CN117081460A - Variable frequency controller and control method thereof - Google Patents
Variable frequency controller and control method thereof Download PDFInfo
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- CN117081460A CN117081460A CN202310864768.2A CN202310864768A CN117081460A CN 117081460 A CN117081460 A CN 117081460A CN 202310864768 A CN202310864768 A CN 202310864768A CN 117081460 A CN117081460 A CN 117081460A
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- 238000000034 method Methods 0.000 title claims description 15
- 230000002159 abnormal effect Effects 0.000 claims abstract description 47
- 230000001681 protective effect Effects 0.000 claims abstract description 37
- 238000006243 chemical reaction Methods 0.000 claims abstract description 24
- 238000012937 correction Methods 0.000 claims description 24
- 238000005070 sampling Methods 0.000 claims description 16
- 238000001914 filtration Methods 0.000 claims description 12
- 230000005856 abnormality Effects 0.000 claims description 6
- 239000003990 capacitor Substances 0.000 claims description 5
- 230000000670 limiting effect Effects 0.000 claims description 5
- 238000012545 processing Methods 0.000 claims description 3
- 230000002411 adverse Effects 0.000 abstract description 8
- 230000002829 reductive effect Effects 0.000 abstract description 5
- 238000013461 design Methods 0.000 abstract description 3
- 230000000694 effects Effects 0.000 abstract description 3
- 238000010586 diagram Methods 0.000 description 12
- 230000002035 prolonged effect Effects 0.000 description 5
- 238000005516 engineering process Methods 0.000 description 3
- 238000004378 air conditioning Methods 0.000 description 1
- 238000004134 energy conservation Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000007935 neutral effect Effects 0.000 description 1
- 230000036961 partial effect Effects 0.000 description 1
- 230000001052 transient effect Effects 0.000 description 1
Classifications
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P29/00—Arrangements for regulating or controlling electric motors, appropriate for both AC and DC motors
- H02P29/02—Providing protection against overload without automatic interruption of supply
- H02P29/024—Detecting a fault condition, e.g. short circuit, locked rotor, open circuit or loss of load
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P29/00—Arrangements for regulating or controlling electric motors, appropriate for both AC and DC motors
- H02P29/02—Providing protection against overload without automatic interruption of supply
- H02P29/024—Detecting a fault condition, e.g. short circuit, locked rotor, open circuit or loss of load
- H02P29/0241—Detecting a fault condition, e.g. short circuit, locked rotor, open circuit or loss of load the fault being an overvoltage
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P29/00—Arrangements for regulating or controlling electric motors, appropriate for both AC and DC motors
- H02P29/02—Providing protection against overload without automatic interruption of supply
- H02P29/032—Preventing damage to the motor, e.g. setting individual current limits for different drive conditions
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Control Of Electric Motors In General (AREA)
Abstract
A variable frequency controller comprises a processor and a conversion circuit, wherein the conversion circuit converts a power supply voltage into a first voltage, and the first voltage is input to the processor; the processor samples the input first voltage in real time and obtains a digital signal, and if the processor detects that the value of the digital signal is smaller than or equal to a preset abnormal threshold value and lasts for a preset time period, the processor judges that the power supply voltage is abnormal and takes protective measures or early warning for the variable frequency controller and/or the motor according to a preset program. Therefore, the power supply voltage can be continuously monitored, corresponding measures can be timely taken, and adverse effects on the variable frequency controller and the motor when the power supply voltage is abnormal can be prevented. In addition, the conversion circuit for converting the power supply voltage into the first voltage comprises a first diode, a second diode, a first resistor, a second resistor and a third resistor, namely the circuit structure is relatively simple, and the hardware design cost can be reduced.
Description
The application discloses a divisional application with the name of a variable frequency controller and a control method thereof for the application of 2017, 12, 28 and 201711462537. X.
[ field of technology ]
The application relates to the technical field of control, in particular to a variable frequency controller and a control method thereof.
[ background Art ]
The latest technology in the current air conditioning industry is a frequency conversion technology, and is characterized by energy conservation, environmental protection and high reliability; wherein the high reliability is mainly reflected in a wide input voltage range.
However, the variable frequency controller and/or the motor needs to be protected in time when the power supply voltage changes, because the variable frequency controller and/or the motor is adversely affected when the voltage changes instantly.
[ application ]
It is an object of embodiments of the present application to provide a variable frequency controller and a control method, which facilitate reducing the adverse effect of supply voltage variations on the variable frequency controller and/or the motor.
A variable frequency controller capable of being used to drive a motor, the variable frequency controller comprising a processor and a conversion circuit; the conversion circuit can convert the power supply voltage into a first voltage which can be identified by the processor, and the processor acquires the first voltage to obtain a digital signal corresponding to the first voltage;
the processor acquires the first voltage at certain sampling intervals, and when the processor detects that the value of the digital signal is smaller than or equal to a preset abnormal threshold value and a preset time period is continued, the processor judges that the power supply voltage is abnormal, and the processor takes protective measures or early warning for the variable frequency controller and/or the motor according to a preset program;
the conversion circuit comprises a first diode, a second diode, a first resistor, a second resistor and a third resistor;
the first diode and the second diode are used for rectifying the power supply voltage and obtaining a first direct current voltage; the anode of the first diode and the anode of the second diode are connected with the power supply voltage end; the cathode of the first diode is connected with the cathode of the second diode;
the first resistor and the second resistor are connected in series and are used for dividing the first direct-current voltage to obtain a second direct-current voltage; one end of the first resistor is connected with the cathode of the first diode and the cathode of the second diode, and the other end of the first resistor is grounded through the second resistor;
the third resistor is used for limiting the second direct-current voltage, and the second direct-current voltage passes through the third resistor to obtain the first voltage; one end of the third resistor is connected with the first resistor and the second resistor, and the other end of the third resistor is connected to the processor.
A control method applied to the variable frequency controller described above, the variable frequency controller being capable of being used to drive a motor;
the control method comprises the following steps:
step S1, continuously sampling the first voltage by the processor at each sampling interval, and acquiring the first voltage by the processor to obtain a digital signal corresponding to the first voltage;
step S2, the processor judges whether the value of the digital signal is smaller than or equal to the preset abnormal threshold value; if yes, the count value is increased by 1, and the step S3 is carried out; if not, the count value is cleared and returns to the execution step S1;
step S3, the processor judges whether the count value is equal to a preset value; if yes, go to step S4; if not, returning to execute the step S2;
s4, the processor judges that the power supply voltage is abnormal, and the processor takes protective measures or early warning for the variable frequency controller and/or the motor according to a preset program; and returns to step S1.
Wherein, the initial value of the count value is zero, and the preset value is determined by the preset time period and the sampling interval.
The variable frequency controller comprises a processor and a conversion circuit, wherein the power supply voltage is processed by the conversion circuit to obtain a first voltage, the processor collects the first voltage to obtain a digital signal, the processor judges that the power supply voltage is abnormal according to the fact that the value of the detected digital signal is smaller than or equal to an abnormal threshold value within a preset time period, and the processor takes protective measures or early warning for the variable frequency controller and/or the motor according to a preset program, so that the power supply voltage abnormality can be found in advance, corresponding measures are taken, further the power supply voltage abnormality has adverse effects on the variable frequency controller and the motor, and the service life of the variable frequency controller and/or the motor is prolonged. In addition, the conversion circuit for converting the power supply voltage into the first voltage comprises a first diode, a second diode, a first resistor, a second resistor and a third resistor, namely the circuit structure is relatively simple, and the hardware design cost can be reduced.
Drawings
FIG. 1 is a schematic diagram illustrating the connection of one embodiment of a variable frequency controller provided by the present application;
FIG. 2 is a schematic diagram of a theoretical waveform of the supply voltage Uac under ideal conditions;
fig. 3 is a schematic diagram of a theoretical waveform of the first voltage Uad under ideal conditions;
fig. 4 is a schematic diagram of theoretical waveforms of the voltage value corresponding to the abnormal threshold value Umin and the first voltage Uad in an ideal case;
fig. 5 is a schematic diagram of a theoretical waveform of the first direct current voltage Udc1 in an ideal case;
fig. 6 is a schematic diagram of a theoretical waveform of the second direct current voltage Udc2 in an ideal case;
fig. 7 is a schematic flow chart of a part of an embodiment of a control method provided by the present application.
Detailed Description
The technical features and advantages of the embodiments of the present application are described in detail below with reference to the accompanying drawings.
Referring to fig. 1 to 6, fig. 1 is a schematic connection diagram of a variable frequency controller 1 provided by the present application, the variable frequency controller 1 can be used to drive a motor 2, and the motor 2 can be used to drive a compressor. The variable frequency controller 1 comprises a processor 11 and a conversion circuit 12; the conversion circuit 12 can convert the supply voltage Uac into a first voltage Uad which can be identified by the processor 11, and the processor 11 collects the first voltage Uad to obtain a digital signal corresponding to the first voltage Uad; the processor 11 collects the first voltage Uad at certain sampling intervals, when the processor 11 detects that the value of the digital signal is smaller than or equal to a preset abnormal threshold value Umin and a preset time period is continued, the processor 11 judges that the power supply voltage Uac is abnormal, and the processor 11 takes protective measures or early warning for the variable frequency controller 1 and/or the motor 2 according to a preset program, so that the power supply voltage can be monitored in real time, early warning or timely taking protective measures can be carried out to prevent the power supply voltage abnormality from adversely affecting the variable frequency controller and/or the motor, and the service life of the variable frequency controller and/or the motor can be prolonged; meanwhile, any point on the waveform is possible to be used as an access point, special positions of the waveform such as zero point of the waveform do not need to be selected, the control is simpler, and the universality and convenience of the control are improved.
Specifically, the preset time period is greater than or equal to half of the period of the theoretical supply voltage Uac, the frequency of the theoretical domestic supply voltage is usually 50Hz, the period of the supply voltage is 20ms, and half of the period of the supply voltage is 10ms, so that in order to simplify the program design, the sampling interval may be set to be greater than or equal to 1ms, and the preset time period may be determined according to the sampling interval and the sampling times. The preset time period is more than or equal to half of the period of the theoretical power supply voltage Uac, so that misjudgment can be prevented, the points in the duration equal to half of the period of the theoretical power supply voltage Uac can be ensured to be covered, and the control precision is improved.
FIG. 2 is a schematic diagram of a theoretical waveform of a supply voltage Uac under ideal conditions, in which the peak voltage V1, V1 of the supply voltage Uac is equal to 311V when the supply voltage is normal, the frequency of the supply voltage is typically 50HZ, the period T of the supply voltage is 20ms, and half of the period T/2 of the supply voltage is 10ms; of course, the supply voltage is different according to the region and the country, and it is impossible to achieve an ideal voltage waveform. After the supply voltage Uac is processed by the conversion circuit 12, a first voltage is obtained, which can be input to the processor 11, and the processor 11 collects the first voltage Uad to obtain a digital signal. Fig. 3 is a schematic diagram of a theoretical waveform of the first voltage Uad, in which the first voltage Uad is a dc ripple voltage, and in which the peak voltage V2 of the first voltage Uad is less than 311V when the voltage is normal, and the period is T/2. Anomalies in the supply voltage Uac, including voltage drops, voltage interruptions and voltage sags, the supply voltage loop will produce instantaneous high currents, adversely affecting the variable frequency controller 1 and the motor 2. Therefore, the processor 11 sets the abnormal threshold value Umin, and in this embodiment, the voltage value corresponding to the abnormal threshold value Umin is determined according to the first voltage obtained by processing the lower limit value of the normal range of the power supply voltage Uac by the conversion circuit 12. The lower limit value of the normal range of the power supply voltage Uac is set according to the actual engineering condition or according to the actual requirement. Fig. 4 is a schematic diagram of theoretical waveforms of the voltage value corresponding to the abnormal threshold value Umin and the first voltage in an ideal case;
the power supply voltage Uac is processed by the conversion circuit 12 to obtain a first voltage Uad, the processor 11 samples the first voltage Uad in real time and obtains a digital signal, the processor 11 continuously samples the first voltage Uad at certain sampling intervals, and when the processor 11 detects that the value of the digital signal is smaller than or equal to a preset abnormal threshold value Umin and a preset time period is continued, the processor 11 determines that the power supply voltage Uac is abnormal, and the processor 11 takes protective measures or early warning for the variable frequency controller 1 and/or the motor 2 according to a preset program. The preset program includes a first case: when the processor 11 determines that the supply voltage Uac is abnormal, the processor 11 takes protective measures or early warning for the variable frequency controller 1 and/or the motor 2, wherein taking protective measures for the motor includes cutting off the power supply output to the motor or reducing the frequency and/or amplitude of the voltage output to the motor, and taking protective measures for the variable frequency controller 1 includes bringing part of the functional modules of the variable frequency controller into a protective state. Therefore, the protection measures are taken only when the power supply voltage is abnormal, so that the motor and/or the variable frequency controller can be protected, and the service life of the protected parts is prolonged.
The preset program further includes a second case: when the processor 11 judges that the power supply voltage Uac is abnormal, the processor 11 does not take protective measures or early warning for the variable frequency controller 1 and/or the motor 2 temporarily, when the processor judges that the power supply voltage Uac is abnormal, the processor 11 counts through the counter, the accumulated value is accumulated when the power supply voltage Uac is continuously abnormal, the accumulated value is obtained, if the accumulated value is clear before the accumulated value reaches a preset value and the power supply voltage Uac is not abnormal, and when the accumulated value reaches the preset value, the processor 11 takes protective measures or early warning for the variable frequency controller 1 and/or the motor 2, wherein taking protective measures for the motor 2 comprises cutting off the power supply output to the motor 2 or reducing the frequency and/or the amplitude of the voltage output to the motor 2, and taking protective measures for the variable frequency controller 1 comprises enabling part of functional modules of the variable frequency controller 1 to enter a protective state; in this way, by accumulating the abnormal condition of the power supply voltage at least twice, misjudgment is reduced, and thus the influence on the system is caused.
The abnormal threshold value Umin can be a value or a range, and when the abnormal threshold value Umin is a range, different protection measures and early warning programs can be set according to the relation between the digital signal and the range. The processor 11 presets an upper limit value and a lower limit value, and the abnormality threshold value Umin includes a range between the upper limit value and the lower limit value; when the processor 11 detects that the value of the digital signal is less than or equal to the upper limit value and continues for a preset period of time, but at least part of the value of the digital signal is greater than or equal to the lower limit value, the processor 11 changes the output control signal, and reduces the frequency and/or amplitude or early warning of the voltage output to the motor 2; when the values of all the digital signals obtained by the processor 11 in the preset time period are smaller than the lower limit value, the processor 11 stops outputting the control signal, and the motor 2 stops working.
The variable frequency controller 1 further comprises a driving module 15, the driving module 15 can be used for driving the motor 2, the processor 11 can output PWM signals to the driving module 15, and the protection measures comprise that the processor 11 stops outputting the PWM signals to drive the IPM driving module 15, and the motor 2 stops working; of course, the driving module may also be formed by other types of circuits connected with discrete components, and the control signal may also be other signals.
The variable frequency controller 1 further comprises an active power factor correction module 14, the active power factor correction module 14 being connected to the IPM driving module 15; after correction and boosting by the active power factor correction module 14, a stable direct-current voltage is obtained and supplied to the IPM driving module 15, and the IPM driving module 15 can drive the motor 2. The protection measures include the processor 11 sending out a control signal, turning off the active power factor correction module 14, and protecting the internal components of the active power factor correction module 14 so that the active power factor correction module 14 is in a protection state.
The variable frequency controller 1 also comprises a relay switch 17 and a thermistor 18, and the thermistor 18 is connected with the power supply voltage Uac; the relay switch 17 is connected to both ends of the thermistor 18; characteristics of thermistor 18: the thermistor 18 is a positive temperature coefficient thermistor, and as the temperature rises, the resistance value increases, so that the current limiting effect is achieved; when the power supply voltage Uac is normal, the relay switch 17 is in a closed state, and the relay switch 17 corresponds to a wire, and current flows through the relay switch 17 and does not flow through the thermistor 18; the protection measures include that when the processor 11 judges that the supply voltage Uac is abnormal, the processor 11 sends out a driving signal, the relay switch 17 is opened, and if the supply voltage is recovered to be normal at the next moment, the transient high current generated by the supply voltage loop can be prevented from adversely affecting the variable frequency controller 1 and the motor 2 by utilizing the characteristics of the thermistor 18.
The variable frequency controller also comprises a rectifying and filtering module 13 and a switching power supply 16, wherein the rectifying and filtering module 13 is respectively connected with a live wire L and a zero wire N of the power supply voltage Uac, and the power supply voltage can be only two live wires L. After the power supply voltage Uac is rectified and filtered by the rectifying and filtering module 13, a stable direct current voltage, namely a third direct current voltage, is obtained. The rectification filter module 13 is respectively connected with the relay 17, the switching power supply 16 and the active power factor correction module 14, the power supply voltage Uac is respectively connected to the switching power supply 16 and the active power factor correction module 14 through the relay 17 and the rectification filter module 13 in sequence, the rectification filter module 13 is connected to the active power factor correction module 14, the stable third direct current voltage obtained after the rectification filter module 13 carries out rectification filter treatment on the power supply voltage Uac is further corrected and boosted through the active power factor correction module 14, and the stable third direct current voltage is obtained after the active power factor correction module 14 carries out further correction and boosting treatment. The rectifying and filtering module 13 is connected to the switching power supply 16, and the switching power supply 16 is respectively connected to the processor 11, the active power factor correction module 14 and the relay switch 17; the stabilized third direct current voltage obtained after the rectification and filtering module 13 performs rectification and filtering treatment on the power supply voltage Uac is input to the switching power supply 16; the more stable dc voltage (i.e., the fifth dc voltage) obtained after the processing of the switching power supply 16 is supplied to the processor 11, the active power factor correction module 14, and the relay switch 17, respectively.
The variable frequency controller 1 includes a conversion circuit 12, and the conversion circuit 12 includes a first diode 121a, a second diode 121b, a first resistor 122a, a second resistor 122b, a third resistor 122c, and a first capacitor 123a. The first diode 121a and the second diode 121b are used for rectifying the supply voltage Uac and obtaining a first direct voltage Udc1. Fig. 5 is a schematic diagram of a theoretical waveform of the first direct current voltage Udc1 in an ideal case, the theoretical peak value is V1, and the period is T/2. The anode of the first diode 121a and the anode of the second diode 121b are both connected to a power supply voltage, in this embodiment, the live wire L of the power supply voltage Uac is connected to the anode of the first diode 121a, the neutral wire N of the power supply voltage Uac is connected to the anode of the second diode 121b, and of course, when the power supply voltage has only two live wires, the anode of the second diode 121b is connected to the other live wire of the power supply voltage. The cathode of the first diode 121a is connected to the cathode of the second diode 121 b. The first resistor 122a and the second resistor 122b are connected in series, and are used for dividing the first direct current voltage Udc1 to obtain a second direct current voltage Udc2. Fig. 6 is a schematic diagram of a theoretical waveform of the second dc voltage Udc2, with a theoretical peak value V2 and a period T/2, in an ideal case. One end of the first resistor 122a is connected with the cathode of the first diode 121a and the cathode of the second diode 121b, and the other end of the first resistor 122a is grounded through the second resistor 122 b; the third resistor 122c is used for limiting the second direct current voltage Udc2, and the second direct current voltage Udc2 passes through the third resistor 122c to obtain a first voltage Uad; one end of the third resistor 122c is connected to both the first resistor 122a and the second resistor 122b, and the other end of the third resistor 122c is connected to the processor 11 and grounded through the first capacitor 123a. The first capacitor 123a is used for filtering the first voltage Uad input to the processor 11 to remove the high-frequency interference signal. The circuit structure of the conversion circuit 12 is relatively simple, the hardware design cost can be reduced, and the conversion circuit 12 can be used for realizing the real-time conversion of the power supply voltage Uac, so that the system has real-time performance.
The present application provides a control method which can be used for the above-described variable frequency controller 1, the variable frequency controller 1 can be used for driving the motor 2, and the motor 2 can be used for driving the compressor.
Referring to fig. 7, fig. 7 is a schematic partial flow chart of an embodiment of a control method provided by the present application. The control method comprises the following steps:
step S1, the processor 11 continuously samples the first voltage Uad at each sampling interval, and the processor 11 collects the first voltage Uad to obtain a digital signal corresponding to the first voltage Uad;
step S2, the processor 11 judges whether the value of the digital signal is smaller than or equal to a preset abnormal threshold value Umin; if yes, the count value is increased by 1, and the step S3 is carried out; if not, the count value is cleared and returns to execute the step S1;
step S3, the processor 11 judges whether the count value is equal to a preset value; if yes, go to step S4; if not, returning to execute the step S2;
step S4, the processor 11 judges that the power supply voltage Uac is abnormal, and the processor 11 takes protective measures or early warning for the variable frequency controller 1 and/or the motor 2 according to a preset program; and returns to step S1.
The initial value of the count value is zero, and the preset value is determined according to a preset time period and a sampling interval.
Therefore, the power supply voltage Uac can be monitored in real time, the abnormity can be early warned in advance or protective measures can be timely taken to prevent the power supply voltage abnormity from adversely affecting the variable frequency controller and/or the motor, and the service life of the variable frequency controller and/or the motor can be prolonged; meanwhile, any point on the waveform is possible to be used as an access point, special positions of the waveform such as zero point of the waveform do not need to be selected, the control is simpler, and the universality and convenience of the control are improved.
In the embodiment of the control method provided by the application, the preset program includes a first case: when the processor 11 determines that the supply voltage Uac is abnormal, the processor 11 takes protective measures or early warning for the variable frequency controller 1 and/or the motor 2, wherein the taking protective measures for the motor 2 comprises cutting off the power supply output to the motor 2 or reducing the frequency and/or amplitude of the voltage output to the motor 2, and the taking protective measures for the variable frequency controller 1 comprise enabling part of functional modules of the variable frequency controller 1 to enter a protective state; therefore, the protection measures are taken only when the power supply voltage is abnormal, so that the motor and/or the variable frequency controller can be protected, and the service life of the protected parts is prolonged.
The preset program further includes a second case: when the processor 11 determines that the supply voltage Uac is abnormal, the processor 11 does not take protective measures or early warning for the variable frequency controller 1 and/or the motor 2 temporarily, when the processor 11 determines that the supply voltage Uac is abnormal, the processor 11 counts through the counter, the supply voltage is accumulated to obtain an accumulated value when the supply voltage is continuously abnormal, the accumulated value is cleared before reaching a preset value, if the condition that the supply voltage is not abnormal occurs, the processor 11 takes protective measures or early warning for the variable frequency controller 1 and/or the motor 2 when the accumulated value reaches the preset value, wherein taking protective measures for the motor 2 comprises cutting off the power supply output to the motor 2 or reducing the frequency and/or the amplitude of the voltage output to the motor 2, and taking protective measures for the variable frequency controller 1 comprises enabling part of functional modules of the variable frequency controller 1 to enter a protective state. In this way, by accumulating the abnormal condition of the power supply voltage at least twice, misjudgment is reduced, and thus the influence on the system is caused.
In the above control method, the abnormal threshold value Umin may be a value or a range, and when the abnormal threshold value Umin is a range, different protection measures and early warning programs may be set according to the relationship between the digital signal and the range. The processor 11 presets an upper limit value and a lower limit value, and the abnormality threshold value Umin includes a range between the upper limit value and the lower limit value; when the processor 11 detects that the value of the digital signal is less than or equal to the upper limit value and continues for a preset period of time, but at least part of the value of the digital signal is greater than or equal to the lower limit value, the processor 11 changes the output control signal, and reduces the frequency and/or amplitude or early warning of the voltage output to the motor 2; when the values of all the digital signals obtained by the processor 11 in the preset time period are smaller than the lower limit value, the processor 11 stops outputting the control signal, and the motor stops working.
It should be noted that: the above embodiments are only for illustrating the present application and not for limiting the technical solutions described in the present application, and although the present application has been described in detail with reference to the above embodiments, it should be understood by those skilled in the art that the present application may be modified or substituted by equivalent embodiments without departing from the spirit and scope of the present application and all modifications thereof are intended to be included in the scope of the claims of the present application.
Claims (10)
1. A variable frequency controller capable of being used to drive a motor, the variable frequency controller comprising a processor and a conversion circuit; the conversion circuit can convert the power supply voltage into a first voltage which can be identified by the processor, and the processor acquires the first voltage to obtain a digital signal corresponding to the first voltage;
the processor acquires the first voltage at certain sampling intervals, and when the processor detects that the value of the digital signal is smaller than or equal to a preset abnormal threshold value and a preset time period is continued, the processor judges that the power supply voltage is abnormal, and the processor takes protective measures or early warning for the variable frequency controller and/or the motor according to a preset program;
the conversion circuit comprises a first diode, a second diode, a first resistor, a second resistor and a third resistor;
the first diode and the second diode are used for rectifying the power supply voltage and obtaining a first direct current voltage; the anode of the first diode and the anode of the second diode are connected with the power supply voltage end; the cathode of the first diode is connected with the cathode of the second diode;
the first resistor and the second resistor are connected in series and are used for dividing the first direct-current voltage to obtain a second direct-current voltage; one end of the first resistor is connected with the cathode of the first diode and the cathode of the second diode, and the other end of the first resistor is grounded through the second resistor;
the third resistor is used for limiting the second direct-current voltage, and the second direct-current voltage passes through the third resistor to obtain the first voltage; one end of the third resistor is connected with the first resistor and the second resistor, and the other end of the third resistor is connected to the processor.
2. The variable frequency controller of claim 1, wherein: the conversion circuit further comprises a first capacitor, and the other end of the third resistor is grounded through the first capacitor.
3. The variable frequency controller of claim 1, wherein: the variable frequency controller also comprises a driving module, the driving module is used for driving the motor, the processor is used for outputting control signals to the driving module, the processor stops outputting control signals to the driving module, and the motor stops working.
4. A variable frequency controller according to claim 3, wherein: the variable frequency controller further comprises a relay switch and a thermistor, wherein the thermistor is connected with the power supply voltage, the relay switch is connected to two ends of the thermistor, and when the processor judges that the power supply voltage is abnormal, the relay switch is controlled to be disconnected.
5. The variable frequency controller of claim 4, wherein: the variable frequency controller also comprises a rectifying and filtering module, a switching power supply and an active power factor correction module;
the rectification filter module is respectively connected with the relay, the switching power supply and the active power factor correction module, and the power supply voltage is respectively connected to the switching power supply and the active power factor correction module through the relay and the rectification filter module in sequence;
the active power factor correction module is connected to the driving module; the third direct current voltage obtained after the rectification and filtering module performs rectification and filtering treatment on the power supply voltage is input into the active power factor correction module, and the fourth direct current voltage obtained after the correction and boosting treatment of the active power factor correction module is supplied to the driving module;
the switching power supply is respectively connected to the processor, the active power factor correction module and the relay switch; and the third direct current voltage obtained after the rectifying and filtering module carries out rectifying and filtering treatment on the power supply voltage is input to the switching power supply, and the fifth direct current voltage obtained after the processing of the switching power supply is respectively supplied to the processor, the active power factor correction module and the relay switch.
6. The variable frequency controller according to any one of claims 1 to 5, wherein: the preset program includes: when the processor judges that the power supply voltage is abnormal, the processor takes protective measures or early warning for the variable frequency controller and/or the motor, wherein the protective measures for the motor comprise cutting off the power supply output to the motor or reducing the frequency and/or amplitude of the voltage output to the motor, and the protective measures for the variable frequency controller comprise enabling part of functional modules of the variable frequency controller to enter a protective state.
7. The variable frequency controller according to any one of claims 1 to 5, wherein: the preset program includes: when the processor judges that the power supply voltage is abnormal, the processor counts through a counter, the power supply voltage is accumulated to obtain an accumulated value when the power supply voltage is continuously abnormal, the accumulated value is cleared when the power supply voltage is not abnormal before reaching a preset value, and when the accumulated value reaches the preset value, the processor takes protective measures or early warning for the variable frequency controller and/or the motor, wherein the taking protective measures for the motor comprises cutting off the power supply output to the motor or reducing the frequency and/or amplitude of the voltage output to the motor, and the taking protective measures for the variable frequency controller comprise enabling part of functional modules of the variable frequency controller to enter a protective state.
8. The variable frequency controller of claim 1, wherein the predetermined period of time is determined by a sampling interval and a number of samples, the predetermined period of time being greater than or equal to half of the supply voltage period.
9. The variable frequency controller according to claim 1, wherein the processor presets an upper limit value and a lower limit value, the abnormality threshold value including a range between the upper limit value and the lower limit value; when the processor detects that the value of the digital signal is smaller than or equal to the upper limit value and lasts for one preset time period, but at least part of the value of the digital signal is larger than or equal to the lower limit value, the processor changes the output control signal, reduces the frequency and/or amplitude or early warning of the voltage output to the motor; and when the values of all the digital signals obtained by the processor in the preset time period are smaller than the lower limit value, the processor stops outputting the control signal, and the motor stops working.
10. A control method applied to the variable frequency controller according to any one of claims 1 to 9, which can be used to drive a motor;
the control method comprises the following steps:
step S1, continuously sampling the first voltage by the processor at each sampling interval, and acquiring the first voltage by the processor to obtain a digital signal corresponding to the first voltage;
step S2, the processor judges whether the value of the digital signal is smaller than or equal to the preset abnormal threshold value; if yes, the count value is increased by 1, and the step S3 is carried out; if not, the count value is cleared and returns to the execution step S1;
step S3, the processor judges whether the count value is equal to a preset value; if yes, go into
S4, a step of S4; if not, returning to execute the step S2;
s4, the processor judges that the power supply voltage is abnormal, and the processor takes protective measures or early warning for the variable frequency controller and/or the motor according to a preset program; and returns to execute the step S1;
wherein, the initial value of the count value is zero, and the preset value is determined by the preset time period and the sampling interval.
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| CN113701306B (en) * | 2021-08-31 | 2022-09-09 | 佛山市顺德区美的电子科技有限公司 | Protection control method and device for compressor in air conditioner and motor controller |
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| CN102901936B (en) * | 2012-10-19 | 2015-04-22 | 海信（山东）空调有限公司 | Poweroff detection method of alternating current power supply and poweroff protection method of direct current inverter compressor |
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