CN-122000996-A - Transient state synchronous stability evaluation method and system for grid-structured power generation equipment

CN122000996ACN 122000996 ACN122000996 ACN 122000996ACN-122000996-A

Abstract

The invention discloses a method and a system for evaluating transient synchronous stability of network-structured power generation equipment, which are used for acquiring main circuit parameters and control parameters of the network-structured power generation equipment, constructing a transient equivalent model of the network-structured power generation equipment, constructing a Lyapunov energy function V λ of the network-structured power generation equipment according to the transient equivalent model of the system, determining initial state points of a final stage of the network-structured power generation equipment according to whether faults are cleared or not, substituting the initial state points of the final stage into the Lyapunov energy function V λ , calculating to obtain total energy V of the network-structured power generation equipment of the final stage, judging whether balance points exist in the final stage according to the transient equivalent model of the network-structured power generation equipment, if yes, calculating critical energy V cr of the final stage, if the total energy V is smaller than the critical energy V cr , judging to be transient synchronous stability, otherwise judging to be synchronous instability, if not, judging to be synchronous instability. The invention solves the problem of difficult modeling frame by frame in the complex switching process.

Inventors

CHEN YANDONG
LUO CONG
LUO QING
XIE ZHIWEI
Gao Minggun
ZHANG HANYU
LI JINGTAO
ZHANG JINGYU

Assignees

湖南大学

Dates

Publication Date: 20260508
Application Date: 20260106

Claims (9)

1. The transient state synchronous stability evaluation method of the grid-structured power generation equipment is characterized by comprising the following steps of: s1, acquiring main circuit parameters and control parameters of the grid-structured power generation equipment, and constructing a transient equivalent model of the grid-structured power generation equipment; S2, constructing a Lyapunov energy function V λ of the grid-structured power generation equipment according to the system transient equivalent model; S3, judging a final stage according to whether the fault is cleared or not, and determining an initial state point of the final stage of the grid-built power generation equipment according to whether the fault is cleared or not; S4, substituting initial state points of the final stage into a Lyapunov energy function V λ , and calculating to obtain total energy V of the net-structured power generation equipment of the final stage; S5, judging whether a balance point exists in the final stage according to the transient equivalent model of the grid-structured power generation equipment, if so, calculating critical energy V cr in the final stage, if the total energy V is smaller than the critical energy V cr , judging that transient synchronization is stable, otherwise, judging that synchronization is unstable, and if not, judging that synchronization is unstable.
2. The method for evaluating transient synchronous stability of grid-built power generation equipment according to claim 1, wherein the specific implementation process for judging whether the fault is cleared comprises the steps of judging that a power grid is in a normal working condition if V g =V N and the fault is cleared, judging that the power grid is in a fault working condition if V g <V N and the fault is not cleared, wherein V N is a rated voltage of the power grid and V g is a voltage of the power grid.
3. The method for evaluating transient synchronous stability of a grid-structured power generation device according to claim 1, wherein the transient equivalent model of the grid-structured power generation device is expressed as: ; wherein J is the inertia of the grid-structured power generation equipment, Angular frequency deviation is provided for the grid-built power generation equipment, Angular frequency is provided for the grid-built power generation equipment, For rated angular frequency, P ref is the reference power of the grid-structured power generation equipment, P is the output active power of the grid-structured power generation equipment, delta is the power angle of the grid-structured power generation equipment, E is the output voltage of the grid-structured power generation equipment, D is damping, K is the reactive ring sagging system, Q ref is the reactive reference value, Q is the output reactive power, D q is the reactive sagging system, E 0 is the rated voltage, 、 First and second derivatives of delta, Is the first order derivative of E.
4. The method for evaluating transient synchronization stability of a grid-structured power generation equipment according to claim 1, wherein the energy function V λ of the grid-structured power generation equipment lyapunov is expressed as: ; Wherein X g is the line reactance, R g is the line resistance, Z g is the line impedance, Delta 0 is the power angle of the steady-state operating point x u1 before failure, J is the inertia of the grid-built power generation equipment, The method is characterized in that angular frequency deviation is carried out on the grid-formed power generation equipment, D is damping, D q is a reactive sagging system, E is output voltage of the grid-formed power generation equipment, J is inertia of the grid-formed power generation equipment, and V g is power grid voltage.
5. The method for evaluating transient synchronization stability of a grid-structured power generation device according to claim 1, wherein the specific implementation process of step S3 includes that if the fault is not cleared, the initial state point of the final stage is a steady-state operation point x u1 before the fault, and if the fault is cleared, the initial state point of the final stage is a operation point x u2 at the moment of clearing the fault.
6. The method for evaluating transient synchronous stability of a grid-structured power generation apparatus according to claim 1, wherein the total energy V of the final-stage grid-structured power generation apparatus is expressed as: ; Wherein, delta u is the initial state point power angle, E u is the fault initial point voltage, lambda is more than or equal to 0 and less than or equal to 1, R g is line resistance, Z g is line impedance, Q ref is reactive reference value, D q is reactive droop system, E 0 is rated voltage, delta 0 is the power angle of the steady state working point x u1 before fault, J is the inertia of the grid-structured power generation equipment, and V g is the power grid voltage.
7. The method for evaluating transient synchronous stability of a grid-structured power generation device according to claim 1, wherein the critical energy V cr of the final stage system is the energy corresponding to the unstable balance point of the final stage system, expressed as: ; Wherein, the Indicating the work angle of the unstable equilibrium point, The voltage of the unstable balance point is represented, R g is line resistance, Z g is line impedance, Q ref is a reactive reference value, D q is a reactive droop system, E 0 is rated voltage, delta 0 is the work angle of a stable working point x u1 before failure, J is the inertia of the grid-formed power generation equipment, and V g is the power grid voltage. The method of claim 1, wherein the step of determining whether the balance point exists comprises comparing the reference power P ref of the grid-formed power generation device with the output active power P, and if P ref > P, the balance point does not exist, otherwise.
8. A transient synchronous stability evaluation system of a network-structured power generation device, comprising a memory, a processor and a computer program stored on the memory, wherein the processor executes the computer program to implement the steps of the method of one of claims 1 to 8.
9. A computer-readable storage medium, on which a computer program/instruction is stored, characterized in that the computer program/instruction, when executed by a processor, implements the steps of the method according to one of claims 1 to 8.

Description

Transient state synchronous stability evaluation method and system for grid-structured power generation equipment Technical Field The invention relates to a new energy power generation control technology, in particular to a method and a system for evaluating transient state synchronous stability of network-structured power generation equipment for controlling frequent switching scenes. Background The grid-structured power generation equipment is used as a core component of a new energy grid-connected system, has the characteristic of actively supporting the voltage and the frequency of a power grid, and is widely applied to the fields of distributed power generation, micro-grids and the like. The virtual impedance-based current limiting strategy is a key technology for fault ride-through of grid-built power generation equipment, and can maintain a grid-built operation mode during faults, and limit fault current amplitude while maintaining active supporting capability. The virtual impedance control shows control switching characteristics in transient processes, and the switching time sequence and the triggering condition of the virtual impedance control can change the transient behavior and the stability characteristics of the system obviously. The traditional transient state synchronous stability evaluation method is based on the assumption of constant control parameters, such as an equal area method, and cannot cope with system model mutation caused by control switching, and the phase trajectory method relies on state space continuity, is difficult to process state jump caused by switching, and has certain limitations. Therefore, developing a transient synchronous stability assessment method capable of accurately adaptively controlling frequent switching conditions becomes a key for guaranteeing safe and stable operation of the grid-built power generation equipment. Therefore, how to evaluate the transient state synchronous stability of the grid-structured power generation equipment under the control frequent switching working condition is a technical problem to be solved. Disclosure of Invention Aiming at the defects of the prior art, the invention provides the transient state synchronization stability evaluation method for the grid-structured power generation equipment, which realizes the transient state synchronization stability evaluation of the grid-structured equipment under the control switching action through the energy boundary threshold value and avoids the frame-by-frame modeling of the complex switching process. In order to solve the technical problems, the technical scheme adopted by the invention is that the transient state synchronous stability evaluation method of the grid-structured power generation equipment comprises the following steps: s1, acquiring main circuit parameters and control parameters of the grid-structured power generation equipment, and constructing a transient equivalent model of the grid-structured power generation equipment; S2, constructing a Lyapunov energy function V λ of the grid-structured power generation equipment according to the system transient equivalent model; S3, judging a final stage according to whether the fault is cleared or not, and determining an initial state point of the final stage of the grid-built power generation equipment according to whether the fault is cleared or not; S4, substituting initial state points of the final stage into a Lyapunov energy function V λ, and calculating to obtain total energy V of the net-structured power generation equipment of the final stage; S5, judging whether a balance point exists in the final stage according to the transient equivalent model of the grid-structured power generation equipment, if so, calculating critical energy V cr in the final stage, if the total energy V is smaller than the critical energy V cr, judging that transient synchronization is stable, otherwise, judging that synchronization is unstable, and if not, judging that synchronization is unstable. In the invention, if the fault is cleared, the final stage is determined to be in a normal state, the power grid voltage is restored to the rated value, the virtual impedance control is exited, otherwise, the final stage is determined to be in a fault state, the power grid voltage maintains the fault level, and the virtual impedance is always activated. The invention can evaluate the stability of the system no matter what dynamic path (such as virtual impedance step investment and parameter gradual change adjustment) the system experiences in the control switching process, and only needs to compare the energy V of the 'final' stage of the grid-structured power generation equipment with the critical energy Vcr, thereby avoiding the frame-by-frame modeling of the complex switching process. Specifically, if the energy V in the final stage is smaller than the critical energy Vcr, it indicates that the system does not exceed the critical stability bound