KR100449911B1 - Method for controlling switching angle using self-tuning control of a switched reluctance motor - Google Patents

Abstract

The present invention provides a switching angle control method using self-tuning control of a switched reluctance motor for controlling the turn on / off angle in a self-tuning manner by using an encoder pulse and a phase current value in order to maximize the torque and efficiency of the switched reluctance motor. To provide.

To this end, the present invention fixes the turn-on angle of the converter and samples the output of the encoder pulses generated from the encoder of the switched reluctance motor for a predetermined time to compare the difference between the number of previously stored pulses and the current pulse number. A first adjustment step of adjusting the turn-off angle corresponding to the number of pulses according to the torque by a predetermined angle deviation, and adjusting the turn-off angle at which the maximum torque is generated for the switched reluctance motor. A second adjustment for adjusting the turn-on angle by a predetermined angle deviation so that a maximum speed is generated by comparing the difference between the maximum value of the previously stored phase current and the maximum value of the current phase current by receiving the phase current value from the converter. The first adjusting step and the second adjusting step to maximize the torque and efficiency of the switched reluctance motor. It is characterized in that it is made to repeat the system infinitely.

Description

Method for controlling switching angle using self-tuning control of a switched reluctance motor}

The present invention relates to a switching angle control method by self-tuning control of a switched reluctance motor, and more particularly, by applying a self-tuning method to obtain the maximum torque and efficiency of the switched reluctance motor, an optimum turn on / off angle It relates to a switching angle control method by self-tuning control of a switched reluctance motor for determining the.

Recently, according to the progress of commercialized research on Switched Reluctance Motor (SRM), it is widely applied as a driving device of various home appliances such as a washing machine, a refrigerator, an air conditioner, and various transportation machines.

The switched reluctance motor has no winding, commutator or permanent magnet in the rotor, and has a lower manufacturing cost than a general-purpose induction motor due to its mechanical structure, and the power switching elements of each phase are connected in series with each of the phase windings so that a short circuit of the switching elements is prevented. It is not generated and the circuit configuration of the converter for driving the motor is simpler than that of a general induction motor or brushless motor, and the high torque characteristics require load torque proportional to the square or cubic of the motor rotation speed. There is an advantage that can be met.

On the other hand, such a switched reluctance motor is difficult to be applied to devices in the precision field because of the effects of voltage ripple, negative torque, and magnetic saturation in driving related equipment. Efforts are being made actively.

That is, FIG. 1 is a diagram showing a circuit configuration of a general switched reluctance motor, and the switched reluctance motor shown in the drawing exemplarily shows four-phase 8/6 poles.

As shown in FIG. 1, the switched reluctance motor is manufactured in a multi-phase, and includes a stator 2 wound around a phase winding 4 in each phase, and a phase winding wire wound around each phase of the stator 2. Rotor 6, which is rotated by receiving magnetic force generated according to the phase of current from 4), performs switching to turn on / off current applied to phase winding 4 according to a predetermined input pulse signal. Switching elements TR1 and TR2, and diodes D1 and D2 for protecting each of the switching elements TR1 and TR2 from the counter electromotive force generated from the phase winding line 4, respectively.

The drive circuit of the switched reluctance motor having such a configuration controls the phase with respect to the current of the phase winding 4 wound on each phase of the stator 2 by switching the switching elements TR1 and TR2 to rotate the rotor 6. ) Can be rotated forward or reverse.

The switched reluctance motor is a magnetic structure having a double salient pole, which maximizes the use of the reluctance torque. The torque is based on the principle that the inductance of the excitation winding is generated in the maximum direction. To generate this torque, the magnetic structure must be designed so that the inductance of the stator's winding wire changes with the position of the rotor.

In general, the torque of the motor is derived from the energy coefficient Coenergy due to the nonlinearity of the magnetic circuit. The switched reluctance motor ignores the mutual inductance between phases because there is little crosslinking flux with other phases in its structure. Accordingly, the magnetic energy coefficient W _c for inducing torque of the motor is as shown in Equation 1 below.

Here, i represents the current of the phase winding, and L represents the inductance.

On the other hand, the torque T for each phase of the motor stator 2 is a partial derivative of the energy coefficient with respect to the position angle θ of the rotor 6, as shown in Equation 2 below.

At this time, when the energy coefficient W _c of Equation 1 is substituted into the torque equation of Equation 2, the torque T is summarized as in Equation 3 below.

That is, as shown in Equation 3, it can be seen that the generated torque of the switched reluctance motor is proportional to the square of the phase current and is proportional to the slope of the inductance with respect to the position angle, so that the torque is proportional to the square of the current. Thus, torque can be generated regardless of the direction of the phase current, and positive torque or negative torque is generated according to the rate of change of inductance.

Next, FIG. 2 is a waveform diagram showing torque characteristics of the switched reluctance motor shown in FIG.

2A shows an inductance profile for each phase of the switched reluctance motor according to the position angle θ, in which the inductance is increased in the period θ _{s to} θ ₁ , and the decrease interval θ ₂ to the θ ₃ ) and constant intervals θ _{1 to} θ ₂ and θ _{3 to} θ ₀ .

On the other hand, as shown in FIG. 2B, when a constant excitation current flows through the upper winding line of the motor rotor, as shown in FIG. 2C, the constant torque occurs in the increase range θ _{s to} θ ₁ , while the decrease period of the inductance is shown. At (θ _{2 to} θ ₃ ), negative torque having the same magnitude as the positive torque is generated.

Therefore, if the excitation current is constantly applied to the switched reluctance motor, the positive torque and the negative torque cancel each other, and the axial torque of the motor becomes zero, so that the desired rotational torque cannot be obtained. It is necessary to accurately detect the position of the rotor and to perform the switching excitation according to the position of the rotor in order to prevent the damage and to obtain an effective rotational torque.

That is, FIG. 3 is a waveform diagram exemplarily illustrating a state in which a torque characteristic is improved by a change in current shape by switching angle control of a switched reluctance motor.

3A to 3E show a four-phase switching excitation method that generates an ideal axial torque by flowing a switching excitation current according to the rotor angular position of a four-phase 8 / 6-pole switched reluctance motor. .

At this time, the output torque generated in the shaft of the switched reluctance motor is generated as the sum of the torques generated by the excitation current of each phase, as shown in Figure 3f, such output torque (T _out ) of the four-phase As shown in Equation 4.

On the other hand, the waveform of the output torque as shown in Figure 3f is obtained by the ideal phase current, the shape of the phase current is determined by the non-linear inductance profile in the actual switched reluctance motor, it is compared with Figures 3b to 3e It is difficult to form the same ideal phase current, and therefore, in a switched reluctance motor, a large pulsation component is contained in the torque as compared with other general motors.

As described above, the switched reluctance motor is a continuous transient wave in the form of a pulse in which the current applied to the upper winding of the rotor is subjected to operating conditions such as rotation speed, applied voltage, turn-on / off angle, and load torque. Accordingly, the waveform of the current is variously changed, so the pulse current shape has a greater effect on efficiency than other motors in general.

In particular, it is known that the control of the switching angle according to the position of the rotor in the operating condition of the switched reluctance motor has a great influence on the efficiency of the motor, and the turn-on / off angle is adjusted to improve the efficiency of the motor. There is an active research to form a proper current waveform.

However, in the conventional switched reluctance motor, when the turn-off is performed later than the proper turn-off angle in the operating characteristics according to the turn-on / off-angle adjustment, a ripple current is generated in the reduction region of the inductance. While negative torque is generated, the total torque is reduced, while if the turn-off time is too fast, sufficient static torque cannot be obtained.

As a result, the negative torque can be reduced by moving the turn-off angle forward regardless of the turn-on angle, but the positive torque is reduced by moving the turn-off angle too forward. Similarly, if the turn-off angle is fixed and the turn-on angle is adjusted, there is little change in efficiency until the rated torque, but there is little current ripple when it is turned on later to increase the torque of the motor. Only can not maintain the maximum torque.

In addition, when the turn-on time is fast, current ripple occurs in the inductance reduction region, thereby generating reverse torque. Accordingly, the total torque is reduced to reduce the efficiency of the motor.

Recently, after obtaining the inductance value of the motor using a simulation tool such as MAXWELL or FLUX, a method of using a ROM table by calculating an appropriate turn-on / off angle through a program such as SIMULINK has been developed. However, this method not only takes a long time to obtain a desired turn-on / off angle, but also requires a separate simulation tool, and applies a value for a change in the operating state of the motor as a predetermined parameter value during the simulation process. Therefore, it is difficult to calculate accurate data.

Accordingly, the present invention has been made to solve the above-mentioned conventional problems, and an object thereof is to turn-on / off angles in a self-tuning manner by using encoder pulses and phase current values in order to maximize torque and efficiency of a switched reluctance motor. It is to provide a switching angle control method by self-tuning control of a switched reluctance motor for controlling.

1 is a view showing a circuit configuration of a general switched reluctance motor,

2 is a waveform diagram showing torque characteristics of the switched reluctance motor shown in FIG. 1;

3 is a waveform diagram exemplarily illustrating a state in which torque characteristics are improved by a change in current shape by switching angle control of a switched reluctance motor;

Figure 4 is a graph showing the shape of the phase current according to the turn-on / off angle adjustment of the switched reluctance motor to which the present invention is applied,

5A to 5C are waveform diagrams exemplarily illustrating shapes of phase currents and torques formed by switching in the case of performing excitation for actual switching in a switched reluctance motor to which the present invention is applied;

FIG. 6 is a graph showing an example of fixing a turn-off angle and adjusting a turn-on angle with respect to a speed change and a load change of a switched reluctance motor; FIG.

7 is a graph illustrating an example of adjusting a turn-on angle while maintaining a constant dwell angle with respect to speed variation and load variation of a switched reluctance motor.

8A through 8C are graphs exemplarily illustrating shapes of instantaneous torque that change according to an adjustment timing of a turn-off angle when the turn-on angle of a switched reluctance motor is fixed.

9A to 9C are graphs illustrating the shape of the instantaneous torque that changes according to the adjustment time of the turn-on angle after the appropriate turn-off angle is determined in the switched reluctance motor.

10 is a view showing the configuration of a switching angle control device of a switched reluctance motor to which the control method of the present invention is applied;

11 is a view showing a configuration of a drive circuit of a switched reluctance motor to which the present invention is applied;

12 is a flowchart for explaining an operation of a switching angle control method by self-tuning control of a switched reluctance motor according to the present invention;

13A and 13B show waveform states of current and voltage measured when a switched reluctance motor is generally operated at a fixed turn-on / off angle;

FIG. 14 is a view showing a waveform state of a speed generated when a switched reluctance motor is operated at a fixed turn-on / off angle as shown in FIGS. 13A and 13B;

15A and 15B show waveform states of current and voltage measured when a switched reluctance motor is generally operated at a fixed turn-on angle;

FIG. 16 is a view showing a waveform state of a speed generated when a switched reluctance motor is operated at a fixed turn-on angle as shown in FIGS. 15A and 15B;

17A and 17B are diagrams illustrating waveform states of currents and voltages measured in a steady state when a switched reluctance motor is operated by receiving an encoder pulse and controlling a turn-on / off angle;

FIG. 18 is a view illustrating a waveform state of a velocity generated when an encoder pulse is fed back to control a turn-on / off angle as in FIGS. 17A and 17B;

19A and 19B illustrate current and voltage measured in a steady state of a switched reluctance motor by performing an optimum turn-on / off angle control using feedback control and phase current of an encoder pulse according to a preferred embodiment of the present invention. Drawing showing the waveform state of

20A and 19B are diagrams illustrating waveform states of speeds generated when a switched reluctance motor is operated by turn-on / off angle control according to the present invention.

<Description of the symbols for the main parts of the drawings>

10: rectifier, 12: converter,

14: switched reluctance motor (SRM), 16: load,

18: encoder, 20: microcontroller,

T1-T8: switching element, D1-D8: diode.

According to the present invention to achieve the above object, by fixing the turn-on angle of the converter and sampling the output of the encoder pulse generated from the encoder of the switched reluctance motor for a predetermined time and the number of previously stored pulses and the current pulse number A first adjustment step of adjusting the turn-off angle corresponding to the number of pulses according to the maximum torque by a predetermined angle deviation by comparing the difference of the two and the turn-off of generating the maximum torque for the switched reluctance motor. When the off angle is adjusted, the turn-on angle is set by a predetermined angle deviation to receive the phase current value from the converter and compare the difference between the maximum value of the previously stored phase current and the maximum value of the current phase current. A second adjustment step of adjusting and subtracting, and maximizing the torque and efficiency of the switched reluctance motor. Provided is a switching angle control method by self-tuning control of a switched reluctance motor, characterized in that the first adjustment step and the second adjustment step are repeated indefinitely.

Hereinafter, the present invention configured as described above will be described in detail with reference to the accompanying drawings.

That is, Figure 4 is a graph showing the shape of the phase current according to the turn-on / off angle adjustment of the switched reluctance motor to which the present invention is applied.

As shown in FIG. 4, in a switched reluctance motor, the current current of a motor having a square wave pulse is classified into three shapes of A, B, and C waveforms by the turn-on / off angle of phase current. .

Turns have a margin of as much as in the figure, the rotor position in order to establish a sufficient current to generate a torque angle (θ _min) prior to the advance (Advance) the angle _{θ AD (= θ min -θ max} ) - a on- do. In addition, the current established according to the advance angle has three shapes such that the current decreases, is constant, or increases in the torque generation section after the rotor position angle θ _min .

On the other hand, in order to formulate the relationship between the shape of the phase current and the operating conditions, it is necessary to set a voltage equation for the motor phase winding circuit, the voltage equation is as shown in Equation 5 below.

Where I is the phase current, r is the resistance of the winding, ω is the rotational angular velocity, L is the inductance, and θ is the position angle of the rotor.

The voltage equation in Equation 5 is the first differential equation of the phase current i with respect to the rotor position angle θ, and the phase current and the operation are divided by the current establishment section and the torque generation section at the rotor position angle. Derivation of the relationship with the condition is as follows.

Here, the phase current in the current establishment section is assumed to be zero because the resistance is small and can be ignored by referring to Equation 5, and the inductance value is constant at L _min in the current establishment section (θ _on θ _max ). DL / dθ = 0. Therefore, the voltage equation in this section is as shown in Equation 6 below.

Therefore, the solution of the phase current according to the position angle [theta] of the rotor is expressed by the following equation (7).

That is, the current value established at the rotor position angle θ _min in FIG. 4 is determined by the magnitude of the advance angle θ _AD when the voltage and speed are constant.

Also, for the phase current in the torque generation section, if the inductance increases linearly with linearity when the position angle of the rotor is θ _min <θ <θ _off , the inductance is a function of the angle θ as shown in Equation 8 below. Can be set as

Here, K _L means the slope of the inductance.

On the other hand, if the functional equation of Equation (8) is differentiated with respect to the position angle (θ), then dL (θ) / dθ = K _L , and the voltage equation is the current (Eq. It is summarized by the first derivative of i).

If Equation 9 is rearranged with respect to di (θ) / dθ, it is expressed as Equation 10 below.

In the above Equation 10, the molecule of the right term determines the sign of the current slope with respect to the angle, and when the molecular term is defined as the slope of the inductance K _i , it can be expressed as Equation 11 below.

Here, the slope K _i of the inductance is a reference for determining the shape of the phase current with respect to three current waveforms A, B, and C in FIG. 4. That is, in the torque generation section, the shape of the phase current may be determined by operating conditions such as the applied voltage E, the rotation speed ω, the inductance slope K _L , and the instantaneous current i.

On the other hand, after the current is established, such as the current waveform of B in the current shape as shown in Figure 4, the current waveform that is constantly maintained in the torque generation period is called a flat-top current, As shown in Equation 11, when K _i is zero and the initial value of I is equal to I _f in the torque generation period, the applied voltage is as shown in Equation 12 below.

In Equation 12, the rated current has the same value as the voltage E applied to the motor and the velocity electromotive force (ωK _L i) generated from the motor. The torque generated in the shaft has a small ripple and high efficiency.

Meanwhile, the initial constant current I _f at the position angle θK _min is directly proportional to the advance angle θ _AD as shown in Equation 13 to Equation 13 below.

On the other hand, to compare and analyze the efficiency characteristics between the rated current and other currents, the effectiveness of the current waveforms of A, B, and C in the torque generation section under the assumption that the torque and speed are constant regardless of the linear condition and the phase current type. Assuming that the values are the same as I _T , the loss and input and output can be analyzed as follows.

First, since the excitation current flows in the current establishment section and no torque is generated, the relationship between the respective losses (P _{loss_A} , Pl _{oss_B} and P _{loss_C} ) for the current waveforms of A, B, and C in this section is _expressed by Equation 14 below. Will appear as

P _{loss_A} > Pl _{oss_B} > P _{loss_C}

Here, it is assumed that the effective value of each current is the same as I _T in the torque generation section, and K _L for each current is the same under linear conditions. Therefore, Equation 3 can be summarized as in Equation 15 below.

In fact, the current waveforms of A and B can be viewed linearly because there is little effect of saturation since the current decreases or remains constant as the overlap angle of the rotor poles increases. However, in the current waveform of C, since the superposition angle of the rotor increases and the current increases, the saturation of the magnetic circuit is increased. Therefore, since the slope of the equivalent inductance K _L becomes small in the current waveform of C, the generated torque has a relationship as shown in Equation 16 below when the generated torques are T _A , T _B and T _C.

T _A = T _B > T _C

Here, the driving conditions have no change in speed and torque, and when the input power in the torque generation section is P, the effective value of each current and the applied voltage are the same, so that they have the same input power. And when each efficiency is (eta) _a , (eta) _b, and (eta) _c , an efficiency is given by following formula (17).

In general, the reduction in torque generated by saturation depends on the degree of saturation and is designed to adequately saturate the magnetic circuit at rated load. Therefore, the current waveform of C, which is highly affected by saturation, will have the lowest efficiency, and the loss in the current establishment section has very small resistance, which has little effect on efficiency. The efficiency of the current waveform of B is higher than that of the current waveform. The resulting efficiency relationship is summarized as in Equation 18 below.

That is, it can be proved that, among the current shapes in FIG. 4, the flat current waveform, like the current waveform of B, has the highest efficiency compared to other currents. However, the above conclusion is a limiting case that can only occur when there is no change in torque value when operating at a constant speed, and is actually turned on / off after applying a constant power to a dedicated inverter of a switched reluctance motor. When the angle is changed, it can be seen that the operating speed increases and the average torque increases. After all, when the turn-on angle is advanced in the current waveform state of B, the effect of the efficiency generated by the variation of speed and torque is greater than the effect of efficiency due to the loss due to the winding resistance. Assuming that the speed and the average torque increase significantly, the efficiency relationship shown in Equation 19 is established.

As described above, the phase current of the switched reluctance motor should be switched to be close to the shape of the ideal rated current so that the pulsation of the torque can be reduced as much as possible.

Therefore, in turn-on and turn-off switching of the switched reluctance motor, inductance increases when turning on at a position angle θ _min or an inductance rising interval θ _{min to} θ _max (see FIG. 4). Due to the insufficient establishment of the current, in order to establish a sufficient current for torque, it is necessary to turn on in the minimum inductance period θ _{0 to} θ _min before the interval.

In addition, in order to extinguish the current, since the extinguishing time of the current actually exists when the turn-off is performed, it must be turned off with a certain extinguishing time before the negative torque region θ _{2 to} θ ₃ .

Next, FIGS. 5A to 5C are waveform diagrams exemplarily illustrating shapes of phase currents and torques formed by switching in the case of exciting an actual switching for a switched reluctance motor to which the present invention is applied.

As shown in FIG. 5, according to the operating characteristics of each switching section of the switched reluctance motor, turn-on is performed in this section to establish a phase current sufficient to generate torque in the minimum inductance section θ _{0 to} θ _min . In the magnetization section θ _on- θ _min , the angle is a section for applying magnetization to the windings and this angle is referred to as the advance angle Θ _AD . In this section, the waveform of the phase current changes according to the rotational speed of the motor, the applied voltage, the winding resistance and the advance angle, and the turn-on is always preferably performed at θ _on before θ _min .

In addition, in the inductance rising section θ _min θ _max , the rotor and stator poles start to overlap at the position angle θ _min where the minimum inductance section ends, and the value of the inductance increases from the position angle. At θ _max , the maximum value L _max is obtained.

On the other hand, assuming that the motor rotates at a constant angular velocity (ω), ignoring the magnetic nonlinearity is as shown in Equation 5, where multiplying the phase current (i) by both ends of Equation 6 is the following equation Equation 20 is shown.

Here, when the switched reluctance motor is operated, part of Ei is converted into mechanical output, and part of the rest is accumulated as magnetic energy. However, when turned off in this section, some of the magnetic energy is returned to the mechanical output and some to the power source.

In addition, θ _{on to} θ _off are the sections in which the switch of the inverter is turned on. This angle is referred to as the dwell angle Θ _dw , and θ _{min to} θ _off are the effective generation periods of the torque. It is the generation period of torque and defines this angle as torque angle (Θ _TQ ).

In addition, θ _max θ θ ₂ is a section in which inductance is kept constant as L _{max, and} is a section in which torque does not occur, and corresponds to a dead zone, which is due to the difference between the width of the stator pole and the rotor pole. Occurs. On the other hand, in the inductance reduction section θ _{2 to} θ ₃ , which is the next section, this section is set to suppress negative torque.

In θ _{2 to} θ ₃ , the inductance decreases linearly to L _min . This section generates negative torque and demagnetizes it. When current flows in this section, Mechanical energy due to torque is returned to the power source. That is, the section performs a regeneration operation and is also used as braking torque. This is one of the most important features of a switched reluctance motor that allows quadrant operation with instantaneous switching of the circuit.

Currently, the constant control of the dwell angle and the constant control of the torque angle are common in the method of controlling the switching on angle and the switching off angle according to the load. In order to reduce the pulsating torque, it is necessary to adjust the magnitude of the peak current in the section where the torque is generated. If possible, it should be suppressed.

In order to suppress the fluctuation of the current, it is possible to calculate the firing angle without fluctuation in the magnitude of the current in the torque generating section. Since the inductance value in Equation 7 is constant at the minimum L _min , dL / dθ = 0 and the resistance It is small and can be ignored, and the voltage equation can be summarized as in Equation 21 below.

Therefore, the solution of the phase current according to the position angle θ of the rotor is expressed by the following equation (22).

That is, the established current value is determined by the magnitude of the advance angle θ _AD when the voltage and speed are constant, and controlling the advance angle Θ _AD according to the variable load detects the load current and provides a simple feedback circuit. It becomes possible by configuring. This is a method of establishing a constant current at all times by setting an advance angle Θ _AD proportional thereto as the load torque increases and the required load current increases.

Meanwhile, in the method of determining the turn-on / off angle, when the input voltage is fixed in the converter of the switched reluctance motor, the torque of the motor is controlled by the turn-on / off angle of the phase switch. Alternatively, the method of determining the turn-off angle may be divided into two methods of FIGS. 6 and 7, that is, constant control of the dwell angle and constant control of the torque angle.

6 is a graph illustrating an example of fixing a turn-off angle and adjusting a turn-on angle with respect to speed variation and load variation of a switched reluctance motor.

6 is a method of fixing the turn-off angle, which fixes the turn-off angle and adjusts the turn-on angle for a variable speed or load variation. The efficiency is small until the rated output, but if the turn-on angle is greatly moved forward to increase the motor torque, current flows even in the inductance reduction area, resulting in negative torque, thereby reducing the efficiency.

7 is a graph illustrating an example of adjusting a turn-on angle while maintaining a constant dwell angle with respect to speed variation and load variation of a switched reluctance motor.

7 is a method of controlling a constant dwell angle, and adjusts the turn-on angle while keeping the dwell angle θ _dw constant for a variable speed or load variation. Therefore, even if the speed is increased or the load is increased, if the turn-on angle is moved forward to maintain a constant speed, the influence of the negative torque is not large, but the drive is unstable at the time of overload because the limit of the rated output is large.

Therefore, it is necessary to turn off at an appropriate point other than the turn-off angle determined by the fixed dwell angle control method or the fixed turn-off angle method with respect to the position of the turn-on angle and the phase current. It is very difficult to maintain high efficiency and maximum torque by setting the turn-off angle as the initial value when the turn-on angle changes due to load variation.

On the other hand, when the turn-off angle is fixed while the turn-on angle is fixed, when the turn-off angle is near the maximum value of the inductance profile, a large negative torque occurs because the current also flows in the inductance reduction region. Torque decreases.

As the turn-off angle moves forward, the current flowing in the inductance reduction region gradually decreases, and the generation of negative torque gradually decreases, increasing the total torque. However, when the dwell angle (θ _dw ) is further reduced beyond the turn-off angle where the highest torque appears, the total torque decreases. In this region, torque pulsation occurs and the efficiency decreases drastically. As a limit for overload appears. When the turn-on angles are different, the turn-off angle at which the maximum torque appears does not maintain a constant dwell angle.

8A through 8C are graphs exemplarily illustrating shapes of instantaneous torques that change according to an adjustment timing of the turn-off angle when the turn-on angle of the switched reluctance motor is fixed.

According to FIG. 8A, the instantaneous torque shown when turning off at a time earlier than the turn-off angle at which the maximum torque occurs is shown, and since the torque is not generated, the efficiency is high while the torque is not large. Unstable to load fluctuations.

On the other hand, FIG. 8B shows the instantaneous torque that appears when turning off near the highest point of the inductance profile. The positive torque is large while the negative torque is generated largely so that the total torque is reduced.

Figure 8c shows the instantaneous torque that appears when the turn-off at the appropriate turn-off time to generate the maximum torque when the turn-on angle time is fixed, the minute torque is generated but the positive torque is large, so the total torque Is the maximum value.

Next, FIGS. 9A to 9C are graphs exemplarily illustrating shapes of instantaneous torques that change according to adjustment timings of turn-on angles after an appropriate turn-off angle is determined in a switched reluctance motor.

In FIG. 9A, the instantaneous torque that appears when the turn-on is performed after the turn-on angle at which the maximum torque is generated is shown. This is a high torque generation efficiency while the torque is not large, and thus is unstable to the load fluctuation.

On the other hand, Figure 9b shows the instantaneous torque that appears when the turn-on at a point ahead of the turn-on angle at which the maximum torque occurs, which is very large while the negative torque is generated so that the total torque is It can only decrease.

FIG. 9C shows a time when the proper turn-on for generating the maximum torque is made and the appropriate turn-off angle is found accordingly, and the torque is generated larger than when only the turn-off angle is controlled. It is slightly larger than it is, but the total torque is maximum.

10 is a view showing the configuration of a switching angle control device of a switched reluctance motor to which the control method of the present invention is applied.

As shown in FIG. 10, the switching angle control device of the switched reluctance motor to which the method of the present invention is applied includes a rectifier 10, a converter 12, a switched reluctance motor 14, a load 16, an encoder. 18 and the microcontroller 20.

In the same figure, the rectifier 10 converts AC power applied from the outside into DC power and supplies the same to the converter 12.

The converter 12 turns the current applied to the rotor side winding of the switched reluctance motor 14 by converting the DC power from the rectifier 10 into alternating current under the control of the microcontroller 20. -The motor is driven by performing on / off switching control.

As illustrated in FIG. 11, the converter 12 includes a plurality of switching elements T1 to T8 connected to respective phase windings A, B, C, and D of the switched reluctance motor 14, respectively. And a plurality of diodes D1 to D8.

The plurality of switching elements T1 to T8 are made of a field effect transistor such as a MOSFET capable of fast chopping at 400V and 10A, and the plurality of diodes D1 to D8 are fast recovery diodes of 600V and 16A. Diode).

The encoder 18 is a position sensor for detecting the position of the rotor of the switched reluctance motor 14 to generate an encoder pulse, which is an absolute position encoder, an incremental encoder, Any of optical couplers may be applied.

The microcontroller 20 determines and controls the optimum turn-on / off angle by a self-tuning method when the load 16 changes or when the motor speed is changed. _applied to the encoder pulse from the encoder 18 and the switched reluctance motor 14 from the converter 12 in the state of performing turn-on / off at the point of _on ) and the turn-off angle Θ _off . The maximum torque and the maximum speed are generated by adjusting the turn-on angle and the turn-off angle, respectively, by applying the phase current value.

Here, the microcontroller 20 first fixes the turn-on angle and determines the turn-off angle. The microcontroller 20 determines the number of encoder pulses during the sampling time and the value previously stored in the internal memory. Comparing the results, the turn-off angle is increased or decreased by ΔΘ respectively by the self-tuning method to obtain the maximum torque.

In addition, when the optimum turn-off angle is determined by continuously repeating the turn-off angle of the turn-off angle, the microcontroller 20 sets the maximum value of the phase current at an initial set turn-on angle to a current value and a previously stored value. Compare and compare the turn-on angle by advancing the turn-on angle and self-tuning the turn-off angle by increasing or decreasing the turn-on angle by ΔΘ to get the maximum speed.

On the other hand, since the turn-on angle and turn-off angle are dependent on each other, the above-described routine is repeated several times to determine an appropriate turn-on / off angle.

Next, the operation of the present invention made as described above will be described in detail with reference to the flowchart of FIG.

First, in the embodiment of the present invention initially set the turn-on / off of each respective set to Θ _on, Θ _off, and the appropriate turn-off angle (Θ _off) the initial value of the four-phase switched reluctance maximum inductance profile in the motor of the Assuming a position of 30 °, 10 ° smaller than this is set as the initial turn-off angle and the turn-on angle is set to 0 ° (step S10).

In this state, the microcontroller 20 may call T (n) the number of pulses obtained from the current sampling time of the encoder pulses received from the encoder 18, and the number of pulses immediately before is called T (n-1). When the difference value is obtained, the difference value Dif (n) is represented by Equation 23 (step S11).

Dif (n) = T (n)-T (n-1)

Next, the microcontroller 20 calculates a difference between the current difference value Dif (n) and the previous difference value Dif (n-1) (step S12).

In this state, the microcontroller 20 determines whether the current maximum speed H_Speed is smaller than the current encoding pulse number T (n), and the current maximum speed H_Speed is the current encoding. If it is determined that the number of pulses is smaller than the number of pulses T (n) (YES in step S13), the number of encoding pulses T (n) equal to the current maximum speed H_Speed is stored (step S14).

However, if it is determined in the microprocessor 20 that the current maximum speed H_Speed is not smaller than the current encoding pulse number T (n) according to the determination result of step S13, the encoding pulse according to the current speed value is determined. The number T (n) is compared with the maximum speed value thus far and stored as a compare variable (step S15).

Then, the microcontroller 20 sets the number of encoding pulses T (n) according to the previous speed value and the number of encoding pulses T (n-1) according to the current speed value to be the same. Then, the speed difference value Dif (n-1) and the current speed difference value Dif (n) are set to be the same (step S16).

On the other hand, the microprocessor 20 is a result value (Delta) according to a comparison result between the previous speed difference value Dif (n-1) calculated in the step S12 and the current speed difference value Dif (n). Is determined to be smaller than the variable k, and if it is determined not to be small, the process returns to step S10 and repeats the process from step S10 to step S16. However, the variable k corresponds to the speed tolerance limit.

However, if it is determined that the result value Delta is smaller than an arbitrary variable k according to the determination result of step S17, it is determined whether the difference value Dif (n) exists within a given allowable limit value m. It judges (step S18).

If it is determined that the difference value Dif (n) exists within a given allowable threshold value m, that is, m <Dif (n) || When Dif (n) <-m, the microprocessor 20 determines the optimum turn-off angle Θ _op as the current time is the turn-off angle at which the maximum torque is formed, and the current turn-off angle. The loop is repeated to move the equation turn-off angle Θ _off forward by an angle deviation ΔΘ as shown in 24 below (step S19).

Further, when the microprocessor 20 determines that the difference value Dif (n) is Dif (m) <-m in the left region based on the turn-off angle (YES in step S20), the current turn By repeating the loop at the off angle, the turn-off angle Θ _off is reduced by the angle deviation ΔΘ as shown in Equation 25 (step S21).

That is, if the speed is constant, the turn-off angle Θ _off does not change, but the turn-off angle Θ _off for the variable turn-on angle that changes when a load is applied or when the input speed changes. The self-tuning method automatically determines the optimal turn-off angle to operate.

As noted above, the appropriate turn-off angle Θ_opAfter you find, set the turn-on angle by 1 step (0.5 °)_on Since the microcontroller 20 is advanced at 0 °, the microcontroller 20 sets a random variable whose comparison value, which is the difference between the maximum number of past pulses H_speed and the current number of sampled pulses T (n) ( If it is determined to be greater than k), that is, if Compare <= 0, the loop is repeated at the current turn-on angle, and the turn-on angle (Θ)_on)of The angle deviation is shifted by -ΔΘ (step S23).

Meanwhile, the microcontroller 20 determines that a comparison value between the phase current value N_Ad converted in the current processor AD channel and the phase current value O_Ad converted in the AD channel of the previous processor is greater than a predetermined variable x. (YES in step S24), the process proceeds to step S23, and the loop is repeated at the turn-on angle of the present time, as shown in Equation 26 below._on)of It will move by the angle deviation (-ΔΘ).

However, when the microcontroller 20 determines that the comparison value of the converted phase current value N_Ad in the current processor AD channel and the converted phase current value O_Ad in the AD channel of the previous processor is greater than any other predetermined variable y, In other words, when Compare <-m, the turn-on angle (Θ) is repeated by repeating the turn-on angle through a loop at the present time._on)of The angle deviation is shifted by + ΔΘ (step S26).

However, according to the result of the determination of step S25, the microcontroller 20 may select another random comparison value of the converted phase current value N_Ad in the current processor AD channel and the converted phase current value O_Ad in the AD channel of the previous processor. If it is determined that it is not larger than the variable y, the operation of the motor is normally performed by determining the turn-off angle Θ _off and the turn- _on angle Θ _on at the appropriate turn-on / off angle Θ _op . (Step S27).

As a result, since the turn-off angle and turn-on angle are mutually dependent, Θ _off and Θ _on hardly change when the speed is constant, such as when changing the turn-off angle. The turn-on angle is changed by one step as usual, and then the appropriate turn-off angle is found again. The above method is repeatedly repeated in software to find the optimum turn-on / off angle by itself.

On the other hand, when the speed is constant, that is, Θ _off and Θ _on are almost unchanged in the normal state, but when the load is applied or the input power is changed, when the input speed is changed, it is reset according to the changing situation. The turn-off angle and turn-on angle are automatically determined by the self-tuning method in order to determine the optimum turn-on / off angle.

13A and 13B show waveform states of currents and voltages measured when a switched reluctance motor is generally operated at a fixed turn-on / off angle, and FIG. 14 is fixed as shown in FIGS. 13A and 13B. The figure shows the waveform state of the speed generated when the switched reluctance motor is operated at the turned-on / off angle. The speed measured at the steady state is about 470 rpm.

15A and 15B illustrate waveforms of current and voltage measured when a switched reluctance motor is operated at a fixed turn-on angle, and FIG. 16 is fixed as shown in FIGS. 15A and 15B. This is a diagram showing the waveform state of the speed generated when the switched reluctance motor is operated at the turn-on angle.The speed measured at the steady state is about 576 (rpm), and the algorithm is the default setting.The turn-on angle is 0. The turn-off angle was set to 10 ° and the self-tuning method was used to find the appropriate turn-off angle.

17A and 17B are diagrams illustrating waveform states of current and voltage measured in a normal state when a switched reluctance motor is operated by receiving an encoder pulse and controlling a turn-on / off angle, and FIG. 18 illustrates FIG. 17A. And FIG. 17B is a diagram illustrating a waveform state of a velocity generated when an encoder pulse is fed back to control a turn-on / off angle.

In the figure, the initial operating condition is to control the turn-on / off angle by self-tuning, leaving the turn-on / off angle obtained by constant input power, load, and open-loop control as the initial value. It became.

Here, the voltage waveform shown in FIG. 17A is a turn-on / off angle shake, and the voltage waveform is distorted due to the influence of EMF, and in FIG. 18, a slight waveform slumps in a steady state. In the high-speed operation state, it can be seen that there are some limits in controlling two control target turn-on / off angles with an encoder pulse which is one control element.

19A and 19B are then measured in the steady state of a switched reluctance motor by performing optimum turn-on / off angle control using feedback control of the encoder pulse and phase current in accordance with a preferred embodiment of the present invention. 20A and 19B are diagrams illustrating waveform states of current and voltage, and FIG. 20 illustrates waveform states of speeds generated when a switched reluctance motor is operated by turn-on / off angle control according to the present invention as shown in FIGS. 19A and 19B. The figure shown.

In the figure, the initial operating conditions are set to self-tuning with encoder pulses and phase current, leaving the turn-on / off angle obtained by constant input power and load and open-loop control as initial values. -On / off angle was controlled.

In the figure, it can be seen from the voltage waveform that the influence of the EMF is significantly reduced compared to the conventional method using only the encoder pulse, and it can be seen that the speed trend is reduced and the speed is greatly improved in the steady state.

As a result, in case of controlling with encoder pulse and phase current value, the negative torque due to EMF effect is reduced, and the average torque is greatly improved. As the speed is increased through the fixed input power, the efficiency can be improved simultaneously. .

It is a matter of course that the present invention having the above-described embodiments can be variously modified and implemented without departing from the technical spirit of the present invention without departing from the embodiments.

As described above, according to the present invention, by using the encoder pulse and the phase current generated from the encoder of the switched reluctance motor to find the optimal turn-on / off angle to operate the motor, the basic set by the conventional self-tuning It is possible to remove the limitation to obtain the maximum torque in the speed, to significantly reduce the unstable operation and the transient state of the speed ratio, which are the limit points in the method using only the encoder pulse, and to enable precise control. This has the effect that the response speed can be increased.

In addition, the use of separate simulation equipment eliminates the hassle of turning-on / off angles that can produce the maximum torque, and the production line of the factory that does not require severe load fluctuations or rapid response. As well as steel mills, it is effective to be widely applied to various home appliances.

Claims (1)

The number of pulses according to the maximum torque by fixing the turn-on angle of the converter and sampling the output of the encoder pulses from the encoder of the switched reluctance motor for a certain time and comparing the difference between the number of previously stored pulses and the current pulses. A first adjusting step of adjusting the turn-off angles corresponding to each other by a predetermined angle deviation; When the turn-off angle of the maximum torque is generated for the switched reluctance motor, the phase current value from the converter is input to compare the difference between the maximum value of the previously stored phase current and the maximum value of the current phase current. And a second adjustment step of adjusting the turn-on angle by a predetermined angle deviation so as to generate a maximum speed. And a self-tuning control method of the switched reluctance motor, characterized in that the first adjustment step and the second adjustment step are repeated indefinitely in order to maximize the torque and efficiency of the switched reluctance motor.