Double-fed wind turbine generator fault current analysis and controller parameter identification method, storage medium and equipment

Abstract

The invention discloses a doubly-fed wind turbine generator fault current analysis and controller parameter identification method, a storage medium and equipment, and belongs to the technical field of electric power. The method aims at solving the problems that an existing identification method for the double-fed fan in the fault state is low in identification precision, depends on optimization algorithm performance and is not suitable for practical engineering due to the fact that an identification scene is too ideal. According to the method, firstly, an accurate and detailed doubly-fed fan topology, an RSC controller and an LVRT control strategy are established, and then a detailed doubly-fed fan fault current analytic expression is obtained through derivation of a mathematical model; a reactive support coefficient, a reactive voltage threshold and a maximum current are determined through a voltage drop fault test, then a rotor reactive current reference value is obtained according to a voltage drop value corresponding to a new fault, the reactive support coefficient and the reactive voltage threshold, and a power current reference value is obtained by combining the maximum current. And controller parameters in the RSC controller are identified based on the fault current analytical expression.

Description

Technical Field

[0001] The present invention belongs to the field of electric power technology, and in particular relates to a method for calculating fault current of a doubly-fed wind turbine generator and a method for identifying controller parameters, a storage medium and a device. Background Art

[0002] Establishing a doubly-fed wind turbine model that is consistent with the actual low voltage ride-through (LVRT) short-circuit fault response characteristics is the premise and basis for conducting safety and stability analysis of power systems with a high proportion of new energy. The black-boxing of the manufacturer's converter controller parameters makes the simulation model unable to restore the actual wind turbine characteristics. Therefore, the identification of the controller parameters that dominate the external characteristics of the doubly-fed wind turbine has important engineering significance. The existing dynamic characteristics analysis of doubly-fed wind turbines under fault conditions is mainly based on the comparative mining of characteristics of numerical simulation data, lacking analysis of the physical mechanism of doubly-fed wind turbines. The identification method has the problems of low identification accuracy, reliance on the performance of the identification algorithm, and the identification scenario is too idealized and not suitable for actual engineering. In response to the above problems, the present invention proposes a step-by-step parameter identification method based on detailed analysis of short-circuit current. First, based on the dynamic characteristics of the doubly-fed wind turbine LVRT output and the universal doubly-fed wind turbine LVRT control strategy, the LVRT control strategy parameters are identified. Then, the controller parameters are identified through the detailed analytical formula of the doubly-fed wind turbine short-circuit current proposed by the present invention. Finally, by comparing the simulation examples with the actual wind turbine controller recording data, it is verified that the detailed short-circuit analytical expression proposed in the present invention has a clear physical mechanism, accurate characterization and high applicability. The parameter identification method based on this analytical expression has the advantages of high accuracy, independence from the identification algorithm and applicability to actual engineering.

[0003] Researchers have developed a variety of solutions for wind turbine fault current analysis and parameter identification methods, such as:

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

[0005] 2. Ling Yu et al., “Analysis of Transient Characteristics of Doubly Fed Wind Turbine Generators under Symmetrical Voltage Faults”, Proceedings of the CSEE, 2022, 42(18): 6871-6880. This article derives the analytical formula of rotor fault current by analyzing the flux 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 article adjusts the transfer function of the doubly fed wind turbine according to typical type I and type II systems, and obtains a simplified calculation model of fault current taking into account converter excitation regulation.

[0007] 4. Zheng Tao et al. published “Analysis of stator current of doubly-fed wind turbine considering different grid voltage drop levels”, Power System Protection and Control, 2015, 43(01): 81-87. The article considers the influence of the controller, derives the second-order dynamic equation of rotor current under transient state and solves it. However, the ideal scenario is limited in the solution process, and the analytical result is not universal.

[0008] 5. Chang Y et al. published “Fault Current Analysis of Type-3 WTs Considering Sequential Switching of Internal Control and Protection Circuits in MultiTime Scales during LVRT” IEEE Transactions on Power Systems, 2018, 33(6): 6894-6903. This article analyzes and summarizes the sequential switching characteristics, nonlinearity, and high-order coupling characteristics of the transient characteristics of doubly fed wind turbines. By appropriately simplifying, the stator fault current analytical formula is obtained, which provides a very good idea for studying the mathematical laws of the transient behavior of doubly fed wind turbines. However, the controller integral constant, a key parameter, is ignored in the derivation process, which cannot meet the requirements of parameter identification for model accuracy.

[0009] 6. "Frequency Domain Method for Parameter Identification of Doubly-Fed Wind Turbine Grid-Side Controller" by Pan Xueping et al., Power System Technology, 2015, 39(03): 634-638. The article derived the transfer functions of the rotor-side and grid-side controllers of the doubly-fed wind turbine, and identified the parameters of the dual closed-loop structure controller by setting a step response by superimposing a pseudo-random signal on the reference value. However, some manufacturers' controllers cannot set a step disturbance at the reference value, and the sensitivity of the inner loop controller parameters of the dual closed-loop structure identification is low, resulting in large errors in the identification results.

[0010] 7. "Study on parameter identification method of doubly-fed wind turbine converter based on M sequence" by Xu Raoqi et al., Power System Technology, 2022, 46(02): 578-586. The article proposes to superimpose an M-sequence pseudo-random signal on the measured signal to excite the control system transfer function and identify the controller parameters through the sine-cosine identification algorithm. However, this method requires changing the secondary side circuit structure, which is relatively complicated in practical applications.

[0011] 8. Guo Qiang et al. published "Parameter Decoupling Identification Method for Low Voltage Ride-Through Model of Doubly-Fed Generation System Considering Recovery Transient Process", High Voltage Technology, 2021, 47(10): 3430-3440. This article sets a fault disturbance to separately identify the LVRT control strategy parameters and controller parameters, thereby realizing the identification of the wind turbine LVRT control parameters. However, this method relies on the performance and parameters of the intelligent identification algorithm and has the problem of local optimal solution.

[0012] In summary, the existing research on short-circuit current analysis of doubly fed wind turbines has problems such as single usage scenario, a large number of approximate simplifications in the derivation process, and low accuracy, and it is mainly focused on the Crowbar protection circuit. According to the grid-connected regulations of many countries, wind turbines need to have the ability to provide reactive current to the grid to support voltage recovery during the LVRT process. When the Crowbar circuit is working, the converter needs to be locked to put the doubly fed wind turbine in an out-of-control state, which cannot meet this requirement. Therefore, more and more doubly fed wind turbines use Chopper protection circuits that can continue to excite during faults. The existing dynamic characteristics analysis of doubly fed wind turbines under fault conditions is mainly based on the characteristics comparison and mining of numerical simulation data, lacking analysis of the physical mechanism of doubly fed wind turbines. The identification method has the problems of low identification accuracy, dependence on optimization algorithm performance, and identification scenarios that are too idealized and not suitable for actual engineering. In addition, the main problems in the existing parameter identification are that the proposed method remains at the theoretical simulation level, is not suitable for actual engineering, the identification conditions are relatively harsh, and the identification performance depends on the intelligent identification algorithm. There is an urgent need for an accurate and efficient fault current analysis formula and controller parameter identification method for doubly fed wind turbines. Summary of the invention

[0013] The purpose of the present invention is to solve the problems of low identification accuracy in the existing identification method of the double-fed wind turbine under fault state, and the problems of reliance on optimization algorithm performance and identification scenario being too idealized and not applicable to actual engineering.

[0014] A method for analyzing fault current of a doubly-fed wind turbine and identifying controller parameters, wherein 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 the 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] In the formula, 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 electrical angular velocity, ψ r is the rotor flux; j represents an imaginary number;

[0017] Parameter identification is performed 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] In the formula, i st is the steady-state component of the stator current under fault conditions, i tr is the transient component of stator current under fault condition, i str is the sub-transient component of the stator current under fault conditions, 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 industrial frequency angular velocity; L m is the mutual inductance of 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, first determine the reactive support coefficient k and reactive voltage threshold u set and the maximum current I max, and then based on the controller parameter K p , K i Identification of

[0022] Determine k and u set and I max The process includes: conducting voltage drop fault test, collecting terminal voltage u s , as well as the rotor current and active current; the rotor current is used as the rotor reactive current reference value i during the fault period rref_q , combined with u s and reactive current reference value i rref_q Get the reactive support coefficient k and reactive voltage threshold u set ; Use the active current as the reference value of the rotor active current during the fault period i rref_p , combined with the active current reference value i rref_p and reactive current reference value i rref_q Get the maximum current I max ;

[0023] Based on the controller parameter K p , K i The identification process includes: when a new fault occurs, according to the voltage drop value u corresponding to the new fault s And reactive support coefficient k, reactive voltage threshold u set Get the rotor reactive current reference value i rref_q , based on i rref_q and the maximum current I max Get the active current reference value i rref_p , change i rref_q and i rref_p As the real part and imaginary part, replace i in the analytical expression (19) of the fault current 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 .

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

[0025] Furthermore, the leakage inductance coefficient

[0026] Furthermore, according to u s and reactive current reference value i rref_q Get the reactive support coefficient k and reactive voltage threshold u set The process is based on achieved.

[0027] Furthermore, combined with the active current reference value i rref_p and reactive current reference value i rref_q Get the maximum current I max The process is based on achieved.

[0028] Furthermore, 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 Laplace transformed from the time domain to the frequency domain to obtain equation (9);

[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] Substituting the rotor flux equation into the stator flux equation, we get the frequency domain equation:

[0033]

[0034] Transform the rotor current of the rotor flux equation to the frequency domain as shown in equation (11);

[0035]

[0036] Substitute equation (11) and equation (10) into the rotor voltage equation (9), replace the rotor flux and rotor current in equation (9), and sort out the stator flux equation as shown in equation (11);

[0037]

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

[0039]

[0040] Where s is the Laplace operator;

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

[0042]

[0043] In the formula,

[0044] Transforming the stator voltage equation to the frequency domain is shown in equation (15):

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

[0046] In the formula, ψ s0 is the stator flux before the fault;

[0047] Substituting formula (14) into formula (15) yields:

[0048]

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

[0050]

[0051] In the formula, u sf is the voltage after the fault;

[0052] The residue method is used to perform inverse Laplace transform on equation (16) to obtain the analytical expression of the fault current under the stator winding.

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

[0054]

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

[0056] ψ s =L s i s +L m i r(3)

[0057] ψ r =L m i s +L r i r (4)

[0058] In the formula, ψ s , r are the stator and rotor flux, L s , L r are the stator and rotor winding self-inductance, L m is the mutual inductance of stator and rotor windings.

[0059] A computer storage medium stores at least one instruction, which is loaded and executed by a processor to implement a method for analyzing fault current of a doubly-fed wind turbine set and identifying controller parameters.

[0060] A device for analyzing fault current of a doubly-fed wind turbine and identifying controller parameters, the device comprising a processor and a memory, the memory storing at least one instruction, the at least one instruction being loaded and executed by the processor to implement the method for analyzing fault current of a doubly-fed wind turbine and identifying controller parameters.

[0061] Compared with the prior art, the present invention has the following beneficial effects:

[0062] In terms of short-circuit current analysis, the proposed detailed fault current analysis expression under the stator winding of the doubly-fed wind turbine solves the problem that the current short-circuit current analysis research does not consider the influence of converter excitation at the time of fault occurrence, has a single applicable scenario and is greatly simplified. The simulation example proves that the formula has the advantages of clear physical mechanism, high accuracy of short-circuit current analysis and applicability to various LVRT fault scenarios.

[0063] In terms of controller parameter identification, the current double-fed wind turbine parameter identification method has the problems of large inner loop parameter identification error, difficulty in implementation in actual engineering, and reliance on the performance of intelligent optimization algorithms. Based on the LVRT control strategy and the analytical expression of the fault current under the stator winding, the present invention proposes an ASI method that accurately identifies the LVRT control strategy and the key parameters of the controller by step-by-step identification. The identification accuracy is high. The proposed method has the advantages of high accuracy, simple and practical method, clear principle, and no reliance on optimization algorithms, which can provide analysis basis for simulation modeling, equipment selection, safety and stability analysis, and protection calculation of high-proportion new energy power systems. In general, the present invention provides a more efficient, accurate, and practical method for fault characteristic analysis of double-fed wind turbines, which plays an important role in promoting the technical development and practical application of the wind power field. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Figure 1 It is a doubly-fed wind turbine structure.

[0065] Figure 2 Identification process of controller parameter method. DETAILED DESCRIPTION

[0066] The present invention first establishes an accurate and detailed doubly-fed wind turbine topology, RSC controller and LVRT control strategy, then obtains a detailed doubly-fed wind turbine fault current analytical formula through the derivation of a mathematical model, and finally identifies the doubly-fed wind turbine parameters based on the doubly-fed wind turbine fault current recording measured on site through a differential evolution intelligent algorithm. The present invention is described in detail below in conjunction with a specific implementation method. Specific implementation method one:

[0068] This embodiment is a method for analyzing fault current of a doubly-fed wind turbine and identifying controller parameters, comprising the following steps:

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

[0070] Wind turbines convert wind energy into mechanical energy. The wind turbine drives the induction generator through a gearbox. The stator side of the generator is directly connected to the grid and is the main power transmission path. The rotor side is excitation regulated by a back-to-back converter. See the topology for details. Figure 1As shown. The protection circuit adopts Chopper, which is connected in parallel at both ends of the DC bus and consists of a switch in series with an energy-consuming resistor. When a low voltage fault occurs, the switch is closed, and the energy-consuming resistor consumes excess energy to keep the DC bus voltage stable, so that the doubly fed wind turbine continues to work during the fault. Since the mechanical part has a huge moment of inertia and the fault duration is very short, the rotor speed is still very close to the value before the fault during the grid short-circuit fault. Therefore, the present invention 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 present invention 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 the basic mathematical model for studying the problem of a doubly-fed wind turbine under power short-circuit faults. 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 the stator and rotor voltages, R s , R r are the stator and rotor winding resistances, i s 、i r are the stator and rotor currents, respectively, s , r are the stator and rotor flux respectively, ω s is the power frequency angular velocity, ω r is the rotor electrical angular velocity.

[0075] The magnetic 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] Where, L s , L r are the stator and rotor winding self-inductance, L m is the mutual inductance of stator and rotor windings.

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

[0080] The RSC controller adjusts the rotor excitation by controlling the rotor current and rotor voltage, thus realizing indirect control of the stator current. The rotor current is used as the control object, the proportional integral (PI) is used as the controller, and the feedforward term is added to eliminate the dq axis coupling effect, realize active and reactive decoupling control and enhance the regulation performance of the controller. The rotor voltage equation under the control of 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, which is determined by the LVRT control strategy expressed by equations (7) and (8) under fault conditions. The default phase-locked loop can quickly synchronize with the grid voltage before and after the fault.

[0083] During the fault period, the doubly-fed wind turbine adjusts the reactive current injected into the grid according to the grid connection standard and the depth of the voltage drop to achieve the purpose of controlling 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 double-fed wind turbine should generate during the fault period, k is the reactive support coefficient, u set is the reactive voltage threshold, u s is the terminal voltage, I n is the rated current.

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

[0087]

[0088] In the formula, irref_q It is the reference value of rotor reactive current during fault period.

[0089] In order to maximize reactive support during the fault period, reactive power priority control is often used. Therefore, the reference value of active current during the fault period will be updated by the reactive priority principle shown in formula (8):

[0090]

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

[0092] 3. Analysis of short-circuit current of double-fed wind turbine:

[0093] Performing Laplace transform on the rotor voltage equation in equation (2) from time domain to frequency domain yields equation (9).

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

[0095] In the formula, ψ r0 is the rotor flux before the fault.

[0096] The leakage inductance coefficient is known to be Substituting equation (4) into equation (3) yields the frequency domain equation:

[0097]

[0098] Transforming the rotor current of equation (4) into the frequency domain yields 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 sort out the stator flux equation as shown in equation (12).

[0101]

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

[0103]

[0104] Where s is the Laplace operator.

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

[0106]

[0107] In the formula,

[0108] Transforming the stator voltage equation to the frequency domain is 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 formula (14) into formula (15) yields:

[0112]

[0113] After the fault occurs, the stator voltage u s (s) appears in the form of a step response in equation (16), see equation (17). The rotor reference value i rref It appears in the form of a step response as shown in equation (18), and its 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] By using the residue method to perform inverse Laplace transformation on equation (16), the analytical expression of the fault current under the stator winding can be obtained:

[0117]

[0118] Among them, i st is the steady-state component of the stator current under fault conditions, i tr is the transient component of stator current under fault condition, i str is the sub-transient component of stator current under fault condition; L st is the steady-state component inductance, L tr is the transient component inductance; ω fis the transient component oscillation frequency, T1 is the transient component attenuation factor, and T2 is the sub-transient component attenuation factor; i s0 is the stator current before the fault;

[0119] In this embodiment,

[0120] i str =i s0 -i st +i tr , REAL and IMAG represent the real and imaginary parts of a complex number; t represents time.

[0121] From the analysis of formula (19), it can be seen that after a three-phase short-circuit fault occurs in the power grid, the stator current (stator short-circuit current) of the doubly fed wind turbine in the fault state contains three components in the dq coordinate system, namely: steady-state component, transient component and sub-transient component. Steady-state component i st Appearing in the form of direct current, the short-circuit current will eventually stabilize to this component over a long time scale. tr , with frequency ω f Oscillation, the current component that gradually decays with the attenuation factor T1. By analyzing T1, it can be seen that in order to ensure that the transient component can be effectively attenuated, it is necessary to reasonably design the PI controller parameters. str , the exponential decay with an attenuation factor of T2 usually only acts within a few tens of milliseconds at the beginning of the fault.

[0122] See also Figure 2 The method for identifying fault current of a doubly-fed wind turbine generator system in this embodiment includes:

[0123] S1. Voltage drop faults are tested on the actual doubly-fed wind turbine generator set, the manufacturer's black box model, and the semi-physical simulation model of the actual unit controller. In this implementation, 20%, 35%, 50%, and 75% voltage drop faults are set on the grid side of the doubly-fed wind turbine; the terminal voltage u is collected. s , as well as stator current, rotor current and active current;

[0124] S2, u s Substitute the control strategy equation (7) and replace i in the control strategy equation (7) with the rotor current. rref_q , active current replacement control strategy analytical formula (8) in which i rref_p , identify k, u set and I max ;

[0125] S3. When a new fault occurs, the new voltage drop value u sSubstitute into the control strategy analytical formula (7) and calculate the i in the control strategy analytical formula (7) rref_q , change i rref_q Substitute into the control strategy analytical formula (8) to calculate i rref_p , change i rref_q and i rref_p As the real part and imaginary part, replace i in the analytical expression (19) of the fault current rref Input reference value of

[0126] S4. Select any voltage drop fault condition and identify the controller parameter K based on the fault current analytical expression (19): p , K i . Specific implementation method 2:

[0128] This embodiment is a computer storage medium, in which at least one instruction is stored. The at least one instruction 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 set.

[0129] It should be understood that the instructions include computer program products, software or computerized methods corresponding to any method described in the present invention; the instructions can be used to program a computer system, or other electronic device. Computer storage media may include readable media on which instructions are stored, which may include but are not limited to magnetic storage media, optical storage media; magneto-optical storage media include read-only memory ROM, random access memory RAM, erasable programmable memory (e.g., EPROM and EEPROM) and flash memory layers, or other types of media suitable for storing electronic instructions. Specific implementation method three:

[0131] This embodiment is a device for analyzing fault current of a doubly-fed wind turbine and identifying controller parameters. The device includes a processor and a memory. It should be understood that the device includes any device including a processor and a memory described in the present invention. The device may also include other units and modules that perform display, interaction, processing, control, and other functions through signals or instructions.

[0132] At least one instruction is stored in the memory, and the at least one instruction is loaded and executed by the processor to implement the method for analyzing fault current and identifying controller parameters of a doubly-fed wind turbine set.

[0133] Those skilled in the art will appreciate that at least one instruction stored is a computer program product corresponding to the method or system. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present application may adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes. The scheme in the embodiment of the present application can be implemented in various computer languages, for example, object-oriented programming language Java and literal scripting language JavaScript, etc.

[0134] The present application is described with reference to the flowcharts and / or block diagrams of the methods, systems, and computer program products according to the embodiments of the present application, and may also be used for corresponding devices. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0135] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0136] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0137] Although the preferred embodiments of the present application have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present application.

[0138] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

[0139] The above calculation examples of the present invention are only used to explain the calculation model and calculation process of the present invention in detail, and are not intended to limit the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the scope of protection of the present invention.

Claims

1. A method for analyzing fault current of a doubly-fed wind turbine and identifying controller parameters. 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 the fault in the RSC controller is 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 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 electrical angular velocity, ψ r is the rotor flux; j represents an imaginary number; It is characterized in that Parameter identification is performed based on the analytical expression of the fault current under the stator winding of the doubly fed wind turbine; The analytical expression of the fault current under the stator winding is: In the formula, i st is the steady-state component of the stator current under fault conditions, i tr is the transient component of stator current under fault condition, i str is the sub-transient component of the stator current under fault conditions, 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 of 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; Before parameter identification, first determine the reactive support coefficient k and reactive voltage threshold u set and the maximum current I max , and then based on the controller parameter K p , K i Identification of Determine k and u set and I max The process includes: conducting voltage drop fault test, collecting terminal voltage u s , as well as the rotor current and active current; the rotor current is used as the rotor reactive current reference value i during the fault period rref_q , combined with u s and reactive current reference value i rref_q Get the reactive support coefficient k and reactive voltage threshold u set ; Use the active current as the reference value of the rotor active current during the fault period i rref_p , combined with the active current reference value i rref_p and reactive current reference value i rref_q Get the maximum current I max ; Based on the controller parameter K p , K i The identification process includes: when a new fault occurs, according to the voltage drop value u corresponding to the new fault s And reactive support coefficient k, reactive voltage threshold u set Get the rotor reactive current reference value i rref_q , based on i rref_q and the maximum current I max Get the active current reference value i rref_p , change i rref_q and i rref_p As the real part and imaginary part, replace i in the analytical expression (19) of the fault current 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 generator set according to claim 1, characterized in that: The steady-state component inductance The transient component inductance L s , L r are the stator and rotor winding self-inductances, σ is the leakage inductance coefficient; the transient component oscillation frequency R s is the stator winding resistance; T1 is the transient component attenuation factor, The T2 is the sub-transient component attenuation factor, REAL and IMAG represent the real and imaginary parts of a complex number.

3. The method for fault current analysis and controller parameter identification of a doubly-fed wind turbine generator set 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 generator set according to any one of claims 1 to 3, characterized in that: Combined with u s and reactive current reference value i rref_q Get the reactive support coefficient k and reactive voltage threshold u set The process is based on achieved.

5. The method for fault current analysis and controller parameter identification of a doubly-fed wind turbine generator set according to claim 4, characterized in that: Combined with the active current reference value i rref_p and reactive current reference value i rref_q Get the maximum current I max The process is based on achieved.

6. A method for fault current analysis and controller parameter identification of a doubly-fed wind turbine generator set according to claim 5, characterized in that: The analytical expression of the fault current under the stator winding is obtained by the following steps: The rotor voltage equation of the doubly-fed induction generator DFIM in the synchronous speed coordinate system is Laplace transformed from the time domain to the frequency domain to obtain equation (9); In the formula, ψ r0 is the rotor flux before the fault; Substituting the rotor flux equation into the stator flux equation, we get the frequency domain equation: Transform the rotor current of the rotor flux equation to the frequency domain as shown in equation (11); Substitute equation (11) and equation (10) into the rotor voltage equation (9), replace the rotor flux and rotor current in equation (9), and sort out the stator flux equation as shown in equation (11); The frequency domain expression of the rotor voltage equation under the controller is: Where s is the Laplace operator; Substituting equation (10), equation (11) and equation (13) into equation (12), we can obtain: In the formula, Transforming the stator voltage equation to the frequency domain is 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 is the stator flux before the fault; Substituting formula (14) into formula (15) yields: After the fault occurs, the stator voltage u s (s) is obtained in the form of step response in equation (16) to obtain equation (17); the rotor reference value i rref Equation (18) is obtained in the form of step response; In the formula, u sf is the voltage after the fault; The residue method is used to perform inverse Laplace transform on equation (16) to obtain the analytical expression of the fault current under the stator winding.

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

8. The method for fault current analysis and controller parameter identification of a doubly-fed wind turbine generator set according to claim 6, characterized in that: The rotor flux equation and the stator flux equation 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 , r are the stator and rotor flux, L s , L r are the stator and rotor winding self-inductance, L m is the mutual inductance of stator and rotor windings.

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

10. A device for analyzing fault current and identifying controller parameters of a doubly-fed wind turbine generator set, characterized in that: The device includes a processor and a memory, wherein the memory stores at least one instruction, and the at least one instruction is loaded and executed by the processor to implement a method for fault current analysis and controller parameter identification of a doubly-fed wind turbine set as described in any one of claims 1 to 8.

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