Phase reconstruction and potential energy function-based network construction type converter pre-synchronization method and system

Abstract

The invention discloses a phase reconstruction and potential energy function-based pre-synchronization method and system for a network-constructed converter, and the method comprises the steps: calculating an original phase difference between a power grid phase and a converter phase of the network-constructed converter, reconstructing the original phase difference through employing a shortest path principle, and obtaining a target phase difference; deriving the improved potential energy function based on the target phase difference to obtain a control gradient, calculating a gain by using a Pade approximation adaptive gain function based on the target phase difference, calculating a proportional term based on the control gradient and the gain, and generating a final frequency instruction based on the proportional term in combination with conditional integral compensation and safety amplitude limiting. And pre-synchronizing the network-forming converter according to the final frequency instruction, thereby radically eliminating the inherent phase angle jump in the traditional pre-synchronizing process, ensuring that the system can be converged to the synchronization point under any initial phase difference, and effectively eliminating the steady-state error, thereby improving the pre-synchronizing capability of the converter and improving the reliability of the system. And the robustness and safety of the grid connection process are enhanced.

Description

Technical Field

[0001] This invention relates to the fields of power electronic control and new power system grid connection technology, and particularly to a pre-synchronization method and system for grid-type converters based on phase reconstruction and potential energy function. Background Technology

[0002] Grid-Forming (GFM) converters, with their ability to actively construct voltage and frequency, are core devices for addressing the weakening of the power grid caused by the integration of high-proportion renewable energy sources. Before grid connection, the converter must perform pre-synchronization control to ensure that the phase of its output voltage is consistent with the phase of the power grid, thus avoiding destructive inrush currents at the moment of closing the circuit.

[0003] Existing technologies typically utilize phase-locked loops (PLLs) to obtain grid phase. However, traditional PLL-based pre-synchronization control architectures suffer from two inherent mechanistic flaws: 1. Mathematical Step Change caused by phase modulus calculation: Phase-locked loop output grid phase g Phase generated by the converter itself inv Essentially, they are all [0,2]. A periodic sawtooth wave signal within the interval. The control system performs a subtraction operation on these two signals to obtain the phase error. At the time of phase period reversal (i.e., 2k), (At this point), discontinuous mathematical steps may occur.

[0004] For example, when g =0.01rad, inv =6.27 rad (close to 2) When the two are physically only about 0.02 rad apart, the mathematical result of a direct subtraction is approximately -6.26 rad. For a traditional linear PI (proportional-integral) controller, this 2... Sudden changes can be misinterpreted as large physical errors, causing the controller to output extremely large frequency adjustment commands, resulting in violent system oscillations.

[0005] 2. Reversal point ( Control Deadlock at ): Traditional control strategies mostly rely on q-axis voltage ( u q Approximately equal to sin The goal is to approach zero. When the phase difference... = When, sin( When the value is 0, the control variable returns to zero, causing the system to fall into a "deadlock" state and become unable to converge automatically.

[0006] Under strong grid conditions, the grid voltage is rigid and has high damping, so the aforementioned shocks may be absorbed by the grid. However, under the typical weak grid or islanded conditions of new power systems, the system impedance is high and extremely fragile, with poor disturbance rejection capability. The aforementioned "inherent phase jump shocks" and "deadlock-induced loss of control" are sufficient to cause voltage collapse, grid connection failure, or even converter damage. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a pre-synchronization method and system for grid-connected converters based on phase reconstruction and potential energy function, which can improve the pre-synchronization capability of the converter and enhance the robustness and safety of the grid connection process.

[0008] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A pre-synchronization method for a grid-type converter based on phase reconstruction and potential energy function includes the following steps: Calculate the original phase difference between the grid phase and the converter phase of the grid-type converter; The original phase difference is reconstructed using the shortest path principle to obtain the target phase difference; The control gradient is obtained by differentiating the improved potential energy function based on the target phase difference. The gain is calculated using an adaptive gain function with Pad approximation based on the target phase difference; Calculate the scaling term based on the control gradient and the gain; The final frequency command is generated based on the proportional term by combining conditional integral compensation and safety limiting. The grid-type converter is pre-synchronized according to the final frequency command.

[0009] To solve the above-mentioned technical problems, another technical solution adopted by the present invention is as follows: A pre-synchronization system for a grid-type converter based on phase reconstruction and potential energy function includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the various steps in the aforementioned pre-synchronization method for a grid-type converter based on phase reconstruction and potential energy function.

[0010] The beneficial effects of this invention are as follows: The original phase difference between the grid phase and the converter phase of the grid-type converter is calculated; the original phase difference is reconstructed using the shortest path principle to obtain the target phase difference; the improved potential function is differentiated based on the target phase difference to obtain the control gradient; the gain is calculated using the Pad approximation adaptive gain function based on the target phase difference; the proportional term is calculated based on the control gradient and gain; and the final frequency command is generated based on the proportional term using conditional integral compensation and safety limiting. The grid-type converter is pre-synchronized according to the final frequency command. This method reconstructs the phase difference using the shortest path principle, fundamentally eliminating the inherent phase angle jump in the traditional pre-synchronization process, enabling the system to operate smoothly even under weak grid conditions. By utilizing the improved potential function combined with the Pad approximation adaptive gain function, the system is guaranteed to operate smoothly under any initial phase difference (including...). All of them can converge to the synchronization point and effectively eliminate steady-state errors, thereby improving the pre-synchronization capability of the converter and enhancing the robustness and safety of the grid connection process. Attached Figure Description

[0011] Figure 1 This is a flowchart of a pre-synchronization method for a grid-type converter based on phase reconstruction and potential energy function according to an embodiment of the present invention. Figure 2 This is a schematic diagram of a grid-type converter pre-synchronization system based on phase reconstruction and potential energy function according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the pre-synchronization logic of a grid-type converter in a pre-synchronization method based on phase reconstruction and potential energy function according to an embodiment of the present invention. Figure 4 This invention relates to an improved potential energy function and its gradient characteristic curve in a pre-synchronization method for a grid-type converter based on phase reconstruction and potential energy function, as described in an embodiment of the present invention. Detailed Implementation

[0012] To explain in detail the technical content, objectives, and effects of the present invention, the following description is provided in conjunction with the embodiments and accompanying drawings.

[0013] Before detailing the embodiments of this application, some related concepts will first be explained: Grid-type converters: They have the ability to actively construct grid voltage and frequency, and can simulate the inertial response and damping characteristics of synchronous generators, providing dynamic support for modern power systems; Padé Approximant: A rational polynomial approximation method proposed by the French mathematician Henri Padé, which achieves nonlinear approximation by constructing rational functions.

[0014] In existing technologies, under typical weak grid or islanded conditions in new power systems, the system impedance is high and extremely fragile, with poor disturbance rejection capability. The step impact caused by phase-mode calculation and the failure of anti-phase point regulation are enough to cause voltage collapse, grid connection failure, or even converter damage.

[0015] To at least solve the above problems, please refer to Figure 1 This invention provides a pre-synchronization method for a grid-type converter based on phase reconstruction and potential energy function, comprising the following steps: Calculate the original phase difference between the grid phase and the converter phase of the grid-type converter; The original phase difference is reconstructed using the shortest path principle to obtain the target phase difference; The control gradient is obtained by differentiating the improved potential energy function based on the target phase difference. The gain is calculated using an adaptive gain function with Pad approximation based on the target phase difference; Calculate the scaling term based on the control gradient and the gain; The final frequency command is generated based on the proportional term by combining conditional integral compensation and safety limiting. The grid-type converter is pre-synchronized according to the final frequency command.

[0016] As described above, the beneficial effects of this invention are as follows: The original phase difference between the grid phase and the converter phase of the grid-type converter is calculated; the original phase difference is reconstructed using the shortest path principle to obtain the target phase difference; the improved potential function is differentiated based on the target phase difference to obtain the control gradient; the gain is calculated using the Pad approximation adaptive gain function based on the target phase difference; the proportional term is calculated based on the control gradient and gain; the final frequency command is generated based on the proportional term using conditional integral compensation and safety limiting; and the grid-type converter is pre-synchronized according to the final frequency command. This method reconstructs the phase difference using the shortest path principle, fundamentally eliminating the inherent phase angle jump in the traditional pre-synchronization process, enabling the system to operate smoothly even under weak grid conditions. By utilizing the improved potential function combined with the Pad approximation adaptive gain function, the system is guaranteed to operate smoothly under any initial phase difference (including...). All of them can converge to the synchronization point and effectively eliminate steady-state errors, thereby improving the pre-synchronization capability of the converter and enhancing the robustness and safety of the grid connection process.

[0017] Furthermore, the original phase difference is reconstructed using the shortest path principle to obtain the target phase difference, specifically as follows: ; In the formula, Indicates the target phase difference. Indicates the original phase difference. This indicates the point of phase reversal.

[0018] As described above, the shortest path principle can remap the phase difference to [- , The continuous interval eliminates the phase difference jump caused by the subtraction of sawtooth waves from a mathematical perspective, ensuring that the signal input to the controller truly reflects the physical phase distance.

[0019] Furthermore, the improved potential energy function is specifically as follows: ; In the formula, This represents the improved potential energy function; The control gradient specifically refers to: ; In the formula, Gradient This indicates the control gradient.

[0020] As described above, by improving the potential energy function and utilizing the even symmetry property of the cosine function, this function perfectly fits [- , ] interval, and in = The gradient at the non-zero point completely solves the problem of traditional schemes losing their adjustment capability at the antiphase point.

[0021] Furthermore, the gain is calculated using an adaptive gain function with Pad approximation based on the target phase difference, specifically as follows: ; In the formula, This represents the adaptive gain function of the Pad approximation. K min Represents the steady-state signal gain. K max Indicates the maximum dynamic gain. C This represents the sensitivity parameter.

[0022] As described above, using the adaptive gain function with Pad's approximation to calculate the gain ensures that the gain is calculated within [- , Global convergence over continuous intervals.

[0023] Further, based on the control gradient and the gain, a scaling term is calculated, specifically as follows: ; In the formula, Indicates the proportion.

[0024] As can be seen from the above description, using the control gradient and gain calculation ratio as the basis for pre-synchronization ensures more accurate and effective pre-synchronization.

[0025] Furthermore, generating the final frequency command based on the proportional term by combining conditional integral compensation and safety limiting includes: Set the integration enable threshold and integration disable threshold based on the phase inversion point; If the absolute value of the target phase difference is less than the integral activation threshold, then an integral term is calculated based on the target phase difference to activate integral control; If the absolute value of the target phase difference is greater than the integration shutdown threshold, then the integration term is smoothed and reset. The total frequency adjustment is calculated based on the integral term and the proportional term. The total frequency adjustment is hard-limited to obtain the final frequency command.

[0026] Furthermore, the integral term is calculated based on the target phase difference, specifically as follows: ; In the formula, Indicates time k The integral term, Indicates time k The integral term of -1, T s Indicates the sampling period.

[0027] Furthermore, the total frequency adjustment is calculated based on the integral term and the proportional term, specifically as follows: ; In the formula, Indicates the total frequency adjustment. This represents the integral term.

[0028] As can be seen from the above description, the combination of conditional integral compensation and safety limiting eliminates steady-state error and ensures the physical safety and reliability of the control quantity.

[0029] Furthermore, after pre-synchronizing the grid-type converter according to the final frequency command, the process further includes: Determine whether the absolute value of the target phase difference is less than a preset phase error allowable threshold and whether the absolute value of the final frequency command is less than a preset frequency deviation allowable threshold. If both are true, then phase synchronization is confirmed to be complete. Otherwise, return to the step of calculating the original phase difference between the grid phase and the converter phase of the grid-type converter.

[0030] As can be seen from the above description, pre-synchronization is more effectively achieved by using a dual threshold determination.

[0031] Please refer to Figure 2Another embodiment of the present invention provides a pre-synchronization system for a grid-type converter based on phase reconstruction and potential energy function, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the various steps of the above-described pre-synchronization method for a grid-type converter based on phase reconstruction and potential energy function.

[0032] The above-described pre-synchronization method and system for grid-type converters based on phase reconstruction and potential function of the present invention are applicable to weak power grids (low short-circuit ratio) and islanded operating conditions. The following is a detailed description of the implementation method: Please refer to Figure 1 One embodiment of the present invention is as follows: A pre-synchronization method for a grid-type converter based on phase reconstruction and potential energy function includes the following steps: S1. Calculate the original phase difference between the grid phase and the converter phase of the grid-type converter.

[0033] Specifically, the grid voltage is acquired in real time using a synchronous rotating coordinate system phase-locked loop (SRF-PLL) with a PLL phase acquisition module. u g Output grid phase g [0,2 Simultaneously, the output voltage of the grid-type converter is obtained. u inv and converter phase inv [0,2 ); Calculate the original phase difference between the grid phase and the converter phase, such as Figure 3 As shown, specifically: = g - inv .

[0034] at this time There are 2 The risk of step transition.

[0035] S2. Reconstruct the original phase difference using the shortest path principle (i.e., shortest path normalization) to obtain the target phase difference, specifically: ; In the formula, Indicates the target phase difference. Indicates the original phase difference. This indicates the point of phase reversal.

[0036] This step strictly limits the error to [-]. , Regardless of phase changes, there will be no jump problem, such as... Figure 3 As shown, this step can be achieved using the phase angle jump module.

[0037] S3. Based on the target phase difference, differentiate the improved potential energy function to obtain the control gradient.

[0038] Specifically, the improved potential energy function is as follows: ; In the formula, This represents the improved potential energy function.

[0039] The control gradient specifically refers to: ; In the formula, Gradient This indicates the control gradient. For example... Figure 3 As shown, this step can be implemented using an adaptive control module.

[0040] The "virtual energy" representing the system, at the synchronization point ( =0) is the lowest energy level. Gradient (proportional to sin( / 2)) represents "slope" or "driving force". Using this gradient, the system moves along the direction of the fastest energy decrease (the negative gradient direction), thus naturally converging to the synchronization point.

[0041] like Figure 4 As shown, the blue solid line represents the improved potential energy function, which utilizes the even symmetry property of the cosine function to adapt to [- , The domain of ], it is There is a unique global minimum at point =0. V=0 (synchronization point), at the boundary = The system reaches its maximum value V=1 at this point, and its structure ensures that the system energy converges towards the synchronization point. The red dashed line represents the control gradient. V=sin( / 2), utilizing the odd symmetry property of the sine function, the gradient is at A value greater than 0 is considered positive. When the value is less than 0, it is negative and the direction is automatically adjusted accordingly.

[0042] Symmetry explanation: Since the cosine term in the improved potential energy function is an even function (cos(-x)=cos(x)), this function is even in [- , The interval is symmetric about the origin. When it is negative (i.e., the converter phase is ahead), the gradient term sin( / 2) Automatically negative, generating a reverse adjustment force, therefore, [0,2 The original domain of ) is moved to [- , ].

[0043] S4. Calculate the gain based on the target phase difference using an adaptive gain function approximated by Pad, specifically as follows: ; In the formula, This represents the adaptive gain function of the Pad approximation. K min Represents the steady-state signal gain. K max Indicates the maximum dynamic gain. C This represents the sensitivity parameter.

[0044] in, K min , K max , C The parameters are preset positive real numbers; the adaptive gain function of the Pad approximation ensures that the gain is always greater than zero in the entire domain and increases smoothly as the absolute value of the error increases.

[0045] S5. Calculate the scaling term based on the control gradient and the gain, specifically: ; In the formula, Indicates the proportion.

[0046] S6. Combining conditional integral compensation and safety limiting, generate the final frequency command based on the proportional term, specifically including S61-S65: S61. Set the integration enable threshold and integration disable threshold based on the inversion point, specifically as follows: on = / 6; off = / 5; In the formula, on This indicates the threshold for enabling points. off This indicates the threshold for closing the integration feature.

[0047] This setting is mainly based on two considerations: preventing integral saturation and preventing control jitter. (1) Preventing integral saturation and overshoot: The main purpose of integral control is to eliminate steady-state error. However, in transient processes with large phase differences (such as the moment of startup or large disturbances), if integral control is enabled, "integral saturation" will occur due to excessive error accumulation, which in turn will cause system overshoot or oscillation. Therefore, it is better to enable integral control when the error is relatively small (entering the system). on = / 6 The integral is activated only when the error is within approximately 30°, while the proportional element is used for rapid adjustment when the error is large. (2) Constructing a hysteresis interval to prevent control jitter: The reason for setting this is off = / 5 > on = / 6 is used to create a hysteresis comparison range. Without this difference (i.e., the on and off thresholds are the same), when the system is disturbed and the phase difference fluctuates slightly around the threshold, the integrator will frequently turn on and off, causing control signal jitter. Therefore, this value is set... off > on This ensures the stability of the control state: the system must be "close enough" ( / 6) Points are only enabled at this stage, but "slight deviation" is allowed. / 5) Instead of immediately shutting down the integration, it enhances robustness against noise interference; (3) Basis for numerical selection: on = / 6 (30°) is an empirical value. Within this range, the system linearity is good and it is suitable for fine-tuning by integral intervention.

[0048] S62. If the absolute value of the target phase difference is less than the integral activation threshold, then an integral term is calculated based on the target phase difference to activate integral control, specifically: ; In the formula, Indicates time k The integral term, Indicates time k The integral term of -1, T s Indicates the sampling period. More specifically, it represents the frequency adjustment calculated by the integral controller at that sampling moment. This value is updated in real time according to the activation or reset logic, and the calculation method depends on the current system state.

[0049] In one alternative implementation, the sampling period is 100 microseconds.

[0050] S63. If the absolute value of the target phase difference is greater than the integration shutdown threshold, then the integration term is smoothed and reset.

[0051] To prevent the control variable from suddenly returning to zero and causing system shock, the integral term is not directly forced to zero. Instead, its value is gradually made to approach zero with a certain slope or attenuation factor, which is called smooth reset processing.

[0052] S64. Calculate the total frequency adjustment amount based on the integral term and the proportional term, such as... Figure 3 As shown, specifically: ; In the formula, Indicates the total frequency adjustment. This represents the integral term.

[0053] S65. Perform hard limiting on the total frequency adjustment to obtain the final frequency command. .

[0054] The hard clipping process includes a hard clipping feature that conforms to industry standards and provides sufficient margin, such as... 2.8 rad / s, such as Figure 3 As shown, this can be achieved through the safety constraint module.

[0055] S7. Perform pre-synchronization on the grid-type converter according to the final frequency command.

[0056] The specific pre-synchronization process is as follows: (1) Superimposed frequency command: The calculated final frequency command The rated angular frequency superimposed on the grid converter 0 (usually 100) ≈ 314 rad / s The instantaneous output angular frequency command of the converter is obtained from the converter. inv : ; (2) Integral phase generation: The modulator inside the grid converter outputs the instantaneous angular frequency command. inv Time integration is performed to generate the phase angle of the output voltage. inv : ; (3) Eliminating phase difference (physical compensation): (a) when When the integral speed is greater than 0, the phase of the grid-type converter shifts forward (to catch up with the grid). (b) When When the integral speed is less than 0, the phase of the grid-type converter shifts backward (waiting for the grid).

[0057] Through this dynamic frequency fine-tuning, the phase of the grid converter is ultimately adjusted. inv Phase with the power grid g Completely coincident (i.e.) 0), complete pre-synchronization.

[0058] S8. Determine the absolute value of the target phase difference. Is it less than the preset phase error allowable threshold? And the absolute value of the final frequency command | | Less than the preset frequency deviation allowable threshold If both are true, then phase and synchronization are confirmed; otherwise, return to execute S1. Figure 3 As shown, this can be achieved through a synchronization judgment module. In one optional implementation, after determining the phase and completing synchronization, the... Set to 0.

[0059] This refers to the maximum absolute value of the phase difference allowed for grid connection, for example, set to 0.05. rad Only when the phase difference is monitored in real time Only when the value is less than this is the phase considered close enough to meet the angle condition for grid connection and closing. The maximum allowable absolute value of the frequency deviation for grid connection requires not only "phase coincidence" but also "uniform speed" (i.e., the converter frequency is relatively stable and no longer subject to drastic adjustments). Only when the frequency fluctuation is less than... Only then is it considered safe for the system to be connected to the grid.

[0060] In summary, the pre-synchronization method for grid-type converters based on phase reconstruction and potential energy function of the present invention calculates the original phase difference between the grid phase and the converter phase of the grid-type converter. It reconstructs the original phase difference using the shortest path principle to obtain the target phase difference. Based on the target phase difference, it differentiates the improved potential energy function to obtain the control gradient. Based on the target phase difference, it calculates the gain using an adaptive gain function with Pad's approximation. Based on the control gradient and gain, it calculates the proportional term. Combining conditional integral compensation and safety limiting, it generates the final frequency command based on the proportional term. Pre-synchronization of the grid-type converter is performed according to the final frequency command. By reconstructing the phase difference using the shortest path principle, it eliminates the inherent phase angle jump in the traditional pre-synchronization process from the root, enabling the system to operate smoothly even under weak grid conditions. By utilizing the improved potential energy function combined with the adaptive gain function with Pad's approximation, it ensures that the system operates smoothly under any initial phase difference (including...). All of them can converge to the synchronization point and effectively eliminate steady-state errors, thereby improving the pre-synchronization capability of the converter and enhancing the robustness and safety of the grid connection process; the dual threshold determination ensures that pre-synchronization is achieved more effectively.

[0061] According to another aspect of the invention, Figure 2 This is a schematic diagram illustrating a pre-synchronization system for a grid-type converter based on phase reconstruction and potential energy function according to an embodiment of the present invention. The electronic device includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the various steps of the pre-synchronization method for a grid-type converter based on phase reconstruction and potential energy function as described above.

[0062] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent modifications made based on the content of the present invention specification and drawings, or direct or indirect applications in related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A pre-synchronization method for a grid-type converter based on phase reconstruction and potential energy function, characterized in that, Including the following steps: Calculate the original phase difference between the grid phase and the converter phase of the grid-type converter; The original phase difference is reconstructed using the shortest path principle to obtain the target phase difference; The control gradient is obtained by differentiating the improved potential energy function based on the target phase difference. The gain is calculated using an adaptive gain function with Pad approximation based on the target phase difference; Calculate the scaling term based on the control gradient and the gain; The final frequency command is generated based on the proportional term by combining conditional integral compensation and safety limiting. The grid-type converter is pre-synchronized according to the final frequency command.

2. The pre-synchronization method for a grid-type converter based on phase reconstruction and potential energy function according to claim 1, characterized in that, The original phase difference is reconstructed using the shortest path principle to obtain the target phase difference, specifically: ； In the formula, Indicates the target phase difference. Indicates the original phase difference. This indicates the point of phase reversal.

3. The pre-synchronization method for a grid-type converter based on phase reconstruction and potential energy function according to claim 2, characterized in that, The improved potential energy function is specifically as follows: ； In the formula, This represents the improved potential energy function; The control gradient specifically refers to: ； In the formula, Gradient This indicates the control gradient.

4. The pre-synchronization method for a grid-type converter based on phase reconstruction and potential energy function according to claim 3, characterized in that, The gain is calculated using an adaptive gain function with Pad approximation based on the target phase difference, specifically as follows: ； In the formula, This represents the adaptive gain function of the Pad approximation. K min Represents the steady-state signal gain. K max Indicates the maximum dynamic gain. C This represents the sensitivity parameter.

5. The pre-synchronization method for a grid-type converter based on phase reconstruction and potential energy function according to claim 4, characterized in that, The scaling term is calculated based on the control gradient and the gain, specifically as follows: ； In the formula, Indicates the proportion.

6. The pre-synchronization method for a grid-type converter based on phase reconstruction and potential energy function according to claim 5, characterized in that, The generation of the final frequency command based on the proportional term, combining conditional integral compensation and safety limiting, includes: Set the integration enable threshold and integration disable threshold based on the phase inversion point; If the absolute value of the target phase difference is less than the integral activation threshold, then an integral term is calculated based on the target phase difference to activate integral control; If the absolute value of the target phase difference is greater than the integration shutdown threshold, then the integration term is smoothed and reset. The total frequency adjustment is calculated based on the integral term and the proportional term. The total frequency adjustment is hard-limited to obtain the final frequency command.

7. The pre-synchronization method for a grid-type converter based on phase reconstruction and potential energy function according to claim 6, characterized in that, The integral term is calculated based on the target phase difference, specifically as follows: ； In the formula, Indicates time k The integral term, Indicates time k The integral term of -1, T s Indicates the sampling period.

8. The pre-synchronization method for a grid-type converter based on phase reconstruction and potential energy function according to claim 6, characterized in that, The total frequency adjustment is calculated based on the integral term and the proportional term, specifically as follows: ； In the formula, Indicates the total frequency adjustment. This represents the integral term.

9. The pre-synchronization method for a grid-type converter based on phase reconstruction and potential energy function according to claim 1, characterized in that, After pre-synchronizing the grid-type converter according to the final frequency command, the process further includes: Determine whether the absolute value of the target phase difference is less than a preset phase error allowable threshold and whether the absolute value of the final frequency command is less than a preset frequency deviation allowable threshold. If both are true, then phase synchronization is confirmed to be complete. Otherwise, return to the step of calculating the original phase difference between the grid phase and the converter phase of the grid-type converter.

10. A pre-synchronization system for a grid-type converter based on phase reconstruction and potential energy function, 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 each step of the pre-synchronization method for a grid-type converter based on phase reconstruction and potential energy function as described in any one of claims 1 to 9.

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