CN-122000987-A - Transient synchronous stability assessment method and device for phase-locked synchronous converter system under energy view angle

CN122000987ACN 122000987 ACN122000987 ACN 122000987ACN-122000987-A

Abstract

The invention relates to a transient synchronization stability evaluation method and a transient synchronization stability evaluation device of a phase-locked synchronous converter system under an energy view angle, which belong to the field of new energy grid connection and solve the problem of transient synchronization stability evaluation of the phase-locked synchronous converter at the present stage; according to the law of conservation of energy, a branch energy function of a phase-locked synchronous converter system considering transient synchronous influence of a phase-locked loop is established, branch energy and port energy indexes based on information entropy are established, and stability margin of a key branch and a phase-locked synchronous converter element in a network is quantitatively estimated based on local network measurement information. The invention can accurately and quantitatively identify the stability margin of the key branch circuit and the key phase-locked synchronous converter of the system, and provides a new visual angle and tool for transient synchronous stability evaluation of the high-permeability renewable resource system.

Inventors

SUN ZHENGLONG
LIU NAIYUAN
ZHANG RUI
LI ZEWEI
YANG HAO
CAI GUOWEI

Assignees

东北电力大学

Dates

Publication Date: 20260508
Application Date: 20251225

Claims (8)

1. The method for evaluating the transient state synchronous stability of the phase-locked synchronous converter system under the energy view angle is characterized by comprising the following steps of: S1, constructing port energy functions of all elements in a phase-locked synchronous converter system; Step S2, establishing a phase-locked synchronous converter system branch energy function considering the transient synchronous influence of the phase-locked loop according to the energy conservation law; And S3, constructing branch energy and port energy indexes based on information entropy, and quantitatively evaluating the stability margin of a key branch and a phase-locked synchronous converter element in a network based on local network measurement information.
2. The method for evaluating transient synchronization stability of an energy view synchronous phase-locked converter system according to claim 1, wherein the synchronous phase-locked converter system in step S1 can be regarded as a complex system formed by interconnecting a synchronous phase-locked converter and its control subsystem, synchronous machine subsystem, load subsystem and power network. In the process of recovering the system three-phase short circuit fault to the stable balance point, the port energy of the phase-locked synchronous converter, the generator, the load and the branch circuit is oscillated, but the total energy of the four parts is kept. In the actual system analysis, defining the boundary of the target system according to the port interconnection structure, and defining the port energy as follows: Where (P i )、(Q i ) represents the active power and reactive power flowing through the i-port, respectively, and (V i )、(θ i ) represents the voltage and phase angle of the corresponding node, respectively.
3. The method for evaluating the transient synchronization stability of a phase-locked synchronous converter system under an energy view angle according to claim 2, wherein the transient energy functions of each component part of the phase-locked synchronous converter system are performed during transient faults; the port energy (E GFLi ) of the ith synchronous converter and its control subsystem can be expressed as: the port energy (EsGi) of the ith synchronous machine and its control subsystem can be expressed as: The port energy (E Li ) of the ith load subsystem may be expressed as: Except for the phase-locked synchronous converter and the synchronous machine node, the rest nodes in the power grid are regarded as load nodes. The power network (ij) includes all n nodes in the grid and their connection lines, the port energy (E ij ) of which can be expressed as:
4. The method for evaluating transient synchronization stability of an energy view angle phase-locked synchronous converter system according to claim 1 or 3, wherein the step S2 comprises: Step S201, analyzing an electric power system consisting of n nodes by using an energy conservation law. The node current equation may be expressed according to kirchhoff's current law: Wherein (I ij )、(I GFLi )、(I SGi )、(I Li ) represents the real-time current of the branch (I-j) from the node I to the node j, the current of the phase-locked synchronous converter and the synchronous machine entering the system, and the current of the system entering the load, which are n-dimensional complex vectors. (n B )、(n GFL )、(n SG )、(n L ) respectively represents the number of nodes in the network, the number of phase-locked synchronous converters, the number of synchronous machines and the number of loads, and can be met at any time in the running process of the system. Step S202, according to the research target, the power system described by the port energy structure can be arbitrarily divided into an object system and an external system acting on the object system. However, in any case divided in the grid, the ports between the subsystems are inevitably branches connecting nodes or segments made up of branches, the port energy representing the transient energy flow at a point on the branches. In order to accurately map transient synchronous stability characteristics of the phase-locked synchronous converter in a system, I is divided into a steady-state component (I s ) and a transient component (delta I). The steady state node current equation at this time can be expressed as: in the formula, The current of the branch (i-j) from node i to node j, from the phase locked synchronous converter and synchronous machine into the system, and the steady state current into the load are shown, respectively. Since the transient component (Δi) plays a decisive role in the increase of potential energy, the node transient current equation can be derived from (Δi=i-I s ): In step S203, the total transient energy of the four types of network elements is always conserved, and the law of conservation of energy is satisfied. In the transient stabilization process of the system, energy interaction exists between the phase-locked synchronous converter and the branch circuit. In step S204, ports between subsystems are inevitably connected to each other through branches, and port energy represents a transient energy flow at a point on the branches. Therefore, the transient synchronization stability of the phase-locked synchronous converter is evaluated according to the key branch in the identification network.
5. The method for evaluating the transient synchronization stability of a phase-locked synchronous converter system under an energy view angle according to claim 4, wherein the transient stability characteristics of internal components of the phase-locked synchronous converter are maintained. The instability characteristics of the current transformer are mapped into the network due to the energy interaction between the phase locked synchronous current transformer and the legs. By utilizing the port energy to express the transient energy aggregation effect, complex control process calculation is avoided, the modeling process is simplified, and the difficulty of energy function construction is reduced.
6. The method for evaluating transient synchronization stability of an energy view angle phase-locked synchronous converter system according to claim 1, wherein the step S3 comprises: in step S301, we disclose transient behavior of the pll according to the aggregation effect of the port energy and the distribution characteristics of the branch energy. Therefore, two transient state synchronization stability evaluation indexes based on information entropy are provided based on the forms of port energy and branch energy. Step S302, information entropy reflects the evolution sequence of natural phenomena, and is widely used for describing the uncertainty and stability of the system. For a complex nonlinear system, the information entropy can measure the disorder and chaos of the system state, and the equilibrium state of the system is judged through the change of the information entropy value. Based on the entropy balance principle and based on the distribution characteristics of the network branch potential energy and the branch energy in the transient process, the transient synchronization stability quantitative information entropy branch energy stability index (IEBSI) is presented as: The magnitude of (H l ) reflects the impact of disturbances and faults on the network energy distribution. Thus, the size of IEBSI indicates the severity of the disturbance in the GFL-VSC system. In step S303, the port energy of each component of the system is not dependent on the internal electrical quantity of the phase-locked synchronous converter, but only on the output power of the phase-locked synchronous converter and the voltage and phase angle of the bus. In order to locate the position of the phase-locked synchronous converter with transient instability, an information entropy port energy stability index (IEPSI) is proposed based on the aggregation effect of port energy and is expressed as follows: The magnitude of (H 2 ) reflects the influence of disturbance and faults on the port energy of the phase-locked synchronous converter. Thus, IEBSI indicates whether the port energy of the phase locked synchronous converter exceeds a critical threshold.
7. The method for evaluating transient synchronization stability of an energy view synchronous converter system according to claim 6, wherein the calculation of IEBSI and IEPSI is critical for identifying critical branches of the system oscillation center region and evaluating contributions of different phase-locked synchronous converters. Before calculating the two indexes, the energy of each branch of the system and the port energy of the phase-locked synchronous converter are required to be calculated respectively.
8. An apparatus for using the method for evaluating transient synchronization stability of the phase-locked synchronous converter system under energy viewing angle according to any one of claims 1 to 7, comprising: The data acquisition module is used for acquiring the electric power data of each generator in the system required by subsequent calculation, and judging whether the three-phase short circuit fault exists in the electric power system through monitoring the circuit and the nodes. After fault detection, collecting power supply and voltage phase angle signals through PMUs distributed in a network; The calculation module is used for processing and calculating the electric data of each generator in the system acquired by the acquisition module, and calculating the branch energy in the system after the fault and the port energy of the synchronous machine and the phase-locked synchronous converter by using an energy equation to obtain IEBSI and IEPSI indexes of each element and branch; And the comparison module is used for comparing and analyzing the calculation results of the calculation module and sequencing the results in descending order. Quantitatively identifying the stability margin of a key branch circuit of the system and a key phase-locked synchronous converter according to the results of IEBSI and IEPSI indexes shown in table 1; And a feedback module for providing useful feedback to the decision support system.

Description

Transient synchronous stability assessment method and device for phase-locked synchronous converter system under energy view angle Technical Field The invention relates to the technical field of power systems, in particular to a transient synchronization stability evaluation method and device of a phase-locked synchronization converter system under an energy view angle. Background Along with the continuous promotion of low-carbon energy transformation, renewable energy and auxiliary resources are connected into a power grid through a power electronic converter, and synchronization is realized through phase-locked loop control. But this also brings new control interactions and instability problems. With the continuous increase of renewable energy proportion, it becomes important to ensure transient synchronous stability of a power system based on a phase-locked synchronous converter. The equal area criteria, the lyapunov direct method, the phase diagram method and the energy function method are commonly used to analyze and evaluate the transient synchronous stability of synchronous generator based systems. Although effective, the equal area criterion method has stronger conservation because impedance fluctuation and damping effect caused by frequency change are ignored. The Lyapunov method has a perfect theoretical framework and is widely suitable for a high-order nonlinear system, but the construction of corresponding functions is challenging, and the results are often too conservative. The phase diagram method is intuitive and easy to understand, but cannot provide a standard for evaluating transient synchronization stability. These methods have inherent disadvantages in assessing transient synchronization stability of phase locked synchronous converter systems. And because of the complex interactions between a large number of phase-locked synchronous converters and the power system, transient synchronous stability assessment of the power system with high renewable resource permeability is challenging. Although some measurement-based transient synchronization stability evaluation methods have been proposed, their application is limited due to the difficulty in measuring and acquiring internal parameters of the phase-locked synchronous converter. Content of the application In view of the above analysis, the present invention aims to provide a method for evaluating transient synchronization stability of a phase-locked synchronous converter system under an energy view angle, so as to quantitatively evaluate the transient synchronization stability of the phase-locked synchronous converter by using only local network measurement information. The problem of stable operation of the system after new energy grid connection is solved. The aim of the invention is mainly realized by the following technical scheme: the invention discloses a transient synchronous stability assessment method of a phase-locked synchronous converter system under an energy view angle, which comprises the following steps: S1, constructing port energy functions of all elements in a phase-locked synchronous converter system; Step S2, establishing a phase-locked synchronous converter system branch energy function considering the transient synchronous influence of the phase-locked loop according to the energy conservation law; And S3, constructing branch energy and port energy indexes based on information entropy, and quantitatively evaluating the stability margin of a key branch and a phase-locked synchronous converter element in a network based on local network measurement information. Preferably, according to at least one embodiment of the present invention, the phase-locked synchronous converter system described in step S1 may be regarded as a complex system formed by phase-locked synchronous converters and their control subsystems, synchronous machine subsystems, load subsystems and power network interconnections. In the process of recovering the system three-phase short circuit fault to the stable balance point, the port energy of the phase-locked synchronous converter, the generator, the load and the branch circuit is oscillated, but the total energy of the four parts is kept. In the actual system analysis, defining the boundary of the target system according to the port interconnection structure, and defining the port energy as follows: in the formula, Respectively indicate the flow throughThe active power and reactive power of the port,Representing the voltage and phase angle of the corresponding node, respectively. Preferably, according to at least one embodiment of the present invention, the transient energy function of each component of the synchronous converter system is phase locked during a transient fault; Said first Station phase-locked synchronous converter and port energy of control subsystem thereofCan be expressed as: Said first Station synchronous machine and port energy of control subsystem thereofCan be expressed as Said