JP2007209181A - Control unit of three-phase alternating current motor, and method and control program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a three-phase alternating current motor, which simplifies a controlling method, for example, to enable sub-harmonic modulation, and further to decrease DC voltage to be used, in an induction motor by means of a five-leg inverter. <P>SOLUTION: A control unit 10 includes phase voltage command value conversion means 14 and switching pattern determining means 16. The phase voltage command value conversion means 14 inputs respective phase voltage command values of induction motors IM1, IM2, and converts the respective phase voltage command values in question so that the phase voltage command values of the induction motors IM1, IM2 at a leg 125 become the same sine wave. The switching pattern determining means 16 determines switching patterns of a switch S11, etc. by performing pulse with modulation using the phase voltage command values converted by the phase voltage command value conversion means 14. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention is an apparatus and method for independently controlling two three-phase AC motors using a 5-leg inverter having a configuration in which two electronic switches connected in series are connected in parallel to each other. And a control program. The three-phase AC motor is, for example, a three-phase induction motor (hereinafter simply referred to as “induction motor”). A “leg” is a configuration in which two electronic switches are connected in series, that is, a single-phase half-bridge inverter.

  To control one induction motor, one 3-leg inverter is required. Therefore, as shown in FIG. 14 [1], two independent three-leg inverters 91 and 92 are generally required to independently control the two induction motors IM1 and IM2 connected in parallel to the DC power supply line 90. become. However, this requires two 3-leg inverters, which is not preferable in terms of size reduction, weight reduction, price reduction, and the like. Therefore, as shown in FIG. 14 [2], the two induction motors IM1 and IM2 are independently controlled by using a 5-leg inverter 93 obtained by reducing one leg from the two 3-leg inverters 91 and 92. Technology has been proposed. (For example, the following patent document 1).

  The 5-leg inverter 93 is obtained by sharing one leg among the two 3-leg inverters 91 and 92 by the two induction motors IM1 and IM2, thereby forming five legs. That is, one leg is commonly connected to both w phases of induction motors IM1 and IM2, and the other leg is connected only to one u phase and v phase of induction motors IM1 and IM2.

  At this time, a problem in performing PWM control is switching of legs commonly connected to both induction motors IM1 and IM2. That is, if normal PWM control such as subharmonic modulation is used as it is, inconsistency occurs in the switching signal sent to this common leg when the induction motors IM1 and IM2 are controlled independently.

  Therefore, the modulation period is divided into two equal parts. In the first half, the modulation related to the induction motor IM1 is performed and the line voltage applied to the induction motor IM2 is set to zero. In the second half, the line voltage applied to the induction motor IM1 is set to zero. Modulates IM2. In other words, the induction motor IM1 is controlled based on the three line voltage command values in the first half of the modulation period, and then the three-phase induction motor IM2 is controlled based on the three line voltage command values in the second half of the modulation period. To do.

  Non-Patent Document 1 describes “extended 2-arm modulation” which will be described in detail later.

JP 20003-339189 A Kimura, Hitsuji, Matsuse: "Independent control vector control and extended 2-arm modulation of two PMSMs with a 5-leg inverter", 2005 IEEJ National Convention, 4-094 Enrique Ledezma, Brenden McGrath, Alfred Munoz, and Thomas A. Lipo: “DualAC-Drive System With a Reduced Switch Count”, IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, Vol.37, No.5 pp.1325-1333 (2001)

  However, since the 5-leg inverter 93 modulates the induction motors IM1 and IM2 in half of the normal modulation period, there is a problem that a DC voltage twice that of a normal one is required. In addition, the induction motor IM1 is controlled based on the three line voltage command values in the first half of the modulation period, and then the three-phase induction motor IM2 is controlled based on the three line voltage command values in the second half of the modulation period. Thus, the control method has become complicated. On the other hand, even with the extended two-arm modulation, there is a problem that the DC voltage used is still high.

  Accordingly, an object of the present invention is to provide a control device or the like that can simplify the control method, enable sub-harmonic modulation, for example, and reduce the DC voltage to be used.

  The control device according to the present invention includes first to fifth legs among first to fifth legs of a configuration (five-leg inverter) in which five legs each having two electronic switches connected in series are connected in parallel. The first induction motor is controlled using the second and fifth legs, and the second induction motor is controlled using the third, fourth, and fifth legs. And the control apparatus which concerns on this invention was equipped with the phase voltage command value conversion means and the switching pattern determination means, It is characterized by the above-mentioned. The phase voltage command value conversion means inputs the phase voltage command values of the first and second induction motors, and the sine with the same phase voltage command values of the first and second three-phase AC motors in the fifth leg. Each phase voltage command value is converted so as to be a wave. The switching pattern determining means determines the switching pattern of the electronic switch by performing pulse width modulation using each phase voltage command value converted by the phase voltage command value converting means.

  The first and second induction motors share the fifth leg. In the prior art, the switching signal of the fifth leg for driving the first induction motor and the switching signal of the fifth leg for driving the second induction motor were different at the same time. Therefore, since the contradiction occurs in the switching signal of the fifth leg when using the normal PWM control, the modulation period is divided into two equal parts, the first induction motor is driven in the first half, and the second induction motor in the second half. It needed complicated control to drive. In addition, by dividing the modulation period into two equal parts and driving the first and second induction motors in each period, the time for applying a voltage to each induction motor is halved. It was doubled.

  In contrast, in the present invention, the input phase voltage command values are converted so that the phase voltage command values of the first and second three-phase AC motors in the fifth leg are the same sine wave. That is, the switching signal of the fifth leg for driving the first induction motor and the switching signal of the fifth leg for driving the second induction motor can be made the same. For this reason, since there is no contradiction in these switching signals, simple control such as subharmonic modulation can be used. In addition, since it is not necessary to divide the modulation period into two and drive the first and second induction motors in each period, the DC voltage to be used is also reduced.

  In the extended two-arm modulation, the input phase voltage command value is converted so that the phase voltage command value in the fifth leg becomes zero. In this case, the line voltage is the difference between positive and zero, or the difference between negative and zero. On the other hand, in the present invention, the input phase voltage command values are converted so that the phase voltage command values in the fifth leg are sine waves. In this case, the line voltage is a difference between positive and negative, or a difference between negative and positive. That is, according to the present invention, the line voltage can be increased as compared with the extended two-arm modulation, so that the DC voltage to be used can be decreased.

For example, the phase voltage command value conversion means operates as follows. The phases of the first three-phase AC motor are u1, v1, w1, the phase voltage command values are v ^* _um1 , v ^* _vm1 , v ^* _wm1 , and the phases of the second three-phase AC motor are u2, v2. , _W2 , where these phase voltage command values are v ^* _um2 , v ^* _vm2 , v ^* _wm2 , and phase voltage command values corresponding to the same sine wave are v ' ^* _w , each phase voltage command value v ^* _um1 , V ^* _vm1 , and v ^* _wm1 are input, and these are _converted into respective phase voltage command values v ^* _um1− v ^* _wm1 + v ′ ^* _w , v ^* _vm1− v ^* _wm1 + v ′ ^* _w , v ′ ^* _w In addition, each phase voltage command value v ^* _um2 , v ^* _vm2 , v ^* _wm2 is input, and each phase voltage command value v ^* _um2− v ^* _wm2 + v ′ ^* _w , v ^* _vm2− v ^* _wm2 + v ′. ^* _w , v ' ^* _w is converted.

For example, the switching pattern determination unit operates as follows. The first three-phase AC motor based on the magnitude relationship between each phase voltage command value v ^* _um1− v ^* _wm1 + v ′ ^* _w , v ^* _vm1− v ^* _wm1 + v ′ ^* _w , v ′ ^* _w and the carrier signal _Is determined based on the magnitude relationship between each phase voltage command value v ^* _um2− v ^* _wm2 + v ′ ^* _w , v ^* _vm2− v ^* _wm2 + v ′ ^* _w , v ′ ^* _w and the carrier signal. The switching pattern for the second three-phase AC motor is determined, and the switching pattern for the first three-phase AC motor and the switching pattern for the second three-phase AC motor are the same in the fifth leg. Decide to be. Each phase voltage command value v ^* _um1 , v ^* _vm1 , v ^* _wm1 , v ^* _um2 , v ^* _vm2 , v ^* _wm2 consists of a sine wave signal, for example. The carrier wave signal is, for example, a triangular wave signal or a sawtooth wave signal. Further, the pulse width modulation may be subharmonic modulation. Subharmonic modulation is pulse width modulation when the frequency of the carrier signal is sufficiently higher than the frequency of each phase voltage command value.

  The control method according to the present invention captures the operation of each means of the control device according to the present invention as a procedure. The control program according to the present invention is for causing a computer to execute each step of the control method according to the present invention.

  According to the present invention, by converting each phase voltage command value so that the phase voltage command value in the fifth leg shared by the first and second three-phase AC motors is a sine wave, Since the switching signal of the fifth leg for driving the three-phase AC motor and the switching signal of the fifth leg for driving the second three-phase AC motor can be made the same, such as sub-harmonic modulation Simple control can be used. In addition, it is not necessary to divide the modulation period into two equal parts and drive the first and second three-phase AC motors in each period, and the line voltage can be made higher than in the case of the extended two-arm modulation. DC voltage can also be lowered.

  FIG. 1 is a block diagram showing an embodiment of a control device according to the present invention. FIG. 2 is a circuit diagram showing a configuration of a 5-leg inverter. FIG. 3 is a block diagram showing phase voltage command value conversion means in the control device of FIG. Hereinafter, description will be given based on these drawings.

  As shown in FIG. 2, the 5-leg inverter 12 is composed of five legs 121,... Connected in series with two electronic switches S 11,. Are voltage-type PWM inverters that convert the DC voltage E into an AC voltage by alternately turning on and off the switches S11,. Leg 121 is composed of switches S11 and S12, leg 122 is composed of switches S21 and S22, leg 123 is composed of switches S31 and S32, leg 124 is composed of switches S41 and S42, and leg 125 is composed of switches S51 and S52.

  In the leg 121, the switches S11 and S12 are not turned on at the same time. This is because the DC voltage E is short-circuited. On the other hand, in the leg 121, the switches S11 and S12 are not simultaneously turned off. This is to keep the output current continuous. That is, one of the switches S11 and S12 is always on and the other is off. The same applies to the legs 122 to 125.

The switches S11, S21, S31, S41, and S51 constitute the upper arm 131, and the switches S12, S22, S32, S42, and S52 constitute the lower arm 132. For example, the switches S11,.
gate bipolar transistor). In the switches S11,..., Feedback diodes connected in antiparallel to the transistors provide a path for delayed current. The IGBT is only an example, and a power MOSFET or the like may be used instead.

  As shown in FIGS. 1 and 2, the control device 10 controls the induction motor IM1 using the legs 121, 122, and 125, and controls the induction motor IM2 using the legs 123, 124, and 125. As shown in FIG. 1, the control device 10 includes a phase voltage command value conversion unit 14 and a switching pattern determination unit 16. The phase voltage command value conversion means 14 inputs the phase voltage command values of the induction motors IM1 and IM2, and the phase voltage command values of the induction motors IM1 and IM2 in the leg 125 become the same sine wave. Convert voltage command value. The switching pattern determination means 16 determines the switching pattern of the switches S11,... By performing pulse width modulation using each phase voltage command value converted by the phase voltage command value conversion means. As shown in FIG. 3, the phase voltage command value conversion means 14 includes a front stage 141 and a rear stage 142.

  FIG. 4 is a functional block diagram of the entire control system including the control device 10. Hereinafter, description will be given based on FIG. 1 and FIG.

  This control system is a general system composed of vector control. Further, in order to be able to control the induction motors IM1 and IM2 independently, the induction motors IM1 and IM2 are constituted by separate algorithms. 4 correspond to the control device 10 and the 5-leg inverter 12 in FIG. Except for the induction motors IM1 and IM2 and the 5-leg inverter 12, each block including the control device 10 is realized by a computer program.

Next, since the control methods for the induction motors IM1 and IM2 are the same, the outline of the operation will be described with the subscripts 1 and 2 omitted. First, a necessary torque command τ ^* _e is calculated by PI control based on the actual speed ω _r and the speed command ω ^* _r . Then, based on the torque command τ ^* _e and the secondary magnetic flux command Φ ^{e *} _dr , a torque component current command i ^{e *} _qs and an excitation component current i ^{e *} _ds are obtained, and the actual current i ^e _qs , corresponding to these respectively. based on the i ^e _ds, PI control, coordinate transformation, and obtaining the necessary voltage through a two-to-three phase conversion. These voltages are phase voltage command values v ^* _um , v ^* _vm , and v ^* _wm , and are output to the control device 10. Also, the primary currents i _um , i _vm , i _wm are detected, the actual currents i ^e _qs , i ^e _ds are obtained from the primary currents i _um , i _vm , i _wm , and fed back to calculate the coordinate transformation. Use. The above processing is executed separately for induction motors IM1 and IM2. That is, general vector control is performed independently in each induction motor IM1, IM2.

Furthermore, in this embodiment, it is necessary to match the frequencies of the induction motors IM1 and IM2. In terms of FIG. 4, is that to match the angular frequency command omega ^* ₂ angular frequency command omega ^* ₁ and the induction motor IM2 of the induction motor IM1. Therefore, based on the angular frequency command omega ^* ₂ angular frequency command omega ^* ₁ and the induction motor IM2 of the induction motor IM1, it calculates the secondary magnetic flux correction command .DELTA..PHI ^{e *} _dr1 of the induction motor IM1 required by the PI control. Then, a new secondary magnetic flux command Φ ^{e *} _{dr1_ref} of the induction motor IM1 is obtained by adding to the secondary magnetic flux command Φ ^{e *} _dr1 of the original induction motor IM1. Here, the frequency of the induction motor IM1 is set to the frequency of the induction motor IM2, but the reverse is also possible.

  FIG. 5 is a flowchart showing the operation of the control device 10. FIG. 6 is a waveform diagram showing the phase voltage command value before conversion. FIG. 6 [1] is for the induction motor IM1, and FIG. 6 [2] is for the induction motor IM2. FIG. 7 is a waveform diagram showing the phase voltage command value after the conversion at the front stage 141. FIG. 7 [1] is for the induction motor IM1, and FIG. 7 [2] is for the induction motor IM2. FIG. 8 is a waveform diagram showing the phase voltage command value after conversion by the rear stage 142. FIG. 8 [1] is for the induction motor IM1, and FIG. 8 [2] is for the induction motor IM2. FIG. 9 is a waveform diagram showing a switching pattern based on the phase voltage command value of FIG. 8 [1]. FIG. 10 is a waveform diagram showing a switching pattern based on the phase voltage command value of FIG. 8 [2]. FIG. 11 is a waveform diagram showing the output line voltage based on the switching pattern of FIG. FIG. 12 is a waveform diagram showing the output line voltage based on the switching pattern of FIG. The following description will be given with reference to FIGS. 1 to 3 as appropriate, centering on FIGS. 6 to 12, the unit of time on the horizontal axis is [s], the unit of phase voltage command value and output line voltage is [V], and the switching pattern “1” is on and “0” is off. It is.

First, each phase of the induction motor IM1 is u1, v1, w1, these phase voltage command values are v ^* _um1 , v ^* _vm1 , v ^* _wm1 , each phase of the induction motor IM2 is u2, v2, w2, and these The phase voltage command values are v ^* _um2 , v ^* _vm2 , and v ^* _wm2, and the phase voltage command value corresponding to a sine wave is v ' ^* _w .

First, the phase voltage command value conversion means 14 _inputs each phase voltage command value v ^* _um1 , v ^* _vm1 , v ^* _wm1 (step 101), and these are inputted to each phase voltage command value v ^* _um1− v ^* _wm1 + v. ' ^* _w , v ^* _vm1 -v ^* _wm1 + v' ^* _w , v ' ^* _w (step 102), and the phase voltage command values v ^* _um2 , v ^* _vm2 , v ^* _wm2 are input (step 101), these are _converted into respective phase voltage command values v ^* _um2− v ^* _wm2 + v ′ ^* _w , v ^* _vm2− v ^* _wm2 + v ′ ^* _w , v ′ ^* _w (step 102).

More specifically, the pre-stage unit 141 of the phase voltage command value conversion means 14 _inputs the phase voltage command values v ^* _um1 , v ^* _vm1 , v ^* _wm1 , v ^* _um2 , v ^* _vm2 , v ^* _wm2 , Each phase voltage command value v ^* _u1 , v ^* _v1 , v ^* _u2 , v ^* _v2 , v ^* _w of the following equation is calculated (FIG. 3).

v ^* _u1 = v ^* _um1− v ^* _wm1
v ^* _v1 = v ^* _vm1 -v ^* _wm1
v ^* _u2 = v ^* _um2− v ^* _wm2
v ^* _v2 = v ^* _vm2 -v ^* _wm2
v ^* _w = 0 (∵v ^* _w1 = v ^* _wm1− v ^* _wm1 = 0, v ^* _w2 = v ^* _wm2− v ^* _wm2 = 0) (A)

Equation (A) is a phase voltage command value used in the extended two-arm modulation. Subsequently, the post-stage unit 142 inputs the phase voltage command values v ^* _u1 , v ^* _v1 , v ^* _u2 , v ^* _v2 , and v ^* _w obtained in the pre-stage unit 141, and a phase voltage command composed of a sine wave. Using the values v ′ ^* _w , the phase voltage command values v ′ ^* _u1 , v ′ ^* _v1 , v ′ ^* _u2 , v ′ ^* _v2 , and v ′ ^* _w of the following equations are calculated (FIG. 3).

v ′ ^* _u1 = v ^* _u1 + v ′ ^* _w
v ′ ^* _v1 = v ^* _v1 + v ′ ^* _w
v ′ ^* _u2 = v ^* _u2 + v ′ ^* _w
v ′ ^* _v2 = v ^* _v2 + v ′ ^* _w
v ′ ^* _w = v ′ ^* _w (B)

As shown in FIG. 6 [1], the phase voltage command values v ^* _um1 , v ^* _vm1 , and v ^* _wm1 for the induction motor IM1 are each composed of a sine wave signal and are 120 ° out of phase with each other. Similarly, the phase voltage command values v ^* _um2 , v ^* _vm2 , and v ^* _wm2 for the induction motor IM2 are each composed of a sine wave signal and are 120 ° out of phase with each other. The phase voltage command values v ^* _um1 , v ^* _vm1 , and v ^* _wm1 and the phase voltage command values v ^* _um2 , v ^* _vm2 , and v ^* _wm2 have different amplitudes and substantially the same frequency and phase.

Subsequently, the switching pattern determination means 16 determines the switching pattern for the induction motor IM1 based on the magnitude relationship between the phase voltage command values v ′ ^* _u1 , v ′ ^* _v1 , v ′ ^* _w and the triangular wave signal, Based on the magnitude relationship between the phase voltage command values v ′ ^* _u2 , v ′ ^* _v2 , v ′ ^* _w and the triangular wave signal, the switching pattern for the induction motor IM2 is determined (step 103, FIG. 8). Specifically, each phase voltage command value v ′ ^* _u1 ,... Is compared with a triangular wave signal, and when each phase voltage command value v ′ ^* _u1 ,. Control is performed to turn on the switches S11, S21, S31, S41, and S51 on the arm 131 side (FIGS. 9 and 10). Note that the switches S12, S22, S32, S42, and S52 on the lower arm 132 side operate in reverse to the switches S11, S21, S31, S41, and S51 on the upper arm 131 side. Thus, the operation of the switching pattern determining means 16 is subharmonic modulation.

FIG. 8 [1] shows the phase voltage command values v ′ ^* _u1 , v ′ ^* _v1 , and v ′ ^* _w after conversion. Similarly, FIG. 8 [2] shows converted phase voltage command values v ′ ^* _u2 , v ′ ^* _v2 , and v ′ ^* _w . As shown in FIG. 8, the triangular wave signal for the induction motor IM1 and the triangular wave signal for the induction motor IM2 have the same amplitude, the same frequency, and the same phase. As a result, since it is a comparison between two completely identical triangular wave signals and a sinusoidal phase voltage command value v ′ ^* _w , switching in the leg 125 is performed using the switching pattern for the induction motor IM1 and the switching pattern for the induction motor IM2. The pattern is the same (bottom stage in FIG. 9, bottom part in FIG. 10).

  Finally, the switching pattern determination means 16 outputs each switching pattern shown in FIGS. 9 and 10 to the 5-leg inverter 12 (step 104). As a result, as shown in FIGS. 11 and 12, an output line voltage is generated based on the switching pattern. At this time, the switch S11 is the u phase of the induction motor IM1, the switch S21 is the v phase of the induction motor IM1, the switch S31 is the u phase of the induction motor IM2, the switch S41 is the v phase of the induction motor IM2, and the switch S51 is the induction motor IM1, Since it corresponds to the respective phase voltage commands of both w phases of IM2, the output line voltage is as follows.

Induction motor IM1: between uv S11-S21 / vw S21-S51 / wu S51-S11
Induction motor IM2: between uv S31-S41 / vw S41-S51 / wu S51-S31

  Next, the control device 10 of the present embodiment will be described in more detail with reference to the drawings with a focus on mathematical formulas.

<1>. Since the extended two-arm modulation 5-leg inverter connects the w phases of two induction motors in common, a switching method applicable to the 3-leg inverter cannot be applied. Non-Patent Document 1 describes that independent control of two induction motors is possible by using extended two-arm modulation applicable to a 5-leg inverter. In the extended 2-arm modulation, the voltage command value to be given to each leg is given as shown in the front stage 141 of FIG. Here, the original u, v, and w phase voltage command values v ^* _um1 , v ^* _vm1 , v ^* _wm1 , which are vector control outputs of the induction motor _IM1 , and the original u, which are vector control outputs of the induction motor IM2. It is assumed that the voltage command values v ^* _um2 , v ^* _vm2 , and v ^* _wm2 for the v and w phases are given by the following equations.

^{_{v * um1 = (E 1/}} 2) sin (ω 1 t + φ 1)
^{_{v * vm1 = (E 1/}} 2) sin (ω 1 t-2π / 3 + φ 1)
^{_{v * wm1 = (E 1/}} 2) sin (ω 1 t-4π / 3 + φ 1) ··· (1)

^{_{v * um2 = (E 2/}} 2) sin (ω 2 t + φ 2)
^{_{v * vm2 = (E 2/}} 2) sin (ω 2 t-2π / 3 + φ 2)
^{_{v * wm2 = (E 2/}} 2) sin (ω 2 t-4π / 3 + φ 2) ··· (2)

ω i: power source angular frequency of motor i (i = 1, 2) φ i: phase angle of motor i (i = 1, 2) E ₁ and E ₂ are variables.

At this time, the voltage command values given to the legs 121 to 125 are given as follows from the equations (1) and (2), respectively.

^{_{v * u1 = v * um1 -v}} * wm1 = (√3E 1/2) sin (ω 1 t-π / 6 + φ 1)
^{_{v * v1 = v * vm1 -v}} * wm1 = (√3E 1/2) sin (ω 1 t-π / 2 + φ 1)
^{_{v * u2 = v * um2 -v}} * wm2 = (√3E 2/2) sin (ω 2 t-π / 6 + φ 2)
^{_{v * v2 = v * vm2 -v}} * wm2 = (√3E 2/2) sin (ω 2 t-π / 2 + φ 2)
v ^* _w = 0 (∵v ^* _w1 = v ^* _wm1− v ^* _wm1 = 0, v ^* _w2 = v ^* _wm2− v ^* _wm2 = 0) (3)

  Since the maximum voltage applied to each leg is E / 2, the constraint conditions in this case are as follows.

0 <E ₁ <E / √3
_{0 <E 2 <E / √3} ··· (4)

  From the equations (3) and (4), the maximum value of the line voltage is E / 2. Since the voltage utilization factor is a ratio between the magnitude of the DC link voltage and the maximum value of the line voltage that can be output, the voltage utilization factor is 50% when extended two-arm modulation is used.

<2> Voltage utilization rate improvement method The voltage utilization rate improvement method used in the present embodiment is the case where the drive conditions of the two induction motors are not extremely different when vector control is applied, that is, the same speed command and non- A situation is assumed in which a balanced load is applied or when substantially the same speed command and a balanced load are applied. Under such conditions, it is possible to match the voltage phase and frequency of both induction motors by correcting the magnetic flux command value (Non-Patent Document 2).

  In the voltage utilization rate improvement method in this embodiment, it is assumed that the voltage phase and frequency of both induction motors are the same. Under such assumptions, appropriate phase voltage command values for improving the voltage utilization factor are obtained. Based on this assumption, the equations (1) and (2) can be rewritten as follows.

^{_{v * um1 = (E 1/}} 2) sin (ωt + φ)
^{_{v * vm1 = (E 1/}} 2) sin (ωt-2π / 3 + φ)
^{_{v * wm1 = (E 1/}} 2) sin (ωt-4π / 3 + φ) ··· (5)

^{_{v * um2 = (E 2/}} 2) sin (ωt + φ)
^{_{v * vm2 = (E 2/}} 2) sin (ωt-2π / 3 + φ)
^{_{v * wm2 = (E 2/}} 2) sin (ωt-4π / 3 + φ) ··· (6)

^{_{v * u1 = v * um1 -v}} * wm1 = (√3E 1/2) sin (ωt-π / 6 + φ)
^{_{v * v1 = v * vm1 -v}} * wm1 = (√3E 1/2) sin (ωt-π / 2 + φ)
^{_{v * u2 = v * um2 -v}} * wm2 = (√3E 2/2) sin (ωt-π / 6 + φ)
^{_{v * v2 = v * vm2 -v}} * wm2 = (√3E 2/2) sin (ωt-π / 2 + φ)
v ^* _w = 0 (∵v ^* _w1 = v ^* _wm1− v ^* _wm1 = 0, v ^* _w2 = v ^* _wm2− v ^* _wm2 = 0) (7)

  In the extended two-arm modulation, w phase is used as a reference, and 0 is given as the phase voltage command value. On the other hand, in this embodiment, a voltage utilization factor is improved by applying a sine wave voltage to the w phase. In the present embodiment, the voltage command values given to the legs 121 to 125 are assumed as follows.

v ′ ^* _u1 = v ^* _u1 + v ′ ^* _w
v ′ ^* _v1 = v ^* _v1 + v ′ ^* _w
v ′ ^* _u2 = v ^* _u2 + v ′ ^* _w
v ′ ^* _v2 = v ^* _v2 + v ′ ^* _w
v ′ ^* _w = v ′ ^* _w (8)

From the equations (7) and (8), if v ′ ^* _w is determined so as to satisfy the following constraint conditions, the output line voltage is √3E / 2, so the voltage utilization rate is 86.6%. Can be raised.

0 <E ₁ <E
_{0 <E 2 <E ··· (} 9)

  From equation (9), the constraints of equation (8) are as follows.

0 ≤ v ' ^* _u1 ≤ E / 2
0 ≤ v ' ^* _v1 ≤ E / 2
0 ≤ v ' ^* _u2 ≤ E / 2
0 ≤ v ' ^* _v2 ≤ E / 2
0 ≦ v ′ ^* _w ≦ E / 2 (10)

The amplitudes of v ^* _ui and v ^* _vi are u ^* _i and v ^* _i , and the amplitudes of v ' ^* _ui , v' ^* _vi and v ' ^* _w are u' ^* _i , v ' ^* _i and w' ^* . To do. Here, i = 1,2. At this time, the following equation holds.

u ^* ₁ = √3E _1/2
v ^* ₁ = √3E _1/2
u ^* ₂ = √3E _{2/2
^{v * 2 = √3E 2/2}} ··· (11)

Moreover, when drawing a vector diagram regarding the induction motor IM1 from the equations (5) to (8), it is as shown in FIG. However, v ^* _um1 is used as a reference axis. A similar vector diagram can be drawn for the induction motor IM2. Note that v ′ ^* _w is a sine wave synchronized with v ^* _wm1 (and v ^* _wm2 ). This facilitates later analysis.

Using the cosine theorem, u ′ ^* ₁ and v ′ ^* ₁ can be obtained, but u ′ ^* ₁ = v ′ ^* ₁ from equation (11). Therefore, it is only necessary to obtain v ′ ^* _w such that v ′ ^* _u1 and v ′ ^* _u2 satisfy the constraint equation (10). With respect to the induction motor IM1, the following inequality is established from FIG. 13 and the equation (10).
_{^{u '* 1 2 = u *}} 1 2 + w' * 2 -√3u * 1 w '* ≦ E 2/4 ··· (12)

From the equation (12), the following function is obtained.
_{f (x 1) = x 1} 2 -√3x 1 + 1 ≦ (E / E 1) 2/3 = E '/ 3 ··· (13)
However,
x ₁ = w ′ ^* / u ^* ₁ (14)

Similarly, the following function is obtained for the induction motor IM2.
_{f (x 2) = x 2} 2 -√3x 2 + 1 ≦ (E / E 2) 2/3 = E '' / 3 ··· (15)
However,
x ₂ = w ′ ^* / u ^* ₂ (16)

Assuming that w ′ ^* is proportional to E ₁ ,
w ' ^* = mE ₁ (17)
far. When m = 0, the extended 2-arm modulation is used.

Also, assuming that E ₁ is proportional to E ₂ ,
E ₁ = kE ₂ (18)
far. However,
0 ≦ k ≦ ∞ (19)

When the equation (15) is rewritten using the equations (16) to (17), the following inequality is obtained.
f (k) = 4 m ² k ² / 3-2mk + 1 ≦ k ² E ′ / 3 (20)

Furthermore, when a new function g is used, the equation (20) can be written as follows.
g (k) = (4m ² −E ′) k ² / 3−2mk + 1 ≦ 0 (21)
here,
g (k) = f (k) −k ² E ′ / 3 (22)

What is necessary is just to define m so that (21) Formula may be satisfy | filled with respect to k which satisfy | fills Formula (19).
4m ² −E ′ = 0 (23)
At this time,
w ' ^* = E / 2 (24)
It becomes.

If Expression (24) is satisfied, Expression (21) is rewritten to a function of only E _{2, and} therefore does not depend on the value of E ₁ . Further, for all E ₁ satisfying the expression (9), the expression (21) is established with all the values of k satisfying the expression (19). That is, the formula (21) is also established for all E ₂ satisfying the formula (9).

Next, the induction motor IM1 is considered. When k = 1, since x1 = x2 and E ′ = E ″, the expression (13) is the same as the expression (15). Since equation (15) holds for all E ₂ satisfying the constraint condition (9) in the range of all k satisfying the equation (19), the constraint condition (9) is considered when the equation (18) is considered. This holds for all E ₁ satisfying the equation. Since the expression (13) is a function of E ₁ , it holds true for all E ₂ satisfying the constraint condition (9).

From the above,
v ′ ^* _w = (E / 2) sin (ωt−4π / 3 + φ) (25)
By giving the voltage command value to the common leg 125, it becomes possible to give the voltage command value satisfying the expression (10) to each leg 121-125. Eventually, the voltage command values given to the legs 121 to 125 are as follows from the equations (3), (8), and (25).

^{_{v '* u1 = (√3E 1}} /2) sin (ωt-π / 6 + φ)
+ (E / 2) sin (ωt-4π / 3 + φ)
^{_{v '* v1 = (√3E 1}} /2) sin (ωt-π / 2 + φ)
+ (E / 2) sin (ωt-4π / 3 + φ)
^{_{v '* u2 = (√3E 2}} /2) sin (ωt-π / 6 + φ)
+ (E / 2) sin (ωt-4π / 3 + φ)
^{_{v '* v2 = (√3E 2}} /2) sin (ωt-π / 2 + φ)
+ (E / 2) sin (ωt-4π / 3 + φ)
v ′ ^* _w = (E / 2) sin (ωt−4π / 3 + φ) (26)

FIG. 7 shows a waveform of the voltage command value when the extended two-arm modulation is applied, and FIG. 8 shows a waveform of the voltage command value when the present embodiment is applied. When the voltage command value is given as in the equation (26), the equation (13) becomes maximum when E ₁ = E. Therefore, when the extended two-arm modulation is compared with this embodiment, the legs 121 to 125 are compared. The maximum value of the voltage command value is 36.6% lower in this embodiment than in the extended two-arm modulation. That is, in this embodiment, the voltage utilization rate can be increased by 36.6% compared to the extended two-arm modulation.

<3. Summary>
In the extended two-arm modulation, the voltage command value applied to the w-phase, which is a common leg, is set to zero. On the other hand, in this embodiment, two induction motors are driven by vector control, and the w phase (leg 125) and other legs are driven under the condition that the drive conditions of the two induction motors are not extremely different. By giving appropriate voltage command values to 121 to 124, it is possible to increase the voltage utilization rate to 86.6%.

  Needless to say, the present invention is not limited to the above embodiment. For example, a synchronous motor may be used instead of the induction motor. In the vector control in this case, as is well known, some changes such as using a rotor position sensor instead of the speed sensor are required.

It is a block diagram which shows one Embodiment of the control apparatus which concerns on this invention. It is a circuit diagram which shows the structure of a 5 leg inverter. It is a block diagram which shows the phase voltage command value conversion means in the control apparatus of FIG. It is a functional block diagram of the whole control system containing the control apparatus of FIG. It is a flowchart which shows operation | movement of the control apparatus of FIG. It is a wave form diagram which shows the phase voltage command value before conversion, FIG. 6 [1] is for induction motor IM1, and FIG. 6 [2] is for induction motor IM2. It is a wave form diagram which shows the phase voltage command value after conversion in the front | former part of a phase voltage command value conversion means, FIG. 7 [1] is for induction motor IM1, and FIG. 7 [2] is for induction motor IM2. FIGS. 8A and 8B are waveform diagrams showing phase voltage command values after conversion at the rear stage of the phase voltage command value conversion means, in which FIG. 8 [1] is for the induction motor IM1, and FIG. 8 [2] is for the induction motor IM2. It is a wave form diagram which shows the switching pattern based on the phase voltage command value of FIG. 8 [1]. It is a wave form diagram which shows the switching pattern based on the phase voltage command value of FIG. 8 [2]. It is a wave form diagram which shows the output line voltage based on the switching pattern of FIG. It is a wave form diagram which shows the output line voltage based on the switching pattern of FIG. It is a vector diagram which shows each phase voltage command value in the control apparatus of FIG. It is a circuit diagram which shows a prior art, FIG. 14 [1] is a 1st example, FIG. 14 [2] is a 2nd example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Control apparatus 12 5 leg inverters 121-125 leg 14 phase voltage command value conversion means 141 front part 142 back stage 16 switching pattern determination means IM1, IM2 induction motor (three-phase AC motor)
v ^* _um1 , v ^* _vm1 , v ^* _wm1 , v ^* _um2 , v ^* _vm2 , v ^* _wm2 phase voltage command values before conversion v ' ^* _u1 , v' ^* _v1 , v ' ^* _u2 , v' ^* _v2 , v ' ^* _w phase voltage command value after conversion S11, S21, S31, S41, S51, S12, S22, S32, S42, S52 switch

Claims (9)

Of the first to fifth legs having two electronic switches connected in series and five legs connected in parallel, the first, second and fifth legs are used to In the apparatus for controlling a three-phase AC motor and controlling a second three-phase AC motor using the third, fourth and fifth legs,
The phase voltage command values of the first and second three-phase AC motors are input, and the phase voltage command values of the first and second three-phase AC motors in the fifth leg are the same sine wave. A phase voltage command value converting means for converting each phase voltage command value,
Switching pattern determining means for determining a switching pattern of the electronic switch by performing pulse width modulation using each phase voltage command value converted by the phase voltage command value converting means;
A control device for a three-phase AC motor, comprising: The phases of the first three-phase AC motor are u1, v1, and w1, the phase voltage command values are v ^* _um1 , v ^* _vm1 , and v ^* _wm1 , and the phases of the second three-phase AC motor are u2. , V2, w2, when these phase voltage command values are v ^* _um2 , v ^* _vm2 , v ^* _wm2 , and the phase voltage command values corresponding to the same sine wave are v ′ ^* _w ,
The phase voltage command value conversion means _inputs the phase voltage command values v ^* _um1 , v ^* _vm1 , and v ^* _wm1, and inputs them into the phase voltage command values v ^* _um1− v ^* _wm1 + v ′ ^* _w , v ^* _vm1− v ^* _wm1 + v ′ ^* _w , v ′ ^* _w, and the phase voltage command values v ^* _um2 , v ^* _vm2 , v ^* _wm2 are input, and these are _converted to the phase voltage command values v ^*. _um2 −v ^* _wm2 + v ′ ^* _w , v ^* _vm2 −v ^* _wm2 + v ′ ^* _w , v ′ ^* _w ,
The control device for a three-phase AC motor according to claim 1. The switching pattern determining means includes
Based on the magnitude relationship between each phase voltage command value v ^* _um1− v ^* _wm1 + v ′ ^* _w , v ^* _vm1− v ^* _wm1 + v ′ ^* _w , v ′ ^* _w and the carrier signal, the first three phases While determining the switching pattern for the AC motor,
Based on the magnitude relationship between the respective phase voltage command values v ^* _um2− v ^* _wm2 + v ′ ^* _w , v ^* _vm2− v ^* _wm2 + v ′ ^* _w , v ′ ^* _w and the carrier signal, the second three Determining the switching pattern for the phase AC motor;
And the switching pattern for the first three-phase AC motor and the switching pattern for the second three-phase AC motor are determined so that the switching pattern in the fifth leg is the same.
The control device for a three-phase AC motor according to claim 2. The phase voltage command values v ^* _um1 , v ^* _vm1 , v ^* _wm1 , v ^* _um2 , v ^* _vm2 , and v ^* _wm2 are sine wave signals.
The control device for a three-phase AC motor according to claim 3. The carrier signal comprises a triangular wave signal or a sawtooth wave signal,
The control device for a three-phase AC motor according to claim 3. The pulse width modulation is sub-harmonic modulation;
The control device for a three-phase AC motor according to any one of claims 1 to 5. The three-phase AC motor is a three-phase induction motor;
The control apparatus of the three-phase alternating current motor of any one of Claims 1 thru | or 6.

In a method of controlling the first and second three-phase AC motors using a five-leg inverter having a configuration in which five legs each having two electronic switches connected in series are connected in parallel,
Each phase voltage command value of the first and second three-phase AC motors is input, and the first and second three-phase AC motors in the leg common to the first and second three-phase AC motors A phase voltage command value conversion step for converting each phase voltage command value so that the phase voltage command values of
A switching pattern determination step for determining a switching pattern of the electronic switch by performing pulse width modulation using each phase voltage command value converted in the phase voltage command value conversion step;
A control method for a three-phase AC motor, comprising:
In a program for controlling the first and second three-phase AC motors using a 5-leg inverter having a configuration in which two legs each having two electronic switches connected in series are connected in parallel,
Each phase voltage command value of the first and second three-phase AC motors is input, and the first and second three-phase AC motors in the leg common to the first and second three-phase AC motors A phase voltage command value conversion step for converting each phase voltage command value so that the phase voltage command values of
A switching pattern determining step for determining a switching pattern of the electronic switch by performing pulse width modulation using each phase voltage command value converted in the phase voltage command value converting step;
A computer-executable control program for a three-phase AC motor.

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