阅读说明：本技术 电励磁双凸极电机驱动充电一体化系统的电流协同控制方法 (Current cooperative control method of doubly salient electro-magnetic motor driving and charging integrated system ) 是由 魏佳丹 陈锦春 翟相煜 赵晓聪 周波 杨明 于 2021-07-08 设计创作，主要内容包括：本发明公开了一种电励磁双凸极电机驱动充电一体化系统的电流协同控制方法,所述电励磁双凸极电机驱动充电一体化系统采用级联变换器结构,并且将电励磁双凸极电机的励磁绕组复用为前级DC-DC变换器的滤波电感,根据电励磁双凸极电机的定转子相对位置确定转子坐标系dq轴,采用矢量控制方式通过后级逆变器驱动电励磁双凸极电机；根据电流协同控制策略给出励磁电流给定值和电枢交轴电流给定值,并结合母线电压环调节输出功率以实现动态模式下的直流母线电压控制。本发明能够有效降低复用励磁绕组的电励磁双凸极电机的稳态系统铜损,提高电机调速动态性能,提高级联变换器系统的稳定性。(The invention discloses a current cooperative control method of an electro-magnetic doubly salient motor driving and charging integrated system, wherein the electro-magnetic doubly salient motor driving and charging integrated system adopts a cascade converter structure, an excitation winding of an electro-magnetic doubly salient motor is multiplexed into a filter inductor of a front-stage DC-DC converter, a rotor coordinate system dq axis is determined according to the relative position of a stator and a rotor of the electro-magnetic doubly salient motor, and the electro-magnetic doubly salient motor is driven by a rear-stage inverter in a vector control mode; and giving an excitation current given value and an armature quadrature axis current given value according to a current cooperative control strategy, and regulating output power by combining a bus voltage ring to realize direct current bus voltage control in a dynamic mode. The invention can effectively reduce the steady-state system copper loss of the electric excitation doubly-salient motor with the multiplexing excitation winding, improve the speed regulation dynamic performance of the motor and improve the stability of the cascade converter system.)

1. A current cooperative control method of an electro-magnetic doubly salient motor driving and charging integrated system is characterized by comprising the following steps:

(1) constructing an electro-magnetic doubly salient motor driving and charging integrated system; the system adopts a cascade converter structure, and an excitation winding of an electrically excited doubly salient motor is multiplexed into a filter inductor of a preceding-stage DC-DC converter;

(2) determining a dq axis of a rotor coordinate system according to the relative position of a stator and a rotor of the electro-magnetic doubly salient motor, establishing a mathematical model of the electro-magnetic doubly salient motor, and driving the electro-magnetic doubly salient motor through a rear-stage inverter in a vector control mode to obtain an average value of electromagnetic torque;

(3) and giving an excitation current given value and an armature quadrature axis current given value according to a current cooperative control strategy, and regulating output power by combining a bus voltage ring to realize direct current bus voltage control in a dynamic mode.

2. The current cooperative control method of the integrated system of doubly salient electro-magnetic motor driving and charging as claimed in claim 1, wherein said step (2) is implemented as follows:

the position where the central line of the rotor teeth is superposed with the central line of the stator teeth is the d-axis of the motor and leads the d-axis by a mechanical angle (90/P)_r) The position of (D) is q-axis, wherein P_rEquivalent pole pairs of the motor;

according to an established mathematical model of the electro-magnetic doubly salient motor under the dq coordinate system, a torque equation is obtained as follows:

wherein L is_fdFor transforming the mutual inductance between the field winding and the armature winding to an inductance value, i, on the straight axis of the rotor coordinate system_fFor exciting current, i_qIs armature quadrature axis current, i_dFor armature direct axis current, L_fqFor transforming the mutual inductance between the field winding and the armature winding to an inductance value, theta, on the straight axis of the rotor coordinate system_rA mechanical angle of the motor;

by controlling i_dUnder the control mode of 0, the mutual inductance between the excitation winding and the armature winding of the electric excitation doubly salient motor mainly has 5 and 7 harmonics, and the expression of the output torque of the electric excitation doubly salient motor is as follows:

wherein M is_f1、M_f5、M_f7The amplitudes theta in the rotor rotation coordinate system corresponding to the fundamental wave, 5 th harmonic wave and 7 th harmonic wave of mutual inductance between the excitation winding and the armature winding in the natural coordinate system_eIs the electrical angle of the motor, theta_m1、θ_m5、θ_m7The initial phase angles of mutual inductance fundamental wave, 5-order harmonic wave and 7-order harmonic wave between the excitation winding and the armature winding;

the average value of the electromagnetic torque obtained after neglecting the alternating current component in the electromagnetic torque is:

3. the current cooperative control method of the integrated system for driving and charging an electro-magnetic doubly salient motor according to claim 1, wherein the cooperative control strategy in the step (3) is to give a given value of an excitation current and a given value of an armature quadrature axis current according to the system operation state respectively, and when the operation speed error of the electro-magnetic doubly salient motor in the system is less than a threshold value n₀Judging that the system operates in a steady-state mode, and obtaining an exciting current given value and an armature quadrature axis current given value according to a minimum copper loss control strategy; when the error of the rotating speed is larger than the threshold value n₀The system is judged to operate in a dynamic mode according to the maximum excitation control strategyAnd when the given value of the exciting current and the given value of the armature quadrature axis current are reached, the dynamic steady-state performance of the system is improved, and the stability of the system is improved.

4. The current cooperative control method of the integrated system of doubly salient electro-magnetic motor driving and charging as claimed in claim 1, wherein the implementation process of adjusting the output power in combination with the bus voltage loop to implement the dc bus voltage control in the dynamic mode is as follows:

when the system operates in a dynamic mode, the instantaneous input and output power difference of the system is judged according to the bus voltage error, the bus voltage error is output through a PI controller, the PI output is subtracted from the given value of the quadrature axis current to serve as a new given value of the quadrature axis current, the output power is adjusted to reduce the bus voltage fluctuation caused by the instantaneous input and output power difference of the system, and the stability of the system is maintained.

5. The current cooperative control method of the doubly salient electro-magnetic motor driving and charging integrated system as claimed in claim 3, wherein the implementation process of obtaining the given value of the exciting current and the given value of the quadrature axis current of the armature according to the minimum copper loss control strategy is as follows:

determining a constraint condition when the copper loss is minimum, wherein the system works in a steady state mode, and the copper loss of a motor winding is as follows:

wherein i_f1For the first field winding current, i_f2For the second field winding current, R_fFor each field winding resistance, R_sResistance of armature winding of each phase;

the copper loss of the motor winding is the sum of two square terms, and the product of the two terms is not changed when the electromagnetic torque output is not changed, so that the copper loss of the motor is only minimum when the two square terms are correspondingly equal:

the average electromagnetic torque before and after current distribution is:

wherein i_f ^*Given value of exciting current i_q ^*Setting a given value of exciting current;

the excitation current under minimum copper loss control is given by:

the given value of the armature current of the electric excitation doubly salient motor is obtained by dividing the given value of the exciting current by the output of a rotating speed regulator of a rear-stage motor driving system so as to ensure that the output power of the system is unchanged.

6. The current cooperative control method of the integrated system of driving and charging an electro-magnetic doubly salient motor according to claim 3, wherein the steady-state mode is that the maximum input power of the integrated system of driving and charging an electro-magnetic doubly salient motor is constantly larger than the output power:

wherein, ω is_mThe mechanical angular speed of the motor;

battery voltage U in doubly salient electro-magnetic motor driving and charging integrated system_bThe requirements are satisfied:

wherein i_f ^*(_max) For maximum value of given value of exciting current, omega_m(_max) The maximum mechanical angular speed of the motor is obtained; namely, when other conditions are not changed, the battery voltage restricts the system output power range under the current cooperative control method.

7. The current cooperative control method of the doubly salient electro-magnetic machine driving and charging integrated system as claimed in claim 3, wherein the given value of the exciting current of the doubly salient electro-magnetic machine is an allowable maximum current value, and the given value of the q-axis armature current is obtained by dividing the given value of the exciting current by the output of the rotation speed regulator in a maximum excitation control mode in which the given value of the exciting current and the given value of the quadrature axis current of the armature are obtained according to a maximum excitation control strategy, so that the output torque of the doubly salient electro-magnetic machine is increased, the maximum input power of a preceding-stage DC-DC converter in the system is increased, and the fluctuation of the bus voltage caused by the input and output power difference of the system is reduced.

Technical Field

The invention belongs to the field of motor systems and control, and particularly relates to a current cooperative control method of an electro-magnetic doubly salient motor driving and charging integrated system.

Background

In recent years, the electric vehicle industry has been rapidly developed, and there are three charging methods for electric vehicles: (1) the vehicle-mounted charging mode is that the vehicle-mounted charger is used for charging the storage battery, the storage battery can be charged in any place with a socket, and the convenience is very high, but due to the limitation of weight and volume, the vehicle-mounted charger is generally low in power level and low in charging speed, is generally suitable for night charging, and reduces the utilization rate of the electric automobile; (2) charging is carried out on a charging pile, the power of the charging pile is generally more than 50kW, the weight and the volume of the charging pile are large, the price is high, special maintenance is needed, a large number of charging stations are needed along with the increase of electric automobiles, and the problems of overlarge infrastructure investment and the like exist; (3) the battery replacement mode is a mode of directly replacing batteries, although the mode can rapidly supplement electric energy, a large number of battery replacement stations need to be built, and at present, batteries of electric automobiles do not have unified standards at home, so that the popularization difficulty is high, and the construction cost is high. The current vehicle-mounted charging mode generally adopts an additional vehicle-mounted charger and is limited by the cost of the vehicle-mounted charger and the limited space of the electric automobile, so that the capacity of the existing vehicle-mounted charger is limited, the electric automobile is difficult to be charged conveniently and quickly, and the use convenience of the electric automobile is influenced. However, the power converter for the electric automobile driving motor has the capability of power bidirectional flow, the capacity is matched with the storage battery, if the driving converter can be utilized to be combined with the motor winding to form an on-vehicle charger for charging the storage battery, the integration of the driving function and the charging function of the power converter is realized, the electric control components of the electric automobile can be fully utilized, the cost can be effectively reduced, the weight and the size are reduced, the electric automobile is not dependent on the charging pile, and the charging can be carried out quickly and conveniently. Therefore, the integration of the driving and charging functions of the electric automobile becomes a more critical technology in the development of the new energy automobile industry.

At present, driving motors of electric vehicles are generally classified into permanent magnet motors and non-permanent magnet motors, wherein permanent magnet motors are mainly used in china and japan and include Permanent Magnet Synchronous Motors (PMSM) and brushless direct current motors (BLDC), and Induction Motors (IM) and Switched Reluctance Motors (SRM) are mostly used in europe, the united states and the industry. The PMSM has incomparable advantages in the aspects of starting performance, peak efficiency, torque ripple and the like, but the PMSM is generally complex in structure and high in design difficulty. The BLDC adopts square wave control, so that the control mode is simple, the structure is simple, the high-speed performance is good, and compared with a PMSM, the problem of obvious torque fluctuation exists. PMSM and BLDC all belong to permanent-magnet machine, because the existence of permanent magnet, all have the cost higher, the permanent magnet is easy to lose the problem of magnetism under the high temperature vibration environment. IM is characterized by simple structure and low price, but has the problem of large loss, and is generally suitable for high-power commercial electric vehicles. SRMs are simpler in construction and have a high fault tolerance, but are also commonly used in large commercial electric vehicles due to torque ripple and noise problems, and the range of use of SRMs is limited to some extent due to the relatively low power density.

The electric excitation double salient pole motor (DSEM) is similar to a switched reluctance motor in structure, a stator and a rotor of the DSEM are all in a salient pole type structure, but the DSEM is provided with an excitation winding and an armature winding, the manufacturing cost of the motor is greatly reduced by adopting direct current winding excitation, the excitation current is controllable, weak magnetic acceleration is very easy to realize, and the DSEM is high in reliability and also has a great advantage of being used for an electric automobile driving motor. The invention patent ZL20171445250.6 provides a driving and charging integrated system of an electro-magnetic doubly salient motor based on a split excitation winding, the excitation winding is used as a filter inductor of a front-stage DCDC converter in a form of a cascade converter, but the input power is limited by constant excitation control, large copper loss can be generated particularly under a light load condition, and the advantage of flexible and controllable excitation current of the electro-magnetic doubly salient motor is not well utilized.

The motor system with the excitation winding and the armature winding also comprises a magnetic flux switching motor, a variable reluctance motor, a hybrid excitation motor and the like, and the excitation current of the motor which is flexible and controllable can be used for optimizing the driving performance of the motor system. For example, the sixth harmonic component in the output torque of the variable reluctance motor is reduced through exciting current harmonic injection, and the steady-state performance of the motor system is improved; or multiple harmonic components in the output torque of the variable reluctance motor are respectively injected into corresponding frequency excitation current harmonics to realize lower torque ripple; the researchers also propose a cooperative control strategy of the exciting current and the armature current of the hybrid excitation motor at different rotating speeds, and realize maximum torque current ratio (MTPA) control at low speed and flux weakening control at high speed. Therefore, considering that the excitation current and the armature current of the electro-magnetic doubly salient motor have the same flexibility and are closely related to the power mutually coupled with the cascade converter, the driving and charging integrated system based on the electro-magnetic doubly salient motor can further optimize the performance of the motor and the stability of the system from the perspective of current cooperative control in a driving mode, and has good research significance.

Disclosure of Invention

The purpose of the invention is as follows: in order to solve the problems in the prior art, the invention provides a current cooperative control method of an electro-magnetic doubly salient motor driving and charging integrated system, which adopts different current cooperative control strategies when the system is in a dynamic and stable state, and improves the dynamic and stable state performance of the motor in a driving mode.

The technical scheme is as follows: the invention provides a current cooperative control method of an electric excitation double-salient motor driving and charging integrated system, which specifically comprises the following steps:

(1) constructing an electro-magnetic doubly salient motor driving and charging integrated system; the system adopts a cascade converter structure, and an excitation winding of an electrically excited doubly salient motor is multiplexed into a filter inductor of a preceding-stage DC-DC converter;

(2) determining a dq axis of a rotor coordinate system according to the relative position of a stator and a rotor of the electro-magnetic doubly salient motor, establishing a mathematical model of the electro-magnetic doubly salient motor, and driving the electro-magnetic doubly salient motor through a rear-stage inverter in a vector control mode to obtain an average value of electromagnetic torque;

(3) and giving an excitation current given value and an armature quadrature axis current given value according to a current cooperative control strategy, and regulating output power by combining a bus voltage ring to realize direct current bus voltage control in a dynamic mode.

Further, the step (2) is realized as follows:

the position where the central line of the rotor teeth is superposed with the central line of the stator teeth is the d-axis of the motor and leads the d-axis by a mechanical angle (90/P)_r) The position of (D) is q-axis, wherein P_rEquivalent pole pairs of the motor;

according to an established mathematical model of the electro-magnetic doubly salient motor under the dq coordinate system, a torque equation is obtained as follows:

wherein L is_fdFor transforming the mutual inductance between the field winding and the armature winding to an inductance value, i, on the straight axis of the rotor coordinate system_fFor exciting current, i_qIs armature quadrature axis current, i_dFor armature direct axis current, L_fqFor transforming the mutual inductance between the field winding and the armature winding to an inductance value, theta, on the straight axis of the rotor coordinate system_rA mechanical angle of the motor;

by controlling i_dUnder the control mode of 0, the mutual inductance between the excitation winding and the armature winding of the electric excitation doubly salient motor mainly has 5 and 7 harmonics, and the expression of the output torque of the electric excitation doubly salient motor is as follows:

wherein M is_f1、M_f5、M_f7The rotor rotation coordinates corresponding to fundamental wave, 5 th harmonic wave and 7 th harmonic wave of mutual inductance between the excitation winding and the armature winding under a natural coordinate systemAmplitude under the system, θ_eIs the electrical angle of the motor, theta_m1、θ_m5、θ_m7The initial phase angles of mutual inductance fundamental wave, 5-order harmonic wave and 7-order harmonic wave between the excitation winding and the armature winding;

the average value of the electromagnetic torque obtained after neglecting the alternating current component in the electromagnetic torque is:

further, the cooperative control strategy in the step (3) is to respectively give a given value of exciting current and a given value of armature quadrature axis current according to the system running state, and when the running speed error of the doubly salient electro-magnetic motor in the system is less than a threshold value n₀Judging that the system operates in a steady-state mode, and obtaining an exciting current given value and an armature quadrature axis current given value according to a minimum copper loss control strategy; when the error of the rotating speed is larger than the threshold value n₀And judging that the system operates in a dynamic mode, and obtaining an exciting current given value and an armature quadrature axis current given value according to a maximum excitation control strategy, thereby realizing the promotion of the dynamic steady-state performance of the system and improving the stability of the system.

Further, the implementation process of adjusting the output power in combination with the bus voltage loop to implement the dc bus voltage control in the dynamic mode is as follows:

when the system operates in a dynamic mode, the instantaneous input and output power difference of the system is judged according to the bus voltage error, the bus voltage error is output through a PI controller, the PI output is subtracted from the given value of the quadrature axis current to serve as a new given value of the quadrature axis current, the output power is adjusted to reduce the bus voltage fluctuation caused by the instantaneous input and output power difference of the system, and the stability of the system is maintained.

Further, the implementation process of obtaining the given value of the exciting current and the given value of the armature quadrature axis current according to the minimum copper loss control strategy is as follows:

determining a constraint condition when the copper loss is minimum, wherein the system works in a steady state mode, and the copper loss of a motor winding is as follows:

wherein i_f1For the first field winding current, i_f2For the second field winding current, R_fFor each field winding resistance, R_sResistance of armature winding of each phase;

the copper loss of the motor winding is the sum of two square terms, and the product of the two terms is not changed when the electromagnetic torque output is not changed, so that the copper loss of the motor is only minimum when the two square terms are correspondingly equal:

the average electromagnetic torque before and after current distribution is:

wherein i_f ^*Given value of exciting current i_q ^*Setting a given value of exciting current;

the excitation current under minimum copper loss control is given by:

the given value of the armature current of the electric excitation doubly salient motor is obtained by dividing the given value of the exciting current by the output of a rotating speed regulator of a rear-stage motor driving system so as to ensure that the output power of the system is unchanged.

Further, the steady-state mode is that the maximum input power of the doubly salient electro-magnetic motor driving and charging integrated system is constantly larger than the output power:

wherein, ω is_mIs electricityMechanical angular velocity;

battery voltage U in doubly salient electro-magnetic motor driving and charging integrated system_bThe requirements are satisfied:

wherein the content of the first and second substances,for maximum value of given value of exciting current, omega_m(max)The maximum mechanical angular speed of the motor is obtained; namely, when other conditions are not changed, the battery voltage restricts the system output power range under the current cooperative control method.

Further, under the condition that the given value of the exciting current and the given value of the armature quadrature axis current are obtained according to the maximum excitation control strategy and are in a maximum excitation control mode, the given value of the exciting current of the electric excitation doubly salient motor is an allowed maximum current value, and the given value of the q-axis armature current is obtained by dividing the given value of the exciting current by the output of the rotating speed regulator, so that the maximum input power of a preceding-stage DC-DC converter in a system can be increased while the output torque of the electric excitation doubly salient motor is improved, and the fluctuation of bus voltage caused by the input and output power difference of the system is reduced.

Has the advantages that: compared with the prior art, the invention has the beneficial effects that: 1. compared with a traditional drive control strategy of an electro-magnetic doubly salient motor, the excitation current and armature current cooperative control strategy provided by the invention can effectively reduce the steady-state copper loss and the dynamic regulation performance of the system; 2. compared with the driving mode control strategy of the original constant excitation control doubly salient electro-magnetic motor driving and charging integrated system, the current cooperation control strategy provided by the invention can adjust the instantaneous input and output power difference of the system, expand the output power range of the motor and improve the stability of the system.

Drawings

FIG. 1 is a block diagram of current cooperative control of an electric excitation doubly salient motor drive and charging integrated system;

FIG. 2 is a schematic diagram of the positions of d and q axes of an electro-magnetic doubly salient motor;

FIG. 3 is a steady state simulation waveform diagram of the driving mode of the electro-magnetic doubly salient motor system, wherein (a) is a current waveform diagram of a first section of the exciting winding, and (b) is a current waveform diagram of a second section of the exciting winding, (c) is a voltage waveform diagram of a bus, and (d) is a current waveform diagram of an armature quadrature axis, (e) is a three-phase current waveform diagram, and (f) is a rotating speed waveform diagram;

FIG. 4 is a waveform diagram of steady-state copper loss values of the system under different load conditions;

FIG. 5 is a waveform diagram showing the simulation of the acceleration process of an electro-magnetic doubly salient machine, in which (a) is an excitation current waveform diagram, (b) is an A-phase current waveform diagram, (c) is a bus voltage waveform diagram, and (d) is a rotation speed waveform diagram;

FIG. 6 is a waveform diagram of simulation of speed reduction process of an electro-magnetic doubly salient machine, in which (a) is an exciting current waveform diagram, (b) is an A-phase current waveform diagram, (c) is a bus voltage waveform diagram, and (d) is a rotating speed waveform diagram;

FIG. 7 is a simulation waveform diagram of the loading process of an electro-magnetic doubly salient motor, in which (a) is an excitation current waveform diagram, (b) is an A-phase current waveform diagram, (c) is a bus voltage waveform diagram, and (d) is a rotating speed waveform diagram;

FIG. 8 is a waveform diagram of the unloading process simulation of the electro-magnetic doubly salient machine, in which (a) is an excitation current waveform diagram, (b) is an A-phase current waveform diagram, (c) is a bus voltage waveform diagram, and (d) is a rotating speed waveform diagram.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings.

The invention provides a current cooperative control method of an electro-magnetic doubly salient motor driving and charging integrated system, which is applied to the electro-magnetic doubly salient motor driving and charging integrated system multiplexing an excitation winding, the system adopts a cascade converter structure, the excitation winding of an electro-magnetic doubly salient motor is multiplexed into a filter inductor of a preceding-stage DC-DC converter, a rotor coordinate system dq axis is determined according to the relative position of a stator and a rotor of the electro-magnetic doubly salient motor, and the electro-magnetic doubly salient motor is driven by a rear-stage inverter in a vector control mode; and giving an exciting current set value and an armature alternating current set value according to a current cooperative control strategy, and regulating output power by combining a bus voltage ring to realize direct current bus voltage control in a dynamic mode, so that the system stability and efficiency are improved while the system electromagnetic torque output requirement is ensured. The current cooperative controller judges the dynamic steady state of the system according to the rotating speed error, the minimum copper loss control is adopted in the steady state, the maximum input power and the output power of the two-stage converter are balanced while the copper loss of the system is reduced, the maximum excitation control is adopted in the dynamic state, the dynamic response of the system is improved, and the output power is adjusted by combining a bus voltage ring so as to realize the direct current bus voltage control in the dynamic mode.

Fig. 1 shows a schematic diagram of an architecture and a control strategy of an electric excitation double-salient-pole motor driving and charging integrated system, and the specific implementation process is as follows:

the d-axis and q-axis positions of the doubly salient electro-magnetic motor are determined according to the relative position of a stator and a rotor, the position of the coincidence of the center line of rotor teeth and the center line of stator teeth is the d-axis of the motor, and the mechanical angle (90/P) of the d-axis is advanced_r) The position of (q) is the q-axis. Wherein, P_rIs the equivalent pole pair number of the motor. According to an established mathematical model of the electro-magnetic doubly salient motor under the dq coordinate system, a torque equation is obtained as follows:

wherein L is_fdFor transforming the mutual inductance between the field winding and the armature winding to an inductance value, i, on the straight axis of the rotor coordinate system_fFor exciting current, i_qIs armature quadrature axis current, i_dFor armature direct axis current, L_fqFor transforming the mutual inductance between the field winding and the armature winding to an inductance value, theta, on the straight axis of the rotor coordinate system_rIs a mechanical angle of the motor.

12/10A polar electro-magnetic doubly salient motor, the position leading the d-axis by 9 degrees is the q-axis, and the schematic diagram of the positions of the d-axis and the q-axis is shown in figure 2.

By controlling i_dUnder the control mode of 0, the mutual inductance between the excitation winding and the armature winding of the electric excitation doubly salient motor mainly has 5 and 7 times of harmonic waves, and the electric excitation doubly salient motor has the advantages of high efficiency, low cost and low costThe expression for the output torque of a pole machine is:

wherein M is_f1、M_f5、M_f7The amplitudes theta in the rotor rotation coordinate system corresponding to the fundamental wave, 5 th harmonic wave and 7 th harmonic wave of mutual inductance between the excitation winding and the armature winding in the natural coordinate system_eIs the electrical angle of the motor, theta_m1、θ_m5、θ_m7The initial phase angles of mutual inductance fundamental wave, 5-order harmonic wave and 7-order harmonic wave between the excitation winding and the armature winding.

The average value of the electromagnetic torque obtained after neglecting the alternating current component in the electromagnetic torque is:

the system current cooperative control strategy is to give a given value of exciting current and a given value of armature quadrature axis current according to the system running state respectively, and when the running speed error of the doubly salient electro-magnetic motor in the system is less than a threshold value n₀When the system is judged to operate in a steady-state mode, the current cooperative controller obtains an exciting current given value and an armature quadrature axis current given value according to a minimum copper loss control strategy; when the error of the rotating speed is larger than the threshold value n₀And if the system is judged to be in a dynamic mode, the current cooperative controller obtains an exciting current given value and an armature quadrature axis current given value according to a maximum exciting control strategy, so that the dynamic steady-state performance of the system is improved, and the stability of the system is improved.

If the armature winding resistance Rs of the 12/10 polar electro-magnetic doubly salient motor is 0.2 Ω, the field winding resistance Rf is 0.4 Ω.

And the minimum copper loss control strategy obtains a constraint condition when the minimum copper loss is required to be determined in the implementation process of obtaining the given value of the exciting current and the given value of the quadrature axis current of the armature. When the system works in a steady-state mode, the copper loss of the motor winding is as follows:

wherein i_f1For the first field winding current, i_f2For the second field winding current, R_fFor each field winding resistance, R_sIs the armature winding resistance of each phase.

The copper loss of the motor winding is the sum of two square terms, and the product of the two terms is not changed when the electromagnetic torque output is not changed, so that the copper loss of the motor is only minimum when the two square terms are correspondingly equal:

and substituting the armature winding resistance and the excitation winding resistance to obtain:

i_q ^*＝1.63299i_f ^*

in order to keep the stable operation of the system, the average electromagnetic torque output by the electrically excited doubly salient motor needs to be ensured to be unchanged before and after distribution control of the exciting current and the armature current of the motor, and the average electromagnetic torque before and after current distribution can be obtained as follows:

wherein i_f ^*Given value of exciting current i_q ^*The given value of the exciting current.

The excitation current given under minimum copper loss control can be calculated as:

the given value of the armature current of the electric excitation doubly salient motor is obtained by dividing the given value of the exciting current by the output of a rotating speed regulator of a rear-stage motor driving system so as to ensure that the output power of the system is unchanged.

In order to ensure the stability of the system, the maximum input power of the system is constantly larger than the output power in a steady-state working mode:

wherein, ω is_mIs the mechanical angular velocity of the motor.

The given value of the exciting current is directly related to the output torque of the system, and the minimum copper loss control strategy regulates the exciting current according to the output power in a steady state, so that the output power range of the system is expanded.

In order to meet the power matching of the system and ensure the balance of the input power and the output power of the system, the voltage U of a battery in the system_bThe requirements are satisfied:

wherein the content of the first and second substances,for maximum value of given value of exciting current, omega_m(max)The maximum mechanical angular velocity of the motor.

When the system operates in a dynamic mode, namely a maximum excitation control mode, the given value of the exciting current of the electric excitation doubly salient motor, which is given by the current cooperative controller, is an allowable maximum current value, and the given value of the q-axis armature current is obtained by dividing the output of the rotating speed regulator by the given value of the exciting current, so that the maximum input power of a front-stage DC-DC converter in the system can be increased while the output torque of the electric excitation doubly salient motor is improved, and the fluctuation of the bus voltage caused by the input and output power difference of the system is reduced.

The instantaneous input and output power difference of the system is judged according to the bus voltage error, the bus voltage error is output through a PI controller, the PI output is subtracted from the given value of the quadrature axis current to serve as a new given value of the quadrature axis current, the output power is adjusted, the bus voltage fluctuation caused by the instantaneous input and output power difference of the system is reduced, and the stability of the system is maintained.

Matlab/Simulink simulation is carried out on the driving and charging integrated system of the electro-magnetic doubly salient motor and the corresponding working condition of the system according to a specific implementation mode. The parameters of the electro-magnetic doubly salient motor are as follows: the resistance value of each section of excitation winding is 0.4 omega, the inductance value of each section of excitation winding is 13mH, the resistance value of the armature winding is 0.1 omega, and the inductance value of the armature winding is 5.6 mH. The simulation working condition is as follows: the voltage of the storage battery is 72V, the voltage of the bus is 120V, the given rotating speed of the motor is 200rpm, and the load torque is 8.5 N.m. The simulation verification of the dynamic and steady-state characteristics of the current cooperative control system under the working condition is carried out, and the method comprises the following embodiments.

When the system operates in a steady state, the minimum copper loss control is adopted for the cascade converter, and the given value of the exciting current and the given value of the q-axis current of the armature are given by the current cooperative controller. Fig. 3(a) to 3(h) show steady-state simulation waveforms of the system driving mode in the current cooperative control mode. The two sections of exciting currents are equal in size, the average value is about 3.18A, and the current ripple is about 0.1A. The bus voltage stably follows the given value of 120V, and the voltage ripple is about 0.2V. Therefore, the front-stage DCDC converter can control the exciting current and the bus voltage to be kept stable, and provides input power for the rear-stage inverter. The effective value of the three-phase current of the later-stage electro-magnetic doubly salient motor is 3.66A, the sine degree is good, and the average value of the q-axis current after coordinate transformation is 5.17A. The rotation speed is stabilized at a given speed of 200rpm, and the copper loss of the system is 16.13W. The cascade converter can effectively control the motor to stably operate, and the exciting current and the armature q-axis current meet the proportional relation of minimum copper loss constraint. The steady-state copper loss value of the system under different load conditions is shown in fig. 4, it can be seen that the copper loss of the system increases along with the increase of the load torque, and the minimum copper loss control can control the copper loss of the system to be at a lower level under light load.

Fig. 5 and 6 show simulated waveform diagrams of the accelerating and decelerating process of the electro-magnetic double-salient pole motor. As can be seen in fig. 5(a) to 5(d), before the motor is accelerated, the system adopts the minimum copper loss control, the exciting current is 3.86A, and the effective value of the phase current is 4.47A. The field current is increased to a maximum of 8A at the start of acceleration to accommodate the increase in output power, with the phase current increased to 13.33A. Due to the control of the maximum exciting current and the regulation of the input power by the preceding-stage DCDC converter, the bus voltage drops by 1V in the acceleration process and basically keeps stable, which shows that the cascade converter has no larger instantaneous input and output power difference in the acceleration process and has better stability. After 120ms to reach the given rotation speed of 400rpm, the system is switched to the minimum copper loss control. The minimum copper loss control is also adopted before and after the motor speed reduction process in fig. 6(a) to 6(d), when the speed reduction is started, the exciting current and the armature current are both reduced to the minimum value, and the bus voltage is increased by about 4.7V due to the feedback energy of the motor. The motor is decelerated to 200rpm after 260ms, and the armature current can be adjusted by the voltage ring additionally arranged in the inverter control to balance the input and output power difference, so that the bus voltage can be controlled in a certain range, and the system stability is not influenced.

The motor loading process waveforms are shown in fig. 7(a) to 7 (d). The rotation speed is not greatly fluctuated during loading, so that the system is always controlled in a minimum copper loss running state, and the armature current and the exciting current are simultaneously increased to adapt to the improvement of the output power. The rotating speed falls by 5rpm in the loading process, and the steady state is recovered after 220 ms. The steady phase current effective value is 6.05A, and the exciting current is 5.25A. The unloading process waveforms are shown in fig. 8(a) to 8 (d). Due to the decrease of the output power, the rotation speed is increased by 5rpm, and the steady state is recovered after 250 ms. After unloading, the armature current and the exciting current are reduced simultaneously, and the copper loss of the system is kept to be minimum while the output power is reduced. The effective value of the unloaded phase current is 3.81A, and the exciting current is 3.31A. The excitation current is increased along with the increase of the output power due to the control of the minimum copper loss in the loading and unloading processes of the motor, namely the maximum input power of the system is changed along with the output power, and the stable operation of the cascade converter with tight power coupling is facilitated.

Therefore, the current cooperative control strategy can keep the system to operate in a minimum copper loss state in a steady state, the maximum excitation control can balance the input and output power difference of the system in the speed regulation process, the added bus voltage ring can keep the bus voltage stable in an allowed range, and the dynamic response performance and stability of the system are improved. The simulation result can verify the correctness and the effectiveness of the proposed current cooperative control strategy.

The above description is only a preferred embodiment of the present invention, and it should be understood that various equivalent substitutions and modifications within the spirit and scope of the present invention, which are obvious to those skilled in the art, are also included in the protection scope of the present invention.