Method and system for controlling power plant during network frequency fluctuations

Abstract

A method (300) and a corresponding controller (100) for controlling a power plant, such as a wind power plant (12), comprising at least one generator (14). The power plant (12) has a variable available power output due, at least in part, to variability of the energy source powering the at least one generator (14). The method (300) includes receiving (302) a measurement frequency of a power network (16) to which the power plant (12) is connected, and determining (304) whether the measurement frequency falls within a first frequency sub-band (54, 56, 58, 60) that overlaps a frequency dead zone (52) defined by the network. Outputting (306) a first control signal based at least in part on the measured frequency, the first control signal indicating: a first power offset applied to a baseline frequency profile of the power plant (12) to generate a setpoint for controlling a power characteristic of the power plant (12); or a setpoint for controlling a power characteristic of the power plant (12), the setpoint being based on a first power offset applied to a baseline frequency curve of the power plant. The baseline frequency profile may be offset from and vary with the available power output.

Description

Technical Field

[0001] The present disclosure relates to methods and systems for regulating the power output of a power plant. Background Art

[0002] Regulators and operators of electricity networks expect connected power plants to comply with a "grid code" and provide specific services to the electricity network.

[0003] For example, some operators require power plants to support the power network when the measured frequency of the power network deviates from the normal operating range or the permitted range (also known as the frequency emergency dead zone).

[0004] Power plants that employ generators that rely on variable energy sources, such as wind turbines or solar panels, may face particular challenges in providing such support. For example, the potential power output of such power plants varies in unpredictable ways.

[0005] It is an object of the present invention to address one or more of the disadvantages associated with the prior art. Summary of the invention

[0006] According to a first aspect, there is provided a method of controlling a power plant, the power plant comprising at least one generator, the power plant having a variable available power output due at least in part to variability of an energy source powering the at least one generator, the method comprising:

[0007] receiving the measured frequency of the electricity network to which the power plant is connected;

[0008] determining whether the measurement frequency falls within a first frequency sub-band, the first frequency sub-band overlapping a frequency dead zone defined by the network; and

[0009] In response to the measured frequency falling within the first frequency sub-band and based at least in part on the measured frequency, outputting a first control signal, the first control signal indicating:

[0010] a first power offset applied to a baseline (reference) frequency curve of the power plant to generate a set point for controlling a power characteristic of the power plant; or

[0011] A set point for controlling a power characteristic of a power plant is provided, the set point being based on a first power offset applied to a baseline frequency curve of the power plant.

[0012] 2022P00023WOCN(JAJNN)

[0013] This approach can help power plants that experience variable power output due to energy variability to better provide frequency support services.

[0014] Optionally, the position of the baseline frequency curve on the power axis varies at least in part depending on the available power output of the power plant. For example, the baseline frequency curve may maintain its general shape but shift in a positive or negative direction on the power axis as available power increases or decreases, respectively.

[0015] For example, the baseline frequency curve may be a power-frequency ("Pf") curve of the type known to skilled artisans.

[0016] The first frequency sub-band may be bounded by a first frequency and a second frequency, wherein:

[0017] The first frequency is lower than the second frequency;

[0018] The second frequency is less than or equal to the nominal frequency of the electricity network; and

[0019] The first power offset is a positive value.

[0020] Optionally, when the first power offset is a positive value, the baseline frequency curve may be further deviated from the available power output. For example, where the first frequency sub-band is below the nominal frequency of the power network, such that the first power offset is intended to provide frequency support in the form of increased power in response to the measured frequency falling within the first frequency sub-band, it may be desirable to first implement an additional baseline offset in the form of increased spinning reserve to ensure that sufficient spinning reserve is available to provide the first power offset when required.

[0021] The value of the first power offset at the second frequency may be zero, resulting in a stepless transition of the set point as the measurement frequency decreases below the second frequency.

[0022] As the measured network frequency decreases from the second frequency toward the first frequency, the first power offset will:

[0023] In a first frequency range, the value increases; and

[0024] In a second frequency range lower than the first frequency range, the frequency is kept constant or increases at a lower rate.

[0025] The first frequency range may be continuous with the second frequency range, and the first frequency range and the second frequency range may cover the entire first frequency sub-band.

[0026] The method may include:

[0027] determining whether the measurement frequency falls within a second frequency sub-band, the second frequency sub-band overlapping a frequency dead zone defined by the network; and

[0028] In response to the measured frequency falling within the second sub-band and based at least in part on the measured frequency, outputting the 2022P00023WOCN(JAJNN)

[0029] Second control signal, the second control signal indicates:

[0030] a second power offset applied to a baseline frequency curve of the power plant to generate a set point for controlling a power characteristic of the power plant; or

[0031] A set point for controlling a power characteristic of the power plant is based on a second power offset applied to a baseline frequency curve of the power plant.

[0032] The second sub-band may be defined by a third frequency and a fourth frequency, wherein:

[0033] The third frequency is lower than the fourth frequency;

[0034] The third frequency is higher than or equal to the nominal frequency of the electricity network; and

[0035] The second power offset is a negative value.

[0036] The value of the second power offset at the third frequency may be zero, so that the setpoint transitions steplessly as the measurement frequency rises above the third frequency.

[0037] As the measured network frequency increases above the third frequency toward the fourth frequency, the first power offset may be:

[0038] In the third frequency range, the value decreases; and

[0039] In a fourth frequency range higher than the third frequency range, the rate is kept constant or decreased at a lower rate.

[0040] The third frequency range may be continuous with the fourth frequency range, and the third frequency range and the fourth frequency range may cover the entire second sub-band.

[0041] The method may include, in response to the measurement frequency falling within the further sub-band and based at least in part on the measurement frequency, outputting a further control signal indicating:

[0042] an additional power offset which is applied to a baseline frequency curve of the power plant to generate a set point for controlling a power characteristic of the power plant; or

[0043] a set point for controlling a power characteristic of the power plant, the set point being based on an additional power offset applied to a baseline frequency curve of the power plant;

[0044] Therein, the additional frequency sub-band does not overlap with a network defined frequency dead zone or any other sub-band.

[0045] According to a second aspect, there is provided a method of controlling a power plant, the method comprising:

[0046] The method of the first aspect is implemented if and only if the measurement frequency falls within the subband for determining that the frequency support mode is in the running state.

[0047] The method may include, at the beginning of the period in which the frequency support mode is determined to be in operation, curtailing the power output of the power plant to provide sufficient additional spinning reserve to support the application of the baseline frequency support mode to the base frequency support mode.

[0048] The maximum value of any power offset on the line.

[0049] Optionally, the amount by which power output of the power plant is curtailed is reduced based at least in part on an amount of power available via a short term overproduction mode of one or more generators of the power plant.

[0050] According to a third aspect, there is provided a power plant controller configured to perform the method of the first aspect or the second aspect.

[0051] According to a fourth aspect, a computer-readable storage medium is provided, the computer-readable storage medium comprising instructions, which, when executed by a computer, cause the computer to execute the above method.

[0052] Within the scope of the present invention, the various aspects, embodiments, examples and alternatives listed in the preceding paragraphs, claims and / or the following description and drawings, in particular their individual features, may be used independently or in any combination. That is, all embodiments and / or features of any embodiment may be combined in any manner and / or combination unless these features are incompatible. The applicant reserves the right to amend any originally filed claim or to submit any new claim accordingly, including the right to amend any originally filed claim to be subordinate to any other claim and / or to include any features of any other claim, even though the claim was not originally made in this manner. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] One or more embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0054] Figure 1 schematically shows an electric power network connected to a wind power plant including a power plant controller;

[0055] Figure 2 Shows Figure 1 A system diagram of a control module of a power plant controller according to an embodiment of the present invention;

[0056] Figure 3 Shows Figure 2 Example Pf curve of the control module;

[0057] Figure 4 An example of dividing the frequency emergency dead zone into several sub-bands is shown;

[0058] Figure 5 The baseline Pf curve is shown;

[0059] Figure 6 The Pf offset curve is shown;

[0060] Figure 7 Shows the Figure 6 Output Pf curve of Pf offset curve;

[0061] Figure 8 Another Pf shift curve is shown;

[0062] Fig. 9 Shows the Figure 8 Output Pf curve of Pf offset curve;

[0063] Fig.10 shows an output Pf curve based on another Pf offset curve;

[0064] 2022P00023WOCN(JAJNN)

[0065] Fig.11 Another Pf shift curve is shown;

[0066] Fig.12 Shows the Fig.11 An output Pf curve of another Pf offset curve;

[0067] Fig.13 Another Pf shift curve is shown;

[0068] Fig.14 Shows the Fig.13 An output Pf curve of another Pf offset curve;

[0069] Fig.15 and Fig.16 Additional Pf shift curves are shown;

[0070] Fig.17 A method of controlling a power plant is shown;

[0071] Fig.18 and Fig.19 Additional output Pf curves are shown; and

[0072] Fig. 20The functional components of a power plant controller are shown. DETAILED DESCRIPTION

[0073] Generally speaking, the present invention relates to methods and systems for controlling the power characteristics of a power plant that employs at least one generator that relies on a variable energy source.

[0074] Such generators may include renewable energy generators such as wind turbines, photovoltaic panels, concentrated solar thermal plants, wave generators, etc. The potential power output of such power plants varies in an unpredictable manner, especially in the short term (e.g., within a period of seconds or minutes). The term "power characteristics" encompasses characteristics including real power output, reactive power output, and / or voltage level.

[0075] The present disclosure relates to methods and systems for providing such control within one or more frequency sub-bands that fall within an acceptable or permitted frequency range, referred to as a frequency emergency dead zone. In this context, a frequency emergency dead zone is defined as a frequency range defined by a grid operator. The corresponding grid code (i.e., the network operating rules established by the grid operator) requires all power plant operators to modify the operation of their power plants when the grid frequency exceeds the emergency dead zone.

[0076] For example, if the frequency exceeds the emergency dead zone, power plant operators need to reduce the output of their power plants, and in extreme overfrequency conditions, may even need to shut down one or more power plants. Conversely, if the frequency is below the emergency dead zone, power plant operators must increase the power output of their power plants, depending on the ability of each power plant to actually increase their output. The deviation of the grid frequency outside the frequency emergency dead zone indicates that the power network is under great pressure due to the imbalance between power load and power supply.

[0077] In the event of such frequency deviation, the electricity network operator may require the generator to take certain actions. For example, if the network frequency drops below the frequency emergency dead zone, the generator may be required to provide support to the network, for example by increasing the power output of one or more power plants. Alternatively, as 2022P00023WOCN(JAJNN)

[0078] If the network frequency exceeds the frequency emergency dead band, generators may be required to support the network, for example by reducing the power output of one or more power plants.

[0079] Even if the network frequency remains within the frequency emergency dead zone, power plant operators can support the network by increasing or decreasing the power output of their power plants based on the deviation of the current frequency from the network's nominal operating frequency.

[0080] Power plants that rely on controllable energy sources, such as gas or coal, can provide this support by selectively turning down or up their power output as needed. Power plants that rely on variable energy sources are generally less controllable. This is especially true in terms of absolute power output due to the variability of their energy sources.

[0081] The present disclosure relates to methods and systems for controlling a power plant including at least one generator. The power plant has a variable available power output due at least in part to the variability of an energy source that powers the at least one generator. A determination is made as to whether a measured frequency of a power network to which the power plant is connected is within a frequency sub-band that overlaps a frequency dead zone defined by the network. If the frequency falls within the frequency sub-band, and based at least in part on the measured frequency, a first control signal is output.

[0082] The first control signal may indicate a first power offset that may be applied to a baseline frequency curve (such as a Pf curve) of the power plant to generate a set point for controlling a power characteristic of the power plant.

[0083] Alternatively, the first control signal may be indicative of a set point for controlling a power characteristic of the power plant, the set point being based on a first power offset applied to a baseline frequency curve of the power plant.

[0084] In either case, the position of the baseline frequency curve on the power axis may vary at least in part based on the available power output of the power plant. For example, when wind speed decreases, the available power output will correspondingly decrease. Thus, the baseline frequency curve will be negatively offset on the power axis.

[0085] The position of the baseline frequency curve on the power axis can also change based on a request from the grid operator. For example, the grid operator might issue a request for a power plant to cut its output to 50% of the currently possible power (e.g. given the current wind speed), in which case power output would be reduced accordingly.

[0086] According to implementation conditions, several frequency sub-bands overlapping the frequency emergency dead zone may be used, and the first control signal may be outputted according to which sub-band the measured frequency falls into.

[0087] Figure 1 An example architecture is illustrated in which a power plant generating electricity based at least in part on variable energy generators is connected to a main grid or wider electricity network.

[0088] exist Figure 1 In the example shown, the power plant is a wind power plant (WPP). As the skilled person will appreciate, a WPP comprises at least one wind turbine generator (WTG) and is also referred to as a wind farm 2022P00023WOCN(JAJNN)

[0089] Or a wind farm. A WTG is often referred to as a "wind turbine". The examples shown are representative only, and the skilled person will appreciate that other specific architectures are possible. In other embodiments, a power plant may include one or more different types of generators, including those that generate electricity based on variable energy sources as described above.

[0090] In other embodiments, the power plant may take the form of a hybrid power plant having a combination of different types of power plants, optionally including one or more generators and / or energy sources with controllable power output (i.e., not unpredictably variable), such as gas or coal-fired turbines, battery energy storage, pumped hydro storage, etc.

[0091] The present invention thus relates to any power plant having at least one generator for generating electricity from a variable energy source and is not specific to Figure 1 Wind power plants and generators in the field.

[0092] The components of wind power plants and power grids are conventional and therefore familiar to the skilled person. Figure 1 It is contemplated that other known components may be incorporated in addition to or in place of the components shown and described. Such variations are well within the capabilities of the skilled artisan.

[0093] Figure 1 An electric power system 10 is shown incorporating a WPP 12. In this example, the WPP 12 includes a plurality of WTGs 14 and a power plant controller 22 (hereinafter referred to as PPC 22). Each of the plurality of WTGs 14 converts wind energy into electrical energy, which is transferred from the WPP 12 to a main power network or "main grid" 16 for distribution as active power and / or current.

[0094] Although Figure 1 Although not shown in the figure, the WPP 12 may also include compensation equipment, such as a static synchronous compensator (STATCOM) or other types of synchronous compensators, which are configured to provide reactive power or reactive current support as needed. The WPP 12 may also include a battery energy storage system.

[0095] Each of the WTGs 14 is associated with a respective WTG controller 15. In other embodiments, a group of WTGs may share a semi-centralized WTG controller, so that the number of WTG controllers is less than the WTGs. As will be appreciated by the skilled person, the WTG controller 15 may be viewed as a computer system capable of operating the WTG 14 in the manner specified herein, and may include a plurality of modules that control the various components of the WTG, or may include only one controller. The computer system of the WTG controller 15 may operate according to software downloaded via a communications network or software programmed thereon via a computer-readable storage medium.

[0096] During normal operation of the WPP 12, the WTG controller 15 operates to implement the active and reactive current and / or power set points received from the PPC 22, thereby providing frequency and voltage support to the main grid 16. In special circumstances (such as the grid frequency deviating from the emergency dead zone), the WTG controller 15 operates to 2022P00023WOCN(JAJNN)

[0097] The predetermined network requirements are met. The WTG controller 15 can also protect the WTG 14 from any potentially harmful conditions, such as overspeed conditions in high winds.

[0098] The WPP 12 also includes a connection network 18 for connecting the WPP 12 to a main grid 16 (also referred to as a main power network). In this example, the WPP 12 and the main grid 16 are connected at a point of interconnection (PoI) 20, which is an interface between the WPP 12 and the main grid 16. The PoI 20 may also be referred to as a point of common coupling, which may be abbreviated as "PCC" or "PoCC".

[0099] A power plant controller (PPC) 22 is connected to the main grid 16 at a point of measurement (PoM) 24 and to the WTG controller 15. For example, the PPC 22 may be configured to receive one or more measurement signals from the PoM 24, which may include measurement values ​​of the power supply from the WPP 12 to the main grid 16 and / or a frequency level of the main grid 16. The role of the PPC 22 is to act as a command and control interface between the WPP 12 and the grid 16, more specifically, between the WPP 12 and a grid operator 26, such as a transmission system operator (TSO) or a distribution system operator (DSO). The WPP 12 is able to change its power or current output according to the set point received from the PPC 22.

[0100] like Figure 1 As shown, the PPC 22 is a suitable computer system for executing the controls and commands described herein and thus may incorporate a processing module 28 , a connection module 30 , a storage module 32 , and a sensing module 34 .

[0101] The connection module 30 , storage module 32 , and / or sensing module 34 are configured to provide information indicative of a frequency level of the main grid 16 and a power level, current level, and / or voltage level of the WTG 14 and / or WPP 12 to the processing module 28 .

[0102] For example, the sensing module 34 may receive such information directly from one or more connected sensors, such as sensors at the PoM 24, and transmit the information to the processing module 28. Alternatively or additionally, the information may be determined by one or more systems connected to the connection module 30, such as the WTG controller 15, and transmitted to the processing module 28 via the connection module 30. In each case, the determined information may be permanently or temporarily stored in the storage module 32, and the processing module 28 may call up the information from the storage module 32 as needed. The PPC 22 may also receive information about the grid 16 and / or local buses, substations, and networks from an energy management system (not shown).

[0103] As part of its operation, the PPC 22 generates a dispatch signal and sends the dispatch signal to the WTG controller 15. The WTG controller 15 controls the WTG 14 according to the setpoints contained within the dispatch signal.

[0104] In a frequency event, when the frequency level of the main grid 16 deviates from the frequency emergency dead zone, the PPC 22 operates the WTG 14 to provide frequency support for the grid 16. The frequency emergency dead zone is usually the grid 2022P00023WOCN(JAJNN)

[0105] A small area around the operating frequency (typically 50 Hz, or in some examples 60 Hz, measured at PoI 20 or PoM 24) of 16. For example, the operating frequency may be 50 Hz and the upper and lower frequency limits of the frequency emergency deadband may be + / - 0.5 Hz.

[0106] According to the above control strategy, in one example, the PPC 22 may issue a dispatch signal configured to control one or more power characteristics of the WTG 14 to provide such frequency support. For example, the dispatch signal may be configured to control the active power output, reactive power output, and / or voltage level of the WTG 14 to support the frequency level to return to the frequency emergency dead zone.

[0107] For example, in an under-frequency event where the frequency level of the grid 16 drops below the lower limit of the dead band, the PPC 22 may provide frequency support by scheduling (dispatching) an increased active power set point (i.e., a set point for causing the WTG 14 to increase the active power supplied to the grid 16) to the WTG 14. Similarly, in an over-frequency event where the grid frequency rises above the upper limit of the dead band, the PPC 22 may reduce the active power supply by scheduling a reduced active power set point, thereby providing frequency support.

[0108] Figure 2 A program, algorithm or "control module" 100 is illustrated that forms part of the processing module 28 of the PPC 22 for determining and dispatching such set points during frequency events, in accordance with an embodiment of the present invention. The control module 100 includes a controller 101 that contains a program, algorithm or control scheme for generating set points for dispatch to the WTG controller 15 based on the measured frequency of the grid 16, as will be described in more detail below.

[0109] In particular, when the frequency level of the connected main grid 16 is outside the frequency dead band, the control module 100 is configured to receive a measured frequency level of the connected main grid 16 or information indicative of the frequency level, and determine a set point for controlling one or more power characteristics of the WTG 14 based on the frequency level.

[0110] It will be appreciated that the measured frequency level provides an accurate measurement of the grid frequency, for example with a resolution in the order of mHz or μHz. In one example, the measured frequency level may be filtered to remove noise associated with the measurement. For example, the measured frequency level may be noise filtered to ignore negligible changes, i.e., changes between consecutive measurements that are below a corresponding upper or lower threshold. The control module 100 may receive such noise filtered measurement signals, or may determine such signals on its own by applying a suitable noise filter.

[0111] The one or more power characteristics of the WTG 14 controlled by the control module 100 may include the active power output, reactive power output, or voltage level of one or more WTGs in the WTG 14. However, for simplicity, in the following description, the example control module 100 is configured to control the active power output of WTG 142022P00023WOCN(JAJNN), and the determined set point is an active power set point for controlling the active power output. However, this example is not intended to limit the scope of the present invention.

[0112] Typically, the active power setpoint may be determined based on a measured frequency level of the connected mains grid 16 and may vary with the measured frequency level in a corresponding manner.

[0113] For example, the control module 100 may be configured to determine an active power set point that may start from a baseline value and increase (i.e., increase at a constant rate) or decrease (i.e., decrease at a constant rate) based on the measured frequency level. The active power set point is typically based on an active power command received from an external entity (e.g., a grid operator or owner) that is capable of sending commands to the power plant. Here, the baseline value may correspond to an estimate of the available active power that the WPP 12 can supply to the main grid 16, such as a maximum power output that can be supplied to the main grid 16 under corresponding conditions (e.g., given wind speed conditions).

[0114] To this end, the control module 100 may include one or more lookup tables 102 (eg, Figure 2 As shown in FIG. 1 , the lookup table 102 includes active power target values ​​corresponding to frequency level measurements and / or predetermined ramp rates (slopes) for increasing or decreasing power levels.

[0115] For example, the lookup table 102 may include a Pf curve for matching the frequency level measurement value (f) with the corresponding active power target value P(f). Figure 3 An example Pf curve of the type familiar to the skilled person is shown.

[0116] The example Pf curve shows a frequency dead band DB, which defines a frequency range within which the active power target value P(f) is substantially constant. The example Pf curve also shows a prescribed increase in the active power target value P(f) when the frequency level drops below the frequency dead band DB (during an underfrequency event), and a prescribed decrease in the active power target value P(f) when the frequency level rises above the frequency dead band DB (during an overfrequency event).

[0117] As shown in this example, as the frequency level further deviates from the frequency dead zone DB, the prescribed increase and / or decrease of the active power target value P(f) may include a step change of the active power target value P(f) and / or define one or more different slopes of the change of the active power target value P(f). For example, the Pf curve may be divided into a series of frequency bands, and as the frequency level further deviates from the frequency dead zone DB, the slope of the Pf curve may increase or decrease in the continuous frequency band. In addition, in some examples, the Pf curve may also include minimum and / or maximum frequency levels, such as Figure 3 As shown, when the frequency level is exceeded, the active power target value P(f) can be kept substantially constant.

[0118] Additionally or alternatively, the lookup table 102 may include predetermined ramp rates in the form of one or more predetermined ramp-up rates and / or ramp-down rates for increasing or decreasing the power level, respectively, according to corresponding conditions of the WPP 12 and / or the grid 162022P00023WOCN(JAJNN). For example, the lookup table 102 may include one or more predetermined ramp-up rates or ramp-down rates corresponding to frequency level measurements, changes in measured frequency levels, power levels, and / or active power target values ​​(such as active power target values ​​corresponding to measured frequency levels).

[0119] For example, during an overfrequency event, the control module 100 may be configured to access the lookup table 102 to determine a corresponding rate of decrease to proportionally decrease the power level (and the active power set point) in accordance with the corresponding increase in the measured frequency level. In this manner, the control module 100 may support the main grid 16 to return to the frequency dead zone by controlling the WTG 14 to generate less active power. Subsequently, when the measured frequency level returns to the frequency dead zone, the control module 100 may be configured to compare the power level with a baseline value and (based on the comparison) determine a rate of increase from the lookup table 102 to restore the power level to the baseline value.

[0120] Various methods of determining an active power set point based on deviations of a measured frequency level of the connected grid 16 from an emergency dead band are known in the art, and it should be understood that the above examples are not intended to limit the scope of the present invention.

[0121] Within the emergency dead zone, it may be advantageous to further control the power characteristics of the power plant based on the varying measured network frequency. For example, the emergency dead zone may be divided into one or more sub-bands, each of which overlaps the emergency dead zone. In certain embodiments, each of the one or more sub-bands is completely contained within the emergency dead zone. Alternatively, one or more sub-bands may extend outside the emergency dead zone.

[0122] Figure 4 is a Pf diagram showing an emergency dead zone 52 divided into four frequency sub-bands: a first sub-band 54 , a second sub-band 56 , a third sub-band 58 , and a fourth sub-band 60 .

[0123] The first sub-band 54 extends from a first frequency 62 at the lower end of the emergency dead zone 52 to a second higher frequency 64 within the emergency dead zone 52. The second sub-band 56 extends from the second frequency 64 to a third higher frequency 66. The third sub-band 58 extends from a fourth frequency 68 to a fifth higher frequency 70. The fourth sub-band 60 extends from the fifth frequency 70 to a sixth higher frequency 72 at the upper end (top end) of the emergency dead zone 52.

[0124] The region 73 between the third frequency 66 and the fourth frequency 68 does not form part of any sub-band. In other embodiments, the region 73 may be wider or narrower than shown, or may be omitted, so that the third frequency 66 and the fourth frequency 68 are the same.

[0125] Although the first frequency 62 falls on the lower boundary of the emergency dead zone 52 and the sixth frequency 72 falls on the higher boundary (upper boundary) of the emergency dead zone 52, the skilled person will understand that in other embodiments, 2022P00023WOCN(JAJNN)

[0126] The first sub-band 54 and / or the fourth sub-band 60 may at least partially fall outside the emergency dead zone 52 .

[0127] Figure 5 is a diagram showing a baseline curve in the form of a baseline Pf curve 74 that maps the network frequency to the active power set point of the WPP 12. For clarity, the baseline Pf curve 74 is shown as Figure 3 A simplified version of the graph shown. The first to fourth sub-bands 54-60 are plotted along the frequency axis.

[0128] According to the general principle described above, the baseline Pf curve 74 is a constant value when the network frequency value falls within the emergency dead zone 52 , increases as the network frequency drops below the emergency dead zone 52 , and decreases as the network frequency rises above the emergency dead zone 52 .

[0129] The output power represented by the baseline Pf curve 74 varies as the available output power of the WPP 12 varies. The values ​​of the baseline Pf curve 74 within the emergency deadband 52 may correspond to an estimate of the available active power that the WPP 12 can supply to the main grid 16, such as the maximum “rated” amount of power that can be supplied to the main grid 16 under current conditions (such as wind speed conditions).

[0130] For example, when wind speed decreases, the maximum available power output of wind turbine 14 will also decrease. This will effectively shift baseline Pf curve 74 downward along the vertical axis. When wind speed increases, the opposite will occur. Within a certain range of wind speeds, baseline Pf curve 74 will maintain the same general shape, but will shift up and down along the vertical axis based on wind speed and other network operating requirements known to those skilled in the art.

[0131] During the normal operating mode, the WPP 12 may operate based on the baseline Pf curve 74. When it is desired to provide frequency support to the main grid 16 within one or more of the sub-bands 54-60, one or more corresponding offset curves may be used in conjunction with the baseline Pf curve 74 to provide a set point for the WPP 12 to provide the desired frequency support.

[0132] For example, Figure 6 is a Pf diagram showing a first Pf offset curve 76 that is applied when it is intended to provide frequency support within the third sub-band 58. The first Pf offset curve 76 has a value of zero below the fourth frequency 68, drops to a value of -1 MW at the fifth frequency 70, and has a value of -1 MW above the fifth frequency 70. The skilled person will appreciate that the offset value of -1 MW is given as an example only. The actual offset value for any particular implementation will be selected based on factors such as the power generation capabilities of the WPP 12, local network conditions, and other commercial and technical factors that the skilled person will appreciate.

[0133] Figure 7 is a Pf graph showing a first output Pf curve 78, which is a baseline Pf curve 74 (from Figure 5 ) and the first Pf offset curve 76 (from Figure 6 At the network frequency below the fourth frequency 68, the first output Pf curve 78 is equal to the baseline Pf curve 742022P00023WOCN(JAJNN)

[0134] The effect above the fifth frequency 70 is that the baseline Pf curve 74 is shifted downward by 1 MW.

[0135] The first output Pf curve 78 is used to generate the set point for the WPP 12. If the measured network frequency increases above the fourth frequency 68, the value of the power characteristic set point dispatched to the WPP 12 gradually decreases as the frequency increases through the third sub-band 58. In the case of a wind power plant, this may mean feathering the turbine blades, controlling the power converter, or otherwise reducing the total amount of power generated. The value of the power characteristic set point dispatched to the WPP 12 then remains constant as the measured network frequency increases through the fourth sub-band 60, and then decreases further as the measured network frequency increases above the sixth frequency 72.

[0136] Figure 8 is a Pf diagram showing a second Pf offset curve 80. The second Pf offset curve 80 is similar to the first Pf offset curve 76 in that it is applied when it is intended to provide frequency support within the third sub-band 58. For network frequencies below the fifth frequency 70, the second Pf offset curve 80 is the same as the first Pf offset curve 76. However, as the network frequency rises above the fifth frequency 70, the value of the second Pf offset curve 80 returns to zero.

[0137] Fig. 9is a Pf graph showing a second output Pf curve 82, which is a baseline Pf curve 74 (from Figure 5 ) and the second Pf offset curve 80 (from Figure 8 ). At a network frequency below the fifth frequency 70, the second output Pf curve 82 is the same as the first output Pf curve 78. However, when the network frequency is above the fifth frequency 70, the baseline Pf curve 74 does not shift as in the case of the first output Pf curve. Therefore, the WPP 12 is able to generate more power in this region than in the case of the first output Pf curve 78.

[0138] The selection between applying the first Pf offset curve 76 or the second Pf offset curve 80 may be guided or controlled by business arrangements between the operator of the WPP 12, network regulations, and other factors as will be appreciated by the skilled artisan.

[0139] The first Pf offset curve 76 and the second Pf offset curve 80 may be modified in any desired manner, as will be understood by the skilled person. For example, the lifting angle within the third subband 58 and the maximum offset caused by the first Pf offset curve 76 and the second Pf offset curve 80 may be increased or decreased.

[0140] Similarly, the shapes of the first Pf offset curve 76 and the second Pf offset curve 80 within the third sub-band 58 may also be modified in different embodiments. Fig.10 8 is a Pf diagram showing a third Pf shift curve 84. In the third sub-band 58, the third Pf shift curve 84 includes a rising and falling portion 83 and a constant portion 85.

[0141] 2022P00023WOCN(JAJNN)

[0142] Other modifications may also include introducing a ramp portion to avoid drastic step changes in power output due to small changes in frequency. Alternatively, or in addition, the potential negative effects of such step changes may be controlled or mitigated based on the maximum rate of change applied by the PPC 22 or WTG controller 15.

[0143] Fig.118 is a Pf diagram showing a fourth Pf offset curve 88, which is applied when it is intended to provide frequency support within the fourth sub-band 60. The fourth Pf offset curve 88 has a value of zero below the fifth frequency 70, drops to a value of -1 MW at the sixth frequency 72, and has a value of -1 MW above the sixth frequency 72. The skilled person will understand that the offset value of -1 MW is given as an example only. The actual offset value of any particular implementation will be selected based on factors such as the power generation capabilities of the WPP 12, local network conditions, and other commercial and technical factors that the skilled person will understand.

[0144] Fig.12 is a Pf diagram showing a third output Pf curve 89, which is a baseline Pf curve 74 (from Figure 5 ) and the fourth Pf offset curve 88 (from Fig.10 At network frequencies below the fifth frequency 70, the third output Pf curve 89 is identical to the baseline Pf curve 74. Above the sixth frequency 72, the effect is that the baseline Pf curve 74 is shifted downward by 1 MW.

[0145] The third output Pf curve 89 is used to generate the set point for the WPP 12. If the measured network frequency increases above the fifth frequency 70, the value of the power characteristic set point dispatched to the WPP 12 gradually decreases as the frequency increases through the fourth sub-band 60. In the case of a wind farm, this may mean feathering the turbine blades, controlling the power converter, or otherwise reducing the total amount of power generated. As the measured network frequency increases beyond the sixth frequency 72 at the upper boundary of the fourth sub-band 60, the value of the power characteristic set point dispatched to the WPP 12 decreases further due to the downward slope of the baseline Pf curve in this region.

[0146] Fig.13 is a Pf diagram showing a fifth Pf offset curve 90. The fifth Pf offset curve 90 is similar to the fourth Pf offset curve 88 in that it is applied when it is intended to provide frequency support within the fourth sub-band 60. For network frequencies below the sixth frequency 72, the fifth Pf offset curve 90 is the same as the first Pf offset curve 76. However, as the network frequency rises above the sixth frequency 72, the value of the fifth Pf offset curve 90 returns to zero.

[0147] Fig.14 is a Pf diagram showing a fourth output Pf curve 91, which is a baseline Pf curve 74 (from Figure 5 ) and the fifth Pf offset curve 90 (from Fig.13). At a network frequency below the sixth frequency 72, the fourth output Pf curve 91 is the same as the third output Pf curve 89. However, when the network frequency is above the sixth frequency 72, the baseline Pf curve 742022P00023WOCN(JAJNN)

[0148] There is no shift as in the case of the third output Pf curve. Therefore, the WPP 12 is able to generate more power in this region than in the case of the third output Pf curve 89.

[0149] The selection between applying the third Pf offset curve 89 or the fourth Pf offset curve 91 may be guided or controlled by commercial arrangements between the operator of the WPP 12, grid regulations, and other factors as will be appreciated by the skilled person. Nevertheless, the skilled person will appreciate that, according to grid regulations, Fig.13 The fifth Pf offset curve 90 (and Fig.14 The fourth output Pf curve 91 in FIG. 5 may not be allowed. When the grid frequency leaves the frequency emergency dead zone 52, increasing the power supplied to the grid will increase the stress on the grid, which is exactly the opposite of the expected situation. Nevertheless, for the purpose of technical explanation, this article still uses it as an example.

[0150] As with the first Pf offset curve 76 and the second Pf offset curve 80, the fourth Pf offset curve 88 and the fifth Pf offset curve 90 may be modified in any desired manner, as will be appreciated by a skilled person. For example, the lifting angle within the fourth sub-band 60, as well as the maximum offset caused by the fourth Pf offset curve 88 and the fifth Pf offset curve 90 may be increased or decreased.

[0151] Similarly, the shapes of the fourth Pf offset curve 88 and the fifth Pf offset curve 90 within the fourth sub-band 60 may also be modified in different embodiments, such as by including similar Fig.10 The lifting and constant parts of those parts are described.

[0152] Fig.15 is a Pf diagram showing a sixth Pf offset curve 92 that is applied when it is intended to provide frequency support within the second sub-band 56. The sixth Pf offset curve 92 has a value of zero above the third frequency 66, rises to a value of +1 MW at the second frequency 64, and has a value of +1 MW below the second frequency 64. The skilled person will appreciate that the offset value of +1 MW is given as an example only. The actual offset value for any particular implementation will be selected based on factors such as the power generation capabilities of the WPP 12, local network conditions, and other commercial and technical factors that the skilled person will appreciate.

[0153] Fig.15 Also shown is a seventh Pf shift curve 93 (dashed line) which is identical to the sixth Pf shift curve 92 for frequencies above the second frequency 64 but has a constant value of zero for frequencies below the second frequency 64 .

[0154] Fig.16 0023WOCN(JAJNN)

[0155] The actual offset value for any particular implementation will be selected based on factors such as the power generation capabilities of the WPP 12, local network conditions, and other commercial and technical factors that will be understood by the skilled artisan.

[0156] Fig.16 Also shown is a ninth Pf shift curve 95 (dashed line) which is identical to the eighth Pf shift curve 94 for frequencies above the first frequency 62 but has a constant value of zero for frequencies below the first frequency 62 .

[0157] Any of the sixth Pf offset curve 92, the seventh Pf offset curve 93, the eighth Pf offset curve 94, and the ninth Pf offset curve 95 may be applied to the baseline Pf curve 74 in a manner similar to that described with respect to the first output Pf curve 78, the second output Pf curve 82, and the third output Pf curve 89 to generate one or more additional output Pf curves. Such additional output curves may be used to generate set points that are dispatched to the WTG controller 15.

[0158] The selection of which Pf offset curves to apply to the baseline Pf curve 74 may be guided or controlled by business arrangements between the operator of the WPP 12, network regulations, and other factors as will be appreciated by the skilled artisan.

[0159] Any or all of the sixth to ninth Pf offset curves 92, 93, 94, 95 may be modified in any desired manner, as will be understood by the skilled person. For example, the lifting angle within any of the corresponding sub-bands 54 and 56, as well as the maximum offset caused by the Pf offset curve, may be increased or decreased.

[0160] Similarly, the shapes of any or all of the sixth to ninth Pf offset curves 92, 93, 94, 95 in the first sub-band 54 and the second sub-band 56 may also be modified in different embodiments. Other modifications may also include introducing a ramp portion to avoid a sharp step change in power output due to a slight change in frequency (e.g., Figure 8 Alternatively, or in addition, the potential negative effects of such a step change may be controlled or mitigated based on a maximum rate of change applied by the PPC 22 or WTG controller 15.

[0161] The skilled person will appreciate that any combination of these Pf offset curves may be applied to any combination of sub-bands.

[0162] In particular, the control module 100 is configured to implement a method of controlling a power plant, which method will now be referred to as Fig.17 Give a description.

[0163] Fig.17 A method 300 of controlling a power plant such as WPP 12 is shown. In this initial example, the method is applied to only one frequency sub-band. This sub-band may be the only sub-band to which the method is applied, 2022P00023WOCN(JAJNN)

[0164] It may also be one of several sub-bands that overlap with a network defined emergency dead zone, any or all of which may be implemented by the operator of the WPP 12.

[0165] The method 300 includes receiving 302 a measured frequency of the main grid 16 and then determining 304 whether the measured frequency falls within a first frequency sub-band.

[0166] If it is determined that the measurement frequency falls within the first sub-band, a first control signal is output 306 and the method returns to step 302 .

[0167] If the measurement frequency does not fall within the first sub-band, the method returns to step 302 .

[0168] Depending on the embodiment, the first control signal may indicate a first power offset, or a set point for controlling a power characteristic of the power plant, wherein the set point includes the first power offset. Figure 18-20 Various implementation options are described in more detail.

[0169] If the measured frequency is lower than the nominal operating frequency of the power network, the first power offset may be a positive value; if the measured frequency is higher than the nominal operating frequency of the power network, the first power offset may be a negative value.

[0170] Optionally, the value of the first power offset at the second frequency is zero, so that as the measured frequency decreases below the second frequency, the set point transitions steplessly. A non-limiting example of such a transition is the sixth and seventh offset curves 92 and 93 at the third frequency 66 ( Fig.15 ), and the eighth and ninth deviation curves 94 and 95 at the second frequency 64 ( Fig.16 ).

[0171] Optionally, while repeating steps 302 and 304, as the measured network frequency decreases from the second frequency toward the first frequency, the first power offset will:

[0172] In a first frequency range, the value increases; and

[0173] In a second frequency range lower than the first frequency range, the frequency is kept constant or increases at a lower rate.

[0174] The first frequency range may be continuous with the second frequency range, and the first frequency range and the second frequency range may cover the entire first sub-band.

[0175] The method optionally includes determining whether the measured frequency falls within a second frequency sub-band, the second frequency sub-band overlapping a network-defined frequency dead band. In response to the measured frequency falling within the second sub-band, and based at least in part on the measured frequency, the method includes outputting a second control signal indicating a second power offset or a set point for controlling a power characteristic of the power plant, the set point being based on the second power offset applied to a baseline frequency curve of the power plant.

[0176] Optionally, similar to the first frequency sub-band, as the measurement frequency enters the second frequency sub-band from the lower frequency 2022P00023WOCN(JAJNN)

[0177] Subband, stepless transition of set points.

[0178] Similar to the first frequency sub-band, as the measured network frequency increases in the second frequency sub-band, the value of the first power offset may decrease in the third frequency range, and then remain constant or decrease at a lower rate in a fourth frequency range higher than the third frequency range. The third frequency range may be continuous with the fourth frequency range, and the third frequency range and the fourth frequency range may cover the entire second sub-band.

[0179] One or more additional subbands may be defined within the emergency dead zone, each additional subband being within the network defined frequency dead zone but not overlapping any other subband. The method may then include, in response to the measurement frequency falling within the additional subband and based at least in part on the measurement frequency, scheduling an additional control signal indicating:

[0180] an additional power offset which is applied to a baseline frequency curve of the power plant to generate a set point for controlling a power characteristic of the power plant; or

[0181] A set point for controlling a power characteristic of a power plant, the set point being based on an additional power offset applied to a baseline frequency curve of the power plant.

[0182] In certain embodiments, different frequency support modes may be supported. For example, in one embodiment, an operator of the PPC 22 may switch between a baseline mode, in which a setpoint is generated in response to a measured frequency of the grid 16 using a baseline Pf curve 74, and a frequency support mode, in which any combination of the offset curves of the first through fourth sub-bands 54-60 are applied to the frequency within the emergency dead zone 52.

[0183] Fig.18 An output Pf curve 96 is shown, which is generated by adding the baseline Pf curve 74 to a separate offset curve for each of the first through fourth sub-bands 54-60. The output Pf curve 96 is used when the operator of the PPC 22 elects to provide frequency support on all of the first through fourth sub-bands 54-60 (which may be the result of negotiations with the grid operator 26, or the result of a commercial bidding process, or the like).

[0184] In an alternative embodiment, the operator of PPC 22 may choose to provide frequency support only on a subset of possible sub-bands. For example, the operator of PPC 22 may choose to provide frequency support only on the third and fourth frequency bands. Fig.19 An output Pf curve 97 for providing such support is shown, which is generated by adding the baseline Pf curve 74 to a separate offset curve for each of the third and fourth sub-bands 58 and 60 .

[0185] exist Fig.18 and Fig.19 In the example of , each of the sub-band offset curves includes a rising and falling portion (similar to Fig.10 The lifting part 83 shown in FIG. 8 ) and the constant part (similar to Fig.10 2022P00023WOCN(JAJNN) shown in

[0186] Constant portion 85). However, the skilled person will appreciate that each individual offset curve may have any shape and / or slope angle in any combination. For example, some sub-band offset curves may employ a constant portion while other sub-band offset curves do not employ a constant portion.

[0187] Alternatively, the shape of each subband offset curve may be fixed, in which case the operator of PPC 22 need only select which subband offset curves (if any) to implement at any particular time. Alternatively, the shape of some or all of the subband offset curves may vary over time as desired.

[0188] It should be understood that the term "offset" is used broadly. For example, "offset" includes a literal offset, i.e., a value applied to a baseline curve. For example, an offset can be a positive or negative value (or in the case of an offset curve, a curve or set of positive or negative values) that is added to, subtracted from, or otherwise applied to a baseline Pf curve to provide the frequency support described.

[0189] "Offset" also includes an arrangement in which the PPC 22 is programmed to implement a Pf output curve whose shape can be changed by adjusting program parameters. Optionally, the parameters can be adjustable to offset the Pf curve within any or all sub-bands as desired. The parameters can also be set so that no frequency support is provided in any sub-band. The net result is that a single, adjustable Pf curve is used, with only the parameter setting determining whether frequency support is provided in any sub-band. The net effect is an offset relative to the baseline curve, even though the independent individual offsets are not directly added to or subtracted from the individual baseline Pf curves.

[0190] In addition to dealing with the variability in available power output of WPP 12 due to the unpredictable nature of its energy sources, when providing frequency support services it may also need to modify power output to ensure any contractual or network rule based requirements are met.

[0191] When not providing frequency support services (such as those described herein), the WPP 12 may operate with a certain amount of spinning reserve, which may be a requirement of the grid operator 26. The spinning reserve effectively cuts the output power of a generator or power plant below its current theoretical maximum power output under current generation conditions, by a certain offset. The offset is effectively power in reserve unless and until it is needed. For example, it may involve the WPP 12 generating less than the maximum power output possible under current generation conditions to ensure that sufficient overhead power is available to support the network in the event that the frequency drops below the emergency dead zone 52.

[0192] In some cases, additional rotation reserves may be implemented to support the frequency support methods described herein. For example, when the WPP 12 intends to provide one or more sub-bands below the nominal operating frequency of the network 2022P00023WOCN(JAJNN)

[0193] When providing frequency support, it is desirable to ensure that sufficient power is available to implement the power offset profiles corresponding to these sub-bands.

[0194] For example, the baseline Pf curve 74 (see Figure 5 ) may be the result of applying the additional spinning reserve offset indicated by arrow 98 to the starting baseline curve 99 over the full width of the curve 99 (the skilled person will appreciate that the starting baseline curve 99 may itself be the result of applying a spinning reserve offset (not shown) to the maximum power output curve for given power generation conditions).

[0195] One way to ensure adequate power when providing frequency support as described herein is to offset (i.e., reduce) the active power of the WPP 12 by the maximum offset of any sub-band for which the WPP 12 intends to provide frequency support. However, this is only necessary when one or more of the sub-bands for which frequency support is provided is below the nominal operating frequency of the network.

[0196] For example, refer to Fig.18 If frequency support is provided only in sub-band 56, the maximum positive offset required is represented by reference symbol 406 (i.e., relative to the power level between sub-bands 56 and 58 where no frequency support is provided). This is true even if frequency support is to be provided in frequency sub-bands 58 and / or 60, since they do not require additional rotation reserve.

[0197] In contrast, if frequency support is to be provided in frequency sub-band 54, the maximum positive offset required is represented by reference symbol 408 (again relative to the power level between frequency sub-bands 56 and 58 where frequency support is not provided). This is true even if frequency support is to be provided in any combination of frequency sub-bands 56, 58, and 60, as they either do not need to provide a positive power offset (sub-bands 58 and 60) or only need to provide a smaller positive power offset than required for sub-band 54 (sub-band 56).

[0198] Additional spinning reserve offsets may be implemented during any time period that provides frequency support.

[0199] The skilled person will appreciate that any desired offset may be implemented on all generators within the plant, or any suitable combination thereof. For example, if a 10MW plant with 10 x 1MW generators requires an offset of 1MW, then each generator may reduce its output power by 0.1MW, half of the generators may each reduce their output by 0.2MW, or both generators may each reduce their output by 0.5MW. It will also be appreciated that different generators may reduce their power by different amounts.

[0200] In the case of a hybrid power plant, it may be desirable to provide the required power offset by controlling the amount of power contributed by the non-variable generator. For example, the power output of a gas power plant or a battery energy storage system forming part of a power plant may vary its output level to provide the required power offset.

[0201] 2022P00023WOCN(JAJNN)

[0202] Another option to provide the required offset is to use a short-term overproduction mode. For example, some manufacturers offer an option to allow the WTG to produce more than its registered or nominal power output (usually calculated based on mechanical engineering fatigue loads at a specific site) for a relatively short period of time.

[0203] A WPP, such as WPP 12 , may use this short-term overproduction mode to provide at least a portion of the additional spinning reserve offset when providing frequency support at a measured frequency that is below the network nominal operating frequency.

[0204] For example, a WTG with a registered or nominal power of 3 MW may provide an overproduction mode during which the WTG is able to temporarily generate 3.3 MW. During normal operation, when no frequency support is provided and not operating in a short-term overproduction mode, the WTG may output up to 3 MW. For example, when providing frequency support at the measurement frequency within the first sub-band 54, it may be necessary to provide a power offset (i.e., an additional spinning reserve) of, for example, 0.2 MW.

[0205] Without the variability of the short term overproduction pattern, during a period when the wind is strong enough for the WTG to output 3MW of its registered or rated power, the WTG would need to reduce power output by the required 0.2MW power offset, limiting its production to 2.8MW, at which point the measured frequency means that no frequency support is currently required.

[0206] However, by enabling the short term overproduction mode, the WTG can continue to operate at its nominal power of 3 MW. Only when the measured frequency falls into the first sub-band 54 does the WTG need to increase its power output to the overproduction range. Furthermore, the WTG only needs to increase its power output according to the offset curve of the first sub-band 54, which only requires the use of 0.2 MW of the available overproduction capacity.

[0207] Even if the excess capacity is insufficient to provide all of the additional spinning reserve offset, it may still reduce the amount of curtailment required to provide the necessary additional spinning reserve.

[0208] Therefore, when the WTG provides frequency support for sub-bands below the grid nominal operating frequency, curtailment of the WTG output power can be reduced or even avoided to ensure that sufficient spinning reserve offset is available in the event that the measured frequency falls into these sub-bands.

[0209] Fig. 20 A functional block diagram is shown that illustrates additional non-limiting examples of how the present power plant control method may be implemented. Each example assumes the use of four sub-bands, such as the first through fourth sub-bands 54-60 described above. However, the skilled artisan will appreciate that the present invention (including with reference to Fig. 20 The principles described in the related content) apply to any combination of any other number of sub-bands overlapping with the frequency emergency dead zone.

[0210] Fig. 20 An arrangement is shown in which the PPC 22 is provided via a baseline module 400, a frequency support module 2022P00023WOCN (JAJNN)

[0211] 402 and master scheduler 404 provide frequency control. Each of baseline module 400, frequency support module 402 and master scheduler 404 may be implemented by software, firmware, hardware, or any suitable combination thereof, as will be appreciated by a skilled person. Similarly, the functionality described may be distributed among any software, firmware, and / or hardware modules that may be distributed throughout the power generation network in any suitable manner.

[0212] The frequency support module 402 receives the measured frequency f and the power command P com . Power command P com is a numerical value representing the power that the WPP should provide, for example, to the grid. com Can come from the grid operator or the owner of the WPP. Based on f and P com , the frequency support module 402 generates a value P reserve and P delta .

[0213] P reserve represents an additional spinning reserve offset which, as described above, the power plant may need to implement in order to provide frequency support in a sub-band below the nominal operating frequency of the network. For example, if it is intended to provide frequency support within the second sub-band 56 and the maximum power offset within the second sub-band 56 alone is 2 MW, then P reserve If frequency support is only intended to be provided within the first sub-band 54, and the maximum power offset within the first sub-band 54 alone is 3 MW, then P reserve It will be 3MW.

[0214] It should be noted that in cases where frequency support is expected, the baseline Pf curve should be replaced by P reserveFor example, if only one hour of frequency support is provided for the first sub-band 54 (eg, between noon and 13:00), then based on the above example, P reserve The value of will become 3 MW at noon. If the frequency falls within the first sub-band 54 between noon and 13:00, then an additional spinning reserve offset is available. The skilled person will appreciate that if the measured frequency does not fall within the relevant sub-band within the time range for which the frequency support has been agreed, then the spinning reserve may not actually be used.

[0215] It should also be noted that the additional rotation reserve may be cumulative. For example, if frequency support is to be provided within the first sub-band 54 and the second sub-band 56 in the above example, then P reserve The value of may be 5 MW (ie, the sum of 3 MW of the first sub-band 54 and 2 MW of the second sub-band 56 ).

[0216] P delta is a power offset value that indicates the amount of offset that the baseline module 400 applies to the baseline Pf curve because the measured frequency falls within a sub-band for which the power plant operator has agreed to provide frequency support.

[0217] The baseline module 400 receives the measured frequencies f, P com , P avail , P reserve and P delta When no frequency support is provided for any subband within the frequency emergency dead zone 52, the baseline module 400 uses the frequencies f and P avail or P com , based on the value of the baseline Pf curve at the current network frequency, the power reference value P is determined ref If P com Lower than P avail , then use P com ; and if P avail Lower than P com , then use P avail .2022P00023WOCN(JAJNN)

[0218] In the latter case, the WPP cannot comply with the power command but will provide as much power as possible, thus avail .

[0219] In addition to f, P com and P avail In addition, the baseline module 400 also uses P when providing frequency support reserve and P delta As mentioned above, if the frequency sub-band supported by the provided frequency is required, P reserve The baseline Pf curve will change from P on the power axiscom or P avail The P frequency is shifted downwards to provide any necessary additional spinning reserve. Typically this will be in the context of providing frequency support for a sub-band below the nominal operating frequency of the electricity network. If no additional spinning reserve is required, then P reserve The value of is zero.

[0220] Any spinning reserve required to provide frequency support within a particular sub-band (eg, the first sub-band 54 or the second sub-band 56) may be attributable, at least in part, to P avail and P com For example, if P is within the subband where a rotation reserve is required com Lower than P avail , the Pf curve may not be shifted down to provide the necessary rotation reserve, or at least the amount by which the Pf curve must be shifted down may be reduced.

[0221] For example, a power plant that is to provide frequency support within the second sub-band 54 may need to provide a spinning reserve of 0.3 MW during the period in which frequency support is provided. avail and P com If the current is the same, the output of the power plant would need to be reduced by a full 0.3MW to provide the required spinning reserve. com P avail If the power plant output is lower, for example, by 0.1 MW, then the output of the power plant only needs to be higher than its current output (i.e., P com ) output can be reduced by 0.2MW, because P com Less than P avail The remaining 0.1MW is already available. com P avail If the power output is at least 0.3 MW lower (in the given example), then there is no need to reduce the power output at all, because due to P com P avail At least 0.3MW lower, the required spinning reserve can be fully provided within the existing curtailment.

[0222] When the value of f remains outside any sub-band that provides frequency support, P delta The value of will remain zero, and the P output of the baseline module 400 ref The value of is determined based on the value of the baseline Pf curve at the current frequency. ref This may take the form of a set point for the power plant.

[0223] If the value of f is moved into a subband where frequency support is being provided, then P delta The value of will increase or decrease according to the corresponding Pf offset curve. Then, the P output by the baseline module 400 refThe value of the baseline Pf curve is based on the value of the current f. delta The numerical offset is determined by .

[0224] Based on the P received from the baseline module 400 ref value, the master scheduler 404 generates a separate set point P setpoint_GEN0 , P setpoint_GEN1 , ..., P setpoint_GEN9 , and send them to their respective generators.

[0225] The master dispatcher 404 can modify the dispatch schedule to each generator based on any requirements of the power plant or each generator.

[0226] Setpoints sent to the generators. For example, if any one generator has the lowest power output, the master scheduler 404 may attempt to avoid sending setpoints to those generators that are below their respective lowest power outputs.

[0227] For example, the minimum power output of a WTG may correspond to, for example, 20% of its rated power output. Any set point corresponding to a value lower than the minimum power output will cause the WTG to pause (i.e., reduce its power output to zero). Pausing a WTG is generally undesirable because starting and stopping can cause increased wear on components such as bearings. In addition, the reduced speed associated with low power output may make it difficult for the WTG to quickly increase its power output when needed. Therefore, the master scheduler 404 may do its best to ensure that no WTG is paused. For example, a power plant may reduce the set points of other generators in the power plant (which are better able to reduce their power output). For example, the power output of a battery storage system may be reduced, possibly even to zero, in preference to pausing the WTG.

[0228] The skilled person will appreciate that reference to sending a set point to a generator includes sending any information indicative of a power characteristic to which the set point relates, and includes sending the set point to a local controller of one or more generators, such as the WTG controller 15 .

[0229] As shown by dashed line 406, Fig. 20 In a slightly revised version of the arrangement, P delta can be directly provided to the master scheduler 404. In this case, the baseline module 400 will not ref Application delta Instead, the main scheduler uses P ref and P delta The setpoint for the generator is generated directly.

[0230] The frequency support method described above may be implemented within any suitable control function or module associated with one or more generators or power plants. In addition to the PPC 22 described above, the frequency support method may also be performed locally by a controller of one or more generators, such as the WTG controller 15. The method may also be performed remotely from a PPC via software, firmware, and / or hardware, and the required set points are provided to the PPC for forwarding to its associated power plant.

[0231] Regardless of the method implemented, a lookup table or curve of Pf offset values ​​can be accessed to determine a set point for controlling the power characteristics of the power plant. The lookup table or curve can be accessed via a communication network (such as an IP-based wired or wireless network). Alternatively, a table or curve of Pf offset values ​​can also be stored locally.

[0232] A fallback scheme may be used to allow frequency support to continue even in the event of a communication breakdown between the PPC 22 and the WTG controller 15. The PPC 22 may supply one or more Pf curves to each WTG controller 15, which the WTG controllers will use in the event of a failure of the communication link between the PPC 22 and the WTG controller 15.

[0233] 2022P00023WOCN(JAJNN)

[0234] For example, PPC 12 may provide a baseline Pf curve and one or more offset curves for any subband for which frequency support is to be provided. Alternatively, an output Pf curve may be provided, implicitly incorporating the required offsets, as described above.

[0235] Optionally, the or each Pf curve may be provided with a period of application, or at least a failure time. For example, every hour, the PPC 22 may pass a new Pf curve to its WTG controller for use in the next hour. If communications are interrupted during the hour when the current Pf curve is applied, the WTG controller may generate a set point based on the current Pf curve, independently of the PPC 22. If the communication interruption lasts for more than the time period of the specified Pf curve, the WTG controller 15 may continue to use the same Pf curve, fall back to a default Pf curve (e.g., a baseline Pf curve), shut down their corresponding WTGs, or may implement any other suitable behavior.

[0236] When the PPC 22 loses communication with a remote control system (such as a cloud-based control system operated by the owner or operator of the PPC), a related alternative method can be used. For example, the Pf curve for the next day, for example, can be provided to the PPC 22, for example, on an hourly basis. In the event that any PPC 22 loses communication with its control system, an appropriate Pf curve can still be implemented.

[0237] The skilled person will appreciate that the time periods mentioned in the preceding paragraphs (such as hours or days) are merely examples and any other suitable time period or time period may be used, depending on the implementation.

[0238] Optionally, any additional power generated or reduced by applying a frequency support offset to the baseline Pf curve may be recorded for technical and / or commercial purposes. For example, the system may record the difference between the current baseline Pf curve and any offset Pf value applied because the measured frequency falls within a sub-band for which the power plant operator has agreed to provide frequency support. This may be accomplished by integrating or averaging the offset values ​​over a suitable time period. In this way, the cumulative amount of power generated or reduced by providing frequency support services over any desired period of time may be determined.

[0239] The accumulated power may be recorded at any desired resolution. For example, if the commercial agreement providing frequency support is in hours, then it may be convenient to record the accumulated power at a resolution of no more than one hour. Shorter term records (e.g., on the order of seconds or minutes) may be summed to produce hourly values, and larger values ​​(daily, monthly, yearly, etc.) may be determined accordingly.

[0240] It will be appreciated that various changes and modifications may be made to the examples described above without departing from the scope of the present invention.

Claims

1. A method of controlling a power plant, the power plant comprising at least one generator, the power plant having a variable available power output due at least in part to variability in an energy source powering the at least one generator, the method comprising: receiving a measured frequency of an electric power network to which the power plant is connected; determining whether the measurement frequency falls within a first frequency sub-band, the first frequency sub-band overlapping a frequency dead zone defined by a network; as well as In response to the measured frequency falling within the first frequency sub-band, and based at least in part on the measured frequency, outputting a first control signal, the first control signal indicating: a first power offset applied to a baseline frequency curve of the power plant to generate a set point for controlling a power characteristic of the power plant; or A set point for controlling a power characteristic of the power plant is provided, the set point being based on a first power offset applied to a baseline frequency curve of the power plant.

2. The method according to claim 1, wherein: The position of the baseline frequency curve on the power axis varies depending at least in part on the available power output of the power plant.

3. The method according to claim 1 or 2, wherein: The first frequency sub-band is defined by a first frequency and a second frequency, wherein: The first frequency is lower than the second frequency; The second frequency is lower than or equal to the nominal frequency of the electricity network; and The first power offset is a positive value.

4. The method according to claim 3, wherein: The value of the first power offset at the second frequency is zero, so that as the measurement frequency drops below the second frequency, the setpoint transitions steplessly.

5. The method according to claim 3 or 4, wherein: As the measured network frequency decreases from the second frequency toward the first frequency, the first power offset will be: 2022P00023WOCN(JAJNN) In a first frequency range, the value increases; and In a second frequency range lower than the first frequency range, the frequency is kept constant or increases at a lower rate.

6. The method according to claim 5, wherein: The first frequency range is continuous with the second frequency range; and The first frequency range and the second frequency range cover the entire first frequency sub-band.

7. The method according to any one of claims 3 to 6, comprising: determining whether the measurement frequency falls within a second frequency sub-band, the second frequency sub-band overlapping a frequency dead zone defined by the network; as well as In response to the measured frequency falling within the second sub-band and based at least in part on the measured frequency, outputting a second control signal, the second control signal indicating: a second power offset applied to a baseline frequency curve of the power plant to generate a set point for controlling a power characteristic of the power plant; or A set point for controlling a power characteristic of the power plant is provided, the set point being based on a second power offset applied to a baseline frequency curve of the power plant.

8. The method according to claim 7, wherein: The second sub-band is defined by a third frequency and a fourth frequency, wherein: The third frequency is lower than the fourth frequency; The third frequency is higher than or equal to the nominal frequency of the power network; and The second power offset is a negative value.

9. The method according to claim 8, wherein: The value of the second power offset at the third frequency is zero, so that the setpoint transitions steplessly as the measurement frequency rises above the third frequency.

10. The method according to any one of claims 7 to 9, wherein: As the measured network frequency rises above the third frequency toward the fourth frequency, the first power offset will be: 2022P00023WOCN(JAJNN) In the third frequency range, the values ​​decrease; as well as In a fourth frequency range higher than the third frequency range, the rate is kept constant or decreased at a lower rate.

11. The method according to claim 10, wherein: The third frequency range is continuous with the fourth frequency range; and The third frequency range and the fourth frequency range cover the entire second sub-band.

12. A method according to any preceding claim, wherein: In response to the measured frequency falling within the additional sub-band, and based at least in part on the measured frequency, outputting an additional control signal, the additional control signal indicating: a further power offset applied to a baseline frequency curve of the power plant to generate a set point for controlling a power characteristic of the power plant; or a set point for controlling a power characteristic of the power plant, the set point being based on an additional power offset applied to a baseline frequency curve of the power plant; The additional frequency sub-band is located within a frequency dead zone defined by the network but does not overlap with any other sub-band.

13. A method of controlling a power plant, the method comprising: The method according to any preceding claim is performed if and only if the measured frequency falls within a sub-band in which the frequency support mode is determined to be in operation.

14. The method according to claim 13, comprising: At the beginning of a period in which the frequency support mode is determined to be operational, the power output of the power plant is curtailed to provide sufficient additional spinning reserve to support the maximum value of any power offset applied to the baseline curve.

15. A power plant controller configured to perform a method according to any one of the preceding claims.

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