Permanent magnet synchronous motor control method, air conditioner and storage medium

Abstract

The invention provides a permanent magnet synchronous motor control method, an air conditioner and a storage medium. The method comprises the steps that a permanent magnet synchronous motor is controlled to operate according to a preset motor current-frequency ratio; when the given current and the given rotation frequency meet the condition of switching rotation speed closed-loop estimation operation, the given current is controlled to be gradually reduced at a preset amplitude, and a direct-axis estimation counter electromotive force amplitude and a quadrature-axis estimation counter electromotive force amplitude under the estimation rotation coordinate system after the given current is reduced each time are obtained; and when the direct-axis estimated counter electromotive force amplitude is equal to the quadrature-axis estimated counter electromotive force amplitude, switching to rotating speed closed-loop estimation operation. Meanwhile, the given rotation frequency is corrected by adopting an electromagnetic power high-frequency component. By applying the permanent magnet synchronous motor control method, speed smoothing of switching from motor current-frequency ratio control to rotating speed closed-loop estimation control can be realized in both the light-load state and the heavy-load state of the motor. And by adopting the frequency correction method disclosed by the invention, the electromagnetic torque oscillation is smaller, and the stability margin is more sufficient.

Description

Technical Field

[0001] The present invention relates to the technical field of permanent magnet synchronous motors, and in particular, to a permanent magnet synchronous motor control method, an air conditioner using the permanent magnet synchronous motor control method, and a computer-readable storage medium using the permanent magnet synchronous motor control method. Background Art

[0002] At present, variable frequency air conditioner outdoor compressors and fans generally use permanent magnet synchronous motors. Due to cost constraints and restrictions on the use environment, the motors generally operate without position sensors. In medium and high speed situations, an estimation method based on back-EMF can be used. The back-EMF estimation method can be based on a stationary coordinate system or a rotating coordinate system. The rotating coordinate system estimation method has the advantages of simple implementation and small estimation signal lag at high speed. However, when the motor is in a low speed or stationary state, the back-EMF signal is small and the signal-to-noise ratio is low, so the back-EMF estimation method cannot be used. Generally, the motor current-to-frequency ratio (I / F) control is used to make the motor run to a certain speed and then switch to back-EMF estimation (speed closed-loop estimation) operation, but the switching process is difficult to adapt to light load and heavy load, so that the switching speed in the two states is smooth and reliable.

[0003] In addition, in some special occasions, I / F control is required to run at a high speed. For example, the outdoor fan has a high negative speed under the action of external wind. At this time, it is necessary to use I / F to drag from negative speed to positive speed. The frequency of the rotating vector under I / F control is given by the controller in an open loop, which will cause the motor rotor speed to oscillate. The higher the speed, the more obvious it is. In severe cases, there will be a large difference between the given rotating frequency and the actual motor frequency, which will lead to loss of control.

[0004] Therefore, a more optimized permanent magnet synchronous motor control method needs to be considered. Summary of the invention

[0005] The first object of the present invention is to provide a permanent magnet synchronous motor control method that can achieve speed smoothing by switching from motor current-frequency ratio control to speed closed-loop estimation control under both light-load and heavy-load conditions of the motor.

[0006] A second object of the present invention is to provide an air conditioner that can achieve speed smoothing by switching from motor current-to-frequency ratio control to speed closed-loop estimation control under both light-load and heavy-load conditions of the motor.

[0007] A third object of the present invention is to provide a computer-readable storage medium that can achieve speed smoothing by switching from motor current-to-frequency ratio control to speed closed-loop estimation control under both light-load and heavy-load conditions of the motor.

[0008] In order to achieve the above-mentioned first purpose, the permanent magnet synchronous motor control method provided by the present invention includes: controlling the operation of the permanent magnet synchronous motor with a preset motor current-frequency ratio; when the given current and the given rotation frequency meet the conditions for switching the speed closed-loop estimation operation, controlling the given current to be gradually reduced with a preset amplitude, and obtaining the direct-axis estimated back-EMF amplitude and the cross-axis estimated back-EMF amplitude in the estimated rotating coordinate system after each reduction of the given current; when the direct-axis estimated back-EMF amplitude and the cross-axis estimated back-EMF amplitude are equal, switching to the speed closed-loop estimation operation.

[0009] It can be seen from the above scheme that the permanent magnet synchronous motor control method of the present invention gradually reduces the given current amplitude in the process of switching from motor current-frequency ratio control to speed closed-loop estimation control, and at the same time judges the direct-axis estimated back-electromotive force amplitude and the quadrature-axis estimated back-electromotive force amplitude. When the two are equal, it switches to speed closed-loop estimation operation, thereby making the speed switching smooth under heavy load and light load conditions and having good adaptability.

[0010] In a further embodiment, the given current and the given rotational frequency satisfy the conditions for switching the speed closed-loop estimation operation, including: the given current reaches a preset current and the given rotational frequency reaches a preset frequency.

[0011] It can be seen that when the given current reaches the preset current and the given rotation frequency reaches the preset frequency, it means that the motor current-frequency ratio control stage is in a stable state, and the speed closed-loop estimation operation switching can be performed to ensure the stability of the switching.

[0012] In a further scheme, after controlling the given current to gradually decrease with a preset amplitude, before obtaining the direct-axis estimated back-electromotive force and the quadrature-axis estimated back-electromotive force amplitude in the estimated rotating coordinate system after each reduction of the given current, it also includes: confirming that the given current after reduction is greater than the preset minimum current value.

[0013] In a further solution, when it is confirmed that the reduced given current is greater than the preset minimum current value, if the reduced given current is less than or equal to the preset minimum current value, the speed closed-loop estimation operation is switched.

[0014] It can be seen that in order to avoid the switching out of control due to the current being too small, it is necessary to confirm that the given current after the reduction is greater than the preset minimum current value before the next adjustment. If the given current after the reduction is less than or equal to the preset minimum current value, it will directly switch to the speed closed-loop estimation operation to ensure the stability of the operation.

[0015] In a further scheme, the step of obtaining the direct-axis estimated back EMF amplitude and the cross-axis estimated back EMF amplitude in the estimated rotating coordinate system after each reduction of the given current includes: using a back EMF observer to obtain the direct-axis estimated back EMF and the cross-axis estimated back EMF, respectively obtaining the absolute values ​​of the direct-axis estimated back EMF and the cross-axis estimated back EMF, and obtaining the direct-axis estimated back EMF amplitude and the cross-axis estimated back EMF amplitude.

[0016] It can be seen that by acquiring the absolute values ​​of the direct-axis estimated back EMF and the quadrature-axis estimated back EMF respectively, the amplitude of the direct-axis estimated back EMF and the amplitude of the quadrature-axis estimated back EMF can be confirmed.

[0017] In a further solution, the step of controlling the operation of the permanent magnet synchronous motor with a preset motor current-frequency ratio includes: using the high-frequency component of the electromagnetic power to correct the original given rotation frequency to obtain the given rotation frequency.

[0018] It can be seen that in the motor current-frequency ratio control stage, the magnitude of the electromagnetic torque is proportional to the cosine of the angle difference Δθ between the given rotating coordinate and the actual rotating coordinate, and the actual motor speed will always affect the magnitude of Δθ, thereby affecting the electromagnetic torque. The change of the electromagnetic torque does not go through any adjustment process, and the damping coefficient is extremely small. When the load fluctuates, it is very easy to cause the motor speed and electromagnetic torque to oscillate. The peak value of Δθ during the oscillation process is easy to exceed the stable range, causing the motor current-frequency ratio control stage to lose control. Therefore, in order to increase the damping coefficient of the electromagnetic torque dynamic process, it is necessary to use the high-frequency component of the electromagnetic power to correct the original given rotation frequency, thereby avoiding the oscillation of the power angle, and will not cause loss of control due to the peak value of the oscillation exceeding the stable range of the power angle, thereby enhancing stability.

[0019] In a further embodiment, the given rotation frequency is obtained by the following formula: in, is the original given rotation frequency, is the frequency correction, ΔTe is the fluctuation component of the electromagnetic torque, kp is the gain coefficient; △Pem is the fluctuation component of the electromagnetic power; p is the number of motor poles.

[0020] In a further embodiment, the electromagnetic power fluctuation component is obtained by the following formula:

[0021] ΔPem=Pem-Pem_LPF, Among them, U α , U β is the voltage in the stationary coordinate system, I α , I β is the current in the stationary coordinate system, is the low-pass filter transfer function, and Rs is the motor phase resistance.

[0022] It can be seen that by using electromagnetic power to perform frequency correction on the electromagnetic torque waveform, the oscillation duration is shorter, the electromagnetic torque converges to the load torque faster, the oscillation peak is smaller, and the stability is higher.

[0023] In order to achieve the second objective of the present invention, the present invention provides an air conditioner including a processor and a memory, wherein the memory stores a computer program, and when the computer program is executed by the processor, the steps of the above-mentioned permanent magnet synchronous motor control method are implemented.

[0024] In order to achieve the third objective of the present invention, the present invention provides a computer-readable storage medium on which a computer program is stored. When the computer program is executed by a controller, the steps of the above-mentioned permanent magnet synchronous motor control method are implemented. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a flow chart of an embodiment of a permanent magnet synchronous motor control method of the present invention.

[0026] Figure 2 It is a schematic diagram of estimated rotation coordinates and actual rotation coordinates in an embodiment of the permanent magnet synchronous motor control method of the present invention.

[0027] Figure 3 It is a waveform diagram of a given current switched at various stages when the motor is in a heavy-load state in an embodiment of the permanent magnet synchronous motor control method of the present invention.

[0028] Figure 4 It is a waveform diagram of a given current switched at various stages when the motor is in a light-load state in an embodiment of the permanent magnet synchronous motor control method of the present invention.

[0029] Figure 5 It is a schematic diagram of the electromagnetic torque waveform without frequency correction when the motor speed is 400 rpm in the embodiment of the permanent magnet synchronous motor control method of the present invention.

[0030] Figure 6 It is a schematic diagram of the electromagnetic torque waveform of conventional frequency correction using electric power when the motor speed is 400 rpm in the embodiment of the permanent magnet synchronous motor control method of the present invention.

[0031] Figure 7 It is a schematic diagram of an electromagnetic torque waveform when the electromagnetic power is used for frequency correction when the motor speed is 400 rpm in an embodiment of the permanent magnet synchronous motor control method of the present invention.

[0032] Figure 8 It is a schematic diagram of a current waveform obtained without frequency correction when the air conditioner outdoor fan is in a headwind state in an embodiment of the permanent magnet synchronous motor control method of the present invention.

[0033] Fig. 9 It is a schematic diagram of a current waveform obtained after frequency correction based on electromagnetic power when the air conditioner outdoor fan is in a headwind state in an embodiment of the permanent magnet synchronous motor control method of the present invention.

[0034] The present invention is further described below in conjunction with the accompanying drawings and embodiments. DETAILED DESCRIPTION

[0035] Permanent magnet synchronous motor control method embodiment:

[0036] The permanent magnet synchronous motor control method of the present invention is a computer program applied to an air conditioner and is used to control the permanent magnet synchronous motor.

[0037] like Figure 1 As shown, in this embodiment, when the permanent magnet synchronous motor control method is working, step S1 is first executed to control the operation of the permanent magnet synchronous motor with a preset motor current-frequency ratio. The permanent magnet synchronous motor is controlled with the motor current-frequency ratio at startup, and is controlled with the preset motor current-frequency ratio, wherein the preset motor current-frequency ratio can be set according to different speed requirements.

[0038] When the permanent magnet synchronous motor is controlled to run in the motor current-frequency ratio mode, step S2 is executed to determine whether the given current and the given rotation frequency meet the conditions for switching the speed closed-loop estimation operation. When the permanent magnet synchronous motor is started, the permanent magnet synchronous motor needs to be controlled in the motor current-frequency ratio mode and needs to reach a certain speed before switching to the speed closed-loop estimation operation stage. In order to confirm the timing of the switch, it is necessary to confirm that the conditions for switching the speed closed-loop estimation operation are met.

[0039] In this embodiment, the given current and the given rotation frequency satisfy the conditions for switching the speed closed-loop estimation operation, including: the given current reaches the preset current and the given rotation frequency reaches the preset frequency. When the given current reaches the preset current and the given rotation frequency reaches the preset frequency, it means that the motor current-frequency ratio control stage is in a stable state, and the motor speed reaches the preset speed, and the speed closed-loop estimation operation can be switched, thereby ensuring the stability of the switching.

[0040] In order to smoothly switch between the motor current-to-frequency ratio control phase and the speed closed-loop estimation operation phase, the switching process needs to be controlled. In order to better illustrate the implementation principle of the present invention, the principle of this solution is described below.

[0041] The voltage equation of the permanent magnet synchronous motor in the actual rotating coordinate system is as follows:

[0042]

[0043] Where Rs is the motor phase resistance, Id is the direct axis current, Iq is the quadrature axis current, Ud is the direct axis voltage, Uq is the quadrature axis voltage, Ld is the direct axis inductance, Lq is the quadrature axis inductance, w is the motor angular velocity, and E is the motor back electromotive force. When there is an angle difference Δθ between the estimated rotating coordinates and the actual rotating coordinates, such as Figure 2 shown.

[0044] The voltage equation of the permanent magnet synchronous motor in the estimated rotating coordinate system is as follows:

[0045]

[0046] in, Represents x (such as AC and DC voltage and current) in The quantity of the coordinate system, represents the estimated speed, Ed is the motor back electromotive force The component on the axis, Eq is the motor back EMF The components on the axis, the equation is as follows:

[0047] In medium and high speed applications, based on the estimated voltage equation in the rotating coordinate system, the observer calculates Ed and Ed, and then estimates the speed through the phase-locked loop. The rotor position is obtained by integrating again. This process is also called speed closed-loop estimation. The tracking goal of the phase-locked loop is to make Ed converge to 0. At this time, Δθ also converges to 0, so the estimated rotation coordinates coincide with the actual rotation coordinates, thus achieving the goal of rotor position estimation.

[0048] Under the motor current-to-frequency ratio control, the given rotating coordinates can be regarded as estimated rotating coordinates. There is always an angle difference Δθ between the given rotating coordinates and the actual rotating coordinates. This Δθ is the power angle. According to the power angle self-balancing principle, when Δθ is in the range of 0 to π (Δθ is positive when the given rotating coordinate lags behind the actual rotating coordinate), the current-to-frequency ratio control stage can operate stably. Under the premise of stable operation of the current-to-frequency ratio control stage, it can be considered that the actual motor speed is equal to the given rotating vector speed, and the value in the observer equation can be Using a given rotating vector frequency as input, the observer can obtain Ed and Eq, and the calculated Ed is always non-zero. Therefore, whether Ed tends to 0 is the essential difference between closed-loop estimation and flow-frequency ratio control.

[0049] From the above analysis of speed closed-loop estimation and flow-to-frequency ratio control, it can be concluded that the essence of the switching process between the motor's flow-to-frequency ratio control and the speed closed-loop estimation control is the process of Δθ converging to 0, which is also the process of Ed converging to 0. If Δθ changes too much before and after the switching, it will bring a large speed shock to the switching process. Therefore, in order to make the switching process smooth, Δθ should be as small as possible in the flow-to-frequency ratio control stage. In the flow-to-frequency ratio control stage, the electromagnetic torque expression is as follows:

[0050] Where Kt is the motor torque constant. When the load torque is constant and Δθ is within the stable range, according to the power angle self-balancing principle, if The decrease in the electromagnetic torque causes the motor speed to decrease, which in turn causes the electromagnetic torque to increase, thus reaching a new balance. Decrease to make Δθ approach 0 as much as possible. However, if Δθ is too small, it is easy for the flow-to-frequency ratio control stage to be at the edge of the stable interval, and the stable domain is insufficient. Considering the above, Δθ should be around 45° before switching in the flow-to-frequency ratio control stage. In this way, the stability of the flow-to-frequency ratio control stage can be guaranteed, and at the same time, Δθ before and after switching can be avoided. Moreover, when Δθ is 45°, abs(Ed)=abs(Eq), and switching can be performed through simple judgment, which is simple to implement and avoids obtaining Δθ by calculating the inverse tangent of Ed, Eq.

[0051] Based on the above principle, when executing step S2, if the given current and the given rotation frequency do not meet the conditions for switching the speed closed-loop estimation operation, then continue to execute step S2 for continuous detection. When the given current and the given rotation frequency meet the conditions for switching the speed closed-loop estimation operation, execute step S3 to control the given current to decrease by a preset amplitude. The preset amplitude can be preset according to experimental data. By controlling the given current to decrease by a preset amplitude, Δθ is made to approach 45°.

[0052] After the given current is controlled to decrease by the preset amplitude, step S4 is executed to determine whether the given current after the decrease is greater than the preset minimum current value. In order to avoid the switching out of control due to the current being too small, it is necessary to confirm that the given current after the decrease is greater than the preset minimum current value before the next adjustment is performed.

[0053] If it is confirmed that the given current after reduction is greater than the preset minimum current value, step S5 is executed to obtain the direct-axis estimated back EMF amplitude and the cross-axis estimated back EMF amplitude in the estimated rotating coordinate system after each reduction of the given current. Among them, the preset minimum current value is pre-set according to experimental data. In this embodiment, the step of obtaining the direct-axis estimated back EMF amplitude and the cross-axis estimated back EMF amplitude in the estimated rotating coordinate system after each reduction of the given current includes: using a back EMF observer to obtain the direct-axis estimated back EMF and the cross-axis estimated back EMF, respectively obtaining the absolute values ​​of the direct-axis estimated back EMF and the cross-axis estimated back EMF, and obtaining the direct-axis estimated back EMF amplitude and the cross-axis estimated back EMF amplitude.

[0054] After obtaining the direct-axis estimated back EMF amplitude and the quadrature-axis estimated back EMF amplitude, execute step S6 to determine whether the direct-axis estimated back EMF amplitude and the quadrature-axis estimated back EMF amplitude are equal. Since the direct-axis estimated back EMF amplitude and the quadrature-axis estimated back EMF amplitude are equal when Δθ is 45°, the switching condition can be confirmed to be met by the direct-axis estimated back EMF amplitude and the quadrature-axis estimated back EMF amplitude being equal.

[0055] If the direct-axis estimated back EMF amplitude and the quadrature-axis estimated back EMF amplitude are not equal, continue to execute step S3, further reduce the given current, and make Δθ approach 45°. When the direct-axis estimated back EMF amplitude and the quadrature-axis estimated back EMF amplitude are equal, execute step S7 and switch to the speed closed-loop estimation operation. If the direct-axis estimated back EMF amplitude and the quadrature-axis estimated back EMF amplitude are equal, it means that Δθ is 45 at this time, so the motor can be controlled to switch to the speed closed-loop estimation operation.

[0056] In addition, when executing step S4, if the given current after the reduction is less than or equal to the preset minimum current value, step S7 is executed to switch to the speed closed-loop estimation operation. If the given current after the reduction is less than or equal to the preset minimum current value, the motor is directly controlled to switch to the speed closed-loop estimation operation to ensure the stability of the operation.

[0057] To further illustrate the technical effects of the present invention, see Figure 3 and Figure 4 , Figure 3 It is a waveform diagram of the given current in each stage when the motor is switched under heavy load. Figure 4 It is a waveform diagram of the given current in each stage when the motor is switched under light load. Figure 3 and Figure 4 It can be seen that the current before switching is larger when the motor is in a heavy load state, and smaller when the motor is in a light load state. Through the switching process control of the present invention, the switching speed under heavy load and light load conditions can be smooth and have better adaptability.

[0058] In addition, during the motor current-to-frequency ratio control stage, the magnitude of the electromagnetic torque is proportional to the cosine of the angle difference Δθ between the given rotating coordinate and the actual rotating coordinate, and the actual motor speed will always affect the magnitude of Δθ, which in turn affects the electromagnetic torque. When the electromagnetic torque changes without any adjustment process, the damping coefficient is extremely small. When the load fluctuates, it is very easy to cause the motor speed and electromagnetic torque to oscillate. The peak value of Δθ during the oscillation process easily exceeds the stable range, causing the motor current-to-frequency ratio control stage to lose control. Therefore, it is necessary to increase the damping coefficient of the electromagnetic torque dynamic process to avoid oscillation of the power angle.

[0059] In this embodiment, the step of controlling the operation of the permanent magnet synchronous motor with a preset motor current-frequency ratio includes: using the high-frequency component of electromagnetic power to correct the original given rotation frequency to obtain the given rotation frequency. In order to increase the damping coefficient of the electromagnetic torque dynamic process, it is necessary to use the high-frequency component of electromagnetic power to correct the original given rotation frequency, thereby avoiding the oscillation of the power angle, and will not cause loss of control due to the peak value of the oscillation exceeding the stable range of the power angle, thereby enhancing stability.

[0060] The principle of using the high-frequency component of electromagnetic power to correct the original given rotation frequency is explained below.

[0061] The electromagnetic torque expression Small signal analysis yields: Where dx represents the increment of x and Δθ0 represents the static point of Δθ. dΔθ can be expressed as: Thus we get:

[0062] The correction for a given rotation frequency is shown below: in, is the original given rotation frequency, is the frequency correction, expressed as Among them, ΔTe is the fluctuation component of electromagnetic torque, and kp is the gain coefficient.

[0063] The following is an analysis of the change process of the electromagnetic torque after adding frequency correction:

[0064] First, when the load torque increases, the rotor speed decreases, the error angle increases, and the electromagnetic torque increases. At this time, the fluctuation component of the electromagnetic torque is positive, and the frequency correction amount is The electromagnetic torque generated is negative, and the final synthetic electromagnetic torque increment decreases.

[0065] Secondly, assuming that the load torque remains unchanged, but the electromagnetic torque fluctuates, when the fluctuation component of the electromagnetic torque is positive, the frequency correction value is The electromagnetic torque generated is negative. When the fluctuation component of the electromagnetic torque is negative, the frequency correction The electromagnetic torque generated is positive, and the fluctuation of the electromagnetic torque is finally suppressed, making the electromagnetic torque tend to be stable.

[0066] From the above analysis, it can be seen that after increasing the frequency correction amount, the dynamic characteristics of the electromagnetic torque slow down, and the electromagnetic torque damping coefficient increases, which avoids the oscillation of the power angle and does not cause loss of control due to the peak value of the oscillation exceeding the stable range of the power angle, thereby enhancing stability.

[0067] In order to obtain the fluctuation component of the electromagnetic torque, the fluctuation component of the electromagnetic power can be divided by the given rotation vector frequency. The fluctuation component of the electromagnetic torque is obtained by the following formula: Among them, p is the number of motor poles, and △Pem is the electromagnetic power fluctuation component.

[0068] The electromagnetic power fluctuation component is obtained by the following formula:

[0069] ΔPem=Pem-Pem_LPF,

[0070]

[0071] Among them, U α , U β is the voltage in the stationary coordinate system, Iα , I β is the current in the stationary coordinate system, Pem is the electromagnetic power, Pem_LPF is the DC component of the electromagnetic power obtained by using a low-pass filter, is the low-pass filter transfer function H(s).

[0072] In order to be implemented on a digital controller, the low-pass filter transfer function H(s) needs to be discretized. In order to better retain the low-frequency characteristics after discretization, the zero-pole matching method is used to discretize it, with a sampling time of 0.0133s. The low-pass filter transfer function H(z) after discretization is:

[0073] In order to demonstrate the advantages of the revised present invention, the following examples are given.

[0074] For example, when the motor speed is 400 rpm, the load torque jumps from 0 to 0.6 Nm in 1.5 s. Figure 5 The figure shows the electromagnetic torque waveform without frequency correction. It can be seen from the figure that the electromagnetic torque continues to oscillate and the motor speed also continues to oscillate. Figure 6 The figure shows the electromagnetic torque waveform of the traditional method of using electric power for frequency correction. Figure 7 The figure shows the electromagnetic torque waveform of the present invention using electromagnetic power for frequency correction. By comparison, it can be seen that the oscillation duration of the present invention is shorter, and the electromagnetic torque converges to the load torque faster. And from the previous analysis, it can be seen that the smaller the electromagnetic torque oscillation peak, the farther Δθ is from the stability boundary, the more sufficient the stability margin is, and it can resist larger load disturbances. Figure 5 The peak value of electromagnetic torque oscillation is 0.98Nm. Figure 6 The oscillation peak value is 0.83Nm, Figure 7 The oscillation peak value in the embodiment is 0.78Nm. By comparison, it can be seen that the oscillation peak value of the present invention is the smallest and the stability margin is more sufficient.

[0075] For another example, when the air conditioner outdoor fan is in headwind state, before the fan is started, the winding is short-circuited first, and the motor speed and position under headwind are obtained, and then the current-frequency ratio is controlled. Figure 8 The current waveform without frequency correction is shown in FIG. 1 . It can be seen that the current has obvious oscillations and the motor is in a state of out-of-step. After the frequency correction of the electromagnetic power in the present invention, the current waveform obtained is as follows: Fig. 9 As shown, compared Figure 8 It can be seen that the current oscillation has dropped significantly and the current-to-frequency ratio control process has been running stably.

[0076] From the above, it can be seen that the permanent magnet synchronous motor control method of the present invention gradually reduces the given current amplitude in the process of switching from motor current-frequency ratio control to speed closed-loop estimation control, and at the same time judges the direct-axis estimated back-electromotive force amplitude and the quadrature-axis estimated back-electromotive force amplitude. When the two are equal, it switches to speed closed-loop estimation operation, thereby making the speed switching smooth under heavy load and light load conditions and having good adaptability.

[0077] Air conditioner embodiment:

[0078] The air conditioner of this embodiment includes a controller, and the controller implements the steps in the above-mentioned permanent magnet synchronous motor control method embodiment when executing a computer program.

[0079] For example, the computer program can be divided into one or more modules, one or more modules are stored in the memory and executed by the controller to complete the present invention. One or more modules can be a series of computer program instruction segments that can complete specific functions, and the instruction segments are used to describe the execution process of the computer program in the air conditioner.

[0080] The air conditioner may include, but is not limited to, a controller and a memory. Those skilled in the art will appreciate that the air conditioner may include more or fewer components, or a combination of certain components, or different components, for example, the air conditioner may also include input and output devices, network access devices, buses, etc.

[0081] For example, the controller may be a central processing unit (CPU), other general controllers, digital signal processors (DSP), application specific integrated circuits (ASIC), field programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general controller may be a microcontroller or any conventional controller, etc. The controller is the control center of the air conditioner, and uses various interfaces and lines to connect the various parts of the entire air conditioner.

[0082] The memory can be used to store computer programs and / or modules. The controller realizes various functions of the air conditioner by running or executing the computer programs and / or modules stored in the memory and calling the data stored in the memory. For example, the memory can mainly include a program storage area and a data storage area, wherein the program storage area can store an operating system, an application required for at least one function (such as a sound receiving function, a sound conversion to text function, etc.), etc.; the data storage area can store data created according to the use of the mobile phone (such as audio data, text data, etc.), etc. In addition, the memory can include a high-speed random access memory, and can also include a non-volatile memory, such as a hard disk, a memory, a plug-in hard disk, a smart memory card (Smart Media Card, SMC), a secure digital (Secure Digital, SD) card, a flash card (Flash Card), at least one disk storage device, a flash memory device, or other volatile solid-state storage devices.

[0083] Computer readable storage medium embodiment:

[0084] If the air conditioner integrated module of the above embodiment is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the implementation of all or part of the process in the above permanent magnet synchronous motor control method embodiment can also be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium. When the computer program is executed by the controller, the steps of the above permanent magnet synchronous motor control method embodiment can be implemented. Among them, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form. The storage medium may include: any entity or device capable of carrying computer program code, recording medium, U disk, mobile hard disk, disk, optical disk, computer memory, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), electric carrier signal, telecommunication signal and software distribution medium. It should be noted that the content contained in the computer-readable medium can be appropriately increased or decreased according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, the computer-readable medium does not include electric carrier signal and telecommunication signal.

[0085] It should be noted that the above are only preferred embodiments of the present invention, but the design concept of the invention is not limited thereto, and any non-substantial modifications made to the present invention using this concept also fall within the protection scope of the present invention.

Claims

1. A permanent magnet synchronous motor control method, characterized in that: include: Control the operation of permanent magnet synchronous motor with preset motor current-frequency ratio; When the given current and the given rotation frequency meet the conditions for switching the speed closed-loop estimation operation, controlling the given current to be gradually reduced by a preset amplitude, and obtaining the direct axis estimated back-electromotive force amplitude and the quadrature axis estimated back-electromotive force amplitude in the estimated rotation coordinate system after each reduction of the given current; When the direct-axis estimated back-EMF amplitude and the quadrature-axis estimated back-EMF amplitude are equal, the operation is switched to the speed closed-loop estimation operation.

2. The permanent magnet synchronous motor control method according to claim 1, characterized in that: The conditions for a given current and a given rotation frequency to satisfy the switching speed closed-loop estimation operation include: The given current reaches a preset current and the given rotation frequency reaches a preset frequency.

3. The permanent magnet synchronous motor control method according to claim 1, characterized in that: After controlling the given current to be gradually reduced with a preset amplitude, before obtaining the direct axis estimated back electromotive force and the quadrature axis estimated back electromotive force amplitude in the estimated rotating coordinate system after each reduction of the given current, the method further includes: It is confirmed that the given current after reduction is greater than a preset minimum current value.

4. The permanent magnet synchronous motor control method according to claim 3, characterized in that: When it is confirmed that the given current after reduction is greater than the preset minimum current value, if the given current after reduction is less than or equal to the preset minimum current value, switching to the speed closed-loop estimation operation is performed.

5. The permanent magnet synchronous motor control method according to claim 1, characterized in that: The step of obtaining the direct axis estimated back electromotive force amplitude and the quadrature axis estimated back electromotive force amplitude in the estimated rotating coordinate system after the given current is reduced each time comprises: Use the back-EMF observer to obtain the direct-axis estimated back-EMF and the quadrature-axis estimated back-EMF. The absolute values ​​of the direct-axis estimated back-electromotive force and the quadrature-axis estimated back-electromotive force are acquired respectively to obtain the direct-axis estimated back-electromotive force amplitude and the quadrature-axis estimated back-electromotive force amplitude.

6. The permanent magnet synchronous motor control method according to claims 1 to 5, characterized in that: The steps of controlling the operation of a permanent magnet synchronous motor with a preset motor current-to-frequency ratio include: The original given rotation frequency is corrected by utilizing the high frequency component of the electromagnetic power to obtain the given rotation frequency.

7. The permanent magnet synchronous motor control method according to claim 6, characterized in that: The given rotation frequency is obtained by the following formula: in, is the original given rotation frequency, is the frequency correction, ΔTe is the fluctuation component of the electromagnetic torque, kp is the gain coefficient; △Pem is the electromagnetic power fluctuation component; p is the number of motor poles.

8. The permanent magnet synchronous motor control method according to claim 7, characterized in that: The electromagnetic power fluctuation component is obtained by the following formula: ΔPem=Pem-Pem_LPF, Among them, U α , U β is the voltage in the stationary coordinate system, I α , I β is the current in the stationary coordinate system, is the low-pass filter transfer function, and Rs is the motor phase resistance.

9. An air conditioner, comprising a processor and a memory, characterized in that: The memory stores a computer program, and when the computer program is executed by the processor, the steps of the permanent magnet synchronous motor control method according to any one of claims 1 to 8 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by the controller, the steps of the permanent magnet synchronous motor control method according to any one of claims 1 to 8 are implemented.

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