A position sensorless control method for voltage feed-forward permanent magnet synchronous motor

Abstract

The application discloses a voltage feedforward type permanent magnet synchronous motor position sensorless control method, aiming at the problem of the steady-state error of the conventional phase-locked loop in the traditional voltage feedforward method during dynamic speed regulation, an improved phase-locked loop is constructed, a feedforward speed reconstruction strategy is innovatively proposed, a feedforward speed component is obtained by using the stator voltage and mathematical operation, coarse adjustment of the estimated speed is realized, the closed-loop adjustment of the conventional phase-locked loop to the position error signal is reserved, the phase-locked loop estimated speed component is obtained to eliminate the error, the accurate estimated speed is obtained by superimposing the two speed components, and the rotor position is obtained after integration; the application can completely eliminate the position steady-state error under the acceleration and deceleration conditions without affecting the steady-state performance of the motor, significantly improves the dynamic speed regulation performance and the anti-interference ability, is suitable for the permanent magnet synchronous motor driving system which is high in control precision and dynamic response requirement under the medium and high speed conditions, and has wide engineering application value.

Description

Technical Field

[0001] This invention relates to the control of permanent magnet synchronous motors, and more particularly to a sensorless control method for a voltage-feedforward permanent magnet synchronous motor. Background Technology

[0002] Permanent magnet synchronous motors (PMSMs) are widely used in marine electric propulsion systems, electric railway traction systems, and industrial automation equipment due to their advantages such as simple structure, high power density, and wide speed range. In high-performance vector control systems, the traditional method of using mechanical sensors (such as encoders) to obtain rotor position and speed information suffers from problems such as reduced system reliability, increased installation and maintenance costs, and complex structural design. Therefore, sensorless control technology has become a research hotspot in recent years.

[0003] Sensorless control methods can be categorized by speed range into salient pole model methods suitable for zero-speed and low-speed applications, and fundamental wave model methods suitable for medium- and high-speed applications. Among these, the voltage-feedforward sensorless control method (hereinafter referred to as the voltage-feedforward method) has promising applications in the control of medium- and high-speed permanent magnet synchronous motors due to its advantages such as simple structure, accurate position estimation, and low computational load. This method achieves rotor position and speed estimation through three steps: voltage-feedforward decoupling, position error construction, and position estimation. Its position estimation stage is equivalent to a second-order conventional phase-locked loop (PLL).

[0004] However, conventional second-order phase-locked loops exhibit significant steady-state errors under speed ramp input conditions (i.e., motor acceleration and deceleration). Theoretical analysis shows that this steady-state error is directly proportional to the speed acceleration and inversely proportional to the integral gain, as expressed mathematically: (in This represents the amplitude of the rotational acceleration. (This refers to the integral gain). In practical applications, this steady-state error can cause the estimated position to lag behind the actual position, resulting in decreased speed and torque response, current fluctuations, and in severe cases, even instability of the drive system, making it unable to meet the requirements of high dynamic speed regulation.

[0005] In existing improvement schemes, some scholars have upgraded the phase-locked loop to a third-order system by adding a speed feedforward stage to eliminate steady-state errors. However, these schemes may rely on... The back EMF signal (not applicable to voltage feedforward methods) or the presence of flux linkage errors affecting system performance make it difficult to directly apply to voltage feedforward sensorless control methods. Therefore, it is urgent to design a novel improved phase-locked loop (PLL) specifically for the characteristics of voltage feedforward methods to enhance the dynamic speed regulation performance and anti-interference capability of permanent magnet synchronous motors. Summary of the Invention

[0006] This application provides a voltage-feedback permanent magnet synchronous motor sensorless control method, which overcomes the shortcomings of the existing voltage-feedback method using conventional phase-locked loops in terms of insufficient dynamic speed regulation performance and steady-state error under acceleration and deceleration conditions. It provides a voltage-feedback sensorless control method combined with an improved phase-locked loop, which significantly improves the dynamic response speed and anti-interference capability of the motor while ensuring steady-state performance.

[0007] This application provides a sensorless control method for a voltage-feedback permanent magnet synchronous motor, including the following steps: Step S1, establish a real synchronous coordinate system ( d - q Coordinate system) and estimated synchronous coordinate system ( (Coordinate system), to obtain the voltage model and coordinate transformation relationship of the permanent magnet synchronous motor in two coordinate systems; Step S2, in In the coordinate system, a specific voltage feedforward decoupling term is used to decouple the current loop and extract the rotor position error signal; the specific voltage feedforward decoupling term is: in, For stator winding resistance, , These are the d-axis and q-axis current command values, respectively. To estimate the rotational speed, , These are the d-axis and q-axis inductances, respectively. Step S3, construct an improved phase-locked loop, which includes a feedforward speed component calculation module and a phase-locked loop estimated speed component calculation module: Feedforward speed component calculation module: for the decoupled... axis, Axis current regulator output voltage , Perform the inverse Park transform to obtain shaft voltage , The feedforward speed component is obtained through arctangent operation, differentiation, and low-pass filtering. ; Phase-locked loop (PLL) speed estimation component calculation module: This module uses a conventional PLL to perform closed-loop adjustment on the position error signal extracted in step 2 to obtain the PLL-estimated speed component. The feedforward speed component and the phase-locked loop estimated speed component are superimposed to obtain the final estimated speed. ,right Integrating yields the estimated rotor position. Based on estimated rotor position and estimated rotational speed This enables sensorless vector control of permanent magnet synchronous motors.

[0008] Preferably, the voltage model of the permanent magnet synchronous motor in the real synchronous coordinate system in step 1 is as follows: in, , These are the stator voltages along the d-axis and q-axis, respectively. , These are the stator currents along the d-axis and q-axis, respectively. This represents the actual rotor angular velocity. For permanent magnet flux linkage; the voltage and current transformation relationship between the two coordinate systems is as follows: In the formula, For position estimation error, This represents the actual rotor position.

[0009] Preferably, the specific process for extracting the rotor position error signal in step 2 is as follows: superimposing a specific voltage feedforward decoupling term with the output voltage of the current regulator to obtain... Stator voltage in coordinate system , Substituting into the simplified model of the estimated synchronous coordinate system voltage, we obtain: Constructing a unit amplitude position error signal using trigonometric function relationships: in, This is a reference value for the magnetic flux linkage of permanent magnets.

[0010] Preferably, in step 3, the feedforward speed component The calculation process includes: right , Perform the inverse Park transform: After arctangent operation, differentiation, and low-pass filtering, the following is obtained: In the formula, For differential operators, This is the cutoff frequency of the low-pass filter.

[0011] Preferably, the improved phase-locked loop is a third-order system, and its closed-loop transfer function is: The error transfer function is: in, For proportional gain, This is the integral gain.

[0012] Preferably, the improved phase-locked loop parameter design adopts a zero-point coincidence scheme, specifically the following steps: based on the system phase margin (PM) and cutoff frequency... Calculate the coincident zero points Sum of coefficients : based on , and Solving for the given information yields the following results. , , ,in: The proportional gain is obtained by solving the simultaneous equations. Integral gain and low-pass filter cutoff frequency .

[0013] This application also proposes a permanent magnet synchronous motor drive system, which adopts the above-mentioned voltage feedforward sensorless control method combined with an improved phase-locked loop to realize the estimation and control of rotor position and speed.

[0014] Preferably, the permanent magnet synchronous motor drive system includes a frequency converter, a permanent magnet synchronous motor, a load unit, and a controller, wherein the controller is configured using the method described above.

[0015] One or more technical solutions provided in the embodiments of this application have at least the following technical effects or advantages: The improved phase-locked loop achieves coarse speed adjustment by feeding forward speed components, making the estimated speed quickly approach the actual speed. At the same time, the estimation error is eliminated by closed-loop regulation of the phase-locked loop. Theoretically, it can completely eliminate the steady-state error under speed ramp input, and significantly improve the dynamic speed regulation performance. The improved phase-locked loop is a third-order system. Compared with the traditional second-order phase-locked loop, under dynamic conditions such as acceleration and deceleration and sudden load changes, the position estimation error is smaller (fluctuation does not exceed 3°), the speed estimation fluctuation is less than 1 rpm, the current regulation is more stable, and there is no obvious overshoot phenomenon. The improved parameter design method for phase-locked loops is scientific and reasonable. It enhances the system stability margin through zero-point coincidence configuration, and the parameter tuning process is simple and easy to implement in engineering. The method retains the advantages of simple structure and low computational load of the voltage feedforward method, does not affect the steady-state performance of the motor, and has stronger anti-interference ability. Under the condition of sudden load change, the speed error is reduced to 48% of the traditional method, and the current impact is significantly reduced. The method of this invention is highly versatile and applicable not only to voltage feedforward sensorless control, but also to other sensorless control methods and motor drive systems, thus having broad engineering application value. Attached Figure Description

[0016] Figure 1 This represents the phase relationship between the actual synchronization coordinate system and the estimated synchronization coordinate system in this application; Figure 2 This is a block diagram illustrating the conventional voltage feedforward decoupling principle in this application; Figure 3 This is a block diagram illustrating the principle of the position estimation method based on specific voltage feedforward decoupling in this application. Figure 4 This is a basic structural block diagram of a conventional orthogonal phase-locked loop in this application; Figure 5 This is a schematic diagram illustrating the principle of the feedforward rotation speed in this application; Figure 6 This is a block diagram of the improved phase-locked loop principle incorporating a novel feedforward rotation speed in this application; Figure 7 This is a comparison chart of the steady-state performance test results under rated operating conditions in this application; Figure 8 This is a comparison chart of the dynamic speed regulation test results under rated torque conditions with an acceleration of 200 rpm / s in this application. Figure 9 This is a comparison chart of the dynamic speed regulation test results under resistive load conditions with an acceleration of 200 rpm / s in this application; Figure 10 The figures show a comparison of the experimental results of load change at rated speed in this application; where (a) is the experimental result using a conventional phase-locked loop and (b) is the experimental result using an improved phase-locked loop. Detailed Implementation

[0017] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific implementation methods.

[0018] Example 1 1. Coordinate system establishment and voltage model construction like Figure 1 As shown, a real synchronous coordinate system is established ( d - q Coordinate system) and estimated synchronous coordinate system ( Coordinate systems). The true synchronous coordinate system has the rotor's current position as the d-axis and a 90° lead over the rotor's actual position as the q-axis; the estimated synchronous coordinate system has the estimated rotor position as the direct axis and a 90° lead over the estimated position as the quadrature axis. Position estimation error. .

[0019] Ignoring transient current processes, the voltage model of a permanent magnet synchronous motor in the real synchronous coordinate system is as follows: The voltage and current transformation relationship between the two coordinate systems is as follows: 2. Voltage feedforward decoupling and position error extraction exist In the coordinate system, a specific voltage feedforward decoupling term is used to decouple the current loop, eliminating the coupling effect between the d-axis and q-axis currents. The specific voltage feedforward decoupling term is: Compare it with the output voltage of the current regulator , Superimpose to obtain Stator voltage in coordinate system: Substituting the estimated synchronous coordinate system voltage model into the simplified form, we obtain the current regulator output containing only the position error signal: By constructing a unit amplitude position error signal using trigonometric function relationships, the influence of parameter variations on position estimation can be eliminated. 3. Improve the design and parameter tuning of the phase-locked loop. like Figure 3 As shown, the improved phase-locked loop includes a feedforward speed component calculation module and a phase-locked loop estimated speed component calculation module. The speed estimation accuracy and dynamic response speed are improved through a dual-path design of "coarse adjustment + fine adjustment".

[0020] (1) Calculation of feedforward speed component right , Perform the inverse Park transform to obtain Shaft voltage: right and The ratio is used to perform arctangent calculation to obtain rotor position-related information. After differentiation and low-pass filtering, the feedforward speed component is obtained. To achieve coarse speed adjustment: (2) Calculation of speed component estimation by phase-locked loop A conventional phase-locked loop (PLL) is used to perform closed-loop regulation on the extracted position error signal, and the PLL output is used to estimate the rotational speed component via a PI controller. This enables fine-tuning of the rotational speed and eliminates estimation errors.

[0021] Rotational speed and position estimation By superimposing the feedforward speed component and the phase-locked loop estimated speed component, the final estimated speed is obtained: right Integrating yields the estimated rotor position. This enables accurate estimation of the rotor position.

[0022] Parametric design method The phase-locked loop was improved to a third-order system, and a zero-point reconciliation scheme was used for parameter tuning to improve the system stability margin. The specific steps are as follows: S1: Based on the system phase margin (PM) and cutoff frequency Calculate the coincident zero points Sum of coefficients : S2: Based on , and Solving for the given information yields the following results. , , ; S3: Combined , , The proportional gain was calculated. Integral gain and low-pass filter cutoff frequency .

[0023] 4. Sensorless vector control Based on estimated rotor position and estimated rotational speed This enables vector control of permanent magnet synchronous motors, including current regulation, voltage feedforward decoupling, and other processes, to achieve speed and torque control of the motor.

[0024] Example 2 1. Coordinate system establishment and voltage model construction The parameters of the permanent magnet synchronous motor are set as follows: q-axis inductance Stator winding resistance Permanent magnet magnetic flux d-axis inductance (Seldom-pole motor).

[0025] Establish a real synchronous coordinate system ( d - q Coordinate system) and estimated synchronous coordinate system ( Coordinate system) Figure 1 As shown, the position estimation error The voltage model in the real synchronous coordinate system is as follows: 2. Voltage feedforward decoupling and position error extraction Employing specific voltage feedforward decoupling terms, such as Figure 2 As shown: By superimposing it with the output voltage of the current regulator, a unit amplitude position error signal is constructed: 3. Improve the design and parameter tuning of the phase-locked loop. like Figure 3 , Figure 4 , Figure 5 , Figure 6 As shown, the system phase margin is set. Cutoff frequency The calculation yields: Set the low-pass filter cutoff frequency Solving the system of equations simultaneously, we get: Further calculations yielded the proportional gain. Integral gain .

[0026] Calculation of feedforward speed component: By superimposing the feedforward speed component and the phase-locked loop estimated speed component, the final estimated speed is obtained. The estimated rotor position is obtained after integration. .

[0027] 4. Experimental verification An experimental platform was built with the inverter's DC bus voltage at 270V, a switching frequency of 10kHz, and the controller's internal current sampling and control frequency at 20kHz. Experimental results show that: (1) Figure 7 shows the steady-state performance test results under rated operating conditions. From top to bottom, the estimated rotor speed is shown in Figure 7. d shaft and q Shaft current, speed error, and rotor position error; Figure 7(a) shows the experimental results using a conventional phase-locked loop, and Figure 7(b) shows the experimental results using the improved phase-locked loop proposed in this invention. It can be seen that under rated operating conditions, the position errors of both the improved phase-locked loop and the conventional phase-locked loop are within [the specified range]. Within this range, the steady-state performance is comparable: (2) Figure 8 shows the dynamic speed regulation test results at an acceleration of 200 rpm / s under rated torque conditions. From top to bottom, the estimated rotor speed is shown. d shaft and q Shaft current, speed error, and rotor position error; Figure 8(a) shows the experimental results using a conventional phase-locked loop, and Figure 8(b) shows the experimental results using the improved phase-locked loop proposed in this invention. It can be seen that under the rated torque and acceleration of 200 rpm / s, the position error of the conventional phase-locked loop during acceleration and deceleration is 6.6° to -6.8°, while the position error fluctuation of the improved phase-locked loop does not exceed 3°, and the speed fluctuation is less than 1 rpm; (3) Figure 9 shows the dynamic speed regulation test results using a conventional phase-locked loop (PLL) and an improved PLL for position estimation under resistive load conditions with an acceleration of 200 rpm / s. From top to bottom, the estimated rotor speed is shown in Figure 9. d shaft and q Shaft current, speed error, and rotor position error; Figure 9(a) shows the experimental results using a conventional phase-locked loop, and Figure 9(b) shows the experimental results using the improved phase-locked loop proposed in this invention. It can be seen that under resistive load conditions, the position error of the conventional phase-locked loop is 8.8°~-9.2°, and the maximum speed error is 6.4 rpm. The improved phase-locked loop has no obvious overshoot, and the current change is stable. (4) Figure 10 shows the experimental results of load change at rated speed, showing rotor speed, speed error, rotor position, position error, and so on. d shaft and q The waveforms of shaft current and three-phase current are shown; Figure 10(a) shows the experimental results using a conventional phase-locked loop, and Figure 10(b) shows the experimental results using the improved phase-locked loop proposed in this invention. It can be seen that under sudden load changes, the position error of the improved phase-locked loop is reduced to -5.1° (compared to -9.6° for the conventional phase-locked loop), and the speed error is reduced to 48% of that of the traditional method.

[0028] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention. The embodiments described in this specific embodiment are all preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made according to the structure, shape, and principle of the present invention should be covered within the scope of protection of the present invention. Although preferred embodiments of the present invention have been described, those skilled in the art, once they understand the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the present invention. Obviously, those skilled in the art can make various modifications and variations to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention also intends to include these modifications and variations.

Claims

1. A sensorless control method for a voltage-feedforward permanent magnet synchronous motor, characterized in that, Includes the following steps: Step S1, establish a real synchronous coordinate system ( d - q Coordinate system) and estimated synchronous coordinate system ( (Coordinate system), to obtain the voltage model and coordinate transformation relationship of the permanent magnet synchronous motor in two coordinate systems; Step S2, in In the coordinate system, a specific voltage feedforward decoupling term is used to decouple the current loop and extract the rotor position error signal; the specific voltage feedforward decoupling term is: in, For stator winding resistance, , These are the d-axis and q-axis current command values, respectively. To estimate the rotational speed, , These are the d-axis and q-axis inductances, respectively. Step S3, construct an improved phase-locked loop, which includes a feedforward speed component calculation module and a phase-locked loop estimated speed component calculation module: Feedforward speed component calculation module: for the decoupled... axis, Axis current regulator output voltage , Perform the inverse Park transform to obtain shaft voltage , The feedforward speed component is obtained through arctangent operation, differentiation, and low-pass filtering. ; Phase-locked loop (PLL) speed estimation component calculation module: This module uses a conventional PLL to perform closed-loop adjustment on the position error signal extracted in step 2 to obtain the PLL-estimated speed component. The feedforward speed component and the phase-locked loop estimated speed component are superimposed to obtain the final estimated speed. ,right Integrating yields the estimated rotor position. Based on estimated rotor position and estimated rotational speed This enables sensorless vector control of permanent magnet synchronous motors.

2. The sensor control method according to claim 1, characterized in that, The voltage model of the permanent magnet synchronous motor in the real synchronous coordinate system in step 1 is as follows: in, , These are the stator voltages along the d-axis and q-axis, respectively. , These are the stator currents along the d-axis and q-axis, respectively. This represents the actual rotor angular velocity. For permanent magnet flux linkage; the voltage and current transformation relationship between the two coordinate systems is as follows: In the formula, For position estimation error, This represents the actual rotor position.

3. The sensor control method according to claim 1, characterized in that, The specific process for extracting the rotor position error signal in step 2 is as follows: The specific voltage feedforward decoupling term is superimposed with the current regulator output voltage to obtain... Stator voltage in coordinate system , Substituting into the simplified model of the estimated synchronous coordinate system voltage, we obtain: Constructing a unit amplitude position error signal using trigonometric function relationships: in, This is a reference value for the magnetic flux linkage of permanent magnets.

4. The sensor control method according to claim 1, characterized in that, The feedforward speed component in step 3 The calculation process includes: right , Perform the inverse Park transform: After arctangent operation, differentiation, and low-pass filtering, the following is obtained: In the formula, For differential operators, This is the cutoff frequency of the low-pass filter.

5. The sensor control method according to claim 1, characterized in that, The improved phase-locked loop is a third-order system, and its closed-loop transfer function is: The error transfer function is: in, For proportional gain, This is the integral gain.

6. The sensor control method according to claim 5, characterized in that, The improved phase-locked loop parameter design adopts a zero-point coincidence scheme, and the specific steps are as follows: Based on the system phase margin (PM) and cutoff frequency Calculate the coincident zero points Sum of coefficients : based on , and Solving for the given information yields the following results. , , ,in: The proportional gain is obtained by solving the simultaneous equations. Integral gain and low-pass filter cutoff frequency .

7. A voltage-feedback permanent magnet synchronous motor sensorless control system, characterized in that, The sensor control method described in any one of claims 1-6 is used to estimate and control the rotor position and speed.

8. The voltage-feedforward sensorless control system according to claim 7, characterized in that, It includes a frequency converter, a permanent magnet synchronous motor, a load unit, and a controller, wherein the controller is configured to perform the sensor control method according to any one of claims 1-6.

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