Interconnected power grid frequency control method and system based on disturbance compensation

Abstract

The application discloses an interconnected power grid frequency control method and system based on disturbance compensation, and belongs to the technical field of power system automation. The method comprises the following steps: compensating and calculating the load connected to the interconnected power grid by using a nonlinear disturbance observer, and estimating a load disturbance variable; the load disturbance variable is brought into a control sequence, the output of a model predictive controller is compensated, and a control variable at each moment is calculated as an input variable of the interconnected power grid. The nonlinear disturbance compensator is set to bring the disturbance variable into the control sequence, and the control variable more suitable for the disturbance is calculated at each moment, so that the frequency control effect is better.

Description

Technical Field

[0001] This invention relates to the field of power system automation technology, specifically to a frequency control method and system for interconnected power grids based on disturbance compensation. Background Technology

[0002] Automatic Generation Control (AGC) falls under the category of secondary frequency regulation in power systems and is a crucial component of the Energy Management System (EMS). AGC research can be broadly categorized into two aspects: Load Frequency Control (LFC) and Economic Dispatch Control (EDC). In addition, AGC must ensure that the exchange power on adjacent tie lines remains at planned levels. When a large-scale load is connected to the power system, fluctuations occur in grid frequency and tie line exchange power. AGC units rapidly adjust these two grid indicators to their rated values ​​by changing their own output.

[0003] Patent application CN104037772A discloses a control method that includes both regional ACE vector feedback control and system state feedback control, thus improving the dynamic performance of the system and reducing the power balance recovery time after grid disturbances. In the research of grid frequency control methods, Model Predictive Control (MPC) has been widely used in grid frequency control due to its ease of handling constraints and its ability to effectively combat environmental uncertainties and time delays.

[0004] The paper "Robust Distributed Model Predictive Load Frequency Control for Interconnected Power Systems" improves a parameter-adjustable robust predictive control algorithm to address load disturbances and uncertainties in interconnected power grids. Simulation results show that the proposed algorithm has strong robustness. The paper "Explicit MPC Based on the Galerkin Method for AGC Considering Volatile Generations" introduces an explicit model predictive controller (AGC) that considers fluctuations in generation to achieve the goal of responding to generation fluctuations without violating operational and safety constraints, ensuring good control performance. The paper "Robust Model Predictive Control of Gate-Controlled Series Capacitor for LFC of Power Systems" combines deterministic and uncertain MPC, demonstrating the robustness of the scheme in dealing with load uncertainty, wind power fluctuations, and parameter uncertainties.

[0005] Patent application CN 108631330 A discloses an Automatic Generation Control (AGC) method based on system structure compensation. Since the presence of distributed generation links complicates traditional AGC, this paper takes a photovoltaic (PV) power system as an example and studies how to eliminate the adverse effects on frequency control of AGC in a distributed generation system under uncertain power generation conditions. By adding a transfer function compensation link between the controller and the actuator, compensation is achieved for the controller, and the intermediate link parameters are optimized using a particle swarm optimization algorithm. The core is to set the PI controller's control frequency deviation to 0, and by introducing a series compensation link, adjust the system structure to reduce the frequency fluctuations caused by the uncertainty of the distributed generation system on AGC, thereby achieving stable control of the interconnected power grid AGC system. Its purpose is to reduce the frequency fluctuations caused by sudden changes in PV power output on AGC, while PV outputs active power.

[0006] The aforementioned literature and patents have improved the algorithm at different levels, enhancing its robustness in dealing with disturbances. However, power systems are relatively complex, and the timing and severity of disturbances are often difficult to predict. Directly assuming the magnitude of disturbances during research is obviously not realistic. Ignoring the magnitude of disturbances and directly using the controller for frequency control may lead to model mismatch, causing the frequency of the entire power system to deviate from the standard value, seriously affecting the safe and stable operation of the power system. Summary of the Invention

[0007] The technical problem to be solved by this invention is to reduce the impact of disturbance uncertainty on power systems.

[0008] The present invention solves the above-mentioned technical problems through the following technical means:

[0009] On the one hand, this invention proposes a frequency control method for interconnected power grids based on disturbance compensation, the method comprising:

[0010] The load disturbance variables are estimated by using a nonlinear disturbance observer to perform compensation calculations on the loads connected to the interconnected power grid.

[0011] The load disturbance variables are incorporated into the control sequence to compensate the output of the model predictive controller, and the control variables at each time step are calculated as the input variables of the interconnected power grid.

[0012] The formula for the control variable is expressed as follows:

[0013]

[0014] Among them, S u To control the unit coefficient response matrix from the input variable u to the output variable y, T y and T u Let R(k+1) be the weighted matrix, R(k+1) be the reference output sequence of the model predictive controller at time k+1, Δx(k) be the increment of the state variables of the interconnected power grid at time k, and y be the weighted matrix. c (k) represents the increment of the output variable of the interconnected power grid at time k. S is the estimated increment of the load disturbance variable at time k. x I and S w Let T be the corresponding coefficient matrix, and T denote the matrix transpose.

[0015] This invention addresses the impact of sudden disturbances on power systems by treating the loads connected to the interconnected grid as disturbance variables. It utilizes a nonlinear disturbance compensator as compensation in the model predictive controller, incorporating the disturbance variable into the control sequence. The invention calculates control variables more specifically tailored to the disturbance at each time step, using these variables as input variables to the interconnected grid, thus achieving control over the grid. Compared to traditional model predictive control algorithms that ignore the magnitude of disturbances and directly use the controller for frequency control, this invention calculates control variables taking the disturbance variable into account at each time step, resulting in a more accurate state sequence for the controlled object and thus superior frequency control performance.

[0016] Furthermore, the state-space equation of the interconnected power grid AGC system is:

[0017]

[0018] Where A, B, C, and R are the state matrix, input matrix, output matrix, and perturbation matrix, respectively; y i(k) represents the actual value of the output variable of each selected interconnected control area, x(k) represents the estimated value of the state variable at time k; Δu(k) represents the increment of the input variable of the interconnected power grid at time k, and w(k) represents the load disturbance variable at time k.

[0019] Furthermore, the state variable x, input variable u, output variable y, and load disturbance variable w of the interconnected power grid are respectively:

[0020] x=[Δf1 ΔP t1 ΔX g1 ΔP T Δf2 ΔP t2 ΔX g2 ] T

[0021] u=[ΔP r1 ΔP r2 ] T

[0022] y = [ACE1 ACE2 Δf1 Δf2 ΔP] T ] T

[0023] w=[ΔP L1 ΔP L2 ] T

[0024] Wherein, Δf1 and Δf2 are the system frequency deviations of the two regions constituting the interconnected power grid, and ΔP t1 and ΔP t2 Let ΔX be the offset of generator output power between the two regions. g1 and ΔX g2 ΔP represents the position increment of the speed controller in the two regions. T For the switching power deviation of the tie line, ΔP r1 and ΔP r2 ACE1 and ACE2 represent the ACG regulation power of the two regions, respectively, and ΔP represents the control deviation between the two regions. L1 and ΔP L2 The load disturbance amounts for the two regions.

[0025] Furthermore, the nonlinear perturbation observer is represented as:

[0026]

[0027]

[0028] Among them, z d Let λ(x) be a variable inside the observer, and z be a function within the observer. dLet l(x) be the variable inside the observer, and l(x) be the gain, satisfying... For z d The first derivative of , x is the state variable of the interconnected power grid, u is the input variable of the interconnected power grid, A is the state matrix, and B is the input matrix. The estimated load disturbance variable.

[0029] Furthermore, this invention proposes an interconnected power grid frequency control system based on disturbance compensation. The system includes: a model predictive controller, a nonlinear disturbance observer, and an interconnected power grid. The output of the interconnected power grid is connected to the output of the model predictive controller. The state variables, input variables, and load damping coefficient of the interconnected power grid serve as inputs to the nonlinear disturbance observer. The output of the model predictive controller serves as the input variable of the interconnected power grid. The output of the nonlinear disturbance observer serves as compensation for the output variable of the model predictive controller. The load connected to the interconnected power grid serves as the disturbance variable. Wherein:

[0030] The nonlinear disturbance observer is used to perform compensation calculations for loads connected in the interconnected power grid and to estimate load disturbance variables;

[0031] The model predictive controller is used to incorporate the load disturbance variable into the control sequence, compensate the output of the model predictive controller, and calculate the control variable at each time moment as the input variable of the interconnected power grid.

[0032] The formula for the control variable is expressed as follows:

[0033]

[0034] Among them, S u To control the unit coefficient response matrix from the input variable u to the output variable y, T y and T u Let R(k+1) be the weighted matrix, R(k+1) be the reference output sequence of the model predictive controller at time k+1, Δx(k) be the increment of the state variables of the interconnected power grid at time k, and y be the weighted matrix. c (k) represents the increment of the output variable of the interconnected power grid at time k. S is the estimated increment of the load disturbance variable at time k. x I and S w Let T be the corresponding coefficient matrix, and T denote the matrix transpose.

[0035] Furthermore, the state-space equation of the interconnected power grid AGC system is:

[0036]

[0037] Where A, B, C, and R are the state matrix, input matrix, output matrix, and perturbation matrix, respectively; y i (k) represents the actual value of the output variable of each selected interconnected control area, x(k) represents the estimated value of the state variable at time k; Δu(k) represents the increment of the input variable of the interconnected power grid at time k, and w(k) represents the load disturbance variable at time k.

[0038] Furthermore, the state variable x, input variable u, output variable y, and load disturbance variable w of the interconnected power grid are respectively:

[0039] x=[Δf1 ΔP t1 ΔX g1 ΔP T Δf2 ΔP t2 ΔX g2 ] T

[0040] u=[ΔP r1 ΔP r2 ] T

[0041] y = [ACE1 ACE2 Δf1 Δf2 ΔP] T ] T

[0042] w=[ΔP L1 ΔP L2 ] T

[0043] Wherein, Δf1 and Δf2 are the system frequency deviations of the two regions constituting the interconnected power grid, and ΔP t1 and ΔP t2 Let ΔX be the offset of generator output power between the two regions. g1 and ΔX g2 ΔP represents the position increment of the speed controller in the two regions. T For the switching power deviation of the tie line, ΔP r1 and ΔP r2 ACE1 and ACE2 represent the ACG regulation power of the two regions, respectively, and ΔP represents the control deviation between the two regions. L1 and ΔP L2 The load disturbance amounts for the two regions.

[0044] Furthermore, the nonlinear perturbation observer is represented as:

[0045]

[0046]

[0047] Among them, z dLet λ(x) be a variable inside the observer, and z be a function within the observer. d Let l(x) be the variable inside the observer, and l(x) be the gain, satisfying... For z d The first derivative of , x is the state variable of the interconnected power grid, u is the input variable of the interconnected power grid, A is the state matrix, and B is the input matrix. The estimated load disturbance variable.

[0048] The advantages of this invention are:

[0049] (1) To address the impact of sudden disturbances on the power system, this invention treats the loads connected to the interconnected grid as disturbance variables and utilizes a nonlinear disturbance compensator as compensation for the model predictive controller. The disturbance variables are incorporated into the control sequence, and control variables more specifically tailored to the disturbance are calculated at each moment as input variables to the interconnected grid, thus achieving control over the interconnected grid. Compared to traditional model predictive control algorithms that ignore the magnitude of disturbances and directly use the controller for frequency control, this invention calculates control variables taking the disturbance variables into account at each moment, resulting in a more accurate state sequence for the controlled object and thus achieving better frequency control performance.

[0050] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0051] Figure 1 This is a flowchart illustrating the frequency control method for interconnected power grids based on disturbance compensation in this invention.

[0052] Figure 2 This is a schematic diagram of the dynamic model of the interconnected power grid in two regions in this invention;

[0053] Figure 3 This is a block diagram of the disturbance compensation control principle in this invention;

[0054] Figure 4 This is a schematic diagram illustrating the changes in input variables when no disturbance compensation is set in this invention;

[0055] Figure 5 This is a schematic diagram of the input variables when setting disturbance compensation in this invention;

[0056] Figure 6 This is a schematic diagram comparing the regional control error ACE in this invention;

[0057] Figure 7 This is a schematic diagram comparing the frequency control deviation Δf in this invention;

[0058] Figure 8The interconnection power deviation ΔP in this invention T Comparison diagram. Detailed Implementation

[0059] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, 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.

[0060] Reference Figure 1 This invention proposes a frequency control method for interconnected power grids based on disturbance compensation, the method comprising the following steps:

[0061] S10. Use a nonlinear disturbance observer to perform compensation calculations on the loads connected to the interconnected power grid and estimate the load disturbance variables;

[0062] S20. The load disturbance variable is incorporated into the control sequence, the output of the model predictive controller is compensated, and the control variable at each moment is calculated as the input variable of the interconnected power grid.

[0063] The formula for the control variable is expressed as follows:

[0064]

[0065] Among them, S u To control the unit coefficient response matrix from the input variable u to the output variable y, T y and T u Let R(k+1) be the weighted matrix, R(k+1) be the reference output sequence of the model predictive controller at time k+1, Δx(k) be the increment of the state variables of the interconnected power grid at time k, and y be the weighted matrix. c (k) represents the increment of the output variable of the interconnected power grid at time k. S is the estimated increment of the load disturbance variable at time k. x I and S w Let T be the corresponding coefficient matrix, and T denote the matrix transpose.

[0066] It should be noted that, to address the impact of sudden grid connection disturbances on the power system, this embodiment treats the load connected to the interconnected grid as a disturbance variable. A nonlinear disturbance observer is used to incorporate this disturbance variable into the control sequence, and at each time step, a more disturbance-specific control variable is calculated as the input variable for the interconnected grid. Furthermore, by using all original parameters as the system state and estimating the disturbance based on this state, the generated sequence controls frequency fluctuations, resulting in better frequency control performance.

[0067] It should be understood that the interconnected power grid frequency control scheme provided in this embodiment differs from the related technical solutions mentioned in the background section. Taking the scheme disclosed in invention patent application CN108631330A as an example, it addresses the impact of sudden changes in photovoltaic power output on the power system. The photovoltaic output active power is compensated by adding a transfer function compensation link between the controller and the actuator. The intermediate link parameters are optimized using a particle swarm optimization algorithm, without estimating the magnitude of the photovoltaic output, focusing only on the frequency control effect. In contrast, this embodiment treats the interconnected power grid load as a disturbance variable. The disturbance (load) absorbs active power. By estimating the magnitude of the disturbance variable and incorporating it into the control sequence to control the frequency deviation, the impact of sudden disturbances on the power system is addressed.

[0068] In one embodiment, this embodiment first establishes as shown in the appendix. Figure 2 The dynamic model of the two-region interconnected power grid shown is as follows: Figure 2 In this context, Δf represents the system's frequency deviation; ΔP t ΔX represents the generator output power offset. g For governor position increment; ΔP I-II For the active power deviation of the tie line; ΔP r AGC adjustment power; ACE is the zone control deviation; ΔP L R is the load disturbance; B1 and B2 are the frequency offset factors; D is the load damping coefficient; M is the unit's moment of inertia; T is the load disturbance. t T is the time constant of the thermal power unit; g T is the turbine time constant; I-II This is the power synchronization coefficient for the tie line.

[0069] The state-space equation of the interconnected power grid AGC system is:

[0070]

[0071] Where A, B, C, and R are the state matrix, input matrix, output matrix, and perturbation matrix, respectively; y i (k) represents the actual value of the output variable of each selected interconnected control area, x(k) represents the estimated value of the state variable at time k; Δu(k) represents the increment of the input variable of the interconnected power grid at time k, and w(k) represents the load disturbance variable at time k.

[0072] The state variable x, input variable u, output variable y, and load disturbance variable w of the interconnected power grid are selected as follows:

[0073] x=[Δf1 ΔP t1 ΔX g1 ΔPT Δf2 ΔP t2 ΔX g2 ] T

[0074] u=[ΔP r1 ΔP r2 ] T

[0075] y = [ACE1 ACE2 Δf1 Δf2 ΔP] T ] T

[0076] w=[ΔP L1 ΔP L2 ] T

[0077] Wherein, Δf1 and Δf2 are the system frequency deviations of the two regions constituting the interconnected power grid, and ΔP t1 and ΔP t2 Let ΔX be the offset of generator output power between the two regions. g1 and ΔX g2 ΔP represents the position increment of the speed controller in the two regions. T For the switching power deviation of the tie line, ΔP r1 and ΔP r2 ACE1 and ACE2 represent the ACG regulation power of the two regions, respectively, and ΔP represents the control deviation between the two regions. L1 and ΔP L2 The load disturbance amounts for the two regions.

[0078] When the objective function takes the partial derivative with respect to the increment of the input variable At time k, the optimal control sequence considering load disturbance can be obtained as follows:

[0079] ΔU * (k)=(S u T T y T T y S u +T u T T u ) -1 S u T T y T T y [R(k+1)-S x Δx(k)-Iy c (k)-S w Δw(k)]

[0080] In the formula: Su To control the unit coefficient response matrix from input u to output y, T y and T u Let R(k+1) be the weighting matrix, R(k+1) be the reference output sequence at time k+1, Δx(k) be the state variable increment at time k, and y be the weighting matrix. c (k) represents the increment of the output variable of the interconnected power grid at time k, Δw(k) represents the increase of the disturbance variable at time k, and S x I and S w This is the corresponding coefficient matrix.

[0081] In one embodiment, specifically, the principle of using a nonlinear interference controller to compensate for interference terms is as follows: Figure 3 As shown, Figure 3 In the diagram, x, u, y, and d represent the state variables, input variables, output variables, and disturbance variables of the power grid, respectively; y r Here, e is the reference value for the output variable, and u is the deviation of the output variable. p and u c These represent the control variables calculated by the model predictive controller and the compensation control variables calculated by the nonlinear disturbance compensator, respectively. D is the load damping coefficient, and the research object is... Figure 2 The disturbance considered for compensation in the two interconnected power grids shown is w = [ΔP]. L1 ΔP L2 ] T The possibility of continuous changes in disturbances in a power grid is usually extremely small, therefore it is considered that... For a two-region interconnected system, the formula for the nonlinear disturbance observer is expressed as follows:

[0082]

[0083]

[0084] Among them, z d Let λ(x) be a variable inside the observer, and z be a function within the observer. d Let l(x) be the variable inside the observer, and l(x) be the gain, satisfying... For z d The first derivative of , x is the state variable of the interconnected power grid, u is the input variable of the interconnected power grid, A is the state matrix, and B is the input matrix. The estimated load disturbance variable.

[0085] The estimated load disturbance variable Substituting the above optimal control sequence, we obtain the perturbation-estimated control variables in step S20 above.

[0086] Currently, when using the MPC algorithm to adjust frequency, the impact of disturbances is usually ignored. The control effect is ensured by continuously adjusting the magnitude of Δu(k) in each feedback correction stage. The control scheme assumes w(k) = [0 0], and the impact of disturbances is not reflected in the control variables. However, due to the randomness of the occurrence time and level of disturbances, their magnitude cannot be directly collected. As can be seen from the state-space equation of the two-region interconnected power grid AGC system, the accurate system state x(k+1) cannot be obtained when predicting the output, thus making output prediction impossible. If disturbances are directly ignored, a large disturbance w(k) will severely affect the controller's performance.

[0087] This embodiment incorporates disturbance variables into the control sequence by setting a nonlinear disturbance compensator, and calculates more targeted control variables for the disturbance at each time step. All original parameters are system states; disturbances are estimated based on these states, and the generated sequence is applied to the controlled object to control frequency fluctuations, resulting in better control performance.

[0088] In addition, refer to Figure 3 This invention also proposes an interconnected power grid frequency control system based on disturbance compensation. The system includes a model predictive controller, a nonlinear disturbance observer, and an interconnected power grid. The output of the interconnected power grid is connected to the output of the model predictive controller. The state variables, input variables, and load damping coefficient of the interconnected power grid serve as the inputs of the nonlinear disturbance observer. The output of the model predictive controller serves as the input variable of the interconnected power grid. The output of the nonlinear disturbance observer serves as compensation for the output variable of the model predictive controller. The load connected to the interconnected power grid serves as the disturbance variable. Wherein:

[0089] The nonlinear disturbance observer is used to perform compensation calculations for loads connected in the interconnected power grid and to estimate load disturbance variables;

[0090] The model predictive controller is used to incorporate the load disturbance variable into the control sequence, compensate the output of the model predictive controller, and calculate the control variable at each time moment as the input variable of the interconnected power grid.

[0091] The formula for the control variable is expressed as follows:

[0092]

[0093] Among them, S u To control the unit coefficient response matrix from the input variable u to the output variable y, T y and T u Let R(k+1) be the weighted matrix, R(k+1) be the reference output sequence of the model predictive controller at time k+1, Δx(k) be the increment of the state variables of the interconnected power grid at time k, and y be the weighted matrix. c(k) represents the increment of the output variable of the interconnected power grid at time k. S is the estimated increment of the load disturbance variable at time k. x I and S w Let T be the corresponding coefficient matrix, and T denote the matrix transpose.

[0094] In one embodiment, the state-space equation of the interconnected power grid AGC system is:

[0095]

[0096] Where A, B, C, and R are the state matrix, input matrix, output matrix, and perturbation matrix, respectively; y i (k) represents the actual value of the output variable of each selected interconnected control area, x(k) represents the estimated value of the state variable at time k; Δu(k) represents the increment of the input variable of the interconnected power grid at time k, and w(k) represents the load disturbance variable at time k.

[0097] In one embodiment, the state variable x, input variable u, output variable y, and load disturbance variable w of the interconnected power grid are respectively:

[0098] x=[Δf1 ΔP t1 ΔX g1 ΔP T Δf2 ΔP t2 ΔX g2 ] T

[0099] u=[ΔP r1 ΔP r2 ] T

[0100] y = [ACE1 ACE2 Δf1 Δf2 ΔP] T ] T

[0101] w=[ΔP L1 ΔP L2 ] T

[0102] Wherein, Δf1 and Δf2 are the system frequency deviations of the two regions constituting the interconnected power grid, and ΔP t1 and ΔP t2 Let ΔX be the offset of generator output power between the two regions. g1 and ΔX g2 ΔP represents the position increment of the speed controller in the two regions. T For the switching power deviation of the tie line, ΔP r1 and ΔP r2ACE1 and ACE2 represent the ACG regulation power of the two regions, respectively, and ΔP represents the control deviation between the two regions. L1 and ΔP L2 The load disturbance amounts for the two regions.

[0103] In one embodiment, the nonlinear perturbation observer is represented as:

[0104]

[0105]

[0106] Among them, z d Let λ(x) be a variable inside the observer, and z be a function within the observer. d Let l(x) be the variable inside the observer, and l(x) be the gain, satisfying... For z d The first derivative of , x is the state variable of the interconnected power grid, u is the input variable of the interconnected power grid, A is the state matrix, and B is the input matrix. The estimated load disturbance variable.

[0107] This invention addresses the impact of sudden disturbances on power systems by treating the loads connected to the interconnected grid as disturbance variables. It utilizes a nonlinear disturbance compensator as compensation in the model predictive controller, incorporating the disturbance variable into the control sequence. The invention calculates control variables more specifically tailored to the disturbance at each time step, using these variables as input variables to the interconnected grid, thus achieving control over the grid. Compared to traditional model predictive control algorithms that ignore the magnitude of disturbances and directly use the controller for frequency control, this invention calculates control variables taking the disturbance variable into account at each time step, resulting in a more accurate state sequence for the controlled object and thus superior frequency control performance.

[0108] It should be noted that other embodiments or implementation methods of the interconnected power grid frequency control system based on disturbance compensation described in this invention can refer to the above-described method embodiments, and will not be repeated here.

[0109] To verify the effectiveness of the method proposed in this patent, a system was built. Figure 2 The dynamic model of the two interconnected power grids is shown in Table 1. Specific parameters are detailed in Table 1, including the tie-line power synchronization coefficient T. p The value is 0.867. In the MPC controller, the prediction time domain is set to P=3, the control time domain is set to M=1, the sampling time interval is Δt=0.1s, the prediction variable error weight is Q=100I (I is the identity matrix), the control variable sequence weight is R=I, and the simulation time is 60s.

[0110] Table 1 Dynamic characteristic parameters of the interconnected AGC system

[0111]

[0112]

[0113] To demonstrate the effectiveness of the proposed control strategy, this simulation considers a case of a continuous large disturbance, specifically a disturbance ΔP occurring at 10 s. L1 The initial disturbance was 0.2 pu. At 15 seconds, an additional 0.3 pu was added to the model, resulting in a total load of 0.5 pu after 15 seconds. The control sequence generated using this scheme is shown below, with and without disturbance estimation as follows: Figure 4 and Figure 5 As shown.

[0114] analyze Figure 4 and Figure 5 The results show that when the disturbance level is large and continuous, the changes in the input variable differ significantly with and without disturbance compensation. Without disturbance compensation, the input variable begins to change at 10.1 s, while with disturbance compensation, it begins to change at 10.0 s. This indicates that the control variable lags behind the disturbance variable, and disturbance estimation can eliminate the influence of this inertial link. Furthermore, due to the presence of disturbance estimation, Figure 5 The magnitudes of the control variables are maintained at a high level. Therefore, when the input variables for disturbance compensation are applied to the turbine, the effects of the disturbance can be quickly adjusted, avoiding prolonged occurrence of frequency errors and tie-line power exchange errors.

[0115] Comparison of control effects Figures 6 to 8 As shown, neither frequency control strategy exhibits overshoot when the disturbance level is large. When the disturbance variable in the optimal control sequence at time k is set to [0 0] by default, the model predictive control, with its feedback correction mechanism, can essentially guarantee the control effect. Furthermore, the state sequence of the controlled object at each time k+1 after disturbance estimation is more accurate, resulting in better control performance. This demonstrates the effectiveness and rationality of the disturbance-compensated interconnected power grid frequency control strategy proposed in this embodiment when addressing interconnected power grid frequency control.

[0116] This embodiment incorporates the disturbance variable into the control sequence by setting a nonlinear disturbance compensator, and calculates a more disturbance-specific control variable as the input variable for the interconnected power grid at each time step. The effectiveness of the proposed control strategy is verified through simulation. A continuous large disturbance is considered and simulated on a two-region interconnected power grid. The results demonstrate that the method proposed in this embodiment has better frequency control performance compared to methods that do not incorporate the disturbance variable into the control sequence.

[0117] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," 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, the 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.

[0118] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0119] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A frequency control method for interconnected power grids based on disturbance compensation, characterized in that, The method includes: The load disturbance variables are estimated by using a nonlinear disturbance observer to perform compensation calculations on the loads connected to the interconnected power grid. The load disturbance variables are incorporated into the control sequence to compensate the output of the model predictive controller, and the control variables at each time step are calculated as the input variables of the interconnected power grid. The formula for the control variable is expressed as follows: in, To control the input variables u To output variables y The unit coefficient response matrix, and For weighted matrices, for k The model predicts the controller reference output sequence at time +1. for k The increment of the state variables of the interconnected power grid at time t, for k The increment of the output variable of the interconnected power grid at time t, For estimation k The increment of the load disturbance variable at time t. , and Let T be the corresponding coefficient matrix, and T denote the matrix transpose. The state-space equation of the interconnected power grid AGC system is: in, , , , These are the state matrix, input matrix, output matrix, and disturbance matrix, respectively. The actual values ​​of the output variables for each selected interconnected control region. for k State variable estimates at time t; for k The increment of the input variables of the interconnected power grid at time t, for k The load disturbance variable at the specified time; The nonlinear perturbation observer is represented as: in, For variables inside the observer, For functions in the observer, For gain, satisfying , for The first derivative, x Let these be the state variables of the interconnected power grid. u For the input variables of the interconnected power grid, A The state matrix, B For the input matrix, The estimated load disturbance variable.

2. The frequency control method for interconnected power grids based on disturbance compensation as described in claim 1, characterized in that, The state variables of the interconnected power grid x Input variables u Output variables y and load disturbance variables w They are respectively: in, and The system frequency deviation between the two regions constituting the interconnected power grid, and This represents the offset of generator output power between the two regions. and The position increment of the speed controller in the two regions. For the offset of the switching power of the tie line, and Adjust the ACG power for the two regions. and The control deviation between the two regions, and The load disturbance amounts for the two regions.

3. A frequency control system for interconnected power grids based on disturbance compensation, characterized in that, The system includes: a model predictive controller, a nonlinear disturbance observer, and an interconnected power grid. The output of the interconnected power grid is connected to the output of the model predictive controller. The state variables, input variables, and load damping coefficients of the interconnected power grid serve as inputs to the nonlinear disturbance observer. The output of the model predictive controller serves as the input variable of the interconnected power grid. The output of the nonlinear disturbance observer serves as compensation for the output variable of the model predictive controller. The load connected to the interconnected power grid serves as the disturbance variable. Wherein: The nonlinear disturbance observer is used to perform compensation calculations for loads connected in the interconnected power grid and to estimate load disturbance variables; The model predictive controller is used to incorporate the load disturbance variable into the control sequence, compensate the output of the model predictive controller, and calculate the control variable at each time moment as the input variable of the interconnected power grid. The formula for the control variable is expressed as follows: in, To control the input variables u To output variables y The unit coefficient response matrix, and For weighted matrices, for k The model predicts the controller reference output sequence at time +1. for k The increment of the state variables of the interconnected power grid at time t, for k The increment of the output variable of the interconnected power grid at time t, For estimation k The increment of the load disturbance variable at time t. , and Let T be the corresponding coefficient matrix, and T denote the matrix transpose. The state-space equation of the interconnected power grid AGC system is: in, , , , These are the state matrix, input matrix, output matrix, and disturbance matrix, respectively. The actual values ​​of the output variables for each selected interconnected control region. for k State variable estimates at time t; for k The increment of the input variables of the interconnected power grid at time t, for k The load disturbance variable at the specified time; The nonlinear perturbation observer is represented as: in, For variables inside the observer, For functions in the observer, For gain, satisfying , for The first derivative, x Let these be the state variables of the interconnected power grid. u For the input variables of the interconnected power grid, A The state matrix, B For the input matrix, The estimated load disturbance variable.

4. The frequency control method for interconnected power grids based on disturbance compensation as described in claim 3, characterized in that, The state variables of the interconnected power grid x Input variables u Output variables y and load disturbance variables w They are respectively: in, and The system frequency deviation between the two regions constituting the interconnected power grid, and This represents the offset of generator output power between the two regions. and The position increment of the speed controller in the two regions. For the offset of the switching power of the tie line, and Adjust the ACG power for the two regions. and The control deviation between the two regions, and The load disturbance amounts for the two regions.

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