New energy acceptance capability assessment method considering power grid inertia and frequency modulation capability constraint

Abstract

The invention provides a new energy acceptance capability assessment method considering power grid inertia and frequency modulation capability constraint, and the method comprises the following steps: S1, determining the initial new energy permeability of a new energy system, and determining an equivalent inertia time constant and unit adjustment power of a power system based on the initial new energy permeability; s2, determining the response frequency under the disturbance of the new energy access system based on the equivalent inertia time constant and the unit regulation power; s3, respectively determining a first maximum permeability, a second maximum permeability and a third maximum permeability of the new energy system by taking the response frequency under the disturbance of the new energy access system as a constraint; s4, screening out a minimum value from the first maximum permeability, the second maximum permeability and the third maximum permeability, and taking the minimum value as the new energy acceptance capability of the power system; the new energy maximum permeability can be accurately and objectively evaluated, the new energy consumption level is improved, and accurate data support is provided for safe and stable operation of a power grid.

Description

Technical Field

[0001] The present invention relates to a power grid evaluation method, and in particular to a new energy acceptance capacity evaluation method taking into account power grid inertia and frequency regulation capacity constraints. Background Art

[0002] Renewable energy sources such as wind power and photovoltaics are increasingly being adopted due to their green, pollution-free, and zero-carbon emissions advantages. However, as the penetration of renewable energy in power systems continues to increase, grid frequency stability issues are becoming increasingly prominent. When large-scale renewable energy is integrated into the grid, a significant number of synchronous generators are displaced, which not only reduces the system's moment of inertia but also weakens the system's primary frequency regulation capability, seriously threatening the system's frequency stability. Therefore, from the perspective of ensuring system frequency stability, accurately assessing renewable energy acceptance capacity or estimating its maximum penetration rate is crucial for the safe and stable operation of large-scale renewable energy grid-connected power systems.

[0003] In the existing technology, the penetration rate estimation or absorption capacity assessment of new energy power systems is currently mainly carried out from two aspects: simulation modeling and analytical calculation. Related studies take into account load uncertainty and changes in wind speed, sunshine, etc., and use software simulation to simulate the random combination of different stability standards and different emergencies. Simulation analysis obtains the maximum penetration rate of distributed wind power or photovoltaics at different locations; however, due to the limitations of simulation modeling and computing capabilities, software simulation methods are not suitable for complex networks or changeable external actual operating environments, and their practicality is poor.

[0004] In terms of analytical calculation, some studies have proposed to estimate the maximum renewable energy power capacity connected to the grid based on the approximate value of the maximum deviation of the grid frequency based on sensitivity analysis; relevant researchers have also proposed to establish a comprehensive grid frequency response model that includes renewable energy, and established relevant indicators such as frequency security, to analytically calculate the penetration power limit of wind power and photovoltaic renewable energy. However, the existing analytical calculation method does not take the grid inertia into account, nor does it consider the relationship between frequency stability and penetration rate, which makes the final evaluation results inaccurate and difficult to guide the safe and stable operation of the grid.

[0005] Therefore, in order to solve the above technical problems, it is urgent to propose a new technical means. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide a method for evaluating the renewable energy acceptance capacity that takes into account the constraints of grid inertia and frequency regulation capacity. By determining the frequency based on the time inertia of the grid, both grid inertia and frequency regulation changes are taken into account. The three aspects of frequency are constrained and the maximum penetration rate of the grid is solved, thereby determining the renewable energy acceptance capacity of the grid. The final result is more reliable and accurate, and can provide accurate data support for the grid's acceptance of renewable energy, thereby improving the level of renewable energy absorption.

[0007] The present invention provides a method for evaluating the renewable energy acceptance capacity taking into account grid inertia and frequency regulation capacity constraints, comprising the following steps:

[0008] S1. Determine the initial new energy penetration rate of the new energy system, and determine the equivalent inertia time constant and unit regulation power of the power system based on the initial new energy penetration rate;

[0009] S2. Determine the response frequency of the new energy access system under disturbance based on the equivalent inertia time constant and unit regulation power;

[0010] S3. Determine the first maximum permeability, the second maximum permeability, and the third maximum permeability of the new energy system, respectively, based on the response frequency of the new energy access system under disturbance.

[0011] S4. Filter out a minimum value from the first maximum permeability, the second maximum permeability, and the third maximum permeability, and use the minimum value as the new energy acceptance capacity of the power system.

[0012] Furthermore, determining the initial new energy penetration rate of the new energy system specifically includes:

[0013]

[0014] Where: η represents the initial new energy penetration rate, S C Represents the grid-connected capacity of new energy power sources in the power system, S Gi represents the rated capacity of the i-th synchronous generator in the power system, n represents the number of synchronous generators in the original power system before the new energy system is connected, and m represents the number of synchronous generators replaced by the new energy system after the new energy system is connected.

[0015] Furthermore, the equivalent inertia time constant of the power system is determined based on the initial new energy penetration rate, including:

[0016]

[0017] Among them: H sys Represents the equivalent inertia time constant of the power system, H j represents the inertia time constant of the jth synchronous generator, S Gj Represents the rated capacity of the jth synchronous generator in the power system.

[0018] Furthermore, based on the initial renewable energy penetration rate, the unit regulation power of the power system is determined to include:

[0019]

[0020] Among them: Ksys Indicates unit regulation power, ΔP G represents the change in active power of the power system during the frequency regulation phase, Δf represents the change in frequency during the frequency regulation process of the power system, and P N Indicates the rated power of the power system, F N Indicates the rated frequency of the power system.

[0021] Furthermore, the response frequency of the new energy access system under disturbance is determined based on the equivalent inertia time constant and the unit regulation power, specifically including:

[0022]

[0023] in: f sys (t) represents the response frequency of the system under disturbance, T G It represents the action time constant of the power system speed regulator, and ΔP represents the active power shortage value under power system disturbance.

[0024] Furthermore, determining the first maximum permeability specifically includes:

[0025] Taking the frequency change rate of the power system after the disturbance as the constraint boundary, the constraint equation is:

[0026]

[0027] The first maximum permeability is determined by the following formula:

[0028]

[0029] Where: η1 represents the first maximum penetration rate, the first maximum penetration rate represents the maximum penetration rate obtained under the power system frequency change constraint boundary, R max Indicates the upper limit of the frequency change rate after a power system disturbance.

[0030] Furthermore, determining the second maximum permeability specifically includes:

[0031] Taking the minimum value of the dynamic frequency of the power system after the disturbance as the constraint boundary, the constraint equation is:

[0032]

[0033] The second maximum permeability η2 is determined by the following formula:

[0034]

[0035] Where: f sysmax Indicates the minimum allowable operating frequency value after the power system is disturbed.

[0036] Furthermore, determining the third maximum permeability specifically includes:

[0037] Taking the quasi-steady-state frequency deviation of the power system after the disturbance as the constraint boundary, the constraint equation is:

[0038] Δf sys (t)| t→∞ >Δf smax ;

[0039] The third maximum permeability η3 is determined by the following formula:

[0040]

[0041] Where: Δf smax It indicates the maximum allowable difference between the quasi-steady-state frequency and the frequency during normal operation of the system after the power system is disturbed and the frequency of the system under the control of the first frequency regulation.

[0042] The beneficial effects of the present invention are as follows: Through the present invention, the frequency is determined by taking the time inertia of the power grid into account, thereby taking into account the power grid inertia and frequency modulation changes, and taking into account various types of operating boundary constraints such as the frequency change rate under system disturbance, the minimum value of the dynamic frequency, and the quasi-steady-state frequency deviation, so that the maximum penetration rate of new energy can be accurately and objectively evaluated, thereby improving the level of new energy consumption and providing accurate data support for the safe and stable operation of the power grid.

[0043] The acquisition of parameters in the entire process is simpler and more convenient, and the calculation process is simpler, faster and has a wider range of adaptability. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0045] Figure 1 Flowchart of the present invention.

[0046] Figure 2 The system frequency response curve of the present invention taking into account the grid inertia response and primary frequency regulation change process of the high-proportion new energy power system;

[0047] Figure 3 A test system in an embodiment of the present invention;

[0048] Figure 4 To test the simulation situation related to the new energy penetration rate and frequency change rate of the system under the constraint boundary of the system frequency change rate;

[0049] Figure 5 To test the system's new energy penetration rate and the simulation of the minimum dynamic frequency under the constraint boundary of the minimum dynamic frequency;

[0050] Figure 6To test the system's new energy penetration rate and quasi-steady-state frequency deviation under the constraint boundary of quasi-steady-state frequency deviation, the simulation situation is carried out. DETAILED DESCRIPTION

[0051] The present invention is further described in detail below:

[0052] The present invention provides a method for evaluating the renewable energy acceptance capacity taking into account grid inertia and frequency regulation capacity constraints, comprising the following steps:

[0053] S1. Determine the initial new energy penetration rate of the new energy system, and determine the equivalent inertia time constant and unit regulation power of the power system based on the initial new energy penetration rate;

[0054] S2. Determine the response frequency of the new energy access system under disturbance based on the equivalent inertia time constant and unit regulation power;

[0055] S3. Determine the first maximum permeability, the second maximum permeability, and the third maximum permeability of the new energy system, respectively, based on the response frequency of the new energy access system under disturbance.

[0056] S4. Filter out a minimum value from the first maximum permeability, the second maximum permeability, and the third maximum permeability, and use the minimum value as the new energy acceptance capacity of the power system.

[0057] Among them, the first, second and third in the above are not to sort the size of each value, but to distinguish the maximum penetration rate under three different constraints, and then select the maximum penetration rate with the smallest value among the maximum penetration rates under these three different constraints as the new energy acceptance capacity indicator of the power system. Therefore, through the above method, the frequency is determined by the time inertia of the power grid, so that the inertia of the power grid and the frequency regulation changes are taken into account, and various types of operating boundary constraints such as the frequency change rate under system disturbance, the minimum value of dynamic frequency, and the quasi-steady-state frequency deviation are taken into account, so that the maximum penetration rate of new energy can be accurately and objectively evaluated, the level of new energy absorption is improved, and accurate data support is provided for the safe and stable operation of the power grid; the parameter acquisition of the whole process is simpler and more convenient, and the calculation process is simpler, faster, and has a wider range of adaptability.

[0058] In this embodiment, determining the initial new energy penetration rate of the new energy system specifically includes:

[0059]

[0060] Where: η represents the initial new energy penetration rate, S C Represents the grid-connected capacity of new energy power sources in the power system, S Girepresents the rated capacity of the i-th synchronous generator in the power system, n represents the number of synchronous generators in the original power system before the new energy system is connected, m represents the number of synchronous generators replaced by the new energy system after the new energy system is connected, and when the new energy power generation replaces part of the synchronous generator power supply, the number of remaining synchronous generator power supplies in the system is nm units.

[0061] In this embodiment, determining the equivalent inertia time constant of the power system based on the initial new energy penetration rate specifically includes:

[0062]

[0063] Among them: H sys Represents the equivalent inertia time constant of the power system, H j represents the inertia time constant of the jth synchronous generator, S Gj Represents the rated capacity of the jth synchronous generator in the power system. Since renewable energy generation generally does not provide inertia, the equivalent inertia time constant H of the power system sys It decreases as the penetration rate of new energy increases.

[0064] The unit regulation power of the power system determined based on the initial new energy penetration rate includes:

[0065]

[0066] Among them: K sys Indicates unit regulation power, ΔP G represents the change in active power of the power system during the frequency regulation phase, Δf represents the change in frequency during the frequency regulation process of the power system, and P N Indicates the rated power of the power system, F N Indicates the rated frequency of the power system.

[0067] In this embodiment, determining the response frequency of the new energy access system under disturbance based on the equivalent inertia time constant and the unit regulation power specifically includes:

[0068]

[0069] in: f sys (t) represents the response frequency of the system under disturbance, T G It represents the action time constant of the power system speed regulator, and ΔP represents the active power shortage value under power system disturbance.

[0070] When the power grid experiences an active power shortage disturbance, the system frequency drops. New energy power generation equipment usually operates in maximum power point tracking mode and does not participate in primary frequency regulation, while the system's conventional synchronous generators participate in inertia response and primary frequency regulation response. Therefore, the inertia response and primary frequency regulation changes of the power grid after a high proportion of new energy is connected to the power system are taken into account. Figure 2 As shown, the dynamic change trajectory of the frequency is determined by the above response frequency formula.

[0071] In this embodiment, determining the first maximum permeability specifically includes:

[0072] Taking the frequency change rate of the power system after the disturbance as the constraint boundary, the constraint equation is:

[0073]

[0074] The first maximum permeability is determined by the following formula:

[0075]

[0076] Where: η1 represents the first maximum penetration rate, the first maximum penetration rate represents the maximum penetration rate obtained under the power system frequency change constraint boundary, R max Indicates the upper limit of the frequency change rate after a power system disturbance.

[0077] Determining the second maximum permeability specifically includes:

[0078] Taking the minimum value of the dynamic frequency of the power system after the disturbance as the constraint boundary, the constraint equation is:

[0079]

[0080] The second maximum permeability η2 is determined by the following formula:

[0081]

[0082] Where: f sysmax Indicates the minimum allowable operating frequency value after the power system is disturbed.

[0083] Determining the third maximum permeability specifically includes:

[0084] Taking the quasi-steady-state frequency deviation of the power system after the disturbance as the constraint boundary, the constraint equation is:

[0085] Δf sys (t)| t→∞ >Δf smax ;

[0086] The third maximum permeability η3 is determined by the following formula:

[0087]

[0088] Where: Δf smax It indicates the maximum allowable difference between the quasi-steady-state frequency and the frequency during normal operation of the system after the power system is disturbed and the frequency of the system under the control of the first frequency regulation.

[0089] The present invention is further described in detail below with a specific example:

[0090] like Figure 3 As shown, IEEE10 machine 39 nodes are selected to verify the effectiveness of the new energy acceptance capacity evaluation method of the present invention. All synchronous generators in the system have the same parameters, the inertia time constant is 10s, the rated capacity is 1000MVA, the active output is 500MW, the system frequency is 50Hz, and all loads are set to a constant power load model. In the test system, wind farms are used to replace some synchronous generators, and the wind turbines do not provide inertia support technology, and the rated capacity of the system is guaranteed to remain unchanged. The system N-1 situation, that is, the exit of a synchronous generator in the system is used as a disturbance event to evaluate the frequency security issues brought about by the new energy acceptance capacity or penetration rate.

[0091] Set the boundary constraint R in the test case max =0.48Hz / s, f sysmax =49.35Hz and Δf smax =0.2Hz, according to the method of the present invention, the new energy penetration rates corresponding to the respective constraint boundary conditions can be determined as: η1 = 55%, η2 = 50% and η3 = 38%. Therefore, without considering the intervention of the system frequency safety and stability control means, the new energy penetration rate value η sys =38% is the system's renewable energy acceptance capacity assessment value, which ensures safe and stable frequency of renewable energy access. This assessment also verifies the necessity of renewable energy frequency control to effectively improve the system's absorption capacity. Figure 4 、 Figure 5 and Figure 6 They are the simulations of the new energy penetration rate and system frequency change rate, dynamic frequency minimum value, and quasi-steady-state frequency deviation variables of the test system under the above three types of constraint boundaries. sys Only when all three constraints are within the safety range can the proposed method achieve the desired maximum renewable energy penetration rate. Simulation results demonstrate that the proposed method can meet the technical requirements of multiple frequency safety indicators. It is foreseeable that if a higher proportion of renewable energy sources, such as wind and photovoltaic power, are integrated into the power system, the proposed method for assessing renewable energy acceptance capacity from the perspective of ensuring system frequency stability will become more practical and more effective.

[0092] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. 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 purpose 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 renewable energy acceptance capacity taking into account grid inertia and frequency regulation capacity constraints, comprising the following steps: S1. Determine the initial new energy penetration rate of the new energy system, and determine the equivalent inertia time constant and unit regulation power of the power system based on the initial new energy penetration rate; S2. Determine the response frequency of the new energy access system under disturbance based on the equivalent inertia time constant and unit regulation power; S3. Determine the first maximum permeability, the second maximum permeability, and the third maximum permeability of the new energy system, respectively, based on the response frequency of the new energy access system under disturbance. S4. Filter out a minimum value from the first maximum permeability, the second maximum permeability, and the third maximum permeability, and use the minimum value as the new energy acceptance capacity of the power system.

2. The method for evaluating the renewable energy acceptance capacity taking into account grid inertia and frequency regulation capacity constraints according to claim 1, characterized in that: Determining the initial new energy penetration rate of the new energy system specifically includes: Where: η represents the initial new energy penetration rate, S C Represents the grid-connected capacity of new energy power sources in the power system, S Gi represents the rated capacity of the i-th synchronous generator in the power system, n represents the number of synchronous generators in the original power system before the new energy system is connected, and m represents the number of synchronous generators replaced by the new energy system after the new energy system is connected.

3. The method for evaluating the renewable energy acceptance capacity taking into account grid inertia and frequency regulation capacity constraints according to claim 1, characterized in that: The equivalent inertia time constant of the power system determined based on the initial new energy penetration rate specifically includes: Among them: H sys Represents the equivalent inertia time constant of the power system, H j represents the inertia time constant of the jth synchronous generator, S Gj Represents the rated capacity of the jth synchronous generator in the power system.

4. The method for evaluating the renewable energy acceptance capacity taking into account grid inertia and frequency regulation capacity constraints according to claim 3 is characterized by: The unit regulation power of the power system determined based on the initial new energy penetration rate includes: Among them: K sys Indicates unit regulation power, ΔP G represents the change in active power of the power system during the frequency regulation phase, Δf represents the change in frequency during the frequency regulation process of the power system, and P N Indicates the rated power of the power system, F N Indicates the rated frequency of the power system.

5. The method for evaluating the renewable energy acceptance capacity taking into account grid inertia and frequency regulation capacity constraints according to claim 4 is characterized by: The response frequency of the new energy access system under disturbance is determined based on the equivalent inertia time constant and unit regulation power, including: in: f sys (t) represents the response frequency of the system under disturbance, T G It represents the action time constant of the power system speed regulator, and ΔP represents the active power shortage value under power system disturbance.

6. The method for evaluating the renewable energy acceptance capacity taking into account grid inertia and frequency regulation capacity constraints according to claim 5, characterized in that: Determining the first maximum permeability specifically includes: Taking the frequency change rate of the power system after the disturbance as the constraint boundary, the constraint equation is: The first maximum permeability is determined by the following formula: Where: η1 represents the first maximum penetration rate, the first maximum penetration rate represents the maximum penetration rate obtained under the power system frequency change constraint boundary, R max Indicates the upper limit of the frequency change rate after a power system disturbance.

7. The method for evaluating the renewable energy acceptance capacity taking into account grid inertia and frequency regulation capacity constraints according to claim 5, characterized in that: Determining the second maximum permeability specifically includes: Taking the minimum value of the dynamic frequency of the power system after the disturbance as the constraint boundary, the constraint equation is: The second maximum permeability η2 is determined by the following formula: Where: f sysmax Indicates the minimum allowable operating frequency value after the power system is disturbed.

8. The method for evaluating the renewable energy acceptance capacity taking into account grid inertia and frequency regulation capacity constraints according to claim 5, characterized in that: Determining the third maximum permeability specifically includes: Taking the quasi-steady-state frequency deviation of the power system after the disturbance as the constraint boundary, the constraint equation is: Δf sys (t)| t→∞ >Δf smax ; The third maximum permeability η3 is determined by the following formula: Where: Δf smax It indicates the maximum allowable difference between the quasi-steady-state frequency and the frequency during normal operation of the system after the power system is disturbed and the frequency of the system under the control of the first frequency regulation.

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