Method for evaluating frequency modulation capability of wind storage station, hierarchical frequency modulation control method and device of distributed wind storage system and medium

Abstract

The application discloses a frequency modulation capability evaluation method of a wind storage station, a hierarchical frequency modulation control method and device of a distributed wind storage system and a medium. The frequency modulation capability evaluation method considers the wake effect to calculate the effective kinetic energy of each wind turbine and then calculates the frequency modulation capability factor of the wind turbine, and considers the state of charge of the energy storage to calculate the frequency modulation capability factor of each energy storage, and finally sums the frequency modulation capability factors of all wind turbines and energy storages in the wind storage station to obtain the frequency modulation capability of the wind storage station. The hierarchical frequency modulation control method firstly evaluates the frequency modulation capability of each wind storage station in the distributed wind storage system, and then performs hierarchical frequency modulation control on the distributed wind storage system based on the calculated frequency modulation capabilities of the wind turbines, the energy storages and the wind storage stations. The application considers the influence of the wake effect and the state of charge on the frequency modulation capability of the wind storage system in view of the development trend of the new energy power system, and realizes the maximization of the frequency modulation capability of the distributed wind storage system.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of new energy power system, and particularly relates to a frequency modulation capability evaluation method of a wind storage station, and a hierarchical frequency modulation control method and device of a decentralized wind storage system. BACKGROUND

[0002] With the rapid development of wind power generation and large-scale grid connection, the inertia and frequency modulation capacity of the power system decrease, and the grid specification requires wind power to participate in frequency modulation to provide additional standby power and inertia (European Commission Regulation, "Establishing a network code on requirements for grid connection of high voltage direct current systems and direct current connected power park modules," Official J.Eur.Union, vol.59, no.241, pp.1-65, 2016). However, due to the inherent volatility, intermittency, randomness and other characteristics of wind speed, the frequency modulation capacity of the wind turbine is limited and cannot meet the frequency modulation power demand of the power system. Energy storage has accurate, fast and flexible power response capability, which can improve the frequency response speed and frequency modulation performance of the wind turbine. Therefore, the wind farm needs to be equipped with certain energy storage to meet the frequency modulation power demand.

[0003] The frequency modulation control of the wind storage system faces the challenge of not maximizing the frequency modulation capability. On the one hand, considering different geographical locations, environmental differences, wake effects, etc., different wind turbines in the wind farm may be in different operating states. How to differentially allocate frequency modulation power will determine whether the wind turbine can maximize frequency support. On the other hand, considering the state of charge and frequency modulation cost of the energy storage, long-time high-power participation in frequency modulation is not conducive to the operation of the energy storage. How to coordinate the wind turbine and the energy storage to participate in frequency modulation together and realize complementary advantages is the key to maximizing the frequency modulation capability of the wind storage system. Therefore, it is urgent to study a control method that can maximize the frequency modulation capability of the wind storage system. SUMMARY

[0004] To solve the above problems, the present application provides a frequency modulation capability evaluation method of a wind storage station, and a hierarchical frequency modulation control method and device of a decentralized wind storage system, which considers the influence of the wake effect and the state of charge on the frequency modulation capability of the wind storage system to maximize the frequency modulation capability of the decentralized wind storage system in view of the development trend of the new energy power system.

[0005] To achieve the above technical purposes, the present application adopts the following technical solutions:

[0006] A method for evaluating frequency modulation capability of a wind storage station, comprising:

[0007] Based on the wind speed considering the wake effect of the wind turbine in the wind storage station, the effective kinetic energy of each wind turbine participating in frequency modulation in the wind storage station is calculated;

[0008] Based on the effective kinetic energy of the wind turbine, the frequency modulation capability factor of each wind turbine is calculated based on the maximum effective kinetic energy of the respective wind turbine; wherein the maximum effective kinetic energy is the maximum value of the effective kinetic energy calculated based on the wind speed considering the wake effect and the safe speed limit value of the wind turbine;

[0009] Based on the state of charge of the energy storage and the overcharge and overdischarge limit, the frequency modulation capability factor of each energy storage participating in frequency modulation in the wind storage station is calculated;

[0010] The frequency modulation capability factors of all wind turbines and energy storages in the wind storage station are summed up to obtain the frequency modulation capability of the wind storage station.

[0011] Further, based on the wind speed considering the wake effect of the wind turbine in the wind storage station, the effective kinetic energy of each wind turbine is calculated, and the specific calculation formula is:

[0012] ΔE WT,m =ΔE k,m +ΔE p,m (1)

[0013]

[0014] Wherein, m in each lower right subscript represents the mth wind turbine participating in frequency modulation in the wind storage station; ΔE WT,m is the effective kinetic energy of the mth wind turbine, and the subscripts k and p are used to distinguish the rotor kinetic energy increment and wind energy capture increment therein, i.e. ΔE k,m is the rotor kinetic energy increment of the mth wind turbine, ΔE p,m is the wind energy capture increment of the mth wind turbine; t0 is the start time of frequency modulation, t is the end time of frequency modulation; P m is the input mechanical power of the wind turbine, P e is the output electromagnetic power of the wind turbine, H WT,m is the moment of inertia of the wind turbine, ω r,m is the rotor speed of the wind turbine, ω r0,m is the initial rotor speed of the wind turbine; P m0 is the initial input mechanical power of the wind turbine, ρ is the air density, A is the rotor area, V m is the wind speed of the wind turbine considering the wake effect, C p (λ,β) is the wind energy conversion efficiency coefficient, λ and β represent the tip speed ratio and the pitch angle respectively; is the wind energy conversion efficiency coefficient corresponding to the current wind speed under the rated maximum rotor speed of the wind turbine;

[0015] The effective kinetic energy of the fan is calculated based on the maximum effective kinetic energy of each fan, and the frequency modulation capability factor of each fan is obtained, specifically:

[0016]

[0017] where C WT,m represents the frequency modulation capability factor of the mth fan, represents the maximum effective kinetic energy of the fan considering the wake effect, and respectively represent the maximum rotor kinetic energy increment and the maximum wind energy capture increment of the fan; ω r,max and ω r,min respectively represent the maximum and minimum safe rotational speed of the fan; is the wind energy conversion efficiency coefficient corresponding to the minimum rotor rotational speed of the fan at the current wind speed.

[0018] Further, based on the state of charge of the energy storage and the overcharge and overdischarge limit, the frequency modulation capability factor of each energy storage participating in frequency modulation in the wind storage station is calculated, specifically:

[0019] The current state of charge SOC n of each energy storage is calculated.

[0020]

[0021] where SOC n0 represents the initial state of charge of the nth energy storage battery, I n,c represents the outflow current of the nth energy storage battery, Q represents the rated capacity of the nth energy storage battery; t0 is the start time of frequency modulation, and t is the end time of frequency modulation;

[0022] Based on the current state of charge, the frequency modulation capability factor of each energy storage is calculated:

[0023]

[0024] where C ES,n represents the frequency modulation capability factor of the nth energy storage battery, SOC n,max and SOC n,min respectively represent the maximum and minimum values of the state of charge of the nth energy storage battery.

[0025] A frequency modulation capability evaluation device of a wind storage station, comprising:

[0026] An effective kinetic energy calculation module, configured to calculate the effective kinetic energy of each fan participating in frequency modulation in the wind storage station based on the wind speed considering the wake effect of the fan in the wind storage station;

[0027] The fan frequency modulation capability calculation module is configured to: based on the effective kinetic energy of the fan, and taking the maximum effective kinetic energy of each fan as a reference, calculate a frequency modulation capability factor of each fan, wherein the maximum effective kinetic energy is a maximum value of the effective kinetic energy calculated based on the wind speed considering the wake effect and the safety rotating speed limit value of the fan.

[0028] The energy storage frequency modulation capability calculation module is configured to: based on the state of charge of the energy storage and the overcharge and overdischarge limit, calculate a frequency modulation capability factor of each energy storage participating in frequency modulation in the wind storage station.

[0029] The wind storage station frequency modulation capability summary module is configured to: sum the frequency modulation capability factors of all the fans and energy storages in the wind storage station to obtain the frequency modulation capability of the wind storage station.

[0030] A computer readable storage medium having a computer program stored thereon, the computer program being executed by a processor to implement the method of any of the above.

[0031] A hierarchical frequency modulation control method of a distributed wind storage system, first, the frequency modulation capability of each wind storage station in the distributed wind storage system is evaluated by using the frequency modulation capability evaluation method of the wind storage station of any of the above; then, based on the frequency modulation capability of each wind storage station obtained by evaluation, the frequency modulation capability factors of each fan and each energy storage, the distributed wind storage system is controlled in layers as follows: system layer, station layer and fan / energy storage unit layer.

[0032] Further, the hierarchical frequency modulation control specifically includes:

[0033] In the system layer, the required power for frequency modulation is distributed to each wind storage station according to the proportion of the frequency modulation capability of each wind storage station in the sum of the frequency modulation capability of all wind storage stations;

[0034] In the station layer, the primary frequency modulation power of the power allocated to the wind storage station is borne by the fan, and the inertia response power and the part of the fan frequency modulation capacity that is insufficient are borne by the energy storage;

[0035] In the fan and energy storage unit layer, the frequency modulation power of the fan allocated by the station layer is distributed to each fan according to the proportion of the frequency modulation capability factor of each fan in the sum of the frequency modulation capability factors of all fans; the frequency modulation power of the energy storage allocated by the station layer is further distributed to each energy storage according to the proportion of the frequency modulation capability factor of each energy storage in the sum of the frequency modulation capability factors of all energy storages.

[0036] Further, the required power for system frequency modulation is obtained by calculation as follows:

[0037]

[0038] wherein ΔP WEK dr and K in denote the droop coefficient and the inertia coefficient, respectively, f ac and f ac,ref denote the real-time frequency and the reference frequency in the power grid, respectively.

[0039] Further, the power required for system frequency regulation is proportionally allocated to each wind storage site, denoted as:

[0040]

[0041] where ΔP WE,i denotes the frequency regulation power allocated to the i-th wind storage site, ΔP WE denotes the power required for system frequency regulation, C WE,i denotes the frequency regulation capability of the i-th wind storage site in the distributed wind storage system, and I denotes the total number of wind storage sites included in the distributed wind storage system.

[0042] Further, the frequency regulation power respectively allocated to the wind turbine and the energy storage at the site level is calculated as:

[0043] ΔP WT,i = K WT,i × (f ac - f ac,ref ) (13)

[0044] ΔP ES,i = K ES,i × (ΔP WE,i - ΔP WT,i ) (14)

[0045] where ΔP WE,i denotes the frequency regulation power allocated to the i-th wind storage site, ΔP WT,i and ΔP ES,i denote the frequency regulation power respectively allocated to the wind turbine and the energy storage at the i-th wind storage site, K WT,i and K ES,i denote the frequency regulation coefficients of the wind turbine and the energy storage, f ac and f ac,ref denote the real-time frequency and the reference frequency in the power grid, respectively.

[0046] Further, the frequency regulation power allocated to the wind turbine at the site level is proportionally allocated to each wind turbine, denoted as:

[0047]

[0048] The frequency regulation power allocated to the energy storage at the site level is proportionally allocated to each energy storage, denoted as:

[0049]

[0050] wherein, ΔP WT,m represents the frequency modulation power allocated by the ith wind storage station to the mth wind turbine, C WT,m represents the frequency modulation capability factor of the nth storage energy in the ith wind storage station, N is the number of storage energies in the ith wind storage station, ΔP WT,i represents the frequency modulation power borne by the storage energy in the ith wind storage station.

[0051] ΔP ES,n represents the frequency modulation power allocated by the ith wind storage station to the nth storage energy, C WT,m represents the frequency modulation capability factor of the nth storage energy in the ith wind storage station, N is the number of storage energies in the ith wind storage station, ΔP ES,i represents the frequency modulation power borne by the storage energy in the ith wind storage station.

[0052] A hierarchical frequency modulation control device of a distributed wind storage system, comprising the frequency modulation capability evaluation device and the hierarchical frequency modulation control module of any one of the above, and further comprising a hierarchical frequency modulation control module; the hierarchical frequency modulation control module comprises:

[0053] a system layer power distribution submodule, configured to: at the system layer, distribute the system frequency modulation required power to each wind storage station according to the proportion of the frequency modulation capability of each wind storage station in the sum of the frequency modulation capabilities of all wind storage scenes;

[0054] a station layer power distribution submodule, configured to: at the station layer, for the power allocated to the wind storage station, bear the primary frequency modulation power by the wind turbine, and bear the inertia response power and the part of the wind turbine frequency modulation capacity by the storage energy;

[0055] a unit layer power distribution submodule, configured to: at the wind turbine and storage energy unit layer, distribute the frequency modulation power of the station layer to each wind turbine according to the proportion of the frequency modulation capability factor of each wind turbine in the sum of the frequency modulation capability factors of all wind turbines; and distribute the frequency modulation power of the station layer to each storage energy according to the proportion of the frequency modulation capability factor of each storage energy in the sum of the frequency modulation capability factors of all storage energies.

[0056] A computer readable storage medium, having stored thereon a computer program, the computer program being executed by a processor to implement the hierarchical frequency modulation control method of the distributed wind storage system of any one of the above.

[0057] Advantages

[0058] Compared with the prior art, the advantages of the present application are:

[0059] The application not only considers the influence of the wake effect on the frequency modulation capability of the wind farm, but also considers the influence of the system inertia and the state of charge of the energy storage, realizes the maximum frequency support control, and has high practical value in new power system frequency modulation and the like. BRIEF DESCRIPTION OF DRAWINGS

[0060] Figure 1 is a hierarchical control flow diagram of the maximum wind storage system frequency support capability of the application;

[0061] Figure 2 is a topological structure diagram of an example;

[0062] Figure 3 is a real-time frequency simulation diagram;

[0063] Figure 4 is an active power output simulation diagram of part of wind turbines in the No. 1 wind storage station;

[0064] Figure 5 is a rotor speed simulation diagram of part of wind turbines in the No. 1 wind storage station;

[0065] Figure 6 is an active power output simulation diagram of energy storage in the No. 1 wind storage station;

[0066] Figure 7 is a state of charge simulation diagram of energy storage in the No. 1 wind storage station;

[0067] Figure 8 is a frequency modulation capability simulation diagram of part of wind turbines in the No. 1 wind storage station under the hierarchical frequency modulation control method of the application;

[0068] Figure 9 is a frequency modulation capability simulation diagram of different wind storage stations under the hierarchical frequency modulation control method of the application. DETAILED DESCRIPTION

[0069] The embodiment of the application is described in detail below, which is developed based on the technical solution of the application, gives a detailed implementation mode and specific operation process, and further explains and describes the technical solution of the application.

[0070] Embodiment 1

[0071] The embodiment provides a frequency modulation capability evaluation method of a wind storage station, which comprises the following steps.

[0072] Step 1, based on the wind speed considering the wake effect of wind turbines in the wind storage station, the effective kinetic energy of each wind turbine participating in frequency modulation in the wind storage station is calculated.

[0073] The wind turbine usually utilizes the kinetic energy stored in the rotor to perform frequency modulation, which causes the rotor speed to decrease. When the rotor speed of the wind turbine decreases, the maximum wind energy conversion efficiency coefficient corresponding to the optimal rotor speed of the wind wheel The wind speed will be reduced, thus the wind energy captured by the wind turbine will also be reduced. Therefore, the effective kinetic energy of the mth wind turbine participating in the frequency modulation is as follows, including the rotor kinetic energy increment and the wind energy capture increment:

[0074] ΔE WT,m = ΔE k,m + ΔE p,m (1)

[0075]

[0076] wherein m in each lower right subscript represents the mth wind turbine participating in the frequency modulation in the wind storage station; ΔE WT,m is the effective kinetic energy of the mth wind turbine, and the subscripts k and p are used to distinguish the rotor kinetic energy increment and the wind energy capture increment therein, i.e. ΔE k,m is the rotor kinetic energy increment of the mth wind turbine, ΔE p,m is the wind energy capture increment of the mth wind turbine; t0 is the start time of the frequency modulation, t is the end time of the frequency modulation; P m is the mechanical power input of the wind turbine, P e is the electromagnetic power output of the wind turbine, H WT,m is the moment of inertia of the wind turbine, ω r,m is the rotor speed of the wind turbine, ω r0,m is the initial rotor speed of the wind turbine; P m0 is the initial mechanical power input of the wind turbine, ρ is the air density, A is the rotor area, V m is the wind speed of the wind turbine considering the wake effect, C p (λ, β) is the wind energy conversion efficiency coefficient, λ and β represent the tip speed ratio and the pitch angle, respectively; is the wind energy conversion efficiency coefficient of the wind turbine corresponding to the current wind speed under the rated maximum rotor speed,

[0077] Step 2, based on the effective kinetic energy of the wind turbine, the frequency modulation capacity factor of each wind turbine is calculated based on the maximum effective kinetic energy of the respective wind turbine; wherein the maximum effective kinetic energy is the maximum value of the effective kinetic energy calculated based on the wind speed considering the wake effect and the safe speed limit value of the wind turbine:

[0078]

[0079] wherein C WT,m represents the frequency modulation capacity factor of the mth wind turbine, represents the maximum effective kinetic energy of the wind turbine considering the wake effect, and represent the maximum rotor kinetic energy increment and the maximum wind energy capture increment of the wind turbine, respectively; ω r,max and ω r,min represent the maximum and minimum safe speed of the wind turbine, respectively; The wind energy conversion efficiency coefficient of the wind turbine corresponding to the minimum rotor speed of the current wind speed.

[0080] When the wind turbine operates at the rated maximum rotor speed ω r,max , C WT,m reaches a maximum value of 1, at which time the wind turbine has the strongest frequency modulation capability; when the wind turbine operates at the rated minimum rotor speed ω r,min , C WT,m reaches a minimum value of 0, at which time the wind turbine does not have frequency modulation capability.

[0081] Step 3, based on the state of charge of the energy storage and the overcharge and overdischarge limit, calculate the frequency modulation capability factor of each energy storage participating in frequency modulation in the wind storage station.

[0082] In order to ensure the safe operation of the energy storage during frequency modulation and avoid overcharge or overdischarge, the state of charge of the energy storage needs to be considered to evaluate the frequency modulation capability of the energy storage. The energy storage has active power and electric quantity limits when participating in frequency modulation.

[0083] First, calculate the current state of charge SOC n of each energy storage:

[0084]

[0085] where SOC n0 represents the initial state of charge of the nth energy storage battery, I n,c represents the outflow current of the nth energy storage battery, Q n represents the rated capacity of the nth energy storage battery; t0 is the start time of frequency modulation, and t is the end time of frequency modulation;

[0086] A state of charge that is too high or too low will affect the service life of the energy storage. During frequency modulation, the state of charge should be controlled within a safe range. Therefore, based on the current state of charge, calculate the frequency modulation capability factor of each energy storage:

[0087]

[0088] where C ES,n represents the frequency modulation capability factor of the nth energy storage battery, SOC n,max and SOC n,min represent the maximum and minimum values of the state of charge of the nth energy storage battery, respectively.

[0089] When the real-time state of charge of the energy storage is greater than SOC max , C ES,n will be greater than 1. At this time, the energy storage has surplus frequency modulation capability. When the real-time state of charge of the energy storage is less than SOC min , C ES,n will be less than 0. At this time, the energy storage will weaken the frequency modulation capability of the wind storage system to ensure the safe operation of the wind storage system.

[0090] Step 4, summing up the frequency modulation capability factors of all wind turbines and energy storage in the wind storage station to obtain the frequency modulation capability of the wind storage station. The frequency modulation capability of the wind storage station at different nodes of the power system is defined as C WE,i :

[0091]

[0092] wherein i represents the i th wind storage station, M represents the total number of wind turbines in the station, and N represents the total number of energy storage power stations in the station.

[0093] Embodiment 2

[0094] The embodiment provides a frequency modulation capability evaluation device of a wind storage station, comprising:

[0095] an effective kinetic energy calculation module, configured to calculate the effective kinetic energy of each wind turbine participating in frequency modulation in the wind storage station by considering the wake effect of the wind turbine in the wind storage station;

[0096] a wind turbine frequency modulation capability calculation module, configured to calculate the frequency modulation capability factor of each wind turbine based on the effective kinetic energy of the wind turbine, taking the maximum effective kinetic energy of each wind turbine considering the wake effect as a reference;

[0097] an energy storage frequency modulation capability calculation module, configured to calculate the frequency modulation capability factor of each energy storage participating in frequency modulation in the wind storage station based on the state of charge of the energy storage and the overcharge and overdischarge limit;

[0098] a wind storage station frequency modulation capability summary module, configured to sum up the frequency modulation capability factors of all wind turbines and energy storage in the wind storage station to obtain the frequency modulation capability of the wind storage station.

[0099] The embodiment provides a frequency modulation capability evaluation device of a wind storage station, comprising:

[0100] Embodiment 3

[0101] A computer readable storage medium, having a computer program stored thereon, wherein the computer program is executed by a processor to implement the frequency modulation capability evaluation method of the wind storage station according to the embodiment 1.

[0102] Embodiment 4

[0103] The embodiment provides a hierarchical frequency modulation control method of a distributed wind storage system, which adopts the frequency modulation capability evaluation method of the wind storage station according to the embodiment 1 to evaluate the frequency modulation capability of each wind storage station in the distributed wind storage system, and then performs hierarchical frequency modulation control on the distributed wind storage system based on the calculated frequency modulation capability of each wind turbine, each energy storage and each wind storage station.Figure 1 as shown.

[0104] The hierarchical frequency control method is divided into three levels, namely the system layer, the station layer and the unit layer. The system layer is responsible for coordinating the participation of wind storage systems in different nodes in the system in frequency modulation; the station layer is responsible for coordinating the participation of wind farms and energy storage power stations in frequency modulation; the unit layer is responsible for coordinating the participation of wind turbines and energy storage battery units in frequency modulation.

[0105] 1) At the system layer, when the system has a frequency deviation, the wind storage system should have similar frequency modulation characteristics as traditional generators, not only providing additional inertia to delay the frequency deviation, but also providing additional capacity to participate in frequency modulation, the active power ΔP WE as follows:

[0106]

[0107] where K dr and K in represent the droop coefficient and the inertia coefficient respectively, f ac and f ac,ref represent the real-time frequency and the reference frequency in the power grid respectively.

[0108] Considering that the distributed wind storage systems are distributed in different nodes in the system, the power required for frequency modulation should be reasonably allocated to different wind storage stations. Specifically, according to the proportion of the frequency modulation capacity of each wind storage station in the sum of the frequency modulation capacity of all wind storage stations, the power required for frequency modulation is allocated to each wind storage station:

[0109]

[0110] where ΔP WE,i represents the frequency modulation power allocated to the i th wind storage station, ΔP WE represents the power required for system frequency modulation, C WE,i represents the frequency modulation capacity of the i th wind storage station in the distributed wind storage system, and I represents the total number of wind storage stations included in the distributed wind storage system.

[0111] 2) At the station layer, the reference power allocated by the system layer should be shared by the wind farm and the energy storage power station. Considering the uncertainty of wind speed and the difference in operating conditions of wind turbines, the wind farm does not have sufficient inertia response capacity. Therefore, the inertia response part of the reference power and the part of the wind farm frequency modulation capacity that is insufficient are borne by the energy storage power station which has a faster response speed. Compared with the primary frequency modulation power borne by the wind farm, the inertia response power borne by the energy storage is smaller, which can effectively avoid long-term high-power discharge of the energy storage power station and improve the service life of the energy storage. The active power for frequency modulation of the wind farm and the energy storage power station is as follows:

[0112] ΔP WT,i = K WT,i × (fac -f ac,ref ) (13)

[0113] ΔP ES,i =K ES,i ×(ΔP WE,i -ΔP WT,i ) (14)

[0114] Where ΔP WE,i represents the frequency regulation power allocated to the i-th wind storage station, ΔP WT,i and ΔP ES,i They represent the frequency regulation power assigned to wind turbines and energy storage by the i-th wind-storage station, K WT,i and K ES,i Represent the frequency modulation coefficients of the wind turbine and energy storage, f ac and f ac,ref Represent the real-time frequency and reference frequency in the power grid respectively.

[0115] 3) At the unit level, the reference power allocated at the site level should be shared by each wind turbine in the wind farm and each energy storage unit in the energy storage plant. Considering the different operating conditions of different units, their frequency regulation capabilities also vary. Based on the frequency regulation capability factors introduced above, the active power injected by each unit can be reasonably and effectively allocated. The frequency regulation power injected by the wind turbines and energy storage units is as follows:

[0116]

[0117] Example 5

[0118] This embodiment provides a hierarchical frequency regulation control device for a distributed wind-storage system, comprising the frequency regulation capability evaluation device described in Example 2, and also comprising a hierarchical frequency regulation control module.

[0119] The hierarchical frequency modulation control module includes:

[0120] The system-level power allocation submodule is used to: at the system level, allocate the power required for system frequency regulation to each wind-storage station according to the proportion of the frequency regulation capacity of each wind-storage station to the sum of the frequency regulation capacity of all wind-storage scenarios;

[0121] The station-level power allocation submodule is used to: at the station level, for the power allocated to the wind and energy storage station, assign the primary frequency regulation power to the wind turbines, while assigning the inertial response power and insufficient wind turbine frequency regulation capacity to the energy storage.

[0122] The unit layer power distribution submodule is configured to: in the fan and energy storage unit layer, distribute the frequency modulation power of the station layer to each fan according to the proportion of the frequency modulation capability factor of each fan in the sum of the frequency modulation capability factors of all fans; and distribute the frequency modulation power of the station layer to each energy storage according to the proportion of the frequency modulation capability factor of each energy storage in the sum of the frequency modulation capability factors of all energy storages.

[0123] The embodiment provides a hierarchical frequency modulation control device for the distributed wind storage system, and is used for implementing the hierarchical frequency modulation control method in the embodiment 4, wherein specific implementation methods of the modules are the same as those in the embodiment 4, and the embodiment 5 will not be described again.

[0124] Embodiment 6

[0125] The embodiment provides a computer readable storage medium, and a computer program is stored in the computer readable storage medium, wherein the computer program is executed by a processor to implement the frequency modulation capability evaluation method of the wind storage station in the embodiment 4.

[0126] The distributed wind storage system shown in Figure 2 is used as a test system. The test system includes two wind storage stations, the first wind storage station has nine fans, and the second wind storage station has sixteen fans. Due to the wake effect, the rotor speeds of the upstream and downstream fans are different. Each wind storage station is equipped with an energy storage power station, and the state of charge of the energy storage units in the energy storage power station is different. The local power grid has four synchronous generators equipped with speed governors, so the synchronous generators will participate in system frequency modulation. Three nodes in the system have constant power loads, the system rated voltage is 220kv, and the rated frequency is 50Hz.

[0127] In order to illustrate the effectiveness and superiority of the application, different control methods are used in the test system in Figure 2 for simulation verification. They are the fan non-participation frequency modulation method, the wind storage separate frequency modulation method and the method proposed in the application. The test is carried out on the MATLAB / Simulink platform. It is assumed that the load of the seventh node suddenly increases by 40% at 5s, and the time delay of the frequency signal transmitted to the fan is 200ms.

[0128] The real-time frequency response results of each different method are shown in Figure 3 . Compared with the fan non-participation frequency modulation method, the other two control methods can effectively improve the lowest point of the frequency and slow down the frequency drop. Compared with the wind storage separate frequency modulation, the proposed method can better alleviate the frequency deviation and has better inertial response.

[0129] Figures 4-7 The dynamic process of the wind storage system under different frequency modulation methods is given. In Figure 4 and Figure 5Different colors represent different control methods, and different line types represent wind turbines with different wind speeds due to wake effects. Select 3 wind turbines with different wind speeds in No. 1 wind farm as an example. Figure 4 is the active power output of part of the wind turbines in No. 1 wind storage station. Compared with the wind storage separate frequency modulation method, the method can adaptively adjust the frequency modulation power of the wind turbine according to the quantified frequency modulation capability factor. Wind turbines with different initial kinetic energy can output different power increments to support the frequency. Figure 5 is the rotor speed simulation diagram of part of the wind turbines in No. 1 wind storage station. Compared with the wind storage separate frequency modulation method, the method can make the wind turbine with larger rotor speed release more rotor kinetic energy to maximize the frequency modulation capability, and the wind turbine with lower rotor speed can release less rotor kinetic energy to prevent the wind turbine from reaching the minimum speed limit. The traditional wind storage separate frequency modulation method will cause the rotor speed to be lower than the minimum value, which is not conducive to the subsequent recovery of the rotor speed. The proposed method can limit the rotor speed within a safe range.

[0130] Figure 6 is the active power output simulation diagram of the energy storage in No. 1 wind storage station. Compared with the wind storage separate frequency modulation method, the method can output more active power to participate in frequency modulation. Because the method uses an adaptive frequency modulation capability factor, it can coordinate different energy storage units to maximize the output of frequency modulation power. Due to the inertia response control, the method can output more power to participate in frequency modulation faster than the wind storage separate frequency modulation method, slow down the frequency deviation and help the frequency recovery. Figure 7 is the state of charge simulation diagram of the energy storage in No. 1 wind storage station. The method can output more active power while limiting the state of charge of the energy storage within a safe range. Figure 8 is the frequency modulation capability simulation diagram of part of the wind turbines in No. 1 wind storage station under the control of the method. When the wind turbine participates in system frequency modulation, the wind turbine with a larger frequency modulation capability factor will release more rotor kinetic energy to participate in frequency support. Therefore, the frequency modulation capability factor decreases faster. Figure 9 is the frequency modulation capability simulation diagram of different wind storage stations under the control of the method. Because the number of wind turbines in No. 2 wind farm is large, the frequency modulation capability factor before frequency modulation is large. During the frequency modulation process, the wind storage station with stronger frequency modulation capability will output more active power to participate in frequency modulation.

[0131] The above is only a preferred embodiment of the present application, and is not intended to limit the present application in any other form, and any modification or equivalent change made according to the technical essence of the present application still falls within the scope of the present application.

Claims

1. A hierarchical frequency modulation control method of a distributed wind storage system, characterized by, First, the frequency modulation capability evaluation method of the wind storage station is used to evaluate the frequency modulation capability of each wind storage station in the distributed wind storage system; then, based on the frequency modulation capability of each wind storage station, the frequency modulation capability factors of each wind turbine and each energy storage, the distributed wind storage system is controlled in layers as follows: system layer, station layer and wind turbine / energy storage unit layer; The frequency modulation capability evaluation method of the wind storage station is used to evaluate the frequency modulation capability of each wind storage station in the distributed wind storage system, which comprises: Based on the wind speed considering the wake effect of the wind turbine in the wind storage station, the effective kinetic energy of each wind turbine participating in frequency modulation in the wind storage station is calculated; Based on the effective kinetic energy of the wind turbine, the frequency modulation capability factor of each wind turbine is calculated based on the maximum effective kinetic energy of the respective wind turbine; wherein the maximum effective kinetic energy is the maximum value of the effective kinetic energy calculated based on the wind speed considering the wake effect and the safety speed limit of the wind turbine; Based on the state of charge and overcharge and overdischarge limit of the energy storage, the frequency modulation capability factor of each energy storage participating in frequency modulation in the wind storage station is calculated; The frequency modulation capability factors of all wind turbines and energy storages in the wind storage station are summed up to obtain the frequency modulation capability of the wind storage station; The hierarchical frequency modulation control specifically comprises: At the system layer, the required power for frequency modulation is distributed to each wind storage station according to the proportion of the frequency modulation capability of each wind storage station in the sum of the frequency modulation capability of all wind storage stations; At the station layer, the primary frequency modulation power of the power distributed to the wind storage station is borne by the wind turbine, and the inertia response power and the part of the wind turbine frequency modulation capacity that is insufficient are borne by the energy storage; At the wind turbine / energy storage unit layer, the frequency modulation power of the wind turbine distributed by the station layer is distributed to each wind turbine according to the proportion of the frequency modulation capability factor of each wind turbine in the sum of the frequency modulation capability factors of all wind turbines; the frequency modulation power of the energy storage distributed by the station layer is further distributed to each energy storage according to the proportion of the frequency modulation capability factor of each energy storage in the sum of the frequency modulation capability factors of all energy storages.

2. The hierarchical frequency control method of the distributed wind storage system according to claim 1, wherein, The required power for system frequency modulation is calculated as follows: where ΔP WE represents the power required for system frequency modulation, K dr and K in represent the droop coefficient and the inertia coefficient, respectively, f ac and f ac,ref represent the real-time frequency and the reference frequency in the power grid, respectively.

3. The hierarchical frequency control method of the distributed wind storage system according to claim 1, wherein, The required power for system frequency modulation is distributed to each wind storage station according to the proportion, which is represented as: where ΔP WE,i represents the frequency modulation power allocated to the i-th wind storage site, ΔP WE represents the power required for system frequency modulation, C WE,i represents the frequency modulation capability of the i-th wind storage site in the distributed wind storage system, and I represents the total number of wind storage sites included in the distributed wind storage system.

4. The hierarchical frequency control method of the distributed wind storage system according to claim 1, wherein, at the field The frequency modulation power borne by the wind turbine and the energy storage at the station layer is calculated as follows: ΔP WT,i = K WT,i × (f ac -f ac,ref ) (13) ΔP ES,i = K ES,i × (ΔP WE,i - ΔP WT,i ) (14) where ΔP WE,i represents the frequency modulation power allocated to the ith wind storage site, ΔP WT,i and ΔP ES,i respectively represent the frequency modulation power assumed by the wind turbine and the energy storage of the ith wind storage site, K WT,i and K ES,i respectively represent the frequency modulation coefficients of the wind turbine and the energy storage, f ac and f ac,ref respectively represent the real-time frequency and the reference frequency in the power grid.

5. The hierarchical frequency control method of the distributed wind storage system according to claim 1, wherein, The frequency modulation power of the wind turbine distributed by the station layer is distributed to each wind turbine according to the proportion, which is represented as: The frequency modulation power of the energy storage distributed by the station layer is distributed to each energy storage according to the proportion, which is represented as: wherein ΔP WT,m represents the frequency modulation power allocated by the ith wind storage station to the mth wind turbine, C WT,m represents the frequency modulation capability factor of the mth wind turbine in the ith wind storage station, M is the number of wind turbines in the ith wind storage station, ΔP WT,i represents the frequency modulation power assumed by the wind turbine from the ith wind storage station; ΔP ES,n represents the frequency modulation power allocated to the nth energy storage of the ith wind storage station, C ES,n represents the frequency modulation capability factor of the nth energy storage in the ith wind storage station, N is the number of energy storages in the ith wind storage station, ΔP ES,i represents the frequency modulation power undertaken by the energy storage of the ith wind storage station.

6. The hierarchical frequency control method of the distributed wind storage system according to claim 1, wherein, Based on the wind speed considering the wake effect of the wind turbine in the wind storage station, the effective kinetic energy of each wind turbine is calculated, and the specific calculation formula is as follows: ΔE WT,m = ΔE k,m + ΔE p,m (1) wherein m in each subscript at the lower right corner represents the mth wind turbine participating in the frequency regulation in the wind storage station; ΔE WT,m is the effective kinetic energy of the mth wind turbine, and the subscripts k and p are used to distinguish the rotor kinetic energy increment and the wind energy capture increment therein, i.e., ΔE k,m is the rotor kinetic energy increment of the mth wind turbine, ΔE p,m is the wind energy capture increment of the mth wind turbine; t0 is the start time of the frequency regulation, and t is the end time of the frequency regulation; P m is the mechanical power input to the wind turbine, P e is the electromagnetic power output from the wind turbine, H WT,m is the moment of inertia of the wind turbine, ω r,m is the rotor speed of the wind turbine, ω r0,m is the initial rotor speed of the wind turbine; P m0 is the initial mechanical power input to the wind turbine, ρ is the air density, A is the rotor area, V m is the wind speed considering the wake effect of the wind turbine, C p (λ, β) is the wind energy conversion efficiency coefficient, λ and β represent the tip speed ratio and the pitch angle, respectively; is the wind energy conversion efficiency coefficient corresponding to the wind turbine at the current wind speed and the rated maximum rotor speed; Based on the effective kinetic energy of the wind turbine, the frequency modulation capability factor of each wind turbine is calculated based on the maximum effective kinetic energy of the respective wind turbine, and the specific calculation formula is as follows: where C WT,m represents the frequency modulation capability factor of the mth wind turbine, represents the maximum effective kinetic energy of the wind turbine considering the wake effect, and respectively represent the maximum rotor kinetic energy increment and the maximum wind energy capture increment of the wind turbine; ω r,max and ω r,min respectively represent the maximum and minimum safe rotational speed of the wind turbine; is the wind energy conversion efficiency coefficient of the wind turbine corresponding to the minimum rotor rotational speed under the current wind speed.

7. The hierarchical frequency control method of the distributed wind storage system according to claim 1, wherein, Based on the state of charge and overcharge and overdischarge limit of the energy storage, the frequency modulation capability factor of each energy storage participating in frequency modulation in the wind storage station is calculated, and the specific calculation formula is as follows: calculating a current state of charge SOC for each energy storage n : wherein SOC n0 represents the initial state of charge of the nth energy storage cell, I n,c represents the outflow current of the nth energy storage cell, Q n represents the rated capacity of the nth energy storage cell; t0is the start time of frequency modulation, and t is the end time of frequency modulation; The frequency modulation capability factor of each energy storage is calculated based on the current state of charge: Among them, C ES,n Represents the frequency regulation capability factor of the nth energy storage battery, SOC n,max and SOC n,min They represent the maximum and minimum state of charge of the nth energy storage battery respectively.

8. A hierarchical frequency modulation control device of a distributed wind storage system, characterized in that, The frequency modulation capability evaluation device further comprises a hierarchical frequency modulation control module. The hierarchical frequency modulation control module is configured to perform hierarchical frequency modulation control on the distributed wind storage system according to the frequency modulation capability of each wind storage station, the frequency modulation capability factor of each wind turbine and each energy storage, and the hierarchical frequency modulation control is performed in the system layer, the station layer and the wind turbine / energy storage unit layer. The hierarchical frequency modulation control module comprises: The system layer power distribution submodule is configured to distribute the system frequency modulation required power to each wind storage station in proportion to the frequency modulation capability of each wind storage station in the system layer. The station layer power distribution submodule is configured to distribute the power allocated to the wind storage station to the wind turbine for primary frequency modulation, and to the energy storage for inertia response and the part of the wind turbine frequency modulation capacity that is insufficient. The unit layer power distribution submodule is configured to distribute the frequency modulation power allocated to the wind turbine from the station layer to each wind turbine in proportion to the frequency modulation capability factor of each wind turbine, and to distribute the frequency modulation power allocated to the energy storage from the station layer to each energy storage in proportion to the frequency modulation capability factor of each energy storage. The frequency modulation capability evaluation device comprises: The effective kinetic energy calculation module is configured to calculate the effective kinetic energy of each wind turbine participating in frequency modulation in the wind storage station based on the wind speed considering the wind turbine wake effect in the wind storage station. The wind turbine frequency modulation capability calculation module is configured to calculate the frequency modulation capability factor of each wind turbine based on the effective kinetic energy of the wind turbine and the maximum effective kinetic energy of each wind turbine. The energy storage frequency modulation capability calculation module is configured to calculate the frequency modulation capability factor of each energy storage participating in frequency modulation in the wind storage station based on the state of charge of the energy storage and the overcharge and overdischarge limit. The wind storage station frequency modulation capability summary module is configured to sum the frequency modulation capability factors of all wind turbines and energy storages in the wind storage station to obtain the frequency modulation capability of the wind storage station.

9. The hierarchical frequency control device of the distributed wind storage system according to claim 8, wherein, The system frequency modulation required power is calculated as follows: where ΔP WE represents the power required for frequency modulation, K dr and K in represent the droop coefficient and the inertia coefficient, respectively, f ac and f ac,ref represent the real-time frequency and the reference frequency in the power grid, respectively.

10. The hierarchical frequency control device of the distributed wind storage system according to claim 8, wherein, The system frequency modulation required power is distributed to each wind storage station in proportion, which is represented as follows: where ΔP WE,i represents the frequency modulation power allocated to the i-th wind storage site, ΔP WE represents the power required for system frequency modulation, C WE,i represents the frequency modulation capability of the i-th wind storage site in the distributed wind storage system, and I represents the total number of wind storage sites included in the distributed wind storage system.

11. The hierarchical frequency control device of the distributed wind storage system of claim 8, wherein, at the site The frequency modulation power respectively borne by the wind turbine and the energy storage in the station layer is calculated as follows: ΔP WT,i = K WT,i × (f ac -f ac,ref ) (13) ΔP ES,i = K ES,i × (ΔP WE,i - ΔP WT,i ) (14) where ΔP WE,i represents the frequency modulation power allocated to the i-th wind storage station, ΔP WT,i and ΔP ES,i represent the frequency modulation power assumed by the wind turbine and the energy storage of the i-th wind storage station, K WT,i and K ES,i represent the frequency modulation coefficients of the wind turbine and the energy storage, f ac and f ac,ref represent the real-time frequency and the reference frequency in the power grid, respectively.

12. The hierarchical frequency control device of the distributed wind storage system according to claim 8, wherein, The frequency modulation power allocated to the wind turbine from the station layer is distributed to each wind turbine in proportion, which is represented as follows: The frequency modulation power allocated to the energy storage from the station layer is distributed to each energy storage in proportion, which is represented as follows: wherein ΔP WT,m represents the frequency modulation power allocated by the ith wind storage station to the mth wind turbine, C WT,m represents the frequency modulation capability factor of the mth wind turbine in the ith wind storage station, M is the number of wind turbines in the ith wind storage station, ΔP WT,i represents the frequency modulation power assumed by the wind turbine from the ith wind storage station; ΔP ES,n represents the frequency modulation power allocated to the nth energy storage of the ith wind storage station, C ES,n represents the frequency modulation capability factor of the nth energy storage in the ith wind storage station, N is the number of energy storages in the ith wind storage station, ΔP ES,i represents the frequency modulation power undertaken by the energy storage of the ith wind storage station.

13. The hierarchical frequency control device of the distributed wind storage system according to claim 8, wherein, The effective kinetic energy of each wind turbine is calculated based on the wind speed considering the wind turbine wake effect in the wind storage station, and the specific calculation formula is as follows: ΔE WT,m = ΔE k,m + ΔE p,m (1) wherein m in each subscript at the lower right corner represents the mth wind turbine participating in the frequency regulation in the wind storage station; ΔE WT,m is the effective kinetic energy of the mth wind turbine, and the subscripts k and p are used to distinguish the rotor kinetic energy increment and the wind energy capture increment therein, i.e., ΔE k,m is the rotor kinetic energy increment of the mth wind turbine, ΔE p,m is the wind energy capture increment of the mth wind turbine; t0 is the start time of the frequency regulation, and t is the end time of the frequency regulation; P m is the mechanical power input to the wind turbine, P e is the electromagnetic power output from the wind turbine, H WT,m is the moment of inertia of the wind turbine, ω r,m is the rotor speed of the wind turbine, ω r0,m is the initial rotor speed of the wind turbine; P m0 is the initial mechanical power input to the wind turbine, ρ is the air density, A is the rotor area, V m is the wind speed considering the wake effect of the wind turbine, C p (λ, β) is the wind energy conversion efficiency coefficient, λ and β represent the tip speed ratio and the pitch angle, respectively; is the wind energy conversion efficiency coefficient corresponding to the wind turbine at the current wind speed and the rated maximum rotor speed. The frequency modulation capability factor of each wind turbine is calculated based on the effective kinetic energy of the wind turbine and the maximum effective kinetic energy of each wind turbine, and the specific calculation formula is as follows: where C WT,m represents the frequency modulation capability factor of the mth wind turbine, represents the maximum effective kinetic energy of the wind turbine considering the wake effect, and respectively represent the maximum rotor kinetic energy increment and the maximum wind energy capture increment of the wind turbine; ω r,max and ω r,min respectively represent the maximum and minimum safe rotational speed of the wind turbine; is the wind energy conversion efficiency coefficient of the wind turbine corresponding to the current wind speed and the minimum rotor rotational speed.

14. The hierarchical frequency control device of the distributed wind storage system according to claim 8, wherein, The frequency modulation capability factor of each energy storage participating in frequency modulation in the wind storage station is calculated based on the state of charge of the energy storage and the overcharge and overdischarge limit, and the specific calculation formula is as follows: calculating a current state of charge SOC for each energy storage n : wherein SOC n0 represents the initial state of charge of the nth energy storage cell, I n,c represents the outflow current of the nth energy storage cell, Q n represents the rated capacity of the nth energy storage cell; t0 is the start time of frequency modulation, and t is the end time of frequency modulation; The frequency modulation capability factor of each energy storage is calculated based on the current state of charge: where C ES,n represents the frequency modulation capability factor of the nth energy storage battery, SOC n,max and SOC n,min respectively represent the maximum and minimum values of the state of charge of the nth energy storage battery.

15. A computer readable storage medium having stored thereon a computer program, characterized in that, The computer program is executed by the processor to implement the hierarchical frequency modulation control method of the distributed wind storage system according to any one of claims 1-7.

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