A novel phase-locked loop implementation method, motor speed estimation and control method and system.

Abstract

This invention discloses a novel phase-locked loop (PLL) implementation method, motor speed estimation and control method, and system. By constructing a back-EMF observation model of a synchronous rotating reference frame, it explores the uniqueness of the d-axis and q-axis components of the back-EMF observation within the range [0, 2π) at their maximum and minimum phase angle solutions. A phase angle cost function is then designed, using the maximum or minimum value of the d-axis or q-axis component of the back-EMF observation as the phase angle cost function. The phase angles from 0 to 2π are then divided into a finite set of discrete phase angles. An iterative algorithm and the phase angle cost function are used to evaluate all these discrete phase angles, ultimately obtaining the phase angle with the smallest static error as the optimal phase angle. In summary, this invention can accurately estimate the phase angle and speed of a permanent magnet motor, avoids the PI controller of traditional PLLs, reduces complex parameter tuning processes, improves dynamic response performance, and reduces computational burden.

Description

Technical Field

[0001] This invention belongs to the field of motor control technology, and more specifically relates to a novel phase-locked loop implementation method, motor speed estimation and control method and system, especially showing outstanding performance in applications such as permanent magnet motors and permanent magnet rotary motors. Background Technology

[0002] Permanent magnet motors, with their high efficiency, high precision, and high-response speed, are widely used in industrial automation, transportation, medical devices, and aerospace. However, the use of traditional speed sensors increases system complexity and cost, and may affect reliability in harsh environments. To address this, sensorless speed control technology has emerged, directly estimating speed and position information from electrical parameters such as motor current and voltage, thereby achieving high-precision control. This technology not only simplifies system structure and reduces costs but also improves system reliability and adaptability, making it particularly suitable for scenarios with high requirements for space, cost, and stability, such as precision machining, medical equipment, and electric vehicle drive systems.

[0003] However, current mainstream sensorless control methods typically require the use of PI phase-locked loops (PLLs), which suffer from complex parameter tuning and the inability of a single parameter to meet the needs of various operating conditions. Among these, PLLs based on finite phase angle sets consider the continuous variation of the motor phase angle within 0 to 2π, and discretize the phase angles based on the concept of finite control sets to obtain a finite number of position regions. However, existing finite phase angle set PLLs suffer from cumbersome search processes and low efficiency. To improve the efficiency of phase angle calculation, some experts have proposed an iterative search strategy based on a bisection method, continuously narrowing the interval to obtain an estimate closest to the true phase angle. Simultaneously, to obtain the optimal phase angle from a finite number of regions, a cost function is defined to evaluate the fit of each phase angle. The cost function is defined as follows: , Let be the actual phase angle, the observed phase angle value, and the phase angle observation error, and E be the back electromotive force amplitude; however, when the cost function is minimized, i.e. When it is 0, at this time If the value is 0 or π, two different phase angles can be estimated, which means that the phase-locked loop (PLL) based on this cost function cannot obtain the accurate grid voltage phase angle, and there may be a large phase error or even cause the system to lose stability.

[0004] To address this problem, M. Abdelrahem proposed a PLL based on a finite set of phase angles and designed two inner and outer loops to obtain the index as... i and j Optimal phase angle First, six candidate phase angles were defined in the outer ring. Substituting these phase angles into a predefined cost function yielded a relatively optimal phase angle. In the inner ring, M. Abdelrahem designed an iterative method based on bisection and defined... , and These represent the incremental phase angle and the optimal phase angle obtained in the previous step, respectively. j =1, 2. The scheme proposed by M. Abdelrahem sets the phase angle evaluation to 24 iterations, including 6 iterations in the outer loop and 18 iterations in the inner loop. Therefore, the phase angle estimation accuracy is π / 6 / 2. 9 =0.001rad.

[0005] In summary, this method assumes that the phase angle of the outer loop is evaluated a certain number of times. a The number of phase angle evaluations for the inner loop is b Then the phase angle estimation accuracy is π / a / 2 b / 2 The number of phase angle evaluations is a + b However, in order to obtain the highest phase angle estimation accuracy with minimal computational burden, a+b should be as small as possible. a ×2 b / 2 The values ​​should be as large as possible, where a and b are both positive integers. Based on this principle, when a + b ≤ 24, four optimal solutions can be found: [a, b] = [6, 18], [3, 20], [4, 20], and [2, 22]. When a = 6 and b = 18, the phase angle is evaluated 24 times, and the phase angle estimation accuracy is π / 6 / 2. 9 =0.001 rad. Meanwhile, if a=3, b=20, it can be found that the phase angle estimation accuracy is the same as the iterative method of M. Abdelrahem, while the number of phase angle evaluations is reduced to 23, indicating a reduction in computational burden. Furthermore, if a=4, b=20, or a=2, b=22, it can be found that the number of phase angle evaluations is 24, the same as the iterative method of M. Abdelrahem, but the phase angle estimation accuracy is improved to π / 4 / 210=π / 2 / 211= 0.000767 rad. This means that if the computational burden remains constant, the phase angle estimation accuracy can be improved by redesigning the two search loops using [a, b]=[4, 20] or [2, 22].

[0006] Although the PLL method proposed by M. Abdelrahem can obtain the phase angle with a smaller computational burden, it is still not optimal. There is room for improvement in the search method of iterative phase-locked loops. It is necessary to achieve the same or similar search accuracy in a shorter number of steps and improve the search efficiency. Summary of the Invention

[0007] To address the problems of complex parameter tuning and the inability of a single parameter to meet the needs of various operating conditions in traditional PI phase-locked loops (PLLs), and the limited search efficiency and accuracy of PLLs based on finite phase angle sets, which restricts their application in motor control, this invention provides a novel method for implementing a PLL, a motor speed estimation and control method, and a system. Specifically, this invention designs a synchronous rotating reference frame... dq The back EMF observation model creatively proposes a novel phase angle cost function, further improving the iterative method proposed by M. Abdelrahem, enhancing the dynamic convergence speed and steady-state convergence accuracy of the phase-locked loop, achieving more efficient searching, and greatly improving search efficiency and accuracy.

[0008] Therefore, the present invention provides the following technical solution:

[0009] On one hand, the present invention provides a novel method for implementing a phase-locked loop, applied to phase angle search of a motor, comprising:

[0010] Construct a model of the back electromotive force observation in a synchronously rotating reference frame dq;

[0011] Design a phase angle cost function based on the back electromotive force observation model;

[0012] Among them, the maximum or minimum value of the d-axis component or q-axis component of the back electromotive force observation is used as the phase angle cost function;

[0013] For the current control cycle, a bisection method is introduced to search for the optimal phase angle of the current control cycle, wherein the candidate phase angle is updated during the iterative search process based on the phase angle cost function.

[0014] The back electromotive force observation model is as follows:

[0015] ;

[0016] In the formula, the subscripts "d" and "q" represent the coordinate axes corresponding to the synchronously rotating reference frame dq; E m For the back electromotive force e αβ The amplitude; θ is the actual phase angle; θ opt The phase angle is obtained from the phase-locked loop; and These are the d-axis and q-axis components of the back electromotive force observation, respectively. and These are the α-axis and β-axis components of the back electromotive force observation, respectively.

[0017] Optionally, based on the d-axis component of the back electromotive force observations in the range [0, 2π). and q-axis components The phase angle at the maximum and minimum values ​​is unique, and the phase angle cost function is any one of the following four functions, specifically:

[0018] ;

[0019] In the formula, These are four different expressions of the phase angle cost function, where max() is the maximum value function and min() is the minimum value function.

[0020] Optionally, in the process of introducing the bisection method to search for the optimal phase angle of the current control cycle, after the iteration termination condition is met, the optimal phase angle of the current iteration is determined based on the phase angle cost function, and then the phase error is compensated for the current optimal phase angle to obtain the optimal phase angle of the current control cycle.

[0021] in, The corresponding phase errors are 3π / 2, π / 2, 0, π.

[0022] Optionally, the process of introducing the binary search method to find the optimal phase angle for the current control cycle is as follows:

[0023] The phase angles from 0 to 2π are divided into a finite number of discrete phase angles. From these, three candidate phase angles with a phase angle difference of 2π / 3 are selected and evaluated. Then, the phase angles with the maximum / minimum phase angle cost function are determined, denoted as θ. (1) Then proceed to the iterative optimization step;

[0024] The iterative optimization step is as follows: Let n be a positive integer greater than or equal to 2, and let the phase angle θ (n-1) θ (n-1) +2π / 3 n θ (n-1) -2π / 3 n As candidate phase angles, the phase angles with the maximum / minimum phase angle cost function are determined from them, denoted as θ. (n) ;

[0025] After the n value reaches the preset value, the current phase θ (n) Compensating for phase error yields the optimal phase angle θ opt .

[0026] Secondly, the technical solution of the present invention also provides a method for estimating motor speed, which includes the following steps in each control cycle of the motor:

[0027] Using the above-mentioned novel phase-locked loop implementation method, the optimal phase angle of the current control cycle is obtained, and the optimal phase angle is used for coordinate transformation and motor speed calculation;

[0028] The motor speed is calculated using the optimal phase angle.

[0029] The coordinate transformation refers to converting the synchronously rotating reference system dq to the two-phase stationary coordinate system αβ, as shown in the formula:

[0030] ;

[0031] The formula for motor speed is:

[0032] ;

[0033] In the formula, i α i β Let i represent the α-axis and β-axis components of the current in the two-phase stationary coordinate system, respectively; d i q These are the d-axis and q-axis components of the current in the synchronously rotating reference frame, respectively. , The optimal phase angles at time t and t-1 are ω, respectively. r Where N is the motor speed, N is the calculation step size, and T is the motor speed. s To control the period, t represents time and k represents the current time. For example, if k is 2 o'clock and the calculation step size N is 1 minute, then the above formula represents the average value from 1:59 to 2 o'clock.

[0034] In three aspects, the technical solution of the present invention provides a motor control method, in which at least the following steps are performed in each control cycle of the motor:

[0035] Obtain the αβ axis stator current i of the motor during the current control cycle. αβ (t) and voltage vector u αβ (t);

[0036] Using the αβ axis stator current i αβ (t) and voltage vector u αβ (t), the back electromotive force of the two-phase stationary coordinate system αβ is obtained by the observer;

[0037] Using the above-mentioned novel phase-locked loop implementation method, the optimal phase angle for the current control cycle is obtained;

[0038] The motor speed is calculated based on the optimal phase angle.

[0039] Given the d-axis current reference value i dref =0; for motor speed ω r With reference value of rotational speed ω ref The difference is used for PI control to obtain the q-axis current reference value i. qref ;

[0040] Based on the optimal phase angle θ optd-axis current reference value i dref and q-axis current reference value i qref Convert to the αβ axis to obtain the αβ axis stator current reference value i. αβref ;

[0041] Using the αβ axis stator current reference value i αβref The optimal voltage vector is selected and used to generate an inverter switching signal. Then, in the next control cycle, the inverter switching signal is applied to the inverter of the motor to achieve motor control.

[0042] Fourthly, the technical solution of the present invention also provides a novel phase-locked loop, which is implemented by using hardware modules, software modules, or a combination of hardware and software modules to realize the above-mentioned novel phase-locked loop.

[0043] In addition, the present invention provides a motor control system, which includes at least the above-mentioned novel phase-locked loop, acquisition module, observer, current prediction module, optimal vector selection module, and PI module.

[0044] The acquisition module acquires the αβ axis stator current i of the motor during the current control cycle. αβ (t) and voltage vector u αβ (t);

[0045] The observer utilizes the αβ-axis stator current i of the motor during the current control cycle. αβ (t) and voltage vector u αβ (t), calculate the observed back electromotive force, and transmit it to the novel phase-locked loop;

[0046] The novel phase-locked loop calculates the optimal phase angle of the current control cycle using the back electromotive force observation value, and calculates the motor speed using the optimal phase angle;

[0047] The PI module measures the motor speed ω. r With reference value of rotational speed ω ref The difference is used for PI control to obtain the q-axis current reference value i. qref Wherein, the d-axis current reference value i dref =0;

[0048] The current prediction module uses the back electromotive force observation value to predict the current.

[0049] The optimal vector selection module utilizes the αβ axis stator current reference value i αβref The optimal voltage vector is selected based on the current prediction results. The optimal voltage vector is used to generate an inverter switching signal. In the next control cycle, the inverter switching signal is applied to the inverter of the motor to realize motor control.

[0050] In six aspects, the present invention also provides a computer-readable storage medium storing a computer program that is invoked by a processor to implement:

[0051] The steps of the above-mentioned novel phase-locked loop implementation method, the steps of the above-mentioned motor speed estimation method, or the steps of the above-mentioned motor control method.

[0052] The following beneficial effects can be achieved through the above technical solutions conceived in this invention:

[0053] (1) Compared with the mainstream PI phase-locked loop speed estimation method, the new phase-locked loop provided by this invention is based on a finite phase angle set phase-locked loop. It has a simple structure, does not require a complicated parameter tuning process, and can meet the requirements of various working conditions. At the same time, by using the new phase angle cost function proposed in this invention, the obtained phase angle can be converged to a determined maximum value according to the number of search or the amount of computation, resulting in good steady-state performance. Meanwhile, since there is no integral element of the PI controller, its dynamic speed is greatly improved. The algorithm is simple, the amount of computation is small, and it does not depend on the initial value.

[0054] (2) Compared with existing similar technologies, the phase-locked loop based on a finite phase angle set provided by this invention has a more efficient search efficiency and a significantly improved search accuracy under the same computational burden. The maximum phase angle error (accuracy) of the technical solution of this invention is π / 3. n The phase angle evaluation count is 2. n +1, where n is the number of iterations in this invention. Especially compared to [ a , b Compared to [4, 20], the advantages of the present invention include:

[0055] Under the same / similar steady-state accuracy of the phase-locked loop, the number of iterative search times was reduced from 24 to 17, alleviating the computational burden;

[0056] With the same / similar number of iterations, the maximum phase angle error (accuracy) ranges from π / 4 / 2. 10 =π / 2 / 2 11 =0.000767 rad increased to π / 3 11 = 0.000018rad, which improves steady-state accuracy. Attached Figure Description

[0057] Figure 1 A flowchart illustrating a permanent magnet motor speed estimation method based on a novel phase-locked loop provided in an embodiment of the present invention;

[0058] Figure 2 The novel phase-locked loop search steps provided in this embodiment of the invention;

[0059] Figure 3A block diagram of a sensorless control strategy for a permanent magnet motor based on a novel phase-locked loop provided in an embodiment of the present invention. Detailed Implementation

[0060] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0061] In this invention, the terms "first," "second," etc. (if present) in the invention and the accompanying drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0062] In the following description, unless otherwise specified, the basic principle for the use of symbols is as follows: the subscript "αβ" represents the component of the αβ axis, and the subscripts "α" and "β" represent the α-axis component and β-axis component of the αβ axis parameter in the corresponding two-phase stationary coordinate system, respectively; the subscript "dq" represents the component of the dq axis, and the subscripts "d" and "q" represent the d-axis component and q-axis component of the dq axis parameter in the corresponding synchronously rotating reference system, respectively.

[0063] To address the issue that existing iterative search methods for phase-locked loops (PLLs) based on finite phase angle sets suffer from limited search efficiency and accuracy, thus restricting their application in motor control, this invention provides a novel method for implementing a PLL. This method involves designing a synchronous rotating reference frame. dq The back EMF observation model creatively proposes a novel phase angle cost function and iterative optimization to increase the dynamic convergence speed and steady-state convergence accuracy of the phase-locked loop (PLL), significantly improving search efficiency and accuracy. Furthermore, based on this finite phase angle PLL, a permanent magnet motor speed estimation method replaces the traditional PI controller, offering controllable steady-state error and a substantial improvement in dynamic response speed. Finally, the phase angle obtained from the finite phase angle PLL is used for coordinate transformation and speed calculation, thereby improving the control performance of the permanent magnet motor and solving the problems of complex parameter tuning and the inability of a single parameter to meet the requirements of various operating conditions in traditional PI PLL-based speed estimation methods.

[0064] The following embodiments will be described in detail using a permanent magnet motor as an example. It should be understood that this is only an example, and when the technical concept of the present invention is applied to other types of motors, the corresponding motor model will be adapted accordingly.

[0065] Based on the above concepts, this invention provides a method for estimating the speed of a permanent magnet motor based on a finite phase angle phase-locked loop, the process of which is as follows: Figure 1As shown, the specific steps include:

[0066] Step 1: Calculate the observed values ​​of the αβ axis back electromotive force based on the back electromotive force observation method. Specifically:

[0067] (1);

[0068] In this context, the superscript "^" indicates the observed quantity, and the subscripts "α" and "β" indicate the corresponding coordinate axes α and β. u ab =[ u a , u b ] T , i ab =[ i a , i b ] T , e αβ = [ e α , e β ] T These are the inverter's output voltage vector, stator current vector, and back electromotive force, respectively, with T being the matrix transpose symbol. u a , u b These are the output voltage vectors. u ab α-axis components and β-axis components; i a , i b These are the stator current vectors. i ab α-axis components and β-axis components; e α , e β They are back electromotive force e αβ α-axis components and β-axis components; back electromotive force e αβ The observed values, Stator current vector i ab The observed values, R s It is the stator resistance. L s For stator inductance, kSMO The sliding mode gain is represented by `sign()`, which is the sign function, and the current error is represented by `current()`. .

[0069] Step 2: Design a phase-locked loop with limited phase angles.

[0070] This invention transforms the back electromotive force observations obtained by the observer to the d- and q-axis coordinate systems and designs a synchronously rotating reference system. dq The back electromotive force in is:

[0071] (2);

[0072] Where the subscripts “d” and “q” represent the coordinate axes dq corresponding to the synchronously rotating reference system; E m Take the back electromotive force observation value The amplitude; i This is the actual phase angle; i opt The phase angle is obtained from the phase-locked loop. and These are the d-axis and q-axis components of the back electromotive force observation, respectively. and These are the α-axis and β-axis components of the back electromotive force observation, respectively.

[0073] From formula (2), it can be seen that the d-axis component of the back electromotive force observation in the range [0, 2π) is... and q-axis components The phase angle solutions for the maximum and minimum values ​​are unique; therefore, the choice is to make... Maximum or minimum value, or select Phase angle with maximum or minimum value i opt As the optimal phase angle, the phase angle cost function can be any one of the following four functions, specifically:

[0074] (3);

[0075] In the formula, These are four different expressions of the phase angle cost function, where max() is the maximum value function and min() is the minimum value function.

[0076] The embodiments of the present invention enable The phase angle with the largest value i opt Taking the optimal phase angle as an example, i.e., the phase angle cost function From formula (2), we can see that Maximum means Minimum, that is , Therefore, the optimal phase angle is obtained through an iterative algorithm. After that, it is also necessary to consider Compensation is performed to obtain the actual phase angle, which is then used for motor control. Similarly, it can be deduced that... The corresponding phase errors are π / 2, 0, and π.

[0077] Based on the above theoretical analysis, this invention uses a phase angle cost function. For example, a novel and improved iterative search method is proposed to reduce the computational burden and improve the accuracy of phase estimation, such as... Figure 2 As shown in the figure i opt To determine the optimal phase angle, the following steps are performed:

[0078] Step 1: Evaluate three candidate phase angles with a phase angle difference of 2π / 3 to find the one that makes the cost function... g PLL The optimal phase is maximized, and this phase is denoted as... i (1) , Figure 1 middle i (1) =0; It should be understood that the first iteration adds three new phase angles to be evaluated.

[0079] Step 2, set the three candidate phase angles as follows: i (1) , i (1) +2π / 9 and i (1) -2π / 9, and evaluate it to find the cost function that makes g PLL The largest optimal phase angle is denoted as . i (2) , Figure 1 middle i (2) =2π / 9; It should be understood that, starting from the second iteration, only two new phase angles to be evaluated are added each time, which is enough to perform a trisection search of the feasible region.

[0080] Step 3, set the three candidate phase angles as follows: i (2) , i (2) +2π / 27 and i (2) -2π / 27, and perform evaluation to find the cost function that makes g PLL The largest optimal phase angle is denoted as . i (3) , Figure 1middle i (3) =2π / 9 + 2π / 27;

[0081] Therefore, it can be deduced that in step n, the three candidate phase angles are set as follows: i (n-1) , i (n-1) +2π / 3 n , i (n-1) -2π / 3 n And evaluate it to find the cost function. g PLL The maximum optimal phase angle is recorded as i (n) Following this step, perform an iterative search, substituting the two newly added candidate phase angles into the cost function to obtain the cost function. g PLL The maximum optimal phase angle is obtained by iterating repeatedly until the iteration termination condition is met. Finally, it is necessary to determine the optimal phase angle based on the given conditions. i opt = i (n) +3π / 2 compensates for phase error, the maximum phase angle error after compensation. eth max : e i max =π / 3 n This metric is used to evaluate phase angle accuracy and determine the number of iterations. Furthermore, the above steps are performed a total of 2 times. n +1 cost function calculations, meaning that only the first round calculates the cost for 3 candidate phase angles. Although 3 are compared in each subsequent round, one of them uses the result from the previous round, so the computational load decreases.

[0082] It should be noted that the technical solution of this invention is fundamentally different from the M. Abdelrahem method. In the M. Abdelrahem method, the feasible region is divided into 6 equal parts in the first iteration; the second iteration determines the region where the optimal phase angle is located (the upper and lower halves); subsequent iterations further divide it into two equal parts. The technical solution of this invention, by utilizing the designed objective function and the already evaluated phase angle information, eliminates the need for determining the region where the optimal phase angle is located (in the second iteration) in the M. Abdelrahem method. In comparison, the technical solution of this invention has higher search efficiency. For example, the results are compared in Table 1 below:

[0083] Table 1 Comparison of Results

[0084]

[0085] Step 3: Based on the aforementioned finite phase angle phase-locked loop, the optimal phase angle for the current control cycle is obtained in each control cycle. The optimal phase angle is used for coordinate transformation and motor speed calculation; then, the motor speed is calculated using the optimal phase angle. This process avoids the use of traditional phase-locked loop PI controllers, reduces complex parameter tuning processes, and improves the dynamic response performance of the phase-locked loop.

[0086] It should be understood that the optimal phase angle obtained by this invention i opt It can be used for coordinate transformation and speed calculation in control systems. (See below:)

[0087] The process of using the optimal phase angle for coordinate transformation and speed calculation includes the following expression for coordinate transformation:

[0088] (4);

[0089] rotational speed oh r The calculation formula is:

[0090] (5);

[0091] in, i α , i β These are the α and β axis components of the current in the two-phase stationary coordinate system, respectively. i d , i q These are the d-axis and q-axis components of the current in the synchronously rotating reference frame, respectively. i opt For the optimal phase angle, oh r This refers to the motor speed. N To calculate the step size, T s To control the period, t represents time and k represents the current moment.

[0092] It should be understood that Steps 1-3 constitute the motor speed estimation method provided by the technical solution of this invention. The embodiment of this invention provides a novel phase-locked loop implementation method, which includes the following steps:

[0093] S1: Construct a model of the back electromotive force observation in the synchronously rotating reference frame dq;

[0094] S2: Design a phase angle cost function based on the back EMF observation model; wherein, the maximum or minimum value of the d-axis component or q-axis component of the back EMF observation is used as the phase angle cost function;

[0095] S3: For the current control cycle, a bisection method is introduced to search for the optimal phase angle of the current control cycle, wherein the candidate phase angle is updated during the iterative search process based on the phase angle cost function.

[0096] It should also be understood that if the calculated motor speed is used in motor control, then a motor control method is implemented, which specifically includes the following steps in each control cycle of the motor:

[0097] Step 1: Obtain the αβ axis stator current of the motor during the current control cycle. i αβ ( t ) and voltage vector u αβ ( t );

[0098] Step 2: Utilizing the αβ axis stator current i αβ ( t ) and voltage vector u αβ ( t The back electromotive force of the two-phase stationary coordinate system αβ is obtained by the observer;

[0099] Step 3: Using the above-described novel phase-locked loop implementation method, obtain the optimal phase angle for the current control cycle;

[0100] Step 4: Calculate the motor speed based on the optimal phase angle;

[0101] Step 5: Specify the d-axis current reference value i dref =0; for motor speed oh r Compared with the speed reference value oh ref The difference is used for PI control to obtain the q-axis current reference value. i qref ;

[0102] Step 6: Based on the optimal phase angle i opt d-axis current reference value i dref and q-axis current reference value i qref Convert to the αβ axis to obtain the αβ axis stator current reference value. i αβref ;

[0103] Step 7: Use the αβ axis stator current reference value i αβrefThe optimal voltage vector is selected and used to generate the inverter switching signal. Then, in the next control cycle, the inverter switching signal is applied to the motor inverter to achieve motor control.

[0104] Taking the application of permanent magnet motors as an example, the optimal phase angle i opt It can be used for coordinate transformation and speed calculation in control, realizing motor speed estimation. It corresponds to a sensorless control strategy for permanent magnet motors based on a finite phase angle phase-locked loop. The control block diagram is shown below. Figure 3 As shown, the process is as follows: Figure 1 As shown, it includes the following steps T1 to T8.

[0105] T1. Obtain the αβ axis stator current of the permanent magnet motor during the current control cycle. i αβ ( t ) and voltage vector u αβ ( t );

[0106] T2. Calculate the back electromotive force observation value based on the back electromotive force observer. ;

[0107] T3. Obtain the phase angle from a finite phase angle phase-locked loop. i opt Calculate the rotational speed oh r ;

[0108] T4, Given d-axis current reference value i dref =0; for rotational speed oh r Compared with the speed reference value oh ref The difference is used for PI control to obtain the q-axis current reference value. i qref ;

[0109] T5, based on phase angle i opt d-axis current reference value i dref and q-axis current reference value i qref Convert to the αβ axis to obtain the αβ axis stator current reference value. i αβref ;

[0110] T6. For each selectable voltage vector, correlate it with the αβ axis stator current. i αβ ( t ) and back electromotive force observations Substituting the values ​​into the mathematical model of the permanent magnet motor, the predicted current is obtained, expressed as:

[0111] (6);

[0112] In the formula, for t Predicted current at time +1 for t Current sampling value at time 10:00 R s It is a primary resistor. T s To control the cycle, For stator inductance, t Indicates the time.

[0113] T7. Calculate the predicted current and the reference value of the αβ axis predicted current. i αβref The degree of difference between them is used as a cost function;

[0114] (7);

[0115] T8. Select the voltage vector with the minimum cost function as the voltage vector for the next control cycle. u αβ ( t +1), after generating the corresponding inverter switching signal, in the next control cycle, the generated switching signal is applied to the inverter used to control the permanent magnet motor. Depending on the driving status of the switching transistors, there are a total of 8 voltage vectors. U 0- U 7. The voltage vectors are shown in Table 2.

[0116] In practical applications, the three-phase windings of the permanent magnet motor are connected to the midpoints of the three-phase bridge arms of the inverter. In the inverter, each phase bridge arm has a switching transistor installed at its upper and lower ends. S a , S b , S c These represent the drive signals of the upper switching transistors of the bridge arms connected to the A, B, and C phase windings of the permanent magnet motor, respectively. 1 represents a high level, and 0 represents a low level. It's easy to understand that a high level is the level that turns on the upper switching transistor and turns off the lower switching transistor of the bridge arm, while a low level is the level that turns off the upper switching transistor and turns on the lower switching transistor.

[0117] Table 2 8 voltage vectors

[0118]

[0119] In other embodiments, the present invention also provides a novel phase-locked loop, which is implemented by a hardware module, a software module, or a combination of hardware and software modules.

[0120] It should be understood that the hardware components of the novel phase-locked loop and the connections between them are existing technologies, and this invention does not specifically limit them. Any technical solution employing hardware modules, software modules, or a combination of both all meet the requirements of this invention and fall within its protection scope.

[0121] In other embodiments, comparison Figure 3 The present invention provides a motor control system, which includes at least the above-mentioned novel phase-locked loop, acquisition module, observer, current prediction module, optimal vector selection module and PI module;

[0122] The acquisition module collects the αβ axis stator current i of the motor during the current control cycle. αβ (t) and voltage vector u αβ (t); The observer utilizes the αβ axis stator current of the motor during the current control cycle. i αβ ( t ) and voltage vector u αβ ( t The back electromotive force observation is calculated and transmitted to the new inverter.

[0123] The new phase-locked loop calculates the optimal phase angle of the current control cycle using the back electromotive force observation, and calculates the motor speed using the optimal phase angle.

[0124] PI module, for motor speed oh r Compared with the speed reference value oh ref The difference is used for PI control to obtain the q-axis current reference value. i qref Among them, the d-axis current reference value i dref =0.

[0125] The current prediction module uses back electromotive force observations to predict the current.

[0126] The optimal vector selection module utilizes the αβ axis stator current reference value. i αβref The optimal voltage vector is selected based on the current prediction results. The optimal voltage vector is used to generate the inverter switching signal. In the next control cycle, the inverter switching signal is applied to the inverter of the motor to realize motor control.

[0127] In other embodiments, the present invention also provides a computer-readable storage medium storing a computer program that is invoked by a processor to implement:

[0128] The steps of the above-described novel phase-locked loop implementation method, the steps of the above-described motor speed estimation method, or the steps of the above-described motor control method.

[0129] For details on the implementation of each step, please refer to the description in the foregoing method embodiments.

[0130] The readable storage medium is a computer-readable storage medium, which can be an internal storage unit of the hardware and software device described in any of the foregoing embodiments, such as the hard drive or memory of the controller. The readable storage medium can also be an external storage device of the controller, such as a plug-in hard drive, Smart MediaCard (SMC), Secure Digital (SD) card, or Flash Card equipped on the controller. Further, the readable storage medium can include both internal storage units and external storage devices of the controller. The readable storage medium is used to store the computer program and other programs and data required by the controller. The readable storage medium can also be used to temporarily store data that has been output or will be output.

[0131] Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned readable storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0132] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-readable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code. This application refers to flowchart illustrations and / or instructions executed by a processor of a method, apparatus (system), and computer program product according to embodiments of this application to create means for implementing the functions specified in one or more flowchart illustrations and / or one or more block diagrams. These computer program instructions may also be stored in a computer-readable storage medium capable of directing a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means that implement the functions specified in one or more flowchart illustrations and / or one or more block diagrams. These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process, such that the instructions, which execute on the computer or other programmable apparatus, provide steps for implementing the functions specified in one or more flowcharts and / or one or more blocks of a block diagram.

[0133] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A novel method for implementing a phase-locked loop (PLL), applied to phase angle search of a motor, characterized in that, include: Construct a model of the back electromotive force observation in a synchronously rotating reference frame dq; Design a phase angle cost function based on the back electromotive force observation model; Among them, the maximum or minimum value of the d-axis component or q-axis component of the back electromotive force observation is used as the phase angle cost function; For the current control cycle, a binary search method is introduced to find the optimal phase angle for the current control cycle, wherein the candidate phase angle is updated during the iterative search process based on the phase angle cost function; In the process of introducing the bisection method to search for the optimal phase angle of the current control cycle, after the iteration termination condition is met, the optimal phase angle of the current iteration is determined based on the phase angle cost function, and then the optimal phase angle of the current iteration is compensated for the phase error to obtain the optimal phase angle of the current control cycle. Based on the d-axis component of the back electromotive force observations in the range [0, 2π). and q-axis components The phase angle at the maximum and minimum values ​​is unique, and the phase angle cost function is any one of the following four functions, specifically: `max()` is the maximum value function, `min()` is the minimum value function, and `phase angle cost function` is the minimum value function. The corresponding phase errors are 3π / 2, π / 2, 0, π; The process of introducing the binary search method to find the optimal phase angle for the current control cycle is as follows: The phase angles from 0 to 2π are divided into a finite number of discrete phase angles. From these, three candidate phase angles with a phase angle difference of 2π / 3 are selected and evaluated. Then, the phase angles with the maximum / minimum phase angle cost function are determined, denoted as θ. (1) Then proceed to the iterative optimization step; The iterative optimization step is as follows: Let n be a positive integer greater than or equal to 2, and let the phase angle θ (n-1) θ (n-1) +2π / 3 n θ (n-1) -2π / 3 n As candidate phase angles, the phase angles with the maximum / minimum phase angle cost function are determined from them, denoted as θ. (n) ; After the n value reaches the preset value, the current phase θ (n) Compensating for phase error yields the optimal phase angle θ opt .

2. The method according to claim 1, characterized in that: The back electromotive force observation model is as follows: ； In the formula, E m For the back electromotive force e αβ The amplitude; θ is the actual phase angle; θ opt The phase angle is obtained from the phase-locked loop; and These are the d-axis and q-axis components of the back electromotive force observation, respectively. and These are the α-axis and β-axis components of the back electromotive force observation, respectively.

3. A method for estimating motor speed, characterized in that: Each control cycle of the motor includes the following steps: Using the implementation method of the novel phase-locked loop according to any one of claims 1-2, the optimal phase angle of the current control cycle is obtained, and the optimal phase angle is used for coordinate transformation and motor speed calculation; The motor speed is calculated using the optimal phase angle. The coordinate transformation refers to converting the synchronously rotating reference system dq to the two-phase stationary coordinate system αβ, as shown in the formula: ； The formula for motor speed is: ； In the formula, i α i β Let i represent the α-axis and β-axis components of the current in the two-phase stationary coordinate system, respectively; d i q These are the d-axis and q-axis components of the current in the synchronously rotating reference frame, respectively. , The optimal phase angles at time t and t-1 are ω, respectively. r Where N is the motor speed, N is the calculation step size, and T is the motor speed. s To control the period, t represents time.

4. A motor control method, characterized in that: In each control cycle of the motor, at least the following steps shall be performed: Obtain the αβ axis stator current i of the motor during the current control cycle. αβ (t) and voltage vector u αβ (t); Using the αβ axis stator current i αβ (t) and voltage vector u αβ (t), the back electromotive force of the two-phase stationary coordinate system αβ is obtained by the observer; Using the implementation method of the novel phase-locked loop according to any one of claims 1-2, the optimal phase angle of the current control cycle is obtained; The motor speed is calculated based on the optimal phase angle. Given the d-axis current reference value i dref =0; for motor speed ω r With reference value of rotational speed ω ref The difference is used for PI control to obtain the q-axis current reference value i. qref ; Based on the optimal phase angle θ opt d-axis current reference value i dref and q-axis current reference value i qref Convert to the αβ axis to obtain the αβ axis stator current reference value i. αβref ; Using the αβ axis stator current reference value i αβref The optimal voltage vector is selected and used to generate an inverter switching signal. Then, in the next control cycle, the inverter switching signal is applied to the inverter of the motor to achieve motor control.

5. A motor control system, characterized in that: It includes at least an acquisition module, an observer, a current prediction module, an optimal vector selection module, a PI module, and a novel phase-locked loop implemented by the method described in any one of claims 1-2; The acquisition module acquires the αβ axis stator current i of the motor during the current control cycle. αβ (t) and voltage vector u αβ (t); The observer utilizes the αβ-axis stator current i of the motor during the current control cycle. αβ (t) and voltage vector u αβ (t), calculate the observed back electromotive force, and transmit it to the novel phase-locked loop; The novel phase-locked loop calculates the optimal phase angle of the current control cycle using the back electromotive force observation value, and calculates the motor speed using the optimal phase angle; The PI module measures the motor speed ω. r With reference value of rotational speed ω ref The difference is used for PI control to obtain the q-axis current reference value i. qref Wherein, the d-axis current reference value i dref =0; The current prediction module uses the back electromotive force observation value to predict the current. The optimal vector selection module utilizes the αβ axis stator current reference value i αβref The optimal voltage vector is selected based on the current prediction results. The optimal voltage vector is used to generate an inverter switching signal. In the next control cycle, the inverter switching signal is applied to the inverter of the motor to realize motor control.

6. A computer-readable storage medium, characterized in that: The computer program is stored and is invoked by the processor to implement: The steps of the implementation method of the novel phase-locked loop according to any one of claims 1-2, the steps of the motor speed estimation method according to claim 3, or the steps of the motor control method according to claim 4.

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