A method, device, medium and equipment for calculating a fan fault current peak value

Abstract

The application discloses a kind of fan fault current peak value calculation method, device, medium and equipment.This application collects the operating parameters and structural parameters of each double-fed fan under different fault scenarios in history, using these parameters, this application can not only determine the structural characteristics of each double-fed fan under different fault voltage drop degree, but also accurately obtain the initial operating state of fan.Combining the time point of each fault occurrence in the preset fault time period, the initial operating state of each double-fed fan, each fault voltage drop degree value, and genetic algorithm, this application can efficiently calculate the time when each fault current reaches peak value.Further, based on these time points and the first and second fault current peak value expressions derived from the rotor current time domain expression under two different voltage drop degrees, according to the first and second fault current peak value expressions, this application can accurately calculate each fault current peak value under various factors.

Description

Technical Field

[0001] The present invention relates to the field of calculation of peak value of fault current of a wind turbine, and in particular to a calculation method, device, medium and equipment of peak value of fault current of a wind turbine. Background Art

[0002] As the global demand for sustainable energy grows, new energy technologies, particularly wind power generation, are emerging at an unprecedented rate, becoming a key strategy for addressing energy shortages and reducing greenhouse gas emissions. Wind power, with its clean and renewable nature, has not only injected strong momentum into the green development of the global economy and society, but also led to profound changes in the energy structure, opening up new avenues for humanity to explore more environmentally friendly and efficient energy utilization methods. Doubly-fed wind turbines (DFIGs), among others, have achieved widespread global adoption due to their high energy efficiency, excellent stability, and flexible power regulation. Their unique DFIG variable frequency speed regulation technology not only improves wind energy conversion efficiency but also enhances the adaptability and stability of power grids. They are widely used in various sectors, including the power industry, metallurgy, and mining, becoming a key force in promoting the development of clean energy.

[0003] However, DFIGs have a unique structure and fault characteristics that differ significantly from traditional synchronous motors. The widespread and high-capacity integration of wind power into the grid will impact the stability of existing power systems, potentially challenging the normal operation of existing equipment. For example, DFIGs employ different fault ride-through strategies for different fault voltage drops, resulting in differences in the fault current and its calculated peak value. These issues hinder existing technologies from accurately calculating the peak fault current of doubly-fed wind turbines under these multiple factors. Summary of the Invention

[0004] The present invention provides a method, device, medium and equipment for calculating the peak value of a fault current of a wind turbine, so as to solve the problem in the prior art that the peak value of the fault current of a doubly-fed wind turbine cannot be accurately calculated under multiple factors.

[0005] In a first aspect, the present application provides a method for calculating a peak fault current of a wind turbine, comprising:

[0006] Obtain the operating parameters and structural parameters of each doubly fed wind turbine under different historical fault scenarios;

[0007] According to the structural parameters, each fault voltage drop value of each doubly-fed wind turbine is obtained;

[0008] According to the operating parameters, the initial operating state of each doubly fed wind turbine is obtained;

[0009] Calculate the time when each fault current reaches its peak value based on the time point of each fault occurrence within the preset fault time period, the initial operating state of each doubly fed wind turbine, the value of each fault voltage drop and the genetic algorithm;

[0010] The peak values ​​of the fault currents are calculated based on the time when the fault currents reach their peak values, the first fault current peak value expression and the second fault current peak value expression; wherein the first fault current peak value expression and the second fault current peak value expression are calculated based on the rotor current time domain expressions under two voltage drop levels.

[0011] The present application can accurately capture the fault current dynamics of the doubly fed wind turbine under the influence of multiple factors by comprehensively considering the initial state of the doubly fed wind turbine, the fault voltage drop value, and the time point of the fault occurrence. By optimizing the search for the fault time point and the voltage drop degree according to the genetic algorithm, the present application not only improves the calculation efficiency, but also can simulate the current response of the doubly fed wind turbine under different fault conditions. Furthermore, by analyzing the time domain expression of the rotor current under mild and severe voltage drops, the present application derives the first and second fault current peak expressions, thereby being able to accurately calculate the fault current peak under the influence of multiple factors. This multi-factor comprehensive analysis method makes the present application more accurate in calculating the fault current peak of the doubly fed wind turbine, improves the prediction capability and response strategy of the power system when facing complex power grid faults, and solves the problem in the prior art that the fault current peak of the doubly fed wind turbine cannot be accurately calculated under multiple factors.

[0012] As a preferred embodiment of the first aspect, the initial operating state of each doubly fed wind turbine is obtained according to the operating parameters, specifically:

[0013] The initial operating state of each doubly-fed wind turbine includes each rotor self-inductance and mutual inductance parameters, each slip rate and each parameter of the system internal control.

[0014] In this preferred embodiment, the present application can provide accurate initial conditions for the current response of the doubly fed wind turbine in the event of a grid fault by obtaining in detail the initial operating state of each doubly fed wind turbine, including the rotor self-inductance and mutual inductance parameters, slip rate, and system internal control parameters. These parameters are key factors affecting the current behavior of the wind turbine during a fault. Therefore, accurately mastering these operating parameters enables this method to more realistically simulate the response characteristics of the wind turbine in the actual grid in subsequent calculations. This method based on precise initial states improves the accuracy of fault current peak calculations, thereby providing reliable data support for the stability analysis of the power system and the design of protection devices, and enhancing the adaptability and safety of the power system to faults.

[0015] As a preferred embodiment of the first aspect, the fault current peak expression and the second fault current peak expression are calculated based on the rotor current time domain expressions under two voltage sag levels, specifically:

[0016] When the voltage of each doubly-fed wind turbine is greater than a preset threshold, it is determined to be a first voltage drop level; otherwise, it is determined to be a second voltage drop level;

[0017] The first fault current peak expression is calculated based on the first rotor current time domain expression under the first voltage sag level;

[0018] The second fault current peak expression is calculated based on the second rotor current time-domain expression at the second voltage sag level.

[0019] In this preferred embodiment, the present application can accurately capture the current response of the doubly fed wind turbine under different grid fault severities by distinguishing between two different voltage drop levels and determining the time domain expression of the rotor current accordingly. Specifically, when the wind turbine voltage is greater than a preset threshold, the system determines it as a minor fault (first voltage drop level) and uses the corresponding first rotor current time domain expression to calculate the fault current peak; on the contrary, when the voltage is lower than the preset threshold, the system determines it as a serious fault (second voltage drop level), and the second rotor current time domain expression is used to calculate the fault current peak. This method enables the present application to dynamically adjust the calculation model according to the severity of the actual grid fault, thereby more accurately predicting the fault current peak of the doubly fed wind turbine under different fault conditions. This method based on conditional judgment and time domain analysis improves the flexibility and accuracy of the calculation, provides a more accurate theoretical basis for power system fault analysis, protection device design and system stability, and enhances the system's adaptability and safety to different fault scenarios.

[0020] As a preferred embodiment of the first aspect, the first fault current peak expression is calculated based on the first rotor current time-domain expression at the first voltage sag level, specifically:

[0021] According to the stator-rotor voltage and flux equation under rotor side excitation control, the time domain expression of the first rotor current is calculated;

[0022] According to the time-domain expression of the first rotor current, the first fault current peak expression is calculated.

[0023] The calculation obtains the first fault current peak expression, specifically:

[0024] The first fault current peak expression is:

[0025]

[0026] Where α1 and α2 are the values ​​related to the rotor side excitation control parameters, A s_rsc 、B s_rsc 、C s_rsc is the stator current coefficient for rotor side excitation control, τ s is the inverse of the stator side decay time constant under the rotor side excitation control, ω1 is the synchronous angular velocity value, t x The time when the fault occurs.

[0027] In this preferred embodiment, the present application first accurately calculates the first rotor current time-domain expression based on the stator-rotor voltage and flux equations by controlling the rotor-side excitation under minor fault conditions. This is because it provides a detailed description of the rotor current changes of the doubly-fed wind turbine under minor voltage drops. Subsequently, using this first rotor current time-domain expression, the present method further derives the first fault current peak expression, thereby accurately predicting the fault current peak of the doubly-fed wind turbine under minor grid fault conditions. This calculation method based on actual current changes not only improves the accuracy of the prediction, but also provides more reliable data support for fault analysis and protection device design of the power system, enhancing the system's response capability to minor faults and overall stability.

[0028] As a preferred embodiment of the first aspect, the second fault current peak expression is calculated based on the second rotor current time domain expression at the second voltage sag level, specifically:

[0029] According to the stator flux value and rotor flux value after the crowbar protection is activated, the time domain expression of the second rotor current and the stator current are calculated;

[0030] The second fault current peak expression is calculated based on the second rotor current time domain expression and the stator current.

[0031] The calculation obtains the second fault current peak expression, specifically:

[0032] The second fault current peak expression is:

[0033]

[0034] Where A, B, and C are the preset stator current coefficient expressions. are the phase values ​​of expressions A, B, and C respectively, τ rc is the inverse of the rotor side decay time constant, ω1 is the synchronous angular velocity value, t x The time when the fault occurs.

[0035] In this preferred embodiment, the present application aims at the activation of the crowbar protection in the case of severe faults. First, the time domain expression of the second rotor current and the stator current are accurately calculated based on the stator flux value and the rotor flux value, because it provides a detailed description of the current changes of the doubly fed wind turbine under severe voltage drops. Based on these time domain expressions, the present method further derives the second fault current peak expression, thereby being able to accurately predict the fault current peak of the doubly fed wind turbine under severe grid fault conditions. This calculation method based on actual current changes not only improves the accuracy of the prediction, but also provides more reliable data support for fault analysis and protection device design of the power system, enhancing the system's response capability to severe faults and overall stability.

[0036] In a second aspect, the present application provides a device for calculating a peak value of a fault current of a wind turbine, the device comprising an acquisition module, a first calculation module, and a second calculation module;

[0037] The acquisition module is used to obtain the operating parameters and structural parameters of each doubly fed wind turbine under different historical fault scenarios;

[0038] According to the structural parameters, each fault voltage drop value of each doubly-fed wind turbine is obtained;

[0039] According to the operating parameters, the initial operating state of each doubly fed wind turbine is obtained;

[0040] The first calculation module is used to calculate the time when each fault current reaches a peak value according to the time point when each fault occurs within a preset fault time period, the initial state of each doubly fed wind turbine and the value of each fault voltage drop;

[0041] The second calculation module is used to calculate the peak values ​​of each fault current based on the time when each fault current reaches a peak value, the first fault current peak expression and the second fault current expression; wherein the first fault current peak expression and the second fault current peak expression are calculated based on the rotor current time domain expression under two voltage drop levels.

[0042] This device uses three modules to divide the work and coordinate the work to better accurately calculate the fault current under multiple factors. This application can accurately capture the fault current dynamics of the doubly fed wind turbine under the influence of multiple factors by comprehensively considering the initial state of the doubly fed wind turbine, the fault voltage drop value, and the time point of the fault. According to the genetic algorithm, the fault time point and the voltage drop degree are optimized and searched. This application not only improves the calculation efficiency, but also can simulate the current response of the doubly fed wind turbine under different fault conditions. Furthermore, by analyzing the time domain expression of the rotor current under mild and severe voltage drops, this application derives the first and second fault current peak expressions, so as to accurately calculate the fault current peak under the influence of multiple factors. This multi-factor comprehensive analysis method makes this application more accurate in calculating the fault current peak of the doubly fed wind turbine, improves the prediction ability and response strategy of the power system when facing complex power grid faults, and solves the problem in the existing technology that the fault current peak of the doubly fed wind turbine cannot be accurately calculated under multiple factors.

[0043] In a third aspect, the present application provides a computer-readable storage medium, the computer-readable storage medium including a stored computer program. When the computer program is executed, the device containing the computer-readable storage medium is controlled to execute the method for calculating a peak value of a wind turbine fault current. This method has the same beneficial effects as the method for calculating a peak value of a wind turbine fault current provided in the first aspect of the present application.

[0044] In a fourth aspect, the present application provides a terminal device comprising a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, wherein when the processor executes the computer program, it implements any one of the methods for calculating the peak value of the wind turbine fault current as described in the first aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 : A flow chart of an embodiment of a method for calculating a peak value of a wind turbine fault current provided by the present application;

[0046] Figure 2 : A structural diagram of an embodiment of specific factors considered for calculating the peak value of the fault current of a doubly-fed wind turbine provided by the present application;

[0047] Figure 3 : A structural diagram of an embodiment of specific factors of the DFIG grid-connected simulation model provided by this application;

[0048] Figure 4 : A schematic flow chart of an embodiment of the calculation of the fault current peak value of a doubly-fed wind turbine provided by the present application;

[0049] Figure 5: A structural diagram of an embodiment of the present application showing a comparison between a simulated current peak value and a calculated current peak value when the crowbar protection is engaged;

[0050] Figure 6 : A structural diagram of an embodiment of the present application for comparing the simulated current peak value with the calculated current peak value under RSC continuous excitation control;

[0051] Figure 7 : A structural schematic diagram of an embodiment of a device for calculating a peak value of a wind turbine fault current provided in the present application. DETAILED DESCRIPTION

[0052] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0053] Example 1

[0054] Please refer to Figure 1 , which is a method for calculating the peak value of a wind turbine fault current provided by an embodiment of the present invention.

[0055] In this embodiment, the process of the method for calculating the peak value of the wind turbine fault current in this application is described in detail through steps S01 to S05.

[0056] S01: Obtain the operating parameters and structural parameters of each doubly-fed wind turbine under different historical fault scenarios.

[0057] S02: Obtaining respective fault voltage drop values ​​of respective doubly-fed wind turbines according to the structural parameters.

[0058] S03: Obtaining the initial operating state of each doubly-fed wind turbine according to the operating parameters.

[0059] As a preferred embodiment of the first embodiment, the need to obtain the operating parameters and structural parameters in steps S01-S03 is because:

[0060] According to the analysis and calculation of the expressions under different fault ride-through strategies, the factors affecting the peak calculation of the doubly fed wind turbine can be summarized. They can be mainly divided into wind turbine parameters and external fault factors, such as Figure 2 As shown in the figure, the wind turbine parameters include structural parameters (including stator and rotor self-inductance and mutual inductance parameters) and operating parameters (including slip rate s value, system internal control parameters α1, α2, β1 and β2). External fault factors include fault time t fault And fault voltage drop degree kc .

[0061] According to the analysis, when the system is operating normally, the structural parameters and operating parameters of the fan are all known quantities. The parameter values ​​of different fans are different. For each fan, it is necessary to obtain the actual parameter value of the fan in advance and substitute it into the calculation. For external fault factors, since the fault situation cannot be predicted in advance, different actual fault scenarios need to be considered, that is, different fault time t fault and different fault voltage drop degrees k c Considering the above factors, we need to first obtain the initial operating state parameters of the fan, and then determine a specific operating condition (i.e. determine t fault and k c After obtaining the parameters, substitute them into the peak value calculation expression of the double-fed wind turbine fault current to calculate the specific value of the peak value in this case.

[0062] In this preferred embodiment, the present application can identify and summarize the key factors that affect the peak value of the fault current of the doubly fed wind turbine by deeply analyzing the expressions under different fault ride-through strategies, and divide these factors into two categories: wind turbine parameters and external fault factors. Wind turbine parameters include stator and rotor self-inductance and mutual inductance parameters, slip rate, and system internal control parameters. These are known when the system is operating normally, and their specific values ​​need to be obtained in advance for each wind turbine for calculation. External fault factors include unpredictable fault time and voltage drop degree, which requires considering multiple possible fault scenarios during calculation. Taking these factors into consideration, the present application first obtains the initial operating state parameters of the wind turbine, and then determines the specific working conditions, including fault time and voltage drop degree, and substitutes these parameters into the peak calculation expression to calculate the fault current peak value under specific circumstances.

[0063] S04: Calculate the time when each fault current reaches a peak value based on the time point when each fault occurs within a preset fault time period, the initial operating state of each doubly fed wind turbine, the value of each fault voltage drop and the genetic algorithm.

[0064] As a preferred embodiment of the first embodiment, the fault current peak expression and the second fault current peak expression are calculated based on the rotor current time domain expressions under two voltage sag levels, specifically:

[0065] When the voltage of each doubly-fed wind turbine is greater than a preset threshold, it is determined to be a first voltage drop level; otherwise, it is determined to be a second voltage drop level, and the preset threshold is 0.4;

[0066] The first fault current peak expression is calculated based on the first rotor current time domain expression under the first voltage sag level;

[0067] The second fault current peak expression is calculated based on the second rotor current time-domain expression at the second voltage sag level.

[0068] Furthermore, the specific calculation method of the rotor current time domain expression is:

[0069] When the saturation of the magnetic circuit is ignored and the motor convention is adopted, the stator and rotor voltage and flux equations of the doubly fed wind turbine in the dq two-phase rotating coordinate system can be expressed as:

[0070]

[0071]

[0072] Among them, the subscript s represents the stator side electrical quantity, the subscript r represents the rotor side electrical quantity, U, i, r represents voltage, current, magnetic flux and resistance respectively; L s , L r are the self-inductance values ​​of the stator and rotor sides of the fan respectively; L m is the mutual inductance value on the stator and rotor sides, and the three satisfy the relationship: L s =L m +L σs ,L r =L m +L σr , where L σs , L σr are the leakage inductance values ​​of the stator and rotor sides respectively; ω1 is the synchronous angular velocity value, s is the slip rate when the fan is running, and s=(ω1-ω r ) / ω1, where ω r is the rotor speed value.

[0073] According to the rotor flux equation (2), we can get:

[0074]

[0075] in, Indicates the stator side flux value, i r Indicates the rotor side current value, i s represents the stator side current value. Substituting it into the rotor flux equation, we can get:

[0076]

[0077] in, Represents the rotor side flux value. Substituting the above formula into the rotor voltage equation, the relationship between the stator side current and flux is:

[0078]

[0079] Among them, i sc Indicates the stator side current value after the crowbar protection is activated, L D =L s L r -L m 2 , R r ' is the resistance value of the crowbar protection. From this, we can deduce the stator flux value after the crowbar is put into operation in the dq synchronous rotating coordinate system:

[0080]

[0081] Among them, τ sc is the inverse of the stator side decay time constant, and its expression is τ sc =R s L r / L D ; t0 is the time when the fault occurs; U0 is the per-unit value of the initial fault voltage, ω1 is the fundamental angular frequency, k c is the per-unit voltage drop. Combining the stator and rotor voltage and flux equations, the stator and rotor current time domain expressions can be solved as follows:

[0082]

[0083]

[0084]

[0085] C=i sc(0) -AB(10)

[0086] In this preferred embodiment, the present application can accurately capture the current response of the doubly fed wind turbine under different grid fault severities by distinguishing between two different voltage drop levels and determining the time domain expression of the rotor current accordingly. Specifically, when the wind turbine voltage is greater than a preset threshold, the system determines it as a minor fault (first voltage drop level) and uses the corresponding first rotor current time domain expression to calculate the fault current peak; on the contrary, when the voltage is lower than the preset threshold, the system determines it as a serious fault (second voltage drop level), and the second rotor current time domain expression is used to calculate the fault current peak. This method enables the present application to dynamically adjust the calculation model according to the severity of the actual grid fault, thereby more accurately predicting the fault current peak of the doubly fed wind turbine under different fault conditions. This method based on conditional judgment and time domain analysis improves the flexibility and accuracy of the calculation, provides a more accurate theoretical basis for power system fault analysis, protection device design and system stability, and enhances the system's adaptability and safety to different fault scenarios.

[0087] As a preferred embodiment of the first embodiment, the first fault current peak expression is calculated based on the first rotor current time domain expression under the first voltage sag level, specifically:

[0088] When the fault is minor, the DFIG maintains its outer power loop control, with the rotor-side converter (RSC) still controlling its output. When the grid voltage fluctuates or a fault occurs, the RSC excitation control can adjust control strategies and parameters to suppress rotor overcurrent and overvoltage, regulating the generator's operating status and output characteristics to address grid faults and fluctuations. This improves the DFIG's fault ride-through capability and ensures stable operation during grid faults.

[0089] According to the principle of flux conservation, the stator flux will not mutate at the moment of fault. Therefore, the stator flux after the fault has two components: one is the steady-state component of the stator flux corresponding to the residual voltage at the machine end. The second is the stator flux transient component corresponding to the voltage drop, which decays with the stator time constant. for:

[0090]

[0091] Where: τ s_rsc =R s L r / L D According to the stator and rotor flux equation, we can obtain:

[0092]

[0093] From this, the rotor voltage equation can be obtained. Combining the above equations, the second-order differential equation of the rotor current can be obtained as follows:

[0094]

[0095] Where: β1, β2, β r is a value related to the RSC inner and outer loop control parameters. Solving the above equation, the stator current analytical expression under dq synchronous rotating coordinates is obtained:

[0096]

[0097] Where A s_rsc 、B s_rsc 、C s_rsc To take into account the stator current coefficient of RSC control, the specific expression is:

[0098]

[0099]

[0100]

[0101] In the formula: It can be seen that in the three-phase stationary coordinate system, the DFIG stator short-circuit current taking into account RSC control contains forced components, transient DC components and transient natural components; the rotor current contains forced difference frequency components, attenuated speed frequency components and natural components.

[0102] In this preferred embodiment, the present application first accurately calculates the first rotor current time-domain expression based on the stator-rotor voltage and flux equations by controlling the rotor-side excitation under minor fault conditions. This is because it provides a detailed description of the rotor current changes of the doubly-fed wind turbine under minor voltage drops. Subsequently, using this first rotor current time-domain expression, the present method further derives the first fault current peak expression, thereby accurately predicting the fault current peak of the doubly-fed wind turbine under minor grid fault conditions. This calculation method based on actual current changes not only improves the accuracy of the prediction, but also provides more reliable data support for fault analysis and protection device design of the power system, enhancing the system's response capability to minor faults and overall stability.

[0103] As a preferred embodiment of the first embodiment, the second fault current peak expression is calculated based on the second rotor current time domain expression at the second voltage sag level, specifically:

[0104] When a serious fault occurs on the grid side, the crowbar protection on the DFIG side will be activated. According to the principle of flux conservation, when the DFIG generator-side voltage suddenly drops at the moment of a fault, its stator flux remains continuous due to physical properties and does not undergo an instantaneous sudden change. This characteristic results in a complex stator flux structure after the fault, which includes both a steady-state component corresponding to the generator-side residual voltage and a transient component induced in the stator flux due to the sudden voltage drop. The stator flux after the fault is expressed as:

[0105]

[0106] Where: τ sc is the inverse of the stator side decay time constant, and its expression is τ sc =R s L r / L D ; t0 is the time when the fault occurs; U0 is the per-unit value of the initial fault voltage; ω1 is the fundamental angular frequency. According to the rotor flux equation, we can get:

[0107]

[0108] Substituting it into the rotor flux equation, we can get:

[0109]

[0110] Among them, L s , L r are the self-inductance values ​​of the stator and rotor sides of the fan respectively; L m is the mutual inductance value on the stator and rotor sides, L D =L r L s -L m 2 After the crowbar protection is activated, the rotor side converter will be locked. At this time, the RSC control loses its function and the rotor side voltage value suddenly drops to 0, that is, U r =0. After the crowbar protection is activated, an additional resistor value Rc is introduced into the rotor side circuit. This change causes the total resistance value on the rotor side to change from the original resistance value Rr to Rr' = Rr + Rc, forming a new resistance configuration. Therefore, after the crowbar is activated, not only the voltage distribution on the rotor side is changed, but also the electromagnetic coupling relationship between the stator and rotor is profoundly affected. Substituting Equation (6) into the rotor voltage equation, the relationship between the current and flux on the stator side is obtained as follows:

[0111]

[0112] Where: is the rotor flux vector after the crowbar protection is put into use; R r ' is the equivalent resistance value of the rotor side after the crowbar protection is put into use, and its expression is R r '=R r +R c , R c L is the crowbar protection resistor value; D =L s L r -L m 2 Combining equations (3) and (5), we can obtain The expression of stator current and its component coefficient values ​​can be further obtained as follows.

[0113]

[0114]

[0115]

[0116] C=i sc(0) -AB(25)

[0117] Where: i sc(0) is the stator current vector during normal operation of the wind turbine; τ rc is the inverse of the rotor side decay time constant, expressed as Rr 'L s / L D Converting Equation (6) to the abc three-phase stationary coordinate system, its time domain expression is:

[0118]

[0119] Furthermore, according to the above calculation of the time domain expression of the fault current of the DFIG under different fault strategies, the fault time is set to t fault The time when the current reaches its maximum value is t max , t x =t max -t fault , and then based on equations (14) and (26), the calculation expressions of the fault current peak value in the two stages are obtained. The peak value when the crowbar protection is activated is:

[0120]

[0121] Combining the specific expressions of each formula, we can get that both expression A and expression B are related to the crowbar protection resistance value R' r , fan operation slip rate s, various fan parameters, fault voltage drop degree k c The C expression is related to the initial value of the fault current and the above factors. In addition to the factors mentioned above, the peak value of the fault current is also related to the specific time value of the fault.

[0122] During the RSC excitation control stage, the peak value of the fault current is:

[0123]

[0124] in, For expression A s_rsc 、B s_rsc 、C s_rsc It can be seen that for the fault current in the RSC continuous excitation control stage, A s_rsc The expression is related to the fan operating slip rate s, various fan parameters, and fault voltage drop degree k c Related, in addition, B s_rsc The expression is also related to the system's internal control parameters β1 and β2, C s_rsc The expression is also related to the set current value i r_ref Related to the system's internal control parameters α1 and α2.

[0125] In this preferred embodiment, the present application first accurately calculates the first rotor current time-domain expression based on the stator-rotor voltage and flux equations by controlling the rotor-side excitation under minor fault conditions. This is because it provides a detailed description of the rotor current changes of the doubly-fed wind turbine under minor voltage drops. Subsequently, using this first rotor current time-domain expression, the present method further derives the first fault current peak expression, thereby accurately predicting the fault current peak of the doubly-fed wind turbine under minor grid fault conditions. This calculation method based on actual current changes not only improves the accuracy of the prediction, but also provides more reliable data support for fault analysis and protection device design of the power system, enhancing the system's response capability to minor faults and overall stability.

[0126] S05: Calculate each fault current peak value according to the time when each fault current reaches a peak value, the first fault current peak value expression and the second fault current expression.

[0127] As a preferred embodiment of the first embodiment, the peak values ​​of the fault currents are calculated based on the time when the fault currents reach their peak values, the first fault current peak value expression, and the second fault current expression, specifically:

[0128] ① Obtain the initial operating status value of the fan;

[0129] ②Set fault time t fault The value of , consider the interval [t, t+T];

[0130] ③At the fixed time t fault Under this condition, set the time t when the fault current reaches the peak value max The value range is [t fault ,t fault +2T];

[0131] ④Set the fault voltage drop level k c The value of , consider the interval [0.1, 0.8];

[0132] ⑤ At fault time t fault When fixed, the peak current I under this fault condition is calculated by combining the fault current expression of the doubly fed wind turbine max ;

[0133] ⑥ Set the step size Δt, let t0 = t0 + Δt, and determine whether t0 at this time is within the considered interval. If so, return to the first step and recalculate.

[0134] The specific calculation flow chart is as follows Figure 3 shown.

[0135] like Figure 4In the DFIG grid-connected system shown in , a three-phase short-circuit fault is set at the grid-connected line Line at different fault times. The fault voltage value at the outlet of the doubly fed wind turbine is measured to obtain the output time-domain current value of the doubly fed wind turbine under different combinations of fault times and fault voltage drop levels. In addition, through the specific calculation flow chart of the doubly fed wind turbine fault current peak value considering multiple factors mentioned above, the comparison between the calculated and actual peak values ​​of the doubly fed wind turbine under various fault conditions can be calculated more accurately. Figure 5 and Figure 6 As shown. Among them, 1-k c is the per-unit value of the voltage after the fault.

[0136] according to Figure 5 and Figure 6 It can be seen that under different fault condition combinations, the measured error between the calculated value of the fault current peak value of the doubly fed wind turbine proposed by the present invention considering multiple factors and the actual value of each peak value is small, which proves the correctness of the peak calculation method proposed. In addition, it should be noted that the time t corresponding to the fault current reaching the maximum value is max and failure time t fault There is a nonlinear relationship between them, which cannot be directly calculated in practice. Due to the large number of fault combinations between the two, a genetic algorithm heuristic search algorithm can be used to search and calculate the peak current of the doubly fed wind turbine under different fault combinations. The basic process of the genetic algorithm is as follows:

[0137] Basic process of genetic algorithm:

[0138] Initialization: Create an initial population, where each individual is generated randomly or initialized according to a specific strategy.

[0139] Calculate the fitness value of each individual in the population.

[0140] Iterative evolution:

[0141] Selection: According to the fitness value, a certain number of individuals are selected as parents.

[0142] Crossover: Perform a crossover operation on the selected parent individuals to generate new offspring individuals.

[0143] Mutation: Mutate offspring individuals with a certain probability.

[0144] Replacement or merging: adding offspring individuals to the population, replacing some or all of the original individuals to form a new generation of population.

[0145] Calculate fitness: Calculate the fitness value of each individual in the new population.

[0146] Termination condition check: Check whether the preset termination conditions (such as maximum number of iterations, fitness threshold, number of times without obvious improvement, etc.) are met.

[0147] If the termination condition is met, the current optimal individual is output as the approximate optimal solution to the problem; otherwise, return to step 2 to continue iteration.

[0148] According to the value range of the two variables, the fault time t is obtained by the genetic algorithm heuristic search algorithm. fault The value of the current reaches the maximum value interval t max ∈[t0,t0+2T], which can reduce the simulation time under different fault conditions and directly obtain the fault and different fault voltage drop degrees k c The maximum peak current value under the combination.

[0149] The present application can accurately capture the fault current dynamics of the doubly fed wind turbine under the influence of multiple factors by comprehensively considering the initial state of the doubly fed wind turbine, the fault voltage drop value, and the time point of the fault occurrence. By optimizing the search for the fault time point and the voltage drop degree according to the genetic algorithm, the present application not only improves the calculation efficiency, but also can simulate the current response of the doubly fed wind turbine under different fault conditions. Furthermore, by analyzing the time domain expression of the rotor current under mild and severe voltage drops, the present application derives the first and second fault current peak expressions, thereby being able to accurately calculate the fault current peak under the influence of multiple factors. This multi-factor comprehensive analysis method makes the present application more accurate in calculating the fault current peak of the doubly fed wind turbine, improves the prediction capability and response strategy of the power system when facing complex power grid faults, and solves the problem in the prior art that the fault current peak of the doubly fed wind turbine cannot be accurately calculated under multiple factors.

[0150] Example 2

[0151] Please refer to Figure 7 , which is a calculation device for the wind turbine fault current peak value provided in an embodiment of the present application.

[0152] In this embodiment, the device for calculating the peak value of the fault current of a wind turbine includes an acquisition module 10 , a first calculation module 20 and a second calculation module 30 .

[0153] The acquisition module 10 is used to acquire the operating parameters and structural parameters of each doubly-fed wind turbine under different historical fault scenarios; and obtain the fault voltage drop degree value of each doubly-fed wind turbine based on the structural parameters.

[0154] The initial operating state of each doubly-fed wind turbine is obtained according to the operating parameters.

[0155] As a preferred embodiment of the second embodiment, the need to obtain the operating parameters and structural parameters in the above steps is because:

[0156] According to the analysis and calculation of the expressions under different fault ride-through strategies, the factors affecting the peak calculation of the doubly fed wind turbine can be summarized. They can be mainly divided into wind turbine parameters and external fault factors, such as Figure 2 As shown in the figure, the wind turbine parameters include structural parameters (including stator and rotor self-inductance and mutual inductance parameters) and operating parameters (including slip rate s value, system internal control parameters α1, α2, β1 and β2). External fault factors include fault time t fault And fault voltage drop degree k c .

[0157] According to the analysis, when the system is operating normally, the structural parameters and operating parameters of the fan are all known quantities. The parameter values ​​of different fans are different. For each fan, it is necessary to obtain the actual parameter value of the fan in advance and substitute it into the calculation. For external fault factors, since the fault situation cannot be predicted in advance, different actual fault scenarios need to be considered, that is, different fault time t fault and different fault voltage drop degrees k c Considering the above factors, we need to first obtain the initial operating state parameters of the fan, and then determine a specific operating condition (i.e. determine t fault and k c After obtaining the parameters, substitute them into the peak value calculation expression of the double-fed wind turbine fault current to calculate the specific value of the peak value in this case.

[0158] In this preferred embodiment, the present application can identify and summarize the key factors that affect the peak value of the fault current of the doubly fed wind turbine by deeply analyzing the expressions under different fault ride-through strategies, and divide these factors into two categories: wind turbine parameters and external fault factors. Wind turbine parameters include stator and rotor self-inductance and mutual inductance parameters, slip rate, and system internal control parameters. These are known when the system is operating normally, and their specific values ​​need to be obtained in advance for each wind turbine for calculation. External fault factors include unpredictable fault time and voltage drop degree, which requires considering multiple possible fault scenarios during calculation. Taking these factors into consideration, the present application first obtains the initial operating state parameters of the wind turbine, and then determines the specific working conditions, including fault time and voltage drop degree, and substitutes these parameters into the peak calculation expression to calculate the fault current peak value under specific circumstances.

[0159] The first calculation module 20 is used to calculate the time when each fault current reaches a peak value based on the time point of each fault occurrence within a preset fault time period, the initial operating state of each doubly fed wind turbine, the value of each fault voltage drop and the genetic algorithm.

[0160] As a preferred embodiment of the second embodiment, the fault current peak expression and the second fault current peak expression are calculated based on the rotor current time domain expressions under two voltage sag levels, specifically:

[0161] When the voltage of each doubly-fed wind turbine is greater than a preset threshold, it is determined to be a first voltage drop level; otherwise, it is determined to be a second voltage drop level, and the preset threshold is 0.4;

[0162] The first fault current peak expression is calculated based on the first rotor current time domain expression under the first voltage sag level;

[0163] The second fault current peak expression is calculated based on the second rotor current time-domain expression at the second voltage sag level.

[0164] Furthermore, the specific calculation method of the rotor current time domain expression is:

[0165] When the saturation of the magnetic circuit is ignored and the motor convention is adopted, the stator and rotor voltage and flux equations of the doubly fed wind turbine in the dq two-phase rotating coordinate system can be expressed as:

[0166]

[0167]

[0168] Among them, the subscript s represents the stator side electrical quantity, the subscript r represents the rotor side electrical quantity, U, i, r represents voltage, current, magnetic flux and resistance respectively; L s , L r are the self-inductance values ​​of the stator and rotor sides of the fan respectively; L m is the mutual inductance value on the stator and rotor sides, and the three satisfy the relationship: L s =L m +L σs ,L r =L m +L σr , where L σs , L σr are the leakage inductance values ​​of the stator and rotor sides respectively; ω1 is the synchronous angular velocity value, s is the slip rate when the fan is running, and s=(ω1-ω r ) / ω1, where ω r is the rotor speed value.

[0169] According to the rotor flux equation (30), we can get:

[0170]

[0171] in, Indicates the stator side flux value, ir Indicates the rotor side current value, i s represents the stator side current value. Substituting it into the rotor flux equation, we can get:

[0172]

[0173] in, Represents the rotor side flux value. Substituting the above formula into the rotor voltage equation, the relationship between the stator side current and flux is:

[0174]

[0175] Among them, i sc Indicates the stator side current value after the crowbar protection is activated, L D =L s L r -L m 2 , R r ' is the resistance value of the crowbar protection. From this, we can deduce the stator flux value after the crowbar is put into operation in the dq synchronous rotating coordinate system:

[0176]

[0177] Among them, τ sc is the inverse of the stator side decay time constant, and its expression is τ sc =R s L r / L D ; t0 is the time when the fault occurs; U0 is the per-unit value of the initial fault voltage, ω1 is the fundamental angular frequency, k c is the per-unit voltage drop. Combining the stator and rotor voltage and flux equations, the stator and rotor current time domain expressions can be solved as follows:

[0178]

[0179]

[0180]

[0181] C=i sc(0) -AB(38)

[0182] In this preferred embodiment, the present application can accurately capture the current response of the doubly fed wind turbine under different grid fault severities by distinguishing between two different voltage drop levels and determining the time domain expression of the rotor current accordingly. Specifically, when the wind turbine voltage is greater than a preset threshold, the system determines it as a minor fault (first voltage drop level) and uses the corresponding first rotor current time domain expression to calculate the fault current peak; on the contrary, when the voltage is lower than the preset threshold, the system determines it as a serious fault (second voltage drop level), and the second rotor current time domain expression is used to calculate the fault current peak. This method enables the present application to dynamically adjust the calculation model according to the severity of the actual grid fault, thereby more accurately predicting the fault current peak of the doubly fed wind turbine under different fault conditions. This method based on conditional judgment and time domain analysis improves the flexibility and accuracy of the calculation, provides a more accurate theoretical basis for power system fault analysis, protection device design and system stability, and enhances the system's adaptability and safety to different fault scenarios.

[0183] As a preferred embodiment of the second embodiment, the first fault current peak expression is calculated based on the first rotor current time domain expression under the first voltage sag level, specifically:

[0184] When the fault is minor, the DFIG maintains its outer power loop control, with the rotor-side converter (RSC) still controlling its output. When the grid voltage fluctuates or a fault occurs, the RSC excitation control can adjust control strategies and parameters to suppress rotor overcurrent and overvoltage, regulating the generator's operating status and output characteristics to address grid faults and fluctuations. This improves the DFIG's fault ride-through capability and ensures stable operation during grid faults.

[0185] According to the principle of flux conservation, the stator flux will not mutate at the moment of fault. Therefore, the stator flux after the fault has two components: one is the steady-state component of the stator flux corresponding to the residual voltage at the machine end. The second is the stator flux transient component corresponding to the voltage drop, which decays with the stator time constant. for:

[0186]

[0187] Where: τ s_rsc =R s L r / L D According to the stator and rotor flux equation, we can obtain:

[0188]

[0189] From this, the rotor voltage equation can be obtained. Combining the above equations, the second-order differential equation of the rotor current can be obtained as follows:

[0190]

[0191] Where: β1, β2, β r is a value related to the RSC inner and outer loop control parameters. Solving the above equation, the stator current analytical expression under dq synchronous rotating coordinates is obtained as:

[0192]

[0193] Where A s_rsc 、B s_rsc 、C s_rsc To take into account the stator current coefficient of RSC control, the specific expression is:

[0194]

[0195]

[0196]

[0197] In the formula: It can be seen that in the three-phase stationary coordinate system, the DFIG stator short-circuit current taking into account RSC control contains forced components, transient DC components and transient natural components; the rotor current contains forced difference frequency components, attenuated speed frequency components and natural components.

[0198] In this preferred embodiment, the present application first accurately calculates the first rotor current time-domain expression based on the stator-rotor voltage and flux equations by controlling the rotor-side excitation under minor fault conditions. This is because it provides a detailed description of the rotor current changes of the doubly-fed wind turbine under minor voltage drops. Subsequently, using this first rotor current time-domain expression, the present method further derives the first fault current peak expression, thereby accurately predicting the fault current peak of the doubly-fed wind turbine under minor grid fault conditions. This calculation method based on actual current changes not only improves the accuracy of the prediction, but also provides more reliable data support for fault analysis and protection device design of the power system, enhancing the system's response capability to minor faults and overall stability.

[0199] As a preferred embodiment of the second embodiment, the second fault current peak expression is calculated based on the second rotor current time domain expression under the second voltage sag level, specifically:

[0200] When a serious fault occurs on the grid side, the crowbar protection on the DFIG side will be activated. According to the principle of flux conservation, when the DFIG generator-side voltage suddenly drops at the moment of a fault, its stator flux remains continuous due to physical properties and does not undergo an instantaneous sudden change. This characteristic results in a complex stator flux structure after the fault, which includes both a steady-state component corresponding to the generator-side residual voltage and a transient component induced in the stator flux due to the sudden voltage drop. The stator flux after the fault is expressed as:

[0201]

[0202] Where: τ sc is the inverse of the stator side decay time constant, and its expression is τ sc =R s L r / L D ; t0 is the time when the fault occurs; U0 is the per-unit value of the initial fault voltage; ω1 is the fundamental angular frequency. According to the rotor flux equation, we can get:

[0203]

[0204] Substituting it into the rotor flux equation, we can get:

[0205]

[0206] Among them, L s , L r are the self-inductance values ​​of the stator and rotor sides of the fan respectively; L m is the mutual inductance value on the stator and rotor sides, L D =L r L s -L m 2 After the crowbar protection is activated, the rotor side converter will be locked. At this time, the RSC control loses its function and the rotor side voltage value suddenly drops to 0, that is, U r = 0. After the crowbar protection is activated, an additional resistance value Rc is introduced into the rotor side circuit. This change causes the total resistance value on the rotor side to change from the original resistance value Rr to Rr' = Rr + Rc, forming a new resistance configuration. Therefore, after the crowbar is activated, not only the voltage distribution on the rotor side is changed, but also the electromagnetic coupling relationship between the stator and rotor is profoundly affected. Substituting Equation (34) into the rotor voltage equation, the relationship between the current and flux on the stator side is obtained as follows:

[0207]

[0208] Where: is the rotor flux vector after the crowbar protection is put into use; R r ' is the equivalent resistance value of the rotor side after the crowbar protection is put into use, and its expression is R r'=R r +R c , R c L is the crowbar protection resistor value; D =L s L r -L m 2 Combining equations (31) and (33), we can obtain The expression of stator current and its component coefficient values ​​can be further obtained as follows.

[0209]

[0210]

[0211]

[0212] C=i sc(0) -AB(53)

[0213] Where: i sc(0) is the stator current vector during normal operation of the wind turbine; τ rc is the inverse of the rotor side decay time constant, expressed as R r 'L s / L D Converting Equation (34) to the abc three-phase stationary coordinate system, its time domain expression is:

[0214]

[0215] Furthermore, according to the above calculation of the time domain expression of the fault current of the DFIG under different fault strategies, the fault time is set to t fault The time when the current reaches its maximum value is t max , t x =t max -t fault , and then based on equations (42) and (54), the calculation expressions of the fault current peak value in the two stages are obtained. The peak value under the crowbar protection is:

[0216]

[0217] Combining the specific expressions of each formula, we can get that both expression A and expression B are related to the crowbar protection resistance value R' r , fan operation slip rate s, various fan parameters, fault voltage drop degree k c The C expression is related to the initial value of the fault current and the above factors. In addition to the factors mentioned above, the peak value of the fault current is also related to the specific time value of the fault.

[0218] During the RSC excitation control stage, the peak value of the fault current is:

[0219]

[0220] in, For expression A s_rsc 、B s_rsc 、C s_rsc It can be seen that for the fault current in the RSC continuous excitation control stage, A s_rsc The expression is related to the fan operating slip rate s, various fan parameters, and fault voltage drop degree k c Related, in addition, B s_rsc The expression is also related to the system's internal control parameters β1 and β2, C s_rsc The expression is also related to the set current value i r_ref Related to the system's internal control parameters α1 and α2.

[0221] In this preferred embodiment, the present application first accurately calculates the first rotor current time-domain expression based on the stator-rotor voltage and flux equations by controlling the rotor-side excitation under minor fault conditions. This is because it provides a detailed description of the rotor current changes of the doubly-fed wind turbine under minor voltage drops. Subsequently, using this first rotor current time-domain expression, the present method further derives the first fault current peak expression, thereby accurately predicting the fault current peak of the doubly-fed wind turbine under minor grid fault conditions. This calculation method based on actual current changes not only improves the accuracy of the prediction, but also provides more reliable data support for fault analysis and protection device design of the power system, enhancing the system's response capability to minor faults and overall stability.

[0222] The second calculation module 30 is used to calculate each fault current peak value according to the time when each fault current reaches a peak value, the first fault current peak value expression and the second fault current expression.

[0223] As a preferred embodiment of the second embodiment, the peak values ​​of the fault currents are calculated based on the time when the fault currents reach their peak values, the first fault current peak value expression, and the second fault current expression, specifically:

[0224] ⑦ Obtain the initial operating status value of the fan;

[0225] ⑧Set fault time t fault The value of , consider the interval [t, t+T];

[0226] ⑨At this fixed time t fault Under this condition, set the time t when the fault current reaches the peak value max The value range is [t fault,t fault +2T];

[0227] ⑩Set the fault voltage drop level k c The value of , consider the interval [0.1, 0.8];

[0228] At the fault time t fault When fixed, the peak current I under this fault condition is calculated by combining the fault current expression of the doubly fed wind turbine max ;

[0229] Set the step size Δt, let t0 = t0 + Δt, and determine whether t0 at this time is within the considered interval. If so, return to the first step and recalculate.

[0230] The specific calculation flow chart is as follows Figure 3 shown.

[0231] like Figure 4 In the DFIG grid-connected system shown in , a three-phase short-circuit fault is set at the grid-connected line Line at different fault times. The fault voltage value at the outlet of the doubly fed wind turbine is measured to obtain the output time-domain current value of the doubly fed wind turbine under different combinations of fault times and fault voltage drop levels. In addition, through the specific calculation flow chart of the doubly fed wind turbine fault current peak value considering multiple factors mentioned above, the comparison between the calculated and actual peak values ​​of the doubly fed wind turbine under various fault conditions can be calculated more accurately. Figure 5 and Figure 6 Where 1-kc is the per-unit value of the voltage after the fault.

[0232] according to Figure 5 and Figure 6 It can be seen that under different fault condition combinations, the measured error between the calculated value of the fault current peak value of the doubly fed wind turbine proposed by the present invention considering multiple factors and the actual value of each peak value is small, which proves the correctness of the peak calculation method proposed. In addition, it should be noted that the time t corresponding to the fault current reaching the maximum value is max and failure time t fault There is a nonlinear relationship between them, which cannot be directly calculated in practice. Due to the large number of fault combinations between the two, a genetic algorithm heuristic search algorithm can be used to search and calculate the peak current of the doubly fed wind turbine under different fault combinations. The basic process of the genetic algorithm is as follows:

[0233] Basic process of genetic algorithm:

[0234] Initialization: Create an initial population, where each individual is generated randomly or initialized according to a specific strategy.

[0235] Calculate the fitness value of each individual in the population.

[0236] Iterative evolution:

[0237] Selection: According to the fitness value, a certain number of individuals are selected as parents.

[0238] Crossover: Perform a crossover operation on the selected parent individuals to generate new offspring individuals.

[0239] Mutation: Mutate offspring individuals with a certain probability.

[0240] Replacement or merging: adding offspring individuals to the population, replacing some or all of the original individuals to form a new generation of population.

[0241] Calculate fitness: Calculate the fitness value of each individual in the new population.

[0242] Termination condition check: Check whether the preset termination conditions (such as maximum number of iterations, fitness threshold, number of times without obvious improvement, etc.) are met.

[0243] If the termination condition is met, the current optimal individual is output as the approximate optimal solution to the problem; otherwise, return to step 2 to continue iteration.

[0244] According to the value range of the two variables, the fault time t is obtained by the genetic algorithm heuristic search algorithm. fault The value of the current reaches the maximum value interval t max ∈[t0,t0+2T], which can reduce the simulation time under different fault conditions and directly obtain the fault and different fault voltage drop degrees k c The maximum peak current value under the combination.

[0245] This device uses three modules to divide the work and coordinate the work to better accurately calculate the fault current under multiple factors. This application can accurately capture the fault current dynamics of the doubly fed wind turbine under the influence of multiple factors by comprehensively considering the initial state of the doubly fed wind turbine, the fault voltage drop value, and the time point of the fault. According to the genetic algorithm, the fault time point and the voltage drop degree are optimized and searched. This application not only improves the calculation efficiency, but also can simulate the current response of the doubly fed wind turbine under different fault conditions. Furthermore, by analyzing the time domain expression of the rotor current under mild and severe voltage drops, this application derives the first and second fault current peak expressions, so as to accurately calculate the fault current peak under the influence of multiple factors. This multi-factor comprehensive analysis method makes this application more accurate in calculating the fault current peak of the doubly fed wind turbine, improves the prediction ability and response strategy of the power system when facing complex power grid faults, and solves the problem in the existing technology that the fault current peak of the doubly fed wind turbine cannot be accurately calculated under multiple factors.

[0246] Example 3:

[0247] An embodiment of the present application provides a computer-readable storage medium, wherein the computer-readable storage medium includes a stored computer program, wherein when the computer program is executed, the device where the computer-readable storage medium is located is controlled to execute the method for calculating the peak value of a wind turbine fault current;

[0248] Wherein, if the method for calculating the peak value of the fault current of a wind turbine is implemented in the form of a software functional unit and used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the present invention implements all or part of the processes in the above-mentioned embodiment method, and can also be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium, and when the computer program is executed by a processor, it can implement the steps of the above-mentioned various method embodiments. Wherein, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form. The computer-readable medium may include: any entity or device that can carry the computer program code, recording medium, USB flash drive, mobile hard disk, magnetic disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signal, telecommunication signal and software distribution medium, etc.

[0249] Example 4

[0250] The present application provides a terminal device, including a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor. When the processor executes the computer program, it implements any one of the methods for calculating the peak value of the wind turbine fault current as described in Example 1.

[0251] The specific embodiments described above further illustrate the objectives, technical solutions, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. In particular, it should be noted that any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included within the scope of protection of the present invention for those skilled in the art.

Claims

1. A method for calculating the peak value of a wind turbine fault current, characterized in that: include: Obtain the operating parameters and structural parameters of each doubly fed wind turbine under different historical fault scenarios; According to the structural parameters, each fault voltage drop value of each doubly-fed wind turbine is obtained; According to the operating parameters, the initial operating state of each doubly fed wind turbine is obtained; Calculate the time when each fault current reaches its peak value based on the time point of each fault occurrence within the preset fault time period, the initial operating state of each doubly fed wind turbine, the value of each fault voltage drop and the genetic algorithm; The peak values ​​of the respective fault currents are calculated based on the time when the respective fault currents reach their peak values, the first fault current peak value expression, and the second fault current peak value expression; wherein the first fault current peak value expression and the second fault current peak value expression are calculated based on the rotor current time domain expressions under two voltage sag levels, specifically: When the voltage of each doubly-fed wind turbine is greater than a preset threshold, it is determined to be a first voltage drop level; otherwise, it is determined to be a second voltage drop level; The first fault current peak expression is calculated based on the first rotor current time-domain expression under the first voltage sag level; the first fault current peak expression is calculated based on the first rotor current time-domain expression under the first voltage sag level, specifically: According to the stator-rotor voltage and flux equation under rotor side excitation control, the time domain expression of the first rotor current is calculated; According to the time-domain expression of the first rotor current, a first fault current peak expression is calculated; The second fault current peak expression is calculated based on the second rotor current time domain expression under the second voltage sag level; The calculation obtains the first fault current peak expression, specifically: The first fault current peak expression is: Where α1 and α2 are the values ​​related to the rotor side excitation control parameters, A s_rsc 、B s_rsc 、C s_rsc is the stator current coefficient for rotor side excitation control, τ s is the inverse of the stator side decay time constant under the rotor side excitation control, ω1 is the synchronous angular velocity value, t x The time when the fault occurs.

2. The method for calculating the peak value of the fault current of a wind turbine according to claim 1, characterized in that: The initial operating state of each doubly-fed wind turbine is obtained according to the operating parameters, specifically: The initial operating state of each doubly-fed wind turbine includes each rotor self-inductance and mutual inductance parameters, each slip rate and each parameter of the system internal control.

3. The method for calculating the peak value of the fault current of a wind turbine according to claim 1, characterized in that: The second fault current peak expression is calculated based on the second rotor current time domain expression under the second voltage sag level, specifically: According to the stator flux value and rotor flux value after the crowbar protection is activated, the time domain expression of the second rotor current and the stator current are calculated; The second fault current peak expression is calculated based on the second rotor current time domain expression and the stator current.

4. The method for calculating the peak value of the fault current of a wind turbine according to claim 3, characterized in that: The calculation obtains the second fault current peak expression, specifically: The second fault current peak expression is: Where A, B, and C are the preset stator current coefficient expressions. are the phase values ​​of expressions A, B, and C respectively, τ rc is the inverse of the rotor side decay time constant, ω1 is the synchronous angular velocity value, t x The time when the fault occurs.

5. A device for calculating the peak value of a wind turbine fault current, characterized in that: It includes an acquisition module, a first calculation module and a second calculation module; The acquisition module is used to obtain the operating parameters and structural parameters of each doubly fed wind turbine under different historical fault scenarios; According to the structural parameters, each fault voltage drop value of each doubly-fed wind turbine is obtained; According to the operating parameters, the initial operating state of each doubly fed wind turbine is obtained; The first calculation module is used to calculate the time when each fault current reaches a peak value according to the time point when each fault occurs within a preset fault time period, the initial state of each doubly fed wind turbine and the value of each fault voltage drop; The second calculation module is configured to calculate each fault current peak value based on the time when each fault current reaches a peak value, the first fault current peak value expression, and the second fault current peak value expression; wherein the first fault current peak value expression and the second fault current peak value expression are calculated based on the rotor current time domain expression under two voltage sag levels, specifically: When the voltage of each doubly-fed wind turbine is greater than a preset threshold, it is determined to be a first voltage drop level; otherwise, it is determined to be a second voltage drop level; The first fault current peak expression is calculated based on the first rotor current time-domain expression under the first voltage sag level; the first fault current peak expression is calculated based on the first rotor current time-domain expression under the first voltage sag level, specifically: According to the stator-rotor voltage and flux equation under rotor side excitation control, the time domain expression of the first rotor current is calculated; According to the time-domain expression of the first rotor current, a first fault current peak expression is calculated; The second fault current peak expression is calculated based on the second rotor current time domain expression under the second voltage sag level; The calculation obtains the first fault current peak expression, specifically: The first fault current peak expression is: Where α1 and α2 are the values ​​related to the rotor side excitation control parameters, A s_rsc 、B s_rsc 、C s_rsc is the stator current coefficient for rotor side excitation control, τ s is the inverse of the stator side decay time constant under the rotor side excitation control, ω1 is the synchronous angular velocity value, t x The time when the fault occurs.

6. A computer-readable storage medium, characterized in that The computer-readable storage medium includes a stored computer program, wherein when the computer program is executed, the device where the computer-readable storage medium is located is controlled to execute the method for calculating the peak value of the wind turbine fault current according to any one of claims 1 to 4.

7. A terminal device, characterized in that: The method comprises a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, wherein when the processor executes the computer program, the method for calculating the peak value of the fault current of the wind turbine according to any one of claims 1 to 4 is implemented.

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