CN-122020119-A - New energy networking flexible-direct system fault current sequence component characteristic characterization method

CN122020119ACN 122020119 ACN122020119 ACN 122020119ACN-122020119-A

Abstract

The invention provides a fault current sequence component characteristic characterization method of a new energy networking flexible-straight system, which comprises the steps of considering a fault ride-through control strategy of alternating current sending line side equipment in the new energy networking flexible-straight system, and establishing an equivalent sequence network diagram of the system; solving analysis expressions of fault current sequence components on two sides of a line under different fault types based on an equivalent sequence network diagram, quantifying fault current sequence components corresponding to each fault type through the analysis expressions, extracting influence parameters of the fault current sequence components, and representing fault current sequence component characteristics by combining the analysis expressions. According to the invention, the fault current sequence components under different fault types are quantified through the system, the association rule of the influence parameters and the fault current sequence components is represented, theoretical basis is provided for the formulation, optimization and parameter adjustment of a conventional control strategy, the suitability and operation reliability of the control strategy for different fault scenes are remarkably improved, and technical support can be directly provided for the safe and stable operation of the new energy networking flexible and straight system.

Inventors

WANG ZENGPING
HUANG XINRAN
WANG TONG
LV ZHE
SHEN YAQI

Assignees

华北电力大学

Dates

Publication Date: 20260512
Application Date: 20260126

Claims (10)

1. The new energy networking flexible-direct system fault current sequence component characteristic characterization method is characterized by comprising the following steps of: Considering a fault ride-through control strategy of alternating current sending line side equipment in a new energy networking flexible direct current system, and establishing an equivalent sequence network diagram of the system; Based on the fault ride-through control strategy and the equivalent sequence network diagram, solving an analytic expression of fault current sequence components on two sides of a line under different fault types; Quantifying fault current sequence components corresponding to each fault type through the analysis expression; Extracting influence parameters of the fault current sequence component based on fault control characteristics of a new energy networking flexible direct system; and according to the analysis expression and the influence parameter association, fault current sequence component characteristics are represented.
2. The method for characterizing fault current sequence component characteristics of a new energy grid-constructed flexible-direct system according to claim 1, wherein the fault ride-through control strategy comprises low-voltage ride-through control of a new energy converter and virtual synchronous machine fault ride-through control of a flexible-direct converter station; The low-voltage ride through control of the new energy converter comprises reactive current support control and negative sequence current suppression control; The virtual synchronous machine fault ride-through control of the soft direct current converter station comprises power reference value switching, internal potential adjustment and virtual impedance input control.
3. The method for characterizing fault current sequence components of a new energy grid flexible and straight system according to claim 2, wherein the fault types comprise single-phase earth faults, two-phase-to-phase faults and two-phase earth faults.
4. The method for characterizing fault current sequence components of a new energy networking flexible-direct system according to claim 3, wherein in the equivalent sequence network diagram, the single-phase earth fault corresponding system positive sequence network, the negative sequence network and the zero sequence network are connected in series at a fault point; the positive sequence network and the negative sequence network of the two-phase-to-phase fault corresponding system are connected in parallel at a fault point; And the two-phase grounding faults correspond to the positive sequence network, the negative sequence network and the zero sequence network of the system and are connected in parallel at fault points.
5. The method for characterizing fault current sequence components of a new energy grid-formation flexible-direct system according to claim 3 or 4, wherein extracting the influencing parameters comprises: And selecting the adjusting parameters of the fault ride-through control and/or the inherent physical parameters of the fault scene as the influencing parameters.
6. The method for characterizing fault current sequence component characteristics of a new energy grid-formation flexible-direct system according to claim 5, wherein the influencing parameters comprise potential reference values in a virtual synchronous machine of a flexible-direct converter station and transition resistances of fault points.
7. The method for characterizing fault current sequence components of a new energy grid-formation flexible-direct system according to claim 6, further comprising: Constructing a simulation model which needs to be matched with the topological structure of the new energy networking flexible-straight system and the fault ride-through control characteristic of the equipment based on the simulation platform; Verifying through a control variable method according to the characterization result of the fault current sequence component characteristics, and outputting a verification result; And performing method evaluation and/or correction based on the verification result.
8. The method for characterizing fault current sequence component characteristics of a new energy networking flexible-direct system according to claim 7, wherein in the control variable method, the value range of potential reference values in a virtual synchronous machine is determined based on rated voltage of a flexible-direct converter station and a fault ride-through control strategy.
9. The method for characterizing fault current sequence component characteristics of a new energy grid-constructed flexible and straight system according to claim 8, wherein in the control variable method, the value range of the transition resistance at least comprises the minimum equivalent grounding resistance to the maximum equivalent grounding resistance under a fault scene; the transition resistance range also includes typical fault ground resistance values.
10. The method for characterizing the fault current sequence component characteristics of the new energy grid-formation flexible-direct system according to claim 1, wherein an analytical expression is obtained by solving a node current equation and a loop voltage equation of the equivalent sequence grid diagram based on the electrical characteristics of system equipment.

Description

New energy networking flexible-direct system fault current sequence component characteristic characterization method Technical Field The invention relates to the technical field of electric power, in particular to a new energy grid-structured flexible-direct system fault current sequence component characteristic characterization method. Background Under the drive of a carbon reduction target, a new energy source through-grid flexible direct delivery system becomes one of important application technologies, two sides of an alternating current delivery line are both power electronic equipment, after faults, the alternating current delivery line is influenced by fault ride-through control, fault current shows obvious weak feed controlled characteristics, and the difference between the fault current and the fault characteristics of a traditional synchronous machine system is obvious. However, the existing protection strategy is still designed based on the power frequency quantity fault characteristics of the traditional synchronous machine system, and is difficult to adapt to the fault current change in a new scene. The prior art focuses on system stability analysis and low-pass control strategy optimization, and the specific characteristic research of fault current sequence components on two sides of an alternating current line is insufficient, so that a conventional control strategy lacks a targeted adjustment basis in practical application, and further the conventional control strategy cannot be accurately adapted to system states under different fault types and different parameter conditions, and the reliability and the suitability of a control effect are affected. In conclusion, the new energy networking flexible direct system AC line fault current sequence component has insufficient representation capability, so that the conventional control strategy lacks basis, and the technical problems of poor suitability and reliability exist. Disclosure of Invention Aiming at the problems existing in the prior art, the invention provides a method capable of definitely representing the fault current sequence component characteristics of a new energy grid-structured flexible-direct system, so as to solve the problems. In order to achieve the above purpose, the technical scheme adopted by the invention is as follows: The invention provides a new energy networking flexible-direct system fault current sequence component characteristic characterization method, which comprises the following steps: Considering a fault ride-through control strategy of alternating current sending line side equipment in a new energy networking flexible direct current system, and establishing an equivalent sequence network diagram of the system; Based on the fault ride-through control strategy and the equivalent sequence network diagram, solving an analytic expression of fault current sequence components on two sides of a line under different fault types; Quantifying fault current sequence components corresponding to each fault type through the analysis expression; Extracting influence parameters of the fault current sequence component based on fault control characteristics of a new energy networking flexible direct system; and according to the analysis expression and the influence parameter association, fault current sequence component characteristics are represented. Optionally, the fault ride-through control strategy comprises low-voltage ride-through control of the new energy converter and virtual synchronous machine fault ride-through control of the flexible direct current converter station; The low-voltage ride through control of the new energy converter comprises reactive current support control and negative sequence current suppression control; The virtual synchronous machine fault ride-through control of the soft direct current converter station comprises power reference value switching, internal potential adjustment and virtual impedance input control. Optionally, the fault types include single-phase-to-earth faults, two-phase-to-phase faults, and two-phase-to-earth faults. Optionally, in the equivalent sequence network diagram, the single-phase earth fault corresponds to a positive sequence network, a negative sequence network and a zero sequence network of the system which are connected in series at a fault point; the positive sequence network and the negative sequence network of the two-phase-to-phase fault corresponding system are connected in parallel at a fault point; And the two-phase grounding faults correspond to the positive sequence network, the negative sequence network and the zero sequence network of the system and are connected in parallel at fault points. Optionally, extracting the influencing parameter includes: And selecting the adjusting parameters of the fault ride-through control and/or the inherent physical parameters of the fault scene as the influencing parameters. Optionally, the influencing parameters include