Fault current analysis of doubly-fed wind turbine and identification method of controller parameters, storage medium and equipment

Abstract

The method for analyzing fault current of a doubly-fed wind turbine and identifying parameters of a controller, a storage medium and equipment belong to the technical field of electric power. In order to solve the problems of low identification accuracy of the existing identification method under the fault state of the doubly-fed wind turbine and the dependence on the performance of the optimization algorithm and the idealization of the identification scene which is not applicable to actual engineering, the present application first establishes an accurate and detailed topology of the doubly-fed wind turbine, an RSC controller and an LVRT control strategy, then obtains a detailed fault current analytical expression of the doubly-fed wind turbine through mathematical model derivation, determines a reactive power support coefficient, a reactive power voltage threshold and a maximum current through voltage drop fault test, then obtains a rotor reactive current reference value according to a voltage drop value corresponding to a new fault and the reactive power support coefficient and the reactive power voltage threshold, combines the maximum current to obtain a power current reference value, and further identifies the controller parameters in the RSC controller based on the fault current analytical expression.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of electric power, and particularly relates to a fault current calculation method for a doubly-fed wind power generator, a controller parameter identification method, a storage medium and equipment. BACKGROUND

[0002] Establishing a doubly-fed wind turbine model consistent with the actual low voltage ride through (LVRT) short-circuit fault response characteristics is a prerequisite and foundation for safety and stability analysis of new energy high-proportion power systems. The black-box controller parameters of manufacturers make it impossible to restore the actual wind turbine characteristics in the simulation model, so the identification of controller parameters that dominate the external characteristics of doubly-fed wind turbines has important engineering significance. Existing dynamic characteristic analysis of doubly-fed wind turbines in fault state is mainly based on characteristic comparison and excavation of numerical simulation data, lacks analysis of the physical mechanism level of doubly-fed wind turbines, and the identification method has problems such as low identification accuracy, dependence on identification algorithm performance, and idealization of identification scenarios that are not suitable for actual engineering. In view of the above problems, the present application proposes a parameter step-by-step identification method based on detailed analysis of short-circuit current. First, based on the LVRT output dynamic characteristics of the doubly-fed wind turbine and the general LVRT control strategy of the doubly-fed wind turbine, the LVRT control strategy parameters are identified. Then, the controller parameters are identified through the detailed short-circuit current analysis expression of the doubly-fed wind turbine proposed by the present application. Finally, through comparison of simulation examples and actual wind turbine controller recording data, it is verified that the detailed short-circuit analysis expression proposed by the present application has clear physical mechanism, accurate representation and high applicability, and the parameter identification method based on the analysis expression has the advantages of high accuracy, independence on identification algorithm and applicability to actual engineering.

[0003] For wind turbine fault current analysis and parameter identification method, researchers have a variety of solutions, for example:

[0004] 1. Pan Wenxia et al. published "Short-circuit current calculation of doubly-fed machine considering Crowbar resistance" in Proceedings of the CSEE, 2016, 36(13):3629-3634+3382. This article ignores the influence of the controller during the fault, establishes a transient equivalent circuit of the doubly-fed wind turbine containing Crowbar, and derives a three-phase short-circuit expression.

[0005] 2. Ling Yu et al. published "Transient characteristics analysis of doubly-fed wind power generator under symmetrical voltage fault" in Proceedings of the CSEE, 2022, 42(18):6871-6880. This article derives a rotor fault current analytical expression by analyzing the flux linkage dynamics of the doubly-fed wind turbine, but does not consider the regulation characteristics of the converter.

[0006] 3. Kong X, et al. Study of Fault Current Characteristics of the DFIG Considering Dynamic Response of the RSC. IEEE Transactions on Energy Conversion, 2014, 29(2): 278-287. This paper sets the transfer function of the doubly-fed wind turbine as a typical type I and type II system, and obtains a simplified calculation model of the fault current considering the excitation regulation of the converter.

[0007] 4. Zheng T, et al. Analysis of Stator Current of Doubly-Fed Wind Turbines Considering Different Grid Voltage Dips. Power System Protection and Control, 2015, 43(01): 81-87. This paper considers the influence of the controller, derives the second-order dynamic equation of the rotor current in the transient state and solves it, but the ideal scene is limited in the solving process, and the analytical results are not universal.

[0008] 5. Chang Y, et al. Fault Current Analysis of Type-3 WTs Considering Sequential Switching of Internal Control and Protection Circuits in Multi Time Scales during LVRT. IEEE Transactions on Power Systems, 2018, 33(6): 6894-6903. This paper analyzes and summarizes the sequential switching characteristics, nonlinearity, and high-order coupling characteristics of the transient characteristics of the doubly-fed wind turbine, and obtains an analytical expression of the stator fault current by appropriate simplification, which provides a very good idea for studying the mathematical laws of the transient behavior of the doubly-fed wind turbine. However, the key parameter of the integral constant of the controller is ignored in the derivation process, which cannot meet the requirement of parameter identification for model accuracy.

[0009] 6. Pan X, et al. Frequency Domain Method for Parameter Identification of Grid-Side Controller of Doubly-Fed Wind Turbines. Power System Technology, 2015, 39(03): 634-638. This paper derives the transfer function of the rotor-side and grid-side controllers of the doubly-fed wind turbine, sets a step response by superimposing a pseudo-random signal on the reference value, and identifies the parameters of the double-closed-loop controller. However, some manufacturers' controllers cannot set a step disturbance on the reference value, and the sensitivity of the double-closed-loop structure in identifying the parameters of the inner controller is low, resulting in large errors in the identification results.

[0010] 7. Xu RQ, et al. Research on parameter identification method of doubly-fed wind turbine converter based on M sequence. Power System Technology, 2022, 46(02): 578-586, which proposes to superimpose an M sequence pseudo-random signal excitation control system transfer function on the measurement signal, and identify the controller parameters through sine and cosine identification algorithm, but this method needs to change the secondary circuit structure, which is complex in actual application.

[0011] 8. Guo Q, et al. Parameter decoupling identification method of doubly-fed wind turbine system low voltage ride through model considering recovery transient process. High Voltage Technology, 2021, 47(10): 3430-3440, which separates the LVRT control strategy parameters and the controller parameters by setting fault disturbance, and realizes the identification of wind turbine LVRT control parameters, but this method depends on the performance and parameters of intelligent identification algorithm, and there is a problem of local optimal solution.

[0012] In summary, the existing research on the analysis of short-circuit current of doubly-fed wind turbine has the problems of single use scene, a large number of approximate simplification in derivation process, and low accuracy, and mainly focuses on Crowbar protection circuit. According to the grid connection regulations of many countries, wind turbines need to provide reactive current to support voltage recovery during LVRT process, and Crowbar circuit needs to lock the converter to make the doubly-fed wind turbine in an uncontrollable state, which cannot meet this requirement. Therefore, more and more doubly-fed wind turbines use Chopper protection circuit which can continuously excite during fault. The existing dynamic characteristic analysis of doubly-fed wind turbine in fault state is mainly based on the characteristic comparison of numerical simulation data, and lacks analysis of the physical mechanism of doubly-fed wind turbine. The identification method has the problems of low identification accuracy, dependence on optimization algorithm performance, and idealized identification scene which is not suitable for actual engineering. Moreover, the existing parameter identification mainly has the problems that the proposed method stays at the theoretical simulation level, is not suitable for engineering practice, has strict identification conditions, and the identification performance depends on intelligent identification algorithm. Therefore, an accurate and efficient doubly-fed wind turbine fault current analysis and controller parameter identification method is needed. SUMMARY

[0013] The purpose of the present application is to solve the problems of low identification accuracy and dependence on optimization algorithm performance and idealized identification scene which is not suitable for actual engineering of the existing identification method of doubly-fed wind turbine in fault state.

[0014] A doubly-fed wind turbine fault current analysis and controller parameter identification method, the electrical part of the doubly-fed wind turbine includes an induction generator DFIM, a rotor-side converter RSC, a grid-side converter GSC, and an RSC controller; the rotor voltage before and after fault in the RSC controller is as follows:

[0015] ur = K p (i rref -i r )+K i ∫(i rref -i r )dt+R r i r +jω r ψ r

[0016] where K p is the proportional coefficient of the PI controller, K i is the integral coefficient of the PI controller; i r is the rotor current, i rref is the rotor current reference value; R r is the rotor winding resistance, ω r is the rotor electric angular velocity, ψ r is the rotor flux; j represents an imaginary number;

[0017] Parameter identification based on the analytical expression of the fault current under the stator winding of the doubly-fed wind turbine;

[0018] The analytical expression of the fault current under the stator winding is:

[0019]

[0020] where i st is the steady-state component of the stator current in the fault state, i tr is the transient component of the stator current in the fault state, i str is the sub-transient component of the stator current in the fault state, i str = i s0 -i st +i tr , i s0 is the stator current before the fault; u sf is the voltage after the fault; ω s is the power frequency angular velocity; L m is the mutual inductance between the stator and rotor windings; L st is the steady-state component inductance; L tr is the transient component inductance; ω f is the transient component oscillation frequency; ψ s0 is the stator flux before the fault; T1 is the transient component attenuation factor; T2 is the sub-transient component attenuation factor; t is time;

[0021] Before parameter identification, the reactive power support coefficient k, the reactive voltage threshold u set and the maximum current I maxThen, based on the identification of the controller parameters K p , K i ;

[0022] The process of determining k, u set and I max includes: performing a voltage drop fault test, collecting the machine terminal voltage u s , and the rotor current and active current; taking the rotor current as the rotor reactive current reference value i rref_q during the fault, combining the reactive support coefficient k and the reactive voltage threshold u s obtained according to u rref_q and the reactive current reference value i set ; taking the active current as the rotor active current reference value i rref_p during the fault, combining the active current reference value i rref_p and the reactive current reference value i rref_q to obtain the maximum current I max ;

[0023] The process of identifying the controller parameters K p , K i based on the identification of the controller parameters K p , K i includes: when a new fault occurs, obtaining the rotor reactive current reference value i rref_q according to the voltage drop value u s corresponding to the new fault and the reactive support coefficient k, the reactive voltage threshold u set , obtaining the active current reference value i rref_p based on i rref_q and the maximum current I max , replacing i rref in the fault current analytical expression (19) with i rref_q and i rref_p as the real part and the imaginary part; then selecting an arbitrary voltage drop fault condition, and identifying the controller parameters K p , K i based on the fault current analytical expression (19).

[0024] Further, the steady-state component inductance The transient component inductance L s , L r are the self-inductance of the stator and rotor windings, respectively, and σ is the leakage inductance coefficient; the transient component oscillation frequency R s is the resistance of the stator winding; T1 is the transient component damping factor, T2 is the sub-transient component damping factor, REAL, IMAG represent the real part and the imaginary part of a complex number.

[0025] Further, the leakage inductance coefficient

[0026] Further, in combination with the active current reference value i s and the reactive current reference value i rref_q , the process of obtaining the reactive support coefficient k and the reactive voltage threshold value u set is implemented according to .

[0027] Further, in combination with the active current reference value i rref_p and the reactive current reference value i rref_q , the process of obtaining the maximum current I max is implemented according to .

[0028] Further, the analytical expression of the fault current under the stator winding is obtained by the following steps:

[0029] The rotor voltage equation of the doubly-fed induction generator DFIM in the synchronous speed coordinate system is subjected to Laplace transformation from the time domain to the frequency domain, and formula (9) is obtained.

[0030] u r (s) = R r i r (s) + sψ r (s) - ψ r0 +jω r ψ r (s) (9)

[0031] In the formula, ψ r0 is the rotor flux before the fault;

[0032] The rotor flux equation is brought into the stator flux equation to obtain the frequency domain equation:

[0033]

[0034] The rotor current of the rotor flux equation is transformed to the frequency domain, and formula (11) is obtained.

[0035]

[0036] Formula (11) and formula (10) are substituted into the rotor voltage equation formula (9), the rotor flux and the rotor current in formula (9) are replaced, and the stator flux equation is obtained by arranging formula (11).

[0037]

[0038] The frequency domain expression of the rotor voltage equation under the control of the controller is:

[0039]

[0040] where s is Laplace operator;

[0041] Substituting equation (10), equation (11) and equation (13) into equation (12) can obtain:

[0042]

[0043] where,

[0044] The stator voltage equation is transformed to frequency domain as equation (15):

[0045] u s (s) = R s i s (s) + sψ s (s) - ψ s0 + jω s ψ s (s) (15)

[0046] where ψ s0 is the pre-fault stator flux linkage;

[0047] Substituting equation (14) into equation (15) can obtain:

[0048]

[0049] After the fault occurs, the stator voltage u s (s) is obtained in the form of step response in equation (16) as equation (17); the rotor reference value i rref is obtained in the form of step response as equation (18);

[0050]

[0051] where u sf is the post-fault voltage;

[0052] The Laplace inverse transformation is performed on equation (16) by using the residue method to obtain the analytical expression of the fault current under the stator winding.

[0053] Further, the rotor voltage equation of the doubly-fed induction generator DFIM in the synchronous speed coordinate system is

[0054]

[0055] Further, the rotor flux linkage equation and the stator flux linkage equation are as follows:

[0056] ψ s = L s i s + L m i r(3)

[0057] psi r =L m i s +L r i r (4)

[0058] In the formula, psi s , psi r Be the stator, rotor flux, L s , L r Be the stator, rotor winding self-induction, L m Be the stator winding mutual inductance.

[0059] A computer storage medium, the storage medium has at least one instruction, the at least one instruction is loaded and executed by the processor to realize the one kind of doubly-fed wind turbine fault current analysis and the identification method of controller parameter.

[0060] A doubly-fed wind turbine fault current analysis and controller parameter identification device, the device includes a processor and a memory, the memory has at least one instruction, the at least one instruction is loaded and executed by the processor to realize the one kind of doubly-fed wind turbine fault current analysis and the identification method of controller parameter.

[0061] Compared with the prior art, the beneficial effects of the present application are that:

[0062] In the aspect of short-circuit current analysis, the proposed detailed fault current analysis expression under the stator winding of doubly-fed wind turbine solves the problems that the current short-circuit current analysis research does not consider the influence of exciter at the moment of fault, the application scene is single, and a large number of simplifications. Through example simulation, it is proved that the formula has the advantages of clear physical mechanism, high accuracy of short-circuit current analysis and application to various LVRT fault scenes.

[0063] In the aspect of controller parameter identification, in view of the problems of current double-fed fan parameter identification method, such as large inner loop parameter identification error, difficulty in actual engineering implementation and dependence on intelligent optimization algorithm performance, the application proposes an ASI method for accurately identifying the LVRT control strategy and the key parameters of the controller through step-by-step identification based on the LVRT control strategy and the fault current analytical expression under the stator winding, the identification accuracy is high, and the proposed method is verified to have the advantages of high accuracy, simple and practical method, clear principle and independence from optimization algorithm through simulation examples and measured wave comparison, and can provide analysis basis for high proportion of new energy power system simulation modeling, equipment selection, safety and stability analysis and protection calculation and the like. Overall, the application provides a more efficient, more accurate and more practical method for fault characteristic analysis of double-fed wind turbine, which has important promoting effect on the technical development and practical application of the wind power field. BRIEF DESCRIPTION OF DRAWINGS

[0064] Figure 1 The double-fed fan structure.

[0065] Figure 2 The identification process of the controller parameter method. DETAILED DESCRIPTION

[0066] The application first establishes an accurate and detailed double-fed fan topology, RSC controller and LVRT control strategy, then obtains a detailed double-fed fan fault current analytical expression through mathematical model derivation, and finally identifies the double-fed fan parameters according to the field measured double-fed fan fault current recording wave through the differential evolution intelligent algorithm. The application will be described in detail in combination with the specific embodiments. Specific embodiment one:

[0068] The embodiment is a double-fed wind turbine fault current analysis and controller parameter identification method, which comprises the following steps:

[0069] The double-fed fan mainly comprises a mechanical part and an electrical part, the mechanical part comprises a wind turbine and a gear box, the electrical part comprises an induction generator (DFIM), a rotor side converter (RSC), a grid side converter (GSC) and a controller, the controller comprises an RSC controller and a GSC controller, and the RSC controller is used in the subsequent process of the embodiment.

[0070] The wind turbine converts wind energy into mechanical energy. The wind turbine drives the induction generator to rotate through the gear box. The stator side of the generator is directly connected with the power grid and is the main power transmission path. The rotor side is excited and regulated through the back-to-back converter. The topology structure is shown in Figure 1The protection circuit adopts a Chopper, which is connected in parallel across the DC bus and is composed of a switch and a power dissipation resistor in series. When a low voltage fault occurs, the switch is closed and the power dissipation resistor dissipates the excess energy to maintain the DC bus voltage stable, so that the doubly-fed wind turbine can continue to work during the fault. Since the mechanical part has a huge moment of inertia, the fault duration is very short, and the rotor speed during the power grid short-circuit fault is still very close to the value before the fault. Therefore, the application makes a constant speed assumption before and after the fault, and does not pay too much attention to the mechanical part. Since the short-circuit current contributed by the grid-side converter is much smaller than the fault current contributed by the stator, the transient characteristic modeling in the application mainly focuses on the stator current controlled by the RSC controller.

[0071] 1. Doubly-fed induction generator model:

[0072] The full-order Park model of the doubly-fed induction generator (DFIM) is a basic mathematical model for studying the doubly-fed wind turbine under power short-circuit fault. The stator and rotor voltage equations in the synchronous speed coordinate system are shown in equations (1) and (2).

[0073]

[0074] In the formula, u s , u r are stator and rotor voltages, R s , R r are stator and rotor winding resistances, i s , i r are stator and rotor currents, ψ s , ψ r are stator and rotor fluxes, ω s is the power frequency angular velocity, and ω r is the rotor electric angular velocity.

[0075] The flux equations are shown in equations (3) and (4).

[0076] ψ s = L s i s + L m i r (3)

[0077] ψ r = L m i s + L r i r (4)

[0078] In the formula, L s , L r are stator and rotor winding self-inductances, and L m is the stator-rotor winding mutual inductance.

[0079] 2. RSC controller structure and LVRT control strategy:

[0080] The RSC controller realizes the indirect control of stator current by controlling the rotor excitation adjustment of rotor current and rotor voltage. With rotor current as the control object, proportional integral (PI) is used as the controller, and a feedforward term is added to eliminate the dq axis coupling effect, realize active and reactive decoupling control, and strengthen the adjustment performance of the controller. The rotor voltage equation controlled by the controller before and after the fault is shown in equation (5):

[0081] u r = K p (i rref -i r ) + K i ∫(i rref -i r )dt + R r i r +jω r ψ r (5)

[0082] In the formula, K p is the proportional coefficient of the PI controller, K i is the integral coefficient of the PI controller, i rref is the rotor current reference value, and the LVRT control strategy under fault conditions is determined by equations (7) and (8). The phase-locked loop can quickly synchronize with the grid voltage before and after the fault.

[0083] During the fault duration of the doubly-fed wind turbine, the reactive current injected into the grid is adjusted according to the voltage drop depth according to the grid connection standard, so as to control the reactive power and support the grid voltage recovery:

[0084] i Q =k·(uset-us)·I n (6)

[0085] In the formula, i Q is the reactive current that the doubly-fed wind turbine should generate during the fault, k is the reactive power support coefficient, u set is the reactive voltage threshold, u s is the terminal voltage, and I n is the rated current.

[0086] The reactive current of the doubly-fed wind turbine is completely emitted by the stator, and the stator current is controlled by the RSC controller to emit the rotor current. Equation (6) is transformed into rotor current as shown in equation (7);

[0087]

[0088] In the formula, irref_q is the rotor active current reference value during fault, i

[0089] In order to provide maximum reactive power support during fault, the reactive power priority control is usually adopted. Therefore, the reference value of active current during fault will be updated by the reactive power priority principle shown in equation (8):

[0090]

[0091] where i rref_p is the rotor active current reference value during fault, i p_normal is the steady-state value of active current before fault, I max is the maximum current.

[0092] 3. Short-circuit current analysis of DFIG:

[0093] The Laplace transform is applied to the rotor voltage equation (2) to convert it from time domain to frequency domain, and equation (9) is obtained.

[0094] u r (s) = R r i r (s) + sψ r (s) - ψ r0 + jω r ψ r (s) (9)

[0095] where ψ r0 is the rotor flux before fault.

[0096] The leakage coefficient is known as Substitute equation (4) into equation (3) to obtain the frequency domain equation:

[0097]

[0098] The rotor current of equation (4) is transformed to frequency domain as shown in equation (11).

[0099]

[0100] Substitute equation (11) and equation (10) into the rotor voltage equation (9), replace the rotor flux and rotor current in equation (9), and rearrange to obtain the stator flux equation as shown in equation (12).

[0101]

[0102] The frequency domain expression of the rotor voltage equation under the control of the controller is:

[0103]

[0104] where s is the Laplace operator.

[0105] Substituting equation (10), equation (11) and equation (13) into equation (12) can obtain:

[0106]

[0107] In the formula,

[0108] The stator voltage equation is transformed into the frequency domain as shown in equation (15):

[0109] u s (s) = R s i s (s) + sψ s (s) - ψ s0 + jω s ψ s (s) (15)

[0110] In the formula, ψ s0 is the stator flux before the fault.

[0111] Substituting equation (14) into equation (15) can obtain:

[0112]

[0113] After the fault occurs, the stator voltage u s (s) appears in the form of a step response in equation (16), as shown in equation (17). The rotor reference value i rref appears in the form of a step response as shown in equation (18), and the amplitude is in vector form, the imaginary part is equation (7), and the real part is equation (8).

[0114]

[0115] In the formula, u sf is the voltage after the fault.

[0116] The residue method is used to inverse Laplace transform equation (16) to obtain the analytical expression of the fault current under the stator winding:

[0117]

[0118] Wherein, i st is the steady-state component of the stator current in the fault state, i tr is the transient component of the stator current in the fault state, and i str is the sub-transient component of the stator current in the fault state; L st is the steady-state component inductance, L tr is the transient component inductance; ω fLet T1 be the transient component oscillation frequency, T2 be the transient component attenuation factor, and T3 be the subtransient component attenuation factor; i s0 This refers to the stator current before the fault.

[0119] In this embodiment, i str =i s0 -i st +i tr , REAL and IMAG represent finding the real and imaginary parts of a complex number, respectively; t represents time.

[0120] Analysis of equation (19) shows that after a three-phase short-circuit fault occurs in the power grid, the stator current (stator short-circuit current) of the doubly-fed induction generator (DFIG) under fault conditions contains three components in the dq coordinate system: steady-state component, transient component, and subtransient component. Steady-state component i st It appears in the form of DC, and over a long time scale, the short-circuit current will eventually stabilize at this component. The transient component is a component with an amplitude of i. tr With frequency ω f The oscillation is a current component that gradually decays with an attenuation factor T1. Analysis of T1 shows that to ensure effective attenuation of the transient component, it is necessary to rationally design the PI controller parameters. The subtransient component has an amplitude of i. str The attenuation factor is T2, which is an exponential decay and usually only affects the first few tens of milliseconds after the fault occurs.

[0121] See Figure 2 The fault current identification method for doubly-fed wind turbines described in this embodiment includes:

[0122] S1. Voltage dip faults are tested on the actual doubly-fed induction generator (DFIG) wind turbine, the manufacturer's black-box model, and the actual unit controller's semi-physical simulation model. In this embodiment, voltage dip faults of 20%, 35%, 50%, and 75% are set on the grid side of the DFIG wind turbine; the terminal voltage u is collected. s , as well as stator current, rotor current and active current;

[0123] S2, u s Substituting the control strategy into equation (7), the rotor current replaces i in the control strategy equation (7). rref_q In the analytical formula (8) of the active current replacement control strategy, i rref_p Identify k and u set and I max ;

[0124] S3. When a new fault occurs, the new voltage drop value u will be... s Substituting into the control strategy analytical expression (7), we can calculate i in the control strategy analytical expression (7).rref_q , i rref_q is substituted into the control strategy analytical expression (8) to calculate i rref_p , i rref_q and i rref_p is substituted into the fault current analytical expression (19) as the input reference value of i rref ;

[0125] S4, select any voltage drop fault condition, identify the controller parameters K p , K i based on the fault current analytical expression (19). Specific implementation two:

[0127] The embodiment is a computer storage medium, and the storage medium stores at least one instruction. The at least one instruction is loaded and executed by a processor to implement the method for identifying fault current and controller parameters of a doubly-fed wind turbine.

[0128] It should be understood that the instructions include a computer program product, software or computerized method corresponding to any method described in the present application; the instructions can be used to program a computer system or other electronic device. The computer storage medium can include a readable medium having instructions stored thereon, and can include but is not limited to a magnetic storage medium, an optical storage medium, a magneto-optical storage medium, a read-only memory (ROM), a random access memory (RAM), an erasable programmable memory (such as an EPROM and an EEPROM), and a flash memory layer, or other types of media suitable for storing electronic instructions. Specific implementation three:

[0130] The embodiment is a device for identifying fault current and controller parameters of a doubly-fed wind turbine, and the device includes a processor and a memory. It should be understood that any device described in the present application includes a processor and a memory, and the device can also include other units, modules, etc. that display, interact, process, control, etc. through signals or instructions, and other functions;

[0131] The memory stores at least one instruction, and the at least one instruction is loaded and executed by the processor to implement the method for identifying fault current and controller parameters of a doubly-fed wind turbine.

[0132] Those skilled in the art will appreciate that at least one of the instructions stored is a computer program product of a method or system. Accordingly, the present application can take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application can take the form of a computer program product on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROMs, optical storage devices, etc.) embodying computer readable program code thereon. The embodiments of the present application can be implemented using various computer languages such as the object-oriented programming language Java and the interpreted scripting language JavaScript, etc.

[0133] The present application is described with reference to the flowchart and / or block diagram illustrations of the methods, systems and computer program products according to embodiments of the present application. It will be understood that each block of the flowchart and / or block diagrams, and combinations of blocks in the flowchart and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general purpose computer, special purpose computer, embedded processing element or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart and / or block diagram block or blocks. Figure 1 one or more functions specified in the flowchart and / or block diagram block or blocks. Figure 1 one or more functions specified in the flowchart and / or block diagram block or blocks.

[0134] These computer program instructions can also be stored in a computer- readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instructions which implement the flowchart and / or block diagram block or blocks. Figure 1 one or more functions specified in the flowchart and / or block diagram block or blocks. Figure 1 one or more functions specified in the flowchart and / or block diagram block or blocks.

[0135] These computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the flowchart and / or block diagram block or blocks. Figure 1 one or more functions specified in the flowchart and / or block diagram block or blocks. Figure 1 one or more functions specified in the flowchart and / or block diagram block or blocks.

[0136] While the preferred embodiments of the application have been described, additional variations and modifications can be made to the embodiments by those skilled in the art once they learn of the basic inventive concepts. Therefore, the appended claims are intended to cover all such modifications and variations as fall within the true scope of the application.

[0137] Obviously, various modifications and changes can be made to the present application without departing from the spirit and scope thereof. Accordingly, it is intended that all such modifications and changes be included within the scope of the application as defined in the following claims and their equivalents.

[0138] The above examples of the present application are only to illustrate the calculation model and calculation process of the present application, and are not intended to limit the embodiments of the present application. Based on the above description, other different forms of changes or variations can be made by those skilled in the art, and it is impossible to enumerate all the embodiments here. Any obvious changes or variations derived from the technical solutions of the present application are still within the protection scope of the present application.

Claims

1. A method for fault current analysis and controller parameter identification of a doubly-fed induction generator (DFIM) wind turbine, wherein the electrical components of the DFIM wind turbine include an induction generator (DFIM), a rotor-side converter (RSC), a grid-side converter (GSC), and an RSC controller; the rotor voltages of the RSC controller before and after the fault are as follows: at r =K p (and rref -and r )+K i ∫(i rref -and r )dt+R r and r +jω r ψ r In the formula, K p K is the proportional gain of the PI controller. i i represents the integral coefficient of the PI controller; r For rotor current, i rref This is the reference value for the rotor current; R r ω is the rotor winding resistance. r Let ψ be the rotor's electric angular velocity. r The rotor flux linkage; j represents the imaginary number; Its features are, Parameter identification is performed based on the analytical expression of fault current under the stator winding of a doubly fed wind turbine. The analytical expression for the fault current under the stator winding is as follows: In the formula, i st This refers to the steady-state component of the stator current under fault conditions. i tr This refers to the transient component of the stator current under fault conditions. i str i represents the subtransient component of the stator current under fault conditions. str =i s0 -i st +i tr i s0 The stator current before the fault; u sf The voltage after the fault; ω s L is the angular velocity at power frequency. m For mutual inductance between stator and rotor windings; L st For steady-state component inductance; L tr For transient component inductance; ω f ψ is the oscillation frequency of the transient component. s0 T1 represents the stator flux linkage before the fault; T2 represents the transient component attenuation factor; T3 represents the subtransient component attenuation factor; and t represents time. Before performing parameter identification, the reactive power support coefficient k and the reactive power voltage threshold u must first be determined. set and maximum current I max Then, based on the controller parameter K p K i Identification; Determine k, u set and I max The process includes: performing voltage drop fault tests and collecting terminal voltage u. s The rotor current and active current are also considered; the rotor current is used as the reference value for the rotor reactive current during a fault. rref_q Combined with u s and reactive current reference value i rref_q The reactive power support coefficient k and the reactive power voltage threshold u are obtained. set The active current is used as the reference value i for the rotor active current during the fault period. rref_p Combined with the active current reference value i rref_p and reactive current reference value i rref_q Obtain the maximum current I max ; Based on the controller parameter K p K i The identification process includes: when a new fault occurs, based on the voltage drop value u corresponding to the new fault... s And reactive power support coefficient k, reactive power voltage threshold u set Obtain the rotor reactive current reference value i rref_q Based on i rref_q and maximum current I max Obtain the reference value of power current i rref_p , change i rref_q and i rref_p As the real and imaginary parts of the fault current analytical expression (19), i rref Then, select any voltage drop fault condition and identify the controller parameter K based on the fault current analytical expression (19). p K i .

2. The method for fault current analysis and controller parameter identification of a doubly-fed wind turbine according to claim 1, characterized in that, steady-state component inductance The transient component inductance L s L r These are the stator and rotor winding self-inductances, respectively, with σ being the leakage inductance coefficient; the transient component oscillation frequency... R s The stator winding resistance is T1; T1 is the transient component attenuation factor. T2 is the subtransient component attenuation factor. REAL and IMAG represent finding the real and imaginary parts of a complex number, respectively.

3. The method for fault current analysis and controller parameter identification of a doubly-fed wind turbine according to claim 2, characterized in that, The leakage inductance coefficient 4. A method for fault current analysis and controller parameter identification of a doubly-fed wind turbine according to any one of claims 1 to 3, characterized in that, Combined with u s and reactive current reference value i rref_q The reactive power support coefficient k and the reactive power voltage threshold u are obtained. set The process is based on Implementation, ψ s For stator flux linkage, I n This is the rated current.

5. The method for fault current analysis and controller parameter identification of a doubly-fed induction generator (DFIG) wind turbine according to claim 4, characterized in that, Combined with active current reference value i rref_p and reactive current reference value i rref_q Obtain the maximum current I max The process is based on Implementation, i p_normal This represents the steady-state value of the active current before the fault occurs.

6. The method for fault current analysis and controller parameter identification of a doubly-fed induction generator (DFIG) wind turbine according to claim 5, characterized in that, The analytical expression for the fault current under the stator winding is obtained through the following steps: By performing a Laplace transform on the rotor voltage equation of the doubly fed induction generator (DFIM) in the synchronous speed coordinate system, we can obtain equation (9) from the time domain to the frequency domain. you r (s)=R r I r (s)+sψ r (s)-ψ r0 +jω r ψ r (s) (9) In the formula, ψ r0 R represents the rotor flux linkage before the fault. s This refers to the stator winding resistance. Substituting the rotor flux linkage equation into the stator flux linkage equation yields the frequency domain equation: The rotor current in the rotor flux equation is transformed to the frequency domain as shown in equation (11); Substituting equations (11) and (10) into the rotor voltage equation (9), and replacing the rotor flux and rotor current in equation (9), the stator flux equation is derived as shown in equation (11). The frequency domain expression of the rotor voltage equation under controller control is: In the formula, s is the Laplace operator; Substituting equations (10), (11), and (13) into equation (12) yields: In the formula, The stator voltage equation is transformed to the frequency domain as shown in equation (15): you s (s)=R s I s (s)+sψ s (s)-ψ s0 +jω s ψ s (s) (15) In the formula, ψ s0 Stator flux linkage before the fault; Substituting equation (14) into equation (15) yields: After the fault occurs, the stator voltage u s (s) In equation (16), equation (17) is obtained in the form of a step response; rotor reference value i rref Equation (18) is obtained in the form of a step response; In the formula, u sf The voltage after the fault; The Laplace inverse transformation of equation (16) is performed using the residue method to obtain the analytical expression for the fault current under the stator winding.

7. The method for fault current analysis and controller parameter identification of a doubly-fed wind turbine according to claim 6, characterized in that, The rotor voltage equation of a doubly fed induction generator (DFIM) in the synchronous velocity coordinate system is:

8. The method for fault current analysis and controller parameter identification of a doubly-fed wind turbine according to claim 6, characterized in that, The rotor flux linkage equations and stator flux linkage equations are as follows: ψ s =L s i s +L m i r (3) ψ r =L m i s +L r i r (4) In the formula, ψ s ψ r These are the stator and rotor flux linkages, respectively, L s L r The self-inductance of the stator and rotor windings are respectively, L m This refers to the mutual inductance between the stator and rotor windings.

9. A computer storage medium, characterized in that, The storage medium stores at least one instruction, which is loaded and executed by a processor to implement the method for fault current analysis and controller parameter identification of a doubly fed wind turbine as described in any one of claims 1 to 8.

10. A device for fault current analysis and controller parameter identification of a doubly-fed induction generator (DFIG) wind turbine, characterized in that, The device includes a processor and a memory, the memory storing at least one instruction, which is loaded and executed by the processor to implement the method for fault current analysis and controller parameter identification of a doubly fed wind turbine as described in any one of claims 1 to 8.

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