Double-fed wind power grid-connected system low-frequency oscillation suppression method and system and medium

Abstract

The invention provides a doubly-fed wind power grid-connected system low-frequency oscillation suppression method, which comprises the following steps of: respectively installing rotating speed sensors on a wind turbine and a doubly-fed wind turbine generator, and determining an angular rotating speed difference between the wind turbine and the doubly-fed wind turbine generator; determining an angular velocity difference increment during the low-frequency oscillation period of the doubly-fed wind power grid-connected system; and designing an additional power system stabilizer, inputting the angular velocity difference increment into the additional power system stabilizer, and superposing the output of the additional power system stabilizer on an active power control link of a doubly-fed unit rotor side converter, so that the low-frequency oscillation of the doubly-fed wind power grid-connected system can be suppressed. From the perspective of the doubly-fed wind turbine generator, the designed additional stabilizer is simple in structure, low-frequency oscillation of output power of the DFIG can be effectively restrained, dispatching of output of a power system unit is not needed, introduction of a new oscillation mode is avoided, and stable operation of the doubly-fed wind turbine generator merged into a power network is guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of wind power generation, and in particular to a method, system and medium for suppressing low-frequency oscillation of a double-fed wind power grid-connected system. Background Art

[0002] In order to promote the energy revolution and build a new energy system, renewable energy represented by wind energy is gradually replacing traditional fossil energy, and wind power generation accounts for an increasingly higher proportion in the power system. At the same time, the doubly-fed wind power generation system controls the frequency, phase and amplitude of the rotor current through the excitation converter, and then indirectly controls the output power on the stator side. It has the characteristics of a wide speed regulation range, a small rotor excitation converter capacity, and power decoupling control. It has become the mainstream generator type in wind farms. However, when the wind speed of the wind farm changes suddenly or is disturbed by the outside world, the low-frequency oscillation problem caused by the double mass blocks of the doubly-fed wind turbine will affect the output power of the wind farm, resulting in low-frequency oscillation of the power network that is strongly coupled with the wind farm. And due to the power electronics of the new power system, the inertia and damping level of the power system are decreasing, which will make this problem increasingly prominent.

[0003] In order to suppress the low-frequency oscillation caused by the integration of the doubly-fed wind power system into the power grid, some scholars have studied the method of using load to suppress oscillation, but the suppression method based on load regulation is difficult to ensure the real-time suppression of low-frequency oscillation after a fault occurs; some researchers have also proposed to design an additional damping controller on the wind farm active control loop and the photovoltaic power station controller, and suppress the DFIG low-frequency oscillation by controlling the output of the photovoltaic power station. However, this method is more complex to control and is limited to the wind-solar combined system, which may introduce new oscillation modes in the system. Therefore, in order to achieve the safe, stable and economical operation of the wind power grid-connected system, designing an additional power system stabilizer for the doubly-fed wind power grid-connected system, and then suppressing the output power fluctuation of the DFIG itself is the ultimate solution.

[0004] At present, there are some solutions to the study of low-frequency oscillation suppression strategies for doubly fed wind power grid-connected systems, and the following literature has been published: (1) Y. Suxiang, L. Haoming. Additional damping torque control of DFIG-based wind turbine considering the three-mass shaft model [J]. International Journal of Power and Energy Systems, 2021, 41 (4): 245-251. (2) Liu Xinyu, Wang Sen, Zeng Long, et al. Adaptive additional control strategy for doubly fed wind farms to suppress low-frequency oscillations in the power grid [J]. Journal of Shanghai Jiaotong University, 2023, 57 (9): 1156-1164. Among them, literature (1) is based on the three-mass block model, considering the torsional vibration of the wind turbine and the DFIG connection shaft, and proposes a method of using an additional damping torque controller to suppress low-frequency oscillations by using the modal decoupling analysis method. This method effectively suppresses the oscillation of the wind turbine output torque and the DFIG rotor speed, and accelerates the oscillation recovery process. However, the dual-mass model is more widely used in actual doubly fed wind power systems, and the effectiveness of this scheme has not been verified under the dual-mass model. Reference (2) designed a rotor flux controller and proposed an adaptive additional damping control method based on rotor flux deviation. When low-frequency oscillation occurs in the system, this method can quickly adjust the DFIG output active power and suppress the low-frequency oscillation of the system. However, this method increases the complexity of the control system, and the parameters of the rotor flux controller have a great influence on the adaptive additional damping control. The reasonable design of the rotor flux controller parameters is not discussed. Summary of the invention

[0005] In view of the problems existing in the prior art, a method, system and medium for suppressing low-frequency oscillation of a doubly-fed wind power grid-connected system are provided. An additional power system stabilizer with the incremental angular velocity difference between the wind turbine and the doubly-fed unit rotor as input is introduced into the active power control link of the doubly-fed wind turbine rotor-side converter to improve the grid-connected stability of the doubly-fed induction wind turbine.

[0006] The first aspect of the present invention provides a method for suppressing low-frequency oscillation of a doubly-fed wind power grid-connected system, comprising:

[0007] Install speed sensors on the wind turbine and the doubly-fed wind turbine generator set respectively to determine the angular speed difference between the wind turbine and the doubly-fed wind turbine generator set rotors;

[0008] Determining the angular velocity difference increment during low frequency oscillation of the doubly-fed wind power grid-connected system;

[0009] The angular velocity difference increment is input into an additional power system stabilizer, and the output of the additional power system stabilizer is superimposed on the active power control link of the rotor-side converter of the doubly-fed unit, so as to suppress the low-frequency oscillation of the doubly-fed wind power grid-connected system.

[0010] As a preferred solution, the working process of the additional power system stabilizer includes:

[0011] Measure the low-frequency oscillation frequency of the rotor speed of the doubly-fed wind turbine under small disturbance conditions;

[0012] Establishing the transfer function between the electromagnetic torque increment and the active power increment;

[0013] Determine the amplitude and phase characteristics near the low frequency oscillation frequency based on the transfer function;

[0014] Setting an additional stabilizer transfer function according to amplitude and phase characteristics;

[0015] The angular velocity difference increment is superimposed on the transfer function of the additional stabilizer as the output of the additional stabilizer.

[0016] As a preferred solution, the process of measuring the low-frequency oscillation frequency of the rotor speed of the doubly-fed wind turbine set under small disturbance conditions includes: establishing a time domain simulation model of the doubly-fed wind power grid-connected system without an additional stabilizer, and after setting a small disturbance, measuring the low-frequency oscillation frequency of the rotor speed of the doubly-fed wind turbine set.

[0017] As a preferred solution, the setting of the additional stabilizer transfer function according to the amplitude and phase characteristics specifically includes:

[0018] Determine the phase compensation, gain and DC isolation parameters of the additional power system stabilizer, and combine the determined amplitude and phase characteristics to obtain the additional stabilizer transfer function:

[0019]

[0020] Among them, s is the Laplace operator, K Pc , K Pi , K Pd They are phase compensation term, DC isolation term, gain term, T P1 , T P2 are their lead / lag correction time constants, T Pw is the time constant of the DC isolation link.

[0021] As a preferred solution, the output of the additional stabilizer is P g_ref =K P ·Δω, where Δω is the angular velocity difference increment.

[0022] A second aspect of the present invention provides a system including a memory and a processor, wherein the memory stores a computer program that can be loaded by the processor and executes the method for suppressing low-frequency oscillation of a doubly-fed wind power grid-connected system according to the first aspect.

[0023] A third aspect of the present invention provides a computer-readable storage medium having computer program instructions stored thereon, which, when executed by a processor, are used to implement a process corresponding to the method for suppressing low-frequency oscillations in a doubly-fed wind power grid-connected system described in the first aspect.

[0024] Compared with the prior art, the beneficial effects of adopting the above technical solution are as follows: the additional stabilizer designed by the present invention from the perspective of the doubly-fed wind turbine itself has a simple structure and can effectively suppress the low-frequency oscillation of the DFIG's own output power, without the need to dispatch the output of the power system units, while avoiding the introduction of new oscillation modes, thereby ensuring the stable operation of the doubly-fed wind power system when it is integrated into the power grid. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a flow chart of the low-frequency oscillation suppression method for the doubly-fed wind power grid-connected system proposed by the present invention.

[0026] Figure 2 The figure is a block diagram of active power-current loop control of a rotor-side converter including an additional power system stabilizer in one embodiment of the present invention.

[0027] Figure 3 This is a low-frequency oscillation simulation waveform diagram before and after installing an additional power system stabilizer in one embodiment of the present invention. DETAILED DESCRIPTION

[0028] Embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar modules or modules with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be construed as limitations on the present application. On the contrary, the embodiments of the present application include all changes, modifications and equivalents that fall within the spirit and connotation of the appended claims.

[0029] Using the complex torque analysis method, it can be known that the low-frequency oscillation damping ratio of the doubly-fed induction wind power system is greatly affected by the electrical damping torque coefficient. Based on this, the embodiment of the present invention proposes a method for suppressing low-frequency oscillations in a doubly-fed wind power grid-connected system. By introducing an additional power system stabilizer with the incremental angular velocity difference between the wind turbine and the doubly-fed unit as input into the active power control link of the rotor-side converter of the doubly-fed wind turbine unit, the low-frequency oscillation damping ratio of the doubly-fed wind power grid-connected system can be effectively improved, and finally the small-disturbance stability of the doubly-fed wind power grid-connected system can be improved. Please refer to Figure 1 , the specific plan is as follows:

[0030] Step 1: Install speed sensors on the wind turbine and the doubly-fed wind turbine generator set respectively to determine the angular speed difference between the wind turbine and the doubly-fed wind turbine generator set rotors.

[0031] In this embodiment, the speed sensors are installed on the wind turbine and the double-fed wind turbine generator set to determine the wind turbine speed ω in real time. t 、DFIG (Doubly fed Induction Generator) rotor speed ω r At this time, the angular velocity difference ω between the wind turbine and DFIG rotor can be calculated Δ＝ ω t- ω r .

[0032] Step 2: during the period of low-frequency oscillation in the doubly-fed wind power grid-connected system, determine the angular velocity difference increment.

[0033] Since this method mainly realizes the suppression of low-frequency oscillation, during the period of low-frequency oscillation in the double-fed wind power grid-connected system, the angular velocity difference at this time is calculated by the installed speed sensor, and then the angular velocity difference increment Δω compared with the period when no low-frequency oscillation occurs is calculated. Δ .

[0034] Step 3: Increase the angular velocity difference by Δω Δ The additional power system stabilizer is inputted into the additional power system stabilizer, and the output P of the additional power system stabilizer is g_ref By superimposing it on the active power control link of the rotor-side converter of the doubly-fed unit, the low-frequency oscillation of the doubly-fed wind power grid-connected system can be suppressed.

[0035] Specifically, the design and process of the additional power system stabilizer are provided in this embodiment:

[0036] Firstly, a time domain simulation model of the doubly-fed wind power grid-connected system without an additional stabilizer is established. After setting a small disturbance, the low-frequency oscillation frequency ω of the rotor speed of the doubly-fed wind turbine is measured. osc .

[0037] Then establish the electromagnetic torque increment ΔT e and the active power increment ΔP g The transfer function G p .

[0038] Then, the low-frequency oscillation frequency ω is determined according to the transfer function. osc The amplitude and phase characteristics nearby.

[0039] Then, according to the determined amplitude-phase characteristics and the power system stabilizer parameter setting formula, the phase compensation, gain and DC isolation link parameters of the additional power system stabilizer are determined, and the transfer function of the additional stabilizer is further determined, as follows:

[0040]

[0041] Among them, s is the Laplace operator, K Pc , K Pi , K Pd They are phase compensation term, DC isolation term, gain term, T P1 、T P2 are their lead / lag correction time constants, T Pw is the time constant of the DC isolation link.

[0042] Finally, based on the transfer function of the additional stabilizer and the input angular velocity increment Δω Δ , we can get the output P of the additional stabilizer g_ref , that is, P g_ref =K P ·Δω.

[0043] like Figure 2 As shown in the figure, the additional power system stabilizer is introduced into the active power control link of the rotor-side converter, so that the controller output P g_ref The active output P of the doubly-fed wind turbine g , Unit active power command Participate in the PI control of the rotor-side converter active power outer loop, and then obtain the new current reference value of the current inner loop Final DFIG rotor current reference value With the actual value i rq Together they participate in the PI control of the inner current loop of the rotor-side converter.

[0044] Figure 3 The damping ratio and system simulation waveform corresponding to the low-frequency oscillation mode before and after the control strategy proposed by the present invention are displayed. Figure 3 It can be seen that when a three-phase symmetrical short-circuit fault occurs in the system, by adopting the low-frequency oscillation suppression method proposed in the present invention, the damping ratio corresponding to the low-frequency oscillation mode of the DFIG wind power system increases from 0.0280 to 0.1123, the low-frequency oscillation damping of the double-fed induction wind power system is improved to a certain extent, and the wind turbine speed ω t , double-fed unit rotor speed ω r , and the transition time of the double-mass torsion angle θ from being disturbed to restoring the steady state is significantly reduced, and at the same time, the active power oscillation of the double-fed grid-connected output is significantly suppressed. The method of the present invention achieves the expected effect.

[0045] In summary, by adopting the suppression method proposed in the present invention, utilizing the coupling relationship between the output active power increment of the doubly-fed unit and the electromagnetic torque increment of the unit, introducing an additional power system stabilizer with the rotor angular velocity difference increment as input in the active power control link of the rotor-side converter, and reasonably setting the parameters of each link according to the oscillation information, the electrical damping coefficient of the low-frequency oscillation mode of the doubly-fed wind turbine unit can be reduced, the low-frequency oscillation mode damping can be improved, and the small-disturbance stability of the doubly-fed wind power grid-connected system can be ensured.

[0046] In particular, according to an embodiment of the present application, the process described above with reference to the flowchart can be implemented as a computer software program. For example, an embodiment of the present application includes a computer program product, which includes a computer program carried on a computer readable medium, and the computer program includes a program code for executing the method shown in the flowchart.

[0047] It should be noted that the computer-readable medium shown in the embodiment of the present application may be a computer-readable signal medium or a computer-readable storage medium or any combination of the above two. The computer-readable storage medium may be, for example, - but not limited to - an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, device or device, or any combination of the above. More specific examples of computer-readable storage media may include, but are not limited to: an electrical connection with one or more wires, a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM), a flash memory, an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the above. In the present application, a computer-readable storage medium may be any tangible medium containing or storing a program, which may be used by an instruction execution system, device or device or used in combination with it. In the present application, a computer-readable signal medium may include a data signal propagated in a baseband or as part of a carrier wave, wherein a computer-readable program code is carried. Such propagated data signals may take a variety of forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination of the above. Computer-readable signal media may also be any computer-readable medium other than computer-readable storage media, which may send, propagate, or transmit programs for use by or in conjunction with an instruction execution system, apparatus, or device. The program code contained on the computer-readable medium may be transmitted using any appropriate medium, including but not limited to: wireless, wired, etc., or any suitable combination of the above.

[0048] The flowchart and block diagram in the accompanying drawings illustrate the possible architecture, functions and operations of the system, method and computer program product according to various embodiments of the present application. Wherein, each box in the flowchart or block diagram can represent a module, a program segment, or a part of the code, and the above-mentioned module, program segment, or a part of the code contains one or more executable instructions for realizing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the box can also occur in a different order from the order marked in the accompanying drawings. For example, two boxes represented in succession can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each box in the block diagram or flowchart, and the combination of boxes in the block diagram or flowchart can be implemented with a dedicated hardware-based system that performs a specified function or operation, or can be implemented with a combination of dedicated hardware and computer instructions.

[0049] The units involved in the embodiments described in this application may be implemented by software or hardware, and the units described may also be set in a processor. The names of these units do not, in some cases, constitute limitations on the units themselves.

[0050] As another aspect, the present application further provides a computer program product or a computer program, the computer program product or the computer program including computer instructions, the computer instructions being stored in a computer-readable storage medium. A processor of a computer device reads the computer instructions from the computer-readable storage medium, and the processor executes the computer instructions, so that the computer device executes the method for suppressing low-frequency oscillation of a double-fed wind power grid-connected system described in the above embodiment.

[0051] As another aspect, the present application also provides a computer-readable medium, which may be included in the electronic device described in the above embodiment; or may exist independently without being assembled into the electronic device. The above computer-readable medium carries one or more programs, and when the above one or more programs are executed by an electronic device, the electronic device implements the low-frequency oscillation suppression method of the double-fed wind power grid-connected system described in the above embodiment.

[0052] It should be noted that, although several modules or units of the equipment for action execution are mentioned in the above detailed description, this division is not mandatory. In fact, according to the embodiments of the present application, the features and functions of two or more modules or units described above can be embodied in one module or unit. On the contrary, the features and functions of one module or unit described above can be further divided into being embodied by multiple modules or units.

[0053] Through the description of the above implementation methods, it is easy for those skilled in the art to understand that the example implementation methods described here can be implemented by software or by combining software with necessary hardware. Therefore, the technical solution according to the implementation methods of the present application can be embodied in the form of a software product, which can be stored in a non-volatile storage medium (which can be a CD-ROM, a USB flash drive, a mobile hard disk, etc.) or on a network, and includes several instructions to enable a computing device (which can be a personal computer, a server, a touch terminal, or a network device, etc.) to execute the method according to the implementation methods of the present application.

[0054] For those skilled in the art, the specific meanings of the above terms in the present invention can be understood in specific situations; the drawings in the embodiments are used to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0055] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A method for suppressing low-frequency oscillation of a double-fed wind power grid-connected system, characterized in that: include: Install speed sensors on the wind turbine and the doubly-fed wind turbine generator set respectively to determine the angular speed difference between the wind turbine and the doubly-fed wind turbine generator set rotors; Determining the angular velocity difference increment during low frequency oscillation of the doubly-fed wind power grid-connected system; An additional power system stabilizer is designed, and the angular velocity difference increment is input into the additional power system stabilizer. The output of the additional power system stabilizer is then superimposed on the active power control link of the rotor-side converter of the doubly-fed unit, so as to suppress the low-frequency oscillation of the doubly-fed wind power grid-connected system.

2. The method for suppressing low-frequency oscillation of a doubly-fed wind power grid-connected system according to claim 1, characterized in that: The design process of the additional power system stabilizer includes: Measure the low-frequency oscillation frequency of the rotor speed of the doubly-fed wind turbine under small disturbance conditions; Establishing the transfer function between the electromagnetic torque increment and the active power increment; Determine the amplitude and phase characteristics near the low frequency oscillation frequency based on the transfer function; Setting an additional stabilizer transfer function according to amplitude and phase characteristics; The angular velocity difference increment is superimposed on the transfer function of the additional stabilizer as the output of the additional stabilizer.

3. The method for suppressing low-frequency oscillation of a doubly-fed wind power grid-connected system according to claim 2, characterized in that: The process of measuring the low-frequency oscillation frequency of the rotor speed of the doubly-fed wind turbine under small disturbance conditions includes: establishing a time domain simulation model of the doubly-fed wind power grid-connected system without an additional stabilizer, and measuring the low-frequency oscillation frequency of the rotor speed of the doubly-fed wind turbine after setting a small disturbance.

4. The method for suppressing low-frequency oscillation of a doubly-fed wind power grid-connected system according to claim 3, characterized in that: The additional stabilizer transfer function is set according to the amplitude and phase characteristics, specifically comprising: Determine the phase compensation, gain and DC isolation parameters of the additional power system stabilizer, and combine the determined amplitude and phase characteristics to obtain the additional stabilizer transfer function: Among them, s is the Laplace operator, K Pc , K Pi , K Pd They are phase compensation term, DC isolation term, gain term, T P1 , T P2 are their lead / lag correction time constants, T Pw is the time constant of the DC isolation link.

5. The method for suppressing low-frequency oscillation of a doubly-fed wind power grid-connected system according to claim 4, characterized in that: The output of the additional stabilizer is P g_ref =K P ·Δω, where Δω is the angular velocity difference increment.

6. A system, characterized in that: It comprises a memory and a processor, wherein the memory stores a computer program that can be loaded by the processor and executes the method for suppressing low-frequency oscillation of a doubly-fed wind power grid-connected system according to any one of claims 1 to 5.

7. A computer-readable storage medium having computer program instructions stored thereon, characterized in that: When the program instructions are executed by the processor, they are used to implement the process corresponding to the method for suppressing low-frequency oscillation of a doubly-fed wind power grid-connected system according to any one of claims 1 to 5.

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