Converter element replacement method

Abstract

This invention relates to the field of converter maintenance technology, specifically a method for replacing converter components. Based on the converter's operating environment and conditions, a dynamic lifespan correction factor for each converter component is calculated in real time. Then, based on the nominal lifespan of the converter component, a dynamic equivalent lifespan is obtained, where is determined by the ambient temperature cumulative damage factor or total damage degree. The replacement cycle T is determined by: , and K is a safety factor. By setting the ambient temperature cumulative damage factor or total damage degree, the fixed cycle limitation is broken, avoiding over-maintenance or under-maintenance caused by timed replacement. By introducing a dynamic lifespan correction factor, the component replacement cycle is dynamically corrected from a fixed nominal lifespan to an equivalent lifespan that varies with actual operating conditions.

Description

Technical Field

[0001] This invention relates to the field of converter maintenance technology, and in particular to a method for replacing converter components. Background Technology

[0002] The converter is connected between the generator and the public power grid. In wind power generation systems, it is generally used in conjunction with a doubly-fed generator. Most of them are air-cooled four-quadrant doubly-fed converters, which are usually installed at the base of the tower.

[0003] In actual wind farm operation and maintenance, converters are one of the common causes of downtime. Due to limited space at the tower installation location, replacing them entirely is often time-consuming, labor-intensive, and costly. Therefore, from the perspective of system design and operation and maintenance economy, emphasizing the modular design of converters, condition monitoring capabilities, and the on-site maintainability and replaceability of key components is of great practical significance.

[0004] Therefore, in designing and evaluating doubly-fed converters, in addition to focusing on their electrical performance and control strategies, in-depth research on the lifespan control of their key components and the replacement methods for each component has become crucial for promoting cost reduction and efficiency improvement in the wind power industry. Summary of the Invention

[0005] In this section, as well as in the abstract and title of this application, some simplifications or omissions may be made to avoid obscuring the purpose of this section, the abstract, and the title of this application, and such simplifications or omissions shall not be used to limit the scope of the invention.

[0006] To address the shortcomings of existing technologies, one objective of this invention is to provide a method for replacing converter components.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: a converter component replacement method, which calculates the dynamic life correction factor of each converter component in real time based on the converter operating environment and conditions. And based on the nominal life of the converter components. The dynamic equivalent lifetime is obtained. , making ,in, Damage caused by cumulative environmental temperature factors or total damage The decision-making condition for the replacement cycle T is as follows: K is the safety factor.

[0008] As a preferred embodiment of the converter component replacement method of the present invention, wherein: the ambient temperature cumulative damage factor The damage to the IGBT module in the converter element due to the influence of ambient temperature is defined as follows: , in, This means that the operating time of the IGBT module is divided into n tiny time periods; Indicates each time period The average core temperature of the IGBT module is recorded within the module. The IGBT module at this temperature The theoretical lifespan is as follows.

[0009] As a preferred embodiment of the converter component replacement method of the present invention, wherein: the total damage degree The expression is: , in, Instantaneous wear sum; This represents the maximum permissible wear amount.

[0010] As a preferred embodiment of the converter component replacement method of the present invention, wherein: Defined as follows: for the circuit breaker in the converter element, the amount of wear generated by each breaking event is proportional to the square of the breaking current and the arcing time, specifically: , in, This represents the wear caused by the j-th break. The wear coefficient is related to the contact material and the arc-extinguishing chamber structure; This refers to the instantaneous current during the breaking process; This represents the duration of arc burning.

[0011] As a preferred embodiment of the converter component replacement method of the present invention, wherein: The wear is defined as the cumulative wear caused by each disconnection event starting from the commissioning of the circuit breaker in the converter element, specifically: , in, It represents the total number of segments up to time t.

[0012] As a preferred embodiment of the converter component replacement method of the present invention, wherein: Defined as the number of times a device is allowed to break at its rated breaking current. , , in, It is the amount of wear per cycle under rated breaking conditions.

[0013] As a preferred embodiment of the converter component replacement method of the present invention, wherein: Damage caused by cumulative environmental temperature factors The decision is as follows: .

[0014] As a preferred embodiment of the converter component replacement method of the present invention, wherein: It is determined by the total damage degree The decision is as follows: .

[0015] The present invention provides a method for replacing converter components with the following advantages: it accumulates damage factors due to ambient temperature. or total damage This setting breaks the fixed cycle limitation, avoiding over-maintenance or under-maintenance caused by scheduled replacements, by introducing... This reduces the component replacement cycle from a fixed nominal lifespan. Dynamically corrected to equivalent life that varies with actual operating conditions Furthermore, environmental temperature cumulative damage factors were proposed for different types of components. and total damage Two models are available, allowing for timely replacement based on the properties of different types of components in the converter. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a flowchart of the converter component replacement method of the present invention.

[0018] Figure 2 These are the front and rear views of the converter of the present invention.

[0019] Figure 3 This is a schematic diagram of the replacement structure for the IGBT module.

[0020] Figure 4 This is a schematic diagram of the circuit breaker replacement structure. Detailed Implementation

[0021] To make the objectives, features, and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0022] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0023] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0024] Example 1

[0025] Reference Figure 1 This is the first embodiment of the present invention. This embodiment provides a method for replacing converter components. By setting the replacement cycle T judgment condition, each component of the converter can be replaced before the end of its lifespan, thus avoiding downtime caused by replacing components after they are damaged.

[0026] The method specifically includes the following steps: S1. Collect converter data based on the converter's operating environment and conditions; S2. Calculate the dynamic lifetime correction factor for each converter element in real time. And based on the nominal life of the converter components. The dynamic equivalent lifetime is obtained. , making ,in, Damage caused by cumulative environmental temperature factors or total damage Decide.

[0027] Among them, the IGBT module in the converter element adopts the ambient temperature cumulative damage factor. The decision was made to replace the circuit breaker based on its total damage level. The decision has been made to change.

[0028] S3, based on replacement cycle This is used as a condition to determine whether to trigger a replacement. Here, K is the safety factor.

[0029] Example 2

[0030] This is the second embodiment of the present invention. Unlike the previous embodiment, this embodiment provides an environmental temperature cumulative damage factor. Damage factors accumulate through ambient temperature. The settings allow for targeted control of the replacement cycle of the IGBT modules in the converter.

[0031] Specifically, environmental temperature cumulative damage factor This formula is used to quantify the thermal fatigue damage caused by long-term stress at different junction temperatures in IGBT modules. , The entire operating cycle of the IGBT module is divided into several small time periods based on temperature changes. The damage amount in each time period is equal to the damage amount in that time period. At this temperature Theoretical lifespan allowed for operation The ratio. When cumulative damage When the value reaches 1, it indicates that the module has reached the end of its thermal fatigue life.

[0032] in, This means that the operating time of the IGBT module is divided into n tiny time periods; Indicates each time period The average core temperature of the IGBT module is recorded within the module. The IGBT module at this temperature The theoretical lifespan is as follows.

[0033] Furthermore, dynamic lifetime correction factor Damage factors accumulated by ambient temperature The decision is expressed as: , This refers to the remaining lifespan of the IGBT module at the current moment, after deducting the thermal fatigue damage already incurred.

[0034] When the new module is put into operation , As the module withstands long-term temperature shocks, Start from 0 and gradually increase. Correspondingly, it gradually decreases from 1. If the cumulative damage... This indicates that 25% of the module's thermal fatigue life has been consumed, leaving 75% of its remaining life. When cumulative damage When it approaches 1, A value approaching 0 indicates that the module has reached the end of its design life.

[0035] Furthermore, the dynamic equivalent lifespan and replacement cycle are determined. IGBT modules have a nominal lifespan at the time of manufacture. (For example, the manufacturer specifies a continuous operating life of 20 years under standard conditions). However, in actual operation, due to varying temperature stresses, its equivalent life will dynamically change. This invention addresses this by providing a dynamic equivalent life... To reflect this change: , Replacement cycle The judgment condition is: , in The safety factor (usually 0.8 to 0.95) is used to reserve a certain safety margin to avoid sudden failure of the module before it reaches its theoretical life limit.

[0036] The following explanation uses the IGBT module in a photovoltaic inverter as an example, with the following parameters: nominal lifespan Year; Rated reference point: at junction temperature At (373K), the theoretical lifespan is 200,000 hours; Monitoring system: Records the average junction temperature of the IGBT every 10 minutes.

[0037] Assume the module has been running for 3 years (approximately 26,280 hours). The controller will divide the entire runtime into hourly intervals ( The time was divided into hours, and the average junction temperature within each hour was extracted. The monitoring data and calculation process are shown in the table below: The numerical calculation of the cumulative damage factor D(t) due to ambient temperature is shown in Table 1 below: Table 1

[0038] After three years of cumulative calculations, the cumulative damage was obtained. .but: Dynamic lifetime correction factor ; Dynamic equivalent lifetime Year; Take safety factor The change cycle warning point is: Year.

[0039] Since the module has been in operation for 3 years, far from reaching the required 11.1 years, the system determines it to be in good health and does not require replacement at this time. The system will continue to update hourly. and When the running time approaches the warning point, the IGBT module should be replaced.

[0040] Furthermore, Damage caused by cumulative environmental temperature factors The decision, specifically, is as follows: When the replacement cycle When necessary, the IGBT module should be replaced.

[0041] The rest of the structure is the same as in Example 2.

[0042] Example 3

[0043] This is the third embodiment of the present invention. Unlike the previous embodiment, this embodiment provides a total damage degree. Through total damage The settings allow for targeted control of the replacement cycle of the converter circuit breaker.

[0044] Total damage The expression is, ,in, Instantaneous wear sum; This is the maximum permissible wear amount. This value reflects the health status of the circuit breaker contact system: when When the value is close to 1, it indicates that the wear is nearing its limit and replacement should be considered.

[0045] Specifically, cumulative wear The instantaneous wear caused by each disconnection event starting from when the circuit breaker is put into operation. The sum of . For each break event. Instantaneous wear Calculated using the following integral formula: , in: For the first The instantaneous current flowing through the contacts during the second disconnection process (in A); The arc duration during this break (in seconds) is the time from the moment the contacts separate until the arc is finally extinguished. The wear coefficient is related to physical properties such as contact material and arc-extinguishing chamber structure, and can be determined experimentally (e.g., for silver-based contacts). Desirable ).

[0046] integral The cumulative effect of arc energy during the breaking process (proportional to the heat generated by the arc) was calculated, and this heat directly leads to electrical wear of the contact material. In the actual monitoring system, the current waveform during the breaking process can be recorded in real time by a high-speed sampling circuit, and the integral value can be calculated using a numerical integration method.

[0047] Cumulative wear Updated over time: , in Up to the current time The total number of times the circuit breaker has tripped.

[0048] Defined as the instantaneous wear caused by each breaking event of a circuit breaker in a converter element, which is proportional to the square of the breaking current and the arcing time, specifically: , in, The instantaneous wear caused by the j-th break; The wear coefficient is related to the contact material and the arc-extinguishing chamber structure; This refers to the instantaneous current during the breaking process; This represents the duration of arc burning.

[0049] The wear is defined as the cumulative wear caused by each disconnection event starting from the commissioning of the circuit breaker in the converter element, specifically: , in, It represents the total number of segments up to time t.

[0050] Defined as the maximum permissible wear under rated breaking current, this value characterizes the total wear limit that a circuit breaker can withstand before reaching the end of its service life. This value is typically calculated from the rated electrical life parameters provided by the circuit breaker manufacturer. .

[0051] For the circuit breaker at its rated breaking current The number of rated breaks allowed at (e.g., 1000A) (e.g., 5000 times).

[0052] This refers to the standard wear amount caused by a single breakage under rated breaking conditions, the value of which is obtained experimentally as the integral value under rated breaking conditions. The average value is Multiply by a coefficient Later can be obtained .

[0053] Dynamic lifetime correction factor From total damage Decide: , This represents the remaining lifespan of the circuit breaker. When the circuit breaker is brand new... , As wear and tear accumulates, Gradually decrease to 0.

[0054] Furthermore, the dynamic equivalent life and replacement cycle are determined, and the circuit breaker has a nominal life at the time of manufacture. (For example, the manufacturer specifies a 20-year operating life under standard conditions). However, in actual operation, due to the accumulation of break-in wear, its equivalent life will be shortened. This invention addresses this by using dynamic equivalent life... To reflect this change: , If a circuit breaker has accumulated total damage... ,but Its dynamic equivalent lifetime is .

[0055] Replacement cycle The judgment condition is: , in A safety factor (usually 0.8~0.95) is used to reserve a certain safety margin. When the actual operating time... Reaching or exceeding When necessary, the circuit breaker should be replaced.

[0056] The following explanation uses a circuit breaker in a wind farm converter as an example.

[0057] The parameters are as follows: nominal lifespan Year; Rated breaking current Rated number of breaks Second-rate; The single-cycle wear amount under rated breaking conditions was measured experimentally. (Dimensionless relative value), then (Relative total wear and tear); Wear coefficient Already implied in In actual calculations, each segmentation... It is possible We obtain, where the denominator is... This is the integral value under the rated breaking condition.

[0058] Assume the circuit breaker has been in operation for 3 years, during which time a total of 120 tripping events have occurred. The cumulative wear is calculated by recording the current waveform of each trip using a monitoring system. .but: Total damage ; Dynamic lifetime correction factor ; Dynamic equivalent lifetime Year; If a safety factor is taken Then change the periodic warning point. Year.

[0059] Since the system has been running for 3 years, far from reaching the required 11.7 years, replacement is not currently necessary. The system will continuously monitor each breakpoint event and update dynamically. and It will give a prompt when the running time is close to the warning point.

[0060] Through the above method, the present invention can dynamically assess the life consumption of the circuit breaker based on the actual breaking stress it bears, avoiding over-maintenance or under-maintenance caused by traditional fixed-cycle replacement, and significantly improving the operational reliability and economy of the converter.

[0061] It should be noted that replacement shall be performed only if the aforementioned replacement conditions are met. Before replacement, the converter shall undergo pre-processing, which includes safety isolation, auxiliary shutdown, safety standby, and protection against electric shock.

[0062] Before replacement, the converter is pre-treated, including safety isolation, auxiliary shutdown, safety standby, and protection against electric shock.

[0063] Specifically, the pre-processing includes de-energizing the converter, disconnecting the generator stator and power supply, and disconnecting the secondary or primary side switches of the transformer substation.

[0064] To assist in shutdown, a mechanical brake device is used to lock the generator rotor, ensuring absolute personnel safety, protecting equipment, and preventing damage. The mechanical brake device uses existing technology and will not be described in detail here.

[0065] Please wait safely for at least 5 minutes after completing the above steps to ensure that the intermediate circuit capacitors have completely discharged.

[0066] To prevent electric shock, use a multimeter to test the voltage of metal parts that need to be touched or may be touched during maintenance to avoid electric shock.

[0067] Pre-processing of the converter ensures the safety of personnel maintaining the converter.

[0068] Furthermore, the replacement process includes: first, disconnecting the connection; second, disassembling the main body; and third, reversing the order of the replacement.

[0069] The first step of disconnection includes: disconnecting the signal and control circuits by removing the optical fiber, sampling line, and control line; disconnecting the auxiliary power supply and ground by disconnecting the auxiliary power socket, adapter, and protective ground wire; disconnecting the main circuit by loosening or removing the bolts connecting the copper busbar, DC busbar, and high-current terminals; and recording the disconnected cables and terminals by labeling them.

[0070] Ideally, when removing the fiber optic cable, grip the connector firmly and pull it out vertically to ensure that the bending radius of the fiber optic cable is greater than 35mm.

[0071] The second step of disassembling the main body includes: releasing mechanical fasteners, removing all screws, clamps or brackets that secure the component to the cabinet or base plate; removing the old component, and smoothly moving the component out of its installation position.

[0072] The third step, reverse restoration, includes: installing new components, positioning them, and initially fixing them; restoring mechanical fixation to the main circuit, tightening the fixing screws and main circuit connection screws to the specified torque; restoring auxiliary and signal circuits, connecting the ground wire and auxiliary power supply, and finally connecting all signal lines and optical fibers; post-installation inspection: checking that all connections are secure and correct, and cleaning up tools and debris on site.

[0073] Work process, refer to Figures 2 to 4 : First, make preparations and pay attention to the following points:

[0074] Before replacement, disconnect the generator stator and power supply; after completing the above operations, wait 5 minutes to ensure that the intermediate circuit capacitors have discharged completely; after each thunderstorm, the surge protector and front-end protective fuses need to be checked for integrity. If the fuse status device pops up, it means that the fuse is damaged and needs to be replaced; during maintenance, a multimeter should be used to test the voltage of metal parts that need to be touched or may be touched to avoid electric shock.

[0075] Second, the replacement steps for IGBT module 100 include: Disconnect the fiber optic cable and sampling cable 101 from the module to be replaced. Disconnect the adapter 102. Loosen the ground screw 103. Loosen the DC bus screw 104. Loosen the screws securing the module 105. Pull out the module, replace it with the new module, and then install it in reverse order of the above steps.

[0076] Specifically, disconnect the fiber optic cable and sampling line 101 of the module to be replaced, as well as the corresponding adapter 102; wait for the IGBT module 100 to cool down; loosen the ground screw 103, DC bus screw 104 and module fixing screw 105 in sequence; vertically clamp and pull out the IGBT module 100, replace it with the new IGBT module 100 and install it in the reverse order above.

[0077] To replace the IGBT module 100, first disconnect the low-voltage connection, then disconnect the fiber optic cable and sampling line 101 of the module to be replaced, to prevent excessive bending of the fiber optic cable and sampling line 101 from damaging the interface. At the same time, disconnect the corresponding adapter 102. Wait for the IGBT module 100 to cool down to below 50°C. Its temperature can be confirmed by the temperature sensor on the module or an infrared thermometer. After that, disconnect the high-voltage power and grounding. Then, loosen and remove the grounding screw 103, DC bus screw 104, and module fixing screw 105 in sequence. Removing the screws in order can prevent mechanical stress or short circuits during the removal process. Then, pull out the IGBT module 100 in a direction parallel to the guide rail and push the new IGBT module 100 into place. Install in the reverse order above, that is, first tighten the module fixing screw, then connect the DC bus screw, and then connect the grounding screw. Finally, restore the connections of all fiber optic cables, sampling lines, and adapters.

[0078] It should be noted that IGBT modules are quite heavy and should be moved with care; even after the power to the converter is turned off for 5 minutes, the power modules and other components still need some time to cool down to prevent burns.

[0079] Third, the replacement steps for circuit breaker 200: Disconnect all terminals. Loosen the mounting screws. Loosen the busbar screws. Remove circuit breaker 200 and replace it with a new one. Then reverse the steps above to restore the circuit.

[0080] Preferably, when T≥K×L e (t) If the conditions are not met, the converter must be inspected regularly. If any abnormality is found, repair and / or replacement shall be performed. In extreme cases, inspection shall be performed and replacement shall be performed immediately if any abnormality is found.

[0081] The rest of the structure is the same as in Example 3.

[0082] In summary, by pre-setting the replacement cycle and steps for each component, safe and rapid replacement of components is achieved.

[0083] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for replacing converter components, characterized in that: Based on the converter's operating environment and conditions, the dynamic life correction factor for each converter component is calculated in real time. And based on the nominal life of the converter components. The dynamic equivalent lifetime is obtained. , making ,in, Damage caused by cumulative environmental temperature factors or total damage Decide; The condition for determining the replacement cycle T is: K is the safety factor.

2. The converter component replacement method as described in claim 1, characterized in that: The environmental temperature cumulative damage factor The damage to the IGBT module (100) in the converter element due to the influence of ambient temperature is defined as follows: ， in, This means that the operating time of the IGBT module is divided into n tiny time periods; Indicates each time period The average core temperature of the IGBT module is recorded within the module. The IGBT module at this temperature The theoretical lifespan is as follows.

3. The converter component replacement method as described in claim 1, characterized in that: The total damage The expression is: ， in, Instantaneous wear sum; This represents the maximum permissible wear amount.

4. The converter component replacement method as described in claim 3, characterized in that: The Defined as the amount of wear generated by each breaking event of the circuit breaker in the converter element, which is proportional to the square of the breaking current and the arcing time, specifically: ， in, The instantaneous wear caused by the j-th break; The wear coefficient is related to the contact material and the arc-extinguishing chamber structure; This refers to the instantaneous current during the breaking process; This represents the duration of arc burning.

5. The converter component replacement method as described in claim 4, characterized in that: The The wear is defined as the cumulative wear caused by each interruption event starting from the start of operation of the circuit breaker (200) in the converter element, specifically: ， in, It represents the total number of segments up to time t.

6. The converter component replacement method as described in any one of claims 3 to 5, characterized in that: The Defined as the number of times a device is allowed to break at its rated breaking current. , ， in, It is the amount of wear per cycle under rated breaking conditions.

7. The converter component replacement method as described in claim 1 or 2, characterized in that: The Damage caused by cumulative environmental temperature factors The decision is as follows: 。 8. The converter component replacement method as described in any one of claims 1, 3 to 5, characterized in that: The It is determined by the total damage degree The decision is as follows: 。

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