KR20200088549A - A Direct Torque Control Method of Switched Reluctance Motor - Google Patents

Abstract

The present invention relates to a direct torque control method of a switched reluctance motor (SRM) and, more particularly, to a direct torque control method of an SRM which reduces torque ripple and load loss (copper loss) by removing the negative phase torque, thereby increasing SRM efficiency. According to the direct torque control method of SRM according to an embodiment of the present invention, with first to third phases, a rotor rotates counterclockwise from the first phase to the second phase, from the second phase to the third phase, and from the third phase to the first phase, and interworks with an inverter. According to the rotor angle of the SRM, the inverter is controlled to increase the inductance of the first phase, decrease the inductance of the second phase, and start chopping of the first phase when the inductance of the third phase starts to decrease. In addition, the inverter is controlled to increase the inductance of the first phase, decrease the inductance of the third phase, and end the chopping of the first phase past the point in time when the inductance of the second phase starts to increase by inversion. In addition, the inverter is controlled to start commutation from the first phase to the second phase.

Description

SRM's Direct Torque Control Method of Switched Reluctance Motor

The present invention relates to a direct torque control method of the SRM, more specifically to eliminate the negative phase torque (negative phase torque) to reduce the torque ripple (torque ripple) and load loss (copper loss) to improve the SRM efficiency It relates to a direct torque control method of SRM.

A switched reluctance motor (hereinafter referred to as SRM) is a motor in which a switching control device is combined, and both a stator and a rotor have a protruding structure.

In particular, the winding is wound only on the stator part, and there is no type of winding or permanent magnet on the rotor part, so the structure is simple.

Due to these structural features, it has a considerable advantage in terms of production and production, has good starting characteristics, such as a DC motor, and has high torque, but requires little maintenance and repair, and torque and efficiency per unit volume. And since it has excellent characteristics in many parts such as the rating of the converter, the field of use is gradually increasing.

On the other hand, direct torque control (DTC) is a high performance torque control method capable of generating a constant output torque that is widely adopted in AC motors.

However, in the conventional direct torque control (DTC), the torque output of the SRM is maintained by supplementation of positive and negative phase torque, and the DTC has a problem of causing a higher load loss.

In addition, the conventional DTC has a problem of lower efficiency than full load.

Korean Registered Patent Publication No. 10-17181188, title of the invention "4 phase 8/6 SRM for driving low voltage fan" (Registration date 2017.03.14.)

The present invention was created to solve the above-mentioned problems, and thus eliminates negative phase torque, thereby reducing torque ripple and load loss, so that the direct torque of SRM improves SRM efficiency. The purpose is to provide a control method.

In order to achieve the above object, the direct torque control method of the SRM according to an embodiment of the present invention has a first to third phase (rotor) from the first phase to the second phase, the second A method of controlling SRM interlocked with an inverter while rotating counterclockwise from a phase to a third phase and from the third phase to the first phase,

에 따라 상기 인버터는,Rotor angle of the SRM

Depending on the inverter,

The inductance of the first phase is increased, the inductance of the second phase is decreased, and the chopping of the first phase is controlled to start when the inductance of the third phase starts to decrease,

The inductance of the first phase is increased, the inductance of the third phase is reduced, and the first phase of the chopping is over after the point where the inductance of the second phase starts to increase by being inverted. It is controlled to start commutation from phase to the second phase.

According to the present invention, there is an advantage of having a competitive torque control response and low current consumption.

In addition, there is an advantage of reducing torque ripple and load loss (copper loss).

In addition, there is an advantage that the negative phase torque is eliminated.

In addition, there is an advantage that the reference flux can be adjusted based on different load conditions.

In addition, there is an advantage that efficiency and current consumption are improved over full load conditions.

1 is a diagram showing a three-phase asymmetric half-bridge converter circuit.
2 is a view showing a possible driving circuit of the half-bridge converter.
3 is a diagram showing a sector and voltage vector of direct torque control (DTC).
4 is a diagram showing an available voltage vector of a three-phase half-bridge converter.
5 is a diagram illustrating a switching table of direct torque control (DTC).
6 is a diagram illustrating a schematic diagram of a direct torque control (DTC) of a conventional SRM.
7 is a view showing an inductance sector.
8 is a diagram illustrating a negative phase torque generating mechanism.
9 is a view showing a sector definition (sector definition) proposed in the present invention.
10 is a diagram showing a switching table of phase A and phase B related sectors.
11 is a diagram showing a switching table of phase B and phase C related sectors.
12 is a diagram showing a switching table of phase C and phase A related sectors.
13 is a diagram showing voltage vectors of phase A and phase B related sectors.
14 is a diagram showing voltage vectors of phase B and phase C related sectors.
15 is a diagram showing voltage vectors of phase C and phase A related sectors.
16 is a diagram showing a schematic diagram of a direct torque control (DTC) proposed by the present invention.
17 is a diagram illustratively showing a waveform proposed by the present invention.

First, prior to describing the present invention in detail, the present invention is not intended to be limited to specific embodiments, and should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

When an element is said to be "connected" or "connected" to another component, it is understood that other components may be directly connected to or connected to the other component, but there may be other components in between. It should be. On the other hand, when a component is said to be "directly connected" or "directly connected" to another component, it should be understood that no other component exists in the middle.

The terms used in this specification are only used to describe specific embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, the terms "include" or "have" are intended to indicate that there are features, numbers, steps, operations, components, parts or combinations thereof described in the specification, and one or more other features. It should be understood that the existence or addition possibilities of fields or numbers, steps, operations, components, parts or combinations thereof are not excluded in advance.

In addition, terms such as “…unit”, “…unit”, and “…module” described in the specification mean a unit that processes at least one function or operation, which may be implemented by hardware or software or a combination of hardware and software. Can.

In addition, the components of the embodiments described with reference to the drawings are not limited to those embodiments, and may be implemented to be included in other embodiments within the scope of maintaining the technical spirit of the present invention. Although the description is omitted, it is natural that a plurality of embodiments may be reimplemented as one integrated embodiment.

In addition, in the description with reference to the accompanying drawings, the same components are given the same or related reference numerals regardless of the reference numerals, and redundant descriptions thereof will be omitted. In the description of the present invention, when it is determined that the detailed description of the related known technology may unnecessarily obscure the subject matter of the present invention, the detailed description will be omitted.

In addition, in the drawing, there is a part in which the size ratio between elements is expressed somewhat differently, or there is a part in which sizes between parts that are combined with each other are expressed differently, but the difference in the expressions shown in the drawings is easy for those skilled in the field. Since it is understandable parts, a separate description is omitted.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Although the present invention has been described with reference to the embodiments shown in the drawings, it is described as one embodiment, whereby the technical spirit of the present invention and its core configuration and operation are not limited.

1 shows a three-phase asymmetric half-bridge converter circuit, FIG. 2 shows a possible drive circuit of the half-bridge converter, and FIG. 3 shows a sector and voltage vector of direct torque control (DTC). to be.

In addition, Figure 4 is a diagram showing the available voltage vector of the three-phase half-bridge converter, Figure 5 is a diagram showing a switching table of the direct torque control (DTC), Figure 6 is a direct torque control (DTC) of a conventional SRM It is a diagram showing a schematic diagram for.

In addition, FIG. 7 is a diagram showing an inductance sector, FIG. 8 is a diagram showing a negative phase torque generating mechanism, and FIG. 9 is a sector definition proposed in the present invention definition).

In addition, FIG. 10 is a diagram showing a switching table of phase A and phase B related sectors, FIG. 11 is a diagram showing a switching table of phase B and phase C related sectors, and FIG. 12 is a phase C and phase A related sector. It is a diagram showing a switching table.

Also, FIG. 13 is a diagram showing voltage vectors of phase A and phase B related sectors, FIG. 14 is a diagram showing voltage vectors of phase B and phase C related sectors, and FIG. 15 is phase C and phase A related sectors. It is a diagram showing a voltage vector of.

In addition, FIG. 16 is a diagram showing a schematic diagram of a direct torque control (DTC) proposed by the present invention, and FIG. 17 is a view showing a waveform proposed by the present invention by way of example.

The present invention is a modified torque control strategy, a three-phase switched reluctance motor (SRM) based on a Direct Torque Control (DTC) method to remove negative phase torque. ).

Also, the hysteresis DTC proposed in the present invention uses only one-phase conduction and two-phase conduction instead of using two-phase conduction and three-phase conduction.

The conventional method has a high rated current (rms current) to maintain a high torque response and low torque ripple, and a high peak positive phase torque to compensate for a negative phase torque. There was a problem requiring phase torque.

In the present invention, switching sectors, voltage vectors, and switching tables are all reconfigured in consideration of SRM inductance characteristics.

The method proposed in the present invention shows a competitive torque control response and low current consumption, and negative phase torque is eliminated.

In addition, the method proposed in the present invention can adjust the reference flux based on different load conditions, so that efficiency and current consumption are full load conditions. ).

In general, direct torque control (DTC) is a high-performance torque control method first developed for AC machines.

In recent decades, direct torque control (DTC) has been successfully applied to switched reluctance equipment (SRMs) with the efforts of numerous researchers.

The discussion made here according to one embodiment of the present invention is described based on a three-phase 6/4 SRM having a three-phase asymmetric half-bridge converter configuration shown in FIG. 1, but other configurations, namely, four-phase or five-phase, or The same may be applied to 8/6 and the like.

In the case of an asymmetric half-bridge converter, as shown in Fig. 2, there are three operation modes or stages: magnetization, freewheel, and demagnetization.

In conventional SRM-DTC, six voltage vectors are used to simultaneously control magnetic flux and torque, and they are evenly separated by 60° in space.

The space is equally divided into six sectors labeled S1, S2, S3, S4, S5, and S6 for one electrical period shown in FIG. 3.

In this whole space, the available voltage vectors that can be taken are listed in FIG. 4.

However, the selection depends on the flux error, torque error, and corresponding sector, and one voltage vector will be appropriately selected according to the switching table in FIG. 5.

Figure 6 shows the overall schematic diagram of a conventional DTC, the present invention is derived from the conventional DTC in some summary.

Compared to other control methods of SRM, the DTC method has several very different features.

(One). Similar to the DTC method of the AC motor, the conventional SRM-DTC controls the output angle by controlling the power angle or accelerating or decelerating the stator flux vector.

(2). For the same load torque, the power angle has a negative correlation with the reference flux. That is, an increase or decrease in the reference flux decreases or increases the power angle to maintain the same output torque. In addition, even if the reference flux is different, the same output torque can be generated.

(3). The power angle is a function of load torque and reference flux.

(4). The RMS current (rms current) is closely related to the reference flux, but not the load torque. This explanation is generally not true because other control methods require high current to achieve high torque. Since the copper loss is directly connected to the rms current, efficiency can be optimized by selecting the appropriate value of the reference flux.

(5). Increasing the RMS current does not necessarily increase the output torque, and other RMS currents may correspond to the same output torque.

(6). The maximum negative phase torque is related to the reference flux. When the reference flux increases, the negative phase torque must be increased to maintain the same torque and compensate with a high positive torque. Reducing the reference flux is an effective way to reduce the negative phase torque. However, it cannot be completely eliminated by applying only a low reference flux. This is one of the reasons why the conventional SRM-DTC is less efficient because the area for generating negative torque during DTC operation is relatively large.

(7). Since (4) uses a fixed reference flux in the entire load range, it can be seen that the current consumption at load and full load is almost the same. Only the power angle is changed to meet torque requirements. The load loss in light load condition is almost the same as the load loss in full load condition, indicating unnecessary loss. It is well known that in other control methods, the current must be low, so the load loss should be low under light load conditions.

In addition, the SRM operation depends on the switching operation of the converter. The phase is continuously excited when the corresponding power switch is turned on and off.

Because of these characteristics, SRM cannot generate a constant continuous torque, so it has a relatively torque ripple characteristic.

Torque ripple not only prevents smooth rotation in the SRM, but is also one of the main causes of vibration, so removal is desirable.

Also, it is difficult to control in the turn off phase or commutaion phase, and consequently it is not easy to determine how torque is allocated between phases.

In addition, direct torque control (DTC) is a high-performance torque control method capable of generating a constant output torque widely adopted in AC motors.

However, the torque output of SRM in DTC is maintained by the complement of positive and negative phase torque, and DTC compared to Direct Instantaneous Torque Control (DITC) and Torque Sharing Function method. Causes higher load loss.

In addition, conventional DTCs have lower efficiencies than full loads.

Therefore, in the present invention, direct torque control (DTC) is modified to eliminate negative phase torque and reduce load loss using a new sector, voltage vector, and switching table.

The generation of negative phase torque is a unique drawback of conventional DTCs due to improper segmentation of sectors and improper selection of voltage vectors.

The negative torque is what most control methods try to eliminate, such as when turning the turn off angle forward to avoid tail current reaching the negative inductance slope region. Since this is an undesirable situation, it is possible to properly divide the sectors and create an appropriate switching table to eliminate negative phase torque.

Further, in order to understand how a negative phase torque is generated, the inductance sector can be superimposed with a conventional DTC sector as shown in FIG. 7. The negative torque generation mechanism is shown in FIG. 8.

For example, consider the overlapping portion of sector S2 and sector L-11-1.

As shown in FIG. 8, phase A and C are generally turned off because the inductance profiles of phases A and C fall because they are facing phase B.

However, in sector S2, voltage vectors V6, V8, V20 and V22 are used to adjust torque and magnetic flux. Examining the phase component of each vector shows that vectors V20 and V22 turn on phase A and vector V6 tries to turn on phase C.

As a result, negative torques of phases A and C are generated. The same conclusion can also be made by observing different sector parts.

Due to this mechanism, negative phase torque could never be eliminated in conventional direct torque control (DTC). The solution to avoid this situation is to avoid using a vector that can generate a negative phase torque. Thanks to the construction of the asymmetric half-bridge converter, more vectors are available than the bridge converter.

Therefore, the sector proposed in the present invention is composed of a chopping sector and a two-phase sector (commutation sector and fast demagnetization sector) as shown in FIGS. 9 to 15.

That is, in a single phase sector such as A chopping, B chopping, and C chopping, only a single phase stimulus (one of A phase, B phase or C phase) is used to adjust torque.

For reference, when chopping is applied, for example, 0 to 5 V, the voltage applied to the gates of the switches Q1 and Q2 is not applied in series of 5 V, but is generally processed by dividing 0 to 5 V into small pieces. .

In addition, in the commutation sector, the principle of DTC is used to adjust torque and magnetic flux.

In addition, in fast demagnetization sectors, the outgoing phase is turned off and the excitation of the input phase is used to regulate the torque.

As illustrated in FIGS. 9 to 15, in one electrical period, a sector is divided into three for each group in all three groups, and the inductance in the entire group is always reduced. There is one phase (reverse torque phase).

As such, if the negative torque phase in each group is always off, the negative torque of the step can be avoided.

And it is achieved by defining a voltage vector in such a way that the negative torque phase component remains at zero.

10 to 12, selection of vectors or switching tables in one group is shown. The magnetic flux is controlled in a closed loop only in the commutation sector.

13 to 15 are diagrams illustrating voltage vectors according to phases to help understanding.

)에 따른 자속(Ψ), 토크(T), 전류(i)의 파형을 예시적으로 도시한 도면이다.In addition, FIG. 16 is a schematic diagram of a direct torque control (DTC) proposed by the present invention, and FIG. 17 is a rotor angle (

This is a diagram showing waveforms of magnetic flux (Ψ), torque (T), and current (i) according to ).

Therefore, in the direct torque control method of the SRM according to an embodiment of the present invention, the rotor has a first to third phase, and the rotor moves from the first phase to the second phase, and from the second phase to the third phase. , A method of controlling SRM interlocked with an inverter while rotating counterclockwise from the third phase to the first phase,

에 따라 상기 인버터는,Rotor angle of the SRM

Depending on the inverter,

The inductance of the first phase is increased, the inductance of the second phase is decreased, and the chopping of the first phase is controlled to start when the inductance of the third phase starts to decrease,

The inductance of the first phase is increased, the inductance of the third phase is reduced, and the first phase of the chopping is over after the point where the inductance of the second phase starts to increase by being inverted. Commutation is controlled to start from phase to the second phase,

After commutation starts from the first phase to the second phase, the inductance of the second phase is still increased, the inductance of the third phase is decreased, and the inductance of the first phase is reversed and reduced. It is controlled such that commutation from the first phase to the second phase ends and fast demagnetization of the first phase starts.

The inductance of the second phase is increased, the inductance of the third phase is decreased, and the fast demagnetization of the first phase is controlled to end at a time when the inductance of the first phase starts to decrease by inversion. .

The direct torque control method of the SRM according to an embodiment of the present invention can expect the following effects.

According to the present invention, there is an advantage of having a competitive torque control response and low current consumption.

In addition, there is an advantage of reducing torque ripple and load loss (copper loss).

In addition, there is an advantage that the negative phase torque is eliminated.

In addition, there is an advantage in that the reference flux can be adjusted based on different load conditions.

In addition, there is an advantage that efficiency and current consumption are improved over full load conditions.

The above description is merely illustrative of the technical idea of the present invention, and those of ordinary skill in the art to which the present invention pertains may make various modifications, changes, and substitutions without departing from the essential characteristics of the present invention. will be.

Therefore, the embodiments disclosed in the present invention and the accompanying drawings are not intended to limit the technical spirit of the present invention, but to explain the scope of the technical spirit of the present invention. .

The scope of protection of the present invention should be interpreted by the claims below, and all technical spirits within the scope equivalent thereto should be interpreted as being included in the scope of the present invention.

Claims (3)

The rotor having a first to third phase rotates counterclockwise from the first phase to the second phase, from the second phase to the third phase, and from the third phase to the first phase. In the direct torque control method of the SRM interlocked with the inverter,
Rotor angle of the SRM

Depending on the inverter,
The inductance of the first phase is increased, the inductance of the second phase is decreased, and the chopping of the first phase is controlled to start when the inductance of the third phase starts to decrease,
The inductance of the first phase is increased, the inductance of the third phase is decreased, and the first phase of chopping is over after a point in time when the inductance of the second phase starts to increase by being inverted. A method of controlling direct torque of an SRM, characterized in that commutation is controlled to start from a phase to the second phase. According to claim 1,
After commutation from the first phase to the second phase is started, the inductance of the second phase is still increased, the inductance of the third phase is decreased, and the inductance of the first phase is reversed to decrease. The direct torque control method of the SRM, characterized in that it is controlled such that commutation is ended from the first phase to the second phase and fast demagnetization of the first phase is started. According to claim 2,
The inductance of the second phase is increased, the inductance of the third phase is decreased, and the fast demagnetization of the first phase is controlled to end at a time when the inductance of the first phase starts to decrease by inversion. SRM direct torque control method characterized in that.

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