Pmsm sensorless starting method based on load estimation and dynamic speed regulation

Abstract

The application discloses a PMSM sensorless starting method based on load estimation and dynamic speed regulation, and belongs to the technical field of permanent magnet synchronous motors. q0 The load torque T l0 is estimated, then the acceleration and the set value of the q-axis current are calculated according to the target speed, and finally the q-axis current is adjusted according to the input signals and the operation condition of the system, so that the high-performance dynamic speed regulation function is realized. Through the load estimation before operation and the control of the q-axis current amplitude during operation, the acceleration and the speed can be dynamically regulated in the open-loop operation, the stability of the open-loop starting is effectively improved, and the PMSM open-loop starting control under the condition of no position sensor is realized.

Description

Technical Field

[0001] This invention relates to the field of sensorless control technology for permanent magnet synchronous motors, and particularly to a sensorless start-up method for PMSMs based on load estimation and dynamic speed regulation. Background Technology

[0002] Permanent magnet synchronous motors (PMSMs) possess advantages such as small size, high power density, high efficiency, simple structure, low noise, and fast dynamic response, making them widely used in various industrial fields. In practical applications, vector control is the most widely adopted control strategy for PMSM drive systems. However, to obtain accurate position information in real time, position detection devices such as Hall effect sensors or photoelectric encoders are typically installed in the motor. This undoubtedly increases the system's cost and complexity, and reduces its anti-interference capability and overall reliability. Therefore, low-cost, high-precision, and high-reliability sensorless control technology for PMSMs has become a research hotspot both domestically and internationally.

[0003] Sensorless control algorithms typically divide the motor's speed range into zero-low speed and medium-high speed stages for separate study. Among these, I / F open-loop start control and high-frequency injection are the two most commonly used methods when the motor is running at zero-low speed.

[0004] I / F open-loop startup involves setting the given current i along the d-axis and q-axis during the startup process. d * =0, i q * =i N And the desired acceleration 'a' creates a gradually accelerating rotating magnetic field in the motor, which in turn drives the rotor to rotate. Wherein, parameter i... q * Setting this is the most crucial step, as it determines the maximum load the motor can handle. If i q * If the value is too small, the load-bearing capacity is weak, and the motor cannot start normally. If i q * The motor has a relatively large capacity and can operate under heavy loads, but its power consumption increases significantly when the load decreases. Furthermore, during open-loop operation, the motor can only operate at the set desired acceleration, and speed adjustment is impossible once the speed stabilizes. Therefore, relevant parameters must be set according to the motor's operating environment and expected speed before open-loop operation, resulting in poor applicability, portability, and stability. Summary of the Invention

[0005] To overcome the problems of poor applicability of open-loop starting, difficulty in setting parameters, and inability to adjust speed during the starting and speed stabilization phases, this invention provides a sensorless starting method for PMSM based on load estimation and dynamic speed regulation.

[0006] In order to achieve the above object, the technical scheme adopted by the present application is:

[0007] The PMSM sensorless starting method based on load estimation and dynamic speed regulation comprises the following steps:

[0008] (1) Angle setting: according to the initial position θ0 of the rotor of the permanent magnet synchronous motor, the q * axis angle is set to be the same as the actual q axis angle.

[0009] (2) Load estimation stage: let the given current i d * = 0, i q * = 0, then gradually increase i q * , and detect the currents i α and i β of the static two-phase α-β coordinate system, and compare them with the calculated α-β axis theoretical current value; when the difference between them is large, it indicates that the rotor will start to rotate, at this time it is the critical point of the equal electromagnetic torque and load torque, and the q axis critical current is i q0 , and the estimated load torque is T l0 .

[0010] (3) Starting stage: according to the given acceleration a ref of the starting stage, rotate the q * axis, and calculate the reference value i q of i * , continue to increase i qref q on the basis of i * q0 = i q * , so that i q * = i qref . If the given acceleration a ref changes during the period, update the value of i qref , increase or decrease i q * , so that i q * = i qref .

[0011] (4) Speed regulation stage: when accelerated to the target speed ω ref , enter the stable stage, at this time a ref = 0, and the motor speed remains constant. If the target speed ω ref changes at this time, i.e. speed regulation is needed, then the given acceleration a ref and i qref are recalculated, and iq * .

[0012] Further, in the step (2), the α-β axis theory current value i α * , i β * and the estimated load torque T l0 is calculated by the following method:

[0013]

[0014]

[0015]

[0016] wherein θ0 is the initial position of the rotor, p is the number of pole pairs, is the permanent magnet flux linkage, i q0 is the q-axis critical current.

[0017] Further, the condition for the rotor to enter the critical point is:

[0018]

[0019] Further, in the step (3), the acceleration a as the parameter of open-loop starting can be set according to the size relationship between the current speed and the target speed:

[0020]

[0021] wherein a ref is the acceleration setting value, a max is the upper limit of the acceleration, ω ref is the target speed, and ω * is the open-loop given speed.

[0022] Further, in the step (3), the q-axis current reference value i qref is calculated according to the following formula:

[0023]

[0024] wherein B is the viscous coefficient, J is the moment of inertia, T ε is the torque margin.

[0025] Further, the method for changing (increasing or decreasing) i q * to i qref is:

[0026]

[0027] wherein 2i represents the change amount of i q * in each time interval Δt, represents the value at the current moment, represents the value at the next moment.

[0028] Further, in the step (4), the setting of the target rotating speed can be given by the input of the system.

[0029] Advantages:

[0030] Compared with the prior art, the present application has the following advantages:

[0031] 1. Different from the case that the three important parameters of acceleration, target rotating speed and current amplitude can only be set as fixed values in the traditional open-loop starting method, the present application can realize dynamic adjustment of the acceleration and rotating speed, and automatically set the current amplitude. The limitation that the open-loop starting parameters cannot be changed during the operation of the motor is eliminated, and the difficulty of parameter setting is reduced.

[0032] 2. The acceleration in the starting stage is not a fixed value, but changes with the actual rotating speed and the target rotating speed, which can reduce the fluctuation of the open-loop starting process and make the rotating speed curve more smooth.

[0033] 3. Without increasing any sensor and while maintaining the simplicity of the open-loop starting method, the size of the load can be estimated before the starting of the motor, so that the setting of the i q * is not too large, and the power consumption of the motor is reduced.

[0034] 4. The open-loop starting method disclosed in the present application can be used in the low and medium speed domain in the position sensorless control algorithm, and has small calculation amount, which is convenient for implementation and popularization and application. Different medium and high speed domain position sensorless control algorithms can be flexibly matched, and the rotating speed is adjusted according to the required switching rotating speed, the position sensorless control algorithm in the full speed domain is realized, and the purposes of reducing the cost of the control system and improving the reliability and robustness of the system are achieved. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 is a system structure block diagram of a PMSM sensorless starting method based on load estimation and dynamic speed regulation proposed in the present application;

[0036] Figure 2 is a schematic diagram of the open-loop starting coordinate axis relationship;

[0037] Figure 3 is a corresponding curve of the acceleration reference value, the target rotating speed and the given rotating speed;

[0038] Figure 4The target speed curve and the actual speed curve are shown in a simulation example according to the present invention;

[0039] Figure 5 This is a reference acceleration curve based on a simulation example of the present invention;

[0040] Figure 6 The actual q-axis current curve and the reference q-axis current curve are shown in a simulation example according to the present invention. Detailed Implementation

[0041] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0042] The sensorless start-up method for PMSM based on load estimation and dynamic speed regulation includes the following steps:

[0043] (1) Setting the angle: Based on the initial position θ0 of the permanent magnet synchronous motor rotor, set q * The angle of the axis is set to be the same as the actual q-axis angle.

[0044] (2) Load estimation stage: Let the given current i d * =0, i q * =0, then i q * Gradually increase the current, while simultaneously detecting the current i in the stationary two-phase α-β coordinate system. α and i β The value is then compared with the calculated theoretical current values ​​for the α-β axes. When the difference between the two is large, it indicates that the rotor is about to start rotating. This is the critical point where the electromagnetic torque equals the load torque. Let the critical current for the q-axis be i. q0 The estimated load torque is T. l0 .

[0045] (3) Entering the start-up phase: according to the acceleration a given in the start-up phase. ref Rotation q * axis, and calculate i q * Reference value i qref , in i q * =i q0 Continue to increase i q * , making i q * =i qref If an acceleration a is given during the periodref Variable, then update i qref The value of i q * , increase or decrease i q * = i qref .

[0046] (4) Speed regulation phase: when the target speed ω ref is reached, the stable phase is entered, in which a ref = 0, and the motor speed remains constant. If the target speed ω ref is changed, i.e. speed regulation is required, the given acceleration a ref and i qref are recalculated, and i q is adjusted accordingly. * .

[0047] In step (2), the α-β axis theoretical current value i α * , i β * and the estimated load torque T l0 are calculated as follows:

[0048]

[0049]

[0050]

[0051] where θ0 is the initial position of the rotor, p is the number of pole pairs, is the permanent magnet flux linkage, i q0 is the q-axis critical current.

[0052] The condition for the rotor to enter the critical point is:

[0053]

[0054] In step (3), the acceleration a is set as a parameter for open-loop starting, and can be set according to the size relationship between the current speed and the target speed:

[0055]

[0056] where a ref is the acceleration setting value, a max is the upper limit of the acceleration, ω ref is the target speed, and ω * is the open-loop given speed.

[0057] In step (3), the q-axis current reference value i qref is calculated according to the following formula:

[0058]

[0059] where B is the viscous coefficient, J is the moment of inertia, T ε is the torque margin.

[0060] i q * the method for changing (increasing or decreasing) to i qref is as follows:

[0061]

[0062] where k i represents the change amount of i q * in each time interval Δ4, represents the value at the current time, represents the value at the next time.

[0063] In step (4), the setting of the target speed can be given by the input of the system, such as numerical input or handle input.

[0064] As shown in Figure 1 , the open-loop control system of the permanent magnet synchronous motor is composed of a permanent magnet synchronous motor, a driving circuit, a current controller, and an SVPWM module. Since it is an open-loop control, no position detection device and speed loop are needed. When running, the set values of acceleration and current are calculated according to the input target speed and upper limit of acceleration, and current closed-loop control is performed;

[0065] Then the reference acceleration is integrated, and the obtained reference angle is used for inverse Park transformation and Clark transformation to realize control in the case of no position sensor;

[0066] The principle of traditional I / f open-loop starting is to give the amplitude of the current vector i q * and acceleration, so that the rotor rotates following the speed of i q * , and finally reaches stability.

[0067] The relationship between the d-q coordinate system of the motor rotation and the d * -q * coordinate system of the given current vector is as shown in Figure 2 , wherein the d * -q * axis rotates at a given acceleration, and since the value of i d * is always 0, the actual current vector i always coincides with the q * axis, that is, i q* ;

[0068] The d-axis coincides with the rotor, and the position of the dq-axis depends on the position of the rotor. The angle θ1 between the two coordinate systems affects the magnitude of the electromagnetic torque. During the startup process, θ1 often decreases from a large value to a small value and gradually approaches a stable value.

[0069] When the motor is running in a stable state, there is T. e =T l ,Right now

[0070]

[0071] It can be seen that the actual current vector i q * The current component on the d-axis does not coincide with the q-axis, and since the current component on the d-axis does not contribute to the electromagnetic torque, the motor's current utilization and energy conversion efficiency are low in this state. Furthermore, because the magnitude of the included angle θ1 is unknown, it is impossible to determine the stable operating region of the motor, and therefore impossible to adjust the motor's speed, load, current, and other operating parameters. Otherwise, even a slight mistake could cause the motor to lose its steps and stop abruptly, causing impact and damage to the system's mechanical structure and circuit components.

[0072] To address these issues, this invention first adjusts the load torque T based on the critical point of torque balance before open-loop startup. l Make an estimate, and then calculate a based on the target speed of the motor. ref and i qref The current loop is controlled so that when the target speed of the motor changes and the operating state needs to be changed, a ref and i qref It will also change dynamically, thereby achieving dynamic speed adjustment.

[0073] like Figure 3 As shown, acceleration a ref It is based on the target rotational speed ω ref Given the rotational speed ω * and the upper limit of acceleration a max This is jointly determined; when the given rotational speed is relatively small, the maximum acceleration a is used as the determining factor. max Acceleration is performed, and as the given rotational speed approaches the target rotational speed, the acceleration gradually decreases.

[0074] Among them, a max The value can be determined by the limitations of the actual operating environment or given by system input settings. For example, for electric vehicles, the travel of the accelerator pedal corresponds to different upper limits of acceleration. The deeper the pedal is pressed, the greater the corresponding acceleration. max The larger the pedal, the shallower it is depressed, corresponding to a. max The smaller the value, the more the driver can adjust the vehicle's acceleration when starting by increasing or decreasing the throttle.

[0075] The mechanical equation of the motor is used in step (3) to calculate i qref

[0076]

[0077] Wherein, p is the number of pole pairs, λ is the flux linkage The inertia J is a parameter of the motor itself, T l0 , a ref , ω * are known quantities, in order to make the motor still be able to operate stably under certain load disturbance, a torque margin T ε is set, and the viscous friction Bω * increases with the increase of the rotating speed, so that when the rotating speed changes, iq ref is also adjusted in real time.

[0078] The following will be described according to Figure 4 , 5 , 6 of the simulation example of the application, the example is accelerated at 0.5s, and the rotating speed is regulated at 2s;

[0079] From the rotating speed curve of Figure 4 , it can be seen that the method used in the application can make the rotating speed quickly reach the target value without overshoot, and the acceleration of the motor is relatively large at the initial start, and when the rotating speed approaches the target value, the acceleration gradually decreases, so that the rotating speed is more stable;

[0080] From the reference acceleration curve of Figure 5 , it can be seen that when the motor is accelerated and the rotating speed is regulated, the acceleration curve will dynamically respond, and then change the operating state of the motor;

[0081] Figure 6 The reference value i qref of the q-axis current in the d-q coordinate system is basically the same as the actual value i q , which shows that the angle θ1 between the d-q and d * -q * coordinate systems is small, the current utilization rate and energy conversion efficiency of the motor are high.

[0082] For those skilled in the art, it can be understood that various changes, modifications, replacements and variations can be made to the embodiments without departing from the principles and spirits of the application. Therefore, from any aspect, the embodiments should be regarded as guidance and are non-limiting, the scope of the application is defined by the appended claims rather than the above description, the embodiments of the application are only used to limit the application, and any modification, equivalent replacement, improvement, etc. within the spirits and principles of the application should be included in the protection scope of the application.

Claims

1. A PMSM position sensorless open-loop starting method based on load estimation and dynamic speed regulation, characterized in that, The method comprises the following steps: (1) Set angle: according to the initial position of the rotor of the permanent magnet synchronous motor , q * The angle of the shaft is set to be the same as the actual q-axis angle; (2) Load estimation stage: Let the given current i d * = 0, i q * = 0, then gradually increase i q * , while detecting the current i α and i β of the stationary two-phase α-β coordinate system, and compare them with the calculated α-β axis theoretical current i α * , i β * , when , it means that the rotor will start to rotate, which is the critical point of the equal electromagnetic torque and load torque, and the q-axis critical current is i q0 , and the estimated load torque is ; (3) Entering the starting phase: according to the given acceleration a ref Rotating q * Axis, and calculating i q * Reference value i qref , on the basis of i q * =i q0 Continue to increase i q * , make i q * =i qref If the given acceleration a ref Changes during the period, update the value of i qref Increase or decrease i q * , make i q * =i qref ; (4) Speed regulation stage: when accelerating to the target speed ω ref , the system enters the stable stage, in which a ref = 0, the motor speed remains constant; if the target speed ω ref changes at this time, i.e. speed regulation is needed, the given acceleration a ref and i qref are recalculated and adjusted accordingly i q * ; In the step (3), the acceleration a is set as a parameter of open-loop starting according to the size relationship between the current speed and the target speed. ； In the formula, is an acceleration set value, is an acceleration upper limit, is a target rotational speed, is an open-loop given rotational speed.

2. The load estimation and dynamic speed regulation based PMSM position sensorless open-loop starting method according to claim 1, wherein, In the step (2), the α-β axis theoretical current value i α * , i β * and the estimated load torque is calculated as follows: ； ； ； wherein, is the initial position of the rotor, p is the number of pole pairs, is the permanent magnet flux linkage, i q0 is the q-axis critical current.

3. The load estimation and dynamic speed regulation based PMSM position sensorless open-loop starting method according to claim 2, wherein, In the step (3), the q-axis current reference value i is calculated in accordance with the following equation qref : ； where B is the viscous coefficient, J is the moment of inertia, is the torque margin.

4. The load estimation and dynamic speed regulation based PMSM position sensorless open-loop starting method according to claim 3, characterized in that, i q * The method for changing the increase or decrease to i qref is: ； In the formula, denotes the value of each time interval denotes the value of each time interval q * denotes the change amount of each time interval, denotes the value of the current time, denotes the value of the next time.

5. The load estimation and dynamic speed regulation based PMSM position sensorless open-loop starting method according to claim 1, wherein, In the step (4), the target speed is set by the input of the system.

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