Method and system for calculating frequency static characteristic coefficients of different wind and light feed-in proportions

Abstract

The invention discloses a method and system for calculating frequency static characteristic coefficients of different wind and light feed-in proportions, and relates to the technical field of power system frequency characteristic analysis, and the method comprises the steps: building a frequency response model according to the mechanical and electromagnetic torque relation of a synchronous generator; analyzing the frequency domain and the time domain of the frequency response, and calculating a dynamic frequency index; and calculating a proportional relation between the lowest frequency variation and the wind-solar direct current to obtain a power frequency static characteristic coefficient. According to the method for calculating the frequency static characteristic coefficients of the different wind-light feed-in proportions, a new frequency response model is deduced, the limitation that a traditional method cannot be applied in a complex scene is solved, the influence of different wind-light direct-current proportions on the dynamic characteristics of a system is quantified, the safety and adaptability of power grid operation are improved, and the method is suitable for large-scale popularization and application. The frequency static characteristic coefficients under different wind and light direct current access proportions can be obtained without complex calculation, the calculation efficiency is improved, and the method has better effects in the aspects of limitation, safety and calculation efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of power system frequency characteristic analysis, and in particular to a method for calculating frequency static characteristic coefficients with different wind and solar power feed-in ratios. Background Art

[0002] In recent years, the widespread application of wind power and photovoltaic power generation technologies around the world has prompted the power system to gradually transform towards a high proportion of new energy. Due to its cleanliness and sustainability, wind and solar energy have become an important technical means to achieve the goal of carbon neutrality. However, unlike traditional synchronous generators, wind and solar energy have the characteristics of randomness, volatility and intermittency, which leads to more complex dynamic adjustment requirements for power system operation. In order to ensure the stability of grid frequency after the access of new energy, academia and engineering communities have proposed a variety of frequency response models and analysis methods to optimize system operation efficiency and improve its anti-interference ability.

[0003] Although the existing frequency response models perform well in traditional synchronous generator systems, their limitations are particularly obvious in complex scenarios considering island operation or high-proportion wind-solar DC feed-in. First, the traditional method fails to accurately reflect the impact of wind-solar DC power access on the system inertia and frequency regulation capability, which makes the prediction accuracy of dynamic frequency changes low. Secondly, most models rely on complex calculation processes and it is difficult to quickly solve the frequency static characteristic coefficients under different wind-solar DC ratios, which limits their practicality in engineering. In addition, the existing models focus more on the system response under a single disturbance and lack quantitative analysis of the law of frequency static characteristic changes. Therefore, the current technology cannot provide a simple, fast and engineering-applicable solution to achieve effective calculation of the frequency static characteristic coefficient under changes in the wind-solar DC ratio. Summary of the invention

[0004] In view of the above-mentioned problems, the present invention is proposed.

[0005] Therefore, the technical problem solved by the present invention is: the existing power system frequency response analysis method has high computational complexity, insufficient practicality, lack of rapid solution to the frequency static characteristic coefficient, and how to achieve optimization of efficient quantitative analysis of the frequency static characteristic coefficient under changes in the wind-solar-DC access ratio.

[0006] To solve the above technical problems, the present invention provides the following technical solutions: a method for calculating the frequency static characteristic coefficients of different wind-solar feed-in ratios, comprising constructing a frequency response model according to the relationship between the mechanical and electromagnetic torques of the synchronous generator; analyzing the frequency domain and time domain of the frequency response to calculate the dynamic frequency index; calculating the minimum frequency change and the wind-solar DC ratio relationship to obtain the power frequency static characteristic coefficient.

[0007] As a preferred solution of the method for calculating the frequency static characteristic coefficient of different wind and solar power feed-in ratios described in the present invention, the relationship between the mechanical and electromagnetic torques of the synchronous generator includes that for a single synchronous generator, the speed deviation per unit value of the synchronous generator is expressed as:

[0008]

[0009] Among them, Δω ri is the speed deviation per unit value of the synchronous machine, M i is the inertia time of the synchronous machine, ΔT mi and ΔT ei are the mechanical torque and electromagnetic torque increments of the synchronous generator respectively.

[0010] As a preferred solution of the method for calculating the frequency static characteristic coefficients of different wind and solar power feed-in ratios described in the present invention, wherein: the construction of the frequency response model includes deriving the approximate relationship between the unbalanced power and unbalanced torque of the synchronous machine in the form of a per-unit value according to the conversion relationship between power and torque, which is expressed as:

[0011] ΔP mi -ΔP ei =ΔT mi -ΔT ei

[0012] Where ΔP mi and ΔP ei are the mechanical power and electromagnetic power of the synchronous generator respectively, and the relationship between the unbalanced power and the speed of the synchronous machine is expressed as:

[0013]

[0014] If there are n synchronous generators, and Δω r1 =Δω r2 =…=Δω rn =Δω r , the aggregate form is expressed as:

[0015]

[0016] The proportion of wind and solar DC access system is expressed as:

[0017]

[0018] Where P W and P G They are the active power of wind-solar DC and the active power of synchronous machine, the proportion of synchronous machine is 1-η. When wind-solar DC is not included, the frequency response is expressed as:

[0019]

[0020] in, is the undamped natural oscillation frequency, is the damping ratio, let ΔP d For a step disturbance, the response of the frequency response model is expressed as:

[0021]

[0022] Among them, P step It is the unit value of the active step amplitude with the sum of the rated capacities of all synchronous generators when no wind-solar DC is connected as the reference value.

[0023] As a preferred solution of the method for calculating the frequency static characteristic coefficients of different wind and solar power feed-in ratios of the present invention, the frequency domain and time domain of the analytical frequency response include frequency domain and time domain analytical expressions as follows:

[0024]

[0025]

[0026]

[0027]

[0028] Among them, ω r is the damped oscillation frequency.

[0029] As a preferred solution of the method for calculating the frequency static characteristic coefficient of different wind-solar feed-in ratios described in the present invention, the calculation of the dynamic frequency index includes obtaining the relationship between the dynamic frequency index and the wind-solar DC ratio according to the frequency domain and time domain solutions of the system frequency response. According to the initial value theorem and the final value theorem of the Laplace transform, the initial frequency change rate is expressed as:

[0030]

[0031] After adding wind and solar DC, it is expressed as:

[0032] M T·new =M T (1-η)

[0033]

[0034] Among them, the higher the proportion of wind power and photovoltaic DC, the greater the initial frequency change rate, and the steady-state frequency is expressed as:

[0035]

[0036] After adding wind power and photovoltaic DC, it is expressed as:

[0037]

[0038]

[0039] Among them, the larger the proportion of wind power and photovoltaic DC, the larger the steady-state frequency. The lowest frequency point time and the lowest frequency change are expressed as:

[0040]

[0041]

[0042] Among them, t nadir is the time when the frequency drops to the lowest point, Δf nadir is the frequency change at the lowest frequency point.

[0043] As a preferred solution of the method for calculating the frequency static characteristic coefficient of different wind-solar feed-in ratios described in the present invention, wherein: the calculation of the relationship between the minimum frequency change and the wind-solar DC ratio includes that the frequency minimum point time and the minimum frequency change are functions of the natural oscillation frequency, the damping ratio and the damped oscillation frequency, and the relationship between the wind-solar DC ratio and the natural oscillation frequency, the damping ratio and the damped oscillation frequency is analyzed. After the wind-solar DC is connected, the influence of the wind-solar DC ratio change on the natural oscillation frequency is expressed as follows:

[0044]

[0045] When using typical parameters, K L R≈2×0.05=0.1≈0, the effect of the change in the wind-solar DC ratio on the natural oscillation frequency is expressed as:

[0046]

[0047] The effect of the change in wind-solar DC ratio on the damping ratio is expressed as:

[0048]

[0049] The impact of the change in wind-solar DC ratio on the minimum frequency change is expressed as:

[0050]

[0051]

[0052] When K L When R≈2×0.05=0.1≈0, the effect of the change in wind-solar DC ratio on the change in the minimum frequency is expressed as:

[0053]

[0054] Among them, the greater the proportion of wind and solar DC access, the greater the change in the minimum frequency, and the wind and solar DC access proportion is inversely proportional to the lowest frequency point.

[0055] As a preferred solution of the method for calculating the frequency static characteristic coefficients of different wind and solar power feed-in ratios described in the present invention, wherein: the power frequency static characteristic coefficient obtained includes the power frequency static characteristic coefficient expressed as:

[0056]

[0057] Among them, R and K L They are the system aggregation adjustment coefficient and the load frequency factor respectively. When the wind-solar-DC ratio changes, the power frequency static characteristic coefficient is expressed as:

[0058]

[0059] Among them, the larger the proportion of wind and solar DC, the smaller the power frequency static characteristic coefficient, and the smaller the overall frequency adjustment ability of the system. It is a linear relationship, and the slope is the unit adjustment power of the original system generator.

[0060] Another object of the present invention is to provide a frequency static characteristic coefficient calculation system for different wind-solar power feed-in ratios, which can calculate the power frequency static characteristic coefficient through the relationship between the minimum frequency change and the wind-solar power DC access ratio through the characteristic coefficient module, thereby solving the problem that the current calculation of the frequency static characteristic coefficient relies on a complex multivariable coupling process and has low calculation efficiency.

[0061] As a preferred solution of the frequency static characteristic coefficient calculation system for different wind-solar feed-in ratios described in the present invention, it includes: a model construction module, a frequency index module, and a characteristic coefficient module; the model construction module is used to construct a frequency response model according to the relationship between the mechanical and electromagnetic torques of the synchronous generator; the frequency index module is used to analyze the frequency domain and time domain of the frequency response and calculate the dynamic frequency index; the characteristic coefficient module is used to calculate the minimum frequency change and the wind-solar DC ratio relationship to obtain the power frequency static characteristic coefficient.

[0062] A computer device includes a memory and a processor, wherein the memory stores a computer program, and is characterized in that the processor executes the computer program to implement the steps of a method for calculating frequency static characteristic coefficients of different wind and solar power feed-in ratios.

[0063] A computer-readable storage medium having a computer program stored thereon, characterized in that when the computer program is executed by a processor, the steps of a method for calculating frequency static characteristic coefficients of different wind and solar power feed-in ratios are implemented.

[0064] Beneficial effects of the present invention: The method for calculating the frequency static characteristic coefficients of different wind-solar DC feed-in ratios provided by the present invention is based on the frequency response model of the traditional synchronous generator, combined with the dynamic characteristics of the wind-solar DC access ratio, to derive the frequency response model, which solves the limitation that the traditional method is not applicable in complex scenarios. By quantifying the impact of different wind-solar DC ratios on the dynamic characteristics of the system, the safety and adaptability of the power grid operation are improved. The frequency static characteristic coefficients under different wind-solar DC access ratios can be quickly obtained without complex calculations, which reduces the technical threshold for project implementation and improves the calculation efficiency. The present invention achieves better results in terms of limitations, safety and calculation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. Among them:

[0066] Figure 1 An overall flow chart of a method for calculating frequency static characteristic coefficients for different wind-solar feed-in ratios provided in the first embodiment of the present invention.

[0067] Figure 2 A synchronous machine aggregation model diagram of a method for calculating frequency static characteristic coefficients for different wind and solar power feed-in ratios provided in the first embodiment of the present invention.

[0068] Figure 3 A speed regulator feedback link diagram of a method for calculating frequency static characteristic coefficients for different wind and solar power feed-in ratios provided in the first embodiment of the present invention.

[0069] Figure 4 A speed regulator aggregation model diagram of a method for calculating frequency static characteristic coefficients for different wind and solar power feed-in ratios provided in the first embodiment of the present invention.

[0070] Figure 5 A method for calculating the frequency static characteristic coefficients of different wind and solar power feed-in ratios provided in the first embodiment of the present invention and a system frequency response model diagram of a speed regulator are provided.

[0071] Figure 6 A system frequency response model diagram of a method for calculating frequency static characteristic coefficients with different wind-solar feed-in ratios provided in the first embodiment of the present invention.

[0072] Figure 7 A schematic diagram of different wind-solar direct current proportions of a method for calculating frequency static characteristic coefficients with different wind-solar feed-in ratios provided in the first embodiment of the present invention.

[0073] Figure 8 A frequency response model diagram of a system with different wind-solar-DC ratios according to a method for calculating frequency static characteristic coefficients with different wind-solar-DC feed-in ratios provided in the first embodiment of the present invention.

[0074] Fig. 9 A diagram showing the variation of power frequency static characteristic coefficients of a power grid system with different wind power ratios according to a method for calculating frequency static characteristic coefficients with different wind-solar power feed-in ratios provided in a second embodiment of the present invention.

[0075] Fig.10 This is an overall module diagram of a frequency static characteristic coefficient calculation system for different wind and solar power feed-in ratios provided in the third embodiment of the present invention. DETAILED DESCRIPTION

[0076] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the drawings of the specification. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in the art without creative work should fall within the scope of protection of the present invention.

[0077] Example 1

[0078] Reference Figure 1 , is an embodiment of the present invention, and provides a method for calculating frequency static characteristic coefficients of different wind and solar power feed-in ratios, including:

[0079] S1: Construct a frequency response model based on the relationship between the mechanical and electromagnetic torques of the synchronous generator.

[0080] Furthermore, the mechanical and electromagnetic torque relationships of a synchronous generator are included for a single synchronous generator.

[0081] It should be noted that the speed deviation per unit value of the synchronous machine is expressed as:

[0082]

[0083] Among them, Δω ri is the speed deviation per unit value of the synchronous machine, M i is the inertia time of the synchronous machine, ΔT mi and ΔT ei are the mechanical torque and electromagnetic torque increments of the synchronous generator respectively.

[0084] Furthermore, constructing the frequency response model includes based on the conversion relationship between power and torque.

[0085] It should be noted that the approximate relationship between the unbalanced power and unbalanced torque of the synchronous machine in the derivation per unit value form is expressed as:

[0086] ΔP mi -ΔP ei =ΔT mi -ΔT ei

[0087] Among them, ΔP mi and ΔP ei are the mechanical power and electromagnetic power of the synchronous generator respectively, and the relationship between the unbalanced power and the speed of the synchronous machine is expressed as:

[0088]

[0089] If there are n synchronous generators, and Δω r1 =Δω r2 =… =Δω rn =Δω r , the aggregate form is expressed as:

[0090]

[0091] The proportion of wind and solar DC access system is expressed as:

[0092]

[0093] Where P W and P G They are the active power of wind-solar DC and the active power of synchronous machine, the proportion of synchronous machine is 1-η. When wind-solar DC is not included, the frequency response is expressed as:

[0094]

[0095]

[0096] in, is the undamped natural oscillation frequency, is the damping ratio, let ΔP d For a step disturbance, the response of the frequency response model is expressed as:

[0097]

[0098]

[0099] Among them, P step It is the unit value of the active step amplitude with the sum of the rated capacities of all synchronous generators when no wind-solar DC is connected as the reference value.

[0100] It should also be noted that, assuming that all the systems are reheat turbine generator sets, ignoring the smaller time constants of the governor and steam chamber, and only retaining the turbine reheat time constant, the feedback block diagram of the governor frequency regulation is obtained as follows: Figure 3 As shown, K mi is the effective gain factor, F Hi is the high pressure cylinder power proportional coefficient, T Ri is the turbine reheat time constant, R i is the speed regulator’s adjustment coefficient, and the speed regulator’s aggregation model is further obtained as Figure 4 As shown, [K m ,T R ,F H ]According to the proportionality factor Weighted, in, K m For example, The system frequency response model taking into account the speed regulator is as follows Figure 5 As shown, taking into account the frequency regulation effect of the load, the system frequency response model is obtained as follows Figure 6 As shown, is the aggregate frequency response factor of the load. When the sum of the rated capacity of the entire system is selected as the benchmark capacity, the values ​​of power, time constant and regulation coefficient are equivalent to the typical parameters of a single synchronous machine.

[0101] It should also be noted that in a multi-unit large-capacity power system, assuming that the active power of the synchronous generator matches the inertia and frequency regulation capability of the synchronous generator, under different proportions, ΔP d unchanged, assuming that wind and solar DC do not participate in frequency adjustment, ΔP W =0,M T becomes 1-η times of the original value, K L unchanged, ΔP m Right now becomes 1-η times of the original value, but the remaining adjustment parameter T R 、F H and K m The system frequency response model under different proportions of wind and solar DC is as follows: Figure 8 shown.

[0102] S2: Analyze the frequency domain and time domain of the frequency response and calculate the dynamic frequency index.

[0103] Furthermore, analyzing the frequency domain and the time domain of the frequency response includes frequency domain and time domain analysis.

[0104] It should be noted that the frequency domain and time domain analysis are expressed as:

[0105]

[0106]

[0107]

[0108]

[0109] Among them, ω r is the damped oscillation frequency.

[0110] Furthermore, the calculation of the dynamic frequency index includes obtaining the relationship between the dynamic frequency index and the proportion of wind-solar DC based on the frequency domain and time domain solutions of the system frequency response.

[0111] It should be noted that according to the initial value theorem and final value theorem of Laplace transform, the initial frequency change rate is expressed as:

[0112]

[0113] After adding wind and solar DC, it is expressed as:

[0114] M T·new =M T (1-η)

[0115]

[0116] Among them, the higher the proportion of wind power and photovoltaic DC, the greater the initial frequency change rate, and the steady-state frequency is expressed as:

[0117]

[0118] After adding wind power and photovoltaic DC, it is expressed as:

[0119]

[0120]

[0121] Among them, the larger the proportion of wind power and photovoltaic DC, the larger the steady-state frequency. The lowest frequency point time and the lowest frequency change are expressed as:

[0122]

[0123]

[0124] Among them, t nadir is the time when the frequency drops to the lowest point, Δf nadir is the frequency change at the lowest frequency point.

[0125] It should also be noted that the dynamic frequency indicators include the initial frequency change rate, the lowest frequency point time, the lowest frequency change, and the steady-state frequency.

[0126] S3: Calculate the minimum frequency change and the wind-solar-DC ratio to obtain the power frequency static characteristic coefficient.

[0127] Furthermore, the relationship between the minimum frequency change and the wind-solar DC ratio is calculated, including the frequency minimum point time and the minimum frequency change, which is a function of the natural oscillation frequency, the damping ratio and the damped oscillation frequency.

[0128] It should be noted that, by analyzing the relationship between the wind-solar DC ratio and the natural oscillation frequency, the damping ratio and the damped oscillation frequency, after the wind-solar DC is connected, the impact of the change in the wind-solar DC ratio on the natural oscillation frequency is expressed as follows:

[0129]

[0130] When using typical parameters, K L R≈2×0.05=0.1≈0, the effect of the change in the wind-solar DC ratio on the natural oscillation frequency is expressed as:

[0131]

[0132] The effect of the change in wind-solar DC ratio on the damping ratio is expressed as:

[0133]

[0134] The impact of the change in wind-solar DC ratio on the minimum frequency change is expressed as:

[0135]

[0136]

[0137] When K L When R≈2×0.05=0.1≈0, the effect of the change in wind-solar DC ratio on the change in the minimum frequency is expressed as:

[0138]

[0139] Among them, the greater the proportion of wind and solar DC access, the greater the change in the minimum frequency, and the wind and solar DC access proportion is inversely proportional to the lowest frequency point.

[0140] It should also be noted that it is approximately assumed that when the wind-solar DC ratio changes, the natural oscillation frequency remains unchanged, the damping ratio remains unchanged, the damped oscillation frequency remains approximately unchanged, and the time of the lowest frequency point remains approximately unchanged.

[0141] Furthermore, the power-frequency static characteristic coefficient is obtained including the power-frequency static characteristic coefficient.

[0142] It should be noted that the power frequency static characteristic coefficient is expressed as:

[0143]

[0144] Among them, R and K L They are the system aggregation adjustment coefficient and the load frequency factor respectively. When the wind-solar-DC ratio changes, the power frequency static characteristic coefficient is expressed as:

[0145]

[0146] Among them, the larger the proportion of wind and solar DC, the smaller the power frequency static characteristic coefficient, and the smaller the overall frequency adjustment ability of the system. It is a linear relationship, and the slope is the unit adjustment power of the original system generator.

[0147] Example 2

[0148] Reference Fig. 9 , which is an embodiment of the present invention, provides a method for calculating the frequency static characteristic coefficient of different wind and solar power feed-in ratios. In order to verify the beneficial effects of the present invention, scientific demonstration is carried out through economic benefit calculation and simulation experiments.

[0149] The experiment built a simulation model based on the IEEE 140-node system, and conducted frequency response analysis under different wind power access ratios. In the experimental model, the wind power access ratio gradually increased from 10% to 60%, and data was sampled at 5 fixed ratios. To ensure the accuracy of the experiment, the simulation set the system disturbance to a 100MW step load change, and the initial frequency was set to 50Hz.

[0150] In the simulation platform, grid models under conditions of 10%-60% wind power access ratio are defined respectively, the generator and load response parameters are adjusted, step load disturbance is applied to each model, the initial frequency change rate, the minimum frequency change and the lowest frequency time are observed, the steady-state frequency and the frequency static characteristic coefficient are recorded, the anti-interference ability score is calculated, and the system recovery ability is evaluated. During the experiment, each set of data is simulated and verified three times, and the average value is taken to improve the reliability and accuracy of the data.

[0151] As shown in Table 1, the rate of change of the initial frequency of the system gradually increases with the increase of the proportion of wind power access, indicating that the higher the proportion of wind power access, the weaker the initial anti-interference ability of the system, the inertia decreases, resulting in more drastic frequency changes, and the minimum frequency change shows a larger negative value. The increase in the proportion of wind power access makes the system frequency offset larger, indicating that the system stability decreases, and the time of the lowest frequency point increases slightly, reflecting that the system response speed is limited. The frequency regulation time delay caused by the high proportion of wind power access may affect the system's rapid recovery ability. The steady-state frequency drops from 49.8Hz to 48.8Hz, indicating that it is difficult for the system to recover to the ideal frequency under the condition of high proportion of wind power access, and the frequency regulation ability is significantly reduced. The frequency static characteristic coefficient shows a linear downward trend, which verifies the assumption that the higher the proportion of wind power access, the weaker the frequency adjustment ability. The anti-interference ability score drops from 9 to 4, indicating that the high proportion of wind power access has a negative impact on the overall stability of the system.

[0152] Table 1 Experimental data table

[0153]

[0154]

[0155] Example 3

[0156] Reference Fig.10 , which is an embodiment of the present invention, provides a frequency static characteristic coefficient calculation system for different wind and solar power feeding ratios, including: a model building module, a frequency index module, and a characteristic coefficient module.

[0157] The model building module is used to construct a frequency response model based on the relationship between the mechanical and electromagnetic torques of the synchronous generator; the frequency index module is used to analyze the frequency domain and time domain of the frequency response and calculate the dynamic frequency index; the characteristic coefficient module is used to calculate the minimum frequency change and the wind-solar-DC proportional relationship to obtain the power frequency static characteristic coefficient.

[0158] If the function is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, server, or network device, etc.) to perform all or part of the steps of the methods of each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk, etc. Various media that can store program codes.

[0159] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute instructions), or in conjunction with such instruction execution systems, devices or apparatuses. For the purposes of this specification, "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in conjunction with such instruction execution systems, devices or apparatuses.

[0160] More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection with one or more wires (electronic device), a portable computer disk case (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be a paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, deciphering, or processing in another suitable manner as necessary, and then stored in a computer memory.

[0161] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, multiple steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc. It should be noted that the above embodiments are only used to illustrate the technical solution of the present invention and are not limited. Although the present invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solution of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

[0162] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for calculating frequency static characteristic coefficients of different wind and solar power feed-in ratios, characterized in that: include: According to the relationship between mechanical and electromagnetic torque of synchronous generator, a frequency response model is constructed; Analyze the frequency domain and time domain of frequency response and calculate dynamic frequency indicators; The minimum frequency change and the wind-solar-DC ratio are calculated to obtain the power frequency static characteristic coefficient.

2. The method for calculating frequency static characteristic coefficients of different wind and solar power feed-in ratios according to claim 1, characterized in that: The relationship between the mechanical and electromagnetic torques of the synchronous generator includes that for a single synchronous generator, the speed deviation per unit value of the synchronous machine is expressed as: Among them, Δω ri is the speed deviation per unit value of the synchronous machine, M i is the inertia time of the synchronous machine, ΔT mi and ΔT ei are the mechanical torque and electromagnetic torque increments of the synchronous generator respectively.

3. The method for calculating frequency static characteristic coefficients of different wind and solar power feed-in ratios according to claim 2, characterized in that: The frequency response model is constructed by deriving an approximate relationship between the unbalanced power and the unbalanced torque of the synchronous machine in the form of a per-unit value according to the conversion relationship between power and torque, which is expressed as: ΔP mi -ΔP ei =ΔT mi -ΔT ei Among them, ΔP mi and ΔP ei are the mechanical power and electromagnetic power of the synchronous generator respectively, and the relationship between the unbalanced power and the speed of the synchronous machine is expressed as: If there are n synchronous generators, and Δω r1 =Δω r2 =… =Δω rn =Δω r , the aggregate form is expressed as: The proportion of wind and solar DC access system is expressed as: Where P W and P G They are the active power of wind-solar DC and the active power of synchronous machine, the proportion of synchronous machine is 1-η. When wind-solar DC is not included, the frequency response is expressed as: in, is the undamped natural oscillation frequency, is the damping ratio, let ΔP d For a step disturbance, the response of the frequency response model is expressed as: Among them, P step It is the unit value of the active step amplitude with the sum of the rated capacities of all synchronous generators when no wind-solar DC is connected as the reference value.

4. The method for calculating frequency static characteristic coefficients of different wind and solar power feed-in ratios according to claim 3, characterized in that: The frequency domain and time domain of the analytical frequency response include frequency domain and time domain analytical expressions as follows: Among them, ω r is the damped oscillation frequency.

5. The method for calculating frequency static characteristic coefficients of different wind and solar power feed-in ratios according to claim 4, characterized in that: The calculation of the dynamic frequency index includes obtaining the relationship between the dynamic frequency index and the proportion of wind and solar DC according to the frequency domain and time domain solutions of the system frequency response. According to the initial value theorem and the final value theorem of Laplace transform, the initial frequency change rate is expressed as: After adding wind and solar DC, it is expressed as: M T·new =M T (1st) Among them, the higher the proportion of wind power and photovoltaic DC, the greater the initial frequency change rate, and the steady-state frequency is expressed as: After adding wind power and photovoltaic DC, it is expressed as: Among them, the larger the proportion of wind power and photovoltaic DC, the larger the steady-state frequency. The lowest frequency point time and the lowest frequency change are expressed as: Among them, t nadir is the time when the frequency drops to the lowest point, Δf nadir is the frequency change at the lowest frequency point.

6. The method for calculating frequency static characteristic coefficients of different wind and solar power feed-in ratios according to claim 5, characterized in that: The calculation of the relationship between the minimum frequency change and the wind-solar direct current ratio includes the frequency minimum point time and the minimum frequency change, which is a function of the natural oscillation frequency, the damping ratio and the damped oscillation frequency. The relationship between the wind-solar direct current ratio and the natural oscillation frequency, the damping ratio and the damped oscillation frequency is analyzed. After the wind-solar direct current is connected, the influence of the wind-solar direct current ratio change on the natural oscillation frequency is expressed as follows: When using typical parameters, K L R≈2×0.05=0.1≈0, the effect of the change in the wind-solar DC ratio on the natural oscillation frequency is expressed as: The effect of the change in wind-solar DC ratio on the damping ratio is expressed as: The impact of the change in wind-solar DC ratio on the minimum frequency change is expressed as: When K L When R≈2×0.05=0.1≈0, the effect of the change in wind-solar DC ratio on the change in the minimum frequency is expressed as: Among them, the greater the proportion of wind and solar DC access, the greater the change in the minimum frequency, and the wind and solar DC access proportion is inversely proportional to the lowest frequency point.

7. The method for calculating frequency static characteristic coefficients of different wind and solar power feed-in ratios according to claim 6, characterized in that: The power-frequency static characteristic coefficient obtained includes the power-frequency static characteristic coefficient expressed as: Among them, R and K L They are the system aggregation adjustment coefficient and the load frequency factor respectively. When the wind-solar-DC ratio changes, the power frequency static characteristic coefficient is expressed as: Among them, the larger the proportion of wind and solar DC, the smaller the power frequency static characteristic coefficient, and the smaller the overall frequency adjustment ability of the system. It is a linear relationship, and the slope is the unit adjustment power of the original system generator.

8. A system using the method for calculating frequency static characteristic coefficients of different wind and solar power feed-in ratios as claimed in any one of claims 1 to 7, characterized in that: Including model building module, frequency index module, characteristic coefficient module; The model building module is used to build a frequency response model according to the relationship between the mechanical and electromagnetic torques of the synchronous generator; The frequency index module is used to analyze the frequency domain and time domain of the frequency response and calculate the dynamic frequency index; The characteristic coefficient module is used to calculate the minimum frequency change and the wind-solar-DC proportional relationship to obtain the power frequency static characteristic coefficient.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of the method for calculating frequency static characteristic coefficients for different wind and solar power feed-in ratios according to any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method for calculating frequency static characteristic coefficients for different wind and solar power feed-in ratios according to any one of claims 1 to 7 are implemented.

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