阅读说明：本技术 一种感应电机矢量控制调速系统的能效优化方法 (Energy efficiency optimization method of vector control speed regulation system of induction motor ) 是由 夏加宽 梁宗伟 张荣津 苏杭 侯婷婷 于 2020-11-17 设计创作，主要内容包括：一种感应电机矢量控制调速系统的能效优化方法,它是在感应电机考虑铁耗的数学模型的基础上,分析电机的转矩和输入功率考虑了铁耗的表达式,用定子电流表示转矩与输入功率2的比,当转矩与传统的最优磁链的能效优化方法相比,本方法考虑更全面,既考虑了感应电机中铁耗的影响,又通过一定负载转矩下使电机输入功率最小,来达到减小电机损耗的目的,也考虑了铁耗对电压解耦的影响,以及磁通观测器的设计。不仅提高了电机的能效水平,增强了系统的稳定性和抗干扰能力,而且易于实现。输入功率比最大时,对应的励磁电流可使得感应电机的能效水平提高。(An energy efficiency optimization method for a vector control speed regulation system of an induction motor is characterized in that on the basis of a mathematical model of the induction motor considering iron loss, an expression of the torque and the input power of the motor considering the iron loss is analyzed, the ratio of the torque to the input power is represented by stator current 2, and when the torque is compared with the traditional energy efficiency optimization method of the optimal flux linkage, the method considers more comprehensively, not only considers the influence of the iron loss in the induction motor, but also minimizes the input power of the motor under certain load torque to achieve the purpose of reducing the motor loss, also considers the influence of the iron loss on voltage decoupling, and designs a flux observer. The energy efficiency level of the motor is improved, the stability and the anti-interference capability of the system are enhanced, and the system is easy to realize. When the input power ratio is maximum, the corresponding exciting current can improve the energy efficiency level of the induction motor.)

1. The energy efficiency optimization method of the vector control speed regulating system of the induction motor is characterized in that based on the principle of maximum torque input power ratio, the given exciting current is as follows:

when the motor is started and reaches a steady state, according to the running state of the motor, the given excitation current is divided into:

(1) when torque T of the motor_LWhen equal to 0, the exciting current is given by i_sdIs I₁，I₁Is the minimum excitation current.

(2) When torque T of the motor_LWhen > 0, exciting current gives i_sdIs X i_sqWherein X is input according to the maximum torqueThe proportional coefficient of the dq axis current at the input power ratio and is equation k₁X²+k₂X+k₃A solution of 0, wherein:

(3) to ensure that the field current is not too large, when X i_sq≥I₂When i is_sd＝I₂In which I₂Is the maximum field current allowed by the motor. In general, the excitation current is given by:

2. the optimal excitation current given energy efficiency optimization control system according to claim 1, further comprising a voltage decoupling equation considering iron loss as:

wherein the content of the first and second substances,

3. the optimal excitation current given energy efficiency optimization control system according to claim 1, wherein a rotor flux linkage observer considering iron loss is designed:

wherein the content of the first and second substances,

Technical Field

The invention belongs to the technical field of alternating current induction motors and control thereof, and particularly relates to an energy efficiency optimization method of an induction motor vector control speed regulation system under the limitation of multiple conditions.

Background

The variable-frequency speed regulation method of the alternating current motor mainly comprises constant-voltage frequency ratio speed regulation and variable-voltage variable-frequency speed regulation, and the variable-voltage variable-frequency speed regulation method is divided into vector control and direct torque control. The vector control mode can realize decoupling control of motor excitation and torque, so that an alternating current speed regulating system and a direct current speed regulating system are the same to realize double closed-loop control of rotating speed and current, the calculated amount is small compared with direct torque control, software and hardware are easy to realize, and the performance requirement of dragging load can be met, so that the double closed-loop control method is widely applied.

The vector control of the induction motor comprises the following steps: the magnetic field orientation of the rotor, the magnetic field orientation of the stator and the magnetic field orientation of the air gap are widely applied due to the advantages that the magnetic field of the rotor is easy to observe, each vector after orientation is easy to decouple and the like.

The principle of the rotor magnetic field orientation vector control is as follows: the dynamic mathematical model of the induction motor in a three-phase natural coordinate system is decomposed in a two-phase rotating coordinate system through Clarke and Park transformation matrixes, particularly, stator current is decoupled into an exciting current component and a torque current component, the exciting current component and the torque current component are respectively subjected to closed-loop control, and the control effect same as that of a direct current motor can be achieved.

The control system for the orientation of the magnetic field of the rotor of an induction machine is usually constant flux-setting during operation, i.e. the excitation current is constant and rated. However, when the motor is operated in a light load state, iron loss of the motor due to the exciting current becomes a main loss other than copper loss. If the exciting current can be reduced when the motor runs under light load, the iron loss can be greatly reduced without influencing the steady-state running of the motor. Only because the motor adopts vector control, similar to a direct current motor, the reduction of the exciting current can cause the increase of the torque current, and the copper consumption can also increase along with the increase of the torque current. The key point of the energy efficiency optimization of the induction motor is to select proper excitation current setting so that the sum of copper consumption and iron consumption is minimum after optimization. The literature proposes that the relation between the efficiency of the motor and the excitation current of the motor is derived according to a mathematical model of the induction motor, and the corresponding excitation current when the efficiency of the motor is maximum is obtained, however, the mathematical model of the method does not consider the iron loss parameter, and the efficiency of the motor is taken as an optimization target, so that the actual energy efficiency optimization effect of the method is not ideal.

Disclosure of Invention

Aiming at the existing problems, the invention provides an energy efficiency optimization method of an induction motor based on a rotor magnetic field orientation vector control speed regulation system by combining a mathematical model of the induction motor considering iron loss.

In order to realize the energy efficiency optimization effect of the induction motor, the invention provides an energy efficiency optimization method based on the optimal excitation current given by the maximum torque input power ratio, which specifically comprises the following steps:

when the motor is started and reaches a steady state, according to the running state of the motor, the optimal exciting current is given as:

1) when torque T of the motor_LWhen equal to 0, the exciting current is given by i_sdIs I₁，I₁Is the minimum excitation current.

2) When torque T of the motor_LWhen > 0, exciting current gives i_sdIs Xi_sqWhere X is the scaling factor of dq axis current at maximum torque to input power ratio and is equation k₁X²+k₂X+k₃A solution of 0, wherein:

3) to ensure that the exciting current is not too large, when Xi_sq≥I₂When i is_sd＝I₂In which I₂Is the maximum field current allowed by the motor. In general, the excitation current is given by:

4) the voltage decoupling equation considering iron loss is:

wherein the content of the first and second substances,

5) the rotor flux linkage observer considering iron loss is designed as follows:

wherein the content of the first and second substances,

the specific technical effects of the invention are embodied as follows:

1) the energy efficiency level of a vector control system of the induction motor based on the rotor magnetic field orientation is improved, the proportional coefficient of the dq axis current is calculated in a mode of the maximum torque input power ratio, the optimal exciting current set value of the exciting current is obtained by multiplying the proportional coefficient and the torque current, and the energy efficiency optimization of the operation of the induction motor is realized.

2) A voltage decoupling method considering iron loss is provided for a vector control system for the orientation of the rotor magnetic field of the induction motor, and the stability and the anti-interference capability of the control system are improved.

3) A flux linkage observer considering iron loss is designed, and a basis is provided for accurate magnetic field orientation of a control system.

4) And combining the maximum torque input power ratio energy efficiency optimization strategy with the directional vector control of the rotor magnetic field of the induction motor.

In general, compared with the traditional energy efficiency optimization method of the optimal flux linkage, the method has the advantages that the consideration is more comprehensive, the influence of iron loss in the induction motor is considered, the input power of the motor is minimized under a certain load torque, the purpose of reducing the loss of the motor is achieved, the influence of the iron loss on voltage decoupling is also considered, and the design of a flux observer is also considered. The energy efficiency level of the motor is improved, the stability and the anti-interference capability of the system are enhanced, and the system is easy to realize.

Drawings

FIG. 1 is a schematic diagram of a rotor field oriented vector control system for an induction machine based on maximum torque to input power ratio;

FIG. 2 is a flow chart of the operation of the rotor field oriented vector control system of the induction machine based on the maximum torque to input power ratio;

Detailed Description

In order to clearly and clearly show the objects, technical solutions and effects of the present invention, the present invention will be further described in detail 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 do not limit the invention. In addition, in the embodiments of the present invention described below, the technical features may be combined with each other as long as they do not conflict with each other.

In order to improve the energy efficiency level of an induction motor rotor magnetic field orientation vector control system, the invention provides an energy efficiency optimization method based on the optimal excitation current given by the maximum torque input power ratio.

When the induction machine takes into account iron time, the mathematical model in the dq coordinate system is as follows:

voltage equation:

current equation:

the flux linkage equation:

the torque equation:

the motor input power equation: p_input＝u_sdi_sd+u_sqi_sq (5)

In the formulae (1) to (5), ω_sIs the synchronous rotational speed angular frequency; omega_rIs the rotor speed angular frequency; omega_sl＝ω_s-ω_rIs the angular frequency of the rotation difference; r_s、R_rAnd R_mRespectively a stator resistor, a rotor resistor and an iron loss equivalent resistor; l is_s、L_r、L_mThe self inductance and mutual inductance of the stator and the rotor are respectively; l is_sσ、L_rσRespectively determining leakage inductance of the stator and the rotor; i.e. i_sd、i_sq、i_rd、i_rqStator and rotor currents of dq axes, respectively; i.e. i_Rmd、i_RmqThe dq axis iron loss equivalent currents are respectively; i.e. i_Lmd、i_LmqAre dq-axis excitation currents, respectively; u. of_sd、u_sqThe dq-axis stator voltages, respectively; psi_sd、ψ_sq、ψ_rd、ψ_rqThe dq axis stator and rotor magnetic chains are respectively, and P is the pole pair number of the motor.

When the coordinate system is rotor field oriented and in steady state operation:

by substituting formula (6) into formulae (1) to (3), it is possible to obtain:

wherein the content of the first and second substances,and:

according to equations (7) - (8), the torque and input power of the motor can be expressed as:

wherein the content of the first and second substances,

according to formulae (9) - (10), can be in i_sd-i_sqDrawing a curve of the torque equation and the input power equation on a plane that takes into account the iron losses, it can be easily found, according to the lagrange's theorem, that the input power is minimal when the torque curve and the input power curve are tangent at one point, and that if and only if their gradient vectors are parallel at the tangent point then there are:

wherein θ isAndthe included angle therebetween. The cross product of the gradient vectors is calculated by:

for equation (12), if and only if the value of this equation is zero, so thatAndin parallel, then there are:

combining formulae (7) to (10) to obtain:

let X be the proportional coefficient of the dq-axis current, i.e.And formula (14) is substituted, then simplified to:

k₁X²+k₂X+k₃＝0 (15)

wherein the content of the first and second substances,

and solving the equation (15), namely obtaining a proportional coefficient of the dq axis current when the maximum torque input power ratio is obtained. i.e. i_sqThe current component corresponding to the motor torque is determined by the load of the motor, and when the motor is in a steady state, the current component can be obtained by coordinate transformation of the detected stator current, and then multiplied by the solved proportional coefficient to obtain the corresponding exciting current given value i_sdAnd the size of the exciting current is readjusted to realize the high-energy-efficiency operation of the induction motor.

Due to variation of torque of the motor, i_sqThe change can cause the calculated optimal given value of the exciting current to be too small or too large, so that the optimal given value of the exciting current is limited:

wherein, T_LIs the load torque of the motor, I₁、I₂Is a given limit value for the field current of the motor.

Combining the equations (1), (7) and (8), the voltage decoupling equation of the induction motor considering the iron loss is as follows:

wherein the content of the first and second substances,combining equations (1), (2), (3) and (7), (8), a rotor flux linkage observer considering iron loss is obtained:

wherein the content of the first and second substances,

fig. 1 is a functional block diagram of a system. The device comprises a rotating speed PI regulator 1, a torque PI regulator 2, an excitation current regulator 3, a space vector SVPWM module 4, a three-phase voltage source inverter 5, a voltage and current detection module 6, a stator current decoupling module 7, a rotor magnetic field observation module 8 considering iron loss, a voltage decoupling module 9 considering iron loss, a current proportionality coefficient calculation module 10 based on the maximum torque input power ratio, an optimal excitation current setting module 11, an induction motor 12 and a photoelectric encoder 13.

Setting of rotational speedWith actual speed omega_rMaking a difference to realize rotating speed closed loop, processing the difference value by a rotating speed PI regulator 1, sending the difference value to a torque PI regulator 2, and outputting a given value of voltage; the rotor field observer 8 for observing the position θ and ω of the rotor field by calculating the voltage current real-time value detected by the voltage and current detection module 6 according to equation (19) in consideration of the iron loss_s(ii) a The stator current decoupling module 7 decouples the three-phase stator currents into torque current components in the synchronous rotation dq coordinate systemi_sqAnd an excitation component i_sdA real-time value of (c); the current proportionality coefficient calculation module 10 calculates the value of the proportionality coefficient X according to the formula (15) and the operation parameters of the motor; the optimal excitation current setting module 11 is used for giving a given value of the excitation current according to the formula (16), and sending the given value of the excitation current into the excitation current regulator 3 after the given value is different from an actual value; the voltage decoupling module 9 considering iron loss calculates a decoupling compensation value of voltage according to the formula (17); the given voltage values output by the torque PI regulator 2 and the excitation current regulator 3 are sent to the space vector SVPWM module 4 after voltage compensation of a voltage decoupling module 9 considering iron loss; the space vector SVPWM module 4 modulates six groups of pulses meeting the control requirement and sends the six groups of pulses to the three-phase voltage source inverter 5. The voltage inverted by the three-phase voltage source inverter 5 is input to the induction motor 12, so that the motor meets the control requirement and operates stably and efficiently. The photoelectric encoder 13 is responsible for detecting the rotating speed omega of the induction motor 12 in real time_rAnd fed back into the control system.

Fig. 2 is a flow chart of the operation of the field oriented vector control system of the induction machine rotor based on the maximum torque input power ratio proposed by the present invention.

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.