Method for prioritization of power production in a power plant comprising wind turbine generators

Abstract

The invention relates to a method for controlling power production from a power plant (100) comprising a plurality of power production units. The method involves setting a maximum allowed power production (Pmax) for each power production unit in a selection of one or more power production units of a second priority (pl2) to a non-zero value, wherein the maximum allowed power production (Pmax) is determined depending on whether a first power production gap (Pgap1) is greater than or less than zero, and depending on a comparison of the first power production gap (Pgap1) with a second available power production capacity (Paval_pl2) of the selection of one or more power production units of the second priority (pl2).

Description

Technical Field

[0001] The present invention relates to the control of a power plant comprising multiple power output units, particularly a power plant having one or more wind turbines, and to the determination of priority power production in each power output unit of the power plant. Background Technology

[0002] In a power plant that comprises multiple power-generating units such as wind turbines and possibly photovoltaic solar panels, the plant operator or owner may have specific objectives and preferences for operating the power-generating units. For example, the owner may wish to increase the power production of some power-generating units while reducing the power production of others, for instance, in order to extend the lifespan or maintenance periods of some power-generating units by reducing the load inevitably caused by power production.

[0003] Therefore, a control method is needed that enables operators or owners to control the operation of power plants, for example, relative to wear and load of individual units, revenue and other power production-related parameters, and combinations thereof, such as revenue taking wear into account. Summary of the Invention

[0004] One object of the present invention is to improve the control of power plants to alleviate one or more of the aforementioned problems; therefore, a method is provided that provides improved control.

[0005] In a first aspect of the invention, a method is provided for controlling power output from a power plant comprising a plurality of power output units, each power output unit including at least one wind turbine generator, wherein the power plant is connected to a power grid for supplying electricity from the power output units to the grid, and the power plant can be controlled to produce power based on power plant benchmarks, the method comprising...

[0006] - Determine the first available power production capacity for the selection of one or more power production units with the highest priority.

[0007] - Determine the first power production gap as the difference between the power benchmark and the first available power production capacity.

[0008] - Determine whether the first power production gap is greater than or less than zero.

[0009] - Set the maximum permissible power production of each power production unit in the selection of one or more power production units of the second priority to a non-zero value, wherein the maximum permissible power production depends on whether the first power production gap is greater than or less than zero, and depends on a comparison of the first power production gap with the second available power production capacity of the selection of one or more power production units of the second priority.

[0010] Advantageously, by prioritizing the power production of power-producing units based on associated priority levels, operators of power-producing units can optimize power plant operations, for example, relative to wear and load, revenue, and other power production-related parameters of each unit, as well as combinations thereof, such as revenue taking wear into account.

[0011] The method may further include the steps of selecting one or more power output units of a first priority and selecting one or more power output units of a second priority.

[0012] In one embodiment, at least one, such as both, of the selections of first and second priority power output units each includes at least two power output units.

[0013] According to one embodiment, the setting of the maximum allowable power production for each of the one or more power production units of the second priority includes,

[0014] - If it is determined that the first power production gap is less than zero, the maximum allowable power production of the one or more power production units of the second priority is set according to the minimum power setpoint of the power production unit, where the minimum power setpoint represents the minimum possible power production setpoint of the power production unit.

[0015] According to one embodiment, the method includes selecting one or more power output units of a first priority and selecting one or more power output units of a second priority based on operating conditions of the power output units.

[0016] For example, operating conditions may involve load history, estimated or predetermined remaining lifespan, remaining time until the next maintenance, and / or other long-term conditions, i.e., conditions related to actual short-term conditions.

[0017] This choice can be made based on operating conditions, or on other factors such as the price of electricity per unit of power produced, or in combination with other factors.

[0018] Alternatively or additionally, this selection can also be arbitrarily made, for example, based on user preference. For instance, the operator of the power output unit can manually determine this selection.

[0019] According to one embodiment, the selection of the one or more power output units of the first and second priorities is maintained for different values ​​of the power plant reference or for changes in the power plant reference.

[0020] Advantageously, the prioritization of power production in power output units does not depend on power plant benchmarks, but rather focuses on optimizing long-term power production independent of variations in power plant benchmarks.

[0021] If the highest priority power-producing unit is capable of producing the required power, lower priority power-producing units can be paused. However, because wind speeds and incident solar energy are constantly changing, this pause can be changed to a release command at the next moment. These alternating changes between pauses when power production is zero and releases when power production is non-zero lead to increased wear and tear on the power-producing units. Advantageously, instead of simply pausing the power-producing units, the maximum permissible power production of one or more power-producing units is set to the minimum power setpoint for a given technology. Thus, power-producing units such as wind turbines are set to a power production mode, but limited to producing as little power as possible.

[0022] According to one embodiment, the setting of the maximum allowable power production for each of the one or more power production units of the second priority includes,

[0023] - If it is determined that the first power production gap is greater than zero and the second available power production capacity is less than the first power production gap, then the maximum allowable power production of the one or more power production units of the second priority is set according to the nominal power setpoint of the unit.

[0024] Advantageously, if the first priority power production unit is unable to produce the required power and the second available power production capacity is also insufficient, the maximum permissible power production of the lower priority power production unit is maximized to the nominal power value in order to maximize the power production of the second priority power production unit.

[0025] According to one embodiment, the setting of the maximum allowable power production Pmax for each of the one or more power production units of the second priority includes,

[0026] - If it is determined that the first power production gap is greater than zero and the second available power production is greater than the first power production gap, then the maximum allowable power production of the one or more power production units of the second priority is set according to the distribution of the first power production gap in the one or more power production units of the second priority.

[0027] Advantageously, if the first priority power production unit is unable to produce the required power, but the second available power production capacity is sufficient, the maximum allowable power production of the lower priority power production unit is set according to the distribution of the power production required for the remaining power, so that the lower priority power production unit produces the remaining required power, but not more, so as to allow the first priority power production unit to maintain the highest possible power production.

[0028] According to one embodiment, the distribution of the first power production gap is subject to a constraint that stipulates that the maximum permissible power production of any one of the one or more power production units of the second priority cannot be lower than the minimum power setpoint.

[0029] Advantageously, by ensuring that the distribution of power production gaps does not lead to the maximum permissible power production falling below the technical minimum power, any power production unit shutdown can be avoided.

[0030] According to one embodiment, the method further includes

[0031] - Determine the second power production gap as the difference between the first power production gap and the second available power production capacity.

[0032] - Determine whether the second power production gap is greater than or less than zero.

[0033] - Set the maximum permissible power production of each power production unit in the selection of one or more power production units of the third priority to a non-zero value, wherein the maximum permissible power production depends on whether the second power production gap is greater than or less than zero, and depends on the comparison of the second power production gap with the third available power production capacity of the selection of one or more power production units of the third priority.

[0034] Advantageously, by prioritizing the power production of power-producing units based on multiple associated priority levels, the operators of power-producing units are able to optimize the operation of power plants at multiple priority levels.

[0035] According to one embodiment, the setting of the maximum allowable power production for each of the one or more power production units of the third priority includes,

[0036] - If it is determined that the second power production gap is less than zero, then the maximum allowable power production of the one or more power production units of the third priority is set according to the minimum power setpoint of the power production unit, where the minimum power setpoint represents the minimum possible power production setpoint of the power production unit.

[0037] According to one embodiment, the setting of the maximum allowable power production for each of the one or more power production units of the third priority includes,

[0038] - If it is determined that the second power production gap is greater than zero and the third available power production capacity is less than the second power production gap, then the maximum allowable power production is set according to the nominal power setpoint of the one or more power production units of the third priority.

[0039] Advantageously, if the first and second priority power production units are unable to produce the required power, and the third available power production capacity is also insufficient, the maximum permissible power production of the lower priority power production units is maximized to the nominal power value in order to maximize the power production of the second priority power production units.

[0040] According to one embodiment, the setting of the maximum allowable power production for each of the one or more power production units of the third priority includes,

[0041] - If it is determined that the second power production gap is greater than zero and the third available power production is greater than the second power production gap, then the maximum allowable power production of the one or more power production units of the third priority is set according to the distribution of the second power production gap in the one or more power production units of the third priority.

[0042] Advantageously, if the first and second priority power production units are unable to produce the required power, but the third available power production capacity is sufficient, the maximum allowable power production of the lower priority power production units is set according to the distribution of the power production required for the remaining power, so that the lower priority power production units produce the remaining required power, but not more, so as to allow the first and second priority power production units to maintain the highest possible power production.

[0043] According to one embodiment, the distribution of the second power production gap is subject to a constraint that stipulates that the maximum permissible power production of any one of the power production units of the third priority cannot be lower than the minimum power setpoint.

[0044] According to one embodiment, the method includes operating power production units using the selection of one or more power production units of a first priority, the selection of one or more power production units of a second priority, and optionally the selection of one or more power production units of a third priority, such that the power production of the one or more power production units of the first priority is maximized under power plant references. Maximizing power production may include determining and scheduling power setpoints for each power production unit to the first priority power production unit.

[0045] According to one embodiment, the selection of one or more power output units with a first priority, the selection of one or more power output units with a second priority, and optionally the selection of one or more power output units with a third priority are predetermined. Advantageously, the priority level of the power output units can be determined based on known parameters such as remaining lifetime, load history, maintenance intervals, and other parameters related to power production.

[0046] According to one embodiment, in the event of a communication failure between the power plant controller and any power output unit, the method includes stopping the operation of the power output unit according to the method, wherein the power production of the one or more power output units of a first priority is subject to maximizing power plant benchmarks.

[0047] Advantageously, by ceasing the determination of maximum power production based on priority levels, any undue curtailment can be avoided. That is, whenever the central controller loses communication with any power production unit, the calculation of the maximal allowed power production value may become inaccurate, potentially leading to incorrect curtailment decisions from that function. With the priority-based procedure stopped, normal power production control can be invoked.

[0048] According to one embodiment, the method includes operating the power plant in a reduced mode, wherein the power reference is less than the nominal power plant power.

[0049] Based on the above implementation, the power plant's baseline, first, second, and optional third available power production capacity and maximum permissible power production represent the active power level.

[0050] A second aspect of the invention relates to a central controller for controlling power production in a power plant comprising a plurality of power output units, each power output unit including at least one wind turbine generator, wherein the power plant is connected to a power grid for supplying power from the power output units to the grid, wherein the central controller is arranged to determine a maximum permissible power production and control the power output units based on power plant references, and wherein the central controller is arranged to perform the method according to the first aspect.

[0051] A third aspect of the invention relates to a power plant comprising a plurality of power output units and a central controller according to a second aspect, wherein the power output units include at least one wind turbine generator.

[0052] The fourth aspect of the invention relates to a computer program article comprising software code adapted to control a power plant when executed on a data processing system, the computer program article being adapted to perform the method of the first aspect.

[0053] In general, aspects and embodiments of the present invention can be combined and coupled in any possible manner within the scope of the invention. These and other aspects, features, and / or advantages of the invention will become apparent and will be elucidated from the embodiments described below. Attached Figure Description

[0054] The embodiments of the present invention will be described by way of example only, with reference to the accompanying drawings, wherein...

[0055] Figure 1 This diagram shows a power plant that includes multiple power generation units and wind turbines.

[0056] Figure 2 An embodiment of a central controller for a power plant is shown, and

[0057] Figure 3 Flowcharts illustrating various embodiments of the present invention. Detailed Implementation

[0058] Figure 1 A power plant 100 is shown, comprising a plurality of power output units 101 such as wind turbines. The power plant 100 may be a renewable power plant comprising only renewable power output units. Generally, the power output units 101 may consist of different types of power output units, such as different types of renewable power output units, such as solar power output units 103 (e.g., photovoltaic solar panels) and wind turbines. According to one embodiment, at least one of the power output units 101 of the power plant 100 is a wind turbine. The power plant 100 may include at least three identical or different types of power output units 101, i.e., a mixture of different types of power output units. For example, the power plant 100 may consist only of wind turbines 102, in which case there are at least three wind turbines 102. In another embodiment, the power plant 100 includes at least two wind turbines 102 and at least one or two other power output units 101.

[0059] The power plant can be connected to a power grid (not shown) to supply power from the power generation unit 101 to the grid.

[0060] Power plant 100 is controlled by a central controller 110. The central controller 110 is configured to control power production from power output units 101 according to a power plant reference Pref, which defines the required electricity to be supplied from power plant 100 to the grid. Furthermore, the central controller is configured to schedule power setpoints Pset to the power output units, i.e., to schedule individual power setpoints for the required power production to each power output unit 101. The power setpoints Pset can be determined by the central controller 110 based on the power plant reference Pref, such that the sum of the power setpoints Pset corresponds to the power plant reference Pref.

[0061] The central controller 110 can also be configured to control the reactive power production of the power plant, grid frequency control, and / or other functions such as determining the maximum permissible power production value Pmax 190.

[0062] Throughout the description, the power reference is used for the power demand of the wind power plant, while the power setpoint is used for the power demand of each power output unit.

[0063] Therefore, the goal of the central controller 110, which consists of a central controller, is to ensure that the required power (e.g., from the transmission system operator (TSO)) is delivered as quickly as possible, which applies to both increases and decreases in the power plant baseline Pref.

[0064] The wind turbine 102 may include a tower and a rotor with at least one rotor blade (such as three blades). The rotor is connected to a nacelle mounted on top of the tower and is adapted to drive a generator located within the nacelle. The rotor is rotatable in the presence of wind. The rotational energy of the rotor blades caused by the wind is transferred to the generator via a shaft. Thus, the wind turbine is able to convert the kinetic energy of the wind into mechanical energy by means of the rotor blades, and subsequently into electrical energy by means of the generator. The generator may include a power converter for converting alternating current (AC) to direct current (DC) and a power inverter for converting DC to AC for injection into the power grid.

[0065] The generator of the wind turbine 102 or other power production unit 101 can be controlled to produce power corresponding to a power setpoint Pset provided by the central controller 110. For the wind turbine, the output power can be adjusted according to the power setpoint by adjusting the pitch of the rotor blades or by controlling the power converter to adjust power production. Similar adjustment possibilities exist for other power production units 101.

[0066] Here, any reference to power, such as the power plant reference Pref, the power setpoint Pset_i, the available power Paval_i, and other power values, can define active, reactive, or apparent power levels.

[0067] The available power Paval_i of the wind turbine 102 can be determined based on the current wind speed and other parameters limiting power production. For example, the available power Paval_i can be defined as the maximum possible power output of the wind turbine under given wind conditions. Therefore, the available power will approximate the power output of a power curve optimized according to the power of a specific turbine. The power curve used here is understood as a power curve optimized for the power factor (Cp) of a specific turbine. In other words, the power curve represents the maximum power output of the turbine under normal operation as a function of wind speed.

[0068] like Figure 1As shown, according to one embodiment, power output units 101 can be arranged as selections of one or more power output units 101 with different priorities. For example, power output units 101 can be arranged or grouped into selections of one or more power output units 101 with a first priority pl1, selections of one or more power output units 101 with a second priority pl2, and selections of power output units 101 with priorities optionally from three pl3 to optionally four pl4 or higher priority levels pln. In principle, each selection can include only one power output unit 101, such that the number of priorities is equal to the number of power output units 101.

[0069] Figure 2 An example is shown showing the arrangement of the central controller 110 and power output unit 101 in the selection of priorities pl1, pl2, pl3, although the power output units can be grouped into more priority levels.

[0070] The central controller 110 can be configured to dispatch a power setpoint Pset_i to each power output unit 101, wherein the power setpoint is used by the power controller of each power output unit, such as a wind turbine 102, to control power output based on the supplied power setpoint. The power setpoint Pset_i can be determined based on a power reference Pref and other possible input signals such as the available power Paval_i of each power output unit.

[0071] For wind turbine 102, the available power Paval_i is the power available from wind turbine 102 at a given time, calculated based on the current wind speed and other parameters limiting power production. For other power-generating units such as photovoltaic solar panels, the available power Paval_i can be determined based on the incident solar energy and the performance characteristics of the solar panels.

[0072] The central controller 110 is configured to determine the available power production capacity Paval_pl1, Paval_pl2, ... Paval_pln of selected power production units 101 with different priorities ranging from a first priority pl1 to one or more higher priorities pl2, ..., pln. The available power production capacity Paval_plx of a given selection of power production units 101 is determined based on the available power Paval_i of each power production unit, for example, by summing the available power Paval_i of units 101 in a given priority group pl1, ..., pln.

[0073] The central controller 110 is further configured to determine the maximum permissible power production value Pmax for each power production unit 101 selected from one or more of the power production units 101 of second or higher priority pl2, ..., pln. The maximum permissible power production value Pmax may be provided as individual power levels for each power production unit, or it may be a common power level for two or more power production units. For example, a maximum permissible power production value Pmax_pl2_i may be determined for each power production unit selected from the unit 101 of priority pl2. The maximum permissible power production value Pmax is determined based on the available power production capacity Paval_pl2, ..., Paval_pln of the selected power production units 101 of second or higher priority pl2, ..., pln, as described in detail elsewhere.

[0074] Power output unit 101 has an associated nominal power specification Pnom, which specifies the maximum power level that power output unit 101 is capable of producing, maximum power production limits, recommended power production limits, or other specifications of the nominal power setpoint Pnom. The nominal power setpoint Pnom can be provided as individual power levels for each power output unit, or it can be a common power level for two or more power output units.

[0075] The power production of each power production unit 101 can be constrained according to a minimum power setpoint Pmin. The minimum power setpoint Pmin can be provided as an individual power level for each power production unit, or it can be a common power level for two or more power production units. For the wind turbine 102, the minimum power setpoint Pmin can be given from the power production specification; that is, the minimum power setpoint is defined by a minimum power production capacity or other defined minimum power limit such as a user-defined power limit. For the solar panel, the minimum power setpoint can be defined according to the solar panel's specification. Therefore, the minimum power setpoint Pmin represents the minimum possible power production setpoint of the power production unit 101.

[0076] Therefore, the maximum allowable power production specification Pmax of the power production unit 101 can be set at least to the nominal power setpoint Pnom and the minimum power setpoint Pmin.

[0077] The selection of power output units 101 with first, second, and / or higher priorities pl1, pl2, ..., pln can be predetermined or based on rules. For example, the prioritization of power output units can be based on load history, estimated or planned remaining lifespan, remaining time until the next maintenance, and the electricity price per unit of power produced, including combinations thereof. For instance, some power output units with high cumulative loads but relatively long time until the next maintenance can be given low priority to limit additional load. Power output units with lower planned remaining lifespans but otherwise satisfactory performance can be given high priority. Power output units with high electricity prices can be given high priority to maximize operating revenue.

[0078] The selection can be maintained as long as changes in the conditions used to determine the selection (such as remaining lifetime or any other conditions mentioned above) do not lead to a change in the selection of the power production units, i.e., different priorities are assigned. Alternatively, if the selection is predetermined, for example, determined by the operator, the selection can be maintained as long as necessary. Therefore, the selection can be maintained regardless of the power plant baseline or the power produced by the power production units.

[0079] Priority levels pl1, ..., pln prioritize each power-producing unit relative to its active power production. Therefore, the power production of one or more power-producing units 101 of first priority pl1 takes precedence over lower priority pl2, ..., pln. For example, the power output of the power-producing units of first priority pl1 can be constrained by maximizing the power plant reference Pref, i.e., controlling them to produce as much power as possible, while lower priority power-producing units are controlled to produce surplus power that might not be produced by the first priority units by reducing or suspending these lower priority units. Therefore, one or more power-producing units 101 of first priority pl1 can be operated to produce maximum power up to the power plant reference Pref.

[0080] Additionally, the priority associated with the selection of power output units can be used to prioritize the release and suspension of power output units 101, such as wind turbine 102, during operation determined according to priorities pl1, ... pln, based on the maximum permissible power production Pmax. Thus, if necessary, the power output unit 101 selected with the highest priority, i.e., the unit 101 with the first priority pl1, can be released first and suspended last. Conversely, if necessary, the power output unit 101 selected with the lowest priority, such as the unit 101 with the third priority pl3, can be released last and suspended first.

[0081] Power plant 100 is characterized by its nominal plant power Pplantnom, i.e., its nominal power production capacity. Power plant 100 can operate in a reduced-capacity mode, where the power reference Pref is less than the nominal plant power Pplantnom.

[0082] Figure 3 Various embodiments of the present invention are shown:

[0083] In step 300, it is initially determined whether there is a communication failure in the communication between the power plant controller 110 and any power output unit 101.

[0084] In step 301, if a communication failure occurs, the operation of the power production unit 101 is stopped so that the power production of the power production unit 101 of the first priority pl1 is maximized by the power plant reference Pref.

[0085] In step 302, if there is no communication failure, the power output unit of the first priority pl1 is controlled to produce as much power as possible up to the power plant reference Pref.

[0086] Further in step 302, the first available power production capacity Paval_pl1 of the power production unit selected for the first priority pl1 is determined. Additionally, the first power production gap Pgap1 is determined as the difference between the power reference Pref and the first available power production capacity Paval_pl1, i.e., Pref - Paval_pl1.

[0087] In step 303, it is determined whether the first power production gap Pgap1 is greater than or less than zero. For ease of explanation and simplicity, the case where Pgap equals zero is included in the "greater than" or "less than" decision.

[0088] In step 304, if it is determined that the first power production gap Pgap1 is less than zero, or less than or equal to zero, meaning that the power production unit of the first priority pl1 is fully capable of producing power according to the power plant reference Pref, then the maximum allowable power production Pmax of the one or more power production units 101 of the second priority pl2 is set as the minimum power setpoint Pmin, that is, the minimum power setpoint Pmin associated with each power production unit, wherein the setpoint Pmin may be different for different power production units.

[0089] Further in step 304, if there are power output units 101 with priorities lower than the second priority pl2, such as the third and fourth priorities pl3, pl4, the maximum allowable power output Pmax of these lower priority power output units 101 is also set as the minimum power setpoint Pmin.

[0090] In step 305, it is determined that if the first power production gap Pgap1 is greater than zero and the second available power production capacity Paval_pl2 is less than the first power production gap Pgap1, that is, Paval_pl2 < Pgap1, it means that the available power selected by the second priority is not sufficient to meet the remaining power demand.

[0091] In step 306, if step 305 is answered as yes, the maximum allowable power production Pmax of the power output unit 101 with the second priority pl2 is set to the nominal power set point Pnom to allow the power output unit with the second priority to produce as much power as possible. Similarly, different power output units may have different nominal power set points.

[0092] In step 307, if step 305 is answered as no, since the second available power production capacity Paval_pl2 is greater than the first power production gap Pgap1, which means that the available power production capacity selected by the second priority is sufficient to meet the remaining power demand, the maximum allowable power production Pmax of the power output unit 101 with the second priority pl2 is set according to the distribution of the first power production gap Pgap1 among the power output units 101 with the second priority pl2. For example, Pgap1 can be evenly divided among the power output units with the second priority. In another embodiment, the first power gap Pgap1 can be distributed depending on the available power production capacity Paval_i of each power output unit, for example, according to the relationship between the available power production capacity of different power output units with the second priority pl2 and the first power gap Pgap1, for example, determined according to the ratio Paval_i / Pgap1. Thus, the power output unit 101 with the highest available power production capacity Paval_pl2 can be provided with a higher power production level Pmax than the power output unit 101 with the lowest available power production capacity Paval_pl2. The embodiments of distributing the first power gap Pgap1 are equivalently applicable to the distribution of other power gaps Pgap2,...Pgapn.

[0093] The distribution of the first power production gap Pgap1 among the power output units 101 may imply in some cases that the Pmax of one or more of the power output units is set to a value lower than Pmin, which is not desirable. To avoid this situation, the distribution of the first power production gap Pgap1 can be performed such that the maximum allowable power production Pmax of any one of the one or more power output units 101 with the second priority pl2 cannot be less than the minimum power set point Pmin.

[0094] Therefore, generally, steps 302-307 provide a method in which, for each power production unit in the selection of one or more power production units 101 of the second priority pl2, the maximum permissible power production Pmax is set to a non-zero value, wherein the maximum permissible power production Pmax depends on whether the first power production gap Pgap1 is greater than or less than zero and depends on a comparison of the first power production gap Pgap1 with the second available power production capacity Paval_pl2 of the selection of the one or more power production units 101 of the second priority pl2.

[0095] In the case of selecting a power production unit including the third priority pl3 in power plant 100, the second power production gap Pgap2 is determined as the difference between the first power production gap Pgap1 and the second available power production capacity Paval_pl2, and it is determined whether the second power production gap Pgap2 is greater than or less than zero.

[0096] If the second power production gap Pgap2 is determined to be less than zero, then the maximum permissible power production Pmax of the one or more power production units 101 of the third priority pl3 is determined according to their minimum power setpoint Pmin. This follows the example in step 304 when there is a selection of power production units with a priority lower than pl2 and Pgap 1 is less than zero. Therefore, in this case, the determination of the second power production gap Pgap2 is unnecessary because if Pgap1 < 0, then Pgap2 < 0 if this is followed.

[0097] Further in step 306, when the power plant 100 includes the selection of power production units of the third priority pl3, since the available power Paval_pl2 of the power production units of the second priority pl2 is insufficient to meet the first power production gap Pgap1, the determined second power production gap Pgap2 will be greater than zero.

[0098] Further in step 306, if it is determined that the third available power production capacity Paval_pl3 is less than the second power production gap Pgap2, it means that the available power production capacity of the third priority selection pl3 is insufficient to meet the remaining power demand, and the maximum allowable power production Pmax of the one or more power production units 101 of the third priority pl3 is set as the nominal power setpoint Pnom.

[0099] Further in step 306, if it is determined that the third available power production capacity Paval_pl3 is greater than the second power production gap Pgap2, it means that the available power production capacity of the third priority pl3 is sufficient to meet the remaining power demand. The maximum allowable power production Pmax of the one or more power production units 101 of the third priority pl3 is determined according to the distribution of the second power production gap Pgap2 in the one or more power production units 101 of the third priority pl3.

[0100] Further in step 307, when the power plant 100 includes the selection of power production units of the third priority pl3, since the available power Paval_pl2 of the power production units of the second priority pl2 is sufficient to satisfy the first power production gap Pgap1, the determined second power production gap Pgap2 will be less than zero. Then, the maximum allowable power production Pmax of the one or more power production units 101 of the third priority pl3 is set according to its minimum power setpoint Pmin.

[0101] In the case of selecting a power production unit 101 with priority pl4 or higher up to pln in the wind turbine park, the determination of the maximum allowable power production Pmax follows the principles described above.

[0102] Therefore, in general, when the power production unit includes the selection of a power production unit with a third priority pl3 or lower priority, the above-described principle for determining the maximum permissible power production Pmax provides a method in which, for each power production unit 101 selected from one or more power production units 101 with a third priority pl3 or lower priority pl4, ..., pln, the maximum permissible power production Pmax is set to a non-zero value, wherein the maximum permissible power production Pmax depends on whether the relevant power production gap Pgap2, ..., Pgapn is greater than or less than zero and is determined by comparing the power production gap with the available power production capacity Paval_pl3, ..., Paval_pln of the selection of the one or more power production units.

[0103] The central controller can be configured such that the maximum allowable power production value Pmax of one or more of the power production units can be set according to other user preferences, or according to the maximum allowable power production value Pmax determined by the user, regardless of the priority pl1, ..., pln associated with the power production unit of interest.

[0104] Although the invention has been described in conjunction with specific embodiments, it should not be construed as being limited in any way to the presented embodiments. The scope of the invention should be interpreted in accordance with the appended set of claims. In the context of the claims, the terms "comprising" or "comprises" do not exclude other possible elements or steps. Furthermore, references such as "a" or "an" should not be construed as excluding multiple elements. The use of reference numerals for elements shown in the figures in the claims should also not be construed as limiting the scope of the invention. Moreover, individual features mentioned in different claims may be advantageously combined, and mentioning these features in different claims does not preclude the possibility and advantage of combining features.

Claims

1. A method for controlling power production from a power plant (100), the power plant comprising a plurality of power production units (101), the power production units comprising at least one wind turbine generator, the power plant being connected to an electrical grid for supplying electrical power from the power production units to the electrical grid, and wherein the power plant is controllable to produce power depending on a power plant reference (Pref), - determining a first available power production capability (Paval_pl1) of a selection of one or more power production units (101) of a first priority (pl1), - determining a first power production gap (Pgap1) as a difference between the power plant reference (Pref) and the first available power production capability (Paval_pl1), - determining whether the first power production gap (Pgap1) is greater or less than zero, - setting a maximum allowed power production (Pmax) of each power production unit in a selection of one or more power production units (101) of a second priority (pl2) to a non-zero value, wherein the maximum allowed power production (Pmax) is determined depending on whether the first power production gap (Pgap1) is greater or less than zero, and depending on a comparison of the first power production gap (Pgap1) with a second available power production capability (Paval_pl2) of the selection of the one or more power production units (101) of the second priority (pl2), wherein the method further comprises maintaining the selection of the one or more power production units of the first and second priority for different values of the power plant reference or for changes in the power plant reference.

2. The method according to claim 1, wherein the setting of the maximum allowed power production (Pmax) of each of the one or more power production units (101) of the second priority (pl2) comprises, - if it is determined that the first power production gap (Pgap1) is less than zero, setting the maximum allowed power production (Pmax) of the one or more power production units (101) of the second priority (pl2) in accordance with a minimum power set point (Pmin) of the one or more power production units (101) of the second priority (pl2), wherein the minimum power set point represents a minimum possible power production set point of the power production unit.

3. The method according to claim 1 or 2, further comprising selecting the one or more power production units of the first priority and selecting the one or more power production units of the second priority based on operating conditions of the power production units.

4. The method according to claim 1 or 2, wherein the setting of the maximum allowed power production (Pmax) of each of the one or more power production units (101) of the second priority (pl2) comprises, - if it is determined that the first power production gap (Pgap1) is greater than zero, and the second available power production capability (Paval_pl2) is less than the first power production gap (Pgap1), setting the maximum allowed power production (Pmax) of the one or more power production units (101) of the second priority (pl2) in accordance with a nominal power set point (Pnom) of the one or more power production units (101) of the second priority (pl2).

5. The method according to claim 1 or 2, wherein the setting of the maximum allowed power production (Pmax) of each of the one or more power production units (101) of the second priority (pl2) comprises, - setting the maximum allowed power production (Pmax) of the one or more power production units (101) of the second priority (pl2) according to a distribution of the first power production gap (Pgap1) among the one or more power production units (101) of the second priority (pl2) if it is determined that the first power production gap (Pgap1) is greater than zero and the second available power production capability (Paval_pl2) is greater than the first power production gap (Pgap1).

6. The method according to claim 5, wherein the distribution of the first power production gap (Pgap1) is subject to a constraint that the maximum allowed power production (Pmax) of any of the one or more power production units (101) of the second priority (pl2) cannot be less than a minimum power setpoint (Pmin).

7. The method according to claim 1 or 2, further comprising - determining a second power production gap (Pgap2) as a difference between the first power production gap (Pgap1) and the second available power production capability (Paval_pl2), - determining whether the second power production gap (Pgap2) is greater than or less than zero, - setting the maximum allowed power production (Pmax) of each power production unit in the selection of one or more power production units (101) of a third priority (pl3) to a non-zero value, wherein the maximum allowed power production (Pmax) is determined depending on whether the second power production gap (Pgap2) is greater than or less than zero and depending on a comparison of the second power production gap (Pgap2) with a third available power production capability (Paval_pl3) of the selection of the one or more power production units (101) of the third priority (pl3).

8. The method according to claim 7, wherein the setting of the maximum allowed power production (Pmax) of each of the one or more power production units (101) of the third priority (pl3) comprises, - setting the maximum allowed power production (Pmax) of the one or more power production units (101) of the third priority (pl3) according to a minimum power setpoint (Pmin) of the one or more power production units (101) of the third priority (pl3) if it is determined that the second power production gap (Pgap2) is less than zero, wherein the minimum power setpoint represents a minimum possible power production setpoint of a power production unit.

9. The method according to claim 7, wherein the setting of the maximum allowed power production (Pmax) of each of the one or more power production units (101) of the third priority (pl3) comprises, - if it is determined that the second power production gap (Pgap2) is greater than zero and the third available power production (Paval_pl3) is less than the second power production gap (Pgap2), then the maximum allowed power production (Pmax) of the one or more power production units (101) according to the third priority (pl3) is set according to the nominal power set point (Pnom) of the one or more power production units (101) according to the third priority (pl3).

10. The method according to claim 7, wherein the setting of the maximum allowed power production (Pmax) of each of the one or more power production units (101) according to the third priority (pl3) comprises, - if it is determined that the second power production gap (Pgap2) is greater than zero and the third available power production capability (Paval_pl3) is greater than the second power production gap (Pgap2), then the maximum allowed power production (Pmax) of the one or more power production units (101) according to the third priority (pl3) is set according to a distribution of the second power production gap (Pgap2) among the one or more power production units (101) according to the third priority (pl3).

11. The method according to claim 10, wherein the distribution of the second power production gap (Pgap2) is subject to a constraint that the maximum allowed power production (Pmax) of any of the one or more power production units (101) according to the third priority (pl3) cannot be less than a minimum power set point (Pmin).

12. The method according to claim 1 or 2, comprising operating the power production units with the selection of the one or more power production units (101) according to the first priority (pl1), the selection of the one or more power production units (101) according to the second priority (pl2), and optionally the selection of the one or more power production units (101) according to the third priority (pl3), such that the power production of the one or more power production units (101) according to the first priority (pl1) is subject to the power plant reference (Pref) being maximized.

13. The method according to claim 1 or 2, wherein the selection of the one or more power production units (101) according to the first priority (pl1), the selection of the one or more power production units (101) according to the second priority (pl2), and optionally the selection of the one or more power production units (101) according to the third priority (pl3) are predetermined selections.

14. The method according to claim 1 or 2, in case of a communication failure between the power plant controller (110) and any of the power production units, stopping operating the power production units according to the method, wherein the power production of the one or more power production units (101) according to the first priority (pl1) is subject to the power plant reference (Pref) being maximized.

15. The method according to claim 1 or 2, comprising operating the power plant in a curtailment mode in which the power plant reference (Pref) is less than the nominal plant power (Pplantnom).

16. A central controller (110) for controlling power production of a power plant (100), the power plant comprising a plurality of power production units (101), the power production units comprising at least one wind turbine generator, wherein the power plant is connected to an electrical grid for supplying electrical power from the power production units to the electrical grid, and wherein the central controller is arranged for determining a maximum allowed power production (Pmax) and for controlling the power production units (101) in accordance with a power plant reference (Pref), and the central controller is arranged for performing the method according to any of claims 1-14.

17. A power plant (100) comprising a plurality of power production units (101), the power production units comprising at least one wind turbine generator, and a central controller (110) according to claim 16.

18. A computer program product comprising software code adapted to control a power plant (100) when executed on a data processing system, the computer program product being adapted to perform the method of any of claims 1-15.

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