Method and device for estimating rotor position of permanent magnet synchronous motor

Abstract

The invention relates to a method and a device for estimating the rotor position of a permanent magnet synchronous motor. The method comprises the following steps: determining d-axis current and d-axis voltage of the permanent magnet synchronous motor according to three-phase sampling current of the permanent magnet synchronous motor; the d-axis counter electromotive force and the rotor rotation speed of the permanent magnet synchronous motor are determined through a direct estimation algorithm; when the rotation speed of the rotor is greater than a preset speed threshold value, judging whether the absolute value of the d-axis counter electromotive force is less than or equal to an absolute value threshold value; under the condition that the absolute value of the d-axis counter electromotive force is larger than an absolute value threshold value, the given current is adjusted to adjust the d-axis counter electromotive force until the absolute value of the d-axis counter electromotive force is smaller than or equal to the absolute value threshold value; and under the condition that the absolute value of the d-axis counter electromotive force is smaller than or equal to the absolute value threshold value, the direct estimation algorithm is switched into an observer algorithm. By means of the method, the technical problem that large errors are prone to occurring in the observer algorithm when the permanent magnet synchronous motor conducts estimation algorithm switching is solved.

Description

Technical Field

[0001] The present application relates to the field of motors, and in particular to a method and device for estimating the rotor position of a permanent magnet synchronous motor. Background Art

[0002] During the control process of a permanent magnet synchronous motor, if you need to determine its rotor position, you can do so by installing an encoder inside the motor. However, in the refrigeration industry, permanent magnet synchronous motors used as compressors pay great attention to the air tightness of the cylinder, so it is impossible to install an encoder like a conventional motor to obtain the rotor position.

[0003] In the prior art, a permanent magnet synchronous motor used as a compressor usually uses an open-loop control method that directly estimates the back electromotive force to estimate the rotor position at low speeds. When the speed reaches a certain value, it switches to a more accurate closed-loop control method using an observer algorithm to estimate the rotor position.

[0004] If the observer algorithm is expected to obtain a more accurate estimation result, it is necessary to input the accurate rotor position into the observer algorithm at the switching moment of the two algorithms to achieve closed-loop control. However, the open-loop control method of direct back-EMF estimation usually has a certain error, resulting in inaccurate rotor position, which in turn makes the observer algorithm prone to large errors. Summary of the invention

[0005] The present application provides a method and device for estimating the rotor position of a permanent magnet synchronous motor to solve the technical problem that when the permanent magnet synchronous motor switches from an open-loop control method of directly estimating back electromotive force to a closed-loop control method of an observer algorithm, a large error is easily generated in the observer algorithm.

[0006] In a first aspect, the present application provides a method for estimating a rotor position of a permanent magnet synchronous motor, the method comprising:

[0007] Determine the d-axis current and d-axis voltage of the permanent magnet synchronous motor according to the three-phase sampling current of the permanent magnet synchronous motor; wherein the three-phase sampling current is generated after a given current is input to the permanent magnet synchronous motor;

[0008] Processing the d-axis current and the d-axis voltage of the permanent magnet synchronous motor by a direct estimation algorithm to determine the d-axis back electromotive force and the rotor rotation speed of the permanent magnet synchronous motor;

[0009] In the case where the rotor rotation speed is greater than a preset speed threshold, determining whether the absolute value of the d-axis back electromotive force is less than or equal to a preset absolute value threshold;

[0010] When the absolute value of the d-axis back electromotive force is greater than the absolute value threshold, adjusting the given current to adjust the d-axis back electromotive force until the absolute value of the d-axis back electromotive force is less than or equal to the absolute value threshold;

[0011] When the absolute value of the d-axis back electromotive force is less than or equal to the absolute value threshold, the direct estimation algorithm is switched to an observer algorithm to estimate the rotor position of the permanent magnet synchronous motor through the observer algorithm.

[0012] In a feasible embodiment of the present application, determining the d-axis current and the d-axis voltage of the permanent magnet synchronous motor according to the three-phase sampled current of the permanent magnet synchronous motor includes:

[0013] Performing Clark transformation on the three-phase sampled current to determine the d-axis current of the permanent magnet synchronous motor;

[0014] Park transformation is performed on the three-phase sampled current to determine the d-axis voltage of the permanent magnet synchronous motor.

[0015] In a feasible embodiment of the present application, the d-axis current and the d-axis voltage of the permanent magnet synchronous motor are processed by a direct estimation algorithm to determine the d-axis back electromotive force and the rotor rotation speed of the permanent magnet synchronous motor, including:

[0016] Acquire motor parameters of the permanent magnet synchronous motor; wherein the motor parameters at least include d-axis inductance, motor resistance and motor pole pair number of the permanent magnet synchronous motor;

[0017] The d-axis inductance, the d-axis current, the d-axis voltage, the motor resistance and the number of motor pole pairs are processed by the motor d-axis model in the direct estimation algorithm to determine the d-axis back electromotive force of the permanent magnet synchronous motor; wherein the motor d-axis model is expressed as:

[0018] U d =L d ×p×I d +R s ×I d +E d ;

[0019] Among them, U d is the d-axis voltage, L d is the d-axis inductance, p is the number of motor pole pairs, I d is the d-axis current, R s is the motor resistance, E d is the d-axis back electromotive force;

[0020] The rotor rotation speed is determined based on the d-axis back electromotive force.

[0021] In a feasible embodiment of the present application, the motor parameters further include q-axis inductance, and determining the rotor rotation speed according to the d-axis back electromotive force includes:

[0022] Acquire the q-axis current and q-axis voltage of the permanent magnet synchronous motor; wherein the q-axis current and q-axis voltage of the permanent magnet synchronous motor are determined based on the Clark transformation and Park transformation of the three-phase sampling current;

[0023] The q-axis inductance, the q-axis current, the q-axis voltage, the motor resistance and the number of motor pole pairs are processed by the motor q-axis model in the direct estimation algorithm to determine the q-axis back electromotive force of the permanent magnet synchronous motor; wherein the motor q-axis model is expressed as:

[0024] U q =L q ×p×I q +R s ×I q +E q ;

[0025] Among them, U q is the q-axis voltage, L q is the q-axis inductance, I q is the q-axis current, E q is the q-axis back electromotive force;

[0026] The rotor rotation speed is determined according to the d-axis back electromotive force and the q-axis back electromotive force.

[0027] In a feasible embodiment of the present application, determining the rotor rotation speed according to the d-axis back electromotive force and the q-axis back electromotive force includes:

[0028] The d-axis back electromotive force and the q-axis back electromotive force are calculated by a rotor rotation speed formula to determine the rotor rotation speed; wherein the rotor rotation speed formula is:

[0029]

[0030] Among them, ω e is the rotor rotation speed, K e is the preset back electromotive force constant.

[0031] In a feasible embodiment of the present application, when the absolute value of the d-axis back electromotive force is greater than the absolute value threshold, adjusting the given current to adjust the d-axis back electromotive force until the absolute value of the d-axis back electromotive force is less than or equal to the absolute value threshold, includes:

[0032] When the absolute value of the d-axis back electromotive force is greater than the absolute value threshold and the d-axis back electromotive force is greater than 0, reducing the given current until the absolute value of the d-axis back electromotive force is less than or equal to the absolute value threshold;

[0033] When the absolute value of the d-axis back electromotive force is greater than the absolute value threshold and the d-axis back electromotive force is less than 0, the given current is increased until the absolute value of the d-axis back electromotive force is less than or equal to the absolute value threshold.

[0034] In a feasible embodiment of the present application, after switching the direct estimation algorithm to the observer algorithm, the method further includes:

[0035] After the observer algorithm runs for a preset time, calculating an estimation error of the observer algorithm;

[0036] When the estimated error is less than or equal to a preset error threshold, controlling to continue estimating the rotor position of the permanent magnet synchronous motor by using the observer algorithm;

[0037] When the estimated error is greater than the error threshold, the permanent magnet synchronous motor is controlled to stop.

[0038] In a second aspect, the present application provides a device for estimating the rotor position of a permanent magnet synchronous motor, the device comprising:

[0039] A first determination module is used to determine the d-axis current and d-axis voltage of the permanent magnet synchronous motor according to the three-phase sampling current of the permanent magnet synchronous motor; wherein the three-phase sampling current is generated after a given current is input to the permanent magnet synchronous motor;

[0040] A second determination module is used to process the d-axis current and the d-axis voltage of the permanent magnet synchronous motor by a direct estimation algorithm to determine the d-axis back electromotive force and the rotor rotation speed of the permanent magnet synchronous motor;

[0041] A judging module, configured to judge whether the absolute value of the d-axis back electromotive force is less than or equal to a preset absolute value threshold value when the rotation speed of the rotor is greater than a preset speed threshold value;

[0042] an adjustment module, configured to adjust the given current to adjust the d-axis back electromotive force when the absolute value of the d-axis back electromotive force is greater than the absolute value threshold, until the absolute value of the d-axis back electromotive force is less than or equal to the absolute value threshold;

[0043] A switching module is used to switch the direct estimation algorithm to an observer algorithm when the absolute value of the d-axis back electromotive force is less than or equal to the absolute value threshold, so as to estimate the rotor position of the permanent magnet synchronous motor through the observer algorithm.

[0044] In a third aspect, the present application provides a permanent magnet synchronous motor, comprising: at least one communication interface; at least one bus connected to the at least one communication interface; at least one processor connected to the at least one bus; and at least one memory connected to the at least one bus, wherein the processor is configured to execute a method for estimating the rotor position of a permanent magnet synchronous motor as described in any one of the embodiments of the first aspect above.

[0045] In a fourth aspect, the present application provides a refrigeration device, which includes the permanent magnet synchronous motor as described in the third aspect above.

[0046] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0047] The technical solution provided in the embodiment of the present application adjusts the given current before switching the direct estimation algorithm to the observer algorithm, thereby adjusting the absolute value of the d-axis back electromotive force of the permanent magnet synchronous motor to be less than the absolute value threshold. Only when the absolute value of the d-axis back electromotive force is less than the absolute value threshold, the direct estimation algorithm is switched to the observer algorithm.

[0048] In the technical solution provided in the present application, the absolute value of the d-axis back electromotive force of the permanent magnet synchronous motor is less than the absolute value threshold, indicating that the d-axis back electromotive force of the permanent magnet synchronous motor is close to 0. d =-ω e ×K e ×sinθ, where θ is the error angle between the estimated rotor position and the actual rotor position. When the d-axis back electromotive force approaches 0, since the rotor rotation speed of the current permanent magnet synchronous motor is not 0, it means that θ approaches 0, and the estimated rotor position is basically consistent with the actual rotor position. At this time, switching the direct estimation algorithm to the observer algorithm can ensure that the initial input rotor estimated position of the observer algorithm is more accurate when performing closed-loop control, thereby solving the technical problem that the observer algorithm is prone to large errors when the permanent magnet synchronous motor switches from the open-loop control method of direct back electromotive force estimation to the closed-loop control method of the observer algorithm. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0050] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0051] One or more embodiments are exemplarily described by pictures in the corresponding drawings, and these exemplified descriptions do not constitute limitations on the embodiments. Elements with the same reference numerals in the drawings represent similar elements, and unless otherwise stated, the figures in the drawings do not constitute proportional limitations.

[0052] Figure 1 A schematic flow chart of a method for estimating the rotor position of a permanent magnet synchronous motor provided in an embodiment of the present application;

[0053] Figure 2 An overall flow chart of a method for estimating the rotor position of a permanent magnet synchronous motor provided in an embodiment of the present application;

[0054] Figure 3 A schematic diagram of the structure of a permanent magnet synchronous motor rotor position estimation device provided in an embodiment of the present application;

[0055] Figure 4 A schematic diagram of the structure of a permanent magnet synchronous motor provided in an embodiment of the present application. DETAILED DESCRIPTION

[0056] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0057] The disclosure below provides many different embodiments or examples to implement different structures of the present invention. In order to simplify the disclosure of the present invention, the parts and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present invention. In addition, the present invention can repeat reference numbers and / or letters in different examples. This repetition is for the purpose of simplification and clarity, and does not itself indicate the relationship between the various embodiments and / or settings discussed.

[0058] In order to solve the technical problem in the prior art that a permanent magnet synchronous motor is prone to large errors in the observer algorithm when the open-loop control method of direct back-electromotive force estimation is switched to a closed-loop control method of an observer algorithm, the present application provides a method and device for estimating the rotor position of a permanent magnet synchronous motor, which can avoid large errors in the observer algorithm when the permanent magnet synchronous motor is switched from an open-loop control method of direct back-electromotive force estimation to a closed-loop control method of an observer algorithm.

[0059] Figure 1 A flow chart of a method for estimating the rotor position of a permanent magnet synchronous motor provided in an embodiment of the present application is provided. Figure 1 The present invention provides a method for estimating the rotor position of a permanent magnet synchronous motor, which specifically includes the following steps:

[0060] S1: determining the d-axis current and d-axis voltage of the permanent magnet synchronous motor according to the three-phase sampling current of the permanent magnet synchronous motor; wherein the three-phase sampling current is generated after a given current is input into the permanent magnet synchronous motor;

[0061] Specifically, the executor of a method for estimating the rotor position of a permanent magnet synchronous motor provided in an embodiment of the present application can be a motor controller of the permanent magnet synchronous motor. After the permanent magnet synchronous motor is powered on and starts running, the motor controller inputs a given current into the permanent magnet synchronous motor, and obtains a three-phase sampling current generated by the permanent magnet synchronous motor based on the given current, thereby determining the d-axis current and d-axis voltage of the permanent magnet synchronous motor based on the three-phase sampling current.

[0062] In a feasible embodiment of the present application, the three-phase sampling current can be obtained through a current sampling resistor arranged on the permanent magnet synchronous motor.

[0063] During the startup process of the permanent magnet synchronous motor, the given current input by the motor controller to the permanent magnet synchronous motor increases in proportion to the increase in the rotor rotation speed of the permanent magnet synchronous motor, thereby controlling the startup of the permanent magnet synchronous motor. It can be understood that the process of inputting a given current to the permanent magnet synchronous motor to control the startup of the permanent magnet synchronous motor is actually the IF control process.

[0064] In some practical implementation scenarios of the present application, after the permanent magnet synchronous motor is powered on, the motor controller inputs a given current to the permanent magnet synchronous motor at intervals, and the given current input each time gradually increases with the rotor rotation speed of the rotor of the permanent magnet synchronous motor. For any given current, the motor controller obtains the three-phase sampling current of the permanent magnet synchronous motor through the current sampling resistor, thereby calculating the d-axis current and d-axis voltage of the permanent magnet synchronous motor corresponding to the current given current.

[0065] In a feasible embodiment of the present application, determining the d-axis current and d-axis voltage of the permanent magnet synchronous motor according to the three-phase sampled current of the permanent magnet synchronous motor includes:

[0066] Clark transformation is performed on the three-phase sampled current to determine the d-axis current of the permanent magnet synchronous motor;

[0067] Park transformation is performed on the three-phase sampled current to determine the d-axis voltage of the permanent magnet synchronous motor.

[0068] Specifically, Clark transformation and Park transformation are two commonly used coordinate transformations in vector control, which are used to convert the voltage or current in the three-phase coordinate system (abc) into the voltage or current in the two-phase coordinate system (dq). Clark transformation is performed on the three-phase sampled current to determine the d-axis current of the permanent magnet synchronous motor. At the same time, the q-axis current of the permanent magnet synchronous motor can also be determined in the Clark transformation; Park transformation is performed on the three-phase sampled current to determine the d-axis voltage of the permanent magnet synchronous motor. At the same time, the q-axis voltage of the permanent magnet synchronous motor can also be determined in the Park transformation.

[0069] S2: Processing the d-axis current and d-axis voltage of the permanent magnet synchronous motor by a direct estimation algorithm to determine the d-axis back electromotive force and rotor rotation speed of the permanent magnet synchronous motor;

[0070] Specifically, for any given input current, the motor controller calculates the d-axis current and d-axis voltage of the permanent magnet synchronous motor, processes the d-axis current and d-axis voltage of the permanent magnet synchronous motor through a direct estimation algorithm, and determines the d-axis back electromotive force and rotor rotation speed of the permanent magnet synchronous motor under the current given current.

[0071] In a feasible embodiment of the present application, the d-axis current and the d-axis voltage of the permanent magnet synchronous motor are processed by a direct estimation algorithm to determine the d-axis back electromotive force and the rotor rotation speed of the permanent magnet synchronous motor, including:

[0072] Obtaining motor parameters of the permanent magnet synchronous motor; wherein the motor parameters include at least the d-axis inductance, motor resistance and motor pole pair number of the permanent magnet synchronous motor;

[0073] The d-axis inductance, d-axis current, d-axis voltage, motor resistance and motor pole pair number are processed by the motor d-axis model in the direct estimation algorithm to determine the d-axis back electromotive force of the permanent magnet synchronous motor; wherein the motor d-axis model is expressed as:

[0074] U d =L d ×p×I d +R s ×I d +E d;

[0075] Among them, U d is the d-axis voltage, L d is the d-axis inductance, p is the number of motor pole pairs, I d is the d-axis current, R s is the motor resistance, E d is the d-axis back electromotive force;

[0076] The rotor rotation speed is determined based on the d-axis back EMF.

[0077] Specifically, the motor controller obtains the motor parameters of the permanent magnet synchronous motor, and the motor parameters are only related to the motor model of the permanent magnet synchronous motor and are the inherent properties of the permanent magnet synchronous motor. In a feasible embodiment of the present application, the motor controller obtains the motor parameters of the permanent magnet synchronous motor from its own storage area, and these motor parameters are recorded in the storage area of ​​the motor controller when the permanent magnet synchronous motor leaves the factory.

[0078] The motor parameters include at least the d-axis inductance, motor resistance and motor pole pair number of the permanent magnet synchronous motor. After obtaining the motor parameters, the motor controller calls the motor d-axis model in the direct estimation algorithm to process the d-axis inductance, d-axis current, d-axis voltage, motor resistance and motor pole pair number, thereby determining the d-axis back electromotive force of the permanent magnet synchronous motor.

[0079] In a feasible embodiment of the present application, the motor d-axis model is expressed as follows:

[0080] U d =L d ×p×I d +R s ×I d -L q ×ω e ×I q +E d ;

[0081] Among them, U d is the d-axis voltage, L d is the d-axis inductance, L q is the q-axis inductance, I q is the q-axis current, ω e is the rotor rotation speed, p is the number of motor pole pairs, I d is the d-axis current, R s is the motor resistance, E d is the d-axis back electromotive force.

[0082] However, when a given current is input to the permanent magnet synchronous motor, the rotor rotation speed of the permanent magnet synchronous motor is relatively small, and at the same time, the d-axis inductance and q-axis voltage of the permanent magnet synchronous motor are also relatively small. For the convenience of calculation, in a preferred embodiment of the present application, the motor d-axis model is expressed as shown in the following formula:

[0083] U d =L d ×p×I d +R s ×I d +E d .

[0084] Based on the motor d-axis model in the above embodiment, when the d-axis voltage, the number of motor pole pairs, the d-axis current, the d-axis inductance and the motor resistance are known, the motor controller can calculate the d-axis back electromotive force of the permanent magnet synchronous motor. The calculation method of the d-axis back electromotive force of the permanent magnet synchronous motor is shown in the following formula:

[0085] E d =U d -L d ×p×I d +R s ×I d .

[0086] After determining the d-axis back electromotive force of the permanent magnet synchronous motor, the motor controller determines the rotor rotation speed of the permanent magnet synchronous motor under the current given current according to the d-axis back electromotive force of the permanent magnet synchronous motor.

[0087] In a feasible embodiment of the present application, the motor parameters also include q-axis inductance, and the rotor rotation speed is determined according to the d-axis back electromotive force, including:

[0088] Obtaining the q-axis current and q-axis voltage of the permanent magnet synchronous motor; wherein the q-axis current and q-axis voltage of the permanent magnet synchronous motor are determined based on the Clark transformation and Park transformation of the three-phase sampling current;

[0089] The q-axis inductance, q-axis current, q-axis voltage, motor resistance and motor pole pair number are processed by the motor q-axis model in the direct estimation algorithm to determine the q-axis back electromotive force of the permanent magnet synchronous motor; wherein the motor q-axis model is expressed as:

[0090] U q =L q ×p×I q +R s ×I q +E q ;

[0091] Among them, U q is the q-axis voltage, L qis the q-axis inductance, I q is the q-axis current, E q is the q-axis back electromotive force;

[0092] The rotor rotation speed is determined based on the d-axis back electromotive force and the q-axis back electromotive force.

[0093] Specifically, in the above embodiment, the three-phase sampling current is subjected to Clark transformation and Park transformation to obtain the d-axis current and d-axis voltage of the permanent magnet synchronous motor, while obtaining the q-axis current and q-axis voltage of the permanent magnet synchronous motor, and the motor controller obtains the q-axis current and q-axis voltage of the permanent magnet synchronous motor.

[0094] After obtaining the q-axis current, q-axis voltage and q-axis inductance, the motor controller calls the motor q-axis model in the direct estimation algorithm to process the q-axis inductance, q-axis current, q-axis voltage, motor resistance and the number of motor pole pairs to determine the q-axis back electromotive force of the permanent magnet synchronous motor.

[0095] In a feasible embodiment of the present application, the motor q-axis model is expressed as follows:

[0096] U q =L q ×p×I q +R s ×I q -L d ×ω e ×I d +E q ;

[0097] Among them, U q is the q-axis voltage, L q is the q-axis inductance, I q is the q-axis current, E q is the q-axis back electromotive force.

[0098] Similarly, when a given current is input to the permanent magnet synchronous motor, the rotor rotation speed of the permanent magnet synchronous motor is relatively small, and at the same time, the d-axis inductance and q-axis voltage of the permanent magnet synchronous motor are also relatively small. For the convenience of calculation, in a preferred embodiment of the present application, the motor q-axis model is expressed as shown in the following formula:

[0099] U q =L q ×p×I q +R s ×I q +E q .

[0100] Based on the motor q-axis model in the above embodiment, when the q-axis voltage, the number of motor pole pairs, the q-axis current, the q-axis inductance and the motor resistance are known, the motor controller can calculate the q-axis back electromotive force of the permanent magnet synchronous motor. The calculation method of the q-axis back electromotive force of the permanent magnet synchronous motor is shown in the following formula:

[0101] E q =U q -L q ×p×I q +R s ×I q .

[0102] After obtaining the d-axis back electromotive force and the q-axis back electromotive force of the permanent magnet synchronous motor, the motor controller calculates the d-axis back electromotive force and the q-axis back electromotive force through the rotor rotation speed formula to determine the rotor rotation speed. In a feasible embodiment of the present application, the rotor rotation speed formula is:

[0103]

[0104] Among them, K e is the preset back electromotive force constant.

[0105] It can be seen that through the above embodiment, the motor controller first calculates the d-axis voltage, d-axis current, q-axis voltage and q-axis current of the permanent magnet synchronous motor, and then calculates the d-axis back electromotive force and q-axis back electromotive force of the permanent magnet synchronous motor based on the d-axis voltage, d-axis current, q-axis voltage and q-axis current of the permanent magnet synchronous motor, thereby obtaining the rotor rotation speed based on the d-axis back electromotive force and q-axis back electromotive force of the permanent magnet synchronous motor.

[0106] It can be understood that for any given current, the motor controller calculates the d-axis voltage, d-axis current, q-axis voltage, q-axis current, d-axis back electromotive force, q-axis back electromotive force and rotor rotation speed corresponding to the given current.

[0107] S3: when the rotor rotation speed is greater than a preset speed threshold, determining whether the absolute value of the d-axis back electromotive force is less than or equal to a preset absolute value threshold;

[0108] Specifically, the motor controller obtains the speed threshold and absolute value threshold of the threshold from its own storage area, compares the speed threshold with the calculated rotor rotation speed, and when the rotor rotation speed is greater than the preset speed threshold, takes the absolute value of the d-axis back electromotive force, compares the absolute value of the d-axis back electromotive force with the absolute value threshold, and determines whether the absolute value of the d-axis back electromotive force is less than or equal to the preset absolute value threshold.

[0109] In a feasible embodiment of the present application, the speed threshold and the absolute value threshold are measured by technicians in the laboratory and pre-stored in the storage area of ​​the motor controller. In some specific examples, the speed threshold can be set to 10% of the maximum rotor rotation speed of the permanent magnet synchronous motor.

[0110] In a feasible embodiment of the present application, when the rotor rotation speed is less than or equal to a preset speed threshold, the steps S1-S2 described above are continued to input a given current that increases continuously with the rotor rotation speed into the permanent magnet synchronous motor.

[0111] S4: when the absolute value of the d-axis back electromotive force is greater than the absolute value threshold, adjusting the given current to adjust the d-axis back electromotive force until the absolute value of the d-axis back electromotive force is less than or equal to the absolute value threshold;

[0112] Specifically, when the absolute value of the d-axis back electromotive force is greater than the absolute value threshold, it means that the d-axis back electromotive force is not close to 0. d =-ω e ×K e ×sinθ, we can see that the d-axis back electromotive force does not approach 0, so sinθ does not approach 0. Since θ is the error angle between the estimated rotor position and the actual rotor position, and at this time ω e is small, which means that θ does not approach 0, that is, the error angle between the estimated rotor position and the actual rotor position is large, and the estimated rotor position does not match the actual rotor position.

[0113] To reduce the error angle between the estimated rotor position and the actual rotor position, the motor controller adjusts the given current to adjust the d-axis back electromotive force so that the absolute value of the d-axis back electromotive force is less than or equal to the absolute value threshold.

[0114] In a feasible embodiment of the present application, when the absolute value of the d-axis back electromotive force is greater than the absolute value threshold, adjusting the given current to adjust the d-axis back electromotive force until the absolute value of the d-axis back electromotive force is less than or equal to the absolute value threshold, includes:

[0115] When the absolute value of the d-axis back electromotive force is greater than the absolute value threshold and the d-axis back electromotive force is greater than 0, reducing the given current until the absolute value of the d-axis back electromotive force is less than or equal to the absolute value threshold;

[0116] When the absolute value of the d-axis back electromotive force is greater than the absolute value threshold and the d-axis back electromotive force is less than 0, the given current is increased until the absolute value of the d-axis back electromotive force is less than or equal to the absolute value threshold.

[0117] Specifically, when the absolute value of the d-axis back electromotive force is greater than the absolute value threshold and the d-axis back electromotive force is greater than 0, it means that the change in the internal magnetic flux of the permanent magnet synchronous motor causes a positive voltage to be generated in the d-axis direction, and the permanent magnet synchronous motor discharges in this direction. The mechanical energy of the permanent magnet synchronous motor is converted into electrical energy, and the permanent magnet synchronous motor is in a continuous braking process. At this time, the rotor rotation speed of the permanent magnet synchronous motor is slower than the rotation speed provided by the given current.

[0118] Therefore, in a feasible embodiment of the present application, the rotor rotation speed of the permanent magnet synchronous motor can be synchronized with the rotation speed provided by a given current by accelerating the rotor rotation speed of the permanent magnet synchronous motor, so that the absolute value of the d-axis back electromotive force is less than or equal to the absolute value threshold.

[0119] However, accelerating the rotor rotation speed of the permanent magnet synchronous motor easily causes the rotor rotation speed of the permanent magnet synchronous motor to be too fast, affecting the operation of the permanent magnet synchronous motor. Therefore, in a preferred embodiment of the present application, the given current is increased so that the rotor rotation speed of the permanent magnet synchronous motor is synchronized with the rotation speed provided by the given current, thereby making the absolute value of the back electromotive force on the d-axis less than or equal to the absolute value threshold.

[0120] In a feasible embodiment of the present application, the given current can be increased based on a preset gradient. For example, when the motor controller detects that the absolute value of the current d-axis back electromotive force is greater than the absolute value threshold and the d-axis back electromotive force is less than 0, the motor controller increases the current given current by a preset value at regular intervals.

[0121] In a feasible embodiment of the present application, if the given current is continuously increased, the given current will be too large and damage the permanent magnet synchronous motor. Therefore, in a feasible embodiment of the present application, a current threshold is set in the motor controller. When the given current increases to the current threshold, the given current is no longer increased, but the permanent magnet synchronous motor is controlled to perform shutdown protection, thereby avoiding damage to the permanent magnet synchronous motor by excessive given current.

[0122] When the absolute value of the d-axis back electromotive force is greater than the absolute value threshold and the d-axis back electromotive force is less than 0, it means that a reverse voltage is generated on the d-axis, which is consuming electrical energy and converting it into mechanical energy, thereby increasing the electromagnetic torque. The electrical energy of the permanent magnet synchronous motor is converted into mechanical energy, and the permanent magnet synchronous motor is in a continuous acceleration process. At this time, the rotor rotation speed of the permanent magnet synchronous motor is faster than the rotation speed provided by the given current.

[0123] Therefore, in a feasible embodiment of the present application, the rotor rotation speed of the permanent magnet synchronous motor can be synchronized with the rotation speed provided by a given current by slowing down the rotor rotation speed of the permanent magnet synchronous motor, so that the absolute value of the d-axis back electromotive force is less than or equal to the absolute value threshold.

[0124] However, slowing down the rotor rotation speed of the permanent magnet synchronous motor easily makes the d-axis back electromotive force of the permanent magnet synchronous motor difficult to observe. Therefore, in a preferred embodiment of the present application, the given current is reduced so that the rotor rotation speed of the permanent magnet synchronous motor is synchronized with the rotation speed provided by the given current, thereby making the absolute value of the d-axis back electromotive force less than or equal to the absolute value threshold.

[0125] In a feasible embodiment of the present application, the given current can be reduced based on a preset gradient. For example, when the motor controller detects that the absolute value of the current d-axis back electromotive force is greater than the absolute value threshold and the d-axis back electromotive force is greater than 0, the motor controller reduces the current given current by a preset value at intervals.

[0126] S5: when the absolute value of the d-axis back electromotive force is less than or equal to the absolute value threshold, switching the direct estimation algorithm to the observer algorithm to estimate the rotor position of the permanent magnet synchronous motor through the observer algorithm;

[0127] Specifically, when the absolute value of the d-axis back electromotive force is less than or equal to the absolute value threshold, it means that the d-axis back electromotive force is close to 0. d =-ω e ×K e × sinθ, we know that the d-axis back electromotive force approaches 0, then sinθ approaches 0, and since θ is the error angle between the estimated rotor position and the actual rotor position, and the permanent magnet synchronous motor is in motion at this time, ω e It is not 0, which means that θ approaches 0, that is, the error angle between the estimated rotor position and the actual rotor position is 0, and the estimated rotor position is basically consistent with the actual rotor position.

[0128] When the estimated rotor position is basically consistent with the actual rotor position, the direct estimation algorithm is switched to the observer algorithm, so that the initial input value of the observer algorithm is more accurate, so that the observer algorithm can estimate the rotor position of the permanent magnet synchronous motor more accurately in the subsequent period.

[0129] In a feasible embodiment of the present application, the observer algorithm is specifically a Lumberg observer, and the specific implementation of the Lumberg observer is prior art and will not be described in detail here.

[0130] In a feasible embodiment of the present application, in order to further verify the accuracy of the observer algorithm, after switching the direct estimation algorithm to the observer algorithm, the method further includes:

[0131] After the observer algorithm runs for a preset time, calculating the estimation error of the observer algorithm;

[0132] When the estimated error is less than or equal to a preset error threshold, the control continues to estimate the rotor position of the permanent magnet synchronous motor through an observer algorithm;

[0133] When the estimated error is greater than the error threshold, the permanent magnet synchronous motor is controlled to stop.

[0134] Based on all the above embodiments, it can be understood that the technical solution provided in the embodiments of the present application adjusts the given current before switching the direct estimation algorithm to the observer algorithm, thereby adjusting the absolute value of the d-axis back electromotive force of the permanent magnet synchronous motor to be less than the absolute value threshold. Only when the absolute value of the d-axis back electromotive force is less than the absolute value threshold, the direct estimation algorithm is switched to the observer algorithm.

[0135] The technical solution provided in the above embodiments of the present application solves the technical problem that the observer algorithm is prone to large errors when the permanent magnet synchronous motor switches from an open-loop control method based on direct back electromotive force estimation to a closed-loop control method based on the observer algorithm.

[0136] Figure 2 The overall flow chart of a method for estimating the rotor position of a permanent magnet synchronous motor provided in an embodiment of the present application is as follows: Figure 2 middle, I ref Indicates the given current, U d represents the d-axis voltage, I d represents the d-axis current, U q represents the q-axis voltage, I q represents the q-axis current, E d represents the d-axis back electromotive force, ω e represents the rotor rotation speed, Y represents the estimation error, ω set Indicates the speed threshold, E set represents the absolute value threshold, I set Indicates the current threshold, Y set Represents the error threshold.

[0137] Figure 3 A schematic diagram of a permanent magnet synchronous motor rotor position estimation device provided in an embodiment of the present application, referring to Figure 3 , corresponding to the above method embodiment, a permanent magnet synchronous motor rotor position estimation device provided in the embodiment of the present application specifically includes a first determination module 301, a second determination module 302, a judgment module 303, an adjustment module 304 and a switching module 305, wherein:

[0138] The first determination module 301 is used to determine the d-axis current and d-axis voltage of the permanent magnet synchronous motor according to the three-phase sampled current of the permanent magnet synchronous motor; wherein the three-phase sampled current is generated after the permanent magnet synchronous motor is input with a given current;

[0139] A second determination module 302 is used to process the d-axis current and d-axis voltage of the permanent magnet synchronous motor by a direct estimation algorithm to determine the d-axis back electromotive force and rotor rotation speed of the permanent magnet synchronous motor;

[0140] A judgment module 303 is used to judge whether the absolute value of the d-axis back electromotive force is less than or equal to a preset absolute value threshold when the rotor rotation speed is greater than a preset speed threshold;

[0141] an adjustment module 304, configured to adjust the given current to adjust the d-axis back electromotive force when the absolute value of the d-axis back electromotive force is greater than the absolute value threshold, until the absolute value of the d-axis back electromotive force is less than or equal to the absolute value threshold;

[0142] The switching module 305 is used to switch the direct estimation algorithm to the observer algorithm when the absolute value of the d-axis back electromotive force is less than or equal to the absolute value threshold, so as to estimate the rotor position of the permanent magnet synchronous motor through the observer algorithm.

[0143] In a feasible embodiment of the present application, the first determining module 301 includes:

[0144] A first determining unit, configured to perform Clark transformation on the three-phase sampled current to determine the d-axis current of the permanent magnet synchronous motor;

[0145] The second determining unit is used to perform Park transformation on the three-phase sampled current to determine the d-axis voltage of the permanent magnet synchronous motor.

[0146] In a feasible embodiment of the present application, the second determining module 302 includes:

[0147] An acquisition unit, used to acquire motor parameters of the permanent magnet synchronous motor; wherein the motor parameters at least include the d-axis inductance, motor resistance and motor pole pair number of the permanent magnet synchronous motor;

[0148] The processing unit is used to process the d-axis inductance, d-axis current, d-axis voltage, motor resistance and motor pole pair number through the motor d-axis model in the direct estimation algorithm to determine the d-axis back electromotive force of the permanent magnet synchronous motor; wherein the motor d-axis model is expressed as:

[0149] U d =L d ×p×I d +R s ×I d +E d ;

[0150] Among them, U d is the d-axis voltage, L d is the d-axis inductance, p is the number of motor pole pairs, I dis the d-axis current, R s is the motor resistance, E d is the d-axis back electromotive force;

[0151] The third determining unit is used to determine the rotor rotation speed according to the d-axis back electromotive force.

[0152] In a feasible embodiment of the present application, the third determining unit includes:

[0153] An acquisition subunit, used for acquiring the q-axis current and q-axis voltage of the permanent magnet synchronous motor; wherein the q-axis current and q-axis voltage of the permanent magnet synchronous motor are determined based on the Clark transformation and Park transformation of the three-phase sampling current;

[0154] The processing subunit is used to process the q-axis inductance, q-axis current, q-axis voltage, motor resistance and the number of motor pole pairs through the motor q-axis model in the direct estimation algorithm to determine the q-axis back electromotive force of the permanent magnet synchronous motor; wherein the motor q-axis model is expressed as:

[0155] U q =L q ×p×I q +R s ×I q +E q ;

[0156] Among them, U q is the q-axis voltage, L q is the q-axis inductance, I q is the q-axis current, E q is the q-axis back electromotive force;

[0157] The determination subunit is used to determine the rotor rotation speed according to the d-axis back electromotive force and the q-axis back electromotive force.

[0158] In a feasible embodiment of the present application, determining a subunit includes:

[0159] The calculation unit is used to calculate the d-axis back electromotive force and the q-axis back electromotive force through the rotor rotation speed formula to determine the rotor rotation speed; wherein the rotor rotation speed formula is:

[0160]

[0161] Among them, ω e is the rotor rotation speed, K e is the preset back electromotive force constant.

[0162] In a feasible embodiment of the present application, the adjustment module 304 includes:

[0163] a first adjustment unit, configured to reduce a given current when the absolute value of the d-axis back electromotive force is greater than an absolute value threshold and the d-axis back electromotive force is greater than 0, until the absolute value of the d-axis back electromotive force is less than or equal to the absolute value threshold;

[0164] The second adjustment unit is used to increase the given current when the absolute value of the d-axis back electromotive force is greater than the absolute value threshold and the d-axis back electromotive force is less than 0 until the absolute value of the d-axis back electromotive force is less than or equal to the absolute value threshold.

[0165] In a feasible embodiment of the present application, the device further includes:

[0166] A calculation module, used for calculating an estimation error of the observer algorithm after the observer algorithm runs for a preset time;

[0167] A first control module, configured to control the continuous estimation of the rotor position of the permanent magnet synchronous motor by using an observer algorithm when the estimated error is less than or equal to a preset error threshold;

[0168] The second control module is used to control the permanent magnet synchronous motor to stop when the estimated error is greater than the error threshold.

[0169] like Figure 4 As shown, the embodiment of the present application provides a permanent magnet synchronous motor, including a processor 401, a communication interface 402, a memory 403 and a communication bus 404, wherein the processor 401, the communication interface 402, and the memory 403 communicate with each other through the communication bus 404.

[0170] Memory 403, used for storing computer programs;

[0171] In one embodiment of the present application, the processor 401 is used to execute the program stored in the memory 403 to implement a method for estimating the rotor position of a permanent magnet synchronous motor provided by any of the above method embodiments, for example, including:

[0172] Determine the d-axis current and d-axis voltage of the permanent magnet synchronous motor according to the three-phase sampling current of the permanent magnet synchronous motor; wherein the three-phase sampling current is generated after a given current is input into the permanent magnet synchronous motor;

[0173] The d-axis current and d-axis voltage of the permanent magnet synchronous motor are processed by a direct estimation algorithm to determine the d-axis back electromotive force and rotor rotation speed of the permanent magnet synchronous motor;

[0174] When the rotor rotation speed is greater than a preset speed threshold, determining whether the absolute value of the d-axis back electromotive force is less than or equal to a preset absolute value threshold;

[0175] When the absolute value of the d-axis back electromotive force is greater than the absolute value threshold, adjusting the given current to adjust the d-axis back electromotive force until the absolute value of the d-axis back electromotive force is less than or equal to the absolute value threshold;

[0176] When the absolute value of the d-axis back electromotive force is less than or equal to the absolute value threshold, the direct estimation algorithm is switched to the observer algorithm to estimate the rotor position of the permanent magnet synchronous motor through the observer algorithm.

[0177] An embodiment of the present application also provides a refrigeration device, which includes a permanent magnet synchronous motor as described in any one of the above embodiments, and the permanent magnet synchronous motor can execute a permanent magnet synchronous motor rotor position estimation method as described in any one of the above method embodiments.

[0178] The device embodiments described above are merely illustrative, wherein the units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0179] Through the description of the above implementation methods, those skilled in the art can clearly understand that each implementation method can be implemented by means of software plus a general hardware platform, and of course, by hardware. Based on this understanding, the above technical solution is essentially or the part that contributes to the relevant technology can be embodied in the form of a software product, and the computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, a disk, an optical disk, etc., including a number of instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or some parts of the embodiments.

[0180] It should be understood that the terms used herein are only for the purpose of describing specific example embodiments and are not intended to be limiting. Unless the context clearly indicates otherwise, the singular forms "one", "an" and "said" as used herein may also be meant to include plural forms. The terms "include", "comprise", "contain", and "have" are inclusive, and therefore specify the existence of stated features, steps, operations, elements and / or parts, but do not exclude the existence or addition of one or more other features, steps, operations, elements, parts, and / or combinations thereof. The method steps, processes, and operations described herein are not interpreted as necessarily requiring them to be performed in the specific order described or illustrated, unless the execution order is clearly indicated. It should also be understood that additional or alternative steps may be used.

[0181] The foregoing is merely a specific embodiment of the present invention, which enables those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for estimating the rotor position of a permanent magnet synchronous motor, characterized in that: The method comprises: Determine the d-axis current and d-axis voltage of the permanent magnet synchronous motor according to the three-phase sampling current of the permanent magnet synchronous motor; wherein the three-phase sampling current is generated after a given current is input to the permanent magnet synchronous motor; Processing the d-axis current and the d-axis voltage of the permanent magnet synchronous motor by a direct estimation algorithm to determine the d-axis back electromotive force and the rotor rotation speed of the permanent magnet synchronous motor; In the case where the rotor rotation speed is greater than a preset speed threshold, determining whether the absolute value of the d-axis back electromotive force is less than or equal to a preset absolute value threshold; When the absolute value of the d-axis back electromotive force is greater than the absolute value threshold, adjusting the given current to adjust the d-axis back electromotive force until the absolute value of the d-axis back electromotive force is less than or equal to the absolute value threshold; When the absolute value of the d-axis back electromotive force is less than or equal to the absolute value threshold, the direct estimation algorithm is switched to an observer algorithm to estimate the rotor position of the permanent magnet synchronous motor through the observer algorithm.

2. The method according to claim 1, characterized in that Determining the d-axis current and d-axis voltage of the permanent magnet synchronous motor according to the three-phase sampled current of the permanent magnet synchronous motor includes: Performing Clark transformation on the three-phase sampled current to determine the d-axis current of the permanent magnet synchronous motor; Park transformation is performed on the three-phase sampled current to determine the d-axis voltage of the permanent magnet synchronous motor.

3. The method according to claim 1, characterized in that The d-axis current and the d-axis voltage of the permanent magnet synchronous motor are processed by a direct estimation algorithm to determine the d-axis back electromotive force and the rotor rotation speed of the permanent magnet synchronous motor, including: Acquire motor parameters of the permanent magnet synchronous motor; wherein the motor parameters at least include d-axis inductance, motor resistance and motor pole pair number of the permanent magnet synchronous motor; The d-axis inductance, the d-axis current, the d-axis voltage, the motor resistance and the number of motor pole pairs are processed by the motor d-axis model in the direct estimation algorithm to determine the d-axis back electromotive force of the permanent magnet synchronous motor; wherein the motor d-axis model is expressed as: U d =L d ×p×I d +R s ×I d +E d ; Among them, U d is the d-axis voltage, L d is the d-axis inductance, p is the number of motor pole pairs, I d is the d-axis current, R s is the motor resistance, E d is the d-axis back electromotive force; The rotor rotation speed is determined based on the d-axis back electromotive force.

4. The method according to claim 3, characterized in that The motor parameters also include q-axis inductance, and determining the rotor rotation speed according to the d-axis back electromotive force includes: Acquire the q-axis current and q-axis voltage of the permanent magnet synchronous motor; wherein the q-axis current and q-axis voltage of the permanent magnet synchronous motor are determined based on the Clark transformation and Park transformation of the three-phase sampling current; The q-axis inductance, the q-axis current, the q-axis voltage, the motor resistance and the number of motor pole pairs are processed by the motor q-axis model in the direct estimation algorithm to determine the q-axis back electromotive force of the permanent magnet synchronous motor; wherein the motor q-axis model is expressed as: U q =L q ×p×I q +R s ×I q +E q ; Among them, U q is the q-axis voltage, L q is the q-axis inductance, I q is the q-axis current, E q is the q-axis back electromotive force; The rotor rotation speed is determined according to the d-axis back electromotive force and the q-axis back electromotive force.

5. The method according to claim 4, characterized in that Determining the rotor rotation speed according to the d-axis back electromotive force and the q-axis back electromotive force includes: The d-axis back electromotive force and the q-axis back electromotive force are calculated by a rotor rotation speed formula to determine the rotor rotation speed; wherein the rotor rotation speed formula is: Among them, ω e is the rotor rotation speed, K e is the preset back electromotive force constant.

6. The method according to claim 1, characterized in that When the absolute value of the d-axis back electromotive force is greater than the absolute value threshold, adjusting the given current to adjust the d-axis back electromotive force until the absolute value of the d-axis back electromotive force is less than or equal to the absolute value threshold, comprises: When the absolute value of the d-axis back electromotive force is greater than the absolute value threshold and the d-axis back electromotive force is greater than 0, reducing the given current until the absolute value of the d-axis back electromotive force is less than or equal to the absolute value threshold; When the absolute value of the d-axis back electromotive force is greater than the absolute value threshold and the d-axis back electromotive force is less than 0, the given current is increased until the absolute value of the d-axis back electromotive force is less than or equal to the absolute value threshold.

7. The method according to claim 1, characterized in that After switching the direct estimation algorithm to the observer algorithm, the method further includes: After the observer algorithm runs for a preset time, calculating an estimation error of the observer algorithm; When the estimated error is less than or equal to a preset error threshold, controlling to continue estimating the rotor position of the permanent magnet synchronous motor by using the observer algorithm; When the estimated error is greater than the error threshold, the permanent magnet synchronous motor is controlled to stop.

8. A device for estimating the rotor position of a permanent magnet synchronous motor, characterized in that: The device comprises: A first determination module is used to determine the d-axis current and d-axis voltage of the permanent magnet synchronous motor according to the three-phase sampling current of the permanent magnet synchronous motor; wherein the three-phase sampling current is generated after a given current is input to the permanent magnet synchronous motor; A second determination module is used to process the d-axis current and the d-axis voltage of the permanent magnet synchronous motor by a direct estimation algorithm to determine the d-axis back electromotive force and the rotor rotation speed of the permanent magnet synchronous motor; A judging module, configured to judge whether the absolute value of the d-axis back electromotive force is less than or equal to a preset absolute value threshold value when the rotation speed of the rotor is greater than a preset speed threshold value; an adjustment module, configured to adjust the given current to adjust the d-axis back electromotive force when the absolute value of the d-axis back electromotive force is greater than the absolute value threshold, until the absolute value of the d-axis back electromotive force is less than or equal to the absolute value threshold; A switching module is used to switch the direct estimation algorithm to an observer algorithm when the absolute value of the d-axis back electromotive force is less than or equal to the absolute value threshold, so as to estimate the rotor position of the permanent magnet synchronous motor through the observer algorithm.

9. A permanent magnet synchronous motor, comprising a memory, a processor, a communication interface and a communication bus, wherein the memory stores a computer program that can be run on the processor, and the memory and the processor communicate through the communication bus and the communication interface, characterized in that: When the processor executes the computer program, the method for estimating the rotor position of the permanent magnet synchronous motor as described in any one of claims 1 to 7 is implemented.

10. A refrigeration device, characterized in that: The refrigeration device comprises the permanent magnet synchronous motor as claimed in claim 9.

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