Wind storage frequency response model construction method

Abstract

The invention relates to a wind storage frequency response model construction method. The method comprises the following steps: firstly, analyzing the frequency response characteristic of a wind turbine generator, and considering the influence of virtual inertia control and the influence of pitch angle control under the condition of high permeability, so as to construct a frequency response model considering the wind speed uncertainty; secondly, analyzing frequency response characteristics of energy storage to obtain energy storage additional power and thermal power generating unit additional power, and combining the energy storage additional power and the thermal power generating unit additional power with a frequency response model considering wind speed uncertainty to construct an overall frequency response model of the wind storage system; and finally, combining the control logic of energy storage priority and fan cooperation with the overall frequency response model of the wind storage system so as to construct a wind storage frequency response model. Compared with the prior art, the method can accurately and effectively describe the frequency response characteristics of the wind storage system.

Description

Technical Field

[0001] The present invention relates to the technical field of dynamic frequency analysis of power systems, and particularly to a method for constructing a frequency response model of a wind energy storage system. Background Art

[0002] With the large-scale access of new energy, the power system is undergoing a major transformation in its energy structure. The penetration rates of new energy sources such as wind power and photovoltaic power are continuously increasing, while the proportion of traditional thermal power units is gradually decreasing, and the power grid is gradually showing the characteristics of "double highs". The uncertainty and low inertia characteristics of new energy output pose challenges to the stable operation of the power grid, resulting in significant changes in the frequency characteristics of the power system. As a tool for quickly predicting the frequency extreme value, the frequency response model can provide an important reference for frequency control.

[0003] Wind energy storage combined frequency regulation is a promising solution to address the frequency stability challenge. However, the frequent frequency regulation of wind turbines not only accelerates the wear of wind turbine generators and shortens their service life, but also the regulation capacity of wind turbine generators is greatly affected by wind conditions. In addition, for wind turbine generators to participate in frequency regulation, they need to deviate from the maximum power tracking point, resulting in a reduction in wind energy utilization rate and economy. The control logic of "energy storage first and wind turbines cooperate synergistically" can avoid such deficiencies, but it requires frequent use of energy storage for frequency regulation, which also involves cost-benefit. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for constructing a frequency response model of a wind energy storage system to overcome the defects existing in the above-mentioned prior art.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] According to one aspect of the present invention, a method for constructing a frequency response model of a wind energy storage system is provided. The method includes the following steps:

[0007] According to the frequency response characteristics of wind turbine generators in the wind energy storage system, and considering the influence of virtual inertia control and pitch angle control under high penetration conditions, a frequency response model considering wind speed uncertainty is constructed;

[0008] According to the frequency response characteristics of energy storage in the wind energy storage system, the additional power generation of energy storage and the additional power generation of thermal power units are obtained, and they are combined with the frequency response model considering wind speed uncertainty to construct an overall frequency response model of the wind energy storage system;

[0009] Considering the time series factor, the time series control logic of "energy storage first and wind turbines cooperate synergistically" is combined with the overall frequency response model of the wind energy storage system to construct a frequency response model of the wind energy storage system.

[0010] As a preferred technical solution, the frequency response characteristics of wind turbine generators include at least one of wind speed uncertainty and wind turbine frequency response characteristics.

[0011] As a preferred technical solution, the specific formula for the influence of virtual inertia control is:

[0012]

[0013] Among them, ΔTe1 is the virtual inertia torque deviation, s is the complex frequency domain variable, s = σ + jω, σ is the real part, which is the attenuation or growth rate of the signal, jω is the imaginary part, which is the frequency of the signal, ω is the rotor speed, ΔPe1 is the active power output of the wind turbine, and R ω is the droop proportionality coefficient, k ω is the gain, and Δf(s) is the frequency change.

[0014] As a preferred technical solution, the specific formula for the influence of pitch angle control is:

[0015] ΔTe2(s) = 2k p ωΔω(s)

[0016] Among them, ΔTe2 is the dynamic vibration damping torque deviation, k p is the proportional factor of the mechanical power input to the wind turbine, ω is the rotor speed, and Δω(s) is the rotor speed deviation.

[0017] As a preferred technical solution, the specific formula for the frequency response model considering wind speed uncertainty is:

[0018]

[0019] Among them, ΔP W is the additional power generation of the wind turbine, s is the complex frequency domain variable, s = σ + jω, σ is the real part, which is the attenuation or growth rate of the signal, jω is the imaginary part, which is the frequency of the signal, ω is the rotor speed, η W is the wind power penetration rate, H w is the WTG virtual inertia time constant, v is the wind speed, is the optimal wind energy utilization coefficient, λ ref is the optimal tip speed ratio, k C is the partial derivative with respect to the tip speed ratio, k ω is the gain, k p is the proportional factor of the mechanical power input to the wind turbine, k b is the inertia control proportionality factor, k β is the partial derivative with respect to the pitch angle, a, b, and c are inertia control related parameters, q, g are pitch angle control related parameters, Δv is the wind speed change, Δf is the frequency change, and R ω is the droop proportionality coefficient. As a preferred technical solution, the specific formula for the additional power generation of energy storage is:

[0020] ΔPE = -kΔf

[0021] where ΔP E is the additional power generation of energy storage, k is the proportional coefficient of energy storage frequency additional control, and Δf is the frequency change.

[0022] As an optimal technical solution, the specific formula for the additional power generation of thermal power units is:[[]]

[0023]

[0024] where ΔP R is the additional power generation of thermal power units, η R is the proportion of thermal power units, R is the governor droop coefficient, F H is the steam turbine characteristic coefficient, T R is the equivalent inertia time constant of the steam turbine, s is the complex frequency domain variable, and Δf is the frequency change.

[0025] As an optimal technical solution, the specific formula for the overall frequency response model of the wind - energy storage system is:[[]]

[0026]

[0027] where η R is the proportion of thermal power units, H sys is the equivalent inertia time constant of the system, ΔP R is the additional power generation of thermal power units, ΔP E is the additional power generation of energy storage, ΔP W is the additional power generation of wind turbines, that is, the frequency response model considering wind speed uncertainty, ΔP L is the disturbance power, D sys is the active power frequency response coefficient of the system load, and Δf is the frequency change.

[0028] As an optimal technical solution, the specific timing control logic of energy storage priority and fan cooperation in the method is:[[]]

[0029] 0 - t 1 ′ moment, detect whether the overall frequency change rate of the wind - energy storage system exceeds the limit. If it exceeds the limit, the overall frequency change of the wind - energy storage system is supported by the system inertia until t 1 ′ moment; if it does not exceed the limit, directly use energy storage for inertia support and frequency modulation and then end the control;

[0030] t 1 ′ moment, the overall frequency change of the wind - energy storage system is switched to be supported by energy storage;

[0031] t 2When the energy storage reaches its maximum output at time t', if the overall frequency change rate of the wind-storage system does not exceed the limit, the energy storage is used for inertia support and frequency regulation; if the overall frequency change rate of the wind-storage system exceeds the limit, the wind turbines are used for inertia support and frequency regulation to reduce the overall frequency change rate of the wind-storage system;

[0032] t 3 At time t', stop frequency regulation and end the control;

[0033] where t 1 ' < t 2 ' < t 3 '.

[0034] As a preferred technical solution, when using the energy storage for inertia support and frequency regulation, the frequency regulation effect is determined by the charging characteristics and reflected by the energy storage power. The charging characteristics include the frequency regulation capacity provided by the energy storage, the state of charge of the battery, and the charging rate. The specific formula for the frequency regulation effect is:

[0035] P E = γ SOC (t) * P

[0036] where P E is the energy storage power, γ SOC (t) is the state of charge of the battery at time t, and P is the rated power of the energy storage.

[0037] According to another aspect of the present invention, a wind-storage frequency response model construction system is provided. The system includes a wind turbine analysis module, an energy storage analysis module, and a timing control module;

[0038] The wind turbine analysis module constructs a frequency response model considering wind speed uncertainty based on the frequency response characteristics of the wind turbines in the wind-storage system and considering the influence of virtual inertia control and pitch angle control in the case of high penetration;

[0039] The energy storage analysis module obtains the additional power of the energy storage and the additional power of the thermal power unit according to the frequency response characteristics of the energy storage in the wind-storage system, and combines it with the frequency response model considering wind speed uncertainty to construct the overall frequency response model of the wind-storage system;

[0040] The timing control module considers timing factors and combines the timing control logic of giving priority to the energy storage and coordinating with the wind turbines with the overall frequency response model of the wind-storage system to construct the wind-storage frequency response model.

[0041] As a preferred technical solution, in this system, the frequency response characteristics of the wind turbines include at least one of wind speed uncertainty and the frequency response characteristics of the wind turbines.

[0042] As a preferred technical solution, in this system, the specific formula for the influence of virtual inertia control is:

[0043]

[0044] Among them, ΔTe1 is the virtual inertia torque deviation, s is the complex frequency domain variable, s = σ + jω, where σ is the real part, which is the attenuation or growth rate of the signal, jω is the imaginary part, which is the frequency of the signal, ω is the rotor speed, ΔPe1 is the active power output of the wind turbine, and R ω is the droop ratio coefficient, and k ω is the gain, and Δf(s) is the frequency change amount.

[0045] As a preferred technical solution, in this system, the specific formula for the influence of pitch angle control is:

[0046] ΔTe2(s) = 2k p ωΔω(s)

[0047] Among them, ΔTe2 is the dynamic vibration damping torque deviation, and k p is the mechanical power input ratio factor of the fan, ω is the rotor speed, and Δω(s) is the rotor speed deviation.

[0048] As a preferred technical solution, in this system, the specific formula for the frequency response model considering wind speed uncertainty is:

[0049]

[0050] Among them, ΔP W is the additional power generation of the wind turbine, s is the complex frequency domain variable, s = σ + jω, where σ is the real part, which is the attenuation or growth rate of the signal, jω is the imaginary part, which is the frequency of the signal, ω is the rotor speed, η W is the wind power penetration rate, H w is the WTG virtual inertia time constant, v is the wind speed, is the optimal wind energy utilization coefficient, λ ref is the optimal tip speed ratio, k C is the partial derivative with respect to the tip speed ratio, k ω is the gain, k p is the mechanical power input ratio factor of the fan, k b is the inertia control ratio factor, k β is the partial derivative with respect to the pitch angle, a, b, and c are inertia control related parameters, q, g are pitch angle control related parameters, Δv is the wind speed change amount, Δf is the frequency change amount, and R ω is the droop ratio coefficient.

[0051] As a preferred technical solution, in this system, the specific formula for the additional power generation of the energy storage is:

[0052] ΔPE = -kΔf

[0053] Where, ΔP E is the additional power generation of the energy storage, k is the proportional coefficient of the energy storage frequency additional control, and Δf is the frequency change.

[0054] As an optimized technical solution, in this system, the specific formula for the additional power generation of the thermal power unit is as follows:

[0055]

[0056] Where, ΔP R is the additional power generation of the thermal power unit, η R is the proportion of the thermal power unit, R is the governor droop coefficient, F H is the characteristic coefficient of the steam turbine, T R is the equivalent inertia time constant of the steam turbine, s is the complex frequency domain variable, and Δf is the frequency change.

[0057] As an optimized technical solution, in this system, the specific formula for the overall frequency response model of the wind energy storage system is as follows:

[0058]

[0059] Where, η R is the proportion of the thermal power unit, H sys is the equivalent inertia time constant of the system, ΔP R is the additional power generation of the thermal power unit, ΔP E is the additional power generation of the energy storage, ΔP W is the additional power generation of the wind turbine, that is, the frequency response model considering the uncertainty of the wind speed, ΔP L is the disturbance power, D sys is the active power frequency response coefficient of the system load, and Δf is the frequency change.

[0060] As an optimized technical solution, in this system, the specific timing control logic for the energy storage to take priority and the wind turbines to cooperate is as follows:

[0061] 0 - t 1 ′ moment, detect whether the overall frequency change rate of the wind energy storage system exceeds the limit. If it exceeds the limit, the overall frequency change of the wind energy storage system is supported by the system inertia until t 1 ′ moment; if it does not exceed the limit, directly use the energy storage for inertia support and frequency modulation and then end the control;

[0062] t 1 ′ moment, the overall frequency change of the wind energy storage system is switched to be supported by the energy storage;

[0063] t 2When the energy storage reaches its maximum output at time t′, if the overall frequency change rate of the wind - energy storage system does not exceed the limit, the energy storage is used for inertia support and frequency regulation; if the overall frequency change rate of the wind - energy storage system exceeds the limit, the wind turbines are used for inertia support and frequency regulation to reduce the overall frequency change rate of the wind - energy storage system.

[0064] t 3 At time t′, stop frequency regulation and end the control.

[0065] Where t 1 ′ < t 2 ′ < t 3 ′.

[0066] As a preferred technical solution, in this system, when using the energy storage for inertia support and frequency regulation, the frequency - regulation effect is determined by the charging characteristics and reflected by the energy - storage power. The charging characteristics include the frequency - regulation capacity provided by the energy storage, the state of charge of the battery, and the charging rate. The specific formula for the frequency - regulation effect is:

[0067] P E = γ SOC (t)*P

[0068] Where P E is the energy - storage power, γ SOC (t) is the state of charge of the battery at time t, and P is the rated power of the energy storage.

[0069] According to another aspect of the present invention, there is provided an electronic device, including a memory and a processor. A computer program is stored on the memory, and when the processor executes the program, it implements a method for constructing a wind - energy storage frequency - response model as described above.

[0070] According to another aspect of the present invention, there is provided a computer - readable storage medium, on which a computer program is stored. When the program is executed by a processor, it implements a method for constructing a wind - energy storage frequency - response model as described above.

[0071] Compared with the prior art, the present invention has the following beneficial effects:

[0072] 1. In the present invention, first, according to the frequency - response characteristics of the wind turbines in the wind - energy storage system, and considering the influence of virtual - inertia control and pitch - angle control under high - penetration conditions, a frequency - response model considering wind - speed uncertainty is constructed; then, according to the frequency - response characteristics of the energy storage in the wind - energy storage system, the additional power of the energy storage and the additional power of the thermal power unit are obtained, and combined with the frequency - response model considering wind - speed uncertainty, so as to construct the overall frequency - response model of the wind - energy storage system; finally, considering the time - series factor, the time - series control logic of giving priority to the energy storage and coordinating with the wind turbines is combined with the overall frequency - response model of the wind - energy storage system, so as to construct the wind - energy storage frequency - response model. This improves the effectiveness and accuracy of judging the frequency - response characteristics of complex wind - power systems.

[0073] 2. In the method of the present invention, the specific timing control logic of energy storage priority and fan coordination is as follows: from 0 to t 1 ′ moment, detect whether the frequency change rate exceeds the limit. If it exceeds the limit, the frequency change is supported by the thermal power unit for inertia until t 1 ′ moment; if it does not exceed the limit, directly use energy storage for inertia support and frequency modulation and then end the control; at t 1 ′ moment, the frequency change is supported by energy storage; at t 2 ′ moment, when the energy storage reaches the maximum output, if the frequency change rate does not exceed the limit, use energy storage for inertia support and frequency modulation; if the frequency change rate exceeds the limit, use the wind turbine for inertia support and frequency modulation to reduce the frequency change rate; at t 3 ′ moment, stop frequency modulation and end the control; where t 1 ′ < t 2 ′ < t 3 ′. At the same time, considering the low inertia characteristics and wind power output uncertainty characteristics presented by new energy power stations under high penetration, when the synchronous generator set cannot meet the system inertia demand, virtual inertia control technology is used to make the fan and energy storage generate virtual inertia, cooperate with the synchronous generator set to jointly undertake frequency modulation; improve the reliability and stability of the method.

[0074] 3. In the present invention, the overall frequency response model of the wind energy storage system constructed includes disturbance power, additional power generation of energy storage, and additional power generation of thermal power units. Based on this frequency response model, timing factors are introduced, and the frequency response characteristics obtained after considering the frequency modulation timing are compared with the traditional frequency response characteristics. It can more accurately describe the dynamic behavior of the wind energy storage system in the actual frequency modulation process; helps to reveal the influence mechanism of different frequency modulation timings on the frequency response. When analyzing the frequency response characteristics of a relatively complex system, it provides a frequency response model in the frequency domain that can more accurately reflect the system frequency change. BRIEF DESCRIPTION OF THE DRAWINGS

[0075] Figure 1 It is a schematic diagram of the steps of a method for constructing a wind energy storage frequency response model in the present invention;

[0076] Figure 2 It is a frequency response diagram considering wind speed uncertainty in the present invention;

[0077] Figure 3 It is a simplified frequency response model structure diagram of the wind energy storage system under timing in the present invention;

[0078] Figure 4 It is a schematic diagram of the frequency response difference of systems with different penetration rates in the embodiment;

[0079] Figure 5 It is a frequency response control logic flowchart of the wind energy storage system under timing in the present invention;

[0080] Figure 6 Structural diagram of the wind-storage frequency response model simulation system in the embodiment;

[0081] Figure 7 Active power change diagram in the present invention;

[0082] Figure 8 System frequency response diagrams under four cases with different considered ranges in the embodiment. Detailed implementation manners

[0083] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0084] Traditional frequency response models focus on evaluating the overall impact of the active power contributions of each module on the system frequency, but ignore the importance of the time sequence difference of the frequency regulation response. As a part of the frequency response, the arrangement of the frequency regulation time sequence will significantly affect the system's frequency recovery process and frequency stability. A frequency response model that ignores the frequency regulation time sequence may not accurately reflect the dynamic characteristics of the system. Especially in the scenario of high-penetration new energy, the frequent participation of intermittent power sources such as wind power and photovoltaic power, as well as energy storage devices, in frequency regulation makes the optimization of the frequency regulation time sequence more important and complex. Therefore, it is necessary to introduce the time sequence factor into the frequency response model to more accurately describe the frequency response characteristics of the system and provide a more reliable theoretical tool for frequency control and stability analysis.

[0085] To seek the optimal balance between frequency response characteristics and economy, it is of great significance to deeply study the frequency response model under time sequence, which helps to reveal the influence mechanism of different frequency regulation time sequences on the frequency response and provides a theoretical basis for optimizing the wind-storage combined frequency regulation strategy and improving the system economy.

[0086] Embodiment 1

[0087] In this embodiment, a method for constructing a wind-storage frequency response model is applied. This method is as Figure 1 shown and includes the following steps:

[0088] According to the frequency response characteristics of wind turbines in the wind-storage system and considering the influence of virtual inertia control and pitch angle control under high-penetration conditions, a frequency response model considering wind speed uncertainty is constructed;

[0089] Based on the frequency response characteristics of energy storage in the wind - energy storage system, the additional power of energy storage and the additional power of thermal power units are obtained, and they are combined with the frequency response model considering wind speed uncertainty to construct the overall frequency response model of the wind - energy storage system;

[0090] Considering the time - series factors, the time - series control logic of giving priority to energy storage and coordinating with wind turbines is combined with the overall frequency response model of the wind - energy storage system to construct the frequency response model of wind - energy storage.

[0091] In this embodiment, the frequency response characteristics of wind turbines include wind speed uncertainty and the frequency response characteristics of wind turbines.

[0092] In this embodiment, the first step of considering the uncertainty of wind speed is to consider the influence of virtual inertia control. The general method of wind turbine generator (WTG) for short - term frequency control of the power grid is virtual inertia control, that is, to increase the additional active power reference value related to the change of system frequency. The typical additional virtual inertia frequency control scheme is proportional - derivative control, and the virtual inertia torque deviation is as follows:

[0093]

[0094] where ΔTe1 is the virtual inertia torque deviation, ω is the rotor speed, ΔPe1 is the active power output of the wind turbine, R ω is the droop ratio coefficient, k ω is the gain, and Δf(s) is the frequency change.

[0095] In this embodiment, the second step of considering the uncertainty of wind speed is to consider the influence of pitch - angle control. The dynamic vibration - damping torque based on pitch - angle control can be regarded as a function of the rotor speed, and the change of the dynamic vibration - damping torque can be expressed as the change of the rotor speed:

[0096] ΔTe2(s)=2k p ωΔω(s)

[0097] where ΔTe2 is the dynamic vibration - damping torque deviation, k p is the proportion factor of the mechanical power input to the wind turbine, ω is the rotor speed, and Δω(s) is the rotor speed deviation.

[0098] Combining the above results of considering the influence of virtual inertia control and the influence of pitch - angle control, it is not difficult to obtain that the frequency response characteristics of the wind turbine are as follows:

[0099]

[0100] Furthermore, the frequency response model considering wind speed uncertainty can be solved as follows:

[0101]

[0102] Among them, ΔPe(s) is the fan frequency response characteristic, and ΔP W is the additional power generation of the wind turbine generator set. H w is the virtual inertia time constant of the WTG, v is the wind speed, is the optimal wind energy utilization coefficient, λ ref is the optimal tip speed ratio, k C is the partial derivative of the tip speed ratio, k β is the partial derivative of the pitch angle. a, b, and c are parameters related to inertial control, q and g are parameters related to pitch angle control, Δv is the change in wind speed, Δf is the change in frequency, and s is the complex frequency domain variable.

[0103] In this embodiment, the frequency response diagram considering wind speed uncertainty obtained by using the frequency response model of wind speed uncertainty is as Figure 2 shown. Among them, the black line represents the ramp wind speed, the blue line represents the constant wind speed, and the red line represents the step wind speed.

[0104] In this embodiment, after constructing the frequency response model considering wind speed uncertainty, the frequency response characteristics of energy storage are analyzed. In this embodiment, a lead-acid battery is taken as an example to analyze its frequency characteristics.

[0105] In this embodiment, first, the state of charge of the battery at time t is solved as follows:

[0106]

[0107] Among them, γ SOC (t) is the state of charge of the battery at time t, Q N is the rated capacity of the battery, i B (t) is the magnitude of the battery current at time t, and Q B is the remaining capacity of the battery at time t.

[0108] In this embodiment, then the stored energy of the battery is solved as follows:

[0109] E B = ∫u B i B d(1 - γ SOC ) = u B Q N γ SOC_0

[0110] Among them, E B is the stored energy of the battery, u B is the rated voltage of the battery, i B is the rated current of the battery, and Q Nis the rated capacity of the battery, γ SOC_0 is the state of charge of the battery in the initial state.

[0111] In this embodiment, by analogy with a synchronous motor, the stored energy of the battery can be obtained as follows:

[0112]

[0113] where E B is the stored energy of the battery, J vir_B is the virtual moment of inertia of the battery, w s is the angular velocity of the power grid, u B is the rated voltage of the battery, Q N is the rated capacity of the battery, γ SOC (t) is the state of charge of the battery at time t.

[0114] Then, solve for the virtual moment of inertia of the battery as follows:

[0115]

[0116] where J vir_B is the virtual moment of inertia of the battery, u B is the rated voltage of the battery, Q N is the rated capacity of the battery, γ SOC (t) is the state of charge of the battery at time t, J s is the inherent moment of inertia of the synchronous motor, E B is the stored energy of the battery, γ SOC_0 is the state of charge of the battery in the initial state, k s =(Δγ SOC / γ SOC_0 ) / (Δw w / w s ) is the ratio of the rate of change of the state of charge of the battery to the rate of change of the speed of the synchronous motor, E k is the kinetic energy of the rotor of the synchronous motor.

[0117] In this embodiment, the general method for the energy storage to participate in the power grid frequency regulation control is frequency additional control, and the specific formula for the additional power generation of the energy storage is as follows:

[0118] ΔP E =-kΔf

[0119] where ΔP E is the additional power generation of the energy storage, k is the proportional coefficient of the frequency additional control of the energy storage, and Δf is the frequency change.

[0120] In this embodiment, the simplified frequency response model structure of the wind - energy storage system over time is as Figure 3 shown. In the figure, η W is the wind power penetration rate, ηR = 1 - η W where η is the proportion of thermal power units, R is the governor droop coefficient, F H is the characteristic coefficient of the steam turbine, T R is the equivalent inertia time constant of the steam turbine, H sys is the equivalent inertia time constant of the system, D sys is the active power frequency response coefficient of the system load, k E is the proportional coefficient of the additional frequency control of energy storage, T E is the response time constant of the current inner loop control, ΔP L is the disturbance power, ΔP W is the additional power generated by the wind turbine, ΔP E is the additional power generated by the energy storage, ΔP R is the additional power generated by the thermal power unit. The serial numbers ① and ② are the frequency regulation time sequences. It can be obtained from Figure 3 that the frequency response of the overall wind - energy storage system can be expressed as follows:

[0121] ΔP E = -kΔf

[0122]

[0123] where η R is the proportion of thermal power units, H sys is the equivalent inertia time constant of the system, ΔP R is the additional power generated by the thermal power unit, ΔP E is the additional power generated by the energy storage, ΔP W is the additional power generated by the wind turbine, ΔP L is the disturbance power, D sys is the active power frequency response coefficient of the system load, and Δf is the frequency change.

[0124] Compared with the traditional power system, the frequency response ability of the future new - energy - rich and low - inertia power system with high penetration rate is reduced. The impact of the new - energy penetration rate on maintaining the frequency safety and stability of the system cannot be ignored.

[0125] In this embodiment, the frequency response differences when the wind - power penetration rates are 0%, 10%, 15%, and 25% are as Figure 4 shown. In the figure, the blue line represents the case of a 0% penetration rate, the red line represents the case of a 10% penetration rate, the yellow line represents the case of a 15% penetration rate, and the purple line represents the case of a 25% penetration rate. It is not difficult to see that when the penetration rate increases, the maximum frequency change rate of the system increases, the frequency deviation becomes larger, and the equivalent inertia of the system gradually decreases, which has an impact on the frequency safety and stability of the system.

[0126] In this embodiment, after constructing the overall frequency response model of the wind-storage system, a control logic of giving priority to energy storage and coordinating with wind turbines is adopted to construct the wind-storage frequency response model. When the energy storage reaches its maximum output, if the frequency change rate does not exceed the limit, the energy storage is used for inertia support and frequency regulation; if the frequency change rate exceeds the limit, the wind turbines are used for inertia support and frequency regulation to reduce the frequency change rate until the frequency change rate does not exceed the limit, and then the energy storage is used for inertia support and frequency regulation.

[0127] In this embodiment, the frequency response control logic process of the wind-storage system under time series is as Figure 5 shown Figure 5 in, first, the disturbance power ΔP L is monitored to obtain the frequency modulation additional power ΔP(i) at the i-th moment, and then the overall frequency change rate of the wind-storage system is detected whether it exceeds the limit, that is whether it is greater than zero; if it is not greater than zero, the energy storage is directly used for inertia support and frequency regulation and then the control ends, which is expressed by the formula as:

[0128] P E = ΔP(i + 1)+P W2

[0129] P W2 = -P W1

[0130] In the formula, P E is the energy storage power, ΔP(i + 1) is the frequency modulation additional power at the (i + 1)-th moment, P W1 is the power of the wind turbine at time series 1, and P W2 is the power of the wind turbine at time series 2.

[0131] If is greater than zero, the overall frequency change of the wind-storage system is supported by the system's inertia, that is supporting Δf until the t 1 ' moment, and its frequency modulation effect is:

[0132] P E = γ SOC (t)*P

[0133] In the formula, P E is the energy storage power, γ SOC (t) is the state of charge of the battery at the t-th moment, and P is the rated power of the energy storage.

[0134] At this time, it is judged whether the energy storage power is less than the power required by the gap, that is, P E < P 缺 ;

[0135] If the energy storage power is less than the power required by the gap, that is, when the energy storage reaches its maximum output, and the overall frequency change rate of the wind - energy storage system exceeds the limit, the wind turbine is used for inertia support and frequency modulation to reduce the overall frequency change rate of the wind - energy storage system, that is:

[0136] ΔP = P E + P W1

[0137] In the formula, ΔP is the additional power for frequency modulation, P E is the energy storage power, and P W1 is the power of the wind turbine at time sequence 1.

[0138] If the energy storage power is greater than or equal to the power required by the gap, that is, when the energy storage reaches its maximum output, and the overall frequency change rate of the wind - energy storage system does not exceed the limit, the energy storage is used for inertia support and frequency modulation, that is:

[0139] ΔP = P E

[0140] In the formula, ΔP is the additional power for frequency modulation, P E is the energy storage power.

[0141] t 3 ′ moment, stop frequency modulation and end the control; the additional power for frequency modulation at the (i + 1) - th moment is:

[0142] ΔP(i + 1)=ΔP L -ΔP;

[0143] In the formula, ΔP(i + 1) is the additional power for frequency modulation at the (i + 1) - th moment, ΔP L is the disturbance power, and ΔP is the additional power for frequency modulation.

[0144] The control logic considers the wind - energy storage coordination time sequence, with the principle of giving priority to energy storage and the wind turbine cooperating. The specific process is as follows:

[0145] 0 - t 1 ′ moment, detect whether the overall frequency change rate of the wind - energy storage system exceeds the limit. If it exceeds the limit, the overall frequency change of the wind - energy storage system is supported by the system's inertia until t 1 ′ moment; if it does not exceed the limit, directly use the energy storage for inertia support and frequency modulation and then end the control;

[0146] t 1 ′ moment, the overall frequency change of the wind - energy storage system is transferred to be supported by the energy storage;

[0147] t 2When the energy storage reaches its maximum output at time t', if the overall frequency change rate of the wind - energy storage system does not exceed the limit, the energy storage is used for inertia support and frequency regulation; if the overall frequency change rate of the wind - energy storage system exceeds the limit, the wind turbines are used for inertia support and frequency regulation to reduce the overall frequency change rate of the wind - energy storage system.

[0148] t 3 At time t', stop frequency regulation and end the control.

[0149] Where t 1 ' < t 2 ' < t 3 '.

[0150] Among them, using a synchronous generator for inertia support means using the system for inertia support, which refers to the inertia support provided by a traditional synchronous generator. In a power system, the rotor of a generator has a large moment of inertia and can absorb or release energy when the system is disturbed, thereby slowing down the rate of frequency change. The synchronous generator in this embodiment is a thermal power unit.

[0151] Using energy storage for inertia support is to use an energy storage system, such as a battery or a supercapacitor, to charge and discharge quickly and simulate the inertial response of a traditional generator. When frequency fluctuations occur, the energy storage system quickly provides or absorbs energy to help maintain frequency stability.

[0152] Using wind turbines for inertia support is to use virtual synchronous generator technology to simulate the inertial response of a synchronous generator. Wind turbines are usually connected to the power grid through converters and do not traditionally provide inertial support. However, modern wind turbines can use specific control strategies, such as virtual synchronous generator technology, to simulate the inertial response of a synchronous generator. This strategy can enable wind turbines to provide inertial support similar to that of traditional generators when the grid frequency changes.

[0153] The frequency - regulation effect is determined by the frequency - regulation capacity provided by the energy storage, the state of charge, and the charge - rate (States of Charge, SOC) characteristics. The specific formula is as follows:

[0154] P E = γ SOC (t)*P

[0155] Where P E is the energy - storage power, γ SOC (t) is the state of charge of the battery at time t, and P is the rated power of the energy storage.

[0156] In this embodiment, when the energy storage reaches its maximum output, if the frequency change rate meets the system requirements and the frequency regulation capacity is sufficient, both inertia support and frequency regulation are performed by the energy storage; during the process of the energy storage reaching its maximum output, if the frequency change rate cannot be effectively suppressed, the wind turbine needs to provide short-term active support to the system, and the kinetic energy of the turbine rotor is released to reduce the system frequency change rate; after the active power support ΔP of the wind turbine to the system W ends, the wind turbine ends the frequency regulation task, and then the energy storage provides active power support to the wind turbine to help shorten the rotational speed recovery time.

[0157] In this embodiment, taking the construction of a simulation model as an example, the constructed simulation model is as Figure 6 shown. The model includes simulation units G1, G2, G3, loads L1, L2, L3, and transformers T1, T2, T3, T4, T5. The components are connected by 12 buses BUS, namely BUS1 to BUS12. G1 is connected to T1 via BUS1, and T1 is connected to two branches via BUS4:

[0158] One branch is connected to L1 via BUS5, and BUS5 is connected to BUS7. One of the remaining three ports of BUS7 is connected to T2, T2 is connected to G2 via BUS2, one end is connected to T4 via BUS11, T4 is connected to T5 via BUS10, T5 is connected to the energy storage and the wind turbine via BUS12, and one end is connected to BUS8, and L3 is connected to BUS8;

[0159] The other branch is connected to L2 via BUS6, and BUS6 is connected to BUS9. BUS9 is connected to T3, T3 is connected to G3 via BUS3, and one end is connected to BUS8; L3 is connected to BUS8.

[0160] According to Figure 6 the simulation model, the following four scenarios are set. Scenario 1: The inertia and primary frequency regulation timings are not considered; Scenario 2: The wind-storage coordination timing is not considered; Scenario 3: The wind-storage coordination timing is considered; Scenario 4: Only the system inertia support is considered.

[0161] In this embodiment, the active power changes of each system based on Scenario 3 are as Figure 7 shown. The blue line represents the system power, the orange line represents the energy storage system power, the yellow line represents the wind turbine energy storage power, and the purple line represents the wind turbine power. It can Figure 7 be easily seen that at the initial stage of the disturbance, the energy storage system detects the system frequency change and responds quickly, reaching the maximum output of the energy storage within a short time, but it still fails to meet the system transient power deficit; then the wind turbine releases the kinetic energy of the rotor, generates electromagnetic power in a short time to meet the system transient power deficit, and enters the primary frequency regulation state.

[0162] In this embodiment, after the wind turbine finishes the frequency regulation task, on the one hand, the energy storage provides support to it, accelerating its recovery of rotational speed and entering the normal power generation state, and on the other hand, it continues to provide power support to the system.

[0163] In this embodiment, the system frequency response diagrams under different set scenarios are as Figure 8 shown. Among them, the black line is the system frequency response in scenario a, that is, the system frequency response when the wind-storage coordination timing is not considered; the blue line is the system frequency response in scenario b, that is, the system frequency response when the inertia timing is not considered; the red line is the system frequency response in scenario c, that is, the system frequency response when the wind-storage coordination timing is considered; the green line is the system frequency response in scenario d, that is, the system frequency response when only inertia is considered.

[0164] In this embodiment, from Figure 8 it is not difficult to see that compared with scenario d, scenario a does not reflect the timing relationship between the stored inertia and primary frequency regulation; scenario b does not reflect the wind-storage coordinated control; scenario c adds an active power support link for the wind turbine compared with scenario b, providing a good support for suppressing the frequency change rate, which verifies the effectiveness of a method for constructing a wind-storage frequency response model applied in this embodiment for judging the frequency response characteristics of a relatively complex system.

[0165] Embodiment 2

[0166] In this embodiment, a system for constructing a wind-storage frequency response model is adopted. The system includes a wind turbine analysis module, an energy storage analysis module, and a timing control module;

[0167] The wind turbine analysis module constructs a frequency response model considering wind speed uncertainty according to the frequency response characteristics of the wind turbine in the wind-storage system and considering the influence of virtual inertia control and pitch angle control under high penetration. The frequency response characteristics of the wind turbine include wind speed uncertainty and the frequency response characteristics of the fan.

[0168] The energy storage analysis module obtains the additional power of the energy storage and the additional power of the thermal power unit according to the frequency response characteristics of the energy storage in the wind-storage system, and combines it with the frequency response model considering wind speed uncertainty, thereby constructing an overall frequency response model of the wind-storage system;

[0169] The timing control module considers the timing factor, combines the timing control logic of giving priority to the energy storage and coordinating with the fan, and combines it with the overall frequency response model of the wind-storage system, thereby constructing a wind-storage frequency response model.

[0170] In this embodiment, in the wind turbine analysis module, the first step of considering the uncertainty of wind speed is to consider the impact of virtual inertia control. The general method for a wind turbine generator (WTG) to participate in the short-term frequency control of the power grid is virtual inertia control, that is, to increase the additional active power reference value related to the change of the system frequency. A typical additional virtual inertia frequency control scheme is proportional derivative control, where the virtual inertia torque deviation is as follows:

[0171]

[0172] where ΔTe1 is the virtual inertia torque deviation, ω is the rotor speed, ΔPe1 is the active power output of the wind turbine, R ω is the droop ratio coefficient, k ω is the gain, and Δf(s) is the frequency change.

[0173] In this embodiment, in the wind turbine analysis module, the second step of considering the uncertainty of wind speed is to consider the impact of pitch angle control. The dynamic damping torque based on pitch angle control can be regarded as a function of the rotor speed, and the change of the dynamic damping torque can be expressed as the change of the rotor speed:

[0174] ΔTe2(s) = 2k p ωΔω(s)

[0175] where ΔTe2 is the dynamic damping torque deviation, k p is the proportional factor of the mechanical power input to the fan, ω is the rotor speed, and Δω(s) is the rotor speed deviation.

[0176] Combining the above results of considering the impact of virtual inertia control and pitch angle control, it is not difficult to obtain the frequency response characteristics of the fan as follows:

[0177]

[0178] Furthermore, the frequency response model considering the uncertainty of wind speed can be solved as follows:

[0179]

[0180]

[0181] where ΔPe(s) is the frequency response characteristic of the fan, ΔP W is the additional power generation of the wind turbine, H w is the virtual inertia time constant of the WTG, v is the wind speed, is the optimal wind energy utilization coefficient, λ ref is the optimal tip speed ratio, k C is the partial derivative with respect to the tip speed ratio, kβ is the partial derivative with respect to the pitch angle, a, b, and c are parameters related to inertia control, q, g are parameters related to pitch angle control, Δv is the change in wind speed, Δf is the change in frequency, and s is a complex frequency domain variable.

[0182] In this embodiment, in the wind turbine analysis module, the frequency response diagram considering wind speed uncertainty obtained by using the frequency response model of this wind speed uncertainty is as Figure 2 shown. Among them, the black line represents the ramp wind speed, the blue line represents the constant wind speed, and the red line represents the step wind speed.

[0183] In this embodiment, in the energy storage analysis module, after constructing the frequency response model considering wind speed uncertainty, the frequency response characteristics of the energy storage are analyzed. In this embodiment, taking the lead-acid battery as an example, its frequency characteristics are analyzed.

[0184] In the energy storage analysis module, first solve the state of charge of the battery at time t, as follows:

[0185]

[0186] where γ SOC (t) is the state of charge of the battery at time t, Q N is the rated capacity of the battery, i B (t) is the magnitude of the battery current at time t, Q B is the remaining capacity of the battery at time t.

[0187] Then solve the stored energy of the battery, as follows:

[0188] E B = ∫u B i B d(1 - γ SOC ) = u B Q N γ SOC_0

[0189] where E B is the stored energy of the battery, u B is the rated voltage of the battery, i B is the rated current of the battery, Q N is the rated capacity of the battery, γ SOC_0 is the state of charge of the battery in the initial state.

[0190] In this embodiment, by analogy with the synchronous motor, the stored energy of the battery can be obtained as follows:

[0191]

[0192] where E BStore energy for the battery, J vir_B Virtual inertia of the battery, w s Angular velocity of the power grid, u B Rated voltage of the battery, Q N Rated capacity of the battery, γ SOC (t) is the state of charge of the battery at time t.

[0193] Then, solve for the virtual inertia of the battery as follows:

[0194]

[0195] Among them, J vir_B is the virtual inertia of the battery, u B is the rated voltage of the battery, Q N is the rated capacity of the battery, γ SOC (t) is the state of charge of the battery at time t, J s is the inherent inertia of the synchronous motor, E B is the energy stored in the battery, γ SOC_0 is the initial state of charge of the battery, k s =(Δγ SOC / γ SOC_0 ) / (Δw w / w s ) is the ratio of the rate of change of the state of charge of the battery to the rate of change of the speed of the synchronous motor, E k is the kinetic energy of the synchronous motor rotor.

[0196] In this embodiment, the energy storage participates in the power grid frequency regulation control method, which is generally frequency addition control. The specific formula for the additional power generation of the energy storage is as follows:

[0197] ΔP E =-kΔf

[0198] Among them, ΔP E is the additional power generation of the energy storage, k is the proportional coefficient of the energy storage frequency addition control, and Δf is the frequency change.

[0199] In this embodiment, in the timing control module, the simplified frequency response model structure of the wind - energy storage system at different times is as Figure 3 shown. In the figure, η W is the wind power penetration rate, η R =1 - η W is the proportion of thermal power units, R is the governor droop coefficient, F H is the characteristic coefficient of the steam turbine, T R is the equivalent inertia time constant of the steam turbine, H sys is the equivalent inertia time constant of the system, D sys is the active power - frequency response coefficient of the system load, k Eis the proportional coefficient of the additional control of the energy storage frequency, T E is the response time constant of the inner current loop control, ΔP L is the disturbance power, ΔP W is the additional power generated by the wind turbine, ΔP E is the additional power generated by the energy storage, ΔP R is the additional power generated by the thermal power unit, and the serial numbers ① and ② are the frequency modulation time sequences. It can be seen from Figure 3 that the frequency response of the overall wind-storage system can be expressed as follows:

[0200] ΔP E = -kΔf

[0201]

[0202] where η R is the proportion of the thermal power unit, H sys is the equivalent inertia time constant of the system, ΔP R is the additional power generated by the thermal power unit, ΔP E is the additional power generated by the energy storage, ΔP W is the additional power generated by the wind turbine, ΔP L is the disturbance power, D sys is the active power frequency response coefficient of the system load, and Δf is the frequency change.

[0203] Compared with the traditional power system, the frequency response ability of the future new energy power system with high penetration and low inertia is reduced, and the impact of the new energy penetration rate on maintaining the frequency safety and stability of the system cannot be ignored.

[0204] In this embodiment, when the wind power penetration rates are 0%, 10%, 15%, and 25% respectively, the frequency response differences are as shown in Figure 4 the figure. The blue line in the figure is the case where the penetration rate is 0%, the red line in the figure is the case where the penetration rate is 10%, the yellow line in the figure is the case where the penetration rate is 15%, and the purple line in the figure is the case where the penetration rate is 25%. It is not difficult to see that when the penetration rate increases, the maximum frequency change rate of the system increases, the frequency deviation becomes larger, and the equivalent inertia of the system gradually decreases, which has an impact on the frequency safety and stability of the system.

[0205] In this embodiment, after constructing the overall frequency response model of the wind-storage system in the energy storage analysis module, the control logic of giving priority to the energy storage and coordinating with the wind turbines is adopted in the timing control module, so as to construct the wind-storage frequency response model. When the energy storage reaches its maximum output, if the frequency change rate does not exceed the limit, the energy storage is used for inertia support and frequency modulation; if the frequency change rate exceeds the limit, the wind turbines are used for inertia support and frequency modulation to reduce the frequency change rate until the frequency change rate does not exceed the limit, and then the energy storage is switched to be used for inertia support and frequency modulation.

[0206] In this embodiment, in the timing control module, the frequency response control logic flow of the wind-storage system under timing is as follows Figure 5 shown Figure 5 In it, first, the disturbance power ΔP L is monitored to obtain the additional frequency modulation power ΔP(i) at the i-th moment, and then the overall frequency change rate of the wind-storage system is detected to determine whether it exceeds the limit, that is whether it is greater than zero; if it is not greater than zero, then the energy storage is directly used for inertia support and frequency modulation, and the control ends. That is, it is expressed by the formula as:

[0207] P E = ΔP(i + 1)+P W2

[0208] P W2 = -P W1

[0209] In the formula, P E is the energy storage power, ΔP(i + 1) is the additional frequency modulation power at the (i + 1)-th moment, P W1 is the power of the wind turbine at timing 1, and P W2 is the power of the wind turbine at timing 2.

[0210] If is greater than zero, the overall frequency change of the wind-storage system is supported by the system's inertia, that is supporting Δf until the t 1 ' moment, and its frequency modulation effect is:

[0211] P E = γ SOC (t)*P

[0212] In the formula, P E is the energy storage power, γ SOC (t) is the state of charge of the battery at the t-th moment, and P is the rated power of the energy storage.

[0213] At this time, it is judged whether the energy storage power is less than the power required by the gap, that is, P E < P 缺 ;

[0214] If the energy storage power is less than the power required by the gap, that is, when the energy storage reaches its maximum output, and the overall frequency change rate of the wind-storage system exceeds the limit, then the wind turbine is used for inertia support and frequency modulation to reduce the overall frequency change rate of the wind-storage system, that is:

[0215] ΔP = P E + P W1

[0216] In the formula, ΔP is the additional frequency modulation power, and P ELet the energy storage power be \(P\). W1 It is the power of the wind turbine at time sequence 1.

[0217] If the energy storage power is greater than or equal to the power required by the gap, that is, when the energy storage reaches its maximum output, and the overall frequency change rate of the wind - energy storage system does not exceed the limit, then the energy storage is used for inertia support and frequency modulation, that is:

[0218] \(\Delta P = P\) E

[0219] In the formula, \(\Delta P\) is the additional power for frequency modulation, and \(P\) E is the energy storage power.

[0220] At time \(t'\), stop frequency modulation and end the control; the additional power for frequency modulation at time \(i + 1\) is: 3

[0221] \(\Delta P(i + 1)=\Delta P\) L -\(\Delta P\);

[0222] In the formula, \(\Delta P(i + 1)\) is the additional power for frequency modulation at time \(i + 1\), \(\Delta P\) L is the disturbance power, and \(\Delta P\) is the additional power for frequency modulation.

[0223] The control logic considers the wind - energy storage coordination time sequence, with the principle of giving priority to energy storage and the wind turbine cooperating. The specific process is as follows:

[0224] From \(0\) to \(t'\), detect whether the overall frequency change rate of the wind - energy storage system exceeds the limit. If it exceeds the limit, the overall frequency change of the wind - energy storage system is supported by the system's inertia until time \(t'\); if it does not exceed the limit, directly use the energy storage for inertia support and frequency modulation and then end the control; 1 1

[0225] At time \(t'\), the overall frequency change of the wind - energy storage system is supported by the energy storage; 1

[0226] At time \(t'\), when the energy storage reaches its maximum output, if the overall frequency change rate of the wind - energy storage system does not exceed the limit, use the energy storage for inertia support and frequency modulation; if the overall frequency change rate of the wind - energy storage system exceeds the limit, use the wind turbine for inertia support and frequency modulation to reduce the overall frequency change rate of the wind - energy storage system; 2

[0227] At time \(t'\), stop frequency modulation and end the control; 3

[0228] Among them, \(t'\lt t''\lt t'''\). 1 2 3

[0229] Among them, using a synchronous generator for inertia support means using the system for inertia support, referring to the inertia support provided by a traditional synchronous generator. In a power system, the rotor of a generator has a large moment of inertia and can absorb or release energy when the system is disturbed, thereby slowing down the rate of frequency change. The synchronous generator in this embodiment is a thermal power unit.

[0230] Using energy storage for inertia support means using an energy storage system, such as a battery or a supercapacitor, to charge and discharge quickly and simulate the inertial response of a traditional generator. When frequency fluctuations occur, the energy storage system quickly provides or absorbs energy to help maintain frequency stability.

[0231] Using a wind turbine for inertia support means using virtual synchronous generator technology to simulate the inertial response of a synchronous generator. Wind turbines are usually connected to the power grid through converters and traditionally do not provide inertial support. However, modern wind turbines can simulate the inertial response of a synchronous generator through specific control strategies, such as using virtual synchronous generator technology. This strategy can enable wind turbines to provide inertial support similar to that of traditional generators when the grid frequency changes.

[0232] Its frequency modulation effect is determined by the frequency modulation capacity provided by the energy storage, the state of charge, and the charge rate (States of Charge, SOC) characteristics. The specific formula is as follows:

[0233] P E =γ SOC (t)*P

[0234] Among them, P E is the energy storage power, γ SOC (t) is the state of charge of the battery at time t, and P is the rated power of the energy storage.

[0235] In this embodiment, if the energy storage reaches its maximum output, the rate of frequency change meets the system requirements and the frequency modulation capacity is sufficient, then both inertia support and frequency modulation are carried out by the energy storage; if the rate of frequency change cannot be effectively suppressed during the process of the energy storage reaching its maximum output, then the wind turbine needs to provide short-term active support to the system, and the kinetic energy of the wind turbine rotor is released to reduce the rate of frequency change of the system; after the active power support ΔP W of the wind turbine to the system ends, the wind turbine ends the frequency modulation task, and then the energy storage provides active power support to the wind turbine to help shorten the speed recovery time.

[0236] In this embodiment, taking the construction of a simulation model as an example, the constructed simulation model is as Figure 6As shown, the model includes simulated units G1, G2, G3, loads L1, L2, L3 and transformers T1, T2, T3, T4, T5. The devices are connected by 12 busbars BUS, namely BUS1 to BUS12. G1 is connected to T1 via BUS1, and T1 is connected to two branches via BUS4:

[0237] One branch is connected to L1 via BUS5, and BUS5 is connected to BUS7. One end of the remaining three ports of BUS7 is connected to T2, which is connected to G2 via BUS2, one end is connected to T4 via BUS11, T4 is connected to T5 via BUS10, T5 is connected to the energy storage and the wind turbine via BUS12, one end is connected to BUS8, and BUS8 is connected to L3;

[0238] The other branch is connected to L2 via BUS6, and is connected to BUS9 via BUS6, BUS9 is connected to T3, T3 is connected to G3 via BUS3, and one end is connected to BUS8; BUS8 is connected to L3.

[0239] according to Figure 6 The simulation model is set up in the following four scenarios: Scenario 1: Inertia and primary frequency regulation timing are not considered; Scenario 2: Wind-storage coordination timing is not considered; Scenario 3: Wind-storage coordination timing is considered; Scenario 4: Only system inertia support is considered.

[0240] In this embodiment, the active power changes of each system based on situation three are as follows: Figure 7 As shown. The blue line represents the system power, the orange line represents the energy storage system power, the yellow line represents the wind turbine energy storage power, and the purple line represents the wind turbine power. Figure 7 It is not difficult to see that at the beginning of the disturbance, the energy storage system detects the system frequency change and responds quickly, reaching the maximum energy storage output in a short time, but it is still unable to meet the system's transient power shortage; then the wind turbine releases the rotor kinetic energy, generates electromagnetic power in a short time to meet the system's transient power shortage, and enters a frequency modulation state.

[0241] In this embodiment, after the wind turbine completes the frequency regulation task, the energy storage provides support to the wind turbine to accelerate its speed recovery to enter the normal power generation state, and on the other hand, continues to provide power support to the system.

[0242] In this embodiment, the system frequency response diagrams under different set situations are as follows: Figure 8 As shown. The black line is the system frequency response in case a, that is, the system frequency response when the wind-storage coordination sequence is not considered; the blue line is the system frequency response in case b, that is, the system frequency response when the inertia sequence is not considered; the red line is the system frequency response in case c, that is, the system frequency response when the wind-storage coordination sequence is considered; the green line is the system frequency response in case d, that is, the system frequency response when only inertia is considered.

[0243] In this embodiment, from Figure 8 Figure 8 , it is not difficult to see that in case a compared with case d, the timing relationship between the storage inertia and the primary frequency regulation is not reflected; in case b, the wind-storage coordinated control is not reflected; in case c, compared with case b, the active power support link of the wind turbine is added, which provides a good support for suppressing the frequency change rate, verifying the effectiveness of a wind-storage frequency response model construction system adopted in this embodiment for judging the frequency response characteristics of a relatively complex system.

[0244] Embodiment 3

[0245] In this embodiment, an electronic device is adopted, including a memory and a processor. A computer program is stored on the memory. When the processor executes the program, the following method for constructing a wind-storage frequency response model is realized. The method includes the following steps:

[0246] According to the frequency response characteristics of the wind turbines in the wind-storage system, and considering the influence of virtual inertia control and the influence of pitch angle control under the condition of high penetration rate, a frequency response model considering wind speed uncertainty is constructed;

[0247] According to the frequency response characteristics of the energy storage in the wind-storage system, the additional power generation of the energy storage and the additional power generation of the thermal power unit are obtained, and they are combined with the frequency response model considering wind speed uncertainty, so as to construct an overall frequency response model of the wind-storage system;

[0248] Considering the timing factor, the timing control logic of giving priority to the energy storage and coordinating the cooperation of the wind turbines is combined with the overall frequency response model of the wind-storage system, so as to construct a wind-storage frequency response model.

[0249] In this embodiment, in the wind turbine analysis module, the first step of considering the uncertainty of the wind speed is to consider the influence of virtual inertia control. The general method for the wind turbine generator (WTG) to participate in the short-term frequency control of the power grid is virtual inertia control, that is, an additional active power reference value related to the system frequency change is increased. A typical additional virtual inertia frequency control scheme is proportional-derivative control, where the virtual inertia torque deviation is as follows:

[0250]

[0251] where, ΔTe1 is the virtual inertia torque deviation, ω is the rotor speed, ΔPe1 is the active power output of the wind turbine, R ω is the droop ratio coefficient, k ω is the gain, and Δf(s) is the frequency change.

[0252] In this embodiment, in the wind turbine analysis module, the second step of considering the uncertainty of wind speed is to consider the influence of pitch angle control. The dynamic damping torque based on pitch angle control can be regarded as a function of rotor speed, and the change of dynamic damping torque can be expressed as the change of rotor speed:

[0253] ΔTe2(s) = 2k p ωΔω(s)

[0254] where ΔTe2 is the dynamic damping torque deviation, k p is the proportionality factor of the mechanical power input to the fan, ω is the rotor speed, and Δω(s) is the rotor speed deviation.

[0255] Combining the above results of considering the influence of virtual inertia control and pitch angle control, it is not difficult to obtain the frequency response characteristics of the fan as follows:

[0256]

[0257] Furthermore, the frequency response model considering wind speed uncertainty can be solved as follows:

[0258]

[0259] where ΔPe(s) is the frequency response characteristic of the fan, ΔP W is the additional power generation of the wind turbine, H w is the virtual inertia time constant of the WTG, v is the wind speed, is the optimal wind energy utilization coefficient, λ ref is the optimal tip speed ratio, k C is the partial derivative with respect to the tip speed ratio, k β is the partial derivative with respect to the pitch angle, a, b, and c are the parameters related to inertia control, q, g are the parameters related to pitch angle control, Δv is the wind speed change, Δf is the frequency change, and s is the complex frequency domain variable.

[0260] In this embodiment, in the wind turbine analysis module, the frequency response diagram considering wind speed uncertainty obtained by using the frequency response model of wind speed uncertainty is as Figure 2 shown. Among them, the black line represents the ramp wind speed, the blue line represents the constant wind speed, and the red line represents the step wind speed.

[0261] In this embodiment, in the energy storage analysis module, after constructing the frequency response model considering wind speed uncertainty, the frequency response characteristics of the energy storage are analyzed. In this embodiment, a lead-acid battery is taken as an example to analyze its frequency characteristics.

[0262] In the energy storage analysis module, first, the state of charge of the battery at time t is solved as follows:

[0263]

[0264] Among them, γ SOC (t) is the state of charge of the battery at time t, Q N is the rated capacity of the battery, i B (t) is the magnitude of the battery current at time t, Q B is the remaining capacity of the battery at time t.

[0265] Then solve for the stored energy of the battery as follows:

[0266] E B = ∫u B i B d(1 - γ SOC ) = u B Q N γ SOC_0

[0267] Among them, E B is the stored energy of the battery, u B is the rated voltage of the battery, i B is the rated current of the battery, Q N is the rated capacity of the battery, γ SOC_0 is the state of charge of the battery in the initial state.

[0268] In this embodiment, by analogy with a synchronous motor, the stored energy of the battery can be obtained as follows:

[0269]

[0270] Among them, E B is the stored energy of the battery, J vir_B is the virtual moment of inertia of the battery, w s is the angular velocity of the power grid, u B is the rated voltage of the battery, Q N is the rated capacity of the battery, γ SOC (t) is the state of charge of the battery at time t.

[0271] Then solve for the virtual moment of inertia of the battery as follows:

[0272]

[0273] Among them, J vir_B is the virtual moment of inertia of the battery, u B is the rated voltage of the battery, Q N is the rated capacity of the battery, γ SOC (t) is the state of charge of the battery at time t, J s is the inherent moment of inertia of the synchronous motor, E BStore energy for the battery, γ SOC_0 The state of charge of the battery in the initial state, k s =(Δγ SOC / γ SOC_0 ) / (Δw w / w s ) is the ratio of the rate of change of the state of charge of the battery to the rate of change of the synchronous motor speed, E k is the kinetic energy of the synchronous motor rotor.

[0274] In this embodiment, the energy storage participating in the power grid frequency modulation control method is generally frequency additional control, and the specific formula for the additional power generation of the energy storage is as follows:

[0275] ΔP E =-kΔf

[0276] Among them, ΔP E is the additional power generation of the energy storage, k is the proportional coefficient of the energy storage frequency additional control, and Δf is the frequency change.

[0277] In this embodiment, in the timing control module, the simplified frequency response model structure of the wind and energy storage system is as Figure 3 shown. In the figure, η W is the wind power penetration rate, η R =1-η W is the proportion of thermal power units, R is the governor droop coefficient, F H is the steam turbine characteristic coefficient, T R is the equivalent inertia time constant of the steam turbine, H sys is the equivalent inertia time constant of the system, D sys is the active power frequency response coefficient of the system load, k E is the proportional coefficient of the energy storage frequency additional control, T E is the current inner loop control response time constant, ΔP L is the disturbance power, ΔP W is the additional power generation of the wind turbine, ΔP E is the additional power generation of the energy storage, ΔP R is the additional power generation of the thermal power unit, and the serial numbers ① and ② are the frequency modulation time sequences. From Figure 3 it can be obtained that the frequency response of the overall wind and energy storage system can be expressed as follows:

[0278] ΔP E =-kΔf

[0279]

[0280] Among them, η R is the proportion of thermal power units, H sys is the equivalent inertia time constant of the system, ΔP R is the additional power generation of the thermal power unit, ΔP EFor the additional power of energy storage, ΔP W For the additional power of wind turbines, ΔP L For the disturbance power, D sys For the active power frequency response coefficient of the system load, Δf is the frequency change.

[0281] Compared with the traditional power system, the frequency response ability of the future new energy low-inertia power system with high penetration rate is reduced, and the impact of the new energy penetration rate on maintaining the frequency safety and stability of the system cannot be ignored.

[0282] In this embodiment, the frequency response differences when the wind power penetration rates are 0%, 10%, 15%, and 25% respectively are as follows Figure 4 shown. In the figure, the blue line is for the case of 0% penetration rate, the red line is for the case of 10% penetration rate, the yellow line is for the case of 15% penetration rate, and the purple line is for the case of 25% penetration rate. It is not difficult to see that when the penetration rate increases, the maximum frequency change rate of the system increases, the frequency deviation becomes larger, and the equivalent inertia of the system gradually decreases, which has an impact on the frequency safety and stability of the system.

[0283] In this embodiment, after constructing the overall frequency response model of the wind-storage system in the energy storage analysis module, the control logic of giving priority to energy storage and coordinating with wind turbines is adopted in the time sequence control module, so as to construct the wind-storage frequency response model. When the energy storage reaches its maximum output, if the frequency change rate does not exceed the limit, the energy storage is used for inertia support and frequency modulation; if the frequency change rate exceeds the limit, the wind turbines are used for inertia support and frequency modulation to reduce the frequency change rate until the frequency change rate does not exceed the limit, and then the energy storage is used for inertia support and frequency modulation.

[0284] In this embodiment, in the time sequence control module, the frequency response control logic process of the wind-storage system under time sequence is as follows Figure 5 shown Figure 5 In it, first monitor the disturbance power ΔP L , obtain the additional frequency modulation power ΔP(i) at the i-th moment, and then detect whether the overall frequency change rate of the wind-storage system exceeds the limit, that is whether it is greater than zero; if is not greater than zero, directly use the energy storage for inertia support and frequency modulation and then end the control, that is, expressed by the formula as

[0285] P E =ΔP(i + 1)+P W2

[0286] P W2 =-P W1

[0287] In the formula, P ELet \(P\) be the energy storage power, and \(\Delta P(i + 1)\) be the additional frequency regulation power at the \((i + 1)\)-th moment, \(P\) W1 is the power of the wind turbine at time sequence 1, \(P\) W2 is the power of the wind turbine at time sequence 2.

[0288] If is greater than zero, the overall frequency change of the wind - storage system is provided by the system's inertia, that is support \(\Delta f\) until \(t\) 1 ' moment, and its frequency regulation effect is:

[0289] \(P\) E =\(\gamma\) SOC (t)\(\times P\)

[0290] In the formula, \(P\) E is the energy storage power, \(\gamma\) SOC (t) is the state of charge of the battery at time \(t\), and \(P\) is the rated power of the energy storage.

[0291] At this time, it is judged whether the energy storage power is less than the power required by the gap, that is \(P\) E \(< P\) 缺 ;

[0292] If the energy storage power is less than the power required by the gap, that is, when the energy storage reaches its maximum output, the overall frequency change rate of the wind - storage system exceeds the limit, then the wind turbine is used for inertia support and frequency regulation to reduce the overall frequency change rate of the wind - storage system, that is:

[0293] \(\Delta P = P\) E +\(P\) W1

[0294] In the formula, \(\Delta P\) is the additional frequency regulation power, \(P\) E is the energy storage power, \(P\) W1 is the power of the wind turbine at time sequence 1.

[0295] If the energy storage power is greater than or equal to the power required by the gap, that is, when the energy storage reaches its maximum output, the overall frequency change rate of the wind - storage system does not exceed the limit, then the energy storage is used for inertia support and frequency regulation, that is:

[0296] \(\Delta P = P\) E

[0297] In the formula, \(\Delta P\) is the additional frequency regulation power, \(P\) E is the energy storage power.

[0298] At \(t\) 3 ' moment, stop frequency regulation and end the control; the additional frequency regulation power at the \((i + 1)\)-th moment is:

[0299] \(\Delta P(i + 1)=\Delta P\) L -\(\Delta P\);

[0300] where ΔP(i + 1) is the additional power for frequency regulation at the (i + 1)-th moment, ΔP L is the disturbance power, and ΔP is the additional power for frequency regulation.

[0301] The control logic considers the coordinated timing of wind and energy storage, with the principle of giving priority to energy storage and coordinating with wind turbines. The specific process is as follows

[0302] From 0 to t 1 ′ moment, it is detected whether the overall frequency change rate of the wind and energy storage system exceeds the limit. If it exceeds the limit, the overall frequency change of the wind and energy storage system is supported by the system inertia until t 1 ′ moment; if it does not exceed the limit, the energy storage is directly used for inertia support and frequency regulation, and then the control ends;

[0303] At t 1 ′ moment, the overall frequency change of the wind and energy storage system is switched to be supported by the energy storage;

[0304] At t 2 ′ moment, when the energy storage reaches its maximum output, if the overall frequency change rate of the wind and energy storage system does not exceed the limit, the energy storage is used for inertia support and frequency regulation; if the overall frequency change rate of the wind and energy storage system exceeds the limit, the wind turbines are used for inertia support and frequency regulation to reduce the overall frequency change rate of the wind and energy storage system;

[0305] At t 3 ′ moment, the frequency regulation is stopped and the control ends;

[0306] where t 1 ′ < t 2 ′ < t 3 ′.

[0307] Among them, using a synchronous generator for inertia support means using the system for inertia support, which refers to the inertia support provided by a traditional synchronous generator. In a power system, the rotor of a generator has a large moment of inertia and can absorb or release energy when the system is disturbed, thereby slowing down the rate of frequency change. The synchronous generator in this embodiment is a thermal power unit.

[0308] Using energy storage for inertia support means using an energy storage system, such as a battery or a supercapacitor, to charge and discharge quickly to simulate the inertial response of a traditional generator. When frequency fluctuations occur, the energy storage system quickly provides or absorbs energy to help maintain frequency stability

[0309] Using a wind turbine for inertia support is a technology that uses virtual synchronous generator technology to simulate the inertial response of a synchronous generator. Wind turbines are usually connected to the power grid through converters and traditionally do not provide inertial support. However, modern wind turbines can use specific control strategies, such as virtual synchronous generator technology, to simulate the inertial response of a synchronous generator. This strategy enables wind turbines to provide inertial support similar to that of traditional generators when the grid frequency changes.

[0310] Its frequency regulation effect is determined by the frequency regulation capacity provided by the energy storage, the state of charge, and the charging rate (States of Charge, SOC) characteristics. The specific formula is as follows:

[0311] P E =γ SOC (t)*P

[0312] Where, P E is the energy storage power, γ SOC (t) is the state of charge of the battery at time t, and P is the rated power of the energy storage.

[0313] In this embodiment, if the energy storage reaches its maximum output, the frequency change rate meets the system requirements and the frequency regulation capacity is sufficient, then both inertia support and frequency regulation are performed by the energy storage; if the frequency change rate cannot be effectively suppressed during the process of the energy storage reaching its maximum output, the wind turbine needs to provide short-term active support to the system, and the wind turbine rotor releases kinetic energy to reduce the system frequency change rate; after the wind turbine provides active power support ΔP W to the system, the wind turbine ends the frequency regulation task, and then the energy storage provides active power support to the wind turbine to help shorten the rotational speed recovery time.

[0314] In this embodiment, taking the construction of a simulation model as an example, the constructed simulation model is as Figure 6 shown. The model includes simulation units G1, G2, G3, loads L1, L2, L3, and transformers T1, T2, T3, T4, T5. The devices are connected by 12 buses BUS, namely BUS1 to BUS12. G1 is connected to T1 via BUS1, and T1 is connected to two branches via BUS4:

[0315] One branch is connected to L1 via BUS5, and BUS5 is connected to BUS7. One of the remaining three ports of BUS7 is connected to T2, T2 is connected to G2 via BUS2, one end is connected to T4 via BUS11, T4 is connected to T5 via BUS10, T5 is connected to the energy storage and the wind turbine via BUS12, one end is connected to BUS8, and L3 is connected to BUS8;

[0316] The other branch is connected to L2 via BUS6, and is connected to BUS9 via BUS6, BUS9 is connected to T3, T3 is connected to G3 via BUS3, and one end is connected to BUS8; BUS8 is connected to L3.

[0317] according to Figure 6 The simulation model is set up in the following four scenarios: Scenario 1: Inertia and primary frequency regulation timing are not considered; Scenario 2: Wind-storage coordination timing is not considered; Scenario 3: Wind-storage coordination timing is considered; Scenario 4: Only system inertia support is considered.

[0318] In this embodiment, the active power changes of each system based on situation three are as follows: Figure 7 As shown. The blue line represents the system power, the orange line represents the energy storage system power, the yellow line represents the wind turbine energy storage power, and the purple line represents the wind turbine power. Figure 7 It is not difficult to see that at the beginning of the disturbance, the energy storage system detects the system frequency change and responds quickly, reaching the maximum energy storage output in a short time, but it is still unable to meet the system's transient power shortage; then the wind turbine releases the rotor kinetic energy, generates electromagnetic power in a short time to meet the system's transient power shortage, and enters a frequency modulation state.

[0319] In this embodiment, after the wind turbine completes the frequency regulation task, the energy storage provides support to the wind turbine on the one hand, accelerating its recovery of rotation speed to enter a normal power generation state, and on the other hand, continues to provide power support to the system.

[0320] In this embodiment, the system frequency response diagrams under different settings are as follows: Figure 8 As shown. The black line is the system frequency response in case a, that is, the system frequency response when the wind-storage coordination sequence is not considered; the blue line is the system frequency response in case b, that is, the system frequency response when the inertia sequence is not considered; the red line is the system frequency response in case c, that is, the system frequency response when the wind-storage coordination sequence is considered; the green line is the system frequency response in case d, that is, the system frequency response when only inertia is considered.

[0321] In this embodiment, from Figure 8 It is not difficult to see that, compared with case d, case a does not reflect the timing relationship between storage inertia and primary frequency regulation; case b does not reflect the coordinated control of wind and storage; compared with case b, case c adds the active support link of wind turbines, which provides good support for suppressing the frequency change rate, confirming the effectiveness of a wind-storage frequency response model construction system used in this embodiment for judging the frequency response characteristics of more complex systems.

[0322] Example 4

[0323] In this embodiment, a computer-readable storage medium is adopted, on which a computer program is stored. When the program is executed by a processor, a method for constructing a wind-storage frequency response model as described below is implemented. The method includes the following steps:

[0324] According to the frequency response characteristics of wind turbines in a wind-storage system, and considering the influence of virtual inertia control and pitch angle control under high penetration conditions, a frequency response model considering wind speed uncertainty is constructed;

[0325] According to the frequency response characteristics of energy storage in the wind-storage system, the additional power generation of energy storage and the additional power generation of thermal power units are obtained, and they are combined with the frequency response model considering wind speed uncertainty, so as to construct an overall frequency response model of the wind-storage system;

[0326] Considering the time series factor, the time series control logic of giving priority to energy storage and coordinating with wind turbines is combined with the overall frequency response model of the wind-storage system, so as to construct a wind-storage frequency response model.

[0327] In this embodiment, in the wind turbine analysis module, the first step of considering the uncertainty of wind speed is to consider the influence of virtual inertia control. The general method of a wind turbine generator (WTG) for short-term frequency control of the power grid is virtual inertia control, that is, an additional active power reference value related to the change of the system frequency is increased. A typical additional virtual inertia frequency control scheme is proportional-derivative control, where the virtual inertia torque deviation is as follows:

[0328]

[0329] where ΔTe1 is the virtual inertia torque deviation, ω is the rotor speed, ΔPe1 is the active power output of the wind turbine, R ω is the droop ratio coefficient, k ω is the gain, and Δf(s) is the frequency change.

[0330] In this embodiment, in the wind turbine analysis module, the second step of considering the uncertainty of wind speed is to consider the influence of pitch angle control. The dynamic vibration damping torque based on pitch angle control can be regarded as a function of the rotor speed, and the change of the dynamic vibration damping torque can be expressed as the change of the rotor speed:

[0331] ΔTe2(s) = 2k p ωΔω(s)

[0332] where ΔTe2 is the dynamic vibration damping torque deviation, k p is the mechanical power input ratio factor of the wind turbine, ω is the rotor speed, and Δω(s) is the rotor speed deviation.

[0333] Combining the above results considering the influence of virtual inertia control and pitch angle control, it is not difficult to obtain the frequency response characteristics of the wind turbine as follows:

[0334]

[0335] Furthermore, the frequency response model considering wind speed uncertainty can be solved as follows:

[0336]

[0337]

[0338] where ΔPe(s) is the frequency response characteristic of the wind turbine, ΔP W is the additional power generation of the wind turbine generator set, H w is the virtual inertia time constant of the WTG, v is the wind speed, is the optimal wind energy utilization coefficient, λ ref is the optimal tip speed ratio, k C is the partial derivative of the tip speed ratio, k β is the partial derivative of the pitch angle, a, b, and c are parameters related to inertia control, q, g are parameters related to pitch angle control, Δv is the wind speed change, Δf is the frequency change, and s is the complex frequency domain variable.

[0339] In this embodiment, in the wind turbine generator set analysis module, the frequency response diagram considering wind speed uncertainty obtained by using the frequency response model of wind speed uncertainty is as shown in Figure 2 the figure. Among them, the black line represents the ramp wind speed, the blue line represents the constant wind speed, and the red line represents the step wind speed.

[0340] In this embodiment, in the energy storage analysis module, after constructing the frequency response model considering wind speed uncertainty, the frequency response characteristics of the energy storage are analyzed. In this embodiment, a lead-acid battery is taken as an example to analyze its frequency characteristics.

[0341] In the energy storage analysis module, first, the state of charge of the battery at time t is solved as follows:

[0342]

[0343] where γ SOC (t) is the state of charge of the battery at time t, Q N is the rated capacity of the battery, i B (t) is the magnitude of the battery current at time t, Q B is the remaining capacity of the battery at time t.

[0344] Then, the stored energy of the battery is solved as follows:

[0345] E B = ∫ u B i B d(1 - γ SOC ) = u B Q N γ SOC_0

[0346] Among them, E B is the energy stored in the battery, u B is the rated voltage of the battery, i B is the rated current of the battery, Q N is the rated capacity of the battery, γ SOC_0 is the state of charge of the battery at the initial state.

[0347] In this embodiment, by analogy with a synchronous motor, the energy stored in the battery can be obtained as follows:

[0348]

[0349] Among them, E B is the energy stored in the battery, J vir_B is the virtual moment of inertia of the battery, w s is the angular velocity of the power grid, u B is the rated voltage of the battery, Q N is the rated capacity of the battery, γ SOC (t) is the state of charge of the battery at time t.

[0350] Then, solve for the virtual moment of inertia of the battery as follows:

[0351]

[0352] Among them, J vir_B is the virtual moment of inertia of the battery, u B is the rated voltage of the battery, Q N is the rated capacity of the battery, γ SOC (t) is the state of charge of the battery at time t, J s is the inherent moment of inertia of the synchronous motor, E B is the energy stored in the battery, γ SOC_0 is the state of charge of the battery at the initial state, k s = (Δγ SOC / γ SOC_0 ) / (Δw w / w s ) is the ratio of the rate of change of the state of charge of the battery to the rate of change of the speed of the synchronous motor, E k is the kinetic energy of the rotor of the synchronous motor.

[0353] In this embodiment, the energy storage participates in the power grid frequency regulation control method, which is generally frequency additional control. The specific formula for the additional power generation of the energy storage is as follows:

[0354] ΔP E =-kΔf

[0355] Where, ΔP E is the additional power generation of the energy storage, k is the proportional coefficient of the energy storage frequency additional control, and Δf is the frequency change.

[0356] In this embodiment, in the timing control module, the simplified frequency response model structure of the wind - energy storage system at different times is as Figure 3 shown. In the figure, η W is the wind power penetration rate, η R =1 - η W is the proportion of thermal power units, R is the governor droop coefficient, F H is the steam turbine characteristic coefficient, T R is the equivalent inertia time constant of the steam turbine, H sys is the system equivalent inertia time constant, D sys is the active power - frequency response coefficient of the system load, k E is the proportional coefficient of the energy storage frequency additional control, T E is the current inner - loop control response time constant, ΔP L is the disturbance power, ΔP W is the additional power generation of the wind turbine, ΔP E is the additional power generation of the energy storage, ΔP R is the additional power generation of the thermal power unit, and the serial numbers ① and ② are the frequency regulation time sequences. From Figure 3 it can be obtained that the frequency response of the overall wind - energy storage system can be expressed as follows:

[0357] ΔP E =-kΔf

[0358]

[0359] Where, η R is the proportion of thermal power units, H sys is the system equivalent inertia time constant, ΔP R is the additional power generation of the thermal power unit, ΔP E is the additional power generation of the energy storage, ΔP W is the additional power generation of the wind turbine, ΔP L is the disturbance power, D sys is the active power - frequency response coefficient of the system load, and Δf is the frequency change.

[0360] Compared with the traditional power system, the frequency response ability of the future new - energy - based power system with high penetration and low inertia decreases, and the impact of the new - energy penetration rate on maintaining the frequency safety and stability of the system cannot be ignored.

[0361] In this embodiment, the frequency response differences when the wind power penetration rates are 0%, 10%, 15%, and 25% respectively are as follows Figure 4 shown. In the figure, the blue line represents the case where the penetration rate is 0%, the red line represents the case where the penetration rate is 10%, the yellow line represents the case where the penetration rate is 15%, and the purple line represents the case where the penetration rate is 25%. It is not difficult to see that when the penetration rate increases, the maximum frequency change rate of the system increases, the frequency deviation becomes larger, and the equivalent inertia of the system gradually decreases, which has an impact on the frequency safety and stability of the system.

[0362] In this embodiment, after constructing the overall frequency response model of the wind-storage system in the energy storage analysis module, the control logic of giving priority to energy storage and coordinating with wind turbines is adopted in the timing control module, so as to construct the wind-storage frequency response model. When the energy storage reaches its maximum output, if the frequency change rate does not exceed the limit, the energy storage is used for inertia support and frequency modulation; if the frequency change rate exceeds the limit, the wind turbines are used for inertia support and frequency modulation to reduce the frequency change rate until the frequency change rate does not exceed the limit, and then the energy storage is switched to be used for inertia support and frequency modulation.

[0363] In this embodiment, in the timing control module, the frequency response control logic process of the wind-storage system under timing is as follows Figure 5 shown. Figure 5 Among them, first, the disturbance power ΔP L is monitored to obtain the frequency modulation additional power ΔP(i) at the i-th moment, and then the overall frequency change rate of the wind-storage system is detected to see if it exceeds the limit, that is, to see if it is greater than zero; if is not greater than zero, the energy storage is directly used for inertia support and frequency modulation and then the control ends. That is, expressed by the formula:

[0364] P E =ΔP(i + 1)+P W2

[0365] P W2 =-P W1

[0366] In the formula, P E is the energy storage power, ΔP(i + 1) is the frequency modulation additional power at the (i + 1)-th moment, P W1 is the power of the wind turbine at timing 1, and P W2 is the power of the wind turbine at timing 2.

[0367] If is greater than zero, the overall frequency change of the wind-storage system is supported by the system's inertia, that is, supporting Δf continues until the t 1 ′ moment, and its frequency modulation effect is:

[0368] P E = γ SOC (t) * P

[0369] Wherein, P E is the energy storage power, γ SOC (t) is the state of charge of the battery at time t, and P is the rated power of the energy storage.

[0370] At this time, it is judged whether the energy storage power is less than the power required by the gap, that is, P E < P 缺 ;

[0371] If the energy storage power is less than the power required by the gap, that is, when the energy storage reaches the maximum output, the overall frequency change rate of the wind - energy storage system exceeds the limit, then the wind turbine is used for inertia support and frequency modulation to reduce the overall frequency change rate of the wind - energy storage system, that is:

[0372] ΔP = P E + P W1

[0373] Wherein, ΔP is the additional power for frequency modulation, P E is the energy storage power, and P W1 is the power of the wind turbine at time sequence 1.

[0374] If the energy storage power is greater than or equal to the power required by the gap, that is, when the energy storage reaches the maximum output, the overall frequency change rate of the wind - energy storage system does not exceed the limit, then the energy storage is used for inertia support and frequency modulation, that is:

[0375] ΔP = P E

[0376] Wherein, ΔP is the additional power for frequency modulation, and P E is the energy storage power.

[0377] At time t 3 ', stop frequency modulation and end the control; the additional power for frequency modulation at time i + 1 is:

[0378] ΔP(i + 1) = ΔP L - ΔP;

[0379] Wherein, ΔP(i + 1) is the additional power for frequency modulation at time i + 1, ΔP L is the disturbance power, and ΔP is the additional power for frequency modulation.

[0380] The control logic considers the wind - energy storage coordination time sequence, and takes energy storage first and fan cooperation as the principle. The specific process is as follows:

[0381] 0 - t 1At time t', detect whether the overall frequency change rate of the wind-storage system exceeds the limit. If it exceeds the limit, the overall frequency change of the wind-storage system is supported by the system's inertia until time t 1 '; if it does not exceed the limit, directly use the energy storage for inertia support and frequency regulation and then end the control;

[0382] t 1 '; at this time, the overall frequency change of the wind-storage system is supported by the energy storage;

[0383] t 2 '; when the energy storage reaches its maximum output at time t'', if the overall frequency change rate of the wind-storage system does not exceed the limit, use the energy storage for inertia support and frequency regulation; if the overall frequency change rate of the wind-storage system exceeds the limit, use the wind turbine for inertia support and frequency regulation to reduce the overall frequency change rate of the wind-storage system;

[0384] t 3 '; at time t''', stop frequency regulation and end the control;

[0385] where t 1 ' < t 2 ' < t 3 '.

[0386] Among them, using a synchronous generator for inertia support means using the system for inertia support, which refers to the inertia support provided by a traditional synchronous generator. In a power system, the rotor of a generator has a large moment of inertia and can absorb or release energy when the system is disturbed, thereby slowing down the rate of frequency change. The synchronous generator in this embodiment is a thermal power unit.

[0387] Using energy storage for inertia support is to use an energy storage system, such as a battery or a supercapacitor, to charge and discharge quickly and simulate the inertial response of a traditional generator. When frequency fluctuations occur, the energy storage system quickly provides or absorbs energy to help maintain frequency stability

[0388] Using a wind turbine for inertia support is to use virtual synchronous generator technology to simulate the inertial response of a synchronous generator. Wind turbines are usually connected to the power grid through converters and do not traditionally provide inertial support. However, modern wind turbines can use specific control strategies, such as virtual synchronous generator technology, to simulate the inertial response of a synchronous generator. This strategy can enable wind turbines to provide inertial support similar to that of traditional generators when the grid frequency changes.

[0389] Its frequency regulation effect is determined by the frequency regulation capacity provided by the energy storage, the state of charge, and the charging rate (States of Charge, SOC) characteristics. The specific formula is as follows:

[0390] P E = γ SOC (t) * P

[0391] where P E is the energy storage power, γ SOC (t) is the state of charge of the battery at time t, and P is the rated power of the energy storage.

[0392] In this embodiment, when the energy storage reaches its maximum output, if the frequency change rate meets the system requirements and the frequency regulation capacity is sufficient, both inertia support and frequency regulation are performed by the energy storage; when the energy storage reaches its maximum output, if the frequency change rate cannot be effectively suppressed, the wind turbine needs to provide short-term active support to the system, and the wind turbine rotor releases kinetic energy to reduce the system frequency change rate; after the wind turbine provides active power support ΔP W to the system, the wind turbine ends the frequency regulation task, and then the energy storage provides active power support to the wind turbine to help shorten the speed recovery time.

[0393] In this embodiment, taking the construction of a simulation model as an example, the constructed simulation model is as Figure 6 shown. The model includes simulation units G1, G2, G3, loads L1, L2, L3, and transformers T1, T2, T3, T4, T5. The devices are connected by 12 buses BUS, namely BUS1 to BUS12. G1 is connected to T1 via BUS1, and T1 is connected to two branches via BUS4:

[0394] One branch is connected to L1 via BUS5, and BUS5 is connected to BUS7. One of the remaining three ports of BUS7 is connected to T2, T2 is connected to G2 via BUS2, one end is connected to T4 via BUS11, T4 is connected to T5 via BUS10, T5 is connected to the energy storage and the wind turbine via BUS12, one end is connected to BUS8, and L3 is connected to BUS8;

[0395] The other branch is connected to L2 via BUS6, and BUS6 is connected to BUS9. BUS9 is connected to T3, T3 is connected to G3 via BUS3, and one end is connected to BUS8; L3 is connected to BUS8.

[0396] According to Figure 6 the simulation model, the following four scenarios are set. Scenario 1: The timing of inertia and primary frequency regulation is not considered; Scenario 2: The timing of wind-energy storage coordination is not considered; Scenario 3: The timing of wind-energy storage coordination is considered; Scenario 4: Only system inertia support is considered.

[0397] In this embodiment, the active power changes of each system based on Scenario 3 are as Figure 7 shown. The blue line represents the system power, the orange line represents the energy storage system power, the yellow line represents the wind turbine energy storage power, and the purple line represents the wind turbine power. From Figure 7It is not difficult to see that in the initial stage of the disturbance, the energy storage system detects the change in the system frequency and responds quickly, reaching the maximum output of the energy storage within a short time. However, it still fails to meet the system's transient power deficit. Then the wind turbine releases the rotor kinetic energy, generates electromagnetic power in a short time to meet the system's transient power deficit, and enters the primary frequency regulation state.

[0398] In this embodiment, after the wind turbine finishes the frequency regulation task, on the one hand, the energy storage provides support for it to accelerate its rotation speed recovery and enter the normal power generation state, and on the other hand, it continues to provide power support for the system.

[0399] In this embodiment, the system frequency response diagrams under different scenarios are set as Figure 8 shown. Among them, the black line is the system frequency response in scenario a, that is, the system frequency response without considering the time sequence of wind-storage coordination; the blue line is the system frequency response in scenario b, that is, the system frequency response without considering the inertia time sequence; the red line is the system frequency response in scenario c, that is, the system frequency response considering the wind-storage coordination time sequence; the green line is the system frequency response in scenario d, that is, the system frequency response only considering inertia.

[0400] In this embodiment, from Figure 8 it is not difficult to see that compared with scenario d, scenario a does not reflect the time sequence relationship between storage inertia and primary frequency regulation; scenario b does not reflect the wind-storage coordinated control; scenario c adds the active power support link of the wind turbine compared with scenario b, which provides a good support for suppressing the frequency change rate, verifying the effectiveness of a wind-storage frequency response model construction system adopted in this embodiment for judging the frequency response characteristics of a relatively complex system.

[0401] As mentioned above, the above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of various equivalent modifications or substitutions, and these modifications or substitutions should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A method for constructing a wind storage frequency response model, characterized in that: The method comprises the following steps: According to the frequency response characteristics of wind turbines in the wind storage system, and considering the influence of virtual inertial control and pitch angle control under high penetration, a frequency response model considering wind speed uncertainty is constructed; According to the frequency response characteristics of energy storage in the wind-storage system, the additional power of energy storage and the additional power of thermal power units are obtained, which are combined with the frequency response model considering wind speed uncertainty to construct the overall frequency response model of the wind-storage system. Taking timing factors into consideration, the timing control logic of energy storage priority and wind turbine coordination is combined with the overall frequency response model of the wind-storage system to construct a wind-storage frequency response model.

2. A method for constructing a wind storage frequency response model according to claim 1, characterized in that: The frequency response characteristics of the wind turbine generator set include at least one of wind speed uncertainty and wind turbine frequency response characteristics.

3. A method for constructing a wind storage frequency response model according to claim 1, characterized in that: The specific formula for the influence of the virtual inertia control is: Among them, ΔTe1 is the virtual inertia torque deviation, s is the complex frequency domain variable, s = σ + jω, σ is the real part, which is the attenuation or growth rate of the signal, jω is the imaginary part, which is the frequency of the signal, ω is the rotor speed, ΔPe1 is the active power output of the wind turbine, R ω is the droop proportional coefficient, k ω is the gain, and Δf(s) is the frequency change.

4. A method for constructing a wind storage frequency response model according to claim 1, characterized in that: The specific formula for the influence of the pitch angle control is: ΔTe2(s)=2k p ωΔω(s) Among them, ΔTe2 is the dynamic damping torque deviation, k p is the fan input mechanical power proportional factor, ω is the rotor speed, and Δω(s) is the rotor speed deviation.

5. The method for constructing a wind storage frequency response model according to claim 1, characterized in that: The specific formula of the frequency response model considering wind speed uncertainty is: Among them, ΔP W is the additional power of the wind turbine, s is a complex frequency domain variable, s = σ + jω, σ is the real part, is the attenuation or growth rate of the signal, jω is the imaginary part, is the frequency of the signal, ω is the rotor speed, η W is the wind power penetration rate, H w is the virtual inertia time constant of WTG, v is the wind speed, is the optimal wind energy utilization coefficient, λ ref is the optimal tip speed ratio, k C for Partial derivative of tip speed ratio, k ω is the gain, k p is the fan input mechanical power proportionality factor, k b is the inertial control proportional factor, k β for The derivative of the pitch angle, a, b and c are the inertial control related parameters, q and g are the pitch angle control related parameters, Δv is the wind speed change, Δf is the frequency change R ω is the droop proportional coefficient.

6. A method for constructing a wind storage frequency response model according to claim 1, characterized in that: The specific formula for the energy storage power increase is: ΔP E =-kΔf Among them, ΔP E is the additional power generated by energy storage, k is the additional control proportional coefficient of energy storage frequency, and Δf is the frequency change.

7. The method for constructing a wind storage frequency response model according to claim 1, characterized in that: The specific formula for the additional power generation of the thermal power unit is: Among them, ΔP R The additional power of the thermal power unit, η R is the proportion of thermal power units, R is the speed regulator adjustment coefficient, F H is the turbine characteristic coefficient, T R is the equivalent inertia time constant of the steam turbine, s is the complex frequency domain variable, and Δf is the frequency change.

8. The method for constructing a wind storage frequency response model according to claim 1, characterized in that: The specific formula of the overall frequency response model of the wind storage system is: Among them, η R is the proportion of thermal power units, H sys is the system equivalent inertia time constant, ΔP R Increase the power of the thermal power unit, ΔP E To increase the power of energy storage, ΔP W is the additional power of the wind turbine, that is, the frequency response model considering the uncertainty of wind speed, ΔP L is the disturbance power, D sys is the system load active frequency response coefficient, and Δf is the frequency change.

9. A method for constructing a wind storage frequency response model according to claim 1, characterized in that: The timing control logic of energy storage priority and wind turbine coordination is specifically as follows: At time 0-t1′, check whether the overall frequency change rate of the wind-storage system exceeds the limit. If it exceeds the limit, the overall frequency change of the wind-storage system is supported by the system inertia until time t1′; if it does not exceed the limit, the energy storage is directly used for inertia support and frequency modulation before ending the control; At t1′, the overall frequency change of the wind-storage system is supported by energy storage; When the energy storage reaches the maximum output at time t2′, if the overall frequency change rate of the wind-storage system does not exceed the limit, the energy storage is used for inertia support and frequency regulation; if the overall frequency change rate of the wind-storage system exceeds the limit, the wind turbines are used for inertia support and frequency regulation to reduce the overall frequency change rate of the wind-storage system; At t3′, stop frequency modulation and end control; Among them, t1′<t2′<t3′.

10. A method for constructing a wind storage frequency response model according to claim 9, characterized in that: When energy storage is used for inertia support and frequency modulation, the frequency modulation effect is determined by the charging characteristics and is reflected by the energy storage power. The charging characteristics include the frequency modulation capacity provided by the energy storage, the state of charge of the battery, and the charging rate. The specific formula for the frequency modulation effect is: P E =γ SOC (t)*P Among them, P E is the energy storage power, γ SOC (t) is the battery charge state at time t, and P is the rated power of the energy storage.

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