A method for evaluating the equivalent inertia of inertial response load considering RoCoF

Abstract

This invention discloses a method for evaluating the equivalent inertia of a load considering RoCoF inertia response in the field of inertia assessment. The method includes the following steps: first, establishing an IRL response model considering RoCoF; then, establishing a power system frequency response model involving IRL based on the IRL response model; next, establishing an inertia assessment model of the power system frequency response model involving IRL based on the established power system frequency response model involving IRL; and finally, establishing an equivalent inertia assessment model of IRL based on the established power system frequency response model involving IRL. This invention proposes the possibility of IRL providing response in the early stages of a grid fault, coordinating load-side inertia response resources with generation-side resources for effective control of the grid's RoCoF during the inertia response phase; simultaneously, it proposes an equivalent inertia assessment method of IRL to quantify novel inertia response resources under the same inertia system and fully reflect the ability of these inertia response resources to support the grid frequency after disturbance.

Description

Technical Field

[0001] This invention belongs to the field of inertia assessment, specifically relating to a method for assessing the equivalent inertia of inertia response load taking into account RoCoF. Background Technology

[0002] In recent years, the proportion of new energy sources in my country has been continuously increasing. Traditional synchronous generators are gradually being replaced, while new energy sources connected to the grid via converters decouple power and frequency, leading to a gradual decrease in the power system's inertia level. When a low-inertia system experiences a fault, it is highly susceptible to a rapid drop in system frequency, a deterioration in the RoCoF index, exceeding the response capabilities of various frequency control and recovery measures, and ultimately resulting in a grid-wide collapse. RoCoF has become an important indicator for evaluating the operational safety of the power grid after a fault. Summary of the Invention

[0003] To address the shortcomings of existing technologies, the present invention aims to provide a method for evaluating the equivalent inertia of inertia response load that takes into account RoCoF, thereby solving the problems mentioned in the background art.

[0004] The objective of this invention can be achieved through the following technical solutions:

[0005] A method for evaluating the equivalent inertia of inertial response load taking into account RoCoF includes the following steps:

[0006] Step 1: First, establish an IRL response model considering RoCoF, and then establish a power system frequency response model with IRL participation based on the IRL response model.

[0007] Step 2: Then, based on the power system frequency response model with IRL participation established in Step 1, establish the power system frequency response model inertia evaluation model with IRL participation. Finally, based on the established power system frequency response model inertia evaluation model with IRL participation, establish the IRL equivalent inertia evaluation model.

[0008] Preferably, the IRL response model expression in step 1 is as follows:

[0009]

[0010] In the formula, n is the total number of action thresholds in the IRL response model; ΔP L The value of the IRL response is denoted by ; m represents any threshold value in the action threshold range; P L This represents the maximum response size of the IRL.

[0011] Preferably, the power system frequency response model involving RL is expressed as follows:

[0012]

[0013] Preferably, the IRL equivalent inertia evaluation model is expressed as follows:

[0014]

[0015] The beneficial effects of this invention are:

[0016] 1. The method of this invention deeply explores the flexibility of load-side inertial response, proposes the possibility of IRL providing response in the early stage of grid faults, and coordinates the effective control of grid RoCoF by load-side inertial response resources and generation-side resources during the inertial response stage; at the same time, it proposes an IRL equivalent inertial assessment method to quantify the new inertial response resources under the same inertial system and fully reflect the ability of the inertial response resources to support the grid frequency after disturbance. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a flowchart of the method in an embodiment of the present invention;

[0019] Figure 2 This is a schematic diagram of the IRL linear response strategy in an embodiment of the present invention;

[0020] Figure 3 This is a schematic diagram of the SFR model involving IRL in an embodiment of the present invention. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Please see Figure 1 As shown, this embodiment provides a method for evaluating the equivalent inertia of the inertia response load (IRL) taking into account RoCoF, including the following steps:

[0023] Step 1: First, establish an IRL response model considering RoCoF, and then establish a power system frequency response model with IRL participation based on the IRL response model.

[0024] The process of establishing the IRL response model for RoCoF includes:

[0025] The IRL response model divides the action threshold into n equally spaced levels, such as Figure 2 As shown, at RoCoF values ​​of |df / dt|1, |df / dt|2, ..., |df / dt| n When to engage in action. Figure 2 The middle vertical axis represents the IRL response quantity ΔP L The horizontal axis represents different RoCoF response threshold levels |df / dt|. When RoCoF is detected to be lower than the set value (indicating an active power deficit in the power system), the grid-connected IRL will automatically disconnect the power supply for a period of time to prevent the grid frequency from dropping too quickly. The IRL response is positively correlated with the detected RoCoF. Since RoCoF is usually maximum at the beginning of the fault and then gradually decreases, the IRL response is also maximum at the beginning of the fault. When the inertial response phase ends and the system enters primary frequency regulation, the IRL also gradually decreases as RoCoF decreases, eventually fully recovering operation. The IRL response model expression is as follows:

[0026]

[0027] In the formula, n is the total number of action thresholds in the IRL response model; ΔP L The value of the IRL response is denoted by ; m represents any threshold value in the action threshold range; P L This represents the maximum response size of the IRL.

[0028] Based on the IRL response model, the specific response process is as follows:

[0029] 1) In the initial stage of a fault, |df / dt| is extremely large. After the fault, a certain response time margin needs to be reserved for the IRL. Therefore, when the grid's |df / dt| is detected to be greater than |df / dt|, n When this happens, a short response delay is allowed for the IRL, during which the response quantity is 0;

[0030] 2) As RoCoF gradually decreases, when the detected grid |df / dt| is lower than the threshold |df / dt| in the response strategy... m When (1≤m≤n-1), the IRL starts providing a size of mP. L / n response;

[0031] 3) When RoCoF drops to |df / dt|0, power on all IRLs and they start working. At this point, the IRLs no longer provide a response, and RoCoF will approach 0, ending the inertia response phase.

[0032] The process of establishing a power system frequency response model with the participation of IRL includes:

[0033] The ultimate goal of IRL's participation in inertial response is to achieve coordinated control of RoCoF by load-side and generator-side inertial response resources. Therefore, the established inertial response model needs to simultaneously include the inertial response components of both the IRL and the synchronous machine. The traditional power system frequency response (SFR) model expression is as follows:

[0034]

[0035] In the formula, F H T is the reheat coefficient; R D is the time constant of the reheat generator unit; H is the damping factor; K is the inertial constant; m The mechanical power gain factor is Δω(s); the frequency deviation in the Laplace domain is Δω(s); P step (s) represents the system power deficit.

[0036] Based on the established IRL response model considering RoCoF, the discrete response strategy is transformed into a continuous response strategy through linear fitting. The fitted IRL response model is expressed as follows:

[0037] ΔP L (s)=k L sΔω(s)

[0038] In the formula, k L This represents the slope corresponding to the IRL response strategy.

[0039] By incorporating the fitted IRL into the SFR model, we can obtain the SFR model involving the IRL, such as... Figure 3 As shown, the model is specifically expressed as follows:

[0040]

[0041] Step 2: Then, based on the power system frequency response model with IRL participation established in Step 1, establish the power system frequency response model inertia evaluation model with IRL participation. Finally, based on the established power system frequency response model inertia evaluation model with IRL participation, establish the IRL equivalent inertia evaluation model.

[0042] The total inertia of the system can be calculated by the ratio of the system disturbance power to the RoCoF at a certain moment of the disturbance. Therefore, in the SFR model involving IRL, the system inertia is evaluated, and the equivalent inertia evaluation model is established as follows:

[0043]

[0044] In the formula, RoCoF max The RoCoF value at a certain moment is a perturbation; f N The standard frequency is 50Hz; H sysThe total inertia of the SFR model system involving IRL; ΔP step This represents a system power deficit. In the system RoCoF... max To match the power deficit ΔP in the power grid step Given that the equivalent inertial constant H of the system is... sys It can be calculated.

[0045] Given that the inertia of the synchronous generator in the system is known, the equivalent inertia H of the IRL can be obtained using the following formula. L Size:

[0046]

[0047] In the formula, Q sys Total system capacity; Let I be the capacity of the i-th synchronous generator in the system; I is the total number of generators in the system. The inertial constant of the i-th synchronous generator in the system; Q L H represents the grid-connected capacity of the IRL in the system. L It is the equivalent inertial constant of IRL.

[0048] Based on the established power system frequency response model inertia assessment model involving IRL, the parameter H can be obtained. sys The size, and at the same time in parameter Q sys , Q L Given that everything is known, the IRL equivalent inertia evaluation model can be obtained, as follows:

[0049]

[0050] To verify the accuracy of the IRL equivalent inertia assessment method proposed in this invention and its applicability to existing thermal power unit inertia measurement systems, two models are set up for simulation comparison, as shown in Table 1:

[0051] Table 1. Design of Two Comparative Models

[0052]

[0053] Ensure that the total system inertia of Model 1 and Model 2 in Table 1 is the same, where the IRL equivalent inertia H in Model 2 is... L The evaluation method proposed in this invention is used to obtain the results. If the two models have the same RoCoF under the same power grid fault scenario and within the same observation time window, it proves that the IRL equivalent inertia evaluation method is accurate. The comparison results obtained by the two models are shown in Table 2.

[0054] Table 2. RoCoF error considering the IRL equivalent inertia assessment method

[0055]

[0056] Table 2 shows the effects of two models with different system inertia on the RoCoF index under the same fault scenario, as well as the RoCoF error considering the IRL equivalent inertia assessment method. As can be seen from Table 2, in the SFR+IRL model using the IRL equivalent inertia assessment method, the simulation RoCoF error is less than 1% compared to the SFR model. Therefore, the IRL equivalent inertia assessment method proposed in this invention can be incorporated into the existing thermal power unit inertia measurement system and has high accuracy.

[0057] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0058] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0059] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0060] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0061] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for evaluating the equivalent inertia of inertial response load considering RoCoF, characterized in that, Includes the following steps: Step 1: First, establish an IRL response model considering RoCoF, and then establish a power system frequency response model with IRL participation based on the IRL response model. The IRL response model expression in step 1 is as follows: In the formula, n This represents the total number of action threshold levels for the IRL response model. The magnitude of the IRL response; m It represents any level among the action thresholds; This represents the maximum response value of the IRL. The specific response process of the IRL response model includes: In the early stages of the malfunction, Extremely large, requiring a certain response time margin for the IRL after a fault, therefore, when the power grid is detected... Greater than When this happens, a short response delay is allowed for the IRL, during which the response quantity is 0; As RoCoF gradually decreases, when the power grid is detected... Below the threshold in the response strategy At that time, the IRL begins to provide a size of The response; When RoCoF is as low as When all IRLs are powered on and begin working, the IRLs no longer provide a response, and RoCoF will approach 0, ending the inertia response phase. In step 1, the power system frequency response model involving IRL needs to incorporate the fitted IRL response model into the traditional power system frequency response (SFR) model. The expression for the traditional power system frequency response (SFR) model is as follows: In the formula, This is the reheat coefficient; is the time constant of the reheat generator unit; D is the damping factor; H is the inertial constant; This refers to the mechanical power gain factor. The frequency deviation in the Laplace domain; This is due to a power deficit in the system. The fitted IRL response model is expressed as follows: In the formula, The slope corresponding to the IRL response strategy; Step 2: Then, based on the power system frequency response model with IRL participation established in Step 1, establish the power system frequency response model inertia evaluation model with IRL participation. Finally, based on the established power system frequency response model inertia evaluation model with IRL participation, establish the IRL equivalent inertia evaluation model. The power system frequency response model inertia evaluation model in step 2, in which IRL participates, is as follows: In the formula, To disturb a certain moment value; The standard frequency is 50Hz; The total inertia of the SFR model system with IRL participation; This is due to a power deficit in the system.

2. The method for evaluating the equivalent inertia of inertial response load taking into account RoCoF as described in claim 1, characterized in that, The frequency response model of the power system involving RL is expressed as follows: 。 3. The method for evaluating the equivalent inertia of inertial response load considering RoCoF according to claim 2, characterized in that, The equivalent inertia of IRL is obtained by the following formula. Size: In the formula, Total system capacity; Let be the capacity of the i-th synchronous generator in the system; I This represents the total number of generators in the system. The first in the system i The inertial constant of a synchronous generator; This represents the grid-connected capacity of the IRL in the system; It is the equivalent inertial constant of IRL.

4. The method for evaluating the equivalent inertia of inertial response load taking into account RoCoF according to claim 3, characterized in that, The IRL equivalent inertia assessment model is expressed as follows: 。 5. A system for evaluating the equivalent inertia of inertial response load taking into account RoCoF, characterized in that, The system is used to implement the inertia response load equivalent inertia assessment method considering RoCoF as described in any one of claims 1-4, the system comprising: The initial module is used to establish a power system frequency response model involving IRL; The molding module is used to establish an IRL equivalent inertia evaluation model.

6. A RoCoF-based inertia response load equivalent inertia assessment controller, storing a program for running the RoCoF-based inertia response load equivalent inertia assessment system of claim 5.

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