A grid-connected wind power parallel system coordinated frequency modulation method based on inversion sliding mode control

Abstract

The application discloses a kind of based on inversion sliding mode control's network wind power parallel system coordination frequency modulation method, belong to wind power grid connection technical field.The method is by real-time monitoring wind turbine active power, wind speed and grid frequency, power reference value is dynamically adjusted in combination with inversion control strategy, and estimates and compensates external disturbance using compensation function observer, enhances system robustness;While designing pitch angle attitude inverse solution module optimizes wind turbine power output, uses sliding mode adaptive control strategy to improve dynamic response capability.Simulation results show that the application can significantly improve the frequency modulation accuracy and stability of system, reduce the influence of frequency fluctuation on wind turbine, provide technical support for efficient operation of wind power grid connection system.

Description

Technical Field

[0001] This invention belongs to the field of wind power grid connection control technology, specifically, it relates to a collaborative frequency regulation method for grid-connected wind power parallel systems based on inversion sliding mode control. Background Technology

[0002] With the rapid development of renewable energy, wind power is playing an increasingly important role in power systems, and wind power grid connection has become a crucial component of modern power grids. However, due to the fluctuating and intermittent nature of wind energy, wind power grid-connected systems face numerous challenges in frequency regulation. Traditional frequency regulation methods, such as droop control and inertial response strategies, can alleviate frequency fluctuations to some extent, but their slow response speed and insufficient regulation accuracy make them unsuitable for the high-quality frequency regulation requirements of modern power grids. Especially under load fluctuations or system disturbances, traditional control strategies often fail to quickly and effectively adjust wind turbine power output, leading to decreased system frequency stability and potentially causing severe oscillations in the turbine shaft system, affecting the reliability and lifespan of the wind turbine units. Therefore, improving the frequency regulation capability and stability of wind power grid-connected systems has become a critical technical issue that urgently needs to be addressed.

[0003] In existing technologies, wind power parallel systems typically employ a single control strategy to address frequency fluctuations. However, this approach exhibits significant limitations under complex operating conditions. For instance, when the frequency deviates from the target value, traditional control strategies struggle to dynamically adjust turbine power output based on real-time wind speed and grid conditions, resulting in insufficient system frequency regulation capability. Furthermore, external disturbances and system uncertainties further exacerbate the instability of wind power grid-connected systems, making turbine power output prone to drastic fluctuations and thus affecting the overall operational quality of the power grid. To address these issues, a novel control method is urgently needed that can rapidly respond to frequency changes, precisely adjust power output, and enhance system robustness. Summary of the Invention

[0004] The purpose of this invention is to provide a collaborative frequency regulation method for grid-connected wind power parallel systems based on inversion sliding mode control, which mainly solves the technical problems of slow response speed, insufficient regulation accuracy and poor system stability in the frequency regulation process of existing wind power parallel systems.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for coordinated frequency regulation of grid-connected wind power parallel systems based on inversion sliding mode control includes the following steps:

[0007] S1. Establish a mathematical model for a grid-connected wind power system with two parallel turbines;

[0008] S2, Design a controller based on inversion sliding mode control to adjust the power output of the wind turbine according to the dynamic changes in grid frequency fluctuations, wind speed changes, and pitch angle adjustment; wherein, the controller includes:

[0009] The compensation function observer is used to provide feedback compensation for the power output of the second wind turbine in a grid-connected wind power dual-turbine parallel system.

[0010] The pitch angle attitude inverse solution module is used to adjust the total available power state of the grid-connected wind turbines by using the power state input from the second wind turbine in the wind turbine duo.

[0011] The sliding mode adaptive control module generates an active power reference value for the two wind turbines in the grid based on the total available power state of the two wind turbines, thereby effectively guiding the power output of the wind turbines to converge towards the active power reference value, thus realizing grid frequency regulation.

[0012] Furthermore, in the mathematical model of step S1, the power output expression of the second wind turbine in the grid-connected wind power dual-unit parallel system is as follows:

[0013]

[0014] In the formula, , where f(k) represents the grid frequency deviation, and f is the grid frequency. N Indicates the rated frequency of the power grid. The wind speed is represented by k1 and k2, which are control gains, representing the effects of frequency deviation and wind speed on power output, respectively.

[0015] Furthermore, the expression for the available power state of the second wind turbine after feedback compensation by the compensation function observer is as follows:

[0016]

[0017] In the formula, P WT2 (k) is the power output of the second wind turbine, P max2 That is the maximum power output of the second wind turbine. It is the feedback compensation obtained through the compensation function observer, which represents the impact of external disturbances on power output;

[0018] The formula for calculating feedback compensation is as follows:

[0019]

[0020] In the formula, e1(k) is the systematic error. L1 represents the difference between the power output of the second wind turbine and the power reference value of the second wind turbine, and L1 is the gain of the compensation function observer.

[0021] Finally, the final expression for the available power state β2(k) of the second wind turbine can be obtained as follows:

[0022] .

[0023] Furthermore, the control method for the pitch angle attitude inverse kinematics module is as follows:

[0024] Design a control law based on the relationship between the total available power state ψ(k) of the two wind turbines in the grid and the available power state β2(k) of the second wind turbine:

[0025] ;

[0026] In the formula, P total It is the calculated value of the total power in a parallel system;

[0027] A pitch angle adjustment formula is designed to control the pitch angle and thus adjust the power output of the wind turbine; the expression for the pitch angle adjustment formula is as follows:

[0028]

[0029] Where θ(k) represents the pitch angle of the wind turbine.

[0030] Furthermore, the control method of the sliding mode adaptive control module is as follows:

[0031] Design the sliding surface for sliding mode control, and define the sliding surface s(k) as the total available power state ψ(k) and the active power reference value P. ref The error between (k), that is:

[0032] ;

[0033] Design a control law u(k) that causes the total available power state ψ(k) to converge toward the sliding surface s(k), enabling the system to converge quickly to the target state; the expression for the control law u(k) is:

[0034]

[0035] in, It is the control gain, which represents the response speed of the control system; sign() is the sign function.

[0036] An adaptive mechanism is introduced to dynamically adjust the control gain based on the size of the sliding surface s(k). Adaptive gain The expression is:

[0037]

[0038] in, It is the initial gain. It is the adaptive coefficient, which represents the adjustment range of gain as the error increases.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] (1) This invention designs a sliding surface through a sliding mode adaptive control module and introduces an adaptive gain adjustment mechanism to enable the system to quickly converge to the target power state. Under conditions of sudden load increase or wind speed fluctuation, it can dynamically track and compensate for the system power deficit, significantly reduce the frequency oscillation amplitude, solve the problem of power output adjustment lag under traditional strategies, and effectively improve the system's response speed and adjustment accuracy to frequency fluctuations.

[0041] (2) The present invention sets up a compensation function observer, which calculates the error between the power output of the second wind turbine and the reference value in real time, and feeds back to compensate for the impact of external disturbances on the power output. This mechanism can accurately estimate and cancel disturbances, avoiding the negative impact of large fluctuations in wind turbine speed and active power on shaft stability under traditional control strategies. It not only ensures the stable operation of the power grid frequency, but also reduces the damage of power oscillations to the wind turbine, and extends the service life of the equipment.

[0042] (3) This invention integrates the advantages of inversion control and sliding mode control. By using the pitch angle attitude inversion module to correlate the available power state of the second wind turbine with the total available power state of the system, the power output of the two grid-connected wind turbines is adjusted in a coordinated manner. This coordinated strategy breaks through the bottleneck of traditional single control, can adapt to complex scenarios such as frequent wind speed changes and sudden load changes, improves the overall frequency regulation capability and stability of the multi-turbine parallel system, and broadens the applicable scope of wind power grid-connected systems.

[0043] (4) The controller of the present invention combines grid frequency deviation, wind speed change and pitch angle adjustment to dynamically adjust the wind turbine power output (such as considering the frequency deviation Δf(k) and wind speed influence in the power output expression of the second wind turbine). This design realizes precise dynamic optimization of wind turbine power output, ensuring that the system can maintain a stable frequency level when wind speed fluctuates or the frequency deviates from the rated value, thus improving the operational reliability of the wind power grid connection system. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of the coordinated frequency regulation control of the grid-connected wind power parallel system in this invention;

[0045] Figure 2 This is a schematic diagram of the mode switching control strategy based on inversion control in this invention;

[0046] Figure 3 This is a schematic diagram of the simulation results of the system angular frequency change in this invention;

[0047] Figure 4This is a schematic diagram of the simulation results of the wind turbine angular velocity change in this invention;

[0048] Figure 5 This is a schematic diagram of the simulation results of wind power active power variation in this invention. Detailed Implementation

[0049] The present invention will be further described below with reference to the accompanying drawings and embodiments. The embodiments of the present invention include, but are not limited to, the following embodiments.

[0050] like Figure 1 , 2 As shown, the present invention discloses a method for coordinated frequency regulation of grid-connected wind power parallel systems based on inversion sliding mode control. Its core lies in combining the advantages of inversion control and sliding mode control. By monitoring key parameters such as the output active power of the wind turbine, wind speed, and grid frequency in real time, the reference value of the wind turbine input power is dynamically adjusted, thereby achieving rapid response and precise regulation to system frequency fluctuations.

[0051] Firstly, in actual operation, the structure of a grid-connected wind power dual-unit parallel system is as follows: Figure 1 As shown, the output active power of the two grid-connected wind turbines directly affects the actual frequency of the power grid. The rated frequency of the power grid is denoted as f. N Frequency deviation is defined as According to the system design, the power output P of the second fan is... WT2 (k) is affected by wind speed v(k) and grid frequency f(k). The power output formula is as follows:

[0052] ;

[0053] When the system detects a frequency deviation from the target value, the controller adjusts the current wind speed accordingly. The available power status of the wind turbine is assessed using the frequency deviation Δf(k), and a new active power reference value P is generated. ref This reference value is used to optimize the power output of the two wind turbines, ensuring the system maintains stable operation even under conditions of significant frequency fluctuations. The compensation function observer plays a crucial role in this process. Through the compensation function observer... External disturbances are estimated in real time and compensated for in terms of power output. The available power state β2(k) of the second wind turbine is calculated using the following formula:

[0054] .

[0055] To accurately estimate external disturbances and uncertainties, the compensation function observer compensates for the impact of these disturbances on the system by calculating the error e1(k) in real time. The error calculation formula is as follows: , where P WT2(k) represents the actual power output of the second wind turbine, P ref2 (k) is its power reference value. The feedback compensation formula for the compensation function observer is:

[0056] in This is the gain of the compensation function observer. Through the above design, the compensation function observer can estimate external disturbances in real time and provide feedback compensation. This is applied to the system's power output adjustment. Combining the above formulas, the final expression for the available power state of the second wind turbine is:

[0057] .

[0058] This mechanism significantly improves the robustness of the system, enabling it to maintain a stable operating state when faced with external disturbances.

[0059] In the design of the pitch angle attitude inverse kinematics module, the input is the available power state β2(k) of the second wind turbine, and the output is the total available power state ψ(k) of the wind turbine. The relationship between the total available power state ψ(k) and the available power state β2(k) is given by the formula... The formula, when transformed, becomes the control law for the pitch angle attitude inverse kinematics module: , where P max2 P represents the maximum power output of the second wind turbine. total This is the calculated total power of the system. By adjusting the pitch angle θ(k), the power output of the wind turbine is optimized to match grid frequency fluctuations and wind speed variations. Specifically, the pitch angle is adjusted using the formula... Achieved. Through the above design, the pitch angle attitude inverse kinematics module can dynamically adjust the wind turbine's pitch angle according to the input power state, thereby achieving precise control of the wind turbine's power output.

[0060] Sliding mode adaptive control strategy is one of the core technologies of this invention, and its design goal is to improve the dynamic response capability of the system. The sliding surface s(k) is defined as the total available power state ψ(k) and the target power reference value P. ref The error between (k), i.e. The expression for the sliding mode control law u(k) is:

[0061] in This refers to the control gain, and `sign()` is the sign function. To cope with external disturbances and dynamic changes in the system, an adaptive gain adjustment mechanism is introduced, which dynamically adjusts the control gain based on the magnitude of the sliding surface `s(k)`. Adaptive gain adjustment formula ,in It is the initial gain. This refers to the adaptive coefficient. Through the above design, the sliding mode adaptive control strategy can quickly converge to the target power reference value even under conditions of large frequency fluctuations, reducing the impact of external disturbances on the system.

[0062] In practical applications, the effectiveness of the control strategy proposed in this invention was verified through simulation. On the simulation platform, a load surge condition was designed to compare the frequency changes before and after applying the proposed control strategy. Experimental results show that after adopting the control strategy of this invention, the system frequency oscillation amplitude is significantly reduced, the wind turbine speed recovery is more stable, and the impact of load switching on the system and wind turbine units is reduced. Specifically, at the 10th second, the load... With a sudden increase of 150MW, the change in the system angular frequency is as follows: Figure 3 As shown, the change in the angular velocity of the fan is as follows: Figure 4 As shown, the change in active power of wind power is as follows: Figure 5 As shown in the figure, the traditional control is droop control, while the ASM control is the inverse sliding mode control proposed in this invention. Simulation results show that the wind power grid-connected system under traditional control requires a significant dynamic adjustment of the electromagnetic power output of the wind turbine to cope with disturbances during fault periods. This results in large fluctuations in the active power and speed of the wind turbine in response to the additional control, negatively impacting the stability of the turbine's shaft system. However, by adopting the control strategy of this invention, the expansion state of the unbalanced power during system disturbances is estimated, and the active power output of the wind turbine is optimized and adjusted to dynamically track and compensate for the system's power deficit, reducing the power oscillation of the wind turbine under disturbances. Therefore, the control strategy of this invention not only improves the dynamic stability of the system but also ensures the stability of the wind turbine itself.

[0063] In practical applications, the control strategy of this invention can be widely used in wind power grid-connected systems, especially under conditions of significant frequency fluctuations. For example, under conditions of frequent wind speed changes or sudden load changes, the control strategy of this invention can quickly respond to frequency fluctuations and effectively regulate the system frequency by dynamically adjusting the power output of the wind turbines. Furthermore, the control strategy of this invention can also be applied to scenarios where multiple wind turbines operate in parallel, further improving the system's frequency regulation capability and stability by coordinating the power output of each turbine.

[0064] In summary, this invention achieves dynamic adjustment of the power output of two wind turbines by real-time monitoring of parameters such as wind speed and grid frequency, combined with inversion control and sliding mode control strategies. This effectively improves the frequency regulation capability and stability of the system, reduces the impact of external disturbances on the system, and ensures the efficient operation of the wind power grid-connected system.

[0065] The above embodiments are merely one of the preferred embodiments of the present invention and should not be used to limit the scope of protection of the present invention. Any modifications or refinements made to the main design concept and spirit of the present invention that are not of substantial significance, but solve the same technical problem as the present invention, should be included within the scope of protection of the present invention.

Claims

1. A method for coordinated frequency regulation of a grid-connected wind power parallel system based on inversion sliding mode control, characterized in that, The method comprises the following steps: S1, establishing a mathematical model of the grid-connected wind power double-machine parallel system; S2, designing a controller based on backstepping sliding mode control, which is used to adjust the power output of the wind turbine according to the grid frequency fluctuation, wind speed change and pitch angle adjustment dynamic change; wherein the controller comprises: A compensation function observer is used to feedback compensate the power output of the second wind turbine of the grid-connected wind power double-machine parallel system; wherein the expression of the available power state of the feedback compensated second wind turbine of the compensation function observer is: where P WT2 (k) is the power output of the second wind turbine, max2 is the maximum power output of the second wind turbine, is the feedback compensation obtained by the compensating function observer, representing the influence of external disturbances on the power output. The calculation formula of the feedback compensation is as follows: where e1(k) is the system error, represents the difference between the power output of the second turbofan and the power reference value of the second turbofan, and L1 is the gain of the compensating function observer. Finally, the final expression of the available power state β2(k) of the second wind turbine is: ； A pitch angle attitude inverse solution module is used to adjust the total available power state of the grid-connected wind power double-machine parallel system through the power state input by the second wind turbine in the wind power double-machine; wherein the control method of the pitch angle attitude inverse solution module is as follows: According to the relationship between the total available power state ψ(k) of the grid-connected wind power double-machine and the available power state β2(k) of the second wind turbine, a control law is designed: ； where P is the calculated value of the total power in the interconnected system; and total is the calculated value of the total power in the interconnected system; and A pitch angle adjustment formula is designed to control the pitch angle and adjust the power output of the wind turbine; wherein the expression of the pitch angle adjustment formula is: Wherein θ(k) represents the pitch angle of the wind turbine; A sliding mode adaptive control module is used to generate the active power reference value of the grid-connected wind power double-machine based on the total available power state of the grid-connected wind power double-machine, and then effectively guide the power output of the wind turbine to converge to the active power reference value, so as to realize the grid frequency regulation.

2. The grid-connected wind power parallel system coordinated frequency modulation method based on inversion sliding mode control according to claim 1, characterized in that, In the mathematical model of step S1, the power output expression of the second wind turbine of the grid-connected wind power double-machine parallel system is as follows: wherein is the grid frequency deviation, f(k) represents the grid frequency, f N represents the grid rated frequency, represents the wind speed, k1 and k2 are control gains, respectively representing the influence of the frequency deviation and the wind speed on the power output.

3. The method of claim 2, wherein the method is characterized by, The control method of the sliding mode adaptive control module is as follows: The sliding mode control sliding surface is designed, and the sliding surface s(k) is defined as the error between the total available power state ψ(k) and the active power reference value P ref (k). ； The control law u(k) is designed to make the total available power state ψ(k) converge to the sliding surface s(k), so that the system quickly converges to the target state; wherein the expression of the control law u(k) is: wherein is a control gain, which indicates the response speed of the control system, and sign() is a sign function. An adaptive mechanism is introduced to dynamically adjust the control gain according to the size of the sliding surface s(k) ; adaptive gain The expression is: wherein is the initial gain, is an adaptation coefficient, representing the adjustment amplitude of the gain with increasing error.

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