A subdivision vector direct torque control method for three-phase permanent magnet synchronous motor

Abstract

The present invention discloses a subdivided vector direct torque control method for a three-phase permanent magnet synchronous motor, comprising: directly changing the action time of the three-phase voltage as needed to obtain a sufficient number of subdivided vectors; formulating a voltage vector selection table according to the sector where the flux is located and the torque and flux change requirements output by a hysteresis controller; formulating a basic voltage action schedule based on the subdivided voltage vectors; controlling the on-time of the three-phase bridge arm switch tube within a switching cycle to generate the required voltage vector; in a three-phase permanent magnet synchronous motor, the subdivided vector direct torque control method for reducing torque pulsation adopts the above process to effectively simplify the synthesis process of the subdivided voltage vector.

Description

Technical Field

[0001] The present invention relates to the technical field of motor control, and in particular to a subdivision vector direct torque control method for a three-phase permanent magnet synchronous motor. Background Art

[0002] The direct torque control of three-phase permanent magnet synchronous motor uses the three-phase inverter voltage U a 、U b 、U c The resulting six non-zero vectors, V1 to V6, and two zero vectors, V0 and V7, are directly output based on the torque and flux errors. This motor control method offers advantages such as a simple control structure and rapid torque control, resulting in significant interest in direct torque control of three-phase permanent magnet synchronous motors. However, a drawback of direct torque control of three-phase permanent magnet synchronous motors is the large torque ripple that can easily induce motor resonance.

[0003] In order to reduce the torque ripple, the subdivision vector direct torque control method can be used, which is to convert the voltage U a 、U b 、U c The obtained 6 non-zero vectors V1~V6 are used as basic voltage vectors, and then further synthesized into new voltage vectors in pairs, thereby subdividing more voltage vectors. Using more subdivided vectors for direct torque control can effectively reduce torque ripple. However, the existing vector synthesis calculation method is relatively complicated. Figure 2 As shown in the figure, V e is the vector to be synthesized, and the process is a 、U b 、U c The present invention proposes a three-phase permanent magnet synchronous motor subdivision vector direct torque control method, which is to adjust the three-phase basic voltage U a 、U b 、U c In a switching cycle T s The required subdivision vector can be generated by the action time, and then the generated subdivision vector is used for direct torque control. The generation process of the subdivision vector in this method is more direct, simple and efficient. The voltage vector generation method of the present invention is as follows Figure 3 shown. Summary of the Invention

[0004] The purpose of the present invention is to provide a subdivision vector direct torque control method for a three-phase permanent magnet synchronous motor. The method generates a required voltage vector by controlling the action time of the three-phase basic voltage within a switching cycle. This method simplifies the synthesis process of the voltage vector, as described below: Step 1: Subdivide a sufficient number of subdivision vectors as required, and obtain a subdivision vector three-phase voltage action time table. This article takes the subdivision of 18 vectors as an example;

[0005] Step 2: Create a voltage vector selection table based on the flux sector and the torque and flux change requirements output by the hysteresis controller.

[0006] Step 3: Derive a direct torque control model of the three-phase permanent magnet synchronous motor based on the mathematical model of the three-phase permanent magnet synchronous motor;

[0007] Step 4: Determine a sufficiently small voltage vector switching period T s , so that in a T s The motor can continue to operate normally;

[0008] Step 5: When the motor is running, the speed PI loop calculates the reference torque T * And the set reference flux

[0009] Step 6: Continuously detect the voltage and current of the motor stator and calculate the real-time torque T of the motor e and real-time magnet links

[0010] Step 7: The hysteresis controller is based on the torque error ΔT e and flux linkage error Output the corresponding status, and combine it with the sector where the current magnetic flux is located to select the corresponding subdivision vector from the vector table;

[0011] Step 8: According to the three-phase basic voltage action schedule, control the three-phase bridge arm in a switching cycle T s Within the opening time, the corresponding subdivision vector can be output to perform direct torque control on the motor;

[0012] Step 9: Repeat steps 5 to 8 continuously, and the motor can complete the torque control;

[0013] The advantages of the present invention compared with the prior art are that when synthesizing the required voltage vector, it is only necessary to control the three-phase basic voltage in one switching cycle T s The required voltage vector can be synthesized within the action time, which simplifies the voltage vector synthesis process. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 Three-phase permanent magnet synchronous motor voltage vector generation circuit

[0015] Figure 2 Existing voltage vector synthesis method

[0016] Figure 3 The voltage vector generation method of this method

[0017] Figure 4 Three-phase permanent magnet synchronous motor vector subdivision diagram

[0018] Figure 5 Block diagram of direct torque vector subdivision control system for three-phase permanent magnet synchronous motor DETAILED DESCRIPTION

[0019] The following is combined with Figure 1-5 The present invention is described in detail in detail:

[0020] Step 1: Subdivide enough subdivision vectors as needed, and obtain the subdivision vector three-phase voltage action time table. This article takes the subdivision of 18 vectors as an example. The vector subdivision diagram is as follows: Figure 4 As shown, the subdivision vector three-phase voltage action time is shown in the following table, in which T s is one switching cycle.

[0021] Table 1 Three-phase basic voltage action time table

[0022]

[0023]

[0024] Step 2: Create a voltage vector selection table based on the flux sector and the torque and flux change requirements output by the hysteresis controller:

[0025] When the rotor flux is in sector N, the flux changes according to the output of the hysteresis controller. and torque change ΔT e It can be divided into 4 cases. The voltage vector selection table corresponding to the 4 cases is shown in Table 2. The table uses the voltage vector selection of V ±4 ,V ±7 For example, the voltage vector selection can be adjusted as needed.

[0026] Table 2S N Sector vector selection table

[0027]

[0028] In the above table, the value range of N is 1 to 18. Indicates that the magnetic linkage needs to be increased. Indicates that the magnetic flux needs to be reduced; ΔT e =1 means the torque needs to be increased, ΔT e=0 means decrease.

[0029] The rotor's motion position is divided into 18 sectors of end-to-end loops according to the synthesized 18 voltage vectors. When the rotor flux angle is in sector N, the flux change output by the hysteresis controller is and torque change ΔT e Select the vector from the vector selection table for direct torque control. When the calculated voltage vector subscript is greater than 18 or less than 0, a cyclic selection is performed.

[0030] Step 3: Derive a direct torque control model of the three-phase permanent magnet synchronous motor based on the mathematical model of the three-phase permanent magnet synchronous motor;

[0031] The mathematical model of the three-phase permanent magnet synchronous motor is shown in the following equations, and the motor flux and torque equations are shown below:

[0032]

[0033] Formula description: is the stator flux Components on the d and q axes after Park transformation; is the rotor flux; i d 、i q is the component of the stator current on the d and q axes; n p is the number of motor pole pairs;

[0034] Step 4: Determine the switching period T of the voltage vector that is small enough s , so that in a T s The motor can continue to operate normally;

[0035] Step 5: When the motor is running, the speed PI loop calculates the reference torque T * and the set reference flux

[0036] Step 6: Continuously detect the voltage and current of the motor stator and calculate the measured torque T e and measured magnetic flux

[0037] 1) The current three-phase instantaneous current i of the motor a ,i b ,i c and the rotor position angle θ, and according to the following formula we can get i d ,i q

[0038]

[0039]

[0040] 2) i obtained by calculation d ,i q and motor inherent parameters According to formula (1), T e and

[0041] 3) T e and Input hysteresis controller;

[0042] Step 7: The hysteresis controller is based on the torque error ΔT e and flux linkage error Output the corresponding status, and combine it with the sector where the current magnetic flux is located to select the corresponding subdivision vector from the vector table;

[0043] Step 8: According to the three-phase basic voltage action schedule, control the three-phase bridge arm in a switching cycle T s Within the opening time, the corresponding subdivision vector can be output to perform direct torque control on the motor;

[0044] Step 9: Repeat steps 5 to 8 continuously, and the motor can complete the torque control;

[0045] The three-phase permanent magnet synchronous motor subdivision vector direct torque control implemented according to the above steps can effectively simplify the synthesis process of the subdivision voltage vector.

Claims

1. A subdivision vector direct torque control method for a three-phase permanent magnet synchronous motor, characterized in that: The control method comprises the following steps: 1) According to the rules of the inverter to generate voltage vector, control the three-phase basic voltage U a ,U b ,U c 18 synthetic voltage vectors can be generated by using different proportions of , and the 18 synthetic voltage vectors are shown in Table 1; 2) Based on these 18 voltage vectors, a vector table is developed in combination with the sector position and the torque and flux change requirements; 3) When the motor is running, according to the change of magnetic flux and torque change ΔT e Requirement, select the appropriate vector from the vector table; 4) According to the selected vector, U a ,U b ,U c Control the inverter output according to the three-phase basic voltage action schedule; Table 1 Three-phase basic voltage action time table Table 1 T s is one switching cycle.

2. A subdivision vector direct torque control method for a three-phase permanent magnet synchronous motor according to claim 1, characterized in that The vector table selection is shown in Table 2; Table 2S N Sector vector selection table In the above table, the value range of N is 1 to 18. Indicates that the magnetic linkage needs to be increased. Indicates that the magnetic flux needs to be reduced; ΔT e =1 means the torque needs to be increased, ΔT e =0 means the torque needs to be reduced; The rotor's motion position is divided into 18 sectors of end-to-end loops according to the synthesized 18 voltage vectors. When the rotor flux angle is in sector N, the flux change output by the hysteresis controller is and torque change ΔT e Select the vector from the vector selection table for direct torque control. When the calculated voltage vector subscript is greater than 18 or less than 0, a cyclic selection is performed.

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