JP2017046406A - Rotation position detection device and rotation position detection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rotation position detection device capable of maintaining position estimation accuracy even in a control state in which a modulation factor is high.SOLUTION: A rotation position detection device comprises: an inverter circuit driving a three-phase permanent magnet motor; a current detection section detecting each phase current output from the inverter circuit; a current variation detection section detecting a variation of each phase current; and a rotation position detection section obtaining arithmetic results including information of a rotation position from current variations of two phases detected in a period when lower side arms of any two phases out of three phases constituting the inverter circuit are ON and a period when lower side arms of three phases are ON and a current variation of one phase excluding the two phases detected in a period when the lower side arms of the three phases are ON, and detecting the rotation position of the permanent magnet motor from the arithmetic results.SELECTED DRAWING: Figure 1

Description

  Embodiments described herein relate generally to an apparatus and a method for detecting a rotational position of a permanent magnet motor.

  Conventionally, as one method for estimating the rotational position of a permanent magnet synchronous motor, Patent Document 1 uses a current differential value during voltage application to detect a rotational position capable of supplying a sinusoidal current with an inexpensive configuration. A scheme has been proposed. In this method, the current change amount when the zero voltage vector is generated is obtained based on the motor phase voltage equation, and the rotational position information of the motor included in the current change amount is used.

JP 2007-336641 A

However, in the method as disclosed in Patent Document 1, when the modulation rate is increased by rotating the motor at a high speed or the like, as shown in FIG. 8, the zero voltage for detecting the current change amount as compared with the case shown in FIG. Since the vector output period is shortened, there is a problem that the position estimation accuracy is lowered.
Therefore, a rotational position detection device and a rotational position detection method that can maintain position estimation accuracy even in a control state with a high modulation rate are provided.

  The rotational position detection device according to the embodiment includes an inverter circuit that drives a three-phase permanent magnet motor, a current detection unit that detects each phase current output from the inverter circuit, and a current that detects a change amount of the phase current. Of the three-phase arms constituting the change amount detecting unit and the inverter circuit, the two-phase lower arm is detected during the period when the two-phase lower arm is on and the three-phase lower arm is detected during the period. A calculation result including rotational position information from a two-phase current change amount and a one-phase current change amount excluding the two phases, which is detected while the lower arm of the three phases is on. And a rotational position detector that detects the rotational position of the permanent magnet motor from the calculation result.

The figure which is one Embodiment and shows the structure of a motor control apparatus A diagram representing the voltage generated by the inverter circuit as a space vector The figure which shows each phase voltage value of the motor at the time of outputting each voltage vector Timing chart showing a state in which current change amounts dIv, dIw, dIu are detected within the PWM cycle The figure which shows the relation between the rotational position of the motor, the induced voltage, and the estimated difference value on the time axis The figure which shows an example of a structure of a rotation position calculating part FIG. 4 equivalent view for explaining the prior art (part 1) FIG. 4 equivalent diagram for explaining the prior art (part 2)

  Hereinafter, an embodiment will be described with reference to FIGS. 1 to 6. FIG. 1 is a functional block diagram showing the configuration of the motor control device. The DC power source 1 is a power source that drives a permanent magnet synchronous motor (hereinafter simply referred to as a motor) 2 having a permanent magnet in a rotor. The DC power source 1 may be one obtained by converting an AC power source into DC. The inverter circuit 3 is configured by connecting six switching elements, for example, N-channel MOSFETs 4U +, 4Y +, 4W +, 4U−, 4Y−, 4W−, in a three-phase bridge, and is generated by a PWM generation unit 5 described later. A voltage for driving the motor 2 is generated based on six switching signals for three phases.

  The voltage detector 6 detects the voltage VDC of the DC power supply 1. The current detection unit 7 is generally composed of a current sensor using a shunt resistor, Hall CT, and the like and a signal processing circuit, and detects currents Iu, Iv, Iw flowing through the motor 2. FIG. 1 illustrates a case where three (7U, 7V, 7W) are arranged on the lower side of each phase of the inverter circuit 3. As another form, each inverter circuit 3 is arranged on the upper side of each phase. May be placed on phase output line.

  The current change amount detection unit 8 detects a three-phase current value based on signals t1, t2, and t3 from a detection timing signal generation unit 9 to be described later, and calculates respective change amounts dIu, dIv, and dIw. As the detection timing, the amount of change between two detections is obtained by three detections, so there are two types of change amounts for three phases, for a total of six signals.

  In FIG. 1, the current differential values output from the current change amount detection unit 8 are dIa, dIb, and dIc, depending on the area of the space vector in the switching pattern of the inverter circuit 3 as will be described later. Since the voltage vector to be used is different, the notation is simplified. That is, a, b, and c correspond to any of u, v, and w. The notation (bc0) indicates that the lower switch of either one of the b and c phases is turned on “1”, and the lower switch of the other and the a phase is turned off “0”. The arrangement of “bc0” is not a fixed arrangement of “1, 0” (see equations (1) to (3) described later).

  The induced voltage calculation unit 10 (rotational position detection unit) calculates three-phase induced voltage difference estimated values Euvw, Evwu, and Ewuv from the detected three-phase current change amounts dIu, dIv, and dIw. The rotational position calculator 11 (rotational position detector) calculates the rotational position detected value θc of the motor 2 from the estimated values Euvw, Evwu, and Ewuv. The three-phase voltage command value generation unit 12 generates three-phase voltage command values Vu, Vv, and Vw from the voltage amplitude command value Vamp and the voltage phase command value φv that are command values.

  The duty generation unit 13 calculates the modulation commands Du, Dv, Dw for each phase by dividing the three-phase voltage command values Vu, Vv, Vw by the DC voltage VDC. The PWM generation unit 5 compares the three-phase modulation commands Du, Dv, and Dw with a triangular wave carrier to generate a PWM signal pulse for each phase. A dead time is added to the pulses per phase, and switching signals U +, U−, V +, V−, W +, W− output to the N-channel MOSFET 44 above and below the three phases are generated.

  In the above configuration, the motor 2, the inverter circuit 3, and the PWM generator 5 are not included in the rotational position detection device 14. The rotation position detector 14 plus the PWM generator 5 constitutes a motor controller 15.

  Next, an outline of the rotational position detection method in the present embodiment will be described with reference to FIGS. When the voltage generated by the inverter circuit 3 is represented by a space vector as shown in FIG. 2, it is divided into six actual voltage vectors and two zero voltage vectors. Here, the voltage vector V1 (100) indicates a voltage generated in a state where the U-phase upper switch (FET 4U +) is on and the V-phase and W-phase lower switches (FET 4Y−, 4W−) are on. FIG. 3 shows the phase voltage values of the motor 2 when the voltage vectors are output.

ｄＩｖ(100)-(000):電圧ベクトルＶ１及びＶ０印加時の時刻ｔ１−ｔ３間のＶ相電流変化量[A]
ｄＩｗ(100)-(000):電圧ベクトルＶ１及びＶ０印加時の時刻ｔ１−ｔ３間のＷ相電流変化量[A]
ｄＩｕ(100):電圧ベクトルＶ０印加時の時刻ｔ１−ｔ２間のＵ相電流変化量[A]
Ｅｖ，Ｅｗ，Ｅｕ：ｖ，ｗ，ｕ相の誘起電圧[V]
θ:モータ回転位置[rad]
Ｌ:モータ相インダクタンス[H]
ω:モータ角速度[rad/s]
φｆ:電機子鎖交磁束[Wb]
ここで、（１）式の右辺第１項及び第２項が、回転位置θに対して変化する信号となっている。このように、発生する電圧ベクトルＶ１(100)，Ｖ０(000)に応じて誘起電圧差分推定値Ｅvwuを演算することで、モータ２の回転位置に基づく信号を得ることができる。これを利用して回転位置検出を行う。 For example, as shown in FIG. 4, the timings t <b> 1 to t <b> 1 shown in the figure are output during a period in which the voltage vector V <b> 1 (100) in which only the U-phase upper switch is on and the zero voltage vector V <b> 0 (000) are output. The difference value of the three-phase current detected at t3 is expressed by the following equation.

dIv (100)-(000): V phase current change amount [A] between time t1 and time t3 when voltage vectors V1 and V0 are applied
dIw (100)-(000): W phase current change amount [A] between time t1 and time t3 when voltage vectors V1 and V0 are applied
dIu (100): U-phase current change amount [A] between time t1 and time t2 when voltage vector V0 is applied
Ev, Ew, Eu: v, w, u phase induced voltage [V]
θ: Motor rotation position [rad]
L: Motor phase inductance [H]
ω: Motor angular velocity [rad / s]
φf: Armature flux linkage [Wb]
Here, the first term and the second term on the right side of the equation (1) are signals that change with respect to the rotational position θ. Thus, the signal based on the rotational position of the motor 2 can be obtained by calculating the induced voltage difference estimated value Evwu according to the generated voltage vectors V1 (100) and V0 (000). Using this, the rotational position is detected.

ｄＩｗ(010)-(000):電圧ベクトルＶ３及びＶ０印加時の時刻ｔ１−ｔ３間のＷ相電流変化量[A]
ｄＩｕ(010)-(000):電圧ベクトルＶ３及びＶ０印加時の時刻ｔ１−ｔ３間のＵ相
ｄＩｖ(000):電圧ベクトルＶ０印加時の時刻ｔ１−ｔ２間のＶ相電流変化量[A]
電流変化量[A]
セクタ４及び５については（３）式により誘起電圧差分推定値Ｅuvwを演算する。

ｄＩｕ(001)-(000):電圧ベクトルＶ５及びＶ０印加時の時刻ｔ１−ｔ３間のＵ相電流変化量[A]
ｄＩｖ(001)-(000):電圧ベクトルＶ５及びＶ０印加時の時刻ｔ１−ｔ３間のＶ相
ｄＩｗ(000):電圧ベクトルＶ０印加時の時刻ｔ１−ｔ２間のＷ相電流変化量[A]
電流変化量[A] As shown in FIG. 2, assuming that the six areas of the space vector are sectors 1 to 6, for the sectors 2 and 3, the induced voltage difference estimated value Ewuv is calculated by equation (2).

dIw (010)-(000): W-phase current change amount [A] between time t1 and time t3 when voltage vectors V3 and V0 are applied
dIu (010)-(000): U phase between time t1 and t3 when voltage vector V3 and V0 are applied dIv (000): V phase current change amount between time t1 and t2 when voltage vector V0 is applied [A]
Current change [A]
For sectors 4 and 5, the induced voltage difference estimated value Euvw is calculated by equation (3).

dIu (001)-(000): U-phase current change amount [A] between time t1-t3 when voltage vectors V5 and V0 are applied
dIv (001)-(000): V phase between time t1 and t3 when voltage vectors V5 and V0 are applied dIw (000): W phase current change amount between time t1 and t2 when voltage vector V0 is applied [A]
Current change [A]

  FIG. 5 shows induced voltage difference estimated values Evwu, Ewuv, and Evwu that change according to the induced voltage of each phase. The thin lines indicate all the waveforms over one period of electrical angle, and the portions indicated by the thick lines are actually (1) to (3) according to the voltage sectors 1 to 6. The section of the waveform detected by the equation is shown. By using the estimated values Evwu, Ewuv, and Evwu of the thick line portion for each sector and detecting the respective zero cross points, the rotational position can be obtained. That is, the induced voltage difference estimated values Evwu, Ewuv, and Evwu correspond to “calculation results including rotational position information”.

  Here, the operation of each unit in this embodiment will be described again. The current change amount detection unit 8 detects the current change amount of each phase from the current detected by the current detection unit 7 at a predetermined timing. The timings t1 to t3 for detecting the current change amount are periods in which the zero voltage vector and each actual voltage vector are generated as shown in the equations (1) to (3) and FIG. Therefore, the detection timing signals t <b> 1 to t <b> 3 from the detection timing signal generation unit 9 are output to the current change amount detection unit 8 after the duty Du, Dv, Dw of each phase is determined by the duty generation unit 13. The induced voltage calculation unit 10 calculates a numerical value proportional to the induced voltage from the equations (1) to (3).

  FIG. 6 shows an example of the configuration of the rotational position calculation unit 11. The comparators 21u, 21v, and 21w compare the calculated induced voltage difference estimated values Evwu, Ewuv, and Evwu with threshold values, and generate pulse-shaped signals. As shown in FIG. 5, the pulse signals obtained according to the respective induced voltage difference estimated values have different rotational positions depending on which phase of the induced voltage is used according to the voltage vector. For this reason, the θc ′ calculator 22 switches the pulse to be used as appropriate using the duty Du, Dv, Dw of each phase.

Next, the obtained signal θc ′ is input to the speed calculation unit 23 and the rotational position correction unit 24. The speed calculator 23 calculates the motor speed detection value θc from the amount of change at the timing when the signal θc ′ changes, using equation (4). Further, the rotational position correction unit 24 corrects the amount of change from the change of the signal θc ′ to the next change using the motor speed detection value ωc and the signal θc ′ using the equation (5). The signal θc′z ⁻¹ is the previous value when the signal θc ′ changes, t is the elapsed time since the signal θc ′ changes, and is cleared to zero when the signal θc ′ changes. By these processes, a position detection value θc corresponding to the rotational position θ of the motor is obtained.

The three-phase voltage command value generation unit 12 shown in FIG. 1 calculates a three-phase voltage command value based on the obtained rotational position θc, for example, as shown in equation (6). The voltage amplitude command value Vamp is the magnitude of the applied voltage, and φv is the phase difference of each phase voltage with respect to the induced voltage phase.

The generated three-phase voltage command values Vu, Vv, and Vw are normalized by being divided by the DC power supply voltage VDC in the duty generator 13 as shown in the equation (7), and modulated commands (duty) Du, Dv, Dw. Further, these duties Du, Dv, and Dw are compared with the triangular wave carrier, converted into each phase PWM signal, and input to each FET 4 of the inverter circuit 3 to generate a voltage for driving the motor 2.

  As described above, according to the present embodiment, when the current detection unit 7 detects each phase current output from the inverter circuit 3, the current change amount detection unit 8 detects the change amount of each phase current. The induced voltage calculation unit 10 is detected during a period in which an arbitrary two-phase lower arm is on and a period in which a three-phase lower arm is on, among the three-phase arms constituting the inverter circuit 3. From the two-phase current change amount and the one-phase current change amount excluding the two phases detected during the period when the lower arm of the three phases is on, the rotational position is expressed by the equations (1) to (3). , The induced voltage difference estimated values Evwu, Ewuv, Evwu are obtained. The rotational position calculator 11 detects the rotational position θc of the permanent magnet motor from the calculation result.

As a result, the motor control device 15 can be constituted by an inexpensive arithmetic unit, and a sine wave current can be applied to the motor 2. Further, the present invention can be applied to a motor having no magnetic saliency, and the motor can be driven even at a high modulation rate. Furthermore, since the period for detecting the current change amount can be long, noise resistance is also improved.
Further, since the current detection units 7u, 7v, and 7w are arranged between the three-phase lower arm constituting the inverter circuit 3 and the negative power supply line, the lower FETs 4U−, 4V−, and 4W− Each phase current can be detected during the ON period.

(Other embodiments)
The current detector 7 may be disposed between the two-phase lower arm and the negative power supply line, and the remaining one-phase current may be obtained by calculation.
The current detection unit may be a CT (Current Trans) instead of a shunt resistor.
As the switching element, an IGBT, a power transistor, or a wide gap semiconductor such as SiC or GaN may be used in addition to the MOSFET.

Although the rotation position calculation unit 11 uses a pulse by comparison with a threshold value, the rotation position may be obtained by direct calculation.
Although several embodiments of the present invention have been described, these embodiments have been presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  In the drawings, 2 is a permanent magnet synchronous motor, 3 is an inverter circuit, 7U, 7V, and 7W are resistance elements (current detection units), 8 is a current change amount detection unit, 10 is an induced voltage calculation unit (rotation position detection unit), Reference numeral 11 denotes a rotational position calculation unit (rotational position detection unit), 14 denotes a rotational position detection device, and 15 denotes a motor control device.

Claims (3)

An inverter circuit for driving a three-phase permanent magnet motor;
A current detector for detecting each phase current output from the inverter circuit;
A current change amount detection unit for detecting a change amount of the phase current;
Of the three-phase arms constituting the inverter circuit,
A current change amount of the two phases detected during a period in which the lower arm of any two phase is on and a period in which the lower arm of the three phase is on;
A calculation result including rotational position information is obtained from a current change amount of one phase excluding the two phases detected during a period when the lower arm of the three phases is on, and the permanent result is obtained from the calculation result. A rotational position detection apparatus comprising: a rotational position detection unit that detects a rotational position of a magnet motor.   The rotational position detection device according to claim 1, wherein the current detection unit is disposed between a three-phase lower arm constituting the inverter circuit and a negative power supply line.   Detected during the period when any two-phase lower arm is on and the period when the three-phase lower arm is on, among the three-phase arms that constitute the inverter circuit that drives the three-phase permanent magnet motor The calculation includes rotational position information from the two-phase current change amount and the one-phase current change amount excluding the two phases detected during the period when the lower arm of the three phases is on. A rotation position detection method for obtaining a result and detecting a rotation position of the permanent magnet motor from the calculation result.

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