CN108574427B

CN108574427B - Frequency converter brake unit and frequency converter

Info

Publication number: CN108574427B
Application number: CN201710142898.XA
Authority: CN
Inventors: 赵妍峰; 姚吉隆; 石磊; 刘泽伟
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 2017-03-10
Filing date: 2017-03-10
Publication date: 2022-06-28
Anticipated expiration: 2037-03-10
Also published as: CN108574427A

Abstract

The invention discloses a frequency converter brake unit and a frequency converter. Wherein, converter brake unit includes: a main braking circuit comprising: a main brake resistor and an IGBT brake pipe; the main brake resistor and the IGBT brake pipe are connected in series between direct current buses of the frequency converter; a bypass circuit, comprising: an auxiliary brake resistor and a normally open contactor switch; the auxiliary brake resistor is connected in series with the normally open contactor switch and then connected in parallel with the IGBT brake pipe; and a control driving module, which is configured to control the IGBT brake pipe to work when the voltage between the direct current buses of the frequency converter is higher than a set first voltage threshold value; when the voltage between the direct current buses of the frequency converter is higher than a set second voltage threshold value, controlling the switch of the normally open contactor to be closed, and controlling the IGBT brake pipe to be disconnected; wherein the second voltage threshold is greater than the first voltage threshold. The technical scheme of the invention can meet the braking requirement of the motor and prolong the service life of the braking circuit and the frequency converter.

Description

Frequency converter brake unit and frequency converter

Technical Field

The invention relates to a frequency converter, in particular to a frequency converter brake unit and a frequency converter.

Background

The frequency converter has wide application in the field of industrial control, and the application occasions of a plurality of frequency converter driving motors need to have the braking function, namely the capability of quick stop and quick speed reduction, and the application occasions also comprise the application occasions of quick stop of fans and pumps. When the motor is braked, the deceleration operation of the motor enables the regenerated energy to be fed back to a direct current bus of the frequency converter through an inverter circuit of the frequency converter, and the voltage of the bus is increased. When the bus voltage exceeds the limit value, the frequency converter may be damaged.

To solve this problem, one method that is currently widely used in industrial applications is to add a braking circuit to the dc bus of the frequency converter, the braking circuit usually comprising a braking resistor and an IGBT braking pipe connected in series. When the motor brakes, the IGBT brake pipe is conducted to connect the brake resistor into the circuit, so that the regenerative energy fed back to the direct-current bus of the frequency converter is consumed in the form that the current flows through the brake resistor to generate heat, the effect of protecting the frequency converter is achieved, and the braking time of the motor is shortened.

However, in practical application, a brake circuit is found to have a fault, which also causes a potential safety hazard of the frequency converter system. When the brake resistor or the IGBT brake pipe is opened, the brake circuit is not connected with the frequency converter circuit, and the brake circuit does not play a role in brake protection, so that the frequency converter can be damaged; when the IGBT brake pipe is short-circuited, the IGBT brake pipe is always conducted, so that the brake resistor is always in a power-on state, and the brake resistor can be burnt out and a fire can be caused due to long-time power-on heating.

To this end, the person skilled in the art is also working to find other frequency converter braking solutions.

Disclosure of Invention

In view of the above, the present invention provides a frequency converter brake unit on one hand and a frequency converter on the other hand, so as to meet the braking requirement of the motor and improve the service life of the brake circuit and the frequency converter.

The invention provides a frequency converter brake unit, which comprises:

a primary braking circuit, comprising: a main brake resistor and an IGBT brake pipe; the main brake resistor and the IGBT brake pipe are connected in series between direct current buses of a frequency converter;

a bypass circuit, comprising: an auxiliary brake resistor and a normally open contactor switch; the auxiliary brake resistor is connected in series with the normally open contactor switch and then connected in parallel with the IGBT brake pipe; and

the control driving module is configured to control the IGBT brake pipe to work when the voltage between the direct current buses of the frequency converter is higher than a set first voltage threshold value; when the voltage between the direct current buses of the frequency converter is higher than a set second voltage threshold value, controlling the switch of the normally open contactor to be closed, and controlling the IGBT brake pipe to be disconnected; wherein the second voltage threshold is greater than the first voltage threshold.

In the scheme, the bypass circuit is arranged for the IGBT brake pipe in the embodiment of the invention, and when the braking power is greater than a set power threshold value, the bypass circuit can be used for braking instead of the IGBT brake pipe, so that the IGBT brake pipe can be protected to the maximum extent from being overheated, overcurrent or damaged and the like.

In one embodiment, the control driving module is further configured to, after controlling the normally open contactor switch to be closed and the IGBT brake pipe to be opened, if the voltage between the dc buses of the frequency converter is reduced to a third voltage threshold, control the IGBT brake pipe to operate, then control the normally open contactor switch to be opened, and finally control the IGBT brake pipe to be opened; wherein the third voltage threshold is less than the first voltage threshold.

In the scheme, the zero-voltage attraction of the normally open contactor switch in the bypass circuit can be realized by firstly switching on the bypass circuit and then switching off the IGBT brake pipe in the process of controlling the IGBT brake pipe to be switched to the bypass circuit; in the process of controlling the bypass circuit to be switched to the IGBT brake pipe, the IGBT brake pipe is firstly switched on and then the bypass circuit is switched off, so that zero current switching-off of a normally open contactor switch in the bypass circuit can be realized. Thus, the requirement for the normally open contactor switch in the bypass circuit can be reduced, and the cost is further reduced.

In one embodiment, when the control driving module controls the IGBT brake pipe to operate, the control driving module adjusts a duty ratio of a driving signal for driving the IGBT brake pipe to perform braking according to a principle that a loss of the IGBT brake pipe is minimized, and makes a voltage between dc buses of the frequency converter lower than a set first voltage threshold. In the scheme, the duty ratio of the driving signal for driving the IGBT brake pipe to brake is adjusted according to the principle that the loss of the IGBT brake pipe is the lowest, so that the driving signal for driving the IGBT brake pipe to brake is not fixed and unchanged, the loss of the IGBT brake pipe is the lowest under the condition that the voltage between the direct current buses of the frequency converter is lower than the set second voltage threshold, and the service life of the IGBT brake pipe is further prolonged.

In one embodiment, the control driving module is further configured to control the IGBT brake pipe to be turned off if the voltage between the dc buses of the frequency converter is reduced to a third voltage threshold when the IGBT brake pipe is controlled to operate; the third voltage threshold is less than the first voltage threshold. In the scheme, a brake quitting mechanism is arranged on the basis of the IGBT brake pipe, so that normal operation can be recovered when braking is not needed.

In one embodiment, the main brake circuit further comprises a normally closed contactor switch connected in series in a branch of the main brake resistor and the IGBT brake pipe;

the control driving module is further configured to control the normally open contactor switch to be closed and the normally closed contactor switch to be opened when the IGBT brake pipe is determined to be over-current, over-heat or damaged.

In the scheme, the normally closed contactor switch is arranged on the main brake circuit, so that when an IGBT brake pipe is over-current, over-heat or damaged, the normally open contactor switch is controlled to be closed, the normally closed contactor switch is controlled to be opened, the brake loop can be switched to the bypass loop to brake, and the normal work of the frequency converter brake unit can be guaranteed. Otherwise, when the IGBT brake pipe is short-circuited, if no normally closed contactor switch on the main brake circuit exists, the brake circuit can brake through the circuit of the IGBT brake pipe until the voltage is too low and the machine is stopped.

In one embodiment, the inverter brake unit further comprises: the main contactor control module is connected with the control end of a contactor switch in the frequency converter power supply loop;

the control drive module is further configured to control the main contactor control module to open the contactor switch in the frequency converter power supply loop when the IGBT brake pipe is determined to be over-current, over-heat or damaged.

According to the scheme, the main contactor control module is further arranged in the frequency converter brake unit, so that when the IGBT brake pipe is in overcurrent, overheat or damage, the contactor switch in the frequency converter power supply loop can be disconnected through the main contactor control module, and the frequency converter is prevented from being damaged continuously.

In one embodiment, the inverter brake unit further comprises: a passive control circuit connected between the direct current buses of the frequency converter and configured to control the normally open contactor switch to be closed when the voltage between the direct current buses of the frequency converter is higher than a set fourth voltage threshold; the fourth voltage threshold is greater than the second voltage threshold.

In one embodiment, the passive control circuit includes: the breakdown diode is connected with the current-limiting resistor in series and then connected with a coil of the normally-open contactor switch. The passive control circuit can avoid possible damage of the frequency converter caused by the fact that the brake function cannot be realized when the drive control module is abnormal, so that the brake unit of the frequency converter and the frequency converter can be further protected.

In one embodiment, the inverter brake unit further comprises: an overvoltage protection varistor connected between the dc busbars of the frequency converter and configured to conduct when a voltage between the dc busbars of the frequency converter is higher than a set fifth voltage threshold; the fifth voltage threshold is greater than the second voltage threshold. The overvoltage protection piezoresistor can further protect the frequency converter brake unit and the frequency converter per se under the condition of higher overvoltage among direct-current buses of the frequency converter under various conditions.

In one embodiment, the inverter brake unit further comprises: a power supply circuit connected between the DC buses of the frequency converter and configured to supply power to the control drive module. The power supply circuit in the scheme can directly utilize the voltage between the direct current buses of the frequency converter to provide power for the control driving module, so that an external power supply can be saved.

In one embodiment, the control drive module comprises:

a voltage sampling module connected between the direct current buses of the frequency converter and configured to collect a voltage between the direct current buses;

a driving module respectively connected to the control terminal of the IGBT brake pipe and the coil of the normally open contactor switch, and configured to send driving signals to the IGBT brake pipe and the normally open contactor switch under the control of a control module; and

The control module is respectively connected with the voltage sampling module and the driving module, and is configured to receive the voltage collected by the voltage sampling module and send a control signal for driving the IGBT brake pipe to work to the driving module when the voltage is higher than a set first voltage threshold; and when the voltage is higher than a set second voltage threshold value, sequentially sending control signals for closing the normally open contactor switch and disconnecting the IGBT brake pipe to the driving module.

The specific implementation scheme in the embodiment is simple in structure and easy to implement.

In one embodiment, the control drive module further comprises: a current sampling module connected in series with the main brake circuit and configured to collect the brake current flowing through the main brake resistor;

the control module is also configured to determine that short-circuit damage of the IGBT brake pipe occurs if the braking current collected by the current sampling module is still received under the condition that the normally-open contactor switch is switched off and the driving module is not controlled to drive the IGBT brake pipe to brake; under the condition that a normally open contactor switch is switched off, and when a driving module is controlled to drive the IGBT brake pipe to brake, if the brake current collected by the current sampling module cannot be received, the IGBT brake pipe is determined to be broken and damaged.

In the embodiment, whether the IGBT brake pipe is short-circuited or damaged due to short circuit can be detected by detecting the current condition acquired by the current sampling module under different conditions, and the scheme is simple to implement and high in accuracy.

In one embodiment, the main brake circuit includes a normally closed contactor switch connected in series across a branch of the main brake resistor and the IGBT brake pipe;

the control module is further configured to control the driving module to open the normally closed contactor switch under the condition that the normally open contactor switch is opened, and record a first voltage value V1 collected by the voltage sampling module at a first moment; then controlling a driving module to close the normally closed contactor switch, controlling the driving module to drive the IGBT brake pipe to brake, and recording a second voltage value V2 acquired by a voltage sampling module at a second moment; judging whether the second voltage value V2 is equal to the first voltage value V1, and if so, determining that the open-circuit damage of the IGBT brake pipe occurs; under the condition that the normally open contactor switch is opened and the normally closed contactor switch is closed, recording a third voltage value V3 acquired by the voltage sampling module at a third moment; then controlling a driving module to drive the IGBT brake pipe to brake, and recording a fourth voltage value V4 acquired by a voltage sampling module at a fourth moment; judging whether the fourth voltage value V4 is equal to the third voltage value V3, and if so, determining that short-circuit damage of the IGBT brake pipe occurs; the difference between the second moment and the first moment is a first preset duration; the difference between the fourth moment and the third moment is a second preset duration.

In the embodiment, a current sampling module is not required to be added, only the voltage values acquired by the voltage sampling module under different conditions are required to be compared, whether short circuit or short circuit damage occurs to the IGBT brake pipe can be detected, and the scheme is also easy to realize.

The invention provides a frequency converter, which comprises a frequency converter brake unit of any one of the above implementation modes. Also, the inverter has various advantageous effects of the inverter braking unit described above.

Drawings

The foregoing and other features and advantages of the invention will become more apparent to those skilled in the art to which the invention relates upon consideration of the following detailed description of a preferred embodiment of the invention with reference to the accompanying drawings, in which:

FIG. 1 is a schematic structural diagram of a brake unit of a frequency converter according to an embodiment of the present invention;

FIG. 2 is a schematic structural diagram of a brake unit of a frequency converter according to another embodiment of the present invention;

FIG. 3 is a schematic diagram of a passive control circuit according to an example of the present invention;

fig. 4 is a schematic structural diagram of a brake unit of a frequency converter according to another embodiment of the present invention.

Wherein the reference numbers are as follows:

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail by referring to the following examples.

Fig. 1 is a schematic structural diagram of a brake unit of a frequency converter according to an embodiment of the present invention. As shown in fig. 1, the inverter brake unit 1 may include: a main braking circuit 10, a bypass circuit 20, a control drive module 30 and a power supply circuit 40.

Wherein, main braking circuit 10 includes: a main brake resistor R1 and an IGBT brake pipe; the main brake resistor R1 and the IGBT brake pipe are connected in series between the direct current bus P + and P-of a frequency converter, namely, one end of the main brake resistor R1 is connected with the positive direct current bus P + of the frequency converter, the other end is connected with the collector electrode of the IGBT brake pipe, and the emitter electrode of the IGBT brake pipe is connected with the negative direct current bus P-of the frequency converter.

The bypass circuit 20 includes: an auxiliary brake resistor R2 and a normally open contactor switch K2; the auxiliary brake resistor R2 and the normally open contactor switch K2 are connected in series and then connected in parallel with the IGBT brake pipe, namely, one end of the auxiliary brake resistor R2 is connected with the collector of the IGBT brake pipe, the other end of the auxiliary brake resistor R2 is connected with one end of the normally open contactor switch K2, and the other end of the normally open contactor switch K2 is connected with the negative direct current bus P-of the frequency converter.

The control driving module 30 is respectively connected with a control end (such as a grid) of the IGBT brake pipe (IGBT) and a control end (such as a coil) of the normally-open contactor switch (K2), and is configured to control the IGBT brake pipe to work when the voltage between a direct current bus P + and a direct current bus P-of the frequency converter is higher than a set first voltage threshold; and when the voltage between the direct current bus P + and the direct current bus P-of the frequency converter is higher than a set second voltage threshold value, controlling the switch K2 of the normally open contactor to be closed, and controlling the IGBT brake pipe to be opened, so that the brake current is diverted to the bypass circuit 20 by the IGBT brake pipe. In this embodiment, when the braking power is greater than the power threshold, the normally open contactor switch K2 is controlled to be closed first, and then the IGBT braking pipe is controlled to be opened, so as to: zero voltage pull-in of the normally open contactor switch K2 is achieved during switching from the IGBT brake pipe to the bypass branch 20.

In addition, the control driving module 30 may be further configured to determine whether the voltage between the dc bus P +, P-of the frequency converter is reduced to a third voltage threshold after controlling the normally open contactor switch K2 to be closed and the IGBT brake pipe to be opened, and if so, control the IGBT brake pipe to operate, so that the braking current is diverted from the bypass circuit 20 to the IGBT brake pipe, then control the normally open contactor switch K2 to be opened, and finally control the IGBT brake pipe port, so as to stop the braking control of the frequency converter. Wherein the third voltage threshold is lower than the first voltage threshold. In this embodiment, when the voltage between the dc bus P +, P-of the frequency converter is reduced to the third voltage threshold, the IGBT brake pipe is controlled to work first, and then the normally open contactor switch K2 is controlled to be turned off, so as to: zero current opening of the normally open contactor switch K2 is achieved during switching to the IGBT brake pipe by the bypass branch 20.

When the control driving module 30 controls the IGBT brake pipe to work, the duty ratio of the driving signal for driving the IGBT brake pipe to brake may be adjusted according to the principle that the loss of the IGBT brake pipe is the lowest, and the voltage between the dc bus P +, P-of the frequency converter is lower than the set first voltage threshold.

In this embodiment, when the IGBT brake pipe is controlled to operate, if it is monitored that the voltage between the dc bus P + and P-of the frequency converter decreases to the third voltage threshold, the IGBT brake pipe is controlled to be turned off, and the brake control of the frequency converter is stopped.

The supply circuit 40 is connected between the dc busses P +, P-of the frequency converter and is configured to supply power to the control drive module 30.

Fig. 2 is a schematic structural diagram of a brake unit of a frequency converter according to another embodiment of the present invention. As shown in fig. 2, the inverter brake unit 2 may further include, in addition to the main brake circuit 10, the bypass circuit 20, the control drive module 30, and the power supply circuit 40: a main contactor control module 50, a passive control circuit 60 and an over-voltage protection varistor MOV.

In this embodiment, the main brake circuit 10 may further include a normally closed contactor switch K1 connected in series to a branch of the main brake resistor R1 and the IGBT brake pipe, and in fig. 2, one end of the normally closed contactor switch K1 is connected to the non-positive dc bus P + connection end of R1, and the other end is connected to the collector of the IGBT brake pipe.

Accordingly, the control drive module 30 may be further configured to control the normally open contactor switch K2 to close and the normally closed contactor switch K1 to open when it is determined that the IGBT brake pipe is over-current, over-temperature, or damaged.

In other embodiments, normally closed contactor switch K1 may not be used.

In this embodiment, the main contactor control module 50 is configured to be connected to the coils of a contactor switch (not shown) in the inverter supply circuit. Accordingly, the control drive module 30 may be further configured to control the main contactor control module 50 to open the contactor switches in the inverter supply circuit upon determining that the IGBT brake pipe is over-current, over-temperature, or damaged.

In this embodiment, the passive control circuit 60 is connected between the dc bus P +, P-of the inverter and is configured to control the normally open contactor switch K2 to close when the voltage between the dc bus P +, P-of the inverter is higher than a set fourth voltage threshold. Wherein the fourth voltage threshold is greater than the second voltage threshold.

There are many specific implementations of the passive control circuit 60, and a schematic diagram of the passive control circuit 60 according to an example of the present invention is shown in fig. 3. As shown in fig. 3, the passive control circuit 60 may include a breakdown diode BOD and a current limiting resistor R3, the breakdown diode BOD and the current limiting resistor R3 are connected in series and then connected to the coil of the normally open contactor switch K2, that is, one end of the breakdown diode BOD is connected to the positive dc bus P + of the frequency converter, the other end is connected to one end of the resistor R3, the other end of the resistor R3 is connected to one end of the coil of the normally open contactor switch K2, and the other end of the coil of the normally open contactor switch K2 is connected to the negative dc bus P-of the frequency converter. When the voltage between the direct current bus P + and P-of the frequency converter is higher than a set third voltage threshold value, the breakdown diode BOD is conducted, the coil of the normally open contactor switch K2 is conducted, and the contact attraction of the normally open contactor switch K2 is controlled.

An overvoltage protection varistor MOV is connected between the dc rails P +, P-of the frequency converter and is designed to switch on when the voltage between the dc rails P +, P-of the frequency converter is higher than a set fifth voltage threshold. In this embodiment, the fifth voltage threshold is higher than the fourth voltage threshold.

In other embodiments, the main contactor control module 50, the passive control circuit 60 and the over-voltage protection varistor MOV may be set according to actual requirements, and may include any one or two of the three, for example.

In addition, the control and driving module 30 may have various internal implementation forms as long as it can implement the control and driving functions described above. For convenience of implementation, one of the implementation structures is listed below.

Fig. 4 is a schematic structural diagram of a brake unit of a frequency converter according to another embodiment of the present invention. As shown in fig. 4, the inverter brake unit 3 can likewise comprise the individual functional modules of fig. 2. In addition, the control driving module 30 may specifically include: a voltage sampling module 31, a current sampling module 32, a driving module 33 and a control module 34. In other embodiments, the inverter braking unit may not include the current sampling module 32.

The voltage sampling module 31 is connected between the dc buses P + and P-of the frequency converter, and is configured to collect the voltage between the dc buses P + and P-. The voltage sampling module 31 may be implemented in various forms, and may be, for example, a voltage sensor or a voltage sampling circuit.

The current sampling module 32 is connected in series with the main brake circuit 10 and is configured to collect the brake current flowing through the main brake resistor R1. The current sampling module 32 may be implemented in various forms, and may be, for example, a current sensor or a current sampling circuit.

The driving module 33 is connected to the gate of the IGBT brake pipe and the coil of the normally open contactor switch K2, respectively, and is configured to send driving signals to the IGBT brake pipe and the normally open contactor switch K2 under the control of the control module 34. The driving module 33 may be various driving circuits capable of driving.

The control module 34 is connected to the voltage sampling module 31, the current sampling module 32 and the driving module 33, and is configured to calculate braking power according to the voltage collected by the voltage sampling module 31 and the braking current collected by the current sampling module 32, and send a control signal for driving the IGBT brake pipe to perform braking operation to the driving module 33 when the voltage is higher than a set first voltage threshold and the braking power is smaller than the power threshold; and when the voltage is higher than the set second voltage threshold, the braking power is larger than the power threshold, and control signals for closing the normally open contactor switch K2 and opening the IGBT braking pipe are sequentially sent to the driving module 33.

In other embodiments, the control module 34 may also calculate the braking power according to the voltage collected by the voltage sampling module 31 and the braking current collected by the current sampling module 32, and send a control signal for driving the IGBT brake pipe to operate to the driving module 33 when the calculated braking power is smaller than a set power threshold; and when the braking power is greater than the power threshold, sequentially sending control signals for closing a normally open contactor switch K2 and disconnecting the IGBT braking pipe to the driving module 33.

In this embodiment, when the voltage collected by the voltage sampling module 31 is higher than the set first voltage threshold, the control module 34 first controls the driving module 33 to drive the normally open contactor switch K2 to be closed, and then controls the driving module 33 to open the IGBT brake pipe, so as to: and zero-voltage pull-in of the normally open contactor switch K2 is realized in the process of switching the IGBT brake pipe to the bypass branch.

The control module 34 is further configured to determine whether the voltage between the dc bus P +, P-of the frequency converter is reduced to a set third voltage threshold value according to the voltage collected by the voltage sampling module 31 after controlling the normally open contactor switch K2 to be closed and the IGBT brake pipe IGBT to be opened, and if so, send a control signal for driving the IGBT brake pipe to operate to the driving module 33, and send a control signal for opening the normally open contactor switch K2 to the driving module 33. In this embodiment, the control module 34 first controls the driving module 33 to drive the IGBT brake pipe to work, and then controls the driving module to open the normally open contactor switch K2 for the following purposes: zero current opening of the normally open contactor switch K2 is achieved during switching to the IGBT brake pipe by the bypass branch 20.

When the control module 34 sends a control signal for driving the IGBT brake pipe to operate to the driving module 33, the driving module 33 may be controlled to adjust a duty ratio of a driving signal for driving the IGBT brake pipe to perform braking according to a principle that a loss of the IGBT brake pipe is minimized, and a voltage between a dc bus P +, P-of the frequency converter is lower than a set first voltage threshold. The loss of the IGBT brake pipe comprises switching loss and conduction loss, the switching loss is increased when the switching frequency is high, but the conduction loss is small, and the bus voltage is closer to a straight line during braking; on the contrary, when the switching frequency is low, the switching loss becomes small, but the conduction loss is large, and the voltage fluctuation of the brake bus is large. In practical application, the two factors can be comprehensively weighed according to requirements to select a proper switching frequency to achieve the minimum overall loss.

When the IGBT brake pipe is controlled to work, if the voltage between the direct current bus P + and the direct current bus P-of the frequency converter is monitored to be reduced to a set third voltage threshold value, the IGBT brake pipe is controlled to be disconnected, and the brake control of the frequency converter is stopped.

Where the main braking circuit 10 includes a normally closed contactor switch K1, the drive module 33 may be further connected to a coil of a normally closed contactor switch K1 configured to send a drive signal to the normally closed contactor switch K1 under the control of the control module 34. Accordingly, the control module 34 may be further configured to control the drive module 33 to close the normally open contactor switch K2 and open the normally closed contactor switch K1 upon determining that the IGBT brake pipe is over-current, over-temperature, or damaged.

Where the inverter brake unit includes a main contactor control module 50, the control module 34 may be further configured to control the main contactor control module 50 to open the contactor switches in the inverter supply circuit upon determining that the IGBT brake pipe is over-current, over-temperature, or damaged.

In the embodiment of the present invention, the control module 34 may determine whether the IGBT brake pipe has overcurrent, overheat, or damage according to the voltage condition collected by the voltage sampling module 31, or may also determine whether the IGBT brake pipe has overcurrent, overheat, or damage according to the brake current collected by the current sampling module 32.

For example, when the bypass branch 20 is not operated, that is, when the normally open contactor switch K2 is turned off, the driving module 33 is controlled to turn off the normally closed contactor switch K1, and at a first time, a first voltage value V1 collected by the voltage sampling module 31 is recorded; then controlling the driving module 33 to close the normally closed contactor switch K1, controlling the driving module 33 to output an IGBT driving signal to the IGBT brake pipe, and recording a second voltage value V2 acquired by the voltage sampling module 31 at a second moment; if V2 is equal to V1, the control module 34 may determine that an open circuit damage of the IGBT brake pipe has occurred. And the difference between the second moment and the first moment is a first preset duration. When the bypass branch 20 does not work, the normally closed contactor switch K1 keeps a closed state, the driving module 33 does not send an IGBT driving signal to the IGBT brake pipe, and at a third moment, a third voltage value V3 collected by the voltage sampling module 31 is recorded; then, the driving module 33 is controlled to output an IGBT driving signal to the IGBT brake pipe, and at a fourth time, a fourth voltage value V4 acquired by the voltage sampling module 31 is recorded; if V4 is equal to V3, the control module 34 may determine that a short circuit damage of the IGBT brake pipe has occurred. And the difference between the fourth moment and the third moment is a second preset duration.

For another example, when the judgment is performed according to the braking current, when the bypass branch 20 does not work, that is, when the normally open contactor switch K2 is turned off, under the precondition that there is no IGBT driving signal, if the current sampling module 32 still detects the braking current, the control module 34 may judge that the short circuit damage of the IGBT braking pipe occurs; when the bypass branch 20 is not working, and under the precondition that there is an IGBT driving signal, the current sampling module 32 cannot detect the braking current, and the control module 34 can determine that the IGBT braking tube is broken.

In addition, whether the IGBT brake tube is over-current or not can be judged by comparing the current value acquired by the current sampling module 32 with a set current threshold value, that is, when the current value acquired by the current sampling module 32 is greater than the set current threshold value, it is judged that the IGBT brake tube is over-current, otherwise, no over-current occurs.

In addition, in other embodiments, the inverter braking unit may further include: an alarm module (not shown) connected to the control module 34 is configured to send an alarm message when the control module 34 determines that the IGBT brake pipe has an overcurrent, overheat, or damage condition.

In addition, in other embodiments, the inverter braking unit may further include: a temperature detection module (not shown) connected to the control module 34 is configured to detect the temperature of the IGBT brake pipe and provide the detected temperature to the control module 34, so that the control module 34 can determine whether the IGBT brake pipe is overheated according to the temperature of the IGBT brake pipe and a preset temperature threshold.

In addition, in other embodiments, the control module 34 may be further connected to an external control (not shown), and configured to receive a control signal from the external control and perform a corresponding operation according to the control signal.

The frequency converter in the embodiment of the present invention may include any of the above-described implementation forms of the frequency converter brake unit.

In addition, in the process of controlling the IGBT brake pipe to be switched to the bypass circuit, the bypass circuit is firstly switched on and then the IGBT brake pipe is switched off, so that zero-voltage attraction of a normally open contactor switch in the bypass circuit can be realized; in the process of controlling the bypass circuit to be switched to the IGBT brake pipe, the IGBT brake pipe is firstly switched on and then the bypass circuit is switched off, so that zero current switching-off of a normally open contactor switch in the bypass circuit can be realized. Thus, the requirement for the normally open contactor switch in the bypass circuit can be reduced, and the cost is further reduced.

Furthermore, the duty ratio of the driving signal for driving the IGBT brake pipe to brake is adjusted according to the principle that the loss of the IGBT brake pipe is the lowest, so that the driving signal for driving the IGBT brake pipe to brake is not fixed and unchanged, the loss of the IGBT brake pipe is the lowest under the condition that the voltage between the direct current buses of the frequency converter is lower than the set second voltage threshold, and the service life of the IGBT brake pipe is further prolonged.

In addition, through set up normally closed contactor switch on the main braking circuit, can appear overcurrent, overheated or damage when IGBT brake pipe, through control normally open contactor switch is closed, and control normally closed contactor switch disconnection, can make the braking circuit can switch to the bypass circuit and brake to can guarantee the normal work of converter braking unit. Otherwise, when the IGBT brake pipe is short-circuited, if no normally closed contactor switch on the main brake circuit exists, the brake circuit can brake through the circuit of the IGBT brake pipe until the voltage is too low and the machine stops.

In addition, by further arranging the main contactor control module in the frequency converter brake unit, when the IGBT brake pipe is in overcurrent, overheat or damage, the contactor switch in the frequency converter power supply loop can be switched off through the main contactor control module, so that the frequency converter is prevented from being damaged continuously.

Further, the arrangement of the passive control circuit can avoid possible damage of the frequency converter caused by the fact that the brake function cannot be realized when the drive control module is abnormal, so that the brake unit of the frequency converter and the frequency converter can be further protected.

In addition, the arrangement of the overvoltage protection piezoresistor can further comprise the condition that higher overvoltage occurs between direct current buses of the frequency converter under various conditions, and can further protect a braking unit of the frequency converter and the frequency converter.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.

Claims

1. A transducer brake unit, comprising:

a main braking circuit (10) comprising: a main brake resistor (R1) and an IGBT brake pipe (IGBT); the main brake resistor (R1) and the IGBT brake pipe (IGBT) are connected in series between direct current buses (P +, P-) of a frequency converter;

a bypass circuit (20) comprising: an auxiliary brake resistor (R2) and a normally open contactor switch (K2); the auxiliary brake resistor (R2) is connected in series with the normally-open contactor switch (K2) and then connected in parallel with the IGBT brake pipe (IGBT); and

A control drive module (30) configured to control the drive of the motor

When the voltage between direct current buses (P +, P-) of the frequency converter is higher than a set first voltage threshold value, controlling an IGBT brake pipe (IGBT) to work;

when the voltage between direct current buses (P +, P-) of the frequency converter is higher than a set second voltage threshold value, firstly controlling the normally open contactor switch (K2) to be closed to connect the bypass circuit (20), and then controlling the IGBT brake pipe (IGBT) to be disconnected; wherein the second voltage threshold is greater than the first voltage threshold.

2. The inverter brake unit of claim 1, wherein the control drive module (30) is configured to:

after the normally open contactor switch (K2) is controlled to be closed and the IGBT brake pipe (IGBT) is disconnected, if the voltage between the direct current buses (P +, P-) of the frequency converter is reduced to a set third voltage threshold value, the IGBT brake pipe (IGBT) is controlled to work;

then controlling the normally open contactor switch (K2) to be opened;

finally, controlling the IGBT brake pipe (IGBT) to be disconnected; wherein the third voltage threshold is less than the first voltage threshold.

3. The inverter brake unit according to claim 1, wherein the control drive module (30) adjusts the duty cycle of the drive signal for driving the IGBT brake pipe (IGBT) to brake according to the principle that the IGBT brake pipe (IGBT) has the lowest loss when controlling the IGBT brake pipe (IGBT) to operate, and the voltage between the dc buses (P +, P-) of the inverter is lower than the set first voltage threshold.

4. The inverter brake unit according to claim 1, wherein the control drive module (30) is configured to control the IGBT brake pipe (IGBT) to be turned off if the voltage across the dc bus (P +, P-) of the inverter decreases to a third voltage threshold when the IGBT brake pipe (IGBT) is controlled to operate; the third voltage threshold is less than the first voltage threshold.

5. Inverter brake unit according to claim 1, characterized in that the main brake circuit (10) further comprises a normally closed contactor switch (K1) connected in series in the branch of the main brake resistor (R1) and the IGBT brake pipe (IGBT);

the control drive module (30) is configured to control the normally open contactor switch (K2) to be closed and the normally closed contactor switch (K1) to be opened when the IGBT brake pipe (IGBT) is determined to be over-current, over-heat or damaged.

6. The inverter brake unit of claim 5, further comprising: a main contactor control module (50) connected to a control terminal of a contactor switch in the frequency converter power supply loop;

the control drive module (30) is configured to control the main contactor control module (50) to open contactor switches in the inverter supply circuit upon determining that the IGBT brake pipe (IGBT) is over-current, over-temperature or damaged.

7. The inverter brake unit of claim 1, further comprising: a passive control circuit (60) connected between the direct current busses (P +, P-) of the frequency converter, configured to control the closing of the normally open contactor switch (K2) when the voltage between the direct current busses (P +, P-) of the frequency converter is higher than a set fourth voltage threshold; the fourth voltage threshold is greater than the second voltage threshold.

8. Frequency converter brake unit according to claim 7, characterized in that the passive control circuit (60) comprises: a breakdown diode (BOD) and a current limiting resistor (R3), wherein

The breakdown diode (BOD) is connected with the current limiting resistor (R3) in series and then is connected with a coil of the normally open contactor switch (K2).

9. The inverter brake unit of claim 1, further comprising: an overvoltage protection varistor (MOV) connected between the direct current busses (P +, P-) of the frequency converter, which is configured to conduct when the voltage between the direct current busses (P +, P-) of the frequency converter is higher than a set fifth voltage threshold; the fifth voltage threshold is greater than the second voltage threshold.

10. The inverter brake unit of claim 1, further comprising: and the power supply circuit (40) is connected between the direct current buses (P +, P-) of the frequency converter and supplies power to the control driving module (30).

11. Inverter brake unit according to one of claims 1 to 10, characterized in that the control drive module (30) comprises:

the voltage sampling module (31) is connected between the direct current buses (P +, P-) of the frequency converter and is used for collecting the voltage between the direct current buses (P +, P-);

the driving module (33) is respectively connected with the control end of the IGBT brake pipe (IGBT) and the coil of the normally-open contactor switch (K2), and sends driving signals to the IGBT brake pipe (IGBT) and the normally-open contactor switch (K2) under the control of a control module (34); and

the control module (34), which is connected to the voltage sampling module (31) and the drive module (33), is designed to be able to detect the voltage

Receiving the voltage collected by the voltage sampling module (31), and sending a control signal for driving the IGBT brake pipe (IGBT) to work to the driving module (33) when the voltage is higher than a set first voltage threshold;

And when the voltage is higher than a set second voltage threshold value, sequentially sending control signals for closing the normally open contactor switch (K2) and opening the IGBT brake pipe (IGBT) to the driving module (33).

12. Inverter brake unit according to claim 11, characterized in that the control drive module (30) further comprises: a current sampling module (32) connected in series with the main brake circuit (10) and configured to sample the brake current flowing through the main brake resistor (R1);

the control module (34) is further configured to determine that short-circuit damage of the IGBT brake pipe (IGBT) occurs if the braking current collected by the current sampling module (32) is still received when the normally-open contactor switch (K2) is turned off and the driving module (33) is not controlled to drive the IGBT brake pipe (IGBT) to brake; when a normally open contactor switch (K2) is turned off and a control driving module (33) drives the IGBT brake pipe (IGBT) to brake, if the brake current collected by the current sampling module (32) cannot be received, the IGBT brake pipe (IGBT) is determined to be broken and damaged.

13. Inverter brake unit according to claim 11, characterized in that the main brake circuit (10) comprises a normally closed contactor switch (K1) connected in series on the branch of the main brake resistor (R1) and the IGBT brake pipe (IGBT);

The control module (34) is further configured to control the drive module (33) to open the normally closed contactor switch (K1) when the normally open contactor switch (K2) is opened, and to record a first voltage value V1 collected by the voltage sampling module (31) at a first moment; then controlling a driving module (33) to close the normally closed contactor switch (K1), controlling the driving module (33) to drive the IGBT brake pipe (IGBT) to brake, and recording a second voltage value V2 acquired by a voltage sampling module (31) at a second moment; judging whether the second voltage value V2 is equal to the first voltage value V1, and if so, determining that the IGBT brake pipe (IGBT) is broken; when the normally-open contactor switch (K2) is opened and the normally-closed contactor switch (K1) is closed, recording a third voltage value V3 acquired by the voltage sampling module (31) at a third moment; then controlling a driving module (33) to drive the IGBT brake pipe (IGBT) to brake, and recording a fourth voltage value V4 acquired by a voltage sampling module (31) at a fourth moment; judging whether the fourth voltage value V4 is equal to the third voltage value V3, and if so, determining that short-circuit damage of the IGBT brake pipe (IGBT) occurs; the difference between the second moment and the first moment is a first preset duration; the difference between the fourth moment and the third moment is a second preset duration.

14. Frequency converter, characterized in that it comprises a frequency converter brake unit according to any one of claims 1 to 13.