Wind turbine generator frequency modulation method based on virtual inertia control
By using virtual inertia control, the output power of the wind turbine is adjusted by frequency, rotational speed, and pitch angle, which solves the problem of insufficient inertia of the wind turbine and improves frequency stability and economy.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-29
- Publication Date
- 2026-03-13
AI Technical Summary
Wind turbines cannot effectively provide inertia support in the power system, resulting in frequency fluctuations and insufficient frequency regulation capabilities. Existing technologies suffer from secondary frequency drops and reduced economic efficiency.
By adopting a virtual inertia control method, the output power and pitch angle of the wind turbine are adjusted through frequency, speed and pitch angle control to realize the virtual inertia response of the wind turbine, providing short-term active power support and long-term inertia support.
This improves the wind turbine's ability to withstand system frequency fluctuations, ensures system frequency stability and economical operation, reduces secondary frequency drops, and enhances the economic benefits of wind farms.
Smart Images
Figure CN121663665A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a technology in the field of power grid control, specifically a frequency regulation method for wind turbine generators based on virtual inertia control. Background Technology
[0002] In traditional power systems, inertia primarily originates from the rotational inertia of the synchronous generator rotor. The rotor's rotational frequency is directly coupled to the grid frequency, and the rotor speed determines the grid frequency. In power systems, active power needs to be balanced. When the system experiences power deficits or surpluses, the synchronous generator releases or absorbs kinetic energy through its rotor to compensate for the power imbalance. Therefore, active power imbalances will lead to fluctuations in the system frequency.
[0003] Compared to traditional synchronous generator systems, wind turbines are connected to the grid via power electronic converters and employ a maximum power point tracking (MPPT) control strategy. In this control mode, without additional control components, the wind turbine's operating state is decoupled from the system frequency. When power fluctuations occur, the turbine cannot adjust its output power in a timely manner and cannot effectively participate in the system's inertial response and primary frequency regulation. Its equivalent inertia is close to zero, making it unable to respond to changes in system frequency. Therefore, wind turbines cannot directly provide the inertial support required by the system.
[0004] To enable wind turbines to participate in grid frequency regulation, existing technologies primarily utilize the rotor kinetic energy of the generator set to simulate inertia, allowing them to participate in primary frequency regulation when grid frequency fluctuates. However, due to the relatively small amount of kinetic energy stored in the turbine rotor, it typically cannot provide long-term power support for inertial response and primary frequency regulation, thus limiting the frequency regulation capability. Utilizing rotor kinetic energy for inertial support is currently the mainstream control method for wind turbines. This method can achieve maximum power point tracking during normal operation to ensure economic efficiency, but it may cause secondary frequency drops and turbine stability issues when exiting frequency regulation. Alternatively, operating the wind turbine in a reduced-load state to provide power reserves can also enable frequency regulation. Related technologies mainly focus on overspeeding the turbine rotor to reduce load and changing the turbine pitch angle to reduce load. The reduced-load control method provides the wind turbine with power reserves and greater inertial support capability, but it operates in a reduced-load state during normal operation, reducing the utilization rate of wind energy and lowering the economic benefits of the wind farm. Summary of the Invention
[0005] This invention addresses the shortcomings of existing technologies that cannot provide inertial support to the power system by controlling the output power of wind turbines when large power disturbances occur. It proposes a wind turbine frequency regulation method based on virtual inertia control. This method fully utilizes the wind turbine's ability to rapidly adjust active power output. Frequency control converts the rotational kinetic energy stored in the rotor into temporary active power support; speed control suppresses rapid frequency fluctuations, preventing secondary drops while quickly restoring the rotor speed to its original operating state; and pitch angle control gives the wind turbine a larger power reserve capacity, providing inertial support for extended periods during frequency response, thereby improving the system's frequency stability.
[0006] This invention is achieved through the following technical solution:
[0007] This invention relates to a wind turbine frequency regulation method based on virtual inertia control. The method calculates the first power correction amount of the wind turbine based on ① the actual frequency change rate of the system and the difference between the system frequency and the reference frequency; calculates the second power correction amount of the wind turbine based on ② the change in wind turbine speed; and obtains the reference power based on the wind turbine speed through a maximum power point tracking control strategy using ③ the collected wind turbine speed, thereby obtaining the desired active power output of the wind turbine. Simultaneously, the method calculates the additional value of the wind turbine pitch angle based on the difference between the measured system frequency and the reference frequency, and calculates the optimized wind turbine pitch angle using the additional value and the current wind turbine pitch angle. Finally, the wind turbine control system executes the method to obtain the desired active power output of the wind turbine after the power control and pitch angle control processes, thus achieving frequency regulation.
[0008] The first power correction amount is based on the collected system measurement frequency f. mea After differentiation and low-pass filtering, the gain coefficient K is applied. d Simultaneously, the system measurement frequency f collected will be... mea With reference frequency f ref After calculating the difference and performing amplitude limiting, the proportional gain coefficient K is applied. p The result was as follows:
[0009] The second power correction amount is based on the collected fan speed ω. w After differentiation and low-pass filtering, the speed differential control coefficient K is applied. ω Specifically, the results are as follows:
[0010] The wind turbine is expected to output active power P e =P ref +ΔP1-ΔP2, where: P refThis refers to the active power of the wind turbine in maximum power point tracking mode, which is obtained by using the maximum power point tracking control strategy based on the collected wind turbine speed.
[0011] The optimized fan blade pitch angle β1 is based on the collected system measurement frequency f. mea With reference frequency f ref After calculating the difference and performing amplitude limiting, the proportional gain coefficient K is applied. p Then, the gain coefficient K is further applied. β The difference between the current and the previous impeller pitch angles is obtained as follows: β1 = β - K p K β (f ref -f mea ).
[0012] This invention relates to a system for implementing the above method, comprising: a frequency response control unit, a speed response control unit, and a pitch angle control unit, wherein: the frequency response control unit measures the frequency f according to the system. mea The information is processed by differentiating the frequency deviation, then low-pass filtering is applied to the differentiated signal, and finally a gain coefficient K is applied to the filtered signal. d Simultaneously, the difference between the measured frequency and the reference frequency is calculated, the result of which is then amplitude-limited, and finally the proportional gain coefficient K is applied. p After the signal is limited, the power correction amount ΔP1 of the wind turbine is obtained; the speed response control unit uses the wind turbine speed ω w As the input, the fan speed is first differentiated, then the differentiated signal is low-pass filtered, and the speed differential control coefficient K is applied. ω The power correction ΔP2 of the wind turbine is obtained from the differentiated rotational speed; the pitch angle control unit limits the input frequency change based on the frequency change information, and then applies the gain coefficient K. β Upon receiving the speed-limited signal, the corrected pitch angle β1 is obtained. Finally, the obtained power corrections ΔP1 and ΔP2, along with the corrected pitch angle β1, are transmitted to the wind turbine's control system. The control system integrates all corrections and adjusts the turbine output. Technical effect
[0013] This invention integrates three influencing factors—system frequency, turbine speed, and turbine pitch angle—to derive a virtual inertia control method for wind turbines, incorporating power control and pitch angle control mechanisms. The desired active power output of the wind turbine is obtained by adjusting the reference output power and pitch angle. Compared to existing technologies, this invention possesses virtual inertia characteristics, providing inertia support to the system during disturbances, thereby enhancing the system's anti-disturbance capabilities and ensuring its safe and stable operation. Attached Figure Description
[0014] Figure 1This is a flowchart of the present invention;
[0015] Figure 2 A comparison of the system's frequency response under sudden load increases;
[0016] Figure 3 A comparison of the output characteristics of wind turbine units under sudden load increases;
[0017] Figure 4 A comparison of wind turbine speed curves during a sudden load increase. Detailed Implementation
[0018] This embodiment takes a permanent magnet direct-drive wind turbine as an example. An IEEE 3-machine 9-bus simulation model was built using PSCAD / EMTDC simulation software. In this simulation system, the initial frequency is 50Hz, the selected wind speed scenario is a constant wind speed of 12m / s, and the power deficit is set to a 10% load surge at t=50s. The frequency change curve of the bus where the load is located is measured. The following methods are used... Figure 1 The wind turbine frequency regulation method based on virtual inertia control shown above calculates the first power correction amount of the wind turbine based on the changes in the system measurement frequency collected by ① and the difference between it and the reference frequency; calculates the second power correction amount of the wind turbine based on the changes in the wind turbine speed collected by ②; and obtains the reference power based on the wind turbine speed collected by ③ through a maximum power point tracking control strategy, thereby obtaining the actual active power output of the wind turbine. At the same time, the additional value of the wind turbine pitch angle is obtained based on the difference between the collected system measurement frequency and the reference frequency. The additional value is then used to calculate the wind turbine pitch angle after optimization by the additional frequency control link. Finally, the wind turbine control system executes the method to obtain the expected active power output of the wind turbine after the power control link and the pitch angle control link, thus realizing frequency regulation.
[0019] like Figure 2 As shown, the frequency response curves of the system under sudden load increase are compared. When the wind turbine does not have an additional virtual inertia control, the frequency deviation is the largest, with the lowest point being 49.557Hz. After adding the virtual inertia control, the lowest frequency point increases to 49.593Hz, the maximum frequency deviation decreases from 0.443Hz to 0.407Hz, and the maximum frequency change rate of the system decreases from 0.0981Hz / s to 0.0855Hz / s, indicating that the inertia response performance of the system is better.
[0020] like Figure 3 The figure shows the characteristics of the active power output of the wind turbine after a sudden load increase. As can be seen from the figure, without the virtual inertia control element, the wind turbine output remains basically constant when the system experiences a power deficit. When the virtual inertia control element is added, the wind turbine output begins to increase after 50 seconds, and at this time, the power output of the wind turbine increases along with the decrease in wind turbine speed.
[0021] like Figure 4 The figure shows the wind turbine speed curves under different control strategies after a sudden load increase. When the turbine is in MPPT mode, the turbine speed is basically stable at 1.0 pu. When a power deficit occurs in the system after 50 seconds, the speed remains unchanged, and no additional power is generated. In the virtual inertia control strategy, after a power deficit occurs in the system after 50 seconds, the turbine speed begins to decrease, reaching a minimum of approximately 0.85 pu. Subsequently, due to the inertia control stage, the additional power generated by the turbine decreases, and the speed gradually increases. After the system frequency response stage ends, the turbine speed returns to the initial startup state, first increasing and then gradually recovering to a stable state of 1.0 pu.
[0022] Compared with existing technologies, this method adds virtual inertia control based on system frequency, turbine speed and turbine pitch angle to the wind turbine control stage. This allows the wind turbine to have virtual inertia, enabling it to respond to system frequency changes and participate in grid frequency regulation when the system experiences power deficit. This increases the output power of the wind turbine, thereby increasing the minimum frequency point, reducing the frequency change rate, and making the system's frequency response capability better and frequency stability stronger.
[0023] The above-described specific implementations can be partially adjusted by those skilled in the art in different ways without departing from the principles and purpose of the present invention. The scope of protection of the present invention is defined by the claims and is not limited to the above-described specific implementations. All implementation schemes within the scope of the claims are bound by the present invention.
Claims
1. A frequency regulation method for wind turbine generators based on virtual inertia control, characterized in that, The first power correction of the wind turbine is calculated based on the changes in the system measurement frequency collected in ① and its difference from the reference frequency. The second power correction of the wind turbine is calculated based on the changes in the wind turbine speed collected in ②. The reference power is obtained through the maximum power point tracking control strategy based on the wind turbine speed collected in ③, and then the actual active power output of the wind turbine is obtained. At the same time, the additional value of the wind turbine pitch angle is obtained based on the difference between the collected system measurement frequency and the reference frequency. The additional value is calculated with the current wind turbine pitch angle to obtain the wind turbine pitch angle after optimization by the additional frequency control link. Finally, the wind turbine control system executes the calculation to obtain the expected active power output of the wind turbine after the power control link and the pitch angle control link, thus realizing frequency regulation.
2. The wind turbine frequency regulation method based on virtual inertia control according to claim 1, characterized in that, The first power correction amount is based on the collected system measurement frequency f. mea After differentiation and low-pass filtering, the gain coefficient K is applied. d Simultaneously, the system measurement frequency f collected will be... mea With reference frequency f ref After calculating the difference and performing amplitude limiting, the proportional gain coefficient K is applied. p The result was as follows:
3. The wind turbine frequency regulation method based on virtual inertia control according to claim 1, characterized in that, The second power correction amount is based on the collected fan speed ω. w After differentiation and low-pass filtering, the speed differential control coefficient K is applied. ω Specifically, the results are as follows:
4. The wind turbine frequency regulation method based on virtual inertia control according to claim 1, characterized in that, The wind turbine is expected to output active power P e =P ref +ΔP1-ΔP2, where: P ref This refers to the active power of the wind turbine in maximum power point tracking mode, which is obtained by using the maximum power point tracking control strategy based on the collected wind turbine speed.
5. The wind turbine frequency regulation method based on virtual inertia control according to claim 1, characterized in that, The optimized fan blade pitch angle β1 is based on the collected system measurement frequency f. mea With reference frequency f ref After calculating the difference and performing amplitude limiting, the proportional gain coefficient K is applied. p Then, the gain coefficient K is further applied. β The difference between the current and the previous impeller pitch angles is obtained as follows: β1 = β - K p K β (f ref -f mea ).
6. A wind turbine frequency regulation system based on virtual inertia control implementing the method of any one of claims 1-5, characterized in that, include: The system comprises a frequency response control unit, a speed response control unit, and a pitch angle control unit, wherein the frequency response control unit operates based on the system's measured frequency f. mea The information is processed by differentiating the frequency deviation, then low-pass filtering is applied to the differentiated signal, and finally a gain coefficient K is applied to the filtered signal. d Simultaneously, the difference between the measured frequency and the reference frequency is calculated, the difference result is limited, and then the proportional gain coefficient K is applied. p After the signal is limited, the power correction amount ΔP1 of the wind turbine is obtained; the speed response control unit uses the wind turbine speed ω w As the input, the fan speed is first differentiated, then the differentiated signal is low-pass filtered, and the speed differential control coefficient K is applied. ω The power correction ΔP2 of the wind turbine is obtained from the differentiated rotational speed; the pitch angle control unit limits the input frequency change based on the frequency change information, and then applies the gain coefficient K. β Upon receiving the speed-limited signal, the corrected pitch angle β1 is obtained. Finally, the obtained power corrections ΔP1 and ΔP2, along with the corrected pitch angle β1, are transmitted to the wind turbine control system. The control system integrates all corrections and adjusts the turbine output.