System of determining warm-up period of power converter and related method

Abstract

To determine a warm-up period of a power converter.SOLUTION: The present disclosure relates to a method (300) of determining a warm-up period of a power converter (20) of a wind turbine (1). The method (300) comprises determining (301) a first indicator indicative of when the power converter (20) has been inactive. Further, the method (300) comprises at least partially determining (302) the period of warming up based on the first indicator. A power converter assembly is also disclosed.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure relates to a system and method for determining a warm-up period of a power converter of a wind turbine.

Background Art

[0002] Today, wind turbines are generally used to supply power to the power grid. This type of wind turbine generally includes a tower and a rotor disposed on the tower. The rotor typically includes a hub and a plurality of blades and is configured to rotate under the influence of wind on the blades. This rotation usually generates torque that is transmitted directly ( "direct drive") to the generator via the rotor shaft or using a gearbox. In this way, the generator generates electricity that can be supplied to the power grid. Further, the wind turbine includes a power converter that converts the electricity generated by the generator to match the power grid.

[0003] If the wind turbine stops for some reason, for example, due to a power failure, grid disturbance, or maintenance, the humidity of wind turbine components such as the wind turbine generator and the wind turbine power converter is not controlled, and condensation may occur on these components. This may be particularly relevant when the wind turbine is an offshore wind turbine.

[0004] Condensation within the converter can cause the tracking surface to ground, potentially leading to a ground fault if the converter's electronics are not dried before restarting the generator. Similarly, full operating voltages and currents, when operating at certain temperatures and humidity levels, can damage the power semiconductors within the converter. Furthermore, moisture absorption by insulation layers or dehumidifiers, when functioning correctly, can cause the absorbent material to detach due to rapid vapor expansion, which can degrade the insulation over time. Additionally, water absorption can significantly reduce the dielectric properties of the insulator. Reinitializing a power converter without drying the insulator can cause dielectric breakdown.

[0005] Therefore, in order to safely restart the power converter, it must first be heated and dried. There are several methods for verifying the condition of the converter, for example, by performing a manual inspection to check whether the power converter is suitable for restarting the wind turbine. This is a cumbersome task, and furthermore, manual inspection is quite difficult in offshore wind turbines due to limited access.

[0006] In such cases, a possible way to ensure that the converter is dry and that the wind turbine can be safely restarted is to pump warm fluid through the converter for a period of time. Such a period may be, for example, between 8 and 24 hours. The wind turbine will not start operation until the warm-up period is complete. If the warm-up period is too short, restarting the converter may be unsafe. If the warm-up period is too long, the annual energy yield of the wind turbine may be excessively reduced. Examples of this disclosure provide methods and systems for determining an appropriate warm-up period for a converter. [Overview of the Initiative]

[0007] In a first aspect, a method for determining a period for warming up a power converter of a wind turbine is disclosed. The method includes the step of determining a first indicator (first metric) that shows the time the power converter has been inactive. Furthermore, the method also includes determining a period for at least partial warming up based on the first indicator.

[0008] According to this first aspect, this method makes it possible to determine an appropriate warm-up period based on the period during which the power converter has been inactive, without the need for further measurements. This results in a fairly simple and robust method that does not rely on temperature or humidity sensors. Furthermore, this method can establish a warm-up period without performing complex and time-consuming visual inspections.

[0009] In another embodiment, a power converter assembly is disclosed. The power converter assembly is configured to determine a warm-up period. The power converter includes a processor configured to determine a first indicator of the time the power converter has been inactive. The processor is also configured to determine a warm-up period at least in part based on the first indicator.

[0010] According to this additional embodiment, the power converter assembly can determine its warm-up period from parameters that are easy to determine, robust, and independent of peripheral hardware. This also simplifies the assembly time of the power converter assembly and reduces the risk of potential malfunctions.

[0011] Throughout this disclosure, the terms “power converter” and “converter” are used interchangeably. Furthermore, it may be understood that the warm-up period (or warm-up time) may be a series of heating and / or drying processes. Thus, the warm-up period may include a specific period due to a given heating process, or multiple periods due to different heating and drying processes.

[0012] Non-limiting examples of this disclosure are described below with reference to the attached drawings. [Brief explanation of the drawing]

[0013] [Figure 1] A perspective view of a wind turbine according to one embodiment is shown. [Figure 2] A detailed internal diagram of the nacelle of a wind turbine according to one embodiment is shown. [Figure 3] This is a flowchart illustrating an exemplary method for determining the duration of the power converter warm-up period. [Figure 4] A second value of the warm-up period as a function of the cooling medium with respect to the dew point temperature difference in one embodiment is shown. [Figure 5] This is a flowchart illustrating another exemplary method for determining the duration of the warm-up period for a power converter.

[0014] In these diagrams, the same reference numerals are used to represent the same components. [Modes for carrying out the invention]

[0015] Figure 1 shows a perspective view of an example of a wind turbine 1. As shown, the wind turbine 1 includes a tower 2 extending from a support surface 3, a nacelle 4 attached to the tower 2, and a rotor 5 coupled to the nacelle 4. The rotor 5 includes a rotatable hub 6 and at least one rotor blade 7 coupled to the hub 6 and extending outward from the hub 6. For example, in the illustrated example, the rotor 5 includes three rotor blades 7. However, in another embodiment, the rotor 5 may include three or more or fewer rotor blades 7. Each rotor blade 7 may be spaced apart from the hub 6 to facilitate the rotation of the rotor 5, allowing kinetic energy from the wind to be transferred to available mechanical energy and then to electrical energy. For example, the hub 6 may be rotatably coupled to a generator 10 (Figure 2) located within or forming part of the nacelle 4 to generate electrical energy. In this example, the wind turbine is an onshore wind turbine; in other examples, it may be an offshore wind turbine.

[0016] Figure 2 shows a simplified internal diagram of an example of a nacelle 4 of a direct-drive wind turbine 1. As shown in the figure, the generator 10 may be located inside the nacelle 4 or between the nacelle 4 and the rotor 5. Generally, the generator 10 can be coupled to the rotor 5 of the wind turbine 1 to generate electricity from the rotational energy produced by the rotor 5. For example, the rotor 5 of the wind turbine may include a hub 6 coupled to the rotor 12 of the generator 10, which rotates with it. Thus, the rotation of the hub 6 can drive the rotor 12 of the generator 10.

[0017] In Figure 2, the wind turbine rotor 5 may be rotatably mounted to the support frame 9 via two rotor bearings 8. In other examples, the support frame 9 does not penetrate the hub 6, and the rotor is supported by a single rotor bearing 8, commonly called the main bearing.

[0018] The generator 10 may include a rotor 12 and a stator 13. The stator may be rigidly mounted to a support frame 9. The rotor may be rotatably mounted to the stator via a generator bearing 14 so that the rotor rotates about an axis relative to the stator.

[0019] The generator 10 may be electrically coupled to the converter 20. The wind turbine converter 20 can adapt the generator's output power to the requirements of the power grid. In this example, the converter 20 is located inside the nacelle 4, but in other examples, it may be located elsewhere on the wind turbine, for example, in the upper or lower tower section. In large offshore wind turbines, the converter may be a medium-voltage converter with a nominal voltage of, for example, 2kV to 5kV, reducing electrical losses and expensive cables.

[0020] Figure 3 is a flowchart of an exemplary method for determining the warm-up period for a wind turbine power converter. Method 300 includes, in block 301, determining a first indicator that shows the time the power converter has been inactive. Furthermore, Method 300 includes, in block 302, determining a warm-up period that is at least partially warm-up based on the first indicator. The warm-up of the wind turbine power converter may be performed by passing a warm liquid, such as hot water, through a warm liquid conduit to the power converter for the determined warm-up period.

[0021] In some examples, the determination of the first indicator may be based on the time the cooling pump was inactive (idle time). Thus, even if the power converter is inactive, if the cooling pump or cooling system that controls the temperature (and humidity) of the power converter is in continuous operation, the warm-up period can be shortened or eliminated. Since the cooling pump can be connected to an auxiliary power source, the shutdown of the power converter does not necessarily mean that the cooling pump is inactive. In certain grid loss situations, the cooling pump may be shut down with the power converter, but may recover power when an auxiliary power source is connected. Thus, in other embodiments, the first indicator may be determined based on the period between when the auxiliary generator is started and when the wind turbine is connected to the power grid. In a further example, the first indicator may be determined by comparing the timestamp of the start of the power grid outage with the timestamp of the end of the power grid outage. The above comparison may be provided by a dedicated device such as a network fault detector, or may be performed by other electronic components such as the processor of the power converter assembly.

[0022] Also, the first value (V1) of the warm-up period may be based on the first indicator. Further, the first value (V1) may be selected from a plurality of discrete values based on the first indicator. More precisely, the first value (V1) of the warm-up period may be 0 when the first indicator is below a minimum threshold, i.e., when the first indicator of the time the power converter was inactive is below 60 minutes. Other magnitudes of the minimum threshold, such as 45 minutes, 75 minutes, or shorter or longer times and intermediate times, can also be implemented. Further, the first indicator can be based on any of the前述 disclosed embodiments, such as the time the cooling pump was inactive.

[0023] <PRESERVE_TAG_START> <PRESERVE_TAG_END>

Table 1

[0024] Similarly, the first non-zero discrete value during the warm-up period is determined when the first indicator exceeds the minimum threshold. In an embodiment, as shown in Table 1, when the first indicator indicating the time that the power converter was inactive exceeds 60 minutes (1 hour), the first non-zero discrete value may be 2 hours. Further, the plurality of non-zero discrete values of the warm-up period associated with the first indicator may vary with the increment in the first indicator. Thus, the first value (V1) during the warm-up period can be set to 2 hours for indicator values between 1 hour and 4 hours, 4 hours for indicator values between 4 hours and 8 hours, and 8 hours for indicator values between 8 hours and 16 hours. Further, the plurality of discrete values of the period for warming up associated with the first indicator can include a maximum first value of 24 hours. The maximum warm-up period can be related to the magnitude of the first indicator exceeding 24 hours, i.e., the period during which the cooling pump was inactive for more than 24 hours, or other periods. In other embodiments, the period of the warm-up period can be doubled with a constant increment in the first indicator, i.e., an increment every 3 hours in the first indicator.

[0025] Furthermore, method 300 can further include determining the temperature of the cooling medium (Tc) of the power converter. The temperature of the cooling medium (Tc) can be determined by measuring the temperature of the cooling medium (refrigerant: coolant) itself or by estimating the temperature based on other parameters such as the temperature of the cooling medium conduit. Method 300 may also include determining the warm-up period at least partially based on the cooling medium temperature. Thus, the value of the warm-up period may be based on the absolute value of the determined cooling medium temperature (Tc). Further, method 300 may include estimating the dew point (Dp) and determining the warm-up period at least partially based on the difference between the cooling medium temperature (Tc) and the estimated dew point (Dp).

[0026] In some examples, the dew point (Dp) can be determined by measuring the air temperature and humidity inside the power converter. This can be done inside or around the power converter. In further examples, the warm-up period may be zero for coolant temperatures (Tc) higher than a predetermined coolant temperature threshold (Tth). The predetermined coolant temperature threshold (Tth) may be about 25°C, but other temperatures may be selected depending on the atmospheric conditions or the nature and arrangement of the electronic components in the power converter.

[0027] Furthermore, in method 300, a second indicator (second index) showing the warm-up period is determined based on the difference between the cooling medium temperature (Tc) and the estimated dew point (Dp). The warm-up period can also be selectively set based on either the first or second indicator.

[0028] Furthermore, the first value (V1) of the warm-up period may be based on the first indicator, and the second value (V2) of the warm-up period may be based on the second indicator. In this way, the warm-up period can be selected as the lowest value (V1, V2) among the first and second values.

[0029] Furthermore, the second value (V2) for the warm-up period may decrease linearly as a function of the temperature difference between the cooling medium temperature (Tc) and the dew point (Dp).

[0030] Figure 4 shows an example of a possible linear relationship between the second value (V2) and the aforementioned temperature difference. Therefore, if the difference between the cooling medium temperature (Tc) and the dew point (Dp) is greater than 6 degrees, the second value (V2) of the warm-up period may be 0. While a 6-degree difference represents an exemplary temperature threshold, a larger or smaller temperature difference can be selected as the temperature threshold. On the other hand, if the difference between the cooling water temperature (Tc) and the dew point (Dp) is close to 0, the second value (V2) of the warm-up period may be 6 hours. As discussed in relation to a given cooling medium temperature threshold (Tth), specific specifications of the power converter components may require different relationships between the temperature difference and the warm-up period. Therefore, the relationship shown in Figure 4 may be shifted upward or downward, may have different slopes, or may be defined by a function other than a linear polynomial.

[0031] Furthermore, in some examples, temperature and humidity may be measured at multiple locations inside or around the power converter. In this case, the determination of the second value (V2) of the warm-up period may be based on the minimum difference between the cooling medium temperature (Tc) and the dew point (Dp).

[0032] Figure 5 is a flowchart of another example of Method 500 for determining the warm-up period of a wind turbine power converter after a system shutdown period. In particular, Figure 5 shows that Method 500 includes the step of determining a first indicator in block 501 that shows the amount of time the power converter has been inactive. Furthermore, Method 500 also includes the step of determining a first value (V1) of the warm-up period in block 502, at least in part, based on the first indicator. Furthermore, Method 500 also includes the step of determining the temperature of the cooling medium (Tc) of the power converter in block 503. Furthermore, Method 500 includes the step of estimating the dew point (Dp) in block 504 and the step of determining a second value (V2) of the warm-up period in block 505, based on the difference between the cooling medium temperature (Tc) and the dew point (Dp). Next, in block 506, the length of the warm-up period is selected as the minimum value of the first (V1) and second (V2) values ​​of the warm-up period.

[0033] In some examples, method 500 may include assigning a zero value to a second value (V2) of the warm-up period when the cooling medium temperature (Tc) exceeds a predetermined cooling medium temperature threshold (Tth).

[0034] In another embodiment, a power converter assembly configured to determine the duration of a warm-up period is disclosed. The power converter assembly includes a processor configured to determine a first indicator (301) indicating the amount of time the power converter has been inactive. Furthermore, the processor is configured to determine the warm-up period at least partially based on the first indicator.

[0035] Furthermore, the power converter assembly may include a temperature sensor configured to measure the cooling medium temperature (Tc) of the power converter, a temperature sensor configured to measure the internal or ambient air temperature of the power converter, and a humidity sensor configured to measure the internal or ambient air humidity of the power converter. Alternatively, a selection from previously disclosed sensors may be included. In addition, the processor may be configured to estimate the dew point (Dp) based on the measured air temperature and humidity, and to determine a warm-up period at least partially based on the difference between the cooling medium temperature (Tc) and the dew point (Dp).

[0036] In other examples, the warm-up period may be based on the absolute value of the cooling medium temperature (Tc). Alternatively, the processor may be configured to select the warm-up period as the minimum value between a first value (V1) and a second value (V2).

[0037] The power converter assembly can be configured to perform any of the steps included in any of the embodiments of the disclosed method, and may include additional devices that perform the same steps as needed.

[0038] This description uses examples to disclose this teaching, including preferred embodiments, and to enable a person skilled in the art to carry it out, including manufacturing and using any device or system, and carrying out any incorporated method. The patentable scope is defined by the claims and may include other examples that may arise for a person skilled in the art. Such other examples are intended to be within the claims if they have structural elements that are not different from the literal language of the claims, or if they include equivalent structural elements that are not substantially different from the literal language of the claims. Aspects from the various embodiments described, as well as other known equivalents to each such aspect, may be mixed and harmonized by a person skilled in the art to construct additional embodiments and techniques in accordance with the principles of this application. Where reference numerals related to drawings are enclosed in parentheses within the claims, they are intended solely to increase the understanding of the claims and should not be construed as limiting the claims. [Explanation of symbols]

[0039] 10: Wind turbine 12: Ground 14: Support system 15: Tower 16: Nacelle 18: Rotor 20: Hub 22: Rotor blade 24: Blade root 26: Load transfer area 28: Wind direction 30: Rotor shaft 32: Pitch system 34: Pitch shaft 36: Wind turbine control device 38: Yaw shaft 40: Processor 42: Generator 44: Main shaft 46: Gearbox 48: High-speed shaft 50: Coupling 52: Main frame 54: Decoupling support means 56: Yaw drive mechanism 58: Weather measurement system 60: Main front support bearing 62: Rear support bearing 64: Drive train 66: Pitch assembly 68: Pitch drive system 70: Sensor 72: Pitch bearing 74: Pitch drive motor 76: Pitch drive gearbox 78: Pitch drive pinion 80: Pitch control system 84: Generator 86: Cavity 88: Interior 90: Trans

Claims

1. A method (300) for determining a period for warming up a power converter (20) of a wind turbine (1), comprising: Determining (301) a first indicator of the amount of time the power converter (20) has been inactive; determining (302) a warm-up period at least in part based on a first indicator; determining (503) the temperature of the cooling medium of the power converter; estimating a dew point temperature; determining a warm-up period based on a difference between the estimated dew point temperature and the cooling medium temperature; A method comprising:

2. The method (300) of claim 1, wherein the first indicator is determined based on an amount of time the cooling system has been inactive.

3. 2. The method (300) of claim 1, wherein the wind turbine is in a grid off period and the first indicator is determined based on a period between when the auxiliary generator is turned on and when the wind turbine is connected to the grid.

4. 2. The method (300) of claim 1, wherein the wind turbine is in a period of grid outage and the first indicator is determined by comparing a grid outage start timestamp and a grid outage end timestamp.

5. The method (300) of claim 1, wherein the warm-up period is zero for coolant temperatures above a predetermined coolant temperature threshold.

6. 2. The method (300) of claim 1, wherein a second indicator indicative of the warm-up period is determined based on a difference between the cooling medium temperature and the estimated dew point, and the warm-up period is determined based on either the first indicator or the second indicator.

7. 7. The method (300) of claim 6, wherein a first value for the warm-up period is based on a first indicator, a second value for the warm-up period is based on a second indicator, and the warm-up period is selected (506) as the smallest of the first value and the second value.

8. 8. The method (300) of claim 7, wherein the first value of the warm-up period is zero when the first indicator is below a minimum threshold, and the second value of the warm-up period is zero when the temperature difference is greater than a temperature difference threshold.

9. 8. The method (300) of claim 7, wherein the second value of the warm-up period decreases linearly as a function of the temperature difference between the coolant temperature and the dew point.

10. 8. The method of claim 7, wherein temperature and humidity are measured at multiple locations within the power converter, and the determination of the second value of the warm-up period is based on a minimum difference between the coolant temperature and the dew point.

11. 11. The method (300) of any one of claims 1 to 10, further comprising the step of warming up a power converter (20) of a wind turbine (1) by passing a warm fluid through the power converter (20) for a determined warm-up period.

12. 1. A power converter assembly configured to determine a period of warm-up, comprising: a processor configured to determine a first indicator of a time the power converter is inactive; The processor is further configured to determine the warm-up period based at least in part on the first indicator; a temperature sensor configured to measure a temperature of a cooling medium of the power converter; a temperature sensor configured to measure a temperature of the air; a humidity sensor configured to measure the humidity of the air; further comprising The processor is further configured to estimate a dew point temperature based on the measured air temperature and humidity, and to determine the warm-up period also based on a temperature difference between the cooling medium temperature and the dew point temperature.

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