Method and apparatus for distribution of inertia requirements for wind storage systems

Abstract

The application provides a kind of wind storage system inertia demand distribution method and device, method includes: based on frequency variation rate, frequency variation constraint respectively determines the first minimum inertia demand and the second minimum inertia demand of system;Select the larger value as the minimum inertia demand in both;Based on wind turbine speed safety constraint and output power constraint, the upper limit of the output power of energy storage and inertia response time, the maximum virtual inertia that wind turbine and energy storage can provide is evaluated;Based on the maximum virtual inertia that wind turbine can provide and the virtual inertia that energy storage can provide at disturbance, the inertia demand is distributed.The application obtains the minimum inertia demand associated with it by frequency variation rate and frequency variation respectively, considers the two minimum inertia demand values comprehensively, obtains the final inertia required by wind storage system.In this process, the application also considers the virtual inertia demand under the constraints of wind turbine speed and output power variation, completes the inertia demand distribution of wind power and energy storage.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wind power, in particular to a wind storage system inertia demand distribution method and device. BACKGROUND

[0002] In a power system with high penetration of wind power, the frequency response capability of the system gradually decreases due to the intermittency and instability of wind power. Therefore, the system needs sufficient inertia to cope with the frequency changes caused by wind power fluctuations and ensure stable operation of the power system. The wind storage system combines wind turbine generators and energy storage devices to provide virtual inertia support, thereby meeting the inertia demand of the system.

[0003] Currently, there are three main ways to achieve the inertia demand of the wind storage system. The first is to provide virtual inertia for wind turbine generators, which can provide virtual inertia by adjusting their control strategies. For example, during the frequency drop stage, when the system inertia is insufficient, wind turbines can be given priority to provide virtual inertia. The second is the coordinated control of energy storage devices, which can play an important role in wind storage systems. Through feedforward and feedback control, the rotors of energy storage devices and wind turbine generators are controlled to generate power increments, thereby meeting the inertia response demand of the system. Intelligent scheduling and optimization control can also be implemented in wind storage systems to ensure stable operation of the system. This includes adjusting the charging and discharging strategy of the energy storage system according to the state of wind energy and the power grid, and implementing coordinated control between wind energy and energy storage devices.

[0004] However, the current evaluation method for the inertia demand of the wind storage system still has the following defects: the existing method mainly relies on the system frequency response model or the maximum frequency change rate allowed value, lacks comprehensive consideration, and leads to incomplete and inaccurate evaluation of the system inertia demand. The existing method does not fully consider key constraints such as wind turbine speed safety constraints, power constraints, energy storage output power upper limits, and inertia response time when evaluating the inertia demand of the wind storage system, which may lead to overly optimistic or unsafe evaluation results. SUMMARY

[0005] Therefore, the present application provides a wind storage system inertia demand distribution method and device to solve at least one of the above problems.

[0006] To achieve the above purpose, the present application adopts the following scheme:

[0007] According to a first aspect of the present application, a method for distributing inertia demand of a wind storage system is provided, the method comprising: determining a first minimum inertia demand of the wind storage system based on a frequency rate of change constraint; determining a second minimum inertia demand of the wind storage system based on a frequency change constraint; selecting a larger value between the first minimum inertia demand and the second minimum inertia demand as a minimum inertia demand of the wind storage system, and selecting the first minimum inertia demand as the minimum inertia demand of the wind storage system if the first minimum inertia demand and the second minimum inertia demand are equal; evaluating a maximum virtual inertia that can be provided by a wind turbine based on a wind turbine speed safety constraint and an output power constraint; evaluating a virtual inertia that can be provided by an energy storage during a disturbance based on an upper limit of an output power of the energy storage and an inertia response time; and distributing the inertia demand based on the minimum inertia demand, the maximum virtual inertia that can be provided by the wind turbine, and the virtual inertia that can be provided by the energy storage during the disturbance.

[0008] As an embodiment of the present application, the determining of the first minimum inertia demand of the wind storage system based on the frequency rate of change constraint in the method comprises: calculating the first minimum inertia demand that satisfies a frequency rate of change safety requirement according to a system frequency response equation and in combination with a preset maximum allowed value of the frequency rate of change.

[0009] The system frequency response equation is:

[0010] 2H s df / dt = - ΔP d ;

[0011] wherein H S is a system inertia time constant, f is a frequency, and ΔP d is a disturbance power.

[0012] The first minimum inertia demand is:

[0013]

[0014] wherein H Smin1 is the first minimum inertia demand, and f max is the maximum allowed value of the frequency rate of change.

[0015] As an embodiment of the present application, the determining of the second minimum inertia demand of the wind storage system based on the frequency change constraint in the method comprises: calculating the second minimum inertia demand that satisfies a frequency change safety requirement according to a system frequency response model containing wind power and in combination with a preset maximum allowed value of the frequency change.

[0016] The system frequency response model is:

[0017]

[0018] where H Smin2 is the second minimum inertia requirement, ΔP d is the disturbance power, Δf max is the system frequency change, F1 is H smin2 as a function of ΔP d and Δf max , F2 is ΔP d as a function of H smin2 and Δf max .

[0019] As an embodiment of the present application, the fan speed safety constraint in the above method is:

[0020]

[0021] where Δω max1 is the maximum change in fan speed under the speed safety constraint; ω r0 is the initial fan speed value; ω rmax is the maximum speed when the fan is running safely; ω rmin is the minimum speed when the fan is running safely;

[0022] The output power constraint is:

[0023]

[0024] where P ew is the fan output electromagnetic power; k opt is the maximum power tracking proportionality coefficient; ω0 is the cut-in speed of the fan entering the maximum power tracking zone; P n is the rated power of the fan; ω r is the rotor speed;

[0025] The maximum virtual inertia that the fan can provide is evaluated by:

[0026]

[0027] H vw_max is the maximum inertia time constant of the fan, H w is the virtual inertia time constant of the fan, ω e is the synchronous angular velocity, t h is the inertia response time required when the frequency drops to the minimum value, v min is the minimum wind speed, v max is the maximum wind speed.

[0028] As an embodiment of the present application, the evaluation of the virtual inertia that the energy storage can provide at the time of disturbance based on the output power upper limit of the energy storage and the inertia response time in the above method includes:

[0029] The energy storage is equivalent to a synchronous generator, and a virtual rotor motion equation of the energy storage is obtained:

[0030]

[0031] Wherein, H vB is a virtual inertia time constant of the energy storage, ω is a virtual rotor speed of the energy storage after being equivalent to a synchronous generator, P mB , P eB are respectively a mechanical power and an electromagnetic power of the energy storage after being equivalent to a synchronous generator.

[0032] In an inertia response time, the virtual rotor motion equation is integrated on both sides to obtain a virtual inertia provided by the energy storage in a disturbance:

[0033]

[0034] Wherein, ω is a virtual rotor speed of the energy storage after being equivalent to a synchronous generator, ω0 is an initial value, ω1 is a measured value, t h is an inertia response time required when the frequency drops to a minimum value.

[0035] According to a second aspect of the present application, a device for distributing inertia demand of a wind energy storage system is provided, the device comprising: a first demand determining unit configured to determine a first minimum inertia demand of the wind energy storage system based on a frequency rate constraint; a second demand determining unit configured to determine a second minimum inertia demand of the wind energy storage system based on a frequency variation constraint; a minimum demand determining unit configured to select a larger value between the first minimum inertia demand and the second minimum inertia demand as a minimum inertia demand of the wind energy storage system, and select the first minimum inertia demand as the minimum inertia demand of the wind energy storage system if the first minimum inertia demand and the second minimum inertia demand are equal; a wind turbine evaluating unit configured to evaluate a maximum virtual inertia provided by the wind turbine based on a wind turbine speed safety constraint and an output power constraint; an energy storage evaluating unit configured to evaluate a virtual inertia provided by the energy storage in a disturbance based on an output power upper limit of the energy storage and an inertia response time; and an inertia distributing unit configured to distribute the inertia demand based on the minimum inertia demand, the maximum virtual inertia provided by the wind turbine, and the virtual inertia provided by the energy storage in the disturbance.

[0036] As an embodiment of the present application, the first demand determining unit is specifically configured to calculate the first minimum inertia demand satisfying a frequency rate safety requirement according to a system frequency response equation and in combination with a preset maximum allowed value of the frequency rate.

[0037] The system frequency response equation is:

[0038] 2H s df / dt = - ΔP d ;

[0039] wherein H S is a system inertia time constant, f is a frequency, and ΔP d is a disturbance power;

[0040] The first minimum inertia requirement is:

[0041]

[0042] wherein H Smin1 is the first minimum inertia requirement, f max is a maximum allowed value of a frequency change rate.

[0043] As an embodiment of the present application, the second requirement determining unit is specifically configured to: according to a system frequency response model containing wind power, in combination with a preset maximum allowed value of a frequency change amount, calculate a second minimum inertia requirement that meets a frequency change amount safety requirement.

[0044] The system frequency response model is:

[0045]

[0046] wherein H Smin2 is the second minimum inertia requirement, ΔP d is a disturbance power, and Δf max is a system frequency change amount, F1 is H smin2 a function of ΔP d and Δf max , and F2 is ΔP d a function of H smin2 and Δf max .

[0047] As an embodiment of the present application, the wind turbine speed safety constraint is:

[0048]

[0049] wherein Δω max1 is a maximum change value of the wind turbine speed under the speed safety constraint, ω r0 is an initial speed value of the wind turbine, ω rmax is a maximum speed during safe operation of the wind turbine, and ω rmin is a minimum speed during safe operation of the wind turbine.

[0050] The output power constraint is:

[0051]

[0052] wherein P ew is an output electromagnetic power of the wind turbine, and k optis a maximum power tracking proportional coefficient; ω0is a cut-in speed of the wind turbine entering a maximum power tracking area; P n is a rated power of the wind turbine; ω r is a rotor speed;

[0053] The maximum virtual inertia that the wind turbine can provide is evaluated by the following formula:

[0054]

[0055] wherein H vw_max is a maximum inertia time constant of the wind turbine, H w is a virtual inertia time constant of the wind turbine, ω e is a synchronous angular velocity, t h is an inertia response time required when the frequency drops to the minimum value, v min is a minimum wind speed, v max is a maximum wind speed.

[0056] As an embodiment of the present application, the above-mentioned energy storage evaluation unit evaluates the virtual inertia that the energy storage can provide at the time of disturbance based on the output power upper limit of the energy storage and the inertia response time, and includes:

[0057] The energy storage is equivalent to a synchronous generator to obtain a virtual rotor motion equation of the energy storage:

[0058]

[0059] wherein H vB is a virtual inertia time constant of the energy storage; ω is a virtual rotor speed of the energy storage after being virtually a synchronous generator; P mB , and P eB are a mechanical power and an electromagnetic power of the energy storage after being virtually a synchronous generator, respectively;

[0060] The virtual rotor motion equation is integrated on both sides within the inertia response time to obtain the virtual inertia that the energy storage can provide at the time of disturbance:

[0061]

[0062] wherein ω is a virtual rotor speed of the energy storage after being virtually a synchronous generator, ω0is an initial value, ω1is a measured value, and t h is an inertia response time required when the frequency drops to the minimum value.

[0063] According to a third aspect of the present application, an electronic device is provided, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the above-mentioned method when executing the computer program.

[0064] According to a fourth aspect of the present application, a computer readable storage medium is provided, which stores a computer program, and the computer program, when executed by a processor, implements the steps of the above method.

[0065] The method and device for distributing inertia demand of the wind storage system provided by the application take the frequency change rate and the frequency change amount as core parameters for evaluating the inertia demand of the system, obtain the minimum inertia demand associated with the frequency change rate and the frequency change amount respectively, and obtain the final inertia demand of the wind storage system by comprehensively considering the two minimum inertia demand values. In this process, the application considers the virtual inertia demand under the constraints of the wind turbine speed and the output power change amount to avoid the operation risk of the wind turbine after the additional virtual inertia control, reduce the online monitoring demand, complete the frequency early warning, improve the reliability of the inertia support of the wind power, and complete the inertia demand distribution of the wind power and the energy storage. The application can effectively reflect the sensitivity and stability of the system to the frequency change, and provide a solid foundation for formulating and optimizing the new energy frequency modulation strategy. BRIEF DESCRIPTION OF DRAWINGS

[0066] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description only constitute some embodiments of the application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative labor. In the drawings:

[0067] Figure 1 is a flowchart of a method for distributing inertia demand of a wind storage system provided by an embodiment of the application;

[0068] Figure 2 is a schematic diagram of the evaluation result of the system inertia demand under the constraint of the frequency change rate provided by an embodiment of the application;

[0069] Figure 3 is a schematic diagram of the evaluation result of the system inertia under the constraint of the frequency change amount provided by an embodiment of the application;

[0070] Figure 4 is a schematic diagram of the change amount of the wind turbine speed under the safety constraint provided by an embodiment of the application;

[0071] Figure 5 is a schematic diagram of various responses under different control modes provided by an embodiment of the application;

[0072] Figure 6 is a structural schematic diagram of a device for distributing inertia demand of a wind storage system provided by an embodiment of the application;

[0073] Figure 7 is a structural schematic diagram of an electronic device provided by an embodiment of the application. DETAILED DESCRIPTION

[0074] In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, further detailed description of the embodiments of the present application will be given below with reference to the drawings. Herein, the illustrative embodiments of the present application and the description thereof are used to explain the present application but not to limit the present application.

[0075] As Figure 1 shown is a flowchart of a method for distributing inertia demand of a wind storage system according to an embodiment of the present application. The method comprises the following steps:

[0076] Step S101: determining a first minimum inertia demand of the wind storage system based on a frequency rate of change constraint.

[0077] This step aims to calculate the minimum inertia required for the wind storage system to meet the safety requirement of the frequency rate of change, so as to ensure that the frequency rate of change does not exceed the safety limit when a disturbance occurs.

[0078] Step S102: determining a second minimum inertia demand of the wind storage system based on a frequency change constraint.

[0079] This step is similar to step S101, but focuses on the frequency change rather than the rate of change. This step ensures that the frequency change does not exceed the safety limit when a disturbance occurs, and more comprehensively considers the stability of the system.

[0080] Step S103: selecting the larger value between the first minimum inertia demand and the second minimum inertia demand as the minimum inertia demand of the wind storage system, and if the first minimum inertia demand and the second minimum inertia demand are equal, selecting the first minimum inertia demand as the minimum inertia demand of the wind storage system.

[0081] This step compares the two minimum inertia demands calculated in steps S101 and S102, and selects the larger value as the final minimum inertia demand of the wind storage system. This is because only when both the frequency rate of change and the frequency change constraints are met can the safe and stable operation of the system be ensured, and if the two values are equal, either one of them is selected as the final result.

[0082] Step S104: evaluating the maximum virtual inertia that can be provided by the wind turbine based on the wind turbine speed safety constraint and the output power constraint.

[0083] This step evaluates the maximum virtual inertia that can be provided by the wind turbine, taking into account the operating constraints of the wind turbine. The specific method is: according to the upper and lower constraints of the wind turbine speed safety and the output power constraint of the wind turbine, the maximum virtual inertia that can be provided by the wind turbine is evaluated.

[0084] Step S105: based on the output power upper limit of the energy storage and the inertia response time, evaluating the virtual inertia that the energy storage can provide during the disturbance.

[0085] The energy capacity and the power capacity of the energy storage are both key parameters of the energy storage, and generally the energy storage is required to have a charging and discharging duration of not less than 2-3 hours. Since the frequency response duration of the system is short, theoretically the energy reserve of the energy storage can meet the frequency modulation demand of the system, so the power configuration of the energy storage will be the main constraint index for measuring the inertia support thereof. In order to fully exert the frequency support potential of the energy storage, the present application evaluates the virtual inertia that the energy storage can provide during the disturbance based on the output power upper limit of the energy storage and the inertia response time.

[0086] Step S106: allocating the inertia demand based on the minimum inertia demand, the maximum virtual inertia that the wind turbine can provide and the virtual inertia that the energy storage can provide during the disturbance.

[0087] This step allocates the inertia demand according to the minimum inertia demand of the wind- energy storage system determined in step S103, and the maximum virtual inertia that the wind turbine and the energy storage can provide evaluated in steps S104 and S105. The allocation strategy can be optimized according to the characteristics and operating state of the wind turbine and the energy storage, for example, the virtual inertia is preferentially provided by the wind turbine, and when the inertia provided by the wind turbine is insufficient, the energy storage is used to supplement. The goal of the allocation is to ensure that the total virtual inertia of the wind- energy storage system meets the minimum inertia demand, and maximizes the frequency response capability of the wind- energy storage system.

[0088] Preferably, the determination of the first minimum inertia demand of the wind- energy storage system based on the frequency change rate constraint in step S101 can specifically include: calculating the first minimum inertia demand under the safety requirement of the frequency change rate according to the system frequency response equation and in combination with the preset maximum allowed value of the frequency change rate.

[0089] At the initial stage of the disturbance, the unbalanced power of the wind- energy storage system mainly comes from the disturbance power ΔP d At this time, the frequency response equation can be expressed as:

[0090] 2H s df / dt = - ΔP d (1)

[0091] In the above formula, Hs is the inertia time constant of the system, f is the frequency, and ΔP d is the disturbance power.

[0092] Therefore, under the safety requirement of the frequency change rate, the minimum inertia demand of the system can be expressed as:

[0093]

[0094] In the above formula, H Smin1 is the first minimum inertia demand, and f is the frequency change rate.max This is the maximum permissible value for the rate of change of frequency.

[0095] According to equation (2) above, under the constraints of frequency change rate and disturbance, the minimum inertia requirement of the wind-storage system can be evaluated, such as Figure 2 As shown. In a certain regional power grid, based on system operating conditions and data, if the estimated disturbance power does not exceed 10% of the total capacity, i.e., ΔP d =0.1pu Under this condition, once the maximum allowable frequency change rate is set, the minimum inertia requirement of the wind-storage system can be obtained. Referring to existing regulations, in this embodiment, the maximum allowable frequency change rate is set to 0.5Hz / s, i.e. Therefore, the system's inertia requirement is 5s under the constraint of the rate of change of frequency.

[0096] Preferably, the determination of the second minimum inertia requirement of the wind-storage system based on the frequency change constraint in step S102 may specifically include: calculating the second minimum inertia requirement that meets the frequency change safety requirements based on the system frequency response model containing wind power and the preset maximum allowable value of frequency change.

[0097] Even under abnormal conditions, the frequency deviation of a power system should remain within the required operating range. The power imbalance is most severe in the initial stage of a disturbance, at which point the rate of frequency change is primarily determined by the system inertia. However, in the dynamic process following the initial disturbance, the system frequency change Δf... max It is closely related to many parameters, such as wind power penetration rate ρ and power disturbance ΔP. d The system inertial time constant Hs, synchronous machine parameters, etc. Calculation of frequency changes requires establishing a system frequency response model including wind power. The functional relationship of the system frequency response model established in this application can be expressed as:

[0098]

[0099] Among them, H Smin2 For the second minimum inertia requirement, ΔP d Let Δf be the disturbance power. max F1 is the system frequency change, where H is the frequency change. Smin2 Regarding ΔP d and Δf max The function, F2 is ΔP d Regarding H smin2 and Δf max The function.

[0100] According to the equations of the frequency response model, the functions F1, F2 and ΔP d , Δf max and H Smin2 Related. Wherein, Δf maxThe frequency safety regulation can be determined, and the function relationship between the power disturbance amount and the system inertia demand can be established through functions F1 and F2, and then the system inertia demand evaluation process under the frequency change constraint is completed.

[0101] According to formula (3), under the frequency change constraint, the inertia demand of the wind storage system under the constraint can be evaluated according to the grid new energy penetration rate and the disturbance power. The wind power penetration rate is set to 50%, the synchronous machine inertia time constant is generally taken as 5-10s, ΔPd is taken as 0.14-0.16pu, Δf max is taken as 0.9-1Hz, the evaluation result is as shown in Figure 3 , and the system demand under the frequency change constraint can be obtained. If ΔP d =0.144pu, Δf max =1Hz, the system inertia demand under the frequency change constraint is 5s. After meeting the demand, the fluctuation amplitude of the system frequency can be limited.

[0102] At the same time, the frequency change rate and the change constraint are met, the inertia demand H smin of the wind storage system is taken as two larger evaluation results, which can be expressed as

[0103] H smin = max(H smin1 ,H smin2 ) (4)

[0104] According to formulas (2), (3) and (4), the power supply needs to provide necessary inertia support to ensure frequency safety. However, the grid connection of new energy makes it difficult to meet the safety requirements of system frequency change rate and change. At present, although virtual inertia control has been proposed, the wind and storage inertia demand has not been clearly defined, resulting in insufficient basis for parameter design of additional controllers. Therefore, the wind and storage inertia demand is further defined through subsequent steps S104-S106, and the demand allocation is performed.

[0105] Preferably, in step S104, the maximum virtual inertia that can be provided by the wind turbine is evaluated based on the wind turbine speed safety constraint and the output power constraint, because the virtual inertia of the wind turbine is closely related to its own operating state and system frequency. Therefore, to avoid the operating risk of the wind turbine after adding the virtual inertia control, reduce the online monitoring demand, complete the frequency early warning, and analyze the virtual inertia demand under the wind turbine speed and output power constraints, the reliability of the wind power inertia support can be improved.

[0106] The wind turbine speed safety constraint and the output power constraint in step S104 will be introduced below:

[0107] (1) Wind turbine speed safety constraint

[0108] When the power system is disturbed, the wind turbine needs to release kinetic energy to compensate for the lack of system power. When the disturbance power ΔP d is positive, i.e. the system power is insufficient, the wind turbine needs to release its stored kinetic energy to make up for the unbalanced power, resulting in a decrease in rotor speed ω r . Conversely, when the disturbance power ΔP d is negative, i.e. the system power is excessive, the wind turbine needs to absorb the excess energy and convert it into kinetic energy, so that the rotor speed ω r increases. To ensure the stable operation of the wind turbine under different disturbance conditions, its speed must meet certain constraints, which can be expressed in mathematical form. These constraints are of great significance to the safe and stable operation of the wind turbine and the frequency regulation of the power system. Therefore, the wind turbine speed safety constraint in the embodiment can be expressed as formula (5) below:

[0109]

[0110] where Δω max1 is the maximum change in wind turbine speed under speed safety constraints; ω r0 is the initial speed value of the wind turbine; ω rmax is the maximum speed of the wind turbine in safe operation; and ω rmin is the minimum speed of the wind turbine in safe operation.

[0111] (2) Output power constraint

[0112] To ensure the safe operation of the wind turbine, the output power needs to be limited within the constraint range. The wind turbine output power constraint can be expressed as:

[0113]

[0114] where P ew is the electromagnetic power output of the wind turbine; k opt is the maximum power tracking proportionality coefficient; ω0 is the cut-in speed of the wind turbine entering the maximum power tracking zone; P n is the rated power of the wind turbine; and ω r is the rotor speed.

[0115] According to formula (6), the power support limit of the wind turbine under power constraints can be expressed as:

[0116]

[0117] When the wind turbine participates in inertia response, its rotor motion equation can be expressed as:

[0118] ΔP w = P mw - P ew = 2H w ω r dωr / dt (8)

[0119] where ΔP w , P mw and P ew are the power variation, mechanical power and electromagnetic power of the fan respectively, and H w is the inherent inertia time constant of the fan.

[0120] According to equations (7) and (8), the maximum speed variation Δω max2 of the fan in the inertia response time can be obtained by integrating both sides of the equation under the power constraint, and is expressed as:

[0121]

[0122] To meet the above two constraints simultaneously, the maximum speed variation of the fan should take the minimum value of the two. Taking a 2MW fan as an example, H w = 4s, k opt = 1 / (1.23), ω rmax = 1.2pu, ω rmin = 0.8pu, t h = 3.09s, the maximum speed variation Δω max of the fan under different initial speeds can be obtained according to equations (5) and (9), as shown in FIG. 1. Figure 4 Figure 4 is the speed variation diagram when ΔP d > 0 and ΔP d < 0. Taking ΔP d > 0 as an example, when ω r0 is small, the kinetic energy reserve of the fan rotor is insufficient, but there is sufficient power support margin, and Δω max is mainly limited by the speed safety constraint; when ω r0 > 0.989pu, the kinetic energy reserve of the fan rotor is sufficient, but the power support margin is insufficient, and Δω r0 is mainly limited by the fan power constraint. When ω max = 0.989pu, Δω d can reach a maximum value of 0.189pu.

[0123] Similarly, when ΔP d < 0 and ω r0 is small, Δω max depends on the fan power constraint; when ω r0 > 1.063pu, Δω max depends on the speed safety constraint. And when ω r0 = 1.063pu, Δω max can reach a maximum value of 0.137pu.

[0124] Taking frequency drop as an example, combining formula (5) and (9), Δω max may be expressed as:

[0125]

[0126] Under the frequency deviation constraint condition of 1 Hz, the change range of synchronous angular frequency is 0.98-1 pu, in order to conservatively evaluate the virtual inertia of the fan, Δω e = 0.02, according to formula (10), the maximum virtual inertia of the fan can be expressed as:

[0127]

[0128] wherein, H vw_max is the maximum inertia time constant of the fan, H w is the virtual inertia time constant of the fan, ω e is the synchronous angular velocity, t h is the inertia response time required when the frequency drops to the minimum value, v min is the minimum wind speed, v max is the maximum wind speed, v h = 0.989ω e ·R t / (λ opt p n N t ), λ opt is the optimal tip speed ratio of the fan, N t is the gear ratio of the fan gearbox, R t is the radius of the fan blade, p n is the number of pole pairs of the fan.

[0129] Preferably, the virtual inertia that the energy storage can provide during the disturbance based on the output power upper limit of the energy storage and the inertia response time in the above step S105 can include:

[0130] The energy storage is equivalent to a synchronous generator, and the virtual rotor motion equation of the energy storage is obtained:

[0131]

[0132] wherein, H vB is the virtual inertia time constant of the energy storage; ω is the virtual rotor speed of the energy storage after being virtually synchronized as a synchronous generator; P mB , P eB are the mechanical power and electromagnetic power of the energy storage after being virtually synchronized as a synchronous generator respectively.

[0133] During the inertia response time, the above formula (12) is integrated on both sides to obtain the virtual inertia that the energy storage can provide during the disturbance:

[0134]

[0135] Wherein: ω is the virtual rotor speed after the energy storage virtual synchronous machine, ω0 is the initial value, ω1 is the measured value, t h is the inertia response time required when the frequency drops to the minimum value.

[0136] According to formula (13), the upper limit of the energy storage output power is closely related to the virtual inertia reserve, which can be constrained by power limitation in inertia evaluation. In order to realize offline calculation and complete frequency early warning in advance, formula (13) can be used in actual operation to conservatively evaluate the virtual inertia of the energy storage according to the power reserve of the energy storage under the condition of frequency constraint, so as to reduce the demand for online real-time test and facilitate the distribution of wind storage inertia.

[0137] As can be seen from the above, the distribution method of the inertia demand of the wind storage system proposed in the application takes the frequency change rate and the frequency change as the core parameters for evaluating the system inertia demand, obtains the minimum inertia demand associated with the frequency change rate and the frequency change respectively, and obtains the final inertia demand of the wind storage system by comprehensively considering the two minimum inertia demand values. In this process, the application avoids the operation risk of the wind turbine after adding virtual inertia control, reduces the demand for online monitoring, completes the frequency early warning, considers the virtual inertia demand under the constraint of the wind turbine speed and the output power change, improves the reliability of the wind power inertia support, and completes the distribution of the wind power and the inertia demand of the energy storage. The application can effectively reflect the sensitivity and stability of the system to frequency change, and provide a solid foundation for formulating and optimizing the new energy frequency modulation strategy.

[0138] The above effects will be further described through a specific example as follows:

[0139] Taking ΔP d >0 as an example, ρ=50%, the reference wind turbine parameters, for the selection of wind speed, the wind speed is 8m / s in this paper. According to the real-time wind speed calculation formula, the initial speed of the wind turbine ω r0 =0.84pu can be obtained, and the maximum virtual inertia H vw_max , H vB_max of the wind and the storage are 6.7s and 3.9s respectively. The disturbance reference power ΔP d1 is 0.08pu, and ΔP d2 is 0.147pu.

[0140] Under the wind cooperative control strategy, the disturbance load suddenly increases by 0.15pu, and according to the system inertia evaluation result graph, the minimum inertia demand H smin of the system is 7.5s, and since ΔP d >ΔP d2At this time, the energy storage should also have the ability of active frequency support, and the synchronous generator and the wind turbine complete the inertia support of the system. According to the frequency modulation instruction and the simulation parameters, the inertia response time of the system is 4.80s.

[0141] From Figure 5 (a), when the inertia control is not added, the inertia response time is 3.16s, which is consistent with the theoretical calculation value. At the initial moment of the disturbance, the frequency change rate of the system is 0.90Hz / s, and the frequency drop depth Δfh is 1.12Hz, which does not meet the frequency safety constraint.

[0142] If the differential inertia control is used, under the inertia support of the wind turbine and the energy storage, the frequency drop amplitude Δfh of the system is 1.03Hz, and the frequency drop speed at the initial moment of the disturbance is 0.75Hz / s. Compared with no control, the control effect is improved to a certain extent, but it still cannot meet the frequency safety constraint. During the frequency recovery period, the wind and the storage do not have timely closed-loop control, which leads to difficult frequency recovery and large overshoot.

[0143] If the collaborative control strategy is used in the wind storage system, the frequency drop depth Δfh of the system is 0.92Hz, and the maximum frequency change rate is 0.49Hz / s, which meets the preset frequency safety requirement. According to the simulation result in Figure 5 (b), Δωr=0.037, pu=11.62rad / s, which is close to the evaluation result of the maximum change amount of the rotating speed Δω max , so the maximum potential of the new energy to rapidly respond to the frequency is stimulated, and H vw =6.76s can be obtained. Further, Hs=7.58s is greater than H smin 7.5, and Hs is the inertia time constant of the system, which is the virtual inertia time constant of the wind power plus the virtual inertia time constant of the energy storage.

[0144] The inertia demand of the system has been met. In addition, the inertia response time th is 4.81s, which is consistent with the calculation result. During the frequency recovery stage, the overshoot amount of the system frequency is obviously reduced because the wind storage additional controller is closed in time after the inertia response time is reached.

[0145] As Figure 6 shown is a structure schematic diagram of a wind storage system inertia demand distribution device provided by an embodiment of the application, the device comprises: a first demand determining unit 610, a second demand determining unit 620, a minimum demand determining unit 630, a wind turbine evaluation unit 640, an energy storage evaluation unit 650 and an inertia distribution unit 660, which are sequentially connected. Wherein:

[0146] The first demand determining unit 610 is configured to determine a first minimum inertia demand of the wind storage system based on a frequency change rate constraint.

[0147] The second demand determining unit 620 determines a second minimum inertia demand of the wind storage system based on the frequency variation constraint.

[0148] The minimum demand determining unit 630 selects a larger value between the first minimum inertia demand and the second minimum inertia demand as the minimum inertia demand of the wind storage system, and selects the first minimum inertia demand as the minimum inertia demand of the wind storage system if the first minimum inertia demand is equal to the second minimum inertia demand.

[0149] The wind turbine evaluating unit 640 evaluates a maximum virtual inertia that can be provided by the wind turbine based on the wind turbine rotating speed safety constraint and the output power constraint.

[0150] The energy storage evaluating unit 650 evaluates a virtual inertia that can be provided by the energy storage during the disturbance based on the output power upper limit of the energy storage and the inertia response time.

[0151] The inertia distribution unit 660 distributes the inertia demand based on the minimum inertia demand of the system, the maximum virtual inertia that can be provided by the wind turbine, and the virtual inertia that can be provided by the energy storage during the disturbance.

[0152] Preferably, the first demand determining unit 610 is specifically configured to: calculate the first minimum inertia demand that meets the frequency variation rate safety requirement according to a system frequency response equation and in combination with a preset maximum allowed value of the frequency variation rate.

[0153] The system frequency response equation is:

[0154] 2H s df / dt=-ΔP d ;

[0155] wherein H S is a system inertia time constant, f is a frequency, and ΔP d is a disturbance power.

[0156] The first minimum inertia demand is:

[0157]

[0158] wherein H Smin1 is the first minimum inertia demand, and f max is the maximum allowed value of the frequency variation rate.

[0159] Preferably, the second demand determining unit 620 is specifically configured to: calculate the second minimum inertia demand that meets the frequency variation safety requirement according to a system frequency response model containing wind power and in combination with a preset maximum allowed value of the frequency variation.

[0160] The system frequency response model is:

[0161]

[0162] where H Smin2 is the second minimum inertia demand, ΔP d is the disturbance power, Δf max is the system frequency variation, F1 is H smin2 as a function of ΔP d and Δf max , F2 is ΔP d as a function of H smin2 and Δf max .

[0163] Preferably, the above-mentioned fan speed safety constraint is:

[0164]

[0165] where Δω max1 is the maximum variation of the fan speed under the speed safety constraint; ω r0 is the initial speed value of the fan; ω rmax is the maximum speed of the fan when it is operating safely; ω rmin is the minimum speed of the fan when it is operating safely;

[0166] The output power constraint is:

[0167]

[0168] where P ew is the electromagnetic output power of the fan; k opt is the maximum power tracking proportionality coefficient; ω0 is the cut-in speed of the fan entering the maximum power tracking zone; P n is the rated power of the fan; ω r is the rotor speed;

[0169] The maximum virtual inertia that the fan can provide is evaluated by:

[0170]

[0171] where H vw_max is the maximum inertia time constant of the fan, H w is the virtual inertia time constant of the fan, ω e is the synchronous angular speed, t h is the inertia response time required when the frequency drops to the minimum value, v min is the minimum wind speed, v max is the maximum wind speed.

[0172] Preferably, the energy storage evaluation unit 650 evaluates the virtual inertia provided by the energy storage during the disturbance based on the upper limit of the output power of the energy storage and the inertia response time, and the evaluation includes:

[0173] The energy storage is equivalent to a synchronous generator, and a virtual rotor motion equation of the energy storage is obtained:

[0174]

[0175] Wherein, H vB is a virtual inertia time constant of the energy storage; ω is a virtual rotor speed of the energy storage after being virtually connected to a synchronous generator; P mB , P eB are mechanical power and electromagnetic power of the energy storage after being virtually connected to the synchronous generator, respectively.

[0176] During the inertia response time, the virtual rotor motion equation is integrated on both sides to obtain the virtual inertia provided by the energy storage during the disturbance:

[0177]

[0178] Wherein, ω is a virtual rotor speed of the energy storage after being virtually connected to a synchronous generator, ω0 is an initial value, ω1 is a measured value, t h is an inertia response time required when the frequency drops to the minimum value.

[0179] Detailed descriptions of the above units can be referred to the corresponding descriptions in the foregoing method embodiments, and will not be described here.

[0180] As can be seen from the above, the wind storage system inertia demand distribution device provided by the application takes the frequency change rate and the frequency change amount as core parameters for evaluating the system inertia demand, obtains the minimum inertia demand associated with the frequency change rate and the frequency change amount respectively, and obtains the final inertia demand of the wind storage system by comprehensively considering the two minimum inertia demand values. In this process, the application avoids the operation risk of the wind turbine after the additional virtual inertia control, reduces the online monitoring demand, completes the frequency early warning, considers the virtual inertia demand under the constraint of the wind turbine speed and the output power change amount, improves the reliability of the wind power inertia support, and completes the wind power and energy storage inertia demand distribution. The application can effectively reflect the sensitivity and stability of the system to the frequency change, and provides a solid foundation for formulating and optimizing the new energy frequency modulation strategy.

[0181] Figure 7 is a schematic diagram of an electronic device provided by an embodiment of the application. Figure 7The electronic device shown is a general data processing device, which includes a general computer hardware structure, at least including a processor 801 and a memory 802. The processor 801 and the memory 802 are connected through a bus 803. The memory 802 is suitable for storing one or more instructions or programs executable by the processor 801. The one or more instructions or programs are executed by the processor 801 to implement the steps in the above-mentioned wind storage system inertia demand allocation method.

[0182] The above-mentioned processor 801 can be a stand-alone microprocessor, or a set of one or more microprocessors. Thus, the processor 801 performs processing of data and control of other devices by executing commands stored in the memory 802, thereby implementing the method flow of the embodiments of the application as described above. The bus 803 connects the above-mentioned components together, while connecting the above-mentioned components to a display controller 804 and a display device, and an input / output (I / O) device 805. The input / output (I / O) device 805 can be a mouse, a keyboard, a modem, a network interface, a touch input device, a body-sensing input device, a printer, and other devices known in the art. Typically, the input / output (I / O) device 805 is connected to the system through an input / output (I / O) controller 806.

[0183] The memory 802 can store software components, such as an operating system, a communication module, an interaction module, and an application program. Each of the above-mentioned modules and application programs corresponds to a set of executable program instructions for completing one or more functions and the methods described in the embodiments of the application.

[0184] The embodiments of the application also provide a computer readable storage medium, which stores a computer program, the computer program being executed by a processor to implement the steps of the above-mentioned wind storage system inertia demand allocation method.

[0185] The wind storage system inertia demand allocation method and device provided by the application take the frequency change rate and the frequency change amount as the core parameters for evaluating the system inertia demand, respectively obtain the minimum inertia demand associated with the frequency change rate and the frequency change amount, and obtain the final inertia demand of the wind storage system by comprehensively considering the two minimum inertia demand values. In this process, the application avoids the operation risk after the additional virtual inertia control of the wind turbine, reduces the online monitoring demand, completes the frequency early warning, considers the virtual inertia demand under the constraints of the wind turbine speed and the output power change amount, improves the reliability of the wind power inertia support, and completes the wind power and energy storage inertia demand allocation. The application can effectively reflect the sensitivity and stability of the system to frequency change, and provide a solid foundation for formulating and optimizing the new energy frequency modulation strategy.

[0186] The preferred embodiments of the application are described above with reference to the accompanying drawings. Many features and advantages of the embodiments are apparent from the detailed specification, and it is therefore intended by the appended claims to cover all such features and advantages of the embodiments within their true spirit and scope. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the embodiments of the present application to the exact construction and operation

[0187] Those skilled in the art will appreciate that embodiments of the present application can be devised for a method, a system, or a computer program product. Accordingly, the present application can take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application can take the form of a computer program product on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROMs, optical storage devices, etc.) embodying computer-readable program code.

[0188] The present application is described herein with reference to the flowchart illustrations and / or block diagrams of the methods, apparatus (systems) and computer program products according to embodiments of the application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general purpose computer, special purpose computer, embedded processing system or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart Figure 1 one or more functions specified in the flowchart block or blocks. Figure 1 means for performing each of the functions specified in the flowchart block or blocks.

[0189] These computer program instructions can also be stored in a computer- readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instructions which implement the flowchart Figure 1 one or more functions specified in the flowchart block or blocks. Figure 1 means for performing each of the functions specified in the flowchart block or blocks.

[0190] These computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the flowchart Figure 1 one or more functions specified in the flowchart block or blocks. Figure 1 means for performing each of the functions specified in the flowchart block or blocks.

[0191] The above-described specific embodiments further illustrate the objects, technical solutions and advantages of the present application. It should be understood that the above-described specific embodiments are merely for the purpose of illustrating the present application, and are not intended to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for allocating the inertia requirement of a wind-storage system, characterized in that, The method includes: The first minimum inertia requirement of the wind storage system is determined based on the frequency change rate constraint. The second minimum inertia requirement of the wind storage system is determined based on the frequency change constraint. The larger of the first minimum inertia requirement and the second minimum inertia requirement is selected as the minimum inertia requirement of the wind storage system. If the first minimum inertia requirement and the second minimum inertia requirement are equal, the first minimum inertia requirement is selected as the minimum inertia requirement of the wind storage system. Based on the wind turbine speed safety constraints and output power constraints, the maximum virtual inertia that the wind turbine can provide is evaluated; Based on the upper limit of energy storage output power and inertial response time, evaluate the virtual inertia that energy storage can provide under disturbance; The inertia requirement is allocated based on the minimum inertia requirement, the maximum virtual inertia that the wind turbine can provide, and the virtual inertia that the energy storage can provide during disturbances.

2. The method for allocating the inertia requirement of a wind-storage system as described in claim 1, characterized in that, The determination of the first minimum inertia requirement of the wind-storage system based on the frequency change rate constraint includes: Based on the system frequency response equation and the preset maximum allowable value of frequency change rate, the first minimum inertia requirement that meets the safety requirements of frequency change rate is calculated. The system frequency response equation is: 2H s df / dt=-ΔP d ; Among them, H S Let f be the system's inertial time constant, f be the frequency, and ΔP be the system's time constant. d The disturbance power; The first minimum inertia requirement is: Among them, H Smin1 For the first minimum inertia requirement, f max This is the maximum permissible value for the rate of change of frequency.

3. The method for allocating the inertia requirement of a wind-storage system as described in claim 1, characterized in that, The determination of the second minimum inertia requirement of the wind storage system based on frequency variation constraints includes: Based on the system frequency response model including wind power, and combined with the preset maximum allowable value of frequency change, the second minimum inertia requirement that meets the safety requirements of frequency change is calculated. The system frequency response model is as follows: Among them, H Smin2 For the second minimum inertia requirement, ΔP d Let Δf be the disturbance power. max F1 is the system frequency change, where H is the frequency change. smin2 Regarding ΔP d and Δf max The function, F2 is ΔP d Regarding H smin2 and Δf max The function.

4. The method for allocating the inertia requirement of a wind-storage system as described in claim 1, characterized in that, The safety constraint on the fan speed is: Where, Δω max1 ω represents the maximum change in fan speed under speed safety constraints. r0 ω is the initial speed of the fan. rmax The maximum operating speed for safe operation of the fan; ω rmin The minimum operating speed for safe operation of the fan; The output power constraint is: Among them, P ew To output electromagnetic power to the fan; k opt ω0 is the maximum power point tracking proportional coefficient; P is the starting speed of the wind turbine when entering the maximum power point tracking region; n The rated power of the fan; ω r This refers to the rotor speed; The maximum virtual inertia that the wind turbine can provide is evaluated by the following formula: Among them, H vw_max H is the maximum inertial time constant of the wind turbine. w Let ω be the virtual inertial time constant of the wind turbine. e For synchronous angular velocity, t h v is the inertial response time required for the frequency to drop to its lowest value. min For minimum wind speed, v max This represents the maximum wind speed.

5. The method for allocating the inertia requirement of a wind-storage system as described in claim 1, characterized in that, The assessment of the virtual inertia that energy storage can provide during disturbances, based on the upper limit of energy storage output power and inertial response time, includes: By equating the energy storage to a synchronous generator, the virtual rotor motion equations of the energy storage can be obtained: Wherein: H vB ω is the virtual inertial time constant of the energy storage; P is the virtual rotor speed after the energy storage is virtualized into a synchronous machine; mB P eB These are the mechanical power and electromagnetic power of the energy storage virtualized as a synchronous machine, respectively. Integrating both sides of the virtual rotor motion equation simultaneously within the inertial response time yields the virtual inertia that the energy storage can provide during disturbance: Where: ω is the virtual rotor speed after the energy storage is simulating a synchronous machine, ω0 is the initial value, ω1 is the measured value, and t is the t value. h This is the inertial response time required for the frequency to drop to its lowest value.

6. A device for distributing the inertia demand of a wind-storage system, characterized in that, The device includes: The first demand determination unit is used to determine the first minimum inertia requirement of the wind storage system based on the frequency change rate constraint. The second requirement determination unit determines the second minimum inertia requirement of the wind storage system based on the frequency change constraint. The minimum requirement determination unit is used to select the larger value between the first minimum inertia requirement and the second minimum inertia requirement as the minimum inertia requirement of the wind storage system. If the first minimum inertia requirement and the second minimum inertia requirement are equal, the first minimum inertia requirement is selected as the minimum inertia requirement of the wind storage system. The wind turbine evaluation unit is used to evaluate the maximum virtual inertia that the wind turbine can provide based on wind turbine speed safety constraints and output power constraints; An energy storage assessment unit is used to assess the virtual inertia that the energy storage can provide during disturbances, based on the upper limit of the energy storage's output power and the inertial response time. An inertia allocation unit is used to allocate inertia requirements based on the minimum inertia requirement, the maximum virtual inertia that the wind turbine can provide, and the virtual inertia that the energy storage can provide during disturbances.

7. The device for distributing the inertia requirement of a wind-storage system as described in claim 6, characterized in that, The first requirement determination unit is specifically used to: calculate the first minimum inertia requirement that meets the safety requirements of the frequency change rate based on the system frequency response equation and the preset maximum allowable value of the frequency change rate; The system frequency response equation is: 2H s df / dt=-ΔP d ; Among them, H S Let f be the system's inertial time constant, f be the frequency, and ΔP be the system's time constant. d The disturbance power; The first minimum inertia requirement is: Among them, H Smin1 For the first minimum inertia requirement, f max This is the maximum permissible value for the rate of change of frequency.

8. The device for distributing the inertia requirement of a wind-storage system as described in claim 6, characterized in that, The second requirement determination unit is specifically used to: calculate the second minimum inertia requirement that meets the safety requirements of frequency change based on the system frequency response model including wind power and the preset maximum allowable value of frequency change; The system frequency response model is as follows: Among them, H Smin2 For the second minimum inertia requirement, ΔP d Let Δf be the disturbance power. max F1 is the system frequency change, where H is the frequency change. smin2 Regarding ΔP d and Δf max The function, F2 is ΔP d Regarding H smin2 and Δf max The function.

9. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the method according to any one of claims 1 to 5.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1 to 5.

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