JP2011101508A - Motor controller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor controller reducing a rasping magnetic sound into low noise by dispersing the one generated from a motor in a two-phase modulation having a switching loss smaller than a three-phase modulation. <P>SOLUTION: The motor controller includes an inverter circuit 5 including switching elements 3a to 3f in a three-phase bridge connection converting DC into AC, and a controller 2 switching each of the switching elements 3a to 3f for the inverter circuit 5 and controlling the motor 6 connected to the inverter circuit 5 in the two-phase modulation. The controller 2 varies each time of t5 and t6 periods without changing the total time of t5 and t6 periods of the switching patterns of zero vectors (000) existing in the first half and second half of a carrier period. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a motor control device that controls a motor by two-phase modulation using an inverter circuit.

In the conventional motor control device, low noise and low vibration are realized by adding an ON period and an OFF period to the two-phase modulation while maintaining the phase voltage of the motor (see, for example, Patent Document 1).
In another motor control device, the harsh magnetism generated by the motor is changed by randomly changing the switching timing without changing the total time of a plurality of OFF periods (zero vectors) within a predetermined period in the three-phase modulation. Noise is reduced by dispersing sound (see, for example, Patent Document 2).

Japanese Patent Laying-Open No. 2005-176565 (6th page, FIG. 4) JP 2002-277074 A (page 3-4, FIG. 2, FIG. 5)

However, the control device described in Patent Document 1 adds an ON period and an OFF period to the two-phase modulation in order to reduce noise, and the switching pattern increases to increase the switching loss, that is, the power consumption increases. There is a problem.
Moreover, since the technique described in Patent Document 2 cannot be realized by two-phase modulation, which has a smaller loss than three-phase modulation, there is a problem that the loss increases, that is, power consumption increases, compared to two-phase modulation.

  The present invention has been made to solve the above-described problems. In two-phase modulation in which switching loss is smaller than that in three-phase modulation, it is possible to reduce noise by dispersing harsh magnetic sounds generated from a motor. An object of the present invention is to obtain a motor control device that can be used.

  The motor control device according to the present invention switches an inverter circuit having a switching element of a three-phase bridge connection that converts direct current into alternating current, and switches each switching element of the inverter circuit, and the motor connected to the inverter circuit is subjected to two-phase modulation. A control unit that controls the switching pattern so as to vary each time of the switching pattern without changing the total time of the switching pattern of the switching element for cutting off the energization to the motor every predetermined period. It is a thing.

  In the present invention, since each time of the switching pattern is changed without changing the total time of the switching pattern of the switching element for cutting off the energization to the motor at every predetermined period, it is generated from the motor. It can disperse harsh magnetic sounds and achieve high efficiency and low noise motor control.

It is a circuit diagram which shows the outline of the motor control apparatus in Embodiment 1 of this invention. It is a figure which shows the switching pattern of each switching element at the time of the three-phase modulation in the space vector method using the motor control apparatus of Embodiment 1. FIG. It is a timing diagram which shows the switching pattern of each switching element in A of FIG. It is a figure which shows the switching pattern of each switching element in the conventional two-phase modulation. It is a figure which shows the switching pattern of each switching element in the conventional two-phase modulation. FIG. 5 is a timing chart showing a switching pattern of each switching element at the time of two-phase modulation in the motor control device of the first embodiment with respect to FIG. 4. FIG. 10 is a timing diagram showing a switching pattern of each switching element during two-phase modulation in another form of the first embodiment. FIG. 6 is a timing chart showing a switching pattern of each switching element at the time of two-phase modulation in the motor control device of the second embodiment with respect to FIG. 5. FIG. 10 is a timing diagram showing a switching pattern of each switching element during two-phase modulation in another form of the second embodiment.

Embodiment 1 FIG.
FIG. 1 is a circuit diagram showing an outline of a motor control device according to Embodiment 1 of the present invention.
In FIG. 1, an inverter circuit 5 connected to a DC power source 1 includes three-phase bridge connection switching elements 3a to 3f (for example, bipolar transistors, IGBTs, FETs, etc.) and anti-parallel to each of the switching elements 3a to 3f. It is composed of diodes 4a to 4f that are connected and circulate the motor current. The switching elements 3a to 3c and the diodes 4a to 4c are referred to as a high side, and the switching elements 3d to 3f and the diodes 4d to 4f are referred to as a low side.

  The control unit 2 is composed of, for example, a microcomputer or a DSP, and switches (ON / OFF) the switching elements 3a to 3f of the inverter circuit 5 with a predetermined switching pattern (driving signal), so that the DC voltage of the DC power source 1 is an arbitrary voltage. -It converts into the frequency three-phase alternating current, and controls the drive of the motor 6 connected to the output terminal of the inverter circuit 5 by two-phase modulation.

FIG. 2 is a diagram showing a switching pattern of each switching element at the time of three-phase modulation in the space vector method using the motor control device of the first embodiment.
Numbers such as (100) shown in FIG. 2 indicate the operating states of the switching elements 3a to 3f of the U phase (3a, 3d), V phase (3b, 3e), and W phase (3c, 3f) from the left. . In (100), 1 indicates that the U-phase high-side switching element 3a is ON and the low-side switching element 3d is OFF, and 0 in the center indicates that the V-phase low-side switching element 3e is ON and the high-side side. The switching element 3b is turned off. Further, 0 at the right end turns on the W-phase low-side switching element 3f and turns off the high-side switching element 3c.

  Further, p and n shown in FIG. 2 indicate the high side and the low side, respectively. For example, Up indicates the switching element 3a on the U phase high side, and Un indicates the switching element 3d on the low side of the U phase. ing. t1 to t4 are periods (time) of the switching patterns of the switching elements 3a to 3f, and the total time (t1 to t4) is the carrier period. In FIG. 2, for the sake of simplicity of explanation, a dead time (Td) for preventing a short circuit between the high side and the low side of each switching element 3 a to 3 f is omitted.

Assuming that the direction in which the vector of Vin shown in the drawing turns clockwise is positive, generally, the motor 6 is rotated in a certain direction, for example, in the CW (clockwise) direction, A → B →... F → A The Vin vector may be rotated by increasing the angle θ so as to move the section. For example, in A, the Vin vector is generated by combining the (100) vector and the (110) vector, and the relationship between the angle θ (θ = 0 to 60 °) and t1, t2, t3, and t4 is calculated by the following equation. It can ask for.
K = Vin / Vdc (1)
t1 = 1/2 × t4 = 1/4 × (1−Ksin (θ + 60 °) −Ksinθ) · T (2)
t2 = 1/2 × KTsin (60 ° −θ) (3)
t3 = 1/2 × KTsinθ (4)
Here, Vin is a voltage applied to the motor 6, Vdc is a bus voltage, T is a carrier period, and K is a modulation rate.

  The vector of t1 described above is (000) and the vector of t4 is (111), which is a period in which the motor 6 is not energized (hereinafter referred to as “zero vector”). Further, t2 and t3 other than the zero vector are periods in which the motor 6 is energized (hereinafter referred to as “real vector”). When Vin> Vdc, K> 1 and the above equations (1) to (4) are calculated, and t1 and t4 become negative. In this case, (t1 + t2 + t3) × 2 + t4 = T and t1 The motor 6 can be controlled even when K> 1 by appropriately limiting each period from t1 to t4 so that t4 is 0 or more.

FIG. 3 is a timing chart showing the switching pattern of each switching element in FIG. 2A, and FIGS. 4 and 5 are timing charts showing the switching pattern of each switching element in the conventional two-phase modulation.
In FIG. 4, the t4 period of the zero vector (111) shown in FIG. The switching patterns of the switching elements 3a to 3f of two-phase modulation when Wn is attached to Hi are shown. FIG. 5 shows a case where t1 period of zero vector (000) shown in FIG. 3 is inserted into t4 period of zero vector (111) to make t4 + t1 × 2 period, Up is pasted on Hi, and Un is pasted on Lo. The switching pattern of each switching element 3a-3f of 2 phase modulation is shown. By switching from the three-phase modulation to the two-phase modulation, the switching frequency of each of the switching elements 3a to 3f becomes 2/3 and the switching loss can be reduced without changing the voltage applied to the motor. This is a well-known technique that enables highly efficient motor control. The selection of the attaching method as shown in FIGS. 4 and 5 is appropriately determined from the viewpoints of motor control stability and noise.

  Here, when the rotation speed and load of the motor 6 are stable, Vin has a substantially constant value, and therefore, t1 and t4 are substantially constant periods based on the results of the above-described equations (1) to (4). . Therefore, the period (t1 + t4 / 2) of the zero vector (000) in FIG. 4 is constant, and switching of the U-phase switching elements 3a and 3d occurs at a constant carrier cycle. Similarly, since the period (t4 + t1 × 2) of the zero vector (111) in FIG. 5 is constant, the switching of the W-phase switching elements 3c and 3f occurs at a constant carrier cycle. The switching of the switching elements 3a to 3f at a constant carrier cycle generates annoying magnetic sound from the motor 6. As a countermeasure against this magnetic sound, the carrier frequency may be set to a high frequency range (for example, 20 kHz or more) that is outside the human audible range, but there is a problem that the switching frequency becomes high and the switching loss is greatly increased.

Next, two-phase modulation in the first embodiment will be described with reference to FIG.
FIG. 6 is a timing chart showing switching patterns of the respective switching elements at the time of two-phase modulation in the motor control device of the first embodiment with respect to FIG.

For FIG. 4, as shown in FIG. 6, the t2, t3 × 2 period of the real vector (100) (110) within one carrier period (predetermined period) is not changed, and exists in the first half and the second half of the carrier period. Without changing the total time of the t5 and t6 periods of the switching pattern of the zero vector (000) to be performed, the times of the first t5 period and the latter t6 period of the switching pattern are varied randomly or according to an appropriate rule (t1). × 2 + t4 = t5 + t6). The period t5 and t6 in the case of changing at random can be obtained, for example, by calculation of the following equation.
t5 = (t1 × 2 + t4) × α (5)
t6 = (t1 × 2 + t4) −t5 (6)
Here, α represents a random number from 0 to 1. This control can be performed in the same manner in each section of B to F other than A in FIG.
Note that the calculation can be simplified by calculating the logical product of t5 (t1 × 2 + t4) and a random number in order to suppress the calculation load on the control unit 2.

  As described above, in the first embodiment, it is possible to change the total time of the switching patterns (t5, t6) of the switching elements 3a to 3f for cutting off the energization of the motor 6 for each carrier period without changing the total time. Each time of the switching pattern is made variable. Therefore, the carrier frequency component can be dispersed into other frequency components, and as a result, the annoying magnetic sound of the carrier frequency component from the motor 6 can be suppressed, and motor control with high efficiency and low noise can be realized.

  In the first embodiment, each time of the first t5 period and the second t6 period is varied randomly or by an appropriate rule within one carrier cycle. However, the present invention is not limited to this. For example, as shown in FIG. 7, the total of two real vectors (100) existing in one carrier cycle without changing the length (time) of the t3 × 2 period of the real vector (110) in one carrier cycle. Without changing the time (t7, t8), it is possible to change the period of t7, t8 randomly or according to an appropriate rule, and to suppress the harsh magnetic sound by changing the characteristics of the magnetic sound from the motor 6. .

The t7 and t8 periods in the case of varying at random can be obtained, for example, by calculation of the following equation.
t7 = (t2 × 2) × α (7)
t8 = (t2 × 2) −t7 (8)
The control in this case can also be performed in the same manner in each section of B to F other than A in FIG.
In addition, in order to reduce the calculation load on the control unit 2, the calculation can be simplified by taking a logical product of (t2 × 2) and a random number in the t7 period.

Embodiment 2. FIG.
In the second embodiment, each time of the switching pattern is varied without changing the total time of the switching patterns of the switching elements 3a to 3f for energizing the motor 6 every carrier period (predetermined period). It is a thing. The circuit configuration of the motor control device of the second embodiment is the same as that of the first embodiment shown in FIG.

Next, two-phase modulation in the second embodiment will be described with reference to FIG.
FIG. 8 is a timing chart showing a switching pattern of each switching element at the time of two-phase modulation in the motor control device of the second embodiment with respect to FIG.
For FIG. 5, as shown in FIG. 8, the t4 + t1 × 2 period of the zero vector (111) in one carrier period and the t3 period of the real vector (110) are not changed, and in the first half and the second half of the one carrier period. Without changing the total time of t9 and t10 periods of the existing real vector (100), the times of the first t9 period and the latter t10 period are varied randomly or according to an appropriate rule (t2 × 2 = t9 + t10). The t9 and t10 periods in the case of random variation can be obtained, for example, by calculation of the following equation.
t9 = (t2 × 2) × α (9)
t10 = (t2 × 2) −t9 (10)
This control can be performed in the same manner in each section of B to F other than A in FIG.
Note that the calculation can be simplified by taking the logical product of t9 (t2 × 2) and a random number in order to suppress the calculation load on the control unit 2.

  As described above, in the second embodiment, the switching pattern of each switching element 3a to 3f for energizing the motor 6 is changed for each carrier cycle without changing the total time of the switching patterns (t9, t10). Each time is made variable. Therefore, the carrier frequency component can be dispersed into other frequency components, and as a result, the annoying magnetic sound of the carrier frequency component from the motor 6 can be suppressed, and motor control with high efficiency and low noise can be realized.

  In the second embodiment, the respective times of the t9 and t10 periods are changed without changing the total time of the t9 and t10 periods of the real vector (100) existing in the first half and the second half of one carrier cycle. However, the present invention is not limited to this. For example, as shown in FIG. 9, the length (time) of the t4 + t1 × 2 period of the zero vector (111) in one carrier cycle is not changed, and two real zero vectors (110) existing in the one carrier cycle are not changed. It is also possible to suppress unpleasant magnetic sounds by changing the frequency characteristics of the magnetic sound from the motor 6 by changing the t11, t12 period at random or by an appropriate rule without changing the total time.

The t11 and t12 periods when randomly varying can be obtained by, for example, calculation of the following equation.
t11 = (t3 × 2) × α (11)
t12 = (t3 × 2) −t11 (12)
The control in this case can also be performed in the same manner in each section of B to F other than A in FIG.
In addition, in order to reduce the calculation load on the control unit 2, the calculation can be simplified by taking the logical product of (t2 × 2) and a random number in the t9 period.

  1 DC power supply, 2 control unit, 3a to 3f switching element, 4a to 4f diode, 5 inverter circuit, 6 motor.

Claims (2)

An inverter circuit having a switching element of a three-phase bridge connection that converts direct current into alternating current;
A controller that switches each switching element of the inverter circuit and controls the motor connected to the inverter circuit by two-phase modulation;
The said control part changes each time of the switching pattern, without changing the total time of the switching pattern of the switching element for interrupting | blocking the electricity supply to a motor for every predetermined period. An inverter circuit having a switching element of a three-phase bridge connection that converts direct current into alternating current;
A controller that switches each switching element of the inverter circuit and controls the motor connected to the inverter circuit by two-phase modulation;
The said control part changes each time of the switching pattern, without changing the total time of the switching pattern of the switching element for supplying with electricity to a motor for every predetermined period.

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