High-proportion new energy power system inertia response determination method and system based on frequency lowest point constraint, and storage medium

Abstract

The invention discloses a high-proportion new energy power system inertia response determination method and system based on frequency lowest point constraint and a storage medium. Firstly, the influence of inertia response and primary frequency modulation response on system frequency is deduced, and substitution modes of related control parameters of the inertia response and the primary frequency modulation response are obtained; then, in combination with a typical unit frequency domain control block diagram, establishing a related model in simulink; and finally, traversing possible control parameters in the system to obtain an alternative relationship between inertia response and primary frequency modulation response under the constraint of the lowest point of the frequency, and further determining the inertia response capability required by the system for maintaining safe and stable operation of the frequency.

Description

Technical Field

[0001] This invention belongs to the field of power technology, specifically relating to a method, system, and storage medium for determining the inertia response of a high-proportion new energy power system based on the constraint of the lowest frequency point. Background Technology

[0002] Driven by the global energy transition and the "dual-carbon" goal, renewable energy is developing rapidly. However, renewable energy units are connected to the grid via power electronic converters, resulting in significant differences in operating characteristics compared to traditional synchronous generators. Because power electronic converters lack rotating parts, they cannot provide inertia support, and they are often in maximum power point tracking (MPPT) mode, making it difficult for them to participate in primary frequency regulation. In high-proportion renewable energy power systems, the shortage of inertia and frequency regulation resources severely threatens frequency stability.

[0003] In the past, when determining the inertial response requirements, only the impact of the inertial response on the system frequency was usually considered, often neglecting the role of other frequency regulation auxiliary resources, especially primary frequency regulation resources. This could lead to waste due to the redundant allocation of multiple resources. In new power systems where the proportion of new energy sources is gradually increasing, this phenomenon will be even more pronounced.

[0004] Therefore, there is an urgent need for a method that comprehensively considers primary frequency regulation resources in high-proportion renewable energy power systems to determine the required inertial response of the system. Summary of the Invention

[0005] Purpose of the invention: To address the problems of frequency instability in new energy power systems and waste of inertia resources and other frequency regulation resources caused by the lack of inertia in existing technologies, this invention provides a method, system, and storage medium for determining the inertia response of a high-proportion new energy power system based on the constraint of the lowest frequency point. After fully considering the frequency security requirements of the new power system, the inertia response required by the system under the premise of ensuring the safe operation of the system is obtained.

[0006] Technical solution:

[0007] This invention proposes a method for determining the inertia response of a high-proportion renewable energy power system based on the constraint of the lowest frequency point, comprising:

[0008] S1: Model the system frequency response process of a single synchronous generator unit, analyze the influence of inertial response and primary frequency regulation response on the system frequency, obtain the control parameters related to the system frequency response, and select the two with the highest correlation.

[0009] S2: Based on the frequency domain control block diagram of the synchronous generator, establish a simulation model of the system frequency response, set control parameters, detect the time domain change curve of the system frequency after being disturbed, and obtain the lowest point of the system frequency and the occurrence time.

[0010] S3: Traverse the control parameters in the simulation model, repeat S2, record the lowest point and occurrence time of the system frequency under each set of control parameters, draw the set boundary curve based on the recorded results, and obtain the system inertia response requirements.

[0011] Furthermore, the modeling of the system frequency response process for a single synchronous generator unit includes:

[0012] Ignoring the influence of the exciter unit, the output and frequency changes of the synchronous generator unit under the influence of inertia follow the following pattern:

[0013]

[0014] in, For generator mechanical power, To meet load requirements, This refers to the system frequency deviation. The inertia constant is expressed as the rotor's kinetic energy at rated speed divided by the rated power; the system state before the disturbance is the rated steady state, and the disturbance power is the difference between the generator's mechanical power and the load demand. ;

[0015] Considering the negative feedback effect of components in the synchronous generator on the system frequency after a frequency disturbance, the transfer function of the frequency response process is simplified by performing an inverse Laplace transform to obtain the system frequency in the time domain. Relationship with disturbance power:

[0016]

[0017]

[0018] In the above formula Indicates the system disturbance power. Let be the system inertia constant. This is the speed regulation coefficient of the speed controller. The system damping coefficient is... The reheat time constant is For high-pressure turbine fraction.

[0019] Furthermore, the control parameters are obtained through the system frequency in the frequency domain and time domain. The relationship with the disturbance power is obtained, including the governor time constant T. G Steam box time constant T C Reheat time constant T R High-pressure turbine fractional F H The system inertia constant H, the speed regulator speed regulation coefficient R, and the system damping coefficient D.

[0020] Furthermore, the correlation is determined by assessing the sensitivity of each control parameter based on the lowest system frequency value, and this sensitivity is expressed as... , The lowest frequency value, The more sensitive the control parameter is, the higher its correlation with the system's frequency response.

[0021] Furthermore, the simulation model for establishing the system frequency response is built using the Simulink tool, including:

[0022] (1) Create a step module at the input end, set its step time to t, the initial value to 0, and the final value to ΔP. L ;

[0023] (2) Create a transfer fcn module, set the numerator coefficient to [1] and the denominator coefficient to [2*HD], and regard it as a rotor module;

[0024] (3) Create a transfer fcn module, set the numerator coefficient to [1], and the denominator coefficient to [T]. G 1] Create a gain module, set the gain to R, and connect the two modules in series as a speed controller module;

[0025] (4) Create a transfer fcn module, set the numerator coefficient to [1], and the denominator coefficient to [T]. C [1] is considered a steam box module;

[0026] (5) Create a transfer fcn module, set the numerator coefficient to [1-FH], and the denominator coefficient to [T]. R 1] Create a gain module, set the gain to FH, and connect the two modules in parallel as a reheater module;

[0027] (6) Create a gain module, a to workspace module and a scope module at the output end, and set the gain of the gain module to 50;

[0028] (7) Use signal lines to connect the input terminal, rotor module and output terminal in series. Lead out a signal line from the output terminal to connect the speed controller module, steam box module and reheater module in series. Finally, connect the negative feedback to the signal line at the input terminal.

[0029] (8) In MATLAB, the parameter ΔP L H, D, T G R, T C F H and T R Assign a value.

[0030] Furthermore, the time-domain variation curve is output through the scope module, with the horizontal axis representing time and the vertical axis representing frequency. The frequency deviation of the system frequency after a large disturbance under set parameters is obtained through the time-domain variation curve, and the lowest frequency point of the system is calculated.

[0031] Furthermore, the control parameters in the traversal simulation model include:

[0032] (1) Perform a first traversal of a control parameter from smallest to largest;

[0033] (2) For each current value of the control parameter, perform a second traversal of the other control parameter from large to small until the lowest point of the system frequency output in the Simulink simulation no longer satisfies the frequency safety constraint.

[0034] Furthermore, the step of drawing the set boundary curve includes:

[0035] Using the two control parameters or their reciprocals as the horizontal and vertical axes of the set boundary curve, respectively, we obtain the set boundary that meets the system frequency requirements. This boundary is considered as the mutual substitution relationship between the inertial response and the first-order frequency modulation response under extreme scenarios. The part corresponding to the boundary curve and above is the system frequency safety region, representing the system inertial response requirements.

[0036] On the other hand, the present invention also proposes a computer system including a memory, a processor, and a computer program stored in the memory, wherein the processor executes the computer program to implement the steps of any of the foregoing methods.

[0037] On the other hand, the present invention also proposes a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of any of the aforementioned methods.

[0038] Beneficial effects:

[0039] This invention provides a method, system, and storage medium for determining the inertia response of a high-proportion renewable energy power system based on frequency minimum point constraints. Compared with previous simple system frequency constraints, its main advantages include:

[0040] (1) This invention derives the influence of inertia response and primary frequency modulation response on system frequency through precise constraint design and response substitution mechanism, and obtains the substitution method of related control parameters of the two; this invention effectively alleviates the dilemma of system inertia loss after the increase of new energy proportion through this substitution method, and fills the application gap of traditional constraints in high new energy scenarios.

[0041] (2) This invention breaks through the previous model of "independent supply" of inertial response and primary frequency regulation response. It innovatively determines the required inertial response capability based on the system's primary frequency regulation capability, without having to allocate two types of resources in full to meet the demand, thereby directly saving the economic cost of inertial supply. Attached Figure Description

[0042] Figure 1 This is a flowchart of a method for determining the inertia response of a high-proportion new energy power system based on the constraint of the lowest frequency point, as proposed in this invention.

[0043] Figure 2 This is a block diagram of the frequency domain control of a typical synchronous machine;

[0044] Figure 3 The simplified block diagram of the synchronous machine frequency domain control;

[0045] Figure 4 This is a typical Simulink control model for thermal power units;

[0046] Figure 5 The time-domain frequency variation curve of the unit after a power drop;

[0047] Figure 6 The inertia and primary frequency modulation replacement boundary are required to meet the minimum frequency requirement of the system. Detailed Implementation

[0048] The present invention will be further explained below with reference to the accompanying drawings and specific embodiments. The present invention provides a method for determining the inertia response of a high-proportion renewable energy power system based on the constraint of the lowest frequency point. Under the premise of ensuring safe system operation, the required inertia response and primary frequency regulation response of the system are mutually substituted to save inertia supply costs and ensure the safe and economical operation of the power grid. Specifically, it includes the following steps:

[0049] Step 1: Model the system frequency response process of a single synchronous generator unit, deduce the influence of inertial response and primary frequency regulation response on the system frequency, and derive the substitution method for the relevant control parameters of the two.

[0050] After neglecting the influence of the exciter unit, the output and frequency changes of the synchronous generator unit, due to inertia, basically follow the following formula:

[0051]

[0052] in, For generator mechanical power, To meet load requirements, This represents the system frequency deviation. The inertia constant is expressed as the rotor's kinetic energy at rated speed divided by the rated power, used to measure the unit's inertia level. Assuming the system state before the disturbance is at rated steady state, i.e., the generated power equals the load demand before the disturbance, it is expressed as... The actual disturbance power is the generator mechanical power. With load requirements The difference This is equivalent to the difference between the generator mechanical power disturbance and the load demand disturbance. .

[0053] To model the frequency response of a single synchronous generator unit, the influence of components such as the speed governor must be considered. These components exhibit negative feedback effects on the system frequency after frequency disturbances. The frequency domain control block diagram of a single synchronous generator after modeling is as follows: Figure 2 As shown, it includes: a positive feedback channel simulating the rotor characteristics of a thermal power unit, and a negative feedback channel composed of a reheater module, a steam box module, and a governor module. The figure shows... Indicates the disturbance power. This indicates the compensation power generated by devices such as speed controllers. This represents the actual power affecting the rotor output frequency. The system's frequency response is mainly related to the following parameters: T G T represents the time constant of the speed controller. C T represents the steam box time constant. R F represents the reheat time constant. H H represents the high-pressure turbine fraction, and K represents the inertia constant. m R is used to characterize the performance of the speed governor. Because T... C T G T R Much smaller, it is simplified in subsequent analysis, resulting in a simplified unit frequency domain control block diagram as follows: Figure 3 As shown, it includes: a positive feedback channel simulating the rotor properties of a thermal power unit, and a negative feedback channel composed of the feedback coefficients of the reheater and governor modules. The figure shows... This indicates the frequency output of the system under large disturbances.

[0054] Let a = T R b=F H Then the frequency domain transfer function of the overall frequency response is:

[0055]

[0056] Performing an inverse Laplace transform on the transfer function, which is still quite complex, we introduce the following five intermediate parameters to simplify the final representation:

[0057]

[0058] Obtain the system frequency in the time domain The relationship with the disturbance power is as follows:

[0059]

[0060] In the above formula Indicates the system disturbance power. Let be the system inertia constant. This is the speed regulation coefficient of the speed controller. The system damping coefficient is... The reheat time constant is For high-pressure turbine fraction.

[0061] To evaluate the primary frequency regulation performance and inertia response performance required by the system, it is necessary to find an index that can measure the system's frequency security performance and is simultaneously affected by primary frequency regulation and inertia. The system's minimum frequency constraint satisfies both of these conditions.

[0062] When the system frequency When the frequency deviation reaches its lowest point, the first derivative of the frequency deviation with respect to time is 0, and we have:

[0063]

[0064] In the formula This represents the system's maximum frequency deviation. This is the time corresponding to the system's maximum frequency deviation. The system frequency at the moment corresponding to the maximum frequency deviation of the system. This is the minimum safe frequency threshold, used to constrain the lowest frequency point of the system.

[0065] The parameter T in the above analysis process R H, F H A sensitivity analysis was performed on the influence of D and R on the minimum system frequency. The sensitivity is expressed as... , For T R H, F H The parameter changes of D and R are shown in Table 1 in this embodiment.

[0066] Table 1. Sensitivity analysis results of the system's minimum frequency to various parameters.

[0067] parameter <![CDATA[T R ]]> H <![CDATA[F H ]]> D R Minimum value 4 3 0.1 0 0.03 Maximum value 11 9 0.35 2 0.08 Sensitivity -0.01 0.03 1.35 0.05 -9.14

[0068] Table 1 shows that the minimum system frequency is most affected by the speed regulator's speed adjustment R. Additionally, the system inertia constant H significantly influences the time it takes for the minimum to occur. The impact is significant, therefore it is also included in the factors affecting the lowest point of the system frequency.

[0069] The above analysis shows that the lowest system frequency is strongly correlated with the parameters related to the inertia response and the primary frequency modulation response. Therefore, by constraining the lowest system frequency, the requirements for the primary frequency modulation response and inertia response of the system can be obtained.

[0070] Step 2: Based on a typical unit frequency domain control block diagram, build the relevant model in Simulink.

[0071] Because the relationship between the system's lowest frequency point obtained in step 1 and the parameters related to the inertial response and primary frequency modulation response is highly complex, it is necessary to establish a relevant model to assist in the analysis. Simulink is a visualization simulation tool in MATLAB, developed by MathWorks. Simulink is a modular graph environment used for multi-domain simulation and model-based design.

[0072] In this embodiment, the Simulink model established based on the frequency domain control block diagram of the thermal power unit is as follows: Figure 4 As shown, the Simulink model includes an input step module for simulating possible system disturbances, a positive channel transfer fcn module for simulating the rotor characteristics of the thermal power unit, a combined module formed by cascading the negative feedback transfer fcn module and gain module for simulating governor characteristics, a negative feedback transfer fcn module for simulating steam box characteristics, a combined module formed by paralleling the negative feedback transfer fcn module and gain module for simulating reheater characteristics, an output gain module for inverse-scaling the output frequency deviation per-unit value to a named value, an output to workspace module for exporting data to the MATLAB workspace for data analysis, and an output scope module for directly observing the system's frequency response. The steam box and reheater modules can be ignored or have their parameters kept unchanged after simplification. The specific steps for building the Simulink model include:

[0073] (1) Create a step module at the input end, set its step time to t, the initial value to 0, and the final value to ΔP. L ;

[0074] (2) Create a transfer fcn module, set the numerator coefficient to [1] and the denominator coefficient to [2*HD], and regard it as a rotor module;

[0075] (3) Create a transfer fcn module, set the numerator coefficient to [1] and the denominator coefficient to [TG 1], create a gain module, set the gain to R, and connect the two modules in series as a speed controller module;

[0076] (4) Create a transfer fcn module, set the numerator coefficient to [1] and the denominator coefficient to [TC 1], and regard it as a steam box module;

[0077] (5) Create a transfer fcn module, set the numerator coefficient to [1-FH] and the denominator coefficient to [TR 1], create a gain module, set the gain to FH, and connect the two modules in parallel as a reheater module;

[0078] (6) Create a gain module, a to workspace module and a scope module at the output end, and set the gain of the gain module to 50;

[0079] (7) Use signal lines to connect the input terminal, rotor module and output terminal in series. Lead out a signal line from the output terminal to connect the speed controller module, steam box module and reheater module in series. Finally, the negative feedback is connected to the input terminal signal line.

[0080] The initial parameters of the unit were changed by assigning values ​​to various parameters in MATLAB. The initial parameters for a typical thermal power unit power sudden change test are shown in Table 2.

[0081] Table 2 Initial parameters of the Simulink model

[0082] <![CDATA[Disturbance power ΔP L > -12% <![CDATA[Governor time constant T G > 0.231 System inertia H 3.5s Speed ​​regulator speed regulation coefficient R 0.061 Load damping coefficient D 1.2% <![CDATA[Reheat time constant T R > 10 <![CDATA[High pressure turbine fraction F H > 0.278 <![CDATA[Steam chest time constant T C > 0.363

[0083] Use the step module in Simulink to generate a system step disturbance ΔP at a fixed time. L The scope module is used to represent the output frequency response as a time-domain curve. The lowest point of this curve is the maximum frequency deviation of the system.

[0084] After a sudden 12% drop in total power in the system within 0.5 seconds, the typical unit's frequency time-domain change curve is as follows: Figure 5 As shown, Figure 5 The horizontal axis represents time, and the vertical axis represents frequency. This curve shows how the system frequency changes over time. It is used to analyze and obtain the frequency deviation of the system frequency after a large disturbance under set parameters, and then to calculate the lowest frequency point of the system.

[0085] Step 3: Traverse all possible control parameters in the system to obtain the substitution relationship between the inertial response and the primary frequency modulation response under the constraint of the lowest frequency point, and further determine the required inertial response capability.

[0086] The specific steps include:

[0087] (1) Perform the first traversal of the speed regulator coefficient R from small to large. Specifically, set the initial value of R to 0.059 and increase it step by step in increments of 0.005 until it reaches 0.1.

[0088] (2) For each current value of R, perform a second traversal of the system inertia constant H from large to small. Specifically, set the initial value of H to 3s and decrease it step by step in 0.5s until the lowest point of the system frequency output in the Simulink simulation no longer meets the frequency safety constraint.

[0089] Although there is no unified standard for a specific lower frequency limit, in general frequency modulation response scenarios, when the frequency drops below 48.5Hz, a single frequency modulation is not only ineffective, but may also exacerbate system deterioration due to the generator disconnection. Therefore, setting 49Hz as the lowest frequency point under system disturbance is reasonable.

[0090] (3) Since H and 1 / R are nearly linear in the substitution relationship, we use H and 1 / R to plot the curves and connect all the H and 1 / R sets that just meet the minimum frequency requirement of the system. The set curve is shown in the figure. Figure 6 As shown, the area above and above the curve represents the system's frequency safety region, which dictates the system's inertia response requirements.

[0091] Through the above process, the inertial response requirements of the system are obtained by comprehensively considering the impact of primary frequency regulation resources. While ensuring the frequency safety and stability of the high-proportion new energy power system, the waste of frequency regulation resources and inertial resources caused by multiple configurations is greatly reduced.

Claims

1. A method for determining the inertia response of a high-proportion renewable energy power system based on the constraint of the lowest frequency point, characterized in that, include: S1: Model the system frequency response process of a single synchronous generator unit, analyze the influence of inertial response and primary frequency regulation response on the system frequency, obtain the control parameters related to the system frequency response, and select the two control parameters with the highest correlation. S2: Based on the frequency domain control block diagram of the synchronous generator, establish a simulation model of the system frequency response, set control parameters, detect the time domain change curve of the system frequency after being disturbed, and obtain the lowest point of the system frequency and the occurrence time. S3: Traverse the control parameters in the simulation model, repeat S2, record the lowest point and occurrence time of the system frequency under each set of control parameters, draw the set boundary curve based on the recorded results, and obtain the system inertia response requirements.

2. The inertia response determination method according to claim 1, characterized in that, The modeling of the system frequency response process for a single synchronous generator unit includes: Ignoring the influence of the exciter unit, the output and frequency changes of the synchronous generator unit under the influence of inertia follow the following pattern: in, For generator mechanical power, To meet load requirements, This refers to the system frequency deviation. The inertia constant is expressed as the rotor's kinetic energy at rated speed divided by the rated power; the system state before the disturbance is the rated steady state, and the disturbance power is the difference between the generator's mechanical power and the load demand. ; Considering the negative feedback effect of components in the synchronous generator on the system frequency after a frequency disturbance, the transfer function of the frequency response process is simplified by performing an inverse Laplace transform to obtain the system frequency in the time domain. Relationship with disturbance power: In the above formula Indicates the system disturbance power. Let be the system inertia constant. This refers to the speed regulation coefficient of the speed controller. The system damping coefficient is... The reheat time constant is For high-pressure turbine fraction.

3. The inertia response determination method according to claim 2, characterized in that, The control parameters are obtained through the system frequency in the frequency domain and the time domain. The relationship with the disturbance power is obtained, including the governor time constant T. G Steam box time constant T C Reheat time constant T R High-pressure turbine fractional F H The system inertia constant H, the speed regulator speed regulation coefficient R, and the system damping coefficient D.

4. The inertia response determination method according to claim 3, characterized in that, The correlation is determined by assessing the sensitivity of each control parameter based on the lowest system frequency value, and the sensitivity is expressed as... , The lowest frequency value, The more sensitive the control parameter is, the higher its correlation with the system's frequency response.

5. The inertia response determination method according to claim 4, characterized in that, The simulation model for establishing the system frequency response is built using the Simulink tool, including: (1) Create a step module at the input end, set its step time to t, the initial value to 0, and the final value to ΔP. L ; (2) Create a transfer fcn module, set the numerator coefficient to [1] and the denominator coefficient to [2*HD], and regard it as a rotor module; (3) Create a transfer fcn module, set the numerator coefficient to [1], and the denominator coefficient to [T]. G 1] Create a gain module, set the gain to R, and connect the two modules in series as a speed controller module; (4) Create a transfer fcn module, set the numerator coefficient to [1], and the denominator coefficient to [T]. C [1] is considered a steam box module; (5) Create a transfer fcn module, set the numerator coefficient to [1-FH], and the denominator coefficient to [T]. R 1] Create a gain module, set the gain to FH, and connect the two modules in parallel as a reheater module; (6) Create a gain module, a to workspace module and a scope module at the output end, and set the gain of the gain module to 50; (7) Use signal lines to connect the input terminal, rotor module and output terminal in series. Lead out a signal line from the output terminal to connect the speed controller module, steam box module and reheater module in series. Finally, the negative feedback is connected to the signal line at the input terminal. (8) In MATLAB, the parameter ΔP L H, D, T G R, T C F H and T R Perform the assignment.

6. The inertia response determination method according to claim 5, characterized in that, The time-domain variation curve is output through the scope module, with the horizontal axis representing time and the vertical axis representing frequency. The frequency deviation of the system frequency after a large disturbance under set parameters is obtained through the time-domain variation curve, and the lowest frequency point of the system is calculated.

7. The inertia response determination method according to claim 6, characterized in that, The control parameters in the traversal simulation model include: (1) Perform a first traversal of a control parameter from smallest to largest; (2) For each current value of the control parameter, perform a second traversal of the other control parameter from large to small until the lowest point of the system frequency output in the Simulink simulation no longer satisfies the frequency safety constraint.

8. The inertia response determination method according to claim 7, characterized in that, The drawing of the set boundary curve includes: Using the two control parameters or their reciprocals as the horizontal and vertical axes of the set boundary curve, respectively, we obtain the set boundary that meets the system frequency requirements. This boundary is considered as the mutual substitution relationship between the inertial response and the first-order frequency modulation response under extreme scenarios. The part corresponding to the boundary curve and above is the system frequency safety region, representing the system inertial response requirements.

9. A computer system comprising a memory, a processor, and a computer program stored in the memory, characterized in that, The processor executes the computer program to implement the steps of any of the methods of claims 1 to 8.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of any of the methods described in claims 1 to 8.

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