Frequency converter overcurrent protection control method

Abstract

The invention discloses a frequency converter overcurrent protection control method, and belongs to the technical field of frequency converter control. The technical problem that over-current protection control of the frequency converter is not reliable is solved. According to the technical scheme, a first single-chip microcomputer module and a second single-chip microcomputer module are connected to jointly receive a detection signal and output a control signal and are set to be in a master-slave communication mode, a master single-chip microcomputer is used for outputting a variable frequency driving signal, and a slave single-chip microcomputer is used for monitoring the operation state of the master single-chip microcomputer; when an overcurrent state occurs, the master single-chip microcomputer and the slave single-chip microcomputer respond at the same time, the slave single-chip microcomputer confirms whether the master single-chip microcomputer operates normally or not, if the master single-chip microcomputer operates normally, restarting is allowed after the first duration, and the interval duration of each restarting is gradually prolonged, so that the effect of improving the working and using reliability is achieved.

Description

Technical Field

[0001] The present application relates to the technical field of inverter control, and in particular to an inverter overcurrent protection control method. Background Art

[0002] In water pump applications, the failure rate of variable frequency drives is high. The main damage is caused by overcurrent. The failure to provide reliable protection under overcurrent conditions is the main cause of overcurrent damage.

[0003] The unreliability of overcurrent protection is manifested in the following aspects: 1) The microcontroller fails to respond to overcurrent in time; 2) After overcurrent, the output of 6 PWM channels cannot be shut down reliably; 3) The MCU cannot respond to overcurrent after it crashes; 4) Due to frequent overcurrent in a short period of time, cumulative overcurrent damage is caused.

[0004] In order to solve the above problems, the present invention provides a method. Summary of the invention

[0005] In view of the above-mentioned problems of the prior art, in order to provide a more reliable overcurrent protection function, the present application provides a frequency converter overcurrent protection control method.

[0006] To achieve the above objectives and other related objectives, this application adopts the following technical solutions: A frequency converter overcurrent protection control method, the frequency converter comprises an input end, a rectifier, a filter, an inverter, and an output end connected in sequence, and also comprises a main circuit on-off control module, a first single-chip computer module, a second single-chip computer module, an IGBT drive module, and a current detection module, the main circuit on-off control module is connected between the rectifier and the inverter to perform on-off control, the IGBT drive module is connected to the inverter, and the current detection module provides a detection signal to the first single-chip computer module and the second single-chip computer module; The first single-chip microcomputer module and the second single-chip microcomputer module are connected to jointly receive the detection signal and output the control signal and are set to a master-slave communication mode, wherein the master single-chip microcomputer is used to output the variable frequency drive signal, and the slave single-chip microcomputer is used to monitor the operating status of the master single-chip microcomputer; When an overcurrent state occurs, the master MCU and the slave MCU respond at the same time. The slave MCU confirms whether the master MCU is running normally. If normal, it is allowed to restart after a first interval, and the interval between each restart is gradually extended.

[0007] Preferably, when an overcurrent state occurs, the input of the inverter is disconnected, and the energy stored in the capacitor is used to perform self-inspection of the IGBT module. After the self-inspection is normal, restarting is allowed after a second time interval, otherwise the input is directly disconnected without restarting.

[0008] Preferably, the detection signal includes an overcurrent signal and a current signal, the current signal is monitored in real time, and the overcurrent signal simultaneously triggers an interrupt service module in the master microcontroller and the slave microcontroller, and the interrupt service module is used to output a circuit breaker protection signal.

[0009] Preferably, the main circuit on-off control module includes a first relay circuit, a second relay circuit, a first AND gate circuit and a second AND gate circuit. The first relay circuit receives two control signals from the master single-chip microcomputer and the slave single-chip microcomputer through the first AND gate circuit, and the second relay circuit receives the other two control signals from the master single-chip microcomputer and the slave single-chip microcomputer through the second AND gate circuit.

[0010] Preferably, a resistor RT is connected in series on the main circuit, the normally open switch of the first relay circuit is connected in series with the normally open switch of the second relay circuit, and the normally open switch of the second relay circuit is connected in parallel to the resistor RT.

[0011] Preferably, the IGBT driving module receives the second driving prohibition signal sent from the main single-chip microcomputer and the first driving prohibition signal sent from the single-chip microcomputer through an OR gate circuit.

[0012] Preferably, the slave microcontroller communicates with the master microcontroller through the UART port. When either party fails to receive information from the other party for a preset period of time, it indicates that the other party is abnormal. The microcontroller of the normal party performs circuit breaker protection, prohibits driving the inverter module, and triggers an alarm signal. The abnormal party will reset and restart after the abnormality.

[0013] Preferably, when the overcurrent state occurs, the main single-chip microcomputer triggers the circuit breaker protection and starts to self-check the 6-way IGBT drive module signal. If the self-check result is normal, the slave single-chip microcomputer is informed that the IGBT drive module is normal, and the drive can be restarted after a preset delay. If the self-check is abnormal, the slave single-chip microcomputer is also informed that the drive will no longer be performed and an alarm is sounded. The preset delay time is determined by the slave microcontroller. After the preset time is reached, the slave microcontroller resets the control signal. After that, the master microcontroller can control the main circuit on-off control module and output the drive to the inverter part, thereby driving the operation of the motor.

[0014] In summary, the present application includes at least one of the following beneficial technical effects: 1. Two single-chip microcomputers are used to complete the functions of the frequency converter. One is the main single-chip microcomputer, which is used to realize the frequency conversion drive function, and the other is the monitoring single-chip microcomputer. Its main functions are: to confirm whether the main single-chip microcomputer is operating normally; when major abnormal conditions such as overcurrent occur, it completes overcurrent protection together with the main control single-chip microcomputer; 2. The time interval between each restart is gradually extended, which is in line with user habits and more intelligent in terms of security and control; 3. The reliability of use has made a qualitative leap. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a block diagram of a local structure of an embodiment of the present application; Figure 2 is a schematic diagram of an application circuit of an embodiment of the present application; Figure 3 is a task processing flow chart of the main single-chip microcomputer in an embodiment of the present application; Figure 4 It is the interrupt task flow chart of the main microcontroller; Figure 5 It is the task processing flow chart from the single chip microcomputer; Figure 6 It is the task flow chart from the microcontroller interrupt.

[0016] Description of main reference numerals: 100, input end; U1, rectifier; E1, filter; U2, inverter; 200, output end; 300, main circuit on / off control module; 400, first single-chip microcomputer module; 500, second single-chip microcomputer module; 600, IGBT drive module; 700, current detection module; IC4, first AND gate circuit; IC3, second AND gate circuit; M, motor. DETAILED DESCRIPTION

[0017] The following describes the embodiments of the present application through specific examples, and those skilled in the art can easily understand other advantages and effects of the present application from the contents disclosed in this specification. The present application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0018] It should be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present application. The illustrations only show the components related to the present application rather than being drawn according to the number, shape and size of the components in actual implementation. In actual implementation, the type, quantity and proportion of each component can be changed at will, and the component layout type may also be more complicated.

[0019] The specific implementation methods of the present application will be further described below in conjunction with the accompanying drawings.

[0020] Example: The present application discloses a method for controlling overcurrent protection of a frequency converter. Figure 1 and Figure 2 As shown in the figure, the frequency converter includes an input terminal 100, a rectifier U1, a filter E1, an inverter U2, and an output terminal 200 connected in sequence, and also includes a main circuit on-off control module 300, a first single-chip module 400, a second single-chip module 500, an IGBT drive module 600, and a current detection module 700. Figure 2 In the figure, the input terminal 100 is: L1, L2 and L3 three-phase power input, two phases of which can be directly used as the power supply for the power module U3, and the power module can output VDD, VCC and other voltages that meet the working requirements of the hardware module. The rectifier part is a rectifier bridge module U1. In the inverter, the RT resistor usually refers to the thermistor, and its resistance value changes with the external temperature. It is used here for overheating protection. The RS resistor is used for current sampling. The filter part is an electrolytic capacitor E1, and it can also be used for energy storage. The inverter part is a three-phase bridge inverter circuit composed of MOS tubes, and its output end is used to connect the motor M to achieve variable frequency control of the motor.

[0021] The main circuit on-off control module is connected between the rectifier and the inverter for on-off control, the IGBT drive module is connected to the inverter, and the current detection module provides detection signals to the first single-chip microcomputer module and the second single-chip microcomputer module. The detection signals here are current signals and overcurrent signals.

[0022] The first single-chip microcomputer module and the second single-chip microcomputer module are connected to jointly receive detection signals and output control signals and are set to a master-slave communication mode, wherein the master single-chip microcomputer is used to output variable frequency drive signals, and the slave single-chip microcomputer is used to monitor the operating status of the master single-chip microcomputer.

[0023] When an overcurrent state occurs, the master MCU and the slave MCU respond at the same time. The slave MCU confirms whether the master MCU is running normally. If normal, it is allowed to restart after a first interval, and the interval between each restart is gradually extended.

[0024] Circuit breaker protection means that after disconnecting the bus power supply, the power stored in the filter capacitor on the bus is used to detect whether the inverter circuit is normal. The two single-chip microcomputers are connected to each other through an interface to realize the interactive function. The monitoring single-chip microcomputer determines whether the main single-chip microcomputer is operating normally according to the interactive situation. The interactive interface generally uses a UART port, and other methods can also be used without affecting the present invention.

[0025] When an overcurrent condition occurs, the inverter input is disconnected and the energy stored in the capacitor is used to perform self-test on the IGBT module. If the self-test is normal, restart is allowed after a second interval. Otherwise, the input is directly disconnected without restarting.

[0026] The detection signal includes an overcurrent signal and a current signal. The current signal is monitored in real time. The overcurrent signal simultaneously triggers an interrupt service module in the master microcontroller and the slave microcontroller. The interrupt service module is used to output a circuit breaker protection signal.

[0027] exist Figure 2 It can be seen that the main circuit on-off control module includes a first relay circuit, a second relay circuit, a first "AND" gate circuit and a second "AND" gate circuit. The first relay circuit receives two control signals from the master microcontroller and the slave microcontroller through the first "AND" gate circuit, and the second relay circuit receives the other two control signals from the master microcontroller and the slave microcontroller through the second "AND" gate circuit.

[0028] A resistor RT is connected in series to the main circuit, the normally open switch of the first relay circuit is connected in series to the normally open switch of the second relay circuit, and the normally open switch of the second relay circuit is connected in parallel to the resistor RT.

[0029] The IGBT driving module receives the second driving prohibition signal sent from the main single chip and the first driving prohibition signal sent from the single chip through an OR gate circuit. The second driving prohibition signal or the first driving prohibition signal can control the circuit breaker protection separately.

[0030] Combination Figure 3-Figure 6 , the IO1 pin of the second single-chip microcomputer IC1 outputs a signal RLY11, the IO2 pin outputs a signal RLY12, and the IO3 pin outputs a signal first prohibited from driving; similarly, the IO1 pin of the first single-chip microcomputer IC2 outputs a signal RLY21, the IO2 pin outputs a signal RLY22, and the IO3 pin outputs a signal first prohibited from driving.

[0031] The two input signals of the first AND gate circuit IC4 are RLY11 and RLY21. The two input signals of the second AND gate circuit IC3 are RLY12 and RLY22.

[0032] It can be seen that two single-chip microcomputers need to work together to realize the control of relay K1 or K2. When two single-chip microcomputers, for example, the IO1 pins of both single-chip microcomputers are high, IC4 outputs a high level, relay K1 is powered and closed. When the IO2 pins of both single-chip microcomputers are high, IC3 outputs a high level, relay K2 is powered and closed.

[0033] The slave MCU communicates with the master MCU through the UART port. When either party fails to receive information from the other party for a preset period of time, it indicates that the other party is abnormal. The normal MCU performs circuit breaker protection, prohibits driving the inverter module, and triggers an alarm signal. The abnormal party will reset and restart after the abnormality.

[0034] When the overcurrent state occurs, the main MCU triggers the circuit breaker protection and starts to self-check the 6-way IGBT drive module signals. If the self-check result is normal, the slave MCU is informed that the IGBT drive module is normal and the drive can be restarted after a preset delay. If the self-check is abnormal, the slave MCU is also informed and no drive is performed thereafter, and an alarm is sounded.

[0035] The preset delay time is determined by the slave microcontroller. After the preset time is reached, the slave microcontroller resets the control signal. After that, the master microcontroller can control the main circuit on-off control module and output the drive to the inverter part, thereby driving the operation of the motor.

[0036] During normal operation, the slave MCU will periodically read the information of the master MCU. The master MCU should respond within a certain period of time. If there is no response, it is considered that the master MCU is abnormal. If the master MCU does not receive information from the slave MCU within a certain period of time, it is considered that the slave MCU is abnormal, and the master MCU actively stops driving and indicates a fault.

[0037] Two single-chip microcomputers are used to complete the functions of the frequency converter. One is the main single-chip microcomputer, which is used to realize the variable frequency drive function, and the other is the monitoring single-chip microcomputer. Its main functions are: to confirm whether the main single-chip microcomputer is operating normally; when major abnormal conditions such as overcurrent occur, it completes overcurrent protection together with the main control single-chip microcomputer, allowing restart after an interval. The time interval between each restart is gradually extended, which is in line with user habits and is more intelligent in safety and control.

[0038] When overcurrent occurs, as long as one of the two microcontrollers responds to the overcurrent interrupt, the drive output can be disabled to protect the power components.

[0039] U4 is a current amplification and overcurrent signal generation circuit. This circuit is a conventional circuit and is well known in the art. The overcurrent signal will be sent to the external interrupt pins of the two single-chip microcomputers at the same time. When overcurrent occurs, any single-chip microcomputer can respond to the interrupt and prohibit the drive through IC5. When the relay K1 is cut off, the input power supply can no longer charge the capacitor E1. At this time, the electric energy stored in E1 can be used to perform self-test on the 6-way IGBT. The power supply of the present invention is independent, and the power supply module used is a conventional module. The role of independent power supply is: when K1 is disconnected, the capacitor E1 has no power, and the single-chip microcomputer still has power.

[0040] After overcurrent, the main control microcontroller starts self-testing the 6-way IGBT after K1 is disconnected. If the self-test result is normal, the monitoring microcontroller is informed that the IGBT is normal and can be restarted after a certain delay. If the self-test is abnormal, the monitoring microcontroller is also informed and will no longer be driven and an alarm will be sounded.

[0041] The delay time is determined by the monitoring microcontroller. After the delay time is reached, the monitoring microcontroller releases the control of K1 and also releases the prohibition signal to the drive circuit. After that, the main control microcontroller can control K1 to close and output the drive to the 6-way IGBT, thereby driving the operation of the motor.

[0042] Usually, if overcurrent occurs multiple times within a long period of time, it means that the water pump is abnormal. At this time, the drive should be stopped to avoid damaging the water pump.

[0043] The above embodiments are only illustrative of the principles and effects of the present application, and are not intended to limit the present application. Anyone familiar with the technology may modify or change the above embodiments without violating the spirit and scope of the present application. Therefore, any equivalent changes made based on the structure, shape, and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A frequency converter overcurrent protection control method, the frequency converter comprises an input end, a rectifier, a filter, an inverter, and an output end connected in sequence, and also comprises a main circuit on-off control module, a first single-chip microcomputer module, a second single-chip microcomputer module, an IGBT drive module, and a current detection module, the main circuit on-off control module is connected between the rectifier and the inverter to perform on-off control, the IGBT drive module is connected to the inverter, and the current detection module provides a detection signal to the first single-chip microcomputer module and the second single-chip microcomputer module; It is characterized in that The first single-chip microcomputer module and the second single-chip microcomputer module are connected to jointly receive the detection signal and output the control signal and are set to a master-slave communication mode, wherein the master single-chip microcomputer is used to output the variable frequency drive signal, and the slave single-chip microcomputer is used to monitor the operating status of the master single-chip microcomputer; When an overcurrent state occurs, the master MCU and the slave MCU respond at the same time. The slave MCU confirms whether the master MCU is running normally. If normal, it is allowed to restart after a first interval, and the interval between each restart is gradually extended.

2. The inverter overcurrent protection control method according to claim 1, characterized in that: When an overcurrent condition occurs, the inverter input is disconnected and the energy stored in the capacitor is used to perform self-test on the IGBT module. If the self-test is normal, restart is allowed after a second interval. Otherwise, the input is directly disconnected without restarting.

3. The inverter overcurrent protection control method according to claim 1, characterized in that: The detection signal includes an overcurrent signal and a current signal. The current signal is monitored in real time. The overcurrent signal simultaneously triggers an interrupt service module in the master microcontroller and the slave microcontroller. The interrupt service module is used to output a circuit breaker protection signal.

4. A frequency converter overcurrent protection control method according to claim 3, characterized in that: The main circuit on-off control module includes a first relay circuit, a second relay circuit, a first AND gate circuit and a second AND gate circuit. The first relay circuit receives two control signals from the master single-chip microcomputer and the slave single-chip microcomputer through the first AND gate circuit, and the second relay circuit receives the other two control signals from the master single-chip microcomputer and the slave single-chip microcomputer through the second AND gate circuit.

5. A frequency converter overcurrent protection control method according to claim 4, characterized in that: A resistor RT is connected in series to the main circuit, the normally open switch of the first relay circuit is connected in series to the normally open switch of the second relay circuit, and the normally open switch of the second relay circuit is connected in parallel to the resistor RT.

6. The inverter overcurrent protection control method according to claim 1, characterized in that: The IGBT driving module receives the second driving prohibition signal sent from the main single-chip microcomputer and the first driving prohibition signal sent from the single-chip microcomputer through an OR gate circuit.

7. The inverter overcurrent protection control method according to claim 1, characterized in that: The slave MCU communicates with the master MCU through the UART port. When either party fails to receive information from the other party for a preset period of time, it indicates that the other party is abnormal. The normal MCU performs circuit breaker protection, prohibits driving the inverter module, and triggers an alarm signal. The abnormal party will reset and restart after the abnormality.

8. The inverter overcurrent protection control method according to claim 7, characterized in that: When the overcurrent state occurs, the main MCU triggers the circuit breaker protection and starts to self-check the 6-way IGBT drive module signal. If the self-check result is normal, the slave MCU is informed that the IGBT drive module is normal and the drive can be restarted after a preset delay. If the self-check is abnormal, the slave MCU is also informed that the drive will no longer be performed and an alarm will be sounded. The preset delay time is determined by the slave microcontroller. After the preset time is reached, the slave microcontroller resets the control signal. After that, the master microcontroller can control the main circuit on-off control module and output the drive to the inverter part, thereby driving the operation of the motor.

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