CN108574427B - Inverter braking unit and inverter - Google Patents

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

Inverter braking unit and inverter

technical field

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

Background technique

Inverter has a wide range of uses in the field of industrial control. Many applications of inverter-driven motors require braking function, that is, the ability to quickly stop and quickly decelerate, which also includes rapid shutdown of fans and pumps. When the motor is braked, the deceleration of the motor makes the regenerative energy fed back to the DC bus of the inverter through the inverter circuit of the inverter, resulting in an increase in the bus voltage. When the bus voltage exceeds the limit, it may cause damage to the inverter.

In order to solve this problem, a method that is widely used in industrial applications is to add a braking circuit to the DC bus of the inverter. The braking circuit usually includes series-connected braking resistors and IGBT braking tubes. When the motor is braking, the IGBT brake tube is turned on and the braking resistor is connected to the circuit, so that the regenerative energy fed back to the DC bus of the inverter is consumed in the form of heat generated by the current flowing through the braking resistor, thus protecting the inverter. and shorten the braking time of the motor.

However, in practical application, it is found that the braking circuit will also fail, which will also cause the safety hazard of the inverter system. When the braking resistor or IGBT brake tube is open, the braking circuit is not connected to the inverter circuit, and it does not play the role of braking protection, which may cause damage to the inverter; and when the IGBT brake tube is short-circuited, the The IGBT brake tube is always on, so that the braking resistor is always energized. Long-term energization and heating may cause the braking resistor to burn out and possibly cause a fire.

For this reason, those skilled in the art are still working on finding other solutions for the braking of the frequency converter.

SUMMARY OF THE INVENTION

In view of this, the present invention proposes a frequency converter braking unit on the one hand, and a frequency converter on the other hand, which is used to meet the braking requirements of the motor and improve the service life of the braking circuit and the frequency converter.

A frequency converter braking unit provided by the present invention includes:

a main braking circuit, comprising: a main braking resistor and an IGBT braking tube; the main braking resistor and the IGBT braking tube are connected in series between the DC bus of a frequency converter;

a bypass circuit, comprising: an auxiliary braking resistor and a normally open contactor switch; after the auxiliary braking resistor and the normally open contactor switch are connected in series, they are connected in parallel with the IGBT brake tube; and

a control driving module, which is configured to control the IGBT brake tube to work when the voltage between the DC bus bars of the frequency converter is higher than a set first voltage threshold; When the voltage is higher than the set second voltage threshold, the normally open contactor switch is controlled to be closed, and the IGBT brake tube is controlled to be disconnected; wherein the second voltage threshold is greater than the first voltage threshold.

It can be seen from the above solution that since a bypass circuit is set for the IGBT brake tube in the embodiment of the present invention, when the braking power is greater than a set power threshold, the bypass circuit can be used instead of the IGBT brake tube for control. Therefore, the IGBT brake tube can be protected to the greatest extent from overheating or overcurrent or damage.

In one embodiment, the control and drive module is further configured to control the normally open contactor switch to be closed and the IGBT brake tube to be disconnected, if the voltage between the DC bus bars of the frequency converter drops to a set value If the third voltage threshold is determined, the IGBT brake tube is controlled to work, then the normally open contactor switch is controlled to be turned off, and finally the IGBT brake tube is controlled to be turned off; wherein the third voltage threshold is less than the first voltage threshold.

In the above scheme, in the process of controlling the IGBT brake tube to switch to the bypass circuit, by first turning on the bypass circuit and then disconnecting the IGBT brake tube, the zero-voltage pull-in of the normally open contactor switch in the bypass circuit can be realized; By first turning on the IGBT brake tube and then disconnecting the bypass circuit in the process of controlling the bypass circuit to switch to the IGBT brake tube, the zero-current disconnection of the normally open contactor switch in the bypass circuit can be realized. In this way, the requirement for the normally open contactor switch in the bypass circuit can be reduced, further reducing the cost.

In one embodiment, when controlling the IGBT brake tube to work, the control and drive module adjusts the driving signal for driving the IGBT brake tube to perform braking according to the principle of minimizing the loss of the IGBT brake tube. The duty cycle is set so that the voltage between the DC bus bars of the frequency converter is lower than the set first voltage threshold. In this solution, by adjusting the duty ratio of the driving signal for driving the IGBT brake tube to perform braking according to the principle of minimizing the loss of the IGBT brake tube, the IGBT brake tube is driven to perform braking. The signal is not fixed, so that the loss of the IGBT brake tube can be minimized under the condition that the voltage between the DC bus bars of the inverter is lower than the set second voltage threshold, which further prolongs the use of the IGBT brake tube. life.

In one embodiment, the control and drive module is further configured to, when controlling the operation of the IGBT brake tube, if the voltage between the DC buses of the frequency converter drops to a set third voltage threshold, control the The IGBT brake tube is disconnected; the third voltage threshold is smaller than the first voltage threshold. In this solution, a brake exit mechanism is set based on the IGBT brake tube, so as to return to normal operation when no braking is required.

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

The control and drive module is further configured to control the normally open contactor switch to close and control the normally closed contactor switch to open when it is determined that the IGBT brake tube is overcurrent, overheated or damaged.

In the above solution, by setting the normally closed contactor switch on the main braking circuit, when the IGBT brake tube is overcurrent, overheated or damaged, the normally open contactor switch can be controlled to close, and the normally closed contactor switch can be controlled. When the contactor switch is disconnected, the braking circuit can be switched to the bypass circuit for braking, so as to ensure the normal operation of the braking unit of the inverter. Otherwise, when the IGBT brake pipe is short-circuited, if there is no normally closed contactor switch on the main brake circuit, the brake circuit will always brake through the circuit of the IGBT brake pipe until the voltage is too low to stop.

In one embodiment, the inverter braking unit further includes: a main contactor control module, which is connected to the control end of the contactor switch in the inverter power supply circuit;

The control driving module is further configured to control the main contactor control module to open a contactor switch in the inverter power supply circuit when it is determined that the IGBT brake tube is overcurrent, overheated or damaged.

In this solution, by further setting the main contactor control module in the braking unit of the inverter, the power supply of the inverter can be disconnected through the main contactor control module when the IGBT brake tube is over-current, overheated or damaged. contactor switch in the loop to avoid further damage to the drive.

In one embodiment, the frequency converter braking unit further comprises: a passive control circuit connected between the DC bus bars of the frequency converter and configured so that the voltage between the DC bus bars of the frequency converter is higher than a set value. When the fourth voltage threshold is determined, the normally open contactor switch is controlled to be closed; the fourth voltage threshold is greater than the second voltage threshold.

In one embodiment, the passive control circuit includes: a breakdown diode and a current limiting resistor, the breakdown diode and the current limiting resistor are connected in series with the coil of the normally open contactor switch. Among them, the setting of the passive control circuit can avoid the possible damage of the inverter caused by the failure of the braking function when the drive control module is abnormal, so as to further protect the braking unit of the inverter and the inverter itself.

In one embodiment, the frequency converter braking unit further comprises: an overvoltage protection varistor connected between the DC bus bars of the frequency converter and configured so that the voltage between the DC bus bars of the frequency converter is high It is turned on when the set fifth voltage threshold is set; the fifth voltage threshold is greater than the second voltage threshold. Among them, the setting of the overvoltage protection varistor can further include the situation of high overvoltage between the DC busbars of the inverter under various circumstances, which can further protect the braking unit of the inverter and the inverter itself.

In one embodiment, the frequency converter braking unit further comprises: a power supply circuit, which is connected between the DC bus bars of the frequency converter and is configured to supply power to the control driving module. The power supply circuit in this scheme can directly use the voltage between the DC bus bars of the inverter to provide power for the control drive module, thereby saving external power.

In one embodiment, the control and drive module includes:

a voltage sampling module, which is connected between the DC buses of the frequency converter and is configured to collect the voltage between the DC buses;

A drive module, which is respectively connected to the control end of the IGBT brake tube and the coil of the normally open contactor switch, is configured to drive the IGBT brake tube and the normally open contactor switch to the control module under the control of a control module. The open contactor switch sends a drive signal; and

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

The specific embodiment in this embodiment has a simple structure and is easy to implement.

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

The control module is further configured to, when the normally open contactor switch is disconnected and the drive module is not controlled to drive the IGBT brake tube to perform braking, if it still receives the control signal collected by the current sampling module. If there is a dynamic current, it is determined that the short-circuit damage of the IGBT brake tube has occurred; in the case that the normally open contactor switch is disconnected, and the control drive module drives the IGBT brake tube for braking, if it cannot receive all the According to the braking current collected by the current sampling module, it is determined that the circuit breakage of the IGBT brake tube has occurred.

In this embodiment, by detecting the current conditions collected by the current sampling module under different conditions, it is possible to detect whether the IGBT brake tube is short-circuited or damaged by short-circuit, and the solution is simple to implement and has high accuracy.

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

The control module is further configured to control the drive module to disconnect the normally closed contactor switch when the normally open contactor switch is disconnected, and record the first voltage value V1 collected by the voltage sampling module at the first moment. Then control the drive module to close the normally closed contactor switch, and control the drive module to drive the IGBT brake tube to brake, at the second moment, record the second voltage value V2 collected by the voltage sampling module; determine the second voltage Whether the value V2 is equal to the first voltage value V1, if so, it is determined that the disconnection damage of the IGBT brake tube has occurred; in the case that the normally open contactor switch is open and the normally closed contactor switch is closed, at the third moment , record the third voltage value V3 collected by the voltage sampling module; then control the driving module to drive the IGBT brake tube to brake, and at the fourth moment, record the fourth voltage value V4 collected by the voltage sampling module; determine the fourth voltage value Whether V4 is equal to the third voltage value V3, if so, it is determined that the short-circuit damage of the IGBT brake tube has occurred; wherein, there is a difference between the second time and the first time by a first preset time; the fourth time and the third time The time difference is a second preset time period.

In this embodiment, there is no need to add a current sampling module, and it is only necessary to compare the voltage values collected by the voltage sampling module under different conditions to detect whether the IGBT brake tube is short-circuited or damaged by short-circuit, and this solution is also easy to implement.

A frequency converter provided by the present invention includes the frequency converter braking unit of any one of the above-mentioned implementations. Likewise, the frequency converter has various beneficial effects of the above-mentioned frequency converter braking unit.

Description of drawings

The above-mentioned and other features and advantages of the present invention will be more apparent to those of ordinary skill in the art by describing the preferred embodiments of the present invention in detail below with reference to the accompanying drawings, in which:

1 is a schematic structural diagram of a frequency converter braking unit in an embodiment of the present invention;

2 is a schematic structural diagram of a frequency converter braking unit in another embodiment of the present invention;

3 is a schematic structural diagram of a passive control circuit in an example of the present invention;

FIG. 4 is a schematic structural diagram of a frequency converter braking unit in another embodiment of the present invention.

Among them, the reference numerals are as follows:

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the following examples are used to further describe the present invention in detail.

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

The main braking circuit 10 includes: a main braking resistor R1 and an IGBT braking tube; the main braking resistor R1 and the IGBT braking tube are connected in series between the DC busbars P+ and P- of a frequency converter, that is, the main braking One end of the dynamic resistor R1 is connected to the positive DC bus P+ of the inverter, the other end is connected to the collector of the IGBT brake tube, and the emitter of the IGBT brake tube is connected to the negative DC bus P- of the inverter.

The bypass circuit 20 includes: an auxiliary braking resistor R2 and a normally open contactor switch K2; after the auxiliary braking resistor R2 and the normally open contactor switch K2 are connected in series, they are connected in parallel with the IGBT brake tube, that is, the auxiliary braking resistor R2 One end of the IGBT is connected to the collector of the IGBT brake tube, the other end is connected to one end of the normally open contactor switch K2, and the other end of the normally open contactor switch K2 is connected to the negative DC bus P- of the inverter.

The control and drive module 30 is respectively connected with the control terminal (eg gate) of the IGBT brake tube (IGBT) and the control terminal (eg coil) of the normally open contactor switch (K2), and is configured to When the voltage between the DC busbars P+ and P- of the inverter is higher than the set first voltage threshold, the IGBT brake tube is controlled to work; the voltage between the DC busbars P+ and P- of the inverter is higher than the set value. At the second voltage threshold, the normally open contactor switch K2 is controlled to be closed, and the IGBT brake pipe is controlled to be disconnected, so that the braking current is diverted from the IGBT brake pipe to the bypass circuit 20 . In this embodiment, when the braking power is greater than the power threshold, the purpose of controlling the normally open contactor switch K2 to be closed first, and then controlling the IGBT brake tube to be disconnected is to: switch from the IGBT brake tube to the side The zero-voltage pull-in of the normally open contactor switch K2 is realized in the process of the branch circuit 20 .

In addition, the control and drive module 30 may be further configured to determine whether the voltage between the DC busbars P+ and P- of the inverter is reduced to a set value after controlling the normally open contactor switch K2 to be closed and the IGBT brake tube to be disconnected. The third voltage threshold, if yes, control the IGBT brake tube to work, so that the braking current is diverted from the bypass circuit 20 to the IGBT brake tube, then control the normally open contactor switch K2 to disconnect, and finally control the IGBT brake tube port , thereby stopping the brake control of the inverter. Wherein, the third voltage threshold is lower than the above-mentioned first voltage threshold. In this embodiment, when the voltage between the DC busbars P+ and P- of the inverter drops to the third voltage threshold, the purpose of first controlling the IGBT brake tube to work, and then controlling the normally open contactor switch K2 to disconnect is to : In the process of switching from the bypass branch 20 to the IGBT brake tube, the zero-current disconnection of the normally open contactor switch K2 is realized.

Wherein, when controlling the IGBT brake tube to work, the control driving module 30 can adjust the duty cycle of the driving signal used to drive the IGBT brake tube for braking according to the principle of minimizing the loss of the IGBT brake tube, and make the inverter The voltage between the DC busbars P+ and P- is lower than the set first voltage threshold.

In this embodiment, when the IGBT brake tube is controlled to work, if it is monitored that the voltage between the DC bus bars P+ and P- of the inverter drops to the set third voltage threshold, the IGBT brake tube is controlled to be turned off open to stop the brake control of the inverter.

The power supply circuit 40 is connected between the DC bus bars P+ and P- of the frequency converter, and is configured to supply power to the control driving module 30 .

FIG. 2 is a schematic structural diagram of a frequency converter braking unit in another embodiment of the present invention. As shown in FIG. 2 , in addition to the main braking circuit 10 , the bypass circuit 20 , the control driving module 30 and the power supply circuit 40 , the inverter braking unit 2 may further include: a main contactor control module 50 , a Source control circuit 60 and overvoltage protection varistor MOV.

In this embodiment, the main braking circuit 10 may further include a normally closed contactor switch K1, which is connected in series with the main braking resistor R1 and the branch of the IGBT brake tube. In FIG. 2, one end of the normally closed contactor switch K1 is connected in series. It 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 tube.

Correspondingly, the control driving module 30 may be further configured to control the normally open contactor switch K2 to close and control the normally closed contactor switch K1 to open when it is determined that the IGBT brake tube is overcurrent, overheated or damaged.

In other embodiments, the 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 coil of the contactor switch (not shown in the figure) in the power supply circuit of the inverter. Accordingly, the control driving module 30 may be further configured to control the main contactor control module 50 to open the contactor switch in the inverter power supply circuit when it is determined that the IGBT brake tube is overcurrent, overheated or damaged.

In this embodiment, the passive control circuit 60 is connected between the DC busbars P+ and P- of the inverter, and is configured so that the voltage between the DC busbars P+ and P- of the inverter is higher than the set fourth When the voltage threshold is reached, control the normally open contactor switch K2 to close. Wherein, the fourth voltage threshold is greater than the above-mentioned second voltage threshold.

The passive control circuit 60 may have various specific implementations, and FIG. 3 shows a schematic structural diagram of the passive control circuit 60 in an example of the present invention. 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 with 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 inverter, the other end is connected to one end of the resistor R3, and the other end of the resistor R3 is connected to one end of the coil of the normally open contactor switch K2, the normally open contactor switch K2 The other end of the coil is connected to the negative DC bus P- of the inverter. When the voltage between the DC busbars P+ and P- of the inverter is higher than the set third voltage threshold, the breakdown diode BOD is turned on, the coil of the normally open contactor switch K2 is turned on, and the control of the normally open contactor switch K2 Contact pulls.

The overvoltage protection varistor MOV is connected between the DC busbars P+ and P- of the inverter, and is configured to be configured such that when the voltage between the DC busbars P+ and P- of the inverter is higher than the set fifth voltage threshold on. In this embodiment, the fifth voltage threshold is higher than the above-mentioned fourth voltage threshold.

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

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

FIG. 4 is a schematic structural diagram of a frequency converter braking unit in another embodiment of the present invention. As shown in FIG. 4 , the frequency converter braking unit 3 may also include each functional module in 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 also not include the current sampling module 32 .

The voltage sampling module 31 is connected between the DC bus bars P+ and P- of the frequency converter, and is configured to collect the voltage between the DC bus bars P+ and P-. The voltage sampling module 31 may have various implementation forms, such as a voltage sensor or a voltage sampling circuit.

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

The driving module 33 is respectively connected to the gate of the IGBT brake tube and the coil of the normally open contactor switch K2, and is configured to send driving signals to the IGBT brake tube 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, and the like.

The control module 34 is respectively connected with the voltage sampling module 31, the current sampling module 32 and the driving module 33, and is configured to 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, When the voltage is higher than the set first voltage threshold and the braking power is less than the power threshold, a control signal for driving the IGBT brake tube to perform braking is sent to the drive module 33; when the voltage is higher than the set second voltage threshold When the voltage threshold braking power is greater than the power threshold, a control signal for closing the normally open contactor switch K2 and disconnecting the IGBT brake tube is sequentially sent to the drive 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. When the calculated braking power is less than the set power threshold, Then send the control signal to drive the IGBT brake tube to work to the drive module 33; when the braking power is greater than the power threshold, send to the drive module 33 sequentially to close the normally open contactor switch K2 and disconnect the IGBT brake tube. control signal.

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 drive module 33 to drive the normally open contactor switch K2 to close, and then controls the drive module 33 to open The purpose of the IGBT brake tube is to realize the zero-voltage pull-in of the normally open contactor switch K2 in the process of switching from the IGBT brake tube to the bypass branch.

The control module 34 is further configured to judge whether the voltage between the DC busbars P+ and P- of the inverter is based on the voltage collected by the voltage sampling module 31 after controlling the normally open contactor switch K2 to be closed and the IGBT brake tube IGBT to be disconnected. The voltage is reduced to the set third voltage threshold. If yes, a control signal for driving the IGBT brake tube to work is sent to the drive module 33 , and a control signal for disconnecting the normally open contactor switch K2 is sent to the drive module 33 . In this embodiment, the control module 34 first controls the drive module 33 to drive the IGBT brake tube to work, and then controls the drive module to disconnect the normally open contactor switch K2 for the purpose of switching from the bypass branch 20 to the IGBT brake tube In the process of realizing the zero current disconnection of the normally open contactor switch K2.

Wherein, when the control module 34 sends a control signal for driving the IGBT brake tube to work to the drive module 33, it can control the drive module 33 to adjust the IGBT brake tube for braking according to the principle of minimizing the loss of the IGBT brake tube. The duty cycle of the driving signal is set, and the voltage between the DC busbars P+ and P- of the frequency converter is lower than the set first voltage threshold. Among them, the loss of the IGBT brake tube includes switching loss and conduction loss. When the switching frequency is high, the switching loss will increase, but the conduction loss will be smaller, and the bus voltage will be closer to a straight line during braking. On the contrary, when the switching frequency is low, the switching loss will change. Small, but the conduction loss will be larger, and the voltage fluctuation of the braking bus will be larger. In practical applications, these two factors can be comprehensively weighed according to the needs to select an appropriate switching frequency to minimize the overall loss.

When controlling the IGBT brake tube to work, if it is monitored that the voltage between the DC busbars P+ and P- of the inverter drops to the set third voltage threshold, the IGBT brake tube is controlled to be disconnected, and the inverter is stopped. brake control.

When the main braking circuit 10 includes the normally closed contactor switch K1 , the drive module 33 may be further connected to the coil of the normally closed contactor switch K1 , and is configured to send the 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 driving module 33 to close the normally open contactor switch K2 and open the normally closed contactor switch K1 when it is determined that the IGBT brake tube is overcurrent, overheated or damaged.

When the inverter braking unit includes the main contactor control module 50, the control module 34 may be further configured to control the main contactor control module 50 to disconnect the inverter when it is determined that the IGBT brake tube is overcurrent, overheated or damaged. contactor switch in the power supply circuit of the device.

In the embodiment of the present invention, the control module 34 can judge whether the IGBT brake tube is overcurrent, overheated or damaged according to the voltage condition collected by the voltage sampling module 31 , or can also judge whether the IGBT brake tube is overcurrent, overheated or damaged according to the voltage condition collected by the voltage sampling module 31 , or can also be judged according to the braking current collected by the current sampling module 32 . Determine whether the IGBT brake tube has overcurrent, overheating or damage.

For example, when judging according to the DC bus voltage, when the bypass branch 20 does not work, that is, when the normally open contactor switch K2 is disconnected, the control drive module 33 disconnects the normally closed contactor switch K1, and at the first At the moment, record the first voltage value V1 collected by the voltage sampling module 31; then control the driving module 33 to close the normally closed contactor switch K1, and control the driving module 33 to output the IGBT driving signal to the IGBT brake tube, and at the second moment, record the voltage The second voltage value V2 collected by the sampling module 31; if V2=V1, the control module 34 can determine that the breakage of the IGBT brake tube has occurred. The difference between the second moment and the first moment is a first preset time period. When the bypass branch 20 does not work, the normally closed contactor switch K1 remains closed, and the drive module 33 does not send the IGBT drive signal to the IGBT brake tube. At the third moment, the third voltage collected by the voltage sampling module 31 is recorded. After that, the control drive module 33 outputs the IGBT drive signal to the IGBT brake tube, and at the fourth moment, the fourth voltage value V4 collected by the voltage sampling module 31 is recorded; if V4=V3, the control module 34 can determine the occurrence of IGBT control. Short-circuit damage to the moving tube. The difference between the fourth moment and the third moment is a second preset time period.

For another example, when judging 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, and on the premise that there is no IGBT drive signal, if the current sampling module 32 If the braking current is still detected, the control module 34 can determine that the short-circuit damage of the IGBT brake tube occurs; when the bypass branch 20 does not work, under the premise that there is an IGBT drive signal, the current sampling module 32 cannot detect If the braking current is exceeded, the control module 34 can determine that the IGBT brake tube is damaged due to open circuit.

In addition, by comparing the current value collected by the current sampling module 32 with a set current threshold, it can be determined whether overcurrent occurs in the IGBT brake tube, that is, when the current value collected by the current sampling module 32 is greater than the set current threshold , then it is judged that the IGBT brake tube has overcurrent, otherwise, there is no overcurrent.

In addition, in other embodiments, the inverter braking unit may further include: an alarm module (not shown in the figure) connected to the control module 34 and configured to determine that the control module 34 determines that there is an overcurrent in the IGBT brake tube, In the event of overheating or damage, an alarm message is sent out through the alarm module.

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

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

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

It can be seen from the above solution that since a bypass circuit is set for the IGBT brake tube in the embodiment of the present invention, when the braking power is greater than a set power threshold, the bypass circuit can be used instead of the IGBT brake tube for control. Therefore, the IGBT brake tube can be protected to the greatest extent from overheating or overcurrent or damage.

In addition, in the process of controlling the IGBT brake tube to switch to the bypass circuit, the bypass circuit is first turned on and then the IGBT brake tube is turned off, so that the zero-voltage pull-in of the normally open contactor switch in the bypass circuit can be realized; In the process of controlling the bypass circuit to switch to the IGBT brake tube, first turn on the IGBT brake tube and then disconnect the bypass circuit, which can realize the zero-current disconnection of the normally open contactor switch in the bypass circuit. In this way, the requirement for the normally open contactor switch in the bypass circuit can be reduced, further reducing the cost.

Further, by adjusting the duty ratio of the drive signal for driving the IGBT brake tube to perform braking according to the principle of minimizing the loss of the IGBT brake tube, the driving signal for driving the IGBT brake tube to perform braking is adjusted. It is not fixed, so that the loss of the IGBT brake tube can be minimized and the service life of the IGBT brake tube can be further extended under the condition that the voltage between the DC busbars of the inverter is lower than the set second voltage threshold. .

In addition, by arranging a normally closed contactor switch on the main braking circuit, when the IGBT brake tube is overcurrent, overheated or damaged, the normally open contactor switch can be controlled to be closed, and the normally closed contactor can be controlled When the switch is disconnected, the braking circuit can be switched to the bypass circuit for braking, so as to ensure the normal operation of the braking unit of the inverter. Otherwise, when the IGBT brake pipe is short-circuited, if there is no normally closed contactor switch on the main brake circuit, the brake circuit will always brake through the circuit of the IGBT brake pipe until the voltage is too low to stop.

In addition, by further setting the main contactor control module in the inverter braking unit, when the IGBT brake tube is overcurrent, overheated or damaged, the main contactor control module can be used to disconnect the power supply circuit of the inverter. contactor switch to avoid further damage to the inverter.

Further, the setting of the passive control circuit can avoid possible damage to the inverter caused by the inability to realize the braking function when the drive control module is abnormal, thereby further protecting the braking unit of the inverter and the inverter itself.

In addition, the setting of the overvoltage protection varistor can further include the situation of high overvoltage between the DC bus of the inverter under various circumstances, which can further protect the braking unit of the inverter and the inverter itself.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the scope of the present invention. within the scope of protection.

Claims (14)

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.

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