CN-121566431-B - Simulation analysis method and system for active power distribution network comprising variable frequency load

CN121566431BCN 121566431 BCN121566431 BCN 121566431BCN-121566431-B

Abstract

The invention discloses a simulation analysis method and a simulation analysis system for an active power distribution network comprising variable frequency loads, wherein the simulation analysis method comprises the steps of establishing models of the variable frequency loads at different levels, establishing steady-state power-voltage characteristic models of the variable frequency loads at static characteristic modeling layers, transient response models at dynamic response characteristic modeling layers, harmonic current injection models at harmonic characteristic modeling layers, frequency-power characteristic models at frequency response characteristic modeling layers and control logic models at control mode modeling layers, carrying out organic coupling on the models at different levels, determining input interface variables, output interface variables, internal state variables and coupling equations to determine variable frequency load comprehensive models, adopting a strategy of layering setting and joint optimization to set model parameters of the models at different levels to determine final variable frequency load comprehensive models, and carrying out simulation analysis on the active power distribution network based on the final variable frequency load comprehensive models.

Inventors

YIN XIAODONG
LIU JUNJIE
LIU JIAN
WANG JIAN
HUANG JUNJUN
SUN JIAHAO
SUN WENBO
YI SHUHUI
WANG GENRONG

Assignees

中国电力科学研究院有限公司

Dates

Publication Date: 20260508
Application Date: 20260120

Claims (12)

1. A method for simulation analysis of an active power distribution network comprising variable frequency loads, the method comprising: Establishing steady-state power-voltage characteristic models of variable frequency loads at static characteristic modeling layers, transient response models at dynamic response characteristic modeling layers, harmonic current injection models at harmonic characteristic modeling layers, frequency-power characteristic models at frequency response characteristic modeling layers and control logic models at control mode modeling layers; organically coupling the models of different layers, and determining input interface variables, output interface variables, internal state variables and coupling equations to determine a variable frequency load comprehensive model; Setting model parameters of different layers of models by adopting a strategy of layering setting and joint optimization, and determining a final variable frequency load comprehensive model; performing simulation analysis on the active power distribution network based on a final variable frequency load comprehensive model; The method for determining the variable frequency load comprehensive model comprises the following steps of organically coupling models of different layers, determining input interface variables, output interface variables, internal state variables and coupling equations, and determining the variable frequency load comprehensive model, wherein the method comprises the following steps: The input interface variables are determined as variables transferred from the power distribution network to the variable frequency load comprehensive model and comprise node voltage V (t), frequency f (t) and phase angle theta (t); The variable of the output interface is determined as the variable fed back to the distribution network from the variable frequency load comprehensive model, and the variable frequency load comprehensive model comprises fundamental wave active power P 1 (t), fundamental wave reactive power Q 1 (t) and various subharmonic currents I h (t); The internal state variables are determined as variables transferred between the layer models, and comprise a control state S (t), a dynamic state X (t) and a set power Pset (t); The coupling equation is determined as: Fundamental active power: , Fundamental reactive power: , Harmonic current: , Wherein, the 、 Active power and reactive power calculated for the static characteristic model respectively; Is a dynamic response transfer function; is a frequency response function; for the control state function, s=0, When the value of 0,S is =1, The method is determined by a climbing control sub-model and a variable load control sub-model; Harmonic currents calculated for the harmonic characteristic model; The coupling calculation of the variable frequency load comprehensive model is carried out according to the following sequence: (1) Acquisition from a distribution network ; (2) The control mode layer judges the start-stop state S (t) and calculates the set power ; (3) Static property layer computation 、 ; (4) Frequency response layer computation ; (5) Solving differential equation by dynamic response layer to obtain ; (6) Harmonic property layer computation ; (7) Will be And feeding back to the power distribution network.
2. The method of claim 1, wherein the method establishes the steady state power-voltage characteristic model by: , , Or (b) , , Wherein, P is active power, Q is reactive power; And Respectively rated voltage Active power and reactive power, V is actual voltage; And All are voltage indexes; =0 represents constant power; =1 represents constant current; =2 represents constant impedance; =1, =1, coefficient 、、、、、 Determined by least squares fitting.
3. The method of claim 1, wherein the method builds the transient response model using the following manner, comprising: For the load with the response speed smaller than the preset response speed, a first-order inertia link is adopted, and the method comprises the following steps: , for loads with overshoot or oscillation in the response process, a second-order inertial link is adopted, including: , Wherein, the The transfer function is a first-order inertial link transfer function; K is gain; Is a time constant; The transfer function is a second-order oscillation link transfer function; Is a natural frequency which is set to be a natural frequency, Is the damping ratio; is a Laplacian operator; Is the angular frequency.
4. The method of claim 1, wherein the method establishes the harmonic current injection model by: , Wherein, I h is h harmonic current, I h0 is h harmonic current amplitude under rated voltage, beta h is h harmonic voltage index, and theta h is h harmonic phase angle; Rated voltage, and V is actual voltage.
5. The method of claim 1, wherein the method establishes the frequency-power characteristic model by: when the frequency deviation is within the preset frequency deviation range, a linear model is adopted, and the method comprises the following steps: when the frequency deviation is not in the preset frequency deviation range, adopting a quadratic polynomial model, wherein the quadratic polynomial model comprises the following steps: , Wherein, the And The active power variable quantity and the reactive power variable quantity are respectively; K f,P and K f,Q are respectively the frequency adjustment coefficient of active power and the frequency adjustment coefficient of reactive power; And The primary frequency adjustment coefficient and the secondary frequency adjustment coefficient of the active power are respectively.
6. The method of claim 1, wherein the method builds the control logic model by: establishing a start-stop control sub-model, comprising: When (when) Or (b) When the delay reaches the stop delay, the machine stops, S=0, When (when) +ΔV<V< -When Δv and s=0, restarting after the delay reaches the restart delay, s=1; Establishing a climbing control sub-model, comprising: , establishing a variable load control sub-model, comprising: , Setting a PWM modulation mode, a control mode, a switching frequency, dead time and direct current bus voltage; wherein S is an operation state, 0 represents shutdown, 1 represents operation, V is actual voltage, and t is sampling time; And The voltage protection method comprises the steps of respectively obtaining a minimum threshold value and a maximum threshold value of voltage protection, wherein DeltaV is a voltage recovery margin; Is the climbing rate; p is the actual output power of the variable frequency load; to set power; is a deviation signal; 、、 Is a PID parameter; Is the deviation signal at the moment of the integral variable tau.
7. The method of claim 1, wherein the model parameters of the different level models are set by using a strategy of hierarchical setting and joint optimization, and determining the final variable frequency load comprehensive model comprises: When the steady-state power-voltage characteristic model is a polynomial model, the parameter setting is performed by adopting a least square method based on the steady-state operation data; for the transient response model, performing parameter setting by adopting a time domain fitting or frequency domain identification method based on disturbance test data; For a harmonic current injection model, carrying out parameter setting by adopting a fast Fourier transform and a least square method based on harmonic measurement data; for the frequency-power characteristic model, based on frequency disturbance test data, performing parameter setting by adopting a linear regression or polynomial fitting method; for the control logic model, setting control logic parameters based on control system design parameters and operation records; on the basis of layered setting, a nonlinear optimization algorithm is adopted to adjust global parameters so as to minimize the overall error of the model and determine a final variable frequency load comprehensive model, wherein the optimization objective function is as follows: , Wherein J is an overall optimization objective function value, w 1 、w 2 and w 3 are weight coefficients, 、、 Calculating a value for a model of the measurement point i; 、、 is the actual measurement value of the measurement point i, and h is the number of harmonics.
8. The method according to claim 1, wherein the method further comprises: when the load operating conditions change, the model parameters are updated with the new measurement data.
9. The method according to claim 1, wherein the method further comprises: When a plurality of variable frequency loads of the same type exist in the power distribution network, an equivalent aggregation model is established by adopting a statistical aggregation method to simulate based on the equivalent aggregation model, wherein parameters of the equivalent aggregation model are weighted averages of parameters of each single load, and weights are rated capacities of the loads.
10. A simulation analysis system for an active power distribution network comprising variable frequency loads, the system comprising: the model building unit is used for building models of variable frequency loads at different levels and comprises a steady-state power-voltage characteristic model of the variable frequency loads at a static characteristic modeling layer, a transient response model at a dynamic response characteristic modeling layer, a harmonic current injection model at a harmonic characteristic modeling layer, a frequency-power characteristic model at a frequency response characteristic modeling layer and a control logic model at a control mode modeling layer; The model coupling unit is used for carrying out organic coupling on models of different layers, and determining an input interface variable, an output interface variable, an internal state variable and a coupling equation so as to determine a variable frequency load comprehensive model; The parameter setting unit is used for setting model parameters of different layers of models by adopting a strategy of layering setting and joint optimization, and determining a final variable frequency load comprehensive model; the simulation analysis unit is used for carrying out simulation analysis on the active power distribution network based on the final variable frequency load comprehensive model; The model coupling unit is used for carrying out organic coupling on models of different layers to determine an input interface variable, an output interface variable, an internal state variable and a coupling equation so as to determine a variable frequency load comprehensive model, and comprises the following steps: The input interface variables are determined as variables transferred from the power distribution network to the variable frequency load comprehensive model and comprise node voltage V (t), frequency f (t) and phase angle theta (t); The variable of the output interface is determined as the variable fed back to the distribution network from the variable frequency load comprehensive model, and the variable frequency load comprehensive model comprises fundamental wave active power P 1 (t), fundamental wave reactive power Q 1 (t) and various subharmonic currents I h (t); The internal state variables are determined as variables transferred between the layer models, and comprise a control state S (t), a dynamic state X (t) and a set power Pset (t); The coupling equation is determined as: Fundamental active power: , Fundamental reactive power: , Harmonic current: , Wherein, the 、 Active power and reactive power calculated for the static characteristic model respectively; Is a dynamic response transfer function; is a frequency response function; for the control state function, s=0, When the value of 0,S is =1, The method is determined by a climbing control sub-model and a variable load control sub-model; Harmonic currents calculated for the harmonic characteristic model; The coupling calculation of the variable frequency load comprehensive model is carried out according to the following sequence: (1) Acquisition from a distribution network ; (2) The control mode layer judges the start-stop state S (t) and calculates the set power ; (3) Static property layer computation 、 ; (4) Frequency response layer computation ; (5) Solving differential equation by dynamic response layer to obtain ; (6) Harmonic property layer computation ; (7) Will be And feeding back to the power distribution network.
11. A computer readable storage medium, on which a computer program is stored, characterized in that the program, when being executed by a processor, implements the steps of the method according to any one of claims 1-9.
12. An electronic device, comprising: The computer-readable storage medium of claim 11, and One or more processors configured to execute the programs in the computer-readable storage medium.

Description

Simulation analysis method and system for active power distribution network comprising variable frequency load Technical Field The invention relates to the technical field of modeling and simulation of power systems, in particular to a simulation analysis method and a simulation analysis system of an active power distribution network containing variable-frequency loads. Background With the rapid development of power electronics technology and the deep advancement of energy transformation, electric power systems are undergoing a deep revolution. The proportion of variable frequency load in the distribution network is increasingly increased, and the variable frequency load is expected to account for more than 60% of the total load of the distribution network in 2030. The variable frequency load mainly comprises a variable frequency air conditioner (accounting for about 30%), a variable frequency motor (accounting for about 25%), an electric car charging pile (accounting for about 20%), a data center (accounting for about 15%) and other power electronic loads (accounting for about 10%). The variable frequency load has the remarkable characteristics that (1) the load presents strong nonlinearity due to a power electronic conversion link, a traditional linear model cannot be accurately described, (2) time variability is that load power is rapidly changed along with factors such as a control strategy and environmental conditions, (3) quick response is that the response speed of the variable frequency load to voltage and frequency disturbance is 1-2 orders of magnitude faster than that of the traditional load, (4) harmonic pollution is that a large amount of harmonic current is generated, so that the power quality of a power grid is reduced, (5) frequency sensitivity is that part of variable frequency load is sensitive to frequency variation, system frequency stability is affected, and (6) control complexity is that multiple control modes and control strategies are involved, and modeling difficulty is high. The characteristics have important influence on the stable operation and the electric energy quality of the power distribution network, and are mainly characterized in that (1) voltage fluctuation is increased, namely node voltage deviation is increased by 10-20%, harmonic pollution is serious, namely Total Harmonic Distortion (THD) exceeds standard, partial node THD reaches 15-25%, power factor is reduced, namely reactive power demand is increased, and the power factor is reduced from 0.95 to below 0.85, (4) frequency stability is reduced, namely the frequency response characteristic of the variable frequency load influences system inertia and damping, (5) malfunction of a protection device, namely relay protection malfunction rate is increased by more than 30% due to harmonic and rapid power change, (6) equipment life is shortened, namely equipment such as a transformer, a capacitor and the like is overheated due to electric energy quality deterioration, and the life is shortened by 20-30%. An accurate variable frequency load model is the basis for solving the above problems. At present, the variable frequency load modeling mainly comprises the following problems of 1. The precision of a traditional model is insufficient, 2. The modeling is difficult due to characteristic coupling, the static characteristic, the dynamic characteristic and the harmonic characteristic of the traditional model are often mixed and modeled to cause serious coupling among model parameters, 3. The control mode modeling is not complete, 4. The parameter setting method is imperfect, 5. The interpretation is poor, and 6. The data demand is large and difficult to obtain. These problems severely restrict the accurate modeling and simulation analysis of the active power distribution network, and influence the planning design, the optimized operation and the stable control of the power distribution network. Therefore, a high-precision variable frequency load modeling method is urgently needed, and the method is used for simulation analysis of an active power distribution network containing variable frequency loads. Disclosure of Invention The invention provides a simulation analysis method and a simulation analysis system for an active power distribution network containing variable frequency loads, which aim to solve the problem of how to perform simulation analysis on the active power distribution network containing high-proportion variable frequency loads. In order to solve the above problems, according to an aspect of the present invention, there is provided a simulation analysis method of an active power distribution network including a variable frequency load, the method comprising: Establishing steady-state power-voltage characteristic models of variable frequency loads at static characteristic modeling layers, transient response models at dynamic response characteristic modeling layers, harmonic current injection models at harmonic