JP2013150491A - Control device for switched reluctance motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress generation of power loss at a semiconductor switch.SOLUTION: The control device 20 for switched reluctance motor, controlled by switching an electric current running through a winding of each phase of a switched reluctance motor 53 with a semiconductor switch, controls so that the semiconductor switch is an on state when an electric voltage is applied to a body diode of the semiconductor switch in the forward direction and hence an electric current running through the body diode is brought into the semiconductor switch, thereby suppressing power loss at the body diode.

Description

  The present invention relates to a control device for a switched reluctance motor.

  A rotor having a plurality of salient poles, a stator having a plurality of inward salient poles arranged so as to surround the rotor, and windings wound around the inward salient poles. There is known a switched reluctance motor that magnetically attracts an inward salient pole to magnetically attract the salient pole of the rotor to generate rotational torque in the rotor (see, for example, Patent Documents 1 and 2). .

  When controlling such a switched reluctance motor, the current flowing through the winding is turned on / off by a semiconductor switch (for example, FET) connected to each winding to magnetically place the salient pole of the rotor on the inward salient pole. Control is performed by generating a rotational torque in the rotor by suction.

JP 2007-028866 A JP 2007-236135 A

  Incidentally, a semiconductor switch such as an FET has a parasitic diode called a body diode connected in parallel to the switch. A regenerative current or a reflux current may flow through such a body diode. In this case, power loss occurs according to the forward voltage and current. If the forward bias voltage of the body diode is 2 V and a current of 300 A is passed, 600 W (= 2 × 300) of power is lost.

  Therefore, an object of the present invention is to provide a control device for a switched reluctance motor capable of reducing power loss in a semiconductor switch.

In order to solve the above-described problems, the present invention provides a control device for a switched reluctance motor that controls a current flowing through a winding of each phase of the switched reluctance motor by switching with a semiconductor switch. When a forward voltage is applied to the diode, the semiconductor switch is controlled to be in an on state, and the current flowing through the body diode is passed to the semiconductor switch, thereby reducing the power loss in the body diode. It is characterized by reducing.
According to such a configuration, it is possible to reduce power loss in the semiconductor switch.

In addition to the above invention, another invention is characterized in that the semiconductor switch is controlled to be in an on state when a return current or a regenerative current is passed through the windings of the respective phases.
According to such a configuration, it is possible to reduce the loss that occurs when the return current or the regenerative current passes through the body diode.

In addition to the above invention, another invention is characterized in that the semiconductor switch is turned from an on state to an off state when a phase current flowing through each of the windings becomes a predetermined threshold value or less.
According to such a configuration, by appropriately setting the threshold value, it is possible to reliably reduce the loss that occurs when the return current or the regenerative current passes through the body diode.

According to another invention, in addition to the above-mentioned invention, the winding includes a plurality of phases connected to each other at a neutral point, and the semiconductor switch has a current flowing from each phase toward the neutral point. Alternatively, the current from the neutral point to each phase is supplied by switching according to the rotational position of the rotor.
According to such a configuration, it is possible to further reduce power loss in the control device by increasing the control efficiency.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the control apparatus of the switched reluctance motor which can reduce the loss of the electric power in a semiconductor switch.

It is a block diagram which shows the structural example of the control apparatus of the switched reluctance motor which concerns on embodiment of this invention. It is a figure which shows the structural example of the arm driver shown in FIG. It is a figure which shows the detailed structural example of SR motor shown in FIG. It is a figure which shows the state of electricity supply of SR motor shown in FIG. It is a figure which shows the state of the semiconductor switch in a prior art example, and the relationship of a phase current. It is a figure which shows the state of the area a of FIG. It is a figure which shows the state of the area b of FIG. It is a figure which shows the state of the area c of FIG. It is a figure which shows the relationship of the state of the semiconductor switch in this embodiment, and a phase current. It is a figure which shows the state of the area a of FIG. It is a figure which shows the state of the area b of FIG. It is a figure which shows the state of the area c of FIG. It is a figure which shows the other structural example of the arm driver shown in FIG.

  Next, an embodiment of the present invention will be described.

(A) Description of Configuration of Embodiment FIG. 1 is a diagram illustrating a control device for a switched reluctance motor according to an embodiment of the present invention. As shown in this figure, a control device 20 for a switched reluctance motor includes an accelerator detection unit 21, an energization signal output unit 22, a drive signal output unit 23, a PWM (Pulse Width Modulation) output unit 24, a current control processing unit 25, An energization OFF timing determination processing unit 26, an energization OFF threshold generation unit 27, a current detection processing unit 28, an energization timing determination unit 29, a map storage unit 30, a position detection unit 31, and a rotation speed detection unit 32; SR (Switched) is performed by the arm driver 51 according to the operation amount of the accelerator 10.
Reluctance) The motor 53 is controlled.

  Here, the accelerator detection unit 21 detects an operation amount (for example, a stepping amount by the driver) of the accelerator 10 provided in the vehicle and notifies the current control processing unit 25 and the energization timing determination unit 29.

  The energization signal output unit 22 is based on the rotational position of the rotor of the SR motor 53 detected by the position detection unit 31 and the information indicating the energization timing supplied from the energization timing determination unit 29 and the semiconductor switch (NH , NL (details will be described later with reference to FIG. 2)). The drive signal output unit 23 is a rotation position of the rotor of the SR motor 53 detected by the position detection unit 31, information supplied from the energization timing determination unit 29, information from the PWM output unit 24, and energization OFF timing determination. Based on the information from the processing unit 26, the semiconductor switch (UH, UL, VH, VL, WH, WL (details will be described later with reference to FIG. 2)) of the arm driver 51 is driven.

  The PWM output unit 24 supplies information for PWM control to the drive signal output unit 23 based on the signal output from the current control processing unit 25. The current control processing unit 25 performs control so that a current corresponding to the accelerator operation amount is output based on information from the accelerator detection unit 21 and information from the current detection processing unit 28.

  The energization OFF timing determination processing unit 26 compares the information from the current detection processing unit 28 with the energization OFF threshold supplied from the energization OFF threshold generation unit 27, and determines the timing for turning off the phase current energization. Then, the determination result is output to the drive signal output unit 23. The energization OFF threshold value generation unit 27 generates a threshold value for turning off energization and supplies the threshold value to the energization OFF timing determination processing unit 26.

  The current detection processing unit 28 detects currents flowing in the U, V, and W phases of the SR motor 53 based on the current sensor 52 and supplies them to the current control processing unit 25 and the energization OFF timing determination processing unit 26.

  The energization timing determination unit 29 includes an advance angle and an energization angle corresponding to information corresponding to the accelerator operation amount supplied from the accelerator detection unit 21 and information indicating the rotation speed of the SR motor 53 supplied from the rotation speed detection unit 32. Is obtained from the advance angle map 30a and the energization angle map 30b stored in the map storage unit 30, and supplied to the energization signal output unit 22 and the drive signal output unit 23.

  The position detector 31 detects the rotational position of the rotor of the SR motor 53 based on the signal output from the rotation sensor 54 and supplies the detected position to the energization signal output unit 22, the drive signal output unit 23, and the rotation speed detection unit 32. To do. The rotation speed detection unit 32 obtains the rotation speed of the SR motor 53 based on the information indicating the rotation position of the rotor output from the position detection unit 31 and notifies the energization timing determination unit 29 of the rotation speed.

  The battery 50 is configured by a secondary battery such as a lead storage battery, a nickel cadmium battery, a nickel hydride battery, or a lithium ion battery, and supplies AC power to the SR motor 53 via the arm driver 51.

  The arm driver 51 switches the DC power output from the battery 50 in accordance with the drive signals supplied from the energization signal output unit 22 and the drive signal output unit 23, and supplies the DC power to the windings constituting each phase of the SR motor 53. To do.

  FIG. 2 shows a configuration example of the arm driver 51. As shown in this figure, the arm driver 51 is configured by connecting a total of eight FETs (Field Effect Transistors) as semiconductor switches. Here, each semiconductor switch has a body diode in a parallel connection state. This body diode is a parasitic diode formed by a PN junction formed between the source and drain and the substrate.

  As shown in FIG. 2, the semiconductor switches NH and NL are connected in series, these connection points are connected to the neutral point 64 of the winding of the SR motor 53, and both ends are connected to the battery 50. The semiconductor switches UH and UL are connected in series, these connection points are connected to the U phase of the winding, and both ends are connected to the battery 50. The semiconductor switches VH and VL are connected in series, these connection points are connected to the V phase of the winding, and both ends are connected to the battery 50. The semiconductor switches WH and WL are connected in series, these connection points are connected to the W phase of the winding, and both ends are connected to the battery 50. The semiconductor switches NH and NL are switching-controlled by the energization signal output unit 22, and the semiconductor switches UH to WH and UL to WL are switching-controlled by the drive signal output unit 23. Note that a capacitor 65 for reducing high-frequency noise is connected to the battery 50 in parallel.

  U, V, and W phase windings are wound around the stator salient poles Su, Sv, and Sw that face each other across the rotation shaft of the SR motor 53. One end of each phase winding is connected to each other at a neutral point 64 and connected to a connection point between the semiconductor switches NH and NL, and the other end is connected to a connection point between the semiconductor switches UH to WH and UL to WL. ing.

  As shown in FIG. 3, the SR motor 53 includes a stator S and a rotor R disposed so as to be rotatable with respect to the stator S. The stator S includes a stator core SC in which a plurality of stator salient poles (Su, Sv, Sw) are integrally formed, and a U phase, a V phase, and a W phase wound around the stator salient poles (Su, Sv, Sw), respectively. Windings (U, V, W). A plurality of rotor salient poles (R1, R2, R3, R4) are integrally formed on the rotor R.

  The rotation sensor 54 detects the rotational position of the rotor R of the SR motor 53 and outputs it to the position detector 31.

(B) Description of Operation Principle of Embodiment Next, the operation of this embodiment will be described. In the following, in order to clarify the features of the present embodiment, the operation principle of the SR motor 53 is described first, then the operation of the conventional example is described, and then the operation of the present embodiment is described.

  First, the operation principle of the SR motor 53 will be described. FIG. 4 is a diagram showing the on / off state of the semiconductor switch and the state of energization to each phase. In FIG. 4, the horizontal axis indicates the rotational position of the rotor R, the vertical axis indicates the on or off state of each semiconductor switch (“high” indicates on and “low” indicates off), and the arrow flows through the current. Shows direction. As shown in FIG. 4, there are six stages (a) to (f) for driving the SR motor 53. In the stage (a), the semiconductor switches NH and UL are turned on. As a result, the current output from the battery 50 shown in FIG. 2 flows through the U-phase winding through the semiconductor switch NH and the neutral point 64, and returns to the battery 50 through the semiconductor switch UL. As a result, the U-phase stator salient poles Su are magnetized, so that the rotor salient poles located in the vicinity are attracted. Next, in the stage (b), the semiconductor switches NL and VH are turned on, and the current output from the battery 50 flows through the V-phase winding through the semiconductor switch VH, and the neutral point 64 and the semiconductor switch. It returns to the battery 50 via NL. As a result, the V-phase stator salient poles Sv are magnetized, so that the rotor salient poles located in the vicinity are attracted. Next, in the stage (c), the semiconductor switches NH and WL are turned on, and the current output from the battery 50 flows through the W-phase winding through the semiconductor switch NH and the neutral point 64, and the semiconductor switch It returns to the battery 50 via WL. As a result, the W-phase stator salient poles Sw are magnetized, so that the rotor salient poles located in the vicinity are attracted. In the stage (d), the semiconductor switches NL and UH are turned on, and current flows through the semiconductor switch UH, the U phase, the neutral point 64, and the semiconductor switch NL in this order to magnetize the U phase. In the stage (e), the semiconductor switches NH and VL are turned on, and current is passed through the semiconductor switch NH, the neutral point 64, the V phase, and the semiconductor switch VL in this order to magnetize the V phase. In the stage (f), the semiconductor switches NL and WH are turned on, and current flows in the order of the semiconductor switch WH, the W phase, the neutral point 64, and the semiconductor switch NL, and the W phase is magnetized. Thus, the stator salient poles are magnetized in the order of U, V, and W, so that the rotor salient poles are attracted to the stator salient poles and the rotor R rotates. Further, by alternately passing the current from the winding toward the neutral point 64 and the current from the neutral point 64 toward the winding, it is possible to prevent the current from continuing to flow in the phase immediately before the currently energized phase. Thus, the influence of the residual magnetic field can be reduced and a larger torque can be obtained.

  Next, the operation of the prior art will be described with reference to FIGS. FIG. 5 shows changes in the state of the semiconductor switch and the phase current in the stages (a) and (b) shown in FIG.

  At the beginning of the U-phase energization section, the semiconductor switch NH is turned on as shown in FIG. 5A, and the semiconductor switch UL is turned on as shown in FIG. As shown in FIG. 5 (G), the U-phase current Iu increases. When the U-phase current Iu exceeds a predetermined threshold, the semiconductor switch UL is repeatedly turned on / off, and PWM control is performed. As a result, the U-phase current Iu maintains a substantially constant value as shown in FIG.

  FIG. 6 shows a state in the section a in FIG. As shown in FIG. 6, in the section a, as indicated by the dashed arrow in the figure, the current that has passed through the semiconductor switch NH flows to the U-phase winding, and then passes through the semiconductor switch UL to reach the battery 50. Return. As a result, a current in the direction indicated by the dashed arrow flows through the U-phase winding.

In FIG. 5, when the U-phase energization section ends, the process shifts to the V-phase energization section. At the beginning of the V-phase energization section, as shown in FIGS. 5B and 5E, the semiconductor switch NL is turned on and the semiconductor switch VH is turned on. FIG. 7 shows a state in the interval b. As shown in FIG. 7A, when the semiconductor switches VH and NL are turned on, a current passes through the V phase as indicated by a broken arrow. At this time, the U-phase regenerative current is regenerated to the battery 50 via the semiconductor switch NL and the body diode of the semiconductor switch UH. When the current flowing in the V phase exceeds a predetermined threshold value, PWM control is started, and the semiconductor switch VH is turned on / off as shown in FIGS. 7B and 7C. More specifically, as shown in FIG. 7B, when the semiconductor switch VH is turned on, a current is supplied to the V phase via the semiconductor switches VH and NL. At this time, the U-phase regenerative current is regenerated to the battery 50 via the body diode of the semiconductor switch UH. As shown in FIG. 7C, when the semiconductor switch VH is turned off, a reflux current flows in the V phase through the body diode of the semiconductor switch VL and the semiconductor switch NL. At this time, the U-phase regenerative current is regenerated to the battery 50 via the body diode of the semiconductor switch UH. And when Iu which is a U-phase electric current becomes "0", it transfers to the area c.

  In section c, as shown in FIG. 5, the semiconductor switch NL is kept on and the semiconductor switch VH repeats the on / off operation. As a result, as shown in FIG. 5H, Iv that is the V-phase current is held substantially constant.

  FIG. 8 shows a state in the interval c. When the semiconductor switch VH is turned on, as shown in FIG. 8A, a current is passed to the V phase via the semiconductor switches VH and NL. When the semiconductor switch VH is turned off, as shown in FIG. 8B, a reflux current is passed to the V phase through the body diode of the semiconductor switch VL and the semiconductor switch NL.

  The operation described above is repeatedly executed in the order of U, V, and W phases, and the rotor R rotates by supplying current to the U, V, and W windings.

  By the way, in the conventional example shown above, as shown in FIGS. 7 and 8, the regenerative current and the reflux current are passed to the body diode. If the forward voltage of the body diode is 2 V, for example, and these currents are 300 A, the loss in the body diode reaches about 600 W (= 2 × 300), so that power is wasted. The heat radiator for cooling the heat generated by the body diode becomes large.

  Next, the operation of this embodiment will be described with reference to FIGS. In this embodiment, when a forward bias voltage is applied to the body diode by a regenerative current and a return current, the semiconductor switch having the body diode is turned on, as compared with the conventional example. The power loss is reduced by passing the current through the semiconductor switch instead of the body diode. More specifically, for example, assuming that the on-resistance of the semiconductor switch is 4 mΩ and a current of 300 A flows, the loss is 360 W (= 300 × 300 × 0.004), which is compared with 600 W described above. The loss is reduced by about 240W.

  Based on FIG. 1, the operation of the present embodiment will be described in detail. When the accelerator 10 is operated, the accelerator detector 21 detects the operation amount of the accelerator 10. For example, the operation amount of the accelerator 10 is detected in a range of 0 to 100%, and a current command value corresponding to the detected value is supplied to the current control processing unit 25 and the energization timing determination unit 29.

  Based on the rotation speed of the SR motor 53 supplied from the rotation speed detection unit 32 and the current command value supplied from the accelerator detection unit 21, the energization timing determination unit 29 determines from the advance angle map 30a and the conduction angle map 30b. The corresponding advance angle and energization angle are acquired and supplied to the energization signal output unit 22 and the drive signal output unit 23. Here, the energization angle is an angle at which the semiconductor switches NH and NL are kept on. Further, the advance angle refers to this advanced angle when the timing at which switching is started precedes the timing at which the winding inductance increases. More specifically, the winding inductance increases as the stator salient pole and the rotor salient pole approach each other, reaches a peak when they face each other, and decreases as they move away from each other. At this time, the semiconductor switch starts a switching operation before the angle at which the inductance increases, and this leading angle is referred to as an advance angle. The energization signal output unit 22 and the drive signal output unit 23 adjust the timings of the energization signal and the drive signal based on the advance angle and the energization angle supplied from the energization timing determination unit 29.

  The current control processing unit 25 compares the current command value supplied from the accelerator detection unit 21 with the current detection value supplied from the current detection processing unit 28, and outputs a comparison result to the PWM output unit 24. The PWM output unit 24 performs PWM control on the drive signal output unit 23 based on the comparison result output from the current control processing unit 25.

  The energization OFF threshold generation unit 27 generates an energization OFF threshold for determining that energization of each phase is turned off, and supplies the energization OFF timing determination processing unit 26. The energization OFF timing determination processing unit 26 compares the threshold supplied from the energization OFF threshold generation unit 27 with the current detection value supplied from the current detection processing unit 28, determines the timing for turning off energization, and drives the drive signal. This is supplied to the output unit 23.

  With the above operation, the energization signal output unit 22 refers to the energization angle and the advance angle supplied from the energization timing determination unit 29, and based on the position of the rotor R supplied from the position detection unit 31, the semiconductor switches NL, Control NH. Further, the drive signal output unit 23 refers to the energization angle and the advance angle supplied from the energization timing determination unit 29, and based on the position of the rotor R supplied from the position detection unit 31, the semiconductor switches UH to WH, UL to While controlling WL, PWM control and energization off timing control of these semiconductor switches are performed based on the PWM output unit 24 and energization OFF timing determination processing unit 26.

  FIG. 9 is a diagram showing temporal changes in the semiconductor switch and the phase current. In the section a shown in this figure, the semiconductor switch NH is turned on and the semiconductor switch UL is turned on. Thereby, the U-phase current Iu flows. FIG. 10 is a diagram illustrating a current in the section a. As shown in this figure, in the section a, the U-phase current Iu is supplied from the battery 50 to the U-phase winding via the semiconductor switches NH and UL. As a result, the U-phase stator protrusion is excited, so that the rotor protrusion is attracted and rotational torque is generated.

  Since the section b shown in FIG. 9 is a V-phase energization section, the semiconductor switch NL is turned on and the semiconductor switch VH is turned on. At this time, in this embodiment, the semiconductor switch UH is turned on. As a result, as shown in FIGS. 11A to 11C, the current flowing through the U-phase winding is regenerated to the battery 50 via the semiconductor switch UH instead of the body diode. FIG. 11A shows a state in which the semiconductor switch VH is kept on at the beginning of the interval b. The U-phase regenerative current is regenerated to the battery 50 via the semiconductor switch UH, and the V-phase A current for excitation is supplied to the winding via the semiconductor switches VH and NL.

  FIGS. 11B and 11C show a state where the semiconductor switch VH is PWM-controlled in the section b. In the present embodiment, when the semiconductor switch VH is turned off, the semiconductor switch VL is turned on. As a result, the return current flowing in the V phase flows through the V phase winding via the semiconductor switch VL, not the body diode. For this reason, power loss due to the body diode can be reduced.

  FIG. 12 shows a state in the section c shown in FIG. FIG. 12A shows the current when the semiconductor switch VH is turned on in the interval c, and the V-phase winding is excited from the battery 50 via the semiconductor switches VH and NL. Current is supplied. FIG. 12B shows a case where the semiconductor switch VH is turned off. In the present embodiment, when the semiconductor switch VH is turned off, the semiconductor switch VL is turned on, so that the return current is communicated to the V-phase winding via the semiconductor switch VL instead of the body diode. For this reason, power loss due to the body diode can be reduced. The semiconductor switches VH and VL are driven by complementary signals having a dead time with respect to the high-side or low-side signal as shown in FIG. 9 so that the semiconductor switches VH and VL are not turned on simultaneously.

  As described above, in this embodiment, the semiconductor switch having the body diode that is forward biased is controlled to be in the ON state at the timing when the return current and the regenerative current are communicated. Thereby, since these currents flow not in the body diode but in the semiconductor switch, the power loss in the body diode can be reduced, so that the power efficiency of the control device 20 can be improved. Further, since heat generation can be suppressed by reducing the loss, the radiator of the semiconductor switch can be miniaturized and the size of the entire apparatus can be miniaturized.

(C) Description of Modified Embodiment It goes without saying that the above embodiment is merely an example, and the present invention is not limited to the case described above. For example, in the above embodiment, the semiconductor switch is turned on for both the return current and the regenerative current. For example, the semiconductor switch is turned on for one of these. May be. Alternatively, the semiconductor switch may be turned on when the current value of the return current or the regenerative current is larger than a predetermined threshold value. Specifically, for example, when the rotational speed is low, the reflux current increases and the regenerative current decreases, and when the rotational speed is high, the reflux current decreases and the regenerative current increases. May be configured such that a reflux current is passed through the semiconductor switch and a regenerative current is passed through the semiconductor switch when the rotational speed is high. In addition, the control of the present embodiment described above may not be performed in all phases, but may be performed only in a specific phase, or may be performed by thinning out phases.

  In the above embodiment, the arm driver 51 constituted by a total of eight semiconductor switches has been described as an example. For example, the present invention is applied to an arm driver constituted by a total of 12 semiconductor switches shown in FIG. It is also possible to apply. In the example of FIG. 13, there are six sets of two semiconductor switches connected in series, and windings of U, V, and W are arranged between the two sets of semiconductor switches. Even in such a configuration, when the body diode is forward-biased due to the return current and the regenerative current, the loss in the body diode can be reduced by turning on the semiconductor switch having the body diode. it can.

  In the above embodiment, the SR motor 53 has been described with an example in which the stator salient poles are 6 poles and the rotor salient poles are 4 poles, but other combinations may be used.

DESCRIPTION OF SYMBOLS 10 Accelerator 20 Control apparatus 21 Accelerator detection part 22 Energization signal output part 23 Drive signal output part 24 PWM output part 25 Current control process part 26 Energization OFF timing determination process part 27 Energization OFF threshold value generation part 28 Current detection process part 29 Energization timing determination Unit 30 Storage unit 31 Position detection unit 32 Rotation speed detection unit 50 Battery 51 Arm driver 52 Current sensor 53 SR motor 54 Rotation detection sensor

Claims (4)

In a control device for a switched reluctance motor that controls the current flowing through the winding of each phase of the switched reluctance motor by switching with a semiconductor switch,
When a forward voltage is applied to the body diode of the semiconductor switch, the semiconductor switch is controlled to be in an on state, and a current flowing through the body diode is passed to the semiconductor switch. Reduce power loss in body diodes,
A control device for a switched reluctance motor.   2. The switched reluctance motor control device according to claim 1, wherein the semiconductor switch is controlled to be turned on when a return current or a regenerative current passes through the windings of the respective phases.   3. The switched reluctance motor control device according to claim 1, wherein when the phase current flowing through each of the windings becomes equal to or less than a predetermined threshold, the semiconductor switch is turned from on to off. The winding has a plurality of phase windings interconnected at a neutral point;
The semiconductor switch supplies a current from each phase toward the neutral point or a current from the neutral point toward each phase by switching according to the rotational position of the rotor.
The control device for a switched reluctance motor according to any one of claims 1 to 3.