Actual power grid new energy maximum permeability assessment method considering frequency stability

Abstract

The invention discloses an actual power grid new energy maximum permeability evaluation method considering frequency stability, and relates to the technical field of power system optimization and evaluation, and the method comprises the steps: analyzing a frequency safety and stability boundary, and determining the maximum active disturbance in actual power grid operation; calculating a frequency intensity index critical value based on the disturbance magnitude and the frequency safety and stability boundary, gradually replacing the synchronous machine with the new energy, respectively calculating frequency intensity indexes of the system under different permeability during active power increase and decrease disturbance, and drawing a curve of the frequency intensity indexes changing along with the permeability of the new energy; and calculating the new energy maximum permeability of the system under the disturbance of active power increase and decrease, and performing evaluation and planning of new energy access. According to the method, the curve of the frequency intensity index changing along with the new energy permeability is drawn, so that the evaluation result is more accurate and reliable, and better effects are achieved in the aspects of new energy access, power grid planning and operation and power grid safety and stability.

Description

Technical Field

[0001] The present invention relates to the technical field of power system optimization and evaluation, and in particular to a method for evaluating the maximum penetration rate of new energy in an actual power grid taking frequency stability into consideration. Background Art

[0002] With the continuous growth of global energy demand and the improvement of environmental protection awareness, the penetration rate of renewable energy in the power system continues to increase. The randomness and intermittency of renewable energy have brought challenges to the frequency stability of the power system. When evaluating the maximum penetration rate of renewable energy in the actual power grid, the existing technology often adopts a static model-based method, ignoring the dynamic characteristics of the actual power grid operation. In the power system, the frequency stability problem directly affects the reliability of power supply. Therefore, evaluating the maximum penetration rate of renewable energy in the power grid, that is, the maximum proportion of renewable energy in the total power generation of the power grid under the premise of ensuring frequency stability, is of great significance for power grid planning and operation.

[0003] At present, the evaluation of the maximum penetration rate of renewable energy in the power grid mainly relies on traditional static analysis methods. These methods often assume that the power grid operates in a steady state and ignore the dynamic characteristics of the power grid in actual operation. The limitation of this method is that it cannot accurately predict the actual performance of the frequency stability of the power grid when it is disturbed by the active power brought by the access of renewable energy. Since the output power of renewable energy is affected by factors such as weather conditions and sunshine intensity, its volatility is large, and this volatility may have an adverse effect on the frequency stability of the power grid. In order to more accurately evaluate the frequency stability of the power grid when the penetration rate of renewable energy increases, an evaluation method that can consider the dynamic characteristics of the power grid is needed. When evaluating the penetration rate of renewable energy, the existing related technologies usually only focus on the static characteristics of the power grid, but ignore the dynamic response of the power grid in actual operation. This method may lead to a large deviation between the evaluation results and the actual operation, thereby affecting the evaluation and planning of renewable energy access. When evaluating the penetration rate of renewable energy, the existing related technologies do not use frequency intensity indicators for quantitative analysis, which makes the evaluation results lack comparability and operability. In the evaluation process, the existing technologies do not fully consider the interaction between renewable energy and synchronous machines, resulting in inaccurate evaluation results. 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 that the existing power system optimization and evaluation technical methods have large deviations in evaluation results, lack of comparability and operability, and inaccurate evaluation process, and the problem of how to accurately evaluate the maximum penetration rate of new energy in the actual power grid.

[0006] To solve the above technical problems, the present invention provides the following technical solutions: a method for evaluating the maximum penetration rate of new energy in an actual power grid considering frequency stability, comprising analyzing the frequency safety and stability boundary to determine the maximum active power disturbance in the actual power grid operation; calculating the critical value of the frequency strength index based on the disturbance size and the frequency safety and stability boundary, gradually replacing the synchronous machine with new energy, and calculating the frequency strength index of the system at different penetration rates when the active power is increased or decreased, and drawing a curve of the frequency strength index changing with the new energy penetration rate; calculating the maximum penetration rate of new energy in the system under the disturbance of increased or decreased active power, and conducting evaluation and planning of new energy access.

[0007] As a preferred solution of the method for evaluating the maximum penetration rate of new energy in the actual power grid considering frequency stability described in the present invention, wherein: the analysis of the frequency safety and stability boundary includes performing an inspection of the power system n-1, based on the maximum Δf<+0.6Hz when the frequency rises and the maximum Δf<-0.8Hz when the frequency drops, the frequency safety and stability boundary used in the evaluation; under different operating modes, according to the calculation of the maximum locking corresponding frequency rise|Δf in BPA 1max |、Maximum power loss corresponding frequency drop|Δf 2max |, the lower frequency deviation from the rated frequency value meets the national standard requirements for frequency safety and stability, that is, |Δf 1max |=0.6Hz、

[0008] Δf 2max |=0.8Hz.

[0009] As a preferred solution of the method for evaluating the maximum penetration rate of new energy in the actual power grid considering frequency stability described in the present invention, the maximum active disturbance includes the maximum active disturbances in the two scenarios of active increase and active decrease, and the maximum active increase disturbance is the disturbance caused by the maximum blocking, which is recorded as P 0+ , the maximum active power reduction disturbance is the disturbance caused by the maximum loss power supply, denoted as P 0- .

[0010] As a preferred solution of the method for evaluating the maximum penetration rate of new energy in an actual power grid considering frequency stability described in the present invention, wherein: the calculation of the critical value of the frequency strength index includes, and the relationship between the critical value of the frequency strength index and the disturbance size and frequency is expressed as:

[0011]

[0012] Among them, α 1min is the critical value of the indicator corresponding to the increase of active power, α 2min It is the critical value of the indicator corresponding to the reduction of active power.

[0013] As a preferred solution of the method for evaluating the maximum penetration rate of new energy in an actual power grid considering frequency stability described in the present invention, the curve of drawing the frequency strength index as the penetration rate of new energy includes gradually replacing the synchronous machine with new energy, calculating the frequency strength index of the system at different penetration rates when the active power is increased and decreased respectively, and drawing the curve of the frequency strength index as the penetration rate of new energy changes; when all new energy equipment in the power grid is replaced by synchronous machines, the initial penetration rate is 0, and the frequency response of the power system after the disturbance is calculated in the two scenarios of maximum DC blocking and maximum loss power supply, which is expressed as:

[0014]

[0015] Among them, P 0 represents the initial maximum active disturbance, Δω 1 (s) is the common mode frequency in the two scenarios of maximum DC blocking and maximum power loss, G i (s) is the frequency-active power transfer function of the power generation equipment connected to the i-th node; the power generation equipment model is reduced by unified structure approximation, and the unified structure model is expressed as:

[0016]

[0017] Among them, the parameter J u,i , D u,i , K u,i is the unified structural parameter of the i-th device, respectively J u,i Indicates effective inertia, D u,i represents the effective damping, K u,i Represents the effective adjustment coefficient, which is obtained by approximating the actual power response with the power response of the unified structure model, and approximating the actual power response of the device with a linear combination of three trajectories: the differential of the frequency, the frequency itself, and the integral of the frequency; the simplified system frequency response Δω u (s) has only two orders, expressed as:

[0018]

[0019] Among them, J us , D us , is the sum of the unified structural parameters of each power generation equipment, ΔP L (s) represents the change in system load; solving the unified structural model parameters of each power generation equipment is converted into a parameter optimization problem, which is expressed as:

[0020]

[0021] stΔP i (s) = G i (s)Δω(s)

[0022] ΔP' i (s) = G u,i (s)Δω(s)

[0023] Where ΔP i (t) and ΔP' i (t) are the actual power response of the i-th power generation equipment and the power response of the unified structure approximation, ΔP i (s) and ΔP' i (s) are the actual power response of the i-th power generation equipment in the s-domain and the power response of the unified structure approximation, Δω(s) is the representation of the system frequency change in the s-domain, t 0 and t f are the initial and final moments of the time period of interest, respectively, and t 0 Take the disturbance start time, t f Take 1.5 times the lowest frequency time, J u,i , D u,i and 1 / K u,i As the parameter to be optimized; the iterative process includes estimating the initial value of the unified structural parameters of all power generation equipment in the system, substituting the unified structural parameters into the approximate system frequency response expression to obtain the approximate common mode frequency Δω u (s), based on Δω u (s) Solve the optimization problem and update the unified structural parameters of the device, iterating until the parameters converge; calculate the frequency intensity index α as:

[0024]

[0025] Each time the synchronous machine in the system is replaced by a new energy device, the new energy penetration rate is adjusted, and the frequency intensity index of the system under the maximum blocking and maximum power loss is repeatedly calculated at each penetration rate. The new energy penetration rate λ is expressed as:

[0026]

[0027] Among them, S w is the capacity of new energy access in the system, S is the total capacity of all generator sets in the system; based on the calculated data, curves of frequency intensity index changing with new energy penetration rate under the two scenarios of maximum DC blocking and maximum power loss are drawn.

[0028] As a preferred solution of the method for evaluating the maximum penetration rate of new energy in the actual power grid considering frequency stability described in the present invention, the maximum penetration rate of new energy includes a frequency strength index-permeability relationship curve based on the maximum DC blocking and maximum loss power supply scenarios, and the critical value α of the system frequency strength index under the two disturbance scenarios of active increase and decrease, respectively. 1min, α 2min , the maximum penetration rate of new energy in the computing system under two scenarios γ max最大闭锁 , γ max最大切机 .

[0029] As a preferred solution of the method for evaluating the maximum penetration rate of new energy in the actual power grid considering frequency stability described in the present invention, wherein: the evaluation and planning of new energy access includes the maximum penetration rate of new energy based on the two scenarios of maximum DC blocking and maximum loss power supply γ max最大闭锁 , γ max最大切机 , calculate the maximum penetration rate of new energy in the power grid, expressed as:

[0030] γ max =min{γ max最大闭锁 ,γ max最大切机}

[0031] Among them, γ max It indicates the maximum penetration rate of renewable energy in the power grid, and the evaluation and planning of renewable energy access are carried out based on the calculation results.

[0032] Another object of the present invention is to provide an actual power grid new energy maximum penetration rate assessment system taking into account frequency stability, which can evaluate and plan new energy access by calculating the system's new energy maximum penetration rate under disturbances of increased and decreased active power, thereby solving the problem of low frequency stability in current power system optimization and assessment technologies.

[0033] As a preferred solution of the actual power grid new energy maximum penetration rate assessment system considering frequency stability described in the present invention, it includes: a disturbance analysis module, a curve drawing module, and a parameter evaluation module; the disturbance analysis module is used to analyze the frequency safety and stability boundary and determine the maximum active power disturbance in the actual power grid operation; the curve drawing module is used to calculate the critical value of the frequency strength index based on the disturbance size and the frequency safety and stability boundary, gradually replace the synchronous machine with new energy, calculate the frequency strength index of the system under different penetration rates when the active power is increased and decreased, and draw a curve of the frequency strength index changing with the new energy penetration rate; the parameter evaluation module is used to calculate the maximum new energy penetration rate of the system under the disturbance of active power increase and decrease, and evaluate and plan the access of new energy.

[0034] A computer device includes a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement a method for evaluating the maximum penetration rate of new energy in an actual power grid considering frequency stability.

[0035] A computer-readable storage medium stores a computer program, which, when executed by a processor, implements the steps of a method for evaluating the maximum penetration rate of new energy in an actual power grid taking into account frequency stability.

[0036] Beneficial effects of the present invention: The method for evaluating the maximum penetration rate of new energy in an actual power grid considering frequency stability provided by the present invention realizes a quantitative understanding of the frequency stability of the power grid when it is subjected to the maximum active power disturbance by analyzing the frequency safety and stability boundary, and provides a basis for the subsequent calculation of the frequency strength index, so that the calculation result of the frequency strength index is more in line with the actual operation of the power grid, and the maximum active power disturbance in the actual power grid operation is determined, and key data is provided for the frequency stability evaluation of the power grid, thereby providing a scientific basis for the maximum penetration rate evaluation of new energy; by drawing a curve of the frequency strength index changing with the new energy penetration rate, the changing trend of the power grid frequency stability at different penetration rates is analyzed, thereby providing a reference basis for the access of new energy, and making the evaluation result more accurate and reliable; by calculating the maximum penetration rate of new energy, the safe and stable operation of the power grid is guaranteed, guidance is provided for the long-term operation and development of the power grid, and the rational use of new energy and the sustainable development of the power grid are promoted. The present invention achieves better results in terms of new energy access, power grid planning and operation, and power grid safety and stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0038] Figure 1 An overall flow chart of a method for evaluating the maximum penetration rate of renewable energy in an actual power grid taking frequency stability into consideration, provided in accordance with the first embodiment of the present invention.

[0039] Figure 2 A frequency maximum deviation change graph a of an actual power grid new energy maximum penetration rate assessment method considering frequency stability is provided in accordance with a second embodiment of the present invention.

[0040] Figure 3 A graph a showing the change in frequency drop depth coefficient of a method for evaluating the maximum penetration rate of new energy in an actual power grid taking frequency stability into consideration, provided in accordance with a second embodiment of the present invention.

[0041] Figure 4 FIG. b is a diagram of the maximum frequency deviation change of an actual power grid new energy maximum penetration rate assessment method considering frequency stability provided in the second embodiment of the present invention.

[0042] Figure 5 A frequency drop depth coefficient variation diagram b of an actual power grid new energy maximum penetration rate assessment method considering frequency stability is provided in accordance with the second embodiment of the present invention.

[0043] Figure 6 An overall flow chart of an actual power grid new energy maximum penetration rate assessment system considering frequency stability provided in the third embodiment of the present invention. DETAILED DESCRIPTION

[0044] 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.

[0045] Example 1

[0046] Reference Figure 1 , which is an embodiment of the present invention, provides a method for evaluating the maximum penetration rate of renewable energy in an actual power grid considering frequency stability, comprising:

[0047] S1: Analyze the frequency safety and stability boundary and determine the maximum active disturbance in actual power grid operation.

[0048] Furthermore, the analysis of the frequency safety and stability boundary includes the inspection of the power system n-1, based on the maximum Δf<+0.6Hz when the frequency rises and the maximum Δf<-0.8Hz when the frequency falls, and the frequency safety and stability boundary used in the evaluation; under different operating modes, according to the calculation of the maximum blocking corresponding frequency rise|Δf in BPA 1max |、Maximum power loss corresponding frequency drop|Δf 2max |, the lower frequency deviation from the rated frequency value meets the national standard requirements for frequency safety and stability, that is, |Δf 1max |=0.6Hz、

[0049] Δf 2max |=0.8Hz.

[0050] It should be noted that the maximum active power disturbance includes the maximum active power disturbances in the two scenarios of active power increase and active power reduction. The maximum active power increase disturbance is the disturbance caused by the maximum blocking, which is recorded as P 0+ , the maximum active power reduction disturbance is the disturbance caused by the maximum loss power supply, denoted as P 0- .

[0051] It should also be noted that by analyzing the frequency safety and stability boundaries, it can be determined that under the premise of ensuring the stability of the grid frequency, renewable energy can account for the maximum proportion of the total power generation of the grid, which provides a scientific basis for the access of renewable energy and ensures that the access of renewable energy will not have an adverse impact on the frequency stability of the grid.

[0052] S2: Calculate the critical value of the frequency intensity index based on the disturbance size and the frequency safety and stability boundary, gradually replace the synchronous machine with new energy, calculate the frequency intensity index of the system under different penetration rates when the active power increases and decreases, and draw a curve of the frequency intensity index changing with the new energy penetration rate.

[0053] Furthermore, the calculation of the critical value of the frequency intensity index includes that the relationship between the critical value of the frequency intensity index and the disturbance size and frequency is expressed as:

[0054]

[0055] Among them, α 1min is the critical value of the indicator corresponding to the increase of active power, α 2min It is the critical value of the indicator corresponding to the decrease in active power. It should be noted that the curve of drawing the frequency intensity index as the penetration rate of new energy includes gradually replacing the synchronous machine with new energy, calculating the frequency intensity index of the system at different penetration rates when the active power increases and decreases, and drawing the curve of the frequency intensity index as the penetration rate of new energy changes; when all new energy equipment in the power grid is replaced by synchronous machines, the initial penetration rate is 0, and the frequency response of the power system after the disturbance is calculated in the two scenarios of maximum DC blocking and maximum loss of power supply, which is expressed as:

[0056]

[0057] Among them, P 0 represents the initial maximum active disturbance, Δω 1 (s) is the common mode frequency in the two scenarios of maximum DC blocking and maximum power loss, G i (s) is the frequency-active power transfer function of the power generation equipment connected to the i-th node; the power generation equipment model is reduced by unified structure approximation, and the unified structure model is expressed as:

[0058]

[0059] Among them, the parameter J u,i , D u,i , K u,i is the unified structural parameter of the i-th device, respectively J u,i Indicates effective inertia, D u,i represents the effective damping, K u,i Represents the effective adjustment coefficient, which is obtained by approximating the actual power response with the power response of the unified structure model, and approximating the actual power response of the device with a linear combination of three trajectories: the differential of the frequency, the frequency itself, and the integral of the frequency; the simplified system frequency response Δω u (s) has only two orders, expressed as:

[0060]

[0061] Among them, J us , D us , is the sum of the unified structural parameters of each power generation equipment, ΔP L (s) represents the change in system load; solving the unified structural model parameters of each power generation equipment is converted into a parameter optimization problem, which is expressed as:

[0062]

[0063] stΔP i (s) = G i (s)Δω(s)

[0064] ΔP' i (s) = G u,i (s)Δω(s)

[0065] Where ΔP i (t) and ΔP' i (t) are the actual power response of the i-th power generation equipment and the power response of the unified structure approximation, ΔP i (s) and ΔP' i (s) are the actual power response of the i-th power generation equipment in the s-domain and the power response of the unified structure approximation, Δω(s) is the representation of the system frequency change in the s-domain, t 0 and t f are the initial and final moments of the time period of interest, respectively, and t 0 Take the disturbance start time, t f Take 1.5 times the lowest frequency time, J u,i , D u,i and 1 / K u,i As the parameter to be optimized; the iterative process includes estimating the initial value of the unified structural parameters of all power generation equipment in the system, substituting the unified structural parameters into the approximate system frequency response expression to obtain the approximate common mode frequency Δω u (s), based on Δω u (s) Solve the optimization problem and update the unified structural parameters of the device, iterating until the parameters converge; calculate the frequency intensity index α as:

[0066]

[0067] Each time the synchronous machine in the system is replaced by a new energy device, the new energy penetration rate is adjusted, and the frequency intensity index of the system under the maximum blocking and maximum power loss is repeatedly calculated at each penetration rate. The new energy penetration rate λ is expressed as:

[0068]

[0069] Among them, S w is the capacity of new energy access in the system, S is the total capacity of all generator sets in the system; based on the calculated data, curves of frequency intensity index changing with new energy penetration rate under the two scenarios of maximum DC blocking and maximum power loss are drawn.

[0070] It should also be noted that by plotting the frequency intensity index as the new energy penetration rate changes, we can intuitively observe the changing trend of the grid frequency stability at different penetration rates, thereby providing a reference for the access of new energy and comprehensively evaluating the impact of the new energy penetration rate on the grid frequency stability.

[0071] S3: Calculate the maximum penetration rate of renewable energy in the system under disturbances of active power increase and decrease, and conduct evaluation and planning of renewable energy access.

[0072] Furthermore, the maximum penetration rate of renewable energy includes the relationship curves of frequency intensity index-penetration rate under the two scenarios of maximum DC blocking and maximum power loss, which correspond to the critical value α of system frequency intensity index under the two scenarios of active power increase and decrease disturbance respectively. 1min , α 2min , the maximum penetration rate of new energy in the computing system under two scenarios γ max最大闭锁 , γ max最大切机 .

[0073] It should be noted that the evaluation and planning of new energy access includes the maximum penetration rate of new energy based on the two scenarios of maximum DC blocking and maximum power loss γ max最大闭锁 , γ max最大切机 , calculate the maximum penetration rate of new energy in the power grid, expressed as:

[0074] γ max =min{γ max最大闭锁 ,γ max最大切机}

[0075] It should also be noted that by calculating the maximum penetration rate of renewable energy, the maximum penetration rate of renewable energy can be accurately determined, providing a scientific basis for the planning and operation of the power grid, ensuring that the access of renewable energy will not have an adverse effect on the frequency stability of the power grid, thereby ensuring the safe and stable operation of the power grid.

[0076] Example 2

[0077] Reference Figure 2-Figure 5 , which is an embodiment of the present invention, provides a method for evaluating the maximum penetration rate of new energy in an actual power grid considering frequency stability. In order to verify the beneficial effects of the present invention, scientific demonstration is carried out through economic benefit calculation and simulation experiments.

[0078] Firstly, based on the BPA model of an actual provincial power grid, the maximum penetration rate of renewable energy allowed to be connected to the system under the dry waist mode is analyzed. The BPA data can be used to calculate the proportion of renewable energy in the entire system under the dry waist operation mode, that is, the penetration rate of the system is 54.46% at this time. The operation data can be referred to Table 1.

[0079] Table 1 Basic operation data table under dry waist operation mode

[0080]

[0081] Referring to Table 2, according to the power disturbance in the BPA data under the dry waist operation mode of the power grid in 2025 (penetration rate 54.46%), and the corresponding frequency response time domain waveform, the frequency trajectory of a single machine can be approximated by a damped sine curve in a relatively short time, that is, the various frequency regulation capabilities of the original system can be characterized by unified structural model parameters. First, the unified structural parameters under each operation mode (under the initial penetration rate) can be calculated.

[0082] Table 2 System unified structural parameters at current penetration rate (54.46%)

[0083]

[0084] Through the information in the BPA data, it can be determined that the maximum active power reduction disturbance that may exist under the n-1 disturbance in the dry waist operation mode is VP340-VP330. It is 1500MW when the line has single-pole locking, which is used as the maximum DC locking power for n-1 verification, that is, P0+=1500MW; the maximum active power reduction disturbance that may exist under the n-1 disturbance in the dry waist operation mode is 850MW when G22.0 has power loss, which is used as the maximum loss power power for n-1 verification, that is, P0-=850MW.

[0085] The critical value of the frequency intensity index is calculated based on the disturbance size and the frequency safety and stability boundary, α 1min =1250.16, α 2min =531.22.

[0086] Assume that all new energy equipment is replaced by synchronous machines, that is, the initial penetration rate is 0. At this time, each time the new energy equipment is used to replace the synchronous machine in the system, that is, the new energy penetration rate gradually increases, calculate the frequency strength index of the system under each penetration rate when it is subjected to maximum blocking: frequency drop depth coefficient α, maximum frequency deviation, and draw a curve of maximum frequency deviation and frequency strength index changing with new energy penetration rate, such as Figure 2 , Figure 3 As shown in the figure, it can be seen that the maximum penetration rate of new energy equipment corresponding to the maximum DC blocking under the dry waist operation mode is γ KYmax最大闭锁=69.10%, when the penetration rate reaches 69.10%, the maximum frequency deviation of the system just reaches 0.6Hz. If the penetration rate increases further, the safety and stability requirement of the maximum deviation within 0.6Hz when the frequency rises will no longer be met.

[0087] Assume that all new energy equipment is replaced by synchronous machines, that is, the initial penetration rate is 0. At this time, each time the new energy equipment is used to replace the synchronous machine in the system, that is, the new energy penetration rate gradually increases, calculate the frequency strength index of the system under each penetration rate when it is subjected to the maximum loss of power supply, including the frequency drop depth coefficient α and the maximum frequency deviation, and draw the curve of the maximum frequency deviation and frequency strength index changing with the new energy penetration rate, such as Figure 4 , Figure 5 As shown in the figure, the maximum penetration rate of new energy equipment corresponding to the maximum DC blocking under the dry waist operation mode is γ KYmax最大损失电源 =86.87%. When the penetration rate reaches 86.87%, the maximum frequency deviation of the system just reaches 0.8Hz. If the penetration rate increases further, it will no longer meet the safety and stability requirements of the maximum deviation within 0.8Hz when the frequency drops. Combining the maximum penetration rate requirements under the maximum DC blocking and maximum loss power supply, the maximum penetration rate of new energy under the dry waist operation mode can be obtained as follows:

[0088] γ KYmax =min{γ KYmax最大闭锁 ,γ KYmax最大损失电源 =69.10%

[0089] When the system's new energy is at its maximum penetration rate (69.10%), the system's effective frequency modulation parameters and frequency intensity indicators are shown in Table 3.

[0090] Table 3 Effective frequency modulation parameters and frequency intensity index at maximum permeability (69.10%)

[0091]

[0092] Therefore, when only considering the constraints of frequency safety and stability, the capacity of existing new energy equipment can be further increased, and the penetration rate can be increased from the current 54.46% to 69.10% under the dry-waist operation mode (other conditions remain unchanged). That is, the power grid can further increase the installed capacity and operating proportion of new energy and make full use of existing renewable resources.

[0093] Example 3

[0094] Reference Figure 6 , which is an embodiment of the present invention, provides an actual power grid new energy maximum penetration rate evaluation system considering frequency stability, including a disturbance analysis module, a curve drawing module, and a parameter evaluation module.

[0095] The disturbance analysis module is used to analyze the frequency safety and stability boundary and determine the maximum active power disturbance in actual power grid operation; the curve drawing module is used to calculate the critical value of the frequency intensity index based on the disturbance size and the frequency safety and stability boundary, gradually replace the synchronous machine with new energy, and calculate the frequency intensity index of the system under different penetration rates when the active power increases and decreases, and draw a curve of the frequency intensity index changing with the new energy penetration rate; the parameter evaluation module is used to calculate the maximum new energy penetration rate of the system under the disturbance of active power increase and decrease, and to evaluate and plan the access of new energy.

[0096] 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.

[0097] 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.

[0098] 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.

[0099] 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 embodiment, a plurality of 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, any one of the following technologies known in the art or their combination can be used to implement: 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 thereto. 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 all be included in the scope of the claims of the present invention.

[0100] 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 evaluating the maximum penetration rate of renewable energy in an actual power grid considering frequency stability, characterized in that: include: Analyze the frequency safety and stability boundary and determine the maximum active disturbance in actual power grid operation; The critical value of the frequency intensity index is calculated based on the disturbance size and the frequency safety and stability boundary. The synchronous machine is gradually replaced by new energy. The frequency intensity index of the system under different penetration rates when the active power increases and decreases is calculated respectively, and the frequency intensity index curve is drawn with the change of new energy penetration rate. Calculate the maximum penetration rate of renewable energy in the system under disturbances of active power increase and decrease, and evaluate and plan the access of renewable energy.

2. The method for evaluating the maximum penetration rate of renewable energy in actual power grid considering frequency stability according to claim 1, characterized in that: The analysis of the frequency safety and stability boundary includes performing an inspection of the power system n-1, based on the maximum Δf<+0.6Hz when the frequency rises and the maximum Δf<-0.8Hz when the frequency falls, and the frequency safety and stability boundary used in the evaluation; Under different operating modes, the maximum locking corresponding frequency rise |Δf according to the calculation in BPA 1max |、Maximum power loss corresponding frequency drop|Δf 2max |, the lower frequency deviation from the rated frequency value meets the national standard requirements for frequency safety and stability, that is, |Δf 1max |=0.6Hz、|Δf 2max |=0.8Hz.

3. The method for evaluating the maximum penetration rate of renewable energy in actual power grid considering frequency stability according to claim 2, characterized in that: The maximum active power disturbance includes the maximum active power disturbances in the two scenarios of active power increase and active power reduction. The maximum active power increase disturbance is the disturbance caused by the maximum blocking, which is recorded as P 0+ , the maximum active power reduction disturbance is the disturbance caused by the maximum loss power supply, denoted as P 0- .

4. The method for evaluating the maximum penetration rate of renewable energy in actual power grid considering frequency stability according to claim 3, characterized in that: The calculation of the critical value of the frequency intensity index includes: the relationship between the critical value of the frequency intensity index and the disturbance size and frequency is expressed as: Among them, α 1min is the critical value of the indicator corresponding to the increase of active power, α 2min It is the critical value of the indicator corresponding to the reduction of active power.

5. The method for evaluating the maximum penetration rate of renewable energy in actual power grid considering frequency stability according to claim 4, characterized in that: The drawing of the curve of the frequency intensity index changing with the penetration rate of new energy includes gradually replacing the synchronous machine with new energy, calculating the frequency intensity index of the system under different penetration rates when the active power increases and decreases, and drawing the curve of the frequency intensity index changing with the penetration rate of new energy; When all new energy equipment in the power grid is replaced by synchronous machines, the initial penetration rate is 0. Under the two scenarios of maximum DC blocking and maximum power loss, the frequency response of the power system after the disturbance is calculated and expressed as: Where P0 represents the initial maximum active disturbance, Δω1(s) is the common mode frequency under the two scenarios of maximum DC blocking and maximum power loss, G i (s) is the frequency-active power transfer function of the power generation equipment connected to the i-th node; The unified structure approximation is used to reduce the order of the power generation equipment model, and the unified structure model is expressed as: Among them, the parameter J u,i , D u,i , K u,i is the unified structural parameter of the i-th device, respectively J u,i Indicates effective inertia, D u,i represents the effective damping, K u,i It represents the effective adjustment coefficient, which is obtained by approximating the actual power response with the power response of the unified structure model, and approximating the actual power response of the device with a linear combination of three trajectories: the differential of the frequency, the frequency itself, and the integral of the frequency; Simplified system frequency response Δω u (s) has only two orders, expressed as: Among them, J us , D us , is the sum of the unified structural parameters of each power generation equipment, ΔP L (s) represents the change in system load; Solving the unified structural model parameters of each power generation equipment is transformed into a parameter optimization problem, which can be expressed as: stΔP i (s)=G i (s)Give(s) ΔP' i (s)=G u,i (s)Give(s) Among them, ΔP i (t) and ΔP' i (t) are the actual power response of the i-th power generation equipment and the power response of the unified structure approximation, ΔP i (s) and ΔP' i (s) are the actual power response of the i-th power generation equipment in the s-domain and the power response of the unified structure approximation, Δω(s) is the representation of the system frequency change in the s-domain, t0 and t f are the initial and final moments of the time period of interest, t0 is the start time of the disturbance, t f Take 1.5 times the lowest frequency time, J u,i , D u,i and 1 / K u,i As the parameter to be optimized; The iterative process includes estimating the initial values ​​of the unified structural parameters of all power generation equipment in the system, substituting the unified structural parameters into the approximate system frequency response expression to obtain the approximate common mode frequency Δω u (s), based on Δω u (s) Solve the optimization problem and update the unified structural parameters of the device, iterating repeatedly until the parameters converge; The calculated frequency intensity index α is expressed as: Each time the synchronous machine in the system is replaced by a new energy device, the new energy penetration rate is adjusted, and the frequency intensity index of the system under the maximum blocking and maximum power loss is repeatedly calculated at each penetration rate. The new energy penetration rate λ is expressed as: Among them, S w is the capacity of new energy access in the system, and S is the total capacity of all generators in the system; Based on the calculated data, curves are drawn showing the changes in frequency intensity index with the penetration rate of new energy under the two scenarios of maximum DC blocking and maximum power loss.

6. The method for evaluating the maximum penetration rate of renewable energy in actual power grid considering frequency stability according to claim 5, characterized in that: The maximum penetration rate of new energy includes the relationship curve between frequency intensity index and penetration rate under the two scenarios of maximum DC blocking and maximum power loss, which respectively correspond to the critical value α of system frequency intensity index under the two scenarios of active power increase and decrease. 1min , α 2min , the maximum penetration rate of new energy in the computing system under two scenarios γ max最大闭锁 , γ max最大切机 .

7. The method for evaluating the maximum penetration rate of renewable energy in actual power grid considering frequency stability according to claim 6, characterized in that: The evaluation and planning of new energy access includes the maximum penetration rate of new energy based on the two scenarios of maximum DC blocking and maximum power loss γ max最大闭锁 , γ max最大切机 , calculate the maximum penetration rate of new energy in the power grid, expressed as: c max =min{γ max最大闭锁 ,c max最大切机 Among them, γ max It indicates the maximum penetration rate of renewable energy in the power grid, and the evaluation and planning of renewable energy access are carried out based on the calculation results.

8. A system using the method for evaluating the maximum penetration rate of new energy in an actual power grid considering frequency stability as described in any one of claims 1 to 7, characterized in that: Including disturbance analysis module, curve drawing module, parameter evaluation module; The disturbance analysis module is used to analyze the frequency safety and stability boundary and determine the maximum active disturbance in the actual power grid operation; The curve drawing module is used to calculate the critical value of the frequency intensity index based on the disturbance size and the frequency safety and stability boundary, gradually replace the synchronous machine with new energy, calculate the frequency intensity index of the system under different penetration rates when the active power increases and decreases, and draw a curve of the frequency intensity index changing with the new energy penetration rate; The parameter evaluation module is used to calculate the maximum penetration rate of new energy in the system under the disturbance of active power increase and decrease, and to evaluate and plan the access of new energy.

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 evaluating the maximum penetration rate of new energy in an actual power grid considering frequency stability are implemented as described in any one of claims 1 to 7.

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 evaluating the maximum penetration rate of new energy in an actual power grid considering frequency stability are implemented as described in any one of claims 1 to 7.

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