CN-121984078-A - Converter transient power angle stability analysis method and system based on linear parameter change controller

CN121984078ACN 121984078 ACN121984078 ACN 121984078ACN-121984078-A

Abstract

The invention discloses a method and a system for analyzing transient power angle stability of a converter based on a linear parameter change controller. The method comprises the steps of establishing a small signal dynamic model of a power synchronous type grid-connected converter, constructing a mathematical model considering power filtering and current loop dynamics by directing output current to a d-axis of a dq coordinate system, designing a linear parameter change controller, adjusting control parameters in real time through parameter vectors, realizing decoupling control of active power and reactive power, ensuring stable operation of a system in an inversion mode and a rectification mode, and analyzing transient power angle stability of the system under large disturbance based on Lyapunov stability theory and combining a linearization method and a direct method. The synchronous stability problem of the traditional grid-following type converter is effectively solved without depending on the voltage information of the phase-locked loop and the grid-connected point, the adaptability and the operation reliability of the system under the weak current network condition are obviously improved, and an important technical support is provided for the safe and stable operation of the new energy power system.

Inventors

WANG GUANGSHENG
LIU YAN
Tang June
XU XING
YU WEI
SUN YONGZHONG
Gui Liangmou
WANG HAO
WU CHENG
Wan Yunbao
ZHOU XIN
WANG LAMEI

Assignees

国网江西省电力有限公司九江供电分公司

Dates

Publication Date: 20260505
Application Date: 20251024

Claims (10)

1. A converter transient power angle stability analysis method based on a linear parameter change controller is characterized by comprising the following steps: Establishing a small signal dynamic model of the power synchronous grid-connected converter, wherein the small signal dynamic model is constructed based on the dq axis component relation of the output voltage and the output current of the converter, and takes the first-order inertia characteristic of a current loop and a filtering link of power calculation into consideration; Designing a linear parameter change controller based on the small signal dynamic model, adaptively adjusting parameters of the controller along with the running state of the system, constructing an ideal diagonal open-loop transfer function matrix, and solving the transfer function matrix of the controller; Performing characteristic analysis on the linear parameter change controller, wherein the characteristic analysis comprises robustness analysis under the power grid impedance estimation error and influence analysis of frequency deviation on power steady-state error; And carrying out transient power angle stability analysis on the power synchronous type heel-net converter based on a Lyapunov stability theory, wherein the transient power angle stability analysis comprises the steps of judging the stability of a system steady-state balance point by using a Lyapunov linearization method and evaluating the robustness and attraction domain of the system under large disturbance by using a Lyapunov direct method.
2. The method for analyzing the transient power angle stability of the converter based on the linear parameter variation controller according to claim 1, wherein the constructing the small signal dynamic model of the power synchronous type grid-connected converter comprises the following steps: When the output current A of the converter is aligned with the d axis in the dq rotating coordinate system, i q =0, and the relation between the output current and the voltage of the converter is obtained, wherein the expression is as follows: i dq ＝I d +j0, v i,dq ＝V i cosθ+jV i sinθ, Wherein θ represents an included angle between the output voltage of the converter and the output current of the converter, I d 、I q is a dq axis component of the output current of the converter, and V i represents an amplitude of the output voltage; based on the relation between the output voltage and the current of the converter, the active power and the reactive power are determined, and the expression is: Wherein u id 、u iq 、i d 、i q is the value of the output voltage and the output current of the converter under the dq coordinate system respectively; Introducing small disturbance delta theta and delta I d at a steady-state working point (theta 0 ,I d ), and deducing the small signal dynamic model, wherein the expression is as follows: Wherein, theta 0 is the initial included angle between the voltage and the current of the working point converter, I d,ref is the component reference of the output current d of the converter, and omega is the estimated angular frequency of the converter.
3. The method for analyzing transient power angle stability of a converter based on a linear parameter variation controller according to claim 1, wherein the small signal dynamic model further considers: the current inner loop is equivalent to a first-order inertia link, and the time inertia constant is T 1 ; the active power and reactive power calculation signals are filtered by a second-order low-pass filter GPQ-L, and the closed loop transfer function of the filter is as follows: where ζ is the damping ratio of the filter and ω c is the turning frequency of the filter.
4. The method for analyzing transient power angle stability of a converter based on a linear parameter variation controller according to claim 1, wherein said designing the linear parameter variation controller comprises: Selecting a parameter vector x= [ I d,0 θ 0 ], wherein I d,0 is a current peak value output by the converter, and theta 0 is an initial included angle between the output voltage and the output current of the converter; an ideal open loop transfer function matrix is set as a diagonal matrix D, and the expression is: wherein p is an ideal constant value, s is apparent power; According to the transfer function matrix of the small signal dynamic model and the ideal open loop transfer function matrix, solving the transfer function matrix of the controller, wherein the expression is as follows: In the formula, I d,0 is the peak value of the current output by the converter, which can be obtained by monitoring the output current of the converter in real time.
5. The method for analyzing the transient power angle stability of the converter based on the linear parameter variation controller according to claim 1, wherein the constraints of the transfer function matrix of the controller are as follows: The transfer function of the system adopting the linear parameter change controller is a stable system no matter the power direction of the system is output or absorption; the system can keep stable operation in both inversion and rectification modes; The system bandwidth does not change with the steady state operating point.
6. The method for analyzing the transient power angle stability of the converter based on the linear parameter variation controller according to claim 1, wherein the power grid impedance estimation error robustness analysis in the characteristic analysis comprises: when the power grid impedance estimation has errors, the closed loop transfer function of the current loop is as follows: Wherein k p 、k i is the proportional and integral coefficient of the PI controller, L, R is the equivalent inductance and resistance value of the power grid, and k' p is the proportional value after zero pole cancellation; the system is stable under the condition that the impedance estimation coefficient k 1 ＝k 2 =k is proved by the Lawscriterion; The root trace analysis proves that the system can still keep stable under the condition of k 1 ≠k 2 .
7. The method for analyzing transient power angle stability of a converter based on a linear parameter variation controller according to claim 1, wherein the analyzing of frequency deviation influence in the characteristic analysis comprises: the relation between the frequency deviation delta omega and the power steady-state error is deduced, and the expression is: Δω=M 11 ΔP+M 12 ΔQ, Wherein M 11 、M 12 is a proportional term coefficient in the controller, and DeltaP and DeltaQ are power deviations; when the system has frequency deviation, the active power and the reactive power output by the converter generate steady-state errors, and the droop characteristic similar to the grid-structured control is presented.
8. The method for analyzing the transient power angle stability of the converter based on the linear parameter variation controller according to claim 1, wherein the transient power angle stability analysis comprises: Judging the local stability of the system by solving the feature value of the jacobian matrix of the system state equation at the balance point by using a Lyapunov linearization method; Constructing an energy function V (y) by using a Lyapunov direct method, and evaluating the stability and the robustness of the system under large disturbance by judging the negativity of the derivative of the energy function V (y), wherein, The energy function V (y) satisfies: When y=0, V (y) =0; when y+.0, V (y) >0; When y is not equal to 0,
9. The method for analyzing the transient power angle stability of the current transformer based on the linear parameter variation controller according to claim 1, wherein the transient power angle stability analysis further comprises a system parameter estimation step: under the simplified condition of neglecting the line resistance, estimating the output voltage of the converter according to the power grid voltage, the line reactance and the output power; substituting the estimated converter output voltage into a stability criterion for judging the stability and attraction domain of the current working point of the system.
10. The utility model provides a converter transient state power angle stability analysis system based on linear parameter change controller which characterized in that includes: the construction module is configured to establish a small signal dynamic model of the power synchronous grid-connected converter, the small signal dynamic model is constructed based on the dq axis component relation of the output voltage and the output current of the converter, and the first-order inertia characteristic of a current loop and a filtering link of power calculation are considered; The design module is configured to design a linear parameter change controller based on the small signal dynamic model, the parameters of the controller are adaptively adjusted along with the running state of the system, and an ideal diagonal open-loop transfer function matrix is constructed and solved; the first analysis module is configured to perform characteristic analysis on the linear parameter change controller, and comprises robustness analysis under the power grid impedance estimation error and influence analysis of frequency deviation on the power steady-state error; The second analysis module is configured to perform transient power angle stability analysis on the power synchronous type grid-connected converter based on a Lyapunov stability theory, and comprises the steps of judging the stability of a system steady-state balance point by using a Lyapunov linearization method and evaluating the robustness and the attraction domain of the system under large disturbance by using a Lyapunov direct method.

Description

Converter transient power angle stability analysis method and system based on linear parameter change controller Technical Field The invention belongs to the technical field of transient analysis of converters, and particularly relates to a method and a system for analyzing the stability of a transient power angle of a converter based on a linear parameter change controller. Background With the large-scale grid connection of new energy power generation equipment, the power generation equipment duty ratio of a traditional power system in a power grid is gradually reduced, and the system inertia is continuously reduced due to the continuous increase of the number of power generation equipment taking a converter as an energy conversion interface. In practical application, the grid-connected converter can be divided into two main control strategies, namely a grid-built control strategy and a grid-following control strategy according to the synchronous mode. The converter under the control mode of the grid-structured control strategy estimates the power grid frequency required by synchronization through the active power frequency sagging control, but when the power grid has short circuit faults and causes voltage drop, a large amount of reactive power needs to be rapidly injected into the power grid, and excessive reactive current injection can cause the problems of over-current, large fluctuation change of instantaneous output power and the like, so that the requirement on equipment is relatively high. The converter under the control mode of the follow-up network control strategy depends on the tracking of the phase-locked loop (PLL) to the voltage of the power grid to realize the synchronization with the power grid, so the power angle stability of the converter is extremely dependent on the performance of the phase-locked loop. Meanwhile, the existing research shows that the grid connection of the large-scale grid-connected converter can reduce the power angle stability of the system, and the negative damping effect introduced by the phase-locked loop at low frequency can cause poor power angle stability of the phase-locked loop at a weak current network. Disclosure of Invention The invention provides a method and a system for analyzing transient power angle stability of a converter based on a linear parameter change controller, which are used for solving the technical problem that the power angle stability of a phase-locked loop in a weak current network is poor due to a negative damping effect introduced by the phase-locked loop at a low frequency. In a first aspect, the present invention provides a method for analyzing transient power angle stability of a converter based on a linear parameter variation controller, including: Establishing a small signal dynamic model of the power synchronous grid-connected converter, wherein the small signal dynamic model is constructed based on the dq axis component relation of the output voltage and the output current of the converter, and takes the first-order inertia characteristic of a current loop and a filtering link of power calculation into consideration; Designing a linear parameter change controller based on the small signal dynamic model, adaptively adjusting parameters of the controller along with the running state of the system, constructing an ideal diagonal open-loop transfer function matrix, and solving the transfer function matrix of the controller; Performing characteristic analysis on the linear parameter change controller, wherein the characteristic analysis comprises robustness analysis under the power grid impedance estimation error and influence analysis of frequency deviation on power steady-state error; And carrying out transient power angle stability analysis on the power synchronous type heel-net converter based on a Lyapunov stability theory, wherein the transient power angle stability analysis comprises the steps of judging the stability of a system steady-state balance point by using a Lyapunov linearization method and evaluating the robustness and attraction domain of the system under large disturbance by using a Lyapunov direct method. In a second aspect, the present invention provides a transient power angle stability analysis system of a converter based on a linear parameter variation controller, including: the construction module is configured to establish a small signal dynamic model of the power synchronous grid-connected converter, the small signal dynamic model is constructed based on the dq axis component relation of the output voltage and the output current of the converter, and the first-order inertia characteristic of a current loop and a filtering link of power calculation are considered; The design module is configured to design a linear parameter change controller based on the small signal dynamic model, the parameters of the controller are adaptively adjusted along with the running state of the system, and an ideal diagonal ope