Power transmission line harmonic transmission characteristic analysis method and system considering ultra-high-order harmonics

Abstract

The invention discloses a power transmission line harmonic transfer characteristic analysis method and system considering ultrahigh harmonics, and the method comprises the steps: defining a harmonic transfer coefficient in a power transmission line and the characteristic impedance of the power transmission line, and obtaining a phasor expression of a harmonic voltage and a harmonic current changing with the position based on a uniform transmission line equation; considering boundary conditions of the power transmission line to obtain a voltage equation capable of reflecting harmonic voltage of any point on the power transmission line; frequency-dependent impedance and frequency-dependent admittance correction factors are introduced, the harmonic transfer coefficient and the characteristic impedance are corrected, and a corrected voltage equation is obtained; and carrying out transmission line harmonic transfer characteristic analysis based on the corrected voltage equation. According to the method, the propagation characteristics of the ultra-high-order harmonics in the power transmission line are considered, the power transmission line frequency variation parameter correction factors are introduced, the distortion phenomenon of the harmonic transmission coefficient and the characteristic impedance in the ultra-high-frequency power transmission line is corrected, and the limitation that the ultra-high-order harmonics cannot be considered in a traditional harmonic transmission model is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of harmonic analysis, and particularly to a method and system for analyzing the harmonic transfer characteristics of transmission lines considering ultra-high order harmonics. Background Art

[0002] The statements in this part only provide background technical information related to the present invention and do not necessarily constitute prior art.

[0003] With the wide application of pulse width modulation technology and the continuous increase of the switching frequency of power electronic converters, the problem of ultra-high order harmonics in power systems has become increasingly serious. As a medium for electric energy transmission, transmission lines are widely distributed in the distribution network. In long-line power transmission systems, due to the distributed parameter characteristics of transmission lines, the standing wave effect will force harmonics to oscillate and amplify on the line, resulting in serious distortion of the transmission line voltage and voltage over-limit. Therefore, when the transmission line has a certain length, its distributed parameter characteristics must be considered.

[0004] In addition, the distributed parameters of transmission lines will be distorted as the harmonic order increases, and the distortion phenomenon will also be significantly enhanced as the harmonic order increases, which will lead to errors in the analysis and calculation of harmonic transfer.

[0005] Currently, the modeling of the harmonic transfer characteristics of transmission lines has been studied. The common method is to build an equivalent circuit of the lumped parameter model of the transmission line, establish a harmonic transfer model of the transmission line, and use the method of connecting multiple π-type equivalent circuits in series to simulate the equivalent circuit of the long transmission line. However, the lumped parameter model equivalent the actually uniformly distributed impedance and admittance to a two-port network (only containing one impedance), so the simulation accuracy of the harmonic transfer model of the transmission line is not high, and the equivalent process is cumbersome; in addition, it is also difficult to consider the frequency-varying characteristics of the parameters, which affects the calculation accuracy. Summary of the Invention

[0006] To solve the above problems, the present invention proposes a method and system for analyzing the harmonic transfer characteristics of transmission lines considering ultra-high order harmonics. Considering the influence of ultra-high order harmonics on the parameters of transmission lines, when constructing the harmonic voltage equation, a correction factor is introduced to correct the propagation coefficient and characteristic impedance, which can improve the model accuracy, reduce the complexity of model calculation, and improve the operation speed.

[0007] In some embodiments, the following technical solutions are adopted:

[0008] A method for analyzing the harmonic transfer characteristics of transmission lines considering ultra-high order harmonics, comprising:

[0009] Establish a uniform transmission line equation according to the equivalent model of the distributed parameter line;

[0010] Define the harmonic transfer coefficient and the characteristic impedance of the transmission line, and obtain the phasor expressions of the harmonic voltage and harmonic current varying with position based on the uniform transmission line equation;

[0011] Considering the boundary conditions of the transmission line, obtain the voltage equation that can reflect the harmonic voltage at any point on the transmission line;

[0012] Introduce the frequency-varying impedance and frequency-varying admittance correction factors to correct the harmonic transfer coefficient and the characteristic impedance, and obtain the corrected voltage equation;

[0013] Analyze the harmonic transfer characteristics of the transmission line based on the corrected voltage equation.

[0014] As a further solution, obtain the voltage equation that can reflect the harmonic voltage at any point on the transmission line, specifically:

[0015]

[0016] Among them, γ is the harmonic transfer coefficient in the transmission line, and Z c is the characteristic impedance of the transmission line; is the voltage at position x on the transmission line, is the voltage of the harmonic voltage source at the head end of the transmission line, and Z t is the load impedance at the end of the transmission line, l is the length of the transmission line, x is the distance from the head end on the transmission line, Z0 is the fundamental wave impedance of the transmission line, Y0 is the fundamental wave admittance of the transmission line, R0 is the fundamental wave resistance of the transmission line, L0 is the fundamental wave inductance of the transmission line, G0 is the fundamental wave conductance of the transmission line, and C0 is the fundamental wave capacitance of the transmission line.

[0017] As a further solution, introduce the frequency-varying impedance and frequency-varying admittance correction factors to correct the harmonic transfer coefficient and the characteristic impedance. The corrected harmonic transfer coefficient is:

[0018]

[0019] The corrected characteristic impedance is:

[0020]

[0021] Among them, r0, g0, l0, and b0 are the fundamental wave resistance, conductance, inductance, and susceptance respectively, and z h , y h are correction factors, which are solved by the vector fitting method.

[0022] As a further solution, the fitting function of the correction factor is specifically:

[0023]

[0024] Among them, an is the pole of the fitting function, c n is the residue, s is the Laplace operator, d and h are both constants, N is the number of poles, and n is the nth pole.

[0025] As a further solution, the corrected voltage equation is specifically:

[0026]

[0027] where is the phasor of the hth harmonic voltage at the line head, Z th is the hth harmonic load impedance at the line end; γ h is the corrected harmonic transfer coefficient, Z ch is the corrected characteristic impedance, l is the length of the transmission line, and x is the distance from the line head on the transmission line.

[0028] As a further solution, based on the corrected voltage equation, the harmonic transfer characteristics of the transmission line are analyzed, specifically including: ignoring resistance and conductance, assuming the line is open, and obtaining the amplification factor of the harmonic voltage at a certain position on the transmission line compared to the harmonic voltage source at the line head, specifically:

[0029]

[0030] where l h , b h are the frequency-varying inductance and susceptance correction factors that vary under different magnetic fluxes for different frequencies of harmonics; l0 and b0 are the fundamental inductance and susceptance respectively, M h (x) is the amplification factor of the harmonic voltage at a certain position on the transmission line compared to the harmonic voltage source at the line head, ω h is the angular frequency of the hth harmonic, l is the length of the transmission line, and x is the distance from the line head on the transmission line.

[0031] As a further solution, based on the corrected voltage equation, the harmonic transfer characteristics of the transmission line are analyzed, specifically including: given the current boundary conditions, ignoring resistance and conductance, assuming the line is open, and obtaining the amplification factor of the harmonic current at a certain position on the transmission line compared to the harmonic current source at the line head, specifically:

[0032]

[0033] where γ h is the corrected harmonic transfer coefficient, M I (x) is the amplification factor of the harmonic current at a certain position on the transmission line compared to the harmonic current source at the line head, l is the length of the transmission line, and x is the distance from the line head on the transmission line.

[0034] As a further solution, the harmonic transfer characteristics of the transmission line are analyzed based on the corrected voltage equation, specifically including: by the superposition theorem, separately making the harmonic voltage source at the head end of the closed-loop transmission line and the harmonic voltage source at the tail end act alone, obtaining the amplification factor of the harmonic voltage at any point on the closed-loop transmission line relative to the harmonic voltage source at the head end, specifically:

[0035]

[0036] Among them, is the harmonic voltage at the head end of the line, k is the amplitude of the harmonic voltage source at the tail end of the line / the harmonic voltage source at the head end of the line, and θ h is the phase of the harmonic voltage source at the tail end of the line - the phase of the harmonic voltage source at the head end of the line.

[0037] In some other embodiments, the following technical solution is adopted:

[0038] A system for analyzing the harmonic transfer characteristics of a transmission line considering ultra-high-order harmonics, including:

[0039] A voltage equation establishment module, configured to establish a uniform transmission line equation according to the equivalent model of the distributed parameter line; define the harmonic transfer coefficient and the characteristic impedance of the transmission line, and obtain the phasor expressions of the harmonic voltage and the harmonic current varying with position based on the uniform transmission line equation; consider the boundary conditions of the transmission line to obtain a voltage equation that can reflect the harmonic voltage at any point on the transmission line;

[0040] A voltage equation correction module, configured to introduce frequency-variable impedance and frequency-variable admittance correction factors to correct the harmonic transfer coefficient and the characteristic impedance, and obtain a corrected voltage equation;

[0041] A harmonic transfer characteristic analysis module, configured to analyze the harmonic transfer characteristics of the transmission line based on the corrected voltage equation.

[0042] In some other embodiments, the following technical solution is adopted:

[0043] A terminal device includes a processor and a memory. The processor is used to implement instructions; the memory is used to store multiple instructions, and the instructions are adapted to be loaded and executed by the processor to perform the above-mentioned method for analyzing the harmonic transfer characteristics of a transmission line considering ultra-high-order harmonics.

[0044] Compared with the prior art, the beneficial effects of the present invention are:

[0045] (1) The present invention fully considers the propagation characteristics of ultra-high-order harmonics in transmission lines. By introducing a frequency-variable parameter correction factor for transmission lines, the distortion phenomena of harmonic transfer coefficients and characteristic impedances in transmission lines at ultra-high frequencies are corrected, thereby constructing a transmission line harmonic transfer model considering ultra-high-order harmonics, solving the limitation that traditional harmonic transfer models cannot consider ultra-high-order harmonics, and improving the accuracy of harmonic analysis.

[0046] (2) The present invention establishes a transmission line ultra-high-order harmonic transfer model based on distributed parameter lines. Through the harmonic voltage / current source at the head end of the line and the impedance at the end of the line, the voltage / current distribution characteristics on the line can be obtained, which can intuitively reflect the relationship between the line current / voltage distribution characteristics and the end impedance, and a closed-loop current / voltage transfer model can be established by opening the end, overcoming the problem of incomplete consideration of ultra-high-order reflected waves caused by not considering the end impedance in traditional methods.

[0047] Other features and advantages of the present invention will be partially given in the following description, partially become obvious from the following description, or be understood through the practice of this aspect. Brief Description of the Drawings

[0048] Figure 1 It is a flowchart of the method for analyzing the harmonic transfer characteristics of a transmission line considering ultra-high-order harmonics in an embodiment of the present invention;

[0049] Fig. 2(a) is an equivalent circuit diagram of an open-loop transmission line in an embodiment of the present invention;

[0050] Fig. 2(b) is a differential equivalent circuit diagram of distributed parameters of an open-loop transmission line in an embodiment of the present invention;

[0051] Figure 3 It is an equivalent circuit diagram of a closed-loop transmission line in an embodiment of the present invention. Detailed Description of the Embodiment

[0052] It should be noted that the following detailed description is illustrative and is intended to provide further description of the present application. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present application belongs.

[0053] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0054] Embodiment 1

[0055] In one or more embodiments, a method for analyzing the harmonic transfer characteristics of a transmission line considering ultra-high order harmonics is disclosed. Combining Figure 1 , the specific process is as follows:

[0056] S101: According to the equivalent model of the distributed parameter line, establish the equation of the uniform transmission line.

[0057] In this embodiment, according to the open-loop transmission line equivalent circuit diagram and the open-loop transmission line distributed parameter differential equivalent circuit diagram in Fig. 2(a) and Fig. 2(b), the specific equation of the uniform transmission line is:

[0058]

[0059] In the formula, u(x,t) and i(x,t) are the voltage u and current i at position x on the transmission line at time t, respectively. R0, L0, G0, and C0 are the fundamental wave resistance, fundamental wave inductance, fundamental wave conductance, and fundamental wave capacitance, respectively.

[0060] S102: Define the harmonic transfer coefficient in the transmission line and the characteristic impedance of the transmission line. Based on the equation of the uniform transmission line, obtain the phasor expressions of the harmonic voltage and harmonic current varying with position, thereby converting the transmission line equation from a time-domain time-varying equation to a frequency-domain phasor equation. In the frequency domain, the phasor represents the previous time-varying characteristics, which is equivalent to simplifying the two variables of distance x and time t in the original equation to only one variable of distance x.

[0061] Since u(x,t) and i(x,t) are both functions of distance x and time t, they can be converted into phasor forms in the time domain to simplify the calculation. Thus, u(x,t) can be abbreviated as U(x), and i(x,t) can be abbreviated as I(x).

[0062] From Equation (1), the expressions of voltage and current are:

[0063]

[0064] In the formula:

[0065]

[0066] Among them, γ is the harmonic transfer coefficient in the transmission line, and Z c is the characteristic impedance of the transmission line; R0 is the fundamental wave resistance of the transmission line, L0 is the fundamental wave inductance of the transmission line, G0 is the fundamental wave conductance of the transmission line, and C0 is the fundamental wave capacitance of the transmission line.

[0067] Among them, A and B are the undetermined coefficients of the voltage equation, is the phasor of the voltage wave propagating forward, is the phasor of the voltage wave propagating backward, is the phasor of the current wave for forward propagation, is the phasor of the current wave for backward propagation, Z0 is the fundamental wave impedance, and Y0 is the fundamental wave admittance.

[0068] It can be seen from the formula that: U + (x) has an amplitude attenuation as x increases, and U - (x) has an amplitude attenuation as x decreases. Therefore, U + (x) can be regarded as the incident wave propagating from the starting end to the ending end, and U - (x) can be understood as the reflected wave propagating from the ending end to the starting end.

[0069] S103: Considering the boundary conditions of the transmission line, a voltage equation that can reflect the harmonic voltage at any point on the transmission line is obtained.

[0070] Specifically, it can be seen from Figure 2 that the boundary conditions of the transmission line are:

[0071]

[0072] According to the boundary conditions, the voltage equation is:

[0073]

[0074] Among them, is the voltage at the starting end of the transmission line, is the voltage at the ending end of the line, is the current at the ending end of the transmission line; is the voltage of the harmonic voltage source at the starting end of the transmission line, Z t is the load impedance at the ending end of the transmission line; γ is the harmonic transfer coefficient in the transmission line, Z c is the characteristic impedance of the transmission line; is the voltage at x on the transmission line, l is the length of the transmission line, x is the distance from the starting end on the transmission line, Z0 is the fundamental wave impedance of the transmission line, Y0 is the fundamental wave admittance of the transmission line, R0 is the fundamental wave resistance of the transmission line, L0 is the fundamental wave inductance of the transmission line, G0 is the fundamental wave conductance of the transmission line, and C0 is the fundamental wave capacitance of the transmission line.

[0075] S104: Introduce the frequency-variable impedance and frequency-variable admittance correction factors to correct the harmonic transfer coefficient and the characteristic impedance, and obtain the corrected voltage equation.

[0076] In this embodiment, according to the frequency-variable characteristics of the transmission line, the frequency-variable impedance correction factor Z h and the frequency-variable admittance correction factor Y h are introduced to correct the harmonic transfer coefficient and the characteristic impedance;

[0077] Z h = r h + jl h+r0 + jωl0 = z h +r0 + jωl0(6)

[0078] Y h = g h + jb h +g0 + jωb0 = y h +g0 + jωb0(7)

[0079] where r h , l h , g h , b h are the frequency-varying resistance, inductance, conductance, and susceptance correction factors that vary with different magnetic fluxes at different harmonic frequencies, respectively. r0, g0, l0, and b0 are the fundamental wave resistance, conductance, inductance, and susceptance, respectively.

[0080] Define Z h and Y h as correction factors, both of which can be solved by vector fitting. The fitting function is:

[0081]

[0082] where a n is the pole of the fitting function, c n is the residue, s is the Laplace operator, d and h are both constants, N is the number of poles, and n is the nth pole.

[0083] To obtain the above rational approximation function f(s), it is necessary to first apply harmonic voltages of each order to the transmission line, measure the harmonic impedance and harmonic admittance correction factor values Z h and Y h of the transmission line at different frequencies, obtain a set of sparse sampled complex frequency-domain impedance data, and perform data normalization processing.

[0084] Then, extract features from the input correction factors (Z h or Y h ) through an encoder network (CNN or Transformer), use the decoder network to map the encoded features to the poles a n , residues (residues) c n and the constant term parameters d and h of the frequency-varying rational function, and apply causality constraints during the decoding process to force the real part of the poles to be negative to make the fitting function converge. Constrain the non-negativity of the real part of the output rational function in the full frequency band through the regularization term of the loss function to ensure that the cable itself does not emit energy, that is, to ensure that the model conforms to the passivity frequency-varying law. Finally, sort and prune the generated poles based on the residue amplitude, dynamically adjust the number of effective poles, and generate a compact frequency-varying model of Z h or Y h .

[0085] The corrected harmonic transfer coefficient and characteristic impedance are as follows:

[0086]

[0087]

[0088] Among them, Z th are the phasor of the hth harmonic voltage at the line head and the hth harmonic load impedance at the line end, respectively.

[0089] In this embodiment, by correcting the harmonic transfer coefficient and characteristic impedance, the frequency-varying characteristics of the line can be taken into account after correction, making the analysis and calculation more accurate.

[0090] Thus, Equation (5) can be transformed into:

[0091]

[0092] where h is the harmonic order; it can be simplified using hyperbolic sine and hyperbolic cosine functions as:

[0093]

[0094] The simplified formula is more convenient for calculation.

[0095] S105: Analyze the harmonic transfer characteristics of the transmission line based on the corrected voltage equation.

[0096] In this embodiment, the analysis of the harmonic transfer characteristics of the transmission line specifically includes:

[0097] (1) According to the actual application conditions, ignore the resistance and conductance in the expression, assume the line is open, and simplify the expression according to the infinitesimal theory to obtain the amplification factor of the harmonic voltage at a certain position on the transmission line compared to the harmonic voltage source at the line head.

[0098] Since the analysis is of harmonics, ωl0 and ωb0 are much larger than r h and g h , so r h and g h can be ignored when analyzing the amplification factor. At this time, Equation (12) can be simplified according to the infinitesimal theory as:

[0099]

[0100] When the line end is open, Z th is infinite, and the above equation can be written as:

[0101]

[0102] The harmonic amplification factor of the harmonic voltage source at position x on the transmission line compared to the harmonic voltage source at the line head is:

[0103]

[0104] where l h , b h are the frequency-variable inductance and susceptance correction factors that change under different magnetic fluxes for different frequencies of harmonics respectively; l0 and b0 are the fundamental inductance and susceptance respectively, M h (x) is the amplification factor of a certain position on the transmission line compared to the harmonic voltage source at the line head, ω h is the angular frequency of the hth harmonic, l is the total length of the line, and x is the position at a distance x from the line head.

[0105] The harmonic voltage amplification factor at any position on the transmission line compared to the harmonic voltage source at the line head can be obtained from the above formula.

[0106] (2) Given the current boundary conditions, according to the actual application conditions, selectively ignore the resistance and conductance in the expression, assume the line is open, and simplify the expression according to the infinitesimal theory to obtain the amplification factor of a certain position on the transmission line compared to the harmonic current source at the line head.

[0107] If the initial current and the terminal impedance are given, the relationship between the current amplification factor and the distance on the transmission line can be deduced.

[0108] That is, given the boundary conditions:

[0109]

[0110] The relationship between the current amplification factor and the distance on the transmission line can be obtained as:

[0111]

[0112] When the line is open at the end, Z t is infinite, and the above formula can be written as:

[0113]

[0114] where is the current at the line head, is the harmonic current source at the head, is the voltage at the line end, is the current at the line end, and Z t is the equivalent impedance of the line.

[0115] The amplification factor of any position on the transmission line compared to the harmonic current source at the line head can be obtained from the above formula.

[0116] (3) By the superposition theorem, the harmonic voltage source at the head end of the closed-loop transmission line and the harmonic voltage source at the tail end act separately, and the amplification factor of the harmonic voltage at any point on the closed-loop transmission line relative to the head end is obtained.

[0117] Figure 3 The equivalent model of the closed-loop transmission line is shown. When the line end is not open, that is, there is also a harmonic source at the line end, the superposition theorem can be used for analysis based on the conclusion of the open-loop amplification factor formula:

[0118] U sh1 When acting alone, the line end can be regarded as short-circuited, that is, Z in equation (12) th approaches 0, and at this time equation (12) can be written as:

[0119]

[0120] U sh2 When acting alone,

[0121]

[0122] where, U sh1 is the harmonic voltage source at the head end, U sh2 is the harmonic voltage source at the tail end, is the voltage at position x on the line when the harmonic voltage source at the head end acts alone, is the voltage at position x on the line when the harmonic voltage source at the tail end acts alone.

[0123] Therefore,

[0124]

[0125] For the convenience of analysis, it can be assumed that the amplitudes of U sh1 and U sh2 differ by k times and the phases differ by θ h times, then equation (21) becomes:

[0126]

[0127] Therefore, the amplification factor at any position is:

[0128]

[0129] where, is the harmonic voltage at the head end of the line, k is the amplitude of the harmonic voltage source at the tail end of the line / the harmonic voltage source at the head end of the line, θ h is the phase of the harmonic voltage source at the tail end of the line - the phase of the harmonic voltage source at the head end of the line.

[0130] The amplification factor of the harmonic voltage at any position on the closed-loop transmission line relative to the head end can be obtained from the above formula.

[0131] In this embodiment, through the above analysis of the amplification factor of the harmonic voltage at any position on the open-loop transmission line relative to the harmonic voltage source at the head end, the amplification factor of the harmonic current at any position compared to the harmonic current source at the head end of the line, and the amplification factor of the harmonic voltage at any position on the closed-loop transmission line relative to the head end, the following subsequent work can be further carried out:

[0132] (1) By analyzing the transfer characteristics of high-order harmonics (such as the 11th, 13th and higher orders), determine the key frequency bands of harmonic amplification or attenuation, and design passive filters (such as high-pass filters) or active power filters (APF) accordingly.

[0133] (2) Identify the resonance points of the system at specific frequencies (such as the series / parallel resonance formed by high-order harmonics and line capacitance and inductance), and adjust the grid parameters (such as reactor configuration, capacitor bank switching strategy).

[0134] (3) For the broadband harmonics generated by wind power and photovoltaic inverters (such as the high-order harmonics of 2 - 5 kHz near the switching frequency), analyze their transfer laws in the transmission line and formulate grid connection control strategies.

[0135] Embodiment 2

[0136] In one or more embodiments, a transmission line harmonic transfer characteristic analysis system considering ultra-high-order harmonics is disclosed, which specifically includes:

[0137] A voltage equation establishment module, which is used to establish a uniform transmission line equation according to the distributed parameter line equivalent model; define the harmonic transfer coefficient and the characteristic impedance of the transmission line, and obtain the phasor expressions of the harmonic voltage and harmonic current varying with position based on the uniform transmission line equation; considering the boundary conditions of the transmission line, obtain the voltage equation that can reflect the harmonic voltage at any point on the transmission line.

[0138] A voltage equation correction module, which is used to introduce frequency-variable impedance and frequency-variable admittance correction factors to correct the harmonic transfer coefficient and the characteristic impedance, and obtain the corrected voltage equation.

[0139] A harmonic transfer characteristic analysis module, which is used to analyze the harmonic transfer characteristics of the transmission line based on the corrected voltage equation.

[0140] It should be noted that the specific implementation manners of the above modules are exactly the same as those in Embodiment 1 and will not be elaborated here.

[0141] Embodiment 3

[0142] In one or more embodiments, a terminal device is disclosed, which includes a processor and a memory. The processor is configured to implement instructions; the memory is configured to store a plurality of instructions, and the instructions are adapted to be loaded and executed by the processor to perform the analysis method for transmission line harmonic transfer characteristics considering ultra-high order harmonics described in the first embodiment.

[0143] It should be understood that in this embodiment, the processor may be a central processing unit (CPU), and the processor may also be other general-purpose processors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor or the processor may also be any conventional processor, etc.

[0144] The memory may include a read-only memory and a random access memory, and provide instructions and data to the processor. A part of the memory may also include a non-volatile random access memory. For example, the memory may also store information about the device type.

[0145] In the implementation process, each step of the above method may be completed by the integrated logic circuit in the hardware of the processor or the instructions in the form of software.

[0146] Although the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, it is not a limitation on the protection scope of the present invention. Those skilled in the art should understand that based on the technical solutions of the present invention, various modifications or deformations that can be made by those skilled in the art without creative efforts are still within the protection scope of the present invention.

Claims

1. A method for analyzing the harmonic transfer characteristics of a transmission line considering ultra-high order harmonics, characterized in that, Including: Establish a uniform transmission line equation according to the equivalent model of the distributed parameter line; Define the harmonic transfer coefficient and the characteristic impedance of the transmission line in the power line, and obtain the phasor expressions of the harmonic voltage and harmonic current varying with position based on the uniform transmission line equation; Considering the boundary conditions of the transmission line, obtain a voltage equation that can reflect the harmonic voltage at any point on the transmission line; Considering the boundary conditions of the transmission line, obtain a voltage equation that can reflect the harmonic voltage at any point on the transmission line; Introduce the frequency-variable impedance and frequency-variable admittance correction factors, correct the harmonic transfer coefficient and the characteristic impedance, and obtain the corrected voltage equation; Conduct an analysis of the harmonic transfer characteristics of the transmission line based on the corrected voltage equation.

2. The method for analyzing the harmonic transfer characteristics of a transmission line considering ultra-high order harmonics according to claim 1, characterized in that, Obtain a voltage equation that can reflect the harmonic voltage at any point on the transmission line, specifically: Among them, γ is the harmonic transfer coefficient in the transmission line, and Z c is the characteristic impedance of the transmission line; is the voltage at position x on the transmission line, is the voltage of the harmonic voltage source at the head end of the transmission line, and Z t is the load impedance at the end of the transmission line, l is the length of the transmission line, x is the distance from the head end on the transmission line, Z0 is the fundamental wave impedance of the transmission line, Y0 is the fundamental wave admittance of the transmission line, R0 is the fundamental wave resistance of the transmission line, L0 is the fundamental wave inductance of the transmission line, G0 is the fundamental wave conductance of the transmission line, and C0 is the fundamental wave capacitance of the transmission line.

3. The method for analyzing the harmonic transfer characteristics of a transmission line considering ultra-high order harmonics as described in claim 1, wherein Introduce the frequency-variable impedance and frequency-variable admittance correction factors, correct the harmonic transfer coefficient and the characteristic impedance, and the corrected harmonic transfer coefficient is: The corrected characteristic impedance is: where r0, g0, l0, and b0 are the fundamental wave resistance, conductance, inductance, and susceptance respectively, and z h , y h are correction factors, which are solved by the vector fitting method.

4. The method for analyzing the harmonic transfer characteristics of a transmission line considering ultra-high order harmonics according to claim 3, characterized in that The fitting function of the correction factor is specifically: where a n is the pole of the fitting function, c n is the residue, s is the Laplace operator, d and h are both constants, N is the number of poles, and n is the n-th pole.

5. The method for analyzing the harmonic transfer characteristics of a transmission line considering ultra-high order harmonics according to claim 1, wherein The specific corrected voltage equation is: wherein, is the phasor of the h-th harmonic voltage at the line head, Z th is the h-th harmonic load impedance at the line end; γ h is the corrected harmonic transfer coefficient, Z ch is the corrected characteristic impedance, l is the length of the transmission line, and x is the distance from the line head on the transmission line.

6. The method for analyzing the harmonic transfer characteristics of a transmission line considering ultra-high order harmonics according to claim 1, wherein, Conduct an analysis of the harmonic transfer characteristics of the transmission line based on the corrected voltage equation, specifically including: ignoring the resistance and conductance, assuming the line is open, and obtaining the amplification factor of the harmonic voltage at a certain position on the transmission line compared to the harmonic voltage source at the line head, specifically: where, l h , b h are the frequency-varying inductance and susceptance correction factors that vary with different magnetic fluxes at different harmonic frequencies respectively; l0 and b0 are the fundamental inductance and susceptance respectively, M h (x) is the amplification factor of the harmonic voltage source at a certain position on the transmission line compared to the line's head end, ω h is the angular frequency of the h-th harmonic, l is the length of the transmission line, and x is the distance from the head end on the transmission line.

7. The analysis method for harmonic transfer characteristics of a transmission line considering ultra-high order harmonics according to claim 1, characterized in that Conduct an analysis of the harmonic transfer characteristics of the transmission line based on the corrected voltage equation, specifically including: given the current boundary conditions, ignoring the resistance and conductance, assuming the line is open, and obtaining the amplification factor of the harmonic current at a certain position on the transmission line compared to the harmonic current source at the line head, specifically: Among them, γ h is the corrected harmonic transfer coefficient, M I (x) is the amplification factor of the harmonic current source at a certain position on the transmission line compared to the harmonic current source at the line head, l is the length of the transmission line, and x is the distance from the head of the transmission line.

8. The method for analyzing the harmonic transfer characteristics of a transmission line considering ultra-high-order harmonics according to claim 1, characterized in that Conduct an analysis of the harmonic transfer characteristics of the transmission line based on the corrected voltage equation, specifically including: through the superposition theorem, separately making the harmonic voltage source at the head of the closed-loop transmission line and the harmonic voltage source at the end act alone, and obtaining the amplification factor of the harmonic voltage at any point on the closed-loop transmission line relative to the harmonic voltage source at the head, specifically: Among them, is the harmonic voltage at the line head, k is the amplitude of the harmonic voltage source at the line end / the harmonic voltage source at the line head, and θ h is the phase of the harmonic voltage source at the line end - the phase of the harmonic voltage source at the line head.

9. A transmission line harmonic transfer characteristic analysis system considering ultra-high order harmonics, characterized in that Including: A voltage equation establishment module for establishing a uniform transmission line equation according to the equivalent model of the distributed parameter line; Define the harmonic transfer coefficient and the characteristic impedance of the transmission line in the power line, and obtain the phasor expressions of the harmonic voltage and harmonic current varying with position based on the uniform transmission line equation; Considering the boundary conditions of the transmission line, obtain a voltage equation that can reflect the harmonic voltage at any point on the transmission line; A voltage equation correction module for introducing the frequency-variable impedance and frequency-variable admittance correction factors, correcting the harmonic transfer coefficient and the characteristic impedance, and obtaining the corrected voltage equation; A harmonic transfer characteristic analysis module for conducting an analysis of the harmonic transfer characteristics of the transmission line based on the corrected voltage equation.

10. A terminal device, comprising a processor and a memory, the processor being configured to implement instructions; the memory being configured to store a plurality of instructions, characterized in that, The instruction is suitable for being loaded and executed by a processor for the method for analyzing the harmonic transfer characteristics of a transmission line considering ultra-high-order harmonics as described in any one of claims 1-8.

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