CN110365275B - Method for controlling high-speed operation of switched reluctance motor without position sensor - Google Patents
Method for controlling high-speed operation of switched reluctance motor without position sensor Download PDFInfo
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- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
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- H02P25/089—Sensorless control
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Abstract
The invention relates to a method for controlling the high-speed operation of a switched reluctance motor without a position sensor, which detects the magnitude of phase current and phase voltage in real time, calculates the phase inductance in a phase current existing interval by adopting a flux linkage integral mode, selects an inductance threshold value to intersect with an unsaturated area at the top of the phase inductance to obtain an estimated pulse and a special rotor position point, calculates the motor rotating speed and the rotor position angle by using the estimated pulse, and corrects the calculated rotor position angle by using the special rotor position point, thereby obtaining real-time rotor position information and realizing the control of the switched reluctance motor without the position sensor. The invention can effectively avoid the influence of phase inductance saturation on the control of the position-free sensor when the switched reluctance motor is in an on-load operation, has low hardware requirement and simple realization, and is suitable for the control of the position-free sensor operation at high speed in the switched reluctance motor.
Description
Technical Field
The invention relates to a position-sensorless high-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 a motor with a double salient pole structure, a stator is provided with a winding in a centralized mode, a rotor is not provided with any winding, and a stator and a rotor are formed by silicon steel sheets in an overlapped mode. Therefore, the switched reluctance motor has the advantages of firm structure, low cost, high reliability and the like. Meanwhile, due to the simple structure and the absence of the permanent magnet inside, the motor is particularly suitable for high-speed operation compared with other motors. Opening device
The stator windings of each phase of the switched reluctance motor are controlled by a separate driving circuit, and the phases are mutually independent, so that the switched reluctance motor has higher fault-tolerant capability. By adjusting the on-off angle, PWM duty ratio and on-phase current amplitude of the switched reluctance motor, stable and reliable operation of the motor in a wide rotating speed range can be realized. Based on the advantages, the switched reluctance motor is widely applied to the fields of household appliances, aerospace, new energy automobiles, industrial production and the like.
The operation of the switched reluctance motor needs to detect the position information of the rotor, and the main rotor position detection method at present is to install a position sensor inside the motor body, which increases the volume and the cost of the motor. In addition, under some severe working environments, the detection precision of the sensor can be influenced, and even the position sensor can be damaged, so that the research on the switched reluctance motor position-sensorless technology has very important significance. The control algorithm of the switched reluctance motor without the position sensor can be divided into a starting method, a low-speed operation method and a medium-high speed operation method according to the operation rotating speed of the motor. For the start-up and low-speed operation phases, most of the research is currently carried out on the basis of a non-conducting phase pulse injection method. When the rotating speed of the motor is increased, the follow current time of the winding is prolonged, the ratio of the non-conduction area occupied by the follow current interval is increased, and the time of the electric cycle is reduced after the rotating speed is increased, so that the pulse injection interval is reduced, and finally the control without the position sensor is influenced. Therefore, when the motor is operated at a high speed, the position sensorless control needs to be realized by using the on-phase current. However, when the motor is loaded, the phase current is large, the calculated inductance is in a saturated state, and the position information of the rotor cannot be accurately reflected.
Disclosure of Invention
The invention provides a motor position-sensorless high-speed operation control method based on an inductance top valve value method, aiming at solving the problems in the prior art.
In order to achieve the purpose, the technical scheme provided by the invention is as follows: a method for controlling the high-speed operation of a switched reluctance motor without a position sensor is characterized by comprising the following steps:
step one, sampling the magnitude of three-phase current and phase voltage in real time, and calculating a flux linkage value in a phase current existing interval by using a flux linkage integral method;
step two, obtaining phase inductance by utilizing the flux linkage value calculated in the step one;
selecting an inductance threshold value, intersecting the inductance threshold value with an unsaturated area at the top of the phase inductor to obtain an estimated pulse and a special rotor position point, and calculating the rotating speed of the motor by using the time between the falling edges of two adjacent estimated pulses;
and step four, integrating the calculated motor rotating speed to obtain a rotor position angle, and correcting the calculated angle by using a special rotor position point, so that a real-time position angle of the rotor is obtained, and the position-sensor-free control of the motor is realized.
The technical scheme is further designed as follows: the calculation formula for calculating the winding flux linkage by the flux linkage integral method in the first step is as follows:
ψ(n+1)＝ψ(n)+[U(n)-Ri(n)]T
where ψ (n +1) and ψ (n) are flux linkage values calculated in the n +1 th and nth calculation periods, respectively, u (n) and i (n) are phase voltage and phase current values sampled in the nth calculation period, respectively, R is a winding resistance value, and T is a flux linkage calculation period.
And setting a current threshold value in the process of calculating the flux linkage of the winding by using a flux linkage integral method in the first step, and clearing the flux linkage value obtained by integral when the conducting phase is switched off and the current is less than the threshold value.
The current threshold is 0.2A.
The step of calculating the phase inductance in the step two is as follows:
step 2.1, when the phase current is smaller than the current threshold value ITHWhen the phase inductance value is zero;
step 2.2, when the phase current is larger than the threshold value, calculating the phase inductance value according to the following formula,
where L is the calculated inductance, ψ is the winding flux calculated by step a, and i is the phase current.
The method for selecting the inductance threshold in the third step comprises the following steps:
and selecting the inductance corresponding to one position as an inductance threshold value in the interval from the current of the turn-off phase to the angle corresponding to the moment when the current of the turn-off phase is continued to be below the saturation current to the angle of the alignment position of the stator and the rotor.
And when the conducting phase is switched off and the current flows below the saturation current, selecting a corresponding inductance threshold value.
The method for calculating the rotating speed of the motor in the third step comprises the following steps:
and setting the time T between the falling edges of two adjacent estimated pulses, and calculating the motor rotating speed according to the following formula:
wherein N is the motor speed.
The method for calculating the position angle of the rotor in real time in the fourth step comprises the following steps:
and calculating a real-time rotor position angle according to the following formula by utilizing the motor rotating speed and the special rotor position point:
wherein, theta (n +1) and theta (n) are respectively the rotor position angle calculated in the n +1 th and the first calculation period, t0For angle calculation period, θ0In order to estimate the rotor position corresponding to the falling time of the pulse, i.e. the rotor special position point, S is the time corresponding to the falling edge of the estimated pulse, and when S is equal to 1, the level change of the estimated pulse generates the falling edge.
Compared with the prior art, the technical scheme of the invention has the following technical effects:
1. the invention aims at the position-sensorless control of the switched reluctance motor in the high-speed operation stage, calculates the phase inductance by using the current of the phase conduction interval and the related discontinuous current interval, and obtains the estimated pulse by comparing the phase conduction interval and the related discontinuous current interval with the preset inductance threshold value, thereby calculating the motor rotating speed and the real-time rotor position angle, realizing the position-sensorless control of the switched reluctance motor, and avoiding the problems of the traditional pulse injection method that the pulse injection interval is reduced after the motor rotating speed is increased and the inductance calculation is inaccurate.
2. The invention can effectively solve the problem that the conduction phase inductance is saturated and can not accurately reflect the position information of the rotor, when the conduction is disconnected, the current flows below the saturation current, then the inductance threshold value is selected, the estimated pulse obtained by first crossing the phase inductance is only related to the position of the rotor and is not influenced by the saturation current any more.
3. The invention realizes the control of the switched reluctance motor without a position sensor under the loading state in the middle and high speed operation stage, and has convenient realization, simple calculation and low hardware requirement.
Drawings
FIG. 1 is a hardware block diagram of electromagnetic characteristic curve calculation in an embodiment of the present invention;
FIG. 2 is a schematic of flux linkage and inductance calculations;
FIG. 3 is a flow chart of inductance calculation;
FIG. 4 is a schematic diagram of inductance calculation at different currents;
FIG. 5 is a schematic diagram of inductance top-threshold position estimation.
Detailed Description
The invention is described in detail below with reference to the figures and the specific embodiments.
Examples
Fig. 1 is a hardware block diagram of electromagnetic characteristic curve calculation, in which alternating current is supplied to a power circuit through an isolation transformer, a voltage regulator, a rectifier bridge, and a filter capacitor, and arbitrary regulation of direct current voltage at a bus terminal is realized by the voltage regulator. And a digital processor STM32F407 is adopted to convert phase current and phase voltage signals acquired by the current sensor and the voltage sensor into electric signals suitable for being input into the controller through a conditioning circuit, and then algorithm operation is carried out to obtain an electromagnetic characteristic curve.
Step one, sampling the magnitude of three-phase current and phase voltage in real time, and calculating a flux linkage value in a phase current existing interval by using a flux linkage integral method;
step two, obtaining phase inductance by utilizing the flux linkage value calculated in the step one;
selecting an inductance threshold value, intersecting the inductance threshold value with an unsaturated area at the top of the phase inductor to obtain an estimated pulse and a special rotor position point, and calculating the rotating speed of the motor by using the time between the falling edges of two adjacent estimated pulses;
and step four, integrating the calculated motor rotating speed to obtain a rotor position angle, and correcting the calculated angle by using a special rotor position point, so that a real-time position angle of the rotor is obtained, and the position-sensor-free control of the motor is realized.
Fig. 2 is a schematic diagram of the flux linkage and inductance calculation, and in order to improve the continuity of the inductance calculation, the controller executes the inductance calculation program once every 50 μ s. The following describes the phase inductance calculation steps in detail with reference to the inductance calculation flowchart of fig. 3, specifically as follows:
the phase voltage equation obtained according to the basic law of the circuit is as follows:
wherein, U is the voltage at two ends of the winding; r is phase winding resistance; i is the phase winding current; psi is the flux linkage.
The winding flux linkage expression is therefore:
the flux linkage psi is related to the current and rotor position angle and can be expressed as:
ψ(i,θ)＝L(θ，i)·i
where L (θ, i) is the phase inductance.
In a digital controller, the flux linkage of each phase winding can be represented in the form of digital integral as follows:
ψ(n+1)＝ψ(n)+[U(n)-Ri(n)]T
where ψ (n +1) and ψ (n) are flux linkage values calculated in the n +1 th and nth calculation periods, respectively, u (n) and i (n) are phase voltage and phase current values sampled in the nth calculation period, respectively, R is a winding resistance value, and T is a flux linkage calculation period, that is, a controller interruption period.
namely, it is
And calculating to obtain the phase inductance, and if the current is reduced to be below a current threshold value, namely the current is small, setting the inductance to be zero.
And 4, exiting the interrupt program and waiting for the next interrupt to come.
In this embodiment, after the phase inductance is calculated, the position sensorless control of the motor is realized by using an inductance top threshold value method.
The method comprises the steps of obtaining estimated pulses and special rotor position points by selecting an inductance threshold value and intersecting the inductance threshold value with an unsaturated region at the top of a phase inductance, and then calculating the rotating speed of a motor by using the time between the falling edges of two adjacent estimated pulses;
and setting the time T between the falling edges of two adjacent estimated pulses, and calculating the motor rotating speed according to the following formula:
wherein N is the motor speed.
And then, integrating the calculated motor rotating speed to obtain a rotor position angle, and correcting the calculated angle by using a special rotor position point, so that a real-time position angle of the rotor is obtained, and the position-sensor-free control of the motor is realized.
The method for calculating the real-time rotor position angle comprises the following steps:
and calculating a real-time rotor position angle according to the following formula by utilizing the motor rotating speed and the special rotor position point:
wherein, theta (n +1) and theta (n) are respectively calculated in the n +1 th and the first calculation periodObtaining the rotor position angle t0For angle calculation period, θ0In order to estimate the rotor position corresponding to the falling time of the pulse, i.e. the rotor special position point, S is the time corresponding to the falling edge of the estimated pulse, and when S is equal to 1, the level change of the estimated pulse generates the falling edge.
Fig. 4 is a schematic diagram of calculated waveforms of inductance at different currents. Wherein, 1 is the current waveform under the condition that the current chopping limit is higher during heavy load, 2 is the current waveform under the condition that the current chopping limit is lower during light load, 3 is the unsaturated inductance waveform calculated under the condition of light load, and 4 is the saturated inductance waveform calculated under the condition of heavy load. It can be seen that when the load is increased, the current of the conducting region is increased, the inductor enters a saturated state, the estimated value of the inductor shows a descending trend, and the inductor is obviously concave. When the phase is turned off, the current drops rapidly below the saturation current, and the saturation inductance also rises rapidly to the non-saturation inductance in the top region of the inductor. Therefore, when the inductor is saturated, the phase inductance is affected by the current and cannot accurately reflect the position information of the rotor.
To solve this problem, the present embodiment uses the top unsaturated region portion of the inductor to perform position estimation. Referring to fig. 5, a schematic diagram of inductance top valve position estimation is shown, where the switched reluctance machine phase inductance is related to both current and rotor position if the phase current reaches or exceeds the saturation current value. Otherwise, the current is irrelevant, and only the position angle is relevant; in this embodiment, the inductance threshold value is an angle corresponding to a time when the off-phase current continues to flow below the saturation current, and in a position interval between the angle of the stator and rotor alignment position, the inductance corresponding to a certain position (which may be a position other than the stator and rotor alignment position point) is selected as the threshold value. In the figure, 5 is the unsaturated inductance, 6 is the saturated inductance, 7 is the on-phase off position, 8 is the inductance top threshold, and 9 is the corresponding time between the two estimated pulse falling edges. When the conduction is disconnected, the current rapidly drops below the current saturation limit, and the saturated inductor 6 also rapidly rises to the unsaturated inductor 5, so that when the phase inductance rises to the unsaturated inductor, the inductance threshold is selected to intersect with the unsaturated inductor in the region to obtain an estimated pulse. Using the time 9 between the falling edges of adjacent estimated pulsesThe motor speed and the rotor position angle can be calculated, and then the special position point theta is obtained by estimating the pulse falling edge moment0And correcting the position of the rotor to finally obtain real-time rotor position information, thereby realizing the control of the switched reluctance motor without a position sensor. In order to reduce the current follow current interval and avoid generating large negative torque, the turn-off angle should be advanced as much as possible.
According to the position-sensorless control method based on the inductance top valve value method, the estimation pulse is obtained by utilizing the inductance top unsaturated region and the preset inductance threshold value, so that the motor rotating speed and the real-time rotor position are calculated, and the method is suitable for high-speed operation in the motor. The whole control process can realize the control without the position sensor only by detecting the phase current and the phase voltage, and has low hardware requirement and simple realization. Meanwhile, the unsaturated inductor is calculated by utilizing the current follow current stage in the algorithm, so that the influence of saturation of the conductive inductor is avoided, and the heavy-load operation of the motor can be realized.
The technical solutions of the present invention are not limited to the above embodiments, and all technical solutions obtained by using equivalent substitution modes fall within the scope of the present invention.
Claims (4)
1. A method for controlling the high-speed operation of a switched reluctance motor without a position sensor is characterized by comprising the following steps:
step one, sampling the magnitude of three-phase current and phase voltage in real time, and calculating a flux linkage value in a phase current existing interval by using a flux linkage integral method; setting a current threshold value in the process of calculating the flux linkage of the winding by a flux linkage integral method, and clearing the flux linkage value obtained by integral when the conducting phase is switched off and the current is less than the threshold value;
step two, obtaining phase inductance by utilizing the flux linkage value calculated in the step one;
the step of calculating the phase inductance is:
step 2.1, when the phase current is smaller than the current threshold value ITHWhen the phase inductance value is zero;
step 2.2, when the phase current is larger than the threshold value, calculating the phase inductance value according to the following formula,
wherein, L is an inductance calculated value, psi is a winding flux linkage calculated in the step one, and i is a phase current;
selecting an inductance threshold value, intersecting the inductance threshold value with an unsaturated area at the top of the phase inductor to obtain an estimated pulse and a special rotor position point, and calculating the rotating speed of the motor by using the time between the falling edges of two adjacent estimated pulses;
the selection method of the inductance threshold value comprises the following steps:
selecting an inductance corresponding to a position as an inductance threshold value in an interval from a turn-off phase current to an angle corresponding to a moment when the turn-off phase current is below a saturation current to an angle corresponding to an alignment position of a stator and a rotor; when the conducting phase is turned off and the current flows below the saturation current, selecting a corresponding inductance threshold value;
integrating the calculated motor rotating speed to obtain a rotor position angle, and correcting the calculated angle by using a special rotor position point to obtain a real-time position angle of the rotor, so that the position-sensor-free control of the motor is realized;
the method for calculating the real-time rotor position angle comprises the following steps:
and calculating a real-time rotor position angle according to the following formula by utilizing the motor rotating speed and the special rotor position point:
wherein θ (n +1) and θ (n) are the rotor position angles calculated in the n +1 th and n-th calculation periods, respectively, t0For angle calculation period, θ0In order to estimate the rotor position corresponding to the falling time of the pulse, namely the rotor special position point, S is the time corresponding to the falling edge of the estimated pulse, when S is equal to 1, the level change of the estimated pulse generates the falling edge, and N is the motor rotating speed.
2. The method for controlling the sensorless high-speed operation of the switched reluctance motor according to claim 1, wherein the formula for calculating the winding flux linkage by the flux linkage integration method in the first step is as follows:
ψ(n+1)＝ψ(n)+[U(n)-Ri(n)]T
where ψ (n +1) and ψ (n) are flux linkage values calculated in the n +1 th and nth calculation periods, respectively, u (n) and i (n) are phase voltage and phase current values sampled in the nth calculation period, respectively, R is a winding resistance value, and T is a flux linkage calculation period.
3. The method for controlling the sensorless high-speed operation of the switched reluctance motor according to claim 2, wherein: the current threshold is 0.2A.
4. The method for controlling the sensorless high-speed operation of the switched reluctance motor according to claim 1, wherein the method for calculating the rotation speed of the motor in the third step comprises the following steps:
and (3) setting the time T between the falling edges of two adjacent estimated pulses, and calculating the motor rotating speed by the following formula:
wherein N is the motor speed.
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