Optimal control method for torque and efficiency of distributed dual-field enhanced permanent magnet flat wire motor

Abstract

The present invention discloses a method for optimal control of torque and efficiency of a distributed dual-magnetic field enhanced permanent magnet flat wire motor in the field of special motors. The method adopts front and rear wheel motors with different power and mechanical characteristics as the front and rear wheel drive motors of an electric vehicle respectively, calculates a given speed value, constructs an evaluation function, and traverses and calculates the set torque distribution coefficient to obtain the torque distribution reference value of the front and rear wheel motors corresponding to the torque distribution coefficient with the smallest evaluation function value; divides the operating area of ​​the front and rear wheel motors into a magnetization area, a demagnetization area, and a weak magnetic area according to the real-time speed and turning speed of the front and rear wheel motors; when the motor enters different areas, different AC and DC flux reference values ​​are obtained according to different control methods; then the AC and DC axis flux amplitudes and torque values ​​at the next moment are predicted, and a cost function is constructed; the voltage vector that minimizes the cost function is output to control the motor operation, thereby improving the overall efficiency of the distributed drive electric vehicle and achieving efficient and stable operation under full-speed working conditions.

Description

Technical Field

[0001] The present invention belongs to the field of special motor control, in particular the field of new energy vehicle motor drive control, and specifically provides a method for controlling the torque and efficiency of a permanent magnet flat wire drive motor driven by front and rear wheels. Background Art

[0002] With increasing environmental protection demands, electric vehicles are being placed on a higher level of energy conservation. Compared to traditional single-motor drive systems, electric vehicles with dual drive motors can effectively distribute torque according to varying operating conditions. This effective torque distribution improves the efficiency of the drive motors and plays a decisive role in overall vehicle performance. Therefore, research on key technologies for dual-motor torque distribution strategies is crucial for the transformation of the automotive industry and for advancing the research and development of new energy vehicles.

[0003] Field-enhanced permanent magnet flat-wire motors feature a wide constant power speed regulation range, strong overload capacity, low no-load back EMF, and resistance to permanent magnet demagnetization. Their flat-wire winding technology reduces motor size, increases power density, and improves noise performance. However, the "skin effect" also increases AC losses. Overall, field-enhanced permanent magnet flat-wire motors have broad application prospects in distributed electric vehicle drive systems. Therefore, research on field-enhanced permanent magnet flat-wire motor control technology in the full speed range is of great practical significance.

[0004] Currently, when it comes to torque distribution, strategies are often designed from the perspective of the electric vehicle's overall structure, ignoring the characteristics of the drive motor itself. Ignoring the drive motor's characteristics prevents it from maintaining optimal control under complex and changing operating conditions, reducing the vehicle's overall efficiency and generating unnecessary losses during driving. Therefore, torque distribution strategies should be designed with the drive motor's characteristics in mind to improve the performance of distributed electric vehicles under variable operating conditions. Summary of the Invention

[0005] The purpose of the present invention is to overcome the shortcomings of the existing technology and propose a method for optimal control of torque and efficiency of a distributed magnetic field enhanced permanent magnet flat wire motor, so as to realize effective torque distribution and optimal efficiency control of dual drive motors with different operating characteristics under variable operating conditions, and adapt to the control requirements of distributed electric vehicles in complex driving habits and complex road conditions.

[0006] The technical solution adopted in the present invention is:

[0007] The front and rear wheel motors with different power and mechanical characteristics are used as the front and rear wheel drive motors of the electric vehicle respectively;

[0008] Feedback speed n of the front and rear wheel motors f反馈 、nb反馈 The difference after comparison is adjusted by PI to obtain the synchronous error compensation value n 补 , calculate the speed given value K f , K b is the speed compensation coefficient, n is the actual speed;

[0009] Constructing an evaluation function P f损 、P b损 is the total loss of the front and rear wheel motors, η f ,η b is the dynamic efficiency of the front and rear wheel motors, i sf 、i sd is the stator current amplitude of the front and rear wheel motors;

[0010] The set torque distribution coefficient β is calculated ergodicly, 0<β<1, and the torque distribution reference value T of the front and rear wheel motors corresponding to the torque distribution coefficient β with the minimum evaluation function g value is obtained. f * = βT d and T b *=(1-β)T d , T d is the total torque;

[0011] According to the actual speed n and turning speed of the front and rear wheel motors, the operating area is divided into the magnetization area, demagnetization area, and weak magnetic area. When the motor enters different areas, different cross-axis flux reference values ​​ψ are obtained according to different control methods. q * and the direct-axis flux reference value ψ d * ;

[0012] First, obtain the cross-axis magnetic flux amplitude ψ by magnetic flux observation q (k), direct axis flux amplitude ψ d (k), torque angle δ(k) and stator flux angle δ s (k), and then predict the next moment of the cross-axis and direct-axis magnetic flux amplitude ψ q (k+1),ψ d (k+1) and torque value T e (k+1), front wheel motor torque reference value T e *=T f *, rear wheel motor torque reference value T e *=T b *, construct the cost function This will make the cost function g m The minimum voltage vector is output to control the motor operation.

[0013] Furthermore, when the actual speed n<front wheel motor turning speed nX , the front wheel motor runs in the magnetization area; when n X ≤n≤Rated speed of front wheel motor n fM , the front wheel motor runs in the demagnetization area; when n>n fM , the front wheel motor runs in the weak magnetic area; when the actual speed n< the rear wheel motor turning speed n Y , the rear wheel motor operates in the magnetization area; when n Y ≤n≤Rear wheel motor rated speed n bM , the rear wheel motor runs in the demagnetization area; when n>n bM , the rear wheel motor operates in the weak magnetic area.

[0014] Furthermore, the torque distribution coefficient characteristic value is calculated M=1.45~1.65, N=1.5~1.8, λ f ,λ b They are the salient pole rates of the front and rear wheel motors respectively; when the actual speed n <n X When the total torque T d ≤Rear wheel motor rated torque T bM , the total torque T output by the front wheel motor d ; If the total torque T d >Rear wheel motor rated torque T bM , then the torque distribution coefficient β is greater than or equal to the characteristic value β λ Torque distribution; when n X ≤n≤Rated speed of front wheel motor n fM When the torque distribution coefficient β is greater than or equal to the characteristic value β λ Perform torque distribution; when the actual speed n>n fM When T d ≤T bM , then the total torque T output by the rear wheel motor d ; When the total torque T d >Rear wheel motor rated torque T bM , then the torque distribution coefficient β is less than the characteristic value β λ Perform torque distribution.

[0015] Furthermore, when the motor enters the magnetization region, the quadrature-axis flux reference value ψ q * and the direct-axis flux reference value ψ d * : When the motor enters the demagnetization area, The difference between the actual motor flux value and the reference flux value is modulated by PI to obtain the flux compensation value Δψ A ; When the motor enters the field weakening area, i dlimis the d-axis current when the motor runs at rated speed, i qlim is the q-axis current when the motor runs at rated speed, ψ f is the permanent magnet flux of the motor, i d *、i q *Direct-axis current and quadrature-axis current, respectively.

[0016] The beneficial effects of the present invention are:

[0017] (1) The present invention is the first to use the characteristics of the drive motor as an important distribution factor in the torque distribution strategy and set the characteristic value of the torque distribution coefficient. Combined with the real-time working conditions of the distributed electric vehicle, the front and rear wheel drive motor working modes are distributed to give full play to the advantages of the front and rear wheel drive magnetic field enhanced permanent magnet flat wire motors and improve the overall efficiency of the distributed drive electric vehicle.

[0018] (2) The present invention realizes the full-speed model prediction direct torque control strategy of electric vehicles based on the mapping relationship between the speed operation area and the flux state of the magnetic field enhanced permanent magnet flat wire motor, combined with the flux partition control and model prediction direct torque control, to meet the requirements of efficient and stable operation of the magnetic field enhanced permanent magnet flat wire motor under full-speed working conditions.

[0019] (3) The present invention constructs a new evaluation function based on the efficiency of drive motors with different operating characteristics and the loss distribution characteristics of different drive motors. It outputs the optimal torque distribution coefficient through real-time traversal calculation and coordinates the control of the dual drive motors based on the cross-coupling method. This ensures that the dual motors of distributed electric vehicles always operate in the high-efficiency area under variable operating conditions and the overall comprehensive energy efficiency of the system is optimal. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A block diagram of the control system for realizing the front and rear wheel drive magnetic field enhancement type permanent magnet flat wire motor of the present invention;

[0021] Figure 2 for Figure 1 Speed-torque diagram of the dual-field-enhanced permanent magnet flat wire motor for front and rear wheel drive;

[0022] Figure 3 for Figure 1 The topology of the field-enhanced permanent magnet flat wire motor for mid- and rear-wheel drive;

[0023] Figure 4 for Figure 1 Block diagram of the control system for a single magnetic field-enhanced permanent magnet flat wire motor. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and implementation examples. It should be understood that the specific examples described herein are only used to illustrate the present invention and are not intended to limit the present invention.

[0025] See also Figure 1 The control system block diagram of the distributed dual-field-enhanced permanent magnet flat wire drive motor shown in the figure adopts two distributed magnetic field-enhanced permanent magnet flat wire motors, namely, dual-field-enhanced permanent magnet flat wire motors for front and rear wheel drive as the front and rear wheel drive motors of the electric vehicle. The two magnetic field-enhanced permanent magnet flat wire motors have different power and mechanical characteristics. Specifically, the power of the front wheel drive magnetic field-enhanced permanent magnet flat wire motor (i.e., FI-IPM motor f, hereinafter referred to as "front wheel motor f") is P f , the maximum torque is T f The power of the rear wheel drive magnetic field enhanced permanent magnet flat wire motor b (ie FI-IPM motor b, hereinafter referred to as "rear wheel motor b") is P b , the maximum torque is T b Among them, the power P of the front wheel motor f f Greater than the power P of the rear wheel motor b b , P f It's P b M times, M = 1.45 ~ 1.65, P f =(1.45~1.65)P b The maximum torque T of the front wheel motor f f Greater than the maximum torque T of the rear wheel motor b b , is T b N times, N = 1.5 ~ 1.8, T f =(1.5~1.8)T b The front wheel motor f has the characteristics of low speed, high torque and high efficiency, and its salient pole ratio λ f The range is 0.4 to 0.6; the rear wheel motor has high speed and high efficiency characteristics, and its salient pole ratio λ b The range is 0.2 to 0.3.

[0026] The present invention utilizes a dynamic efficiency and torque collaborative distribution module to distribute the torque of the front and rear wheel motors f and b, adopts the front and rear full-speed domain model predictive direct torque control (i.e., full-speed domain MPDTC) as the drive motor control strategy, and adopts cross-coupling control to achieve dual drive motor collaborative control. Figure 1 The inputs of the dynamic efficiency and torque coordination module are: the dynamic efficiency η of the front and rear wheel motors f and b f and η b , the actual speed n and total torque T required by the vehicle operation d , the direct axis current and quadrature axis current i of the front wheel motor f df * and iqf *、Direct axis current i of rear wheel motor b db * and quadrature axis current i qb *, three-phase current i of front and rear wheel motors f, b abc_f and i abc_b , a total of 10 input parameters. The output of the dynamic efficiency and torque coordinated distribution module is the torque distribution reference value T allocated to the front and rear wheel motors f, b f * and T b *, torque distribution reference value T f * and T b * Input into the full speed range MPDTC of the front and rear wheel motors f and b respectively.

[0027] The electrical angles of the front wheel motor f and the rear wheel motor b are collected by the encoder, and the feedback speeds n of the front wheel motor f and the rear wheel motor b are obtained after the electrical angles are differentiated. f反馈 and n b反馈 The feedback speed n of the front wheel motor f f反馈 and the feedback speed n of the rear wheel motor b b反馈 The difference after comparison is adjusted by PI to obtain the synchronous error compensation value n 补 Synchronous error compensation value n 补 Multiply the speed compensation coefficient K of the front and rear wheel motors f and b respectively f , K b , and the compensated speed n is obtained respectively 补 K f 、n 补 K b .

[0028] Calculate the actual speed n and feedback speed n required by the vehicle f反馈 、n b反馈 , speed after compensation n 补 K f 、n 补 K b The difference is the speed setting value

[0029]

[0030] The speed given value will be obtained The full-speed domain MPDTC of the front and rear wheel motors f and b are input respectively, and the front and rear full-speed domain MPDTC are then combined with the torque distribution reference value T f *、T b *, full-speed model predictive direct torque control is adopted for the front and rear wheel motors f and b respectively to ensure efficient operation of the front and rear wheel motors f and b in the full speed range.

[0031] like Figure 2 The speed-torque curves of the front and rear wheel motors f and b are shown, where T fM The corresponding curve is the speed (n)-torque (T) curve of the front wheel motor f. The elliptical line 1 is the high efficiency area of ​​the front wheel motor f. T fM 、n fM 、n X are the rated torque, rated speed and turning speed of the front wheel motor f respectively; T bM The corresponding curve is the speed-torque curve of the rear wheel motor b. The elliptical line No. 2 is the high efficiency area of ​​the rear wheel motor b. bM 、n bM 、n Y The rated torque, rated speed and turning speed of the rear wheel motor b are determined according to the characteristics of the front and rear wheel motors f and b and the actual working conditions. X 、n Y , turning speed n X 、n Y Must be lower than the rated speed n M .

[0032] like Figure 3 The topology of rear-wheel motor b is shown. Rear-wheel motor b uses a 12-layer flat wire structure per phase. Each phase's six-layer flat wires are connected to form a Y-shaped structure, forming two Y-shaped structures. Rear-wheel motor b uses an 8-leg inverter. Each phase's two six-layer flat wires are connected to the center of each half-bridge driver. The neutral points of the two Y-shaped structures are connected to the center of the half-bridge drivers sharing the DC bus. A1, A2, B1, B2, C1, and C2 represent the two six-layer flat wire conductor windings of each phase, respectively. N1 and N2 are the two Y-shaped structure neutral points.

[0033] Figure 4 for Figure 1 The single magnetic field enhanced permanent magnet flat wire motor control system block diagram in the figure takes the front wheel motor f as an example. The dynamic efficiency η of the front and rear wheel motors f and b is obtained based on the efficiency MAP diagram of the front and rear wheel motors f and b and the real-time operating conditions of the vehicle. f ,η b , as follows:

[0034] By setting the torque distribution coefficient β (0<β<1), the output torque T of the front and rear wheel motors f and b can be obtained. f 、T b :

[0035]

[0036] The total torque T d =T f +T b .

[0037] According to the efficiency MAP diagram of the front and rear wheel motors f, b and the vehicle operating conditions, the output torque T corresponding to the front and rear wheel motors f, b can be obtained by using the table lookup method. f 、T b The motor dynamic efficiency η f ,η b , the total torque T d And the motor dynamic efficiency η f ,η b They are input to the dynamic efficiency and torque coordination distribution module.

[0038] The dynamic efficiency and torque coordination module optimizes overall energy efficiency and AC losses in the flat conductor windings, and distributes torque optimally to the front and rear wheel motors f and b as follows:

[0039] (1) According to the DC axis current of the front and rear wheel motors f and b, combined with the motor loss equations, the total loss P of the front and rear wheel motors f and b can be obtained. f损 、P b损 as follows:

[0040] Inverter losses mainly include conduction loss and switching loss, which can be equivalent to:

[0041]

[0042] Where: P ON_IGBT , P ON_Doi are the conduction losses of IGBT and diode respectively; P SW_IGBT is the IGBT switching loss; i A is the three-phase current i abc amplitude; λ1, λ2, λ3, λ4 are inverter loss constants.

[0043] Taking the front wheel motor f as an example (the same applies to the rear wheel motor b), the copper loss and iron loss of the motor can be expressed as:

[0044]

[0045] Where: P Cu , P Fe are the motor copper loss and iron loss respectively; R s is the armature resistance; R c is the iron loss equivalent resistance; i df * and i qf * is the direct-axis current and quadrature-axis current of the front-wheel motor f; i dc ,i qc are the equivalent current components of d-axis and q-axis iron loss, respectively, and their calculation formulas are as follows:

[0046]

[0047] Where: L df , L qf are the d-axis and q-axis inductances of the front wheel motor respectively; ψ ff is the permanent magnet flux of the front wheel motor; ω f is the electrical angular velocity of the front wheel motor, P is the number of motor pole pairs.

[0048] The calculation method for the copper loss and iron loss of the rear wheel motor b is similar to that of the front wheel motor f, and the copper loss and iron loss of the rear wheel motor b are obtained. The total loss of the front and rear wheel motors f and b is:

[0049]

[0050] Wherein, subscripts f and b represent the front and rear wheel motors, respectively.

[0051] (2) Since the stator current amplitude of the front and rear wheel motors f and b directly determines the AC loss of the flat wire conductor winding, the stator current amplitude i of the front and rear wheel motors f and b can be calculated based on the AC and DC axis currents of the front and rear wheel motors f and b. sf 、i sb :

[0052]

[0053] (3) According to the dynamic efficiency η of the front and rear wheel motors f and b f ,η b and the total loss P of the front and rear wheel motors f and b f损 、P b损 and the stator amplitude i of the front and rear wheel motors f and b sf 、i sd Construct the evaluation function g:

[0054]

[0055] (4) The accuracy of the alternative torque distribution coefficient β is determined according to the real-time operating conditions of the distributed electric vehicle, and the alternative torque distribution coefficient β is traversed and calculated. If the torque distribution coefficient β (0<β<1) is divided into 100 equal parts, 0, 0.01, ... 1 are traversed and calculated, and finally the torque distribution reference value T corresponding to the torque distribution coefficient β with the smallest evaluation function g value is obtained. f * and T b * Output, respectively sent to the front and rear wheel motors f, b full speed range MPDTC. The corresponding torque distribution reference value T f * and T b *The calculation formula is:

[0056] The two full-speed MPDTCs use full-speed model predictive direct torque control for the front and rear wheel motors f and b to ensure efficient operation in all speed ranges. The details are as follows:

[0057] (1) Figure 4 As shown, the three-phase current i of the motor is detected by the current sensor. abc , three-phase current i abc The quadrature and direct axis current i is obtained by coordinate transformation q (k), i d (k), k represents the current moment. The motor’s electrical angle θ is detected by the encoder, and the quadrature and direct axis current i q (k), i d (k) and the electrical angle θ are input into the current-type flux observer to obtain the quadrature-axis flux amplitude ψ q (k), direct axis flux amplitude ψ d (k), torque angle δ(k), stator flux angle δ s (k) as follows:

[0058]

[0059] Among them, ψ f is the permanent magnet flux of the motor, L d and L q is the d and q axis inductance, δ s (k) is the applied alternative voltage vector (U 1～6 ) caused by the stator flux angle, α=V s (k)*Δt / ψ s (k), V s (k) is the applied alternative voltage vector (U 1～6 ), U1, U2, U3, U4, U5, U6 are alternative voltage vectors, ψ s (k) is the stator flux at time k, and Δt is the action time.

[0060] (2) The cross-axis flux amplitude ψ q (k), direct axis flux amplitude ψ d (k), torque angle δ(k), stator flux angle δ s (k) is input into the DC-axis flux linkage and electromagnetic torque prediction model. 1～6 ), after Δt time, according to the geometric relationship of the flux change, the cosine theorem can be used to calculate the quadrature and direct axis flux and the stator flux amplitude at the next moment k+1, as shown in the following formulas:

[0061]

[0062] Where, ψ d (k+1),ψd (k) are the direct-axis magnetic flux at time k+1 and time k respectively; ψ q (k+1),ψ q (k) are the quadrature-axis magnetic flux at time k+1 and time k respectively; ψ s (k+1),ψ s (k) are the stator flux at time k+1 and time k respectively; θ q ,θ d are the angles between the applied voltage vector and the quadrature and direct axis flux linkages; θ v is the angle between the applied voltage vector and the stator flux; V s (k) is the applied alternative voltage vector (U 1～6 ).

[0063] Then the torque angle δ(k+1) at time k+1 is:

[0064]

[0065] Based on the stator flux amplitude ψ at the next moment s (k+1) and torque angle δ(k+1), combined with the torque equation, the torque value T at the next moment can be obtained e (k+1):

[0066]

[0067] Where p is the number of motor pole pairs.

[0068] (3) Figure 4 In the example, the speed setting value of the front wheel motor f is With feedback speed n f反馈 By comparison, we get the speed n f差 =n f *-n f反馈 , the speed n f差 Input to the flux partition control module. Speed ​​n f差 The motor stator current amplitude i is obtained by PI regulation in the flux partition control module. s .

[0069] At the same time, the feedback speed n f反馈 , inverter DC bus voltage U dc , cross-axis flux amplitude ψ q (k), direct axis flux amplitude ψ d (k) The common input is input into the flux partition control module.

[0070] The flux partition control module is based on the actual speed n and turning speed n of the front and rear wheel motors f and b. X 、n Y, the front and rear wheel motors f, b operating area is divided into magnetization area, demagnetization area, weak magnetic area: when the actual speed n < turning speed n X , the front wheel motor f runs in the magnetization area; when the turning speed n X ≤actual speed n≤rated speed n fM , the front wheel motor f runs in the demagnetization area; when the actual speed n> rated speed n fM , the front wheel motor f runs in the weak magnetic field area. When the actual speed n< turning speed n Y , the rear wheel motor runs in the magnetization area; when the turning speed n Y ≤actual speed n≤rated speed n bM , the rear wheel motor runs in the demagnetization area; when the actual speed n> rated speed n bM , the rear wheel motor runs in the weak magnetic zone. When the motor enters different zones, different cross-axis flux reference values ​​ψ are obtained according to different control methods. q * and the direct-axis flux reference value ψ d * Specifically:

[0071] When the motor enters the magnetization region, the maximum torque per flux ratio (MTPF) control is used to output the quadrature-axis flux reference value ψ as follows: q * and the direct-axis flux reference value ψ d * :

[0072]

[0073] Where ψ f is the permanent magnet flux of the motor, and the direct axis current i d * and quadrature axis current i q *for:

[0074]

[0075] Where i s is the motor stator current amplitude.

[0076] The flux partition control module converts the direct axis current i d * and quadrature axis current i q * Input to the dynamic efficiency and torque coordinated distribution module, for the front wheel motor f, the flux partition control module output i d * and i q * is the direct axis current i df * and quadrature axis current i qf *; For the rear wheel motor b, the flux partition control module outputs i d * and i q* is the direct axis current i db * and quadrature axis current i qb *i d * and i q *, i.e. i d *=i df *,i db *,i q *=i qf *,i qb *.

[0077] When the motor enters the demagnetization area, flux feedback compensation control is adopted: the actual motor flux value obtained by the flux observer is compared with the reference flux value, and the difference is modulated by PI to obtain the flux compensation value Δψ A , at this time the flux limit value is ψ Alim , ψ Alim is the stator flux amplitude when the motor runs at the turning speed, which is calculated offline using the following formula:

[0078]

[0079] Among them, i dA is the d-axis current when the motor runs at the turning speed, i qA is the q-axis current when the motor runs at the turning speed.

[0080] Flux compensation value Δψ A Compensation direct axis flux ψ d *, realize the effective demagnetization of the direct axis and output the corresponding quadrature axis flux reference value ψ q * and the direct-axis flux reference value ψ d * :

[0081]

[0082] When the motor enters the field weakening area, the flux feedback compensation control is adopted to perform field weakening speed increase and output the corresponding quadrature axis flux reference value ψ q * and the direct-axis flux reference value ψ d * , at this time the flux limit value is ψ lim , ψ lim is the stator flux amplitude when the motor runs at rated speed, which is calculated offline using the following formula:

[0083]

[0084] Among them, i dlim is the d-axis current when the motor runs at rated speed, i qlim is the q-axis current when the motor runs at rated speed.

[0085] Cross-axis flux reference value ψ q * and the direct-axis flux reference value ψ d * for

[0086]

[0087] (4) Using the next moment's quadrature axis flux amplitude ψ q (k+1) and the direct axis flux amplitude ψ d (k+1) and the torque value T at the next moment e (k+1) and the quadrature-axis flux reference value ψ q * and the direct-axis flux reference value ψ d * And the torque reference value T e *(For front wheel motor T e *=T f *; For rear wheel motor T e *=T b *. ), construct the cost function g m The cost function g m The first part is the square of the relative error of the predicted torque, and the latter part is the square of the relative error of the direct-axis flux and the quadrature-axis flux. Using the relative error method, the cost function is converted into a dimensionless quantity:

[0088]

[0089] (5) will make the cost function g m The inverter switching signal S corresponding to the minimum voltage vector A 、S B 、S C To output to the inverter, to achieve efficient operation of FI-IPM flat wire motor in full speed range, U dc is the inverter DC bus voltage.

[0090] The preferred embodiment of the present invention is: the dynamic efficiency and torque coordinated distribution module performs torque distribution by respectively comparing the actual speed n of the vehicle output with the rated speed n of the front and rear wheel motors f and b. fM 、n bM and turning speed n X 、n Y Compare the magnitudes of the two torques respectively and calculate the total torque T d The rated torque T of the front and rear wheel motors f and b are respectively fM 、T bM Compare the size relationship and then assign the working mode of the front and rear wheel motors f and b. The details are as follows:

[0091] (1) Establish the torque distribution coefficient characteristic value β according to the characteristics of the front and rear wheel motors f and b λ As follows:

[0092]

[0093] M is the power P of the front wheel motor f f and the power P of the rear wheel motor b b Multiples of, M = 1.45 ~ 1.65, N is the maximum torque T of the front wheel motor f f and the maximum torque T of the rear wheel motor b b Multiples of, N = 1.5 ~ 1.8, λ f is the saliency of the front wheel motor f, λ f The range is 0.4 to 0.6; λ is the saliency of the rear wheel motor b, λ b The range is 0.2 to 0.3.

[0094] According to the torque distribution coefficient characteristic value β λ And establish the torque distribution coefficient β (0<β<1) to determine the working mode. When the torque distribution coefficient β is greater than or equal to the characteristic value β λ When the torque distribution coefficient β is less than the characteristic value β λ When , it is the second working mode, i.e., model = 2. This limits the torque distribution coefficient under different working conditions and effectively utilizes the high efficiency area of ​​the field-enhanced permanent magnet flat wire motor for front and rear wheel drive.

[0095] (2) When the actual speed n required by the system is less than the turning speed n of the front wheel motor X When the total torque T d ≤Rear wheel motor rated torque T bM , the total torque T output by the front wheel motor d , the rear wheel motor is only responsible for coordinating the speed of the dual motors; if the total torque T d >Rear wheel motor rated torque T bM , the dynamic efficiency and torque collaborative distribution module performs torque distribution, adopts the model = 1 working mode, and the torque distribution coefficient β is greater than or equal to the characteristic value β λ Distributes torque to the front and rear wheels.

[0096] (3) Current wheel motor turning speed n X ≤actual speed n≤front wheel motor rated speed n fM When , the dynamic efficiency and torque coordinated distribution module performs torque distribution, and adopts the model=1 working mode to distribute torque to the front and rear wheel motors.

[0097] (4) When the actual speed n> the rated speed n of the front wheel motorfM When the total torque T d ≤Rear wheel motor rated torque T bM , then the total torque T output by the rear wheel motor d , the front wheel motor is only responsible for coordinating the speed of the dual motors; if the total torque T d >Rear wheel motor rated torque T bM , the dynamic efficiency and torque collaborative distribution module performs torque distribution, and adopts the model=2 working mode, then the torque distribution coefficient β is less than the characteristic value β λ Distributes torque between the front and rear wheel motors.

[0098] Therefore, the distributed dual-magnetic field enhanced permanent magnet flat wire drive motor torque and efficiency optimal control proposed in the present invention takes the drive motor characteristics as an important allocation factor in the torque allocation strategy and establishes the torque allocation coefficient characteristic value. In combination with the real-time working conditions of the distributed electric vehicle, the front and rear wheel motors f and b are allocated to work modes to give full play to the advantages of the front and rear wheel motors f and b, thereby improving the overall efficiency of the distributed drive electric vehicle. The present invention realizes the electric vehicle full-speed domain model prediction direct torque control strategy based on the mapping relationship between the speed operation area and the flux state of the magnetic field enhanced permanent magnet flat wire motor, combines flux partition control and model prediction direct torque control, and meets the requirements of efficient and stable operation of the magnetic field enhanced permanent magnet flat wire motor under full-speed domain working conditions; the present invention constructs a new evaluation function based on the efficiency of the drive motors with different operating characteristics and the loss distribution characteristics of different drive motors, outputs the optimal torque allocation coefficient through real-time traversal calculation, and collaboratively controls the dual drive motors based on the cross-coupling method, thereby achieving the distributed electric vehicle under variable operating conditions. The dual motors always operate in the high-efficiency area and the overall comprehensive energy efficiency of the system is optimized. Compared with existing control technologies, the present invention comprehensively considers the efficiency of drive motors with different operating characteristics and the loss distribution characteristics of different drive motors, greatly improving the overall performance of distributed electric vehicles.

[0099] The above implementation cases are only used to illustrate the design ideas and features of the present invention. Its purpose is to enable technical personnel in this field to understand the content of the present invention and implement it accordingly. The scope of protection of the present invention is not limited to the above implementation cases. Therefore, any equivalent changes or modifications made according to the principles and design ideas disclosed by the present invention are within the scope of protection of the present invention.

Claims

1. A method for optimal control of torque and efficiency of a distributed dual-field enhanced permanent magnet flat wire motor, characterized by: The front and rear wheel motors with different power and mechanical characteristics are used as the front and rear wheel drive motors of the electric vehicle respectively; Feedback speed n of the front and rear wheel motors f反馈 、n b反馈 The difference after comparison is adjusted by PI to obtain the synchronous error compensation value n 补 , calculate the speed given value K f , K b is the speed compensation coefficient, n is the actual speed; Constructing an evaluation function P f损 、P b损 is the total loss of the front and rear wheel motors, η f ,η b is the dynamic efficiency of the front and rear wheel motors, i sf 、i sd is the stator current amplitude of the front and rear wheel motors; The set torque distribution coefficient β is calculated ergodicly, 0<β<1, and the torque distribution reference value T of the front and rear wheel motors corresponding to the torque distribution coefficient β with the minimum evaluation function g value is obtained. f * = βT d and T b *=(1-β)T d , T d is the total torque; According to the actual speed and turning speed of the front and rear wheel motors, the operating area is divided into the magnetization area, demagnetization area, and weak magnetic area. When the motor enters different areas, different cross-axis flux reference values ​​ψ are obtained according to different control methods. q * and the direct-axis flux reference value ψ d * ; First, obtain the cross-axis magnetic flux amplitude ψ by magnetic flux observation q (k), direct axis flux amplitude ψ d (k), torque angle δ(k) and stator flux angle δ s (k), and then predict the next moment of the cross-axis and direct-axis magnetic flux amplitude ψ q (k+1),ψ d (k+1) and torque value T e (k+1), front wheel motor torque reference value T e *=T f *, rear wheel motor torque reference value T e *=T b *, construct the cost function This will make the cost function g m The minimum voltage vector is output to control the motor operation.

2. The method for optimizing torque and efficiency of a distributed dual-field enhanced permanent magnet flat wire motor according to claim 1 is characterized by: The power of the front wheel motor is 1.45 to 1.65 times that of the rear wheel motor, and the maximum torque of the front wheel motor is 1.5 to 1.8 times that of the rear wheel motor. The front wheel motor has the characteristics of low speed, high torque and high efficiency, and the rear wheel motor has the characteristics of high speed and high efficiency. The salient pole ratio λ of the front wheel motor is λ. f The range is 0.4 to 0.6, and the saliency rate of the rear wheel motor is in the range of 0.2 to 0.

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3. The method for optimizing torque and efficiency of a distributed dual-field enhanced permanent magnet flat wire motor according to claim 1 is characterized by: The rear wheel motor adopts a 12-layer flat wire structure per phase. The 6-layer flat wires of each phase are connected into a Y-shaped structure, forming two Y-shaped structures in total. The rear wheel motor adopts an 8-bridge arm inverter. The two 6-layer flat wires of each phase are respectively connected to the centers of the two half-bridge drivers. The neutral points of the two Y-shaped structures are respectively connected to the centers of the half-bridge drivers with a common DC bus.

4. The method for optimizing torque and efficiency of a distributed dual-field enhanced permanent magnet flat wire motor according to claim 1 is characterized by: When the actual speed n<front wheel motor turning speed n X , the front wheel motor runs in the magnetization area; when n X ≤n≤Rated speed of front wheel motor n fM , the front wheel motor runs in the demagnetization area; when n>n fM , the front wheel motor runs in the weak magnetic area; when the actual speed n< the rear wheel motor turning speed n Y , the rear wheel motor operates in the magnetization area; when n Y ≤n≤Rear wheel motor rated speed n bM , the rear wheel motor runs in the demagnetization area; when n>n bM , the rear wheel motor operates in the weak magnetic area.

5. The method for optimizing torque and efficiency of a distributed dual-field enhanced permanent magnet flat wire motor according to claim 4 is characterized by: Calculate the characteristic value of the torque distribution coefficient λ f ,λ b are the saliency rates of the front and rear wheel motors, respectively; When the actual speed n <n X When the total torque T d ≤Rear wheel motor rated torque T bM , the total torque T output by the front wheel motor d ; If the total torque T d >Rear wheel motor rated torque T bM , then the torque distribution coefficient β is greater than or equal to the characteristic value β λ Perform torque distribution; When n X ≤n≤Rated speed of front wheel motor n fM When the torque distribution coefficient β is greater than or equal to the characteristic value β λ Perform torque distribution; When the actual speed n>n fM When T d ≤T bM , then the total torque T output by the rear wheel motor d ; When the total torque T d >Rear wheel motor rated torque T bM , then the torque distribution coefficient β is less than the characteristic value β λ Perform torque distribution.

6. The method for optimizing torque and efficiency of a distributed dual-field enhanced permanent magnet flat wire motor according to claim 4 is characterized by: When the motor enters the magnetization area, the quadrature axis flux reference value ψ q * and the direct-axis flux reference value ψ d * : When the motor enters the demagnetization area, The difference between the actual motor flux value and the reference flux value is modulated by PI to obtain the flux compensation value Δψ A ; When the motor enters the field weakening area, i dlim is the d-axis current when the motor runs at rated speed, i qlim is the q-axis current when the motor runs at rated speed, ψ f is the permanent magnet flux of the motor, i d *、i q *Direct-axis current and quadrature-axis current, respectively.

7. The method for optimizing torque and efficiency of a distributed dual-field enhanced permanent magnet flat wire motor according to claim 1 is characterized in that: The loss is: Taking the front wheel motor as an example, the copper loss and iron loss of the motor are: , then the total loss of the front and rear wheel motors is: Subscripts f and b represent the front and rear wheel motors respectively; P ON_IGBT , P ON_Doi are the conduction losses of IGBT and diode respectively; P SW_IGBT is the IGBT switching loss; i A is the three-phase current i abc amplitude; λ1, λ2, λ3, λ4 are inverter loss constants; P Cu , P Fe are the motor copper loss and iron loss respectively; R s is the armature resistance; R c is the iron loss equivalent resistance; i df * and i qf * is the direct-axis current and quadrature-axis current of the front-wheel motor f; i dc ,i qc are the equivalent current components of d-axis and q-axis iron loss respectively.

8. The method for optimizing torque and efficiency of a distributed dual-field enhanced permanent magnet flat wire motor according to claim 7 is characterized by: The equivalent current components of the d and q axis iron losses are: L df , L qf are the d-axis and q-axis inductances of the front and rear wheel motors respectively; ψ ff is the permanent magnet flux of the front wheel motor; ω f is the electrical angular velocity of the front wheel motor, P is the number of motor pole pairs.

9. The method for optimizing torque and efficiency of a distributed dual-field enhanced permanent magnet flat wire motor according to claim 1, wherein: ψ f is the permanent magnet flux of the motor, L d and L q is the d and q axis inductance, δ s (k) is the stator flux linkage angle caused by applying the alternative voltage vector, α = V s (k)*Δt / ψ s (k), V s (k) is the applied alternative voltage vector, ψ s (k) is the stator flux at time k, and Δt is the action time.

10. The method for optimizing torque and efficiency of a distributed dual-field enhanced permanent magnet flat wire motor according to claim 1, wherein: θ q ,θ d are the angles between the applied voltage vector and the quadrature and direct axis flux, θ v is the angle between the applied voltage vector and the stator flux; V s (k) is the applied alternative voltage vector and p is the number of motor pole pairs.

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