Over-temperature protection method for variable frequency drive device and variable frequency drive device

Abstract

The application provides an over-temperature protection method of a variable frequency driving device and the variable frequency driving device, wherein the method comprises the following steps: obtaining the input voltage of a power supply circuit and the output voltage and output current of a driving circuit in real time during the operation of an alternating current motor, calculating the preliminary over-temperature threshold of a power module of the driving circuit, comparing the preliminary over-temperature threshold with the maximum temperature value allowed by the power module to determine the final over-temperature threshold, obtaining the temperature of the power module, judging whether the temperature of the power module exceeds the final over-temperature threshold, adjusting the speed instruction when the final over-temperature threshold is exceeded, and enabling the driving circuit to drive the alternating current motor to work according to the adjusted speed instruction. Thus, the over-temperature threshold of the power module is adjusted adaptively according to the input voltage, the output voltage and the output current, and the speed instruction is adjusted according to the over-temperature threshold, so that the temperature of the power device of the power factor correction circuit and the inverter circuit is prevented from being too high.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of variable frequency drive, in particular to an over-temperature protection method of a variable frequency drive device and a variable frequency drive device. BACKGROUND

[0002] In the related art, in order to improve the overall efficiency of the variable frequency drive and solve the problem of power harmonic pollution, power factor correction technology is widely used in various variable frequency drive systems, such as air purification fan drive, variable frequency air conditioner drive, variable frequency refrigerator drive, etc. The power tube of the power factor correction circuit and the power module (IPM module) of the inverter circuit are the main heat generating devices. When the devices are working, the heat generated is large. When the heat dissipation condition is not good, the temperature will rise sharply. When the temperature of the power device exceeds the junction temperature, the circuit will be damaged, resulting in the entire system unable to operate normally.

[0003] The power module of the existing variable frequency drive system usually has a built-in temperature sensor, which can collect a relatively accurate temperature. When the temperature is high, the protection action of limiting frequency, reducing frequency or stopping is taken to prevent over-temperature. Different input voltages, input powers, switching frequencies and environmental temperatures will affect the temperature rise of the power tube of the power factor correction circuit. Since the power tube does not have a built-in temperature sensor, it is difficult to directly obtain the real-time temperature value for over-temperature protection. For example, when the PFC switching frequency is high, the power tube loss of the PFC is high, and its temperature rise is higher than that of the IPM module, and changes faster. If a temperature sensor is arranged on the power tube, the thermal conductivity is low, the power tube temperature rises fast, it is difficult to accurately reflect the power tube temperature, and the installation is complex, the consistency is poor, and the cost is high. SUMMARY

[0004] The present application aims to at least solve one of the above technical problems in the art. To this end, one object of the present application is to provide an over-temperature protection method of a variable frequency drive device, which adjusts the over-temperature threshold of the power module adaptively according to the input voltage, output voltage and output current, and adjusts the speed command according to the over-temperature threshold, thereby preventing the temperature of the power device of the power factor correction circuit and the inverter circuit power module from being too high.

[0005] A second object of the present application is to provide a variable frequency drive device.

[0006] To achieve the above object, the over-temperature protection method of the variable frequency driving device according to the first aspect of the present application is provided, the variable frequency driving device comprises a power supply circuit, a power factor correction circuit, a driving circuit, a sampling circuit, an interface circuit and a control circuit, the interface circuit is connected with the control circuit, the control circuit is connected with the power supply circuit, the driving circuit and the sampling circuit respectively, the power supply circuit is connected with the power factor correction circuit and the sampling circuit respectively, the power factor correction circuit is connected with the driving circuit, the driving circuit is connected with the sampling circuit and an AC motor respectively, the control circuit receives a speed instruction sent by the interface circuit, and adjusts the driving circuit to drive the AC motor to work according to the speed instruction, the over-temperature protection method comprises the following steps: in the process of the operation of the AC motor, the control circuit acquires the input voltage of the power supply circuit and the output voltage and output current of the driving circuit collected by the sampling circuit in real time; the preliminary over-temperature threshold of the power module of the driving circuit is calculated according to the input voltage of the power supply circuit and the output voltage and output current of the driving circuit; the preliminary over-temperature threshold is compared with the maximum temperature value allowed by the power module to determine the final over-temperature threshold; the temperature of the power module is acquired, and it is judged whether the temperature of the power module exceeds the final over-temperature threshold, so that the speed instruction is adjusted when the final over-temperature threshold is exceeded, so that the driving circuit drives the AC motor to work according to the adjusted speed instruction.

[0007] According to the over-temperature protection method of the variable frequency driving device, in the process of the operation of the AC motor, the control circuit acquires the input voltage of the power supply circuit and the output voltage and output current of the driving circuit collected by the sampling circuit in real time; the preliminary over-temperature threshold of the power module of the driving circuit is calculated according to the input voltage of the power supply circuit and the output voltage and output current of the driving circuit; the preliminary over-temperature threshold is compared with the maximum temperature value allowed by the power module to determine the final over-temperature threshold; the temperature of the power module is acquired, and it is judged whether the temperature of the power module exceeds the final over-temperature threshold, so that the speed instruction is adjusted when the final over-temperature threshold is exceeded, so that the driving circuit drives the AC motor to work according to the adjusted speed instruction; thereby, the over-temperature threshold of the power module is adaptively adjusted according to the input voltage, the output voltage and the output current, and the speed instruction is adjusted according to the over-temperature threshold, so as to prevent the temperature of the power device of the power factor correction circuit and the inverter circuit power module from being too high.

[0008] In addition, the over-temperature protection method of the variable frequency driving device according to the above-mentioned embodiments of the present application can have the following additional technical features:

[0009] Optionally, the power supply circuit comprises a filter circuit and a rectifier circuit, and the filter circuit and the rectifier circuit are used for rectifying and filtering the input alternating current, so that the sampling circuit collects the rectified and filtered input voltage.

[0010] Optionally, the drive circuit comprises an inverter circuit and a PWM drive circuit, and the PWM drive circuit drives the power module of the inverter circuit according to the PWM signal output by the control circuit, so that the alternating current motor works according to the speed instruction.

[0011] Optionally, the preliminary over-temperature threshold of the power module of the drive circuit is calculated according to the following formula:

[0012] P in =A1P out +B1

[0013]

[0014] T prot =A2I in +B2

[0015] wherein P in is the input power, P out is the output power, A1 and B1 are coefficients obtained by linear fitting by taking several power points in the input power range, recording the measured input power and the calculated output power; I in is the input current, V in is the input voltage, determined according to the power factor of the input power supply, and the value is between 0 and 1; T prot is the preliminary over-temperature threshold, A2 and B2 are coefficients obtained by linear fitting by taking several voltage points in the input voltage range, the alternating current motor running at several input power points, and measuring the real-time temperature of the power tube of the power factor correction circuit by using a precision temperature acquisition instrument, recording the corresponding input current I in , the temperature T IPM of the power module when the power tube of the power factor correction circuit reaches the required over-temperature threshold.

[0016] Optionally, the preliminary over-temperature threshold is compared with the maximum temperature value allowed by the power module to determine the final over-temperature threshold, including: judging whether the preliminary over-temperature threshold is greater than the maximum temperature value allowed by the power module; if the preliminary over-temperature threshold is greater than the maximum temperature value allowed by the power module, the maximum temperature value allowed by the power module is taken as the final over-temperature threshold; if the preliminary over-temperature threshold is less than or equal to the maximum temperature value allowed by the power module, the preliminary over-temperature threshold is taken as the final over-temperature threshold.

[0017] Optionally, if the temperature of the power module exceeds the final over-temperature threshold, the speed instruction is reduced by a preset speed difference value to obtain a current speed instruction, and the driving circuit is adjusted to drive the AC motor to work according to the current speed instruction.

[0018] To achieve the above object, the second aspect of the present application provides a variable frequency driving device, comprising: a power supply circuit, which rectifies and filters input AC power to obtain a processed input voltage; a power factor correction circuit, which is connected with the power supply circuit, and improves input power factor by controlling power tube on-off; a driving circuit, which is connected with the power factor correction circuit, and is used to drive AC motor to work; a sampling circuit, which is connected with the power supply circuit and the driving circuit respectively, and is used to collect input voltage of the power supply circuit and output voltage of the driving circuit in real time; an interface circuit, which is used to obtain a speed instruction signal; a control circuit, which is connected with the interface circuit, the sampling circuit and the driving circuit respectively, receives the speed instruction sent by the interface circuit, and adjusts the driving circuit to drive the AC motor to work according to the speed instruction, and obtains input voltage of the power supply circuit and output voltage and output current of the driving circuit collected by the sampling circuit in real time during the operation of the AC motor; calculates a preliminary over-temperature threshold of the power module of the driving circuit according to the input voltage of the power supply circuit and the output voltage and output current of the driving circuit; compares the preliminary over-temperature threshold with the maximum temperature value allowed by the power module to determine a final over-temperature threshold; obtains the temperature of the power module, and judges whether the temperature of the power module exceeds the final over-temperature threshold, so as to adjust the speed instruction when the final over-temperature threshold is exceeded, so that the driving circuit drives the AC motor to work according to the adjusted speed instruction.

[0019] According to the variable frequency driving device, the input alternating current is rectified and filtered by the power supply circuit to obtain a processed input voltage; the power factor correction circuit is connected with the power supply circuit, and the power factor correction circuit improves the input power factor by controlling the on-off of the power tube; the driving circuit is connected with the power factor correction circuit, and the driving circuit is used for driving the alternating current motor to work; the sampling circuit is connected with the power supply circuit and the driving circuit respectively, and the sampling circuit is used for collecting the input voltage of the power supply circuit and the output voltage of the driving circuit in real time; the interface circuit is used for obtaining a speed instruction signal; the control circuit is connected with the interface circuit, the sampling circuit and the driving circuit respectively, the control circuit receives the speed instruction sent by the interface circuit, adjusts the driving circuit to drive the alternating current motor to work according to the speed instruction, and obtains the input voltage of the power supply circuit and the output voltage and output current of the driving circuit collected by the sampling circuit in real time during the operation of the alternating current motor; the preliminary over-temperature threshold of the power module of the driving circuit is calculated according to the input voltage of the power supply circuit and the output voltage and output current of the driving circuit; the preliminary over-temperature threshold is compared with the maximum temperature value allowed by the power module to determine the final over-temperature threshold; the temperature of the power module is obtained, and it is judged whether the temperature of the power module exceeds the final over-temperature threshold, so that the speed instruction is adjusted when the final over-temperature threshold is exceeded, so that the driving circuit drives the alternating current motor to work according to the adjusted speed instruction; thus, the over-temperature threshold of the power module is adjusted adaptively according to the input voltage, the output voltage and the output current, and the speed instruction is adjusted according to the over-temperature threshold, so as to prevent the temperature of the power device of the power factor correction circuit and the inverter circuit power module from being too high.

[0020] In addition, the variable frequency driving device according to the above-mentioned embodiments of the application can have the following additional technical features:

[0021] Optionally, the preliminary over-temperature threshold of the power module of the driving circuit is calculated according to the following formula:

[0022] P in =A1P out +B1

[0023]

[0024] T prot =A2I in +B2

[0025] wherein P in is the input power, P out is the output power, A1 and B1 are a plurality of power points in the input power range, and the coefficients are obtained by linear fitting after recording and measuring the input power and the calculated output power; I in is the input current, V in is the input voltage, According to the power factor of the input power supply, the value is between 0 and 1; T prot A2 and B2 are several voltage points in the input voltage range, the AC motor runs at several input power points, and the real-time temperature of the power tube of the power factor correction circuit is measured by using a precision temperature collection instrument. When the power tube of the power factor correction circuit reaches the required over-temperature threshold, the corresponding input current I in , the temperature T of the power module IPM , the coefficient obtained by linear fitting.

[0026] Optionally, the control circuit is further configured to determine whether the preliminary over-temperature threshold is greater than the maximum temperature value allowed by the power module; if the preliminary over-temperature threshold is greater than the maximum temperature value allowed by the power module, the maximum temperature value allowed by the power module is taken as the final over-temperature threshold; if the preliminary over-temperature threshold is less than or equal to the maximum temperature value allowed by the power module, the preliminary over-temperature threshold is taken as the final over-temperature threshold.

[0027] Optionally, the control circuit is further configured to subtract a preset speed difference value from the speed instruction to obtain a current speed instruction if the temperature of the power module exceeds the final over-temperature threshold, and adjust the driving circuit to drive the AC motor to work according to the current speed instruction. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is a flowchart of an over-temperature protection method of a variable frequency drive device according to an embodiment of the present application;

[0029] Figure 2 is a flowchart of an over-temperature protection method of a variable frequency drive device according to an embodiment of the present application;

[0030] Figure 3 is a block diagram of a variable frequency drive device according to an embodiment of the present application;

[0031] Figure 4 is a block diagram of a variable frequency drive device according to an embodiment of the present application. DETAILED DESCRIPTION

[0032] Embodiments of the present application are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference signs represent the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by reference to the accompanying drawings are exemplary and are intended to explain the present application, and cannot be understood as a limitation of the present application.

[0033] To better understand the above technical solutions, exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. Instead, these embodiments are provided to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0034] In order to better understand the above technical solution, the above technical solution will be described in detail below with reference to the accompanying drawings and specific implementation methods.

[0035] Figure 1 and Figure 3 As shown, the variable frequency drive device 10 includes a power supply circuit 15, a power factor correction circuit 11, a drive circuit 12, a sampling circuit 16, an interface circuit 14 and a control circuit 13. The interface circuit 14 is connected to the control circuit 13. The control circuit 13 is respectively connected to the power supply circuit 15, the drive circuit 12 and the sampling circuit 16. The power supply circuit 15 is respectively connected to the power factor correction circuit 11 and the sampling circuit 16. The power factor correction circuit 11 is connected to the drive circuit 12. The drive circuit 12 is respectively connected to the AC motor 10a and the sampling circuit 16. The control circuit 13 receives a speed instruction sent by the interface circuit 14 and adjusts the drive circuit 12 according to the speed instruction to drive the AC motor 10a to work. The overtemperature protection method includes the following steps:

[0036] Step 101 : During the operation of the AC motor, the control circuit acquires in real time the input voltage of the power circuit and the output voltage and output current of the drive circuit collected by the sampling circuit.

[0037] As an example, Figure 4 As shown, the power supply circuit 15 includes a filter circuit 151 and a rectifier circuit 152 . The filter circuit 151 and the rectifier circuit 152 are used to rectify and filter the input AC power so that the sampling circuit 16 can collect the input voltage after rectification and filtering.

[0038] That is to say, the input voltage sampled by the sampling circuit 16 is the voltage after the AC voltage is rectified.

[0039] It should be noted that the power supply circuit 15 further includes a switching power supply circuit 153 .

[0040] As an example, Figure 4 As shown, the drive circuit 12 includes an inverter circuit 121 and a PWM drive circuit 123. The PWM drive circuit 123 drives the power module of the inverter circuit 121 according to the PWM signal output by the control circuit 13, so as to drive the AC motor 10a to work according to the speed instruction.

[0041] As an embodiment, as shown in Figure 4 The control circuit 13 includes a memory 131 and a processing circuit 132.

[0042] Step 102, calculate the preliminary over-temperature threshold of the power module of the driving circuit according to the input voltage of the power supply circuit and the output voltage and output current of the driving circuit.

[0043] As an embodiment, the preliminary over-temperature threshold of the power module of the driving circuit is calculated according to the following formula:

[0044] P in =A1P out +B1

[0045]

[0046] T prot =A2I in +B2

[0047] Wherein, P in is the input power, P out is the output power, A1 and B1 are the coefficients obtained by linear fitting by taking several power points in the input power range, recording the measured input power and the calculated output power; I in is the input current, V in is the input voltage, determined according to the power factor of the input power supply, the value is between 0 and 1; T prot is the preliminary over-temperature threshold, A2 and B2 are the coefficients obtained by linear fitting by taking several voltage points in the input voltage range, the AC motor runs at several input power points, and the real-time temperature of the power tube of the power factor correction circuit is measured by using a precision temperature collection instrument, and the corresponding input current I in , the temperature T IPM of the power module when the power tube of the power factor correction circuit reaches the required over-temperature threshold is recorded.

[0048] Step 103, compare the preliminary over-temperature threshold with the maximum temperature value allowed by the power module to determine the final over-temperature threshold.

[0049] As an embodiment, it is judged whether the preliminary over-temperature threshold is greater than the maximum temperature value allowed by the power module; if the preliminary over-temperature threshold is greater than the maximum temperature value allowed by the power module, the maximum temperature value allowed by the power module is taken as the final over-temperature threshold; if the preliminary over-temperature threshold is less than or equal to the maximum temperature value allowed by the power module, the preliminary over-temperature threshold is taken as the final over-temperature threshold.

[0050] It should be noted that the maximum temperature value allowed by the power module is determined by the power module.

[0051] Step 104, acquiring the temperature of the power module, determining whether the temperature of the power module exceeds the final over-temperature threshold, so as to adjust the speed command when the final over-temperature threshold is exceeded, so that the driving circuit drives the AC motor to work according to the adjusted speed command.

[0052] As an embodiment, if the temperature of the power module exceeds the final over-temperature threshold, the speed command is reduced by a preset speed difference value to obtain a current speed command, and the driving circuit drives the AC motor to work according to the current speed command.

[0053] That is, if the temperature of the power module exceeds the final over-temperature threshold, over-temperature protection is performed, that is, the speed command is reduced by a preset speed difference value to obtain a current speed command, and the driving circuit drives the AC motor to work according to the current speed command; if the temperature of the power module does not exceed the final over-temperature threshold, the speed command is not adjusted, and the original set speed command is run to work.

[0054] As a specific embodiment, as shown in the following steps: Figure 4

[0055] S1, measuring the input rectified voltage V in .

[0056] S2, measuring the driving output voltage V d , V q , output current I d , I q , and calculating the output power P out according to the relationship:

[0057]

[0058] S3, calculating the output power P in according to the relationship:

[0059] P in =A1P out +B1

[0060] Wherein, A1 and B1 are coefficients obtained by linear fitting by taking several power points in the input power range, recording the measured input power and the calculated output power.

[0061] S4, calculating the input current I in according to the relationship:

[0062]

[0063] Wherein, According to the power factor of the input power supply, the value is between 0 and 1. ​

[0064] S5, calculate the over-temperature threshold T of the inverter power module according to the relationship prot :

[0065] T prot =A2I in +B2

[0066] Wherein, A2 and B2 are the coefficients obtained by linear fitting, I is the input current, T is the temperature of the power module, and T is the real-time temperature of the power module measured by the precision temperature collector. in IPM

[0067] S6, compare the over-temperature threshold T and the maximum temperature value T allowed by the power module to determine the final over-temperature threshold T. prot max th .

[0068] That is, compare the calculated over-temperature threshold T and the maximum temperature value T allowed by the power module to determine the final over-temperature threshold T, if T > T, then T = T, otherwise T = T. prot max th prot max th max th prot .

[0069] S7, measure the temperature T of the power module, and determine whether the temperature of the power module exceeds the over-temperature threshold T, after determining the speed command, return to execute S1. IPM th

[0070] That is, measure the temperature T of the power module, and determine whether the temperature T of the power module exceeds the over-temperature threshold T, if T > T, subtract the set speed difference value from the original set speed command as the current speed command, otherwise run according to the current speed command, and return to S1 for execution. IPM IPM th IPM th

[0071] ​​​​​​​​​​​​​​​​​​​In summary, the over-temperature protection method of the variable frequency driving device according to the embodiment of the present application, in the process of operation of the AC motor, the control circuit acquires the input voltage of the power supply circuit and the output voltage and output current of the driving circuit collected by the sampling circuit in real time; calculates the preliminary over-temperature threshold of the power module of the driving circuit according to the input voltage of the power supply circuit and the output voltage and output current of the driving circuit; compares the preliminary over-temperature threshold with the maximum temperature value allowed by the power module to determine the final over-temperature threshold; acquires the temperature of the power module, judges whether the temperature of the power module exceeds the final over-temperature threshold, so as to adjust the speed command when the final over-temperature threshold is exceeded, so that the driving circuit drives the AC motor to work according to the adjusted speed command; thus, the over-temperature threshold of the power module is adjusted adaptively according to the input voltage, output voltage and output current, and the speed command is adjusted according to the over-temperature threshold, thereby preventing the temperature of the power device of the power factor correction circuit and the inverter circuit power module from being too high.

[0072] In addition, as shown in Figure 3 and Figure 4 , the variable frequency driving device 10 of the embodiment of the present application comprises a power supply circuit 15, a power factor correction circuit 11, a driving circuit 12, a sampling circuit 16, an interface circuit 14 and a control circuit 13.

[0073] The power supply circuit 15 rectifies and filters the input AC power to obtain a processed input voltage; the power factor correction circuit 11 is connected with the power supply circuit 15, and the power factor correction circuit 11 improves the input power factor by controlling the on-off of the power tube; the driving circuit 12 is connected with the power factor correction circuit 11, and the driving circuit 12 is used to drive the AC motor 10a to work; the sampling circuit 16 is connected with the power supply circuit 15 and the driving circuit 12 respectively, and the sampling circuit 16 is used to collect the input voltage of the power supply circuit and the output voltage of the driving circuit in real time; the interface circuit 14 is used to acquire the speed command signal; the control circuit 13 is connected with the interface circuit 14, the sampling circuit 16 and the driving circuit 12 respectively, the control circuit 13 receives the speed command sent by the interface circuit 14, and adjusts the driving circuit 12 to drive the AC motor to work according to the speed command, and in the process of operation of the AC motor 10a, the control circuit 13 acquires the input voltage of the power supply circuit 15 and the output voltage and output current of the driving circuit 12 collected by the sampling circuit in real time; calculates the preliminary over-temperature threshold of the power module of the driving circuit 12 according to the input voltage of the power supply circuit 15 and the output voltage and output current of the driving circuit 12; compares the preliminary over-temperature threshold with the maximum temperature value allowed by the power module to determine the final over-temperature threshold; acquires the temperature of the power module, judges whether the temperature of the power module exceeds the final over-temperature threshold, so as to adjust the speed command when the final over-temperature threshold is exceeded, so that the driving circuit drives the AC motor to work according to the adjusted speed command.

[0074] As an embodiment, the power supply circuit 15 comprises a filter circuit 151 and a rectifier circuit 152, which are used to rectify and filter the input AC power so as to collect the rectified and filtered input voltage by the sampling circuit 16.

[0075] As an embodiment, the drive circuit 12 comprises an inverter circuit 121 and a PWM drive circuit 123, which drives the power module of the inverter circuit 121 according to the PWM signal output by the control circuit 13, so as to drive the AC motor 10a to work according to the speed command.

[0076] That is, the power factor correction circuit 11 controls the power tube to adjust the input voltage and current phase according to a certain switching frequency and duty cycle, so as to improve the input power factor. The sampling circuit 16 collects the temperature, voltage and current of the power module in real time. The drive circuit 12 comprises an inverter circuit 121 and a PWM drive circuit 123. The control circuit 13 receives the speed command signal sent by the interface circuit 14, and adjusts the drive circuit 12 to drive the AC motor 10a to work according to the speed command signal. The control circuit 13 calculates the input current according to the signal sent by the sampling circuit 16 during the operation of the AC motor 10a, and calculates the over-temperature threshold value, monitors the temperature of the power drive module in real time to determine the current speed command; the PWM drive circuit 123 drives the power module of the inverter circuit 121 according to the PWM signal, so as to drive the AC motor 10a to work according to the speed command.

[0077] As an embodiment, the preliminary over-temperature threshold value of the power module of the drive circuit is calculated according to the following formula:

[0078] P in =A1P out +B1

[0079]

[0080] T prot =A2I in +B2

[0081] Wherein, P in is the input power, P out is the output power, A1 and B1 are the coefficients obtained by linear fitting by recording and measuring the input power and the calculated output power at several power points in the input power range; I in is the input current, V in is the input voltage, According to the power factor of the input power supply, the value is between 0 and 1; T protA2 and B2 are several voltage points in the input voltage range, the AC motor runs at several input power points, and the real-time temperature of the power tube of the power factor correction circuit is measured by using a precision temperature collection instrument. The input current I corresponding to the power tube of the power factor correction circuit reaching the required over-temperature threshold value is recorded in , the temperature T of the power module IPM , the coefficient obtained by linear fitting.

[0082] As an embodiment, the control circuit 13 is further configured to determine whether the preliminary over-temperature threshold value is greater than the maximum temperature value allowed by the power module; if the preliminary over-temperature threshold value is greater than the maximum temperature value allowed by the power module, the maximum temperature value allowed by the power module is taken as the final over-temperature threshold value; if the preliminary over-temperature threshold value is less than or equal to the maximum temperature value allowed by the power module, the preliminary over-temperature threshold value is taken as the final over-temperature threshold value.

[0083] As an embodiment, the control circuit 13 is further configured to subtract a preset speed difference value from the speed instruction to obtain a current speed instruction if the temperature of the power module exceeds the final over-temperature threshold value, and adjust the driving circuit to drive the AC motor to work according to the current speed instruction.

[0084] It should be noted that the foregoing example of the over-temperature protection method of the variable frequency driving device is also applicable to the variable frequency driving device of the present embodiment, which will not be described here again.

[0085] In summary, according to the variable frequency driving device of the embodiment of the present application, the input alternating current is rectified and filtered by the power supply circuit to obtain the processed input voltage; the power factor correction circuit is connected with the power supply circuit, and the power factor correction circuit improves the input power factor by controlling the on-off of the power tube; the driving circuit is connected with the power factor correction circuit, and the driving circuit is used to drive the alternating current motor to work; the sampling circuit is connected with the power supply circuit and the driving circuit respectively, and the sampling circuit is used to collect the input voltage of the power supply circuit and the output voltage of the driving circuit in real time; the interface circuit is used to obtain the speed instruction signal; the control circuit is connected with the interface circuit, the sampling circuit and the driving circuit respectively, the control circuit receives the speed instruction sent by the interface circuit, adjusts the driving circuit to drive the alternating current motor to work according to the speed instruction, and obtains the input voltage of the power supply circuit and the output voltage and output current of the driving circuit collected by the sampling circuit in real time during the operation of the alternating current motor; the preliminary over-temperature threshold of the power module of the driving circuit is calculated according to the input voltage of the power supply circuit and the output voltage and output current of the driving circuit; the preliminary over-temperature threshold is compared with the maximum temperature value allowed by the power module to determine the final over-temperature threshold; the temperature of the power module is obtained, and it is judged whether the temperature of the power module exceeds the final over-temperature threshold, so that the speed instruction is adjusted when the final over-temperature threshold is exceeded, so that the driving circuit drives the alternating current motor to work according to the adjusted speed instruction; thus, the over-temperature threshold of the power module is adjusted adaptively according to the input voltage, the output voltage and the output current, and the speed instruction is adjusted according to the over-temperature threshold, so as to prevent the temperature of the power device of the power factor correction circuit and the inverter circuit power module from being too high.

[0086] Those skilled in the art will appreciate that embodiments of the present application can be supplied as a method, a system, or a computer program product. Accordingly, the present application can take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present application can take the form of a computer program product on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROMs, optical storage media, etc.) embodying computer readable program code.

[0087] The present application is described in reference to the flowcharts and / or block diagrams of the methods, apparatus (systems) and computer program products according to the embodiments of the present application. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, and the combination of the flows and / or blocks in the flowcharts and / or block diagrams can be realized by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device produce a device for implementing the functions described in the flowcharts and / or block diagrams. Figure 1 one flow or multiple flows and / or blocksFigure 1 means for performing the function specified in the block or blocks.

[0088] These computer program instructions can also be stored in a computer- readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instructions which implement the flow Figure 1 flow or flows and / or blocks Figure 1 means for performing the function specified in the block or blocks.

[0089] These computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the flow Figure 1 flow or flows and / or blocks Figure 1 steps for performing the function specified in the block or blocks.

[0090] It is noted that in the claims the word "comprising" does not exclude not having other parts than those specified in the claim. The word "a" or "an" preceding a plural reference to items does not exclude a larger number for these items. The application can be implemented by means of both hardware and software, and any combination of hardware and software. In the claims, any reference signs placed between two different groups of claims shall not be construed as applying the

[0091] While the preferred embodiments of the application have been described, additional variations and modifications can be made to the preferred embodiments by those skilled in the art once they learn of the basic inventive concepts. Therefore, the appended claims are intended to cover all such variations and modifications as fall within the scope of the application.

[0092] It is clear that the application is susceptible to numerous modifications and variations all falling within the scope of the application. Accordingly, this application is intended to embrace all such modifications and variations that fall within the scope of the claims, together with all equivalents thereof.

[0093] In the description of the application, it should be understood that the terms "first", "second" are used only for descriptive purposes and are not to be construed as indicating or implying relative importance or an indicated number of technical features. Therefore, the features defined as "first", "second" can explicitly or implicitly include one or more of the features. In the description of the application, the meaning of "a plurality of" is two or more, unless otherwise explicitly specified and limited.

[0094] In the present application, unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connecting", "fixing" and the like should be understood broadly, for example, it can be fixed connection, or detachable connection, or integrated; it can be mechanical connection, or electrical connection; it can be directly connected, or indirectly connected through intermediate medium, or it can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0095] In the present application, unless otherwise explicitly specified and limited, the first feature is "on" or "under" the second feature, which can be direct contact between the first and second features, or indirect contact between the first and second features through intermediate medium. Moreover, the first feature "above", "over" and "on" the second feature can be directly above or obliquely above the first feature, or only indicate that the horizontal height of the first feature is higher than that of the second feature. The first feature "below", "under" and "under" the second feature can be directly below or obliquely below the first feature, or only indicate that the horizontal height of the first feature is less than that of the second feature.

[0096] In the description of the present application, the description of the terms "one embodiment", "some embodiments", "example", "specific example" or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In the present application, the illustrative description of the above terms should not be understood as necessarily referring to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine the different embodiments or examples described in the present application and the features of the different embodiments or examples, without contradiction.

[0097] Although the embodiments of the present application have been shown and described above, it should be understood that the above embodiments are exemplary and cannot be construed as limiting the present application, and those skilled in the art can make changes, modifications, replacements and variations to the above embodiments within the scope of the present application.

Claims

1. A method for over-temperature protection of a variable frequency drive device, characterized in that: The variable frequency drive device includes a power supply circuit, a power factor correction circuit, a drive circuit, a sampling circuit, an interface circuit and a control circuit. The interface circuit is connected to the control circuit. The control circuit is respectively connected to the power supply circuit, the drive circuit and the sampling circuit. The power supply circuit is respectively connected to the power factor correction circuit and the sampling circuit. The power factor correction circuit is connected to the drive circuit. The drive circuit is respectively connected to the sampling circuit and the AC motor. The control circuit receives a speed instruction sent by the interface circuit and adjusts the drive circuit according to the speed instruction to drive the AC motor to work. The over-temperature protection method includes the following steps: During the operation of the AC motor, the control circuit acquires in real time the input voltage of the power circuit and the output voltage and output current of the drive circuit collected by the sampling circuit; According to T prot =A2I in +B2 calculates the preliminary over-temperature threshold, T prot is the preliminary over-temperature threshold, A2 and B2 are several voltage points within the input voltage range, the AC motor is operated at several input power points, and a precision temperature collector is used to measure the real-time temperature of the power tube of the power factor correction circuit. The corresponding input current I is recorded when the power tube of the power factor correction circuit reaches the required over-temperature threshold. in , the temperature of the power module T IPM , the coefficients obtained by linear fitting; comparing the preliminary over-temperature threshold with a maximum temperature value allowed by the power module to determine a final over-temperature threshold; The temperature of the power module is obtained, and it is determined whether the temperature of the power module exceeds the final over-temperature threshold, so that the speed instruction is adjusted when the temperature exceeds the final over-temperature threshold, so that the drive circuit drives the AC motor to work according to the adjusted speed instruction.

2. The over-temperature protection method of the variable frequency drive device according to claim 1, characterized in that: The power supply circuit includes a filter circuit and a rectifier circuit. The filter circuit and the rectifier circuit are used to perform rectification and filtering on the input alternating current, so that the sampling circuit can collect the input voltage after rectification and filtering.

3. The over-temperature protection method of the variable frequency drive device according to claim 2, characterized in that: The driving circuit includes an inverter circuit and a PWM driving circuit. The PWM driving circuit drives the power module of the inverter circuit according to the PWM signal output by the control circuit, so as to drive the AC motor to work according to the speed instruction.

4. The over-temperature protection method of the variable frequency drive device according to claim 3, characterized in that: Calculate the input current using the following formula: P in =A1P out +B1 Among them, P in is the input power, P out is the output power, A1 and B1 are the coefficients obtained by linear fitting by taking several power points in the input power range and recording the measured input power and the calculated output power; I in is the input current, V in is the input voltage, Determined by the power factor of the input power supply and the value is between 0 and 1.

5. The over-temperature protection method of the variable frequency drive device according to claim 1, characterized in that: Comparing the preliminary over-temperature threshold with the maximum temperature value allowed by the power module to determine a final over-temperature threshold, including: Determining whether the preliminary over-temperature threshold is greater than a maximum temperature value allowed by the power module; If the preliminary over-temperature threshold is greater than the maximum temperature value allowed by the power module, the maximum temperature value allowed by the power module is used as the final over-temperature threshold; If the preliminary over-temperature threshold is less than or equal to the maximum temperature value allowed by the power module, the preliminary over-temperature threshold is used as the final over-temperature threshold.

6. The over-temperature protection method of the variable frequency drive device according to claim 1, characterized in that: If the temperature of the power module exceeds the final over-temperature threshold, a preset speed difference is subtracted from the speed instruction to obtain a current speed instruction, and the drive circuit is adjusted according to the current speed instruction to drive the AC motor to operate.

7. A variable frequency drive device, characterized in that: include: A power supply circuit, which performs rectification and filtering on the input AC power to obtain a processed input voltage; The power factor correction circuit is connected to the power supply circuit and improves the input power factor by controlling the on and off of the power tube; A drive circuit is connected to the power factor correction circuit, and is used to drive the AC motor to work; The sampling circuit is connected to the power supply circuit and the drive circuit respectively, and is used to collect the input voltage of the power supply circuit and the output voltage of the drive circuit in real time; An interface circuit, the interface circuit is used to obtain a speed command signal; The control circuit is connected to the interface circuit, the sampling circuit and the drive circuit respectively. The control circuit receives the speed instruction sent by the interface circuit, and adjusts the drive circuit to drive the AC motor to work according to the speed instruction. In addition, during the operation of the AC motor, the control circuit obtains the input voltage of the power circuit and the output voltage and output current of the drive circuit collected by the sampling circuit in real time; according to T prot =A2I in +B2 calculates the preliminary over-temperature threshold, T prot is the preliminary over-temperature threshold, A2 and B2 are several voltage points within the input voltage range, the AC motor is operated at several input power points, and a precision temperature collector is used to measure the real-time temperature of the power tube of the power factor correction circuit. The corresponding input current I is recorded when the power tube of the power factor correction circuit reaches the required over-temperature threshold. in , the temperature of the power module T IPM , the coefficient obtained by linear fitting; comparing the preliminary over-temperature threshold with the maximum temperature value allowed by the power module to determine the final over-temperature threshold; obtaining the temperature of the power module, and judging whether the temperature of the power module exceeds the final over-temperature threshold, so as to adjust the speed command when the final over-temperature threshold is exceeded, so that the drive circuit drives the AC motor to work according to the adjusted speed command.

8. The variable frequency drive device according to claim 7, characterized in that: Calculate the input current using the following formula: P in =A1P out +B1 Among them, P in is the input power, P out is the output power, A1 and B1 are the coefficients obtained by linear fitting by taking several power points in the input power range and recording the measured input power and the calculated output power; I in is the input current, V in is the input voltage, Determined by the power factor of the input power supply and the value is between 0 and 1.

9. The variable frequency drive device according to claim 7, characterized in that: The control circuit is further configured to determine whether the preliminary over-temperature threshold is greater than the maximum temperature value allowed by the power module; If the preliminary over-temperature threshold is greater than the maximum temperature value allowed by the power module, the maximum temperature value allowed by the power module is used as the final over-temperature threshold; If the preliminary over-temperature threshold is less than or equal to the maximum temperature value allowed by the power module, the preliminary over-temperature threshold is used as the final over-temperature threshold.

10. The variable frequency drive device according to claim 7, wherein: The control circuit is further configured to, if the temperature of the power module exceeds the final over-temperature threshold, subtract a preset speed difference from the speed instruction to obtain a current speed instruction, and adjust the drive circuit to drive the AC motor to operate according to the current speed instruction.

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