Frequency trajectory optimization control method for high proportion wind power system based on state reconstruction
By designing an equivalent form of frequency-frequency change rate and a PI controller, time dependence is eliminated, and optimized control of the frequency trajectory of a high-proportion wind power system is achieved. This solves the problem of insufficient frequency stability in existing wind power systems and improves the robustness and frequency stability of the system.
Patent Information
- Application Number
- CN202611131360.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-07-29
- Publication Date
- 2026-08-25
AI Technical Summary
Existing technologies rely on accurate modeling and timing information of the frequency response characteristics of wind power systems, which leads to reduced control robustness and makes it difficult to effectively improve the frequency stability of high-proportion wind power systems.
A frequency trajectory optimization control method based on state reconstruction is adopted. By designing the equivalent form of frequency-frequency change rate, the time dependency is eliminated. The frequency regulation power of the wind turbine is generated by the PI controller, and the frequency trajectory optimization control is achieved, which only depends on the frequency information of the wind power system.
It improves the robustness of frequency control in wind power systems, eliminates overshoot and convex frequency minimums in traditional frequency responses, ensures frequency safety margin under maximum anticipated disturbances, and significantly improves system frequency stability.
Smart Images
Figure CN122639082A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of wind turbine frequency optimization control technology, and relates to a control and regulation technology for equipment used in conjunction with a power supply system, specifically a high-proportion wind power system frequency trajectory optimization control method based on state reconstruction. Background Technology
[0002] The large-scale integration of wind turbines significantly reduces the power system's inertia level and weakens its frequency regulation capability, greatly increasing the risk of power system frequency instability under high-power deficit accidents. To improve the frequency stability of high-proportion wind power systems, wind turbines should possess active frequency support capabilities.
[0003] As power generation equipment connected to and cooperating with the power supply system, the control and regulation strategies of wind turbines directly affect their active power response and transient frequency regulation performance during system disturbances. Precise control and regulation of the active power output of wind turbines enables them to actively adjust their output power during system disturbances, fully leveraging the advantages of power electronic devices in terms of flexibility and adaptability. Frequency regulation control strategies for wind turbines can be designed according to system requirements, thereby optimizing the frequency trajectory of high-proportion wind power systems. Existing model-based methods rely on accurate modeling of the system's frequency response characteristics. However, the governor model of a real synchronous generator is complex, and modeling errors are unavoidable and can adversely affect control performance. Model-free methods rely on accurate time information, which is difficult to obtain accurately in practice, leading to decreased control robustness.
[0004] Therefore, how to fully utilize the flexibility of wind turbine control while avoiding dependence on time information is an urgent problem to be solved. Summary of the Invention
[0005] To address the problems existing in the prior art, the present invention aims to propose a high-proportion wind power system frequency trajectory optimization control method based on state reconstruction. This invention derives an equivalent form of the "frequency-frequency change rate" of the reference frequency trajectory based on the selected frequency trajectory. Then, based on this equivalent form, a PI controller that relies solely on power system frequency information is designed to adjust the wind turbine output and optimize the wind power system frequency trajectory. This method relies solely on wind power system frequency information, eliminating the time dependency of the reference frequency trajectory, avoiding the impact of time information accuracy on control performance, and effectively ensuring the robustness of the PI controller.
[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The frequency trajectory optimization control method for high-proportion wind power systems based on state reconstruction includes the following steps: Step 1: To meet the requirements of stable operation of wind power systems, the frequency trajectory of wind power systems is optimized and designed to obtain the time-domain expression of the frequency trajectory. The designed frequency trajectory meets the requirement that the lowest frequency point of the wind power system does not exceed the limit under the maximum expected disturbance. Step 2: Based on the frequency trajectory designed in Step 1, differentiate the frequency trajectory to obtain the time-domain expression of the frequency change rate; Step 3: Based on the time-domain expression of the frequency trajectory designed in Step 1 and the time-domain expression of the frequency change rate obtained in Step 2, eliminate the time variable and obtain the equivalent form of frequency-frequency change rate corresponding to the designed frequency trajectory, so as to eliminate the explicit time dependence in the frequency trajectory generation process. Step 4: Based on the equivalent form of frequency-frequency change rate corresponding to the frequency trajectory obtained in Step 3, generate a reference frequency change rate using the measured frequency, and integrate the reference frequency change rate to obtain the reconstructed reference frequency trajectory. This makes the generation of the reference frequency trajectory independent of time, realizing the reconstruction of the state as the reference frequency. Step 5: Using the difference between the measured frequency and the reconstructed reference frequency as input, construct a PI controller, and generate the frequency regulation power of the wind turbine generator through the PI controller to adjust the output of the wind turbine generator, so that the frequency of the wind power system tracks the reconstructed reference frequency trajectory, thereby realizing the optimized control of the frequency trajectory of the high-proportion wind power system.
[0007] In step 1, the designed frequency trajectory is essentially the step response of a first-order system, without overshoot, thus eliminating the overshoot phenomenon and convex minimum frequency point in traditional frequency responses. Its time-domain expression is: (1) in, For time variables, The time-domain representation of the designed frequency trajectory; and These represent the amplitude and the decay time constant, respectively.
[0008] To ensure that the designed frequency trajectory does not exceed the limit at the lowest frequency point of the wind power system under the maximum anticipated disturbance, the amplitude of the frequency trajectory... The following design method is adopted (2) in, This represents the maximum potential power deficit disturbance of the wind power system (which can generally be set as a percentage of the actual load). This indicates the actual power deficit disturbance of the wind power system. This indicates the maximum permissible frequency deviation for normal operation of the wind power system; In addition, based on the actual power deficit disturbance of the wind power system The initial frequency change rate, the decay time constant of the frequency trajectory With amplitude The following relationships exist between them. (3) in, This represents the inertial time constant of the wind power system.
[0009] In step 1, frequency trajectory optimization design is first performed to provide a clear transient frequency dynamic target for wind turbine frequency regulation control, transforming the frequency response of the wind power system from passive support after disturbances to active shaping oriented towards the target trajectory. The designed frequency trajectory further considers the requirement that the lowest frequency point does not exceed the limit under the maximum anticipated disturbance, ensuring frequency safety margin under the most unfavorable power deficit situation.
[0010] In step 2, the derivative of the frequency trajectory designed in step 1 is taken to obtain the time-domain expression of the frequency change rate of the designed frequency trajectory, as follows: (4) in, This represents the rate of change of frequency.
[0011] In step 3, the time variable is eliminated. The quantitative relationship between frequency and rate of change of frequency, i.e., the equivalent form of frequency-rate of change of frequency corresponding to the frequency trajectory, is as follows: (5) In step 3, the frequency-frequency change rate equivalent form can preserve the dynamic change law of the designed frequency trajectory, while eliminating explicit time dependence, so that the subsequent reference frequency trajectory can be generated online according to the system frequency state.
[0012] In step 4, the state reconstruction generates a reference frequency change rate based on the frequency-frequency change rate equivalent form obtained in step 3 using the measured frequency, and then integrates to obtain the reconstructed reference frequency trajectory, i.e. (6) in, s Represents a Laplace complex variable. and These are the complex frequency domain forms of the obtained reconstructed reference frequency trajectory and the rate of change of the reconstructed reference frequency, respectively. This is the complex frequency domain form of the measured frequency.
[0013] In step 4, the reference frequency trajectory is reconstructed using the measured frequency because the equivalent form of frequency-frequency change rate obtained in step 3 has transformed the dynamic law of the designed trajectory into a correspondence between frequency state and frequency change rate. Therefore, substituting the measured frequency into this equivalent form yields the reference frequency change rate in the current state, and integration forms the reconstructed reference frequency trajectory. This reconstruction process transforms the generation of the reference frequency trajectory from time-driven to state-driven, relying solely on wind power system frequency measurement information to achieve online generation of the reference trajectory. This avoids the adverse effects of inaccurate time information on trajectory generation and control performance, improving the robustness of the control method.
[0014] In step 5, the reference frequency generated in step 4 of the wind turbine frequency regulation control based on the PI controller is used as the reference input. The output of the wind turbine is adjusted by the feedback of the PI controller so that the frequency of the wind power system tracks the reference frequency. Thus, the PI controller no longer depends on the time signal and can realize the feedback reshaping of the frequency trajectory only by the state (wind power system frequency) measurement.
[0015] In step 5, the difference between the measured frequency and the reconstructed reference frequency is used as the input to the PI controller. This is to adjust the active power output of the wind turbine in real time based on the frequency trajectory tracking error, so that the frequency of the wind power system gradually approaches the reconstructed reference frequency trajectory. Since the reconstructed reference frequency trajectory is generated by the frequency state, the PI controller only needs to use the frequency measurement information to realize the feedback reshaping of the frequency trajectory, no longer relying on the time signal. Therefore, it can reduce the adverse effects of time information error on the control effect and improve the simplicity of engineering implementation and control robustness.
[0016] Compared with the prior art, the present invention has the following advantages: 1. This invention combines reference frequency trajectory generation and wind turbine frequency regulation control through state reconstruction, transforming the frequency control problem of high-proportion wind power systems into a frequency trajectory tracking problem. Frequency trajectory feedback reshaping can be achieved solely by relying on wind power system frequency measurement information, avoiding dependence on precise frequency response models and accurate time information. The control structure is clear and has strong engineering feasibility. 2. This invention designs the frequency trajectory as a first-order system step response, giving it no overshoot characteristics. It eliminates the convex minimum frequency point in the traditional frequency response from the trajectory design level, which can significantly improve the minimum frequency point of the wind power system. 3. In the frequency trajectory parameter design, this invention considers the maximum potential power deficit disturbance, the actual power deficit disturbance, and the maximum allowable frequency deviation of the wind power system, which can ensure that the designed reference frequency trajectory does not exceed the limit at the lowest frequency point under the maximum expected disturbance and is robust to power deficit disturbance. 4. Based on the equivalent form of frequency-frequency change rate, this invention reconstructs the reference frequency trajectory using the measured frequency. The reference frequency trajectory generation process does not depend on the time signal, which can avoid the impact of the accuracy of time information on control performance and has strong control robustness. Attached Figure Description
[0017] Figure 1 This is a time-independent frequency trajectory tracking control structure block diagram.
[0018] Figure 2 This is a diagram of the IEEE 39-node simulation system.
[0019] Figure 3 These are the power output curves of wind turbines under different disturbance magnitudes.
[0020] Figure 4 It represents the system frequency trajectory under different disturbance magnitudes.
[0021] Figure 5 These are the wind turbine output curves corresponding to different transient frequency support control strategies under load step disturbance.
[0022] Figure 6 These are the system frequency curves corresponding to different transient frequency support control strategies under load step disturbances.
[0023] Figure 7 These are the wind turbine output curves corresponding to different transient frequency support control strategies under generator tripping disturbances.
[0024] Figure 8 These are the system frequency curves corresponding to different transient frequency support control strategies under generator tripping disturbances. Detailed Implementation
[0025] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.
[0026] The overall control framework of the method of this invention is as follows: Figure 1 As shown, based on the measured frequency and power deficit disturbance Generate reference frequency trajectory A PI controller is used to control the error between the measured frequency and the reconstructed reference frequency. Achieve reconfiguration reference frequency tracking to generate frequency-modulated power for wind turbines. The following steps are taken to optimize the frequency trajectory of the wind power system: Step 1: To meet the stable operation requirements of the wind power system, the frequency trajectory of the wind power system is optimized, resulting in its time-domain expression. The designed frequency trajectory satisfies the requirement that the lowest frequency point of the wind power system does not exceed the limit under the maximum anticipated disturbance. Specifically, the designed frequency trajectory adopts a first-order system step response form, and the dynamic response process does not generate overshoot, thereby eliminating the overshoot phenomenon and convex lowest frequency point in traditional frequency responses. Its time-domain expression is as follows: (1) in, For time variables, The time-domain representation of the designed frequency trajectory; and These represent the amplitude of the frequency trajectory and the decay time constant of the frequency trajectory, respectively.
[0027] To ensure that the designed frequency trajectory does not exceed the limit at the lowest frequency point of the wind power system under the maximum anticipated disturbance, the amplitude of the frequency trajectory... The following design method is adopted (2) in, This represents the maximum potential power deficit disturbance of the wind power system (which can generally be set as a percentage of the actual load). This indicates the actual power deficit disturbance of the wind power system. This indicates the maximum permissible frequency deviation for normal operation of the wind power system; In addition, based on the actual power deficit disturbance of the wind power system The initial frequency change rate is given by (3) in, This represents the rate of change of frequency at the initial moment. This represents the inertial time constant of the wind power system.
[0028] The decay time constant of the frequency trajectory can be obtained. With amplitude The following relationships exist between them. (4) Step 2: Based on the frequency trajectory designed in Step 1 as shown in Equation (1), the time-domain expression of the frequency change rate is obtained by differentiating the frequency trajectory as follows: (5) in, The time-domain form representing the rate of change of the designed frequency trajectory.
[0029] Step 3: Based on the time-domain expression of the rate of change of frequency obtained in Step 2, as shown in Equation (5), the time-varying variables can be... The part is further represented as (6) Substituting equation (6) into the time-domain reference frequency trajectory shown in equation (1) eliminates the time variable, yielding the frequency-frequency rate of change equivalent form of the designed frequency trajectory. This eliminates the explicit time dependency in the frequency trajectory generation process. (7) Step 4: Based on the frequency-frequency change rate equivalent form shown in equation (7) obtained in Step 3, substitute the measured frequency into the frequency-frequency change rate equivalent form to generate the reference frequency change rate. Integrate the reference frequency change rate to obtain the reconstructed reference frequency trajectory. This makes the generation of the reference frequency trajectory independent of time, realizing the reconstruction of the state as the reference frequency. (8) in, s Represents a Laplace complex variable. and These are the complex frequency domain forms of the obtained reconstructed reference frequency trajectory and the rate of change of the reconstructed reference frequency, respectively. This is the complex frequency domain form of the measured frequency.
[0030] Step 5: Using the deviation between the measured power system frequency and the reconstructed reference frequency shown in equation (8) as input, construct a PI controller, and use the PI controller to control the error between the measured frequency and the reconstructed reference frequency. Achieve frequency tracking of the reference frequency to generate frequency-modulated power for wind turbines. This allows for the adjustment of wind turbine output, enabling the wind power system frequency to track the reconstructed reference frequency trajectory, thereby achieving optimized control of the frequency trajectory of a high-proportion wind power system.
[0031] Example: Based on the standard IEEE 39-bus system, a simulation system considering the connection of multiple wind turbines was constructed. The system structure is as follows: Figure 2 As shown. Figure 2 In this table, G1~G10 represent synchronous generators, and their speed control system adopts the classic IEEE G1 speed governor model. The parameters of the synchronous generators and speed control system are shown in Table 1. The sum of the capacities of all synchronous generators is selected as the system capacity benchmark, i.e. The total active power load of the system is 6097.1 MW, and the frequency response coefficient of the active power load is 2. After conversion to the reference value, the system damping coefficient is obtained as follows: In addition, an equivalent wind turbine is connected at busbars 3 / 9 / 16 / 17 / 23. The equivalent wind turbine is formed by aggregating multiple wind turbines with identical parameters and operating conditions. The basic parameters of the single wind turbine used for aggregation are shown in Table 2.
[0032] Table 1 Parameters of Synchronous Generator and its Speed Control System Note: The other parameter values for the IEEE G1 model are as follows. , , , , , .
[0033] Table 2 Wind Turbine Generator Parameters To verify the robustness of the method of this invention to different power deficit disturbances, simulation tests were conducted under a series of power deficit disturbance conditions. The wind turbine output under different disturbance magnitudes is as follows: Figure 3 As shown, the corresponding system frequency trajectory is as follows: Figure 4 As shown. By Figure 3 It can be seen that when a power deficit disturbance occurs, the wind turbine releases corresponding rotor kinetic energy and outputs frequency-modulated power according to the degree of disturbance; as the power deficit disturbance increases, the frequency-modulated power provided by the wind turbine increases accordingly, indicating that the method of the present invention can adaptively adjust the frequency support capability of the wind turbine according to the magnitude of the disturbance, so that its output power matches the system's power deficit demand. Figure 4 It can be seen that for various disturbances not exceeding the maximum potential power deficit disturbance, no convex frequency minimum point appears during the frequency decrease process, and the frequency minimum point remains within an acceptable range. This indicates that the method of the present invention has strong adaptability and robustness to the magnitude of power deficit disturbances.
[0034] To further verify the effectiveness of the present invention's method compared to existing wind turbine transient frequency support control strategies, three comparative control schemes were set up: virtual inertia-droop control, adaptive virtual inertia-droop control, and square wave inertia control, denoted as Method 1, Method 2, and Method 3, respectively. In all control schemes, the wind turbine operates in maximum power point tracking mode before the disturbance, participating in system frequency regulation only by releasing rotor kinetic energy, and the wind turbine returns to its steady-state operating point after frequency regulation ends.
[0035] Figure 5-8 The output curves of wind turbines and the system frequency trajectory are presented under two typical power deficit disturbances using different wind turbine frequency support control strategies. The corresponding maximum system frequency offsets are shown in Table 3. Figure 5 and Figure 7 The comparison of wind turbine output results shows that, during the frequency regulation period, the method of this invention can provide greater frequency regulation power compared to other transient frequency support control strategies. This indicates that the method of this invention can more fully utilize the frequency regulation capability of wind turbines, providing more effective transient frequency support for the system during disturbances, thereby significantly improving the system's minimum frequency and enhancing system frequency stability. Figure 6 and Figure 8 The frequency trajectory comparison results show that the method of the present invention can effectively eliminate the convex frequency minimum point in the traditional frequency response and keep the system frequency minimum point at a higher level. Therefore, under different forms of power deficit disturbances, the method of the present invention can shape the system frequency trajectory into the desired optimal form, significantly improving the system frequency minimum point compared to existing transient frequency support control methods, thereby improving system frequency stability.
[0036] Table 3 Comparison of maximum frequency offset of the system under different transient frequency support control strategies for wind turbines Using the maximum frequency offset as the evaluation index, under load step disturbance, the maximum frequency offset of the method of this invention is -0.2215Hz, which is better than -0.3860Hz of virtual inertia-droop control, -0.3202Hz of adaptive virtual inertia-droop control, and -0.3267Hz of square wave inertia control, with relative performance improvements of 42.62%, 30.82%, and 32.20%, respectively. Under generator trip disturbance, the maximum frequency offset of the method of this invention is -0.2246Hz, which is better than -0.3791Hz of virtual inertia-droop control, -0.3106Hz of adaptive virtual inertia-droop control, and -0.3292Hz of square wave inertia control, with relative performance improvements of 40.75%, 27.69%, and 31.77%, respectively.
Claims
1. A frequency trajectory optimization control method for high-proportion wind power systems based on state reconstruction, characterized in that, Includes the following steps: Step 1: To meet the requirements of stable operation of wind power systems, the frequency trajectory of wind power systems is optimized and designed to obtain the time-domain expression of the frequency trajectory. The designed frequency trajectory meets the requirement that the lowest frequency point of the wind power system does not exceed the limit under the maximum expected disturbance. Step 2: Based on the frequency trajectory designed in Step 1, differentiate the frequency trajectory to obtain the time-domain expression of the frequency change rate; Step 3: Based on the time-domain expression of the frequency trajectory designed in Step 1 and the time-domain expression of the frequency change rate obtained in Step 2, eliminate the time variable and obtain the equivalent form of frequency-frequency change rate corresponding to the designed frequency trajectory, so as to eliminate the explicit time dependence in the frequency trajectory generation process. Step 4: Based on the equivalent form of frequency-frequency change rate corresponding to the frequency trajectory obtained in Step 3, generate a reference frequency change rate using the measured frequency, and integrate the reference frequency change rate to obtain the reconstructed reference frequency trajectory, so that the generation of the reference frequency trajectory is independent of time, and realize the state as reference frequency reconstruction. Step 5: Using the difference between the measured frequency and the reconstructed reference frequency as input, construct a PI controller, and generate the frequency regulation power of the wind turbine generator through the PI controller to adjust the output of the wind turbine generator, so that the frequency of the wind power system tracks the reconstructed reference frequency trajectory, thereby achieving optimized control of the frequency trajectory of the high-proportion wind power system.
2. The frequency trajectory optimization control method for high-proportion wind power systems based on state reconstruction as described in claim 1, characterized in that, In step 1, the designed frequency trajectory is the step response form of a first-order system and does not have overshoot. Its time-domain expression is: （1） in, For time variables, The time-domain representation of the designed frequency trajectory; and These represent the amplitude of the frequency trajectory and the decay time constant of the frequency trajectory, respectively.
3. The frequency trajectory optimization control method for high-proportion wind power systems based on state reconstruction as described in claim 2, characterized in that, To ensure that the designed frequency trajectory does not exceed the limit at the lowest frequency point of the wind power system under the maximum anticipated disturbance, the amplitude of the frequency trajectory... The following design method is adopted （2） in, This represents the maximum potential power deficit disturbance of the wind power system. This indicates the actual power deficit disturbance of the wind power system. This indicates the maximum permissible frequency deviation for normal operation of the wind power system; Furthermore, based on the actual power deficit disturbance of the wind power system The initial frequency change rate, the decay time constant of the frequency trajectory With amplitude The following relationships exist between them. （3） in, This represents the inertial time constant of the wind power system.
4. The frequency trajectory optimization control method for high-proportion wind power systems based on state reconstruction as described in claim 1, characterized in that, In step 2, the derivative of the frequency trajectory designed in step 1 is taken to obtain the time-domain expression of the frequency change rate of the designed frequency trajectory, as follows: （4） in, The time-domain form representing the rate of change of the designed frequency trajectory. This refers to the actual power deficit disturbance of the wind power system. Let be the inertial time constant of the wind power system. This represents the decay time constant of the frequency trajectory.
5. The frequency trajectory optimization control method for high-proportion wind power systems based on state reconstruction as described in claim 1, characterized in that, In step 3, the time variable is eliminated based on the time-domain expression of the frequency trajectory designed in step 1 and the time-domain expression of the frequency change rate obtained in step 2. The equivalent form of the frequency-frequency change rate corresponding to the designed frequency trajectory is obtained, and the expression is as follows: （5） in, The time-domain form representing the rate of change of the designed frequency trajectory. The time-domain representation of the designed frequency trajectory. The decay time constant representing the frequency trajectory. This refers to the actual power deficit disturbance of the wind power system. Let be the inertial time constant of the wind power system.
6. The frequency trajectory optimization control method for high-proportion wind power systems based on state reconstruction as described in claim 1, characterized in that, In step 4, based on the equivalent form of frequency-frequency change rate corresponding to the frequency trajectory obtained in step 3, the measured frequency is substituted into the equivalent form to generate a reference frequency change rate. The reference frequency change rate is then integrated to obtain the reconstructed reference frequency trajectory. （6） in, s Represents a Laplace complex variable. and These are the complex frequency domain forms of the obtained reconstructed reference frequency trajectory and the rate of change of the reconstructed reference frequency, respectively. This is the complex frequency domain form of the measured frequency; The decay time constant representing the frequency trajectory. This refers to the actual power deficit disturbance of the wind power system. Let be the inertial time constant of the wind power system.
7. The frequency trajectory optimization control method for high-proportion wind power systems based on state reconstruction as described in claim 1, characterized in that, In step 5, the difference between the measured frequency and the reconstructed reference frequency is used as input to construct a PI controller, which generates the frequency regulation power of the wind turbine generator. The output of the wind turbine generator is adjusted by feedback through the PI controller so that the power system frequency tracks the reconstructed reference frequency. The PI controller relies only on the power system state, i.e., the frequency measurement information, and does not rely on the time signal, thereby realizing the feedback reshaping of the power system frequency trajectory.