CN112670961A - Short-circuit protection device and protection method for bus of frequency converter - Google Patents
Short-circuit protection device and protection method for bus of frequency converter Download PDFInfo
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- CN112670961A CN112670961A CN201910979256.4A CN201910979256A CN112670961A CN 112670961 A CN112670961 A CN 112670961A CN 201910979256 A CN201910979256 A CN 201910979256A CN 112670961 A CN112670961 A CN 112670961A
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Abstract
The invention provides a short-circuit protection device and a short-circuit protection method for a bus of a frequency converter, which comprise a bus short-circuit detection module, a shunt release and a circuit breaker, wherein the bus short-circuit detection module, the shunt release and the circuit breaker are arranged in the frequency converter; the control circuit judges whether the bus is short-circuited or not according to the sampled voltage and judges whether a disconnection signal is sent or not within the shortest time, so that the function of quickly protecting the short-circuit condition of the laminated bus is realized. The invention detects the short circuit fault through the voltage at the initial stage of the short circuit, the short circuit current does not rise to a larger value, and the consequence of large-area burning caused by the short circuit is avoided. The invention realizes the protection function only through a simple circuit, does not need to add a complex module, does not need to replace devices when the original state is recovered after short circuit, and reduces the manufacturing and maintenance cost.
Description
Technical Field
The invention belongs to the technical field of short circuit detection and protection, and particularly relates to a short circuit protection device and a short circuit protection method for a frequency converter bus.
Background
The frequency converter used in the field of frequency conversion and speed regulation generally comprises a rectifying module, an electrifying buffer module, a filtering energy storage module, an inversion module, a control module, a driving module and other different modules. According to the case analysis of the field damage of a plurality of frequency converters, the following results are found: when the internal devices of the modules such as the rectifying module, the power-on buffer module, the inversion module, the control module and the driving module are damaged, the internal devices are only damaged in the modules, the damage of the adjacent modules cannot be caused, and once the filtering energy storage module is short-circuited, the corresponding rectifying module, the power-on buffer module, the inversion module and the like are all damaged fatally, so that the whole frequency converter needs to be replaced. Therefore, the situation is worst when the filtering energy storage module is short-circuited, and the generated loss is the largest.
The filtering energy storage module is a concentration unit of energy and high voltage and mainly comprises three parts, namely a bus, an electrolytic capacitor and a voltage-sharing resistor. The electrolytic capacitor and the voltage-sharing resistor are designed with larger safety distance and space in the structural form to avoid the short circuit, and the electrolytic capacitor and the voltage-sharing resistor are subjected to insulation strengthening treatment at other places except the wiring terminal, so that the electrolytic capacitor and the voltage-sharing resistor cannot generate short circuit in production, transportation or severe environment. The buses are different, and the smaller the parasitic inductance of the bus is, the better the parasitic inductance of the bus is required to be, due to the requirement of the peak voltage of the IGBT (Insulated Gate Bipolar Transistor) when the IGBT is turned off, and the method for reducing the parasitic inductance can only adopt the stacked structure design for the buses. Referring to fig. 3, the stacked structure design results in very small safety distance between internal wires of the bus, and the positive wire, the middle wire and the negative wire of the bus are insulated and isolated completely by the insulation paper. The possibility that the insulating paper is cut, scratched and broken exists in the production, transportation, wiring and maintenance processes, once the insulating paper is damaged, the insulating failure generates a short circuit phenomenon, and therefore the maximum risk point of the short circuit of the filtering energy storage module is the short circuit of the laminated bus. Therefore, how to quickly protect the frequency converter in the case of short circuit of the laminated bus becomes an important research point.
For the situation of bus short circuit, the following method is generally adopted for protection at present:
1. a method of overcurrent disconnection for a power distribution circuit breaker. The conventional universal frequency converter generally has no special circuit or protection logic designed for short circuit of a bus, and can only protect the bus by means of instantaneous overcurrent of a power distribution circuit breaker configured by a user when the bus is short-circuited. This method has significant drawbacks: the current of the bus short circuit is not large in the initial stage, and the short circuit current can be reached to cause the circuit breaker to trip only when the short circuit becomes more serious after a certain time, and the time is more than 400 milliseconds. The instantaneous protection value of the circuit breaker reaches 8 times of rated current, when the input current value reaches 8 times of the protection value of the circuit breaker, an electrolytic capacitor, a rectifier bridge and the like in the frequency converter are completely damaged, and a high-voltage electric arc possibly generated during short circuit can damage the IGBT, so that the method for protecting the circuit breaker can only protect fire, personal safety and the like, and cannot protect devices of the frequency converter.
2. And judging whether the capacitance short circuit exists or not according to the saturation characteristic of the IGBT. For example, in patent No. CN102957133A, an overcurrent protection IGBT is connected in series to the negative bus, and whether the bus is overcurrent is determined by the saturation characteristics of the IGBT. The method has the advantages of high response speed and reasonable and accurate overcurrent protection value, and is far superior to the method for overcurrent through the circuit breaker. However, the disadvantages of this method are very significant: the added over-current protection IGBT has high cost, and a driver, a heat dissipation system, a connecting copper bar and the like which are matched with the IGBT to work can add extra cost to the system, and the corresponding volume can be increased; on the other hand, the method can effectively protect the capacitance short circuit problem generated in the operation process of the machine, but if the short circuit occurs in the capacitance when the machine is in a standby state, even if the capacitance starts to burn, the current value flowing through the bus is not large, and the method cannot protect the capacitance short circuit.
3. A method of connecting fuses directly in series on a bus. When the capacitor is short-circuited, the capacitor is protected by disconnecting the fuse, the method is quick in response, and software is not needed to participate in judgment and control. However, the disadvantages of this method are very significant: fuse and connection copper bar etc. can add extra cost for the system to need to change after the fuse disconnection just can normal operating, increased the maintenance cost.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: the utility model provides a short-circuit protection device and a protection method for a frequency converter bus, which are used for realizing the function of quickly protecting the short-circuit condition of a laminated bus.
The technical scheme adopted by the invention for solving the technical problems is as follows: a frequency converter bus short-circuit protection device comprises a bus short-circuit detection module, a shunt release and a circuit breaker, wherein the bus short-circuit detection module, the shunt release and the circuit breaker are arranged in a frequency converter; the frequency converter comprises a rectifying module, an electrifying buffer module, an energy storage filtering module and an inverting module which are sequentially connected in series, wherein a bus short circuit detection module is connected between the positive end and the negative end of a direct current bus of the energy storage filtering module in parallel through a detection input end and is used for detecting the voltage between the positive end and the negative end of the direct current bus and judging whether short circuit occurs or not; the bus short-circuit detection module is respectively connected with the signal input ends of the shunt release KT1 and the contactor KM1 of the power-on buffering module through the signal output end and is used for sending a disconnection signal; the shunt release KT1 is connected with the circuit breaker through a transmission mechanism and is used for breaking the circuit breaker when receiving a breaking signal; the circuit breaker comprises an incoming circuit breaker QF1 and a second circuit breaker QF2, or the circuit breaker comprises an incoming circuit breaker QF 1; the contact of the incoming line breaker QF1 is connected in series in an incoming line three-phase alternating current power supply main loop of the frequency converter, and the contact of the second breaker QF2 is connected in series in a direct current bus loop of the frequency converter and used for breaking the current flowing through a direct current bus of the frequency converter by breaking the breaker contacts; the contactor KM1 is connected in parallel at two ends of the upper electricity buffer resistor R1 and is used for closing a contact to bypass the upper electricity buffer resistor R1 when the power-on charging is finished and opening the contact when an opening signal is received, so that the current flowing through a direct current bus of the frequency converter is disconnected; the bus short circuit detection module comprises a first sampling circuit M1, a second sampling circuit M2 and a control circuit; the detection input ends of the first sampling circuit M1 and the second sampling circuit M2 are respectively connected in parallel with two ends of a first series capacitor C1 and a second series capacitor C2 of an energy storage filter module of the frequency converter, the signal output ends of the first sampling circuit M1 and the second sampling circuit M2 are respectively connected with the signal input end of a control circuit and used for sampling voltages at two ends of the energy storage filter capacitor, converting the voltages into low-voltage analog signals and sending the low-voltage analog signals to the control circuit, and the control circuit is used for presetting short-circuit threshold voltage and short-circuit threshold time, judging a short-circuit state and sending a disconnection signal.
According to the scheme, the second circuit breaker QF2 and the power-on buffer resistor R1 are sequentially connected in series with the positive end of a direct-current bus of a power-on buffer module of the frequency converter, and the shunt release KT1 is connected with the second circuit breaker QF2 through a transmission mechanism and is used for receiving a protection signal PC sent by a bus short-circuit detection module and breaking the second circuit breaker QF2 so as to break the current flowing through the power-on buffer resistor R1; the contact of the contactor KM1 is connected in parallel at two ends of a series circuit of the second breaker QF2 and the power-on buffer resistor R1, and the contactor KM1 is used for receiving a contactor signal CC sent by the bus short circuit detection module and disconnecting the contact of the contactor KM 1.
According to the scheme, the incoming line breaker QF1 comprises three switches which are respectively connected in series with three-phase input power lines L1, L2 and L3 of the frequency converter in a linked and on-off mode, the shunt release KT1 is connected with the incoming line breaker QF1 through a transmission mechanism, and the shunt release KT1 is used for receiving a protection signal PC sent by the bus short-circuit detection module, breaking the incoming line breaker QF1 to break the three-phase input power supply of the frequency converter and finally breaking the current flowing through a direct-current bus of the frequency converter.
A short-circuit protection method for a bus of a frequency converter comprises the following steps:
s1: presetting short-circuit threshold voltage U in control circuit of bus short-circuit detection moduleSAnd short circuit threshold time TS；
S2: the first sampling circuit M1 detects the voltage U obtained by the first series capacitor C1C1Converted into analog quantity signal U1And sent to the control circuit; the second sampling circuit M2 detects the voltage U obtained by the second series capacitor C2C2Converted into analog quantity signal U2And sent to the control circuit; the control circuit records the duration T of the voltage;
s3: the control circuit judges whether short circuit occurs, if short circuit does not occur, step S2 is executed; if short circuit occurs, a disconnection signal is sent to enable the protection device to complete corresponding actions, and step S4 is executed;
s4: the control circuit judges whether the short-circuit fault is eliminated; if the short-circuit fault is not eliminated, continuously sending a disconnection signal; if the short-circuit fault is eliminated, the off signal is stopped, and step S2 is executed.
Further, if the shunt release KT1 is connected to the second circuit breaker QF2, the step S3 specifically includes:
the control circuit respectively compares the voltages U1Voltage U2And short-circuit voltage threshold value USOf the value of (c), and the duration T and the short-circuit time threshold TSThe size of (2):
if U is1＞US、U2＞USAnd T > TSIf no short circuit occurs, the short circuit status is marked as A, and step S2 is executed;
if U is1＜US、U2＞USAnd T > TSJudging that the first series capacitor C1 is short-circuited, marking the short-circuit state as B, sending a protection signal PC to disconnect the shunt release KT1 and the second breaker QF2 by the control circuit, sending a contactor signal CC to disconnect the contact of the contactor KM1, and prompting a user that the first series capacitor C1 is short-circuited;
if U is1＞US、U2＜USAnd T > TSJudging that the second series capacitor C2 is short-circuited, marking the short-circuit state as C, sending a protection signal PC to disconnect the shunt release KT1 and the second breaker QF2 by the control circuit, sending a contactor signal CC to disconnect the contact of the contactor KM1, and prompting a user that the second series capacitor C2 is short-circuited;
if U is1＜US、U2＜USAnd T > TSAnd judging that the bus is directly short-circuited, marking the short-circuit state as D, sending a protection signal PC to disconnect the shunt release KT1 and the second breaker QF2 by the control circuit, sending a contactor signal CC to disconnect the contact of the contactor KM1, and prompting a user that the bus is short-circuited.
Further, if the shunt release KT1 is connected with the incoming line breaker QF1, in step S3, the specific steps are as follows:
the control circuit respectively compares the voltages U1Voltage U2And short-circuit voltage threshold value USOf the value of (c), and the duration T and the short-circuit time threshold TSThe size of (2):
if U is1＞US、U2＞USAnd T > TSIf no short circuit occurs, the short circuit status is marked as A, and step S2 is executed;
if U is1＜US、U2＞USAnd T > TSIf the first series capacitor C1 is judged to be short-circuited, the short-circuit state is marked as B, the control circuit sends a protection signal PC to disconnect the shunt release KT1 to break the incoming line breaker QF1, and a user is prompted that the first series capacitor C1 is short-circuited;
if U is1＞US、U2＜USAnd T > TSIf the second series capacitor C2 is judged to be short-circuited, the short-circuit state is marked as C, the control circuit sends a protection signal PC to disconnect the shunt release KT1 to break the incoming line breaker QF1, and a user is prompted that the second series capacitor C2 is short-circuited;
if U is1＜US、U2＜USAnd T > TSAnd judging that the bus is directly short-circuited, marking the short-circuit state as D, sending a protection signal PC by the control circuit to disconnect the shunt release KT1 to break the incoming line breaker QF1, and prompting a user that the bus is short-circuited.
The invention has the beneficial effects that:
1. according to the frequency converter bus short-circuit protection device, the sampling circuit of the capacitor voltage is added in the energy storage filtering unit configured in the conventional frequency converter, whether the capacitor voltage is lower than a set value is detected, the control circuit judges whether the bus is short-circuited according to the sampled voltage and judges whether a disconnection signal is sent in the shortest time, and therefore the function of quickly protecting the short-circuit condition of the laminated bus is achieved.
2. The short-circuit fault is detected through the voltage at the initial stage of short circuit, the response action is carried out within 1-10 milliseconds, the short-circuit current does not rise to a large value within the period of time, other devices in the frequency converter cannot be greatly damaged, and the bad influence of large-area black burning caused by short circuit is avoided.
3. The invention realizes the protection function only through a simple circuit, does not need to add a complex module, does not need to replace devices when the original state is recovered after short circuit, and reduces the manufacturing and maintenance cost.
Drawings
Fig. 1 is a circuit diagram of embodiment 1 of the present invention.
Fig. 2 is a circuit diagram of embodiment 2 of the present invention.
FIG. 3 is a diagram of the internal components and overall formation of a laminated bus bar according to an embodiment of the present invention.
Fig. 4 is a flow chart of an embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.
The frequency converter comprises a rectifying module, an electrifying buffer module, an energy storage filtering module and an inversion module which are sequentially connected in series. The circuit breaker comprises an incoming line circuit breaker QF1 and a second circuit breaker QF2, wherein the incoming line circuit breaker QF1 comprises three switches which are respectively connected in series with three-phase input power lines L1, L2 and L3 of the frequency converter in a linkage on-off mode and used for switching on, switching off and switching off three-phase alternating-current power supplies under normal and abnormal loop conditions. The rectifying module comprises a three-phase diode rectifying bridge consisting of six diodes D1-D6 and is used for converting a three-phase alternating current power supply of an incoming line into a direct current power supply. The power-on buffer module comprises a power-on buffer resistor R1 and a contactor KM1 which are connected in parallel; the power-on buffer resistor R1 is used for buffering the impact current of the direct current loop in the power-on process and charging the capacitor of the energy storage filter module; the contact of the contactor KM1 is normally open, and the contact is closed after the power-on is completed, so that the power-on buffer resistor R1 is bypassed. The energy storage filtering module comprises a first series capacitor C1 and a second series capacitor C2 which are connected in series, and a first voltage-sharing resistor R2 and a second voltage-sharing resistor R3 which are respectively connected in parallel at two ends of the first series capacitor C1 and the second series capacitor C2; the energy storage filtering module is connected in parallel between the positive end and the negative end of the direct current bus and used for smoothing the direct current power supply after filtering and rectifying. The inversion module comprises a three-phase inversion bridge consisting of six IGBTs (insulated gate bipolar transistors) Q1-Q6 and is used for converting direct-current voltage into equivalent alternating-current voltage and outputting the equivalent alternating-current voltage.
Referring to fig. 1, in embodiment 1 of the present invention, a bus short-circuit detection module is connected in parallel between the positive terminal and the negative terminal of a dc bus of an energy storage filter module through a detection input terminal, and is configured to detect a voltage between the positive terminal and the negative terminal of the dc bus and determine whether a short circuit occurs. The bus short circuit detection module comprises a first sampling circuit M1, a second sampling circuit M2 and a control circuit; the detection input ends of the first sampling circuit M1 and the second sampling circuit M2 are respectively connected in parallel with two ends of a first series capacitor C1 and a second series capacitor C2 of an energy storage filter module of the frequency converter, the signal output ends of the first sampling circuit M1 and the second sampling circuit M2 are respectively connected with the signal input end of a control circuit and used for sampling voltages at two ends of the energy storage filter capacitor, converting the voltages into low-voltage analog signals and sending the low-voltage analog signals to the control circuit, and the control circuit is used for presetting short-circuit threshold voltage and short-circuit threshold time, judging a short-circuit state and sending a disconnection signal. The bus short circuit detection module is respectively connected with signal input ends of a shunt release KT1 and a contactor KM1 through a signal output end, and the shunt release KT1 is connected with a second circuit breaker QF2 through a transmission mechanism; the second circuit breaker QF2 is a miniature circuit breaker, the contact is normally closed, and can be manually switched on and switched off, and can also be switched off by a control circuit through a shunt release KT1, and the second circuit breaker QF2 and an upper electricity buffer resistor R1 are sequentially connected in series at the positive end of a direct current bus of an upper electricity buffer module of the frequency converter; the shunt release KT1 is used for receiving a protection signal PC sent by the bus short-circuit detection module and breaking the second circuit breaker QF2, so that the current flowing through the power-on buffer resistor R1 is cut off; the contact of the contactor KM1 is connected in parallel at two ends of the series circuit of the second breaker QF2 and the upper electricity buffer resistor R1; the contactor KM1 is used for receiving a contactor signal CC sent by the bus short-circuit detection module and opening the contact of the contactor KM1 so as to break the current of the direct-current bus. A second breaker QF2 is added in a loop of a power-on buffer resistor R1 configured in a conventional frequency converter, so that the energy storage filtering unit and the incoming line side are completely disconnected physically when a bus is short-circuited, continuous energy transmission from the incoming line side to the energy storage filtering module through a contactor KM1 or the power-on buffer resistor R1 is avoided when the short-circuit occurs, and the circuit is protected from being burnt.
The single chip microcomputer is used as a control chip for controlling the current, the action time of the single chip microcomputer is 1-10 microseconds, the action time of the second breaker QF2 and the contactor KM1 is 1-10 milliseconds, the response time to a short circuit state is very short, the short circuit accident cannot be expanded, and a short circuit point does not have large-area burning traces. After the second breaker QF2 and the contactor KM1 are disconnected, the power-on buffering module is thoroughly disconnected with the energy storage filtering module at the rear stage and the input side of a user, no energy is output to the energy storage filtering module at the input side, and the safety of the energy storage filtering module and the inversion module is ensured; meanwhile, the rectifier module does not have energy to circulate, so that the rectifier module is safe. Therefore, the safety of the whole frequency converter is guaranteed, and the problems that if the bus is short-circuited in the conventional frequency converter configuration, energy is continuously input to the direct-current bus through the upper buffer resistor R1 at the input side, so that the series capacitor of the energy storage filter module is ignited and the rectifier module is damaged are solved.
Referring to fig. 2, in embodiment 2 of the present invention, the configuration of the bus short-circuit detection module and the connection relationship in the frequency converter are completely the same as those in embodiment 1, the shunt release KT1 is connected with the incoming line breaker QF1 through a transmission mechanism, and the incoming line breaker QF1 includes three switches connected in series to three-phase input power lines L1, L2, and L3 of the frequency converter respectively; the shunt release KT1 is used for receiving a protection signal PC sent by the bus short-circuit detection module, breaking the incoming line breaker QF1 so as to break a three-phase input power supply of the frequency converter, and finally breaking the current flowing through the direct-current bus of the frequency converter. The tripping time of the incoming line breaker QF1 in the embodiment reaches 100-200 milliseconds, and the protection speed is slightly slower than that in the embodiment 1, but the purpose of protecting a direct current bus can also be achieved; and after the incoming line breaker QF1 breaks the three-phase incoming line power supply, the secondary control loop of the user side is powered off, and the requirement of protecting the frequency converter and the user circuit is met.
Referring to fig. 4, a method for protecting a short circuit of a bus of a frequency converter includes the following steps:
s1: presetting short-circuit threshold voltage U in control circuit of bus short-circuit detection moduleSAnd short circuit threshold time TS。
S2: the first sampling circuit M1 detects the voltage U obtained by the first series capacitor C1C1Converted into analog quantity signal U1And sent to the control circuit; the second sampling circuit M2 detects the voltage U obtained by the second series capacitor C2C2Converted into analog quantity signal U2And sent to the control circuit; the control circuit records the duration T of the voltage.
S3: the control circuit respectively compares the voltages U1Voltage U2And short-circuit voltage threshold value USOf the value of (c), and the duration T and the short-circuit time threshold TSAccording to different connection conditions, making actions;
when the shunt release KT1 is connected with the second breaker QF2, the judgment is as follows:
if U is1＞US、U2＞USAnd T > TSIf no short circuit occurs, the short circuit status is marked as A, and step S2 is executed;
if U is1＜US、U2＞USAnd T > TSJudging that the first series capacitor C1 is short-circuited, marking the short-circuit state as B, sending a protection signal PC to disconnect the shunt release KT1 and the second breaker QF2 by the control circuit, sending a contactor signal CC to disconnect the contact of the contactor KM1, and prompting a user that the first series capacitor C1 is short-circuited;
if U is1＞US、U2＜USAnd T > TSJudging that the second series capacitor C2 is short-circuited, marking the short-circuit state as C, sending a protection signal PC to disconnect the shunt release KT1 and the second breaker QF2 by the control circuit, sending a contactor signal CC to disconnect the contact of the contactor KM1, and prompting a user that the second series capacitor C2 is short-circuited;
if U is1＜US、U2＜USAnd T > TSJudging that the bus is directly short-circuited, marking the short-circuit state as D, and sending a protection signal PC by a control circuit to disconnect the shunt excitationThe buckle KT1 breaks the second breaker QF2, sends a contactor signal CC to break a contact of the contactor KM1, and prompts a user that a bus is short-circuited;
when the shunt release KT1 is connected with the incoming line breaker QF1, the judgment is as follows:
if U is1＞US、U2＞USAnd T > TSIf no short circuit occurs, the short circuit status is marked as A, and step S2 is executed;
if U is1＜US、U2＞USAnd T > TSIf the first series capacitor C1 is judged to be short-circuited, the short-circuit state is marked as B, the control circuit sends a protection signal PC to disconnect the shunt release KT1 to break the incoming line breaker QF1, and a user is prompted that the first series capacitor C1 is short-circuited;
if U is1＞US、U2＜USAnd T > TSIf the second series capacitor C2 is judged to be short-circuited, the short-circuit state is marked as C, the control circuit sends a protection signal PC to disconnect the shunt release KT1 to break the incoming line breaker QF1, and a user is prompted that the second series capacitor C2 is short-circuited;
if U is1＜US、U2＜USAnd T > TSAnd judging that the bus is directly short-circuited, marking the short-circuit state as D, sending a protection signal PC by the control circuit to disconnect the shunt release KT1 to break the incoming line breaker QF1, and prompting a user that the bus is short-circuited.
S4: the control circuit judges whether the short-circuit fault is eliminated; if the short-circuit fault is not eliminated, a disconnection signal is continuously sent out, so that the circuit breaker can be disconnected again when a user manually closes the circuit breaker and powers on the circuit breaker; and if the short-circuit fault is eliminated, stopping sending a disconnection signal, enabling the frequency converter to normally operate after the user manually closes the circuit breaker and powers on the circuit breaker, and executing the step S2.
The above embodiments are only used for illustrating the design idea and features of the present invention, and the purpose of the present invention is to enable those skilled in the art to understand the content of the present invention and implement the present invention accordingly, and the protection scope of the present invention is not limited to the above embodiments. Therefore, all equivalent changes and modifications made in accordance with the principles and concepts disclosed herein are intended to be included within the scope of the present invention.
Claims (6)
1. The utility model provides a converter busbar short-circuit protection device which characterized in that: the system comprises a bus short-circuit detection module, a shunt release and a circuit breaker which are arranged in a frequency converter; the frequency converter comprises a rectifying module, an electrifying buffer module, an energy storage filtering module and an inverting module which are sequentially connected in series, wherein a bus short circuit detection module is connected between the positive end and the negative end of a direct current bus of the energy storage filtering module in parallel through a detection input end and is used for detecting the voltage between the positive end and the negative end of the direct current bus and judging whether short circuit occurs or not; the bus short-circuit detection module is respectively connected with the signal input ends of the shunt release KT1 and the contactor KM1 of the power-on buffering module through the signal output end and is used for sending a disconnection signal; the shunt release KT1 is connected with the circuit breaker through a transmission mechanism and is used for breaking the circuit breaker when receiving a breaking signal; the circuit breaker comprises an incoming circuit breaker QF1 and a second circuit breaker QF2, or the circuit breaker comprises an incoming circuit breaker QF 1; the contact of the incoming line breaker QF1 is connected in series in an incoming line three-phase alternating current power supply main loop of the frequency converter, and the contact of the second breaker QF2 is connected in series in a direct current bus loop of the frequency converter and used for breaking the current flowing through a direct current bus of the frequency converter by breaking the breaker contacts; the contactor KM1 is connected in parallel at two ends of the upper electricity buffer resistor R1 and is used for closing a contact to bypass the upper electricity buffer resistor R1 when the power-on charging is finished and opening the contact when an opening signal is received, so that the current flowing through a direct current bus of the frequency converter is disconnected; the bus short circuit detection module comprises a first sampling circuit M1, a second sampling circuit M2 and a control circuit; the detection input ends of the first sampling circuit M1 and the second sampling circuit M2 are respectively connected in parallel with two ends of a first series capacitor C1 and a second series capacitor C2 of an energy storage filter module of the frequency converter, the signal output ends of the first sampling circuit M1 and the second sampling circuit M2 are respectively connected with the signal input end of a control circuit and used for sampling voltages at two ends of the energy storage filter capacitor, converting the voltages into low-voltage analog signals and sending the low-voltage analog signals to the control circuit, and the control circuit is used for presetting short-circuit threshold voltage and short-circuit threshold time, judging a short-circuit state and sending a disconnection signal.
2. The short-circuit protection device for the bus of the frequency converter according to claim 1, characterized in that: the second circuit breaker QF2 and the power-on buffer resistor R1 are sequentially connected in series at the positive end of a direct-current bus of a power-on buffer module of the frequency converter, and the shunt release KT1 is connected with the second circuit breaker QF2 through a transmission mechanism and is used for receiving a protection signal PC sent by the bus short-circuit detection module and breaking the second circuit breaker QF2 so as to break the current flowing through the power-on buffer resistor R1; the contact of the contactor KM1 is connected in parallel at two ends of a series circuit of the second breaker QF2 and the power-on buffer resistor R1, and the contactor KM1 is used for receiving a contactor signal CC sent by the bus short circuit detection module and disconnecting the contact of the contactor KM 1.
3. The short-circuit protection device for the bus of the frequency converter according to claim 1, characterized in that: the incoming line breaker QF1 comprises three switches which are respectively connected in series with three-phase input power lines L1, L2 and L3 of the frequency converter in a linked and on-off mode, a shunt release KT1 is connected with the incoming line breaker QF1 through a transmission mechanism, and the shunt release KT1 is used for receiving a protection signal PC sent by the bus short-circuit detection module, breaking the incoming line breaker QF1 to break the three-phase input power supply of the frequency converter and finally breaking the current flowing through a direct-current bus of the frequency converter.
4. The method for protecting the short-circuit protection device of the frequency converter bus based on any one of claims 1 to 3 is characterized in that: the method comprises the following steps:
s1: presetting short-circuit threshold voltage U in control circuit of bus short-circuit detection moduleSAnd short circuit threshold time TS；
S2: the first sampling circuit M1 detects the voltage U obtained by the first series capacitor C1C1Converted into analog quantity signal U1And sent to the control circuit; the second sampling circuit M2 detects the voltage U obtained by the second series capacitor C2C2Converted into analog quantity signal U2And sent to the control circuit; the control circuit records the duration T of the voltage;
s3: the control circuit judges whether short circuit occurs, if short circuit does not occur, step S2 is executed; if short circuit occurs, a disconnection signal is sent to enable the protection device to complete corresponding actions, and step S4 is executed;
s4: the control circuit judges whether the short-circuit fault is eliminated; if the short-circuit fault is not eliminated, continuously sending a disconnection signal; if the short-circuit fault is eliminated, the off signal is stopped, and step S2 is executed.
5. The protection method according to claim 4, characterized in that: if the shunt release KT1 is connected to the second breaker QF2, the step S3 specifically includes:
the control circuit respectively compares the voltages U1Voltage U2And short-circuit voltage threshold value USOf the value of (c), and the duration T and the short-circuit time threshold TSThe size of (2):
if U is1＞US、U2＞USAnd T > TSIf no short circuit occurs, the short circuit status is marked as A, and step S2 is executed;
if U is1＜US、U2＞USAnd T > TSJudging that the first series capacitor C1 is short-circuited, marking the short-circuit state as B, sending a protection signal PC to disconnect the shunt release KT1 and the second breaker QF2 by the control circuit, sending a contactor signal CC to disconnect the contact of the contactor KM1, and prompting a user that the first series capacitor C1 is short-circuited;
if U is1＞US、U2＜USAnd T > TSJudging that the second series capacitor C2 is short-circuited, marking the short-circuit state as C, sending a protection signal PC to disconnect the shunt release KT1 and the second breaker QF2 by the control circuit, sending a contactor signal CC to disconnect the contact of the contactor KM1, and prompting a user that the second series capacitor C2 is short-circuited;
if U is1＜US、U2＜USAnd T > TSJudging that the bus is directly short-circuited and marking the short-circuit state as D, sending a protection signal PC by a control circuit to disconnect a shunt release KT1 and a second breaker QF2, sending a contactor signal CC to disconnect a contact of a contactor KM1 and promptingThe outdoor bus is short-circuited.
6. The protection method according to claim 4, characterized in that: if the shunt release KT1 is connected with the incoming line breaker QF1, in step S3, the specific steps are as follows:
the control circuit respectively compares the voltages U1Voltage U2And short-circuit voltage threshold value USOf the value of (c), and the duration T and the short-circuit time threshold TSThe size of (2):
if U is1＞US、U2＞USAnd T > TSIf no short circuit occurs, the short circuit status is marked as A, and step S2 is executed;
if U is1＜US、U2＞USAnd T > TSIf the first series capacitor C1 is judged to be short-circuited, the short-circuit state is marked as B, the control circuit sends a protection signal PC to disconnect the shunt release KT1 to break the incoming line breaker QF1, and a user is prompted that the first series capacitor C1 is short-circuited;
if U is1＞US、U2＜USAnd T > TSIf the second series capacitor C2 is judged to be short-circuited, the short-circuit state is marked as C, the control circuit sends a protection signal PC to disconnect the shunt release KT1 to break the incoming line breaker QF1, and a user is prompted that the second series capacitor C2 is short-circuited;
if U is1＜US、U2＜USAnd T > TSAnd judging that the bus is directly short-circuited, marking the short-circuit state as D, sending a protection signal PC by the control circuit to disconnect the shunt release KT1 to break the incoming line breaker QF1, and prompting a user that the bus is short-circuited.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201910979256.4A CN112670961A (en) | 2019-10-15 | 2019-10-15 | Short-circuit protection device and protection method for bus of frequency converter |
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| Application Number | Priority Date | Filing Date | Title |
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| CN201910979256.4A CN112670961A (en) | 2019-10-15 | 2019-10-15 | Short-circuit protection device and protection method for bus of frequency converter |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113629669A (en) * | 2021-07-23 | 2021-11-09 | 国网浙江省电力有限公司宁波供电公司 | Short-circuit current flexible limiting method based on quick switch |
| CN113644631A (en) * | 2021-09-17 | 2021-11-12 | 锦浪科技股份有限公司 | Processing method for half bus short circuit |
| WO2023082712A1 (en) * | 2021-11-12 | 2023-05-19 | 珠海格力电器股份有限公司 | Capacitor detection apparatus and method, and motor control device |
-
2019
- 2019-10-15 CN CN201910979256.4A patent/CN112670961A/en active Pending
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113629669A (en) * | 2021-07-23 | 2021-11-09 | 国网浙江省电力有限公司宁波供电公司 | Short-circuit current flexible limiting method based on quick switch |
| CN113644631A (en) * | 2021-09-17 | 2021-11-12 | 锦浪科技股份有限公司 | Processing method for half bus short circuit |
| WO2023082712A1 (en) * | 2021-11-12 | 2023-05-19 | 珠海格力电器股份有限公司 | Capacitor detection apparatus and method, and motor control device |
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