A double-vector cascade torque flux control method for permanent magnet synchronous motor

Abstract

The application relates to a double-vector cascade type torque flux linkage control method of a permanent magnet synchronous motor, and belongs to the technical field of motor control. The method comprises the following steps: calculating a stator flux linkage and motor electromagnetic torque, extending an alternative voltage vector, and decomposing the electromagnetic torque into active torque and reactive torque through motor instantaneous power theory; the optimal voltage vector is selected as the voltage vector corresponding to the minimum value through two-stage active torque value function calculation and one-stage flux linkage value function calculation. The application can quickly and accurately calculate the voltage vector which makes the torque and flux linkage error zero at the same time, successfully eliminates the weight factor without corresponding calculation theory in the value function, realizes the control of the torque and flux linkage of the permanent magnet synchronous motor, avoids the torque pulsation problem caused by flux linkage coupling, and the calculation and synthesis of the voltage vector are relatively simple.

Description

Technical Field

[0001] This invention relates to the field of motor control technology, specifically to a dual-vector cascaded torque flux control method for permanent magnet synchronous motors. Background Technology

[0002] With the successful development of rare-earth permanent magnet materials, the performance of permanent magnet synchronous motors (PMSMs) was significantly improved in the 1960s. Currently, neodymium iron boron (NdFeB) and ferrite permanent magnet materials are widely used to manufacture motor rotors. Furthermore, the use of permanent magnets not only improves motor operating efficiency but also gives PMSMs advantages such as high power density, small size, light weight, and large starting torque. Therefore, PMSMs are widely used in high-precision and high-reliability fields. Their application and development rely heavily on high-performance control strategies; good dynamic and steady-state performance are fundamental requirements for PMSM control. Currently, the main vector control strategies for PMSMs include: Field Oriented Control (FOC), Direct Torque Control (DTC), and Model Predictive Control (MPC).

[0003] Model predictive control (MDC) is characterized by its simple principle, ease of implementation, and fast dynamic response. It can also effectively handle complex problems involving nonlinearity, multiple variables, and multiple constraints. Furthermore, the value function in MDC can incorporate multiple different control objectives, nonlinear limitations, overcurrent protection, common-mode voltage limits, and switching frequency limits. Therefore, in high-performance applications, MDC can flexibly meet these control requirements simultaneously, gradually becoming another high-quality control method for permanent magnet synchronous motors.

[0004] Although model predictive control has many advantages, it still has some shortcomings due to factors such as fixed voltage vector direction and amplitude, limited number of selectable voltage vectors, and lack of corresponding calculation theory for weighting factors in the value function.

[0005] How to eliminate the weighting factor of the value function based on the extended alternative voltage vector, and how to reduce the calculation process of the duty cycle are all technical problems that need to be solved.

[0006] Current motor control primarily focuses on torque control, neglecting stator flux control. Torque calculation requires stator flux, creating a coupling relationship between them. Excessive pulsation in the stator flux leads to degraded torque control performance. The current method for simultaneously controlling torque and flux is deadbeat torque flux control, where the most crucial step is calculating the reference voltage vector. Traditional deadbeat torque flux control calculates the reference voltage vector using torque PI loops and flux PI loops. The introduction of PI loops compromises the excellent dynamic performance of torque control, and PI loop parameter tuning is complex. Furthermore, some researchers have derived reference voltage vector calculation formulas using coordinate transformations in two-phase stationary coordinate systems (αβ) and two-phase rotating coordinate systems (dq). However, this method requires cumbersome coordinate transformations and imposes a significant computational burden on the controller. Summary of the Invention

[0007] Technical problems to be solved

[0008] To address the problem of limited base voltage vector of two-level inverters in existing dual-vector model predictive torque flux control, this invention provides a dual-vector cascaded torque flux control method for permanent magnet synchronous motors.

[0009] Technical solution

[0010] A method for controlling the torque flux linkage of a permanent magnet synchronous motor with dual vector cascades is characterized by the following steps:

[0011] S1. Acquire the three-phase stator current i through a current sensor. s The three-phase stator voltage u is reconstructed from the voltage value acquired by the DC bus voltage sensor and the inverter switching state. s ; Calculate the stator flux linkage ψ s With the electromagnetic torque T of the motor e ;

[0012] S2. Expand the alternative voltage vector and use the instantaneous power theory of the motor to calculate the electromagnetic torque T. e Decomposed into active torque T ep and reactive torque T eq ;

[0013] S3. Based on the calculation of the first-level active torque value function, select the three corresponding voltage vectors that minimize the value function value as the candidate voltage vectors for the second-level reactive torque value function.

[0014] S4. Substitute the three candidate voltage vectors selected in the first stage into the reactive torque value function of the second stage for calculation. Sort the three value function values, select the two with the smallest values, and use the corresponding voltage vectors as the two candidate voltage vectors for the flux linkage value function of the third stage.

[0015] S5. Substitute the two candidate voltage vectors selected in the second stage into the third stage flux prediction model, calculate the value function value through the third stage flux value function, and select the voltage vector with the smallest value as the optimal voltage vector.

[0016] S6. Apply the optimal voltage vector to the two-level inverter and input it into the motor to control the motor's torque and flux linkage.

[0017] A further technical solution of the present invention: the stator flux linkage ψ in S1 s and the electromagnetic torque T of the motor e The calculation method is as follows:

[0018] In a three-phase stationary coordinate system, the stator current i s With stator flux linkage ψ s The relationship between them is:

[0019] ψ s =∫(u s -R s i s )dt

[0020] In a three-phase stationary coordinate system, the stator flux linkage ψ s With the electromagnetic torque T of the motor e The relationship between them is:

[0021]

[0022] Where T e P is the electromagnetic torque. n ψ is the number of pole pairs of the permanent magnet; s For stator flux linkage; i s For stator current; u s This refers to the three-phase stator voltage; R s This is the stator resistance.

[0023] A further technical solution of the present invention: The extended alternative voltage vector in S2 is specifically: the basic voltage vector is synthesized into a voltage vector by means of a fixed duty cycle, wherein the duty cycle includes two fixed types: 0.5 / 0.5 and 0.25 / 0.75; according to the principle of average equivalence, all alternative voltage vectors can be synthesized by using the two fixed duty cycles.

[0024] A further technical solution of the present invention: In step S2, the electromagnetic torque is decomposed into active torque T using the instantaneous power of the motor.ep and reactive torque T eq The calculation method is as follows:

[0025]

[0026] Where ψ sp i is the active component of the stator flux linkage; sp ψ is the active component of the stator current. sq i is the reactive component of the stator flux linkage; sq This represents the reactive component of the stator current.

[0027] A further technical solution of the present invention: the first-level active power value function in S3 is:

[0028]

[0029] in, The active component of the reference electromagnetic torque; This represents the active component of the electromagnetic torque in the first beat.

[0030] A further technical solution of the present invention: the second-level reactive power value function in S4 is:

[0031]

[0032] in, This is the reactive component of the second-phase electromagnetic torque.

[0033] A further technical solution of the present invention: the third-level magnetic flux linkage value function in S5 is:

[0034]

[0035] in, This is a reference value for the stator flux linkage; For the first stator magnetic flux linkage; For the second-phase stator flux linkage.

[0036] A computer system is characterized by comprising: one or more processors, and a computer-readable storage medium for storing one or more programs, wherein when the one or more programs are executed by the one or more processors, the one or more processors cause the one or more processors to implement the method described above.

[0037] A computer-readable storage medium is characterized by storing computer-executable instructions, which, when executed, are used to implement the above-described method.

[0038] Beneficial effects

[0039] This invention provides a dual-vector cascaded torque flux control method for permanent magnet synchronous motors. Compared with existing technologies, this invention can quickly and accurately select the voltage vector that makes both torque and flux errors zero. The number of candidate voltage vectors is expanded to meet the requirement of expanding candidate voltage vectors. The three-stage series predictive control structure meets the requirement of eliminating the weighting factor of the value function, realizes separate control of torque and flux, avoids torque pulsation problems caused by flux coupling, and simplifies the calculation of voltage vectors. The entire process does not require complex duty cycle calculations and can simultaneously control the motor's torque and flux.

[0040] 1. Based on the principle of average equivalence, the eight basic voltage vectors of the two-level inverter are expanded to obtain 26 alternative voltage vectors, which can effectively improve the motor control performance.

[0041] 2. To address the issue of weighting factors in the value function due to the different dimensions of torque and flux linkage, this method proposes a three-stage series control model, which eliminates the weighting factors in the value function. The value function is constructed by combining active power and flux linkage, and reactive power and flux linkage respectively, thus eliminating the weighting factors while avoiding the coupling of torque and flux linkage.

[0042] 3. By synthesizing the optimal voltage vector using a fixed duty cycle, the computational complexity is reduced. Attached Figure Description

[0043] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0044] Figure 1 Schematic diagram of predictive torque flux linkage control principle of a three-stage series model for a permanent magnet synchronous motor;

[0045] Figure 2 A schematic diagram of the extended alternative voltage vector using a fixed duty cycle method;

[0046] Figure 3 A schematic diagram of first-stage voltage vector selection using six basic voltage vectors;

[0047] Figure 4 A schematic diagram of second-stage voltage vector selection using six basic voltage vectors;

[0048] Figure 5 A schematic diagram of third-level voltage vector selection using six basic voltage vectors;

[0049] Figure 6 Flowchart of predicted torque flux control for a three-stage series model of a permanent magnet synchronous motor. Detailed Implementation

[0050] 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.

[0051] Based on the principle of average equivalence of vector action, this invention proposes a cascaded control method built on a dual-vector model predictive control approach, aiming to simultaneously control torque and flux linkage and eliminate weighting factors in the value function. This invention utilizes a cascaded structure to eliminate weighting factors in the value function of predictive control and synthesizes the optimal voltage vector using a fixed duty cycle. The dual-vector cascaded torque and flux linkage control method proposed in this invention does not require complex and tedious duty cycle calculations or the determination of weighting factors through trial and error, and can simultaneously control the motor's torque and flux linkage.

[0052] Reference Figure 1 This invention provides a dual-vector cascaded torque flux control method for a permanent magnet synchronous motor, comprising a speed PI controller, an MPTA module, a current detection module, a phase voltage calculation module, a torque and flux estimation module, a position and speed detection module, a three-phase two-level inverter, and a permanent magnet synchronous motor. The control block diagram is shown below. Figure 1 As shown. The specific steps are as follows:

[0053] S1. Acquire the three-phase stator current i through a current sensor. s The three-phase stator voltage u is reconstructed from the voltage value acquired by the DC bus voltage sensor and the inverter switching state. s The rotational speed ω is obtained by a photoelectric encoder. e Combined with angle information σ, the given rotational speed value ω e * The actual rotational speed ω obtained by the photoelectric encoder e By comparison, the speed error information is obtained, and the speed error is input into the speed PI loop to obtain the electromagnetic torque reference value T. e * ;

[0054] S2. Calculate the stator flux linkage ψ s With the electromagnetic torque T of the motor e And the estimated electromagnetic torque value T e The electromagnetic torque T obtained through the speed loop PI controller e * By comparing given values, the torque error is obtained.

[0055] In a three-phase stationary coordinate system, the stator current i sWith stator flux linkage ψ s The relationship between them is:

[0056] ψ s =∫(u s -R s i s )dt (1-1)

[0057] In a three-phase stationary coordinate system, the stator flux linkage ψ s With the electromagnetic torque T of the motor e The relationship between them is:

[0058]

[0059] Where T e P is the electromagnetic torque. n ψ is the number of pole pairs of the permanent magnet; s For stator flux linkage; i s For stator current, u s R is the three-phase stator voltage. s This is the stator resistance.

[0060] S3. Expand the alternative voltage vector and decompose the electromagnetic torque into active torque T using the instantaneous power theory of the motor (PQ theory). ep and reactive torque T eq ;

[0061] A two-level inverter can output eight basic voltage vectors, including two zero vectors: U0 (000) and U7 (111), and six non-zero voltage vectors: U1 (001), U2 (010), U3 (011), U4 (100), U5 (101), and U6 (110). Extended voltage vectors can be synthesized using two fixed duty cycle methods based on the average equivalent principle, for example: U 11 =0.75U1 + 0.25U2; U 12 = 0.5U1 + 0.5U2. The candidate voltage vectors can be expanded to 26 using the above method. The candidate voltage vector table after expansion using a fixed duty cycle is as follows: Figure 2 As shown. Taking the first sector as an example, U in the figure 11 =0.75U1 + 0.25U2, U 12 =0.5U1+0.5U2, U 63 =0.75U1 + 0.25U6, U 62 =0.5U1+0.5U6; In this way, the number of candidate voltage vectors can be expanded from 8 to 26.

[0062] The instantaneous active power and reactive power of three phases are defined as follows:

[0063]

[0064] Where p is the instantaneous active power; q is the instantaneous reactive power; U is the instantaneous voltage vector U=(u a u b u c ) T I is the instantaneous current vector I = (i a i b i c ) T .

[0065] When transforming variables from a three-phase stationary coordinate system to a two-phase stationary coordinate system, the principle of constant power is applied:

[0066]

[0067] The instantaneous power in the two-phase stationary coordinate system (PQ coordinate system) is obtained as follows:

[0068]

[0069] Stator voltage equations in a two-phase stationary coordinate system:

[0070]

[0071] Instantaneous power equation:

[0072]

[0073] The instantaneous power of the stator magnetic field is:

[0074]

[0075] Stator self-flux equation:

[0076]

[0077] The electromagnetic active torque and electromagnetic reactive torque can be decomposed as follows:

[0078]

[0079] Where R s For stator resistance; L s Stator inductance; ψ r It is a permanent magnet flux linkage.

[0080] S4. Based on the calculation of the first-stage active torque value function, select the three corresponding voltage vectors that minimize the value function value as the candidate voltage vectors for the second-stage reactive torque value function.

[0081] The vector partitioning of the optimal vector is determined based on the direct torque method, reducing the number of candidate voltage vectors from 26 to 6.

[0082] Vector partitioning, Table 1 sector division

[0083]

[0084] Table 2 shows the voltage vectors contained in the first sector.

[0085] <![CDATA[U1]]> <![CDATA[U 11 ]]> <![CDATA[U 12 ]]> <![CDATA[U 63 ]]> <![CDATA[U 62 ]]> <![CDATA[U0]]>

[0086] Taking the first sector as an example, and designing the first-level active power value function as follows:

[0087]

[0088] Table 3 shows the first-order value function values ​​corresponding to the voltage vectors contained in the first sector.

[0089] <![CDATA[U1]]> <![CDATA[U 11 ]]> <![CDATA[U 12 ]]> <![CDATA[U 63 ]]> <![CDATA[U 62 ]]> <![CDATA[U0]]> <![CDATA[g 1U1 ]]> <![CDATA[g 1U11 ]]> <![CDATA[g 1U12 ]]> <![CDATA[g 1U63 ]]> <![CDATA[g 1U62 ]]> <![CDATA[g 1U0 ]]>

[0090] By comparing g 1U1 g 1U11 g 1U12 g 1U63 g 1U62 g 1U0 Based on the magnitude of the values, the three voltage vectors with the smallest values ​​are selected as candidate voltage vectors for the second stage. For example, the three smallest values ​​are g... 1U1 g 1U11 g 1U12 Then the selected voltage vectors are U1 and U2. 11 U 12 As an alternative voltage vector for the second stage. For example... Figure 3 As shown, the three value function values ​​g with the smallest values ​​are selected. 1U1 g 1U11 g 1U12 The corresponding alternative voltage vectors U1 and U 11 U 12 It serves as the output of the first-level active power control system and the input of the second-level reactive power control system.

[0091] S5. Substitute the three candidate voltage vectors selected in the first stage into the reactive torque value function of the second stage for calculation. Sort the three value function values, select the two with the smallest values, and use the corresponding voltage vectors as the two candidate voltage vectors for the flux linkage value function of the third stage.

[0092] The second-level reactive power value function is designed as follows:

[0093]

[0094] Table 4. Value function values ​​of the second-level candidate voltage vectors selected in the first level.

[0095] <![CDATA[U1]]> <![CDATA[U 11 ]]> <![CDATA[U 12 ]]> <![CDATA[g 1U1 ]]> <![CDATA[g 1U11 ]]> <![CDATA[g 1U12 ]]>

[0096] The three voltage vectors selected from the first stage are input to the second stage, and g is compared. 2U1 g 2U11 g 2U12 Based on the magnitude of the values, the two corresponding voltage vectors with the smallest values ​​are selected as candidate voltage vectors for the third stage. For example... Figure 4 As shown, the two value function values ​​g with the smallest values ​​are selected. 2U1 g 2U11 The corresponding alternative voltage vectors U1 and U 11 It serves as the output of the second-level reactive power control system and the input of the third-level motor flux linkage control system.

[0097] S6. Substitute the two candidate voltage vectors selected in the second stage into the third stage flux prediction model, calculate the value function value through the third stage flux value function, and select the voltage vector with the smallest value as the optimal voltage vector.

[0098] The third-level magnetic flux linkage value function is designed as follows:

[0099]

[0100] Table 5 shows the first-order value function values ​​corresponding to the voltage vectors contained in the first sector.

[0101] <![CDATA[U1]]> <![CDATA[U 11 ]]> <![CDATA[g 3U1 ]]> <![CDATA[g 3U11 ]]>

[0102] The two voltage vectors selected from the second stage are input to the third stage, and g is compared. 3U1 g 3U11 The magnitude of the values ​​is used to select the voltage vector with the smallest value as the optimal voltage vector input to the control system to control the motor's torque and flux linkage. For example... Figure 5 As shown, the value of g with the smallest value is selected. 3U11 The corresponding alternative voltage vector U 11 As the output of the third-level motor flux linkage control system, this voltage vector is applied to the motor through a two-level inverter to control the motor.

[0103] S7. The base voltage vector is synthesized into the selected voltage vector through a fixed duty cycle and applied to the two-level inverter to input into the motor to control the motor torque and flux linkage.

[0104] This method operates with two fixed duty cycles: 0.5 / 0.5 and 0.25 / 0.75. According to the principle of average equivalence, all alternative voltage vectors can be synthesized by using the two fixed duty cycles.

[0105] The predictive torque flux linkage control process of a three-stage series model for a permanent magnet synchronous motor is as follows: Figure 6 As shown in the figure, the main processes include three-phase current sampling, flux torque estimation, one-time delay compensation, vector partition determination, continuous three-level value function judgment, and synthesis of the optimal vector.

[0106] It should be noted that the term "comprising" or any other variation thereof is intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0107] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for controlling the torque flux linkage of a permanent magnet synchronous motor using a dual-vector cascaded configuration, characterized in that... The steps are as follows: S1. Collect three-phase stator current through a current sensor. The three-phase stator voltage is reconstructed from the voltage values ​​acquired by the DC bus voltage sensor and the inverter switching states. ; Calculate stator flux linkage With motor electromagnetic torque ; S2. Expand the alternative voltage vector and use the instantaneous power theory of the motor to convert the electromagnetic torque... Decomposed into active torque and reactive torque In step S2, the electromagnetic torque is decomposed into active torque using the instantaneous power of the motor. and reactive torque The calculation method is as follows: in This represents the active component of the stator flux linkage; This refers to the active component of the stator current; This is the reactive component of the stator flux linkage; This refers to the reactive component of the stator current. S3. Based on the calculation of the first-level active torque value function, select the three corresponding voltage vectors that minimize the value function value as candidate voltage vectors for the second-level reactive torque value function; the first-level active power value function in S3 is: in, The active component of the reference electromagnetic torque; This is the active component of the electromagnetic torque in the first beat; S4. Substitute the three candidate voltage vectors selected in the first stage into the second-stage reactive torque value function for calculation. Sort the three value function values, select the two with the smallest values, and use the corresponding voltage vectors as the two candidate voltage vectors for the third-stage flux linkage value function. The second-stage reactive power value function in S4 is: in, This is the reactive component of the second-phase electromagnetic torque; S5. Substitute the two candidate voltage vectors selected in the second stage into the third-stage flux linkage prediction model, calculate the value function value using the third-stage flux linkage value function, and select the voltage vector with the smallest value as the optimal voltage vector; the third-stage flux linkage value function in S5 is: in, This is a reference value for the stator flux linkage; For the first stator magnetic flux linkage; For the second phase of stator flux linkage; S6. Apply the optimal voltage vector to the two-level inverter and input it into the motor to control the motor's torque and flux linkage.

2. The method for controlling the torque flux linkage of a permanent magnet synchronous motor with a dual-vector cascade configuration according to claim 1, characterized in that: The stator magnetic flux in S1 and motor electromagnetic torque The calculation method is as follows: In a three-phase stationary coordinate system, the stator current With stator flux The relationship between them is: In a three-phase stationary coordinate system, the stator flux With motor electromagnetic torque The relationship between them is: in Electromagnetic torque; The number of pole pairs of the permanent magnet; For stator flux linkage; Stator current; This refers to the three-phase stator voltage; This is the stator resistance.

3. The method for controlling the torque flux linkage of a permanent magnet synchronous motor with a dual-vector cascade configuration according to claim 2, characterized in that: The extended alternative voltage vector in S2 specifically involves synthesizing the base voltage vector into a voltage vector using a fixed duty cycle. The duty cycle includes two fixed values: 0.5 / 0.5 and 0.25 / 0.

75. According to the principle of average equivalence, all alternative voltage vectors can be synthesized by using the two fixed duty cycles.

4. A computer system, characterized in that... include: One or more processors, a computer-readable storage medium for storing one or more programs, wherein, when the one or more programs are executed by the one or more processors, the one or more processors cause the one or more processors to implement the method of claim 1.

5. A computer-readable storage medium, characterized in that... The device stores computer-executable instructions, which, when executed, are used to implement the method of claim 1.

Images