Double-fan air conditioner and control method for single inverter and double motors of double-fan air conditioner

Abstract

The invention discloses a double-fan air conditioner and a single-inverter and double-motor control method thereof. The control method comprises the steps that three-phase currents of a master motor and a slave motor which are the same in type and connected to the same inverter are collected, Park conversion is conducted to obtain d-axis components and q-axis components, and the observation angular frequency of the master motor is obtained through a position observer; calculating error angles of the master motor and the slave motor, controlling errors of the error angles through feedback, outputting a product of a motor speed difference reference value and the error angles, and obtaining a d-axis component compensation value idcomp through PI control; inputting a main motor angular frequency reference value in a speed control loop, outputting d-axis and q-axis component reference values of the current of the main motor, and compensating the d-axis component reference value of the current of the main motor with idcomp to obtain a final d-axis component reference value of the current of the main motor; and inputting the q-axis component reference value and the q-axis component reference value into a current control loop, generating a duty ratio signal of pulse width modulation, and controlling a master motor and a slave motor to rotate a voltage vector. According to the invention, through d-axis current injection compensation, system stability is realized.

Description

Technical Field

[0001] This invention belongs to the field of air conditioning technology, and more specifically, relates to a dual-fan air conditioner and a control method for a single inverter and dual motors. Background Technology

[0002] Currently, dual-fan air conditioning systems require both motors to operate at the same speed. However, this presents several challenges in practical applications, including but not limited to: 1. High cost: Traditional control methods use two inverters to control the two motors separately, resulting in high drive control costs; 2. System susceptibility to malfunction: If a traditional control strategy is used for dual-motor control with a single inverter, the inverter can only generate corresponding drive signals based on the main motor's speed and rotor position. The electrical signals of the slave motors are not involved in the control, and the slave motor current cannot be directly controlled. Due to load imbalance and motor consistency issues, the slave motor speeds can diverge, leading to system malfunction.

[0003] For example, but not limited to, prior art document 1 (CN118713526A) discloses a control method for a single-inverter dual permanent magnet synchronous motor. This method directly connects an additional motor in parallel on a single-motor drive platform, using only existing hardware. An observer is designed to estimate the position and speed information of the parallel motor for use in the dual-parallel motor controller design. The adaptive observer needs to obtain the rotor speed and position information of the master motor through an encoder. Prior art document 2 (CN119582670A) discloses a backlash-eliminating control method and device for a single-inverter dual-motor parallel system based on an extended state observer. Through the design and application of the extended state observer, it effectively compensates for disturbances caused by backlash and improves the system's control performance. The rotor positions of both the master and slave motors are obtained through encoders. However, both prior art document 1 and prior art document 2 are for applications with position sensors, and their control algorithms are relatively complex. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a control method for a dual-fan air conditioner and its single-inverter dual-permanent magnet synchronous motor. The method employs a control approach that injects compensation into the d-axis current of the main motor. The compensation signal includes the speed and rotor position of the slave motor, thereby achieving indirect control of the slave motor and ensuring system stability. This solves the technical problem that traditional control strategies for single-inverter dual-motor control can cause the slave motor speed to diverge, leading to system malfunction.

[0005] The present invention adopts the following technical solution.

[0006] The first aspect of the present invention provides a control method for a single inverter with two motors, wherein the two motors are of the same model, namely a master motor and a slave motor, and are both connected to the three-phase AC output terminal of the same single inverter. The control method includes the following steps:

[0007] The three-phase currents of the master and slave motors are collected, and the Park transform is performed on the three-phase currents to obtain the d-axis and q-axis components. The position observer is used to obtain the observed angular frequency of the master motor.

[0008] The error angle θ between the master and slave motors is calculated based on the d-axis and q-axis components and the observed angular frequency of the master motor. d Error angle θ is controlled by feedback. d Error Δθ d Reference value for the difference in output motor speed Error angle θ d Reference value of the difference between motor speed and speed The product of these components is used to obtain the d-axis component compensation value i through PI control. dcomp ;

[0009] The speed control loop inputs the main motor angular frequency reference value and outputs the d-axis and q-axis component reference values ​​of the main motor current to obtain the d-axis component compensation value i. dcomp The d-axis component reference value of the compensated main motor current is used to obtain the final reference value of the d-axis component of the main motor current.

[0010] The final reference values ​​of the d-axis component and q-axis component of the main motor current are input into the current control loop to generate a pulse width modulated duty cycle signal, which controls the rotational voltage vectors of the main and slave motors.

[0011] Preferably, the error angle θ is controlled by feedback. d Error Δθ d Reference value for the difference in output motor speed include:

[0012] Reference value for motor speed difference Integrate to obtain a reference value for the error angle. Error angle θ d Reference value of error angle The difference is the error angle θ. d Error Δθ d For the error Δθ d Perform PI control to obtain a reference value for the motor speed difference.

[0013] Preferably, the calculation of the master and slave motor error angle θ based on the d-axis components, q-axis components, and the observed angular frequency of the master motor is... d It can be expressed by the following formula:

[0014]

[0015] In the formula:

[0016] i d1i q1 The d-axis and q-axis components of the main motor current, i d2 i q2 These are the d-axis and q-axis components of the motor current.

[0017] R s L s , λ f The resistance, inductance, and flux linkage of the master motor and slave motor;

[0018] ω r The main motor's observed angular frequency,

[0019] θ d The main and secondary motor error angles.

[0020] Preferably, the d-axis and q-axis components of the motor voltage output by the current control loop are inversely transformed and then fed into the SVPWM stage to generate the duty cycle signal for controlling the inverter.

[0021] Preferably, obtaining the observed angular frequency of the main motor using a position observer includes:

[0022] The d- and q-axis components of the motor voltage and the main motor current are input into the position observer to obtain the actual observed angular frequency ω of the main motor. r .

[0023] A second aspect of the present invention provides a dual-fan air conditioner, comprising: a controller, an inverter, and two motors, namely a main motor and a slave motor, wherein the input terminals of the two motors are connected to the three-phase AC output terminal of the same single inverter, and the controller performs the control method as described in the first aspect.

[0024] Preferably, the motor is a permanent magnet synchronous motor.

[0025] Preferably, the dual-fan air conditioner further includes: a rectifier and a filter capacitor;

[0026] The rectifier converts the three-phase AC power into DC power through uncontrolled rectification. After passing through the filter capacitor C1, the DC power is connected to the input terminal of the inverter.

[0027] A third aspect of the present invention provides an electronic device including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the computer program, when loaded onto the processor, implements the control method according to the first aspect.

[0028] A fourth aspect of the present invention provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the control method according to the first aspect.

[0029] Compared with existing technologies, the beneficial effects of this invention include at least the following: indirect control of the slave motor can be achieved through d-axis current injection compensation, thus ensuring system stability; and reducing the number of inverters lowers controller costs. Specifically, this invention employs a single-inverter control strategy for dual motors, using a compensation injection method into the d-axis current of the main motor for single-inverter dual-motor control. Since the compensation information includes the speed and rotor position information of the slave motor, indirect control of the slave motor can be achieved, thus ensuring system stability. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of a single inverter dual-motor topology provided according to an embodiment of the present invention;

[0031] Figure 2 This is a schematic diagram of the master-slave motor dq-axis coordinate system provided according to an embodiment of the present invention;

[0032] Figure 3 This is a schematic diagram of d-axis compensation current control provided according to an embodiment of the present invention;

[0033] Figure 4 This is a system control block diagram provided according to an embodiment of the present invention;

[0034] Figure 5 This is a schematic diagram comparing the effects before and after compensation according to an embodiment of the present invention. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of this invention. The described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the spirit of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this invention.

[0036] Embodiment 1 of the present invention provides a control method for a single-inverter dual permanent magnet synchronous motor, such as... Figure 1 As shown, two permanent magnet synchronous motors are connected to the three-phase AC output terminal of the same single inverter, serving as the master motor and slave motor, respectively. The control method includes the following steps:

[0037] Step 1: Acquire the three-phase currents of the master and slave motors, perform Park transform on the three-phase currents to obtain the d-axis and q-axis components, and use a position observer to obtain the observed angular frequency ω of the master motor. r .

[0038] Step 2: As Figure 4 As shown, the d-axis and q-axis components of the currents of the master and slave motors and the observed angular frequency ω of the master motor are...r Substituting this into the d-axis current injection compensation circuit, we obtain the d-axis component compensation value i of the main motor current. dcomp ,like Figure 3 As shown, the d-axis current injection compensation stage calculates the rotor angle difference between the master and slave motors, i.e., the error angle θ, based on the input parameters. d The error angle θ is controlled by PI. d Error Δθ d It can output a reference value for the motor speed difference. Error angle θ d Reference value of the difference between motor speed and speed The product of these two values, when processed by PI control, yields the d-axis component compensation value i related to the motor speed and rotor position. dcomp .

[0039] Among them, the reference value for the motor speed difference The reference value of the error angle can be obtained by integration. Error angle θ d Reference value of error angle The difference is the error angle θ. d Error Δθ d .

[0040] The calculation of the rotor angle difference between the master and slave motors, i.e., the error angle θ, is described. d It can be expressed as follows: (1)

[0041]

[0042] In the formula:

[0043] i d1 i q1 These are the d-axis and q-axis components of the main motor current, i d2 i q2 These are the d-axis and q-axis components of the motor current, respectively, obtained by performing Park transform on the master and slave motor currents acquired by the current sensor.

[0044] R s L s , λ f The resistance, inductance, and flux linkage of the master and slave motors can be obtained from the motor datasheet.

[0045] ω r The observed angular frequency of the main motor can be obtained through the main motor state observer.

[0046] like Figure 2 As shown, θ d The difference in rotor angle between the motor and the main motor, i.e., the error angle, is expressed by the following formula (2):

[0047] θ d =θ2-θ1 (2)

[0048] In the formula:

[0049] θ d θ2 and θ1 are the rotor angle difference between the slave motor and the master motor, the rotor angle of the slave motor, and the rotor angle of the master motor, respectively.

[0050] The error angle θ d The calculation formula can be obtained through the following steps, specifically including:

[0051] The voltage equations for the two motors are established and expressed as follows (3):

[0052]

[0053] In the formula:

[0054] v d1 v q1 These are the d-axis and q-axis components of the main motor voltage.

[0055] Transforming formula (3), we obtain the relationship between the slave motor current and the main motor current, expressed as formulas (4) and (5) below:

[0056]

[0057] Transforming formulas (4) and (5), we obtain the following formulas (6) and (7):

[0058]

[0059] By combining formulas (6) and (7), the difference in rotor angle between the motor and the main motor can be solved to obtain the expression for formula (1).

[0060] Step 3: Input the reference value of the main motor angular frequency into the speed control loop, and output the reference values ​​of the d-axis and q-axis components of the main motor current into the speed control loop. Compensate the reference value of the d-axis component of the main motor current with the compensation value of the d-axis component of the main motor current obtained in Step 2 to obtain the final reference value of the d-axis component of the main motor current.

[0061] Step 4: Input the final reference value of the d-axis component and the reference value of the q-axis component of the main motor current into the current control loop to generate a pulse width modulated duty cycle signal to control the rotational voltage vector of the main and slave motors.

[0062] The d-axis and q-axis components of the motor voltage output by the current control loop are inversely transformed and then fed into the SVPWM stage to generate the duty cycle signal for controlling the inverter.

[0063] The process of obtaining the observed angular frequency of the main motor using a position observer includes: inputting the d-axis and q-axis components of the motor voltage and the main motor current into the position observer to obtain the actual observed angular frequency ω of the main motor. r .

[0064] Embodiment 2 of the present invention provides a dual-fan air conditioner, including: motor 1, motor 2, inverter, rectifier, and controller;

[0065] Both motor 1 and motor 2 are dual permanent magnet synchronous motors, and both are connected to the three-phase output terminal of the inverter. That is to say, the rotational voltage vector V of motor 1 and motor 2 s For the purpose of clearly introducing the technical solution of the present invention, motor 1 is the master motor and motor 2 is the slave motor. It can be understood that using either of the two dual permanent magnet synchronous motors as the master motor and the other as the slave motor falls within the scope of the present invention. The configuration of motors 1 and 2 as master and slave is only an example but not a limitation.

[0066] The three-phase input terminal of the rectifier is connected to the three-phase power supply, and the DC output terminal of the rectifier is connected to the DC input terminal of the inverter via the filter capacitor C1.

[0067] The controller performs the control method as described in Example 1.

[0068] Embodiment 3 of the present invention provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the computer program is loaded onto the processor, it implements the control method described in Embodiment 1.

[0069] Embodiment 4 of the present invention provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the control method according to Embodiment 1.

[0070] like Figure 5 As shown in the figure, the comparison between the master and slave motor speeds and currents before and after using d-axis current injection compensation is illustrated. It can be seen from the figure that with the traditional control strategy, as the slave motor speed increases, the motor exhibits speed oscillations, eventually leading to system instability. However, with the control strategy proposed in this paper, the speed difference between the master and slave motors is zero, the master and slave motor currents are identical, and the system operates stably.

[0071] It is worth noting that in the embodiments of the present invention, "steps + numbers" is only an expression for clearly describing a specific implementation method of a dual-fan air conditioner and its single inverter dual-motor control method, and is not an absolute restriction on the order of the steps. Under the guidance of the core concept of the present invention, changing the order of these steps to obtain the same or similar technical effects all fall within the scope of the present invention.

[0072] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention.

Claims

1. A control method for a single inverter and two motors, characterized in that, The two motors are of the same model, designated as the master motor and slave motor, respectively, and are both connected to the three-phase AC output terminal of the same single inverter. The control method includes the following steps: The three-phase currents of the master and slave motors are collected, and the Park transform is performed on the three-phase currents to obtain the d-axis and q-axis components. The position observer is used to obtain the observed angular frequency of the master motor. The error angle θ between the master and slave motors is calculated based on the d-axis and q-axis components and the observed angular frequency of the master motor. d Error angle θ is controlled by feedback. d Error Δθ d Reference value for the difference in output motor speed Error angle θ d Reference value of the difference between motor speed and speed The product of these components is used to obtain the d-axis component compensation value i through PI control. dcomp ; The speed control loop inputs the main motor angular frequency reference value and outputs the d-axis and q-axis component reference values ​​of the main motor current to obtain the d-axis component compensation value i. dcomp The d-axis component reference value of the compensated main motor current is used to obtain the final reference value of the d-axis component of the main motor current. The final reference values ​​of the d-axis component and q-axis component of the main motor current are input into the current control loop to generate a pulse width modulated duty cycle signal, which controls the rotational voltage vectors of the main and slave motors.

2. The control method for a single inverter with dual motors according to claim 1, characterized in that: The error angle θ is controlled by feedback. d Error Δθ d Reference value for the difference in output motor speed include: Reference value for motor speed difference Integrate to obtain a reference value for the error angle. Error angle θ d Reference value of error angle The difference is the error angle θ. d Error Δθ d For the error Δθ d Perform PI control to obtain a reference value for the motor speed difference.

3. The control method for a single inverter with dual motors according to claim 1, characterized in that: The error angle θ between the master and slave motors is calculated based on the d-axis and q-axis components and the observed angular frequency of the master motor. d It can be expressed by the following formula: In the formula: i d1 i q1 The d-axis and q-axis components of the main motor current, i d2 i q2 These are the d-axis and q-axis components of the motor current. R s L s , λ f The resistance, inductance, and flux linkage of the master motor and slave motor; ω r The main motor's observed angular frequency, θ d The main and secondary motor error angles.

4. The control method for a single inverter with dual motors according to claim 1, characterized in that: The d-axis and q-axis components of the motor voltage output by the current control loop are inversely transformed and then fed into the SVPWM stage to generate the duty cycle signal for controlling the inverter.

5. The control method for a single inverter with dual motors according to claim 4, characterized in that: The method of obtaining the observed angular frequency of the main motor using a position observer includes: The d- and q-axis components of the motor voltage and the main motor current are input into the position observer to obtain the actual observed angular frequency ω of the main motor. r .

6. A dual-fan air conditioner, characterized in that, include: The system comprises a controller, an inverter, and two motors, designated as a master motor and a slave motor, respectively. The input terminals of both motors are connected to the three-phase AC output terminal of the same single inverter, and the controller performs the control method as described in any one of claims 1 to 5.

7. A dual-fan air conditioner according to claim 6, characterized in that: The motor is a permanent magnet synchronous motor.

8. A dual-fan air conditioner according to claim 6 or 7, characterized in that: The dual-fan air conditioner also includes: a rectifier and a filter capacitor; The rectifier converts the three-phase AC power into DC power through uncontrolled rectification. After passing through the filter capacitor C1, the DC power is connected to the input terminal of the inverter.

9. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the computer program is loaded into the processor, it implements the control method according to any one of claims 1 to 5.

10. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, it implements the control method according to any one of claims 1 to 5.

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