Control method for stable output of interconnected power system

Abstract

The invention provides a control method for stable output of an interconnected power system. The control method comprises the following steps: S1, establishing a kinetic equation of a mathematical model of a target interconnected power system; s2, obtaining an error evolution equation; s3, obtaining an interconnection system coupling equation; s4, replacing the initial control target function with the actual control target function, inputting the actual control target function into the interconnection system coupling equation, tracking the actual control target function by the interconnection system coupling equation, generating a real-time system error value, and performing control target tracking; s5, when the real-time system error value is not zero, the system outputs a target value which is not accurately tracked; at the moment, replacing the actual control target function with a real-time system error value, and executing S4 again; and when the real-time system error value is zero, the system output value reaches the target value, the interconnection system coupling equation stops error adjustment, and the power system stably outputs. According to the invention, the problems of voltage and current fluctuation, frequency oscillation and the like of the system can be effectively suppressed.

Description

Technical Field

[0001] The present invention relates to the technical field of interconnected power systems, and more particularly, to a control method for stable output of an interconnected power system. Background Art

[0002] The development of power systems tends to be in the direction of wide-area and intelligent development. Major power systems are connected through networks to form a large interconnected power system across the country, making the transmission of electric energy simple and convenient. However, the interconnection of power systems makes the system more complex, with more interference factors, and the system stability problem has become one of the control difficulties. In recent years, some interconnected power systems have also encountered situations of system voltage and frequency distortion, seriously affecting the reliability of power supply. The classical traditional control theory has an ineffective control effect on the stability of such complex systems.

[0003] In recent years, with the rapid development of power grid technology, there has been a phenomenon that conventional power systems can no longer meet the growing electricity load demand. Therefore, interconnected power systems have gradually emerged. At the same time, with the growth of the power output demand of the power generation part, the grid connection of distributed generation power sources and traditional power grids has gradually emerged, and a more flexible and efficient new type of interconnected power system has been formed. Its complexity has been further improved, resulting in frequent occurrence of external disturbances that cause the system to finally become unstable. Power systems often experience asynchronous operation, frequency collapse, and voltage collapse due to being disturbed. Especially when affected by various external factors and the nonlinear characteristics of the system itself, power systems will exhibit chaotic oscillation phenomena, causing a huge impact on the operation of the entire interconnected power grid. The chaotic oscillation is often accompanied by severe chattering phenomena, increasing the complexity and uncertainty of the entire power network and endangering the safe and reliable operation of the system. These problems are the focus of the stability research of interconnected power systems.

[0004] An interconnected power system is a typical complex dynamic system with characteristics such as strong coupling, complex variables, and many interference factors. Therefore, chaotic phenomena often occur. The existence of this phenomenon causes hazards such as unstable system voltage and frequency oscillation, and even large-scale power outages, which will seriously affect the power supply reliability of the power grid. Therefore, it is of great significance to adopt an effective and fast control method to control the interconnected power system. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to propose a control method for stable output of an interconnected power system to solve the technical problems of unstable voltage and frequency oscillation in existing interconnected power systems.

[0006] The technical means adopted by the present invention are as follows:

[0007] A control method for stable output of an interconnected power system includes the following steps:

[0008] S1. Establish the dynamic equation of the mathematical model of the target interconnected power system;

[0009] S2. Set the initial control objective function and the system error expression of the dynamic equation to obtain the evolution equation of the error;

[0010] S3. Apply coupling control to the mathematical model of the target interconnected power system, set the coupling function to couple the second-order interconnected power system model with the evolution equation of the error, and obtain the interconnected system coupling equation;

[0011] S4. Substitute the actual control objective function for the initial control objective function and input it into the interconnected system coupling equation to generate a real-time system error value for control objective tracking;

[0012] S5. When the real-time system error value is not zero, the system output fails to accurately track the target value; at this time, substitute the real-time system error value for the actual control objective function and re-execute S4;

[0013] When the real-time system error value is zero, the system output value reaches the target value, the interconnected system coupling equation stops error adjustment, realizes system target value tracking, and the power system outputs stably.

[0014] Further, S1 specifically includes the following steps:

[0015] Referring to the actual performance index, based on the mathematical model, obtain the dynamic equation of the mathematical model of the target interconnected power system with periodic load;

[0016] The original dynamic equation of the mathematical model of the target interconnected power system is:

[0017]

[0018] In the formula, δ is the phase angle difference between the excitation potential and the terminal voltage, with the unit of rad; ω is the angular velocity of the generator, with the unit of rad / s; P s is the amplitude of the electromagnetic power, P m is the amplitude of the mechanical power, P k is the amplitude of the electromagnetic disturbance, P e is the amplitude of the load disturbance, with the unit of W; α is the electromagnetic power disturbance frequency, β is the load disturbance frequency, with the unit of Hz; H is the equivalent moment of inertia, with the unit of kg·m 2 ; D is the equivalent damping coefficient, with the unit of N.m.s / rad, τ is a dimensionless time variable, with the unit of s;

[0019] Perform coordinate transformation on the original dynamic equation to obtain the dynamic equation of the mathematical model of the target interconnected power system. The coordinate transformation is as follows: x1 = δ, ρ = P m / P s ,v = P k / P s ,μ = P e / P s , The dynamic equation of the mathematical model of the target interconnected power system is as follows:

[0020]

[0021] Furthermore, S2 specifically includes the following steps:

[0022] Set the initial control objective function as The system error expressions are e1 = x1 - s and e2 = x2 - s, then the evolution equation of the error of the dynamic equation of the mathematical model of the target interconnected power system is:

[0023]

[0024] Wherein,

[0025]

[0026] Furthermore, S3 specifically includes the following steps:

[0027] Set the coupling functions as M1 = f(s) - U and M2 = f(s) - V. By coupling the dynamic equation of the mathematical model of the target interconnected power system with the evolution equation of the error, the coupled equation of the interconnected system is obtained, and the formula is as follows:

[0028]

[0029] The coefficient matrix J therein is the Jacobi matrix, and the formula is as follows:

[0030]

[0031] Use the eigenvalue analysis method to determine the system stability of the coupled equation of the interconnected system. The eigenvalue equation corresponding to the Jacobi matrix is:

[0032]

[0033] Obtain λ i1 = -1, λ i2 = -ε. According to the stability theory, if all the eigenvalues obtained from the eigenvalue equation corresponding to the Jacobi matrix are negative values, then when t → ∞, the error variable Prove that the system has been effectively suppressed.

[0034] Furthermore, S4 specifically includes the following steps:

[0035] Set the actual control objective function as s = Asint, and take the amplitude A = 0.5; the coupling equation of the interconnected system tracks the external signal in real time under the conditions of arbitrary initial values and uncertain system disturbances, and generates the real-time system error value based on the system error expression.

[0036] Further, the interconnected power system is composed of two power systems connected to each other through a tie line, and each power system can be simplified into a power system with a second-order dynamic model.

[0037] The present invention also provides a storage medium, which includes a stored program. When the program runs, it executes the control method for the stable output of the interconnected power system as described in any one of the above.

[0038] The present invention also provides an electronic device, which includes a memory, a processor, and a computer program stored on the memory and executable on the processor. The processor executes the control method for the stable output of the interconnected power system as described in any one of the above through the running of the computer program.

[0039] Compared with the prior art, the present invention has the following advantages:

[0040] The present invention breaks through the limitation of the system tracking target signal type, takes any type of external signal given as the input as the target value, selects a specific coupling function to simplify the complex nonlinear system control model, and effectively optimizes the control process of the complex system. The system is coupled with the external signal through the coupling function to achieve the tracking of the external signal, and effectively suppresses the fluctuations of signals such as the voltage of the system in a short time. The simulation and verification show that the control technology has the advantages of simple method, fast timeliness, and good control effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0042] Figure 1 It is a flowchart of the method of the present invention.

[0043] Figure 2 It is an evolution diagram of the state variables of the present invention over time.

[0044] Figure 3 It is a phase diagram of the state equation of the present invention.

[0045] Figure 4 It is an evolution diagram of the system state variables of the present invention over time. Detailed implementation manners

[0046] To enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0047] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned accompanying drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0048] The present invention takes a second-order interconnected power system (i.e., a power system in which two power systems are interconnected by a tie line and each system can be simplified to a second-order dynamic model) as the research object, and proposes an effective method for controlling the stable output of the interconnected power system. By inputting an external signal of any given type and coupling the second-order interconnected power system with the external signal, the system can track this external signal, thereby effectively suppressing problems such as voltage, current fluctuations and frequency oscillations of the system. The present invention further verifies this control technology through simulation, and finds that this method is simple and effective.

[0049] As Figure 1 shown, the present invention provides a control method for the stable output of an interconnected power system, including the following steps:

[0050] S1. Establish the dynamic equation of the mathematical model of the target interconnected power system;

[0051] Based on the actual performance index, the dynamic equation of the mathematical model of the target interconnected power system with periodic load is obtained based on the mathematical model;

[0052] The original dynamic equation of the mathematical model of the target interconnected power system is:

[0053]

[0054] where δ is the phase angle difference between the excitation potential and the terminal voltage, with the unit of rad; ω is the angular velocity of the generator, with the unit of rad / s; P s 、P m 、P k and P e are the amplitudes of electromagnetic power, mechanical power, electromagnetic disturbance, and load disturbance respectively, with the unit of W; α and β represent the electromagnetic power disturbance frequency and the load disturbance frequency respectively, with the unit of Hz; H is the equivalent moment of inertia, with the unit of kg·m 2 ; D is the equivalent damping coefficient, with the unit of N.m.s / rad, τ is a dimensionless time variable, with the unit of s;

[0055] To facilitate the analysis of the dynamic characteristics of the above interconnected power system, a coordinate transformation is performed on the original dynamic equation to obtain the dynamic equation of the mathematical model of the target interconnected power system. The coordinate transformation is as follows: x1 = δ, ρ = P m / P s , v = P k / P s , μ = P e / P s , The dynamic equation of the mathematical model of the target interconnected power system is:

[0056]

[0057] where the parameters are ε = 0.4, μ = 0.02, ρ = 0.2, η = γ = 0.8, v = 1.3. The evolution of the state variables of the simulation system over time and the phase diagram are as shown in Figure 2 and Figure 3 .

[0058] S2. Set the initial control objective function and the system error expression of the dynamic equation to obtain the evolution equation of the error;

[0059] Set the external signal, that is, the initial control objective function, as The system error expression is e1 = x1 - s, e2 = x2 - s. Then the evolution equation of the error of the dynamic equation of the mathematical model of the target interconnected power system is:

[0060]

[0061] where,

[0062]

[0063] S3. Apply coupling control to the mathematical model of the target interconnected power system, set the coupling function to couple the second-order interconnected power system model with the evolution equation of the error, and obtain the interconnected system coupling equation;

[0064] Set the coupling functions as \(M_1 = f(s)-U\) and \(M_2 = f(s)-V\). By coupling the dynamic equations of the mathematical model of the target interconnected power system with the evolution equations of the errors, the coupling equations of the interconnected system are obtained as follows:

[0065]

[0066] The coefficient matrix therein is the Jacobi matrix, as follows:

[0067]

[0068] Use the eigenvalue analysis method to determine the system stability of the coupling equations of the interconnected system. The eigenvalue equation corresponding to the Jacobi matrix is:

[0069]

[0070] Obtain \(\lambda\) i1 \(=-1\), \(\lambda\) i2 \(=-\varepsilon\). According to the stability theory, if all the eigenvalues obtained from the eigenvalue equation corresponding to the Jacobi matrix are negative, then when \(t\rightarrow\infty\), the error variable It is proved that the system is effectively suppressed.

[0071] S4. Replace the initial control objective function with the actual control objective function and input it into the coupling equations of the interconnected system to generate a real-time system error value for control objective tracking;

[0072] Set the external signal, i.e., the actual control objective function, as \(s = A\sin t\), and take the amplitude \(A = 0.5\). The coupling equations of the interconnected system track the external signal in real time under the conditions of arbitrary initial values (i.e., \(x_1\) and \(x_2\)) and uncertain system disturbances, and generate a real-time system error value based on the system error expression.

[0073] S5. When the real-time system error value is not zero, the system output fails to accurately track the target value; at this time, replace the actual control objective function with the real-time system error value and re-execute S4, and introduce error adjustment through the coupling function to improve the tracking accuracy of the system for the external signal;

[0074] When the real-time system error value is zero, the system output value reaches the target value, the coupling equations of the interconnected system stop error adjustment, realize system target value tracking, and the power system outputs stably.

[0075] The evolution simulation of the state variables of the interconnected power system over time is as Figure 4As shown. Through the analysis of the simulation diagram, it can be seen that under any initial value conditions of the system and under the condition of uncertain system disturbances, by coupling the system through the coupling function, the system can be quickly stabilized at the set target function in about 15s. The error between the system state variable and the tracking target value tends to 0, effectively suppressing the chattering phenomenon of the system, making the system operate stably and achieving the expected goal. This reflects the advantages of the reasonable coupling function adopted in the present invention to achieve coupling control. This method can effectively make the controlled system track the target value in a short time under uncertain parameter conditions for similar model systems, enabling the system to operate quickly and stably. Experiments show that this method is accurate and effective.

[0076] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for controlling stable output of an interconnected power system, characterized in that: The steps include: S1. Establish the dynamic equations of the mathematical model of the target interconnected power system; S2, setting the initial control objective function and system error expression of the dynamic equation to obtain the error evolution equation; S3, applying coupling control to the mathematical model of the target interconnected power system, setting a coupling function to couple the second-order interconnected power system model with the error evolution equation, and obtaining the interconnected system coupling equation; S4, replacing the initial control objective function with the actual control objective function, inputting it into the interconnected system coupling equation, generating a real-time system error value, and performing control target tracking; S5, when the real-time system error value is not zero, the system output fails to accurately track the target value; at this time, the real-time system error value is used to replace the actual control objective function and S4 is re-executed; When the real-time system error value is zero, the system output value reaches the target value, the interconnected system coupling equation stops error adjustment, the system target value tracking is achieved, and the power system output is stable.

2. The method for controlling the stable output of an interconnected power system according to claim 1, characterized in that: S1 specifically includes the following steps: With reference to actual performance indicators, a dynamic equation of a mathematical model of a target interconnected power system with periodic loads is obtained based on a mathematical model; The original dynamic equation of the mathematical model of the target interconnected power system is: Where, δ is the phase difference between the excitation potential and the terminal voltage, in rad; ω is the generator angular velocity, in rad / s; P s is the amplitude of electromagnetic power, P m is the amplitude of mechanical power, P k is the amplitude of electromagnetic disturbance, P e is the amplitude of the load disturbance, in W; α is the electromagnetic power disturbance frequency, β is the load disturbance frequency, in Hz; H is the equivalent moment of inertia, in kg·m 2 ; D is the equivalent damping coefficient, the unit is Nms / rad, τ is a dimensionless time variable, the unit is s; The original dynamic equation is transformed into coordinates to obtain the dynamic equation of the mathematical model of the target interconnected power system. The coordinate transformation is as follows: x1 = δ, ρ=P m / P s , v = P k / P s , μ=P e / P s , The dynamic equation of the mathematical model of the target interconnected power system is:

3. The method for controlling the stable output of an interconnected power system according to claim 2, characterized in that: S2 specifically includes the following steps: Set the initial control objective function as The system error expressions are e1=x1-s and e2=x2-s, then the error evolution equation of the dynamic equation of the mathematical model of the target interconnected power system is: in, 4. The method for controlling the stable output of an interconnected power system according to claim 3, characterized in that: S3 specifically includes the following steps: The coupling functions are set as M1 = f(s)-U and M2 = f(s)-V. The dynamic equation of the mathematical model of the target interconnected power system and the error evolution equation are combined through the coupling function to obtain the interconnected system coupling equation, which is as follows: The coefficient matrix J is the Jacobi matrix, and the formula is as follows: The eigenvalue analysis method is used to determine the system stability of the interconnected system coupling equation. The eigenvalue equation corresponding to the Jacobi matrix is: Get λ i1 = -1, λ i2 =-ε. According to the stability theory, the eigenvalues ​​obtained from the eigenvalue equation corresponding to the Jacobi matrix are all negative. When t→∞, the error variable Prove that the system is effectively suppressed.

5. The method for controlling the stable output of an interconnected power system according to claim 1, characterized in that: S4 specifically comprises the following steps: The actual control objective function is set to s=Asint, and the amplitude is A=0.5; the interconnected system coupling equation tracks the external signal in real time under the conditions of arbitrary initial values ​​and uncertain system disturbances, and generates a real-time system error value based on the system error expression.

6. The method for controlling the stable output of an interconnected power system according to claim 1, characterized in that: The interconnected power system is a power system in which two power systems are interconnected via a tie line, and each power system can be simplified as a second-order dynamic model.

7. A storage medium, characterized in that: The storage medium includes a stored program, wherein when the program is run, the method for controlling the stable output of the interconnected power system as described in any one of claims 1 to 6 is executed.

8. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: The processor executes the method for controlling stable output of an interconnected power system according to any one of claims 1 to 6 by running the computer program.

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