Pump storage motor stator grounding fault positioning method based on eigenmode function

Abstract

The application discloses a pump storage motor stator grounding fault positioning method based on an eigenmode function, and comprises the following steps: decomposing A, B, C and N phase voltage signals of the pump storage motor into eigenmode functions through modal decomposition, calculating standard deviations of different eigencomponents, determining a fundamental wave when a standard deviation of a certain component is smaller than a threshold value, distinguishing the fundamental wave and a third harmonic wave, and respectively calculating a grounding fault position of the fundamental wave positioning and a grounding fault position of the third harmonic wave positioning based on potential functions and minimum phase difference functions of the fundamental wave and the third harmonic wave. The unique fault point solution is obtained through joint fault position determination of the fundamental wave and the third harmonic wave. Compared with a calculation method of using steady-state voltage parameters after the pump storage motor stator grounding fault positioning, the application solves the problem of transient waveform transient change at the moment of the stator grounding fault, realizes rapid discovery and accurate measurement of the fault position, and is suitable for positioning requirements of the stator grounding fault of the variable speed pump storage unit.

Description

Technical Field

[0001] This invention relates to a method for analyzing stator grounding faults in motors, and particularly to a method for analyzing stator grounding faults in pumped hydro storage motors. Background Technology

[0002] Large and medium-sized pumped storage generators have large stators and complex wiring, making it extremely time-consuming and labor-intensive to accurately locate grounding faults. Traditional equipment for locating generator stator bar grounding faults requires current injection, applying a grounding current greater than 5A to the equipment to visually locate the grounding point. This can potentially burn out the stator core, causing even greater damage. Especially for large generators, repairing the core requires significant financial resources, specialized materials, tools, and instruments, as well as qualified personnel. Furthermore, the loss of electricity during power outages for maintenance results in substantial economic losses. Summary of the Invention

[0003] The purpose of this invention is to address the aforementioned deficiencies in the prior art and to provide a device and method for locating grounding fault points in the stator bars of generators, taking into account the waveform characteristics of grounding fault data in large and medium-sized pumped storage generators.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a method for locating stator grounding faults in pumped storage generators based on intrinsic mode functions, comprising the following steps: (1) The real-time voltage and current of the three-phase stator and neutral point of the pumped storage motor are collected and stored using an LC filter. The cutoff frequency of the LC filter is between 150Hz and 250Hz. (2) Read the data, find the local extreme points based on the intrinsic modulus function, connect the maxima to form the upper envelope, connect the minima to form the lower envelope, calculate the mean signal lines of the upper and lower envelopes, subtract the mean signals of the upper and lower envelopes from the input signal to obtain the intermediate signal, and calculate the residual of the input signal. Where Sn is the input sequence, Fn is the intrinsic modulus function, and the sequence is generated using extreme points; if the standard deviation (where h) n (t) represents the data point value. If the population mean is greater than the threshold, and the condition is not met, the intrinsic mode function is further decomposed. (3) When the standard deviation When the data is less than the threshold, the data is uploaded to the host computer, and the host computer software is used to perform Fourier decomposition to obtain the fundamental and third harmonic amplitudes. (4) Select the stator winding parameters and winding distribution diagram of a specific motor to establish a planetary (candidate solution) position candidate set for the location of the ground fault; establish the correlation between the fault location phase and the branch through the phase relationship of different branches on each phase; (5) Using the fundamental planetary rule, the candidate points for the ground fault location under the fundamental information are determined by the host computer software; the initial position and mass of the planet (candidate solution) are randomly generated, and the objective function value adopts the minimum phase function; the solar point is selected as the neutral point position, the planetary point is selected as the candidate position of the fault point, and the Cartesian distance is selected as the phase difference between the fault point position and the neutral point position; the positioning results are sorted according to the probability, and the positioning position with the highest fault probability under the fundamental sorting is selected.

[0005] (6) During global search, planets move towards the sun; during local search, local perturbation optimization is used to avoid getting trapped in local optima. (7) Using the third harmonic planetary rule, the host computer software determines the candidate points for the grounding fault location under the third harmonic information; global search and local search planetary positioning are performed, and the positioning results are sorted according to the probability. The positioning location with the highest fault probability under the third harmonic sorting is selected.

[0006] (8) Based on the combined fundamental wave information and the third harmonic information, the location of the stator grounding fault of the pumped storage motor is obtained; the location with the highest fault probability is selected under the fundamental wave and third harmonic sorting.

[0007] Compared with existing technologies, the advantages of this invention are: (1) Based on the modular function decomposition, the received three-phase and neutral point voltages are decomposed into intrinsic modular functions. By observing the intrinsic modular function image, the motor fault status can be judged. This can effectively avoid the problem of speed in judging the stator grounding fault status of pumped storage motor, enabling rapid judgment and location of fault status and suppressing noise interference.

[0008] (2) This invention utilizes the intrinsic modulus function characteristics to adaptively decompose the three-phase and neutral point voltage signals, resulting in a more stable signal decomposition process, avoiding noise interference, and achieving higher accuracy in fault phase identification. Attached Figure Description

[0009] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments or related technologies will be briefly introduced below.

[0010] Figure 1 This is the circuit schematic diagram of the present invention; Figure 2 This is the hardware architecture of the present invention; Figure 3 This is a flowchart of the invention; Figure 4 It is the envelope of the intrinsic modulus function of this invention. Detailed Implementation

[0012] To better understand the above-mentioned objectives, features and advantages of the present invention, the technical solution of the present invention will be further described in a non-limiting detail below with reference to the accompanying drawings and specific embodiments.

[0013] like Figure 1 As shown, the stator A phase of the pumped storage motor is grounded, and the grounding resistance is... R f C g The capacitance to ground is given. A, B, C, and N are the terminals of phases A, B, and C, and the neutral point, respectively. Point N carries an equivalent resistance R. N Grounding, R N Grounding resistance or grounding resistance via neutral point grounding transformer; the terminals of phases A, B, and C are connected to the power grid via transformer T; like Figure 2 As shown, the endpoints of phases A, B, and C, and the endpoint of neutral point N are connected to LC filters, with the LC filter cutoff frequency between 150Hz and 250Hz. After filtering, the filters are connected to the analog sampling port of the microprocessor, where approximately 10 cycles (0.2s) are collected.

[0014] like Figure 4 As shown, an upper envelope is formed by connecting the maxima of about 10 cycles, and a lower envelope is formed by connecting the minima. The mean signal lines of the upper and lower envelopes are calculated. The intermediate signal is obtained by subtracting the mean signal of the upper and lower envelopes from the input signal. The residual and standard deviation are calculated. When the standard deviation is less than the threshold, the data is uploaded to the host computer.

[0015] In the host computer, numerical simulation is performed using self-developed host computer software to complete the constraints of the fundamental wave planetary rule and the third harmonic planetary rule, thereby realizing the location of the motor stator grounding fault.

[0016] according to Figure 3 As shown in the flowchart, the process of locating the fault point using the above procedure is as follows: I. Fault phase identification at the end of generator stator bar.

[0017] The A, B, C, and N voltage sensors are respectively the terminals of the A, B, and C phases of the motor and the neutral point. Passive LC filtering is used to eliminate high-order harmonics. II. Data Acquisition and Modular Function Decomposition.

[0018] The analog sampling port of the microprocessor collects data for about 10 cycles (0.2s), with no less than 240 data points. Using these data points, the maximum points form the upper envelope, and the minimum points form the lower envelope. The mean signal lines of the upper and lower envelopes are calculated, and the residuals and standard deviations are calculated.

[0019] III. Troubleshooting.

[0020] When the standard deviation is less than the threshold, the data is uploaded to the host computer. In the host computer, the fundamental wave planetary rule and the third harmonic planetary rule constraints are completed to realize the location of the motor stator grounding fault.

[0021] IV. Results Analysis.

[0022] The results of stator grounding fault location were analyzed, and numerical simulation was performed using self-developed host computer software.

[0023] By selecting the stator winding parameters and winding distribution diagram of a specific motor, a candidate set of planetary (candidate solution) locations for the ground fault is established; by establishing the phase relationship between different branches on each phase, the correlation between the fault location phase and the branch is established. Using the fundamental wave planetary rule, the host computer software determines the candidate points for grounding fault locations under fundamental wave information; the initial position and mass of the planets (candidate solutions) are randomly generated, and the objective function value adopts the minimum phase function; the solar point is selected as the neutral point position, the planetary point is selected as the candidate fault point position, and the Cartesian distance is selected as the phase difference between the fault point position and the neutral point position; the positioning results are sorted according to the probability, and the positioning position with the highest fault probability under the fundamental wave sorting is selected.

[0024] During global search, planets move toward the sun; during local search, local perturbation optimization is used to avoid getting trapped in local optima. Using the third harmonic planetary rule, the host computer software determines the candidate points for grounding fault location under the third harmonic information; global search and local search planetary positioning are performed, and the positioning results are sorted according to probability. The location with the highest fault probability under the third harmonic sorting is selected.

[0025] By combining the candidate ground fault locations under fundamental wave information and the candidate ground fault locations under third harmonic information, the location of the stator ground fault of the pumped storage motor is obtained; the location with the highest fault probability under the fundamental wave and third harmonic sorting is selected.

[0026] It should be noted that the above preferred embodiments are merely illustrative of the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for locating stator grounding faults in pumped storage generators based on intrinsic mode functions, comprising the following steps: (1) The real-time voltage and current of the three-phase stator and neutral point of the pumped storage motor are collected and stored using an LC filter; (2) Read the data, find the local extreme points based on the principle of intrinsic mode function, connect the maximum points to form the upper envelope, connect the minimum points to form the lower envelope, find the mean signal line of the upper and lower envelopes, subtract the mean signal of the upper and lower envelopes from the input signal to obtain the intermediate signal, calculate the residual, if the standard deviation is greater than the threshold, the condition is not met, and the intrinsic mode function is decomposed again. (3) When the standard deviation is less than the threshold, the data is uploaded to the host computer, and the amplitude of the fundamental wave and the third harmonic is obtained by Fourier decomposition; (4) Using the fundamental wave planetary rule, determine the candidate locations of ground faults under fundamental wave information; (5) Using the third harmonic planetary rule, determine the candidate locations of ground faults under the third harmonic information; (6) By combining the ground fault location candidate points under the fundamental wave information and the ground fault location candidate points under the third harmonic information, the location of the stator ground fault of the pumped storage motor is obtained.

2. The method for locating stator grounding faults of pumped storage generators based on intrinsic mode functions according to claim 1, characterized in that: The LC filter cutoff frequency is between 150Hz and 250Hz; The residual of the input signal is ,in, Given the input sequence, The sequence is generated using extreme points, which are the eigenmode functions. Standard deviation ,in For data point values, This is the overall mean.

3. The method for locating stator grounding faults of pumped storage generators based on intrinsic mode functions according to claim 1, characterized in that: After the sampled voltages of phases A, B, C and N voltage transformers are filtered by LC, the microprocessor performs data reading, intrinsic modulus function calculation and standard deviation processing, and then uploads the data to the host computer via data line. The self-developed host computer software is used to realize numerical simulation, complete the fundamental wave planetary rule and the third harmonic planetary rule constraint, and realize the location of motor stator grounding fault.

4. The method for locating stator grounding faults of pumped storage generators based on intrinsic mode functions according to claim 1, characterized in that: By selecting the stator winding parameters and winding distribution diagram of a specific motor, a candidate set of planetary (candidate solutions) locations for the ground fault is established; by establishing the phase relationship between different branches on each phase, the correlation between the fault location phase and the branch is established.

5. The method for locating stator grounding faults of pumped storage generators based on intrinsic mode functions according to claim 1, characterized in that: The initial position and mass of the planet (candidate solution) are randomly generated, and the objective function value adopts the minimum phase function; the solar point is selected as the neutral point position, the planet point is selected as the candidate position of the fault point, and the Cartesian distance is selected as the phase difference between the fault point position and the neutral point position. During the global search, planets move towards the sun; during the local search, local perturbation optimization is used to avoid getting trapped in local optima.

6. The method for locating stator grounding faults of pumped storage generators based on intrinsic mode functions according to claim 5, characterized in that: Planetary positioning was performed using both fundamental and third harmonic waves for global and local searches, respectively. The positioning results were sorted according to probability, and the location with the highest probability of failure was selected based on the fundamental and third harmonic wave rankings.

Images