阅读说明：本技术 一种永磁同步电机最大转矩电流比控制方法 (Maximum torque current ratio control method for permanent magnet synchronous motor ) 是由 张晓� 史军伟 王越 毋少楠 张辉 于 2020-05-19 设计创作，主要内容包括：本发明公开了一种永磁同步电机最大转矩电流比(MTPA)控制方法,包括：根据永磁同步电机的数学模型推导电磁转矩与定子电流矢量角的关系；根据电磁转矩与定子电流矢量角的关系得到单位电流电磁转矩与定子电流矢量角的关系式；根据在MTPA控制下单位电流电磁转矩对定子电流矢量角的导数为零,对当前定子电流矢量角做出调整以得到最优定子电流矢量角；根据定子电流参考值和最优定子电流矢量角得到交、直轴电流给定值,从而实现永磁同步电机的控制。本发明方法不依赖电机参数,能够根据当前运行状况自动调整定子电流矢量角到最佳MTPA运行点,具有良好的动态性能,实用性强。(The invention discloses a control method of maximum torque current ratio (MTPA) of a permanent magnet synchronous motor, which comprises the following steps: deducing the relation between the electromagnetic torque and the stator current vector angle according to a mathematical model of the permanent magnet synchronous motor; obtaining a relational expression of unit current electromagnetic torque and stator current vector angle according to the relation between the electromagnetic torque and the stator current vector angle; adjusting the current stator current vector angle to obtain the optimal stator current vector angle according to the fact that the derivative of the unit current electromagnetic torque to the stator current vector angle under the control of MTPA is zero; and obtaining the set values of the alternating-axis current and the direct-axis current according to the reference value of the stator current and the optimal stator current vector angle, thereby realizing the control of the permanent magnet synchronous motor. The method of the invention does not depend on motor parameters, can automatically adjust the stator current vector angle to the optimal MTPA operation point according to the current operation condition, and has good dynamic performance and strong practicability.)

1. A control method for the maximum torque current ratio of a permanent magnet synchronous motor is characterized by comprising the following steps:

step 1: deducing the relation between the electromagnetic torque and the stator current vector angle according to a mathematical model of the permanent magnet synchronous motor under a dq synchronous rotation coordinate system;

step 2: obtaining a relational expression of unit current electromagnetic torque and stator current vector angle according to the relation between the electromagnetic torque and the stator current vector angle;

and step 3: adjusting the current stator current vector angle to the optimal vector angle according to the fact that the derivative of the unit current electromagnetic torque to the stator current vector angle is zero under the control of MTPA;

and 4, step 4: and obtaining the alternating-axis current set value and the direct-axis current set value according to the stator current set value and the optimal stator current vector angle, and realizing the maximum torque current ratio control of the permanent magnet synchronous motor.

2. The method for controlling the maximum torque current ratio of the permanent magnet synchronous motor according to claim 1, wherein the relation between the electromagnetic torque and the stator electric vector angle obtained by the mathematical model of the permanent magnet synchronous motor in the step 1 is as follows:

3. the method for controlling the maximum torque current ratio of the permanent magnet synchronous motor according to claim 1, wherein the relation between the unit current electromagnetic torque and the stator current vector angle in the step 2 is as follows:

4. the method for controlling the maximum torque to current ratio of the permanent magnet synchronous motor according to claim 1, wherein the derivative of the electromagnetic torque per unit current to the stator current vector angle in the step 3 is as follows:

5. the method for controlling the maximum torque current ratio of the permanent magnet synchronous motor according to claim 1, wherein the adjustment strategy of the stator current vector angle in the step 3 is represented as follows:

γ(k+1)＝γ(k)+Δγ。

6. the method as claimed in claim 5, wherein the adjustment increment of the stator current vector angle is expressed as:

Technical Field

The invention relates to a control method of a permanent magnet synchronous motor, in particular to a control method of a maximum torque current ratio of the permanent magnet synchronous motor.

Background

The permanent magnet synchronous motor has the advantages of small volume, high efficiency, high power density and the like, is widely applied to the field of new energy electric automobiles, and occupies a very important position.

When the permanent magnet synchronous motor works below the basic speed, the loss generated by the current on the stator resistor accounts for a large proportion. If the loss is to be reduced, the stator current of the motor needs to be reduced on the premise that the loading capacity of the motor is not changed. The MTPA control minimizes the stator current under the condition that the output electromagnetic torque is not changed, so that the MTPA control can reduce copper consumption, thereby achieving higher operation efficiency. There are various methods for MTPA control, such as: formula method, curve fitting method. The method relies on constant motor parameters, but the parameters of the motor inevitably change in actual operation, so that the parameters deviate from an actual MTPA control track curve, and the expected effect cannot be achieved.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention provides the maximum torque-current ratio control method of the permanent magnet synchronous motor, which does not depend on motor parameters and calculates the MTPA control track in real time according to the inherent properties of the MTPA control method, thereby realizing accurate MTPA control.

The invention is realized by the following technical scheme: a control method for the maximum torque current ratio of a permanent magnet synchronous motor specifically comprises the following steps:

obtaining the relation between the stator current and the orthogonal and direct axis currents under the dq synchronous rotation coordinate system:

in the formula i_dIs a direct axis current, i_qIs quadrature axis current, i_sIs the stator current and gamma is the stator current vector angle.

Obtaining the relation between the electromagnetic torque and the stator current vector angle according to the relation between the electromagnetic torque and the orthogonal and orthogonal axis currents:

in the formula, T_eIs an electromagnetic torque, P_nFor number of pole pairs, psi, of the motor_fIs a permanent magnet flux linkage, L_dIs a direct-axis inductor, L_qIs a quadrature axis inductor.

Obtaining a relation expression of the unit current electromagnetic torque relative to the stator current vector angle according to the relation between the electromagnetic torque and the stator current vector angle:

obtaining the derivative of the unit current electromagnetic torque to the stator current vector angle according to the relational expression of the unit current electromagnetic torque to the stator current vector angle:

when the machine is operating at the MTPA control point, the derivative of the unit current electromagnetic torque with respect to the stator current vector angle is zero, i.e. the derivative is zero

And adjusting the stator current vector angle according to the value of the derivative of the unit current electromagnetic torque to the stator current vector angle so as to reach an optimal point. The adjustment strategy of the stator current vector angle is as follows:

γ(k+1)＝γ(k)+△γ

wherein γ (k) is a stator current vector angle at the moment k, and the adjustment increment Δ γ of the stator current vector angle is as follows:

compared with the prior art, the method and the device have the advantages that the optimal stator current vector angle in the current running state is obtained by utilizing the property that the derivative of the single-bit current electromagnetic torque to the stator current vector angle is zero under the control of the MTPA, so that the accurate MTPA control is realized. The method is not influenced by the operating condition and the motor parameter change, has strong robustness, simplifies the calculation amount of MTPA control, improves the system operating speed, can track the MTPA control track in real time, and has good dynamic performance.

Drawings

The invention is further illustrated below with reference to the figures and examples.

FIG. 1 shows the stator current i according to the invention_sAnd quadrature axis current i_qDirect axis current i_dA relationship diagram of (1);

FIG. 2 is a graph of the torque of the PMSM of the present invention as a function of stator current vector angle;

FIG. 3 is a control flow diagram of the present invention;

fig. 4 is a schematic diagram of the current relationship of the motor at the MTPA control point in the present invention.

Detailed Description

The following describes a maximum torque current ratio control method of a permanent magnet synchronous motor according to the present invention in further detail with reference to the accompanying drawings and specific embodiments. Advantages and features of the present invention will become apparent from the claims and the following detailed description. It is to be noted that the drawings are in simplified form and are not to precise scale, which is provided for the purpose of facilitating and clearly facilitating the description of the embodiments of the present invention.

The present invention will be further explained below.

Under the dq synchronous rotation coordinate system, the electromagnetic torque equation of the built-in permanent magnet synchronous motor is as follows:

the electromagnetic torque of the interior permanent magnet synchronous motor is composed of reluctance torque and permanent magnet torque according to the formula (1). WhereinIn order to be a reluctance torque,is a permanent magnet torque. With reference to fig. 1, the relationship between the stator current and the orthogonal and orthogonal axis currents is obtained:

taking equation (2) into equation (1), obtaining a relational expression of electromagnetic torque and stator current vector angle:

stator current i in equation (3)_sShifting terms to obtain an expression of unit current electromagnetic torque:

the reluctance torque and the permanent magnet torque change with the stator current vector angle as shown in fig. 2. According to equation (4), the derivative of the unit current electromagnetic torque to the stator current vector angle is obtained:

when the motor is operating at the MTPA trajectory control point, the derivative of the unit current electromagnetic torque to the stator current vector angle is equal to zero:

solving the formula (6) to obtain a stator current vector angle expression of the MTPA track control point:

the formula (7) contains motor parameters, and the motor parameters can be changed in the actual control only according to the formula (7)

The actual control trajectory will be shifted by performing MTPA control, so the stator current vector angle needs to be adjusted to achieve optimal MTPA control. If the current motor operating point is not on the MTPA track, the derivative of the unit current electromagnetic torque to the stator current vector angle is not zero, so that the stator current vector angle needs to be adjusted to the optimal stator current vector angle corresponding to the current MTPA control point. With reference to fig. 2 and fig. 4, when the derivative of the unit current electromagnetic torque to the stator current vector angle is greater than zero, it indicates that the current stator current vector angle is smaller than the optimal vector angle, and the stator current vector angle needs to be increased; when the derivative of the unit current electromagnetic torque to the stator current vector angle is less than zero, the current stator current vector angle is larger than the optimal vector angle, and the stator current vector angle needs to be reduced; when the derivative of the unit current electromagnetic torque to the stator current vector angle is equal to zero, it indicates that the present stator current vector angle does not need to be adjusted. Therefore, the stator current vector angle is adjusted according to the derivative value of the unit current electromagnetic torque to the stator current vector angle so as to reach the optimal MTPA control point under the current running state.

According to the above description, the adjustment strategy of the stator current vector angle is:

γ(k+1)＝γ(k)+△γ (8)

the adjustment increment delta gamma of the stator current vector angle is as follows:

an expression of the given values of the alternating-axis current and the direct-axis current can be obtained according to the formula (8):

the AC and DC axis current reference values are fed into a PI current regulator, so that accurate MTPA control can be realized.

The invention is not the best known technology.

The above embodiments are merely illustrative of the technical concepts and features of the present invention, and the purpose of the embodiments is to enable those skilled in the art to understand the contents of the present invention and implement the present invention, and not to limit the protection scope of the present invention. All equivalent changes and modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.