CN213341630U - Bus protection device of frequency converter and frequency converter - Google Patents
Bus protection device of frequency converter and frequency converter Download PDFInfo
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- CN213341630U CN213341630U CN202022040573.0U CN202022040573U CN213341630U CN 213341630 U CN213341630 U CN 213341630U CN 202022040573 U CN202022040573 U CN 202022040573U CN 213341630 U CN213341630 U CN 213341630U
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Abstract
The utility model discloses a generating line protection device and converter of converter, the device includes: a sampling unit and a control unit; the sampling unit is configured to sample the bus voltage of the frequency converter to obtain a bus voltage sampling value and a common-mode voltage sampling value; the control unit is configured to determine the state of the bus voltage of the frequency converter according to the bus voltage sampling value and the common-mode voltage sampling value; and protecting the bus voltage of the frequency converter according to the state of the bus voltage of the frequency converter. The utility model discloses a problem that the inaccurate energy repayment that leads to the false triggering of busbar voltage sampling can be solved to the scheme, reaches the effect that promotes busbar voltage sampling accuracy in order to avoid the false triggering energy repayment.
Description
Technical Field
The utility model belongs to the technical field of the compressor, concretely relates to generating line protection device and converter of converter especially relate to a generating line voltage under-voltage detection and protection device and converter for converter.
Background
In the protection of a frequency converter bus of a magnetic suspension centrifuge, when the bus voltage sampling link is abnormal, for example, the sampling line is in poor contact, the energy feedback can be triggered by mistake to cause the bus voltage to rise, so that a magnetic suspension bearing directly falls down to smash a shaft in a high-speed rotating state.
The above is only for the purpose of assisting understanding of the technical solutions of the present invention, and does not represent an admission that the above is the prior art.
SUMMERY OF THE UTILITY MODEL
An object of the utility model is to provide a bus bar protection device and converter of converter to solve the inaccurate problem that leads to the false triggering energy repayment of busbar voltage sampling, reach the effect that promotes busbar voltage sampling accuracy in order to avoid the false triggering energy repayment.
The utility model provides a generating line protection device of converter, include: a sampling unit and a control unit; the sampling unit is configured to sample the bus voltage of the frequency converter to obtain a bus voltage sampling value and a common-mode voltage sampling value; the control unit is configured to determine the state of the bus voltage of the frequency converter according to the bus voltage sampling value and the common-mode voltage sampling value; and protecting the bus voltage of the frequency converter according to the state of the bus voltage of the frequency converter.
In some embodiments, the sampling unit includes: a first differential sampling circuit and a second differential sampling circuit; the sampling unit samples the bus voltage of the frequency converter, and comprises: the first differential sampling circuit is configured to sample a bus voltage positive electrode and a bus voltage negative electrode of the frequency converter to obtain a bus voltage sampling value; the second differential sampling circuit is configured to sample a bus voltage positive electrode of the frequency converter and a shell ground voltage to obtain a common-mode voltage sampling value.
In some embodiments, the first differential sampling circuit and the second differential sampling circuit are identical in structure; the first differential sampling circuit includes: the differential sampling circuit comprises a differential sampling circuit body, a clamping module and a feedforward module; the number of the clamping modules is two, and one of the two clamping modules is arranged at the inverting input end of the differential sampling circuit body; the other clamping module of the two clamping modules is arranged at the non-inverting input end of the differential sampling circuit body; the feedforward module is bridged at the inverting input end and the non-inverting input end of the differential sampling circuit body.
In some embodiments, the control unit determines the state of the bus voltage of the frequency converter from the bus voltage sample value and the common mode voltage sample value, including: determining whether the bus voltage sampling value is greater than a first reference voltage, and determining whether the common mode voltage sampling value is greater than a second reference voltage; if the bus voltage sampling value is less than or equal to a first reference voltage and the common-mode voltage sampling value is less than or equal to a second reference voltage, determining that the state of the bus voltage of the frequency converter is a first state; and if the bus voltage sampling value is greater than a first reference voltage and/or the common-mode voltage sampling value is greater than a second reference voltage, determining that the state of the bus voltage of the frequency converter is a second state.
In some embodiments, the protecting, by the control unit, the bus voltage of the frequency converter according to the state of the bus voltage of the frequency converter includes: under the condition that the bus voltage state of the frequency converter is in a first state, controlling the frequency converter to enter an energy feedback process; under the condition that the bus voltage state of the frequency converter is in a second state, if the bus voltage sampling value is larger than a first reference voltage, reporting that the bus voltage sampling of the frequency converter is abnormal and stopping the frequency converter; and if the common-mode voltage sampling value is larger than a second reference voltage, reporting that the bus voltage of the frequency converter is grounded abnormally and stopping the frequency converter.
With the above device phase-match, the utility model discloses another aspect provides a converter, include: the bus protection device of the frequency converter is described above.
Therefore, the utility model discloses a scheme is through carrying out the difference sampling to busbar voltage and generating line common mode voltage, according to busbar voltage and generating line common mode voltage's state, confirms the actual behavior of converter unit to in time protect when the actual behavior of converter unit appears unusually, solve the inaccurate problem that leads to the false triggering energy repayment of busbar voltage sampling, reach the effect that promotes busbar voltage sampling accuracy in order to avoid the false triggering energy repayment.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by the practice of the invention.
The technical solution of the present invention is further described in detail by the accompanying drawings and examples.
Drawings
Fig. 1 is a schematic structural diagram of an embodiment of a bus bar protection device of a frequency converter according to the present invention;
FIG. 2 is a schematic diagram of an embodiment of a bus voltage sampling module in a frequency converter system;
FIG. 3 is a schematic block diagram of another embodiment of a bus voltage sampling module in the frequency converter system;
FIG. 4 is a schematic diagram of an embodiment of a voltage differential sampling circuit;
FIG. 5 is a schematic diagram of another embodiment of a voltage differential sampling circuit;
FIG. 6 is a schematic diagram of a structure and truth table of an embodiment of an under-voltage detection protection circuit;
FIG. 7 is a truth table diagram of an embodiment of the brown-out detection protection circuit;
FIG. 8 is a schematic flow chart illustrating an embodiment of a bus undervoltage protection process;
fig. 9 is a schematic diagram of a bus protection flow of an embodiment of the bus protection device of the frequency converter of the present invention;
fig. 10 is a schematic flow chart illustrating an embodiment of determining a state of a bus voltage of the inverter in the bus bar protection device of the present invention;
fig. 11 is a schematic flow chart of an embodiment of protecting the bus voltage of the frequency converter in the bus protection device of the frequency converter of the present invention.
Detailed Description
To make the purpose, technical solution and advantages of the present invention clearer, the following will combine the embodiments of the present invention and the corresponding drawings to clearly and completely describe the technical solution of the present invention. It is to be understood that the embodiments described are only some embodiments of the invention, and not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative work belong to the protection scope of the present invention.
According to the utility model discloses an embodiment provides a generating line protection device of converter. Referring to fig. 1, a schematic structural diagram of an embodiment of the apparatus of the present invention is shown. The bus protection device of the frequency converter can be applied to a motor system such as a compressor system, and can comprise: a sampling unit and a control unit.
Specifically, the sampling unit can be configured to sample a bus voltage of the frequency converter to obtain a bus voltage sampling value and a common mode voltage sampling value.
In some embodiments, the sampling unit can include: a first differential sampling circuit and a second differential sampling circuit.
The sampling unit samples the bus voltage of the frequency converter, and comprises:
the first differential sampling circuit can be configured to sample a bus voltage positive electrode and a bus voltage negative electrode of the frequency converter to obtain a bus voltage sampling value.
The second differential sampling circuit can be configured to sample a bus voltage positive electrode of the frequency converter and a shell ground voltage to obtain a common-mode voltage sampling value.
For example: the bus protection of the common mode frequency converter of the shell ground PE by the bus voltage positive electrode DC + is increased, so that the grounding state can be detected, the grounding state of the frequency converter can be detected, and the problem of faults caused by the fact that the frequency converter cannot be grounded is solved; when the bus voltage positive pole DC + or the bus voltage negative pole DC-causes inaccurate sampling due to poor contact of a sampling line, the actual bus voltage state can be judged by detecting the potential difference between the bus voltage positive pole DC + and the shell ground PE, so that the false triggering energy feedback is prevented, the system failure is prevented, the accuracy of a sampling circuit is improved, and the false triggering energy feedback is prevented.
Therefore, by the differential sampling design of the bus voltage and the bus common-mode voltage, the bus voltage and the bus common-mode voltage are subjected to differential sampling design, the sampling accuracy is ensured, and the false triggering energy feedback is prevented.
In some embodiments, the first differential sampling circuit and the second differential sampling circuit are identical in structure. The first differential sampling circuit can include: the differential sampling circuit comprises a differential sampling circuit body, a clamping module and a feedforward module. The differential sampling circuit body can include: the circuit comprises a comparator, an anti-phase sampling module such as two resistors R1 arranged at an anti-phase input terminal of the comparator, an in-phase sampling module such as another two resistors R1 arranged at an in-phase input terminal of the comparator, and an output resistor R arranged at an output end of the comparator, wherein the output resistor R can output sampled bus voltage sampling values and common mode voltage sampling values. The output resistor R is also connected to ground via a capacitor C. A resistor R2 is arranged between the inverting input end of the comparator and the output end of the comparator, and the non-inverting input end of the comparator is grounded through another resistor R2. Wherein the content of the first and second substances,
the number of the clamping modules is two, and one of the two clamping modules is arranged at the inverting input end of the differential sampling circuit body; and the other clamping module of the two clamping modules is arranged at the non-inverting input end of the differential sampling circuit body. Preferably, the two clamping modules may be symmetrically arranged at the inverting input end and the non-inverting input end of the differential sampling circuit body.
For example: the sampling circuit carries out differential sampling, and the voltage sampling value is as follows:
d1 and D2 are clamping diodes for clamping the voltage between U + and U-, which are the range of the supply voltage of the operational amplifier. The voltage differential sampling circuit is additionally provided with D1 and D2 serving as clamping diodes, the voltage is clamped between U + and U-, the U + and the U-are power supply voltage ranges of the operational amplifier, and the clamping diodes are used for preventing the voltage from exceeding the power supply voltage of the chip.
The feedforward module is bridged at the inverting input end and the non-inverting input end of the differential sampling circuit body. Specifically, the feed-forward module may be connected across an input side of the inverting input terminal of the differential sampling circuit body (i.e., a side of the inverting sampling module away from the inverting input terminal of the comparator) and an input side of the non-inverting input terminal of the differential sampling circuit body (i.e., a side of the non-inverting sampling module away from the non-inverting input terminal of the comparator).
For example: the sampling circuit carries out differential sampling, and the effect of the in-phase input end and the reverse-phase input end of the operational amplifier across the resistor R0 is to provide a feedforward signal, inhibit the signal overshoot and improve the anti-interference capability of the sampling circuit. A crossover resistor R0 is added at the non-inverting input end and the inverting input end of the operational amplifier, and the cross-over resistor R0 has the functions of providing a feedforward signal, inhibiting signal overshoot and improving the anti-interference capability of the sampling circuit. The resistance R0 improves the anti-interference capability of the sampling circuit.
Therefore, by adopting the clamping diode and the bridging resistor to carry out sampling feedforward design, the abnormal phenomenon that the bus voltage pump rises due to energy feedback can be solved, and the sampling anti-interference performance is improved.
In particular, the control unit can be configured to determine the state of the bus voltage of the frequency converter from the bus voltage sample values and the common mode voltage sample values; and protecting the bus voltage of the frequency converter according to the state of the bus voltage of the frequency converter.
Therefore, the actual operation condition of the unit is determined by judging the bus voltage and the bus common-mode voltage state, the diagnosis of the abnormal state and the design of the protection circuit are realized, the accuracy of the sampling circuit can be improved, and the false triggering energy feedback is prevented.
In some embodiments, the determining, by the control unit, the state of the bus voltage of the frequency converter according to the bus voltage sampled value and the common mode voltage sampled value can include:
the control unit is specifically further configured to determine whether the bus voltage sample value is greater than a first reference voltage, and determine whether the common mode voltage sample value is greater than a second reference voltage. Wherein the first reference voltage is such as threshold voltage UREF1A second reference voltage, e.g. a threshold voltage, of UREF2。
The control unit is specifically configured to determine that the state of the bus voltage of the frequency converter is the first state if the bus voltage sampling value is less than or equal to a first reference voltage and the common-mode voltage sampling value is less than or equal to a second reference voltage. The first state is a state that the frequency converter can normally enter an energy feedback process.
The control unit is specifically configured to determine that the state of the bus voltage of the frequency converter is the second state if the bus voltage sampling value is greater than the first reference voltage and/or the common mode voltage sampling value is greater than the second reference voltage. And the second state is a fault state of the frequency converter.
For example: in the bus voltage under-voltage protection, when the bus voltage is set to be lower than 400V, the bus voltage is in an under-voltage state, and the threshold voltage is UREF1. Bus voltage sampling value and threshold voltage UREF1And after comparison, the output level signal FODC is sent to a main control chip of the frequency converter for processing. When the bus voltage sampling value UDCGreater than threshold voltage UREF1Then the output signal fo.dc is high; when the bus voltage sampling value UDCLess than threshold voltage UREF1The output signal fo.dc is low.
When the common mode voltage of the bus is set to be lower than 200V, the bus is in an undervoltage stateThreshold voltage of UREF2. Common mode voltage sampling value and threshold voltage UREF2And after comparison, outputting a level signal FO.PE to a main control chip of the frequency converter for processing. When the common mode voltage sampling value UDC-PEGreater than threshold voltage UREF2If yes, the output signal fo.pe is high level; when the bus voltage sampling value UDC-PELess than threshold voltage UREF2The output signal fo.pe is low.
Therefore, the bus voltage state and the bus common-mode voltage state are judged through the undervoltage detection protection circuit and the truth table, and are sent to the main control chip for processing after being subjected to OR logic; and the undervoltage protection function is realized according to the truth table operation result by combining the comparison circuit and the truth table operation circuit.
In some embodiments, the protecting the bus voltage of the frequency converter by the control unit according to the state of the bus voltage of the frequency converter may include:
the control unit is specifically configured to control the frequency converter to enter an energy feedback process under the condition that the bus voltage state of the frequency converter is in the first state, so that the motor stops rotating, and the magnetic suspension bearing stably falls off the shaft.
The control unit is specifically configured to report that the bus voltage sampling of the frequency converter is abnormal and stop if the bus voltage sampling value is greater than a first reference voltage under the condition that the bus voltage state of the frequency converter is a second state; and if the common-mode voltage sampling value is larger than a second reference voltage, reporting that the bus voltage of the frequency converter is grounded abnormally and stopping the frequency converter.
For example: and after carrying out OR operation on the FO.DC and the FO.PE, outputting a level signal FO.TZ to a main control chip of the frequency converter for processing. When fo.dc and fo.pe are both low, the output signal fo.tz is low, triggering energy feedback. Otherwise, the output level signal fo.tz is high level, and no energy feedback is triggered. Through OR operation, the energy feedback is only started when the FO.TZ is at a low level, so that the probability of triggering the energy feedback by mistake is reduced.
Therefore, bus voltage and bus common-mode voltage are collected through a bus voltage sampling module, and the bus voltage sampling module is a sampling resistance plate; only when the bus voltage and the bus common-mode voltage sampling result are in an undervoltage state at the same time, the frequency converter controller judges that the unit is undervoltage, immediately enters energy feedback and is shut down due to faults; when one of the bus voltage or the bus common-mode voltage is abnormal in sampling, the frequency converter controller judges that the sampling is abnormal, and the unit is stopped in a fault but does not trigger energy feedback; the problem of inaccurate sampling caused by poor contact of the sampling line can be avoided, so that the accuracy of the sampling circuit is improved.
Through a large amount of experimental verifications, adopt the technical scheme of the utility model, through carrying out the difference sampling to busbar voltage and generating line common mode voltage, according to busbar voltage and generating line common mode voltage's state, confirm the actual behavior of converter unit to in time protect when the actual behavior of converter unit appears unusually, can improve magnetic suspension centrifuge's system reliability.
According to the utility model discloses an embodiment still provides a converter corresponding to the generating line protection device of converter. The frequency converter may be capable of comprising: the bus protection device of the frequency converter is described above.
Following the green, intelligent and energy-saving times, the magnetic suspension centrifuge has developed a peak with the characteristics of oil-free, friction-free and high efficiency. The magnetic suspension centrifugal machine adopts an advanced magnetic suspension bearing technology, has no contact friction in the operation process, and greatly improves the rotating speed of the motor. In order to meet the special requirements of high rotating speed, stable floating shaft falling and the like of the magnetic suspension centrifuge, a special frequency converter for the magnetic suspension centrifuge needs to be developed. When the magnetic suspension centrifugal machine is in normal operation, if the bus voltage caused by the three-phase input power failure or other abnormal conditions is lower than the voltage threshold of the power supply of the frequency converter and the power supply of the bearing controller, the power supply of the frequency converter and the power supply of the bearing controller is lost, and the magnetic suspension bearing directly falls down to smash the shaft in a high-speed rotation state. Therefore, the special frequency converter for the magnetic suspension centrifuge needs to have an energy feedback function, so that under abnormal conditions, the energy of the idling of the motor is fed back to the bus, and the voltage of the bus is maintained above 400V until the magnetic suspension bearing stops rotating and stably falls off the shaft.
Fig. 2 is a schematic structural diagram of an embodiment of a bus voltage sampling module in a frequency converter system. In fig. 2, the rectification module adopts IGBT controllable rectification and also diode uncontrolled rectification. In the inverter system shown in fig. 2, the bus voltage is detected by the bus voltage sampling module, and the energy feedback function is triggered when the bus voltage is lower than 400V. When a certain link of bus voltage sampling is abnormal, for example, the sampling line is in poor contact, the bus voltage sampling value is 0, the actual bus voltage is 670V, energy feedback can be triggered by mistake, the bus voltage pump rises above the voltage threshold of the power supply of the frequency converter and the power supply of the bearing controller, the power supply of the frequency converter and the power supply of the bearing controller can be lost, and the magnetic suspension bearing directly drops and smashes a shaft in a high-speed rotating state. Therefore, bus voltage sampling is a crucial link, and the accuracy of bus voltage sampling must be ensured.
In some embodiments, in order to solve the problem that inaccurate bus voltage sampling leads to the false triggering energy repayment, the utility model discloses a scheme provides a bus voltage under-voltage detection and protection method for converter, can improve magnetic suspension centrifuge's system reliability, is applicable to magnetic suspension centrifuge converter control field.
The utility model discloses a scheme, through the differential sampling design of busbar voltage and generating line common mode voltage, ensures the accuracy of sampling. Therefore, by adopting the bus voltage and bus common mode voltage differential sampling design, the abnormal phenomenon that the bus voltage sampling is inaccurate due to poor contact and other factors is solved, namely the problem of inaccurate sampling caused by poor contact of a sampling line is solved, so that the accuracy of the sampling circuit is improved, and the false triggering energy feedback is prevented.
The utility model discloses a scheme takes clamping diode and bridging resistance to sample the feedforward design, can solve the abnormal phenomenon that the energy repayment leads to the bus voltage pump to rise, improves sampling interference immunity.
The utility model discloses a scheme is through judging busbar voltage and generating line common mode voltage state, confirms the unit actual motion condition, realizes the diagnosis of abnormal state and protection circuit's design. Therefore, the logic for triggering energy feedback is provided, the grounding state of the frequency converter can be detected through bus common-mode voltage differential sampling design, the problem of faults caused by the fact that the frequency converter is not grounded is solved, and the grounding state can be detected.
Fig. 3 is a schematic structural diagram of another embodiment of a bus voltage sampling module in the frequency converter system. As shown in fig. 3, the bus voltage and the bus common mode voltage are collected by a bus voltage sampling module, which is a sampling resistor plate. When one of the bus voltage or the bus common-mode voltage is abnormal in sampling, the frequency converter controller judges that the sampling is abnormal, and the unit is stopped in a fault but does not trigger energy feedback. And only when the bus voltage and the bus common-mode voltage sampling result are in an undervoltage state at the same time, the frequency converter controller judges that the unit is undervoltage, immediately enters energy feedback and is shut down due to faults. The method can avoid the problem of inaccurate sampling caused by poor contact of the sampling line, thereby improving the accuracy of the sampling circuit.
In the frequency converter system shown in fig. 3, bus protection of the common mode frequency converter of the shell ground PE by the bus voltage positive electrode DC + is added, so that the ground state can be detected, the detection of the ground state of the frequency converter can be realized, and the problem of failure caused by the non-reliable ground of the frequency converter is solved; when the bus voltage positive pole DC + or the bus voltage negative pole DC-causes inaccurate sampling due to poor contact of a sampling line, the actual bus voltage state can be judged by detecting the potential difference between the bus voltage positive pole DC + and the shell ground PE, so that the false triggering energy feedback is prevented, the system failure is prevented, the accuracy of a sampling circuit is improved, and the false triggering energy feedback is prevented.
Fig. 4 and 5 are schematic structural diagrams of an embodiment of a voltage differential sampling circuit. Differential sampling is performed by the sampling circuits shown in fig. 4 and 5, and the voltage sampling values are:
where D1 and D2 are clamping diodes to clamp the voltage between U + and U-which are the operational amplifier supply voltage ranges. The operational amplifier non-inverting input end and the inverting input end are connected across the resistor R0 to provide feedforward signals, inhibit signal overshoot and improve the anti-interference capability of the sampling circuit.
In the example shown in fig. 4 and 5, the voltage differential sampling circuit adds D1 and D2 as clamp diodes to clamp the voltage between U + and U-, which are the operational amplifier supply voltage range, and the clamp diodes prevent the voltage from exceeding the chip supply voltage.
In the examples shown in fig. 4 and 5, a cross-over resistor R0 is added to the non-inverting input terminal and the inverting input terminal of the operational amplifier, and the functions are to provide a feed-forward signal, suppress signal overshoot, and improve the anti-interference capability of the sampling circuit. The resistance R0 improves the anti-interference capability of the sampling circuit.
Fig. 6 and 7 are schematic diagrams of structures and truth tables of an embodiment of the brown-out detection protection circuit. The bus voltage under-voltage protection circuit is shown in fig. 6 and 7, and is set to be in an under-voltage state when the bus voltage is lower than 400V, and the threshold voltage is UREF1. Bus voltage sampling value and threshold voltage UREF1And after comparison, the output level signal FODC is sent to a main control chip of the frequency converter for processing. When the bus voltage sampling value UDCGreater than threshold voltage UREF1Then the output signal fo.dc is high; when the bus voltage sampling value UDCLess than threshold voltage UREF1The output signal fo.dc is low.
When the common mode voltage of the bus is set to be lower than 200V, the bus is in an undervoltage state, and the threshold voltage is UREF2. Common mode voltage sampling value and threshold voltage UREF2And after comparison, outputting a level signal FO.PE to a main control chip of the frequency converter for processing. When the common mode voltage sampling value UDC-PEGreater than threshold voltage UREF2If yes, the output signal fo.pe is high level; when the bus voltage sampling value UDC-PELess than threshold voltage UREF2The output signal fo.pe is low.
And after carrying out OR operation on the FO.DC and the FO.PE, outputting a level signal FO.TZ to a main control chip of the frequency converter for processing. When fo.dc and fo.pe are both low, the output signal fo.tz is low, triggering energy feedback. Otherwise, the output level signal fo.tz is high level, and no energy feedback is triggered. Through OR operation, the energy feedback is only started when the FO.TZ is at a low level, so that the probability of triggering the energy feedback by mistake is reduced.
In the examples shown in fig. 6 and 7, the under-voltage detection protection circuit and the truth table are used to determine the bus voltage status and the bus common-mode voltage status, and the bus voltage status and the bus common-mode voltage status are sent to the main control chip for processing after the or logic. And the undervoltage protection function is realized according to the truth table operation result by combining the comparison circuit and the truth table operation circuit.
In the above embodiment, whether the bus voltage is under-voltage is actually determined by detecting the bus voltage sampling signal and the bus common mode voltage sampling signal, or detecting 2 bus voltage sampling values may be substituted, and if both the two bus voltage sampling values are lower than the threshold voltage, it is determined that the bus voltage is under-voltage fault actually, and energy feedback is immediately performed.
When only 1 bus voltage is detected, false alarm faults caused by loose wiring and other reasons exist, therefore 1 bus voltage sampling signal is led out more as a redundancy design, and the two bus voltage sampling points are consistent. For example: collecting two paths of bus voltages as a redundancy design, wherein sampling points of the two paths of bus voltages are consistent, when any one path of bus voltage is abnormal in sampling and the other path of bus voltage is normal in sampling, reporting a bus voltage sampling abnormal fault, and not triggering energy feedback, and checking whether a bus voltage sampling module of the frequency converter is abnormal or whether the bus voltage sampling line is in poor contact; when the two paths of bus voltage sampling signals are lower than a set threshold value at the same time, energy feedback can be started, and the probability of false triggering of energy feedback is reduced.
Fig. 8 is a schematic diagram of the bus bar undervoltage protection process. As shown in fig. 8, a software processing logic flow of a bus voltage under-voltage detection and protection method for a frequency converter can include:
And 2, judging whether the FO.TZ signal is equal to 0 or not, if the FO.TZ signal is equal to 0, judging that the bus voltage is in an undervoltage state by the main control chip, immediately entering energy feedback, ensuring that the bus voltage is stably maintained above 400V until the motor stops rotating, stably dropping the shaft by the magnetic suspension bearing, and emergently stopping the unit. And if FO.TZ is equal to 1, the main control chip judges that the bus voltage is not undervoltage and does not trigger energy feedback.
And 3, judging whether the FO.DC signal is equal to 0 or not, if the FO.DC signal is equal to 0, judging that the bus voltage is abnormal by the main control chip, reporting abnormal protection of bus voltage sampling, and stopping the unit without triggering energy feedback. If fo.dc equals 1, the fo.pe signal is detected.
And 4, judging whether the FO.PE is equal to 0 or not, if the FO.PE is equal to 0, judging that the grounding is abnormal by the main control chip, reporting grounding abnormal protection, and stopping the unit without triggering energy feedback. And if the FO.PE is equal to 1, the unit is in a normal operation state, and the bus voltage and the bus common mode voltage sampling value are continuously detected.
In the above embodiments, the parameters including the specific values are exemplary, and need not be exactly equal to the corresponding values, and should be determined according to actual situations.
In the above embodiment, the IGBT controllable rectifier module used may be replaced by a diode uncontrolled rectifier module.
Since the processing and functions implemented by the frequency converter of this embodiment substantially correspond to the embodiments, principles, and examples of the apparatus shown in fig. 1, reference may be made to the related descriptions in the foregoing embodiments without details in the description of this embodiment.
Through a large amount of tests verification, adopt the technical scheme of the utility model, through to busbar voltage, and busbar common mode voltage carries out the difference sampling, according to busbar voltage and busbar common mode voltage's state, confirm the actual behavior of converter unit, in time protect when the actual behavior of converter unit appears unusually, solve factors such as bad contact and lead to the unsafe abnormal phenomenon of busbar voltage sampling, the inaccurate problem of sampling because of sampling line contact failure leads to has been solved promptly, therefore gain the accuracy that improves sampling circuit, prevent the false triggering energy repayment.
According to the embodiment of the present invention, a bus protection method corresponding to a frequency converter of the frequency converter is also provided, as shown in fig. 9, the present invention provides a schematic flow diagram of an embodiment of the method. The bus protection method of the frequency converter can be applied to a motor system such as a compressor system, and can comprise the following steps: step S110 and step S120.
In step S110, the bus voltage of the frequency converter is sampled to obtain a bus voltage sampling value and a common mode voltage sampling value.
In some embodiments, the specific process of sampling the bus voltage of the frequency converter in step S110 to obtain the bus voltage sampling value and the common mode voltage sampling value can include: sampling a bus voltage positive electrode and a bus voltage negative electrode of the frequency converter to obtain a bus voltage sampling value; and sampling the bus voltage anode of the frequency converter and the shell ground voltage to obtain a common-mode voltage sampling value.
For example: the bus protection of the common mode frequency converter of the shell ground PE by the bus voltage positive electrode DC + is increased, so that the grounding state can be detected, the grounding state of the frequency converter can be detected, and the problem of faults caused by the fact that the frequency converter cannot be grounded is solved; when the bus voltage positive pole DC + or the bus voltage negative pole DC-causes inaccurate sampling due to poor contact of a sampling line, the actual bus voltage state can be judged by detecting the potential difference between the bus voltage positive pole DC + and the shell ground PE, so that the false triggering energy feedback is prevented, the system failure is prevented, the accuracy of a sampling circuit is improved, and the false triggering energy feedback is prevented.
Therefore, by the differential sampling design of the bus voltage and the bus common-mode voltage, the bus voltage and the bus common-mode voltage are subjected to differential sampling design, the sampling accuracy is ensured, and the false triggering energy feedback is prevented.
At step S120, determining a state of the bus voltage of the frequency converter according to the bus voltage sampling value and the common mode voltage sampling value; and protecting the bus voltage of the frequency converter according to the state of the bus voltage of the frequency converter.
Therefore, the actual operation condition of the unit is determined by judging the bus voltage and the bus common-mode voltage state, the diagnosis of the abnormal state and the design of the protection circuit are realized, the accuracy of the sampling circuit can be improved, and the false triggering energy feedback is prevented.
In some embodiments, a specific process of determining the state of the bus voltage of the frequency converter according to the bus voltage sampling value and the common mode voltage sampling value in step S120 can be referred to as the following exemplary description.
Referring to fig. 10, a flowchart of an embodiment of determining the state of the bus voltage of the frequency converter in the method of the present invention is further illustrated, where the specific process of determining the state of the bus voltage of the frequency converter in step S120 may include: step S210 to step S230.
Step S210, determining whether the bus voltage sampling value is greater than a first reference voltage, and determining whether the common mode voltage sampling value is greater than a second reference voltage. Wherein the first reference voltage is such as threshold voltage UREF1) A second reference voltage, e.g. a threshold voltage, of UREF2。
Step S220, if the bus voltage sampling value is less than or equal to a first reference voltage and the common mode voltage sampling value is less than or equal to a second reference voltage, determining that the state of the bus voltage of the frequency converter is a first state.
Step S230, if the bus voltage sampling value is greater than a first reference voltage, and/or the common mode voltage sampling value is greater than a second reference voltage, determining that the state of the bus voltage of the frequency converter is a second state.
For example: in the bus voltage under-voltage protection, when the bus voltage is set to be lower than 400V, the bus voltage is in an under-voltage state, and the threshold voltage is UREF1. Bus voltage sampling value and threshold voltage UREF1After comparison, the output level signal FO.DC is sent to the frequency converterAnd the main control chip of the device carries out processing. When the bus voltage sampling value UDCGreater than threshold voltage UREF1Then the output signal fo.dc is high; when the bus voltage sampling value UDCLess than threshold voltage UREF1The output signal fo.dc is low.
When the common mode voltage of the bus is set to be lower than 200V, the bus is in an undervoltage state, and the threshold voltage is UREF2. Common mode voltage sampling value and threshold voltage UREF2And after comparison, outputting a level signal FO.PE to a main control chip of the frequency converter for processing. When the common mode voltage sampling value UDC-PEGreater than threshold voltage UREF2If yes, the output signal fo.pe is high level; when the bus voltage sampling value UDC-PELess than threshold voltage UREF2The output signal fo.pe is low.
Therefore, the bus voltage state and the bus common-mode voltage state are judged through the undervoltage detection protection circuit and the truth table, and are sent to the main control chip for processing after being subjected to OR logic; and the undervoltage protection function is realized according to the truth table operation result by combining the comparison circuit and the truth table operation circuit.
In some embodiments, in step S120, a specific process of protecting the bus voltage of the frequency converter according to the state of the bus voltage of the frequency converter can be referred to the following exemplary description.
Referring to fig. 11, the following describes a specific process of protecting the bus voltage of the frequency converter in step S120, which includes: step S310 and step S320.
Step S310, under the condition that the bus voltage state of the frequency converter is in the first state, controlling the frequency converter to enter an energy feedback process so as to stop the motor and stabilize the shaft falling of the magnetic suspension bearing.
Step S320, under the condition that the bus voltage state of the frequency converter is in a second state, if the bus voltage sampling value is greater than a first reference voltage, reporting that the bus voltage sampling of the frequency converter is abnormal and stopping the frequency converter; and if the common-mode voltage sampling value is larger than a second reference voltage, reporting that the bus voltage of the frequency converter is grounded abnormally and stopping the frequency converter.
For example: and after carrying out OR operation on the FO.DC and the FO.PE, outputting a level signal FO.TZ to a main control chip of the frequency converter for processing. When fo.dc and fo.pe are both low, the output signal fo.tz is low, triggering energy feedback. Otherwise, the output level signal fo.tz is high level, and no energy feedback is triggered. Through OR operation, the energy feedback is only started when the FO.TZ is at a low level, so that the probability of triggering the energy feedback by mistake is reduced.
Therefore, bus voltage and bus common-mode voltage are collected through a bus voltage sampling module, and the bus voltage sampling module is a sampling resistance plate; only when the bus voltage and the bus common-mode voltage sampling result are in an undervoltage state at the same time, the frequency converter controller judges that the unit is undervoltage, immediately enters energy feedback and is shut down due to faults; when one of the bus voltage or the bus common-mode voltage is abnormal in sampling, the frequency converter controller judges that the sampling is abnormal, and the unit is stopped in a fault but does not trigger energy feedback; the problem of inaccurate sampling caused by poor contact of the sampling line can be avoided, so that the accuracy of the sampling circuit is improved.
Since the processing and functions implemented by the method of this embodiment basically correspond to the embodiments, principles and examples of the frequency converter, reference may be made to the related descriptions in the foregoing embodiments without being detailed in the description of this embodiment.
Through a large number of tests, the technical scheme of the embodiment is adopted, differential sampling is carried out on the bus voltage and the bus common-mode voltage, the actual operation condition of the frequency converter unit is determined according to the states of the bus voltage and the bus common-mode voltage, so that the actual operation condition of the frequency converter unit is timely protected when the actual operation condition of the frequency converter unit is abnormal, the grounding state of the frequency converter can be detected, the problem that the frequency converter cannot be grounded is solved, the grounding state can be detected, and the detection reliability of the bus voltage is improved.
In summary, it is readily understood by those skilled in the art that the advantageous modes described above can be freely combined and superimposed without conflict.
The above description is only an example of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the claims of the present invention.
Claims (6)
1. A bus bar protection device of a frequency converter is characterized by comprising: a sampling unit and a control unit; wherein the content of the first and second substances,
the sampling unit is configured to sample the bus voltage of the frequency converter to obtain a bus voltage sampling value and a common-mode voltage sampling value;
the control unit is configured to determine the state of the bus voltage of the frequency converter according to the bus voltage sampling value and the common-mode voltage sampling value; and protecting the bus voltage of the frequency converter according to the state of the bus voltage of the frequency converter.
2. The bus bar protection device of a frequency converter according to claim 1, wherein the sampling unit comprises: a first differential sampling circuit and a second differential sampling circuit;
the sampling unit samples the bus voltage of the frequency converter, and comprises:
the first differential sampling circuit is configured to sample a bus voltage positive electrode and a bus voltage negative electrode of the frequency converter to obtain a bus voltage sampling value;
the second differential sampling circuit is configured to sample a bus voltage positive electrode of the frequency converter and a shell ground voltage to obtain a common-mode voltage sampling value.
3. The bus bar protection device of the frequency converter according to claim 2, wherein the first differential sampling circuit and the second differential sampling circuit are identical in structure; the first differential sampling circuit includes: the differential sampling circuit comprises a differential sampling circuit body, a clamping module and a feedforward module; wherein the content of the first and second substances,
the number of the clamping modules is two, and one of the two clamping modules is arranged at the inverting input end of the differential sampling circuit body; the other clamping module of the two clamping modules is arranged at the non-inverting input end of the differential sampling circuit body;
the feedforward module is bridged at the inverting input end and the non-inverting input end of the differential sampling circuit body.
4. The bus bar protection device of the frequency converter according to any one of claims 1 to 3, wherein the control unit determines the state of the bus bar voltage of the frequency converter according to the bus bar voltage sampled value and the common mode voltage sampled value, including:
determining whether the bus voltage sampling value is greater than a first reference voltage, and determining whether the common mode voltage sampling value is greater than a second reference voltage;
if the bus voltage sampling value is less than or equal to a first reference voltage and the common-mode voltage sampling value is less than or equal to a second reference voltage, determining that the state of the bus voltage of the frequency converter is a first state;
and if the bus voltage sampling value is greater than a first reference voltage and/or the common-mode voltage sampling value is greater than a second reference voltage, determining that the state of the bus voltage of the frequency converter is a second state.
5. The bus bar protection device of the frequency converter according to claim 4, wherein the control unit protects the bus bar voltage of the frequency converter according to the state of the bus bar voltage of the frequency converter, and comprises:
under the condition that the bus voltage state of the frequency converter is in a first state, controlling the frequency converter to enter an energy feedback process;
under the condition that the bus voltage state of the frequency converter is in a second state, if the bus voltage sampling value is larger than a first reference voltage, reporting that the bus voltage sampling of the frequency converter is abnormal and stopping the frequency converter; and if the common-mode voltage sampling value is larger than a second reference voltage, reporting that the bus voltage of the frequency converter is grounded abnormally and stopping the frequency converter.
6. A frequency converter, comprising: a bus bar protection device of a frequency converter according to any one of claims 1 to 5.
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| CN202022040573.0U CN213341630U (en) | 2020-09-17 | 2020-09-17 | Bus protection device of frequency converter and frequency converter |
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| CN202022040573.0U CN213341630U (en) | 2020-09-17 | 2020-09-17 | Bus protection device of frequency converter and frequency converter |
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| CN213341630U true CN213341630U (en) | 2021-06-01 |
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