KR101842781B1 - Device and method for detecting rotational position - Google Patents

Abstract

A rotational position detecting device of an embodiment includes an inverter circuit for driving a three-phase permanent magnet motor, a current detecting section for detecting each phase current output from the inverter circuit, a current variation amount detecting section for detecting a variation amount of the phase current, Wherein a current change amount of the two phases detected during a period in which the lower arm of any two phases of the three-phase arm constituting the inverter circuit is on and a period in which the lower arm of the three phases are on, And a rotational position detecting section for obtaining an operation result including information on the rotational position from the current change amount of one phase other than the two phases and detecting the rotational position of the permanent magnet motor from the calculation result.

Description

Technical Field [0001] The present invention relates to a rotational position detecting device and a rotational position detecting method,

An embodiment of the present invention relates to an apparatus and method for detecting the rotational position of a permanent magnet motor.

As a conventional method of estimating the rotational position of a permanent magnet synchronous motor, a patent document 1 proposes a rotational position detecting system capable of energizing a sinusoidal current with an inexpensive configuration by using current differential values during voltage application . In this method, the current change amount at the time of generation of the zero voltage vector is obtained based on the phase voltage equation of the motor, and the rotation position information of the motor included in the current change amount is used.

Japanese Patent Laid-Open No. 2007-336641

However, in the method according to Patent Document 1, when the modulation rate is increased by rotating the motor at high speed, as shown in Fig. 8, the output of the zero voltage vector for detecting the current change amount There is a problem that the accuracy of position estimation is lowered because the period is shortened.

Therefore, a rotational position detecting device and a rotational position detecting method capable of maintaining position estimation accuracy even in a control state with a high modulation rate are provided.

A rotational position detecting device of an embodiment includes an inverter circuit for driving a three-phase permanent magnet motor, a current detecting section for detecting each phase current output from the inverter circuit, a current variation amount detecting section for detecting a variation amount of the phase current, Wherein a current change amount of the two phases detected during a period in which the lower arm of any two phases of the three-phase arm constituting the inverter circuit is on and a period in which the lower arm of the three phases are on, And a rotational position detecting section for obtaining an operation result including information on the rotational position from the current change amount of one phase other than the two phases and detecting the rotational position of the permanent magnet motor from the calculation result.

Fig. 1 is a diagram showing a configuration of a motor control apparatus as one embodiment. Fig.
2 is a diagram showing a voltage generated by an inverter circuit as a space vector;
Fig. 3 is a diagram showing respective phase voltage values of the motor when each voltage vector is outputted; Fig.
Figure 4 is within the PWM period, the current change amount dI _v, a timing chart showing a state of detecting the dI _{w, u} dI.
5 is a time-axis diagram showing the relationship between the rotational position of the motor, the induced voltage, and the estimated difference value;
6 is a diagram showing an example of a configuration of a rotational position calculating section;
Fig. 7 is a view similar to Fig. 4 (first) for explaining the prior art;
Fig. 8 is a view similar to Fig. 4 (second) illustrating the prior art.

Hereinafter, one embodiment will be described with reference to Figs. 1 to 6. Fig. 1 is a functional block diagram showing a configuration of a motor control device. The DC power supply 1 is a power source for driving a permanent magnet synchronous motor (hereinafter simply referred to as a motor) 2 having permanent magnets in its rotor. The direct current power source 1 may be an alternating current power source converted into a direct current. The inverter circuit 3 is constituted by connecting three switching elements, for example, N-channel MOSFETs 4U +, 4Y +, 4W +, 4U-, 4Y- and 4W- And generates a voltage for driving the motor 2 based on six switching signals for three phases generated in the three-phase inverter circuit.

The voltage detector 6 detects the voltage VDC of the DC power supply 1. A current detector 7 generally includes a shunt resistor or a Hall current sensor and a signal processing circuit using the CT, etc., detects a current I _u, I _v, I _w flowing through the motor (2). 1 shows a case where three (7U, 7V, 7W) are arranged on the lower side of each of the phases of the inverter circuit 3, and in the case of being arranged on the upper side of each phase, Output line.

The current change amount detection unit 8 detects the three-phase current value based on the signals t1, t2, and t3 from the detection timing signal generation unit 9 to be described later, and calculates the respective change amounts dI _u , dI _v , dI _w . Since the detection timing finds the amount of change for two times by detecting three times, the amount of change becomes six signals in total for two types for three phases.

1, dIa, dIb, and dIc denote the current differential values output from the current variation detection section 8, but this is not limited to the area of the space vector in the switching pattern of the inverter circuit 3 , Since the voltage vector to be used is different, the notation is simplified. That is, a, b, and c correspond to any one of u, v, and w. The notation of (bc0) indicates that either one of the lower switches of the b and c phases is ON and the other switch and the lower switch of the a-phase are OFF " 0 & 1 " is not fixed (see equations (1) to (3) described later).

Induced voltage calculation unit 10 (rotational position detection unit) calculates the current change amount dI _{u, v} dI, the induced voltage difference estimated value from the three-phase dI _w E _{uvw, vwu} E, E _wuv on the detected three. The rotational position calculating section 11 (rotational position detection unit) calculates the estimated value E _uvw, E _vwu, the rotational position detection value of the motor (2) from E _wuv θ _c. The three-phase voltage command value generator 12 generates three-phase voltage command values V _u , V _v , V _w from the voltage amplitude command value V _amp and the voltage phase command value φ _v , which are command values.

The duty generating unit 13 calculates the modulation instructions D _u , D _v , and D _w of each phase by dividing the three-phase voltage command values V _u , V _v , and V _w by the dc voltage VDC. The PWM generation unit 5 compares the three-phase modulation instructions D _u , D _v , and D _w with the carriers of the triangular waveform to generate PWM signal pulses of each phase. U +, V +, V-, W +, W-, which are output to the N-channel MOSFET 44 of the upper and lower three phases, respectively.

In the above configuration, the rotational position detecting device 14 is constituted by excluding the motor 2, the inverter circuit 3 and the PWM generating section 5. [ The motor control device 15 is constituted by adding the PWM generating section 5 to the rotational position detecting device 14. [

Next, an outline of the rotational position detecting method according to the present embodiment will be described with reference to Figs. 2 to 5. Fig. The voltage generated by the inverter circuit 3 is divided into six real voltage vectors and two zero voltage vectors as shown in FIG. Here, the voltage vector V ₁ (100) is a voltage vector V ₁ (100) in which the upper switch (FET 4U +) of the U phase is ON, the lower phase switch of the V phase and W phase (FETs 4Y- and 4W-) . 3 shows the phase voltage values of the motor 2 when the respective voltage vectors are output.

For example 4, the timing diagram showing the on period during which the voltage in only the high side switch of the U is turned on vector V ₁ (100) and a zero voltage vector V ₀ (000) are output, and the drawing t1 The difference values of the three-phase currents detected at the time points t1 to t3 are expressed by the following equations.

_{dI v (100) - (000} ): the voltage vector V ₁ and V-phase current amount of change in time for t1-t3 is the time of V ₀ [A]

_{dI w (100) - (000} ): W phase current change amount of the voltage vector V ₁ and V ₀ during time t1-t3 at the time of the application [A]

dI _{u (100)} : U phase current variation [A] during time t1-t2 when voltage vector V ₀ is applied;

E _v , E _w , E _u : induced voltage on v, w, u [V]

θ: Motor rotation position [rad]

L: Motor phase inductance [H]

ω: Angular velocity of motor [rad / s]

φ _f : armature coupling flux [Wb]

Here, the first and second terms on the right side of the equation (1) are signals changing with respect to the rotational position [theta]. Thus, a signal based on the rotational position of the motor 2 can be obtained by calculating the induced voltage difference estimation value E _{vwu according} to the generated voltage vectors V ₁ (100) and V ₀ (000). And rotational position detection is performed using this.

Then, as shown in Fig. 2, if the six regions in the space vector are sectors 1 to 6, the induced voltage difference estimation value E _wuv is calculated by Equation (2) for Sectors 2 and 3.

_{dI w (010) - (000} ): W phase current change amount of the voltage vector V for ₃ and V ₀ is the time t1-t3 at the time of [A]

_{dI u (010) - (000} ): U -phase current change amount of the voltage vector V for ₃ and V ₀ is the time t1-t3 at the time of [A]

dI _{v (000):} V phase current change amount of the voltage vector V ₀ is applied for a time t1-t2 during the [A]

And for the sectors 4 and 5, the induced voltage difference estimation value _Euvw is calculated by Equation (3).

A U phase current variation [A] during time t1-t3 when voltage vector V ₅ and V _{0 are} applied, d _{U u (001) - (000)}

_{dI v (001) - (000} ): V of the voltage vector V for ₅ and V ₀ is the time t1-t3 at the time of the current change amount [A]

dI _{w (000):} voltage vector W phase current amount of change in time for the time t1-t2 is V ₀ [A]

FIG. 5 shows the induced voltage difference estimation values E _vwu , E _wuv , and E _vwu that vary according to the induced voltage of each phase. The portions denoted by thin lines are all waveforms over one period of each electrical period, and the portion indicated by bold lines is a section of the waveform detected by Equations 1 to 3 according to the voltage sectors 1 to 6 . The estimated value of the thick line part for each sector using the E _{vwu, wuv} E, E _vwu and can be determined by detecting the rotational position of the respective zero-cross point. That is, the induced voltage difference estimation values E _vwu , E _wuv , and E _vwu correspond to a "calculation result including information on the rotational position".

Here, the operation of each unit in the present embodiment will be described again. The current change amount detection unit 8 detects the current change amount of each phase at a predetermined timing from the current detected by the current detection unit 7. Timings t1 to t3 for detecting the amount of current change are periods in which a zero voltage vector and each of the actual voltage vectors are generated, as shown in Equations (1) to (3) and FIG. Therefore, the detection timing signals t1 to t3 from the detection timing signal generation section 9 are output to the current variation detection section 8 after the duty D _u , D _v , and D _w of each phase are determined by the duty generation section 13 do. The induced voltage calculating unit 10 calculates a value proportional to the induced voltage from Equations (1) to (3).

Fig. 6 shows an example of the configuration of the rotational position calculating section 11. Fig. The comparators 21u, 21v, and 21w compares the calculated induced voltage difference estimates E _vwu , E _wuv , and E _vwu with threshold _values to generate a pulse-like signal. As shown in Fig. 5, the pulse signal obtained according to each induced voltage difference estimation value is different in rotational position depending on which phase of the induced voltage is used depending on the voltage vector. For this reason, the? _C 'computing unit 22 uses the duty D _u , D _v , and D _w of each phase to switch pulses used appropriately.

Then, the obtained signal? _C 'is input to the speed calculating section 23 and the rotational position correcting section 24. The speed calculating section 23 calculates the motor speed detection value? _C from the change amount at the timing at which the signal? _C 'changes, using Equation (4). Further, the rotational position correcting unit 24 corrects the amount of change during the period from the change of the signal? _C 'to the next change using the motor speed detection value? _C and the signal? _C ' . Signal θ _c is the last time value when 'z ^-1 is a signal θ _c "is changed, the signal t' is a time elapsed after the change, the signal θ _c, θ _c is cleared to zero when changes. By this processing, the position detection value? _C corresponding to the rotational position? Of the motor is obtained.

The three-phase voltage command value generator 12 shown in FIG. 1 calculates the three-phase voltage command value, for example, as shown in Equation (6) based on the obtained rotation position? _C. The voltage amplitude command value V _amp is the magnitude of the applied voltage, and _{v v} is the phase difference of each phase voltage relative to the induced voltage phase.

Voltage command value on the generated 3 V _u, V _v, V _w are normalized be divided by the DC power supply voltage VDC according to the duty generator 13, as shown in Equation (7), a modulation command (duty) D _u, D _v , D _w . The duty D _u , D _v , and D _w are compared with the triangular wave carrier to be converted into the phase PWM signals, input to the respective FETs 4 of the inverter circuit 3, .

As described above, according to the present embodiment, when the current detecting section 7 detects each phase current outputted from the inverter circuit 3, the current variation detecting section 8 detects the variation amount of each phase current. The induced voltage calculation unit 10 calculates the induced voltage based on the current variation amount of the two phases detected during the period in which the lower arm of any two phases among the three phase arms constituting the inverter circuit 3 is on and the period in which the lower arm of the three phases is on, , An arithmetic result in which the information on the rotational position is included in the current variation _{amounts of} one phase other than the two phases detected during the period in which the lower arm of the three phases is on is _expressed by Equations (1) to (3) , E _wuv , and E _vwu . The rotation position calculation unit 11 detects the rotation position? _C of the permanent magnet motor from the calculation result.

Thereby, the motor control device 15 can be constituted by an inexpensive computer, and the motor 2 can be supplied with a sinusoidal current. Further, the present invention can be applied to a motor having no magnetic polarity, and the motor can be driven even at a high modulation rate. Further, since the period for detecting the amount of current change can be held longer, the noise immunity is also improved.

Since the current detecting portions 7u, 7v, and 7w are disposed between the lower arm and the negative power supply line of the three phases constituting the inverter circuit 3, the lower FETs 4U-, 4V-, and 4W- It is possible to detect each phase current in the ON period.

(Other Embodiments)

The current detection unit 7 may be disposed between the lower arm of the two phases and the negative power supply line and the current of the remaining one phase may be calculated.

The current detection unit may be CT (Current Trans) instead of a shunt resistor.

The switching element may be an IGBT or a power transistor in addition to the MOSFET, or a wide-gap semiconductor such as SiC or GaN.

Although the rotation position calculation unit 11 uses pulses by comparison with the threshold value, the rotation position may be obtained by direct calculation.

While several embodiments of the present invention have been described, these embodiments are provided by way of example and are not intended to limit the scope of the invention. These new embodiments can be implemented in various other forms, and various omissions, substitutions, and alterations can be made without departing from the gist of the invention. These embodiments and their modifications fall within the scope and spirit of the invention, and are included in the scope of the invention as defined in the claims and their equivalents.

Claims (3)

An inverter circuit for driving the three-phase permanent magnet motor,
A current detector for detecting each phase current output from the inverter circuit,
A current change amount detecting unit for detecting a change amount of the phase current;
Among the three-phase arms constituting the inverter circuit,
_{(100) - (000) of} the two phases detected during a period in which the lower arm of any two phases is on and a period in which the lower arm of the third phase is on, dI _{w (100) - (000)} , dI _{w (010) - (000)} , dl _{u (010) - (000)} , dl _{u (001) - (000)} , dI _{v (001) - (000)}
A current change amount dI _{u (100) of} one phase other than the two phases, which is detected in a period in which the lower arm of the third phase is on, dI _{v (000)} , the induced voltage difference estimation value E _vwu from dI _{w (000)} by the equations (1) to (3) E _wuv , E _uvw is obtained,
Equation (1)

Equation (2)

Equation (3)

The estimated values E _vwu , E _wuv , The position signal? _C 'is periodically obtained by comparing _Euvw with a threshold value,
The position signal θ _c rotation position detecting apparatus having a rotational position detector for detecting the rotational position of the motor by the sum of the angular velocity integration value of the permanent magnet motor obtained from "the last time values and said position signal θ _c ' . The rotational position detecting device according to claim 1, wherein the current detecting unit is disposed between a lower arm of three phases constituting the inverter circuit and a minus side power supply line. The current change amount dI _{v (} 2) of the two phases detected during a period in which the lower arm of any two phases is on and a period in which the lower arm of the three phases are on, of the three-phase arm constituting the inverter circuit for driving the three- _{100) - (000)} , dI _{w (100) - (000)} , dI _{w (010) - (000)} , dl _{u (010) - (000)} , dl _{u (001) - (000)} , dI _{v (001) - (000)} , a current change amount dI _{u (100) of} one phase other than the two phases detected during a period in which the lower arm of the third phase is on, dI _{v (000)} , the induced voltage difference estimation value E _vwu from dI _{w (000)} by the equations (1) to (3) E _wuv , E _uvw is obtained,
Equation (1)

Equation (2)

Equation (3)

The estimated values E _vwu , E _wuv , The position signal? _C 'is periodically obtained by comparing _Euvw with a threshold value,
The position signal θ _c and by the sum of the angular velocity integration value of the permanent magnet motor obtained from "the last time values and said position signal θ _c, the rotational position detecting method for detecting a rotation position of the motor.

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