Insulation risk point prediction method for power conversion equipment

Abstract

The invention relates to an insulation risk point prediction method for power conversion equipment, and the method comprises the steps: building a three-dimensional geometric model of the power conversion equipment, and determining the physical property parameters and electric field analysis boundary conditions of a structure; establishing a finite element model of the equipment, and calculating electric field intensity distribution of the whole field domain of the equipment; drawing an electric field distribution cloud picture of each position of the equipment, and obtaining a simulation insulation risk point of the power conversion equipment according to the electric field distribution cloud picture; comprehensive discharge positioning experiments of a direct current side and an alternating current side are respectively carried out on the power conversion equipment, and whether spark discharge occurs at a simulation insulation risk point of the equipment is emphatically monitored; and comparing the insulation risk point of the power conversion equipment in the electric field simulation experiment with the spark discharge position of the discharge positioning experiment equipment, and confirming the insulation risk point of the power conversion equipment. An insulation risk point is effectively predicted and accurately positioned through a method of combining electric field simulation and an actual spark discharge test, a reference basis is provided for design and optimization of an insulation structure of equipment, and the operation reliability is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of insulation risk assessment of power conversion equipment, and in particular to a method for predicting insulation risk points of power conversion equipment by combining simulation calculation with experiment. Background Art

[0002] With the rapid development of the new energy industry, renewable energy sources such as photovoltaic and wind power generation have been widely used around the world. In these new energy systems, power conversion equipment such as inverters and rectifiers play a vital role. In recent years, the insulation problem of related equipment has become increasingly prominent. In actual operation, insulation failure not only causes equipment damage and shutdown, but may also cause serious accidents such as fire. For example, insulation breakdown in power conversion equipment often leads to partial discharge, which in turn causes fire, causing huge economic losses and safety hazards. Therefore, improving the insulation reliability of power conversion equipment has become the key to ensuring the safe operation of new energy systems.

[0003] Traditional insulation detection methods mainly include partial discharge detection, withstand voltage test and infrared imaging. For power conversion equipment with complex structures, traditional detection methods are difficult to accurately locate insulation weaknesses, affecting the effectiveness of fault prevention. The development of electric field simulation technology provides a new means for predicting insulation risks. By establishing a three-dimensional model of the equipment and performing electric field analysis, possible insulation risk points can be predicted during the design phase. However, relying solely on simulation analysis may lead to deviations between the results and the actual situation due to model simplification and solution accuracy issues. Therefore, verifying the simulation results in combination with actual experiments has become an important way to improve the accuracy of insulation risk prediction.

[0004] Patent application number CN201410714659.3 discloses a method for testing the withstand voltage of insulating rods, which can quantitatively and qualitatively analyze and determine the insulation performance of insulating rods. This method may cause damage to the insulation of the equipment during the test process, and usually has a detection effect only after the fault has occurred. Summary of the invention

[0005] In order to solve the above-mentioned defects existing in the prior art, the purpose of this application is to provide a method for predicting insulation risk points and their comprehensive positioning of power conversion equipment by combining simulation calculation and experiment, and to predict and comprehensively locate insulation risk points of power conversion equipment with complex and large structures in the field of new energy. This method not only improves the accuracy of insulation risk prediction, but also provides a scientific basis in the equipment design stage, effectively prevents the occurrence of accidents such as fire, and improves the safety and operational reliability of new energy systems. It has important application value and promotion prospects.

[0006] The present invention is achieved through the following technical solutions.

[0007] A method for predicting insulation risk points of power conversion equipment is provided, comprising:

[0008] Establish a three-dimensional geometric model based on the structure of the power conversion equipment to determine the physical parameters of the power conversion equipment structure and the boundary conditions for electric field analysis;

[0009] According to the three-dimensional geometric model, physical parameters and boundary conditions of electric field analysis, a finite element model of the power conversion equipment is established to calculate the electric field intensity distribution of the entire field of the power conversion equipment;

[0010] Draw the electric field distribution cloud map of each position of the power conversion equipment according to the electric field intensity distribution of the whole field, and obtain the simulated insulation risk points of the power conversion equipment according to the electric field distribution cloud map;

[0011] Conduct comprehensive discharge location experiments on the DC and AC sides of the power conversion equipment, focusing on monitoring whether spark discharge occurs at the simulated insulation risk points of the equipment;

[0012] Compare the insulation risk points of the power conversion equipment in the electric field simulation experiment with the spark discharge positions of the discharge positioning experiment equipment to confirm the insulation risk points of the power conversion equipment.

[0013] Preferably, the power conversion device includes an inverter and a rectifier.

[0014] Preferably, the physical property parameters include conductivity σ and dielectric constant ε r ; The boundary conditions include the voltage and grounding conditions of the input and output terminals.

[0015] Preferably, the electric field intensity distribution of the entire field of the power conversion device is calculated, and in a three-dimensional electric field solver, the electric field intensity E is equal to the negative value of the potential gradient.

[0016] Preferably, the position where the electric field intensity is the largest in the concentrated area of ​​the electric field in the electric field distribution cloud map is regarded as the insulation risk point of the power conversion equipment in the simulation experiment.

[0017] Preferably, a comprehensive discharge positioning experiment is performed on the DC side and the AC side of the power conversion equipment, including:

[0018] Build an experimental circuit, connect the AC / DC withstand voltage power supply, current limiting resistor, voltage measuring device, and the power conversion equipment to be tested to the circuit, and perform a no-load test;

[0019] In the DC side discharge positioning test, the DC input terminal of the device under test is connected to a high-voltage DC power supply, and the other end of the device is grounded; in the AC side discharge positioning test, the AC input terminal of the device under test is connected to a high-voltage AC power supply, and the opposite end of the device is grounded.

[0020] Preferably, a comprehensive discharge positioning experiment is carried out on the DC side and the AC side of the power conversion equipment respectively. The voltage is boosted according to the step-by-step voltage boosting method, with the AC / DC withstand voltage power supply voltage ≥20kV and the current limiting resistor value being 1-10kΩ; the voltage is boosted starting from the voltage value of the factory withstand voltage test, and the voltage is increased by 1kV for 1 minute until it stabilizes. After monitoring for no discharge, the voltage is continued to be boosted until a discharge point appears; the voltage boost is stopped and the power supply is turned off to determine the specific location where the spark discharge occurs.

[0021] Preferably, the insulation risk points of the equipment in the electric field simulation experiment are compared with the spark discharge positions of the discharge positioning experiment equipment to confirm the insulation risk points of the power conversion equipment. If the simulated insulation risk points are consistent with the spark discharge positions of the discharge positioning experiment equipment, they are confirmed as the insulation risk points of the power conversion equipment. If they are inconsistent, the physical parameters of the power conversion equipment structure and the boundary conditions of the electric field analysis are adjusted to re-obtain the simulated insulation risk points of the power conversion equipment.

[0022] The present invention adopts the above technical solution, which has the following beneficial effects:

[0023] 1. Rapidly identify the insulation weak areas of the power conversion equipment through the full-field electric field strength distribution results, thereby predicting the possible insulation risk points. This provides a basis for preventive maintenance, reduces the risk of unexpected failures during equipment operation, and thus reduces the equipment's operation and maintenance costs and improves economic benefits. Based on the full-field electric field strength distribution data, the structural design and component layout of the power conversion equipment can be optimized, thereby reducing the electric field concentration effect and improving the insulation performance and long-term stability of the equipment.

[0024] 2. Through the discharge location experiment, the spark discharge position is monitored and recorded, and the specific location of the discharge can be accurately determined, which is of great significance for fault diagnosis and prevention of potential problems in electrical equipment. The step-up method is used for testing to verify the insulation performance of the equipment at different voltage levels to ensure its safety and reliability under actual working conditions.

[0025] 3. The present invention aims at power conversion equipment with complex and large structures. By combining electric field simulation with actual spark discharge testing, it can effectively predict and accurately locate insulation risk points, provide a reference basis for the insulation structure design and optimization of the equipment, and thus improve its operational reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The drawings described herein are used to provide a further understanding of the present invention, constitute a part of the present application, and do not constitute an improper limitation of the present invention. In the drawings:

[0027] Figure 1 It is a flow chart of the overall method of the present invention;

[0028] FIG2( a ) is a geometric model of the DC side of the inverter according to an embodiment of the present invention;

[0029] FIG2( b ) is a geometric model of the AC side of the inverter according to an embodiment of the present invention;

[0030] FIG2( c ) is a geometric model of the inverter according to an embodiment of the present invention;

[0031] FIG3( a ) is a finite element model of the DC side and AC side of the inverter in an embodiment of the present invention;

[0032] FIG3( b ) is a finite element model of the whole inverter in an embodiment of the present invention;

[0033] FIG4( a ) is a cloud diagram of the electric field distribution at the transformer position on the AC side of the inverter according to an embodiment of the present invention;

[0034] FIG4( b ) is a cloud diagram of the electric field distribution of the three-phase busbar and the circuit breaker position on the AC side of the inverter in an embodiment of the present invention;

[0035] FIG4( c ) is a diagram showing the electric field distribution of the three-phase output position of the inverter on the AC side in an embodiment of the present invention;

[0036] FIG4( d ) is an electric field distribution diagram of the connection position between the three-phase output on the AC side of the inverter and the circuit breaker in an embodiment of the present invention;

[0037] FIG5( a ) is a circuit connection diagram of a DC side discharge positioning experiment in an embodiment of the present invention;

[0038] FIG5( b ) is a circuit connection diagram of an AC side discharge positioning experiment in an embodiment of the present invention;

[0039] Figure 6 This is a spark discharge experiment result diagram in an embodiment of the present invention. DETAILED DESCRIPTION

[0040] The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments. The exemplary embodiments and descriptions of the present invention are used to explain the present invention but are not intended to limit the present invention.

[0041] like Figure 1 As shown, an insulation risk point prediction method for a power conversion device provided by an embodiment of the present invention comprises the following steps:

[0042] S1, establishing a geometric model according to the structure of the power conversion device, and determining the physical parameters of the power conversion device structure and the boundary conditions of the electric field analysis.

[0043] The power conversion equipment includes but is not limited to inverters and rectifiers. This embodiment takes the inverter as an example. A three-dimensional geometric model is established based on the actual structure and size of the inverter. For complex geometric bodies, the model is simplified according to the principle that the electrical connection relationship of each part structure remains unchanged, and the physical parameters of the power conversion equipment structure and the boundary conditions of the electric field analysis are determined.

[0044] The structure of the inverter includes the DC side, AC side and casing. The DC side includes input, fuse, circuit breaker, output conductor and insulation baffle. The AC side includes inverter output, transformer, circuit breaker and three-phase output conductor and insulation baffle.

[0045] The physical properties of the inverter structure include: conductivity σ and relative dielectric constant ε r .

[0046] According to the actual working conditions of the inverter, determine the electric field boundary conditions of the inverter, including: the voltage of the DC input and output terminals, the voltage of the AC input and output terminals, and the casing grounding conditions.

[0047] S2, establish a finite element model of the power conversion equipment and perform a finite element solution of the electric field distribution.

[0048] According to the three-dimensional geometric model, physical parameters and boundary conditions of the inverter structure, a finite element model was established using ANSYS Maxwell. The model includes: housing, DC side components and AC side components. The electrostatic field solver was selected to calculate the electric field distribution of the inverter.

[0049] In the three-dimensional electric field solver, in order to find the relationship between the electric field intensity E and the source field, the potential function potential is introduced As an auxiliary quantity. In a linear, uniform, isotropic dielectric, Gauss's theorem of electrostatics and the constitutive equation of the medium are:

[0050]

[0051] D=εE

[0052] Where E is the electric field strength (V / m); D is the electric flux density (C / m 2 ), ρ is the charge density (C / m3), ε is the dielectric constant of the medium (F / m); It represents the gradient, which means that the directional derivative of the function at this point reaches the maximum value along this direction.

[0053] The electric field strength E is defined as the negative value of the potential gradient, expressed as:

[0054]

[0055] Potential Satisfies the differential equation:

[0056]

[0057] S3, drawing an electric field distribution cloud map of each position of the power conversion equipment according to the electric field intensity distribution of the entire field, and obtaining the insulation risk points of the power conversion equipment according to the electric field distribution cloud map.

[0058] The electric field distribution cloud map of each position on the DC side and AC side of the inverter can intuitively reflect the concentrated area of ​​the electric field. When the electric field is concentrated, the free electrons or charged ions in the medium will be accelerated under the action of the electric field and obtain higher kinetic energy. When the electric field strength reaches a critical value, it will cause dielectric breakdown discharge. In this embodiment, the position with the largest electric field strength in the concentrated area of ​​the electric field in the electric field distribution cloud map is regarded as the insulation risk point of the power conversion equipment in the simulation experiment.

[0059] S4, conduct comprehensive discharge positioning experiments on the DC side and AC side of the power conversion equipment, focusing on monitoring whether spark discharge occurs at the simulated insulation risk points of the equipment.

[0060] When a sufficiently high voltage is applied across the device, the electric field strength is concentrated at weak locations or defects, which are more likely to cause breakdown. When local breakdown occurs, an ionization channel is formed, along which electrons and ions move, generating an instantaneous current. At the same time, the high temperature and light generated by the current are spark discharges. Monitor the location where the spark appears and identify insulation risk points.

[0061] Design and build the experimental circuit. The experimental equipment includes: AC / DC power supply, current limiting resistor, high-voltage probe, and the inverter to be tested. During the DC side discharge positioning test, build the experimental circuit, connect the AC / DC withstand voltage power supply, current limiting resistor, voltage measuring device, and the power conversion equipment to be tested to the circuit, and perform a no-load test. In the DC side discharge positioning test, connect the DC input terminal of the device to be tested to the high-voltage DC power supply, and the device casing is grounded; in the AC side discharge positioning test, connect the three-phase AC input terminal of the device to be tested in parallel and then connect it to the high-voltage AC power supply, and the device casing is grounded.

[0062] The voltage is increased according to the step-by-step voltage-boosting method. The AC and DC withstand voltage power supply voltage is ≥20kV, and the current-limiting resistance value is 1-10kΩ. Specifically, the voltage is increased from the voltage value of the factory withstand voltage test. Wait for 1 minute for each increase of 1kV. Use a camera to record and monitor whether the equipment has spark discharge. Until the discharge point appears, stop the voltage boost and turn off the power supply to determine the specific location of the spark discharge. The experimental results show that the spark discharge occurs at the position between the three-phase busbars connected to the AC side circuit breaker above it.

[0063] S5, compare and analyze the finite element electric field calculation results with the discharge positioning experiment results to confirm their consistency and differences, and comprehensively identify the insulation risk points of the power conversion equipment.

[0064] Since simulation calculations have high requirements for mesh accuracy, the complex model structure is simplified, and the finite element calculation results are easier to converge. During the spark discharge positioning experiment, the structure of the inverter equipment to be tested is complex, but it is closer to the actual situation. If the simulated insulation risk point is consistent with the spark discharge position of the discharge positioning experiment equipment, it is confirmed as the insulation risk point of the power conversion equipment.

[0065] If there is a possible deviation between the experimental discharge point and the simulation prediction result, the physical parameters of the power conversion device structure and the boundary conditions of the electric field analysis are adjusted to re-obtain the simulated insulation risk point of the power conversion device.

[0066] The present invention is further illustrated by simulation experiments below.

[0067] (1) Determine the structure of the power conversion equipment and establish a geometric model; determine the physical parameters of the power conversion equipment structure; and determine the boundary conditions for electric field analysis.

[0068] The three-dimensional geometric model of the inverter is established as shown in Figure 2 (a), (b), and (c). Except for the metal conductors such as DC input, fuse, circuit breaker, DC output, inverter output, transformer, circuit breaker, three-phase output and shell in the model, the physical properties of other insulating materials are determined by referring to the digital numbers in the figure, see Table 1.

[0069] Table 1 Physical parameters of array solder joints and packaging structures

[0070]

[0071] The input and output voltages are set according to the actual working conditions of the inverter. The DC input voltage is 1600V, and the AC side refers to its rated voltage of 630V. The output voltage is set to a peak voltage of 527V. The electric field distribution is the most severe under this working condition, which is more meaningful for reference.

[0072] (2) Establish a finite element model of the power conversion equipment as shown in Figure 3(a) and (b), and perform a finite element solution of the electric field distribution. Obtain the insulation risk points of the power conversion equipment based on the electric field intensity distribution results of the entire field.

[0073] Based on the geometric model, physical parameters and boundary conditions of the inverter, a finite element model as shown in Figures 3(a) and (b) is established to perform finite element solution of the electric field distribution and obtain the electric field distribution cloud map at each position of the inverter.

[0074] Comparing the electric field strengths of the electric field concentration areas at various locations, the highest electric field strength of the AC side inverter in Figure 4(a) is 7.5724×10 4 V / m, the highest electric field strength in Figure 4(b) is 1.0432×10 5 V / m, the highest electric field strength in Figure 4(c) is 9.1596×10 4 V / m, the highest electric field strength in Figure 4(d) is 9.3223×10 4 V / m. Among them, Figure 4(c) is the electric field distribution cloud map around the three-phase busbar position connected to the AC side circuit breaker. The electric field intensity is the largest at the electric field concentration area, and this position is regarded as the insulation risk point of the inverter simulation.

[0075] (3) Comprehensive discharge positioning experiments were carried out on the DC side and AC side of the power conversion equipment. The experimental circuits were designed and constructed as shown in Figures 5(a) and (b), with a focus on monitoring whether spark discharge occurred at the simulated insulation risk points of the equipment.

[0076] The voltage is increased by the step-by-step voltage step-up method. The AC and DC withstand voltage power supply voltage is ≥ 20kV, and the current limiting resistor value is 1-10kΩ. Specifically, the voltage is increased from the voltage value of the factory withstand voltage test. After each increase of 1kV, wait for 1 minute. Use a camera to record and monitor the location where spark discharge occurs in the equipment. The experimental results are obtained as follows: Figure 6 shown.

[0077] The finite element electric field calculation results are compared and analyzed with the discharge positioning experiment results to confirm their consistency and differences, and comprehensively identify the insulation risk points of the power conversion equipment.

[0078] In this embodiment, the insulation risk point predicted by the simulation calculation is consistent with the insulation risk point obtained by the spark discharge experiment.

[0079] If the insulation risk point predicted by the simulation calculation is inconsistent with the insulation risk point obtained by the spark discharge experiment, the finite element simulation analysis model of the power conversion equipment is improved, and the above steps (1) to (3) are repeated to re-obtain the simulated insulation risk point of the power conversion equipment.

[0080] It can be seen from the above embodiments and drawings that the method of the present invention can effectively predict and accurately locate insulation risk points, provide a reference basis for the insulation structure design and optimization of the equipment, and thus improve its operational reliability.

Claims

1. A method for predicting insulation risk points of power conversion equipment, characterized in that: include: Establish a three-dimensional geometric model based on the structure of the power conversion equipment to determine the physical parameters of the power conversion equipment structure and the boundary conditions for electric field analysis; According to the three-dimensional geometric model, physical parameters and boundary conditions of electric field analysis, a finite element model of the power conversion equipment is established to calculate the electric field intensity distribution of the entire field of the power conversion equipment; Draw the electric field distribution cloud map of each position of the power conversion equipment according to the electric field intensity distribution of the whole field, and obtain the simulated insulation risk points of the power conversion equipment according to the electric field distribution cloud map; Conduct comprehensive discharge location experiments on the DC and AC sides of the power conversion equipment, focusing on monitoring whether spark discharge occurs at the simulated insulation risk points of the equipment; Compare the insulation risk points of the power conversion equipment in the electric field simulation experiment with the spark discharge positions of the discharge positioning experiment equipment to confirm the insulation risk points of the power conversion equipment.

2. The insulation risk point prediction method of the power conversion equipment according to claim 1, characterized in that: The power conversion device includes an inverter and a rectifier.

3. The insulation risk point prediction method of the power conversion equipment according to claim 1, characterized in that: The physical property parameters include conductivity σ and dielectric constant ε; the boundary conditions include voltages at the input and output ends and grounding conditions.

4. The insulation risk point prediction method of the power conversion equipment according to claim 1, characterized in that: Calculate the electric field strength distribution of the entire field of power conversion equipment, including: In the 3D electric field solver, the electric field strength E is equal to the negative value of the potential gradient, expressed as: In the formula, Represents the gradient, which means that the directional derivative of the function at this point reaches the maximum value along this direction; Indicates electric potential; Potential Satisfies the differential equation: Where ρ is the charge density and ε is the dielectric constant of the medium.

5. The insulation risk point prediction method of the power conversion equipment according to claim 1, characterized in that: The location with the maximum electric field intensity in the concentrated area of ​​the electric field in the electric field distribution cloud map is regarded as the insulation risk point of the power conversion equipment in the simulation experiment.

6. The insulation risk point prediction method of the power conversion equipment according to claim 1, characterized in that: Conduct comprehensive discharge positioning experiments on the DC side and AC side of the power conversion equipment, including: Build an experimental circuit, connect the AC / DC withstand voltage power supply, current limiting resistor, voltage measuring device, and the power conversion equipment to be tested to the circuit, and perform a no-load test; In the DC side discharge positioning test, the DC input terminal of the device under test is connected to a high-voltage DC power supply, and the other end of the device is grounded; in the AC side discharge positioning test, the AC input terminal of the device under test is connected to a high-voltage AC power supply, and the opposite end of the device is grounded.

7. The insulation risk point prediction method of the power conversion equipment according to claim 1, characterized in that: Carry out comprehensive discharge positioning experiments on the DC and AC sides of the power conversion equipment respectively. The voltage is boosted according to the step-by-step voltage boosting method. The AC / DC withstand voltage power supply voltage is ≥20kV and the current limiting resistor value is 1-10kΩ. Start boosting from the voltage value of the factory withstand voltage test. Wait for 1 minute for each increase of 1kV until the voltage stabilizes. Continue boosting after monitoring for no discharge until a discharge point appears. Stop boosting and turn off the power supply to determine the specific location where the spark discharge occurs.

8. The insulation risk point prediction method of the power conversion equipment according to claim 1, characterized in that: Compare the insulation risk point of the equipment in the electric field simulation experiment with the spark discharge position of the discharge positioning experiment equipment to confirm the insulation risk point of the power conversion equipment. If the simulated insulation risk point is consistent with the spark discharge position of the discharge positioning experiment equipment, it is confirmed as the insulation risk point of the power conversion equipment. If there is any inconsistency, the finite element simulation analysis model of the power conversion equipment is improved to re-obtain the simulation insulation risk points of the power conversion equipment.

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