Robust model prediction control method for centerline-sharing open-winding asynchronous motor driving system

Abstract

The invention provides a robust model prediction control method for a centerline-shared open-winding asynchronous motor driving system, the system is composed of two three-phase four-leg converters and an open-winding asynchronous motor, and the method comprises the following steps: sampling three-phase stator current of the open-winding asynchronous motor and converting the three-phase stator current to obtain a current component; calculating a voltage reference value by using the current component and lumped disturbance of the previous period; determining voltage vectors of the two three-phase four-leg converters according to the conduction state of the power device, and calculating voltage values corresponding to the voltage vectors; calculating the value of a first cost function by using the voltage value of the voltage vector of the first three-phase four-leg converter to obtain a first optimal voltage vector; calculating the value of a second cost function according to the voltage value corresponding to the first optimal voltage vector and the voltage value of the voltage vector of a second three-phase four-leg converter, and determining a second optimal voltage vector; and respectively controlling the two three-phase four-leg converters by using the values of the switching states corresponding to the two optimal voltage vectors, and calculating the lumped disturbance observed in the period. According to the invention, robust model prediction control is realized, and the current control precision during parameter mismatch is improved.

Description

Technical Field

[0001] The 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 neutral open-winding asynchronous motor drive system. 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 [L.Xu,ZQZhu and L.Yan,"Low Switching Frequency SPWMStrategies for Open-Winding Machine With Low Current Harmonics,"in IEEETransactions on Industry Applications,vol.58,no.2,pp.2042-2054,March-April2022.] and [N.Chai and W.Hu,"A Fault-Tolerant Scheme Against the Open-SwitchFailure in Open-End Winding PMSM System With Isolated DC bus,"in IEEETransactions on Energy Conversion,vol.38,no.3,pp.2227-2230,Sept.2023] studied the low switching frequency and fault-tolerant control strategies of independent DC bus open-winding motor drive systems. Although this type of topology allows flexible selection of the DC bus voltage of the two converters to achieve multi-mode flexible control, it is difficult to achieve fault-tolerant control during motor phase failure due to the lack of a neutral line. The literature [Wang Wei, Jiang Yixin, Wang Zheng, et al. A review of zero-sequence current suppression technology for open-winding motor systems with a 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 a common DC bus. Although this type of topology adds a neutral line and can achieve fault-tolerant control during motor phase failure by flexibly adjusting the zero-sequence current, it is difficult to achieve independent and flexible adjustment of the DC bus voltages of the two converters because the DC buses of the two converters are directly connected together.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 common neutral topology open winding asynchronous motor drive control method [P]. Anhui Province: CN201910862730.5, 2021-07-20.] studied a common neutral open winding motor drive system control strategy. This type of topology not only increases the neutral line, but also retains the ability of the two converters to independently and flexibly adjust the DC bus voltage. However, when the fault-tolerant control strategy is implemented when the motor fails, a large current will pass through the bus capacitor, increasing the current stress of the bus capacitor and affecting the service life of the capacitor. In addition, the existing common neutral open winding motor drive system mostly adopts a vector control strategy based on space vector modulation. This strategy has the disadvantages of being more complex to implement and requiring the design of multiple sets of proportional integral controller parameters. In recent years, model predictive control technology has attracted extensive attention due to its advantages of flexible control, simple implementation, and multi-objective control. However, there are few reports on the research of model predictive control strategy for common neutral open-winding motor drive system.

[0004] In summary, the independent DC bus topology requires two independent DC power supplies and lacks a neutral line, making it difficult to achieve fault-tolerant operation after a motor phase failure. Although the common DC bus topology has a neutral line and can achieve fault-tolerant operation after a motor phase failure, the DC voltages of the two converters are connected together and always remain consistent and cannot be adjusted. Although the common neutral topology has both a neutral line and two independent DC bus power supplies, when the motor has a phase failure and is in fault-tolerant operation, a large current will flow through the neutral line, which will increase the current stress of the bus capacitor and easily cause damage to the bus capacitor. In addition, the existing common neutral open-winding motor drive system mostly adopts a vector control strategy based on space vector modulation, which has the disadvantages of being complex to implement and requiring the design of multiple sets of proportional integral controller parameters. In recent years, model predictive control technology has received widespread attention due to its advantages of flexible control, simple implementation, and multi-objective control. However, there are few reports on the research on the model predictive control strategy of the common neutral open-winding motor drive system, and the conventional model predictive control strategy based on the motor mathematical model has problems such as poor parameter robustness. Summary of the invention

[0005] Aiming at the technical problems that the bus capacitor current stress is large and the bus capacitor is easily damaged when the conventional common neutral open-winding asynchronous motor drive system has a phase failure and is in fault-tolerant operation, and the conventional common neutral open-winding asynchronous motor drive system mostly adopts a more complex space vector modulation strategy and a conventional model predictive control strategy that is seriously dependent on the mathematical model of the motor, the present invention proposes a robust model predictive control method for a common neutral open-winding asynchronous motor drive system based on a dual three-phase four-bridge-arm converter. The studied common neutral open-winding asynchronous motor drive based on a dual three-phase four-bridge-arm converter adopts a bridge arm composed of fully controlled devices to replace the virtual capacitor bridge arm in the conventional common neutral open-winding topology, thereby making the neutral current control more flexible and reducing the current stress of the bus capacitor. The proposed robust model predictive control strategy adopts a disturbance observer to perform lumped disturbance observation, and uses the observed disturbance to replace the motor model to construct a prediction model, thereby realizing robust model predictive control and improving the current control accuracy when the parameters are mismatched.

[0006] In order to achieve the above object, 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 is composed of two three-phase four-bridge-arm converters and an open-winding asynchronous motor, and 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 steps are as follows:

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

[0008] Step 2, using the current components of the α-axis, β-axis and γ-axis and the lumped disturbances of the α-axis, β-axis and γ-axis observed in the previous cycle to calculate the voltage reference value in the αβγ three-dimensional stationary coordinate system;

[0009] Step 3: According to the conduction states of the power devices on the four bridge arms of the two three-phase four-bridge-arm converters, respectively define the values ​​of the switch states corresponding to the four bridge arms of the two three-phase four-bridge-arm converters; and determine 16 voltage vectors of the two three-phase four-bridge-arm converters according to the values ​​of different switch states;

[0010] Step 4: Calculate the voltage value of the voltage vector in the αβγ three-dimensional stationary coordinate system according to the switch state values ​​of 16 voltage vectors of the two three-phase four-bridge-arm converters;

[0011] Step 5, calculating 16 values ​​of first cost functions according to the voltage reference value in the αβγ three-dimensional stationary coordinate system and the voltage values ​​of 16 voltage vectors of the first three-phase four-bridge-arm converter in the αβγ three-dimensional stationary coordinate system, comparing the values ​​of the 16 first cost functions and selecting the voltage vector that minimizes the value of the first cost function as the first optimal voltage vector;

[0012] Step 6, calculating 16 values ​​of second cost functions according to 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 16 voltage vectors of the second three-phase four-bridge-arm converter in the αβγ three-dimensional stationary coordinate system, comparing the values ​​of the 16 second cost functions, and selecting the voltage vector that minimizes the value of the second cost function as the second optimal voltage vector;

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

[0014] Preferably, 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 devices and the lower power devices of the fourth bridge arm of the two three-phase four-bridge-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:

[0016]

[0017] Among them, u αref represents the voltage reference value on the α-axis in the αβγ three-dimensional stationary coordinate system, u βref represents the voltage reference value on the β axis, u γref represents the voltage reference value on the γ axis, i αref It represents the stator current reference value on the α axis of the open-winding asynchronous motor, i βref It represents the stator current reference value on the β axis of the open-winding asynchronous motor, i γref It represents the stator current reference value on the γ axis of the open-winding asynchronous motor, T s represents the control period, d is the proportional coefficient between the α axis and the β axis, i α It represents the current component of the abc three-phase stator current of the open-winding asynchronous motor on the α axis, i β It represents the current component of the abc three-phase stator current of the open-winding asynchronous motor on the β axis, i γIt represents the current component of the abc three-phase stator current of the open-winding asynchronous motor on the γ axis; L 1s Indicates the stator leakage inductance of the open-winding asynchronous motor, F α_est0 represents the lumped disturbance of the α-axis estimated in the previous cycle, F β_est0 represents the lumped disturbance of the β axis estimated in the previous cycle, F γ_est0 represents the lumped disturbance of the γ-axis estimated in the previous period.

[0018] Preferably, the method of transforming the three-phase stator current into the αβγ three-dimensional stationary coordinate system to obtain the current components of the α axis, β axis and γ axis respectively is: transforming the abc three-phase stator current i of the open-winding asynchronous motor a 、i b 、i c Transformed to the αβγ three-dimensional stationary coordinate system, the current components i of the α, β and γ axes are obtained α 、i β 、i γ for:

[0019]

[0020] 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 It represents the c-phase stator current of the open-winding asynchronous motor;

[0021] The proportionality coefficients of the α-axis and the β-axis σ represents the magnetic flux leakage coefficient, and L s Indicates the stator inductance of the open-winding asynchronous motor, L m Represents the mutual inductance of the open-winding asynchronous motor, L r It represents the rotor inductance of the open-winding asynchronous motor;

[0022] The aggregate disturbance F estimated in the previous cycle α_est0 、F β_est0 、F γ_est0 They are obtained from the aggregate disturbance observed in the previous cycle after a control cycle delay;

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

[0024]

[0025] Among them, i dref is the excitation current reference value of the open-winding asynchronous motor, i qrefis 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.

[0026] Preferably, the switch state corresponding to the first bridge arm of the first three-phase four-bridge-arm converter is defined 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 ;

[0027] 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 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 a1 =0;

[0028] 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 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 b1 =0;

[0029] 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 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 c1 =0;

[0030] 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 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 01 =0;

[0031] The 16 voltage vectors V of the first three-phase four-leg converter 1_i satisfy:

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

[0047] 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;

[0048] 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 Sb2 , 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 ;

[0049] 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 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 a2 =0;

[0050] 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 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 b2 =0;

[0051] 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 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 c2 =0;

[0052] 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 bridge 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;

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

[0071]

[0072] 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 value, Uα1_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;

[0073] According to the definition of the 16 voltage vectors V of the second three-phase four-leg converter 2_i The corresponding switch state values ​​are used to 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:

[0074]

[0075] 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 value S a2 , S b2 , S c2 and S 02 , 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.

[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, k1 is the first weight coefficient; U α1_i Represents the i-th voltage vector V1_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; 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;

[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 weight coefficient, 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 Voltage value on the γ axis; U α1_m , U β1_m , U γ1_m They are the first optimal voltage vector V 1_m The voltage value on the α-axis, the voltage value on the β-axis, and the voltage value on the γ-axis.

[0082] Preferably, the 16 first cost functions g obtained by comparison are 1i The value is selected so that the first cost function g 1i The voltage vector V that takes the minimum value 1_i Denoted as the first optimal voltage vector V 1_m , where m represents the first cost function g 1i Take the subscript of the voltage vector with the minimum value, where m is one of 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 is selected 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 second cost function g 2i The subscript of the voltage vector with the minimum value is n, which is a value among 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16.

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

[0085]

[0086] Where η represents the observer gain, which must satisfy η>0. represents the initial value of the calculated α-axis current, i α It represents the component of the abc three-phase stator current of the open-winding asynchronous motor on the α axis, represents the initial value of the calculated β-axis current, i β It represents the component of the abc three-phase stator current of the open-winding asynchronous motor on the β axis, i α represents the current component of the α axis, i β Represents the current component of the β axis;

[0087] Estimate the lumped disturbance F on the γ axis γ_est for:

[0088]

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

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

[0091] The calculated initial value of the γ-axis current is is the calculated γ-axis current Delay one control cycle T s After getting.

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

[0093]

[0094] Among them, U α1_m Represents the first optimal voltage vector V 1_m The corresponding voltage value on the α axis, U β1_m Represents the first optimal voltage vector V 1_m The corresponding voltage value on the β axis, m is one of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16; U α2_n The second optimal voltage vector V 2_n The corresponding voltage value on the α axis, U β2_n The second optimal voltage vector V 2_n The corresponding voltage value on the β axis, n is 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] Among them, ω r represents the rotor angular velocity 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 Indicates the rotor resistance of an open-winding asynchronous motor;

[0097] The calculated γ-axis current for:

[0098]

[0099] Among them, U γ1_m Represents the first optimal voltage vector V 1_m The corresponding voltage value on the γ axis; U γ2_nThe second optimal voltage vector V 2_n The corresponding voltage value on the γ-axis; β1 represents the first γ-axis observer gain, β2 represents the second γ-axis observer gain, and β1>0, β2>0 must be satisfied.

[0100] Compared with the prior art, the invention has the following beneficial effects: the common neutral open-winding asynchronous motor drive system is composed of two three-phase four-bridge-arm converters and an open-winding asynchronous motor. The robust model predictive control method of the invention constructs three disturbance observers to respectively observe the lumped disturbances of the α-axis, β-axis and γ-axis, designs the prediction model using the observed lumped disturbances, and adopts a method of first selecting the optimal voltage vector output by the first three-phase four-bridge-arm converter and then selecting the optimal voltage vector output by the second three-phase four-bridge-arm converter to determine the optimal voltage vector output by the two three-phase four-bridge-arm converters in each control cycle, thereby realizing the robust model predictive control of the common neutral open-winding asynchronous motor based on the dual three-phase four-bridge-arm converter. The invention adopts three disturbance observers to observe the lumped disturbance, and uses the observed lumped disturbance to replace the motor model to design the prediction model. When the motor parameters are mismatched, the disturbance observer can automatically compensate for the lumped disturbance changes caused by the parameter mismatch, thereby improving the accuracy of the prediction model, and then significantly improving the robustness of the model predictive control strategy to parameter mismatch. Since the method proposed in the present invention utilizes the observed lumped disturbance to replace the motor model to construct a prediction model, it has stronger parameter robustness to motor parameter mismatch and higher current control accuracy when the motor parameter mismatch occurs. BRIEF DESCRIPTION OF THE DRAWINGS

[0101] 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.

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

[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 the present invention.

[0104] Figure 3 The present invention provides a flow chart of the robust model predictive control method.

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

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

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

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

[0109] Figure 8 The simulation results of the conventional model predictive control strategy based on the motor mathematical model and parameters are shown in Figure 1, where (a) is the α-axis current reference value i αref and the actual value i α (b) is the local enlarged view of area A in (a), and (c) is the α-axis current error waveform.

[0110] Fig. 9 The simulation results of the robust model predictive control method proposed in the present invention are shown in Figure 1, where (a) is the α-axis current reference value i αref and the actual value i α (b) is the local enlarged view of area A in (a), and (c) is the α-axis current error waveform. DETAILED DESCRIPTION

[0111] 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.

[0112] like Figure 3 As shown, a robust model predictive control method for a common neutral open-winding asynchronous motor drive system is provided. The common neutral open-winding asynchronous motor drive system is composed of two three-phase four-leg converters and an open-winding asynchronous motor. Figure 2 As shown, in the topological structure of the common neutral open-winding asynchronous motor drive system based on dual three-phase four-bridge-arm converters studied by the present invention, 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 through the neutral line; and Figure 1 Compared with the topology of the common neutral open-winding asynchronous motor drive system based on the conventional virtual capacitor bridge arm, Figure 1 The topology uses two three-phase three-leg converters with bus capacitors to construct the neutral point of the neutral line. Figure 2 The topology shown uses the fourth bridge arm of two three-phase four-bridge arm converters to construct the neutral line, thereby increasing the flexibility of neutral line current control and reducing the current stress of the bus current. The present 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] Use current sensor to 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 components i of the α, β and γ axes α 、i β 、i γ ,satisfy:

[0115]

[0116] 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.

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

[0118] According to the obtained current i α 、i β 、i γ , calculate the voltage reference value u in the αβγ three-dimensional stationary coordinate system αref 、u βref 、u γref ,satisfy:

[0119]

[0120] Among them, u αrefrepresents the voltage reference value on the α-axis in the αβγ three-dimensional stationary coordinate system, u βref represents the voltage reference value on the β axis, u γref represents the voltage reference value on the γ axis, i αref It represents the stator current reference value on the α axis of the open-winding asynchronous motor, i βref It represents the stator current reference value on the β axis of the open-winding asynchronous motor, i γref It represents the stator current reference value on the γ axis of the open-winding asynchronous motor, T s represents the control period, which is generally selected between 50μs and 100μs. d is the proportional coefficient between the α-axis and the β-axis, satisfying σ represents the magnetic flux leakage coefficient, which satisfies L s Indicates the stator inductance of the open-winding asynchronous motor, L m Represents the mutual inductance of the open-winding asynchronous motor, L r Indicates the rotor inductance of the open-winding asynchronous motor, L 1s Indicates the stator leakage inductance of the open-winding asynchronous motor, F α_est0 represents the lumped disturbance of the α-axis estimated in the previous cycle, F β_est0 represents the lumped disturbance of the β axis estimated in the previous cycle, F γ_est0 represents the lumped disturbance of the γ axis estimated in the previous cycle, F α_est0 、F β_est0 、F γ_est0 The stator current reference value i is obtained by the lumped disturbance observed in the previous cycle after a control cycle delay. αref 、i βref 、i γref The calculation method satisfies:

[0121]

[0122] 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.

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

[0124] 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 ;

[0125] 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;

[0126] 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;

[0127] 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;

[0128] 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.

[0129] 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:

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

[0146] 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 ;

[0147] 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;

[0148] 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;

[0149] 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;

[0150] 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 bridge 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;

[0151] 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:

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

[0168] Step 4: Calculate the voltage value of the voltage vector in the αβγ three-dimensional stationary coordinate system according to the switch state values ​​of the 16 voltage vectors of the two three-phase four-bridge-arm converters.

[0169] According to the definition of the first three-phase four-leg converter 16 voltage vectors V 1_i (i=1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16) The value of the switch state corresponding to 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:

[0170]

[0171] 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 (i=1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16) The value S of the switch state corresponding to a1 , S b1 , S c1 and S 01 , 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_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 γ axis.

[0172] 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) The value of the switch state corresponding to 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:

[0173]

[0174] 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) The value S of the switch state corresponding to a2 , S b2 , S c2 and S 02 , 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.

[0175] Step 5. Calculate the values ​​of 16 first cost functions according to the voltage reference value in the αβγ three-dimensional stationary coordinate system and the voltage values ​​of the 16 voltage vectors of the first three-phase four-bridge 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 voltage reference value u αref 、u βref 、u γref And the 16 voltage vectors V of the first three-phase four-bridge-leg converter are obtained 1_i (i=1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16) The voltage value U on the α axis corresponds to α1_i , the voltage value U on the β axis β1_i , the voltage value U on the γ axis γ1_i Substitute the following formulas in turn to calculate 16 first cost functions g 1i The value of (i=1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16) satisfies:

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

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

[0179] Compare the 16 first cost functions g calculated 1i (i=1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16) value, select the value that makes g 1i The voltage vector V that takes the minimum value 1_i is the optimal voltage vector, and this vector is recorded as the first optimal voltage vector V 1_m , where m represents g 1i The subscript of the voltage vector with the minimum value is m, which is a value among 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16.

[0180] Step six, calculate the values ​​of 16 second cost functions according to 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-bridge 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 voltage reference value u αref 、u βref 、u γref , the first optimal voltage vector V 1_m The corresponding voltage value on the α axis is U α1_m , U on the β axis β1_m , U on the γ axis γ1_m (m is a value among 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16) and the 16 voltage vectors V of the second three-phase four-bridge-leg converter obtained 2_i(i=1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16) The voltage value U on the α axis corresponds to α2_i , the voltage value U on the β axis β2_i , the voltage value U on the γ axis γ2_i Substitute the following formulas in turn to calculate 16 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) satisfies:

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

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

[0184] Compare the 16 calculated second cost functions g 2i (i=1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16) values ​​are selected 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, and this vector is recorded as the second optimal vector V 2_n , where n represents g 2i The subscript of the voltage vector with the minimum value is n, which is a value among 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16.

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

[0186] Select the first optimal voltage vector V 1_m and the second optimal voltage vector V 2_nThe optimal voltage vectors are outputted as the final optimal voltage vectors of the first three-phase four-bridge-arm converter and the second three-phase four-bridge-arm converter, respectively, 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 robust model predictive control of the open-winding asynchronous motor. Since the control method adopts a disturbance observer to observe the lumped disturbance, and uses the observed disturbance to replace the motor model to construct the prediction model and the model predictive control strategy, the method is no longer affected by the parameters such as the motor stator resistance, so when the motor parameters are mismatched, the parameter robustness of the method proposed by the present invention is stronger.

[0187] like Figure 5 and Figure 6 As shown, the lumped disturbance F of the α axis at the current moment α_est , the lumped disturbance F of 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, represents the calculated α-axis current, represents the calculated β-axis current, U α1_m Represents the first optimal voltage vector V 1_m The corresponding voltage value on the α axis, U β1_m Represents the first optimal voltage vector V 1_m The corresponding voltage value on the β axis (m is one of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16); U α2_n The second optimal voltage vector V 2_n The corresponding voltage value on the α axis, U β2_n The second optimal voltage vector V 2_n The corresponding voltage value on the β axis (n is one of 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, represents the initial value of the calculated α-axis current, i α It represents the component of the abc three-phase stator current of the open-winding asynchronous motor on the α axis, represents the initial value of the calculated β-axis current, i β represents the component of the abc three-phase stator current of the open-winding asynchronous motor on the β axis, s represents the Laplace operator, ω s Represents the synchronous angular frequency of the open-winding asynchronous motor, satisfying:

[0191]

[0192] Among them, ω r represents the rotor angular velocity 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 Indicates 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 calculated initial value of the α-axis current is and the calculated initial value of the β-axis current The calculation method meets the following steps: the calculated α-axis current Delay one control cycle T s The current obtained is the initial value of the α-axis current The calculated β-axis current Delay one control cycle T s The current obtained is the initial value of the β-axis current

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

[0197] Step 1: Calculate the current according to the following formula satisfy:

[0198]

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

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

[0201]

[0202] The calculated initial value of the γ-axis current is is the calculated γ-axis current Delay one control cycle T s After getting.

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

[0204] according to Figure 5 , Figure 6 and Figure 7 The lumped disturbance observation can be realized, and then according to Figure 3 The robust model predictive control method proposed by the present invention can be realized. Figure 4 The speed outer loop and current inner loop dual-loop control strategy of the common neutral open-winding asynchronous motor drive system based on the dual three-phase four-bridge-arm converter can be realized. Among them, the speed outer loop adopts a proportional integral controller (PI controller), and the PI controller outputs the torque current reference value i of the open-winding asynchronous motor. qref The current inner loop adopts the robust model predictive control method of the present invention.

[0205] like Figure 4 As shown, the specific implementation of the method proposed by the present invention is:

[0206] First, according to 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 Among them, the motor speed n r The measured angular velocity ω r Calculated, n p Indicates the number of motor pole pairs.

[0207] Second, according to the given torque current reference value i qref , excitation current reference value i dref and zero sequence current reference value i 0ref , after coordinate transformation, the current reference value i is obtained αref 、i βref 、i γref Among them, i dref Determined by the rated excitation current of the motor, i 0ref Usually set to 0.

[0208] Third, according to the current reference value i αref 、i βref 、i γref , current feedback value i α 、i β 、i γ and the aggregate 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 aggregate disturbance F observed in the previous period is α_est0 、F β_est0 、F γ_est0 The F observed in this period α_est 、F β_est 、F γ_est Obtained by delaying one control cycle.

[0209] Fourth, according to the voltage values ​​of the 16 voltage vectors of the first three-phase four-bridge-arm converter in the αβγ three-dimensional stationary coordinate system and the voltage reference value u αref 、u βref 、u γref , calculate the first cost function g 1i (i=1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16) and compare the first cost function g 1i The size of g 1i The voltage vector with the minimum value is the first optimal voltage vector V 1_m , where m represents the first cost function g 1i The subscript of the voltage vector with the minimum value is m, which is a value among 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16.

[0210] Fifth, according to the first optimal voltage vector V 1_mThe voltage value in the αβγ three-dimensional stationary coordinate system (m is one of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16) and 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 are used to calculate the second cost function g 2i (i=1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16), and by comparing 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 g 2i The subscript of the voltage vector with the minimum value is n, which is a value among 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 is output to the first three-phase four-bridge-arm converter to realize the control of the first three-phase four-bridge-arm converter and to convert the second optimal voltage vector V 2_n The corresponding switch state is output to the second three-phase four-bridge-arm converter to realize the control of the second three-phase four-bridge-arm converter.

[0212] Seventh, according to 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 Observe the aggregate 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 Be prepared.

[0213] 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.

[0214] Table 1 Open winding asynchronous motor parameters

[0215]

[0216] During simulation, the motor reference speed n ref Set to 1500r / min, the load torque suddenly increases from 0Nm to 15Nm at 0.4s, 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 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 in the proportional-integral regulator of the outer speed loop is 0.15, the integral coefficient is 7, the current inner loop adopts the conventional model predictive control strategy based on the motor mathematical model and parameters and the robust model predictive control method proposed in the present invention, the first weight coefficient k1 is set to 0.5, the second weight 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 shown in Figure 2. Figure 8 As shown, the simulation results of the method proposed by the present invention are as follows Fig. 9 As shown. During simulation, the stator resistance R used in the controller s It is 4 times the true value to test the control effect of the two methods when the parameters mismatch occurs due to changes in factors such as temperature.

[0217] contrast Figure 8 and Fig. 9 It can be seen that when the load changes suddenly, both the conventional method and the method proposed in the present invention can achieve fast current tracking control. s There is an error. The current error of the conventional method is large, and the maximum error can reach 1.85A. Figure 8 As shown in (c). The method proposed in the present invention uses a lumped disturbance observer for disturbance observation and compensation, thereby improving parameter robustness. The current error is in the stator resistance R s When mismatched, the maximum error is still small, about 1.58A. Fig. 9 As shown in (c). Figure 8 and Fig. 9 It can be seen that the method proposed in the present invention still has better current control accuracy when the parameters are mismatched, which reflects the usefulness 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 principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A robust model predictive control method for a common neutral open-winding asynchronous motor drive system, characterized in that: The common neutral open-winding asynchronous motor drive system is composed of two three-phase four-bridge-arm converters and an open-winding asynchronous motor, and 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 steps are as follows: Step 1, sampling the three-phase stator current of the open-winding asynchronous motor, and transforming the three-phase stator current to an αβγ three-dimensional stationary coordinate system to obtain current components of the α-axis, β-axis and γ-axis respectively; Step 2, using the current components of the α-axis, β-axis and γ-axis and the lumped disturbances of the α-axis, β-axis and γ-axis observed in the previous cycle to calculate the voltage reference value in the αβγ three-dimensional stationary coordinate system; Step 3: According to the conduction states of the power devices on the four bridge arms of the two three-phase four-bridge-arm converters, respectively define the values ​​of the switch states corresponding to the four bridge arms of the two three-phase four-bridge-arm converters; and determine 16 voltage vectors of the two three-phase four-bridge-arm converters according to the values ​​of different switch states; Step 4: Calculate the voltage value of the voltage vector in the αβγ three-dimensional stationary coordinate system according to the switch state values ​​of 16 voltage vectors of the two three-phase four-bridge-arm converters; Step 5, calculating 16 values ​​of first cost functions according to the voltage reference value in the αβγ three-dimensional stationary coordinate system and the voltage values ​​of 16 voltage vectors of the first three-phase four-bridge-arm converter in the αβγ three-dimensional stationary coordinate system, comparing the values ​​of the 16 first cost functions and selecting the voltage vector that minimizes the value of the first cost function as the first optimal voltage vector; Step 6, calculating 16 values ​​of second cost functions according to 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 16 voltage vectors of the second three-phase four-bridge-arm converter in the αβγ three-dimensional stationary coordinate system, comparing the values ​​of the 16 second cost functions, and selecting the voltage vector that minimizes the value of the second cost function as the second optimal voltage vector; Step 7: Use the value of the switch state corresponding to the first optimal voltage vector to control the first three-phase four-bridge-arm converter, and use the value of the switch state corresponding to the second optimal voltage vector to control the second three-phase four-bridge-arm converter; at the same time, calculate the lumped disturbances of the α-axis, β-axis and γ-axis observed in this period.

2. The robust model predictive control method for a common neutral open-winding asynchronous motor drive system according to claim 1, characterized in that: 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 devices and the lower power devices of the fourth bridge arm of the two three-phase four-bridge-arm converters are directly connected through the neutral line.

3. The robust model predictive control method for a common neutral open-winding asynchronous motor drive system according to claim 1 or 2, characterized in that: The method for calculating the voltage reference value on the αβγ three-dimensional stationary coordinate system is: Among them, u αref represents the voltage reference value on the α-axis in the αβγ three-dimensional stationary coordinate system, u βref represents the voltage reference value on the β axis, u γref represents the voltage reference value on the γ axis, i αref It represents the stator current reference value on the α axis of the open-winding asynchronous motor, i βref It represents the stator current reference value on the β axis of the open-winding asynchronous motor, i γref It represents the stator current reference value on the γ axis of the open-winding asynchronous motor, T s represents the control period, d is the proportional coefficient between the α axis and the β axis, i α It represents the current component of the abc three-phase stator current of the open-winding asynchronous motor on the α axis, i β It represents the current component of the abc three-phase stator current of the open-winding asynchronous motor on the β axis, i γ It represents the current component of the abc three-phase stator current of the open-winding asynchronous motor on the γ axis; L 1s Indicates the stator leakage inductance of the open-winding asynchronous motor, F α_est0 represents the lumped disturbance of the α-axis estimated in the previous cycle, F β_est0 represents the lumped disturbance of the β axis estimated in the previous cycle, F γ_est0 represents the lumped disturbance of the γ-axis estimated in the previous period.

4. The robust model predictive control method for a common neutral open-winding asynchronous motor drive system according to claim 3, characterized in that: The method of transforming the three-phase stator current into the αβγ three-dimensional stationary coordinate system to obtain the current components of the α-axis, β-axis and γ-axis respectively is as follows: transforming the abc three-phase stator current i of the open-winding asynchronous motor into a 、i b 、i c Transformed to the αβγ three-dimensional stationary coordinate system, the current components i of the α, β and γ axes are obtained α 、i β 、i γ for: 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 It represents the c-phase stator current of the open-winding asynchronous motor; The proportionality coefficients of the α-axis and the β-axis σ represents the magnetic flux leakage coefficient, and L s Indicates the stator inductance of the open-winding asynchronous motor, L m Represents the mutual inductance of the open-winding asynchronous motor, L r It represents the rotor inductance of the open-winding asynchronous motor; The aggregate disturbance F estimated in the previous cycle α_est0 、F β_est0 、F γ_est0 They are obtained from the aggregate disturbance observed in the previous cycle after a control cycle delay; 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.

5. The robust model predictive control method for a common neutral open-winding asynchronous motor drive system according to claim 3, characterized in that: 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 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 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 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 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 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 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 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 01 =0; 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 1_7 ; 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 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 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 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 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 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 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, define S 02 =1; when the upper power device of the fourth bridge 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; 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 ; Calculate 16 voltage vectors V 1_i Voltage value U in the αβγ three-dimensional stationary coordinate system α1_i , U β1_i , U γ1_ The method is: 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 value, 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; According to the definition of the 16 voltage vectors V of the second three-phase four-leg converter 2_i The corresponding switch state values ​​are used to 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 value S a2 , S b2 , S c2 and S 02 , 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.

6. The robust model predictive control method for a common neutral open-winding asynchronous motor drive system according to claim 4 or 5, characterized in that: The first cost function g 1i for: Mr 1i =|in αref -IN α1_i |+|in βref -IN β1_i |+k1|u γref -IN γ1_i |; Where i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, k1 is the first weight coefficient; U α1i 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; 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; The second cost function g 2i for: Mr 2i =|in αref -(IN α1_m -IN α2_i )| + |in βref -(IN β1_m -IN β2_i )|+k2|u γref -(IN γ1_m -IN γ2_i )|; Where i = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, k2 is the second weight coefficient, 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 Voltage value on the γ axis; U α1_m , U β1_m , U γ1_m They are the first optimal voltage vector V 1_m The voltage value on the α-axis, the voltage value on the β-axis, and the voltage value on the γ-axis.

7. The robust model predictive control method for a common neutral open-winding asynchronous motor drive system according to claim 6, characterized in that: Compare the 16 first cost functions g calculated 1i The value is selected so that the first cost function g 1i The voltage vector V that takes the minimum value 1_i Denoted as the first optimal voltage vector V 1_m , where m represents the first cost function g 1i Take the subscript of the voltage vector with the minimum value, where m is one of 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 is selected 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 second cost function g 2i The subscript of the voltage vector with the minimum value is n, which is a value among 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16.

8. The robust model predictive control method for a common neutral open-winding asynchronous motor drive system according to claim 4, 5 or 7, characterized in that: The method for calculating the aggregate disturbance of the α-axis, β-axis and γ-axis observed in this period is: estimate the aggregate disturbance F α_est , lumped disturbance F β_est for: Where η represents the observer gain, which must satisfy η>0. represents the initial value of the calculated α-axis current, i α It represents the component of the abc three-phase stator current of the open-winding asynchronous motor on the α axis, represents the initial value of the calculated β-axis current, i β It represents the component of the abc three-phase stator current of the open-winding asynchronous motor on the β axis, i α represents the current component of the α axis, i β Represents the current component of the β axis; Estimate the lumped disturbance F on the γ axis γ_est for: Where β2 represents the second γ-axis observer gain, represents the initial value of the calculated γ-axis current, i γ It represents the current component of the abc three-phase stator current of the open-winding asynchronous motor on the γ-axis, and s represents the Laplace operator.

9. The robust model predictive control method for a common neutral open-winding asynchronous motor drive system according to claim 8, characterized in that: The calculated initial value of the α-axis current is and the calculated initial value of the β-axis current The calculation method is: the calculated α-axis current Delay one control cycle T s The current obtained is the initial value of the α-axis current The calculated β-axis current Delay one control cycle T s The current obtained is the initial value of the β-axis current The calculated initial value of the γ-axis current is is the calculated γ-axis current Delay one control cycle T s After getting.

10. The robust model predictive control method for a common neutral open-winding asynchronous motor drive system according to claim 9, characterized in that: The calculated α-axis current β axis current The method is: Among them, U α1_m Represents the first optimal voltage vector V 1_m The corresponding voltage value on the α axis, U β1_m Represents the first optimal voltage vector V 1_m The corresponding voltage value on the β axis, m is one of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16; U α2_n The second optimal voltage vector V 2_n The corresponding voltage value on the α axis, U β2_n The second optimal voltage vector V 2_n The corresponding voltage value on the β axis, n is 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: Among them, ω r represents the rotor angular velocity 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 Indicates the rotor resistance of an open-winding asynchronous motor; The calculated γ-axis current for: Among them, U γ1_m Represents the first optimal voltage vector V 1_m The corresponding voltage value on the γ axis; U γ2_n The second optimal voltage vector V 2_n The corresponding voltage value on the γ-axis; β1 represents the first γ-axis observer gain, β2 represents the second γ-axis observer gain, and β1>0, β2>0 must be satisfied.

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