Fan fault current peak value calculation method and device, medium and equipment

Abstract

The invention discloses a fan fault current peak value calculation method and device, a medium and equipment. According to the method, the operation parameters and the structure parameters of the double-fed fans in different historical fault scenes are collected, and the parameters are utilized, so that the structure characteristics of the double-fed fans under different fault voltage drop degrees can be determined, and the initial operation states of the fans can be accurately obtained. In combination with the occurrence time point of each fault in the preset fault time period, the initial operation state of each double-fed fan, each fault voltage drop degree value and the genetic algorithm, the time when each fault current reaches the peak value can be efficiently calculated. Furthermore, based on the time points and a first fault current peak expression and a second fault current peak expression deduced for rotor current time domain expressions under two different voltage drop degrees, according to the first fault current peak expression and the second fault current peak expression, each fault current peak can be accurately calculated 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 world's thirst for sustainable energy grows, new energy technologies, especially wind power generation technology, are rising at an unprecedented rate and becoming a key strategy for coping with energy shortages and reducing greenhouse gas emissions. With its clean and renewable characteristics, wind power generation has not only injected strong impetus into the green development of the global economy and society, but also led to profound changes in the transformation of energy structure, opening up new ways for mankind to explore more environmentally friendly and efficient ways of energy utilization. Among them, the doubly fed wind turbine (DFIG) has been widely used in the world due to its advantages of high efficiency, energy saving, good stability and flexible power adjustment. Its unique doubly fed variable frequency speed regulation technology not only improves the efficiency of wind energy conversion, but also enhances the adaptability and stability of the power grid. It is widely used in many fields such as the power industry, metallurgy, and mining, and has become an important force in promoting the development of clean energy.

[0003] However, DFIG has a special structure and fault characteristics, which are significantly different from traditional synchronous motors. The large-scale and large-capacity access of wind power to the grid will affect the stability of the existing power system, making the normal operation of existing equipment challenging. For example, DFIG will adopt different fault ride-through strategies when there are different fault voltage drops, and the fault current and its calculated peak value at this time are also different. These problems make it impossible for existing technologies to accurately calculate the fault current peak of the doubly fed wind turbine under 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 double-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 value of a 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 double-fed wind turbine is obtained;

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

[0009] According to the time point of each fault occurrence within the preset fault time period, the initial operating state of each double-fed wind turbine, the value of each fault voltage drop and the genetic algorithm, the time when each fault current reaches the peak value is calculated;

[0010] According to the time when each fault current reaches a peak value, the first fault current peak expression and the second fault current expression, each fault current peak value is calculated; 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.

[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. According to the genetic algorithm, the fault time point and the voltage drop degree are optimized and searched. 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 rotor current time domain expression under slight and severe voltage drops, the present application derives the first and second fault current peak expressions, so that the fault current peak under the influence of multiple factors can be accurately calculated. 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 ability and response strategy of the power system when facing complex power grid faults, so as to solve the problem that the fault current peak of the doubly-fed wind turbine cannot be accurately calculated under multiple factors in the prior art.

[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 parameter, 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 power grid fault by obtaining the initial operating state of each doubly fed wind turbine in detail, including 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, accurate knowledge of these operating parameters enables the present method to more realistically simulate the response characteristics of the wind turbine in an actual power 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 drop levels, specifically:

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

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

[0018] The second fault current peak expression is calculated based on the second rotor current time domain expression at the second voltage drop 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 fault analysis of the power system, design of protection devices, and system stability, and enhances the adaptability and safety of the system 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 drop 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, which is 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 failure occurred.

[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. Because it provides a detailed description of the rotor current changes of the doubly-fed wind turbine under minor voltage drop levels. Subsequently, using this first rotor current time domain expression, the present method further derives the first fault current peak expression, thereby being able to accurately predict 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 of the power system and the design of protection devices, enhancing the system's responsiveness 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 drop level, specifically:

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

[0030] The second fault current peak value 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, which is specifically:

[0032] The second fault current peak expression is:

[0033]

[0034] In the formula, 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 failure occurred.

[0035] In this preferred embodiment, the present application aims at the crowbar protection in severe fault conditions, and first accurately calculates the time domain expression of the second rotor current and the stator current 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, so that the fault current peak of the doubly fed wind turbine can be accurately predicted 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 of the power system and the design of protection devices, 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 for calculating a peak value of a fault current of a wind turbine 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 double-fed wind turbine under different historical fault scenarios;

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

[0041] The second calculation module 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 expression and the second fault current peak 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 rotor current time domain expression under mild and severe voltage drops, this application derives the first and second fault current peak expressions, so that the fault current peak under the influence of multiple factors can be accurately calculated. 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, so as to solve the problem that the fault current peak of the doubly fed wind turbine cannot be accurately calculated under multiple factors in the prior art.

[0043] In a third aspect, the present application provides a computer-readable storage medium, the computer-readable storage medium including 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 a method for calculating a peak value of a fault current of a wind turbine as described. Its beneficial effect is the same as the method for calculating a peak value of a fault current of a wind turbine 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 a 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 fault current of a wind turbine provided in the present application;

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

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

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

[0049] Figure 5: A structural schematic diagram of an embodiment of the comparison between the current peak simulation value and the calculated value under the crowbar protection provided by the present application;

[0050] Figure 6 : A structural schematic diagram of an embodiment of the comparison between the current peak value simulation value and the calculated value under RSC continuous excitation control provided by the present application;

[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 be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0053] Embodiment 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 fault current of the wind turbine in this application is described in detail through steps S01-S05.

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

[0057] S02: Obtaining each fault voltage drop degree value of each doubly-fed wind turbine 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 value 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), and 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 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 times t fault And different fault voltage drop degree k c Considering the above factors, it is necessary 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 each parameter, substitute it 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 crossing 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, which 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 operating conditions, including the 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 according to 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 drop 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 degree, otherwise, it is determined to be a second voltage drop degree, 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 at the first voltage drop level;

[0067] The second fault current peak expression is calculated based on the second rotor current time domain expression at the second voltage drop 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 electrical quantity on the stator side, the subscript r represents the electrical quantity on the rotor side, U, i, r represents voltage, current, flux linkage 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 of 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 of formula (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 get:

[0076]

[0077] in, Represents the flux value on the rotor side. Substituting the above formula into the rotor voltage equation, the relationship between the current and flux on the stator side 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, it can be deduced that the stator flux value after the Crowbar is put into operation in the dq synchronous rotating coordinate system is:

[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 unit value of the initial fault voltage, ω1 is the fundamental frequency, k c is the voltage drop per unit value. Combining the stator and rotor voltage and flux equations, the stator and rotor current time domain expression can be solved as:

[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 fault analysis of the power system, design of protection devices, and system stability, and enhances the adaptability and safety of the system 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 drop level, specifically:

[0088] When the fault is minor, the DFIG keeps the power outer loop control intact, and the output is still controlled by the rotor-side converter (RSC) excitation. When the grid voltage fluctuates or fails, the RSC excitation control can adjust the control strategy and parameters, suppress rotor overcurrent and overvoltage, and adjust the operating status and output characteristics of the generator to cope with grid faults and fluctuations, improve the fault ride-through capability of the doubly fed wind turbine, and ensure that it can still operate stably during grid faults.

[0089] According to the principle of flux conservation, the stator flux will not change suddenly at the moment of fault. Therefore, the stator flux after the fault has two components: one is the stator flux steady-state component corresponding to the residual pressure 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 get:

[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 the value related to the RSC inner and outer loop control parameters. Solving the above equation, the stator current analytical formula under dq synchronous rotating coordinates is obtained:

[0096]

[0097] In the formula, 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 stator short-circuit current of the DFIG controlled by RSC 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. Because it provides a detailed description of the rotor current changes of the doubly-fed wind turbine under minor voltage drop levels. Subsequently, using this first rotor current time domain expression, the present method further derives the first fault current peak expression, thereby being able to accurately predict 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 of the power system and the design of protection devices, enhancing the system's responsiveness 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 under the second voltage drop degree, 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 machine-end voltage drops suddenly at the moment of fault, its stator flux remains continuous due to physical characteristics and will not change suddenly. This characteristic leads to a complex stator flux structure after the fault, which includes both the steady-state component corresponding to the machine-end residual voltage and the transient component induced in the stator flux due to the voltage drop. The stator flux expression after the fault is:

[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 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 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 put into use, an additional resistance value Rc is introduced into the rotor side circuit. This change causes the total resistance value of 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 put into use, not only the voltage distribution on the rotor side is changed, but also the electromagnetic coupling relationship between the stator and the rotor is profoundly affected. Substituting equation (6) into the rotor voltage equation, the relationship between the current and the 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 coefficients 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 of the wind turbine during normal operation; τ rc is the inverse of the rotor side decay time constant, expressed as Rr 'L s / L D Transforming 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 doubly fed wind turbine under different fault strategies, the fault time is set to t fault The time when the current reaches the maximum value is t max , t x =t max -t fault , and then based on equations (14) and (26), the peak value calculation expression of the fault current in the two stages is obtained. The peak value under the input of the crowbar protection is:

[0120]

[0121] Combining the specific expressions of each formula, we can get that both expression A and expression B are consistent with the crowbar protection resistance value R' r , fan running 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 fault current peak value 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 running 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. Because it provides a detailed description of the rotor current changes of the doubly-fed wind turbine under minor voltage drop levels. Subsequently, using this first rotor current time domain expression, the present method further derives the first fault current peak expression, thereby being able to accurately predict 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 of the power system and the design of protection devices, enhancing the system's responsiveness 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 the 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 the fault time t fault The value of , consider the interval [t, t+T];

[0130] ③At 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];

[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, and 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 fault times and fault voltage drop degree combinations. In addition, through the above-mentioned doubly fed wind turbine fault current peak specific calculation flow chart considering multiple factors, the peak value calculated value and actual value comparison 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 values ​​between the calculated fault current peak value of the doubly fed wind turbine considering multiple factors proposed in the present invention and the actual values ​​of each peak value are small, which proves the correctness of the proposed peak calculation method. In addition, it should be noted that the time t corresponding to the fault current reaching the maximum value max and failure time t fault There is a nonlinear relationship between them, and it is impossible to directly calculate them in practice. Since there are many combinations of fault conditions between the two, a genetic algorithm heuristic search algorithm can be used here to search and calculate the peak current of the double-fed wind turbine under different fault combinations. The basic process of the genetic algorithm is as follows:

[0137] The 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 merger: Add 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 iterating.

[0148] According to the range of values ​​of the two variables, the failure time t is obtained by using 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 fault And different fault voltage drop degree k c The maximum current peak 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. According to the genetic algorithm, the fault time point and the voltage drop degree are optimized and searched. 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 rotor current time domain expression under slight and severe voltage drops, the present application derives the first and second fault current peak expressions, so that the fault current peak under the influence of multiple factors can be accurately calculated. 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 ability and response strategy of the power system when facing complex power grid faults, so as to solve the problem that the fault current peak of the doubly-fed wind turbine cannot be accurately calculated under multiple factors in the prior art.

[0150] Embodiment 2

[0151] Please refer to Figure 7 , which is a calculation device for the peak value of the wind turbine fault current 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 values ​​of each doubly-fed wind turbine according to the structural parameters.

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

[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 value 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), and 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 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 times t fault And different fault voltage drop degree k c Considering the above factors, it is necessary 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 crossing 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, which 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 operating conditions, including the 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 according to the time point when each fault occurs within a preset fault time period, the initial operating state of each doubly fed wind turbine, each fault voltage drop value and a 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 drop 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 degree, otherwise, it is determined to be a second voltage drop degree, 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 at the first voltage drop level;

[0163] The second fault current peak expression is calculated based on the second rotor current time domain expression at the second voltage drop 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 electrical quantity on the stator side, the subscript r represents the electrical quantity on the rotor side, U, i, r represents voltage, current, flux linkage 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 of 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 of formula (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 get:

[0172]

[0173] in, Represents the flux value on the rotor side. Substituting the above formula into the rotor voltage equation, the relationship between the current and flux on the stator side 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, it can be deduced that the stator flux value after the Crowbar is put into operation in the dq synchronous rotating coordinate system is:

[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 unit value of the initial fault voltage, ω1 is the fundamental frequency, k c is the voltage drop per unit value. Combining the stator and rotor voltage and flux equations, the stator and rotor current time domain expression can be solved as:

[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 fault analysis of the power system, design of protection devices, and system stability, and enhances the adaptability and safety of the system 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 drop level, specifically:

[0184] When the fault is minor, the DFIG keeps the power outer loop control intact, and the output is still controlled by the rotor-side converter (RSC) excitation. When the grid voltage fluctuates or fails, the RSC excitation control can adjust the control strategy and parameters, suppress rotor overcurrent and overvoltage, and adjust the operating status and output characteristics of the generator to cope with grid faults and fluctuations, improve the fault ride-through capability of the doubly fed wind turbine, and ensure that it can still operate stably during grid faults.

[0185] According to the principle of flux conservation, the stator flux will not change suddenly at the moment of fault. Therefore, the stator flux after the fault has two components: one is the stator flux steady-state component corresponding to the residual pressure 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 get:

[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 the value related to the RSC inner and outer loop control parameters. Solving the above equation, the stator current analytical formula under dq synchronous rotating coordinates is obtained:

[0192]

[0193] In the formula, 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 stator short-circuit current of the DFIG controlled by RSC 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. Because it provides a detailed description of the rotor current changes of the doubly-fed wind turbine under minor voltage drop levels. Subsequently, using this first rotor current time domain expression, the present method further derives the first fault current peak expression, thereby being able to accurately predict 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 of the power system and the design of protection devices, enhancing the system's responsiveness 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 drop degree, 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 machine-end voltage drops suddenly at the moment of fault, its stator flux remains continuous due to physical characteristics and will not change suddenly. This characteristic leads to a complex stator flux structure after the fault, which includes both the steady-state component corresponding to the machine-end residual voltage and the transient component induced in the stator flux due to the voltage drop. The stator flux expression after the fault is:

[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 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 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 put into use, an additional resistance value Rc is introduced into the rotor side circuit. This change causes the total resistance value of 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 put into use, not only the voltage distribution on the rotor side is changed, but also the electromagnetic coupling relationship between the stator and the rotor is profoundly affected. Substituting equation (34) into the rotor voltage equation, the relationship between the current and the flux on the stator side is obtained as:

[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 coefficients 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 of the wind turbine during normal operation; τ rc is the inverse of the rotor side decay time constant, expressed as R r 'L s / L D Transforming 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 doubly fed wind turbine under different fault strategies, the fault time is set to t fault The time when the current reaches the maximum value is t max , t x =t max -t fault , and then based on equations (42) and (54), the peak value calculation expression of the fault current in the two stages is 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 consistent with the crowbar protection resistance value R' r , fan running 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 fault current peak value 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 running 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. Because it provides a detailed description of the rotor current changes of the doubly-fed wind turbine under minor voltage drop levels. Subsequently, using this first rotor current time domain expression, the present method further derives the first fault current peak expression, thereby being able to accurately predict 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 of the power system and the design of protection devices, enhancing the system's responsiveness 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 the 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, and 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 fault times and fault voltage drop degree combinations. In addition, through the above-mentioned doubly fed wind turbine fault current peak specific calculation flow chart considering multiple factors, the peak value calculated value and actual value comparison of the doubly fed wind turbine under various fault conditions can be calculated more accurately. Figure 5 and Figure 6 As shown in Figure 1, 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 values ​​between the calculated fault current peak value of the doubly fed wind turbine considering multiple factors proposed in the present invention and the actual values ​​of each peak value are small, which proves the correctness of the proposed peak calculation method. In addition, it should be noted that the time t corresponding to the fault current reaching the maximum value max and failure time t fault There is a nonlinear relationship between them, and it is impossible to directly calculate them in practice. Since there are many combinations of fault conditions between the two, a genetic algorithm heuristic search algorithm can be used here to search and calculate the peak current of the double-fed wind turbine under different fault combinations. The basic process of the genetic algorithm is as follows:

[0233] The 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 merger: Add 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 iterating.

[0244] According to the range of values ​​of the two variables, the failure time t is obtained by using 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 fault And different fault voltage drop degree k c The maximum current peak 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 rotor current time domain expression under mild and severe voltage drops, this application derives the first and second fault current peak expressions, so that the fault current peak under the influence of multiple factors can be accurately calculated. 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, so as to solve the problem that the fault current peak of the doubly fed wind turbine cannot be accurately calculated under multiple factors in the prior art.

[0246] Embodiment three:

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

[0248] Wherein, the calculation method of the peak value of the fault current of a wind turbine, if implemented in the form of a software functional unit and used as an independent product, can be stored in a computer-readable storage medium. Based on such an 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 the computer program can implement the steps of the above-mentioned various method embodiments when executed by the processor. 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, etc. The computer-readable medium may include: any entity or device capable of carrying the computer program code, recording medium, U disk, mobile hard disk, magnetic disk, optical disk, computer memory, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), electric carrier signal, telecommunication signal and software distribution medium, etc.

[0249] Embodiment 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, and when the processor executes the computer program, it implements any one of the methods for calculating the peak value of a wind turbine fault current as described in Example 1.

[0251] The specific embodiments described above further illustrate the purpose, technical solutions and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. It is particularly pointed out that for those skilled in the art, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the scope of protection of the present invention.

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 double-fed wind turbine is obtained; According to the operating parameters, the initial operating state of each doubly-fed wind turbine is obtained; According to the time point of each fault occurrence within the preset fault time period, the initial operating state of each double-fed wind turbine, the value of each fault voltage drop and the genetic algorithm, the time when each fault current reaches the peak value is calculated; According to the time when each fault current reaches a peak value, the first fault current peak expression and the second fault current expression, each fault current peak value is calculated; 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.

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 parameter, 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 fault current peak expression and the second fault current peak expression are calculated based on the rotor current time domain expressions under two voltage drop levels, specifically: When the voltage of each double-fed wind turbine is greater than a preset threshold, it is determined to be a first voltage drop degree, otherwise, it is determined to be a second voltage drop degree; The first fault current peak expression is calculated based on the first rotor current time domain expression at the first voltage drop level; The second fault current peak expression is calculated based on the second rotor current time domain expression at the second voltage drop level.

4. The method for calculating the peak value of the fault current of a wind turbine according to claim 3, characterized in that: The first fault current peak expression is calculated based on the first rotor current time domain expression under the first voltage drop 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, the first fault current peak expression is calculated.

5. The method for calculating the peak value of the fault current of a wind turbine according to claim 4, characterized in that: The calculation obtains the first fault current peak expression, which is 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 failure occurred.

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

7. The method for calculating the peak value of the fault current of a wind turbine according to claim 6, characterized in that: The calculation obtains the second fault current peak expression, which is specifically: The second fault current peak expression is: In the formula, 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 failure occurred.

8. A device for calculating the peak value of a fault current of a wind turbine, 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 double-fed wind turbine under different historical fault scenarios; According to the structural parameters, each fault voltage drop value of each double-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 double-fed wind turbine and the value of each fault voltage drop; The second calculation module 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 expression and the second fault current peak 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.

9. 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 fault current of a wind turbine as claimed in any one of claims 1 to 7.

10. 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 as claimed in any one of claims 1 to 7 is implemented.

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