Field loss protection method for rod-controlled power supply generator based on variable excitation current criterion

Abstract

The invention belongs to the technical field of excitation loss protection of rod-controlled power generators, and particularly relates to an excitation loss protection method of a rod-controlled power generator based on a variable excitation current criterion. Constructing a variable excitation current criterion by using the excitation current changing along with the power P; according to the static stability boundary of the generator, constructing a static stability boundary impedance criterion of the generator end measurement impedance; constructing an inverse reactive power criterion according to the output reactive power of the generator; measuring and calculating the measured impedance Z of the generator end; and when the excitation current If meets the variable excitation current criterion, the field loss protection is delayed to trip through t2 + t3, and if the measured impedance Z and the reactive power Qs at the same time meet the static stability boundary impedance criterion and the inverse reactive power criterion, the field loss protection is delayed to accelerate to trip through t3. According to the invention, under the condition of excitation loss caused by parallel operation of two rod-controlled power generators, excitation loss protection misoperation is effectively prevented.

Description

Technical Field

[0001] The invention belongs to the technical field of demagnetization protection of a rod-controlled power supply generator, and in particular relates to a demagnetization protection method of a rod-controlled power supply generator with a variable excitation current criterion. Background Art

[0002] The control rod drive mechanism power supply system (CRDM for short) is an independent power supply system dedicated to the control rod drive mechanism (CRDM for short). It adjusts the power output to the CRDM hook coil according to the operation requirements of lifting, inserting or holding the rod.

[0003] At the same time, the existing fixed excitation voltage criterion is set to 0.8 to 0.9 times the no-load excitation voltage, which can reflect complete demagnetization faults, but it is difficult to reflect low excitation faults under load conditions. Accident experience shows that because the fixed excitation current criterion is set too high under light load conditions, it cannot be used as a basis for the generator to cross the static stability limit. So far, many nuclear power plants in China have experienced false demagnetization protection due to performance errors of two machines. If the rod-controlled power supply fails and no power is output, the control rod will lose the reaction force provided by the claw of the drive mechanism and will quickly fall into the core under the action of gravity, causing a reactor shutdown accident. It is necessary to propose a reliable rod-controlled power supply generator demagnetization protection method to ensure the safe and stable operation of the control rod drive mechanism and its power supply system.

[0004] Accordingly, how to develop a simple, reliable and easy-to-operate demagnetization protection method for a rod-controlled power generator is becoming one of the technical problems to be solved urgently in this field. Summary of the invention

[0005] The purpose of the present invention is to provide a demagnetization protection method for a rod-controlled power supply generator with a variable excitation current criterion. In the event of a demagnetization fault in the rod-controlled power supply generator, a demagnetization protection method is proposed with the variable excitation current as the main criterion, the static boundary impedance criterion and the reverse reactive power criterion as the acceleration criteria, so that the demagnetization fault situation can be accurately judged and the demagnetization protection can be correctly operated.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A method for protecting a generator from demagnetization of a rod-controlled power supply with a variable excitation current criterion is provided. The variable excitation current criterion is constructed by using the excitation current that changes with the power P; the static stability boundary impedance criterion of the generator end measurement impedance is constructed according to the generator static stability boundary; the reverse reactive power criterion is constructed according to the generator output reactive power; the generator end measurement impedance is measured and calculated as Z; when the excitation current I fWhen the variable excitation current criterion is met, the demagnetization protection will trip after a delay of t2+t3. If the measured impedance Z and reactive power Qs at the machine end meet the static boundary impedance criterion and the reverse reactive power criterion at the same time, the demagnetization protection will accelerate the tripping after a delay of t3. In the event of demagnetization when two rod-controlled power generators are running in parallel, the demagnetization protection can be effectively prevented from malfunctioning.

[0008]

[0009] Variable excitation current criterion:

[0010]

[0011] Where I op.0 is the minimum excitation current setting value, P op.0 is the corresponding minimum action power, X d is the per unit value of synchronous reactance, I f0 is the no-load excitation current of the generator, S n is the rated capacity, K is the reliability coefficient, and K>1 is set.

[0012] K is taken as 1.2.

[0013] Static stability boundary impedance criterion: After the generator loses its magnetism, the impedance trajectory measured at the machine end will enter the static stability boundary circle action boundary of the fourth quadrant from the first quadrant over time. Since the rod-controlled power supply is not connected to the grid, the generator is directly connected to the load through the export bus, and the contact reactance X s is zero, the diameter of the static circle is X B =X d , the measured impedance at the generator end is Z, the reliability coefficient is set to K, and the static boundary impedance criterion action equation is:

[0014]

[0015] Reverse reactive power criterion: Let the reactive power absorbed by the generator be Q 逆 , set the reliability coefficient to K, and set the reverse reactive power protection criterion to avoid the generator static stability limit reactive power Qs:

[0016] Q 逆 >|Q s | / K (6)

[0017] In the above formula, Q s Is a negative value.

[0018] The rotor low current criterion is selected as the main protection criterion, and the machine end impedance criterion and reverse reactive power criterion are introduced as auxiliary protection criteria.

[0019] A rod-controlled power generator demagnetization protection device with variable excitation current criterion includes a variable excitation current criterion module, which uses a direct-axis synchronous reactance Xd, a rated capacity Sn, a no-load excitation current If0, a reliability coefficient K, and a minimum excitation current setting value Iop.0 to construct a variable excitation current criterion; a static boundary impedance criterion module, which uses a direct-axis synchronous reactance Xd and a reliability coefficient K to construct a static boundary impedance criterion;

[0020] The reverse reactive power criterion module uses the bus voltage U and the reliability coefficient K to construct the reverse reactive power criterion; the measurement module measures the generator excitation current If, the machine-end voltage U, the machine-end current I, the generator output active power P, and the reactive power Q; the machine-end measurement impedance calculation module measures the impedance Z on the computer side; the tripping module, when the excitation current If meets the variable excitation current criterion, the demagnetization protection trips after a delay of t2+t3. If on this basis, the machine-end measured impedance Z meets the static boundary impedance criterion and the reactive power Qs meets the reverse reactive power criterion, the demagnetization protection accelerates the tripping after a delay of t3.

[0021] The reliability coefficient K is set to 1.2.

[0022] A demagnetization protection system for a rod-controlled power generator with a variable excitation current criterion, comprising a computer-readable storage medium and a processor; the computer-readable storage medium is used to store executable instructions; the processor is used to read the executable instructions stored in the computer-readable storage medium and execute a demagnetization protection method for a rod-controlled power generator with a variable excitation current criterion; a non-transient computer-readable storage medium, on which a computer program is stored, and when the computer program is executed by the processor, the demagnetization protection method for a rod-controlled power generator with a variable excitation current criterion is implemented.

[0023] The beneficial effects achieved by the present invention are:

[0024] (1) The present invention redesigns the criterion for demagnetization protection of the rod-controlled power generator. Instead of identifying demagnetization faults only by excitation current, voltage or machine-end impedance, variable excitation current is used as the main criterion, and static boundary impedance criterion and reverse reactive power criterion are used as acceleration criteria. This effectively solves the problem of malfunction of demagnetization protection under certain circumstances and can accurately reflect the demagnetization fault scenario of the rod-controlled power generator.

[0025] (2) The rod-controlled power generator demagnetization protection method and system according to the variable excitation current criterion of the present invention can be applied to rod-controlled power generator scenarios with different parameters, can accurately operate when a demagnetization fault occurs in the rod-controlled power generator, and has the characteristics of reliability, easy operation, and strong applicability. Therefore, it is particularly suitable for the application of rod-controlled power generators in nuclear power plants, and reduces the risk of safe and stable operation of such rod-controlled power generators, which is of great significance. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is the overall schematic diagram of the power supply of the control rod power drive mechanism of a nuclear power plant;

[0027] Figure 2 It is the action characteristic curve of variable excitation current criterion;

[0028] Figure 3 It is a logic diagram of the de-excitation protection method of the rod-controlled power supply generator with variable excitation current criterion;

[0029] Figure 4 It is the excitation current and variable excitation protection action current under different fault scenarios;

[0030] Figure 5 It is the action status of the machine-side impedance criterion under different fault scenarios;

[0031] Figure 6 It is the protection action status of reverse reactive power criterion under different fault scenarios. DETAILED DESCRIPTION

[0032] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0033] The present invention proposes a demagnetization protection method, device, system and medium for a rod-controlled power supply generator with a variable excitation current criterion. The method includes: constructing a variable excitation current criterion using an excitation current that changes with power P; constructing a static stability boundary impedance criterion for the generator end measurement impedance according to the generator static stability boundary; constructing a reverse reactive power criterion according to the generator output reactive power; measuring and calculating the generator end measurement impedance as Z; when the excitation current If meets the variable excitation current criterion, the demagnetization protection trips after a t2+t3 delay. If the machine end measurement impedance Z and the reactive power Qs meet the static stability boundary impedance criterion and the reverse reactive power criterion at the same time, the demagnetization protection accelerates the trip after a t3 delay. The present invention can effectively solve the problem of false operation of the demagnetization protection in complex situations such as demagnetization of two rod-controlled power supply generators running in parallel, and at the same time has the characteristics of simplicity, reliability, easy operation, and strong applicability.

[0034] Table 1

[0035]

[0036] The rod control power supply system consists of two motor generator sets, excitation regulation module, motor power supply circuit, generator output circuit, and related electrical protection circuit. Under normal operating conditions, the two motor generator sets run in parallel. Figure 1 shown.

[0037] (1) Criteria for variable excitation current

[0038] Ignoring the stator resistance and leakage reactance of the generator, under the critical out-of-step condition δ=90°, calculate the excitation current corresponding to the static stability limit, and obtain the excitation current per unit value:

[0039]

[0040] In X ad In the base value system, the reference excitation current I fB and no-load excitation current I f0 Satisfy I fB =X ad I f0 Substituting into formula (1), the nominal value of the excitation current at the static limit is:

[0041]

[0042] Formula (2) shows that at the static boundary the rotor current I f It is proportional to the output power P. This formula can be used to form the variable excitation protection criterion. The action characteristic diagram is a straight line passing through the origin. However, in actual operation, when the active power is small (such as no-load), the protection action value determined by the static stability limit is too small. At this time, there is a dead zone in the traditional variable excitation protection. In order to avoid this situation, the fixed excitation criterion should be used under low active power. The action equation of the variable excitation current protection criterion combined with the static stability limit is:

[0043]

[0044] Where I op.0 is the minimum excitation current setting value, P op.0 is the corresponding minimum action power, X d is the per unit value of synchronous reactance, I f0 is the no-load excitation current of the generator, and K is the reliability coefficient. Since the load changes significantly within a moving rod cycle, the fluctuation of the electromagnetic power of the generator is very significant. In order to avoid repeated activation of protection caused by power fluctuations at the static boundary, K>1 is set, and 1.2 is taken in this paper.

[0045] The action characteristic curve of variable excitation current criterion is shown in Figure 2 .

[0046] After a demagnetization fault occurs, the excitation current will quickly drop below the static stability limit setting value, but in practice the decay of the synchronous potential is often slow, and the action of the excitation low current element does not mean that the generator has reached the static stability limit. This advanced action characteristic of the rotor side protection criterion is conducive to the handling of demagnetization faults, but there is also a certain degree of uncertainty, and a long delay is often set in engineering. In order to improve the quickness of protection, stator side demagnetization criteria such as impedance criteria and reverse reactive power criteria can be added as auxiliary criteria.

[0047] (2) Static Stability Boundary Impedance Criterion

[0048] After the generator loses its magnetism, the impedance trajectory measured at the machine end will enter the static boundary circle action boundary of the fourth quadrant from the first quadrant over time. This is the principle of the machine end impedance demagnetization protection criterion. Since the rod-controlled power supply is not connected to the grid, the generator is directly connected to the load through the export bus, and the contact reactance X s is zero, the diameter of the static circle is X B =X d Let the measured impedance at the generator end be Z, and the reliability coefficient be K. The static boundary impedance criterion action equation is:

[0049]

[0050] (3) Reverse reactive power criterion

[0051] Assuming that the bus voltage remains unchanged during the demagnetization process, when the generator reaches the static stability limit δ=90°, the generator output reactive power is:

[0052] Q s =-U 2 / X d (5)

[0053] In the above formula, Q s It is a negative value, indicating that the generator absorbs reactive power from the system when it reaches the static stability limit after losing magnetism, and the absorption amount is a constant. Let the reactive power absorbed by the generator be Q 逆 , set the reliability coefficient to K, and set the reverse reactive power protection criterion to avoid the generator static stability limit reactive power Qs:

[0054] Q 逆 >|Q s | / K (6)

[0055] Based on the above criteria characteristics, according to the rod-controlled power generator's demand for advanced demagnetization protection, the rotor low current criterion is still selected as the main protection criterion, and the machine-end impedance criterion and reverse reactive power criterion are introduced as auxiliary protection criteria to solve the problem of insufficient reliability and long delay of a single rotor criterion. The demagnetization protection logic block diagram is designed as follows: Figure 3 As shown:

[0056] Simulation verification of demagnetization protection optimization scheme:

[0057] There are obvious differences between the generator of the CRDM power supply device and the conventional grid-connected generator. It is necessary to verify the feasibility of the protection scheme in the rod-controlled power supply device through simulation tests.

[0058] (1) Simulation verification of variable excitation current criteria

[0059] The variable excitation protection criterion mainly solves the problem that the fixed excitation criterion has imperfect action characteristics under different generator output powers. op.0 When set to 0.1A, the corresponding protection actions under various demagnetization fault scenarios are shown in Figure 4 :

[0060] according to Figure 4 It can be seen that in the case of a complete demagnetization fault, the excitation current quickly enters the protection action area, while the protection triggering time is longer after a partial demagnetization fault, and the action time varies significantly due to different working conditions. The action time of the variable excitation protection criterion under each fault scenario is recorded in Table 1.

[0061] (2) Simulation verification of machine-side impedance criterion

[0062] According to formula (4), the boundary setting of the static circle action is performed. The single machine demagnetization fault is set to occur at 10s in the simulation model. The impedance change trajectory of the demagnetization generator terminal is obtained under different fault scenarios as follows: Figure 5 As shown:

[0063] according to Figure 5 , the impedance circle criterion can work normally under the complete demagnetization fault of the CRDM system, but under the condition of the moving rod, due to the characteristics of the periodic change of the rod control power supply load, it takes a long time for the impedance trajectory to completely enter the static circle; under the partial demagnetization fault, the impedance trajectory shows the characteristics of oscillation at the boundary of the static circle. The action time is recorded in Table 1.

[0064] (3) Simulation verification of inverse reactive power criterion

[0065] According to formula (6), the reverse reactive protection action value is set to -0.1MW. The demagnetization fault is set to occur at 10s. The simulated waveforms of reactive power output of the demagnetization fault generator under different operating conditions are as follows Figure 6 As shown:

[0066] according to Figure 6 It can be seen that the reverse reactive power protection criterion can operate normally under the condition of complete demagnetization fault, but it takes a long time for the reactive power to completely cross the static stability limit under the moving rod condition. The operation time is recorded in Table 1.

[0067] Based on the above simulation tests, Figure 4 Where t1 = 1s, t2 = 5s, t3 = 0.5s, the triggering time of each protection criterion and the demagnetization protection exit time of the protection logic under different fault scenarios are shown in Table 1:

[0068] The present invention improves the traditional demagnetization protection method of the rod-controlled power supply generator, and designs the main criterion of the variable excitation current criterion and the accelerated criterion of the static boundary impedance criterion and the reverse reactive power criterion, so as to solve the malfunction problem of the demagnetization protection of the rod-controlled power supply generator. At the same time, it has the characteristics of simplicity, reliability, easy operation, strong applicability, etc., and is therefore particularly suitable for application occasions of demagnetization faults of rod-controlled power supply generators.

[0069] The embodiment of the present invention further provides a rod-controlled power supply generator demagnetization protection device with variable excitation current criterion, comprising:

[0070] Variable excitation current criterion module, using the direct-axis synchronous reactance X d , Rated capacity S n , no-load excitation current I f0 , reliability coefficient K, minimum excitation current setting value I op.0 Construct variable excitation current criterion;

[0071] Static boundary impedance criterion module, using the direct-axis synchronous reactance X d , the reliability coefficient K is used to construct the static stability boundary impedance criterion;

[0072] The inverse reactive power criterion module uses the bus voltage U and the reliability coefficient K to construct the inverse reactive power criterion;

[0073] Measuring module, measuring the generator excitation current I f , machine end voltage U, machine end current I, generator output active power P, reactive power Q;

[0074] The machine side measures the impedance calculation module, and the computer side measures the impedance Z;

[0075] Trip module, when the excitation current I f When the variable excitation current criterion in S101 is met, the demagnetization protection trips after a delay of t2+t3. If on this basis, the measured impedance Z at the machine end meets the static boundary impedance criterion in S102 and the reactive power Q s When the reverse reactive power criterion in S103 is met, the demagnetization protection accelerates tripping after a delay of t3.

[0076] Among them, the reliability coefficient K is set to 1.2.

[0077] Another embodiment of the present invention provides a rod-controlled power supply generator demagnetization protection system with variable excitation current criterion, comprising: a computer-readable storage medium and a processor;

[0078] The computer-readable storage medium is used to store executable instructions;

[0079] The processor is used to read the executable instructions stored in the computer-readable storage medium and execute the demagnetization protection method for the rod-controlled power supply generator with variable excitation current criterion.

[0080] Another embodiment of the present invention provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the demagnetization protection method for a rod-controlled power supply generator with a variable excitation current criterion.

[0081] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application may adopt the form of a computer program product implemented in one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that include computer-usable program code.

[0082] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0083] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0084] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0085] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for protecting a generator from demagnetization of a rod-controlled power supply with a variable excitation current criterion, characterized in that: The variable excitation current criterion is constructed by using the excitation current that changes with the power P; the static stability boundary impedance criterion of the generator end measurement impedance is constructed according to the static stability boundary of the generator; the reverse reactive power criterion is constructed according to the generator output reactive power; the generator end measurement impedance is measured and calculated as Z; when the excitation current I f When the variable excitation current criterion is met, the demagnetization protection will trip after a delay of t2+t3. If the measured impedance Z and reactive power Qs at the machine end meet the static boundary impedance criterion and the reverse reactive power criterion at the same time, the demagnetization protection will accelerate the tripping after a delay of t3. In the event of demagnetization when two rod-controlled power generators are running in parallel, the demagnetization protection can be effectively prevented from malfunctioning.

2. The method for protecting a generator from demagnetization of a rod-controlled power supply with variable excitation current criterion according to claim 1 is characterized in that:

3. The method for protecting a generator from demagnetization of a rod-controlled power supply with variable excitation current criterion according to claim 1 is characterized in that: Variable excitation current criterion: Where I op.0 is the minimum excitation current setting value, P op.0 is the corresponding minimum action power, X d is the per unit value of synchronous reactance, I f0 is the no-load excitation current of the generator, S n is the rated capacity, K is the reliability coefficient, and K>1 is set.

4. The method for protecting a generator from demagnetization of a rod-controlled power supply with variable excitation current criterion according to claim 3 is characterized in that: K is taken as 1.

2.

5. The method for protecting a generator from demagnetization of a rod-controlled power supply with variable excitation current criterion according to claim 3 is characterized in that: Static stability boundary impedance criterion: After the generator loses its magnetism, the impedance trajectory measured at the machine end will enter the static stability boundary circle action boundary of the fourth quadrant from the first quadrant over time. Since the rod-controlled power supply is not connected to the grid, the generator is directly connected to the load through the export bus, and the contact reactance X s is zero, the diameter of the static circle is X B =X d , the measured impedance at the generator end is Z, the reliability coefficient is set to K, and the static boundary impedance criterion action equation is:

6. The method for protecting a generator from demagnetization of a rod-controlled power supply with variable excitation current criterion according to claim 1, characterized in that: Reverse reactive power criterion: Let the reactive power absorbed by the generator be Q 逆 , set the reliability coefficient to K, and set the reverse reactive power protection criterion to avoid the generator static stability limit reactive power Qs: Q 逆 >|Q s | / K (6) In the above formula, Q s Is a negative value.

7. The method for protecting a generator from demagnetization of a rod-controlled power supply with variable excitation current criterion according to claim 1 is characterized in that: The rotor low current criterion is selected as the main protection criterion, and the machine end impedance criterion and reverse reactive power criterion are introduced as auxiliary protection criteria.

8. A rod-controlled power generator demagnetization protection device with variable excitation current criterion, characterized in that: include: The variable excitation current criterion module uses the direct-axis synchronous reactance Xd, rated capacity Sn, no-load excitation current If0, reliability coefficient K, and minimum excitation current setting value Iop.0 to construct the variable excitation current criterion; the static boundary impedance criterion module uses the direct-axis synchronous reactance Xd and reliability coefficient K to construct the static boundary impedance criterion; the reverse reactive power criterion module uses the bus voltage U and reliability coefficient K to construct the reverse reactive power criterion; the measurement module measures the generator excitation current If, the machine-end voltage U, the machine-end current I, the generator output active power P, and the reactive power Q; the machine-end measurement impedance calculation module measures the impedance Z at the computer end; the tripping module, when the excitation current If meets the variable excitation current criterion, the demagnetization protection trips after a delay of t2+t3. If on this basis, the machine-end measurement impedance Z meets the static boundary impedance criterion and the reactive power Qs meets the reverse reactive power criterion, the demagnetization protection accelerates the tripping after a delay of t3.

9. The rod-controlled power generator demagnetization protection device with variable excitation current criterion according to claim 8 is characterized in that: The reliability coefficient K is set to 1.

2.

10. A rod-controlled power generator demagnetization protection system with variable excitation current criterion, characterized in that: It includes a computer-readable storage medium and a processor; the computer-readable storage medium is used to store executable instructions; the processor is used to read the executable instructions stored in the computer-readable storage medium and execute the demagnetization protection method for a rod-controlled power generator with a variable excitation current criterion; a non-transient computer-readable storage medium, on which a computer program is stored, and when the computer program is executed by the processor, the demagnetization protection method for a rod-controlled power generator with a variable excitation current criterion is implemented.

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