Discharge control device and method of frequency converter, frequency converter and magnetic suspension unit

Abstract

The invention discloses a discharge control device and method of a frequency converter, the frequency converter and a magnetic levitation unit, and the device comprises an auxiliary contact of a main circuit breaker, which can feed the on-off information of the main circuit breaker back to a main control unit; the main control unit receives the on-off information of the main circuit breaker fed back by the auxiliary contact of the main circuit breaker; the on-off information of the main circuit breaker is closing information of the main circuit breaker or opening information of the main circuit breaker; if the received on-off information of the main circuit breaker is the switching-on information of the main circuit breaker, the switch unit is controlled to be switched off so as to switch off a connection path between the power-off unit and the bus; and if the received on-off information of the main circuit breaker is the opening information of the main circuit breaker, the switch unit is controlled to be switched on so as to switch on the connection path between the discharge unit and the bus, so that the discharge unit discharges the voltage on the bus. According to the scheme, the working state of the discharging unit is controlled according to the switching-on and switching-off information of the frequency converter, reliable discharging of bus voltage is ensured, and power consumption is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of frequency converters, and specifically relates to a discharge control device and method of a frequency converter, a frequency converter and a magnetic levitation unit, and in particular to a bus discharge control device and method of an onboard high-power frequency converter of a magnetic levitation unit, a frequency converter and a magnetic levitation unit. Background Art

[0002] In response to green environmental protection, oil-free and frictionless high-speed magnetic levitation centrifuges have been rapidly developed. As one of the core components of the magnetic levitation centrifuge unit, the magnetic levitation centrifuge inverter needs to stably adjust the speed of the magnetic bearing of the magnetic levitation centrifuge, and its reliability is particularly important.

[0003] The input voltage of the onboard high-power inverter of the magnetic levitation unit is the three-phase AC 380V grid voltage. Its working principle is to convert the grid voltage whose original frequency and voltage cannot be changed into an AC voltage whose frequency and voltage can be changed at any time through rectification and inversion technology, and then input it into the compressor to stably adjust the speed of the magnetic levitation bearing.

[0004] Since the bus voltage of a high-power inverter is as high as 500 V (volts) or even higher, when manual operation is required inside the inverter, such as internal maintenance and fault handling, the inverter cabinet door needs to be opened for operation. The inverter needs to disconnect the unit power supply and wait until the bus voltage is completely discharged before operation can be performed inside the inverter cabinet.

[0005] However, since there is a large bus capacitor (i.e. bus capacitor) on the bus of the high-power inverter, and since it acts as a "big battery" inside the inverter, it has the same voltage as the bus. When the front end of the inverter is disconnected from the power supply, the rectifier stops working and the bus capacitor begins to discharge. However, if the bus capacitor discharges by itself, the discharge time will be very long. Therefore, in the relevant scheme, high-power inverters generally use a discharge plate connected to the bus for discharge. The power resistor on the discharge plate will accelerate the discharge of the bus capacitor to achieve rapid discharge of the bus. Although this method can accelerate the rapid discharge of the bus capacitor, since the discharge plate is connected to the bus, it consumes power every moment, which increases the invisible energy consumption of the inverter and increases the operating cost of the unit.

[0006] The above contents are only used to assist in understanding the technical solution of the present invention and do not constitute an admission that the above contents are prior art. Summary of the invention

[0007] The object of the present invention is to provide a discharge control device and method for a frequency converter, a frequency converter and a magnetic levitation unit, so as to solve the problem that a high-power frequency converter of a unit (such as a magnetic levitation unit) in a related scheme generally adopts a discharge plate connected to the bus for discharge, and the discharge plate continuously consumes power and increases the operating cost of the unit, so as to achieve the effect of ensuring reliable discharge of the bus voltage and reducing the power consumption of the discharge plate by controlling the working state of the discharge plate according to the closing and opening conditions of the frequency converter.

[0008] The present invention also aims to provide a discharge control device, method, inverter and magnetic levitation unit of a frequency converter to solve the problem that the bus discharge situation cannot be grasped in real time in related schemes, so as to display the working status of the discharge board to display the bus voltage discharge situation after the frequency converter is powered off. The operator can only operate after the bus voltage discharge is completed, thereby reducing the operating risk of the operator and improving the safety.

[0009] The present invention provides a discharge control device for a frequency converter, wherein the frequency converter has a main circuit breaker, a rectifier unit, a bus, and an inverter unit arranged in sequence; the discharge control device for the frequency converter comprises: a discharge unit, a switch unit, and a main control unit; the positive end of the bus is connected to the first connection end of the discharge unit through the switch unit; the second connection end of the discharge unit is connected to the negative end of the bus; wherein the main circuit breaker has an auxiliary contact; the auxiliary contact of the main circuit breaker can feed back the on-off information of the main circuit breaker to the main control unit; the main control unit is used to receive the main circuit breaker information; the on-off information of the main circuit breaker fed back by the auxiliary contact of the circuit breaker; the on-off information of the main circuit breaker is the closing information of the main circuit breaker, or the opening information of the main circuit breaker; if the received on-off information of the main circuit breaker is the closing information of the main circuit breaker, the switch unit is controlled to be turned off to disconnect the connection path between the discharge unit and the bus; if the received on-off information of the main circuit breaker is the opening information of the main circuit breaker, the switch unit is controlled to be turned on to connect the connection path between the discharge unit and the bus, so that the discharge unit discharges the voltage on the bus.

[0010] In some embodiments, it also includes: a display unit; the display unit has an optical fiber receiving module and a display module; the discharge unit has a power resistor module and an optical fiber transmitting module; the first connection end of the power resistor module is connected to the switch unit, and the second connection end of the power resistor module is connected to the negative end of the bus; the control end of the optical fiber transmitting module is connected to the sampling end of the power resistor module; wherein the optical fiber transmitting module is used to transmit an optical fiber signal when the discharge unit discharges the voltage on the bus; the optical fiber receiving module is used to receive the optical fiber signal and transmit the received optical fiber signal to the display module; the display module is used to light up a preset discharge indicator light based on the optical fiber signal transmitted by the optical fiber receiving module to display the state of the discharge unit discharging the voltage on the bus, until the discharge unit finishes discharging the voltage on the bus, and then the preset discharge indicator light is extinguished.

[0011] In some embodiments, the discharge unit further has a first current limiting resistor module, a second current limiting resistor module, and a voltage-stabilizing diode module; the power resistor module includes: a first resistor module, a second resistor module and a third resistor module; wherein the first connection end of the first resistor module, as the first connection end of the power resistor module, is connected to the switch unit; the second connection end of the first resistor module is connected to the first connection end of the second resistor module; the second connection end of the second resistor module is connected to the first connection end of the third resistor module; the second connection end of the third resistor module, as the second connection end of the power resistor module, is connected to the negative end of the bus; the second connection end of the second resistor module, as the sampling end of the power resistor module, is connected to the control end of the optical fiber transmitting module after passing through the first current limiting resistor module and the second current limiting resistor module; the grounding end of the optical fiber transmitting module is connected to the negative end of the bus; the common end of the first current limiting resistor module and the second current limiting resistor module is connected to the cathode of the voltage-stabilizing diode module; the anode of the voltage-stabilizing diode module is connected to the negative end of the bus.

[0012] In some embodiments, the main control unit includes: a main chip, and a control module; the switch unit includes: a first relay module; the control module includes: a second relay module; the second relay module is arranged between a preset power supply and a coil of the first relay module; the positive end of the busbar is connected to the first connection end of the discharge unit through the contact of the first relay module; the contact of the first relay module is a normally closed contact; wherein, if the main control unit receives the on-off information of the main circuit breaker as the closing information of the main circuit breaker, the switch unit is controlled to be disconnected, including: the main chip is used to generate a first control signal based on the closing information of the main circuit breaker; the control module is used to generate a first control signal based on the closing information of the main circuit breaker; The first control signal controls the second relay module to connect the connection path between the preset power supply and the coil of the first relay module, so that the coil of the first relay module is energized and the contacts of the first relay module are disconnected; the main control unit controls the switch unit to connect if the received on-off information of the main circuit breaker is the opening information of the main circuit breaker, including: the main chip is used to generate the second control signal based on the opening information of the main circuit breaker; the control module is used to control the second relay module to disconnect the connection path between the preset power supply and the coil of the first relay module based on the second control signal, so that the coil of the first relay module is de-energized and the contacts of the first relay module are closed.

[0013] In some embodiments, the control module further comprises: a signal input module, a first diode module, a switch tube module, and a third current limiting resistor module; wherein the first control signal or the second control signal is input to the control end of the switch tube module after passing through the signal input module; a preset first DC power supply is connected to the cathode of the first diode module; an anode of the first diode module is connected to the first connection end of the switch tube module; a second connection end of the switch tube module is connected to a digital ground; a preset first DC power supply is connected to the first connection end of the coil of the second relay module after passing through the third current limiting resistor module; a second connection end of the coil of the second relay module is connected to the first connection end of the switch tube module; a first connection end of the contact of the second relay module is connected to a preset power supply, a second connection end of the contact of the second relay module is suspended, and a third connection end of the contact of the second relay module is connected to the power supply end of the coil of the first relay module; wherein when the third connection end of the contact of the second relay module is connected to the first connection end, the coil of the first relay module is energized; when the third connection end of the contact of the second relay module is connected to the second connection end, the coil of the first relay module is de-energized.

[0014] In some embodiments, the control module also has: a second diode module; the second diode module includes: a light emitting diode; wherein a preset first DC power supply is connected to the anode of the second diode module after passing through the third current limiting resistor module; the cathode of the second diode module is connected to the first connection end of the coil of the second relay module.

[0015] In some embodiments, the control module further has: a filtering module; the signal input module includes: a fourth current limiting resistor module, a fifth current limiting resistor module, a first voltage dividing module, a second voltage dividing module, and a NOT gate module; wherein, the preset second DC power supply is input to the input end of the NOT gate module after passing through the first current limiting resistor module; the first control signal or the second control signal is input to the input end of the NOT gate module after passing through the second current limiting resistor module; the output end of the NOT gate module is connected to the digital ground after passing through the first voltage dividing resistor module and the second voltage dividing resistor module; the filtering module is connected in parallel with the second voltage dividing resistor module; the common end of the first voltage dividing resistor module and the second voltage dividing resistor module is connected to the control end of the switch tube module.

[0016] Matching the above device, the present invention provides a frequency converter on another aspect, including: the discharge control device of the frequency converter described above.

[0017] Matching the above-mentioned device, the present invention further provides a magnetic levitation unit, including: the discharge control device of the frequency converter described above, or including the frequency converter described above.

[0018] Matching the above-mentioned device, another aspect of the present invention provides a discharge control method of a frequency converter, comprising: feeding back the on-off information of the main circuit breaker to the main control unit through the auxiliary contacts of the main circuit breaker; receiving the on-off information of the main circuit breaker fed back by the auxiliary contacts of the main circuit breaker through the main control unit; the on-off information of the main circuit breaker is the closing information of the main circuit breaker, or the opening information of the main circuit breaker; if the received on-off information of the main circuit breaker is the closing information of the main circuit breaker, controlling the switch unit to be disconnected to disconnect the connection path between the discharge unit and the bus; if the received on-off information of the main circuit breaker is the opening information of the main circuit breaker, controlling the switch unit to be connected to connect the connection path between the discharge unit and the bus, so that the discharge unit discharges the voltage on the bus.

[0019] Therefore, the solution of the present invention is to set a switch unit (such as an external relay KM1) between the discharge plate and the bus in the inverter (such as a high-power inverter of a magnetic levitation unit) in the circuit formed by the discharge plate and the bus, specifically, to set a switch unit (such as an external relay KM1) between the discharge plate and the bus; and set a control module (such as a control circuit of the external relay KM1) for the switch unit, and the control module can be set in the main board of the inverter; when the main chip in the main board of the inverter detects that the main circuit breaker of the inverter is closed, the main chip controls the switch unit to be disconnected through the control module, so that the discharge plate is cut out when the inverter is working; when the main chip in the main board of the inverter detects that the main circuit breaker of the inverter is opened, the main chip controls the switch unit to be closed through the control module, so that the discharge plate is connected when the inverter is stopped, and the voltage on the bus of the inverter (i.e., the bus voltage) is discharged; thereby, by controlling the working state of the discharge plate according to the closing and opening conditions of the inverter, it is ensured that the bus voltage is reliably discharged and the power consumption of the discharge plate is reduced.

[0020] Furthermore, the scheme of the present invention displays the working status of the discharge board. For example, a fiber optic transmitter is provided in the discharge board. When the discharge board is discharging, a fiber optic signal is transmitted to the main control display screen of the inverter through the fiber optic transmitter so that the main control display screen lights up the discharge indicator light of the discharge board to display that the discharge board is discharging. When the discharge of the discharge board is completed, the main control display screen turns off the discharge indicator light of the discharge board to display that the discharge of the discharge board is completed. Thus, by displaying the working status of the discharge board, the discharge status of the bus voltage after the inverter is powered off is displayed, and the operator can only operate after the bus voltage is discharged, thereby reducing the operating risk of the operator and improving safety.

[0021] Other features and advantages of the present invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the present invention.

[0022] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a structural schematic diagram of an embodiment of a discharge control device for a frequency converter of the present invention;

[0024] Figure 2 It is a schematic diagram of the topological structure of the frequency converter and the discharge device;

[0025] Figure 3 Schematic diagram of the circuit principle of the discharge plate;

[0026] Figure 4 It is the schematic diagram of the control circuit principle of the discharge board;

[0027] Figure 5 This is a schematic diagram of the action flow of the discharge board when the inverter is closed;

[0028] Figure 6 This is a schematic diagram of the action flow of the discharge board when the inverter is opened;

[0029] Figure 7 It is a flow chart of an embodiment of a discharge control method for a frequency converter of the present invention. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the specific embodiments of the present invention and the corresponding drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0031] Considering that the high-power inverters of the units (such as magnetic levitation units) in the relevant schemes generally use a discharge board connected to the bus for discharge, the discharge board continuously consumes power and increases the operating cost of the unit. At the same time, there are certain safety hazards in the inverter bus discharge in the relevant schemes, because the inverter mainboard power supply is provided by the large power supply inside the inverter, and this inverter mainboard power supply is drawn from the bus. When the bus voltage drops to a certain value, the inverter mainboard power supply will no longer work, and the inverter mainboard will also stop working. Naturally, the communication between the inverter and the main control will also be disconnected. At this moment, the main control still displays the bus voltage before the communication is disconnected. Since it is impossible to obtain the real-time information of the bus voltage, the staff may start operating in the inverter cabinet before the bus discharge is completed, which poses a certain risk to personnel safety.

[0032] Therefore, the scheme of the present invention proposes a discharge control device for a frequency converter, specifically a bus discharge control device for an airborne high-power frequency converter of a magnetic levitation unit. The discharge board working state is autonomously controlled by a main chip, so as to increase the flexibility of the frequency converter bus discharge, reduce the unit operation cost, and solve the problem that the frequency converter discharge board continuously consumes power and increases the unit operation cost; and, the data is transmitted to the main control through optical fiber to achieve real-time control of the bus discharge status, and the real-time bus voltage discharge status is grasped after the frequency converter is powered off, so as to ensure the safety of the staff's operation and solve the problem that the bus discharge status cannot be grasped in real time.

[0033] According to an embodiment of the present invention, a discharge control device for a frequency converter is provided. Figure 1The structure diagram of an embodiment of the device of the present invention is shown in FIG. The frequency converter comprises a main circuit breaker, a rectifier unit (such as a rectifier), a busbar, and an inverter unit (such as an inverter) arranged in sequence. In the scheme of the present invention, Figure 1 As shown, the discharge control device of the frequency converter includes: a discharge unit (such as Figure 2 The discharge plate shown), the switch unit (such as Figure 2 The external relay KM1 shown), and the main control unit (such as Figure 2 The main board shown in the figure); the busbar has a positive end (such as DC+) and a negative end (such as DC-); the positive end of the busbar is connected to the first connection end of the discharge unit after passing through the switch unit; the second connection end of the discharge unit is connected to the negative end of the busbar; the main control unit is connected to the auxiliary contact of the main circuit breaker; the switch unit has a control end, a first connection end and a second connection end; the main control unit is also connected to the control end of the switch unit; the positive end of the busbar is connected to the first connection end of the switch unit, and the first connection end of the discharge unit is connected to the second connection end of the switch unit.

[0034] Wherein, the main circuit breaker has an auxiliary contact; the auxiliary contact of the main circuit breaker can feed back the on-off information of the main circuit breaker to the main control unit; the on-off information of the main circuit breaker is the closing information of the main circuit breaker, or the opening information of the main circuit breaker; specifically, when the main circuit breaker is closed, the auxiliary contact of the main circuit breaker feeds back a signal of a first preset level (such as a high-level signal) to the main control unit, and when the main circuit breaker is opened, the auxiliary contact of the main circuit breaker feeds back a signal of a second preset level (such as a low-level signal) to the main control unit; the signal of the first preset level is used to represent the closing of the main circuit breaker, and the signal of the second preset level is used to represent the opening of the main circuit breaker;

[0035] The main control unit is used to receive the on-off information of the main circuit breaker fed back by the auxiliary contacts of the main circuit breaker; the on-off information of the main circuit breaker is the closing information of the main circuit breaker, or the opening information of the main circuit breaker.

[0036] The main control unit is further configured to control the switch unit to be disconnected if the received on / off information of the main circuit breaker is the closing information of the main circuit breaker, so as to disconnect the connection path between the discharge unit and the busbar.

[0037] The main control unit is further used to control the switch unit to be turned on if the received on-off information of the main circuit breaker is the opening information of the main circuit breaker, so as to connect the connection path between the discharge unit and the busbar, so that the discharge unit discharges the voltage on the busbar.

[0038] The solution of the present invention is applicable to the field of high-power inverter control. The solution of the present invention provides a bus discharge control device for an airborne high-power inverter of a magnetic levitation unit. The main chip autonomously controls the working state of the discharge board, increases the flexibility of the inverter bus discharge, solves the problem of the inverter discharge board continuously consuming power and increasing the unit operating cost, and reduces the unit operating cost.

[0039] In some embodiments, the discharge control device of the frequency converter further includes: a display unit (such as Figure 2 The display unit comprises an optical fiber receiving module (such as an optical fiber receiver of the main control display screen) and a display module (such as the display part of the main control display screen).

[0040] The discharge unit has a power resistor module (such as Figure 3 The resistors R6, R7, R8, R9, R10, R11, R12, R13 and R14 shown in the figure), and the optical fiber transmission module (such as Figure 3 The optical fiber transmitter JK1 is shown; the first connection end of the power resistor module is connected to the switch unit, and the second connection end of the power resistor module is connected to the negative end of the bus; the control end of the optical fiber transmitting module is connected to the sampling end of the power resistor module.

[0041] Wherein, the optical fiber transmitting module is used to transmit an optical fiber signal when the discharge unit discharges the voltage on the bus.

[0042] The optical fiber receiving module is used to receive the optical fiber signal and transmit the received optical fiber signal to the display module.

[0043] The display module is used to light up a preset discharge indicator light based on the optical fiber signal transmitted by the optical fiber receiving module to display the state of the discharge unit discharging the voltage on the bus, and then turn off the preset discharge indicator light after the discharge unit finishes discharging the voltage on the bus.

[0044] In order to solve the problem of continuous power consumption of the discharge board during the operation of the high-power inverter, and the problem of the inability to control the bus voltage discharge in real time after the inverter is disconnected, which easily leads to safety hazards. The solution of the present invention proposes a bus discharge control device for the airborne high-power inverter of the magnetic levitation unit. The topology diagram of the bus discharge control device for the airborne high-power inverter of the magnetic levitation unit is as follows: Figure 2 shown. Figure 2 Figure 1 is a schematic diagram of the topological structure of the frequency converter and the discharge device. Figure 2As shown, the topological structure of the frequency converter and the discharge device includes: a main circuit breaker, a rectifier unit, a bus, a bus capacitor (such as capacitor C0), a discharge board, a main board, a main control display screen, and an inverter unit. The AC power supply on the grid side outputs AC power to the motor M after passing through the main circuit breaker, the positive module, the bus capacitor (such as capacitor C0), and the inverter unit. The bus is located between the rectifier unit and the inverter unit, and the bus capacitor is located between the positive end (such as DC+) and the negative end (such as DC-) of the bus. The positive end (such as DC+) of the bus is connected to the first end of the discharge board through the contact of the external relay KM1, and the second end of the discharge board is connected to the negative end (such as DC-) of the bus. The contact of the main circuit breaker is fed back to the input end of the main board, and the output end of the main board outputs the control signal FDB of the external relay KM1 to the coil of the external relay KM1. The optical fiber communication end of the discharge board is transmitted to the input end of the main control through the optical fiber; the communication end of the main control display screen communicates data with the communication end of the main board. The positive end of the busbar (such as DC+) is connected to the negative end (-) of the contact of the external relay KM1, and the positive end (+) of the contact of the external relay KM1 is connected to the first end of the discharge board.

[0045] In the solution of the present invention, the main board connects a wire to the external relay KM1 through the FDB pin, thereby controlling Figure 3 The discharge board circuit shown is connected to the busbar for operation. The entire discharge device controls the working state of the discharge board by collecting the closing status of the main circuit breaker by the main board: when the main circuit breaker is closed, the auxiliary contacts of the main circuit breaker will feed back the closing information to the main board, and then the main board will control the external relay KM1 to operate, thereby controlling the discharge board to be disconnected from the busbar; similarly, when the main circuit breaker is opened, the opening signal is collected by feedback from the auxiliary contacts of the main circuit breaker (that is, the auxiliary contacts of the main circuit breaker will feed back the opening information of the main circuit breaker to the main board), and the main board will control the external relay KM1 to operate, thereby controlling the discharge board to be connected to the busbar, thereby performing rapid discharge through the discharge board. In the scheme of the present invention, the flexibility of the inverter busbar discharge is increased, the unit operating cost is reduced, and the problem of the inverter discharge board continuously consuming power and increasing the unit operating cost is solved.

[0046] At the same time, in the scheme of the present invention, the discharge board has a fiber optic transmitter JK1, and the main control display screen has a fiber optic receiver. When the discharge board is connected to the bus and powered on, the fiber optic transmitter JK1 on the discharge board will continue to output an optical signal to the fiber optic receiver on the main control display screen. After receiving the optical signal, the fiber optic receiver will output a high level, and finally input it into the main control chip of the main control display screen through level conversion. After receiving the level, the main control chip will display a discharge indicator light on the display screen. Until the bus voltage drops to 0V, the fiber optic transmitter JK1 stops outputting the optical signal. After the main control display screen fails to receive the optical signal, the main control chip will control the display screen to turn off the discharge indicator light. The staff can judge the discharge of the bus voltage by observing the on and off of the discharge indicator light on the main control display screen, thereby eliminating the safety hazards of live operation. In the scheme of the present invention, the real-time discharge of the bus voltage is grasped after the inverter is powered off, reducing the risk of personnel operation and solving the problem of not being able to grasp the bus discharge in real time.

[0047] In the scheme of the present invention, the main chip autonomously controls the working state of the discharge plate, increases the flexibility of the inverter bus discharge, can solve the problem of the inverter discharge plate continuously consuming power and increasing the unit operation cost, and reduce the unit operation cost; at the same time, through optical fiber transmission to the main control to achieve real-time control of the bus discharge situation, grasp the real-time bus voltage discharge situation after the inverter is powered off, solve the problem of not being able to grasp the bus discharge situation in real time, and reduce the risk of personnel operation. The scheme of the present invention is simple and reliable, improves the safety and application performance of the inverter, and enables the inverter to meet the requirements of most application occasions.

[0048] In some embodiments, the discharge unit further comprises a first current limiting resistor module (such as Figure 3 The resistor R15 shown in FIG. 1 ), the second current limiting resistor module (such as Figure 3 The resistor R16 shown), and the voltage stabilizing diode module (such as Figure 3 The voltage regulator diode D3 shown in the figure); the power resistor module includes: a first resistor module, a second resistor module and a third resistor module.

[0049] Among them, the first connection end of the first resistor module, as the first connection end of the power resistor module, is connected to the switching unit; the second connection end of the first resistor module is connected to the first connection end of the second resistor module; the second connection end of the second resistor module is connected to the first connection end of the third resistor module; the second connection end of the third resistor module, as the second connection end of the power resistor module, is connected to the negative end of the bus.

[0050] The second connection end of the second resistor module serves as the sampling end of the power resistor module, and is connected to the control end of the optical fiber transmitting module after passing through the first current limiting resistor module and the second current limiting resistor module; the grounding end of the optical fiber transmitting module is connected to the negative end of the bus.

[0051] The common end of the first current limiting resistor module and the second current limiting resistor module is connected to the cathode of the voltage zener diode module; the anode of the voltage zener diode module is connected to the negative end of the busbar.

[0052] Figure 3 Figure 1 is a schematic diagram of the circuit principle of the discharge plate. Figure 3 As shown, the circuit of the discharge board mainly includes: power resistors, voltage stabilizing diode D3 and optical fiber transmitter JK1. The power resistors include: resistors R6, R7, R8, R9, R10, R11, R12, R13, R14, R15 and R16. Resistors R6, R7 and R8 are connected in parallel to form a first resistor module, resistors R9, R10 and R11 are connected in parallel to form a second resistor module, and resistors R12, R13 and R14 are connected in parallel to form a third resistor module. The positive end of the bus (such as DC+) is connected to the negative end of the bus (such as DC-) after passing through the first resistor module, the second resistor module and the third resistor module. The common end of the second resistor module and the third resistor module is connected to the control pin of the optical fiber transmitter JK1 after passing through resistors R15 and R16. The ground pin of the optical fiber transmitter JK1 is connected to the negative end of the bus (such as DC-). The common end of the resistor R15 and the resistor R16 is connected to the cathode of the Zener diode D3; the anode of the Zener diode D3 is connected to the negative end of the bus (such as DC-).

[0053] Figure 3 In the figure, the fiber optic transmitter JK1 is a fiber optic transmitter seat. The pin of the fiber optic transmitter JK1 connected to the resistor R16 is the control pin of the fiber optic transmitter JK1, and the other pins of the fiber optic transmitter JK1 are ground pins. Resistors R6, R7, R8, R9, R10, R11, R12, R13, and R14 are all ordinary large-resistance power resistors, which are the "main force" of the busbar rapid discharge; resistors R15 and R16 are current limiting resistors. Since the busbar voltage is in a discharge state, the voltage is always changing, so the voltage regulator diode D3 is required to stabilize the power supply voltage of the fiber optic transmitter seat at about 5V. When the discharge board is connected to the busbar, the power resistor will accelerate the discharge of the busbar. At the same time, the fiber optic transmitter seat will send a bright light signal to the main control through the optical fiber. At this time, the discharge indicator light on the main control display screen will light up until the busbar voltage is completely discharged, the fiber optic transmitter seat stops emitting light, the busbar indicator light on the main control display screen goes out, and the busbar discharge is completed.

[0054] In the solution of the present invention, the internal circuit of the discharge board is redesigned, and the information is transmitted to the main control through optical fiber to achieve real-time control of the bus discharge situation, so as to grasp the real-time bus voltage discharge situation after the inverter is powered off, ensuring the safety of staff operation.

[0055] In some embodiments, the main control unit includes: a main chip (such as a DSP chip of a frequency converter), and a control module (such as a control circuit of an external relay KM1); the switch unit includes: a first relay module (such as an external relay KM1); the control module includes: a second relay module (such as a solid-state relay K1); the second relay module is arranged between a preset power supply and the coil of the first relay module; the positive end of the bus is connected to the first connection end of the discharge unit through the contacts of the first relay module; the contacts of the first relay module are normally closed contacts.

[0056] Wherein, if the received on-off information of the main circuit breaker is the closing information of the main circuit breaker, the main control unit controls the switch unit to be disconnected, including:

[0057] The main chip is used to generate a first control signal (such as a DSP chip outputting a high-level signal through the FDB.0_DSP pin) based on the closing information of the main circuit breaker.

[0058] The control module is used to control the second relay module to connect a connection path between a preset power supply and the coil of the first relay module based on the first control signal, so that the coil of the first relay module is energized and the contacts of the first relay module are disconnected.

[0059] Figure 5 This is a schematic diagram of the discharge board's action flow when the inverter is closed. Figure 5 As shown in the figure, the action flow of the inverter closing discharge board includes:

[0060] Step 11, when the unit is powered on, the inverter causes the bus to start charging (i.e., charging the bus capacitor) through the charging circuit. At this time, the inverter mainboard is powered on and starts working, and then step 12 is executed.

[0061] Step 12. After the bus charging is completed (i.e., the bus capacitor is charged), the main board will also determine whether the main circuit breaker is closed through the signal fed back from the auxiliary contact of the main circuit breaker: if so, execute step 13; otherwise, determine that the inverter is abnormal, that is, if it is determined that the main circuit breaker is not closed, then the inverter is abnormal.

[0062] Among them, since there will be an auxiliary contact inside the main circuit breaker in the inverter, when the main circuit breaker is closed, the auxiliary contact of the main circuit breaker will close, and the auxiliary contact of the main circuit breaker will transmit a high level to the main chip of the mainboard, thereby judging that the main circuit breaker has been closed; on the contrary, if the auxiliary contact of the main circuit breaker continues to give a low level to the main chip, the main chip judges that the main circuit breaker is in the open state.

[0063] Step 13. If it is determined that the main circuit breaker is closed, the main board will output a 24V voltage to the external relay KM1 of the discharge board, and the external relay KM1 will be energized. The internal coil of the external relay KM1 will be energized to generate suction on the contacts, and the contacts of the external relay KM1 will be disconnected; then the main board will detect whether the discharge board is disconnected from the busbar and then determine whether the relay KM1 is operating normally: if it is detected that the discharge board is disconnected from the busbar normally, the inverter and the unit can be started and operated normally; if it is detected that the discharge board is not disconnected from the busbar, execute step 14.

[0064] Among them, the optical signal emitted by the discharge board to the optical fiber receiver of the main control through the optical fiber transmitter JK1 will be transmitted to the main board through the data communication terminal of the main control, so that the main board determines whether the discharge board is disconnected from the bus: if the main board receives the optical signal transmitted by the main control communication, it is determined that the discharge board is not disconnected from the bus; if the main board does not receive the optical signal transmitted by the main control communication, it is determined that the discharge board is disconnected from the bus.

[0065] Step 14: If it is detected that the discharge board is not disconnected from the busbar, an abnormal discharge board fault will be reported, and then the inverter will be reported as abnormal, so the unit cannot be started and operated.

[0066] In the related scheme, the discharge board of the inverter is directly connected to the bus. Although the discharge board will accelerate the discharge of the bus when the inverter is powered off, when the inverter is in normal operation, the power consumption of the inverter is increased due to the continuous discharge of the discharge board. In addition, the discharge board is in working state for a long time, and the components of the internal circuit of the discharge board are seriously heated, which will accelerate the damage of the components in the long run. The scheme of the present invention, by changing the wiring device of the discharge board, can autonomously control the working state of the discharge board through the main chip, thereby increasing the flexibility of the inverter bus discharge, solving the problem that the inverter discharge board continuously consumes power and increases the operating cost of the unit, and reducing the operating cost of the unit.

[0067] The main control unit controls the switch unit to be turned on if the received on / off information of the main circuit breaker is the opening information of the main circuit breaker, comprising:

[0068] The main chip is used to generate a second control signal (such as a DSP chip outputting a low-level signal through the FDB.0_DSP pin) based on the opening information of the main circuit breaker.

[0069] The control module is used to control the second relay module to disconnect the connection path between the preset power supply and the coil of the first relay module based on the second control signal, so that the coil of the first relay module loses power and the contacts of the first relay module are closed.

[0070] Figure 6 This is a schematic diagram of the action flow of the discharge board when the inverter is disconnected. Figure 6 As shown in the figure, the action flow of the discharge board when the inverter is opened includes:

[0071] Step 21. After the unit is shut down, the inverter mainboard will detect whether the main circuit breaker is open: if the main circuit breaker is open, execute step 22; if the main circuit breaker is not open, the operator needs to manually press the emergency stop button to complete the main circuit breaker opening, and then execute step 22.

[0072] Step 22, the main board will output a 0V voltage to the external relay KM1 of the discharge board, the external relay KM1 loses power, the coil of the external relay KM1 loses suction, the contacts of the external relay KM1 close, and then execute step 23.

[0073] Step 23, the main board detects whether the discharge board is successfully connected to the bus: if it is detected that the discharge board is connected to the bus, execute step 24; if it is detected that the discharge board is not connected to the bus, the inverter reports a fault of abnormal discharge board connection and initiates a prompt. Do not open the door of the inverter cabinet at this time. You can only wait for the bus voltage to naturally drop to 0V after a while, and then execute step 25, that is, open the door of the inverter cabinet according to the steps for subsequent inspection and maintenance work.

[0074] Step 24: If it is detected that the discharge board has been successfully connected to the bus, the discharge board starts to work, the bus discharges, and the bus discharge indicator on the main control display lights up. At this time, the bus voltage drops rapidly until the bus discharge indicator on the main control display goes out, which means that the bus voltage is completely discharged. Then, you can execute step 25, that is, open the cabinet door of the inverter cabinet according to the steps for subsequent inspection and maintenance.

[0075] Step 25. Open the door of the inverter cabinet according to the steps and carry out subsequent inspection and maintenance work.

[0076] In the scheme of the present invention, by changing the wiring device of the discharge board, the working state of the discharge board can be independently controlled by the main chip, and the control of the discharge board can reduce the additional power consumption of the inverter, and the discharge board can work when it is needed and disconnect when it is not needed, thereby increasing the flexibility of the inverter bus discharge, solving the problem of the inverter discharge board continuously consuming power and increasing the operating cost of the unit, and reducing the operating cost of the unit.

[0077] In some embodiments, the control module further comprises: a signal input module, a first diode module (such as Figure 4 The diode D1 shown), the switch tube module (such as Figure 4 The transistor Q1 shown), the third current limiting resistor module (such as Figure 4 Resistor R5 shown).

[0078] Among them, the first control signal generated by the main chip based on the closing information of the main circuit breaker, or the second control signal generated by the main chip based on the opening information of the main circuit breaker, is used as the input signal of the control module; the first control signal or the second control signal, after passing through the signal input module, is input to the control end of the switch tube module (such as Figure 4 The base of the transistor Q1 shown in FIG. 1 is connected to the cathode of the first diode module. The anode of the first diode module is connected to the first connection terminal of the switch tube module (such as Figure 4 The collector of the transistor Q1 shown in FIG. 1 ); the second connection end of the switch module (such as Figure 4 The emitter of transistor Q1 shown in the figure is connected to the digital ground (such as Figure 4 The digital ground DGND shown). The preset first DC power supply (such as +5VD) is connected to the first connection end of the coil of the second relay module after passing through the third current limiting resistor module; the second connection end of the coil of the second relay module is connected to the first connection end of the switch tube module. The contacts of the second relay module have a first connection end, a second connection end and a third connection end, the first connection end of the contacts of the second relay module is connected to a preset power supply, the second connection end of the contacts of the second relay module is suspended, and the third connection end of the contacts of the second relay module is connected to the power supply end of the coil of the first relay module; wherein, when the third connection end of the contacts of the second relay module is connected to the first connection end, the coil of the first relay module is energized; when the third connection end of the contacts of the second relay module is connected to the second connection end, the coil of the first relay module is de-energized. Figure 4 In the example shown, the solid-state relay K1 is an inter-board solid-state relay on the main board, the external relay KMI is an external relay between the main board and the discharge board, and the solid-state relay K1 controls the action of the external relay KM1.

[0079] In the scheme of the present invention, by controlling the on and off of the first relay module under the control of the main chip through a control module composed of a signal input module, a first diode module, a switch tube module, a third current limiting resistor module, and a second relay module, the on and off of the first relay module can be reliably controlled, thereby achieving reliable on and off between the discharge plate and the bus. The working state of the discharge plate can be autonomously controlled by the main chip, thereby increasing the flexibility of the inverter bus discharge and reducing the unit operation cost.

[0080] In some embodiments, the control module further comprises: a second diode module; the second diode module comprises: a light emitting diode (such as Figure 4 The light emitting diode D2 shown in the figure). Wherein, the preset first DC power supply (such as +5VD) is connected to the anode of the second diode module after passing through the third current limiting resistor module; the cathode of the second diode module is connected to the first connection end of the coil of the second relay module.

[0081] In the solution of the present invention, by providing a light emitting diode D2 in the control module, the state of whether the second relay module is powered or not can be displayed, which is convenient for users to check.

[0082] In some embodiments, the control module further comprises: a filtering module (such as Figure 4 The capacitor C1 shown); the signal input module includes: a fourth current limiting resistor module (such as Figure 4 The resistor R1 shown in FIG. 1 ), the fifth current limiting resistor module (such as Figure 4 The resistor R2 shown in FIG. 1 ), the first voltage divider module (such as Figure 4 The resistor R3 shown in FIG. Figure 4 The resistor R4 shown), and the NOT gate module (such as Figure 4 The NOT gate U1 shown).

[0083] Wherein, the preset second DC power supply (such as Figure 4 +3.3VD as shown), after passing through the first current limiting resistor module, it is input to the input end of the NOT gate module; the first control signal or the second control signal, after passing through the second current limiting resistor module, is input to the input end of the NOT gate module; the output end of the NOT gate module, after passing through the first voltage dividing resistor module and the second voltage dividing resistor module, is connected to the digital ground (such as Figure 4 The filter module is connected in parallel with the second voltage-dividing resistor module. The common end of the first voltage-dividing resistor module and the second voltage-dividing resistor module is connected to the control end of the switch tube module.

[0084] Figure 4 The control circuit diagram of the discharge plate is shown in Figure 2. Figure 2 As shown in the circuit of the main board, the control circuit of the discharge board controls the external relay KM1 to control whether the discharge board is connected to the bus. Figure 4 As shown, the control circuit of the discharge board includes: resistor R1, resistor R2, resistor R3, resistor R4, resistor R5, NOT gate U1, capacitor C1, diode D1, light emitting diode D2, transistor Q1, and solid-state relay K1. Among them, the DC power supply (+3.3VD) is input to the input end of the NOT gate U1 after passing through the resistor R1; the control signal (FDB.0_DSP) output by the main chip (such as DSP chip) of the main board is input to the input end of the NOT gate U1 after passing through the resistor R2. The output end of the NOT gate U1 is connected to the base of the transistor Q1 after passing through the resistor R3, and the base of the transistor Q1 is also connected to the digital ground DGND after passing through the parallel capacitor C1 and resistor R4. The DC power supply (+5VD) is connected to the cathode of the diode D1, and the anode of the diode D1 is connected to the collector of the transistor Q1; the emitter of the transistor Q1 is connected to the digital ground DGND. The DC power supply (+5VD) is connected to the anode of the light-emitting diode D2 through the resistor R5, the cathode of the light-emitting diode D2 is connected to the first connection end of the coil of the solid-state relay K1, and the second connection end of the coil of the solid-state relay K1 is connected to the collector of the transistor Q1. The first connection end of the contact of the coil of the solid-state relay K1 is connected to the +24V power supply, and the second connection end of the contact of the coil of the solid-state relay K1 is connected to the FDB pin. 3.3VD is a pull-up power supply, which pulls the high level output by the main chip to a stable 3.3V voltage through a pull-up resistor (such as resistor R1), ensuring that the power input into the non-gate U1 is a stable 3.3V high level.

[0085] exist Figure 4 In the example shown, resistors R1, R2, R3, R4 and R5 are all fixed resistors, among which resistors R1, R2 and R5 are current limiting resistors, and resistors R3 and R4 are voltage dividing resistors. The specific resistance values ​​can be designed according to the actual situation. The voltage dividing ratio. Capacitor C1 mainly plays a filtering role. NOT gate U1 is a logic chip NOT gate. When a high level is input to the logic chip NOT gate, the logic chip NOT gate will output a low level. Diode D1 is a freewheeling diode, and light-emitting diode D2 can emit light. When transistor Q1 is turned on, current flows out through light-emitting diode D2, thereby lighting up light-emitting diode D2.

[0086] exist Figure 4In the example shown, the digital signal processor (DSP) chip controls the solid-state relay K1 to control the external relay KM1 of the discharge board, thereby controlling the working state of the discharge board. When the main circuit breaker of the inverter is opened, the auxiliary contacts of the main circuit breaker will promptly feed back the opening signal to the DSP chip, and the DSP chip will output a low level and input it to the input end of the NOT gate U1 through the FDB.0_DSP pin, and then the output end of the NOT gate U1 will output a high level. The high-level signal is divided by resistors R3 and R4 to obtain a gate voltage, and the gate voltage is input into the base of the transistor Q1 to turn on the transistor Q1. At this time, due to the reverse cutoff characteristics of the diode D1, the diode D1 cannot flow current, and the current provided by +5VD can only flow through the resistor R5 and the light-emitting diode D2, so that the light-emitting diode D2 lights up, and then flows into the coil of the solid-state relay K1, and finally flows through the transistor Q1 to DGND. At this time, since current flows into the coil of the solid-state relay K1, magnetic force is generated to attract the internal contacts of the solid-state relay K1 to disconnect the +24V power supply and the FDB pin, thereby disconnecting the power supply of the external relay KM1, and the coil of the external relay KM1 loses power, and the contacts of the external relay KM1 are connected, which in turn prompts the discharge board to connect to the busbar for rapid discharge. The contacts of the external relay KM1 are normally closed contacts.

[0087] When the main circuit breaker of the inverter is closed, the DSP chip outputs a high level to the input end of the NOT gate U1, and then the output end of the NOT gate U1 will output a low level into the gate of the transistor Q1 (that is, the base of the transistor Q1), thereby causing the transistor Q1 to be cut off, resulting in no current flowing through the circuit where the entire light-emitting diode D2 is located, and the coil of the solid-state relay K1 loses current. The internal contacts of the solid-state relay K1 will pop open and connect the pin FDB to +24V. At this time, the coil of the external relay KM1 is energized, the internal coil of the external relay KM1 is activated, and the contacts of the external relay KM1 are disconnected, so the discharge board is disconnected from the bus and the discharge work stops.

[0088] In the solution of the present invention, by changing the wiring device of the discharge board, the working state of the discharge board can be independently controlled by the main chip, thereby increasing the flexibility of the inverter bus discharge and reducing the operating cost of the unit.

[0089] In the above embodiment, some control scenarios of the control scheme for high-power inverter discharge are listed. The scheme can be modified according to the actual situation and applied to other control scenarios. The scheme is not limited to the parameters designed in the example, and the parameters in the circuit can be adjusted and changed according to the actual application.

[0090] In the scheme of the present invention, the discharge board is discharged by connecting multiple power resistors in parallel, and the optical fiber transmitter is continuously powered by the voltage stabilizing diode D3; the main board samples the closing status of the main circuit breaker, and then controls the external relay KM1 of the controller discharge board to operate, thereby controlling the working state of the discharge board. In the scheme of the present invention, it is not limited to using the coil of the external relay of the discharge board to obtain power to control the discharge action. This scheme can be more automated. For example, the frequency converter itself can collect and judge whether the discharge board needs to work, that is, the main board judges whether the main circuit breaker is closed through the auxiliary contacts of the main circuit breaker and then judges whether the discharge board needs to work, and then controls the external relay KM1 and the discharge board. During the discharge operation, the completion status of the inverter bus discharge can be seen through the main control display screen of the unit without opening the inverter, which greatly reduces the work risk and ensures the personal safety of the staff.

[0091] The technical solution of the present invention is adopted, by setting a switch unit (such as an external relay KM1) between the discharge board set on the bus in the inverter (such as a high-power inverter of a magnetic levitation unit), and specifically setting a switch unit (such as an external relay KM1) between the discharge board and the bus; and setting a control module (such as a control circuit of the external relay KM1) for the switch unit, and the control module can be set in the main board of the inverter; when the main chip in the main board of the inverter detects that the main circuit breaker of the inverter is closed, the main chip controls the switch unit to be disconnected through the control module, so that the discharge board is cut out when the inverter is working; when the main chip in the main board of the inverter detects that the main circuit breaker of the inverter is opened, the main chip controls the switch unit to be closed through the control module, so that the discharge board is connected when the inverter is stopped, and the voltage on the bus of the inverter (that is, the bus voltage) is discharged; thereby, by controlling the working state of the discharge board according to the closing and opening conditions of the inverter, it is ensured that the bus voltage is reliably discharged and the power consumption of the discharge board is reduced.

[0092] Furthermore, the working status of the discharge board is displayed, for example, a fiber optic transmitter is set in the discharge board, and when the discharge board is discharging, a fiber optic signal is transmitted to the main control display screen of the inverter through the fiber optic transmitter so that the main control display screen lights up the discharge indicator light of the discharge board to display that the discharge board is discharging; when the discharge board is completely discharged, the main control display screen turns off the discharge indicator light of the discharge board to display that the discharge board is completely discharged; thus, by displaying the working status of the discharge board, the discharge status of the bus voltage after the inverter is powered off is displayed, and the operator can only operate after the bus voltage is completely discharged, thereby reducing the operating risk of the operator and improving safety.

[0093] According to an embodiment of the present invention, a frequency converter corresponding to the discharge control device of the frequency converter is also provided. The frequency converter may include: the discharge control device of the frequency converter described above.

[0094] Since the processing and functions implemented by the frequency converter of this embodiment basically correspond to the embodiments, principles and examples of the device, for the details not described in this embodiment, please refer to the relevant descriptions in the aforementioned embodiments and will not be repeated here.

[0095] According to an embodiment of the present invention, a magnetic suspension unit corresponding to the discharge control device of the frequency converter is also provided. The magnetic suspension unit may include: the discharge control device of the frequency converter described above, or the frequency converter described above.

[0096] Since the processing and functions implemented by the magnetic levitation unit of this embodiment basically correspond to the embodiments, principles and examples of the device, for the details not described in this embodiment, please refer to the relevant descriptions in the aforementioned embodiments and will not be repeated here.

[0097] According to an embodiment of the present invention, a discharge control method for a frequency converter corresponding to the discharge control device for the frequency converter is also provided. Figure 7 The flow chart of an embodiment of the method of the present invention is shown in FIG. The discharge control method of the frequency converter may include: step S110 to step S130.

[0098] At step S110, the on-off information of the main circuit breaker is fed back to the main control unit through the auxiliary contact of the main circuit breaker. The on-off information of the main circuit breaker is the closing information of the main circuit breaker or the opening information of the main circuit breaker; specifically, when the main circuit breaker is closed, the auxiliary contact of the main circuit breaker feeds back a signal of a first preset level (such as a high-level signal) to the main control unit, and when the main circuit breaker is opened, the auxiliary contact of the main circuit breaker feeds back a signal of a second preset level (such as a low-level signal) to the main control unit; the signal of the first preset level is used to represent the closing of the main circuit breaker, and the signal of the second preset level is used to represent the opening of the main circuit breaker.

[0099] In step S120, the main control unit receives on-off information of the main circuit breaker fed back by the auxiliary contacts of the main circuit breaker; the on-off information of the main circuit breaker is closing information of the main circuit breaker or opening information of the main circuit breaker.

[0100] In step S130, through the main control unit, if the received on-off information of the main circuit breaker is the closing information of the main circuit breaker, the switch unit is controlled to be disconnected to disconnect the connection path between the discharge unit and the busbar.

[0101] At step S140, through the main control unit, if the received on-off information of the main circuit breaker is the opening information of the main circuit breaker, the switch unit is controlled to be turned on to connect the connection path between the discharge unit and the bus, so that the discharge unit discharges the voltage on the bus.

[0102] In the solution of the present invention, the main chip autonomously controls the working state of the discharge board, thereby increasing the flexibility of the inverter bus discharge, solving the problem of the inverter discharge board continuously consuming power and increasing the unit operating cost, and reducing the unit operating cost.

[0103] Since the processing and functions implemented by the method of this embodiment basically correspond to the embodiments, principles and examples of the aforementioned frequency converter, for the details not fully described in the description of this embodiment, please refer to the relevant descriptions in the aforementioned embodiments, and no further elaboration will be made here.

[0104] In summary, it is easy for those skilled in the art to understand that, under the premise of no conflict, the above-mentioned advantageous methods can be freely combined and superimposed.

[0105] The above description is only an embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present invention shall be included in the scope of the claims of the present invention.

Claims

1. A discharge control device for a frequency converter, characterized in that: The frequency converter has a main circuit breaker, a rectifier unit, a bus, and an inverter unit arranged in sequence; the discharge control device of the frequency converter includes: a discharge unit, a switch unit, and a main control unit; the positive end of the bus is connected to the first connection end of the discharge unit after passing through the switch unit; the second connection end of the discharge unit is connected to the negative end of the bus; wherein, The main circuit breaker has an auxiliary contact; the auxiliary contact of the main circuit breaker can feed back the on-off information of the main circuit breaker to the main control unit; The main control unit is used to receive the on-off information of the main circuit breaker fed back by the auxiliary contact of the main circuit breaker; the on-off information of the main circuit breaker is the closing information of the main circuit breaker, or the opening information of the main circuit breaker; If the received on / off information of the main circuit breaker is the closing information of the main circuit breaker, controlling the switch unit to be turned off to disconnect the connection path between the discharge unit and the busbar; If the received on / off information of the main circuit breaker is the opening information of the main circuit breaker, the switch unit is controlled to be turned on to connect the connection path between the discharge unit and the busbar, so that the discharge unit discharges the voltage on the busbar.

2. The discharge control device of the frequency converter according to claim 1, characterized in that: Also includes: Display unit; The display unit comprises an optical fiber receiving module and a display module; The discharge unit comprises a power resistor module and an optical fiber transmitting module; the first connection end of the power resistor module is connected to the switch unit, and the second connection end of the power resistor module is connected to the negative end of the bus; the control end of the optical fiber transmitting module is connected to the sampling end of the power resistor module; wherein, The optical fiber transmitting module is used to transmit an optical fiber signal when the discharge unit discharges the voltage on the bus; The optical fiber receiving module is used to receive the optical fiber signal and transmit the received optical fiber signal to the display module; The display module is used to light up a preset discharge indicator light based on the optical fiber signal transmitted by the optical fiber receiving module to display the state of the discharge unit discharging the voltage on the bus, and then turn off the preset discharge indicator light after the discharge unit finishes discharging the voltage on the bus.

3. The discharge control device of the frequency converter according to claim 2, characterized in that: The discharge unit further comprises a first current limiting resistor module, a second current limiting resistor module, and a voltage stabilizing diode module; the power resistor module comprises: a first resistor module, a second resistor module, and a third resistor module; wherein, The first connection end of the first resistor module, as the first connection end of the power resistor module, is connected to the switch unit; the second connection end of the first resistor module is connected to the first connection end of the second resistor module; the second connection end of the second resistor module is connected to the first connection end of the third resistor module; the second connection end of the third resistor module, as the second connection end of the power resistor module, is connected to the negative end of the busbar; The second connection end of the second resistor module, as the sampling end of the power resistor module, is connected to the control end of the optical fiber transmission module after passing through the first current limiting resistor module and the second current limiting resistor module; the grounding end of the optical fiber transmission module is connected to the negative end of the busbar; The common end of the first current limiting resistor module and the second current limiting resistor module is connected to the cathode of the voltage zener diode module; the anode of the voltage zener diode module is connected to the negative end of the busbar.

4. The discharge control device for a frequency converter according to any one of claims 1 to 3, characterized in that: The main control unit includes: a main chip and a control module; the switch unit includes: a first relay module; the control module includes: a second relay module; the second relay module is arranged between a preset power supply and a coil of the first relay module; the positive end of the busbar is connected to the first connection end of the discharge unit through the contact of the first relay module; the contact of the first relay module is a normally closed contact; in, The main control unit controls the switch unit to disconnect if the received on / off information of the main circuit breaker is the closing information of the main circuit breaker, comprising: The main chip is used to generate a first control signal based on the closing information of the main circuit breaker; The control module is used to control the second relay module to connect a connection path between a preset power supply and the coil of the first relay module based on the first control signal, so that the coil of the first relay module is energized and the contacts of the first relay module are disconnected; The main control unit controls the switch unit to be turned on if the received on / off information of the main circuit breaker is the opening information of the main circuit breaker, comprising: The main chip is used to generate a second control signal based on the opening information of the main circuit breaker; The control module is used to control the second relay module to disconnect the connection path between the preset power supply and the coil of the first relay module based on the second control signal, so that the coil of the first relay module loses power and the contacts of the first relay module are closed.

5. The discharge control device for a frequency converter according to claim 4, characterized in that: The control module further comprises: a signal input module, a first diode module, a switch module, and a third current limiting resistor module; wherein: The first control signal or the second control signal is input to the control end of the switch tube module after passing through the signal input module; A preset first DC power supply is connected to the cathode of the first diode module; an anode of the first diode module is connected to the first connection end of the switch tube module; and a second connection end of the switch tube module is connected to the digital ground; The preset first DC power supply is connected to the first connection end of the coil of the second relay module after passing through the third current limiting resistor module; the second connection end of the coil of the second relay module is connected to the first connection end of the switch tube module; The first connection end of the contact of the second relay module is connected to a preset power supply, the second connection end of the contact of the second relay module is suspended, and the third connection end of the contact of the second relay module is connected to the power supply end of the coil of the first relay module; wherein, when the third connection end of the contact of the second relay module is connected to the first connection end, the coil of the first relay module is energized; when the third connection end of the contact of the second relay module is connected to the second connection end, the coil of the first relay module is de-energized.

6. The discharge control device for a frequency converter according to claim 5, characterized in that: The control module further comprises: a second diode module; the second diode module comprises: a light emitting diode; wherein, The preset first DC power supply is connected to the anode of the second diode module after passing through the third current limiting resistor module; the cathode of the second diode module is connected to the first connection end of the coil of the second relay module.

7. The discharge control device for a frequency converter according to claim 5 or 6, characterized in that: The control module further comprises: a filter module; the signal input module comprises: a fourth current limiting resistor module, a fifth current limiting resistor module, a first voltage dividing module, a second voltage dividing module, and a NOT gate module; wherein, The preset second DC power supply is input to the input end of the NOT gate module after passing through the first current limiting resistor module; the first control signal or the second control signal is input to the input end of the NOT gate module after passing through the second current limiting resistor module; the output end of the NOT gate module is connected to the digital ground after passing through the first voltage dividing resistor module and the second voltage dividing resistor module; the filter module is connected in parallel with the second voltage dividing resistor module; A common end of the first voltage-dividing resistor module and the second voltage-dividing resistor module is connected to a control end of the switch tube module.

8. A frequency converter, characterized in that: include: A discharge control device for a frequency converter as claimed in any one of claims 1 to 7.

9. A magnetic levitation unit, characterized in that: include: A discharge control device for a frequency converter as claimed in any one of claims 1 to 7, or a frequency converter as claimed in claim 8.

10. A discharge control method for a frequency converter corresponding to the discharge control device for a frequency converter according to any one of claims 1 to 7, characterized in that: include: Feedback the on / off information of the main circuit breaker to the main control unit through the auxiliary contacts of the main circuit breaker; Receiving, through the main control unit, on / off information of the main circuit breaker fed back by the auxiliary contacts of the main circuit breaker; The on / off information of the main circuit breaker is the closing information of the main circuit breaker or the opening information of the main circuit breaker; If the received on / off information of the main circuit breaker is the closing information of the main circuit breaker, controlling the switch unit to be turned off to disconnect the connection path between the discharge unit and the busbar; If the received on / off information of the main circuit breaker is the opening information of the main circuit breaker, the switch unit is controlled to be turned on to connect the connection path between the discharge unit and the busbar, so that the discharge unit discharges the voltage on the busbar.

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