Dynamic power tracking-based virtual inertia control method for doubly-fed wind turbine generator

Abstract

The invention belongs to the technical field of double-fed wind turbine generator virtual quantity regulation and control, and particularly relates to a double-fed wind turbine generator virtual inertia control method based on dynamic power tracking. Comprising the following steps: compiling a maximum power point tracking database under different wind speed conditions and different fan rotating speed conditions; the frequency change amplitude of the system is detected, and MPPT curve adjustment is carried out when the frequency drops or climbs and exceeds a set per unit value; when the system frequency drops, the MPPT curve is moved to the left side, the electromagnetic power output of the generator set is increased, and the kinetic energy of a rotor is released to participate in inertial frequency response; when the system frequency climbs, the MPPT curve is moved to the right side, electromagnetic power output of the generator set is reduced, and electric energy is absorbed and converted into rotor kinetic energy to participate in inertial frequency response; and after the inertial response is completed, the fan gradually returns to the optimal MPPT output point at the current wind speed. The inertia response link is added in the control module of the DFIG wind turbine generator, so that the fan can quickly respond to the system frequency change.

Description

Technical Field

[0001] The present invention belongs to the technical field of virtual quantity control of a doubly-fed wind turbine generator set, and in particular relates to a virtual inertia control method of a doubly-fed wind turbine generator set based on dynamic power tracking. Background Art

[0002] As the global demand for renewable energy continues to grow, wind power generation has been widely used as a clean and sustainable form of energy. In particular, the doubly-fed induction generator (DFIG) has become the mainstream configuration of wind turbines due to its flexible power control and high energy conversion efficiency. However, with the increase in wind power penetration, the frequency stability problem of the power grid has become increasingly prominent.

[0003] In traditional power systems, synchronous generators rely on the inertia of their mechanical rotors to provide a natural frequency response. When the grid load changes suddenly or fails, the synchronous generator can temporarily provide or absorb energy through its rotational kinetic energy, thereby slowing down the frequency change. However, wind turbines, especially those based on DFIG, lack natural inertial response capabilities because their rotor speed is not synchronized with the synchronous speed of the grid. This results in wind turbines being unable to effectively support and stabilize the grid frequency like synchronous generators when the grid frequency fluctuates.

[0004] Although DFIG wind turbines lack the inherent inertial response capability of synchronous turbines, the rotational kinetic energy contained in their rotors is actually a potential inertial resource. The rotors of wind turbines usually have a large moment of inertia, especially at high wind speeds, when the rotors have a richer kinetic energy reserve. Therefore, if this part of the rotational kinetic energy can be utilized through appropriate control strategies, DFIG wind turbines can also simulate the inertial response of synchronous turbines to a certain extent.

[0005] To solve the above problems, researchers proposed the concept of "virtual inertia" control. Virtual inertia control aims to simulate the inertial response behavior of synchronous generators by enabling wind turbines to release or absorb rotor kinetic energy when the grid frequency changes through control algorithms. This method can not only enhance the frequency stability of the grid, but also improve the quality and reliability of wind power grid connection.

[0006] However, traditional virtual inertia control methods usually face the following challenges: First, the inertia response time lags. Due to the complex control links of DFIG wind turbines, the response speed is relatively slow, which may lead to the inability to respond to frequency fluctuations in a timely manner. Second, the inertia size is difficult to adjust dynamically. The virtual inertia value in traditional methods is often fixed, and the inertia size cannot be dynamically adjusted according to the actual needs of the power grid. Third, the control accuracy is insufficient. Under different wind speed and load conditions, the accuracy and effect of traditional inertia control strategies may not be sufficient to meet the requirements of power grid stability. Summary of the invention

[0007] The present invention proposes a virtual inertia control method for a doubly-fed wind turbine based on dynamic power tracking. By adding an inertia response link to the control module of the DFIG wind turbine, the wind turbine can quickly respond to system frequency changes. In addition, by introducing a dynamic power tracking coefficient into the control system of the DFIG wind turbine, flexible control of the inertia response capability of the wind turbine can be achieved.

[0008] In order to solve the above technical problems, the technical solution adopted by the present invention includes: A virtual inertia control method for a doubly-fed wind turbine generator system based on dynamic power tracking comprises the following steps: S1. Compile a maximum power point tracking database under different wind speed conditions and different wind turbine speed conditions; S2, detecting the amplitude of the system frequency change, when the system frequency drops and the amplitude exceeds the per-unit value, jump to step S31, when the system frequency rises and the amplitude exceeds the per-unit value, jump to step S41; S31. When the system frequency drops, the maximum power point tracking curve is moved to the left, the MPPT operating point of the wind turbine at the current wind speed is increased, the output reference value at this time is tracked, and the electromagnetic power output of the generator set is increased to perform inertial frequency response; S32, during the frequency modulation process, the electromagnetic power is increased, the mechanical power remains in the state before the adjustment in step S31, and the rotor change rate of the wind turbine is less than 0; the rotor speed is gradually reduced until the electromagnetic power and the mechanical power are balanced again; S41. When the system frequency rises, the maximum power point tracking curve is moved to the right, the MPPT operating point of the wind turbine at the current wind speed decreases, the output reference value at this time is tracked, and the electromagnetic power output of the generator set is reduced to perform inertial frequency response; S42, during the frequency modulation process, the electromagnetic power is reduced, the mechanical power remains in the state before the adjustment in step S41, and the rotor change rate of the wind turbine is greater than 0; the rotor speed gradually increases until the electromagnetic power and the mechanical power reach a balance again; S5. After the inertial response process is completed, the fan is at a non-optimal operating point, and the fan output reference value is reset to the MPPT output value at the current wind speed; through the recovery of the fan speed, the fan gradually returns to the optimal MPPT output point at the current wind speed.

[0009] Furthermore, in the process of steps S31-S32, when the frequency drops, the adjustment of the maximum power point tracking curve is achieved by raising the operating point of the wind turbine from the initial point A to a new reference point B, where the rotor speed of the reference point B is the same as that of the initial point A, and the output power of the reference point B is higher than the output power of the initial point A.

[0010] Furthermore, in the process of steps S41-S42, when the frequency climbs, the adjustment of the maximum power point tracking curve is achieved by lowering the operating point of the wind turbine from the initial point A to a new reference point D, where the rotor speed of the reference point D is the same as that of the initial point A, and the output power of the reference point D is lower than the output power of the initial point A.

[0011] Furthermore, during steps S31-S32, the rotor kinetic energy of the DFIG wind turbine is released to increase the active output and participate in the inertial frequency response of the system; during steps S41-S42, the rotor electrical energy of the DFIG wind turbine is released to reduce the active output and participate in the inertial frequency response of the system.

[0012] Furthermore, during the inertial frequency response of the system, the balance between electromagnetic power and mechanical power is achieved by controlling the rotor speed change of the fan to provide a fast inertial response when the frequency changes.

[0013] Furthermore, the dynamic power tracking coefficient is used to flexibly adjust the virtual inertia coefficient to improve the accuracy and efficiency of the inertial response.

[0014] Furthermore, the control system of the wind turbine generator system includes a sensor for detecting frequency changes, a controller for dynamically adjusting the MPPT curve, and a power conversion module for executing inertial response.

[0015] The beneficial effects of the present invention are: The present invention relates to a virtual inertia control method of a doubly-fed wind turbine set based on dynamic power tracking, which aims to enhance the frequency stability of a power grid. The method achieves a fast inertia frequency response by introducing a dynamic power tracking coefficient into the control module of a doubly-fed induction generator (DFIG) wind turbine set. When the power grid frequency fluctuates, the wind turbine control system can adjust the maximum power point tracking (MPPT) curve in real time, thereby releasing or absorbing the rotor kinetic energy to participate in the inertia response, suppressing the frequency drop rate and increasing the lowest point of the frequency drop. Through this method, the wind turbine can automatically return to the optimal operating point after completing the inertia response, thereby ensuring a balance between technical and economic benefits. The present invention has the advantages of real-time response capability, flexible inertia adjustment capability and enhanced frequency stability, and is suitable for the frequency adjustment requirements of power grids with high wind power penetration.

[0016] The method described in the present invention can adjust the power output of the wind turbine in real time when the system frequency changes, thereby achieving rapid frequency response; it has flexible inertia regulation, and through a dynamic power tracking strategy, it can flexibly adjust the virtual inertia coefficient according to the actual needs of the power grid, thereby making the inertia response more accurate and efficient; it enhances frequency stability, and through rapid frequency response and inertia regulation, the method can effectively suppress the system frequency drop rate, increase the lowest point of the frequency drop, and thus enhance the stability of the power grid. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The present invention is a block diagram of a virtual inertia control method for a doubly-fed wind turbine generator system based on dynamic power tracking.

[0018] Figure 2 This is a graph showing the MPPT operation curve changes of the wind turbine generator set of the present invention. DETAILED DESCRIPTION

[0019] In order to better understand the present invention, the content of the present invention is further clearly described below in conjunction with the embodiments and the accompanying drawings, but the protection content of the present invention is not limited to the following embodiments. In the following description, a large number of specific details are provided to provide a more thorough understanding of the present invention. However, it is obvious to those skilled in the art that the present invention can be implemented without one or more of these details.

[0020] See also Figure 1-2 , the purpose of this embodiment is to disclose a virtual inertia control method of a doubly-fed wind turbine generator system based on dynamic power tracking. Figure 1 The block diagram of the virtual inertia control method of the doubly-fed wind turbine generator system based on dynamic power tracking is shown in the figure. The MPPT operation curve of the wind turbine generator system changes as follows: Figure 2 The specific implementation process of this method is as follows.

[0021] A virtual inertia control method for a doubly-fed wind turbine generator system based on dynamic power tracking includes the following steps S1-S5.

[0022] S1. Compile a maximum power point tracking (MPPT) database under different wind speed conditions and different wind turbine speed conditions.

[0023] S2. Detect the change amplitude of the system frequency. When the system frequency drops and the amplitude exceeds the per-unit value of 0.2 Hz, jump to step S31. When the system frequency rises and the amplitude exceeds the per-unit value of 0.2 Hz, jump to step S41.

[0024] S31. When the system frequency drops, the maximum power point tracking (MPPT) curve of the DFIG wind turbine moves to the left, and the MPPT operating point of the wind turbine at the current wind speed increases from point A to point B, tracking the output reference value at this time, thereby reducing the rotor speed and absorbing the rotor kinetic energy from the system into electrical energy, increasing the electromagnetic power output of the generator set for inertial frequency response.

[0025] S32, during the frequency modulation process, the electromagnetic power is immediately increased, the mechanical power remains at point A before the adjustment in step S31, and the rotor change rate of the wind turbine is less than 0; the rotor speed will gradually decrease until Figure 2 At point C, the electromagnetic power and mechanical power are balanced again.

[0026] S41. When the system frequency rises, the maximum power point tracking (MPPT) curve of the DFIG wind turbine moves to the right. The MPPT operating point of the wind turbine at the current wind speed decreases from point A to point D, tracking the output reference value at this time, thereby increasing the rotor speed and absorbing electrical energy from the system into rotor kinetic energy, reducing the electromagnetic power output of the generator set for inertial frequency response; S42, during the frequency modulation process, the electromagnetic power immediately decreases, the mechanical power still maintains the state of point A before the adjustment in step S41, and the rotor change rate of the wind turbine is greater than 0. The rotor speed will gradually increase until the electromagnetic power and mechanical power reach a balance again at point E.

[0027] S5. After the inertial response process is completed, the fan is in a non-optimal operating point, and the fan output reference value will be reset to the MPPT output value at the current wind speed; through the recovery of the fan speed, the fan gradually returns to the optimal MPPT output point A at the current wind speed, achieving optimal operation in terms of technology and economic benefits.

[0028] In the process of steps S31-S32, when the frequency drops, the adjustment of the maximum power point tracking curve is achieved by raising the operating point of the wind turbine from the initial point A to a new reference point B, the rotor speed of the reference point B is the same as that of the initial point A, and the output power of the reference point B is higher than the output power of the initial point A. In the process of steps S41-S42, when the frequency rises, the adjustment of the maximum power point tracking curve is achieved by lowering the operating point of the wind turbine from the initial point A to a new reference point D, the rotor speed of the reference point D is the same as that of the initial point A, and the output power of the reference point D is lower than the output power of the initial point A.

[0029] During the dynamic change process of steps S31-S32, the rotor kinetic energy of the DFIG wind turbine set is released to increase the active output and participate in the inertial frequency response of the system; during the dynamic change process of steps S41-S42, the rotor electrical energy of the DFIG wind turbine set is released to reduce the active output and participate in the inertial frequency response of the system.

[0030] In addition, during the inertial frequency response process of the system, the balance between electromagnetic power and mechanical power is achieved by controlling the rotor speed change of the wind turbine to provide a fast inertial response when the frequency changes. The dynamic power tracking coefficient is used to flexibly adjust the virtual inertia coefficient to improve the accuracy and efficiency of the inertial response. The control system of the wind turbine includes a sensor for detecting frequency changes, a controller for dynamically adjusting the MPPT curve, and a power conversion module for performing inertial response.

[0031] When the per-unit value of the maximum output power at the initial state point A is set to 0.48, the speed of the wind turbine is 9.6 m / s, and the per-unit value is 0.95, when the system frequency drops, the specific implementation process of the method in this embodiment is described as follows.

[0032] A virtual inertia control method for a doubly-fed wind turbine generator system based on dynamic power tracking includes the following adjustment processes S1-S5.

[0033] S1. Compile a maximum power point tracking (MPPT) database under different wind speed conditions and different wind turbine speeds between 6m / s and 14m / s.

[0034] S2. Detect the change amplitude of the system frequency. When the system frequency drops and the amplitude exceeds the per-unit value of 0.3 Hz, jump to step S31. When the system frequency rises and the amplitude exceeds the per-unit value of 0.2 Hz, jump to step S41.

[0035] S31. When the system frequency drops, the maximum power point tracking (MPPT) curve of the DFIG wind turbine moves to the left, and the MPPT operating point of the wind turbine at the current wind speed increases from point A (0.95, 0.48) to point B (0.95, 0.52), tracking the output reference value at this time, thereby reducing the rotor speed and absorbing the rotor kinetic energy from the system into electrical energy, increasing the electromagnetic power output of the generator set for inertial frequency response.

[0036] S32. During the frequency modulation process, the electromagnetic power is immediately increased to the standard value of 0.52, and the mechanical power remains at point A before the adjustment in step 3 (a). The rotor change rate of the wind turbine is less than 0. The rotor speed will gradually decrease until the electromagnetic power and mechanical power reach a balance again at point C (0.82, 0.47).

[0037] During the dynamic change process of step S31-32, the rotor kinetic energy of the DFIG wind turbine is released to increase the active output and participate in the inertial frequency response of the system.

[0038] S5. After the inertial response process is completed, the fan is at a non-optimal operating point, and the fan output reference value will be reset to the MPPT output value at the current wind speed; through the recovery of the speed, the fan gradually returns to point A (0.95, 0.48).

[0039] In this embodiment, the coordinates of the per unit value of the wind turbine rotor speed and output power are point A (0.95, 0.48), point B (0.95, 0.52), and point C (0.82, 0.47), respectively.

[0040] When the per-unit value of the maximum output power at the initial state point A is set to 0.48, the speed of the wind turbine is 9.6 m / s, and the per-unit value is 0.95, when the system frequency climbs, the specific implementation process of the method in this embodiment is described as follows.

[0041] A virtual inertia control method for a doubly-fed wind turbine generator system based on dynamic power tracking includes the following adjustment process: S1. Compile a maximum power point tracking (MPPT) database under different wind speed conditions and different wind turbine speeds between 6m / s and 14m / s.

[0042] S2. Detect the amplitude of the system frequency change. When the system frequency rises and the amplitude is 0.3 Hz, which exceeds the per-unit value of 0.2 Hz, jump to step S41.

[0043] S41. When the system frequency rises, the maximum power point tracking (MPPT) curve of the DFIG wind turbine moves to the right. The MPPT operating point of the wind turbine at the current wind speed drops from point A (0.95, 0.48) to point D (0.95, 0.25), tracking the output reference value at this time, thereby increasing the rotor speed and converting the electrical energy absorbed from the system into rotor kinetic energy, reducing the electromagnetic power output of the generator set for inertial frequency response.

[0044] S42. During the frequency modulation process, the electromagnetic power decreases immediately, while the mechanical power remains at point A (0.95, 0.48) before the adjustment in step 3 (b), and the rotor change rate of the wind turbine is greater than 0. The rotor speed will gradually increase until the electromagnetic power and mechanical power reach a balance again at point E (1.15, 0.4).

[0045] During the dynamic change process of step S41-42, the rotor electrical energy of the DFIG wind turbine is released to reduce the active output and participate in the inertial frequency response of the system.

[0046] S5. After the inertial response process is completed, the fan is at a non-optimal operating point, and the fan output reference value will be reset to the MPPT output value at the current wind speed; through the recovery of the speed, the fan gradually returns to point A (0.95, 0.48).

[0047] In this embodiment, the coordinates of the per unit value of the wind turbine rotor speed and output power are point A (0.95, 0.48), point D (0.95, 0.25), and point E (1.15, 0.4), respectively.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Other modifications or equivalent substitutions made to the technical solution of the present invention by ordinary technicians in the field should be included in the scope of the claims of the present invention as long as they do not depart from the spirit and scope of the technical solution of the present invention.

Claims

1. A virtual inertia control method for a doubly-fed wind turbine generator system based on dynamic power tracking, characterized in that: The following steps are involved: S1. Compile a maximum power point tracking database under different wind speed conditions and different wind turbine speed conditions; S2, detecting the amplitude of the system frequency change, when the system frequency drops and the amplitude exceeds the per-unit value, jump to step S31, when the system frequency rises and the amplitude exceeds the per-unit value, jump to step S41; S31. When the system frequency drops, the maximum power point tracking curve is moved to the left, the MPPT operating point of the wind turbine at the current wind speed is increased, the output reference value at this time is tracked, and the electromagnetic power output of the generator set is increased to perform inertial frequency response; S32, during the frequency modulation process, the electromagnetic power is increased, the mechanical power remains in the state before the adjustment in step S31, and the rotor change rate of the wind turbine is less than 0; The rotor speed gradually decreases until the electromagnetic power and mechanical power are balanced again; S41. When the system frequency rises, the maximum power point tracking curve is moved to the right, the MPPT operating point of the wind turbine at the current wind speed decreases, the output reference value at this time is tracked, and the electromagnetic power output of the generator set is reduced to perform inertial frequency response; S42, during the frequency modulation process, the electromagnetic power is reduced, the mechanical power remains in the state before the adjustment in step S41, and the rotor change rate of the wind turbine generator set is greater than 0; The rotor speed gradually increases until the electromagnetic power and mechanical power are balanced again; S5. After the inertial response process is completed, the fan is at a non-optimal operating point, and the fan output reference value is reset to the MPPT output value at the current wind speed; through the recovery of the fan speed, the fan gradually returns to the optimal MPPT output point at the current wind speed.

2. The virtual inertia control method of a doubly-fed wind turbine generator system based on dynamic power tracking according to claim 1 is characterized in that: During steps S31-S32, when the frequency drops, the adjustment of the maximum power point tracking curve is achieved by raising the operating point of the wind turbine from the initial point A to a new reference point B, where the rotor speed of the reference point B is the same as that of the initial point A, and the output power of the reference point B is higher than the output power of the initial point A.

3. The virtual inertia control method of a doubly-fed wind turbine generator system based on dynamic power tracking according to claim 2 is characterized in that: During steps S41-S42, when the frequency rises, the adjustment of the maximum power point tracking curve is achieved by lowering the operating point of the wind turbine from the initial point A to a new reference point D, where the rotor speed of the reference point D is the same as that of the initial point A, and the output power of the reference point D is lower than the output power of the initial point A.

4. The virtual inertia control method of a doubly-fed wind turbine generator system based on dynamic power tracking according to claim 3 is characterized in that: During steps S31-S32, the rotor kinetic energy of the DFIG wind turbine is released to increase the active output and participate in the inertial frequency response of the system; during steps S41-S42, the rotor electrical energy of the DFIG wind turbine is released to reduce the active output and participate in the inertial frequency response of the system.

5. The virtual inertia control method of a doubly-fed wind turbine generator system based on dynamic power tracking according to claim 4 is characterized in that: During the inertial frequency response of the system, the balance between electromagnetic power and mechanical power is achieved by controlling the rotor speed change of the fan to provide a fast inertial response when the frequency changes.

6. The virtual inertia control method of a doubly-fed wind turbine generator system based on dynamic power tracking according to claim 5, characterized in that: The dynamic power tracking coefficient is used to flexibly adjust the virtual inertia coefficient to improve the accuracy and efficiency of inertial response.

7. A virtual inertia control method for a doubly-fed wind turbine generator system based on dynamic power tracking according to claim 6, characterized in that: The control system of the wind turbine generator system includes a sensor for detecting frequency changes, a controller for dynamically adjusting the MPPT curve, and a power conversion module for performing inertial response.

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