Common-centerline open-winding asynchronous motor driving system and model prediction control method

Abstract

The invention provides a centerline-shared open-winding asynchronous motor driving system and a model prediction control method, and the centerline-shared open-winding asynchronous motor driving system comprises two three-phase four-leg converters and an open-winding asynchronous motor. Each bridge arm of the two three-phase four-bridge-arm converters is formed by connecting an upper-end power device and a lower-end power device in series, and the upper-end power devices and the lower-end power devices of the first three bridge arms of the two three-phase four-bridge-arm converters serve as output ends and are connected with the two ends of a three-phase winding of the open-winding asynchronous motor respectively; the upper end power device and the lower end power device of the fourth bridge arm of the two three-phase four-bridge arm converters are directly connected; the invention further discloses a model prediction control method of the centerline-shared open-winding asynchronous motor driving system. According to the neutral-line-sharing open-winding asynchronous motor driving system, the control freedom degree of the open-winding motor driving system is increased, multi-mode operation of the motor can be achieved, the current stress of the direct-current bus capacitor is reduced, and the calculation complexity is greatly reduced through the model prediction control method.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronics and electric drive, and in particular to a common neutral open-winding asynchronous motor drive system and a model predictive control method. Background Art

[0002] In recent years, with the rapid development of new energy vehicles, shield machines and other technologies, asynchronous motors have been widely used due to their low cost and high reliability. In order to improve the operating efficiency of asynchronous motor drive systems, reduce torque ripple and improve reliability, open-winding asynchronous motor drive systems have also received extensive attention and research.

[0003] The existing open-winding asynchronous motor drive system can be divided into three topological forms: independent DC bus, common DC bus and common neutral line. The literature [Sun Dan, Lin Bin, Chen Min, et al. Cooperative control of dual inverters for open-winding permanent magnet synchronous motors for HEV [J]. Journal of Electric Machines and Control, 2016, 20(02): 29-35.] studied the power and voltage distribution strategy of open-winding permanent magnet synchronous motors powered by independent DC bus, and the literature [Kasoju Bharath Kumar, and Kunisetti V. Praveen Kumar. A Reduced Voltage Vector Strategy-Based PTC of OEW-PMSM Drives [J]. IEEE Transactions on Industrial Electronics, vol. 71, no. 10, pp. 11948-11956, Oct. 2024] studied the model predictive direct torque control method of open-winding permanent magnet synchronous motors powered by independent DC bus. However, this independent DC bus open-winding motor drive system has no zero-sequence current. When a single-phase winding open-circuit fault occurs in the motor, this topology is difficult to achieve fault-tolerant operation. The literature [Sun Dan, Zhao Chen, Ke Weihuang, et al. Improved direct torque control of common DC bus open-winding permanent magnet synchronous motor based on reconstructed voltage vector [J]. Transactions of the Chinese Society of Electrical Engineering, 2022, 37(07): 1644-1653.] studied the improved direct torque control strategy of common DC bus open-winding permanent magnet synchronous motor and achieved torque pulsation suppression. The literature [Z. Zhang, X. Wang, D. Xiao, Y. Zhou, M. He and Z. Wang. A Novel 3-D Space Vector Modulation Strategy for Open-End Winding PMSM [J]. IEEE Transactions on Industrial Electronics, vol. 71, no. 8, pp. 8536-8547, Aug. 2024] studied the three-dimensional space vector modulation strategy of the open-end permanent magnet synchronous motor with a common DC bus, which also significantly reduced the torque ripple. However, the DC sides of the two converters of this common DC bus open-end motor drive system are connected together and always remain equal, and the DC bus voltage values ​​of the two converters cannot be adjusted independently, which reduces the flexibility of the system.In order to achieve independent adjustment of the DC bus voltage of the two converters and realize fault-tolerant control of the open-winding motor during single-phase open-circuit fault through zero-sequence current, a common neutral open-winding motor drive system topology and its vector control strategy are studied in the literature [Wang Shun, Yang Shuying, Li Yi, et al. Research on three-dimensional space vector pulse width modulation strategy of common neutral open-winding topology [J]. Proceedings of the CSEE, 2023, 43(03):1163-1177.], literature [Li Yi, Wang Fusheng, Yang Shuying, et al. Research on vector control strategy of permanent magnet synchronous motor based on floating bridge common neutral open-winding topology [J]. Proceedings of the CSEE, 2022, 42(13):4942-4955.] and literature [Yang Shuying, Hu Xiaohai, Fu Huan, et al. Research on control strategy of open-winding asynchronous motor based on common neutral topology [J]. Proceedings of the CSEE, 2020, 40(11):3681-3691.]. However, the neutral line of this topology is composed of the neutral points of the DC bus capacitors of the two converters connected together. When the motor has a single-phase open circuit fault and needs to be operated for fault tolerance, a large zero-sequence current will flow through the neutral line, which will increase the current stress of the DC bus capacitor and accelerate the aging of the DC bus capacitor. In addition, this topology makes it difficult to achieve multi-mode operation of the motor and cannot reduce motor losses through multi-mode operation. Summary of the invention

[0004] In view of the technical problems that the fault-tolerant operation of the existing common neutral open-winding motor drive system will accelerate the aging of the DC bus capacitor and make it difficult to achieve multi-mode operation and reduce losses, the present invention proposes a common neutral open-winding asynchronous motor drive system and a model predictive control method. Based on two three-phase four-arm converters, the DC voltages of the two converters of the open-winding asynchronous motor drive system can be independently adjusted while retaining the neutral line. The common neutral open-winding asynchronous motor drive system increases the control freedom of the open-winding motor drive system. The model predictive control method greatly reduces the calculation complexity, and realizes high-performance current control of the motor drive system with low complexity.

[0005] In order to achieve the above-mentioned purpose, the technical solution of the present invention is implemented as follows: a common neutral open-winding asynchronous motor drive system, comprising: two three-phase four-bridge-arm converters and an open-winding asynchronous motor, each bridge arm of the two three-phase four-bridge-arm converters is composed of an upper power device and a lower power device connected in series, and the upper power devices and the lower power devices of the first three bridge arms of the two three-phase four-bridge-arm converters are respectively connected to the two ends of the three-phase winding of the open-winding asynchronous motor as output ends; the upper power device and the lower power device of the fourth bridge arm of the two three-phase four-bridge-arm converters are directly connected.

[0006] Preferably, the upper power device and the lower power device are both composed of fully controlled power electronic devices and uncontrolled diodes connected in anti-parallel; the two three-phase four-bridge arm converters each include a first bridge arm, a second bridge arm, a third bridge arm and a fourth bridge arm.

[0007] The output ends of the first bridge arms of the two three-phase four-bridge-arm converters are respectively connected to the two ends of the stator a-phase winding of the open-winding asynchronous motor, the output ends of the second bridge arms of the two three-phase four-bridge-arm converters are respectively connected to the two ends of the stator b-phase winding of the open-winding asynchronous motor, the output ends of the third bridge arms of the two three-phase four-bridge-arm converters are respectively connected to the two ends of the stator c-phase winding of the open-winding asynchronous motor, and the output ends of the fourth bridge arms of the two three-phase four-bridge-arm converters are directly connected together;

[0008] The positive ends of the four bridge arms of the two three-phase four-bridge-arm converters are connected together and connected to the positive ends of their respective DC bus power supplies, and the negative ends of the four bridge arms of the two three-phase four-bridge-arm converters are connected together and connected to the negative ends of their respective DC bus power supplies.

[0009] Preferably, a capacitor C is provided between the positive end and the negative end of the DC bus power supply, and the capacitor C is connected in parallel with each bridge arm;

[0010] The upper power device S of the first bridge arm of the first three-phase four-bridge arm converter 11 and the lower power device S 12 Series connection, the upper power device S 11 and the lower power device S 12 The midpoint between is the output end; the upper power device S of the second bridge arm of the first three-phase four-bridge-arm converter 13 and the lower power device S 14 Series connection, the upper power device S 13 and the lower power device S 14 The midpoint between them is the output end; the upper power device S of the third bridge arm of the first three-phase four-bridge-arm converter 15 and the lower power device S 16 Series connection, the upper power device S 15 and the lower power device S 16 The midpoint between them is the output end; the upper power device S of the fourth bridge arm of the first three-phase four-bridge-arm converter 17 and the lower power device S 18 Series connection, the upper power device S 17 and the lower power device S 18 The midpoint between 1 The upper power device S of the first bridge arm of the second three-phase four-bridge-arm converter 21 and the lower power device S 22 Series connection, the upper power device S21 and the lower power device S 22 The midpoint between is the output end; the upper power device S of the second bridge arm of the second three-phase four-bridge-arm converter 23 and the lower power device S 24 Series connection, the upper power device S 23 and the lower power device S 24 The midpoint of is the output end; the upper power device S of the third bridge arm of the second three-phase four-bridge-arm converter 25 and the lower power device S 26 Series connection, the upper power device S 25 and the lower power device S 26 The midpoint between is the output end; the upper power device S of the fourth bridge arm of the second three-phase four-bridge-arm converter 27 and the lower power device S 28 Series connection, the upper power device S 27 and the lower power device S 28 The midpoint between 2 The two ends a of the a-phase stator winding of the open-winding asynchronous motor 1 and a 2 The two ends b of the stator winding of the b phase of the open-winding asynchronous motor are connected to the output end of the first bridge arm of the first three-phase four-bridge-arm converter and the output end of the first bridge arm of the second three-phase four-bridge-arm converter respectively; 1 and b 2 The two ends of the stator winding of the c-phase of the open-winding asynchronous motor are connected to the output end of the second bridge arm of the first three-phase four-bridge-arm converter and the output end of the second bridge arm of the second three-phase four-bridge-arm converter respectively; 1 and c 2 The output end of the third bridge arm of the first three-phase four-bridge-arm converter and the output end of the third bridge arm of the second three-phase four-bridge-arm converter are connected respectively; the output end of the fourth bridge arm of the first three-phase four-bridge-arm converter is connected to the output end of the third bridge arm of the second three-phase four-bridge-arm converter; 1 and the output end o of the fourth bridge arm of the second three-phase four-bridge-arm converter 2 directly connected together; the positive ends of the four bridge arms of the first three-phase four-bridge-arm converter are connected together and connected to the positive end of the first DC bus power supply, and the negative ends of the four bridge arms of the first three-phase four-bridge-arm converter are connected together and connected to the negative end of the first DC bus power supply; the positive ends of the four bridge arms of the second three-phase four-bridge-arm converter are connected together and connected to the positive end of the second DC bus power supply, and the negative ends of the four bridge arms of the second three-phase four-bridge-arm converter are connected together and connected to the negative end of the second DC bus power supply.

[0011] A model predictive control method for a common neutral open-winding asynchronous motor drive system, the steps of which are as follows:

[0012] Step S1, defining the switch states of the four bridge arms of the two three-phase four-bridge-arm converters, and determining the value of the switch state according to the on or off state of the upper and lower power devices on the bridge arms, defining 16 voltage vectors according to the values ​​of the switch states of the four bridge arms, and respectively calculating the voltage values ​​of the 16 voltage vectors of the two three-phase four-bridge-arm converters in the αβγ three-dimensional stationary coordinate system;

[0013] Step S2: sampling the abc three-phase stator current i of the open-winding asynchronous motor a 、i b 、i c , and the stator current i a 、i b 、i c Switching to the αβγ three-dimensional stationary coordinate system, we get the current i α 、i β 、i γ ;

[0014] Step S3: According to the obtained current i α 、i β The mathematical model of the open-winding asynchronous motor is used to calculate the rotor flux ψ of the open-winding asynchronous motor. rα , rβ ;

[0015] Step S4: According to the obtained current i α 、i β 、i γ and the rotor flux of the open-winding asynchronous motor ψ rα , rβ , calculate the voltage reference value u in the αβγ three-dimensional stationary coordinate system αref 、u βref 、u γref ;

[0016] Step S5: According to the obtained voltage reference value u αref 、u βref Calculate the voltage values ​​on the α-axis and the β-axis of the αβγ three-dimensional stationary coordinate system corresponding to the 8 voltage vectors with odd subscripts of the first three-phase four-bridge-arm converter to obtain the values ​​of the 8 first cost functions; compare the values ​​of the 8 first cost functions, and select the voltage vector that makes the first cost function take the minimum value as the first optimal voltage vector;

[0017] Step S6: According to the obtained voltage reference value u αref 、u βref, the voltage values ​​on the α-axis and β-axis corresponding to the first optimal voltage vector and the voltage values ​​on the α-axis and β-axis corresponding to the 8 voltage vectors with odd subscripts of the second three-phase four-bridge-arm converter, and 8 values ​​of the second cost function are calculated; the magnitudes of the 8 second cost function values ​​obtained are compared, and the voltage vector of the second three-phase four-bridge-arm converter that makes the second cost function take the minimum value is selected as the second optimal voltage vector;

[0018] Step S7: According to the voltage reference value u on the γ axis γref and the voltage values ​​on the γ axis corresponding to the first optimal voltage vector and its adjacent vectors, the second optimal vector and its adjacent vectors, and calculate the third cost function g 3 , the fourth cost function g 4 , the fifth cost function g 5 And the sixth cost function g 6 The value of the third cost function g 3 , the fourth cost function g 4 , the fifth cost function g 5 And the sixth cost function g 6 The value of is taken into consideration, and the voltage vector corresponding to the cost function with the minimum value among the four cost functions is selected as the final optimal vector of the first three-phase four-bridge-arm converter and the second three-phase four-bridge-arm converter, which are used to control the first three-phase four-bridge-arm converter and the second three-phase four-bridge-arm converter respectively, thereby realizing the model predictive control of the open-winding asynchronous motor.

[0019] Preferably, the implementation method of step S1 is:

[0020] Define the switch state corresponding to the first bridge arm of the first three-phase four-bridge-arm converter as S a1 , define the switch state corresponding to the second bridge arm of the first three-phase four-bridge-arm converter as S b1 , define the switch state corresponding to the third bridge arm of the first three-phase four-bridge-arm converter as S c1 , define the switch state corresponding to the fourth bridge arm of the first three-phase four-bridge-arm converter as S 01 ;

[0021] When the upper power device of the first bridge arm of the first three-phase four-bridge-arm converter is turned on and the lower power device is turned off, the switch state S is defined. a1 =1; when the upper power device of the first bridge arm of the first three-phase four-bridge-arm converter is turned off and the lower power device is turned on, the switch state S is defined a1 =0;

[0022] When the upper power device of the second bridge arm of the first three-phase four-bridge-arm converter is turned on and the lower power device is turned off, the switch state S is defined. b1=1; when the upper power device of the second bridge arm of the first three-phase four-bridge-arm converter is turned off and the lower power device is turned on, the switch state S is defined b1 =0;

[0023] When the upper power device of the third bridge arm of the first three-phase four-bridge-arm converter is turned on and the lower power device is turned off, the switch state S is defined. c1 =1; when the upper power device of the third bridge arm of the first three-phase four-bridge-arm converter is turned off and the lower power device is turned on, the switch state S is defined c1 =0;

[0024] When the upper power device of the fourth bridge arm of the first three-phase four-bridge-arm converter is turned on and the lower power device is turned off, the switch state S is defined. 01 =1; when the upper power device of the fourth bridge arm of the first three-phase four-bridge-arm converter is turned off and the lower power device is turned on, the switch state S is defined 01 =0;

[0025] Define the 16 voltage vectors V of the first three-phase four-leg converter 1 i satisfy:

[0026] When S a1 =0, S b1 =0, S c1 =0, S 01 = 0, the corresponding voltage vector is defined as V 1_1 ;

[0027] When S a1 =0, S b1 =0, S c1 =0, S 01 =1, the corresponding voltage vector is defined as V 1_2 ;

[0028] When S a1 =0, S b1 =0, S c1 =1, S 01 = 0, the corresponding voltage vector is defined as V 1_3 ;

[0029] When S a1 =0, S b1 =0, S c1 =1, S 01 =1, the corresponding voltage vector is defined as V 1_4 ;

[0030] When S a1 =0, S b1 =1, S c1 =0, S01 = 0, the corresponding voltage vector is defined as V 1_5 ;

[0031] When S a1 =0, S b1 =1, S c1 =0, S 01 =1, the corresponding voltage vector is defined as V 1_6 ;

[0032] When S a1 =0, S b1 =1, S c1 =1, S 01 = 0, the corresponding voltage vector is defined as V 1_7 ;

[0033] When S a1 =0, S b1 =1, S c1 =1, S 01 =1, the corresponding voltage vector is defined as V 1_8 ;

[0034] When S a1 =1, S b1 =0, S c1 =0, S 01 = 0, the corresponding voltage vector is defined as V 1_9 ;

[0035] When S a1 =1, S b1 =0, S c1 =0, S 01 =1, the corresponding voltage vector is defined as V 1_10 ;

[0036] When S a1 =1, S b1 =0, S c1 =1, S 01 = 0, the corresponding voltage vector is defined as V 1_11 ;

[0037] When S a1 =1, S b1 =0, S c1 =1, S 01 =1, the corresponding voltage vector is defined as V 1_12 ;

[0038] When S a1 =1, S b1 =1, S c1 =0, S 01 = 0, the corresponding voltage vector is defined as V1_13 ;

[0039] When S a1 =1, S b1 =1, S c1 =0, S 01 =1, the corresponding voltage vector is defined as V 1_14 ;

[0040] When S a1 =1, S b1 =1, S c1 =1, S 01 = 0, the corresponding voltage vector is defined as V 1_15 ;

[0041] When S a1 =1, S b1 =1, S c1 =1, S 01 =1, the corresponding voltage vector is defined as V 1_16 ; Wherein, i=1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16;

[0042] Define the switch state corresponding to the first bridge arm of the second three-phase four-bridge-arm converter as S a2 , define the switch state corresponding to the second bridge arm of the second three-phase four-bridge-arm converter as S b2 , define the switch state corresponding to the third bridge arm of the second three-phase four-bridge-arm converter as S c2 , define the switch state corresponding to the fourth bridge arm of the second three-phase four-bridge-arm converter as S 02 ;

[0043] When the upper power device of the first bridge arm of the second three-phase four-bridge-arm converter is turned on and the lower power device is turned off, the switch state S is defined. a2 =1; when the upper power device of the first bridge arm of the second three-phase four-bridge-arm converter is turned off and the lower power device is turned on, the switch state S is defined a2 =0;

[0044] When the upper power device of the second bridge arm of the second three-phase four-bridge-arm converter is turned on and the lower power device is turned off, the switch state S is defined. b2 =1; when the upper power device of the second bridge arm of the second three-phase four-bridge-arm converter is turned off and the lower power device is turned on, the switch state S is defined b2 =0;

[0045] When the upper power device of the third bridge arm of the second three-phase four-bridge-arm converter is turned on and the lower power device is turned off, the switch state S is defined. c2=1; when the upper power device of the third bridge arm of the second three-phase four-bridge-arm converter is turned off and the lower power device is turned on, the switch state S is defined c2 =0;

[0046] When the upper power device of the fourth bridge arm of the second three-phase four-bridge-arm converter is turned on and the lower power device is turned off, the switch state S is defined. 02 =1; when the upper power device of the fourth arm of the second three-phase four-leg converter is turned off and the lower power device is turned on, the switch state S is defined 02 =0;

[0047] Define the 16 voltage vectors V of the second three-phase four-leg converter 2_i satisfy:

[0048] When S a2 =0, S b2 =0, S c2 =0, S 02 = 0, the corresponding voltage vector is defined as V 2_1 ;

[0049] When S a2 =0, S b2 =0, S c2 =0, S 02 =1, the corresponding voltage vector is defined as V 2_2 ;

[0050] When S a2 =0, S b2 =0, S c2 =1, S 02 = 0, the corresponding voltage vector is defined as V 2_3 ;

[0051] When S a2 =0, S b2 =0, S c2 =1, S 02 =1, the corresponding voltage vector is defined as V 2_4 ;

[0052] When S a2 =0, S b2 =1, S c2 =0, S 02 = 0, the corresponding voltage vector is defined as V 2_5 ;

[0053] When S a2 =0, S b2 =1, S c2 =0, S 02 =1, the corresponding voltage vector is defined as V 2_6 ;

[0054] When S a2 =0, S b2 =1, S c2 =1, S 02 = 0, the corresponding voltage vector is defined as V 2_7 ;

[0055] When S a2 =0, S b2 =1, S c2 =1, S 02 =1, the corresponding voltage vector is defined as V 2_8 ;

[0056] When S a2 =1, S b2 =0, S c2 =0, S 02 = 0, the corresponding voltage vector is defined as V 2_9 ;

[0057] When S a2 =1, S b2 =0, S c2 =0, S 02 =1, the corresponding voltage vector is defined as V 2_10 ;

[0058] When S a2 =1, S b2 =0, S c2 =1, S 02 = 0, the corresponding voltage vector is defined as V 2_11 ;

[0059] When S a2 =1, S b2 =0, S c2 =1, S 02 =1, the corresponding voltage vector is defined as V 2_12 ;

[0060] When S a2 =1, S b2 =1, S c2 =0, S 02 = 0, the corresponding voltage vector is defined as V 2_13 ;

[0061] When S a2 =1, S b2 =1, S c2 =0, S 02 =1, the corresponding voltage vector is defined as V 2_14 ;

[0062] When Sa2 =1, S b2 =1, S c2 =1, S 02 = 0, the corresponding voltage vector is defined as V 2_15 ;

[0063] When S a2 =1, S b2 =1, S c2 =1, S 02 =1, the corresponding voltage vector is defined as V 2_16 .

[0064] Preferably, according to the definition of the 16 voltage vectors V of the first three-phase four-bridge-leg converter 1_i The corresponding switch state S a1 , S b1 , S c1 and S 01 Calculate the 16 voltage vectors V 1_i Voltage value U in the αβγ three-dimensional stationary coordinate system α1_i , U β1_i , U γ1_i for:

[0065]

[0066] Among them, U dc1 represents the DC bus voltage of the first three-phase four-bridge-arm converter, S a1_i , S b1_i , S c1_i and S 01_i Respectively represent the i-th voltage vector V 1_i The corresponding switch state S a1 , S b1 , S c1 and S 01 The value of U α1_i Represents the i-th voltage vector V 1_i Voltage value on the α axis, U β1_i Represents the i-th voltage vector V 1_i Voltage value on the β axis, U γ1_i Represents the i-th voltage vector V 1_i Voltage value on the γ axis; where i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16;

[0067] According to the definition of the 16 voltage vectors V of the second three-phase four-leg converter 2_i The corresponding switch state value S a2 , S b2 , S c2 and S02 , calculate 16 voltage vectors V 2_i Voltage value U in the αβγ three-dimensional stationary coordinate system α2_i , U β2_i , U γ2_i for:

[0068]

[0069] Among them, U dc2 represents the DC bus voltage of the second three-phase four-bridge-leg converter, S a2_i , S b2_i , S c2_i and S 02_i Respectively represent the i-th voltage vector V 2_i The corresponding switch state S a2 , S b2 , S c2 and S 02 The value of U α2_i Represents the i-th voltage vector V 2_i Voltage value on the α axis, U β2_i Represents the i-th voltage vector V 2_i Voltage value on the β axis, U γ2_i Represents the i-th voltage vector V 2_i The voltage value on the γ axis.

[0070] Preferably, the current i in step S2 α 、i β 、i γ The calculation method is:

[0071]

[0072] Among them, i a represents the stator current of phase a of the open-winding asynchronous motor, i b represents the b-phase stator current of the open-winding asynchronous motor, i c represents the c-phase stator current of the open-winding asynchronous motor, i α It represents the component of the abc three-phase stator current of the open-winding asynchronous motor on the α axis, i β It represents the component of the abc three-phase stator current of the open-winding asynchronous motor on the β axis, i γ It represents the component of the abc three-phase stator current of the open-winding asynchronous motor on the γ axis;

[0073] The rotor flux linkage ψ of the open-winding asynchronous motor rα , rβ for:

[0074]

[0075] Among them, ψ rα is the component of the rotor flux of the open-winding asynchronous motor on the α-axis, ψ rβ is the component of the rotor flux of the open-winding asynchronous motor on the β axis, L m represents the mutual inductance of the open-winding asynchronous motor, T r is the rotor time constant, satisfying T r =L r / R r , L r Represents the rotor inductance of an open-winding asynchronous motor, R r represents the rotor resistance of the open-winding asynchronous motor, ω r represents the rotor angular velocity of the open-winding asynchronous motor, s represents the Laplace operator, and j represents 90 degrees ahead;

[0076] The voltage reference value u on the αβγ three-dimensional stationary coordinate system αref 、u βref 、u γref for:

[0077]

[0078] Among them, u αref represents the voltage reference value on the α axis, u βref represents the voltage reference value on the β axis, u γref represents the voltage reference value on the γ axis, i αref represents the stator current reference value of the open-winding asynchronous motor on the α-axis, i βref represents the stator current reference value of the open-winding asynchronous motor on the β axis, i γref represents the stator current reference value of the open-winding asynchronous motor on the γ axis, T s It represents the control period, and a, b, c, and d are 4 coefficients.

[0079] Preferably, the eight first cost functions g 1k The value of is calculated as:

[0080] g 1k =|u αref -U α1_(2*k-1) |+|u βref -U β1_(2*k-1) |

[0081] Where k = 1, 2, 3, 4, 5, 6, 7, 8, U α1_(2*k-1) and U β1_(2*k-1) They represent the eight voltage vectors V with odd subscripts of the first three-phase four-bridge-arm converter. 1_(2*k-1) The corresponding voltage value on the α-axis and the voltage value on the β-axis;

[0082] The eight second cost functions g2k The value of is calculated as:

[0083] g 2k =|u αref -(U α1_(2*m-1) -U α2_(2*k-1) )|+|u βref -(U β1_(2*m-1) -U β2_(2*k-1) )|

[0084] Among them, U α1_(2*m-1) and U β1_(2*m-1) They are the first optimal voltage vector V 1_(2*m-1) The corresponding voltage values ​​on the α-axis and β-axis, U α2_(2*k-1) and U β2_(2*k-1) They are the eight voltage vectors V with odd subscripts of the second three-phase four-bridge-arm converter. 2_(2*k-1) The corresponding voltage values ​​on the α-axis and β-axis;

[0085] The calculation of the third cost function g 3 , the fourth cost function g 4 , the fifth cost function g 5 And the sixth cost function g 6 The methods for the values ​​are:

[0086] g 3 =|u γref -(U γ1_(2*m-1) -U γ2_(2*n-1) )|

[0087] g 4 =|u γref -(U γ1_2*m -U γ2_(2*n-1) )|

[0088] g 5 =|u γref -(U γ1_(2*m-1) -U γ2_2*n )|

[0089] g 6 =|u γref -(U γ1_2*m -U γ2_2*n )|

[0090] Among them, U γ1_(2*m-1) , U γ1_2*m , U γ2_(2*n-1) , U γ2_2*n The first optimal vector V 1_(2*m-1) and its adjacent vector V 1_2*m , the second optimal vector V 2_(2*n-1) and its adjacent vector V 2_2*n The corresponding voltage value on the γ axis.

[0091] Preferably, the first cost function g is selected so that 1k The voltage vector V that takes the minimum value 1_(2*k-1) is the optimal voltage vector, denoted as the first optimal voltage vector V 1_(2*m-1) , where (2*m-1) means that the first cost function g 1k Take the subscript of the voltage vector with the minimum value, where m is a value among 1, 2, 3, 4, 5, 6, 7, 8;

[0092] Compare 8 second cost functions g 2k The value is selected to make the second cost function g 2k The voltage vector V that takes the minimum value 2_(2*k-1) is the optimal voltage vector, recorded as the second optimal voltage vector V 2_(2*n-1) , where (2*n-1) means that the second cost function g 2k Take the subscript of the voltage vector with the minimum value, where n is a value among 1, 2, 3, 4, 5, 6, 7, 8;

[0093] Select the third cost function g 3 , the fourth cost function g 4 , the fifth cost function g 5 And the sixth cost function g 6 The voltage vector V corresponding to the cost function with the minimum value 1_p and V 2_q They are output as the final optimal vectors of the first three-phase four-bridge-arm converter and the second three-phase four-bridge-arm converter respectively, where p represents a value between (2*m-1) and 2*m, q represents a value between (2*n-1) and 2*n, and m and n are both values ​​between 1, 2, 3, 4, 5, 6, 7, and 8.

[0094] Preferably, the coefficient σ represents the magnetic leakage coefficient and satisfies L s represents the stator inductance of an open-winding asynchronous motor, R s Indicates the stator resistance of the open-winding asynchronous motor, L 1s Indicates the stator leakage inductance of an open-winding asynchronous motor;

[0095] The stator current reference value i αref 、i βref 、i γref The calculation method is:

[0096]

[0097] Among them, i dref is the excitation current reference value of the open-winding asynchronous motor, iqref is the torque current reference value of the open-winding asynchronous motor, i 0ref is the zero-sequence current reference value of the open-winding asynchronous motor, θ r is the angle of the rotor magnetic field of an open-winding asynchronous motor.

[0098] Compared with the prior art, the beneficial effects of the present invention are as follows: the common neutral line open winding asynchronous motor drive system proposed in the present invention can not only realize the independent regulation of the DC voltage of the two converters, but also use the fourth bridge arm of the two converters to construct the neutral line, realize the flexible and adjustable zero-sequence current, reduce the current stress of the DC bus capacitor, enhance the control flexibility of the common neutral line open winding asynchronous motor drive system, and realize multi-mode operation to reduce system losses. At the same time, the low-complexity model predictive control method proposed in the present invention adopts the hierarchical iterative principle of first selecting the first optimal vector output by the first three-phase four-bridge arm converter, then selecting the second optimal vector output by the second three-phase four-bridge arm converter, and finally optimizing the zero-sequence component to determine the final optimal vector, which can reduce the number of online optimization of the optimal vector from 256 times to 20 times, significantly reducing the computational complexity. BRIEF DESCRIPTION OF THE DRAWINGS

[0099] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0100] Figure 1 This is the topology diagram of a conventional common neutral open winding electric drive system.

[0101] Figure 2 This is a topology diagram of the common neutral open-winding asynchronous motor drive system based on the dual three-phase four-bridge-arm converter proposed in the present invention.

[0102] Figure 3 The figure is a flow chart of the model predictive control method proposed in the present invention.

[0103] Figure 4 This is a control block diagram of the common neutral open-winding asynchronous motor drive system and its model predictive control strategy proposed by the present invention.

[0104] Figure 5 The simulation results of the conventional 256-iteration model predictive control strategy are shown in Figure 1, where (a) is the speed and (b) is the current.

[0105] Figure 6 The simulation results of the low-complexity model predictive control strategy with 20 iterations proposed in the present invention, where (a) is the speed and (b) is the current. DETAILED DESCRIPTION

[0106] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0107] Example 1

[0108] like Figure 2 As shown, a common neutral line open-winding asynchronous motor drive system proposed in the present invention comprises: two three-phase four-bridge-arm converters and an open-winding asynchronous motor, each bridge arm of the two three-phase four-bridge-arm converters is composed of two upper and lower power devices connected in series, the power device is composed of a fully controlled power electronic device and an uncontrolled diode connected in anti-parallel, the fully controlled power electronic device is a switch tube, which provides a forward path for the current, and the diode is an uncontrolled device, which provides a reverse path for the current; between the upper and lower power devices of each bridge arm is the output signal of the bridge arm; the output of the first bridge arm of the two three-phase four-bridge-arm converters is respectively connected to To both ends of the stator a phase winding of the open-winding asynchronous motor; the outputs of the second bridge arms of the two three-phase four-bridge-arm converters are respectively connected to both ends of the stator b phase winding of the open-winding asynchronous motor; the outputs of the third bridge arms of the two three-phase four-bridge-arm converters are respectively connected to both ends of the stator c phase winding of the open-winding asynchronous motor; the outputs of the fourth bridge arms of the two three-phase four-bridge-arm converters are directly connected together; the positive ends of the four bridge arms of the two three-phase four-bridge-arm converters are respectively connected together and connected to the positive ends of their respective DC bus bars; the negative ends of the four bridge arms of the two three-phase four-bridge-arm converters are respectively connected together and connected to the negative ends of their respective DC bus bars. Figure 1 Compared with the conventional common neutral open-winding electric drive system, the fourth bridge arm of the two three-phase four-bridge-arm converters is also composed of two power devices in series. On the one hand, this structure can flexibly adjust the zero-sequence current through the fourth bridge arm to reduce the current stress of the bus capacitor. On the other hand, it can also make the open-winding asynchronous motor work in multiple modes. For example, if the power supply voltage U dc1 Greater than U dc2 , when the motor runs in the low speed area, the output voltage vector of the first three-phase four-bridge-arm converter can be V 1_1 , that is, S a1 =0, S b1 =0, S c1 =0, S 01=0, at this time, only the voltage output by the second three-phase four-bridge-arm converter acts on the open-winding asynchronous motor, which can not only meet the voltage demand of the open-winding asynchronous motor when running at low speed, but also reduce the voltage peak acting on the open-winding asynchronous motor, thereby reducing system losses and improving efficiency; when the motor runs in the medium-speed area, the voltage demand of the motor increases, which can make the output voltage vector of the second three-phase four-bridge-arm converter V 2_1 , that is, S a2 =0, S b2 =0, S c2 =0, S 02 =0, at this time, only the voltage output by the first three-phase four-bridge-arm converter acts on the open-winding asynchronous motor, which can not only meet the voltage requirements of the open-winding asynchronous motor when running at medium speed, but also reduce system losses and improve efficiency; when the motor runs in the high-speed area, the two three-phase four-bridge-arm converters can work at the same time, thereby further increasing the voltage acting on both ends of the motor to meet the requirements of high-speed operation of the motor. That is, the proposed common-neutral open-winding asynchronous motor drive system based on two three-phase four-bridge-arm converters can enable the motor to select different operating modes when running in different speed areas, thereby significantly reducing the losses of the converter and the motor and improving the efficiency of the system. A capacitor C is provided between the positive and negative ends of the DC bus, and the capacitor C is connected in parallel with each bridge arm. The capacitor C mainly serves to stabilize and support the DC bus power supply voltage.

[0109] The output ends of the three bridge arms of the two three-phase three-bridge-arm converters of the independent DC bus open-winding electric drive system and the common DC bus open-winding electric drive system are respectively connected to the two ends of the a-phase, b-phase, and c-phase windings of the open-winding asynchronous motor. The difference between the independent DC bus open-winding electric drive system and the conventional common DC bus open-winding electric drive system is the number of DC buses. The two three-phase three-bridge-arm converters of the independent DC bus open-winding electric drive system are respectively connected to the two ends of different DC buses, and the three bridge arms of the two three-phase three-bridge-arm converters of the common DC bus open-winding electric drive system are all connected to the two ends of a DC bus.

[0110] like Figure 2 As shown, the first three-phase four-bridge-arm converter is composed of a first bridge arm, a second bridge arm, a third bridge arm and a fourth bridge arm, and the upper end power device of the first bridge arm is S 11 , the lower power device is S 12 , upper power device S 11 and the lower power device S 12 Series connection, the upper power device S 11 and the lower power device S 12 The midpoint between is the output end of the first bridge arm. The upper power device of the second bridge arm is S 13 , the lower power device is S 14 , upper power device S13 and the lower power device S 14 Series connection, the upper power device S 13 and the lower power device S 14 The midpoint between is the output end. The upper power device of the third bridge arm is S 15 , the lower power device is S 16 , upper power device S 15 and the lower power device S 16 Series connection, the upper power device S 15 and the lower power device S 16 The midpoint between is the output end. The upper power device of the fourth bridge arm is S 17 , the lower power device is S 18 ; Upper power device S 17 and the lower power device S 18 Series connection, the upper power device S 17 and the lower power device S 18 The midpoint between 1 The second three-phase four-bridge-arm converter is composed of a first bridge arm, a second bridge arm, a third bridge arm and a fourth bridge arm, and the upper power device of the first bridge arm is S 21 , the lower power device is S 22 , upper power device S 21 and the lower power device S 22 Series connection, the upper power device S 21 and the lower power device S 22 The midpoint between is the output end. The upper power device of the second bridge arm is S 23 , the lower power device is S 24 , upper power device S 23 and the lower power device S 24 Series connection, the upper power device S 23 and the lower power device S 24 The midpoint of is the output end; the upper power device of the third bridge arm is S 25 , the lower power device is S 26 , upper power device S 25 and the lower power device S 26 Series connection, the upper power device S 25 and the lower power device S 26 The midpoint between is the output end. The upper power device of the fourth bridge arm is S 27 , the lower power device is S 28 ; Upper power device S 27 and the lower power device S 28 Series connection, the upper power device S 27 and the lower power device S 28The midpoint between the two ends of the stator winding of the open-winding asynchronous motor is the output end. 1 and a 2 The two ends b of the stator winding of the b phase of the open-winding asynchronous motor are connected to the output end of the first bridge arm of the first three-phase four-bridge-arm converter and the output end of the first bridge arm of the second three-phase four-bridge-arm converter respectively; 1 and b 2 The two ends of the stator winding of the c-phase of the open-winding asynchronous motor are connected to the output end of the second bridge arm of the first three-phase four-bridge-arm converter and the output end of the second bridge arm of the second three-phase four-bridge-arm converter respectively; 1 and c 2 The output end of the third bridge arm of the first three-phase four-bridge-arm converter and the output end of the third bridge arm of the second three-phase four-bridge-arm converter are connected respectively; the output end of the fourth bridge arm of the first three-phase four-bridge-arm converter is connected to the output end of the third bridge arm of the second three-phase four-bridge-arm converter; 1 and the output end o of the fourth bridge arm of the second three-phase four-bridge-arm converter 2 Directly connected together; the four bridge arm positive ends of the first three-phase four-bridge arm converter are connected together and connected to the DC bus power supply U of the three-phase four-bridge arm converter dc1 The positive end of the first three-phase four-bridge-arm converter is connected together with the four bridge-arm negative ends, and connected to the three-phase four-bridge-arm converter DC bus power supply U dc1 The positive ends of the four bridge arms of the second three-phase four-bridge-arm converter are connected together and connected to the DC bus power supply U of the three-phase four-bridge-arm converter. dc2 The positive end of the second three-phase four-bridge-arm converter is connected together with the negative ends of the four bridge arms, and connected to the DC bus power supply U of the three-phase four-bridge-arm converter. dc2 The negative terminal.

[0111] The present invention also sets the fourth bridge arm of the three-phase four-bridge arm converter to be composed of two upper and lower power devices connected in series. Compared with the existing common neutral line open-winding electric drive system, this topology can not only increase the control flexibility of the neutral line current and reduce the current stress of the bus capacitor, but also enable the system to work in multiple operating modes, so that the open-winding asynchronous motor can select different operating modes when working in low, medium and high speed ranges, reduce the loss of the motor and the converter, and improve efficiency.

[0112] Example 2

[0113] like Figure 3 As shown, an embodiment of the present invention provides a model predictive control method for a common neutral open-winding asynchronous motor drive system, and the specific steps are as follows:

[0114] Step 1: define the switch states of the four bridge arms of the first three-phase four-bridge-arm converter, and determine the value of the switch state according to the on or off state of the upper and lower power devices.

[0115] Define the switch state corresponding to the first bridge arm of the first three-phase four-bridge-arm converter as S a1 , define the switch state corresponding to the second bridge arm of the first three-phase four-bridge-arm converter as S b1 , define the switch state corresponding to the third bridge arm of the first three-phase four-bridge-arm converter as S c1 , define the switch state corresponding to the fourth bridge arm of the first three-phase four-bridge-arm converter as S 01 .

[0116] When the upper power device of the first bridge arm of the first three-phase four-bridge-arm converter is turned on and the lower power device is turned off, define S a1 =1; when the upper power device of the first bridge arm of the first three-phase four-bridge-arm converter is turned off and the lower power device is turned on, define S a1 =0;

[0117] When the upper power device of the second bridge arm of the first three-phase four-bridge-arm converter is turned on and the lower power device is turned off, define S b1 =1; when the upper power device of the second bridge arm of the first three-phase four-bridge-arm converter is turned off and the lower power device is turned on, define S b1 =0;

[0118] When the upper power device of the third bridge arm of the first three-phase four-bridge-arm converter is turned on and the lower power device is turned off, define S c1 =1; when the upper power device of the third bridge arm of the first three-phase four-bridge-arm converter is turned off and the lower power device is turned on, define S c1 =0;

[0119] When the upper power device of the fourth bridge arm of the first three-phase four-bridge-arm converter is turned on and the lower power device is turned off, define S 01 =1; when the upper power device of the fourth bridge arm of the first three-phase four-bridge-arm converter is turned off and the lower power device is turned on, define S 01 =0.

[0120] The above definition is mainly to facilitate the use of switch states to describe the working state of the first three-phase four-bridge-arm converter, thereby facilitating the establishment of the mathematical model of the first three-phase four-bridge-arm converter. This is also a common working state description method and mathematical modeling method for power electronic converters.

[0121] Step 2: Define 16 voltage vectors according to the switch state values ​​of the four bridge arms of the first three-phase four-bridge-arm converter.

[0122] Define the 16 voltage vectors V of the first three-phase four-leg converter 1_i(i=1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16) satisfies:

[0123] When S a1 =0, S b1 =0, S c1 =0, S 01 = 0, the corresponding voltage vector is defined as V 1_1 ;

[0124] When S a1 =0, S b1 =0, S c1 =0, S 01 =1, the corresponding voltage vector is defined as V 1_2 ;

[0125] When S a1 =0, S b1 =0, S c1 =1, S 01 = 0, the corresponding voltage vector is defined as V 1_3 ;

[0126] When S a1 =0, S b1 =0, S c1 =1, S 01 =1, the corresponding voltage vector is defined as V 1_4 ;

[0127] When S a1 =0, S b1 =1, S c1 =0, S 01 = 0, the corresponding voltage vector is defined as V 1_5 ;

[0128] When S a1 =0, S b1 =1, S c1 =0, S 01 =1, the corresponding voltage vector is defined as V 1_6 ;

[0129] When S a1 =0, S b1 =1, S c1 =1, S 01 = 0, the corresponding voltage vector is defined as V 1_7 ;

[0130] When S a1 =0, S b1 =1, S c1 =1, S 01 =1, the corresponding voltage vector is defined as V1_8 ;

[0131] When S a1 =1, S b1 =0, S c1 =0, S 01 = 0, the corresponding voltage vector is defined as V 1_9 ;

[0132] When S a1 =1, S b1 =0, S c1 =0, S 01 =1, the corresponding voltage vector is defined as V 1_10 ;

[0133] When S a1 =1, S b1 =0, S c1 =1, S 01 = 0, the corresponding voltage vector is defined as V 1_11 ;

[0134] When S a1 =1, S b1 =0, S c1 =1, S 01 =1, the corresponding voltage vector is defined as V 1_12 ;

[0135] When S a1 =1, S b1 =1, S c1 =0, S 01 = 0, the corresponding voltage vector is defined as V 1_13 ;

[0136] When S a1 =1, S b1 =1, S c1 =0, S 01 =1, the corresponding voltage vector is defined as V 1_14 ;

[0137] When S a1 =1, S b1 =1, S c1 =1, S 01 = 0, the corresponding voltage vector is defined as V 1_15 ;

[0138] When S a1 =1, S b1 =1, S c1 =1, S 01 =1, the corresponding voltage vector is defined as V 1_16 .

[0139] The above definition is mainly to facilitate the use of voltage vectors to describe the 16 working states of the first three-phase four-bridge-arm converter, thereby facilitating the establishment of the mathematical model of the first three-phase four-bridge-arm converter. This is also a common working state description method and mathematical modeling method for power electronic converters.

[0140] Step 3: Calculate the voltage values ​​of 16 voltage vectors in the αβγ three-dimensional stationary coordinate system.

[0141] According to the 16 voltage vectors V of the first three-phase four-leg converter defined in step 2 1_i (i=1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16) corresponding switch state value S a1 , S b1 , S c1 and S 01 , calculate 16 voltage vectors V 1_i (i=1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16) Voltage value U in the αβγ three-dimensional stationary coordinate system α1_i , U β1_i , U γ1_i (i=1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16), satisfying:

[0142]

[0143] Among them, U dc1 represents the DC bus voltage of the first three-phase four-bridge-arm converter, S a1_i , S b1_i , S c1_i and S 01_i Respectively represent the i-th voltage vector V described in step 2 1_i (i=1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16) corresponding to the switch state S a1 , S b1 , S c1 and S 01 The value of U α1_i Represents the i-th voltage vector V 1_i (i=1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16) Voltage value on the α axis, U β1_i Represents the i-th voltage vector V 1_i (i=1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16) Voltage value on the β axis, U γ1_iRepresents the i-th voltage vector V 1_i (i=1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16) voltage value on the γ axis.

[0144] Step 4, define the switching state of the four bridge arms of the second three-phase four-bridge-arm converter, and determine the value of the switching state according to the on or off state of the upper and lower power devices; define 16 voltage vectors according to the values ​​of the switching state of the four bridge arms of the second three-phase four-bridge-arm converter, and calculate the voltage values ​​of the 16 voltage vectors of the second three-phase four-bridge-arm converter in the αβγ three-dimensional stationary coordinate system.

[0145] Define the switch state corresponding to the first bridge arm of the second three-phase four-bridge-arm converter as S a2 , define the switch state corresponding to the second bridge arm of the second three-phase four-bridge-arm converter as S b2 , define the switch state corresponding to the third bridge arm of the second three-phase four-bridge-arm converter as S c2 , define the switch state corresponding to the fourth bridge arm of the second three-phase four-bridge-arm converter as S 02 .

[0146] When the upper power device of the first bridge arm of the second three-phase four-bridge-arm converter is turned on and the lower power device is turned off, define S a2 =1; when the upper power device of the first bridge arm of the second three-phase four-bridge-arm converter is turned off and the lower power device is turned on, define S a2 =0;

[0147] When the upper power device of the second bridge arm of the second three-phase four-bridge-arm converter is turned on and the lower power device is turned off, define S b2 =1; when the upper power device of the second bridge arm of the second three-phase four-bridge-arm converter is turned off and the lower power device is turned on, define S b2 =0;

[0148] When the upper power device of the third bridge arm of the second three-phase four-bridge-arm converter is turned on and the lower power device is turned off, define S c2 =1; when the upper power device of the third bridge arm of the second three-phase four-bridge-arm converter is turned off and the lower power device is turned on, define S c2 =0;

[0149] When the upper power device of the fourth bridge arm of the second three-phase four-bridge-arm converter is turned on and the lower power device is turned off, define S 02 =1; when the upper power device of the fourth arm of the second three-phase four-bridge-arm converter is turned off and the lower power device is turned on, define S 02 =0.

[0150] Define the 16 voltage vectors V of the second three-phase four-leg converter 2_i (i=1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16) satisfies:

[0151] When S a2 =0, S b2 =0, S c2 =0, S 02 = 0, the corresponding voltage vector is defined as V 2_1 ;

[0152] When S a2 =0, S b2 =0, S c2 =0, S 02 =1, the corresponding voltage vector is defined as V 2_2 ;

[0153] When S a2 =0, S b2 =0, S c2 =1, S 02 = 0, the corresponding voltage vector is defined as V 2_3 ;

[0154] When S a2 =0, S b2 =0, S c2 =1, S 02 =1, the corresponding voltage vector is defined as V 2_4 ;

[0155] When S a2 =0, S b2 =1, S c2 =0, S 02 = 0, the corresponding voltage vector is defined as V 2_5 ;

[0156] When S a2 =0, S b2 =1, S c2 =0, S 02 =1, the corresponding voltage vector is defined as V 2_6 ;

[0157] When S a2 =0, S b2 =1, S c2 =1, S 02 = 0, the corresponding voltage vector is defined as V 2_7 ;

[0158] When S a2 =0, S b2 =1, Sc2 =1, S 02 =1, the corresponding voltage vector is defined as V 2_8 ;

[0159] When S a2 =1, S b2 =0, S c2 =0, S 02 = 0, the corresponding voltage vector is defined as V 2_9 ;

[0160] When S a2 =1, S b2 =0, S c2 =0, S 02 =1, the corresponding voltage vector is defined as V 2_10 ;

[0161] When S a2 =1, S b2 =0, S c2 =1, S 02 = 0, the corresponding voltage vector is defined as V 2_11 ;

[0162] When S a2 =1, S b2 =0, S c2 =1, S 02 =1, the corresponding voltage vector is defined as V 2_12 ;

[0163] When S a2 =1, S b2 =1, S c2 =0, S 02 = 0, the corresponding voltage vector is defined as V 2_13 ;

[0164] When S a2 =1, S b2 =1, S c2 =0, S 02 =1, the corresponding voltage vector is defined as V 2_14 ;

[0165] When S a2 =1, S b2 =1, S c2 =1, S 02 = 0, the corresponding voltage vector is defined as V 2_15 ;

[0166] When S a2 =1, S b2 =1, S c2 =1, S 02=1, the corresponding voltage vector is defined as V 2_16 .

[0167] According to the definition of the 16 voltage vectors V of the second three-phase four-leg converter 2_i (i=1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16) corresponding switch state value S a2 , S b2 , S c2 and S 02 , calculate 16 voltage vectors V 2_i (i=1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16) Voltage value U in the αβγ three-dimensional stationary coordinate system α2_i , U β2_i , U γ2_i (i=1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16), satisfying:

[0168]

[0169] Among them, U dc2 represents the DC bus voltage of the second three-phase four-bridge-leg converter, S a2_i , S b2_i , S c2_i and S 02_i Respectively represent the i-th voltage vector V 2_i (i=1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16) corresponding to the switch state S a2 , S b2 , S c2 and S 02 The value of U α2_i Represents the i-th voltage vector V 2_i (i=1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16) Voltage value on the α axis, U β2_i Represents the i-th voltage vector V 2_i (i=1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16) Voltage value on the β axis, U γ2_i Represents the i-th voltage vector V 2_i (i=1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16) voltage value on the γ axis.

[0170] Step 5: Sample the abc three-phase stator current i of the open-winding asynchronous motor a、i b 、i c , and transform it to the αβγ three-dimensional stationary coordinate system to obtain the current i α 、i β 、i γ , and satisfy:

[0171]

[0172] Among them, i a represents the stator current of phase a of the open-winding asynchronous motor, i b represents the b-phase stator current of the open-winding asynchronous motor, i c represents the c-phase stator current of the open-winding asynchronous motor, i α It represents the component of the abc three-phase stator current of the open-winding asynchronous motor on the α axis, i β It represents the component of the abc three-phase stator current of the open-winding asynchronous motor on the β axis, i γ It represents the component of the abc three-phase stator current of the open-winding asynchronous motor on the γ axis.

[0173] Step 6: The current i obtained in step 5 α 、i β The mathematical model of the open-winding asynchronous motor is used to calculate the rotor flux ψ of the open-winding asynchronous motor. rα , rβ , and satisfy:

[0174]

[0175] Among them, ψ rα is the component of the rotor flux of the open-winding asynchronous motor on the α-axis, ψ rβ is the component of the rotor flux of the open-winding asynchronous motor on the β axis, L m represents the mutual inductance of the open-winding asynchronous motor, T r is the rotor time constant, satisfying T r =L r / R r , L r Represents the rotor inductance of an open-winding asynchronous motor, R r represents the rotor resistance of the open-winding asynchronous motor, ω r represents the rotor angular velocity of the open-winding asynchronous motor, s represents the Laplace operator, and j represents 90 degrees ahead.

[0176] Step 7: The current i obtained in step 5 α 、i β 、i γ And the rotor flux ψ obtained in step 6 rα , rβ, calculate the voltage reference value u in the αβγ three-dimensional stationary coordinate system αref 、u βref 、u γref , and satisfy:

[0177]

[0178] Among them, u αref represents the voltage reference value on the α axis, u βref represents the voltage reference value on the β axis, u γref represents the voltage reference value on the γ axis, i αref represents the stator current reference value of the open-winding asynchronous motor on the α-axis, i βref represents the stator current reference value of the open-winding asynchronous motor on the β axis, i γref represents the stator current reference value of the open-winding asynchronous motor on the γ axis, T s represents the control period, a, b, c, d are 4 coefficients, which respectively satisfy σ represents the magnetic leakage coefficient and satisfies L s represents the stator inductance of an open-winding asynchronous motor, R s Indicates the stator resistance of the open-winding asynchronous motor, L 1s Indicates the stator leakage inductance of an open-winding asynchronous motor. Stator current reference value i αref 、i βref 、i γref The calculation method satisfies:

[0179]

[0180] Among them, i dref is the excitation current reference value of the open-winding asynchronous motor, usually determined by the rated excitation current, i qref is the torque current reference value of the open-winding asynchronous motor, which is usually determined by the output of the speed outer loop. 0ref is the zero-sequence current reference value of the open-winding asynchronous motor, usually set to 0, θ r is the angle of the rotor magnetic field of an open-winding asynchronous motor.

[0181] Step 8: The voltage reference value u obtained in step 7 αref 、u βref And the eight voltage vectors V with odd subscripts of the first three-phase four-bridge-arm converter obtained in step 3 1_(2*k-1) (k=1,2,3,4,5,6,7,8), that is, the voltage vector V 1_1 、V 1_3 、V 1_5 、V 1_7 、V 1_9 、V1_11 、V 1_13 、V 1_15 The corresponding voltage value on the α axis is U α1_(2*k-1) , the voltage value U on the β axis β1_(2*k1) Substitute (k=1,2,3,4,5,6,7,8) into the following formula in turn to calculate the 8 first cost functions g 1k The value of (k=1,2,3,4,5,6,7,8) satisfies:

[0182] g 1k =|u αref -U α1_(2*k-1) |+|u βref -U β1_(2*k-1) |

[0183] Among them, g 1k represents the first cost function (k=1, 2, 3, 4, 5, 6, 7, 8).

[0184] The first cost function g 1k Represents the error between the α-axis and β-axis voltage reference values ​​required by the open-winding asynchronous motor drive system and the α-axis and β-axis voltage values ​​output by the first three-phase four-bridge-arm converter. The smaller the error, the closer the α-axis and β-axis voltage values ​​output by the first three-phase four-bridge-arm converter are to the required voltage values, which also means that the α-axis and β-axis current control error is the smallest.

[0185] Step 9: Compare the 8 first cost functions g calculated in step 8 1k (k=1,2,3,4,5,6,7,8) value, select the first cost function g 1k The voltage vector V that takes the minimum value 1_(2*k-1) (k=1,2,3,4,5,6,7,8) is the optimal voltage vector, and this vector is recorded as the first optimal voltage vector V 1_(2*m-1) , where (2*m-1) means that the first cost function g 1k The subscript of the voltage vector with the minimum value is m, which is one of 1, 2, 3, 4, 5, 6, 7, 8. Here, we choose to make the first cost function g 1k The minimum voltage vector is taken as the optimal vector because g 1k When the minimum value is taken, the error between the α-axis and β-axis voltage reference values ​​required by the open-winding asynchronous motor drive system and the α-axis and β-axis voltage values ​​output by the first three-phase four-bridge-arm converter is the smallest, which also means that the α-axis and β-axis current control error is the smallest at this time.

[0186] Step 10: Substitute the voltage reference value u obtained in step 7 αref 、u βref , the first optimal voltage vector V obtained in step nine 1_(2*m-1)The corresponding voltage value on the α axis is U α1_(2*m-1) , U on the β axis β1_(2*m-1) (m is a value among 1, 2, 3, 4, 5, 6, 7, 8) and the eight voltage vectors V with odd subscripts of the second three-phase four-bridge-arm converter obtained in step 4 2_(2*k-1) (k=1,2,3,4,5,6,7,8), that is, the voltage vector V 2_1 、V 2_3 、V 2_5 、V 2_7 、V 2_9 、V 2_11 、V 2_13 、V 2_15 The corresponding voltage value on the α axis is U α2_(2*k-1) , the voltage value U on the β axis β2_(2*k-1) Substitute (k=1,2,3,4,5,6,7,8) into the following formula in turn to calculate 8 second cost functions g 2k The value of (k=1,2,3,4,5,6,7,8) satisfies:

[0187] g 2k =|u αref -(U α1_(2*m-1) -U α2_(2*k-1) )|+|u βref -(U β1_(2*m-1) -U β2_(2*k-1) )|

[0188] Among them, g 2k represents the second cost function (k=1, 2, 3, 4, 5, 6, 7, 8). The second cost function g 2k Represents the error between the α-axis and β-axis voltage reference values ​​required by the open-winding asynchronous motor drive system when two three-phase four-bridge-arm converters act simultaneously and the voltage difference between the first three-phase four-bridge-arm converter and the second three-phase four-bridge-arm converter. Since the difference between the α-axis and β-axis voltage values ​​output by the two three-phase four-bridge-arm converters represents the phase voltage on the open-winding asynchronous motor, g 2k The smaller it is, the closer the phase voltage on the open-winding asynchronous motor is to the required voltage value, which also means that the α-axis and β-axis current control errors of the open-winding asynchronous motor are the smallest.

[0189] Step 11: Compare the 8 second cost functions g calculated in step 10 2k (k=1,2,3,4,5,6,7,8) value, select the second cost function g 2k The voltage vector V that takes the minimum value 2_(2*k-1) (k=1,2,3,4,5,6,7,8) is the optimal voltage vector, and this vector is recorded as the second optimal vector V 2_(2*n-1), where (2*n-1) means that the second cost function g 2k The subscript of the voltage vector with the minimum value is n, which is one of 1, 2, 3, 4, 5, 6, 7, 8. Here, the second cost function g is selected. 2k The minimum voltage vector is taken as the optimal vector because g 2k When the minimum value is taken, the error between the α-axis and β-axis voltage reference values ​​required by the open-winding asynchronous motor drive system and the voltage value difference output by the two three-phase four-bridge-arm converters is the smallest, which also means that the α-axis and β-axis current control errors are the smallest when the two three-phase four-bridge-arm converters work simultaneously.

[0190] Step 12: The voltage reference value u on the γ axis calculated in step 7 is γref , the first optimal vector V obtained in step nine 1_(2*m-1) and its adjacent vector V 1_2*m (where (2*m-1) represents the first cost function g 1k Take the subscript of the voltage vector with the minimum value, where m is a value among 1, 2, 3, 4, 5, 6, 7, 8), the second optimal vector V obtained in step 11 2_(2*n-1) and its adjacent vector V 2_2*n (where (2*n-1) represents the second cost function g 2k The voltage value U on the γ axis corresponding to the voltage vector with the minimum value (n is one of 1, 2, 3, 4, 5, 6, 7, 8) γ1_(2*m-1) (calculated in step 3), U γ1_2*m (calculated in step 3), U γ2_(2*n-1) (calculated in step 4), U γ2_2*n (Calculated in step 4) are substituted into the following formula to calculate the third cost function g 3 , the fourth cost function g 4 , the fifth cost function g 5 And the sixth cost function g 6 The values ​​of satisfy:

[0191] g 3 =|u γref -(U γ1_(2*m-1) -U γ2_(2*n-1) )|

[0192] g 4 =|u γref -(U γ1_2*m -U γ2_(2*n-1) )|

[0193] g 5 =|u γref -(U γ1_(2*m-1) -U γ2_2*n )|

[0194] g 6 =|u γref -(U γ1_2*m -U γ2_2*n )|

[0195] Among them, g 3 represents the third cost function, g 4 represents the fourth cost function, g 5 represents the fifth cost function, g 6 Denotes the sixth cost function. g 3 , g 4 , g 5 , g 6 It represents the error between the γ-axis voltage reference value required by the open-winding asynchronous motor drive system and the difference between the γ-axis voltage values ​​output by the two three-phase four-bridge-arm converters. The smaller the values ​​of these four cost functions are, the smaller the γ-axis voltage control error is, and the smaller the γ-axis current control error is.

[0196] Step 13: Compare the four cost functions g obtained in step 12 3 , g 4 , g 5 and g 6 The value is selected, and the voltage vector V corresponding to the cost function with the minimum value among the four cost functions is selected. 1_p and V 2_q They are output as the final optimal vectors of the first three-phase four-bridge-arm converter and the second three-phase four-bridge-arm converter, respectively, and are used to control the first three-phase four-bridge-arm converter and the second three-phase four-bridge-arm converter, respectively, so as to realize the model predictive control of the open-winding asynchronous motor; wherein, p represents a value between (2*m-1) and 2*m (m is a value among 1,2,3,4,5,6,7,8), and q represents a value between (2*n-1) and 2*n (n is a value among 1,2,3,4,5,6,7,8). The optimal voltage vector V is obtained through the above optimization process. 1_p and V 2_q , and make them output as the final optimal vector of the first three-phase four-bridge-arm converter and the second three-phase four-bridge-arm converter respectively, which can achieve the goal of minimizing the current control error of the α-axis, β-axis and γ-axis, that is, the actual current of the α-axis, β-axis and γ-axis can track the current reference value of the α-axis, β-axis and γ-axis, thereby realizing the current control of the open-winding asynchronous motor.

[0197] Figure 4 The control block diagram of the common neutral open winding asynchronous motor drive system and its model predictive control strategy proposed by the present invention is shown in FIG. Figure 4 As shown, the model predictive control strategy proposed in the present invention is composed of a speed outer loop and a current inner loop. The speed outer loop is determined by the set speed reference value nref and the measured speed feedback value n r The proportional integral controller (PI controller) is used to construct the torque current reference value i qref .i dref 、i qref and i 0ref The current inner loop executes the model predictive control method proposed in the present invention, and the output is the optimal voltage vector V 1_p and V 2_q Finally, V 1_p and V 2_q The corresponding switch states are used to control two three-phase four-bridge-arm converters respectively, thereby achieving the goal of current control of the open-winding asynchronous motor. Figure 4 In, n p Indicates the number of motor poles and speed feedback value n r is the measured motor rotor angular velocity ω r Calculated. Synchronous angular frequency ω s The rotor angular velocity ω r The rotor magnetic field angle θ is calculated by the slip frequency. r By the synchronous angular frequency ω s Points are obtained.

[0198] In order to verify the effectiveness of the present invention, a simulation is carried out. The motor parameters used in the simulation are shown in Table 1.

[0199] Table 1 Open winding asynchronous motor parameters

[0200]

[0201] During the simulation, the motor reference speed is set to 1500r / min. At 0.4s, the load torque suddenly increases from 0Nm to 15Nm. The excitation current reference value i dref Set to 2.7637A, the speed loop output is the torque current reference value i qref , zero sequence current reference value i 0ref Assuming 0A, the DC side voltage U of the first three-phase four-bridge converter dc1 is 400V, and the DC side voltage U dc2 The voltage is 200V, the proportional coefficient of the proportional-integral controller of the speed outer loop is 0.15, and the integral coefficient is 7. The current inner loop adopts the conventional 256-iteration model predictive control strategy and the low-complexity model predictive control strategy of 20 iterations proposed in the present invention. The simulation results of the conventional method are as follows: Figure 5 As shown, the simulation results of the method proposed by the present invention are as follows Figure 6 As shown. Figure 5 and Figure 6It can be seen that both the conventional method and the method proposed in the present invention can achieve fast tracking and anti-disturbance control of the speed, verifying the effectiveness of the method proposed in the present invention. At the same time, since a three-phase four-bridge-arm converter has a total of 16 output voltage vectors, two three-phase four-bridge-arm converters have a total of 256 output voltage vectors after combination. The conventional method requires online optimization of these 256 voltage vectors to obtain the optimal vector, while the method proposed in the present invention only requires 20 online optimization operations for the voltage vector. Therefore, the amount of calculation of the model predictive control method proposed in the present invention has been greatly reduced, reflecting the superiority of the method proposed in the present invention.

[0202] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A common neutral open winding asynchronous motor drive system, characterized in that: include: Two three-phase four-bridge-arm converters and an open-winding asynchronous motor, each bridge arm of the two three-phase four-bridge-arm converters is composed of an upper power device and a lower power device connected in series, the upper power devices and the lower power devices of the first three bridge arms of the two three-phase four-bridge-arm converters are respectively connected to the two ends of the three-phase winding of the open-winding asynchronous motor as output ends; the upper power device and the lower power device of the fourth bridge arm of the two three-phase four-bridge-arm converters are directly connected.

2. The common neutral open winding asynchronous motor drive system according to claim 1, characterized in that: The upper power device and the lower power device are both composed of fully controlled power electronic devices and uncontrolled diodes connected in anti-parallel; the two three-phase four-bridge arm converters each include a first bridge arm, a second bridge arm, a third bridge arm and a fourth bridge arm, The output ends of the first bridge arms of the two three-phase four-bridge-arm converters are respectively connected to the two ends of the stator a-phase winding of the open-winding asynchronous motor, the output ends of the second bridge arms of the two three-phase four-bridge-arm converters are respectively connected to the two ends of the stator b-phase winding of the open-winding asynchronous motor, the output ends of the third bridge arms of the two three-phase four-bridge-arm converters are respectively connected to the two ends of the stator c-phase winding of the open-winding asynchronous motor, and the output ends of the fourth bridge arms of the two three-phase four-bridge-arm converters are directly connected together; The positive ends of the four bridge arms of the two three-phase four-bridge-arm converters are connected together and connected to the positive ends of their respective DC bus power supplies, and the negative ends of the four bridge arms of the two three-phase four-bridge-arm converters are connected together and connected to the negative ends of their respective DC bus power supplies.

3. The common neutral open winding asynchronous motor drive system according to claim 2, characterized in that: A capacitor C is provided between the positive end and the negative end of the DC bus power supply, and the capacitor C is connected in parallel with each bridge arm; The upper power device S of the first bridge arm of the first three-phase four-bridge arm converter 11 and the lower power device S 12 Series connection, the upper power device S 11 and the lower power device S 12 The midpoint between is the output end; the upper power device S of the second bridge arm of the first three-phase four-bridge-arm converter 13 and the lower power device S 14 Series connection, the upper power device S 13 and the lower power device S 14 The midpoint between them is the output end; the upper power device S of the third bridge arm of the first three-phase four-bridge-arm converter 15 and the lower power device S 16 Series connection, the upper power device S 15 and the lower power device S 16 The midpoint between them is the output end; the upper power device S of the fourth bridge arm of the first three-phase four-bridge-arm converter 17 and the lower power device S 18 Series connection, the upper power device S 17 and the lower power device S 18 The midpoint o1 between the two is the output end; the upper power device S of the first bridge arm of the second three-phase four-bridge-arm converter 21 and the lower power device S 22 Series connection, the upper power device S 21 and the lower power device S 22 The midpoint between is the output end; the upper power device S of the second bridge arm of the second three-phase four-bridge-arm converter 23 and the lower power device S 24 Series connection, the upper power device S 23 and the lower power device S 24 The midpoint of is the output end; the upper power device S of the third bridge arm of the second three-phase four-bridge-arm converter 25 and the lower power device S 26 Series connection, the upper power device S 25 and the lower power device S 26 The midpoint between is the output end; the upper power device S of the fourth bridge arm of the second three-phase four-bridge-arm converter 27 and the lower power device S 28 Series connection, the upper power device S 27 and the lower power device S 28 The midpoint o2 between the two ends is the output end; the two ends a1 and a2 of the a-phase stator winding of the open-winding asynchronous motor are respectively connected to the output end of the first bridge arm of the first three-phase four-bridge-arm converter and the output end of the first bridge arm of the second three-phase four-bridge-arm converter; the two ends b1 and b2 of the b-phase stator winding of the open-winding asynchronous motor are respectively connected to the output end of the second bridge arm of the first three-phase four-bridge-arm converter and the output end of the second bridge arm of the second three-phase four-bridge-arm converter; the two ends c1 and c2 of the c-phase stator winding of the open-winding asynchronous motor are respectively connected to the output end of the third bridge arm of the first three-phase four-bridge-arm converter and the output end of the third bridge arm of the second three-phase four-bridge-arm converter The output end of the arm; the output end o1 of the fourth bridge arm of the first three-phase four-bridge-arm converter and the output end o2 of the fourth bridge arm of the second three-phase four-bridge-arm converter are directly connected together; the positive ends of the four bridge arms of the first three-phase four-bridge-arm converter are connected together and connected to the positive end of the first DC bus power supply, and the negative ends of the four bridge arms of the first three-phase four-bridge-arm converter are connected together and connected to the negative end of the first DC bus power supply; the positive ends of the four bridge arms of the second three-phase four-bridge-arm converter are connected together and connected to the positive end of the second DC bus power supply, and the negative ends of the four bridge arms of the second three-phase four-bridge-arm converter are connected together and connected to the negative end of the second DC bus power supply.

4. The model predictive control method for a common neutral open-winding asynchronous motor drive system according to any one of claims 1 to 3, characterized in that: The steps are as follows: Step S1, defining the switch states of the four bridge arms of the two three-phase four-bridge-arm converters, and determining the value of the switch state according to the on or off state of the upper and lower power devices on the bridge arms, defining 16 voltage vectors according to the values ​​of the switch states of the four bridge arms, and respectively calculating the voltage values ​​of the 16 voltage vectors of the two three-phase four-bridge-arm converters in the αβγ three-dimensional stationary coordinate system; Step S2: sampling the abc three-phase stator current i of the open-winding asynchronous motor a 、i b 、i c , and the stator current i a 、i b 、i c Switching to the αβγ three-dimensional stationary coordinate system, we get the current i α 、i β 、i γ ; Step S3: According to the obtained current i α 、i β The mathematical model of the open-winding asynchronous motor is used to calculate the rotor flux ψ of the open-winding asynchronous motor. rα , rβ ; Step S4: According to the obtained current i α 、i β 、i γ and the rotor flux of the open-winding asynchronous motor ψ rα , rβ , calculate the voltage reference value u in the αβγ three-dimensional stationary coordinate system αref 、u βref 、u γref ; Step S5: According to the obtained voltage reference value u αref 、u βref Calculate the voltage values ​​on the α-axis and the β-axis of the αβγ three-dimensional stationary coordinate system corresponding to the 8 voltage vectors with odd subscripts of the first three-phase four-bridge-arm converter to obtain the values ​​of the 8 first cost functions; compare the values ​​of the 8 first cost functions, and select the voltage vector that makes the first cost function take the minimum value as the first optimal voltage vector; Step S6: According to the obtained voltage reference value u αref 、u βref , the voltage values ​​on the α-axis and β-axis corresponding to the first optimal voltage vector and the voltage values ​​on the α-axis and β-axis corresponding to the 8 voltage vectors with odd subscripts of the second three-phase four-bridge-arm converter, and 8 values ​​of the second cost function are calculated; the magnitudes of the 8 second cost function values ​​obtained are compared, and the voltage vector of the second three-phase four-bridge-arm converter that makes the second cost function take the minimum value is selected as the second optimal voltage vector; Step S7: According to the voltage reference value u on the γ axis γref As well as the voltage values ​​on the γ-axis corresponding to the first optimal voltage vector and its adjacent vectors, the second optimal vector and its adjacent vectors, calculate the values ​​of the third cost function g3, the fourth cost function g4, the fifth cost function g5 and the sixth cost function g6; compare the values ​​of the third cost function g3, the fourth cost function g4, the fifth cost function g5 and the sixth cost function g6, and select the voltage vector corresponding to the cost function with the minimum value among the four cost functions as the final optimal vector of the first three-phase four-bridge-arm converter and the second three-phase four-bridge-arm converter, respectively, for controlling the first three-phase four-bridge-arm converter and the second three-phase four-bridge-arm converter, thereby realizing model predictive control of the open-winding asynchronous motor.

5. The model predictive control method for a common neutral open-winding asynchronous motor drive system according to claim 4, characterized in that: The implementation method of step S1 is: Define the switch state corresponding to the first bridge arm of the first three-phase four-bridge-arm converter as S a1 , define the switch state corresponding to the second bridge arm of the first three-phase four-bridge-arm converter as S b1 , define the switch state corresponding to the third bridge arm of the first three-phase four-bridge-arm converter as S c1 , define the switch state corresponding to the fourth bridge arm of the first three-phase four-bridge-arm converter as S 01 ; When the upper power device of the first bridge arm of the first three-phase four-bridge-arm converter is turned on and the lower power device is turned off, the switch state S is defined. a1 =1; when the upper power device of the first bridge arm of the first three-phase four-bridge-arm converter is turned off and the lower power device is turned on, the switch state S is defined a1 =0; When the upper power device of the second bridge arm of the first three-phase four-bridge-arm converter is turned on and the lower power device is turned off, the switch state S is defined. b1 =1; when the upper power device of the second bridge arm of the first three-phase four-bridge-arm converter is turned off and the lower power device is turned on, the switch state S is defined b1 =0; When the upper power device of the third bridge arm of the first three-phase four-bridge-arm converter is turned on and the lower power device is turned off, the switch state S is defined. c1 =1; when the upper power device of the third bridge arm of the first three-phase four-bridge-arm converter is turned off and the lower power device is turned on, the switch state S is defined c1 =0; When the upper power device of the fourth bridge arm of the first three-phase four-bridge-arm converter is turned on and the lower power device is turned off, the switch state S is defined. 01 =1; when the upper power device of the fourth bridge arm of the first three-phase four-bridge-arm converter is turned off and the lower power device is turned on, the switch state S is defined 01 =0; Define the 16 voltage vectors V of the first three-phase four-leg converter 1_i satisfy: When S a1 =0, S b1 =0, S c1 =0, S 01 = 0, the corresponding voltage vector is defined as V 1_1 ; When S a1 =0, S b1 =0, S c1 =0, S 01 =1, the corresponding voltage vector is defined as V 1_2 ; When S a1 =0, S b1 =0, S c1 =1, S 01 = 0, the corresponding voltage vector is defined as V 1_3 ; When S a1 =0, S b1 =0, S c1 =1, S 01 =1, the corresponding voltage vector is defined as V 1_4 ; When S a1 =0, S b1 =1, S c1 =0, S 01 = 0, the corresponding voltage vector is defined as V 1_5 ; When S a1 =0, S b1 =1, S c1 =0, S 01 =1, the corresponding voltage vector is defined as V 1_6 ; When S a1 =0, S b1 =1, S c1 =1, S 01 = 0, the corresponding voltage vector is defined as V 17 ; When S a1 =0, S b1 =1, S c1 =1, S 01 =1, the corresponding voltage vector is defined as V 1_8 ; When S a1 =1, S b1 =0, S c1 =0, S 01 = 0, the corresponding voltage vector is defined as V 1_9 ; When S a1 =1, S b1 =0, S c1 =0, S 01 =1, the corresponding voltage vector is defined as V 1_10 ; When S a1 =1, S b1 =0, S c1 =1, S 01 = 0, the corresponding voltage vector is defined as V 1_11 ; When S a1 =1, S b1 =0, S c1 =1, S 01 =1, the corresponding voltage vector is defined as V 1_12 ; When S a1 =1, S b1 =1, S c1 =0, S 01 = 0, the corresponding voltage vector is defined as V 1_13 ; When S a1 =1, S b1 =1, S c1 =0, S 01 =1, the corresponding voltage vector is defined as V 1_14 ; When S a1 =1, S b1 =1, S c1 =1, S 01 = 0, the corresponding voltage vector is defined as V 1_15 ; When S a1 =1, S b1 =1, S c1 =1, S 01 =1, the corresponding voltage vector is defined as V 1_16 ; Wherein, i=1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16; Define the switch state corresponding to the first bridge arm of the second three-phase four-bridge-arm converter as S a2 , define the switch state corresponding to the second bridge arm of the second three-phase four-bridge-arm converter as S b2 , define the switch state corresponding to the third bridge arm of the second three-phase four-bridge-arm converter as S c2 , define the switch state corresponding to the fourth bridge arm of the second three-phase four-bridge-arm converter as S 02 ; When the upper power device of the first bridge arm of the second three-phase four-bridge-arm converter is turned on and the lower power device is turned off, the switch state S is defined. a2 =1; when the upper power device of the first bridge arm of the second three-phase four-bridge-arm converter is turned off and the lower power device is turned on, the switch state S is defined a2 =0; When the upper power device of the second bridge arm of the second three-phase four-bridge-arm converter is turned on and the lower power device is turned off, the switch state S is defined. b2 =1; when the upper power device of the second bridge arm of the second three-phase four-bridge-arm converter is turned off and the lower power device is turned on, the switch state S is defined b2 =0; When the upper power device of the third bridge arm of the second three-phase four-bridge-arm converter is turned on and the lower power device is turned off, the switch state S is defined. c2 =1; when the upper power device of the third bridge arm of the second three-phase four-bridge-arm converter is turned off and the lower power device is turned on, the switch state S is defined c2 =0; When the upper power device of the fourth bridge arm of the second three-phase four-bridge-arm converter is turned on and the lower power device is turned off, the switch state S is defined. 02 =1; when the upper power device of the fourth arm of the second three-phase four-bridge-arm converter is turned off and the lower power device is turned on, the switch state S is defined 02 =0; Define the 16 voltage vectors V of the second three-phase four-leg converter 2_i satisfy: When S a2 =0, S b2 =0, S c2 =0, S 02 = 0, the corresponding voltage vector is defined as V 2_1 ; When S a2 =0, S b2 =0, S c2 =0, S 02 =1, the corresponding voltage vector is defined as V 2_2 ; When S a2 =0, S b2 =0, S c2 =1, S 02 = 0, the corresponding voltage vector is defined as V 2_3 ; When S a2 =0, S b2 =0, S c2 =1, S 02 =1, the corresponding voltage vector is defined as V 2_4 ; When S a2 =0, S b2 =1, S c2 =0, S 02 = 0, the corresponding voltage vector is defined as V 2_5 ; When S a2 =0, S b2 =1, S c2 =0, S 02 =1, the corresponding voltage vector is defined as V 2_6 ; When S a2 =0, S b2 =1, S c2 =1, S 02 = 0, the corresponding voltage vector is defined as V 2_7 ; When S a2 =0, S b2 =1, S c2 =1, S 02 =1, the corresponding voltage vector is defined as V 2_8 ; When S a2 =1, S b2 =0, S c2 =0, S 02 = 0, the corresponding voltage vector is defined as V 2_9 ; When S a2 =1, S b2 =0, S c2 =0, S 02 =1, the corresponding voltage vector is defined as V 2_10 ; When S a2 =1, S b2 =0, S c2 =1, S 02 = 0, the corresponding voltage vector is defined as V 2_11 ; When S a2 =1, S b2 =0, S c2 =1, S 02 =1, the corresponding voltage vector is defined as V 2_12 ; When S a2 =1, S b2 =1, S c2 =0, S 02 = 0, the corresponding voltage vector is defined as V 2_13 ; When S a2 =1, S b2 =1, S c2 =0, S 02 =1, the corresponding voltage vector is defined as V 2_14 ; When S a2 =1, S b2 =1, S c2 =1, S 02 = 0, the corresponding voltage vector is defined as V 2_15 ; When S a2 =1, S b2 =1, S c2 =1, S 02 =1, the corresponding voltage vector is defined as V 2_16 .

6. The model predictive control method for a common neutral open-winding asynchronous motor drive system according to claim 4, characterized in that: According to the definition of the first three-phase four-leg converter 16 voltage vectors V 1_i The corresponding switch state S a1 , S b1 , S c1 and S 01 Calculate the 16 voltage vectors V 1_i Voltage value U in the αβγ three-dimensional stationary coordinate system α1_i , U β1_i , U γ1_i for: Among them, U dc1 represents the DC bus voltage of the first three-phase four-bridge-arm converter, S a1_i , S b1_i , S c1_i and S 01_i Respectively represent the i-th voltage vector V 1_i The corresponding switch state S a1 , S b1 , S c1 and S 01 The value of U α1_i Represents the i-th voltage vector V 1_i Voltage value on the α axis, U β1_i Represents the i-th voltage vector V 1_i Voltage value on the β axis, U γ1_i Represents the i-th voltage vector V 1_i Voltage value on the γ axis; where i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16; According to the definition of the 16 voltage vectors V of the second three-phase four-leg converter 2_i The corresponding switch state value S a2 , S b2 , S c2 and S 02 , calculate 16 voltage vectors V 2_i Voltage value U in the αβγ three-dimensional stationary coordinate system α2_i , U β2_i , U γ2_i for: Among them, U dc2 represents the DC bus voltage of the second three-phase four-bridge-leg converter, S a2_i , S b2_i , S c2_i and S 02_i Respectively represent the i-th voltage vector V 2_i The corresponding switch state S a2 , S b2 , S c2 and S 02 The value of U α2_i Represents the i-th voltage vector V 2_i Voltage value on the α axis, U β2_i Represents the i-th voltage vector V 2_i Voltage value on the β axis, U γ2_i Represents the i-th voltage vector V 2_i The voltage value on the γ axis.

7. The model predictive control method for a common neutral open-winding asynchronous motor drive system according to claim 6, characterized in that: In step S2, the current i α 、i β 、i γ The calculation method is: Among them, i a represents the stator current of phase a of the open-winding asynchronous motor, i b represents the b-phase stator current of the open-winding asynchronous motor, i c represents the c-phase stator current of the open-winding asynchronous motor, i α It represents the component of the abc three-phase stator current of the open-winding asynchronous motor on the α axis, i β It represents the component of the abc three-phase stator current of the open-winding asynchronous motor on the β axis, i γ It represents the component of the abc three-phase stator current of the open-winding asynchronous motor on the γ axis; The rotor flux linkage ψ of the open-winding asynchronous motor rα , rβ for: Among them, ψ rα is the component of the rotor flux of the open-winding asynchronous motor on the α-axis, ψ rβ is the component of the rotor flux of the open-winding asynchronous motor on the β axis, L m represents the mutual inductance of the open-winding asynchronous motor, T r is the rotor time constant, satisfying T r =L r / R r , L r Represents the rotor inductance of an open-winding asynchronous motor, R r represents the rotor resistance of the open-winding asynchronous motor, ω r represents the rotor angular velocity of the open-winding asynchronous motor, s represents the Laplace operator, and j represents 90 degrees ahead; The voltage reference value u on the αβγ three-dimensional stationary coordinate system αref 、u βref 、u γref for: Among them, u αref represents the voltage reference value on the α axis, u βref represents the voltage reference value on the β axis, u γref represents the voltage reference value on the γ axis, i αref represents the stator current reference value of the open-winding asynchronous motor on the α-axis, i βref represents the stator current reference value of the open-winding asynchronous motor on the β axis, i γref represents the stator current reference value of the open-winding asynchronous motor on the γ axis, T s It represents the control period, and a, b, c, and d are 4 coefficients.

8. The model predictive control method for a common neutral open-winding asynchronous motor drive system according to any one of claims 5 to 7, characterized in that: The 8 first cost functions g 1k The value of is calculated as: Mr 1k =|in αref -IN α1_(2*k-1) |+|in βref -IN β1_(2*k-1) | Where k = 1, 2, 3, 4, 5, 6, 7, 8, U α1_(2*k-1) and U β1_(2*k-1) They represent the eight voltage vectors V with odd subscripts of the first three-phase four-bridge-arm converter. 1_(2*k-1) The corresponding voltage value on the α-axis and the voltage value on the β-axis; The eight second cost functions g 2k The value of is calculated as: Mr 2k =|in αref -(IN α1_(2*m-1) -IN α2_(2*k-1) )|+|in βref -(IN β1_(2*m-1) -IN β2_(2*k-1) )| Among them, U α1_(2*m-1) and U β1_(2*m-1) They are the first optimal voltage vector V 1_(2*m-1) The corresponding voltage values ​​on the α-axis and β-axis, U α2_(2*k-1) and U β2_(2*k-1) They are the eight voltage vectors V with odd subscripts of the second three-phase four-bridge-arm converter. 2_(2*k-1) The corresponding voltage values ​​on the α-axis and β-axis; The methods for calculating the values ​​of the third cost function g3, the fourth cost function g4, the fifth cost function g5 and the sixth cost function g6 are respectively: Among them, U γ1_(2*m-1) , U γ1_2*m , U γ2_(2*n-1) , U γ2_2*n The first optimal vector V 1_(2*m-1) and its adjacent vector V 1_2*m , the second optimal vector V 2_(2*n-1) and its adjacent vector V 2_2*n The corresponding voltage value on the γ axis.

9. The model predictive control method for a common neutral open-winding asynchronous motor drive system according to claim 8, characterized in that: Choose the first cost function g 1k The voltage vector V that takes the minimum value 1_(2*k-1) is the optimal voltage vector, denoted as the first optimal voltage vector V 1_(2*m-1) , where (2*m-1) means that the first cost function g 1k Take the subscript of the voltage vector with the minimum value, where m is a value among 1, 2, 3, 4, 5, 6, 7, 8; Compare 8 second cost functions g 2k The value is selected to make the second cost function g 2k The voltage vector V that takes the minimum value 2_(2*k-1) is the optimal voltage vector, recorded as the second optimal voltage vector V 2_(2*n-1) , where (2*n-1) means that the second cost function g 2k Take the subscript of the voltage vector with the minimum value, where n is a value among 1, 2, 3, 4, 5, 6, 7, 8; Select the voltage vector V corresponding to the minimum cost function among the third cost function g3, the fourth cost function g4, the fifth cost function g5 and the sixth cost function g6. 1_p and V 2_q They are output as the final optimal vectors of the first three-phase four-bridge-arm converter and the second three-phase four-bridge-arm converter respectively, where p represents a value between (2*m-1) and 2*m, q represents a value between (2*n-1) and 2*n, and m and n are both values ​​between 1, 2, 3, 4, 5, 6, 7, and 8.

10. The model predictive control method for a common neutral open-winding asynchronous motor drive system according to claim 7, characterized in that: The coefficient σ represents the magnetic leakage coefficient and satisfies L s represents the stator inductance of an open-winding asynchronous motor, R s Indicates the stator resistance of the open-winding asynchronous motor, L 1s Indicates the stator leakage inductance of an open-winding asynchronous motor; The stator current reference value i αref 、i βref 、i γref The calculation method is: Among them, i dref is the excitation current reference value of the open-winding asynchronous motor, i qref is the torque current reference value of the open-winding asynchronous motor, i 0ref is the zero-sequence current reference value of the open-winding asynchronous motor, θ r is the angle of the rotor magnetic field of an open-winding asynchronous motor.

Images