Method and system for simulating active characteristics of low voltage ride-through of direct-drive wind turbine

Abstract

The present invention provides a method and system for simulating the active characteristics of low voltage ride-through of a direct-drive wind turbine. The system comprises a current locking module at the moment of low voltage ride-through and a current locking module at the end of low voltage ride-through, which obtain a current signal at the moment of low voltage ride-through and a current signal at the end of low voltage ride-through according to an active current reference signal and a low voltage ride-through trigger signal; an active current control module during the low voltage ride-through period obtains an active current command value during the low voltage ride-through period according to a low voltage ride-through trigger signal and the current signal at the moment of low voltage ride-through; a low voltage ride-through recovery stage control module obtains an active current command value during the low voltage ride-through recovery period according to a low voltage ride-through trigger signal, a low voltage ride-through recovery trigger signal and the current signal at the end of low voltage ride-through; a normal stage control module obtains an active current command value during the normal stage according to a normal stage signal, a DC voltage command value and an actual DC voltage value; and the signal output module is used to obtain and output the active current command value, so as to accurately reproduce the active characteristics of the 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 active characteristics of low voltage ride-through 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 simulation. 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 connection 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 order to cope with this change, it is necessary to accurately simulate the low voltage ride-through and recovery process of direct-drive wind turbines. The active power characteristics of direct-drive wind turbines during the low voltage ride-through process have an important impact on the voltage and frequency characteristics of the power system. Therefore, it is a very critical task to simulate the electromagnetic transient characteristics of the active power of direct-drive wind turbines during low voltage ride-through. Summary of the invention

[0003] One object of the present invention is to provide a method for simulating active characteristics of low voltage ride-through of a direct-drive wind turbine, and to accurately reproduce the active characteristics of an actual direct-drive wind turbine after low voltage ride-through. Another object of the present invention is to provide a system for simulating active characteristics of low voltage ride-through of a direct-drive wind turbine. 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 active characteristic simulation system, comprising:

[0005] A low-breakthrough moment current locking module is used to obtain a low-breakthrough moment current signal according to an active current reference signal and a low-breakthrough trigger signal;

[0006] A low-breakthrough end current locking module is used to obtain a low-breakthrough end current signal according to an active current reference signal and a low-breakthrough trigger signal;

[0007] An active current control module during the low-breakthrough period, used to obtain an active current command value during the low-breakthrough period according to the low-breakthrough trigger signal and the current signal at the low-breakthrough moment;

[0008] A low-breakthrough recovery stage control module, used to obtain an active current command value during the low-breakthrough recovery period according to the low-breakthrough trigger signal, the low-breakthrough recovery trigger signal and the low-breakthrough end current signal;

[0009] A normal stage control module, used for obtaining a normal stage active current command value according to a normal stage signal, a DC voltage command value and an actual DC voltage value;

[0010] The signal output module is used to obtain and output the active current command value according to the active current command value during the low-breakthrough period, the active current command value during the low-breakthrough recovery period and the active current command value in the normal stage.

[0011] Preferably, the low-breakthrough moment current locking module comprises a low-pass filtering unit and a low-breakthrough moment current unit;

[0012] The low-pass filtering unit is used to perform low-pass filtering on the active current reference signal entering the low-pass moment;

[0013] The low-breakthrough moment current unit is used to control the output of the active current reference signal after low-pass filtering by using the low-breakthrough trigger signal as a trigger pulse to form the low-breakthrough moment current signal.

[0014] Preferably, the low-breakthrough end current locking module comprises a low-breakthrough duration unit, a signal selection unit and an end signal output unit;

[0015] The low wear duration unit is used to use the low wear trigger signal as a trigger pulse to control the clock signal output to form a low wear trigger time signal, subtract the low wear trigger time signal from the clock signal to obtain a low wear duration signal, and control the output of the low wear duration according to the low wear trigger signal;

[0016] The signal selection unit is used for adding the low penetration duration output by the low penetration duration unit to a first preset constant and comparing the result with a preset threshold value, and outputting a first intermediate signal if the sum of the low penetration duration and the first preset constant is greater than the preset threshold value; otherwise, outputting a second intermediate signal;

[0017] The end signal output unit is used to control the output of the active current reference signal after low-pass filtering according to the first intermediate signal to obtain a low-pass end current signal.

[0018] Preferably, the active current control module during the low-breakthrough period is used to multiply the low-breakthrough trigger signal and the low-breakthrough moment current signal to obtain the active current command value during the low-breakthrough period.

[0019] Preferably, the low-breakdown recovery stage control module includes a PI control unit, an active current forming unit and a signal output unit;

[0020] The PI control unit is used to perform PI regulation on the low-break recovery trigger signal multiplied by the second preset constant according to the low-break trigger signal and obtain a second intermediate signal after slope limiting;

[0021] The active current forming unit is used for multiplying the low-breakthrough end current signal and the low-breakthrough recovery trigger signal and adding the signal to the second intermediate signal to obtain an active current command intermediate value;

[0022] The signal output unit is used to multiply the active current command intermediate value by the low-breakthrough recovery trigger signal to output the active current command value during the low-breakthrough recovery period.

[0023] Preferably, the conventional stage control module includes a reference signal unit, a conventional signal unit and a signal processing unit;

[0024] The reference signal unit is used to subtract the DC voltage command value from the DC voltage actual value and multiply the result by the base value conversion coefficient, and perform PI adjustment on the converted signal to obtain a third intermediate signal;

[0025] The conventional signal unit is used to output a preset fourth intermediate signal according to the conventional stage signal;

[0026] The signal processing unit is used for multiplying the third intermediate signal and the fourth intermediate signal to obtain an active current command value in a normal stage.

[0027] Preferably, the signal output module is used to add the active current command value during the low-breakthrough period, the active current command value during the low-breakthrough recovery period and the active current command value in the normal stage to obtain the active current command value.

[0028] The present invention also discloses a method for simulating active characteristics of low voltage ride-through of a direct-drive wind turbine, comprising:

[0029] A current signal at the low penetration moment is obtained according to an active current reference signal and a low penetration trigger signal;

[0030] A low-breakthrough end current signal is obtained according to an active current reference signal and a low-breakthrough trigger signal;

[0031] Obtaining an active current command value during the low-breakthrough period according to the low-breakthrough trigger signal and the current signal at the low-breakthrough moment;

[0032] Obtaining an active current command value during a low-breakthrough recovery period according to a low-breakthrough trigger signal, a low-breakthrough recovery trigger signal and the low-breakthrough end current signal;

[0033] The normal stage active current command value is obtained according to the normal stage signal, the DC voltage command value and the actual DC voltage value;

[0034] The active current command value is obtained and outputted according to the active current command value during the low-voltage break-through period, the active current command value during the low-voltage break-through recovery period and the active current command value during the normal stage.

[0035] Preferably, obtaining the low-breakthrough moment current signal according to the active current reference signal and the low-breakthrough trigger signal specifically includes:

[0036] Perform low-pass filtering on the active current reference signal entering the low-breakthrough moment;

[0037] The low-pass trigger signal is used as a trigger pulse to control the output of the active current reference signal after low-pass filtering to form the low-pass moment current signal.

[0038] Preferably, obtaining the low-breakthrough end current signal according to the active current reference signal and the low-breakthrough trigger signal specifically includes:

[0039] Using a low-through trigger signal as a trigger pulse to control the output of a clock signal to form a low-through trigger time signal, subtracting the low-through trigger time signal from the clock signal to obtain a low-through duration signal, and controlling the output of the low-through duration according to the low-through trigger signal;

[0040] Adding the low penetration duration output by the low penetration duration unit to a first preset constant and comparing the result with a preset threshold, if the sum of the low penetration duration and the first preset constant is greater than the preset threshold, outputting a first intermediate signal, otherwise, outputting a second intermediate signal;

[0041] The output of the active current reference signal after low-pass filtering is controlled according to the first intermediate signal to obtain a low-pass end current signal.

[0042] Preferably, obtaining the active current command value during the low-breakthrough recovery period according to the low-breakthrough trigger signal, the low-breakthrough recovery trigger signal and the low-breakthrough end current signal specifically includes:

[0043] According to the low penetration trigger signal, a low penetration recovery trigger signal multiplied by a second preset constant is PI-regulated and slope-limited to obtain a second intermediate signal;

[0044] Multiplying the low-breakthrough end current signal and the low-breakthrough recovery trigger signal and adding the resultant signal to the second intermediate signal to obtain an active current command intermediate value;

[0045] The active current command intermediate value is multiplied by the low-breakthrough recovery trigger signal to output the active current command value during the low-breakthrough recovery period.

[0046] Preferably, the step of obtaining the normal stage active current command value according to the normal stage signal, the DC voltage command value and the DC voltage actual value specifically includes:

[0047] The DC voltage command value and the DC voltage actual value are subtracted and then multiplied by the base value conversion coefficient, and the converted signal is subjected to PI adjustment to obtain a third intermediate signal;

[0048] Outputting a preset fourth intermediate signal according to the conventional stage signal;

[0049] The third intermediate signal and the fourth intermediate signal are multiplied to obtain the active current command value in the normal stage. The present invention proposes an electromagnetic transient characteristic simulation system for the active characteristics of low voltage crossing of a direct-drive wind turbine, wherein a low-crossing moment current locking module provides a low-crossing moment current signal for an active current control module during the low-crossing period, and a low-crossing end current locking module provides a low-crossing end current signal for a low-crossing recovery stage control module. Finally, the active current command value is obtained through calculation by the active current control module during the low-crossing period, the low-crossing recovery stage control module and the normal stage control module. The present invention can be applied to the analysis of the active characteristics of direct-drive wind turbines during and after low voltage faults and the study of their impact on system stability, laying a solid foundation for studying the impact of direct-drive wind turbines on various stabilities such as system frequency stability and voltage stability after they are connected to the power system. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] 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.

[0051] Figure 1 A structural diagram showing a specific embodiment of the direct-drive wind turbine low voltage ride-through active characteristic simulation system of the present invention;

[0052] Figure 2 A structural diagram showing a current locking module at the low voltage ride-through moment of a specific embodiment of the direct-drive wind turbine low voltage ride-through active characteristic simulation system of the present invention;

[0053] Figure 3 A circuit structure diagram of a current locking module at the low voltage ride-through moment in a specific example of a direct-drive wind turbine low voltage ride-through active characteristic simulation system of the present invention is shown;

[0054] Figure 4 A structural diagram showing a low voltage ride-through end current locking module of a specific embodiment of the direct-drive wind turbine low voltage ride-through active characteristic simulation system of the present invention;

[0055] Figure 5 A circuit structure diagram of a low voltage ride-through end current locking module in a specific example of a direct-drive wind turbine low voltage ride-through active characteristic simulation system of the present invention is shown;

[0056] Figure 6 A circuit structure diagram showing an active current control module during a low voltage ride-through period in a specific example of a direct-drive wind turbine low voltage ride-through active current characteristic simulation system of the present invention;

[0057] Figure 7 A structural diagram showing a low voltage ride through recovery stage control module of a specific embodiment of the direct-drive wind turbine low voltage ride through active characteristic simulation system of the present invention;

[0058] Figure 8 A circuit structure diagram of a low voltage ride-through recovery stage control module in a specific example of a direct-drive wind turbine low voltage ride-through active characteristic simulation system of the present invention is shown;

[0059] Fig. 9 A structural diagram showing a conventional stage control module of a specific embodiment of a direct-drive wind turbine low voltage ride-through active characteristic simulation system of the present invention;

[0060] Fig.10 A circuit structure diagram of a conventional stage control module in a specific example of a direct-drive wind turbine low voltage ride-through active characteristic simulation system of the present invention is shown;

[0061] Fig.11 A circuit structure diagram showing a signal output module in a specific example of the direct-drive wind turbine low voltage ride-through active characteristic simulation system of the present invention;

[0062] Figure 12(a)-Figure 12(b) A comparison chart showing the test results of the direct-drive wind turbine low voltage ride-through active characteristic simulation system of the present invention and the RT-Lab experimental system under high wind conditions;

[0063] Figure 13(a)-Figure 13(b) A comparison chart showing the test results of the direct-drive wind turbine low voltage ride-through active characteristic simulation system of the present invention and the RT-Lab experimental system under low wind conditions;

[0064] Fig.14 A flowchart showing a specific embodiment of the method for simulating active characteristics of low voltage ride-through of a direct-drive wind turbine according to the present invention;

[0065] Fig.15 A schematic diagram showing the structure of a computer device suitable for implementing an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0066] 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.

[0067] According to one aspect of the present invention, this embodiment discloses a direct-drive wind turbine low voltage ride-through active characteristic simulation system. Figure 1As shown, in this embodiment, the system includes a low-breakthrough moment current locking module 10, a low-breakthrough end current locking module 20, a low-breakthrough period active current control module 30, a low-breakthrough recovery stage control module 40, a normal stage control module 50 and a signal output module 60.

[0068] The low-breakthrough moment current locking module 10 is used to obtain a low-breakthrough moment current signal according to an active current reference signal and a low-breakthrough trigger signal.

[0069] The low wear-through end current locking module 20 is used to obtain a low wear-through end current signal according to the active current reference signal and the low wear-through trigger signal.

[0070] The active current control module 30 during the low-power wear period is used to obtain the active current command value during the low-power wear period according to the low-power wear trigger signal and the current signal at the low-power wear moment.

[0071] The low-breakthrough recovery stage control module 40 is used to obtain the active current command value during the low-breakthrough recovery period according to the low-breakthrough trigger signal, the low-breakthrough recovery trigger signal and the low-breakthrough end current signal.

[0072] The normal stage control module 50 is used to obtain the normal stage active current command value according to the normal stage signal, the DC voltage command value and the DC voltage actual value.

[0073] The signal output module 60 is used to obtain and output the active current command value according to the active current command value during the low-breakthrough period, the active current command value during the low-breakthrough recovery period and the active current command value during the normal stage.

[0074] The present invention proposes an electromagnetic transient characteristic simulation system for the active characteristics of low voltage ride-through of a direct-drive wind turbine, wherein a low voltage ride-through moment current locking module 10 provides a low voltage ride-through moment current signal Id_LVRT_start for an active current control module 30 during the low voltage ride-through period, and a low voltage ride-through end current locking module 20 provides a low voltage ride-through end current signal Id_LVRT_end for a low voltage ride-through recovery stage control module 40. Finally, the active current command value Id_ref is obtained through calculation by the active current control module 30 during the low voltage ride-through period, the low voltage ride-through recovery stage control module 40 and the normal stage control module 50. The present invention can be applied to the analysis of the active characteristics of a direct-drive wind turbine during and after a low voltage fault and the study of its impact on system stability, laying a solid foundation for studying the impact of direct-drive wind turbines on various stabilities such as system frequency stability and voltage stability after they are connected to the power system.

[0075] In a preferred embodiment, Figure 2As shown, the low-breakthrough moment current locking module 10 includes a low-pass filtering unit 11 and a low-breakthrough moment current unit 12. The low-pass filtering unit 11 is used to perform low-pass filtering on the active current reference signal entering the low-breakthrough moment. The low-breakthrough moment current unit 12 is used to use the low-breakthrough trigger signal as a trigger pulse to control the output of the low-pass filtered active current reference signal to form the low-breakthrough moment current signal.

[0076] More preferably, the low breakdown current locking module 10 can be implemented by a circuit structure. The circuit structure can be formed by various actual components or simulated by a software program. In a specific example, Figure 3 As shown, the low-pass filter unit 11 includes a first low-pass filter circuit, and the low-pass moment current unit 12 includes a first sampling and holding circuit. The signal input end of the first low-pass filter circuit is used to receive an active current reference signal and perform low-pass filtering on the active current reference signal. The signal output end of the first low-pass filter circuit is connected to the signal input end of the first sampling and holding circuit, and is used to transmit the low-pass filtered active current reference signal to the first sampling and holding circuit. The trigger signal input end of the first sampling and holding circuit is used to receive a low-pass trigger signal, and the low-pass trigger signal is used as a trigger pulse to control the output of the low-pass filtered active current reference signal to form the low-pass moment current signal. The signal output end of the first sampling and holding circuit is used to output the low-pass moment current signal.

[0077] It can be understood that in this specific example, the low-pass trigger signal LVRT_dur (1 after entering the low-pass state and 0 for the rest of the time) is used as the trigger pulse of the first sampling and holding circuit, and the result of the active current reference signal after low-pass filtering at the moment of entering the low-pass state is recorded, and the output active current reference signal after low-pass filtering is output as the current signal Id_LVRT_start at the low-pass moment. The active current reference signal is selected because the high-frequency noise in the actual signal of the active current is too large. The frequency threshold of the first low-pass filter circuit can preferably be set larger, such as 100rand / s. It should be noted that the amplitude limiting of the current inner loop PI controller and the amplitude limiting of the modulation ratio of the modulation control may affect the effect of the active current tracking command value during the low-pass period.

[0078] In a preferred embodiment, Figure 4As shown, the low wear end current locking module 20 includes a low wear duration unit 21, a signal selection unit 22 and an end signal output unit 23. The low wear duration unit 21 is used to use the low wear trigger signal as a trigger pulse to control the clock signal output to form a low wear trigger time signal, subtract the low wear trigger time signal from the clock signal to obtain a low wear duration signal, and control the output of the low wear duration according to the low wear trigger signal. The signal selection unit 22 is used to add the low wear duration output by the low wear duration unit 21 to a first preset constant and then compare it with a preset threshold. If the low wear duration is greater than the preset threshold after adding the first preset constant, the first intermediate signal is output, otherwise, the second intermediate signal is output. The end signal output unit 23 is used to control the output of the active current reference signal after low-pass filtering according to the first intermediate signal to obtain a low wear end current signal.

[0079] More preferably, the low wear-through end current locking module 20 can be implemented by a circuit structure. The circuit structure can be formed by various actual components or can be simulated by a software program. In a specific example, Figure 5 As shown, the low-pass duration unit 21 includes a second sampling and holding circuit, a first adder and a first signal selection circuit, the signal selection unit 22 includes a second adder and a second signal selection circuit, and the end signal output unit 23 includes a second low-pass filter circuit and a third sampling and holding circuit.

[0080] Among them, the signal input end of the second sampling and holding circuit is used to receive a clock signal, the trigger signal input end is used to receive a low-penetration trigger signal, and the signal output end is connected to a signal input end of the first adder, and is used to transmit the formed low-penetration trigger time signal to the first adder. Another signal input end of the first adder is used to receive a clock signal, and the signal output end is connected to a signal input end of the first signal selection circuit, and is used to transmit the low-penetration duration signal to the first signal selection circuit. Another signal input end of the first signal selection circuit is used to receive a low-penetration trigger signal, and the signal output end is connected to the signal input end of the second adder, and is used to control the low-penetration duration to be output to the second adder according to the low-penetration trigger signal. The signal output end of the second adder is connected to a signal input end of the second signal selection circuit, and is used to add the low-penetration duration and the first preset constant -1 and transmit it to the second signal selection circuit. The signal output end of the second signal selection circuit is connected to the trigger signal input end of the third sampling and holding circuit, and the output first intermediate signal or the second intermediate signal is used as the trigger signal of the third sampling and holding circuit. The signal input end of the second low-pass filter circuit is used to receive the active current reference signal, and the signal output end is connected to the signal input end of the third sampling and holding circuit, and is used to transmit the active current reference signal after low-pass filtering to the third sampling and holding circuit. The third sampling and holding circuit is used to make the output of the active current reference signal after low-pass filtering obtain a low-pass end current signal when the trigger signal is the first intermediate signal.

[0081] It can be understood that, in this specific example, according to the low wear trigger signal LVRT_dur (1 after entering the low wear state, 0 for the rest of the time) as the trigger pulse of the sampling and holding circuit 1, the clock signal of the low wear trigger moment is recorded, and subtracted from the clock signal to obtain the low wear duration. The first signal selection circuit is controlled by LVRT_dur, and the first signal selection circuit is selected to output the low wear duration after entering the low wear state, and 0 is selected to output for the rest of the time. The output of the first signal selection circuit is multiplied by -1 and input to the second signal selection circuit, and the threshold value Time_LVRT_Steady of the second signal selection circuit is set, which is 0.04 in this example. The second signal selection circuit is used to output 1 when the low wear duration is greater than Time_LVRT_Steady, otherwise it outputs 0. Finally, according to the second signal selection circuit as the trigger pulse of the third sampling and holding circuit, the result after low wear duration is the active current reference signal at the time of Time_LVRT_Steady after low-pass filtering is recorded, and it is output as the low wear end current signal (Id_LVRT_end).

[0082] In a preferred embodiment, the active current control module 30 during the low-breakthrough period is used to multiply the low-breakthrough trigger signal and the low-breakthrough moment current signal to obtain the active current command value during the low-breakthrough period.

[0083] More preferably, the active current control module 30 during the low wear period can be implemented by a circuit structure. The circuit structure can be formed by various actual components or simulated by a software program. In a specific example, Figure 6 As shown, the active current control module 30 during the low wear period includes a first multiplier. The two signal input terminals of the first multiplier are respectively used to receive the low wear trigger signal and the current signal at the low wear moment, and the low wear trigger signal and the current signal at the low wear moment are multiplied to obtain the active current command value during the low wear period and output it. Among them, the low wear trigger signal LVRT_dur is 1 after entering the low wear state, and is 0 at other times.

[0084] In a preferred embodiment, Figure 7 As shown, the low wear recovery stage control module 40 includes a PI control unit 41, an active current forming unit 42 and a signal output unit 43. The PI control unit 41 is used to perform PI regulation on the low wear recovery trigger signal multiplied by the second preset constant according to the low wear trigger signal and obtain a second intermediate signal after slope limiting. The active current forming unit 42 is used to multiply the low wear end current signal and the low wear recovery trigger signal and add the low wear recovery trigger signal to the second intermediate signal to obtain an active current command intermediate value. The signal output unit 43 is used to multiply the active current command intermediate value with the low wear recovery trigger signal to output the active current command value during the low wear recovery period.

[0085] More preferably, the low wear recovery stage control module 40 can be implemented by a circuit structure. The circuit structure can be formed by various actual components or simulated by a software program. In a specific example, Figure 8 As shown, the PI control unit 41 includes a second multiplier, a third multiplier, a fourth multiplier, a third adder, an integrator and a slope limiter. The active current forming unit 42 includes a fifth multiplier and a sixth multiplier. The signal output unit 43 includes a fourth adder, a third signal selection circuit and a seventh multiplier.

[0086] Wherein, the two signal input ends of the second multiplier are respectively used to receive the low wear recovery trigger signal and the second preset constant (-1), and the signal output end is connected to the signal input ends of the third multiplier and the fourth multiplier, and is used to transmit the low wear recovery trigger signal multiplied by the second preset constant to the third multiplier and the fourth multiplier. The signal output end of the third multiplier is connected to a signal input end of the third adder, and the signal output end of the third adder is connected to the signal input end of the slope limiter, and the signal output end of the slope limiter is connected to a signal input end of the fourth adder. The signal output end of the fourth multiplier is connected to a signal input end of the integrator, and the other signal input end of the integrator is used to receive the low wear trigger signal. The signal output end of the integrator is connected to another signal input end of the third adder. The two signal input ends of the fifth multiplier are respectively used to receive the low wear end current and the constant, and when the constant is 1, the low wear end current is output. The signal output end of the fifth multiplier is connected to a signal input end of the sixth multiplier, the other signal input end of the sixth multiplier is used to receive the low wear recovery trigger signal, the signal output end is connected to another signal input end of the fourth adder, and the sixth multiplier is used to multiply the low wear end current with the low wear recovery trigger signal and transmit it to the fourth adder. The signal output end of the fourth adder is connected to a signal input end of the seventh multiplier, and is used to add the received signal to obtain the active current command value and transmit it to the seventh multiplier. A signal input end of the third signal selection circuit is used to receive the low wear recovery trigger signal, and the signal output end is connected to another signal input end of the seventh multiplier, and is used to transmit the low wear recovery trigger signal to the seventh multiplier. The seventh multiplier is used to multiply the received active current command value and the low wear recovery trigger signal to obtain the active current command value during the low wear recovery period and output it. It can be understood that a PI controller is formed by the third multiplier, the fourth multiplier, the third adder and the integrator, and the input of the PI controller is the result of multiplying the low-penetration recovery trigger signal LVRT_recover (1 after entering the low-penetration recovery state and 0 for the rest of the time) by -1, and the result calculated by the PI controller is output to the slope limiter. The integrator of the PI controller will return to zero when the low-penetration trigger signal has a rising edge (when entering the low-penetration). The low-penetration end current Id_LVRT_end is multiplied by the low-penetration recovery trigger signal (the active current command value at the start of the low-penetration recovery stage can be obtained), and is added to the result after the PI controller is input to the slope limiter (the slope limiter determines the rising speed of the active current during the low-penetration recovery period) to obtain the active current command value during the low-penetration recovery period. Finally, in order to ensure that the output is zero for the rest of the time except the low-penetration recovery period, the output active current command value is multiplied by the low-penetration recovery trigger signal to obtain the active current command value during the low-penetration recovery period and output it.

[0087] In a preferred embodiment, Fig. 9As shown, the conventional stage control module 50 includes a reference signal unit 51, a conventional signal unit 52 and a signal processing unit 53. The reference signal unit 51 is used to subtract the DC voltage command value from the DC voltage actual value and multiply it by the base value conversion coefficient, and perform PI adjustment on the converted signal to obtain a third intermediate signal. The conventional signal unit 52 is used to output a preset fourth intermediate signal according to the conventional stage signal. The signal processing unit 53 is used to multiply the third intermediate signal and the fourth intermediate signal to obtain the conventional stage active current command value.

[0088] More preferably, the conventional stage control module 50 can be implemented by a circuit structure. The circuit structure can be formed by various actual components or can be simulated by a software program. Fig.10 As shown, the reference signal unit 51 includes a fifth adder, an eighth multiplier and a PI controller. The normal signal unit 52 includes a fourth signal selection circuit. The signal processing unit 53 includes a ninth multiplier.

[0089] Among them, the two signal receiving ends of the fifth adder are respectively used to receive the DC voltage command value and the DC voltage actual value, and the signal output end is connected to the signal input end of the eighth multiplier, and is used to transmit the difference after the DC voltage command value and the DC voltage actual value are subtracted to the eighth multiplier. The signal output end of the eighth multiplier is connected to the signal input end of the PI controller, and is used to perform PI regulation on the signal after the DC voltage command value and the DC voltage actual value are subtracted and then multiplied by the base value conversion coefficient to obtain a third intermediate signal. A signal input end of the fourth signal selection circuit is used to receive a normal stage signal, and the signal output end is connected to a signal input end of the ninth multiplier. Another signal input end of the ninth multiplier is connected to the signal output end of the PI controller, and is used to multiply the third intermediate signal and the fourth intermediate signal to obtain a normal stage active current command value.

[0090] It can be understood that after the DC voltage command value is subtracted from the actual value of the DC voltage, it is multiplied by the per-unit value base value conversion coefficient and input into the PI controller. The output of the PI controller is multiplied by the normal stage signal LVRT_end (1 when the fan is not in the low-breakthrough or low-breakthrough recovery period, and 0 for the rest of the time) to obtain the final normal stage active current command value as the output.

[0091] In a preferred embodiment, the signal output module 60 is used to add the active current command value during the low-breakthrough period, the active current command value during the low-breakthrough recovery period and the active current command value in the normal stage to obtain the active current command value.

[0092] More preferably, the signal output module 60 can be implemented by a circuit structure. The circuit structure can be formed by various actual components or can be simulated by a software program. Fig.11 As shown, the signal output module 60 includes a sixth adder. The three signal input terminals of the sixth adder are respectively used to receive the active current command value during the low-breakthrough period, the active current command value during the low-breakthrough recovery period and the active current command value in the normal stage and add them to obtain the active current command value.

[0093] It should be noted that the specific structure of some circuits in this embodiment is not shown. Those skilled in the art can set the specific structure of the circuit as needed according to the functions implemented by each circuit. This is common knowledge in the art and will not be described again here.

[0094] During the simulation experiment, the direct-drive wind turbine low voltage ride-through active characteristic simulation system of the present invention is 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 are carried out under high wind conditions and low wind conditions, respectively. The results obtained by using the present invention are compared with the results obtained by the RT-Lab test based on the actual controller. The comparison results are as follows: Figure 12(a)-Figure 12(b) and Figure 13(a)-Figure 13(b) As shown. It can be seen from the simulation experiment results that the electromagnetic transient characteristics simulation method and system for the low voltage ride-through active characteristics of the direct-drive wind turbine proposed in the present invention can reproduce the characteristics of the RT-Lab physical controller, and then reproduce the low voltage ride-through active characteristics of the actual direct-drive wind turbine controller. Therefore, the new active current control model proposed in the present invention can be used to simulate the active characteristics of the direct-drive wind turbine in the entire process of low voltage ride-through under different wind conditions and fault conditions.

[0095] Based on the same principle, this embodiment also discloses a method for simulating the active characteristics of low voltage ride-through of a direct-drive wind turbine. Fig.14 As shown, in this embodiment, the method includes:

[0096] S100: Obtaining a current signal at the low penetration moment according to an active current reference signal and a low penetration trigger signal.

[0097] S200: Obtaining a low-breakthrough end current signal according to the active current reference signal and the low-breakthrough trigger signal.

[0098] S300: obtaining an active current command value during the low-voltage breakout period according to the low-voltage breakout trigger signal and the current signal at the low-voltage breakout moment.

[0099] S400: obtaining an active current command value during the low-voltage wear-through recovery period according to the low-voltage wear-through trigger signal, the low-voltage wear-through recovery trigger signal and the low-voltage wear-through end current signal.

[0100] S500: Obtaining a normal-stage active current command value according to a normal-stage signal, a DC voltage command value and an actual DC voltage value.

[0101] S600: Obtaining an active current command value according to the active current command value during the low-voltage breakout period, the active current command value during the low-voltage breakout recovery period, and the active current command value during the normal stage.

[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.15 , 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.15 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 including 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 active characteristic simulation system, characterized in that: include: A low-breakthrough moment current locking module is used to obtain a low-breakthrough moment current signal according to an active current reference signal and a low-breakthrough trigger signal; A low-breakthrough end current locking module is used to obtain a low-breakthrough end current signal according to an active current reference signal and a low-breakthrough trigger signal; An active current control module during the low-breakthrough period, used to obtain an active current command value during the low-breakthrough period according to the low-breakthrough trigger signal and the current signal at the low-breakthrough moment; A low-breakthrough recovery stage control module, used to obtain an active current command value during the low-breakthrough recovery period according to the low-breakthrough trigger signal, the low-breakthrough recovery trigger signal and the low-breakthrough end current signal; A normal stage control module, used for obtaining a normal stage active current command value according to a normal stage signal, a DC voltage command value and an actual DC voltage value; A signal output module, used for obtaining an active current command value according to the active current command value during the low-breakthrough period, the active current command value during the low-breakthrough recovery period and the active current command value during the normal stage; The low-breakthrough moment current locking module comprises a low-pass filtering unit and a low-breakthrough moment current unit; The low-pass filtering unit is used to perform low-pass filtering on the active current reference signal entering the low-pass moment; The low-breakthrough moment current unit is used to control the output of the active current reference signal after low-pass filtering by using the low-breakthrough trigger signal as a trigger pulse to form the low-breakthrough moment current signal; The low-breakthrough end current locking module includes a low-breakthrough duration unit, a signal selection unit and an end signal output unit; The low wear duration unit is used to use the low wear trigger signal as a trigger pulse to control the clock signal output to form a low wear trigger time signal, subtract the low wear trigger time signal from the clock signal to obtain a low wear duration signal, and control the output of the low wear duration according to the low wear trigger signal; The signal selection unit is used for adding the low penetration duration output by the low penetration duration unit to a first preset constant and comparing the result with a preset threshold value, and outputting a first intermediate signal if the sum of the low penetration duration and the first preset constant is greater than the preset threshold value; otherwise, outputting a second intermediate signal; The end signal output unit is used to control the output of the active current reference signal after low-pass filtering according to the first intermediate signal to obtain a low-pass end current signal.

2. The direct-drive wind turbine low voltage ride-through active characteristic simulation system according to claim 1 is characterized in that: The active current control module during the low-breakthrough period is used to multiply the low-breakthrough trigger signal and the low-breakthrough moment current signal to obtain the active current command value during the low-breakthrough period.

3. The direct-drive wind turbine low voltage ride-through active characteristic simulation system according to claim 1, characterized in that: The low-breakdown recovery stage control module includes a PI control unit, an active current forming unit and a signal output unit; The PI control unit is used to perform PI regulation on the low-break recovery trigger signal multiplied by the second preset constant according to the low-break trigger signal and obtain a second intermediate signal after slope limiting; The active current forming unit is used for multiplying the low-breakthrough end current signal and the low-breakthrough recovery trigger signal and adding the signal to the second intermediate signal to obtain an active current command intermediate value; The signal output unit is used to multiply the active current command intermediate value by the low-breakthrough recovery trigger signal to output the active current command value during the low-breakthrough recovery period.

4. The direct-drive wind turbine low voltage ride-through active characteristic simulation system according to claim 1, characterized in that: The conventional stage control module includes a reference signal unit, a conventional signal unit and a signal processing unit; The reference signal unit is used to subtract the DC voltage command value from the DC voltage actual value and multiply the result by the base value conversion coefficient, and perform PI adjustment on the converted signal to obtain a third intermediate signal; The conventional signal unit is used to output a preset fourth intermediate signal according to the conventional stage signal; The signal processing unit is used for multiplying the third intermediate signal and the fourth intermediate signal to obtain an active current command value in a normal stage.

5. The direct-drive wind turbine low voltage ride-through active characteristic simulation system according to claim 1, characterized in that: The signal output module is used to add the active current command value during the low-breakthrough period, the active current command value during the low-breakthrough recovery period and the active current command value in the normal stage to obtain the active current command value.

6. A method for simulating active characteristics of low voltage ride-through of a direct-drive wind turbine, characterized in that: include: A current signal at the low penetration moment is obtained according to an active current reference signal and a low penetration trigger signal; A low-breakthrough end current signal is obtained according to an active current reference signal and a low-breakthrough trigger signal; Obtaining an active current command value during the low-breakthrough period according to the low-breakthrough trigger signal and the current signal at the low-breakthrough moment; Obtaining an active current command value during a low-breakthrough recovery period according to a low-breakthrough trigger signal, a low-breakthrough recovery trigger signal and the low-breakthrough end current signal; The normal stage active current command value is obtained according to the normal stage signal, the DC voltage command value and the actual DC voltage value; The active current command value is obtained according to the active current command value during the low-voltage breakout period, the active current command value during the low-voltage breakout recovery period, and the active current command value during the normal stage; The step of obtaining the current signal at the low penetration moment according to the active current reference signal and the low penetration trigger signal specifically includes: Perform low-pass filtering on the active current reference signal entering the low-breakthrough moment; Using the low-pass trigger signal as a trigger pulse to control the output of the active current reference signal after low-pass filtering to form the low-pass moment current signal; The step of obtaining the low-breakthrough end current signal according to the active current reference signal and the low-breakthrough trigger signal specifically includes: Using a low-through trigger signal as a trigger pulse to control the output of a clock signal to form a low-through trigger time signal, subtracting the low-through trigger time signal from the clock signal to obtain a low-through duration signal, and controlling the output of the low-through duration according to the low-through trigger signal; Adding the low penetration duration output by the low penetration duration unit to a first preset constant and comparing the result with a preset threshold, if the sum of the low penetration duration and the first preset constant is greater than the preset threshold, outputting a first intermediate signal, otherwise, outputting a second intermediate signal; The output of the active current reference signal after low-pass filtering is controlled according to the first intermediate signal to obtain a low-pass end current signal.

7. The method for simulating active characteristics of low voltage ride through of a direct-drive wind turbine according to claim 6, characterized in that: The step of obtaining the active current command value during the low-breakthrough recovery period according to the low-breakthrough trigger signal, the low-breakthrough recovery trigger signal and the low-breakthrough end current signal specifically includes: According to the low penetration trigger signal, a low penetration recovery trigger signal multiplied by a second preset constant is PI-regulated and slope-limited to obtain a second intermediate signal; Multiplying the low-breakthrough end current signal and the low-breakthrough recovery trigger signal and adding the resultant signal to the second intermediate signal to obtain an active current command intermediate value; The active current command intermediate value is multiplied by the low-breakthrough recovery trigger signal to output the active current command value during the low-breakthrough recovery period.

8. The method for simulating active characteristics of low voltage ride through of a direct-drive wind turbine according to claim 6, characterized in that: The step of obtaining the normal stage active current command value according to the normal stage signal, the DC voltage command value and the DC voltage actual value specifically includes: The DC voltage command value and the DC voltage actual value are subtracted and then multiplied by the base value conversion coefficient, and the converted signal is subjected to PI adjustment to obtain a third intermediate signal; Outputting a preset fourth intermediate signal according to the conventional stage signal; The third intermediate signal and the fourth intermediate signal are multiplied to obtain the active current command value in the normal stage.

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