Wind turbine operation transition

Abstract

A method is provided for transitioning operation of a wind turbine (100) to an energy harvesting mode in which the wind turbine (100) operates to generate electrical power from wind energy. An energy storage system (50) associated with the wind turbine (100) is configured to provide electrical power to the auxiliary system (10) when the wind turbine is not generating or receiving sufficient electrical power to power the auxiliary system (10). The method includes operating the wind turbine (100) in a first operating mode (72) that stops providing electrical power to one or more auxiliary power consumers (12, 13, 14) of a first group (11) of the auxiliary system (10), acquiring environmental data including at least one of wind data and weather data, and determining whether the acquired environmental data satisfies a predetermined condition. Operation of the wind turbine (100) is transitioned to an energy harvesting mode (74) when predetermined conditions are met, where transitioning operation to the energy harvesting mode (74) includes supplying power from the energy storage system (50) to one or more auxiliary power consumption devices (12, 13, 14) of the first group (11).

Description

[Technical Field]

[0001] The present invention relates to a method for transitioning the operation of a wind turbine into an energy harvesting mode, and further to a corresponding control system and computer program for controlling the operation of a wind turbine.

[0002] background Wind turbines extract energy from moving wind currents and generate electricity that is typically supplied to a power grid. In weak wind conditions or to perform service work, wind turbines can be shut down and restarted using power from the power grid. Similarly, in strong wind conditions that exceed the wind speeds for which the wind turbine was designed, the wind turbine can be shut down or transitioned to an operating state that minimizes loads on the structure due to the respective environmental conditions. This can also occur in offshore wind turbines that experience excessive wave loads or extreme wind conditions.

[0003] Wind turbines may become disconnected from the power grid due to, for example, a grid failure or a failure of any intermediate system. Some wind turbines may also be disconnected from the grid and operate, for example, in an islanded mode. It is known to equip such wind turbines with devices that generate electrical energy to facilitate starting the wind turbine after it has been shut down. A typical example is a generator coupled to a diesel engine that generates the power required for starting. Starting a wind turbine requires a large amount of power because multiple wind turbine systems, including large power consumers, must be operated. For example, the yaw drive and pitch drive may consume a significant amount of power. In particular, the wind turbine rotor must be aligned with the wind direction by operating the yaw drive. Preparing the wind turbine's pitch system for operation requires pressurizing the hydraulic pitch system, and the electric pitch system may require energy recovery for the emergency pitch system. Furthermore, the wind turbine's power conversion hardware must be primed for operation, for example, by charging the DC bus of the power converter, which may include a relatively large capacitor. It is also necessary to initiate operation of the cooling system, which may include operating a fan and circulating a cooling fluid.

[0004] Because a significant amount of energy is consumed during start-up, the respective electrical energy supply system may become depleted after start-up or after a predetermined small number of starts. Therefore, further start-up attempts may become impossible. This can be problematic, particularly in situations where the wind turbine needs to be shut down again immediately after start-up. Energy levels must then be restored in the system supplying electrical energy for start-up, which in some situations may be impossible or may only be possible after a significant delay and may require significant effort (e.g., refueling the diesel generators of an offshore wind turbine). Therefore, it is desirable to avoid such a reduction in the energy available for start-up in a wind turbine. It is also desirable to avoid excessive energy consumption, which could rapidly deplete such energy storage systems, particularly in the case of wind turbines that are disconnected from the grid.

[0005] Document WO 2021 / 069045 relates to a method for transitioning a wind turbine from a sleep state to an active state when the measured wind speed exceeds a wake-up threshold. Prior to comparing the measured wind speed with the wake-up threshold, either the wind speed or the wake-up threshold is adjusted based on the results of at least one previous transition of the wind turbine from a sleep state.

[0006] overview There is therefore a need to improve the operation of such wind turbines by mitigating at least some of the above-mentioned drawbacks, and in particular to reduce the likelihood of depletion of the respective energy storage systems provided on the wind turbines.

[0007] The above-mentioned needs are met by the features of each independent claim. Each dependent claim describes embodiments of the invention.

[0008] According to one aspect, a method for transitioning operation of a wind turbine to an energy harvesting mode in which the wind turbine operates to generate electrical power from wind energy is provided. An energy storage system associated with the wind turbine is configured to supply electrical power to the auxiliary system when the wind turbine is not generating or receiving sufficient electrical power to power its auxiliary system, for example, when the wind turbine is not connected to the grid (e.g., when there is no grid connection, when the wind turbine is disconnected from the power grid, or when the wind turbine is only receiving a portion of the required electrical power from the power grid). The method includes operating the wind turbine in a first operating mode (e.g., which may be referred to as a sleep mode) in which the wind turbine does not generate electrical power from the wind energy. In the first operating mode, electrical power is stopped from being supplied to one or more auxiliary power consumers in a first group of the auxiliary power system. Furthermore, in the first operating mode, electrical power is supplied from the energy storage system to one or more auxiliary power consumers in a second group of the auxiliary power system. The method further includes acquiring environmental data including at least one of wind data and weather data, and determining whether the acquired environmental data satisfies a predetermined condition, where the predetermined condition includes at least one of a wind speed threshold, a wind speed range in which the wind turbine is operable to generate electrical power, a wind speed trend threshold, or a predetermined energy threshold for expected energy production. The method also includes transitioning operation of the wind turbine to an energy harvesting mode if the predetermined condition is met, where transitioning operation to the energy harvesting mode includes supplying power from the energy storage system to a first group of one or more auxiliary power consuming devices.

[0009] In this way, stored energy is conserved, particularly since operation in the first operating mode allows only one group of auxiliary power consumers to receive power while another group, which may include a larger load, does not. The power consumption of the first group of power consumers may be (significantly) greater than the power consumption of the second group of power consumers. At the same time, the wind turbine remains operational, thereby enabling an automatic transition to energy harvesting mode. Furthermore, by performing such a transition based on predetermined conditions, it can be ensured that the transition occurs only when wind conditions allow for the generation of sufficient power. For example, the conditions can be selected such that at least one amount of electrical energy greater than the amount of electrical energy required to start the wind turbine is generated (i.e., the transition is performed). The generated power can be used, for example, to recharge the energy storage system, which prevents the energy storage system from being depleted and allows repeated starts. In particular, relatively rapid and repeated restart failures or restart attempts can be avoided due to a long-term return to energy harvesting.

[0010] The energy harvesting mode may be, in particular, an autonomous operating mode, in which auxiliary systems of the wind turbine can be powered from the electricity generated by the wind turbine. Thus, the wind turbine can operate without a grid connection, i.e., in a grid-disconnected state, which may be due to the absence of a grid connection or the wind turbine being disconnected from the grid. In some examples, in the first operating mode or during the transition to the energy harvesting mode, a small auxiliary source of power from the grid may still be present. However, during the first operating mode and during the transition, the main power source (e.g., more than 50%, more than 75%, or more than 90%) is provided by the energy storage system. Preferably, during the first operating mode and during the transition to the energy harvesting mode, all of the power source is provided by the energy storage system. If the condition is not met, the wind turbine can continue operating in the first operating mode. It will be apparent that the first operating mode may itself comprise different operating modes, for example a sleep mode in which only the second group of auxiliary power consumers is supplied with power, and another operating mode in which only some of the second group of auxiliary power consumers or no power is supplied to the second group of auxiliary power consumers at all. Furthermore, the transition from the first operating mode to the energy harvesting mode may be made via an intermediate operating mode, which may for example be referred to as a "local power mode", in which the first group of auxiliary power consumers and the second group of auxiliary power consumers are supplied with power from the energy storage system (e.g. all auxiliary power consumers are supplied with power), but the wind turbine is not yet generating power from the wind.

[0011] A wind turbine may include an energy storage system, for example, the energy storage system may be included within the wind turbine or may be located adjacent to the wind turbine tower.

[0012] A (signal) trend of a system parameter and / or environmental parameter, e.g., wind speed trend, can be a parameter that represents the magnitude and / or direction in which a system parameter and / or environmental parameter, e.g., wind speed, is occurring or changing. The trend can indicate whether the system parameter and / or environmental parameter is increasing or decreasing over time. Thus, the trend can indicate the direction and / or magnitude of the occurrence / change of the system parameter and / or environmental parameter. In certain embodiments, a prediction or forecast of the system parameter and / or environmental parameter can be determined based on the trend of the system parameter and / or environmental parameter. Preferably, the prediction or forecast can be further based on current or actual indicators of the system parameter and / or current or actual indicators of the environmental parameter.

[0013] The trend threshold may be a threshold for such a trend. The trend threshold may, for example, indicate a maximum and / or minimum value for such a trend.

[0014] In one example, determining whether the predetermined condition is met includes determining an indication of expected energy production during operation of the wind turbine in the energy harvesting mode when the transition occurs.

[0015] In one example, the wind speed thresholds of the predetermined conditions may include a minimum cut-in wind speed threshold that is equal to or greater than the wind speed value at which the wind turbine is operable to generate power, and / or a maximum cut-in wind speed threshold that is equal to or less than the wind speed value at which the wind turbine is operable to generate power. These thresholds may thus determine whether the current conditions are within the operating range of the wind turbine based on the acquired environmental data, thereby increasing the chances of successful startup of the wind turbine, and in particular, the chances of generating a sufficient amount of power after startup of the wind turbine. The minimum cut-in wind speed threshold (also abbreviated as minimum threshold) may be smaller than the maximum cut-in wind speed threshold (also abbreviated as maximum threshold herein). The maximum and minimum thresholds define the operating wind speed range of the wind turbine (relative to the cut-in wind speed), and may in particular define the wind speed range for each condition.

[0016] In one example, acquiring environmental data (particularly in the form of wind data) can include acquiring wind speed data and time-filtering the wind speed data. Determining whether the predetermined condition is met can include comparing the time-filtered wind speed data with a wind speed threshold (e.g., a maximum threshold and / or a minimum threshold) and / or a wind speed range. The predetermined condition can be met if the time-filtered wind speed is above the minimum threshold and below the maximum threshold or within the wind speed range, but additional conditions can also be applied, such as those described below. Such conditions can be specifically referred to as "wind speed conditions." Using the respective time-filtered data can have the advantage of increasing the reliability of determining whether sufficient power generation has been achieved by startup. Time filtering can be performed, for example, by averaging. For example, a moving average with a predetermined window length, for example, 1 s to 10,000 s, preferably 100 s to 5,000 s, for example, 100 s to 1,000 s, can be applied to the wind speed data. The wind speed data can be acquired by measuring data, and the wind turbines can have respective wind sensors. The wind speed data may also be obtained by receiving data from a data source, such as an external data source providing respective wind speed data, or from a local controller, such as a wind farm controller or a wind turbine controller of another wind turbine. Furthermore, such temporal filtering may prevent the wind turbine from responding unreliably to sudden changes in wind speed that may cause the wind turbine to start up unreliably, i.e., when short gusts occur or when the wind speed temporarily drops below a maximum threshold during strong wind conditions.

[0017] According to some examples, the predetermined condition can include a wind speed trend threshold. Determining whether the predetermined condition is met can include comparing a wind speed trend derived from the acquired wind data to the wind speed trend threshold. The trend can be, among other things, a direction in which the wind speed is occurring, i.e., whether the wind speed is increasing or decreasing over time. Taking such trends into account can further increase the chances of the wind turbine generating a sufficient amount of energy in harvesting mode. Deriving the wind speed trend can include, for example, comparing wind speed data time-filtered with a first time constant and wind speed data time-filtered with a second time constant, for example, by subtracting the current wind speed filtered with a moving average having a longer time window from the current wind speed filtered with a moving average having a shorter window. The moving average can use, for example, two different window lengths, for example, a first window length of 1 s to 500 s and a second window length of 500 s to 1000 s. The wind speed trend can also be derived by comparing an average wind speed obtained from wind speed data at a first time point with an average wind speed obtained from wind speed data at a second time point different from the first time point (e.g., by subtracting wind speeds averaged over two different time points). When observing two different time points, they may have a time difference of, for example, 100 s to 5000 s, for example, 100 s to 1000 s, for example, 500 s.

[0018] A condition that uses a wind speed trend threshold can be referred to as a wind speed trend condition. For example, a wind speed trend condition can be satisfied when a weaker wind speed reaches the minimum wind speed threshold and the wind speed trend indicates an increasing wind speed, i.e., when the derived trend is higher than a wind speed trend threshold (e.g., 0 m / s). A wind speed trend condition can also be satisfied when a stronger wind condition reaches the maximum wind speed threshold and the wind speed trend indicates a decreasing wind speed, i.e., when the derived wind speed trend is lower than a wind speed trend threshold (e.g., 0 m / s). As mentioned above, the maximum or minimum threshold is related to the cut-in threshold. It should be noted that the 0 m / s threshold is merely an example of a wind speed trend threshold, and it is clear that this threshold can be set when a stronger trend is required, such as above 2 m / s, above 3 m / s, above 4 m / s, or above for increasing wind speeds, or above -1 m / s, -2 m / s, -3 m / s, or above for decreasing wind speeds. The wind speed trend thresholds can be different for light wind conditions and strong wind conditions, both of which may require different trends, and such different trend thresholds can be used in predetermined conditions.

[0019] In one example, the predetermined condition includes a wind speed condition including a wind speed threshold and / or wind speed range, and a wind speed trend condition including a wind speed trend threshold. The predetermined condition may be met if both the wind speed condition and the wind speed trend condition are met (the wind speed and wind speed trend condition combined). Therefore, requiring that both of these conditions be met may further reduce the chance of the energy storage system being depleted and increase the chance of generating a sufficient amount of energy in the energy harvesting mode.

[0020] If the (time-filtered) wind speed is sufficiently within the operating range of the wind turbine, the predetermined condition can be determined to be met. In one example, the predetermined condition can include, for example, a first wind speed condition including a wind speed threshold (i.e., a first minimum threshold and a first maximum threshold) and / or a wind speed range. The predetermined condition can further include a second wind speed condition including a second wind speed threshold and / or a second wind speed range (e.g., referred to as a "sufficient wind speed condition"). The second threshold or range can be particularly stricter than the first threshold or range. For example, the second wind speed threshold can include a second minimum cut-in wind speed threshold that is greater than the first minimum threshold, a second maximum cut-in wind speed threshold that is less than the first maximum cut-in wind speed threshold, and / or the second wind speed range can be narrower and located within the first wind speed range. If the second wind speed condition is met, the predetermined condition can be considered to be met. Such a second wind speed condition therefore likely allows the wind turbine to start up and generate the desired amount of electrical energy without needing to check for additional conditions, provided the wind speed is well within the operating range. Because the second wind speed condition is more severe, the first wind speed condition is also met. In particular, the second wind speed condition may be met when the (time-filtered) wind speed represented by the acquired wind data is above or below a respective second wind speed threshold or within a second wind speed range.

[0021] In one example, the wind speed threshold and / or wind speed range can be variable and determined based on the amount of energy stored in the energy storage system, thus ensuring that in cases where there is little energy remaining in the storage system, the wind turbine is only transitioned into energy harvesting mode when there is a sufficiently high chance that a sufficient amount of electrical energy will be generated.

[0022] For example, if a smaller amount of energy is stored, the wind speed threshold can be set to a more stringent value and / or the wind speed range can be set to a narrower range. If a larger amount of energy is stored, the wind speed threshold can be set to a less stringent value and / or the wind speed range can be set to a wider range. A more stringent value may mean, for example, that the minimum threshold is set to a higher value (i.e., a higher wind speed is required before transitioning the wind turbine's operating mode) and / or that the maximum threshold is set to a lower value (transitioning occurs only at lower wind speeds). Thus, the minimum and maximum thresholds adapted in this way may correspond to narrower ranges. The time-filtered wind speed data can be compared to the adapted thresholds / ranges in this way to determine whether the wind speed condition is met.

[0023] The wind speed threshold and / or wind speed range may be, for example, a function of the amount of energy stored in the energy storage system, and thus the threshold or range may be adapted according to the function as the amount of stored energy changes.

[0024] The function may be, for example, a linear function that depends linearly on the amount of stored energy. For example, the thresholds or range boundaries may vary linearly between minimum and maximum values ​​for each threshold or boundary depending on the amount of stored energy. As an example, the minimum cut-in wind speed threshold may vary linearly from a lower predetermined value for a larger amount of stored energy, e.g., 3 m / s to 4 m / s, to a higher predetermined value for a smaller amount of stored energy, e.g., 5 m / s to 7 m / s. However, a corresponding linear change may occur in the opposite direction for the maximum cut-in wind speed threshold. Thus, if the available stored energy is high, if a start attempt fails (e.g., the wind speed drops below the minimum cut-out threshold again), a sufficient amount of energy remains and a start attempt can be made as soon as possible. If the available stored energy is low, start-up, i.e., transition to harvesting mode, may be attempted only if there is a good chance of success, i.e., if it is certain that a sufficient amount of energy will be generated. The function defining the dependency of each threshold or range on the amount of stored energy may be based on the amount of energy consumed upon transition to harvesting mode for each wind turbine, and may also take into account an additional safety margin.

[0025] In one example, obtaining weather data can include obtaining a forecast of wind conditions for a future period, for example by forecasting wind conditions, modeling future wind conditions, obtaining forecasts of wind conditions from external data sources, etc. For example, wind speed, temperature, barometric pressure, and / or other environmental parameters can be measured and used to model, predict, or forecast individual wind conditions. This can be done locally at the wind turbine, for example by the respective wind turbine controller, or at the wind farm level (wind farm controller), or at an external processing facility. The wind conditions can include wind speed and possibly wind direction.

[0026] Determining whether the predetermined condition is satisfied may include, for example, comparing the predicted wind conditions with a wind speed threshold and / or a wind speed range. Preferably, the predetermined condition is satisfied if, at a future time, the predicted wind conditions satisfy the wind speed threshold (above a minimum threshold or below a maximum threshold) and / or are within a wind speed range (which may be referred to as a "predicted wind speed condition"). Thus, a transition of the wind turbine can be prepared in time, for example, by supplying power to the respective auxiliary power consumption devices before the respective wind speeds are reached. For example, transitioning the operation of the wind turbine to the energy harvesting mode may include performing this transition before or at a future time. The transition may, for example, begin at a future time minus the time required for the wind turbine's transition procedure to transition to the energy harvesting mode.

[0027] Furthermore, the prediction or modeling can take into account wind direction, time of day, day of the month, solar irradiance, precipitation level, and any historical trends of the disclosed parameters, for example, of any sensors available to measure the respective parameters. Furthermore, it can also be based on weather forecasts obtained from external data sources. The prediction of wind conditions can be based, for example, on measured wind speeds, obtained meteorological information, information obtained from external services, for example, from weather services, and in particular can be model-based.

[0028] In one example, obtaining weather data can include predicting ice conditions. Each ice condition can be a condition in which icing of the rotor blades can occur. The prediction of the ice conditions can be using any of the prediction methods described above and / or can use dedicated sensors and / or load monitoring methods adapted to detect the presence or absence of ice on the rotor blades.

[0029] Determining whether the acquired environmental data meets the predetermined condition may include adjusting a wind speed threshold and / or a wind speed range when the presence or absence of ice conditions is detected or predicted. Additionally or alternatively, determining whether the acquired environmental data meets the predetermined condition when ice conditions are detected or predicted may include determining that the condition is not met if the respective ice formation is detected or predicted, i.e., determining that the wind turbine operation is not transitioned to the energy harvesting mode.

[0030] According to the above-described implementation, if the forecast predicts a return of wind speed to the operating range in the future period, the wake-up of each wind turbine can be scheduled based on the time required for the turbine to reach production after being started (e.g., 5 minutes) and the expected time for the wind conditions to reach the operating range. Thus, the wind turbine can be ready to start without delay as the wind conditions arrive. For example, at the wind farm level, each wind turbine can be scheduled for start-up at different times depending on when the respective wind conditions reach each wind turbine.

[0031] In one example, the acquired environmental data can be local to the location of the wind turbine or the location of the wind turbine group. The transition can be performed individually for the wind turbine or the wind turbine group based on the local environmental data for each wind turbine or each wind turbine group. The wind turbine group can comprise, for example, two, three, four or more wind turbines, which can be located adjacent to each other. In particular, the wind turbines of a group can experience similar wind conditions.

[0032] The method may include, for example, first transitioning the operation mode of wind turbines of the wind farm to the energy harvesting mode for those wind turbines located closest to an upcoming change in wind conditions that is predicted to meet a predetermined criterion, and subsequently transitioning operation of further wind turbines that are further away from the location where the upcoming change in wind conditions first occurred. The time difference between the wake-ups may correspond to the time required for the wind speed change to travel through the wind farm from the first location to the second location.

[0033] In a further example, determining whether a predetermined condition is met can include determining a continuous period of time during which predicted wind conditions are (substantially) within a wind speed range. Determining whether a predetermined condition is met can further include estimating an amount of energy predicted to be generated by the wind turbine within the continuous period of time and comparing the estimated amount of energy with a predetermined energy threshold. The predetermined energy threshold can be greater than an amount of energy required to transition the wind turbine from the first operating mode to the energy harvesting mode. The condition can be met if the estimated amount of energy meets or exceeds the predetermined energy threshold (which can be referred to as a "predicted energy generation condition"). Therefore, ensuring that the predicted energy generation is greater than the amount of energy consumed during start-up can ensure that the energy storage system is not depleted. The predicted continuous period of time can, among other things, allow for recovery of energy used for start-up. The energy threshold may further include an additional energy margin, for example, 20% to 100%, e.g., 40% to 60%, of the amount of energy required to transition the wind turbine operation to harvesting mode. It will also be apparent that the predicted wind conditions may be time filtered or smoothed so that small and short-term outliers in the forecast data do not cause interruptions in the predicted continuous period. If the period is too short to generate a sufficient amount of energy, the condition will not be met and no transition will occur.

[0034] As a further example, a predetermined condition may be determined to be met if the continuous period exceeds a predetermined duration threshold (which may be referred to as a "predicted harvesting period condition"). Such a duration threshold may similarly ensure that a sufficient amount of energy is generated after starting up the wind turbine, but is less accurate as it depends on the predicted wind speed but does not take into account the amount of energy actually generated.

[0035] It should be apparent that the predetermined conditions may include one or a combination of the various conditions disclosed herein, e.g., the predetermined conditions may be satisfied if one of the umbrella conditions herein is satisfied. The predetermined conditions may include, for example, at least one of a combined wind speed condition or wind speed trend condition, a sufficient wind speed condition, a predicted wind speed condition, a predicted energy generation condition, and a predicted harvesting period condition, and preferably at least two, three, or more of these conditions. In some examples, the predetermined conditions may include at least a wind speed condition or wind speed trend condition and a sufficient wind speed condition. In other examples, the predetermined conditions may include at least a predicted energy generation condition and, optionally, a predicted wind speed condition and / or a predicted harvesting period condition. Thus, if one or more of the predetermined conditions are satisfied, the wind turbine may be transitioned to an energy harvesting mode.

[0036] Determining whether the predetermined condition is met can be performed external to the wind turbine, for example by a wind farm controller or by a computing system external to the wind farm, but can also be performed by the wind turbine controller, in the former case the transition of operation of the wind turbine can be performed by communicating a respective control command to the wind turbine.

[0037] In one example, when the wind turbine is operating in the energy harvesting mode and a second predetermined condition is satisfied, the method can include transitioning the operation of the wind turbine to the first operating mode. The second predetermined condition can be similar to the first predetermined condition described above, but can also include, for example, a cutout threshold and / or a cutout wind speed range, such as a minimum cutout wind speed below which the second criterion is satisfied or a maximum cutout wind speed above which the second criterion is satisfied. The cutout wind speed threshold and / or the cutout wind speed range of the second predetermined condition can be different from the first predetermined condition described above, particularly to provide hysteresis so as to reduce the number of transitions between the first operating mode and the energy harvesting mode. In other words, the minimum cutout wind speed threshold can be smaller than the minimum cut-in wind speed threshold, the maximum cutout wind speed threshold can be larger than the maximum cut-in wind speed threshold, and / or the cutout wind speed range can be wider than the first wind speed range mentioned.

[0038] In one example, obtaining weather data can include obtaining a forecast of wind conditions for a future period of time, and determining whether the second predetermined condition is met can include comparing the forecasted wind conditions with a cutout wind speed range and determining a second (continuous) period during which the forecasted wind conditions are outside the cutout wind speed range. If the wind turbine is operating in the energy harvesting mode and the second period of time is shorter than the predetermined maintenance period, operation of the wind turbine is maintained in the energy harvesting mode for the second period of time. Thus, if the forecast predicts a short duration of wind speeds outside the operating range, shutting down the wind turbine, i.e., entering the first operating mode, can be prevented if the period is sufficiently short. In particular, the predetermined maintenance period can be determined based on the amount of energy consumed during startup that would be required if the wind turbine transitioned to the first operating mode. In particular, the period can be selected such that energy is saved by transitioning to a first operating mode in which less energy is consumed, and that if operation is maintained in harvesting mode during a second period in which low wind speeds prevail, the energy returned to harvesting mode is less than the energy consumed, thus avoiding further depletion of the energy storage system by such measures.

[0039] Obviously, such operation can also be performed when the wind speed is below or above the operating range of the wind turbine. If the wind speed is above the operating range and the wind turbine continues to operate in energy harvesting mode, conventional measures can be taken to protect the wind turbine from rotor blade pitch-out at high wind speeds, etc., but the first group of auxiliary power consumers remains powered and active.

[0040] The method may further comprise increasing the amount of energy stored in the energy storage system when operating in the energy harvesting mode, wherein, as described above, in the energy harvesting mode the first group of auxiliary power consumers are powered on and operate using the generated electrical energy (autonomous operation), for example to align the wind turbine with the wind direction, control blade pitch, etc.

[0041] The first group of auxiliary power consumers may include components that are not critical to determining sufficient wind conditions for return to operation and / or components that provide command and control capabilities (which may be included in the second group). For example, the first group of auxiliary power consumers may include one or more actuators or drives configured to operate components of the wind turbine. The first group of auxiliary power consumers may include one or a combination of a wind turbine yaw system, a wind turbine pitch system, a wind turbine hoisting system, a wind turbine work lift, a wind turbine cooling system, and a wind turbine environmental management system (which may include, for example, a temperature control and a humidity control).

[0042] The second group of auxiliary power consumers may include one or more devices configured to communicate with and control the wind turbine and obtain wind conditions. For example, the consumers may include wind sensors of the wind turbine, a wind turbine controller and / or a wind turbine communication device (which may, for example, provide for external communication, such as receiving data, e.g., environmental data, and receiving control commands from an external site). Thus, in the first operating mode, the control and communication system and possibly the sensor system may be operated, which allows the wind turbine to determine the time to transition back to the energy harvesting mode with low energy consumption.

[0043] The first group of auxiliary power consumers may have a combined power requirement of more than 100 kW, for example 100 kW to 1000 kW, or 200 kW to 500 kW, for example 250 kW to 400 kW. The second group of auxiliary power consumers may have a combined power requirement of less than 50 kW, preferably less than 10 kW, for example 0.1 kW to 10 kW, or 0.2 kW to 5 kW, for example less than 2 kW. Thus, significant power consumption savings may be achievable when operating in the first operating mode (e.g. sleep mode).

[0044] The first group of auxiliary power consumers may have an operating voltage above 300V, in particular between 300V and 1000V. They can be powered from a three-phase power supply. The second group of auxiliary power consumers may have an operating voltage below 300V, for example between 100V and 250V. They can be powered by a single-phase supply, as they do not need to drive particularly large motors. The above values ​​may be referred to as the nominal rated power and nominal rated voltage of the respective consumers.

[0045] The energy storage system may preferably be a rechargeable energy storage system. The system may include at least one of a battery energy storage system (BESS), a hydrogen storage system including a hydrogen storage device and a hydrogen conversion system configured to generate electrical energy from the stored hydrogen, a flywheel energy storage system, a capacitor (e.g., supercapacitor) energy storage system, or a thermal storage system including a heat storage device and a conversion system configured to generate electrical power from the stored thermal energy. Preferably, a BESS or a hydrogen storage system is provided. In some examples, the energy storage system may include a fossil fuel-driven generator in which energy is stored in the form of a generator (e.g., a diesel generator) powered by a fossil fuel, although this is less preferred because the energy storage system is not rechargeable.

[0046] According to another aspect, a wind turbine control system is configured to, among other things, control the operation of a wind turbine to transition to an energy harvesting mode in which the wind turbine operates to generate electrical power from wind energy. An energy storage system associated with the wind turbine is configured to provide electrical power to the auxiliary systems when the wind turbine is not generating or receiving sufficient electrical power to power the auxiliary systems. The control system can be configured to perform a method according to any of the configurations and embodiments described herein.

[0047] According to another aspect, there is provided a wind turbine having such a control system and further an energy storage system, which may be located within the tower of the wind turbine, for example on a tower platform within the tower or adjacent to the tower.

[0048] According to another aspect, there is provided a computer program for controlling operation of a wind turbine, wherein an energy storage system associated with the wind turbine is configured to provide power to an auxiliary system when the wind turbine is not generating or receiving sufficient power to power the auxiliary system, the computer program including control instructions that, when executed by a processing unit of a control system for controlling operation of the wind turbine, cause the processing unit to perform a method having any of the features described herein.

[0049] The method can be performed by a control system or a wind turbine having any of the configurations described herein. The method can further include any of the steps described herein with respect to the control system or the wind turbine. Similarly, the control system can be configured to perform the method of any of the embodiments and examples disclosed herein.

[0050] It is to be understood that the features mentioned above and below can be used not only in the respective combinations shown, but also in other combinations or alone without departing from the scope of the invention. In particular, unless stated to the contrary, each feature of the various aspects and embodiments of the invention can be combined with each other.

[0051] The above and other features and advantages of the present invention will become more apparent from the following detailed description read in conjunction with the accompanying drawings, in which like reference numerals refer to like elements. [Brief explanation of the drawings]

[0052] [Figure 1] 1 is a schematic diagram illustrating a wind turbine including a control system according to an embodiment. [Figure 2] 1 is a schematic diagram illustrating transitions between various operational modes of a wind turbine according to one embodiment. [Figure 3] FIG. 10 is a schematic diagram illustrating graphs when wind speed, wind speed trend, and wind force trend conditions are met, according to one embodiment. [Figure 4] FIG. 2 is a schematic diagram illustrating a graph of the dependency of a wind speed threshold on the amount of energy stored in an energy storage system of a wind turbine, according to one embodiment. [Figure 5] 1 is a first portion of a flowchart illustrating a method for controlling a wind turbine according to an embodiment. [Figure 6] 6 is a second part of the flowchart of FIG. 5.

[0053] Detailed Description Embodiments and / or examples of the present invention will now be described in detail with reference to the accompanying drawings. It should be understood that the following description of each embodiment is provided for illustrative purposes only and should not be construed in a limiting sense. It should be noted that the drawings should be considered as schematic representations only, and that the elements therein are not necessarily drawn to scale relative to each other. Rather, the representations of various elements have been selected so that their function and general purpose will be apparent to those skilled in the art. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms unless the context clearly dictates otherwise. Terms such as "comprising," "having," "including," and "containing" should be construed as open-ended (i.e., meaning "including, but not limited to") unless expressly stated otherwise.

[0054] FIG. 1 schematically illustrates a wind turbine 100 according to one embodiment, which may include a wind turbine power system 110 including a generator 111 and a power conditioning system 112. The power system 110 may have any known configuration and topology, such as a full converter topology or a doubly-fed induction generator (DFIG) topology, in which a power conditioning device 112, in particular a power converter, may be connected to the rotor winding of the generator to condition the generated power. Furthermore, a wind turbine transformer 115 may be provided to convert the generated power to a desired voltage level before being fed to an external power supply network 200 or, alternatively, before being fed to one or more local consumers. In the embodiment of FIG. 1, the wind turbine 100 is connected to an external power supply network 200, e.g., a power grid, which may in this case be a grid that can supply power to the wind turbine 100, in particular for operating the wind turbine 100 during periods of low wind, for maintenance work, or in other situations in which the wind turbine itself does not generate power. By using the respective switches, in particular the switchgear 201, the wind turbine 100 can be disconnected from the external power grid 200, for example in response to the occurrence of a grid fault or other event that causes the grid connection to be unavailable. In other embodiments, there may be no connection to the external power grid 200 at all (i.e., the external power grid 200 is optional). Such a wind turbine may, for example, supply power to one or more local consumers, but may not supply power to the wind turbine 100 via its own connections to the local consumers. Such operation may also be referred to as island operation.The solution provides for transition of the wind turbine to autonomous operation (energy harvesting mode) for a wind turbine that is normally connected to the grid but that has been disconnected from the grid for a given reason (e.g. by opening switch 201), or for a wind turbine that is not normally connected to the grid and operates to supply power to power consumers within or nearby the wind turbine (local power consumers), or for a wind turbine for which the power grid is unable to provide sufficient power to operate the auxiliary systems of the wind turbine. Such autonomous operation avoids damage or potential damage associated with long shutdowns of the wind turbine and achieves avoidance of exposure of wind turbine components to external humidity and temperature, which is particularly important for offshore wind turbines.

[0055] When there is no grid connection or the grid connection is disconnected, the wind turbine 100 can operate in an energy harvesting mode, in which the power system 110 supplies power to the auxiliary system 10, including the auxiliary power grid 40 and the auxiliary power consumers 12-14; 22-25. A challenge in operating a wind turbine in a grid-disconnected state is that power from the wind may not always be available to maintain power supply to the auxiliary system 10, for example, if environmental conditions are outside the wind turbine's operating range or if a failure occurs in one of the wind turbine systems required for power generation. Environmental conditions that can affect wind turbine operation include excessively high or low wind speeds or excessively high or low ambient temperatures. Failures may include failures in the wind turbine's pitch system, yaw system, monitoring system, control system, or power conversion system.

[0056] The auxiliary system 10 may include an energy storage system 50 configured to provide electrical energy for operating (at least a portion of) the auxiliary system 10 when there is no power or insufficient power available from the external grid 200 and no power available from the power system 110. The energy storage system 50 may provide power to the auxiliary power grid 40, which distributes the power to the auxiliary power consumers. For example, a switch (not shown), e.g., a three-way switch, may be used to control the power source for the auxiliary power grid 40. Such a switch may be switchable to transfer power supply between the wind turbine power system 110 and the energy storage system 50, and may also be switchable to disconnect the two power sources from the auxiliary system depending on the operating mode of the wind turbine.

[0057] The auxiliary power consumers can be divided into at least a first group 11 and a second group 21. The power supply to at least the first group 11, preferably both groups 11 and 21, can be controlled separately. The consumers in the first group 11 are generally not important for determining wind conditions sufficient to return the wind turbine to operation and / or for determining command and control capabilities. The first group 11 can include, for example, relatively large power consumers, e.g., having a relatively high power rating, and can include, in particular, one or more devices. Examples include the yaw system 12, the pitch system 13, and the cooling system 14. Other systems included in the first group 11 can include a crane hoist, a work lift, a high-power outlet, and an environmental system, including an AC system for controlling temperature and humidity within the wind turbine. The combined power rating of the auxiliary power consumers in the first group 11 can be, for example, in the range of 250 kW to 400 kW. Typically, each consumer can receive a three-phase AC voltage supply in the voltage range of 300 V to 1000 V, e.g., 400 V or 690 V. These consumers thus consume large amounts of power, which is needed to maintain the operation of the wind turbine 100, e.g., to track the wind direction using the yaw drive 12, to control the rotational speed of the rotor using the pitch system 13, etc.

[0058] The auxiliary power consumers of the second group 21 may include consumers that are important for determining the presence of sufficient wind conditions to return the wind turbine 100 to operation and / or for command generation and control capabilities. The second group 21 may include low power consumers, i.e., having a relatively low nominal power rating, such as the wind turbine controller 25 and the communication interface 23. The system may further include a wind turbine monitoring system 22 that may include a wind sensor, but the controller 25 may also obtain respective wind information from sensors external to the wind turbine 100 via the communication interface 23. The second group 21 may include auxiliary power consumers that receive a single-phase power supply, in particular with a voltage in the range of 100V to 300V, for example 110V or 230V. The consumers of the second group 21 may have a combined nominal power rating of 0.1 kW to 10 kW, for example 0.3 kW to 5 kW, preferably less than 2 kW or less than 1 kW. The auxiliary power consumers of the second group 21 are able to control the operation of the wind turbine 100 and communicate with the outside world, for example to receive control commands (e.g. from a wind farm controller) and / or to receive environmental data and / or to provide monitoring data, even when none of the main mechanical systems of the wind turbine can actually operate.

[0059] The wind turbine controller 25 may form part of the control system 20 and may include a processing unit 26, which may include a microprocessor, an application specific integrated circuit, a digital signal processor, etc. The wind turbine controller 25 may further include a memory 27, coupled to the processing unit 26, storing control instructions that, when executed by the processing unit 26, cause the processing unit 26 to perform any of the methods described herein. The memory 27 may include volatile and non-volatile memory, in particular a hard disk drive, flash memory, RAM, ROM, EEPROM, etc. The wind turbine controller 25 may further include other components not explicitly shown, such as respective input / output interfaces to the components to be controlled, shown in dashed lines in FIG. 1 , a user interface including a display and input means, and other components common to computer systems. The communication interface 23 and / or the monitoring unit 22 may also form part of the control system 20.

[0060] 1, a switch 42 in the form of a circuit breaker may be connected between the energy storage system 50 and the first group 11 so that the power supply to the consumers in the first group 11 is controlled independently from the consumers in the second group 21. Thus, the power supply from the energy storage system 50 to the auxiliary power consumers in the first group 11 may be stopped (discontinued) to reduce energy consumption. As will be described in more detail below, the controller 25 may operate the wind turbine 100 in various operating modes that may selectively activate or cut off power supply to the consumers in the first group 11.

[0061] Optionally, a separate second storage device in the form of an uninterruptible power supply (UPS) 45 may be connected in line on the power supply path from the energy storage system 50 to the consumers of the second group 21. Such a UPS may ensure that short-term power outages, such as a transition between power sources (e.g. via a respective switch) or a failure in any of the available power systems, do not result in an immediate loss of control, monitoring and / or communication capabilities of the wind turbine.

[0062] The energy storage system 50 can be implemented in several different forms. Implementations can include, among others, a battery energy storage system (BESS) and a hydrogen storage system, as shown in FIG. 1 . However, other implementations or embodiments are also contemplated, such as a flywheel storage system, a (super)capacitor storage system, a thermal storage system, etc., or a diesel generator. Preferably, the system 50 is rechargeable. The description provided herein is applicable to any of these possible implementations or embodiments. When implemented as a hydrogen storage system, the wind turbine 100 can include a hydrogen production system that uses power provided by the power system 110 to produce hydrogen gas during operation of the wind turbine 100. Such a hydrogen production system can receive water from a water source and produce hydrogen gas by electrolysis. The produced hydrogen gas can then be stored in a hydrogen reservoir within the wind turbine and / or in an external hydrogen collection tank (not shown). The energy storage system 50 can also include a fuel cell that generates electrical energy from the hydrogen stored in the reservoir and supplies it to the auxiliary grid 40.

[0063] The control system 20 of the wind turbine 100 may include a wind turbine controller 25 that may control and / or communicate with multiple components of the wind turbine, including the communication interface 23, the monitoring unit 22, the energy storage system 50, the power system 110, the switches 42, the UPS 45 and the auxiliary system 10, in particular the consumers of the first group 11 and the consumers of the second group 21. The control system 20 may also control a switch 201 for isolating the wind turbine from the external grid 200, the wind turbine transformer 115 and other components of the wind turbine 100, although the individual control and communication connections are not shown in Figure 1.

[0064] It will be apparent that topologies other than that shown in Figure 1 can be used with the solutions disclosed herein. For example, energy storage system 50 can be connected as an online UPS and include a bypass (avoiding the need for UPS 45), or can be connected to feed UPS 45 (as switch 42 is not required when only second group 21 is powered), or other configurations are contemplated and within the scope of the present disclosure.

[0065] The control system 20 can operate the wind turbine 100 in an energy harvesting mode, in which the power system 110 provides all or a majority (more than 50%, more than 70% or more than 90%) of the power required to operate the auxiliary system 10, i.e., generates power from wind energy. In this operating mode, both groups 11 and 21 and preferably all auxiliary power consumers are supplied with power. The energy harvesting mode can in particular be an autonomous operating mode.

[0066] When conditions for operating wind turbine 100 in such a harvesting mode are not provided (e.g., wind speed is outside the operating range), control system 20 can operate wind turbine 100 in a first operating mode, which can be or include a sleep mode. In this first operating mode, power supply to first group 11 can be stopped, and second group 21 can receive all or a majority (more than 50%, more than 70%, or more than 90%) of its power from energy storage system 50. In particular, power system 110 may not be supplying or receiving power from power grid 200 (if such a grid exists at all). Thus, the above-described operating mode can keep monitoring and control functions of wind turbine 100 active, while energy consumption can be kept low because the primary auxiliary loads of group 11 are not powered.

[0067] The control system 20 can operate the wind turbine 100 in different operating modes, as shown in FIG. 2 . When the wind turbine 100 is connected to a grid 200 (if present), the wind turbine can operate in a grid mode 75, which may include the traditional operating state of a grid-connected wind turbine. In grid mode 75, power from the grid or generated power can be used to charge or maintain the energy storage system 50 at a full charge state. Grid mode 75 is optional and cannot be used in wind turbines without a grid connection. The monitoring unit 22 can monitor the status of the grid and, if it detects that the grid is no longer available or has been disconnected, can transition the operation of the wind turbine to a grid-disconnected operation, described below. In mode 75, the wind turbine can operate in an area 83 where power is supplied to the auxiliary system 10 from an external power grid.

[0068] The wind turbine 100 may further be operable in the energy harvesting mode 74 described above, in which the generator 111 converts rotational mechanical power from the wind turbine rotor into electrical power supplied to the auxiliary systems 10, including the energy storage system 50, and possibly to local loads (autonomous operating area 82).

[0069] In the operating region 81, the auxiliary system 10, or at least its components, can be supplied with power from the energy storage system 50. In the operating region 81, the power system 110 does not generate power, and the wind turbine may not receive power from the grid 200 (if present), or at least may not receive a sufficient amount of power to power the auxiliary system 10 (e.g., less than 50%, 20%, or 10% of the required power). The operating modes in this region 81 can include a first operating mode 72 (sleep mode) and also a so-called local power mode 71 (second operating mode). In the local power mode, two groups 11, 21 of auxiliary power consumers, preferably all of them, can be supplied with power from the energy storage system 50. Furthermore, the wind turbine can operate in a sleep mode 73 (third operating mode), in which no power is supplied to the auxiliary system 10 and the wind turbine can be substantially completely shut down.

[0070] The arrows in FIG. 2 illustrate possible transitions between these operating modes. Even when not connected to an external power grid and before energy harvesting begins, the wind turbine can operate in local power mode 71. This mode may be provided to initiate wind turbine operation or to keep the wind turbine ready for energy generation. For example, wind tracking can be performed (operation of the yaw system) to establish the alignment of the wind turbine rotor with the wind, as can system cooling (circulation of cooling fluid), heating, and dehumidification. Additionally, a power conditioning device 112 can be prepared for operation (e.g., to charge DC link capacitors) and, for example, the hydraulic system of the pitch system can be placed under a predetermined pressure. When starting of the wind turbine is to begin, the wind turbine's pitch system 13 can be operated to allow rotor speed acceleration. Once the wind turbine rotor reaches cut-in rotor speed, operation can transition to energy harvesting mode 74. Thus, in the case of a transition from sleep mode 72 to energy harvesting mode 74, the transition may be made via local power mode 71, i.e. the transition may involve operating the wind turbine in second operating mode 71. It is clear that the transition involves a significant consumption of energy from storage system 50, due to the need to operate a large number of loads of group 21.

[0071] A transition to hibernation mode 73 may occur in response to the amount of energy in storage system 50 reaching a minimum level to ensure that the energy storage system is not further depleted and that sufficient energy is available for manual start-up. A transition from grid-connected operating mode 75 to standalone operating mode 74, which is not connected to the grid, may similarly occur via local power mode 71.

[0072] To reduce energy consumption of the storage system 50 and thus reduce the risk of depleting available energy, the transition from sleep mode 72 to energy harvesting mode 74 can occur when the control system 20 determines that predetermined conditions are met. Thus, a failed start-up attempt can be avoided. In particular, the predetermined conditions can be selected to increase the likelihood that more energy will be recovered in the harvesting mode than is required for the start-up attempt (i.e., for the transition). The wake-up sequence, i.e., the transition to mode 74, can consume between 15 kWh and 20 kWh of stored energy, depending on the size and type of turbine.

[0073] The wind turbine may be prevented from operating in energy harvesting mode 74 due to a user command to stop power generation, the occurrence of a fault, wind speeds that are too low to generate power, wind speeds that are too high to generate power, and / or other environmental conditions that prevent such operation. If any of these occur, the control system may transition the wind turbine's operation into sleep mode 72, thereby ensuring that a low level of power is consumed by the energy storage system 50 while maintaining power supply to systems necessary to resume operation. If the wind turbine is shut down during sleep mode due to a fault or user command, the fault must be cleared and any user command must be released to allow the turbine to resume operation. If the wind turbine is shut down due to wind speeds (too high or too low), the monitoring unit 22 may continue to monitor wind conditions or may obtain wind conditions via the communication interface 23, while the wind turbine controller 25 may decide when to attempt to restart the wind turbine in sleep mode.

[0074] Time filtering of the measured or received wind speed data can be used to prevent the turbine from responding to sudden changes in wind speed, which may be unreliable, and to start up (if shut down due to light wind) or to detach (if shut down due to strong wind) from short gusts of wind. The time filtered wind speed may be an average, in particular a moving average, for example a moving window average with a window length of 1 s to 10000 s, preferably 50 s to 1000 s, for example 100 s to 200 s.

[0075] The filtered wind speed v filter is the minimum cut-in wind speed threshold thresh min_cut-in (min threshold for low wind speed shutdowns) above which the wind turbine can be restarted. Similarly, if the wind turbine is shut down due to high wind speeds, the maximum cut-in wind speed threshold thresh max_cut-in (abbreviated as maximum threshold) can be used. v filter >thresh min_cut-in (low wind speed) or v filter <thresh max_cut-in (due to high wind speeds) The wind speed condition can be defined as being satisfied when

[0076] Therefore, the wind speed range of the cut-in wind speed can be defined by these thresholds, and the wind speed condition shall be met if the filtered wind speed falls within this cut-in wind speed range.

[0077] Furthermore, to avoid short-term exceedances of the respective thresholds resulting in start-up attempts, the historical wind speed trends v trend Historical trend wind speeds can be taken into account. Historical trend wind speeds can be obtained from a combination of time-filtered wind speeds. For example, historical trend wind speeds can be calculated by the difference between the current values ​​of time-filtered wind speeds, each filtered with a different window length. v trend=v filter(length1) -v filter(length2) can be determined as: Here, the filter lengths can be, for example, length1=120s and length2=600s. Obviously, instead of using different filter lengths, any other known method for determining trends can be used, such as the difference between two average values ​​of the same length at two different times or curve fitting. In this way, a wind speed trend condition can be defined, which can be expressed as: v trend >thresh trend_min (low wind speed) or v trend <thresh trend_max (due to high wind speeds) It can be said that the condition is satisfied when

[0078] The trend thresholds can be set to any wind speed in the range of 0 m / s to 99 m / s or 0 m / s to -99 m / s, respectively.

[0079] For example, the limits for the minimum and maximum wind speed thresholds are: thresh min_cut-in =3.5m / s thresh max_cut-in =22m / s and the wind speed trend threshold can be set to thresh trend_min =0 m / s thresh trend_max =0 m / s can be set to.

[0080] A trend threshold of 0 m / s means that the wind speed trend must be positive when entering the operating range from a low wind speed, and negative when entering the operating range from a high wind speed (i.e., wind speed decreasing in history). A higher or lower value for the trend threshold, e.g., thresh trend_min= 1m / s, 2m / s or 3m / s and threshold trend_max It is clear that the trend conditions can be made stricter by selecting =-1 m / s, -2 m / s or -3 m / s.

[0081] If both the wind speed condition and the wind speed trend condition are met, it may be determined that a predetermined condition for transitioning to the energy harvesting mode is met.

[0082] Furthermore, if the time-filtered wind speed is sufficiently inside the operating range, a second wind speed condition can be defined that includes a second threshold value having a sufficient safety margin relative to the threshold value of the first wind speed condition described above, i.e., the respective range defined by the second threshold value is narrower and is within the range defined by the first threshold value described above. If the second wind speed condition (which can be referred to as a "sufficient wind speed criterion") is met, historical wind speed trends do not need to be considered. The second wind speed condition can be used, for example, after an outage period (operation in sleep mode) due to a user command or a turbine failure scenario. The second wind speed condition can be: v fi1ter >thresh_suff min_cut-in (low wind speed) or v fi1ter <thresh_suff max_cut-in (due to high wind speeds) can be said to be satisfied if where thresh_suff min_cut-in is the second minimum cut-in wind speed threshold (sufficient wind conditions), thresh_suff max_cut-in is the second maximum cut-in wind speed threshold (sufficient wind conditions). Each threshold is stricter than the first threshold (i.e., closer to the inside of the operating range), e.g., thresh_suff min_cut-in =6 m / s thresh_suff max_cut-in =20m / s It can be set as follows.

[0083] Thus, if the time-filtered wind speed rises above the second minimum threshold or falls below the second maximum threshold, the second wind speed condition, and thus the predetermined condition, may be satisfied, which may cause the control system 20 to transition the wind turbine into energy harvesting mode 74.

[0084] The top graph 300 of FIG. 3 shows an example wind speed filtered with a window length of 120 s (curve 301) and an example wind speed filtered with a window length of 600 s (curve 302). Additionally, a second wind speed threshold (thresh_suff min_cut-in ) is shown (curve 303). A second graph 304 shows the wind speed trend values ​​(curve 305) determined as shown above from the curves in the first graph 300. Additionally, a wind speed trend threshold 306 (thresh trend_min ) are also shown.

[0085] A third graph 308 shows a Boolean value for whether a first combination of wind speed condition and wind speed trend condition is met, based on the data in graphs 300 and 304 (a minimum wind speed threshold of 3.5 m / s). Here, it can be seen from graph 304 that the minimum threshold is always met, but the trend condition is met (Boolean value is 1) for only a portion of the curve. It is clear that as soon as the Boolean value becomes 1, the wind turbine transitions to energy harvesting mode and then continues to operate in that mode until the wind speed falls below the minimum cutout threshold (or exceeds the maximum cutout threshold). In other words, the change in the Boolean value shown in graph 308 is not a transition of operating modes.

[0086] The energy consumed by transitioning to energy harvesting mode (wake-up attempt) may be an important factor to justify in order to be able to recover the energy consumed by performing a wake-up when the wind turbine starts operating to generate power. If the level of energy stored in the storage system 50 is low, the wind conditions should be well inside the operating wind speed range to ensure that a long operating period occurs after wake-up. This can be taken into consideration to determine the wind speed threshold mentioned above by using the energy available in the energy storage system 50. Threshold thresh min_cut-in and thresh max_cut-in can be selected, for example, depending on, and in particular as a function of, the amount of energy stored in the storage system 50. An example of this function is shown in FIG. 4, which shows curve 401 for a wake-up situation in light winds, i.e., the minimum threshold. The x-axis shows the amount of energy available and the y-axis shows the value of the minimum threshold. The value of the minimum threshold can vary from 3.5 m / s when the available energy is at its maximum to 6 m / s when the available energy is at its minimum.

[0087] Thus, when the available energy is high, a start can be attempted as soon as possible because there is sufficient energy remaining if the start attempt fails. When the available energy is low, a start is attempted only if a successful start is assured. Curve 401 can be defined based on the amount of energy consumed in a wake-up attempt for a given type of turbine, with a safety margin added. These are merely example values, and it will be apparent that values ​​can be selected depending on the desired operating characteristics and operating conditions.

[0088] In addition to the combined wind speed or trend condition and sufficient wind speed condition described above, the control system 20 can also use further conditions as part of the predetermined conditions to transition operation to the energy harvesting mode. For example, a weather forecast can be used, and in particular wind conditions can be predicted. Such predictions can be based on local measurements made at the wind turbine using the monitoring unit 22 and / or weather information obtained via the communication interface 23. The monitoring unit 22 can include sensors that monitor not only wind speed and direction, but also temperature and air pressure. Based on these signals, weather forecast models can be used by the control system 20 to make predictions and / or form expectations of future wind conditions. Such models can be implemented using the wind turbine controller 25 and / or using a wind farm controller (not shown) external to the wind turbine 100, which may be part of the control system 20. Other signals, such as time of day, day of the month, solar irradiance, precipitation level, and any available sensor data or external data historical trends, can also be used as inputs to such models.

[0089] The prediction or the obtained forecast data may also take into account the risk of icing on the rotor blades, which may reduce the reliability of the above-mentioned conditions. Ice detection may be performed using sensors in unit 22, or a load monitoring method may be performed by unit 22 to detect the presence or absence of ice. If rotor icing is detected, control system 20 may, for example, prevent wake-up from sleep mode 72 or change the required wind speed for wake-up, i.e., set stricter values ​​for the respective wind speed thresholds or wind speed ranges (e.g., set a higher minimum threshold or a lower maximum threshold).

[0090] Alternatively or in combination with model-based predictions, weather information from available weather services can be obtained via communication interface 23 and used to predict wind conditions and / or icing conditions. This predicted information can be communicated from the wind farm controller to wind turbine controller 25, or can be processed externally to the wind turbine controller (e.g., by the wind farm controller) and only basic command signals (e.g., signals to transition operation modes) can be communicated to wind turbine 100. If weather forecast information is processed externally to wind turbine controller 25, for example by checking whether the respective conditions are fulfilled, further benefits can be obtained, for example by coordinating the wake-up of the wind turbine from a sleep mode.

[0091] If the forecast predicts that the wind speed will return to the operating range at a predetermined future time or for a predetermined future period, the predicted wind speed (which may be filtered or already smoothed with a respective time constant, depending on the model used) can be checked by comparing it with the respective wind speed threshold, e.g., the minimum and / or maximum thresholds mentioned above. The forecast data can further allow estimation, for example, of how long, e.g., for how many consecutive periods, the wind speed is expected to remain within the operating range, i.e., not drop below the minimum cutout wind speed or not rise above the maximum cutout wind speed. In other words, wind speed trends may not be taken into account in the predicted wind speed data. The transition to energy harvesting mode (wake-up) can be scheduled for each wind turbine based on the time required for start-up and generation (e.g., 5 minutes) and the expected arrival time of the respective wind conditions that allow the transition. In this way, the wind turbine can be ready to start without delay when wind conditions permit. Also, in large wind farms, the control system may command the wind turbines of the farm closest to the incoming wind conditions to wake up from sleep mode early, and then wake up subsequent wind turbines based on the predicted rate at which the wind speed change (i.e., the qualifying wind speed) is expected to progress through the wind farm.

[0092] In addition to checking whether the predicted wind speed falls within the respective wind speed thresholds, the amount of expected energy generation can also be taken into account. If the forecast predicts that the wind speed will return to the operating range for a short period at a predetermined future time, the amount of energy consumed during startup can be compared to the amount of energy expected to be generated by the wind turbine during that period when energy generation is possible. If the predicted energy generation allows for the recovery of the energy used for the transition of operation (i.e., the energy to recharge the energy storage system at least to the previous level) plus a predetermined margin (e.g., at least 30%, 40%, or 50% of the energy required for the transition), the wind turbine can be commanded by the control system 20 to perform a wake-up and transition, for example, as described above. For purposes herein, the expected amount of generated energy can be compared to respective energy thresholds, which can include the amount required for recovery and a margin, and the transition occurs if the expected amount is greater than the threshold. If the period is too short and the expected energy generation is not sufficient to recover the energy consumed during startup, no wake-up command is issued. This action can therefore ensure that the energy storage system 50 is not depleted.

[0093] If the wind turbine is already operating in energy harvesting mode 74 and the forecast predicts that wind speeds outside the operating range will occur for a predetermined period of time, and operation continues without transitioning to sleep mode 72 (i.e., continues operation in local power mode 71) for that period of time, the amount of energy consumed by the wind turbine can be estimated. This estimated amount of energy can be compared to the amount of energy required to operate the wind turbine in sleep mode for that period of time, transition operation to and from sleep mode. If it is estimated that the required energy is insufficient to transition to sleep mode, operation can continue for that period of time without transitioning to sleep mode 72 (the wind turbine could, for example, transition to mode 71 for a short time if wind conditions are outside the operating range and then return to energy harvesting mode 74). Avoiding such short transitions to sleep mode can result in further energy savings.

[0094] The flowcharts of FIGS. 5 and 6 provide an overview of the respective operation of the wind turbine 100, where a method can be performed by the control system 20 that controls the operation of the wind turbine 100. In step S10, the wind turbine is enabled to operate in a sleep mode. In step S11, environmental data can be acquired, for example, by measuring wind speed and optionally other data, e.g., meteorological data using the monitoring unit 22 and / or by receiving respective data via the communication interface 23. Furthermore, the storage status of the energy storage system 50 can be acquired to estimate the amount of available energy. In step S12, a prediction regarding the wind speed can be obtained, for example, by modeling the wind speed based on the acquired meteorological data or by receiving respective prediction data via the interface 23. In step S13, minimum and maximum thresholds (or corresponding respective cut-in wind speed ranges) can be determined based on the amount of energy stored in the storage system 50, for example, as described above with reference to FIG. 4.

[0095] In step S14, it can be checked whether a predetermined condition is met. As detailed above, this can include checking for multiple conditions, and the predetermined condition can be met if one of these conditions is met. The checks can include, for example, checking for a combined wind speed condition or a wind speed trend condition, checking for a sufficient wind speed condition (a narrower second wind speed range), checking for future wind speed conditions, i.e., whether the predicted wind speed meets a respective wind speed threshold or wind speed range, whether the amount of energy estimated to be generated in a future time period (when wind conditions are predicted to fall within the operating range) is greater than a respective predetermined energy threshold, etc. In step S15, it can be determined whether one of these conditions, and therefore the predetermined condition, is met. If not, operation can continue in sleep mode in step S10.

[0096] If one of the conditions is met in step S15, the controller can transition operation to the energy harvesting mode in step S16. Step S16 can include, for example, operation in local power mode 71 to supply power to the wind turbine system as needed, start wind tracking using the yaw drive, and start rotor acceleration using the pitch drive. In step S17, the transition is complete and the wind turbine can operate in energy harvesting mode 74. In step S18, it can be checked whether the energy harvesting mode should be stopped, for example, whether the wind speed has dropped below a minimum cut-out wind speed threshold or risen above a maximum cut-out wind speed threshold. It is clear that the cut-out thresholds can be set differently from the cut-in thresholds, in particular, they can be set to lower values ​​(for minimum cut-out) or higher values ​​(for maximum cut-out). In other words, a certain amount of hysteresis can be provided to avoid frequent changes between sleep mode and energy harvesting mode. Other conditions that may cause the wind turbine to leave energy harvesting mode that may be checked for in step S18 may include the occurrence of a fault in the wind turbine that inhibits operation, receiving an operator command to cease operation, determining the need for self-preservation action (which occurs periodically) (e.g., untangling tower cables, automatic diagnostics of safety systems, etc.), and / or determining that the energy storage system is fully charged.

[0097] If the condition is not met in step S18, for example if the wind speed is still within the operating range, operation in the energy harvesting mode in step S17 can continue. Otherwise, operation can be transitioned back to sleep mode in step S10. As outlined above, such a transition can also occur via local power mode 71 (e.g., to safely slow down the wind turbine rotor). Also, as mentioned above, if the wind speed drops outside the operating range, but only for a sufficiently short period of time, this can also be checked in step S18, and operation in the energy harvesting mode in step S17 can continue.

[0098] It is clear that some of the steps shown in FIGS. 5 and 6 are optional, such as step S12 (in some cases, forecast data may not be used) or step S13 (in some cases, threshold adaptation may not be performed). Alternatively, only forecast data may be used, without other steps and respective conditions of the method. Preferably, the method can base the transition decision on forecast data, especially the predicted wind speed, if the forecast data is available with sufficient quality (e.g., sufficient reliability). Otherwise, the method can base the decision on actual monitored data, for example, using combined wind speed or wind speed trend conditions and sufficient wind speed conditions. Thus, a reliable operation can be achieved that minimizes the risk of exhaustion of the energy storage system 50. In particular, failed attempts and rapid succession of restarts of the wind turbine, which may exhaust the energy storage system 50, can be avoided.

[0099] It will be apparent that the control system 20 can include a wind turbine controller 25, which is capable of performing the above-described methods. Alternatively or additionally, the wind turbine controller 25 can include a wind farm controller, which can perform the above-described methods, for example by sending respective control signals to one or more wind turbines to cause a transition of an operating mode. The control system 20 can also be implemented as a distributed control system, in which some functions (e.g., wind speed prediction) are performed by the wind farm controller, while other functions (e.g., monitoring and evaluation of wind speed data, transition of an operating mode) are performed by the wind turbine controller 25. Other implementations are also possible.

[0100] While particular embodiments have been disclosed herein, various changes and modifications can be made without departing from the scope of the invention, which embodiments are to be considered in all respects as illustrative and not restrictive, and all changes that come within the meaning and range of equivalency of the appended claims are intended to be embraced therein.

Claims

1. 1. A method of transitioning operation of a wind turbine (100) to an energy harvesting mode in which the wind turbine operates to generate electrical power from wind energy, comprising: an energy storage system (50) associated with the wind turbine (100) configured to supply power to the auxiliary system (10) of the wind turbine when the wind turbine is not generating or receiving enough power to power its auxiliary system (10); The method comprises: - operating the wind turbine (100) in a first operating mode (72) in which the wind turbine (100) does not generate electrical power from wind energy, and in the first operating mode (72), stopping the supply of electrical power to one or more auxiliary electrical power consumers (12, 13, 14) of a first group (11) of the auxiliary system (10) and supplying electrical power from the energy storage system (50) to one or more auxiliary electrical power consumers (22, 23, 25) of a second group (21) of the auxiliary system (10); - acquiring environmental data including at least one of wind data and weather data; determining whether the acquired environmental data satisfies a predetermined condition, wherein the predetermined condition includes at least one of a wind speed threshold, a wind speed range in which the wind turbine (100) is operable to generate power, a wind speed trend threshold (306), or a predetermined energy threshold for expected energy production; - transitioning operation of the wind turbine (100) to the energy harvesting mode (74) if the predetermined condition is met, wherein transitioning operation to the energy harvesting mode (74) comprises supplying power from the energy storage system (50) to one or more auxiliary power consumers (12, 13, 14) of the first group (11); Including, the predetermined conditions include the wind speed trend threshold (306); the wind speed threshold and / or the wind speed range are variable and are determined based on the amount of energy stored in the energy storage system; method.

2. 2. The method of claim 1, wherein the wind speed thresholds among the predetermined conditions include a minimum cut-in wind speed threshold that is greater than or equal to a wind speed value at which the wind turbine (100) is operable to generate power, and / or a maximum cut-in wind speed threshold that is less than or equal to a wind speed value at which the wind turbine (100) is operable to generate power.

3. acquiring the environmental data includes acquiring wind speed data and time filtering the wind speed data; determining whether the predetermined condition is met comprises comparing the time-filtered wind speed data (301) with the wind speed threshold and / or the wind speed range; The method of claim 1.

4. 2. The method of claim 1, wherein determining whether the predetermined condition is met comprises comparing a wind speed trend (305) derived from the acquired wind data to the wind speed trend threshold (306).

5. The method further comprises: deriving the wind speed trend (305) by comparing the time-filtered wind speed data filtered with a first time constant with the time-filtered wind speed data filtered with a second time constant, or by comparing an average wind speed obtained from the wind speed data for a first time point with an average wind speed obtained from the wind speed data for a second time point different from the first time point; 5. The method of claim 4, comprising:

6. the predetermined conditions include a wind speed condition including the wind speed threshold and / or the wind speed range, and a wind speed trend condition further including the wind speed trend threshold; The predetermined condition is satisfied when the wind speed condition and the wind speed trend condition are satisfied. The method of claim 1.

7. the predetermined conditions include a first wind speed condition including the wind speed threshold and / or the wind speed range, and a second wind speed condition further including a second wind speed threshold (303) and / or a second wind speed range; the second wind speed threshold (303) is greater than the wind speed threshold when the wind speed threshold is a minimum threshold, and is less than the wind speed threshold when the wind speed threshold is a maximum threshold; and / or the second wind speed ranges are narrower than the first wind speed ranges and are located within the first wind speed ranges, When the second wind speed condition is satisfied, the predetermined condition is satisfied. The method of claim 1.

8. If the amount of stored energy is smaller, the wind speed threshold is set to a more stringent value and / or the wind speed range is set to a narrower range; If a larger amount of energy is stored, the wind speed threshold is set to a less stringent value and / or the wind speed range is set to a wider range. The method of claim 1.

9. obtaining the meteorological data includes obtaining a forecast of wind conditions for a future period; determining whether the predetermined condition is met includes comparing the predicted wind conditions with the wind speed threshold and / or the wind speed range; The predetermined condition is satisfied when the predicted wind conditions at a future time satisfy the wind speed threshold and / or are within the wind speed range. The method of claim 1.

10. obtaining the meteorological data includes obtaining a forecast of wind conditions for a future period; determining whether the predetermined condition is met includes determining a continuous period of time during which the predicted wind conditions are within the wind speed range; Determining whether the predetermined condition is satisfied further comprises: - estimating the amount of energy expected to be generated by the wind turbine (100) within said consecutive time periods; comparing the estimated amount of energy with a predetermined energy threshold greater than the amount of energy required to transition the operation of the wind turbine from the first operational mode (72) to the energy harvesting mode (74), wherein the condition is met if the estimated amount of energy meets or exceeds the predetermined energy threshold; and / or further comprising determining that the condition is met if the continuous period exceeds a predetermined duration threshold. Including, The method of claim 1.

11. the acquired environmental data is local to the location of the wind turbine (100) or the location of a group of wind turbines; the transition is performed individually for each wind turbine (100) or each wind turbine group based on the local environmental data for each wind turbine (100) or each wind turbine group. The method of claim 1.

12. If the wind turbine (100) is operating in the energy harvesting mode (74) and a second predetermined condition is met, the method includes transitioning operation of the wind turbine (100) to the first operating mode (72); obtaining the meteorological data includes obtaining a forecast of wind conditions for a future period; Determining whether the second predetermined condition is satisfied includes: - comparing the predicted wind conditions with the cut-out wind speed range; determining a second time period during which the predicted wind conditions are outside the cutout wind speed range; Including, If the wind turbine (100) is operating in the energy harvesting mode (74) and the second period of time is shorter than a maintenance period of time, operation of the wind turbine (100) is maintained in the energy harvesting mode (74) during the second period of time. The method of claim 1.

13. 1. A wind turbine control system configured to control a transition of operation of a wind turbine into an energy harvesting mode (74) in which the wind turbine (100) operates to generate electrical power from wind energy, the system comprising: an energy storage system (50) associated with the wind turbine (100) configured to supply power to the auxiliary system (10) when the wind turbine (100) is not generating or receiving enough power to power the auxiliary system (10); The control system (20) is configured to carry out the method according to any one of claims 1 to 12. Wind turbine control systems.

14. 1. A computer program for controlling operation of a wind turbine, comprising: an energy storage system (50) associated with the wind turbine (100) configured to supply power to the auxiliary system (10) when the wind turbine (100) is not generating or receiving enough power to power the auxiliary system (10); The computer program comprises control instructions which, when executed by a processing unit (26) of a control system (20) controlling operation of the wind turbine (100), cause the processing unit (26) to perform the method of any one of claims 1 to 12. Computer program.

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