CN109390914B - Protection method and device for charging circuit of frequency converter - Google Patents
Protection method and device for charging circuit of frequency converter Download PDFInfo
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- CN109390914B CN109390914B CN201710655015.5A CN201710655015A CN109390914B CN 109390914 B CN109390914 B CN 109390914B CN 201710655015 A CN201710655015 A CN 201710655015A CN 109390914 B CN109390914 B CN 109390914B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/10—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers
- H02H7/12—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers
- H02H7/1216—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers for AC-AC converters
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M5/00—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases
- H02M5/40—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc
- H02M5/42—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters
- H02M5/44—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac
- H02M5/453—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac using devices of a triode or transistor type requiring continuous application of a control signal
- H02M5/458—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
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Abstract
The disclosure relates to a protection method and a device for a frequency converter charging circuit, which are used for protecting the frequency converter charging circuit; the method comprises the following steps: after a charging circuit of the frequency converter is electrified, sampling the voltage of a direct current bus; acquiring the change rate of the direct-current bus voltage in real time according to the sampling value of the direct-current bus voltage; judging whether the change rate of the direct current bus voltage meets a first preset condition or not, and recording a voltage value when the change rate of the direct current bus voltage meets the first preset condition as a reference voltage value; acquiring a current voltage value; judging whether a voltage difference value between the current voltage value and the reference voltage value meets a second preset condition or not, and judging that the relay is in an abnormal connection state when the second preset condition is met; and cutting off the output of the frequency converter in response to the abnormal connection state. This openly can avoid generating heat because of charging resistor and lead to the converter shell scaling loss to reach the effect of protection converter charging circuit.
Description
Technical Field
The present disclosure relates to the field of electrical technologies, and in particular, to a method and an apparatus for protecting a charging circuit of a frequency converter.
Background
The frequency converter is a device for converting constant-voltage constant-frequency alternating current into variable-voltage variable-frequency alternating current, and is used for meeting the requirement of variable-frequency speed regulation of an alternating current motor.
The main circuit of the frequency converter is a power conversion part for providing a voltage-regulating frequency-modulating power supply, and the basic structure of the main circuit of the frequency converter is shown in figure 1 and comprises the following components: a rectifying circuit 10, a charging circuit 20, a braking circuit 30 and an inverter circuit 40; the charging circuit 20 includes a charging resistor 21, an energy storage capacitor 22, and a relay 23 connected in parallel to the charging resistor 21. The working principle of the frequency converter is as follows: the rectifying circuit 10 converts the received alternating current into direct current, the direct current charges the energy storage capacitor 22 through the charging resistor 21, and the relay 23 is closed after the charging reaches a certain degree so as to enable the charging resistor 21 to be short-circuited, thereby maintaining the normal operation of the frequency converter. Therefore, at the moment of electrifying the frequency converter, the charging current can be limited by using the charging resistor, so that the voltage at two ends of the energy storage capacitor is slowly increased, and the rectifier bridge is protected. Based on the structure, when the frequency converter is in an operating state, if the relay 23 contact in the charging circuit is opened, direct current flows through the charging resistor 21, so that the charging resistor 21 generates heat, and the shell of the frequency converter is easy to burn due to long-time operation.
It is to be noted that the information disclosed in the above background section is only for enhancement of understanding of the background of the present disclosure, and thus may include information that does not constitute prior art known to those of ordinary skill in the art.
Disclosure of Invention
An object of the present disclosure is to provide a method and an apparatus for protecting a charging circuit of a frequency converter, thereby overcoming, at least to some extent, one or more of the problems due to the limitations and disadvantages of the related art.
Additional features and advantages of the disclosure will be set forth in the detailed description which follows, or in part will be obvious from the description, or may be learned by practice of the disclosure.
According to one aspect of the present disclosure, a protection method for a frequency converter charging circuit is provided, which is used for protecting the frequency converter charging circuit; the frequency converter charging circuit comprises a charging resistor connected in series on a direct current bus and a relay connected in parallel with the charging resistor; the protection method comprises the following steps:
after the charging circuit of the frequency converter is electrified, sampling the voltage of a direct current bus;
acquiring the change rate of the direct-current bus voltage in real time according to the sampling value of the direct-current bus voltage;
judging whether the change rate of the direct current bus voltage meets a first preset condition or not, and recording a voltage value when the change rate of the direct current bus voltage meets the first preset condition as a reference voltage value when the change rate of the direct current bus voltage meets the first preset condition;
acquiring a current voltage value;
judging whether a voltage difference value between the current voltage value and the reference voltage value meets a second preset condition or not, and judging that the relay is in an abnormal connection state when the voltage difference value between the current voltage value and the reference voltage value meets the second preset condition;
and responding to the abnormal connection state to cut off the output of the frequency converter.
In an exemplary embodiment of the present disclosure, the second preset condition is: a voltage difference between the current voltage value and the reference voltage value is greater than a reference voltage difference.
In an exemplary embodiment of the present disclosure, the second preset condition is: the duration that the voltage difference between the current voltage value and the reference voltage value is greater than the reference voltage difference exceeds a preset time.
In an exemplary embodiment of the present disclosure, the protection method further includes:
and after the relay is judged to be in the abnormal connection state, responding to the abnormal connection state and sending an alarm to prompt a fault.
In an exemplary embodiment of the present disclosure, the sampling the dc bus voltage after power-on includes:
and measuring the voltage of the direct current bus by using a divider resistor, a voltage transformer or an isolation optical coupling.
According to another aspect of the present disclosure, there is provided a protection device for a frequency converter charging circuit, for protecting the frequency converter charging circuit; the frequency converter charging circuit comprises a charging resistor connected in series on a direct current bus and a relay connected in parallel with the charging resistor; the protection device includes:
the sampling module is used for sampling the voltage of the direct current bus after the charging circuit of the frequency converter is electrified;
the first detection module is used for acquiring the change rate of the direct-current bus voltage in real time according to the sampling value of the direct-current bus voltage;
the first judging module is used for judging whether the change rate of the direct-current bus voltage meets a first preset condition or not, and recording a voltage value when the change rate of the direct-current bus voltage meets the first preset condition as a reference voltage value when the change rate of the direct-current bus voltage meets the first preset condition;
a second detection module for obtaining the current voltage value
The second judging module is used for judging whether a voltage difference value between the current voltage value and the reference voltage value meets a second preset condition or not, and judging that the relay is in an abnormal connection state when the voltage difference value between the current voltage value and the reference voltage value meets the second preset condition;
and the control module is used for responding to the abnormal connection state and cutting off the output of the frequency converter.
In an exemplary embodiment of the present disclosure, the second preset condition is: a voltage difference between the current voltage value and the reference voltage value is greater than a reference voltage difference.
In an exemplary embodiment of the present disclosure, the second preset condition is: the duration that the voltage difference between the current voltage value and the reference voltage value is greater than the reference voltage difference exceeds a preset time.
In an exemplary embodiment of the present disclosure, the protection device further includes:
and the alarm module is used for responding to the abnormal connection state to send out an alarm to prompt faults after judging that the relay is in the abnormal connection state.
In an exemplary embodiment of the present disclosure, the sampling module includes:
the voltage dividing resistor is used for measuring the voltage of the direct current bus by utilizing the voltage dividing resistor; alternatively, the first and second electrodes may be,
the voltage transformer is used for measuring the voltage of the direct current bus by utilizing the voltage transformer; alternatively, the first and second electrodes may be,
and the isolation optocoupler is used for measuring the voltage of the direct current bus by utilizing the isolation optocoupler.
According to the protection method and device for the frequency converter charging circuit, the connection state of the relay is judged by detecting the change of the direct-current bus voltage, and the output of the frequency converter is cut off when the abnormal connection of the relay is judged, so that the purpose of protecting the frequency converter charging circuit is achieved. On one hand, the connection state of the relay is judged according to the voltage change difference, so that the influence of measurement errors caused by signal interference on the judgment result can be reduced as much as possible; on the other hand, when the relay is abnormally connected, the output of the frequency converter is automatically cut off, so that the phenomenon of resistance heating caused by the fact that direct current flows through the charging resistor can be effectively avoided, the shell of the frequency converter is prevented from being burnt, and the problem of protecting a charging circuit of the frequency converter is intelligently solved.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present disclosure and together with the description, serve to explain the principles of the disclosure. It is to be understood that the drawings in the following description are merely exemplary of the disclosure, and that other drawings may be derived from those drawings by one of ordinary skill in the art without the exercise of inventive faculty.
Fig. 1 schematically shows a schematic structural diagram of a main circuit of a frequency converter in the prior art;
fig. 2 schematically illustrates a protection method schematic of a frequency converter charging circuit in an exemplary embodiment of the disclosure;
FIG. 3 schematically illustrates a sampling curve of a DC bus voltage in an exemplary embodiment of the present disclosure;
FIG. 4 is a schematic diagram illustrating a variation curve of a filter capacitor, an output current and a direct current bus current after a relay is disconnected in an exemplary embodiment of the disclosure;
fig. 5 schematically illustrates a protection device schematic of a frequency converter charging circuit in an exemplary embodiment of the disclosure.
Detailed Description
Example embodiments will now be described more fully with reference to the accompanying drawings. Example embodiments may, however, be embodied in many different forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of example embodiments to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to give a thorough understanding of embodiments of the disclosure. One skilled in the relevant art will recognize, however, that the subject matter of the present disclosure can be practiced without one or more of the specific details, or with other methods, components, devices, steps, and the like. In other instances, well-known technical solutions have not been shown or described in detail to avoid obscuring aspects of the present disclosure.
Furthermore, the drawings are merely schematic illustrations of the present disclosure and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and thus their repetitive description will be omitted. Some of the block diagrams shown in the figures are functional entities and do not necessarily correspond to physically or logically separate entities. These functional entities may be implemented in the form of software, or in one or more hardware modules or integrated circuits, or in different networks and/or processor devices and/or microcontroller devices.
In this exemplary embodiment, a method for protecting a charging circuit of a frequency converter is provided, which is used to protect the charging circuit of the frequency converter. Referring to fig. 1, the circuit structure of the frequency converter may include: a rectifying circuit 10, a charging circuit 20, a braking circuit 30 and an inverter circuit 40; the charging circuit 20 comprises a charging resistor 21 connected in series on a direct current bus, a relay 23 connected in parallel with the charging resistor 21, and an energy storage capacitor 22; the input end of the charging resistor 21 is connected to the output end of the rectifying circuit 10, and the output end of the energy storage capacitor 22 is connected to the input end of the braking circuit 30.
Based on this, as shown in fig. 2, the protection method of the frequency converter charging circuit may include:
s1, sampling the voltage of the direct current bus after the charging circuit of the frequency converter is powered on;
s2, acquiring the change rate of the direct current bus voltage in real time according to the sampling value of the direct current bus voltage;
s3, judging whether the change rate of the direct current bus voltage meets a first preset condition or not, and recording a voltage value when the change rate of the direct current bus voltage meets the first preset condition as a reference voltage value when the change rate of the direct current bus voltage meets the first preset condition;
s4, acquiring a current voltage value;
s5, judging whether the voltage difference between the current voltage value and the reference voltage value meets a second preset condition, and judging that the relay is in an abnormal connection state when the voltage difference between the current voltage value and the reference voltage value meets the second preset condition;
and S6, responding the abnormal connection state and cutting off the output of the frequency converter.
According to the protection method for the frequency converter charging circuit, the connection state of the relay is judged by detecting the change of the direct-current bus voltage, and the output of the frequency converter is cut off when the abnormal connection of the relay is judged, so that the purpose of protecting the frequency converter charging circuit is achieved. On one hand, the connection state of the relay is judged according to the voltage change difference, so that the influence of measurement errors caused by signal interference on the judgment result can be reduced as much as possible; on the other hand, when the relay is abnormally connected, the output of the frequency converter is automatically cut off, so that the phenomenon of resistance heating caused by the fact that direct current flows through the charging resistor can be effectively avoided, the shell of the frequency converter is prevented from being burnt, and the problem of protecting a charging circuit of the frequency converter is intelligently solved.
The respective steps of the protection method of the inverter charging circuit in the present exemplary embodiment will be described in detail below.
In step S1, after the frequency converter charging circuit is powered on, the dc bus voltage is sampled.
The direct-current bus voltage is a continuously-changing waveform, the direct-current bus voltage is sampled, a plurality of sampling values based on a certain sampling frequency can be obtained, a continuously-changing sampling curve can be drawn according to the plurality of sampling values, and the sampling curve reflects the change rule of the direct-current bus voltage.
In this exemplary embodiment, the power-on refers to a charging process of the frequency converter, specifically, a process of charging the energy storage capacitor 22 in the charging circuit of the frequency converter; after the charging is completed, the control circuit shorts the charging resistor 21 through the contact of the relay 23 to complete the power-on process of the frequency converter.
For example, when the charging circuit 20 of the frequency converter is powered on, the rectifying circuit 10 converts the received ac power into dc power, the energy storage capacitor 22 is charged through the charging resistor 21, after the charging reaches a certain degree, the control circuit closes the relay 23 to short-circuit the charging resistor 21, the power-on process of the frequency converter is completed, and at this time, the dc bus voltage is sampled to obtain the sampling curve shown in fig. 3.
On this basis, the sampling of the dc bus voltage may specifically include the following method:
measuring the voltage of the direct current bus by using a divider resistor; the method comprises the following steps that a voltage division resistor network is connected in parallel to a direct current bus to measure the voltage of the direct current bus, and a voltage signal obtained by voltage division is sent to a control center to be subjected to operation processing to obtain the voltage of the direct current bus;
or, measuring the voltage of the direct current bus by using a voltage transformer; the principle is that the voltage of a direct current bus is used as input, and the voltage of one side of a voltage transformer is in corresponding proportion to the voltage of the direct current bus; alternatively, the first and second electrodes may be,
measuring the voltage of the direct current bus by using an isolation optical coupler; i.e. the process is repeated. The method comprises the steps that a linear isolation optocoupler is arranged on a direct current bus, and the direct current bus voltage is measured through optocoupler based on the input end and the output end of a linear optocoupler.
In this exemplary embodiment, the sampling method of the dc bus voltage is not specifically limited, and other methods besides the three methods may also be used to perform sampling measurement.
In step S2, the change rate of the dc bus voltage is obtained in real time according to the sampled value of the dc bus voltage.
In the present exemplary embodiment, the change rate of the dc bus voltage refers to a change value of the dc bus voltage per unit time, and the change rate can reflect a change degree (including a change width and a change speed) of the dc bus voltage.
For example, when the dc bus voltage suddenly changes, i.e. the dc bus voltage suddenly decreases in fig. 3, the change rate △ V of the dc bus voltage at the sudden change moment can be obtained according to the sampling value of the dc bus voltage, and the first preset condition is assumed to be △ V0>5V, the rate of change △ V of the dc bus voltage is 5.2V, and comparing the rate of change △ V with a first preset condition shows that the rate of change △ V satisfies the first preset condition, at this time, the next step may be performed, otherwise, the dc bus voltage continues to be sampled and the rate of change of the dc bus voltage is obtained.
In step S3, it is determined whether the change rate of the dc bus voltage satisfies a first preset condition, and when the change rate of the dc bus voltage satisfies the first preset condition, a voltage value at which the change rate of the dc bus voltage satisfies the first preset condition is recorded as a reference voltage value.
The first preset condition refers to a threshold value of the change degree of the direct-current bus voltage; that is, when the change rate of the dc bus voltage reaches the threshold value, the dc bus voltage needs to be further detected to obtain the related voltage change information, otherwise, the change does not need to be considered.
In this exemplary embodiment, the reference voltage value is a voltage value when the change rate of the dc bus voltage satisfies a first preset condition, and is a specific value in a certain voltage change period, but the reference voltage value is continuously changed during the whole operation process of the frequency converter. For example, the voltage of the direct current bus has a first sudden change, and the change rate of the first sudden change meets a first preset condition, at this time, a corresponding voltage value needs to be recorded as a reference voltage value; however, a condition for limiting whether the frequency converter continues to operate is further set in the subsequent step, and if the voltage change at this time does not meet the subsequent condition, the frequency converter still normally operates, so that the direct-current bus voltage may also have a second sudden change; if the change rate of the second sudden change of the dc bus voltage also satisfies the first preset condition, the reference voltage value at this time is different from the first reference voltage value.
It should be noted that: the voltage value recorded in the step is the voltage value when the change rate of the direct current bus voltage meets the first preset condition, but not the voltage value when the direct current bus voltage starts to be sampled.
For example, referring to fig. 3, when the dc bus voltage starts to suddenly change at time T1 and the change rate of the dc bus voltage at this time is known to satisfy the first preset condition according to the real-time detection data, the voltage value V1 at this time is recorded as the reference voltage value, and assuming that the change rate △ V of the dc bus voltage at time T1 is 5.2V, the first preset condition △ V is satisfied0>5V, and the recording voltage value V1 is 6V as the reference voltage value.
In step S4, the current voltage value is acquired.
In this example embodiment, the current voltage value refers to a voltage value detected in real time. And taking the recorded voltage value as a reference voltage value when the change rate of the direct current bus voltage meets a first preset condition, wherein the direct current bus voltage may be in a change state all the time after the reference voltage value is taken as the current voltage value, and the voltage value detected in real time at the moment is taken as the current voltage value.
For example, referring to fig. 3, after V1 is recorded as the reference voltage value, the current voltage value V2 is obtained in real time, and the voltage difference between the current voltage value and the reference voltage value is V2-V1; assuming that the reference voltage V1 is 6V and the current voltage V2 is 0.9V, the voltage difference V2-V1 is 5.1V.
In step S5, it is determined whether the voltage difference between the current voltage value and the reference voltage value satisfies a second preset condition, and when the voltage difference between the current voltage value and the reference voltage value satisfies the second preset condition, it is determined that the relay is in an abnormal connection state.
In the present exemplary embodiment, the abnormal connection state of the relay indicates that the contact of the relay is opened, and when the contact of the relay is in the open state, the dc current flows through the charging point resistor, which causes the charging resistor to generate heat, and the long duration further causes the burning of the casing of the inverter.
In this step, the second preset condition may be set as: a voltage difference between the current voltage value and the reference voltage value is greater than a reference voltage difference.
That is, the second preset condition is a threshold value set for a voltage difference between the current voltage value and the reference voltage value, and the connection state of the relay needs to be determined only when the voltage difference is greater than or equal to the threshold value.
For example, after V1 is recorded as the reference voltage value, the current voltage value V2 is obtained in real time, and the voltage difference between the current voltage value and the reference voltage value is V2-V1, and at this time, the voltage difference V2-V1 is compared with the reference voltage difference; assuming that the reference voltage value V1 is 6V, the current voltage value V2 is 0.9V, and the reference voltage difference is 5V, and the voltage difference V2-V1 is 5.1V larger than the reference voltage difference 5V, it is known that the voltage difference between the current voltage value and the reference voltage value satisfies the second preset condition.
On this basis, considering that the circuit structure of the frequency converter is complex and changeable, and any one of the components has a problem, which may cause a change in the dc bus voltage, in order to prevent a misjudgment caused by non-relay disconnection, the second preset condition may be further set as: the duration that the voltage difference between the current voltage value and the reference voltage value is greater than the reference voltage difference exceeds a preset time.
That is, the second preset condition sets a reference voltage difference value as a first threshold value for the voltage difference value between the current voltage value and the reference voltage value, and sets a preset time as a second threshold value for the duration time that the voltage difference value is greater than the reference voltage difference value, and the connection state of the relay needs to be determined only if the two conditions are met, so as to ensure that misdetermination cannot be caused due to other reasons other than the disconnection of the relay.
For example, after V1 is recorded as a reference voltage value, a current voltage value V2 is obtained in real time, and a voltage difference between the current voltage value and the reference voltage value is V2-V1, and the voltage difference is maintained for a period of time △ T, at this time, the voltage difference V2-V1 is compared with the reference voltage difference, when the voltage difference V2-V1 is greater than the reference voltage difference, the duration of this state is further compared with a preset time, if the duration is also greater than the preset time, the voltage difference between the current voltage value and the reference voltage value satisfies a second preset condition, so that the relay can be determined to be in an abnormal connection state, and assuming that the reference voltage value V1 is 6V, the current voltage value V2 is 0.9V, the reference voltage difference is 5V, the preset time is 30s, at this time, the voltage difference V2-V1 is 5.1V and continues to be greater than the reference voltage difference 1V, and the second preset condition is satisfied.
In step S6, the output of the inverter is cut off in response to the abnormal connection state.
After the relay is judged to be in the abnormal connection state, an alarm can be given out in response to the abnormal connection state to prompt a fault, and then the output of the frequency converter is cut off.
For example, when the relay is determined to be in an abnormal connection state, it is indicated that the contact of the relay is disconnected, and at this time, the frequency converter may send out an alarm to prompt a fault, where the alarm prompting manner may be a light prompt or a sound prompt; on the basis, in order to prevent the charging resistor from being overheated, the output of the frequency converter should be cut off in time.
Fig. 4 is a schematic diagram showing changes of the filter capacitor, the output current and the dc bus current after the relay is turned off. After the relay is disconnected, the direct current flows through the charging resistor, the voltage of the filter capacitor is reduced, and the direct current bus current and the output current are reduced at the same time.
In this exemplary embodiment, a protection device for a charging circuit of a frequency converter is provided, which is used to protect the charging circuit of the frequency converter. Referring to fig. 1, the circuit structure of the frequency converter may include: a rectifying circuit 10, a charging circuit 20, a braking circuit 30 and an inverter circuit 40; the charging circuit 20 comprises a charging resistor 21 connected in series on a direct current bus, a relay 23 connected in parallel with the charging resistor 21, and an energy storage capacitor 22; the input end of the charging resistor 21 is connected to the output end of the rectifying circuit 10, and the output end of the energy storage capacitor 22 is connected to the input end of the braking circuit 30.
Based on this, as shown in fig. 5, the protection device of the frequency converter charging circuit may include:
the sampling module 501 is configured to sample a dc bus voltage after the charging circuit of the frequency converter is powered on;
the first detection module 502 is configured to obtain a change rate of the dc bus voltage in real time according to the sampling value of the dc bus voltage;
a first determining module 503, configured to determine whether a change rate of the dc bus voltage meets a first preset condition, and record, when the change rate of the dc bus voltage meets the first preset condition, a voltage value when the change rate of the dc bus voltage meets the first preset condition as a reference voltage value;
a second detection module 504, configured to obtain a current voltage value;
a second determining module 505, configured to determine whether a voltage difference between the current voltage value and the reference voltage value meets a second preset condition, and determine that the relay is in an abnormal connection state when the voltage difference between the current voltage value and the reference voltage value meets the second preset condition;
and a control module 506, configured to cut off an output of the frequency converter in response to the abnormal connection state.
According to the protection device for the frequency converter charging circuit, the connection state of the relay is judged by detecting the change of the direct-current bus voltage, and the output of the frequency converter is cut off when the abnormal connection of the relay is judged, so that the purpose of protecting the frequency converter charging circuit is achieved.
In this example embodiment, the sampling module 501 may include:
the voltage dividing resistor is used for measuring the voltage of the direct current bus by utilizing the voltage dividing resistor; alternatively, the first and second electrodes may be,
the voltage transformer is used for measuring the voltage of the direct current bus by utilizing the voltage transformer; alternatively, the first and second electrodes may be,
and the isolation optocoupler is used for measuring the voltage of the direct current bus by utilizing the isolation optocoupler.
It should be noted that: the sampling device for the dc bus voltage in the present exemplary embodiment is not particularly limited, and other devices may be used to sample and measure the dc bus voltage.
In this example embodiment, the second preset condition may be: a voltage difference between the current voltage value and the reference voltage value is greater than a reference voltage difference. That is, the second preset condition is a threshold value set for a voltage difference value between the current voltage value and the reference voltage value.
On this basis, considering that the circuit structure of the frequency converter is complex and changeable, and any one of the components has a problem, which may cause a change in the dc bus voltage, in order to prevent a misjudgment caused by non-relay disconnection, the second preset condition may be further set as: the duration that the voltage difference between the current voltage value and the reference voltage value is greater than the reference voltage difference exceeds a preset time. That is, the second preset condition not only sets a reference voltage difference value as the first threshold value for the voltage difference value between the current voltage value and the reference voltage value, but also sets a preset time as the second threshold value for the duration that the voltage difference value is greater than the reference voltage difference value.
In this exemplary embodiment, the protection device may further include: the alarm module 507 is used for responding to the abnormal connection state to send out an alarm to prompt a fault after judging that the relay is in the abnormal connection state, and then cutting off the output of the frequency converter, so that the working state of the frequency converter can be prompted to workers in time for maintenance; the alarm prompting mode can be light prompting or sound prompting and the like.
It should be noted that: the specific details of each module unit in the protection device of the frequency converter charging circuit have been described in detail in the protection method of the corresponding frequency converter charging circuit, and therefore are not described herein again.
It should be noted that although in the above detailed description several modules or units of the device for action execution are mentioned, such a division is not mandatory. Indeed, the features and functionality of two or more modules or units described above may be embodied in one module or unit, according to embodiments of the present disclosure. Conversely, the features and functions of one module or unit described above may be further divided into embodiments by a plurality of modules or units.
Moreover, although the steps of the methods of the present disclosure are depicted in the drawings in a particular order, this does not require or imply that the steps must be performed in this particular order, or that all of the depicted steps must be performed, to achieve desirable results. Additionally or alternatively, certain steps may be omitted, multiple steps combined into one step execution, and/or one step broken down into multiple step executions, etc.
Through the above description of the embodiments, those skilled in the art will readily understand that the exemplary embodiments described herein may be implemented by software, or by software in combination with necessary hardware. Therefore, the technical solution according to the embodiments of the present disclosure may be embodied in the form of a software product, which may be stored in a non-volatile storage medium (which may be a CD-ROM, a usb disk, a removable hard disk, etc.) or on a network, and includes several instructions to enable a computing device (which may be a personal computer, a server, a mobile terminal, or a network device, etc.) to execute the method according to the embodiments of the present disclosure.
Other embodiments of the disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the disclosure disclosed herein. This application is intended to cover any variations, uses, or adaptations of the disclosure following, in general, the principles of the disclosure and including such departures from the present disclosure as come within known or customary practice within the art to which the disclosure pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the disclosure being indicated by the following claims.
Claims (8)
1. A protection method of a frequency converter charging circuit is used for protecting the frequency converter charging circuit; the frequency converter charging circuit comprises a charging resistor connected in series on a direct current bus and a relay connected in parallel with the charging resistor; the method is characterized by comprising the following steps:
after the charging circuit of the frequency converter is electrified, sampling the voltage of a direct current bus;
acquiring the change rate of the direct-current bus voltage in real time according to the sampling value of the direct-current bus voltage;
judging whether the change rate of the direct current bus voltage meets a first preset condition or not, and recording a voltage value when the change rate of the direct current bus voltage meets the first preset condition as a reference voltage value when the change rate of the direct current bus voltage meets the first preset condition;
acquiring a current voltage value;
judging whether a voltage difference value between the current voltage value and the reference voltage value meets a second preset condition or not, and judging that the relay is in an abnormal connection state when the voltage difference value between the current voltage value and the reference voltage value meets the second preset condition;
cutting off the output of the frequency converter in response to the abnormal connection state,
wherein the first preset condition is as follows: the rate of change of the dc bus voltage reaches a threshold value,
the second preset condition is as follows: a voltage difference between the current voltage value and the reference voltage value is greater than a reference voltage difference.
2. The protection method for the charging circuit of the frequency converter according to claim 1, wherein the second preset condition is: the duration that the voltage difference between the current voltage value and the reference voltage value is greater than the reference voltage difference exceeds a preset time.
3. The protection method of the frequency converter charging circuit according to claim 1 or 2, characterized in that the protection method further comprises:
and after the relay is judged to be in the abnormal connection state, responding to the abnormal connection state and sending an alarm to prompt a fault.
4. The method of claim 1, wherein the sampling the dc bus voltage after power-up comprises:
and measuring the voltage of the direct current bus by using a divider resistor, a voltage transformer or an isolation optocoupler.
5. A protection device of a frequency converter charging circuit is used for protecting the frequency converter charging circuit; the frequency converter charging circuit comprises a charging resistor connected in series on a direct current bus and a relay connected in parallel with the charging resistor; characterized in that the protection device comprises:
the sampling module is used for sampling the voltage of the direct current bus after the charging circuit of the frequency converter is electrified;
the first detection module is used for acquiring the change rate of the direct-current bus voltage in real time according to the sampling value of the direct-current bus voltage;
the first judging module is used for judging whether the change rate of the direct-current bus voltage meets a first preset condition or not, and recording a voltage value when the change rate of the direct-current bus voltage meets the first preset condition as a reference voltage value when the change rate of the direct-current bus voltage meets the first preset condition;
a second detection module for obtaining the current voltage value
The second judging module is used for judging whether a voltage difference value between the current voltage value and the reference voltage value meets a second preset condition or not, and judging that the relay is in an abnormal connection state when the voltage difference value between the current voltage value and the reference voltage value meets the second preset condition;
a control module for cutting off the output of the frequency converter in response to the abnormal connection state,
wherein the first preset condition is as follows: the rate of change of the dc bus voltage reaches a threshold value,
the second preset condition is as follows: a voltage difference between the current voltage value and the reference voltage value is greater than a reference voltage difference.
6. The protection device of the inverter charging circuit of claim 5, wherein the second preset condition is: the duration that the voltage difference between the current voltage value and the reference voltage value is greater than the reference voltage difference exceeds a preset time.
7. The protection device of the frequency converter charging circuit according to claim 5 or 6, characterized in that the protection device further comprises:
and the alarm module is used for responding to the abnormal connection state to send out an alarm to prompt faults after judging that the relay is in the abnormal connection state.
8. The protection device of the frequency converter charging circuit of claim 5, wherein the sampling module comprises:
the voltage dividing resistor is used for measuring the voltage of the direct current bus by utilizing the voltage dividing resistor; alternatively, the first and second electrodes may be,
the voltage transformer is used for measuring the voltage of the direct current bus by utilizing the voltage transformer; alternatively, the first and second electrodes may be,
and the isolation optocoupler is used for measuring the voltage of the direct current bus by utilizing the isolation optocoupler.
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| CN201710655015.5A CN109390914B (en) | 2017-08-03 | 2017-08-03 | Protection method and device for charging circuit of frequency converter |
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| CN201710655015.5A CN109390914B (en) | 2017-08-03 | 2017-08-03 | Protection method and device for charging circuit of frequency converter |
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| CN109390914A CN109390914A (en) | 2019-02-26 |
| CN109390914B true CN109390914B (en) | 2020-03-27 |
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| CN112701767A (en) * | 2020-12-10 | 2021-04-23 | 珠海格力电器股份有限公司 | Charging control device and method of motor controller and motor |
| CN114295974B (en) * | 2021-12-30 | 2023-11-10 | 上海儒竞智控技术有限公司 | Method and circuit for detecting failure of precharge relay |
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Address after: 214028 Jiangsu city in Wuxi Province, Wuxi national hi tech Industrial Development Zone Le Xing Lu Industrial Park LS Patentee after: Lexing electric (Wuxi) Co., Ltd Address before: 214028 Jiangsu city in Wuxi Province, Wuxi national hi tech Industrial Development Zone Le Xing Lu Industrial Park LS Patentee before: LS INDUSTRIAL SYSTEMS Co.,Ltd. |