KR20090099617A - Ditc of srm drive system using 4-level converter - Google Patents

Abstract

A DITC(Direct Instantaneous Torque Control) system of an SRM(Switched Reluctance Motor) is provided to improve dynamic characteristic and efficiency through excitation and demagnetization using a four-level converter. A torque estimator(510) estimates the torque using a phase current and a rotator position. A hysteresis controller(520) produces a state signal of the outgoing phase and the incoming phase. A switching table unit(530) switches the state signal of the incoming phase and the output phase into a switching signal with four modes. A four-level converter(540) supplies a power terminal voltage to the SRM in a mode 1. The four-level converter returns the current of the coil to the power in the mode 0. The four-level converter supplies the power terminal voltage and the boost capacitor voltage to the SRM in the mode 2. The four-level converter collects the energy stored in the coil to the capacitor in the mode -2.

Description

SL instantaneous torque control system using 4-level converter {DITC OF SRM DRIVE SYSTEM USING 4-LEVEL CONVERTER}

The present invention relates to a direct instantaneous torque control (DITC) system and a method of SRM using a four-level converter.

Switched Reluctance Motor (hereinafter referred to as 'SRM') has low manufacturing cost, simple structure, robust structure, high torque ratio to rotor volume, stability, controllability and efficiency. great. However, SRM generates high torque ripple compared to other motors due to the independent characteristics of torque generation due to the double projecting structure and the independent phase.

 Recently, various control techniques have been proposed to reduce high natural torque ripple. However, in general, when the phases are superimposed to reduce the torque ripple, the dynamic response is slow by using a relatively large leading angle. Compared with the conventional control schemes, the proposed Direct Instantaneous Torque Control (DITC) and four-level converters produce a gentle output torque in all areas and reduce the leading angle. By using this, fast dynamic characteristics can be obtained.

An object of the present invention is to provide a drive control system and method of the SRM using a four-level converter for suppressing high natural torque ripple and generating a constant torque output.

 Another technical problem to be achieved by the present invention is to provide a drive control system and method of the SRM using a four-level converter with improved dynamic characteristics and efficiency through rapid excitation and potato.

 Another technical problem to be achieved by the present invention is to provide a drive control system and method of the SRM using a four-level converter with improved dynamic characteristics and efficiency by reducing the leading angle.

 Another technical problem to be achieved by the present invention is to provide a drive control system and method of the SRM using a four-level converter that can improve the performance of the converter and improve the selection of complex control gains or complex control methods.

SRM's direct instantaneous torque control (DITC) system using a four-level converter is a torque estimator and rotor that estimates torque by 3-D torque look-up table using detected phase current and rotor position. A switching rule is selected according to the position of the hysteresis controller. The hysteresis controller generates status signals of incoming and outgoing phases based on hysteresis control in response to the difference between the estimated torque and the reference torque (torque error). In the switching table section and mode 1, which switch to a switching signal composed of (Mode 1, Mode 0, Mode -2 and Mode 2), the power supply voltage is supplied to the SRM. In Mode 0, the coil current is returned to the power supply. In the 2, the power supply voltage and the boost capacitor voltage are supplied to the SRM. In the mode -2, the 4-level converter unit recovers the energy stored in the coil to the capacitor to control the SRM operation. It includes.

The converter unit controls the operation by dividing into three areas. In the area 1, the excitation voltage is formed in the first phase to shorten the excitation current formation time, and in the area 2, the negative voltage is applied in the second phase so that the potato current is quickly recovered. In the region 3, it is preferable to quickly form a potato current in the first phase.

The four-level converter includes a boost capacitor (Ccd), a power switch (Qcd) and a diode (Dcd) in the asymmetric converter. In mode 1, the power supply voltage is supplied through the diode (Dcd), and in mode 2, the power switch ( Qcd) is turned on so that the power supply voltage and the voltage of the boost capacitor Ccd are applied on both, and in mode -2, energy stored in the coil is preferably recovered in the boost capacitor Ccd.

1B) 및 회전자와 고정자가 완전히 정렬되어 인덕턴스가 최대로 되는 지점(

2B)에 의하여 나뉘어지며,

1B 및

2B 사이의 영역에서는 전원단 전압 및 승압을 위한 부스트 커패시터 전압이 인가되도록 상태신호를 생성하는 것이 바람직하다.Switching rules are different switching rules in each of the three zones, and the three zones are the points at which the rotor begins to align with the stator (

1B) and the point where the rotor and stator are completely aligned so that the inductance is maximized (

Divided by 2B),

1B and

In the region between 2B, it is preferable to generate a state signal such that a power supply voltage and a boost capacitor voltage for boosting are applied.

The switching rule is a different switching rule in each of the three regions, and the state signals (inlet phase, outflow phase) of the region 1 include (0,0), (0,2) and (1,1), and the region 2 The state signals of the incoming and outgoing phases include (0,0), (0,1) and (1,1) .The state signals of the area 3 (the incoming and outgoing phases) are (-2,0). ), (-2,1) and (-2,2).

The switching rule is a different switching rule in each of the three regions, and the state signals (inrush and outflow) of region 1 further include (-2,0) and (2,2), and the path of the switching rule is torque In response to an error, (-2,0), (0,0), (0,2), (1,1) and (2,2) are moved, and the status signal of the area 2 (pulling phase, outflow phase) Further includes (-2,0) and (2,2), and the path of the switching rule corresponds to (-2,0), (0,0), (0,1), (1, 1) and (2,2), and the path of the switching rule of the area 3 moves (-2,0), (-2,1) and (-2,2) in response to the torque error, and the load When is changed to more than a predetermined value, the status signal preferably includes (-2, -2), (-2,0) and (-2,2).

The method of direct instantaneous torque control (DITC) of SRM using a four-level converter includes estimating torque by using a 3-D torque look-up table using the detected phase current and rotor position, and the position of the rotor. Selects a switching rule according to the method and generates a state signal of the incoming and outgoing phases based on the hysteresis control in response to the difference between the estimated torque and the reference torque (torque error). , Switching to a switching signal consisting of mode 0, mode -2 and mode 2), and in mode 1, supply voltage of the power supply terminal to SRM, in mode 0, return the coil current to the power supply, and in mode 2, supply voltage And supplying a boost capacitor voltage to the SRM, and in mode -2, recovering the energy stored in the coil to the capacitor to control the SRM operation.

1B) 및 회전자와 고정자가 완전히 정렬되어 인덕턴스가 최대로 되는 지점(

2B)에 의하여 나뉘어지며, 영역1의 스위칭 룰의 경로는 토크 에러에 대응하여 상태신호(인입상, 유출상)가 (-2,0),(0,0),(0,2),(1,1) 및 (2,2)인 지점을 이동하며, 영역2의 스위칭 룰의 경로는 토크 에러에 대응하여 상태신호(인입상, 유출상)가 (-2,0),(0,0),(0,1),(1,1) 및 (2,2)인 지점을 이동하며, 영역3의 스위칭 룰의 경로는 토크 에러에 대응하여 상태신호(인입상, 유출상)가 (-2,0), (-2,1) 및 (-2,2)인 지점을 이동하며, 부하가 기설정된 값 이상으로 변하는 경우에는 상태신호가 (-2,-2), (-2,0) 및 (-2,2)인 지점을 이동하는 것이 바람직하다.Switching rules are different switching rules in each of the three zones, and the three zones are the points at which the rotor begins to align with the stator (

1B) and the point where the rotor and stator are completely aligned so that the inductance is maximized (

2B), and the path of the switching rule of the area 1 has (-2,0), (0,0), (0,2), ( 1,1) and (2,2) points are moved, and the path of the switching rule of the area 2 corresponds to the torque error, and the state signals (pulling phase, outflow phase) are (-2,0), (0,0). ), (0,1), (1,1), and (2,2), and the path of the switching rule in the area 3 corresponds to the torque error, and the state signal (pulling phase, outflow phase) is (- 2,0), (-2,1) and (-2,2), and if the load changes more than the preset value, the status signal is (-2, -2), (-2,0) It is preferable to move the points () and (-2,2).

As described above, according to the present invention, it is possible to provide an SRM system and a control method capable of outputting a gentle torque.

In addition, according to the present invention, it is possible to provide an SRM system and a method of controlling the same having high dynamic characteristics and efficiency through rapid excitation and decay current due to the additional high elevated voltage of the four-level converter.

In addition, according to the present invention, it is possible to provide an SRM system and a method of controlling the same, which have improved dynamic characteristics and improved efficiency by reducing the leading angle.

In addition, according to the present invention, it is possible to control to reduce the torque ripple by applying the DITC based on the hysteresis control to control without the selection of complicated control gain.

 As described above, although the present invention has been described by way of limited embodiments and drawings, the present invention is not limited thereto and is intended by those skilled in the art to which the present invention pertains. Of course, various modifications and variations are possible within the scope of equivalent claims.

1 is a diagram illustrating an example of an asymmetric bridge converter.

The asymmetric bridge converter shown in FIG. 1 is in the form of a representative power converter in an SRM drive system. In the case of the asymmetric bridge converter, the independent control of each phase is easy, which is very useful for applying a technique of reducing torque ripple through superposition of phases.

2 is a diagram illustrating an example of an operation mode of an asymmetric bridge converter. 2, the asymmetric bridge converter has three modes, defined as states 1, 0 and -1, respectively.

The figure on the left shows State 1 of the asymmetric bridge converter. While the two switches are turned on, the source voltage Vs is supplied to the phase windings. The figure in the middle shows state 0 of the asymmetric converter. One switch and one diode are turned on and the phase current is at reflux. The figure on the right shows State-1 of the asymmetric converter. Both switches are turned off and the phase voltage is -Vs. Potato currents recover energy with an elevated power capacitor. The DITC method uses these three states to produce a gentle torque.

 In traditional current control, the torque ripple generated by the subdivision section is large. The best way to reduce torque ripple is to provide a constant output torque during SRM operation.

_onB,

_1B,

_2B이다.

_onB 및

_onC는 선행각(advanced angle)으로서 부하 및 동작 속도에 의존적이다.

_1B는 회전자가 고정자와 정렬되기 시작하는 지점으 로 B상의 인덕턴스 변화가 시작되는 지점이다.

_2B는 A상에 대해 회전자와 고정자가 완전히 정렬되는 지점으로 A상의 인덕턴스가 최대가 되는 지점이다.3 is a view showing the principle of the operation method of the DITC method of the SRM using an asymmetric converter. Referring to FIG. 3, in order to apply the DITC method, the phase inductance section is divided into three regions according to the SRM geometry and load state. The boundaries of the three zones

_onB ,

_1B ,

_2B .

_onB and

_onC is the advanced angle as the load and It depends on the speed of operation.

_1B is the point at which the rotor begins to align with the stator, where the change in inductance on B begins.

_2B is the point where the rotor and stator are completely aligned with respect to phase A, and the inductance of phase A is maximized.

 In area 1, the output instantaneous torque is generated by phase A. Zone 2 includes the reflux zone and is a very important section for generating a constant instantaneous torque. In region 2, the B phase current is established and starts to produce instantaneous torque. At the same time, the change in inductance is drastically reduced, so that the output torque is also drastically reduced. The main output torque is generated by phase B and the lack is generated by phase A.

  In the region 3, the phase A inductance starts to decrease, and when the current flows, a negative torque is generated, so the energy must be reduced to a power source through a fast potato. Also, phase B should output constant torque in this area.

4A to 4C illustrate DITC techniques of an asymmetric converter. To get a gentle torque, a DITC technique based on hysteresis loops was used.

Referring to FIG. 4A, the combined state of the incoming and outgoing phases is indicated by points (-1, -1), (0,0) and (1,1).

Referring to FIG. 4B, the combined state of the inlet phase and the outflow phase is represented by points (-1,0), (0,0), (0,1), and (1,1), and the solid line is a control rule of the hysteresis loop. to be.

In the DITC technique of the asymmetrical converter, the same control method is applied to the area 1 and the area 2 as the general control method. In area 3, states (-1, -1), (-1,0) and (-1, -1) must be included according to the principles of the DITC method. State (-1,0) was added to improve the dynamic performance of the torque.

In Fig. 4C, the control method of region 3 is shown. Since the A phase has to return the magnetic field energy to the power stage capacitor, the A phase must maintain state -1, and the B phase can change between states 0 and 1. As a method for improving torque, states (-1, -1) were added in this control method.

 5 is a block diagram of an SRM drive control system using a four-level converter according to the present invention. SRM drive control system using a four-level converter according to the present invention is a torque estimation unit (Torque Estimation) (510), hysteresis controller (Hysteresis Controller) (520), switching table (Switching Table) (530), 4-level 4-leverl converter 540 is included. The torque estimator 510 and the hysteresis controller 520 are very important in the DITC method.

6 is a view showing the operation principle of the SRM drive control system using a four-level converter according to the present invention.

_onB,

_1B,

_2B이다.

_onB 및

_onC는 선행각(advanced angle)으로서 부하 및 동작 속도에 의존적이다.

_1B는 회전자가 고정자와 정렬되기 시작하는 지점으로 B상의 인덕턴스 변화가 시작되는 지점이다.

_2B는 A상에 대해 회전자와 고정자가 완전히 정렬되는 지점으로 A상의 인덕턴스가 최대가 되는 지점이다.In Figure 6, the boundaries of the three regions are

_onB ,

_1B ,

_2B .

_onB and

_onC is an advanced angle that depends on load and operating speed.

_1B is the point at which the rotor starts to align with the stator, where the change in inductance on B begins.

_2B is the point where the rotor and stator are completely aligned with respect to phase A, and the inductance of phase A is maximized.

In the case of SRM, when voltage is applied in the inductance rising section, torque is generated as much as the magnitude of the inductance of the rotor and the amount of current flowing at this time. Therefore, no torque is generated in the section where the inductance does not change (that is, the section 1 (Region1) section in the L _B 612). Therefore, if current is supplied in this section, torque is not generated, which is a loss. In order to reduce such a loss, it is preferable to apply a voltage in the region 2 (Region2) in the case of the L _B 612, but the current cannot increase significantly because the inductance is changing. If a current is supplied to a phase corresponding to L _B 612 in the section of FIG. 6, the bottom of FIG. 6 is shown. In practice, the ideal phase current 623 is formed. Even if a current is supplied in region 2, a high voltage is applied in this section so that an ideal phase current 623 is formed. When a high voltage is applied, the current rises quickly in a short time, thereby obtaining an actual phase current 625, which is a desired type of current. In addition, it can improve the performance by quickly refluxing the current in a similar manner as above in the period when all phases are turned off.

The torque estimator 510 calculates the estimated torque by using a 3-D table using the current and the rotor position of each phase. That is, the torque is estimated by referring to the 3D torque look-up table stored in the memory based on the current detected in each phase and the angle detected by the encoder. The stored 3D look-up table is obtained through actual or FEM simulation. By using such a simple search torque table, complicated torque calculations can be replaced and torque calculation time can be reduced.

The hysteresis control unit 520 selects a switching rule according to the position of the rotor, and generates the state signals of the incoming and outgoing phases based on the hysteresis control in response to the torque error. The torque error is the difference between the reference torque and the estimated torque, where torque error = reference torque-estimated torque. In applying the DITC technique, instead of using the same DITC rule in all sections, switching rules are determined differently according to the position of the rotor. Using the detected position of the rotor, one of the three switching rules shown in Figs. 6A to 6C is selected and used.

7A to 7C are diagrams showing an example of the DITC technique using the 4-level converter according to the present invention.

Referring to FIG. 7A, the control method of the region 1 is as follows. In area 1, mode 2 is available. By applying a high voltage, a fast excitation current is established in phase B, and the driving efficiency is improved by the fast established current. Phase A produces main torque. The selection technique of the state of the region 1 is shown in Fig. 7A. In region 1, (0,0), (1,1) and (0,2) must be included, and states (2,2) and (-2,0) are optional states for considering torque response.

The control method of the area 2 will be described with reference to FIG. 7B. In region 2, the state technique is very similar to asymmetrical converters in the same region, where state (-2,0) was used instead of state (-1,0), and state (2,2) was added. Through the high negative voltage, the energy accumulated in A phase is rapidly demagnetized to improve the dynamic characteristics of torque. In region 2, (1,1), (0,1) and (0,0) are used. The other states are used for the dynamic torque response.

The control method of the area 3 will be described with reference to FIG. 7C. In region 3, state -2 performs the potato through rapid reflux on phase A, which can reduce the negative torque to improve driving efficiency. Phase B produces main torque. In Fig. 7C the general operation of region 3 is shown. In this case, states (-2,0), (-2,1) and (-2,2) are required. If the load suddenly changes, the dynamic mode of region 3 is replaced by the normal mode, which is shown in the right figure of FIG. 7C.

The switching table unit 530 converts the state signal into a switching signal to drive the power converter. The hysteresis control unit 520 converts the state signal generated into a switching signal composed of four operation modes (mode 1, mode 0, mode -2 and mode 2).

The four-level converter 540 controls the SRM operation using the switching signal. The four-level converter unit 540 supplies the power terminal voltage to the SRM in mode 1, and in the mode 0 to return the current of the coil to the power supply side, in mode 2 to supply the power terminal voltage and the boost capacitor voltage to the SRM, mode In -2, the energy stored in the coil is recovered by the capacitor to control the SRM operation.

Since the four-level converter 540 has four states (2, 1, 0, -2), the general control technique of DITC using an asymmetric converter is not suitable for the four-level converter. In a four-level converter, as a result, fast potato through mode 2 and mode -2, fast excitation and reflux of the phase current is possible. For this reason, the 4-level converter has higher efficiency and dynamic performance than the drive system using asymmetric converter.

8A is a diagram illustrating an example of a four-level converter according to the present invention. The four-level converter shown in FIG. 8A is proposed for three-phase SRM. Referring to FIG. 8, the four-level converter 540 includes an additional boosted capacitor C _CD 820, a power switch Q _CD 830, and a diode D _CD 840 in addition to the traditional asymmetric converter. . The boost capacitor C _CD 820 and DC capacitor (C _DC ) 810 store the potato current during the switching turn-off, so the phase current is quickly demagnetized, which simultaneously causes the phase current to be simultaneously applied to the boost capacitor and the DC capacitor (power capacitor). It is refluxed. The boost capacitor then produces a highly elevated voltage. For fast phase current generation, the additionally high charged voltage delivers power switch Q _CD 830 to the next excitation phase winding.

The four-level converter is configured by adding a boost capacitor (C _CD ) 820 for boosting together with a DC capacitor (C _DC ) 810 for keeping the power supply voltage constant. The capacitance of the boost capacitor is very important when designing a four-level converter. Larger capacitors are advantageous in that small voltage ripple can be obtained and stable DC voltage can be supplied to the SRM. However, it increases the cost of the SRM drive system. Small capacitors, on the other hand, cause unstable DC voltages and difficult control of the system.

From the principle of the four-level converter, the boost capacitor recovers the energy accumulated in the phase winding through the reflux mode, and supplies a high voltage by supplying a voltage to the circuit in parallel with the power supply voltage. Thus, potatoes can be run for a short time. Of course, the reflux energy is related to the load and the voltage change depends on the initial boost voltage and the capacitor size. Thus, a suitable capacitor size can be obtained from a given load, a given initial voltage and a given voltage change.

FIG. 8B is a diagram illustrating an example of an operation mode of a four-level converter, and FIG. 8C is a diagram illustrating an example of the DITC rules of each mode of FIG. 8B.

8B, Mode 1, Mode 0, Mode-2, and Mode 2 are shown from the left. FIG. 8C is a diagram illustrating an example of the DITC rule of each mode of FIG. 8B. 8c shows the magnitude of the voltage.

In mode 1, Q _Ah and Q _AL are turned on so that V _CDC, the power supply voltage, is supplied to A phase. Therefore, the voltage has the same voltage as mode1 of FIG. 8C.

In mode 0, Q _Ah is turned off and Q _AL is turned on to return the current in the coil to the power supply side. The voltage applied to the phase is zero as shown in mode0 of FIG. 8C.

In mode 2, Q _Ah and Q _{AL ,} Q _CD The switches are all turned on so that both the supply voltage and the voltage at the top capacitor are applied to the phase, so that the voltage of V _CDC + V _CCD is applied to the phase. This state is called a state in which a high voltage is applied, that is, mode 2. In this state, when all the switches are turned off, the energy stored in the coil is recovered to C _CD and C _DC so that the voltage becomes a low voltage state, that is, the mode -2 state. This is displayed as 0,1, -1,2, -2 on the screen for creating DITC rules.

In mode 2 of FIG. 8B, the DC link voltage V _dc and the rising voltage V _cd are supplied to an excited phase winding, and the excited phase current is quickly established by the highly charged voltage V _dc + V _cd . Similarly, the potato current decreases rapidly during mode -2 by the negatively biased voltage-(V _dc + V _cd ).

Referring to FIG. 8B, mode -2 is shown where mode 1 (normal excitation mode) and mode 0 (rotation mode) are the same as the asymmetric converter when Q _cd is turned off.

Analyzing the efficiency of a four-level converter, it is possible to rapidly increase the excitation current due to the voltage charged in the boost capacitor stage and fast potato to return the energy to the boost capacitor stage. That is, the excitation time and potato time can be reduced. This means that the loss of the coil and the loss of resistance of the switch generated by supplying current in the section where no torque is generated are reduced. In addition, by performing a fast potato, it is possible to use a wide range of torque generation, it is possible to reduce the negative torque to improve the dynamic torque characteristics and control characteristics of the entire system. This means that although the switches and diodes used for the control of the booth capacitor add some loss, the reduced loss is sufficient to offset this loss. As such, the efficiency of the SRM drive system can be improved.

9 is a diagram illustrating an example of a 3-D table for selecting a capacitor. In FIG. 9, the torque is 0.7 [Nm]. As the capacitance of the capacitor decreases, the voltage ripple of the boost capacitor increases. As the boost voltage increases, the voltage ripple of the boost capacitor decreases.

10 is a flowchart of a direct instantaneous torque control (DITC) method of SRM using a four-level converter according to the present invention.

The torque is estimated by using the 3-D torque look-up table using the detected phase current and the rotor position (S1100).

The switching rule is selected according to the position of the rotor, and the state signals of the incoming and outgoing phases are generated based on the hysteresis control in response to the difference (torque error) between the estimated torque and the reference torque (S1200).

Switching rules are applied to different switching rules in three areas. The three zones are divided into zones 1, 2 and 3 by the point at which the rotor begins to align with the stator (?? 1B) and the point at which the rotor and the stator are fully aligned so that the inductance is maximized (?? 2B). Divided. For a detailed description of the switching rule and the state signal in each area, refer to FIGS. 6 and 7A to 7C.

The path of the switching rule in the area 1 has the state signals (pulling phase, outflow phase) corresponding to the torque error (-2,0), (0,0), (0,2), (1,1) and (2). Move the point at, 2). The switching rule is shown in FIG. 7A.

The path of the switching rule in the area 2 has (-2,0), (0,0), (0,1), (1,1) and ( Move the point 2,2). The switching rule is shown in Figure 7b.

The path of the switching rule in the area 3 moves to the point where the state signals (pulling phase, outflow phase) are (-2,0), (-2,1) and (-2,2) in response to the torque error, and the load If is changed to more than the preset value, the position signals (-2, -2), (-2,0) and (-2,2) are moved. The switching rule is shown in Figure 7c.

The status signal is converted into a switching signal composed of four operation modes (mode 1, mode 0, mode -2 and mode 2) (S1300).

In mode 1, the power supply voltage is supplied to the SRM. In mode 0, the coil current is returned to the power supply. In mode 2, the power supply voltage and the boost capacitor voltage are supplied to the SRM. In mode -2, energy stored in the coil is supplied. The SRM operation is controlled by recovering the capacitor (S1400).

11 shows the efficiency of a four-level converter in accordance with the present invention. Referring to FIG. 11, the improvement in efficiency at different boost voltages is shown. That is, it shows how the performance changes depending on the size of the boost capacitor. Compared with the asymmetric converter, as the load and speed increase, it can be seen that the efficiency of the four-level converter increases at the same rising voltage.

12A and 12B are diagrams illustrating inductance and torque profile simulations in an SRM drive system, respectively. In order to clarify the DITC method of the SRM drive based on the four-level converter, the control method of the proposed method is shown using MATLAB. The 3D torque and inductance table of the motor used is shown.

13A and 13B show an asymmetric converter and a four-level converter, respectively. The leading angle for the DITC technique in the asymmetric converter of FIG. 13A is larger than the case where the four-level converter of FIG. 13B is applied. The rapid excitation and demagnetization of the four-level converter allows for the rapid establishment of excitation currents and the recovery of the demagnetization currents. Referring to the four-level converter of Figure 13b, it can be seen that the leading angle is shorter.

14A to 14D show torque step response characteristics of an asymmetric converter and a four-level converter, respectively. 14A and 14B show simulation results of torque step responses of an asymmetric converter and a four-level converter in DITC 500 [rmp] and 0.7 [Nm], respectively. 14C and 14D show the torque step response results in the DITC 500 [rmp], 0.2-0.7 [Nm]. Because of the additional high rising voltage of the four-level converter, the response time (0.2 ms) of the four-level converter of FIG. 14D is shorter than the response time (0.4 ms) of the asymmetric converter of FIG. 14C. Therefore, the DITC method of the SRM drive based on the four-level converter has better dynamic characteristics than the asymmetric method. From these simulation results, SRM drive systems based on four-level converters have lower torque ripple and performance compared to asymmetric converter drive systems.

15A to 15F illustrate excitation currents and motor operations of the asymmetric converter and the four-level converter according to the present invention, respectively. In the experiments of FIG. 15A (asymmetric converter) and FIG. 15B (4-level converter), the SRM operates at 400 [rpm] and the output torque is 0.7 [Nm]. In the experiments of Fig. 15C (asymmetric converter) and Fig. 15D (4-level converter), the SRM operates at 500 [rpm] and the output torque is 0.7 [Nm]. In the experiments of Fig. 15E (asymmetric converter) and Fig. 15F (4-level converter), the SRM operates at 1400 [rpm] and the output torque is 0.6 [Nm].

Compared to the asymmetrical converter, it can be seen that in the four-level converter, the excitation current is generated more quickly and the leading angle can be reduced.

16A and 16B are diagrams illustrating dynamic characteristics according to torque changes of the asymmetric converter and the four-level converter, respectively. 16A and 16B, when the torque command value changed from 0.2 [Nm] to 0.7 [Nm], it was confirmed that each torque response followed the command torque. However, when compared with the general asymmetric converter (0.8ms), it can be seen that the DITC system using the four-level converter (0.4ms) shows a faster dynamic response characteristics.

1 is a diagram illustrating an example of an asymmetric bridge converter;

2 is a diagram illustrating an example of an operation mode of an asymmetric bridge converter;

3 is a view showing the principle of the operation method of the DITC method of the SRM using an asymmetric converter,

4A to 4C are diagrams illustrating a DITC technique of an asymmetric converter,

5 is a block diagram of an SRM drive control system using a four-level converter according to the present invention;

6 is a view showing the operation principle of the SRM drive control system using a four-level converter according to the present invention,

7a to 7c are views showing an example of the DITC technique using a four-level converter according to the present invention,

8A illustrates an example of a four-level converter according to the present invention;

8B is a diagram illustrating an example of an operation mode of a four-level converter;

FIG. 8C is a diagram illustrating an example of the DITC rules in each mode of FIG. 8B;

9 illustrates an example of a 3-D table for selecting capacitors;

10 is a flowchart of a direct instantaneous torque control (DITC) method of SRM using a four-level converter according to the present invention;

11 shows the efficiency of a four-level converter in accordance with the present invention;

12A and 12B show inductance and torque profile simulations in an SRM drive system, respectively;

13A and 13B show an asymmetric converter and a four-level converter, respectively;

14A to 14D show torque step response characteristics of an asymmetric converter and a four-level converter, respectively;

15A to 15F illustrate excitation current and motor operation of the asymmetric converter and the four-level converter according to the present invention, respectively; and

16A and 16B are diagrams illustrating dynamic characteristics according to torque changes of the asymmetric converter and the four-level converter, respectively.

Claims (8)

A torque estimator for estimating torque by a 3-D torque look-up table using the detected phase current and rotor position; A hysteresis controller which selects a switching rule according to the position of the rotor and generates a state signal of an incoming phase and an outflow phase based on hysteresis control in response to the difference (torque error) between the estimated torque and the reference torque; A switching table unit for converting the state signal into a switching signal composed of four operation modes (mode 1, mode 0, mode -2 and mode 2); And In mode 1, the power supply voltage is supplied to the SRM, in mode 0, the current of the coil is returned to the power supply side, in mode 2, the power supply voltage and the boost capacitor voltage are supplied to the SRM, and in mode -2, the power is stored in the coil. And a four-level converter for recovering energy into a capacitor to control the SRM operation. The method of claim 1, The converter unit is divided into three areas to control the operation, In region 1, an excitation voltage is formed on the first phase so as to shorten the excitation current formation time. In the region 2, a negative voltage is formed on the second phase so that the potato current can be recovered quickly. In area 3, a direct instantaneous torque control (DITC) system of SRM using a four-level converter in which a potato current is rapidly formed in the first phase. The method of claim 1, The four-level converter includes a boost capacitor (Ccd), a power switch (Qcd) and a diode (Dcd) in the asymmetric converter, In the mode 1, a power supply voltage is supplied through the diode Dcd, and in the mode 2, the power switch Qcd is turned on to apply both the power supply voltage and the voltage of the boost capacitor Ccd. And a direct instantaneous torque control (DITC) system of SRM using a four-level converter in which the energy stored in the coil is recovered to the boost capacitor (Ccd) in the mode-2. The method of claim 1, The switching rule is a different switching rule in each of the three areas, The three zones represent the point at which the rotor begins to align with the stator (

1B) and the point where the rotor and the stator are completely aligned so that the inductance is maximized (

2B) divided by the above

1B and

SRM direct instantaneous torque control (DITC) system using a four-level converter to generate a status signal in the region between the 2B power supply voltage and boost capacitor voltage for boosting. The method according to claim 1 or 4, The switching rule is a different switching rule in each of the three areas, The state signals (intake phase, outflow phase) of the area 1 include (0,0), (0,2) and (1,1), The state signal (inlet phase, outflow phase) of the area 2 includes (0,0), (0,1) and (1,1), The instantaneous torque control (DITC) of the SRM using the four-level converter including (-2,0), (-2,1) and (-2,2) is performed. ) system The method of claim 5, The switching rule is a different switching rule in each of the three areas, The state signal (intake phase, outflow phase) of the area 1 further includes (-2,0) and (2,2), and the path of the switching rule corresponds to (-2,0), ( 0,0), (0,2), (1,1) and (2,2) The state signal (inlet phase, outflow phase) of the area 2 further includes (-2,0) and (2,2), and the path of the switching rule corresponds to (-2,0), ( 0,0), (0,1), (1,1) and (2,2) The path of the switching rule in the area 3 moves (-2,0), (-2,1) and (-2,2) in response to a torque error, and the state when the load changes above a predetermined value. Direct instantaneous torque control (DITC) system of SRM using a four-level converter, the signal comprising (-2, -2), (-2,0) and (-2,2). Estimating torque by a 3-D torque look-up table using the detected phase current and rotor position; Selecting a switching rule according to the position of the rotor, and generating a state signal of an incoming phase and an outflow phase based on hysteresis control in response to a difference (torque error) between the estimated torque and a reference torque; Converting the status signal into a switching signal composed of four operation modes (mode 1, mode 0, mode -2 and mode 2); And In mode 1, the power supply voltage is supplied to the SRM, in mode 0, the current of the coil is returned to the power supply side, in mode 2, the power supply voltage and the boost capacitor voltage are supplied to the SRM, and in mode -2, the power is stored in the coil. Recovering energy to a capacitor to control the SRM operation; Direct instantaneous torque control (DITC) method of SRM using a four-level converter comprising a. The method of claim 7, The switching rule is a different switching rule in each of the three areas, The three regions are divided by the point at which the rotor starts to align with the stator (?? B) and the point at which the rotor and the stator are completely aligned so that the inductance is maximized (?? 2B), The path of the switching rule in the region 1 has a state signal (pulling phase, outflow phase) corresponding to (2,0), (0,0), (0,2), (1,1) and ( 2,2) to move the point, The path of the switching rule in the area 2 has (-2,0), (0,0), (0,1), (1,1) and ( 2,2) to move the point, The path of the switching rule in the area 3 moves to a point where the state signals (pulling phase, outflow phase) are (-2,0), (-2,1) and (-2,2) in response to a torque error, Direct instantaneous torque of the SRM using a four-level converter that moves the point where the status signals are (-2, -2), (-2,0) and (-2,2) when the load changes above a preset value. Control (DITC) method.

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