Comprehensive analysis method and system for matching between loss-of-excitation protection and excitation limitation of generator

Abstract

The present invention relates to a comprehensive analysis method and system for the matching between loss-of-excitation protection and excitation limitation of a generator. The method comprises: acquiring basic parameters of a generator set; performing power plane calculation on each protection and limitation condition on the basis of the basic parameters, so as to obtain data under a power plane of each protection and limitation condition; acquiring preset operating condition data; performing calculation on the basis of the preset operating condition data and the data under the power plane of each protection and limitation condition, so as to obtain a reactive power limit value corresponding to each protection and limitation condition; and performing comprehensive analysis on the matching between loss-of-excitation protection and excitation limitation on the basis of the reactive power limit value corresponding to each protection and limitation condition. The present invention can implement a complex logic calculation related to the rapid and automatic conversion of loss-of-excitation admittance, an impedance circle and a power circle, thus replacing the original manual complex calculation, and significantly improving the calculation efficiency; and the present invention can also implement comprehensive analysis for the matching between loss-of-excitation protection, low excitation limitation, a generator power limit and a stator overcurrent limitation, thus greatly improving the predictability of a risk during a test process and the accuracy of test data.

Description

Comprehensive analysis method and system for matching between generator de-excitation protection and excitation limitation Technical Field

[0001] The present invention relates to the technical field of generator demagnetization protection and excitation limitation, and more particularly to a method and system for comprehensive analysis of matching between generator demagnetization protection and excitation limitation. Background Art

[0002] With the construction of large-scale interconnected power grids featuring a high proportion of renewable energy, the problem of excess reactive power during peak and valley loads is becoming increasingly serious. This has led to higher grid-side requirements for the demagnetization and phase-leading operation of large-capacity nuclear power generators. Before commercial operation, nuclear power units are required by the National Energy Administration to meet 25 countermeasures: "Generators must be capable of phase-leading operation. Generators of 100 MW and above must achieve a power factor of -0.95 to -0.97 at rated output." Furthermore, nuclear power plants are required to fully activate grid-related protection devices, including generator demagnetization protection, underexcitation limiting, and maximum stator current limiting, during special phase-leading tests. However, in practice, to ensure safe and stable operation, the protection settings set for phase-leading depth are relatively shallow, and the initial setting values ​​often fail to meet the aforementioned grid standards. This creates a conflict between safe unit operation and countermeasure requirements. During phase-leading tests, the maximum phase-leading depth of the generators, affected by demagnetization protection, cannot meet the National Energy Administration's countermeasure requirements, resulting in a high risk of tripping during the test. At the same time, manufacturers also specify the output curve power limits for generator design based on manufacturing process characteristics before shipment. Furthermore, the phase-leading operation in the demagnetization mode reduces the stator voltage. With active power remaining constant and reactive power gradually decreasing, the stator current increases rapidly. If the stator overcurrent exceeds the limit, it will cause stator winding heating and insulation damage. The above four aspects appear independent, with independent and distinct protection principles and setting schemes. However, in actual operation, they are inevitably mutually constrained and closely linked. Improper setting or configuration of any one aspect can cause oscillation and instability in the unit and grid, and even serious damage to the generator. Therefore, comprehensive verification of their compatibility before operation with unknown risks is particularly important and critical.

[0003] The protection setting and limit parameter selection of existing technical solutions are completed independently and are unrelated to each other. There is a lack of systematic and scientific comprehensive matching analysis, and the independent setting results of each party are prone to conflict. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method and system for comprehensive analysis of the matching performance of generator demagnetization protection and excitation limitation.

[0005] The technical solution adopted by the present invention to solve its technical problems is: constructing a comprehensive analysis method for the matching of generator demagnetization protection and excitation limitation, including the following steps: obtaining basic parameters of the generator set; performing power plane calculation of protection and limitation conditions based on the basic parameters to obtain data under the power plane of the protection and limitation conditions; obtaining preset operating condition data; performing calculation based on the preset operating condition data and the data under the power plane of the protection and limitation conditions to obtain a reactive power limit value corresponding to the protection and limitation conditions; and performing a comprehensive analysis of the matching of demagnetization protection and excitation limitation based on the reactive power limit value corresponding to the protection and limitation conditions, the generator power limit, and the stator overcurrent limit value.

[0006] Preferably, the protection and restriction conditions include: impedance-type demagnetization protection or admittance-type demagnetization protection; the data of the protection and restriction conditions under the power plane include: data of the impedance-type demagnetization protection under the power plane or data of the admittance-type demagnetization protection under the power plane; if the protection and restriction conditions are impedance-type demagnetization protection, then the power plane calculation of the protection and restriction conditions based on the basic parameters to obtain the data of the protection and restriction conditions under the power plane includes: obtaining impedance-type demagnetization protection parameters; the impedance-type demagnetization protection parameters include: the sum of the system reactance value and the reactance value on the high-voltage side of the main transformer and the synchronous reactance value during steady-state operation of the generator; determining the demagnetization protection action boundary equation on the impedance plane based on the sum of the system reactance value and the reactance value on the high-voltage side of the main transformer and the synchronous reactance value during steady-state operation of the generator; performing power circle equation conversion on the demagnetization protection action boundary equation on the impedance plane to obtain a conversion equation; performing power plane data conversion on the conversion equation to obtain the data of the impedance-type demagnetization protection under the power plane.

[0007] Preferably, if the protection and restriction conditions are admittance-type demagnetization protection, then performing power plane calculations of the protection and restriction conditions based on the basic parameters to obtain data under the power plane of the protection and restriction conditions includes: obtaining admittance-type demagnetization protection parameters; the admittance-type demagnetization protection parameters include: an inclination angle, a susceptance value, and a conductance value; determining an admittance demagnetization protection action boundary equation based on the inclination angle, the susceptance value, and the conductance value; performing power circle equation conversion on the admittance demagnetization protection action boundary equation based on the relationship between the active power, reactive power, and stator voltage of the generator stator and the susceptance value and conductance value, to obtain data of the admittance-type demagnetization protection under the power plane.

[0008] Preferably, the protection and restriction conditions include: low excitation restriction of the excitation system; the data under the power plane of the protection and restriction conditions include: active and reactive data of the generator under the power plane of low excitation restriction; the power plane calculation of the protection and restriction conditions based on the basic parameters to obtain the data under the power plane of the protection and restriction conditions includes: obtaining the active power and reactive power of the low excitation restriction of the generator; calculating according to the active power and reactive power of the low excitation restriction of the generator to obtain the data under the power plane of low excitation restriction.

[0009] Preferably, the calculation based on the active power and reactive power of the generator stator to obtain the data under the power plane with low excitation limitation includes: calculating using linear interpolation method based on the active power and reactive power with low excitation limitation of the generator to obtain the data under the power plane with low excitation limitation.

[0010] Preferably, the protection and restriction conditions include: the power limit of the output curve of the generator; the data under the power plane of the protection and restriction conditions include: the data of the power limit of the output curve of the generator under the power plane; the power plane calculation of the protection and restriction conditions based on the basic parameters to obtain the data under the power plane of the protection and restriction conditions includes: obtaining the active power of the output curve power limit of the generator and the reactive power of the output curve power limit; calculating according to the active power of the output curve power limit of the generator and the reactive power of the output curve power limit, to obtain the data under the power plane of the reactive power limit corresponding to each active output of the generator.

[0011] Preferably, the calculation is performed based on the active power of the output curve of the power limit of the generator and the reactive power of the output curve power limit to obtain the data on the power plane corresponding to the reactive power limit under each active output of the generator, including: the linear interpolation method is used to perform calculation based on the active power of the output curve power limit of the generator and the reactive power of the output curve power limit to obtain the data on the power plane corresponding to the reactive power limit under each active output of the generator.

[0012] Preferably, the protection and restriction conditions include: stator overcurrent restriction; the data under the power plane of the protection and restriction conditions include: data under the power plane of stator overcurrent restriction; the power plane calculation of the protection and restriction conditions based on the basic parameters to obtain the data under the power plane of the protection and restriction conditions includes: determining the constraint relationship between the generator stator current, stator voltage and reactive power, active power; performing power conversion on the constraint relationship to obtain the data under the power plane of the stator overcurrent restriction.

[0013] Preferably, the reactive power limit values ​​corresponding to the protection and restriction conditions include: a demagnetization protection reactive power limit value, an excitation underexcitation reactive power limit value, a generator reactive power limit value, and a stator overcurrent reactive power limit value; and performing a comprehensive analysis of the matching between demagnetization protection and excitation restriction based on the reactive power limit values ​​corresponding to the protection and restriction conditions includes: without considering the reduction in terminal voltage, judging whether the stator overcurrent reactive power limit value, the demagnetization protection reactive power limit value, the generator reactive power limit value, and the excitation underexcitation reactive power limit value decrease in sequence under the set active power of the generator; if so, judging that the comprehensive matching between demagnetization protection and excitation restriction is reasonable; if not, judging that the comprehensive matching between demagnetization protection and excitation restriction is unreasonable.

[0014] Preferably, the method further comprises: outputting a comprehensive analysis result of the matching between demagnetization protection and excitation limitation and displaying it graphically.

[0015] The present invention also provides a system for comprehensively analyzing the matching of demagnetization protection and excitation limitation of a generator, comprising: a basic parameter acquisition unit for acquiring basic parameters of a generator set; a power plane conversion calculation unit for performing power plane calculations for protection and limitation conditions based on the basic parameters to obtain data under the power plane of the protection and limitation conditions; an operating data acquisition unit for acquiring preset operating condition data; a limit value calculation unit for performing calculations based on the preset operating condition data and the data under the power plane of the protection and limitation conditions to obtain reactive power limit values ​​corresponding to the protection and limitation conditions; and a comprehensive matching analysis unit for performing comprehensive analysis of the matching of demagnetization protection and excitation limitation based on the reactive power limit values ​​corresponding to the protection and limitation conditions. The present invention also provides a storage medium storing a computer program suitable for being loaded by a processor to execute the steps of the above-described method for comprehensively analyzing the matching of demagnetization protection and excitation limitation of a generator.

[0016] The method and system for comprehensively analyzing the matching of demagnetization protection and excitation limitation of a generator according to the present invention have the following beneficial effects: including: obtaining basic parameters of the generator set; performing power plane calculations of protection and limitation conditions based on the basic parameters to obtain data under the power plane of the protection and limitation conditions; obtaining preset operating condition data; performing calculations based on the preset operating condition data and the data under the power plane of the protection and limitation conditions to obtain reactive power limit values ​​corresponding to the protection and limitation conditions; and performing comprehensive analysis of the matching of demagnetization protection and excitation limitation based on the reactive power limit values ​​corresponding to the protection and limitation conditions. The present invention can realize complex logical calculations for rapid and automatic conversion of demagnetization admittance and impedance circles to power circles, replacing the original complex manual calculations and significantly improving calculation efficiency. At the same time, it can perform comprehensive analysis of the matching between demagnetization protection, low excitation limitation, generator power limit, and stator overcurrent limitation, greatly improving the predictability of risks during the test process and the accuracy of test data. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0018] 1 is a flow chart of a method for comprehensive analysis of the matching performance of generator demagnetization protection and excitation limitation provided by the present invention;

[0019] FIG2 is a schematic diagram of an impedance-type demagnetization protection type provided by the present invention;

[0020] FIG3 is a schematic diagram of the admittance type demagnetization protection type provided by the present invention;

[0021] FIG4 is a diagram showing a power limit curve of a generator provided by the present invention;

[0022] FIG5 is a schematic diagram of the comprehensive analysis result output interface provided by the present invention;

[0023] FIG6 is a schematic diagram of a comprehensive analysis of the unit setting operating conditions provided by the present invention;

[0024] FIG7 is a block diagram of the principle of the comprehensive analysis system for generator demagnetization protection and excitation limit matching provided by the present invention. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0026] At present, large-scale generator sets are equipped with demagnetization protection, and low excitation limit is configured in the microcomputer excitation regulator. Most of the existing nuclear power plants have not calculated whether the set values ​​between them can be correctly matched, and there is a possibility of protection mismatch. In the actual verification, the low excitation limit is calculated on the PQ power plane, and the demagnetization protection is analyzed on the RX impedance plane or the GB admittance plane. In order to verify the parameter matching relationship between the two, it is necessary to reduce the two to the same plane. At the same time, the demagnetization protection boundary should be adjusted within the generator limit power and stator overcurrent limit range, and must not exceed the minimum limit boundary of the two. Based on this, the present invention uses a power plane that can intuitively characterize the state of the unit for verification, and uniformly reduces the above conditions to the power plane for comprehensive matching analysis.

[0027] Figure 1 shows the process of an embodiment of a method for comprehensive analysis of the matching between generator demagnetization protection and excitation limitation provided by the present invention. Specifically, as shown in Figure 1, the method for comprehensive analysis of the matching between generator demagnetization protection and excitation limitation includes the following steps: Step S101. Obtain basic parameters of the generator set.

[0028] Specifically, in embodiments of the present invention, the basic parameters of a generator set include, but are not limited to, manufacturer-provided power limit parameters (such as the generator's active power limit and reactive power limit), demagnetization protection configuration types (including impedance-type demagnetization protection and admittance-type demagnetization protection) and parameters (such as impedance-type demagnetization protection parameters and admittance-type demagnetization protection parameters), and excitation system underexcitation limit configuration parameters. Impedance-type demagnetization protection parameters include, but are not limited to, resistance, reactance, the sum of the system reactance and the main transformer high-voltage side reactance, synchronous reactance during steady-state operation, measured current, and measured voltage. Admittance-type demagnetization protection parameters include, but are not limited to, conductance, susceptance, tilt angle, and stator voltage. In embodiments of the present invention, the basic parameters of a generator set can be obtained using any existing method, such as directly retrieving them from a system database or directly input by the user.

[0029] Step S102: Perform power plane calculations for protection and restriction conditions based on basic parameters to obtain data for the power plane of the protection and restriction conditions. Specifically, in this embodiment, the protection and restriction conditions include impedance-type demagnetization protection or admittance-type demagnetization protection. Correspondingly, the power plane data for the protection and restriction conditions includes data for impedance-type demagnetization protection or admittance-type demagnetization protection at the power plane. Among them, if the protection and restriction conditions are impedance-type demagnetization protection, the power plane calculation of the protection and restriction conditions is performed according to the basic parameters, and the data under the power plane of the protection and restriction conditions are obtained, including: obtaining the impedance-type demagnetization protection parameters; the impedance-type demagnetization protection parameters include: the sum of the system reactance value and the reactance value on the high-voltage side of the main transformer and the synchronous reactance value during steady-state operation of the generator; according to the sum of the system reactance value and the reactance value on the high-voltage side of the main transformer and the synchronous reactance value during steady-state operation of the generator, the demagnetization protection action boundary equation on the impedance plane is determined; the demagnetization protection action boundary equation on the impedance plane is transformed into a power circle equation to obtain a transformation equation; the transformation equation is converted into power plane data to obtain the data of the impedance-type demagnetization protection under the power plane. If the protection and restriction conditions are admittance-type demagnetization protection, a power plane calculation of the protection and restriction conditions is performed based on basic parameters, and the data obtained under the power plane of the protection and restriction conditions include: obtaining admittance-type demagnetization protection parameters; the admittance-type demagnetization protection parameters include: tilt angle, susceptance value, and conductance value; determining the admittance demagnetization protection action boundary equation based on the tilt angle, susceptance value, and conductance value; and performing a power circle equation conversion on the admittance demagnetization protection action boundary equation based on the relationship between the active power, reactive power, and stator voltage of the generator stator and the susceptance value and conductance value, to obtain the data of the admittance-type demagnetization protection under the power plane.

[0030] In the embodiment of the present invention, the protection device can be divided into impedance-type demagnetization protection and admittance-type demagnetization protection according to different judgment principles. Therefore, demagnetization protection can be divided into impedance-type demagnetization protection and admittance-type demagnetization protection. Among them, the schematic diagram of the impedance-type demagnetization protection type is shown in Figure 2. Specifically, the impedance-type demagnetization protection collects the measured values ​​of the positive sequence current and positive sequence voltage of the generator, calculates the measured impedance and uses this as the main judgment criterion. Among them, when the measured impedance exceeds the limit, the impedance-type demagnetization protection device will be activated. The measured impedance can be represented by Z, Z=R+jX, that is, the measured impedance coordinates under the current working conditions can be drawn on the coordinate plane with resistance R as the horizontal coordinate and reactance X as the vertical coordinate. It can be seen from the relay protection setting guide that the impedance-type demagnetization protection boundary is set in the form of an impedance circle, and the upper and lower vertices of the circle are X1 and X2, respectively, as shown in Figure 1. Furthermore, since X1 and X2 are known parameters, the demagnetization protection action boundary equation on the impedance plane can be obtained as follows:

[0031] (1).

[0032] Furthermore, the radius of the circle is r= 、The center of the circle is (0, a= ) can be used to transform the impedance circle to obtain the transformation equation, where the transformation equation can be expressed as:

[0033] (2).

[0034] The protection judgment of impedance type demagnetization protection is made according to the relative position of the generator set operating parameters and the circle. When the measured impedance of the generator set is outside the impedance circle, the generator set operates stably and the protection is locked. When it is inside the impedance circle, the protection action trips. Specifically, according to the single-phase power calculation, the current I and voltage U at the same measurement point satisfy the relationship , ,in The power factor angle is the angle between current and voltage. Substituting it into formula (2), we can get:

[0035] (3).

[0036] The calculation expressions of active power P and reactive power Q are , Substituting into formula (3), we can get the following after simplification:

[0037] (4).

[0038] Rewriting (4) into the equation of a standard circle, we can obtain the following equation:

[0039] (5).

[0040] The circle represented by formula (5) is the action boundary of the impedance-type demagnetization protection configured for the generator on the power plane, and its center is on the Q axis. It should be noted that this conversion relationship is derived based on the formula for single-phase power, which is the same as the derivation result of the formula for three-phase power. Formula (5) can be directly used for on-site calculations. The demagnetization protection uses the generator stator as the measurement point. Therefore, according to the actual operating conditions, when the stator active power P, stator voltage U and protection configuration are known, the limit value of the impedance-type protection scheme on the regulated reactive power can be directly obtained, completing the coordinate transformation of the impedance plane and the power plane, and the generator stator reactive limit The calculation method is shown in formula (6).

[0041] (6).

[0042] Among them, formula (6) can be used to calculate the data of impedance-type demagnetization protection in the power plane.

[0043] Admittance type demagnetization protection is based on the generator stator admittance measurement value. When the measured admittance exceeds the protection set value, the protection action is initiated. The measured admittance Y=G+jB can be plotted in a coordinate plane with the conductance value G as the ordinate and the susceptance value B as the abscissa. The generator demagnetization admittance criterion is composed of three independent protection characteristics, as shown in Figure 3. In Figure 3, the inclination angles of the three characteristics are 、 、 , the susceptance values ​​are 、 、 . Characteristics 1 and 2 simulate the static stability limit of the generator, corresponding to the static stability circle and asynchronous circle in the impedance type demagnetization protection plane. When the measured admittance value is on the left side of characteristics 1 and 2, it is determined that the static stability is lost; Characteristic 3 simulates the dynamic stability limit of the generator, corresponding to the dynamic stability limit of the unit under the extreme working condition of three-phase short circuit of the external system. When the measured admittance value is on the left side of characteristic 3, it is determined that the dynamic stability is lost. Since the three-stage protection is all in the action area on the left side of the straight line, the calculation method is the same, and there is only a numerical difference. Therefore, take the admittance type demagnetization protection stage I as an example for explanation. Specifically, the inclination angle of the admittance type demagnetization protection stage I is known and susceptance , then the action boundary equation of admittance demagnetization protection is:

[0044] (7).

[0045] Furthermore, the active power P, reactive power Q, stator voltage U and admittance value of the generator stator have the following relationship:

[0046] (8).

[0047] Substitute equation ⑧ into equation ⑦ and multiply the coordinate axes of the admittance plane by , converting the protection boundary to the power plane, we can get the admittance demagnetization protection boundary equation:

[0048] (9).

[0049] The reactive limit value of admittance type demagnetization protection can be further obtained: as follows:

[0050] (10).

[0051] Among them, formula (10) can calculate the data of the admittance type demagnetization protection in the power plane.

[0052] In this embodiment, the protection and restriction conditions also include: low excitation restriction of the excitation system. Correspondingly, the data under the power plane of the protection and restriction conditions include: active and reactive data of the generator under the power plane of low excitation restriction. Herein, performing power plane calculations of the protection and restriction conditions based on basic parameters to obtain the data under the power plane of the protection and restriction conditions includes: obtaining the active power and reactive power of the generator under the low excitation restriction; and performing calculations based on the active power and reactive power of the generator under the low excitation restriction to obtain the data under the power plane of low excitation restriction. Furthermore, in this embodiment, performing calculations based on the active power and reactive power of the generator stator to obtain the data under the power plane of low excitation restriction includes: performing calculations based on the active power and reactive power of the generator under the low excitation restriction using a linear interpolation method to obtain the data under the power plane of low excitation restriction. Low excitation limit is also called under-excitation limit. The purpose of under-excitation limit is to prevent artificial or system automatic reduction of reactive power, which may cause the generator to lose magnetism or even lose step due to insufficient excitation, and to limit the reactive power absorbed by the generator to avoid excessively low generator voltage, factory power and high-voltage bus voltage. Specifically, the low excitation limit curve of the excitation regulator is adjusted using a PQ curve composed of multiple points. Taking the ABB excitation system, which currently has a large market share in the industry, as an example, 6 basic points are selected to form a broken line based on the maximum leading phase capability obtained from the test of each active platform of the generator to draw the PQ curve for limit adjustment. The limit curve y=f ( Q , P ) The above 6 basic points selection principles: S N For rated apparent power, press P=0, P=0.2S N , P=0.4S N , P=0.6S N , P=0.8S N , P=1.0S N , and combined with the unit phase leading test results, select the corresponding reactive power Q to adjust the low excitation limit curve. The low excitation reactive power limit can be obtained by linear interpolation, so we can get:

[0053] (11).

[0054] In formula (11), P is the active power of the preset working condition, and are the active power limits corresponding to the low excitation limit discrete points, , They are the reactive power limits corresponding to the discrete points respectively; where, assuming P is at the low excitation limit discrete point and Between. Formula (11) can calculate the data under the power plane of low excitation limit. In this embodiment, the protection and restriction conditions include: the power limit of the output curve of the generator. Correspondingly, the data under the power plane of the protection and restriction conditions include: the data of the power limit of the output curve of the generator under the power plane. Among them, the power plane calculation of the protection and restriction conditions is performed according to the basic parameters, and the data under the power plane of the protection and restriction conditions is obtained, which includes: obtaining the active power of the output curve power limit of the generator and the reactive power of the output curve power limit; calculating according to the active power of the output curve power limit of the generator and the reactive power of the output curve power limit, and obtaining the data under the power plane corresponding to the reactive power limit under each active output of the generator. Furthermore, calculating the generator's reactive power limit data under the power plane based on the active power and reactive power at the power limit of the generator's output curve includes: using linear interpolation to calculate the reactive power limit data under the power plane corresponding to each active output of the generator. Specifically, a power limit diagram is drawn based on the manufacturer's manufacturer's limits for stable operation of the generator at various power factors. The power limits of a large-capacity nuclear power unit are shown in Figure 4, where the horizontal axis represents the unit's active power P and the vertical axis represents the unit's reactive power Q. The unit's maximum allowable leading-phase operation capability under the corresponding active power platform must not exceed the boundary corresponding to the lower semicircle (underexcited portion). Therefore, when determining the generator's active power under operating conditions, the corresponding reactive power limit can be obtained through table lookup and linear interpolation. This is the limit boundary allowed by the manufacturer's design. The vertical line in Figure 4 indicates the maximum leading-phase reactive power limit. In the embodiment of the present invention, the manufacturer power boundary reactive limit value can be obtained by using a linear interpolation method, and thus, it can be obtained:

[0055] (12).

[0056] In formula (12), P is the active power of the preset working condition, and are the active power limits corresponding to the discrete points of the power limit boundary, , They are discrete points corresponding to reactive power limits; where P is assumed to be at the power limit boundary discrete point and Between. Formula (12) can calculate the data under the power plane of the reactive power limit of the generator. In this embodiment, the protection and restriction conditions also include: stator overcurrent limit. Correspondingly, the data under the power plane of the protection and restriction conditions include: data under the power plane of the stator overcurrent limit. Among them, the power plane calculation of the protection and restriction conditions based on the basic parameters to obtain the data under the power plane of the protection and restriction conditions includes: determining the constraint relationship between the stator current, stator voltage and reactive power and active power of the generator; performing power conversion on the constraint relationship to obtain the data under the power plane of the stator overcurrent limit. Specifically, when the stator voltage of the generator set is within the normal range and the power is within the rated value during normal delayed phase operation, the stator current will not exceed the limit. However, in the process of gradually advancing the phase while keeping the active power output of the generator unchanged, the stator voltage gradually decreases and the stator current will increase at a faster rate, causing the stator winding temperature to rise. Therefore, the stator current will become a constraint on the generator's advancing phase capability. According to the phase-advancing test guideline DL / T1523-2016, the stator current of the generator is subject to certain constraints during operation. It should not exceed the rated current during long-term operation and should be coordinated with the generator stator overcurrent protection. The stator current and reactive power have a constraint relationship as shown in formula (13). When the critical value of the stator current (i.e., the stator current limit) is When the stator current limit is It can be calculated by formula (14).

[0057] (13).

[0058] (14).

[0059] Among them, formula (14) can be used to calculate the data under the power plane of stator overcurrent limitation.

[0060] Step S103. Obtain preset operating condition data. In this embodiment, the preset operating condition data includes: the active power and stator voltage of the generator. The preset operating condition data can be set according to actual conditions. Step S104. Calculate based on the preset operating condition data and the data in the power plane of the protection and restriction conditions to obtain reactive power limit values ​​corresponding to the protection and restriction conditions. In this embodiment, the reactive power limit values ​​corresponding to the protection and restriction conditions include: the reactive power limit value for loss of excitation protection, the reactive power limit value for underexcitation, the reactive power limit value for the generator, and the reactive power limit value for stator overcurrent. Among them, when the protection and limitation conditions are: impedance type demagnetization protection, the demagnetization protection reactive power limit is calculated by the data of the impedance type demagnetization protection under the power plane, that is, it is calculated by formula (6); when the protection and limitation conditions are: admittance type demagnetization protection, the demagnetization protection reactive power limit is calculated by the data of the admittance type demagnetization protection under the power plane, that is, it is calculated by formula (10); when the protection and limitation conditions are: excitation system low excitation limit, the low excitation reactive power limit is calculated by the data under the power plane of the low excitation limit, that is, it is calculated by formula (11); when the protection and limitation conditions are: generator reactive power limit, the generator reactive power limit is calculated by the data under the power plane of the generator reactive power limit, that is, it is calculated by formula (12); when the protection and limitation conditions are: stator overcurrent limit, the stator overcurrent reactive power limit is calculated by the data under the power plane of the stator overcurrent limit, that is, it is calculated by formula (14).

[0061] Step S105: Perform a comprehensive analysis of the matching between demagnetization protection and excitation limitation based on the reactive power limit value corresponding to the protection and limitation conditions. In this embodiment, performing a comprehensive analysis of the matching between demagnetization protection and excitation limitation based on the reactive power limit value corresponding to the protection and limitation conditions includes: determining whether the stator overcurrent reactive power limit, the demagnetization protection reactive power limit, the generator reactive power limit, and the excitation underexcitation reactive power limit decrease in sequence under the set active power of the generator, without considering the reduction in terminal voltage; if so, determining that the comprehensive matching between demagnetization protection and excitation limitation is reasonable; if not, determining that the comprehensive matching between demagnetization protection and excitation limitation is unreasonable. Specifically, in step S104, the demagnetization protection reactive power limit, the underexcitation reactive power limit, the generator reactive power limit, and the stator overcurrent reactive power limit are calculated. A comprehensive matching analysis is performed on the obtained demagnetization protection reactive power limit, underexcitation reactive power limit, generator reactive power limit, and stator overcurrent reactive power limit. Without considering the reduction in terminal voltage, a determination is made as to whether the stator overcurrent reactive power limit, the demagnetization protection reactive power limit, the generator reactive power limit, and the underexcitation reactive power limit decrease in sequence under a certain generator active power. If so, the comprehensive matching between demagnetization protection and excitation limitation is determined to be reasonable; otherwise, the comprehensive matching between demagnetization protection and excitation limitation is determined to be unreasonable. The set active power can be determined based on actual application.

[0062] Furthermore, in this embodiment, the method for comprehensively analyzing the compatibility of demagnetization protection and excitation limits for generators further includes outputting and graphically displaying the results of the comprehensive analysis of the compatibility of demagnetization protection and excitation limits. Specifically, after calculating the limits corresponding to the protection and limit conditions, a corresponding comprehensive analysis graph can be generated and displayed, as shown in Figure 5. The table on the left in Figure 5 shows the input of protection and preset or given parameters, while the right side shows a "comprehensive analysis graph of unit set operating conditions" automatically generated after the comprehensive compatibility analysis. The comprehensive analysis graph of unit set operating conditions is shown in Figure 6. As can be seen from Figure 6, the results of the automatic comprehensive matching analysis can intuitively and clearly show that when the active power of the unit represented by the vertical axis is at or below the rated power, the low-excitation limit curve of the excitation system (curve A1 in Figure 6) is ahead of the power limit output curve allowed by the design during equipment manufacturing (curve A2 in Figure 6). At the same time, it should be within the action curve of the demagnetization protection setting value (curve A3 in Figure 6) and ultimately limited to the range of the generator maximum stator current limit curve (curve A4 in Figure 6). A good matching result can be obtained between the various protections and limitations. After all the above-mentioned relevant parameters are put into operation, the safety and stability of the system and the unit will be maintained, and the points on all curves can accurately display specific values ​​(displayed in the comprehensive analysis data table), realizing the true transformation of the comprehensive matching research from qualitative analysis to quantitative analysis, and the research results have made a qualitative leap. In the comprehensive analysis diagram, if there is a serious crossing of the curves below the rated active power, it means that the protection and limit parameters corresponding to the crossed curves do not match, and they need to be reset or adjusted. Completing the comprehensive analysis of the matching of protection and limit parameters in the static state before the unit is started can effectively avoid accidental tripping caused by malfunction of protection or ineffective limitation in advance.

[0063] As shown in FIG7 , the present invention further provides a system for comprehensively analyzing the matching performance of demagnetization protection and excitation limitation of a generator. The system comprises: a basic parameter acquisition unit 701 for acquiring basic parameters of a generator set; a power plane conversion calculation unit 702 for performing power plane calculations of protection and limitation conditions based on the basic parameters to obtain data under the power plane of the protection and limitation conditions; an operating data acquisition unit 703 for acquiring preset operating condition data; a limit value calculation unit 704 for performing calculations based on preset operating condition data and data under the power plane of protection and limitation conditions to obtain reactive power limit values ​​corresponding to the protection and limitation conditions; and a matching comprehensive analysis unit 705 for performing comprehensive analysis of the matching performance of demagnetization protection and excitation limitation based on the reactive power limit values ​​corresponding to the protection and limitation conditions.

[0064] In the existing technical solution, the configuration principle of the generator demagnetization protection is to determine whether the unit has a demagnetization fault based on the measured impedance or admittance angle, and the power plane is the most intuitive representation of the unit status on site. The protection action boundary cannot directly depict the safe operation boundary of the unit, and it is necessary to convert, calculate, and judge the impedance circle plane and the power circle plane. At the same time, the amount of comprehensive information calculation involved in the low excitation limit of the power plane, the comparison and mutual restraint between the power limit range of the generator design and manufacturing, etc. is large. At the same time, it is necessary to perform multiple repeated calculations and logical relationship verifications under various power platform state conditions. It is laborious and time-consuming to complete manually. Any manual calculation or human logical judgment error in any link will result in incorrect conclusions, which may cause oscillation and instability of the unit and the power grid, and even cause serious damage to the generator, seriously endangering the safe operation of the nuclear power plant and the power grid. The present invention studies the power plane conversion of demagnetization protection and low excitation limitations in generator set protection, realizes complex logical calculations for rapid and automatic conversion between impedance circle and power circle, and replaces complex manual calculations with intelligent processing methods, which greatly improves measurement efficiency, avoids problems caused by human errors, and ensures the safe operation of nuclear power plants and power grids.

[0065] Furthermore, in existing solutions, the low-excitation limit parameters are determined by adjusting the phase-leading depth curve values ​​during specialized tests. However, before the first deep phase-leading test, the low-excitation parameters are not accurately adjusted and are set based solely on empirical values. During the test, if the low-excitation parameters do not match the demagnetization protection setting, the low-excitation link will not function during the test, triggering a trip due to demagnetization protection, resulting in test failure and the inability to obtain the low-excitation limit parameters required by the power grid. The present invention accurately determines the low-excitation limit values ​​through quantitative analysis and calculation, thus avoiding the problems caused by inaccurate or unavailable low-excitation parameters.

[0066] Furthermore, existing solutions use the power limit curve directly based on the manufacturer's design as the generator's static stability limit boundary condition, which increases the stability control range and is inaccurate and unscientific. This approach may not always correspond to the unit's actual operating conditions, making the unit susceptible to overcontrol risks beyond the static stability limit during regulation. The system also lacks systematic calculation and adjustment of stator overcurrent limits and comprehensive analysis of their correlations, which can lead to failures during deep phase-leading operation, causing stator overcurrent, and potentially causing equipment overheating and insulation damage. The present invention calculates the corresponding limits using a linear interpolation method, avoiding the problems associated with directly using the manufacturer's power limit curve as a boundary condition. Furthermore, the present invention enables a comprehensive analysis of the logical relationships between any unit's demagnetization protection, underexcitation limit, generator power limit, and stator overcurrent limit under static conditions, significantly improving the predictability of risks during testing. Specifically, the specific coordination and operation between the various units in the generator demagnetization protection and excitation limit matching comprehensive analysis system can be found in the aforementioned generator demagnetization protection and excitation limit matching comprehensive analysis method, and will not be further elaborated here.

[0067] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other. For the devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple, and the relevant parts can be referred to the method section. Professionals can also further appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented by electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described in terms of function in the above description. The above embodiments are only for illustrating the technical concepts and features of the present invention. Their purpose is to enable people familiar with this technology to understand the content of the present invention and implement it accordingly, and they cannot limit the scope of protection of the present invention. All equivalent changes and modifications made to the scope of the claims of the present invention should fall within the scope of the claims of the present invention.

Claims

1. A comprehensive analysis method for matching between generator demagnetization protection and excitation limitation, characterized in that: The following steps are involved: Obtaining basic parameters of the generator set; performing power plane calculation of protection and restriction conditions according to the basic parameters to obtain data under the power plane of protection and restriction conditions; Acquire preset operating condition data; perform calculations based on the preset operating condition data and the data under the power plane of the protection and restriction conditions to obtain the reactive power limit value corresponding to the protection and restriction conditions; perform a comprehensive analysis on the matching of demagnetization protection and excitation limitation based on the reactive power limit value corresponding to the protection and restriction conditions, the generator power limit and the stator overcurrent limit value.

2. The comprehensive analysis method for matching between generator demagnetization protection and excitation limitation according to claim 1 is characterized in that: The protection and restriction conditions include: impedance demagnetization protection or admittance demagnetization protection; the data of the protection and restriction conditions under the power plane include: data of the impedance demagnetization protection under the power plane or data of the admittance demagnetization protection under the power plane; if the protection and restriction conditions are impedance demagnetization protection, then the power plane calculation of the protection and restriction conditions based on the basic parameters to obtain the data of the protection and restriction conditions under the power plane includes: obtaining impedance demagnetization protection parameters; the impedance demagnetization protection parameters include: the sum of the system reactance value and the reactance value on the high-voltage side of the main transformer and the synchronous reactance value of the generator during steady-state operation; according to the sum of the system reactance value and the reactance value on the high-voltage side of the main transformer and the synchronous reactance value of the generator during steady-state operation, determine the demagnetization protection action boundary equation on the impedance plane; perform power circle equation conversion on the demagnetization protection action boundary equation on the impedance plane to obtain the conversion equation; perform power plane data conversion on the conversion equation to obtain the data of the impedance demagnetization protection under the power plane.

3. The comprehensive analysis method for matching between generator demagnetization protection and excitation limitation according to claim 2 is characterized in that: If the protection and restriction condition is admittance type demagnetization protection, then the power plane calculation of the protection and restriction condition is performed according to the basic parameters to obtain the data of the protection and restriction condition under the power plane, including: obtaining the admittance type demagnetization protection parameters; the admittance type demagnetization protection parameters include: inclination angle, susceptance value and conductance value; determining the admittance demagnetization protection action boundary equation according to the inclination angle, the susceptance value and the conductance value; performing power circle equation conversion on the admittance demagnetization protection action boundary equation according to the relationship between the active power, reactive power and stator voltage of the generator stator and the susceptance value and the conductance value, to obtain the data of the admittance type demagnetization protection under the power plane.

4. The method for comprehensive analysis of generator demagnetization protection and excitation limitation matching according to claim 1 is characterized in that: The protection and restriction conditions include: low excitation restriction of the excitation system; the data under the power plane of the protection and restriction conditions include: active and reactive data of the generator under the power plane of low excitation restriction; the power plane calculation of the protection and restriction conditions based on the basic parameters to obtain the data under the power plane of the protection and restriction conditions includes: obtaining the active power and reactive power of the low excitation restriction of the generator; calculating according to the active power and reactive power of the low excitation restriction of the generator to obtain the data under the power plane of low excitation restriction.

5. The method for comprehensive analysis of generator demagnetization protection and excitation limitation matching according to claim 4 is characterized in that: The method of calculating based on the active power and reactive power of the generator stator to obtain the data on the power plane with low excitation limitation includes: calculating based on the active power with low excitation limitation and the reactive power with low excitation limitation of the generator using linear interpolation method to obtain the data on the power plane with low excitation limitation.

6. The method for comprehensive analysis of generator demagnetization protection and excitation limitation matching according to claim 1 is characterized in that: The protection and restriction conditions include: the power limit of the output curve of the generator; the data under the power plane of the protection and restriction conditions include: the data of the power limit of the output curve of the generator under the power plane; the power plane calculation of the protection and restriction conditions based on the basic parameters to obtain the data under the power plane of the protection and restriction conditions includes: obtaining the active power of the output curve power limit of the generator and the reactive power of the output curve power limit; calculating according to the active power of the output curve power limit of the generator and the reactive power of the output curve power limit, to obtain the data under the power plane of the reactive power limit corresponding to each active output of the generator.

7. The method for comprehensive analysis of generator demagnetization protection and excitation limitation matching according to claim 6 is characterized in that: The calculation based on the active power at the power limit of the output curve of the generator and the reactive power at the power limit of the output curve to obtain the data on the power plane corresponding to the reactive power limit at each active output of the generator includes: calculating based on the active power at the power limit of the output curve of the generator and the reactive power at the power limit of the output curve by using linear interpolation method to obtain the data on the power plane corresponding to the reactive power limit at each active output of the generator.

8. The method for comprehensive analysis of generator demagnetization protection and excitation limitation matching according to claim 1, characterized in that: The protection and restriction conditions include: stator overcurrent limitation; the data under the power plane of the protection and restriction conditions include: data under the power plane of stator overcurrent limitation; the power plane calculation of the protection and restriction conditions based on the basic parameters to obtain the data under the power plane of the protection and restriction conditions includes: determining the constraint relationship between the stator current, stator voltage and reactive power and active power of the generator; performing power conversion on the constraint relationship to obtain the data under the power plane of the stator overcurrent limitation.

9. The method for comprehensive analysis of the matching between generator demagnetization protection and excitation limitation according to any one of claims 1 to 8, characterized in that: The reactive power limit values ​​corresponding to the protection and restriction conditions include: a demagnetization protection reactive power limit value, an excitation underexcitation reactive power limit value, a generator reactive power limit value, and a stator overcurrent reactive power limit value; the comprehensive analysis of the matching of demagnetization protection and excitation limitation based on the reactive power limit values ​​corresponding to the protection and restriction conditions includes: without considering the reduction of the terminal voltage, judging whether the reactive power limit value of the stator overcurrent, the demagnetization protection reactive power limit value, the generator reactive power limit value, and the excitation underexcitation reactive power limit value decrease in sequence under the premise of setting the active power of the generator; if so, judging that the comprehensive matching of demagnetization protection and excitation limitation is reasonable; if not, judging that the comprehensive matching of demagnetization protection and excitation limitation is unreasonable.

10. The method for comprehensive analysis of generator demagnetization protection and excitation limitation matching according to claim 1, characterized in that: The method further comprises: outputting a comprehensive analysis result of the matching between demagnetization protection and excitation limitation and displaying it graphically.

11. A comprehensive analysis system for matching between generator demagnetization protection and excitation limitation, characterized in that: include: A basic parameter acquisition unit, used to acquire the basic parameters of the generator set; a power plane conversion calculation unit, used to perform power plane calculation of protection and restriction conditions according to the basic parameters, and obtain data under the power plane of protection and restriction conditions; an operation data acquisition unit, used to acquire preset operating condition data; A limit value calculation unit, used to calculate according to the preset working condition data and the data under the power plane of the protection and restriction conditions to obtain a reactive power limit value corresponding to the protection and restriction conditions; The matching comprehensive analysis unit is used to perform a comprehensive analysis on the matching of demagnetization protection and excitation limitation according to the reactive power limitation value corresponding to the protection and limitation conditions, the generator power limit and the stator overcurrent limitation value.

12. A storage medium, characterized in that: The storage medium stores a computer program, and the computer program is suitable for being loaded by a processor to execute the steps of the method for comprehensive analysis of the matching of generator demagnetization protection and excitation limitation as described in any one of claims 1 to 10.

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