Adjustment method, system and equipment for improving short-circuit ratio of new energy field station and medium

Abstract

The invention relates to the technical field of articles for old people, in particular to an adjusting method, system, equipment and medium for improving the short circuit ratio of a new energy station, and the method comprises the steps: calculating a first target index and a second target index of the new energy station, and switching a part of grid-connected converters into a virtual synchronous generator control mode; when the second target index does not meet the short-circuit ratio control requirement, changing the equivalent impedance of the grid-connected point by adjusting the virtual impedance of the virtual synchronous generator so as to reduce the second target index of the new energy station; and when the grid fault causes the voltage drop of the grid-connected point, reactive voltage control is carried out through the virtual exciter of the virtual synchronous generator, and voltage support is provided for the grid-connected point. The method has the beneficial effects that flexible and efficient dynamic adjustment is realized by using the virtual synchronous generator, the system operation efficiency is improved, and the short-circuit ratio of a new energy field station is improved by combining virtual impedance and a reactive power support function, so that the operation capability of the new energy field station in a weak power grid is enhanced.

Description

Technical Field

[0001] This invention relates to the field of elderly care products technology, and in particular to a method, system, equipment and medium for adjusting the short-circuit ratio of new energy power plants. Background Technology

[0002] Against the backdrop of global energy transition, new energy power generation technologies such as solar and wind power have developed rapidly, and their proportion in the power system continues to rise. New energy power generation typically achieves grid connection using power electronic converters, exhibiting current-source characteristics during operation, unlike the voltage-source characteristics of traditional synchronous generators. However, with the continuous expansion of the scale of new energy power generation, its grid connection characteristics have brought new challenges to the stable operation of the power system.

[0003] The lack of inertia and reactive power regulation capabilities in renewable energy converters compared to traditional synchronous generators leads to decreased grid voltage support and dynamic stability. Under weak grid conditions, renewable energy power plants face challenges such as voltage dips, frequency fluctuations, and reduced system stability during grid connection. The short-circuit ratio is a key indicator of the grid's ability to withstand disturbances; a decrease in this ratio increases system operational risks. Existing solutions rely on devices such as Static Var Compensators (SVCs) and Static Synchronous Compensators (STATCOMs) to improve the short-circuit ratio, but these devices suffer from high costs, complex maintenance, and insufficient dynamic response. Summary of the Invention

[0004] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0005] In a first aspect, the present invention provides a method for adjusting the short-circuit ratio of new energy power plants, including calculating a first target index and a second target index of the new energy power plant, and switching some grid-connected converters to virtual synchronous generator control mode;

[0006] When the second target indicator does not meet the short-circuit ratio control requirements, the equivalent impedance at the grid connection point is changed by adjusting the virtual impedance of the virtual synchronous generator in order to reduce the second target indicator of the new energy power station.

[0007] When a grid fault causes a voltage drop at the grid connection point, reactive voltage control is performed through the virtual exciter of the virtual synchronous generator to provide voltage support for the grid connection point.

[0008] As a preferred embodiment of the method for adjusting the short-circuit ratio of new energy power stations according to the present invention, the calculation of the first target index and the second target index of the new energy power station includes,

[0009] The first target indicator is determined based on the ratio of short-circuit capacity to grid-connected capacity;

[0010] The minimum of the critical short-circuit ratio under voltage stability constraint and the critical short-circuit ratio under power angle stability constraint is determined as the second target index.

[0011] As a preferred embodiment of the method for adjusting the short-circuit ratio of new energy power stations according to the present invention, the method includes: changing the equivalent impedance at the grid connection point by adjusting the virtual impedance of the virtual synchronous generator, including:

[0012] By adjusting the virtual impedance of the virtual synchronous generator, the maximum output power and critical output power of the grid-connected renewable energy power station are increased, so that the updated second target indicator is met:

[0013] The updated second target indicator is smaller than the original second target indicator.

[0014] As a preferred embodiment of the method for adjusting the short-circuit ratio of new energy power stations according to the present invention, the method includes: adjusting the virtual impedance of the virtual synchronous generator, including...

[0015] Change the equivalent access impedance of the virtual synchronous generator;

[0016] The power limit of the renewable energy power station is recalculated based on the modified equivalent access impedance in order to adjust the virtual impedance.

[0017] As a preferred embodiment of the method for adjusting the short-circuit ratio of new energy power plants according to the present invention, the method includes: reactive power voltage control through a virtual exciter of a virtual synchronous generator to provide voltage support for the grid connection point, including:

[0018] Reactive power commands are generated by utilizing the reactive power-voltage droop characteristics of a virtual synchronous generator, and the amplitude of the virtual internal potential is dynamically adjusted based on the instantaneous reactive power deviation to raise the voltage at the grid connection point.

[0019] As a preferred embodiment of the method for adjusting the short-circuit ratio of new energy power plants according to the present invention, the method includes: dynamically adjusting the virtual internal potential amplitude based on the instantaneous reactive power deviation, including:

[0020] The reactive power deviation is processed by an integrator to obtain the effective value of the virtual internal potential phase voltage, which is then converted into an instantaneous potential value.

[0021] As a preferred embodiment of the method for adjusting the short-circuit ratio of new energy power plants according to the present invention, the switching ratio of some grid-connected converters is dynamically determined according to the degree of deviation of the second target index. The greater the degree of deviation, the higher the switching ratio.

[0022] In a second aspect, the present invention provides an adjustment system for improving the short-circuit ratio of new energy power plants, comprising: a calculation and switching module for calculating a first target index and a second target index of the new energy power plant, and switching some grid-connected converters to virtual synchronous generator control mode;

[0023] The adjustment module is used to reduce the second target index of the new energy power station by adjusting the virtual impedance of the virtual synchronous generator to change the equivalent impedance of the grid connection point when the second target index does not meet the short-circuit ratio control requirements.

[0024] The control module is used to control reactive voltage through the virtual exciter of the virtual synchronous generator when the voltage at the grid connection point drops due to a grid fault, so as to provide voltage support for the grid connection point.

[0025] Thirdly, the present invention provides a computer device, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps of the method described above.

[0026] Fourthly, the present invention provides a computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the steps of the method described above.

[0027] Compared with existing technologies, the beneficial effects of this invention are as follows: By calculating the short-circuit ratio and critical short-circuit ratio indicators of new energy power plants, some grid-connected converters are switched to virtual synchronous generator (VSG) control mode, effectively improving the operating capability of new energy power plants under weak grid conditions; when the second target indicator does not meet the short-circuit ratio control requirements, the maximum output power and critical output power of grid-connected new energy power plants are increased by adjusting the virtual impedance of the VSG, thereby reducing the critical short-circuit ratio; when a grid fault causes a voltage drop at the grid connection point, reactive power voltage control is performed using the virtual exciter of the VSG to provide voltage support for the grid connection point, ensuring the stable operation of the grid. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 A flowchart illustrating the adjustment method for improving the short-circuit ratio of new energy power plants. Detailed Implementation

[0030] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0031] Example 1, referring to Figure 1 This is the first embodiment of the present invention, which provides a method for adjusting the short-circuit ratio of new energy power plants, including:

[0032] S100: Calculates the first and second target indicators of the new energy power station and switches some grid-connected converters to virtual synchronous generator control mode;

[0033] S200: When the second target indicator does not meet the short-circuit ratio control requirements, the equivalent impedance of the grid connection point is changed by adjusting the virtual impedance of the virtual synchronous generator to reduce the second target indicator of the new energy power station.

[0034] S300: When a grid fault causes a voltage drop at the grid connection point, reactive voltage control is performed through the virtual exciter of the virtual synchronous generator to provide voltage support for the grid connection point.

[0035] It should be noted that in renewable energy power generation systems, renewable energy power plants are typically connected to the grid via power electronic converters, whose output characteristics are current-source type, significantly different from the voltage-source characteristics of traditional synchronous generators. Under weak grid conditions, the grid impedance is high, and the output current of renewable energy power plants causes a significant voltage drop, leading to a voltage sag at the grid connection point. Simultaneously, the output power of renewable energy power plants is greatly affected by natural factors such as weather, resulting in frequent power fluctuations, which further exacerbates grid instability. Furthermore, while traditional reactive power compensation equipment can improve the short-circuit ratio, it is costly, complex to maintain, and its dynamic response speed is insufficient to meet the rapidly changing needs of renewable energy power plants.

[0036] Therefore, to address the aforementioned problems, this invention, through steps S100-S300, firstly calculates the first and second target indicators of the new energy power station, identifies the short-circuit ratio status of the power grid, and switches some grid-connected converters to virtual synchronous generator control mode, giving them characteristics similar to traditional synchronous generators; secondly, when the second target indicator does not meet the short-circuit ratio control requirements, the virtual impedance of the virtual synchronous generator is adjusted to change the equivalent impedance at the grid connection point, optimizing the output characteristics of the new energy power station, reducing the critical short-circuit ratio, and enhancing the operational capability of the weak power grid; finally, when a grid fault causes a voltage drop at the grid connection point, the virtual exciter of the virtual synchronous generator is used for reactive power voltage control, quickly providing voltage support and stabilizing the grid voltage, thereby effectively improving the short-circuit ratio of the new energy power station and ensuring stable and reliable grid operation.

[0037] Example 2, refer to Figure 1 As an embodiment of the present invention, based on the above embodiment, a method for adjusting the short-circuit ratio of new energy power plants is provided.

[0038] In this embodiment of the application, step S100 calculates the first target index and the second target index of the new energy power station, and switches some grid-connected converters to virtual synchronous generator control mode, including the following steps A1-A3:

[0039] Understandably, the first target metric is the short-circuit ratio (SCR), and the second target metric is the critical short-circuit ratio (CSCR).

[0040] A1: The first target indicator is determined based on the ratio of short-circuit capacity to grid-connected capacity;

[0041] It should be noted that most renewable energy power plants use grid-connected converters based on phase-locked loops (PLLs) to connect to the AC grid. Typically, grid-connected renewable energy power plants have an ideal current loop, exhibiting external characteristics of a current source. The output current through the current loop has an amplitude of I. L Phase is current And grid connection point voltage phase δ L The current at the grid connection point of a grid-connected power station is output from a phase-locked loop, therefore it can be expressed as an amplitude of I. L Phase is current

[0042] That is, the short-circuit capacity of the grid-type substation. and grid-connected capacity It can be represented as:

[0043]

[0044] In the formula: U N The nominal voltage at the grid connection point; It is an AC equivalent voltage source with an amplitude of E and a phase angle of 0°; The amplitude is Z L Phase angle is The connection impedance of the grid-type station; for . conjugate.

[0045] Furthermore, the SCR index of grid-connected renewable energy power plants (SCR) L It can be represented as:

[0046]

[0047] In one optional implementation, the short-circuit ratio calculation in step A1 can also be based on distributed power source parameters. That is, parameters such as rated capacity, maximum output power, output characteristic curve, and grid connection voltage level of each distributed power source in the new energy power station are collected, and grid parameters such as rated voltage and system impedance at the grid connection point are also collected. For each distributed power source, its short-circuit capacity is calculated (the formula is short-circuit capacity = grid connection voltage squared / system impedance). Then, the short-circuit ratio of the distributed power source is calculated based on the ratio of its rated capacity to its short-circuit capacity. Furthermore, the short circuits of all distributed power sources in the new energy power station are statistically analyzed to calculate the total short-circuit ratio of the station, which is obtained by dividing the total short-circuit capacity by the total grid connection capacity.

[0048] In another optional implementation, the short-circuit ratio calculation in step A1 can also be based on real-time monitoring data. That is, voltage monitors, current monitors, and power monitors are installed at the grid connection point and key locations of the new energy power station to collect voltage, current, and power data of the grid connection point in real time. The collected voltage, current, and power data are processed and analyzed in real time using a data acquisition system to calculate the real-time impedance of the grid connection point. Based on the real-time impedance and the grid connection capacity of the new energy power station, the short-circuit ratio is dynamically calculated. The formula is: short-circuit ratio = short-circuit capacity of new energy power station / grid connection capacity, where the short-circuit capacity can be obtained by dividing the square of the grid connection voltage by the real-time impedance.

[0049] A2: The minimum value between the critical short-circuit ratio under voltage stability constraint and the critical short-circuit ratio under power angle stability constraint is determined as the second target index;

[0050] It should be noted that since the critical short-circuit ratio is the SCR corresponding to the maximum active power output of a renewable energy power plant under a given reactive power condition, the minimum value of the SCR of a grid-connected power plant can be taken as the CSCR index of the grid-connected power plant by calculating the SCR under voltage stability constraints and power angle stability constraints respectively. L :

[0051] Specifically, under voltage stability constraints, the active power P is established. L Reactive power Q L Output voltage U L The steady-state equation is as follows:

[0052]

[0053] In the formula: R L For connecting resistors to grid-type substations; L L To connect the reactor to the grid-type substation; ω n This is the rated angular frequency of the power grid.

[0054] When there is only one solution for voltage in equation (3), the system has an equilibrium point, and the maximum voltage U of the system under critical stable operation is... m Corresponding maximum output power P m for:

[0055]

[0056] At this time, the critical short-circuit ratio (CSCR) of the new energy power station under voltage stability constraints L1 for:

[0057]

[0058] Furthermore, under the power angle stability constraint, the conditions that the grid-type power station needs to meet are:

[0059]

[0060] In the formula: K p K is the proportional gain of the phase-locked loop; I δ represents the integral coefficient of the phase-locked loop; Le It is the equilibrium point of the work angle.

[0061] Then the critical active power P output by the grid-type renewable energy power station c for:

[0062]

[0063] At this time, the critical short-circuit ratio (CSCR) of the new energy power station under the power angle stability constraint is... L2 for:

[0064]

[0065] Therefore, the CSCR index corresponding to the active power limit output of a grid-type renewable energy power station under a given reactive power condition is CSCR. L for:

[0066] CSCR L =max(CSCR L1 ,CSCR L2 (9)

[0067] In one optional implementation, the critical short-circuit ratio calculation in step A2 can also be based on machine learning model prediction. This involves collecting historical operating data from renewable energy power plants, including voltage, current, power, and fault records, as well as information on the power grid topology and line parameters. The data undergoes preprocessing operations such as cleaning and normalization to ensure quality and consistency. Further features related to the short-circuit ratio, such as voltage fluctuation amplitude, peak current, power change rate, and fault duration, are extracted and used as input variables for the machine learning model. A suitable machine learning algorithm, such as a neural network, support vector machine, or random forest, is selected to train the model on the collected data (using the short-circuit ratio from historical data as the target variable, adjusting model parameters through iterative optimization algorithms to ensure accurate prediction of the short-circuit ratio). The model is then validated using some data not used in training to evaluate its accuracy and generalization ability. Based on the validation results, the model is optimized (e.g., adjusting hyperparameters, adding features) to improve its predictive performance. Finally, the real-time collected operating data from renewable energy power plants is input into the trained machine learning model, and the model output is the predicted critical short-circuit ratio.

[0068] In another optional implementation, the critical short-circuit ratio calculation in step A2 can also be based on system fault simulation to determine the critical short circuit. That is, a detailed model of the renewable energy power station and its grid connection is established using power system simulation software (which should include the grid topology, parameters of each component (such as line impedance, transformer turns ratio, etc.), and detailed configuration of the renewable energy power station (such as converter parameters, control strategies, etc.)). Various possible grid fault scenarios (such as short-circuit faults, open-line faults, load surges, etc.) are simulated, and different fault locations, fault types, and fault durations are set to comprehensively evaluate the operating characteristics of the renewable energy power station under different fault conditions. Simulation is performed for each set fault scenario, and key data such as voltage, current, and power of the renewable energy power station are recorded during the fault occurrence. Based on the data obtained from the simulation, the short-circuit ratio of the renewable energy power station under different fault scenarios is calculated, and the relationship between the system stability after the fault and the short-circuit ratio is analyzed. The short-circuit ratio that makes the system in a critical stable state is determined as the critical short-circuit ratio.

[0069] A3: The switching ratio of some grid-connected converters is dynamically determined based on the degree of deviation from the second target indicator. The greater the deviation, the higher the switching ratio.

[0070] It should be noted that grid-connected converters based on phase-locked loops exhibit good stability under strong grid conditions, but perform poorly under weak grid conditions (high grid impedance). Therefore, it is proposed to replace some grid-connected converters with virtual synchronous generator (VSG) control. VSG control simulates the operating characteristics of a synchronous generator, enabling the converter to have voltage support capability, thereby enhancing the overall system stability.

[0071] Specifically, the VSG control simulates the second-order equations of motion of the synchronous generator, and its basic control equations are as follows:

[0072]

[0073] In the formula: P ref This is the active power reference value; P e ω is the active power reference value; D is the damping coefficient; ω is the actual virtual rotational speed; ω N J is the virtual rotational speed reference value; J is the virtual inertia; θ ref The phase angle of the virtual internal potential; k q Q is the reactive power-voltage droop factor. ref This is the reactive power reference value; Q e This represents the actual reactive power value; E ref U0 represents the virtual internal potential amplitude; U0 represents the basic voltage value.

[0074] As can be seen from the above equation (10), the VSG simulates the second-order motion equation of the synchronous generator rotor. It has two parts: active-frequency and reactive-voltage control. At the same time, it can provide a certain inertia and damping for the power grid, and its voltage and current inner loop can be used for virtual impedance control.

[0075] Ideally, by introducing VSG control, renewable energy power plants can operate better under weak grid conditions. VSG control not only provides flexible control of active and reactive power, but also enhances the grid's inertia and damping by simulating the characteristics of synchronous generators, thereby improving the overall stability and reliability of the system. This is of great significance for the large-scale integration of renewable energy into the grid.

[0076] In this embodiment of the application, when the second target indicator does not meet the short-circuit ratio control requirement in step S200, the equivalent impedance of the grid connection point is changed by adjusting the virtual impedance of the virtual synchronous generator to reduce the second target indicator of the new energy power station, including the following steps B1-B2:

[0077] It is understandable that when the critical short-circuit ratio of a new energy power station does not meet the requirements, that is,

[0078] CSCR L ≥SCR L(11)B1: By adjusting the virtual impedance of the virtual synchronous generator, the maximum output power and critical output power of the grid-connected renewable energy power station are increased so that the updated second target index is met:

[0079] The updated second target indicator is smaller than the original second target indicator;

[0080] It should be noted that, by adjusting the virtual impedance through VSG, and after the grid-connected converters of the grid-connected renewable energy power stations adopt VSG control, the connection impedance of the grid-connected and grid-connected renewable energy power stations can be expressed as:

[0081]

[0082] In the formula: For grid impedance; To match the line impedance of grid-type new energy power stations; Grid-type renewable energy power station access impedance; The impedance of the lines for grid-type new energy power stations; For VSG virtual impedance;

[0083] Furthermore, the node output current of a grid-type renewable energy power station satisfies:

[0084]

[0085] In the formula: Output current for nodes in grid-type renewable energy power stations; For grid-connected voltage of grid-type renewable energy power stations;

[0086] Furthermore, the output capacity of a grid-type renewable energy power station can be written as:

[0087]

[0088] In the formula: for conjugate; U M for The amplitude.

[0089] It should be noted that, as can be seen from equation (14), the output capacity of a grid-type new energy power station is related to its access impedance. By adjusting the virtual impedance, the output capacity of the grid-type new energy power station can be kept within the design value.

[0090] B2: Adjusting the virtual impedance of the virtual synchronous generator, including,

[0091] Change the equivalent access impedance of the virtual synchronous generator;

[0092] The power limit of the renewable energy power station is recalculated based on the modified equivalent access impedance in order to adjust the virtual impedance.

[0093] It should be noted that, as can be seen from equation (13), the output current of the grid-connected new energy power station Affecting the output current of grid-connected renewable energy power plants The size, therefore, the grid connection point voltage of the grid-connected new energy power station can be expressed as:

[0094]

[0095] Furthermore, after grid-connected renewable energy power stations are connected, the equivalent voltage of grid-connected renewable energy power stations... and equivalent access impedance They are respectively:

[0096]

[0097] Furthermore, according to equations (4) and (7), the maximum output power P of the grid-type new energy power station is... m,eq and critical output power P c,eq It can be reformulated as:

[0098]

[0099] In the formula: Where R L,eq and L L,eq These are the equivalent access resistance and equivalent access reactance of grid-connected new energy power stations, respectively.

[0100] Furthermore, it can be seen from equations (16), (17), and (18) that after a grid-connected renewable energy power station is connected, its maximum output power P can be increased by adjusting its virtual impedance. m,eq and critical output power P c,eq By increasing the CSCR index of the grid-connected stations, and combining equations (5) and (8), we can see that the new CSCR index is CSCR. L.eq It can be represented as:

[0101]

[0102] And CSCR L.eq CSCR should be met L >SCR L >CSCR L.eq By adjusting the virtual impedance of grid-type renewable energy power stations, the critical short-circuit ratio of sub-grid-type renewable energy power stations is reduced, thereby improving the weak grid operation capability of renewable energy power stations.

[0103] For multi-site and grid-type new energy power stations, the short-circuit ratio (SCR) of grid-type power station j is... L,j It can be represented as:

[0104]

[0105] In the formula: To achieve the same equivalent voltage as the grid-connected new energy power station j; U Nj The nominal voltage of grid-connected new energy power station j; To provide the self-impedance of grid-connected new energy power station j; and These are the short-circuit capacities of grid-connected new energy power stations j and i, respectively. is the conversion factor; n is the number of grid-connected new energy power stations.

[0106] Furthermore, considering the dynamic interaction between multiple power stations, the CSCR of grid-connected new energy power stations can be obtained by calculating the output power under different system operating states.

[0107] In one optional implementation, the adjustment of virtual impedance in step B2 can be achieved through software algorithms. Specifically, using system identification technology, a precise mathematical model is established based on historical and real-time monitoring data of the renewable energy power plant. This model identifies key parameters affecting virtual impedance (such as grid impedance, converter parameters, reactive power, etc.). Advanced control algorithms (such as Model Predictive Control (MPC), Sliding Mode Variable Structure Control (SMC), etc.) are employed to dynamically calculate the optimal virtual impedance value based on real-time monitoring of the grid status and system model. This enables precise control of the voltage and power at the grid connection point. Furthermore, a virtual impedance adjustment module is integrated into the control software of the grid-connected converter. This module adjusts the converter's control parameters (such as reactive power commands, voltage regulation coefficients, etc.) in real time based on the output of the intelligent control algorithm, thereby achieving dynamic adjustment of virtual impedance and optimizing the operational performance of the renewable energy power plant.

[0108] In another optional implementation, the virtual impedance adjustment in step B2 can also be achieved based on hardware configuration. Specifically, adjustable reactors and capacitor banks are installed on the AC side of the grid-connected converter in the renewable energy power plant. By changing the inductance of the reactor or the capacitance of the capacitor, the equivalent impedance of the grid-connected converter can be directly adjusted. Furthermore, within the converter, power electronic devices with adjustable impedance functions (such as insulated-gate bipolar transistors (IGBTs)) are used. By changing parameters such as the switching frequency and duty cycle of these devices, the output impedance of the converter can be adjusted. Even further, a multi-stage adjustable impedance regulation circuit can be designed. Based on different operating conditions and control requirements, different combinations of reactors and capacitors or adjustments to the parameters of the power electronic devices can be made to achieve multi-stage adjustment of the virtual impedance, thus meeting the flexible control requirements of the renewable energy power plant for grid connection voltage and power.

[0109] In this embodiment of the application, when a grid fault causes a voltage drop at the grid connection point, step S300 involves reactive voltage control via a virtual exciter of a virtual synchronous generator to provide voltage support for the grid connection point, including the following steps C1-C2:

[0110] C1: Reactive power commands are generated by the reactive power-voltage droop characteristics of the virtual synchronous generator, and the amplitude of the virtual internal potential is dynamically adjusted according to the instantaneous reactive power deviation to raise the voltage at the grid connection point.

[0111] It should be noted that the VSG has a virtual exciter, which can simulate the reactive voltage droop characteristics of a synchronous machine:

[0112] Q m =Q set +K v (U n -U) (21)

[0113] In the formula: Q m For VSG reactive power command; Q set K is the given value for reactive power. v U is the voltage droop coefficient. n U is the effective value of the rated phase voltage; U is the effective value of the capacitor phase voltage.

[0114] Preferably, Equation (21) shows that VSG can adjust reactive power output according to voltage deviation to achieve reactive voltage regulation.

[0115] Furthermore, the average instantaneous reactive power Q over half a power frequency cycle e It can be represented as:

[0116]

[0117] In the formula: T line For power frequency period; u a u b u c i is the voltage across the filter capacitor. a i b i c It is a three-phase current.

[0118] C2: Dynamically adjusts the virtual internal potential amplitude based on the instantaneous reactive power deviation, including,

[0119] The reactive power deviation is processed by an integrator to obtain the effective value of the virtual internal potential phase voltage, which is then converted into an instantaneous potential value.

[0120] It should be noted that the reactive power deviation is integrated to obtain the virtual internal potential value of VSG:

[0121]

[0122] In the formula: E v is the effective value of the phase voltage of the VSG virtual internal potential; K is the reactive power integral coefficient.

[0123] Preferably, through the integral stage, the VSG can adjust the virtual internal potential based on the reactive power deviation, thereby achieving dynamic regulation of the grid connection point voltage.

[0124] Furthermore, the amplitude of the virtual internal potential of VSG can be obtained through equations (21), (22), and (23), and thus the instantaneous value of the virtual internal potential can be obtained:

[0125]

[0126] In the formula: e a e b e c To simulate the potential of a synchronous generator; θ is the virtual internal potential phase angle.

[0127] Then we can obtain the dynamic model of VSG participating in voltage regulation:

[0128]

[0129] In the formula: Q represents e Small disturbances near the steady-state operating point; X represents a small disturbance of U near its steady-state operating point; X is the reactance.

[0130] Preferably, the dynamic model reflects the VSG's ability to rapidly regulate reactive power and voltage during grid faults.

[0131] In one optional implementation, providing voltage support for the grid connection point in step S300 can be based on providing voltage support through an energy storage system. That is, an energy storage system, such as a battery energy storage system or a supercapacitor energy storage system, is connected to the grid connection point of the new energy power station (these energy storage devices have rapid charging and discharging capabilities and can provide or absorb a large amount of reactive power in a short time). Voltage monitoring equipment is installed to collect grid connection point voltage data in real time. When a voltage drop is detected, the energy storage system responds quickly, converting the stored DC power into AC power through an inverter and injecting it into the grid to provide reactive power support, thereby raising the grid connection point voltage. Intelligent control algorithms (such as fuzzy control, neural network control, etc.) are used to dynamically adjust the output reactive power of the energy storage system according to the severity and duration of the voltage drop to ensure that the voltage quickly returns to the normal range.

[0132] In another optional implementation, providing voltage support to the grid connection point in step S300 can also be based on a dynamic voltage regulator (DVR). This involves installing a DVR at the grid connection point of the renewable energy plant. The DVR is a power electronic device used to improve grid voltage quality, capable of quickly detecting and compensating for voltage dips. The DVR monitors the grid connection point voltage in real time, and when a voltage dip is detected, it quickly calculates the required compensation voltage. By injecting a compensation voltage that is in phase with but opposite in amplitude to the voltage dip, the impact of the voltage dip is offset, maintaining the stability of the grid connection point voltage. Furthermore, the DVR coordinates with other equipment in the renewable energy plant (such as converters and reactive power compensation devices). During voltage dips, the DVR undertakes the primary voltage support task, while simultaneously optimizing the reactive power output of the converter and the adjustment of other reactive power compensation devices to improve the overall system's voltage support capability.

[0133] In summary, this invention effectively improves the operational capability of renewable energy power plants under weak grid conditions by calculating the short-circuit ratio and critical short-circuit ratio indices and switching some grid-connected converters to Virtual Synchronous Generator (VSG) control mode. When the second target index does not meet the short-circuit ratio control requirements, the maximum output power and critical output power of the grid-connected renewable energy power plant are increased by adjusting the virtual impedance of the VSG, thereby reducing the critical short-circuit ratio. When a grid fault causes a voltage drop at the grid connection point, reactive power voltage control is performed using the virtual exciter of the VSG to provide voltage support for the grid connection point and ensure the stable operation of the grid. Simultaneously, the switching ratio of some grid-connected converters is dynamically determined, further optimizing the operating status of the renewable energy power plant.

[0134] Example 3 illustrates a method for adjusting the short-circuit ratio of a renewable energy power station. It should be noted that the technical solution of this system for adjusting the short-circuit ratio of a renewable energy power station is based on the same concept as the method described above. Details not described in detail in the system for adjusting the short-circuit ratio of a renewable energy power station in this example can be found in the description of the method described above.

[0135] This embodiment also provides an adjustment system for improving the short-circuit ratio of new energy power stations, including:

[0136] The calculation and switching module is used to calculate the first and second target indicators of the new energy power station and switch some grid-connected converters to virtual synchronous generator control mode.

[0137] The adjustment module is used to reduce the second target index of the new energy power station by adjusting the virtual impedance of the virtual synchronous generator to change the equivalent impedance of the grid connection point when the second target index does not meet the short-circuit ratio control requirements.

[0138] The control module is used to control reactive voltage through the virtual exciter of the virtual synchronous generator when the voltage at the grid connection point drops due to a grid fault, so as to provide voltage support for the grid connection point.

[0139] This embodiment also provides an electronic device suitable for adjusting the short-circuit ratio of new energy power plants, including: a memory and a processor; the memory is used to store computer-executable instructions, and the processor is used to execute the computer-executable instructions to implement the method for adjusting the short-circuit ratio of new energy power plants as proposed in the above embodiment.

[0140] This embodiment also provides a storage medium storing a computer program that, when executed by a processor, implements the adjustment method for improving the short-circuit ratio of new energy power stations as proposed in the above embodiments.

[0141] The storage medium proposed in this embodiment and the adjustment method for improving the short-circuit ratio of new energy power stations proposed in the above embodiments belong to the same inventive concept. Technical details not described in detail in this embodiment can be found in the above embodiments, and this embodiment has the same beneficial effects as the above embodiments.

[0142] Based on the above description of the implementation methods, those skilled in the art will clearly understand that the present invention can be implemented using software and necessary general-purpose hardware, and of course, it can also be implemented using hardware. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as a computer floppy disk, read-only memory (ROM), random access memory (RAM), flash memory, hard disk, or optical disk, etc., including several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods of the various embodiments of the present invention.

[0143] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for adjusting the short-circuit ratio of new energy power plants, characterized in that: include, Calculate the first and second target indicators of the new energy power station, and switch some grid-connected converters to virtual synchronous generator control mode; When the second target indicator does not meet the short-circuit ratio control requirements, the equivalent impedance of the grid connection point is changed by adjusting the virtual impedance of the virtual synchronous generator in order to reduce the second target indicator of the new energy power station. When a grid fault causes a voltage drop at the grid connection point, reactive voltage control is performed through the virtual exciter of the virtual synchronous generator to provide voltage support for the grid connection point.

2. The method for adjusting the short-circuit ratio of new energy power plants as described in claim 1, characterized in that: The calculation of the first and second target indicators for new energy power stations includes, The first target indicator is determined based on the ratio of short-circuit capacity to grid-connected capacity; The minimum value between the critical short-circuit ratio under voltage stability constraint and the critical short-circuit ratio under power angle stability constraint is determined as the second target index.

3. The method for adjusting the short-circuit ratio of new energy power plants as described in claim 2, characterized in that: The method of changing the equivalent impedance at the grid connection point by adjusting the virtual impedance of the virtual synchronous generator includes, By adjusting the virtual impedance of the virtual synchronous generator, the maximum output power and critical output power of the grid-connected renewable energy power station are increased, so that the updated second target indicator is met: The updated second target indicator is smaller than the original second target indicator.

4. The method for adjusting the short-circuit ratio of new energy power plants as described in claim 3, characterized in that: The adjustment of the virtual impedance of the virtual synchronous generator includes, Change the equivalent access impedance of the virtual synchronous generator; The power limit of the new energy power station is recalculated based on the modified equivalent access impedance in order to adjust the virtual impedance.

5. The method for adjusting the short-circuit ratio of new energy power plants as described in claim 4, characterized in that: The reactive voltage control achieved through the virtual exciter of the virtual synchronous generator to provide voltage support for the grid connection point includes, The reactive power command is generated by the reactive power-voltage droop characteristic of the virtual synchronous generator, and the virtual internal potential amplitude is dynamically adjusted according to the instantaneous reactive power deviation to raise the grid connection point voltage.

6. The method for adjusting the short-circuit ratio of new energy power plants as described in claim 5, characterized in that: The dynamic adjustment of the virtual internal potential amplitude based on the instantaneous reactive power deviation includes, The reactive power deviation is processed by an integrator to obtain the effective value of the virtual internal potential phase voltage, which is then converted into an instantaneous potential value.

7. A method for adjusting the short-circuit ratio of new energy power plants as described in any one of claims 1-6, characterized in that: The switching ratio of the grid-connected converters is dynamically determined based on the degree of deviation from the second target indicator; the greater the deviation, the higher the switching ratio.

8. An adjustment system for improving the short-circuit ratio of new energy power plants, using the method described in any one of claims 1-7, characterized in that, include: The calculation and switching module is used to calculate the first and second target indicators of the new energy power station and switch some grid-connected converters to virtual synchronous generator control mode. The adjustment module is used to reduce the second target index of the new energy power station by adjusting the virtual impedance of the virtual synchronous generator to change the equivalent impedance of the grid connection point when the second target index does not meet the short-circuit ratio control requirements. The control module is used to control reactive voltage through the virtual exciter of the virtual synchronous generator when the voltage at the grid connection point drops due to a grid fault, so as to provide voltage support for the grid connection point.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the method according to any one of claims 1 to 7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1 to 7.

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