A new energy station hierarchical control method and system

Abstract

The application discloses a new energy station hierarchical control method and system, the method comprises the following steps: obtaining the short-circuit ratio and the ratio of equivalent reactance to equivalent resistance of each new energy station at the access point of the new energy station in a new energy base; dividing all the new energy stations into SSI-I level stations, SSI-II level stations and SSI-III level stations according to the short-circuit ratio and the ratio of equivalent reactance to equivalent resistance of each new energy station; controlling each grid-connected device in the SSI-I level station by using a station-level controller; controlling each grid-connected device and each network-constructing device in the SSI-II level station by using the station-level controller, and controlling the grid-connected point of the SSI-II level station as a PV node; controlling each grid-connected device and each network-constructing device in the SSI-III level station by using the station-level controller or using a grid-connected network-constructing fusion control strategy. By using the scheme, different control strategies can be adopted for new energy stations of different levels, so that the new energy stations can stably operate under different system intensities.

Description

Technical Field

[0001] This application generally relates to the fields of new energy power generation and power transmission technology. More specifically, this application relates to a hierarchical control method and system for new energy power plants. Background Technology

[0002] As the global energy structure accelerates its transition to a low-carbon model, new energy power generation, represented by wind and solar power, has become a core driving force for the sustainable development of the power system. The large-scale application of new energy sources has yielded significant results in optimizing the energy structure and reducing carbon emissions, but their high proportion of grid integration has also raised complex technical challenges. Especially in large-scale new energy bases such as those in remote desert areas, due to the vast geographical area, long transmission distances, and weak conventional power support, the surge in the proportion of new energy sources has led to a sharp decline in system strength. The power grid exhibits typical characteristics of a weak grid, including low inertia, weak damping, and a low short-circuit ratio, giving rise to multiple stability issues.

[0003] In terms of system characteristics, the long electrical distance between renewable energy units and the main grid, and insufficient support from synchronous power sources such as thermal power, lead to a significant increase in voltage sensitivity, making them prone to severe voltage fluctuations when power flow changes rapidly. In actual operation, the sending-end grid frequently faces problems such as transient overvoltage and voltage instability. Furthermore, the interaction between renewable energy units and weak grids (such as the interaction between doubly-fed wind turbines and series compensation lines, and the coupling between photovoltaic / direct-drive units and weak grids) can easily induce low-frequency / subsynchronous / supersynchronous oscillations, forcing the grid to adopt a conservative operation strategy that limits renewable energy output. Existing technologies mostly use synchronous condensers and grid-based energy storage (such as supercapacitor grid-based SVG) to improve short-circuit ratio and voltage support capabilities, but they have significant drawbacks: First, the initial investment and operation and maintenance costs of traditional synchronous condensers are high, significantly increasing the economic cost of renewable energy systems; second, the dynamic characteristics of existing grid-based equipment are not well adapted to the rapid power regulation requirements in scenarios with a high proportion of renewable energy, and the correlation mechanism between regulation capability and system parameters is not yet clear; third, the dynamic support strategies for anticipated faults and emergencies lack regionally differentiated design, making it difficult to cope with the multi-scale stability problems of wide-area power grids.

[0004] In view of this, there is an urgent need to provide a hierarchical control scheme for new energy power plants to overcome the shortcomings of existing technologies and improve the overall performance and stability of new energy power generation systems. Summary of the Invention

[0005] In order to at least solve one or more of the technical problems mentioned above, this application proposes a graded control scheme for new energy power stations in several aspects.

[0006] In a first aspect, this application provides a hierarchical control method for new energy power stations, comprising: acquiring the short-circuit ratio and the ratio of equivalent reactance to equivalent resistance of each new energy power station connected to the grid at the connection point of the new energy power station in a large-scale new energy base; classifying all new energy power stations into SSI-I level, SSI-II level, and SSI-III level power stations according to the short-circuit ratio and the ratio of equivalent reactance to equivalent resistance of each new energy power station; wherein, an SSI-I level power station consists of grid-connected equipment, an SSI-II level power station consists of grid-connected equipment and grid-building equipment, and an SSI-III level power station consists of grid-connected equipment and grid-building equipment; using a power station-level controller to control each grid-connected equipment in the SSI-I level power station, and controlling the grid connection point of the SSI-I level power station as a PV node, wherein each grid-connected equipment in the SSI-I level power station... The grid-connected equipment adopts PQ control; the site-level controller is used to control each grid-connected equipment and each network-building equipment in the SSI-II level site, and the grid connection point of the SSI-II level site is controlled as a PV node. Among them, each grid-connected equipment in the SSI-II level site adopts PQ control; the site-level controller is used to control each grid-connected equipment and each network-building equipment in the SSI-III level site, or a grid-connected and network-building integrated control strategy is adopted, and the grid connection point of the SSI-III level site is controlled as a PV node, and each grid-connected equipment and each network-building equipment in the SSI-III level site is controlled as a PV node. Among them, in the process of controlling each grid-connected equipment and each network-building equipment in the SSI-III level site, each grid-connected equipment and each network-building equipment in the SSI-III level site adopts PV control.

[0007] In some embodiments, the short-circuit ratio of the SSI-I level station is in a first short-circuit ratio range, and the ratio of the equivalent reactance to the equivalent resistance of the SSI-I level station is in a first ratio range.

[0008] In some embodiments, during the process of using a station-level controller to control each grid-connected device in an SSI-I level station, the station-level controller controls the active power and voltage at the grid connection point of the SSI-I level station and performs the following steps: obtaining the active power and reactive power commands issued by the station-level controller to each grid-connected device in the SSI-I level station; and each grid-connected device in the SSI-I level station outputs power according to the active power and reactive power commands.

[0009] In some embodiments, the short-circuit ratio of the SSI-II level substation is in a second short-circuit ratio range, and the ratio of the equivalent reactance to the equivalent resistance of the SSI-II level substation is in a second ratio range; wherein, the upper limit of the second short-circuit ratio range is less than the lower limit of the first short-circuit ratio range; and the lower limit of the second ratio range is greater than the upper limit of the first ratio range.

[0010] In some embodiments, during the process of using a station-level controller to control each grid-connected device and each grid-connecting device in an SSI-II level station, the station-level controller controls the active power and voltage at the grid connection point of the SSI-II level station according to active power and voltage commands, and performs the following steps: obtaining active power and reactive power commands issued by the station-level controller to each grid-connected device in the SSI-II level station; each grid-connected device in the SSI-II level station outputs power according to the active power and reactive power commands; configuring a corresponding number of grid-connecting devices in the SSI-II level station according to the short-circuit ratio and the ratio of equivalent reactance to equivalent resistance of all grid-connected devices in the SSI-II level station, and the short-circuit ratio and the ratio of equivalent reactance to equivalent resistance of the SSI-II level station; and using the station-level controller to control the grid-connecting devices to operate according to the grid conditions.

[0011] In some embodiments, the short-circuit ratio of the SSI-III level station is in the third short-circuit ratio range, and the ratio of the equivalent reactance to the equivalent resistance of the SSI-III level station is in the third ratio range; the upper limit of the third short-circuit ratio range is less than the lower limit of the second short-circuit ratio range; and the lower limit of the third ratio range is greater than the upper limit of the second ratio range.

[0012] In some embodiments, when using a site-level controller to control each grid-connected device and each grid-connecting device within an SSI-III level site, or adopting a grid-connection and grid-connection fusion control strategy, the site-level controller controls the active power and voltage at the grid connection point of the SSI-III level site and performs the following steps: determining whether the current grid is a weak grid or an extremely weak grid; in response to the current grid being a weak grid, the site-level controller sends active power and voltage commands to each grid-connected device and each grid-connecting device within the SSI-III level site, controlling each grid-connected device and each grid-connecting device within the SSI-III level site as a PV node; in response to the current grid being an extremely weak grid, the site-level controller controls each grid-connected device and each grid-connecting device within the SSI-III level site to adopt a grid-connection and grid-connection fusion control strategy through active power and voltage commands or through active power and reactive power commands.

[0013] In some embodiments, during the process of the site-level controller sending active power and voltage commands to each grid-connected device and each grid-connecting device in the SSI-III level site, and controlling each grid-connected device and each grid-connecting device in the SSI-III level site as a PV node, the following steps are performed: determining whether there is grid frequency fluctuation or grid power deficit; in response to the absence of grid frequency fluctuation or grid power deficit, the site-level controller adjusts the active power and voltage of each grid-connected device in the SSI-III level site according to the active power and voltage commands, so that the voltage of each grid-connected device is a set voltage value ... In the event of grid frequency fluctuations or grid power shortages, a station-level controller is used to adjust the active power of each grid-connected device within the SSI-III level station to achieve primary frequency regulation. Based on the short-circuit ratio and the ratio of equivalent reactance to equivalent resistance of all grid-connected devices within the SSI-III level station, and the short-circuit ratio and the ratio of equivalent reactance to equivalent resistance of the SSI-III level station itself, a corresponding number of grid-connected devices are configured within the SSI-III level station. The station-level controller is then used to adjust the active power and voltage of each grid-connected device within the SSI-III level station according to active power and voltage commands, ensuring that the voltage of each grid-connected device is at the set voltage value.

[0014] In some embodiments, during the process of the station-level controller controlling each grid-connected device and each grid-connecting device in the SSI-III level station to adopt a grid-connected and grid-connected integrated control strategy through active power and voltage commands or active power and reactive power commands, the following steps are performed: determining whether the real-time state of the power grid is a first state or a second state; in response to the real-time state of the power grid being the first state, adjusting the active power and voltage of each grid-connected device in the SSI-III level station according to the active power and voltage commands using the station-level controller, so that the voltage of each grid-connected device in the SSI-III level station is a set voltage value; in response to the real-time state of the power grid being the second state, adjusting the active power and reactive power of each grid-connecting device in the SSI-III level station according to the active power and reactive power commands using the station-level controller, so that the voltage of each grid-connecting device in the SSI-III level station is a set voltage value.

[0015] In the second aspect, this application provides a hierarchical control system for new energy power stations, employing the hierarchical control method for new energy power stations as described in any embodiment of the first aspect. The system includes: an analysis and calculation module for obtaining the short-circuit ratio and the ratio of equivalent reactance to equivalent resistance of each connected new energy power station at the new energy power station access point in a large-scale new energy base; a new energy power station hierarchical module for classifying all new energy power stations into SSI-I level, SSI-II level, and SSI-III level power stations based on their short-circuit ratios and the ratio of equivalent reactance to equivalent resistance, wherein an SSI-I level power station consists of grid-connected equipment, an SSI-II level power station consists of grid-connected equipment and grid-building equipment, and an SSI-III level power station consists of grid-connected equipment and grid-building equipment; and a first hierarchical control module for controlling each grid-connected equipment within an SSI-I level power station using a station-level controller, thereby controlling the SSI-I level power station's... The grid connection point is controlled as a PV node, where each grid-connected device in the SSI-I level station uses PQ control; the second hierarchical control module is used to control each grid-connected device and each network-building device in the SSI-II level station using a station-level controller, controlling the grid connection point of the SSI-II level station as a PV node, where each grid-connected device in the SSI-II level station uses PQ control; the third hierarchical control module is used to control each grid-connected device and each network-building device in the SSI-III level station using a station-level controller or using a grid-connection-network fusion control strategy, controlling the grid connection point of the SSI-III level station as a PV node, and controlling each grid-connected device and each network-building device in the SSI-III level station as a PV node, where during the control of each grid-connected device and each network-building device in the SSI-III level station, each grid-connected device and each network-building device in the SSI-III level station uses PV control.

[0016] Using the graded control scheme for renewable energy power plants provided above, this embodiment classifies all renewable energy power plants into SSI-I, SSI-II, and SSI-III levels based on their short-circuit ratio and the ratio of equivalent reactance to equivalent resistance. This allows for the graded identification of the different impacts of each power plant on grid stability. By employing differentiated control strategies for SSI-I, SSI-II, and SSI-III power plants, stable operation of renewable energy power plants under varying system intensities is ensured. Compared to previous unified control methods, this graded control strategy offers greater flexibility in responding to grid environments of varying intensities, improving the adaptability and stability of multi-power plant systems.

[0017] Furthermore, in some embodiments, during the process of using a station-level controller to control each grid-connected device in an SSI-I level station, the station-level controller directly controls the active power and voltage of the SSI-I level station at the grid connection point, ensuring that the overall electrical characteristics of the SSI-I level station meet the requirements of the power grid or dispatch instructions. The station-level controller controls the power output of each grid-connected device according to the active power and reactive power instructions, which can achieve accurate power tracking and meet the needs of power grid dispatch.

[0018] Furthermore, in some embodiments, during the control of each grid-connected device and each grid-building device within an SSI-II level power station using a station-level controller, the station-level controller controls the power output of each grid-connected device based on active and reactive power commands, achieving precise power tracking and meeting grid dispatch requirements. Simultaneously, based on the electrical characteristics of the entire SSI-II level power station and its internal grid-connected devices, the number of grid-building devices to be configured is intelligently determined, allowing for dynamic adjustment of grid-building capabilities according to grid strength and the station's own needs. By configuring grid-building devices, the stable operation capability of SSI-II level power stations under weak grid conditions can be effectively improved, reducing grid disconnection or power output limitations caused by grid weakness. In addition, the station-level controller enables grid-building devices to operate according to grid conditions, allowing them to not only simply output power but also actively respond to voltage and frequency fluctuations in the grid, enabling the power station to adapt more intelligently and flexibly to the ever-changing grid environment.

[0019] Furthermore, in some embodiments, when the current power grid is a weak grid, the station-level controller sends active power and voltage commands to each grid-connected device and each grid-connecting device within the SSI-III level station, controlling all grid-connected and grid-connecting devices within the SSI-III level station as PV nodes. When the current power grid is an extremely weak grid, the station-level controller controls each grid-connected and grid-connecting device within the SSI-III level station to adopt a grid-connected and grid-connecting integrated control strategy through active power and voltage commands or active power and reactive power commands. This enables all devices to be unified as PV nodes under weak grid conditions, allowing for centralized voltage control and active power output across the entire station, effectively stabilizing the voltage of the weak grid. Simultaneously, under extremely weak grid conditions, the advantages of both grid-connected and grid-connecting devices can be fully utilized and organically combined to maximize the station's stable operation capability and grid support capability under extremely harsh grid conditions. Attached Figure Description

[0020] The above and other objects, features, and advantages of exemplary embodiments of this application will become readily understood by reading the following detailed description with reference to the accompanying drawings. In the drawings, several embodiments of this application are illustrated by way of example and not limitation, and the same or corresponding reference numerals denote the same or corresponding parts, wherein:

[0021] Figure 1 An exemplary flowchart of the hierarchical control method for new energy power stations according to an embodiment of this application is shown;

[0022] Figure 2 An exemplary flowchart illustrating how a site-level controller controls each network-connected device within an SSI-I level site, according to an embodiment of this application, is shown.

[0023] Figure 3 An exemplary flowchart illustrating the control of each network-connecting device and each network-building device within an SSI-II level site according to an embodiment of this application is shown;

[0024] Figure 4 An exemplary flowchart illustrating an embodiment of this application is provided for controlling or employing a network integration control strategy for each network-connecting device and each network-building device within an SSI-III level site.

[0025] Figure 5 An exemplary flowchart illustrating the control of each network-connecting device and each network-building device in an SSI-III level field is shown in an embodiment of this application.

[0026] Figure 6 An exemplary flowchart illustrating the implementation of a network integration control strategy for each network-connecting device and each network-building device in an SSI-III level field is shown in an embodiment of this application.

[0027] Figure 7 An exemplary structural block diagram of the hierarchical control system for new energy power stations according to an embodiment of this application is shown. Detailed Implementation

[0028] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0029] It should be understood that the terms "comprising" and "including" used in the specification and claims of this application indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0030] It should also be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application. As used in this specification and claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used in this specification and claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes such combinations.

[0031] In existing technologies, in scenarios involving multi-stage voltage boosting and long-distance transmission from renewable energy bases with capacities of tens of millions of kilowatts, voltage stability issues exhibit spatial differences due to the electrical distance between renewable energy plants and the main power grid or voltage support points (such as traditional synchronous power sources and flexible DC converter stations). In the near-field region, tight electrical coupling makes sudden load changes prone to high- and low-voltage ride-through failures and cascading voltage collapses. In the mid-field region, the interaction of multi-source broadband impedances leads to significant broadband oscillation risks. In the far-field region, excessive electrical distance and limited transmission capacity result in voltage collapse and transmission capacity bottlenecks. Furthermore, the existing power grid architecture, based on traditional power source design, cannot adapt to the dynamic demands of multi-stage renewable energy aggregation and transmission, especially under different transmission modes of "point-to-grid" and "grid-to-grid," where the system short-circuit ratio differs significantly. However, existing grid configurations lack targeted control strategies, making it difficult to balance the contradiction between rapid power regulation and voltage support. This results in insufficient system strength, and AC grids with weak synchronous support at the sending end exhibit characteristics of low inertia, weak damping, and low short-circuit ratios, leading to various forms of stability problems.

[0032] In view of this, the embodiments of this application provide a hierarchical control scheme for new energy power stations, which can realize differentiated control and networking schemes for point-to-grid transmission, including near-area, mid-area and far-area. Differentiated control and networking schemes are adopted for grid-to-grid transmission, different short-circuit ratios and different ratios of equivalent reactance to equivalent resistance, thereby improving the adaptability and stability of multi-power station systems.

[0033] Figure 1 An exemplary flowchart of a hierarchical control method 100 for new energy power stations according to an embodiment of this application is shown.

[0034] like Figure 1 As shown, in step S110, the short-circuit ratio and the ratio of equivalent reactance to equivalent resistance of each new energy power station connected to the new energy power station are obtained at the new energy power station access point of the new energy base.

[0035] In the embodiments of this application, the short-circuit ratio of each renewable energy power station is the ratio of the short-circuit capacity at the grid connection point of each renewable energy power station to the equivalent power of the renewable energy after considering the influence of other renewable energy power stations. The short-circuit ratio of a renewable energy power station reflects its resistance to disturbances; the higher the short-circuit ratio, the stronger the renewable energy power station.

[0036] In some embodiments of this application, the short-circuit ratio of each renewable energy power station is obtained through the BPA procedure. In other embodiments of this application, the short-circuit ratio of each renewable energy power station can also be obtained through other methods, and this application does not impose any limitations on this method.

[0037] In the embodiments of this application, the ratio of the equivalent reactance to the equivalent resistance of the new energy power station reflects the impedance characteristics of the new energy power station and affects the transient response and stability of the new energy power station.

[0038] In the embodiments of this application, new energy power stations are divided into far-field, medium-field, and near-field zones based on their electrical distance from the main power grid or voltage support points (such as traditional synchronous power sources, flexible DC converter stations, etc.). Near-field zones are close to the main power grid or voltage support points (such as traditional thermal power plants, flexible DC converter stations), with short electrical distances (small ratio of equivalent reactance to equivalent resistance) and high grid strength (large short-circuit ratio), but may experience voltage collapse due to concentrated grid connection of new energy sources and load fluctuations. Medium-field zones are between near-field and far-field zones, with moderate electrical distances (moderate ratio of equivalent reactance to equivalent resistance) and low grid strength (moderate short-circuit ratio), and are prone to broadband oscillations (such as subsynchronous / supersynchronous oscillations) caused by interaction between new energy power stations and the grid. Far-field zones are far from the main grid or voltage support points, with long electrical distances (large ratio of equivalent reactance to equivalent resistance) and low grid strength (small short-circuit ratio), facing voltage collapse and insufficient transmission capacity problems. Therefore, the short-circuit ratio of the near zone > the short-circuit ratio of the middle zone > the short-circuit ratio of the far zone, and the ratio of the equivalent reactance to the equivalent resistance of the near zone < the ratio of the equivalent reactance to the equivalent resistance of the middle zone < the ratio of the equivalent reactance to the equivalent resistance of the far zone.

[0039] After completing step S110, in step S120, all new energy power stations are classified into SSI-I level power stations, SSI-II level power stations, and SSI-III level power stations according to the short-circuit ratio and the ratio of equivalent reactance to equivalent resistance of each new energy power station.

[0040] In the embodiment of the present application, the System Strength Index (abbreviated as SSI) is used as a comprehensive index for evaluating the system strength of each new energy station. Specifically, the system strength index is comprehensively characterized by the short-circuit ratio of each new energy station and the ratio of equivalent reactance to equivalent resistance. The higher the short-circuit ratio of a new energy station is, the greater the system strength index of the corresponding new energy station will be; the smaller the ratio of equivalent reactance to equivalent resistance of a new energy station is, the smaller the system strength index of the corresponding new energy station will be.

[0041] In the embodiment of the present application, the short-circuit ratio of a SSI-Class I station falls within a first short-circuit ratio interval, and the ratio of equivalent reactance to equivalent resistance of the SSI-Class I station falls within a first ratio interval.

[0042] In the embodiment of the present application, the short-circuit ratio of a SSI-Class II station falls within a second short-circuit ratio interval, and the ratio of equivalent reactance to equivalent resistance of the SSI-Class II station falls within a second ratio interval. Specifically, the upper limit value of the second short-circuit ratio interval is smaller than the lower limit value of the first short-circuit ratio interval, and the lower limit value of the second ratio interval is greater than the upper limit value of the first ratio interval.

[0043] In the embodiment of the present application, the short-circuit ratio of a SSI-Class III station falls within a third short-circuit ratio interval, and the ratio of equivalent reactance to equivalent resistance of the SSI-Class III station falls within a third ratio interval. Specifically, the upper limit value of the third short-circuit ratio interval is smaller than the lower limit value of the second short-circuit ratio interval, and the lower limit value of the third ratio interval is greater than the upper limit value of the second ratio interval. That is, the relationship among the short-circuit ratios corresponding to the SSI-Class I station, the SSI-Class II station and the SSI-Class III station respectively is: the short-circuit ratio corresponding to the SSI-Class I station > the short-circuit ratio corresponding to the SSI-Class II station > the short-circuit ratio corresponding to the SSI-Class III station. The relationship among the ratios of equivalent reactance to equivalent resistance corresponding to the SSI-Class I station, the SSI-Class II station and the SSI-Class III station respectively is: the ratio of equivalent reactance to equivalent resistance corresponding to the SSI-Class I station < the ratio of equivalent reactance to equivalent resistance corresponding to the SSI-Class II station < the ratio of equivalent reactance to equivalent resistance corresponding to the SSI-Class III station.

[0044] Through the above arrangement, new energy stations located in the near area are taken as SSI-Class I stations, new energy stations located in the middle area are taken as SSI-Class II stations, and new energy stations located in the far area are taken as SSI-Class III stations.

[0045] In the embodiment of the present application, the first short-circuit ratio interval, the second short-circuit ratio interval, the third short-circuit ratio interval, the first ratio interval, the second ratio interval and the third ratio interval can be set according to actual needs and historical experience, which is not limited herein in the present application.

[0046] In the embodiments of this application, all new energy power stations are classified into SSI-I, SSI-II and SSI-III level power stations according to the short-circuit ratio and the ratio of equivalent reactance to equivalent resistance of each new energy power station. This allows the new energy power stations to be classified according to the system strength index characterized by the short-circuit ratio and the ratio of equivalent reactance to equivalent resistance, thereby adopting different control strategies for different new energy power stations based on the magnitude of the system strength index.

[0047] Specifically, SSI-I level sites consist of network-connecting equipment, SSI-II level sites consist of network-connecting equipment and network-building equipment, and SSI-III level sites consist of network-connecting equipment and network-building equipment.

[0048] After completing step S120, in step S130, the site-level controller is used to control each grid-connected device in the SSI-I level site, and the grid connection point of the SSI-I level site is controlled as a PV node.

[0049] Specifically, in the process of controlling each network-connected device in an SSI-I level site, PQ control is adopted for each network-connected device in an SSI-I level site.

[0050] In the embodiments of this application, during the process of using a station-level controller to control each grid-connected device in an SSI-I level station, the station-level controller controls the active power and voltage at the grid connection point of the SSI-I level station according to active power and voltage commands.

[0051] Specifically, the station-level controller controls the active power and voltage at the grid connection point of the SSI-I level station based on active power and voltage commands, thus controlling the grid connection point of the SSI-I level station as a PV node. By controlling the grid connection point of the SSI-I level station as a PV node, it ensures that the overall electrical characteristics presented by the SSI-I level station meet the requirements of the power grid or dispatch commands.

[0052] In the embodiments of this application, the active power and voltage commands are set according to actual needs and historical experience, and this application does not impose any restrictions on them.

[0053] In the embodiments of this application, the specific process of using a site-level controller to control each network-connected device within an SSI-I level site can be found in [reference needed]. Figure 2 .

[0054] Figure 2 An exemplary flowchart illustrating how a site-level controller controls each network-connected device within an SSI-I level site, according to an embodiment of this application, is shown.

[0055] like Figure 2As shown, in step S210, the active power and reactive power commands issued by the site-level controller to each grid-connected device within the SSI-I level site are obtained. In step S220, each grid-connected device within the SSI-I level site outputs power according to the active power and reactive power commands.

[0056] In the embodiments of this application, the grid-following device may be a grid-following inverter or the like, and this application does not impose any restrictions.

[0057] In the embodiments of this application, since the SSI-I level power station is a new energy power station located in the near-field area, there is a high-low voltage ride-through problem in the near-field area, and the voltage collapses when the load fluctuates significantly. At this time, it is necessary to maintain the voltage stability of the grid connection point, which serves as the interface between the new energy power station and the weak grid.

[0058] Specifically, the station-level controller sends parameter commands (such as active / reactive power limits) to the grid-connected equipment to dynamically adjust its control loop (such as PLL bandwidth and current loop gain), thereby suppressing voltage fluctuations.

[0059] In the embodiments of this application, the active power and reactive power commands of each grid-connected device in the aforementioned SSI-I level station include active power setting values ​​and reactive power setting values. The active power setting values ​​and reactive power setting values ​​are set according to actual needs and historical experience, and this application does not impose any restrictions on them.

[0060] In the embodiments of this application, by setting active power setpoints and reactive power setpoints, it is ensured that the active power (P) and reactive power (Q) output by each grid-connected device in the SSI-I level substation match the grid demand.

[0061] After completing step S120, in step S140, a site-level controller is used to control each grid-connected device and each network-building device within the SSI-II level site, controlling the grid connection point of the SSI-II level site as a PV node. Specifically, each grid-connected device within the SSI-II level site is controlled using PQ (Power Qualifier) ​​control.

[0062] In the embodiments of this application, since the SSI-II level power station is a new energy power station located in the central region, the central region is prone to broadband oscillations (such as subsynchronous / supersynchronous oscillations) caused by the interaction between the new energy power station and the power grid. Therefore, the grid-connected equipment and grid-building equipment within the SSI-II level power station are controlled. By introducing and controlling the grid-building equipment, the strength of the local power grid is actively enhanced at the grid connection point, which itself reduces the risk of subsynchronous / supersynchronous oscillations. In addition, the grid-connected equipment within the SSI-II level power station adopts PQ control, which enables each grid-connected equipment to strictly execute the dispatch instructions sent by the SSI-II level power station, ensuring the execution of the power generation plan. Moreover, complex voltage / frequency regulation logic is not required, reducing equipment costs and operation and maintenance difficulty.

[0063] In the embodiments of this application, during the process of using a station-level controller to control each grid-connected device and each grid-building device in an SSI-II level station, the station-level controller controls the active power and voltage at the grid connection point of the SSI-II level station according to active power and voltage commands.

[0064] Specifically, the station-level controller controls the active power and voltage at the grid connection point of the SSI-II level power station based on active power and voltage commands, controlling the grid connection point of the SSI-II level power station as a PV node. This allows the SSI-II level power station to connect to the grid as a unified and controllable unit, actively providing voltage support and accurately outputting active power. This not only greatly enhances the grid friendliness and support capabilities of renewable energy power stations, but also simplifies grid dispatching and management, and lays the foundation for improving system stability and optimizing resource utilization.

[0065] In the embodiments of this application, the specific processes involved in controlling each network-connecting device and each network-building device within an SSI-II level site using a site-level controller can be found in [reference needed]. Figure 3 .

[0066] Figure 3 An exemplary flowchart illustrating the control of each network-connecting device and each network-building device within an SSI-II level site according to an embodiment of this application is shown.

[0067] like Figure 3 As shown, in step S310, the active power and reactive power commands issued by the station-level controller to each grid-connected device within the SSI-II level station are obtained. In step S320, each grid-connected device within the SSI-II level station outputs power according to the active power and reactive power commands. In step S330, based on the short-circuit ratio and the ratio of equivalent reactance to equivalent resistance of all grid-connected devices within the SSI-II level station, and the short-circuit ratio and the ratio of equivalent reactance to equivalent resistance of the SSI-II level station itself, a corresponding number of grid-connected devices are configured within the SSI-II level station. In step S340, the station-level controller controls the grid-connected devices to operate according to the grid conditions.

[0068] In the embodiments of this application, the active power and reactive power commands of each grid-connected device in the aforementioned SSI-II level station include active power setting values ​​and reactive power setting values. The active power setting values ​​and reactive power setting values ​​are set according to actual needs and historical experience, and this application does not impose any restrictions on them.

[0069] In the embodiments of this application, by setting active power setpoints and reactive power setpoints, it is ensured that the active power (P) and reactive power (Q) output by each grid-connected device in the SSI-II level substation match the grid demand.

[0070] In the embodiments of this application, in step S330, a corresponding number of grid-connecting devices are configured based on the difference between the short-circuit ratio of all grid-connected devices in the SSI-II level power station and the short-circuit ratio of the SSI-II level power station, and the difference between the ratio of the equivalent reactance to the equivalent resistance of all grid-connected devices in the SSI-II level power station and the ratio of the equivalent reactance to the equivalent resistance of the SSI-II level power station, in order to provide dynamic reactive power support. After configuring the corresponding number of grid-connecting devices, the short-circuit ratio of the SSI-II level power station is in the second short-circuit ratio range, and the ratio of the equivalent reactance to the equivalent resistance of the SSI-II level power station is in the second ratio range.

[0071] By comparing the short-circuit ratio of all grid-connected equipment within the power station with that of an SSI-II level power station, and by comparing the ratio of equivalent reactance to equivalent resistance of all grid-connected equipment within an SSI-II level power station with that of the SSI-II level power station, the gap between the current system characteristics and the desired characteristics is quantified. This gap directly reflects the strength and amount of characteristic adjustment that the grid-connected equipment needs to compensate for. Due to their voltage source characteristics, grid-connected equipment is highly adept at quickly responding and providing or absorbing reactive power. The direct objective of configuring grid-connected equipment is to provide dynamic reactive power support. Through this dynamic reactive power support and the electrical characteristics of the grid-connected equipment itself, the short-circuit ratio of the entire SSI-II level power station is increased to the second short-circuit ratio range, and the ratio of equivalent reactance to equivalent resistance is adjusted to the second ratio range, enhancing the voltage support strength of the power station at the grid connection point. During grid disturbances, the voltage is less likely to experience significant drops or rises.

[0072] After executing step S120, in step S150, a site-level controller is used to control each grid-connected device and each network-building device within the SSI-III level site, or a grid-connected and network-building integrated control strategy is adopted to control the grid connection point of the SSI-III level site as a PV node, and to control each grid-connected device and each network-building device within the SSI-III level site as a PV node. Specifically, during the control of each grid-connected device and each network-building device within the SSI-III level site, PV control is used for both.

[0073] In the embodiments of this application, since SSI-III level power stations are new energy power stations located in remote areas, these areas face problems of voltage collapse and insufficient transmission capacity. Therefore, a combined grid-connected and grid-connected control strategy is adopted to control each grid-connected device and each grid-connected device within the SSI-III level power station. This allows the SSI-III level power station to actively establish and maintain the voltage at its grid connection point. When the grid voltage is low or disturbances occur, it can quickly provide a large amount of dynamic reactive power support to prevent further voltage drops, thereby effectively preventing voltage collapse. Furthermore, in the process of controlling each grid-connected and grid-connected device within the SSI-III level power station, PV control is used for all grid-connected and grid-connected devices. By mobilizing all devices within the SSI-III level power station to participate in voltage control, the grid connection point voltage can be stabilized to the maximum extent, effectively suppressing voltage fluctuations and preventing voltage exceedances. Unified PV control, especially allowing grid-connected devices to participate in voltage stabilization under PV mode, can effectively enhance the voltage stability margin of the power station and improve its survivability and continuous operation capability under weak grid conditions.

[0074] The specific process involved in step S150 in the embodiments of this application can be found in [reference needed]. Figure 4 .

[0075] Figure 4 An exemplary flowchart of an embodiment of this application is shown, illustrating the control of each network-connecting device and each network-building device within an SSI-III level site, or the adoption of a network-connecting-network fusion control strategy.

[0076] like Figure 4 As shown, in step S410, it is determined whether the current power grid is a weak grid or an extremely weak grid. In response to the current power grid being a weak grid, in step S420, the station-level controller sends active power and voltage commands to each grid-connected device and each grid-connecting device within the SSI-III level station, controlling all grid-connected devices and grid-connecting devices within the SSI-III level station as PV nodes. In response to the current power grid being an extremely weak grid, in step S430, the station-level controller controls each grid-connected device and each grid-connecting device within the SSI-III level station to adopt a grid-connected and grid-connecting integrated control strategy via active power and voltage commands or via active power and reactive power commands.

[0077] The specific process involved in step S420 in the embodiments of this application can be found in the following documents. Figure 5 .

[0078] Figure 5 An exemplary flowchart illustrating the control of each network-connecting device and each network-building device in an SSI-III level field is shown in an embodiment of this application.

[0079] like Figure 5As shown, in step S510, it is determined whether there is grid frequency fluctuation or grid power deficit. In response to the absence of grid frequency fluctuation or grid power deficit, in step S520, the station-level controller adjusts the active power and voltage of each grid-connected device within the SSI-III level station according to active power and voltage commands, ensuring that the voltage of each grid-connected device is at the set voltage value. In response to the presence of grid frequency fluctuation or grid power deficit, in step S530, the station-level controller adjusts the active power of each grid-connected device within the SSI-III level station to achieve primary frequency regulation. During the execution of step S510, in step S540, based on the short-circuit ratio and the ratio of equivalent reactance to equivalent resistance of all grid-connected devices within the SSI-III level station, and the short-circuit ratio and the ratio of equivalent reactance to equivalent resistance of the SSI-III level station itself, a corresponding number of grid-connected devices are configured within the SSI-III level station. Next, in step S550, the station-level controller adjusts the active power and voltage of each grid-connecting device in the SSI-III level station according to the active power and voltage commands, so that the voltage of each grid-connecting device is the set voltage value.

[0080] In the embodiments of this application, when there are no grid frequency fluctuations or grid power deficits, i.e., when the grid is stable, PV control is adopted for each grid-connected device in the SSI-III level substation, and a corresponding number of grid-building devices are configured. These grid-building devices also adopt PV control and work collaboratively with the grid-connected devices. This ensures that the grid-connected devices continuously provide a solid voltage reference and support for the substation, jointly maintaining voltage stability and ensuring planned active power output. This provides strong voltage support for remote weak grids and effectively prevents voltage collapse. Simultaneously, when the grid is stable, adopting PV control for the grid-building devices allows them to smoothly integrate into the overall operation strategy of the SSI-III level substation, behaving consistently with the grid-connected devices and avoiding unnecessary control mode switching or potential coordination complexities. Furthermore, adopting PV control for both the grid-connected devices and the configured grid-building devices ensures that the substation outputs active power strictly according to dispatch instructions, improving the predictability and reliability of power output.

[0081] In the embodiments of this application, when there are grid frequency fluctuations or grid power shortages, i.e. grid instability, the primary frequency regulation function of the grid-connected equipment can quickly adjust the active power to respond to frequency deviations, which can quickly respond to frequency events, provide critical frequency support for the grid, and reduce the risk of frequency collapse.

[0082] In the embodiments of this application, a corresponding number of grid-connected devices are configured based on the difference between the short-circuit ratio of all grid-connected devices in an SSI-III level power station and the short-circuit ratio of the SSI-III level power station, and the difference between the ratio of the equivalent reactance to the equivalent resistance of all grid-connected devices in an SSI-II level power station and the ratio of the equivalent reactance to the equivalent resistance of the SSI-III level power station, in order to provide dynamic reactive power support. This ensures that after configuring the corresponding number of grid-connected devices, the short-circuit ratio of the SSI-III level power station is within the third short-circuit ratio range, and the ratio of the equivalent reactance to the equivalent resistance of the SSI-III level power station is within the third ratio range.

[0083] By comparing the short-circuit ratios of all grid-connected equipment within an SSI-III level power station with the overall short-circuit ratio of the SSI-III level power station, and comparing the ratios of equivalent reactance to equivalent resistance of all grid-connected equipment within an SSI-II level power station with the same ratio of the SSI-III level power station, the network-connecting equipment is precisely calculated and configured. This proactively raises the short-circuit ratio and the ratio of equivalent reactance to equivalent resistance of the entire SSI-III level power station to the third short-circuit ratio range and the third ratio range, enabling the SSI-III level power station to cope with extremely harsh grid conditions or meet ultra-high-level grid connection requirements. The configured network-connecting equipment provides robust dynamic reactive power support; its quantity and characteristics are precisely calculated based on the differences in short-circuit ratios and the corresponding differences in the ratio of equivalent reactance to equivalent resistance, ensuring that the reactive power support capability precisely meets the requirement of raising the power station characteristics to the corresponding range. By proactively configuring network equipment, the strength of SSI-III level substations is fundamentally changed and enhanced, making them extremely resilient to disturbances such as grid faults and load surges, and significantly improving the reliability and continuity of power supply.

[0084] The specific process involved in step S430 in the embodiments of this application can be found in [reference needed]. Figure 6 .

[0085] Figure 6 An exemplary flowchart illustrating the implementation of a network integration control strategy for each network-connecting device and each network-building device in an SSI-III level field according to an embodiment of this application is shown.

[0086] like Figure 6As shown, in step S610, it is determined whether the real-time state of the power grid is in the first state or the second state. In response to the real-time state of the power grid being in the first state, in step S620, the station-level controller adjusts the active power and voltage of each grid-connected device within the SSI-III level station according to active power and voltage commands, so that the voltage of each grid-connected device within the SSI-III level station is at the set voltage value. In response to the real-time state of the power grid being in the second state, in step S630, the station-level controller adjusts the active power and reactive power of each grid-connected device within the SSI-III level station according to active power and reactive power commands, so that the voltage of each grid-connected device within the SSI-III level station is at the set voltage value.

[0087] In the embodiments of this application, the first state is the normal working state, and the second state is the abnormal or high fluctuation scenario state.

[0088] In the embodiments of this application, by adopting different control strategies in the first state and the second state respectively, the control focus can be dynamically switched or adjusted according to the real-time state of the power grid, so that the power station can respond to different power grid operating conditions in a targeted manner.

[0089] In the embodiments of this application, by making the grid-connected equipment actively used for active power output and voltage maintenance (PV control) in the first state, the grid-connected equipment is mainly relied upon for efficient power generation and conventional voltage support.

[0090] In the embodiments of this application, precise active and reactive power control is performed on the grid-connected equipment in the second state to stabilize the voltage, rapidly mobilizing the powerful voltage source characteristics and dynamic reactive power support capabilities of the grid-connected equipment to stabilize the situation. By controlling the grid-connected equipment with active and reactive power commands to achieve the voltage target, more direct, faster, and stronger voltage support and dynamic reactive power response can be provided than traditional PV control, effectively suppressing voltage fluctuations and preventing voltage collapse.

[0091] Through the above process, by assigning grid-connected or grid-connecting equipment to the primary tasks based on grid demand, it is possible to avoid having certain equipment operate in their extreme or unsuitable modes for extended periods. This can potentially optimize equipment operation and reduce unnecessary losses. This enables SSI-III level power plants to proactively adapt to grid changes, leveraging the respective advantages of grid-connected and grid-connecting equipment under different operating conditions to achieve power generation tasks optimally and provide strong grid support (especially voltage support).

[0092] In summary, through the hierarchical control scheme for renewable energy power plants provided above, this embodiment classifies all renewable energy power plants into SSI-I, SSI-II, and SSI-III levels based on their short-circuit ratios and the ratio of equivalent reactance to equivalent resistance. This hierarchical approach effectively identifies the different impacts of each power plant on grid stability. By employing differentiated control strategies for SSI-I, SSI-II, and SSI-III power plants, stable operation of renewable energy power plants under varying system intensities is ensured. Compared to previous unified control methods, this hierarchical control strategy offers greater flexibility in responding to grid environments of varying intensities, enhancing the adaptability and stability of multi-power plant systems.

[0093] Furthermore, in some embodiments, during the process of using a station-level controller to control each grid-connected device in an SSI-I level station, the station-level controller directly controls the active power and voltage of the SSI-I level station at the grid connection point, ensuring that the overall electrical characteristics of the SSI-I level station meet the requirements of the power grid or dispatch instructions. The station-level controller controls the power output of each grid-connected device according to the active power and reactive power instructions, which can achieve accurate power tracking and meet the needs of power grid dispatch.

[0094] Furthermore, in some embodiments, during the control of each grid-connected device and each grid-building device within an SSI-II level power station using a station-level controller, the station-level controller controls the power output of each grid-connected device based on active and reactive power commands, achieving precise power tracking and meeting grid dispatch requirements. Simultaneously, based on the electrical characteristics of the entire SSI-II level power station and its internal grid-connected devices, the number of grid-building devices to be configured is intelligently determined, allowing for dynamic adjustment of grid-building capabilities according to grid strength and the station's own needs. By configuring grid-building devices, the stable operation capability of SSI-II level power stations under weak grid conditions can be effectively improved, reducing grid disconnection or power output limitations caused by grid weakness. In addition, the station-level controller enables grid-building devices to operate according to grid conditions, allowing them to not only simply output power but also actively respond to voltage and frequency fluctuations in the grid, enabling the power station to adapt more intelligently and flexibly to the ever-changing grid environment.

[0095] Furthermore, in some embodiments, when the current power grid is a weak grid, the station-level controller sends active power and voltage commands to each grid-connected device and each grid-connecting device within the SSI-III level station, controlling all grid-connected and grid-connecting devices within the SSI-III level station as PV nodes. When the current power grid is an extremely weak grid, the station-level controller controls each grid-connected and grid-connecting device within the SSI-III level station to adopt a grid-connected and grid-connecting integrated control strategy through active power and voltage commands or active power and reactive power commands. This enables all devices to be unified as PV nodes under weak grid conditions, allowing for centralized voltage control and active power output across the entire station, effectively stabilizing the voltage of the weak grid. Simultaneously, under extremely weak grid conditions, the advantages of both grid-connected and grid-connecting devices can be fully utilized and organically combined to maximize the station's stable operation capability and grid support capability under extremely harsh grid conditions.

[0096] This application also provides a hierarchical control system for new energy power stations, which can be implemented using the aforementioned hierarchical control method 100 for new energy power stations, or other methods. This application does not impose any restrictions on this method.

[0097] Figure 7 An exemplary structural block diagram of the hierarchical control system for new energy power stations according to an embodiment of this application is shown.

[0098] like Figure 7 As shown, the system 700 includes an analysis and calculation module 710, a new energy power station classification module 720, a first classification control module 730, a second classification control module 740, and a third classification control module 750. In the embodiments of this application, the analysis and calculation module 710, the new energy power station classification module 720, the first classification control module 730, the second classification control module 740, and the third classification control module 750 may be individual units or integrated into the same integrated circuit; this application does not impose any restrictions here.

[0099] Specifically, the analysis and calculation module 710 is used to obtain the short-circuit ratio and the ratio of equivalent reactance to equivalent resistance of each new energy power station connected to the new energy power station at the new energy power station access point of the new energy base.

[0100] Specifically, the new energy power station classification module 720 is used to classify all new energy power stations into SSI-I, SSI-II, and SSI-III levels based on their short-circuit ratio and the ratio of equivalent reactance to equivalent resistance. Specifically, SSI-I level power stations consist of grid-connected equipment, SSI-II level power stations consist of both grid-connected and grid-building equipment, and SSI-III level power stations consist of both grid-connected and grid-building equipment.

[0101] Specifically, the first hierarchical control module 730 is used to control each grid-connected device within the SSI-I level station using a station-level controller, controlling the grid connection point of the SSI-I level station as a PV node. Specifically, each grid-connected device within the SSI-I level station uses PQ control.

[0102] Specifically, the second-level control module 740 is used to control each grid-connected device and each grid-building device within the SSI-II level station using a station-level controller, controlling the grid connection point of the SSI-II level station as a PV node. Specifically, each grid-connected device within the SSI-II level station uses PQ control.

[0103] Specifically, the third-level control module 750 is used to control each grid-connected device and each network-building device within the SSI-III level station using a station-level controller, or to adopt a grid-connected and network-building integrated control strategy to control the grid connection point of the SSI-III level station as a PV node, and to control each grid-connected device and each network-building device within the SSI-III level station as a PV node. Specifically, during the control of each grid-connected device and each network-building device within the SSI-III level station, PV control is used for both.

[0104] When system 700 uses the aforementioned hierarchical control method 100 for new energy power stations, the analysis and calculation module 710 executes step S110, the new energy power station hierarchical module 720 executes step S120, the first hierarchical control module 730 executes step S130, the second hierarchical control module 740 executes step S140, and the third hierarchical control module 750 executes step S150. The specific execution process can be found above and will not be repeated here.

[0105] While numerous embodiments of this application have been shown and described herein, it will be apparent to those skilled in the art that such embodiments are provided by way of example only. Many modifications, alterations, and alternatives will arise for those skilled in the art without departing from the spirit and intent of this application. It should be understood that various alternatives to the embodiments of this application described herein may be employed in the practice of this application. The appended claims are intended to define the scope of protection of this application and therefore cover equivalents or alternatives within the scope of these claims.

Claims

1. A hierarchical control method for new energy power stations, characterized in that, include: The short-circuit ratio and the ratio of equivalent reactance to equivalent resistance of each new energy power station connected to the new energy power station are obtained at the new energy power station access point in the new energy base. Based on the short-circuit ratio and the ratio of equivalent reactance to equivalent resistance of each new energy power station, all new energy power stations are divided into SSI-I level power stations, SSI-II level power stations and SSI-III level power stations. Among them, SSI-I level power stations consist of grid-connected equipment, SSI-II level power stations consist of grid-connected equipment and grid-building equipment, and SSI-III level power stations consist of grid-connected equipment and grid-building equipment. A site-level controller is used to control each grid-connected device in the SSI-I level site. The grid connection point of the SSI-I level site is controlled as a PV node. The grid-connected devices in the SSI-I level site are controlled by PQ. A site-level controller is used to control each network-connecting device and each network-building device in the SSI-II level site. The grid connection point of the SSI-II level site is controlled as a PV node. Among them, each network-connecting device in the SSI-II level site is controlled by PQ. A site-level controller is used to control each grid-connected device and each network-building device within the SSI-III level site, or a grid-connected and network-building integrated control strategy is adopted. The grid connection point of the SSI-III level site is controlled as a PV node, and each grid-connected device and each network-building device within the SSI-III level site is controlled as a PV node. In the process of controlling each grid-connected device and each network-building device within the SSI-III level site, PV control is used for each grid-connected device and each network-building device within the SSI-III level site.

2. The hierarchical control method for new energy power stations according to claim 1, characterized in that, The short-circuit ratio of the SSI-I level power station is in the first short-circuit ratio range, and the ratio of the equivalent reactance to the equivalent resistance of the SSI-I level power station is in the first ratio range.

3. The hierarchical control method for new energy power stations according to claim 2, characterized in that, In the process of using a site-level controller to control each grid-connected device within an SSI-I level site, the site-level controller controls the active power and voltage at the grid connection point of the SSI-I level site and executes the following steps: Obtain the active and reactive power commands issued by the site-level controller to each grid-connected device in the SSI-I level site; Each grid-connected device in an SSI-I level site outputs power according to active and reactive power commands.

4. The hierarchical control method for new energy power stations according to claim 2, characterized in that, The short-circuit ratio of the SSI-II level station is in the second short-circuit ratio range, and the ratio of the equivalent reactance to the equivalent resistance of the SSI-II level station is in the second ratio range. Wherein, the upper limit of the second short-circuit ratio interval is less than the lower limit of the first short-circuit ratio interval; The lower limit of the second ratio interval is greater than the upper limit of the first ratio interval.

5. The hierarchical control method for new energy power stations according to claim 4, characterized in that, In the process of using a site-level controller to control each grid-connected device and each grid-building device within an SSI-II level site, the site-level controller controls the active power and voltage at the grid connection point of the SSI-II level site according to active power and voltage commands, and executes the following steps: Obtain the active and reactive power commands issued by the site-level controller to each grid-connected device in the SSI-II level site; Each grid-connected device in an SSI-II level site outputs power according to active and reactive power commands; Based on the short-circuit ratio and the ratio of equivalent reactance to equivalent resistance of all grid-connected equipment in the SSI-II level station, and the short-circuit ratio and the ratio of equivalent reactance to equivalent resistance of the SSI-II level station, configure the corresponding number of grid-connected equipment in the SSI-II level station. The grid-connected equipment is controlled by a station-level controller to operate according to the grid conditions.

6. The hierarchical control method for new energy power stations according to claim 4, characterized in that, The short-circuit ratio of the SSI-III level power station is in the third short-circuit ratio range, and the ratio of the equivalent reactance to the equivalent resistance of the SSI-III level power station is in the third ratio range. The upper limit of the third short-circuit ratio interval is less than the lower limit of the second short-circuit ratio interval; The lower limit of the third ratio interval is greater than the upper limit of the second ratio interval.

7. The hierarchical control method for new energy power stations according to claim 6, characterized in that, When using a site-level controller to control each grid-connected device and each grid-building device within an SSI-III level site, or when employing a combined grid-connection and grid-building control strategy, the site-level controller controls the active power and voltage at the grid connection point of the SSI-III level site and executes the following steps: Determine whether the current power grid is a weak grid or an extremely weak grid; In response to the current weak grid, the station-level controller sends active power and voltage commands to each grid-connected device and each grid-connecting device in the SSI-III level station, controlling each grid-connected device and each grid-connecting device in the SSI-III level station as a PV node. In response to the current extremely weak power grid, the station-level controller controls each grid-connected device and each grid-connected device in the SSI-III level station to adopt a grid-connected and grid-connected integrated control strategy through active power and voltage commands or active power and reactive power commands.

8. The hierarchical control method for new energy power stations according to claim 7, characterized in that, During the process of the site-level controller sending active power and voltage commands to each grid-connected device and each grid-connecting device in the SSI-III level site, and controlling each grid-connected device and each grid-connecting device in the SSI-III level site as a PV node, the following steps are performed: Determine if there are power grid frequency fluctuations or power grid deficits; In response to the absence of grid frequency fluctuations or grid power deficits, a station-level controller is used to adjust the active power and voltage of each grid-connected device in the SSI-III level station according to active power and voltage commands, so that the voltage of each grid-connected device is the set voltage value. In response to grid frequency fluctuations or grid power deficits, a station-level controller is used to adjust the active power of each grid-connected device in an SSI-III level station to achieve primary frequency regulation. Based on the short-circuit ratio and the ratio of equivalent reactance to equivalent resistance of all grid-connected equipment in the SSI-III level station, and the short-circuit ratio and the ratio of equivalent reactance to equivalent resistance of the SSI-III level station, configure the corresponding number of grid-connected equipment in the SSI-III level station. The active power and voltage of each grid-connecting device in the SSI-III level field station are adjusted according to the active power and voltage commands by the field station-level controller, so that the voltage of each grid-connecting device is the set voltage value.

9. The hierarchical control method for new energy power stations according to claim 7, characterized in that, During the process of the site-level controller controlling each grid-connected device and each grid-connecting device in an SSI-III level site using active power and voltage commands or active power and reactive power commands, and adopting a grid-connected integrated control strategy, the following steps are performed: Determine whether the real-time state of the power grid is in state one or state two; In response to the real-time state of the power grid being in the first state, the station-level controller adjusts the active power and voltage of each grid-connected device in the SSI-III level station according to the active power and voltage commands, so that the voltage of each grid-connected device in the SSI-III level station is the set voltage value. In response to the real-time state of the power grid being in the second state, the station-level controller adjusts the active and reactive power of each grid-connecting device in the SSI-III level station according to active and reactive power commands, so that the voltage of each grid-connecting device in the SSI-III level station is the set voltage value.

10. A hierarchical control system for new energy power stations, characterized in that, The system employs the hierarchical control method for new energy power stations as described in any one of claims 1-9, wherein the system comprises: The analysis and calculation module is used to obtain the short-circuit ratio and the ratio of equivalent reactance to equivalent resistance of each new energy power station connected to the new energy power station at the new energy power station access point in the new energy base. The new energy power station classification module is used to classify all new energy power stations into SSI-I level, SSI-II level, and SSI-III level power stations based on their short-circuit ratio and the ratio of equivalent reactance to equivalent resistance. Among them, SSI-I level power stations consist of grid-connected equipment, SSI-II level power stations consist of grid-connected equipment and grid-building equipment, and SSI-III level power stations consist of grid-connected equipment and grid-building equipment. The first hierarchical control module is used to control each grid-connected device in the SSI-I level station using a station-level controller, and to control the grid connection point of the SSI-I level station as a PV node. The grid-connected devices in the SSI-I level station are controlled by PQ. The second hierarchical control module is used to control each grid-connected device and each grid-building device in the SSI-II level station using a station-level controller, and to control the grid connection point of the SSI-II level station as a PV node. Among them, each grid-connected device in the SSI-II level station is controlled by PQ. The third-level control module is used to control each grid-connected device and each network-building device in the SSI-III level station using a station-level controller or to adopt a grid-connected and network-building integrated control strategy to control the grid connection point of the SSI-III level station as a PV node, and to control each grid-connected device and each network-building device in the SSI-III level station as a PV node. In the process of controlling each grid-connected device and each network-building device in the SSI-III level station, PV control is used for each grid-connected device and each network-building device in the SSI-III level station.

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