Inertia characterization and active regulation and control method for virtual flux linkage of doubly-fed fan

Abstract

The invention discloses a double-fed fan virtual flux linkage inertia characterization and active regulation and control method, which is based on an electromagnetic transient theory, defines a core parameter of stator flux linkage inertia, and gives a stator flux linkage inertia analytical expression containing variables such as motor parameters and rotor current control gain. Deeply analyzing an action mechanism of flux linkage inertia on a stator voltage dynamic characteristic and a rotor induced electromotive force change rule through electromagnetic coupling; the invention provides a stator virtual flux linkage inertia regulation and control method for different fault stages, aiming at the reactive rapid support requirement in the transient process of a power system and the safe operation constraint problems of over-current, over-voltage and the like of a converter. According to the method, the spontaneous reactive response during voltage disturbance of the doubly-fed fan can be improved, so that the voltage support strength is enhanced, and the problems of rotor overvoltage and overcurrent during voltage disturbance are effectively suppressed.

Description

Technical Field

[0001] The present invention relates to the technical field of wind power generation, and in particular to a method for characterizing and actively regulating the virtual flux inertia of a doubly-fed wind turbine. Background Art

[0002] Doubly-fed induction motors (DFIMs) continue to dominate onshore wind power installations due to their advantages, including small excitation converter capacity, low operating costs, and high efficiency. However, the stator windings of DFIMs are directly coupled to the grid, and their operating state is significantly affected by grid voltage fluctuations. When a short-circuit fault occurs in the grid, the dynamic process of the stator flux not only easily causes overcurrent in the rotor windings, but also directly affects the dynamic reactive power support capability of the wind turbine. my country's wind turbine grid-connected standards explicitly require that wind turbines have rapid and continuous reactive power support capabilities in the event of a grid voltage fault. Therefore, revealing the mechanism by which the dynamic characteristics of the stator flux affect the rotor overcurrent and reactive power support capability has become a key issue that needs to be addressed.

[0003] When a short-circuit fault occurs in the power grid, the stator flux enters a transient state containing a DC component due to electromagnetic induction. This DC component, through electromagnetic coupling between the stator and rotor, induces an induced potential on the rotor side that is related to the flux change rate. Since the rotor-side converter capacity is typically only 30% to 40% of the rated capacity, when the induced potential exceeds its control range, overcurrent will be generated in the rotor winding, seriously threatening the safe operation of the converter. The transient process of the stator flux not only determines the dynamic response of the rotor-side electrical quantities, but its attenuation characteristics also affect the self-support capability of the stator reactive current through the electromagnetic inertia effect. It is a key factor in converter safety and grid voltage support during faults.

[0004] Current research on the transient overvoltage and overcurrent problems of doubly fed wind turbines mainly focuses on improving rotor-side protection. The first type is to limit overcurrent by adding hardware devices such as crowbar circuits, but this solution will cause the converter to absorb reactive power from the grid, weakening the unit's voltage support capability. The second type is to suppress overcurrent by optimizing the rotor current control algorithm. Although this can effectively alleviate the rotor-side overvoltage and overcurrent problems to a certain extent, its research mainly revolves around the independent regulation of the rotor current, and research on the dynamic response characteristics of the stator flux under electromagnetic coupling is still insufficient. Existing methods often do not fully consider the direct impact of the dynamic characteristics of the stator flux on the rotor induced voltage, and have not yet established an effective coupling control mechanism between the flux transient process and the rotor-side stress.

[0005] In the study of reactive power support control, existing methods primarily achieve active reactive power generation by adjusting control structures and optimizing algorithms. Control structure optimization typically involves introducing auxiliary control elements, such as virtual inductance, to achieve active voltage support. Other approaches include the use of novel control strategies such as matching control, inertial synchronization control, and virtual oscillator control. Optimization control algorithms primarily include model-predictive power algorithms, hybrid optimization control algorithms, and adaptive control parameter regulation algorithms. However, when focusing on reactive power support, existing methods fail to fully consider the electromagnetic induction nature of voltage fluctuations and the inertial nature of magnetic flux. Consequently, a systematic analytical framework for voltage support capability from the perspective of the entire stator flux transient process has yet to be established. Specifically, relevant research has failed to fully establish a model for the intrinsic correlation between magnetic flux dynamics, rotor lateral stress, and grid voltage support. Furthermore, the critical modulation role of stator flux inertia during transient processes has been insufficiently explored, leaving room for optimization in strategies that balance equipment safety constraints with grid support requirements.

[0006] This invention innovatively introduces the concept of generalized inertia from the perspective of energy coupling. By defining stator flux inertia, it links grid voltage support with rotor-side stress constraints. The key technical point of this invention is to consider the flux decay process as the response of the flux inertia characteristics to external perturbations and to explore the mechanism by which flux inertia affects voltage support and rotor-side stress constraints. Summary of the Invention

[0007] The purpose of the present invention is to address the deficiencies of existing research and provide a method for characterizing and actively regulating the stator virtual flux inertia of a doubly fed wind turbine, so as to maximize the voltage support capability of the doubly fed wind turbine during low voltage ride-through.

[0008] The object of the present invention is achieved through the following technical solution: a method for characterizing and actively controlling the virtual flux inertia of a doubly fed wind turbine, comprising the following two steps:

[0009] (1) Characterization of virtual flux inertia of doubly fed wind turbine, including:

[0010] (1.1) By analogy with the second-order dynamic equation of the synchronous machine, the second-order equation of magnetic flux inertia is defined as:

[0011]

[0012] Where: J ψ is the flux inertia of the flux inertia response process, Δψ s Indicates the stator flux change, D ψ Assuming to be the deviation coefficient of steady-state flux linkage, ΔU represents the grid voltage change;

[0013] (1.2) Based on step (1.1), the expression of the inherent stator flux inertia J1 of the doubly fed wind turbine when the rotor is in the open circuit state is obtained:

[0014] J1=(L ls +L m ) / R s

[0015] Where: L ls Indicates the stator winding leakage inductance, L m Represents the mutual inductance between the stator and rotor windings, R s represents the stator resistance;

[0016] (1.3) Based on step (1.1), the synthetic flux inertia J considering the rotor current control effect is obtained when the rotor current of the doubly fed wind turbine is actively controlled by the rotor-side converter. ψ expression:

[0017]

[0018] Where: g represents the rotor current transient control gain coefficient in the rotor-side converter control;

[0019] (2) Active control method of virtual flux inertia of doubly fed wind turbine, specifically including:

[0020] (2.1) Design the rotor current transient control gain coefficient g to achieve hierarchical control of the virtual flux inertia of the doubly fed wind turbine; calculate the maximum allowable value of the stator time constant τ s_max , get the maximum transient current control gain g max :

[0021]

[0022] (2.2) According to the voltage drop depth, the current gain in the fault transient process is designed in sections, and the transient current gain parameter g under different grid voltage drop depths is determined:

[0023] g=g max (0.9-U t )

[0024] Where: U t Indicates the per-unit voltage of the doubly-fed wind turbine grid-connected point; the transient current gain coefficient g is set to 0 under normal grid operation; when U t When the current is less than the preset threshold, it is determined that the power grid has entered a fault state from normal operation, and the transient current gain parameter g is set in the range of (0, g max ) to increase the total stator flux inertia; when the grid voltage returns to U t When it is greater than or equal to the preset threshold, it is determined to be fault cleared, and the g setting range is (-g max, 0), which is equivalent to reducing the total stator magnetic inertia.

[0025] Furthermore, the step (1.2) includes:

[0026] In the process from fault occurrence to recovery, the stator flux includes the forced component ψ sf and the free component ψ sn ; Use AC component and transient DC component to form the stator current affected by the fault degree: i s =i sAC +i sDC ;in:

[0027] i sDC =ψ sn / (L ls +L m )

[0028] Where i sAC represents the AC component of the stator fault process, i sDC Indicates the DC component of the stator fault process, L ls Indicates stator leakage inductance, L m represents the mutual inductance between stator and rotor;

[0029] Assuming the fault severity h = 1, this means that the grid voltage has completely dropped, that is, the grid voltage drops to zero after the fault. The stator voltage equation can be obtained as follows:

[0030] u s =(i sAC +i sDC )R s +p(ψ sf +ψ sn )

[0031] Where: p represents the differential operator, ψ sf and ψ sn They represent the forced component and free component in the stator flux during the process from fault occurrence to recovery;

[0032]

[0033] Assumptions but:

[0034]

[0035] Where: τ s represents the decay time constant of the stator flux; ψ sDC represents the initial value of the free component of the stator flux;

[0036]

[0037] The transient stator flux deviation Δψ is written as the rotor speed differential solution of the synchronous machine rotor motion equation, and we can get:

[0038]

[0039] After a fault occurs, the stator flux steady-state value is uniquely determined by the fault severity h. Since the steady-state flux amplitude can be directly characterized by h, the flux deviation coefficient D ψ It can be omitted, and the inherent magnetic inertia expression is obtained: J1=(L ls +L lr ) / R s °

[0040] Furthermore, the step (1.3) includes:

[0041] In the synchronous rotating coordinate system, considering the active control of the rotor current by the rotor-side converter, the stator voltage equation and the flux current relationship can be combined to derive the flux dynamic equation as follows:

[0042]

[0043] Where: sd and ψ sq represents the dq-axis component of the stator flux in the synchronous rotating coordinate system; u sd and u sq represents the dq-axis component of the stator voltage in the synchronous rotating coordinate system; i rd and i rq represents the dq-axis components of the rotor current in the synchronous rotating coordinate system;

[0044] Incorporating transient rotor current control into the rotor converter allows the following control to be achieved:

[0045]

[0046] Where: g is the transient current control gain, which represents the modulation capability of the rotor-side converter control on flux decay; and is the total given value of the rotor current in the transient process; and is the rotor current given value under normal working conditions; and Added setpoint for transient process;

[0047] Considering only the attenuation of the transient DC component, the stator flux transient equation in the dq axis coordinates is obtained:

[0048]

[0049] Finally, the synthetic magnetic inertia J when taking into account the rotor current control is obtained ψ expression

[0050]

[0051] Where: J ψ Represents the total flux inertia taking into account the influence of rotor current.

[0052] The present invention also provides an electronic device, comprising a memory and a processor, wherein the memory is coupled to the processor; wherein the memory is used to store program data, and the processor is used to execute the program data to implement the above-mentioned method for characterizing and actively controlling the virtual flux inertia of a doubly fed wind turbine.

[0053] The present invention also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the above-mentioned method for characterizing and actively regulating the virtual flux inertia of a doubly-fed wind turbine.

[0054] The present invention also provides a computer program product, including a computer program, which, when executed by a processor, implements the above-mentioned method for characterizing and actively regulating the virtual flux inertia of a doubly-fed wind turbine.

[0055] The present invention has the beneficial effect of utilizing the stator flux transient process to combine the voltage support capability of a doubly-fed wind turbine to the grid during low-voltage conditions with the rotor's overvoltage and overcurrent issues, using the energy-based inertia consideration. An expression for flux inertia is provided, and virtual flux inertia is controlled via the rotor current loop. Furthermore, a method for adaptively adjusting virtual flux inertia at different fault stages is provided to achieve the maximum voltage support capability of the doubly-fed wind turbine to the grid while meeting the grid-connected specifications for wind turbine low-voltage ride-through capability. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for the description. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0057] Figure 1 Schematic diagram of the topological structure of the doubly-fed wind turbine grid-connected system of the present invention;

[0058] Figure 2 This is a schematic diagram of the rotor current loop control structure adopted by the present invention;

[0059] Figure 3 This is a diagram of transient current gain control rules during the entire process of grid voltage drop fault according to the present invention;

[0060] Figure 4 This is the output waveform of the double-fed wind turbine when the grid voltage drops under traditional vector control;

[0061] Figure 5 This is the output waveform of the doubly-fed wind turbine using the virtual flux inertia active control method when the grid voltage drops;

[0062] Figure 6 This is a schematic diagram of an electronic device provided by the present invention. DETAILED DESCRIPTION

[0063] In order to describe the present invention in more detail, the present invention will be further explained below with reference to the accompanying drawings and implementation examples.

[0064] (1) Characterization method of virtual flux inertia of doubly fed wind turbine:

[0065] (1.1) By analogy with the second-order equation of synchronous machine dynamics, the second-order equation of magnetic flux inertia is defined as follows:

[0066]

[0067] Where: J ψ is the flux inertia of the flux inertia response process, Δψ s Indicates the stator flux change, D ψ Assume that is the deviation coefficient of steady-state flux (characterizing the normalized deviation of steady-state flux relative to the rated flux), ΔU represents the grid voltage change. When ΔU is not 0, solving the differential equation of formula (1) yields:

[0068]

[0069] (1.2) The mathematical model of the doubly fed wind turbine is established in the stationary abc coordinate system, and the network control based on virtual synchronization is adopted. The main circuit topology and control structure of the system are as follows: Figure 1 As shown. Wherein, the subscript sabc represents the stator electrical quantity in the stationary abc coordinate system; the subscript rabc represents the rotor electrical quantity in the stationary abc coordinate system; the subscript ref represents the reference value; R line and L line Respectively represent the line resistance and inductance between the grid connection point and the grid fault point; R g and L g Represents the filter resistance and filter inductance. In the stationary abc coordinate system, the stator flux and stator voltage equations can be expressed as:

[0070]

[0071] Where: u s 、i s , ψ sare stator voltage, current and flux components respectively; u r 、i r , ψ r are the rotor voltage, current and flux components respectively; R s 、R r are stator and rotor resistance respectively; L ls Indicates the stator winding leakage inductance, L lr Indicates the rotor winding leakage inductance, L m represents the mutual inductance between the stator and rotor windings, and t is the time. The dynamic equation of the stator flux can be expressed as:

[0072]

[0073] Solve the first-order differential equation of the stator flux dynamic equation to obtain the stator transient flux ψ when the voltage drops s expression:

[0074]

[0075] Where: h is the grid voltage drop degree due to fault; U m is the grid voltage amplitude; τ s is the decay time constant of the stator flux; ω s is the synchronous speed of the power grid; j is the imaginary unit.

[0076] (1.3) When the rotor is in the open circuit state, the steps to calculate the inherent inertia of the doubly fed wind turbine stator are:

[0077] In the process from fault occurrence to recovery, the stator flux includes the forced component ψ sf and the free component ψ sn The stator current affected by the fault degree is composed of AC component and transient DC component: i s =i sAC +i sDC .in:

[0078] i sDC =ψ sn / (L ls +L m ) (6)

[0079] Where i sAC represents the AC component of the stator fault process, i sDC Indicates the DC component of the stator fault process, L ls Indicates stator leakage inductance, L m Represents the mutual inductance between stator and rotor.

[0080] Assuming the fault severity h = 1, this means that the grid voltage has completely dropped, that is, the grid voltage drops to zero after the fault. The stator voltage equation can be obtained as follows:

[0081] u s =(i sAC +i sDC )R s +p(ψ sf +ψ sn ) (7)

[0082] Where: p represents the differential operator, ψ sf and ψ sn They represent the forced component and free component in the stator flux from fault occurrence to recovery.

[0083]

[0084] Combining equations (6) and (8), we can obtain:

[0085]

[0086] Assumptions Substituting into the above formula (9) we can get:

[0087]

[0088] Where: τ s represents the decay time constant of the stator flux; ψ sDC The initial value of the free component of the stator flux is represented by . The decay time constant τ of the stator flux can be obtained from formula (10). s :

[0089]

[0090] The stator flux deviation value Δψ in the transient process s Written in the form of differential solution of the rotor speed equation of the synchronous machine rotor motion equation, we can get:

[0091]

[0092] After a fault occurs, the stator flux steady-state value is uniquely determined by the fault severity h. Since the steady-state flux amplitude can be directly characterized by h, the flux deviation coefficient D ψ Can be omitted. Further combined with formula (11), the decay time constant of the stator flux transition process can be determined, and then the inherent flux inertia expression can be obtained: J1=(L ls +L lr ) / R s .

[0093] (1.4) When the rotor current is actively controlled by the rotor-side converter, the steps to obtain the total stator flux inertia of the doubly fed wind turbine are as follows:

[0094] In the synchronous rotating coordinate system, considering the active control of the rotor current by the rotor-side converter, the stator voltage equation and the flux current relationship can be combined to derive the flux dynamic equation as follows:

[0095]

[0096] Where: sd and ψ sq represents the dq-axis component of the stator flux in the synchronous rotating coordinate system; u sd and u sq represents the dq-axis component of the stator voltage in the synchronous rotating coordinate system; i rd and i rq represents the dq-axis component of the rotor current in the synchronous rotating coordinate system. Equation (11) shows that the introduction of the rotor current changes the attenuation characteristics of the stator flux transient process through electromagnetic coupling: the rotor-side converter can introduce an additional damping term into the stator flux dynamic equation by controlling the amplitude and phase of the rotor current, thereby actively adjusting the flux change speed. The present invention controls the rotor current through the rotor-side converter so that:

[0097]

[0098] Where: g is the transient current control gain, which represents the modulation capability of the rotor-side converter control on flux decay; and is the total given value of the rotor current in the transient process; and is the rotor current given value under normal working conditions; and is the given value added in the transient process. The improved rotor-side converter control structure is as follows: Figure 2 As shown. Among them, the transient current gain link is obtained by formula (12); u rd and u rq represents the dq-axis component of the rotor voltage in the synchronous rotating coordinate system; R r represents the rotor resistance; ω slip σL r In the term, ω slip Indicates the slip angular velocity; σL r represents the transient inductance, which is used to eliminate the cross-coupling term ω s ψ sd and ω s ψ sq .

[0099] Under the condition that only the transient DC component attenuation is considered, the regulation relationship of the rotor current on the stator flux in equation (12) is substituted into equation (11) to obtain:

[0100]

[0101] Combining the electromagnetic transient equation and the stator flux dynamic equation (15), combined with the definition of flux inertia, the synthetic flux inertia J taking into account the rotor current control effect can be obtained. ψ expression:

[0102]

[0103] Where: J ψ Characterizes the total flux inertia taking into account the influence of rotor current. It consists of two parts. One part is the stator inherent flux inertia J1, which is used to characterize the flux inertia characteristics of the motor itself; the other part is the virtual flux inertia gJ1 / (1-g) equivalent to the rotor current control.

[0104] (2) Actively control the virtual flux inertia of the doubly fed wind turbine:

[0105] (2.1) Determine the value of the rotor transient current gain coefficient g

[0106] This step mainly adjusts the virtual flux inertia according to different fault stages and grid voltage drop levels. Usually, the stator DC flux is designed to decay within at least 625ms, requiring the stator time constant τ s The maximum is about 156.25ms. For the general motor model, the stator time constant τ s =(L ls +L m ) / R s , if τ s If the current is less than 156.25ms, the flux inertia increase control proposed by the present invention is suitable, and the maximum transient current gain g max :

[0107]

[0108] The stator time constant τ in the motor model experimentally verified by the present invention s It is about 117.27ms, so the maximum transient current gain can be obtained:

[0109] g max =1-(117.27 / 156.25)≈0.25 (18)

[0110] Where: g max Indicates the maximum value of transient current gain, τ s_max The value is 156.25ms. According to the national standard "GB / T19963.1-2021 Technical Regulations for Wind Farm Connection to the Power System", when the voltage at the wind turbine grid connection point drops below 80% of the nominal voltage, the increase in its reactive current must strictly match the degree of voltage change. The specific relationship is:

[0111] ΔI t =K t ×(0.9-U t )×I N (19)

[0112] Where: ΔI t Indicates the reactive current increment output by the fan when the voltage drops, K t Indicates the dynamic reactive current proportional coefficient of the fan, and its value range is generally between 1.5 and 3. t Indicates the per-unit value of the grid-connected point voltage, I N Indicates the rated output current of the fan.

[0113] (2.2) Determine the active control mechanism of virtual flux inertia during the entire grid voltage fault process

[0114] Based on the above analysis, the current gain during the fault transient process needs to be designed in sections according to the voltage sag depth and the maximum output limit of the converter, so as to determine the transient current gain parameters under different voltage conditions:

[0115] g=g max (0.9-U t ) (20)

[0116] In order to achieve the control objectives of enhancing the reactive power support capability during the voltage drop phase, accelerating the stator transient flux decay and suppressing the rotor side overvoltage / overcurrent during the voltage recovery phase, it is necessary to dynamically adjust the virtual flux inertia parameters during the transient process: an active control rule for the transient current gain g during the fault period is added, such as Figure 3 As shown, the specific description is:

[0117] Under normal operation of the power grid, the transient current gain coefficient g is set to 0; when U t When the value is less than 0.9, the grid is judged to have entered a fault state from normal operation, and the setting range of the transient current gain parameter g is (0, g max ), with a typical value of 0.5g max , in order to increase the total stator flux inertia and improve the reactive support capacity during the fault period; when the grid voltage recovers to U t When ≥0.9, it is determined as fault removal, and the g setting range is (-g max , 0), its typical value is -0.5g max , which is equivalent to reducing the total stator flux inertia, accelerating transient flux decay and suppressing rotor side overvoltage / overcurrent.

[0118] To better demonstrate the effectiveness of the proposed method, the following simulation experiments were performed. The simulation parameters are shown in Table 1. To verify the effectiveness and accuracy of the proposed method, a simulation platform was built in MATLAB / Simulink.

[0119] Table 1 Key parameters of 5.5kW doubly-fed wind turbine

[0120]

[0121] Figure 4 It shows the simulated waveform of the doubly-fed wind turbine grid-connected system when a voltage drop of 0.6pu occurs in the power grid at 1.4s without any control. Figure 5 This figure shows the simulated waveforms of a doubly-fed wind turbine grid-connected system when the adaptive flux inertia control proposed in this invention is implemented, during a 1.4s grid voltage dip of 0.6 pu. It can be seen that the implementation of adaptive flux inertia control strengthens reactive power support and minimizes voltage dips during a fault. After the fault is cleared, the voltage and current overcurrent on the rotor are significantly suppressed and improved.

[0122] In summary, the method for characterizing and actively controlling the virtual flux inertia of a doubly fed wind turbine described in the present invention has the following significant features: 1) the stator flux transient process is utilized to combine the voltage support capability of the doubly fed wind turbine to the power grid during the low-voltage process with the overvoltage and overcurrent problems of the rotor, and to consider the inertia from the energy perspective; 2) an expression for the flux inertia is given and the control of the virtual flux inertia is achieved through the rotor current loop; 3) a method for adaptively adjusting the virtual flux inertia at different stages of a fault is given to achieve the maximum voltage support capability of the doubly fed wind turbine to the power grid while meeting the grid-connected specification requirements for the low-voltage ride-through capability of the wind turbine.

[0123] Figure 6 This is a schematic diagram of the structure of an electronic device provided by an embodiment of the present invention. Figure 6 The electronic device provided in this embodiment includes: a memory and a processor, wherein the memory is used to store information including program instructions, and the processor is used to control the execution of the program instructions. When the program instructions are loaded and executed by the processor, the above-mentioned method of virtual flux inertia characterization and active control of a doubly fed wind turbine is implemented.

[0124] It should be noted that, in addition to Figure 6 In addition to the memory and processor shown, the electronic device may also include other hardware according to its actual functions, which will not be described in detail.

[0125] The present invention also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the above-mentioned method for characterizing and actively regulating the virtual flux inertia of a doubly-fed wind turbine.

[0126] The present invention also provides a computer program product, including a computer program, which, when executed by a processor, implements the above-mentioned method for characterizing and actively regulating the virtual flux inertia of a doubly-fed wind turbine.

[0127] Those skilled in the art will appreciate that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code.

[0128] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the steps in the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0129] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0130] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0131] The above embodiments are intended only to illustrate the design concepts and features of the present invention. Their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. The scope of protection of the present invention is not limited to the above embodiments. Therefore, any equivalent changes or modifications made based on the principles and design concepts disclosed in the present invention are within the scope of protection of the present invention.

Claims

1. A method for characterizing and actively controlling virtual flux inertia of a doubly-fed wind turbine, characterized in that: It includes the following two steps: (1) Characterization of virtual flux inertia of doubly fed wind turbine, including: (1.1) By analogy with the second-order dynamic equation of the synchronous machine, the second-order equation of magnetic inertia is defined as: Where: J ψ is the flux inertia of the flux inertia response process, Δψ s Indicates the stator flux change, D ψ Assuming to be the deviation coefficient of steady-state flux linkage, ΔU represents the grid voltage change; (1.2) Based on step (1.1), the expression of the inherent stator flux inertia J1 of the doubly fed wind turbine when the rotor is in the open circuit state is obtained: J1=(L ls +L m ) / R s Where: L ls Indicates the stator winding leakage inductance, L m Represents the mutual inductance between the stator and rotor windings, R s represents the stator resistance; (1.3) Based on step (1.1), the synthetic flux inertia J considering the rotor current control effect is obtained when the rotor current of the doubly fed wind turbine is actively controlled by the rotor-side converter. ψ expression: Where: g represents the rotor current transient control gain coefficient in the rotor-side converter control; (2) Active control method of virtual flux inertia of doubly fed wind turbine, specifically including: (2.1) Design the rotor current transient control gain coefficient g to implement hierarchical control of the virtual flux inertia of the doubly fed wind turbine; calculate the maximum allowable value of the stator time constant τ s_max , get the maximum transient current control gain g max : (2.2) According to the voltage drop depth, the current gain in the fault transient process is designed in sections, and the transient current gain parameter g under different grid voltage drop depths is determined: g=g max ·(0.9-U t ) Where: U t Indicates the per-unit voltage of the doubly fed wind turbine grid-connected point; the transient current gain coefficient g is set to 0 under normal grid operation; when U t When the current is less than the preset threshold, it is determined that the power grid has entered a fault state from normal operation, and the transient current gain parameter g is set in the range of (0, g max ) to increase the total stator flux inertia; when the grid voltage returns to U t When it is greater than or equal to the preset threshold, it is determined to be fault cleared, and the g setting range is (-g max , 0), which is equivalent to reducing the total stator magnetic inertia.

2. The method according to claim 1, characterized in that The step (1.2) comprises: In the process from fault occurrence to recovery, the stator flux includes the forced component ψ sf and the free component ψ sn ; Use AC component and transient DC component to form the stator current affected by the fault degree: i s =i sAC +i sDC ;in: I sDC =ψ sn / (L ls +L m ) Where i sAC represents the AC component of the stator fault process, i sDC Indicates the DC component of the stator fault process, L ls Indicates stator leakage inductance, L m represents the mutual inductance between stator and rotor; Assuming the fault severity h = 1, this means that the grid voltage has completely dropped, that is, the grid voltage drops to zero after the fault. The stator voltage equation can be obtained as follows: you s =(i sAC +i sDC )R s +p(ψ sf +ψ sn ) Where: p represents the differential operator, ψ sf and ψ sn They represent the forced component and free component in the stator flux during the process from fault occurrence to recovery; Assumptions but: Where: τ s represents the decay time constant of the stator flux; ψ sDC represents the initial value of the free component of the stator flux; The transient stator flux deviation Δψ is written as the rotor speed differential solution of the synchronous machine rotor motion equation, and we can get: After a fault occurs, the stator flux steady-state value is uniquely determined by the fault severity h. Since the steady-state flux amplitude can be directly characterized by h, the flux deviation coefficient D ψ It can be omitted, and the inherent magnetic inertia expression is obtained: J1=(L ls +L lr ) / R s .

3. The method according to claim 2, characterized in that The step (1.3) comprises: In the synchronous rotating coordinate system, considering the active control of the rotor current by the rotor-side converter, the stator voltage equation and the flux current relationship can be combined to derive the flux dynamic equation as follows: Where: sd and ψ sq represents the dq-axis component of the stator flux in the synchronous rotating coordinate system; u sd and u sq represents the dq-axis component of the stator voltage in the synchronous rotating coordinate system; i rd and i rq represents the dq-axis components of the rotor current in the synchronous rotating coordinate system; Incorporating transient rotor current control into the rotor converter allows the following control to be achieved: Where: g is the transient current control gain, which represents the modulation capability of the rotor-side converter control on flux decay; and is the total given value of the rotor current in the transient process; and is the rotor current given value under normal working conditions; and Added setpoint for transient process; Considering only the attenuation of the transient DC component, the stator flux transient equation in the dq axis coordinates is obtained: Finally, the synthetic magnetic inertia J when taking into account the rotor current control is obtained ψ expression Where: J ψ Represents the total flux inertia taking into account the influence of rotor current.

4. An electronic device comprising a memory and a processor, characterized in that: The memory is coupled to the processor; wherein, the memory is used to store program data, and the processor is used to execute the program data to implement a virtual flux inertia characterization and active control method of a doubly fed wind turbine as described in any one of claims 1-3 above.

5. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, a method for characterizing and actively controlling the virtual flux inertia of a doubly-fed wind turbine as described in any one of claims 1 to 3 is implemented.

6. A computer program product comprising a computer program, characterized in that When the computer program is executed by a processor, the method for characterizing and actively regulating the virtual flux inertia of a doubly-fed wind turbine as described in any one of claims 1 to 3 is implemented.

Images