阅读说明：本技术 一种多直流电机并联系统及电流控制方法 (Multi-direct-current motor parallel system and current control method ) 是由 李伟华 王炜 罗黎明 赵国璋 马义波 董建威 赵宇 于 2020-05-06 设计创作，主要内容包括：本发明公开了一种多直流电机并联系统及电流控制方法,将位置传感器经转速计算单元得到的速度反馈到速度调节模块,将永磁同步电机电流检测传感器得到的电机电流经电流重构计算单元得到电流值并反馈至电流调节模块；将参考速度和反馈速度信号在速度比较器的作用下得到速度误差,在PI控制器的作用下得到电流；经参考电流计算单元得到参考电流；将得到的参考电流和重构获得的电流值在电流比较器的作用下得到电流误差,然后在滞环控制比较器的作用下得到占空比；将占空比经过PWM脉冲宽度调制单元得到脉冲控制信号,进而通过控制(n+1)相逆变器中开关管的通断来驱动电机的运转。本发明在满足生产需求的条件下,同时能够降低总谐波失真率,并提高工业生产的安全性,减少能源消耗。(The invention discloses a multi-direct current motor parallel system and a current control method.A speed obtained by a position sensor through a rotating speed calculation unit is fed back to a speed regulation module, and a motor current obtained by a permanent magnet synchronous motor current detection sensor is fed back to a current regulation module through a current reconstruction calculation unit to obtain a current value; obtaining a speed error by the reference speed and the feedback speed signal under the action of a speed comparator, and obtaining a current under the action of a PI controller; obtaining a reference current through a reference current calculating unit; obtaining a current error by using the obtained reference current and a current value obtained by reconstruction under the action of a current comparator, and then obtaining a duty ratio under the action of a hysteresis control comparator; and (3) obtaining a pulse control signal by the duty ratio through a PWM (pulse width modulation) unit, and further driving the motor to run by controlling the on-off of a switching tube in the (n +1) phase inverter. The invention can reduce the total harmonic distortion rate, improve the safety of industrial production and reduce the energy consumption under the condition of meeting the production requirement.)

1. A parallel current control method for multiple direct current motors is characterized by comprising the following steps:

s1, initializing the system, and obtaining the speed omega of the position sensor through a rotating speed calculating unit₁、…、ω_nFeeding back to the speed regulation module to obtain motor current X from the current detection sensor of the permanent magnet synchronous motor₁、…、X_nObtaining a current value I through a current reconstruction computing unit₁、…、I_n+1And feeding back to the current regulation module;

s2, referring to the speed omega_1ref、…、ω_nrefAnd the feedback speed signal ω of step S1₁、ω₂Obtaining a speed error e under the action of a speed comparator_w1、…、e_wnVelocity error e_w1、…、e_wnObtaining current I under the action of PI controller_m1、…、I_mn；

S3, converting the current I obtained in the step S2 into_m1、…、I_mnObtaining a reference current I through a reference current calculation unit_1ref、…、I_(n+1)ref；

S4, converting the reference current I obtained in the step S3 into a reference current I_1ref、…、I_(n+1)refAnd reconstructing the obtained current value I in step S1₁、…、I_n+1Obtaining a current error e under the action of a current comparator_I1、…、e_I(n+1)Error in current e_I1、…、e_I(n+1)Obtaining duty ratio H under the action of hysteresis control comparator₁、…、H_n+1；

S5, converting the duty ratio H obtained in the step S4 into the duty ratio H₁、…、H_n+1And obtaining a pulse control signal through a PWM (pulse width modulation) unit, and further driving the motor to run by controlling the on-off of a switching tube in the (n +1) phase inverter.

2. The multiple dc motor parallel system and the current control method according to claim 1, wherein the speed error e is determined in step S2_w1、…、e_wnThe method specifically comprises the following steps:

e_wi＝w_iref-w_i

current I_m1、…、I_mnComprises the following steps:

I_mi＝K_Pe_wi+K_I∫e_widt

wherein, i is 1, …, n, K_PAnd K_ITo control the gain.

3. The multiple DC motor parallel system and the current control method according to claim 1,

in step S3, the current I is referenced_1ref、…、I_(n+1)refThe method specifically comprises the following steps:

calculating the current I₁、…、I_n+1The method specifically comprises the following steps:

wherein, X₁、…、X_nIs the motor current obtained by the current detection sensor of the permanent magnet synchronous motor.

4. The multiple DC motor parallel system and the current control method according to claim 1,

in step S4, the output H of the current hysteresis comparison controller_iThe method specifically comprises the following steps:

wherein Q represents a value equal to the value output at the previous time, which is the threshold of the hysteresis comparison controller, e_IiIs the current error and is the input to the hysteresis comparison controller.

5. The multiple DC motor parallel system and the current control method according to claim 4,

error of current e_IiThe method specifically comprises the following steps:

e_Ii＝I_iref-I_i。

6. the multiple direct current motor parallel system and the current control method according to claim 1, wherein in step S5, the PWM pulse width modulation unit generates a pulse signal for controlling the on/off of the inverter switching tubes, and the switching logic generating function is:

wherein, i is 1, …, n +1, the output pulse control signal 1 and 0 level control the on-off of the upper and lower switch tubes of the bridge arm.

7. A multi-direct current motor parallel system is characterized in that the current control method of claim 1 is adopted, the system comprises n PI controllers, the n PI controllers are sequentially connected with a reference current calculation unit, a current hysteresis control comparator, a PWM (pulse width modulation) unit, an n +1 phase voltage source inverter and n parallel direct current motors, and the direct current motors M are connected with the direct current motors M in parallel₁、…、M_nThe position sensor is connected with the speed regulation module through a rotating speed calculation unit, the current detection sensor of the permanent magnet synchronous motor is connected with the current regulation module through a current reconstruction calculation unit, the motor rotating speed and the reference rotating speed obtained by the position sensor through the rotating speed calculation unit obtain current values under the action of a PI controller, the reference current obtained by the current value through the reference current calculation unit and the current obtained by the motor current through the current reconstruction calculation unit obtain current errors under the action of the current regulation module, and the current errors are under the action of a current hysteresis control comparatorAnd then obtaining the duty ratio, obtaining two paths of complementary signals for controlling the on-off of the upper power switch tube and the lower power switch tube of each bridge arm in the inverter through a PWM (pulse width modulation) unit, respectively controlling the on-off of the upper power switch tube and the lower power switch tube of each bridge arm in the voltage source type inverter, and realizing the reverse operation of the motor by changing the reference speed.

8. The multiple direct current motor parallel system and the current control method according to claim 7, wherein the n +1 phase voltage source inverter includes n +1 bridge arms L₁、…、L_n+1And 2(n +1) power switch tubes T₁、…、T_2(n+1)First leg L₁Comprising switching tubes T connected in series₁And T₂N-th arm L_nComprising switches T connected in series_2n-1And T_2nArm L of the (n +1) th arm_n+1Comprising switches T connected in series_2n+1And T_2n+2(ii) a Power switch tube T₁And a power switch tube T₂Is node a₁Point, power switch tube T_2n-1And a power switch tube T_2nIs node a_nPoint, power switch tube T_2n+1And a power switch tube T_2n+2Is node a_n+1Point, node a₁、…、a_n、a_n+1Connected with n parallel motors, n +1 bridge arms L₁、…、L_n+1After being connected in parallel, the DC power supply is connected with a common DC power supply.

Technical Field

The invention belongs to the technical field of multi-motor control, and particularly relates to a multi-direct-current motor parallel system and a current control method.

Background

In industrial production, such as cement kiln, paper making, textile and the like, in order to improve the flexibility of the structure of the driving system, reduce the volume of the motor and reduce the energy consumption, a plurality of motor cooperative driving control systems are widely applied. Compared with a triangular carrier wave, the hysteresis comparison controller has the advantages of no need of a carrier wave, simple hardware circuit, real-time control mode and the like, and becomes an important research direction of a multi-motor cooperative drive control system.

Disclosure of Invention

The technical problem to be solved by the present invention is to provide a multiple dc motor parallel system and a current control method, which can improve the flexibility of a driving system, reduce the occupied area of a motor, reduce energy consumption, and have real-time performance, high precision and high reliability.

The invention adopts the following technical scheme:

a parallel current control method for multiple direct current motors comprises the following steps:

s1, initializing the system, and obtaining the speed omega of the position sensor through a rotating speed calculating unit₁、…、ω_nFeeding back to the speed regulation module to obtain motor current X from the current detection sensor of the permanent magnet synchronous motor₁、…、X_nObtaining a current value I through a current reconstruction computing unit₁、…、I_n+1And feeding back to the current regulation module;

s2, referring to the speed omega_1ref、…、ω_nrefAnd the feedback speed signal ω of step S1₁、ω₂Obtaining a speed error e under the action of a speed comparator_w1、…、e_wnVelocity error e_w1、…、e_wnObtaining current I under the action of PI controller_m1、…、I_mn；

S3, converting the current I obtained in the step S2 into_m1、…、I_mnObtaining a reference current I through a reference current calculation unit_1ref、…、I_(n+1)ref；

S4, converting the reference current I obtained in the step S3 into a reference current I_1ref、…、I_(n+1)refAnd reconstructing the obtained current value I in step S1₁、…、I_n+1Obtaining a current error e under the action of a current comparator_I1、…、e_I(n+1)Error in current e_I1、…、e_I(n+1)Obtaining duty ratio H under the action of hysteresis control comparator₁、…、H_n+1；

S5, converting the duty ratio H obtained in the step S4 into the duty ratio H₁、…、H_n+1And obtaining a pulse control signal through a PWM (pulse width modulation) unit, and further driving the motor to run by controlling the on-off of a switching tube in the (n +1) phase inverter.

Specifically, in step S2, the speed error e_w1、…、e_wnThe method specifically comprises the following steps:

e_wi＝w_iref-w_i

current I_m1、…、I_mnComprises the following steps:

I_mi＝K_Pe_wi+K_I∫e_widt

wherein, i is 1, …, n, K_PAnd K_ITo control the gain.

Specifically, in step S3, the current I is referenced_1ref、…、I_(n+1)refThe method specifically comprises the following steps:

specifically, in step S4, the output H of the current hysteresis comparison controller_iThe method specifically comprises the following steps:

wherein Q represents a value equal to the value output at the previous time,comparing the threshold of the controller for hysteresis, e_IiIs the current error and is the input to the hysteresis comparison controller.

Further, the current error e_IiThe method specifically comprises the following steps:

e_Ii＝I_iref-I_i。

specifically, in step S5, the switching logic generating function of the pulse signal generated by the PWM unit for controlling the switching of the inverter switching tube is:

wherein, i is 1, …, n +1, the output pulse control signal 1 and 0 level control the on-off of the upper and lower switch tubes of the bridge arm.

According to another technical scheme, the current control method of claim 1 is adopted, the current control method comprises n PI controllers, the n PI controllers are sequentially connected with a reference current calculation unit, a current hysteresis control comparator, a PWM (pulse width modulation) unit, an n +1 phase voltage source inverter and n parallel direct current motors, and the direct current motor M is connected with the reference current calculation unit, the current hysteresis control comparator, the n +1 phase voltage source inverter and the n parallel direct current motors in parallel₁、…、M_nThe position sensor is connected with the speed regulation module through a rotating speed calculation unit, the current detection sensor of the permanent magnet synchronous motor is connected with the current regulation module through a current reconstruction calculation unit, the motor rotating speed and the reference rotating speed obtained by the position sensor through the rotating speed calculation unit are subjected to the action of a PI controller to obtain current values, the reference current obtained by the current value through the reference current calculation unit and the current obtained by the motor current through the current reconstruction calculation unit are subjected to the action of the current regulation module to obtain current errors, the current errors are subjected to the action of a current hysteresis control comparator to obtain duty ratios, two paths of complementary signals for controlling the on-off of upper and lower power switching tubes of each bridge arm in the inverter are obtained through a PWM (pulse width modulation) unit, and the complementary signals areAnd controlling the on-off of the upper power switch tube and the lower power switch tube of each bridge arm in the voltage source type inverter, and realizing the reverse operation of the motor by changing the reference speed.

Specifically, the n + 1-phase voltage source inverter includes n +1 bridge arms L₁、…、L_n+1And 2(n +1) power switch tubes T₁、…、T_2(n+1)First leg L₁Comprising switching tubes T connected in series₁And T₂N-th arm L_nComprising switches T connected in series_2n-1And T_2nArm L of the (n +1) th arm_n+1Comprising switches T connected in series_2n+1And T_2n+2(ii) a Power switch tube T₁And a power switch tube T₂Is node a₁Point, power switch tube T_2n-1And a power switch tube T_2nIs node a_nPoint, power switch tube T_2n+1And a power switch tube T_2n+2Is node a_n+1Point, node a₁、…、a_n、a_n+1Connected with n parallel motors, n +1 bridge arms L₁、…、L_n+1After being connected in parallel, the DC power supply is connected with a common DC power supply.

Compared with the prior art, the invention has at least the following beneficial effects:

the invention relates to a method for controlling the parallel current of multiple direct current motors, which is characterized in that a duty ratio signal obtained by a current hysteresis control comparator is subjected to a PWM (pulse width modulation) unit to obtain two paths of complementary pulse control signals, the on-off of a switching tube in a voltage source inverter is controlled, and the operation of a voltage positive and negative driving motor in an armature winding of the motor is further obtained, so that the current output response is fast, the overshoot is small, the waveform is stable, the motor can be ensured to operate better in a preset range, the requirements of actual production and life are met, and the method can be widely applied to industries such as cement kilns, papermaking, textiles and the like. The flexibility of a driving system is improved, the occupied area of a motor is reduced, the energy consumption is reduced, the control method has the advantages of real-time performance, high precision, high reliability and increased load capacity, and a hysteresis current comparator in the control method is adopted due to the advantages of no need of carrier waves, cost reduction, real-time response and the like; and a double closed-loop system is adopted, so that the error can be reduced, the control precision is improved, and the stable operation of the motor is ensured.

Further, in step S2, the reference rotation speed and the speed obtained by the rotation speed calculation unit can form a negative feedback loop, and the current value is obtained by the PI controller. The negative feedback loop can reduce the rotating speed error, and meanwhile, the current value of the control motor can be obtained through the controller.

Further, in step S3, a reference current value may be obtained through the current calculating unit, and the obtained current value is obtained through a certain synthesizing method, that is, the reference current calculating unit, and is used as an input end of the hysteresis comparison controller.

Further, in step S4, the current error can be reduced, and the reference current value and the current value obtained by the current calculation unit form a negative feedback loop, so that the current error value output by the control motor can be reduced. And meanwhile, an input pulse duty ratio signal for controlling the PWM pulse production unit is obtained under the action of the hysteresis comparison controller.

Further, the duty ratio signal in step S4 generates a signal for controlling the on/off of the inverter switching tube under the action of the PWM pulse generating unit, so as to drive the motor to perform four-quadrant operation. Because of the adoption of digital circuit signals, the method has the advantages of strong anti-interference capability, capability of transmitting signals remotely and the like

Furthermore, a duty ratio signal obtained by the current hysteresis control comparator is subjected to a PWM (pulse width modulation) unit to obtain two paths of complementary pulse control signals, and the on-off of a switching tube in the voltage source type inverter is controlled, so that the operation of a positive and negative voltage driving motor in an armature winding of the motor is obtained. Not only the load capacity of operation has been improved, the security of further guaranteeing the motor work moreover.

The utility model provides a many direct current motor parallel system, adopts many motors parallelly connected, can break through the limitation of single motor operation ability, can guarantee industrial production's steady operation simultaneously, and the current hysteresis comparator does not need the carrier wave, and the hardware circuit is simple, can reduce the cost of actual generation and application, and belongs to the real-time control mode, can realize the quick response of electric current, and the electric current following performance is fast simultaneously, the error is little.

In conclusion, the invention can reduce the total harmonic distortion rate, improve the safety of industrial production and reduce the energy consumption under the condition of meeting the production requirement.

The technical solution of the present invention is further described in detail by the accompanying drawings and embodiments.

Drawings

FIG. 1 is a schematic diagram of a hysteresis comparison controller according to the present invention;

FIG. 2 is a block diagram of the hysteresis comparison control PWM signal generation in the present invention;

FIG. 3 is a schematic diagram of an inverter of the present invention;

FIG. 4 is a schematic diagram illustrating the generation principle of the hysteresis control PWM signal according to the present invention;

FIG. 5 is a schematic view of current hysteresis control of a multi-DC motor parallel system according to the present invention;

fig. 6 is a flow chart of a current hysteresis control algorithm of a multi-dc motor parallel system according to the present invention.

Detailed Description

In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

Referring to fig. 5, the present invention provides a parallel system of multiple dc motors, including n parallel dc motors, n PI controllers, a reference current calculating unit, n +1 current hysteresis comparing controllers, a PWM pulse width modulating unit, an (n +1) phase voltage source inverter, a current detecting sensor of a permanent magnet synchronous motor, a position sensor, and a dc power supply.

The PI controller is sequentially connected with a reference current calculation unit and a current hysteresis controlA comparator, a PWM pulse width modulation unit, an (n +1) phase voltage source inverter, and n parallel DC motors, and a DC motor M₁、…、M_nAnd the permanent magnet synchronous motor current detection sensor is connected with the current regulation module through the current reconstruction calculation unit.

The method comprises the steps that the motor rotating speed and the reference rotating speed obtained by a position sensor through a rotating speed calculating unit are subjected to the action of a PI controller to obtain current values, the reference current obtained by the current value through a reference current calculating unit and the current value obtained by the motor current through a current reconstruction calculating unit are subjected to the action of a current adjusting module to obtain current errors, the current errors are subjected to the action of a hysteresis comparison controller to obtain duty ratios, and the duty ratios are subjected to a PWM pulse width modulation unit to obtain two paths of complementary signals for controlling the on-off of upper and lower power switching tubes of each bridge arm in an inverter.

Referring to fig. 3, the n +1 phase voltage source inverter consists of (n +1) bridge arms L₁、…、L_n+1And 2(n +1) power switch tubes T₁、…、T_2(n+1)Wherein first arm L₁By a switching tube T₁-T₂Connected by n-th arm L_nBy a switch T_2n-1-T_2nConnected as (n +1) th arm L_n+1By a switch T_2n+1-T_2n+2And (4) connecting.

Take first leg L₁Power switch tube T in₁And a power switch tube T₂Is node a₁Taking n < th > bridge arm L_nPower switch tube T in_2n-1And a power switch tube T_2nIs node a_nTaking the (n +1) th arm L_n+1Power switch tube T in_2n+1And a power switch tube T_2n+2Is node a_n+1Point, node a₁、…、a_nAnd a DC motor M₁、…、M_nIs connected with the positive pole of the direct current motor M₁、…、M_nIs connected in parallel with the node a_n+1Connected (n +1) bridge arms L₁、…、L_n+1After being connected in parallel, the DC power supply is connected with a common DC power supply.

The working principle of the current hysteresis comparison controller is as follows:

referring to fig. 1 and 2, the reference input signal ω is set according to the operation requirement_1ref、…、ω_nrefMeasuring the motor rotation speed omega obtained by the rotation speed calculating unit by using the position sensor₁、…、ω_nWith reference speed omega_1ref、…、ω_nrefObtaining a speed error e under the action of a speed adjusting module_w1、…、e_wnThe speed error is obtained as current I under the action of PI controller_m1、…、I_mnThe current I_m1、…、I_mnThe reference current I is obtained by calculation through a reference current calculation unit_1ref、…、I_(n+1)refThe measured current X of the motor₁、…、X_nI obtained by reconstruction calculation₁、…、I_n+1And a reference current I_1ref、…、I_(n+1)refObtaining a current error e through a current regulation module_I1、…、e_I(n+1)The current error obtains a duty ratio signal H under the action of a current hysteresis control comparator₁、…、H_n+1The duty ratio signal obtains two paths of complementary signals under the action of a PWM (pulse width modulation) unit, the on-off of upper and lower power switching tubes of each bridge arm in the voltage source type inverter is respectively controlled, and the reference speed omega is changed_1ref、…、ω_nrefTo realize the reverse running of the motor.

Please refer to fig. 4, duty ratio H₁、…、H_n+1The logical expression function of (a) is:

when the current error e of the input terminal_I1、…、e_I(n+1)When the voltage is larger than the preset voltage, outputting a high level;

when the current error e of the input terminal_I1、…、e_I(n+1)When the voltage is less than minus, outputting low level;

when the current error e of the input terminal_I1、…、e_I(n+1)If it is greater than-and less than-the output level is kept at the value of the previous time. Wherein, represents hysteresis controller threshold, 2 represents hysteresisThe loop compares the hysteresis width of the controller.

When duty ratio H₁、…、H_n+1When the voltage is high level, the output end T of the PWM unit at the moment₁、…、T_2n-1Is at a low level, T₂、…、T_2n+2At a high level, the switch tubes D are respectively connected₁、…、D_2n-1Cut-off and switching tube D₂、…、D_2n+2Is conducted to output current I₁、…、I_n+1The value becomes smaller.

Similarly, when the switch tube D₁、…、D_2n-1Conducting and switching tube D₂、…、D_2n+2When turned off, the output current I is further enabled₁、…、I_n+1The value becomes larger, and the effect of following the current can be better achieved.

The duty ratio signal obtained by the current hysteresis control comparator passes through the PWM (pulse width modulation) unit to obtain two paths of complementary pulse control signals, and the on-off of a switching tube in the voltage source type inverter is controlled, so that the operation of a positive and negative voltage driving motor in an armature winding of the motor is obtained.

Referring to fig. 6, a method for controlling parallel current of multiple dc motors according to the present invention includes the following steps:

s1, initializing the system, and obtaining the speed omega of the position sensor through a rotating speed calculating unit₁、…、ω_nFeeding back to the speed regulation module, and obtaining the current X of the motor by the current detection sensor of the permanent magnet synchronous motor₁、…、X_nThe current value I obtained by the current reconstruction computing unit₁、…、I_n+1Feeding back to the current regulation module;

s2, referring to the speed omega_1ref、…、ω_nrefAnd step S1 feeding back speed signal omega₁、ω₂Obtaining a speed error e under the action of a speed comparator_w1、…、e_wnThe velocity error e_w1、…、e_wnObtaining current I under the action of PI controller_m1、…、I_mn；

Error in velocity e_w1、…、e_wnThe method specifically comprises the following steps:

e_wi＝w_iref-w_i

where i is 1, …, n, the reference speed is ω_1ref、…、ω_nrefThe feedback speed signal is ω₁、…、ω_n。

Error in velocity e_w1、…、e_wnObtaining current I under the action of PI controller_m1、…、I_mnThe current I_m1、…、I_mnThe specific expression of (1) is:

I_mi＝K_Pe_wi+K_I∫e_widt

wherein, i is 1, …, n, K_PAnd K_IFor controlling the gain, the speed error is e_w1、…、e_wn。

S3, converting the current I obtained in the step S2 into_m1、…、I_mnObtaining a reference current I through a reference current calculation unit_1ref、…、I_(n+1)refThe motor current signal obtained by the current detection sensor in step S1 is X₁、…、X_nThe current value I can be obtained by a current reconstruction calculation unit₁、…、I_n+1；

Reference current I_1ref、…、I_(n+1)refThe method specifically comprises the following steps:

wherein the reference current is I_1ref、…、I_(n+1)ref。

Current I₁、…、I_n+1The method specifically comprises the following steps:

wherein, X₁、…、X_nIs the motor current obtained by the current detection sensor of the permanent magnet synchronous motor.

S4, converting the reference current I obtained in the step S3 into a reference current I_1ref、…、I_(n+1)refAnd current I₁、…、I_n+1Obtaining a current error e under the action of a current comparator_I1、…、e_I(n+1)The current error e_I1、…、e_I(n+1)Obtaining duty ratio H under the action of hysteresis control comparator₁、…、H_n+1；

Error of current e_I1、…、e_I(n+1)The method specifically comprises the following steps:

e_Ii＝I_iref-I_i

where I is 1, …, n +1, the reference current is I_1ref、…、I_(n+1)ref。

Duty cycle H₁、…、H_n+1The method specifically comprises the following steps:

where i is 1, …, n +1, Q represents a value equal to the value output at the previous time, which is the threshold of the hysteresis comparison controller, e_IiAs current error and as input to a hysteresis comparison controller, H_iIs the output of the hysteresis comparison controller.

S5, converting the duty ratio H obtained in the step S4 into the duty ratio H₁、…、H_n+1And obtaining a pulse control signal through a PWM (pulse width modulation) unit, and further driving the motor to run by controlling the on-off of a switching tube in the (n +1) phase inverter.

The switching logic generating function of the pulse signal which is generated by the PWM unit and controls the on-off of the inverter switching tube is as follows:

wherein, i is 1, …, n +1, the output pulse control signal 1 and 0 level control the on-off of the upper and lower switch tubes of the bridge arm.

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. The components of the embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The multi-direct current motor parallel system and the current control method can be widely applied to industries such as cement kilns, papermaking and textile industries. The flexibility of a driving system can be improved, the occupied area of a motor is reduced, energy consumption is reduced, and the control method has the advantages of real-time performance, high precision and high reliability.

In order to improve the flexibility of the structure of the driving system, reduce the volume of the motor and reduce the energy consumption, a plurality of motor cooperative driving control systems are widely applied.

In summary, on the basis of the PI controller, the PWM pulse width modulation unit, the inverter, and the like, in order to accelerate the real-time response of the output current, reduce the total harmonic distortion rate, improve the safety in industrial generation, and the like, the present invention designs a control strategy for controlling the inverter by hysteresis comparison to drive the multiple motors to operate in parallel. The scheme can realize fast current output response, small overshoot and stable waveform, ensures better operation of the motor in a preset range, and meets the requirements of actual production and life.

The above-mentioned contents are only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited thereby, and any modification made on the basis of the technical idea of the present invention falls within the protection scope of the claims of the present invention.