Low-frequency oscillation simulation test method and system based on double-side power supply model

Abstract

The invention discloses a low-frequency oscillation simulation test method and system based on a double-side power supply model, and the method comprises the steps: providing a low-frequency oscillation signal output and oscillation power control algorithm suitable for simulating a power system based on the double-side power supply model according to the periodic oscillation, damped oscillation and out-of-step oscillation of low-frequency oscillation. The amplitude and the power of oscillation signals are controlled by modifying impedance parameters of power supplies, circuits and transformers on the two sides, a frequency superposition algorithm is provided for out-of-step oscillation, and the accuracy and the reliability of the signals are improved by considering different impedances under different frequencies; according to the method, the key electrical quantity during low-frequency oscillation of the power system is simulated through a practical and reliable algorithm, and great convenience is provided for research and test in the aspect of low-frequency oscillation of broadband oscillation monitoring equipment.

Description

Technical Field

[0001] The present invention relates to a method and system for simulating and testing low-frequency oscillations, and particularly to a method and system for simulating and testing low-frequency oscillations based on a bilateral power supply model. Background Art

[0002] With the development of modern power systems, the access of a high proportion of new energy and power electronic devices has given rise to new spatial and temporal characteristics of power system oscillations. Due to the influence of internal or external factors in the "dual-high" power system, the interaction between power electronic devices and between them and the power grid causes electrical quantities to fluctuate periodically over time, and the oscillation frequency varies within a wide range (0 - 2500 Hz). This dynamic process is called wide-frequency oscillation of the power system. Wide-frequency oscillation is classified according to the oscillation frequency band of power, including low-frequency oscillation (0.1 Hz - 2.5 Hz), sub-synchronous oscillation (2.5 Hz - 45 Hz), super-synchronous oscillation (55 Hz - 95 Hz), medium-frequency band oscillation (95 Hz - 300 Hz), and high-frequency band oscillation (300 Hz - 2500 Hz). The power grid is a complex non-linear system, and the high proportion of power electronics makes the analysis and suppression of power system oscillations more difficult.

[0003] For frequency oscillations, traditional PMUs generally use low-pass filters to ensure the measurement of signals in the range of 45 - 55 Hz to guarantee measurement accuracy, which cannot meet the requirements of wide-frequency oscillation measurement. With the deepening of research, both State Grid and Southern Power Grid have formulated relevant technical specifications for wide-frequency oscillation measurement devices, and the research of equipment has gradually become standardized and attempts to replace traditional PMUs.

[0004] Currently, in order to verify the performance of wide-frequency oscillation measurement devices, methods such as RTDS simulation, power quality testers, and dynamic simulation tests are usually adopted. However, RTDS simulation is costly and difficult to apply in engineering practice. Power quality testers cannot truly reflect the deficiencies of grid oscillation problems. Although dynamic simulation tests are accurate and reliable, they are complex to operate and costly, and cannot be flexibly used in engineering. Summary of the Invention

[0005] Object of the Invention: The object of the present invention is to provide a method for simulating and testing low-frequency oscillations based on a bilateral power supply model to effectively evaluate the operating performance of the power system under different low-frequency oscillation patterns. On the other hand, a system for simulating and testing low-frequency oscillations based on a bilateral power supply model is provided.

[0006] Technical Solution: A method for simulating and testing low-frequency oscillations based on a bilateral power supply model according to the present invention includes the following steps:

[0007] (1) Classify the low-frequency oscillations of the power grid into three oscillation patterns, namely periodic oscillation, damped oscillation, and out-of-step oscillation;

[0008] (2) Adjust the voltage, frequency, and internal resistance parameters of the power supplies on both sides of the bilateral power supply model, as well as the line impedance and transformer impedance, according to different low-frequency oscillation patterns, to generate a target oscillation simulation signal, where the target oscillation simulation signal includes voltage, current, and oscillation power;

[0009] (3) The testing equipment outputs the corresponding oscillation simulation signal.

[0010] Preferably, it is characterized in that step 2 specifically includes:

[0011] (21) When the low-frequency oscillation pattern is periodic oscillation or decaying oscillation, fix the power supply parameters of one side of the bilateral power supply model, set the other side to an infinite system, and analyze according to the single-machine infinite-bus system model;

[0012] (22) When the low-frequency oscillation pattern is out-of-step oscillation, analyze according to the bilateral power supply model, and use the frequency superposition algorithm to improve the model accuracy.

[0013] Preferably, the model adopted for the periodic oscillation in step 21 is:

[0014] δ = δ0 + Δδ m cos(ω osc t);

[0015] The corresponding power angle difference is:

[0016] Δδ(t) = Δω(t)t = Δδ m cos(ω osc t);

[0017] Among them, δ0 represents the initial power angle, and ω osc represents the low-frequency oscillation frequency.

[0018] Preferably, the calculation formula for the target oscillation simulation signal of the periodic oscillation is:

[0019]

[0020] Among them, I(t) represents the instantaneous value of the current, U G (t) represents the generator terminal voltage, U L (t) represents the bus voltage at the line head, P represents the oscillation power, E represents the generator voltage, and U represents the system voltage.

[0021] Preferably, the model adopted for the decaying oscillation in step 21 is:

[0022]

[0023] The corresponding power angle difference is:

[0024]

[0025] Among them, τ represents the oscillation decay time constant.

[0026] Preferably, the calculation formula for the target oscillation simulation signal of the damped oscillation is:

[0027]

[0028]

[0029] Preferably, the calculation formula for the target oscillation simulation signal of the out-of-step oscillation using the model in step 22 is:

[0030]

[0031] Among them, I swi represents the oscillating current after superposition, U P (t) represents the voltage of node P, U Q (t) represents the voltage of node Q, δ” represents the power angle difference between the two power sources, E P and E Q respectively represent the voltages of the two generators.

[0032] A low-frequency oscillation simulation test system based on a two-sided power source model according to the present invention includes:

[0033] A two-sided power source model for simulating the supply and demand sides of a power system;

[0034] A test signal output module for outputting a target oscillation simulation signal;

[0035] A data acquisition and analysis module for acquiring and analyzing test signals and comparing and analyzing them with an actual power grid;

[0036] A control module for adjusting the voltage, frequency, and internal resistance parameters of the two power sources on both sides of the two-sided power source model, as well as the line impedance and transformer impedance, and controlling the operation of the model according to the set oscillation pattern.

[0037] A computer device includes one or more processors, a memory, and one or more programs, wherein the one or more programs are stored in the memory and are configured to be executed by the one or more processors, and when the program is executed by the processor, it implements the steps of a low-frequency oscillation simulation test method based on a two-sided power source model according to any one of claims 1-7.

[0038] A computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, it implements the steps of a low-frequency oscillation simulation test method based on a two-sided power source model according to any one of claims 1-7.

[0039] Beneficial effects: Compared with the prior art, the present invention has the following remarkable advantages: 1. The simulation method based on the bilateral power source oscillation model can be used to simulate different oscillation types and power conditions, and can effectively evaluate the operating performance of the power system under different low-frequency oscillation patterns; 2. It can simulate three low-frequency oscillation conditions of periodic oscillation, decaying oscillation, and out-of-step oscillation, providing a more practical means for in-depth study of low-frequency oscillation characteristics and influences; 3. By simulating and generating accurate low-frequency and ultra-low-frequency oscillation signals, it provides a more effective research tool for researchers. Description of the Drawings

[0040] Figure 1 It is a schematic diagram of the out-of-step bilateral power source oscillation model and equivalent circuit of the present invention;

[0041] Figure 2 It is a schematic diagram of the single-machine infinite system and equivalent circuit of the present invention. Detailed Embodiments

[0042] The technical solution of the present invention will be described in detail below with reference to the drawings.

[0043] Embodiment 1

[0044] This embodiment provides a low-frequency oscillation simulation test method based on a bilateral power source model. For the simulation test of low-frequency periodic oscillation, the algorithm is solidified in the test equipment through a program, and one side of the power source and the line impedance are used as setting parameters.

[0045] When the simulation test equipment outputs, the voltage U of the infinite system remains a constant value. By adjusting δ0, Δδ m and ω osc to control the oscillation power, relevant oscillation simulation signals are output; according to the static stability limit and the actual operation, the value of δ0 is in the range of 30° - 60°, and the typical value can be 60°. To ensure stability, δ0 + Δδ m should be less than 90°; when δ0 is 60°, Δδ m should be within 30°, and the typical value can be 15°; the low-frequency oscillation frequency ω osc has a value range of 0.1 - 2.5 Hz.

[0046] Let the modulus of the generator impedance be X G , the modulus of the transformer impedance be X T , and the modulus of the line impedance be X L ;

[0047] X ∑ = X G + X T + X L ;

[0048] The power angle difference can be expressed as:

[0049] Δδ(t) = Δω(t)t = Δδ m cos(ω osc t);

[0050] Then the instantaneous current value is:

[0051]

[0052] The generator outlet voltage is:

[0053]

[0054] The voltage of the bus at the head of the line is:

[0055]

[0056] According to the classical stability theory, the oscillating power is expressed as:

[0057]

[0058] δ = δ0 + Δδ m cos(ω osc t);

[0059] Among them, Δδ(t) represents the power angle difference, I(t) represents the instantaneous current value, U G (t) represents the generator outlet voltage, U L (t) represents the voltage of the bus at the head of the line, P represents the oscillating power, E represents the generator voltage, and U represents the system voltage.

[0060] When the tester outputs, the current and voltage on the primary or secondary side of the transformer can be selected as the test data according to needs.

[0061] Embodiment 2

[0062] For the simulation test of low-frequency decaying oscillation, it can be slightly modified on the basis of the periodic oscillation test. Only an oscillation decay time constant τ needs to be additionally considered, which can generally be taken as several seconds.

[0063] The power angle difference can be expressed as:

[0064]

[0065] Then the instantaneous current value is:

[0066]

[0067] The generator outlet voltage is:

[0068]

[0069] The voltage of the bus at the head of the line is:

[0070]

[0071] The oscillating power is expressed as:

[0072]

[0073] where Δδ(t) represents the power angle difference, I(t) represents the instantaneous value of current, U G (t) represents the generator terminal voltage, U L (t) represents the bus voltage at the head of the line, P represents the oscillating power, E represents the generator voltage, and U represents the system voltage.

[0074] Embodiment 3

[0075] When the oscillation diverges, the power angle difference is a function of the oscillation growth. The final result is that the generator angular frequency significantly deviates from the system frequency, and this difference can be directly reflected by the difference in frequencies on both sides. Therefore, for the out-of-step oscillation test, the algorithm is solidified in the test equipment through a program. The frequencies of the bilateral power supplies are adjusted, and the bilateral power supply model is simplified into two unilateral models based on the system frequencies on each side. Using the superposition algorithm, the electrical quantities at different system frequencies are derived respectively, and finally superimposed together to obtain the required electrical quantities.

[0076] Suppose the electromotive forces of the synchronous generators on both sides are respectively:

[0077] E P (t) = e P sin(2πf1t + δ0);

[0078] E Q (t) = e Q sin(2πf2t);

[0079] The frequencies f1 and f2 of the power supplies on both sides need to take appropriate values, and the oscillation period should not exceed 3 seconds at most, and the typical value can be taken as 1 - 3 seconds. f1 can be taken as 50.33 - 51 Hz, and f2 can be taken as 50.00 Hz. Based on the bilateral power supply model, the total impedance Z ∑ = Z P + Z PQ + Z Q , and the impedance angle is The oscillating current I swi and the voltages at points P and Q are obtained according to the frequency superposition algorithm.

[0080] Only considering F P :

[0081] The instantaneous value of the current is:

[0082]

[0083] The voltage of node P is:

[0084]

[0085] The voltage of node Q is:

[0086]

[0087] Only considering E Q when:

[0088] The instantaneous value of the current is:

[0089]

[0090] The voltage of node P is:

[0091]

[0092] The voltage of node Q is:

[0093]

[0094] After superposition, the oscillating current I swi , the voltage of node P and the voltage of node Q are obtained;

[0095]

[0096] The oscillating power is expressed as:

[0097]

[0098] Among them, I swi represents the oscillating current obtained after superposition, U P (t) represents the voltage of node P, U Q (t) represents the voltage of node Q, δ” represents the power angle difference between the two sides of the power source, F P , E Q respectively represent the generator voltages on both sides; during the test, the electrical quantities at point P or point Q can be selected according to needs.

Claims

1. A low-frequency oscillation simulation test method based on a bilateral power supply model, characterized in that Including: (1) Classify the low-frequency oscillations of the power grid into three oscillation forms, namely periodic oscillation, damped oscillation, and out-of-step oscillation; (2) According to different low-frequency oscillation forms, adjust the voltage, frequency, and internal resistance parameters of the power supplies on both sides of the bilateral power supply model, as well as the line impedance and transformer impedance, to generate a target oscillation simulation signal, where the target oscillation simulation signal includes voltage, current, and oscillation power; (3) The test equipment outputs the corresponding oscillation simulation signal.

2. The low-frequency oscillation simulation test method according to claim 1, characterized in that Step 2 specifically includes: (21) When the low-frequency oscillation form is periodic oscillation or damped oscillation, fix the power supply parameters on one side of the bilateral power supply model and set the other side to an infinite system, and analyze according to the single-machine - infinite system model; (22) When the low-frequency oscillation form is out-of-step oscillation, analyze according to the bilateral power supply model and use the frequency superposition algorithm.

3. The low-frequency oscillation simulation test method according to claim 2, characterized in that The model adopted for the periodic oscillation in Step 21 is: δ = δ0 + Δδ m cos(ω osc t); The corresponding power angle difference is: Δδ(t) = Δω(t)t = Δδ m cos(ω osc t); Among them, δ0 represents the initial power angle, and ω osc represents the low-frequency oscillation frequency.

4. The low-frequency oscillation simulation test method according to claim 3, characterized in that The calculation formula for the target oscillation simulation signal of the periodic oscillation is: Among them, I(t) represents the instantaneous value of current, and U G (t) represents the voltage at the generator outlet, and U L (t) represents the voltage of the bus at the head of the line. P represents the oscillating power, E represents the generator voltage, and U represents the system voltage.

5. The low-frequency oscillation simulation test method according to claim 2, wherein The model adopted for the damped oscillation in Step 21 is: The corresponding power angle difference is: Among them, τ represents the oscillation decay time constant.

6. The low-frequency oscillation simulation test method according to claim 5, wherein, The calculation formula for the target oscillation simulation signal of the damped oscillation is:

7. The low-frequency oscillation simulation test method according to claim 2, wherein The calculation formula for the target oscillation simulation signal of the model adopted for the out-of-step oscillation in Step 22 is: Among them, I swi represents the oscillating current after superposition, and U P (t) represents the voltage of node P, and U Q (t) represents the voltage of node Q. δ” represents the power angle difference between the two power sources, and E P , E Q respectively represent the voltages of the two generators.

8. A low-frequency oscillation simulation test system based on a bilateral power supply model, characterized in that, Including: A bilateral power supply model for simulating the supply and demand sides of the power system; A test signal output module for outputting a target oscillation simulation signal; A data acquisition and analysis module for acquiring and analyzing test signals and comparing and analyzing them with the actual power grid; A control module for adjusting the voltage, frequency, and internal resistance parameters of the power supplies on both sides of the bilateral power supply model, as well as the line impedance and transformer impedance, and controlling the operation of the model according to the set oscillation form.

9. A computer device, characterized in that, Including one or more processors, a memory, and one or more programs, where the one or more programs are stored in the memory and are configured to be executed by the one or more processors, and when the program is executed by the processor, it implements the steps of a method for low-frequency oscillation simulation test based on a bilateral power supply model as described in any one of claims 1-7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the steps of a method for low-frequency oscillation simulation test based on a bilateral power supply model as described in any one of claims 1-7.

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