Permanent magnet synchronous motor sensorless control strategy based on improved phase-locked loop

Abstract

The invention provides a permanent magnet synchronous motor sensorless control strategy based on an improved phase-locked loop. The method comprises the following steps: constructing a permanent magnet synchronous motor model driven by a three-leg inverter; rotating speed closed-loop and current closed-loop control is adopted, a rotating speed controller and a current controller both adopt proportional-integral controllers, and a modulation strategy is SVPWM (space vector pulse width modulation); building a Luenberger observer model, estimating a back electromotive force by taking the acquired voltage and current as input quantities, and then filtering out higher harmonics in a back electromotive force signal by adopting a synchronous frequency extraction filter; and building a dual high-order phase-locked loop, and finally obtaining rotor position information and rotating speed information of the permanent magnet synchronous motor by compensating a position estimation error of the phase-locked loop (PLL). The method can effectively solve the problem that a phase-locked loop has a large estimation error when the position of the rotor is estimated, reduces steady-state errors of the permanent magnet synchronous motor during acceleration or deceleration operation, filters out higher harmonic components in counter electromotive force, and improves the precision of a permanent magnet synchronous motor control system.

Description

TECHNICAL FIELD

[0001] The application relates to the field of power electronic system simulation, and mainly relates to a permanent magnet synchronous motor position sensorless control strategy based on an improved phase-locked loop, which compensates for rotor position estimation error and improves position estimation accuracy. BACKGROUND

[0002] The permanent magnet synchronous motor is widely applied in the electrical drive field due to the characteristics of simple and reliable structure, high efficiency and high power density. The permanent magnet synchronous motor has the characteristics of nonlinearity and strong coupling, and accurate identification of the rotor position is crucial to high-performance control of the permanent magnet synchronous motor. If the angle information is inaccurate, a suitable magnetic field cannot be applied to drive the rotor, and however, the conventional mechanical position or speed sensor has the problems of large volume, high cost, inconvenient installation and low reliability in special application occasions, so the sensorless control technology is widely applied in the electrical drive field. SUMMARY

[0003] The application provides a permanent magnet synchronous motor position sensorless control strategy based on an improved phase-locked loop, which sufficiently compensates for rotor position estimation error, reduces the steady-state error of the permanent magnet synchronous motor in acceleration and deceleration operation, filters out high-order harmonics in the back electromotive force signal, and improves the control performance of the permanent magnet synchronous motor.

[0004] In order to achieve the above-mentioned purpose, the application adopts the following technical scheme, comprising:

[0005] S1. A permanent magnet synchronous motor (PMSM) model driven by a three-bridge arm inverter is built;

[0006] S2. A speed closed loop and a current closed loop control are adopted, and a proportional integral controller is adopted for the speed and current controllers, and an SVPWM modulation strategy is adopted;

[0007] S3. A Luenberger observer model is built to estimate the back electromotive force;

[0008] S4. A double high-order phase-locked loop (DPLL) is built, a synchronous frequency extraction filter (SSF) is first used to filter out high-order harmonics in the back electromotive force signal, then the double phase-locked loop compensates for the position estimation error, and the permanent magnet synchronous motor rotor position information and speed information are obtained; and the high-order phase-locked loop reduces the steady-state error of the permanent magnet synchronous motor in acceleration and deceleration operation.

[0009] The application patent has the following advantages relative to the prior art:

[0010] The double phase-locked loop delays and reconstructs the current signal by introducing the same non-ideal element in front, and the reconstructed current signal and the estimated position signal are phase-locked twice, so that the rotor position estimation error is sufficiently compensated.

[0011] High-order phase-locked loop reduces the steady-state error of permanent magnet synchronous motor when accelerating or decelerating.

[0012] The synchronous frequency extraction filter (SSF) is used to filter out high harmonics in the back electromotive force signal, and the estimation accuracy of the rotor position is improved. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 The structure block diagram of the synchronous frequency extraction filter is shown in the figure;

[0014] Figure 2 The Luenberger observer based on double high-order phase-locked loop is shown in the figure;

[0015] Figure 3 The simulation diagram of estimating the rotor position and the actual rotor position based on the traditional phase-locked loop is shown in the figure;

[0016] Figure 4 The simulation diagram of estimating the rotor position and the actual rotor position based on the double high-order phase-locked loop is shown in the figure;

[0017] Figure 5 The simulation diagram of estimating the rotor position and the actual rotor position based on the traditional phase-locked loop under the acceleration and deceleration operation condition of the system is shown in the figure;

[0018] Figure 6 The simulation diagram of estimating the rotor position and the actual rotor position based on the double high-order phase-locked loop under the acceleration and deceleration operation condition of the system is shown in the figure; DETAILED DESCRIPTION

[0019] In order to make the features and advantages of the present application more obvious and easy to understand, the present application will be further described in detail below with reference to the accompanying drawings.

[0020] A permanent magnet synchronous motor sensorless control strategy based on an improved phase-locked loop includes:

[0021] S1. Build a permanent magnet synchronous motor (PMSM) model driven by a three-bridge arm inverter;

[0022] In the implementation, the present application proposes a model composed of a direct current power supply, a three-bridge arm inverter, and a permanent magnet synchronous motor, and the permanent magnet synchronous motor is driven to work by the three-bridge arm inverter. In the stationary coordinate system (a, β axis system), the mathematical model of the permanent magnet synchronous motor is:

[0023]

[0024] In the formula, u α and u β are stator voltages, R and L are stator resistance and stator inductance of the permanent magnet synchronous motor, p=d / dt is a differential operator, i a , iβ It is the stator current, ψ f It is a permanent magnet flux linkage, ω e θ is the rotor electrical angular velocity, and θ is the motor rotor electrical angle.

[0025] S2. Speed ​​closed-loop and current closed-loop control are adopted. Both speed and current controllers use proportional-integral controllers, and the modulation strategy is SVPWM.

[0026] In practice, the rotor position information of the motor is obtained by measuring the voltage and current of the motor and processing it through the Luneburg observer. The reference voltage vector is obtained after passing through the speed loop and the current loop. Both the speed loop and the current loop use proportional-integral controllers. The switching signal of the three-bridge inverter is generated by SVPWM modulation to drive the permanent magnet synchronous motor.

[0027] S3. Build a Luneburger observer model, estimate the back electromotive force from the sampled two-phase current and voltage, and then estimate the position and speed of the permanent magnet synchronous motor through a phase-locked loop;

[0028] In practice, the voltage and current of the permanent magnet synchronous motor are collected, and then a Luneburger observer is built to estimate the back electromotive force. The observer model is as follows:

[0029]

[0030] The discrete form of the Romberg observer is obtained by using forward difference discretization:

[0031]

[0032] The conditions for the existence of the Luneburg observer constructed above are:

[0033]

[0034] The estimated rotor position can be obtained through a phase-locked loop.

[0035] S4. Construct a dual high-order phase-locked loop (DPLL). First, use a synchronous frequency extraction filter (SSF) to filter out high-order harmonics in the back EMF signal. Then, the dual phase-locked loop compensates for the position estimation error and obtains the rotor position and speed information of the permanent magnet synchronous motor. At the same time, the high-order phase-locked loop reduces the steady-state error of the permanent magnet synchronous motor during acceleration and deceleration.

[0036] In practice, the obtained back EMF signal contains a large number of harmonic components. Although the phase-locked loop can process the back EMF signal to obtain rotor information, it cannot suppress the influence of harmonic components on the accuracy of the observer. In order to improve the observation accuracy of the speed observer, this invention first uses a synchronous frequency extraction filter (SFF) to extract the fundamental component of the back EMF, and then sends the processed signal to obtain rotor information. The block diagram of the synchronous frequency extraction filter is shown below. Figure 1 As shown.

[0037] The transfer function of the synchronization frequency extraction filter is expressed as:

[0038]

[0039] In the formula, ε is the filter gain. The output of the filter is extracted for the synchronization frequency.

[0040] From the above formula, its amplitude-frequency characteristic can be obtained as:

[0041]

[0042] According to the above formula, if the frequency ω equals ω0, then the amplitude of the SFF is equal to 1, and the fundamental component of the back electromotive force signal can pass through the SFF without attenuation. If the input frequency ω is greater than or less than ω0, the amplitude of the SFF will be significantly attenuated. Therefore, the SFF can effectively extract the signal with frequency ω0 and filter out interference from other frequencies.

[0043] Double higher-order phase-locked loops, such as Figure 2 As shown, permanent magnet synchronous motors based on traditional phase-locked loops exhibit steady-state errors during acceleration or deceleration. To address this issue, this invention designs a high-order phase-locked loop (PLL) to eliminate steady-state errors.

[0044] The improved high-order phase-locked loop (PLL) results in the following steady-state errors for the motor under constant speed and acceleration / deceleration conditions:

[0045]

[0046] As can be seen from equations (7) and (8), the improved high-order phase-locked loop can eliminate the steady-state error of the motor and reduce the steady-state error to zero during acceleration or deceleration.

[0047] In order to make the no-load back electromotive force E s With phase current i s To achieve phase-locked loop (PLL) operation, this invention proposes a dual PLL structure, such as... Figure 2 As shown, an improved high-order phase-locked loop is first used to eliminate the steady-state error of the motor when the speed changes, thus achieving a preliminary estimation of the position signal. Then, introducing the same types of non-ideal elements as before, for i...s Perform a delay reconstruction to obtain a current reconstruction signal i. s_d Since the introduced non-ideal components are the same, i s_d Lagging behind i s The phase is Lagging behind E s The phase of the current is then reconstructed. A second higher-order phase-locked loop is then introduced to reconstruct the current signal i. s_d With estimated location By performing a second phase-locked loop, E can be achieved. s with i s Indirect phase-locked loops can be used to obtain the compensation angle Δθ. z Then Δθ z Compensation to estimated position signal The estimated position signal after full compensation can then be obtained.

[0048] The invention is further illustrated below with specific implementation results diagrams:

[0049] In the specific implementation of this invention, compared with traditional phase-locked loop (PLL) control strategies, a novel sensorless control strategy for a permanent magnet synchronous motor based on a Luenberger observer is first built in MATLAB / SIMULINK and compared with conventional control methods through simulation. The reference speed of the permanent magnet synchronous motor is set to 500 rpm. The simulation results of the estimated rotor position and the actual rotor position under the traditional PLL control strategy are shown in the figure below. Figure 3 As shown in the figure, the simulation results of the estimated rotor position and the actual rotor position under the dual high-order phase-locked loop proposed in this invention are as follows. Figure 4 As shown. By Figure 3 It is known that when using a traditional phase-locked loop to estimate the rotor position signal, there is a large phase estimation error. Figure 4 It can be seen that after adopting the dual high-order phase-locked loop scheme proposed in this invention, the rotor position estimation error is sufficiently compensated, verifying the effectiveness of the proposed dual high-order phase-locked loop scheme in compensating for rotor position estimation errors. The reference speed of the permanent magnet synchronous motor is set as acceleration from 500 rpm to 1500 rpm, followed by a period of stabilization and deceleration back to 500 rpm. The simulation results of the estimated rotor position versus the actual rotor position under the traditional phase-locked loop control strategy are shown in the figure below. Figure 5 As shown in the figure, the simulation results of the estimated rotor position and the actual rotor position under the dual high-order phase-locked loop proposed in this invention are as follows. Figure 6 As shown. By Figure 5 , Figure 6It is known that when using a traditional quadrature phase-locked loop (PLL) to estimate the position signal under varying speeds, there is a large phase estimation deviation. However, when using the dual high-order PLL scheme proposed in this invention, the rotor position estimation error is adequately compensated under varying speeds, verifying the effectiveness of the proposed dual high-order PLL scheme in compensating for rotor position estimation errors under acceleration or deceleration conditions.

[0050] Finally, the method described in this application is merely a preferred embodiment and is not intended to limit the scope of protection of this invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. The present invention provides a kind improved phase-locked loop based permanent magnet synchronous motor sensorless control strategy, characterized by, The application relates to a permanent magnet synchronous motor (PMSM) model driven by a three-bridge arm inverter. S1. A three-bridge arm inverter driven permanent magnet synchronous motor (PMSM) model is built; S2. A speed closed loop and a current closed loop control are adopted, the speed and current controllers are proportional integral controllers, and an SVPWM modulation strategy is adopted; S3. A Luenberger observer model is built to estimate the back electromotive force; S4. A double high-order phase-locked loop (DPLL) is built, a synchronous frequency extraction filter (SSF) is used to filter out high-order harmonics in the back electromotive force signal, then the double phase-locked loop compensates the position estimation error to obtain the permanent magnet synchronous motor rotor position information and speed information; meanwhile, the high-order phase-locked loop reduces the steady-state error of the permanent magnet synchronous motor during acceleration and deceleration operation.

2. The improved sensorless control strategy for permanent magnet synchronous motor based on phase-locked loop according to claim 1, characterized in that The model in S1 is composed of a direct current power supply, a three-bridge arm inverter and a permanent magnet synchronous motor, and the permanent magnet synchronous motor is driven by the three-bridge arm inverter to work. In a stationary coordinate system, the mathematical model of the permanent magnet synchronous motor is expressed as: where u α and u β are the stator voltages, R, L are the stator resistance and stator inductance of the permanent magnet synchronous machine, p = d / dt is the differential operator, i a , i β are the stator currents, ψ f is the permanent magnet flux linkage, ω e is the rotor electrical angular velocity, and Θ is the electrical rotor angle.

3. The improved sensorless control strategy for permanent magnet synchronous motor based on phase-locked loop according to claim 1, characterized in that The control strategy in S2 drives the permanent magnet synchronous motor, the motor rotor position information is obtained through the Luenberger observer and the motor voltage and current, the reference voltage vector is obtained after the speed loop and the current loop, the speed loop and the current loop are proportional integral controllers, the three-bridge arm inverter switch signals are generated through SVPWM modulation to drive the permanent magnet synchronous motor to work.

4. The improved sensorless control strategy for permanent magnet synchronous motor based on phase-locked loop according to claim 1, characterized in that The Luenberger observer model in S3 is: The discrete form of the Luenberger observer obtained by forward difference discretization is: The conditions for the Luenberger observer constructed above are: The estimated rotor position is obtained via a phase locked loop 5. The improved PLL-based sensorless control strategy for permanent magnet synchronous motor as claimed in claim 1 wherein The double high-order phase-locked loop in S4 obtains a back electromotive force signal containing a large number of harmonic components, the phase-locked loop can process the back electromotive force signal to obtain the rotor information, but cannot inhibit the influence of the harmonic components on the observer accuracy, in order to improve the observation accuracy of the speed observer, the synchronous frequency extraction filter (SSF) is used to extract the fundamental component of the back electromotive force, and then the processed signal is sent to obtain the rotor information, and the block diagram of the synchronous frequency extraction filter is as shown in Fig.

1. The transfer function of the synchronous frequency extraction filter is expressed as: where ε is the filter gain, is the output result of the synchronous frequency extraction filter. From the above formula, the amplitude-frequency characteristic is: According to the above formula, if the frequency omega is equal to omega0, the amplitude of SFF is equal to 1, and the fundamental component of the back electromotive force signal can pass through SFF without attenuation. If the input frequency omega is greater than or less than omega0, the amplitude of SFF will be greatly attenuated. Therefore, SFF can effectively extract the signal with the frequency of omega0 and filter out the interference of other frequencies. The double high-order phase-locked loop is shown in Fig.

2. The permanent magnet synchronous motor based on the traditional phase-locked loop has a steady-state error during acceleration or deceleration operation. In view of this problem, a high-order phase-locked loop is designed to eliminate the steady-state error. The steady-state error of the motor in the speed constant and acceleration and deceleration state of the improved high-order phase-locked loop is: From formula (7) and formula (8), the improved high-order phase-locked loop can eliminate the steady-state error of the motor, and reduce the steady-state error to zero in the acceleration or deceleration state. In order to make the no-load back electromotive force E s With phase current i s To achieve phase-locked loop (PLL), this invention proposes a dual PLL structure as shown in Figure 2. First, an improved high-order PLL is used to eliminate the steady-state error of the motor during speed changes, thus achieving a preliminary estimation of the position signal. Then, by introducing the aforementioned non-ideal links, i s Perform a delay reconstruction to obtain a current reconstruction signal i. s_d Since the introduced non-ideal components are the same, i s_d Lagging behind i s The phase is Lagging behind E s The phase of the current is then reconstructed. A second higher-order phase-locked loop is then introduced to reconstruct the current signal i. s_d With estimated location By performing a second phase-locked loop, E can be achieved. s with i s Indirect phase-locked loops can be used to obtain the compensation angle Δθ. z Then Δθ z Compensation to estimated position signal The estimated position signal after full compensation can then be obtained.

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