A wind power converter grid connection control method, system, storage medium and device

Abstract

This invention discloses a grid-connected control method, system, storage medium, and device for wind power converters, comprising the following steps: determining the rated value of the current grid connection point voltage and monitoring changes in the voltage amplitude in real time; determining the rated range based on the rated value; when the voltage amplitude is within the rated range, increasing or decreasing the reactive current output according to the relationship between the voltage amplitude and the rated value; when the voltage amplitude exceeds the rated range, calculating the reactive current output according to the relationship between the voltage amplitude and the maximum and minimum values ​​within the rated range. Only the voltage amplitude needs to be monitored, and the reactive current output only needs to be adjusted according to the voltage amplitude, thereby supporting and regulating the grid voltage at the grid connection point. This maximizes the utilization of the converter's own reactive power support capability, enhances the converter's reactive power support capability, and thus ensures the stability of the grid connection point voltage. Sufficiently strong reactive power support capability of the wind turbine ensures a constant grid connection voltage, thereby reducing the pressure on wind farms to regulate the grid connection point voltage and enhancing regulation capabilities.

Description

Technical Field

[0001] This invention belongs to the field of wind power control technology, and relates to a grid-connected control method, system, storage medium and equipment for wind power converters. Background Technology

[0002] Offshore wind power typically uses converters for grid connection. However, the large number of power electronic converters connected to the grid introduces weak grid stability issues. Under weak grid conditions, the interaction between the offshore wind power converter and the weak grid can easily trigger oscillations. Therefore, researching control strategies that can effectively improve the grid-connected stability of converters is of great significance.

[0003] Traditional converters typically employ dual-loop PI control for both voltage and current, such as... Figure 1 As shown, the outer voltage loop primarily maintains a constant DC bus voltage and a constant AC voltage amplitude. This control method ensures that the converter delivers zero reactive power and maximizes the delivery of active power. However, when the AC grid is weak, this control method is prone to insufficient reactive power regulation, leading to oscillations and affecting voltage stability. Summary of the Invention

[0004] The purpose of this invention is to solve the problems of insufficient reactive power regulation capability, voltage stability, and inability to fully utilize reactive current output in the existing technology, and to provide a grid-connected control method, system, storage medium, and device for wind power converters.

[0005] To achieve the above objectives, the present invention employs the following technical solution:

[0006] A grid-connected control method for a wind power converter includes the following steps:

[0007] S1: Determine the rated value of the current grid connection point voltage and monitor the changes in the voltage amplitude at the grid connection point in real time;

[0008] S2: Determine the rated range based on the rated value. When the voltage amplitude is within the rated range, increase or decrease the reactive current output according to the relationship between the voltage amplitude and the rated value.

[0009] S3: When the voltage amplitude exceeds the rated range, calculate the reactive current output based on the relationship between the voltage amplitude and the maximum and minimum values ​​within the rated range.

[0010] A further improvement of the present invention is that:

[0011] Step S2 includes the following steps:

[0012] When the voltage amplitude is within the rated range, the reactive current setpoint is:

[0013] k dr(u ac -U acn )+I q0 (1)

[0014] In the formula, a l o w and a up These are the upper and lower limits of the allowable AC voltage amplitude, respectively. These are the reference values ​​for the active and reactive currents of the inner loop, u. ac k is the voltage amplitude at the grid connection point. dr For the variable adjustment curve coefficient, U acn This refers to the rated voltage amplitude at the grid connection point.

[0015] In step S2, when formula (2):

[0016]

[0017] In the formula, I q0 I is the reactive current required when the grid connection point voltage is at its rated value. max S is the maximum allowable output current of the converter. N U is the rated capacity of the converter. N This is the rated voltage of the converter.

[0018] Step S2 includes the following steps:

[0019] If the current voltage amplitude is less than the rated value but greater than the minimum value of the rated range, the reactive current output will be increased.

[0020] If the current voltage amplitude is greater than the rated value but less than the maximum value of the rated range, the reactive current output will be reduced.

[0021] Step S3 includes the following steps:

[0022] When the voltage amplitude is less than the minimum value of the rated range, i.e., u ac l o w U acn At that time, the output inner loop reactive current is -I qmax +2I q0 ;

[0023] When the voltage amplitude is greater than the minimum value of the rated range, i.e., u ac >a up U acn The inner-loop reactive current output is the maximum reactive current I that the converter can output. qmax .

[0024] In step S1, the rated value is 0.9 pu. ​

[0025] In step S1, the rated range is 0.9 pu-1.1 pu.

[0026] A grid-connected control system for a wind power converter includes a rated value determination module, a non-limit adjustment module, and a limit adjustment module;

[0027] The rated value determination module is used to determine the rated value of the current grid connection point voltage and monitor the changes in the voltage amplitude at the grid connection point in real time.

[0028] The non-over-limit adjustment module is used to determine the rated range based on the rated value. When the voltage amplitude is within the rated range, it increases or decreases the reactive current output according to the relationship between the voltage amplitude and the rated value.

[0029] The over-limit adjustment module is used to calculate the reactive current output based on the relationship between the voltage amplitude and the maximum and minimum values ​​within the rated range when the voltage amplitude exceeds the rated range.

[0030] A terminal device includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of any of the methods described in this invention.

[0031] A computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of any of the methods described in this invention.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] This invention discloses a grid-connected control method for wind power converters. First, the rated voltage value is determined. Using this rated value as a base, the rated voltage range is defined. The maximum and minimum values ​​of the rated range, along with the rated value itself, are used as comparison data for strategy adjustment. Based on the specific situation of the current voltage compared to the comparison values, a corresponding adjustment strategy is specified to control the magnitude of the reactive current output by the converter. This allows the reactive current output to be adjusted in real time in response to voltage changes. This method only requires monitoring the voltage amplitude and adjusting the reactive current output based on the voltage amplitude, thereby supporting and regulating the grid voltage at the grid connection point. It maximizes the utilization of the converter's own reactive power support capability, enhancing its reactive power support capacity and ensuring the stability of the grid connection point voltage. Sufficiently strong reactive power support capability of the wind turbine ensures a constant grid voltage, thus reducing the pressure on wind farms to regulate the grid connection point voltage and enhancing regulation capabilities. Attached Figure Description

[0034] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 This is a control structure diagram for a traditional constant AC voltage amplitude.

[0036] Figure 2 A circuit diagram for connecting a VSC system to a weak AC system;

[0037] Figure 3 Diagram of the control structure with variable adjustment curve;

[0038] Figure 4 A schematic diagram of the variable adjustment curve;

[0039] Figure 5 The root locus diagrams of the VSC system under two control modes are shown.

[0040] Figure 6 The simulation waveforms for the two control strategies are shown below (where a represents the power of the VSC when using traditional constant AC voltage amplitude control; b represents the output phase and grid-connected three-phase voltage when using traditional constant AC voltage amplitude control; c represents the power of the VSC when using variable adjustment curve control; and d represents the output phase and grid-connected three-phase voltage when using variable adjustment curve control). Detailed Implementation

[0041] 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, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0042] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0043] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0044] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper," "lower," "horizontal," or "inner" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use, they are only for the convenience of describing the present invention 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 the present invention. Furthermore, terms such as "first" and "second" are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0045] Furthermore, the use of the term "horizontal" does not imply that the component must be absolutely horizontal, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0046] In the description of the embodiments of the present invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the specific circumstances.

[0047] The present invention will now be described in further detail with reference to the accompanying drawings:

[0048] See Figures 2 to 3 This invention discloses a grid-connected control method for wind power converters. This method can be applied to offshore wind power systems. It replaces the traditional AC voltage amplitude control used in the outer voltage loop with variable regulation curve control. By relaxing the constraint on the voltage amplitude at the grid connection point, it maximizes the utilization of the reactive current output by the converter, enhancing the converter's reactive power support capability and thus ensuring the stability of the grid connection point voltage. Therefore, the improved control strategy has stronger stability under weak grid conditions. By establishing a small-signal model of the offshore wind power grid-connected system, plotting the system root locus, and performing Simulink simulations, the improved control strategy is verified to effectively improve system stability under weak grid conditions, demonstrating significant application advantages and practical value compared to traditional control strategies.

[0049] Specifically:

[0050] See Figure 2 Offshore direct-drive wind power grid-connected systems include grid-side converters, filters, and equivalent AC grid circuits. (See also...) Figure 3The grid-side converter adopts a dual closed-loop control strategy with constant DC bus voltage. The outer loop uses constant DC voltage control and variable regulation curve control, while the inner loop uses current control based on grid connection point current feedback.

[0051] Specifically, the following steps are included:

[0052] First, calculate the magnitude I of the reactive power current output by the system when the voltage amplitude at the grid connection point is at the rated value. q0 .

[0053] Furthermore, different adjustment strategies are implemented based on the actual conditions of the rated values:

[0054] The rated range is determined based on the rated value. When the voltage amplitude is within the rated range, the reactive current output is increased or decreased according to the relationship between the voltage amplitude and the rated value.

[0055] Based on the determined rated range and according to the allowable amplitude variation range of the AC voltage at the grid connection point, typically 0.9 pu-1.1 pu, calculate the maximum reactive current I. q max and I q min .

[0056] If the voltage amplitude at the grid connection point exceeds the allowable range, the reactive power will reach saturation and will not continue to increase or decrease. The reactive power output will remain at its maximum or minimum.

[0057] See Figure 2 The positive direction of the current defined in the control structure can determine the relationship between the AC voltage amplitude and the reactive current.

[0058] When the voltage amplitude at the grid connection point is greater than the rated value but less than the maximum value within the rated range, the converter should generate more capacitive reactive power. Therefore, i should be adjusted. q Increase;

[0059] When the voltage amplitude at the grid connection point is less than the rated value but greater than the minimum value of the rated range, the converter should generate less capacitive reactive power. Therefore, i should be adjusted. q Reduced; therefore, the slope of the reactive current regulation curve is positive, such as Figure 4 As shown.

[0060] Based on the above analysis, by relaxing the constraint on the voltage amplitude at the grid connection point, the reactive current regulation curve formed by the relationship between the reactive current reference value and the voltage amplitude at the grid connection point can be written as a piecewise function:

[0061]

[0062] Further:

[0063]

[0064] alow and a up These are the upper and lower limits of the allowable AC voltage amplitude, respectively. These are the reference values ​​for the active and reactive currents of the inner loop, u. ac k is the voltage amplitude at the grid connection point. dr For the variable adjustment curve coefficient, U acn I is the rated voltage amplitude at the grid connection point. q0 I is the reactive current required when the grid connection point voltage is at its rated value. N I is the rated current output by the converter. max This is the maximum allowable output current of the converter, typically 1.2 times the converter's rated current. N U is the rated capacity of the converter. N This is the rated voltage of the converter. The voltage amplitude versus the inner loop current reference value adjustment curve is shown below. Figure 4 As shown.

[0065] If a low =0.9,a up =1.1 When the grid connection point voltage amplitude is in the range of 0.9pu-1.1pu, the output inner loop current reference value shows a linear decreasing relationship with the grid connection point voltage;

[0066] When the grid connection point voltage is less than 0.9 pu, the reference value for the output inner loop current is -I. q max +2I q0 ;

[0067] When the grid connection point voltage is greater than 1.1 pu, the reference value for the output inner loop current is the maximum reactive current I that the converter can output. qmax .

[0068] Unlike traditional droop curve control methods, this approach considers that offshore wind turbines do not operate at full power continuously under normal conditions. Therefore, when the turbine is not at full capacity, its grid-side converter generates a certain amount of reactive power. This serves to support and regulate the grid voltage at the connection point, ensuring that the AC voltage within a single turbine remains as stable as possible. If the turbine's reactive power support capability is strong enough, the grid voltage can be kept constant, thereby reducing the pressure on the wind farm to regulate the grid voltage.

[0069] The reactive power output of a wind turbine's grid-connected converter depends on the current active power output. When the grid connection voltage is controlled within a certain range, the reactive current output of the converter is adjusted in real time to follow the grid connection voltage. To maximize the utilization of the converter's own reactive power support capacity, a variable adjustment curve control strategy is designed to adjust the reactive power output of the converter in real time, thereby maintaining a stable grid connection voltage.

[0070] This invention also discloses a grid-connected control system for a wind power converter, including a rated value determination module, a non-limit adjustment module, and a limit adjustment module;

[0071] The rated value determination module is used to determine the rated value of the current grid connection point voltage and monitor the changes in the voltage amplitude at the grid connection point in real time.

[0072] The non-over-limit adjustment module is used to determine the rated range based on the rated value. When the voltage amplitude is within the rated range, it increases or decreases the reactive current output according to the relationship between the voltage amplitude and the rated value.

[0073] The over-limit adjustment module is used to calculate the reactive current output based on the relationship between the voltage amplitude and the maximum and minimum values ​​within the rated range when the voltage amplitude exceeds the rated range.

[0074] Furthermore, based on the method disclosed in this invention, this embodiment of the invention also establishes a small-signal model of the above-mentioned grid-connected system, and uses eigenvalue analysis to analyze the small-signal stability of the system:

[0075] First, the small-signal equation for the converter filter circuit is:

[0076]

[0077] Among them, L f For filter inductance, R f For the filter resistor, C f For the filter capacitor, the symbol Δ indicates that this variable is under small disturbances (the following formulas all apply, and will not be repeated). These are the d-q axis currents flowing through the filter from the converter, respectively. The dq-axis currents injected into the grid connection point of the converter are respectively. These are the d-axis and q-axis currents at the converter output, respectively. These are the dq-axis voltages at the grid connection point, ω s This is the system's rated frequency.

[0078] Furthermore, the small-signal equation of the equivalent circuit of the AC power grid is:

[0079]

[0080] in, These are the dq-axis currents injected into the AC grid at the grid connection point, L g R is the equivalent inductance of the power grid. g This is the equivalent resistance of the power grid.

[0081] Furthermore, the small-signal equation for the DC bus voltage is:

[0082]

[0083] Among them, C dc For DC bus capacitance, V dc This is the steady-state value of the DC bus voltage. The steady-state value of the dq-axis voltage at the grid connection point. v is the steady-state value of the dq-axis current injected into the grid connection point. dc This is the DC bus voltage.

[0084] Furthermore, the small-signal equation of the phase-locked loop is:

[0085]

[0086] Where, k ppll k ipll These are the parameters of the phase-locked loop (PLL) PI controller, where θ is the phase angle of the PLL output voltage, and x is the phase angle of the voltage. pll is an intermediate variable of the phase-locked loop PI controller, and is the output of the integrator.

[0087] Furthermore, the small-signal equation for the outer loop of the control system voltage is:

[0088]

[0089] Where x1 is an intermediate variable of the voltage outer loop PI controller and is the output of the integrator.

[0090] Furthermore, the small-signal equation for the inner current loop of the control system is:

[0091]

[0092] Here, x3 and x4 are intermediate variables of the current inner loop PI controller, and x4 is the output of the integrator.

[0093] Furthermore, considering the error between the actual and measured values ​​of the phase-locked loop, its transformation matrix is:

[0094]

[0095] Furthermore, the small-signal model of the system considering phase-locked loop measurement errors can be written as:

[0096]

[0097] in, Matrix A is the state matrix of the system's small-signal model.

[0098] The model parameter settings are shown in Tables 1 and 2. Select L... g =0.7mH increased to L g=0.9mH, the short-circuit ratio decreases accordingly from 2.1 to 1.6. Small-signal models for the two schemes are established, and their characteristic roots are solved. The trajectories of the characteristic roots are plotted on [the graph]. Figure 5 It can be seen that when the equivalent impedance L of the AC system... g When = 0.85mH, the poles of the grid-connected system using the traditional constant AC voltage amplitude control strategy appear on the right side of the imaginary axis, while the poles of the grid-connected system using the variable adjustment curve control strategy remain in the left half of the root plane, proving that it can still maintain stable operation in theory.

[0099] Table 1. VSC circuit parameters connected to the weak AC system

[0100]

[0101] Table 2. PI parameters in the variable adjustment curve control strategy

[0102]

[0103] Figure 5 L is given g =0.7mH increased to L g With a value of 0.9mH, the root locus of the VSC system (poles far from the imaginary axis are not given) shows that the pole distribution of the entire grid-connected system has changed by using variable adjustment curve control. The root locus of the dominant poles in the left half-plane has increased, and only a small number of poles are in the unstable range.

[0104] To further verify the control effect of the proposed variable adjustment curve control in a weak AC system, a control model was established in MATLAB / Simulink according to the parameters in Tables 1 and 2. Figure 6 The model shown is a grid-connected system model connected to a weak current grid. Specific model parameters are as shown above, using traditional constant AC voltage amplitude...

[0105] Simulations were performed for both value control and variable adjustment curve control. The simulation waveforms for both cases are as follows: Figure 6 .

[0106] Figure 6 In the figure, a and b show that when the short-circuit ratio is less than 1.6, the traditional constant AC voltage amplitude control cannot make the grid-connected system work stably. Both the active power and reactive power oscillate at a large amplitude, the bus voltage at the grid connection point is distorted, and the output phase of the phase-locked loop can no longer accurately track the phase change of the bus voltage at the grid connection point. Figure 6In the figure, c and d show that after adopting variable adjustment curve control, the grid-connected system can output stable active and reactive power under weak grid conditions, and the output phase of variable adjustment curve control accurately tracks the phase of the grid connection point voltage, proving that the variable adjustment curve control strategy has good control effect under weak grid conditions.

[0107] A schematic diagram of a terminal device according to an embodiment of the present invention. The terminal device of this embodiment includes: a processor, a memory, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the steps in the various method embodiments described above. Alternatively, when the processor executes the computer program, it implements the functions of each module / unit in the various device embodiments described above.

[0108] The computer program can be divided into one or more modules / units, which are stored in the memory and executed by the processor to complete the present invention.

[0109] The terminal device may be a desktop computer, laptop, handheld computer, or cloud server, etc. The terminal device may include, but is not limited to, a processor and a memory.

[0110] The processor may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc.

[0111] The memory can be used to store the computer program and / or module. The processor implements various functions of the terminal device by running or executing the computer program and / or module stored in the memory and calling the data stored in the memory.

[0112] If the modules / units integrated into the terminal device are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the methods of the above embodiments can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the various method embodiments described above. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include: any entity or device capable of carrying the computer program code, recording media, USB flash drives, portable hard drives, magnetic disks, optical disks, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signals, telecommunication signals, and software distribution media, etc. It should be noted that the content included in the computer-readable medium can be appropriately added or removed according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, computer-readable media do not include electrical carrier signals and telecommunication signals.

[0113] 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 grid-connected control method for a wind power converter, characterized in that, Includes the following steps: S1: Determine the rated value of the current grid connection point voltage and monitor the changes in the voltage amplitude at the grid connection point in real time; S2: Determine the rated range based on the rated value. When the voltage amplitude is within the rated range, increase or decrease the reactive current output according to the relationship between the voltage amplitude and the rated value. S3: When the voltage amplitude exceeds the rated range, calculate the reactive current output based on the relationship between the voltage amplitude and the maximum and minimum values ​​within the rated range; Step S2 includes the following steps: When the voltage amplitude is within the rated range, the reactive current setpoint is: In the formula, The voltage amplitude at the grid connection point. For the variable adjustment curve coefficient, This refers to the rated voltage amplitude at the grid connection point. This represents the reactive current required when the grid connection point voltage is at its rated value. In step S2, in formula (1): In the formula, This is the reactive current required when the grid connection point voltage is at its rated value. The maximum allowable output current of the converter. The rated capacity of the converter, The rated voltage of the converter. This is the reference value for the inner loop active current. This represents the reactive current required when the grid connection point voltage is at its rated value. The rated voltage amplitude at the grid connection point. This is the rated current output by the converter.

2. The grid-connected control method for a wind power converter according to claim 1, characterized in that, Step S2 includes the following steps: If the current voltage amplitude is less than the rated value but greater than the minimum value of the rated range, the reactive current output will be increased. If the current voltage amplitude is greater than the rated value but less than the maximum value of the rated range, the reactive current output will be reduced.

3. The grid-connected control method for a wind power converter according to claim 1, characterized in that, Step S3 includes the following steps: When the voltage amplitude is less than the minimum value of the rated range, that is At that time, the output inner loop reactive current is ; When the voltage amplitude is greater than the maximum value of the rated range, that is The inner-loop reactive current output is the maximum reactive current that the converter can output. ; in, This represents the lower limit coefficient for the allowable amplitude of AC voltage. It is expressed as the rated voltage amplitude at the grid connection point; This represents the reactive current required when the grid connection point voltage is at its rated value. This represents the upper limit coefficient for the allowable amplitude of AC voltage.

4. The grid-connected control method for a wind power converter according to claim 1, characterized in that, In step S1, the rated value is 0.9 pu.

5. The grid-connected control method for a wind power converter according to claim 4, characterized in that, In step S2, the rated range is 0.9 pu-1.1 pu.

6. A wind power converter grid-connected control system for implementing the method of claim 1, characterized in that, Includes a rated value determination module, a non-limit adjustment module, and a limit adjustment module; The rated value determination module is used to determine the rated value of the current grid connection point voltage and monitor the changes in the voltage amplitude at the grid connection point in real time. The non-over-limit adjustment module is used to determine the rated range based on the rated value. When the voltage amplitude is within the rated range, it increases or decreases the reactive current output according to the relationship between the voltage amplitude and the rated value. The over-limit adjustment module is used to calculate the reactive current output based on the relationship between the voltage amplitude and the maximum and minimum values ​​within the rated range when the voltage amplitude exceeds the rated range.

7. A terminal device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the method as described in any one of claims 1-5.

8. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by a processor, it implements the steps of the method as described in any one of claims 1-5.

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