Method of controlling a hybrid power plant connected to an electric power network

Abstract

Aspects of the invention relate to a method (100) of controlling a hybrid power plant (12) connected to an electric power network (26). The hybrid power plant (12) comprises at least two types of renewable energy generators (20; 22; 24) having an active power reserve for supplying an additional amount of active power. The method (100) comprises, during a frequency event detected on the electric power network (26): determining (102) the additional amount of active power to be provided to the electric power network (26) to provide a fast frequency response; calculating (104) a contribution from each type of generator of the at least two types of generators (20; 22; 24) for supplying the additional amount of active power based on a pre-set configuration of the generators (20; 22; 24) and the active power reserve; and generating an active power request and dispatching (106) the active power request to the generators for providing the additional amount in accordance with the calculated contributions.

Description

Technical Field

[0001] This disclosure relates to a method for controlling a hybrid power plant. Aspects of the invention relate to a hybrid power plant controller and a hybrid power plant. Background Technology

[0002] Regulators and operators of power grids expect grid-connected power plants to comply with "grid regulations" and provide special ancillary services to the power grid.

[0003] For example, some operators require power plants to support the power grid when its frequency deviates from normal operating range. A range of control strategies have been developed for wind power plants to provide “fast frequency response.” During these under- or over-frequency events, active power is increased or decreased respectively to offset the frequency deviation when a fast frequency response is provided.

[0004] However, these control strategies are only suitable for wind turbine generators. The increasing prevalence of hybrid power plants, combined with different types of renewable energy generators, necessitates new control strategies that are applicable to all types of generators within the power plant, not just wind turbine generators.

[0005] The purpose of this invention is to address this need. Summary of the Invention

[0006] According to one aspect of the invention, a method is provided for controlling a hybrid power plant connected to an electricity grid, the hybrid power plant comprising at least two types of renewable energy generators having an active power reserve for supplying additional active power to the electricity grid; the method comprising, during an underfrequency event detected on the electricity grid where the frequency level of the electricity grid drops below its nominal frequency: determining an additional amount of active power to be supplied by the hybrid power plant to the electricity grid, thereby providing a rapid frequency response; and calculating, based on a priority sequence configuration of the generators and the active power reserve, a generator from each of the at least two types of generators for supplying the additional active power. The contribution; and generating an active power request based on the calculated contribution and assigning the active power request to the generators for supplying the additional amount, wherein the priority sequence configuration includes a sequence in which generators of the type shall cumulatively provide the maximum possible contribution to the additional amount, wherein at least one type of generator is configured to contribute active power from reserves and use an overboost mechanism, and wherein the sequence includes an inlet for the reserves and an inlet for the overboost, the inlet for the reserves being earlier in the sequence than the inlet for the overboost, and wherein the overboost mechanism is the ability of a type of generator to supply more active power than its rated value for a short period of time.

[0007] During a frequency under-frequency event, the frequency level of the power grid drops below the network's nominal frequency.

[0008] By controlling the generator type according to a preset configuration, power plants can be controlled in a more dynamic manner. While many benefits depend on the operator's control strategies and intentions, using preset configurations offers the overall benefit of improved efficiency in the use of available resources and reserve capacity during frequency events. Dynamic control of the generators also ensures adequate frequency response while allowing for better understanding of how the power plant is operating. This invention is particularly useful for hybrid power plants with multiple different generator types because control can vary in many different ways to react quickly to frequency events, maintain frequency response, and, in some cases, participate in ancillary service markets that are not typically open to renewable power plants.

[0009] Calculating the contribution may include comparing the remaining amount of the extra amount with the available capacity of the generator's reserves, in the order of the generator types in the sequence. If the remaining amount exceeds the generator's available capacity, calculating the contribution may include setting the contribution equal to the available capacity. If the available capacity exceeds the remaining amount, calculating the contribution may include setting the contribution equal to the remaining amount.

[0010] The method may optionally include, during the recovery period following over-boost, when the active power contribution of one type of generator drops below the nominal level, using reserves from a different type of generator to compensate for at least part of the drop during this recovery period. The reserves of this type of generator providing compensation may be reserved solely for compensation. Alternatively, the reserves of this type of generator may be divided into reserves for contributing to the additional amount and reserves for compensation. The generator providing compensation may include battery energy storage devices.

[0011] Calculating the contribution may include comparing the demand ramp rate to a ramp rate limit for a particular type of generator in the sequence. If the demand ramp rate exceeds the ramp rate limit, calculating the contribution may include calculating the contribution from the next type of generator in the sequence to meet the demand ramp rate.

[0012] Hybrid power plants may include at least two types of generators selected from a list that includes: wind turbine generators; battery energy storage systems; and / or photovoltaic generators.

[0013] A hybrid power plant may include a wind turbine generator, a battery energy storage system, and a photovoltaic generator. In a sequence, the wind turbine generator and the photovoltaic generator may be positioned before the battery energy storage system, wherein the preset configuration includes this sequence.

[0014] Subsidiary wind power plants can be supplied as separate types of renewable energy generators to the wind turbine generators of hybrid power plants.

[0015] Within the scope of this application, it is intended that the various aspects, embodiments, examples, and alternatives set forth in the foregoing paragraphs, claims, and / or the following description and drawings, as well as 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 such features are incompatible. Notwithstanding this statement previously, the applicant reserves the right to amend any previously filed claim or accordingly file any new claim, including the right to modify any previously filed claim to be subordinate to any other claim and / or to incorporate any feature of any other claim. Attached Figure Description

[0016] One or more embodiments of the invention will now be described by way of example only, with reference to the accompanying drawings, in which:

[0017] Figure 1 It is a schematic diagram of a hybrid power plant, its connection to the power grid, and its control system.

[0018] Figure 2 This is a chart indicating a decrease in an exemplary frequency;

[0019] Figure 3 It is an operation according to an embodiment of the present invention. Figure 1 The method of hybrid power plant in China; and

[0020] Figures 4 to 10 It is shown in Figure 3 The method is used to determine Figure 1 A diagram illustrating different configurations of generator contributions in a hybrid power plant. Detailed Implementation

[0021] Generally, this application relates to a method for controlling a hybrid power plant to provide additional active power during frequency undercurrent events, and to the configuration of a hybrid power plant controller for implementing such a method. The method utilizes a configuration, which can also be considered a “scheme,” “allocation,” or “control strategy,” according to which the generators of the power plant are employed to provide additional active power. Generally, this configuration may include partitioning, proportionalizing, or segmenting the power supplied by different types of generators in response to a detected frequency event, and this can be achieved, for example, by using a percentage partition between different types of generators or a sequence indicating the order in which the reserve power supplied by different types of generators should be used. Such a method achieves an efficient and complete fast frequency response from the hybrid power plant. Furthermore, this response is configurable, allowing the operator of the power plant or power plant controller to adjust how the fast frequency response is provided. This flexibility ensures that optimal provision of additional active power in response to frequency drops can be achieved.

[0022] As used herein, the term and concept of “Fast Frequency Response” (FFR) are defined as the rapid correction of power imbalances that cause frequency deviations. National or international power grids typically have a nominal frequency, also known as the utility frequency or grid frequency. Around the world, this nominal frequency is typically 50 Hz or 60 Hz. Frequency variations are undesirable because the equipment supplied with electricity is configured to operate at a specific frequency with relatively tight tolerances. Therefore, when the frequency deviates from the nominal frequency (even by less than 1 Hz), it is important to quickly correct the deviation, typically within a few seconds at most. Thus, in these cases, it is desirable to quickly correct the frequency and restore it to its nominal value, and this is provided by FFR. Grid regulations can penalize or disconnect power plants deemed to destabilize the frequency and the grid as a whole and / or fail to respond to frequency deviations.

[0023] FFR encompasses both inertial simulation and inertial simulation control. FFR typically executes over a short timeframe and is dependent on specific grid regulations. Therefore, frequency control during FFR is supplied based on predetermined curves and / or predetermined calculations related to the amount of active power injected into the grid to offset specific frequency variations. FFR should be distinguished from frequency control. Frequency control maintains the frequency level within a small dead zone near the nominal frequency and is the primary response of the system during normal operation. FFR is the system's response under special circumstances, such as when the rate of change of frequency exceeds a threshold or when the frequency deviates out of the dead zone or from its nominal value beyond a threshold. Therefore, as will be discussed in more detail below, FFR depends on one or more triggers.

[0024] The FFR is typically provided by an inertial controller, which operates in conjunction with a frequency controller, both of which are located within the hybrid power plant control system. The inertial controller is configured to determine one or more triggers in the triggering process, thereby determining the additional amount of active power to be requested from the generator, and accordingly dispatching the request for that active power, as appropriate, as a setpoint or reference.

[0025] To help explain the provision of a fast frequency response within a hybrid power plant Figure 1 A typical architecture is shown where a hybrid power plant (HPP) is connected to the main transmission grid as part of a wider power network. An HPP comprises three sub-power plants: a battery energy storage system, a solar sub-power plant, and a wind sub-power plant. More generally, as a skilled reader will understand, an HPP is a power plant that includes at least two different types of renewable energy generators.

[0026] If the term "type" of generator is discussed in this article, it is generally defined in relation to the source of its renewable energy, such that different types of generators generate energy from different renewable energy sources. For example, wind turbine generators in a hybrid power plant can be considered one type of generator because they generate energy from wind. Photovoltaic cells can be another type of generator because they generate energy from a different source than wind (i.e., solar energy). While battery energy storage systems do not directly generate renewable energy, they can be considered another type of generator because they are able to supply energy collected from renewable energy sources in a different way than wind and solar generators. In some embodiments, generators in other power plants can be considered a separate type because they generate energy from renewable energy sources in different locations, even if the source is of the same type. In other words, two wind sub-power plants can be considered different types of generators because they are located in different locations.

[0027] The example shown in the diagram is merely representative, and skilled readers will understand that other specific architectures of an HPP are possible. For example, it is possible for more than three sub-power plants to be incorporated into an HPP, or for an HPP to include only two sub-power plants. Furthermore, skilled readers will understand that the sub-power plants forming an HPP can be composed of a single generator. Therefore, since a sub-power plant can include a single generator, and a hybrid power plant requires two or more sub-power plants, a hybrid power plant can be defined as a power plant that incorporates at least two renewable energy generators, where the power generated by the power plant is generated from at least two different sources of renewable energy. While PV, wind, and battery energy have been discussed in this paper, it will also be understood that other forms of renewable energy generators can be included in an HPP as appropriate, and the concept of reserves described below also applies to other types of generators.

[0028] In some embodiments described herein, the power plant outside the HPP operates in a master-slave architecture. For the purposes of this application and for ease of description, the power plant will be considered part of the HPP during the period in which it operates in such a slave configuration.

[0029] Skilled readers will understand that the methods, systems, and techniques described below can also be applied to power networks with many different configurations. Furthermore, the components of hybrid power plants and power networks are conventional and therefore will be familiar to skilled readers. (Except for...) Figure 1 In addition to the components shown and described, other known components may be incorporated, or other known components may be incorporated as... Figure 1 Alternatives to the components shown and described. Such changes will be within the capabilities of a skilled technician.

[0030] Consider in more detail Figure 1 Power system 10 incorporates HPP 12. HPP 12 comprises three sub-power plants: a solar sub-power plant 14, a wind sub-power plant 16, and a battery energy storage sub-power plant 18. Solar sub-power plant 14 comprises multiple photovoltaic (PV) generators 20 configured to convert solar energy into electrical energy, more commonly referred to as PV cells. Wind sub-power plant 16 comprises multiple wind turbine generators (WTGs) 22 configured to convert wind energy into electrical energy. Battery sub-power plant 18 comprises multiple electrochemical battery cells 24 operable to store and release electrical energy as needed, such as lithium-ion storage units. It would also be possible for a single WTG 20, PV cell 22, or battery cell 24 to be located in each of these sub-power plants 14, 16, and 18. The electrical energy generated or released by each sub-power plant 14, 16, and 18 is transmitted as active current to the main transmission network or main grid 26 for distribution.

[0031] As already discussed, fast frequency response is implemented by providing additional active power to the main grid 26 via HPP 12. Each type of generator is capable of providing additional active power beyond its normal active power generation in at least one manner during fast frequency response.

[0032] First, considering wind power, the WTG 22 is configured to incorporate a so-called "spinning reserve." The spinning reserve includes at least an additional amount of active power generation specifically designated for rapid frequency response. The WTG has a rated power or maximum power generation capacity during normal operation, such as 3MW, and the spinning reserve includes a specified amount of that rated power. For example, a percentage of the rated power can be specifically designated and marked as the spinning reserve. Therefore, the spinning reserve is not used during normal power generation, so that the maximum output of the WTG is a set amount below the rated power. For example, a wind turbine generator may have a nominal power of 3MW, with 10% designated as the spinning reserve. Thus, 0.3MW of the wind turbine generator's power capacity is reserved for responding to underfrequency events, so that the generator's maximum active power generation under normal conditions is 2.7MW.

[0033] Spin reserve can include any WTG that is not currently in use and can therefore be used to increase the generated capacity. Of course, this assumes that the wind speed is high enough to sustain such an increase. Again, using the example of a 3MW rated WTG with 10% spin reserve, if the WTG is only outputting 1.5MW instead of its maximum of 2.7MW, then 1.5MW can still be used as spin reserve.

[0034] WTGs can also supply active power above their rated capacity for short periods of time via an "over-boost" mechanism. Generally, an over-boost mechanism, as used in this article, involves power output from the generator that is above the normal operating level or the normal permissible operating level and can only be maintained for a short period of time (approximately a few seconds or minutes).

[0035] By using an overboost mechanism, the kinetic energy from the rotating components of a wind turbine generator (such as the rotor itself) is utilized and repurposed to provide a brief boost to the released active power. In other words, overboosting is the conversion of kinetic energy into electrical energy in the form of active power. Because the kinetic energy of the rotating components is effectively consumed when using overboosting, there is typically a "recovery" period after the additional active power has been supplied, during which the lost kinetic energy is recovered, and thus the active power output decreases to account for this recovery. The recovery period depends on the wind speed at the time of recovery. Since kinetic energy can be recovered much faster, high wind speeds can make the length of the recovery period negligible.

[0036] As mentioned above, overboosting can only be used for a short period of time; otherwise, the rotor loses too much kinetic energy to return to normal operation. Although, in the case of multiple generators, the duration of overboosting depends on the amount of additional active power requested and the number of turbines with overboosting capability, for each generator, overboosting is typically available for a period of up to 5 or 10 seconds. For example, a high active power injection may allow an overboost of only 10 seconds, while a lower active power injection may allow the overboosting capability to be increased to a longer period, such as 30 seconds or longer.

[0037] The PV generator 20 can also provide an active power reserve in the same manner as described above for WTG 22, which is functionally equivalent to a spinning reserve. For this purpose, a portion of the generator's active power generation capacity needs to be reserved for providing such a reserve. In some cases, the PV generator 20 or the battery energy storage unit 24 can also be configured to provide overboost when conditions permit. For ease of expansion, the PV generator and battery energy storage unit can be configured to provide overboost to the relevant units based on a current higher than the converter's rated current.

[0038] Battery energy storage unit 24 includes a storage device for the storage of charge for supplying active power on demand, a portion of which can be designated as a reserve of active power for rapid frequency response. In some embodiments, the entire capacity of the battery energy storage system can be for the purpose of rapid frequency response, i.e., the battery system is designed and provided entirely for this purpose. In contrast to PV generator 20 and wind turbine generator 22, battery energy storage system 24 is a non-generating system, and therefore the reserve is not an additional amount beyond the generated power, but rather the amount of power stored within the storage device. Since the battery energy storage system requires some charge to release active power, limits or specific amounts of charge can be defined or reserved to provide reserves for certain situations. For example, maximum and minimum levels of the battery system's state of charge can be defined for rapid frequency response, frequency control other than rapid frequency response, and the overall operation of the storage system (other than absolute maximum values ​​(i.e., full charge) and minimum values ​​(i.e., complete depletion).

[0039] Back Figure 1Within each sub-power plant 14, 16, 18, each of the generators 20, 22, 24 is connected to a local power grid (not shown) that links the generators 20, 22, 24. Sub-power plants 14, 16, 18 can also be connected to each other via a suitable inter-sub-power plant power grid (also not shown) or a collector bus. Through this power grid or collector bus, HPP 12 is connected to the main power grid 26 (also referred to as the main power network) via connection network 28. HPP 12 and the main power grid 26 are connected at an interconnection point (PoI) 30, which is the interface between HPP 12 and the main power grid 26. Unless otherwise indicated, references to connected components or connections between components should be assumed to include suitable feeders or transmission lines.

[0040] Figure 1 Each of the generators 20, 22, and 24 within the sub-power plants 14, 16, and 18 is associated with a corresponding generator controller (generally designated 32). In some embodiments, a subset of generators 20, 22, and 24, such as those within the wind sub-power plant 22, may share a single semi-centralized controller, resulting in fewer generator controllers than generators. It will be apparent to those skilled in the art that the generator controller 32 can be considered a computer system capable of operating the PV cells 20, WTG 22, and / or battery cells 24 in the manner specified herein, and may include multiple modules controlling individual components of each generator 20, 22, and 24.

[0041] During the operation of HPP 12, generator controller 32 operates to implement active and reactive current requests received from hybrid power plant controller (HPPC) 34 at its respective generator(s) 20, 22, 24. In some embodiments, HPPC 34 may be directly connected to generators 20, 22, 24 without an intermediate controller, and setpoints may be assigned accordingly.

[0042] HPPC 34 is connected to the power grid 10 at the point of measurement (PoM) 36 and is also directly connected to each of the sub-power plants 14, 16, and 18 of HPP 12. HPPC 34 acts as a command and control interface between HPP 12 and the power grid 26, and more specifically, as a command and control interface between sub-power plants 14, 16, and 18 and the grid operator or transmission system operator (TSO) 38. HPPC 34 is a suitable computer system for executing the controls and commands as described above, and therefore incorporates a processor 40, a connectivity module 42, a memory module 44, and a sensing module 46. Processor 40 incorporates a frequency controller 48 and an inertial controller 50. The inertial controller 50 conventionally functions to provide an inertial response based on changes in active power that depend on frequency. The inertial controller 50 can also provide a frequency response based on frequency deviations as discussed herein. HPPC 34 can also receive information about the power grid 26 and / or the connection network 28 from the energy management system (not shown) or through direct measurement.

[0043] HPPC 34 connects to the connection network 28, thereby allowing monitoring and adjustment of the output of HPP 12 and accurate interpretation of power demand. HPPC 34 measures various parameters representing the state of the grid 26 and HPP 12, and can be used to improve the output of HPP 12 to best meet the requirements of TSO 38 or a set of grid-specific requirements.

[0044] In some embodiments, the HPPC 34 can be configured to communicate with a power plant controller of a separate power plant (not shown) and issue commands for the separate power plant to follow. In these embodiments, the HPPC 34 and the separate power plant controller operate in a master-slave architecture.

[0045] As described above, sub-power plants 14, 16, and 18 of HPP 12 can change their power output in response to commands received from HPPC 34 via specific controllers. It should be noted that... Figure 1 This is a schematic diagram, and therefore the method of transmitting control commands is not explicitly depicted. However, it will be understood that appropriate wiring can be provided to interconnect the HPPC 34 with sub-power plants 14, 16, 18, generators 20, 22, 24, or generator controller 32. The interconnection can be a direct connection or a "point-to-point" connection, or it can be part of a local area network (LAN) operating under an appropriate protocol, such as CAN bus or Ethernet. Furthermore, it should be understood that control commands can be transmitted wirelessly via an appropriate wireless network, rather than using wiring, for example, operating under WiFi™ or ZigBee™ standards (IEEE 802.11 and 802.15.4, respectively).

[0046] As discussed above, HPPC 34 manages HPP 12 according to a set of grid requirements dedicated to the main grid 26. In this description, as implemented by HPPC 34, the focus is on the frequency regulation of the main grid and the FFR provided by HPP 12.

[0047] During frequency deviations, the HPP 12, operated by the HPPC34 according to the embodiments described herein and the methods described herein, employs a fast frequency response to offset the frequency deviation. During an underfrequency event, or "frequency drop," in which the frequency falls below its nominal level, the HPP 12 is configured to increase the frequency level by increasing its active power contribution to the grid. During an overfrequency event, in which the frequency rises above its nominal level, the HPP 12 is configured to respond by reducing its active power output to the grid, thereby decreasing the frequency level.

[0048] The following description focuses on underfrequency events and the fast frequency response to these underfrequency events.

[0049] Figure 2 An exemplary underfrequency event is illustrated. This event can be divided into three approximate periods. In the first period (between time t0 and time t1), the frequency begins to decrease from its nominal frequency, which in this example is 50 Hz. An FFR is provided based on one or more trigger events. During the first period (the so-called "inertia" period), the FFR is increasing and the frequency decrease slows down. During the second period (between time t1 and time t2), the initial rate of change of the frequency decreases, slows down to a minimum frequency value, and begins to increase again. This second period is the period of "primary frequency control" and is the period that provides the FFR. Once the frequency level reaches a plateau within a threshold of the nominal frequency, a third period (between time t2 and t3) begins, during which "secondary frequency control" is performed. Secondary frequency control is frequency control that uses regular frequency control to restore the frequency to the nominal frequency and is therefore not considered part of the FFR.

[0050] As mentioned above, there are differences in frequency control between normal conditions and during FFR. FFR is initiated by one or more trigger events identified at HPPC, specifically within the inertial controller. FFR triggering includes meeting criteria, including: the frequency error value exceeding a threshold, the frequency dropping below a threshold, and the rate of change of the frequency exceeding a threshold. FFR may terminate when one of the following criteria is met: the overboost period ends; the time period since the initial trigger has elapsed; or the frequency error value decreases to an acceptable level / the frequency recovers to a range near the nominal value.

[0051] exist Figure 2In the example, during the first time period, the rate of change of frequency was high and the error value exceeded its threshold, thus triggering and initiating a fast frequency response.

[0052] In response, HPPC 34, and in particular the inertial controller 50, implements one or more control strategies and controls the generator of HPP 12 accordingly. During underfrequency events, HPPC 34 is configured to implement... Figure 3 Method 100. In the first step 102, the additional amount of active power supplied by HPP 12 to the main grid 26 to provide FFR is determined. After the additional amount has been determined, in the next step 104, HPPC 34 calculates the contribution from each type of generator. Figure 1 In this embodiment, the generator types are arranged in sub-power plants, thereby calculating the contribution from each sub-power plant 14, 16, 18. The contribution is used to supply an additional amount of active power to the main grid 26. The contribution is calculated based on a configuration or control strategy set within or by the HPPC 34. Based on the calculated contribution, at the next step 106, the HPPC 34 generates and distributes a request for an additional amount of active power to the local controller 32 or directly to the generators 20, 22, 24. Thus, in other words, when the FFR is active, i.e., after triggering, the HPPC 34 determines the additional active power required to support the restoration of the grid frequency, and then commands the generators 20, 22, 24 to provide that additional active power according to the configuration the HPPC 34 is using in accordance with its operation. Method 100 is repeated at a predetermined frequency to determine new contributions.

[0053] The following text is for reference only. Figures 4 to 10 The configuration and control strategies are described. Figures 4 to 10 This is a chart illustrating how contributions from each type of generator can be made to meet the additional needs of supporting the main power grid. Since each chart has an appropriate legend, additional annotations with figure labels will be provided only where clarity is necessary.

[0054] Figure 4 The first configuration type is shown. In this configuration, the HPPC 34 implements a percentage allocation of the additional amount between generator types or between sub-power plants. In other words, the HPPC 34 determines the additional amount and applies the percentage allocation to the additional amount to determine the contribution required from each type of generator. Figure 4 In this embodiment, 50% of the additional active power for frequency support will be provided by WTG spinning reserve, 30% by PV reserve, and the remaining 20% ​​by battery energy storage system reserve. The total demand for the FFR period is shown as follows. Figure 4The main curve in the image is shown below, with each segment divided according to a percentage.

[0055] These values ​​are used by way of example only, and it will be understood that the percentage segmentation can be changed and reconfigured within the HPPC 34 as needed or according to other criteria. For example, in some embodiments, the percentage segmentation can be configured within the HPPC 34 at installation time and cannot be changed. In other embodiments, the percentage segmentation can be configured by the operator via the operator interface.

[0056] In some embodiments, the percentage segmentation may be in response to data received by HPPC 34 relating to the operation of the power grid 26 and / or HPP 12 and its generators 20, 22, 24. Figure 5 A specific example is shown below. In this example, the available power, which is part of the reserve of WTG 22, fluctuates due to changes in wind speed. Therefore, the change in available power provided by WTG 22 is transmitted to HPPC 34. If it is determined during the comparison between the calculated contribution to WTG 22 and the available power from WTG 22, that WTG 22 is unable to supply its contribution, HPPC 34 can determine a shortage in available active power capacity and temporarily adjust the percentage allocation to increase the contribution of PV 20 and battery energy storage system 24 to fill the shortage.

[0057] like Figure 5 As shown, at time t1, the available power starting from WTG 22 begins to decrease. At each subsequent time point (during which HPPC 34 is calculating the split), the contribution of WTG decreases. When WTG 22 is unable to supply any additional power at all, it can be seen at point t2 that PV 20 and battery storage device 24 provide an additional amount of active power. The split between these two remaining assets is calculated based on a weighted average that divides the shortage according to their original ratios. In the example where the turbine is supplying 50%, the PV is supplying 30%, and the battery storage device is supplying 20%, reducing the turbine percentage to 0% will cause that 50% to be split between the PV and battery storage device according to their original ratios, increasing the contribution of PV by 30% to 60% and the contribution of battery storage device to 40%.

[0058] In this example, HPPC 34 can also receive data from the PV and battery storage systems to ensure that the redistribution of additional amounts does not exceed the available capacity of these two power generation systems. If the capacity of a sub-power plant is exceeded, HPPC 34 can request full capacity from that sub-power plant and recalculate the shortage, thereby determining the further contribution that will be provided by one or more remaining sub-power plants.

[0059] As an alternative to percentage-based allocation, HPPC 34 implements a priority list or sequence of generator types and / or sub-power plants, according to which the additional amount should be satisfied. Based on this configuration, HPPC 34 determines the additional amount and, based on the sequence and capacity of available generators, determines the contribution for each sub-power plant or generator type. Following this sequence, contributions are calculated to equal the maximum additional amount that generator of that type can supply, until the cumulative total of contributions equals the additional amount.

[0060] Figure 6 An example using priority sequences is shown in [the image]. Figure 6 In the example, the reserve of WTG is first in the sequence, followed by the reserve of PV, and finally the reserve of the battery storage system. The power limit / available capacity for each type of generator is shown by black lines identified by reference numerals 62, 72, and 82 for WTG, PV, and battery storage systems, respectively.

[0061] It can be seen that, firstly, in the region between t0 and t1, the extra amount is less than the available capacity of the first type of generator (WTG) in the sequence. Therefore, the reserves of the WTG are used to satisfy the entire extra amount. Since the extra amount is less than the capacity of this type of generator, the request sent to the WTG is equal to the extra amount.

[0062] Subsequently, between t1 and t2, the additional amount exceeds the capacity of the WTG. During this period, HPPC 34 determines that the WTG alone cannot meet the additional amount and therefore requests the maximum contribution from the WTG, which equals the available reserve capacity. HPPC 34 then determines whether the PV can supply the remaining portion of the additional amount after utilizing the available capacity provided by the WTG. As seen between t1 and t2, if the remaining portion is less than the PV's capacity, the remaining portion is requested. If the remaining portion is greater than the PV's capacity, HPPC requests the maximum contribution from the PV and proceeds to the next in the sequence (in this case, the battery energy storage system), determining at each step of the process whether the next in the sequence can meet the remaining portion of the additional amount. Between t2 and t3, the cumulative capacity of the WTG and PV generators is exceeded, so the battery energy storage reserve is used next. The storage reserve can provide the remaining portion of the additional amount, which is the additional amount minus the reserve capacity of the earlier generators (PV generator and WTG) in the sequence. This process continues in this way until the fast frequency response ends.

[0063] If, during the response period, the capacity of one type of generator increases or decreases, the contribution is redistributed accordingly, but the sequence is still utilized. The following... Figure 10 The phenomenon is described and illustrated in the text.

[0064] Although the sequence is strictly indicated here as one generator at a time, the sequence may include multiple types of generators or sub-power plants to be used at once. For example, in the sequence according to the embodiment, WTG and PV may be indicated first, followed by the battery energy storage system. In this embodiment, HPPC 34 initially divides the extra amount between WTG and PV before utilizing the reserves of the battery energy storage system, until the reserve capacity of both is fully utilized.

[0065] In addition to percentage segmentation and sequence implementation, there are several additional features that can be used to improve the fast frequency response of hybrid power plants.

[0066] Figure 6 This illustrates the use of more than one type of generator to initially meet active power demand. This is useful when the ramp rate of one type of generator may not be high enough to initially meet the demand. Figure 7 In the process, the frequency response begins at t0. The sequence configuration is being used in the order of WTG, PV, and battery. Between t0 and t1, it can be seen that initially the WTG's ramp rate is too low to meet the active power demand. Therefore, to meet the demand, active power is also supplied by the PV. The contribution from the PV is maintained until the WTG is increased to a point where the demand is met solely by the WTG or the WTG's capacity is requested.

[0067] When applied in percentage-segmentation mode, the slower ramp rate of WTG compared to PV and battery storage devices can be compensated for by briefly shifting the percentage segment. This principle is consistent with the principles regarding... Figure 5 The same applies, but the available capacity is less than the percentage requested by PPC.

[0068] Of course, it will be understood that the system can be configured to incorporate the slope limit corresponding to the maximum slope rate, at which additional active power may be required.

[0069] As already described, some renewable energy generators (particularly WTGs, and occasionally PV generators) are configured to provide a so-called "overboost" mechanism. Where overboost is possible and permitted, it can be used as an additional "type" of reserve separate from the original reserve. Therefore, for Figure 1 The three sub-power plants in the FFR may have four or even five additional sources of active power.

[0070] Typically, overboosting is used only as a last resort, although it can be used in the same manner as any reserve already described if needed. However, its short-term nature allows it to temporarily boost active power output to meet high additional demand.

[0071] Figure 8 An example of this situation is shown in [the image]. Figure 8 In this context, a sequence configuration is used, where the sequence readouts are: WTG reserve, PV, battery, and WTG overboost. Therefore, as... Figure 8 As shown, initially, when a frequency event occurs, the maximum WTG and PV contributions are requested, and the remaining amount is contributed by the battery storage device. At time t... 过升压 At this point, the required additional amount increases to a level higher than what the storage system can provide, exceeding the storage system's capacity. At this point, the first three types of generators in the sequence are making their maximum contribution by providing their entire available reserve capacity. As a result, the sequence indicates that overboost is the next generation type to meet the demand. Therefore, at t 过升压 After that, in t x In this case, the WTG overboost mechanism is used for as long as possible, or until its contribution is no longer needed.

[0072] As described above, there is a period of time required for the pressure to return to normal after the initial boost. Figure 8 The diagram shows the recovery period after the additional active power level has returned to zero. The recovery causes the active power level to decrease.

[0073] In some embodiments (e.g.) Figure 9 In the embodiment, one or more reserves from other generators within HPP 12 can be used to mitigate overvoltage recovery. For example, such as Figure 9 As shown, battery energy storage reserves can be used to replenish active power levels during recovery periods. In the illustrated embodiment, the battery energy storage system is used during both the FFR and recovery after overboost. However, in other cases, the battery energy storage device can be specifically reserved for use only during overboost recovery. While the battery energy storage system described herein is intended for recovery period compensation, it will be understood that any type of generator or sub-power plant can be used for this purpose.

[0074] Providing this embodiment enables participation in Frequency Control Ancillary Services (FCAS) markets, such as the emergency FCAS market in Australia and the ancillary services market in Ireland. These markets require the continuous provision of additional active power for a predetermined period of time, which can be approximately a few seconds, tens of seconds, or hundreds of seconds. For example, both the Irish and Australian markets have set time ranges such as five minutes or 300 seconds, as well as other ranges. Operating HPP 12 according to the embodiments described herein can increase the time a power plant can provide ancillary services, enabling the possibility of operating and providing additional active power for a continuous period of time, which may be long and perhaps exceed 300 seconds. Figure 10 An example of this situation is shown in the figure.

[0075] exist Figure 10 As can be seen, HPP 12 is operating in priority mode. When a frequency event occurs at 0 seconds, there is no capacity available for WTG reserve support, so PV reserve power is used, where stored active power is being utilized to supplement the remaining amount of additional active power. Once wind power reserves become available at approximately 30 seconds, HPPC 34 reduces the amount of stored power used from the battery energy storage system and increases the active power requested from the WTG. The available capacity of PV and WTG continues to vary throughout the 300-second window. For example, at approximately 200 seconds, the capacity of WTG and PV is high enough that the storage system is not utilized for a 40-second period.

[0076] Between approximately 130 and 160 seconds, it was in Figure 10 The number (1) in the circle indicates that the PV and WTG capacities are low, and the storage reserves for FFR are insufficient to meet full capacity. Therefore, according to the priority sequence, HPPC 34 plays the role of implementing the overboost capability of WTG to compensate for the shortage. After (1), the turbine recovery period occurs, which is compensated by the battery storage reserves.

[0077] While the above description pertains to under-frequency events, it will be understood that in over-frequency events, the frequency may also rise above the nominal frequency. The techniques described above can also be applied to over-frequency events, allowing configurations including percentage segmentation and priority sequences to be applied to how active power from various types of generators is reduced. As will be understood, this will be managed with reference to the minimum feasible output of the generator (particularly the WTG).

[0078] It will be understood that various changes and modifications can be made to this invention without departing from the scope of this application.

Claims

1. A method (100) for controlling a hybrid power plant (12) connected to an electricity network (26), the hybrid power plant (12) comprising at least two types of renewable energy generators (20; 22; 24) having an active power reserve for supplying additional active power to the electricity network (26); the method (100) comprising, during an underfrequency event detected on the electricity network (26) where the frequency level of the electricity network (26) drops below the nominal frequency: Determine (102) the additional amount of active power that will be supplied by the hybrid power plant (12) to the power grid (26) to provide a fast frequency response; Based on the priority sequence configuration of the generators (20; 22; 24) and the active power reserve, calculate (104) the contribution from each of the at least two types of generators (20; 22; 24) for the additional amount of active power supplied; as well as An active power request is generated based on the calculated contribution, and the active power request is assigned (106) to the generator for supplying the additional amount. The priority sequence configuration includes a sequence in which generators of the aforementioned types (20; 22; 24) should cumulatively contribute the maximum possible amount to the additional quantity. In this embodiment, at least one type of generator (20; 22; 24) is configured to contribute active power from a reserve and use an overboost mechanism, and the sequence includes an inlet for the reserve and an inlet for the overboost, the inlet for the reserve being earlier in the sequence than the inlet for the overboost, and the overboost mechanism being the ability of a type of generator to supply active power above its rated value for a short period of time.

2. The method (100) according to claim 1, wherein, The calculation of the contribution (104) includes: comparing the remaining portion of the additional amount with the available capacity of the generators (20; 22; 24) in the order of their types, and wherein if the remaining portion exceeds the available capacity of the generators (20; 22; 24), the contribution is set to be equal to the available capacity, and wherein if the available capacity exceeds the remaining portion, the contribution is set to be equal to the remaining portion.

3. The method (100) according to claim 1, comprising: During the recovery period after over-boosting, one type of generator (20; 22; When the active power contribution of 24) drops below the nominal level, during the recovery period after the over-boost, the reserves of different types of generators (20; 22; 24) are used to compensate for at least part of the drop.

4. The method (100) according to claim 3, wherein, The reserves of the generators (20; 22; 24) of the type provided for compensation are reserved for compensation only.

5. The method (100) according to claim 3, wherein, The reserves of the generators (20; 22; 24) of the aforementioned types are divided into reserves for contributing to the additional amount and reserves for compensation.

6. The method (100) according to any one of claims 3 to 5, wherein, The generators (20; 22; 24) of the type that provide compensation include battery energy storage devices (24).

7. The method (100) according to any one of claims 3 to 5, wherein, The calculation of the contribution (104) includes: comparing the demand slope rate with a slope rate limit for one type of generator (20; 22; 24) in the sequence, and if the demand slope rate exceeds the slope rate limit, calculating the contribution from the next type of generator (20; 22; 24) in the sequence to satisfy the demand slope rate.

8. The method (100) according to any one of claims 1 to 5, wherein, The hybrid power plant (12) includes at least two types of generators (20; 22; 24) selected from a list including the following: wind turbine generator (22); battery energy storage system (24); and / or photovoltaic generator (20).

9. The method (100) according to claim 8, wherein, The hybrid power plant (12) includes a wind turbine generator (22), a battery energy storage system (24), and a photovoltaic generator (20), wherein, in the sequence, the wind turbine generator (22) and the photovoltaic generator (20) are located before the battery energy storage system (24).

10. The method (100) according to claim 8, wherein, The subordinate wind power plant is supplied as a separate type of renewable energy generator to the wind turbine generator (22) of the hybrid power plant (12).

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