Phase angle estimation method for permanent magnet synchronous motor, phase-locked loop and control system

Abstract

This invention belongs to the technical field of motor control and discloses a phase angle estimation method, a phase-locked loop, and a control system for a permanent magnet synchronous motor. The phase angle estimation method includes: using the d-axis component or q-axis component of the observed back electromotive force vector as an evaluation function, using the maximum or minimum value of the evaluation function as the optimization objective, and searching for the optimal candidate phase angle θ in (0, 2π]. opt According to θ opt Estimating the phase angle of a permanent magnet synchronous motor: When the optimization objective is to maximize the d-axis component, =θ opt -π / 2; when the optimization objective is to minimize the d-axis component, =θ opt -3π / 2; when the optimization objective is to maximize the q-axis component, =θ opt When the optimization objective is to minimize the q-axis component, =θ opt -π. This invention enables rapid estimation of the phase angle through a simpler method, thereby significantly improving the dynamic speed response capability of the permanent magnet synchronous motor control system.

Description

Technical Field

[0001] This invention belongs to the field of motor control technology, and more specifically, relates to a phase angle estimation method, phase-locked loop and control system for a permanent magnet synchronous motor. Background Technology

[0002] Permanent magnet synchronous motors have shown great application potential in many cutting-edge fields, such as industrial automated production lines, high-efficiency energy conversion systems, high-end medical equipment, and aerospace exploration, due to their excellent energy efficiency, precise control capabilities, and rapid response characteristics.

[0003] Permanent magnet synchronous motors (PMSMs) traditionally rely on speed sensors for precise control. However, this approach not only increases system complexity and overall cost, but also means that sensor reliability and stability often become limiting factors in extreme or harsh operating environments. Therefore, many experts have researched sensorless control technology. This technology cleverly utilizes the motor's own electrical signals, such as current and voltage, to estimate the motor's speed and position information in real time through advanced algorithms, thereby achieving high-precision sensorless speed measurement of PMSMs.

[0004] Sensorless speed measurement technology not only greatly simplifies the architecture of motor control systems and effectively reduces costs, but more importantly, it significantly enhances the robustness and environmental adaptability of the system. It is particularly suitable for applications with stringent requirements for space layout, cost control, and long-term stable operation, such as semiconductor precision manufacturing, high-end medical imaging equipment, and the power systems of new energy electric vehicles. However, sensorless control strategies rely on phase-locked loops (PLLs) to predict the phase angle of the motor inverter's output current. Currently, mainstream PLL technologies include PI PLL technology and PLL methods based on finite phase sets. The parameter tuning process for PI PLL technology is complex, making it difficult to maintain optimal performance under various operating conditions. Existing PLL methods based on finite phase sets suffer from cumbersome search algorithms and low search efficiency.

[0005] Therefore, there is an urgent need to develop simpler and faster phase-locked loop (PLL) technology to further promote the development and application of sensorless control technology for permanent magnet synchronous motors. Summary of the Invention

[0006] In view of the above-mentioned defects or improvement needs of the existing technology, the present invention provides a phase angle estimation method, phase-locked loop and control system for permanent magnet synchronous motor, the purpose of which is to achieve phase angle estimation quickly through a simpler method.

[0007] To achieve the above objectives, this invention is proposed.

[0008] According to a first aspect of the present invention, a method for estimating the phase angle of a permanent magnet synchronous motor is provided, comprising:

[0009] Using the d-axis component or q-axis component of the back electromotive force observation vector in the dq coordinate system as the evaluation function, and taking the maximum or minimum value of the evaluation function as the optimization objective, the optimal candidate phase angle θ is searched within the phase angle selection range (0, 2π]. opt :

[0010] Based on the optimal candidate phase angle θ opt Estimate the phase angle of the permanent magnet synchronous motor:

[0011] When the optimization objective is to maximize the d-axis component, the estimated phase angle of the permanent magnet synchronous motor is... =θ opt -π / 2;

[0012] When the optimization objective is to minimize the d-axis component, the estimated phase angle of the permanent magnet synchronous motor is... =θ opt -3π / 2;

[0013] When the optimization objective is to maximize the q-axis component, the estimated phase angle of the permanent magnet synchronous motor is... =θ opt ;

[0014] When the optimization objective is to minimize the q-axis component, the estimated phase angle of the permanent magnet synchronous motor is... =θ opt -π.

[0015] According to a second aspect of the present invention, a phase-locked loop for use in a permanent magnet synchronous motor is provided, comprising:

[0016] The candidate phase angle optimization unit is used to find the optimal candidate phase angle θ within the phase angle selection range (0, 2π] by using the d-axis component or q-axis component of the back electromotive force observation vector in the dq coordinate system as the evaluation function and achieving the maximum or minimum value of the evaluation function as the optimization objective. opt ;

[0017] The permanent magnet synchronous motor phase angle estimation unit is used to estimate the optimal candidate phase angle θ. opt Estimate the phase angle of the permanent magnet synchronous motor;

[0018] When the optimization objective is to maximize the d-axis component, the estimated phase angle of the permanent magnet synchronous motor is... =θ opt -π / 2;

[0019] When the optimization objective is to minimize the d-axis component, the estimated phase angle of the permanent magnet synchronous motor is... =θ opt -3π / 2;

[0020] When the optimization objective is to maximize the q-axis component, the estimated phase angle of the permanent magnet synchronous motor is... =θ opt ;

[0021] When the optimization objective is to minimize the q-axis component, the estimated phase angle of the permanent magnet synchronous motor is... =θ opt -π.

[0022] According to a third aspect of the present invention, a control system for a permanent magnet synchronous motor is provided, comprising:

[0023] The Park coordinate transformation module is used to transform the acquired inverter phase current i abc Current i transformed into dq coordinate system dq ;

[0024] The Clark coordinate transformation module is used to transform the acquired inverter phase current i abc Current i transformed into αβ coordinate system αβ ;

[0025] Back EMF observation module, used to receive current i αβ Inverter voltage u in αβ coordinate system αβ Calculate the back electromotive force observation vector in the αβ coordinate system. ;

[0026] The phase-locked loop described above is used to observe the vector based on the back electromotive force. Estimate the phase angle of the inverter phase current And calculate the motor speed ;

[0027] The speed control module is used to control the given motor reference speed. With motor speed After subtraction, the q-axis current reference value i is obtained via a PI controller. qref q-axis current reference value i qref and d-axis current reference value i qref =0 constitutes the current reference value i in the dq coordinate system. dqref ;

[0028] The current control module is used to control the current reference value i. dqref and current i dq After differential calculation, the dq axis voltage reference value is obtained via a PI controller;

[0029] The Park coordinate inverse transformation module is used to transform the phase angle obtained from the phase-locked loop. Transform the dq-axis voltage reference value to the reference voltage u in the αβ coordinate system. αβref ;

[0030] The SVPWM control module is used to control the voltage u according to the reference voltage u.αβref It generates bridge arm switching pulse signals corresponding to each phase of the inverter to control the permanent magnet synchronous motor.

[0031] In summary, compared with the prior art, the technical solutions conceived in this invention have the following main advantages:

[0032] 1. In this invention, based on the analysis of the back electromotive force observation vector, its d-axis component... It can be represented as a sine function, with its q-axis component... It can be stated that the cosine, sine, and cosine functions each have a unique maximum or minimum value in the range (0, 2π]. By finding the phase angle corresponding to the maximum or minimum value, a phase angle estimate close to the actual phase angle can be obtained based on the maximum or minimum value characteristics of the sine and cosine functions. Compared to traditional PI phase-locked loop (PLL) technology, the method proposed in this invention is simpler in design, avoids cumbersome parameter tuning processes, and can flexibly adapt to diverse working conditions. Compared to traditional PLL methods based on finite phase sets, the method proposed in this invention requires less computation and has higher search efficiency. Overall, this invention can quickly estimate the phase angle using a simpler method, thus significantly improving the dynamic speed response capability of the permanent magnet synchronous motor control system.

[0033] 2. Furthermore, this embodiment of the invention also provides a method for searching candidate phase angles. By dividing the phase angles from 0 to 2π into a finite set of discrete phase angles, and then using the principle of axisymmetry to design and an iterative search algorithm of the evaluation function to evaluate the control error of the discrete phase angles, the estimated phase angle value is obtained according to the principle of taking the maximum value of the evaluation function. This improves the accuracy of phase angle and speed calculation, thereby enhancing the control performance of the permanent magnet synchronous motor. Attached Figure Description

[0034] Figure 1 This is a structural block diagram of a permanent magnet synchronous motor control system in one embodiment;

[0035] Figure 2 This is a flowchart of the phase angle estimation method for a permanent magnet synchronous motor according to an embodiment of the present invention;

[0036] Figure 3 This is a schematic diagram of the optimal candidate phase angle search process in one embodiment of the present invention. Detailed Implementation

[0037] 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.

[0038] To facilitate understanding of this invention, a permanent magnet synchronous motor control system based on a finite phase angle phase-locked loop is first introduced. In the following description, unless otherwise specified, the basic principle for symbol representation is as follows: the subscript "αβ" indicates the αβ-axis component, and the subscripts "α" and "β" respectively indicate the α-component and β-axis component of the corresponding αβ-axis parameter; the subscript "dq" indicates the dq-axis component, and the subscripts "d" and "q" respectively indicate the d-component and q-axis component of the corresponding dq-axis parameter; the superscript "^" indicates the observed value of the corresponding variable. For example... Figure 1 The diagram shown is a structural block diagram of a permanent magnet synchronous motor control system in one embodiment, which includes:

[0039] The Park coordinate transformation module is used to transform the acquired inverter phase current i abc Current i transformed into dq coordinate system dq ;

[0040] The Clark coordinate transformation module is used to transform the acquired inverter phase current i abc Current i transformed into αβ coordinate system αβ ;

[0041] Back EMF observation module, used to receive current i αβ Inverter voltage u in αβ coordinate system αβ Calculate the back electromotive force observation vector in the αβ coordinate system. ;

[0042] Phase-locked loop (PLL) is used to observe vectors based on back electromotive force. Estimate the phase angle of the inverter phase current And calculate the motor speed ;

[0043] The speed control module is used to control the given motor reference speed. With motor speed After subtraction, the q-axis current reference value i is obtained via a PI controller. qref q-axis current reference value i qref and d-axis current reference value i dref =0 constitutes the current reference value i in the dq coordinate system. dqref ;

[0044] The current control module is used to control the current reference value i.dqref and current i dq After differential calculation, the dq axis voltage reference value is obtained via a PI controller;

[0045] The Park coordinate inverse transformation module is used to transform the phase angle obtained from the phase-locked loop. Transform the dq-axis voltage reference value to the reference voltage u in the αβ coordinate system. αβref ;

[0046] The SVPWM control module is used to control the voltage u according to the reference voltage u. αβref It generates bridge arm switching pulse signals corresponding to each phase of the inverter to control the permanent magnet synchronous motor.

[0047] Therefore, in the control system of a permanent magnet synchronous motor, it is necessary to estimate the phase angle using a phase-locked loop. However, traditional phase-locked loop (PLL) technology suffers from problems such as complexity and low speed.

[0048] Based on this, the present invention proposes the following improvement scheme.

[0049] Example 1

[0050] This invention provides a method for estimating the phase angle of a permanent magnet synchronous motor, such as... Figure 2 The diagram shows a flowchart of the phase angle estimation method for a permanent magnet synchronous motor according to an embodiment of the present invention. The steps are described in detail below.

[0051] S1. Using the d-axis component or q-axis component of the back electromotive force observation vector in the dq coordinate system as the evaluation function, and taking the maximum or minimum value of the evaluation function as the optimization objective, the optimal candidate phase angle θ is searched within the phase angle selection range (0, 2π]. opt :

[0052] S2. Based on the optimal candidate phase angle θ opt Estimating the phase angle of a permanent magnet synchronous motor: When the optimization objective is to maximize the d-axis component, the estimated phase angle of the permanent magnet synchronous motor is... =θ opt -π / 2; When the optimization objective is to minimize the d-axis component, the estimated phase angle of the permanent magnet synchronous motor is... =θ opt -3π / 2; When the optimization objective is to maximize the q-axis component, the estimated phase angle of the permanent magnet synchronous motor is... =θ opt When the optimization objective is to minimize the q-axis component, the estimated phase angle of the permanent magnet synchronous motor is... =θ opt -π.

[0053] First, a theoretical explanation of the above phase angle estimation method will be given.

[0054] The relationship between the observed back electromotive force vector in the dq coordinate system and the back electromotive force in the αβ coordinate system is analyzed as follows:

[0055]

[0056] In the formula, , These are the d-axis and q-axis components of the back electromotive force observation vector in the dq coordinate system, respectively. , These are the back electromotive force observation vectors in the αβ coordinate system. The α-axis components and β-axis components, Provided directly by the back EMF observation module. This is the actual phase angle. Here, E is the estimated value of the phase angle, and E is the magnitude of the back electromotive force.

[0057] It should be noted that the actual phase angle is unavailable; the phase-locked loop needs to estimate the current phase angle based on other parameters. The closer to the actual phase angle The more accurate the result, the better.

[0058] Based on the above relationships, it can be seen that , Ultimately, this can be expressed as sine and cosine functions as follows:

[0059]

[0060] Both the sine and cosine functions have unique extrema in the range (0, 2π]. By finding the phase angle corresponding to the extrema, we can obtain a phase angle close to the actual value based on the extrema characteristics of the sine and cosine functions. Phase angle estimate In this invention, calculation is not performed directly. Instead, it first searches for the optimal candidate phase angle, and then, based on the properties of the sine and cosine functions, obtains the phase angle estimate from the optimal candidate phase angle. .

[0061] Let the candidate phase angle be denoted as θ. h The optimal candidate phase angle found at the end is denoted as θ. opt .

[0062] For example, for Its phase angle θ h The changing function can be expressed as Traverse candidate phase angles θ h ,like At a certain candidate phase angle θ h Take the maximum value at that point, and record this candidate phase angle as the optimal candidate phase angle θ. optAccording to the maximum value characteristic of the sine function, That is, the optimal candidate phase angle θ opt Compared with the actual phase angle The phase difference is approximately π / 2. Based on this, an estimated phase angle can be obtained. It can also be equivalently represented as .

[0063] Similarly, if At a certain candidate phase angle θ h The minimum value is taken at the specified point, and this candidate phase angle is recorded as the optimal candidate phase angle θ. opt According to the minimum value property of the sine function, That is, the optimal candidate phase angle θ opt Compared with the actual phase angle The phase angle differs by approximately 3π / 2. Based on this, an estimated value for the phase angle can be obtained. It can also be equivalently represented as .

[0064] For example, for Its phase angle θ h The changing function can be expressed as Traverse candidate phase angles θ h ,like At a certain candidate phase angle θ h Take the maximum value at that point, and record this candidate phase angle as the optimal candidate phase angle θ. opt According to the maximum value characteristic of the cosine function, That is, the optimal candidate phase angle θ opt Compared with the actual phase angle The values ​​are roughly the same; based on this, the estimated phase angle can be obtained. .

[0065] Similarly, if At a certain candidate phase angle θ h The minimum value is taken at the specified point, and this candidate phase angle is recorded as the optimal candidate phase angle θ. opt According to the maximum value characteristic of the cosine function, That is, the optimal candidate phase angle θ opt Compared with the actual phase angle The phase difference is approximately π; based on this, an estimated phase angle can be obtained. It can also be equivalently represented as .

[0066] Based on the above analysis, we can then use or For the evaluation function g PLL ,by or The objective is to find the optimal value by selecting the best candidate phase angle θ within the phase angle selection range (0, 2π]. opt Then, directly based on the optimal candidate phase angle θ opt When the phase angle estimate is obtained, the optimization objective is to make At its maximum, the estimated phase angle =θ opt -π / 2; when the optimization objective is to make At its minimum, the estimated phase angle =θ opt -3π / 2; when the optimization objective is to make At maximum, the estimated phase angle of the permanent magnet synchronous motor =θ opt When the optimization goal is to make The estimated phase angle of the permanent magnet synchronous motor at its minimum. =θ opt -π.

[0067] Specifically, when For the evaluation function g PLL When, the evaluation function g PLL The calculation formula is:

[0068]

[0069] When For the evaluation function g PLL When, the evaluation function g PLL The calculation formula is:

[0070]

[0071] In the formula, , These are the α-axis and β-axis components of the back EMF observation vector in the αβ coordinate system, respectively. These parameters are provided by the back EMF observation module. The candidate phase angles to be substituted. Let be the d-axis component of the back electromotive force observation vector in the dq coordinate system. Let q be the q-axis component of the back electromotive force observation vector in the dq coordinate system.

[0072] It should be noted that you only need to choose one of the four methods above.

[0073] In a specific embodiment, a specific optimization method is further provided for S1 as follows.

[0074] S11: Initialize the phase angle selection interval (θ1, θ2] to (0, 2π).

[0075] S12: Based on the current phase angle selection interval, determine two candidate phase angles for comparison. One candidate phase angle is located in the first half of the current selection interval and is θ1 + Δθ / 2, while the other candidate phase angle is located in the second half of the current selection interval and is θ2 - Δθ / 2, where Δθ = 2π / 2. n-1 The angle difference is determined based on the set number of phase angle searches, n, where n ≥ 2.

[0076] S13: Compare the evaluation function values ​​under the current two candidate phase angles, and take the half interval of the candidate phase angle whose evaluation function value is closest to the optimization target as the current selection interval (θ1, θ2).

[0077] S14: Repeat S12~S13 until the search count n is reached. Output the candidate phase angle whose evaluation function value is closest to the optimization target in the last search as the optimal candidate phase angle θ. opt .

[0078] Specifically, the included angle difference Δθ = 2π / 2 is determined based on the set number of search attempts n. n-1 The number of searches, n, is set by the user. Understandably, the larger n is, the more searches are performed and the smaller the error.

[0079] In the first search, the phase angle selection interval is (0, 2π], with a span of 2π. The two candidate phase angles for comparison can be denoted as θ1 = Δθ / 2 and θ2 = 2π - Δθ / 2. The evaluation function values ​​for these two candidate phase angles are calculated respectively. The half-interval containing the candidate phase angle whose evaluation function value is closest to the optimization target is taken as the new phase angle selection interval. For example, when the optimization target is to find the maximum value of the evaluation function, it means that the optimal candidate phase angle θ is... opt The half-interval containing the candidate phase angle with the larger evaluation function value is used as the new phase angle selection interval for the next round of search. When the optimization objective is to find the minimum value of the evaluation function, it indicates that the optimal candidate phase angle θ is found. opt If a candidate phase angle with a smaller evaluation function value is located in the half-interval, that half-interval is used as the new phase angle selection interval, and the search continues in the next round.

[0080] In the second search, the interval span is halved to 2π / 2. Following the same pattern, the interval search continues, and in the third search, the interval span is 2π / 2. 2 And so on, in the nth search, the interval span is 2π / 2 n-1 After n searches, the search range is reduced from the initial 2π to 2π / 2. n-1 The maximum phase angle error can be reduced to ε. θ =π / 2 n-1 .

[0081] like Figure 3 The diagram shown is a schematic representation of the optimal candidate phase angle search process in one embodiment of the present invention. Exemplarily, it is illustrated by... For the evaluation function g PLL ,by Taking the maximum value as the optimization objective, the initial phase angle selection range is (0, 2π], and the two candidate phase angles are θ1 = Δθ / 2 = 2π / 2. n And θ2=2π-Δθ / 2=2π-2π / 2 n ; Calculate the evaluation function g respectively PLL The candidate phase angle with the larger evaluation function is denoted as θ. opt1 If θ opt1 If θ1 is the phase angle, then the phase angle selection range for the second search is (0, π]. The phase angles of the two candidate phase angles θ1 and θ3 are θ1 = Δθ / 2 = 2π / 2 respectively. n And θ3=π-Δθ / 2=π-2π / 2 n If θ opt1 If θ2 is the phase angle, then the phase angle selection range for the second search is (π, 2π]. The phase angles of the two candidate phase angles θ2 and θ3 are θ2 = 2π - Δθ / 2 = 2π - 2π / 2 respectively. n And θ3=π+Δθ / 2=π+2π / 2 n ; Calculate the evaluation function g again PLL The candidate phase angle with the larger evaluation function is denoted as θ. opt2 The search continues according to this pattern. Each search divides the phase angle selection range of this iteration into two halves based on the principle of axisymmetry, retaining the half with the larger evaluation function, until n searches are completed. In the nth search, the range is reduced to 2π / 2. n-1 Select the optimal candidate phase angle θ from them. opt Based on the property that the cosine takes the maximum value, the estimated phase angle can be obtained. For θ opt .

[0082] In the above embodiments, by dividing the phase angle from 0 to 2π into a finite set of discrete phase angles, and then using the principle of axisymmetry to design and an iterative search algorithm for the evaluation function to evaluate the control error of the discrete phase angles, the estimated phase angle value is obtained according to the principle of taking the maximum value of the evaluation function. This improves the accuracy of phase angle and speed calculation, thereby enhancing the control performance of the permanent magnet synchronous motor.

[0083] Example 2

[0084] This invention also proposes a phase-locked loop for use in permanent magnet synchronous motors, comprising:

[0085] The candidate phase angle optimization unit is used to find the optimal candidate phase angle θ within the phase angle selection range (0, 2π] by using the d-axis component or q-axis component of the back electromotive force observation vector in the dq coordinate system as the evaluation function and achieving the maximum or minimum value of the evaluation function as the optimization objective. opt ;

[0086] The permanent magnet synchronous motor phase angle estimation unit is used to estimate the optimal candidate phase angle θ. opt Estimate the phase angle of the permanent magnet synchronous motor;

[0087] When the optimization objective is to maximize the d-axis component, the estimated phase angle of the permanent magnet synchronous motor is... =θ opt -π / 2;

[0088] When the optimization objective is to minimize the d-axis component, the estimated phase angle of the permanent magnet synchronous motor is... =θ opt -3π / 2;

[0089] When the optimization objective is to maximize the q-axis component, the estimated phase angle of the permanent magnet synchronous motor is... =θ opt ;

[0090] When the optimization objective is to minimize the q-axis component, the estimated phase angle of the permanent magnet synchronous motor is... =θ opt -π.

[0091] Furthermore, the candidate phase angle optimization unit includes:

[0092] Initialize the sub-unit to initialize the phase angle selection interval (θ1, θ2] to (0, 2π);

[0093] The search iteration subunit is used to re-execute the search iteration until the search count n is reached. It outputs the candidate phase angle whose evaluation function value is closest to the optimization target in the last search as the optimal candidate phase angle θ. opt Each search iteration includes determining candidate phase angles and comparing evaluation functions;

[0094] Determining candidate phase angles involves: identifying two candidate phase angles for comparison based on the current phase angle selection interval. One candidate phase angle is located in the first half of the current phase angle selection interval and is θ1 + Δθ / 2, while the other candidate phase angle is located in the second half of the current phase angle selection interval and is θ2 - Δθ / 2, where Δθ = 2π / 2. n-1 The angle difference is determined based on the set number of phase angle searches, n, where n ≥ 2;

[0095] The comparison evaluation function includes: comparing the evaluation function values ​​under the current two candidate phase angles, and taking the half interval of the candidate phase angle whose evaluation function value is closest to the optimization target as the current selection interval (θ1, θ2).

[0096] The phase-locked loop described above can implement the phase angle estimation method in Example 1. For specific details, please refer to the description of Example 1, which will not be repeated here.

[0097] Furthermore, the phase-locked loop also includes a motor speed calculation unit, used to calculate the motor speed based on the phase angle estimate obtained in the current control cycle and the phase angle estimate obtained in the previous control cycle. The calculation formula is as follows:

[0098]

[0099] In the formula, This is the estimated phase angle obtained during the current control period t. The phase angle estimate obtained in the previous control cycle t-1 is T. s To control the cycle.

[0100] Example 3

[0101] This invention also proposes a control system for a permanent magnet synchronous motor, comprising:

[0102] The Park coordinate transformation module is used to transform the acquired inverter phase current i abc Current i transformed into dq coordinate system dq .

[0103] The Clark coordinate transformation module is used to transform the acquired inverter phase current i abc Current i transformed into αβ coordinate system αβ .

[0104] Back EMF observation module, used to receive current i αβ Inverter voltage u in αβ coordinate system αβ Calculate the back electromotive force observation vector in the αβ coordinate system. .

[0105] Specifically, the back electromotive force observation vector in the αβ coordinate system can be calculated using the following formula. :

[0106]

[0107] In the formula, For current i αβ The observables, t is time, u αβ =[u α ,u β ] T iαβ =[i α i β ] T e αβ =[e α ,e β ] T These are the inverter's output voltage, current, and back electromotive force vector, respectively. R is the motor speed; s It is the stator resistance, L s Here, m and n are the stator inductance, m and n are the sliding mode gain, and sign() is the sign function. .

[0108] Phase-locked loop (PLL) is used to observe vectors based on back electromotive force. Estimate the phase angle of the inverter phase current And calculate the motor speed .

[0109] Specifically, the phase-locked loop is the phase-locked loop described in Example 2, as detailed above, and will not be repeated here.

[0110] The speed control module is used to control the given motor reference speed. With motor speed After subtraction, the q-axis current reference value i is obtained via a PI controller. qref q-axis current reference value i qref and d-axis current reference value i dref =0 constitutes the current reference value i in the dq coordinate system. dqref .

[0111] The current control module is used to control the current reference value i. dqref and current i dq After differential calculation, the dq axis voltage reference value is obtained through a PI controller.

[0112] The Park coordinate inverse transformation module is used to transform the phase angle obtained from the phase-locked loop. Transform the dq-axis voltage reference value to the reference voltage u in the αβ coordinate system. αβref .

[0113] The SVPWM control module is used to control the voltage u according to the reference voltage u. αβref It generates bridge arm switching pulse signals corresponding to each phase of the inverter to control the permanent magnet synchronous motor.

[0114] The technical features of the embodiments described above can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification. It should be noted that the terms "in one embodiment," "for example," and "again" in this invention are intended to illustrate the invention and are not intended to limit the invention.

[0115] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A method for estimating the phase angle of a permanent magnet synchronous motor, characterized in that, include: Using the d-axis component or q-axis component of the back electromotive force observation vector in the dq coordinate system as the evaluation function, and taking the maximum or minimum value of the evaluation function as the optimization objective, the optimal candidate phase angle θ is searched within the phase angle selection range (0, 2π]. opt : Based on the optimal candidate phase angle θ opt Estimate the phase angle of the permanent magnet synchronous motor: When the optimization objective is to maximize the d-axis component, the estimated phase angle of the permanent magnet synchronous motor is... =θ opt -π / 2; When the optimization objective is to minimize the d-axis component, the estimated phase angle of the permanent magnet synchronous motor is... =θ opt -3π / 2; When the optimization objective is to maximize the q-axis component, the estimated phase angle of the permanent magnet synchronous motor is... =θ opt ; When the optimization objective is to minimize the q-axis component, the estimated phase angle of the permanent magnet synchronous motor is... =θ opt -π; Finding the optimal candidate phase angle θ opt The process includes: S11: Initialize the phase angle selection interval (θ1, θ2] to (0, 2π); S12: Determine two candidate phase angles for comparison based on the current phase angle selection interval. One candidate phase angle is located in the first half of the current phase angle selection interval and is θ1 + Δθ / 2. The other candidate phase angle is located in the second half of the current phase angle selection interval and is θ2 - Δθ / 2, where Δθ = 2π / 2. n-1 The angle difference is determined based on the set number of phase angle searches, n, where n ≥ 2; S13: Compare the evaluation function values ​​under the current two candidate phase angles, and take the half interval of the candidate phase angle whose evaluation function value is closest to the optimization target as the current selection interval (θ1, θ2). S14: Repeat S12~S13 until the search count n is reached. Output the candidate phase angle whose evaluation function value is closest to the optimization target in the last search as the optimal candidate phase angle θ. opt .

2. The phase angle estimation method for a permanent magnet synchronous motor as described in claim 1, characterized in that, When the d-axis component is used as the evaluation function, the evaluation function g PLL The calculation formula is: ； When the q-axis component is used as the evaluation function, the evaluation function g PLL The calculation formula is: ； In the formula, , They are respectively The back electromotive force observation vector in the coordinate system Axial components and Axial components, The candidate phase angles to be substituted. Let be the d-axis component of the back electromotive force observation vector in the dq coordinate system. Let q be the q-axis component of the back electromotive force observation vector in the dq coordinate system.

3. A phase-locked loop for use in a permanent magnet synchronous motor, characterized in that, include: The candidate phase angle optimization unit is used to find the optimal candidate phase angle θ within the phase angle selection range (0, 2π] by using the d-axis component or q-axis component of the back electromotive force observation vector in the dq coordinate system as the evaluation function and achieving the maximum or minimum value of the evaluation function as the optimization objective. opt ; The permanent magnet synchronous motor phase angle estimation unit is used to estimate the optimal candidate phase angle θ. opt Estimate the phase angle of the permanent magnet synchronous motor; When the optimization objective is to maximize the d-axis component, the estimated phase angle of the permanent magnet synchronous motor is... =θ opt -π / 2; When the optimization objective is to minimize the d-axis component, the estimated phase angle of the permanent magnet synchronous motor is... =θ opt -3π / 2; When the optimization objective is to maximize the q-axis component, the estimated phase angle of the permanent magnet synchronous motor is... =θ opt ; When the optimization objective is to minimize the q-axis component, the estimated phase angle of the permanent magnet synchronous motor is... =θ opt -π; The candidate phase angle optimization unit includes: Initialize the sub-unit to initialize the phase angle selection interval (θ1, θ2] to (0, 2π); The search iteration subunit is used to re-execute the search iteration until the search count n is reached. It outputs the candidate phase angle whose evaluation function value is closest to the optimization target in the last search as the optimal candidate phase angle θ. opt Each search iteration includes determining candidate phase angles and comparing evaluation functions; Determining candidate phase angles involves: identifying two candidate phase angles for comparison based on the current phase angle selection interval. One candidate phase angle is located in the first half of the current phase angle selection interval and is θ1 + Δθ / 2, while the other candidate phase angle is located in the second half of the current phase angle selection interval and is θ2 - Δθ / 2, where Δθ = 2π / 2. n-1 The angle difference is determined based on the set number of phase angle searches, n, where n ≥ 2; The comparison evaluation function includes: comparing the evaluation function values ​​under the current two candidate phase angles, and taking the half interval of the candidate phase angle whose evaluation function value is closest to the optimization target as the current selection interval (θ1, θ2).

4. The phase-locked loop as described in claim 3, characterized in that, Also includes: The motor speed calculation unit is used to calculate the motor speed based on the phase angle estimate obtained in the current control cycle and the phase angle estimate obtained in the previous control cycle.

5. The phase-locked loop as described in claim 4, characterized in that, The motor speed calculation unit calculates the motor speed. The formula is: ； In the formula, This is the estimated phase angle obtained during the current control period t. The phase angle estimate obtained in the previous control cycle t-1 is T. s To control the cycle.

6. A control system for a permanent magnet synchronous motor, characterized in that, include: Park coordinate transformation module is used to transform the inverter in Current i in coordinate system αβ Current i transformed into dq coordinate system dq ; The Clark coordinate transformation module is used to transform the acquired inverter phase current i abc Transform into Current i in coordinate system αβ ; Back EMF observation module, used to receive current i αβ Inverter voltage u in αβ coordinate system αβ Calculate the back electromotive force observation vector in the αβ coordinate system. ; The phase-locked loop as described in claim 4 or 5 is used to observe the vector based on the back electromotive force. Estimate the phase angle of the inverter phase current And calculate the motor speed ; The speed control module is used to control the given motor reference speed. With motor speed After subtraction, the q-axis current reference value i is obtained via a PI controller. qref q-axis current reference value i qref and d-axis current reference value i dref =0 constitutes the current reference value i in the dq coordinate system. dqref ; The current control module is used to control the current reference value i. dqref and current i dq After differential calculation, the dq axis voltage reference value is obtained via a PI controller; The Park coordinate inverse transformation module is used to transform the phase angle obtained from the phase-locked loop. Transform the dq-axis voltage reference value to the reference voltage u in the αβ coordinate system. αβref ; The SVPWM control module is used to control the voltage u according to the reference voltage u. αβref It generates bridge arm switching pulse signals corresponding to each phase of the inverter to control the permanent magnet synchronous motor.

7. The control system for the permanent magnet synchronous motor as described in claim 6, characterized in that, The back EMF observation module calculates the back EMF observation vector. The calculation model is as follows: ； In the formula, For current i αβ The observable, t is time. R is the motor speed; s It is the stator resistance, L s Here, m and n are the stator inductance, m and n are the sliding mode gain, and sign() is the sign function. .

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