Direct-drive wind turbine low voltage ride-through control mode switching simulation method and system

Abstract

The present invention provides a method and system for simulating switching of a low voltage ride-through control mode of a direct-drive wind turbine. The system comprises a low voltage ride-through judging module, which is used to obtain a low voltage ride-through trigger signal according to a machine-end voltage, a preset low voltage ride-through threshold value and a low voltage ride-through exit threshold value, and transmit the signal to a grid-side converter control system of the direct-drive wind turbine; a module for judging an active power recovery stage, which is used to obtain a low voltage ride-through recovery trigger signal according to a machine-end voltage, a preset fan exit low voltage ride-through threshold value, the fan active power at the time of entering the low voltage ride-through, and the low voltage ride-through trigger signal, and transmit the signal to a grid-side converter control system of the direct-drive wind turbine; and a module for judging a normal stage, which is used to obtain a normal stage signal according to the low voltage ride-through trigger signal and the low voltage ride-through recovery trigger signal, and transmit the signal to a grid-side converter control system of the direct-drive wind turbine, so as to accurately reproduce the mode switching control logic of an actual direct-drive wind turbine after low voltage ride-through.

Description

Technical Field

[0001] The present invention relates to the technical field of power system experiments, and in particular to a method and system for simulating low voltage ride-through control mode switching of a direct-drive wind turbine. Background Art

[0002] With the increasing application of wind turbines in power systems, obtaining accurate models of wind turbines has become an important task in the field of power system experiments. As a typical type of wind turbine, direct-drive wind turbines are increasingly used in wind farms across the country, so it is very important to accurately simulate direct-drive wind turbines. With the development of the power system, the grid-connected requirements for direct-drive wind turbines are also being updated, especially the requirements for the low voltage ride-through characteristics of direct-drive wind turbines, which have changed significantly in recent years. Power grids in different regions even have different requirements. In response to this change, it is necessary to accurately simulate the low voltage ride-through and recovery process of direct-drive wind turbines. The control mode of direct-drive wind turbines during the entire low voltage ride-through process can be divided into several stages, namely, the low voltage ride-through period stage, the low voltage ride-through active recovery stage, and the normal stage. In the above three stages, the control logic of the direct-drive wind turbine is different. How to judge which stage the direct-drive wind turbine is in and switch its control logic has an important impact on the voltage and frequency characteristics of the direct-drive wind turbine grid-connected system. Therefore, the simulation of the electromagnetic transient model of the low voltage ride-through controller mode switching of the direct-drive wind turbine is a very critical task. Summary of the invention

[0003] One object of the present invention is to provide a method for simulating the switching of a low voltage ride-through control mode of a direct-drive fan, and to accurately reproduce the mode switching control logic of an actual direct-drive fan after the low voltage ride-through. Another object of the present invention is to provide a system for simulating the switching of a low voltage ride-through control mode of a direct-drive fan. Another object of the present invention is to provide a computer device. Another object of the present invention is to provide a readable medium.

[0004] In order to achieve the above objectives, the present invention discloses a direct-drive wind turbine low voltage ride-through control mode switching simulation system, comprising:

[0005] A low voltage ride-through judgment module is used to obtain a low voltage ride-through trigger signal according to the machine-end voltage, a preset low voltage ride-through threshold value and a low voltage ride-through exit threshold value and transmit the signal to the direct-drive wind turbine grid-side converter control system;

[0006] A module for judging the active power recovery stage is used to obtain a low-through recovery trigger signal according to the terminal voltage, a preset wind turbine exit low-through threshold value, the wind turbine active power at the time of entering the low-through trigger signal, and the low-through trigger signal, and transmit it to the direct-drive wind turbine grid-side converter control system;

[0007] The normal stage judgment module is used to obtain a normal stage signal according to the low-breakthrough trigger signal and the low-breakthrough recovery trigger signal and transmit it to the direct-drive wind turbine grid-side converter control system.

[0008] Preferably, the low voltage ride-through determination module comprises a hysteresis determination unit and a signal selection unit;

[0009] The hysteresis judgment unit is used to compare the machine-side voltage with a low voltage ride-through threshold value and a low voltage ride-through exit threshold value, and output a first result if the machine-side voltage is lower than the low voltage ride-through threshold value or the machine-side voltage rises from lower than the low voltage ride-through threshold value to below the low voltage ride-through exit threshold value;

[0010] The signal selection unit is used to output the low-through trigger signal of the first level when the duration of the output of the hysteresis judgment unit as the first result is greater than a preset duration, and otherwise, output the low-through trigger signal of the second level.

[0011] Preferably,

[0012] The hysteresis determination unit includes a hysteresis circuit of the receiver terminal voltage;

[0013] The signal selection unit includes a first sample-and-hold circuit, a first adder, a first signal selection circuit, a second signal selection circuit and a multiplier;

[0014] Among them, the signal input end of the first sampling and holding circuit is connected to the hysteresis circuit, and the signal output end is connected to the signal input end of the first adder; the signal output end of the first adder is connected to a signal input end of the first signal selector; the other signal input end of the first signal selection circuit is connected to the signal output end of the hysteresis circuit; the signal input end of the second signal selection circuit is connected to the signal output end of the first signal selection circuit; one signal input end of the multiplier is connected to the signal output end of the hysteresis circuit, and the other signal input end is connected to the signal output end of the second signal selection circuit, and the signal output circuit of the multiplier is used to output the low-wear trigger signal.

[0015] Preferably, the module for judging the active power recovery stage comprises a first comparison unit, a second comparison unit, a third comparison unit and a signal output unit;

[0016] The first comparison unit is used for comparing the machine-end voltage with the wind turbine exit low-breakthrough threshold value when the low-breakthrough trigger signal is at the first level, and outputting a second result if the machine-end voltage is greater than the wind turbine exit low-breakthrough threshold value;

[0017] The second comparison unit is used to compare the active power of the wind turbine with the active power of the wind turbine at the time of entering the low penetration, and output a third result if the active power of the wind turbine is less than or equal to the active power of the wind turbine at the time of entering the low penetration;

[0018] The third comparison unit is used for outputting a fourth result when the first comparison unit outputs the second result, the second comparison unit outputs the third result, and the low-through trigger signal is at the second level;

[0019] The signal output unit is configured to output the low-penetration recovery trigger signal of a first level when the third comparison unit outputs the fourth result and the second comparison unit outputs the third result, and otherwise, output the low-penetration recovery trigger signal of a second level.

[0020] Preferably,

[0021] The first comparison unit includes a second sampling and holding circuit for receiving and holding the low-through trigger signal, a first comparison circuit for the receiver terminal voltage, and a first AND logic circuit, wherein the second sampling and holding circuit is connected to a signal input terminal of the first AND logic circuit; the other signal input terminal of the first AND logic circuit is connected to a signal output terminal of the first comparison circuit;

[0022] The second comparison unit includes a second comparison circuit receiving the active power of the wind turbine and the active power of the wind turbine at the time of entering the low penetration moment;

[0023] The third comparison unit comprises a second AND logic circuit, a third signal selection circuit, a fourth signal selection circuit, a second adder and a first integrator, wherein two signal input terminals of the second AND logic circuit are respectively connected to the signal output terminal of the first AND logic circuit and the signal output terminal of the second comparison circuit; the signal output terminal of the second AND logic circuit is connected to a signal input terminal of the third signal selection circuit; a signal input terminal of the fourth signal selection circuit is connected to the signal output terminal of the second comparison circuit; two signal input terminals of the second adder are respectively connected to the signal output terminal of the third signal selection circuit and the signal output terminal of the second adder; two signal input terminals of the first integrator are respectively connected to the signal output terminal of the third signal selection circuit and the signal output terminal of the second adder;

[0024] The signal output unit includes a third comparison circuit and a third AND logic circuit, wherein two signal input ends of the third comparison circuit respectively receive the active power of the wind turbine and the active power of the wind turbine entering the low-breakthrough moment; two signal input ends of the third AND logic circuit are respectively connected to the signal output end of the first integrator and the signal output end of the third comparison circuit, and the signal output end of the third AND logic circuit is used to output the low-breakthrough recovery trigger signal.

[0025] Preferably, the normal stage judgment module is used to output the normal stage signal of the first level when the low-breakthrough trigger signal and the low-breakthrough recovery trigger signal are both at the second level, and to output the normal stage signal of the second level when the low-breakthrough trigger signal or the low-breakthrough recovery trigger signal are both at the first level.

[0026] Preferably, the module for determining the normal stage includes an OR logic circuit, a fifth signal selection circuit and a second integrator;

[0027] The two signal input terminals of the OR logic circuit are used to receive the low-throughput trigger signal and the low-throughput recovery trigger signal, and the signal output terminal of the OR logic circuit is connected to a signal input terminal of the fifth signal selection circuit; the two signal input terminals of the second integrator are respectively connected to the signal output terminals of the fifth signal selection circuit and receive the low-throughput trigger signal, and the signal output terminal of the second integrator is used to output the normal stage signal.

[0028] The present invention also discloses a direct-drive wind turbine low voltage ride-through control mode switching simulation method, comprising:

[0029] A low voltage ride-through trigger signal is obtained according to the terminal voltage, the preset low voltage ride-through threshold value and the low voltage ride-through exit threshold value and transmitted to the grid-side converter control system of the direct-drive wind turbine;

[0030] A low penetration recovery trigger signal is obtained according to the terminal voltage, the preset wind turbine exit low penetration threshold value, the wind turbine active power at the time of entering the low penetration and the low penetration trigger signal, and transmitted to the direct-drive wind turbine grid-side converter control system;

[0031] A normal phase signal is obtained according to the low-breakthrough trigger signal and the low-breakthrough recovery trigger signal and transmitted to a direct-drive wind turbine grid-side converter control system.

[0032] Preferably, obtaining the low voltage ride-through trigger signal according to the terminal voltage, the preset low voltage ride-through threshold value and the low voltage ride-through exit threshold value specifically includes:

[0033] Comparing the machine-side voltage with a low voltage ride-through threshold and a low voltage ride-through exit threshold, and outputting a first result if the machine-side voltage is lower than the low voltage ride-through threshold or the machine-side voltage rises from lower than the low voltage ride-through threshold to lower than the low voltage ride-through exit threshold;

[0034] When the duration of the first result is greater than the preset duration, the low-through trigger signal of the first level is output; otherwise, the low-through trigger signal of the second level is output.

[0035] Preferably, obtaining the low-breakthrough recovery trigger signal according to the machine-end voltage, the preset wind turbine exit low-breakthrough threshold value, the wind turbine active power at the time of entering the low-breakthrough moment, and the low-breakthrough trigger signal specifically includes:

[0036] When the low-break trigger signal is at the first level, the machine-end voltage is compared with the wind turbine exit low-break threshold value, and if the machine-end voltage is greater than the wind turbine exit low-break threshold value, a second result is output;

[0037] Compare the active power of the fan with the active power of the fan at the time of entering the low penetration, and if the active power of the fan is less than or equal to the active power of the fan at the time of entering the low penetration, output a third result;

[0038] When the second result is output and the third result is output and the low-through trigger signal is at the second level, a fourth result is output;

[0039] When the fourth result and the third result are output, the low-penetration recovery trigger signal of the first level is output; otherwise, the low-penetration recovery trigger signal of the second level is output.

[0040] Preferably, obtaining the normal phase signal according to the low penetration trigger signal and the low penetration recovery trigger signal specifically includes:

[0041] When the low-penetration trigger signal and the low-penetration recovery trigger signal are both at the second level, the normal stage signal of the first level is output; when the low-penetration trigger signal or the low-penetration recovery trigger signal is both at the first level, the normal stage signal of the second level is output.

[0042] The present invention determines the change of the terminal voltage according to the terminal voltage and the preset low voltage ride-through threshold value and the low voltage ride-through exit threshold value, and then determines whether the direct-drive wind turbine enters the low voltage ride-through state, and obtains a low voltage ride-through trigger signal. Further, a low voltage ride-through recovery trigger signal is obtained according to the terminal voltage, the preset wind turbine exit low voltage ride-through threshold value, the wind turbine active power at the time of entering the low voltage ride-through, and the low voltage ride-through trigger signal, and a conventional stage signal is obtained according to the low voltage ride-through trigger signal and the low voltage ride-through recovery trigger signal. The present invention simulates the active current control instruction transmitted to the grid-side converter control system of the direct-drive wind turbine by obtaining the low voltage ride-through trigger signal, the low voltage ride-through recovery trigger signal, and the conventional stage signal to test the grid-side converter control system. The present invention can reproduce the low voltage ride-through process characteristics of the actual direct-drive wind turbine controller, so as to be used to simulate the control mode switching logic of the direct-drive wind turbine under different wind conditions and low voltage fault conditions, and can be applied to the analysis of the active and reactive characteristics of the direct-drive wind turbine during and after the low voltage fault process and the study of its influence on the system stability, which lays a solid foundation for studying the influence of the direct-drive wind turbine on the system frequency stability, voltage stability and other stability after entering the power system. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0044] Figure 1 A structural diagram showing a specific embodiment of the direct-drive wind turbine low voltage ride-through control mode switching simulation system of the present invention;

[0045] Figure 2 A structural diagram showing a low voltage ride-through module for judging a specific embodiment of a low voltage ride-through control mode switching simulation system for a direct-drive wind turbine according to the present invention;

[0046] Figure 3 A circuit structure diagram of a low voltage ride through module for judging a specific example of a low voltage ride through control mode switching simulation system for a direct-drive wind turbine according to the present invention is shown;

[0047] Figure 4 A structural diagram showing a module for judging the active power recovery phase in a specific embodiment of a low voltage ride-through control mode switching simulation system for a direct-drive wind turbine according to the present invention;

[0048] Figure 5 A circuit structure diagram of a module for determining the active power recovery stage in a specific example of a low voltage ride-through control mode switching simulation system for a direct-drive wind turbine according to the present invention is shown;

[0049] Figure 6 A circuit structure diagram of a module for judging a normal phase in a specific example of a low voltage ride-through control mode switching simulation system for a direct-drive wind turbine according to the present invention is shown;

[0050] Figure 7(a)-Figure 7(c) A comparison chart showing the test results of the direct-drive wind turbine low voltage ride-through control mode switching simulation system of the present invention and the RT-Lab experimental system under high wind conditions;

[0051] Figure 8(a)-Figure 8(c) A comparison chart showing the test results of the direct-drive wind turbine low voltage ride-through control mode switching simulation system of the present invention and the RT-Lab experimental system under low wind conditions;

[0052] Fig. 9 A flowchart showing a specific embodiment of the method for simulating switching of low voltage ride-through control mode of a direct-drive wind turbine according to the present invention;

[0053] Fig.10 A flowchart showing a specific embodiment S100 of the method for simulating switching of low voltage ride-through control mode of a direct-drive wind turbine according to the present invention;

[0054] Fig.11A flowchart showing a specific embodiment S200 of the method for simulating switching of low voltage ride-through control mode of a direct-drive wind turbine according to the present invention;

[0055] Fig.12 A flowchart showing a specific embodiment S300 of the method for simulating switching of low voltage ride-through control mode of a direct-drive wind turbine according to the present invention;

[0056] Fig.13 A schematic diagram showing the structure of a computer device suitable for implementing an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0057] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0058] According to one aspect of the present invention, this embodiment discloses a direct-drive wind turbine low voltage ride-through control mode switching simulation system. Figure 1 As shown, in this embodiment, the system includes a low voltage ride through determination module 10, an active power recovery stage determination module 20 and a normal stage determination module 30.

[0059] The low voltage ride through module 10 is used to obtain a low voltage ride through trigger signal LVRT_dur according to the terminal voltage, a preset low voltage ride through threshold value and a low voltage ride through exit threshold value, and transmit the signal to the direct drive wind turbine grid-side converter control system.

[0060] The active power recovery stage judgment module 20 is used to obtain a low-power recovery trigger signal LVRT_recover according to the machine-end voltage, a preset wind turbine exit low-power penetration threshold value, the wind turbine active power at the time of entering the low-power penetration moment, and the low-power penetration trigger signal LVRT_dur, and transmit it to the direct-drive wind turbine grid-side converter control system.

[0061] The normal stage determining module 30 is used to obtain a normal stage signal LVRT_end according to the low-voltage wear-through trigger signal LVRT_dur and the low-voltage wear-through recovery trigger signal LVRT_recover and transmit the signal to the direct-drive wind turbine grid-side converter control system.

[0062] The present invention determines whether the direct-drive wind turbine enters a low voltage crossing state by determining the change of the machine-end voltage according to the machine-end voltage and the preset low voltage crossing threshold value and the low voltage crossing exit threshold value, thereby obtaining a low voltage crossing trigger signal LVRT_dur. Further, a low voltage crossing recovery trigger signal LVRT_recover is obtained according to the machine-end voltage, the preset fan exit low voltage crossing threshold value, the fan active power at the time of entering the low voltage crossing, and the low voltage crossing trigger signal LVRT_dur, and a normal stage signal LVRT_end is obtained according to the low voltage crossing trigger signal LVRT_dur and the low voltage crossing recovery trigger signal LVRT_recover. The present invention simulates the active current control instruction transmitted to the direct-drive wind turbine grid-side converter control system by obtaining the low voltage crossing trigger signal LVRT_dur, the low voltage crossing recovery trigger signal LVRT_recover, and the normal stage signal LVRT_end to test the grid-side converter control system. The present invention can reproduce the low-voltage penetration process characteristics of an actual direct-drive wind turbine controller, and thus can be used to simulate the control mode switching logic of a direct-drive wind turbine under different wind conditions and low-voltage fault conditions. It can be applied to the analysis of the active and reactive characteristics of a direct-drive wind turbine during and after a low-voltage fault, as well as the study of its impact on system stability, laying a solid foundation for studying the impact of direct-drive wind turbines on system frequency stability, voltage stability and other stabilities after they enter the power system.

[0063] In a preferred embodiment, Figure 2 As shown, the low voltage ride-through judging module 10 includes a hysteresis judging unit 11 and a signal selecting unit 12. The hysteresis judging unit 11 is used to compare the machine-end voltage with the low voltage ride-through threshold value and the low voltage ride-through exit threshold value, and output a first result if the machine-end voltage is lower than the low voltage ride-through threshold value or the machine-end voltage rises from lower than the low voltage ride-through threshold value to lower than the low voltage ride-through exit threshold value. The signal selecting unit 12 is used to output the low voltage ride-through trigger signal LVRT_dur of the first level when the duration of the output of the hysteresis judging unit 11 being the first result is greater than a preset duration, otherwise, output the low voltage ride-through trigger signal LVRT_dur of the second level.

[0064] More preferably, in a specific example, the low voltage ride through determination module 10 can be implemented by a specific circuit structure. Figure 3 As shown, the hysteresis judgment unit 11 includes a hysteresis circuit for the receiver terminal voltage. The signal selection unit 12 includes a first sampling and holding circuit, a first adder, a first signal selection circuit, a second signal selection circuit and a multiplier.

[0065] Among them, the signal input end of the first sampling and holding circuit is connected to the hysteresis circuit, and the signal output end is connected to the signal input end of the first adder; the signal output end of the first adder is connected to a signal input end of the first signal selector; the other signal input end of the first signal selection circuit is connected to the signal output end of the hysteresis circuit; the signal input end of the second signal selection circuit is connected to the signal output end of the first signal selection circuit; one signal input end of the multiplier is connected to the signal output end of the hysteresis circuit, and the other signal input end is connected to the signal output end of the second signal selection circuit, and the signal output circuit of the multiplier is used to output the low-pass trigger signal LVRT_dur.

[0066] In this specific example, the working principle of the low voltage ride-through determination module 10 is as follows: inputting the machine-end voltage into the hysteresis circuit, and by comparing the machine-end voltage with the low voltage ride-through threshold value and the low voltage ride-through exit threshold value of the hysteresis circuit, the hysteresis circuit outputs a first result 1 (first level) when the machine-end voltage is lower than the low voltage ride-through threshold value Venter, or when the machine-end voltage rises from a voltage value lower than Venter to above Venter and is lower than the low voltage ride-through exit threshold value Vout, the output of the hysteresis circuit remains 1. When the machine-end voltage is higher than Vout, 0 (second level) is output, or when the machine-end voltage drops from above Vout to below Vout and is above Venter, the output of the hysteresis circuit remains 0.

[0067] Furthermore, the signal selection unit 12 formed by the first sampling and holding circuit, the first adder, the first signal selection circuit, the second signal selection circuit and the multiplier realizes that when the output signal of the hysteresis circuit is 1 and exceeds the signal selection circuit threshold value (for example, 0.005) of the second signal selection circuit, the output of the third signal selection circuit is 1. The significance of this process is that when the terminal voltage is lower than Venter0.005s, it is considered to enter the low-through state, and the output low-through trigger signal LVRT_durLVRT_dur is set to 1, that is, the low-through trigger signal LVRT_dur of the first level is output, otherwise, the output low-through trigger signal LVRT_durLVRT_dur is set to 0, that is, the low-through trigger signal LVRT_dur of the second level is output.

[0068] In a preferred embodiment, Figure 4 As shown, the active power recovery stage determining module 20 includes a first comparing unit 21 , a second comparing unit 22 , a third comparing unit 23 and a signal output unit 24 .

[0069] The first comparison unit 21 is used to compare the machine-end voltage with the wind turbine exit low-through threshold when the low-through trigger signal LVRT_dur is at the first level, and output a second result if the machine-end voltage is greater than the wind turbine exit low-through threshold.

[0070] The second comparison unit 22 is used to compare the wind turbine active power with the wind turbine active power at the time of entering the low penetration, and output a third result if the wind turbine active power is less than or equal to the wind turbine active power at the time of entering the low penetration.

[0071] The third comparison unit 23 is configured to output a fourth result when the first comparison unit 21 outputs the second result, the second comparison unit 22 outputs the third result, and the low-pass trigger signal LVRT_dur is at the second level.

[0072] The signal output unit 24 is configured to output the low-level recovery trigger signal LVRT_recover of a first level when the third comparison unit 23 outputs the fourth result and the second comparison unit 22 outputs the third result, and otherwise output the low-level recovery trigger signal LVRT_recover of a second level.

[0073] More preferably, in a specific example, Figure 5 As shown, the first comparison unit 21 includes a second sampling and holding circuit for receiving and holding the low-pass trigger signal LVRT_dur, a first comparison circuit for the receiver end voltage, and a first AND logic circuit, wherein the second sampling and holding circuit is connected to a signal input terminal of the first AND logic circuit; and the other signal input terminal of the first AND logic circuit is connected to the signal output terminal of the first comparison circuit.

[0074] The second comparison unit 22 includes a second comparison circuit for receiving the active power of the wind turbine and the active power of the wind turbine at the time of entering the low penetration moment.

[0075] The third comparison unit 23 includes a second AND logic circuit, a third signal selection circuit, a fourth signal selection circuit, a second adder and a first integrator, wherein the two signal input terminals of the second AND logic circuit are respectively connected to the signal output terminal of the first AND logic circuit and the signal output terminal of the second comparison circuit; the signal output terminal of the second AND logic circuit is connected to a signal input terminal of the third signal selection circuit; a signal input terminal of the fourth signal selection circuit is connected to the signal output terminal of the second comparison circuit; the two signal input terminals of the second adder are respectively connected to the signal output terminal of the third signal selection circuit and the signal output terminal of the second adder; the two signal input terminals of the first integrator are respectively connected to the signal output terminal of the third signal selection circuit and the signal output terminal of the second adder.

[0076] The signal output unit 24 includes a third comparison circuit and a third AND logic circuit, wherein the two signal input ends of the third comparison circuit respectively receive the active power of the wind turbine and the active power of the wind turbine entering the low-breakthrough moment; the two signal input ends of the third AND logic circuit are respectively connected to the signal output end of the first integrator and the signal output end of the third comparison circuit, and the signal output end of the third AND logic circuit is used to output the low-breakthrough recovery trigger signal LVRT_recover.

[0077] In this specific example, the working principle of the module 20 for judging the active power recovery stage is as follows: the machine-end voltage and the wind turbine exit low penetration threshold are compared according to the first comparison unit 21. Preferably, the wind turbine exit low penetration threshold can be selected as 0.89. Of course, in other embodiments, the wind turbine exit low penetration threshold can be flexibly selected according to actual needs, and the present invention does not limit this. The second result output by the first comparison unit 21 is used as the original signal for judging the low voltage crossing active power recovery stage. When the machine-end voltage is higher than the wind turbine exit low penetration threshold and there is a first level low penetration trigger signal LVRT_dur, the circuit of the module 20 for judging the active power recovery stage starts to work.

[0078] Furthermore, the second comparison unit 22 compares the active power of the wind turbine with the active power of the wind turbine at the time of entering the low penetration, and outputs a third result, so that "the active power of the wind turbine is less than or equal to the active power of the wind turbine at the time of entering the low penetration" becomes one of the necessary conditions for setting the low penetration recovery starting signal.

[0079] The third comparison unit 23 formed by the second AND logic circuit, the third signal selection circuit, the fourth signal selection circuit, the second adder and the first integrator is used to achieve: when the two inputs of the second AND logic circuit are both 1 and the low-through trigger signal LVRT_dur is 0 (second level), the first integrator (with an output upper limit of 1 and a lower limit of 0) outputs 1 (fourth result); when the low-through trigger signal LVRT_dur changes from 0 to 1 (enters low-through), the first integrator outputs 0.

[0080] The signal output unit 24 composed of the third comparison circuit and the third AND logic circuit is used to achieve: when the output of the first integrator is 1 and the active power of the fan is less than the active power of the fan at the time of entering the low-breakthrough moment, that is, the third comparison unit 23 outputs the fourth result and the second comparison unit 22 outputs the third result, the final output low-breakthrough recovery trigger signal LVRT_recover is 1 (first level), otherwise, the final output low-breakthrough recovery trigger signal LVRT_recover is 0 (second level).

[0081] In a preferred embodiment, the normal stage judgment module 30 is used to output the normal stage signal LVRT_end of the first level when the low-breakthrough trigger signal LVRT_dur and the low-breakthrough recovery trigger signal LVRT_recover are both at the second level, and to output the normal stage signal LVRT_end of the second level when the low-breakthrough trigger signal LVRT_dur or the low-breakthrough recovery trigger signal LVRT_recover are both at the first level.

[0082] More specifically, in a specific example, Figure 6 As shown, the normal phase determination module 30 includes an OR logic circuit, a fifth signal selection circuit and a second integrator.

[0083] Among them, the two signal input terminals of the OR logic circuit are used to receive the low-throughput trigger signal LVRT_dur and the low-throughput recovery trigger signal LVRT_recover, and the signal output terminal of the OR logic circuit is connected to a signal input terminal of the fifth signal selection circuit; the two signal input terminals of the second integrator are respectively connected to the signal output terminal of the fifth signal selection circuit and receive the low-throughput trigger signal LVRT_dur, and the signal output terminal of the second integrator is used to output the normal stage signal LVRT_end.

[0084] In this specific example, the working principle of the normal stage judgment module 30 is: when the low-throughput trigger signal LVRT_dur or the low-throughput recovery trigger signal LVRT_recover is 1 (first level), the normal stage signal LVRT_end is 0 (second level); when the low-throughput trigger signal LVRT_dur and the low-throughput recovery trigger signal LVRT_recover are 0 (second level), the normal stage signal LVRT_end is 1 (first level).

[0085] It should be noted that, in this embodiment, the first level is a high level (1) and the second level is a low level (0) as an example to illustrate the present invention. In other embodiments, the first level and the second level can be set according to actual needs, and the present invention is not limited to this. Among them, the specific structure of some circuits is not shown. Those skilled in the art can set the specific structure of the circuit according to the functions implemented by each circuit as needed. This is common knowledge in the art and will not be repeated here.

[0086] During the simulation experiment, the low voltage ride-through control mode switching simulation system of the direct-drive wind turbine of the present invention was constructed by simulink simulation software and applied to the electromagnetic transient simulation system of the direct-drive wind turbine connected to the infinite power grid. Low voltage tests were carried out under high wind conditions and low wind conditions, respectively. The active and reactive characteristics of the direct-drive wind turbine obtained by the electromagnetic transient model simulation method and system for switching the low voltage ride-through control mode described in the present invention were compared with the results obtained by the RT-Lab test based on the actual controller. The comparison results are as follows: Figure 7(a)-Figure 7(c) and Figure 8(a)-Figure 8(c) It can be seen from the simulation experiment results that the electromagnetic transient model simulation system for switching the low voltage ride-through control mode of the direct-drive wind turbine according to the present invention can reproduce the characteristics of the RT-Lab physical controller, and then reproduce the low voltage ride-through process characteristics of the actual direct-drive wind turbine controller.

[0087] Based on the same principle, this embodiment also discloses a method for simulating switching of a low voltage ride-through control mode of a direct-drive wind turbine. Fig. 9 As shown, the method includes:

[0088] S100: Obtain a low voltage ride-through trigger signal according to the machine-end voltage, a preset low voltage ride-through threshold value and a low voltage ride-through exit threshold value, and transmit the signal to the grid-side converter control system of the direct-drive wind turbine.

[0089] S200: Obtain a low-through recovery trigger signal according to the machine-end voltage, a preset wind turbine exit low-through threshold, the wind turbine active power at the time of entering the low-through and the low-through trigger signal, and transmit it to the direct-drive wind turbine grid-side converter control system.

[0090] S300: Obtain a normal phase signal according to the low-breakthrough trigger signal and the low-breakthrough recovery trigger signal and transmit the signal to a grid-side converter control system of a direct-drive wind turbine.

[0091] In a preferred embodiment, Fig.10 As shown, the step of obtaining the low voltage ride through trigger signal according to the terminal voltage, the preset low voltage ride through threshold value and the low voltage ride through exit threshold value in S100 specifically includes:

[0092] S110: Compare the machine-side voltage with a low voltage ride-through threshold value and a low voltage ride-through exit threshold value, and output a first result if the machine-side voltage is lower than the low voltage ride-through threshold value or the machine-side voltage rises from lower than the low voltage ride-through threshold value to below the low voltage ride-through exit threshold value.

[0093] S120: When the duration of outputting the first result is greater than the preset duration, outputting the low-through trigger signal of the first level; otherwise, outputting the low-through trigger signal of the second level.

[0094] In a preferred embodiment, Fig.11 As shown, the step S200 of obtaining the low penetration recovery trigger signal according to the terminal voltage, the preset wind turbine exit low penetration threshold value, the wind turbine active power at the time of entering the low penetration moment, and the low penetration trigger signal specifically includes:

[0095] S210: When the low-break trigger signal is at the first level, compare the machine-end voltage with the wind turbine exit low-break threshold value, and if the machine-end voltage is greater than the wind turbine exit low-break threshold value, output a second result.

[0096] S220: Compare the active power of the wind turbine with the active power of the wind turbine at the time of entering the low-breakthrough, and if the active power of the wind turbine is less than or equal to the active power of the wind turbine at the time of entering the low-breakthrough, output a third result.

[0097] S230: When the second result is output and the third result is output and the low-through trigger signal is at the second level, a fourth result is output.

[0098] S240: When the fourth result and the third result are output, the low-penetration recovery trigger signal of the first level is output; otherwise, the low-penetration recovery trigger signal of the second level is output.

[0099] In a preferred embodiment, Fig.12 As shown, obtaining the normal phase signal according to the low penetration trigger signal and the low penetration recovery trigger signal in S300 specifically includes:

[0100] S310: When the low-penetration trigger signal and the low-penetration recovery trigger signal are both at the second level, outputting the normal phase signal at the first level.

[0101] S320: When the low-penetration trigger signal or the low-penetration recovery trigger signal is at the first level, outputting the normal phase signal at the second level.

[0102] Since the principle of solving the problem by this method is similar to that of the above system, the implementation of this method can refer to the implementation of the system and will not be repeated here.

[0103] The systems, devices, modules or units described in the above embodiments may be implemented by computer chips or entities, or by products with certain functions. A typical implementation device is a computer device, and specifically, the computer device may be, for example, a personal computer, a laptop computer, a cellular phone, a camera phone, a smart phone, a personal digital assistant, a media player, a navigation device, an email device, a game console, a tablet computer, a wearable device, or a combination of any of these devices.

[0104] In a typical example, a computer device specifically includes a memory, a processor, and a computer program stored in the memory and executable on the processor, and the method described above is implemented when the processor executes the program.

[0105] Reference below Fig.13 , which shows a schematic diagram of the structure of a computer device 600 suitable for implementing an embodiment of the present application.

[0106] like Fig.13 As shown, the computer device 600 includes a central processing unit (CPU) 601, which can perform various appropriate operations and processes according to a program stored in a read-only memory (ROM) 602 or a program loaded from a storage part 608 to a random access memory (RAM) 603. In the RAM 603, various programs and data required for the operation of the system 600 are also stored. The CPU 601, the ROM 602, and the RAM 603 are connected to each other via a bus 604. An input / output (I / O) interface 605 is also connected to the bus 604.

[0107] The following components are connected to the I / O interface 605: an input section 606 including a keyboard, a mouse, etc.; an output section 607 including a cathode ray tube (CRT), a liquid crystal feedback device (LCD), etc., and a speaker, etc.; a storage section 608 including a hard disk, etc.; and a communication section 609 including a network interface card such as a LAN card, a modem, etc. The communication section 609 performs communication processing via a network such as the Internet. A drive 610 is also connected to the I / O interface 605 as needed. A removable medium 611, such as a magnetic disk, an optical disk, a magneto-optical disk, a semiconductor memory, etc., is installed on the drive 610 as needed, so that a computer program read therefrom is installed as needed as the storage section 608.

[0108] In particular, according to an embodiment of the present invention, the process described above with reference to the flowchart can be implemented as a computer software program. For example, an embodiment of the present invention includes a computer program product, which includes a computer program tangibly contained on a machine-readable medium, and the computer program includes program code for executing the method shown in the flowchart. In such an embodiment, the computer program can be downloaded and installed from a network through the communication part 609, and / or installed from the removable medium 611.

[0109] Computer readable media include permanent and non-permanent, removable and non-removable media that can be implemented by any method or technology to store information. Information can be computer readable instructions, data structures, program modules or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technology, compact disk read-only memory (CD-ROM), digital versatile disk (DVD) or other optical storage, magnetic cassettes, magnetic tape magnetic disk storage or other magnetic storage devices or any other non-transmission media that can be used to store information that can be accessed by a computing device. As defined herein, computer readable media does not include temporary computer readable media (transitory media), such as modulated data signals and carrier waves.

[0110] For the convenience of description, the above device is described in various units according to their functions. Of course, when implementing the present application, the functions of each unit can be implemented in the same or multiple software and / or hardware.

[0111] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks 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 produce 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.

[0112] 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.

[0113] 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.

[0114] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[0115] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment or an embodiment in combination with 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.) that contain computer-usable program code.

[0116] The present application may be described in the general context of computer-executable instructions executed by a computer, such as program modules. Generally, program modules include routines, programs, objects, components, data structures, etc. that perform specific tasks or implement specific abstract data types. The present application may also be practiced in distributed computing environments where tasks are performed by remote processing devices connected through a communication network. In a distributed computing environment, program modules may be located in local and remote computer storage media, including storage devices.

[0117] Each embodiment in this specification is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment.

[0118] The above is only an embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.

Claims

1. A direct-drive wind turbine low voltage ride-through control mode switching simulation system, characterized in that: include: A low voltage ride-through judgment module is used to obtain a low voltage ride-through trigger signal according to the machine-end voltage, a preset low voltage ride-through threshold value and a low voltage ride-through exit threshold value and transmit the signal to the direct-drive wind turbine grid-side converter control system; A module for judging the active power recovery stage is used to obtain a low-through recovery trigger signal according to the terminal voltage, a preset wind turbine exit low-through threshold value, the wind turbine active power at the time of entering the low-through trigger signal, and the low-through trigger signal, and transmit it to the direct-drive wind turbine grid-side converter control system; A normal stage determination module is used to obtain a normal stage signal according to the low penetration trigger signal and the low penetration recovery trigger signal and transmit the signal to a direct-drive wind turbine grid-side converter control system; The active power recovery stage judging module comprises a first comparing unit, a second comparing unit, a third comparing unit and a signal output unit; The first comparison unit is used for comparing the machine-end voltage with the wind turbine exit low-breakthrough threshold value when the low-breakthrough trigger signal is at the first level, and outputting a second result if the machine-end voltage is greater than the wind turbine exit low-breakthrough threshold value; The second comparison unit is used to compare the active power of the wind turbine with the active power of the wind turbine at the time of entering the low penetration, and output a third result if the active power of the wind turbine is less than or equal to the active power of the wind turbine at the time of entering the low penetration; The third comparison unit is used for outputting a fourth result when the first comparison unit outputs the second result, the second comparison unit outputs the third result, and the low-through trigger signal is at the second level; The signal output unit is used for outputting the low penetration recovery trigger signal of the first level when the third comparison unit outputs the fourth result and the second comparison unit outputs the third result, otherwise, outputting the low penetration recovery trigger signal of the second level; The first comparison unit includes a second sampling and holding circuit for receiving and holding the low-through trigger signal, a first comparison circuit for the receiver terminal voltage, and a first AND logic circuit, wherein the second sampling and holding circuit is connected to a signal input terminal of the first AND logic circuit; the other signal input terminal of the first AND logic circuit is connected to a signal output terminal of the first comparison circuit; The second comparison unit comprises a second comparison circuit receiving the active power of the wind turbine and the active power of the wind turbine at the time of entering the low penetration moment; The third comparison unit comprises a second AND logic circuit, a third signal selection circuit, a fourth signal selection circuit, a second adder and a first integrator, wherein two signal input terminals of the second AND logic circuit are respectively connected to the signal output terminal of the first AND logic circuit and the signal output terminal of the second comparison circuit; the signal output terminal of the second AND logic circuit is connected to a signal input terminal of the third signal selection circuit; a signal input terminal of the fourth signal selection circuit is connected to the signal output terminal of the second comparison circuit; two signal input terminals of the second adder are respectively connected to the signal output terminal of the third signal selection circuit and the signal output terminal of the second adder; two signal input terminals of the first integrator are respectively connected to the signal output terminal of the third signal selection circuit and the signal output terminal of the second adder; The signal output unit includes a third comparison circuit and a third AND logic circuit, wherein two signal input ends of the third comparison circuit respectively receive the active power of the wind turbine and the active power of the wind turbine entering the low-breakthrough moment; two signal input ends of the third AND logic circuit are respectively connected to the signal output end of the first integrator and the signal output end of the third comparison circuit, and the signal output end of the third AND logic circuit is used to output the low-breakthrough recovery trigger signal.

2. The low voltage ride through control mode switching simulation system according to claim 1, characterized in that: The low voltage ride-through determination module includes a hysteresis determination unit and a signal selection unit; The hysteresis judgment unit is used to compare the machine-side voltage with a low voltage ride-through threshold value and a low voltage ride-through exit threshold value, and output a first result if the machine-side voltage is lower than the low voltage ride-through threshold value or the machine-side voltage rises from lower than the low voltage ride-through threshold value to below the low voltage ride-through exit threshold value; The signal selection unit is used to output the low-through trigger signal of the first level when the duration of the output of the hysteresis judgment unit as the first result is greater than a preset duration, and otherwise, output the low-through trigger signal of the second level.

3. The low voltage ride through control mode switching simulation system according to claim 2, characterized in that: The hysteresis determination unit includes a hysteresis circuit of the receiver terminal voltage; The signal selection unit includes a first sample-and-hold circuit, a first adder, a first signal selection circuit, a second signal selection circuit and a multiplier; Among them, the signal input end of the first sampling and holding circuit is connected to the hysteresis circuit, and the signal output end is connected to the signal input end of the first adder; the signal output end of the first adder is connected to a signal input end of the first signal selector; the other signal input end of the first signal selection circuit is connected to the signal output end of the hysteresis circuit; the signal input end of the second signal selection circuit is connected to the signal output end of the first signal selection circuit; one signal input end of the multiplier is connected to the signal output end of the hysteresis circuit, and the other signal input end is connected to the signal output end of the second signal selection circuit, and the signal output circuit of the multiplier is used to output the low-wear trigger signal.

4. The low voltage ride through control mode switching simulation system according to claim 1, characterized in that: The normal stage judgment module is used to output the normal stage signal of the first level when the low-penetration trigger signal and the low-penetration recovery trigger signal are both at the second level, and to output the normal stage signal of the second level when the low-penetration trigger signal or the low-penetration recovery trigger signal is both at the first level.

5. The low voltage ride through control mode switching simulation system according to claim 4, characterized in that: The module for judging the normal stage includes an OR logic circuit, a fifth signal selection circuit and a second integrator; The two signal input terminals of the OR logic circuit are used to receive the low-throughput trigger signal and the low-throughput recovery trigger signal, and the signal output terminal of the OR logic circuit is connected to a signal input terminal of the fifth signal selection circuit; the two signal input terminals of the second integrator are respectively connected to the signal output terminals of the fifth signal selection circuit and receive the low-throughput trigger signal, and the signal output terminal of the second integrator is used to output the normal stage signal.

6. A method for simulating switching of low voltage ride-through control mode of a direct-drive wind turbine, characterized in that: Based on the direct-drive wind turbine low voltage ride-through control mode switching simulation system according to any one of claims 1 to 5 above, the method comprises: A low voltage ride-through trigger signal is obtained according to the machine-end voltage, the preset low voltage ride-through threshold value and the low voltage ride-through exit threshold value and transmitted to the grid-side converter control system of the direct-drive wind turbine; A low penetration recovery trigger signal is obtained according to the terminal voltage, the preset wind turbine exit low penetration threshold value, the wind turbine active power at the time of entering the low penetration and the low penetration trigger signal, and transmitted to the direct-drive wind turbine grid-side converter control system; A normal phase signal is obtained according to the low-breakthrough trigger signal and the low-breakthrough recovery trigger signal and transmitted to a direct-drive wind turbine grid-side converter control system.

7. The low voltage ride through control mode switching simulation method according to claim 6, characterized in that: The step of obtaining a low voltage ride-through trigger signal according to the terminal voltage, a preset low voltage ride-through threshold value and a low voltage ride-through exit threshold value specifically includes: Comparing the machine-side voltage with a low voltage ride-through threshold and a low voltage ride-through exit threshold, and outputting a first result if the machine-side voltage is lower than the low voltage ride-through threshold or the machine-side voltage rises from lower than the low voltage ride-through threshold to lower than the low voltage ride-through exit threshold; When the duration of the first result is greater than the preset duration, the low-through trigger signal of the first level is output; otherwise, the low-through trigger signal of the second level is output.

8. The low voltage ride through control mode switching simulation method according to claim 6, characterized in that: The step of obtaining the low-breakthrough recovery trigger signal according to the terminal voltage, the preset threshold value for exiting the low-breakthrough of the wind turbine, the active power of the wind turbine at the time of entering the low-breakthrough, and the low-breakthrough trigger signal specifically includes: When the low-break trigger signal is at the first level, the machine-end voltage is compared with the wind turbine exit low-break threshold value, and if the machine-end voltage is greater than the wind turbine exit low-break threshold value, a second result is output; Compare the active power of the fan with the active power of the fan at the time of entering the low penetration, and if the active power of the fan is less than or equal to the active power of the fan at the time of entering the low penetration, output a third result; When the second result is output and the third result is output and the low-through trigger signal is at the second level, a fourth result is output; When the fourth result and the third result are output, the low-penetration recovery trigger signal of the first level is output; otherwise, the low-penetration recovery trigger signal of the second level is output.

9. The low voltage ride through control mode switching simulation method according to claim 6, characterized in that: The obtaining of the normal phase signal according to the low penetration trigger signal and the low penetration recovery trigger signal specifically includes: When the low-penetration trigger signal and the low-penetration recovery trigger signal are both at the second level, the normal stage signal of the first level is output; when the low-penetration trigger signal or the low-penetration recovery trigger signal is both at the first level, the normal stage signal of the second level is output.

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