Multi-motor vector control system of permanent magnet synchronous motor system and its simplified method

Abstract

The invention discloses a multi-motor vector control method based on a semi-centralized open-winding permanent magnet synchronous motor system and a simplified method thereof, belonging to the technical field of motor drive and control. The system is composed of N open-winding three-phase permanent magnet synchronous motors with a common DC bus, N two-level independent inverters, one two-level multiplexing inverter, one speed closed-loop unit, N d-axis current closed-loop units, N q-axis current closed-loop units, one minimum coverage circle calculation unit, N+1 vector control units and N+1 zero vector polarity control units. The reference voltage vectors of the N motors are distributed to the N+1 inverters in a manner of maximum voltage utilization, and then each inverter performs independent vector control and zero vector polarity control to generate a corresponding trigger signal, thereby solving the vector control problem of a semi-centralized open-winding permanent magnet synchronous motor system composed of any number of motors, simplifying the calculation process of the minimum coverage circle, reducing the execution time and improving the execution efficiency.

Description

Technical Field

[0001] The present invention relates to a multi-motor vector control method of a permanent magnet synchronous motor system and a simplified method thereof, and belongs to the technical field of motor drive and control. Background Art

[0002] In a drive system consisting of N motors, a traditional open-winding permanent magnet synchronous motor will require 2N inverters, which will occupy a huge volume and increase the cost. The number of inverters required can be reduced to N+1 by having one side of these motors share a multiplexed inverter. However, these inverters and motors belong to the same control system, which will dramatically increase the overall degree of freedom of the system and is not conducive to the use of traditional vector control methods. Summary of the invention

[0003] Purpose of the invention: The present invention proposes a multi-motor vector control system based on a semi-centralized open-winding permanent magnet synchronous motor system for use in the field of electric drive. The method introduces the concept of the minimum coverage circle, and utilizes the characteristic that the DC bus voltages of the inverters with a common DC bus structure are completely identical, to distribute the reference voltage vectors of N motors to N+1 inverters in a manner with the highest voltage utilization, and then each inverter performs independent vector control and zero vector polarity control to generate a corresponding trigger signal. The vector control problem of a semi-centralized open-winding permanent magnet synchronous motor system composed of any number of motors is solved, and the characteristic of the same speed of coaxial rotating motors or linear motors on the same carrier is utilized to simplify the calculation process of the minimum coverage circle, reduce the execution time, and improve the execution efficiency.

[0004] Technical solution: A semi-centralized open-winding permanent magnet synchronous motor system, the system includes N three-phase open-winding permanent magnet synchronous motors, N+1 two-level voltage source inverters and a multi-motor vector control unit. The N+1 inverters adopt a common DC bus connection mode. Each open-winding motor needs to be powered from both ends at the same time. The N motors are respectively referred to as motor n (n=1,2...N). The positive output terminal of motor n is connected to an independent inverter n, and the negative output terminals of all motors are connected to the same multiplexed inverter N+1; each motor is respectively subjected to current closed-loop control to obtain a reference voltage vector, and then the characteristics of the N+1 inverters sharing a common DC bus are used to adopt a minimum covering circle algorithm to determine the reference voltage vector of the multiplexed inverter N+1, and then determine the reference voltage vector of another N independent inverters n; the N+1 inverters are respectively vector controlled, and zero vectors are distributed according to the polarity of zero-sequence current to suppress zero-sequence current, and finally a switching signal is output. The multi-motor vector control unit samples the current, speed, position of N motors and the DC bus voltage data of the inverter, and generates control signals and sends them to the inverter to control the switching state of the inverter's bridge arm, forming a closed-loop control system of inverter-motor-control unit-inverter.

[0005] The present invention also proposes a multi-motor vector control method based on a semi-centralized open-winding permanent magnet synchronous motor system and a simplified method thereof, and the specific implementation steps are as follows:

[0006] (1) First, the DC bus voltage u dc 、The three-phase current i of N permanent magnet synchronous motors a_n 、i b_n 、i c_n , rotor position angle θ m_n 、Mechanical rotation angular velocity ω m Sampling is performed, and the Clark coordinate transformation is used to obtain the i in the dq0 coordinate system. d_n 、i q_n 、i z_n

[0007]

[0008] Among them, P n is the number of pole pairs; the subscript n represents the value of motor n, n = 1, 2...N;

[0009] (2) The system quadrature axis current reference value i is obtained through the speed regulator. qref and the direct axis current reference value i dref and zero sequence current reference value i zref All are set to 0;

[0010] (3) Obtain the direct axis voltage reference value u of motor n through the d-axis current closed-loop unit-n and the q-axis current closed-loop unit-n dref_n and the direct axis voltage reference value u qref_n And the reference voltage vector in the αβ stationary coordinate system is obtained by Park transformation

[0011]

[0012] (4) The reference voltage vector of N motors Send it to the minimum covering circle calculation unit to calculate the center and radius of the minimum covering circle. The specific process is as follows:

[0013] i) Initialize the center F of the current coverage circle C and radius R C :

[0014] R C =0,F C =(u Cα ,u Cβ )=(0,0)

[0015] ii) Calculate the reference voltage vector of the i-th motor to F C The distance L i :

[0016]

[0017] iii) Determine L i With R C If L i ≤R C , jump to step x); otherwise update the current coverage circle:

[0018]

[0019] And initialize j to 1;

[0020] iv) Calculate the reference voltage vector of the jth motor to F C The distance L j :

[0021]

[0022] v) Judge L j With R C If L j ≤R C , jump to step ix); otherwise update the current coverage circle:

[0023]

[0024] And initialize k to 0;

[0025] vi) Calculate the reference voltage vector of the kth motor to F C The distance L k :

[0026]

[0027] It should be noted that there is no motor 0 in the actual system. Refers to the origin (0,0);

[0028] vii) Determine L k With R C If L k ≤R C , jump to step viii); otherwise update the current coverage circle:

[0029]

[0030] in

[0031]

[0032]

[0033]

[0034] F Cβ =k 1 F Cα -α 1 k 1 +β 1

[0035] viii) Update k=k+1, if k≤j-1; then return to step vi);

[0036] ix) Update j=j+1, if j≤i-1; then return to step iv);

[0037] x) Update i=i+1, if i≤N; then return to step ii);

[0038] xi) Determine the origin (0,0) and the reference voltage vector coordinates of N motors The minimum covering circle with the smallest radius that contains all:

[0039] R SEC =R C ,F SEC =(u Cα ,u Cβ )

[0040] R SEC and F SEC are the radius and center coordinates of the minimum covering circle respectively;

[0041] xii) Perform limit adjustment to ensure the reference voltage vector of N+1 inverters Will not exceed its output capacity, η is the adjustment coefficient:

[0042] η=min{1,R FH / R SEC}

[0043] For the N+1th multiplexing inverter:

[0044]

[0045] For n independent inverters, there are:

[0046]

[0047] (5) The reference voltage vector of N+1 inverters The two-level inverter SVPWM strategy is used to calculate the effective vector duty cycle T of inverter h. e1_h 、T e2_h and zero vector duty cycle T z_h ,Then the zero vector duty ratio is allocated according to the zero sequence current polarity of the corresponding motor.

[0048] For the two-level inverter, there are 8 basic voltage vectors, namely V 0 (0,0,0), V 1 (1,0,0), V 2 (1,1,0), V 3 (0,1,0),V 4 (0,1,1), V 5 (0,0,1),V 6 (1,0,1), V 7 (1,1,1), where V 0 and V 7 is a zero vector, which is used to fill the redundant control cycle. The difference between the two is only the magnitude of the common mode voltage generated, V 7 The maximum positive common-mode voltage will be generated, and V 0 No common-mode voltage is generated.

[0049] For the independent inverter h, when the zero-sequence current of the corresponding motor h is negative, a positive common-mode voltage is required for suppression. The independent inverter h should allocate all zero vector time to V 7 To meet this trend, the same goes for the opposite:

[0050]

[0051] Among them, T 0_h , and T 7_h , respectively, are assigned to inverter h for V 0 and V 7 duty cycle.

[0052] For the multiplexed inverter N+1, it will affect all motors and is located at the negative end of the motor, so V 7 The maximum negative common-mode voltage will be generated, and V 0 No common-mode voltage is generated. When more motor zero-sequence current polarity is positive, more negative common-mode voltage is required for suppression. Multiplexing inverter N+1 should allocate more zero vector time to zero vector V 7 To meet this trend, the same goes for the opposite:

[0053]

[0054] Among them, Q is the number of motors with positive zero-sequence current polarity.

[0055] (6) Based on the result of (5), the driving signals of N+1 inverters are generated to control the switching state of the inverter bridge arm, thereby controlling the motor. At the same time, the motor operation state is sampled and the next control cycle is entered.

[0056] (7) The difference between the simplified method and the simplified method is that in step (4), it is not necessary to set the reference voltage vector coordinates of the N motors and the origin (0,0) into the minimum covering circle calculation unit. By taking advantage of the fixed relative positions of the coaxial rotary motors or the same carrier linear motors, only the reference voltage vector of the motor at the front position is The final motor reference voltage vector and position Substituting the three points (assuming that the motor numbers are arranged by position) and the origin (0,0) into the minimum coverage circle calculation unit, the same result can be calculated. Therefore, no matter how large N is, the amount of calculation of the minimum coverage circle calculation unit can be fixed, thus avoiding exponential explosion.

[0057] Beneficial Effects

[0058] Taking advantage of the fact that the DC bus voltages of the inverters with a common DC bus structure are completely identical, the reference voltage vectors of the N motors are distributed to the N+1 inverters in a manner with the highest voltage utilization rate, and then each inverter performs independent vector control and zero vector polarity control to generate a corresponding trigger signal; the vector control problem of a semi-centralized open-winding permanent magnet synchronous motor system consisting of an arbitrary number of motors is solved, and the fact that the coaxial rotating motors or the linear motors on the same carrier have the same speed is utilized to simplify the calculation process of the minimum coverage circle, reduce the execution time, and improve the execution efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 It is a semi-centralized open-winding permanent magnet synchronous motor topology;

[0060] Figure 2 is a schematic diagram of the minimum covering circle;

[0061] Figure 3 It is a control block diagram of a multi-motor vector control system of a semi-centralized open-winding permanent magnet synchronous motor system;

[0062] Figure 4 It is the experimental waveform of multi-motor vector control method. DETAILED DESCRIPTION

[0063] The following is combined with Figure 1 The technical solution of the present invention is described in detail;

[0064] The present invention proposes a multi-motor vector control system based on a semi-centralized open-winding permanent magnet synchronous motor system, characterized in that the system comprises N three-phase open-winding permanent magnet synchronous motors, N+1 two-level voltage source inverters and a multi-motor vector control unit, the N+1 inverters adopt a common DC bus connection mode, each open-winding motor needs to be powered from both left and right ends at the same time, the N motors are respectively referred to as motor n (n=1,2...N), the positive output terminal of motor n is connected to an independent inverter n, and the negative output terminals of all motors are connected to the same multiplexed inverter N+1; current closed-loop control is performed on each motor to obtain a reference voltage vector, and then the characteristic of the N+1 inverters sharing a DC bus is used to adopt a minimum covering circle algorithm to determine the reference voltage vector of the multiplexed inverter N+1, and then the reference voltage vector of another N independent inverters n is determined; the N+1 inverters are respectively vector controlled, and zero vectors are distributed according to the polarity of zero-sequence current to suppress zero-sequence current, and finally a switching signal is output. The multi-motor vector control unit samples the current, speed, position of N motors and the DC bus voltage data of the inverter, and generates a control signal to send to the inverter to control the switch state of the inverter bridge arm, forming an inverter-motor-control unit-inverter closed-loop control system. The specific implementation steps are as follows:

[0065] (1) Yes Figure 1 The motor system shown in the figure firstly adjusts the DC bus voltage u dc 、The three-phase current i of N permanent magnet synchronous motors a_n 、i b_n 、i c_n , rotor position angle θ m_n 、Mechanical rotation angular velocity ω m Sampling is performed, and the Clark coordinate transformation is used to obtain the i in the dq0 coordinate system. d_n 、i q_n 、i z_n

[0066]

[0067] Among them, P n is the number of pole pairs; the subscript n represents the value of motor n, n = 1, 2...N;

[0068] (2) The system quadrature axis current reference value i is obtained through the speed regulator. qref and the direct axis current reference value i dref and zero sequence current reference value i zref All are set to 0;

[0069] (3) Obtain the direct axis voltage reference value u of motor n through the d-axis current closed-loop unit-n and the q-axis current closed-loop unit-n dref_n and the direct axis voltage reference value uqref_n And the reference voltage vector in the αβ stationary coordinate system is obtained by Park transformation

[0070]

[0071] (4) The reference voltage vector of N motors Send it to the minimum covering circle calculation unit to calculate the center and radius of the minimum covering circle. The specific process is as follows:

[0072] i) Initialize the center F of the current coverage circle C and radius R C :

[0073] R C =0,F C =(u Cα ,u Cβ )=(0,0)

[0074] ii) Calculate the reference voltage vector of the i-th motor to F C The distance L i :

[0075]

[0076] iii) Determine L i With R C The size of L i ≤R C , jump to step x); otherwise update the current coverage circle:

[0077]

[0078] And initialize j to 1;

[0079] iv) Calculate the reference voltage vector of the jth motor to F C The distance L j :

[0080]

[0081] v) Judge L j With R C The size of L j ≤R C , jump to step ix); otherwise update the current coverage circle:

[0082]

[0083] And initialize k to 0;

[0084] vi) Calculate the reference voltage vector of the kth motor to F C The distance L k :

[0085]

[0086] It should be noted that there is no motor 0 in the actual system. Refers to the origin (0,0);

[0087] vii) Determine L k With R C The size of L k ≤R C , jump to step viii); otherwise update the current coverage circle:

[0088]

[0089] in

[0090]

[0091]

[0092]

[0093] F Cβ =k 1 F Cα -α 1 k 1 +β 1

[0094] viii) Update k=k+1, if k≤j-1; then return to step vi);

[0095] ix) Update j=j+1, if j≤i-1; then return to step iv);

[0096] x) Update i=i+1, if i≤N; then return to step ii);

[0097] xi) Determine the origin (0,0) and the reference voltage vector coordinates of N motors The minimum covering circle with the smallest radius that contains all:

[0098] R SEC =R C ,F SEC =(u Cα ,u Cβ )

[0099] R SEC and F SECare the radius and center coordinates of the minimum covering circle respectively. The schematic diagram of the minimum covering circle is as follows Figure 2 As shown;

[0100] xii) Perform limit adjustment to ensure the reference voltage vector of N+1 inverters Will not exceed its output capacity, η is the adjustment coefficient:

[0101] η=min{1,R FH / R SEC}

[0102] For the N+1th multiplexing inverter:

[0103]

[0104] For n independent inverters, there are:

[0105]

[0106] (5) The reference voltage vector of N+1 inverters The two-level inverter SVPWM strategy is used to calculate the effective vector duty cycle T of inverter h. e1_h , T e2_h and zero vector duty cycle T z_h ,Then the zero vector duty ratio is allocated according to the zero sequence current polarity of the corresponding motor.

[0107] For the two-level inverter, there are 8 basic voltage vectors, namely V 0 (0,0,0), V 1 (1,0,0), V 2 (1,1,0), V 3 (0,1,0),V 4 (0,1,1), V 5 (0,0,1),V 6 (1,0,1), V 7 (1,1,1), where V 0 and V 7 is a zero vector, which is used to fill the redundant control cycle. The difference between the two is only the magnitude of the common mode voltage generated, V 7 The maximum positive common-mode voltage will be generated, and V 0 No common-mode voltage is generated.

[0108] For the independent inverter h, when the zero-sequence current of the corresponding motor h is negative, a positive common-mode voltage is required for suppression. The independent inverter h should allocate all zero vector time to V 7 To meet this trend, the same goes for the opposite:

[0109]

[0110] Among them, T 0_h , and T 7_h , respectively, are assigned to inverter h for V 0 and V 7 duty cycle.

[0111] For the multiplexed inverter N+1, it will affect all motors and is located at the negative end of the motor, so V 7 The maximum negative common-mode voltage will be generated, and V 0 No common-mode voltage is generated. When more motor zero-sequence current polarity is positive, more negative common-mode voltage is required for suppression. Multiplexing inverter N+1 should allocate more zero vector time to zero vector V 7 To meet this trend, the same goes for the opposite:

[0112]

[0113] Among them, Q is the number of motors with positive zero-sequence current polarity.

[0114] (6) Based on the result of (5), the driving signals of N+1 inverters are generated to control the switching state of the inverter bridge arm, thereby controlling the motor. At the same time, the motor operation state is sampled and the next control cycle is entered.

[0115] (7) The difference between the simplified method and the simplified method is that in step (4), it is not necessary to set the reference voltage vector coordinates of the N motors and the origin (0,0) into the minimum covering circle calculation unit. By taking advantage of the fixed relative positions of the coaxial rotary motors or the same carrier linear motors, only the reference voltage vector of the motor at the front position is The final motor reference voltage vector and position Substituting the three points (assuming that the motor numbers are arranged by position) and the origin (0,0) into the minimum coverage circle calculation unit, the same result can be calculated. Therefore, no matter how large N is, the amount of calculation of the minimum coverage circle calculation unit can be fixed, thus avoiding exponential explosion.

[0116] In order to verify the effect of the present invention, an experimental verification was carried out. Figure 1 It is a semi-centralized open-winding permanent magnet synchronous motor topology. Figure 2 is a schematic diagram of the minimum covering circle, Figure 3 It is the control block diagram of the multi-motor vector control system of the semi-centralized open-winding permanent magnet synchronous motor system. Figure 4 These are the experimental waveforms of the multi-motor vector control method using the ordinary method and the simplified method respectively.

[0117] contrast Figure 4It can be shown that the ordinary method and the simplified method have the same control performance.

[0118] In order to compare the computational speed of the original method and the simplified method, the actual execution time required per control cycle of the experiment when N=4 is compared as shown in Table 1.

[0119] Table 1 - Computation time comparison

[0120]

[0121] The experimental results in Table 1 show that the simplified method of multi-motor vector control proposed in the present invention has a shorter execution time than its ordinary method.

[0122] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0123] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A multi-motor vector control method based on a semi-centralized open-winding permanent magnet synchronous motor, characterized in that: The control method includes: connecting the negative output terminals of multiple motors to the same multiplexed inverter, performing current closed-loop control on each motor to obtain a reference voltage vector, using a minimum covering circle algorithm to determine the reference voltage vector of the multiplexed inverter, and then determining the reference voltage vector of another independent inverter; and performing vector control on multiple inverters respectively; The specific steps of the multiplexed inverter for vector control are as follows: Will N Motor n , n =1,2… N , motor n The positive output terminal is connected to an independent inverter n , the negative output terminals of all motors are connected to the same multiplexing inverter N +1; Will N +1 reference voltage vector for inverter , h =1,2… N +1, sent to their respective vector control units, and the inverter is calculated using the two-level inverter SVPWM strategy h The effective vector duty cycle T e1_h , T e2_h and zero vector duty cycle T z_h , and then the zero vector duty cycle is allocated according to the zero sequence current polarity of the corresponding motor; For the two-level inverter, there are 8 basic voltage vectors, namely V 0(0,0,0), V 1(1,0,0), V 2(1,1,0), V 3(0,1,0), V 4(0,1,1), V 5(0,0,1), V 6(1,0,1), V 7(1,1,1), where V 0 and V 7 is the zero vector, which is used to fill the redundant control cycle. The difference between the two is only the magnitude of the common mode voltage generated. V 7 will produce the largest positive common-mode voltage, while V 0 does not generate common mode voltage; For independent inverters h , and its corresponding motor h When the zero-sequence current is negative, a positive common-mode voltage is required for suppression. h All zero vector time should be allocated to V 7 To meet this trend, the same goes for the opposite: in, T 0_h and T 7_h Inverter h Assigned to V 0 and V A duty cycle of 7; Multiplexing inverter N +1, it will affect all motors, and it is located at the negative end of the motor, so V 7 will produce the largest negative common-mode voltage, while V 0 does not generate common mode voltage. When more motor zero-sequence current polarity is positive, more negative common mode voltage is required for suppression. N +1 More zero vector time should be allocated to zero vector V 7 To meet this trend, the same goes for the opposite: in, Q is the number of motors with positive zero-sequence current polarity; According to the above results N The driving signal of +1 inverter controls the switching state of the inverter bridge arm, and then controls the motor. At the same time, the motor operating state is sampled and the next control cycle is entered.

2. A multi-motor vector control method based on a semi-centralized open-winding permanent magnet synchronous motor according to claim 1, characterized in that: The multiplexing inverter distributes the zero vector according to the polarity of the zero-sequence current to suppress the zero-sequence current, and finally outputs a switching signal.

3. The multi-motor vector control method based on a semi-centralized open-winding permanent magnet synchronous motor according to claim 1 is characterized in that: The method utilizes the characteristic that the relative positions of the coaxial rotating motors or the same carrier linear motors are fixed, and only substitutes the reference voltage vector of the motor at the front position, the reference voltage vector of the motor at the rear position and the origin into the minimum covering circle calculation unit.

4. A multi-motor vector control system based on a semi-centralized open-winding permanent magnet synchronous motor, the control system is used to implement a multi-motor vector control method based on a semi-centralized open-winding permanent magnet synchronous motor according to claim 1, characterized in that: The control system comprises N Three-phase open-winding permanent magnet synchronous motor, N +1 two-level voltage source inverter and multi-motor vector control unit, N +1 inverter adopts the connection mode of common DC bus. Each open-winding motor needs to be powered from both ends at the same time. N Motor n , n =1,2… N , motor n The positive output terminal is connected to an independent inverter n , the negative output terminals of all motors are connected to the same multiplexing inverter N +1.

5. A multi-motor vector control system based on a semi-centralized open-winding permanent magnet synchronous motor according to claim 4, characterized in that: The control system controls the DC bus voltage U dc and N The three-phase current of each permanent magnet synchronous motor i d_n , i q_n , i z_n , rotor position angle θ m_n , and the common mechanical rotational angular velocity ω m Take samples; Will ω m and mechanical rotation angular velocity ω mref Sent to the speed closed loop unit to get the reference q Shaft current i dref , take zero d The shaft current control makes the reference d Shaft current i dref Always 0; i dref , i d_n , i qref , i d_n Send to n Motor d Axis and q The shaft current closed loop unit obtains the n Reference of the motor q Shaft voltage u dref_n and reference q Shaft voltage u qref_n ,Will u dref_n and u qref_n Transform to αβ Combine all the reference voltage vectors in the coordinate system. N The reference voltage vector of the motor , n =1,2… N , sent to the minimum covering circle calculation unit to obtain N Reference voltage vector for each independent inverter and 1 multiplexed inverter reference voltage vector ;Will N The reference voltage vector of +1 inverter is sent to the respective vector control unit and outputs the switching command, so as to complete the motor closed-loop control and zero-sequence current suppression.

6. A storage medium, characterized in that: The storage medium records the multi-motor vector control system based on the semi-centralized open-winding permanent magnet synchronous motor as described in claim 5.

7. A computing execution device, characterized in that: The calculation execution device is used to calculate the multi-motor vector control system based on the semi-centralized open-winding permanent magnet synchronous motor as described in claim 5.

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