CN-122026479-A - Transient stability analysis method, system, equipment and medium for series-parallel system

CN122026479ACN 122026479 ACN122026479 ACN 122026479ACN-122026479-A

Abstract

The invention discloses a transient stability analysis method, a system, equipment and a medium of a series-parallel system, which belong to the field of electric power systems, and are used for constructing a prototype system for parallel operation of a synchronous generator and an inverter, taking the ratio of the reactance from the internal potential of the synchronous generator to the grid connection point to the reactance from the grid connection point to an infinite grid as a grid connection position parameter, establishing a fourth-order and sixth-order hybrid mechanism model based on the prototype system, fusing a synchronous generator rotor motion equation and an inverter phase-locked loop dynamic model by the fourth-order model, dividing the model into an autonomous subsystem and a coupling module, supplementing a current loop transient process by the sixth-order model to form a combined model of a synchronous generator second-order model and an inverter fourth-order model, analyzing the dynamic four-stage transient process of the phase-locked loop based on the fourth-order and sixth-order hybrid mechanism model, combining the grid connection position parameter and the four-stage transient characteristic, determining the dynamic interaction characteristic of the synchronous generator and the inverter and the regulation and control law of the system transient stability margin by the grid connection position parameter, and evaluating the transient stability of the series system.

Inventors

ZHAO PU
CHEN XIONGFEI
ZHAO DONGMING
HUANG LIZHE
WANG WEI
CHEN XIANGBAO
LI GUIPENG
YAO AIJUN
LV HONGEN
LIU YUN
ZHANG CHI

Assignees

华能新能源股份有限公司河北分公司
中国华能集团清洁能源技术研究院有限公司
华能新能源股份有限公司

Dates

Publication Date: 20260512
Application Date: 20260206

Claims (10)

1. The transient stability analysis method of the series-parallel system is characterized by comprising the following steps of: Constructing a prototype system for parallel operation of a synchronous generator and an inverter, and taking the ratio of the reactance from the internal potential of the synchronous generator to the grid connection point to the reactance from the grid connection point to an infinite power grid as a grid connection position parameter; the method comprises the steps of establishing a fourth-order hybrid mechanism model and a sixth-order hybrid mechanism model based on a prototype system for parallel operation of a synchronous generator and an inverter, wherein the fourth-order hybrid mechanism model is established by fusing a synchronous generator rotor motion equation and an inverter phase-locked loop dynamic model and dividing the model into an autonomous subsystem and a coupling module; analyzing a phase-locked loop dynamic four-stage transient process based on the fourth-order hybrid mechanism model and the sixth-order hybrid mechanism model to obtain four-stage transient characteristics, wherein the phase-locked loop dynamic four-stage comprises a phase-locked angle after fault in-proportion link action stage, a current loop dynamic stabilization stage, a synchronous machine power angle coupling stage and a oscillation stage after fault removal; And determining a regulation rule of the grid-connected position parameter on dynamic interaction characteristics of the synchronous generator and the inverter and a system transient stability margin based on the fourth-order hybrid mechanism model, the sixth-order hybrid mechanism model and the grid-connected position parameter and combining four-stage transient characteristics, and evaluating the transient stability of the series-parallel system based on the regulation rule.
2. The method for analyzing transient stability of a series-parallel system according to claim 1, wherein the grid-connected position parameter is represented by the following formula: Wherein, the As a grid-tie location parameter, For synchronizing the reactance between the generator potential and the grid connection point, Is the reactance between an infinite bus and a grid connection point.
3. The method for analyzing transient stability of a hybrid system according to claim 1, wherein the autonomous subsystem of the fourth-order hybrid mechanism model comprises a converter autonomous subsystem and a synchronous machine autonomous subsystem, the converter autonomous subsystem operates independently of a synchronous generator, the synchronous machine autonomous subsystem operates independently of an inverter, and the coupling module is a dynamic interaction module of the synchronous generator and the inverter.
4. The method for analyzing the transient stability of the series-parallel system according to claim 1, wherein the inverter fourth-order model of the sixth-order hybrid mechanism model consists of an SRF-PLL second-order dynamic model and a current loop transient characteristic model, wherein the current loop transient characteristic model is obtained through deduction through a control loop containing a decoupling term, and the influence of inductance dynamics and line impedance is ignored in the deduction process.
5. The method for analyzing transient stability of a series-parallel system according to claim 1, wherein the time range of the dynamic four phases of the phase-locked loop is that the action phase of the proportional link lasts for 0-40ms, the dynamic stability phase of the current loop lasts for 50-100ms, and the power angle coupling phase of the synchronous machine lasts for 50-100ms.
6. The method for analyzing the transient stability of the series-parallel system according to claim 5, wherein the transient stability evaluation of the series-parallel system comprises steady state stability evaluation and transient stability evaluation; the steady-state stability assessment is carried out based on characteristic value analysis of a fourth-order hybrid mechanism model, specifically, a characteristic value is solved through a system matrix obtained after linearization of the fourth-order hybrid mechanism model, qualitative judgment of small-interference stability of a system is carried out by utilizing a real part symbol of the characteristic value, and quantitative characterization is carried out on small-interference stability margin of the system by combining damping ratio of the characteristic value, so that a small-interference stability assessment result of the system is obtained; The transient stability evaluation is performed based on a phase-locked angle track of a six-order hybrid mechanism model, relative movement of a synchronous generator power angle and an inverter locking angle, and accumulated energy interaction item quantity containing inverter dynamics, and specifically, qualitative judgment of the transient stability of a series-parallel system and quantitative evaluation of a stability margin are completed by judging whether the locking angle track crosses a stability boundary, whether the relative movement of the synchronous generator power angle and the inverter is unbalanced, and whether the accumulated energy interaction item quantity exceeds a system tolerance threshold.
7. The method for analyzing the transient stability of the series-parallel system according to claim 1, further comprising determining an optimal value interval of the grid-connected position parameter based on the regulation rule, wherein the optimal value interval satisfies that dynamic interaction between the synchronous generator and the inverter is stable and the transient stability margin of the system is maximum.
8. The transient stability analysis system of the series-parallel system is characterized by comprising: A prototype system module is built, which is used for building a prototype system for parallel operation of the synchronous generator and the inverter, and the ratio of the reactance from the internal potential of the synchronous generator to the grid connection point to the reactance from the grid connection point to the infinite grid is used as a grid connection position parameter; The method comprises the steps of establishing a fourth-order sixth-order model module, which is used for establishing a fourth-order hybrid mechanism model and a sixth-order hybrid mechanism model based on a prototype system of parallel operation of a synchronous generator and an inverter, wherein the fourth-order hybrid mechanism model is constructed by fusing a synchronous generator rotor motion equation and an inverter phase-locked loop dynamic model and dividing the model into an autonomous subsystem and a coupling module; The phase-locked loop dynamic four-stage transient characteristic is obtained by analyzing a phase-locked loop dynamic four-stage transient process based on the fourth-order hybrid mechanism model and the sixth-order hybrid mechanism model, and the phase-locked loop dynamic four-stage transient characteristic comprises a phase-locked angle after fault in-proportion link action stage, a current loop dynamic stabilization stage, a synchronous machine power angle coupling stage and a fault oscillation stage after fault removal; The transient stability evaluation module is used for determining the regulation and control rule of the grid-connected position parameters on the dynamic interaction characteristics of the synchronous generator and the inverter and the transient stability margin of the system based on the fourth-order hybrid mechanism model, the sixth-order hybrid mechanism model and the grid-connected position parameters and combining the four-stage transient characteristics, and evaluating the transient stability of the series-parallel system based on the regulation and control rule.
9. An electronic device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, the processor implementing the method of series-parallel system transient stability analysis of any one of claims 1-7 when the computer program is executed.
10. A computer readable storage medium storing a computer program which, when executed by a processor, implements the method of transient stability analysis of a hybrid system as claimed in any one of claims 1-7.

Description

Transient stability analysis method, system, equipment and medium for series-parallel system Technical Field The invention belongs to the field of power systems, and particularly relates to a method, a system, equipment and a medium for analyzing transient stability of a series-parallel system. Background Along with the promotion of novel electric power system construction, new energy power generation duty ratio continuously promotes, and the core equipment that new energy incorporated into the power networks is regarded as to the dc-to-ac converter, and its dynamic characteristics produces decisive influence to system stability. In the traditional power system, a mature research system exists for transient stability problems led by a Synchronous Generator (SG), and a relatively complete analysis method is formed in the industry aiming at static instability, small disturbance instability and transient instability mechanisms of a grid-connected converter. However, in a high-proportion new energy access scenario, the system presents the characteristic of series-parallel operation of a Synchronous Generator (SG) and an inverter power supply (IBG). The transient stability mechanism is radically changed due to the dynamic interaction of the SG and the IBG, the existing research fails to fully reveal the cooperative instability mechanism of the SG and the IBG in the series-parallel system, and particularly quantitative analysis means are lacked in the aspects of control strategy switching after the converter fails, influence of grid-connected point positions on the system stability and the like. In addition, grid-connected site selection of the new energy power station has space flexibility, but the prior art does not establish a correlation model of grid-connected site position and system transient stability, so that the influence of different access schemes on the system dynamic performance is difficult to evaluate in a planning stage. This technical gap makes new energy grid-connected designs lack theoretical guidance and may pose potential stability risks. Currently, to analyze the stability of an electrical power system, there are generally the following methods: 1. the time domain simulation method is that for a system, a mathematical model, namely a nonlinear differential-algebraic equation set, can be constructed: where x is a system state variable and y is an algebraic variable, its numerical solution can be obtained by iteration, and it can be generally obtained by an implicit trapezoidal integration method or a newton-radson method, as shown in the formula: then, the value of each moment of the state variable can be obtained through small-step time domain simulation, so that a variable curve in the fault period is obtained, and whether the system is stable or not is judged according to the curve. The method is suitable for analyzing the transient stability of the system. 2. Eigenvalue analysis, which is to linearize the differential equation at steady state operating point for a system: The algebraic variables are eliminated to obtain a state matrix: And further, the damping coefficient and the oscillation frequency of the device can be obtained through eigenvalue solving, so that modal analysis is further carried out. The method is suitable for analyzing the small disturbance stability of the system. 3. The transient energy function method is to construct an energy function of a unit, and the energy function is shown as the following formula: And comparing the energy at the moment of fault removal with critical energy to judge whether the system is stable or not. The method is suitable for analyzing the transient stability of the system. The three methods have advantages and disadvantages, namely, the time domain simulation method can accurately simulate nonlinear large disturbance, but the calculation efficiency is low and the mechanism is not clear, the eigenvalue analysis method can quantify the oscillation mode and guide parameter optimization, but is only suitable for small disturbance and difficult to solve in a high-dimensional system, the transient energy function method (TEF) can rapidly evaluate the stable power angle through an energy threshold, but has insufficient modeling and conservation of results on new energy equipment, and is only suitable for analyzing the system stability under the determined parameters, and if the influence of a specific parameter or structure on the stability is analyzed, the method of violent enumeration can only be used, and the mechanism and principle of the influence cannot be known. Disclosure of Invention The invention aims to solve the problem that the prior art cannot meet the requirements of system stability analysis and planning in a SG and IBG series-parallel operation scene under high-proportion new energy access, and provides a series-parallel system transient stability analysis method, system, equipment and medium, which are based on a multi-order