CN-121984097-A - Network-structured converter presynchronization method and system based on phase reconstruction and potential energy function

CN121984097ACN 121984097 ACN121984097 ACN 121984097ACN-121984097-A

Abstract

The invention discloses a grid-constructed converter presynchronizing method and system based on phase reconstruction and potential energy functions, which are used for calculating an original phase difference between a power grid phase and a converter phase of the grid-constructed converter, reconstructing the original phase difference by using a shortest path principle to obtain a target phase difference, deriving an 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, generating a final frequency instruction based on the proportional term by combining condition integral compensation and safe limiting, presynchronizing the grid-constructed converter according to the final frequency instruction, fundamentally eliminating phase angle inherent jump in the traditional presynchronizing process, ensuring that the system can converge to a synchronization point under any initial phase difference, effectively eliminating steady-state errors, improving presynchronizing capability of the converter, and enhancing robustness and safety of a grid-connected process.

Inventors

TANG YUCHEN
LIN YI
FANG YUDI
YE RONG
OUYANG JINYAN
CAI FENGHUANG
WANG WU

Assignees

国网福建省电力有限公司经济技术研究院
国网福建省电力有限公司

Dates

Publication Date: 20260505
Application Date: 20251215

Claims (10)

1. The method for presynchronizing the grid-structured converter based on the phase reconstruction and the potential energy function is characterized by comprising the following steps: Calculating an original phase difference between the power grid phase and the converter phase of the grid-structured converter; Reconstructing the original phase difference by using a shortest path principle to obtain a target phase difference; deriving an improved potential energy function based on the target phase difference to obtain a control gradient; calculating a gain using a Pade approximated adaptive gain function based on the target phase difference; Calculating a proportional term based on the control gradient and the gain; generating a final frequency instruction based on the proportional term by combining conditional integral compensation and safety clipping; And presynchronizing the grid-structured converter according to the final frequency instruction.
2. The method for presynchronizing the grid-structured converter based on the phase reconstruction and the potential energy function according to claim 1, wherein the original phase difference is reconstructed by using a shortest path principle to obtain a target phase difference, specifically: ; In the formula, Indicating that the target phase difference is to be achieved, Representing the original phase difference, Representing the inversion point.
3. The method for presynchronizing a grid-structured converter based on phase reconstruction and potential energy functions according to claim 2, wherein the improved potential energy functions are specifically: ; In the formula, Representing an improved potential energy function; the control gradient is specifically as follows: ; In the formula, gradient represents a control Gradient.
4. A method of presynchronizing a networked converter based on phase reconstruction and potential energy functions according to claim 3, characterized in that the gain is calculated based on the target phase difference using a pade approximated adaptive gain function, in particular: ; In the formula, An adaptive gain function representing a Pade approximation, K min representing steady-state signal gain, K max representing maximum dynamic gain, and C representing a sensitivity parameter.
5. The method for presynchronizing a grid-formed converter based on phase reconstruction and potential energy functions of claim 4, wherein proportional terms are calculated based on the control gradient and the gain, specifically: ; In the formula, Representing a proportional term.
6. The method of claim 5, wherein generating the final frequency command based on the proportional term in combination with conditional integral compensation and safety clipping comprises: setting an integral on threshold and an integral off threshold based on the inversion point; if the absolute value of the target phase difference is smaller than the integral opening threshold, calculating an integral term based on the target phase difference to activate integral control; If the absolute value of the target phase difference is larger than the integral closing threshold value, carrying out smooth reset processing on an integral term; calculating to obtain a total frequency adjustment quantity according to the integral term and the proportion term; and performing hard limiting processing on the total frequency adjustment quantity to obtain a final frequency instruction.
7. The method for presynchronizing a grid-structured converter based on phase reconstruction and potential energy functions of claim 6, wherein the integral term is calculated based on the target phase difference, specifically: ; In the formula, The integral term representing the instant k is represented, The integral term representing time k-1, T s represents the sampling period.
8. The method for presynchronizing a grid-structured converter based on phase reconstruction and potential energy functions according to claim 6, wherein the total frequency adjustment is calculated according to the integral term and the proportional term, and specifically comprises the following steps: ; In the formula, Indicating the amount of overall frequency adjustment, Representing integral terms.
9. The method for pre-synchronizing a grid-formed converter based on phase reconstruction and potential energy functions of claim 1, further comprising, after pre-synchronizing the grid-formed converter according to the final frequency command: And judging whether the absolute value of the target phase difference is smaller than a preset phase error allowable threshold value, and if so, determining that the phase and the synchronization are completed, otherwise, returning to the step of executing the original phase difference of calculating the power grid phase and the converter phase of the grid-structured converter.
10. A grid-built converter pre-synchronization system based on phase reconstruction and potential energy functions, comprising a memory, a processor and a computer program stored on the memory and executable on the processor, characterized in that the processor implements the steps of a grid-built converter pre-synchronization method based on phase reconstruction and potential energy functions as claimed in any one of claims 1 to 9 when executing the computer program.

Description

Network-structured converter presynchronization method and system based on phase reconstruction and potential energy function Technical Field The invention relates to the technical field of power electronic control and novel power system grid connection, in particular to a grid-structured converter presynchronizing method and system based on phase reconstruction and potential energy functions. Background The Grid-formed (GFM) converter is core equipment for solving the problem of weakening of the power Grid strength caused by high-proportion new energy access due to the capability of actively constructing voltage and frequency. Before grid connection, the converter must execute presynchronization control to keep the phase of the output voltage consistent with the phase of the power grid so as to avoid damaging impact current generated at the moment of switching on. The prior art typically uses a Phase Locked Loop (PLL) to acquire the grid phase. However, there are two inherent mechanism drawbacks to the conventional PLL-based presynchronization control architecture: 1. phase modulo operation induced step shock (MATHEMATICAL STEP CHANGE): phase locked loop output power grid phase g And the phase generated by the converter itselfinv Essentially all are [0,2) Periodic saw-tooth signals within a zone. When the control system performs subtraction on the two signals to obtain phase errorAt the moment of inversion of the phase period (i.e. 2kWhere) a discontinuous mathematical step occurs. For example, wheng=0.01rad,inv =6.27 Rad (near 2) When physically the two differ only by about 0.02rad, the mathematical result of the direct subtraction is about-6.26 rad. For a conventional linear PI (proportional-integral) controller, this modulo-operation induced 2The abrupt change can be misjudged as a larger physical error, so that the controller outputs a very large frequency adjustment instruction, and the system is caused to shake violently. 2. Reversed phase point%) Failure to adjust (Control Deadlock at)): The conventional control strategy is based on q-axis voltage (u q is approximately equal to sin) About zero approach is the goal. When the phase difference is=At the time sin # -) =0, Resulting in zero control, the system falls into a "deadlock" state, failing to converge automatically. Under the working condition of a strong power grid, the power grid has strong voltage rigidity and large damping, and the impact can be absorbed by the power grid. However, under the typical weak current network or island working condition of a novel power system, the system has large impedance, is extremely fragile and has poor disturbance rejection capability. The above-mentioned "intrinsic phase jump surge" and "out of control after deadlock" are sufficient to cause voltage collapse, grid connection failure and even converter damage. Disclosure of Invention The invention aims to solve the technical problem of providing a grid-structured converter presynchronizing method and system based on phase reconstruction and potential energy functions, which can improve the presynchronizing capability of the converter and enhance the robustness and safety of the grid-connected process. In order to solve the technical problems, the invention adopts the following technical scheme: a network-structured converter presynchronizing method based on phase reconstruction and potential energy functions comprises the following steps: Calculating an original phase difference between the power grid phase and the converter phase of the grid-structured converter; Reconstructing the original phase difference by using a shortest path principle to obtain a target phase difference; deriving an improved potential energy function based on the target phase difference to obtain a control gradient; calculating a gain using a Pade approximated adaptive gain function based on the target phase difference; Calculating a proportional term based on the control gradient and the gain; generating a final frequency instruction based on the proportional term by combining conditional integral compensation and safety clipping; And presynchronizing the grid-structured converter according to the final frequency instruction. In order to solve the technical problems, the invention adopts another technical scheme that: The system comprises a memory, a processor and a computer program stored on the memory and capable of running on the processor, wherein the processor realizes each step in the method for presynchronizing the grid-structured converter based on the phase reconstruction and the potential energy function when executing the computer program. The invention has the advantages that the original phase difference of the power grid phase and the converter phase of the grid-structured converter is calculated, the original phase difference is reconstructed by using the shortest path principle, the target phase difference is obtained, the improved potential energy function is deriv