RU2118039C1 - Inductor motor control method - Google Patents

Abstract

FIELD: electrical engineering. SUBSTANCE: currents in motor phase windings are formed by supplying voltage pulses to winding within every period of pickup of motor rotor position. To this end, period between two adjacent leading edges of signal of motor rotor position pickup is measured. Time intervals t1 from moment leading edge of signal of motor rotor position pickup appears to beginning of passage and t2 from moment leading edge of signal of motor rotor position pickup develops to end of current period of signal of motor rotor position pickup are calculated during control cycle by formulas: t1 = T/2-A; 2 = T-A-C, where T is duration of past period of signal of motor rotor position pickup; A is advance, C is shortening which represents time intervals. A ≤ A_max = T/NC ≤ T/N1, where N and N1 are constant coefficients. Voltage pulses are formed without use of current pickups and assemblies associated with them. Motor rotation frequency is stabilized by means of adjustment of advance including stabilization by means of self- stabilization effect and without readjustment. EFFECT: enhanced control. 9 cl, 15 dwg

Description

 The invention relates to electrical engineering, and more specifically to methods of controlling induction-type motors having a gear stator, on which one or more phase windings are located, each of which is fed by unipolar current pulses from the frequency converter, and a gearless winding rotor.

 A known method of controlling a single-phase induction motor (see US patent N 4616165 from 10.10.1986).

This source claims an induction motor with a control system based on a microprocessor. This control system implements a method of controlling the induction motor, which consists in generating currents in the phase windings of the motor by applying voltage pulses to the winding inside each period of the rotor position sensor (DPR), and the time intervals T _a and T _b that determine the times of the beginning and end of the zone voltage supply, respectively, are set as a function of engine speed in a tabular manner. For this, the period of the DPR signal is measured and, based on the measurement results, an address signal of sampling the values of T _a and T _b from the read-only memory (ROM) is generated.

Inside the voltage supply zone, voltage pulses are generated using the signal of the phase current sensor by comparing it with the phase current setting signal I _m . When the phase current reaches the setpoint, a key closure signal is generated for the power frequency converter.

 The disadvantage of this method is the lack of control flexibility, consisting in the ability to configure such a system only for one or more pre-modeled motor operation modes, as well as the need to use a current sensor for each phase motor winding and signal processing devices.

 There is also a method of controlling an induction motor (see US Patent N 4707650 from 11/17/1987).

 This source claims a programmable closed-loop control system for an induction motor, which includes a feedback control loop (OS), an angle regulator and a current regulator based on a single-chip microcontroller. The control loop can be performed with the OS in terms of speed and / or engine torque. In the case of the OS, the speed of the engine is stabilized by speed.

In such a system, a control method is implemented, which consists in the formation of currents in the phase windings of the motor. The formation is as follows. The set value of the engine speed Wr ^{* is} compared with the actual value of the speed Wr calculated using the DPR signal. The signal about the mismatch between the set and actual frequencies is used in the phase current setpoint regulator. Here, the current setting is adjusted so as to stabilize the engine speed. The phase current setpoint signal I ^* is also used in the angle regulator, where it is used to calculate the angular value corresponding to the beginning of the voltage supply zone and the angular width of the voltage supply zone, and then, using the external counters / timers, current generation resolution pulses are generated having the above calculated angular values.

Inside the voltage supply zone, the phase current of the motor is generated in the current regulator by comparing the signal I ^* with the signal of the current sensor, and when the current exceeds the setpoint by a certain amount, one of the inverter switches off, providing a slow current drop, and when the current decreases below the setpoint by a certain amount, the key reopens. At the end of the zone, both IF switches are closed, providing a rapid decrease in current in the phase winding.

 The disadvantage of this method is the need to use current sensors for each phase winding of the motor and the current regulator, as well as the complexity of the calculations when stabilizing the engine speed and adjusting the angle.

 The invention is aimed at increasing the flexibility of controlling an induction motor, as well as simplifying both the hardware and software of the control systems of the induction motor.

For the method of controlling the induction motor, which consists in generating currents in the motor, for which the periods of the signal of the rotor position sensor are measured, at least one voltage pulse is supplied to the phase winding of the motor inside each period of the rotor position sensor, depending on the duration T of the previous period the rotor position sensor determines the time intervals t ₁ from the beginning of the current period of the rotor position sensor to the moment of voltage pulses and t ₂ from the beginning of the current sensor period the position of the rotor until the end of the voltage pulses, analytical formulas are proposed for calculating during the control cycle time intervals t ₁ and t ₂ , according to which the interval t ₁ is determined in accordance with the formula:
t ₁ = T / 2-A (1),
Where
A is the time interval, which is an advance of the moment of supply of the first voltage pulse relative to the time T / 2, and A is chosen such that
0 ≤ A ≤ A _max ,
Where
A _max = T / N (2),
Where
N is a constant coefficient selected within 4 ≤ N ≤ 10,
and the interval t ₂ is determined in accordance with the formula:
t ₂ = TAC (3),
Where
C is the time interval, which is a shortening of the voltage supply zone relative to the time interval T / 2, and C is chosen so that 0 ≤ C ≤ C _max ,
Where
C _max = T / N ₁ ,
Where
N ₁ - constant coefficient, selected within 12 ≤ N ₁ ≤ 30;
and at T <T ₀ - in accordance with the formula
t ₂ = XT - (X-1) T ₀ - A - C (4),
Where
T ₀ - the value of the period of the rotor position sensor, at which the limitation of the engine speed should begin; X is a constant positive coefficient, chosen the greater, the more stringent speed limitation is required.

- не изменяют, где e - максимально допустимая погрешность величины текущего периода датчика положения ротора;
- стабилизируют частоту вращения двигателя путем изменения в пределах от D_min до D_max вспомогательной величины D по результатам сравнения, которое производят один раз за период заданного значения периода датчика положения ротора T^* и текущего значения периода датчика положения ротора T_t, которое принимают равным измеренной длительности предыдущего периода T или вычисляют по результатам измерения нескольких последних периодов таким образом, что при T^* > T_t величину D увеличивают, при T^* < T_t - уменьшают, а при

- не изменяют, а затем величину A вычисляют по формуле:
A = D_max- D,
где
e - максимально допустимая погрешность величины текущего периода датчика положения ротора,
D_max = T/Y, D_min = D_max- A_max;
где
Y - постоянный положительный коэффициент, причем Y ≤ N.In the particular cases described below, the method may further be characterized by one or more of the following features:
- the value of C is proportional to the value of A;
- the position sensor of the rotor of the engine is set so that the front of its signal corresponding to the beginning of the period appears when the rotor tooth is located opposite the stator tooth for traction mode and opposite the stator groove for electromagnetic braking mode;
- in systems where the phase current is generated by the method of maintaining the current near the current setpoint, the value of A is taken to be A _max at the maximum setpoint of the phase current of the motor and reduced in proportion to the decrease of the setpoint;
- the duration of the first voltage pulse is so dependent on A that when A increases from 0 to A _{max, the} duration of the first voltage pulse increases from 0 to the width of the entire voltage supply zone equal to T / 2-C; the duration of the second voltage pulse, if any, is selected less and proportional to the duration of the first; the duration of the remaining voltage pulses, if any, is chosen equal to the duration of the second pulse or the duration of each subsequent voltage pulse after the second is reduced with respect to the duration of the previous one until a certain minimum value is reached, and the duration of the pauses between voltage pulses is chosen equal to each other;
- stabilize the engine speed by changing in the above range the value of A according to the results of the comparison, which is performed once per period, the set value of the period of the rotor position sensor T ^* and the current value of the period of the rotor position sensor T _t , which is taken equal to the measured duration of the previous period T or calculated from the results of measurements of the last several periods in such a way that:
at T ^* > T _{t, the} value of A is decreased, at T ^* <T _{t, it} is increased, and at

- do not change, where e is the maximum permissible error of the value of the current period of the rotor position sensor;
- stabilize the engine speed by changing in the range from D _min to D _max auxiliary value D according to the results of the comparison, which is performed once per period of the set value of the period of the rotor position sensor T ^* and the current value of the period of the rotor position sensor T _t , which is taken equal to the measured the duration of the previous period T or calculated from the results of measurements of the last several periods so that at T ^* > T _{t the} value of D is increased, at T ^* <T _{t it} is reduced, and at

- do not change, and then the value of A is calculated by the formula:
A = D _max - D,
Where
e is the maximum permissible error of the value of the current period of the rotor position sensor,
D _max = T / Y, D _min = D _max - A _max ;
Where
Y is a constant positive coefficient, with Y ≤ N.

 In FIG. 1 is a timing chart explaining formulas (1), (3) (a is the signal of the rotor position sensor; b is the key control signal of one phase of the power frequency converter (IF) supplying the motor; c is the current of the motor phase); in FIG. 2 - time diagrams explaining the formula (4) (a - signal of the rotor position sensor; b - key control signal of one phase of the power frequency converter (IF) supplying the motor); in FIG. 3 - time diagrams explaining the formation of voltage pulses inside the voltage supply zone (a - signal of the rotor position sensor; b - key control signal of one phase of the power frequency converter (FC) supplying the motor and the current of the motor phase at equal voltage pulses after the first; c - the same, but with decreasing voltage pulses in duration; g - the same, with the expansion of the first pulse to the duration of the entire voltage supply zone); in FIG. 4 is an example of the dependence of the duration of the first voltage pulse on the lead; in FIG. 5 is a timing chart explaining the process of stabilization of the rotational speed (a is the signal of the rotor position sensor; b, c is the key control signal of one phase of the power frequency converter (IF) supplying the motor, and the motor phase current at different lead values); in FIG. 6 - time diagrams explaining the effect of self-stabilization in the process of stabilization of the rotational speed (a, b - DPR signals, key management of one phase of a power frequency converter (IF) supplying the motor, and the motor phase current at a constant value of the complement and different instantaneous values of the rotational speed) .

 The proposed control method can be implemented using a microprocessor control system. The control program is designed in such a way that each edge of the DPR signal corresponding to the position of the tooth — the tooth of the stator and rotor of the motor — causes the reading of the contents of the counter — the meter of the duration of the DPR period, its zeroing, and a new start. The control timing diagrams in the current period of the DPR are formed according to the measurement results of the previous period, therefore, the DPR signal in the current period is shown in dashed lines in the drawings. The calculations are carried out at the beginning of the current period, free from the formation of control pulses.

After the time interval t ₁ calculated by formula (1) has elapsed, an open signal is generated for all the keys of the inverter phase (depending on the inverter circuit, one or two), the voltage of the power supply is applied to the motor phase and the current i begins to increase in it (see Fig. 1).

The time interval A means the lead time of the opening of the keys relative to the time T / 2 (which corresponds, for example, to the relative position of the tooth - the groove of the stator and rotor of the motor). For example, we take the time interval A constant. Since the DPR period decreases with increasing rotation frequency, the fraction of the value A in the period grows. In this case, the advance in angular expression is directly proportional to the rotational speed, which is required for controlling an induction motor. This mode can occur at low speeds, while A _max = T / N is greater than A.

With increasing speed decreases the period of the DPR T and, therefore, the time interval A _max , which in the angular expression (A _max [el. Gr.]) Is a constant, is selected from the limits of 90 el. column ≥ A _max [el. column ] ≥ 36 email gr., which correspond to values 4 ≤ N ≤ 10 (360/90 = 4, 360/36 = 10), and expresses the maximum allowable lead.

 Here email. column - electrical degree - an angular value equal to the geometric degree divided by the number of teeth of the rotor of the engine. In this case, the angular distance between the axes of the adjacent teeth of the rotor of the engine and, accordingly, the angular expression of the period of the DPR are 360 e. gr., and the expression of the electric degree in time is T / 360.

When, with a decrease in the DPR period (during acceleration of the engine), A _max becomes less than A, the angular advance value can no longer be increased, since this will lead to an increase in the negative component of the engine torque. From this moment and with a further increase in the speed, take A = A _max .

When changing engine operating modes, the value of A is changed in the range from 0 to A _max . So, when changing the motor current setpoint I _m in systems with phase current generation according to the current setpoint, it is recommended to change A in proportion to the setpoint, setting the maximum current setpoint to A _max . In systems where the phase current is generated by normalizing voltage pulses by the proposed method, it is recommended to change A as a control parameter when stabilizing the engine speed, as will be described below.

After the time t ₂ calculated by formula (2), a closing signal is generated for all the keys of the inverter phase (depending on the inverter circuit, one or two), the voltage of the inverse polarity power supply is applied to the phase winding of the motor through inverse diodes of the inverter and it starts quickly drop current to zero.

 Time C means the shortening of the angular width of the voltage supply zone relative to the value of T / 2 (180 electric gr. - half the period of the DPR), which occurs at a very low engine speed. In this case, analogous to leading, shortening in angular expression is directly proportional to the engine speed.

As an advance, shortening should be limited, the value of C _max [el. gr.] = 12 - 30 email. hail., which correspond to the values of N ₁ from 12 to 30.

The values of A and C are proposed to be taken proportional to each other, for example, in the ratio C = A / 3. The choice of the coefficient of proportionality should not contradict the maximum relations between each other C _max and A _max .

In systems requiring a limitation of engine rotation speed, the value of T _{2 is} calculated taking into account formula (4), which for X = 2 takes the following form:
t ₂ = 2T - T ₀ - A - C.

In this case, when the engine accelerates, when its rotation frequency reaches a value corresponding to the period of the TPR T ₀ , the accelerated collapse of the voltage supply zone to the right begins, as shown in FIG. 2. At the same time, the engine torque drops, the speed stops growing and stabilizes. The greater the coefficient X, the more “hard” the collapse. So, with X = 2, the voltage pulses would completely disappear with an increase in the engine speed by 1.5 times (if we neglect the values of A and C).

From time t ₁ to time t ₂ (inside the voltage supply zone), the phase current can be generated either by the traditional method of maintaining current near the set point using sensors and a current regulator or, for example, by the proposed method without using current sensors, without a current regulator, and auxiliary devices serving these nodes. The formation of currents is performed by force by applying voltage pulses of normalized duration to the phase winding of the motor, during which all the keys of this phase of the inverter are opened, which leads to an increase in the phase current. During pauses between pulses, at least one key of this phase of the inverter is closed, which leads to a decrease in the phase current.

The duration of the first voltage pulse I ₁ is dependent on the lead A and represents the time of the initial rise in phase current. In the general case, this dependence should be nonlinear, since the current in the phase does not increase linearly. In FIG. 4 shows an example of such a relationship. Here, the nonlinear curve is replaced by two straight line segments k ₁ and k ₂ .

When A = T / N, the duration I _{1 of the} first voltage pulse becomes equal to the width of the entire voltage supply zone equal to T / 2-C, and subsequent pulses are no longer formed (Figs. 3d and 4).

The durations of the remaining voltage pulses I ₂ , I ₃ ... are chosen the same, shorter, for example, 4 times the duration of the first voltage pulse I ₁ (Fig. 3b). The durations of pauses P between voltage pulses are also chosen equal to each other, sufficient to implement the frequency protection function of the inverter. The real envelope (I _m ) of the phase i current with this control method differs from the straight line, but in many cases it turns out to be acceptable.

To reduce engine noise, the duration of voltage pulses I ₃ ... following the second pulse is reduced from pulse to pulse until a certain minimum duration I _{min is} reached, as shown in FIG. 3c). In this case, a smooth decrease in the phase current to the end of the voltage supply zone is obtained.

 The motor torque is greater, the greater the amplitude of the phase current.

The duration I _{1 of the} first voltage pulse sets the rise time of the current, and therefore the value to which the current rises, i.e. its amplitude. This duration is unambiguously related to leading A. Since the torque of the motor is greater, the greater the amplitude of the phase current, it is possible to adjust the torque by changing A. Thus, this control method allows you to simply implement the function of stabilizing the engine speed by adjusting the lead.

 It should be noted that with the help of the proposed method, the length of the DPR period is stabilized, which is uniquely related to the engine speed, which allows us to talk about stabilization of the rotation frequency.

регулятор опережения не работает, так как находится в зоне нечувствительности. На фиг. 4 показан процесс уменьшения тока фазы i от огибающей (I_m1) до огибающей (I_m2) при уменьшении опережения от A₁ до A₂ (фиг. 5б, в) под действием регулятора опережения при превышении частотой вращения заданной величины.The lead is varied from 0 to A _max depending on the mismatch of a given T ^* and current T _{t the} duration of the signal period of the rotor position sensor of the motor. If the current value of the DPR period exceeds a predetermined one, then the lead time is increased once per period, and vice versa, until these values are compared with an accuracy of a predetermined value e - the maximum permissible error that determines the accuracy of maintaining the period. Thus, with

advance controller does not work, because it is in the dead zone. In FIG. Figure 4 shows the process of decreasing the phase i current from the envelope (I _m1 ) to the envelope (I _m2 ) when the lead is reduced from A ₁ to A ₂ (Fig. 5b, c) under the action of the lead controller when the speed exceeds a predetermined value.

Stabilization of the speed with the help of such a regulator becomes more effective when applying self-stabilization. To implement this effect, a parameter is introduced - "complement" D, which is taken as a control parameter instead of being advanced (see Fig. 6). If the current duration T _t of the DPR period exceeds a predetermined T ^* , the addition is reduced, and vice versa, until these values are equal to an accuracy of e. Addition vary from D _min to D _max , with D _max = T / Y, D _min = D _max - A _max . Here Y is a constant coefficient, with Y ≤ N, for example, Y = 4.

Then the value of A is calculated by the formula: A = D _max - D (5), and according to the result of the calculation, a current is generated in the above manner.

Self-stabilization works in all modes, but it is easier to explain this effect, assuming that the regulator is in the dead zone and, therefore, the addition does not change. As can be seen from FIG. 6 a, b, with a decrease in the duration of the DPR period from T ₁ to T ₂ , which corresponds to an increase in the rotational speed, and the value of the complement D remains constant, D _max decreases from D _max1 = T ₁ / Y to D _max2 = T ₂ / Y, this, according to (5), the lead is reduced from A ₁ to A ₂ , which leads to a decrease in the current i in the winding from the envelope (I _m1 ) to the envelope (I _m2 ) and, as a consequence, to a decrease in the rotation frequency.

As the current value of the DPR period T _t during stabilization of the rotation frequency, take the measured duration of the past period T, since the present period in which the current is formed is not yet over. To reduce the effect of overshoot during stabilization of the engine speed, it is proposed to take as this value the equivalent value of the DPR period, calculated from the measurement results of several recent periods and, therefore, containing a measure of the acceleration of the engine. For example, the formula is proposed: T _t = 2 • T - T ₀ l _d , where T and T ₀ l _d are the durations of the last and penultimate DPR periods, respectively.

 The lead value A obtained in such a regulator, according to (1), determines the moment of the beginning of the supply of voltage pulses to the phase winding of the induction motor. It also uniquely determines the duration of all voltage pulses inside the voltage supply zone according to the above method, and also determines the moment of the zone end, according to (3). Thus, the proposed method allows you to replace the angle regulator, current regulator and the control loop with OS speed for one simple regulator advancing or additions.

 The technical effect of the invention consists in the possibility of building on the basis of the proposed method of controlling induction motor control systems having ease of implementation, high flexibility and the ability to easily stabilize the engine speed. This effect is achieved through the use of simple formulas that allow you to calculate the main parameters of the control of the inductor motor within each period of the DPR, eliminate the need for compiling and programming tables, as well as by abandoning phase current sensors and, accordingly, all devices associated with them, and applying a simple algorithm for generating phase currents by normalizing voltage pulses.

Claims (9)

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 rotor position sensor are measured, at least one voltage pulse is applied to the phase winding of the motor inside each period of the rotor position sensor, depending on the duration T of the previous the period of the rotor position sensor determine the time intervals t1 from the beginning of the current period of the rotor position sensor to the moment of voltage pulses and t2 from the beginning of the current period of the polo sensor rotation of the rotor to the end of the voltage pulses, characterized in that the interval t1 is determined in accordance with the formula
t1 = T / 2 - A,
where A is the time interval representing an advance of the moment of supply of the first voltage pulse relative to the time T / 2, and A is chosen such that
0 ≤ A ≤ A _max ,
where A _max = T / N,
where N is a constant coefficient selected within 4 ≤ N ≤ 10,
and the interval t2 is determined in accordance with the formula
t2 = T - A - C,
where C is the time interval, which is a shortening of the voltage supply zone relative to the time interval T / 2, and C is chosen such that
0 ≤ C ≤ C _max ,
where C _max = T / N1,
where N1 is a constant coefficient selected within 12 ≤ N1 ≤ 30,
and at T <T ₀ - in accordance with the formula
t2 = XT - (X - 1) T ₀ - A - C,
where T ₀ is the value of the period of the rotor position sensor, at which the limitation of the engine speed should begin;
X is a constant positive coefficient, chosen the greater, the more stringent speed limitation is required.  2. The method according to claim 1, characterized in that the value of C is proportional to the value of A.  3. The method according to claim 1 or 2, characterized in that the rotor position sensor is set so that its signal front corresponding to the beginning of the period appears when the rotor tooth is located opposite the stator tooth for traction mode and opposite the stator groove for electromagnetic braking mode . 4. The method according to any one of claims 1 to 3, characterized in that the value of A is taken equal to A _max at the maximum setting of the phase current of the motor and is reduced in proportion to the decrease in the set point. 5. The method according to any one of claims 1 to 3, characterized in that the duration of the first voltage pulse is so dependent on A that, as A increases from 0 to A _{max, the} duration of the first voltage pulse increases from 0 to the width of the entire voltage supply zone, equal to T / 2 - C, the duration of the second voltage pulse, if any, is selected shorter and proportional to the duration of the first, the duration of the remaining voltage pulses, if any, is normalized, and the duration of the pauses between voltage pulses is chosen equal to each other.  6. The method according to claim 5, characterized in that the durations of the remaining voltage pulses are equal to the duration of the second pulse.  7. The method according to p. 5, characterized in that the duration of each subsequent voltage pulse after the second is reduced with respect to the duration of the previous one until a certain minimum value is reached. 8. The method according to claim 6 or 7, characterized in that they stabilize the engine speed by changing in the above range the value of A according to the results of the comparison, which is performed once per period, the set value of the period of the rotor position sensor T ^* and the current value of the position sensor period rotor Tt, which is taken to be equal to the measured duration of the previous period T or calculated from the results of measurements of the last several periods so that at T ^* > Tt the value of A is reduced, at T ^* <Tt it is increased, and at

- do not change, where e is the maximum permissible error of the value of the current period of the rotor position sensor. 9. The method according to p. 6 or 7, characterized in that they stabilize the engine speed by varying from D _min to D _{max the} auxiliary value D according to the results of the comparison, which is performed once per period, the set value of the period of the rotor position sensor T ^* and the current value of the rotor position transmitter period Tt, which is taken as equal to the measured duration of the preceding period T, or calculated from the measurement results of the last few periods, so that if T ^*> Tt value D is increased, when T ^* <Tt - reduce, and When

- do not change, and then the value of A is calculated by the formula
A = D _max - D,
where e is the maximum permissible error of the value of the current period of the rotor position sensor,
D _max = T / Y, D _min = D _max - A _max ,
where Y is a constant positive coefficient, with Y ≤ N.

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