RU2297091C2 - Inductor motor control process - Google Patents

Abstract

FIELD: electrical engineering.

SUBSTANCE: proposed process is used to control inductor motors including traction motors having toothed stator and rotor by maintaining motor torque equal to actual value at each of m intervals. For generating motor currents voltage pulse supply interval is determined, divided into short intervals, desired phase current is evaluated for each interval n and brought to this value by feeding voltage pulses of definite length.

EFFECT: reduced pulsation of inductor motor torque.

1 cl, 3 dwg

Description

The invention relates to methods for controlling induction motors, including traction, having a gear stator and a rotor.

There is a known method of controlling an induction motor ("current corridor"), which consists in the fact that within each period of the rotor position sensor, voltage pulses are fed to the phase winding of the motor so that the current does not go beyond the "current corridor", i.e. was approximately constant (see Electric locomotive construction: collection of scientific papers by the All-Russian Research and Design Institute of Electric Locomotive OJSC (VELNII OJSC). - 2000. - T.42 - 324 pp. on p.186 and Electrical Engineering magazine No. 6/98, pp. 25-26, Fig. 2c and 4b).

в большом диапазоне при постоянном токе предопределяет большие пульсации момента на валу двигателя, что ведет к преждевременному износу приводного механизма и двигателя, а при использовании индукторного двигателя в качестве тягового провоцирует еще и боксование.Change

in a large range at constant current, it determines large pulsations of the torque on the motor shaft, which leads to premature wear of the drive mechanism and motor, and when using the induction motor as a traction motor, it also provokes boxing.

The closest in technical essence is the method of controlling the induction motor, which consists in generating currents in the motor, for which the periods of the rotor position sensor are measured, inside each period of the rotor position sensor, at least one voltage pulse is fed to the phase winding of the motor, and the time interval is determined applying voltage pulses, divide it into m equal intervals of Δt, the corresponding angle of rotation of the rotor ΔΘ, at the beginning of each of which is introduced the phase current i _n-1 corresponds to yuschee top n-th interval of m, determine the magnitude of the phase current i _n by the formula

where M ₃ (Θ _n ) is the set value of the moment on the n-th interval;

L (Θ _n , i _n-1 ) is the inductance value at the end of the n-th interval at current i _n-1 ;

L (Θ _n-1 , i _n-1 ) is the inductance value at the end of the (n-1) th interval at current i _n-1 ;

i _n-1 - phase current value at the end of the (n-1) -th interval,

moreover, if at the beginning of the nth interval the phase current is greater than the value of i _n , then a voltage pulse is not formed. (See the description of the invention to the patent of the Russian Federation RU 2229194 C2, class 7 Н02Р 8/18, publ. 05.20.2004 Bull. No. 14).

This method has the following disadvantage. If at the beginning of the n-th interval, if the phase current exceeds the value of i _n , the voltage pulse is not generated, then the current value at the end of the n-th interval may turn out to be less than i _n and the change in electromagnetic energy does not correspond to maintaining a given motor moment. Therefore, the average value of the moment in the interval ΔΘ may not correspond to the specified one, which determines the ripple of the engine moment.

The objective of the invention is to reduce the ripple of the torque of the induction motor by maintaining the motor torque equal to the specified at each of m intervals.

The problem is solved by the method of controlling the induction motor, in which the period of the rotor position sensor signal is measured, the time interval for the supply of control pulses inside the rotor position sensor signal is determined, and it is divided into m equal intervals Δt corresponding to the angle of rotation of the rotor in Θ. At the beginning of each of these intervals, enter the value of the phase current i _n-1 corresponding to the beginning of the current n-th interval from m, determine the magnitude of the phase current i _n according to the formula

where M ₃ (Θ _n ) is the set value of the moment on the n-th interval;

L (Θ _n , i _n-1 ) is the inductance value at the end of the n-th interval at current i _n-1 ;

L (Θ _n-1 , i _n-1 ) is the inductance value at the end of the (n-1) th interval at current i _n-1 ;

i _n-1 - phase current value at the end of the (n-1) -th interval,

when the value i _n exceeds the phase current value, a voltage pulse u forms from the beginning of the current n-th interval until the phase current reaches the value i _n . If the phase current exceeds the value of i _n at the beginning of the nth half-period, the time τ elapses from the beginning of the nth interval until the phase current reaches the value of i _n and after a while

Where

r is the active resistance of the phase winding;

L (Θ _n , i _n ) is the value of the inductance at the end of the n-th interval at a current i _n , a constant voltage u is applied to the phase winding.

This ensures that the current reaches the required value at the end of the nth interval, which ensures the change in electromagnetic energy necessary to maintain a constant torque equal to the specified moment on the nth interval.

Figure 1 shows a device for implementing the method; figure 2 - algorithm of the device; figure 3 is a timing chart explaining the determination of the time of voltage supply to the phase winding.

The method is carried out by a microprocessor system, consisting of a block of timers 1, processor 2, random access memory (RAM) 3, read-only memory (ROM) 4, analog-to-digital converter (ADC) 5, driver block 6, transistor block 7, which controls the induction motor 8, with rotor position sensors (DPR) 9. Inputs-outputs of processor 2, RAM 3, ROM 4, inputs of timer block 1, driver block 6 and ADC 5 output are connected by address-data bus 10. The outputs of timer block 1 and DPR 9 are connected with bus interrupt process 2. The current i pa motor 8 is input to the ADC 5. The outputs of the transistor unit 7, energized with DC voltage u, loaded on the inductor winding motor 8.

The processor, RAM, ROM, timer unit, ADC can be integrated into a specialized controller, for example M167-1C (see the product catalog "On-board industrial electronics" JSC "Kaskod", 105037, Moscow, Izmailovskaya pl., 7).

The method is implemented in accordance with the algorithm in figure 2.

The algorithm consists of 4 subprograms that are triggered by interrupt signals from the DPR 9 and the timer block 1 - t ₁ , t ₂ , t _m .

The first subroutine starts at the DPR signal. Enter the code value from the timer T corresponding to the period of the DPR signal (block 11) and start the timer T again (block 12). Then determine the time interval [t ₁ , t ₂ ] (block 13) and start the timers t ₁ and t ₂ in the block of timers 1 (block 14). In block 15, the number of intervals m is determined by multiplying the time interval [t ₁ , t ₂ ] by the value of the maximum allowable switching frequency of the transistors of the transistor block 7. Then, in block 16, the interval Δt of the repetition of determining the required current value i _n and the corresponding rotor angle Δ are determined. The subprogram ends by entering the set value of the moment M ₃ (block 17).

The second subroutine begins upon the arrival of the timer signal t ₁ , which is started in the first subroutine.

In this subroutine, the timer m of the repetition interval is started (block 18) and the value of the unit of repetition interval number is assigned to the number of the repetition interval (block 19).

The timer m periodically generates interrupt signals, according to which the third subroutine is executed, in which the necessary values of the motor current are determined at each calculation repeat interval. For this, in block 20 enter the current value corresponding to the beginning of the interval. Then, in block 21, the inductance values are updated to calculate the desired current value in this interval, which is determined in block 22 in accordance with the formula

where M ₃ (Θ _n ) is the set value of the moment on the n-th interval;

L (Θ _n , i _n-1 ) is the inductance value at the end of the n-th interval at current i _n-1 ;

L (Θ _n-1 , i _n-1 ) is the inductance value at the end of the (n-1) th interval at current i _n-1 ;

i _n-1 - phase current value at the end of the (n-1) -th interval.

In block 23, the calculated value of the current i _n , which must be reached in this interval, is compared with the value of current i _n-1 at the beginning of this interval and, if it is larger, turn on (transistor 24) transistors of the transistor block 7, and when the phase current reaches the value i _n (blocks 25, 26), the transistors of the transistor block 7 are turned off (block 27), removing the voltage u from the phase winding. If the required current value at the end of the interval i _{n is} less than the current value i _n-1 at the beginning of the interval, then the transistors of the transistor block 7 are turned off (block 29), the time is counted (from the beginning of the n-th interval until the phase current reaches i _n (blocks 30 ... 33), then determine the time (block 34)

and after this time (block 35), voltage u is supplied to the phase winding, including transistors (block 36) of transistor block 7. In block 28, the value of the interval number is increased by one, which corresponds to the next interval for repeating the calculations.

The supply of control pulses is stopped by the fourth subroutine with the arrival of an interrupt signal from timer t ₂ , while resetting all the timers (block 37) and turn off the transistor side 7 (block 38).

The proposed method allows, if the current exceeds its required value at the end of the interval, to achieve the necessary value at the end of the interval, providing such a change in electromagnetic energy that implements the maintenance of a given moment of the induction motor, reducing its ripple.

Figure 3 explains the receipt of the formula (1). Curve i ₁ describes the change in the phase current of the induction motor in the absence of voltage on the phase winding. The current decreases exponentially through points with coordinates

(t _n-1 , i _n-1 ) - corresponds to the beginning of the n-th interval;

- соответствует уменьшению тока до величины i_n.

- corresponds to a decrease in current to i _n .

Replacing the exponential of a line passing through two points, we have

Curve i ₁ describes the change in phase current after applying a voltage pulse of amplitude u. The current increases exponentially through points with coordinates

(t ₀ , 0) - corresponds to the intersection of the exponential time axis;

(t _n , i _n ) - corresponds to the end of the n-th interval.

Replacing the exponential line passing through these two points, we have

If voltage u is applied at time t, then until the end of the n-th interval, the current exponentially i ₂ reaches the value i _n , which will provide the necessary value of the moment of the induction motor M ₃ .

To determine the time t of the voltage supply, we equate the currents i ₁ and i ₂

Marking

we have

The time from reaching a falling value of exponentially i ₁ current value i _n to supply voltage u

where Δt = t _n -t _n-1 is the time interval for the supply of voltage pulses.

We determine the time t ₀ . Current i _{2 is} described by the exponent

, соответствующей концу n-го интервала при токе i_n.with time constant

corresponding to the end of the nth interval at current i _n .

For a point with coordinates (t _n , i _n )

from here

Then, given t _n -t ₀ = -k,

and

and the time from the current reaching the value of i _n before applying voltage u

The study of this control method on the same bench where the prototype was tested, showed a decrease in ripple moment of the induction motor, but compared with the prototype by 30% in the zone of nominal and high speeds.

Claims (1)

The method of controlling the induction motor, which consists in generating currents in the motor, for which the periods of the signal of the position sensor of the rotor of the motor are measured, at least one voltage pulse is applied to the phase winding of the motor inside each period of the rotor position sensor, the time interval of the voltage pulse supply is determined, and the voltage is divided it to m equal intervals Δt, corresponding to the rotation angle of the rotor ΔΘ, at the beginning of each of which is introduced the phase current i _n-1 corresponding to the beginning of the current n-th interval of m, op edelyayut phase current value i _n by the formula

where M ₃ (Θ _n ) is the set value of the moment on the n-th interval; L (Θ _n , i _n-1 ) is the inductance value at the end of the n-th interval at current i _n-1 ; L (Θ _n , i _n-1 ) is the value of the inductance at the end of the (n-1) th interval at current i _n-1 ; i _n-1 - phase current value at the end of the (n-1) -th interval, when exceeding the value i _n the magnitude of the phase current formed U voltage pulse from the beginning of the n-th slot until it reaches the phase current values i _n, characterized in that in excess at the beginning of n-th half cycle phase current values i _n count time τ, the elapsed from the beginning of the nth interval until the phase current reaches the value i _n and after a while

Where

r is the active resistance of the phase winding; L (Θ _n , i _n ) is the value of the inductance at the end of the n-th interval at a current i _n , a constant voltage U is applied to the phase winding.

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