Simulation circuit and capacity checking method for all working conditions of network-building type energy storage adaptive micro-grid

Abstract

The invention relates to the technical field of power system simulation and operation control, in particular to a simulation circuit and a capacity checking method of a network construction type energy storage adaptive micro-grid, which comprises a data processing unit, a grid architecture model and a network construction type energy storage module, and is characterized in that the grid architecture model comprises a section I bus, a section II bus, a transformer and a power transmission line; the system further comprises a load unit model and a power supply model. The energy storage unit model, the load unit model and the power supply model are connected with the I-section bus and the II-section bus in a high-voltage direct hanging mode. According to the invention, aiming at the design of the network construction type energy storage module, the capacity distribution and control strategy of the network construction type energy storage module and the adaptive logic of the existing micro-grid component are defined, and the problem that the existing simulation circuit has insufficient attention to the energy storage module is solved; the minimum energy storage capacity is determined by combining the existing load characteristics of the micro-grid through a standardized checking process of sub-bus and sub-working conditions, excess or insufficient capacity configuration is avoided, and the engineering economy and reliability are improved.

Description

Technical Field

[0001] This invention relates to the field of power system simulation and operation control technology, and in particular to a simulation circuit and capacity verification method for a grid-type energy storage-adapted microgrid. Background Technology

[0002] Microgrids, as small-scale power generation and distribution systems integrating distributed renewable energy, loads, and energy storage, need to operate stably in both grid-connected and off-grid modes. Their core challenge lies in the system stability issues caused by random fluctuations in renewable energy output and sudden power surges from impactful loads. Grid-based energy storage, leveraging virtual synchronous generator (VSG) control technology, can provide voltage and frequency support, making it a key device for solving microgrid stability problems.

[0003] In existing technologies, microgrid simulations mostly focus on verifying the overall system operating conditions, without designing a dedicated simulation architecture for the core characteristics of grid-based energy storage. This results in the inability to accurately verify the parameter adaptability and capacity rationality of energy storage modules. Furthermore, the capacity verification methods lack standardized procedures, making it difficult to match the differentiated needs of different bus load characteristics (impact loads, sensitive loads), easily leading to problems of over- or under-configuration of energy storage capacity. In addition, existing simulation circuits do not highlight the synergistic adaptation relationship between grid-based energy storage and existing power and load modules in the microgrid, failing to accurately reflect the effect of energy storage modules on improving system stability. Summary of the Invention

[0004] In this section, as well as in the abstract and title of this application, some simplifications or omissions may be made to avoid obscuring the purpose of this section, the abstract, and the title of this application, and such simplifications or omissions shall not be used to limit the scope of the invention.

[0005] To address the shortcomings of existing technologies, one objective of this invention is to provide a simulation circuit for grid-based energy storage that is compatible with all operating conditions of a microgrid. This circuit clarifies the core design parameters of the energy storage module and its compatibility logic with existing systems. By using a standardized verification process, the optimal capacity configuration is determined, ensuring that grid-based energy storage plays an optimal role in providing stable support under all operating conditions of the microgrid.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a simulation circuit for grid-type energy storage adapted to all operating conditions of a microgrid, comprising: The power grid architecture model includes a bus section I and a bus section II connected by a bus tie, and transmission lines connected to the bus section I and the bus section II by transformers respectively; the power grid architecture model is stored in a data processing unit, which is used to perform simulation calculations and disturbance injection machine data acquisition and analysis; The grid-type energy storage module is connected to the I section bus and the II section bus respectively in a high-voltage direct connection manner to provide voltage and frequency support for the power grid architecture model; The loads within the range of bus section I and bus section II are unequal.

[0007] As a preferred embodiment of the simulation circuit for the grid-type energy storage adapted to all operating conditions of microgrids according to the present invention, the grid-type energy storage module includes multiple sets of energy storage units, and at least one set of the energy storage units is configured on the I-section bus and the II-section bus.

[0008] As a preferred embodiment of the simulation circuit for the grid-type energy storage adapted to all operating conditions of a microgrid according to the present invention, wherein: the energy storage unit integrates a control module, the control module comprising: The frequency adjustment unit is located at the top layer of the control module; the frequency adjustment unit achieves rapid frequency response through virtual inertia simulation, maintaining the system frequency within the range of 49.5Hz to 50.5Hz; A voltage support unit is provided in parallel with the frequency adjustment unit. The voltage support unit is used to detect the bus voltage in real time and dynamically output reactive power through the UQ droop characteristic to maintain the bus voltage within the range of 0.9 to 1.1 per unit. An overcurrent protection unit, as a bottom-level protection module, is connected in series in the output circuit of the energy storage unit; the overcurrent protection unit is set to 1.5 times the short-time overcurrent threshold (10s withstand time), and automatically starts current limiting control when the output current of the energy storage unit exceeds the threshold.

[0009] As a preferred embodiment of the simulation circuit for the grid-type energy storage adapted to all operating conditions of the microgrid described in this invention, it further includes: a load unit model and a power supply model; the load unit model and the power supply model are connected to the I-section bus and the II-section bus through a grid connection point.

[0010] As a preferred embodiment of the simulation circuit for the grid-type energy storage adapted to all operating conditions of the microgrid described in this invention, the load unit model includes an impact load model and a sensitive load model respectively located within the range of the I section bus and the II section bus; The impact load model is used to simulate the combined characteristics of constant current and constant power. The sensitive load model is used to simulate the load characteristics of motors and frequency converters.

[0011] As a preferred embodiment of the simulation circuit for the grid-type energy storage adapted to all operating conditions of the microgrid described in this invention, the power supply model includes: The wind power generation model includes: a newly built wind power electronic model connected within the range of the first bus section and an existing wind power electronic model connected within the range of the second bus section; the wind power generation model adopts an induction generator model and is configured with phase-locked loop constant power control; The photovoltaic power generation model includes: a newly built photovoltaic sub-model connected within the range of the first bus section and an existing photovoltaic sub-model connected within the range of the second bus section; the photovoltaic power generation model adopts MPPT control mode and performs reasonable allocation of reactive power through closed-loop control of voltage outer loop and current inner loop.

[0012] To address the shortcomings of existing technologies, another objective of this invention is to provide a capacity verification method for grid-type energy storage adapted to all operating conditions of microgrids.

[0013] To achieve the above objectives, the present invention adopts the following technical solution: a capacity verification method for grid-type energy storage adapted to all operating conditions of microgrids, which is operated according to the following steps: S1: Define multiple basic operating modes, including grid-connected mode and off-grid mode; each mode includes two operating conditions: large-scale new energy generation and small-scale new energy generation. S2: For each of the basic operating modes, set up a standardized set of disturbance test cases; S3: The disturbance test set is applied sequentially to the simulation circuit of the grid-type energy storage adaptive microgrid under all operating conditions to perform dynamic simulation. The bus voltage, frequency, energy storage unit current and power output data during the simulation are obtained through the data processing unit. S4: Analyze the simulation results data, verify the rationality of the capacity based on the preset stability criteria, and determine the minimum energy storage capacity by dividing the bus.

[0014] As a preferred embodiment of the capacity verification method for grid-type energy storage adapted to all operating conditions of microgrids according to the present invention, wherein: the standardized disturbance test set in step S4 includes at least three of the following disturbance types: Source-side power perturbation is used to simulate abrupt changes in light intensity or wind speed. Load-side power disturbance is used to simulate the sudden addition or removal of large-capacity impact loads; Short circuit faults are used to simulate transient or permanent short circuit faults occurring at different locations in the power grid. The off-grid switching disturbance is used to simulate the dynamic process of a microgrid being forced to switch to off-grid operation due to a severe fault on the main grid side.

[0015] Step S2 involves matching three standardized test items for each basic operating mode: "source-side power disturbance, load-side power disturbance, and fault disturbance (including grid connection / off-grid switching disturbance)". This clarifies the disturbance amplitude, triggering timing, and duration, ensuring that the disturbance scenarios are repeatable and comparable, and covering the extreme operating conditions that the actual system may face.

[0016] As a preferred embodiment of the capacity verification method for grid-type energy storage adapted to the full operating conditions of microgrids described in this invention, step S3 is as follows: the microgrid is built based on DIgSILENT software and the off-grid simulation circuit is used to perform dynamic simulation according to the process of "basic mode loading → disturbance sequence application → real-time data acquisition".

[0017] As a preferred embodiment of the capacity verification method for grid-type energy storage adapted to all operating conditions of microgrids described in this invention, in step S3, under the off-grid renewable energy small-scale generation condition, it is necessary to additionally verify the long-term operational stability of the energy storage unit, and avoid steady-state overload of the energy storage by configuring load shedding and control measures to ensure that the energy storage unit operates within the rated power range for a long time.

[0018] As a preferred embodiment of the capacity verification method for grid-type energy storage adapted to all operating conditions of microgrids according to the present invention, the stability criterion in step S4 includes: The bus voltage is maintained within the range of 0.9 to 1.1 per unit. The system frequency is maintained within the range of 49.5Hz to 50.5Hz; The output current of the energy storage unit shall not exceed 1.5 times the short-time overcurrent threshold.

[0019] As a preferred embodiment of the capacity verification method for grid-type energy storage adapted to all operating conditions of microgrids according to the present invention, the method further includes step S5: Based on the verification results of step S4, suggestions for selecting the overcurrent capacity of grid-type energy storage and suggestions for load shedding strategies are generated.

[0020] As a preferred embodiment of the capacity verification method for grid-type energy storage adapted to the full operating conditions of microgrids described in this invention, step S5 further includes boundary condition verification. When the load ratio of the motor on the II-section bus increases or the voltage tolerance range of the inverter load decreases, the energy storage capacity adaptability needs to be re-simulated and verified. If the stability criterion is not met, it can be optimized by increasing the energy storage capacity or increasing the overcurrent factor to 2.0 times.

[0021] The beneficial effects of this invention are as follows: 1. Highlighting the core position of grid-based energy storage: The simulation circuit is specifically designed for grid-based energy storage modules, clarifying their capacity allocation, control strategies, and adaptation logic with existing microgrid components, thus solving the problem of insufficient attention to energy storage modules in existing simulation circuits.

[0022] 2. Precise capacity verification: Through a standardized verification process based on the busbar and operating conditions, the minimum energy storage capacity is determined in combination with the existing load characteristics of the microgrid (impact loads, sensitive loads), avoiding over- or under-capacity configuration and improving the economic efficiency and reliability of the project. 3. Strong adaptability: The control strategy of the grid-type energy storage module is precisely matched with the characteristics of existing new energy and load modules, which can effectively smooth power fluctuations, support bus voltage, and significantly improve the stability of the microgrid under all operating conditions. 4. Strong engineering guidance: Simulation results can be directly used to guide the capacity configuration, overcurrent capacity selection and stability control strategy design of grid-type energy storage, providing precise technical support for practical engineering applications. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the simulation circuit structure of an embodiment of the present invention; Figure 2 This is a block diagram of the control strategy for the core module of the grid-type energy storage of the present invention; Figure 3 This is a flowchart of the capacity verification method of the present invention; Figure 4 This is a simulated waveform diagram of the transient voltage on the load side of bus section I when the energy storage capacity is 90MW in Example 1. Figure 5 This is a simulation waveform diagram of the overcurrent factor of grid-connected energy storage when the energy storage capacity is 90MW in Example 1; Figure 6 This is a simulated waveform diagram of the transient voltage on the load side of bus section I when the energy storage capacity is 80MW in Example 1. Figure 7 This is a simulated waveform diagram of the transient voltage on the load side of the II section bus when the energy storage capacity is 30MW in Example 2; Figure 8 The above is a simulated waveform diagram of the transient voltage on the load side of bus section II when no energy storage is configured in Example 2. Detailed Implementation

[0025] To make the objectives, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0026] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0027] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0028] Please refer to Figure 1 The present invention provides a simulation circuit for grid-type energy storage adapted to all operating conditions of microgrids, comprising: The data processing unit 500 is used to perform simulation calculations, disturbance injection, and data acquisition and analysis.

[0029] The power grid architecture model 100, stored in the data processing unit 500, includes a first-section bus 101 and a second-section bus 102 connected by a bus tie, and a transmission line 104 connected to the first-section bus 101 and the second-section bus 102 by a transformer 103; wherein the voltage level of the first-section bus 101 and the second-section bus 102 is 35kV, and the voltage level of the transmission line 104 is 220kV.

[0030] The grid-type energy storage module 200 is connected to bus section I 101 and bus section II 102 respectively in a high-voltage direct connection manner to provide voltage and frequency support for the grid architecture model 100.

[0031] To further explain, the grid-type energy storage module 200 includes three sets of energy storage units 201 with a total capacity of 120MW / 240MWh. The I section bus is equipped with two sets of 45MW energy storage units 201, and the II section bus is equipped with one set of 30MW energy storage units.

[0032] like Figure 2 As shown, the energy storage unit 201 integrates a control module, which includes: The frequency regulation unit 201a, located at the top level of the control module 201, achieves rapid frequency response through virtual inertia simulation, maintaining the system frequency within the range of 49.5Hz to 50.5Hz. In the figure, Pset_i represents active power; PIC_i represents actual active power; ∆ωi represents active power deviation, after... (Virtual inertia + damping element) simulates the rotor motion equation of a synchronous generator, outputs the angular frequency deviation ωref_i, and obtains the power angle θi by integrating with the initial angular frequency ω0. Finally, the phase udref of the voltage reference is generated through coordinate transformation; ωset_i=1 represents the rated reference standard of the grid energy storage angular frequency (per unit value is 1).

[0033] The voltage support unit 201b, operating in parallel with the frequency regulation unit 201a, is used to monitor the bus voltage in real time and dynamically output reactive power based on the UQ droop characteristic, maintaining the bus voltage within the range of 0.9 to 1.1 per unit. In the figure, Qset_i represents reactive power; QIC_i represents actual reactive power; and ∆Ei represents reactive power deviation. (Droop coefficient element) simulates the excitation regulation characteristics of a synchronous generator and outputs the internal potential amplitude E0; combined with the voltage reference, it generates udref / uqref (d / q axis reference voltage of the current inductor); Eset_i represents the reference setting value of the internal potential amplitude of the grid-connected energy storage; Eref_i represents the reference setting value of the internal potential amplitude of the grid-connected energy storage.

[0034] The overcurrent protection unit 201c, as a bottom-level protection module, is connected in series in the output circuit of the energy storage unit 201. This unit is set to 1.5 times the short-time overcurrent threshold (10s withstand time). When the output current of the energy storage unit 201 exceeds the threshold, the current limiting control is automatically activated. In the figure, uCd_0 / uCq_0 represents the actual voltage; Kpu+Kiu / s represents the voltage loop; udref / uqref is compared with the actual voltage uCd_0 / uCq_0, and then the inverter control signal uinvd_0 / uinvq_0 is generated through the current loop Kpi+Kii / s; iLdref / iLqref represents the d / q axis components of the current inductance; iLd_0 / iLq_0 represents the actual d / q axis feedback value of the current inductance; ωL represents the inductive reactance parameter of the inductor.

[0035] The circuit principle of the control module is as follows: Active power control loop (frequency stabilization core): The target active power Pset_i is compared with the actual active power of the converter (calculated from uCd_0 and iLd_0) to generate active power deviation ∆ωi; the active power deviation ∆ωi is then processed... (Virtual inertia + damping element) processing, outputting angular frequency deviation ωref_i; angular frequency deviation ωref_i is integrated to generate power angle θi; combined with power angle θi and internal potential reference, the active power control signal is converted into d-axis voltage reference udref through dq coordinate transformation, providing target value for subsequent voltage control.

[0036] Reactive power control loop (core of voltage stability): The target reactive power Qset_i is compared with the actual reactive power of the converter (calculated from uCq_0 and iLq_0) to generate reactive power deviation ∆Ei; the reactive power deviation ∆Ei is then processed... (Droop coefficient stage) processing, output internal potential amplitude adjustment amount, superimposed with internal potential reference E0 to obtain actual internal potential amplitude Eref_i; combined with power angle θi, through dq coordinate transformation, the reactive power control signal is converted into q-axis voltage reference uqref, together with udref to form the complete target signal of converter voltage outer loop.

[0037] Voltage-current dual-loop execution circuit (signal amplification output): Voltage loop regulation: d-axis: udref is compared with uCd_0, and adjusted by the voltage loop Kpu+Kiu / s (proportional-integral regulator) to generate the d-axis inductor current reference iLdref; q-axis: uqref is compared with uCq_0, and adjusted by the same PI regulator to generate the q-axis inductor current reference iLqref. Voltage loop regulation ensures that the converter output voltage tracks the reference value, i.e., maintains a stable bus voltage within the range of 0.9~1.1 pu.

[0038] Current loop regulation: d-axis: iLdref is compared with iLd_0, processed by the current loop Kpi+Kii / s (current PI regulator) and ωL to generate the d-axis inverter control signal uinvd_0; q-axis: iLqref is compared with iLq_0, processed by the same regulation loop to generate the q-axis inverter control signal uinvq_0. Current loop regulation is used to limit the output current to no more than 1.5 times the overcurrent threshold, preventing equipment overload and improving current response speed.

[0039] The converter executes: uinvd_0 / uinvq_0 drives the switching devices of the grid-connected energy storage converter, outputting AC power that matches the reference value, connecting to the 35kV bus, and providing frequency and voltage support for the microgrid.

[0040] To further explain, the load unit model 300 and the power supply model 400 are connected to the I section bus and the II section bus through the grid connection point.

[0041] The load unit model 300 includes an impact load model 301 and a sensitive load model 302, respectively located within the range of bus section I 101 and bus section II 102. Specifically: Section 1 busbar 101 is equipped with a 120MW impact load model 301. The impact load model 301 is a composite model of 70% constant current + 30% constant power, which includes 3 electric boiler sub-models to simulate the composite characteristics of constant current and constant power. It supports a maximum power impact simulation of 120MW. Among them, the electric boiler sub-models include 1 Kangside electric furnace and 2 LF refining furnaces. The Kangside electric furnace supports the simulation of the 80MW power impact curve of the first smelting, and the LF refining furnace supports the simulation of the 25MW power supply heating power curve. All three can be set to start, run or stop simultaneously.

[0042] The impact load model 301 is connected to the 35kV main transformer. The load is relatively stable when the electric boiler is running normally, but the connection and disconnection of the electric boiler will have a power impact on the microgrid. According to the worst-case scenario for the safe and stable operation of the microgrid, and considering a certain margin, the load types and proportions are as follows: The 20MW load on Bus I 101 is all steelmaking load, while the related auxiliary equipment is configured on Bus II 102. Therefore, the 120MW electric boiler load type on Bus I 101 is considered to be mainly constant current and supplemented by constant power, with constant current load accounting for 70% and constant power load accounting for 30%. The maximum limit for simultaneous shutdown of electric boiler loads is 120MW. The load on Bus II 102 is mostly electric motor load and is connected via frequency converters. Frequency converter loads are sensitive loads, and voltage fluctuations can easily cause frequency converter load disconnection. Therefore, the 25MW load on Bus II 102 is designed with electric motor load accounting for 60% and constant current load accounting for 40%. In the simulation, the frequency converter load protection trip setting is 0.90pu.

[0043] Section II bus 102 is equipped with a 25MW sensitive load model 302. Sensitive load model 302 is a composite model of 60% asynchronous motor + 40% frequency converter, used to simulate the load characteristics of motors and frequency converters. It is set with a motor voltage withstand threshold of 0.87pu and a frequency converter trip setting of 0.9pu.

[0044] To further explain, the 400 power supply model includes: Wind power generation model 401: 12.5MW of newly built wind power electronic model 401a connected within the range of bus section 101, and 16.8MW of existing wind power electronic model 401b connected within the range of bus section 102; Wind power generation model 401 adopts an induction generator model, configured with phase-locked loop constant power control, and simulates the change of wind turbine output when the wind speed changes by changing the power setpoint (Pref).

[0045] The photovoltaic power generation model 402 includes: a newly built photovoltaic sub-model 402a with a capacity of 28.8MW connected within the range of bus section I 101, and an existing photovoltaic sub-model 402b with a capacity of 25.7MW connected within the range of bus section II 102. The photovoltaic power generation model 402 participates in system voltage control. The voltage control module monitors the low-voltage bus voltage in real time and achieves closed-loop control through an outer voltage loop and an inner current loop. The outer voltage loop uses voltage feedback to achieve droop characteristics, and the voltage at the micro-source terminal and the reactive current exhibit a linear relationship. By setting the droop coefficient, the reactive power of micro-sources connected to the same low-voltage bus can be rationally allocated.

[0046] Photovoltaic (PV) active power output is significantly affected by external environmental factors. To maximize the absorption of renewable energy sources such as PV, PV systems do not participate in system frequency regulation during normal operation and adopt MPPT (Multi-Level Photovoltaic) control mode. Active power control uses constant DC voltage control, with the DC voltage reference value calculated by the PV modules based on irradiance and module temperature. Reactive power control uses constant reactive power control; typically, PV power generation operates at unity power factor.

[0047] The compatibility between the grid-type energy storage module 200 and the power grid architecture model 100 is as follows: Adaptation to impact loads: For the maximum 120MW power impact characteristics of the 101 electric boiler load on the I-section bus, the energy storage unit 201 has a millisecond-level active power compensation response to suppress voltage fluctuations caused by load switching.

[0048] Adaptation to sensitive loads: In response to the 0.9pu trip setting of the 102 frequency converter on the II bus, the energy storage unit 20 prioritizes the output of reactive power during fault disturbances to prevent the bus voltage from dropping below 0.9pu.

[0049] Adaptation to power supply models: In response to the abrupt changes in wind and solar power, the energy storage unit 201 uses virtual inertia to smooth out power fluctuations and maintain system power balance.

[0050] Please refer to Figure 3 This invention provides a capacity verification method for grid-based energy storage adapted to all operating conditions of a microgrid, which is operated according to the following steps: S1: Defines multiple basic operating modes, including grid-connected mode and off-grid mode; each mode includes two operating conditions: large-scale new energy generation and small-scale new energy generation.

[0051] S2: For each basic operating mode, set up a standardized perturbation test set; this perturbation test set includes at least three of the following perturbation types: Source-side power perturbation is used to simulate abrupt changes in light intensity or wind speed. Load-side power disturbance is used to simulate the sudden addition or removal of large-capacity impact loads; Short circuit faults are used to simulate transient or permanent short circuit faults occurring at different locations in the power grid. The off-grid switching disturbance is used to simulate the dynamic process of a microgrid being forced to switch to off-grid operation due to a severe fault on the main grid side.

[0052] S3: Perform dynamic simulation, and obtain bus voltage, frequency, energy storage unit current and power output data during the simulation process through data processing unit 500 according to the process of "basic mode loading → disturbance sequence application → real-time data acquisition".

[0053] S4: Analyze the simulation results data, verify the rationality of the capacity based on the preset stability criteria, and determine the minimum energy storage capacity for the denominator; the stability criteria include: The bus voltage is maintained within the range of 0.9 to 1.1 per unit. The system frequency is maintained within the range of 49.5Hz to 50.5Hz; The output current of the energy storage unit shall not exceed 1.5 times the short-time overcurrent threshold.

[0054] S5: Based on the verification results of step S4, generate recommendations for the selection of overcurrent capacity of grid-type energy storage and recommendations for load shedding strategies (the load shedding amount in the off-grid scenario of section I bus is the difference between the off-grid power of the main transformer and the adjustable amount of energy storage at the moment of off-grid).

[0055] To further explain, step S5 also includes boundary condition verification. When the load ratio of the motor on the II bus increases or the voltage tolerance range of the inverter load decreases, it is necessary to re-simulate and verify the adaptability of the energy storage capacity. If the stability criterion is not met, it can be optimized by increasing the energy storage capacity or increasing the overcurrent multiple to 2.0 times.

[0056] Example 1

[0057] The first basic approach is to connect to the grid and use small-scale renewable energy generation.

[0058] Test process: Simulate a short circuit fault in the 220kV main line (i.e., transmission line 104) at 1 second, trip all connected lines at 1.1 seconds, and transformer 103 switches off the grid.

[0059] Capacity verification of busbar section 101: like Figure 4 , Figure 5 As shown, when the energy storage capacity is configured to be 90MW (two groups of 45MW), the transient voltage on the load side of the I-section bus 101 is 0.98pu, the overcurrent multiple of the grid-connected energy storage is 1.36pu, the grid-connected energy storage has overload but does not exceed 1.5 times the overcurrent capacity of 10s, so it meets the stability criterion.

[0060] The minimum energy storage capacity of busbar 101 in section I has been determined: like Figure 6 As shown, when the capacity is reduced to 80MW, the transient voltage drops to 0.54pu, which does not meet the requirements. Therefore, reducing the grid capacity based on a 90MW grid-connected energy storage system can easily lead to load voltage instability after grid-connected / off-grid switching. It is recommended that the scale of grid-connected energy storage within the I bus range should not be less than 90MW.

[0061] Example 2

[0062] The first basic approach is to connect to the grid and use small-scale renewable energy generation.

[0063] Test process: A short circuit fault occurred on the 220kV main line (i.e., transmission line 104) at 1 second, and the short circuit fault disappeared at 1.1 seconds.

[0064] Capacity verification of busbar section 102: like Figure 7 As shown, when a 30MW energy storage capacity is configured, the inductive reactive power demand of the motor load increases dramatically after the instantaneous voltage drop. Therefore, after the instantaneous fault disappears, the grid-connected energy storage still outputs 1.5 times the current to support the system voltage. Finally, the transient voltage on the load side of the II section bus 102 is 0.90pu, which meets the stability criterion.

[0065] Minimum energy storage capacity of busbar 102 in section II determined: like Figure 8 As shown, without energy storage, the transient voltage drops to as low as 0.87 pu, posing a significant risk of inverter-sensitive loads disconnecting from the grid, thus failing to meet the requirements. Therefore, the minimum energy storage capacity for bus 102 in section II is 30 MW.

[0066] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A simulation circuit for grid-type energy storage adapted to all operating conditions of a microgrid, characterized in that, include: The power grid architecture model (100) includes a bus section I (101) and a bus section II (102) connected by a bus tie, and transmission lines connected to the bus section I (101) and the bus section II (102) respectively by a transformer (103); The grid-type energy storage module (200) is connected to the I section bus (101) and the II section bus (102) respectively in a high-voltage direct connection manner, and is used to provide voltage and frequency support for the grid architecture model (100); The loads within the range of the first busbar (101) and the second busbar (102) are not equal.

2. The simulation circuit for grid-type energy storage adapted to all operating conditions of microgrids as described in claim 1, characterized in that, The grid-type energy storage module (200) includes multiple sets of energy storage units (201), and at least one set of the energy storage units (201) is configured on the I-section bus (101) and the II-section bus (102).

3. The simulation circuit for grid-type energy storage adapted to all operating conditions of microgrids as described in claim 2, characterized in that, The energy storage unit (201) integrates a control module, which includes: The frequency adjustment unit (201a) is located at the top layer of the control module; the frequency adjustment unit (201a) achieves rapid frequency response through virtual inertia simulation and maintains the system frequency within a preset stability range; The voltage support unit (201b) runs parallel to the frequency adjustment unit (201a); the voltage support unit (201b) is used to detect the bus voltage in real time and dynamically output reactive power to maintain the bus voltage within a preset stability range. The overcurrent protection unit (201c), as a bottom-level protection module, is connected in series in the output circuit of the energy storage unit (201); the overcurrent protection unit (201c) is set with a short-time overcurrent threshold, and when the output current of the energy storage unit (201) exceeds the threshold, the current limiting control is automatically started.

4. The simulation circuit for grid-type energy storage adapted to all operating conditions of microgrids as described in claim 1 or 3, characterized in that, Also includes: Load unit model (300) and power supply model (400); The load unit model (300) and the power supply model (400) are connected to the I section bus (101) and the II section bus (102) through the grid connection point.

5. The simulation circuit for grid-type energy storage adapted to all operating conditions of microgrids as described in claim 4, characterized in that, The load unit model (300) includes an impact load model (301) and a sensitive load model (302) respectively located within the range of the I section busbar (101) and the II section busbar (102). The impact load model (301) is used to simulate the combined characteristics of constant current and constant power; The sensitive load model (302) is used to simulate the load characteristics of motors and frequency converters.

6. The simulation circuit for grid-type energy storage adapted to all operating conditions of microgrids as described in claim 1, 3, or 5, characterized in that, The power supply model (400) includes: The wind power generation model (401) includes: a newly built wind power electronic model (401a) connected within the range of the I section bus (101), and an existing wind power electronic model (401b) connected within the range of the II section bus (102); the wind power generation model (401) adopts an induction generator model and is configured with phase-locked loop constant power control; The photovoltaic power generation model (402) includes: a newly built photovoltaic sub-model (402a) connected within the range of the I section bus (101), and an existing photovoltaic sub-model (402b) connected within the range of the II section bus (102); the photovoltaic power generation model (402) adopts the MPPT control mode and performs reasonable distribution of reactive power through closed-loop control of voltage outer loop and current inner loop.

7. A capacity verification method for grid-connected energy storage adapted to all operating conditions of a microgrid, characterized in that, Follow these steps: S1: Define multiple basic operating modes, including grid-connected mode and off-grid mode; each mode includes two operating conditions: large-scale new energy generation and small-scale new energy generation. S2: For each of the basic operating modes, set up a standardized set of disturbance test cases; S3: Apply the disturbance test set sequentially to the simulation circuit of the grid-type energy storage adaptive microgrid under all operating conditions to perform dynamic simulation; S4: Analyze the simulation results data, verify the rationality of the capacity based on the preset stability criteria, and determine the minimum energy storage capacity by dividing the bus.

8. The capacity verification method for grid-type energy storage adapted to all operating conditions of microgrids as described in claim 7, characterized in that, The standardized perturbation test set in step S4 includes at least three of the following perturbation types: Source-side power perturbation is used to simulate abrupt changes in light intensity or wind speed. Load-side power disturbance is used to simulate the sudden addition or removal of large-capacity impact loads; Short circuit faults are used to simulate transient or permanent short circuit faults occurring at different locations in the power grid. The off-grid switching disturbance is used to simulate the dynamic process of a microgrid being forced to switch to off-grid operation due to a severe fault on the main grid side.

9. The capacity verification method for grid-type energy storage adapted to all operating conditions of microgrids as described in claim 7, characterized in that, The stability criteria in step S4 include: The bus voltage is maintained within the range of 0.9 to 1.1 per unit. The system frequency is maintained within the range of 49.5Hz to 50.5Hz; The output current of the energy storage unit shall not exceed 1.5 times the short-time overcurrent threshold.

10. The capacity verification method for grid-type energy storage adapted to all operating conditions of microgrids as described in claim 7, characterized in that, The method further includes step S5: Based on the verification results of step S4, generate recommendations for the selection of overcurrent capacity of grid-type energy storage and / or recommendations for load shedding and stabilization strategies.

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