Distribution method and device for inertia demand of wind storage system

Abstract

The invention provides a method and a device for distributing inertia demands of a wind storage system. The method comprises the following steps: respectively determining a first minimum inertia demand and a second minimum inertia demand of the system based on a frequency change rate and a frequency variation constraint; the larger value in the two is selected as the minimum inertia demand; based on the fan rotating speed safety constraint, the output power constraint, the output power upper limit of the energy storage and the inertia response time, evaluating the maximum virtual inertia provided by the fan and the energy storage; and inertia demand distribution is carried out based on the maximum virtual inertia provided by the fan and the virtual inertia provided by energy storage during disturbance. According to the method, the minimum inertia demand associated with the frequency change rate and the frequency change quantity is obtained through the frequency change rate and the frequency change quantity, the two minimum inertia demand values are comprehensively considered, and the final inertia required by the wind storage system is obtained. In the process, the virtual inertia demand under the constraint of the rotating speed and the output power variation of the wind turbine is also considered, and wind power and energy storage inertia demand distribution is completed.

Description

Technical Field

[0001] The present invention relates to the field of wind power technology, and in particular to a method and device for allocating inertia requirements of a wind power storage system. Background Art

[0002] In power systems with high wind power penetration, the frequency response capability of the system gradually decreases due to the intermittent and unstable nature of wind power. Therefore, the system needs sufficient inertia to cope with the frequency changes caused by wind power fluctuations and ensure the stable operation of the power system. The wind storage system can provide virtual inertia support by combining wind turbines and energy storage devices to meet the inertia requirements of the system.

[0003] At present, there are three main ways to realize the inertia demand of wind-storage systems. The first is to provide virtual inertia of wind turbines. Wind turbines can provide virtual inertia by adjusting their control strategies. For example, in 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. Energy storage devices can play an important role in the wind-storage combined system. Through feedforward feedback control, the rotors of energy storage devices and wind turbines are controlled to generate power increments to meet the inertia response requirements of the system. Intelligent scheduling and optimized control can also be achieved. The wind-storage combined system needs to achieve intelligent scheduling and optimized control to ensure the stable operation of the system. This includes adjusting the charging and discharging strategies of the energy storage system according to the status of wind energy and the power grid, and realizing coordinated control between wind energy and energy storage devices.

[0004] However, the current evaluation methods for the inertia requirements of wind-storage systems still have the following defects: the existing methods mainly rely on the system frequency response model or the maximum allowable value of the frequency change rate, lack of comprehensive consideration, resulting in an incomplete and inaccurate evaluation of the system inertia requirements. When evaluating the inertia requirements of wind-storage systems, the existing methods do not fully consider key constraints such as wind turbine speed safety constraints, power constraints, and the output power upper limit and inertia response time of energy storage, resulting in the evaluation results being overly optimistic or unsafe. Summary of the invention

[0005] In view of this, the present invention provides a method and device for allocating inertia requirements of a wind-storage system to solve at least one of the above-mentioned problems.

[0006] In order to achieve the above object, the present invention adopts the following scheme:

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

[0008] As an embodiment of the present invention, the method for determining the first minimum inertia requirement of the wind-storage system based on the frequency change rate constraint includes: calculating the first minimum inertia requirement that meets the frequency change rate safety requirement according to the system frequency response equation and in combination with a preset maximum allowable value of the frequency change rate;

[0009] The system frequency response equation is:

[0010] 2H s df / dt=-ΔP d ;

[0011] Among them, H S is the system inertia time constant, f is the frequency, ΔP d is the disturbance power;

[0012] The first minimum inertia requirement is:

[0013]

[0014] Among them, H Smin1 is the first minimum inertia requirement, f max It is the maximum allowable value of the frequency change rate.

[0015] As an embodiment of the present invention, the method for determining the second minimum inertia requirement of the wind power storage system based on the frequency variation constraint includes: calculating the second minimum inertia requirement under the frequency variation safety requirement according to a system frequency response model including wind power and a preset maximum allowable value of the frequency variation;

[0016] The system frequency response model is:

[0017]

[0018] Among them, H Smin2 The minimum inertia requirement, ΔP d is the disturbance power, Δf max is the system frequency change, F1 is H smin2 About ΔP d and Δf max function, F2 is ΔP d About H smin2 and Δf max function.

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

[0020]

[0021] Among them, Δω max1 is the maximum change value of the fan speed under the speed safety constraint; ω r0 is the initial speed of the fan; ω rmax The maximum speed of the fan when it is running safely; rmin Minimum speed for safe operation of the fan;

[0022] The output power constraint is:

[0023]

[0024] Among them, P ew is the electromagnetic power output of the fan; k opt is the maximum power tracking proportional coefficient; ω0 is the cut-in speed of the fan when it enters the maximum power tracking area; P n is the rated power of the fan; r is the rotor speed;

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

[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 inertial 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 invention, in the above method, based on the output power upper limit and inertial response time of the energy storage, evaluating the virtual inertia that the energy storage can provide during disturbance includes:

[0029] Equivalently transform the energy storage into a synchronous generator, and obtain the virtual rotor motion equation of the energy storage:

[0030]

[0031] Where: H vB is the virtual inertia time constant of energy storage; ω is the virtual rotor speed after energy storage is virtualized into synchronous machine; P mB , P eB They are the mechanical power and electromagnetic power after the energy storage is virtualized as a synchronous machine;

[0032] During the inertial response time, both sides of the virtual rotor motion equation are integrated simultaneously to obtain the virtual inertia that the energy storage can provide during disturbance:

[0033]

[0034] Where: ω is the virtual rotor speed after energy storage is virtualized into synchronous machine, ω0 is the initial value, ω1 is the measured value, t h It is the inertial response time required when the frequency drops to the minimum value.

[0035] According to a second aspect of the present invention, there is provided an apparatus for allocating inertia requirements of a wind-storage system, the apparatus comprising: a first demand determination unit, for determining a first minimum inertia requirement of the wind-storage system based on a frequency change rate constraint; a second demand determination unit, for determining a second minimum inertia requirement of the wind-storage system based on a frequency change amount constraint; a minimum demand determination unit, for selecting a larger value between the first minimum inertia requirement and the second minimum inertia requirement as the minimum inertia requirement of the wind-storage system, and if the first minimum inertia requirement and the second minimum inertia requirement are equal, selecting the first minimum inertia requirement as the minimum inertia requirement of the wind-storage system; a wind turbine evaluation unit, for evaluating the maximum virtual inertia that can be provided by the wind turbine based on a wind turbine speed safety constraint and an output power constraint; an energy storage evaluation unit, for evaluating the virtual inertia that can be provided by the energy storage during a disturbance based on an output power upper limit and an inertia response time of the energy storage; and an inertia allocation unit, for allocating inertia requirements based on the minimum inertia requirement, 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 a disturbance.

[0036] As an embodiment of the present invention, the first demand determination unit is specifically used to: calculate the first minimum inertia demand under the frequency change rate safety requirement according to the system frequency response equation and the preset maximum allowable value of the frequency change rate;

[0037] The system frequency response equation is:

[0038] 2H s df / dt=-ΔP d ;

[0039] Among them, H S is the system inertia time constant, f is the frequency, ΔP d is the disturbance power;

[0040] The first minimum inertia requirement is:

[0041]

[0042] Among them, H Smin1 is the first minimum inertia requirement, f max It is the maximum allowable value of the frequency change rate.

[0043] As an embodiment of the present invention, the second demand determination unit is specifically used to: calculate the second minimum inertia demand under the frequency variation safety requirement according to the system frequency response model including wind power and the preset maximum allowable value of the frequency variation;

[0044] The system frequency response model is:

[0045]

[0046] Among them, H Smin2 The minimum inertia requirement, ΔP d is the disturbance power, Δf max is the system frequency change, F1 is H smin2 About ΔP d and Δf max function, F2 is ΔP d About H smin2 and Δf max function.

[0047] As an embodiment of the present invention, the above-mentioned fan speed safety constraint is:

[0048]

[0049] Among them, Δω max1 is the maximum change value of the fan speed under the speed safety constraint; ω r0 is the initial speed of the fan; ω rmax The maximum speed of the fan when it is running safely; rmin Minimum speed for safe operation of the fan;

[0050] The output power constraint is:

[0051]

[0052] Among them, P ew is the electromagnetic power output of the fan; k optis the maximum power tracking proportional coefficient; ω0 is the cut-in speed of the fan when it enters the maximum power tracking area; P n is the rated power of the fan; r is the rotor speed;

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

[0054]

[0055] Among them, 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 inertial 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.

[0056] As an embodiment of the present invention, the energy storage evaluation unit evaluates the virtual inertia that the energy storage can provide during disturbance based on the output power upper limit and inertial response time of the energy storage, including:

[0057] Equivalently transform the energy storage into a synchronous generator, and obtain the virtual rotor motion equation of the energy storage:

[0058]

[0059] Where: H vB is the virtual inertia time constant of energy storage; ω is the virtual rotor speed after energy storage is virtualized into synchronous machine; P mB , P eB They are the mechanical power and electromagnetic power after the energy storage is virtualized as a synchronous machine;

[0060] During the inertial response time, both sides of the virtual rotor motion equation are integrated simultaneously to obtain the virtual inertia that the energy storage can provide during disturbance:

[0061]

[0062] Where: ω is the virtual rotor speed after energy storage is virtualized into synchronous machine, ω0 is the initial value, ω1 is the measured value, t h It is the inertial response time required when the frequency drops to the minimum value.

[0063] According to a third aspect of the present invention, there is provided an electronic device, 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 method when executing the computer program.

[0064] According to a fourth aspect of the present invention, there is provided a computer-readable storage medium having a computer program stored thereon, wherein the computer program implements the steps of the above method when executed by a processor.

[0065] The method and device for allocating inertia requirements of a wind energy storage system proposed in the present invention use the frequency change rate and the frequency change amount as the core parameters for evaluating the inertia requirements of the system, respectively obtain the minimum inertia requirements associated therewith through the frequency change rate and the frequency change amount, and comprehensively consider the two minimum inertia requirements to obtain the final required inertia of the wind energy storage system. In this process, in order to avoid the operational risks of wind turbines after additional virtual inertia control, reduce the demand for online monitoring, and complete frequency early warning, the present invention also considers the virtual inertia requirements under the constraints of wind turbine speed and output power change, improves the reliability of wind power inertia support, and completes the allocation of wind power and energy storage inertia requirements. The present application can effectively reflect the sensitivity and stability of the system to frequency changes, and provide a solid foundation for formulating and optimizing new energy frequency regulation strategies. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art descriptions. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. In the drawings:

[0067] Figure 1 It is a flow chart of a method for allocating inertia requirements of a wind storage system provided in an embodiment of the present application;

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

[0069] Figure 3 is a schematic diagram of system inertia evaluation results under frequency variation constraint provided by an embodiment of the present invention;

[0070] Figure 4 is a schematic diagram of the change in fan speed under safety constraints provided in an embodiment of the present application;

[0071] Figure 5 It is a schematic diagram of various responses under different control modes provided in the embodiments of the present application;

[0072] Figure 6 It is a structural schematic diagram of a distribution device for inertia requirements of a wind storage system provided in an embodiment of the present application;

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

[0074] To make the purpose, technical solution and advantages of the embodiments of the present invention more clear, the embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings. Here, the exemplary embodiments of the present invention and their descriptions are used to explain the present invention, but are not intended to limit the present invention.

[0075] like Figure 1 The figure is a flow chart of a method for allocating inertia requirements of a wind energy storage system provided in an embodiment of the present application, the method comprising the following steps:

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

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

[0078] Step S102: Determine the second minimum inertia requirement of the wind energy storage system based on the frequency change constraint.

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

[0080] Step S103: 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, select the first minimum inertia requirement as the minimum inertia requirement of the wind storage system.

[0081] This step compares the two minimum inertia requirements calculated in steps S101 and S102, and selects the larger value as the final minimum inertia requirement of the wind storage system. This is because only by satisfying the constraints of the frequency change rate and the frequency change amount at the same time can the safe and stable operation of the system be ensured. If the two values ​​are equal, any one of them is selected as the final result.

[0082] Step S104: Based on the wind turbine speed safety constraint and the output power constraint, the maximum virtual inertia that the wind turbine can provide is evaluated.

[0083] This step evaluates the maximum virtual inertia that the fan can provide, and needs to consider the operation constraints of the fan. The specific method is: based on the upper and lower limit constraints of the fan speed safety, and the fan output power constraints, the maximum virtual inertia that the fan can provide is evaluated.

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

[0085] Energy storage energy capacity and power capacity are both key parameters of energy storage, and generally require that the energy storage charging and discharging time should be no less than 2 to 3 hours. Since the system frequency response time is short, theoretically the energy reserve of energy storage can meet the frequency regulation requirements of the system, so the power configuration of energy storage will be the main constraint indicator for measuring its inertial support. In order to give full play to the frequency support potential of energy storage, this application evaluates the virtual inertia of energy storage during disturbances based on the output power upper limit and inertial response time of energy storage.

[0086] Step S106: Allocate 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 disturbance.

[0087] This step allocates the inertia demand according to the minimum inertia demand of the wind-storage system determined in step S103 and the maximum virtual inertia that the wind turbine and energy storage can provide as evaluated in steps S104 and S105. The allocation strategy can be optimized according to the characteristics and operating status of the wind turbine and energy storage. For example, the wind turbine is given priority to provide virtual inertia, and when the inertia provided by the wind turbine is insufficient, it is supplemented by energy storage. The goal of the allocation is to ensure that the total virtual inertia of the wind-storage system meets the minimum inertia demand and maximize the frequency response capability of the wind-storage system.

[0088] Preferably, determining the first minimum inertia requirement of the wind-storage system based on the frequency change rate constraint in the above step S101 may specifically include: calculating the first minimum inertia requirement that meets the frequency change rate safety requirement based on the system frequency response equation and a preset maximum allowable value of the frequency change rate.

[0089] In the early stage of disturbance, the unbalanced power of wind-storage system mainly comes from the disturbance power ΔP d , then the frequency response equation can be expressed as:

[0090] 2H s df / dt=-ΔP d (1)

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

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

[0093]

[0094] In the above formula, H Smin1 is the first minimum inertia requirement, fmax It is the maximum allowable value of the frequency change rate.

[0095] According to the above formula (2), under the constraints of frequency change rate and disturbance, the minimum inertia requirement of the wind energy storage system can be evaluated, as follows: Figure 2 In a regional power grid, according to system operating conditions and data, if the estimated disturbance power does not exceed 10% of the total capacity, that is, ΔP d =0.1pu In this case, when the maximum allowable frequency change rate is set, the minimum inertia requirement of the wind storage system can be obtained. Referring to the existing regulations, the maximum allowable value of the frequency change rate is set to 0.5Hz / s in this embodiment, that is, Then the system inertia requirement is 5s under the frequency change rate constraint.

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

[0097] Even in abnormal conditions, the frequency deviation of the power system should be within the operating requirements. The power imbalance is most serious at the initial stage of the disturbance, and the frequency change rate is mainly determined by the system inertia. However, in the dynamic process after the initial disturbance, the system frequency change Δf max It is closely related to many parameters, such as wind power penetration rate ρ, power disturbance ΔP d , system inertia time constant Hs, synchronous machine parameters, etc. The frequency change calculation requires the establishment of a system frequency response model containing 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 The minimum inertia requirement, ΔP d is the disturbance power, Δf max is the system frequency change, F1 is H Smin2 About ΔP d and Δf max function, F2 is ΔP d About H smin2 and Δf max function.

[0100] According to the equation of the traditional frequency response model, the functions F1, F2 and ΔP d , Δf max and H Smin2 Among them, Δf maxIt can be determined by the frequency safety regulations. Then, the functional relationship between the power disturbance and the system inertia requirement can be established through functions F1 and F2, thereby completing the system inertia requirement evaluation process based on the frequency change constraint.

[0101] According to formula (3), after setting the frequency change constraint, the inertia demand of the wind-storage system under this constraint can be evaluated according to the grid's renewable energy penetration rate and disturbance power. The wind power penetration rate is set to 50%, the synchronous machine inertia time constant is generally 5 to 10 s, ΔPd is 0.14 to 0.16 pu, and Δf max Take 0.9~1Hz, the evaluation results are as follows Figure 3 As shown, it is easy to obtain the system quantity requirements under the frequency change constraint. d =0.144pu,Δf max =1Hz, the system inertia requirement based on the frequency change constraint is 5s. After meeting this requirement, the fluctuation range of the system frequency can be limited.

[0102] At the same time, the frequency change rate and change amount constraints are met, and the inertia demand H of the wind storage system smin Taking two larger evaluation results, it can be expressed as

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

[0104] According to equations (2), (3) and (4), it can be seen that to ensure frequency safety, the power supply needs to provide the necessary inertia support. However, the frequency change rate and change amount of the system are difficult to meet the safety requirements due to the grid connection of new energy. At present, although virtual inertia control has been proposed, the demand for wind and storage inertia has not been clarified, resulting in insufficient basis for parameter design of additional controllers. Therefore, this step further clarifies the demand for wind and storage inertia through subsequent steps S104-S106, and distributes the demand.

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

[0106] The fan speed safety constraint and output power constraint in the above step S104 are respectively described below:

[0107] (1) Fan speed safety constraints

[0108] When the power system is disturbed, the wind turbine needs to release kinetic energy to compensate for the power shortage of the system. d When the system power is insufficient, the fan needs to release its stored kinetic energy to compensate for the unbalanced power, resulting in the rotor speed ω r On the contrary, when the disturbance power ΔP d When it is negative, that is, the system has excess power, the fan needs to absorb the excess energy and convert it into kinetic energy, making the rotor speed ω r To ensure the stable operation of the fan under different disturbance conditions, its speed must meet certain constraints. These constraints can be expressed in corresponding mathematical forms, which are of great significance for the safe and stable operation of the fan and the frequency regulation of the power system. Therefore, the fan speed safety constraint in this embodiment can be expressed as the following formula (5):

[0109]

[0110] Among them, Δω max1 is the maximum change value of the fan speed under the speed safety constraint; ω r0 is the initial speed of the fan; ω rmax The maximum speed of the fan when it is running safely; rmin The minimum speed for safe operation of the fan.

[0111] (2) Output power constraints

[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] Among them, P ew is the electromagnetic power output of the fan; k opt is the maximum power tracking proportional coefficient; ω0 is the cut-in speed of the fan when it enters the maximum power tracking area; P n is the rated power of the fan; r is the rotor speed.

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

[0116]

[0117] When the fan participates in inertial 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 They are the power change and mechanical power of the fan, P ew is the electromagnetic power output of the fan, H w is the inherent inertia time constant of the fan.

[0120] According to equations (7) and (8), by integrating both sides of the equation under power constraints, we can obtain the maximum speed change Δω of the fan during the inertial response time: max2 , expressed as:

[0121]

[0122] In order to satisfy the above two constraints at the same time, the maximum change of the wind turbine speed should be the minimum of the two. Taking a 2MW wind turbine as an example, take H w =4s,k opt =1 / (1.23),ω rmax =1.2pu,ω rmin =0.8pu,t h =3.09s, according to equations (5) and (9), the maximum speed change Δω under different initial speeds of the fan can be obtained: max ,like Figure 4 As shown, Figure 4 ΔP d >0 and ΔP d Schematic diagram of speed change when ΔP <0. d >0, when ω r0 Small, at this time the wind turbine rotor kinetic energy reserve is insufficient, but there is sufficient power support margin, Δω max Mainly limited by the speed safety constraint; when ω r0 >0.989pu, at this time, the wind turbine rotor kinetic energy reserve is sufficient, but the power support margin is insufficient, Δω max Mainly limited by the wind turbine power constraint. r0 =0.989pu, Δω max The maximum value can reach 0.189pu.

[0123] Similarly, when ΔP d <0 and ω r0 When Δω is small, max Depends on the wind turbine power constraint; when ω r0 When >1.063pu, Δω max Depends on the speed safety constraint. And ω r0 =1.063pu, Δω max The maximum value can reach 0.137pu.

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

[0125]

[0126] Under the constraint of 1 Hz frequency deviation, the synchronous angular frequency varies from 0.98 to 1 pu. To conservatively evaluate the virtual inertia of the wind turbine, Δω is taken in this paper. e =0.02, according to formula (10), the maximum virtual inertia of the fan can be expressed as:

[0127]

[0128] Among them, 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 inertial 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 speed ratio of the fan gearbox, R t is the fan blade radius, p n is the number of fan pole pairs.

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

[0130] Equivalently transform the energy storage into a synchronous generator, and obtain the virtual rotor motion equation of the energy storage:

[0131]

[0132] Where: H vB is the virtual inertia time constant of energy storage; ω is the virtual rotor speed after energy storage is virtualized into synchronous machine; P mB , P eB They are respectively the mechanical power and electromagnetic power after the energy storage is virtualized as a synchronous machine.

[0133] During the inertial response time, both sides of the above equation (12) are integrated simultaneously to obtain the virtual inertia that the energy storage can provide during disturbance:

[0134]

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

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

[0137] From the above, it can be seen that the method for allocating the inertia demand of the wind storage system proposed in the present invention uses the frequency change rate and the frequency change amount as the core parameters for evaluating the inertia demand of the system, and obtains the minimum inertia demand associated with them through the frequency change rate and the frequency change amount, respectively. Taking these two minimum inertia demand values ​​into comprehensive consideration, the final required inertia of the wind storage system is obtained. In this process, in order to avoid the operating risks of the wind turbine after the additional virtual inertia control, reduce the demand for online monitoring, and complete the frequency warning, the present invention also considers the virtual inertia demand under the constraints of the wind turbine speed and the output power change amount, improves the reliability of wind power inertia support, and completes the allocation of wind power and energy storage inertia demand. The present application can effectively reflect the sensitivity and stability of the system to frequency changes, and provide a solid foundation for formulating and optimizing new energy frequency regulation strategies.

[0138] The above effect is further described below through a specific example:

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

[0140] Under the wind coordinated control strategy, the disturbance load suddenly increases by 0.15pu. According to the system inertia evaluation result diagram, the system minimum inertia requirement H is obtained. smin is 7.5s, due to ΔP d >ΔP d2At this time, the energy storage should also have the ability to actively support the frequency, and cooperate with the synchronous generator and the fan to complete the inertial support of the system. According to the frequency modulation command and simulation parameters, the system inertial response time is 4.80s.

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

[0142] If differential inertia control is adopted, under the inertial support of wind turbines and energy storage, the frequency drop amplitude Δfh of the system is 1.03Hz, and the frequency drop speed at the beginning of the disturbance is 0.75Hz / s. Although the control effect is improved compared with no control, it still cannot meet the frequency safety constraint. During the frequency recovery period, the wind and energy storage are not locked in time, resulting in difficulty in frequency recovery and large overshoot.

[0143] If the wind-storage system adopts the proposed coordinated control strategy, the system frequency drop depth Δfh is 0.92Hz, and the maximum frequency change rate is 0.49Hz / s, both of which meet the preset frequency safety requirements. Figure 5 The simulation results in (b) show that Δωr = 0.037, pu = 11.62 rad / s, which is consistent with the maximum speed change Δω max The evaluation results are close to those of H, thus maximizing the potential of new energy for rapid response frequency. vw =6.76s. Further, Hs = 7.58s is greater than H smin 7.5, Hs is the system inertia time constant, which is the virtual inertia time constant of wind power plus the virtual inertia time constant of energy storage.

[0144] The inertia requirement of the system has been met. In addition, the inertia response time is 4.81s, which is consistent with the calculated result. In the frequency recovery stage, the overshoot of the system frequency is significantly reduced because the wind storage additional controller is shut down in time after the inertia response time is reached.

[0145] like Figure 6 The structure diagram of a wind energy storage system inertia demand distribution device provided in an embodiment of the present application is shown, the device comprises: a first demand determination unit 610, a second demand determination unit 620, a minimum demand determination unit 630, a wind turbine evaluation unit 640, an energy storage evaluation unit 650 and an inertia distribution unit 660, which are sequentially connected. Among them:

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

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

[0148] The minimum demand determination unit 630 is used to select 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. If the first minimum inertia demand and the second minimum inertia demand are equal, the first minimum inertia demand is selected as the minimum inertia demand of the wind storage system.

[0149] The fan evaluation unit 640 is used to evaluate the maximum virtual inertia that the fan can provide based on the fan speed safety constraint and the output power constraint.

[0150] The energy storage evaluation unit 650 is used to evaluate the virtual inertia that the energy storage can provide during disturbance based on the output power upper limit and inertial response time of the energy storage.

[0151] The inertia allocation unit 660 is used to allocate 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 disturbance.

[0152] Preferably, the first demand determination unit 610 is specifically used to: calculate the first minimum inertia demand under the frequency change rate safety requirement according to the system frequency response equation and the preset maximum allowable value of the frequency change rate;

[0153] The system frequency response equation is:

[0154] 2H s df / dt=-ΔP d ;

[0155] Among them, H S is the system inertia time constant, f is the frequency, ΔP d is the disturbance power;

[0156] The first minimum inertia requirement is:

[0157]

[0158] Among them, H Smin1 is the first minimum inertia requirement, f max It is the maximum allowable value of frequency change rate.

[0159] Preferably, the second demand determination unit 620 is specifically used to: calculate the second minimum inertia demand under the frequency variation safety requirement according to the system frequency response model including wind power and the preset maximum allowable value of the frequency variation;

[0160] The system frequency response model is:

[0161]

[0162] Among them, H Smin2 The minimum inertia requirement, ΔP d is the disturbance power, Δf max is the system frequency change, F1 is H smin2 About ΔP d and Δf max function, F2 is ΔP d About H smin2 and Δf max function.

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

[0164]

[0165] Among them, Δω max1 is the maximum change value of the fan speed under the speed safety constraint; ω r0 is the initial speed of the fan; ω rmax The maximum speed of the fan when it is running safely; rmin Minimum speed for safe operation of the fan;

[0166] The output power constraint is:

[0167]

[0168] Among them, P ew is the electromagnetic power output of the fan; k opt is the maximum power tracking proportional coefficient; ω0 is the cut-in speed of the fan when it enters the maximum power tracking area; P n is the rated power of the fan; r is the rotor speed;

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

[0170]

[0171] Among them, 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 inertial 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 that the energy storage can provide during disturbance based on the output power upper limit and inertial response time of the energy storage, including:

[0173] Equivalently transform the energy storage into a synchronous generator, and obtain the virtual rotor motion equation of the energy storage:

[0174]

[0175] Where: H vB is the virtual inertia time constant of energy storage; ω is the virtual rotor speed after energy storage is virtualized into synchronous machine; P mB , P eB They are the mechanical power and electromagnetic power after the energy storage is virtualized as a synchronous machine;

[0176] During the inertial response time, both sides of the virtual rotor motion equation are integrated simultaneously to obtain the virtual inertia that the energy storage can provide during disturbance:

[0177]

[0178] Where: ω is the virtual rotor speed after energy storage is virtualized into synchronous machine, ω0 is the initial value, ω1 is the measured value, t h It is the inertial response time required when the frequency drops to the minimum value.

[0179] The detailed description of each of the above units can be found in the corresponding description in the aforementioned method embodiment, which will not be further elaborated here.

[0180] From the above, it can be seen that the device for distributing the inertia demand of the wind storage system proposed in the present invention uses the frequency change rate and the frequency change amount as the core parameters for evaluating the inertia demand of the system, and obtains the minimum inertia demand associated with them through the frequency change rate and the frequency change amount, respectively. Taking these two minimum inertia demand values ​​into comprehensive consideration, the final required inertia of the wind storage system is obtained. In this process, in order to avoid the operating risks of the wind turbine after the additional virtual inertia control, reduce the demand for online monitoring, and complete the frequency warning, the present invention also considers the virtual inertia demand under the constraints of the wind turbine speed and the output power change amount, improves the reliability of wind power inertia support, and completes the distribution of wind power and energy storage inertia demand. The present application can effectively reflect the sensitivity and stability of the system to frequency changes, and provide a solid foundation for formulating and optimizing new energy frequency regulation strategies.

[0181] Figure 7 is a schematic diagram of an electronic device provided by an embodiment of the present invention. Figure 7The electronic device shown is a general data processing device, which includes a general computer hardware structure, which at least includes a processor 801 and a memory 802. The processor 801 and the memory 802 are connected via 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 method for allocating inertia requirements of the wind storage system.

[0182] The processor 801 may be an independent microprocessor or a collection of one or more microprocessors. Thus, the processor 801 executes the commands stored in the memory 802 to execute the method flow of the embodiment of the present invention as described above to realize the processing of data and the control of other devices. The bus 803 connects the above-mentioned multiple components together, and at the same time connects the above-mentioned components to the display controller 804 and the display device and the input / output (I / O) device 805. The input / output (I / O) device 805 may be a mouse, a keyboard, a modem, a network interface, a touch input device, a somatosensory input device, a printer, and other devices known in the art. Typically, the input / output (I / O) device 805 is connected to the system via an input / output (I / O) controller 806.

[0183] The memory 802 may store software components such as an operating system, a communication module, an interaction module, and an application program. Each of the modules and applications described above corresponds to a set of executable program instructions that implement one or more functions and methods described in the embodiments of the invention.

[0184] An embodiment of the present invention further provides a computer-readable storage medium having a computer program stored thereon, and when the computer program is executed by a processor, the steps of the method for allocating inertia requirements of the wind-storage system are implemented.

[0185] The method and device for allocating the inertia demand of the wind-storage system proposed in the present invention uses the frequency change rate and the frequency change amount as the core parameters for evaluating the inertia demand of the system, and obtains the minimum inertia demand associated with the frequency change rate and the frequency change amount respectively, and comprehensively considers these two minimum inertia demand values ​​to obtain the final required inertia of the wind-storage system. In this process, in order to avoid the operating risks of the wind turbine after the additional virtual inertia control, reduce the demand for online monitoring, and complete the frequency warning, the present invention also considers the virtual inertia demand under the constraints of the wind turbine speed and the output power change amount, improves the reliability of wind power inertia support, and completes the allocation of wind power and energy storage inertia demand. The present application can effectively reflect the sensitivity and stability of the system to frequency changes, and provide a solid foundation for formulating and optimizing new energy frequency regulation strategies.

[0186] The preferred embodiments of the present invention are described above with reference to the accompanying drawings. Many features and advantages of these embodiments are clear from this detailed description, and therefore the claims are intended to cover all such features and advantages of these embodiments that fall within their true spirit and scope. In addition, since many modifications and changes are easily conceivable to those skilled in the art, it is not intended to limit the embodiments of the present invention to the precise structure and operation illustrated and described, but all suitable modifications and equivalents falling within its scope may be covered.

[0187] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0188] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0189] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0190] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0191] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for allocating inertia requirements of a wind energy storage system, characterized in that: The method comprises: Determining a first minimum inertia requirement of the wind-storage system based on a frequency change rate constraint; Determining a second minimum inertia requirement of the wind storage system based on a frequency change constraint; Selecting 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, selecting the first minimum inertia requirement 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 output power upper limit and inertial response time of energy storage, the virtual inertia that energy storage can provide during disturbance is evaluated; The inertia demand is allocated 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 disturbance.

2. The method for allocating inertia requirements of a wind energy storage system according to claim 1, characterized in that: The determining of the first minimum inertia requirement of the wind energy storage system based on the frequency change rate constraint includes: According to the system frequency response equation and the preset maximum allowable value of the frequency change rate, the first minimum inertia requirement under the frequency change rate safety requirement is calculated; The system frequency response equation is: 2H s df / dt=-ΔP d ; Among them, H S is the system inertia time constant, f is the frequency, ΔP d is the disturbance power; The first minimum inertia requirement is: Among them, H Smin1 is the first minimum inertia requirement, f max It is the maximum allowable value of the frequency change rate.

3. The method for allocating inertia requirements of a wind energy storage system according to claim 1, characterized in that: The determining of the second minimum inertia requirement of the wind energy storage system based on the frequency variation constraint includes: According to the system frequency response model including wind power, combined with the preset maximum allowable value of frequency variation, the second minimum inertia requirement under the frequency variation safety requirement is calculated; The system frequency response model is: Among them, H Smin2 The minimum inertia requirement, ΔP d is the disturbance power, Δf max is the frequency change of the system, F1 is H smin2 About ΔP d and Δf max function, F2 is ΔP d About H smin2 and Δf max function.

4. The method for allocating inertia requirements of a wind energy storage system according to claim 1, characterized in that: The fan speed safety constraint is: Among them, Δω max1 is the maximum change value of the fan speed under the speed safety constraint; ω r0 is the initial speed of the fan; ω rmax The maximum speed of the fan when it is running safely; rmin Minimum speed for safe operation of the fan; The output power constraint is: Among them, P ew is the electromagnetic power output of the fan; k opt is the maximum power tracking proportional coefficient; ω0 is the cut-in speed of the fan when it enters the maximum power tracking area; P n is the rated power of the fan; r is the rotor speed; The maximum virtual inertia that the fan can provide is evaluated by the following formula: Among them, 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 inertial 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.

5. The method for allocating inertia requirements of a wind energy storage system according to claim 1, characterized in that: The above-mentioned output power upper limit and inertial response time based on energy storage, the virtual inertia that energy storage can provide during disturbance evaluation includes: Equivalently transform the energy storage into a synchronous generator, and obtain the virtual rotor motion equation of the energy storage: Where: H vB is the virtual inertia time constant of energy storage; ω is the virtual rotor speed after energy storage is virtualized into synchronous machine; P mB , P eB They are the mechanical power and electromagnetic power after the energy storage is virtualized as a synchronous machine; During the inertial response time, both sides of the virtual rotor motion equation are integrated simultaneously to obtain the virtual inertia that the energy storage can provide during disturbance: Where: ω is the virtual rotor speed after energy storage is virtualized into synchronous machine, ω0 is the initial value, ω1 is the measured value, t h It is the inertial response time required when the frequency drops to the minimum value.

6. A device for distributing inertia requirements of a wind energy storage system, characterized in that: The device comprises: A first demand determination unit, configured to determine a first minimum inertia demand of the wind-storage system based on a frequency change rate constraint; A second demand determination unit, which determines a second minimum inertia demand of the wind storage system based on a frequency change constraint; a minimum demand determination unit, configured to select 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 if the first minimum inertia demand and the second minimum inertia demand are equal, select the first minimum inertia demand as the minimum inertia demand of the wind-storage system; A fan evaluation unit, used to evaluate the maximum virtual inertia that the fan can provide based on the fan speed safety constraint and the output power constraint; An energy storage evaluation unit, used to evaluate the virtual inertia that the energy storage can provide during disturbances based on the output power upper limit and inertial response time of the energy storage; The inertia distribution unit is used to distribute 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 disturbance.

7. The device for distributing inertia requirements of a wind energy storage system according to claim 6, characterized in that: The first demand determination unit is specifically used to: calculate the first minimum inertia demand under the frequency change rate safety requirement according to 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 is the system inertia time constant, f is the frequency, ΔP d is the disturbance power; The first minimum inertia requirement is: Among them, H Smin1 is the first minimum inertia requirement, f max It is the maximum allowable value of the frequency change rate.

8. The device for distributing inertia requirements of a wind energy storage system according to claim 6, characterized in that: The second demand determination unit is specifically used to: calculate the second minimum inertia demand under the frequency variation safety requirement according to the system frequency response model including wind power and the preset maximum allowable value of the frequency variation; The system frequency response model is: Among them, H Smin2 The minimum inertia requirement, ΔP d is the disturbance power, Δf max is the frequency change of the system, F1 is H smin2 About ΔP d and Δf max function, F2 is ΔP d About H smin2 and Δf max 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, the steps of the method according to any one of claims 1 to 5 are implemented.

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

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