A robust model predictive control method for a common neutral open winding asynchronous motor drive system

Abstract

This invention proposes a robust model predictive control method for a common-neutral open-winding asynchronous motor drive system. The system consists of two three-phase four-arm converters and one open-winding asynchronous motor. The steps are as follows: sampling the three-phase stator current of the open-winding asynchronous motor and transforming it to obtain current components; calculating voltage reference values ​​using the current components and the lumped disturbance from the previous cycle; determining the voltage vectors of the two three-phase four-arm converters based on the conduction state of the power devices, and calculating the voltage values ​​corresponding to the voltage vectors; calculating the value of a first cost function using the voltage value of the voltage vector of the first three-phase four-arm converter to obtain a first optimal voltage vector; calculating the value of a second cost function based on the voltage values ​​corresponding to the first optimal voltage vector and the voltage values ​​of the voltage vector of the second three-phase four-arm converter to determine a second optimal voltage vector; controlling the two three-phase four-arm converters respectively using the switching state values ​​corresponding to the two optimal voltage vectors, and calculating the lumped disturbance observed in the current cycle. This invention achieves robust model predictive control and improves the current control accuracy under parameter mismatch.

Description

Technical Field

[0001] This invention relates to the technical field of power electronics and electric drive, and in particular to a robust model predictive control method for a common-center-wire open-winding asynchronous motor drive system. Background Technology

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

[0003] Existing open-winding asynchronous motor drive systems can be divided into three topologies: independent DC bus, common DC bus, and common neutral line. The literature [L. Xu, ZQZhu and L. Yan, "Low Switching Frequency SPWM Strategies for Open-Winding Machine With Low Current Harmonics," in IEEE Transactions on Industry Applications, vol. 58, no. 2, pp. 2042-2054, March-April 2022.] and [N. Chai and W. Hu, "A Fault-Tolerant Scheme Against the Open-Switch Failure in Open-End Winding PMSM System With Isolated DC bus," in IEEE Transactions on Energy Conversion, vol. 38, no. 3, pp. 2227-2230, Sept. 2023] studied low switching frequency and fault-tolerant control strategies for motor drive systems with independent DC bus open windings. Although this type of topology allows for flexible selection of the DC bus voltages of the two converters to achieve flexible multi-mode control, it is difficult to achieve fault-tolerant control when the motor experiences a phase loss fault due to the lack of a neutral line. References [Wang Wei, Jiang Yixin, Wang Zheng, et al. Review of zero-sequence current suppression technology for open-winding motor systems with common DC bus [J]. Proceedings of the CSEE, 2021, 41(05): 1871-1885.] and [Luo Guangzhao, Huang Shuo, Zhou Kai, et al. Phase current reconstruction method, equipment and storage medium for open-winding permanent magnet synchronous motors [P]. Shaanxi Province: CN202311602297.4, 2024-03-15.] studied the zero-sequence current suppression method and current reconstruction strategy for open-winding motor drive systems with common DC bus. Although this type of topology adds a neutral line and can achieve fault-tolerant control during motor phase loss faults through flexible adjustment of zero-sequence current, it is difficult to achieve independent and flexible adjustment of the DC bus voltage of the two converters because the DC buses of the two converters are directly connected.References [Wang Shun, Yang Shuying, Li Yi, et al. Research on three-dimensional space vector pulse width modulation strategy for common-neutral open-winding topology [J]. Proceedings of the CSEE, 2023, 43(03): 1163-1177.] and [Yang Shuying, Hu Xiaohai, Fu Huan, et al. A drive control method for a common-neutral open-winding asynchronous motor [P]. Anhui Province: CN201910862730.5, 2021-07-20.] studied a control strategy for a common-neutral open-winding motor drive system. This type of topology increases the neutral line while retaining the ability to independently and flexibly adjust the DC bus voltage of the two converters. However, when implementing a fault-tolerant control strategy for motor phase loss faults, a large current will flow through the bus capacitor, increasing the current stress on the bus capacitor and affecting its service life. In addition, existing common-neutral open-winding motor drive systems mostly adopt vector control strategies based on space vector modulation. This strategy has disadvantages such as complex implementation and the need to design multiple sets of proportional-integral controller parameters. In recent years, model predictive control technology has attracted widespread attention due to its advantages such as flexible control, simple implementation, and ability to achieve multi-objective control. However, research on model predictive control strategies for common-center-wire open-winding motor drive systems is still scarce.

[0004] In summary, independent DC bus topologies require two independent DC power supplies and lack a neutral line, making it difficult to achieve fault-tolerant operation after a phase loss fault in the motor. While common DC bus topologies have a neutral line, enabling fault-tolerant operation after a phase loss fault, the DC voltages of the two converters are connected together and remain constant, making adjustment impossible. Common neutral line topologies, although possessing both a neutral line and two independent DC bus power supplies, experience a large current flowing through the neutral line during fault-tolerant operation after a phase loss fault, increasing the current stress on the bus capacitor and potentially damaging it. Furthermore, existing common neutral line open-winding motor drive systems often employ vector control strategies based on space vector modulation, which suffers from complex implementation and requires designing multiple sets of proportional-integral controller parameters. In recent years, model predictive control (MMC) technology has gained widespread attention due to its advantages such as flexible control, simple implementation, and ability to achieve multi-objective control. However, research on MMC strategies for common neutral line open-winding motor drive systems is still scarce, and conventional MMC strategies based on motor mathematical models suffer from poor parameter robustness. Summary of the Invention

[0005] To address the technical challenges of conventional common-neutral open-winding asynchronous motor drive systems, such as high bus capacitor current stress and susceptibility to damage during phase-loss fault operation, and the heavy reliance on complex space vector modulation and model predictive control strategies due to their dependence on the motor's mathematical model, this invention proposes a robust model predictive control method for common-neutral open-winding asynchronous motor drive systems based on a dual three-phase four-bridge-arm converter. The proposed method replaces the virtual capacitor bridge arms in conventional common-neutral open-winding topologies with bridge arms composed of fully controlled devices, thereby making neutral current control more flexible and reducing bus capacitor current stress. The proposed robust model predictive control strategy employs a disturbance observer for lumped disturbance observation and uses the observed disturbances to construct a predictive model instead of the motor model, thus achieving robust model predictive control and improving current control accuracy during parameter mismatch.

[0006] To achieve the above objectives, the technical solution of the present invention is implemented as follows: a robust model predictive control method for a common-neutral open-winding asynchronous motor drive system, wherein the common-neutral open-winding asynchronous motor drive system consists of two three-phase four-bridge converters and one open-winding asynchronous motor, and each bridge arm of the two three-phase four-bridge converters is composed of an upper power device and a lower power device connected in series, the steps of which are as follows:

[0007] Step 1: Sample the three-phase stator current of the open-winding asynchronous motor and transform the three-phase stator current to the αβγ three-dimensional stationary coordinate system to obtain the current components of the α-axis, β-axis and γ-axis respectively;

[0008] Step 2: Calculate the voltage reference value on the αβγ three-dimensional stationary coordinate system using the current components of the α-axis, β-axis, and γ-axis, as well as the lumped perturbations of the α-axis, β-axis, and γ-axis observed in the previous cycle.

[0009] Step 3: Based on the conduction state of the power devices on the four arms of the two three-phase four-arm converters, define the values ​​of the switching states corresponding to the four arms of the two three-phase four-arm converters respectively; determine the 16 voltage vectors of the two three-phase four-arm converters based on the values ​​of the different switching states.

[0010] Step 4: Calculate the voltage values ​​of the voltage vectors in the αβγ three-dimensional stationary coordinate system based on the switching states of the 16 voltage vectors of the two three-phase four-arm converters;

[0011] Step 5: Calculate the values ​​of 16 first cost functions based on the voltage reference values ​​in the αβγ three-dimensional stationary coordinate system and the voltage values ​​of the 16 voltage vectors of the first three-phase four-arm converter in the αβγ three-dimensional stationary coordinate system. Compare the values ​​of the 16 first cost functions and select the voltage vector that minimizes the value of the first cost function as the first optimal voltage vector.

[0012] Step 6: Calculate the values ​​of 16 second cost functions based on the voltage reference value in the αβγ three-dimensional stationary coordinate system, the voltage value in the αβγ three-dimensional stationary coordinate system corresponding to the first optimal voltage vector, and the voltage values ​​of the 16 voltage vectors of the second three-phase four-arm converter in the αβγ three-dimensional stationary coordinate system. Compare the values ​​of the 16 second cost functions and select the voltage vector that minimizes the value of the second cost function as the second optimal voltage vector.

[0013] Step 7: Control the first three-phase four-arm converter using the value of the switching state corresponding to the first optimal voltage vector, and control the second three-phase four-arm converter using the value of the switching state corresponding to the second optimal voltage vector; at the same time, calculate the lumped disturbances of the α-axis, β-axis and γ-axis observed in this cycle.

[0014] Preferably, the upper and lower power devices of the first three arms of the two three-phase four-arm converters are connected as output terminals to the two ends of the three-phase winding of the open-winding asynchronous motor, respectively; the upper and lower power devices of the fourth arm of the two three-phase four-arm converters are directly connected through the neutral line.

[0015] Preferably, the method for calculating the voltage reference value in the αβγ three-dimensional stationary coordinate system is as follows:

[0016]

[0017] Among them, u αref u represents the voltage reference value on the α-axis in the αβγ three-dimensional stationary coordinate system. βref u represents the voltage reference value on the β axis. γref Indicates the voltage reference value on the γ-axis, i αref i represents the reference value of the stator current on the α-axis of an open-winding asynchronous motor. βref i represents the reference value of the stator current on the β-axis of an open-winding asynchronous motor. γref T represents the reference value of the stator current on the γ-axis of an open-winding asynchronous motor. s This represents the control period, d is the proportionality coefficient of the α-axis and β-axis, and i α i represents the current component of the three-phase stator current (a, b, c) of an open-winding asynchronous motor on the α-axis. β i represents the current component of the three-phase stator current (a, b, c) of an open-winding asynchronous motor on the β-axis. γL represents the current components of the three-phase stator current (a, b, c) of an open-winding asynchronous motor along the γ-axis. 1s F represents the stator leakage inductance of an open-winding asynchronous motor. α_est0 F represents the lumped disturbance of the α-axis estimated in the previous period. β_est0 F represents the lumped perturbation of the β-axis estimated in the previous period. γ_est0 This represents the lumped perturbation of the γ-axis estimated in the previous period.

[0018] Preferably, the method for transforming the three-phase stator current to the αβγ three-dimensional stationary coordinate system to obtain the current components along the α-axis, β-axis, and γ-axis is as follows: The three-phase stator current i of the open-winding asynchronous motor is... a i b i c Transforming to the αβγ three-dimensional stationary coordinate system, we obtain the current components i along the α-axis, β-axis, and γ-axis. α i β i γ for:

[0019]

[0020] Among them, i a i represents the stator current of phase a of an open-winding asynchronous motor. b i represents the b-phase stator current of an open-winding asynchronous motor. c This represents the c-phase stator current of an open-winding asynchronous motor;

[0021] The scaling factors of the α-axis and β-axis σ represents the leakage flux coefficient, and L s L represents the stator inductance of an open-winding asynchronous motor. m L represents the mutual inductance of an open-winding asynchronous motor. r This represents the rotor inductance of an open-winding asynchronous motor;

[0022] The lumped disturbance F estimated in the previous period α_est0 F β_est0 F γ_est0 These are obtained by delaying the lumped disturbance observed in the previous cycle by one control cycle.

[0023] The stator current reference value i αref i βref i γref The calculation method is as follows:

[0024]

[0025] Among them, i dref i is the reference value for the excitation current of an open-winding asynchronous motor. qrefi is the reference value for the torque current of an open-winding asynchronous motor. 0ref θ is the reference value for the zero-sequence current of an open-winding asynchronous motor. r The angle of the rotor magnetic field of an open-winding asynchronous motor.

[0026] Preferably, the switching state corresponding to the first arm of the first three-phase four-arm converter is defined as S. a1 Define the switching state corresponding to the second arm of the first three-phase four-arm converter as S. b1 Define the switching state corresponding to the third arm of the first three-phase four-arm converter as S. c1 Define the switching state corresponding to the fourth arm of the first three-phase four-arm converter as S. 01 ;

[0027] When the upper power device of the first arm of the first three-phase four-arm converter is turned on and the lower power device is turned off, the switch state S is... a1 =1; When the upper power device of the first arm of the first three-phase four-arm converter is turned off and the lower power device is turned on, the switching state S is 1. a1 =0;

[0028] When the upper power device of the second arm of the first three-phase four-arm converter is turned on and the lower power device is turned off, the switch state S is... b1 =1; When the upper power device of the second arm of the first three-phase four-arm converter is turned off and the lower power device is turned on, the switching state S is 1. b1 =0;

[0029] When the upper power device of the third arm of the first three-phase four-arm converter is turned on and the lower power device is turned off, the switch state S is... c1 =1; When the upper power device of the third arm of the first three-phase four-arm converter is turned off and the lower power device is turned on, the switching state S is 1. c1 =0;

[0030] When the upper power device of the fourth arm of the first three-phase four-arm converter is turned on and the lower power device is turned off, the switch state S is... 01 =1; When the upper power device of the fourth arm of the first three-phase four-arm converter is turned off and the lower power device is turned on, the switching state S is 1. 01 =0;

[0031] The first three-phase four-arm converter has 16 voltage vectors V 1_i satisfy:

[0032] When S a1 =0, S b1 =0, S c1 =0, S01 When = 0, the corresponding voltage vector is defined as V 1_1 ;

[0033] When S a1 =0, S b1 =0, S c1 =0, S 01 When = 1, the corresponding voltage vector is defined as V 1_2 ;

[0034] When S a1 =0, S b1 =0, S c1 =1,S 01 When = 0, the corresponding voltage vector is defined as V 1_3 ;

[0035] When S a1 =0, S b1 =0, S c1 =1,S 01 When = 1, the corresponding voltage vector is defined as V 1_4 ;

[0036] When S a1 =0, S b1 =1,S c1 =0, S 01 When = 0, the corresponding voltage vector is defined as V 1_5 ;

[0037] When S a1 =0, S b1 =1,S c1 =0, S 01 When = 1, the corresponding voltage vector is defined as V 1_6 ;

[0038] When S a1 =0, S b1 =1,S c1 =1,S 01 When = 0, the corresponding voltage vector is defined as V 1_7 ;

[0039] When S a1 =0, S b1 =1,S c1 =1,S 01 When = 1, the corresponding voltage vector is defined as V 1_8 ;

[0040] When S a1 =1,S b1 =0, S c1 =0, S 01 When = 0, the corresponding voltage vector is defined as V1_9 ;

[0041] When S a1 =1,S b1 =0, S c1 =0, S 01 When = 1, the corresponding voltage vector is defined as V 1_10 ;

[0042] When S a1 =1,S b1 =0, S c1 =1,S 01 When = 0, the corresponding voltage vector is defined as V 1_11 ;

[0043] When S a1 =1,S b1 =0, S c1 =1,S 01 When = 1, the corresponding voltage vector is defined as V 1_12 ;

[0044] When S a1 =1,S b1 =1,S c1 =0, S 01 When = 0, the corresponding voltage vector is defined as V 1_13 ;

[0045] When S a1 =1,S b1 =1,S c1 =0, S 01 When = 1, the corresponding voltage vector is defined as V 1_14 ;

[0046] When S a1 =1,S b1 =1,S c1 =1,S 01 When = 0, the corresponding voltage vector is defined as V 1_15 ;

[0047] When S a1 =1,S b1 =1,S c1 =1,S 01 When = 1, the corresponding voltage vector is defined as V 1_16 Where i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16;

[0048] Define the switching state corresponding to the first arm of the second three-phase four-arm converter as S. a2 Define the switching state corresponding to the second arm of the second three-phase four-arm converter as S.b2 Define the switching state corresponding to the third arm of the second three-phase four-arm converter as S. c2 Define the switching state corresponding to the fourth arm of the second three-phase four-arm converter as S. 02 ;

[0049] When the upper power device of the first arm of the second three-phase four-arm converter is turned on and the lower power device is turned off, the switch state S is... a2 =1; When the upper power device of the first arm of the second three-phase four-arm converter is turned off and the lower power device is turned on, the switching state S is 1. a2 =0;

[0050] When the upper power device of the second arm of the second three-phase four-arm converter is turned on and the lower power device is turned off, the switch state S b2 =1; When the upper power device of the second arm of the second three-phase four-arm converter is turned off and the lower power device is turned on, the switching state S is 1. b2 =0;

[0051] When the upper power device of the third arm of the second three-phase four-arm converter is turned on and the lower power device is turned off, the switch state S is... c2 =1; When the upper power device of the third arm of the second three-phase four-arm converter is turned off and the lower power device is turned on, the switching state S is 1. c2 =0;

[0052] When the upper power device of the fourth arm of the second three-phase four-arm converter is turned on and the lower power device is turned off, S is defined as... 02 =1; When the upper power device of the fourth arm of the second three-phase four-arm converter is turned off and the lower power device is turned on, S is defined as 1. 02 =0;

[0053] Define the 16 voltage vectors V of the second three-phase four-arm converter. 2_i satisfy:

[0054] When S a2 =0, S b2 =0, S c2 =0, S 02 When = 0, the corresponding voltage vector is defined as V 2_1 ;

[0055] When S a2 =0, S b2 =0, S c2 =0, S 02 When = 1, the corresponding voltage vector is defined as V 2_2 ;

[0056] When S a2 =0, S b2 =0, S c2 =1,S 02 When = 0, the corresponding voltage vector is defined as V 2_3 ;

[0057] When S a2 =0, S b2 =0, S c2 =1,S 02 When = 1, the corresponding voltage vector is defined as V 2_4 ;

[0058] When S a2 =0, S b2 =1,S c2 =0, S 02 When = 0, the corresponding voltage vector is defined as V 2_5 ;

[0059] When S a2 =0, S b2 =1,S c2 =0, S 02 When = 1, the corresponding voltage vector is defined as V 2_6 ;

[0060] When S a2 =0, S b2 =1,S c2 =1,S 02 When = 0, the corresponding voltage vector is defined as V 2_7 ;

[0061] When S a2 =0, S b2 =1,S c2 =1,S 02 When = 1, the corresponding voltage vector is defined as V 2_8 ;

[0062] When S a2 =1,S b2 =0, S c2 =0, S 02 When = 0, the corresponding voltage vector is defined as V 2_9 ;

[0063] When S a2 =1,S b2 =0, S c2 =0, S 02 When = 1, the corresponding voltage vector is defined as V 2_10 ;

[0064] When S a2 =1,Sb2 =0, S c2 =1,S 02 When = 0, the corresponding voltage vector is defined as V 2_11 ;

[0065] When S a2 =1,S b2 =0, S c2 =1,S 02 When = 1, the corresponding voltage vector is defined as V 2_12 ;

[0066] When S a2 =1,S b2 =1,S c2 =0, S 02 When = 0, the corresponding voltage vector is defined as V 2_13 ;

[0067] When S a2 =1,S b2 =1,S c2 =0, S 02 When = 1, the corresponding voltage vector is defined as V 2_14 ;

[0068] When S a2 =1,S b2 =1,S c2 =1,S 02 When = 0, the corresponding voltage vector is defined as V 2_15 ;

[0069] When S a2 =1,S b2 =1,S c2 =1,S 02 When = 1, the corresponding voltage vector is defined as V 2_16 ;

[0070] Calculate 16 voltage vectors V 1_i The voltage value U in the αβγ three-dimensional stationary coordinate system α1_i U β1_i U γ1_ The method is as follows:

[0071]

[0072] Among them, U dc1 S represents the DC bus voltage of the first three-phase four-arm converter. a1_i S b1_i S c1_i and S 01_i Representing the i-th voltage vector V 1_i The corresponding switch state value, Uα1_i V represents the i-th voltage vector. 1_i The voltage value on the α axis, U β1_i V represents the i-th voltage vector. 1_i The voltage value on the β axis, U γ1_i V represents the i-th voltage vector. 1_i Voltage value on the γ axis;

[0073] Based on the 16 voltage vectors V of the second three-phase four-arm converter as defined 2_i Calculate the 16 voltage vectors V corresponding to the switch states. 2_i The voltage value U in the αβγ three-dimensional stationary coordinate system α2_i U β2_i U γ2_i for:

[0074]

[0075] Among them, U dc2 S represents the DC bus voltage of the second three-phase four-arm converter. a2_i S b2_i S c2_i and S 02_i Representing the i-th voltage vector V 2_i The corresponding switch state value S a2 S b2 S c2 and S 02 U α2_i V represents the i-th voltage vector. 2_i The voltage value on the α axis, U β2_i V represents the i-th voltage vector. 2_i The voltage value on the β axis, U γ2_i V represents the i-th voltage vector. 2_i Voltage value on the γ axis.

[0076] Preferably, the first cost function g 1i for:

[0077] g 1i =|u αref -U α1_i | + |u βref -U β1_i |+k1|u γref -U γ1_i |;

[0078] Where i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, and k1 is the first weighting coefficient; U α1_i V represents the i-th voltage vector.1_i The voltage value on the α axis, U β1_i V represents the i-th voltage vector. 1_i The voltage value on the β axis, U γ1_i V represents the i-th voltage vector. 1_i Voltage value on the γ axis; u αref u represents the voltage reference value on the α axis. βref u represents the voltage reference value on the β axis. γref This represents the voltage reference value on the γ-axis;

[0079] The second cost function g 2i for:

[0080] g 2i =|u αref -(U α1_m -U α2_i )| + |u βref -(U β1_m -U β2_i )|+k2|u γref -(U γ1_m -U γ2_i )|;

[0081] Where i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, k2 is the second weighting coefficient, U α2_i V represents the i-th voltage vector. 2_i The voltage value on the α axis, U β2_i V represents the i-th voltage vector. 2_i The voltage value on the β axis, U γ2_i V represents the i-th voltage vector. 2_i Voltage value on the γ axis; U α1_m U β1_m U γ1_m The first optimal voltage vector V is respectively 1_m Voltage values ​​on the α-axis, β-axis, and γ-axis.

[0082] Preferably, the 16 calculated first cost functions g are compared. 1i The value of the first cost function g is chosen to make the first cost function g... 1i The voltage vector V that takes the minimum value 1_i Let V be the first optimal voltage vector. 1_m Where m represents the value that makes the first cost function g 1i The subscript of the voltage vector with the minimum value is m, which is one of the values ​​1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16.

[0083] Compare the 16 calculated second cost functions g 2i The value of the second cost function g is chosen to make the second cost function g 2i The voltage vector V that takes the minimum value 2_i As the second optimal voltage vector V 2_n , where n represents the value that makes the second cost function g 2i The index of the voltage vector with the minimum value is n, which is one of the values ​​1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16.

[0084] Preferably, the method for calculating the lumped disturbances of the α-axis, β-axis, and γ-axis observed in this period is as follows: estimating the lumped disturbance F α_est Lumped disturbance F β_est for:

[0085]

[0086] Where η represents the observer gain, which must satisfy η>0. i represents the initial value of the calculated α-axis current. α This represents the α-axis components of the three-phase stator currents (a, b, c) of an open-winding asynchronous motor. i represents the initial value of the calculated β-axis current. β i represents the β-axis component of the abc three-phase stator current of an open-winding asynchronous motor. α i represents the current component along the α axis. β Represents the current component along the β axis;

[0087] Estimate the lumped perturbation F along the γ-axis γ_est for:

[0088]

[0089] Where β2 represents the gain of the second γ-axis observer, i represents the initial value of the calculated γ-axis current. γ Let represent the current components of the three-phase stator current (abc) of an open-winding asynchronous motor on the γ-axis, and s represent the Laplace operator.

[0090] Preferably, the initial value of the calculated α-axis current and the initial value of the calculated β-axis current. The calculation method is as follows: calculate the α-axis current. Delay one control cycle T s The obtained current is the initial value of the α-axis current. Calculate the β-axis current Delay one control cycle T s The obtained current is the initial value of the β-axis current.

[0091] The initial value of the calculated γ-axis current It is the calculated γ-axis current Delay one control cycle T s It was obtained later.

[0092] Preferably, the calculated α-axis current β-axis current The method is as follows:

[0093]

[0094] Among them, U α1_m V represents the first optimal voltage vector. 1_m The corresponding voltage value on the α axis, U β1_m V represents the first optimal voltage vector. 1_m The corresponding voltage value on the β-axis, where m is one of the values ​​1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16; U α2_n Represents the second optimal voltage vector V 2_n The corresponding voltage value on the α axis, U β2_n Represents the second optimal voltage vector V 2_n The corresponding voltage value on the β-axis, n is any one of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16; η represents the observer gain, and η > 0; ω s Represents the synchronous angular frequency of an open-winding asynchronous motor, and:

[0095]

[0096] Where, ω r T represents the rotor angular velocity of an open-winding asynchronous motor. r It is the rotor time constant, satisfying T r =L r / R r L r R represents the rotor inductance of an open-winding asynchronous motor. r This represents the rotor resistance of an open-winding asynchronous motor;

[0097] The calculated γ-axis current for:

[0098]

[0099] Among them, U γ1_m V represents the first optimal voltage vector. 1_m The corresponding voltage value on the γ-axis; U γ2_nRepresents the second optimal voltage vector V 2_n The corresponding voltage value on the γ-axis; β1 represents the gain of the first γ-axis observer, and β2 represents the gain of the second γ-axis observer, which must satisfy β1>0 and β2>0.

[0100] Compared with existing technologies, the beneficial effects of this invention are as follows: The common-center-wire open-winding asynchronous motor drive system consists of two three-phase four-arm converters and one open-winding asynchronous motor. The robust model predictive control method of this invention constructs three disturbance observers to observe the lumped disturbances on the α-axis, β-axis, and γ-axis respectively. A predictive model is designed using the observed lumped disturbances. The optimal voltage vector output by the first three-phase four-arm converter is selected first, followed by the optimal voltage vector output by the second three-phase four-arm converter to determine the optimal voltage vector output by the two three-phase four-arm converters in each control cycle. This achieves robust model predictive control of the common-center-wire open-winding asynchronous motor based on dual three-phase four-arm converters. This invention uses three disturbance observers to observe the lumped disturbances and uses the observed lumped disturbances to replace the motor model in designing the predictive model. When motor parameters are mismatched, the disturbance observers can automatically compensate for the changes in lumped disturbances caused by parameter mismatch, thereby improving the accuracy of the predictive model and significantly improving the robustness of the model predictive control strategy to parameter mismatch. Because the method proposed in this invention uses the observed lumped disturbance to construct the prediction model instead of the motor model, it has stronger parameter robustness to motor parameter mismatch and higher current control accuracy when motor parameters are mismatched. Attached Figure Description

[0101] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0102] Figure 1 This is a topology diagram of a conventional common-center open-winding asynchronous motor drive system based on a virtual capacitor bridge arm.

[0103] Figure 2 This is a topology diagram of the common-neutral open-winding electric drive system based on a dual three-phase four-bridge arm converter studied in this invention.

[0104] Figure 3 This is a flowchart of the robust model predictive control method proposed in this invention.

[0105] Figure 4 This is a control block diagram of the robust model predictive control method proposed in this invention.

[0106] Figure 5The α-axis lumped disturbance F proposed in this invention α_est Control block diagram of the observation method.

[0107] Figure 6 The β-axis lumped disturbance F proposed in this invention β_est Control block diagram of the observation method.

[0108] Figure 7 The γ-axis lumped disturbance F proposed in this invention γ_est Control block diagram of the observation method.

[0109] Figure 8 The figure shows the simulation results of a conventional model predictive control strategy based on the mathematical model and parameters of the motor. In this figure, (a) is the reference value of the α-axis current i. αref and actual value i α (a) is a waveform of region A in (b), and (c) is a local magnified view of region A in (a).

[0110] Figure 9 The figure shows the simulation results of the robust model predictive control method proposed in this invention, where (a) is the α-axis current reference value i. αref and actual value i α (a) is a waveform of region A in (b), and (c) is a local magnified view of region A in (a). Detailed Implementation

[0111] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0112] like Figure 3 As shown, a robust model predictive control method for a common-center-wire open-winding asynchronous motor drive system is presented. The common-center-wire open-winding asynchronous motor drive system consists of two three-phase four-bridge converters and one open-winding asynchronous motor. Figure 2 As shown, in the topology of the common neutral open-winding asynchronous motor drive system based on dual three-phase four-bridge-arm converters studied in this invention, each 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 and lower power devices of the first three arms of the two three-phase four-bridge-arm converters are connected as output terminals to the two ends of the three-phase winding of the open-winding asynchronous motor, respectively. The upper and lower power devices of the fourth arm of the two three-phase four-bridge-arm converters are directly connected through the neutral line. Figure 1 Compared to the conventional common-neutral open-winding asynchronous motor drive system topology based on virtual capacitor bridge arms, this is a significant improvement. Figure 1 The topology uses the neutral point of the bus capacitor of two three-phase three-arm converters to construct the neutral line. Figure 2 The illustrated topology uses the fourth arm of two three-phase four-arm converters to construct the neutral line, thereby increasing the flexibility of neutral line current control and reducing the current stress on the bus current. This invention includes the following steps:

[0113] Step 1: Sample the three-phase stator current of the open-winding asynchronous motor and transform the three-phase stator current to the αβγ three-dimensional stationary coordinate system to obtain the current components of the α-axis, β-axis and γ-axis respectively.

[0114] Using a current sensor to sample the abc three-phase stator current i of an open-winding asynchronous motor a i b i c Then, transform it to the αβγ three-dimensional stationary coordinate system to obtain the current components i along the α-axis, β-axis, and γ-axis. α i β i γ ,satisfy:

[0115]

[0116] Among them, i a i represents the stator current of phase a of an open-winding asynchronous motor. b i represents the b-phase stator current of an open-winding asynchronous motor. c i represents the c-phase stator current of an open-winding asynchronous motor. α i represents the α-axis component of the abc three-phase stator current of an open-winding asynchronous motor. β i represents the β-axis component of the abc three-phase stator current of an open-winding asynchronous motor. γ This represents the component of the three-phase stator current (a, b, c) of an open-winding asynchronous motor on the γ-axis.

[0117] Step 2: Calculate the voltage reference value on the αβγ three-dimensional stationary coordinate system using the current components of the α-axis, β-axis, and γ-axis, as well as the lumped disturbances of the α-axis, β-axis, and γ-axis observed in the previous cycle.

[0118] Based on the obtained current i α i β i γ Calculate the voltage reference value u in the three-dimensional stationary coordinate system αβγ. αref u βref u γref ,satisfy:

[0119]

[0120] Among them, u αrefu represents the voltage reference value on the α-axis in the αβγ three-dimensional stationary coordinate system. βref u represents the voltage reference value on the β axis. γref Indicates the voltage reference value on the γ-axis, i αref i represents the reference value of the stator current on the α-axis of an open-winding asynchronous motor. βref i represents the reference value of the stator current on the β-axis of an open-winding asynchronous motor. γref T represents the reference value of the stator current on the γ-axis of an open-winding asynchronous motor. s The control period is typically chosen to be between 50 μs and 100 μs, and d is the proportionality coefficient between the α and β axes, satisfying the following conditions: σ represents the leakage flux coefficient, which satisfies L s L represents the stator inductance of an open-winding asynchronous motor. m L represents the mutual inductance of an open-winding asynchronous motor. r L represents the rotor inductance of an open-winding asynchronous motor. 1s F represents the stator leakage inductance of an open-winding asynchronous motor. α_est0 F represents the lumped disturbance of the α-axis estimated in the previous period. β_est0 F represents the lumped perturbation of the β-axis estimated in the previous period. γ_est0 F represents the lumped perturbation of the γ-axis estimated in the previous period. α_est0 F β_est0 F γ_est0 The stator current reference value i is obtained by delaying the lumped disturbance observed in the previous cycle by one control cycle. αref i βref i γref The calculation method satisfies:

[0121]

[0122] Among them, i dref The reference value for the excitation current of an open-winding asynchronous motor is usually determined by the rated excitation current, i qref The torque current reference value for an open-winding asynchronous motor is typically determined by the output of the outer speed loop. 0ref The zero-sequence current reference value for an open-winding asynchronous motor is usually set to 0, θ. r The angle of the rotor magnetic field of an open-winding asynchronous motor.

[0123] Step 3: Based on the conduction state of the power devices on the four arms of the two three-phase four-arm converters, define the values ​​of the switching states corresponding to the four arms of the two three-phase four-arm converters respectively; determine the 16 voltage vectors of the two three-phase four-arm converters based on the values ​​of the different switching states.

[0124] Define the switching state corresponding to the first arm of the first three-phase four-arm converter as S. a1 Define the switching state corresponding to the second arm of the first three-phase four-arm converter as S. b1 Define the switching state corresponding to the third arm of the first three-phase four-arm converter as S. c1 Define the switching state corresponding to the fourth arm of the first three-phase four-arm converter as S. 01 ;

[0125] When the upper power device of the first arm of the first three-phase four-arm converter is turned on and the lower power device is turned off, S is defined as follows: a1 =1; When the upper power device of the first arm of the first three-phase four-arm converter is turned off and the lower power device is turned on, S is defined as 1. a1 =0;

[0126] When the upper power device of the second arm of the first three-phase four-arm converter is turned on and the lower power device is turned off, S is defined as... b1 =1; When the upper power device of the second arm of the first three-phase four-arm converter is turned off and the lower power device is turned on, S is defined as 1. b1 =0;

[0127] When the upper power device of the third arm of the first three-phase four-arm converter is turned on while the lower power device is turned off, S is defined as... c1 =1; When the upper power device of the third arm of the first three-phase four-arm converter is turned off and the lower power device is turned on, S is defined as 1. c1 =0;

[0128] When the upper power device of the fourth arm of the first three-phase four-arm converter is turned on and the lower power device is turned off, S is defined as... 01 =1; When the upper power device of the fourth arm of the first three-phase four-arm converter is turned off and the lower power device is turned on, S is defined as 1. 01 =0.

[0129] Define the 16 voltage vectors V of the first three-phase four-arm converter 1_i (i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16) satisfies:

[0130] When S a1 =0, S b1 =0, S c1 =0, S 01 When = 0, the corresponding voltage vector is defined as V 1_1 ;

[0131] When Sa1 =0, S b1 =0, S c1 =0, S 01 When = 1, the corresponding voltage vector is defined as V 1_2 ;

[0132] When S a1 =0, S b1 =0, S c1 =1,S 01 When = 0, the corresponding voltage vector is defined as V 1_3 ;

[0133] When S a1 =0, S b1 =0, S c1 =1,S 01 When = 1, the corresponding voltage vector is defined as V 1_4 ;

[0134] When S a1 =0, S b1 =1,S c1 =0, S 01 When = 0, the corresponding voltage vector is defined as V 1_5 ;

[0135] When S a1 =0, S b1 =1,S c1 =0, S 01 When = 1, the corresponding voltage vector is defined as V 1_6 ;

[0136] When S a1 =0, S b1 =1,S c1 =1,S 01 When = 0, the corresponding voltage vector is defined as V 1_7 ;

[0137] When S a1 =0, S b1 =1,S c1 =1,S 01 When = 1, the corresponding voltage vector is defined as V 1_8 ;

[0138] When S a1 =1,S b1 =0, S c1 =0, S 01 When = 0, the corresponding voltage vector is defined as V 1_9 ;

[0139] When S a1 =1,S b1 =0, Sc1 =0, S 01 When = 1, the corresponding voltage vector is defined as V 1_10 ;

[0140] When S a1 =1,S b1 =0, S c1 =1,S 01 When = 0, the corresponding voltage vector is defined as V 1_11 ;

[0141] When S a1 =1,S b1 =0, S c1 =1,S 01 When = 1, the corresponding voltage vector is defined as V 1_12 ;

[0142] When S a1 =1,S b1 =1,S c1 =0, S 01 When = 0, the corresponding voltage vector is defined as V 1_13 ;

[0143] When S a1 =1,S b1 =1,S c1 =0, S 01 When = 1, the corresponding voltage vector is defined as V 1_14 ;

[0144] When S a1 =1,S b1 =1,S c1 =1,S 01 When = 0, the corresponding voltage vector is defined as V 1_15 ;

[0145] When S a1 =1,S b1 =1,S c1 =1,S 01 When = 1, the corresponding voltage vector is defined as V 1_16 .

[0146] Define the switching state corresponding to the first arm of the second three-phase four-arm converter as S. a2 Define the switching state corresponding to the second arm of the second three-phase four-arm converter as S. b2 Define the switching state corresponding to the third arm of the second three-phase four-arm converter as S. c2 Define the switching state corresponding to the fourth arm of the second three-phase four-arm converter as S. 02 ;

[0147] When the upper power device of the first arm of the second three-phase four-arm converter is turned on and the lower power device is turned off, S is defined as follows: a2 =1; When the upper power device of the first arm of the second three-phase four-arm converter is turned off and the lower power device is turned on, S is defined as 1. a2 =0;

[0148] When the upper power device of the second arm of the second three-phase four-arm converter is turned on and the lower power device is turned off, S is defined as... b2 =1; When the upper power device of the second arm of the second three-phase four-arm converter is turned off and the lower power device is turned on, S is defined as 1. b2 =0;

[0149] When the upper power device of the third arm of the second three-phase four-arm converter is turned on and the lower power device is turned off, S is defined as... c2 =1; When the upper power device of the third arm of the second three-phase four-arm converter is turned off and the lower power device is turned on, S is defined as 1. c2 =0;

[0150] When the upper power device of the fourth arm of the second three-phase four-arm converter is turned on and the lower power device is turned off, S is defined as... 02 =1; When the upper power device of the fourth arm of the second three-phase four-arm converter is turned off and the lower power device is turned on, S is defined as 1. 02 =0;

[0151] Define the 16 voltage vectors V of the second three-phase four-arm converter. 2_i (i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16) satisfies:

[0152] When S a2 =0, S b2 =0, S c2 =0, S 02 When = 0, the corresponding voltage vector is defined as V 2_1 ;

[0153] When S a2 =0, S b2 =0, S c2 =0, S 02 When = 1, the corresponding voltage vector is defined as V 2_2 ;

[0154] When S a2 =0, S b2 =0, S c2 =1,S 02 When = 0, the corresponding voltage vector is defined as V2_3 ;

[0155] When S a2 =0, S b2 =0, S c2 =1,S 02 When = 1, the corresponding voltage vector is defined as V 2_4 ;

[0156] When S a2 =0, S b2 =1,S c2 =0, S 02 When = 0, the corresponding voltage vector is defined as V 2_5 ;

[0157] When S a2 =0, S b2 =1,S c2 =0, S 02 When = 1, the corresponding voltage vector is defined as V 2_6 ;

[0158] When S a2 =0, S b2 =1,S c2 =1,S 02 When = 0, the corresponding voltage vector is defined as V 2_7 ;

[0159] When S a2 =0, S b2 =1,S c2 =1,S 02 When = 1, the corresponding voltage vector is defined as V 2_8 ;

[0160] When S a2 =1,S b2 =0, S c2 =0, S 02 When = 0, the corresponding voltage vector is defined as V 2_9 ;

[0161] When S a2 =1,S b2 =0, S c2 =0, S 02 When = 1, the corresponding voltage vector is defined as V 2_10 ;

[0162] When S a2 =1,S b2 =0, S c2 =1,S 02 When = 0, the corresponding voltage vector is defined as V 2_11 ;

[0163] When S a2 =1,S b2 =0, S c2 =1,S 02 When = 1, the corresponding voltage vector is defined as V 2_12 ;

[0164] When S a2 =1,S b2 =1,S c2 =0, S 02 When = 0, the corresponding voltage vector is defined as V 2_13 ;

[0165] When S a2 =1,S b2 =1,S c2 =0, S 02 When = 1, the corresponding voltage vector is defined as V 2_14 ;

[0166] When S a2 =1,S b2 =1,S c2 =1,S 02 When = 0, the corresponding voltage vector is defined as V 2_15 ;

[0167] When S a2 =1,S b2 =1,S c2 =1,S 02 When = 1, the corresponding voltage vector is defined as V 2_16 .

[0168] Step 4: Calculate the voltage values ​​of the voltage vectors in the αβγ three-dimensional stationary coordinate system based on the switching states of the 16 voltage vectors of the two three-phase four-arm converters.

[0169] Based on the definition of the 16 voltage vectors V of the first three-phase four-arm converter 1_i The switch state value S corresponding to (i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16) a1 S b1 S c1 and S 01 Calculate 16 voltage vectors V 1_i The voltage value U of (i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16) 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:

[0170]

[0171] Among them, U dc1 S represents the DC bus voltage of the first three-phase four-arm converter. a1_i S b1_i S c1_i and S 01_i Representing the i-th voltage vector V 1_i The value S of the switch state corresponding to (i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16) a1 S b1 S c1 and S 01 U α1_i V represents the i-th voltage vector. 1_i The voltage value U on the α axis for (i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16) β1_i V represents the i-th voltage vector. 1_i The voltage value U on the β axis for (i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16) γ1_i V represents the i-th voltage vector. 1_i Voltage values ​​on the γ-axis for (i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16).

[0172] Based on the 16 voltage vectors V of the second three-phase four-arm converter as defined 2_i The switch state value S corresponding to (i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16) a2 S b2 S c2 and S 02 Calculate 16 voltage vectors V 2_i The voltage value U of (i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16) 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:

[0173]

[0174] Among them, U dc2 S represents the DC bus voltage of the second three-phase four-arm converter. a2_i S b2_i S c2_i and S 02_i Representing the i-th voltage vector V 2_i The value S of the switch state corresponding to (i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16) a2 S b2 S c2 and S 02 U α2_i V represents the i-th voltage vector. 2_i The voltage value U on the α axis for (i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16) β2_i V represents the i-th voltage vector. 2_i The voltage value U on the β axis for (i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16) γ2_i V represents the i-th voltage vector. 2_i Voltage values ​​on the γ-axis for (i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16).

[0175] Step 5: Calculate the values ​​of 16 first cost functions based on the voltage reference values ​​in the αβγ three-dimensional stationary coordinate system and the voltage values ​​of the 16 voltage vectors of the first three-phase four-arm converter in the αβγ three-dimensional stationary coordinate system. Compare the values ​​of the 16 first cost functions and select the voltage vector that minimizes the value of the first cost function as the first optimal voltage vector.

[0176] The obtained voltage reference value u αref u βref u γref And the 16 voltage vectors V of the first three-phase four-arm converter obtained 1_i The voltage value U on the α axis corresponding to (i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16) α1_i Voltage value U on the β axis β1_i Voltage value U on the γ axis γ1_i Substituting these values ​​into the following formula sequentially, we obtain 16 first cost functions g. 1i The values ​​of (i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16) satisfy:

[0177] g1i =|u αref -U α1_i | + |u βref -U β1_i |+k1|u γref -U γ1_i |

[0178] Among them, g 1i Let i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, and k1 be the first weighting coefficient. When executing the algorithm, the first weighting coefficient k1 is adjusted according to the control effect of the abc three-phase current and zero-sequence current of the open-winding asynchronous motor, and is generally taken between 0.5 and 2.

[0179] Compare the 16 first cost functions g obtained from the calculation 1i The value of (i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16) is chosen to make g... 1i The voltage vector V that takes the minimum value 1_i Let this be the optimal voltage vector, denoted as the first optimal voltage vector V. 1_m Where m represents making g 1i The subscript of the voltage vector with the minimum value is m, which is one of the values ​​1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16.

[0180] Step 6: Calculate the values ​​of 16 second cost functions based on the voltage reference value in the αβγ three-dimensional stationary coordinate system, the voltage value in the αβγ three-dimensional stationary coordinate system corresponding to the first optimal voltage vector, and the voltage values ​​of the 16 voltage vectors of the second three-phase four-arm converter in the αβγ three-dimensional stationary coordinate system. Compare the values ​​of the 16 second cost functions and select the voltage vector that minimizes the value of the second cost function as the second optimal voltage vector.

[0181] The obtained voltage reference value u αref u βref u γref The first optimal voltage vector V obtained 1_m The corresponding voltage value U on the α axis α1_m U on the β axis β1_m U on the γ axis γ1_m (m is any value among 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16) and the resulting 16 voltage vectors V of the second three-phase four-arm converter. 2_iThe voltage value U on the α axis corresponding to (i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16) α2_i Voltage value U on the β axis β2_i Voltage value U on the γ axis γ2_i Substituting these values ​​into the following formula sequentially, we obtain 16 second cost functions g. 2i The values ​​of (i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16) satisfy:

[0182] g2i=|uαref-(Uα1_m-Uα2_i)|+|uβref-(Uβ1_m-Uβ2_i)|+k2|uγref-(Uγ1_m-Uγ2_i)|

[0183] Among them, g 2i The second cost function is represented by (i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16), and k2 is the second weighting coefficient. When executing the algorithm, it is adjusted according to the control effect of the abc three-phase current and zero-sequence current of the open-winding asynchronous motor, and is generally taken between 0.5 and 2.

[0184] Compare the 16 calculated second cost functions g 2i The value of (i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16) is chosen to make the second cost function g... 2i The voltage vector V that takes the minimum value 2_i (i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16) is the optimal voltage vector, denoted as the second optimal vector V. 2_n Where n represents the value that makes g 2i The index of the voltage vector with the minimum value is n, which is one of the values ​​1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16.

[0185] Step 7: Control the first three-phase four-arm converter using the value of the switching state corresponding to the first optimal voltage vector, and control the second three-phase four-arm converter using the value of the switching state corresponding to the second optimal voltage vector; at the same time, calculate the lumped disturbances of the α-axis, β-axis and γ-axis observed in this cycle.

[0186] Select the first optimal voltage vector V 1_m Second optimal voltage vector V 2_nThe outputs are used as the final optimal voltage vectors for the first and second three-phase four-arm converters, respectively, to control the first and second three-phase four-arm converters, thereby achieving robust model predictive control of the open-winding asynchronous motor. Since the above control method uses a disturbance observer to perform lumped disturbance observation and utilizes the observed disturbance to replace the motor model in constructing the predictive model and model predictive control strategy, the method is no longer affected by parameters such as the motor stator resistance. Therefore, when motor parameters are mismatched, the method proposed in this invention exhibits stronger parameter robustness.

[0187] like Figure 5 and Figure 6 As shown, the lumped disturbance F of the α-axis at the current moment α_est Lumped disturbance F along the β axis β_est The estimation method includes the following steps:

[0188] Step S1: Calculate the current according to the following formula. satisfy:

[0189]

[0190] in, This represents the calculated α-axis current. U represents the calculated β-axis current. α1_m V represents the first optimal voltage vector. 1_m The corresponding voltage value on the α axis, U β1_m V represents the first optimal voltage vector. 1_m The corresponding voltage value on the β-axis (m is one of the values ​​1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16); U α2_n Represents the second optimal voltage vector V 2_n The corresponding voltage value on the α axis, U β2_n Represents the second optimal voltage vector V 2_n The corresponding voltage value on the β-axis (n is one of the values ​​1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16); η represents the observer gain, which must satisfy η > 0. i represents the initial value of the calculated α-axis current. α This represents the α-axis components of the three-phase stator currents (a, b, c) of an open-winding asynchronous motor. i represents the initial value of the calculated β-axis current. β Let ω represent the β-axis components of the abc three-phase stator currents of an open-winding asynchronous motor. Let s represent the Laplace operator. s The synchronous angular frequency of an open-winding asynchronous motor is given by:

[0191]

[0192] Where, ω r T represents the rotor angular velocity of an open-winding asynchronous motor. r It is the rotor time constant, satisfying T r =L r / R r L r R represents the rotor inductance of an open-winding asynchronous motor. r This represents the rotor resistance of an open-winding asynchronous motor.

[0193] Step S2: Estimate the lumped disturbance F according to the following formula. α_est Lumped disturbance F β_est ,satisfy:

[0194]

[0195] The initial value of the calculated α-axis current and the initial value of the calculated β-axis current. The calculation method satisfies the following steps: Calculate the α-axis current... Delay one control cycle T s The obtained current is the initial value of the α-axis current. Calculate the β-axis current Delay one control cycle T s The obtained current is the initial value of the β-axis current.

[0196] The lumped disturbance F along the γ axis γ_est The estimation method includes the following steps:

[0197] Step 1: Calculate the current using the following formula. satisfy:

[0198]

[0199] in, U represents the calculated γ-axis current. γ1_m V represents the first optimal voltage vector. 1_m The corresponding voltage value on the γ-axis (m is one of the values ​​1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16); U γ2_n Represents the second optimal voltage vector V 2_n The corresponding voltage value on the γ-axis (n is one of the values ​​1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16); β1 represents the gain of the first γ-axis observer, and β2 represents the gain of the second γ-axis observer, which must satisfy β1>0, β2>0. i represents the initial value of the calculated γ-axis current. γ Let represent the components of the three-phase stator currents abc of an open-winding asynchronous motor on the γ-axis, and s represent the Laplace operator.

[0200] Step 2: Estimate the lumped disturbance F along the γ-axis according to the following formula. γ_est ,satisfy:

[0201]

[0202] The initial value of the calculated γ-axis current It is the calculated γ-axis current Delay one control cycle T s It was obtained later.

[0203] Figure 3 This is a control flowchart of the robust model predictive control strategy proposed in this invention. Figure 4 This is a control block diagram of the robust model predictive control strategy proposed in this invention. Figure 5 , Figure 6 and Figure 7 The lumped disturbance F along the α-axis proposed in this invention is respectively α_est β-axis lumped disturbance F β_est and γ-axis lumped disturbance F γ_est Control block diagram of the observation method.

[0204] according to Figure 5 , Figure 6 and Figure 7 It can achieve lumped disturbance observation, and then based on Figure 3 This enables the implementation of the robust model predictive control method proposed in this invention. Combined with... Figure 4 This invention enables a dual-loop control strategy for a common-neutral open-winding asynchronous motor drive system based on a dual three-phase four-bridge arm converter, consisting of an outer speed loop and an inner current loop. The outer speed loop employs a proportional-integral (PI) controller, which outputs a torque and current reference value i for the open-winding asynchronous motor. qref The robust model predictive control method of this invention is used in the inner current loop.

[0205] like Figure 4 As shown, the specific implementation of the method proposed in this invention is as follows:

[0206] First, based on the measured motor speed n r and the given motor speed reference value n ref The torque current reference value i is obtained through the PI controller. qref Wherein, the motor speed n r The measured angular velocity ω r The calculation yields n p This indicates the number of pole pairs of the motor.

[0207] Second, based on the given torque current reference value i qref Excitation current reference value i dref and zero-sequence current reference value i 0ref The reference current value i is obtained after coordinate transformation. αref i βref i γref Among them, i dref Determined by the rated excitation current of the motor, i 0ref It is usually set to 0.

[0208] Third, based on the current reference value i αref i βref i γref Current feedback value i α i β i γ The lumped disturbance F observed in the previous period α_est0 F β_est0 F γ_est0 Calculate the voltage reference value u αref u βref u γref Among them, the lumped disturbance F observed in the previous period α_est0 F β_est0 F γ_est0 F observed in this period α_est F β_est F γ_est It is obtained by delaying for one control cycle.

[0209] Fourth, based on the voltage values ​​and voltage reference value u of the 16 voltage vectors of the first three-phase four-arm converter in the αβγ three-dimensional stationary coordinate system. αref u βref u γref Calculate the first cost function g 1i The values ​​of (i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16) are compared with the first cost function g. 1i The size of g is obtained. 1i The voltage vector with the minimum value is the first optimal voltage vector V. 1_m Where m represents the value that makes the first cost function g 1i The subscript of the voltage vector with the minimum value is m, which is one of the values ​​1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16.

[0210] Fifth, based on the first optimal voltage vector V 1_mCalculate the second cost function g using the voltage values ​​(m is any one of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16) in the αβγ three-dimensional stationary coordinate system and the voltage values ​​of the 16 voltage vectors of the second three-phase four-arm converter in the αβγ three-dimensional stationary coordinate system. 2i The values ​​of (i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16) are compared with the second cost function g. 2i The size of the second cost function g is obtained. 2i The voltage vector with the minimum value is the second optimal voltage vector V. 2_n Where n represents the value that makes g 2i The index of the voltage vector with the minimum value is n, which is one of the values ​​1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16.

[0211] Sixth, the first optimal voltage vector V 1_m The corresponding switch state output is given to the first three-phase four-arm converter to control the first three-phase four-arm converter and convert the second optimal voltage vector V. 2_n The corresponding switch state is output to the second three-phase four-arm converter to realize the control of the second three-phase four-arm converter.

[0212] Seventh, based on the selected optimal voltage vector V 1_m and V 2_n The corresponding voltage value U α1_m U β1_m U γ1_m and U α2_n U β2_n U γ2_n The synchronous angular frequency ω of the motor s The motor current i α i β i γ The lumped disturbance F observed in this period α_est F β_est F γ_est And calculate the voltage reference value u for the next cycle. αref u βref u γref Make preparations.

[0213] To verify the effectiveness of this invention, simulation verification was performed. The motor parameters used in the simulation are shown in Table 1.

[0214] Table 1 Parameters of Open-Winding Asynchronous Motors

[0215]

[0216] During simulation, the motor reference speed n ref Set to 1500 r / min, at 0.4 s, the load torque suddenly increases from 0 Nm to 15 Nm, and 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 Set to 0A, the DC-side voltage U of the first three-phase four-arm converter dc1 The DC-side voltage U of the second three-phase four-arm converter is 400V. dc2 The voltage is 200V. The proportional coefficient in the outer loop proportional-integral controller is 0.15, and the integral coefficient is 7. The inner loop current uses both a conventional model predictive control strategy based on the motor mathematical model and parameters, and the robust model predictive control method proposed in this invention. The first weighting coefficient k1 is set to 0.5, the second weighting coefficient k2 is set to 0.5, the observer gain η is set to 8000, the first γ-axis observer gain β1 is set to 500, and the second γ-axis observer gain β2 is set to 250000. The simulation results of the conventional method are as follows: Figure 8 As shown, the simulation results of the method proposed in this invention are as follows: Figure 9 As shown. During the simulation, the stator resistor R used in the controller... s The value was set to four times the true value to test the control effectiveness of the two methods when parameter mismatch occurred due to changes in factors such as temperature.

[0217] contrast Figure 8 and Figure 9 It is evident that both conventional methods and the method proposed in this invention can achieve rapid current tracking control during sudden load changes. However, due to the stator resistance R... s There are errors; the current error of conventional methods is relatively large, with a maximum error reaching 1.85A. Figure 8 As shown in (c). The method proposed in this invention improves parameter robustness by employing a lumped disturbance observer for disturbance observation and compensation, and its current error is within the stator resistance R. s Even with mismatch, the error remains small, with a maximum error of approximately 1.58A. Figure 9 As shown in (c). Comparison Figure 8 and Figure 9 It is evident that the method proposed in this invention still exhibits better current control accuracy even with parameter mismatch, demonstrating the advantages and superiority of the proposed method.

[0218] 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 principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A robust model predictive control method for a common-center-wire open-winding asynchronous motor drive system, characterized in that, The common-neutral open-winding asynchronous motor drive system consists of two three-phase four-bridge converters and one open-winding asynchronous motor. Each bridge arm of the two three-phase four-bridge converters is composed of an upper power device and a lower power device connected in series. The steps are as follows: Step 1: Sample the three-phase stator current of the open-winding asynchronous motor and transform the three-phase stator current to the αβγ three-dimensional stationary coordinate system to obtain the current components of the α-axis, β-axis and γ-axis respectively; Step 2: Calculate the voltage reference value on the αβγ three-dimensional stationary coordinate system using the current components of the α-axis, β-axis, and γ-axis, as well as the lumped perturbations of the α-axis, β-axis, and γ-axis observed in the previous cycle. Step 3: Based on the conduction state of the power devices on the four arms of the two three-phase four-arm converters, define the values ​​of the switching states corresponding to the four arms of the two three-phase four-arm converters respectively; determine the 16 voltage vectors of the two three-phase four-arm converters based on the values ​​of the different switching states. Step 4: Calculate the voltage values ​​of the voltage vectors in the αβγ three-dimensional stationary coordinate system based on the switching states of the 16 voltage vectors of the two three-phase four-arm converters; Step 5: Calculate the values ​​of 16 first cost functions based on the voltage reference values ​​in the αβγ three-dimensional stationary coordinate system and the voltage values ​​of the 16 voltage vectors of the first three-phase four-arm converter in the αβγ three-dimensional stationary coordinate system. Compare the values ​​of the 16 first cost functions and select the voltage vector that minimizes the value of the first cost function as the first optimal voltage vector. Step 6: Calculate the values ​​of 16 second cost functions based on the voltage reference value in the αβγ three-dimensional stationary coordinate system, the voltage value in the αβγ three-dimensional stationary coordinate system corresponding to the first optimal voltage vector, and the voltage values ​​of the 16 voltage vectors of the second three-phase four-arm converter in the αβγ three-dimensional stationary coordinate system. Compare the values ​​of the 16 second cost functions and select the voltage vector that minimizes the value of the second cost function as the second optimal voltage vector. Step 7: Control the first three-phase four-arm converter using the switching state value corresponding to the first optimal voltage vector, and control the second three-phase four-arm converter using the switching state value corresponding to the second optimal voltage vector; at the same time, calculate the lumped disturbances of the α-axis, β-axis and γ-axis observed in this cycle; The upper and lower power devices of the first three arms of the two three-phase four-arm converters are connected as output terminals to the two ends of the three-phase winding of the open-winding asynchronous motor, respectively; the upper and lower power devices of the fourth arm of the two three-phase four-arm converters are directly connected through the neutral line.

2. The robust model predictive control method for a common-centerline open-winding asynchronous motor drive system according to claim 1, characterized in that, The method for calculating the voltage reference value in the αβγ three-dimensional stationary coordinate system is as follows: ； Among them, u αref u represents the voltage reference value on the α-axis in the αβγ three-dimensional stationary coordinate system. βref u represents the voltage reference value on the β axis. γref Indicates the voltage reference value on the γ-axis, i αref i represents the reference value of the stator current on the α-axis of an open-winding asynchronous motor. βref i represents the reference value of the stator current on the β-axis of an open-winding asynchronous motor. γref T represents the reference value of the stator current on the γ-axis of an open-winding asynchronous motor. s This represents the control period, d is the proportionality coefficient of the α-axis and β-axis, and i α i represents the current component of the three-phase stator current (a, b, c) of an open-winding asynchronous motor on the α-axis. β i represents the current component of the three-phase stator current (a, b, c) of an open-winding asynchronous motor on the β-axis. γ L represents the current components of the three-phase stator current (a, b, c) of an open-winding asynchronous motor along the γ-axis. 1s F represents the stator leakage inductance of an open-winding asynchronous motor. α_est0 F represents the lumped disturbance of the α-axis estimated in the previous period. β_est0 F represents the lumped perturbation of the β-axis estimated in the previous period. γ_est0 This represents the lumped perturbation of the γ-axis estimated in the previous period.

3. The robust model predictive control method for a common-centerline open-winding asynchronous motor drive system according to claim 2, characterized in that, The method for transforming the three-phase stator current to the αβγ three-dimensional stationary coordinate system to obtain the current components along the α-axis, β-axis, and γ-axis is as follows: The three-phase stator currents i, a, b, and c of the open-winding asynchronous motor are... a i b i c Transforming to the αβγ three-dimensional stationary coordinate system, we obtain the current components i along the α-axis, β-axis, and γ-axis. α i β i γ for: ； Among them, i a i represents the a-phase stator current of an open-winding asynchronous motor. b i represents the b-phase stator current of an open-winding asynchronous motor. c This represents the c-phase stator current of an open-winding asynchronous motor; The scaling factors of the α-axis and β-axis , Represents the leakage flux coefficient, and L s L represents the stator inductance of an open-winding asynchronous motor. m L represents the mutual inductance of an open-winding asynchronous motor. r This represents the rotor inductance of an open-winding asynchronous motor; The lumped disturbance F estimated in the previous period α_est0 F β_est0 F γ_est0 These are obtained by delaying the lumped disturbance observed in the previous cycle by one control cycle. The stator current reference value i αref i βref i γref The calculation method is as follows: ； Among them, i dref i is the reference value for the excitation current of an open-winding asynchronous motor. qref i is the reference value for the torque current of an open-winding asynchronous motor. 0ref θ is the reference value for the zero-sequence current of an open-winding asynchronous motor. r The angle of the rotor magnetic field of an open-winding asynchronous motor.

4. The robust model predictive control method for a common-centerline open-winding asynchronous motor drive system according to claim 3, characterized in that, Define the switching state corresponding to the first arm of the first three-phase four-arm converter as S. a1 Define the switching state corresponding to the second arm of the first three-phase four-arm converter as S. b1 Define the switching state corresponding to the third arm of the first three-phase four-arm converter as S. c1 Define the switching state corresponding to the fourth arm of the first three-phase four-arm converter as S. 01 ; When the upper power device of the first arm of the first three-phase four-arm converter is turned on and the lower power device is turned off, the switch state S is... a1 =1; When the upper power device of the first arm of the first three-phase four-arm converter is turned off and the lower power device is turned on, the switching state S is 1. a1 =0; When the upper power device of the second arm of the first three-phase four-arm converter is turned on and the lower power device is turned off, the switch state S is... b1 =1; When the upper power device of the second arm of the first three-phase four-arm converter is turned off and the lower power device is turned on, the switching state S is 1. b1 =0; When the upper power device of the third arm of the first three-phase four-arm converter is turned on and the lower power device is turned off, the switch state S is... c1 =1; When the upper power device of the third arm of the first three-phase four-arm converter is turned off and the lower power device is turned on, the switching state S is 1. c1 =0; When the upper power device of the fourth arm of the first three-phase four-arm converter is turned on and the lower power device is turned off, the switch state S is... 01 =1; When the upper power device of the fourth arm of the first three-phase four-arm converter is turned off and the lower power device is turned on, the switching state S is 1. 01 =0; The first three-phase four-arm converter has 16 voltage vectors V 1_i satisfy: When S a1 =0, S b1 =0, S c1 =0, S 01 When =0, the corresponding voltage vector is defined as V 1_1 ; When S a1 =0, S b1 =0, S c1 =0, S 01 When =1, the corresponding voltage vector is defined as V 1_2 ; When S a1 =0, S b1 =0, S c1 =1,S 01 When =0, the corresponding voltage vector is defined as V 1_3 ; When S a1 =0, S b1 =0, S c1 =1,S 01 When =1, the corresponding voltage vector is defined as V 1_4 ; When S a1 =0, S b1 =1,S c1 =0, S 01 When =0, the corresponding voltage vector is defined as V 1_5 ; When S a1 =0, S b1 =1,S c1 =0, S 01 When =1, the corresponding voltage vector is defined as V 1_6 ; When S a1 =0, S b1 =1,S c1 =1,S 01 When =0, the corresponding voltage vector is defined as V 1_7 ; When S a1 =0, S b1 =1,S c1 =1,S 01 When =1, the corresponding voltage vector is defined as V 1_8 ; When S a1 =1,S b1 =0, S c1 =0, S 01 When =0, the corresponding voltage vector is defined as V 1_9 ; When S a1 =1,S b1 =0, S c1 =0, S 01 When =1, the corresponding voltage vector is defined as V 1_10 ; When S a1 =1,S b1 =0, S c1 =1,S 01 When =0, the corresponding voltage vector is defined as V 1_11 ; When S a1 =1,S b1 =0, S c1 =1,S 01 When =1, the corresponding voltage vector is defined as V 1_12 ; When S a1 =1,S b1 =1,S c1 =0, S 01 When =0, the corresponding voltage vector is defined as V 1_13 ; When S a1 =1,S b1 =1,S c1 =0, S 01 When =1, the corresponding voltage vector is defined as V 1_14 ; When S a1 =1,S b1 =1,S c1 =1,S 01 When =0, the corresponding voltage vector is defined as V 1_15 ; When S a1 =1,S b1 =1,S c1 =1,S 01 When =1, the corresponding voltage vector is defined as V 1_16 Where i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16; Define the switching state corresponding to the first arm of the second three-phase four-arm converter as S. a2 Define the switching state corresponding to the second arm of the second three-phase four-arm converter as S. b2 Define the switching state corresponding to the third arm of the second three-phase four-arm converter as S. c2 Define the switching state corresponding to the fourth arm of the second three-phase four-arm converter as S. 02 ; When the upper power device of the first arm of the second three-phase four-arm converter is turned on and the lower power device is turned off, the switch state S is... a2 =1; When the upper power device of the first arm of the second three-phase four-arm converter is turned off and the lower power device is turned on, the switching state S is 1. a2 =0; When the upper power device of the second arm of the second three-phase four-arm converter is turned on and the lower power device is turned off, the switch state S b2 =1; When the upper power device of the second arm of the second three-phase four-arm converter is turned off and the lower power device is turned on, the switching state S is 1. b2 =0; When the upper power device of the third arm of the second three-phase four-arm converter is turned on and the lower power device is turned off, the switch state S is... c2 =1; When the upper power device of the third arm of the second three-phase four-arm converter is turned off and the lower power device is turned on, the switching state S is 1. c2 =0; When the upper power device of the fourth arm of the second three-phase four-arm converter is turned on and the lower power device is turned off, S is defined as... 02 =1; When the upper power device of the fourth arm of the second three-phase four-arm converter is turned off and the lower power device is turned on, S is defined as 1. 02 =0; Define the 16 voltage vectors V of the second three-phase four-arm converter. 2_i satisfy: When S a2 =0, S b2 =0, S c2 =0, S 02 When =0, the corresponding voltage vector is defined as V 2_1 ; When S a2 =0, S b2 =0, S c2 =0, S 02 When =1, the corresponding voltage vector is defined as V 2_2 ; When S a2 =0, S b2 =0, S c2 =1,S 02 When =0, the corresponding voltage vector is defined as V 2_3 ; When S a2 =0, S b2 =0, S c2 =1,S 02 When =1, the corresponding voltage vector is defined as V 2_4 ; When S a2 =0, S b2 =1,S c2 =0, S 02 When =0, the corresponding voltage vector is defined as V 2_5 ; When S a2 =0, S b2 =1,S c2 =0, S 02 When =1, the corresponding voltage vector is defined as V 2_6 ; When S a2 =0, S b2 =1,S c2 =1,S 02 When =0, the corresponding voltage vector is defined as V 2_7 ; When S a2 =0, S b2 =1,S c2 =1,S 02 When =1, the corresponding voltage vector is defined as V 2_8 ; When S a2 =1,S b2 =0, S c2 =0, S 02 When =0, the corresponding voltage vector is defined as V 2_9 ; When S a2 =1,S b2 =0, S c2 =0, S 02 When =1, the corresponding voltage vector is defined as V 2_10 ; When S a2 =1,S b2 =0, S c2 =1,S 02 When =0, the corresponding voltage vector is defined as V 2_11 ; When S a2 =1,S b2 =0, S c2 =1,S 02 When =1, the corresponding voltage vector is defined as V 2_12 ; When S a2 =1,S b2 =1,S c2 =0, S 02 When =0, the corresponding voltage vector is defined as V 2_13 ; When S a2 =1,S b2 =1,S c2 =0, S 02 When =1, the corresponding voltage vector is defined as V 2_14 ; When S a2 =1,S b2 =1,S c2 =1,S 02 When =0, the corresponding voltage vector is defined as V 2_15 ; When S a2 =1,S b2 =1,S c2 =1,S 02 When =1, the corresponding voltage vector is defined as V 2_16 ; Calculate 16 voltage vectors V 1_i The voltage value U in the αβγ three-dimensional stationary coordinate system α1_i U β1_i U γ1_ The method is as follows: ； Among them, U dc1 S represents the DC bus voltage of the first three-phase four-arm converter. a1_i S b1_i S c1_i and S 01_i Representing the i-th voltage vector V 1_i The corresponding switch state value, U α1_i V represents the i-th voltage vector. 1_i The voltage value on the α axis, U β1_i V represents the i-th voltage vector. 1_i The voltage value on the β axis, U γ1_i V represents the i-th voltage vector. 1_i Voltage value on the γ axis; Based on the 16 voltage vectors V of the second three-phase four-arm converter as defined 2_i Calculate the 16 voltage vectors V corresponding to the switch states. 2_i The voltage value U in the αβγ three-dimensional stationary coordinate system α2_i U β2_i U γ2_i for: ； Among them, U dc2 S represents the DC bus voltage of the second three-phase four-arm converter. a2_i S b2_i S c2_i and S 02_i Representing the i-th voltage vector V 2_i The corresponding switch state value S a2 S b2 S c2 and S 02 U α2_i V represents the i-th voltage vector. 2_i The voltage value on the α axis, U β2_i V represents the i-th voltage vector. 2_i The voltage value on the β axis, U γ2_i V represents the i-th voltage vector. 2_i Voltage value on the γ axis.

5. The robust model predictive control method for a common-centerline open-winding asynchronous motor drive system according to claim 3 or 4, characterized in that, The first cost function g 1i for: ； Where i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, and k1 is the first weighting coefficient; U α1_i V represents the i-th voltage vector. 1_i The voltage value on the α axis, U β1_i V represents the i-th voltage vector. 1_i The voltage value on the β axis, U γ1_i V represents the i-th voltage vector. 1_i Voltage value on the γ axis; u αref u represents the voltage reference value on the α axis. βref u represents the voltage reference value on the β axis. γref This represents the voltage reference value on the γ-axis; The second cost function g 2i for: ； Where i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, k2 is the second weighting coefficient, U α2_i V represents the i-th voltage vector. 2_i The voltage value on the α axis, U β2_i V represents the i-th voltage vector. 2_i The voltage value on the β axis, U γ2_i V represents the i-th voltage vector. 2_i Voltage value on the γ axis; U α1_m U β1_m U γ1_m The first optimal voltage vector V is respectively 1_m Voltage values ​​on the α-axis, β-axis, and γ-axis.

6. The robust model predictive control method for a common-centerline open-winding asynchronous motor drive system according to claim 5, characterized in that, Compare the 16 first cost functions g obtained from the calculation 1i The value of the first cost function g is chosen to make the first cost function g... 1i The voltage vector V that takes the minimum value 1_i Let V be the first optimal voltage vector. 1_m Where m represents the value that makes the first cost function g 1i The subscript of the voltage vector with the minimum value is m, which is one of the values ​​1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16. Compare the 16 calculated second cost functions g 2i The value of the second cost function g is chosen to make the second cost function g 2i The voltage vector V that takes the minimum value 2_i As the second optimal voltage vector V 2_n Where n represents the value that makes the second cost function g 2i The index of the voltage vector with the minimum value is n, which is one of the values ​​1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16.

7. The robust model predictive control method for a common-center-wire open-winding asynchronous motor drive system according to claim 3, 4, or 6, characterized in that, The method for calculating the lumped disturbances of the α-axis, β-axis, and γ-axis observed in this period is as follows: estimate the lumped disturbance F. α_est Lumped disturbance F β_est for: ； Where η represents the observer gain, which must satisfy η>0. i represents the initial value of the calculated α-axis current. α This represents the α-axis components of the three-phase stator currents (a, b, c) of an open-winding asynchronous motor. i represents the initial value of the calculated β-axis current. β i represents the β-axis component of the abc three-phase stator current of an open-winding asynchronous motor. α i represents the current component along the α-axis. β Represents the current component along the β axis; Estimate the lumped perturbation F along the γ-axis γ_est for: ； Where β2 represents the gain of the second γ-axis observer, i represents the initial value of the calculated γ-axis current. γ Let represent the current components of the three-phase stator current (abc) of an open-winding asynchronous motor on the γ-axis, and s represent the Laplace operator.

8. The robust model predictive control method for a common-center-wire open-winding asynchronous motor drive system according to claim 7, characterized in that, The initial value of the calculated α-axis current and the initial value of the calculated β-axis current. The calculation method is as follows: calculate the α-axis current. Delay one control cycle T s The obtained current is the initial value of the α-axis current. ; calculate the β-axis current Delay one control cycle T s The obtained current is the initial value of the β-axis current. ; The initial value of the calculated γ-axis current It is the calculated γ-axis current Delay one control cycle T s It was obtained later.

9. The robust model predictive control method for a common-center-wire open-winding asynchronous motor drive system according to claim 8, characterized in that, The calculated α-axis current β-axis current The method is as follows: ； Among them, U α1_m V represents the first optimal voltage vector. 1_m The corresponding voltage value on the α axis, U β1_m V represents the first optimal voltage vector. 1_m The corresponding voltage value on the β-axis, m is one of the values ​​1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16; U α2_n Represents the second optimal voltage vector V 2_n The corresponding voltage value on the α axis, U β2_n Represents the second optimal voltage vector V 2_n The corresponding voltage value on the β-axis, n is any one of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16; η represents the observer gain, and η > 0; ω s Represents the synchronous angular frequency of an open-winding asynchronous motor, and: ； Where, ω r T represents the rotor angular velocity of an open-winding asynchronous motor. r It is the rotor time constant, satisfying T r =L r / R r L r R represents the rotor inductance of an open-winding asynchronous motor. r This represents the rotor resistance of an open-winding asynchronous motor; The calculated γ-axis current for: ； Among them, U γ1_m V represents the first optimal voltage vector. 1_m The corresponding voltage value on the γ-axis; U γ2_n Represents the second optimal voltage vector V 2_n The corresponding voltage value on the γ-axis; β1 represents the gain of the first γ-axis observer, and β2 represents the gain of the second γ-axis observer, which must satisfy β1>0 and β2>0.

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