Variable frequency drive method and three-path variable frequency drive circuit

Abstract

This application provides a variable frequency drive method and a three-channel variable frequency drive circuit. The variable frequency drive method includes a rectifier sub-circuit rectifying a first electrical signal sent from an external AC power supply to obtain a second electrical signal, and transmitting the second electrical signal to a correction sub-circuit; a control module sending a first control signal to the correction sub-circuit based on the collected AC voltage, DC voltage, first sampling current, second sampling current, and third sampling current; the correction sub-circuit performing power factor correction on the second electrical signal to obtain a third electrical signal, and transmitting the third electrical signal to an inverter control sub-circuit; sending a second control signal to the inverter control sub-circuit based on the three-phase current; and the inverter control sub-circuit converting the third electrical signal into a drive signal based on the second control signal, and transmitting the drive signal to an external motor to drive the motor. This application reduces the current specification by operating the three channels in parallel, eliminating the need to increase the inductance and saving the space required for the circuit.

Description

Technical Field

[0001] This application relates to the field of electronic circuit technology, and in particular to a frequency conversion drive method and a three-channel frequency conversion drive circuit. Background Technology

[0002] With the advancement of variable frequency air conditioning technology, power factor correction (PFC) technology has been widely applied to the electronic control components of variable frequency air conditioners. Power factor correction plays a crucial role in improving energy efficiency and ensuring stable system operation in variable frequency air conditioning electronic control systems.

[0003] Currently, most variable frequency air conditioner electronic control systems use Boost circuits for power factor correction. In a Boost circuit, current flows through a rectifier bridge, then through an inductor and a diode before being supplied to the motor inverter. However, when the electronic control power is high, the inductor needs to be increased, which results in an excessively large circuit area, requiring a significant amount of space on the electronic control board, and in some cases, the increased inductor cannot even be installed on the electronic control board. Summary of the Invention

[0004] The main purpose of this application is to provide a variable frequency drive method and a three-way variable frequency drive circuit, which aims to solve the technical problem that existing variable frequency drive circuits require increasing the inductance when the electronic control power is large, which requires a lot of space on the electronic control board, and even the increased inductance cannot be installed on the electronic control board.

[0005] To achieve the above objectives, this application provides a variable frequency drive method, the variable frequency drive method comprising: The rectifier circuit rectifies the first electrical signal sent by the external AC power supply to obtain a second electrical signal, and transmits the second electrical signal to the correction circuit, which is a three-way interleaved PFC circuit. Based on the collected AC voltage, DC voltage, first sampling current, second sampling current, and third sampling current, the control module sends a first control signal to the correction sub-circuit. The correction sub-circuit performs power factor correction on the second electrical signal based on the first control signal to obtain a third electrical signal, and transmits the third electrical signal to the inverter control sub-circuit. The control module sends a second control signal to the inverter control sub-circuit based on the three-phase current, wherein the three-phase current is obtained by reconstructing the acquired fourth sampling current; The inverter control sub-circuit converts the third electrical signal into a drive signal based on the second control signal, and transmits the drive signal to an external motor to drive the motor.

[0006] Optionally, the control module sends a first control signal to the correction sub-circuit based on the acquired AC voltage, DC voltage, first sampling current, second sampling current, and third sampling current, including: The control module obtains the first boost ratio coefficient based on the DC voltage and bus voltage command values; the bus voltage command value is determined based on the motor speed and motor parameters. The control module obtains a second boost ratio coefficient, a third boost ratio coefficient, and a fourth boost ratio coefficient based on the first boost ratio coefficient, the first sampling current, the second sampling current, and the third sampling current. The control module obtains a first duty cycle signal, a second duty cycle signal, and a third duty cycle signal based on the second boost ratio coefficient, the third boost ratio coefficient, and the fourth boost ratio coefficient. The control module obtains a first control signal based on the first duty cycle signal, the second duty cycle signal, the third duty cycle signal, and the AC voltage, and sends the first control signal to the correction sub-circuit.

[0007] Optionally, the three-phase current includes a first current, a second current, and a third current. Based on the three-phase current, the control module sends a second control signal to the inverter control sub-circuit, including: The control module generates a three-phase voltage based on the first current, the second current, and the third current; The control module generates a fourth duty cycle signal, a fifth duty cycle signal, and a sixth duty cycle signal based on the DC voltage and the three-phase voltage. The control module generates a second control signal based on the fourth duty cycle signal, the fifth duty cycle signal, and the sixth duty cycle signal, and sends the second control signal to the inverter control sub-circuit.

[0008] Optionally, the method further includes: If the average value of the first sampled current is greater than or equal to the preset current, the control module sends a third control signal to cause the first switch, and / or the second switch, and / or the third switch in the correction sub-circuit to start from the off state to the PWM output state at the power supply zero crossing point; If the duty cycle of the PWM target value corresponding to the first switch, and / or the second switch, and / or the third switch exceeds 10%, then control the duty cycle corresponding to the first switch, and / or the second switch, and / or the third switch to increase by 10% in increments. If the difference between the PWM target value and the actual output value corresponding to the first switch, and / or the second switch, and / or the third switch is less than 10%, then the PWM target value is reached by increasing the actual difference.

[0009] Optionally, the method further includes: When the first sampling current is less than the PFC single-on control threshold, the control module controls the first, second, and third switches in the correction sub-circuit to turn off. When the first sampling current is greater than or equal to the PFC single-on control threshold and less than the PFC double-on control threshold, control one output of the first switch, the second switch and the third switch, and shut down the other two. When the first sampling current is greater than or equal to the PFC dual-on control threshold and less than the PFC triple-on control threshold, control the two outputs of the first switch, the second switch and the third switch, and shut down one of them; When the first sampling current is greater than or equal to the PFC three-way control threshold, the first switch, the second switch and the third switch are controlled to output simultaneously.

[0010] Optionally, the method further includes: When the first and second switches in the correction sub-circuit output simultaneously, or when the first, second, and third switches output simultaneously, the control module controls the other switch and / or the other two switches to operate at reduced derating when it detects that one of the switches is damaged and overcurrent. In one of the derating processes of the other switching transistor, the maximum operating frequency of the motor is reduced by one-third, and / or the maximum operating power of the motor is reduced by one-third; in the other two derating processes of the switching transistor, the maximum operating frequency of the motor is reduced by two-thirds, and / or the maximum operating power of the motor is reduced by two-thirds.

[0011] Optionally, the method further includes: When the first, second, and third switches in the correction sub-circuit output simultaneously, the duty cycle of the first, second, and third switches is automatically adjusted according to the current between the first, second, and third inductors in the correction sub-circuit using the following formula. ; ; ; ; ; ; ; ; ; in, This indicates the duty cycle corresponding to the first switching transistor. This indicates the duty cycle corresponding to the second switching transistor; This indicates the duty cycle corresponding to the third switching transistor; , , Determined based on the average current of the first inductor, the average current of the second inductor, and the average current of the third inductor; , , These are the instantaneous currents of the first inductor, the second inductor, and the third inductor, respectively. , , These are the average currents of the first inductor, the second inductor, and the third inductor, respectively. Output current for AC power supply Average current; The step-up ratio is calculated and limited based on the target bus voltage and the actual bus voltage. and These are preset coefficients; in, , and These are preset coefficients; in, Indicates DC voltage. Indicates the commanded value of the bus voltage; Initial bus voltage command value It is calculated using the following formula: ; in, This refers to the single-phase resistance of the motor. This refers to the d-axis current of the motor. This refers to the q-axis current of the motor. This is the back electromotive force coefficient of the motor; This refers to the q-axis current of the motor. This refers to the d-axis current of the motor. This refers to the motor's commanded speed. Voltage modulation coefficient; Bus voltage command value It is calculated using the following formula: ; in, This refers to the amplitude of the power supply voltage. Bus capacitor nominal voltage value, This is the safety margin set.

[0012] Optionally, the method further includes: Obtain the three-phase current value of the motor , , ; Based on the three-phase current of the motor , , The Clarke transform is used to obtain the motor current in the α and β axes of the two-phase stationary coordinate system. and ; Based on the rotor angle estimate Perform the Park transformation to obtain the actual current values ​​along the D and Q axes in the two-phase rotating coordinate system. , ; Based on the actual current values ​​of the D-axis and Q-axis , Voltage in a two-phase stationary coordinate system , and current , Calculate the estimated values ​​of the effective magnetic flux of the compressor motor in the α and β axis directions of the two-phase stationary coordinate system; The angular error is estimated based on the estimated values ​​of the effective magnetic flux in the α and β axis directions; Estimate the angle error based on the estimated value, and calculate the estimated rotor angle of the compressor motor. and the actual speed of the motor ; Based on the estimated rotor angle of the compressor motor and the actual speed of the motor Calculate the d-axis command current and the q-axis command current; Calculate the Q-axis given voltage value based on the d-axis command current and the q-axis command current. and the given voltage value of the D-axis ; Based on the estimated value of the motor rotor angle right and Perform the inverse Park transformation to obtain the voltage value in the fixed coordinate system. and ; according to and Perform the Clark inverse transform to obtain the three-phase voltage. , and ; Among them, the fourth duty cycle signal, the fifth duty cycle signal, and the sixth duty cycle signal are based on , and Sure.

[0013] Optionally, the actual current values ​​based on the D-axis and Q-axis are... , Voltage in a two-phase stationary coordinate system , and current , The estimated effective magnetic flux of the compressor motor in the α and β axes of the two-phase stationary coordinate system is calculated using the following formula: ; in, and These are the estimated values ​​of the effective magnetic flux of the motor in the α and β axis directions, respectively. and Let be the voltages along the α and β axes, respectively. and Let be the currents along the α and β axes, respectively, and R be the stator resistance. Here are the q-axis inductance parameters of the motor; The angular error is estimated based on the estimated values ​​of the effective magnetic flux in the α and β axes, and is calculated using the following formula: ; The step involves estimating the angle error based on the estimated value and calculating the estimated rotor angle of the compressor motor. and the actual speed of the motor It can be calculated using the following formula: ; in, and These are the proportional-integral parameters, This is the estimated value of the deviation angle. This represents the bandwidth of the speed low-pass filter; The estimated value based on the rotor angle of the compressor motor and the actual speed of the motor Calculate the d-axis command current and q-axis command current using the following formulas: ; in, Give the initial value of the current along the d-axis. The integral control coefficient, This is the d-axis command voltage. This is the q-axis command voltage. This is the DC bus voltage; ; in, and These are the proportional gain and integral gain for speed control, respectively. This is the commanded speed of the motor. Estimate the motor speed. express Integral over time.

[0014] In addition, to achieve the above objectives, this application also provides a three-way frequency conversion drive circuit, which includes: a rectifier sub-circuit, a correction sub-circuit, an inverter control sub-circuit, and a control module, wherein the correction sub-circuit is a dual-channel interleaved PFC circuit; The input terminal of the rectifier circuit is electrically connected to an external AC power supply, the output terminal of the rectifier circuit is electrically connected to the input terminal of the correction circuit, the output terminal of the correction circuit is electrically connected to the input terminal of the inverter control circuit, the output terminal of the inverter control circuit is electrically connected to an external motor, and both the correction circuit and the inverter control circuit are communicatively connected to the control module.

[0015] Optionally, the rectifier circuit includes a first diode, a second diode, a third diode, and a fourth diode; The cathode of the first diode is electrically connected to the first node, and the anode of the first diode is electrically connected to the AC power supply. The cathode of the second diode is electrically connected to the anode of the first diode, and the anode of the second diode is electrically connected to the second node; The cathode of the third diode is electrically connected to the first node, and the anode of the third diode is electrically connected to the AC power supply. The cathode of the fourth diode is electrically connected to the anode of the third diode, and the anode of the fourth diode is electrically connected to the second node; The first node and the second node serve as the output terminals of the rectifier circuit.

[0016] Optionally, the correction sub-circuit includes a first inductor, a second inductor, a third inductor, a first switching transistor, a second switching transistor, and a third switching transistor; The first end of the first inductor is electrically connected to the first end of the second inductor and the first end of the third inductor, respectively. The second end of the first inductor is electrically connected to the source of the first switching transistor. The second end of the first inductor is also electrically connected to the third node. The second end of the second inductor is electrically connected to the source of the second switching transistor, and the second end of the second inductor is also electrically connected to the third node; The second end of the third inductor is electrically connected to the source of the third switching transistor, and the second end of the third inductor is also electrically connected to the third node; The drains of the first switch, the second switch, and the third switch are all electrically connected to the fourth node, which is grounded.

[0017] Optionally, the frequency conversion drive circuit further includes an energy storage capacitor; The energy storage capacitor is positioned between the third node and the fourth node.

[0018] Optionally, the correction sub-circuit further includes a fifth diode, a sixth diode, a seventh diode, a first resistor, a second resistor, and a third resistor; The cathodes of the fifth diode, the sixth diode, and the seventh diode are all electrically connected to the third node. The anode of the fifth diode is electrically connected to the second terminal of the first inductor, the anode of the sixth diode is electrically connected to the second terminal of the second inductor, and the anode of the seventh diode is electrically connected to the second terminal of the third inductor. The first end of the first resistor is electrically connected to the rectifier circuit, and the second end of the first resistor is electrically connected to the drain of the first switching transistor. The first end of the second resistor is electrically connected to the drain of the second switching transistor, and the second end of the second resistor is electrically connected to the fourth node. The first end of the third resistor is electrically connected to the drain of the third switching transistor, and the second end of the third resistor is electrically connected to the fourth node.

[0019] Optionally, the inverter control sub-circuit includes a fourth switch, a fifth switch, a sixth switch, a seventh switch, an eighth switch, and a ninth switch; The source of the fourth switch, the source of the fifth switch, and the source of the sixth switch are all electrically connected to the fifth node. The drain of the fourth switch is electrically connected to the source of the seventh switch, and the drain of the fourth switch is also electrically connected to the U-phase voltage input terminal of the motor. The drain of the fifth switching transistor is electrically connected to the source of the eighth switching transistor, and the drain of the fifth switching transistor is also electrically connected to the V-phase voltage input terminal of the motor. The drain of the sixth switch is electrically connected to the source of the ninth switch, and the drain of the sixth switch is also electrically connected to the W-phase voltage input terminal of the motor. The drains of the seventh switch, the eighth switch, and the ninth switch are all electrically connected to the sixth node. The source of the seventh switch is electrically connected to the U-phase voltage input terminal of the motor; The source of the eighth switch is electrically connected to the V-phase voltage input terminal of the motor. The source of the ninth switch is electrically connected to the W-phase voltage input terminal of the motor.

[0020] Optionally, the frequency conversion drive circuit further includes a fourth resistor; The first end of the fourth resistor is grounded, and the second end of the fourth resistor is electrically connected to the sixth node.

[0021] Compared with the prior art, the embodiments of this application have the following main advantages: This application provides a variable frequency drive method and a three-channel variable frequency drive circuit. The variable frequency drive method includes: a rectifier sub-circuit rectifying a first electrical signal sent from an external AC power source to obtain a second electrical signal, and transmitting the second electrical signal to a correction sub-circuit, wherein the correction sub-circuit is a three-channel interleaved PFC circuit; a control module sending a first control signal to the correction sub-circuit based on the acquired AC voltage, DC voltage, first sampling current, second sampling current, and third sampling current; the correction sub-circuit performing power factor correction on the second electrical signal based on the first control signal to obtain a third electrical signal, and transmitting the third electrical signal to an inverter control sub-circuit; the control module sending a second control signal to the inverter control sub-circuit based on the three-phase current, wherein the three-phase current is obtained by reconstructing the acquired third sampling current; and the inverter control sub-circuit converting the third electrical signal into a drive signal based on the second control signal, and transmitting the drive signal to an external motor to drive the motor.

[0022] The variable frequency drive method provided in this application uses a three-way interleaved PFC circuit for power correction. When the power control is high, the three circuits operate in parallel to reduce the current specification, eliminating the need to increase the inductor and saving circuit space. Furthermore, the variable frequency drive method provides rectification of the AC power signal via a rectifier sub-circuit, power factor correction via a correction sub-circuit, and motor drive via an inverter control sub-circuit. The method improves circuit stability and reliability by increasing the duty cycle by 10% at the power zero-crossing point, enhances compatibility through fault-tolerant derating, and achieves optimal system efficiency by adjusting the target bus voltage according to the actual motor speed. Attached Figure Description

[0023] To more clearly illustrate the solutions in this application, the accompanying drawings used in the description of the embodiments of this application will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a flowchart illustrating the variable frequency drive method provided in an embodiment of this application; Figure 2 This is one of the structural schematic diagrams of the frequency converter drive circuit provided in the embodiments of this application; Figure 3 This is a second schematic diagram of the structure of the frequency converter drive circuit provided in the embodiments of this application; Figure 4 This is one of the waveform diagrams of the counting signal, driving signal, and current signal provided in the embodiments of this application; Figures 5(a)-(c) are two of the waveform diagrams of the counting signal, driving signal, and current signal provided in the embodiments of this application; Figures 6(a)-(c) are three of the waveform diagrams of the counting signal, driving signal, and current signal provided in the embodiments of this application; Figure 7 This is the fourth waveform diagram of the counting signal, driving signal, and current signal provided in the embodiments of this application; Figure 8 This is a waveform diagram of the PWM signal provided in an embodiment of this application; Figure 9 This is a block diagram of the operation control of the PFC control unit in the embodiments of this application; Figure 10 This is a block diagram of the operation and control of the motor control unit in the embodiments of this application.

[0025] Explanation of reference numerals in the attached figures: D1, First diode; D2, Second diode; D3, Third diode; D4, Fourth diode; D5, Fifth diode; D6, Sixth diode; D7, Seventh diode; J1, First node; J2, Second node; J3, Third node; J4, Fourth node; J5, Fifth node; J6, Sixth node; L1, First inductor; L2, Second inductor; L3, Third inductor; K1, First switching transistor; K2, Second switching transistor; K3, Third switching transistor; K4, Fourth switching transistor; K5, Fifth switching transistor; K6, Sixth switching transistor; K7, Seventh switching transistor; K8, Eighth switching transistor; K9, Ninth switching transistor; EC, Energy storage capacitor; R1, First resistor; R2, Second resistor; R3, Third resistor; R4, Fourth resistor. Detailed Implementation

[0026] The frequency conversion drive method provided in this application is applied to a three-way frequency conversion drive circuit. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this application. The terms "comprising" and "having," and any variations thereof, in the description, claims, and accompanying drawings of this application are intended to cover non-exclusive inclusion. The terms "first," "second," etc., in the description, claims, or accompanying drawings of this application are used to distinguish different objects, not to describe a particular order.

[0027] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0028] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings.

[0029] Please see Figure 1 , Figure 1 This is a flowchart illustrating the variable frequency drive method provided in an embodiment of this application. It should be understood that the variable frequency drive method provided in this application is applied to a three-way variable frequency drive circuit, and the variable frequency drive method includes: In step S101, the rectifier circuit rectifies the first electrical signal sent by the external AC power supply to obtain a second electrical signal, and transmits the second electrical signal to the correction circuit, which is a three-way interleaved PFC circuit.

[0030] In step S102, the control module sends a first control signal to the correction sub-circuit based on the collected AC voltage, DC voltage, first sampling current, second sampling current and third sampling current.

[0031] In step S103, the correction sub-circuit performs power factor correction on the second electrical signal based on the first control signal to obtain a third electrical signal, and transmits the third electrical signal to the inverter control sub-circuit.

[0032] In step S104, the control module sends a second control signal to the inverter control sub-circuit based on the three-phase current, wherein the three-phase current is obtained by reconstructing the acquired fourth sampling current.

[0033] In step S105, the inverter control sub-circuit converts the third electrical signal into a drive signal based on the second control signal, and transmits the drive signal to an external motor to drive the motor.

[0034] In this embodiment, the rectifier circuit receives a first electrical signal sent by an AC power source, rectifies the first electrical signal to obtain a second electrical signal, and transmits the second electrical signal to the correction circuit. The first electrical signal is an AC signal, and the second electrical signal is a DC signal.

[0035] The control module sends a first control signal to the correction sub-circuit based on the acquired AC voltage, DC voltage, first sampling current, second sampling current, and third sampling current. Based on the first control signal, the correction sub-circuit performs power factor correction on the second electrical signal to obtain a third electrical signal, and then transmits the third electrical signal to the inverter control sub-circuit.

[0036] Furthermore, the inverter control sub-circuit converts the third electrical signal into a drive signal based on the second control signal, and transmits the drive signal to the external motor to drive the motor. Optionally, the motor is a permanent magnet synchronous motor, and the third electrical signal is a three-phase electrical signal.

[0037] The variable frequency drive method provided in this application uses a three-way interleaved PFC circuit for power correction. When the power control is high, the three circuits operate in parallel to reduce the current specification, eliminating the need to increase the inductor and saving circuit space. Furthermore, the variable frequency drive method provides rectification of the AC power signal via a rectifier sub-circuit, power factor correction via a correction sub-circuit, and motor drive via an inverter control sub-circuit. The method improves circuit stability and reliability by increasing the duty cycle by 10% at the power zero-crossing point, enhances compatibility through fault-tolerant derating, and achieves optimal system efficiency by adjusting the target bus voltage according to the actual motor speed.

[0038] Optionally, the control module sends a first control signal to the correction sub-circuit based on the acquired AC voltage, DC voltage, first sampling current, second sampling current, and third sampling current, including: The control module obtains the first boost ratio coefficient based on the DC voltage and bus voltage command values; the bus voltage command value is determined based on the motor speed and motor parameters. The control module obtains a second boost ratio coefficient, a third boost ratio coefficient, and a fourth boost ratio coefficient based on the first boost ratio coefficient, the first sampling current, the second sampling current, and the third sampling current. The control module obtains a first duty cycle signal, a second duty cycle signal, and a third duty cycle signal based on the second boost ratio coefficient, the third boost ratio coefficient, and the fourth boost ratio coefficient. The control module obtains a first control signal based on the first duty cycle signal, the second duty cycle signal, the third duty cycle signal, and the AC voltage, and sends the first control signal to the correction sub-circuit.

[0039] Please refer to the following: Figure 9 , Figure 9 This is a block diagram of the operation control of the PFC control unit in the embodiments of this application, combined with... Figure 9 This allows us to obtain the operational logic of the PFC control unit in executing flow sharing control and soft start control.

[0040] In this embodiment, the control module obtains a first boost ratio coefficient based on the DC voltage and bus voltage command values. After obtaining the first boost ratio coefficient, it obtains a second, third, and fourth boost ratio coefficient based on the first boost ratio coefficient, a first sampling current, a second sampling current, and a third sampling current. Then, based on the first duty cycle signal, the second duty cycle signal, the third duty cycle signal, and the AC voltage, it obtains a first control signal and sends it to the correction sub-circuit. The first, second, and third duty cycle signals are determined based on the second, third, and fourth boost ratio coefficients.

[0041] Optionally, the three-phase current includes a first current, a second current, and a third current. Based on the three-phase current, the control module sends a second control signal to the inverter control sub-circuit, including: The control module generates a three-phase voltage based on the first current, the second current, and the third current; The control module generates a fourth duty cycle signal, a fifth duty cycle signal, and a sixth duty cycle signal based on the DC voltage and the three-phase voltage. The control module generates a second control signal based on the fourth duty cycle signal, the fifth duty cycle signal, and the sixth duty cycle signal, and sends the second control signal to the inverter control sub-circuit.

[0042] Optionally, the method further includes: If the average value of the first sampled current is greater than or equal to the preset current, the control module sends a third control signal to cause the first switch, and / or the second switch, and / or the third switch in the correction sub-circuit to start from the off state to the PWM output state at the power supply zero crossing point; If the duty cycle of the PWM target value corresponding to the first switch, and / or the second switch, and / or the third switch exceeds 10%, then control the duty cycle corresponding to the first switch, and / or the second switch, and / or the third switch to increase by 10% in increments. If the difference between the PWM target value and the actual output value corresponding to the first switch, and / or the second switch, and / or the third switch is less than 10%, then the PWM target value is reached by increasing the actual difference.

[0043] Specifically, when the average value of the first sampled current is greater than or equal to the preset current, the first switch, and / or the second switch, and / or the third switch are allowed to start from the off state to the PWM output state at the power supply zero-crossing point. Further, when the first switch, and / or the second switch, and / or the third switch are allowed to start from the off state to the PWM output state, if the PWM target duty cycle exceeds 10%, the PWM output is controlled by incrementing by 10% each time. When the difference between the PWM target value and the actual output value is less than 10%, the output value is incremented according to the actual difference to reach the target value, thus completing the soft-start control.

[0044] Optionally, the method further includes: When the first sampling current is less than the PFC single-on control threshold, the control module controls the first, second, and third switches in the correction sub-circuit to turn off. When the first sampling current is greater than or equal to the PFC single-on control threshold and less than the PFC double-on control threshold, control one output of the first switch, the second switch and the third switch, and shut down the other two. When the first sampling current is greater than or equal to the PFC dual-on control threshold and less than the PFC triple-on control threshold, control the two outputs of the first switch, the second switch and the third switch, and shut down one of them; When the first sampling current is greater than or equal to the PFC three-way control threshold, the first switch, the second switch and the third switch are controlled to output simultaneously.

[0045] In this embodiment, when the control module controls the first and second switching transistors to output PWM waveforms, it calculates based on the average value of the AC power supply output current. Controls the first, second, and third switching transistors to turn off, or controls one of the first, second, and third switching transistors to output, or controls two or three of the first, second, and third switching transistors to output simultaneously.

[0046] when When, the first, second, and third switches are turned off; when When one of the first, second, and third switching transistors is controlled, one PWM output is controlled, while the other two are turned off; when When the first, second, and third switching transistors are in operation, the outputs of both the first, second, and third switching transistors are controlled, while one output is turned off; when... At the same time, it controls the three outputs of the first switch, the second switch, and the third switch; in, , , The control thresholds for single-on, double-on, and triple-on PFC are set, and ;Optionally, It is 2A. It is 6A. It is 10A.

[0047] Optionally, the method further includes: When the first and second switches in the correction sub-circuit output simultaneously, or when the first, second, and third switches output simultaneously, the control module controls the other switch and / or the other two switches to operate at reduced derating when it detects that one of the switches is damaged and overcurrent. In one of the derating processes of the other switching transistor, the maximum operating frequency of the motor is reduced by one-third, and / or the maximum operating power of the motor is reduced by one-third; in the other two derating processes of the switching transistor, the maximum operating frequency of the motor is reduced by two-thirds, and / or the maximum operating power of the motor is reduced by two-thirds.

[0048] When the control module controls the first and second switching transistors to output simultaneously, or the first, second, and third switching transistors to output simultaneously, if an overcurrent failure is detected in one of the transistors, only the undamaged transistor and / or the two undamaged transistors will be activated for derating operation. During the derating operation of one transistor, the maximum operating frequency of the motor will be reduced to 1 / 3 of its original value, and / or the maximum operating power will be reduced to 1 / 3 of its original value. During the derating operation of two transistors, the maximum operating frequency of the motor will be reduced to 2 / 3 of its original value, and / or the maximum operating power will be reduced to 2 / 3 of its original value.

[0049] Optionally, when one of the first, second, and third switching transistors is outputting, the duty cycle is calculated using the following formula: ; ; ; in, This indicates the duty cycle corresponding to the first switching transistor. This indicates the duty cycle corresponding to the second switching transistor. This indicates the duty cycle corresponding to the third switch. This represents the instantaneous current of the first inductor. This represents the instantaneous current of the second inductor. This represents the instantaneous current of the third inductor. This represents the boost ratio coefficient. This represents the average current of alternating current.

[0050] When the control module controls the output of the first, second, and third switching transistors, if it detects that the control module temperature is too high and / or the power is too high, it reduces the PFC carrier frequency to reduce the heat generation of the PFC circuit.

[0051] Optionally, the method further includes: When the first, second, and third switches in the correction sub-circuit are outputting simultaneously, the duty cycle of the first, second, and third switches is automatically adjusted according to the current between the first, second, and third inductors in the correction sub-circuit using the following formula.

[0052] Specifically, when the first, second, and third switching transistors output simultaneously, the duty cycles of the first, second, and third switching transistors are automatically adjusted according to the current between the first, second, and third inductors to achieve current sharing control.

[0053] ; ; ; ; ; ; ; ; ; in, This indicates the duty cycle corresponding to the first switching transistor. This indicates the duty cycle corresponding to the second switching transistor. This indicates the duty cycle corresponding to the third switching transistor; , , Determined based on the average current of the first inductor, the average current of the second inductor, and the average current of the third inductor; , , These are the instantaneous currents of the first inductor, the second inductor, and the third inductor, respectively. , , These are the average currents of the first inductor, the second inductor, and the third inductor, respectively. Output current for AC power supply Average current; The step-up ratio is calculated and limited based on the target bus voltage and the actual bus voltage. and These are preset coefficients.

[0054] in, , and These are preset coefficients; in, Indicates DC voltage. Indicates the commanded value of the bus voltage; The selectable setting range is [1.3, 2.5], meaning that the setting is applied when the calculation result is less than 1.3. Set to 1.3, and set to 1.3 when the calculation result is greater than 2.5. It is 2.5.

[0055] Initial bus voltage command value It is calculated using the following formula: ; in, This refers to the single-phase resistance of the motor. This refers to the d-axis current of the motor. This refers to the q-axis current of the motor. This is the back electromotive force coefficient of the motor; This refers to the q-axis current of the motor. This refers to the d-axis current of the motor. This refers to the motor's commanded speed. Voltage modulation coefficient; Bus voltage command value It is calculated using the following formula: ; in, This refers to the amplitude of the power supply voltage. Bus capacitor nominal voltage value, This is the safety margin set.

[0056] When the first, second, and third switching transistors output from both paths, the duty cycle of the first and second switching transistors is automatically adjusted according to the current between the first and second inductors to achieve current sharing control.

[0057] ; ; ; ; ; in, This indicates the duty cycle corresponding to the first switching transistor. This indicates the duty cycle corresponding to the second switching transistor; Determined based on the average current of the first inductor and the average current of the second inductor; and These are the instantaneous currents of the first inductor and the second inductor, respectively; and These are the average currents of the first inductor and the second inductor, respectively. Output current for AC power supply Average current; The step-up ratio is calculated and limited based on the target bus voltage and the actual bus voltage. and These are preset coefficients.

[0058] in, .

[0059] in, Indicates DC voltage. This indicates the commanded value for the bus voltage. Optionally, The setting range is [1.3, 2.5], meaning that when the calculation result is less than 1.3, the setting is... Set to 1.3, and set to 1.3 when the calculation result is greater than 2.5. It is 2.5.

[0060] It should be understood that the bus voltage command value It can be obtained in the following ways: Initial bus voltage command value Calculated from motor speed and motor parameters: ; in, This refers to the single-phase resistance of the motor. This refers to the d-axis current of the motor. This refers to the q-axis current of the motor. This is the back electromotive force coefficient of the motor; This refers to the q-axis current of the motor. This refers to the d-axis current of the motor. This refers to the motor's commanded speed. The voltage modulation coefficient has a value range of [1, 1.547], and KH can be optionally set to 1.1.

[0061] Furthermore, The final bus voltage command value is obtained by limiting the amplitude. : ; in, This refers to the amplitude of the power supply voltage. The nominal voltage value of the bus capacitor can be optionally set to 450V or 500V. Optionally, the safety margin can be set to 30V.

[0062] When the first and third switching transistors output from both paths, the duty cycle of the first and third switching transistors is automatically adjusted according to the current between the first and third inductors to achieve current sharing control.

[0063] When the second and third switching transistors output from both paths, the duty cycle of the second and third switching transistors is automatically adjusted according to the current between the second and third inductors to achieve current sharing control.

[0064] Please see Figures 4-7 .

[0065] in, Figure 4 This diagram shows the waveforms of the counting signal, drive signal, and current signal when all three PFC channels are in the off state (i.e., the first, second, and third switching transistors are all off). Figure 4 The current sampling time point can be obtained when all three PFCs are in the off state.

[0066] Figures 5(a)-(c) show the waveforms of the counting signal, drive signal, and current signal when one PFC is on and two PFCs are off, i.e., when any one of the first, second, or third switching transistors is off. From Figures 5(a)-(c), we can obtain the current sampling time points when one PFC is on and two PFCs are off.

[0067] Figures 6(a)-(c) show the waveforms of the counting signal, drive signal, and current signal when two PFC channels are enabled and one PFC channel is disabled, i.e., when any two of the first, second, and third switching transistors are disabled. The current sampling time points when two PFC channels are enabled and one PFC channel is disabled can be obtained from Figures 6(a)-(c).

[0068] in, Figure 7 This is a schematic diagram of the waveforms of the counting signal, drive signal, and current signal when all three PFC channels are enabled (i.e., the first, second, and third switching transistors are all turned on). Figure 7 The current sampling time point can be obtained when all three PFC channels are in the enabled state.

[0069] Please refer to the following: Figure 10 , Figure 10 This is a block diagram of the operation and control of the motor control unit in the embodiments of this application, combined with... Figure 10 This allows us to obtain the computational logic for generating the duty cycle signal by the motor control unit.

[0070] Specifically, the fourth duty cycle signal, the fifth duty cycle signal, and the sixth duty cycle signal can be generated in the following ways: Obtain the three-phase current value of the motor , , ; Based on the three-phase current of the motor , , The Clarke transform is used to obtain the motor current in the α and β axes of the two-phase stationary coordinate system. and ; Based on the rotor angle estimate Perform the Park transformation to obtain the actual current values ​​along the D and Q axes in the two-phase rotating coordinate system. , ; Based on the actual current values ​​of the D-axis and Q-axis , Voltage in a two-phase stationary coordinate system , and current , Calculate the estimated values ​​of the effective magnetic flux of the compressor motor in the α and β axis directions of the two-phase stationary coordinate system; The angular error is estimated based on the estimated values ​​of the effective magnetic flux in the α and β axis directions; Estimate the angle error based on the estimated value, and calculate the estimated rotor angle of the compressor motor. and the actual speed of the motor ; Based on the estimated rotor angle of the compressor motor and the actual speed of the motor Calculate the d-axis command current and the q-axis command current; Calculate the Q-axis given voltage value based on the d-axis command current and the q-axis command current. and the given voltage value of the D-axis ; Based on the estimated value of the motor rotor angle right and Perform the inverse Park transformation to obtain the voltage value in the fixed coordinate system. and ; according to and Perform the Clark inverse transform to obtain the three-phase voltage. , and ; Among them, the fourth duty cycle signal, the fifth duty cycle signal, and the sixth duty cycle signal are based on , and Sure.

[0071] It should be understood that the first current is the current corresponding to the U-phase voltage, the second current is the current corresponding to the V-phase voltage, and the third current is the current corresponding to the W-phase voltage.

[0072] In this embodiment, the motor current in the α and β axes of the two-phase stationary coordinate system is obtained based on the following formula. and .

[0073] ; ; in, Indicates the first current. This indicates the second current.

[0074] Then, based on the estimated rotor angle value By performing Park transformation through a two-phase stationary-to-two-phase rotating coordinate transformation unit, the actual current values ​​of the D-axis and Q-axis in the two-phase rotating coordinate system were calculated using the following formula. , .

[0075] ; ; Determine the estimated rotor angle of the motor. and motor speed estimate At this time, the above function can be achieved through the magnetic flux observation method. Specifically, it can first be based on the voltage on the two-phase stationary coordinate system. , and current , Calculate the estimated effective magnetic flux of the compressor motor in the α and β axes of a two-phase stationary coordinate system. ; in, and These are the estimated values ​​of the effective magnetic flux of the motor in the α and β axis directions, respectively. and Let be the voltages along the α and β axes, respectively. and Let be the currents along the α and β axes, respectively, and R be the stator resistance. Here are the q-axis inductance parameters of the motor.

[0076] Furthermore, the angular error is estimated based on the estimated values ​​of the effective magnetic flux along the α and β axes: ; Then, calculate the estimated rotor angle of the compressor motor according to the following formula. and the actual speed of the motor : ; in, and These are the proportional-integral parameters, This is the estimated value of the deviation angle. This represents the bandwidth of the speed low-pass filter.

[0077] Furthermore, the d-axis command current is calculated based on the field weakening control module: ; in, Give the initial value of the current along the d-axis. The integral control coefficient, This is the d-axis command voltage. This is the q-axis command voltage. This is the DC bus voltage.

[0078] The q-axis command current is based on the target motor speed. With motor speed estimate The difference is calculated to obtain: ; in, and These are the proportional gain and integral gain for speed control, respectively. This is the commanded speed of the motor. Estimate the motor speed. express Integral over time.

[0079] Furthermore, the Q-axis and D-axis given voltage values ​​are calculated using the following formulas: ; ; in, Give the voltage value to the Q-axis. Give the voltage value to the D-axis. Q-axis command current value, This is the commanded current value for the D-axis. This is the actual Q-axis current. This represents the actual current along the d-axis. and These are the proportional gain and integral gain for D-axis current control, respectively. and These are the proportional gain and integral gain for Q-axis current control, respectively. This is the back EMF coefficient of the motor. and These are the D-axis and Q-axis inductors, respectively. express Integral over time.

[0080] After obtaining the given voltage value on the Q axis and the given voltage value of the D-axis Then, the estimated value can be obtained based on the motor rotor angle. right and The voltage value in the fixed coordinate system is obtained by performing the Park inverse transformation through a two-phase rotating to two-phase stationary coordinate transformation unit. and The specific transformation formula is as follows: ; in, This is the estimated value of the motor rotor angle.

[0081] Furthermore, the voltage value on a fixed coordinate system can be used as a basis. and The three-phase voltage is obtained by performing Clark inverse transformation through a two-phase stationary to three-phase stationary coordinate transformation unit. , and The specific transformation formula is as follows: ; ; ; Then the duty cycle calculation unit can calculate the duty cycle based on the DC bus voltage Udc and the three-phase voltage. , and The duty cycle is calculated to obtain the duty cycle control signals, namely the three-phase duty cycles Du, Dv, and Dw. The specific calculation formulas are as follows: ; ; ; in, This is the DC bus voltage.

[0082] The aforementioned three-phase duty cycle signal includes three pulse width signals, which are calculated and updated in each PWM cycle.

[0083] like Figure 8 As shown, the duty cycle of phase u is... The corresponding calculations were obtained over three consecutive cycles. , , The duty cycle signal is then used to generate a corresponding PWM control signal for the upper bridge arm switch of the u-phase in the inverter via a triangular carrier signal produced by a timer inside the arithmetic control unit. The control signal for the lower bridge arm of the u-phase corresponds to and complements this PWM control signal via three PWM control signals, such as... Figure 8 As shown, therefore Control the upper and lower bridge arm switches of phase U.

[0084] Please see Figure 2 ,like Figure 2 As shown, the three-channel frequency converter drive circuit provided in this application embodiment includes a rectifier sub-circuit, a correction sub-circuit, an inverter control sub-circuit, and a control module. The correction sub-circuit is a three-channel interleaved PFC circuit. The input terminal of the rectifier circuit is electrically connected to an external AC power supply, the output terminal of the rectifier circuit is electrically connected to the input terminal of the correction circuit, the output terminal of the correction circuit is electrically connected to the input terminal of the inverter control circuit, the output terminal of the inverter control circuit is electrically connected to an external motor, and both the correction circuit and the inverter control circuit are communicatively connected to the control module.

[0085] The working principle of the frequency converter drive circuit provided in this application embodiment is as follows: the rectifier circuit receives a first electrical signal sent by the AC power supply, rectifies the first electrical signal to obtain a second electrical signal, and transmits the second electrical signal to the correction circuit. The first electrical signal is an AC signal, and the second electrical signal is a DC signal.

[0086] The control module sends a first control signal to the correction sub-circuit based on the acquired AC voltage, DC voltage, first sampling current, and second sampling current. The correction sub-circuit then performs power factor correction on the second electrical signal based on the first control signal to obtain a third electrical signal, which is then transmitted to the inverter control sub-circuit.

[0087] Optionally, such as Figure 2 As shown, the control module includes a PFC control unit and a motor control unit. The PFC control unit is used to send a first control signal to the correction sub-circuit based on the acquired AC voltage, DC voltage, first sampling current, and second sampling current. Optionally, the first control signal is used to adjust the duty cycle of each switch in the correction sub-circuit, thereby achieving power factor correction for the second electrical signal.

[0088] The control module sends a second control signal to the inverter control sub-circuit based on the three-phase current, which is obtained by reconstructing the third sampled current.

[0089] Optionally, a reconfiguration module can also be set in the drive frequency converter circuit. This reconfiguration module is used to collect the motor current, i.e. the third sampled current, and reconstruct the third sampled current to obtain the three-phase current. It should be understood that the above three-phase current includes the U-phase current value, the V-phase current value, and the W-phase current value.

[0090] As described above, the control module includes a motor control unit, which sends a second control signal to the inverter control sub-circuit based on the three-phase current. Optionally, the second control signal is used to adjust the duty cycle of each switch in the inverter control sub-circuit, thereby driving the motor.

[0091] Furthermore, the inverter control sub-circuit converts the third electrical signal into a drive signal based on the second control signal, and transmits the drive signal to the external motor to drive the motor. Optionally, the motor is a permanent magnet synchronous motor, and the third electrical signal is a three-phase electrical signal.

[0092] The frequency converter drive circuit provided in this application embodiment is designed as a three-way interleaved PFC circuit. This reduces the current specification by operating the three circuits in parallel when the power control is high, eliminating the need to increase the inductor and saving circuit space. Furthermore, the frequency converter drive circuit provided in this application embodiment rectifies the electrical signal sent from the AC power supply through a rectifier sub-circuit, corrects the power factor of the electrical signal through a correction sub-circuit, and drives the motor through an inverter control sub-circuit, thus improving the stability and reliability of the circuit during operation.

[0093] Please see Figure 3 Optionally, the rectifier circuit includes a first diode D1, a second diode D2, a third diode D3, and a fourth diode D4; The cathode of the first diode D1 is electrically connected to the first node J1, and the anode of the first diode D1 is electrically connected to the AC power supply. The cathode of the second diode D2 is electrically connected to the anode of the first diode D1, and the anode of the second diode D2 is electrically connected to the second node J2; The cathode of the third diode D3 is electrically connected to the first node J1, and the anode of the third diode D3 is electrically connected to the AC power supply. The cathode of the fourth diode D4 is electrically connected to the anode of the third diode D3, and the anode of the fourth diode D4 is electrically connected to the second node J2. The first node J1 and the second node J2 serve as the output terminals of the rectifier circuit.

[0094] The rectifier circuit in this embodiment includes a first diode D1, a second diode D2, a third diode D3, and a fourth diode D4. The rectifier circuit is used to rectify the first electrical signal output by the AC power supply, and to rectify the AC signal into a DC signal.

[0095] Please see Figure 3 Optionally, the correction sub-circuit includes a first inductor L1, a second inductor L2, a third inductor L3, a first switch K1, a second switch K2, and a third switch K3; The first end of the first inductor L1 is electrically connected to the first end of the second inductor L2 and the first end of the third inductor L3, respectively. The second end of the first inductor L1 is electrically connected to the source of the first switch K1. The second end of the first inductor L1 is also electrically connected to the third node J3. The second end of the second inductor L2 is electrically connected to the source of the second switch K2, and the second end of the second inductor L2 is also electrically connected to the third node J3; The second end of the third inductor L3 is electrically connected to the source of the third switch K3, and the second end of the third inductor L3 is also electrically connected to the third node J3; The drains of the first switch K1, the second switch K2, and the third switch K3 are all electrically connected to the fourth node J4, which is grounded.

[0096] Please see Figure 3 Optionally, the correction sub-circuit further includes a fifth diode D5, a sixth diode D6, a seventh diode D7, a first resistor R1, a second resistor R2, and a third resistor R3; The cathodes of the fifth diode D5, the sixth diode D6, and the seventh diode D7 are all electrically connected to the third node J3. The anode of the fifth diode D5 is electrically connected to the second terminal of the first inductor L1, the anode of the sixth diode D6 is electrically connected to the second terminal of the second inductor L2, and the anode of the seventh diode D7 is electrically connected to the second terminal of the third inductor L3. The first end of the first resistor R1 is electrically connected to the rectifier circuit, and the second end of the first resistor R1 is electrically connected to the drain of the first switching transistor K1. The first end of the second resistor R2 is electrically connected to the drain of the second switch K2, and the second end of the second resistor R2 is electrically connected to the fourth node J4. The first end of the third resistor R3 is electrically connected to the drain of the third switch K3, and the second end of the third resistor R3 is electrically connected to the fourth node J4.

[0097] The correction sub-circuit in this embodiment includes a first inductor L1, a second inductor L2, a third inductor L3, a first switch K1, a second switch K2, a fifth diode D5, a sixth diode D6, a seventh diode D7, a first resistor R1, a second resistor R2, and a third resistor R3.

[0098] It should be understood that the aforementioned first sampling current can be the current obtained by sampling at the first resistor R1, and can be expressed as: The second sampling current mentioned above can be the current obtained by sampling at the second resistor R2, and can be expressed as: The third sampling current mentioned above can be the current obtained by sampling at the third resistor R3, and can be expressed as: .

[0099] It should be understood that in the embodiments of this application, the correction sub-circuit is designed as a three-way interleaved PFC circuit. The three-way interleaved PFC circuit includes a first PFC, a second PFC, and a third PFC. The first PFC includes a first inductor L1, a first switch K1, and a fifth diode D5. The second PFC includes a second inductor L2, a second switch K2, and a sixth diode D6. The third PFC includes a third inductor L3, a third switch K3, and a seventh diode D7.

[0100] When the first, second, and third PFC channels are all off, the current sampling point is set to the middle position of the count of the waveform generator of the first PFC channel. At the current sampling point, the voltage across the first resistor R1 is collected, and the sampled current is calculated based on the collected voltage and the resistance value of the first resistor R1. .

[0101] When the first PFC is active and the second and third PFCs are off, the current sampling point is set to the midpoint of the first PFC's high-level on state. At this sampling point, the voltage across the first resistor R1 is measured, and the current flowing through R1 is calculated based on the measured voltage across R1 and the resistance value of R1. And calculate the current value of the first inductor L1: .

[0102] When the first and third PFC channels are off, and the second PFC channel is on, the current sampling point is set to the middle position when the second PFC channel is high-level on. At the current sampling point, the voltage across the first resistor R1 and the voltage across the second resistor R2 are collected respectively. Based on the collected voltage across the first resistor R1 and the resistance value of the first resistor R1, the current value flowing through the first resistor R1 is calculated. The current flowing through the second resistor R2 is calculated based on the voltage across the second resistor R2 and the resistance value of the second resistor R2. .

[0103] When the third PFC is enabled and the first and second PFCs are disabled, the current sampling point is set to the midpoint when the third PFC is high-level enabled. At each sampling point, the voltage across the first resistor R1 and the voltage across the third resistor R3 are collected, and the current flowing through the first resistor R1 is calculated based on the collected voltage across R1 and the resistance value of R1. The current flowing through the third resistor R3 is calculated based on the voltage across the third resistor R3 and the resistance value of the third resistor R3. .

[0104] When the first and second PFC channels are enabled and the third PFC channel is disabled, the current sampling point for the first channel is set to the middle position when the PFC is high-level enabled. At this sampling point, the voltage across the first resistor R1 is measured, and the current flowing through the first resistor R1 is calculated based on the measured voltage across R1 and the resistance of R1 itself. The second current sampling point is set to the middle position when the PFC is high-level enabled; the voltage across the second resistor R2 is collected at the current sampling point, and the current flowing through the second resistor is calculated based on the collected voltage across the second resistor R2 and the resistance value of the second resistor. And calculate the current value of the first inductor L1: .

[0105] When the second and third PFC channels are enabled and the first PFC channel is disabled, the current sampling point for the second channel is set to the middle position when the PFC is high-level enabled. At this sampling point, the voltage across the second resistor R2 is measured, and the current flowing through R2 is calculated based on the measured voltage across R2 and the resistance value of the second resistor. The third current sampling point is set to the middle position when the PFC is high-level enabled; at the current sampling point, the voltage across the third resistor R3 is collected, and the current flowing through the third resistor R3 is calculated based on the collected voltage across the third resistor R3 and the resistance value of the third resistor R3. And calculate the total current value: .

[0106] When the first and third PFC channels are enabled and the second PFC channel is disabled, the current sampling point for the first channel is set to the middle position when the PFC is high-level enabled. At this sampling point, the voltage across the first resistor R1 is measured, and the current flowing through the first resistor is calculated based on the measured voltage across R1 and the resistance value of the first resistor. The third current sampling point is set to the middle position when the PFC is high-level enabled; the voltage across the third resistor R3 is sampled at the current sampling point, and the current flowing through the third resistor R3 is calculated based on the sampled voltage across the third resistor R3 and the resistance value of the third resistor R3. And calculate the current value of the first inductor L1: .

[0107] When the first, second, and third PFC channels are all enabled, the current sampling point for the first channel is set to the middle position when the PFC is high-level. At the current sampling point, the voltage across the first resistor R1 is collected, and the current flowing through the first resistor R1 is calculated based on the collected voltage across the first resistor R1 and the resistance of the first resistor R1. The second current sampling point is set to the middle position when the PFC is high-level enabled; the voltage across the second resistor R2 is collected at the current sampling point, and the current flowing through the second resistor R2 is calculated based on the collected voltage across the second resistor R2 and the resistance of the second resistor R2. The third current sampling point is set to the middle position when the PFC is high-level enabled; at the current sampling point, the voltage across the third resistor R3 is collected, and the current flowing through the third resistor R3 is calculated based on the collected voltage across the third resistor R3 and the resistance of the third resistor R3. And calculate the current value of the first inductor L1: .

[0108] Please see Figure 3 Optionally, the frequency conversion drive circuit further includes an energy storage capacitor EC; The energy storage capacitor EC is located between the third node J3 and the fourth node J4.

[0109] In this embodiment, the energy storage capacitor EC is used to smooth and filter the DC output of the correction circuit, and output a smooth DC bus voltage.

[0110] Please see Figure 3 Optionally, the inverter control sub-circuit includes a fourth switch K4, a fifth switch K5, a sixth switch K6, a seventh switch, an eighth switch K8, and a ninth switch K9. The source of the fourth switch K4, the source of the fifth switch K5, and the source of the sixth switch K6 are all electrically connected to the fifth node J5. The drain of the fourth switch K4 is electrically connected to the source of the seventh switch K7, and the drain of the fourth switch K4 is also electrically connected to the U-phase voltage input terminal of the motor. The drain of the fifth switch K5 is electrically connected to the source of the eighth switch K8, and the drain of the fifth switch K5 is also electrically connected to the V-phase voltage input terminal of the motor. The drain of the sixth switch K6 is electrically connected to the source of the ninth switch K9, and the drain of the sixth switch K6 is also electrically connected to the W-phase voltage input terminal of the motor. The drains of the seventh switch K7, the eighth switch K8, and the ninth switch K9 are all electrically connected to the sixth node J6. The source of the seventh switch K7 is electrically connected to the U-phase voltage input terminal of the motor; The source of the eighth switch K8 is electrically connected to the V-phase voltage input terminal of the motor. The source of the ninth switch K9 is electrically connected to the W-phase voltage input terminal of the motor.

[0111] The inverter control sub-circuit in this embodiment includes a fourth switch K4, a fifth switch K5, a sixth switch K6, a seventh switch, an eighth switch K8, and a ninth switch K9.

[0112] The source of the seventh switch K7 is electrically connected to the U-phase voltage input terminal of the motor, the source of the eighth switch K8 is electrically connected to the V-phase voltage input terminal of the motor, and the source of the ninth switch K9 is electrically connected to the W-phase voltage input terminal of the motor. The inverter control sub-circuit drives the motor by transmitting voltage to the U-phase voltage input terminal, the V-phase voltage input terminal, and the W-phase voltage input terminal.

[0113] Please see Figure 3 Optionally, the frequency conversion drive circuit further includes a fourth resistor R4; The first end of the fourth resistor R4 is grounded, and the second end of the fourth resistor R4 is electrically connected to the sixth node J6.

[0114] In this embodiment, the current at the fourth resistor R4 can be sampled to obtain the fourth sampled current, and then the fourth sampled current can be reconstructed to obtain the three-phase current.

[0115] Obviously, the embodiments described above are only some embodiments of this application, not all embodiments. The accompanying drawings show preferred embodiments of this application, but do not limit the patent scope of this application. This application can be implemented in many different forms; rather, the purpose of providing these embodiments is to provide a more thorough and comprehensive understanding of the disclosure of this application. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing specific embodiments, or make equivalent substitutions for some of the technical features. Any equivalent structures made using the content of this application's specification and drawings, directly or indirectly applied to other related technical fields, are similarly within the scope of patent protection of this application.

Claims

1. A variable frequency drive method, characterized by, The frequency conversion drive method includes: The rectifier circuit rectifies the first electrical signal sent by the external AC power supply to obtain a second electrical signal, and transmits the second electrical signal to the correction circuit, which is a three-way interleaved PFC circuit. Based on the collected AC voltage, DC voltage, first sampling current, second sampling current, and third sampling current, the control module sends a first control signal to the correction sub-circuit. The correction sub-circuit performs power factor correction on the second electrical signal based on the first control signal to obtain a third electrical signal, and transmits the third electrical signal to the inverter control sub-circuit. The control module sends a second control signal to the inverter control sub-circuit based on the three-phase current, wherein the three-phase current is obtained by reconstructing the acquired fourth sampling current; The inverter control sub-circuit converts the third electrical signal into a drive signal based on the second control signal, and transmits the drive signal to an external motor to drive the motor.

2. The method of claim 1, wherein, The control module sends a first control signal to the correction sub-circuit based on the acquired AC voltage, DC voltage, first sampling current, second sampling current, and third sampling current, including: The control module obtains the first boost ratio coefficient based on the DC voltage and bus voltage command values; the bus voltage command value is determined based on the motor speed and motor parameters. The control module obtains a second boost ratio coefficient, a third boost ratio coefficient, and a fourth boost ratio coefficient based on the first boost ratio coefficient, the first sampling current, the second sampling current, and the third sampling current. The control module obtains a first duty cycle signal, a second duty cycle signal, and a third duty cycle signal based on the second boost ratio coefficient, the third boost ratio coefficient, and the fourth boost ratio coefficient. The control module obtains a first control signal based on the first duty cycle signal, the second duty cycle signal, the third duty cycle signal, and the AC voltage, and sends the first control signal to the correction sub-circuit.

3. The method according to claim 1, characterized in that, The three-phase current includes a first current, a second current, and a third current. Based on the three-phase current, the control module sends a second control signal to the inverter control sub-circuit, including: The control module generates a three-phase voltage based on the first current, the second current, and the third current; The control module generates a fourth duty cycle signal, a fifth duty cycle signal, and a sixth duty cycle signal based on the DC voltage and the three-phase voltage. The control module generates a second control signal based on the fourth duty cycle signal, the fifth duty cycle signal, and the sixth duty cycle signal, and sends the second control signal to the inverter control sub-circuit.

4. The method according to claim 1, characterized in that, The method further includes: If the average value of the first sampled current is greater than or equal to the preset current, the control module sends a third control signal to cause the first switch, and / or the second switch, and / or the third switch in the correction sub-circuit to start from the off state to the PWM output state at the power supply zero crossing point; If the duty cycle of the PWM target value corresponding to the first switch, and / or the second switch, and / or the third switch exceeds 10%, then control the duty cycle corresponding to the first switch, and / or the second switch, and / or the third switch to increase by 10% in increments. If the difference between the PWM target value and the actual output value corresponding to the first switch, and / or the second switch, and / or the third switch is less than 10%, then the PWM target value is reached by increasing the actual difference.

5. The method according to claim 1, characterized in that, The method further includes: When the first sampling current is less than the PFC single-on control threshold, the control module controls the first, second, and third switches in the correction sub-circuit to turn off. When the first sampling current is greater than or equal to the PFC single-on control threshold and less than the PFC double-on control threshold, control one output of the first switch, the second switch and the third switch, and shut down the other two. When the first sampling current is greater than or equal to the PFC dual-on control threshold and less than the PFC triple-on control threshold, control the two outputs of the first switch, the second switch and the third switch, and shut down one of them; When the first sampling current is greater than or equal to the PFC three-way control threshold, the first switch, the second switch and the third switch are controlled to output simultaneously.

6. The method according to claim 1, characterized in that, The method further includes: When the first and second switches in the correction sub-circuit output simultaneously, or when the first, second, and third switches output simultaneously, the control module controls the other switch and / or the other two switches to operate at reduced derating when it detects that one of the switches is damaged and overcurrent. In one of the derating processes of the other switching transistor, the maximum operating frequency of the motor is reduced by one-third, and / or the maximum operating power of the motor is reduced by one-third; in the other two derating processes of the switching transistor, the maximum operating frequency of the motor is reduced by two-thirds, and / or the maximum operating power of the motor is reduced by two-thirds.

7. The method according to claim 1, characterized in that, The method further includes: When the first, second, and third switches in the correction sub-circuit are outputting simultaneously, the duty cycle of the first, second, and third switches is automatically adjusted according to the current between the first, second, and third inductors in the correction sub-circuit using the following formula. ； ； ； ； ； ； ； ； ； in, This indicates the duty cycle corresponding to the first switching transistor. This indicates the duty cycle corresponding to the second switching transistor. This indicates the duty cycle corresponding to the third switching transistor; , , Determined based on the average current of the first inductor, the average current of the second inductor, and the average current of the third inductor; , , These are the instantaneous currents of the first inductor, the second inductor, and the third inductor, respectively. , , These are the average currents of the first inductor, the second inductor, and the third inductor, respectively. Output current for AC power supply Average current; The step-up ratio is calculated and limited based on the target bus voltage and the actual bus voltage. and These are preset coefficients; in, , and These are preset coefficients; in, Indicates DC voltage. Indicates the commanded value of the bus voltage; Initial bus voltage command value It is calculated using the following formula: ； in, This refers to the single-phase resistance of the motor. This refers to the d-axis current of the motor. This refers to the q-axis current of the motor. The back electromotive force coefficient of the motor; This refers to the q-axis current of the motor. This refers to the d-axis current of the motor. This refers to the motor's commanded speed. Voltage modulation coefficient; Bus voltage command value It is calculated using the following formula: ； in, This refers to the amplitude of the power supply voltage. Bus capacitor nominal voltage value, This is the safety margin set.

8. The method according to claim 1, characterized in that, The method further includes: Obtain the three-phase current value of the motor , , ; Based on the three-phase current of the motor , , The Clarke transform is used to obtain the motor current in the α and β axes of the two-phase stationary coordinate system. and ; Based on the rotor angle estimate Perform the Park transformation to obtain the actual current values ​​along the D and Q axes in the two-phase rotating coordinate system. , ; Based on the actual current values ​​of the D-axis and Q-axis , Voltage in a two-phase stationary coordinate system , and current , Calculate the estimated values ​​of the effective magnetic flux of the compressor motor in the α and β axis directions of the two-phase stationary coordinate system; The angular error is estimated based on the estimated values ​​of the effective magnetic flux in the α and β axis directions; Estimate the angle error based on the estimated value, and calculate the estimated rotor angle of the compressor motor. and the actual speed of the motor ; Based on the estimated rotor angle of the compressor motor and the actual speed of the motor Calculate the d-axis command current and the q-axis command current; Calculate the Q-axis given voltage value based on the d-axis command current and the q-axis command current. and the given voltage value of the D-axis ; Based on the estimated value of the motor rotor angle right and Perform the inverse Park transformation to obtain the voltage value in the fixed coordinate system. and ; according to and Perform the Clark inverse transform to obtain the three-phase voltage. , and ; Among them, the fourth duty cycle signal, the fifth duty cycle signal, and the sixth duty cycle signal are based on , and Sure.

9. The method according to claim 8, characterized in that, The actual current values ​​of the D-axis and Q-axis are used. , Voltage in a two-phase stationary coordinate system , and current , The estimated effective magnetic flux of the compressor motor in the α and β axes of the two-phase stationary coordinate system is calculated using the following formula: ； in, and These are the estimated values ​​of the effective magnetic flux of the motor in the α and β axis directions, respectively. and Let be the voltages along the α and β axes, respectively. and Let be the currents along the α and β axes, respectively, and R be the stator resistance. Here are the q-axis inductance parameters of the motor; The angular error is estimated based on the estimated values ​​of the effective magnetic flux in the α and β axes, and is calculated using the following formula: ； The step involves estimating the angle error based on the estimated value and calculating the estimated rotor angle of the compressor motor. and the actual speed of the motor It can be calculated using the following formula: ； in, and These are the proportional-integral parameters, This is the estimated value of the deviation angle. This represents the bandwidth of the speed low-pass filter; The estimated value based on the rotor angle of the compressor motor and the actual speed of the motor Calculate the d-axis command current and q-axis command current using the following formulas: ； in, Give the initial value of the current along the d-axis. The integral control coefficient, This is the d-axis command voltage. This is the q-axis command voltage. This is the DC bus voltage; ； in, and These are the proportional gain and integral gain for speed control, respectively. This is the commanded speed of the motor. Estimate the speed of the motor. express Integral over time.

10. A three-channel frequency converter drive circuit, characterized in that, The three-way frequency conversion drive circuit includes a rectifier sub-circuit, a correction sub-circuit, an inverter control sub-circuit, and a control module. The correction sub-circuit is a three-way interleaved PFC circuit. The input terminal of the rectifier circuit is electrically connected to an external AC power supply, the output terminal of the rectifier circuit is electrically connected to the input terminal of the correction circuit, the output terminal of the correction circuit is electrically connected to the input terminal of the inverter control circuit, the output terminal of the inverter control circuit is electrically connected to an external motor, and both the correction circuit and the inverter control circuit are communicatively connected to the control module.

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