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CN-115833671-B - Double three-phase motor high-precision model prediction current control system and control method

CN115833671BCN 115833671 BCN115833671 BCN 115833671BCN-115833671-B

Abstract

The invention discloses a double three-phase motor high-precision model prediction current control system and a control method, and relates to the technical field of multiphase motor control. The invention expands the traditional 12 virtual voltage vector control set, designs 24 virtual voltage vectors with equal amplitude and uniform phase angle on the premise of not losing the voltage utilization rate, and improves the control precision. The duty ratio calculation method based on the minimum error is provided, and even under the condition of a single effective virtual voltage vector, the current of a d axis and the current of a q axis can be tracked simultaneously, so that the optimal duty ratio is ensured to be output. In addition, the process of traversing all voltage vectors in the prediction control is simplified, and the calculation load of an algorithm is reduced. The invention effectively improves the precision of model predictive control by expanding a control set and reducing the duty ratio calculation error, reduces 5 and 7 times of harmonic waves and improves torque pulsation. And the calculation amount is low even under the action of 24 voltage vectors, so that the execution efficiency of the algorithm is improved.

Inventors

  • ZHAO WENXIANG
  • CUI JIA
  • JI JINGHUA
  • HUANG LINSEN
  • DU YUXUAN

Assignees

  • 江苏大学

Dates

Publication Date
20260512
Application Date
20220928

Claims (9)

  1. 1. The system software comprises a synthesized 24 virtual voltage vector module, a rotating speed controller, a coordinate conversion module, a time delay module, a prediction module, a duty ratio calculation module, a simplification module and a cost function module; the double three-phase permanent magnet motor consists of two sets of three-phase winding space phase shift 30 DEG, wherein the input end of the inverter is connected with a direct current power supply, the signal end of the inverter is connected with a PWM module, the inverter is of a six-phase two-level topological structure, the output end of the inverter is connected with the double three-phase motor A, B, C, D, E, F and is responsible for converting PWM signals into six-phase sine alternating current required by a driving motor, the position sensor adopts a rotary transformer and is coaxially connected with the double three-phase permanent magnet motor, and the current sensor is connected with the inverter and is responsible for sampling the six-phase current of the motor; The input end of the coordinate conversion module is connected with the current sensor, and the output end of the coordinate conversion module is connected with the delay compensation module and is used for converting six-phase current under a natural coordinate system into current under a rotating coordinate system so as to realize decoupling control; the input end of the delay module is connected with the coordinate transformation module, and the output end of the delay module is connected with the prediction model, so that the problem of one-beat delay caused by sampling of a digital system is solved; The input end of the prediction module is connected with the delay compensation module, the 24 virtual voltage vector module and the position sensor and is responsible for outputting the dq axis current change position under the action of different voltage vectors; The rotating speed controller is controlled by PI to obtain q-axis reference current, the input end of the rotating speed controller is the error between the given rotating speed and the actual rotating speed, and the output end of the rotating speed controller is the reference value of the q-axis current; The input end of the duty ratio calculation module is connected with the rotating speed controller and the prediction model module and is used for calculating the position of the optimal voltage vector and the duty ratio thereof under the action of each voltage vector; The input end of the PWM module is connected with the cost function module, converts the optimal vector and the duty ratio obtained by the software system into corresponding PWM signals, and outputs the PWM signals to the inverter to complete modulation, thereby driving the motor to operate; In the duty ratio calculation module, the duty ratio of the voltage vector action is calculated by using a minimum error method specifically as follows: i d and i q are currents of d axis and q axis respectively, dq coordinate system is used as reference, predicted values of i d and i q under the action of zero voltage vector are recorded as point A (x 1 , y 1 ), predicted values of i d and i q under the action of effective voltage vector are recorded as point B (x 2 , y 2 ), the position of the reference current is C (x 0 , y 0 ), the distance from the point C to the straight line AB is the point with the minimum value of the cost function and the point with the minimum error, and the required voltage vector can be obtained by solving the intersection point of the straight line perpendicular to the C point and the AB and the corresponding duty ratio is obtained.
  2. 2. The control method of a double three-phase motor high-precision model predictive current control system according to claim 1, characterized by comprising the steps of: step 1) constructing 24 virtual voltage vectors; step 2) optimizing the switching sequence of the voltage vectors to normalize the voltage vectors; Step 3) obtaining the rotating speed and the position angle through a position sensor, obtaining six-phase current through a current sensor, and obtaining current under a rotating coordinate system through a coordinate transformation module; step 4) deducing a prediction model of the double three-phase permanent magnet motor; step 5) calculating the duty cycle of the voltage vector action by using a minimum error method; Step 6) simplifying the traversal optimizing process; And 7) selecting an optimal voltage vector and a duty ratio thereof through a cost function, outputting the optimal voltage vector and the duty ratio thereof to a PWM module, and outputting a corresponding voltage vector through modulation of an inverter to complete the whole control.
  3. 3. The control method of a dual three-phase motor high-precision model predictive current control system according to claim 2, wherein the specific steps of step 1) include: the double three-phase permanent magnet motor is configured into a neutral point isolation mode, a six-phase two-level voltage source inverter is adopted for driving, and as the upper switching device and the lower switching device of each bridge arm work in complementary conduction states, each bridge arm has two switching states, the whole inverter has 2 6 =64 switching states, and 64 voltage vectors corresponding to a conversion switch are determined by the following formula: (1); Wherein a=e j30° ,s A ~s F represents the switching state of each bridge arm, U αβ represents the voltage vector of the alpha beta plane, U xy represents the voltage vector of the xy plane, U dc represents the voltage of the direct current bus, the upper bridge arm is turned on to be "1", the upper bridge arm is turned off to be "0", the numbers of the basic voltage vectors are represented by octal combination according to the sequence of ABC and DEF; the virtual voltage vector principle requires that the sum of the effects of the vectors in the harmonic plane is zero, and the synthesis principle is as follows: (2); Wherein, the , Representing the components of the fundamental voltage vectors in the x-axis and the y-axis, D i representing the duty cycle of the action of each fundamental voltage vector; in order to ensure the voltage utilization rate, 12 large vectors and 1 zero vector at the outermost periphery of a fundamental wave plane are selected as basic voltage vectors for synthesizing virtual voltage vectors, and a new virtual voltage vector control set is synthesized by adopting an adjacent three-vector principle, wherein the synthesis principle is as follows: (3); Wherein V i represents an ith virtual voltage vector to be synthesized, wherein i=1, 2, 3..24, u 1st 、u 2nd , and u 3rd represent first, second, and third base voltage vectors, respectively, and superscripts "α", "β", "x", and "y" represent components of the voltage vectors in corresponding coordinate axes, and D 1 、D 2 、D 3 and D 0 represent duty cycles at which the first, second, and third base voltage vectors and the zero vector act, respectively; The amplitude of each basic voltage vector is defined to be 0.59Udc, the starting position is 0 °, the angle between two adjacent voltage vectors is 15 °, and finally 24 virtual voltage vectors are synthesized in the alpha beta plane, and the components of the virtual voltage vectors in the xy plane are zero.
  4. 4. A control method of a dual three-phase motor high-precision model predictive current control system according to claim 3, wherein the specific steps of step 2) include: In order to ensure that the synthesized virtual voltage vectors can be realized in industrial application, the switching sequence of the synthesized 24 virtual voltage vectors is optimized to be standardized, an inner and outer two-layer voltage vector synthesis method is adopted at V 2 、V 6 、V 10 、V 14 、V 18 and V 22 to replace an adjacent three-vector synthesis method, and the finally synthesized 24 virtual voltage vectors are shown in table 1; table 1 is a 24 virtual voltage vector distribution: ; Where u 1 、…u 0 、…u 11 、…u 66 、…u 12 、…u 64 represent the corresponding 64 basic voltage vectors, respectively.
  5. 5. The control method of a dual three-phase motor high-precision model predictive current control system according to claim 4, wherein the specific steps of step 3) include: the position sensor is used for measuring the angular displacement and the angular velocity of a rotating shaft of the rotor, converting the angular displacement and the angular velocity into electric signals and transmitting the electric signals to the controller, and obtaining the rotating speed of the motor and the position angle information of the rotor after decoding; The phase currents of the 6 current sensor sampling motors are recorded as i A 、i B 、i C 、i D 、i E and i F , each variable of a natural coordinate system is converted into a static coordinate system by adopting a VSD coordinate transformation method, and a transformation matrix is as follows: (4); Wherein i α 、i β 、i x 、i y 、i o1 and i o2 represent currents of the α -axis, β -axis, x-axis, y-axis, o 1-axis, o 2-axis of the stationary coordinate system; For a double three-phase permanent magnet motor, only the fundamental component of the alpha beta subspace participates in electromechanical energy conversion, and in order to facilitate the simplified analysis, a static coordinate system is transformed into a synchronous rotation coordinate system, and a transformation matrix is as follows: (5); wherein θ is the rotor position angle, and i d and i q are the d-axis and q-axis currents, respectively; And calculating the current i dq (k) of the motor under the dq rotation coordinate system at the moment k through the coordinate conversion module.
  6. 6. The control method of a dual three-phase motor high-precision model predictive current control system according to claim 5, wherein the specific steps of step 4) include: in the model predictive control system based on the virtual voltage vector, the harmonic plane can be ignored, so that only the related variable of the double three-phase permanent magnet motor on the fundamental plane is considered, the related variable is converted into a rotating coordinate system, and the voltage equation of the motor is obtained by the following steps: (6); Where U d 、u q is the component of U s in the d-axis and q-axis, R s is the stator resistance, L d 、L q 、i d and i q are the dq-axis inductance and current, respectively, Is the magnitude of the permanent magnet flux linkage, Is the electrical angular velocity; discretizing the (6) by adopting an Euler forward formula to obtain: (7); Wherein, the superscript "k" represents the real-time value of dq-axis current and voltage at the moment k, the superscript "k+1" represents the predictive value of dq-axis current at the moment k+1, and T s is the control period; In order to make up for the defect of one beat of delay of the digital controller, a two-step prediction method is adopted to carry out delay compensation, the prediction is carried out again in the step (7), and a final prediction model is obtained as follows: (8); wherein the superscript "pre" indicates the final predicted value of the dq-axis current; the cost function is defined as: (9); where the superscript "×" denotes that the dq axis current is given a reference value, with i d * =0 control.
  7. 7. The method for controlling a dual three-phase motor high-precision model predictive current control system according to claim 6, wherein in step 5), the specific step of calculating the duty cycle of the voltage vector action comprises: (1) Linear equation of AB: (10); (2) Linear equation perpendicular to AB across point C: (11); (3) The coordinates of the point at which the two straight lines intersect are obtained by combining (10) and (11) as follows: (12); Wherein ipre d _duty and ipre q _duty represent predicted values of the dq-axis current after the duty cycle correction; ; (4) The optimal duty ratio of the voltage vector can be obtained according to the intersection point position: (13)。
  8. 8. the control method of a dual three-phase motor high-precision model predictive current control system according to claim 5, wherein the specific steps of step 6) include: (1) The αβ plane is equally divided into four regions, designated G 1 ,G 2 ,G 3 and G 4 , with V 4 、V 10 、V 16 、V 22 as the boundary, and each region contains a virtual voltage vector as shown in the following table: table 1 is a virtual voltage vector partitioning rule: ; (2) Substituting V 1 ,V 7 ,V 13 and V 19 into (5) to obtain the values of the respective cost functions under the action of four voltage vectors, namely J (V 1 ),J(V 7 ),J(V 13 ),J(V 19 ), selecting a vector V 1st with the minimum cost function, and further determining an optimal area; (3) Assuming that V 1st determined in the second step is V 1 , the optimal region is G 1 , calculating the value of the cost function of V 13 and V 13 in G 1 again, selecting a vector V 2nd with the minimum cost function, and determining a second optimal region; (4) Assuming that V 2nd determined in the second step is V 1 , judging the value of the cost function of V 1 and the value of the cost function of two adjacent voltage vectors V 24 and V 2 , and selecting the optimal cost function to determine the final voltage vector sequence number; (5) Other cases and so on, the combinations of all regions are shown in Table two; table 2 selects case combinations for all optimal voltage vectors: ; Through the simplified process, the original prediction process needs to traverse 24 voltage vectors, and only 8 voltage vectors need to be traversed at present, so that the calculation load of an algorithm is reduced, and the efficiency is improved.
  9. 9. The control method of the double three-phase motor high-precision model prediction current control system according to claim 2, wherein the specific step of the step 7) comprises the steps of substituting 24 virtual voltage vectors VV into a prediction model one by one, selecting an optimal voltage vector and a duty ratio acted by the optimal voltage vector through a simplification module, outputting the optimal voltage vector to a PWM module, modulating the optimal voltage vector through an inverter, and outputting the corresponding voltage vector to complete the whole control.

Description

Double three-phase motor high-precision model prediction current control system and control method Technical Field The invention belongs to the technical field of multiphase motor predictive control, and particularly relates to a dual three-phase motor high-precision model predictive current control system and a control method. Background With the rapid development of high-end fields such as transportation, aerospace, national defense and military industry and the like, a motor system is used as a core component of equipment, and the requirements on the motor system are further improved. The multiphase permanent magnet motor has the advantages of high power density, high efficiency, good fault tolerance and the like, and has become the first choice of an advanced motor system. The center point is isolated, and the two sets of windings are connected with each other in a phase shift of 30 degrees, so that the special structure of the double three-phase permanent magnet synchronous motor eliminates 6 times of torque pulsation, and the double three-phase permanent magnet synchronous motor is widely applied. The model predictive control strategy has good performance in the application occasion of the power converter due to the advantages of multivariable control, easy processing of nonlinear constraint and visual and easy realization, and gradually shows good engineering application value. However, the method has the disadvantages of large calculation amount, high torque pulsation and the like. The Chinese patent (202110774817.4) discloses a low-calculation-amount model predictive control method for a dual-motor series system model, which only needs to calculate a cost function of two voltage vectors, so that the calculation amount is relatively reduced, but the method needs to calculate the position of a reference voltage vector, so that two observers are added, and the system becomes complex. The Chinese patent (202210499366.2) discloses a method for reducing the torque ripple and the flux linkage ripple of a permanent magnet synchronous motor, which widens the modulation range by using a plurality of voltage vectors in a single period, and has a certain effect but complex calculation. When the model predictive control algorithm is applied to the field of multiphase motors, the alternative voltage vector of the model predictive control algorithm is exponentially increased, and the calculated amount is relatively increased. Meanwhile, the multiphase motor comprises a harmonic plane, and the harmonic plane must be controlled in the running process of the system, otherwise, the motor performance is not favored, and larger loss is generated. Therefore, in order to promote the application of model predictive control in the field of multiphase motors, there is an urgent need to develop related researches for reducing the computational load of algorithms or related technologies for improving torque and flux linkage pulsation. Disclosure of Invention The invention aims to redesign a control set aiming at the problems of large torque pulsation, heavy calculation load and the like in the model predictive control of the double three-phase permanent magnet motor. The traditional 12 virtual voltage vector control set is expanded, 24 virtual voltage vectors with equal amplitude and uniform phase angle are designed on the premise of not losing the voltage utilization rate, and the control precision is improved. Furthermore, a duty ratio calculation method based on minimum error is provided, even under the condition of single effective virtual voltage vector, the current of d axis and q axis can be tracked at the same time, and the optimal duty ratio is ensured to be output. In addition, the process of traversing all voltage vectors in the prediction control is simplified, and the calculation load of an algorithm is reduced. The invention effectively improves the precision of model predictive control by expanding a control set and reducing the duty ratio calculation error, reduces 5 and 7 times of harmonic waves and improves torque pulsation. And the calculation amount is low even under the action of 24 voltage vectors, so that the execution efficiency of the algorithm is improved. The technical scheme includes that the high-precision model prediction current control system of the double three-phase motor comprises system hardware and system software (realized in programming), wherein the system hardware comprises a double three-phase permanent magnet motor, a direct current power supply, a PWM (pulse-width modulation) module, an inverter, a position sensor and a current sensor, and the system software comprises a synthesized 24 virtual voltage vector module, a rotating speed controller, a coordinate conversion module, a delay module, a prediction module, a duty ratio calculation module, a simplification module and a cost function module; the double three-phase permanent magnet motor consists of two sets of three-phase windin