阅读说明：本技术 一种开关磁阻电机无位置传感器低速运行控制方法 (Low-speed operation control method for switched reluctance motor without position sensor ) 是由 陈昊 桑永豪 尹正凯 周大林 渠苏东 于 2019-11-25 设计创作，主要内容包括：本发明公开了一种开关磁阻电机无位置传感器低速运行控制方法，属于开关磁阻电机控制的技术领域。本发明对开关磁阻电机的导通相绕组的电流采用斩波控制方式，非导通相的绕组的电流采用脉冲注入控制方式，基于此方法可获得整个周期的电流信息，采用单电流阈值法，通过检测某一位置下的电流幅值估计出转子位置信息并进行换相运行，该方法也可以满足在不同电压下的转子位置估计和无位置传感器运行，同时，通过对误差的分析并进行一定的补偿，可以更加精确的控制电机的运行。该方法增强了开关磁阻电机驱动系统的可靠性，适用于开关磁阻电机的低速带载运行。(The invention discloses a position-sensorless low-speed operation control method for a switched reluctance motor, and belongs to the technical field of switched reluctance motor control. The invention adopts a chopping control mode for the current of a conducting phase winding of a switched reluctance motor, adopts a pulse injection control mode for the current of a non-conducting phase winding, can obtain the current information of the whole period based on the method, adopts a single current threshold value method, estimates the position information of a rotor by detecting the current amplitude value at a certain position and carries out phase-change operation, can also meet the requirements of the position estimation of the rotor and the operation without a position sensor under different voltages, and simultaneously can more accurately control the operation of the motor by analyzing errors and carrying out certain compensation. The method enhances the reliability of the driving system of the switched reluctance motor and is suitable for the low-speed on-load operation of the switched reluctance motor.)

1. A switched reluctance motor sensorless low-speed operation control method is characterized by comprising the following steps:

A. driving the switched reluctance motor to operate in a continuous working mode, so that the windings of the motor are sequentially conducted;

B. setting a current threshold according to a peak current waveform chart which changes with the bus voltage at different positions;

C. detecting the current amplitude of each non-conducting phase winding in each electrical cycle in real time, and sending out a position retrieval pulse at a special rotor position reference point equal to a set threshold;

D. estimating a real-time rotating speed and estimating a rotor position according to the angle difference and the time interval of two adjacent position retrieval pulses;

E. and performing error analysis according to the difference value between the estimated position and the actual position, and adding an angle error compensation link in an actual control system to further improve the position-sensor-free control of the switched reluctance motor.

2. The method for controlling the sensorless low-speed operation of the switched reluctance motor according to claim 1, wherein the step a drives the switched reluctance motor to operate in a continuous operation mode, so that the windings of the motor are sequentially conducted by: the switched reluctance motor is driven to continuously run, the current of a conduction interval is limited between the upper limit and the lower limit by controlling the repeated on-off of a main circuit device, so that the conduction phase of the winding works in a current chopping control mode, and a high-frequency low-voltage pulse current injection method is adopted in the non-conduction interval of the winding.

3. The method for controlling the sensorless low-speed operation of the switched reluctance motor according to claim 2, wherein the method for setting a certain current threshold in step B comprises: performing integral operation in a full period according to the relation between the flux linkage of each phase of winding and phase voltage and phase current to determine the flux linkage of each phase of winding, and determining the ratio of the flux linkage of each phase of winding to the phase currentDetermining the full-period inductance value of each phase winding, and finally expressing the inductance, voltage, pulse time and pulse amplitude

4. The method as claimed in claim 3, wherein the step C adopts a single current threshold control method, and when the conducting phase is turned off and the pulse current amplitude in the non-conducting phase is higher than the threshold, a position search pulse is sent out, at which the pulse turns off the previous phase and turns on the next phase, so that A, B, C three phases can be sequentially conducted.

5. The method for controlling sensorless low-speed operation of a switched reluctance motor according to claim 4, wherein the expression for estimating the rotation speed according to the angle difference and the time interval of the position search pulses in two adjacent cycles in step D is:

6. The method for controlling sensorless low speed operation of a switched reluctance motor according to claim 5, wherein the expression for the difference between the estimated position and the actual position in step E is: delta theta_errThe expression for the motor speed is ω t: θ 6 ω Txθ: position angle of adjacent search pulse, T: pulse period, ω: real-time motor speed, x: number of pulses in one on interval, t: for setting a current threshold position I_THThe time to the next pulse rising edge;

based on the switched reluctance motor, when the switched reluctance motor runs at low speed, at least one branch circuit which is used for detecting normal is selected for each phase winding in the switched reluctance motor structure, and a non-conductive phase high-frequency signal injection method, a conductive phase current chopping method, a single current threshold value method, a pulse injection area inductance estimation method, a position estimation area determination method, a low-speed continuous running position estimation method and an angle error compensation method are applied, so that continuous rotor position estimation during low-speed running is realized.

Technical Field

The invention discloses a position-sensorless low-speed operation control method for a switched reluctance motor, and belongs to the technical field of switched reluctance motor control.

Background

The switched reluctance motor is of a double-salient pole type, the stator is provided with centralized windings, and the rotor is free of windings and permanent magnets. The switched reluctance motor is widely applied to occasions such as an electric automobile driving motor, a starting generator, a compressor, textile machinery, flywheel energy storage and the like. In order to ensure reliable and high performance operation of the switched reluctance motor, the rotor position information must be accurately obtained. The traditional switched reluctance motor driving system has certain influence on a speed regulation system due to the fact that the rotor position sensor is installed, cost is increased, debugging difficulty is increased, and therefore the research on the position-free sensing technology of the switched reluctance motor is beneficial to widening of the application range of the switched reluctance motor.

In recent years, many studies have been made by both scholars at home and abroad in the field, and various control methods are proposed to be applied to different rotating speed ranges, wherein the control methods mainly comprise a conducting phase detection method, a non-conducting phase detection method, a detection method based on intelligent control, an additional element detection method and other position estimation algorithms, and the conducting phase detection method comprises a magnetic linkage method, a phase current gradient method, an observer method and a non-conducting phase detection method comprises an excitation pulse method, and a curve fitting method is more applied.

The position sensorless control techniques proposed above all have their respective applicability and limitations, and these methods have their respective advantages and disadvantages. The flux linkage current method is characterized in that flux linkage-current-position angle data are stored in a three-dimensional table, winding phase current and flux linkage data are estimated in real time, and rotor position information is obtained through table lookup. With the application of intelligent control detection methods such as a neural network method, a fuzzy control method, a kalman filtering method and the like to the position-sensorless technology of the switched reluctance motor, the method does not need an accurate system model, and only needs enough training data to fit to obtain the relationship between the rotor position and the current and the flux linkage, so as to complete position estimation. The external anti-series test coil adopts inductance characteristic value comparison to obtain the position of the rotor, but additional hardware is needed, the cost is increased, the control technology without the position sensor mostly depends on a motor flux linkage model, and the universality and the practicability are reduced.

The inductance information is identified by adopting a calculation method of a current slope difference value based on the position-free sensor technology of an inductance linear model, the rotor information can be estimated through a relation model of the inductance and the position, but the zero crossing point of the phase current slope is difficult to detect, and the angle control range is limited.

The position-sensorless technology based on the double current thresholds well separates the conducting phase from the non-conducting phase by setting two thresholds to respectively control the conducting phase and the estimation phase, but the technology increases the calculation amount by using two current thresholds.

Disclosure of Invention

The invention aims to overcome the defects of the background technology, and provides a switched reluctance motor position sensorless rotor position estimation method which is suitable for simple and convenient calculation, the rotor position can be estimated without predicting electromagnetic characteristic data and an accurate mathematical model of the switched reluctance motor, and the technical problems of complicated calculation caused by the fact that the traditional switched reluctance motor position-free methods such as a flux linkage current method, an inductance model method, a double current threshold method, intelligent control and the like depend on motor body parameters are solved.

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

a switched reluctance motor sensorless low-speed operation control method comprises the following steps:

A. driving the switched reluctance motor to operate in a continuous working mode, so that the windings of the motor are sequentially conducted;

B. setting a current threshold according to a peak current waveform chart which changes with the bus voltage at different positions;

C. detecting the current amplitude of each non-conducting phase winding in each electrical cycle in real time, and sending out a position retrieval pulse at a special rotor position reference point equal to a set threshold;

D. and estimating the real-time rotating speed and the rotor position according to the angle difference and the time interval of two adjacent position retrieval pulses.

E. And performing error analysis according to the difference value between the estimated position and the actual position, and adding an angle error compensation link in an actual control system to further improve the position-sensor-free control of the switched reluctance motor.

As a further optimization scheme of the position sensorless low-speed operation control method for the switched reluctance motor, the step a of driving the switched reluctance motor to operate in a continuous working mode so that the method for sequentially conducting the windings of the motor comprises the following steps: the switched reluctance motor is driven to continuously run, the current of a conduction interval is limited between the upper limit and the lower limit by controlling the repeated on-off of a main circuit device, so that the conduction phase of the winding works in a current chopping control mode, and a high-frequency low-voltage pulse current injection method is adopted in the non-conduction interval of the winding.

Further, in the method for controlling the sensorless low-speed operation of the switched reluctance motor, the method for setting a certain current threshold in step B is as follows: performing integral operation in a full period according to the relation between the flux linkage of each phase of winding and phase voltage and phase current to determine the flux linkage of each phase of winding, determining the full period inductance value of each phase of winding according to the ratio of the flux linkage of each phase of winding to the phase current, and finally according to the expression of inductance, voltage, pulse time and pulse amplitudeAnd obtaining peak current oscillograms which change along with the bus voltage at different positions, and setting a current threshold value at a corresponding position according to the oscillograms. Wherein, U is the amplitude of the detection voltage pulse; Δ t is the time interval between two adjacent position search pulses; and Δ i is the increment of the current of the phase winding to be detected in the time Δ t.

Further, the control method for the sensorless low-speed operation of the switched reluctance motor adopts a single current threshold control method in step C, when the conducting phase is turned off and the pulse current amplitude of the non-conducting phase is higher than the threshold, a position retrieval pulse is sent out, the previous phase is turned off at the position of the position retrieval pulse, and the next phase is turned on, so that A, B, C three phases can be sequentially conducted.

Further, the switch magnetic resistanceIn the method for controlling the low-speed operation of the motor without the position sensor, in the step D, the expression of estimating the rotating speed according to the angle difference and the time interval of the position retrieval pulse in two adjacent periods is as follows:

the expression for estimating the rotor position is: θ (k +1) ═ θ (k) + ω Δ T, ω is the real-time rotation speed, Δ θ and Δ T are the angle difference and the time interval of two adjacent position search pulses, θ (k +1) and θ (k) are the estimated values of the rotor position in the k +1 th electrical cycle and the k-th electrical cycle, respectively, and Δ T is the electrical cycle.

Still further, in the method for controlling the sensorless low-speed operation of the switched reluctance motor, in the step E, the expression according to the difference between the estimated position and the actual position is as follows: delta theta_errThe expression for the motor speed is ω t: θ 6 ω Tx, θ: position angle of adjacent search pulse, T: pulse period, ω: real-time motor speed, x: number of pulses in one on interval, t: for setting a current threshold position I_THThe time between the rising edge of the next pulse.

Based on the switched reluctance motor structure, when the switched reluctance motor structure operates at low speed, at least one branch circuit which is used for detecting normal is selected for each phase winding in the switched reluctance motor structure, and a non-conducting phase high-frequency signal injection method, a conducting phase current chopping method, a single current threshold value method, a pulse injection area inductance estimation method, a position estimation area determination method, a low-speed continuous operation position estimation method and an angle error compensation method are applied, so that continuous rotor position estimation during low-speed operation is realized.

Has the advantages that:

by adopting the technical scheme, the invention has the following technical effects: the invention adopts a chopping control mode for the current of a conducting phase winding of a switched reluctance motor, adopts a pulse injection control mode for the current of a non-conducting phase winding, can obtain the current information of the whole period based on the method, adopts a single current threshold value method, estimates the position information of a rotor by detecting the current amplitude value at a certain position and carries out phase-change operation, can also meet the requirements of the position estimation of the rotor and the operation without a position sensor under different voltages, and simultaneously can more accurately control the operation of the motor by analyzing errors and carrying out certain compensation. The method enhances the reliability of the driving system of the switched reluctance motor and is suitable for the low-speed on-load operation of the switched reluctance motor.

Drawings

FIG. 1 is a schematic diagram of a switched reluctance motor sensorless low-speed operation principle based on a single current threshold method;

FIG. 2 is a graph of current peaks as a function of bus voltage at different locations;

FIG. 3 is a flow chart of a full cycle estimation of rotor position;

FIG. 4 is a schematic diagram of an error analysis of estimated and actual positions;

fig. 5 is a block diagram of a speed regulation control system of a switched reluctance motor.

Detailed Description

An embodiment of the invention is further described below with reference to the accompanying drawings:

the invention detects the intersection point position of the latter phase inductance in the ascending region and the former phase inductance in the descending region in each period, namely the position where the latter phase and the former phase inductance of the switched reluctance motor are equal, calculates the real-time rotating speed of the motor through the rotor position pulse signal obtained at the position where the inductances are equal, estimates the rotor position information, and has stronger universality and practicability.

Fig. 1 is a schematic diagram of the low-speed operation principle of a switched reluctance motor sensorless based on a single current threshold method. When the switched reluctance motor operates at a low speed, a current chopping control mode is usually adopted for a conducting phase, and when the conducting phase is switched off, a follow current mode is entered, namely a non-conducting area. The invention injects high-frequency low-voltage pulse into the non-conducting area of the winding, so that the inductance of each electric period is continuous. The pulse current of the latter phase greater than the threshold is extracted as the criterion for the conduction of this phase and simultaneously as the criterion for the previous interruption. The envelope curve of the pulse current of the latter phase can be taken to eliminate error pulse, and the rising interval of the envelope curve is obtained to be used as the conduction interval of the envelope curve, so that the motor can continuously run at low speed with load. In order to further analyze the principle, the phase C is selected as a research object, the running direction of the motor is supposed to be circularly conducted by taking A-B-C as a sequence, at the moment, the pulse current of the phase A behind the phase C is selected as the conduction criterion of the phase C, and is simultaneously used as the turn-off criterion of the phase B of the previous phase, namely, when the pulse amplitude of the phase A is larger than the threshold value, the phase C is conducted, the phase B is turned off, so that the phase change is completed, and the continuous running of the motor is realized. Fig. 1 shows three-phase current, three-phase non-conducting phase pulse current, envelope of three-phase pulse current extracted from a threshold, position search pulse at the on/off time of C phase, conducting interval of C phase, and rotor position estimation, respectively. The envelope curve of the three-phase pulse current in fig. 1 is the extracted pulse current, that is, the pulse current larger than the threshold, and the envelope curve of each phase can be obtained by calculating the difference Δ i between adjacent pulse currents of each phase, so that the envelope curve can be used for judging the conduction interval, and errors generated when the pulse current is compared with the threshold can be eliminated. A pulse signal S1 is generated at the on time and the off time of the C phase of the motor respectively, namely when the amplitude of the A-phase pulse current is larger than a set threshold value, the pulse signal S2 is generated as the on signal of the C phase, when the amplitude of the B-phase pulse current is larger than the set threshold value, the pulse signal S2 is generated as the off signal of the C phase, and the corresponding interval of S1 and S2 in the figure is in the rising interval of the current pulse envelope curve, namely the envelope curve is in a monotone increasing interval, so that the interval is selected as the on interval of the C phase. And in the same way, the conduction interval of the phase A and the phase B can be obtained, so that the continuous operation of the phase change driving motor is carried out.

FIG. 2 is a graph showing the peak current at different locations as a function of bus voltage. The method comprises the steps of sampling each phase current and phase voltage in real time through a voltage sensor and a current sensor, calculating a flux linkage of the switched reluctance motor by using current and voltage data, further calculating phase inductance, and finally obtaining a relational expression of the phase inductance and bus voltage.

Fig. 3 is a flowchart illustrating a full-period rotor position estimation, where the voltage equation of the k-th phase of the switched reluctance motor is shown in equation (1):

in the formula (1), U_kTerminal voltage of winding of k-th phase, i_kIs the winding current of the k-th phase, R_kIs the winding resistance of the k-th phase, psi_kIs the winding flux linkage of the k-th phase.

The expression of the phase winding flux linkage obtained by integrating the two sides is shown as the formula (2):

from the phase winding flux linkage ψ (i, θ), the inductance L (i, θ) and the current i, the winding inductance can be calculated from equation (3):

when the conducting phase is turned off, a high-frequency low-voltage pulse signal is injected into a non-conducting area of the winding, and according to the injected high-frequency low-voltage pulse, the relation between the phase inductance and the bus voltage can be calculated according to the formula (4):

obtaining the real-time rotating speed of the motor according to the formula (5):

in equation (5), ω is the real-time rotation speed, and Δ θ and Δ t represent the angular difference and the time interval between two adjacent position search pulses, respectively.

Estimating any position of the rotor according to the specific rotor position and the real-time rotating speed as shown in the formula (6):

θ(k+1)＝θ(k)+ωΔT (6)

in the formula (6), θ (k) is the position angle estimated at the last sampling time; theta (k +1) is the position angle estimated at the current sampling time, and delta T is the sampling time

Fig. 4 is a schematic diagram illustrating an error analysis of the estimated position and the actual position. According to the single current threshold position-less sensor method, the A phase is taken as a reference picture, and the positions of 15 degrees, 30 degrees and 45 degrees in a 45-degree range of one period are respectively the single current threshold I_THWhen the amplitude of the pulse current is larger than the single current threshold value I of the 15 DEG, 30 DEG or 45 DEG position_THIn practice, the phase change is performed, but in practice, the amplitude of the acquired pulse current is not exactly at the 15 °, 30 ° or 45 ° position, which results in an estimation error. At this time, the C phase is used as an analysis object when being switched on, and according to the analysis of the single current threshold, the switching-on time of the C phase is judged by the estimated phase A phase at the point 2, namely the 30-degree position of the A phase (as shown in figure 4), but the actually acquired pulse current amplitude is larger than the set current threshold I_THIs at point 3, and thus the C-phase opening position is estimated at point 1, and the estimation algorithm misinterprets that point 1 is at the 30 ° position of the a-phase, so that in the control system, each decision point will yield Δ θ_errThe error angle of (2). Therefore, in order to consider the algorithm feasibility, firstly, the angle errors at different rotating speeds are calculated according to the analysis method and are stored in the memory of the processor, an angle error compensation link is added in an actual control system, and the position angle is adjusted in real time through table lookup.

Fig. 5 is a block diagram of a speed regulation control system of a switched reluctance motor. The system consists of a speed outer ring and a current chopping inner ring, and a speed regulator is used for converting a speed error into a given current I^*So as to realize speed regulation. The current setting of each phase is realized through the comprehensive judgment of information such as an opening angle, a closing angle, a rotor position, a rotating direction and the like, and the current setting is compared with the current hysteresis loop fed back actually to generate a control signal of a power electronic device. Comparing the amplitude of the injection pulse current detected when the switched reluctance motor operates with the reference current threshold value to obtain the position information at the moment, thereby completing the position,And (6) estimating the speed.