Contactor driving circuit for frequency converter, control method and device, and frequency converter

Abstract

The invention relates to the technical field of frequency conversion, and discloses a contactor driving circuit for a frequency converter, which comprises a digital processing DSP unit configured to control the level of an output end signal according to a power supply voltage; the output end of the DSP unit comprises an RES signal end and an RELAY signal end; the level conversion unit comprises a level conversion chip; the level conversion chip comprises an enabling end connected with the RES signal end of the DSP unit, a level signal input end connected with the RELAY signal end, and a level signal output end; the optical coupling unit is connected with the level signal output end of the level conversion unit; the input end of the relay control unit is connected with the optocoupler unit, and the output end is connected with the contactor to provide driving voltage for the contactor. The circuit can prevent the contactor from being in a closed state when the variable frequency drive recovers voltage sag in a short time, thereby preventing large charging current from being generated to damage a device. The invention further discloses a control method and device of the contactor driving circuit for the frequency converter and the frequency converter.

Description

Technical Field

[0001] The present application relates to the field of frequency conversion technology, for example, to a contactor drive circuit and control method, device, and frequency converter for a frequency converter. Background Art

[0002] With the development of inverter technology, inverters are gradually being used in the field of high-speed drives to achieve high-speed motor drive control. This places increasing demands on the reliability of inverters at high switching frequencies. When the inverter is powered on, the voltage across the DC bus capacitor cannot change suddenly, so it is equivalent to a short circuit in a short period of time. The inverter will generate a large impact current, which will damage the inverter's rectifier unit and other components.

[0003] The related technology discloses a frequency converter fault protection device and a frequency converter. The frequency converter and the transformer are respectively connected to the power supply. The frequency converter outputs a signal to the contactor to control the start and stop of the motor. The transformer is connected to the safety circuit and the contactor and controls the start and stop of the motor through the safety circuit. The frequency converter and the safety circuit are respectively connected to the protection device. The protection device includes a fault detection module, a wave sealing circuit, and an enabling unit. The protection of the frequency converter is achieved through the protection device.

[0004] In the process of implementing the embodiments of the present disclosure, it is found that there are at least the following problems in the related art:

[0005] The related technology cannot solve the problem that the variable frequency drive generates a large charging current when the voltage is restored after a short-time voltage drop.

[0006] It should be noted that the information disclosed in the above background technology section is only used to enhance the understanding of the background of the present application, and therefore may include information that does not constitute the prior art known to ordinary technicians in the field. Summary of the invention

[0007] In order to provide a basic understanding of some aspects of the disclosed embodiments, a brief summary is given below. The summary is not an extensive review, nor is it intended to identify key / critical components or delineate the scope of protection of these embodiments, but rather serves as a prelude to the detailed description that follows.

[0008] The embodiments of the present disclosure provide a contactor drive circuit and control method, device, and inverter for a frequency converter, so as to prevent the frequency converter from generating a large charging current when recovering from a short-time voltage drop.

[0009] In some embodiments, the circuit comprises:

[0010] The digital signal processing DSP unit is configured to control the level of the output signal according to the power supply voltage; the output end of the DSP unit includes a RES signal end and a RELAY signal end; the level conversion unit includes a level conversion chip; the level conversion chip includes an enable end connected to the RES signal end of the DSP unit, a level signal input end connected to the RELAY signal end, and a level signal output end; the optical coupling unit is connected to the level signal output end of the level conversion unit; the relay control unit has an input end connected to the output end of the optical coupling unit, and an output end connected to a contactor to provide a driving voltage for the contactor.

[0011] In some embodiments, the method comprises:

[0012] Detect the real-time power supply voltage of the DSP unit; according to the real-time power supply voltage, control the output signal of the RES signal terminal to control the state of the contactor.

[0013] In some embodiments, the apparatus comprises:

[0014] A processor and a memory storing program instructions, wherein the processor is configured to execute the control method for a contactor drive circuit of a frequency converter as described above when running the program instructions.

[0015] In some embodiments, the frequency converter comprises:

[0016] The inverter body and the control device for the contactor drive circuit of the inverter as mentioned above are installed on the inverter body.

[0017] The contactor drive circuit, control method, device, and inverter provided in the embodiments of the present disclosure can achieve the following technical effects:

[0018] In the disclosed embodiment, the enabling of the level conversion unit is controlled by the RES signal of the DSP unit. When the power supply voltage (i.e., the bus voltage) changes, the DSP unit can control the enabling status of the level conversion unit. Thereby ensuring that when the power supply voltage is reduced, the level conversion unit is not enabled, and then the optocoupler unit and the relay control unit are disconnected. Then, the driving voltage cannot be provided to the contactor, so that the contactor is in an open state. In this way, it is avoided that when the variable frequency drive recovers from a short-term voltage drop, the contactor is in a closed state, resulting in a large charging current that damages the device.

[0019] The above general description and the following description are exemplary and explanatory only and are not intended to limit the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] One or more embodiments are exemplarily described by corresponding drawings, which do not limit the embodiments. Elements with the same reference numerals in the drawings are shown as similar elements, and the drawings do not constitute a scale limitation, and wherein:

[0021] Figure 1 is a schematic diagram of a topological structure of a frequency converter provided by an embodiment of the present disclosure;

[0022] Figure 2 is a schematic diagram of a contactor drive circuit for a frequency converter provided by an embodiment of the present disclosure;

[0023] Figure 3 is a schematic diagram of another contactor drive circuit for a frequency converter provided by an embodiment of the present disclosure;

[0024] Figure 4 is a schematic diagram of a control method for a contactor drive circuit of a frequency converter provided by an embodiment of the present disclosure;

[0025] Figure 5 is a schematic diagram of another control method for a contactor drive circuit of a frequency converter provided by an embodiment of the present disclosure;

[0026] Figure 6 is a schematic diagram of a control device for a contactor drive circuit of a frequency converter provided by an embodiment of the present disclosure;

[0027] Figure 7 It is a schematic diagram of the topological structure of another inverter provided in an embodiment of the present disclosure.

[0028] Reference numerals:

[0029] 10: rectifier unit; 20: filter unit; 30: inverter unit; 41: contactor; 42: charging resistor; 50: DSP unit; 60: level conversion unit; 61: level conversion chip; 70: optocoupler unit; 80: relay control unit; 200: control device; 100: processor; 101: memory; 102: communication interface; 103: bus. DETAILED DESCRIPTION

[0030] In order to be able to understand the features and technical contents of the embodiments of the present disclosure in more detail, the implementation of the embodiments of the present disclosure is described in detail below in conjunction with the accompanying drawings. The attached drawings are for reference only and are not used to limit the embodiments of the present disclosure. In the following technical description, for the convenience of explanation, a full understanding of the disclosed embodiments is provided through multiple details. However, one or more embodiments can still be implemented without these details. In other cases, to simplify the drawings, well-known structures and devices can be simplified for display.

[0031] The terms "first", "second", etc. in the specification and claims of the embodiments of the present disclosure and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the terms used in this way can be interchanged where appropriate, so that the embodiments of the embodiments of the present disclosure described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions.

[0032] Unless otherwise stated, the term "plurality" means two or more.

[0033] In the embodiment of the present disclosure, the character " / " indicates that the preceding and following objects are in an "or" relationship. For example, A / B indicates: A or B.

[0034] The term "and / or" is a description of the association relationship between objects, indicating that three relationships can exist. For example, A and / or B means: A or B, or, A and B.

[0035] The term "correspondence" may refer to an association relationship or a binding relationship. The correspondence between A and B means that there is an association relationship or a binding relationship between A and B.

[0036] Combination Figure 1 The frequency converter mainly includes a rectifier unit 10, a filter unit 20 and an inverter unit 30. When the frequency converter is powered on, the voltage across the DC bus capacitor cannot change suddenly, so it is equivalent to a short circuit in a short time. The frequency converter will generate a large impact current, which will damage the rectifier unit and other components of the rectifier part. For this reason, a charging resistor 42 is connected in series before the inverter rectifier unit 10 or in series in the DC circuit after the rectifier unit to limit the impact current. Figure 1 In the embodiment, a charging resistor 42 is connected in series after the rectifier unit, and the charging resistor is connected in parallel with a contactor 41. The charging resistor 42 is operated or bypassed by controlling the open or closed state of the contactor 41. It can be understood that when the bus voltage suddenly changes, the contactor is controlled to be open, so that the charging resistor operates to limit the impact current, thereby protecting the components of the inverter.

[0037] However, when the bus voltage of the variable frequency drive suddenly changes, if the contactor is in a closed state, a large impact current (or charging current) will be generated, causing damage to components such as the rectifier unit. Therefore, the embodiment of the present disclosure provides a contactor drive circuit to control the state of the contactor according to the power supply voltage (i.e., the bus voltage). This ensures that the variable frequency drive controls the contactor in the event of a short-term voltage sag, and avoids the contactor being in a closed state when the voltage of the variable frequency drive recovers after a short-term voltage sag.

[0038] Combination Figure 2 , 3As shown, the example of the present disclosure provides a contactor drive circuit for a frequency converter, which is used to provide a drive voltage for the contactor; the circuit includes a DSP (Digital Signal Processing) unit 50, a level conversion unit 60, an optical coupling unit 70 and a relay control unit 80 connected in sequence. Specifically, the output end of the DSP unit includes a RES signal end and a RELAY signal end, and the signal at the output end is controlled according to the voltage signal. The level conversion unit 80 mainly includes a level conversion chip 81, which is used to convert the level signal. Among them, the enable end OE of the level conversion chip is connected to the RES signal end of the DSP unit, that is, the RES signal end of the DSP unit controls whether the level conversion chip is in an enabled state. The level signal input end OA of the level conversion chip is connected to the RELAY signal end of the DSP unit. Set the enable end valid signal of the level conversion unit to a high level; when the level conversion chip is enabled, when the RELAY signal end outputs a low level, the level signal output end YO of the level conversion chip outputs a low level. When the level conversion chip is not enabled, the level signal output end YO of the level conversion chip outputs a high level by default.

[0039] The optocoupler unit 70 connects the level conversion unit 60 and the relay control unit 80 to achieve isolation between the two and provide control reliability. The input end of the optocoupler unit 70 is connected to the level signal output end YO of the level conversion unit 60. Therefore, the level conversion unit outputs a low level signal during normal operation, so the optocoupler unit 70 is turned on when the input signal is a level signal. Furthermore, the relay in the relay control unit 80 is turned on to output a driving voltage, which is supplied to the contactor 41. When the contactor 41 is driven by the voltage, it is closed so that the charging resistor 42 is bypassed. When there is no driving voltage, the contactor 41 is disconnected, and the charging resistor 42 is connected in series in the circuit of the inverter to limit the inrush current.

[0040] Combined with the change of the power supply voltage (i.e., bus voltage), the working principle of the drive circuit is explained. When the power supply voltage is normal, the RES signal end of the DSP unit outputs a low level, and the control level conversion unit works normally. At the same time, the RELAY signal end also outputs a low level, and the output end YO of the level conversion unit outputs a low level. The optocoupler unit is turned on under the action of the low level, and the relay of the relay control unit is energized to output the drive voltage. Then the contactor is closed so that the charging resistor is bypassed. When the power supply voltage drops, the RES signal end of the DSP unit outputs a high level, and the control level conversion unit is not enabled. At the same time, the RELAY signal end also outputs a low level, and the level conversion unit is not enabled to output a high level. The optocoupler unit is disconnected under the action of the high level, and the relay contacts of the relay control unit are disconnected, and the drive voltage cannot be output. Then the contactor is disconnected so that the charging resistor is connected in series in the circuit. During the recovery of the power supply voltage, the charging resistor is disconnected by the contactor to limit the inrush current in the inverter circuit, avoiding the generation of a large charging current, thereby protecting the circuit components from damage.

[0041] The contactor drive circuit for the frequency converter provided by the embodiment of the present disclosure is adopted, and the enabling of the level conversion unit is controlled by the RES signal of the DSP unit. When the power supply voltage changes, the DSP unit can control the enabling status of the level conversion unit. Thereby ensuring that when the power supply voltage is reduced, the level conversion unit is not enabled, and then the optocoupler unit and the relay control unit are disconnected. Then, the driving voltage cannot be provided to the contactor, so that the contactor is in a disconnected state. In this way, it is avoided that when the variable frequency drive recovers from a short-time voltage drop, the contactor is in a closed state, resulting in a large charging current that damages the device.

[0042] like Figure 3 As shown, optionally, the level conversion unit further includes a first pull-up resistor R1 and a first power supply V1. One end of the first pull-up resistor R1 is connected to the level signal input end of the level conversion chip 81. The first power supply V1 is connected to the other end of the first pull-up resistor R1.

[0043] Under normal circumstances, after the inverter is shut down and powered off, the power supply voltage decreases and the DSP unit loses power. At this time, the RELAY signal end of the DSP unit outputs a high-level signal, and the level conversion unit also outputs a high-level signal. As a result, the optocoupler unit is disconnected, the relay is disconnected, and no driving voltage is output to turn off the contactor. However, when the power supply voltage is temporarily reduced, the RELAY signal end may output a low level. When the RES signal end also outputs a low level, the level conversion unit outputs a low level and the relay outputs a driving voltage. In order to avoid this situation, a first pull-up resistor and a first power supply are set. After the DSP unit loses power, the RELAY signal end outputs a high-level signal under the action of the first pull-up resistor and the first power supply. In this way, even if the RES signal end outputs a low level, the output signal of the level conversion module is also a high level because the input signal is a high level. This ensures that the optocoupler unit is in the off state and the relay control unit turns off the driving voltage of the contactor.

[0044] Optionally, the level conversion unit further includes a second pull-up resistor R2 and a second power supply V2. One end of the second pull-up resistor R2 is connected to the level signal output end of the level conversion chip. The second power supply V2 is connected to the other end of the second pull-up resistor.

[0045] As mentioned above, after the inverter is shut down, the power supply voltage decreases and the DSP unit loses power. The level conversion unit is required to output a high level to put the optocoupler unit and the relay control unit in a disconnected state; thereby turning off the drive voltage of the contactor. When the power supply voltage drops briefly, the DSP pulls down the RES signal, causing the enable end of the level conversion chip to be disabled. In this case, even if the RELAY signal end of the DSP still outputs a low level, the output end of the level conversion unit will still output a high level under the action of the second pull-up resistor. Thereby controlling the optocoupler unit and the relay control unit to be in an off state, ensuring that the drive voltage of the contactor is turned off. In this way, when the inverter encounters a short-term voltage drop, it can ensure that the contacts of the contactor are disconnected, and when the voltage recovers, the charging resistor is connected in series in the circuit to play a role.

[0046] Optionally, the relay control unit includes: a fourth power supply V4, a transistor Q1 and a relay K1. The fourth power supply is used to provide a driving voltage for the contactor. The emitter of the transistor Q1 is connected to the fourth power supply, the base is connected to the fourth power supply V4 through a fifth resistor R5, and the base is also connected to the output end of the optocoupler unit. The relay K1 includes a coil and a contact, the coil is connected to the collector of the transistor Q1, one side of the contact is connected to the fourth power supply V4, and the other side is connected to the contactor.

[0047] Here, the output side of the optocoupler unit is a photosensitive transistor, whose collector is connected to the base of the transistor, and the emitter of the photosensitive transistor is connected to one side of the coil of the relay. In this way, when the optocoupler unit is turned on, the transistor of the relay control unit is turned on, and the coil of the relay is energized to generate an adsorption force and the contacts are closed. Then, the contacts of the relay are attracted, and the fourth power supply provides a driving voltage for the contactor. When the optocoupler unit is disconnected, the base of the transistor is at a high level and is not conducting. The relay control unit cuts off the connection between the fourth power supply and the contactor, that is, turns off the driving voltage of the contactor (at this time, there is no voltage output at the J1 terminal of the relay).

[0048] Optionally, the relay control unit further includes: a first diode D1 and a second diode D2. The first diode D1 is connected in parallel to both sides of the coil of the relay K1, and the cathode is connected to the collector of the transistor. The second diode D2 is connected in parallel to the output end of the relay K1, and the anode is connected to the coil of the relay.

[0049] Here, the first diode is set on both sides of the coil and forms a loop with the coil. When the relay is disconnected, the energy of the coil is released. And when the relay is turned on, the current mutation of the contactor can be avoided. Similarly, the second diode is set at the output end, and the output end outputs the driving voltage for controlling the contactor. When the contactor is disconnected, the energy of the coil also needs to be released. At this time, the second diode is used for freewheeling.

[0050] In addition, the contactor drive circuit for the frequency converter also includes a third power supply, a third resistor, a fourth resistor and a sixth resistor. Among them, the third power supply is used to power the optical coupling unit, and the third resistor and the sixth resistor are used for current limiting. The fourth resistor is used to generate a voltage drop. And the first power supply is smaller than the second power supply, and the second power supply and the third power supply can be the same. As an example, the first power supply takes a value of 3.3V, the second power supply and the third power supply both take a value of 5V, and the fourth power supply takes a value of 24V.

[0051] Combination Figure 4 As shown, an embodiment of the present disclosure provides a control method for a contactor drive circuit of a frequency converter, comprising:

[0052] S101, a detection component detects the real-time power supply voltage of the DSP unit.

[0053] S102, the processor controls the output signal of the RES signal terminal according to the real-time power supply voltage to control the state of the contactor.

[0054] Here, the power supply voltage of the DSP unit is detected in real time through the voltage detection element, that is, the bus voltage of the inverter is detected. When it is detected that the bus voltage of the inverter is reduced, in order to avoid a large charging current after the voltage is restored in a short time, the RES signal of the DSP unit is controlled. Thereby, the level conversion unit is controlled to be disabled, and the optocoupler unit and the relay control unit are disconnected. Then the driving voltage of the contactor is turned off, so that the contactor is in a disconnected state. In this way, when the variable frequency drive recovers from a short-term voltage drop, the contactor is in a disconnected state, and the charging resistor is connected in series in the circuit to limit the charging current. When it is detected that the bus voltage of the inverter is normal, the current RES signal is maintained, the level conversion unit is enabled, the optocoupler unit and the relay control unit are turned on, and the contactor is in a conducting state.

[0055] The control method for the contactor drive circuit of the frequency converter provided by the embodiment of the present disclosure is adopted, and the enabling of the level conversion unit is controlled by the RES signal of the DSP unit. When the power supply voltage changes for a short time (i.e., the power supply voltage fluctuates when the power is not shut down), the DSP unit can control the enabling status of the level conversion unit. Thereby ensuring that when the power supply voltage is reduced, the level conversion unit is not enabled, and then the optocoupler unit and the relay control unit are disconnected. Then, the driving voltage cannot be provided to the contactor, so that the contactor is in a disconnected state. In this way, it is avoided that when the variable frequency drive recovers from a short-term voltage drop, the contactor is in a closed state, resulting in a large charging current that damages the device.

[0056] Optionally, at S102, the processor controls the output signal of the RES signal terminal according to the real-time power supply voltage, including:

[0057] in U dc <U dc_min In this case, the processor controls the RES signal terminal to output a low level so that the relay control unit has no driving voltage output.

[0058] Among them, U dc is the real-time supply voltage, U dc_min It is the under protection voltage.

[0059] Here, the under-protection voltage is a critical voltage. Specifically, when the power supply voltage drops to less than the under-protection voltage, if the power supply voltage is restored in a short time and the contactor is in the on state during the power supply voltage conversion process, the inverter circuit will generate a large impact current. When the power supply voltage is greater than or equal to the under-protection voltage, the inverter circuit is safe. Therefore, in the embodiment of the present disclosure, when the power supply voltage is less than the under-protection voltage, the RES signal terminal is controlled to output a low level. At this time, the level conversion unit is not enabled, and the level conversion chip outputs a high level under the action of the second pull-up resistor R2; so that the contactor is in the off state.

[0060] While controlling the RES signal end to output a low level, the RELAY signal end can be controlled to output a high level to ensure that the level conversion chip outputs a high level. However, under the action of the second pull-up resistor, even if the ELAY signal end outputs a low level, the level conversion chip will output a high level. That is, in the absence of the second pull-up resistor, the RELAY signal end needs to be controlled to output a high level.

[0061] In addition, it should be noted that in the above case, the real-time power supply voltage is still greater than the power failure voltage U dc_off The power-off voltage refers to the voltage when the DSP unit loses power (U dc_off <U dc <U dc_min When the DSP unit loses power (i.e., the inverter is shut down normally), the RELAY signal is at the default high level output under the action of the first pull-up resistor R1, and the level at the current limiting resistor R3 is high after passing through the level conversion chip. The optocoupler unit is in the off state, the transistor Q1 and the relay K1 are not conducting, the port J1 of the control contactor has no driving voltage signal output, and the contactor is turned off.

[0062] Combination Figure 5 As shown, the embodiment of the present disclosure provides another control method for a contactor drive circuit of a frequency converter, comprising:

[0063] S201, a detection component detects the real-time power supply voltage of the DSP unit.

[0064] S202, in U dc <U dc_min In this case, the processor controls the RES signal terminal to output a low level so that the relay control unit has no driving voltage output.

[0065] S203, in U dc ≥U dc_min In this case, the processor controls the RES signal terminal to output a high level and controls the RELAY signal terminal to output a low level, so that the relay control unit outputs a driving voltage.

[0066] Here, after the real-time power supply voltage drops for a short time and then recovers, that is, U dc ≥U dc_min , control the RES signal end of the DSP unit to output a high level, enabling the level conversion chip. Control the RELAY signal end to output a low level, the optocoupler unit and the relay control unit are turned on, and then the contactor is closed to bypass the charging resistor. In this way, it is avoided that when the voltage is restored after a short-term voltage drop in the variable frequency drive, the contactor is in a closed state, resulting in a large charging current when the voltage is restored, causing damage to the inverter rectifier unit and other components.

[0067] Combination Figure 6As shown, an embodiment of the present disclosure provides a control device 200 for a contactor drive circuit of a frequency converter, including a processor 100 and a memory 101. Optionally, the device 200 may also include a communication interface 102 and a bus 103. Among them, the processor 100, the communication interface 102, and the memory 101 can communicate with each other through the bus 103. The communication interface 102 can be used for information transmission. The processor 100 can call the logic instructions in the memory 101 to execute the control method for the contactor drive circuit of the frequency converter of the above embodiment.

[0068] In addition, the logic instructions in the memory 101 described above may be implemented in the form of software functional units and when sold or used as independent products, may be stored in a computer-readable storage medium.

[0069] The memory 101 is a computer-readable storage medium that can be used to store software programs and computer executable programs, such as program instructions / modules corresponding to the method in the embodiment of the present disclosure. The processor 100 executes functional applications and data processing by running the program instructions / modules stored in the memory 101, that is, the control method for the contactor drive circuit of the inverter in the above embodiment is implemented.

[0070] The memory 101 may include a program storage area and a data storage area, wherein the program storage area may store an operating system and an application required for at least one function; the data storage area may store data created according to the use of the terminal device, etc. In addition, the memory 101 may include a high-speed random access memory and may also include a non-volatile memory.

[0071] Combination Figure 7 As shown, an embodiment of the present disclosure provides a frequency converter, including: a rectifier unit 10, a filter unit 20, an inverter unit 30, and a charging resistor 42 connected in series to the rectifier unit, and the charging resistor and the contactor 41 are connected in parallel, and the above-mentioned control device 200 for the contactor drive circuit of the frequency converter. The control device 200 for the contactor drive circuit of the frequency converter is connected to the contactor to control the switching state of the contactor. The installation relationship described here is not limited to placement inside the frequency converter, but also includes installation connections with other components of the frequency converter, including but not limited to physical connections, electrical connections or signal transmission connections. It can be understood by those skilled in the art that the control device 200 for the contactor drive circuit of the frequency converter can be adapted to a feasible frequency converter body, thereby realizing other feasible embodiments.

[0072] An embodiment of the present disclosure provides a computer-readable storage medium storing computer-executable instructions, wherein the computer-executable instructions are configured to execute the control method for a contactor drive circuit of a frequency converter.

[0073] The technical solution of the embodiment of the present disclosure can be embodied in the form of a software product, which is stored in a storage medium and includes one or more instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the method described in the embodiment of the present disclosure. The aforementioned storage medium may be a non-transient storage medium, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a disk or an optical disk, and other media that can store program codes.

[0074] The above description and the accompanying drawings fully illustrate the embodiments of the present disclosure so that those skilled in the art can practice them. Other embodiments may include structural, logical, electrical, process and other changes. The embodiments represent only possible changes. Unless explicitly required, separate components and functions are optional, and the order of operation may vary. The parts and features of some embodiments may be included in or replace the parts and features of other embodiments. Moreover, the words used in this application are only used to describe the embodiments and are not used to limit the claims. As used in the description of the embodiments and the claims, unless the context clearly indicates, the singular forms of "a", "an" and "the" are intended to include plural forms as well. Similarly, the term "and / or" as used in this application refers to any and all possible combinations of listings containing one or more associated ones. In addition, when used in the present application, the term "comprise" and its variants "comprises" and / or comprising refer to the presence of stated features, wholes, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or groups thereof. In the absence of further restrictions, the elements defined by the sentence "comprising a ..." do not exclude the presence of other identical elements in the process, method or device comprising the elements. In this article, each embodiment may focus on the differences from other embodiments, and the same and similar parts between the various embodiments may refer to each other. For the methods, products, etc. disclosed in the embodiments, if they correspond to the method part disclosed in the embodiments, then the relevant parts can refer to the description of the method part.

[0075] Those skilled in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software may depend on the specific application and design constraints of the technical solution. The technicians may use different methods for each specific application to implement the described functions, but such implementations should not be considered to exceed the scope of the embodiments of the present disclosure. The technicians may clearly understand that, for the convenience and simplicity of description, the specific working processes of the systems, devices and units described above may refer to the corresponding processes in the aforementioned method embodiments, and will not be repeated here.

[0076] In the embodiments disclosed herein, the disclosed methods and products (including but not limited to devices, equipment, etc.) can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of the units can be only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the coupling or direct coupling or communication connection between each other shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms. The units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the units may be selected according to actual needs to implement this embodiment. In addition, each functional unit in the embodiment of the present disclosure may be integrated in a processing unit, or each unit may exist physically alone, or two or more units may be integrated in one unit.

[0077] The flowchart and block diagram in the accompanying drawings show the possible architecture, function and operation of the system, method and computer program product according to the embodiment of the present disclosure. In this regard, each box in the flowchart or block diagram can represent a module, a program segment or a part of the code, and the module, the program segment or a part of the code contains one or more executable instructions for realizing the specified logical function. In some alternative implementations, the functions marked in the box can also occur in a different order from the order marked in the accompanying drawings. For example, two consecutive boxes can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, which can depend on the functions involved. In the description corresponding to the flowchart and the block diagram in the accompanying drawings, the operations or steps corresponding to different boxes can also occur in a different order from the order disclosed in the description, and sometimes there is no specific order between different operations or steps. For example, two consecutive operations or steps can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, which can depend on the functions involved. Each block in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, may be implemented by a dedicated hardware-based system that performs the specified functions or actions, or may be implemented by a combination of dedicated hardware and computer instructions.

Claims

1. A contactor drive circuit for a frequency converter, characterized in that: include: The digital signal processing DSP unit is configured to control the level of the output terminal signal according to the power supply voltage; The output end of the DSP unit includes a RES signal end and a RELAY signal end; The level conversion unit includes a level conversion chip; the level conversion chip includes an enable terminal connected to the RES signal terminal of the DSP unit, a level signal input terminal connected to the RELAY signal terminal, and a level signal output terminal; An optical coupling unit connected to the level signal output terminal of the level conversion unit; The relay control unit has an input end connected to the output end of the optical coupling unit, and an output end connected to the contactor to provide a driving voltage for the contactor.

2. The circuit according to claim 1, characterized in that The level conversion unit also includes: A first pull-up resistor, one end of which is connected to the level signal input end of the level conversion chip; The first power supply is connected to the other end of the first pull-up resistor.

3. The circuit according to claim 2, characterized in that The level conversion unit also includes: A second pull-up resistor, one end of which is connected to the level signal output end of the level conversion chip; The second power supply is connected to the other end of the second pull-up resistor.

4. The circuit according to claim 1, characterized in that The relay control unit consists of: A fourth power supply, used for providing a driving voltage for the contactor; A triode, the emitter of which is connected to the fourth power supply, the base of which is connected to the fourth power supply via a fifth resistor, and the base of which is also connected to the output end of the optical coupling unit; The relay comprises a coil and a contact, wherein the coil is connected to the collector of the triode, one side of the contact is connected to the fourth power supply, and the other side of the contact is connected to the contactor.

5. The circuit according to claim 4, characterized in that The relay control unit also includes: The first diode is connected in parallel to both sides of the coil of the relay, and the cathode is connected to the collector of the transistor; The second diode is connected in parallel to the output end of the relay, and the positive electrode is connected to the coil of the relay.

6. A control method for a contactor drive circuit of a frequency converter, characterized in that: Based on the circuit according to any one of claims 1 to 5, the method comprises: Detect the real-time power supply voltage of the DSP unit; According to the real-time power supply voltage, the output signal of the RES signal terminal is controlled to control the state of the contactor.

7. The method according to claim 6, characterized in that When the effective signal of the enable terminal of the level conversion unit is at a high level, the output signal of the RES signal terminal is controlled according to the real-time power supply voltage, including: in U dc <U dc_min In the case of , the RES signal terminal is controlled to output a low level so that the relay control unit has no driving voltage output; Among them, U dc is the real-time supply voltage, U dc_min It is the under protection voltage.

8. The method according to claim 7, characterized in that After controlling the RES signal terminal to output a low level, it also includes: in U dc ≥U dc_min In this case, the RES signal terminal is controlled to output a high level, and the RELAY signal terminal is controlled to output a low level, so that the relay control unit outputs a driving voltage.

9. A control device for a contactor drive circuit of a frequency converter, comprising a processor and a memory storing program instructions, characterized in that: The processor is configured to execute the control method for a contactor drive circuit of a frequency converter according to any one of claims 6 to 8 when running the program instructions.

10. A frequency converter, characterized in that: include: Inverter body, The control device for the contactor drive circuit of the inverter as claimed in claim 9 is installed on the inverter body.

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