JP2015070699A - Control circuit of switched reluctance motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow reduction torque ripple by current overlap operation when a high-speed operation is made by a single pulse mode, relating to a control circuit of an SR motor in which the number of legs and the number of wirings are decreased.SOLUTION: In a control circuit, legs of respective phases are connected each other in parallel, a neutral point leg and a DC power source are connected in parallel in theses parallel circuits, and windings of respective phases of an SR motor are respectively connected between a neutral point and a serial connection point of two semiconductor switching elements of respective phase legs. In a state in which a switching element Tof a one-side arm of the neutral point leg is kept ON, the switching element Tof a counter arm of an A phase leg is made to perform switching operation to electrify an A phase winding, which operation is sequentially performed for a leg of other phase.

Description

  The present invention relates to a control circuit for a switched reluctance motor (hereinafter also referred to as an SR motor), and more particularly to a technique for realizing high-speed rotation of an SR motor while reducing the number of components and torque ripple. .

FIG. 3 shows the prior art of the control circuit of the SR motor. In FIG. 3, 1 is a DC power supply (voltage value is E _d ), T _u , T _v , T _w , T _x , T _y , T _z are semiconductor switching elements such as IGBTs, D _u , D _v , D _w , _Dx , _Dy , and _Dz are diodes, and 20 is an SR motor.
Here, the number of phases of the SR motor 20 is three phases, and the control circuit is configured by a total of six legs by an A-phase leg 10A, a B-phase leg 10B, and a C-phase leg 10C each having two legs per phase. Yes.

FIG. 4 is a schematic cross-sectional view of the SR motor 20. Hereinafter, the principle of torque generation of the SR motor 20 will be described with reference to FIG. In FIG. 4, 21 is a stator, 21a is its salient pole, 22 is a rotor, 22a is its salient pole, and 23 is a rotation axis.
Now, the case where the salient pole 21a of the stator 21 and the salient pole 22a of the rotor 22 coincide with each other is “opposing position”, and the salient pole 22a of the rotor 22 is positioned between the two salient poles 21a of the stator 21. The case is defined as “non-opposing position”.

  FIG. 5 is a diagram showing the relationship between the inductance L (θ) with respect to the rotor position θ of the motor 20 and the current (stator winding current) i that generates the driving torque for one phase of the SR motor 20. . As shown in the figure, the inductance L (θ) of the SR motor 20 is the smallest at the non-opposing position, so that the magnetic flux is most difficult to flow.

すなわち、∂Ｌ（θ）／∂θが正の区間に通電すれば駆動トルクが得られ、また、∂Ｌ（θ）／∂θが負の区間に通電すれば制動トルクが得られる。
よって、図６に示すように、ＳＲモータ２０のＡ，Ｂ，Ｃ相について、∂Ｌ（θ）／∂θが正である区間に制御回路から電流ｉ_Ａ，ｉ_Ｂ，ｉ_Ｃをそれぞれ通流すれば、ほぼ一定のトルクを得ることができる。 Here, in order to simplify the description, assuming that the inductance L (θ) changes linearly with respect to the rotor position θ, the torque T of the SR motor 20 is the current i, the inductance L (θ), and the rotation. Using the child position θ, it is expressed by Equation 1.

That is, if ∂L (θ) / ∂θ is energized in a positive section, a driving torque is obtained, and if ∂L (θ) / ∂θ is energized in a negative section, braking torque is obtained.
Therefore, as shown in FIG. 6, the currents i _A , i _B , and i _C are passed from the control circuit to the sections where ∂L (θ) / ∂θ is positive for the A, B, and C phases of the SR motor 20, respectively. If it flows, a substantially constant torque can be obtained.

However, since it is difficult to generate a rectangular wave current as shown in FIGS. 5 and 6 by the control circuit, in practice, the actual current approaches the target value with the ideal current as a rectangular wave as shown in FIG. In this way, the voltage applied to the SR motor 20 is controlled by chopping.
The applied voltage has the following three voltage modes, and the semiconductor switching element of FIG. 3 is switched on and off according to the current pattern. Hereinafter, each voltage mode will be described by taking the A-phase leg 10A of FIG. 3 as an example.

1) Positive voltage mode: A voltage of + E _dc is applied to the A-phase winding. Table 1 shows the on / off state of each element in the A-phase leg 10A at this time.

2) Zero voltage mode: The voltage of the A-phase winding is 0 [V]. Table 2 shows the on / off states of the elements in the A-phase leg 10A at this time.

3) Negative voltage mode: -E _dc voltage is applied to the A-phase winding. Table 3 shows the on / off state of each element in the A-phase leg 10A at this time.

  The positive voltage mode is used when the current is raised, the positive voltage mode and the zero voltage mode are used when the current is controlled to be constant, and the negative voltage mode is used when the current is lowered.

Figure 8 is a waveform diagram of an actual A-phase current _{i A} and B-phase current _{i B.}
As shown in FIG. 8, when launching the B-phase current i _B after the fall of the A-phase current i _A, the torque is reduced to fall when i _A, torque increases at the rising edge of the i _B. That is, in the switch interval T ₁ of the flowing phase, so that the torque ripple is generated.
As a method for solving this problem, as shown in FIG. 9, the B-phase current i _B is raised with a margin of a predetermined time ΔT from the timing when the A-phase current i _A falls, and the torque ripple is reduced. There is technology. This technique is called current overlap because the currents of the two phases overlap.

By the way, as a control circuit of the SR motor 20 for the purpose of simplifying the circuit configuration, a conventional technique described in Patent Document 1 is known.
FIG. 10 shows a control circuit described in Patent Document 1. In this control circuit, two semiconductor switching elements T _u , T _x , T _v , T _y , T _w , T _z such as IGBTs each having a diode connected in anti-parallel are used for each of the A-phase leg 10A ′ and the B-phase. A leg 10B ′ and a C-phase leg 10C ′ are formed, and a parallel circuit of these legs 10A ′, 10B ′, and 10C ′ includes semiconductor switching elements T _m and T _{n each} having a diode connected in antiparallel. The sex point leg 10D is connected in parallel. Here, the diode _{D u, D x, D v} , D y, D w, D z, D m, as the _{D n,} those built to each switching element is used.
CA, CB and CC are the A-phase, B-phase and C-phase windings of the stator of the SR motor 20, and M is a neutral point where one end of each phase winding CA, CB and CC is connected in common. is there.

According to this prior art, the number of elements is reduced from 12 to 8 compared to the circuit of FIG. 3, and the number of legs is also 6 (in FIG. 3, each phase leg is composed of 2 legs. Therefore, the total is reduced from 6) to 4.
Furthermore, one end of each phase winding CA, CB, CC is star-connected, and its neutral point M is connected to the series connection point of the switching elements T _m , T _n , and other than each phase winding CA, CB, CC. end, 'the series connection point of the switching elements _T u, _{T x} of, B-phase leg 10B' a phase leg 10A the _T v of the series connection point of _{T y,} the _T w C-phase leg 10C ', _{T z} The number of wires between the control circuit and each of the phase windings CA, CB, CC is reduced from 6 to 4 in FIG.
For these reasons, the configuration of Patent Document 1 can be simplified compared to the circuit of FIG.

  In addition, the on / off state of each element in FIG. 10 is as shown in Tables 4 to 7 below. However, these on / off states relate to a section from the flow to the A-phase winding CA to the flow to the B-phase winding CB by the control circuit.

1) A phase winding positive voltage mode

2) Phase A winding zero voltage mode

3) A-phase winding negative voltage mode, B-phase winding positive voltage mode In this mode, the switching element T _n and diode D of the fourth leg 10D are determined by the magnitude relationship between the A-phase current i _A and the B-phase current i _{B. n} is turned on and off.

4) A-phase winding negative voltage mode, B-phase winding zero-voltage mode In this mode, the diodes D _m and D _n of the fourth leg 10D are determined by the magnitude relationship between the A-phase current i _A and the B-phase current i _B. ON and OFF are determined.

Furthermore, the control circuit of FIG. 11 described in Patent Document 2 is known as another conventional technique.
In FIG. 11, components having the same functions as those in FIG. Reference numerals 11 and 12 denote pressure equalization lines connected between the A-phase leg 10A ′ and the B-phase leg 10B ′ and between the B-phase leg 10B ′ and the C-phase leg 10C ′.
In this prior art, the number of wires between the control circuit (inverter) and the SR motor is determined by connecting the adjacent two phases with a pressure equalizing line and devising a PWM signal for driving the semiconductor switching element. Similar to 1, the number is reduced to 4.

Patent Document 3 is known as an SR motor excitation method.
This Patent Document 3 describes that the torque ripple of the SR motor is reduced by current overlap as described above. Furthermore, when the SR motor is operated at high speed, a pulse voltage is applied to the windings of each phase, and the phase current increases from 0 [A] to a predetermined peak value within one cycle of the voltage. Then, it is described that it is desirable to drive in a single pulse mode that decreases to 0 [A]. In Patent Document 3, for example, a technique for simplifying the circuit configuration by reducing the number of wirings is not particularly mentioned.

JP 2007-28866 A (paragraphs [0019] to [0013], FIG. 1 etc.) JP 2000-295891 A (paragraphs [0042] to [0046], FIG. 1 etc.) Japanese Patent No. 4141743 (paragraphs [0005], [0006], [0010], [0039], FIG. 3, FIG. 9 etc.)

According to Patent Documents 1 and 2 described above, the circuit configuration can be simplified. However, with respect to the control method for operating the SR motor in the single pulse mode as described in Patent Document 3 using a control circuit having a simplified configuration as in these conventional techniques, Neither is disclosed in the prior art.
Therefore, the problem to be solved by the present invention is to provide a control circuit capable of reducing torque ripple by current overlap operation when performing high-speed operation in a single pulse mode in a control circuit for an SR motor with a reduced number of legs and wires. There is to do.

In order to solve the above-mentioned problem, the invention according to claim 1 is characterized in that a leg for one phase formed by connecting two semiconductor switching elements each having a diode connected in antiparallel in series is n (n is an integer of 3 or more). A neutral point leg having the same configuration as that of the one-phase leg is connected in parallel to the n-phase leg parallel circuit and connected to each other in parallel. A neutral point which is a series connection point of two semiconductor switching elements constituting the neutral point leg by connecting a DC power supply in parallel and a series of two semiconductor switching elements constituting the n-phase leg. In the control circuit of the switched reluctance motor, which is configured by connecting the windings of each phase of the switched reluctance motor between the connection points,
The semiconductor switching element of the opposite arm located on the opposite side of the one-phase leg of the n-phase leg in the state where the semiconductor switching element of the one-side arm of the neutral point leg is always turned on The switching operation is performed on the legs of the n-phase in order, and the torque of the switched reluctance motor is continuously controlled.

  According to a second aspect of the present invention, in the control circuit of the switched reluctance motor according to the first aspect, a single pulse voltage is applied to the semiconductor switching element of the n-phase leg within one cycle. Control is performed in a pulse mode, and control is performed so that the currents flowing in the windings of each phase overlap in a part of the period.

  According to the present invention, in a SR motor control circuit with a reduced number of legs and wires, a single pulse mode operation and a current overlap operation can reduce torque ripple and perform stable high-speed operation.

It is a flowchart which shows operation | movement of embodiment of this invention. It is a waveform diagram of the current and voltage of each phase in the embodiment of the present invention. It is a circuit diagram which shows the prior art of the control circuit of SR motor. It is a typical sectional view of an SR motor. It is the figure which showed the relationship of the inductance and electric current with respect to the rotor position of SR motor about one phase. It is a wave form diagram of each phase current of SR motor. It is a waveform diagram of the current and applied voltage of the SR motor. It is a waveform diagram of the actual A phase current and B phase current of the SR motor. It is a wave form diagram of A phase current and B phase current of SR motor at the time of current overlap. It is a circuit diagram which shows the prior art described in patent document 1. It is a circuit diagram which shows the prior art described in patent document 2.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, the configuration of the control circuit according to this embodiment is the same as that shown in FIG. That is, as shown in FIG. 10, an A-phase leg 10A ′ in which semiconductor switching elements T _u and T _x such as IGBTs are connected in series at both ends of a DC power source 1 (voltage value is E _d ), A B-phase leg 10B ′ in which the semiconductor switching elements T _v and T _y are connected in series and a C-phase leg 10C ′ in which the semiconductor switching elements T _w and T _z are connected in series are connected in parallel to each other. Then, these A phase leg 10A ', B phase leg 10B', the parallel circuit of C-phase leg 10C ', the semiconductor switching element _T m, _{T n} is the neutral point leg 10D connected in series is connected in parallel Yes. D _u , D _x , D _v , D _y , D _w , D _z , D _m , and D _n are diodes connected in antiparallel to the respective switching elements, and CA, CB, and CC are stators of the SR motor. A-phase, B-phase, and C-phase windings, and M is a neutral point.

Here, the semiconductor switching element _{T u, T v, T w} , T x, T y, T z, T m, as the _{T n,} may be used MOSFET in addition IGBT. The diode _{D u, D v, D w} , D x, D y, D z, D m, the _{D n,} it is desirable to use the built-in diode such as an IGBT or MOSFET.

Next, the operation of this control circuit will be described with reference to the flowchart of FIG. 1 and the waveform diagram of FIG.
As shown in FIG. 1, previously always ON the switching element T _n of the lower arm of the neutral leg 10D shown in FIG. 10 (step S1 in FIG. 1). First, at the time of flow of the A-phase winding CA, turning ON the switching element _{T u} of the upper arm of the A-phase leg 10A '(step S2). As a result, the A-phase winding CA enters the positive voltage mode, and the A-phase current i _A is a path of the DC power source 1 → the switching element _Tu → the A-phase winding CA → the neutral point M → the switching element T _n → the DC power source 1. It flows in.

If that was flowed through the C phase winding CC in flowing prior to the A-phase winding CA is, OFF the switching element T _w of the upper arm of the C-phase leg 10C 'after ON the switching element T _u (Step S3). The waveform diagram of FIG. 2 shows an example in which the current is not passed through the C-phase winding CC before the current is passed through the A-phase winding CA.

Then, before interrupting the A-phase current _{i A,} turning ON the switching element _{T v} of the upper arm of the phase B leg 10B '(step S4). As a result, the B-phase winding CB enters the positive voltage mode, and the B-phase current i _B is changed from the DC power source 1 to the switching element T _v → the B-phase winding CB → the neutral point M → the switching element T _n → the DC power source 1. Begins to flow.
Thereafter, when interrupting the A-phase current _{i A} is OFF the switching element _{T u} of the upper arm of the A-phase leg 10A '(step S5). As a result, the A-phase winding CA enters the zero voltage mode, and the A-phase current i _A circulates through the path of the A-phase winding CA → the neutral point M → the switching element T _n → the diode D _x and eventually becomes zero.

Similarly, prior to shutting off the B-phase current _{i B,} turning ON the switching element _{T w} of the upper arm of the C-phase leg 10C '(step S6). Thus, C-phase winding CC is positive voltage mode, C-phase current i _C is the DC power source 1 → switching element T _w → C phase winding CC → neutral point M → path of the switching element T _n → DC power source 1 Begins to flow.
Thereafter, when interrupting the B-phase current _{i B} is in turns OFF the switching element _{T v} of the upper arm of the phase B leg 10B '(step S7). As a result, the B-phase winding CB enters the zero voltage mode, and the B-phase current i _B circulates through the path of the B-phase winding CB → the neutral point M → the switching element T _n → the diode D _y and eventually becomes zero.

Thereafter, by repeating steps S2 to S7 described above, each phase current flows sequentially, and the rotor can be rotated continuously. Note that θ _{1 to} θ ₉ in FIG. 2 are angles corresponding to timings at which the switching elements of the respective phases are turned on and off, and angles corresponding to timings at which the respective phase currents become zero.

  As described above, according to this embodiment, as shown in FIG. 10, in the control circuit in which the configuration is simplified by reducing the number of wires between the number of legs and each phase winding of the SR motor, When performing high-speed operation in the pulse mode, as shown in FIG. 2, it is possible to reduce torque ripple by performing a current overlap operation in which each phase current is overlapped in a partial period.

Although the direction of the current flowing in each phase winding is reversed, advance constantly ON the switching element T _m of a upper arm of the neutral leg 10D, flow of the A-phase winding CA, at the time of shut-off A phase leg 10A 'oN the switching element _{T x} of the lower arm of, and OFF, flows into the B-phase winding CB, the B-phase leg 10B at blocking' to oN, OFF the switching element _{T y} of the lower arm of, C The switching element T _z of the lower arm of the C-phase leg 10C ′ may be turned ON / OFF when the phase winding CC is turned on and off.

  Furthermore, in the above-described embodiment, the example in which the respective phase legs 10A ′, 10B ′, 10C ′ and the neutral point leg 10D are connected to the DC power supply 1 in parallel to drive the three-phase SR motor has been described. The present invention generally includes an (n + 1) -phase leg of the same configuration for driving an SR motor of n (n is an integer of 3 or more) phase, and uses one phase as a neutral point leg. It can be applied to a circuit.

1: DC power supply 10A ': A phase leg 10B': B phase leg 10C ': C phase leg 10D: Neutral point leg 20: Switched reluctance motor (SR motor)
21: Stator 21a: Salient pole 22: Rotor 22a: Salient pole 23: Rotating axis T _u , T _v , T _w , T _x , T _y , T _z , T _m , T _n : Semiconductor switching element D _u , _{D v, D w, D x} , D y, D z, D m, D n: diode CA: A phase winding CB: B-phase winding CC: C phase winding M: neutral

Claims (2)

Legs for one phase formed by connecting two semiconductor switching elements having diodes connected in anti-parallel are connected in parallel for n (n is an integer of 3 or more) phases, and these n phases A neutral point leg having the same configuration as that of the one-phase leg is connected in parallel to a parallel circuit of the minute leg, and a DC power source is connected in parallel to the neutral point leg to constitute the neutral point leg. Between each of the phases of the switched reluctance motor between a neutral point that is a series connection point of the two semiconductor switching elements and a series connection point of the two semiconductor switching elements constituting the leg for the n phase. In the control circuit of the switched reluctance motor configured by connecting the windings,
The semiconductor switching element of the opposite arm located on the opposite side of the one-phase leg of the n-phase leg in the state where the semiconductor switching element of the one-side arm of the neutral point leg is always turned on Switching operation is performed sequentially on the n-phase legs, and the torque of the switched reluctance motor is continuously controlled. Control circuit for reluctance motor. In the control circuit of the switched reluctance motor according to claim 1,
The n-phase leg semiconductor switching elements are controlled by a single pulse mode in which a single pulse voltage is applied within one period, and the current flowing through the windings of each phase is limited during a certain period. A control circuit for a switched reluctance motor, characterized by being controlled to overlap.

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