A control device and method for a frequency converter and a frequency converter

Abstract

The present invention discloses a control device, method and inverter for a frequency converter, the device comprising: each of two or more discharge resistor groups is configured to release the power of the bus capacitor individually under the control of a switch module, and can also release the power of the bus capacitor together with other discharge resistor groups; the switch module is configured to control the number of discharge paths of the bus capacitor connected to the two or more discharge resistor groups according to the release demand of the bus capacitor when the bus capacitor needs to be released, denoted as N, where N is a positive integer; the power of the bus capacitor is released by using the N discharge resistor groups connected to the discharge path of the bus capacitor in the two or more discharge resistor groups. This solution is conducive to improving the safety of the frequency converter by enabling the discharge power of the bus capacitor discharge resistor of the frequency converter to change with actual demand.

Description

Technical Field

[0001] The present invention belongs to the technical field of frequency converters, and specifically relates to a control device, method and frequency converter of a frequency converter, and in particular to a control device, method and frequency converter of a bus capacitor discharge power of a frequency converter. Background Art

[0002] In the inverter used to control the magnetic levitation motor, when the inverter stops or loses power, the DC capacitor (i.e., bus capacitor) is discharged, and the energy of the DC capacitor is consumed by a resistor with a fixed resistance. The fixed resistance resistor consumes the power of the DC capacitor in the form of heat energy, so as to reduce the pump voltage fed back by the motor when the inverter stops, and consume the power of the DC capacitor as soon as possible after the inverter loses power, to ensure that there is no electricity in the inverter cabinet.

[0003] The DC capacitor in the inverter that controls the magnetic levitation motor provides the voltage required for inversion while also supplying power to the bearing controller and inverter main control board of the magnetic levitation motor. When the voltage (i.e., bus voltage) of the bus capacitor (i.e., DC capacitor) is lower than a certain rated value, the inverter main control board and the magnetic levitation bearing controller will lose power, and the bearing will lose control, which may cause power loss, loss of control, and shaft drop. Therefore, in the inverter that controls the magnetic levitation motor, it is not desirable to quickly consume the power of the bus capacitor within a short period of time after the emergency shutdown cuts off the power input, so as to avoid the bus voltage dropping too quickly and falling below the lowest supply voltage of the bearing controller. The inverter will enter the motor energy feedback regulation at the moment of emergency shutdown, and maintain the bus voltage at the reference voltage value for the bearing controller to control the bearing to drop the shaft. The process of entering the energy feedback regulation to voltage stability requires a short adjustment time. During this period, the discharge resistor cannot cause too much power loss to the bus capacitor, so that the bus voltage drops too quickly.

[0004] However, the discharge power of the inverter's bus capacitor discharge resistor cannot change with actual demand, which affects the safety of the inverter.

[0005] 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

[0006] The object of the present invention is to provide a control device, method and inverter of a frequency converter, so as to solve the problem that the discharge power of the bus capacitor discharge resistor of the frequency converter cannot change with actual demand, thereby affecting the safety of the frequency converter, so as to achieve the effect of improving the safety of the frequency converter by making the discharge power of the bus capacitor discharge resistor of the frequency converter change with actual demand.

[0007] The present invention provides a control device of a frequency converter, wherein the frequency converter has a bus capacitor; the control device of the frequency converter comprises: a bus capacitor discharge unit; the bus capacitor discharge unit is arranged at the output end of the bus capacitor; the bus capacitor discharge unit comprises: a discharge resistor module and a switch module; the discharge resistor module comprises: a discharge resistor group, the number of which is more than two; wherein each of the more than two discharge resistor groups is configured to release the electric quantity of the bus capacitor individually under the control of the switch module, and can also release the electric quantity of the bus capacitor together with the remaining discharge resistor groups; the switch module is configured to control the number of discharge paths of the more than two discharge resistor groups connected to the bus capacitor according to the release demand of the electric quantity of the bus capacitor when it is necessary to release the electric quantity of the bus capacitor, which is recorded as N, and N is a positive integer; so as to release the electric quantity of the bus capacitor by using the N discharge resistor groups connected to the discharge path of the bus capacitor in the more than two discharge resistor groups.

[0008] In some embodiments, the two or more discharge resistor groups include: a first resistor group and a second resistor group; the switch module includes: a first switch and a second switch; wherein the second resistor group and the second switch are connected in series to form a first series branch; the first series branch is connected in parallel with the first resistor group to form a first parallel branch; the first parallel branch is connected in series with the first switch to form a second series branch; the first end of the second series branch is connected to the positive end of the bus capacitor; the second end of the second series branch is connected to the negative end of the bus capacitor.

[0009] In some embodiments, in the second series branch, one end of the first switch away from the first parallel branch serves as the first end of the second series branch; one end of the first parallel branch away from the first switch serves as the second end of the second series branch; in the first series branch, one end of the second switch away from the second resistor group is connected to the second end of the second series branch.

[0010] In some implementations, both the first switch and the second switch are contactors.

[0011] In some embodiments, when the amount of electricity of the bus capacitor needs to be released, the switch module controls the number of discharge paths of the bus capacitor to which the two or more discharge resistor groups are connected according to the release requirement of the amount of electricity of the bus capacitor, including any of the following control situations:

[0012] The first control scenario: when the frequency converter is operating normally, the first switch and the second switch are both in a disconnected state, so that the first resistor group and the second resistor group do not release the electricity of the bus capacitor, which is recorded as the first resistor group and the second resistor group are both not working.

[0013] The second control scenario: when the inverter stops normally during normal operation, when the motor controlled by the inverter has stopped, and the input power of the inverter has been cut off, the following is performed: if the bus voltage of the bus capacitor exceeds the set protection value, the first switch is in a closed state, and the second switch is in an open state, so that the first resistor group works and the second resistor group does not work; if the bus voltage of the bus capacitor does not exceed the protection value, the first switch and the second switch are both in an open state, so that the first resistor group and the second resistor group do not work, and the energy feedback process of the motor controlled by the inverter continues to be executed; and, when the energy feedback process of the motor controlled by the inverter ends, if the bearing controller of the motor controlled by the inverter has controlled the bearing to drop, and the main control board of the inverter has been powered off, the first switch and the second switch are both in a closed state, so that the first resistor group and the second resistor group both work.

[0014] The third control situation: when the inverter stops normally during normal operation, wait for the motor controlled by the inverter to stop and the bearing of the motor controlled by the inverter to fall off, then the input power of the inverter is cut off, and execute: if the bus voltage of the bus capacitor exceeds the set protection value, the first switch is in a closed state, and the second switch is in an open state, so that the first resistor group works and the second resistor group does not work; if the bus voltage of the bus capacitor does not exceed the protection value, then: after the bearing of the motor controlled by the inverter has fallen off and the input power of the inverter has been cut off In this case, both the first switch and the second switch are in an open state, so that both the first resistor group and the second resistor group do not work, and after waiting for the bearing controller of the motor controlled by the inverter to control the bearing to fall off and the main control board of the inverter to be powered off, both the first switch and the second switch are in a closed state, so that both the first resistor group and the second resistor group work; when the bearing of the motor controlled by the inverter has not fallen off and / or the input power of the inverter has not been cut off, both the first switch and the second switch are in a closed state, so that both the first resistor group and the second resistor group work.

[0015] In some embodiments, when the electric quantity of the bus capacitor needs to be released, the switch module controls the number of discharge paths of the bus capacitor to which the two or more discharge resistor groups are connected according to the release demand of the electric quantity of the bus capacitor, and further includes any one of the following control situations:

[0016] A first further control scenario: when the inverter shuts down normally during normal operation, after the first resistor group and the second resistor group are not working and the energy feedback process of the motor controlled by the inverter continues to be executed, when the energy feedback process of the motor controlled by the inverter ends, if the bearing controller of the motor controlled by the inverter has controlled the bearing to drop, and the main control board of the inverter has been powered off, the first switch and the second switch are both in a closed state, so that the first resistor group and the second resistor group both work.

[0017] A second further control scenario: when the frequency converter shuts down normally during normal operation, after making the first resistor group and the second resistor group non-operating, and after waiting for the bearing controller of the motor controlled by the frequency converter to control the bearing to drop and the main control board of the frequency converter to be powered off, the first switch and the second switch are both in a closed state, so that the first resistor group and the second resistor group are both operating.

[0018] In some embodiments, it also includes: a sampling unit, a control unit and a driving unit; wherein the sampling unit is configured to sample the bus voltage of the bus capacitor; the control unit is configured to determine the current state of the inverter according to the bus voltage of the bus capacitor, and send a control signal according to the current state of the inverter; wherein the current state of the inverter includes any one of the following states: a first state when the inverter is operating normally, a second state when the inverter is shut down in an emergency, and a third state when the inverter is shut down normally; the switch module is configured to control the number of discharge paths of the bus capacitor connected to the two or more discharge resistor groups according to the control signal when receiving the control signal, so as to achieve: when it is necessary to release the power of the bus capacitor, according to the release demand of the power of the bus capacitor, control the number of discharge paths of the bus capacitor connected to the two or more discharge resistor groups.

[0019] In some embodiments, the driving unit includes: a first signal amplifying module, a second signal amplifying module, a signal inversion module, a first control module and a second control module; when the switch module includes a first switch and a second switch, the control signal output by the control unit is divided into two paths, one path passes through the first signal amplifying module and the first control module, and is output to the first switch as a first control signal; the other path passes through the signal inversion module, the second signal amplifying module and the second control module, and is output to the second switch as a second control signal; wherein the first signal amplifying module is configured to amplify the control signal; the first control module is configured to control the on-off of the output path of the first control signal; the signal inversion module is configured to invert the level of the control signal; the second signal amplifying module is configured to amplify the control signal after the inversion process; the second control module is configured to control the on-off of the output path of the second control signal.

[0020] In some embodiments, when the control unit is powered on, the control unit outputs the control signal: when the level of the control signal is high, the level of the first control signal is high, and the first switch and the second switch are both in an open state; when the level of the control signal is low, the level of the first control signal is low, and the first switch is in a closed state; the level of the second control signal is high, and the second switch is in an open state; when the control unit loses power, the control unit does not output the control signal: the first switch and the second switch are both in a closed state.

[0021] Matching the above device, the present invention further provides a frequency converter, including: the control device of the frequency converter described above.

[0022] Matching the above-mentioned frequency converter, the present invention provides a control method of a frequency converter on another aspect, wherein the frequency converter has a bus capacitor; the control method of the frequency converter comprises: through each of the two or more discharge resistor groups, under the control of the switch module, the power of the bus capacitor can be released individually, and the power of the bus capacitor can be released together with the remaining discharge resistor groups; through the switch module, when it is necessary to release the power of the bus capacitor, according to the release demand of the power of the bus capacitor, the number of discharge paths of the two or more discharge resistor groups connected to the bus capacitor is controlled, denoted as N, where N is a positive integer; the power of the bus capacitor is released by utilizing the N discharge resistor groups connected to the discharge path of the bus capacitor in the two or more discharge resistor groups; wherein the two or more discharge resistor groups and the switch module form a bus capacitor discharge unit; the bus capacitor discharge unit is arranged at the output end of the bus capacitor.

[0023] In some embodiments, the two or more discharge resistor groups include: a first resistor group and a second resistor group; the switch module includes: a first switch and a second switch; wherein the second resistor group and the second switch are connected in series to form a first series branch; the first series branch is connected in parallel with the first resistor group to form a first parallel branch; the first parallel branch is connected in series with the first switch to form a second series branch; the first end of the second series branch is connected to the positive end of the bus capacitor; the second end of the second series branch is connected to the negative end of the bus capacitor.

[0024] In some embodiments, when the amount of electricity of the bus capacitor needs to be released, the number of discharge paths of the bus capacitor to which the two or more discharge resistor groups are connected is controlled according to the release requirement of the amount of electricity of the bus capacitor, including any of the following control situations:

[0025] The first control scenario: when the frequency converter is operating normally, the first switch and the second switch are both in a disconnected state, so that the first resistor group and the second resistor group do not release the electricity of the bus capacitor, which is recorded as the first resistor group and the second resistor group are both not working.

[0026] The second control scenario: when the inverter stops normally during normal operation, when the motor controlled by the inverter has stopped, and the input power of the inverter has been cut off, the following is performed: if the bus voltage of the bus capacitor exceeds the set protection value, the first switch is in a closed state, and the second switch is in an open state, so that the first resistor group works and the second resistor group does not work; if the bus voltage of the bus capacitor does not exceed the protection value, the first switch and the second switch are both in an open state, so that the first resistor group and the second resistor group do not work, and the energy feedback process of the motor controlled by the inverter continues to be executed; and, when the energy feedback process of the motor controlled by the inverter ends, if the bearing controller of the motor controlled by the inverter has controlled the bearing to drop, and the main control board of the inverter has been powered off, the first switch and the second switch are both in a closed state, so that the first resistor group and the second resistor group both work.

[0027] The third control situation: when the inverter stops normally during normal operation, wait for the motor controlled by the inverter to stop and the bearing of the motor controlled by the inverter to fall off, then the input power of the inverter is cut off, and execute: if the bus voltage of the bus capacitor exceeds the set protection value, the first switch is in a closed state, and the second switch is in an open state, so that the first resistor group works and the second resistor group does not work; if the bus voltage of the bus capacitor does not exceed the protection value, then: after the bearing of the motor controlled by the inverter has fallen off and the input power of the inverter has been cut off In this case, both the first switch and the second switch are in an open state, so that both the first resistor group and the second resistor group do not work, and after waiting for the bearing controller of the motor controlled by the inverter to control the bearing to fall off and the main control board of the inverter to be powered off, both the first switch and the second switch are in a closed state, so that both the first resistor group and the second resistor group work; when the bearing of the motor controlled by the inverter has not fallen off and / or the input power of the inverter has not been cut off, both the first switch and the second switch are in a closed state, so that both the first resistor group and the second resistor group work.

[0028] In some embodiments, when the amount of electricity of the bus capacitor needs to be released, the number of discharge paths of the bus capacitor to which more than two discharge resistor groups are connected is controlled according to the release requirement of the amount of electricity of the bus capacitor by means of the switch module, and any one of the following further control situations is also included:

[0029] A first further control scenario: when the inverter shuts down normally during normal operation, after the first resistor group and the second resistor group are not working and the energy feedback process of the motor controlled by the inverter continues to be executed, when the energy feedback process of the motor controlled by the inverter ends, if the bearing controller of the motor controlled by the inverter has controlled the bearing to drop, and the main control board of the inverter has been powered off, the first switch and the second switch are both in a closed state, so that the first resistor group and the second resistor group both work.

[0030] A second further control scenario: when the frequency converter shuts down normally during normal operation, after making the first resistor group and the second resistor group non-operating, and after waiting for the bearing controller of the motor controlled by the frequency converter to control the bearing to drop and the main control board of the frequency converter to be powered off, the first switch and the second switch are both in a closed state, so that the first resistor group and the second resistor group are both operating.

[0031] In some embodiments, it also includes: sampling the bus voltage of the bus capacitor through a sampling unit; determining the current state of the inverter according to the bus voltage of the bus capacitor through a control unit, and sending a control signal according to the current state of the inverter; wherein the current state of the inverter includes any one of the following states: a first state when the inverter is operating normally, a second state when the inverter is shut down in an emergency, and a third state when the inverter is shut down normally; through a switch module, when receiving the control signal, according to the control signal, controlling the number of discharge paths of the bus capacitor connected to the two or more discharge resistor groups, so as to achieve: when it is necessary to release the power of the bus capacitor, according to the release demand of the power of the bus capacitor, controlling the number of discharge paths of the bus capacitor connected to the two or more discharge resistor groups.

[0032] Therefore, the scheme of the present invention forms a bus capacitor discharge unit of the inverter by utilizing more than two groups of resistor modules and switch units (such as more than two switch modules) in series-parallel form; when the motor controlled by the inverter stops or decelerates too quickly, the bus capacitor discharge unit is enabled to consume the excessive pump voltage fed back when the motor controlled by the inverter stops or decelerates too quickly; and, the number of resistor modules connected to the bus capacitor discharge path of the inverter in the two or more groups of resistor modules can be adjusted by switching the switch unit, so as to reduce the discharge power of the bus capacitor discharge unit before the magnetic suspension bearing controlled by the inverter falls, and increase the discharge power of the bus capacitor discharge unit after the magnetic suspension bearing controlled by the inverter falls; thereby, the discharge power of the bus capacitor discharge resistor of the inverter can be changed with actual needs, which is beneficial to improving the safety of the inverter.

[0033] 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.

[0034] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a structural schematic diagram of an embodiment of a control device for a frequency converter of the present invention;

[0036] Figure 2 A topological diagram of an embodiment of a bus capacitor discharge unit of a frequency converter (such as a bus capacitor discharge circuit of a frequency converter);

[0037] Figure 3 A structural schematic diagram of an embodiment of a control signal driving circuit of a bus capacitor discharge unit of a frequency converter;

[0038] Figure 4 An example graph of a curve of an embodiment of the energy feedback bus voltage of the frequency converter;

[0039] Figure 5 A schematic flow chart of a discharge power conversion procedure of a bus capacitor discharge unit of an inverter according to an embodiment of the present invention;

[0040] Figure 6 A flow chart of an embodiment of a method for controlling a frequency converter of the present invention;

[0041] Figure 7 It is a flow chart of an embodiment of automatically controlling a switch module by using a control unit in the method of the present invention;

[0042] Figure 8 It is a structural diagram of the bus voltage sampling module;

[0043] Fig. 9 Schematic diagram of the wiring structure of the first contactor. DETAILED DESCRIPTION

[0044] 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.

[0045] Considering that the discharge power of the busbar capacitor discharge resistor cannot change with the actual situation, it affects the safety of the inverter. Therefore, when the inverter is shut down or powered off, the discharge resistor needs to reduce the discharge power or not discharge before the magnetic bearing falls off the shaft. After the shaft falls off, the discharge power needs to be increased to quickly consume the power in the cabinet.

[0046] In order to enable the inverter to discharge the bus capacitor efficiently in both normal shutdown and emergency shutdown states, and to avoid the bus voltage dropping too quickly during emergency shutdown and power failure, resulting in the magnetic bearing losing power, losing control and falling shaft. According to an embodiment of the present invention, a control device for an inverter is provided. Figure 1 A schematic diagram of the structure of an embodiment of the device of the present invention is shown. The frequency converter has a bus capacitor and also has an inverter unit. The bus capacitor can be a capacitor group or a single capacitor such as a bus capacitor C. The inverter unit is such as an inverter bridge. The control device of the frequency converter includes: a bus capacitor discharge unit. The bus capacitor discharge unit is arranged at the output end of the bus capacitor, specifically between the bus capacitor and the inverter unit. The bus capacitor discharge unit includes: a discharge resistor module and a switch module. The discharge resistor module includes: a discharge resistor group, and the number of the discharge resistor groups is more than two.

[0047] Among them, each of the more than two discharge resistor groups is configured to release the power of the bus capacitor individually under the control of the switch module, and can also release the power of the bus capacitor together with the remaining discharge resistor groups.

[0048] The switch module is configured to control the number of discharge paths of the bus capacitors connected to the two or more discharge resistor groups according to the release demand of the bus capacitors when the power of the bus capacitors needs to be released, which is recorded as N, where N is a positive integer and is less than or equal to the number of the two or more discharge resistor groups. The power of the bus capacitors is released by utilizing the N discharge resistor groups connected to the discharge paths of the bus capacitors among the two or more discharge resistor groups. The release demand of the bus capacitors is the demand for slow or fast release of the power of the bus capacitors.

[0049] The scheme of the present invention provides a control device for the bus capacitor discharge power of a frequency converter, which is used in the bus capacitor discharge process of a high-power frequency converter to adjust the discharge power of the bus capacitor discharge resistor according to different actual conditions, thereby improving the bus capacitor discharge efficiency, reducing the risk of bearing damage, and improving the reliability of the frequency converter.

[0050] In some embodiments, the two or more discharge resistor groups include: a first resistor group and a second resistor group. The first resistor group is such as the first resistor group R1, and the second resistor group is such as the second resistor group R2.

[0051] The switch module includes: a first switch, such as the first switch K1, and a second switch, such as the second switch K2.

[0052] The second resistor group and the second switch are connected in series to form a first series branch. The first series branch is connected in parallel with the first resistor group to form a first parallel branch. The first parallel branch is connected in series with the first switch to form a second series branch.

[0053] The first end of the second series branch is connected to the positive end of the bus capacitor. The second end of the second series branch is connected to the negative end of the bus capacitor.

[0054] Consider the description of bus voltage changes when the inverter is shut down in an emergency, as well as the relationship between the bus voltage and the inverter main control board and magnetic bearing controller. Once the inverter is shut down in an emergency, the frequency drops too quickly, and the motor generates a large pump voltage due to regenerative braking, which is fed back to the bus capacitor. If there is a discharge resistor with a certain discharge power in the bus, and the inverter cuts off the input power, the bus voltage will drop rapidly. The inverter starts energy feedback at the same time as the emergency shutdown, so the bus voltage will increase and stabilize at a certain voltage value. If the minimum voltage during the bus voltage drop stage is lower than the minimum power supply voltage of the magnetic bearing controller due to excessive discharge resistor power, the magnetic bearing will lose power, lose control, and fall off, which will easily damage the bearing.

[0055] Figure 2FIG. 1 is a topological diagram of an embodiment of a bus capacitor discharge unit of a frequency converter (such as a bus capacitor discharge circuit of a frequency converter). Figure 2 As shown, two groups of resistors (such as a first resistor group and a second resistor group) and two switches (such as a first switch and a second switch) are connected in series and parallel (i.e., a mixed form of series and parallel connection) to form an overall bus capacitor discharge structure (such as a bus capacitor discharge unit).

[0056] In some embodiments, in the second series branch, one end of the first switch away from the first parallel branch serves as the first end of the second series branch. One end of the first parallel branch away from the first switch serves as the second end of the second series branch.

[0057] In the first series branch, the second switch is located away from one end of the second resistor group and is connected to the second end of the second series branch.

[0058] exist Figure 2 In the frequency converter shown, the three-phase AC power input terminals (such as U terminal, V terminal and W terminal) are connected to the motor after passing through the first adjustment unit, the rectifier bridge, the bus capacitor, the second adjustment unit and the inverter bridge. An inductor L1 is also provided between the rectifier bridge and the bus capacitor.

[0059] The first regulating unit includes: switch K11, switch K12, switch K13, switch K21, switch K22 and switch K23, resistor R3, resistor R4 and resistor R5. Switch K11, switch K12 and switch K13 are respectively arranged between the U end, V end and W end of the three-phase AC power supply and the input end of the rectifier bridge. Switch K21, switch K22 and switch K23 are respectively connected in series with resistor R3, resistor R4 and resistor R5, and then connected in parallel with switch K11, switch K12 and switch K13. The relationship between them is one-to-one corresponding.

[0060] The second regulating unit is used as the bus capacitor discharge unit of the inverter. Figure 2 As shown, the bus capacitor discharge unit of the frequency converter is arranged on the bus of the frequency converter and is located between the bus capacitor C of the frequency converter and the inverter. The bus capacitor discharge unit of the frequency converter includes: a first resistor group R1, a second resistor group R2, a first switch K1 and a second switch K2. The second resistor group R2 is connected in series with the second switch and then connected in parallel with the first resistor group R1. One end of the parallel branch is connected to the bus where the positive electrode of the bus capacitor C is located after passing through the first switch K1. The other end of the parallel branch is connected to the bus where the negative electrode of the bus capacitor C is located.

[0061] In some schemes, a series branch of a fixed resistor and a switch is connected in parallel with the bus capacitor branch. When the motor decelerates, the switch is turned on and off according to the bus capacitor voltage to discharge the bus capacitor. In other schemes, the charging resistor is switched as the discharge resistor of the bus capacitor through a switch, such as Figure 2 The first regulating unit in Figure 2 The charging resistors such as resistors R3 to R5 are switched as busbar capacitor discharge resistors through special switches. Neither of these two methods satisfies the above-mentioned condition of the discharge power transformation before and after the bearing falls when the inverter controls the emergency stop of the magnetic suspension motor.

[0062] The discharge resistor power of these two methods is fixed. When the inverter stops, the discharge resistor may work due to the high pump voltage. If the fixed discharge power is large, the bus capacitor may be consumed too quickly, causing the magnetic bearing to lose power before the shaft falls, resulting in loss of control. If the fixed discharge power is small, the bus capacitor cannot be consumed quickly after the magnetic bearing falls.

[0063] In some implementations, both the first switch and the second switch are contactors.

[0064] In some examples, Figure 2 In the example shown, the first resistor group R1 and the second resistor group R2 are both resistor combinations of a series of resistors connected in series, and the first switch K1 and the second switch K2 are both composed of switches (such as controllable contactors), and the two contactors are in a closed state when their respective control signals are at a low level. One end of the first contactor is connected to the positive end of the bus, and the other end is connected to one end of the two groups of resistors. One end of the first resistor group R1 is connected to the first contactor, and the other end is connected to the negative end of the bus. One end of the second resistor group R2 is connected to the first contactor, and the other end is connected to the second contactor. One end of the second contactor is connected to the second resistor group R2, and the other end is connected to the negative end of the bus.

[0065] In the above embodiment, the contactor as an on-off switch is only one of the controllable switch options and should be determined according to actual conditions.

[0066] In the above embodiment, the bus capacitor discharge unit of the inverter includes but is not limited to two groups of resistors and two switches, and more discharge power options can be expanded according to actual needs.

[0067] In some embodiments, when the amount of electricity of the bus capacitor needs to be released, the switch module controls the number of discharge paths of the bus capacitor to which the two or more discharge resistor groups are connected according to the release requirement of the amount of electricity of the bus capacitor, including any of the following control situations:

[0068] The first control scenario: the switch module is specifically configured so that when the frequency converter is operating normally, that is, when the frequency converter is operating normally according to the set operating mode, the first switch and the second switch are both in a disconnected state, so that the first resistor group and the second resistor group do not release the electricity of the bus capacitor, which is recorded as the first resistor group and the second resistor group are both not working.

[0069] Second control scenario: the switch module is further configured to execute, when the frequency converter is shut down normally during normal operation, when the motor controlled by the frequency converter is shut down, and the input power of the frequency converter is cut off:

[0070] If the bus voltage of the bus capacitor exceeds a set protection value, the first switch is in a closed state and the second switch is in an open state, so that the first resistor group works and the second resistor group does not work.

[0071] If the bus voltage of the bus capacitor does not exceed the protection value, the first switch and the second switch are both in an open state, so that the first resistor group and the second resistor group are not working, and the energy feedback process of the motor controlled by the inverter continues to be executed. And, when the energy feedback process of the motor controlled by the inverter ends, if the bearing controller of the motor controlled by the inverter has controlled the bearing to drop the shaft, and the main control board of the inverter has been powered off, the first switch and the second switch are both in a closed state, so that the first resistor group and the second resistor group are working.

[0072] The third control scenario: the switch module is further configured to wait for the motor controlled by the inverter to stop and the bearing of the motor controlled by the inverter to fall off before the input power of the inverter is cut off, and execute the following steps when the inverter stops normally during normal operation:

[0073] If the bus voltage of the bus capacitor exceeds a set protection value, the first switch is in a closed state and the second switch is in an open state, so that the first resistor group works and the second resistor group does not work.

[0074] If the bus voltage of the bus capacitor does not exceed the protection value, then: when the bearing of the motor controlled by the inverter has fallen off and the input power of the inverter has been cut off, the first switch and the second switch are both in an open state, so that the first resistor group and the second resistor group are not working, and after the bearing controller of the motor controlled by the inverter has controlled the bearing to fall off and the main control board of the inverter has been powered off, the first switch and the second switch are both in a closed state, so that the first resistor group and the second resistor group are working. When the bearing of the motor controlled by the inverter has not fallen off and / or the input power of the inverter has not been cut off, the first switch and the second switch are both in a closed state, so that the first resistor group and the second resistor group are working.

[0075] pass Figure 2 The bus capacitor discharge unit of the inverter shown can achieve high-efficiency bus capacitor discharge based on the actual bus voltage conditions and under the premise of meeting the magnetic bearing control requirements, solving the problem that the discharge power of the bus capacitor discharge resistor cannot change with the actual conditions, and realizing rapid consumption of power in the inverter cabinet after the inverter cuts off the input power supply, thereby improving the safety and reliability of the inverter.

[0076] In some embodiments, when the electric quantity of the bus capacitor needs to be released, the switch module controls the number of discharge paths of the bus capacitor to which the two or more discharge resistor groups are connected according to the release demand of the electric quantity of the bus capacitor, and further includes any one of the following control situations:

[0077] A first further control scenario: the switch module is further configured to, when the inverter shuts down normally during normal operation, after the first resistor group and the second resistor group are not working and the energy feedback process of the motor controlled by the inverter continues to be executed, when the energy feedback process of the motor controlled by the inverter ends, if the bearing controller of the motor controlled by the inverter has controlled the bearing to drop and the main control board of the inverter has been powered off, then the first switch and the second switch are both in a closed state to make the first resistor group and the second resistor group work.

[0078] Specifically, the switch module is also configured to execute, when the inverter is shut down normally during normal operation, when the motor controlled by the inverter is shut down, and when the input power of the inverter is cut off: if the bus voltage of the bus capacitor does not exceed the protection value, then the first switch and the second switch are both in an open state, so that the first resistor group and the second resistor group do not work, and the energy feedback process of the motor controlled by the inverter continues to be executed. And, when the energy feedback process of the motor controlled by the inverter ends, if the bearing controller of the motor controlled by the inverter has controlled the bearing to drop, and the main control board of the inverter has been powered off, then the first switch and the second switch are both in a closed state, so that the first resistor group and the second resistor group work.

[0079] A second further control scenario: the switch module is further configured to, when the frequency converter is shut down normally during normal operation, make the first resistor group and the second resistor group both inoperative, and wait until the bearing controller of the motor controlled by the frequency converter has controlled the bearing to drop and the main control board of the frequency converter has been powered off, so that the first switch and the second switch are both in a closed state, so that the first resistor group and the second resistor group are both operative.

[0080] Specifically, the switch module is further configured to, when the inverter shuts down normally during normal operation, wait for the motor controlled by the inverter to shut down and the bearing of the motor controlled by the inverter to fall off before the input power of the inverter is cut off, and execute: if the bus voltage of the bus capacitor does not exceed the protection value, then: when the bearing of the motor controlled by the inverter has fallen off and the input power of the inverter has been cut off, the first switch and the second switch are both in an open state so that the first resistor group and the second resistor group do not work, and wait for the bearing controller of the motor controlled by the inverter to control the bearing to fall off and the main control board of the inverter has been powered off, and then the first switch and the second switch are both in a closed state so that the first resistor group and the second resistor group work.

[0081] In order to meet the requirement that the magnetic levitation bearing controller has a stable voltage to control the bearing to stably drop the shaft, the solution of the present invention can disable the bus discharge resistor or make the discharge power small before the bearing drops the shaft, and can increase the bus discharge power after the bearing drops the shaft, quickly consume the electricity in the bus capacitor, and solve the problem that the bus fixed discharge resistor power is too small and the discharge efficiency is too low after the magnetic levitation bearing stably controls the shaft to drop the shaft.

[0082] In some embodiments, the system further comprises: a sampling unit, a control unit and a driving unit. The sampling unit is such as a bus voltage sampling module. The control unit is such as a DSP chip. The driving unit is such as a control signal driving circuit.

[0083] Wherein, the sampling unit is configured to sample the bus voltage of the bus capacitor.

[0084] The control unit is configured to determine the current state of the inverter according to the bus voltage of the bus capacitor, and send a control signal according to the current state of the inverter. The current state of the inverter includes any of the following states: a first state when the inverter is operating normally, a second state when the inverter is in emergency shutdown, and a third state when the inverter is in normal shutdown. The control signal is a signal for controlling the switch module.

[0085] The switch module is configured to, upon receiving the control signal, control the number of discharge paths of the bus capacitor through which the two or more discharge resistor groups are connected according to the control signal, so as to achieve: when it is necessary to release the electricity of the bus capacitor, according to the release requirement of the electricity of the bus capacitor, control the number of discharge paths of the bus capacitor through which the two or more discharge resistor groups are connected.

[0086] Figure 2 The bus capacitor discharge unit of the inverter shown in the figure is specifically the inverter bus capacitor discharge resistor topology, which shows the connection relationship between the bus capacitor and the discharge resistor and the connection relationship between the two sets of discharge resistors and the main control circuit. Figure 2 The discharge resistor portion shown adopts a series branch of a second resistor group and a second switch connected in parallel with the first resistor group, and the parallel branch is further connected in series with the first switch.

[0087] The scheme of the present invention also provides a method for regulating the discharge power of the bus capacitor of the frequency converter. In the scheme of the present invention, two signals are separated through a control signal of a DSP chip, one of which is inverted. The two signals control two switches respectively. If a relay is used as a switch, it is in a closed state by default when power is lost, and in a disconnected state when power is obtained.

[0088] Combined with the inverter power cut-off and the main control board power-off, a DSP chip signal is used to control three discharge states. In this way, combined with the inverter main control board power-on and power-off states, a control signal is used to control three discharge powers. For example, combined with the inverter main control board power-off, a single control signal is used to control three discharge states.

[0089] Combined with the actual situation of bus voltage feedback when the motor stops suddenly, the control logic of the DSP chip controls the discharge power of the bus capacitor to achieve stable power supply before the magnetic bearing drops. In this way, the control logic of the magnetic bearing drops is combined to achieve discharge power switching, such as combining the power-on and power-off status of the equipment, the magnetic bearing control, and the pump voltage to control the discharge power of the bus capacitor. Thus, the discharge power of the discharge resistor in different states can be solved, avoiding the situation where the bus voltage is consumed too quickly when the inverter stops urgently and the magnetic bearing has not dropped, and avoiding the situation where the bus voltage is consumed too slowly when the inverter is powered off and the bearing has dropped.

[0090] exist Figure 2 In the example shown, the main control circuit of the bus capacitor discharge unit of the inverter includes: a bus voltage sampling module, a DSP chip and a control signal driving circuit. The bus voltage sampling module, the DSP chip and the control signal driving circuit are connected in sequence and can output a driving signal to drive the first switch K1 and / or the second switch K2 to operate. Among them, the bus voltage sampling module can use a voltage dividing resistor, such as Figure 8 In the example shown, resistor group three and resistor group four perform voltage division sampling to sample the bus voltage.

[0091] In some embodiments, the driving unit includes: a first signal amplifying module, a second signal amplifying module, a signal negation module (such as a NOT gate module F1 ), a first control module, and a second control module.

[0092] In the case where the switch module includes a first switch and a second switch, the control signal output by the control unit is divided into two paths, one path is output to the first switch as a first control signal after passing through the first signal amplification module and the first control module, and the other path is output to the second switch as a second control signal after passing through the signal inversion module, the second signal amplification module and the second control module.

[0093] The first signal amplification module is configured to amplify the control signal; the first control module is configured to control the on / off of an output path of the first control signal.

[0094] The signal inversion module is configured to invert the level of the control signal.

[0095] The second signal amplifying module is configured to amplify the control signal after the inversion process; the second control module is configured to control the on-off of the output path of the second control signal.

[0096] Figure 3 FIG. 1 is a schematic diagram of a structure of an embodiment of a control signal driving circuit of a bus capacitor discharge unit of a frequency converter. Figure 3 As shown, the control signal driving circuit of the bus capacitor discharge unit of the inverter includes: a first signal amplification module, a second signal amplification module and a NOT gate module F1. Among them, the signal amplification module in the first signal amplification module and the second signal amplification module uses a power chip to convert the 3.3V signal output by the DSP chip into a 5V signal. The first control module uses a first relay, and the second control module uses a second relay. The first switch K1 uses a first contactor, and the second switch K2 uses a second contactor.

[0097] exist Figure 3 In the example shown, the control signal output by the DSP chip is divided into two paths, one path is output to the coil of the first relay after passing through the first signal amplification module, and the other path is output to the coil of the second relay after passing through the NOT gate module F1 and the second signal amplification module. The two ends of the coil of the first relay are pin 1 and pin 2 of the first relay. The output end of the first signal amplification module is connected to pin 1 of the first relay. Pin 2 of the first relay is connected to a 5V DC power supply. Pin 3 of the first relay and pin 5 of the first relay are fixed ends, and pin 4 of the first relay is a movable end located between pin 3 of the first relay and pin 5 of the first relay. Pin 6 of the first relay and pin 8 of the first relay are fixed ends, and pin 7 of the first relay is a movable end located between pin 6 of the first relay and pin 8 of the first relay. Pin 8 of the first relay is connected to terminal JCQ1_1, and pin 7 of the first relay is connected to terminal JCQ1_2. Terminals JCQ1_1 and JCQ1_2 are connected to the two ends of the first contactor to control its own on-off device.

[0098] The first contactor and the second contactor have internal components that control their on and off. If the corresponding contactor is controllable, then there will be access to the control terminal. Terminals JCQ1_1 and JCQ1_2 are the access to the control terminal of the first contactor. The internal control component and terminals JCQ1_1 and JCQ1_2 are as follows: Fig. 9 As shown. Figure 3 In the example shown, when pin 7 and pin 8 of the first relay are connected together, that is, terminal JCQ1_1 and terminal JCQ1_2 are connected, the first contactor (such as Fig. 9 The control device of the contactor KM1 shown in the figure is turned on and energized, thereby controlling the contactor to be turned on, that is, the first switch K1 is turned on. Therefore, in fact, the conduction between the control terminal JCQ1_1 and the terminal JCQ1_2 is controlled, and then the control device of the first contactor is energized, thereby controlling the conduction of the first switch K1.

[0099] The two ends of the coil of the second relay are pin 1 and pin 2 of the second relay. The output end of the second signal amplification module is connected to pin 1 of the second relay. Pin 2 of the second relay is connected to a 5V DC power supply. Pin 3 of the second relay and pin 5 of the second relay are fixed ends, and pin 4 of the second relay is a movable end located between pin 3 of the second relay and pin 5 of the second relay. Pin 6 of the second relay and pin 8 of the second relay are fixed ends, and pin 7 of the second relay is a movable end located between pin 6 of the second relay and pin 8 of the second relay. Pin 8 of the second relay is connected to terminal JCQ1_1, and pin 7 of the second relay is connected to terminal JCQ1_2. Terminals JCQ1_1 and JCQ1_2 are connected to the two ends of the second contactor to control its own on-off device.

[0100] Figure 3 The control signal driving circuit shown includes a signal after amplifying the signal voltage of the control signal output by the DSP chip, and acting on the first relay. The control signal output by the DSP chip is amplified after being inverted, and the amplified signal acts on the second relay. Among them, the control signal output by the DSP chip is divided into two paths, one of which is amplified to control the first relay, and the other is inverted and amplified to control the second relay. In this way, combined with the power-off condition of the DSP chip, a DSP chip port can present three discharge states.

[0101] In the solution of the present invention, the driving circuit of the discharge power switching control signal, such as Figure 3As shown, the 3.3V signal of the DSP chip port controls the on-off of the first relay after voltage signal amplification, and then controls the on-off of the first contactor. At the same time, the signal of the DSP chip port is also controlled by the inverted logic chip (such as the NOT gate module F1), and then controls the on-off of the second relay after voltage amplification, and then controls the on-off of the second contactor. The first contactor and the second contactor are in a closed state when their control signals are low, and in an open state when their control signals are high. Therefore, when the control signal of the DSP chip port is low, the signal received by the first contactor is in a low level state, and the first contactor is in a closed state. The signal received by the second contactor is in a high level state, and the second contactor is in an open state. The first resistor group R1 works and the second resistor group R2 does not work. At this time, the overall discharge resistance value is high and the discharge power is low. When the control signal of the DSP chip port is high, the signal received by the first contactor is in a high level state, and the first contactor is in an open state. The signal received by the second contactor is in a low level state, and the second contactor is in a closed state. Because the first contactor is in the disconnected state, the two groups of resistors (such as the first resistor group R1 and the second resistor group R2) and the bus circuit are in the open circuit state, so that the first resistor group R1 and the second resistor group R2 do not work, and the bus capacitor discharges without resistance. When the main control board is powered off, the main control board has no output signal to the contactor, which is equivalent to both contactors receiving low-level signals, and both contactors are in the closed state, so that the first resistor group R1 works and the second resistor group R2 works. At this time, the overall discharge resistance value is low and the discharge power is the highest.

[0102] Figure 4 FIG. 1 is a curve diagram showing an example of an embodiment of the energy feedback bus voltage of the frequency converter. Figure 4 The energy feedback bus voltage example diagram shown shows the voltage change when the bus is discharged with a fixed resistor when the inverter is shut down urgently. Once the bus is shut down urgently, the motor decelerates and stops to generate a short-term pump voltage, and then the voltage drops due to the inverter cutting off the input power and the bus discharge resistor consumption. If the lowest point of the voltage drop is lower than the lowest power supply voltage of the bearing controller, the bearing will lose power and fall out of control. Energy feedback regulation stabilizes the bus voltage at a certain voltage value until the energy feedback ends.

[0103] In some embodiments, when the control unit is powered on, the control unit outputs the control signal:

[0104] In the case where the level of the control signal is at a high level, the level of the first control signal is at a high level, and both the first switch and the second switch are in an off state.

[0105] When the level of the control signal is low, the level of the first control signal is low, and the first switch is in a closed state. When the level of the second control signal is high, the second switch is in an open state.

[0106] When the control unit loses power, the control unit does not output the control signal: the first switch and the second switch are both in a closed state.

[0107] Figure 5 The figure is a flow chart of a discharge power conversion procedure of a bus capacitor discharge unit of an inverter according to an embodiment of the present invention. Figure 5 The discharge power conversion program flow chart shown in Figure 1 shows the discharge power switching logic corresponding to normal shutdown and emergency shutdown. Figure 5 As shown in FIG. 1 , the execution process of the discharge power conversion program of the bus capacitor discharge unit of the inverter includes:

[0108] Step 1: When the frequency converter operates normally, the control signal output by the DSP chip is set to a high level, and the first resistor group R1 and the second resistor group R2 do not operate.

[0109] That is to say, when the frequency converter operates normally, the control signal at the DSP chip end is at a high level, and both the first resistor group R1 and the second resistor group R2 are in a non-operating state.

[0110] Step 2: When the inverter stops, determine whether the shutdown of the inverter is an emergency shutdown. If so, execute step 3, that is, execute the discharge power control process in the emergency shutdown power-off state. Otherwise, execute step 4, that is, execute the discharge power control process in the normal shutdown power-off state. In other words, two discharge power switching modes are performed according to the two shutdown power-off states, one is the emergency shutdown power-off state, and the other is the normal shutdown power-off state. For example: in the operating state of the inverter, if it is detected that the input voltage of the inverter is lower than a certain rated value, it can be determined as an emergency shutdown.

[0111] Step 3: Execute the discharge power control process in the emergency shutdown power-off state. For details, refer to the following exemplary description (see steps 31 to 33).

[0112] Step 31: When the inverter is shut down urgently, the motor is stopped immediately and the inverter input power is cut off at the same time.

[0113] Step 32: If it is determined to be an emergency shutdown, then determine whether the bus voltage exceeds the protection value, that is, determine whether the bus voltage is higher than the protection value due to the pump-generated voltage.

[0114] If the bus voltage exceeds the protection value, the DSP chip terminal is set to a low level, the first resistor group R1 works, the second resistor group R2 does not work, and the bus voltage is reduced with a smaller discharge power. Then, the process returns to step 32.

[0115] If the bus voltage does not exceed the protection value, if the bus voltage is lower than the protection value, the DSP chip control terminal is set to a high level, and the first resistor group R1 and the second resistor group R2 do not work. At the same time, the energy feedback function of the motor continues to work, adjusting the bus voltage to a reference value, and the bearing controller then stably controls the bearing to drop. Then, step 33 is executed.

[0116] Step 33: As energy feedback ends, the bus voltage continues to drop due to the power consumption of the bearing controller and the inverter main control board until the motor main control board loses power. At this time, it is equivalent to that both relays receive low-level signals, both relays are in a closed state, the first resistor group R1 works, the second resistor group R2 works, and the discharge power is the highest.

[0117] In this way, when the inverter is shut down urgently and the input power is cut off, the solution of the present invention stops the power consumption of the bus discharge resistor under the premise that the bus voltage is not in an excessively high state, thereby avoiding the bus voltage dropping too quickly before the energy feedback regulation makes the bus voltage return to the reference value, causing the magnetic suspension bearing to lose power, lose control and fall off. This solves the problem of the magnetic suspension bearing losing power, losing control and falling off due to excessive consumption of the fixed discharge resistor due to the bus capacitor voltage during emergency shutdown.

[0118] Step 4: Execute the discharge power control process in the normal shutdown and power-off state. For details, refer to the following exemplary description (see steps 41 to 43).

[0119] Step 41: When the inverter is shut down and powered off normally, wait until the motor stops and the bearing has dropped before powering off. Because the inverter is in normal shutdown and the input power is not cut off, the bus has enough voltage to control the magnetic bearing to drop, so there is no need to consider the loss of power and control of the bearing in this shutdown state. When the inverter is shut down, determine whether the bus voltage is higher than the protection value due to the pump voltage.

[0120] If the bus voltage is higher than the protection value, the DSP chip end control signal is set to a low level, the first resistor group R1 works, and the second resistor group R2 does not work, and a smaller discharge power is used to reduce the bus voltage.

[0121] If the bus voltage is not higher than the protection value, step 42 is executed.

[0122] Step 42: When the bus voltage is not higher than the protection value, continue to determine whether the bearing has fallen off and whether the inverter input power has been cut off.

[0123] If the inverter is not powered off, the control signal of the DSP chip port is maintained at a high level, and the first resistor group R1 and the second resistor group R2 do not work. Then, the process returns to step 42 .

[0124] If it is determined that the bearing has fallen off and the inverter input has been powered off, the DSP chip terminal is set to a low level, the first resistor group R1 works, and the second resistor group R2 does not work. Then, step 43 is executed.

[0125] Step 43, wait for the main control board to lose power, so that the first resistor group R1 works, and the second resistor group R2 works, the discharge power is the highest, and the power in the inverter cabinet is consumed quickly.

[0126] In this way, when the motor stops or decelerates too quickly, and the bus voltage becomes too high due to the pump-generated voltage fed back by the motor, the solution of the present invention can enable the bus discharge resistor, sample an appropriate amount of discharge power to consume the excessive voltage, and consume the excessive pump-generated voltage fed back by the motor when it stops, thereby avoiding the bus capacitor being in a high voltage state for a long time, thereby damaging the bus capacitor.

[0127] The technical solution of the present invention is adopted, by utilizing two or more groups of resistor modules and switch units (such as two or more switch modules), in a series-parallel form, to form a bus capacitor discharge unit of the frequency converter. When the motor controlled by the frequency converter stops or decelerates too quickly, the bus capacitor discharge unit is enabled, which can consume the excessive pump voltage fed back when the motor controlled by the frequency converter stops or decelerates too quickly. In addition, the number of resistor modules connected to the bus capacitor discharge path of the frequency converter in the two or more groups of resistor modules can be adjusted by switching the switch unit, so as to reduce the discharge power of the bus capacitor discharge unit before the magnetic suspension bearing controlled by the frequency converter falls, and increase the discharge power of the bus capacitor discharge unit after the magnetic suspension bearing controlled by the frequency converter falls. Therefore, by making the discharge power of the bus capacitor discharge resistor of the frequency converter change with actual needs, it is beneficial to improve the safety of the frequency converter.

[0128] According to an embodiment of the present invention, a frequency converter corresponding to the control device of the frequency converter is also provided. The frequency converter may include: the control device of the frequency converter described above.

[0129] Since the processing and functions implemented by the frequency converter of this embodiment basically correspond to the embodiments, principles and examples of the aforementioned devices, for the details not fully described in this embodiment, please refer to the relevant descriptions in the aforementioned embodiments, and no further elaboration will be made here.

[0130] The technical solution of the present invention is adopted, by using more than two groups of resistance modules and switch units (such as more than two switch modules), in a series-parallel form, to form a bus capacitor discharge unit of the frequency converter. When the motor controlled by the frequency converter stops or decelerates too quickly, the bus capacitor discharge unit is enabled, which can consume the excessive pump voltage fed back when the motor controlled by the frequency converter stops or decelerates too quickly. In addition, the number of resistance modules connected to the bus capacitor discharge path of the frequency converter in the two or more groups of resistance modules can be adjusted by switching the switch unit, so as to reduce the discharge power of the bus capacitor discharge unit before the magnetic suspension bearing controlled by the frequency converter falls, and increase the discharge power of the bus capacitor discharge unit after the magnetic suspension bearing controlled by the frequency converter falls, so as to realize the rapid consumption of the power in the frequency converter cabinet after the frequency converter cuts off the input power supply, thereby improving the safety and reliability of the frequency converter.

[0131] According to an embodiment of the present invention, a control method for a frequency converter corresponding to the frequency converter is also provided. Figure 6 The flow chart of an embodiment of the method of the present invention is shown. The frequency converter has a bus capacitor and an inverter unit. The bus capacitor can be a capacitor group or a single capacitor such as a bus capacitor C. The inverter unit is such as an inverter bridge. The control method of the frequency converter includes: step S110 and step S120.

[0132] At step S110, each of the two or more discharge resistor groups can release the power of the bus capacitor individually under the control of the switch module, or can release the power of the bus capacitor together with the remaining discharge resistor groups.

[0133] At step S120, through the switch module, when it is necessary to release the power of the bus capacitor, according to the release demand of the power of the bus capacitor, the number of the discharge paths of the bus capacitor connected to the two or more discharge resistor groups is controlled, which is recorded as N, where N is a positive integer and is less than or equal to the number of the two or more discharge resistor groups. The power of the bus capacitor is released by using the N discharge resistor groups connected to the discharge path of the bus capacitor among the two or more discharge resistor groups. Among them, the release demand of the power of the bus capacitor is the demand for slow release or fast release of the power of the bus capacitor.

[0134] The two or more discharge resistor groups and the switch module form a bus capacitor discharge unit. The bus capacitor discharge unit is arranged at the output end of the bus capacitor, specifically between the bus capacitor and the inverter unit.

[0135] The scheme of the present invention provides a method for regulating the discharge power of the bus capacitor of a frequency converter, which is used in the discharge process of the bus capacitor of a high-power frequency converter, and adjusts the discharge power of the bus capacitor discharge resistor according to different actual conditions, thereby improving the discharge efficiency of the bus capacitor, reducing the risk of bearing damage, and improving the reliability of the frequency converter.

[0136] In some embodiments, the two or more discharge resistor groups include: a first resistor group and a second resistor group. The first resistor group is such as the first resistor group R1, and the second resistor group is such as the second resistor group R2.

[0137] The switch module includes: a first switch, such as the first switch K1, and a second switch, such as the second switch K2.

[0138] The second resistor group and the second switch are connected in series to form a first series branch. The first series branch is connected in parallel with the first resistor group to form a first parallel branch. The first parallel branch is connected in series with the first switch to form a second series branch.

[0139] The first end of the second series branch is connected to the positive end of the bus capacitor. The second end of the second series branch is connected to the negative end of the bus capacitor.

[0140] Figure 2 FIG. 1 is a topological diagram of an embodiment of a bus capacitor discharge unit of a frequency converter (such as a bus capacitor discharge circuit of a frequency converter). Figure 2 As shown, two groups of resistors (such as a first resistor group and a second resistor group) and two switches (such as a first switch and a second switch) are connected in series and parallel (i.e., a mixed form of series and parallel connection) to form an overall bus capacitor discharge structure (such as a bus capacitor discharge unit).

[0141] In order to meet the requirement that the magnetic levitation bearing controller has a stable voltage to control the bearing to stably drop the shaft, the solution of the present invention can disable the bus discharge resistor or make the discharge power small before the bearing drops the shaft, and can increase the bus discharge power after the bearing drops the shaft, quickly consume the electricity in the bus capacitor, and solve the problem that the bus fixed discharge resistor power is too small and the discharge efficiency is too low after the magnetic levitation bearing stably controls the shaft to drop the shaft.

[0142] Figure 2 The bus capacitor discharge unit of the inverter shown in the figure is specifically the inverter bus capacitor discharge resistor topology, which shows the connection relationship between the bus capacitor and the discharge resistor and the connection relationship between the two sets of discharge resistors and the main control circuit. Figure 2 The discharge resistor portion shown adopts a series branch of a second resistor group and a second switch connected in parallel with the first resistor group, and the parallel branch is further connected in series with the first switch.

[0143] The scheme of the present invention also provides a method for regulating the discharge power of the bus capacitor of the frequency converter. In the scheme of the present invention, two signals are separated through a control signal of a DSP chip, one of which is inverted. The two signals control two switches respectively. If a relay is used as a switch, it is in a closed state by default when power is lost, and in a disconnected state when power is obtained.

[0144] Combined with the inverter power cut-off and the main control board power-off, a DSP chip signal is used to control three discharge states. In this way, combined with the inverter main control board power-on and power-off states, a control signal is used to control three discharge powers. For example, combined with the inverter main control board power-off, a single control signal is used to control three discharge states.

[0145] Combined with the actual situation of bus voltage feedback when the motor stops suddenly, the control logic of the DSP chip controls the discharge power of the bus capacitor to achieve stable power supply before the magnetic bearing drops. In this way, the control logic of the magnetic bearing drops is combined to achieve discharge power switching, such as combining the power-on and power-off status of the equipment, the magnetic bearing control, and the pump voltage to control the discharge power of the bus capacitor. Thus, the discharge power of the discharge resistor in different states can be solved, avoiding the situation where the bus voltage is consumed too quickly when the inverter stops urgently and the magnetic bearing has not dropped, and avoiding the situation where the bus voltage is consumed too slowly when the inverter is powered off and the bearing has dropped.

[0146] exist Figure 2 In the example shown, the main control circuit of the bus capacitor discharge unit of the inverter includes: a bus voltage sampling module, a DSP chip and a control signal driving circuit. The bus voltage sampling module, the DSP chip and the control signal driving circuit are connected in sequence and can output a driving signal to drive the first switch K1 and / or the second switch K2 to operate.

[0147] In some embodiments, when the amount of electricity of the bus capacitor needs to be released, the number of discharge paths of the bus capacitor to which the two or more discharge resistor groups are connected is controlled according to the release requirement of the amount of electricity of the bus capacitor, including any of the following control situations:

[0148] The first control scenario: through the switch module, specifically when the frequency converter is operating normally, that is, when the frequency converter is operating normally according to the set operating mode, the first switch and the second switch are both in a disconnected state, so that the first resistor group and the second resistor group do not release the electricity of the bus capacitor, which is recorded as the first resistor group and the second resistor group are both not working.

[0149] The second control scenario: through the switch module, specifically, when the inverter is normally shut down during normal operation, when the motor controlled by the inverter is shut down, and the input power of the inverter is cut off, executing:

[0150] If the bus voltage of the bus capacitor exceeds a set protection value, the first switch is in a closed state and the second switch is in an open state, so that the first resistor group works and the second resistor group does not work.

[0151] If the bus voltage of the bus capacitor does not exceed the protection value, the first switch and the second switch are both in an open state, so that the first resistor group and the second resistor group are not working, and the energy feedback process of the motor controlled by the inverter continues to be executed. And, when the energy feedback process of the motor controlled by the inverter ends, if the bearing controller of the motor controlled by the inverter has controlled the bearing to drop the shaft, and the main control board of the inverter has been powered off, the first switch and the second switch are both in a closed state, so that the first resistor group and the second resistor group are working.

[0152] The third control scenario: through the switch module, specifically, when the inverter stops normally during normal operation, wait for the motor controlled by the inverter to stop, and the bearing of the motor controlled by the inverter to fall off before the input power of the inverter is cut off, and execute:

[0153] If the bus voltage of the bus capacitor exceeds a set protection value, the first switch is in a closed state and the second switch is in an open state, so that the first resistor group works and the second resistor group does not work.

[0154] If the bus voltage of the bus capacitor does not exceed the protection value, then: when the bearing of the motor controlled by the inverter has fallen off and the input power of the inverter has been cut off, the first switch and the second switch are both in an open state, so that the first resistor group and the second resistor group are not working, and after the bearing controller of the motor controlled by the inverter has controlled the bearing to fall off and the main control board of the inverter has been powered off, the first switch and the second switch are both in a closed state, so that the first resistor group and the second resistor group are working. When the bearing of the motor controlled by the inverter has not fallen off and / or the input power of the inverter has not been cut off, the first switch and the second switch are both in a closed state, so that the first resistor group and the second resistor group are working.

[0155] pass Figure 2The bus capacitor discharge unit of the inverter shown can achieve high-efficiency bus capacitor discharge based on the actual bus voltage conditions and under the premise of meeting the magnetic bearing control requirements, solving the problem that the discharge power of the bus capacitor discharge resistor cannot change with the actual conditions, and realizing rapid consumption of power in the inverter cabinet after the inverter cuts off the input power supply, thereby improving the safety and reliability of the inverter.

[0156] In some embodiments, when the amount of electricity of the bus capacitor needs to be released, the number of discharge paths of the bus capacitor to which more than two discharge resistor groups are connected is controlled according to the release requirement of the amount of electricity of the bus capacitor by means of the switch module, and any one of the following further control situations is also included:

[0157] The first further control scenario: through the switch module, specifically when the inverter shuts down normally during normal operation, when the first resistor group and the second resistor group are not working, and after the energy feedback process of the motor controlled by the inverter continues to be executed, when the energy feedback process of the motor controlled by the inverter ends, if the bearing controller of the motor controlled by the inverter has controlled the bearing to drop, and the main control board of the inverter has been powered off, then the first switch and the second switch are both in a closed state, so that the first resistor group and the second resistor group both work.

[0158] Specifically, the switch module is also configured to execute, when the inverter is shut down normally during normal operation, when the motor controlled by the inverter is shut down, and when the input power of the inverter is cut off: if the bus voltage of the bus capacitor does not exceed the protection value, then the first switch and the second switch are both in an open state, so that the first resistor group and the second resistor group do not work, and the energy feedback process of the motor controlled by the inverter continues to be executed. And, when the energy feedback process of the motor controlled by the inverter ends, if the bearing controller of the motor controlled by the inverter has controlled the bearing to drop, and the main control board of the inverter has been powered off, then the first switch and the second switch are both in a closed state, so that the first resistor group and the second resistor group work.

[0159] A second further control scenario: through the switch module, specifically when the frequency converter is normally shut down during normal operation, the first resistor group and the second resistor group are both not working, and after the bearing controller of the motor controlled by the frequency converter has controlled the bearing to drop and the main control board of the frequency converter has been powered off, the first switch and the second switch are both in a closed state, so that the first resistor group and the second resistor group are both working.

[0160] Specifically, the switch module is further configured to, when the inverter shuts down normally during normal operation, wait for the motor controlled by the inverter to shut down and the bearing of the motor controlled by the inverter to fall off before the input power of the inverter is cut off, and execute: if the bus voltage of the bus capacitor does not exceed the protection value, then: when the bearing of the motor controlled by the inverter has fallen off and the input power of the inverter has been cut off, the first switch and the second switch are both in an open state so that the first resistor group and the second resistor group do not work, and wait for the bearing controller of the motor controlled by the inverter to control the bearing to fall off and the main control board of the inverter has been powered off, and then the first switch and the second switch are both in a closed state so that the first resistor group and the second resistor group work.

[0161] In order to meet the requirement that the magnetic levitation bearing controller has a stable voltage to control the bearing to stably drop the shaft, the solution of the present invention can disable the bus discharge resistor or make the discharge power small before the bearing drops the shaft, and can increase the bus discharge power after the bearing drops the shaft, quickly consume the electricity in the bus capacitor, and solve the problem that the bus fixed discharge resistor power is too small and the discharge efficiency is too low after the magnetic levitation bearing stably controls the shaft to drop the shaft.

[0162] In some embodiments, the method further includes: utilizing a control unit to automatically control the switch module.

[0163] Combine the following Figure 7 The flowchart of an embodiment of the method of the present invention using a control unit to automatically control a switch module further illustrates the specific process of using the control unit to automatically control the switch module, including: step S210 to step S230.

[0164] Step S210: sampling the bus voltage of the bus capacitor through a sampling unit.

[0165] Step S220, by means of a control unit, the current state of the inverter is determined according to the bus voltage of the bus capacitor, and a control signal is sent according to the current state of the inverter. The current state of the inverter includes any of the following states: a first state when the inverter is operating normally, a second state when the inverter is in emergency shutdown, and a third state when the inverter is in normal shutdown. The control signal is a signal for controlling the switch module.

[0166] Step S230, through the switch module, when the control signal is received, according to the control signal, the number of discharge paths of the bus capacitor connected to the two or more discharge resistor groups is controlled to achieve: when it is necessary to release the power of the bus capacitor, according to the release demand of the power of the bus capacitor, the number of discharge paths of the bus capacitor connected to the two or more discharge resistor groups is controlled.

[0167] Among them, the sampling unit is such as a bus voltage sampling module, the control unit is such as a DSP chip, and the driving unit is such as a control signal driving circuit.

[0168] Figure 2 The bus capacitor discharge unit of the inverter shown in the figure is specifically the inverter bus capacitor discharge resistor topology, which shows the connection relationship between the bus capacitor and the discharge resistor and the connection relationship between the two sets of discharge resistors and the main control circuit. Figure 2 The discharge resistor portion shown adopts a series branch of a second resistor group and a second switch connected in parallel with the first resistor group, and the parallel branch is further connected in series with the first switch.

[0169] The scheme of the present invention also provides a method for regulating the discharge power of the bus capacitor of the frequency converter. In the scheme of the present invention, two signals are separated through a control signal of a DSP chip, one of which is inverted. The two signals control two switches respectively. If a relay is used as a switch, it is in a closed state by default when power is lost, and in a disconnected state when power is obtained.

[0170] Combined with the inverter power cut-off and the main control board power-off, a DSP chip signal is used to control three discharge states. In this way, combined with the inverter main control board power-on and power-off states, a control signal is used to control three discharge powers. For example, combined with the inverter main control board power-off, a single control signal is used to control three discharge states.

[0171] Combined with the actual situation of bus voltage feedback when the motor stops suddenly, the control logic of the DSP chip controls the discharge power of the bus capacitor to achieve stable power supply before the magnetic bearing drops. In this way, the control logic of the magnetic bearing drops is combined to achieve discharge power switching, such as combining the power-on and power-off status of the equipment, the magnetic bearing control, and the pump voltage to control the discharge power of the bus capacitor. Thus, the discharge power of the discharge resistor in different states can be solved, avoiding the situation where the bus voltage is consumed too quickly when the inverter stops urgently and the magnetic bearing has not dropped, and avoiding the situation where the bus voltage is consumed too slowly when the inverter is powered off and the bearing has dropped.

[0172] exist Figure 2In the example shown, the main control circuit of the bus capacitor discharge unit of the inverter includes: a bus voltage sampling module, a DSP chip and a control signal driving circuit. The bus voltage sampling module, the DSP chip and the control signal driving circuit are connected in sequence and can output a driving signal to drive the first switch K1 and / or the second switch K2 to operate.

[0173] Figure 3 The present invention is a structural schematic diagram of an embodiment of a control signal driving circuit of a bus capacitor discharge unit of a frequency converter. Figure 3 The control signal driving circuit shown includes a signal after amplifying the signal voltage of the control signal output by the DSP chip, and acting on the first relay. The control signal output by the DSP chip is amplified after being inverted, and the amplified signal acts on the second relay. Among them, the control signal output by the DSP chip is divided into two paths, one of which is amplified to control the first relay, and the other is inverted and amplified to control the second relay. In this way, combined with the power-off condition of the DSP chip, a DSP chip port can present three discharge states.

[0174] In the solution of the present invention, the driving circuit of the discharge power switching control signal, such as Figure 3 As shown, the 3.3V signal of the DSP chip port controls the on-off of the first relay after voltage signal amplification, and then controls the on-off of the first contactor. At the same time, the signal of the DSP chip port is also controlled by the inverted logic chip (such as the NOT gate module F1), and then controls the on-off of the second relay after voltage amplification, and then controls the on-off of the second contactor. The first contactor and the second contactor are in a closed state when their control signals are low, and in an open state when their control signals are high. Therefore, when the control signal of the DSP chip port is low, the signal received by the first contactor is in a low level state, and the first contactor is in a closed state. The signal received by the second contactor is in a high level state, and the second contactor is in an open state. The first resistor group R1 works and the second resistor group R2 does not work. At this time, the overall discharge resistance value is high and the discharge power is low. When the control signal of the DSP chip port is high, the signal received by the first contactor is in a high level state, and the first contactor is in an open state. The signal received by the second contactor is in a low level state, and the second contactor is in a closed state. Because the first contactor is in the disconnected state, the two groups of resistors (such as the first resistor group R1 and the second resistor group R2) and the bus circuit are in the open circuit state, so that the first resistor group R1 and the second resistor group R2 do not work, and the bus capacitor discharges without resistance. When the main control board is powered off, the main control board has no output signal to the contactor, which is equivalent to both contactors receiving low-level signals, and both contactors are in the closed state, so that the first resistor group R1 works and the second resistor group R2 works. At this time, the overall discharge resistance value is low and the discharge power is the highest.

[0175] Figure 4 FIG. 1 is a curve diagram showing an example of an embodiment of the energy feedback bus voltage of the frequency converter. Figure 4 The energy feedback bus voltage example diagram shown shows the voltage change when the bus is discharged with a fixed resistor when the inverter is shut down urgently. Once the bus is shut down urgently, the motor decelerates and stops to generate a short-term pump voltage, and then the voltage drops due to the inverter cutting off the input power and the bus discharge resistor consumption. If the lowest point of the voltage drop is lower than the lowest power supply voltage of the bearing controller, the bearing will lose power and fall out of control. Energy feedback regulation stabilizes the bus voltage at a certain voltage value until the energy feedback ends.

[0176] Figure 5 The figure is a flow chart of a discharge power conversion procedure of a bus capacitor discharge unit of an inverter according to an embodiment of the present invention. Figure 5 The discharge power conversion program flow chart shown in Figure 1 shows the discharge power switching logic corresponding to normal shutdown and emergency shutdown. Figure 5 As shown in FIG. 1 , the execution process of the discharge power conversion program of the bus capacitor discharge unit of the inverter includes:

[0177] Step 1: When the frequency converter operates normally, the control signal output by the DSP chip is set to a high level, and the first resistor group R1 and the second resistor group R2 do not operate.

[0178] That is to say, when the frequency converter operates normally, the control signal at the DSP chip end is at a high level, and both the first resistor group R1 and the second resistor group R2 are in a non-operating state.

[0179] Step 2: When the inverter stops, determine whether the inverter shutdown is an emergency shutdown. If yes, execute step 3, that is, execute the discharge power control process in the emergency shutdown power-off state. Otherwise, execute step 4, that is, execute the discharge power control process in the normal shutdown power-off state. That is to say, two discharge power switching modes are performed according to the two shutdown power-off states, one is the emergency shutdown power-off state, and the other is the normal shutdown power-off state.

[0180] Step 3: Execute the discharge power control process in the emergency shutdown power-off state. For details, refer to the following exemplary description (see steps 31 to 33).

[0181] Step 31: When the inverter is shut down urgently, the motor is stopped immediately and the inverter input power is cut off at the same time.

[0182] Step 32: If it is determined to be an emergency shutdown, then determine whether the bus voltage exceeds the protection value, that is, determine whether the bus voltage is higher than the protection value due to the pump-generated voltage.

[0183] If the bus voltage exceeds the protection value, the DSP chip terminal is set to a low level, the first resistor group R1 works, the second resistor group R2 does not work, and the bus voltage is reduced with a smaller discharge power. Then, the process returns to step 32.

[0184] If the bus voltage does not exceed the protection value, if the bus voltage is lower than the protection value, the DSP chip control terminal is set to a high level, and the first resistor group R1 and the second resistor group R2 do not work. At the same time, the energy feedback function of the motor continues to work, adjusting the bus voltage to a reference value, and the bearing controller then stably controls the bearing to drop. Then, step 33 is executed.

[0185] Step 33: As energy feedback ends, the bus voltage continues to drop due to the power consumption of the bearing controller and the inverter main control board until the motor main control board loses power. At this time, it is equivalent to that both relays receive low-level signals, both relays are in a closed state, the first resistor group R1 works, the second resistor group R2 works, and the discharge power is the highest.

[0186] In this way, when the inverter is shut down urgently and the input power is cut off, the solution of the present invention stops the power consumption of the bus discharge resistor under the premise that the bus voltage is not in an excessively high state, thereby avoiding the bus voltage dropping too quickly before the energy feedback regulation makes the bus voltage return to the reference value, causing the magnetic suspension bearing to lose power, lose control and fall off. This solves the problem of the magnetic suspension bearing losing power, losing control and falling off due to excessive consumption of the fixed discharge resistor due to the bus capacitor voltage during emergency shutdown.

[0187] Step 4: Execute the discharge power control process in the normal shutdown and power-off state. For details, refer to the following exemplary description (see steps 41 to 43).

[0188] Step 41: When the inverter is shut down and powered off normally, wait until the motor stops and the bearing has dropped before powering off. Because the inverter is in normal shutdown and the input power is not cut off, the bus has enough voltage to control the magnetic bearing to drop, so there is no need to consider the loss of power and control of the bearing in this shutdown state. When the inverter is shut down, determine whether the bus voltage is higher than the protection value due to the pump voltage.

[0189] If the bus voltage is higher than the protection value, the DSP chip end control signal is set to a low level, the first resistor group R1 works, and the second resistor group R2 does not work, and a smaller discharge power is used to reduce the bus voltage.

[0190] If the bus voltage is not higher than the protection value, step 42 is executed.

[0191] Step 42: When the bus voltage is not higher than the protection value, continue to determine whether the bearing has fallen off and whether the inverter input power has been cut off.

[0192] If the inverter is not powered off, the control signal of the DSP chip port is maintained at a high level, and the first resistor group R1 and the second resistor group R2 do not work. Then, the process returns to step 42 .

[0193] If it is determined that the bearing has fallen off and the inverter input has been powered off, the DSP chip terminal is set to a low level, the first resistor group R1 works, and the second resistor group R2 does not work. Then, step 43 is executed.

[0194] Step 43, wait for the main control board to lose power, so that the first resistor group R1 works, and the second resistor group R2 works, the discharge power is the highest, and the power in the inverter cabinet is consumed quickly.

[0195] In this way, when the motor stops or decelerates too quickly, and the bus voltage becomes too high due to the pump-generated voltage fed back by the motor, the solution of the present invention can enable the bus discharge resistor, sample an appropriate amount of discharge power to consume the excessive voltage, and consume the excessive pump-generated voltage fed back by the motor when it stops, thereby avoiding the bus capacitor being in a high voltage state for a long time, thereby damaging the bus capacitor.

[0196] 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.

[0197] The technical solution of this embodiment is adopted, by using more than two groups of resistance modules and switch units (such as more than two switch modules), in a series-parallel form, to form a bus capacitor discharge unit of the frequency converter. When the motor controlled by the frequency converter stops or decelerates too quickly, the bus capacitor discharge unit is enabled, which can consume the excessive pump voltage fed back when the motor controlled by the frequency converter stops or decelerates too quickly; and, the number of resistance modules connected to the bus capacitor discharge path of the frequency converter in the two or more groups of resistance modules can be adjusted by switching the switch unit, so as to reduce the discharge power of the bus capacitor discharge unit before the magnetic suspension bearing controlled by the frequency converter falls off, and increase the discharge power of the bus capacitor discharge unit after the magnetic suspension bearing controlled by the frequency converter falls off, so as to avoid the situation that the bus voltage is consumed too quickly when the frequency converter is shut down in an emergency and the magnetic suspension bearing has not fallen off, and avoid the situation that the bus voltage is consumed too slowly when the frequency converter is powered off and the bearing has fallen off.

[0198] 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.

[0199] 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 control device for a frequency converter, characterized in that: The inverter has a bus capacitor; the control device of the inverter includes: a bus capacitor discharge unit; the bus capacitor discharge unit is arranged at the output end of the bus capacitor; the bus capacitor discharge unit includes: a discharge resistor module and a switch module; the discharge resistor module includes: a discharge resistor group, and the number of the discharge resistor groups is more than two; wherein, Each of the two or more discharge resistor groups is configured to release the electric quantity of the bus capacitor individually or together with the other discharge resistor groups under the control of the switch module; The switch module is configured to control the number of the discharge paths of the bus capacitors connected to the two or more discharge resistor groups according to the release demand of the bus capacitors when it is necessary to release the electric quantity of the bus capacitors, where N is a positive integer; so as to release the electric quantity of the bus capacitors by using the N discharge resistor groups connected to the discharge paths of the bus capacitors among the two or more discharge resistor groups; It also includes: a sampling unit, a control unit and a driving unit; wherein, The sampling unit is configured to sample the bus voltage of the bus capacitor; The control unit is configured to determine the current state of the inverter according to the bus voltage of the bus capacitor, and send a control signal according to the current state of the inverter; wherein the current state of the inverter includes any of the following states: a first state when the inverter is operating normally, a second state when the inverter is in emergency shutdown, and a third state when the inverter is shut down normally; The switch module is configured to, upon receiving the control signal, control the number of discharge paths of the bus capacitor through which the two or more discharge resistor groups are connected according to the control signal, so as to achieve: when it is necessary to release the electricity of the bus capacitor, according to the release requirement of the electricity of the bus capacitor, control the number of discharge paths of the bus capacitor through which the two or more discharge resistor groups are connected.

2. The control device of the frequency converter according to claim 1, characterized in that: The two or more discharge resistor groups include: a first resistor group and a second resistor group; The switch module comprises: a first switch and a second switch; in, The second resistor group and the second switch are connected in series to form a first series branch; the first series branch is connected in parallel with the first resistor group to form a first parallel branch; the first parallel branch is connected in series with the first switch to form a second series branch; The first end of the second series branch is connected to the positive end of the bus capacitor; the second end of the second series branch is connected to the negative end of the bus capacitor.

3. The control device of the frequency converter according to claim 2, characterized in that: In the second series branch, one end of the first switch away from the first parallel branch serves as the first end of the second series branch; one end of the first parallel branch away from the first switch serves as the second end of the second series branch; In the first series branch, the second switch is located away from one end of the second resistor group and is connected to the second end of the second series branch.

4. The control device of the frequency converter according to claim 2, characterized in that: The first switch and the second switch are both contactors.

5. The control device of the frequency converter according to claim 2, characterized in that: The switch module, when it is necessary to release the electric quantity of the bus capacitor, controls the number of discharge paths of the bus capacitor connected to the two or more discharge resistor groups according to the release demand of the electric quantity of the bus capacitor, including any of the following control situations: The first control situation: when the frequency converter is operating normally, the first switch and the second switch are both in the disconnected state, so that the first resistor group and the second resistor group do not release the electric quantity of the bus capacitor, which is recorded as the first resistor group and the second resistor group are both not working; The second control situation: when the inverter stops normally during normal operation, when the motor controlled by the inverter has stopped, and the input power of the inverter has been cut off, execute: If the bus voltage of the bus capacitor exceeds a set protection value, the first switch is in a closed state and the second switch is in an open state, so that the first resistor group works and the second resistor group does not work; If the bus voltage of the bus capacitor does not exceed the protection value, the first switch and the second switch are both in an open state, so that the first resistor group and the second resistor group do not work, and the energy feedback process of the motor controlled by the inverter continues to be executed; and, when the energy feedback process of the motor controlled by the inverter ends, if the bearing controller of the motor controlled by the inverter has controlled the bearing to drop the shaft, and the main control board of the inverter has been powered off, the first switch and the second switch are both in a closed state, so that the first resistor group and the second resistor group are both working; The third control situation: when the inverter stops normally during normal operation, wait until the motor controlled by the inverter stops and the bearing of the motor controlled by the inverter falls off, and then the input power of the inverter is cut off, and execute: If the bus voltage of the bus capacitor exceeds a set protection value, the first switch is in a closed state and the second switch is in an open state, so that the first resistor group works and the second resistor group does not work; If the bus voltage of the bus capacitor does not exceed the protection value, then: when the bearing of the motor controlled by the inverter has fallen off and the input power of the inverter has been cut off, the first switch and the second switch are both in an open state, so that the first resistor group and the second resistor group are not working, and after the bearing controller of the motor controlled by the inverter has controlled the bearing to fall off and the main control board of the inverter has been powered off, the first switch and the second switch are both in a closed state, so that the first resistor group and the second resistor group are working; When the bearing of the motor controlled by the inverter has not fallen off and / or the input power of the inverter has not been cut off, the first switch and the second switch are both in a closed state, so that the first resistor group and the second resistor group are both in operation.

6. The control device of the frequency converter according to claim 5, characterized in that: The switch module, when it is necessary to release the electric quantity of the bus capacitor, controls the number of discharge paths of the bus capacitor connected to the two or more discharge resistor groups according to the release demand of the electric quantity of the bus capacitor, and further includes any one of the following further control situations: A first further control situation: when the frequency converter is shut down normally during normal operation, when both the first resistor group and the second resistor group are not working, and after the energy feedback process of the motor controlled by the frequency converter continues to be executed, when the energy feedback process of the motor controlled by the frequency converter ends, if the bearing controller of the motor controlled by the frequency converter has controlled the bearing to drop, and the main control board of the frequency converter has been powered off, the first switch and the second switch are both in a closed state, so that both the first resistor group and the second resistor group are working; A second further control scenario: when the frequency converter shuts down normally during normal operation, after making the first resistor group and the second resistor group non-operating, and after waiting for the bearing controller of the motor controlled by the frequency converter to control the bearing to drop and the main control board of the frequency converter to be powered off, the first switch and the second switch are both in a closed state, so that the first resistor group and the second resistor group are both operating.

7. The control device of the frequency converter according to claim 1, characterized in that: The driving unit comprises: a first signal amplifying module, a second signal amplifying module, a signal inversion module, a first control module and a second control module; In the case where the switch module includes a first switch and a second switch, the control signal output by the control unit is divided into two paths, one path is output to the first switch as a first control signal after passing through the first signal amplification module and the first control module; the other path is output to the second switch as a second control signal after passing through the signal inversion module, the second signal amplification module and the second control module; in, The first signal amplification module is configured to amplify the control signal; The first control module is configured to control the on / off of an output path of the first control signal; The signal inversion module is configured to invert the level of the control signal; The second signal amplifying module is configured to amplify the control signal after the inversion processing; The second control module is configured to control the on / off of an output path of the second control signal.

8. The control device of the frequency converter according to claim 7, characterized in that: in, When the control unit is powered on, the control unit outputs the control signal: When the level of the control signal is high, the level of the first control signal is high, and both the first switch and the second switch are in an off state; When the level of the control signal is low, the level of the first control signal is low, and the first switch is in a closed state; The level of the second control signal is high, and the second switch is in an off state; In the case where the control unit loses power, the control unit does not output the control signal: The first switch and the second switch are both in a closed state.

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

10. A control method for a frequency converter as claimed in claim 9, characterized in that: The inverter has a bus capacitor; the control method of the inverter includes: Through each of the two or more discharge resistor groups, under the control of the switch module, the electric quantity of the bus capacitor can be released individually, or together with the other discharge resistor groups, the electric quantity of the bus capacitor can be released; Through the switch module, when it is necessary to release the electric quantity of the bus capacitor, according to the release demand of the electric quantity of the bus capacitor, the number of the discharge paths of the bus capacitor connected to the two or more discharge resistor groups is controlled, which is recorded as N, and N is a positive integer; so as to release the electric quantity of the bus capacitor by using the N discharge resistor groups connected to the discharge paths of the bus capacitor among the two or more discharge resistor groups; Among them, two or more discharge resistor groups and the switch module form a bus capacitor discharge unit; the bus capacitor discharge unit is arranged at the output end of the bus capacitor.

11. The control method of the frequency converter according to claim 10, characterized in that: The two or more discharge resistor groups include: a first resistor group and a second resistor group; The switch module comprises: a first switch and a second switch; in, The second resistor group and the second switch are connected in series to form a first series branch; the first series branch is connected in parallel with the first resistor group to form a first parallel branch; the first parallel branch is connected in series with the first switch to form a second series branch; The first end of the second series branch is connected to the positive end of the bus capacitor; the second end of the second series branch is connected to the negative end of the bus capacitor.

12. The control method of the frequency converter according to claim 11, characterized in that: By means of the switch module, when it is necessary to release the electric quantity of the bus capacitor, the number of discharge paths of the bus capacitor to which the two or more discharge resistor groups are connected is controlled according to the release demand of the electric quantity of the bus capacitor, including any of the following control situations: The first control situation: when the frequency converter is operating normally, the first switch and the second switch are both in the disconnected state, so that the first resistor group and the second resistor group do not release the electric quantity of the bus capacitor, which is recorded as the first resistor group and the second resistor group are both not working; The second control situation: when the inverter stops normally during normal operation, when the motor controlled by the inverter has stopped, and the input power of the inverter has been cut off, execute: If the bus voltage of the bus capacitor exceeds a set protection value, the first switch is in a closed state and the second switch is in an open state, so that the first resistor group works and the second resistor group does not work; If the bus voltage of the bus capacitor does not exceed the protection value, the first switch and the second switch are both in an open state, so that the first resistor group and the second resistor group do not work, and the energy feedback process of the motor controlled by the inverter continues to be executed; and, when the energy feedback process of the motor controlled by the inverter ends, if the bearing controller of the motor controlled by the inverter has controlled the bearing to drop the shaft, and the main control board of the inverter has been powered off, the first switch and the second switch are both in a closed state, so that the first resistor group and the second resistor group are both working; The third control situation: when the inverter stops normally during normal operation, wait until the motor controlled by the inverter stops and the bearing of the motor controlled by the inverter falls off, and then the input power of the inverter is cut off, and execute: If the bus voltage of the bus capacitor exceeds a set protection value, the first switch is in a closed state and the second switch is in an open state, so that the first resistor group works and the second resistor group does not work; If the bus voltage of the bus capacitor does not exceed the protection value, then: when the bearing of the motor controlled by the inverter has fallen off and the input power of the inverter has been cut off, the first switch and the second switch are both in an open state, so that the first resistor group and the second resistor group are not working, and after the bearing controller of the motor controlled by the inverter has controlled the bearing to fall off and the main control board of the inverter has been powered off, the first switch and the second switch are both in a closed state, so that the first resistor group and the second resistor group are working; When the bearing of the motor controlled by the inverter has not fallen off and / or the input power of the inverter has not been cut off, the first switch and the second switch are both in a closed state, so that the first resistor group and the second resistor group are both in operation.

13. The control method of the frequency converter according to claim 12, characterized in that: By means of the switch module, when it is necessary to release the electric quantity of the bus capacitor, the number of the discharge paths of the bus capacitor connected to the two or more discharge resistor groups is controlled according to the release demand of the electric quantity of the bus capacitor, and any one of the following further control situations is also included: A first further control situation: when the frequency converter is shut down normally during normal operation, when both the first resistor group and the second resistor group are not working, and after the energy feedback process of the motor controlled by the frequency converter continues to be executed, when the energy feedback process of the motor controlled by the frequency converter ends, if the bearing controller of the motor controlled by the frequency converter has controlled the bearing to drop, and the main control board of the frequency converter has been powered off, the first switch and the second switch are both in a closed state, so that both the first resistor group and the second resistor group are working; A second further control scenario: when the frequency converter shuts down normally during normal operation, after making the first resistor group and the second resistor group non-operating, and after waiting for the bearing controller of the motor controlled by the frequency converter to control the bearing to drop and the main control board of the frequency converter to be powered off, the first switch and the second switch are both in a closed state, so that the first resistor group and the second resistor group are both operating.

14. The control method of the frequency converter according to any one of claims 10 to 13, characterized in that: Also includes: Sampling the bus voltage of the bus capacitor by a sampling unit; The control unit determines the current state of the inverter according to the bus voltage of the bus capacitor, and sends a control signal according to the current state of the inverter; wherein the current state of the inverter includes any of the following states: a first state when the inverter is operating normally, a second state when the inverter is in emergency shutdown, and a third state when the inverter is in normal shutdown; Through the switch module, when the control signal is received, the number of discharge paths of the bus capacitor connected to the two or more discharge resistor groups is controlled according to the control signal, so as to achieve: when it is necessary to release the power of the bus capacitor, the number of discharge paths of the bus capacitor connected to the two or more discharge resistor groups is controlled according to the release demand of the power of the bus capacitor.

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