Current analysis method at fault occurrence moment of full-power wind turbine generator and related equipment

Abstract

The invention discloses a full-power type wind turbine generator fault occurrence moment current analysis method and related equipment, and the method comprises the steps: obtaining control parameters and operation parameters of a full-power type wind turbine generator, and when low-voltage fault ride-through is detected, substituting the control parameters and the operation parameters into a fault ride-through controller model, fault current partition logic is combined to obtain fault current analytic expressions corresponding to different fault state intervals, and then the current instruction data are substituted into the fault current analytic expressions under the corresponding fault state intervals, so that current analysis is carried out through the fault current analytic expressions and a closed-loop transfer function, and fault current analysis is carried out through the fault current analytic expressions and the closed-loop transfer function. And obtaining the fault current at the fault occurrence moment of the full-power wind turbine generator. According to the scheme, the control strategy of the active and reactive current during low voltage ride through is analyzed, and the current analysis formula of the fault occurrence moment corresponding to each fault current partition is obtained by combining different fault current partitions, so that the fault current of the unit fault occurrence moment is obtained based on the current analysis formula.

Description

Technical Field

[0001] The present application relates to the technical field of new energy units, and in particular to a current analysis method and related equipment for a full-power wind turbine unit at the time of a fault. Background Art

[0002] Studying the fault current characteristics of new energy units during the entire fault crossing process can provide an important basis for the analysis, control and protection of large-scale access systems for new energy. The transient current components of traditional synchronous generators and asynchronous motors are affected by the characteristics of the motors themselves, and the fault current components are mainly power frequency components and DC quantities. Most new energy units are converter-controlled equipment. The transient fault current is affected by the grid-connected controller. The fault current components contain a large number of non-power frequency components. The traditional short-circuit current calculation method is no longer applicable. The existing current analysis method does not analyze the true relationship between the control parameters and the fault current analysis formula between different fault occurrence intervals for full-power wind turbines, which affects the accuracy and applicability of the current finally obtained. Therefore, how to correctly characterize the fault current of full-power wind turbines at the moment of fault occurrence has become a technical problem that technicians in this field urgently need to solve. Summary of the invention

[0003] The present application provides a current analysis method and related equipment for a full-power wind turbine generator set at the time of fault occurrence, which are used to solve the technical problem of low accuracy of the existing full-power wind turbine generator fault current analysis method.

[0004] In order to solve the above technical problems, the first aspect of the present application provides a current analysis method at the time of a full-power wind turbine fault, comprising:

[0005] According to the grid-connected characteristics of the grid-side converter controller in the full-power wind turbine, a steady-state controller model and a fault-ride-through controller model are constructed;

[0006] Obtain control parameters and operating parameters of full-power wind turbines;

[0007] Determine the fault current partitioning logic according to the preset fault control switching logic;

[0008] When a low voltage fault ride-through is detected, the fault ride-through controller model is substituted according to the control parameters and the operating parameters, and combined with the fault current partitioning logic, the fault current analytical expressions corresponding to different fault state intervals are obtained, wherein the fault state intervals include: a fault occurrence sub-transient interval, a fault transient interval, and a fault steady-state interval;

[0009] The fault current analytical formula and the closed-loop transfer function based on the DC bus voltage outer loop and the current inner loop are used to perform current analysis to obtain the fault current at the time when the full-power wind turbine generator set fault occurs.

[0010] Preferably, the fault ride-through controller model is specifically:

[0011]

[0012]

[0013] In the formula, k p_V is the proportional coefficient of the DC bus voltage outer loop, U dcref is the reference value of DC voltage, P m Inject active power into the DC side, i d_limit is the maximum limit value of the d-axis current, i gq0 is the steady-state value of the q-axis current before the fault; i q_limit is the maximum limit value of q-axis current; K q is the reactive current support factor; U t is the positive sequence voltage at the grid connection point; U in is the low penetration voltage threshold; I N is the rated current of the wind turbine, ΔU dc is the change in DC bus voltage, and δ is the change in grid-connected point voltage.

[0014] Preferably, the analytical formula of the fault current in the sub-transient interval of the fault occurrence specifically includes:

[0015]

[0016]

[0017]

[0018]

[0019] In the formula, is the d-axis fault current in the sub-transient interval of the fault, i gd_B1_1 is the DC bus voltage outer loop component of the d-axis current in the sub-transient interval, i gd_B1_2 is the current component of the d-axis current in the sub-transient interval due to incomplete decoupling, k p is the current inner loop proportional coefficient, R f is the grid-side filter resistance, k i is the current inner loop integral coefficient, T 1 is the voltage filter time constant, T 2 is the PWM delay time constant, L f is the grid-side filter inductor, and C is the DC bus capacitor.

[0020] Preferably, the fault current analytical expression of the fault transient interval specifically includes:

[0021]

[0022]

[0023]

[0024] In the formula, is the d-axis fault current in the transient interval of the fault, is the q-axis fault current in the transient interval of the fault, i max is the maximum current of the fan, i gqref is the reference value of the q-axis grid current, i d_limit is the d-axis grid current limit, k p is the current inner loop proportional coefficient, R f is the grid-side filter resistance, k i is the current inner loop integral coefficient, L f It is the grid-side filter inductor.

[0025] Preferably, the fault control switching logic is specifically:

[0026]

[0027] Where, t 0 is the time when the fault occurs, t 1 is the fault control logic switching time, U in is the low penetration threshold, U fault is the fundamental positive sequence voltage at the grid connection point.

[0028] Preferably, the transfer function expression of the current inner loop is:

[0029]

[0030]

[0031] Where s is the Laplace operator in the frequency domain, i max is the maximum current of the fan, i gqref is the reference value of the q-axis grid current, i d_limit is the d-axis grid current limit, k p is the current inner loop proportional coefficient, R f is the grid-side filter resistance, k i is the current inner loop integral coefficient, L f It is the grid-side filter inductor.

[0032] Preferably, the control parameters and operating parameters include: active power command value, rated voltage on the low-voltage side of the transformer, low-voltage entry threshold, voltage outer loop proportional coefficient, voltage outer loop integral coefficient, d-axis current maximum limit value, current inner loop proportional coefficient, current inner loop integral coefficient, DC bus voltage command value, DC bus capacitance, DC side input power, voltage filter time constant, PWM delay time constant, grid-side filter inductance, grid-side filter resistance, pre-fault reactive current command value and converter total current limit.

[0033] At the same time, the second aspect of the present application provides a current analysis device at the time of a full-power wind turbine fault, comprising:

[0034] A controller model building unit, used to build a steady-state controller model and a fault ride-through controller model according to the grid-connected characteristics corresponding to the grid-side converter controller in the full-power wind turbine generator set;

[0035] A parameter acquisition unit, used to acquire control parameters and operating parameters of a full-power wind turbine generator set;

[0036] A fault current partition logic determination unit, used to determine the fault current partition logic according to a preset fault control switching logic;

[0037] A fault current partition processing unit, for, when a low voltage fault ride-through is detected, substituting the control parameters and the operating parameters into the fault ride-through controller model, and combining the fault current partition logic to obtain fault current analytical expressions corresponding to different fault state intervals, wherein the fault state intervals include: a fault occurrence sub-transient interval, a fault transient interval, and a fault steady-state interval;

[0038] The fault current analysis unit is used to perform current analysis through the fault current analysis formula and a closed-loop transfer function based on a DC bus voltage outer loop and a current inner loop to obtain the fault current at the time when the full-power wind turbine generator set fault occurs.

[0039] A third aspect of the present application provides a current analysis terminal at the time of a full-power wind turbine fault, comprising: a memory and a processor;

[0040] The memory is used to store program codes, and the program codes are used to implement a current analysis method at the time of a fault occurrence of a full-power wind turbine set provided in the first aspect of the present application;

[0041] The processor is used for reading and executing the program code.

[0042] A fourth aspect of the present application provides a computer-readable storage medium, in which program code is stored, and the program code is used to be read and executed by a processor to implement a method for analyzing the current at the moment of a fault in a full-power wind turbine provided in the first aspect of the present application.

[0043] From the above technical solutions, it can be seen that the present application has the following advantages:

[0044] In the present application, by obtaining the control parameters and operating parameters of a full-power wind turbine, when a low-voltage fault ride-through is detected, the control parameters and operating parameters are substituted into the fault ride-through controller model, and combined with the fault current partition logic determined according to the preset fault control switching logic, the fault current analytical expressions corresponding to different fault state intervals are obtained. Then, each current command data is respectively substituted into the fault current analytical expressions under the corresponding fault state intervals, so as to perform current analysis through the fault current analytical expressions and the closed-loop transfer function based on the DC bus voltage outer loop and current inner loop, and obtain the fault current at the moment of a fault in the full-power wind turbine. This solution analyzes the control strategies of active and reactive currents during low-voltage fault ride-through, and combines different fault current partitions to obtain the current analytical expressions corresponding to each fault current partition at the moment of a fault, so as to obtain the fault current at the moment of a fault in the unit based on the current analytical expressions, thereby improving the accuracy and applicability of the obtained current. Description of the Drawings

[0045] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0046] Figure 1 It is a schematic flowchart of an embodiment of a method for analyzing the current at the moment of a fault in a full-power wind turbine provided by the present application.

[0047] Figure 2 It is the internal and external loop control block diagram of the grid-side converter of the full-power wind turbine of the present application.

[0048] Figure 3 It is the current response curve of the full process of low-voltage fault ride-through of the full-power wind turbine of the present application.

[0049] Figure 4 It is the low-voltage ride-through reactive power control logic of the present application.

[0050] Figure 5 It is the low-voltage ride-through active power control logic of the present application.

[0051] Figure 6 This is the current inner loop control block diagram of this application.

[0052] Figure 7 This is the control block diagram of the voltage filtering link of this application.

[0053] Figure 8 This is the PWM delay link control block diagram of this application.

[0054] Fig. 9 A schematic structural diagram of an embodiment of a current analysis device for a full-power wind turbine generator set when a fault occurs provided in the present application.

[0055] Fig.10 A schematic structural diagram of an embodiment of a current analysis terminal for a full-power wind turbine generator set when a fault occurs provided in the present application. DETAILED DESCRIPTION

[0056] The present application provides a current analysis method and related equipment for a full-power wind turbine generator set at the time of fault occurrence, which are used to solve the technical problem of low accuracy of the existing full-power wind turbine generator fault current analysis method.

[0057] In order to make the purpose, features, and advantages of the invention of this application more obvious and easy to understand, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the embodiments described below are only part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0058] First, a detailed description of an embodiment of a current analysis method for a full-power wind turbine generator set at the time of a fault occurrence is provided in the present application, which is as follows:

[0059] See also Figure 1 The present application provides a current analysis method for a full-power wind turbine generator set at the time of a fault, comprising:

[0060] Step 101: construct a steady-state controller model and a fault ride-through controller model according to the grid-connected characteristics corresponding to the grid-side converter controller in the full-power wind turbine generator set;

[0061] It should be noted that the full-power wind turbine uses a group of back-to-back converters to inject wind power into the AC grid. The back-to-back converter decouples the permanent magnet synchronous motor from the grid. The grid-side converter controller is abbreviated as the grid-side controller. The corresponding steady-state controller model is constructed. The grid-side active and reactive current reference values ​​in the steady-state controller model are respectively denoted as i gdref and i gqref ,igdref 、i gqref They are grid-side current reference values ​​i gref At the same time, a fault ride-through controller model is constructed. In the process of constructing the fault ride-through controller model, current analysis is performed based on the closed-loop transfer function of the DC bus voltage outer loop and the current inner loop and the full-power wind turbine fault current analytical formula.

[0062] Step 102, obtaining control parameters and operating parameters of a full-power wind turbine generator set;

[0063] It should be noted that the control parameters and operating parameters of the full-power wind turbine are obtained, including the active power command value P ref , Rated voltage U on low voltage side of transformer N , low penetration threshold U in , voltage outer loop proportional coefficient k p_V , voltage outer loop integral coefficient k i_V , d-axis current maximum limit value i d_limit , current inner loop proportional coefficient k p , current inner loop integral coefficient k i , DC bus voltage command value U dcref , DC bus capacitance C, DC side input power P m , voltage filter time constant T 1 , PWM delay time constant T 2 , grid-side filter inductor L f , grid-side filter resistor R f , reactive current command value before fault i gqref_t0 , total current limit of the converter i max .

[0064] Step 103, determining the fault current partitioning logic according to the preset fault control switching logic;

[0065] It should be noted that, according to the fault control switching logic, the fault current partitioning logic is determined to partition the fault current in the fault occurrence interval.

[0066] Among them, since the full-power wind turbine determines whether to activate the low voltage ride-through control by judging whether the fundamental positive sequence voltage at the grid connection point is lower than the low voltage ride-through threshold. After the fault occurs, the fundamental positive sequence voltage detection value will reach the low voltage ride-through threshold after a period of time. The fault control switching logic mentioned in this embodiment refers to the control logic of the fault control logic switching time, and its specific expression is:

[0067]

[0068] Where, t 0 is the time when the fault occurs, t 1is the fault control logic switching time, U in is the low penetration threshold, U fault It is the fundamental positive sequence voltage at the grid connection point.

[0069] Step 104: when a low voltage fault ride-through is detected, the fault ride-through controller model is substituted according to the control parameters and the operating parameters, and combined with the fault current partitioning logic, the fault current analytical expressions corresponding to different fault state intervals are obtained;

[0070] Among them, the fault state interval includes: fault occurrence sub-transient interval, fault transient interval and fault steady-state interval;

[0071] It should be noted that when a low voltage fault ride-through occurs, the obtained controller parameters are brought into the controller model to obtain the fault current analytical formula i corresponding to different fault state intervals: gdref and i gqref , change i gdref and i gqref The full-power wind turbine fault transfer function diagram is connected to obtain the full-power wind turbine fault current analytical formula corresponding to the low voltage fault.

[0072] Step 105 , performing current analysis using the fault current analytical formula and a closed-loop transfer function based on the DC bus voltage outer loop and the current inner loop to obtain the fault current at the time when the full-power wind turbine generator set fault occurs.

[0073] It should be noted that the fault current analytical expression obtained based on the previous steps is solved in combination with the closed-loop transfer function based on the DC bus voltage outer loop and the current inner loop to analyze the fault current, and thus the fault current of the full-power wind turbine at the time of the fault is obtained based on the solution results.

[0074] More specifically, full-power wind turbines use a set of back-to-back converters to inject wind power into the AC grid, which has significant advantages over doubly-fed wind turbines or other partial power conversion wind turbines. Full-power wind turbines have a lower synchronous speed and can be directly connected to the motor rotor, eliminating the need for a gearbox for speed matching, thereby simplifying the drive chain, significantly improving system efficiency, reducing mechanical noise, and greatly reducing unit failures caused by gearbox problems. In addition, the amount and cost of maintenance after a failure are also greatly reduced, effectively improving the reliability of system operation and the life of the unit.

[0075] Then, by analyzing the fault response curve of the unit, the causes of each transient interval of the fault response curve were summarized, the logical switching sequence in the entire process of fault crossing was clarified, the fault current of the full-power wind turbine unit was classified, and the fault current was divided into detailed areas, completing the time domain analysis of the entire process of different types of fault currents.

[0076] Regarding the mathematical model of the electrical part of the permanent magnet synchronous motor, in the synchronous rotating d / q coordinate system, the generator outputs the instantaneous active power P s and reactive power Q s It can be calculated that:

[0077] (1)

[0078] The mathematical model between the grid-side converter output voltage and the grid voltage can be expressed as:

[0079] (2)

[0080] In the formula, u gd 、u gq 、e gd 、e gq are the d-axis and q-axis voltages of the grid-side converter and the d-axis and q-axis voltages of the grid-side, respectively; i gd 、i gq is the d and q axis current; L f , R f The inductance and resistance of the main circuit.

[0081] The description of the steady-state controller model mentioned in this embodiment is as follows:

[0082] The grid-side converter generally adopts grid voltage oriented vector control. The d-axis outer loop adopts the DC bus voltage outer loop to maintain the balance between the machine-side input active power and the grid-side output active power. The q-axis adopts a reactive current control strategy. Under normal conditions, the reference value of the q-axis current is 0. When the grid-connected point voltage fluctuates, the fault control logic will change the q-axis current reference value to inject reactive power into the grid. The converter voltage command value is as shown in formula (3):

[0083] (3)

[0084] In the formula, , are the output results of the d-axis and q-axis currents through the PI link, and their expressions are:

[0085] (4)

[0086] Where: k p , k i are the proportional coefficient and integral coefficient of the inner current loop.

[0087] i gqref It can be directly given according to the control target, i gdref It is given by the DC bus voltage outer loop calculation, and the expression is:

[0088] (5)

[0089] In the formula, k p_V , k i_V is the proportional coefficient and integral coefficient of the DC bus voltage outer loop, U dcref and U dc are the reference and actual values ​​of the DC voltage.

[0090] The important role of the controller is to control the machine-side converter and the grid-side converter. The controller of the grid-side converter is divided into a steady-state controller and a fault ride-through controller. The steady-state controller model is as follows: Figure 2 As shown, the d-axis current control loop uses a DC bus voltage outer loop to balance the machine-side input power and the grid-side output power, and the q-axis current control loop directly gives a command value to control the reactive power output by the grid-side converter.

[0091] When a voltage fault occurs in the power grid, wind turbines need to generate or absorb a certain amount of reactive power according to the severity of the voltage drop or rise and limit the output of active power when necessary.

[0092] The low voltage fault ride-through response curves of active power and reactive power of wind turbines are as follows: Figure 3 shown.

[0093] analyze Figure 3 It can be seen that 0-t 0 During this period, wind turbines operate in steady-state conditions. The reactive power injected into the grid by the wind turbines is generally maintained at around 0, and the active power operates in steady-state control strategies such as speed control, maximum power tracking control, and power control according to different wind speeds.

[0094] When the power grid is at t 0 When a low voltage fault occurs, the wind turbine detects that the system voltage drops below the threshold and switches to the low voltage ride-through control logic. When the fault control logic is triggered, the command value of the q-axis current during the entire fault process is shown in formula (6):

[0095] (6)

[0096] In the formula, i gq0 is the steady-state value of the q-axis current before the fault; i q_limit is the maximum limit value of q-axis current; K q is the reactive current support factor; U t is the positive sequence voltage at the grid connection point; U in is the low penetration voltage threshold; I N is the rated current of the wind turbine.

[0097] To ensure that wind turbines can effectively generate reactive power to support grid voltage during faults, mainstream units mostly use reactive power priority control, that is, the active current is limited by the output of the reactive current.

[0098] (7)

[0099] In the formula, i max is the maximum current limit.

[0100] Based on the above analysis, the low wear fault control logic can be obtained as follows: Figure 4 and Figure 5 shown.

[0101] Regarding the full-power wind turbine fault current analytical formula in this embodiment, the fault current is calculated in the sub-transient interval at the time when the fault occurs. After the fault occurs, the fundamental positive sequence voltage detection value will reach the low penetration threshold after a period of time. In this interval, the fault control logic module has not yet been switched in. The reference value of the d-axis current is given by the output value of the DC bus voltage outer loop. Considering the limiting effect, the reference value of the d-axis current in the B1 interval is i gdref_B1 As shown in formula (8):

[0102] (8)

[0103] d-axis current inner loop command value i gdref and d-axis current i gd The ideal transfer control block diagram is simplified as follows Figure 6 As shown, gdref with i gd The transfer function expression between is shown in formula (9):

[0104] (9)

[0105] To obtain the sub-transient d-axis current i at the time of fault occurrence gd The time domain expression of gdref To parse i gdref The key is to calculate the DC side voltage U dc The change when the fault occurs. Assuming that the DC bus voltage tracks the DC bus voltage command value at the steady state before the fault occurs, then according to the law of conservation of energy during the fault and the capacitor energy formula, the U after the fault can be obtained. dc The change is shown in formula (10):

[0106] (10)

[0107] To simplify the derivation and calculation process, the following assumptions can be used: the unloading circuit has not yet started, so P chopperSet to 0; the active power Pm injected on the DC side maintains the output level before the fault; the active power Pg output on the grid side is mainly affected by the voltage change at the grid connection point. Based on these assumptions, equation (10) can be simplified to equation (11):

[0108] (11)

[0109] Since this interval is short, the integral part of the voltage outer loop can be ignored. Therefore, the output value of the DC voltage outer loop can be expressed by formula (12):

[0110] (12)

[0111] It can be seen that gdref It is a piecewise function. It behaves as a ramp function before reaching the limit and remains as i after reaching the limit. d_limit No change. Let the time to reach the limit be t limit t can be calculated from the limit value and the slope of the ramp function. limit .t limit The expression of is shown in formula (13):

[0112] (13)

[0113] Substituting equation (12) into equation (9) can obtain the DC bus voltage outer loop component of the d-axis current in the sub-transient interval at the time of fault occurrence, as shown in equation (14):

[0114] (14)

[0115] Where:

[0116] (15)

[0117] The preliminary analysis of the fault current is based on the assumption that the control system is completely decoupled from the main circuit. However, in order to improve the performance of the converter, the controller often extracts the fundamental frequency of the grid side through the power filter for more in-depth control. This process can be equivalently simulated by a first-order inertia link with a large time constant. The effect of the power filter on the fundamental frequency corresponds to the slower decay component. In addition, the delay caused by the switching frequency and sampling frequency of the converter itself can also be equivalent to a first-order inertia link with a small time constant, corresponding to the faster decay component.

[0118] Before the fault occurs, the fundamental voltage and current on the grid side remain stable. At this time, the influence of the first-order inertia link can be ignored, and it is considered that the control system and the main circuit have achieved complete decoupling. After the fault occurs, the existence of the filter inductor in the main circuit prevents the current from changing immediately, so the influence of current decoupling can be ignored. However, the instantaneous drop in the grid voltage shows that the influence of the first-order inertia link on voltage decoupling should not be ignored. Therefore, the decoupling between the control loop and the main circuit is no longer complete during the fault, which affects the calculation of the short-circuit current. This influence on voltage decoupling can be seen through Figure 7 and Figure 8 The control block diagram is shown.

[0119] observe Figure 7 and Figure 8 From the difference between the two, we can find that the structures of the two transfer function control block diagrams are the same, except that the time constants of the inertia links in the two transfer functions are different. Therefore, the frequency domain mathematical models of the step response when the fault occurs are the same except for the time constants of the inertia links. Formula (16) is the frequency domain mathematical model of the step response when the fault occurs. When T is T 1 When T is T 2 It is the frequency domain mathematical model of PWM delay inertia decoupling link.

[0120] (16)

[0121] By performing a reverse transformation on equation (16), its time domain expression is shown in equation (17):

[0122] (17)

[0123] Where:

[0124] (18)

[0125] Combining equations (14) and (17), the analytical solution of the fault current in the sub-transient interval at the time of fault occurrence can be calculated, as shown in equation (19):

[0126] (19)

[0127] Next, the transient interval of the fault current fault is calculated. When the fault control logic module detects that the fundamental positive sequence voltage of the grid connection point is lower than the set low penetration threshold, the fault control logic module switches in. At this time, the d-axis current reference value is shown in formula (20):

[0128] (20)

[0129] Substituting Equation (20) into Equation (9) can obtain the fault current component of the transient interval d-axis current at the fault occurrence moment, as shown in Equation (21):

[0130] (21)

[0131] In the formula:

[0132] (22)

[0133] At this time, the q-axis current reference value is as shown in Equation (23):

[0134] (23)

[0135] The output response frequency-domain mathematical model of the q-axis current at the fault switching moment is the same as that of the d-axis. Substituting Equation (23) into the frequency-domain mathematical model can obtain the fault current component of the transient interval q-axis current at the fault occurrence moment, as shown in Equation (24):

[0136] (24)

[0137] In the formula, .

[0138] The above is a detailed description of an embodiment of the current analysis method at the fault occurrence moment of a full-power wind turbine provided by this application. The following is a detailed description of an embodiment of the current analysis device at the fault occurrence moment of a full-power wind turbine provided by this application.

[0139] Please refer to Fig. 9 , a current analysis device at the fault occurrence moment of a full-power wind turbine provided in the second aspect of this application includes:

[0140] A controller model construction unit 201, configured to construct a steady-state controller model and a fault ride-through controller model according to the grid connection characteristics corresponding to the grid-side converter controller of the full-power wind turbine;

[0141] A parameter acquisition unit 202, configured to acquire the control parameters and operation parameters of the full-power wind turbine;

[0142] A fault current partition logic determination unit 203, configured to determine the fault current partition logic according to a preset fault control switching logic;

[0143] A fault current partition processing unit 204, configured to, when detecting a low-voltage fault ride-through, substitute the control parameters and operation parameters into the fault ride-through controller model, and combine the fault current partition logic to obtain fault current analytical formulas corresponding to different fault state intervals, where the fault state intervals include: the sub-transient interval at the fault occurrence, the transient interval at the fault, and the steady-state interval at the fault;

[0144] The fault current analysis unit 205 is used to perform current analysis through the fault current analysis formula and the closed-loop transfer function based on the DC bus voltage outer loop and the current inner loop to obtain the fault current at the time when the full-power wind turbine generator set fault occurs.

[0145] In addition, if Fig.10 As shown, the embodiment of the present application also provides a current analysis terminal at the time of a full-power wind turbine fault, the implementation types of the terminal include but are not limited to: a personal computer, a cloud server, and an embedded intelligent device, etc. The main components of the terminal include: a memory 33 and a processor 31;

[0146] The memory 33 is used to store program codes, and the program codes are used to implement a current analysis method at the time of a full-power wind turbine generator set fault occurrence provided in the above embodiment;

[0147] The processor 31 is used to read and execute program codes.

[0148] An embodiment of the present application also provides a computer-readable storage medium, in which program code is stored. The program code is used to be read and executed by a processor to implement a current analysis method at the time of a full-power wind turbine fault provided in the above embodiment.

[0149] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the terminals, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0150] In the several embodiments provided in the present application, it should be understood that the disclosed terminals, devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interfaces, devices or units, which can be electrical, mechanical or other forms.

[0151] The terms "first", "second", "third", "fourth", etc. (if any) in the specification of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present application described herein can, for example, be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0152] It should be understood that in the present application, "at least one (item)" means one or more, and "plurality" means two or more. "And / or" is used to describe the association relationship of associated objects, indicating that three relationships may exist. For example, "A and / or B" can mean: only A exists, only B exists, and A and B exist at the same time, where A and B can be singular or plural. The character " / " generally indicates that the objects associated before and after are in an "or" relationship. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single or plural items. For example, at least one of a, b or c can mean: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, c can be single or multiple.

[0153] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0154] In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0155] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk, etc. Various media that can store program codes.

[0156] As described above, the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A current analysis method for a full-power wind turbine generator set at the time of a fault, characterized in that: include: According to the grid-connected characteristics of the grid-side converter controller in the full-power wind turbine, a steady-state controller model and a fault-ride-through controller model are constructed; Obtain control parameters and operating parameters of full-power wind turbines; Determine the fault current partitioning logic according to the preset fault control switching logic; When a low voltage fault ride-through is detected, the fault ride-through controller model is substituted according to the control parameters and the operating parameters, and combined with the fault current partitioning logic, the fault current analytical expressions corresponding to different fault state intervals are obtained, wherein the fault state intervals include: a fault occurrence sub-transient interval, a fault transient interval, and a fault steady-state interval; The fault current analytical formula and the closed-loop transfer function based on the DC bus voltage outer loop and the current inner loop are used to perform current analysis to obtain the fault current at the time when the full-power wind turbine generator set fault occurs.

2. A current analysis method for a full-power wind turbine generator set at the time of fault occurrence according to claim 1, characterized in that: The fault ride-through controller model is specifically: In the formula, k p_V is the proportional coefficient of the DC bus voltage outer loop, U dcref is the reference value of DC voltage, P m Inject active power into the DC side, i d_limit is the maximum limit value of the d-axis current, i gq0 is the steady-state value of the q-axis current before the fault; i q_limit is the maximum limit value of q-axis current; K q is the reactive current support factor; U t is the positive sequence voltage at the grid connection point; U in is the low penetration voltage threshold; I N is the rated current of the wind turbine, ΔU dc is the change in DC bus voltage, and δ is the change in grid connection point voltage.

3. The current analysis method for a full-power wind turbine generator set at the time of fault occurrence according to claim 1, characterized in that: The fault current analytical formula of the sub-transient interval of the fault occurrence specifically includes: In the formula, is the d-axis fault current in the sub-transient interval of the fault, i gd_B1_1 is the DC bus voltage outer loop component of the d-axis current in the sub-transient interval, i gd_B1_2 is the current component of the d-axis current in the sub-transient interval due to incomplete decoupling, k p is the current inner loop proportional coefficient, R f is the grid-side filter resistance, k i is the current inner loop integral coefficient, T1 is the voltage filter time constant, T2 is the PWM delay time constant, L f is the grid-side filter inductor, and C is the DC bus capacitor.

4. The current analysis method for a full-power wind turbine generator set at the time of fault occurrence according to claim 1, characterized in that: The fault current analytical expression of the fault transient interval specifically includes: In the formula, is the d-axis fault current in the transient interval of the fault, is the q-axis fault current in the transient interval of the fault, i max is the maximum current of the fan, i gqref is the reference value of the q-axis grid current, i d_limit is the d-axis grid current limit, k p is the current inner loop proportional coefficient, R f is the grid-side filter resistance, k i is the current inner loop integral coefficient, L f It is the grid-side filter inductor.

5. The current analysis method for a full-power wind turbine generator set at the time of fault occurrence according to claim 1, characterized in that: The fault control switching logic is specifically as follows: Where t0 is the time when the fault occurs, t1 is the time when the fault control logic switches, and U in is the low penetration threshold, U fault is the fundamental positive sequence voltage at the grid connection point.

6. A current analysis method for a full-power wind turbine generator set at the time of fault occurrence according to claim 1, characterized in that: The transfer function expression of the current inner loop is: Where s is the Laplace operator in the frequency domain, i max is the maximum current of the fan, i gqref is the reference value of the q-axis grid current, i d_limit is the d-axis grid current limit, k p is the current inner loop proportional coefficient, R f is the grid-side filter resistance, k i is the current inner loop integral coefficient, L f It is the grid-side filter inductor.

7. A current analysis method for a full-power wind turbine generator set at the time of fault occurrence according to claim 1, characterized in that: The control parameters and operating parameters include: active power command value, rated voltage on the low-voltage side of the transformer, low-voltage entry threshold, voltage outer loop proportional coefficient, voltage outer loop integral coefficient, d-axis current maximum limit value, current inner loop proportional coefficient, current inner loop integral coefficient, DC bus voltage command value, DC bus capacitance, DC side input power, voltage filter time constant, PWM delay time constant, grid side filter inductor, grid side filter resistor, pre-fault reactive current command value and converter total current limit.

8. A current analysis device for a full-power wind turbine generator set at the time of a fault, characterized in that: include: A controller model building unit, used to build a steady-state controller model and a fault ride-through controller model according to the grid-connected characteristics corresponding to the grid-side converter controller in the full-power wind turbine generator set; A parameter acquisition unit, used to acquire control parameters and operating parameters of a full-power wind turbine generator set; A fault current partition logic determination unit, used to determine the fault current partition logic according to a preset fault control switching logic; A fault current partition processing unit, for, when a low voltage fault ride-through is detected, substituting the control parameters and the operating parameters into the fault ride-through controller model, and combining the fault current partition logic to obtain fault current analytical expressions corresponding to different fault state intervals, wherein the fault state intervals include: a fault occurrence sub-transient interval, a fault transient interval, and a fault steady-state interval; The fault current analysis unit is used to perform current analysis through the fault current analysis formula and a closed-loop transfer function based on a DC bus voltage outer loop and a current inner loop to obtain the fault current at the time when the full-power wind turbine generator set fault occurs.

9. A current analysis terminal for a full-power wind turbine generator set when a fault occurs, characterized in that: include: Memory and processor; The memory is used to store program codes, and the program codes are used to implement a current analysis method at the time of a fault occurrence of a full-power wind turbine set as described in any one of claims 1 to 7; The processor is used for reading and executing the program code.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores program code, and the program code is used to be read and executed by a processor to implement a current analysis method at the time of a fault occurrence of a full-power wind turbine generator set as described in any one of claims 1 to 7.

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