CN111505409A - Online detection method and device for bus capacitor of frequency converter - Google Patents
Online detection method and device for bus capacitor of frequency converter Download PDFInfo
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- CN111505409A CN111505409A CN202010238448.2A CN202010238448A CN111505409A CN 111505409 A CN111505409 A CN 111505409A CN 202010238448 A CN202010238448 A CN 202010238448A CN 111505409 A CN111505409 A CN 111505409A
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
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Abstract
The application provides a method and a device for online detection of a bus capacitor of a frequency converter. And then, when the bus capacitor is charged, controlling the upper bridge arm switching tube of the first phase bridge arm and the lower bridge arm switching tube of the second phase bridge arm in the full bridge circuit to be conducted so that the bus capacitor and the motor form a discharge loop. And when the bus capacitor is discharged, controlling the motor to be static, acquiring the voltage change rate between two ends of the bus capacitor and the input current of the motor, and determining the current capacity of the bus capacitor based on the voltage change rate and the input current. And finally determining whether to output an early warning signal based on the current capacity. By adopting the detection mode, the diagnosis process of on-line detection of the capacitance capacity of the bus can be automatically carried out, manual intervention is not needed, and the detection efficiency is improved.
Description
Technical Field
The application relates to the technical field of frequency converters, in particular to a method and a device for online detection of bus capacitance of a frequency converter.
Background
The bus capacitor is an important component forming the frequency converter, and the performance of the bus capacitor directly influences the work of the frequency converter. The bus capacitor of the frequency converter can age gradually along with the increase of the use times and the time, and the phenomena of capacitor capacity reduction, internal resistance value increase, leakage current increase and the like occur. These undesirable factors can add up to each other and gradually increase with aging, eventually leading to bus capacitance failure, which in turn can shut down the frequency converter and even damage other devices within the system. Therefore, the aging condition of the capacitor can be judged by diagnosing the capacitance capacity or the leakage current or the internal resistance of the bus capacitor, so that the capacitor is prevented from being damaged.
At present, the capacity of the bus capacitor in the frequency converter needs to be measured by a professional on site, and time and labor are wasted.
Disclosure of Invention
Therefore, it is necessary to provide a method and a device for online detection of bus capacitance of a frequency converter, aiming at the problem that the capacity of the bus capacitance in the frequency converter needs to be measured on site by professional staff, which is time-consuming and labor-consuming.
A method for detecting bus capacitance of a frequency converter on line comprises the following steps:
acquiring voltages at two ends of a bus capacitor to obtain a first voltage, and determining whether the bus capacitor is charged based on the first voltage and a preset voltage;
when the bus capacitor is charged, controlling an upper bridge arm switching tube of a first phase bridge arm and a lower bridge arm switching tube of a second phase bridge arm in the full-bridge circuit to be conducted so that the bus capacitor and the motor form a discharging loop;
controlling the motor to be static when the bus capacitor is discharged, acquiring the voltage change rate between two ends of the bus capacitor and the input current of the motor, and determining the current capacity of the bus capacitor based on the voltage change rate and the input current;
determining whether to output a warning signal based on the current capacity.
In one embodiment, the step of controlling the motor to be stationary while the bus capacitor is discharged, obtaining a voltage change rate between two ends of the bus capacitor and an input current of the motor, and determining the current capacity of the bus capacitor based on the voltage change rate and the input current comprises:
when the bus capacitor discharges, controlling the motor to be static;
acquiring the voltage change rate between two ends of the bus capacitor;
acquiring the input current of the motor through a current detection module;
determining the current capacity of the bus capacitor based on the voltage change rate and the input current, and calculating according to the following formula:
C＝I/(dU/dt)；
where C is the present capacity of the bus capacitance, I is the input current, and dU/dt is the voltage rate of change.
In one embodiment, the step of determining whether to output a warning signal based on the current capacity includes:
comparing the difference value of the current capacity with the standard capacity to obtain a first difference value;
if the first difference value is larger than a preset capacity threshold value, outputting the early warning signal;
and if the first difference value is smaller than or equal to the preset capacity threshold value, not outputting the early warning signal.
In one embodiment, before the step of determining whether to output an early warning signal based on the current capacity, the method further includes:
judging whether the input current reaches a set threshold value;
when the input current reaches the set threshold value, acquiring voltages at two ends of the bus capacitor and acquiring a second voltage;
controlling an upper bridge arm switching tube of a first phase bridge arm in the IGBT module to be disconnected, acquiring voltages at two ends of the bus capacitor and obtaining a third voltage;
determining a present internal resistance value of the bus capacitor based on the second voltage, the third voltage, and the input current;
and determining whether to output the early warning signal or not based on the current internal resistance value.
In one embodiment, the step of determining whether to output the warning signal based on the current internal resistance value includes:
comparing the difference value of the current internal resistance value with the standard internal resistance value to obtain a second difference value;
if the second difference value is larger than a preset internal resistance threshold value, outputting the early warning signal;
and if the second difference value is less than or equal to the preset internal resistance threshold value, not outputting the early warning signal.
In one embodiment, the step of determining whether the input current reaches a set threshold includes:
comparing the input current to the set threshold;
if the input current is smaller than the set threshold, determining that the input current does not reach the set threshold;
and if the input current is greater than or equal to the set threshold, determining that the input current reaches the set threshold.
In one embodiment, the step of obtaining a voltage across the bus capacitor to obtain a first voltage, and determining whether charging of the bus capacitor is completed based on the first voltage and a preset voltage includes:
obtaining voltages at two ends of the bus capacitor and obtaining a first voltage, and comparing the first voltage with the preset voltage;
if the first voltage is smaller than the preset voltage, determining that the bus capacitor is not charged;
and if the first voltage is greater than or equal to the preset voltage, determining that the charging of the bus capacitor is finished.
In one embodiment, the full-bridge circuit comprises the first phase bridge arm and the second phase bridge arm which are connected in parallel, and the first phase bridge arm and the second phase bridge arm both comprise an upper bridge arm switching tube and a lower bridge arm switching tube which are connected in series.
In one embodiment, the full-bridge circuit further includes a third phase bridge arm, the third phase bridge arm is sequentially connected in parallel with the first phase bridge arm and the second phase bridge arm, and the third phase bridge arm includes an upper bridge arm switching tube and a lower bridge arm switching tube connected in series.
An on-line detection device for bus capacitance of a frequency converter comprises:
the first end of the power switch is used for electrically connecting a power supply;
the input end of the rectification module is electrically connected with the second end of the power switch;
the first end of the bus capacitor is electrically connected with the first electrode of the rectifying module, and the second end of the bus capacitor is electrically connected with the second electrode of the rectifying module;
the first end of the full-bridge circuit is electrically connected with the first end of the bus capacitor, the second end of the full-bridge circuit is electrically connected with the second end of the bus capacitor, and the output end of the full-bridge circuit is used for electrically connecting a motor; and
and the controller is respectively and electrically connected with the control end of the power switch and the control end of the full-bridge circuit and is used for executing the frequency converter bus capacitor online detection method in any embodiment.
In one embodiment, the device for detecting the bus capacitance of the frequency converter on line further includes:
the current detection module, the first end of current detection module with the output electricity of full-bridge circuit is connected, the second end of current detection module with the controller electricity is connected, is used for detecting the input current of motor, and will input current send to the controller.
In one embodiment, the device for detecting the bus capacitance of the frequency converter on line further includes:
and the voltage detection module is connected in parallel at the two ends of the bus capacitor and used for detecting the voltages at the two ends of the bus capacitor and sending the detected voltages at the two ends of the bus capacitor to the controller.
In one embodiment, the device for detecting the bus capacitance of the frequency converter on line further includes:
the locking device is electrically connected with the controller and is used for being mechanically connected with the motor;
and when the bus capacitor discharges, the controller controls the motor to be static through the locking device.
Compared with the prior art, the method and the device for the online detection of the bus capacitor of the frequency converter firstly obtain the voltages at two ends of the bus capacitor to obtain the first voltage, and determine whether the charging of the bus capacitor is finished or not based on the first voltage and the preset voltage. And then, when the bus capacitor is charged, controlling the upper bridge arm switching tube of the first phase bridge arm and the lower bridge arm switching tube of the second phase bridge arm in the full bridge circuit to be conducted so that the bus capacitor and the motor form a discharge loop. And when the bus capacitor is discharged, controlling the motor to be static, acquiring the voltage change rate between two ends of the bus capacitor and the input current of the motor, and determining the current capacity of the bus capacitor based on the voltage change rate and the input current. And finally determining whether to output an early warning signal based on the current capacity. By adopting the detection mode, the diagnosis process of on-line detection of the capacitance capacity of the bus can be automatically carried out, manual intervention is not needed, and the detection efficiency is improved.
Drawings
Fig. 1 is a flowchart of an on-line detection method for a bus capacitor of a frequency converter according to an embodiment of the present application;
fig. 2 is a schematic application diagram of an on-line detection device for bus capacitance of a frequency converter according to an embodiment of the present application;
fig. 3 is a schematic application diagram of an on-line detection device for bus capacitance of a frequency converter according to another embodiment of the present application;
fig. 4 is a partial flowchart of a method for online detection of a bus capacitor of a frequency converter according to another embodiment of the present application;
fig. 5 is a block diagram of a structure of an on-line detection device for a bus capacitor of a frequency converter according to an embodiment of the present application.
10 bus power supply device
100 power switch
101 power supply
200 rectification module
300 bus capacitor
400 full bridge circuit
401 electric machine
410 first phase bridge arm
411 upper bridge arm switch tube
412 lower bridge arm switch tube
420 second phase leg
430 third phase leg
500 controller
600 current detection module
700 voltage detection module
800 locking device
Detailed Description
In order to make the aforementioned objects, features and advantages of the present application more comprehensible, embodiments accompanying the present application are described in detail below with reference to the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. This application is capable of embodiments in many different forms than those described herein and those skilled in the art will be able to make similar modifications without departing from the spirit of the application and it is therefore not intended to be limited to the embodiments disclosed below.
It will be understood that when an element is referred to as being "secured to" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
Referring to fig. 1, an embodiment of the present application provides an on-line detection method for a bus capacitor of a frequency converter, including:
s102: the method comprises the steps of obtaining voltages at two ends of a bus capacitor to obtain a first voltage, and determining whether charging of the bus capacitor is completed or not based on the first voltage and a preset voltage.
In one embodiment, a controller may obtain a voltage across a bus capacitor to obtain a first voltage, and determine whether charging of the bus capacitor is completed based on the first voltage and a preset voltage. Specifically, when the frequency converter enters the detection mode, the controller may obtain voltages at two ends of the bus capacitor through the voltage sensor and obtain the first voltage. In one embodiment, the voltage sensor may be integrated within the controller. In one embodiment, the preset voltage is a voltage when charging of the bus capacitor is completed.
In one embodiment, after the controller obtains the first voltage, the first voltage may be compared with the preset voltage. And if the first voltage is less than the preset voltage, determining that the bus capacitor is not charged, and controlling a three-phase power supply to continue charging the bus capacitor. And if the first voltage is greater than or equal to the preset voltage, determining that the charging of the bus capacitor is finished, and controlling the three-phase power supply to stop charging the bus capacitor at the moment. In one embodiment, the controller may control the three-phase power source to stop charging the bus capacitor through a switch.
S104: and when the bus capacitor is charged, controlling the upper bridge arm switching tube of the first phase bridge arm and the lower bridge arm switching tube of the second phase bridge arm in the full bridge circuit to be conducted so as to enable the bus capacitor and the motor to form a discharging loop.
In one embodiment, the upper bridge arm switching tube and the lower bridge arm switching tube of each phase bridge arm of the full bridge circuit are all in an off state by default.
Referring to fig. 2, in an embodiment, the full bridge circuit 400 includes the first phase leg 410 and the second phase leg 420 connected in parallel, and each of the first phase leg 410 and the second phase leg 420 includes an upper leg switching tube 411 and a lower leg switching tube 412 connected in series. In one embodiment, the upper arm switch 411 may be an IGBT (Insulated Gate Bipolar Transistor). In one embodiment, the upper arm switch 411 may also be a MOSFET (Metal-Oxide-Semiconductor Field-effect transistor). Similarly, the lower arm switching tube 412 may be an IGBT, a MOSFET, or the like.
In one embodiment, when the motor 401 is a dc motor, the full bridge circuit 400 may include only the first phase leg 410 and the second phase leg 420. Namely, the full bridge circuit 400 is a four-switch-transistor full bridge circuit. When it is determined that the bus capacitor 300 is charged completely, the controller 500 may control the upper arm switch tube 411 of the first phase arm 410 and the lower arm switch tube 412 of the second phase arm 420 in the full-bridge circuit 400 to be turned on, so that the bus capacitor 300 and the motor 401 form a discharge loop. The bus capacitor 300 can now be discharged through the windings in the motor 401. During the discharging process of the bus capacitor 300, the controller 500 may lock the motor 401 through the locking device 800, so as to ensure that the motor 401 does not move due to the discharging action.
Referring to fig. 3, in one embodiment, the full bridge circuit 400 further includes a third phase leg 430. The third phase leg 430 is connected in parallel with the first phase leg 410 and the second phase leg 420 in sequence. The third phase bridge leg 430 includes an upper bridge leg switching tube 411 and a lower bridge leg switching tube 412 connected in series. In one embodiment, when the motor 401 can be a three-phase motor, the full bridge circuit 400 can include the first phase leg 410, the second phase leg 420, and the third phase leg 430.
That is, the full-bridge circuit 400 is a six-switch full-bridge circuit. When it is determined that the bus capacitor 300 is charged completely, the controller 500 may control the upper arm switching tube 411 of any one phase arm of the full-bridge circuit 400 and the lower arm switching tube 412 of any one phase arm of the remaining two phases to be turned on, so that the bus capacitor 300 and the motor 401 form a discharge loop. The bus capacitor 300 can now be discharged through the windings in the motor 401. In the process of discharging the bus capacitor 300, the controller 500 may lock the motor 401 through the locking device 800, so as to ensure that the motor 401 does not move due to the influence of the discharging action.
S106: and when the bus capacitor is discharged, controlling the motor to be static, acquiring the voltage change rate between two ends of the bus capacitor and the input current of the motor, and determining the current capacity of the bus capacitor based on the voltage change rate and the input current.
In one embodiment, the controller 500 may control the motor 401 to be stationary through the locking device 800 during the discharging process of the bus capacitor 300. Meanwhile, when the bus capacitor 300 is discharged, the controller 500 may acquire a voltage change rate between both ends of the bus capacitor 300 and an input current of the motor 401, and determine a current capacity of the bus capacitor 300 based on the voltage change rate and the input current.
Specifically, the controller 500 may obtain the voltage change rate between the two ends of the bus capacitor 300 through an internally integrated voltage change rate detector. The controller 500 may also detect an input current of the motor 401 through a current sensor. That is, the controller 500 may detect the output current of the full bridge circuit 400 through a current sensor. In one embodiment, the current sensor may be integrated within the controller 500.
In one embodiment, the controller 500 may determine the present capacity of the bus capacitor 300 based on the voltage rate of change and the input current. Specifically, the current capacity of the bus capacitor 300 can be calculated by the following formula:
C＝I/(dU/dt)；
where C is the present capacity of the bus capacitance, I is the input current, and dU/dt is the voltage rate of change.
S108: determining whether to output a warning signal based on the current capacity.
In one embodiment, the controller 500 may determine whether to output a warning signal based on the current capacity. Specifically, the controller 500 may compare the difference between the current capacity and the standard capacity to obtain a first difference. In one embodiment, the standard capacity may be a capacity of the bus capacitor 300 when shipped from a factory. If the first difference is greater than the preset capacity threshold, the controller 500 outputs the early warning signal to remind maintenance personnel to perform inspection and replacement.
If the first difference is less than or equal to the preset capacity threshold, the controller 500 does not output the early warning signal. Namely, the aging condition of the bus capacitor 300 is within the acceptable range, and at this time, maintenance personnel do not need to be reminded to carry out inspection and replacement. The bus capacitor 300 is detected by adopting the steps, the on-line detection can be carried out automatically in the diagnosis process of the capacity of the bus capacitor 300, manual intervention is not needed, and the efficiency of detection and maintenance is improved.
In one embodiment, the step of controlling the motor to be stationary while the bus capacitor is discharged, obtaining a voltage change rate between two ends of the bus capacitor and an input current of the motor, and determining the current capacity of the bus capacitor based on the voltage change rate and the input current comprises: and controlling the motor to be static when the bus capacitor is discharged. And acquiring the voltage change rate between the two ends of the bus capacitor. And acquiring the input current of the motor through a current detection module. Determining the current capacity of the bus capacitor based on the voltage change rate and the input current, and calculating according to the following formula:
C＝I/(dU/dt)；
where C is the present capacity of the bus capacitance, I is the input current, and dU/dt is the voltage rate of change.
In one embodiment, the controller 500 may control the motor 401 to be stationary via the locking device 800 when the bus capacitor 300 is discharged. In an embodiment, the manner of acquiring the voltage change rate between the two ends of the bus capacitor 300 by the controller 500 may be the manner described in the above embodiments, and details are not repeated here.
In one embodiment, the controller 500 may obtain the input current of the motor 401 through the current detection module 600. It is understood that the specific structure of the current detection module 600 is not limited as long as it has the function of detecting the input current. In one embodiment, the current detection module 600 may be a current sensor. The current detection module 600 may also be a conventional current detection circuit having a current detection function. When the bus capacitor 300 discharges, the controller 500 obtains the input current of the motor 401 in real time through the current detection module 600, and determines the current capacity of the bus capacitor 300 based on the voltage change rate and the input current, so that the capacity of the bus capacitor 300 is automatically detected on line, manual intervention is not needed, and the efficiency of detection and maintenance is improved.
Referring to fig. 4, in an embodiment, before the step of determining whether to output the warning signal based on the current capacity, the method further includes:
s202: and judging whether the input current reaches a set threshold value.
In one embodiment, the controller 500 determines whether the input current reaches a set threshold in real time after acquiring the input current. Specifically, the controller 500 may compare the input current with the set threshold by a difference. If the input current is smaller than the set threshold, it is determined that the input current does not reach the set threshold, and the controller 500 does not operate. If the input current is greater than or equal to the set threshold, it is determined that the input current reaches the set threshold, and then step S204 is executed. In one embodiment, the set threshold may be set according to actual requirements.
S204: and when the input current reaches the set threshold value, acquiring the voltage at two ends of the bus capacitor and acquiring a second voltage.
In one embodiment, when the input current reaches the set threshold, the controller 500 may obtain the voltage across the bus capacitor 300 through a voltage sensor and obtain a second voltage. In one embodiment, the controller 500 may also obtain the voltage across the bus capacitor 300 through a conventional voltage detection circuit.
In one embodiment, the voltage relationship on the discharge circuit formed between the bus capacitor 300 and the motor 401 may be equivalent to: the bus capacitor voltage is equal to the sum of the motor winding partial voltage and the capacitor internal resistance partial voltage. When the input current reaches the set threshold, the second voltage obtained by the controller 500 is the motor winding divided voltage.
S206: and controlling an upper bridge arm switching tube of a first phase bridge arm in the IGBT module to be disconnected, acquiring voltages at two ends of the bus capacitor and obtaining a third voltage.
In one embodiment, the controller 500 can control all the upper arm switching tubes 411 of each phase arm of the full-bridge circuit 400 to be turned off. In step S104, the controller 500 controls the upper arm switch tube 411 of the first phase arm 410 to be turned on, so that in step S206, the upper arm switch tube 411 of the first phase arm 410 in the full-bridge circuit 400 only needs to be turned off. The controller 500 controls the upper arm switching tube 411 to be completely disconnected, that is, the discharging circuit between the bus capacitor 300 and the motor 401 is disconnected at this time. At this time, the controller 500 may obtain the voltage across the bus capacitor 300 through a voltage sensor and obtain a third voltage.
S208: determining a present internal resistance value of the bus capacitor based on the second voltage, the third voltage, and the input current.
In one embodiment, the controller 500 may determine the current internal resistance value of the bus capacitor 300 based on the second voltage, the third voltage and the input current after acquiring the second voltage and the third voltage. Specifically, the controller 500 may calculate the current internal resistance value of the bus capacitor 300 according to the following formula:
R＝(U2-U1)/I
wherein R is the current internal resistance value of the bus capacitor 300. U shape1Is the second voltage. U shape2Is the third voltage.
S210: and determining whether to output the early warning signal or not based on the current internal resistance value.
In one embodiment, the controller 500 may determine whether to output the warning signal based on the current internal resistance value. Specifically, the controller 500 may compare the current internal resistance value with a standard internal resistance value to obtain a second difference value. In one embodiment, the standard internal resistance value may be an internal resistance value measured when the bus capacitor 300 is shipped.
If the second difference is greater than the preset internal resistance threshold, the controller 500 outputs the early warning signal to remind maintenance personnel to perform inspection and replacement. If the second difference is smaller than or equal to the preset internal resistance threshold, the controller 500 does not output the early warning signal. Namely, the aging condition of the bus capacitor 300 is within the acceptable range, and at this time, maintenance personnel do not need to be reminded to carry out inspection and replacement. In this embodiment, the bus capacitor 300 is detected by the above steps, and the diagnosis process of online detecting the internal resistance value of the bus capacitor 300 can be automatically performed without manual intervention, so that the efficiency of detection and maintenance is improved.
In one embodiment, the step of determining whether the input current reaches a set threshold comprises: comparing the input current to the set threshold. And if the input current is smaller than the set threshold, determining that the input current does not reach the set threshold. And if the input current is greater than or equal to the set threshold, determining that the input current reaches the set threshold.
In one embodiment, the controller 500 may compare the input current to the set threshold difference value to obtain a difference comparison result. If the difference comparison result indicates that the input current is smaller than the set threshold, it is determined that the input current does not reach the set threshold, and the controller 500 does not operate at this time. If the difference comparison result is that the input current is greater than or equal to the set threshold, it is determined that the input current reaches the set threshold, and then step S204 is executed.
Referring to fig. 5, an embodiment of the present application provides an on-line detection apparatus 10 for bus capacitance of a frequency converter, including: the power switch 100, the rectifier module 200, the bus capacitor 300, the full bridge circuit 400 and the controller 500. The first terminal of the power switch 100 is electrically connected to a power source 101. The input end of the rectifier module 200 is electrically connected to the second end of the power switch 100. A first end of the bus capacitor 300 is electrically connected to a first electrode of the rectifier module 200. A second end of the bus capacitor 300 is electrically connected to a second electrode of the rectifier module 200. A first terminal of the full bridge circuit 400 is electrically connected to a first terminal of the bus capacitor 300. The second terminal of the full bridge circuit 400 is electrically connected to the second terminal of the bus capacitor 300. The output end of the full bridge circuit 400 is electrically connected with the motor 401. The controller 500 is electrically connected to the control terminal of the power switch 100 and the control terminal of the full-bridge circuit 400, respectively. The controller 500 is configured to execute the method for detecting the bus capacitance of the frequency converter in the any embodiment.
In one embodiment, the type of the power switch 100 is not limited as long as the controller 500 can control the on and off of the power switch 100. In one embodiment, the power switch 100 may be a smart switch. In one embodiment, the power switch 100 may also be a relay switch. The controller 500 controls the power supply 101 to charge the bus capacitor 300 through the power switch 100. Specifically, when the controller 500 controls the power switch 100 to be turned on, the power source 101 charges the bus capacitor 300. When the controller 500 controls the power switch 100 to be turned off, the power source 101 does not charge the bus capacitor 300. In one embodiment, the rectification module 200 may be a rectifier. In one embodiment, the power source 101 may be a three-phase power source.
In one embodiment, the bus capacitor 300 may be plural in number. When the number of the bus capacitors 300 is plural, the line capacitors 300 are sequentially connected in series. In one embodiment, the full bridge circuit 400 may include the first phase leg 410 and the second phase leg 420 connected in parallel (as shown in fig. 2). That is, the full bridge circuit 400 may be a four-switch-transistor full bridge circuit. At this time, the motor 401 electrically connected to the output terminal of the full bridge circuit 400 is a dc motor.
In one embodiment, the full bridge circuit 400 may further include the first phase leg 410, the second phase leg 420, and the third phase leg 430 connected in parallel (as shown in fig. 3). That is, the full bridge circuit 400 may be a full bridge circuit of six switching tubes. The motor 401 electrically connected to the output terminal of the full bridge circuit 400 may be a three-phase motor. In an embodiment, the circuit structures of the first phase bridge arm 410, the second phase bridge arm 420, and the third phase bridge arm 430 may adopt the circuit topology described in the above embodiment, and are not described herein again. In one embodiment, the controller 500 may be replaced with a single chip or an integrated control chip.
In this embodiment, when the bus capacitor 300 is detected online, the bus capacitor 300 can be charged through the cooperation of the controller 500 and the power switch 100. After the bus capacitor 300 is charged, the bus capacitor 300 is discharged through the cooperation of the controller 500 and the full-bridge circuit 400. In the process of charging and discharging the bus capacitor 300, the controller 500 executes the method for detecting the bus capacitor of the frequency converter on line according to any embodiment, so that the on-line detection of the capacity or the internal resistance of the bus capacitor 300 can be automatically realized, manual intervention is not needed, and the efficiency of detection and maintenance is improved.
In one embodiment, the device 10 for detecting bus capacitance of a frequency converter further includes: the current detection module 600. The first end of the current detection module 600 is electrically connected to the output end of the full-bridge circuit 400. A second end of the current detection module 600 is electrically connected to the controller 500. The current detection module 600 is configured to detect an input current of the motor 401 and send the input current to the controller 500.
It is understood that the specific circuit structure of the current detection module 600 is not limited as long as it has the function of detecting the input current of the motor 401. In one embodiment, the current detection module 600 may be a current sensor. In one embodiment, the current detection module 600 may also be a conventional current detection circuit with a current detection function. The controller 500 obtains the input current in real time through the current detection module 600, so as to facilitate subsequent processing.
In one embodiment, the device 10 for detecting bus capacitance of a frequency converter further includes: the voltage detection module 700. The voltage detection module 700 is connected in parallel to two ends of the bus capacitor 300. The voltage detection module 700 is configured to detect voltages at two ends of the bus capacitor 300, and send the detected voltages at two ends of the bus capacitor 300 to the controller 500.
It is understood that the specific circuit structure of the voltage detection module 700 is not limited as long as it has the function of detecting the voltage across the bus capacitor 300. In one embodiment, the voltage detection module 700 may be a voltage sensor. In one embodiment, the voltage detection module 700 may also be a conventional voltage detection circuit with a voltage detection function. The controller 500 obtains the voltages at the two ends of the bus capacitor 300 in real time through the voltage detection module 700.
In one embodiment, the device 10 for detecting bus capacitance of a frequency converter further includes: a locking device 800. The locking device 800 is electrically connected to the controller 500. The locking device 800 is adapted to be mechanically coupled to the motor 401. When the bus capacitor 300 is discharged, the controller 500 controls the motor 401 to be stationary through the locking device 800. In one embodiment, the locking device 800 may include a locking pin, a gear, and a driving motor. The controller 500 may control the motor 401 to be stationary via the locking device 800, so that the bus capacitor 300 is discharged through the windings in the motor 401.
To sum up, this application obtains first voltage through obtaining the voltage at bus capacitor 300 both ends, and confirms based on first voltage and predetermined voltage whether bus capacitor 300 charges and accomplishes. Then, when the bus capacitor 300 is completely charged, the upper arm switching tube 411 of the first phase arm 410 and the lower arm switching tube 412 of the second phase arm 420 in the full bridge circuit 400 are controlled to be conducted, so that the bus capacitor 300 and the motor 401 form a discharge circuit. Controlling the motor 401 to be static when the bus capacitor 300 is discharged, acquiring the voltage change rate between two ends of the bus capacitor 300 and the input current of the motor 401, and determining the current capacity of the bus capacitor 300 based on the voltage change rate and the input current. And finally determining whether to output an early warning signal based on the current capacity. By adopting the detection mode, the diagnosis process of detecting the capacity of the bus capacitor 300 on line can be automatically carried out without manual intervention, and the detection efficiency is improved.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present application, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the concept of the present application, which falls within the scope of protection of the present application. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (10)
1. A method for detecting a bus capacitor of a frequency converter on line is characterized by comprising the following steps:
acquiring voltages at two ends of a bus capacitor to obtain a first voltage, and determining whether the bus capacitor is charged based on the first voltage and a preset voltage;
when the bus capacitor is charged, controlling an upper bridge arm switching tube of a first phase bridge arm and a lower bridge arm switching tube of a second phase bridge arm in the full-bridge circuit to be conducted so that the bus capacitor and the motor form a discharging loop;
controlling the motor to be static when the bus capacitor is discharged, acquiring the voltage change rate between two ends of the bus capacitor and the input current of the motor, and determining the current capacity of the bus capacitor based on the voltage change rate and the input current;
determining whether to output a warning signal based on the current capacity.
2. The method of claim 1, wherein said step of controlling said motor to rest while said bus capacitor is discharging, obtaining a rate of change of voltage across said bus capacitor and an input current to said motor, and determining a present capacity of said bus capacitor based on said rate of change of voltage and said input current comprises:
when the bus capacitor discharges, controlling the motor to be static;
acquiring the voltage change rate between two ends of the bus capacitor;
acquiring the input current of the motor through a current detection module;
determining the current capacity of the bus capacitor based on the voltage change rate and the input current, and calculating according to the following formula:
C＝I/(dU/dt)；
where C is the present capacity of the bus capacitance, I is the input current, and dU/dt is the voltage rate of change.
3. The method of claim 1, wherein the step of determining whether to output a warning signal based on the current capacity comprises:
comparing the difference value of the current capacity with the standard capacity to obtain a first difference value;
if the first difference value is larger than a preset capacity threshold value, outputting the early warning signal;
and if the first difference value is smaller than or equal to the preset capacity threshold value, not outputting the early warning signal.
4. The method of on-line detection of a bus capacitance of a frequency converter of claim 1, wherein prior to the step of determining whether to output a warning signal based on the current capacity, the method further comprises:
judging whether the input current reaches a set threshold value;
when the input current reaches the set threshold value, acquiring voltages at two ends of the bus capacitor and acquiring a second voltage;
controlling an upper bridge arm switching tube of a first phase bridge arm in the IGBT module to be disconnected, acquiring voltages at two ends of the bus capacitor and obtaining a third voltage;
determining a present internal resistance value of the bus capacitor based on the second voltage, the third voltage, and the input current;
and determining whether to output the early warning signal or not based on the current internal resistance value.
5. The method for detecting the bus capacitance of the frequency converter according to claim 4, wherein the step of determining whether to output the warning signal based on the current internal resistance value comprises the steps of:
comparing the difference value of the current internal resistance value with the standard internal resistance value to obtain a second difference value;
if the second difference value is larger than a preset internal resistance threshold value, outputting the early warning signal;
and if the second difference value is less than or equal to the preset internal resistance threshold value, not outputting the early warning signal.
6. The method for detecting the bus capacitance of the frequency converter according to claim 1, wherein the full-bridge circuit comprises a first phase bridge arm and a second phase bridge arm which are connected in parallel, and the first phase bridge arm and the second phase bridge arm each comprise an upper bridge arm switching tube and a lower bridge arm switching tube which are connected in series;
the full-bridge circuit further comprises a third-phase bridge arm, the third-phase bridge arm is sequentially connected with the first-phase bridge arm and the second-phase bridge arm in parallel, and the third-phase bridge arm comprises an upper bridge arm switching tube and a lower bridge arm switching tube which are connected in series.
7. The utility model provides a converter bus capacitance on-line measuring device which characterized in that includes:
a power switch (100), a first end of the power switch (100) is used for electrically connecting a power supply (101);
the input end of the rectification module (200) is electrically connected with the second end of the power switch (100);
a bus capacitor (300), wherein a first end of the bus capacitor (300) is electrically connected with a first electrode of the rectifier module (200), and a second end of the bus capacitor (300) is electrically connected with a second electrode of the rectifier module (200);
a full-bridge circuit (400), a first end of the full-bridge circuit (400) is electrically connected with a first end of the bus capacitor (300), a second end of the full-bridge circuit (400) is electrically connected with a second end of the bus capacitor (300), and an output end of the full-bridge circuit (400) is used for electrically connecting a motor (401); and
a controller (500) electrically connected to the control terminal of the power switch (100) and the control terminal of the full bridge circuit (400), respectively, for performing the method of detecting the bus capacitance of the frequency converter according to any one of claims 1 to 9.
8. The device for detecting the bus capacitance of the frequency converter according to claim 7, further comprising:
the current detection module (600), the first end of current detection module (600) with the output electricity of full-bridge circuit (400) is connected, the second end of current detection module (600) with controller (500) electricity is connected for detect the input current of motor (401), and will input current send to controller (500).
9. The device for detecting the bus capacitance of the frequency converter according to claim 7, further comprising:
and the voltage detection module (700) is connected in parallel with two ends of the bus capacitor (300) and is used for detecting the voltages at two ends of the bus capacitor (300) and sending the detected voltages at two ends of the bus capacitor (300) to the controller (500).
10. The device for detecting the bus capacitance of the frequency converter according to claim 7, further comprising:
a locking device (800) electrically connected with the controller (500) and used for mechanically connecting with the motor (401);
when the bus capacitor (300) is discharged, the controller (500) controls the motor (401) to be static through the locking device (800).
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