JP3250329B2 - Two-phase PWM controller for inverter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a two-phase PW
Apparatus for controlling M (pulse width modulation), that is, two-phase PWM
It relates to a control device.

[0002]

2. Description of the Related Art FIG. 13 shows a configuration of a conventional PWM control device. The device shown in this figure
For example, it constitutes a part of a drive system of an electric vehicle.

The control target of the device shown in this figure is an inverter 10. The inverter 10 converts DC power supplied from a DC power supply (not shown), for example, a main battery mounted on a vehicle, into AC power, and supplies the AC power to a load. In this case,
A three-phase AC motor 12 having U, V, and W phases is used as a load of the inverter 10.

[0004] The inverter 10 has a logarithmic switching element corresponding to the number of phases of the load in order to perform such a power conversion operation. This switching element is a high power switching element such as an IGBT, for example, and is driven by a base drive 14 provided in front of the inverter 10. The base drive 14 drives the inverter 10 based on the PWM signals e _U , e _V , and e _W of the respective phases supplied from the PWM generator 16.

The PWM generator 16 includes a subtractor 18U, 1
A current command generator 20 is provided in front of 8 V and 18 W. The current command generator 20 supplies the current commands I _U ^，, I _V ^＾ , and I _W ^に _対 ^し to the control device shown in FIG. Subtractor 18U, 18V, 18W, the current current command supplied from the command generating portion ^{_{20 I U ^, I V ^}} , I W ^ other, the current sensor 22U which are provided corresponding to each phase of the motor 12,
Line currents I _U , I _V ,
Enter I _W. The subtracters 18U, 18V, 18W subtract the latter from the former, and supply the result to the PWM generator 16. The PWM generator 16 includes subtractors 18U, 18V, 18
It has PI converters 24U, 24V, 24W for converting the output of W into voltage commands e _0U , e _0V , e _0W . The voltage commands e _0U , e _0V , and e _0W obtained by the PI converters 24U, 24V, 24W correspond to the comparators 26U, 26V, 2
6W respectively. In addition, the comparators 26U, 26V, and 26W supply the carrier e _S from the oscillator 28.
Is supplied. Comparators 26U, 26V, 26
W compares the two and outputs the resulting voltage to each phase PWM.
The signals e _U , e _V , and e _W are supplied to the base drive 14.

FIG. 14 shows the contents of normal PWM control executed based on the phase voltage. As shown in this figure, in normal PWM control, a carrier wave e _S having a predetermined waveform such as a triangular wave is compared with each phase voltage command e _0U , e _0V , e _0W respectively, and each phase PWM signal e _U, e _V, e _W is generated. The phase output voltages V _U , V _V , V _W from the inverter 10 to the motor 12 have a pulse width modulation waveform as shown in FIG. 14, and the line voltage of the motor 12, for example, the UV line voltage V _UV is a sine The voltage approximates the wave.

[0007] Such PWM control is performed by the inverter 10
This is a method that is widely used as a driving method. In recent years, for example, in 1983, the National Institute of Electrical Engineers of Japan [6]. 498, pages 574-575, Kim et al., Etc. have developed two-phase PWM control. The two-phase PWM control can also reduce switching loss that increases with an increase in current, such as copper loss, because the number of switching times decreases.

FIG. 15 shows the contents of the two-phase PWM control executed based on the line voltage. The control shown in this figure can be executed by the device configuration shown in FIG.

As shown in FIG. 1, in the voltage commands e _0U , e _0V , and e _0W in the two-phase PWM control, the values are set to the peak value of the carrier wave e _S during a period of about 60 ° in electrical angle. ing. When such a period is determined, switching in the inverter 10 is stopped during this period, and as a result, output voltages of respective phases as shown in FIG. 15 are obtained.

[0010]

However, in the conventional two-phase PWM control, the switching stop period is fixedly set near the voltage peak as shown in FIG. Therefore, when the phase difference of the current with respect to the voltage is large, that is, when the power factor of the load of the inverter is reduced, the effect of reducing the switching loss is not so large. In a remarkable case, the switching is performed at the maximum current, so that the loss is hardly reduced. Further, when a motor is considered as the load of the inverter, the power factor of the motor fluctuates due to an increase in its rotation speed, an increase in torque, and the like. Therefore, when such a load is driven, the switching loss is not significantly reduced even if the switching stop period is fixedly set at the time of the voltage peak.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to make it possible to suitably reduce a switching loss by causing a switching stop period to follow a current peak. I do.

[0012]

In order to achieve the above object, a two-phase modulation PWM control device for an inverter according to the present invention is arranged so that switching of each phase of the inverter is alternately stopped for a predetermined period. A means for generating a PWM signal and supplying the signal to the inverter as a signal for controlling switching; a means for detecting a phase voltage and a line current for at least one of the phases to obtain a power factor angle which is a phase difference between the two; Means for controlling the operation of generating each phase PWM signal based on the determined power factor angle so as to follow the vicinity of the peak of the phase current flowing through the load.

Further, the two-phase modulation PW of the inverter according to the present invention is provided.
The M control device generates a PWM signal for each phase so that switching of each phase of the inverter is alternately stopped for a predetermined period, supplies the PWM signal to the inverter as a signal for controlling switching, and detects a state of a load of the inverter. Means for obtaining a power factor based on the detected state, and means for controlling the generation operation of each phase PWM signal based on the obtained power factor so that the period follows the vicinity of the peak of the line current flowing to the load of the inverter. It is characterized by having.

[0014]

According to the present invention, each phase PWM signal is generated and switching of the inverter is controlled so that switching of each phase of the inverter is alternately stopped for a predetermined period, that is, two-phase PWM control is executed. You. At this time, a phase voltage and a line current are detected for at least one of the phases, and a phase difference (power factor angle) between the two is obtained.
The obtained power factor angle is used for controlling the generation operation of each phase PWM signal. This control is performed such that the switching suspension period of each phase of the inverter follows the vicinity of the peak of the line current flowing to the load of the inverter. Therefore, in the present invention, the switching stop period follows the vicinity of the peak of the current, so that the switching loss that increases as the current increases can be suitably suppressed.

In the present invention, as means for determining the power factor, means for detecting the state of the load of the inverter can be used in addition to means for detecting the phase voltage and the line current. The load of the inverter, for example, the state of the motor, can be estimated from the number of revolutions and the torque. In the present invention, the power factor is obtained based on the load state thus detected, and the following control of the switching stop period is executed based on the obtained power factor. By performing such control, in the present invention, control for reducing switching loss according to the state of the load of the inverter is suitably realized.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. The same components as those of the conventional example shown in FIGS. 13 to 15 are denoted by the same reference numerals, and description thereof will be omitted.

FIG. 1 shows the configuration of a control device according to a first embodiment of the present invention. In this embodiment, U
The phase difference between the phase voltage V _U and the line current I _U, that is, the phase difference detecting unit 30 for detecting a power factor angle φ is provided for phase. The power factor angle φ output from the phase difference detector 30 is supplied to the current command generator 32, and the current command generator 32 controls the switching stop period of the inverter 10 in accordance with the power factor angle φ. Current commands I _U ^＾ , I _V ^，, I _W ^＾
Generate In this embodiment, the subtractor 18
The line current I _V input to _V is generated by the adder 34 based on the line currents I _U and I _W. Phase difference detector 3
0, based on the line voltage V _UV and the line current I _U, the power factor angle φ
Is calculated.

FIGS. 2 to 4 show the contents of the switching stop period follow-up control in this embodiment. In particular, FIG. 2 shows the switching stop period when φ <30 ° (power factor> 0.866), and FIG. 3 shows the switching stop period when φ ≧ 30 ° (power factor ≦ 0.866). FIG.
Indicates a control flow.

[0019] Considering the U-phase as an example, a switching stop period in a conventional two-phase modulation PWM control has been fixedly set with respect to the peak of the U-phase voltage V _U of the motor 12. In other words, so that the U-phase voltage V period peak ± 30 ° of the _U, a switching stop period is set. In the present embodiment, the switching stop period is not the U-phase voltage V _U, the peak of the U phase line current I _U ±
Follow-up setting is made for a period of 30 °, for a total of 60 °.
That is, the switching stop period according to the phase difference serving as the power factor angle φ of the U-phase voltage V _U and U phase line current I _U is set,
As a result, the switching suspension period follows the peak of the U-phase line current I _U. This control is also executed for the V phase and the W phase in this embodiment.

[0020] Thus, in the present embodiment, the line current, for example, the switching stop period so as to be near the peak of I _U is to be follow-up control, the switching loss is effective to increase with increasing current As a result, effects such as downsizing of the cooling system of the inverter 10 and reduction of the heat mass can be realized.

Further, the follow-up control of the switching stop period as shown in FIG. 2 has a predetermined limit. In other words, the switching stop period cannot be set to exceed the section where the three differential relationship is established, that is, to exceed the switching stoppable section shown in FIG. Accordingly, when the power factor angle φ is 30 ° or more, as shown in FIG. 3, the switching suspension period is changed from the peak of the phase voltage (for example, V-phase voltage V _U ) to the line current (for example, U-phase line current). It is set in the range of 60 ° near the peak of I _U ). Such setting corresponds to setting the switching stop period so that the switching loss is reduced most in the switching stoppable section having a spread of 120 °.

Such control can be realized by detecting the power factor angle φ. FIG. 4 illustrates the flow of control in this embodiment, focusing on the method of detecting the power factor angle (phase difference) φ.

As shown in this figure, in the present embodiment, first, the phase difference detection section 30 detects the UV line voltage V _UV.
And the U-phase line current I _U is measured (100, 102).
The measured line voltage V _UV is converted into phase voltage V _U (10
4), the phase difference of the obtained U-phase voltage V _U and U phase line currents I _U, i.e. the power factor angle φ is detected (106). The phase difference detection unit 30 outputs the detected power factor angle φ to the current command generation unit 32
To supply. The current command generator 32 sets the power factor angle φ to 3
It is compared with 0 ° (108), and one of the processes A and B is executed according to the result (110, 112). Process A is an operation when the power factor angle φ is less than 30 °, that is, FIG.
The process B is an operation when the power factor angle φ is 30 ° or more, that is, a control operation as shown in FIG.

FIG. 5 shows a voltage command e in this embodiment.
_0U, e _0V, the waveform of e _{0 W} is shown. The current command generator 32 outputs the power factor angle φ detected by the phase difference detector 30.
Current command I _U ^{^} depending on, I _V ^{^,} by generating I _W ^{^,} FIGS. 5 (a) voltage as shown in ~ (c) instruction e _0U, e _0V, to generate e _{0 W.} This voltage command e _U ,
e _V and e _W each include a switching stop period following the power factor angle φ. As shown in FIGS. _6A to 6C, each of the voltage commands e _0U , e _0V , and e _0W corresponds to the carrier e _S output from the oscillator 28 and the comparator 26U,
Compared at 26V, 26W. The resulting PWM signals e _U , e _V , e _W are supplied to the base drive 14, and as a result, as shown in FIG. 2 or FIG. 3, the switching stop period is added to the phase currents I _U , I _V , I _W. The following two-phase PWM control is realized.

FIG. 7 shows a two-phase PWM in this embodiment.
The relationship between a voltage command waveform related to control and a voltage command waveform related to normal PWM control is shown. As shown in this figure, in the present embodiment, the switching stop period is set according to the power factor angle φ. This figure shows that φ <3
It is a figure at the time of 0 degree.

FIG. 8 shows the configuration of a control device according to a second embodiment of the present invention. The device shown in this figure
This is a configuration in which the function of the phase difference detection unit 30 in the first embodiment is added to the current command generation unit 36. Even in such a configuration, the above-described effects can be obtained.

FIG. 9 shows the configuration of a control device according to a third embodiment of the present invention, and FIG. 10 shows the flow of control thereof.

In this embodiment, the power command angle φ is not detected based on the line current and the phase voltage (directly, the line voltage), but the current command generator 40 is provided from a control device (not shown). Based on the torque command T and the rotation speed of the motor 12 detected by the rotation speed sensor 38, the ROM 4
2, the power factor angle φ is obtained with reference to the table above.

That is, as shown in FIG. 10, the torque command generator 40 inputs the torque command T (114),
Further, the rotational speed N is detected (116). The torque command T is a torque command value for the motor 12, that is, a value indicating a torque value to be output from the motor 12 by current control by the inverter 10. Power factor angle φ of motor 12
Depends largely on the state of the motor 12, for example, torque and rotation speed. Therefore, the values of the torque command T and the rotation speed N can be associated with the power factor angle φ of the motor 12. The table stored on the ROM 42 is
5 is a table that associates a torque command T, a rotation speed N, and a power factor angle φ. In this embodiment, the table on the ROM 42 is referred to by the torque command T and the rotational speed N, and the power factor angle φ is read out (118). The read power factor angle φ is subjected to the same determination as in the first embodiment, and processes A and B are selectively executed.

Therefore, in this embodiment, the same effects as those of the above embodiments can be obtained. Further, since the switching stop period can be set according to the state of the motor 12, which is a load of the inverter 10, switching loss can be suitably reduced according to the state of the motor 12. This leads to improvement in controllability, abolition of the phase difference detection unit 30 for detecting a phase difference, leading to cost reduction and speeding up control. In addition, since the change to the conventional device is small, the realization is easy.

FIG. 11 shows the configuration of a control device according to a fourth embodiment of the present invention. This embodiment detects the power factor angle φ using the phase difference detection unit 30 and controls the carrier wave e _S using the power factor angle φ, thereby realizing the following control of the switching stop period. ing. Therefore, PWM generating unit 44 includes a carrier control unit 46 for controlling the oscillating operation of the carrier e _S based on the power factor angle phi.

More specifically, in this embodiment, the offset of the carrier wave e _S is controlled based on the power factor angle φ output from the phase difference detector 30. That is, the offset is controlled such that the amplitude of the carrier wave e _S coincides with the amplitude of the voltage command during the switching stop period. Thus, voltage e _0U, e _0V, instead of e _{0 W,} by applying predetermined processing to the carrier e _S, it is possible to realize the follow-up control of the switching stop period.

FIG. 12 shows the configuration of a control device according to a fifth embodiment of the present invention. Also in this example,
The PWM generation unit 48 includes a carrier control unit 50, and the carrier control unit 50 realizes offset control of the carrier wave e _S , thereby realizing control of following the phase current during the switching stop period. However, carrier control unit 50 in this embodiment, instead of controlling the carrier e _S based on the power factor angle detected by the phase detector 30 phi, the torque command T and the rotation is supplied from a control device (not shown) Motor 1 detected by number sensor 38
The information of the power factor angle φ is obtained by referring to the table on the ROM 42 based on the rotation speed of 2.

Therefore, in this embodiment, the same effects as in the third embodiment can be obtained.

The present invention is not limited to the configuration of each embodiment described above. For example, inverter 10
Is not limited to the motor 12. Furthermore, the power factor angle φ
The phase on which the detection is based is not limited to the U phase.
The switching suspension period may be smaller than 60 °.

[0036]

As described above, according to the present invention,
Since the phase stop voltage and the line current are detected and the phase difference (power factor angle) thereof is obtained and the switching stop period is controlled to follow the vicinity of the peak of each phase line current, the switching loss that increases as the current increases is reduced. Therefore, the size of the cooling system of the inverter can be reduced and the heat mass can be reduced.

According to the present invention, the state of the load of the inverter (for example, the motor) is detected, and the switching suspension period is controlled to follow the peak of the line current in accordance with the detection result. In addition, the effect of improving the controllability of the load can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a control device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a switching stop period when a power factor angle φ is less than 30 ° in this embodiment.

FIG. 3 is a diagram showing a switching stop period when a power factor angle φ is 30 ° or more in this embodiment.

FIG. 4 is a diagram showing a control flow in this embodiment.

FIG. 5 is a diagram showing a voltage command waveform of each phase in this embodiment, and FIGS. 5A to 5C are diagrams showing voltage command waveforms of U, V, and W phases, respectively.

FIGS. 6A to 6C are diagrams showing a generation process of each phase PWM signal in this embodiment, and FIGS.
It is a figure which shows the PWM signal generation processing of V and W phase.

FIG. 7 shows a voltage command waveform and a normal PW in this embodiment.
It is a figure showing the relation of the voltage command waveform in M control.

FIG. 8 is a block diagram illustrating a configuration of a control device according to a second embodiment of the present invention.

FIG. 9 is a block diagram illustrating a configuration of a control device according to a third embodiment of the present invention.

FIG. 10 is a diagram showing a flow of control in this embodiment.

FIG. 11 is a block diagram illustrating a configuration of a control device according to a fourth embodiment of the present invention.

FIG. 12 is a block diagram illustrating a configuration of a control device according to a fifth embodiment of the present invention.

FIG. 13 is a block diagram illustrating a configuration of a control device according to a conventional example.

FIG. 14 shows a normal PWM executed based on a phase voltage.
It is a figure showing the contents of control.

FIG. 15 shows a two-phase PWM executed based on a line voltage.
FIG. 3 is a block diagram illustrating a configuration of control.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Inverter 12 Motor 14 Base drive 16,44,48 PWM generator 20,32,36,40 Current command generator 22U, 26V, 22W Current sensor 26U, 26V, 26W Comparator 28 Oscillator 30 Phase difference detector 38 Speed sensor 42 ROM 44,50 Carrier wave controller φ Power factor angle Switching stoppable section Switching stop period

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-168895 (JP, A) JP-A-4-217874 (JP, A) JP-A-4-285473 (JP, A) 76199 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) H02M 7/48 G05F 1/70 H02P 7/63

Claims (2)

(57) [Claims] 1. A means for generating a pulse width modulation signal for each phase so that the switching of each phase of the inverter alternately and for a predetermined period is stopped, and supplying the pulse width modulation signal to the inverter as a signal for controlling the switching. A means for detecting a phase voltage and a line current to obtain a power factor angle that is a phase difference between the two; and a pulse width for each phase based on the determined power factor angle so that the period follows the vicinity of the peak of the line current flowing to the load of the inverter. Means for controlling a generation operation of a modulation signal. A two-phase PWM control device for an inverter, comprising: 2. A means for generating a pulse width modulation signal for each phase so that the switching of each phase of the inverter alternately and for a predetermined period is stopped, and supplying the pulse width modulation signal to the inverter as a signal for controlling the switching. Means for detecting and detecting a power factor based on the detected state, and controlling the generation operation of each phase pulse width modulation signal based on the determined power factor so that the period follows the vicinity of the peak of the line current flowing to the load of the inverter. Means for controlling the two-phase PWM of the inverter.