阅读说明：本技术 一种永磁电机弱磁控制策略 (Permanent magnet motor flux weakening control strategy ) 是由 房淑华 王翌丞 于 2020-12-22 设计创作，主要内容包括：本发明公开了一种永磁电机弱磁控制策略,属于多电飞机用永磁电机控制领域；采用弱磁控制方式,将弱磁区域分成四部分,基于前馈控制的方法计算出不同区域所需的弱磁电流并进行给定,控制系统中电流环采用PI控制器,转速环使用改进型自抗扰控制器；使用转矩补偿的方法对自抗扰控制器进行改进,通过检测d-q轴电流分量和电机转速搭建负载转矩观测器对负载转矩进行辨识,并依据前馈补偿的原理对控制器输出进行转矩补偿；本发明解决了传统多电飞机用永磁电机控制系统模型依赖度高、转速不稳,调试复杂的弊端,并对于扰动具有良好的抑制作用,大大提升了系统的鲁棒性与抗干扰能力。(The invention discloses a flux weakening control strategy for a permanent magnet motor, belonging to the field of control of permanent magnet motors for multi-electric airplanes; dividing a weak magnetic area into four parts by adopting a weak magnetic control mode, calculating weak magnetic currents required by different areas based on a feedforward control method, giving the weak magnetic currents, wherein a current loop in a control system adopts a PI (proportional-integral) controller, and a rotating speed loop adopts an improved active disturbance rejection controller; the active disturbance rejection controller is improved by using a torque compensation method, a load torque observer is constructed by detecting d-q axis current components and motor rotating speed to identify load torque, and torque compensation is performed on the output of the controller according to a feed-forward compensation principle; the method overcomes the defects of high dependence degree, unstable rotating speed and complex debugging of the traditional permanent magnet motor control system model for the multi-electric airplane, has good inhibition effect on disturbance, and greatly improves the robustness and the anti-interference capability of the system.)

1. A flux weakening control strategy for a permanent magnet motor, the control strategy comprising:

step 1: establishing a speed ring active disturbance rejection controller model;

step 2: establishing a speed ring improved active disturbance rejection controller model;

and step 3: establishing a motor flux weakening control model based on a feedforward method;

and 4, step 4: controlling the inverter output.

2. The flux weakening control strategy of the permanent magnet motor according to claim 1, wherein in the step 1, the active disturbance rejection controller comprises: a tracking differentiator, an extended state observer, and a nonlinear state error feedback.

3. The flux weakening control strategy of a permanent magnet motor according to claim 2, wherein the operation steps of said active disturbance rejection controller comprise:

step 1: after the acquired actual value and the set rotating speed value of the rotating speed are input into the active disturbance rejection controller, the input differential value is calculated by using the tracking differentiator;

step 2: observing system output, each output derivative and error disturbance of the system by using the extended state observer;

and step 3: the state error of the controlled object can be obtained according to the output of the tracking differentiator and the extended state observer, and the nonlinear state error feedback controls the state error by using a nonlinear function at the moment, so that the initial value of the torque reference value is output.

4. The flux weakening control strategy of the permanent magnet motor according to claim 1, wherein in the step 2, a load torque observer is established for torque identification, d-q axis current and rotating speed are collected at the output side of the motor, a load torque observed value is calculated according to a formula, a torque compensation expression is calculated according to a feed-forward control principle, and the obtained torque is compensated and compensated to the output side of the active disturbance rejection controller to obtain a torque reference value.

5. The field weakening control strategy of the permanent magnet motor according to claim 1, wherein in the step 3, the field weakening area is divided into four parts in combination with the limited current and voltage ranges and the rotation speed range of the motor, a corresponding d-q axis field weakening current calculation formula is given, and a given reference value of the d-q axis current is calculated according to the different speed areas and the torque reference value output by the active disturbance rejection controller.

6. The flux weakening control strategy of the permanent magnet motor according to claim 5, wherein the flux weakening area is divided into: a maximum torque current ratio region, a maximum current region, a flux weakening region, and a maximum torque voltage ratio region.

7. The flux-weakening control strategy of the permanent magnet motor according to claim 1, wherein in the step 4, the given reference value of the d-q axis current is subtracted from the acquired actual value of the d-q axis current, the difference value is inputted to a current PI controller for adjustment, the current PI controller outputs and decouples the difference value to obtain the given reference value of the d-q axis voltage, and then coordinate change and space vector pulse width modulation calculation are performed according to the voltage reference value to control the inverter to output.

Technical Field

The disclosure belongs to the field of permanent magnet motor field weakening control, and particularly relates to a permanent magnet motor field weakening control strategy.

Background

The conventional energy supply system of the airplane has the problems of complex structure, poor reliability, larger carbon emission, low energy efficiency and the like of the airplane and the engine due to the coexistence of multiple energy sources, and the effective load of the airplane is limited due to the larger mass of the power system; under the condition, the efficiency is higher, and lighter and simpler multi-electric and all-electric airplanes gradually get attention of people, which also puts higher requirements on the performance of the motor for the multi-electric airplane.

The motor for the multi-electric airplane puts higher requirements on a driving system: the method has the advantages that the quick response capability to the moving target and the smooth and stable tracking capability are required, so that the motor control for the multi-electric airplane needs targeted countermeasures; the traditional control strategy, such as Proportional Integral (PI) control, has high dependence on the system, and when parameters change and external disturbance exist, the control effect is not ideal; besides the interference from the factors of the motor, the permanent magnet synchronous motor control system for the multi-electric airplane also has the influence of friction torque, wind resistance torque of the air environment and other interference torques; with the continuous development of the multi-electric aircraft, higher requirements are put forward on the noise immunity, reliability and control accuracy in the motor control operation of the multi-electric aircraft.

Disclosure of Invention

Aiming at the defects of the prior art, the purpose of the present disclosure is to provide a flux weakening control strategy for a permanent magnet motor, which solves the problems of high dependence, conflict between response and tracking effects and poor interference rejection performance of a traditional control strategy system model in the prior art.

The purpose of the disclosure can be realized by the following technical scheme:

a permanent magnet motor field weakening control strategy comprises the following steps:

step 1: establishing a speed ring active disturbance rejection controller model;

step 2: establishing a speed ring improved active disturbance rejection controller model;

and step 3: establishing a motor flux weakening control model based on a feedforward method;

and 4, step 4: and controlling the inverter to output.

Further, in the step 1, inputting the acquired actual value of the rotating speed and the set rotating speed value into an active disturbance rejection controller to obtain an initial set value of the torque;

further, after the error value is input into the active disturbance rejection controller, calculating the input differential value by using a tracking differentiator model; observing the system output, each output derivative and the error disturbance of the system by using an extended state observer; the state error of the control object can be acquired using the output from the tracking differentiator and the extended state observer. At the moment, the nonlinear state error feedback controls the state error by using a nonlinear function, and outputs an initial set value of the torque.

Further, in the step 2, a load torque observer is established for torque identification, d-q axis current and rotating speed are collected at the output side of the motor, a load torque observed value is calculated according to a formula, a torque compensation expression is calculated according to a feed-forward control principle, and the obtained torque is compensated and compensated to the output side of the active disturbance rejection controller to obtain a torque reference value.

Further, in the step 3, the current and voltage limited range and the rotating speed interval of the motor are combined, the flux weakening area is divided into four parts, a corresponding d-q axis flux weakening current calculation formula is given, and a given reference value of the d-q axis current is calculated according to the different speed areas and the torque reference value output by the active disturbance rejection controller.

Further, the weak magnetic region is divided into: a maximum torque current ratio region, a maximum current region, a flux weakening region, and a maximum torque voltage ratio region.

Further, in the step 4, the reference value of the d-q axis current and the actual value of the acquired d-q axis current are subtracted, the difference value is input into a current PI controller for regulation, the controller outputs and decouples the difference value to obtain a given reference value of the d-q axis voltage, coordinate change and Space Vector Pulse Width Modulation (SVPWM) calculation are carried out according to the voltage reference value, and the inverter is controlled to output the given reference value.

The beneficial effect of this disclosure: the improved active disturbance rejection controller-based permanent magnet motor flux weakening control strategy for the multi-electric aircraft solves the problems of high dependence degree of a system model and poor disturbance rejection performance under a high-speed condition; because the designed active disturbance rejection control strategy can compensate the output according to the disturbance, the disturbance rejection and the robustness are both good, and the method is suitable for controlling the motor for the multi-electric aircraft. Because the control system does not depend on the accurate parameters of the motor and does not need to deduce a transfer function and a motor parameter observer, a large amount of numerical calculation is reduced, the controller is simple and convenient to design, and the control system is stable and reliable.

Drawings

In order to more clearly illustrate the embodiments or technical solutions in the prior art of the present disclosure, the drawings used in the description of the embodiments or prior art will be briefly described below, and it is obvious for those skilled in the art that other drawings can be obtained based on these drawings without creative efforts.

FIG. 1 is a block diagram of a permanent magnet motor control system for a multi-electric aircraft according to the present invention;

FIG. 2 is a schematic diagram of the flux weakening control process based on the feedforward method;

FIG. 3 is a schematic diagram illustrating the effect of the motor control strategy of the present invention for a multi-electric aircraft compared to the conventional PI control under disturbance;

fig. 4 is a schematic diagram illustrating the effects of the motor active disturbance rejection controller for a multi-electric aircraft according to the present invention before and after compensation.

Detailed Description

The technical solutions in the embodiments of the present disclosure will be clearly and completely described below with reference to the drawings in the embodiments of the present disclosure, and it is obvious that the described embodiments are only a part of the embodiments of the present disclosure, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments disclosed herein without making any creative effort, shall fall within the protection scope of the present disclosure.

A strategy control structure of a permanent magnet motor flux weakening control strategy is shown in figure 1, and active disturbance rejection controllers which take torque set values required by flux weakening control as output variables are respectively established; a weak magnetic control model based on a feedforward method; and performing torque compensation based on feedforward control on the active disturbance rejection control; the method mainly comprises the following steps:

step 1: establishing a speed ring active disturbance rejection controller model;

as shown in fig. 1, the active disturbance rejection controller includes three parts, namely, a Tracking Differentiator (TD), an Extended State Observer (ESO), and a Nonlinear State error feedback (NLSEF); the tracking differentiator can track the input signal and arrange a transition state, so that the control is fast and has no overshoot; the extended state observer is used for observing the output and each order derivative thereof, and meanwhile, taking the internal disturbance and the external variable of the system as the total disturbance to observe and estimate the total disturbance; the nonlinear state error feedback mainly controls the nonlinear combination of the reference input and the error signal of the dilated state, while compensating for the total disturbance observed.

The controller of the speed loop is a first order model. This gives a first order tracking differentiator model:

in the formula: z₁₁To track the state of the processed input values of the differentiator,the table is the state differential quantities of the input values after being processed by the tracking differentiator. ω is a given speed, r is a gain factor, fal () is a non-linear function expressed as:

the first order extended state observer model is:

in the formula: ω denotes the actual speed of acquisition, Z₂₁Representing the observed quantity, Z, of the extended state observer on the output of the system₂₂Representing views of the total disturbanceIn the measurement, β 21 and β 22 are gain coefficients, Z22 represents a differential form of an error observed quantity, and b represents a compensation coefficient.

The first order nonlinear state error feedback model is:

in the formula: u is the output of the nonlinear state error feedback.

Inputting the set rotating speed value into an active disturbance rejection controller, and obtaining the state quantity of the given rotating speed through a tracking differentiator; inputting the collected actual value of the rotating speed into an extended state observer to obtain the state quantity of the actual rotating speed and an observed total error value; and (3) subtracting the given rotating speed state quantity from the actual rotating speed state quantity, feeding back the difference value through a nonlinear state error to obtain an initial output value u0, and adding compensation to the total disturbance observed by the extended state observer to obtain a final output value u, namely the initial value of the torque reference value required to be input into the flux weakening system.

Step 2: establishing a speed ring improved active disturbance rejection controller model; establishing a load torque observer model for identification:

in the formula: te is the electromagnetic torque. J is the inertia coefficient, B is the friction coefficient, and omega is the actual rotating speed. Combining with a feedforward control method, obtaining an expression of torque compensation of the active disturbance rejection controller as follows:

in the formula: p represents a pole pair number, psi f represents a magnetic linkage, Ld and Lq are d-q axis inductances respectively, ido and iqo are observed d-q axis currents, and omega o is an observed rotating speed;

and compensating the calculated torque to the output end of the active disturbance rejection controller to obtain a final torque reference value.

And step 3: establishing a motor flux weakening control model based on a feedforward method; dividing the field weakening area into four parts in combination with the range of voltage and current supplied by a direct current power supply and the interval of the rotating speed, and giving a d-q axis field weakening current calculation formula of each part to obtain a d-q axis current given reference value;

the current and voltage are affected by the supply voltage and current, and the limit range is as follows:

ignoring the stator resistance, the above equation can be written as:

in the formula: ω represents the rotation speed, Ld, Lq and id, iq represents the d-q axis inductance and current, respectively, Udc represents the supplied direct current voltage, and Ismax represents the upper limit of the current accepted by the inverter; ψ f denotes the flux linkage size; therefore, the active range of the current is limited in the intersection of the current circle and the voltage ellipse;

firstly, calculating each critical rotating speed value required by flux weakening; setting the current rotating speed as omega, and setting the target rotating speed as omega; calculating the rotating speed when the voltage ellipse formula in the step (8) passes through the zero point, and calling the rotating speed as boundary speed omega 0; the rotating speed of the motor under the condition of no weak magnetism is called as basic rotating speed omega b, and can be calculated according to the formula (9); the maximum torque voltage ratio curve of the motor is shown as (10), the current working point at the moment can be calculated by combining the maximum torque voltage ratio curve with the current curve in the step (8), and the critical rotating speed entering the maximum torque voltage ratio area can be calculated by substituting the current working point into a voltage curve circular formula, namely omega v; according to the rotating speed critical value, the flux weakening control can be divided into four parts: a maximum torque current ratio region, a maximum current region, a flux weakening region and a maximum torque voltage ratio region;

(L_d-L_q)(L_qi_q)²-(L_d-L_q)(L_di_d+ψ_f)²-ψ_fL_q(L_di_d+ψ_f)＝0 (10)

(1) region of ω < ω b

This region is also called the maximum torque to current ratio (MTPA) region, and the intersection of the MTPA curve and the current circle is referred to as a, as shown in fig. 2 (a). The current operating point C is on the maximum torque to current ratio curve and can be calculated by the following equation:

(2)ω_b＜ω＜ω₀region(s)

This region, also called the Maximum Current (MC) region, moves on the edge of the current limiting circle when the speed increases towards ω but has not yet reached ω, and is therefore always in the maximum current state, as shown in fig. 2(b), operating point C is:

the torque calculated from the operating point at this time is the maximum torque Tmc of the current load:

T_mc＝1.5p(ψ_fi_q+(L_d-L_q)i_di_q) (13)

after the speed reaches ω, the current is calculated according to the torque request. As shown in fig. 2(c) and (D), the intersection D of the voltage curve and the MTPA curve in this state is first calculated, and the current at this point is substituted into the torque equation to calculate, and the torque at this time is called the cut-off torque Td. When the given torque Te > Tmc, the operating point B can be calculated according to equation (12), forcing the given torque to be equal to Tmc; when Td < Te < Tmc, the operating point can be calculated as in equation (14); when Te is less than Td, the working point is the intersection point of the torque curve and the MTPA curve, and the rotating speed at the moment can be calculated by substituting the equation (11).

(3) Region of ω 0< ω < ω v

As shown in fig. 2(e) (f), this region is also called weak magnetic region, and in this region, when ω < ω, the operating point moves on the current boundary, and the calculation formula is the intersection point of the voltage circle and the current circle at this rotation speed (12); when ω is ω, the current is calculated based on the torque request. When the given torque Te is greater than Tmc, the given torque is forced to be equal to Tmc, and the working point is the intersection point of the voltage circle and the current circle; when the given torque Te < Tmc, the working point is the intersection G of the torque curve and the voltage curve at the speed, which can be calculated by using (14);

(4) region of ω v < ω

This region is also referred to as the maximum torque to voltage ratio (MTPV) region, as shown in FIGS. 2(g) (h). When the area is located, firstly, judging whether the speed reaches a preset rotating speed or not; when ω < ω, the operating point moves on the MTPV curve, and the intersection point of the voltage circle and the MTPV curve at the rotation speed is calculated as (15):

when ω is ω, the intersection point of the voltage circle and the MTPV curve is I, and the current is calculated according to the torque request. If the given torque Te is larger than TI, the working point is the point I, and the given torque is forced to be equal to TI; when the given torque Te < TI, the working point at the moment is the intersection point K of the torque curve and the voltage curve, and the working point can be calculated by using the formula (14);

through the steps, the d-q axis current reference value meeting the requirements of the rotating speed and the torque can be obtained.

And 4, step 4: as shown in fig. 1, the reference value of the d-q axis current is subtracted from the actual value of the d-q axis current obtained through collection, the difference value is input into a current PI controller for adjustment, and the current PI controller is output and decoupled to obtain a given reference value of the d-q axis voltage; and carrying out coordinate change and SVPWM calculation according to the voltage given reference value, and controlling the inverter to output.

In order to verify the effectiveness of the provided control strategy, a motor control platform is set up for an experiment; giving a control command of the motor as follows: firstly, no-load rotation is carried out to 2700 rotations, the torque is reduced to 1Nm after 1.2Nm of load is added, and finally the speed is increased to 3000 rotations; as can be seen from fig. 3 and 4, the weak magnetic control based on the active disturbance rejection controller can quickly reach the designated speed, the tracking error is small, the control precision is high, the fluctuation is lower after compensation, the system has better robustness and anti-interference capability, and the requirements of high precision and high stability of the motor for the multi-electric aircraft can be met.

The foregoing illustrates and describes the general principles, principal features, and advantages of the present disclosure. It will be understood by those skilled in the art that the present disclosure is not limited to the embodiments described above, which are presented solely for purposes of illustrating the principles of the disclosure, and that various changes and modifications may be made to the disclosure without departing from the spirit and scope of the disclosure, which is intended to be covered by the claims.