maximum charge and discharge power exceeds the limit is shown in the following formula: Among them, P bi,t is the power regulation instruction of the ith battery unit in the non-maximum charge and discharge group at time t, P bmax It is the maximum charge and discharge power of the battery cell. Charging takes a negative value and discharging takes a positive value.

10. The internal power distribution method of the battery energy storage system according to claim 8, characterized in that: The specific steps of step S5 are as follows: S51. Set the judgment condition for the completion of energy storage system power distribution as: The first condition is: the residual power deviation is 0; The second condition is that the power regulation instructions of all battery units in the energy storage system have reached their respective maximum charge and discharge powers; The third condition is: the state of charge of all battery cells in the energy storage system has exceeded the limit; S52. Determine whether the current power adjustment instruction of the energy storage system satisfies at least one of the determination conditions; If so, it is determined that the power allocation is completed; If not, continue to calculate the remaining power deviation, continue to allocate, and return to step S3.

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