A method, device and medium for reducing a short-circuit ratio critical value of a new energy station

Abstract

The present application belongs to the field of power system grid-connected control technology, and discloses a method, device and medium for reducing the short-circuit ratio critical value of a new energy station, which is applied to a grid-connected system, the grid-connected system comprising a new energy station and a grid-connected line for connecting the new energy station to a power grid, and the new energy station comprising a grid-connected type converter, the method comprising: obtaining the rated capacity and grid-connected voltage level of the new energy station, and determining the preselected capacity of a grid-connected type device with direct current self-synchronization control; deploying the grid-connected type device in parallel on the main power collection bus side of the new energy station, the grid-connected type device being provided with a direct current self-synchronization control loop, and introducing equivalent inertia and damping characteristics into the direct current side voltage loop; and adjusting the parameters of the direct current self-synchronization control loop to reduce the short-circuit ratio critical value of the new energy station. By introducing the grid-connected type device with direct current self-synchronization control function and adjusting the parameters thereof, the short-circuit ratio critical value of the new energy station is reduced without modifying the infrastructure on the power grid side.

Description

Technical Field

[0001] This invention belongs to the field of power system grid connection control technology, specifically relating to a method, equipment, and medium for reducing the critical value of the short-circuit ratio of new energy power plants. Background Technology

[0002] With the large-scale integration of new power technologies such as renewable energy and high-voltage direct current transmission, power electronic converters have been widely used in modern power systems. Currently, in large-scale renewable energy power plants, photovoltaic or wind turbine conversion devices mostly adopt grid-following (GFL) converters. Their control strategies are usually based on phase-locked loops (PLLs) to synchronize the grid voltage phase, thereby achieving regulation of active and reactive power.

[0003] However, under weak grid operating conditions with low short-circuit ratios (SCR) and high system impedance, grid voltage is susceptible to fluctuations due to disturbances, leading to sluggish dynamic response of the phase-locked loop (PLL) and phase tracking errors. This problem can trigger subsynchronous / supersynchronous oscillations and even cause converter disconnection, seriously threatening stable system operation. With the continuous increase in the penetration rate of new energy sources, the risks of grid connection in weak grids are becoming increasingly prominent, and have become a key factor restricting the efficient consumption of new energy and the safe operation of the grid.

[0004] The critical short-circuit ratio (CSCR) for renewable energy power plants connected to the grid is a key indicator for measuring their safe operation under weak grid conditions. The critical short-circuit ratio is mainly affected by the following factors:

[0005] Power grid structural strength: The larger the short-circuit capacity on the power grid side, the stronger the voltage support capability and the better the system's anti-disturbance performance;

[0006] Converter control characteristics: The bandwidth of the phase-locked loop, the control parameters of the current loop and voltage loop, and the filtering characteristics directly determine the dynamic stability margin of the system;

[0007] The access configuration of the power station includes centralized or distributed access, multi-unit parallel operation, bus cascade structure, etc. These factors affect the equivalent impedance distribution and voltage regulation capability.

[0008] If the critical short-circuit ratio of a certain station is too high, it will bring a series of challenges to its planning, construction and operation:

[0009] Increased grid connection thresholds: The requirement for the power grid to have higher short-circuit capacity or to install additional compensation devices limits the range of new energy site selection.

[0010] Increased operational risks: The substations are more dependent on the power grid, making them more prone to tripping the grid due to power grid faults or voltage drops;

[0011] Limited absorption capacity: In order to meet the high critical short-circuit ratio requirements, power plants can often only operate in areas with high grid strength, resulting in some areas rich in wind and solar resources facing reduced power operation due to weak grids. Summary of the Invention

[0012] To address the shortcomings of existing technologies, this invention provides a method, device, and medium for reducing the critical value of the short-circuit ratio in new energy power plants. By connecting a DC self-synchronizing control grid-type device in parallel to the main collector bus of the new energy power plant and adjusting the device parameters, the critical value of the short-circuit ratio is reduced. The introduced grid-type device embeds equivalent inertia and damping elements in its DC-side voltage control loop, enabling the DC link capacitor to not only store energy but also simulate the inertia and damping characteristics of a synchronous generator, thus achieving spontaneous synchronization and active support for the AC power grid.

[0013] This invention provides the following technical solution:

[0014] The first objective of this invention is to provide a method for reducing the critical short-circuit ratio of renewable energy power plants. The method is applied to a grid-connected system, which includes renewable energy power plants and grid-connected lines connecting the renewable energy power plants to the power grid. The renewable energy power plants include grid-connected converters. The method comprises:

[0015] Obtain the rated capacity and grid connection voltage level of the new energy power station to determine the pre-selected capacity of DC self-synchronizing control grid-type equipment;

[0016] The pre-selected capacity of DC self-synchronizing control grid-type equipment is deployed in parallel on the main collector bus side of the new energy power station. The grid-type equipment is equipped with a DC self-synchronizing control loop to introduce equivalent inertia and damping characteristics into the DC side voltage loop.

[0017] The parameters of the DC self-synchronization control loop of the DC self-synchronization control grid-type equipment are tuned to reduce the critical value of the short-circuit ratio of new energy power plants.

[0018] By deploying grid-connected equipment with DC self-synchronization control function in parallel with renewable energy power plants, which mainly use grid-connected converters, and by tuning the parameters of the DC self-synchronization control loop of the grid-connected equipment, the short-circuit ratio threshold of the renewable energy power plants was reduced without modifying the grid-side infrastructure. Through its DC self-synchronization control loop, the grid-connected equipment actively provides virtual inertia and damping support for the system, enhancing the stability of the entire grid-connected system under weak grid conditions and significantly expanding the safe grid-connected operation range of the renewable energy power plants.

[0019] As a further improvement of the present invention, the tuning of the DC self-synchronization control loop parameters of the DC self-synchronization control network equipment includes:

[0020] The preset tuning range of DC self-synchronization control loop parameters includes DC side capacitor value, equivalent damping coefficient, equivalent inertia coefficient, DC voltage tracking coefficient, and DC capacitor voltage reference value.

[0021] The DC-side capacitor value, equivalent damping coefficient, equivalent inertia coefficient, DC capacitor voltage reference value, and DC voltage tracking coefficient are adjusted sequentially, and the critical value of the short-circuit ratio of the new energy power station corresponding to each parameter setting combination is calculated.

[0022] As a further improvement of the present invention, the step of sequentially adjusting the DC-side capacitor value, equivalent damping coefficient, equivalent inertia coefficient, DC capacitor voltage reference value, and DC voltage tracking coefficient includes:

[0023] Based on the rated capacity of the new energy power station and the preset inertial support time, determine the minimum value of the DC side capacitor.

[0024] Adjust the equivalent damping coefficient so that the damping ratio and overshoot of the grid-connected system meet the preset conditions;

[0025] The equivalent damping coefficient is fixed and the equivalent inertia coefficient is adjusted so that the frequency change rate of the grid-connected system meets the preset conditions.

[0026] Adjust the DC capacitor voltage reference value and DC voltage tracking coefficient to balance the active power output and reactive power support capacity of DC self-synchronizing control network equipment.

[0027] A logically clear and hierarchically structured parameter tuning sequence is defined. This sequence follows the objective laws of system stability design: first, ensure hardware capabilities (capacitor values); second, establish a stable foundation (damping coefficient); third, optimize dynamic performance (inertia coefficient); and finally, balance the operating point (voltage parameters). This step-by-step tuning strategy effectively avoids mutual interference between parameters, ensuring that each adjustment targets specific performance indicators. This significantly improves the efficiency of the tuning process and ensures that the grid-connected system possesses sufficient inertial support and good power regulation capabilities while maintaining good damping.

[0028] As a further improvement of the present invention, the tuning of the DC self-synchronization control loop parameters of the DC self-synchronization control network equipment further includes:

[0029] Determine whether the parameter tuning process iterates through the tuning range of each parameter;

[0030] If so, output the parameter corresponding to the minimum critical value of the short-circuit ratio of the new energy power station; otherwise, continue to adjust the parameter within the adjustment range.

[0031] As a further improvement of the present invention, the adjustment of the equivalent damping coefficient to make the damping ratio and overshoot of the grid-connected system meet the preset conditions includes: applying a small signal voltage disturbance in the grid-connected line and obtaining the value of the equivalent damping coefficient that makes the damping ratio and overshoot of the grid-connected system meet the preset conditions.

[0032] As a further improvement of the present invention, the calculation of the critical value of the short-circuit ratio of the new energy power station corresponding to each parameter tuning combination includes:

[0033] Derive the admittance matrix of a grid-connected line based on its impedance.

[0034] A small-signal model for a new energy power station is constructed. The small-signal model is the sum of the small-signal output admittance matrix of the grid-connected converter and the small-signal output admittance matrix of the DC self-synchronous control grid-connected equipment under the current parameter tuning combination.

[0035] Based on the small-signal model of new energy power stations and the admittance matrix of grid-connected lines, the characteristic equation of the grid-connected system is constructed.

[0036] The solution is the grid-connected line inductance value that makes the root of the characteristic equation lie on the imaginary axis. The critical value of the short-circuit ratio of the new energy power station is the reciprocal of the grid-connected line inductance value.

[0037] As a further improvement of the present invention, the construction of the small signal model for the new energy power station includes:

[0038] In the synchronous rotating dq coordinate system, small-signal output admittance matrices of grid-connected converters and DC self-synchronizing grid-connected equipment are established respectively. The small-signal output admittance matrices of grid-connected converters and DC self-synchronizing grid-connected equipment are then transformed to the global xy rotating coordinate system to construct the small-signal model of the new energy power station.

[0039] As a further improvement of the present invention, the small-signal output admittance matrix of the grid-connected converter is derived based on the dynamic equations of the current loop, power control loop and phase-locked loop of the grid-connected converter; the small-signal output admittance matrix of the DC self-synchronizing grid-connected device is derived based on the AC voltage loop, AC current loop and DC self-synchronizing control loop of the DC self-synchronizing grid-connected device.

[0040] A second objective of this invention is to provide a computer device comprising at least one processing unit and at least one storage unit, wherein the storage unit stores a computer program, and when the program is executed by the processing unit, the processing unit performs the aforementioned method.

[0041] A third objective of this invention is to provide a computer-readable storage medium storing a computer program executable by an electronic device, which, when run on the electronic device, causes the electronic device to perform the above-described method.

[0042] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0043] By deploying grid-connected equipment with DC self-synchronization control function in parallel with renewable energy power plants, which mainly use grid-connected converters, and by tuning the parameters of the DC self-synchronization control loop of the grid-connected equipment, the short-circuit ratio threshold of the renewable energy power plants was reduced without modifying the grid-side infrastructure. Through its DC self-synchronization control loop, the grid-connected equipment actively provides virtual inertia and damping support for the system, enhancing the stability of the entire grid-connected system under weak grid conditions and significantly expanding the safe grid-connected operation range of the renewable energy power plants.

[0044] The parameter tuning sequence follows the objective laws of grid-connected system stability design. At the same time, this step-by-step tuning strategy effectively avoids mutual interference between parameters, ensuring that each adjustment is aimed at specific performance indicators, significantly improving the efficiency of the tuning process, and ensuring that the grid-connected system has sufficient inertial support and good power regulation capability while having good damping. Attached Figure Description

[0045] Figure 1 A flowchart of the method provided by the present invention;

[0046] Figure 2 This is a schematic diagram of the grid-connected system targeted by the present invention;

[0047] Figure 3 A schematic diagram of the control structure of a new energy power station that uses a grid-connected converter;

[0048] Figure 4 A schematic diagram of the control structure of a DC self-synchronizing control network-type device;

[0049] Figure 5 A flowchart for parameter tuning of the DC self-synchronization control loop in a DC self-synchronization control network-type device;

[0050] Figure 6 A schematic diagram illustrating the effect of introducing grid-type equipment on improving the stability of new energy power stations;

[0051] Figure 7 This is a schematic diagram illustrating the influence of different DC self-synchronization control loop parameters on the critical value of the short-circuit ratio during parameter tuning. Detailed Implementation

[0052] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0053] The present invention will now be described in further detail with reference to the accompanying drawings:

[0054] like Figure 1 As shown, this embodiment provides a method for reducing the critical value of the short-circuit ratio of renewable energy power plants. The method is applied to a grid-connected system, which includes renewable energy power plants and grid-connected lines connecting the renewable energy power plants to the power grid. The renewable energy power plants include grid-connected converters. The method comprises:

[0055] Obtain the rated capacity and grid connection voltage level of the new energy power station to determine the pre-selected capacity of DC self-synchronizing control grid-type equipment;

[0056] The pre-selected capacity of DC self-synchronizing control grid-type equipment is deployed in parallel on the main collector bus side of the new energy power station. The grid-type equipment is equipped with a DC self-synchronizing control loop to introduce equivalent inertia and damping characteristics into the DC side voltage loop.

[0057] The parameters of the DC self-synchronization control loop of the DC self-synchronization control grid-type equipment are tuned to reduce the critical value of the short-circuit ratio of new energy power plants.

[0058] Unlike grid-based control, grid-forming (GFM) devices do not rely on phase-locked loops (PLLs) for grid synchronization. Instead, they actively construct and support the grid's voltage and frequency through strategies such as virtual synchronizers and droop control. In weak grid conditions with insufficient short-circuit capacity, grid-forming converters can provide virtual inertia and damping characteristics, enhancing voltage and frequency stability. During disturbances, they can suppress fluctuations by adjusting power distribution, thereby widening the system's stable operating boundary. DC self-synchronization control is an emerging grid-forming control technology. This technology uses DC link voltage and reactive power as control targets, achieving voltage regulation and grid synchronization on the DC side. It does not rely on traditional PLL structures; self-synchronization is achieved solely through DC dynamic response. Its active power output is naturally determined by grid power flow, providing a new technical path for system stability under high-proportion renewable energy integration.

[0059] The method provided in this embodiment first requires obtaining the rated capacity P of the grid-connected renewable energy power station. n And the per-unit value, denoted as S GFL Then, based on the rated capacity P of the new energy power stationn And determine the pre-selected capacity S of DC self-synchronizing control grid-type equipment based on grid connection level. GFM The preselected capacity is S GFM The DC self-synchronizing control grid-type equipment is deployed in parallel on the main collector bus side of the new energy power station, such as the grid-connected system of the DC self-synchronizing control grid-type equipment. Figure 2 As shown.

[0060] Specifically, the DC self-synchronization control loop of a DC self-synchronization control network-type device is represented as follows:

[0061]

[0062] In the formula: The output angular frequency of the DC self-synchronizing control network-type equipment. This is the DC capacitor voltage. K is the reference value for the DC capacitor voltage. D K is the equivalent damping coefficient. J K is the equivalent inertia coefficient. T This is the DC voltage tracking coefficient.

[0063] like Figure 5 As shown, the parameters of the DC self-synchronization control loop for the DC self-synchronization control network equipment are tuned, including:

[0064] The preset tuning range of the DC self-synchronization control loop parameters, including the DC side capacitor value C. DC Equivalent damping coefficient K D Equivalent inertia coefficient K J DC voltage tracking coefficient K T and DC capacitor voltage reference value ;

[0065] DC side capacitor value C DC Selection: Based on the rated capacity P of the new energy power station n and the preset inertial support time, according to Determine the DC side capacitor value C DC The minimum value;

[0066] A small-signal voltage disturbance is applied to the grid-connected line to obtain the damping ratio of the grid-connected system. and overshoot The equivalent damping coefficient K D The possible values ​​of ;

[0067] Fixed equivalent damping coefficient K D And adjust the equivalent inertia coefficient K J To make the frequency change rate of the grid-connected system ;

[0068] Adjust DC capacitor voltage reference value and DC voltage tracking coefficient K T To balance the active power output and reactive power support capacity of DC self-synchronizing control grid-type equipment;

[0069] Calculate the critical short-circuit ratio (CSCR) of the new energy power station corresponding to the current parameter tuning combination;

[0070] Determine whether the parameter tuning process iterates through the tuning range of each parameter;

[0071] If so, output the parameter combination corresponding to the minimum value of the short-circuit ratio critical value (CSCR) of the new energy power station; otherwise, continue to adjust each parameter within the adjustment range of each parameter.

[0072] Specifically, calculating the critical value of the short-circuit ratio for new energy power plants includes:

[0073] Derive the admittance matrix Y of the grid-connected line net (s):

[0074]

[0075] In the formula: L grid Let be the reactance of the grid-connected line, and s be the Laplace operator. For the normalized matrix of grid-connected lines, To synchronize rotation speed, The impedance-to-inductance ratio of the grid-connected line;

[0076] Taking the inflow direction to the converter as the positive direction, small-signal output admittance matrices are established for both the grid-connected converter and the DC self-synchronizing grid-connected equipment in the synchronous rotating dq coordinate system. These matrices are then transformed to the global xy rotating coordinate system to construct the small-signal model Y of the new energy power station. st (s); Small signal model Y of new energy power station st (s) is the small-signal output admittance matrix Y of the grid converter. GFL (s) and the small-signal output admittance matrix Y of the DC self-synchronizing control network-type equipment GFM The sum of (s), i.e., Y st (s)=Y GFL (s)+Y GFM (s);

[0077] Among them, the small-signal output admittance matrix Y of the grid converter GFL (s) Based on the dynamic equations of the current loop, power control loop (PQ loop), and phase-locked loop (PLL) of the grid-connected converter, the control structure of the new energy power station using the grid-connected converter is derived as follows: Figure 3As shown; the small-signal output admittance matrix Y of the DC self-synchronizing network-type equipment. GFM (s) Based on the AC voltage loop, AC current loop, and DC self-synchronizing control loop of the DC self-synchronizing network-type equipment, the control structure of the DC self-synchronizing control network-type equipment is derived as follows: Figure 4 As shown;

[0078]

[0079] In the formula: Δ(.) represents the incremental change of the corresponding variable; U GFLxy I GFLxy U GFMxy I GFMxy These are column vectors representing the voltage at the grid node, the current at the grid node, the voltage at the grid node, and the current at the grid node, respectively.

[0080] Based on the small signal model Y of new energy power stations st (s) and the admittance matrix Y of the grid-connected line net (s), construct the characteristic equation of the grid-connected system, which is expressed as:

[0081]

[0082] The root of the critical short-circuit ratio (CSCR) for new energy power plants lies on the imaginary axis, which means it can be used... Substituting the admittance matrices, we get:

[0083]

[0084] The normalized matrix representation of the grid-connected line is as follows:

[0085]

[0086] The closed-loop characteristic equation can be written as:

[0087]

[0088] After unfolding:

[0089]

[0090] The inductance of the grid-connected line when the renewable energy power station is in a critical state is obtained by solving:

[0091]

[0092] The final short-circuit ratio critical value (CSCR) for new energy power plants was obtained:

[0093]

[0094] The critical short-circuit ratio (CSCR) of new energy power plants is the inductance of the grid-connected lines. The reciprocal of.

[0095] In summary, this embodiment addresses the issue of insufficient grid connection stability in large-scale renewable energy power plants primarily using grid-connected converters under weak grid conditions. It proposes a technical solution to reduce the critical short-circuit ratio of the power plant by connecting grid-connected DC self-synchronizing control equipment, and provides specific parameter tuning methods. The core of this solution lies in embedding equivalent inertia and damping elements into the DC-side voltage control loop of the introduced grid-connected equipment. This allows the DC link capacitor to not only store energy but also simulate the inertia and damping characteristics of a synchronous generator, thereby achieving self-synchronization and active support for the AC grid. By systematically tuning key parameters such as equivalent inertia, equivalent damping, and DC voltage reference values, the self-synchronization speed and dynamic response characteristics of the DC self-synchronizing grid-connected equipment can be optimized, effectively enhancing the stability margin of renewable energy power plants under weak grid conditions.

[0096] The effectiveness of the method provided in this embodiment is verified by constructing simulation examples:

[0097] Rated capacity P of grid-type new energy power stations n The pre-selected capacity S of the DC self-synchronizing control grid-connected equipment is 50MVA, with a port voltage level of 0.69kV and a grid-connected bus high-voltage side voltage level of 35kV. GFM Given a system capacity of 50 MVA, the baseline value S is used. base The value is 100MVA, and all subsequent capacity calculations will use per-unit values.

[0098] Constructing a small-signal model Y for renewable energy power stations after connecting to DC self-synchronizing grid-type equipment st (s): It is stipulated that the direction of flow into the converter is positive, and the small-signal model Y of the grid-type equipment is derived separately. GFL (s) and small-signal model Y of network-type equipment GFM (s) followed by the small-signal model Y of the network device GFL (s) and small-signal model Y of network-type equipment GFM (s) sum to obtain Y st (s).

[0099] in accordance with Figure 5 The following process is shown for tuning the parameters of the DC self-synchronization control loop:

[0100] DC side capacitor value C DC Selection:

[0101] Based on rated capacity (rated active power) P n =50MVA, design inertial support time t in ≥1s, according to Determine the DC side capacitor value C DCThe minimum value;

[0102] Setting the equivalent damping coefficient K D Scan K D Until the damping ratio of the grid-connected system and overshoot ;

[0103] Equivalent inertia coefficient K J Fine-tuning: Fixed K D Adjust K J This reduces the frequency variation rate of the grid-connected system within the target SCR range. ;

[0104] DC capacitor voltage reference value and DC voltage tracking coefficient K T Fine-tuning: Balancing active power output and reactive power margin, taking into account both grid connection stability margin and power point tracking performance;

[0105] The critical short-circuit ratio (CSCR) of new energy power plants under different tuning combinations was calculated, and the parameter corresponding to the lowest value was selected. The calculation formula for the critical short-circuit ratio (CSCR) of new energy power plants is as follows:

[0106]

[0107] The final tuning parameter obtained is: K D =750, K J =20, K T =10.

[0108] Build such a system in the MATLAB / Simulink environment Figure 2 The new energy power station shown is equipped with grid-type equipment connected to DC self-synchronization control, to verify the effectiveness and correctness of the method.

[0109] First, based on the parameters in Table 1, the CSCR of the new energy power station without grid-connected equipment was tested. The PI parameters of its dominant link, the phase-locked loop, were set to 10 and 7800 respectively. At this time, from the perspective of the station's PCC point, the critical value was 3.52. After applying a 0.05pu voltage drop disturbance lasting 0.02s at the steady-state equilibrium point, the output active power waveform of the new energy power station showed constant amplitude oscillation. Figure 6 (as shown)

[0110] After connecting the DC self-synchronizing control grid-type equipment in parallel (parameters according to Table 2), without changing the grid-connected power station parameters and grid parameters, and similarly applying a 0.05 pu voltage drop disturbance lasting 0.02 s at the steady-state equilibrium point, the active power waveform output of the renewable energy power station converges (e.g., Figure 6As shown in the figure, the CSCR of the new energy power station is 2.24. This result shows that the method provided in this embodiment effectively improves the small disturbance stability of the grid-connected system, reduces the CSCR of the new energy power station, and significantly expands the safe grid connection range under weak grid conditions.

[0111] at the same time, Figure 7 The CSCR curves of new energy power plants under different parameters within the range of parameters set in the DC self-synchronization control loop of this example are given for auxiliary parameter tuning.

[0112] Table 1

[0113]

[0114] Table 2

[0115]

[0116] This embodiment provides a computer device, including at least one processing unit and at least one storage unit, wherein the storage unit stores a computer program, and when the program is executed by the processing unit, the processing unit performs the above-described method.

[0117] This embodiment provides a computer-readable storage medium storing a computer program executable by an electronic device, which, when run on the electronic device, causes the electronic device to perform the above-described method.

[0118] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for reducing the critical value of the short-circuit ratio of a renewable energy power station, the method being applied to a grid-connected system, the grid-connected system including renewable energy power stations and grid-connected lines connecting the renewable energy power stations to the power grid, the renewable energy power station including a grid-connected converter, characterized in that, The method includes: Obtain the rated capacity and grid connection voltage level of the new energy power station to determine the pre-selected capacity of DC self-synchronizing control grid-type equipment; The pre-selected capacity of DC self-synchronizing control grid-type equipment is deployed in parallel on the main collector bus side of the new energy power station. The grid-type equipment is equipped with a DC self-synchronizing control loop to introduce equivalent inertia and damping characteristics into the DC side voltage loop. The parameters of the DC self-synchronization control loop of the DC self-synchronization control grid-type equipment are tuned to reduce the critical value of the short-circuit ratio of new energy power plants; The parameter tuning includes: preset tuning range of DC self-synchronization control loop parameters, the parameters including DC side capacitor value, equivalent damping coefficient, equivalent inertia coefficient, DC voltage tracking coefficient and DC capacitor voltage reference value; The capacitance value of the DC side capacitor, the equivalent damping coefficient, the equivalent inertia coefficient, the reference value of the DC capacitor voltage, and the DC voltage tracking coefficient are adjusted in sequence, and the critical value of the short-circuit ratio of the new energy power station corresponding to each parameter setting combination is calculated. The sequential adjustment includes: determining the minimum value of the DC-side capacitor based on the rated capacity of the new energy power station and the preset inertial support time; Adjust the equivalent damping coefficient so that the damping ratio and overshoot of the grid-connected system meet the preset conditions; The equivalent damping coefficient is fixed and the equivalent inertia coefficient is adjusted so that the frequency change rate of the grid-connected system meets the preset conditions. Adjust the DC capacitor voltage reference value and DC voltage tracking coefficient to balance the active power output and reactive power support capacity of DC self-synchronizing control network equipment.

2. The method according to claim 1, characterized in that, The tuning of the DC self-synchronization control loop parameters for the DC self-synchronization control network equipment also includes: Determine whether the parameter tuning process iterates through the tuning range of each parameter; If so, output the parameter corresponding to the minimum critical value of the short-circuit ratio of the new energy power station; otherwise, continue to adjust the parameter within the adjustment range.

3. The method according to claim 1, characterized in that, The adjustment of the equivalent damping coefficient to make the damping ratio and overshoot of the grid-connected system meet the preset conditions includes: applying a small signal voltage disturbance in the grid-connected line and obtaining the value of the equivalent damping coefficient that makes the damping ratio and overshoot of the grid-connected system meet the preset conditions.

4. The method according to claim 1, characterized in that, The calculation of the critical short-circuit ratio for each parameter tuning combination corresponding to the new energy power station includes: Derive the admittance matrix of a grid-connected line based on its impedance. A small-signal model for a new energy power station is constructed. The small-signal model is the sum of the small-signal output admittance matrix of the grid-connected converter and the small-signal output admittance matrix of the DC self-synchronous control grid-connected equipment under the current parameter tuning combination. Based on the small-signal model of new energy power stations and the admittance matrix of grid-connected lines, the characteristic equation of the grid-connected system is constructed. The solution is the grid-connected line inductance value that makes the root of the characteristic equation lie on the imaginary axis. The critical value of the short-circuit ratio of the new energy power station is the reciprocal of the grid-connected line inductance value.

5. The method according to claim 4, characterized in that, The small-signal model for constructing new energy power stations includes: In the synchronous rotating dq coordinate system, small-signal output admittance matrices of grid-connected converters and DC self-synchronizing grid-connected equipment are established respectively. The small-signal output admittance matrices of grid-connected converters and DC self-synchronizing grid-connected equipment are then transformed to the global xy rotating coordinate system to construct the small-signal model of the new energy power station.

6. The method according to claim 5, characterized in that, The small-signal output admittance matrix of the grid-connected converter is derived based on the dynamic equations of the current loop, power control loop, and phase-locked loop of the grid-connected converter; the small-signal output admittance matrix of the DC self-synchronizing grid-connected device is derived based on the AC voltage loop, AC current loop, and DC self-synchronizing control loop of the DC self-synchronizing grid-connected device.

7. A computer device, characterized in that, The method includes at least one processing unit and at least one storage unit, wherein the storage unit stores a computer program that, when executed by the processing unit, causes the processing unit to perform the method as described in any one of claims 1 to 6.

8. A computer-readable storage medium, characterized in that, It stores a computer program executable by an electronic device, which, when run on the electronic device, causes the electronic device to perform the method as described in any one of claims 1 to 6.

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