Inverter bus capacitor identification and life dynamic monitoring method

Abstract

The invention relates to an inverter bus capacitance identification and life dynamic monitoring method, and the method comprises the steps: collecting the rotational inertia and speed of a motor when the motor decelerates, determining the mechanical energy generated by the motor, taking the inverter in the deceleration process as a rectifier, considering the conversion efficiency when the inverter is regarded as a rectifier and the efficiency of converting mechanical energy into electric energy, and determining the charging power of a capacitor on a bus based on the mechanical energy generated by the motor; collecting the bus voltage when the motor slows down, and determining the capacitance value of the capacitor based on the bus voltage and the charging power of the capacitor; in the conventional test of the inverter, the direct-current bus capacitance can be simply obtained according to the bus voltage change and speed change of the inverter in the speed reduction process by testing the parameters of the system, such as the rotational inertia of the motor and the real-time bus voltage; and the service life of the capacitor is dynamically monitored based on the capacitance value of the capacitor acquired in real time, so that the safe operation of the whole inverter system is ensured.

Description

Technical Field

[0001] The present invention relates to the field of automatic detection of equipment, and particularly to a method for dynamically monitoring the identification and life of inverter bus capacitors. Background Art

[0002] As an important part of the inverter, the DC bus capacitor mainly functions to maintain the stability of the DC bus voltage. In the conventional period test, the detection of the bus capacitor mainly adopts the sampling method, which may cause the actual capacitance value of the capacitor to exceed the expected range to a certain extent; at the same time, due to the cost problem of the capacitor, the capacitance value often tends to its lower limit value, which may lead to a small capacitance value, resulting in an increase in the ripple of the inverter bus voltage and affecting the performance of the inverter. However, if the capacitance value of each capacitor is tested one by one, it is too cumbersome. Therefore, it is very meaningful to be able to quickly and effectively detect the capacitance value of the capacitor. Summary of the Invention

[0003] In view of the technical problems existing in the prior art, the present invention provides a method for dynamically monitoring the identification and life of inverter bus capacitors. In the conventional test of the inverter, by testing the parameters of the system, such as the motor inertia and the real-time bus voltage, etc., the DC bus capacitor can be easily obtained according to the change of the bus voltage and the speed of the inverter itself during the deceleration process; and based on the capacitance value obtained in real time, the life of the capacitor is dynamically monitored to ensure the safe operation of the entire inverter system.

[0004] According to a first aspect of the present invention, there is provided a method for identifying an inverter bus capacitor, including: Step 1, collecting the motor inertia and speed when the motor decelerates to determine the mechanical energy generated by the motor, regarding the inverter as a rectifier during the deceleration process, considering the conversion efficiency when the inverter is regarded as a rectifier and the efficiency of converting mechanical energy into electrical energy, and determining the charging power of the capacitor on the bus based on the mechanical energy generated by the motor; Step 2, collecting the bus voltage when the motor decelerates, and determining the capacitance value of the capacitor based on the bus voltage and the charging power of the capacitor.

[0005] Based on the above technical solutions, the present invention can also be improved as follows.

[0006] Optionally, the calculation formula for the charging power of the capacitor on the bus in Step 1 is: ; Wherein, is the charging power of the capacitor, is the conversion efficiency when the inverter is regarded as a rectifier, is the efficiency of converting mechanical energy into electrical energy, is the amount of mechanical energy loss, For the loss The time consumed

[0007] Optionally, the calculation formula for the mechanical energy loss is: ; is the moment of inertia of the motor, are respectively the starting angular velocity and the ending angular velocity during the motor deceleration process within the time range.

[0008] 4. The identification method according to claim 1, wherein the calculation formula for determining the capacitance value of the capacitor based on the bus voltage and the charging power of the capacitor in step 2 is: ; Wherein, is the charging power of the capacitor, is the capacitance value of the capacitor, is the bus voltage, and t is time.

[0009] Optionally, the calculation formula for the capacitance value of the capacitor is: ; is the capacitance value of the capacitor, is the conversion efficiency when the inverter is regarded as a rectifier, is the efficiency of converting mechanical energy into electrical energy, is the mechanical energy loss, For the loss The time consumed is the moment of inertia of the motor, are respectively the starting angular velocity and the ending angular velocity during the motor deceleration process within the time range, is the bus voltage, and t is time.

[0010] According to the second aspect of the present invention, there is provided a dynamic monitoring method for the life of an inverter bus capacitor, and the dynamic monitoring method includes: determining the real-time capacitance value of the inverter bus capacitor based on the identification method provided in the embodiments of the present invention; Comparing the calculated capacitance value of the inverter bus capacitor with the designed capacitance value to obtain the capacitance decay rate of each inverter bus capacitor, and performing a safety warning on the inverter bus capacitor whose capacitance decay rate exceeds the set threshold.

[0011] According to the third aspect of the present invention, there is provided an inverter bus capacitor identification system, including: a charging power determination module of the bus capacitor and a capacitance value determination module; The charging power determination module of the bus capacitor is configured to collect the moment of inertia and speed of the motor when the motor decelerates to determine the mechanical energy generated by the motor, regard the inverter during the deceleration process as a rectifier, consider the conversion efficiency when the inverter is regarded as a rectifier and the efficiency of converting mechanical energy into electrical energy, and determine the charging power of the capacitor on the bus based on the mechanical energy generated by the motor; The capacitance value determination module is configured to collect the bus voltage when the motor decelerates, and determine the capacitance value of the capacitor based on the bus voltage and the charging power of the capacitor.

[0012] The dynamic monitoring method for identifying the bus capacitor of the inverter and its life provided by the embodiment of the present invention has small computational complexity, simple method, and can realize the full detection of the bus capacitor of the inverter in the factory environment without additional detection equipment; high reliability, because the detection environment is basically fixed in the factory environment, so the parameters are basically fixed, and the calculated capacitance value has high reliability; it can predict and obtain the capacitance value in real time during the normal operation of the system, does not require additional specific operation, and will not affect the operation of the inverter. Based on the obtained capacitance value, the attenuation of the capacitor is calculated, and corresponding different-level thresholds are set for comparison, so as to monitor the capacitance value attenuation level of the capacitor in real time, so that the after-sales personnel can replace the bus electrolytic capacitor in time, thereby realizing the dynamic monitoring of the life of the bus capacitor of the inverter, dynamically adjusting and protecting the inverter, and effectively improving the reliability and service life of the inverter. Description of the Drawings

[0013] Figure 1 is a flowchart of a method for identifying the bus capacitor of the inverter provided by the present invention; Figure 2 is a schematic diagram of energy feedback when the motor decelerates in an inverter system provided by an embodiment of the present invention; Figure 3 is a schematic diagram of the change process of voltage, speed, and Q-axis current when the motor decelerates in an inverter system provided by an embodiment of the present invention; Figure 4 is a structural block diagram of an inverter bus capacitor identification system provided by the present invention. Detailed Embodiments

[0014] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0015] Figure 1 is a flowchart of a method for identifying the bus capacitor of the inverter provided by the present invention, as Figure 1 shown. The identification method includes: Step 1: Collect the motor inertia and speed during motor deceleration to determine the mechanical energy generated by the motor. Consider the inverter as a rectifier during the deceleration process, taking into account the conversion efficiency when the inverter is regarded as a rectifier and the efficiency of converting mechanical energy into electrical energy. Based on the mechanical energy generated by the motor, determine the charging power of the capacitor on the bus. Step 2: Collect the bus voltage during motor deceleration. Based on the bus voltage and the charging power of the capacitor, determine the capacitance value of the capacitor.

[0016] An inverter bus capacitor identification method provided by the present invention can easily obtain the DC bus capacitor according to the change of the bus voltage and speed of the inverter itself during the deceleration process by testing system parameters such as motor inertia and real-time bus voltage in the conventional test of the inverter.

[0017] Embodiment 1 Embodiment 1 provided by the present invention is an embodiment of an inverter bus capacitor identification method provided by the present invention, which only depends on testing the motor inertia and the energy transfer efficiency between devices without other additional hardware support. Specifically, the embodiment of this identification method includes: Step 1: Collect the motor inertia and speed during motor deceleration to determine the mechanical energy generated by the motor. Consider the inverter as a rectifier during the deceleration process, taking into account the conversion efficiency when the inverter is regarded as a rectifier and the efficiency of converting mechanical energy into electrical energy. Based on the mechanical energy generated by the motor, determine the charging power of the capacitor on the bus.

[0018] In a possible embodiment, during the deceleration process, the inverter can be regarded as a rectifier at this time. Thus, a relational expression between the power output by the inverter and the charging power of the capacitor can be established as:

[0019] In the formula, is the charging power of the capacitor, is the conversion efficiency when the inverter is regarded as a rectifier, are the voltage and current after Clark transformation respectively.

[0020] During the deceleration process, the mechanical energy of the motor is converted into electrical energy and other losses. Thus, the motor can be regarded as a generator at this time. The conversion from the generating power to the electrical power can be expressed as:

[0021] In the formula, is the efficiency of converting mechanical energy into electrical energy, is the amount of mechanical energy loss, is the loss is the time consumed, is the inertia of the motor, They are respectively the starting angular velocity and the ending angular velocity within the time range during the motor deceleration process.

[0022] Specifically, the calculation formula for the charging power of the capacitor on the bus in step 1 is: .

[0023] Step 2: Collect the bus voltage during motor deceleration, and determine the capacitance value of the capacitor based on the bus voltage and the charging power of the capacitor.

[0024] In a possible embodiment, when the motor is in the deceleration process, as the mechanical energy decreases, the energy will be fed back from the motor side to the DC side of the inverter, resulting in an increase in the DC side bus voltage, thereby causing the bus capacitor to charge. Thus, the DC side current can be obtained as:

[0025] In the formula, is the capacitance value of the capacitor, is the bus voltage, t is the time.

[0026] Thus, the charging power of the capacitor is obtained as:

[0027] Substituting formulas (1) and (2) into formula (4) gives

[0028] After arrangement, it can be obtained:

[0029] Thus, the relationship between the moment of inertia and the bus voltage and the mechanical speed is obtained, that is, the DC bus capacitor of the current inverter to be tested can be calculated by calculating the monitored value of the bus voltage and the monitored value of the speed during deceleration.

[0030] As Figure 2 shown is a schematic diagram of energy feedback during motor deceleration in an inverter system provided by an embodiment of the present invention, Figure 3 is a schematic diagram of the change process of voltage, speed, and Q-axis current during motor deceleration in an inverter system provided by an embodiment of the present invention. Combining Figure 2 and Figure 3 it can be known that at moment, the motor starts to decelerate, and the motor output torque gradually decreases, thereby accelerating the motor deceleration process; at moment, the bus voltage reaches the overvoltage stall voltage processing point, and the torque output changes suddenly. However, due to problems such as the mechanical time constant and current loop bandwidth of the motor itself, until The torque change at a certain moment only suppresses the slope of the voltage rise to a certain extent. In principle, any capacitor charging moment can be selected. Here, the moment of is taken as an example: Since the mechanical time constant of the motor is generally larger than the electrical parameters, during the calculation, it is regarded as a uniform change in speed from to time. At the moment of the motor speed is 3000 RPM, and at the moment of the motor speed is 2990 RPM. , at the moment of the voltage change rate , the value of the motor inertia measured by other methods is 2.229 , the mechanical efficiency of the motor , the inverter efficiency . After calculation, the bus capacitor value is 6881 uF, and the actual capacitor value is about 7200 uF with an error of about 4.5%.

[0031] Embodiment 2 Embodiment 2 provided by the present invention is an embodiment of an inverter bus capacitor identification system provided by the present invention. Figure 4 It is a structural diagram of an inverter bus capacitor identification system provided by an embodiment of the present invention. As can be seen from Figure 4 , this embodiment of the identification system includes: a charging power determination module for the bus capacitor and a capacitance value determination module; The charging power determination module for the bus capacitor is used to collect the motor inertia and speed when the motor decelerates to determine the mechanical energy generated by the motor, regard the inverter as a rectifier during the deceleration process, consider the conversion efficiency when the inverter is regarded as a rectifier and the efficiency of converting mechanical energy into electrical energy, and determine the charging power of the capacitor on the bus based on the mechanical energy generated by the motor; The capacitance value determination module is used to collect the bus voltage when the motor decelerates and determine the capacitance value of the capacitor based on the bus voltage and the charging power of the capacitor.

[0032] It can be understood that an inverter bus capacitor identification system provided by the present invention corresponds to the inverter bus capacitor identification methods provided in the foregoing embodiments. The relevant technical features of the inverter bus capacitor identification system can refer to the relevant technical features of the inverter bus capacitor identification method, which will not be elaborated here.

[0033] Embodiment 3 Embodiment 3 provided by the present invention is an embodiment of a method for dynamically monitoring the life of an inverter bus capacitor. This embodiment of the dynamic monitoring method includes: The real-time capacitance value of the inverter bus capacitor determined based on the inverter bus capacitor identification method provided by the embodiment of the present invention.

[0034] Compare the calculated capacitance value of the inverter bus capacitor with the designed capacitance value to obtain the capacitance attenuation rate of each inverter bus capacitor, and issue a safety warning for the inverter bus capacitor whose capacitance attenuation rate exceeds the set threshold.

[0035] In a possible embodiment, the calculation formula for the capacitance attenuation rate is: ; Wherein, is the capacitance attenuation rate, is the calculated capacitance value of the inverter bus capacitor, is the designed capacitance value of the inverter bus capacitor.

[0036] In a possible embodiment, the dynamic monitoring method further includes: Set thresholds of various magnitudes, and issue different levels of warnings or replacement reminders respectively when the capacitance attenuation rate exceeds each threshold.

[0037] It can be understood that a dynamic monitoring method for the life of an inverter bus capacitor provided by the present invention corresponds to the inverter bus capacitor identification method provided by the foregoing embodiments. The relevant technical features of the dynamic monitoring method for the life of an inverter bus capacitor can refer to the relevant technical features of the inverter bus capacitor identification method, which will not be elaborated here.

[0038] A dynamic monitoring method for identifying and life of an inverter bus capacitor provided by an embodiment of the present invention has small calculation amount, simple method, and can realize full detection of the inverter bus capacitor in the factory environment without additional detection equipment; high reliability, because the detection environment is basically fixed in the factory environment, so the parameters are basically fixed, and the calculated capacitance value has high reliability; it can predict and obtain the capacitance value in real time during the normal operation of the system, does not require additional specific operation, and does not affect the operation of the inverter. Based on the obtained capacitance value, the attenuation of the capacitor is calculated, and corresponding thresholds of different levels are set for comparison, so that the capacitance attenuation level of the capacitor can be monitored in real time, so that after-sales personnel can replace the bus electrolytic capacitor in time, thereby realizing dynamic monitoring of the life of the inverter bus capacitor, dynamically adjusting and protecting the inverter, and effectively improving the reliability and service life of the inverter.

[0039] It should be noted that in the above embodiments, the descriptions of the respective embodiments have their own emphases. For parts not described in detail in a certain embodiment, reference may be made to the relevant descriptions of other embodiments.

[0040] Those skilled in the art should understand that the embodiments of the present invention can be provided as a method, a system, or a computer program product. Therefore, the present invention can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk memory, CD-ROM, optical memory, etc.) that contain computer-usable program code.

[0041] The present invention is described with reference to the flowcharts and / or block diagrams of methods, apparatuses (systems), and computer program products according to embodiments of the present invention. It should be understood that each flow and / or block in the flowchart and / or block diagram, as well as the combination of flows and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded computer, or other programmable data processing devices to generate a machine, such that the instructions executed by the processor of the computer or other programmable data processing devices produce means for implementing the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0042] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, such that the instructions stored in the computer-readable memory produce a manufactured article including instruction means that implement the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0043] These computer program instructions can also be loaded onto a computer or other programmable data processing device, such that a series of operation steps are executed on the computer or other programmable device to produce a computer-implemented process, and thus the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0044] Although the preferred embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications to these embodiments once they learn the basic creative concept. Therefore, the appended claims are intended to be construed as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0045] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these modifications and variations.

Claims

1. A method for identifying the bus capacitor of an inverter, characterized in that, The identification method includes: Step 1: Collect the moment of inertia and speed of the motor during deceleration to determine the mechanical energy generated by the motor. Regard the inverter during the deceleration process as a rectifier, consider the conversion efficiency when the inverter is regarded as a rectifier and the efficiency of converting mechanical energy into electrical energy, and determine the charging power of the capacitor on the bus based on the mechanical energy generated by the motor. Step 2: Collect the bus voltage during motor deceleration, and determine the capacitance value of the capacitor based on the bus voltage and the charging power of the capacitor.

2. The identification method according to claim 1, characterized in that The calculation formula for the charging power of the capacitor on the bus in Step ； Among them, is the charging power of the capacitor, is the conversion efficiency when the inverter is regarded as a rectifier, is the efficiency of converting mechanical energy into electrical energy, is the amount of mechanical energy loss, is the loss is the time consumed.

3. The identification method according to claim 2, wherein ​ ； is the moment of inertia of the motor, are respectively the starting angular velocity and the ending angular velocity during the deceleration process of the motor within the time range.

4. The identification method according to claim 1, characterized in that, ​ ； Among them, is the charging power of the capacitor, is the capacitance value of the capacitor, is the bus voltage, and t is the time.

5. The identification method according to claim 1, characterized in that, ​ ； is the capacitance value of the capacitor, is the conversion efficiency when the inverter is regarded as a rectifier, is the efficiency of converting mechanical energy into electrical energy, is the amount of mechanical energy loss, is the loss the time consumed, is the moment of inertia of the motor, are respectively the starting angular velocity and the ending angular velocity within the time range during the motor deceleration process, is the bus voltage, and t is the time.

6. A dynamic monitoring method for the lifespan of an inverter bus capacitor, characterized in that, ​ ​ 7. The dynamic monitoring method according to claim 6, wherein ​ ; wherein, is the capacitance decay rate, is the calculated capacitance value of the inverter bus capacitor, is the designed capacitance value of the inverter bus capacitor.

8. The dynamic monitoring method according to claim 6, wherein ​ ​ 9. An inverter bus capacitor identification system, characterized in that, ​ ​ ​

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