Double-fed wind turbine networking control method giving consideration to fault phase selection and grid-connected guide rule

Abstract

The invention discloses a double-fed wind turbine networking control method considering fault phase selection and a grid-connected guide rule, and belongs to the technical field of new energy power generation. If yes, setting the stator current amplitude reference value as the maximum allowable output current, and setting the power factor angle of the positive sequence current as the positive sequence current power factor angle specified by the grid-connected guide rule; otherwise, constructing an initial solution set containing a stator current amplitude reference value and a positive sequence current power factor angle reference value, solving a feasible solution set enabling the target function to be equal to 90 degrees, and screening a feasible solution subset meeting the minimum reactive current increment; if not, the solution with the maximum active current component is selected, otherwise, the solution with the maximum stator current amplitude is selected, and the reference value of the power outer ring is reconstructed. According to the method, the defect that the relay protection phase selection function requirement and the new energy grid-connected guide rule requirement are not considered in the existing double-fed wind turbine generator grid technology is overcome.

Description

Technical Field

[0001] This invention relates to a grid control method for a doubly fed wind turbine that takes into account both fault phase selection and grid connection guidelines, belonging to the field of new energy power generation technology. Background Technology

[0002] Modern power grids require relay protection systems to have fault phase selection capabilities—by quickly identifying the faulty phase and executing selective tripping, i.e., disconnecting only the faulty phase while maintaining power supply to the healthy phase, thus improving power continuity. However, to meet wind power grid connection specifications, grid-forming doubly-fed induction generators (GFM-DFIGs) need to provide active / reactive power support during grid faults. Their control process significantly alters key electrical quantity characteristics measured by the relay protection system, such as current amplitude and phase. Since these characteristics are the core basis for the fault phase selection device to identify the faulty phase, changes in these characteristics can easily lead to a surge in the risk of incorrect phase selection, such as mistakenly tripping a healthy phase or failing to trip a faulty phase, directly threatening the safe and reliable operation of the power grid.

[0003] Current fault ride-through strategies for GFM-DFIG suffer from a singular focus: they concentrate solely on meeting grid connection specifications for fault current and power, neglecting the interference of fault ride-through control on relay protection phase selection. Existing solutions to the phase selection issue arising from grid connection of renewable energy units mainly fall into two categories: one is to improve the phase selection criteria of the protection device, but this requires hardware upgrades, resulting in high costs and difficulties in widespread adoption; the other is to control the fault characteristics of the unit, but this solution is mainly applicable to directly grid-connected inverters such as photovoltaic units and is difficult to adapt to the complexity of GFM-DFIG due to the electromagnetic coupling characteristics of the motor itself and the coordinated control structure of the rotor-side and grid-side converters. More importantly, neither type of solution simultaneously considers the phase selection function requirements and grid connection specifications. Therefore, existing technologies lack a compatible solution that addresses both the relay protection phase selection function requirements and the requirements of renewable energy grid connection guidelines. Summary of the Invention

[0004] The purpose of this invention is to provide a doubly fed wind turbine grid control method that takes into account both fault phase selection and grid connection guidelines. By reshaping the impedance angle characteristics of the GFM-DFIG, it solves the defect of existing wind turbine grid technology that is difficult to take into account both the relay protection phase selection requirements and the grid connection guidelines.

[0005] To solve the above-mentioned technical problems, the present invention is implemented using the following technical solution.

[0006] This invention provides a grid control method for a doubly fed wind turbine that takes into account both fault phase selection and grid connection guidelines, including:

[0007] Collect the stator active current amplitude before the fault, the positive sequence voltage amplitude before the fault, the positive sequence stator voltage amplitude after the fault, and the positive sequence stator voltage phase offset angle after the fault of the GFM-DFIG, and calculate the equivalent positive sequence impedance of the GFM-DFIG.

[0008] If the absolute value of the deviation between the impedance angle of the equivalent positive sequence impedance and the 90° angle required for fault phase selection does not exceed the preset angle deviation threshold, then the equivalent positive sequence impedance is determined to fall into the first impedance angle reshaping domain, and the following steps are executed:

[0009] Set the stator current amplitude reference value to the maximum allowable output current on the stator side of the GFM-DFIG;

[0010] Set the power factor angle of the positive sequence current of GFM-DFIG to the positive sequence current power factor angle required by the grid connection guidelines;

[0011] If the absolute value of the deviation between the impedance angle of the equivalent positive sequence impedance and the 90° angle required for fault phase selection exceeds the preset angle deviation threshold, then the equivalent positive sequence impedance is determined to fall into the second impedance angle reshaping domain, and the following steps are executed:

[0012] Construct an initial solution set that includes reference values ​​for stator current amplitude and power factor angle of positive sequence current;

[0013] Based on a preset objective function, an iterative optimization algorithm is used to solve the feasible solution set in the initial solution set that sets the preset objective function to 90°. The preset objective function is to reshape the impedance angle of the equivalent positive sequence impedance to 90°.

[0014] Select a subset of feasible solutions from the feasible solution set that meet the grid connection guidelines for minimum reactive current increment;

[0015] If the feasible solution subset is not empty, then select the solution with the largest active current component and set the stator current amplitude reference value and the power factor angle of the positive sequence current.

[0016] If the feasible solution subset is empty, then select the solution with the largest stator current amplitude and set the stator current amplitude reference value and the power factor angle of the positive sequence current.

[0017] The reference values ​​for the outer power control loop of the GFM-DFIG are reconstructed based on the stator current amplitude reference value and the power factor angle of the positive sequence current.

[0018] Furthermore, the reshaping action corresponding to the first impedance angle reshaping domain includes:

[0019] Set the stator current amplitude reference value to the maximum allowable output current on the stator side of the GFM-DFIG;

[0020] Set the power factor angle of the positive sequence current of GFM-DFIG to the positive sequence current power factor angle required by the grid connection guidelines;

[0021] The reshaping action corresponding to the second impedance angle reshaping domain includes:

[0022] Construct an initial solution set that includes reference values ​​for stator current amplitude and power factor angle of positive sequence current;

[0023] Based on a preset objective function, an iterative optimization algorithm is used to solve the feasible solution set in the initial solution set that sets the preset objective function to 90°. The preset objective function is to reshape the impedance angle of the equivalent positive sequence impedance to 90°.

[0024] Select a subset of feasible solutions from the feasible solution set that meet the grid connection guidelines for minimum reactive current increment;

[0025] If the feasible solution subset is not empty, then select the solution with the largest active current component and set the stator current amplitude reference value and the power factor angle of the positive sequence current.

[0026] If the feasible solution subset is empty, then select the solution with the largest stator current amplitude and set the stator current amplitude reference value and the power factor angle of the positive sequence current.

[0027] Furthermore, the equivalent positive sequence impedance Z of the GFM-DFIG DFIG+ The calculation expression is expressed as:

[0028] ;

[0029] In the formula, and These indicate the installation locations of the fault-selecting phase element. The measured positive-sequence voltage fault component and positive-sequence current component, with the subscript + indicating a positive-sequence electrical quantity. This represents the positive sequence impedance value of the step-up transformer on the GFM-DFIG side; This indicates the positive-sequence stator voltage amplitude after the fault. Indicates the positive-sequence stator voltage amplitude before the fault, with subscripts |0| and |0|. These represent the values ​​before and after the fault, respectively. This indicates the phase shift angle of the positive-sequence stator voltage after a fault. This indicates the maximum permissible output current on the stator side of the GFM-DFIG. The value represents the stator active current amplitude before the GFM-DFIG fault, and s represents the operating slip of the GFM-DFIG. The positive sequence current power factor angle required by the grid connection guidelines;

[0030] The positive sequence current power factor angle required by the grid connection guidelines is expressed as:

[0031] ;

[0032] In the formula, This indicates the reactive current increment required by the grid connection guidelines. The symbol for the impedance angle is indicated.

[0033] Furthermore, the first impedance angle reshaping domain and the second impedance angle reshaping domain are respectively represented as follows:

[0034] ;

[0035] In the formula, I and II represent the first impedance angle reshaping domain and the second impedance angle reshaping domain, respectively. This indicates the preset angle deviation threshold. The impedance angle represents the equivalent positive sequence impedance of the GFM-DFIG.

[0036] Furthermore, the initial solution set and the preset objective function are respectively expressed as:

[0037] ;

[0038] In the formula, Let represent the initial solution set, where This indicates the reference value for the stator current amplitude. The power factor angle reference value representing the positive sequence current is indicated by the superscript. Indicates a reference value. The target function is set as a preset objective function. The constraints represent the initial solution set.

[0039] Furthermore, the feasible solution set is represented as:

[0040] ;

[0041] In the formula, This represents the feasible solution set. This indicates the number of preset search points. Represents the initial solution set The first in Reference value of stator current amplitude corresponding to each search point Power factor angle reference value of positive sequence current .

[0042] Furthermore, the feasible subset of solutions is represented as:

[0043] ;

[0044] In the formula, This represents a subset of feasible solutions. Represents the feasible solution set The first in Reference value of stator current amplitude corresponding to each search point Power factor angle reference value of positive sequence current , Represents the feasible solution set The Middle The reactive current components corresponding to each search point This represents the sine function.

[0045] Furthermore, the solution with the largest active current component is expressed as:

[0046] ;

[0047] In the formula, This represents the solution with the largest active current component. Represents a subset of feasible solutions The Middle Reference value of stator current amplitude corresponding to each search point Power factor angle reference value of positive sequence current , Represents a subset of feasible solutions The Middle The active current components corresponding to each search point This indicates taking the maximum value. This represents the cosine function.

[0048] Furthermore, the solution with the largest stator current amplitude is expressed as:

[0049] ;

[0050] In the formula, This represents the solution with the largest stator current amplitude. Represents the feasible solution set The Middle Reference value of stator current amplitude corresponding to each search point Power factor angle reference value of positive sequence current .

[0051] Furthermore, the reference value of the GFM-DFIG outer loop power control loop is expressed as follows:

[0052] ;

[0053] In the formula, Represents the empty set. This represents the reference value of the stator current amplitude within the reshaping domain based on the first impedance angle. Power factor angle reference value of positive sequence current Or the reference value of the stator current amplitude within the second impedance angle reshaping domain. Power factor angle reference value of positive sequence current The active power reference value of the reconstructed GFM-DFIG outer loop power control loop. This represents the reference value of the stator current amplitude within the reshaping domain based on the first impedance angle. Power factor angle reference value of positive sequence current Or the reference value of the stator current amplitude within the second impedance angle reshaping domain. Power factor angle reference value of positive sequence current The reactive power reference value of the reconstructed GFM-DFIG outer loop power control loop.

[0054] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0055] This invention determines the impedance angle reshaping domain based on the relationship between the equivalent positive sequence impedance and the preset angle error. It then employs different strategies to set the stator current amplitude reference value and the power factor angle of the positive sequence current, and reconstructs the GFM-DFIG outer loop power control loop reference value. This proactively identifies the non-overlapping areas between grid connection guidelines and fault phase selection requirements. Within these non-overlapping areas, it actively reshapes the unit's equivalent impedance angle characteristics, eliminating the impact of impedance angle offset on fault phase selection. Simultaneously, it maximizes compliance with grid connection specifications. This allows developers to dynamically switch the GFM-DFIG power control reference value to maximize reactive current increment, active current output, or wind turbine capacity utilization. By reshaping the impedance angle, this invention can directly generate control commands based on the grid voltage drop depth and phase selection sensitivity threshold without modifying relay protection devices or adding detection hardware. It possesses universal applicability and can be expanded to adapt to future new grid-type system access scenarios. Attached Figure Description

[0056] Figure 1 This is a schematic diagram of a doubly fed wind turbine grid control method that takes into account both fault phase selection and grid connection guidelines, provided by an embodiment of the present invention.

[0057] Figure 2 This is a schematic diagram of a test system for a doubly fed wind turbine grid control method that takes into account both fault phase selection and grid connection guidelines, as provided in an embodiment of the present invention.

[0058] Figure 3 This is a control schematic diagram of GFM-DFIG provided in an embodiment of the present invention;

[0059] Figure 4 This is an equivalent diagram of the test system and a schematic diagram of the fault sequence component network provided in the embodiments of the present invention. Detailed Implementation

[0060] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the embodiments of the present invention and the specific features in the embodiments are detailed descriptions of the technical solution of the present invention, rather than limitations thereof. In the absence of conflict, the embodiments of the present invention and the technical features in the embodiments can be combined with each other.

[0061] Example 1

[0062] like Figure 1 As shown, this embodiment introduces a grid control method for a doubly fed wind turbine that takes into account both fault phase selection and grid connection guidelines, including:

[0063] Step 1: Collect the stator active current amplitude before the fault, the positive sequence voltage amplitude before the fault, the positive sequence stator voltage amplitude after the fault, and the positive sequence stator voltage phase offset angle after the fault of the GFM-DFIG, and calculate the equivalent positive sequence impedance of the GFM-DFIG.

[0064] This invention achieves accurate quantitative characterization of the equivalent characteristics of the power grid under GFM-DFIG fault conditions by real-time acquisition of stator electrical parameters before and after a fault and calculation of the equivalent positive sequence impedance of GFM-DFIG. This provides an accurate mathematical basis for dynamic reshaping of impedance angle and significantly improves the reliability of fault phase selection judgment.

[0065] Step 2: Determine the impedance angle reshaping domain in which the equivalent positive sequence impedance falls:

[0066] If the absolute value of the deviation between the impedance angle of the equivalent positive sequence impedance and the 90° angle required for fault phase selection does not exceed the preset angle deviation threshold, then the equivalent positive sequence impedance is determined to fall into the first impedance angle reshaping domain, and the following steps are executed:

[0067] By setting the stator current amplitude reference value as the maximum allowable output current on the stator side of the GFM-DFIG, this invention maximizes fault ride-through capability while meeting the thermal stability constraints of the equipment by setting the upper limit of the stator current amplitude.

[0068] By setting the power factor angle of the positive sequence current of GFM-DFIG to the power factor angle of the positive sequence current required by the grid connection guidelines, this invention ensures that the positive sequence current component meets the reactive power support requirements of the power grid and maintains the system voltage stability by forcing the power factor angle to comply with the grid connection guidelines.

[0069] If the absolute value of the deviation between the impedance angle of the equivalent positive sequence impedance and the 90° angle required for fault phase selection exceeds the preset angle deviation threshold, then the equivalent positive sequence impedance is determined to fall into the second impedance angle reshaping domain, and the following steps are executed:

[0070] Construct an initial solution set that includes reference values ​​for stator current amplitude and power factor angle of positive sequence current;

[0071] Based on a preset objective function, an iterative optimization algorithm is used to solve the feasible solution set in the initial solution set that sets the preset objective function to 90°. The preset objective function is to reshape the impedance angle of the equivalent positive sequence impedance to 90°.

[0072] Select a subset of feasible solutions from the feasible solution set that meet the grid connection guidelines for minimum reactive current increment;

[0073] If the feasible solution subset is not empty, then select the solution with the largest active current component and set the stator current amplitude reference value and the power factor angle of the positive sequence current.

[0074] If the feasible solution subset is empty, then select the solution with the largest stator current amplitude and set the stator current amplitude reference value and the power factor angle of the positive sequence current.

[0075] This invention achieves precise tracking of the 90° impedance angle reshaping target by constructing a multivariable solution space and introducing an iterative optimization mechanism driven by the objective function. At the same time, it effectively reduces system reactive power loss while meeting grid connection specifications by using a minimum reactive current increment screening strategy. It also balances the control flexibility under different constraints by prioritizing active power and current amplitude, ensuring that the optimization results are both economical and feasible.

[0076] This invention constructs an impedance angle reshaping domain determination logic by setting a preset angle deviation threshold, thereby realizing differentiated processing of equivalent impedance characteristics. This ensures rapid response under normal operating conditions while reserving optimization space for non-ideal impedance scenarios.

[0077] Step 3: Reconstruct the reference value of the GFM-DFIG outer loop power control loop based on the stator current amplitude reference value and the power factor angle of the positive sequence current.

[0078] This invention achieves closed-loop reconstruction of the fault response characteristics of GFM-DFIG by injecting the optimized stator current amplitude and power factor angle parameters into the outer power control loop of GFM-DFIG, significantly improving the dynamic response accuracy of the equipment under asymmetric fault scenarios and enhancing its coordinated operation capability with the power grid protection system.

[0079] Example 2

[0080] Based on the same inventive concept as Embodiment 1, this embodiment introduces the implementation steps of a dual-fed wind turbine grid control method that takes into account both fault phase selection and grid connection guidelines. By reshaping the impedance angle characteristics of the GFM-DFIG, without the need for additional hardware modifications, it can ensure the high sensitivity and reliability of the phase selection element of the relay protection system, and maximize the satisfaction of the power and current support requirements of the grid connection guidelines during fault ride-through.

[0081] like Figure 2The diagram shows a test system schematic of a doubly fed wind turbine grid control method that considers both fault phase selection and grid connection guidelines, as provided in this embodiment. B1, B2, and B3 represent the busbars on the grid side, the high-voltage side of the wind farm, and the low-voltage side of the wind farm, respectively. The GFM-DFIG-based wind farm is connected to the grid system on the opposite side via the grid connection lines between the first step-up transformer T2 and the second step-up transformers T1, B1, and B2. The short-circuit fault occurs at point F on the grid connection line; point F is the fault point. The distance from fault point F to busbar B2 on the high-voltage side of the wind farm is L. f The impedances of the fault point F from the grid-side bus B1 and the wind farm-side high-voltage bus B2 are respectively and ; and These represent the internal impedance and electromotive force on the grid side, respectively. In this embodiment, a fault phase selection element R21 is installed at bus B2 on the high-voltage side of the wind farm. The voltage and current vectors measured by the fault phase selection element R21 are respectively... and The current detected at fault point F .

[0082] like Figure 3 The diagram shown is a control schematic of the GFM-DFIG provided in this embodiment. The control structure of the GFM-DFIG mainly includes the control of the rotor-side converter (RSC) and the grid-side converter (GSC). , , They represent current, voltage, and electromotive force, respectively; P and Q represent active power and reactive power, respectively; subscripts , , These represent the electrical quantities on the stator side, RSC side, and GSC side, respectively; subscripts express Axis-synchronous rotating coordinate system; subscript , , They represent Positive and negative zero sequence components of a synchronously rotating coordinate system; subscript , These represent the values ​​before and during the fault, respectively; the superscript * represents the command value; , , , These are stator inductance, rotor inductance, magnetizing inductance, and grid-side filter inductance, respectively. This is the DC bus voltage connecting the RSC side and the GSC side; , These are the grid angular frequency and the doubly-fed wind turbine rotor position angle; and These are the transformation angles generated by the RSC active power outer loop and the GSC phase-locked loop, respectively. This indicates the ratio of the outer loop output frequency of the RSC active power to the power frequency. The deviation value; and These represent the inertia and damping coefficients, respectively. and These represent the reference value and actual output value of the active power in the outer loop after the fault, respectively. and These represent the reference value and actual output value of the reactive power in the outer reactive power loop after the fault, respectively. and These represent the magnitude of the internal potential and the initial magnitude of the internal potential, respectively.

[0083] exist Figure 3 In this process, GSC control maintains the stability of the DC bus voltage of the capacitor. It extracts the phase of the grid voltage through a phase-locked loop and generates a control reference angle, which in turn generates the GSC control signal. Meanwhile, RSC positive-sequence control includes active power control based on the analog synchronous machine rotor motion equations and reactive power control based on reactive power and electromotive force droop characteristics, expressed as:

[0084] ;

[0085] In the formula, This represents differential calculation. This indicates the ratio of the outer loop output frequency of the RSC active power to the power frequency. The deviation value, and These represent the inertia and damping coefficients, respectively. and These represent the reference value and actual output value of the active power in the outer loop after the fault, respectively. and These represent the reference value and actual output value of the reactive power in the outer reactive power loop after the fault, respectively. and These represent the magnitude of the internal potential and the initial magnitude of the internal potential, respectively.

[0086] This embodiment uses active power control based on the rotor motion equation of a synchronous machine and reactive power control based on the reactive power and electromotive force droop characteristics to output the dq-axis voltage difference between the internal electromotive force and the stator terminal voltage. After passing through a virtual impedance, the dq-axis reference value of the GFM-DFIG stator current is obtained, expressed as:

[0087] ;

[0088] In the formula, and These are the stator current outputs of the GFM-DFIG respectively. Axis reference value, and These are the resistive and inductive components of the virtual impedance, respectively. and After the fault Shaft stator voltage and The difference in internal potential, The power frequency angular velocity of the GFM-DFIG connected to the power grid.

[0089] In this embodiment, the dq axis output reference value of the stator current of GFM-DFIG is converted to the rotor side to obtain the rotor current reference value. After current amplitude saturation, that is, the maximum amplitude of the rotor current is, it is output to the inner loop rotor current control, and finally outputs the PWM modulation signal of RSC.

[0090] like Figure 4 As shown, the equivalent diagram and fault sequence network corresponding to the control system are given, where, Figure 4 (a) in the diagram is the equivalent diagram of the control system. Figure 4 In the diagram, (b) represents the positive-sequence fault component network corresponding to the control system. Figure 4 In the diagram, (c) represents the negative-sequence fault component network corresponding to the control system. Figure 4 In the diagram, (d) represents the zero-sequence fault component network corresponding to the control system. , , These represent the positive-sequence, negative-sequence, and zero-sequence fault currents at the fault point, respectively. and The positive sequence current and voltage fault components measured for the fault-selective element. and Negative sequence current and voltage components measured for fault-selective phase elements. and The zero-sequence current and voltage components are measured for the phase selection element. Due to the grounding of the high-voltage side winding of T1, the wind farm is in an electrically isolated state in the zero-sequence fault network.

[0091] according to Figure 4 The sequence current phase relationship between the fault point and the phase selection element can be expressed as:

[0092] ;

[0093] In the formula, , and These are the positive-sequence, negative-sequence, and zero-sequence line impedances of the distance from fault point F to B2, respectively. , and These are the positive-sequence, zero-sequence, and negative-sequence impedances on the grid side, respectively. , and The positive-sequence, negative-sequence, and zero-sequence impedances of the lines between buses B1 and B2 are respectively. This is the zero-sequence impedance of the step-up transformer in the wind farm.

[0094] The fault-selecting phase element operates based on the current phase relationship at the fault point. According to the sequence current phase relationship between the fault point and the phase-selecting element, the positive, negative, and zero sequence current angle values ​​measured by the phase-selecting element must be... , , The angle values ​​of the positive, negative, and zero sequence currents at the fault point , , The bias term on the right side of equation (3) must be zero. The sign of the angle must be indicated. This condition requires... and The angle value must be related to the transformer impedance Z. T Grid impedance Z g It is consistent with the impedance angle characteristics of line ZB1 / B2 l, that is, it satisfies the impedance angle of approximately 90°.

[0095] To meet the requirements of the fault selection element for arg(∆U) m+ / ΔI m+ ) and arg(U m- / I m- To meet the requirement of approximately 90°, this embodiment includes the following steps:

[0096] Step 1: Collect the stator active current amplitude before the fault, the positive sequence voltage amplitude before the fault, the positive sequence stator voltage amplitude after the fault, and the positive sequence stator voltage phase offset angle after the fault of the GFM-DFIG, and calculate the equivalent positive sequence impedance of the GFM-DFIG.

[0097] In this embodiment, the equivalent positive sequence impedance Z of the GFM-DFIG DFIG+ The calculation expression is expressed as:

[0098] ;

[0099] In the formula, and These indicate the installation locations of the fault-selecting phase element. The measured positive-sequence voltage fault component and positive-sequence current component, with the subscript + indicating a positive-sequence electrical quantity. This represents the positive sequence impedance value of the step-up transformer on the GFM-DFIG side; This indicates the positive-sequence stator voltage amplitude after the fault. Indicates the positive-sequence stator voltage amplitude before the fault, with subscripts |0| and |0|. These represent the values ​​before and after the fault, respectively. This indicates the phase shift angle of the positive-sequence stator voltage after a fault. This indicates the maximum permissible output current on the stator side of the GFM-DFIG. The value represents the stator active current amplitude before the GFM-DFIG fault, and s represents the operating slip of the GFM-DFIG. This indicates the positive sequence current power factor angle required by the grid connection guidelines.

[0100] In this embodiment, the positive sequence current power factor angle required by the grid connection guidelines is expressed as:

[0101] ;

[0102] In the formula, This indicates the reactive current increment required by the grid connection guidelines. The symbol for the impedance angle is indicated.

[0103] Step 2: Determine the impedance angle reshaping domain in which the equivalent positive sequence impedance falls:

[0104] In this embodiment, the first impedance angle reshaping domain and the second impedance angle reshaping domain are respectively represented as:

[0105] ;

[0106] In the formula, I and II represent the first impedance angle reshaping domain and the second impedance angle reshaping domain, respectively. This indicates the preset angle deviation threshold. The impedance angle represents the equivalent positive sequence impedance of the GFM-DFIG.

[0107] If the equivalent positive sequence impedance falls into the first impedance angle reshaping domain, it indicates that the fault crossing target guided by the grid connection guideline is compatible with the high-sensitivity fault phase selection. If the equivalent positive sequence impedance falls into the first impedance angle reshaping domain, the impedance characteristic reshaping process will be performed to ensure the performance of fault phase selection.

[0108] Step 2.1: If the absolute value of the deviation between the impedance angle of the equivalent positive sequence impedance and the 90° angle required for fault phase selection does not exceed the preset angle deviation threshold, then the equivalent positive sequence impedance is determined to fall into the first impedance angle reshaping domain, and the following steps are executed:

[0109] Step 2.1.1: Set the stator current amplitude reference value to the maximum allowable output current on the stator side of the GFM-DFIG;

[0110] Step 2.1.2: Set the power factor angle of the positive sequence current of GFM-DFIG to the positive sequence current power factor angle required by the grid connection guidelines.

[0111] Step 2.2: If the absolute value of the deviation between the impedance angle of the equivalent positive sequence impedance and the 90° angle required for fault phase selection exceeds the preset angle deviation threshold, then the equivalent positive sequence impedance is determined to fall into the second impedance angle reshaping domain, and the following steps are executed:

[0112] Step 2.2.1: Construct an initial solution set containing the stator current amplitude reference value and the power factor angle reference value of the positive sequence current;

[0113] Step 2.2.2: Based on the preset objective function, use an iterative optimization algorithm to solve the feasible solution set in the initial solution set that sets the preset objective function to 90°. The preset objective function is to reshape the impedance angle of the equivalent positive sequence impedance to 90°.

[0114] In this embodiment, the initial solution set and the preset objective function are respectively represented as:

[0115] ;

[0116] In the formula, Let represent the initial solution set, where This indicates the reference value for the stator current amplitude. The power factor angle reference value representing the positive sequence current is indicated by the superscript. Indicates a reference value. The target function is set as a preset objective function. The constraints represent the initial solution set.

[0117] This embodiment limits ϕ*f+ to the range of [0°, 90°] to prevent active power backfeeding, which could cause DFIG rotor overspeed and saturate I*sf+ to a maximum of I. s,max To eliminate the risk of overcurrent.

[0118] In this embodiment, the feasible solution set is represented as:

[0119] ;

[0120] In the formula, This represents the feasible solution set. This indicates the number of preset search points. Represents the initial solution set The first in Reference value of stator current amplitude corresponding to each search point Power factor angle reference value of positive sequence current .

[0121] Step 2.2.3: Select a subset of feasible solutions from the feasible solution set that meet the requirements of the grid connection guidelines for minimum reactive current increment;

[0122] In this embodiment, the feasible solution subset is represented as:

[0123] ;

[0124] In the formula, This represents a subset of feasible solutions. Represents the feasible solution set The first in Reference value of stator current amplitude corresponding to each search point Power factor angle reference value of positive sequence current , Represents the feasible solution set The Middle The reactive current components corresponding to each search point This represents the sine function.

[0125] If the feasible solution subset is not empty, then select the solution with the largest active current component and set the stator current amplitude reference value and the power factor angle of the positive sequence current.

[0126] In this embodiment, the solution with the largest active current component is represented as:

[0127] ;

[0128] In the formula, This represents the solution with the largest active current component. Represents a subset of feasible solutions The Middle Reference value of stator current amplitude corresponding to each search point Power factor angle reference value of positive sequence current , Represents a subset of feasible solutions The Middle The active current components corresponding to each search point This indicates taking the maximum value. This represents the cosine function.

[0129] If the feasible solution subset is empty, then select the solution with the largest stator current amplitude and set the stator current amplitude reference value and the power factor angle of the positive sequence current.

[0130] In this embodiment, the solution with the largest stator current amplitude is represented as:

[0131] ;

[0132] In the formula, This represents the solution with the largest stator current amplitude. Represents the feasible solution set The Middle Reference value of stator current amplitude corresponding to each search point Power factor angle reference value of positive sequence current .

[0133] Step 3: Reconstruct the reference value of the GFM-DFIG outer loop power control loop based on the stator current amplitude reference value and the power factor angle of the positive sequence current.

[0134] In this embodiment, the reference value of the GFM-DFIG outer loop power control loop is expressed as:

[0135] ;

[0136] In the formula, Represents the empty set. This represents the reference value of the stator current amplitude within the reshaping domain based on the first impedance angle. Power factor angle reference value of positive sequence current Or the reference value of the stator current amplitude within the second impedance angle reshaping domain. Power factor angle reference value of positive sequence current The active power reference value of the reconstructed GFM-DFIG outer loop power control loop. This represents the reference value of the stator current amplitude within the reshaping domain based on the first impedance angle. Power factor angle reference value of positive sequence current Or the reference value of the stator current amplitude within the second impedance angle reshaping domain. Power factor angle reference value of positive sequence current The reactive power reference value of the reconstructed GFM-DFIG outer loop power control loop.

[0137] Example 3

[0138] Based on the same inventive concept as other embodiments, this embodiment describes a computer-readable storage medium having computer instructions stored thereon, which, when executed by a processor, implement the steps of the methods of Embodiment 1 or 2 described above.

[0139] Example 4

[0140] Based on the same inventive concept as other embodiments, this embodiment introduces a computer program product, including computer instructions that, when executed by a processor, implement the steps of the methods described in Embodiment 1 or 2 above.

[0141] In summary, this invention determines the impedance angle reshaping domain based on the relationship between the equivalent positive sequence impedance and the preset angle error. It then employs different strategies to set the stator current amplitude reference value and the power factor angle of the positive sequence current, and reconstructs the GFM-DFIG outer loop power control loop reference value. This proactively identifies the non-overlapping areas between grid connection guidelines and fault phase selection requirements. Within these non-overlapping areas, it actively reshapes the unit's equivalent impedance angle characteristics, eliminating the impact of impedance angle offset on fault phase selection. Simultaneously, it maximizes compliance with grid connection specifications. This allows developers to dynamically switch the GFM-DFIG power control reference value to maximize reactive current increment, active current output, or wind turbine capacity utilization. By reshaping the impedance angle, this invention can directly generate control commands based on the grid voltage drop depth and phase selection sensitivity threshold without modifying relay protection devices or adding detection hardware. It possesses universal applicability and can be expanded to adapt to future new grid-type system access scenarios.

[0142] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0143] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0144] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0145] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0146] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A doubly-fed wind turbine grid control method that takes into account both faulted phase selection and grid code, characterized in that, The method comprises the following steps: Collecting the stator active current amplitude of the GFM-DFIG before the fault, the positive sequence voltage amplitude before the fault, the positive sequence stator voltage amplitude after the fault, and the phase shift angle of the positive sequence stator voltage after the fault, and calculating the equivalent positive sequence impedance of the GFM-DFIG; If the absolute value of the deviation of the impedance angle of the equivalent positive sequence impedance from the 90° angle required by the fault phase selection is not more than the preset angle deviation threshold, it is determined that the equivalent positive sequence impedance falls into the first impedance angle remodeling domain, and the remodeling action corresponding to the first impedance angle remodeling domain is performed; If the absolute value of the deviation of the impedance angle of the equivalent positive sequence impedance from the 90° angle required by the fault phase selection is more than the preset angle deviation threshold, it is determined that the equivalent positive sequence impedance falls into the second impedance angle remodeling domain, and the remodeling action corresponding to the second impedance angle remodeling domain is performed; The reference value of the outer loop power control ring of the GFM-DFIG is reconstructed according to the stator current amplitude reference value and the power factor angle of the positive sequence current.

2. The DFIG wind turbine grid control method with both faulted phase selection and grid code compliance of claim 1, wherein, The remodeling action corresponding to the first impedance angle remodeling domain comprises: Setting the stator current amplitude reference value as the maximum allowable output current of the stator side of the GFM-DFIG; Setting the power factor angle of the positive sequence current of the GFM-DFIG as the positive sequence current power factor angle required by the grid connection guide; The remodeling action corresponding to the second impedance angle remodeling domain comprises: Constructing an initial solution set containing the stator current amplitude reference value and the power factor angle reference value of the positive sequence current; Solving the feasible solution set in which the preset target function is equal to 90° from the initial solution set by using an iterative optimization algorithm based on the preset target function, and the preset target function is to remodel the impedance angle of the equivalent positive sequence impedance to 90°; Screening a feasible solution subset that meets the minimum reactive current increment required by the grid connection guide from the feasible solution set; If the feasible solution subset is not empty, setting the stator current amplitude reference value and the power factor angle of the positive sequence current by selecting the solution with the maximum active current component; If the feasible solution subset is empty, setting the stator current amplitude reference value and the power factor angle of the positive sequence current by selecting the solution with the maximum stator current amplitude.

3. The DFIG wind turbine grid control method with both faulted phase selection and grid code compliance of claim 2, wherein, The equivalent positive sequence impedance Z of the GFM-DFIG DFIG+ The computational expression is represented as: ； wherein and respectively represent the installation position of the faulted phase selector element measured positive-sequence voltage fault component and positive-sequence current component, subscript + represents the positive-sequence electrical quantity, represents the positive-sequence impedance value of the GFM-DFIG side step-up transformer; represents the positive-sequence stator voltage amplitude after the fault, represents the positive-sequence stator voltage amplitude before the fault, subscript |0| and subscript respectively represent the values before and after the fault, represents the positive-sequence stator voltage phase shift angle after the fault, represents the maximum allowable output current of the stator side of the GFM-DFIG, represents the stator active current amplitude of the GFM-DFIG before the fault, s represents the operating slip of the GFM-DFIG, represents the positive-sequence current power factor angle required by the grid connection guide; The positive sequence current power factor angle required by the grid connection guide is expressed as: ； In the formula, The reactive current increment required by the grid connection guideline The impedance angle symbol is represented.

4. The DFIG wind turbine grid control method according to claim 3, wherein, The first impedance angle remodeling domain and the second impedance angle remodeling domain are respectively expressed as: ； wherein I and II represent the first impedance angle reshaping domain and the second impedance angle reshaping domain, respectively, denotes a preset angle deviation threshold value, denotes an impedance angle of the equivalent positive sequence impedance of the GFM-DFIG.

5. The DFIG wind turbine grid control method with both faulted phase selection and grid code compliance of claim 4, wherein, The initial solution set and the preset target function are respectively expressed as: ； In the formula, denotes an initial solution set, wherein, denotes a stator current amplitude reference value, denotes a power factor angle reference value of the positive sequence current, and a superscript denotes a reference value, is a preset target function, denotes a constraint condition of the initial solution set.

6. The DFIG wind turbine grid control method that takes into account both faulted phase selection and grid code, according to claim 5, characterized in that, The feasible solution set is expressed as: ； In the formula, represents the feasible solution set, represents the preset number of search points, represents the initial solution set The first search point in the stator current amplitude reference value and the power factor angle reference value of the positive sequence current .

7. The DFIG wind turbine grid control method that takes into account both faulted phase selection and grid code, according to claim 6, characterized in that, The feasible solution subset is expressed as: ； wherein represents the feasible solution subset, represents the feasible solution set the stator current amplitude reference value corresponding to the the power factor angle reference value of the positive sequence current , represents the feasible solution set the reactive current component corresponding to the the stator current amplitude reference value corresponding to the represents the sine function.​ 8. The DFIG wind turbine grid control method according to claim 7, wherein, The solution with the maximum active current component is expressed as: ； In the formula, This represents the solution with the largest active current component. Represents a subset of feasible solutions The Middle Reference value of stator current amplitude corresponding to each search point Power factor angle reference value of positive sequence current , Represents a subset of feasible solutions The Middle The active current components corresponding to each search point This indicates taking the maximum value.

9. The DFIG wind turbine grid control method with both faulted phase selection and grid code compliance of claim 7, wherein, The solution with the maximum stator current amplitude is expressed as: ； In the formula, represents the solution of the maximum stator current amplitude, represents the feasible solution set the first search point corresponding to the stator current amplitude reference value and the power factor angle reference value of the positive sequence current .

10. The DFIG wind turbine grid control method of claim 8 or 9, wherein, The reference value of the outer loop power control ring of the GFM-DFIG is expressed as: ； wherein denotes the empty set, denotes a stator current magnitude reference value within a first impedance angle reshaping domain and a power factor angle reference value of the positive sequence current or a stator current magnitude reference value within a second impedance angle reshaping domain and a power factor angle reference value of the positive sequence current a reconstructed active reference value of the GFM-DFIG outer loop power control loop, denotes a stator current magnitude reference value within a first impedance angle reshaping domain and a power factor angle reference value of the positive sequence current or a stator current magnitude reference value within a second impedance angle reshaping domain and a power factor angle reference value of the positive sequence current a reconstructed reactive reference value of the GFM-DFIG outer loop power control loop.

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