A hierarchical control method and system for energy storage device

Abstract

A hierarchical control method and system for an energy storage device, the method comprising: collecting the frequency change rate and frequency deviation, and the state of charge of each energy storage unit; determining whether the energy storage device participates in frequency modulation according to the frequency change rate and the allowable value, the frequency deviation and the allowable value; when participating in frequency modulation, determining the frequency modulation power of each energy storage unit participating in frequency modulation according to the frequency modulation power direction, the maximum and minimum state of charge in each energy storage unit, and the frequency fluctuation degree coefficient; taking the first n energy storage units in the energy storage unit state of charge sorting, if the absolute value of the sum of the frequency modulation powers of the first n energy storage units is not less than the absolute value of the reference frequency modulation power of the energy storage device, the first n energy storage units participate in frequency modulation; if the absolute value of the sum of the frequency modulation powers of all energy storage units is less than the absolute value of the reference frequency modulation power of the energy storage device, all energy storage units participate in frequency modulation. The present invention realizes balanced management of energy storage units with different states of charge, which is conducive to maintaining the service life of the energy storage device.

Description

Technical Field

[0001] The present invention relates to the technical field of energy storage control, and more specifically, to a hierarchical control method and system for an energy storage device. Background Art

[0002] Frequency is one of the key indicators of power grid quality. The dynamic balance between power load and power generation is an important guarantee for the stability of power grid frequency. Therefore, the change of power grid frequency also directly reflects the balance of power supply and demand. When power generation is greater than power load, the power grid frequency increases; conversely, when power load is greater than power generation, the power grid frequency decreases. Wind power generation is clean and low-carbon, and its technology is relatively mature, and its grid-connected capacity is increasing year by year. However, the rotor speed of the current mainstream wind turbines is decoupled from the system frequency, so it does not have frequency response capabilities, which brings great challenges to the system frequency operation. With the large number of new energy generators connected to the power grid and the increase in impact loads, in order to ensure the safe and economical operation of the power grid and improve the power quality of users, the power grid has higher and higher requirements for the frequency regulation of the units.

[0003] In the existing technology, the use of large-scale energy storage systems to replace power plants for frequency regulation has attracted the attention of the industry. Battery energy storage systems have fast response and accurate tracking, so they are more efficient than traditional frequency regulation methods. In recent years, compared with traditional power sources, energy storage has obvious technical advantages in providing frequency regulation for power grids, and its economic benefits will gradually emerge, which can effectively improve the operating efficiency of power systems. Flywheel energy storage (FES) is a representative example. This is an advanced physical energy storage technology. It refers to the use of electric energy to drive the flywheel to rotate at high speed, converting electric energy into mechanical energy, and when needed, the flywheel inertia drags the motor to generate electricity, and the stored mechanical energy is converted into electric energy output. A kind of energy storage method, namely the so-called flywheel discharge. Flywheel energy storage has the characteristics of high power density, fast response speed, long life, maintenance-free, good scalability, and no pollution. Compared with other types of energy storage methods, such as lithium batteries, lead-acid batteries, pumped storage, etc., flywheel energy storage power stations have the advantages of large output power, fast instantaneous response speed, low long-term operation and maintenance cost, safety and reliability, green environmental protection and no pollution. In particular, the discharge power response speed of the flywheel energy storage system is fast, reaching the millisecond level, which can meet the needs of primary frequency control and adopt the flywheel energy storage and the unit to jointly perform primary frequency control.

[0004] However, compared with traditional power equipment and projects, the construction cost of energy storage systems is higher, and maintenance during operation is more important. The status of the power system and the energy storage system should be comprehensively considered to control the depth of energy storage charge and discharge in real time. The state of charge SOC (State of Charge) represents the ratio of the remaining dischargeable power of the energy storage device after a period of use or long-term unused to its fully charged state, and the value range is 0% to 100%. Flywheel energy storage control requires monitoring its energy state and regulating it in combination with grid frequency changes and SOC state. For the frequency regulation control system as a whole, the ideal situation is that the SOC of the energy storage device is 50%, that is, the energy storage device is in an intermediate position where it can both increase the absorption of energy and decrease the compensation of energy, but this brings about an increase in the scale of energy storage investment. Therefore, in the actual application process, the energy storage state and the system frequency characteristics should be comprehensively considered to carry out control. Prior art 1 (CN112018785B) "Flywheel energy storage frequency regulation method and system for receiving-end power grid based on frequency disturbance complementarity" judges the remaining power SOC of the flywheel energy storage device. FES When it is less than 100%, the rated capacity H of the flywheel energy storage device is FES-N Real-time calculation of the required charging capacity H of the flywheel energy storage device FES-C ; According to the frequency fluctuation of the receiving power grid, the real-time computer group needs to change the integrated power H PFC ; According to the frequency disturbance of the receiving grid, according to the required charging capacity H FES-C And the integral power H needs to be changed PFCPerform frequency regulation control of flywheel energy storage. Although the prior art 1 adopts different frequency regulation control methods for the flywheel energy storage device and the unit according to the different frequency disturbances of the power grid, it not only reduces the number of actions of the unit at high frequency and improves the life of the valves and other equipment of the unit, but also can achieve rapid one-time frequency regulation through the flywheel energy storage device, ensuring the economic operation of the flywheel energy storage and the integrated frequency regulation system of the unit, and realizing the stable operation of the flywheel energy storage and the integrated frequency regulation system of the unit. However, with the increase in the construction scale of the energy storage system, the energy storage system includes energy storage units in various operating states, and the charge states of each energy storage unit are different; according to the frequency regulation control strategy proposed in the prior art 1, the difference in the charge state of each energy storage unit is not taken into account, and the energy storage unit will have an unbalanced working phenomenon, which will affect the service life of some energy storage units, thereby reducing the service life of the energy storage system. In addition, it will increase the difficulty and workload of operation and maintenance, which will reduce the economic efficiency of the energy storage system throughout its life cycle. In addition, the series capacity of the energy storage system depends on the energy storage unit with the smallest capacity. Due to differences in the energy storage units themselves, temperature differences and other factors, the available capacity of the energy storage units will be different. The energy storage units with small capacity will be fully charged first when charging and emptied first when discharging, thereby restricting the charging and discharging capabilities of other energy storage units in the energy storage system, resulting in a decrease in the available capacity of the energy storage system. In the prior art 1, the principle of the energy storage system participating in frequency modulation is that the state of charge reaches 100%, and the charging capacity that can participate in frequency modulation is determined according to the rated capacity of the energy storage system by the difference between the current state of charge and 100%. In actual applications, the charging capacity allocated to the energy storage system in the frequency modulation control strategy cannot be fully absorbed by the energy storage system, resulting in the adjustable power allocated to the unit side being too low to meet the actual frequency modulation demand, resulting in the emergence of secondary frequency modulation, which reduces the economy of frequency modulation.

[0005] Therefore, it is necessary to study energy storage layered control to give full play to the advantages of energy storage frequency regulation. Summary of the invention

[0006] In order to solve the deficiencies in the prior art, the purpose of the present invention is to provide a hierarchical control method and system for an energy storage device to realize hybrid energy storage hierarchical control taking into account frequency disturbances, wherein firstly, an upper-level controller is used in combination with the frequency change rate and frequency difference of the grid connection point to judge the degree of frequency disturbance of the current power system, then, a lower-level controller is used in combination with the frequency disturbance degree and the charge state of each energy storage unit to obtain an energy storage action instruction, and finally, the energy storage system responds to the action instruction to participate in frequency control.

[0007] The present invention adopts the following technical solution.

[0008] The energy storage device includes multiple energy storage units, and the energy storage device participates in frequency regulation when the frequency of the power grid fluctuates.

[0009] A hierarchical control method for an energy storage device, comprising:

[0010] Step 1, collecting the frequency change rate and frequency deviation of the current power grid; collecting the state of charge of each energy storage unit, and extracting the maximum state of charge and the minimum state of charge in each energy storage unit;

[0011] Step 2: Determine whether the energy storage device participates in frequency modulation according to the magnitude relationship between the frequency change rate and the allowable value of the frequency change rate, and the magnitude relationship between the frequency deviation and the allowable value of the frequency deviation; when the energy storage device participates in frequency modulation, each energy storage unit takes the maximum value and the minimum value of the state of charge in each energy storage unit as control indicators according to the frequency modulation power direction, and introduces the degree coefficient of frequency fluctuation to determine the frequency modulation power of each energy storage unit participating in frequency modulation;

[0012] Step 3, taking the frequency of a synchronous generator with the same capacity as the reference frequency, and using the energy storage virtual inertia control link to obtain the reference frequency modulation power of the energy storage device;

[0013] Step 4: Sort the charge state of each energy storage unit according to the frequency modulation power direction; take the first n energy storage units in the sorting, if the absolute value of the sum of the frequency modulation powers of the first n-1 energy storage units is less than the absolute value of the reference frequency modulation power of the energy storage device, but the absolute value of the sum of the frequency modulation powers of the first n energy storage units is not less than the absolute value of the reference frequency modulation power of the energy storage device, then the first n energy storage units participate in the frequency modulation;

[0014] Step 5: If the absolute value of the sum of the frequency modulation powers of all energy storage units is less than the absolute value of the reference frequency modulation power of the energy storage device, all energy storage units participate in the frequency modulation.

[0015] In step 1, the state of charge of each energy storage unit is collected and sorted in order from small to large, and the maximum state of charge SOC of each energy storage unit is obtained. max and the minimum state of charge SOC min .

[0016] The allowable value of frequency change rate and frequency deviation is determined according to the power quality standard, among which,

[0017] The allowable value of the frequency change rate is 2HZ / s;

[0018] For power grid systems with a construction scale of not less than 3000MW, the allowable range of frequency deviation is ±0.2HZ; for power grid systems with a construction scale of less than 3000MW, the allowable range of frequency deviation is ±0.5HZ.

[0019] In step 2, when the absolute value of the frequency change rate |df| is not greater than the absolute value of the allowable frequency change rate |ε1|, and the absolute value of the frequency deviation |Δf| is not greater than the absolute value of the allowable frequency deviation |ε2|, the frequency modulation power of each energy storage unit is set to 0, that is, the energy storage device does not participate in frequency modulation.

[0020] Step 2 includes:

[0021] Step 2.1, when the frequency change rate is greater than the allowable value of the frequency change rate or the frequency deviation is greater than the allowable value of the frequency deviation, the frequency modulation power direction of the energy storage device is determined; each energy storage unit determines the first frequency modulation power of each energy storage unit participating in the frequency modulation according to the frequency modulation power direction, taking the maximum value of the state of charge and the minimum value of the state of charge in each energy storage unit as the control index, and introducing the first degree coefficient of the frequency fluctuation;

[0022] Step 2.2, when the frequency change rate is greater than the allowable value of the frequency change rate and the frequency deviation is greater than the allowable value of the frequency deviation, determine the frequency modulation power direction of the energy storage device; each energy storage unit determines the second frequency modulation power of each energy storage unit participating in the frequency modulation according to the frequency modulation power direction, taking the maximum value of the state of charge and the minimum value of the state of charge in each energy storage unit as the control index, and introducing the second degree coefficient of the frequency fluctuation;

[0023] The first degree coefficient and the second degree coefficient are both numbers not greater than 1, and the first degree coefficient is smaller than the second degree coefficient.

[0024] Step 2.1 includes:

[0025] Step 2.1.1, when the absolute value of the frequency change rate |df| is greater than the absolute value of the allowable frequency change rate |ε1|, and the absolute value of the frequency deviation |Δf| is not greater than the absolute value of the allowable frequency deviation |ε2|, determine the frequency modulation power direction of the energy storage device according to the frequency change rate df;

[0026] Step 2.1.2, when the absolute value of the frequency change rate |df| is not greater than the absolute value of the allowable frequency change rate |ε1|, and the absolute value of the frequency deviation |Δf| is greater than the absolute value of the allowable frequency deviation |ε2|, determine the frequency modulation power direction of the energy storage device according to the frequency deviation Δf;

[0027] Step 2.1.3, each energy storage unit determines the first frequency modulation power of each energy storage unit participating in the frequency modulation by taking the maximum and minimum state of charge values ​​in each energy storage unit as control indicators according to the frequency modulation power direction and introducing the first degree coefficient of frequency fluctuation.

[0028] In step 2.1.1, when the frequency change rate df>0, it is determined that the frequency modulation power direction of the energy storage device is in the negative direction, that is, the energy storage device is charging; conversely, when the frequency change rate df<0, it is determined that the frequency modulation power direction of the energy storage device is in the positive direction, that is, the energy storage device is discharging.

[0029] In step 2.1.2, when the frequency deviation Δf>0, it is determined that the frequency modulation power direction of the energy storage device is in the negative direction, that is, the energy storage device is charged; conversely, when the frequency deviation Δf<0, it is determined that the frequency modulation power direction of the energy storage device is in the positive direction, that is, the energy storage device is discharged.

[0030] In step 2.1.3, when the frequency modulation power direction of the energy storage device is negative, the first charging frequency modulation power of the i-th energy storage unit is Satisfies the following relationship:

[0031]

[0032] In the formula,

[0033] SOC i is the charge state of the i-th energy storage unit in the frequency modulation energy storage device,

[0034] SOC max is the maximum value of the state of charge of each energy storage unit in the frequency modulation energy storage device,

[0035] SOC min is the minimum state of charge of each energy storage unit in the frequency modulation energy storage device,

[0036] k1 is the first degree coefficient of frequency fluctuation, and its value range is (0,1],

[0037] P n is the rated active power of the energy storage unit.

[0038] In step 2.1.3, when the frequency modulation power direction of the energy storage device is in the positive direction, the first discharge frequency modulation power of the i-th energy storage unit is Satisfies the following relationship:

[0039]

[0040] In the formula,

[0041] SOC i is the charge state of the i-th energy storage unit in the frequency modulation energy storage device,

[0042] SOC max is the maximum value of the state of charge of each energy storage unit in the frequency modulation energy storage device,

[0043] SOC min is the minimum state of charge of each energy storage unit in the frequency modulation energy storage device,

[0044] k1 is the first degree coefficient of frequency fluctuation, and its value range is (0,1],

[0045] P nis the rated active power of the energy storage unit.

[0046] Step 2.2 includes:

[0047] Step 2.2.1, when the absolute value of the frequency change rate |df| is greater than the absolute value of the allowable frequency change rate |ε1|, and the absolute value of the frequency deviation |Δf| is greater than the absolute value of the allowable frequency deviation |ε2|, the frequency modulation power direction of the energy storage device is determined according to the frequency deviation Δf;

[0048] Step 2.2.2, each energy storage unit takes the maximum and minimum state of charge in each energy storage unit as control indicators according to the frequency modulation power direction, and introduces the second degree coefficient of frequency fluctuation to determine the second frequency modulation power of each energy storage unit participating in the frequency modulation.

[0049] In step 2.2.1, when the frequency deviation Δf>0, it is determined that the frequency modulation power direction of the energy storage device is in the negative direction, that is, the energy storage device is charged; conversely, when the frequency deviation Δf<0, it is determined that the frequency modulation power direction of the energy storage device is in the positive direction, that is, the energy storage device is discharged.

[0050] In step 2.2.2, when the frequency modulation power direction of the energy storage device is in the negative direction, the second charging frequency modulation power of the i-th energy storage unit is Satisfies the following relationship:

[0051]

[0052] In the formula,

[0053] SOC i is the charge state of the i-th energy storage unit in the frequency modulation energy storage device,

[0054] SOC max is the maximum value of the state of charge of each energy storage unit in the frequency modulation energy storage device,

[0055] SOC min is the minimum state of charge of each energy storage unit in the frequency modulation energy storage device,

[0056] k2 is the second degree coefficient of frequency fluctuation, and its value range is (0,1],

[0057] P e is the rated active power of the energy storage unit.

[0058] In step 2.2.2, when the frequency modulation power direction of the energy storage device is in the positive direction, the second discharge frequency modulation power of the i-th energy storage unit is Satisfies the following relationship:

[0059]

[0060] In the formula,

[0061] SOC i is the charge state of the i-th energy storage unit in the frequency modulation energy storage device,

[0062] SOC max is the maximum value of the state of charge of each energy storage unit in the frequency modulation energy storage device,

[0063] SOC min is the minimum state of charge of each energy storage unit in the frequency modulation energy storage device,

[0064] k2 is the second degree coefficient of frequency fluctuation, and its value range is (0,1],

[0065] P e is the rated active power of the battery energy storage system.

[0066] In step 3, the parameters in the energy storage virtual inertia control link include: the classical inertia time constant of the synchronous generator and the damping coefficient; wherein the classical inertia time constant of the synchronous generator is 10 and the damping coefficient is 5.

[0067] Step 4 includes:

[0068] Step 4.1, when the frequency modulation power direction is positive, the frequency modulation power is greater than 0, and the charge state of each energy storage unit is sorted from large to small; starting from the energy storage unit ranked first, the first discharge frequency modulation power or the second discharge frequency modulation power of each energy storage unit is added in turn;

[0069] When added to the nth energy storage unit, if the following relationship is satisfied, the first n energy storage units will participate in frequency modulation:

[0070]

[0071]

[0072] In the formula,

[0073] is the frequency modulation power of the i-th energy storage unit in the descending order of the energy storage unit charge state, wherein the frequency modulation power includes the first discharge frequency modulation power and the second discharge frequency modulation power,

[0074] P ref The reference frequency modulation power for the energy storage device;

[0075] Step 4.2, when the frequency modulation power direction is negative, the frequency modulation power is less than 0, and the charge state of each energy storage unit is sorted from small to large; starting from the energy storage unit ranked first, the first charging frequency modulation power or the second charging frequency modulation power of each energy storage unit is added in turn;

[0076] When added to the mth energy storage unit, if the following relationship is satisfied, the first m energy storage units will participate in frequency modulation:

[0077]

[0078]

[0079] In the formula,

[0080] is the frequency modulation power of the i-th energy storage unit in the ascending order of the state of charge of the energy storage unit, wherein the frequency modulation power includes the first charging frequency modulation power and the second charging frequency modulation power,

[0081] P ref The reference frequency modulation power for the energy storage device;

[0082] A hierarchical control system for an energy storage device, comprising: a collection module, an upper controller, and a lower controller;

[0083] The acquisition module is used to collect the frequency change rate and frequency deviation of the current power grid, and is also used to collect the charge status of each energy storage unit;

[0084] The upper controller is used to determine the frequency fluctuation degree according to the frequency change rate and frequency deviation of the current power grid provided by the acquisition module; the frequency fluctuation degree includes: mild, moderate and severe;

[0085] The lower controller is used to output the control instructions for each energy storage unit in the energy storage device to participate in the frequency modulation according to the frequency fluctuation degree output by the upper controller, and to set the frequency modulation power of each energy storage unit participating in the frequency modulation;

[0086] The energy storage device receives the control instructions from the lower-level controller and the frequency modulation power of each energy storage unit, and adjusts the charging and discharging power of the energy storage device.

[0087] In the upper controller, the frequency fluctuation degree is determined according to the magnitude relationship between the frequency change rate and the allowable value of the frequency change rate, and the magnitude relationship between the frequency deviation and the allowable value of the frequency deviation, including:

[0088] 1) When the absolute value of the frequency change rate is not greater than the absolute value of the allowable value of the frequency change rate, and the absolute value of the frequency deviation is not greater than the absolute value of the allowable value of the frequency deviation, it is determined to be a slight frequency fluctuation;

[0089] 2) When the frequency change rate is greater than the allowable value of the frequency change rate or the frequency deviation is greater than the allowable value of the frequency deviation, it is determined to be a moderate frequency fluctuation;

[0090] 3) When the frequency change rate is greater than the allowable value of the frequency change rate and the frequency deviation is greater than the allowable value of the frequency deviation, it is determined to be a severe frequency fluctuation.

[0091] Under mild frequency fluctuations, the lower-level controller sets the frequency modulation power of each energy storage unit to 0, that is, the energy storage device does not participate in frequency modulation;

[0092] Under moderate frequency fluctuations, the lower-layer controller determines the frequency modulation power direction of the energy storage device. Each energy storage unit uses the maximum and minimum state of charge values ​​in each energy storage unit as control indicators based on the frequency modulation power direction, and introduces the first degree coefficient of frequency fluctuation to determine the first frequency modulation power of each energy storage unit participating in the frequency modulation.

[0093] Under severe frequency fluctuations, the lower-level controller determines the frequency modulation power direction of the energy storage device; each energy storage unit uses the maximum and minimum state of charge values ​​in each energy storage unit as control indicators based on the frequency modulation power direction, and introduces the second degree coefficient of frequency fluctuation to determine the second frequency modulation power of each energy storage unit participating in the frequency modulation.

[0094] Under moderate frequency fluctuations and severe frequency fluctuations, the lower-level controller sorts the charge state of each energy storage unit according to the frequency modulation power direction; takes the first n energy storage units in the sorting, if the absolute value of the sum of the frequency modulation powers of the first n-1 energy storage units is less than the absolute value of the reference frequency modulation power of the energy storage device, but the absolute value of the sum of the frequency modulation powers of the first n energy storage units is not less than the absolute value of the reference frequency modulation power of the energy storage device, then the first n energy storage units participate in the frequency modulation; if the absolute value of the sum of the frequency modulation powers of all energy storage units is less than the absolute value of the reference frequency modulation power of the energy storage device, then all energy storage units participate in the frequency modulation.

[0095] The beneficial effect of the present invention is that, compared with the prior art, the present invention realizes the response power of the energy storage device participating in frequency modulation, takes the maximum or minimum value of the state of charge of each energy storage unit as a control indicator, and also takes the degree of disturbance of the grid frequency as an influencing factor, thereby effectively realizing balanced management of the energy storage units with different states of charge while giving full play to the frequency modulation characteristics of the energy storage device, avoiding the non-balanced working phenomenon of the energy storage device, and facilitating maintaining the service life of the energy storage device.

[0096] The beneficial effects of the present invention include:

[0097] 1) When the grid frequency is slightly disturbed, the energy storage device is controlled not to participate in frequency modulation, effectively avoiding irreversible damage to the energy storage device caused by frequent charging and discharging;

[0098] 2) When the grid frequency is moderately disturbed or severely disturbed, the maximum or minimum value of the state of charge of each energy storage unit is used as the control index to determine the charging and discharging power of the energy storage device participating in the frequency modulation. In practical applications, the charging and discharging power allocated to the energy storage device in the frequency modulation control strategy can be fully accepted and executed by the energy storage device, so that the adjustable power allocated to the unit is accurate and reliable, and the frequency modulation resources are used accurately and reasonably, which improves the control efficiency of the primary frequency modulation and effectively avoids the occurrence of secondary frequency modulation.

[0099] 3) Considering the development and recovery trends of large power grid frequency disturbances, a degree factor is introduced for moderate disturbances, so that the energy storage device can respond to moderate disturbances in a timely manner. At the same time, the energy storage device reserves capacity margin for participating in frequency regulation for subsequent possible severe disturbances, which can further give play to the advantages of timely response and precise control of energy storage devices, and escort the power grid to quickly recover from more serious disturbances and faults. At the same time, it also ensures the stable operation of other units and frequency regulation equipment in the system;

[0100] 4) When the power grid is disturbed, under the hierarchical control strategy, the energy storage device can not only provide frequency regulation services, but also adjust the operating differences of each energy storage unit, thereby improving the overall operating status of the energy storage device, maximizing the available capacity of the energy storage device, and extending the service life of the energy storage device, achieving multiple goals at one stroke.

[0101] 5) Taking the reference frequency modulation power of the energy storage device obtained from the virtual inertia control link as the limit value, combined with the charge state ranking of each energy storage unit, on the basis of participating in frequency modulation, ensure that the energy storage unit should be discharged and charged as much as possible. BRIEF DESCRIPTION OF THE DRAWINGS

[0102] Figure 1 It is a block diagram of the steps of a hierarchical control method of an energy storage device of the present invention;

[0103] Figure 2 It is a schematic diagram of the energy storage virtual inertia control link in one embodiment of the present invention. DETAILED DESCRIPTION

[0104] The present application is further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present application.

[0105] The energy storage device includes multiple energy storage units, and the energy storage device participates in frequency regulation when the frequency of the power grid fluctuates.

[0106] like Figure 1 , a hierarchical control method for an energy storage device, comprising:

[0107] Step 1: Collect the frequency change rate and frequency deviation of the current power grid; collect the state of charge of each energy storage unit, and extract the maximum state of charge and the minimum state of charge in each energy storage unit.

[0108] In step 1, the state of charge of each energy storage unit is collected and sorted in order from small to large, and the maximum state of charge SOC of each energy storage unit is obtained. max and the minimum state of charge SOC min .

[0109] The allowable value of frequency change rate and frequency deviation is determined according to the power quality standard, among which,

[0110] The allowable value of the frequency change rate is 2HZ / s;

[0111] For power grid systems with a construction scale of not less than 3000MW, the allowable range of frequency deviation is ±0.2HZ; for power grid systems with a construction scale of less than 3000MW, the allowable range of frequency deviation is ±0.5HZ.

[0112] Step 2: Determine whether the energy storage device participates in frequency modulation based on the relationship between the frequency change rate and the allowable value of the frequency change rate, and the relationship between the frequency deviation and the allowable value of the frequency deviation; when the energy storage device participates in frequency modulation, each energy storage unit uses the maximum state of charge and the minimum state of charge in each energy storage unit as control indicators based on the frequency modulation power direction, and introduces the degree coefficient of frequency fluctuation to determine the frequency modulation power of each energy storage unit participating in frequency modulation.

[0113] Specifically, in step 2, when the absolute value of the frequency change rate |df| is not greater than the absolute value of the allowable frequency change rate |ε1|, and the absolute value of the frequency deviation |Δf| is not greater than the absolute value of the allowable frequency deviation |ε2|, the frequency modulation power of each energy storage unit is set to 0, that is, the energy storage device does not participate in frequency modulation.

[0114] Step 2 includes:

[0115] Step 2.1, when the frequency change rate is greater than the allowable value of the frequency change rate or the frequency deviation is greater than the allowable value of the frequency deviation, determine the frequency modulation power direction of the energy storage device; each energy storage unit uses the maximum state of charge and the minimum state of charge in each energy storage unit as control indicators according to the frequency modulation power direction, and introduces the first degree coefficient of frequency fluctuation to determine the first frequency modulation power of each energy storage unit participating in the frequency modulation.

[0116] Step 2.1 includes:

[0117] Step 2.1.1, when the absolute value of the frequency change rate |df| is greater than the absolute value of the allowable frequency change rate |ε1|, and the absolute value of the frequency deviation |Δf| is not greater than the absolute value of the allowable frequency deviation |ε2|, determine the frequency modulation power direction of the energy storage device according to the frequency change rate df;

[0118] Step 2.1.2, when the absolute value of the frequency change rate |df| is not greater than the absolute value of the allowable frequency change rate |ε1|, and the absolute value of the frequency deviation |Δf| is greater than the absolute value of the allowable frequency deviation |ε2|, determine the frequency modulation power direction of the energy storage device according to the frequency deviation Δf;

[0119] Step 2.1.3, each energy storage unit determines the first frequency modulation power of each energy storage unit participating in the frequency modulation by taking the maximum and minimum state of charge values ​​in each energy storage unit as control indicators according to the frequency modulation power direction and introducing the first degree coefficient of frequency fluctuation.

[0120] In step 2.1.1, when the frequency change rate df>0, it is determined that the frequency modulation power direction of the energy storage device is in the negative direction, that is, the energy storage device is charging; conversely, when the frequency change rate df<0, it is determined that the frequency modulation power direction of the energy storage device is in the positive direction, that is, the energy storage device is discharging.

[0121] In step 2.1.2, when the frequency deviation Δf>0, it is determined that the frequency modulation power direction of the energy storage device is in the negative direction, that is, the energy storage device is charged; conversely, when the frequency deviation Δf<0, it is determined that the frequency modulation power direction of the energy storage device is in the positive direction, that is, the energy storage device is discharged.

[0122] In step 2.1.3, when the frequency modulation power direction of the energy storage device is negative, the first charging frequency modulation power of the i-th energy storage unit is Satisfies the following relationship:

[0123]

[0124] In the formula,

[0125] SOC i is the charge state of the i-th energy storage unit in the frequency modulation energy storage device,

[0126] SOC max is the maximum value of the state of charge of each energy storage unit in the frequency modulation energy storage device,

[0127] SOC min is the minimum state of charge of each energy storage unit in the frequency modulation energy storage device,

[0128] k1 is the first degree coefficient of frequency fluctuation, and its value range is (0,1],

[0129] Pn is the rated active power of the energy storage unit.

[0130] In step 2.1.3, when the frequency modulation power direction of the energy storage device is in the positive direction, the first discharge frequency modulation power of the i-th energy storage unit is Satisfies the following relationship:

[0131]

[0132] In the formula,

[0133] SOC i is the charge state of the i-th energy storage unit in the frequency modulation energy storage device,

[0134] SOC max is the maximum value of the state of charge of each energy storage unit in the frequency modulation energy storage device,

[0135] SOC min is the minimum state of charge of each energy storage unit in the frequency modulation energy storage device,

[0136] k1 is the first degree coefficient of frequency fluctuation, and its value range is (0,1],

[0137] P n is the rated active power of the energy storage unit.

[0138] Step 2.2, when the frequency change rate is greater than the allowable value of the frequency change rate and the frequency deviation is greater than the allowable value of the frequency deviation, determine the frequency modulation power direction of the energy storage device; each energy storage unit determines the second frequency modulation power of each energy storage unit participating in the frequency modulation according to the frequency modulation power direction, taking the maximum value of the state of charge and the minimum value of the state of charge in each energy storage unit as the control index, and introducing the second degree coefficient of the frequency fluctuation;

[0139] The first degree coefficient and the second degree coefficient are both numbers not greater than 1, and the first degree coefficient is smaller than the second degree coefficient.

[0140] Step 2.2 includes:

[0141] Step 2.2.1, when the absolute value of the frequency change rate |df| is greater than the absolute value of the allowable frequency change rate |ε1|, and the absolute value of the frequency deviation |Δf| is greater than the absolute value of the allowable frequency deviation |ε2|, the frequency modulation power direction of the energy storage device is determined according to the frequency deviation Δf;

[0142] Step 2.2.2, each energy storage unit takes the maximum and minimum state of charge in each energy storage unit as control indicators according to the frequency modulation power direction, and introduces the second degree coefficient of frequency fluctuation to determine the second frequency modulation power of each energy storage unit participating in the frequency modulation.

[0143] In step 2.2.1, when the frequency deviation Δf>0, it is determined that the frequency modulation power direction of the energy storage device is in the negative direction, that is, the energy storage device is charged; conversely, when the frequency deviation Δf<0, it is determined that the frequency modulation power direction of the energy storage device is in the positive direction, that is, the energy storage device is discharged.

[0144] In step 2.2.2, when the frequency modulation power direction of the energy storage device is in the negative direction, the second charging frequency modulation power of the i-th energy storage unit is Satisfies the following relationship:

[0145]

[0146] In the formula,

[0147] SOC i is the charge state of the i-th energy storage unit in the frequency modulation energy storage device,

[0148] SOC max is the maximum value of the state of charge of each energy storage unit in the frequency modulation energy storage device,

[0149] SOC min is the minimum state of charge of each energy storage unit in the frequency modulation energy storage device,

[0150] k2 is the second degree coefficient of frequency fluctuation, and its value range is (0,1],

[0151] P e is the rated active power of the energy storage unit.

[0152] In step 2.2.2, when the frequency modulation power direction of the energy storage device is in the positive direction, the second discharge frequency modulation power of the i-th energy storage unit is Satisfies the following relationship:

[0153]

[0154] In the formula,

[0155] SOC i is the charge state of the i-th energy storage unit in the frequency modulation energy storage device,

[0156] SOC max is the maximum value of the state of charge of each energy storage unit in the frequency modulation energy storage device,

[0157] SOC min is the minimum state of charge of each energy storage unit in the frequency modulation energy storage device,

[0158] k2 is the second degree coefficient of frequency fluctuation, and its value range is (0,1],

[0159] P eis the rated active power of the battery energy storage system.

[0160] Step 3: Take the frequency of the synchronous generator with the same capacity as the reference frequency f n , using the energy storage virtual inertia control link to obtain the energy storage device reference frequency modulation power P ref .

[0161] Specifically, in step 3, if Figure 2 , the parameters in the energy storage virtual inertia control link include: the synchronous generator classic inertia time constant T J , damping coefficient D; among them, the classical inertia time constant of the synchronous generator is 10, and the damping coefficient is 5.

[0162] Step 4, sort the charge states of the energy storage units according to the frequency modulation power direction; take the first n energy storage units in the sorting, if the absolute value of the sum of the frequency modulation powers of the first n-1 energy storage units is less than the absolute value of the reference frequency modulation power of the energy storage device, but the absolute value of the sum of the frequency modulation powers of the first n energy storage units is not less than the absolute value of the reference frequency modulation power of the energy storage device, then the first n energy storage units participate in the frequency modulation.

[0163] Specifically, step 4 includes:

[0164] Step 4.1, when the frequency modulation power direction is positive, the frequency modulation power is greater than 0, and the charge state of each energy storage unit is sorted from large to small; starting from the energy storage unit ranked first, the first discharge frequency modulation power or the second discharge frequency modulation power of each energy storage unit is added in turn;

[0165] When added to the nth energy storage unit, if the following relationship is satisfied, the first n energy storage units will participate in frequency modulation:

[0166]

[0167]

[0168] In the formula,

[0169] is the frequency modulation power of the i-th energy storage unit in the descending order of the energy storage unit charge state, wherein the frequency modulation power includes the first discharge frequency modulation power and the second discharge frequency modulation power,

[0170] P ref The reference frequency modulation power for the energy storage device;

[0171] Step 4.2, when the frequency modulation power direction is negative, the frequency modulation power is less than 0, and the charge state of each energy storage unit is sorted from small to large; starting from the energy storage unit ranked first, the first charging frequency modulation power or the second charging frequency modulation power of each energy storage unit is added in turn;

[0172] When added to the mth energy storage unit, if the following relationship is satisfied, the first m energy storage units will participate in frequency modulation:

[0173]

[0174]

[0175] In the formula,

[0176] is the frequency modulation power of the i-th energy storage unit in the ascending order of the state of charge of the energy storage unit, wherein the frequency modulation power includes the first charging frequency modulation power and the second charging frequency modulation power,

[0177] P ref It is the reference frequency modulation power of the energy storage device.

[0178] Step 5: If the absolute value of the sum of the frequency modulation powers of all energy storage units is less than the absolute value of the reference frequency modulation power of the energy storage device, all energy storage units participate in the frequency modulation.

[0179] A hierarchical control system for an energy storage device, comprising: a collection module, an upper controller, and a lower controller;

[0180] The acquisition module is used to collect the frequency change rate and frequency deviation of the current power grid, and is also used to collect the charge status of each energy storage unit;

[0181] The upper controller is used to determine the frequency fluctuation degree according to the frequency change rate and frequency deviation of the current power grid provided by the acquisition module; the frequency fluctuation degree includes: mild, moderate and severe;

[0182] The lower controller is used to output the control instructions for each energy storage unit in the energy storage device to participate in the frequency modulation according to the frequency fluctuation degree output by the upper controller, and to set the frequency modulation power of each energy storage unit participating in the frequency modulation;

[0183] The energy storage device receives the control instructions from the lower-level controller and the frequency modulation power of each energy storage unit, and adjusts the charging and discharging power of the energy storage device.

[0184] In the upper controller, the frequency fluctuation degree is determined according to the magnitude relationship between the frequency change rate and the allowable value of the frequency change rate, and the magnitude relationship between the frequency deviation and the allowable value of the frequency deviation, including:

[0185] 1) When the absolute value of the frequency change rate is not greater than the absolute value of the allowable value of the frequency change rate, and the absolute value of the frequency deviation is not greater than the absolute value of the allowable value of the frequency deviation, it is determined to be a slight frequency fluctuation;

[0186] 2) When the frequency change rate is greater than the allowable value of the frequency change rate or the frequency deviation is greater than the allowable value of the frequency deviation, it is determined to be a moderate frequency fluctuation;

[0187] 3) When the frequency change rate is greater than the allowable value of the frequency change rate and the frequency deviation is greater than the allowable value of the frequency deviation, it is determined to be a severe frequency fluctuation.

[0188] Under mild frequency fluctuations, the lower-level controller sets the frequency modulation power of each energy storage unit to 0, that is, the energy storage device does not participate in frequency modulation;

[0189] Under moderate frequency fluctuations, the lower-layer controller determines the frequency modulation power direction of the energy storage device. Each energy storage unit uses the maximum and minimum state of charge values ​​in each energy storage unit as control indicators based on the frequency modulation power direction, and introduces the first degree coefficient of frequency fluctuation to determine the first frequency modulation power of each energy storage unit participating in the frequency modulation.

[0190] Under severe frequency fluctuations, the lower-level controller determines the frequency modulation power direction of the energy storage device; each energy storage unit uses the maximum and minimum state of charge values ​​in each energy storage unit as control indicators based on the frequency modulation power direction, and introduces the second degree coefficient of frequency fluctuation to determine the second frequency modulation power of each energy storage unit participating in the frequency modulation.

[0191] Under moderate frequency fluctuations and severe frequency fluctuations, the lower-level controller sorts the charge state of each energy storage unit according to the frequency modulation power direction; takes the first n energy storage units in the sorting, if the absolute value of the sum of the frequency modulation powers of the first n-1 energy storage units is less than the absolute value of the reference frequency modulation power of the energy storage device, but the absolute value of the sum of the frequency modulation powers of the first n energy storage units is not less than the absolute value of the reference frequency modulation power of the energy storage device, then the first n energy storage units participate in the frequency modulation; if the absolute value of the sum of the frequency modulation powers of all energy storage units is less than the absolute value of the reference frequency modulation power of the energy storage device, then all energy storage units participate in the frequency modulation.

[0192] The applicant of the present invention has made a detailed explanation and description of the implementation examples of the present invention in conjunction with the drawings in the specification. However, those skilled in the art should understand that the above implementation examples are only preferred implementation schemes of the present invention, and the detailed description is only to help readers better understand the spirit of the present invention, but not to limit the scope of protection of the present invention. On the contrary, any improvements or modifications based on the inventive spirit of the present invention should fall within the scope of protection of the present invention.

Claims

1. A hierarchical control method for an energy storage device, wherein the energy storage device comprises a plurality of energy storage units, and the energy storage device participates in frequency modulation under frequency fluctuation of a power grid, characterized in that: The method comprises: Step 1, collecting the frequency change rate and frequency deviation of the current power grid; collecting the state of charge of each energy storage unit, and extracting the maximum state of charge and the minimum state of charge in each energy storage unit; Step 2, determining whether the energy storage device participates in frequency modulation according to the magnitude relationship between the frequency change rate and the allowable value of the frequency change rate, and the magnitude relationship between the frequency deviation and the allowable value of the frequency deviation; when the energy storage device participates in frequency modulation, each energy storage unit takes the maximum value of the state of charge and the minimum value of the state of charge in each energy storage unit as control indicators according to the direction of the frequency modulation power, and introduces the degree coefficient of frequency fluctuation to determine the frequency modulation power of each energy storage unit participating in the frequency modulation; including: step 2.1, when the frequency change rate is greater than the allowable value of the frequency change rate or the frequency deviation is greater than the allowable value of the frequency deviation, determining the frequency modulation power direction of the energy storage device; each energy storage unit takes the maximum value of the state of charge and the minimum value of the state of charge in each energy storage unit as control indicators according to the direction of the frequency modulation power The maximum state value and the minimum state of charge value are control indicators, and the first degree coefficient of frequency fluctuation is introduced to determine the first frequency modulation power of each energy storage unit participating in the frequency modulation; step 2.2, when the frequency change rate is greater than the allowable value of the frequency change rate and the frequency deviation is greater than the allowable value of the frequency deviation, determine the frequency modulation power direction of the energy storage device; each energy storage unit takes the maximum state of charge value and the minimum state of charge value in each energy storage unit as the control indicator according to the frequency modulation power direction, and introduces the second degree coefficient of frequency fluctuation to determine the second frequency modulation power of each energy storage unit participating in the frequency modulation; the first degree coefficient and the second degree coefficient are both numbers not greater than 1, and the first degree coefficient is less than the second degree coefficient; Step 3, taking the frequency of a synchronous generator with the same capacity as the reference frequency, and using the energy storage virtual inertia control link to obtain the reference frequency modulation power of the energy storage device; Step 4, sorting the charge state of each energy storage unit according to the frequency modulation power direction; taking the first n energy storage units in the sorting, if the absolute value of the sum of the frequency modulation powers of the first n-1 energy storage units is less than the absolute value of the reference frequency modulation power of the energy storage device, but the absolute value of the sum of the frequency modulation powers of the first n energy storage units is not less than the absolute value of the reference frequency modulation power of the energy storage device, then the first n energy storage units participate in the frequency modulation; including: Step 4.1: When the frequency modulation power direction is positive, the frequency modulation power is greater than 0, and the state of charge of each energy storage unit is sorted from large to small; starting from the first energy storage unit, the first discharge frequency modulation power or the second discharge frequency modulation power of each energy storage unit is added in turn; when added to the nth energy storage unit, if the following relationship is satisfied, the first n energy storage units participate in the frequency modulation: In the formula, is the frequency modulation power of the i-th energy storage unit in the descending order of the energy storage unit charge state, where the frequency modulation power includes the first discharge frequency modulation power, the second discharge frequency modulation power, and P ref The reference frequency modulation power for the energy storage device; Step 4.2, when the frequency modulation power direction is negative, the frequency modulation power is less than 0, and the charge state of each energy storage unit is sorted from small to large; starting from the energy storage unit ranked first, the first charging frequency modulation power or the second charging frequency modulation power of each energy storage unit is added in turn; When added to the mth energy storage unit, if the following relationship is satisfied, the first m energy storage units will participate in frequency modulation: In the formula, is the frequency modulation power of the i-th energy storage unit in the ascending order of the energy storage unit charge state, where the frequency modulation power includes the first charging frequency modulation power, the second charging frequency modulation power, and P ref The reference frequency modulation power for the energy storage device; Step 5: If the absolute value of the sum of the frequency modulation powers of all energy storage units is less than the absolute value of the reference frequency modulation power of the energy storage device, all energy storage units participate in the frequency modulation.

2. The hierarchical control method of the energy storage device according to claim 1, characterized in that: In step 1, the state of charge of each energy storage unit is collected and sorted in order from small to large, and the maximum state of charge SOC of each energy storage unit is obtained. max and the minimum state of charge SOC min .

3. The hierarchical control method of the energy storage device according to claim 1, characterized in that: The allowable value of frequency change rate and frequency deviation is determined according to the power quality standard, among which, The allowable value of the frequency change rate is 2HZ / s; For power grid systems with a construction scale of not less than 3000MW, the allowable range of frequency deviation is ±0.2HZ; for power grid systems with a construction scale of less than 3000MW, the allowable range of frequency deviation is ±0.5HZ.

4. The hierarchical control method of the energy storage device according to claim 3, characterized in that: In step 2, when the absolute value of the frequency change rate |df| is not greater than the absolute value of the allowable frequency change rate |ε1|, and the absolute value of the frequency deviation |Δf| is not greater than the absolute value of the allowable frequency deviation |ε2|, the frequency modulation power of each energy storage unit is set to 0, that is, the energy storage device does not participate in frequency modulation.

5. The hierarchical control method of the energy storage device according to claim 1, characterized in that: Step 2.1 includes: Step 2.1.1, when the absolute value of the frequency change rate |df| is greater than the absolute value of the allowable frequency change rate |ε1|, and the absolute value of the frequency deviation |Δf| is not greater than the absolute value of the allowable frequency deviation |ε2|, determine the frequency modulation power direction of the energy storage device according to the frequency change rate df; Step 2.1.2, when the absolute value of the frequency change rate |df| is not greater than the absolute value of the allowable frequency change rate |ε1|, and the absolute value of the frequency deviation |Δf| is greater than the absolute value of the allowable frequency deviation |ε2|, determine the frequency modulation power direction of the energy storage device according to the frequency deviation Δf; Step 2.1.3, each energy storage unit determines the first frequency modulation power of each energy storage unit participating in the frequency modulation by taking the maximum and minimum state of charge values ​​in each energy storage unit as control indicators according to the frequency modulation power direction and introducing the first degree coefficient of frequency fluctuation.

6. The hierarchical control method of the energy storage device according to claim 5, characterized in that: In step 2.1.1, when the frequency change rate df>0, it is determined that the frequency modulation power direction of the energy storage device is in the negative direction, that is, the energy storage device is charging; conversely, when the frequency change rate df<0, it is determined that the frequency modulation power direction of the energy storage device is in the positive direction, that is, the energy storage device is discharging.

7. The hierarchical control method of the energy storage device according to claim 5, characterized in that: In step 2.1.2, when the frequency deviation Δf>0, it is determined that the frequency modulation power direction of the energy storage device is in the negative direction, that is, the energy storage device is charging; conversely, when the frequency deviation Δf<0, it is determined that the frequency modulation power direction of the energy storage device is in the positive direction, that is, the energy storage device is discharging.

8. The hierarchical control method of the energy storage device according to claim 5, characterized in that: In step 2.1.3, when the frequency modulation power direction of the energy storage device is negative, the first charging frequency modulation power of the i-th energy storage unit is Satisfies the following relationship: In the formula, SOC i is the charge state of the i-th energy storage unit in the frequency modulation energy storage device, SOC max is the maximum value of the state of charge of each energy storage unit in the frequency modulation energy storage device, SOC min is the minimum state of charge of each energy storage unit in the frequency modulation energy storage device, k1 is the first degree coefficient of frequency fluctuation, and its value range is (0, 1], P n is the rated active power of the energy storage unit.

9. The hierarchical control method of the energy storage device according to claim 5, characterized in that: In step 2.1.3, when the frequency modulation power direction of the energy storage device is in the positive direction, the first discharge frequency modulation power of the i-th energy storage unit is Satisfies the following relationship: In the formula, SOC i is the charge state of the i-th energy storage unit in the frequency modulation energy storage device, SOC max is the maximum value of the state of charge of each energy storage unit in the frequency modulation energy storage device, SOC min is the minimum state of charge of each energy storage unit in the frequency modulation energy storage device, k1 is the first degree coefficient of frequency fluctuation, and its value range is (0, 1], P n is the rated active power of the energy storage unit.

10. The hierarchical control method of the energy storage device according to claim 1, characterized in that: Step 2.2 includes: Step 2.2.1, when the absolute value of the frequency change rate |df| is greater than the absolute value of the allowable frequency change rate |ε1|, and the absolute value of the frequency deviation |Δf| is greater than the absolute value of the allowable frequency deviation |ε2|, the frequency modulation power direction of the energy storage device is determined according to the frequency deviation Δf; Step 2.2.2, each energy storage unit takes the maximum and minimum state of charge in each energy storage unit as control indicators according to the frequency modulation power direction, and introduces the second degree coefficient of frequency fluctuation to determine the second frequency modulation power of each energy storage unit participating in the frequency modulation.

11. The hierarchical control method of the energy storage device according to claim 10, characterized in that: In step 2.2.1, when the frequency deviation Δf>0, it is determined that the frequency modulation power direction of the energy storage device is in the negative direction, that is, the energy storage device is charging; conversely, when the frequency deviation Δf<0, it is determined that the frequency modulation power direction of the energy storage device is in the positive direction, that is, the energy storage device is discharging.

12. The hierarchical control method of the energy storage device according to claim 10, characterized in that: In step 2.2.2, when the frequency modulation power direction of the energy storage device is in the negative direction, the second charging frequency modulation power of the i-th energy storage unit is Satisfies the following relationship: In the formula, SOC i is the charge state of the i-th energy storage unit in the frequency modulation energy storage device, SOC max is the maximum value of the state of charge of each energy storage unit in the frequency modulation energy storage device, SOC min is the minimum state of charge of each energy storage unit in the frequency modulation energy storage device, k2 is the second degree coefficient of frequency fluctuation, and its value range is (0, 1], P e is the rated active power of the energy storage unit.

13. The hierarchical control method of the energy storage device according to claim 10, characterized in that: In step 2.2.2, when the frequency modulation power direction of the energy storage device is in the positive direction, the second discharge frequency modulation power of the i-th energy storage unit is Satisfies the following relationship: In the formula, SOC i is the charge state of the i-th energy storage unit in the frequency modulation energy storage device, SOC max is the maximum value of the state of charge of each energy storage unit in the frequency modulation energy storage device, SOC min is the minimum state of charge of each energy storage unit in the frequency modulation energy storage device, k2 is the second degree coefficient of frequency fluctuation, and its value range is (0, 1], P e is the rated active power of the battery energy storage system.

14. The hierarchical control method of the energy storage device according to claim 1, characterized in that: In step 3, the parameters in the energy storage virtual inertia control link include: the classical inertia time constant of the synchronous generator and the damping coefficient; wherein the classical inertia time constant of the synchronous generator is 10 and the damping coefficient is 5.

15. A hierarchical control system for an energy storage device implemented by using the hierarchical control method for an energy storage device according to any one of claims 1 to 14, characterized in that: The hierarchical control system includes: acquisition module, upper controller, lower controller; The acquisition module is used to collect the frequency change rate and frequency deviation of the current power grid, and is also used to collect the charge status of each energy storage unit; The upper controller is used to determine the frequency fluctuation degree according to the frequency change rate and frequency deviation of the current power grid provided by the acquisition module; the frequency fluctuation degree includes: mild, moderate and severe; The lower controller is used to output the control instructions for each energy storage unit in the energy storage device to participate in the frequency modulation according to the frequency fluctuation degree output by the upper controller, and to set the frequency modulation power of each energy storage unit participating in the frequency modulation; The energy storage device receives the control instructions from the lower-level controller and the frequency modulation power of each energy storage unit, and adjusts the charging and discharging power of the energy storage device.

16. The hierarchical control system of the energy storage device according to claim 15, characterized in that: In the upper controller, the frequency fluctuation degree is determined according to the magnitude relationship between the frequency change rate and the allowable value of the frequency change rate, and the magnitude relationship between the frequency deviation and the allowable value of the frequency deviation, including: 1) When the absolute value of the frequency change rate is not greater than the absolute value of the allowable value of the frequency change rate, and the absolute value of the frequency deviation is not greater than the absolute value of the allowable value of the frequency deviation, it is determined to be a slight frequency fluctuation; 2) When the frequency change rate is greater than the allowable value of the frequency change rate or the frequency deviation is greater than the allowable value of the frequency deviation, it is determined to be a moderate frequency fluctuation; 3) When the frequency change rate is greater than the allowable value of the frequency change rate and the frequency deviation is greater than the allowable value of the frequency deviation, it is determined to be a severe frequency fluctuation.

17. The hierarchical control system of the energy storage device according to claim 16, characterized in that: Under mild frequency fluctuations, the lower-level controller sets the frequency modulation power of each energy storage unit to 0, that is, the energy storage device does not participate in frequency modulation; Under moderate frequency fluctuations, the lower-layer controller determines the frequency modulation power direction of the energy storage device. Each energy storage unit uses the maximum and minimum state of charge values ​​in each energy storage unit as control indicators based on the frequency modulation power direction, and introduces the first degree coefficient of frequency fluctuation to determine the first frequency modulation power of each energy storage unit participating in the frequency modulation. Under severe frequency fluctuations, the lower-level controller determines the frequency modulation power direction of the energy storage device; each energy storage unit uses the maximum and minimum state of charge values ​​in each energy storage unit as control indicators based on the frequency modulation power direction, and introduces the second degree coefficient of frequency fluctuation to determine the second frequency modulation power of each energy storage unit participating in the frequency modulation.

18. The hierarchical control system of the energy storage device according to claim 17, characterized in that: Under moderate frequency fluctuations and severe frequency fluctuations, the lower-level controller sorts the charge state of each energy storage unit according to the frequency modulation power direction; takes the first n energy storage units in the sorting, if the absolute value of the sum of the frequency modulation powers of the first n-1 energy storage units is less than the absolute value of the reference frequency modulation power of the energy storage device, but the absolute value of the sum of the frequency modulation powers of the first n energy storage units is not less than the absolute value of the reference frequency modulation power of the energy storage device, then the first n energy storage units participate in the frequency modulation; If the absolute value of the sum of the frequency modulation powers of all energy storage units is less than the absolute value of the reference frequency modulation power of the energy storage device, all energy storage units will participate in the frequency modulation.

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