阅读说明：本技术 一种提高永磁同步电机无位置传感器控制起动性能的方法 (method for improving sensorless control starting performance of permanent magnet synchronous motor ) 是由 童怀 陈新度 黄运保 李志忠 黄国宏 于 2019-07-22 设计创作，主要内容包括：本发明公开了一种提高永磁同步电机无位置传感器控制起动性能的方法,该方法根据开环运行模式下主动旋转磁场的位置角与估算转子位置角的差值大小判断开环运行模式绕组相电流峰值的取值是否与负载大小相匹配,在不匹配时通过重新调整电机绕组相电流峰值大小,直至匹配。本发明方法可以避免负载过重时电机绕组相电流峰值取值偏小,开环起动力矩偏小导致的起动失败；也可以避免负载过轻时,相电流峰值取值过大,开环起动力矩偏大、能量过冲,引起位置开环切入位置闭环阶段转子位置估算的算法不收敛,最终导致起动失败的问题。(The invention discloses a method for improving the starting performance of a permanent magnet synchronous motor without a position sensor, which judges whether the value of the phase current peak value of a winding in an open-loop operation mode is matched with the load according to the difference value of the position angle of an active rotating magnetic field and the position angle of an estimated rotor in the open-loop operation mode, and readjusts the phase current peak value of the winding of the motor until the phase current peak value is matched when the phase current peak value of the winding is not matched. The method can avoid the starting failure caused by the small open-loop starting moment due to the small peak value of the phase current of the motor winding when the load is overweight; the problem that the algorithm for estimating the position of the rotor at the position open-loop cut-in position closed-loop stage is not converged and finally the starting failure is caused due to overlarge phase current peak value, large open-loop starting torque and energy overshoot when the load is too light can be solved.)

1. a method for improving the starting performance of a permanent magnet synchronous motor without a position sensor is characterized by comprising the following steps:

Setting a phase current peak value and an open-loop operation frequency of a motor winding, and generating three-phase sine wave current in the motor winding so as to form an active rotating magnetic field and enable the permanent magnet synchronous motor to work in an open-loop synchronous operation mode; establishing an equation of stator voltage under an actual rotating coordinate system and an equation of stator voltage under an expected rotating coordinate system when an included angle exists between the equation and the actual rotating coordinate system; calculating a current difference value between the current in the expected rotating coordinate system and the current in the actual rotating coordinate system, calculating the back electromotive force of the motor according to the current difference value, and then estimating the position angle of the motor rotor; calculating the position angle of the active rotating magnetic field in the open-loop synchronous operation mode, thereby obtaining the difference value between the position angle and the estimated motor rotor position angle;

Judging whether the value of the phase current peak value of the motor winding is matched with the load size or not according to the size of the difference value, and switching into a position closed-loop operation mode if the value of the phase current peak value of the motor winding is matched with the load size; if not, readjusting the peak value of the phase current of the motor winding until matching; and after the position closed-loop operation mode is switched in, the speed regulation operation of the permanent magnet synchronous motor controlled by the position sensor is carried out.

2. The method for improving the sensorless control starting performance of the permanent magnet synchronous motor according to claim 1, wherein the step of judging whether the value of the phase current peak value of the motor winding is matched with the load size comprises the following steps:

Note theta_errRepresents said difference, I_p0Representing the peak value of the phase current of the motor winding, then:

If 5 < | θ_err< 10 deg., indicating I_p0The values are reasonable and are matched at the moment; if theta_err| 10 ° or | θ_errIf | is less than 5 deg., it indicates I_p0the values of (A) are reasonable and unreasonable, and are not matched at the moment.

3. The method of improving sensorless controlled startability of a PMSM according to claim 1, wherein said re-adjusting motor winding phase current peak magnitude comprises:

If theta_errI > 10 deg. indicating that the load is currently loaded and I_p0If the value of (A) is smaller, then I_p0The value is increased by 1A; if theta_errI < 5 deg. indicating that the current starting load is light and I_p0If the value of (1) is too large, then I is added_p0The value is decreased by 1A.

Technical Field

The invention relates to the technical field of motor control, in particular to a method for improving the starting performance of a permanent magnet synchronous motor without a position sensor.

background

The permanent magnet synchronous motor has the advantages of simple structure, high power density, high efficiency, wide speed regulation range and the like, and is widely applied to the fields of industrial control, household appliances and the like at present. The permanent magnet synchronous motor position sensorless control technology can reduce hardware cost and improve system reliability, and has become a very important research direction in the field of motor control in recent years, for example, in a variable frequency air conditioner compressor, the permanent magnet synchronous motor is in a high-temperature, high-pressure and closed environment, a rotor position sensor cannot be installed, and the permanent magnet synchronous motor position sensorless control technology is very suitable for adopting a position sensorless control scheme. Because the rotor position angle of the permanent magnet synchronous motor is difficult to accurately estimate when the permanent magnet synchronous motor is static or at low speed, and the estimation error of the rotor position has great influence on the starting capability of the permanent magnet synchronous motor, the research for improving the starting capability is very critical in the control scheme of the permanent magnet synchronous motor without the position sensor. In order to solve the problem of estimation of the rotor position angle of the motor when the motor is static, Jia Hongheng et al propose a method for detecting the initial position of the rotor of the permanent magnet synchronous motor based on a high-frequency injection method in the Chinese Motor engineering journal (VOL.27, NO.15), wherein the high-frequency injection method can accurately detect the rotor position angle under the static condition, thereby improving the starting capability of the motor, but the method has the defects of long algorithm execution time, complex implementation process and the like.

the existing variable-frequency air conditioner compressor widely adopts a permanent magnet synchronous motor position-sensorless control technology, a starting mode that open-loop self-synchronous operation is firstly carried out and then a rotor position closed loop is switched is adopted in many cases, the algorithm of the starting scheme has short execution time and is easy to implement in an engineering mode, but the starting capability is not as good as that of a high-frequency injection method, and starting failure is easy to occur when the load is heavier.

Disclosure of Invention

Aiming at the problems in the prior art, the invention aims to provide a method for improving the starting performance of a permanent magnet synchronous motor without a position sensor.

In order to realize the task, the invention adopts the following technical scheme:

A method for improving the starting performance of a permanent magnet synchronous motor without a position sensor comprises the following steps:

Setting a phase current peak value and an open-loop operation frequency of a motor winding, and generating three-phase sine wave current in the motor winding so as to form an active rotating magnetic field and enable the permanent magnet synchronous motor to work in an open-loop operation mode; establishing an equation of stator voltage under an actual rotating coordinate system and an equation of stator voltage under an expected rotating coordinate system when an included angle exists between the equation and the actual rotating coordinate system; calculating a current difference value between the current in the expected rotating coordinate system and the current in the actual rotating coordinate system, calculating the back electromotive force of the motor according to the current difference value, and then estimating the position angle of the motor rotor; calculating the position angle of the active rotating magnetic field in the open-loop operation mode, thereby obtaining the difference value between the position angle and the estimated motor rotor position angle;

Judging whether the value of the phase current peak value of the motor winding is matched with the load size or not according to the size of the difference value, and switching into a position closed-loop operation mode if the value of the phase current peak value of the motor winding is matched with the load size; if not, readjusting the peak value of the phase current of the motor winding until matching; and after the position closed-loop operation mode is switched in, the speed regulation operation of the permanent magnet synchronous motor controlled by the position sensor is carried out.

Further, the determining whether the value of the phase current peak value of the motor winding is matched with the load size includes:

Note theta_errRepresents said difference, I_p0Representing the peak value of the phase current of the motor winding, then:

if 5 < | θ_err< 10 deg., indicating I_p0the values are reasonable and are matched at the moment; if theta_err| 10 ° or | θ_errif | is less than 5 deg., it indicates I_p0The values of (A) are reasonable and unreasonable, and are not matched at the moment.

Further, the re-adjusting the magnitude of the peak value of the phase current of the winding of the motor includes:

If theta_errI > 10 deg. indicating that the load is currently loaded and I_p0If the value of (A) is smaller, then I_p0The value is increased by 1A; if theta_errI < 5 deg. indicating that the current starting load is light and I_p0If the value of (1) is too large, then I is added_p0The value is decreased by 1A.

the invention has the following technical characteristics:

The method judges the phase current peak value I of the winding in the open-loop operation mode according to the difference value of the position angle of the active rotating magnetic field in the open-loop operation mode and the estimated rotor position angle_p0Whether the value of (A) is matched with the load size or not can avoid I when the load is overweight_p0The value is small, and the starting is failed due to small open-loop starting torque; also avoid the load being too light I_p0The value is large, the open-loop starting torque is large, the energy overshoots, and the energy overshoots in the position open-loop switching-in position closed-loop stage cause the non-convergence of the rotor position estimation algorithm, so that the starting failure is caused; through I_p0the start-up characteristics of the permanent magnet synchronous motor can be improved.

Drawings

FIG. 1 is a block diagram of a position sensorless vector control system for a permanent magnet synchronous motor;

FIG. 2 is a γ δ hypothetical coordinate system and a dq coordinate system;

FIG. 3 is I_p0The value of (a) is reasonably selected to successfully start the test waveform;

FIG. 4 is I_p0Too large of a value of (a) results in a failed start-up of the test waveform.

Detailed Description

As shown in fig. 1 to 4, the present invention discloses a method for improving the starting performance of a permanent magnet synchronous motor without a position sensor, comprising the following steps:

Step 1, setting a phase current peak value I of a motor winding_p0And open loop operating frequency omega₀Generating three-phase sine wave current in a motor winding to form an active rotating magnetic field, wherein the permanent magnet synchronous motor works in an open-loop synchronous operation mode;

Wherein, the three-phase sine wave current generated in the permanent magnet synchronous motor winding is expressed as:

in the above formula, I_U,I_V,I_WAre respectively three-phase sine wave current of motor winding I_p0For a set phase current peak value of the motor winding, f₀for open loop operating frequency, t is a time parameter.

Step 2, establishing an equation of the stator voltage under an actual rotating coordinate system;

In the scheme, a stator voltage equation under a dp coordinate system is expressed as follows:

in the above formula, u_d、u_qD-axis voltage and q-axis voltage of the stator winding respectively; i.e. i_d、i_qD-axis current and q-axis current of the stator winding respectively; r_sIs a stator resistor; l is_d、L_qD-axis and q-axis inductors respectively; e is the back electromotive force of the motor; omega is the rotation angular velocity of dq coordinate system; p is a differential operator, and p is d/dt;

Step 3, establishing an equation of the stator voltage under the expected rotation coordinate system when an included angle delta theta exists between the equation and the actual rotation coordinate system;

In this step, the expected rotation coordinate system is a γ δ estimation coordinate system, and a voltage equation of the stator in the coordinate system is:

in the above formula, u_γ、u_δEstimating the stator voltage components i of the gamma and delta axes in the coordinate system for gamma and delta, respectively_γ、i_δStator current components of gamma and delta axes, omega, respectively_MEstimating the angular velocity of rotation of the coordinate system for γ δ, p being a differential operator; delta theta is an included angle between the gamma delta estimation coordinate system and the dq coordinate system, namely a position angle estimation error;

step 4, calculating the current difference value between the current in the expected rotation coordinate system and the current in the actual rotation coordinate system;

In the step 4.1, the method comprises the following steps of,Calculating the actual current i of the motor at the sampling point (n +1)_γ(n+1)、i_δ(n+1)：

in the above formula, T is the sampling time of discrete points, i_γ(n)、i_δ(n) is the actual current of the gamma and delta axis stators of the motor at the sampling point (n), u_γ(n)、u_δ(n) is the actual voltage of the gamma and delta axis stators of the motor at the sampling point (n); omega_Mand (n) is the rotation angular velocity at the sampling point (n) under the expected rotation coordinate system.

Step 4.2, calculating the estimated current i at the sampling point (n +1)_Mγ(n+1)、i_Mδ(n+1)：

In the above formula, e_MRepresenting the motor back electromotive force;

step 4.3, calculating the gamma and delta axis estimated current error delta i at the sampling point (n +1)_γ(n+1)、Δi_δ(n+1)：

Estimating the current error Δ i_γ(n+1)、Δi_δAnd (n +1) is the difference value between the current in the expected rotating coordinate system and the current in the actual rotating coordinate system.

Step 5, calculating the back electromotive force of the motor according to the current difference

e_M(n+1)＝e_M(n)-K_δΔi_δ(n+1)

In the above formula, e_M(n+1)、e_M(n) is the back electromotive force of the motor at the sampling point (n +1) and the sampling point (n), respectively, Delta i_δ(n +1) is the delta axis current error at sample point (n +1), K_δEstimating coefficients for the back emf;

step 6, estimating the motor rotation according to the calculated motor counter electromotive forceSub-position angle theta_M

In the above formula, θ_M(n+1)、θ_M(n) is the position angle of the rotor of the motor at the sampling point (n +1) and the sampling point (n), delta i_γ(n +1) is the gamma axis current difference at sample point (n +1), T is the time interval of sampling, K_Eis the motor back electromotive force coefficient, K_θa rotor position angle compensation coefficient;

step 7, calculating the position angle theta of the active rotating magnetic field in the open-loop synchronous operation mode₀And calculating theta₀And estimating the motor rotor position angle theta_MDifference of (a), i.e. theta_err＝θ₀-θ_M；

Step 8, according to the difference value theta_errJudging the phase current peak value I of the motor winding_p0whether the value of (a) is matched with the load size; if theta_errthe size of (A) is within a reasonable interval, indicating that I_p0If the value is reasonable, executing the step 9 of switching into a position closed-loop operation mode; if theta_errIs not in a reasonable interval, indicating that I_p0If the value is larger or smaller, the step 1 is returned to modify I_p0taking the value of (A);

Wherein, according to the difference theta_errjudging the phase current peak value I of the motor winding_p0Whether the value of (a) matches the load size or not, includes:

(1) If 5 < | θ_err< 10 deg., indicating I_p0the value of (3) is reasonable, and the cut-in position closed-loop operation mode in the step (9) is executed;

(2) If theta_errI > 10 deg. indicating that the load is currently loaded and I_p0If the value of (A) is smaller, returning to the step 1 and adding I_p0Increasing the value by 1A, and then re-executing the steps 1 to 8;

(3) If theta_errI < 5 deg. indicating that the current starting load is light and I_p0If the value of (1) is larger, returning to the step (1) to obtain the value I_p0Reducing the value by 1A, and then re-executing the steps 1 to 8;

and 9, entering a position closed-loop operation mode, and controlling a motor position angle theta to be theta under the control of a non-position sensor_M+θ_err；

And step 10, carrying out speed regulation operation of the permanent magnet synchronous motor without position sensor control in a position closed loop operation mode.

The principle experiment verifies that the adopted compressor is a scroll compressor for a new energy automobile air conditioner, wherein the parameters of the permanent magnet synchronous motor are as follows: number of pole pairs p_n3; stator resistance R_s1.62 Ω; stator straight axis inductance L_d3.5 mH; quadrature axis inductance L_q4.5 mH; back emf coefficient k_e＝30.8V/krpm。

In the specific embodiment of the present invention, the scroll compressor permanent magnet synchronous motor adopts position-sensorless vector control, and as shown in fig. 1, the system control block diagram includes units such as current sampling, rotor position estimation, Clarke and PARK transformation, maximum torque-to-current ratio control (MTPA), speed loop, dq-axis current loop, PARK inverse transformation, SVPWM calculation, and three-phase PWM inverter.

The invention adopts a motor rotor position estimation method based on an assumed coordinate system, a gamma delta assumed coordinate system is established in a PMSM vector control dq synchronous coordinate system as shown in figure 2, a motor rotates anticlockwise, a three-phase stator winding is U, V, W, theta represents an actual position angle of a rotor, and theta represents an actual position angle of the rotor_MRepresenting the estimated position angle of the rotor, theta being the position angle estimation error, and delta theta being theta-theta_M(ii) a e is the actual back-emf, the direction coincides with the q-axis; e.g. of the type_MTo estimate the back emf, the direction coincides with the delta axis.

FIG. 3 is a U-phase current waveform of a motor successfully started, showing a phase current peak value I_p06A, open loop operating frequency f₀Starting load torque T of 8Hz_L1.5Nm, active rotating field position angle theta in open-loop operating mode₀And estimating the rotor position angle theta_MThe experimental test result of the difference is theta_err＝8.3°，I_p0The value 6A is matched with the load size, and the closed-loop operation mode is switched in after the open-loop operation is carried out for 3.5 seconds, as shown in figure 3 because of I_p0Cut-in position closed-loop operation die with reasonable valueAnd (4) successfully starting.

FIG. 4 is a U-phase current waveform of a motor with failed start, maintaining the winding phase current peak value and the open-loop operating frequency of the open-loop operating mode unchanged, i.e., I_p0＝6A，f₀At 8Hz, but the starting load torque is reduced to T_L0.5Nm, when the active rotating magnetic field position angle theta is in the open-loop operation mode₀And estimating the rotor position angle theta_MExperimental test results for the difference increase to θ_errAt 12.7 °, the open loop operation is in the cut-in position closed loop operation mode after 3.5 seconds, as shown in fig. 4, since I_p0The value is large, the open-loop starting torque is large, energy overshoots, the algorithm for estimating the rotor position in the open-loop cut-in position closed-loop stage is not converged, and finally starting failure is caused.