阅读说明：本技术 一种直流偏置型正弦电流电机的最小铜耗控制方法及装置 (Minimum copper consumption control method and device for direct current bias type sinusoidal current motor ) 是由 孔武斌 于子翔 曲荣海 李大伟 于 2020-04-29 设计创作，主要内容包括：本发明公开了一种直流偏置型正弦电流电机的最小铜耗控制方法及装置。根据电机转速的变化,实时改变相电流中直流偏置电流和交流电流的比例,实现电机运行过程中定子铜耗的最小化。本发明不改变直流偏置型正弦电流电机控制系统的硬件结构,通过对所述电机电磁转矩和定子铜耗的理论分析,推导出不同转速下最优的电流分配关系,有效提高直流偏置型正弦电流电机的运行效率,适用于此类电机驱动控制。(The invention discloses a minimum copper consumption control method and device for a direct current bias type sine current motor. According to the change of the rotating speed of the motor, the proportion of the direct current bias current and the alternating current in the phase current is changed in real time, and the minimization of the stator copper loss in the running process of the motor is realized. The invention does not change the hardware structure of the direct current bias type sine current motor control system, deduces the optimal current distribution relation under different rotating speeds through the theoretical analysis of the electromagnetic torque and the stator copper loss of the motor, effectively improves the operating efficiency of the direct current bias type sine current motor and is suitable for the driving control of the motor.)

1. A minimum copper loss control method of a direct current bias sine current motor is characterized by comprising the following steps:

(1) by adjusting the torque set value T_eEnabling the motor rotating speed n to always follow the change of the motor rotating speed given value n;

(2) under the condition of meeting the minimum copper consumption, the motor speed n and the torque given value T are used_eDistributing the given values of d-axis current, q-axis current and 0-axis current to obtain the given value u of the voltage of the dq axis of the stator_d*、u_q*；

(3) According to the given value u of the voltage vector of the dq axis of the stator_d*、u_qGet the phase lag from u_dSum of u_qThe resultant voltage vector of 30 degrees is the resultant voltage vectorMultiplied voltage vector u_α1*、u_β1A first step of; according to the given value u of the voltage vector of the dq axis of the stator_d*、u_qGet the phase lag from u_dSum of u_qThe resultant voltage vector of 150 degrees is the resultant voltage vectorMultiplied voltage vector u_α2*、u_β2*；

(4) For u is paired_iα1*、u_iβ10 axis voltage signal gamma₀Space vector pulse width modulation is carried out on the duty ratio d of the non-zero vector voltage to generate PWM signals 1-6 of A1, B1 and C1 phases, and a first voltage is obtained through a first inverter; for u is paired_iα2*、u_iβ2Performing space vector pulse width modulation to generate PWM signals 7-12 of A2, B2 and C2 phases, and obtaining a second voltage through a second inverter;

(5) and inputting the first voltage and the second voltage into a direct current bias sinusoidal current motor to generate a sinusoidal current signal with direct current bias, so as to realize direct torque control of the direct current bias sinusoidal current motor.

2. The control method of claim 1, wherein the copper loss of the dc-biased sinusoidal current motor is expressed as d-axis current i_dQ-axis current i_qAnd 0 axis current i₀Function of (c):

wherein R is_acIs an AC equivalent resistance, R, of the armature winding_acThe magnitude of the voltage is changed along with the change of the current frequency or the motor rotating speed n; r_dcIs a DC equivalent resistance, and R_dcIndependent of rotational speed。

3. The control method of claim 2, wherein i is set_dSetting the R value to be 0, and utilizing curve fitting to simulate finite element analysis to obtain the R_acIs represented by i_qAnd n is:

R_ac＝c₁i_q ²+(c₂+c₃·n)i_q+(c₄+c₅·n)

wherein, c_i(i ═ 1,2,3,4,5) represents a constant obtained by curve fitting.

4. A control method according to claim 3, wherein (i) corresponds to the minimum copper consumption_q,i₀) In combination, the lagrange function is defined as:

where λ is the lagrange constant.

5. The control method according to claim 4, wherein (i)_q,i₀) The combined solution method comprises the following steps:

and solving a partial derivative of the Lagrange function to obtain:

aiming at the equation set, solving an analytic solution by using a least square method:

i_q＝k₁+k₂T_e+k₃n+k₄T_e ²+k₅T_en

i₀＝k₁₀+k₂₀T_e+k₃₀n+k₄₀T_e ²+k₅₀T_en

wherein k is_i，k_i0(i＝1,2,3,4,5) represent constants obtained by curve fitting.

6. The control method according to claim 5, wherein given values i of d-axis, q-axis and 0-axis currents are distributed_d*、i_qA and i₀The process specifically comprises the following steps:

motor speed n and torque set value T_eInput current distributor according to i_qAnd i₀With T_eN, calculating to obtain i_qA and i₀Simultaneously controlling i_d*＝0。

7. A minimum copper loss control device for a dc-biased sinusoidal current motor, comprising:

a PI regulator (1) for receiving the difference between the given value n of the motor speed and the motor speed n and outputting a given value T of the torque_e*；

A minimum copper current distributor (2) for setting a value T according to the motor speed n and the output torque_eDistributing given values of d-axis current, q-axis current and 0-axis current;

a d-axis current PI regulator (3a) for receiving a d-axis current given value i_dFeedback value of x and zero axis current i_dD-axis voltage given value u is output_d*；

A q-axis current PI regulator (3b) for receiving a q-axis current given value i_qFeedback value of x and zero axis current i_qOutput a given value u of the q-axis voltage_q*；

A 0-axis current PI regulator (3c) for receiving a 0-axis current given value i₀Feedback value of x and zero axis current i₀To output a given value u of zero-axis voltage₀*；

A first voltage phase-shift module (4a) for receiving a given value u of the d-axis voltage_dVoltage set value u of axis x and q_qLag of output phase from u_dSum of u_qThe resultant voltage vector of 30 degrees is the resultant voltage vectorMultiplied voltage vector u_α1*、u_β1*；

A second voltage phase-shift module (4b) for receiving a given value u of the d-axis voltage_dVoltage set value u of axis x and q_qLag of output phase from u_dSum of u_qThe resultant voltage vector of 150 degrees is the resultant voltage vectorMultiplied voltage vector u_α2*、u_β2*；

A first pulse width modulation module (5a) for receiving the voltage vector u_α1*、u_β1And 0 axis voltage signal duty ratio gamma₀Performing space vector pulse width modulation, and outputting PWM signals (pulse width modulation) 1-6 of A1, B1 and C1 phases of the first inverter;

a second pulse width modulation module (5b) for receiving the voltage vector u_α2*、u_β2Duty ratio gamma of voltage signals of x and 0 axes₀Space vector pulse width modulation is performed, and a PWM signal 7-12 of A2, B2 and C2 phases of the second inverter is output.

8. The control apparatus of claim 7, wherein the 0-axis voltage signal duty cycle γ₀Outputting a zero-axis voltage set value u by the 0-axis current PI regulator₀And 2U_dcIs divided to obtain U_dcIs the dc bus voltage.

Technical Field

The invention belongs to the field of alternating current motor driving and control, and particularly relates to a minimum copper consumption control method and device for a direct current bias type sine current motor.

Background

The phase current of the dc offset type sinusoidal current motor contains a dc offset component in addition to an ac component. The alternating current component in the phase current generates a stator magnetic field, the direct current offset component in the phase current generates a rotor magnetic field, and the two magnetic fields interact to generate electromagnetic torque. The size of the magnetic field of the motor rotor can be flexibly adjusted by changing the size of the direct current bias current, so that the motor has excellent speed regulation performance; meanwhile, the motor adopts a double salient pole structure and a stator concentrated winding structure, so that the motor has the advantages of simple and reliable structure and low cost, and has received wide attention at home and abroad in recent years.

When the direct current bias type sine current motor uses a traditional control strategy, the ratio of alternating current to direct current bias current does not change along with the change of the rotating speed in a constant torque interval, although the normal operation of the motor can be realized, the copper consumption of the motor is not optimized according to the rotating speed of the motor, and the operation efficiency of the motor is limited. In addition, different alternating current components and direct current components have different influences on the excitation inductance of the motor, and the traditional control strategy does not consider the nonlinearity of the inductance, so that the torque output capacity of the motor in a constant torque interval is further limited.

With the increase of the rotating speed of the motor, the frequency of alternating current in a motor winding increases, the proportion of alternating current copper consumption is continuously increased under the influence of a skin effect and a proximity effect, and the alternating current copper consumption generated by direct current bias current does not change along with the increase of the rotating speed. In the process of increasing the rotating speed of the motor, the proportion of alternating current is properly reduced, and the direct current bias current is increased, so that the copper consumption of the motor is ensured to be minimum under the condition of certain output torque, and the operating efficiency of the motor in a high-speed interval is improved.

Disclosure of Invention

Aiming at the defects or improvement requirements in the prior art, the invention provides a minimum copper loss control method and device for a direct current bias type sine current motor, and aims to deduce the optimal current distribution relation at different rotating speeds through theoretical analysis of the electromagnetic torque and the stator copper loss of the motor on the premise of not changing the hardware structure of a control system. According to the change of the rotating speed of the motor, the proportion of the direct current bias current and the alternating current in the phase current is changed in real time, the minimization of the stator copper loss in the running process of the motor is realized, and the running efficiency of the direct current bias type sine current motor is effectively improved.

To facilitate understanding of the present invention, the following explains the concept:

when the direct current bias type sine current operates in a constant torque interval, a maximum torque current ratio control mode is generally adopted. The proportion of the effective value of the alternating current to the effective value of the direct current bias current is controlled to be the same, so that the maximum electromagnetic torque is output under the condition that the effective value of the phase current is fixed, and the motor efficiency is improved.

In the field of motor control, generally, an abc three-phase stationary coordinate system is converted to a dq0 synchronous rotating coordinate system using a rotating coordinate conversion matrix. The coordinate axes of an a axis, a b axis and a c axis of the abc three-phase static coordinate system are different from each other by 120 electrical angles in space; d-axis, q-axis and 0-axis of dq0 synchronous rotation coordinate system are perpendicular to each other in three-dimensional space, and the d-axis and the q-axis surround the 0-axis by omega_eThe synchronous rotation speed of (2) is rotated, so that alternating abc three-phase currents in a stationary coordinate system can be converted into direct currents in a dq0 synchronous rotating coordinate system, and the control complexity is further simplified.

In order to achieve the above object, the present invention provides a method for controlling minimum copper loss of a dc offset sinusoidal current motor, according to the characteristics that copper loss generated by ac current in a dc offset sinusoidal current motor winding increases with the increase of the motor rotation speed, and copper loss generated by dc current does not change with the change of the motor rotation speed, theoretical analysis is performed on the motor copper loss and electromagnetic torque by using a finite element analysis method, so that the proportion of ac current is properly reduced in the process of increasing the motor rotation speed, and the dc offset current is increased, thereby ensuring the minimum copper loss of the motor and improving the operation efficiency of the motor in a high-speed interval under the condition of a certain output torque. The method specifically comprises the following steps:

(1) by adjusting the torque set value T_eEnabling the motor rotating speed n to always follow the change of the motor rotating speed given value n;

(2) under the condition of meeting the minimum copper consumption, the motor speed n and the torque given value T are used_eDistributing the given values of d-axis current, q-axis current and 0-axis current to obtain the given value u of the voltage of the dq axis of the stator_d*、u_q*；

(3) According to the given value u of the voltage vector of the dq axis of the stator_d*、u_qGet the phase lag from u_dSum of u_qThe resultant voltage vector of 30 degrees is the resultant voltage vectorMultiplied voltage vector u_α1*、u_β1A first step of; according to the given value u of the voltage vector of the dq axis of the stator_d*、u_qGet the phase lag from u_dSum of u_qThe resultant voltage vector of 150 degrees is the resultant voltage vectorMultiplied voltage vector u_α2*、u_β2*；

(4) For u is paired_iα1*、u_iβ10 axis voltage signal gamma₀Space vector pulse width modulation is carried out on the duty ratio d of the non-zero vector voltage to generate PWM signals 1-6 of A1, B1 and C1 phases, and a first voltage is obtained through a first inverter; for u is paired_iα2*、u_iβ2Performing space vector pulse width modulation to generate PWM signals 7-12 of A2, B2 and C2 phases, and obtaining a second voltage through a second inverter;

(5) and inputting the first voltage and the second voltage into the direct-current bias sinusoidal current motor to generate a sinusoidal current signal with direct-current bias, so as to realize direct torque control of the direct-current bias sinusoidal current motor.

Further, the copper loss of the dc-biased sinusoidal current motor may be expressed as d-axis current i_dQ-axis current i_qAnd 0 axis current i₀Function of (c):

wherein R is_acIs an AC equivalent resistance, R, of the armature winding_acThe magnitude of the voltage is changed along with the change of the current frequency or the motor rotating speed n; r_dcIs a DC equivalent resistance, and R_dcIndependent of the rotational speed.

Further, i is_dSet to 0, simulate finite element analysis using curve fittingObtained R_acIs represented by i_qAnd n is:

R_ac＝c₁i_q ²+(c₂+c₃·n)i_q+(c₄+c₅·n)

wherein, c_i(i ═ 1,2,3,4,5) represents a constant obtained by curve fitting.

Further, (i) corresponding to the condition of minimum copper consumption_q,i₀) In combination, the lagrange function is defined as:

where λ is the lagrange constant.

Further, (i)_q,i₀) The combined solution method comprises the following steps:

and (3) solving a partial derivative of the Lagrange function to obtain:

aiming at the equation set, solving an analytic solution by using a least square method:

i_q＝k₁+k₂T_e+k₃n+k₄T_e ²+k₅T_en

i₀＝k₁₀+k₂₀T_e+k₃₀n+k₄₀T_e ²+k₅₀T_en

wherein k is_i，k_i0(i ═ 1,2,3,4,5) represents a constant obtained by curve fitting.

Further, given values i of d-axis, q-axis and 0-axis currents are distributed_d*、i_qA and i₀The process specifically comprises the following steps:

motor speed n and torque set value T_eInput current distributor according to_qAnd i₀With T_eN, calculating to obtain i_qA and i₀Simultaneously controlling i_d0. Under given speed and load conditions, (i)_q,i₀) The combination of the motor and the motor is in an optimal state, thereby ensuring the minimum copper loss of the motor and improving the operation efficiency of the motor.

According to another aspect of the present invention, there is provided a minimum copper loss control apparatus for a dc-biased sinusoidal current motor, comprising:

a PI regulator for receiving the difference between the given value n of the motor speed and the motor speed n and outputting a given value T of the torque_e*；

A minimum copper loss current distributor for setting value T according to motor speed n and output torque_eDistributing given values of d-axis current, q-axis current and 0-axis current;

a d-axis current PI regulator for receiving d-axis current given value i_dFeedback value of x and zero axis current i_dD-axis voltage given value u is output_d*；

A q-axis current PI regulator for receiving a given value i of the q-axis current_qFeedback value of x and zero axis current i_qOutput a given value u of the q-axis voltage_q*；

A 0-axis current PI regulator for receiving a 0-axis current given value i₀Feedback value of x and zero axis current i₀To output a given value u of zero-axis voltage₀*；

A first voltage phase shift module for receiving a given value u of d-axis voltage_dVoltage set value u of axis x and q_qLag of output phase from u_dSum of u_qThe resultant voltage vector of 30 degrees is the resultant voltage vectorMultiplied voltage vector u_α1*、u_β1*；

A second voltage phase shift module for receiving the given value u of d-axis voltage_dVoltage set value u of axis x and q_qLag of output phase from u_dSum of u_qThe resultant voltage vector of 150 degrees is the resultant voltage vectorMultiplied voltage vector u_α2*、u_β2*；

A first pulse width modulation module for receiving the voltage vector u_α1*、u_β1And 0 axis voltage signal duty ratio gamma₀Performing space vector pulse width modulation, and outputting PWM signals (pulse width modulation) 1-6 of A1, B1 and C1 phases of the first inverter;

a second pulse width modulation module (5b) for receiving the voltage vector u_α2*、u_β2Duty ratio gamma of voltage signals of x and 0 axes₀Space vector pulse width modulation is performed, and a PWM signal 7-12 of A2, B2 and C2 phases of the second inverter is output.

Wherein, the duty ratio gamma of the 0-axis voltage signal₀Outputting a zero-axis voltage given value u by a 0-axis current PI regulator₀And 2U_dcIs divided to obtain U_dcIs the dc bus voltage.

In general, compared with the prior art, the minimum copper loss control strategy provided by the invention derives the optimal current distribution relation at different rotating speeds by theoretical analysis of the electromagnetic torque and the stator copper loss of the motor on the premise of not changing the hardware structure of a control system. According to the change of the rotating speed of the motor, the proportion of the direct current bias current and the alternating current in the phase current is changed in real time, the minimization of the stator copper loss in the running process of the motor is realized, the running efficiency of the direct current bias type sine current motor is effectively improved, and the method is suitable for the drive control of the novel direct current bias type sine current motor.

Drawings

FIG. 1 is a typical phase current waveform for a DC-biased sinusoidal current motor;

FIG. 2 is a main circuit structure diagram of a DC bias type sinusoidal current motor control system;

FIG. 3 is a control block diagram of a minimum copper loss control strategy for a DC-biased sinusoidal current motor;

FIG. 4 is a comparison of current traces for a conventional control strategy and a minimum copper loss control strategy;

fig. 5 is a comparison of motor efficiency for a conventional control strategy and a minimum copper loss control strategy.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

The invention provides a minimum copper loss control method of a direct current bias type sine current motor, which is characterized in that according to the characteristic that copper loss generated by alternating current in a direct current bias type sine current motor winding is increased along with the increase of the rotating speed of the motor and the characteristic that the copper loss generated by the direct current is not changed along with the change of the rotating speed of the motor, the copper loss and the electromagnetic torque of the motor are theoretically analyzed by a finite element analysis method, the proportion of the alternating current is properly reduced in the process of increasing the rotating speed of the motor, the direct current bias current is improved, the minimum copper loss of the motor is ensured under the condition of certain output torque, and the operation efficiency of the motor in a high-speed interval is improved. The method specifically comprises the following steps:

(1) by adjusting the torque set value T_eEnabling the motor rotating speed n to always follow the change of the motor rotating speed given value n;

(2) under the condition of meeting the minimum copper consumption, the motor speed n and the torque given value T are used_eDistributing the given values of d-axis current, q-axis current and 0-axis current to obtain the given value u of the voltage of the dq axis of the stator_d*、u_q*；

(3) According to the given value u of the voltage vector of the dq axis of the stator_d*、u_qGet the phase lag from u_dSum of u_qThe resultant voltage vector of 30 degrees is the resultant voltage vectorMultiplied voltage vector u_α1*、u_β1A first step of; according to the given value u of the voltage vector of the dq axis of the stator_d*、u_qObtainingPhase lagging behind u_dSum of u_qThe resultant voltage vector of 150 degrees is the resultant voltage vectorMultiplied voltage vector u_α2*、u_β2*；

(4) For u is paired_iα1*、u_iβ10 axis voltage signal gamma₀Space vector pulse width modulation is carried out on the duty ratio d of the non-zero vector voltage to generate PWM signals 1-6 of A1, B1 and C1 phases, and a first voltage is obtained through a first inverter; for u is paired_iα2*、u_iβ2Performing space vector pulse width modulation to generate PWM signals 7-12 of A2, B2 and C2 phases, and obtaining a second voltage through a second inverter;

(5) and inputting the first voltage and the second voltage into the direct-current bias sinusoidal current motor to generate a sinusoidal current signal with direct-current bias, so as to realize direct torque control of the direct-current bias sinusoidal current motor.

The invention also provides a minimum copper consumption control device of the direct current bias sine current motor, which is characterized by comprising the following components:

a PI regulator 1 for receiving the difference between the given value n of the motor speed and the motor speed n and outputting a given value T of the torque_e*；

A minimum copper loss current distributor for setting value T according to motor speed n and output torque_eDistributing given values of d-axis current, q-axis current and 0-axis current;

a d-axis current PI regulator 3a for receiving a d-axis current given value i_dFeedback value of x and zero axis current i_dD-axis voltage given value u is output_d*；

A q-axis current PI regulator 3b for receiving a given value i of the q-axis current_qFeedback value of x and zero axis current i_qOutput a given value u of the q-axis voltage_q*；

A 0-axis current PI regulator 3c for receiving a 0-axis current given value i₀Feedback value of x and zero axis current i₀To output a given value u of zero-axis voltage₀*；

First voltage phase-shift module 4a for receiving d-axis voltage set value u_dVoltage set value u of axis x and q_qLag of output phase from u_dSum of u_qThe resultant voltage vector of 30 degrees is the resultant voltage vectorMultiplied voltage vector u_α1*、u_β1*；

A second voltage phase shift module 4b for receiving the given value u of the d-axis voltage_dVoltage set value u of axis x and q_qLag of output phase from u_dSum of u_qThe resultant voltage vector of 150 degrees is the resultant voltage vectorMultiplied voltage vector u_α2*、u_β2*；

A first pulse width modulation module 5a for receiving the voltage vector u_α1*、u_β1And 0 axis voltage signal duty ratio gamma₀Performing space vector pulse width modulation, and outputting PWM signals (pulse width modulation) 1-6 of A1, B1 and C1 phases of the first inverter;

a second pulse width modulation module 5b for receiving the voltage vector u_α2*、u_β2Duty ratio gamma of voltage signals of x and 0 axes₀Space vector pulse width modulation is performed, and a PWM signal 7-12 of A2, B2 and C2 phases of the second inverter is output.

Wherein, the duty ratio gamma of the 0-axis voltage signal₀Outputting a zero-axis voltage given value u by a 0-axis current PI regulator₀And 2U_dcIs divided to obtain U_dcIs the dc bus voltage.

A typical phase current waveform for a dc-biased sinusoidal current motor is shown in fig. 1, where the phase current contains a dc component in addition to an alternating component. The direct current part is used for constructing an excitation magnetic field loop, and the alternating current part is used for generating electromagnetic torque. When the direct current bias type sine current operates in a constant torque interval, a maximum torque current ratio control mode is generally adopted. The proportion of the effective value of the alternating current to the effective value of the direct current bias current is controlled to be the same, so that the maximum electromagnetic torque is output under the condition that the effective value of the phase current is fixed, and the motor efficiency is improved. The output electromagnetic torque of such a machine can be expressed as:

wherein, T_eIs the output electromagnetic torque of a DC-biased sinusoidal current motor, n_rNumber of pole pairs of motor, L₀For exciting the inductance, i_qIs the q-axis current of the motor, i₀Is the 0-axis current of the motor. When the DC bias type sine current motor adopts the maximum torque current ratio operation mode, i_d＝0；I.e. the amplitude of the AC component in the motor winding is equal to the amplitude of the DC bias current by rotation coordinate transformationAnd the effective value of the alternating current component is equal to that of the direct current bias current.

Fig. 2 shows a main circuit configuration diagram of a dc-biased sinusoidal current motor control system, and a three-phase full-bridge inverter is used as a main circuit of the control system to inject a sinusoidal current with dc bias as shown in fig. 1. The three-phase full-bridge inverter consists of 12 power electronic switching tubes (S1-S12), a direct current bus capacitor (C1) and a direct current power supply (U)_dc) And (4) connecting.

The copper loss of a DC-biased sinusoidal current motor can be expressed as d-axis current i_dQ-axis current i_qAnd 0 axis current i₀Function of (c):

wherein R is_acIs an AC equivalent resistance, R, of the armature winding_acIs changed by changing the frequency of the large and small currents or the motor speed n, and is thus represented as R_ac；R_dcIs a DC equivalent resistance, and R_dcIndependent of the rotational speed. Since AC current and DC current are injected into the same armature winding, R is measured when the current frequency is low_ac＝R_dc。

The ac copper loss of the armature winding is related to the diameter, position, current frequency, strength and phase of the conductor, and is mainly affected by the skin effect and proximity effect of the conductor. And estimating the AC copper loss by using a finite element analysis method, and further obtaining the influence of the armature current intensity and frequency on the AC equivalent resistance. Due to i_dDoes not contribute to the output torque, and i_dIncrease only increases copper loss, so i will be_dSetting the R value to be 0, further utilizing curve fitting, and simulating the R value obtained by finite element analysis_acIs represented as i_qAnd n.

R_ac＝c₁i_q ²+(c₂+c₃·n)i_q+(c₄+c₅·n) (3)

Wherein, c_i(i ═ 1,2,3,4,5) represents a constant obtained by curve fitting.

Different (i)_q,i₀) The combination causes a change in the excitation inductance of the machine, as well as a change in the copper losses. In order to obtain the corresponding (i) with the minimum copper consumption under the same output torque condition_q,i₀) In combination, the lagrange function is defined as:

where λ is the lagrange constant.

The excitation inductor L is affected by the saturation effect of the inductor during the operation of the motor₀L changes with the combination of different dq0 axis currents₀(i_d,i_q,i₀). From the above analysis, in the constant torque region, i_dSet to 0. therefore, L₀Is given by_qAnd i₀Determine L₀(i_q,i₀) L obtained by finite element analysis simulation₀And i_qAnd i₀Further using curve fitting, L obtained by finite element analysis simulation₀Is represented by i_qAnd i₀Is expressed by the expression (1).

L₀(i_q,i₀)＝C₁i_q ²+(C₂+C₃·i₀)i_q+(C₄+C₅·i₀) (5)

Wherein, C_i(i ═ 1,2,3,4,5) represents a constant obtained by curve fitting.

And (3) solving a partial derivative of the Lagrange equation in the step (4) to obtain:

and solving an analytic solution by using a least square method according to the equation set. Defining T in a function_eRanges from 0.0p.u. (where p.u. represents a per unit value) to 2.0p.u., the step size is 0.25 p.u.; n ranges from 0r/min to 3000r/min, the step length is 300r/min, and different T can be obtained by solving_eCorresponding optimum (i)_q,i₀) And (4) combining. By curve fitting, i can be obtained_qAnd i₀With T_eAnd n is in a variation relationship:

i_q＝k₁+k₂T_e+k₃n+k₄T_e ²+k₅T_en (7)

i₀＝k₁₀+k₂₀T_e+k₃₀n+k₄₀T_e ²+k₅₀T_en (8)

wherein k is_i，k_i0(i ═ 1,2,3,4,5) represents a constant obtained by curve fitting.

Under the condition of rated output torque, the current tracks corresponding to different rotating speeds of the traditional method and the method of the invention are compared and shown in figure 4, and the motor efficiency corresponding to the current tracks is shown in figure 5. As shown in FIG. 4, the method of the present invention increases with rotational speed, i_qIs gradually decreased by i₀Gradually increasing; in the conventional method, however,i_qand i₀Does not change with the increase of the rotating speed. The reason is that the alternating current copper loss is influenced and increased along with the increase of the rotating speed and the output torque, the proportion of the direct current bias current is properly increased in the process of increasing the rotating speed of the motor, and the copper loss of the motor can be reduced on the premise of certain output torque, as shown in fig. 5, compared with the traditional method, the method disclosed by the invention can effectively improve the efficiency of the motor.

The control schematic diagram of the minimum copper consumption control strategy of the direct current bias type sine current motor is shown in figure 3. The device comprises a rotating speed PI regulator 1, a minimum copper loss current distributor 2, a d-axis current PI regulator 3a, a q-axis current PI regulator 3b, a 0-axis current PI regulator 3c, a first given voltage phase-shifting module 4a, a second given voltage phase-shifting module 4b, a first pulse width regulator 5a, a second pulse width regulator 5b, a double three-phase inverter 6, a direct current offset type sine current motor 7, a speed sensor 8 and a rotating coordinate conversion module 9.

Given torque T of motor_eGiven by the rotational speed PI governor. Measuring the motor speed n and the reference torque T measured by a motor encoder_eInput a current distributor that further distributes given values of d-axis, q-axis, and 0-axis currents according to input parameters: i.e. i_d*、i_qA and i₀Assigning given values of d-, q-and 0-axis currents according to equations (7) and (8): d-axis current is set to a given value i_dSet to 0, calculate i from equation (12) and equation (13), respectively_qA and i₀*. The minimum copper loss control strategy of the invention always keeps the minimum copper loss of the motor under the given load and speed, and under the given speed and load condition, (i)_q,i₀) The combination of the motor and the motor is in an optimal state, thereby ensuring the minimum copper loss of the motor and improving the operation efficiency of the motor.

And the given values of the d-axis current, the q-axis current and the 0-axis current are respectively regulated by a d-axis current PI regulator, a q-axis current PI regulator and a 0-axis current PI regulator. The output voltage u of the d-axis PI regulator and the q-axis PI regulator_d*、u_qAnd rotor position signal theta_rInputting the voltage set value u of the first set of three-phase inverter under the static coordinate system into a rotating coordinate transformation module_α1*、u_β1A first step of; and the given voltage value u of the second three-phase inverter_α2*、u_β2*. Output voltage u of the 0-axis current regulator₀A, and u_α1*、u_β1Inputting the signals into a first pulse width modulator, and generating PWM signals PWM1-6 of a first set of three-phase inverters by using a Space Vector Pulse Width Modulation (SVPWM) principle; u. of₀A and u_α2*、u_β2Input to the second pulse width modulator to generate the PWM signal PWM7-12 for the second inverter. The output voltage of the double three-phase inverter acts on the winding of the direct current bias type sinusoidal current motor, controls the three-phase currents of a, b and c of the winding of the motor, generates the sinusoidal current with the direct current bias corresponding to the input PWM signal as shown in figure 2, and finally realizes the no-difference tracking of the currents of the d, q and 0 axes;

the rotating coordinate transformation module is used for converting a motor rotor position signal theta detected by a speed sensor into a motor rotor position signal theta_rAnd a phase current signal i detected by the current sensor_a、i_b、i_cPerforming a rotation coordinate transformation operation to obtain d, q, 0-axis DC current feedback signals i_d、i_q、i₀。

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.