A variable frequency drive method and variable frequency drive circuit

Abstract

This application provides a variable frequency drive method and a 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 acquired AC voltage, DC voltage, first sampling current, and second 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; 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 two circuits 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 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 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 dual-channel interleaved PFC circuit. Based on the acquired AC voltage, DC voltage, first sampling current, and second 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 collected third sampled 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, and second 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 and a third boost ratio coefficient based on the first boost ratio coefficient, the first sampling current, and the second sampling current. The control module obtains a first duty cycle signal and a second duty cycle signal based on the second boost ratio coefficient and the third boost ratio coefficient; The control module obtains a first control signal based on the first duty cycle signal, the second 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 third duty cycle signal, a fourth duty cycle signal, and a fifth duty cycle signal based on the DC voltage and the three-phase voltage. The control module generates a second control signal based on the third duty cycle signal, the fourth duty cycle signal, and the fifth 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 and / or second switching transistors 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 exceeds 10%, then control the duty cycle corresponding to the first switch and / or the second switch to increase by 10%. If the difference between the PWM target value and the actual output value corresponding to the first switch and / or the second switch is less than 10%, then the PWM target value is reached by increasing the actual difference.

[0009] Optionally, the method further includes: If the first sampling current is less than the PFC single-switch control threshold, the control module controls the first and second 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 and one output of the second switch to be turned off. When the first sampling current is greater than or equal to the PFC dual-open control threshold, the first and second switching transistors are controlled to output simultaneously.

[0010] Optionally, the method further includes: When the first and second switching transistors in the correction sub-circuit are both outputting simultaneously, the control module controls the other switching transistor to operate at a reduced derating when it detects that one of the switching transistors is damaged and overcurrent. In one of the processes of derating another switching transistor, the maximum operating frequency of the motor is reduced by half, and / or the maximum operating power of the motor is reduced by half.

[0011] Optionally, the method further includes: When the first and second switches in the correction sub-circuit output simultaneously, the two PFC carrier frequencies are the same, but their phases differ by 50%. The duty cycles of the first and second switches are automatically adjusted based on the current between the first and second 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; 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; 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 that is 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 ; The third, fourth, and fifth duty cycle signals 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.

[0014] 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.

[0015] In addition, to achieve the above objectives, this application also provides a frequency converter 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.

[0016] 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.

[0017] Optionally, the correction sub-circuit includes a first inductor, a second inductor, a first switching transistor, and a second switching transistor; The first end of the first inductor is electrically connected to the first end of the second inductor, the second end of the first inductor is electrically connected to the source of the first switching transistor, and 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 drains of the first and second switching transistors are both electrically connected to the fourth node, which is grounded.

[0018] 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.

[0019] Optionally, the correction sub-circuit further includes a fifth diode, a sixth diode, a first resistor, and a second resistor; The cathodes of the fifth diode and the sixth diode are both electrically connected to the third node; The anode of the fifth diode is electrically connected to the second terminal of the first inductor, and the anode of the sixth diode is electrically connected to the second terminal of the second 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.

[0020] Optionally, the inverter control sub-circuit includes a third switch, a fourth switch, a fifth switch, a sixth switch, a seventh switch, and an eighth switch. The source of the third switch, the source of the fourth switch, and the source of the fifth switch are all electrically connected to the fifth node. The drain of the third switch is electrically connected to the source of the sixth switch, and the drain of the third switch is also electrically connected to the U-phase voltage input terminal of the motor. 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 V-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 W-phase voltage input terminal of the motor. The drains of the sixth switch, the seventh switch, and the eighth switch are all electrically connected to the sixth node. The source of the sixth switching transistor is electrically connected to the U-phase voltage input terminal of the motor; The source of the seventh switch is electrically connected to the V-phase voltage input terminal of the motor. The source of the eighth switching transistor is electrically connected to the W-phase voltage input terminal of the motor.

[0021] Optionally, the frequency conversion drive circuit further includes a third resistor; The first end of the third resistor is grounded, and the second end of the third resistor is electrically connected to the sixth node.

[0022] 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 variable frequency drive circuit. The variable frequency drive method includes: a rectifier subcircuit 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 subcircuit, wherein the correction subcircuit is a dual-channel interleaved PFC circuit; a control module sending a first control signal to the correction subcircuit based on the acquired AC voltage, DC voltage, first sampling current, and second sampling current; the correction subcircuit 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 subcircuit; the control module sending a second control signal to the inverter control subcircuit based on the three-phase current, wherein the three-phase current is obtained by reconstructing the acquired third sampling current; and the inverter control subcircuit 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.

[0023] The variable frequency drive method provided in this application utilizes a dual-channel interleaved PFC circuit for power correction. When the power control is high, the current specification is reduced by operating the two circuits in parallel, eliminating the need to increase the inductor and saving circuit space. Furthermore, the variable frequency drive method rectifies the AC power signal through a rectifier circuit, corrects the power factor of the signal through a correction circuit, and drives the motor through an inverter control circuit. It improves the stability and reliability of the circuit by increasing the duty cycle by 10% at the power zero-crossing point. Fault-tolerant derating improves compatibility, and optimal system efficiency is achieved by adjusting the target bus voltage according to the actual motor speed. Attached Figure Description

[0024] 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.

[0025] 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 one of the waveform diagrams of the counting signal, driving signal, and current signal provided in the embodiments of this application; Figure 4 This is the second of the waveform diagrams of the counting signal, driving signal, and current signal provided in the embodiments of this application; Figure 5 This is the third waveform diagram of the counting signal, driving signal, and current signal provided in the embodiments of this application; Figure 6 This is the fourth waveform diagram of the counting signal, driving signal, and current signal provided in the embodiments of this application; Figure 7 This is a waveform diagram of the PWM signal provided in an embodiment of this application; Figure 8 This is a second schematic diagram of the structure of the frequency converter drive circuit provided in the embodiments 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.

[0026] 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; J1, First node; J2, Second node; J3, Third node; J4, Fourth node; J5, Fifth node; J6, Sixth node; L1, First inductor; L2, Second 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; EC, Energy storage capacitor; R1, First resistor; R2, Second resistor; R3, Third resistor. Detailed Implementation

[0027] The frequency conversion drive method provided in this application is applied to frequency conversion drive circuits. 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.

[0028] 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.

[0029] 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.

[0030] 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 the variable frequency drive circuit described above, 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 dual-channel interleaved PFC circuit.

[0031] 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 and second sampling current.

[0032] 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.

[0033] 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 third sampled current.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] The variable frequency drive method provided in this application utilizes a dual-channel interleaved PFC circuit for power correction. When the power control is high, the current specification is reduced by operating the two circuits in parallel, eliminating the need to increase the inductor and saving circuit space. Furthermore, the variable frequency drive method rectifies the AC power signal through a rectifier circuit, corrects the power factor of the signal through a correction circuit, and drives the motor through an inverter control circuit. It improves the stability and reliability of the circuit by increasing the duty cycle by 10% at the power zero-crossing point. Fault-tolerant derating improves compatibility, and optimal system efficiency is achieved by adjusting the target bus voltage according to the actual motor speed.

[0039] 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, and second 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 and a third boost ratio coefficient based on the first boost ratio coefficient, the first sampling current, and the second sampling current. The control module obtains a first duty cycle signal and a second duty cycle signal based on the second boost ratio coefficient and the third boost ratio coefficient; The control module obtains a first control signal based on the first duty cycle signal, the second duty cycle signal, and the AC voltage, and sends the first control signal to the correction sub-circuit.

[0040] 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.

[0041] In this embodiment, the control module collects the AC voltage output from the AC power supply. Start-up at midnight enables soft-start control.

[0042] Optionally, the method further includes, when the average value of the first sampled current is greater than or equal to a preset current, the control module sends a third control signal to cause the first switch and / or the second 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 exceeds 10%, then control the duty cycle corresponding to the first switch and / or the second switch to increase by 10%. If the difference between the PWM target value and the actual output value corresponding to the first switch and / or the second 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 and / or second switching transistors are allowed to start from the off state to the PWM output state at the power supply zero-crossing point. Further, when the first and / or second switching transistors 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: If the first sampling current is less than the PFC single-switch control threshold, the control module controls the first and second 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 and one output of the second switch to be turned off. When the first sampling current is greater than or equal to the PFC dual-open control threshold, the first and second switching transistors 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 adjusts the output current based on the AC power supply. Control the first and second switching transistors to turn off, or control one of the first and second switching transistors to output, or control both the first and second switching transistors to output simultaneously.

[0046] when When, control the first and second switching transistors to turn off; when When one of the first and second switching transistors is turned off, the other is turned off; when... At the same time, the first and second switching transistors are controlled to output simultaneously; in, and The threshold values ​​for single-on and double-on PFC control are set, and ;Optionally, It is 2A. It is 7A.

[0047] In this embodiment, when the control module controls one of the first and second switching transistors to output, the output with the shorter output time is determined based on the cumulative working time of the first and second switching transistors.

[0048] Optionally, the method further includes: When the first and second switching transistors in the correction sub-circuit are both outputting simultaneously, the control module controls the other switching transistor to operate at a reduced derating when it detects that one of the switching transistors is damaged and overcurrent. In one of the processes of derating another switching transistor, the maximum operating frequency of the motor is reduced by half, and / or the maximum operating power of the motor is reduced by half.

[0049] When the control module controls the output of the first and second switching transistors, if a faulty overcurrent is detected in one of them, only the undamaged one will be activated for derating operation. During the derating operation, the maximum operating frequency of the motor will be reduced to half of its original value, and / or the maximum operating power will be reduced to half of its original value.

[0050] Optionally, when one of the first and second 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 represents the instantaneous current of the first inductor. This represents the instantaneous current of the second inductor. This represents the boost ratio coefficient. This represents the average current of alternating current.

[0051] When the control module controls the output of the first and second switching transistors, if it detects that the temperature of the control module 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.

[0052] In this embodiment, when the first and second switching transistors output simultaneously, the two PFC carrier frequencies are the same, but their phases differ by 50%. The duty cycles of the first and second switching transistors are automatically adjusted based on the current between the first and second 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; 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.

[0054] in, , and These are preset coefficients.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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 third duty cycle signal, a fourth duty cycle signal, and a fifth duty cycle signal based on the DC voltage and the three-phase voltage. The control module generates a second control signal based on the third duty cycle signal, the fourth duty cycle signal, and the fifth duty cycle signal, and sends the second control signal to the inverter control sub-circuit.

[0059] 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.

[0060] Specifically, the third duty cycle signal, the fourth duty cycle signal, and the fifth 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 ; The third, fourth, and fifth duty cycle signals are based on , and Sure.

[0061] 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.

[0062] 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 .

[0063] ； ; in, Indicates the first current. This indicates the second current.

[0064] 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. , .

[0065] ; 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 the 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.

[0066] 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 value 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.

[0067] 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.

[0068] 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 speed of the motor. express Integral over time.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] The aforementioned three-phase duty cycle signal includes three pulse width signals, which are calculated and updated in each PWM cycle.

[0073] like Figure 7 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 within 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 7 As shown, therefore Control the upper and lower bridge arm switches of phase U.

[0074] Similarly Control the upper and lower bridge arm switches of phase V. Controls the upper and lower bridge arm switches of phase W. Three-phase. , , The duty cycle signal controls six PWM control signals (u, v, w) to generate an equivalent three-phase sinusoidal voltage, thereby driving the motor.

[0075] Please see Figure 8 ,like Figure 8 As shown, the 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 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.

[0076] 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.

[0077] 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.

[0078] Optionally, such as Figure 8 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.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] The frequency converter drive circuit provided in this application embodiment is designed as a dual-channel interleaved PFC circuit. This reduces the current specification by having two parallel circuits operating 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.

[0084] Please see Figure 2 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.

[0085] 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.

[0086] Please see Figure 2 Optionally, the correction sub-circuit includes a first inductor L1, a second inductor L2, a first switch K1, and a second switch K2; The first end of the first inductor L1 is electrically connected to the first end of the second inductor L2, the second end of the first inductor L1 is electrically connected to the source of the first switch K1, and 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 drain of the first switching transistor K1 and the drain of the second switching transistor K2 are both electrically connected to the fourth node J4, which is grounded.

[0087] Please see Figure 2 Optionally, the correction sub-circuit further includes a fifth diode D5, a sixth diode D6, a first resistor R1, and a second resistor R2; The cathodes of the fifth diode D5 and the sixth diode D6 are both 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, and the anode of the sixth diode D6 is electrically connected to the second terminal of the second inductor L2. 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.

[0088] The correction circuit in this embodiment includes a first inductor L1, a second inductor L2, a first switch K1, a second switch K2, a fifth diode D5, a sixth diode D6, a first resistor R1, and a second resistor R2.

[0089] It should be understood that the aforementioned first sampling current can be expressed as the current obtained by sampling at the first resistor R1. The second sampling current mentioned above can be expressed as the current obtained by sampling at the second resistor R2. .

[0090] It should be understood that in the embodiments of this application, the correction sub-circuit is designed as a dual-channel interleaved PFC circuit. The dual-channel interleaved PFC circuit includes a first channel PFC and a second channel PFC. The first channel PFC includes a first inductor L1, a first switch K1 and a fifth diode D5. The second channel PFC includes a second inductor L2, a second switch K2 and a sixth diode D6.

[0091] Please see Figures 3 to 6 , Figures 3 to 6 This is a waveform diagram of the counting signal, drive signal, and current signal provided in the embodiments of this application. It should be understood that when the first switch K1 outputs a high or low level with a certain duty cycle, it indicates that the first PFC is in the on state; when the first switch K1 is always off, it indicates that the first PFC is in the off state. When the second switch K2 outputs a high or low level with a certain duty cycle, it indicates that the second PFC is in the on state; when the second switch K2 is always off, it indicates that the second PFC is in the off state.

[0092] like Figure 3As shown, when both the first and second PFC channels are 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. .

[0093] like Figure 4 As shown, when the first PFC is in the ON state and the second PFC is in the OFF state, the current sampling time point is set to the middle position when the first PFC is high-level ON. At the current sampling time 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 value of the first resistor R1. And the current value of the first inductor L1 is calculated: .

[0094] like Figure 5 As shown, when the first PFC is off and the second PFC is on, the current sampling point is set to the middle position when the second PFC 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, and the current flowing through the first resistor R1 is calculated based on the collected voltage across the first resistor R1 and the resistance value of the first resistor R1. 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. .

[0095] like Figure 6 As shown, when both the first PFC and the second PFC are in the active state, the current sampling time point is set to the midpoint when the first PFC is high-level turned on, and the midpoint when the second PFC is high-level turned on. At the midpoint when the first PFC is high-level turned on, the voltage across the first resistor R1 is sampled, and the current flowing through the first resistor R1 is calculated based on the sampled voltage across R1 and the resistance value of R1. At the midpoint of the second PFC high-level turn-on current sampling point, the voltage across the second resistor R2 is collected, and the current flowing through the second resistor R2 is calculated based on the collected voltage across the second resistor R2 and the resistance value of the second resistor R2. And calculate the current value of the first inductor L1. .

[0096] Please see Figure 2 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.

[0097] 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.

[0098] Please see Figure 2 Optionally, the inverter control sub-circuit includes a third switch K3, a fourth switch K4, a fifth switch K5, a sixth switch K6, a seventh switch and an eighth switch K8; The source of the third switch K3, the source of the fourth switch K4, and the source of the fifth switch K5 are all electrically connected to the fifth node J5. The drain of the third switch K3 is electrically connected to the source of the sixth switch K6, and the drain of the third switch K3 is also electrically connected to the U-phase voltage input terminal of the motor. The drain of the fourth switch K4 is electrically connected to the source of the seventh switch, and the drain of the fourth switch K4 is also electrically connected to the V-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 W-phase voltage input terminal of the motor. The drains of the sixth switch K6, the seventh switch, and the eighth switch K8 are all electrically connected to the sixth node J6. The source of the sixth switch K6 is electrically connected to the U-phase voltage input terminal of the motor. The source of the seventh switch is electrically connected to the V-phase voltage input terminal of the motor. The source of the eighth switch K8 is electrically connected to the W-phase voltage input terminal of the motor.

[0099] The inverter control sub-circuit in this embodiment includes a third switch K3, a fourth switch K4, a fifth switch K5, a sixth switch K6, a seventh switch, and an eighth switch K8.

[0100] The source of the sixth switch K6 is electrically connected to the U-phase voltage input terminal of the motor, the source of the seventh switch is electrically connected to the V-phase voltage input terminal of the motor, and the source of the eighth switch K8 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.

[0101] Please see Figure 2 Optionally, the frequency conversion drive circuit further includes a third resistor R3; The first end of the third resistor R3 is grounded, and the second end of the third resistor R3 is electrically connected to the sixth node J6.

[0102] In this embodiment, the current at the third resistor R3 can be sampled to obtain the third sampled current, and then the third sampled current can be reconstructed to obtain the three-phase current.

[0103] 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 dual-channel interleaved PFC circuit. Based on the acquired AC voltage, DC voltage, first sampling current, and second 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 collected third sampled 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 according to claim 1, characterized in that, 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, 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 and a third boost ratio coefficient based on the first boost ratio coefficient, the first sampling current, and the second sampling current. The control module obtains a first duty cycle signal and a second duty cycle signal based on the second boost ratio coefficient and the third boost ratio coefficient; The control module obtains a first control signal based on the first duty cycle signal, the second 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 third duty cycle signal, a fourth duty cycle signal, and a fifth duty cycle signal based on the DC voltage and the three-phase voltage. The control module generates a second control signal based on the third duty cycle signal, the fourth duty cycle signal, and the fifth 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 and / or second switching transistors 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 exceeds 10%, then control the duty cycle corresponding to the first switch and / or the second switch to increase by 10%. If the difference between the PWM target value and the actual output value corresponding to the first switch and / or the second 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: If the first sampling current is less than the PFC single-switch control threshold, the control module controls the first and second 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 and one output of the second switch to be turned off. When the first sampling current is greater than or equal to the PFC dual-open control threshold, the first and second switching transistors are controlled to output simultaneously.

6. The method according to claim 1, characterized in that, The method further includes: When the first and second switching transistors in the correction sub-circuit are both outputting simultaneously, the control module controls the other switching transistor to operate at a reduced derating when it detects that one of the switching transistors is damaged and overcurrent. In one of the processes of derating another switching transistor, the maximum operating frequency of the motor is reduced by half, and / or the maximum operating power of the motor is reduced by half.

7. 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, the two PFC carrier frequencies are the same, but their phases differ by 50%. The duty cycles of the first and second switches are automatically adjusted based on the current between the first and second 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; 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; 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 that is 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 ; The third, fourth, and fifth duty cycle signals 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 frequency converter drive circuit, characterized in that, The 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 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.

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