Multi-source coordination control method for improving frequency recovery characteristic after power grid disturbance

Abstract

The invention relates to the technical field of power system frequency control, in particular to a multi-source coordination control method for improving frequency recovery characteristics after power grid disturbance, and the method comprises the following steps: S1, obtaining model parameter data of a power system unit and a load; s2, building a unified frequency model including each unit, load and energy storage; s3, based on model predictive control, collecting a system frequency deviation condition and a power system state; s4, establishing a multi-source coordination control model for improving the frequency recovery characteristic of the power grid; and S5, solving the multi-source coordination control model to obtain the output and exit time of energy storage and fan rapid frequency modulation. According to the invention, on the basis of a model prediction control principle, by collecting the state of the power system and coordinating and controlling source-network-storage output, the frequency recovery characteristic after power grid disturbance is improved, and the power grid frequency is prevented from deviating from a rated value for a long time.

Description

Technical Field

[0001] This invention relates to the field of power system frequency control technology, and is a multi-source coordinated control method to improve the frequency recovery characteristics after power grid disturbances. Background Technology

[0002] With the large-scale integration of new energy sources such as wind turbines into the grid, the lack of inertia and primary frequency regulation capability in their power generation equipment to respond to system frequency changes affects the frequency stability of the system. Relying solely on traditional turbines for primary frequency regulation is insufficient to meet the regulation requirements due to limited regulation capacity. To ensure system frequency stability, most existing wind turbines now possess a certain degree of frequency regulation capability.

[0003] Besides wind farms directly participating in grid frequency regulation, the rapid development of energy storage technology has also provided new solutions for frequency regulation. Energy storage has a fast response speed, can quickly control bidirectional power, and has strong power tracking capabilities, which can meet the frequency regulation requirements in various scenarios. However, most current research considers wind turbines or energy storage participating in frequency regulation separately, failing to combine the two simultaneously, and there is very little research on power allocation methods for wind turbines and energy storage on short time scales.

[0004] Therefore, how to coordinate and control wind and energy storage resources and maximize the advantages of wind and energy storage systems in grid frequency regulation is a question worthy of in-depth research. Summary of the Invention

[0005] This invention provides a multi-source coordinated control method to improve the frequency recovery characteristics after power grid disturbances, overcoming the shortcomings of the prior art. It can coordinate and control various frequency regulation resources during the frequency recovery phase and rationally control the output and shutdown timing of the wind and energy storage system.

[0006] The technical solution of this invention is achieved through the following measures: a multi-source coordinated control method for improving frequency recovery characteristics after power grid disturbances, comprising the following steps:

[0007] S1, acquire model parameter data of power system units and loads;

[0008] S2, build a unified frequency model that includes all generating units, loads and energy storage;

[0009] S3, based on model predictive control, collects information on system frequency deviation and power system status;

[0010] S4. Establish a multi-source coordinated control model to improve the frequency recovery characteristics of the power grid;

[0011] S5 solves the multi-source coordinated control model to obtain the output and shutdown timing of energy storage and wind turbine rapid frequency regulation.

[0012] The following are further optimizations and / or improvements to the above-mentioned technical solution:

[0013] In step S1 above, the model parameter data includes model parameters of various types of generating units, load regulation coefficients, and installed capacity of energy storage.

[0014] In step S2 above, the unified frequency model ignores system topology and power flow, considering only the governor-prime mover model of the generator units and the inherent frequency characteristics of the system, ultimately unifying the entire system to a single frequency. The unified frequency model establishes the corresponding functional relationship between power generation and power consumption on both the generation and consumption sides and the power system frequency. The expression for this corresponding functional relationship is as follows:

[0015]

[0016] In the formula, Δf is the system frequency deviation after a large disturbance, and M... eq For system inertia, determined by the inertial characteristics of the entire system unit, D eq ΔP is the load adjustment coefficient. G For the change in total unit output, ΔP L For load output change, ΔP bess For the change in energy storage output, ΔP wind Indicates the output power of the fan via rapid frequency adjustment, P dis This is the power deviation caused by a large disturbance.

[0017] In step S2 above, based on the wind turbine model in the unified frequency model, the slope of the linearized wind turbine's rapid frequency regulation output is calculated according to the initial wind turbine speed, enabling it to have rapid frequency regulation capability by changing the speed; the expression for the wind turbine's rapid frequency regulation is:

[0018] ΔP wind (Δω)=m0·Δω Equation 2

[0019] In the formula, Δω represents the change in fan speed, and m0 represents the linearization slope.

[0020] In step S3 above, the state matrix and output variable matrix of the model predictive control are as follows:

[0021] x(k)=[ΔP G (k),ΔP bess (k),Δω(k),ΔP wind (k),S(k),Δf(k)] T Formula 3

[0022] y(k)=[ΔP G (k),ΔP bess (k),ΔP wind (k),S(k),Δf(k)] T Formula 4

[0023] In the formula, ΔP G For the change in total unit output, ΔP bess For the change in energy storage output, Δω represents the change in wind turbine speed, and ΔP represents the change in energy storage output. wind Let S be the change in wind turbine output, S be the SOC of energy storage, and Δf be the system frequency deviation.

[0024] The aforementioned multi-source coordinated control model introduces the energy storage system's state of charge constraint, generator output upper and lower limit constraint, wind turbine speed regulation constraint, and frequency deviation constraint as safety constraints.

[0025] The above multi-source coordinated control model takes the overall fluctuation of system frequency and the minimum energy storage capacity within the moving time window as the objective function; the expression of the objective function is:

[0026]

[0027] In the formula, Δf(k+i|k) and P bess (k+i|k) represent the predicted values ​​of the system frequency deviation and energy storage power at the current sampling time k to time k+i, respectively. m For the prediction time domain, α and β are weighting coefficients.

[0028] The equations for calculating the weighting factors α and β of the objective function in the above multi-source coordinated control model are as follows:

[0029]

[0030] β = 1 - α (Equation 7)

[0031] In the formula, Δf nl The system frequency deviation Δf is the frequency deviation when no wind storage participates in frequency regulation. UFLS The maximum permissible frequency deviation is represented by C, which is a reference coefficient for the system frequency deviation without energy storage.

[0032] In step S4 above, the state of charge (SOC) constraint of the energy storage system is introduced into the multi-source coordinated control model. The expression for the SOC constraint of the energy storage system is:

[0033] P bess,min ≤P bess (k+i|k)≤P bess,max Formula 8

[0034] S min ≤S(k+i|k)≤S max Formula 9

[0035] In the formula, P bess,max P bess,minS represents the maximum and minimum discharge power of the stored energy; S(k+i|k) is the predicted value of the stored energy SOC at the current sampling time k to the time k+i; S min S max These are the upper and lower limits of the energy storage SOC state, respectively;

[0036] The frequency deviation constraint is introduced into the multi-source coordinated control model, and the expression for the frequency deviation constraint is as follows:

[0037] Δf(k+i|k)≥Δf max Formula 10

[0038] In the formula, Δf(k+i|k) is the predicted value of the system frequency at the current sampling time k to the system frequency at time k+i; Δf max This is the maximum frequency deviation allowed by the power grid;

[0039] The active power output constraint of traditional generator sets is introduced into the multi-source coordinated control model. The expression for the active power output constraint of traditional generator sets is as follows:

[0040] P G,min ≤P G (k+i|k)≤P G,max Formula 11

[0041] In the formula, P G (k+i|k) represents the predicted power of the traditional unit at the current sampling time k to the time k+i, P G,min P G,max These are the minimum and maximum power ratings for traditional generator sets;

[0042] The wind turbine speed regulation constraint is introduced into the multi-source coordinated control model, and the constraint expression is as follows:

[0043] -(ω0-ω min )≤Δω(k+i|k)≤(ω max -ω0) Equation 12

[0044] In the formula, Δω(k+i|k) is the predicted value of the fan speed at the current sampling time k to the time k+i, ω0 is the initial fan speed, and ω min ω max The minimum and maximum permissible speeds.

[0045] In step S5 above, the established multi-source coordinated control model collects power system state variables based on the model predictive control method. By solving the multi-source coordinated control module, the output status and exit timing of wind-storage joint fast frequency regulation are obtained, thereby improving frequency recovery control after grid disturbance.

[0046] This invention is based on power system flow calculation results and unit and load models and their parameters. Combining the fast frequency regulation response of energy storage, it adjusts the wind turbine speed to provide fast frequency regulation power based on the inherent frequency regulation characteristics of wind turbines. Then, based on model predictive control, it coordinates the output of "source-grid-storage" by collecting power system status, thereby improving the frequency recovery characteristics after grid disturbances. Attached Figure Description

[0047] Appendix Figure 1 This is a graph showing the recovery of the system frequency in Example 11.

[0048] Appendix Figure 2 This is a graph showing the energy storage output in Example 11.

[0049] Appendix Figure 3 This is a graph showing the power output of the fan in Example 11. Detailed Implementation

[0050] This invention is not limited to the following embodiments, and specific implementation methods can be determined according to the technical solutions and actual conditions of this invention. Unless otherwise specified, all chemical reagents and chemicals mentioned in this invention are well-known and commonly used chemical reagents and chemicals in the prior art; unless otherwise specified, all percentages in this invention are mass percentages; unless otherwise specified, all solutions in this invention are aqueous solutions with water as the solvent, for example, hydrochloric acid solution is an aqueous solution of hydrochloric acid; room temperature in this invention generally refers to a temperature between 15°C and 25°C, generally defined as 25°C.

[0051] The present invention will be further described below with reference to embodiments:

[0052] Example 1: The multi-source coordinated control method for improving frequency recovery characteristics after power grid disturbances is carried out according to the following steps:

[0053] S1, acquire model parameter data of power system units and loads;

[0054] S2, build a unified frequency model that includes all generating units, loads and energy storage;

[0055] S3, based on model predictive control, collects information on system frequency deviation and power system status;

[0056] S4. Establish a multi-source coordinated control model to improve the frequency recovery characteristics of the power grid;

[0057] S5 solves the multi-source coordinated control model to obtain the output and shutdown timing of energy storage and wind turbine rapid frequency regulation.

[0058] Example 2: As an optimization of the above example, in step S1, the model parameter data includes model parameters of various types of units, load regulation coefficients, and installed capacity of energy storage.

[0059] Example 3: As an optimization of the above example, in step S2, the unified frequency model ignores the system topology and power flow, and only considers the governor-prime mover model of the unit and the inherent frequency characteristics of the system, ultimately unifying the entire system to a single frequency; based on the unified frequency model, the corresponding functional relationship between the power generation side and the power consumption side and the power system frequency is established, and its corresponding functional relationship expression is:

[0060]

[0061] In the formula, Δf is the system frequency deviation after a large disturbance, and M... eq For system inertia, determined by the inertial characteristics of the entire system unit, D eq ΔP is the load adjustment coefficient. G For the change in total unit output, ΔP L For load output change, ΔP bess For the change in energy storage output, ΔP wind Indicates the output power of the fan via rapid frequency adjustment, P dis This is the power deviation caused by a large disturbance.

[0062] Example 4: As an optimization of the above embodiment, in step S2, based on the wind turbine model in the unified frequency model, the slope of the linearized wind turbine's rapid frequency regulation output is calculated according to the initial wind turbine speed, enabling it to have rapid frequency regulation capability by changing the speed; the expression for the wind turbine's rapid frequency regulation is:

[0063] ΔP wind (Δω)=m0·Δω Equation 2

[0064] In the formula, Δω represents the change in fan speed, and m0 represents the linearization slope.

[0065] Example 5: As an optimization of the above example, in step S3, the state matrix and output variable matrix of the model predictive control are as follows:

[0066] x(k)=[ΔP G (k),ΔP bess (k),Δω(k),ΔP wind (k),S(k),Δf(k)] T Formula 3

[0067] y(k)=[ΔP G (k),ΔP bess (k),ΔP wind (k),S(k),Δf(k)] TFormula 4

[0068] In the formula, ΔP G For the change in total unit output, ΔP bess For the change in energy storage output, Δω represents the change in wind turbine speed, and ΔP represents the change in energy storage output. wind Let S be the change in wind turbine output, S be the SOC of energy storage, and Δf be the system frequency deviation.

[0069] Example 6: As an optimization of the above examples, the multi-source coordinated control model introduces the energy storage system's state of charge constraint, generator output upper and lower limit constraint, wind turbine speed regulation constraint, and frequency deviation constraint as safety constraints.

[0070] Example 7: As an optimization of the above examples, the multi-source coordinated control model uses the overall fluctuation of the system frequency and the minimum energy storage capacity within the moving time window as the objective function; the expression of the objective function is:

[0071]

[0072] In the formula, Δf(k+i|k) and P bess (k+i|k) represent the predicted values ​​of the system frequency deviation and energy storage power at the current sampling time k to time k+i, respectively. m For the prediction time domain, α and β are weighting coefficients.

[0073] Example 8: As an optimization of the above example, the calculation equations for the weighting factors α and β of the objective function of the multi-source coordinated control model are as follows:

[0074]

[0075] β = 1 - α (Equation 7)

[0076] In the formula, Δf nl The system frequency deviation Δf is the frequency deviation when no wind storage participates in frequency regulation. UFLS The maximum permissible frequency deviation is represented by C, which is a reference coefficient for the system frequency deviation without energy storage.

[0077] Example 9: As an optimization of the above embodiment, in step S4, the state of charge constraint of the energy storage system is introduced into the multi-source coordinated control model. The expression of the state of charge constraint of the energy storage system is:

[0078] P bess,min ≤P bess (k+i|k)≤P bess,max Formula 8

[0079] S min ≤S(k+i|k)≤S max Formula 9

[0080] In the formula, Pbess,max P bess,min S represents the maximum and minimum discharge power of the stored energy; S(k+i|k) is the predicted value of the stored energy SOC at the current sampling time k to the time k+i; S min S max These are the upper and lower limits of the energy storage SOC state, respectively;

[0081] The frequency deviation constraint is introduced into the multi-source coordinated control model, and the expression for the frequency deviation constraint is as follows:

[0082] Δf(k+i|k)≥Δf max Formula 10

[0083] In the formula, Δf(k+i|k) is the predicted value of the system frequency at the current sampling time k to the system frequency at time k+i; Δf max This is the maximum frequency deviation allowed by the power grid;

[0084] The active power output constraint of traditional generator sets is introduced into the multi-source coordinated control model. The expression for the active power output constraint of traditional generator sets is as follows:

[0085] P G,min ≤P G (k+i|k)≤P G,max Formula 11

[0086] In the formula, P G (k+i|k) represents the predicted power of the traditional unit at the current sampling time k to the time k+i, P G,min P G,max These are the minimum and maximum power ratings for traditional generator sets;

[0087] The wind turbine speed regulation constraint is introduced into the multi-source coordinated control model, and the constraint expression is as follows:

[0088] -(ω0-ω min )≤Δω(k+i|k)≤(ω max -ω0) Equation 12

[0089] In the formula, Δω(k+i|k) is the predicted value of the fan speed at the current sampling time k to the time k+i, ω0 is the initial fan speed, and ω min ω max The minimum and maximum permissible speeds.

[0090] Example 10: As an optimization of the above example, in step S5, the established multi-source coordinated control model collects power system state variables based on the model predictive control method. By solving the multi-source coordinated control module, the output status and exit timing of wind-storage joint fast frequency regulation are obtained, thereby improving the frequency recovery control after grid disturbance.

[0091] Example 11: Taking a provincial power grid in China as an example, the method of the present invention is specifically illustrated:

[0092] First, the typical operating mode file of the power system is read. Based on the power flow calculation results, the initial state of the power system is obtained. Based on the models and parameters of generating units and loads, a unified frequency model of the power grid including energy storage is established. Based on model predictive control, the system state of the established unified frequency model is collected to establish a wind-storage control module to improve the frequency recovery characteristics after disturbances. According to the historical fault of a certain provincial power grid, a fault of large-scale disconnection of new energy sources was selected, resulting in a power deficit of 7000MW. The active power output and disconnection timing of the wind-storage system are determined through the control module. Figure 1 The system frequency recovery under the proposed strategy is demonstrated. Figure 1 It can be seen that because the proposed strategy takes into account the wind and energy storage output during the frequency recovery phase, the frequency recovery performance is better than that of the control strategy. Figure 2 and Figure 3 The output of energy storage and wind turbines was demonstrated. Figure 2 and Figure 3 As can be seen, under the proposed control strategy, the initial power supplied by the combined wind and energy storage is relatively small. As the wind turbines return to MPPT mode, the energy storage provides a larger power output to prevent a secondary frequency drop. Then, as the conventional units gradually respond to the primary frequency regulation, the active power output of the energy storage begins to decrease appropriately after about 25 seconds. However, since the proposed strategy takes into account the system frequency recovery, the energy storage output remains relatively large.

[0093] In summary, this invention provides a multi-source coordinated control method to improve the frequency recovery characteristics after power grid disturbances. Based on the principle of model predictive control, this invention collects power system status data and coordinates the output of power sources, grid, and energy storage, thereby improving the frequency recovery characteristics after power grid disturbances and preventing the power grid frequency from deviating from its rated value for extended periods.

[0094] The above technical features constitute the embodiments of the present invention, which have strong adaptability and implementation effect. Unnecessary technical features can be added or removed according to actual needs to meet the needs of different situations.

Claims

1. A multi-source coordinated control method for improving frequency recovery characteristics after power grid disturbances, characterized in that... Follow these steps: S1, acquire model parameter data of power system units and loads; S2, build a unified frequency model that includes all generating units, loads and energy storage; S3, based on model predictive control, collects information on system frequency deviation and power system status; S4. Establish a multi-source coordinated control model to improve the frequency recovery characteristics of the power grid; S5 solves the multi-source coordinated control model to obtain the output and shutdown timing of energy storage and wind turbine rapid frequency regulation.

2. The multi-source coordinated control method for improving frequency recovery characteristics after power grid disturbances according to claim 1, characterized in that... In step S1, the model parameter data includes model parameters of various types of generating units, load regulation coefficients, and installed capacity of energy storage.

3. The multi-source coordinated control method for improving frequency recovery characteristics after power grid disturbances according to claim 1 or 2, characterized in that... In step S2, the unified frequency model ignores system topology and power flow, considering only the governor-prime mover model of the generator units and the inherent frequency characteristics of the system, ultimately unifying the entire system to a single frequency. Based on the unified frequency model, the corresponding functional relationship between power generation and power consumption on the generation and consumption sides and the power system frequency is established, and its corresponding functional relationship expression is as follows: In the formula, Δf is the system frequency deviation after a large disturbance, and M... eq For system inertia, determined by the inertial characteristics of the entire system unit, D eq ΔP is the load adjustment coefficient. G For the change in total unit output, ΔP L For load output change, ΔP bess For the change in energy storage output, ΔP wind Indicates the output power of the fan via rapid frequency regulation, P dis This is the power deviation caused by a large disturbance.

4. The multi-source coordinated control method for improving frequency recovery characteristics after power grid disturbances according to any one of claims 1 to 3, characterized in that... In step S2, based on the wind turbine model in the unified frequency model, the slope of the linearized wind turbine's rapid frequency regulation output is calculated according to the initial wind turbine speed, enabling it to achieve rapid frequency regulation capability by changing the speed; the expression for the wind turbine's rapid frequency regulation is: ΔP wind (Dω)=m0·Dω Equation 2 In the formula, Δω represents the change in fan speed, and m0 represents the linearization slope.

5. The multi-source coordinated control method for improving frequency recovery characteristics after power grid disturbances according to any one of claims 1 to 4, characterized in that... In step S3, the state matrix and output variable matrix of the model predictive control are as follows: x(k) = [ΔP G (k), ΔP bess (k), Δω(k), ΔP wind (k), S(k), Δf(k)] T Equation 3 y(k) = [ΔP G (k), ΔP bess (k), ΔP wind (k), S(k), Δf(k)] T Equation 4 In the formula, ΔP G For the change in total unit output, ΔP bess For the change in energy storage output, Δω represents the change in wind turbine speed, and ΔP represents the change in energy storage output. wind Let S be the change in wind turbine output, S be the SOC of energy storage, and Δf be the system frequency deviation.

6. The multi-source coordinated control method for improving frequency recovery characteristics after power grid disturbances according to any one of claims 1 to 5, characterized in that... The multi-source coordinated control model introduces the energy storage system's state of charge constraint, generator output upper and lower limit constraint, wind turbine speed regulation constraint, and frequency deviation constraint as safety constraints.

7. The multi-source coordinated control method for improving frequency recovery characteristics after power grid disturbances according to any one of claims 1 to 6, characterized in that... The multi-source coordinated control model takes the overall fluctuation of the system frequency and the minimum energy storage capacity within the moving time window as the objective function; the expression of the objective function is: In the formula, Δf(k+i|k) and P bess (k+i|k) represent the predicted values ​​of the system frequency deviation and energy storage power at the current sampling time k to time k+i, respectively. m For the prediction time domain, α and β are weighting coefficients.

8. The multi-source coordinated control method for improving frequency recovery characteristics after power grid disturbances according to claim 7, characterized in that... The equations for calculating the weighting factors α and β of the objective function in the multi-source coordinated control model are as follows: β = 1 - α Equation 7 In the formula, Δf nl The system frequency deviation Δf is the frequency deviation when no wind storage participates in frequency regulation. UFLS The maximum permissible frequency deviation is represented by C, which is a reference coefficient for the system frequency deviation without energy storage.

9. The multi-source coordinated control method for improving frequency recovery characteristics after power grid disturbances according to claim 7 or 8, characterized in that... In step S4, the state of charge (SOC) constraint of the energy storage system is introduced into the multi-source coordinated control model. The expression for the SOC constraint of the energy storage system is: P bess,min ≤P bess (k+i|k)≤P bess,max Formula 8 S min ≤S(k+i|k)≤S max Formula 9 In the formula, P bess,max P bess,min S represents the maximum and minimum discharge power of the stored energy; S(k+i|k) is the predicted value of the stored energy SOC at the current sampling time k to the time k+i; S min S max These are the upper and lower limits of the energy storage SOC state, respectively; The frequency deviation constraint is introduced into the multi-source coordinated control model, and the expression for the frequency deviation constraint is as follows: Δf(k + i|k) ≥ Δf max Equation 10 In the formula, Δf(k+i|k) is the predicted value of the system frequency at the current sampling time k to the system frequency at time k+i; Δf max This is the maximum frequency deviation allowed by the power grid; The active power output constraint of traditional generator sets is introduced into the multi-source coordinated control model. The expression for the active power output constraint of traditional generator sets is as follows: P G,min ≤P G (k+i|k)≤P G,max Formula 11 In the formula, P G (k+i|k) represents the predicted power of the traditional unit at the current sampling time k to the time k+i, P G,min P G,max These are the minimum and maximum power ratings for traditional generator sets; The wind turbine speed regulation constraint is introduced into the multi-source coordinated control model, and the constraint expression is as follows: -(ω0-ω min )≤Δω(k+i|k)≤(ω max -ω0) formula 12 In the formula, Δω(k+i|k) is the predicted value of the fan speed at the current sampling time k to the time k+i, ω0 is the initial fan speed, and ω min ω max The minimum and maximum permissible speeds.

10. A multi-source coordinated control method for improving frequency recovery characteristics after power grid disturbances according to claim 1, characterized in that... In step S5, the established multi-source coordinated control model collects power system state variables based on the model predictive control method. By solving the multi-source coordinated control module, the output status and exit timing of wind-storage joint fast frequency regulation are obtained, thereby improving frequency recovery control after grid disturbance.

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