CN-121984024-A - Equivalent inertia evaluation method and system considering anti-damping-frequency modulation interference

CN121984024ACN 121984024 ACN121984024 ACN 121984024ACN-121984024-A

Abstract

The invention discloses an equivalent inertia evaluation method and system considering anti-damping-frequency modulation interference, wherein the method comprises the steps of collecting the active power data of each node frequency and equipment port before and after system disturbance, and determining disturbance moment based on frequency information entropy in a sliding window; the method comprises the steps of carrying out interpolation, filtering and per unit pretreatment on subsequent data, obtaining frequency change rate and active power response through self-adaptive fitting, calculating damping-frequency modulation capacity characterization factors, further separating pure inertia components from equipment power response, combining equipment power-frequency response models and sliding window variance optimization, identifying inertia time constants of power electronic equipment and a synchronous machine, finally obtaining power node inertia through aggregation, and obtaining non-power node equivalent inertia according to frequency change rate difference distribution among nodes. The method effectively overcomes the interference of equipment damping and frequency modulation on inertia evaluation, and is suitable for a novel power system with increasingly aggravated power electronics.

Inventors

LIN GANG
LIN XIAOYUAN
LI YONG
MA JUNJIE
WANG WEIYU

Assignees

湖南大学

Dates

Publication Date: 20260505
Application Date: 20260407

Claims (7)

1. An equivalent inertia evaluation method considering anti-damping-frequency modulation interference, which is characterized by comprising the following steps: s1, acquiring frequency measurement signals of all nodes of an electric power system in real time, calculating frequency information entropy based on the distribution characteristics of the frequency measurement signals in a sliding time window, and determining the occurrence time of system power disturbance according to abrupt change of the frequency information entropy; S2, preprocessing a subsequent frequency signal and a subsequent port active power signal by taking the disturbance occurrence moment as a starting point to obtain preprocessed time sequence data; S3, respectively acquiring the instantaneous change rate of the node frequency and the active power response of each power generation device based on the preprocessed time sequence data, calculating the adjustment parameters used for representing and compensating the damping and frequency modulation dynamics of the power generation devices, and calculating the corresponding initial value sequence of the inertia time constant based on the adjustment parameters, the frequency change rate and the active power response through a power-frequency dynamic relation model of the power generation devices; And S4, based on the inertia time constants of the power generation equipment, aggregating the inertia time constants of the power generation equipment connected to the same power supply node to obtain the equivalent inertia of the power supply node, and calculating the equivalent inertia of the non-power supply node according to the relative relation of the frequency change rate between the non-power supply node and the associated power supply node in the area and combining the equivalent inertia of the associated power supply node.
2. The method for evaluating the equivalent inertia considering anti-damping-frequency modulation interference according to claim 1, wherein the step S1 specifically comprises: S11, segmenting the obtained node frequency data by using a sliding time window with the length of n and the step length of 1, and calculating the frequency sample distribution probability after the basic value component is removed in each window; s12, calculating the frequency information entropy of each sliding time window according to the frequency sample distribution probability; And S13, setting a frequency information entropy threshold value as epsilon, and judging the ending moment of the current window as the system disturbance occurrence moment when the frequency information entropy of two adjacent sliding time windows meets the condition that the entropy value of the previous window is smaller than epsilon and the entropy value of the current window is larger than or equal to epsilon.
3. The method for evaluating the equivalent inertia considering anti-damping-frequency modulation interference according to claim 1, wherein the preprocessing in the step S2 comprises interpolating missing data by newton interpolation, and filtering high-frequency noise of the node frequency data by using a low-pass butterworth filter, wherein the cut-off frequency of the low-pass butterworth filter is set to be 0.667Hz.
4. The method for evaluating the equivalent inertia considering anti-damping-frequency modulation interference according to claim 1, wherein the step S3 specifically comprises: S31, fitting a node frequency curve and an equipment port active power curve respectively by adopting self-adaptive variable order polynomial fitting to obtain the frequency change rate and the instantaneous change quantity of the equipment port active power; s32, aiming at synchronous power generation equipment, selecting the lowest frequency point and the like after disturbance as special working points, and calculating a reheating time constant and a first characterization factor of damping-frequency modulation capacity; S33, selecting two short-time working points of the power electronic equipment after disturbance and before primary frequency modulation action of the power electronic equipment, and calculating damping-frequency modulation capacity characterization factors of the power electronic equipment according to a power-frequency response equation and a difference calculation method of the power electronic equipment; S34, selecting two working points with nonzero frequency change rate after disturbance aiming at synchronous power generation equipment, and calculating a second characterization factor of damping-frequency modulation capacity based on a synchronous machine power-frequency response equation; S35, substituting the characterization factors and parameters obtained in the steps S32, S33 and S34 into corresponding equipment power-frequency response models, and calculating an inertia time constant in a set identification time window; S36, calculating variances of all inertial time constant samples in the identification time window, sliding the identification time window, repeating variance calculation, and determining an average value of the inertial time constants in the identification time window corresponding to the minimum sample variance as a final identification result of the inertial time constant of the equipment.
5. The method for evaluating equivalent inertia according to claim 4, wherein in step S31, the order determining method of the adaptive variable order polynomial fitting is to set a fitting deviation tolerance, start fitting from an initial order, and if the deviation between fitting results after adding one order is greater than the fitting deviation tolerance, continue adding the order until the deviation between fitting results obtained by adding the order is less than or equal to the fitting deviation tolerance.
6. The method for evaluating the equivalent inertia considering anti-damping-frequency modulation interference according to claim 1, wherein the step S4 specifically comprises: S41, power supply node inertia aggregation, namely carrying out weighted aggregation calculation on the equipment inertia time constant obtained in the step S3 to obtain inertia of each power supply node; S42, non-power supply node inertia distribution, namely, for any non-power supply node, obtaining the equivalent inertia of the power supply node closest to the power supply node in the electrical area where the non-power supply node is located and the frequency change rate of the power supply node and the non-power supply node, and calculating the equivalent inertia of the non-power supply node according to the difference of the frequency change rates of the power supply node and the non-power supply node.
7. An equivalent inertia assessment system that accounts for anti-damping-frequency modulation disturbances, comprising: The system comprises a data acquisition and disturbance detection module, a frequency information entropy calculation module, a system power disturbance generation module, a power disturbance generation module and a power disturbance detection module, wherein the data acquisition and disturbance detection module is used for acquiring frequency measurement signals of all nodes of a power system in real time, calculating frequency information entropy based on the distribution characteristics of the frequency measurement signals in a sliding time window, and determining the occurrence time of the system power disturbance according to the mutation of the frequency information entropy; the data preprocessing module is used for preprocessing the subsequent frequency signals and the subsequent port active power signals by taking the disturbance occurrence moment as a starting point to obtain preprocessed time sequence data; The equipment inertia time constant identification module is used for respectively acquiring the node frequency instantaneous change rate and the active power response quantity of each power generation equipment based on the preprocessed time sequence data, calculating the adjustment parameters used for representing and compensating the damping and frequency modulation dynamics of the power generation equipment, and calculating through a power-frequency dynamic relation model of the power generation equipment based on the adjustment parameters, the frequency change rate and the active power response quantity to obtain a corresponding inertia time constant initial value sequence; The node equivalent inertia calculation module is used for aggregating the inertia time constants of the power generation equipment connected to the same power supply node based on the inertia time constants of the power generation equipment to obtain the equivalent inertia of the power supply node, and calculating the equivalent inertia of the non-power supply node according to the relative relation of the frequency change rate between the non-power supply node and the associated power supply node in the area and combining the equivalent inertia of the associated power supply node.

Description

Equivalent inertia evaluation method and system considering anti-damping-frequency modulation interference Technical Field The invention relates to the technical field of analysis and control of electric power systems, in particular to an equivalent inertia evaluation method and system considering damping resistance-frequency modulation interference. Background Inertia is a key physical quantity that measures the ability of an electrical power system to resist frequency changes, and is typically expressed in terms of an inertial time constant. In a conventional synchronous machine-based power system, when power disturbance occurs, kinetic energy stored in a rotor of the synchronous machine is spontaneously released, and inertia support is provided to buffer rapid changes of frequency, so that time is striven for frequency modulation actions. However, as the proportion of power generation equipment such as wind power, photovoltaic and the like which are connected through a power electronic converter is continuously increased, the overall inertia level of the system is reduced. This is because such devices do not have a rotating mass per se, or their rotating parts are decoupled from the grid by means of a current transformer, which cannot provide inertia as directly as a synchronous machine. Although some new energy devices simulate inertia response characteristics through a control algorithm, the supporting capacity of the new energy devices is limited and the characteristics of the new energy devices are different from those of the traditional synchronous machines. The reduction in system inertia significantly increases the risk of frequency instability after high power disturbances. Therefore, the inertia actually provided by various devices in the system and the equivalent inertia of each network node are accurately evaluated, and the method has important significance for grasping the safety situation of the system frequency and optimizing the scheduling and control strategy. The existing inertia evaluation method mainly has the following defects that a highly simplified power-frequency first-order model is generally adopted at the equipment level, and the inherent damping effect and the quick response of an active frequency modulation function of equipment are ignored. This results in erroneous accounting of the power response that would otherwise be attributed to damping or primary frequency modulation into the inertial response when identifying the inertial time constant, resulting in a false high identification result and misleading safety assessment. For synchronous machines, the detailed structures of the prime motor and the speed regulator are not considered, so that the model has larger deviation from the actual dynamic state. At the node level, the prior method is not practical because the prior method depends on a simplified model and does not consider the disturbance of the device dynamics or needs the prior information which is difficult to obtain and is the theoretical value of the inertia of the known system. Therefore, a method and system for effectively stripping damping and frequency modulation interference, thereby realizing high-precision and high-confidence assessment of equivalent inertia of equipment and nodes is needed. Disclosure of Invention The invention provides an equivalent inertia evaluation method and an equivalent inertia evaluation system considering anti-damping-frequency modulation interference, wherein the method can effectively strip damping and frequency modulation interference, accurately separate a pure inertia response component of equipment from measurement data, remarkably improve the accuracy of inertia evaluation, and is suitable for a novel power system comprising high-proportion power electronic equipment. In a first aspect, a method for evaluating equivalent inertia considering anti-damping-frequency modulation interference includes: s1, acquiring frequency measurement signals of all nodes of an electric power system in real time, calculating frequency information entropy based on the distribution characteristics of the frequency measurement signals in a sliding time window, and determining the occurrence time of system power disturbance according to abrupt change of the frequency information entropy; S2, preprocessing a subsequent frequency signal and a subsequent port active power signal by taking the disturbance occurrence moment as a starting point to obtain preprocessed time sequence data; s3, respectively acquiring the instantaneous change rate of the node frequency and the active power response of each power generation device based on the preprocessed time sequence data, calculating the adjustment parameters used for representing and compensating the damping and frequency modulation dynamics of the power generation devices, and calculating the corresponding initial value sequence of the inertia time constant based on the adjustment parameters, the fr