A power system frequency support method and system based on centralized energy storage and distributed inverter rotation coordination

Abstract

The application discloses a power system frequency support method and system based on centralized energy storage and distributed inverter rotation cooperation, and belongs to the technical field of power system frequency regulation. The method deploys centralized energy storage units at regional power grid nodes, divides M distributed grid-connected inverters with double-mode operation capability of network construction and network following into N inverter groups, and alternately switches operation modes of each group according to a preset rotation period. In the inverter mode switching window period, the centralized energy storage provides inertia support according to a virtual inertia equation, so that the continuous stability of the system frequency in the switching transition process is ensured. The energy storage participates in peak-valley arbitrage and auxiliary service transactions in the non-switching period, and maximizes economic benefits under the inertia support reserve constraint through day-ahead optimization scheduling. The application replaces scattered distribution and storage with centralized energy storage to reduce investment cost, and realizes fair sharing of network construction type regulation responsibility through grouping rotation.

Description

Technical Field

[0001] This invention belongs to the field of power system frequency regulation technology, specifically relating to a power system frequency support method and system based on centralized energy storage and distributed inverter rotation coordination. Background Technology

[0002] With the rapid increase in the installed capacity of distributed renewable energy sources, represented by photovoltaics, in power distribution networks, distributed photovoltaic systems are connected to the grid via grid-connected inverters. The control mode of these inverters directly determines their interaction characteristics with the grid and their impact on system stability. Traditional grid-connected inverters employ current source control strategies, relying on phase-locked loops (PLLs) to achieve synchronization with the grid. While they operate stably and have high maximum power point tracking efficiency under strong grid conditions, they cannot provide frequency and voltage support to the grid. As the penetration rate of distributed photovoltaics continues to increase, the system's equivalent inertia and short-circuit capacity continue to decline, and the frequency stability margin gradually narrows.

[0003] To enhance the frequency support capability of power systems with a high proportion of distributed photovoltaic (PV) power, some grid-connected inverters need to operate in grid-connected control mode. Grid-connected inverters autonomously establish frequency and voltage references through virtual synchronous machines or droop control algorithms, providing virtual inertia response and primary frequency regulation services to the grid. However, to provide this support capability, grid-connected inverters need to reserve a certain percentage of active power margin (typically 10% to 20% of rated power), resulting in a loss of PV power generation.

[0004] In existing technologies, the frequency support capability of inverters mainly relies on the following solutions. The first is a distributed energy storage solution, where each photovoltaic inverter is equipped with a small energy storage device, which provides inertia and frequency regulation services. This solution suffers from high unit capacity investment costs, low energy storage utilization, and difficult operation and maintenance. The second is a fixed grid-connected configuration solution, where some inverters are permanently set to grid-connected mode. Its main drawback is that the fixed inverters bear additional economic losses in the long term, resulting in poor fairness. The third is a full grid-connected solution, where all inverters operate in grid-connected mode. This solution suffers the most severe power generation losses.

[0005] Therefore, there is a lack of a systematic frequency support method in the existing technology that combines centralized energy storage with inverter grouping and rotation, taking into account both economic efficiency and frequency support capability. Summary of the Invention

[0006] 1. Technical problem to be solved:

[0007] To overcome the shortcomings of the prior art, this invention provides a power system frequency support method and system based on centralized energy storage and distributed inverter rotation. It uses centralized energy storage to replace decentralized distribution and storage to reduce system investment costs, uses a group rotation mechanism to achieve fair sharing of grid-based regulation responsibilities, and provides inertia buffering by centralized energy storage during the inverter mode switching window to ensure the continuous stability of system frequency during the switching transition.

[0008] 2. Technical Solution:

[0009] To solve the above problems, the present invention adopts the following technical solution.

[0010] A power system frequency support method based on centralized energy storage and distributed inverter rotation includes the following steps:

[0011] Step S1: Deploy centralized energy storage units at the common connection point bus of the regional power grid, and divide the M distributed grid-connected inverters with dual-mode operation capability of grid-connected mode and grid-following mode into N inverter groups, where M≥N≥2, and M and N are both integers;

[0012] Step S2: Determine the proportion of the capacity of the inverter groups operating in grid-connected mode out of the total capacity of all inverters among the N inverter groups, denoted as the grid-connected mode capacity proportion. A unified rotation period T is set for each inverter group, and the switching time point of each inverter group is determined according to a preset timing relationship, so that the N inverter groups alternately switch operating modes on the time axis. Each inverter group switches from one of the grid-connected mode and the other of the grid-connected mode at the switching time point, and maintains the switched operating mode for a preset running time. If the switched mode is the grid-connected mode, then the running time is... If the switched mode is a network-based mode, then the runtime is... ;

[0013] Step S3: Each inverter group autonomously triggers mode switching within its respective switching window period based on the relationship between the local voltage and the preset voltage threshold. During the switching window period, the centralized energy storage unit senses the switching event through local frequency detection and automatically calculates and releases the inertia support power using the virtual inertia equation based on the frequency change rate at the common connection point to compensate for the power deficit during the switching transient process. No communication coordination is required between the inverter and the energy storage.

[0014] Step S4: Monitor the grid frequency deviation in real time, and adaptively adjust the rotation cycle T and / or the proportion of inverter capacity operating in grid-connected mode according to the dynamic changes of the frequency deviation. ;

[0015] Step S5: During non-switching periods, schedule the centralized energy storage unit to participate in peak-valley arbitrage and ancillary service market transactions.

[0016] Furthermore, in step S2, the switching time point of the i-th inverter group The following relationship must be satisfied:

[0017] ;

[0018] in, For system reference start time, k is a rotation round counter, with values ​​of 0, 1, 2, ...

[0019] Furthermore, in step S3, the inertia support power provided by the centralized energy storage unit... Calculated using the following virtual inertia equation:

[0020] ;

[0021] in, The equivalent virtual inertia constant for energy storage, df / dt is the rated capacity of the energy storage, and df / dt is the rate of frequency change at the point of common coupling of the power grid.

[0022] Furthermore, step S5 also includes: establishing a day-ahead energy storage scheduling optimization model, wherein the model takes maximizing the overall benefits of energy storage as its objective function.

[0023] ;

[0024] It also includes at least an inertia support backup constraint, which requires that at each switching window time... Energy storage state of charge Not lower than the preset minimum value of inertia support backup , Determined based on maximum inertia compensation power and longest switching window time.

[0025] Furthermore, step S3 further includes: during the switching window period, the centralized energy storage unit simultaneously provides a frequency regulation response, the frequency regulation power of which is... Based on the active-frequency droop coefficient and frequency deviation calculate:

[0026] ;

[0027] in, The active-frequency droop factor for energy storage. For the rated frequency, This refers to the real-time frequency of the power grid.

[0028] Further, in step S4, the adaptive adjustment includes:

[0029] When the frequency deviation When the first threshold is exceeded, the rotation period T is shortened and / or the capacity ratio threshold of the network configuration mode is increased;

[0030] When the frequency deviation When the second threshold is exceeded, all inverters are controlled to switch to grid-connected mode operation, wherein the second threshold is greater than the first threshold.

[0031] Furthermore, in step S3, the total output power of the centralized energy storage unit... Power scheduled for the day The inertia support power and primary frequency modulation power The combination of these three elements enables the multi-functional reuse of the same energy storage hardware.

[0032] Furthermore, the method also includes: monitoring the state of charge of the centralized energy storage unit; when the state of charge is lower than a warning threshold, limiting the output power of the centralized energy storage unit used for inertia support and primary frequency regulation; when the frequency deviation does not exceed the second threshold, and the state of charge is lower than an emergency threshold, preferentially increasing the capacity ratio threshold of the grid-type mode to reduce the dependence on energy storage inertia support.

[0033] Furthermore, within a complete rotation cycle, each inverter group experiences the same proportion of equivalent power generation loss due to operating in grid-connected mode, thereby achieving a fair sharing of economic losses.

[0034] The present invention also provides a power system frequency support system based on centralized energy storage and distributed inverter switching, for implementing the method of any one of claims 1 to 9, the system comprising:

[0035] The centralized energy storage unit is connected to the common coupling point bus of the regional power grid via a bidirectional AC / DC converter;

[0036] M distributed grid-connected inverters, each inverter has dual-mode operation capability of grid-connected mode and grid-following mode, and is divided into N inverter groups;

[0037] A regional collaborative controller, comprising:

[0038] A group management unit is used to perform grouping and rotation cycle configuration of the inverter group;

[0039] The switching control unit is used to generate and send switching configuration parameters containing differentiated voltage thresholds to each inverter group according to the switching cycle and preset timing relationship. After receiving the switching configuration parameters, each inverter group autonomously performs mode switching based on the relationship between local voltage information and the differentiated voltage thresholds.

[0040] The dynamic adjustment unit is used to adaptively adjust the rotation cycle and the capacity ratio of the grid configuration mode based on the real-time monitored grid frequency deviation and energy storage state of charge. And the output strategy of the centralized energy storage unit;

[0041] A collaborative scheduling unit is used to generate and update the inertia support response threshold and strategy parameters of the centralized energy storage unit, enabling the centralized energy storage unit to participate in peak-valley arbitrage and ancillary services according to the day-ahead energy storage scheduling plan during non-switching periods, and to autonomously initiate inertia support when it detects that the local frequency change rate exceeds the limit due to inverter switching; and

[0042] The status monitoring module is used to monitor the operating status of each inverter, the frequency and voltage at the grid common connection point, and the state of charge of the centralized energy storage unit in real time.

[0043] The present invention also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the method described in any of the preceding claims.

[0044] The present invention also provides an electronic device, including a processor, a memory, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the method described in any of the preceding claims.

[0045] 3. Beneficial effects:

[0046] Compared with the prior art, the technical solution provided by this invention has the following advantages:

[0047] (1) Reduced system investment costs and improved energy storage utilization: The present invention adopts centralized energy storage to replace the distributed energy storage scheme. It provides switching transient support for all distributed inverters in the region through a centralized energy storage unit, avoiding the high investment of configuring energy storage for each inverter separately, and significantly reducing system construction costs and operation and maintenance difficulties.

[0048] (2) Fair sharing of regulatory responsibility and economic loss is achieved: Through the group rotation mechanism, the equivalent power generation loss ratio of all inverter groups in a complete rotation cycle due to operation in grid-type mode is exactly the same, which overcomes the defect that some inverters bear economic losses for a long time in the fixed grid-type matching scheme, and improves the fairness and acceptability of system operation.

[0049] (3) Ensures the continuity and smoothness of frequency support: During the transient window of inverter mode switching, each inverter switches autonomously based on the local voltage threshold. The centralized energy storage autonomously senses the switching event through local frequency detection and provides instant inertia support and primary frequency regulation response according to the virtual inertia equation. This effectively compensates for the power deficit caused by inverter mode switching, avoids transient frequency drops or overshoots, and ensures uninterrupted and high-quality frequency support services.

[0050] (4) The invention achieves multi-functional reuse of energy storage hardware and synergistic optimization of system performance: The centralized energy storage unit of the present invention not only provides frequency support for switching transients, but also participates in peak-valley arbitrage and ancillary service markets during non-switching periods, realizing "one storage unit for multiple uses". At the same time, by combining the rapid response of energy storage with the mode rotation of the inverter, the system can adaptively adjust the frequency support strategy, pursue economic optimization under normal conditions, and provide maximum inertia support under emergency conditions, significantly improving the flexibility and resilience of the system.

[0051] It should be noted that the structures not described in this invention are not related to the design points and improvement directions of this invention, and are the same as or can be implemented using existing technologies, so they will not be elaborated here. Attached Figure Description

[0052] Figure 1 This is an architecture diagram of the centralized energy storage and inverter switching coordination system in an embodiment of the present invention;

[0053] Figure 2 This is a functional module structure diagram of the regional collaborative controller in this embodiment of the invention. It is responsible for issuing rotation configuration parameters and energy storage response strategies, but does not directly control the switching execution.

[0054] Figure 3 This is a control principle diagram of centralized energy storage providing inertia support during the switching window in this embodiment of the invention. Detailed Implementation

[0055] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention.

[0056] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0057] Example 1: This example corresponds to step S1 as described in claim 1 and the system architecture as described in claim 10.

[0058] like Figure 1As shown, the system provided by this invention includes: a centralized energy storage unit, M distributed photovoltaic inverters (divided into groups), a regional collaborative controller, and a status monitoring module. The centralized energy storage unit is connected to the 10kV distribution bus (point of common coupling PCC) via a bidirectional AC / DC converter. The M distributed grid-connected inverters are all connected to the same distribution network area, and each inverter hardware simultaneously possesses both grid-connected (GFL) and grid-connected (GFM) control modes.

[0059] The total installed capacity of the system is:

[0060] ;

[0061] In this example, the inverters are evenly divided into N inverter groups G1 to G2. N Rated capacity of each group The regional collaborative controller connects to each inverter group and energy storage unit via fiber optic / 5G communication links. It distributes configuration parameters such as rotation cycles, differentiated voltage thresholds, and energy storage response strategies, and collects operational status data, but does not interfere with the local real-time autonomous execution process of inverter mode switching and energy storage inertia support. Each inverter group autonomously performs mode switching based on the relationship between local voltage information and differentiated voltage thresholds, and the centralized energy storage unit autonomously starts inertia support based on local frequency detection. No communication coordination is required between the two at the switching execution level. The status monitoring module monitors the real-time operating status of each inverter, the frequency and voltage at the PCC, and the energy storage state of charge (SOC).

[0062] Example 2: Inverter Grid-Based Control – Virtual Synchronous Generator Model:

[0063] like Figure 2 As shown, in grid-connected mode, the inverter uses a virtual synchronous generator (VSG) for control. According to Newton's second law, the mechanical equation (rotor motion equation) of the virtual synchronous generator is expressed as:

[0064] ;

[0065] in, Let be the virtual inertia constant (s) of the j-th inverter. The angular velocity of the virtual synchronous generator. and These are virtual mechanical torque and electromagnetic torque, respectively. The damping coefficient is... This is the rated angular velocity. Because... The presence of this property gives the grid-connected inverter inertia during frequency disturbances.

[0066] The electromagnetic torque of the virtual synchronous generator is calculated using three-phase instantaneous power theory:

[0067] ;

[0068] in, The electromagnetic power output by the virtual synchronous generator. , and The terminal potentials of phases A, B, and C are respectively. , and These are the terminal currents for phases A, B, and C, respectively.

[0069] The electromagnetic equations of the virtual synchronous generator are:

[0070] ;

[0071] in, For synchronous inductors, This is the synchronization resistor. Comparing the hardware topology, the output filter inductor is equivalent to a synchronization inductor, and the equivalent resistance of the filter inductor and the power devices are considered as the synchronization resistor. A larger value increases system damping but introduces output voltage deviation. A larger damping level increases damping but leads to deviations in active power command.

[0072] By measuring mechanical torque The adjustment achieves active power control. By instruction and frequency deviation feedback Composition. The active-frequency droop control equation is:

[0073] ;

[0074] The reactive power-voltage droop control equation is:

[0075] ;

[0076] The terminal voltage and reactive power are controlled by adjusting the electromotive force of the virtual synchronous generator:

[0077] ;

[0078] The potential-voltage vector of the virtual synchronous generator is:

[0079] ;

[0080] in, This represents the phase of the virtual synchronous generator. The electromagnetic power output by the virtual synchronous generator is:

[0081] ;

[0082] in, The power angle is the angle of power. When a frequency deviation occurs, the power angle changes automatically, resulting in electromagnetic power adjustment. This process has a time scale of milliseconds.

[0083] Example 3: Inertia Support and Multifunctional Reuse of Centralized Energy Storage

[0084] like Figure 3 As shown, centralized energy storage provides inertia support during the switching window. The energy storage measures the frequency f and the rate of change of frequency df / dt at the point of common coupling in real time using a phase-locked loop algorithm based on a second-order generalized integrator, with a measurement delay of no more than 20 milliseconds. The inertia compensation power of the energy storage is:

[0085] ;

[0086] in, The equivalent virtual inertia constant for energy storage, s The rated apparent power of energy storage. The physical meaning of is the inertial response time constant equivalent to energy storage. The larger the value, the stronger the energy storage response to the rate of frequency change. The minimum value is determined by the following constraints:

[0087] ;

[0088] in, This represents the maximum transient power deficit that may occur during the mode switching window. The safe limit for the rate of frequency change (usually taken as 0.5 to 2.0 Hz / s).

[0089] Energy storage also provides a primary frequency regulation response:

[0090] ;

[0091] in, This is the active-frequency droop factor for energy storage.

[0092] The total power output of energy storage during the switching window is the sum of three terms:

[0093] ;

[0094] in, This is the baseline power (peak-valley arbitrage power) determined by the dispatching authority in the previous day. and These are real-time inertia compensation and frequency modulation response power, respectively. The three power sources are superimposed and reuse the same energy storage hardware to achieve multi-functional operation.

[0095] Energy storage output power is constrained by state of charge (SOC):

[0096] ;

[0097] The dynamic equation for SOC is:

[0098] ;

[0099] in, For charge and discharge efficiency ( When SOC is lower than At that time, the amplitude of the inertia compensation power increases linearly from... Reduce to 0. Specifically:

[0100] ;

[0101] in, This is the margin range (usually 5% to 10%).

[0102] In step 2, the switching time of the i-th inverter group within the rotation cycle T is:

[0103] ;

[0104] in, The system reference start time is k, and the rotation round counter is k. The switching interval between two adjacent groups is k. Ensure that at most one inverter group is in transition at any given time.

[0105] Number of inverter groups simultaneously in grid-connected mode Network capacity ratio Must meet .

[0106] The seamless switchover process consists of three phases. The pre-synchronization phase involves setting up... , , This ensures consistency of state variables. The switching execution phase guarantees continuous output. During the smooth transition phase, the power reference value is transitioned through a first-order low-pass filter.

[0107] ;

[0108] in, To switch instantaneous power, For the target mode steady-state power, This is the time constant (100 milliseconds in this embodiment).

[0109] During the switching window, each inverter group autonomously triggers mode switching based on its local voltage threshold; the centralized energy storage system senses this switching event through local frequency detection and autonomously activates its inertia support, without requiring communication coordination between the two. The power reference value for energy storage during the switching window is:

[0110] ;

[0111] in, This is the baseline power for the current dispatch. To compensate for the sum of the inertia support power and the primary frequency modulation power during the switching transient.

[0112] During a complete replacement cycle, the energy storage capacity consumed by inertia support is:

[0113] ;

[0114] in, Let be the average inertia compensation power for the i-th switching window. This represents the duration of the i-th switching window. Since the switching window is extremely short (no more than 200 milliseconds in this embodiment). Typically, it does not exceed 1% of the total energy storage capacity, and there is almost no capacity competition between inertia support and peak-valley arbitrage.

[0115] The equivalent power generation loss ratio of each inverter group during a complete replacement cycle is:

[0116] ;

[0117] in, Power reserve ratio for grid-connected mode. All inverter groups. All are the same, thus achieving a fair distribution of economic losses among the N inverter groups.

[0118] Example 5: Day-ahead Dispatch Optimization Model for Energy Storage

[0119] In this example, a day-ahead scheduling optimization model for energy storage is established, with the objective function being to maximize the overall benefits of energy storage:

[0120] ;

[0121] in, The time-of-use electricity price for period t. The length of the scheduling period (15 minutes in this embodiment). This refers to the degradation cost of energy storage during the energy storage cycle. The degradation cost is calculated as follows:

[0122] ;

[0123] in, The initial total construction cost of energy storage, This is the cycle life of the energy storage at rated depth of discharge (DOD). This formula amortizes the degradation cost of each charge-discharge cycle into the energy throughput.

[0124] Constraints include: power constraints SOC dynamic equation (Formula (15)) and SOC range constraint (Formula (14)).

[0125] The inertia-supported reserve constraint is the key constraint that distinguishes this invention from traditional energy storage scheduling models.

[0126] ;

[0127] in, For the i-th window switching time, This represents the total number of window switching times within a day. The calculation formula is:

[0128] ;

[0129] in, The maximum inertia compensation power is calculated according to formula (10). The maximum value of the duration of the switching window period. For energy storage discharge efficiency. This constraint ensures that the energy storage has sufficient energy to support inertia at each switching window.

[0130] In this embodiment, the system's equivalent inertia constant includes the inertia contribution of energy storage:

[0131] .

[0132] Example 6: Adaptive Dynamic Adjustment Strategy

[0133] In this example, a graded response is generated based on the dynamic changes in frequency deviation. When the frequency deviation... Exceeding the first threshold (In this embodiment, the frequency is taken as 0.1 to 0.2 Hz), increasing the network capacity threshold:

[0134] ;

[0135] Simultaneously shorten the rotation cycle:

[0136] ;

[0137] Energy storage simultaneously increases frequency regulation output:

[0138] ;

[0139] in, This is the frequency response gain coefficient for energy storage.

[0140] when hour( Typically, 0.5Hz is used (secondary emergency control), forcing all inverters to switch to grid-connected mode, and the system's equivalent inertia reaches its maximum value:

[0141] ;

[0142] After the frequency is restored, the parameters are gradually restored to their normal values:

[0143] ;

[0144] in, The duration of the gradual recovery is set to 30 to 60 seconds in this embodiment to avoid secondary frequency disturbances caused by sudden parameter changes.

[0145] The impact of energy storage state of charge (SOC) on dynamic adjustment strategies: When SOC is below the warning threshold When the SOC is below a certain level, frequency regulation is used to increase the output of energy storage to prevent it from over-discharging; when the SOC is below a certain level... At that time, priority should be given to improving to To reduce reliance on energy storage inertia support—compensate for insufficient energy storage inertia support capacity by increasing the number of grid-connected inverters.

[0146] In this embodiment, the steady-state frequency deviation is determined by the power balance condition:

[0147] ;

[0148] It is evident that the more grid-connected inverters there are, the higher the energy storage droop coefficient becomes. The larger the droop factor, the smaller the steady-state frequency deviation. The addition of centralized energy storage is equivalent to adding a virtual synchronous machine with a large droop factor to the system, significantly enhancing the system's primary frequency regulation capability.

[0149] The present invention also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the above-described method.

[0150] The present invention also provides an electronic device, including a processor, a memory, and a computer program; wherein the processor is connected to the memory, the computer program is stored in the memory, and when the electronic device is running, the processor executes the computer program stored in the memory to cause the electronic device to perform the steps of implementing the above method.

Claims

1. A power system frequency support method based on centralized energy storage and distributed inverter switching, characterized in that, Includes the following steps: Step S1: Deploy centralized energy storage units at the common connection point bus of the regional power grid, and divide the M distributed grid-connected inverters with dual-mode operation capability of grid-connected mode and grid-following mode into N inverter groups, where M≥N≥2, and M and N are both integers; Step S2: Determine the proportion of the capacity of the inverter groups operating in grid-connected mode out of the total capacity of all inverters among the N inverter groups, denoted as the grid-connected mode capacity proportion. A unified rotation period T is set for each inverter group, and the switching time point of each inverter group is determined according to a preset timing relationship, so that the N inverter groups alternately switch operating modes on the time axis. Each inverter group switches from one of the grid-connected mode and the other of the grid-connected mode at the switching time point, and maintains the switched operating mode for a preset running time. If the switched mode is the grid-connected mode, then the running time is... If the switched mode is a network-based mode, then the runtime is... ; Step S3: Each inverter group autonomously triggers mode switching within its respective switching window period based on the relationship between the local voltage and the preset voltage threshold. During the switching window period, the centralized energy storage unit senses the switching event through local frequency detection and automatically calculates and releases the inertia support power using the virtual inertia equation based on the frequency change rate at the common connection point to compensate for the power deficit during the switching transient process. No communication coordination is required between the inverter and the energy storage. Step S4: Monitor the grid frequency deviation in real time, and adaptively adjust the rotation cycle T and / or the capacity ratio of the grid configuration mode according to the dynamic changes of the frequency deviation. ; Step S5: During non-switching periods, schedule the centralized energy storage unit to participate in peak-valley arbitrage and ancillary service market transactions.

2. The method according to claim 1, characterized in that, In step S2, the switching time point of the i-th inverter group The following relationship must be satisfied: ； in, For system reference start time, k is a rotation round counter, with values ​​of 0, 1, 2, ...

3. The method according to claim 1, characterized in that, In step S3, the inertial support power provided by the centralized energy storage unit Calculated using the following virtual inertia equation: ； in, The equivalent virtual inertia constant for energy storage, df / dt is the rated capacity of the energy storage, and df / dt is the rate of frequency change at the point of common coupling of the power grid.

4. The method according to claim 1, characterized in that, Step S5 further includes: establishing a day-ahead energy storage scheduling optimization model, wherein the model takes maximizing the overall benefits of energy storage as the objective function. ； It also includes at least an inertia support backup constraint, which requires that at each switching window time... Energy storage state of charge Not lower than the preset minimum value of inertia support backup , Determined based on maximum inertia compensation power and longest switching window time.

5. The method according to claim 3, characterized in that, Step S3 further includes: during the switching window period, the centralized energy storage unit simultaneously provides a frequency regulation response, the frequency regulation power of which is... Based on the active-frequency droop coefficient and frequency deviation calculate: ； in, The active-frequency droop factor for energy storage. For the rated frequency, This is the real-time frequency of the power grid.

6. The method according to claim 1, characterized in that, In step S4, the adaptive adjustment includes: When the frequency deviation When the first threshold is exceeded, the rotation period T is shortened and / or the capacity ratio threshold of the network configuration mode is increased; When the frequency deviation When the second threshold is exceeded, all inverters are controlled to switch to grid-connected mode operation, wherein the second threshold is greater than the first threshold.

7. The method according to claim 1, characterized in that, In step S3, the total output power of the centralized energy storage unit Power scheduled for the day The inertia support power and primary frequency modulation power The combination of these three elements enables the multi-functional reuse of the same energy storage hardware.

8. The method according to claim 1, characterized in that, Also includes: The state of charge of the centralized energy storage unit is monitored, and when the state of charge is lower than the warning threshold, the output power of the centralized energy storage unit used for frequency support is limited. If the frequency deviation does not exceed the second threshold, and the state of charge is lower than the emergency threshold, the capacity ratio threshold of the grid-type mode is preferentially increased to reduce the dependence on energy storage inertia support.

9. The method according to claim 1, characterized in that, Within a complete rotation cycle, each inverter group experiences the same proportion of equivalent power generation loss due to operating in grid-connected mode, thus achieving a fair sharing of economic losses.

10. A power system frequency support system based on centralized energy storage and distributed inverter switching, characterized in that, The system for implementing the method of any one of claims 1 to 9 comprises: The centralized energy storage unit is connected to the common coupling point bus of the regional power grid via a bidirectional AC / DC converter; M distributed grid-connected inverters, each inverter has dual-mode operation capability of grid-connected mode and grid-following mode, and is divided into N inverter groups; A regional collaborative controller, comprising: A group management unit is used to perform grouping and rotation cycle configuration of the inverter group; The switching control unit is used to generate and send switching configuration parameters containing differentiated voltage thresholds to each inverter group according to the switching cycle and preset timing relationship. After receiving the switching configuration parameters, each inverter group autonomously performs mode switching based on the relationship between local voltage information and the differentiated voltage thresholds. The dynamic adjustment unit is used to adaptively adjust the rotation cycle, the capacity ratio γ of the grid configuration mode, and the output strategy of the centralized energy storage unit based on the real-time monitored grid frequency deviation and energy storage state of charge. A collaborative scheduling unit is used to generate and update the inertia support response threshold and strategy parameters of the centralized energy storage unit, enabling the centralized energy storage unit to participate in peak-valley arbitrage and ancillary services according to the day-ahead energy storage scheduling plan during non-switching periods, and to autonomously initiate inertia support when it detects that the local frequency change rate exceeds the limit due to inverter switching; and The status monitoring module is used to monitor the operating status of each inverter, the frequency and voltage at the grid common connection point, and the state of charge of the centralized energy storage unit in real time.

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