Control method, network-forming converter, energy storage system and electronic device

Abstract

This application discloses a control method, a grid-connected converter, an energy storage system, and an electronic device, belonging to the field of energy storage technology. The control method includes: injecting a disturbance signal of a preset frequency into the grid connection point of the energy storage system, and acquiring a first voltage and a first current at the grid connection point; determining the equivalent impedance amplitude of the grid to which the energy storage system is connected based on the first voltage, the first current, and the preset frequency; obtaining the output impedance of the grid-connected converter of the energy storage system at the preset frequency; calculating the corresponding stability index on the grid side based on the equivalent impedance amplitude and the output impedance; and entering an impedance adaptive mode when the stability index meets preset stability adjustment conditions, so as to adjust the body impedance of the grid-connected converter in the impedance adaptive mode to regulate the stability of the energy storage system. The embodiments of this application improve the stability of the energy storage system.

Description

Technical Field

[0001] This application relates to the field of energy storage technology, specifically to a control method, a grid-type converter, an energy storage system, and electronic equipment. Background Technology

[0002] As the penetration rate of new energy sources such as wind power and photovoltaics in energy storage systems continues to increase, traditional synchronous generators are being largely replaced, leading to reduced inertia and weakened system strength in energy storage systems, and increasingly prominent frequency and voltage stability issues. Grid-Forming (GFM) control technology, which can simulate the operating characteristics of synchronous generators and provide voltage and frequency support to the power grid, has become a key to improving the stability of new energy grid connection.

[0003] Currently, grid-connected converters mostly employ a fixed-parameter dual-loop (active-frequency loop, reactive-voltage loop) control strategy. However, grid strength has a significant impact on the stability of grid-connected energy storage systems: under weak grid conditions (e.g., short-circuit ratio SCR < 2), the system damping is large, enabling stable operation; but under strong grid conditions (e.g., short-circuit ratio SCR > 5), due to the mismatch between the fixed loop gain and the extremely small grid impedance, the system damping weakens, making it highly susceptible to power oscillations in the 10-100Hz frequency band, thus threatening the stability of the energy storage system. Summary of the Invention

[0004] To address the aforementioned technical problems, embodiments of this application provide a control method, apparatus, grid-type converter, energy storage system, and electronic equipment, aiming to improve the stability of the energy storage system.

[0005] Firstly, a control method is provided, comprising the following steps: A disturbance signal of a preset frequency is injected into the grid connection point of the energy storage system, and the first voltage and first current of the grid connection point are collected. Based on the first voltage, the first current, and the preset frequency, the equivalent impedance amplitude of the power grid to which the energy storage system is connected is determined; Obtain the output impedance of the grid-type converter of the energy storage system at the preset frequency; Based on the equivalent impedance magnitude and the output impedance, calculate the corresponding stability index on the power grid side; When the stability index meets the preset stability adjustment conditions, the system enters the impedance adaptive mode to adjust the body impedance of the grid-type converter in order to regulate the stability of the energy storage system.

[0006] Secondly, a control device is provided, which is the energy storage system control device: The acquisition module is used to inject a disturbance signal of a preset frequency into the grid connection point of the energy storage system and acquire the first voltage and first current of the grid connection point. The determining module is used to determine the equivalent impedance amplitude of the power grid to which the energy storage system is connected, based on the first voltage, the first current, and the preset frequency. The acquisition module is used to acquire the output impedance of the grid-type converter of the energy storage system at the preset frequency; The calculation module is used to calculate the stability index corresponding to the power grid side based on the equivalent impedance magnitude and the output impedance. The adjustment module is used to enter the impedance adaptive mode when the stability index meets the preset stability adjustment conditions, so as to adjust the body impedance of the grid-type converter in the impedance adaptive mode to adjust the stability of the energy storage system.

[0007] Thirdly, a grid-type converter is provided, which is applied to an energy storage system, the energy storage system further comprising: at least one set of battery modules; The DC side of the grid-type converter is connected to the battery pack, and its AC side is connected to the power grid, for converting and transmitting electrical energy between the battery pack and the power grid; The grid-type converter is used to execute any of the control methods provided in the embodiments of this application.

[0008] Fourthly, an energy storage system is provided, the energy storage system comprising: At least one battery assembly for storing and releasing DC power; And, grid-type converters.

[0009] Fifthly, an electronic device is also provided, including a processor and a memory, the memory storing a plurality of instructions; the processor loads instructions from the memory to execute the steps of any of the control methods provided in the embodiments of this application.

[0010] Beneficial effects: A disturbance signal of a preset frequency is injected into the grid connection point of the energy storage system, and the first voltage and first current of the grid connection point are collected to obtain electrical data containing the preset frequency for subsequent impedance calculation. Based on the first voltage, first current, and preset frequency, the equivalent impedance amplitude of the grid at the preset frequency can be calculated, thereby obtaining real-time information on grid strength. The output impedance of the grid-connected converter at the preset frequency is obtained, providing a reference benchmark for subsequent quantification of the impedance matching relationship between the grid and the grid-connected converter. The stability index of the grid side is calculated by using the equivalent impedance amplitude and output impedance, which can be used to quantify the impedance matching degree between the grid and the grid-connected converter, thereby identifying grid operating conditions that may cause power oscillations. When the stability index meets the preset stability adjustment conditions, the system enters the impedance adaptive mode and adjusts the body impedance of the grid-connected converter to adapt it to the actual impedance of the grid, thereby suppressing power oscillations caused by impedance mismatch and improving the operational stability of the energy storage system. Attached Figure Description

[0011] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0012] Figure 1 This is a schematic diagram of the structure of an energy storage system provided in an exemplary embodiment of this disclosure; Figure 2 This is a flowchart illustrating the control method provided by an exemplary embodiment of this disclosure; Figure 3 This is a schematic diagram of the structure of the control device provided in an exemplary embodiment of this disclosure; Figure 4 This is a schematic diagram of the internal structure of an electronic device provided in an exemplary embodiment of this disclosure. Detailed Implementation

[0013] 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 embodiments of this application, and not all embodiments. 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.

[0014] In the description of this application, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of the stated features. In the description of this application, "a plurality of" means two or more, unless otherwise explicitly specified.

[0015] "A and / or B" includes the following three combinations: A only, B only, and a combination of A and B.

[0016] The use of "applies to" or "configured to" in this application implies open and inclusive language, which does not exclude the applicability to or configuration to devices performing additional tasks or steps. Additionally, the use of "based on" implies openness and inclusivity, because processes, steps, calculations, or other actions "based on" one or more of the stated conditions or values ​​may in practice be based on additional conditions or values ​​beyond those stated.

[0017] In this application, the term "exemplary" is used to mean "used as an example, illustration, or description." Any embodiment described as "exemplary" in this application is not necessarily to be construed as being more preferred or advantageous than other embodiments. The following description is provided to enable any person skilled in the art to make and use this application. Details are set forth in the following description for purposes of explanation. It should be understood that those skilled in the art will recognize that this application can be made without using these specific details. In other instances, well-known structures and processes are not described in detail to avoid obscuring the description of this application with unnecessary detail. Therefore, this application is not intended to be limited to the embodiments shown, but is consistent with the broadest scope of the principles and features disclosed in this application.

[0018] As the penetration rate of new energy sources such as wind power and photovoltaics in energy storage systems continues to increase, traditional synchronous generators are being largely replaced, leading to reduced inertia and weakened system strength in energy storage systems, and increasingly prominent frequency and voltage stability issues. Grid-Forming (GFM) control technology, which can simulate the operating characteristics of synchronous generators and provide voltage and frequency support to the power grid, has become a key to improving the stability of new energy grid connection.

[0019] Currently, grid-connected converters mostly employ a fixed-parameter dual-loop (active-frequency loop, reactive-voltage loop) control strategy. However, grid strength has a significant impact on the stability of grid-connected energy storage systems: under weak grid conditions (e.g., short-circuit ratio SCR < 2), the system damping is large, enabling stable operation; but under strong grid conditions (e.g., short-circuit ratio SCR > 5), due to the mismatch between the fixed loop gain and the extremely small grid impedance, the system damping weakens, making it highly susceptible to power oscillations in the 10-100Hz frequency band.

[0020] More importantly, the grid strength is not constant in actual operation. As the power generation of new energy sources fluctuates, the equivalent impedance of the grid changes dynamically in real time. Existing control strategies with fixed parameters cannot sense changes in grid impedance in real time, nor can they dynamically adjust control parameters based on the matching relationship between grid impedance and their own output impedance. Therefore, it is difficult to maintain the stability of the energy storage system when the grid strength changes, and there is a risk of oscillation.

[0021] Furthermore, existing technologies lack a stability index that can quantify the strength of the power grid, making it impossible to accurately determine when control parameters need to be adjusted, and also difficult to determine whether stability has been restored after adjustment, resulting in a lack of criteria for adaptive control to enter and exit.

[0022] To address the aforementioned problems, embodiments of this application provide a control method, control device, grid-connected converter, energy storage system, electronic device, computer-readable storage medium, and computer program product. In these embodiments, a disturbance signal of a preset frequency is injected into the grid connection point of the energy storage system, and a first voltage and a first current at that connection point are collected to obtain electrical data containing the preset frequency for subsequent impedance calculation. Based on the first voltage, first current, and preset frequency, the equivalent impedance amplitude of the power grid at the preset frequency can be calculated, thereby obtaining real-time information on the power grid strength. The grid-connected converter is then used to obtain the electrical data containing the preset frequency. The output impedance at a given frequency provides a reference benchmark for quantifying the impedance matching relationship between the power grid and the grid-connected converter. By calculating the stability index on the power grid side using the equivalent impedance amplitude and the output impedance, the degree of impedance matching between the power grid and the grid-connected converter can be quantitatively assessed, thereby identifying power grid operating conditions that may cause power oscillations. When the stability index meets the preset stability adjustment conditions, the system enters an impedance adaptive mode and adjusts the inherent impedance of the grid-connected converter to adapt it to the actual impedance of the power grid, thereby suppressing power oscillations caused by impedance mismatch and improving the operational stability of the energy storage system.

[0023] The control method, control device, grid-type converter, energy storage system, and electronic equipment provided in the embodiments of this application are described in detail below with reference to the accompanying drawings. It should be noted that the order of description of the following embodiments is not intended to limit the preferred order of the embodiments. Although a logical order is shown in the flowcharts, in some cases, the steps shown or described may be performed in a different order than that shown in the drawings.

[0024] like Figure 1 The diagram shown is a schematic diagram of an energy storage system provided by an exemplary embodiment of this disclosure. The energy storage system includes at least one set of battery modules and a grid-type converter (PCS).

[0025] The battery module is used to store and release DC power, with its positive output terminal (V+) and negative output terminal (V-) connected to the DC side of the grid-connected converter, respectively. The battery module can be composed of one or more battery cells connected in series, parallel, or in a mixed configuration, and the specific configuration can be determined according to the capacity requirements of the energy storage system.

[0026] A grid-formed converter (PCS) is a device that connects battery modules to the power grid. Its DC side is connected to the positive and negative terminals of the battery modules to receive DC power from them or to supply DC power for charging. The AC side of the PCS has three-phase output terminals (A, B, C) for connection to the external power grid. The PCS employs grid-forming (GFM) control technology, simulating the operating characteristics of a synchronous generator. It autonomously establishes and maintains the voltage and frequency of the power grid, providing voltage and frequency support. Unlike traditional grid-following converters, PCS maintains its voltage source characteristics even when the grid strength changes, exhibiting inertial response capability.

[0027] The grid-connected converter contains power semiconductor devices and a control unit, enabling bidirectional power conversion: in discharge mode, it converts the DC power output from the battery pack into AC power synchronized with the grid voltage and frequency, and transmits it to the grid through the AC side; in charging mode, it converts the AC power from the grid into DC power to charge the battery pack.

[0028] like Figure 2 The diagram shown is a flowchart illustrating a control method provided by an exemplary embodiment of this disclosure. The energy storage system control method includes steps S21-S25: Step S21: Inject a disturbance signal of a preset frequency into the grid connection point of the energy storage system, and collect the first voltage and first current of the grid connection point.

[0029] Specifically, the grid connection point refers to the common connection point between the AC side of the grid-connected converter in the energy storage system and the power grid, that is, the point where electrical energy flows from the energy storage system into the power grid or from the power grid into the energy storage system. At this grid connection point, the electrical parameters (such as voltage, current, and frequency) of the energy storage system and the external power grid can be directly measured by sensors such as meters and current transformers.

[0030] In this embodiment, a voltage or current disturbance signal with a small amplitude and a preset frequency is injected into the grid connection point (i.e., the output voltage of the grid-connected converter) through the grid-connected converter of the energy storage system. This preset frequency is typically selected within the range of 1Hz to 200Hz, avoiding the energy storage system's power frequency of 50Hz and its integer multiples thereof. A characteristic frequency point within 1-100Hz is preferred, such as 25Hz or 75Hz, to avoid interference with the grid power frequency. The amplitude of the disturbance signal can be controlled within 1% to 5% of the rated output of the grid-connected converter, thereby generating a component that can be used for impedance identification while ensuring the normal operation of the energy storage system.

[0031] After the disturbance signal is injected, the instantaneous voltage and current values ​​at the grid connection point are collected in real time using meters and current transformers installed at the grid connection point. The collected voltage and current data include both the original 50Hz power frequency component of the power grid and the injected preset frequency component. This voltage data is the first voltage, and the current data is the first current.

[0032] In this step, by injecting a small disturbance at the grid connection point and simultaneously collecting the first voltage and first current, voltage and current response data containing a preset frequency component can be obtained without interrupting the normal operation of the energy storage system. This provides a basis for subsequent calculation of the grid's equivalent impedance. The grid connection point serves as the connection point between the energy storage system and the grid; data collection at this point ensures the accuracy of the impedance calculation.

[0033] Step S22: Based on the first voltage, the first current, and the preset frequency, determine the equivalent impedance amplitude of the power grid to which the energy storage system is connected.

[0034] Specifically, the acquired first voltage and first current signals can be processed to extract the components corresponding to a preset frequency. For example, bandpass filters or Fourier transforms can be used to separate the voltage and current amplitudes at the preset frequency from the voltage and current signals. Based on these voltage and current amplitudes, the equivalent impedance amplitude of the power grid at the preset frequency can be calculated.

[0035] The equivalent impedance magnitude reflects the magnitude of the equivalent impedance viewed from the grid connection point to the grid side, and its value changes with the grid strength.

[0036] Furthermore, based on the phase relationship between the first voltage and the first current, the impedance phase angle at the preset frequency can also be obtained. This impedance phase angle reflects the resistance-inductance characteristics of the power grid and can be used for subsequent more comprehensive stability analysis.

[0037] In this step, the equivalent impedance amplitude of the power grid can be calculated in real time using the first voltage, the first current, and the preset frequency, thus providing a basis for quantifying the strength of the power grid.

[0038] Step S23: Obtain the output impedance of the grid-type converter of the energy storage system at the preset frequency.

[0039] Specifically, before the grid-type converter leaves the factory, its output impedance at various frequencies can be determined through offline measurement or theoretical calculation, resulting in a mapping table between the frequency and output impedance of the grid-type converter. This mapping table can be stored in the grid-type converter.

[0040] In this embodiment, the output impedance of the grid converter at a preset frequency can be obtained from the mapping table.

[0041] In this step, the output impedance of the grid-type converter at a preset frequency is obtained, providing a reference value for subsequent comparison with the grid impedance. This value does not change with the grid operating conditions.

[0042] Step S24: Calculate the stability index corresponding to the power grid side based on the equivalent impedance magnitude and the output impedance.

[0043] Specifically, the equivalent impedance amplitude of the power grid and the output impedance of the grid-type converter can be substituted into the preset stability index calculation formula to calculate the stability index on the power grid side.

[0044] For example, the ratio of the two can be calculated to obtain the impedance ratio index. The magnitude of this index reflects the degree of matching between the grid impedance and the grid-type converter impedance: a small ratio indicates that the grid impedance is much smaller than the grid-type converter impedance, corresponding to a strong grid operating condition; a large ratio corresponds to a weak grid operating condition.

[0045] The difference between the two can also be calculated to obtain the impedance difference index. When the index is positive, it indicates that the grid impedance is greater than the grid-type converter impedance; when the index is negative, it indicates that the grid impedance is less than the grid-type converter impedance; the absolute value of the index reflects the degree of deviation between the two.

[0046] The potential resonant frequency of the energy storage system can also be calculated based on the equivalent impedance of the power grid and the output impedance of the grid-type converter. Then, the difference between this frequency and the desired resonant frequency is calculated to obtain the resonant frequency offset index. The larger this offset, the farther the energy storage system deviates from the desired operating point.

[0047] The equivalent impedance of the power grid and the output impedance of the grid-type converter can be substituted into a preset damping ratio estimation model to obtain the estimated damping ratio index. The value of this index reflects the damping strength of the energy storage system: a larger value indicates stronger damping and better stability of the energy storage system; a smaller value indicates weaker damping and a greater susceptibility to oscillations.

[0048] The active power damping index can also be obtained by combining impedance amplitude and phase angle. For example, the active power damping index can be defined as the product of the impedance amplitude ratio and the cosine of the impedance phase angle difference. This index reflects the active power damping characteristics between the power grid and the converter: when the index is large, it indicates that the energy storage system has good damping capability, which is beneficial to suppressing power oscillations; when the index is small, it indicates that the damping is weak and oscillations are prone to occur.

[0049] In this step, a stability index is constructed to quantify the matching relationship between the grid impedance and the grid-type converter impedance into a numerical value, which facilitates subsequent evaluation of the current grid status and the stability of the energy storage system.

[0050] Step S25: When the stability index meets the preset stability adjustment conditions, enter the impedance adaptive mode to adjust the body impedance of the grid-type converter in the impedance adaptive mode, so as to adjust the stability of the energy storage system.

[0051] Specifically, the preset stability adjustment conditions can correspond to a threshold range. The stability index is compared with the threshold range to determine whether to enter the impedance adaptive mode.

[0052] This threshold range can be calibrated based on the operating characteristics of the energy storage system under different grid intensities. For example, when the stability index is less than a certain threshold, it indicates that the current grid impedance is too low and the energy storage system is in a strong grid condition that is prone to power oscillations.

[0053] If the stability index meets the preset adjustment conditions, the control enters impedance adaptive mode. In this mode, the control parameters of the grid-connected converter are adjusted according to the specific value of the current stability index. For example, the virtual impedance setpoint or the current loop gain coefficient is changed, thereby altering the intrinsic impedance presented by the grid-connected converter to the grid. The goal of the adjustment is to adapt the intrinsic impedance of the grid-connected converter to the actual impedance characteristics of the current grid, improving the matching degree between the two. This adjustment process can continue until the stability index no longer meets the adjustment conditions, or other exit conditions are detected.

[0054] In this step, when a change in grid strength is detected that causes the impedance matching state to deviate from the safe range, the impedance of the grid-connected converter is actively adjusted to achieve matching with the grid, thereby suppressing power oscillations caused by impedance mismatch and improving the operational stability of the energy storage system under different grid strengths.

[0055] In some embodiments, the step of determining the equivalent impedance amplitude of the power grid to which the energy storage system is connected based on the first voltage, the first current, and the preset frequency includes steps S221-S222: Step S221: Extract the first voltage amplitude at the preset frequency from the first voltage, and extract the first current amplitude at the preset frequency from the first current.

[0056] Specifically, the first voltage and the first current contain data with multiple frequency components, including the power frequency component of the power grid itself, the injected preset frequency disturbance component, and possibly other harmonic components. To obtain the data at the preset frequency, signal processing is required for the first voltage and the first current. For example, a bandpass filter can be used to extract signal components near the preset frequency, or a Fourier transform can be used to calculate the spectral components at that frequency. Through this processing, the first voltage amplitude at the preset frequency can be obtained from the first voltage; and the first current amplitude at the preset frequency can be obtained from the first current.

[0057] In this step, the first voltage amplitude and the first current amplitude at a preset frequency are separated from the data containing multiple frequency components, providing the necessary input parameters for subsequent calculation of the equivalent impedance of the power grid.

[0058] Step S222: Calculate the equivalent impedance magnitude of the power grid based on the first voltage amplitude and the first current amplitude.

[0059] Specifically, according to circuit principles, for a single-frequency AC signal, the ratio of voltage amplitude to current amplitude is the impedance amplitude at that frequency. Looking from the grid connection point towards the power grid, the power grid can be considered an equivalent circuit composed of resistors, inductors, and other components, where the voltage and current relationship satisfies Ohm's law. Therefore, dividing the first voltage amplitude by the first current amplitude yields the equivalent impedance amplitude looking from the grid connection point towards the power grid.

[0060] The equivalent impedance amplitude reflects the electrical characteristics of the power grid at the current preset frequency. Its value is directly related to the power grid strength: the stronger the power grid, the smaller the equivalent impedance amplitude; the weaker the power grid, the larger the equivalent impedance amplitude.

[0061] In some embodiments, the first voltage is a voltage sequence and the first current is a current sequence. The steps of extracting the first voltage amplitude at the preset frequency from the first voltage and extracting the first current amplitude at the preset frequency from the first current include steps S2211-S2213: Step S2211: Window the voltage sequence with a preset sliding window length, and perform Fourier transform on the windowed voltage sequence to obtain the voltage spectrum component at the preset frequency.

[0062] Specifically, the first voltage is a continuously sampled time-domain voltage sequence. To extract the preset frequency component from this voltage sequence, it needs to be segmented. First, a preset sliding window length is selected, for example, N = 0.25 fs (where fs is the sampling frequency). This length determines the number of data points involved in each calculation. Then, the voltage sequence is truncated using this window, and a window function (such as a Hanning window or a Hamming window) is applied to the truncated data to reduce spectral leakage. Next, a Discrete Fourier Transform is performed on the windowed data segment to convert the time-domain signal to the frequency domain. In the transformed spectrum, the spectral component corresponding to the preset frequency is found. This component is usually represented in complex form, containing both real and imaginary parts.

[0063] In this step, the time-domain voltage sequence is converted into frequency-domain data through a sliding window and Fourier transform, thereby separating the spectral components at the preset frequency and providing a basis for subsequent calculations.

[0064] Step S2212: Window the current sequence with a preset sliding window length, and perform Fourier transform on the windowed current sequence to obtain the current spectrum components at the preset frequency.

[0065] Specifically, the current sequence is processed using the same sliding window length as the voltage sequence. The same window function as for the voltage sequence is applied to the truncated current data segment to maintain processing consistency. Then, a Discrete Fourier Transform is performed on the windowed current data segment to obtain the frequency domain representation of the current signal. In the transformed spectrum, the current spectral component corresponding to a preset frequency is found; this component is also represented in complex form.

[0066] In this step, the same signal processing method is used to separate the spectral components at a preset frequency from the current sequence, ensuring that the voltage spectral components and the current spectral components can be compared accordingly.

[0067] Step S2213: Determine the first voltage amplitude at the preset frequency based on the voltage spectrum component, and determine the first current amplitude at the preset frequency based on the current spectrum component.

[0068] Specifically, the voltage spectrum component is a complex number containing a real part and an imaginary part. The modulus of this complex number is the amplitude of the voltage signal at that frequency. Therefore, by calculating the square root of the sum of the squares of the real and imaginary parts of the complex number, the first voltage amplitude at the preset frequency is obtained. Similarly, by calculating the modulus of the current spectrum component, the first current amplitude at the preset frequency is obtained. These two amplitudes are the response amplitudes of the voltage and current at the preset frequency within the sliding window. As the window slides along the time axis, a series of continuously updated amplitude data can be obtained.

[0069] Both voltage and current spectral components are represented in complex form, with their real and imaginary parts containing phase information. By calculating the difference between the phase angles of the voltage and current spectral components, the phase difference between the first voltage and the first current at a preset frequency can be obtained, and thus the impedance phase angle at that frequency can be derived. For example, assuming the preset frequency is 25Hz, the voltage spectral component at that frequency is 3.0 + j4.0, and the current spectral component is 2.5 + j2.5, obtained through Fourier transform. The real part of the voltage spectral component is 3.0, and the imaginary part is 4.0. Its phase angle can be calculated using the arctangent function: θv = arctan(4.0 / 3.0) ≈ 53.13°; the real part of the current spectral component is 2.5, and the imaginary part is 2.5. Its phase angle θi = arctan(2.5 / 2.5) = 45.00°. The phase difference between the two is Δθ = θv - θi = 8.13°, which is the impedance phase angle of the power grid at a frequency of 25 Hz. When this phase angle is positive, it indicates that the voltage phase leads the current, and the power grid is inductive; if it is negative, it indicates that the voltage phase lags the current, and the power grid is capacitive.

[0070] In this step, the frequency domain complex number is converted into a physically meaningful amplitude by calculating the magnitude of the spectral components, providing accurate input parameters for subsequent calculation of the equivalent impedance of the power grid.

[0071] In some embodiments, prior to the step of injecting a disturbance signal of a preset frequency into the grid connection point of the energy storage system, the method further includes: acquiring a second voltage and a second current at the grid connection point of the energy storage system; Specifically, before injecting a disturbance signal into the grid connection point, the voltage and current transformers installed at the grid connection point are used to collect the second voltage and second current values ​​of the grid connection point as background reference data. At this time, the collected second voltage and second current mainly include the original power frequency components of the power grid and the existing harmonic components in the environment, without the injected disturbance signal superimposed.

[0072] The step of calculating the equivalent impedance magnitude of the power grid based on the first voltage magnitude and the first current magnitude includes steps S2221-S2224: Step S2221: Extract the second voltage amplitude at the preset frequency from the second voltage, and extract the second current amplitude at the preset frequency from the second current. Specifically, the acquired second voltage and second current signals undergo the same signal processing as the first voltage and first current. Since no disturbance signal has been injected at this time, the second voltage and second current should not originally contain a preset frequency component. However, since there may be background noise or harmonics at this frequency in the power grid, the amplitude at this frequency still needs to be extracted as a background value.

[0073] Step S2222: Calculate the voltage amplitude difference at the preset frequency based on the first voltage amplitude and the second voltage amplitude.

[0074] Specifically, the second voltage amplitude is subtracted from the first voltage amplitude to obtain the voltage amplitude difference at a preset frequency. This difference reflects the change in voltage response caused by the injected disturbance signal, eliminating the influence of the background component at that frequency that originally existed in the power grid.

[0075] In this step, by calculating the voltage amplitude difference, the voltage response component caused purely by the injected disturbance is separated, thereby improving the accuracy of impedance measurement.

[0076] Step S2223: Calculate the difference in current amplitude at the preset frequency based on the first current amplitude and the second current amplitude.

[0077] Specifically, the difference between the first and second current amplitudes is obtained by subtracting the first current amplitude from the second current amplitude. This difference reflects the change in current response caused by the injected disturbance signal, and also eliminates the influence of background components.

[0078] In this step, by calculating the difference in current amplitude, the current response component caused purely by the injected disturbance is separated and correlated with the voltage difference, ensuring the accuracy of the impedance calculation.

[0079] Step S2224: Calculate the ratio of the voltage amplitude difference to the current amplitude difference to obtain the equivalent impedance amplitude of the power grid.

[0080] Specifically, the formula for calculating the equivalent impedance amplitude of the power grid is: |Zg(fk)|=ΔV(fk) / ΔI(fk), where fk is the preset frequency, |Zg(fk)| is the equivalent impedance amplitude of the power grid at the preset frequency fk, ΔV(fk) is the voltage amplitude difference at the preset frequency fk, and ΔI(fk) is the current amplitude difference at the preset frequency fk.

[0081] The equivalent impedance magnitude reflects the impedance of the power grid at the current preset frequency fk. The smaller the value, the stronger the power grid; the larger the value, the weaker the power grid.

[0082] Having already obtained the voltage and current spectrum components (both in complex form) at the preset frequency through Fourier transform, we can further calculate the difference between the voltage spectrum components Δv(fk) and the current spectrum components Δi(fk), where: Δv(fk) = first voltage spectrum component - second voltage spectrum component, where the first voltage spectrum component is obtained from the first voltage, and the second voltage spectrum component is obtained from the second voltage. The difference between the current spectrum components Δi(fk) = first current spectrum component - second current spectrum component, where the first current spectrum component is obtained from the first current, and the second current spectrum component is obtained from the second current.

[0083] Then, the complex form of the equivalent impedance of the power grid is obtained through complex division: Zg(fk) = Δv(fk) / Δi(fk) = |Zg(fk)|∠θg(fk), where fk is the preset frequency, Zg(fk) is the complex form of the equivalent impedance of the power grid at the preset frequency fk, Δv(fk) is the difference in voltage spectrum components at the preset frequency fk, Δi(fk) is the difference in current spectrum components at the preset frequency fk, |Zg(fk)| is the magnitude of the equivalent impedance of the power grid at the preset frequency fk, and θg(fk) is the impedance phase angle at the preset frequency fk. In this step, the equivalent impedance magnitude is calculated using the difference method, which effectively eliminates background noise interference and yields a more accurate equivalent impedance magnitude for the power grid. Furthermore, by simultaneously utilizing the difference between complex spectral components, the impedance phase angle can also be obtained, providing a richer data foundation for subsequent stability assessments.

[0084] In some embodiments, there are multiple preset frequencies, and the step of calculating the ratio of the voltage amplitude difference to the current amplitude difference to obtain the equivalent impedance amplitude of the power grid includes steps S22241-S22243: Step S22241: Calculate the ratio of the voltage amplitude difference to the current amplitude difference at each preset frequency to obtain the equivalent impedance amplitude at each preset frequency.

[0085] Specifically, if multiple different frequency points are selected for the preset frequency, the equivalent impedance amplitude is calculated for each preset frequency.

[0086] Step S22242: Calculate the average value of the equivalent impedance amplitude at each preset frequency, and use it as the equivalent impedance amplitude of the power grid.

[0087] Specifically, the equivalent impedance amplitudes at each preset frequency are summed, and then the sum is divided by the total number of preset frequencies to obtain the average value of these equivalent impedance amplitudes. This average value is used as the equivalent impedance amplitude of the power grid for subsequent stability index calculations. Using averaging can integrate information from multiple frequency points and reduce random errors that may be introduced by measurements at a single frequency point.

[0088] Step S22243: Alternatively, calculate the weighted average of the equivalent impedance amplitudes at each preset frequency according to the weights of each preset frequency, and use it as the equivalent impedance amplitude of the power grid.

[0089] Specifically, a weight is assigned to each preset frequency based on grid characteristics or experience. This weight can be set according to the importance of the frequency in the stability assessment; for example, frequencies close to the system's potential resonant frequency are given a higher weight.

[0090] Multiply the equivalent impedance amplitude at each preset frequency by the corresponding weight, then add all the product results together and divide by the sum of all weight coefficients to obtain the weighted average value.

[0091] In this step, by using weighted averaging, different weights can be assigned according to the degree of influence of different frequencies on system stability, so that the final impedance amplitude focuses more on the characteristics of key frequencies, thereby improving the pertinence and accuracy of stability assessment.

[0092] In some embodiments, the stability index includes an impedance ratio, and the step of calculating the stability index corresponding to the grid side based on the equivalent impedance magnitude and the output impedance includes: calculating the ratio of the equivalent impedance magnitude to the output impedance to obtain the impedance ratio.

[0093] Specifically, the formula for calculating the impedance ratio is: λk=|Zg(fk)| / Zc0, where λk is the impedance ratio, |Zg(fk)| is the equivalent impedance amplitude of the power grid at the preset frequency fk, and Zc0 is the output impedance of the grid-type converter at the preset frequency fk.

[0094] The impedance ratio is a dimensionless value that reflects the relative relationship between the grid impedance and the grid-type converter impedance: when the impedance ratio is small, it means that the magnitude of the grid equivalent impedance is much smaller than the output impedance of the grid-type converter, corresponding to a strong grid condition; when the impedance ratio is large, it means that the magnitude of the grid equivalent impedance is close to or exceeds the output impedance of the grid-type converter, corresponding to a weak grid condition.

[0095] In this step, the impedance matching relationship between the power grid and the grid-type converter is quantified into a single numerical index by calculating the ratio of the equivalent impedance magnitude of the power grid to the output impedance of the grid-type converter, which facilitates subsequent quantitative evaluation.

[0096] In some embodiments, the preset stability adjustment conditions include conditions corresponding to strong power grid operating conditions, and the step of satisfying the preset stability adjustment conditions for the stability index includes: determining that the conditions corresponding to the strong power grid operating conditions are met when the impedance ratio is less than a preset strong power grid threshold.

[0097] Specifically, based on the operating characteristics of the energy storage system under different grid intensities, a strong grid threshold is pre-set. This threshold is used to distinguish between strong grid conditions and other operating conditions. This threshold can be obtained through theoretical analysis, simulation, or experimental calibration. For example, the strong grid threshold can be set to 1.5 based on the impedance ratio critical value when the grid short-circuit ratio (SCR) = 2. This strong grid threshold is denoted as λthr, which is the impedance ratio critical value calibrated by the grid-type energy storage system under the grid short-circuit ratio (SCR) = 2 condition. It is the core judgment value for distinguishing between strong and weak grid conditions.

[0098] The impedance ratio is compared with a preset strong grid threshold. If the impedance ratio is less than the strong grid threshold, the current grid is determined to be in a strong grid condition. In this case, the grid impedance is low, which is not well matched with the fixed parameters of the grid-type converter, and is prone to power oscillation. Under these circumstances, the conditions corresponding to the strong grid condition are met, that is, the preset stability adjustment conditions are met, and the impedance adaptive mode can be entered.

[0099] In this step, by setting a strong power grid threshold and comparing it with the real-time impedance ratio, it is possible to accurately identify strong power grid operating conditions that are prone to power oscillations, providing a trigger condition for timely entry into the impedance adaptive mode, thereby effectively suppressing the risk of oscillations caused by impedance mismatch.

[0100] In some embodiments, after entering the impedance adaptive mode, the method further includes: If the impedance ratio is greater than a preset reference threshold, the impedance adaptive mode is exited, wherein the reference threshold is greater than the strong power grid threshold.

[0101] Specifically, during the process of entering and continuously operating in impedance adaptive mode, the current impedance ratio is continuously calculated in real time and compared with a preset reference threshold. This reference threshold is a value greater than the strong grid threshold, used to determine whether the grid has changed from a strong grid operating condition to another operating condition. The reference threshold can be calibrated according to the operating characteristics of the energy storage system, for example, it can be set to several times the strong grid threshold (e.g., 3 times, i.e., the reference threshold is 3λthr (λthr is the aforementioned strong grid threshold). When the real-time calculated impedance ratio λk > 3λthr, it is determined that the grid has left the strong grid operating condition, and the impedance adaptive mode is immediately exited), corresponding to the critical point of extremely weak grid operating conditions. When the detected impedance ratio value is greater than this reference threshold, it indicates that the current grid impedance has increased significantly, the grid strength has weakened significantly, and it is no longer in a strong grid operating condition that is prone to power oscillations. At this time, the impedance adaptive mode is exited, and the system returns to the conventional control mode. After exiting the impedance adaptive mode, the body impedance of the grid-type converter is no longer adjusted according to the impedance ratio to avoid unnecessary parameter adjustments under weak grid operating conditions.

[0102] In this step, by setting a reference threshold greater than the strong grid threshold, a clear exit condition is provided for the impedance adaptive mode, which can exit the adaptive adjustment in a timely manner when the grid strength returns to normal or becomes a weak grid.

[0103] In some embodiments, the step of adjusting the body impedance of the grid converter includes steps S2511-S2512: Step S2511: Obtain the preset first gain.

[0104] Specifically, the first gain can be the reference gain under weak grid conditions. The first gain can be obtained through offline simulation or experimental calibration, reflecting the ideal control strength required for the stable operation of the energy storage system when the grid strength is weak.

[0105] Step S2512: Based on the first gain, the output impedance, and the impedance ratio, adjust the body impedance of the grid-type converter, wherein the adjusted body impedance is positively correlated with the first gain and the output impedance, and negatively correlated with the impedance ratio.

[0106] Specifically, the first gain, the output impedance of the grid-type converter at a preset frequency, and the impedance ratio are substituted into a preset first impedance adjustment algorithm. According to this first impedance adjustment algorithm, the adjusted body impedance of the grid-type converter is directly proportional to the first gain and the output impedance, and inversely proportional to the current impedance ratio. This means that when the first gain is larger or the output impedance is larger, the adjusted body impedance increases accordingly; when the impedance ratio is larger, the adjusted body impedance decreases accordingly.

[0107] The calculation formula for the first impedance adjustment algorithm can be: ZC=Kv1*Zc0 / λk, where ZC is the adjusted body impedance of the grid-type converter, Kv1 is the first gain, Zc0 is the output impedance of the grid-type converter at the preset frequency fk, and λk is the impedance ratio between the grid equivalent impedance and the rated output impedance of the converter.

[0108] In some embodiments, the step of adjusting the body impedance of the grid converter includes steps S2521-S2522: Step S2521: Based on the predetermined mapping relationship between impedance ratio and gain value, determine the second gain corresponding to the impedance ratio.

[0109] Specifically, a mapping relationship is pre-determined and stored, establishing a correspondence between different impedance ratios and their corresponding gain values. This mapping relationship can be obtained through offline simulation, experimental testing, or theoretical analysis, reflecting the optimal gain value required to maintain system stability under different power grid strengths.

[0110] When performing this step, the current impedance ratio is used as input, and the gain value corresponding to the impedance ratio is determined from the mapping relationship by means of table lookup or interpolation calculation, which is used as the second gain.

[0111] The value of the second gain varies with the impedance ratio. When the impedance ratio is small, it corresponds to a strong power grid condition, and the second gain may take a smaller value; when the impedance ratio is large, it corresponds to a weak power grid condition, and the second gain may take a larger value.

[0112] Step S2522: Based on the second gain, the output impedance, and the impedance ratio, adjust the body impedance of the grid-type converter, wherein the adjusted body impedance is positively correlated with the second gain and the output impedance, and negatively correlated with the impedance ratio.

[0113] Specifically, the second gain, the output impedance of the grid-type converter at a preset frequency, and the current impedance ratio are substituted into a preset second impedance adjustment algorithm. According to the second impedance adjustment algorithm, the adjusted body impedance of the grid-type converter is directly proportional to the second gain and the output impedance, and inversely proportional to the current impedance ratio. This means that when the second gain is larger or the output impedance is larger, the adjusted body impedance increases accordingly; when the impedance ratio is larger, the adjusted body impedance decreases accordingly.

[0114] The calculation formula for the second impedance adjustment algorithm can be: ZC=Kv2*Zc0 / λk, where ZC is the adjusted body impedance of the grid-type converter, Kv2 is the second gain, Zc0 is the output impedance of the grid-type converter at the preset frequency fk, and λk is the impedance ratio.

[0115] In this step, by introducing a second gain determined based on the mapping relationship and adjusting the body impedance of the grid-type converter in combination with the impedance ratio, the output of the grid-type converter can be more precisely adapted to different grid strengths, thereby improving the stability of the energy storage system under various operating conditions.

[0116] In some embodiments, the method further includes: When the frequency of the power grid changes, DC power is drawn from the battery components of the energy storage system and converted into AC power before being supplied to the power grid, or the AC power of the power grid is converted into DC power to charge the battery components, so as to provide inertial support to the power grid. In the impedance adaptive mode, at least one execution parameter of the inertial support is determined based on the adjusted body impedance.

[0117] Specifically, during normal operation, the energy storage system continuously monitors changes in the grid frequency. When a deviation from the rated value (e.g., 50 Hz) is detected, the energy storage system activates its inertial support function, using the electrical energy stored in the battery modules to regulate the grid frequency. If the grid frequency decreases, indicating insufficient active power, the energy storage system draws DC power from the battery modules, converts it into AC power synchronized with the grid voltage and frequency via a grid-connected converter, and then supplies it to the grid, providing active power support. If the grid frequency increases, indicating excess active power, the energy storage system converts the grid's AC power into DC power via a grid-connected converter to charge the battery modules, absorbing excess active power from the grid. Through this power regulation, the energy storage system simulates the inertial characteristics of a traditional synchronous generator, providing frequency support to the grid.

[0118] In impedance adaptive mode, the intrinsic impedance of the grid-connected converter has been adjusted according to the current grid strength. At this time, the execution parameters of the inertial support function are also determined based on the adjusted intrinsic impedance. These execution parameters may include the inertia coefficient, droop coefficient, and power response rate, which determine the amplitude and rate of power output or absorption by the energy storage system when the frequency changes. For example, the slope of the active power-frequency droop curve can be adjusted accordingly based on the adjusted intrinsic impedance value: when the adjusted intrinsic impedance indicates a strong grid condition, the droop coefficient can be appropriately reduced to make the inertial response smoother; when the adjusted intrinsic impedance indicates a weak grid condition, the droop coefficient can be appropriately increased to enhance the inertial support. By correlating the inertial support parameters with the intrinsic impedance, the frequency regulation of the energy storage system can adapt to different grid strengths.

[0119] In this step, based on providing inertial support function, the frequency regulation of the energy storage system can be adapted to changes in grid strength by associating the execution parameters of inertial support with the body impedance adjusted in impedance adaptive mode.

[0120] In some embodiments, the energy storage system also includes a digital twin unit and a cloud update interface.

[0121] Specifically, the energy storage system can be configured with a digital twin unit, which operates offline or online, to simulate the gain Kv (e.g., the first gain Kv1 or the second gain Kv2) under different impedance ratios λk. Through digital twin technology, the adjustment effect of the gain under different grid strengths can be simulated without actually affecting the operation of the energy storage system.

[0122] The energy storage system can also be configured with a cloud update interface, which connects to a remote server or cloud platform to remotely refresh the reference parameter table stored in the converter. The reference parameters in the table may include reference gain under weak grid conditions, output impedance of the converter at various frequencies, etc. Through the cloud update interface, the parameters of the energy storage system can be remotely upgraded and optimized without on-site maintenance.

[0123] In this embodiment, by injecting a disturbance signal of a preset frequency, the impedance ratio is calculated, the grid strength is quantified, and the impedance of the grid-connected converter is modified according to the grid strength, achieving adaptive operation between strong and weak grids. Thus, the energy storage system can maintain stable operation under different grid strengths. Experiments show that this control method can effectively suppress power oscillations and maintain stable operation of the energy storage system even under strong grid conditions where the grid short-circuit ratio (SCR) is greater than 10.

[0124] This application embodiment also provides a grid-type converter, which is applied to an energy storage system, the energy storage system further including: at least one set of battery modules; The grid-type converter has its DC side connected to the battery pack and its AC side connected to the power grid, and is used for the conversion and transmission of electrical energy between the battery pack and the power grid. The grid-type converter is used to execute the aforementioned control method. The grid-type converter integrates dedicated functional modules, including: an online impedance identification module for performing grid connection point voltage and current acquisition, disturbance injection, and power grid equivalent impedance calculation steps; an impedance ratio calculation module for performing the impedance ratio λk calculation step; a weak grid judgment module for performing grid condition judgment and adaptive mode entry judgment steps; an impedance adaptive update module for performing real-time adjustment of the converter's own impedance; and an exit judgment module for performing adaptive mode exit condition judgment steps.

[0125] Specifically, this grid-type converter mainly includes a power conversion circuit and a control unit. The power conversion circuit consists of power semiconductor switching devices (such as IGBTs or MOSFETs) and their drive circuits, used to realize the conversion of electrical energy between DC and AC. The control unit typically uses a digital signal processor (DSP) or a microcontroller (MCU), which internally stores computer programs or instructions to implement the aforementioned control methods.

[0126] In terms of physical connection, the DC side of the grid-connected converter is equipped with positive and negative DC bus terminals, which are connected to the positive and negative terminals of the battery modules in the energy storage system, respectively, to obtain DC power from the battery modules or to feed DC power back to the battery modules. The AC side of the grid-connected converter is equipped with three-phase AC output terminals for connection to the external power grid, enabling power exchange with the grid.

[0127] During operation, the grid-connected converter executes the energy storage system control method described in the preceding embodiments through its control unit. Specifically, the control unit controls the grid-connected converter to inject a disturbance signal of a preset frequency into the grid connection point and collects voltage and current data at the grid connection point; calculates the equivalent impedance amplitude of the grid based on the collected voltage and current data; reads the output impedance of the grid-connected converter at the preset frequency from the memory; calculates the stability index; and determines whether to enter the impedance adaptive mode based on the stability index, adjusting the converter's body impedance in the adaptive mode. These operations are completed by the control unit, which controls the on and off of the power switching devices through the drive circuit, thereby changing the converter's output.

[0128] In this embodiment, the grid-type converter, by integrating the above-mentioned control methods, can sense changes in grid impedance in real time and adjust its own output impedance, thereby suppressing power oscillations under strong grid conditions and maintaining stable operation under weak grid conditions.

[0129] like Figure 3 The diagram shown is a schematic representation of the structure of a control device provided in an exemplary embodiment of this disclosure. The control device 30 includes: The acquisition module 31 is used to inject a disturbance signal of a preset frequency into the grid connection point of the energy storage system and acquire the first voltage and first current of the grid connection point. The determining module 32 is used to determine the equivalent impedance amplitude of the power grid to which the energy storage system is connected, based on the first voltage, the first current, and the preset frequency. The acquisition module 33 is used to acquire the output impedance of the grid-type converter of the energy storage system at the preset frequency; Calculation module 34 is used to calculate the stability index corresponding to the power grid side based on the equivalent impedance magnitude and the output impedance. The adjustment module 35 is used to enter the impedance adaptive mode when the stability index meets the preset stability adjustment conditions, so as to adjust the body impedance of the grid-type converter in the impedance adaptive mode to adjust the stability of the energy storage system.

[0130] In some embodiments, the determining module 32 is specifically used for: Extract the first voltage amplitude at the preset frequency from the first voltage, and extract the first current amplitude at the preset frequency from the first current; Based on the first voltage amplitude and the first current amplitude, the equivalent impedance amplitude of the power grid is calculated.

[0131] In some embodiments, the determining module 32 is specifically used for: The voltage sequence is windowed with a preset sliding window length, and the windowed voltage sequence is subjected to Fourier transform to obtain the voltage spectrum components at the preset frequency. The current sequence is windowed with a preset sliding window length, and the windowed current sequence is subjected to Fourier transform to obtain the current spectrum components at the preset frequency. The first voltage amplitude at the preset frequency is determined based on the voltage spectrum component, and the first current amplitude at the preset frequency is determined based on the current spectrum component.

[0132] In some embodiments, before injecting a disturbance signal of a preset frequency into the grid connection point of the energy storage system, the acquisition module 31 is further configured to: acquire the second voltage and second current of the grid connection point of the energy storage system; The determining module 32 is further configured to: Extract the second voltage amplitude at the preset frequency from the second voltage, and extract the second current amplitude at the preset frequency from the second current; Based on the first voltage amplitude and the second voltage amplitude, calculate the voltage amplitude difference at the preset frequency; Based on the first current amplitude and the second current amplitude, calculate the current amplitude difference at the preset frequency; The equivalent impedance magnitude of the power grid is obtained by calculating the ratio of the voltage amplitude difference to the current amplitude difference.

[0133] In some embodiments, there are multiple preset frequencies, and the determining module 32 is further configured to: Calculate the ratio of the voltage amplitude difference to the current amplitude difference at each preset frequency to obtain the equivalent impedance amplitude at each preset frequency; Calculate the average value of the equivalent impedance amplitude at each preset frequency, and use it as the equivalent impedance amplitude of the power grid; Alternatively, based on the weights of each preset frequency, a weighted average of the equivalent impedance amplitudes at each preset frequency can be calculated as the equivalent impedance amplitude of the power grid.

[0134] In some embodiments, the stability metric includes the impedance ratio, and the calculation module 34 is specifically used for: The impedance ratio is obtained by calculating the ratio of the equivalent impedance magnitude to the output impedance.

[0135] In some embodiments, the preset stability adjustment conditions include conditions corresponding to strong power grid operating conditions, and the adjustment module 35 is specifically used for: If the impedance ratio is less than a preset high-voltage power grid threshold, the conditions corresponding to the high-voltage power grid operating condition are determined to be met.

[0136] In some embodiments, after entering the impedance adaptive mode, the adjustment module 35 is further configured to: If the impedance ratio is greater than a preset reference threshold, the impedance adaptive mode is exited, wherein the reference threshold is greater than the strong power grid threshold.

[0137] In some embodiments, the adjustment module 35 is specifically used for: Obtain the preset first gain; Based on the first gain, the output impedance, and the impedance ratio, the body impedance of the grid-type converter is adjusted, wherein the adjusted body impedance is positively correlated with the first gain and the output impedance, and negatively correlated with the impedance ratio.

[0138] In some embodiments, the adjustment module 35 is specifically used for: Based on a predetermined mapping relationship between impedance ratio and gain value, the second gain corresponding to the impedance ratio is determined; Based on the second gain, the output impedance, and the impedance ratio, the body impedance of the grid-type converter is adjusted, wherein the adjusted body impedance is positively correlated with the second gain and the output impedance, and negatively correlated with the impedance ratio.

[0139] In some embodiments, the control device 30 further includes a support module (not shown), the support module being used for: When the frequency of the power grid changes, DC power is drawn from the battery components of the energy storage system and converted into AC power before being supplied to the power grid, or the AC power of the power grid is converted into DC power to charge the battery components, so as to provide inertial support to the power grid. In the impedance adaptive mode, at least one execution parameter of the inertial support is determined based on the adjusted body impedance.

[0140] The control device 30 provided in this application embodiment injects a disturbance signal of a preset frequency into the grid connection point of the energy storage system and collects the first voltage and first current of the grid connection point to obtain electrical data containing the preset frequency for subsequent impedance calculation. Based on the first voltage, first current, and preset frequency, the equivalent impedance amplitude of the power grid at the preset frequency can be calculated, thereby obtaining real-time information on the power grid strength. The output impedance of the grid-type converter at the preset frequency is obtained, providing a reference benchmark for subsequent quantification of the impedance matching relationship between the power grid and the grid-type converter. The stability index of the power grid side is calculated by using the equivalent impedance amplitude and output impedance, which can be used to quantify the impedance matching degree between the power grid and the grid-type converter, thereby identifying power grid operating conditions that may cause power oscillations. When the stability index meets the preset stability adjustment conditions, the device enters the impedance adaptive mode and adjusts the body impedance of the grid-type converter to adapt the grid-type converter to the actual impedance of the power grid, thereby suppressing power oscillations caused by impedance mismatch and improving the operational stability of the energy storage system.

[0141] Figure 4 This is a schematic diagram of the internal structure of an electronic device provided in an exemplary embodiment of this disclosure. The electronic device includes a processor, a memory, an input / output interface, a communication interface, a display unit, and an input device. The processor, memory, and input / output interface are connected via a system bus, and the communication interface, display unit, and input device are also connected to the system bus via the input / output interface. The processor of this electronic device provides computing and control capabilities. The memory of this electronic device includes a non-volatile storage medium and internal memory. The non-volatile storage medium stores an operating system and computer programs. The internal memory provides an environment for the operation of the operating system and computer programs in the non-volatile storage medium. The input / output interface of this electronic device is used for exchanging information between the processor and external devices. The communication interface of this electronic device is used for wired or wireless communication with external terminals; wireless communication can be achieved through Wi-Fi, mobile cellular networks, NFC (Near Field Communication), or other technologies. When the computer program is executed by the processor, it implements a control method. The display unit of the electronic device is used to form a visually visible image. It can be a display screen, a projection device, or a virtual reality imaging device. The display screen can be an LCD screen or an e-ink screen. The input device of the electronic device can be a touch layer covering the display screen, or buttons, trackballs, or touchpads set on the casing of the electronic device, or external keyboards, touchpads, or mice, etc.

[0142] Those skilled in the art will understand that Figure 4The structure shown is only a block diagram of a part of the structure related to the solution of this application, and does not constitute a limitation on the electronic device to which the solution of this application is applied. The specific electronic device may include more or fewer components than shown in the figure, or combine certain components, or have different component arrangements.

[0143] Based on the same inventive concept, embodiments of this application also provide a computer-readable storage medium, which may include: read-only memory (ROM), random access memory (RAM), disk or optical disk, etc.

[0144] Since the computer program stored in the computer-readable storage medium can execute any of the control methods provided in the embodiments of this application, the beneficial effects that any of the control methods provided in the embodiments of this application can achieve can be realized, as detailed in the preceding embodiments, and will not be repeated here.

[0145] Based on the same inventive concept, embodiments of this application also provide a computer program product or computer program, which includes computer instructions stored in a computer-readable storage medium. A processor of an electronic device reads the computer instructions from the computer-readable storage medium and executes the computer instructions, causing the electronic device to perform the methods provided in the various optional implementations of the above embodiments.

[0146] It should be noted that, in the data processing stage, the technical solution of this application has strictly limited the scope of data collection to the minimum necessary to achieve the technical objectives, preventing the acquisition of irrelevant information. For any user information to be collected, the data subject will be clearly informed and their consent obtained. Furthermore, technologies such as encrypted storage and access control are employed to strengthen data security and ensure the security and compliance of the entire data processing process. The technical model and decision-making mechanism are based on objective technical parameters and do not introduce unnecessary parameters such as gender or age that may lead to discrimination, resolutely eliminating algorithmic discrimination and upholding public order and good morals. In addition, the specification fully describes the technical implementation methods, application scenarios, and compliance protection details. The claims are consistent with the content of the specification, key compliance designs are clear and verifiable, and the overall technical design is guided by the protection of public interests and adherence to social ethics, without any circumstances that harm public interests or violate public order and good morals.

[0147] Any reference to memory, database, or other media used in the embodiments provided in this application may include at least one of non-volatile and volatile memory. Non-volatile memory may include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory may include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM may be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM), etc.

[0148] The databases involved in the embodiments provided in this application may include at least one type of relational database and non-relational database. Non-relational databases may include, but are not limited to, blockchain-based distributed databases. The processors involved in the embodiments provided in this application may be general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic devices, quantum computing-based data processing logic devices, etc., and are not limited to these.

[0149] In the above embodiments of the control device, computer-readable storage medium, electronic device, and computer program product, the descriptions of each embodiment have different focuses. Parts not described in detail in a particular embodiment can be referred to in the relevant descriptions of other embodiments. Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes and beneficial effects of the control device, computer-readable storage medium, computer program product, electronic device, and their corresponding units described above can be referred to the description of the control method in the above embodiments, and will not be repeated here.

[0150] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0151] The foregoing has provided a detailed description of a control method, control device, electronic device, computer-readable storage medium, and computer program product provided in the embodiments of this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A control method, characterized in that, Includes the following steps: A disturbance signal of a preset frequency is injected into the grid connection point of the energy storage system, and the first voltage and first current of the grid connection point are collected. Based on the first voltage, the first current, and the preset frequency, the equivalent impedance amplitude of the power grid to which the energy storage system is connected is determined; Obtain the output impedance of the grid-type converter of the energy storage system at the preset frequency; Based on the equivalent impedance magnitude and the output impedance, calculate the corresponding stability index on the power grid side; When the stability index meets the preset stability adjustment conditions, the system enters the impedance adaptive mode to adjust the body impedance of the grid-type converter in order to regulate the stability of the energy storage system.

2. The method according to claim 1, characterized in that, The step of determining the equivalent impedance amplitude of the power grid to which the energy storage system is connected, based on the first voltage, the first current, and the preset frequency, includes: Extract the first voltage amplitude at the preset frequency from the first voltage, and extract the first current amplitude at the preset frequency from the first current; Based on the first voltage amplitude and the first current amplitude, the equivalent impedance amplitude of the power grid is calculated.

3. The method according to claim 2, characterized in that, The first voltage is a voltage sequence, and the first current is a current sequence. The steps of extracting the first voltage amplitude at the preset frequency from the first voltage and extracting the first current amplitude at the preset frequency from the first current include: The voltage sequence is windowed with a preset sliding window length, and the windowed voltage sequence is subjected to Fourier transform to obtain the voltage spectrum components at the preset frequency. The current sequence is windowed with a preset sliding window length, and the windowed current sequence is subjected to Fourier transform to obtain the current spectrum components at the preset frequency. The first voltage amplitude at the preset frequency is determined based on the voltage spectrum component, and the first current amplitude at the preset frequency is determined based on the current spectrum component.

4. The method according to claim 2, characterized in that, Before the step of injecting a disturbance signal of a preset frequency into the grid connection point of the energy storage system, the method further includes: Collect the second voltage and second current at the grid connection point of the energy storage system; The step of calculating the equivalent impedance magnitude of the power grid based on the first voltage magnitude and the first current magnitude includes: Extract the second voltage amplitude at the preset frequency from the second voltage, and extract the second current amplitude at the preset frequency from the second current; Based on the first voltage amplitude and the second voltage amplitude, calculate the voltage amplitude difference at the preset frequency; Based on the first current amplitude and the second current amplitude, calculate the current amplitude difference at the preset frequency; The equivalent impedance magnitude of the power grid is obtained by calculating the ratio of the voltage amplitude difference to the current amplitude difference.

5. The method according to claim 4, characterized in that, The preset frequencies are multiple, and the step of calculating the ratio of the voltage amplitude difference to the current amplitude difference to obtain the equivalent impedance amplitude of the power grid includes: Calculate the ratio of the voltage amplitude difference to the current amplitude difference at each preset frequency to obtain the equivalent impedance amplitude at each preset frequency; Calculate the average value of the equivalent impedance amplitude at each preset frequency, and use it as the equivalent impedance amplitude of the power grid; Alternatively, based on the weights of each preset frequency, a weighted average of the equivalent impedance amplitudes at each preset frequency can be calculated as the equivalent impedance amplitude of the power grid.

6. The method according to claim 1, characterized in that, The stability index includes the impedance ratio. The step of calculating the corresponding stability index on the grid side based on the equivalent impedance magnitude and the output impedance includes: The impedance ratio is obtained by calculating the ratio of the equivalent impedance magnitude to the output impedance.

7. The method according to claim 6, characterized in that, The preset stability adjustment conditions include conditions corresponding to strong power grid operating conditions, and the steps for the stability index to meet the preset stability adjustment conditions include: If the impedance ratio is less than a preset high-voltage power grid threshold, the conditions corresponding to the high-voltage power grid operating condition are determined to be met.

8. The method according to claim 7, characterized in that, After entering the impedance adaptive mode, the method further includes: If the impedance ratio is greater than a preset reference threshold, the impedance adaptive mode is exited, wherein the reference threshold is greater than the strong power grid threshold.

9. The method according to claim 6, characterized in that, The step of adjusting the body impedance of the grid converter includes: Obtain the preset first gain; Based on the first gain, the output impedance, and the impedance ratio, the body impedance of the grid-type converter is adjusted, wherein the adjusted body impedance is positively correlated with the first gain and the output impedance, and negatively correlated with the impedance ratio.

10. The method according to claim 6, characterized in that, The step of adjusting the body impedance of the grid converter includes: Based on a predetermined mapping relationship between impedance ratio and gain value, the second gain corresponding to the impedance ratio is determined; Based on the second gain, the output impedance, and the impedance ratio, the body impedance of the grid-type converter is adjusted, wherein the adjusted body impedance is positively correlated with the second gain and the output impedance, and negatively correlated with the impedance ratio.

11. The method according to any one of claims 1-10, characterized in that, The method further includes: When the frequency of the power grid changes, DC power is drawn from the battery components of the energy storage system and converted into AC power before being supplied to the power grid, or the AC power of the power grid is converted into DC power to charge the battery components, so as to provide inertial support to the power grid. In the impedance adaptive mode, at least one execution parameter of the inertial support is determined based on the adjusted body impedance.

12. A grid-type converter, characterized in that, The grid-type converter is applied to an energy storage system, which further includes at least one set of battery modules; The DC side of the grid-type converter is connected to the battery pack, and its AC side is connected to the power grid, for converting and transmitting electrical energy between the battery pack and the power grid; The grid-type converter is used to perform the control method as described in any one of claims 1-11.

13. An energy storage system, characterized in that, The energy storage system includes: At least one battery assembly for storing and releasing DC power; And, as described in claim 12, the grid-type converter.

14. The energy storage system according to claim 13, characterized in that, The energy storage system also includes a digital twin unit and a cloud update interface; the digital twin unit is used to pre-simulate the combined effect of gain values ​​under different impedance ratios; the cloud update interface is used to remotely refresh the reference parameter table of the grid-type converter.

15. An electronic device, characterized in that, include: A memory that stores computer programs; A processor for executing the computer program in the memory to implement the control method as described in any one of claims 1-11.

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