A method and system for evaluating demagnetization mode of synchronous generator

Abstract

The present disclosure proposes a method and system for evaluating the demagnetization method of a synchronous generator. The method includes obtaining a terminal voltage reference value, mechanical torque, nonlinear coefficients of different demagnetization methods, and a node admittance matrix of the power system wiring structure of the synchronous generator, establishing a demagnetization evaluation overall model, and the demagnetization evaluation overall model includes an excitation system model, a fifth-order model of the synchronous generator, a power grid electromechanical model, and a demagnetization model. The terminal voltage reference value, mechanical torque, and the nonlinear coefficient of any demagnetization method and the node admittance matrix are input into the demagnetization evaluation overall model. Upon receiving a demagnetization instruction, a second excitation voltage is selected as the excitation voltage. If the second excitation voltage meets the requirements, the demagnetization method corresponding to the second excitation voltage is selected for demagnetization. Otherwise, the nonlinear coefficients of other demagnetization methods are replaced to obtain a new second excitation voltage, and then a new demagnetization method is determined. The method disclosed in the present disclosure can improve the accuracy of demagnetization method evaluation.

Description

Technical Field

[0001] The present disclosure relates to the field of calculating demagnetization modes of synchronous generator excitation systems, and in particular to a demagnetization mode evaluation method and system for synchronous generators. Background Art

[0002] Excitation engineers are well aware of the importance of the demagnetization performance of synchronous generator excitation systems for reliable excitation shutdown and protection of the generator rotor circuit. Modern demagnetization methods often utilize a combination of a field breaker and a demagnetization resistor to achieve rotor demagnetization. Reliably analyzing the demagnetization capacity during design is crucial. Demagnetization capacity calculations not only consider the most severe interruption conditions under various fault scenarios, but also the relationship between the stator and rotor flux linkages of the synchronous generator. Furthermore, the output of the excitation regulator cannot immediately drop to zero after the demagnetization command is activated. Therefore, it is necessary to consider multiple fault scenarios under the combined effects of two electromechanical transients to complete demagnetization design calculations and guide the selection and evaluation of demagnetization resistors. Typical demagnetization selection studies only consider the simulation of multiple fault scenarios and, in some cases, restore the generator's electromechanical processes. However, they all strictly set the excitation output after a disturbance to zero. This omission leads to inaccurate estimation of demagnetization capacity, potentially creating safety risks in designs with limited margins.

[0003] The demagnetization design calculation needs to take into account the magnetic flux process of the excitation, D-axis damping and Q-axis damping windings, so a fifth-order or higher synchronous generator model can meet the requirements. The entire demagnetization triggering process includes: after a disturbance occurs (such as a three-phase short circuit at the machine end), the grid-connected switch is tripped and the demagnetization instruction is initiated at the same time, the excitation regulator output is reset to zero after the demagnetization action, and the excitation voltage maintains a natural decay process. Assuming that the magnetic field circuit breaker is tripped instantaneously, the demagnetization resistor is immediately put into the rotor circuit. At this time, the calculation of the rotor excitation current and excitation voltage curves is the key to studying the practicality of the demagnetization design calculation. However, the calculation accuracy of the excitation voltage in the existing technology is not high enough, which makes the evaluation of the demagnetization method not accurate enough, and thus cannot guarantee the reliability and safety of the demagnetization action of the excitation system. Summary of the Invention

[0004] The present disclosure aims to solve one of the technical problems in the related art at least to a certain extent.

[0005] To this end, a first objective of the present disclosure is to propose a demagnetization mode evaluation method for a synchronous generator, so as to improve the accuracy of the demagnetization mode evaluation.

[0006] A second objective of the present disclosure is to provide a de-excitation mode evaluation system for a synchronous generator.

[0007] A third objective of the present disclosure is to provide a device for evaluating a demagnetization mode of a synchronous generator.

[0008] To achieve the above objectives, a first embodiment of the present disclosure provides a method for evaluating a demagnetization mode of a synchronous generator, comprising:

[0009] Obtain the synchronous generator terminal voltage reference value, mechanical torque, nonlinear coefficients of different deexcitation methods, and node admittance matrix of the power system connection structure;

[0010] Establishing a demagnetization assessment overall model, the demagnetization assessment overall model includes an excitation system model, a fifth-order synchronous generator model, a power grid electromechanical model, and a demagnetization model; wherein the input of the excitation system model includes the machine-end voltage reference value, and the output includes a first excitation voltage; the input of the fifth-order synchronous generator model includes the excitation voltage, the mechanical torque, and the stator current, and the output includes the stator voltage, the generator power angle, and the transient excitation voltage; the input of the power grid electromechanical model includes the stator voltage, the generator power angle, and the node admittance matrix, and the output includes the stator current; the input of the demagnetization model includes the transient excitation voltage and the nonlinear coefficient of any demagnetization method, and the output includes the second excitation voltage;

[0011] The machine-end voltage reference value, mechanical torque, nonlinear coefficient of any demagnetization method, and node admittance matrix are input into the demagnetization evaluation overall model; when no demagnetization instruction is received, the first excitation voltage is selected as the excitation voltage; when a demagnetization instruction is received, the second excitation voltage is selected as the excitation voltage; if the second excitation voltage meets the requirements, the demagnetization method corresponding to the second excitation voltage is selected for demagnetization; if the second excitation voltage does not meet the requirements, the nonlinear coefficient of other demagnetization methods is replaced to obtain a new second excitation voltage, and then a new demagnetization method is determined.

[0012] In one embodiment of the present disclosure, it also includes: obtaining the unit technical parameters of the synchronous generator, the unit technical parameters also including rated voltage, rated current, rated active power, rated apparent power, stator resistance, stator leakage reactance, rated no-load excitation current, rated no-load excitation voltage, synchronous reactance value, transient synchronous reactance value, sub-transient synchronous reactance value, transient open-circuit time constant, and sub-transient open-circuit time constant; when establishing the demagnetization assessment overall model, the unit technical parameters are used to normalize the parameters in the demagnetization assessment overall model.

[0013] In one embodiment of the present disclosure, the output of the fifth-order model of the synchronous generator also includes the real-time value of the machine-end voltage, the input of the excitation system model also includes the real-time value of the machine-end voltage, and the excitation system model outputs the first excitation voltage based on the machine-end voltage reference value and the real-time value of the machine-end voltage.

[0014] In one embodiment of the present disclosure, the input of the demagnetization model further includes a subtransient excitation voltage, and the demagnetization model outputs a second excitation voltage based on the transient excitation voltage, the subtransient excitation voltage and a nonlinear coefficient of any demagnetization method.

[0015] In one embodiment of the present disclosure, the excitation system model adopts a power system static stabilizer, and the input of the excitation system model also includes a generator rotor angular velocity change value, an auxiliary voltage transformation value is obtained based on the generator rotor angular velocity change value, and a first excitation voltage is output based on the auxiliary voltage transformation value, the machine-end voltage reference value and the machine-end voltage real-time value.

[0016] In one embodiment of the present disclosure, when establishing the overall demagnetization assessment model, the input and output data of the excitation system model, the fifth-order model of the synchronous generator, the grid electromechanical model and the demagnetization model are matched, and the matching process is to convert the data under different coordinate axes to the same coordinate axis.

[0017] To achieve the above-mentioned objectives, a second embodiment of the present disclosure provides a demagnetization mode evaluation system for a synchronous generator, comprising:

[0018] An acquisition module is used to obtain the terminal voltage reference value, mechanical torque, nonlinear coefficients of different demagnetization methods, and node admittance matrix of the power system connection structure of the synchronous generator;

[0019] a modeling module for establishing a demagnetization assessment overall model, the demagnetization assessment overall model including an excitation system model, a fifth-order synchronous generator model, a power grid electromechanical model, and a demagnetization model; wherein the input of the excitation system model includes the machine-end voltage reference value, and the output includes a first excitation voltage; the input of the fifth-order synchronous generator model includes the excitation voltage, the mechanical torque, and the stator current, and the output includes the stator voltage, the generator power angle, and the transient excitation voltage; the input of the power grid electromechanical model includes the stator voltage, the generator power angle, and the node admittance matrix, and the output includes the stator current; the input of the demagnetization model includes the transient excitation voltage and the nonlinear coefficient of any demagnetization method, and the output includes the second excitation voltage;

[0020] An evaluation module is configured to input the machine-end voltage reference value, mechanical torque, and the nonlinear coefficient and node admittance matrix of any demagnetization method into the demagnetization evaluation overall model; when no demagnetization instruction is received, the first excitation voltage is selected as the excitation voltage; when a demagnetization instruction is received, the second excitation voltage is selected as the excitation voltage; if the second excitation voltage meets the requirements, the demagnetization method corresponding to the second excitation voltage is selected for demagnetization; if the second excitation voltage does not meet the requirements, the nonlinear coefficient of other demagnetization methods is replaced to obtain a new second excitation voltage, thereby determining a new demagnetization method.

[0021] In one embodiment of the present disclosure, the acquisition module is also used to obtain the unit technical parameters of the synchronous generator, and the unit technical parameters also include rated voltage, rated current, rated active power, rated apparent power, stator resistance, stator leakage reactance, rated no-load excitation current, rated no-load excitation voltage, synchronous reactance value, transient synchronous reactance value, sub-transient synchronous reactance value, transient open-circuit time constant, and sub-transient open-circuit time constant; the demagnetization method evaluation system also includes a preprocessing module, and the preprocessing module is used to use the unit technical parameters to perform normalization processing on the parameters in the demagnetization evaluation overall model when establishing the demagnetization evaluation overall model.

[0022] In one embodiment of the present disclosure, the input of the demagnetization model further includes a subtransient excitation voltage, and the demagnetization model outputs a second excitation voltage based on the transient excitation voltage, the subtransient excitation voltage and a nonlinear coefficient of any demagnetization method.

[0023] To achieve the above-mentioned purpose, the third aspect embodiment of the present disclosure proposes a demagnetization method evaluation device for a synchronous generator, comprising: at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions that can be executed by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can execute the demagnetization method evaluation method for a synchronous generator of the first aspect embodiment of the present disclosure.

[0024] In one or more embodiments of the present disclosure, the terminal voltage reference value, mechanical torque, nonlinear coefficients of different demagnetization methods and node admittance matrix of the power system connection structure of the synchronous generator are obtained; a demagnetization evaluation overall model is established, and the demagnetization evaluation overall model includes an excitation system model, a fifth-order model of the synchronous generator, an electromechanical model of the power grid and a demagnetization model; wherein the input of the excitation system model includes the terminal voltage reference value, and the output includes the first excitation voltage; the input of the fifth-order model of the synchronous generator includes the excitation voltage, mechanical torque and stator current, and the output includes the stator voltage, generator power angle and transient excitation voltage; the input of the electromechanical model of the power grid includes the stator voltage, generator power angle and node admittance matrix ... power grid includes the stator voltage, generator power angle and node admittance matrix, and the output includes the first excitation voltage; the input of the fifth-order model of the power grid includes the stator voltage, generator power angle and node admittance matrix, and the output includes the first excitation voltage; the input of the fifth-order model of the power grid includes the stator voltage, generator power angle and node admittance matrix, and the output includes the first excitation voltage; the input of the fifth-order model of the power grid includes the stator voltage, generator power angle and node admitt The output includes the stator current; the input of the demagnetization model includes the transient excitation voltage and the nonlinear coefficient of any demagnetization method, and the output includes the second excitation voltage; the generator terminal voltage reference value, mechanical torque, the nonlinear coefficient of any demagnetization method, and the node admittance matrix are input into the demagnetization evaluation overall model. When no demagnetization instruction is received, the first excitation voltage is selected as the excitation voltage. When a demagnetization instruction is received, the second excitation voltage is selected as the excitation voltage. If the second excitation voltage meets the requirements, the demagnetization method corresponding to the second excitation voltage is selected for demagnetization. If the second excitation voltage does not meet the requirements, the nonlinear coefficient of another demagnetization method is replaced to obtain a new second excitation voltage, and then a new demagnetization method is determined. In this case, the excitation system model, the fifth-order model of the synchronous generator, the electromechanical model of the power grid, and the demagnetization model are integrated to establish the demagnetization evaluation overall model. The obtained generator terminal voltage reference value, mechanical torque, the nonlinear coefficients of different demagnetization methods, and the node admittance matrix of the power system connection structure are input into the demagnetization evaluation overall model to obtain the excitation voltage. This improves the calculation accuracy of the excitation voltage and thus the accuracy of the demagnetization method assessment.

[0025] Additional aspects and advantages of the present disclosure will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the specific embodiments of the present disclosure or the technical solutions in the prior art, the following briefly introduces the drawings required for the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without inventive work. The above and / or additional aspects and advantages of the present disclosure will become obvious and easy to understand from the following description of the embodiments in conjunction with the drawings, among which:

[0027] Figure 1 A flow chart of a method for evaluating a demagnetization mode of a synchronous generator provided by an embodiment of the present disclosure;

[0028] Figure 2 A schematic diagram of the structure of the overall demagnetization evaluation model provided in an embodiment of the present disclosure;

[0029] Figure 3 A schematic diagram of a rotor voltage curve in a linear demagnetization mode provided by an embodiment of the present disclosure;

[0030] Figure 4 A schematic diagram of a rotor current curve in a linear demagnetization mode provided in an embodiment of the present disclosure;

[0031] Figure 5 A schematic diagram of a rotor voltage curve in a nonlinear demagnetization mode provided by an embodiment of the present disclosure;

[0032] Figure 6 A schematic diagram of a rotor current curve in a nonlinear demagnetization mode provided by an embodiment of the present disclosure;

[0033] Figure 7 A block diagram of a demagnetization mode evaluation system for a synchronous generator provided by an embodiment of the present disclosure;

[0034] Figure 8 The block diagram is a device for evaluating a demagnetization mode of a synchronous generator, which is used to implement the method for evaluating a demagnetization mode of a synchronous generator according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0035] Exemplary embodiments will be described in detail herein, with examples illustrated in the accompanying drawings. In the following description, when referring to the drawings, identical numerals in different figures represent identical or similar elements, unless otherwise indicated. The embodiments described in the following exemplary embodiments are not intended to represent all possible implementations consistent with the present disclosure. Rather, they are merely examples of apparatuses and methods consistent with certain aspects of the present disclosure, as detailed in the appended claims.

[0036] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present disclosure. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine different embodiments or examples described in this specification and features of different embodiments or examples, unless they are mutually inconsistent.

[0037] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of the present disclosure, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined. It should also be understood that the term "and / or" used in the present disclosure refers to and includes any or all possible combinations of one or more associated listed items.

[0038] The following describes in detail embodiments of the present disclosure, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present disclosure, and should not be construed as limiting the present disclosure.

[0039] The present disclosure provides a method and system for evaluating a demagnetization mode of a synchronous generator, the main purpose of which is to improve the accuracy of demagnetization mode evaluation.

[0040] In a first embodiment, Figure 1 This is a flow chart of a method for evaluating a demagnetization mode of a synchronous generator provided by an embodiment of the present disclosure. Figure 2 This is a schematic diagram of the structure of the demagnetization evaluation model provided by the embodiment of the present disclosure. Figure 1 As shown, the demagnetization mode evaluation method for a synchronous generator includes the following steps:

[0041] Step S11 , obtaining a terminal voltage reference value of the synchronous generator, mechanical torque, nonlinear coefficients of different demagnetization modes, and a node admittance matrix of the power system connection structure.

[0042] In step S11, the terminal voltage reference value can be expressed as V ref The mechanical torque can be expressed by T m The nonlinear coefficient of different demagnetization methods can be expressed by α.

[0043] In step S11, the node admittance matrix of the power system connection structure can be expressed as Y bus The power system connection structure, for example, sets up a computing environment for a single-machine-infinite system. The node admittance matrix sets up the initial voltage amplitude and phase of each node in the power system connection structure.

[0044] In step S11, the technical parameters of the synchronous generator set are also obtained, and the technical parameters of the synchronous generator set also include the rated voltage U N , rated current I N , Rated active power P N , Rated apparent power SN , stator resistance R a , stator leakage reactance X1, rated no-load excitation current I fN , Rated no-load excitation voltage U fN , synchronous reactance value, transient synchronous reactance value, subtransient synchronous reactance value, transient open circuit time constant, subtransient open circuit time constant. Among them, the synchronous reactance value includes the horizontal axis synchronous reactance value X q Synchronous reactance value X on the vertical axis d ; Transient synchronous reactance value includes transient horizontal axis synchronous reactance value X' q and transient vertical axis synchronous reactance value X' d ; The sub-transient synchronous reactance value includes the sub-transient horizontal axis synchronous reactance value X" q and the sub-transient vertical axis synchronous reactance value X" d ; Transient open circuit time constant includes transient horizontal axis open circuit time constant T' q0 and transient vertical axis open circuit time constant T' d0 ; Subtransient open circuit time constant includes subtransient horizontal axis open circuit time constant T" q0 and subtransient vertical axis open circuit time constant T" d0 The horizontal axis involved in the unit technical parameters is the Q axis in the dq axis, and the vertical axis is the D axis in the dq axis.

[0045] Step S12: establishing a demagnetization assessment overall model, which includes an excitation system model, a fifth-order synchronous generator model, a power grid electromechanical model, and a demagnetization model.

[0046] In step S12, when establishing the overall demagnetization assessment model, the parameters in the overall demagnetization assessment model are normalized using the unit technical parameters. That is, the rotor parameters of the synchronous generator involved in each model in the overall demagnetization assessment model are normalized using the unit technical parameters in the per-unit system.

[0047] The excitation inductance L f , excitation resistance R f , D-axis damping inductance L 1d , D-axis damping resistor R 1d , Q-axis damping inductance L 1q , Q-axis damping resistance R 1q For example, considering the identity of inductance and reactance under per-unit value, the rotor parameters are calculated using formula (1):

[0048]

[0049] Where, ω N is the rated angular velocity, which is generally 314 rad / s for a 50 Hz operating frequency.

[0050] In step S12, the rotor parameters to be normalized are not limited to the excitation inductance L f , excitation resistance R f , D-axis damping inductance L 1d , D-axis damping resistor R 1d , Q-axis damping inductance L 1q , Q-axis damping resistance R 1q , the obtained unit technical parameters can also be used for calculation for other rotor parameters. Among them, the rated voltage U N , rated current I N , Rated active power P N , Rated apparent power S N etc. can be used as denominators to participate in the per-unit processing and calculation of some rotor parameters.

[0051] In step S12, as Figure 2 As shown, the deexcitation assessment overall model includes an excitation system model. Specifically, the input of the excitation system model includes a machine terminal voltage reference value, and the output includes a first excitation voltage.

[0052] In step S12, the input of the excitation system model further includes the real-time value of the generator-end voltage, and the excitation system model outputs a first excitation voltage based on the generator-end voltage reference value and the real-time value of the generator-end voltage.

[0053] In step S12, the excitation system model adopts the power system static stabilizer (i.e., PSS link), and the input of the excitation system model also includes the generator rotor angular velocity change value. The auxiliary voltage transformation value (i.e., PSS link output value) is obtained based on the generator rotor angular velocity change value, and the first excitation voltage is output based on the auxiliary voltage transformation value, the generator terminal voltage reference value, and the generator terminal voltage real-time value. Specifically, the first excitation voltage E fd1 Satisfying formula (2):

[0054]

[0055] V i =-V t +V PSS (2)

[0056] Where K A 、T A Indicates that V ref Indicates the terminal voltage reference value, V t Indicates the real-time value of the terminal voltage, V PSS Represents the output value of the PSS link, and s represents the imaginary part.

[0057] The output value of the PSS link is obtained based on the generator rotor angular velocity change value Δω. Specifically, the angular velocity change value is sequentially and Calculate and obtain the PSS link output value V PSS Among them, K PSS T1, T2, T3, and T4 are key parameters of the excitation regulator PSS link. The key parameters of the excitation regulator PSS link and the key parameters of the excitation regulator PSS link are also included in the unit technical parameters obtained in step S11.

[0058] It should be noted that when the excitation system model is initially calculated, the generator rotor angular velocity change value and the real-time value of the terminal voltage are initial values. In subsequent calculations, the generator rotor angular velocity change value and the real-time value of the terminal voltage are provided by the output data of the fifth-order model of the synchronous generator.

[0059] In step S12, as Figure 2 As shown, the demagnetization assessment overall model includes a fifth-order synchronous generator model (also called a fifth-order synchronous generator electromechanical model). Specifically, the input of the fifth-order synchronous generator model includes the excitation voltage E fd , Mechanical torque (also called prime mover mechanical torque) T m and stator current I dq , the output includes the stator voltage V dq , generator power angle δ and transient excitation voltage. Stator voltage V dq Including D-axis generator stator voltage u d and Q-axis generator stator voltage u q , stator current I dq Including the D-axis generator stator current i d and Q-axis generator stator current i q .

[0060] The fifth-order model of synchronous generator satisfies formula (3):

[0061]

[0062] Where Ψq is the Q-axis stator flux, E d ″ is the D-axis transient excitation voltage, Ψ d is the D-axis stator flux, E q ″ is the Q-axis transient excitation voltage, p represents the differential operator, E q ′ is the Q-axis transient excitation voltage, T J is the unit's moment of inertia, ω is the generator rotor angular velocity, K D is the damping coefficient.

[0063] In some embodiments, as Figure 2 As shown, the output of the fifth-order synchronous generator model also includes the real-time value of the terminal voltage V tThe fifth-order synchronous generator model is connected to the excitation system model. The real-time terminal voltage value and the generator rotor angular velocity change value output by the fifth-order synchronous generator model participate in the calculation of the excitation system model.

[0064] In some embodiments, the output of the fifth-order synchronous generator model also includes electromagnetic power.

[0065] In some embodiments, the fifth-order model of the synchronous generator is further used to send the received stator current to the deexcitation model.

[0066] It should be noted that when the fifth-order model of the synchronous generator is first calculated, the stator current I dq is the initial value. In subsequent calculations, the stator current I dq Provided by the output data of the grid electromechanical model.

[0067] In some embodiments, as Figure 2 As shown, the fifth-order model of the synchronous generator is connected to the selector C, and the output of the selector C is the excitation voltage E fd The input of selector C is connected to the excitation system model and the demagnetization model respectively. When selector C receives the demagnetization instruction M, selector C selects the second excitation voltage E output by the demagnetization model. fd2 If the demagnetization command M is not received, the selector C selects the first excitation voltage E output by the excitation system model. fd1 .

[0068] In step S12, as Figure 2 As shown, the demagnetization assessment overall model includes a demagnetization model. Specifically, the demagnetization model has an input including a transient excitation voltage and a nonlinear coefficient of any demagnetization method, and an output including a second excitation voltage.

[0069] In some embodiments, the input of the demagnetization model in step S12 further includes a subtransient excitation voltage, and the demagnetization model outputs a second excitation voltage based on the transient excitation voltage, the subtransient excitation voltage, and a nonlinear coefficient of any demagnetization method.

[0070] In some embodiments, the input of the deexcitation model in step S12 also includes the stator current, and the deexcitation model outputs the second excitation voltage based on the transient excitation voltage, the subtransient excitation voltage, the stator current and the nonlinear coefficient of any deexcitation method.

[0071] In some embodiments, the output of the deexcitation model also includes an excitation current.

[0072] like Figure 2 As shown, the deexcitation model is connected to the fifth-order model of the synchronous generator. The transient excitation voltage, subtransient excitation voltage, and stator current in the deexcitation model input are from the fifth-order model of the synchronous generator.

[0073] In some embodiments, the second excitation voltage output by the demagnetization model satisfies equation (4):

[0074]

[0075] Where, f is the induced flux of the excitation winding, i f is the excitation current, k is the demagnetization resistance capacity coefficient, and α is the nonlinear coefficient of the demagnetization method. If α=1, it means the demagnetization method is linear resistance demagnetization, and if α<1, it means the demagnetization method is nonlinear resistance demagnetization. f It can be calculated based on the transient excitation voltage, sub-transient excitation voltage, and stator current. The demagnetization model inputs the nonlinear coefficient of each demagnetization method each time to calculate the corresponding second excitation voltage.

[0076] In step S12, as Figure 2 As shown, the overall de-excitation assessment model includes a power grid electromechanical model. Specifically, the input of the power grid electromechanical model includes stator voltage, generator power angle and node admittance matrix, and the output includes stator current.

[0077] like Figure 2 As shown, the grid electromechanical model is connected to the fifth-order model of the synchronous generator. The grid electromechanical model receives the stator voltage and generator power angle output by the fifth-order model of the synchronous generator, and the grid electromechanical model outputs the stator current to the fifth-order model of the synchronous generator.

[0078] In the grid electromechanical model, the output stator current I dq Satisfying formula (5):

[0079] I=Y bus V bus (5)

[0080] Where I is the current value of the natural coordinate corresponding to the stator current. bus is the stator voltage V dq The voltage value of the corresponding natural coordinate satisfies formula (6):

[0081]

[0082] Where V inf is the node voltage of the power grid system. V d is the stator voltage of the D-axis generator, V q is the Q-axis generator stator voltage.

[0083] The stator current under the current dq axis satisfies formula (7):

[0084]

[0085] In the formula, end is the last row value of the column vector after matrix operation

[0086] Step S13: input the machine-end voltage reference value, mechanical torque, nonlinear coefficient of any demagnetization method, and node admittance matrix into the demagnetization evaluation overall model; when no demagnetization instruction is received, select the first excitation voltage as the excitation voltage; when a demagnetization instruction is received, select the second excitation voltage as the excitation voltage; if the second excitation voltage meets the requirements, select the demagnetization method corresponding to the second excitation voltage for demagnetization; if the second excitation voltage does not meet the requirements, replace the nonlinear coefficient of other demagnetization methods to obtain a new second excitation voltage, and then determine a new demagnetization method.

[0087] In step S13, a demagnetization instruction is generated when an external working condition triggers a demagnetization action.

[0088] In step S13, if the second excitation voltage meets the requirements, the demagnetization method corresponding to the second excitation voltage is selected for demagnetization. This means that if the second excitation voltage meets the requirements, the demagnetization method is determined based on the nonlinear coefficient of the demagnetization method obtained for the second excitation voltage. The demagnetization method is the required demagnetization method obtained by evaluation, and demagnetization is performed using the demagnetization method.

[0089] In some embodiments, the second excitation voltage meeting the requirements means satisfying the calculation results and design requirements of the maximum deexcitation voltage.

[0090] In step S12, when establishing the overall demagnetization assessment model, the input and output data of the excitation system model, the fifth-order synchronous generator model, the grid electromechanical model, and the demagnetization model are matched. This matching process involves converting data on different coordinate axes to the same coordinate axis. This completes the matching connection between the interfaces of the excitation system model, the fifth-order synchronous generator model, the grid electromechanical model, and the demagnetization model.

[0091] Figure 3 A schematic diagram of a rotor voltage curve in a linear demagnetization mode provided by an embodiment of the present disclosure; Figure 4 A schematic diagram of a rotor current curve in a linear demagnetization mode provided in an embodiment of the present disclosure; Figure 5 A schematic diagram of a rotor voltage curve in a nonlinear demagnetization mode provided by an embodiment of the present disclosure; Figure 6 This is a schematic diagram of the rotor current curve under the nonlinear demagnetization method provided by an embodiment of the present disclosure.

[0092] A domestic 700MVA implicit synchronous generator set is used as an example to evaluate the demagnetization method. The rated load excitation current of the set is 4625A, the no-load rated excitation current is 1437A, and the rotor resistance is 0.1Ω. The design intends to compare the two demagnetization methods of linear stainless steel resistance and nonlinear zinc oxide resistance (the nonlinear coefficient α is 0.8), that is, setting α=1 and α=0.8. The demagnetization control voltage is 2200V. Under load conditions, a three-phase short circuit fault occurs at the machine end and the magnetic field circuit breaker trips after 0.65s. Using the demagnetization method evaluation method for synchronous generators according to the embodiment of the present disclosure, it is obtained Figure 3 and Figure 4 The calculation results of the excitation voltage (i.e. rotor voltage) and excitation current of the linear de-excitation method shown in FIG, and Figure 5 and Figure 6 The calculation results of the excitation voltage and excitation current of the nonlinear deexcitation method are shown in FIG. Figure 3 and Figure 4 As shown in the figure, at the first second, a short circuit fault occurs and the rotor voltage drops to 0V. After a 0.65s delay, the linear demagnetization resistor is put into operation. The resistor energy consumption in the linear demagnetization mode is 2.64MJ, the maximum excitation current is 6090A, and the maximum demagnetization voltage is 965.6V. Figure 5 and Figure 6 As shown, a short-circuit fault occurs at 1 second, and the rotor voltage drops to 0 V. After a 0.65-second delay, the nonlinear deexcitation resistor switches on. The nonlinear deexcitation resistor dissipates 2.90 MJ of energy, resulting in a maximum excitation current of 6087 A and a maximum deexcitation voltage of 1138 V. Based on the calculated maximum deexcitation voltage and design requirements, a deexcitation method that meets these requirements is selected.

[0093] In the demagnetization mode evaluation method for a synchronous generator according to an embodiment of the present disclosure, the terminal voltage reference value, mechanical torque, nonlinear coefficients of different demagnetization modes and node admittance matrix of the power system connection structure of the synchronous generator are obtained; a demagnetization evaluation overall model is established, and the demagnetization evaluation overall model includes an excitation system model, a fifth-order model of a synchronous generator, an electromechanical model of a power grid and a demagnetization model; wherein the input of the excitation system model includes the terminal voltage reference value, and the output includes the first excitation voltage; the input of the fifth-order model of the synchronous generator includes the excitation voltage, mechanical torque and stator current, and the output includes the stator voltage, generator power angle and transient excitation voltage; the input of the electromechanical model of the power grid includes the stator voltage, generator power angle and node The output of the demagnetization model includes a stator current. The input of the demagnetization model includes the transient excitation voltage and the nonlinear coefficient of any demagnetization method, and the output includes the second excitation voltage. The generator terminal voltage reference value, mechanical torque, the nonlinear coefficient of any demagnetization method, and the node admittance matrix are input into the demagnetization evaluation overall model. When no demagnetization instruction is received, the first excitation voltage is selected as the excitation voltage. When a demagnetization instruction is received, the second excitation voltage is selected as the excitation voltage. If the second excitation voltage meets the requirements, the demagnetization method corresponding to the second excitation voltage is selected for demagnetization. If the second excitation voltage does not meet the requirements, the nonlinear coefficient of another demagnetization method is replaced to obtain a new second excitation voltage, and then a new demagnetization method is determined. In this case, the excitation system model, the fifth-order synchronous generator model, the power grid electromechanical model, and the demagnetization model are integrated to establish the demagnetization evaluation overall model. The obtained generator terminal voltage reference value, mechanical torque, the nonlinear coefficients of different demagnetization methods, and the node admittance matrix of the power system connection structure are input into the demagnetization evaluation overall model to obtain the excitation voltage. This improves the calculation accuracy of the excitation voltage and thus the accuracy of the demagnetization method assessment. In addition, the demagnetization mode evaluation method disclosed in the present invention takes into account the electromechanical model modeling of the fifth-order synchronous generator in the demagnetization process, and can realize the design calculation of the demagnetization capacity of the synchronous generator excitation system, guide and evaluate the selection of demagnetization resistors, and ensure the reliability and safety of the demagnetization action of the excitation system. In addition, it can also be used for small disturbance stability analysis taking into account the demagnetization process, thereby improving the accuracy of small disturbance calculation of the power system. It has low computational complexity, high versatility, and is easy to promote and use.

[0094] The following are system embodiments of the present disclosure, which can be used to implement the method embodiments of the present disclosure. For details not disclosed in the system embodiments of the present disclosure, please refer to the method embodiments of the present disclosure.

[0095] See Figure 7 , Figure 7 This is a block diagram of a demagnetization mode evaluation system for a synchronous generator provided by an embodiment of the present disclosure. The demagnetization mode evaluation system 10 for a synchronous generator includes an acquisition module 11, a modeling module 12, and an evaluation module 13, wherein:

[0096] An acquisition module 11 is used to obtain a terminal voltage reference value of the synchronous generator, mechanical torque, nonlinear coefficients of different demagnetization methods, and a node admittance matrix of the power system connection structure;

[0097] A modeling module 12 is used to establish a demagnetization assessment overall model, which includes an excitation system model, a fifth-order synchronous generator model, a power grid electromechanical model, and a demagnetization model; wherein the input of the excitation system model includes a terminal voltage reference value, and the output includes a first excitation voltage; the input of the fifth-order synchronous generator model includes excitation voltage, mechanical torque, and stator current, and the output includes stator voltage, generator power angle, and transient excitation voltage; the input of the power grid electromechanical model includes stator voltage, generator power angle, and node admittance matrix, and the output includes stator current; the input of the demagnetization model includes transient excitation voltage and the nonlinear coefficient of any demagnetization method, and the output includes a second excitation voltage;

[0098] The evaluation module 13 is used to input the machine-end voltage reference value, mechanical torque, and the nonlinear coefficient and node admittance matrix of any demagnetization method into the demagnetization evaluation overall model. When no demagnetization instruction is received, the first excitation voltage is selected as the excitation voltage. When a demagnetization instruction is received, the second excitation voltage is selected as the excitation voltage. If the second excitation voltage meets the requirements, the demagnetization method corresponding to the second excitation voltage is selected for demagnetization. If the second excitation voltage does not meet the requirements, the nonlinear coefficient of other demagnetization methods is replaced to obtain a new second excitation voltage, and then a new demagnetization method is determined.

[0099] Optionally, the acquisition module 11 is also used to obtain the unit technical parameters of the synchronous generator, which also include rated voltage, rated current, rated active power, rated apparent power, stator resistance, stator leakage reactance, rated no-load excitation current, rated no-load excitation voltage, synchronous reactance value, transient synchronous reactance value, subtransient synchronous reactance value, transient open-circuit time constant, and subtransient open-circuit time constant.

[0100] Optionally, the demagnetization mode assessment system further includes a preprocessing module, which is used to perform normalization processing on parameters in the demagnetization assessment overall model using unit technical parameters when establishing the demagnetization assessment overall model.

[0101] Optionally, the input of the deexcitation model further includes a subtransient excitation voltage, and the deexcitation model outputs a second excitation voltage based on the transient excitation voltage, the subtransient excitation voltage and a nonlinear coefficient of any deexcitation method.

[0102] Optionally, the output of the fifth-order model of the synchronous generator also includes the real-time value of the machine-end voltage, the input of the excitation system model also includes the real-time value of the machine-end voltage, and the excitation system model outputs the first excitation voltage based on the machine-end voltage reference value and the real-time value of the machine-end voltage.

[0103] Optionally, the excitation system model adopts a power system static stabilizer, and the input of the excitation system model also includes the generator rotor angular velocity change value. The auxiliary voltage transformation value is obtained based on the generator rotor angular velocity change value, and the first excitation voltage is output based on the auxiliary voltage transformation value, the machine-end voltage reference value and the machine-end voltage real-time value.

[0104] Optionally, when the modeling module 12 establishes the overall demagnetization assessment model, it matches the input and output data of the excitation system model, the fifth-order synchronous generator model, the power grid electromechanical model and the demagnetization model. The matching process is to convert the data under different coordinate axes to the same coordinate axis.

[0105] It should be noted that the above explanation of the embodiment of the demagnetization method evaluation method for a synchronous generator is also applicable to the demagnetization method evaluation system for a synchronous generator of this embodiment, and will not be repeated here.

[0106] In the demagnetization mode evaluation system for synchronous generators of the embodiment of the present disclosure, an acquisition module acquires the terminal voltage reference value, mechanical torque, nonlinear coefficients of different demagnetization modes and node admittance matrix of the power system connection structure of the synchronous generator; a modeling module establishes a demagnetization evaluation overall model, which includes an excitation system model, a fifth-order model of the synchronous generator, a grid electromechanical model and a demagnetization model; wherein the input of the excitation system model includes the terminal voltage reference value, and the output includes the first excitation voltage; the input of the fifth-order model of the synchronous generator includes the excitation voltage, mechanical torque and stator current, and the output includes the stator voltage, generator power angle and transient excitation voltage; the input of the grid electromechanical model includes the stator voltage, generator power angle and The node admittance matrix, the output includes the stator current; the input of the demagnetization model includes the transient excitation voltage and the nonlinear coefficient of any demagnetization method, and the output includes the second excitation voltage; the evaluation module inputs the machine-end voltage reference value, the mechanical torque, the nonlinear coefficient of any demagnetization method and the node admittance matrix into the demagnetization evaluation total model. When no demagnetization instruction is received, the first excitation voltage is selected as the excitation voltage. When the demagnetization instruction is received, the second excitation voltage is selected as the excitation voltage. If the second excitation voltage meets the requirements, the demagnetization method corresponding to the second excitation voltage is selected for demagnetization. If the second excitation voltage does not meet the requirements, the nonlinear coefficient of other demagnetization methods is replaced to obtain a new second excitation voltage, and then the new demagnetization method is determined. In this case, a demagnetization evaluation overall model is established by integrating the excitation system model, the fifth-order synchronous generator model, the power grid electromechanical model, and the demagnetization model. The obtained synchronous generator terminal voltage reference value, mechanical torque, nonlinear coefficients of different demagnetization methods, and the node admittance matrix of the power system connection structure are used to input the demagnetization evaluation overall model to obtain the excitation voltage. This improves the calculation accuracy of the excitation voltage and thus the accuracy of the demagnetization method evaluation. In addition, the demagnetization method evaluation system disclosed herein takes into account the fifth-order synchronous generator electromechanical model modeling of the demagnetization process, and can realize the design calculation of the demagnetization capacity of the synchronous generator excitation system, guide and evaluate the selection of demagnetization resistors, ensure the reliability and safety of the demagnetization action of the excitation system, and can also be used for small disturbance stability analysis taking into account the demagnetization process, thereby improving the accuracy of small disturbance calculation of the power system. It has low computational complexity, high versatility, and is easy to promote and use.

[0107] According to an embodiment of the present disclosure, the present disclosure further provides a demagnetization mode evaluation device for a synchronous generator, a readable storage medium, and a computer program product.

[0108] Figure 8It is a block diagram of a demagnetization mode evaluation device for a synchronous generator used to implement the demagnetization mode evaluation method for a synchronous generator according to an embodiment of the present disclosure. The demagnetization mode evaluation device for a synchronous generator is intended to represent various forms of digital computers, such as laptop computers, desktop computers, workstations, personal digital assistants, servers, blade servers, mainframe computers, and other suitable computers. The demagnetization mode evaluation device for a synchronous generator can also represent various forms of mobile devices, such as personal digital processing, cellular phones, smart phones, wearable demagnetization mode evaluation devices for synchronous generators, and other similar computing devices. The components, connections and relationships of the components, and functions of the components shown in the present disclosure are merely examples and are not intended to limit the implementation of the present disclosure described and / or required in the present disclosure.

[0109] like Figure 8 As shown, a demagnetization method evaluation device 20 for a synchronous generator includes a computing unit 21, which can perform various appropriate actions and processes according to a computer program stored in a read-only memory (ROM) 22 or a computer program loaded from a storage unit 28 into a random access memory (RAM) 23. RAM 23 may also store various programs and data required for the operation of the demagnetization method evaluation device 20 for a synchronous generator. The computing unit 21, ROM 22, and RAM 23 are connected to each other via a bus 24. An input / output (I / O) interface 25 is also connected to the bus 24.

[0110] Multiple components in the demagnetization method evaluation device 20 for a synchronous generator are connected to an I / O interface 25, including: an input unit 26, such as a keyboard, a mouse, etc.; an output unit 27, such as various types of displays, speakers, etc.; a storage unit 28, such as a magnetic disk, an optical disk, etc., which is communicatively connected to the computing unit 21; and a communication unit 29, such as a network card, a modem, a wireless communication transceiver, etc. The communication unit 29 allows the demagnetization method evaluation device 20 for a synchronous generator to exchange information / data with other demagnetization method evaluation devices for a synchronous generator via a computer network such as the Internet and / or various telecommunication networks.

[0111] The computing unit 21 can be various general-purpose and / or specialized processing components with processing and computing capabilities. Some examples of the computing unit 21 include, but are not limited to, a central processing unit (CPU), a graphics processing unit (GPU), various specialized artificial intelligence (AI) computing chips, various computing units running machine learning model algorithms, a digital signal processor (DSP), and any appropriate processor, controller, microcontroller, etc. The computing unit 21 executes the various methods and processes described above, such as executing a demagnetization method evaluation method for a synchronous generator. For example, in some embodiments, the demagnetization method evaluation method for a synchronous generator can be implemented as a computer software program tangibly embodied in a machine-readable medium, such as a storage unit 28. In some embodiments, part or all of the computer program can be loaded and / or installed into the demagnetization method evaluation device 20 for a synchronous generator via the ROM 22 and / or the communication unit 29. When the computer program is loaded into the RAM 23 and executed by the computing unit 21, one or more steps of the demagnetization method evaluation method for a synchronous generator described above can be performed. Alternatively, in other embodiments, the computing unit 21 may be configured to execute the demagnetization mode evaluation method for a synchronous generator in any other appropriate manner (for example, by means of firmware).

[0112] Various embodiments of the systems and techniques described above in the present disclosure can be implemented in digital electronic circuit systems, integrated circuit systems, field programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), application specific standard products (ASSPs), system-on-chip systems (SOCs), load programmable logic devices (CPLDs) for evaluating demagnetization methods of synchronous generators, computer hardware, firmware, software, and / or combinations thereof. These various embodiments may include being implemented in one or more computer programs that are executable and / or interpreted on a programmable system including at least one programmable processor, which may be a special-purpose or general-purpose programmable processor that can receive data and instructions from a storage system, at least one input device, and at least one output device, and transmit data and instructions to the storage system, the at least one input device, and the at least one output device.

[0113] The program code for implementing the method of the present disclosure can be written in any combination of one or more programming languages. These program codes can be provided to a processor or controller of a general-purpose computer, a special-purpose computer, or other programmable data processing device so that when the program code is executed by the processor or controller, the functions / operations specified in the flow chart and / or block diagram are implemented. The program code can be executed entirely on the machine, partially on the machine, as a stand-alone software package, partially on the machine and partially on a remote machine, or entirely on a remote machine or server.

[0114] In the present disclosure, a machine-readable medium may be a tangible medium that may contain or store a program for use by or in conjunction with an instruction execution system, an apparatus, or a device for evaluating a demagnetization method of a synchronous generator. The machine-readable medium may be a machine-readable signal medium or a machine-readable storage medium. The machine-readable medium may include, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device for evaluating a demagnetization method of a synchronous generator, or any suitable combination of the foregoing. More specific examples of machine-readable storage media may include an electrical connection based on one or more wires, a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device for evaluating a demagnetization method of a synchronous generator, a magnetic storage device for evaluating a demagnetization method of a synchronous generator, or any suitable combination of the foregoing.

[0115] To provide interaction with a user, the systems and techniques described herein can be implemented on a computer having: a display device (e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor) for displaying information to the user; and a keyboard and pointing device (e.g., a mouse or trackball) through which the user can provide input to the computer. Other types of devices can also be used to provide interaction with the user; for example, the feedback provided to the user can be any form of sensory feedback (e.g., visual feedback, auditory feedback, or tactile feedback); and input from the user can be received in any form (including acoustic input, voice input, or tactile input).

[0116] The systems and techniques described herein can be implemented in a computing system that includes back-end components (e.g., as a data server), or a computing system that includes middleware components (e.g., an application server), or a computing system that includes front-end components (e.g., a user computer with a graphical user interface or a web browser through which a user can interact with implementations of the systems and techniques described herein), or a computing system that includes any combination of such back-end components, middleware components, or front-end components. The components of the system can be interconnected by any form or medium of digital data communication (e.g., a communication network). Examples of communication networks include: a local area network (LAN), a wide area network (WAN), the Internet, and a blockchain network.

[0117] A computer system may include a client and a server. The client and server are generally remote from each other and typically interact via a communication network. This client-server relationship is established by computer programs running on the respective computers, establishing a client-server relationship. The server may be a cloud server, also known as a cloud computing server or cloud host, a host product within the cloud computing service ecosystem that addresses the management difficulties and limited scalability of traditional physical hosts and VPS services ("Virtual Private Servers" or simply "VPS"). The server may also be a server in a distributed system or a server integrated with blockchain.

[0118] It should be understood that the various forms of processes shown above can be used to reorder, add, or delete steps. For example, the steps described in this disclosure can be performed in parallel, sequentially, or in a different order, as long as the desired results of the technical solutions disclosed in this disclosure can be achieved. This disclosure is not limited here.

[0119] The above specific embodiments do not constitute a limitation on the scope of protection of this disclosure. Those skilled in the art will appreciate that various modifications, combinations, sub-combinations, and substitutions may be made based on design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this disclosure shall be included within the scope of protection of this disclosure.

Claims

1. A method for evaluating the demagnetization mode of a synchronous generator, characterized in that: include: Obtain the terminal voltage reference value, mechanical torque, nonlinear coefficients of different demagnetization methods, and node admittance matrix of the power system connection structure of the synchronous generator; Establishing a demagnetization assessment overall model, the demagnetization assessment overall model includes an excitation system model, a fifth-order synchronous generator model, a power grid electromechanical model, and a demagnetization model; wherein the input of the excitation system model includes the machine-end voltage reference value, and the output includes a first excitation voltage; the input of the fifth-order synchronous generator model includes the excitation voltage, the mechanical torque, and the stator current, and the output includes the stator voltage, the generator power angle, and the transient excitation voltage; the input of the power grid electromechanical model includes the stator voltage, the generator power angle, and the node admittance matrix, and the output includes the stator current; the input of the demagnetization model includes the transient excitation voltage and the nonlinear coefficient of any demagnetization method, and the output includes the second excitation voltage; Inputting the machine-end voltage reference value, mechanical torque, and the nonlinear coefficient and node admittance matrix of any demagnetization method into the demagnetization evaluation overall model, selecting the first excitation voltage as the excitation voltage when no demagnetization instruction is received, and selecting the second excitation voltage as the excitation voltage when a demagnetization instruction is received; if the second excitation voltage meets the requirements, selecting the demagnetization method corresponding to the second excitation voltage for demagnetization; if the second excitation voltage does not meet the requirements, replacing the nonlinear coefficient of another demagnetization method to obtain a new second excitation voltage, and then determining a new demagnetization method; The output of the fifth-order model of the synchronous generator also includes the real-time value of the terminal voltage, the input of the excitation system model also includes the real-time value of the terminal voltage, the excitation system model adopts the power system static stabilizer, the input of the excitation system model also includes the generator rotor angular velocity change value, the auxiliary voltage transformation value is obtained based on the generator rotor angular velocity change value, and the first excitation voltage is output based on the auxiliary voltage transformation value, the terminal voltage reference value and the real-time value of the terminal voltage. The first excitation voltage E fd1 Satisfies the formula: Where, represents the coefficient, Indicates the terminal voltage reference value, Indicates the real-time value of the terminal voltage. Indicates the output value of the PSS link, represents the imaginary part; The input of the demagnetization model also includes a subtransient excitation voltage. The demagnetization model outputs a second excitation voltage based on the transient excitation voltage, the subtransient excitation voltage, and the nonlinear coefficient of any demagnetization method. The second excitation voltage output by the demagnetization model satisfies the formula: Where, Ψ f is the induced flux of the excitation winding, is the excitation current, k is the demagnetization resistance capacity coefficient, α is the nonlinear coefficient of the demagnetization method. If α=1, it means the demagnetization method is linear resistance demagnetization. If α<1, it means the demagnetization method is nonlinear resistance demagnetization. The excitation current It can be calculated based on the transient excitation voltage, sub-transient excitation voltage, and stator current. The demagnetization model inputs the nonlinear coefficient of a demagnetization method each time to calculate the corresponding second excitation voltage.

2. The demagnetization mode evaluation method for a synchronous generator according to claim 1, characterized in that: Also includes: Obtaining technical parameters of the synchronous generator set, wherein the technical parameters of the synchronous generator set further include rated voltage, rated current, rated active power, rated apparent power, stator resistance, stator leakage reactance, rated no-load excitation current, rated no-load excitation voltage, synchronous reactance value, transient synchronous reactance value, subtransient synchronous reactance value, transient open-circuit time constant, and subtransient open-circuit time constant; When establishing the demagnetization assessment overall model, the parameters in the demagnetization assessment overall model are normalized using the unit technical parameters.

3. The demagnetization mode evaluation method for a synchronous generator according to claim 1, characterized in that: When establishing the overall demagnetization assessment model, the input and output data of the excitation system model, the fifth-order synchronous generator model, the power grid electromechanical model and the demagnetization model are matched. The matching process is to convert the data under different coordinate axes to the same coordinate axis.

4. A demagnetization mode evaluation system for a synchronous generator, characterized in that: include: An acquisition module is used to obtain the terminal voltage reference value, mechanical torque, nonlinear coefficients of different demagnetization methods, and node admittance matrix of the power system connection structure of the synchronous generator; a modeling module for establishing a demagnetization assessment overall model, the demagnetization assessment overall model including an excitation system model, a fifth-order synchronous generator model, a power grid electromechanical model, and a demagnetization model; wherein the input of the excitation system model includes the machine-end voltage reference value, and the output includes a first excitation voltage; the input of the fifth-order synchronous generator model includes the excitation voltage, the mechanical torque, and the stator current, and the output includes the stator voltage, the generator power angle, and the transient excitation voltage; the input of the power grid electromechanical model includes the stator voltage, the generator power angle, and the node admittance matrix, and the output includes the stator current; the input of the demagnetization model includes the transient excitation voltage and the nonlinear coefficient of any demagnetization method, and the output includes the second excitation voltage; an evaluation module, configured to input the machine-end voltage reference value, the mechanical torque, the nonlinear coefficient of any demagnetization method, and the node admittance matrix into the demagnetization evaluation overall model; select the first excitation voltage as the excitation voltage when no demagnetization instruction is received; select the second excitation voltage as the excitation voltage when a demagnetization instruction is received; if the second excitation voltage meets the requirements, select the demagnetization method corresponding to the second excitation voltage for demagnetization; if the second excitation voltage does not meet the requirements, replace the nonlinear coefficient of another demagnetization method to obtain a new second excitation voltage, and then determine a new demagnetization method; The output of the fifth-order model of the synchronous generator also includes the real-time value of the terminal voltage, the input of the excitation system model also includes the real-time value of the terminal voltage, the excitation system model adopts the power system static stabilizer, the input of the excitation system model also includes the generator rotor angular velocity change value, the auxiliary voltage transformation value is obtained based on the generator rotor angular velocity change value, and the first excitation voltage is output based on the auxiliary voltage transformation value, the terminal voltage reference value and the real-time value of the terminal voltage. The first excitation voltage E fd1 Satisfies the formula: Where, represents the coefficient, Indicates the terminal voltage reference value, Indicates the real-time value of the terminal voltage. Indicates the output value of the PSS link, represents the imaginary part; The input of the demagnetization model also includes a subtransient excitation voltage. The demagnetization model outputs a second excitation voltage based on the transient excitation voltage, the subtransient excitation voltage, and the nonlinear coefficient of any demagnetization method. The second excitation voltage output by the demagnetization model satisfies the formula: Where, Ψ f is the induced flux of the excitation winding, is the excitation current, k is the demagnetization resistance capacity coefficient, α is the nonlinear coefficient of the demagnetization method. If α=1, it means the demagnetization method is linear resistance demagnetization. If α<1, it means the demagnetization method is nonlinear resistance demagnetization. The excitation current It can be calculated based on the transient excitation voltage, sub-transient excitation voltage, and stator current. The demagnetization model inputs the nonlinear coefficient of a demagnetization method each time to calculate the corresponding second excitation voltage.

5. The de-excitation mode evaluation system for synchronous generators according to claim 4, characterized in that: The acquisition module is further used to acquire the unit technical parameters of the synchronous generator, and the unit technical parameters also include rated voltage, rated current, rated active power, rated apparent power, stator resistance, stator leakage reactance, rated no-load excitation current, rated no-load excitation voltage, synchronous reactance value, transient synchronous reactance value, sub-transient synchronous reactance value, transient open-circuit time constant, and sub-transient open-circuit time constant; the demagnetization mode evaluation system also includes a preprocessing module, and the preprocessing module is used to use the unit technical parameters to perform normalization processing on the parameters in the demagnetization evaluation overall model when establishing the demagnetization evaluation overall model.

6. A device for evaluating the demagnetization mode of a synchronous generator, characterized in that: include: at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can execute the demagnetization mode evaluation method for a synchronous generator according to any one of claims 1 to 3.

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