A method and system for correcting the lightning strike distance formula for rotating wind turbines

Abstract

This invention relates to wind turbine lightning protection technology, specifically to a method and system for correcting the lightning strike distance formula for rotating wind turbines. This method calculates the lightning strike distance under different lightning current amplitudes using the leader development method and fits the results to obtain a formula relating lightning current and lightning strike distance. Then, based on the results of long-gap discharge tests on rotating wind turbines, and by fitting the test results of long-gap discharge voltage tests under different gap distances and operating conditions, a correction coefficient for the impact of blade rotation on the lightning strike distance of the wind turbine is proposed. Furthermore, lightning current amplitude and blade tip linear velocity are introduced as variables to evaluate the influence of blade rotation on the lightning strike distance. This method can reflect the influence of blade rotation on the lightning strike distance of wind turbines to a certain extent and is applicable to engineering calculations of the lightning strike probability of wind turbine blades.

Description

Technical Field

[0001] This invention belongs to the field of wind turbine lightning protection technology, and specifically relates to a method and system for correcting the lightning strike distance formula for rotating wind turbines. Background Technology

[0002] Wind energy is widely distributed, abundant in resources, and has a long history of development, making it one of the renewable energy sources with the largest construction scale and best development prospects. However, as the installed capacity of wind turbines continues to increase and the height of wind turbines also increases, lightning strikes on wind turbines have gradually become one of the main factors threatening the safe and stable operation of wind farms.

[0003] Wind turbine blades are the most vulnerable and susceptible to lightning strikes. Since each wind turbine may be subjected to numerous lightning strikes during its lifespan, all blades are equipped with lightning protection systems to mitigate the impact of such incidents. The lightning protection characteristics of a wind turbine are primarily influenced by its height, blade lightning arrester structure, and rotational characteristics; therefore, it is necessary to consider these factors in the simulation calculations of lightning shielding for wind turbine blades. Currently, the mainstream lightning shielding calculation models include the electrogeometric model and the leader development model. The electrogeometric model, unable to account for the upward leader, is unsuitable for lightning protection calculations on tall targets. The leader development model has high computational requirements and long calculation times, making it unsuitable for lightning shielding calculations on complex targets such as wind turbines. Therefore, many scholars have proposed using the leader development method to calculate the lightning strike distance of tall targets as a function of lightning current, and combining this with the electrogeometric model to calculate the lightning strike distance for structurally complex targets, thus incorporating the wind turbine's structural height and blade lightning arrester structure into the lightning shielding model considerations. However, current research has not considered the impact of changes in space charge caused by blade rotation and changes in blade tip position on the wind turbine's lightning strike distance in the derivation of experimental data or simulation calculations.

[0004] Therefore, in order to study the lightning strike characteristics of rotating wind turbines, this invention, based on previous research on the electrogeometry method and the pilot development method, considers the influence of blade rotation on the lightning strike capability of wind turbines, and modifies the lightning strike distance formula for rotating wind turbines, proposing a method for modifying the lightning strike distance formula for rotating wind turbines. Summary of the Invention

[0005] To address the problems existing in the background technology, the present invention provides a method for correcting the lightning strike distance formula for rotating wind turbines. This method can reflect the influence of blade rotation on the lightning strike distance of wind turbines to a certain extent and is applicable to the engineering calculation of the lightning strike probability of wind turbine blades.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: a method for correcting the lightning strike distance formula for rotating wind turbines, comprising:

[0007] The lightning strike distance under different lightning current amplitudes was calculated using the lead development method, and the relationship between lightning current and lightning strike distance was obtained by fitting the formula.

[0008] A long-gap discharge test was conducted on a rotating fan to obtain the long-gap discharge voltage of the fan under static and rotating conditions with different gap distances.

[0009] The 50% breakdown voltage of the gap was statistically analyzed when the fan was running at different speeds under different gap distances. Based on the experimentally obtained 50% breakdown voltage and gap distance, the fitting relationship was obtained.

[0010] Find the expression for the strike distance formula;

[0011] Dividing the strike distance formulas for different wind turbine speeds by the strike distance formulas for static conditions yields the influence coefficient K of rotation on strike distance under different lightning currents. R And the lightning strike distance correction coefficient curves under different rotation speeds and lightning current amplitudes;

[0012] The ratio of the distances to different targets at the maximum probability of lightning current amplitude in the region was used as a correction coefficient. Lightning current amplitude and blade tip linear velocity were introduced as variables into the lightning distance correction coefficient to obtain the correction coefficient of blade rotation on the lightning distance.

[0013] In the above-mentioned method for correcting the lightning strike distance formula for rotating wind turbines, the leader development method for calculating the lightning strike distance under different lightning current amplitudes includes:

[0014] Once the leader stabilizes and begins to move, the upward and downward leaders develop at the same rate until the average field strength between their leaders reaches 500 kV / m. At this point, a jump is considered to occur, and the leader connects to the main return stroke. The distance between the leaders at this time is defined as the strike distance R under this lightning current amplitude.

[0015] In the above-mentioned method for correcting the lightning strike distance formula for rotating wind turbines, the step of conducting a long-gap discharge test on the rotating wind turbine includes the following steps:

[0016] A long-gap discharge test platform for a rotating fan was constructed. The platform included a scaled-down fan, arc electrodes, and a discharge breakdown voltage measurement system. The following test parameters were changed during the test:

[0017] (1) Gap distance; The gap distance is the shortest distance between the tip of the fan blade and the arc-shaped electrode. The gap distance shall not be less than 4m, and multiple gap distances shall be selected for testing.

[0018] (2) Operating conditions; tests were conducted on typical static conditions of the fan with blades at different angles and rotating conditions of the fan running at different speeds;

[0019] (3) Results parameters: At least 40 discharges were performed under each operating condition during the test to obtain the discharge voltage of 50% of the long gap of the fan; atmospheric environmental parameters, including temperature, humidity and air pressure, were recorded during each discharge; the obtained discharge voltage results were converted to standard atmospheric pressure conditions.

[0020] In the above-mentioned method for correcting the lightning strike distance formula for rotating wind turbines, the fitting relationship is as follows:

[0021] U 50％ =a×d b

[0022] Among them, U 50％ d is the 50% discharge voltage of the gap, MV; d is the gap distance, m; a and b are the coefficients obtained from the fitting.

[0023] In the above-mentioned method for correcting the lightning strike distance formula for rotating wind turbines, the expression for the strike distance formula is:

[0024] Let the striking distance of the lightning leader to the conductor be r. c The unit is meters (m); the striking distance of the lightning conductor is r. gw The unit is meters; the distance of the impact on the ground is r. g The unit is meters (m), then the ground strike distance coefficient K g and lightning strike distance coefficient K gw They are respectively:

[0025]

[0026]

[0027] According to the leader head potential formula:

[0028] V s =3.7I 2 / 3

[0029] Among them, V s I represents the leader potential, in mV; I represents the lightning current amplitude, in kA.

[0030] Let the gap be U 50％ If the potential Vs of the leader is equal to the potential Vs of the leader before the last strike of the lightning leader, then according to K... g and K gw From the expression, we obtain the expression r for the shot distance formula. c .

[0031] The system for correcting the lightning strike distance formula for rotating wind turbines includes: a fitting module for fitting the lightning strike distance under different lightning current amplitudes to obtain the relationship between lightning current and lightning strike distance; a test module for conducting long-gap discharge tests on rotating wind turbines; and a data processing module for processing the data from the test module to obtain the correction coefficient of blade rotation on lightning strike distance, introducing lightning current amplitude and blade tip linear velocity as variables to evaluate the influence of blade rotation on lightning strike distance.

[0032] An electronic device includes a computer-readable storage medium storing computer-executable instructions; and one or more processors coupled to the computer-readable storage medium and configured to execute the computer-executable instructions such that the device performs a method for correcting the lightning strike distance formula for rotating wind turbines.

[0033] 8. A readable storage medium, characterized in that it stores computer-executable instructions, which, when executed by a processor, configure the processor to execute a method for correcting the lightning strike distance formula for rotating wind turbines.

[0034] Compared with existing technologies, the beneficial effects of this invention are as follows: Based on the results of long-gap discharge tests on rotating wind turbines, this invention proposes a correction coefficient for the lightning strike distance of wind turbines considering rotation. The proposed method for calculating the influence coefficient of blade rotation on the lightning strike distance of wind turbines can reflect the influence of blade rotation on the lightning strike distance of wind turbines to a certain extent, and is applicable to the engineering calculation of the lightning strike probability of wind turbine blades. This invention can provide theoretical support for the design of lightning protection systems for rotating wind turbines and is of great significance for reducing the risk of lightning damage to rotating wind turbines. Attached Figure Description

[0035] Figure 1 This is a curve showing the relationship between the lightning current of each lightning arrester on the blade and its striking distance under static conditions according to an embodiment of the present invention.

[0036] Figure 2 This is a schematic diagram of the blades and lightning protection system of a three-dimensional wind turbine generator model according to an embodiment of the present invention;

[0037] Figure 3 This is the equivalent circuit diagram of the negative polarity operating wave test under long gap according to an embodiment of the present invention;

[0038] Figure 4 These are physical images of a scaled-down fan and an arc electrode according to an embodiment of the present invention;

[0039] Figure 5 These are the curves of the rotational lightning strike distance correction coefficient under different rotational speeds and lightning current amplitudes according to embodiments of the present invention;

[0040] Figure 6 The embodiments of the present invention show the lightning strike distance and lightning current amplitude curves without considering blade rotation and with considering blade rotation. Detailed Implementation

[0041] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0042] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0043] The present invention will be further described below with reference to specific embodiments, but these are not intended to limit the scope of the invention.

[0044] This embodiment presents a method for correcting the lightning strike distance formula for rotating wind turbines. First, based on the leader development method, the lightning strike distance under different lightning current amplitudes is calculated and fitted to obtain a formula relating lightning current and lightning strike distance. Then, based on the results of long-gap discharge tests on rotating wind turbines, by fitting the test results of long-gap discharge voltage under different gap distances and operating conditions, a correction coefficient for the impact of blade rotation on the lightning strike distance of the wind turbine is proposed. Furthermore, lightning current amplitude and blade tip linear velocity are introduced as variables to evaluate the influence of blade rotation on the lightning strike distance. This method can reflect the influence of blade rotation on the lightning strike distance of wind turbines to a certain extent and is suitable for engineering calculations of the lightning strike probability of wind turbine blades.

[0045] This embodiment is achieved through the following technical solution: a method for correcting the lightning strike distance formula for rotating wind turbines, comprising the following steps:

[0046] Step 1: Calculate the lightning strike distance for different lightning current amplitudes based on the leader development method, and fit the results to obtain the formula relating lightning current and lightning strike distance. After the leader stabilizes, the upward and downward leaders develop at the same rate until the average field strength between their leaders reaches 500 kV / m. At this point, a jump is considered to occur, and the leader connects to the main return stroke. The distance between the leaders at this time is defined as the strike distance R for this lightning current amplitude.

[0047] Step 2: Conduct long-gap discharge tests on the rotating fan to obtain the long-gap discharge voltage of the fan under static and rotating conditions at different gap distances. The derivation of the strike distance correction coefficient requires numerous long-gap discharge tests to obtain the 50% breakdown voltage of the gap, and the gap distance should not be less than 4m to ensure that the calculation model can simulate the actual lightning strike process of the target object to a certain extent.

[0048] A long-gap discharge test platform for a rotating fan was constructed. The platform included a scaled-down fan, arc-shaped electrodes, and a discharge breakdown voltage measurement system. To comprehensively obtain the long-gap discharge characteristics of the fan under different operating conditions, the following test parameters were modified during the experiment:

[0049] (1) Gap distance. In order to simulate the actual lightning strike situation as much as possible, the gap distance (i.e. the shortest distance from the tip of the wind turbine blade to the arc-shaped electrode) should not be less than 4m, and multiple gap distances should be selected for testing.

[0050] (2) Operating conditions. Tests were conducted on typical static operating conditions of the fan (i.e., when the blades are at different angles); and on different rotating operating conditions of the fan (i.e., when the fan is running at different speeds, such as medium speed and rated speed).

[0051] (3) Results parameters. At least 40 discharges were carried out under each operating condition during the test to obtain the discharge voltage of 50% of the long gap of the fan. In addition, atmospheric environmental parameters, including temperature, humidity and air pressure, were recorded during each discharge. Due to the long test cycle, the environmental conditions varied between discharges. In order to eliminate the influence of the external environment as much as possible, the obtained discharge voltage results were converted to standard atmospheric pressure conditions.

[0052] Step 3: Statistically analyze the 50% breakdown voltage of the fan at different speeds under different gap distances. Based on the experimentally obtained 50% breakdown voltage and gap distance, the fitting relationship is shown in the following formula:

[0053] U 50％ =a×d b

[0054] Among them, U 50％ d is the 50% discharge voltage of the gap, MV; d is the gap distance, m; a and b are the coefficients obtained from the fitting.

[0055] Step 4, assuming the strike distance of the lightning leader to the conductor is r c (m); The striking distance of the lightning protection wire is r gw (m); the distance of the impact on the ground is r g (m), then the ground strike distance coefficient K g and lightning strike distance coefficient K gw Define the two equations separately:

[0056]

[0057]

[0058] According to the leader head potential formula:

[0059] V s =3.7I 2 / 3

[0060] Among them, V s ν is the leader potential, MV; I is the lightning current amplitude, kA.

[0061] Assuming the gap U 50％ If the potential Vs of the leader is equal to the potential Vs of the leader before the last strike of the lightning leader, then according to K... g and K gw From the expression, we can obtain the expression r for the shot distance formula. c .

[0062] Step 5: Divide the strike distance formula for different wind turbine speeds by the strike distance formula for static conditions to obtain the influence coefficient K of rotation on strike distance under different lightning currents. R The lightning strike distance correction coefficient curves under different rotation speeds and lightning current amplitudes were obtained.

[0063] Step 6: Based on the classical electrical geometry model calculation method, and considering engineering applications, the ratio of the strike distances of different targets when the lightning current amplitude is 30kA (the highest probability of lightning current amplitude in most areas) can be used as a correction coefficient. For the lightning strike characteristics of wind turbines, due to the varying degrees of tip corona discharge and differences in space charge distribution under different lightning currents, blade rotation may cause different migrations and redistributions of space charge at the blade tip. Simultaneously, the tip linear velocities of wind turbines with different capacities also differ significantly, contributing to these differences. Therefore, the lightning current amplitude and tip linear velocity are introduced as variables into the correction coefficient obtained in Step 5 to evaluate the impact of blade rotation on the lightning strike distance, thus obtaining a specific correction coefficient for the lightning strike distance caused by blade rotation.

[0064] This embodiment also provides a system for correcting the lightning strike distance formula of a rotating wind turbine, including: a fitting module for fitting the lightning strike distance under different lightning current amplitudes to obtain the relationship between lightning current and lightning strike distance; a test module for conducting long-gap discharge tests on the rotating wind turbine; and a data processing module for processing the data from the test module to obtain the correction coefficient of blade rotation on the lightning strike distance, introducing the lightning current amplitude and blade tip linear velocity as variables to evaluate the influence of blade rotation on the lightning strike distance.

[0065] An electronic device includes a computer-readable storage medium storing computer-executable instructions; and one or more processors coupled to the computer-readable storage medium and configured to execute the computer-executable instructions such that the device performs a method for correcting the lightning strike distance formula for rotating wind turbines.

[0066] A readable storage medium storing computer-executable instructions that, when executed by a processor, configure the processor to perform a method for correcting the lightning strike distance formula for rotating wind turbines.

[0067] In specific implementation, a method for correcting the lightning strike distance formula for rotating wind turbines includes:

[0068] S1. Based on the pilot development method, the formulas and curves relating the lightning current amplitude to the lightning strike distance of the blade tip lightning arrester, the second lightning arrester, the third lightning arrester, and the blade body near the blade tip lightning arrester under static conditions are obtained, as shown in the attached figure. Figure 1 As shown in the attached figure. The specific 3D physical model of the wind turbine was created in Comsol. The blade length is 35m. Lightning arresters are placed on the blade at the blade tip, 10m from the blade tip, and 20m from the blade tip. The blade tip lightning arrester completely covers the blade tip, as shown in the attached figure. Figure 2 As shown.

[0069] S2. The equivalent circuit diagram for constructing the long-gap test platform is attached. Figure 3 As shown. The scaled-down fan in this embodiment adopts a three-blade structure. The blades are made of glass fiber reinforced composite material. The actual blade length is 37.5m. Based on a 1:30 scale, the simulated fan blade length is 1.25m, as shown in the attached figure. Figure 4 As shown.

[0070] The fan speed is controlled by a power transmission system, which consists of a frequency converter, an asynchronous motor, and a drive belt. The frequency converter adjusts the motor speed, which in turn drives the drive belt, causing the hub to rotate synchronously. This allows the fan blade speed to be adjusted. The relationship between speed and frequency is shown in the following formula:

[0071] n = 60f / p

[0072] Where n is the motor speed, revolutions per minute; f is the inverter frequency; and p is the number of motor pole pairs.

[0073] The following conversion relationship exists between tip linear velocity and blade rotational speed:

[0074]

[0075] Where v is the tip linear velocity (m / s), w is the blade rotational speed (r / min), and l is the blade length (m).

[0076] To simulate the tip linear velocity of a typical MW-class wind turbine at its rated speed, the inverter frequency was selected to be 30Hz. At this speed (w) of 450 r / min, the tip linear velocity was 58.9 m / s. In another rotating condition, the inverter was set to 16.7Hz, and the speed was 250 r / min. Under this condition, the tip linear velocity was approximately 32.7 m / s, simulating the medium-speed operation of the wind turbine. The distance between the wind turbine blades and the arc-shaped electrode is adjustable. By adjusting the relevant parameters of the impulse generator, the impulse voltage generator produces the voltage waveform required for the test, and the voltage waveform is measured using a voltage divider.

[0077] S3. Statistically analyze the 50% breakdown voltage of the gap under static, 250 r / min and 450 r / min operating conditions with a gap distance of 1-8 m. Based on the experimentally obtained 50% breakdown voltage and gap distance, derive the fitting formula. The details are shown in the table below:

[0078] Table 1. Gap breakdown voltage (MV) under different gap distances and rotational speeds.

[0079]

[0080]

[0081] S4. According to the leader head potential formula:

[0082] V s =3.7I 2 / 3

[0083] Among them, V s ν is the leader potential, MV; I is the lightning current amplitude, kA.

[0084] Assuming the gap U 50％ If the potential Vs of the leader is equal to the potential Vs of the leader before the last strike of the lightning leader, then according to K... g and K gw From the expression, we can obtain the expression r for the shot distance formula. c .

[0085] Table 2. Formulas for blow distance under different fan speeds.

[0086]

[0087] S5. Divide the strike distance formulas for 30m / s and 60m / s in the table by the data under static conditions to obtain the influence coefficient K of rotation on strike distance under different lightning currents. R As attached Figure 5 As shown.

[0088] S6. The ratio of the strike distances of different targets when the lightning current amplitude is 30kA (the highest probability of lightning current amplitude in most areas) is used as a correction coefficient. Introducing lightning current amplitude and blade tip linear velocity as variables, the influence of blade rotation on the lightning strike distance is evaluated. Based on this curve, the specific correction coefficients for the impact of blade rotation on the lightning strike distance are obtained as follows:

[0089]

[0090] Among them, K R denoted as the rotational influence coefficient; v is the tip linear velocity of the wind turbine blade, m / s; I is the lightning current amplitude, kA. In the example calculation, the tip linear velocity is 60 m / s, therefore the tip lightning arrester strike distance correction factor is K. R=1.07×I 0.05 The linear velocities at the locations of the second and third lightning arresters are 42 m / s and 25 m / s, respectively, therefore the distance correction factors are K. R =1.04×I 0.036 and K R =1.01×I 0.016 The formula for the strike distance under different angles and lightning rods has been corrected, and the specific correction results are attached. Figure 6 As shown.

[0091] The above are merely preferred embodiments of the present invention and are not intended to limit the implementation methods and protection scope of the present invention. Those skilled in the art should recognize that any equivalent substitutions and obvious changes made based on the content of this specification should be included within the protection scope of the present invention.

Claims

1. A method for correcting the lightning strike distance formula for rotating wind turbines, characterized in that, include: The lightning strike distance under different lightning current amplitudes was calculated using the lead development method, and the relationship between lightning current and lightning strike distance was obtained by fitting the formula. The leader development method for calculating the lightning strike distance under different lightning current amplitudes includes: Once the leader stabilizes and begins to move, the upward leader and the downward leader develop at the same rate until the average field strength between their leader heads reaches 500 kV / m. At this point, a jump is considered to occur, and the leader connects to the main return stroke. The distance between the leaders of the upward leader and the downward leader at this time is defined as the strike distance R under this lightning current amplitude. A long-gap discharge test of a rotating fan was conducted to obtain the long-gap discharge voltage of the fan under static and rotating conditions with different gap distances. The long-gap discharge test of the rotating fan included the following steps: A long-gap discharge test platform for a rotating fan was constructed. The platform included a scaled-down fan, arc electrodes, and a discharge breakdown voltage measurement system. The following test parameters were changed during the test: (1) Gap distance; The gap distance is the shortest distance between the tip of the fan blade and the arc-shaped electrode. The gap distance shall not be less than 4m, and multiple gap distances shall be selected for testing. (2) Operating conditions; tests were conducted on typical static conditions of the fan with blades at different angles and rotating conditions of the fan with the fan running at different speeds; (3) Results parameters: At least 40 discharges were performed under each operating condition during the test to obtain the discharge voltage of 50% of the long gap of the fan; atmospheric environmental parameters, including temperature, humidity and air pressure, were recorded during each discharge; the obtained discharge voltage results were converted to standard atmospheric pressure conditions. The 50% breakdown voltage of the gap was statistically analyzed when the fan was running at different speeds under different gap distances. Based on the experimentally obtained 50% breakdown voltage and gap distance, the fitting relationship was obtained. Find the expression for the strike distance formula; the expression for the strike distance formula is: Let the striking distance of the lightning leader to the conductor be... r c The unit is meters (m); the striking distance of the lightning conductor is r. gw The unit is meters; the impact distance to the ground is... r g The unit is meters (m), then the ground strike distance coefficient is... K g and lightning strike distance coefficient K gw They are respectively: According to the leader head potential formula: V s =3.7 I 2 / 3 in, V s Leader head potential, in mV; I This represents the amplitude of the lightning current, in kA. Set gap U 50% If the potential Vs of the leader is equal to the potential Vs of the leader before the last strike of the lightning leader, then according to K g and K gw The expression for the strike distance formula is obtained from the expression for the strike distance formula. r c ; Dividing the strike distance formulas for different wind turbine speeds by the strike distance formulas for static conditions yields the influence coefficients of rotation on strike distance under different lightning currents. K R And the lightning strike distance correction coefficient curves under different rotation speeds and lightning current amplitudes; The ratio of the distances to different targets at the maximum probability of lightning current amplitude in the region was used as a correction coefficient. Lightning current amplitude and blade tip linear velocity were introduced as variables into the lightning distance correction coefficient to obtain the correction coefficient of blade rotation on the lightning distance.

2. The method for correcting the lightning strike distance formula for rotating wind turbines according to claim 1, characterized in that, The fitting relationship is as follows: IN 50% = a×d b Among them, U 50% d is the 50% discharge voltage of the gap, MV; d is the gap distance, m; a and b are the coefficients obtained from the fitting.

3. A system for correcting the lightning strike distance formula of a rotating wind turbine as described in any one of claims 1-2, characterized in that, include: The fitting module is used to fit the lightning strike distance under different lightning current amplitudes to obtain the relationship between lightning current and lightning strike distance. Test module for long-gap discharge tests of rotating fans; The data processing module is used to process the data from the experimental module, obtain the correction coefficient of blade rotation on lightning strike distance, and introduce lightning current amplitude and blade tip linear velocity as variables to evaluate the influence of blade rotation on lightning strike distance.

4. An electronic device, characterized in that, A computer-readable storage medium storing computer-executable instructions; and one or more processors coupled to the computer-readable storage medium and configured to execute the computer-executable instructions to cause the device to perform the method according to any one of claims 1-2.

5. A readable storage medium, characterized in that, The system stores computer-executable instructions that, when executed by a processor, configure the processor to perform the method according to any one of claims 1-2.

Images