Power system frequency modulation resource evaluation method considering transient frequency security constraint

Abstract

The invention discloses a power system frequency modulation resource evaluation method considering transient frequency security constraints, and relates to the technical field of power system frequency security, comprising the following steps: analyzing frequency response characteristics of a system by constructing a novel power system frequency response model; the frequency safety index of the power system is evaluated by monitoring the frequency change rate and the lowest frequency in real time; and based on the frequency response model and the safety index, evaluating the frequency modulation resource safety domain of the power system and performing visual display. According to the method, the frequency response capability of the power system is reflected more comprehensively by constructing the novel power system frequency response model and comprehensively considering the maximum frequency change rate, the lowest frequency point and the quasi-steady-state frequency deviation of the power system, so that the evaluation accuracy of the frequency security domain is improved, and the evaluation accuracy of the frequency security domain is improved by visually displaying the frequency security domain. Therefore, the power dispatching department can more intuitively modulate the adequacy of the frequency resources, so that rapid decision making and resource combination optimization are facilitated, and the operation frequency stability of the power system is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of power system frequency security, and specifically to a method for evaluating frequency modulation resources in a power system considering transient frequency security constraints. Background Art

[0002] With the development of China's power system, the proportion of new energy sources such as wind and solar in the power system has been continuously increasing. High-penetration new energy not only changes the operating characteristics of the power system but also poses new requirements for the safe operation of the power system. Since traditional large-scale new energy is connected to the grid through power electronic equipment and is decoupled from the system frequency and cannot actively respond to system frequency changes, the frequency response ability of the system has been continuously decreasing, and it may reach the thresholds of under-frequency load shedding and new energy anti-islanding protection. The frequency security problems of the new power system pose severe challenges to the stable operation and safe dispatching of the system frequency, and also restrict the further improvement of the new energy penetration rate. Under this background, grid operators have put forward new requirements for the frequency control ability of new energy, requiring new energy with grid-forming control ability to provide frequency response ability to support system frequency regulation. It is urgent to combine the frequency response characteristics of the new power system, establish a frequency response model, predict the trend of the whole network frequency change, and then optimize the allocation of system frequency modulation resources to ensure the safe operation of the system.

[0003] Inertia response and primary frequency modulation are important links affecting the system frequency response after a fault. The system's ultimate minimum inertia is usually constrained and quantified with the key indicators of the frequency change rate and the lowest point frequency. By establishing a system frequency response model, the near-real-time system frequency modulation ability can be predicted and analyzed at the analysis point, so as to guide the optimization of the allocation of frequency modulation resources. Therefore, it is particularly important to evaluate the frequency modulation resource safety domain of the system under the maximum possible fault, which helps to determine the system's demand for the lowest frequency modulation resources. However, existing evaluation methods for the minimum frequency modulation resources mostly focus on the independent analysis of the system's minimum inertia resources or primary frequency modulation reserve capacity, lacking the joint evaluation of inertia-primary frequency modulation resources, and lacking the visualization display of the corresponding relationship between inertia resources and primary frequency modulation reserve capacity. There is an urgent need to propose a method for evaluating frequency modulation resources in a power system considering transient frequency security constraints. Summary of the Invention

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

[0005] Therefore, the technical problems solved by the present invention are: the existing power system frequency modulation resource evaluation methods have insufficient frequency response ability, incomplete evaluation of the frequency control ability of new energy units, lack of visualization display of frequency security indicators, and the problem of how to comprehensively evaluate the security and effectiveness of various types of frequency modulation resources.

[0006] To solve the above technical problems, the present invention provides the following technical solutions: A method for evaluating frequency regulation resources of a power system considering transient frequency security constraints, including analyzing the frequency response characteristics of the system by constructing a new power system frequency response model; evaluating the frequency security index of the power system by real-time monitoring of the frequency change rate and the lowest frequency; evaluating the frequency regulation resource security domain of the power system based on the frequency response model and the security index and visualizing it.

[0007] As a preferred embodiment of the method for evaluating frequency regulation resources of a power system considering transient frequency security constraints according to the present invention, wherein: the construction of the new power system frequency response model includes constructing a frequency response model including steam turbines, hydro turbines and new energy units.

[0008] As a preferred embodiment of the method for evaluating frequency regulation resources of a power system considering transient frequency security constraints according to the present invention, wherein: the construction of the new power system frequency response model further includes modeling the frequency response characteristics of the steam turbine and establishing a frequency response analysis sub-model of the thermal power unit, expressed as:

[0009]

[0010] Wherein, ΔP R (s) is the change in output power of the non-reheat steam turbine, F H is the high-pressure turbine coefficient, T R is the reheater time constant, T G1 is the time constant of the reheat steam turbine governor, R1 is the droop coefficient of the reheat steam turbine governor, s is the Laplace operator, and Δω is the frequency change rate; modeling the frequency response characteristics of the hydro turbine and establishing a frequency response analysis sub-model of the hydro power unit, expressed as:

[0011]

[0012] Wherein, ΔP H (s) is the change in output power of the hydro turbine, T RT is the reset time constant of the hydro turbine, R P is the permanent droop rate, R T is the temporary droop rate, T W is the water hammer effect time constant, T G2 is the time constant of the hydro turbine governor, R2 is the droop coefficient of the hydro turbine governor; for new energy units based on grid-forming support capabilities, providing simulated inertia and primary frequency regulation capabilities, expressed as:

[0013]

[0014] Wherein, ΔP N is the change in output power of the new energy unit, HN To simulate the inertia time constant, R N and T N are respectively the governor droop coefficient and the governor time constant of the network-forming new energy unit; based on the static frequency characteristics of the load, when the input power of the units in the power system is out of balance with the load power and the frequency of the system changes, the load power of the system will also change accordingly. The frequency regulation effect of the load is expressed as:

[0015]

[0016] where K PF is the frequency regulation effect coefficient of the load, P L is the active power of the system load, and f is the system frequency; when the power system is in a dynamic process, the frequency of the power system is represented by the frequency of the inertia center of the power system. Based on the multi-source frequency regulation resources of the new power system, the equivalent inertia time constant of the equivalent inertia center is calculated and expressed as:

[0017]

[0018] where H sys is the total inertia time constant of the power system, H R is the inertia time constant of the steam turbine unit, H H is the inertia time constant of the steam turbine unit, H N is the inertia time constant of the new energy unit with network-forming control ability, and M and S i are respectively the number of steam turbine units and the rated capacity of the units, and W and S j are respectively the number of hydro turbine units and the rated capacity of the units, and X and S K are respectively the number of network-forming new energy units and the rated capacity of the units; the weighted average method is used to calculate the equivalent inertia damping coefficient, which is expressed as:

[0019]

[0020] where D sys is the equivalent inertia damping coefficient of the power system, Y a is the rated capacity of the a-th unit, D a is the damping coefficient of the a-th unit, and n is the number of units in the power system; when there is unbalanced power in the power system, the frequency response of the power system is calculated and expressed as:

[0021]

[0022] where Δ P d is the power imbalance deficit, Δf is the power system frequency deviation, and t is the time.

[0023] As a preferred solution of the power system frequency regulation resource evaluation method considering transient frequency security constraints according to the present invention, wherein: the real-time monitoring of the rate of change of frequency and the lowest frequency includes using a constructed new power system frequency response model based on simulation software to calculate transient frequency security indicators, including the rate of change of frequency RoCoF, the lowest frequency point FN, and the quasi-steady state frequency deviation QSSFD; when there is a power disturbance, the maximum rate of change of frequency RF of the power system max is the RoCoF index, expressed as:

[0024]

[0025] Define the maximum deviation of the transient frequency of the power system Δf max is the FN index, expressed as:

[0026] Δf max = max(Δf)| t＞0

[0027] Calculate the quasi-steady state frequency deviation as the QSSFD index, expressed as:

[0028] QS = Δf(t ∞ )

[0029] where QS is the quasi-steady state frequency deviation.

[0030] As a preferred solution of the power system frequency regulation resource evaluation method considering transient frequency security constraints according to the present invention, wherein: the evaluation of the frequency security index of the power system includes setting the frequency security index constraint of the power system by restricting the transient frequency security index; define the RoCoF index constraint, expressed as:

[0031] |RF max | ≤ RoCoF M

[0032] where RoCoF M is the preset frequency threshold; define the FN index constraint, expressed as:

[0033] Δf nadir ≤ Δf max

[0034] where Δf nadir is the threshold of under-frequency load shedding; define the QSSFD index constraint, expressed as:

[0035] QS ≤ QS max

[0036] where QS max is the maximum quasi-steady state frequency deviation.

[0037] As a preferred solution of the power system frequency regulation resource evaluation method considering transient frequency security constraints of the present invention, wherein: evaluating the frequency regulation resource security domain of the power system based on the frequency response model and security indicators includes evaluating the frequency regulation resource security domain of the new power system based on the constructed new power system frequency response model and the frequency security indicator constraints of the power system; when the power system conducts frequency regulation resources, the frequency regulation resource constraint is defined as:

[0038] E Hsys ≤E Hmax

[0039] E PFRsys ≤E PFRmax

[0040] Wherein, E Hsys and E PFRsys are the inertia and primary frequency regulation reserve capacity of the power system respectively, and E Hmax and E PFRmax are the configurable inertia resources and the upper limit of the primary frequency regulation reserve capacity of the power system respectively; use the simulation model to predict the frequency response dynamics of the power system, and feedback the results to the security domain evaluation process for cyclic iteration. When the inertia-primary frequency regulation resource security boundary that meets the frequency security constraints and the available frequency regulation capacity upper limit is satisfied, the operating points within the security boundary are the evaluated security domain.

[0041] As a preferred solution of the power system frequency regulation resource evaluation method considering transient frequency security constraints of the present invention, wherein: the visual display includes visually displaying the relationship between frequency security and frequency regulation resources. The dispatching department guides the optimization of the combination of inertia and primary frequency regulation reserve resources according to the position of the operating point within the security domain to ensure the frequency regulation ability of the system.

[0042] Another object of the present invention is to provide a power system frequency regulation resource evaluation system considering transient frequency security constraints, which can analyze the frequency response characteristics of the system by constructing a new power system frequency response model, and solves the problem that the current power system frequency regulation resource evaluation technology has an incomplete evaluation of the frequency control ability of new energy units.

[0043] As a preferred solution of the power system frequency regulation resource evaluation system considering transient frequency security constraints of the present invention, it includes: a frequency response model construction module, a frequency security index evaluation module, and a frequency regulation resource security domain evaluation and visualization display module; the frequency response model construction module is used to analyze the frequency response characteristics of the system by constructing a new power system frequency response model; the frequency security index evaluation module is used to evaluate the frequency security index of the power system by real-time monitoring the frequency change rate and the lowest frequency; the frequency regulation resource security domain evaluation and visualization display module is used to evaluate the frequency regulation resource security domain of the power system based on the frequency response model and the security index and perform visualization display.

[0044] A computer device includes a memory and a processor. The memory stores a computer program, and when the processor executes the computer program, the steps of the power system frequency regulation resource evaluation method considering transient frequency security constraints are implemented.

[0045] A computer-readable storage medium stores a computer program thereon. When the computer program is executed by a processor, the steps of the power system frequency regulation resource evaluation method considering transient frequency security constraints are implemented.

[0046] The beneficial effects of the present invention: The power system frequency regulation resource evaluation method considering transient frequency security constraints provided by the present invention breaks through the limitation of the independent analysis of inertia and primary frequency regulation resources in traditional technologies. By adopting a joint evaluation method, it deeply explores the mutual relationship between frequency regulation resources, making the resource allocation more reasonable and efficient. Based on the constructed new power system frequency response model, by comprehensively considering key parameters such as the maximum frequency change rate, the lowest frequency point, and the quasi-steady state frequency deviation of the system, it can more comprehensively reflect the frequency response ability of the power system while ensuring the calculation speed, thereby improving the evaluation accuracy of the frequency security domain. By visually displaying the frequency security domain, the power dispatching department can more intuitively understand the abundance of frequency regulation resources, which is convenient for quick decision-making and optimizing the resource combination, and improving the operating frequency stability of the power system. The present invention has achieved better effects in terms of accuracy, applicability, and economy. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0048] Figure 1 It is the overall flowchart of a power system frequency regulation resource evaluation method considering transient frequency security constraints provided by the first embodiment of the present invention.

[0049] Figure 2 A novel power system frequency response prediction model diagram for a power system frequency regulation resource evaluation method considering transient frequency security constraints provided by the first embodiment of the present invention.

[0050] Figure 3 A flowchart for evaluating the safety domain of a novel power system frequency regulation resource for a power system frequency regulation resource evaluation method considering transient frequency security constraints provided by the first embodiment of the present invention.

[0051] Figure 4 A diagram of the safety domain of a novel power system frequency regulation resource for a power system frequency regulation resource evaluation method considering transient frequency security constraints provided by the first embodiment of the present invention.

[0052] Figure 5 An example verification diagram of the safety domain of a power system frequency regulation resource evaluation method considering transient frequency security constraints provided by the second embodiment of the present invention.

[0053] Figure 6 A verification diagram of the frequency response curve of the operating point for a power system frequency regulation resource evaluation method considering transient frequency security constraints provided by the second embodiment of the present invention.

[0054] Figure 7 A schematic diagram of the modules of a power system frequency regulation resource evaluation system considering transient frequency security constraints provided by the third embodiment of the present invention. Detailed implementation manners

[0055] To make the above objects, features, and advantages of the present invention more obvious and understandable, the following will describe in detail the specific implementation manners of the present invention with reference to the accompanying drawings of the specification. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0056] Embodiment 1, referring to Figures 1-4 , which is an embodiment of the present invention, provides a power system frequency regulation resource evaluation method considering transient frequency security constraints, including:

[0057] S1: Analyze the frequency response characteristics of the system by constructing a novel power system frequency response model.

[0058] Furthermore, constructing a novel power system frequency response model includes constructing a frequency response model including steam turbines, hydro turbines, and new energy units.

[0059] The establishment of a new power system frequency response model aims to analyze the frequency response characteristics of the power system with a simplified equivalent model, improving the calculation speed while ensuring the accuracy of frequency response prediction.

[0060] It should be noted that the power source types in the current new power system mainly include steam turbines, hydro turbines, wind farms, photovoltaics, etc. Among them, the units participating in frequency regulation are mainly steam turbines, hydro turbines, and some new energy units with grid-forming control. Usually, when analyzing the frequency recovery ability of the power system under severe power imbalance disturbances, the prime mover, governor, and inertia link are mainly considered, while the influence of the electrical part of the generator and the dynamics of the boiler thermal system are ignored.

[0061] Building a new power system frequency response model also includes modeling the frequency response characteristics of steam turbines and establishing a frequency response analysis sub-model for thermal power units, expressed as:

[0062]

[0063] Among them, ΔP R (s) is the change in the output power of a non-reheat steam turbine, F H is the high-pressure turbine coefficient, T R is the reheater time constant, T G1 is the time constant of the reheated steam turbine governor, R1 is the droop coefficient of the reheated steam turbine governor, s is the Laplace operator, and Δω is the frequency change rate; Modeling the frequency response characteristics of hydro turbines and establishing a frequency response analysis sub-model for hydro power units, expressed as:

[0064]

[0065] Among them, ΔP H (s) is the change in the output power of the hydro turbine, T RT is the reset time constant of the hydro turbine, R P is the permanent droop rate, R T is the temporary droop rate, T W is the water hammer effect time constant, T G2 is the time constant of the hydro turbine governor, and R2 is the droop coefficient of the hydro turbine governor.

[0066] Analyzing the grid-forming frequency support ability of new energy units, traditional power grids tracking new energy units cannot effectively provide frequency response. With the development of grid-forming technology, new energy units with grid-forming support ability can provide the following simulated inertia and primary frequency regulation capabilities, expressed as:

[0067]

[0068] Among them, ΔP Nis the change in the output power of the new energy unit, H N is the simulated inertia time constant, R N and T N are respectively the governor droop coefficient and the governor time constant of the network-forming new energy unit.

[0069] Based on the static frequency characteristics of the load, when the balance between the input power and the load power of the units in the power system is lost and the frequency of the system changes, the load power of the system will also change accordingly, thus participating in the regulation effect. The frequency regulation effect of the load is expressed as:

[0070]

[0071] where K PF is the frequency regulation effect coefficient of the load, P L is the active power of the system load, and f is the system frequency.

[0072] When the power system is in a dynamic process, the frequency shows fluctuations around the inertia center frequency. At the same time, as time progresses, the frequency will gradually approach the inertia center frequency of the system. Therefore, the inertia center frequency of the power system is used to represent the system frequency. Based on the multiple frequency regulation resources of the new power system, the equivalent inertia time constant of the equivalent inertia center is calculated and expressed as:

[0073]

[0074] where H sys is the total inertia time constant of the power system, H R is the inertia time constant of the steam turbine unit, H H is the inertia time constant of the steam turbine unit, H N is the inertia time constant of the new energy unit with network-forming control ability, M and S i are respectively the number and the rated capacity of the steam turbine units, W and S j are respectively the number and the rated capacity of the hydro turbine units, X and S K are respectively the number and the rated capacity of the network-forming new energy units; The weighted average method is used to calculate the equivalent inertia damping coefficient, which is expressed as:

[0075]

[0076] where D sys is the equivalent inertia damping coefficient of the power system, Y a is the rated capacity of the a-th unit, D a is the damping coefficient of the a-th unit, and n is the number of units in the power system.

[0077] When there is unbalanced power in the power system, calculate the frequency response of the power system, which is expressed as:

[0078]

[0079] where ΔP d is the power imbalance deficit, Δf is the frequency deviation of the power system, and t is the time.

[0080] It should also be noted that, as Figure 2 shown, for each frequency response link of the aggregated power system frequency response model, according to the output and proportion of each type of unit in the power system, a new power system frequency response model is established.

[0081] S2: Evaluate the frequency security index of the power system by real-time monitoring of the rate of change of frequency and the lowest frequency.

[0082] Furthermore, when the power system has unbalanced power due to faults and other disturbances, the frequency transient process can be divided into three stages: inertia response, primary frequency regulation, and secondary frequency response. Among them, inertial primary frequency regulation can respond within a few seconds, which is crucial for maintaining the safety and stability of the system frequency. The purpose of secondary frequency response is to eliminate the frequency control deviation, and its response time is relatively long. Therefore, it is not considered in the present invention.

[0083] For frequency security index analysis, the main goal of frequency control is to keep the system frequency within the safe range during the transient process after power disturbance. The present invention considers three key stability constraints: rate of change of frequency (RoCoF), lowest frequency point (FN), and quasi-steady state frequency deviation (QSSFD).

[0084] Even further, by real-time monitoring of the rate of change of frequency and the lowest frequency, including based on simulation software, using the constructed new power system frequency response model, calculate the transient frequency security indexes, including rate of change of frequency RoCoF, lowest frequency point FN, and quasi-steady state frequency deviation QSSFD; when there is power disturbance, the maximum rate of change of frequency RF max of the power system is the RoCoF index, which is expressed as:

[0085]

[0086] Define the maximum deviation of the transient frequency of the power system Δf max as the FN index, which is expressed as:

[0087] Δf max = max(Δf)| t＞0

[0088] The calculated quasi-steady-state frequency deviation is the QSSFD index. QSSFD refers to the steady-state frequency deviation after all frequency regulation resources complete the predetermined response, which depends on the planned primary frequency regulation and the load release factor, and is expressed as the deviation between the quasi-steady-state frequency of the system before the addition of secondary frequency regulation and the rated frequency, expressed as:

[0089] QS = Δf(t ∞ )

[0090] where QS is the quasi-steady-state frequency deviation.

[0091] It should be noted that when analyzing the available primary frequency regulation resources of the power system, for the primary frequency regulation reserve resources and conventional synchronous units, the primary frequency regulation capacity refers to the regulating reserve capacity, which is related to the operating conditions of the units and accounts for about 6% - 10% of the rated capacity of the units. With the increase of new energy and its additional frequency control, the primary frequency regulation reserve of the power system can be extended to the sum of all available system resources.

[0092] When analyzing the available inertia resources of the system, the inertia resources of conventional synchronous units depend on the number of units in operation in the system when unbalanced power occurs, while the inertia response of new energy units depends on the sum of the virtual inertia energy sources configured according to their different control methods.

[0093] It should also be noted that evaluating the frequency safety index of the power system includes setting the frequency safety index constraints of the power system by restricting the transient frequency safety index.

[0094] Define the RoCoF index constraint. The purpose is to prevent misoperation of the anti-islanding protection of distributed generation. The maximum rate of change of frequency RF max shall not exceed the preset frequency threshold RoCoF M , and the limit values under different standards are between 0.125Hz / s and 4Hz / s, expressed as:

[0095] |RF max | ≤ RoCoF M

[0096] where RoCoF M is the preset frequency threshold.

[0097] Define the FN index constraint. The purpose is to avoid triggering the first-round threshold of under-frequency load shedding (UFLS). The lowest frequency after the unbalanced power disturbance should not be lower than the threshold of under-frequency load shedding, expressed as:

[0098] Δfnadi r ≤ Δfma x

[0099] where Δf nadir is the threshold of under-frequency load shedding.

[0100] Define the QSSFD index constraint. The purpose is that the quasi-steady-state frequency should return to a certain safe constraint range after the primary frequency regulation action, which is expressed as:

[0101] QS ≤ QS max

[0102] where QS max is the maximum quasi-steady-state frequency deviation.

[0103] It should also be noted that for the transient frequency safety index, especially the constraint of FN is a non-linear equation related to various factors such as the reserve capacity of frequency regulation resources and the governor droop coefficient. The theoretical derivation process is complex, and the results of the linearized model may not be accurate enough. Therefore, when analyzing the transient frequency response index in the present invention, a simulation module is established in the simulation software Simulink, and the constructed new power system frequency response model is used to solve the frequency response results, and the frequency response curve obtained by the simulation platform is sent back to the evaluation algorithm, so as to solve the problem of high-precision calculation of the system frequency dynamic response.

[0104] S3: Based on the frequency response model and safety index, evaluate the frequency regulation resource safety domain of the power system and conduct visual display.

[0105] Furthermore, evaluating the frequency regulation resource safety domain of the power system based on the frequency response model and safety index includes evaluating the frequency regulation resource safety domain of the new power system based on the constructed new power system frequency response model and the frequency safety index constraint of the power system.

[0106] Conduct an energy scenario analysis of the power system, and count the output and proportion of each type of unit at the analysis point of the system. When the power system conducts frequency regulation resources, its maximum value should not exceed the upper limit of the frequency regulation resources that can be configured by the system. Define the frequency regulation resource constraint, which is expressed as:

[0107] E Hsys ≤ E Hmax

[0108] E PFRsys ≤ E PFRmax

[0109] where E Hsys and E PFRsys are the inertia and primary frequency regulation reserve capacity of the power system respectively, and E Hmax and E PFRmax are the upper limits of the inertia resources and primary frequency regulation reserve capacity that can be configured by the power system respectively.

[0110] Predict the frequency response dynamics of the power system using a simulation model, and feedback the results to the security domain evaluation process for iterative cycling. When the inertia-primary frequency regulation resource security boundary that meets the frequency security constraints and the upper limit of available frequency regulation capacity is satisfied, the specific security domain evaluation process is as follows Figure 3 shown. First, select the energy scenario and perform data preprocessing. Then, set the upper limits of inertia and primary frequency regulation reserve resources. Next, perform frequency response evaluation based on the constructed new power system frequency response model. If all security indicators meet the constraints, record the feasible solution. Otherwise, return to the upper limit setting and perform frequency response evaluation again until all security indicators meet the constraints. After recording the feasible solution, determine whether all operating points representing the security boundary have been found. If all have been found, the security domain evaluation ends. If not all have been found, re-evaluate until all operating points representing the security boundary have been found. The operating points within the security boundary are the evaluated security domain, as shown Figure 4 shown. Operating point A is within the security domain. The farther away from the security boundary, the safer it is.

[0111] It should be noted that the visual display includes visualizing the relationship between frequency security and frequency regulation resources. The dispatching department can effectively identify and quantify the adequacy of frequency regulation resources based on the position of the operating point within the security domain, thereby guiding the optimization of the combination of inertia and primary frequency regulation reserve resources to ensure the frequency regulation ability of the system and reduce the risk of security incidents.

[0112] Example 2, referring to Figures 5-6 This is an embodiment of the present invention, providing a method for evaluating frequency regulation resources of a power system considering transient frequency security constraints. To verify the beneficial effects of the present invention, scientific demonstration is carried out through economic benefit calculation and simulation experiments.

[0113] To verify the accuracy and generality of the proposed security domain method, the present invention conducts a simulation experiment. The rated capacity of the system is 12,520 MW, and the proportions of thermal power units, hydropower units, and new energy units are 47.91%, 11.96%, and 24.51% respectively. The other 15.62% are other types of units such as DC and biomass energy. The power-frequency sub-model parameters of each type of unit are shown in Table 1.

[0114] Table 1 Power-frequency sub-model parameters of each type of unit

[0115]

[0116] Set the frequency security constraints of the power system as follows: RoCoF is 0.5 Hz / s, FN is 49.4 Hz, and QSSFD is 0.265 Hz. When 5.4% of the unbalanced power appears in the power system, analyze the frequency response of the current power system and draw the security region as shown in Figure 5. Select the operating points OP1 - OP5 within the security region and draw their frequency response curves according to the frequency response model as Figure 6 shown. It can be observed that the operating point OP1 within the security region can meet all transient frequency security indicators, OP2 does not meet the lowest frequency security indicator, OP3 does not meet both the lowest frequency point and the steady-state frequency deviation indicators, OP4 does not meet the RoCoF indicator, and OP5 does not meet both the lowest frequency point and the steady-state frequency deviation indicators, which is consistent with the evaluation results of the visual security region and verifies the accuracy of the proposed security region evaluation method.

[0117] Example 3, referring to Figure 7 , is an embodiment of the present invention, which provides a power system frequency modulation resource evaluation system considering transient frequency security constraints, including a frequency response model construction module, a frequency security index evaluation module, and a frequency modulation resource security region evaluation and visualization display module.

[0118] Among them, the frequency response model construction module is used to analyze the frequency response characteristics of the system by constructing a new power system frequency response model; the frequency security index evaluation module is used to evaluate the frequency security indicators of the power system by real-time monitoring of the frequency change rate and the lowest frequency; the frequency modulation resource security region evaluation and visualization display module is used to evaluate the frequency modulation resource security region of the power system and perform visualization display based on the frequency response model and security indicators.

[0119] 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, in essence, or the part that contributes to the prior art or a part of this technical solution can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to enable a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods in various embodiments of the present invention. And the aforementioned storage medium includes: USB flash drives, mobile hard disks, read-only memories (ROM, Read-Only Memory), random access memories (RAM, Random Access Memory), magnetic disks, or optical disks, etc., which can store program codes.

[0120] The logic and / or steps represented in the flowchart or otherwise described herein can, for example, be considered as a definable sequence list of executable instructions for implementing logical functions, which can be specifically implemented in any computer-readable medium for use by an instruction execution system, apparatus, or device (such as a computer-based system, a system including a processor, or other systems that can fetch and execute instructions from the instruction execution system, apparatus, or device), or used in conjunction with these instruction execution systems, apparatuses, or devices. For the purposes of this specification, a "computer-readable medium" can be any device that can contain, store, communicate, propagate, or transmit a program for use by or in conjunction with an instruction execution system, apparatus, or device.

[0121] More specific examples (a non-exhaustive list) of computer-readable media include the following: an electrical connection portion (electronic device) having one or more wirings, a portable computer diskette (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disc read-only memory (CDROM). Additionally, a computer-readable medium can even be paper or other suitable media on which a program can be printed, because the program can be obtained electronically, for example, by optically scanning the paper or other media, followed by editing, interpretation, or other suitable processing as necessary, and then stored in a computer memory.

[0122] 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-described 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 in hardware, as in another embodiment, any one or a combination of the following techniques well known in the art can be used: discrete logic circuits having logic gate circuits for implementing logical functions on data signals, application-specific integrated circuits having appropriate combinational logic gate circuits, programmable gate arrays (PGAs), field programmable gate arrays (FPGAs), etc. It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention.

[0123] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A method for evaluating power system frequency regulation resources considering transient frequency security constraints, characterized in that: include: By building a new power system frequency response model, the frequency response characteristics of the system are analyzed; Evaluate the frequency security index of the power system by real-time monitoring of the frequency change rate and minimum frequency; Based on the frequency response model and security indicators, the frequency regulation resource security domain of the power system is evaluated and visualized.

2. The method for evaluating power system frequency regulation resources considering transient frequency security constraints according to claim 1, characterized in that: The construction of a new power system frequency response model includes constructing a frequency response model including a steam turbine, a water turbine and a new energy unit.

3. The method for evaluating power system frequency regulation resources considering transient frequency security constraints according to claim 2, characterized in that: The construction of the new power system frequency response model also includes modeling the frequency response characteristics of the steam turbine and establishing a frequency response analysis sub-model of the thermal power unit, which is expressed as: Among them, ΔP R (s) is the output power change of the non-reheat steam turbine, F H is the high pressure turbine coefficient, T R is the reheater time constant, T G1 is the time constant of the reheat steam turbine governor, R1 is the differential coefficient of the reheat steam turbine governor, s is the Laplace operator, and Δω is the frequency change rate; The frequency response characteristics of the turbine are modeled and the frequency response analysis submodel of the hydropower unit is established, which is expressed as: Among them, ΔP H (s) is the change in turbine output power, T RT is the reset time constant of the turbine, R P is the permanent decline rate, R T is the temporary drop rate, T W is the time constant of water hammer effect, T G2 is the time constant of the turbine speed governor, and R2 is the differential coefficient of the turbine speed governor; Based on the network support capability, the new energy units provide simulated inertia and primary frequency regulation capabilities, which can be expressed as: Among them, ΔP N is the output power change of the new energy unit, H N To simulate the inertia time constant, R N 、T N They are the governor droop coefficient and governor time constant of the grid-connected new energy unit respectively; Based on the static frequency characteristics of the load, when the input power and load power of the units in the power system lose balance and the system frequency changes, the system load power will also change accordingly. The frequency regulation effect of the load is expressed as: Among them, K PF is the frequency regulation effect coefficient of the load, P L is the system load active power, f is the system frequency; When the power system is in a dynamic process, the power system inertia center frequency is used to represent the system frequency. Based on the new power system multi-frequency modulation resources, the equivalent inertia time constant of the equivalent inertia center is calculated and expressed as: Among them, H sys is the total inertia time constant of the power system, H R is the inertia time constant of the steam turbine unit, H H is the inertia time constant of the steam turbine unit, H N is the inertia time constant of the new energy unit with network control capability, M, S i are the number of steam turbine units and the rated capacity of the units, W, S j are the number of turbine units and the rated capacity of the units, X, S K They are the number of grid-connected new energy units and the rated capacity of the units; The weighted average method is used to calculate the equivalent inertia damping coefficient, which is expressed as: Among them, D sys is the equivalent inertia damping coefficient of the power system, Y a is the rated capacity of the ath unit, D a is the damping coefficient of the ath unit, n is the number of units in the power system; When unbalanced power occurs in the power system, the frequency response of the power system is calculated and expressed as: Among them, ΔP d is the power unbalance shortage, Δf is the power system frequency deviation, and t is the time.

4. The method for evaluating power system frequency regulation resources considering transient frequency security constraints according to claim 3, characterized in that: The real-time monitoring of the frequency change rate and the minimum frequency includes calculating transient frequency safety indicators, including the frequency change rate RoCoF, the frequency minimum point FN and the quasi-steady-state frequency deviation QSSFD, based on simulation software and using a new power system frequency response model constructed; When power disturbance occurs, the maximum frequency change rate RF of the power system max is the RoCoF indicator, expressed as: Define the maximum transient frequency deviation Δf of the power system max is the FN indicator, expressed as: Δf max =max(Δf)| t>0 The quasi-steady-state frequency deviation is calculated as the QSSFD index, expressed as: QS=Δf(t ∞ ) Among them, QS is the quasi-steady-state frequency deviation.

5. The method for evaluating power system frequency regulation resources considering transient frequency security constraints according to claim 4, characterized in that: The evaluating the frequency security index of the power system includes setting a frequency security index constraint of the power system by limiting the transient frequency security index; Define the RoCoF indicator constraint, expressed as: |RF max |≤RoCoF M Among them, RoCoF M is the preset frequency threshold; Define the FN indicator constraint, expressed as: Δf nadir ≤Δf max Where Δf nadir is the threshold for under-frequency load shedding; Define the QSSFD indicator constraint, expressed as: QS≤QS max Among them, QS max is the maximum quasi-steady-state frequency deviation.

6. The method for evaluating power system frequency regulation resources considering transient frequency security constraints according to claim 5, characterized in that: The evaluating the frequency regulation resource security domain of the power system based on the frequency response model and the security index includes evaluating the frequency regulation resource security domain of the new power system based on the constructed new power system frequency response model and the frequency security index constraint of the power system; When the power system uses frequency regulation resources, the frequency regulation resource constraints are defined as follows: AND Hsys ≤E Hmax AND PFRsys ≤E PFRmax Among them, E Hsys 、E PFRsys are the power system inertia and primary frequency regulation reserve capacity, E HmaX 、E PFRmax They are the configurable inertia resources of the power system and the upper limit of primary frequency regulation reserve capacity; The simulation model is used to predict the frequency response dynamics of the power system, and the results are fed back to the safety domain assessment process for iterative cycles. When the frequency safety constraints and the inertia-primary frequency regulation resource safety boundary of the upper limit of the available frequency regulation capacity are met, the operating point within the safety boundary is the safety domain being assessed.

7. The method for evaluating power system frequency regulation resources considering transient frequency security constraints according to claim 6, characterized in that: The visualization includes visualization of the relationship between frequency safety and frequency regulation resources. The dispatching department guides the optimization of the combination of inertia and primary frequency regulation reserve resources according to the position of the operating point in the safety domain to ensure the frequency regulation capability of the system.

8. A system using the method for evaluating power system frequency regulation resources considering transient frequency security constraints as claimed in any one of claims 1 to 7, characterized in that: It includes frequency response model construction module, frequency security index evaluation module, frequency modulation resource security domain evaluation and visualization display module; The frequency response model building module is used to analyze the frequency response characteristics of the system by building a new power system frequency response model; The frequency security index evaluation module is used to evaluate the frequency security index of the power system by real-time monitoring of the frequency change rate and the minimum frequency; The frequency regulation resource security domain assessment and visualization display module is used to assess the frequency regulation resource security domain of the power system and perform visualization display based on the frequency response model and security indicators.

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 frequency regulation resources of a power system considering transient frequency security constraints described in 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 evaluating frequency regulation resources of a power system considering transient frequency security constraints according to any one of claims 1 to 7 are implemented.

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