Method for forming permanent magnet synchronous motor non-inductive vector control based on improved phase-locked loop

Abstract

The invention discloses a permanent magnet synchronous motor non-inductive vector control forming method based on an improved phase-locked loop, and the method comprises the following steps: changing a phase discriminator structure of a conventional orthogonal phase-locked loop, and eliminating the influence of a rotating speed signal on the phase-locked loop; according to the improved phase discriminator structure of the A, a loop filter and a voltage-controlled oscillator are combined to form a new improved orthogonal phase-locked loop; the improved orthogonal phase-locked loop is applied to permanent magnet synchronous motor sensorless vector control. After the structure is changed, the complexity is not improved, and the implementation is easy; when the motor realizes positive and negative rotation working conditions, the system zero crossing point does not diverge, and the working condition requirement of positive and negative rotation switching of the permanent magnet synchronous motor can be met.

Description

Technical Field

[0001] This invention belongs to the field of power electronics, and in particular relates to a method for forming sensorless vector control of a permanent magnet synchronous motor based on an improved phase-locked loop. Background Technology

[0002] Built-in permanent magnet synchronous motors are widely used in various fields due to their advantages such as high power density, high efficiency, and simple structure. In vector control, the motor rotor position information is obtained through an encoder installed on the motor, which is the foundation for coordinate transformation and even vector control. However, in wind power generation and new energy fields, motors often operate in harsh environments, and the use of encoders can reduce the reliability of the system.

[0003] To improve system reliability, sensorless control strategies are generally employed in the aforementioned applications. Sensorless control strategies for permanent magnet synchronous motors (PMSMs) are mainly divided into two categories: The first is the high-frequency signal injection method based on the motor's salient pole characteristics. This method is suitable for the zero and low-speed regions and can be further divided into pulsed high-frequency injection, square wave high-frequency injection, and rotating high-frequency injection methods depending on the injected signal. The other category is the model method based on back EMF. This method is suitable for the medium and high-speed speed regions. Common methods for observing rotor position based on back EMF include sliding mode observers and model reference adaptive methods.

[0004] Sensorless control strategies for permanent magnet synchronous motors based on the back EMF observer method often employ phase-locked loops to convert the estimated back EMF into estimated values ​​of speed and position. Figure 1 This is a block diagram of a traditional quadrature phase-locked loop (PLL). A PLL consists of three parts: a phase detector, a loop filter, and a voltage-controlled oscillator (VCO). The structure and parameters of each part directly affect the stability and dynamic performance of the PLL. Traditional quadrature PLLs exhibit divergence points at zero crossings, which can cause the entire system to crash. Summary of the Invention

[0005] The purpose of this invention is to provide a method for forming sensorless vector control of a permanent magnet synchronous motor based on an improved phase-locked loop (PLL). By changing the phase detector structure of the traditional quadrature PLL, the speed sign information in the back EMF is eliminated, thus solving the problem of divergence at zero crossings in traditional quadrature PLLs. The improved PLL can meet the requirements of forward and reverse rotation of the motor, ensuring smooth switching during operation and preventing system divergence.

[0006] The objective of this invention is achieved through the following technical solution: A method for forming sensorless vector control of a permanent magnet synchronous motor based on an improved phase-locked loop, characterized by comprising the following steps: Step A: At the phase detector input of the quadrature phase-locked loop, the input and feedback values ​​are constructed to form a sine and cosine product with square operation. The squared term eliminates the influence of the rotational speed direction signal on the phase-locked loop. Step B: The rotor speed is obtained through the loop filter of the quadrature phase-locked loop, and then the estimated position is obtained through the voltage-controlled oscillator of the quadrature phase-locked loop, realizing sensorless vector control of the permanent magnet synchronous motor and meeting the working conditions of forward and reverse switching of the permanent magnet synchronous motor.

[0007] Step A includes: The input to a quadrature phase-locked loop (quadrature phase-locked loop) is the back electromotive force (EMF), and its mathematical model is expressed as: ; ; in: It is a stationary coordinate system; It is a rotating coordinate system; It is a virtual coordinate system; It is the angle error of the phase-locked loop input; yes The back electromotive force of the shaft; yes The back electromotive force of the shaft; It is the estimated position angle of the phase-locked loop output; It is an equivalent coefficient; It is angular frequency; It is a permanent magnet flux chain; It is the rotor position angle; It is the synchronization angle; The back EMF contains sign information of rotational speed, which leads to reverse failure and DC offset error of rotor position during acceleration and deceleration when applied to sensorless control of permanent magnet synchronous motors. The sum-to-product formula for sine and cosine rotations is used, and its squared term is utilized to eliminate the influence of the rotational speed direction signal on the phase-locked loop, including: ; ; ; Error signal for: ; In the formula: yes The back electromotive force of the shaft; yes Back EMF of the axis; It is the rotor angular frequency.

[0008] Step B includes: estimating the back potential , As the input to the quadrature phase-locked loop (PLL), the rotor speed is obtained after passing through a loop filter. Then, the estimated position is obtained through a voltage-controlled oscillator. .

[0009] This invention modifies the phase detector structure of a traditional quadrature phase-locked loop (PLL) to eliminate the influence of the speed signal on the PLL. Based on the improved phase detector (PD) structure, a new improved quadrature phase-locked loop is formed by combining a loop filter (LF) and a voltage-controlled oscillator (VCO); the improved quadrature phase-locked loop is applied to sensorless vector control of a permanent magnet synchronous motor.

[0010] Compared to traditional orthogonal phase-locked loops, it has the following characteristics and advantages: The structural changes did not increase complexity and were easy to implement. When the motor operates in both forward and reverse directions, the system will not diverge at the zero-crossing point, which can meet the operating requirements of the permanent magnet synchronous motor for switching between forward and reverse directions. Attached Figure Description

[0011] Figure 1 A structural diagram of a traditional orthogonal phase-locked loop.

[0012] Figure 2 Multiple coordinate system diagrams.

[0013] Figure 3 Error phase trajectory diagram of traditional quadrature phase-locked loop.

[0014] Figure 4 The structural block diagram of the improved orthogonal phase-locked loop.

[0015] Figure 5 Block diagram of sensorless control strategy for permanent magnet synchronous motor based on phase-locked loop.

[0016] Figure 6 The waveform changes of the sensorless control of a permanent magnet synchronous motor under forward and reverse rotation conditions based on a traditional quadrature phase-locked loop were verified.

[0017] Figure 7 The waveform changes of the sensorless control of the permanent magnet synchronous motor under forward and reverse rotation conditions based on the improved quadrature phase-locked loop were verified. Detailed Implementation

[0018] The invention is further described below with reference to the accompanying drawings, in which a model is used in conjunction with sensorless vector control of a permanent magnet synchronous motor to verify whether the improved quadrature phase-locked loop is suitable for motor forward and reverse switching conditions. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of the invention.

[0019] A method for forming sensorless vector control of a permanent magnet synchronous motor based on an improved phase-locked loop includes the following steps: Step A: At the phase detector input of the quadrature phase-locked loop, the input and feedback values ​​are constructed to form a sine and cosine product with square operation. The squared term eliminates the influence of the rotational speed direction signal on the phase-locked loop. Step B: The rotor speed is obtained through the loop filter of the quadrature phase-locked loop, and then the estimated position is obtained through the voltage-controlled oscillator of the quadrature phase-locked loop, realizing sensorless vector control of the permanent magnet synchronous motor and meeting the working conditions of forward and reverse switching of the permanent magnet synchronous motor.

[0020] Figure 1 This is a block diagram of a traditional quadrature phase-locked loop (PLL). A PLL consists of three parts: a phase detector, a loop filter, and a voltage-controlled oscillator (VCO). The structure and parameters of each part directly affect the stability and dynamic performance of the PLL. Figure 1 middle, It is an estimate. Back-axis electromotive force component; It is an estimate. Back-axis electromotive force component; It is the input error angle; It is the estimated angular frequency; It is the estimated synchronization angle position.

[0021] When using a back-EMF observer for sensorless control, a phase-locked loop (PLL) is necessary to obtain the motor rotor speed and position. A traditional quadrature PLL uses the output of the back-EMF observer as input, which is then converted into sine and cosine signals by a phase detector (PD), and finally filtered by a loop filter to obtain the position angle and speed. Specifically, the input to the quadrature PLL is the back-EMF, and its mathematical model can be expressed as:

[0022]

[0023] Figure 2 Multiple coordinate system diagrams Figure 2 middle, It is a stationary coordinate system; It is a rotating coordinate system; It is a virtual coordinate system; It is the angle error of the phase-locked loop input; yes The back electromotive force of the shaft; yes The back electromotive force of the shaft; It is the estimated position angle of the phase-locked loop output; It is an equivalent coefficient; It is angular frequency; It is a permanent magnet flux chain; It is the rotor position angle.

[0024] Therefore, it can be seen that the back EMF contains the sign information of the rotational speed. A prominent problem with traditional quadrature phase-locked loops is that a 180° phase difference occurs when the motor rotates in both directions. This leads to reversal failure and significant DC offset error of the rotor position during acceleration and deceleration when applied to sensorless control of permanent magnet synchronous motors.

[0025] Figure 3 Traditional quadrature phase-locked loop error phase trajectory diagram, such as Figure 3 middle, It is the error in angular frequency; This refers to the position angle error. The system converges at (-pi,0) and (pi,0), while diverging at (0,0). Therefore, under PMSM reversal conditions, there is a 180° steady-state error between the rotor position estimated by the traditional quadrature phase-locked loop and the actual value, leading to control failure.

[0026] The velocity sign information introduced by directly calculating the back electromotive force is opposite on the alpha and beta axes. Then, after the error signal is amplified by the phase-locked loop, the error function diverges at (0, 0).

[0027] An improved method for phase-locked loops is to remove the speed sign information from the back electromotive force, so that the system can function in both forward and reverse operation.

[0028]

[0029] It is a stationary coordinate system; It is a rotating coordinate system; It is a virtual coordinate system; The advantage of the proposed phase-locked loop (PLL) is that it eliminates the sign information of the velocity, thus overcoming the divergence problem at zero crossings. Another advantage of the improved PLL is its better steady-state performance, mainly because the error function signal amplification capability of the improved quadrature PLL is increased by 2 times.

[0030] Figure 4 This is a block diagram of the improved quadrature phase-locked loop (PLL). Unlike traditional PLLs, the improved PLL features an improved error signal. for:

[0031] Figure 5This is a block diagram of sensorless vector control for a permanent magnet synchronous motor based on a quadrature phase-locked loop. In the diagram, It is a given rotational speed (Revolutions Per Minute, rpm). It is an estimated rotational speed (rpm); PI stands for Proportional Integral (PI). It is the q-axis reference current (A) provided by the IF control; It is the d-axis reference current (A); 2r / 2s and 2s / 2r represent the transformation between stationary and rotating coordinate systems; First-order low-pass filter (LPF). Permanent magnet synchronous motor (M); Three-phase current sampled from the motor side The stationary coordinate system obtained after coordinate transformation Axis current components; It is after 2r / 2s conversion Reference voltage on the shaft.

[0032] A common strategy for sensorless control of permanent magnet synchronous motors is based on a back EMF observer, which estimates the back EMF. As the input to the quadrature phase-locked loop (PLL), the rotor speed is obtained after passing through a loop filter. Then, the estimated position is obtained through a voltage-controlled oscillator. .

[0033] Figure 6 The waveform changes during sensorless control of a permanent magnet synchronous motor under forward and reverse rotation based on a traditional quadrature phase-locked loop are verified. The figure shows that the system diverges and loses stability when switching between forward and reverse rotation.

[0034] Figure 7 The waveform changes during the verification of sensorless control of a permanent magnet synchronous motor under forward and reverse rotation conditions based on an improved quadrature phase-locked loop (PLL) are shown in the figure. As can be seen from the figure, the improved PLL ensures system stability and prevents divergence during forward and reverse rotation verification.

Claims

1. A method for forming sensorless vector control of a permanent magnet synchronous motor based on an improved phase-locked loop, characterized in that, Includes the following steps: Step A: At the phase detector input of the quadrature phase-locked loop, the input and feedback values ​​are constructed to form a sine and cosine product with square operation. The squared term eliminates the influence of the rotational speed direction signal on the phase-locked loop. Step B: The rotor speed is obtained through the loop filter of the quadrature phase-locked loop, and then the estimated position is obtained through the voltage-controlled oscillator of the quadrature phase-locked loop, realizing sensorless vector control of the permanent magnet synchronous motor and meeting the working conditions of forward and reverse switching of the permanent magnet synchronous motor.

2. The method for forming sensorless vector control of a permanent magnet synchronous motor based on an improved phase-locked loop according to claim 1, characterized in that, Step A includes: The input to a quadrature phase-locked loop (quadrature phase-locked loop) is the back electromotive force (EMF), and its mathematical model is expressed as: ； ； in: It is a stationary coordinate system; It is the angle error of the phase-locked loop input; yes The back electromotive force of the shaft; yes The back electromotive force of the shaft; It is the estimated position angle of the phase-locked loop output; It is an equivalent coefficient; It is angular frequency; It is a permanent magnet flux chain; It is the rotor position angle; It is the synchronization angle; The back EMF contains sign information of rotational speed, which leads to reverse failure and DC offset error of rotor position during acceleration and deceleration when applied to sensorless control of permanent magnet synchronous motors. The sum-to-product formula for sine and cosine rotations is used, and its squared term is utilized to eliminate the influence of the rotational speed direction signal on the phase-locked loop, including: ； ； ； Error signal for: ； In the formula: yes The back electromotive force of the shaft; yes Back EMF of the axis; It is the rotor angular frequency.

3. The method for forming sensorless vector control of a permanent magnet synchronous motor based on an improved phase-locked loop according to claim 1, characterized in that, Step B includes: estimating the back potential , As the input to the quadrature phase-locked loop (PLL), the rotor speed is obtained after passing through a loop filter. Then, the estimated position is obtained through a voltage-controlled oscillator. .

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